Rapid repair of severely earthquake-damaged bridge piers with flexural-shear failure mode
Sun, Zhiguo; Wang, Dongsheng; Du, Xiuli; Si, Bingjun
2011-12-01
An experimental study was conducted to investigate the feasibility of a proposed rapid repair technique for severely earthquake-damaged bridge piers with flexural-shear failure mode. Six circular pier specimens were first tested to severe damage in flexural-shear mode and repaired using early-strength concrete with high-fluidity and carbon fiber reinforced polymers (CFRP). After about four days, the repaired specimens were tested to failure again. The seismic behavior of the repaired specimens was evaluated and compared to the original specimens. Test results indicate that the proposed repair technique is highly effective. Both shear strength and lateral displacement of the repaired piers increased when compared to the original specimens, and the failure mechanism of the piers shifted from flexural-shear failure to ductile flexural failure. Finally, a simple design model based on the Seible formulation for post-earthquake repair design was compared to the experimental results. It is concluded that the design equation for bridge pier strengthening before an earthquake could be applicable to seismic repairs after an earthquake if the shear strength contribution of the spiral bars in the repaired piers is disregarded and 1.5 times more FRP sheets is provided.
Flexural Strengthening of RC Slabs Using a Hybrid FRP-UHPC System Including Shear Connector
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Jiho Moon
2017-01-01
Full Text Available A polymeric hybrid composite system made of UHPC and CFRP was proposed as a retrofit system to enhance flexural strength and ductility of RC slabs. While the effectiveness of the proposed system was confirmed previously through testing three full-scale one-way slabs having two continuous spans, the slabs retrofitted with the hybrid system failed in shear. This sudden shear failure would stem from the excessive enhancement of the flexural strength over the shear strength. In this study, shear connectors were installed between the hybrid system and a RC slab. Using simple beam, only positive moment section was examined. Two full-scale RC slabs were cast and tested to failure: the first as a control and the second using this new strengthening technique. The proposed strengthening system increased the ultimate load carrying capacity of the slab by 70%, the stiffness by 60%, and toughness by 128%. The efficiency of shear connectors on ductile behavior of the retrofitted slab was also confirmed. After the UHPC top is separated from the slab, the shear connector transfer shear load and the slab system were in force equilibrium by compression in UHPC and tension in CFRP.
Experimental research and finite element analysis of bridge piers failed in flexure-shear modes
Institute of Scientific and Technical Information of China (English)
Sun Zhiguo; Si Bingjun; Wang Dongsheng; Guo Xun
2008-01-01
In recent earthquakes,a large number of reinforced concrete (RC) bridges were severely damaged due to mixed flexure-shear failure modes of the bridge piers.An integrated experimental and finite element (FE) analysis study is described in this paper to study the seismic performance of the bridge piers that failed in flexure-shear modes.In the first part,a nonlinear cyclic loading test on six RC bridge piers with circular cross sections is carried out experimentally.The damage states,ductility and energy dissipation parameters,stiffness degradation and shear strength of the piers are studied and compared with each other.The experimental results suggest that all the piers exhibit stable flexural response at displacement ductilities up to four before exhibiting brittle shear failure.The ultimate performance of the piers is dominated by shear capacity due to significant shear cracking,and in some cases,rupturing of spiral bars.In the second part,modeling approaches describing the hysteretic behavior of the piers are investigated by using ANSYS software.A set of models with different parameters is selected and evaluated through comparison with experimental results.The influences of the shear retention coefficients between concrete cracks,the Bauschinger effect in longitudinal reinforcement,the bond-slip relationship between the longitudinal reinforcement and the concrete and the concrete failure surface on the simulated hysteretie curves are discussed.Then,a modified analysis model is presented and its accuracy is verified by comparing the simulated results with experimental ones.This research uses models available in commercial FE codes and is intended for researchers and engineers interested in using ANSYS software to predict the hysteretic behavior of reinforced concrete structures.
Experimental research and finite element analysis of bridge piers failed in flexure-shear modes
Sun, Zhiguo; Si, Bingjun; Wang, Dongsheng; Guo, Xun
2008-12-01
In recent earthquakes, a large number of reinforced concrete (RC) bridges were severely damaged due to mixed flexure-shear failure modes of the bridge piers. An integrated experimental and finite element (FE) analysis study is described in this paper to study the seismic performance of the bridge piers that failed in flexure-shear modes. In the first part, a nonlinear cyclic loading test on six RC bridge piers with circular cross sections is carried out experimentally. The damage states, ductility and energy dissipation parameters, stiffness degradation and shear strength of the piers are studied and compared with each other. The experimental results suggest that all the piers exhibit stable flexural response at displacement ductilities up to four before exhibiting brittle shear failure. The ultimate performance of the piers is dominated by shear capacity due to significant shear cracking, and in some cases, rupturing of spiral bars. In the second part, modeling approaches describing the hysteretic behavior of the piers are investigated by using ANSYS software. A set of models with different parameters is selected and evaluated through comparison with experimental results. The influences of the shear retention coefficients between concrete cracks, the Bauschinger effect in longitudinal reinforcement, the bond-slip relationship between the longitudinal reinforcement and the concrete and the concrete failure surface on the simulated hysteretic curves are discussed. Then, a modified analysis model is presented and its accuracy is verified by comparing the simulated results with experimental ones. This research uses models available in commercial FE codes and is intended for researchers and engineers interested in using ANSYS software to predict the hysteretic behavior of reinforced concrete structures.
Corrections for shear and rotatory inertia on flexural vibrations of beams
Nederveen, C.J.; Schwarzl, F.R.
1964-01-01
Different correction formulae for the influence of shear and rotatory inertia on flexural vibrations of freely supported beams are compared with the exact solution. It appears that in most cases a simple formula is sufficient because of the appearance of a constant which is not accurately known, viz
Flexural-torsional buckling behavior of aluminum alloy beams
Institute of Scientific and Technical Information of China (English)
Xiaonong GUO; Zhe XIONG; Zuyan SHEN
2015-01-01
This paper presents an investigation on the flexural-torsional buckling behavior of aluminum alloy beams （AAB）. First, based on the tests of 14 aluminum alloy beams under concentrated loads, the failure pattern, load- deformation curves, bearing capacity and flexural-torsional buckling factor are studied. It is found that all the beam specimens collapsed in the flexuml-torsional buckling with excessive deformation pattern. Moreover, the span, loading location and slenderness ratio influence the flexural-torsional buckling capacity of beams significantly. Secondly, besides the experiments, a finite element method （FEM） analysis on the flexural-torsional buckling behavior of AAB is also conducted. The main parameters in the FEM analysis are initial imperfection, material property, cross-section and loading scheme. According to the analytical results, it is indicated that the FEM is reasonable to capture mechanical behavior of AAB. Finally, on the basis of the experimental and analytical results, theoretical formulae to estimate the flexural- torsional buckling capacity of AAB are proposed, which could improve the application of present codes for AAB.
Some comments on the experimental behavior of FRC beams in flexure
Campione, Giuseppe; La Mendola, Lidia; Mangiavillano, Maria Letizia; Papia, Maurizio
2008-07-01
In the present paper the experimental results, recently obtained by the authors, regarding the monotonic and the cyclic flexural response of normal and high-strength concrete beams reinforced with steel bars and discontinuous fibers, are shown. From the experimental results, all referred to low values of shear-to-depth ratios, it emerges clearly that the shear failure is brittle especially under cyclic actions highlighting the role of the fibers in the flexural behavior of the beams. The cyclic action produces a significant decay in the stiffness and in the strength capacity of the beams, and the addition of fibers reduces these negative effects. Form theoretical point of view good agreement can be found utilizing the recent analytical model proposed by the authors.
Application of bamboo for flexural and shear reinforcement in concrete beams
Schneider, Nathan Alan
As the developing world is industrializing and people migrate to cities, the need for infrastructure is growing quickly and concrete has become one of the most widely used construction materials. One poor construction practice observed widely across the developing world is the minimal use of reinforcement for concrete structures due to the high cost of steel. As a low-cost, high-performance material with good mechanical properties, bamboo has been investigated as an alternative to steel for reinforcing concrete. The goal of this research is to add to the knowledge base of bamboo reinforced concrete (BRC) by investigating a unique stirrup design and testing the lap-splicing of flexural bamboo reinforcement in concrete beams. Component tests on the mechanical properties of Moso bamboo (Phyllostachys edulis) were performed, including tensile tests and pull-out tests. The results of the component tests were used to design and construct 13 BRC beams which were tested under monotonic gravity loading in 3 and 4-point bending tests. Three types of beams were designed and tested, including shear controlled, flexure controlled, and lap-spliced flexure controlled beams. The test results indicated that bamboo stirrups increased unreinforced concrete beam shear capacities by up to 259%. The flexural bamboo increased beam capacities by up to 242% with an optimal reinforcement ratio of up to 3.9%, assuming sufficient shear capacity. Limitations of the bamboo reinforcement included water absorption as well as poor bonding capability to the concrete. The test results show that bamboo is a viable alternative to steel as tensile reinforcement for concrete as it increases the ultimate capacity of the concrete, allows for high deflections and cracks, and provides warning of impending structural failure.
Institute of Scientific and Technical Information of China (English)
郭猛; 牟在根; 袁泉
2011-01-01
对中高层弯剪型-弯曲型双重抗侧力结构体系的水平位移计算方法进行了研究.将弯曲型子结构视为仅发生弯曲变形的悬臂墙,将弯剪型子结构视为同时发生弯曲变形和剪切变形的Timoshenko悬臂墙,在此基础上建立了弯剪型-弯曲型双重抗侧力结构体系的位移微分方程,结合边界条件,推导了均布荷载等三种荷载下结构的弯曲变形、剪切变形和总水平位移的解析解.探讨了弯剪型-弯曲型双重结构与剪切形-弯曲形双重结构位移计算方法的关系.结果表明,剪切形-弯曲形双重结构可视为弯剪型-弯曲型双重结构在弯剪型子结构抗弯刚度取无穷大时的一种特殊表现形式.%A calculation method of horizontal displacement was studied for the dual structure consisting of flexural-shear substructures and flexural substructures.The flexural substructures are regarded as flexural cantilever walls which exhibit a predominantly flexural behavior,and the flexural-shear substructures are regarded as Timoshenko cantilever walls which exhibit a mixed flexural/shear behavior.On the basis of the above assumptions,a differential equation was established for calculating the displacement of the dual structure.With boundary conditions,the analytical solutions of the displacement,including the flexural deformation,the shear deformation and the total horizontal displacement,were derived when the dual structure was subjected to uniform loads.The relation between the dual structure consisting of flexural-shear substructures flexural substructures and that consisting of shear substructures flexural substructures was discussed,and the result shows that the later can be viewed as a special form of the former where the flexural stiffness of the flexural-shear substructures tends to infinity.
Institute of Scientific and Technical Information of China (English)
无
2006-01-01
With the idea of the phononic crystals, the beams with periodic structure are designed.Flexural vibration through such periodic beams composed of two kinds of materials is studied. The emphasis is laid on the effects of rotary inertia and shear deformation. Based on the vibration equation, plane wave expansion method is provided. The acceleration frequency responses of such beams with finite structure are simulated by the finite element method. The frequency ranges of sharp drops in the calculated acceleration frequency response curves are in good agreement with those in the band structures. The findings will be significant in the application of the periodic beams.
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Guibing Li
2014-05-01
Full Text Available Debonding failure is the main failure mode in flexurally strengthened reinforced concrete beams by externally bonded or near surface mounted fibre reinforced polymer (FRP composites. It is believed that FRP debonding will be initiated if the shear stress on the concrete-FRP interface reaches the tensile strength of concrete. However, it was found through experimental and analytical studies that the debonding mechanism of FRP composites has the potential of shear failure in combination with debonding failure. Moreover, the shear failure probably influences the debonding failure. Presently, there are very little experimental and analytical studies to investigate the influence of shear resistance of reinforced concrete (RC beam on FRP debonding failure. The current study investigates and analyzes the effect of shear resistance on FRP debonding failure based on test results. The analytical results show that the shear resistance of RC beam has a great effect on flexural debonding load-carrying capacity of FRP-strengthened RC beam. The influence of shear resistance on flexural debonding load-carrying capacity must be fully considered in flexural strengthening design of RC beams.
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Edgaras Atutis
2013-12-01
Full Text Available The paper analyzes experimental studies examining the flexuraland shear analysis of the beams reinforced with GFRP bars. Atesting program consisted of two beams reinforced with longitudinalprestressed GFRP tendons, two beams reinforced withlongitudinal GFRP bars and two beams reinforced with longitudinalsteel reinforcement and shear reinforcement of GFRP bars.The experimental flexural and shear strength of concrete beamswere compared with theoretical strength calculated according toa number of design recommendations, and the significance ofprestressing for deflection and cracking was analyzed.
Sharma, Pankaj; Parashar, Sandeep Kumar
2016-05-01
The priority of this paper is to obtain the exact analytical solution for free flexural vibration of FGPM beam actuated using the d15 effect. In piezoelectric actuators, the potential use of d15 effect has been of particular interest for engineering applications since shear piezoelectric coefficient d15 is much higher than the other piezoelectric coupling constants d31 and d33. The applications of shear actuators are to induce and control the flexural vibrations of beams and plates. In this study, a modified Timoshenko beam theory is used where electric potential is assumed to vary sinusoidaly along the thickness direction. The material properties are assumed to be graded across the thickness in accordance with power law distribution. Hamilton`s principle is employed to obtain the equations of motion along with the associated boundary conditions for FGPM beams. Exact analytical solution is derived thus obtained equations of motion. Results for clamped-clamped and clamped-free boundary conditions are presented. The presented result and method shell serve as benchmark for comparing the results obtained from the other approximate methods.
Flexural Behavior of Aluminum Honeycomb Core Sandwich Structure
Matta, Vidyasagar; Kumar, J. Suresh; Venkataraviteja, Duddu; Reddy, Guggulla Bharath Kumar
2017-05-01
and has more strength. By the power press used as forming method we fabricate the honey comb core and stacking the sheets with adhesive as epoxy resin or laser beam welding and sandwich structure will form with two face sheets. Then the specimen is taken to be tested to know the flexural behaviour by the flexural test as 3 point and 4 pont bend test. After testing of two different tests then we get the force vs displacement curve by this we can know the maximum force and by loading configurations and its displacement or deflection then we can calculate flexural stiffness and core shear modulus by the variation of three parameters. Our ultimate aim is to achieve maximum strength by minimum weight.
On the significance of microtubule flexural behavior in cytoskeletal mechanics.
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Mehrdad Mehrbod
Full Text Available Quantitative description of cell mechanics has challenged biological scientists for the past two decades. Various structural models have been attempted to analyze the structure of the cytoskeleton. One important aspect that has been largely ignored in all these modeling approaches is related to the flexural and buckling behavior of microtubular filaments. The objective of this paper is to explore the influence of this flexural and buckling behavior in cytoskeletal mechanics.In vitro the microtubules are observed to buckle in the first mode, reminiscent of a free, simply-supported beam. In vivo images of microtubules, however, indicate that the buckling mostly occurs in higher modes. This buckling mode switch takes place mostly because of the lateral support of microtubules via their connections to actin and intermediate filaments. These lateral loads are exerted throughout the microtubule length and yield a considerable bending behavior that, unless properly accounted for, would produce erroneous results in the modeling and analysis of the cytoskeletal mechanics.One of the promising attempts towards mechanical modeling of the cytoskeleton is the tensegrity model, which simplifies the complex network of cytoskeletal filaments into a combination merely of tension-bearing actin filaments and compression-bearing microtubules. Interestingly, this discrete model can qualitatively explain many experimental observations in cell mechanics. However, evidence suggests that the simplicity of this model may undermine the accuracy of its predictions, given the model's underlying assumption that "every single member bears solely either tensile or compressive behavior," i.e. neglecting the flexural behavior of the microtubule filaments. We invoke an anisotropic continuum model for microtubules and compare the bending energy stored in a single microtubule with its axial strain energy at the verge of buckling. Our results suggest that the bending energy can
Flexural Behavior of Posttensioned Flat Plates Depending on Tendon Layout
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Min Sook Kim
2016-01-01
Full Text Available This paper discusses the experimental results on the flexural behavior and deflections of posttensioned concrete flat plates depending on tendon layout. One reinforced concrete flat plate and two posttensioned concrete flat plates were manufactured and tested. One-way posttensioning layout and two-way posttensioning layout were considered in this paper. The load-deflection behavior and modes of crack are presented from the test results. Posttension systems effectively controlled crack and deflection. One-way and two-way posttensioning layouts both showed similar maximum load. However, serviceability improved with two-way posttensioning layout compared to one-way posttensioning layout. Also, the yield-line theory was applied to predict the ultimate load for the posttensioned flat plates. The comparison between the test results and estimation by yield-line analysis generally showed good agreement.
Modeling of the flexural behavior of ceramic-matrix composites
Kuo, Wen-Shyong; Chou, Tsu-Wei
1990-01-01
This paper examines the effects of matrix cracking and fiber breakage on the flexural behavior of ceramic composite beams. A model has been proposed to represent the damage evolution of the beam, of which the matrix fracture strain is smaller than that of the fibers. Close form solutions of the critical loads for the initiation of matrix cracking and fiber breakage in the tension side of the beam have been found. The effects of thermal residual stresses and fiber/matrix debonding have been taken into account. The initial deviation of the load-deflection curve from linearity is due to matrix cracking, while fiber breakages are responsible for the drop in the load carrying capacity of the beam. The proportional limit as well as the nonlinear behavior of the beam deflection have been identified. The growth of the damaged zone has also been predicted. A three-point bending case is given as a numerical example.
Shear-resistant behavior of light composite shear wall
Institute of Scientific and Technical Information of China (English)
李升才; 董毓利
2015-01-01
Shear test results for a composite wall panel in a light composite structure system are compared with test results for shear walls in Japan. The analysis results show that this kind of composite wall panel works very well, and can be regarded as a solid panel. The composite wall panel with a hidden frame is essential for bringing its effect on shear resistance into full play. Comprehensive analysis of the shear-resistant behavior of the composite wall panel suggests that the shear of the composite shear wall panel can be controlled by the cracking strength of the web shearing diagonal crack.
Shear-Resistant Behavior Analysis of Light Composite Shear Walls
Institute of Scientific and Technical Information of China (English)
李升才; 江见鲸; 于庆荣
2002-01-01
Shear test results for a composite wall panel in a light composite structure system are compared with test results for shear walls in Japan in this paper. The analysis results show that this kind of composite wall panel works very well, and can be regarded as a solid panel. The composite wall panel with a hidden frame is essential for bringing its effect on shear resistance into full play. Comprehensive analysis of the shear-resistant behavior of the composite wall panel suggests that the shear of the composite shear wall panel can be controlled by the cracking strength of the web shearing diagonal crack.
Shear behavior of concrete beams externally prestressed with Parafil ropes
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A.H. Ghallab
2013-03-01
Full Text Available Although extensive work has been carried out investigating the use of external prestressing system for flexural strengthening, a few studies regarding the shear behavior of externally prestressed beams can be found. Five beams, four of them were externally strengthened using Parafil rope, were loaded up to failure to investigate the effect of shear span/depth ratio, external prestressing force and concrete strength on their shear behavior. Test results showed that the shear span to depth ratio has a significant effect on both the shear strength and failure mode of the strengthened beams and the presence of external prestressing force increased the ultimate load of the tested beams by about 75%. Equations proposed by different codes for both the conventional reinforced concrete beams and for ordinary prestressed beams were used to evaluate the obtained experimental results. In general, codes equations showed a high level of conservatism in predicting the shear strength of the beams. Also, using the full strength rather than half of the concrete shear strength in the Egyptian code PC-method improves the accuracy of the calculated ultimate shear strength.
Effect of shear span-to-depth ratio on the shear behavior of BFRP-RC deep beams
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Alhamad Siyam
2017-01-01
Full Text Available This study investigates the shear behavior of deep concrete beams reinforced with basalt fiber reinforced polymer (BFRP bars for flexure without web reinforcements. The experimental testing performed herein consisted of a total of 4 short beams, three of which were reinforced with BFRP and one beam was reinforced with steel bars. The primary test variable was the shear-span-to-effective-depth ratio (a/d and its influence on the beams’ mid-span deflections, shear capacity, load-deformation relationships and the failure modes.
Fatigue behavior of dental resin composites: flexural fatigue in vitro versus 6 years in vivo
Garcia-Godoy, F.; Frankenberger, R.; Lohbauer, U.; Feilzer, A.J.; Krämer, N.
2012-01-01
Objectives: To evaluate fatigue behavior of direct resin composite restorations (Tetric Ceram vs. Grandio) in vitro and in vivo over an observation period of 6 years. Methods: For the in vitro part, Young's moduli (YM) were calculated and both initial (FS: flexural strength) and fatigue flexural
Fatigue behavior of dental resin composites: flexural fatigue in vitro versus 6 years in vivo
F. Garcia-Godoy; R. Frankenberger; U. Lohbauer; A.J. Feilzer; N. Krämer
2012-01-01
Objectives: To evaluate fatigue behavior of direct resin composite restorations (Tetric Ceram vs. Grandio) in vitro and in vivo over an observation period of 6 years. Methods: For the in vitro part, Young's moduli (YM) were calculated and both initial (FS: flexural strength) and fatigue flexural str
Parker, S. D.
2016-12-01
The kinematic evolution of the eastern Snake River Plain (ESRP) remains highly contested. A lack of strike-slip faults bounding the ESRP serves as a primary assumption in many leading kinematic models. Recent GPS geodesy has highlighted possible shear zones along the ESRP yet regional strike-slip faults remain unidentified. Oblique movement within dense arrays of high-angle conjugate normal faults, paralleling the ESRP, occur within a discrete zone of 50 km on both margins of the ESRP. These features have long been attributed to progressive crustal flexure and subsidence within the ESRP, but are capable of accommodating the observed strain without necessitating large scale strike-slip faults. Deformation features within an extensive Neogene conglomerate provide field evidence for dextral shear in a transtensional system along the northern margin of the ESRP. Pressure-solution pits and cobble striations provide evidence for a horizontal ENE/WSW maximum principal stress orientation, consistent with the hypothesis of a dextral Centennial shear zone. Fold hinges, erosional surfaces and stratigraphic datums plunging perpendicular into the ESRP have been attributed to crustal flexure and subsidence of the ESRP. Similar Quaternary folds plunge obliquely into the ESRP along its margins where diminishing offset along active normal faults trends into linear volcanic features. In all cases, orientations and distributions of plunging fold structures display a correlation to the terminus of active Basin and Range faults and linear volcanic features of the ESRP. An alternative kinematic model, rooted in kinematic disparities between Basin and Range faults and parallelling volcanic features may explain the observed downwarping as well as provide a mechanism for the observed shear along the margins of the ESRP. By integrating field observations with seismic, geodetic and geomorphic observations this study attempts to decipher the signatures of crustal flexure and shear along the
Flexural Fatigue Behavior of Polypropylene Fiber Reinforeed Segment Conerete
Institute of Scientific and Technical Information of China (English)
无
2006-01-01
The influence of polypropylene fiber on the flexural fatigue performance of high- strength concrete (HSC), which could be used as cover of reinforcement of segment, was investigate by three-point load bending tests. Also, the flexural fatigue equations of high-strength concrete with and without polypropylene fiber were established through test analysis. The experimental results indicate that the addition of polypropylene fiber can improve the static bending strength of segment concrete, and the important is that it can markedly increase the flexural fatigue performance of the HSC subjected to cyclic bending load. Especially when with 1.37 kg/m3 addition of the fiber was corporate with silica fume and slag powder, the fatigue life of the HSC can be increased by 43.4% compared to that of the segment concrete without fiber,silica fume and slag.
Flexural behavior of bonded post-tensioned concrete beams under strand corrosion
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Zhang, Xuhui [College of Civil Engineering and Mechanics, Xiangtan University, 411105 Xiangtan (China); School of Civil Engineering and Architecture, Changsha University of Science & Technology, 410114 Changsha (China); Industry Key Laboratory of Traffic Infrastructure Security Risk Management (CSUST), 410114 Changsha (China); Wang, Lei, E-mail: leiwlei@hotmail.com [School of Civil Engineering and Architecture, Changsha University of Science & Technology, 410114 Changsha (China); Industry Key Laboratory of Traffic Infrastructure Security Risk Management (CSUST), 410114 Changsha (China); Zhang, Jianren; Ma, Yafei [School of Civil Engineering and Architecture, Changsha University of Science & Technology, 410114 Changsha (China); Industry Key Laboratory of Traffic Infrastructure Security Risk Management (CSUST), 410114 Changsha (China); Liu, Yongming [School for Engineering of Matter, Transport and Energy, Arizona State University, 85281 Tempe, AZ (United States)
2017-03-15
Highlights: • Flexural behavior of bonded PT beams with strand corrosion is experimental tested. • Cracking, stiffness, ultimate strength, failure & ductility of beams are clarified. • A coefficient is proposed to measure incompatible strain between strand & concrete. - Abstract: An experimental test is performed to investigate the flexural behavior of bonded post-tensioned concrete beams under strand corrosion. Eight beams are designed and subjected to accelerated method to different corrosion levels. The initial stiffness of beams is observed by cyclic loading-unloading test during the corrosion procedure. Corrosion effects on concrete cracking, post-cracking stiffness, ultimate strength, failure mode and ductility are then clarified by the flexural test. And, a coefficient is introduced to quantify the incompatible strain between corroded strand and concrete. Results show that the prestress force loss of strand has almost the linear relation with corrosion loss. Strand corrosion affects slightly the initial stiffness of beam before flexural cracking, but degrades significantly the post-cracking stiffness of beam as the corrosion loss exceeds 27.0%. Slight corrosion of strand has little effects on beams flexural behavior. The severe corrosion, however, decreases the number of crack, changes the failure mode form the concrete crushing to strand rupture, degrades the ductility and the ultimate strength of beams, and leads to the incompatible strain between strand and concrete. In the present test, the incompatible strain decreases about 20% of the flexural strength as the corrosion loss exceeds 27.0%.
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M. Ganapathi
1995-01-01
Full Text Available Using degree centigrade continuous, QUAD-8 shear-flexible shell element, based on field consistency principle, the nonlinear free flexural vibrations of anisotropic laminated curved panels are studied. The formulation includes transverse shear deformation, in-plane and rotary inertia effects and geometrical nonlinearity. The element is employed to study the large amplitude dynamic behaviour of cylindrical and spherical shells. The frequency versus amplitude curves are obtained from the dynamic response history. The nonlinear governing equations are solved using Wilson-Theta numerical integration scheme with Theta = 1.4. For each time step, modified Newton-Raphson iterations are employed to achieve equilibrium at the end of that time step. Detailed numerical results are presented, showing the effects of thickness, lamination scheme, material properties and boundary conditions, on nonlinear behaviour.
Flexural Strength and Behavior of Polypropylene Fiber Reinforced Concrete Beams
Institute of Scientific and Technical Information of China (English)
无
2002-01-01
The strength and deformation characteristics of polypropylene fiber reinforced concrete (PFRC) beams were investigated by four-point bending procedures in this paper.Two kinds of polypropylene fibers with different fiber contents (0.2%, 0.5%, 1.0% and 1.5%) by volume were used in the beam, which measured 100×100 mm with a span of 300 mm.It was found that the strength of the reinforced concrete beams was significantly decreased,whereas the flexural toughness was improved,compared to those unreinforced concrete beams.Geometry properties and volume contents of polypropylene fiber were considered to be important factors for improving the flexural toughness.Moreover,the composite mechanism between polypropylene fiber and concrete was analyzed and discussed.
Cyclic Shearing Deformation Behavior of Saturated Clays
Institute of Scientific and Technical Information of China (English)
无
2007-01-01
The apparatus for static and dynamic universal triaxial and torsional shear soil testing is employed to perform stress-controlled cyclic single-direction torsional shear tests and two-direction coupled shear tests under unconsolidated-undrained conditions. Through a series of tests on saturated clay, the effects of initial shear stress and stress reversal on the clay's strain-stress behavior are examined, and the behavior of pore water pressure is studied. The experimental results indicate that the patterns of stress-strain relations are distinctly influenced by the initial shear stress in the cyclic single-direction shear tests. When the initial shear stress is large and no stress reversal occurs, the predominant deformation behavior is characterized by an accumulative effect. When the initial shear stress is zero and symmetrical cyclic stress occurs, the predominant deformation behavior is characterized by a cyclic effect. The pore water pressure fluctuates around the confining pressure with the increase of cycle number. It seems that the fluctuating amplitude increases with the increase of the cyclic stress. But a buildup of pore water pressure does not occur. The deformations of clay samples under the complex initial and the cyclic coupled stress conditions include the normal deviatoric deformation and horizontal shear deformation, the average deformation and cyclic deformation. A general strain failure criterion taking into account these deformations is recommended and is proved more stable and suitable compared to the strain failure criteria currently used.
Cell disaggregation behavior in shear flow.
Snabre, P; Bitbol, M; Mills, P
1987-05-01
The disaggregation behavior of erythrocytes in dextran saline solution was investigated by a light reflectometry technique in a Couette flow and in a plane Poiseuille flow. Dextran concentration and mass average molecular weight of the polymer fraction strongly influence the shear stress dependence of the erythrocyte suspension reflectivity in shear flow and the critical hydrodynamic conditions (shear rate or shear stress) for near-complete cell dispersion. We investigated the influence of cell volume fraction and membrane deformability (heat treatment of the erythrocytes) on the reflectivity of the flowing suspension. This study indicates that the intercell adhesiveness and the shear stress are the only parameters that influence rouleau break-up in steady uniform shear flow, thus eliminating cell volume fraction and membrane deformability as possible factors. However, the critical cross-sectional average shear stress for near-complete cell dispersion through the flow cross-section is shown to depend on the flow pattern. The rotation of cells in a shear flow or the nonuniform shear field in Poiseuille flow indeed increases the flow resistance of cell aggregates. We give a theoretical description of the shear-induced cell disaggregation process in Couette flow and in plane Poiseuille flow. The quantitation of shear forces for cell dispersion provides a way for estimating the surface adhesive energy of the bridging membranes by fluid mechanical technique.
We report the effect of glass fiber structure and the epoxy polymer system on the flexural strength, interlaminar shear stress (ILSS), and energy absorption properties of glass fiber-reinforced polymer (GFRP) composites. Four different GFRP composites were fabricated from two glass fiber textiles of...
Effect of Nanoclay on the Flexural Creep Behavior of Wood/Plastic Composites
Kord, B.; Sheykholeslami, A.; Najafi, A.
2016-01-01
The effect of nanoclay on the short-term flexural creep behavior of polypropylene/wood flour composites was investigated. The results obtained showed that the flexural strength and modulus increased with contentt of nanoclay up to 3 phc and then decreased. The fractional deflection and relative creep decreased with increasing content of nanoclay. X-ray diffraction patterns and transmission electron microscopy revealed that the nanocomposites formed were intercalated. Morphological findings testified that the samples containing 3 phc of nanoclay had the highest degree of intercalation and dispersion.
Experimental studies on behavior of fully grouted reinforced-concrete masonry shear walls
Zhao, Yan; Wang, Fenglai
2015-12-01
An experimental study is conducted on fully grouted reinforced masonry shear walls (RMSWs) made from concrete blocks with a new configuration. Ten RMSWs are tested under reversed cyclic lateral load to investigate the influence of different reinforcements and applied axial stress values on their seismic behavior. The results show that flexural strength increases with the applied axial stress, and shear strength dominated by diagonal cracking increases with both the amount of horizontal reinforcement and applied axial stress. Yield displacement, ductility, and energy dissipation capability can be improved substantially by increasing the amount of horizontal reinforcement. The critical parameters for the walls are derived from the experiment: displacement ductility values corresponding to 15% strength degradation of the walls reach up to 2.6 and 4.5 in the shear and flexure failure modes, respectively; stiffness values of flexure- and shear-dominated walls rapidly degrade to 17%-19% and 48%-57% of initial stiffness at 0.50 D max (displacement at peak load). The experiment suggests that RMSWs could be assigned a higher damping ratio (˜14%) for collapse prevention design and a lower damping value (˜7%) for a fully operational limit state or serviceability limit state.
Directory of Open Access Journals (Sweden)
Yeonho Park
2014-06-01
Full Text Available This study investigates the impact of accelerated aging conditions on the long-term flexural behavior and ductility of reinforced concrete (RC members with glass fiber-reinforced polymer (GFRP bars (RC-GFRP specimen and steel bars (RC-steel specimen. A total of thirty six specimens were designed with different amounts of reinforcement with three types of reinforcing bars (i.e., helically wrapped GFRP, sand-coated surface GFRP and steel. Eighteen specimens were subjected to sustained loads and accelerated aging conditions (i.e., 47 °C and 80% relative humidity in a chamber. The flexural behavior of specimens under 300-day exposure was compared to that of the companion specimens without experiencing accelerated aging conditions. Results indicate that the accelerated aging conditions reduced flexural capacity in not only RC-steel, but also RC-GFRP specimens, with different rates of reduction. Different types of GFRP reinforcement exhibited different rates of degradation of the flexural capacity when embedded in concrete under the same exposure conditions. Several existing models were compared with experimental results for predicting the deflection and deformability index for specimens. Bischoff and Gross’s model exhibited an excellent prediction of the time-dependent deflections. Except for the deformability index proposed by Jaeger, there was no general trend related to the aging duration. This study recommends the need for further investigation on the prediction of the deformability index.
Mesoscale Elucidation of Biofilm Shear Behavior
Barai, Pallab; Mukherjee, Partha P
2015-01-01
Formation of bacterial colonies as biofilm on the surface/interface of various objects has the potential to impact not only human health and disease but also energy and environmental considerations. Biofilms can be regarded as soft materials, and comprehension of their shear response to external forces is a key element to the fundamental understanding. A mesoscale model has been presented in this article based on digitization of a biofilm microstructure. Its response under externally applied shear load is analyzed. Strain stiffening type behavior is readily observed under high strain loads due to the unfolding of chains within soft polymeric substrate. Sustained shear loading of the biofilm network results in strain localization along the diagonal direction. Rupture of the soft polymeric matrix can potentially reduce the intercellular interaction between the bacterial cells. Evolution of stiffness within the biofilm network under shear reveals two regions: a) initial increase in stiffness due to strain stiffe...
Flexural Behavior of Two-Way Sandwiched Slabs
Pachpande, Jivan Vilas
2015-01-01
This dissertation presents the details of the findings of a study focused on evaluating the structural behavior of three-dimensional (3D) cementitious sandwich panels with Expanded Polystyrene (EPS) foam core for two-way slab applications. In this study, both theoretical and finite element numerical analysis procedures were adopted to predict the performance of such slabs under out-of-plane loading conditions. The results from theoretical and finite element analysis were verified by compariso...
Habibi, Meisam K; Samaei, Arash T; Gheshlaghi, Behnam; Lu, Jian; Lu, Yang
2015-04-01
As one of the most renewable resources on Earth, bamboo has recently attracted increasing interest for its promising applications in sustainable structural purposes. Its superior mechanical properties arising from the unique functionally-graded (FG) hierarchical structure also make bamboo an excellent candidate for bio-mimicking purposes in advanced material design. However, despite its well-documented, impressive mechanical characteristics, the intriguing asymmetry in flexural behavior of bamboo, alongside its underlying mechanisms, has not yet been fully understood. Here, we used multi-scale mechanical characterizations assisted with advanced environmental scanning electron microscopy (ESEM) to investigate the asymmetric flexural responses of natural bamboo (Phyllostachys edulis) strips under different loading configurations, during "elastic bending" and "fracture failure" stages, with their respective deformation mechanisms at microstructural level. Results showed that the gradient distribution of the vascular bundles along the thickness direction is mainly responsible for the exhibited asymmetry, whereas the hierarchical fiber/parenchyma cellular structure plays a critical role in alternating the dominant factors for determining the distinctly different failure mechanisms. A numerical model has been likewise adopted to validate the effective flexural moduli of bamboo strips as a function of their FG parameters, while additional experiments on uniaxial loading of bamboo specimens were performed to assess the tension-compression asymmetry, for further understanding of the microstructure evolution of bamboo's outer and innermost layers under different bending states. This work could provide insights to help the processing of novel bamboo-based composites and enable the bio-inspired design of advanced structural materials with desired flexural behavior.
FLEXURAL PROPERTIES AND ORTHOTROPIC SWELLING BEHAVIOR OF BAGASSE/THERMOPLASTIC COMPOSITES
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Seyed Majid Zabihzadeh
2010-05-01
Full Text Available The flexural properties of commercial bagasse-filled polyethylene (PE and polypropylene (PP composites were determined as a function of strain rate at room temperature. The applied strain rates were 1.5 ×10-4, 3.75×10-4, 7.5×10-4, and 1.5×10-3 s-1. The flexural modulus tended to increase linearly for the two types of composites with the logarithm of strain rate. The bending strength of polypropylene composite also behaved in a similar manner, but the polyethylene composite exhibited different behavior in which the MOR values of polyethylene composite didn’t alter appreciably as a function of strain rate. The flexural response of a polypropylene-based composite was found to exhibit higher dependency on strain rate than a polyethylene-based composite. Water absorption of both composites followed the kinetics of a Fickian diffusion process. Water absorption and dimensional instability of PE-based composites were lower than those of PP-based composites. The highest swelling took place in the thickness of the samples, followed by the width and length, respectively.
Shear Behavior of Concrete Beams Reinforced with GFRP Shear Reinforcement
Heecheul Kim; Min Sook Kim; Myung Joon Ko; Young Hak Lee
2015-01-01
This paper presents the shear capacities of concrete beams reinforced with glass fiber reinforced polymer (GFRP) plates as shear reinforcement. To examine the shear performance, we manufactured and tested a total of eight specimens. Test variables included the GFRP strip-width-to-spacing ratio and type of opening array. The specimen with a GFRP plate with a 3×2 opening array showed the highest shear strength. From the test results, the shear strength increased as the strip-width-to-strip-spac...
Shear Behavior of Concrete Beams Reinforced with GFRP Shear Reinforcement
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Heecheul Kim
2015-01-01
Full Text Available This paper presents the shear capacities of concrete beams reinforced with glass fiber reinforced polymer (GFRP plates as shear reinforcement. To examine the shear performance, we manufactured and tested a total of eight specimens. Test variables included the GFRP strip-width-to-spacing ratio and type of opening array. The specimen with a GFRP plate with a 3×2 opening array showed the highest shear strength. From the test results, the shear strength increased as the strip-width-to-strip-spacing ratio increased. Also, we used the experimental results to evaluate whether the shear strength equations of ACI 318-14 and ACI 440.1R can be applied to the design of GFRP shear reinforcement. In the results, the ACI 440 equation underestimated the experimental results more than that of ACI 318.
Institute of Scientific and Technical Information of China (English)
Jinqing Jia; Gang Meng
2015-01-01
This paper presents the results of four partially prestressed ultra⁃high strength concrete beams in flexure. The test results are used to evaluate the effects of prestressing tendon depth and area on flexure behavior of specimen beams. The test results indicate that:the cracking load, yielding load, peak load and stiffness post⁃cracking of specimen beams are enhanced by reducing prestressing tendon depth or increasing prestressing tendon area, and the flexural ductility is improved by increasing prestressing tendon depth or reducing prestressing tendon area. The effect of complex reinforcement index considering the strength of the equivalence principle and the reinforcement position on loading levels under serviceability limit state, flexural strength and displacement ductility factor are studied. The influence coefficient of prestressing tendon kp is introduced in the complex reinforcement index. As the complex reinforcement index increases, the loading levels under serviceability limit state and flexural strength increases linearly, and the displacement ductility factor decreases linearly. The test results also verify the conventional beam flexural theory based on the plane cross⁃section assumption for predicting ultimate flexural strength of partially prestressed ultra⁃high strength concrete beams is valid. After the introduction of the coefficient kp , the calculation method of cracks in code for design of concrete structure in china are appropriated for the specimen beams.
MECHANICAL BEHAVIOR OF AMORPHOUS POLYMERS IN SHEAR
Institute of Scientific and Technical Information of China (English)
张赟; 黄筑平
2004-01-01
Based on the non-equilibrium thermodynamic theory, a new thermo-viscoelastic constitutive model for an incompressible material is proposed. This model can be considered as a kind of generalization of the non-Gaussian network theory in rubber elasticity to include the viscous and the thermal effects. A set of second rank tensorial internal variables was introduced, and in order to adequately describe the evolution of these internal variables, a new expression of the Helmholtz free energy was suggested. The mechanical behavior of the thermo-viscoelastic material under simple shear deformation was studied, and the "viscous dissipation induced" anisotropy due to the change of orientation distribution of molecular chains was examined. Influences of strain rate and thermal softening produced by the viscous dissipation on the shear stress were also discussed. Finally, the model predictions were compared with the experimental results performed by G'Sell et al., thus the validity of the proposed model is verified.
Flexural Behavior of Continuous Bubbled Reinforced Reactive Powder Concrete Flat Slab
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Mohammad Redha K. Mahmood
2017-05-01
Full Text Available This paper presents an experimental investigation on flexural behavior of continuous bubbled reinforced Reactive Powder Concrete (RPC flat slabs. Bubbled slab is one of the various types of voided slabs. It consist of bubbles placed inside a concrete slab which will reduce the self-weight of the structure by about 35% (Tina Lai 2009. On the other hand, using RPC make it possible for structural member to have smaller dimensions due to the great strength of this type of concrete. In this study these two method are used to increase the building spaces dimensions by reducing self-weigh of the structure by using bubbled slabs and to decrease the structural members' dimensions by using RPC have been investigated together. To study the flexural behavior of continuous bubbled flat slabs such as the ultimate load carrying capacity, central deflection and slabs crack pattern at the ultimate load, seven types of slabs were tested. The parameters of the study were type of concrete (RPC and Normal Concrete (NC, bubbles diameter to slab thickness ratio (D/t of (0.6 and 0.7, type of loading (distributed and line load and solid slab. The test results show that the crack pattern and ultimate load capacity as well as maximum deflection depends on all of the mentioned parameters, were by increasing (D/t ratio the ultimate load capacity increases about (7.36%, 5.46% and 16.52% for RPC slabs under distributed load, line load and NC slabs, respectively. The solid slab increases the ultimate load about (4.05% compare to bubbled slab. Also, the line load decreases the ultimate load compare to distributed load by (3.45-5.16% for different (D/t ratio, and using the NC also decreases the ultimate load compare to RPC by (48-52.13% for different (D/t ratio
Shear behavior of sand-expanded polystyrene beads lightweight fills
Institute of Scientific and Technical Information of China (English)
邓安; 肖杨
2008-01-01
Through direct shear and triaxial compression tests, effects of expanded polystyrene (EPS) mass ratios in sand-EPS mixtures and stress status on materials’ shear behavior were investigated. Hyperbolic curves were used to fit relationship between shear stress and shear displacement. The shear behavior is marginally associated with the EPS ratios and normal/confining stresses. Increases of EPS ratios and decreases of normal/confining stresses result in shear strength decreases. The shapes of Mohr-Coulomb’s envelope include linear and piecewise linear types, which are basically determined by the EPS ratio. Such difference is thought related to the embedding or apparent cohesion effect under relatively high EPS ratio conditions. Shear strength parameters can be used for further modeling and design purposes.
Energy Technology Data Exchange (ETDEWEB)
Bellouard, Yves; Clavel, Reymond
2003-07-25
Flexures are used in precision engineering where highly accurate, wear-free, smooth and repeatable motion is desired. Flexures are based on deformation of material to achieve a motion between elastically joined parts. They are used in a variety of precision mechanisms such as high-resolution balances or high accuracy optical positioning stages. Shape memory alloys (SMA) are an attractive option in designing flexures. Superelastic flexures can withstand larger deformations for the same weight as a conventional flexure. In addition, the damping properties of SMA, controllable through the phase transformation, offer new design opportunities for adaptive compliant mechanisms. The martensitic phase transformation can also be used to shift the natural frequency of flexures adding useful functionalities such as vibration rejection. This paper presents design principles of SMA flexures based on non-linear beam theory. Results show a good agreement between measured and predicted data. In addition, experimental results on phase transformation effects on damping behavior are also presented. Both, natural-frequency shift and increased damping were observed in bulk-micro machined flexures using the R-phase transformation. These results demonstrate the feasibility of natural-frequency-tunable flexures.
Institute of Scientific and Technical Information of China (English)
李宁; 李忠献; 谢礼立
2013-01-01
Hollow section piers are often used in reinforced concrete(RC)bridges. It has been proved by earthquake damage investigation that the piers may perform flexure-shear coupling behavior,and eventually lead to pier failure and/or collapse. A fiber-section based RC pier simulation model considering flexure-shear coupling effect was pre-sented in this paper. By introducing bi-axial material constitutive relationship into the determination of fiber deforma-tion status,the sectional stiffness for beam column element can be obtained through the integration of fiber responses. Then the flexure-shear coupling Timoshenko beam element was implemented. The cyclic soften membrane model(CSMM)constitutive relationship was adopted for plane bi-axial RC components in the calculation of the nonlinear characteristic of fibers. The concrete uniaxial material model in CSMM was improved. By assuming the compatibility condition between each fiber and making use of the Newton iteration algorithm,the fiber and section responses were determined. At last,a scaled hollow section pier with quasi-static test result was compared with the numerical model,and the results show good agreement. The strength and stiffness degradation and pinching effect caused by flexure-shear coupling effect are captured by this model. And the fiber model shows sufficient accuracy and computational efficiency.%钢筋混凝土(RC)桥墩构件常采用空心截面，震害调查表明其失效模式多表现为弯剪耦联的非线性破坏。本文提出一种基于纤维截面、考虑弯剪耦联变形的混凝土墩柱模拟模型。首先将双轴材料本构引入纤维材料状态的计算，然后通过纤维截面积分，得到适用于 Timoshenko 梁柱单元的截面刚度矩阵，最终实现考虑弯剪耦联效应的梁柱单元。其中，双轴 RC 本构模型采用往复软化薄膜模型(CSMM)，并对 CSMM 中单轴混凝土滞回模型进行修正。通过引入纤维
Directory of Open Access Journals (Sweden)
Hamrat Mostefa
2014-04-01
Full Text Available This paper presents an experimental study on the flexural strength of reinforced concrete beams made with high performance concrete (HPC and ordinary concrete (OC. We are carried an experimental campaign aimed comes in three points: 1- the study of the law of behavior of the two materials (OC and HPC, 2- the influence of the compressive strength of concrete and the rate of longitudinal reinforcement on the loaddeflection behavior and ductility index, 3- comparative analysis (ACI318, Eurocode 2 and BS8110 against the crack opening. Test results showed that the capacity of the beams in HPC is higher (6% to 20 % than the beams in OC. The use of HPC is more efficient than the OC to delay the first cracking. The average value of the ductility index for the beams in HPC is 1.30 times those beams in OC. The formula for calculating the crack opening derived of the Eurocode 2 gives the best prediction the crack width of beams (for both types of concrete.
Study on Shear Behavior of Concrete-polymer Cement Mortar at Elevated Temperature
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Khuram Rashid
2016-09-01
Full Text Available In this experimental and analytical work, interfacial shear strengths were evaluated at material and member level. Bi-surface shear strength was performed at material level and three-point bending test was conducted at member level. Beams were strengthened by adding steel reinforcement at soffit level and covered by spraying polymer cement mortar (PCM. After curing, strengthened RC beams were exposed to 60 ℃ for 24 hours and tested in three point loading test. Flexural capacity, load deflection relationship and failure modes were observed and compared with the strengthened beams tested at 20 ℃. Reduction in flexural capacity was observed with temperature, failure mode was also shifted from flexural mode to debonding mode of failure at elevated temperature. Ultimate shear load and failure modes were predicted by truss analogy approach. Debonding model was proposed by incorporating bi-surface interfacial shear strength, close agreement were observed between experimental and predicted values.
Institute of Scientific and Technical Information of China (English)
XU Dong-xuan; CHENG Xiang-rong; ZHANG Yu-feng; WANG Jun; CHENG Han-ting
2003-01-01
Denture base made from acrylic resin (polymethyl methacrylate,PMMA) was reinforced by different contents of ultrahigh-modulus polyethylene fiber (UHMPEF).The flexural strength of the denture base was tested,the failure modes and microstructures were investigated with a scanning electron microscope(SEM).The results indicate that 3.5wt%UHMPEF increased the ultimate flexural strength of the denture base.
SHEARING AND WATER RETENTION BEHAVIOR OF UNSATURATED LOAM WITH MODELING
Kiyohara, Yukoh; Kazama, Motoki
Unsaturated triaxial tests were carried out to study deformation behavior, effective stress path and water retention property of consolidated loam during consolidation and shearing processes. Initial matric suction was set as 0, 50, and 90 kPa, and confining pressures (net normal stresses) were set as 100 kPa. Then shearing processes were done under undrained and drained conditions. We clarified the relation between void ratio and Van Genuchten model parameter by using water retention curve. To predict the unsaturated shearing behavior, a modified Cam Clay model considering void ratio dependent Van Genuchten parameter was proposed. Those numerical test results were agreed well with laboratory tests results.
Fracture behaviors under pure shear loading in bulk metallic glasses
Chen, Cen; Gao, Meng; Wang, Chao; Wang, Wei-Hua; Wang, Tzu-Chiang
2016-12-01
Pure shear fracture test, as a special mechanical means, had been carried out extensively to obtain the critical information for traditional metallic crystalline materials and rocks, such as the intrinsic deformation behavior and fracture mechanism. However, for bulk metallic glasses (BMGs), the pure shear fracture behaviors have not been investigated systematically due to the lack of a suitable test method. Here, we specially introduce a unique antisymmetrical four-point bend shear test method to realize a uniform pure shear stress field and study the pure shear fracture behaviors of two kinds of BMGs, Zr-based and La-based BMGs. All kinds of fracture behaviors, the pure shear fracture strength, fracture angle and fracture surface morphology, are systematically analyzed and compared with those of the conventional compressive and tensile fracture. Our results indicate that both the Zr-based and La-based BMGs follow the same fracture mechanism under pure shear loading, which is significantly different from the situation of some previous research results. Our results might offer new enlightenment on the intrinsic deformation and fracture mechanism of BMGs and other amorphous materials.
Institute of Scientific and Technical Information of China (English)
KANG Jingfu; JIANG Yongqi
2008-01-01
By ring test and bend test,the improvement of waste tire rubber particles on the crack-resistance and flexural behaviors of cement-based materials were investigated.Test results show that the cracking time of the ring specimens can be retarded by the incorporation of rubber particles in the cement paste and mortar.The improvement in the crack-resistance depended on the rubber fraction.When the rubber fraction was 20%in volume,the cracking time was retarded about 15 h for the paste and 24 d for the mortar respectively.Flexural properties were evaluated based on the bend test results for both mortar and concrete containing different amount of rubber particles.Test results show that rubberized mortar and concrete specimens exhibit ductile failure and significant deformation before fracture.The ultimate deformations of both mortar and concrete specimen increase more than 2-4 times than control specimens.
Flexural Behavior of Steel-Fiber-Added-RC (SFARC Beams with C30 and C50 Classes of Concrete
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Hamid Pesaran Behbahani
2012-04-01
Full Text Available Although conventional reinforced concrete (RC is the most globally used building material; however, its detrimental structural characteristics such as brittle failure mechanism in tension need to be improved. Discrete and short steel fibers (SFs can be added into the concrete mix to improve its brittleness. The effects of the addition of optimum percentage of SFs on flexural behavior of RC beams have been investigated in this paper. In this study, the optimum percentage of hooked-end SFs with the dimensions of 0.75 mm in diameter and 50 mm in length are added in RC beams with two different classes of concrete (i.e. two different compressive strengths of 30MPa (C30 and 50MPa (C50. In order to determine the optimum percentage of SFs added to the concrete mix, 15 prisms and 30 cubes with 5 different percentages of SFs (i.e. 0%v/v, 0.5%v/v, 1%v/v, 1.5%v/v, and 2%v/v from both C30 and C50 classes of concrete have been tested. Based on the results of the flexural strength and compressive strength tests, it is found that the optimum value is 1% by volume (i.e. 78.5 kg/m3 for the specific type of fiber used in this study. Subsequently, to investigate the flexural behavior of steel fiber added RC (SFARC beams compared to conventional RC beams with no SFs, two RC beams with the dimensions of 170 mm in height, 120 mm in width, and 2400 mm in length, with the SF percentages of 0 and 1%v/v and both having exactly the same steel reinforcement were tested under flexure using a four-point loading test setup for both C30 and C50 classes of concrete. The experimental results show that the SFARC beams with 1% by volume of the SFs have higher first cracking strength, ultimate flexural strength, stiffness, and ductility compared to that of the conventional RC beams with no SFs. Furthermore, the addition of the SFs has more effects on the RC beams with higher compressive strength (50 MPa compared to lower concrete grade (30 MPa.
Laboratory Investigation on Shear Behavior of Rock Joints and a New Peak Shear Strength Criterion
Zhang, Xiaobo; Jiang, Qinghui; Chen, Na; Wei, Wei; Feng, Xixia
2016-09-01
In this study, shear tests on artificial rock joints with different roughness were conducted under five normal stress levels. Test results showed that the shear strength of rock joints had a positive correlation with roughness and the applied normal stress. Observation of joint specimens after shear tests indicated that asperity damage was mainly located in the steep areas facing the shear direction. The damaged joint surfaces tend to be rough, which implies that tensile failure plays an important role in shear behavior. As a result of the anisotropic characteristic of joint roughness, two quantitative 2D roughness parameters, i.e., the revised root-mean-square of asperity angle tan-1( Z 2r) and the maximum contact coefficient C m, were proposed considering the shear direction. The proposed roughness parameters can capture the difference of roughness in forward and reverse directions along a single joint profile. The normalized tensile strength and the proposed roughness parameters were used to perform a rational derivation of peak dilatancy angle. A negative exponential-type function was found to be appropriate to model the peak dilatancy angle. Using the new model of peak dilatancy angle, we obtained a new criterion for peak shear strength of rock joints. The good agreement between test results and predicted results by the new criterion indicated that the proposed criterion is capable of estimating the peak shear strength of rock joints. Comparisons between the new criterion and published models from available literature revealed that the proposed criterion has a good accuracy for predicting the peak shear strength of joints investigated in this study.
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Vijaykumar H.K
2014-07-01
Full Text Available In this paper, commercially available Fly Ash and Epoxy is used for the core material, woven glass fabric as reinforcing skin material, epoxy as matrix/adhesive materials used in this study for the construction of sandwich composite. Analysis is carried out on different proportions of epoxy and fly ash sandwiched composite material for determining the flexural strength and compressive strength, three different proportions of epoxy and fly ash used for the study. Those are 65%-35% (65% by weight fly ash and 35% by weight epoxy resin composite material, 60%-40% and 55%-45% composite material. 60%-40% composite material specimen shows better results in the entire test carried out i.e. Flexure and Compression. The complete experimental results are discussed and presented in this paper.
Shear behavior of reinforced Engineered Cementitious Composites (ECC) beams
DEFF Research Database (Denmark)
Paegle, Ieva; Fischer, Gregor
2010-01-01
This paper describes an experimental investigation of the shear behavior of beams consisting of steel reinforced Engineered Cementitious Composites (ECC). Based on the strain hardening and multiple cracking behavior of ECC, this study investigates the extent to which ECC can improve the shear...... randomly distributed PVA (polyvinyl alcohol) fiber beams with different stirrup spacing and reinforced concrete (RC) beams for comparison. Displacement and strain measurements taken using the ARAMIS photogrammetric data acquisition system by means of processing at high frame rate captured images of applied...
Shear and Flexural Behaviour of R.C.C. Beam With Circular Opening Strengthened By CFRP Sheets
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VinayChakrasali
2015-04-01
Full Text Available This paper explores the behavior of R.C.C. beam with circular opening strengthened by CFRP sheets. In this experimental work five beams were casted, one beam without opening (i.e. solid beam and one with circular post opening and considered as control beams. The remaining three beams were externally strengthened by Carbon fiber reinforced polymer (CFRP sheets with different strengthening schemes i.e. around the opening, inside the opening. These beams were simply supported and tested less than two points loading in the loading frame. The behaviors of such beams were studied in terms of load carrying capacity, load-deflection behavior and cracking patterns. From the test results it is concluded that the ultimate load carrying capacity of the R.C.C. beam strengthened with CFRP sheets increased in the range of 13.01% to 55.32%. Among all the strengthening schemes, the strengthening with CFRP around and inside the opening was found very effective in improving the ultimate load carrying capacity of beam.
Institute of Scientific and Technical Information of China (English)
张勤; 贡金鑫; 马颖
2014-01-01
为研究地震作用下弯剪破坏钢筋混凝土（RC）柱的变形性能，对24根不同剪跨比、轴压比及配箍率的RC柱进行了低周反复试验。分析了剪跨比、轴压比和配箍率对柱滞回曲线、骨架曲线及变形能力的影响，研究了RC柱的地震破坏模式以及不同破坏模式下柱的弯曲位移、剪切位移及滑移位移在总水平位移中所占比例和变化规律。结果表明，反复荷载下RC柱会发生弯曲、剪切及弯剪3种典型破坏。当剪跨比较小、轴压比较大且配箍率较小时，RC柱易发生弯剪破坏或剪切破坏，试件的耗能能力和延性较差，表现为滞回环面积和极限位移较小。当RC柱发生弯剪或剪切破坏时，弯曲位移在总水平位移中所占比例较小，剪切位移所占比例较大，钢筋拔出产生的滑移位移所占比例约为30％～40％。%To investigate the deformation performance of reinforced concrete (RC)columns failing in flexural-shear failure under seismic loading,24 RC square columns with different axial load rati-os,aspect ratios and stirrup ratios were tested under cyclic horizontal loading.The influences of the axial load ratio,aspect ratio and stirrup ratio on the hysteresis loop,envelop curves and deformation capacity were analyzed.The failure modes and the ratios of the deformation components due to flex-ure,shear and anchorage slip to the total deformation of the RC columns in different failure modes were investigated.The results show that under the cyclic loading,the RC columns may exhibit flex-ure failure,shear failure and flexural-shear failure.The column with lower aspect ratio,higher axial load ratio and lower stirrup ratio may fail in brittle shear or flexural-shear,and the corresponding hysteretic energy dissipation capacity and ductility capacity are poor,which are characterized by smaller hysteresis loop area and ultimate displacement.For the column failed in flexural-shear or shear
Shear strength behavior of geotextile/geomembrane interfaces
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Belén M. Bacas
2015-12-01
Full Text Available This paper aims to study the shear interaction mechanism of one of the critical geosynthetic interfaces, the geotextile/geomembrane, typically used for lined containment facilities such as landfills. A large direct shear machine is used to carry out 90 geosynthetic interface tests. The test results show a strain softening behavior with a very small dilatancy (<0.5 mm and nonlinear failure envelopes at a normal stress range of 25–450 kPa. The influences of the micro-level structure of these geosynthetics on the macro-level interface shear behavior are discussed in detail. This study has generated several practical recommendations to help professionals to choose what materials are more adequate. From the three geotextiles tested, the thermally bonded monofilament exhibits the best interface shear strength under high normal stress. For low normal stress, however, needle-punched monofilaments are recommended. For the regular textured geomembranes tested, the space between the asperities is an important factor. The closer these asperities are, the better the result achieves. For the irregular textured geomembranes tested, the nonwoven geotextiles made of monofilaments produce the largest interface shear strength.
Shear strength behavior of geotextile/geomembrane interfaces
Institute of Scientific and Technical Information of China (English)
Belén M. Bacas; Jorge Cañizal; Heinz Konietzky
2015-01-01
This paper aims to study the shear interaction mechanism of one of the critical geosynthetic interfaces, the geotextile/geomembrane, typically used for lined containment facilities such as landfills. A large direct shear machine is used to carry out 90 geosynthetic interface tests. The test results show a strain softening behavior with a very small dilatancy (<0.5 mm) and nonlinear failure envelopes at a normal stress range of 25e450 kPa. The influences of the micro-level structure of these geosynthetics on the macro-level interface shear behavior are discussed in detail. This study has generated several practical recommendations to help professionals to choose what materials are more adequate. From the three geotextiles tested, the thermally bonded monofilament exhibits the best interface shear strength under high normal stress. For low normal stress, however, needle-punched monofilaments are recommended. For the regular textured geomembranes tested, the space between the asperities is an important factor. The closer these asperities are, the better the result achieves. For the irregular textured geomembranes tested, the nonwoven geotextiles made of monofilaments produce the largest interface shear strength.
Flexural behavior of Sisal/Castor oil-Based Polyurethane and Sisal/Phenolic Composites
Directory of Open Access Journals (Sweden)
Andressa Cecília Milanese
2012-04-01
Full Text Available Natural fibers used as reinforcement of polymeric composites are interesting research subjects in polymer technology. Nowadays, these materials are being considered as a way to reinforce timber structures improvement. Fibers with larger structural applications are glass and carbon fibers, however, the use of natural fibers is an economic alternative and present many advantages such as biodegradability and having its origin from a renewable source. Castor oil, a triglyceride vegetable with hydroxyl groups, was reacted with 4,4' methylene diphenyl diisocyanate (MDI to produce the polyurethane matrix. The composites were prepared by compress molding at room temperature using woven sisal fiber as a reinforcement, with and without thermal treatment (at 60 ºC for 72 hours to the fabrics before the composites molding process. The present paper presents the preparation and a flexural caracterization of sisal/polyurethane and sisal/phenolic composites by using the three-point bending. The sisal fibers moisture content influence on the flexural behaviour was also analyzed. Experimental results showed a higher stiffness for the sisal/phenolic composite (11.2 MPa followed by the sisal/polyurethane (3.7 MPa, respectively.
Flexural Behavior of RC Members Using Externally Bonded Aluminum-Glass Fiber Composite Beams
Directory of Open Access Journals (Sweden)
Ki-Nam Hong
2014-03-01
Full Text Available This study concerns improvement of flexural stiffness/strength of concrete members reinforced with externally bonded, aluminum-glass fiber composite (AGC beams. An experimental program, consisting of seven reinforced concrete slabs and seven reinforced concrete beams strengthened in flexure with AGC beams, was initiated under four-point bending in order to evaluate three parameters: the cross-sectional shape of the AGC beam, the glass fiber fabric array, and the installation of fasteners. The load-deflection response, strain distribution along the longitudinal axis of the beam, and associated failure modes of the tested specimens were recorded. It was observed that the AGC beam led to an increase of the initial cracking load, yielding load of the tension steels and peak load. On the other hand, the ductility of some specimens strengthened was reduced by more than 50%. The A-type AGC beam was more efficient in slab specimens than in beam specimens and the B-type was more suitable for beam specimens than for slabs.
Transverse Shear Behavior of a Nomex Core for Sandwich Panels
Nasir, M. A.; Khan, Z.; Farooqi, I.; Nauman, S.; Anas, S.; Khalil, S.; Pasha, A.; Khan, Z.; Shah, M.; Qaiser, H.; Ata, R.
2015-01-01
The out-of-plane transverse shear characteristics of a Nomex honeycomb core have been studied. Finite-element analyses were performed to find the equivalent transverse shear moduli of the honeycomb core by using a unit-cell-based modeling approach with account of the orthotropic nature of Nomex paper. The results obtained are compared with those of three theoretical approaches. The differences between the numerical and theoretical results are attributed to the isotropic behavior of the basic core material considered in the theoretical approaches.
Simulating the Dynamic Behavior of Shear Thickening Fluids
Ozgen, Oktar; Brown, Eric
2015-01-01
While significant research has been dedicated to the simulation of fluids, not much attention has been given to exploring new interesting behavior that can be generated with the different types of non-Newtonian fluids with non-constant viscosity. Going in this direction, this paper introduces a computational model for simulating the interesting phenomena observed in non-Newtonian shear thickening fluids, which are fluids where the viscosity increases with increased stress. These fluids have unique and unconventional behavior, and they often appear in real world scenarios such as when sinking in quicksand or when experimenting with popular cornstarch and water mixtures. While interesting behavior of shear thickening fluids can be easily observed in the real world, the most interesting phenomena of these fluids have not been simulated before in computer graphics. The fluid exhibits unique phase changes between solid and liquid states, great impact resistance in its solid state and strong hysteresis effects. Our...
Shear thickening behavior of nanoparticle suspensions with carbon nanofillers
Energy Technology Data Exchange (ETDEWEB)
Sha, Xiaofei; Yu, Kejing, E-mail: yukejing@gmail.com; Cao, Haijian; Qian, Kun [Ministry of Education, Jiangnan University, Key Laboratory of Eco-textiles (China)
2013-07-15
Suspensions comprised of silica nanoparticle (average diameter: 650 nm) and carbon nanofillers dispersed in polyethylene glycol were prepared and investigated. Rheological measurement demonstrated that the mixed suspensions showed a non-Newtonian flow profile, and the shear thickening effect was enhanced by the addition of carbon nanotubes (CNTs) (main range of diameter: 10-20 nm; length: 5-15 {mu}m; purity: >97 wt%) and graphene nanoplatelets (GNs) (average diameter: >50 nm; average length: 20 {mu}m; purity: >92 wt%). It suggested that better the aggregation effect of dispersed particles was, the more significant the shear thickening effect achieved. The results also revealed that the formation of large nanomaterials clusters could be suitable to explain the phenomena. Furthermore, the trend of shear thickening behavior of the silica suspension with CNTs was more striking than that of GNs. The physical reactions between those multi-dispersed phases had been described by the schematic illustrations in papers. Otherwise, a model was built to explain these behaviors, which could be attributed to the unique structures and inherent properties of these two different nanofillers. And the morphologies of the shear thickening fluid which were examined by transmission electron microscopy confirmed this mechanism.
Shear stress relaxation of dental ceramics determined from creep behavior.
DeHoff, Paul H; Anusavice, Kenneth J
2004-10-01
To test the hypothesis that shear stress relaxation functions of dental ceramics can be determined from creep functions measured in a beam-bending viscometer. Stress relaxation behavior was determined from creep data for the following materials: (1) a veneering ceramic-IPS Empress2 body ceramic (E2V); (2) an experimental veneering ceramic (EXV); (3) a low expansion body porcelain-Vita VMK 68 feldspathic body porcelain (VB); (4) a high expansion body porcelain-Will Ceram feldspathic body porcelain (WCB); (5) a medium expansion opaque porcelain-Vita feldspathic opaque porcelain (VO); and (6) a high expansion opaque porcelain-Will Ceram feldspathic opaque porcelain (WCO). Laplace transform techniques were used to relate shear stress relaxation functions to creep functions for an eight-parameter, discrete viscoelastic model. Nonlinear regression analysis was performed to fit a four-term exponential relaxation function for each material at each temperature. The relaxation functions were utilized in the ANSYS finite element program to simulate creep behavior in three-point bending for each material at each temperature. Shear stress relaxation times at 575 degrees C ranged from 0.03 s for EXV to 195 s for WCO. Knowledge of the shear relaxation functions for dental ceramics at high temperatures is required input for the viscoelastic element in the ANSYS finite element program, which can used to determine transient and residual stresses in dental prostheses during fabrication.
Directory of Open Access Journals (Sweden)
JunHee Kim
2015-03-01
Full Text Available A full-scale experimental program was used in this study to investigate the structural behavior of novel insulated concrete sandwich wall panels (SWPs reinforced with grid-type glass-fiber-reinforced polymer (GFRP shear connectors. Two kinds of insulation-expanded polystyrene (EPS and extruded polystyrene (XPS with 100 mm thickness were incased between the two concrete wythes to meet the increasing demand for the insulation performance of building envelope. One to four GFRP shear grids were used to examine the degree of composite action of the two concrete wythes. Ten specimens of SWPs were tested under displacement control subjected to four-point concentrated loads. The test results showed that the SWPs reinforced with GFRP grids as shear connectors developed a high degree of composite action resulting in high flexural strength. The specimens with EPS foam exhibited an enhanced load-displacement behavior compared with the specimens with XPS because of the relatively stronger bond between insulation and concrete. In addition, the ultimate strength of the test results was compared to the analytical prediction with the mechanical properties of only GRFP grids. The specimens with EPS insulation presented higher strength-based composite action than the ones with XPS insulation.
Nonlinear flexural waves and chaos behavior in finite-deflection Timoshenko beam
Institute of Scientific and Technical Information of China (English)
Shan-yuan ZHANG; Zhi-fang LIU
2010-01-01
Based on the Timoshenko beam theory,the finite-deflection and the axial inertia are taken into account,and the nonlinear partial differential equations for flexural waves in a beam are derived. Using the traveling wave method and integration skills,the nonlinear partial differential equations can be converted into an ordinary differential equation. The qualitative analysis indicates that the corresponding dynamic system has a heteroclinic orbit under a certain condition. An exact periodic solution of the nonlinear wave equation is obtained using the Jacobi elliptic function expansion. When the modulus of the Jacobi elliptic function tends to one in the degenerate case,a shock wave solution is given. The small perturbations are further introduced,arising from the damping and the external load to an original Hamilton system,and the threshold condition of the existence of the transverse heteroclinic point is obtained using Melnikov's method. It is shown that the perturbed system has a chaotic property under the Smale horseshoe transform.
Energy Technology Data Exchange (ETDEWEB)
Chawla, N., E-mail: nchawla@asu.edu [Materials Science and Engineering, Arizona State University Tempe, AZ 85287-6106 (United States); Liaw, P.K. [Department of Materials Science and Engineering, University of Tennessee-Knoxville, Knoxville, TN 37996 (United States); Lara-Curzio, E.; Ferber, M.K.; Lowden, R.A. [High Temperature Materials Laboratory, Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN (United States)
2012-11-15
The effect of fiber fabric orientation, i.e., parallel to loading and perpendicular to the loading axis, on the monotonic and fatigue behavior of plain-weave fiber reinforced SiC matrix laminated composites was investigated. Two composite systems were studied: Nextel 312 (3M Corp.) reinforced SiC and Nicalon (Nippon Carbon Corp.) reinforced SiC, both fabricated by Forced Chemical Vapor Infiltration (FCVI). The behavior of both materials was investigated under monotonic and fatigue loading. Interlaminar and in-plane shear tests were conducted to further correlate shear properties with the effect of fabric orientation, with respect to the loading axis, on the orientation effects in bending. The underlying mechanisms, in monotonic and fatigue loading, were investigated through post-fracture examination using scanning electron microscopy (SEM).
Analytical theory of flexural behavior of concrete beam reinforced with textile-combined steel
Institute of Scientific and Technical Information of China (English)
无
2010-01-01
Textile-reinforced concrete (TRC) is a new high performance cementitious composite material,which not only has superior corrosion resistance but also can effectively limit the development of concrete cracks and make the crack width and spacing of concrete become smaller.However,due to the brittle feature of fiber materials,the TRC structural member has no distinct failure symptom when it arrives at its ultimate load.At the same time,ordinary reinforced concrete (RC) elements have large dead weight and can not efficiently restrict the expansion of the main crack of structures because of the restriction of their special cover thickness.In order to overcome the disadvantages of both the TRC and the RC,a new architecture reinforced with textile-combined steel is proposed in this study,making full use of the advantages of the above two structures.The cover concrete at the tension zone of an RC element is partially replaced with TRC and thus the steel reinforcements replaced with textiles are subtracted.Compared with the old one,the new structure has less dead weight and has the merits of service safety and good durability.The flexural development process of the proper beam with this new structure is investigated in this paper and based on the plane section assumption,analytical equations are derived by using nonlinear analysis theory,including the load-carrying capacity at different stages and moment-curvature relationship and mid-span deflection during the entire loading process.Comparison between the calculated and the experimental results reveals satisfactory agreement and thus verifies the feasibility of the equations.
Matrix Analysis on Flexural Behavior of Thin-walled Box Girder%薄壁箱梁挠曲性能的矩阵分析
Institute of Scientific and Technical Information of China (English)
张元海; 林丽霞; 李乔
2011-01-01
On the basis of the shape function matrix which is established through assuming the homogeneous solution to the governing differential equation for shear lag of the thin-walled box girder as the element displacement function, the formula of the equivalent nodal force of the element under vertical concentrated loads is derived by applying the principle of virtual work. The reasonable warping displacement function of shear lag is proposed for the box girder with the twin-cell cross-section. The plexiglass model of the cantilever box girder with variable cross-sections is calculated, thus validating the effectiveness of the finite segment element in analysis of the box girder with variable cross-sections. The flexural behavior of the prestressed concrete continuous box girder with variable cross-sections is analyzed through a practical example. The results show as follows:The finite segment element has high computing efficiency for the box girder with variable cross-sections; under the action of vertical concentrated loads, the shear lag moment diagram of the box girder is a smooth curve and the absolute value of the shear lag moment is not greater than that of the bending moment at any cross-sections; the shear lag effect increases the mid-span deflection of the continuous box girder significantly, which shall be treated seriously in engineering practice.%在选取薄壁箱梁剪力滞控制微分方程的齐次解作为单元位移函数建立形函数矩阵基础上,运用虚功原理推导竖向集中荷载作用下单元等效节点力公式,提出双室箱梁的合理剪滞翘曲位移函数.通过对变截面悬臂箱梁有机玻璃模型进行计算,验证提出的梁段单元对分析变截面箱梁的有效性.结合实际箱梁算例,分析预应力混凝土变截面连续箱梁的挠曲性能.研究结果表明:所提出的梁段单元用于变截面箱梁分析时,具有较高的计算精度;在竖向集中荷载作用下,箱梁剪滞力矩图是一条
Nonlinear shear behavior of rock joints using a linearized implementation of the Barton–Bandis model
Directory of Open Access Journals (Sweden)
Simon Heru Prassetyo
2017-08-01
Full Text Available Experiments on rock joint behaviors have shown that joint surface roughness is mobilized under shearing, inducing dilation and resulting in nonlinear joint shear strength and shear stress vs. shear displacement behaviors. The Barton–Bandis (BB joint model provides the most realistic prediction for the nonlinear shear behavior of rock joints. The BB model accounts for asperity roughness and strength through the joint roughness coefficient (JRC and joint wall compressive strength (JCS parameters. Nevertheless, many computer codes for rock engineering analysis still use the constant shear strength parameters from the linear Mohr–Coulomb (M−C model, which is only appropriate for smooth and non-dilatant joints. This limitation prevents fractured rock models from capturing the nonlinearity of joint shear behavior. To bridge the BB and the M−C models, this paper aims to provide a linearized implementation of the BB model using a tangential technique to obtain the equivalent M−C parameters that can satisfy the nonlinear shear behavior of rock joints. These equivalent parameters, namely the equivalent peak cohesion, friction angle, and dilation angle, are then converted into their mobilized forms to account for the mobilization and degradation of JRC under shearing. The conversion is done by expressing JRC in the equivalent peak parameters as functions of joint shear displacement using proposed hyperbolic and logarithmic functions at the pre- and post-peak regions of shear displacement, respectively. Likewise, the pre- and post-peak joint shear stiffnesses are derived so that a complete shear stress-shear displacement relationship can be established. Verifications of the linearized implementation of the BB model show that the shear stress-shear displacement curves, the dilation behavior, and the shear strength envelopes of rock joints are consistent with available experimental and numerical results.
Institute of Scientific and Technical Information of China (English)
刘伯权; 刘喜; 吴涛
2015-01-01
Some models have been presented by domestic and foreign scholars for shear capacity of deep reinforced concrete flexural members,but there is still no generally accepted shear theory model.Bayesian theory has been applied to predict and design the bearing capacity for some reinforced concrete members,the reasonability,accuracy and superiority of which have been demonstrated,too.However,the calculation results and accuracy are different for different prior distributions.This paper develops probabilistic shear strength models for reinforced concrete deep flexural members by using of Bayesian multivariate statistical theory based on conjugate prior distribution.These probabilistic models are simplified through the Bayesian parameters removal process.Their performance is confirmed by comparison with 115 collected test results.This shows that the deep flexural members' shear strengths,as obtained by the simplified model based on Bayesian theory,are in good agreement with test results,and they are closer to the experimental values than the results given by models used in many nations' codes.The simplified models can be used in shear strength prediction and design for deep flexural members.%钢筋混凝土深受弯构件由于影响因素多、受力复杂,其计算模型和设计方法未形成统一定论.贝叶斯理论己被应用于钢筋混凝土部分构件承载力的预测和设计中,且合理性、准确性及优越性己得到证明,然其先验分布的选取不同,对计算结果的精度影响不同.采用共轭分布法推导了贝叶斯参数先验分布,利用贝叶斯多元统计理论,建立了基于共轭分布的钢筋混凝土深受弯构件受剪承载力贝叶斯概率模型,通过贝叶斯后验参数剔除法简化概率模型,并结合国内外学者己完成115组钢筋混凝土深受弯构件受剪性能试验结果验证模型.研究表明:基于贝叶斯简化模型得到的深受弯构件受剪承载力与试验结果吻合良好,较各
Behavior of Fiber Glass Bolts, Rock Bolts and Cable Bolts in Shear
Li, Xuwei; Aziz, Naj; Mirzaghorbanali, Ali; Nemcik, Jan
2016-07-01
This paper experimentally compares the shear behavior of fiber glass (FG) bolt, rock bolt (steel rebar bolt) and cable bolt for the bolt contribution to bolted concrete surface shear strength, and bolt failure mode. Two double shear apparatuses of different size were used for the study. The tensile strength, the shear strength and the deformation modulus of bolt control the shear behavior of a sheared bolted joint. Since the strength and deformation modulus of FG bolt, rock bolt and cable bolt obtained from uniaxial tensile tests are different, their shear behavior in reinforcing joints is accordingly different. Test results showed that the shear stiffness of FG bolted joints decreased gradually from the beginning to end, while the shear stiffness of joints reinforced by rock bolt and cable bolt decreased bi-linearly, which is clearly consistent with their tensile deformation modulus. The bolted joint shear stiffness was highly influenced by bolt pretension in the high stiffness stage for both rock bolt and cable bolt, but not in the low stiffness stage. The rock bolt contribution to joint shear strength standardised by the bolt tensile strength was the largest, followed by cable bolts, then FG bolts. Both the rock bolts and cable bolts tended to fail in tension, while FG bolts in shear due to their low shear strength and constant deformation modulus.
Phase behavior and shear alignment in SWNT-surfactant dispersions.
Nativ-Roth, Einat; Yerushalmi-Rozen, Rachel; Regev, Oren
2008-09-01
The effect of single-walled carbon nanotubes (SWNT) on the phase behavior of the cationic surfactant cetyltrimethylammonium bromide (CTAB) in aqueous solutions is investigated at room temperature. Small-angle X-ray scattering (SAXS) and cryogenic transmission electron microscopy (cryo-TEM) are used for characterization of bulk dispersions and nanometrically thin films. Additional carbonaceous additives (fullerenes, multi-walled carbon nanotubes, and carbon black) serve as reference systems. It is found that dispersions of carbonaceous additive (excluding fullerenes) at intermediate surfactant concentrations (below the liquid-crystalline region of the native surfactant) induce demixing and macroscopic phase separation in otherwise homogeneous solutions of CTAB. Two coexisting liquid phases of similar CTAB concentrations are observed, with the carbonaceous species residing within the lower phase. At high CTAB concentrations (liquid-crystal region) the SWNTs are found to incorporate into the ordered lyotropic liquid-crystalline phase while preserving the native d-spacing. Investigation of nanometrically thin films at intermediate surfactant concentrations under external shear reveals shear-induced structure (SIS) in the presence of minute amounts of SWNTs. The effect is found to be exclusive to SWNT and does not occur in dispersions of other carbonaceous additives.
再生混凝土弯折疲劳性能%Investigation on fatigue behavior of recycled aggregate concrete under flexure loading
Institute of Scientific and Technical Information of China (English)
肖建庄; 李宏; 李龙
2012-01-01
The fatigue behaviors of recycled aggregate concrete (RAC) with 100% recycled coarse aggregate (RCA) replacement percentage under flexure loading are tested. The fatigue failure pattern and fatigue strength are analyzed. Based on the analysis of fatigue strain variation in different heights of prism as well as the neutral axis depth, the fatigue damage evolution of RAC is investigated. On the basis of the experimental results and continuum damage mechanics, a flexural fatigue damage model is proposed. The results show that the failure pattern under fatigue flexure loading is basically the same as that under static loading, and a linear relationship exists between the logarithm of fatigue life N of RAC and the stress level S under flexure loading. The flexural fatigue damage model is good enough to verify the fatigue test results. It can be applied to the theoretical and numerical analyses of the RAC fatigue behavior under flexure loading.%完成了再生粗骨料取代率为100％的再生混凝土弯折疲劳试验,对其疲劳破坏现象和疲劳强度进行了分析.通过分析疲劳荷载下再生混凝土棱柱体在不同截面高度处的疲劳应变况以及其中性轴的变化情况,研究了再生混凝土弯折疲劳损伤演化过程.基于试验结果和连续损伤力学,提出了一个再生混凝土弯折疲劳损伤模型.结果表明,弯折疲劳破坏情况与静载作用时基本相似,再生混凝土弯折疲劳S-N曲线呈单对数直线关系.再生混凝土弯折疲劳损伤模型可以很好地验证疲劳试验结果,可用来对再生混凝土梁疲劳性能进行理论和数值分析.
Reliability and flexural behavior of triangular and T-reinforced concrete beams
Al-Ansari, Mohammed S.
2015-12-01
The paper studied the behavior of reinforced concrete triangular and T-beams. Three reinforced concrete beams were tested experimentally and analyzed analytically using the finite element method. Their reliability was also assessed using the reliability index approach. The results showed that the finite element vertical displacements compared well with those obtained experimentally. They also showed that the vertical displacements obtained using the finite element method were larger than those obtained experimentally. This is a strong indication that the finite element results were conservative and reliable. The results showed that the triangular beams exhibited higher ductility at failure than did the T-beam. The plastic deformations at failure of the triangular beams were higher than that of the T-beam. This is a strong indication of the higher ductility of the triangular beams compared to the T-beam. Triangular beams exhibited smaller cracks than did T-beams for equal areas of steel and concrete. The design moment strengths M c computed using the American Concrete Institute (ACI) design formulation were safe and close to those computed using experimental results. The experimental results validated the reliability analysis results, which stated that the triangular beams are more reliable than T-beams for equal areas of steel and concrete.
Experimental and numerical investigation on flexural bond strength behavior of corroded NBS RC beam
Shetty, Akshatha; Venkataramana, Katta; Babu Narayan, K. S.
2015-09-01
Corrosion of reinforcing steel is the most detrimental effect endangering the structural performance. Present investigation has been taken up to study the detrimental effect of corrosion on bond behavior. Experimental and numerical investigation has been carried out for four different levels of corrosion—2.5, 5, 7.5 and 10 %. Loss in mass of reinforcement bar has been taken as the basis to fix corrosion levels. Accelerated corrosion technique has been adopted to control corrosion rate by regulating current over predetermined durations. NBS beams have been investigated for performance. Concrete grade M30 and steel Fe-415 have been used. From the experimental investigation, it has been observed that bond strength degradation of 2.6 % at slip initiation and 2.1 % at end of slip have been observed for every percentage increases in corrosion level. Numerical investigation with concrete is modeled as solid 65 element and reinforcement modeled as Link 8 elements. ANSYS has yielded 3 and 2.4 % bond strength degradation values at initiation and end of slip per percentage increase in corrosion levels.
Directory of Open Access Journals (Sweden)
R. Cedeño-Rosete
2005-01-01
Full Text Available Se presenta la implementación de un programa de cómputo para determinar la capacidad resistente a flexión y cortante de perfiles de acero. La metodología se basa en el criterio de diseño Factores de Carga y Resistencia establecida en el reglamento del Instituto Americano de Construcción en Acero (AISC. Se generan hojas de cálculo en la aplicación Mathcad de fácil utilización. Se plantean dos ejemplos de vigas de acero obteniendo su capacidad resistente a flexión y cortante para cargas uniformes y concentradas y se comparan los resultados con las acciones últimas especificadas. El programa también cumple las funciones de diseño estructural permitiendo al usuario obtener el perfil más económico para la solución de un problema. La aplicación resulta ser un material de interés práctico profesional y de utilidad didáctica para cursos de diseño en acero.A computer program was developed to determine the flexure and shear resistance capacity of steel beams. The methodology was based on the Load Resistance Factor Design (LRFD criteria of the American Institute of Steel Construction code (AISC. Easy to use working spreadsheets were developed using Mathcad. Two examples are solved for steel beams subjected to uniform and concentrated loads, comparing their flexural and shear resistance capacities under these loads. The program also fulfills structural design features allowing the user to obtain the most economic steel shape to solve a problem. The resultant application is of practical professional interest and also serves as additional teaching material in courses of steel design.
Macro and meso characteristics evolution on shear behavior of rock joints
Institute of Scientific and Technical Information of China (English)
李凯辉; 曹平; 张科; 钟涌芳
2015-01-01
Direct shear tests were conducted on the rock joints under constant normal load (CNL), while the acoustic emission (AE) signals generated during shear tests were monitored with PAC Micro-II system. Before and after shearing, the surfaces of rock joints were measured by the Talysurf CLI 2000. By correlating the AE events with the shear stress−shear displacement curve, one can observe four periods of the whole course of shearing of rock joints. By the contrast of AE location and actual damage zone, it is elucidated that the AE event is related to the morphology of the joint. With the increase of shearing times, the shear behavior of rock joints gradually presents from the response of brittle behavior to that of ductile behavior. By combining the results of topography measurement, four morphological parameters of joint surface,Sp (the maximum height of joint surface),N (number of islands),A (projection area) andV (volume of joint) were introduced, which decrease with shearing. Both the joint roughness coefficient (JRC) and joint matching coefficient (JMC) drop with shearing, and the shear strength of rock joints can be predicted by the JRC-JMC model. It establishes the relationship between micro-topography and macroscopic strength, which have the same change rule with shearing.
Locally Corroded Stiffener Effect on Shear Buckling Behaviors of Web Panel in the Plate Girder
Directory of Open Access Journals (Sweden)
Jungwon Huh
2015-01-01
Full Text Available The shear buckling failure and strength of a web panel stiffened by stiffeners with corrosion damage were examined according to the degree of corrosion of the stiffeners, using the finite element analysis method. For this purpose, a plate girder with a four-panel web girder stiffened by vertical and longitudinal stiffeners was selected, and its deformable behaviors and the principal stress distribution of the web panel at the shear buckling strength of the web were compared after their post-shear buckling behaviors, as well as their out-of-plane displacement, to evaluate the effect of the stiffener in the web panel on the shear buckling failure. Their critical shear buckling load and shear buckling strength were also examined. The FE analyses showed that their typical shear buckling failures were affected by the structural relationship between the web panel and each stiffener in the plate girder, to resist shear buckling of the web panel. Their critical shear buckling loads decreased from 82% to 59%, and their shear buckling strength decreased from 88% to 76%, due to the effect of corrosion of the stiffeners on their shear buckling behavior. Thus, especially in cases with over 40% corrosion damage of the vertical stiffener, they can have lower shear buckling strength than their design level.
Shear Strength Behavior of Two Landfill Clay Liners
Institute of Scientific and Technical Information of China (English)
无
2002-01-01
Direct shear tests were conducted to obtain both the shear strength of compacted clay liners (CCLs) specimens and the interface shear strength between compacted clay liner and base soil. These experiments were conducted under the conditions of five different water contents. The experimental results show that shear strength of both CCLs and CCLs/base interface decreases with the increase in the water content of CCLs and base soil. In addition, the considerate concentration of NaCl in leachate has no deteriorating effect on the shear strength of liners. Triaxial shear tests were also conducted on clay liner specimens to obtain total and effective shear strength under a fast compression. The shear strength c'=100 kPa for sand-bentonite, respectively. These results indicate that the compacted clay-bentonite shows normal consolidation, but that the compacted sand-bentonite exhibits over-consolidation.
Seismic behavior of semi-supported steel shear walls
DEFF Research Database (Denmark)
Jahanpour, A.; Jönsson, J.; Moharrami, H.
2012-01-01
During the recent past decade semi-supported steel shear walls (SSSW) have been introduced as an alternative to the traditional type of steel plate shear walls. In this system the shear wall does not connect directly to the main columns of the building frame; instead it is connected to a pair of ...
DEFF Research Database (Denmark)
Paegle, Ieva; Fischer, Gregor
2016-01-01
This paper describes an experimental investigation of the shear behavior of beams consisting of steel Reinforced Engineered Cementitious Composites (R/ECC). This study investigates and quantifies the effect of ECC's strain hardening and multiple cracking behavior on the shear capacity of beams lo...
Chen, Kaihui; Wang, Yu; Xuan, Shouhu; Gong, Xinglong
2017-07-01
To investigate the microstructural evolution dependency on the apparent viscosity in shear-thickening fluids (STFs), a hybrid mesoscale model combined with stochastic rotation dynamics (SRD) and molecular dynamics (MD) is used. Muller-Plathe reverse perturbation method is adopted to analyze the viscosities of STFs in a two-dimensional model. The characteristic of microstructural evolution of the colloidal suspensions under different shear rate is studied. The effect of diameter of colloidal particles and the phase volume fraction on the shear thickening behavior is investigated. Under low shear rate, the two-atom structure is formed, because of the strong particle attractions in adjacent layers. At higher shear rate, the synergetic pair structure extends to layered structure along flow direction because of the increasing hydrodynamics action. As the shear rate rises continuously, the layered structure rotates and collides with other particles, then turned to be individual particles under extension or curve string structure under compression. Finally, at the highest shear rate, the strings curve more severely and get into two-dimensional cluster. The apparent viscosity of the system changes from shear-thinning behavior to the shear-thickening behavior. This work presents valuable information for further understanding the shear thickening mechanism.
Shear Behavior of Novel Prestressed Concrete Beam Subjected to Monotonic and Cyclic Loading
Institute of Scientific and Technical Information of China (English)
余芳; 姚大立; 贾金青; 吴锋
2014-01-01
Prestressed steel ultrahigh-strength reinforced concrete (PSURC) beam is a new type of prestressed con-crete beam, which not only has a considerable compressive strength attributed to the ultrahigh strength concrete, but also ensures a certain degree of ductility at failure due to the existence of structural steel. Five of these beams were monotonically tested until shear failure to investigate the static shear performance including the failure pattern, load-deflection behavior, shear capacity, shear crack width and shear ductility. The experimental results show that these beams have superior shear capacity, crack control ability and shear ductility. To study the shear performance under repeated overloading, seven PSURC beams were loaded in cyclic test simultaneously. The overall shear performance of cycled beams is similar to that of uncycled beams at low load level but different at high load level. The shear capac-ity and crack control ability of cycled beams at high load level are reduced, whereas the shear ductility is improved. In addition, the influences of variables including the degree of prestress, stirrup ratio and load level on the shear perform-ance of both uncycled and cycled beams were also discussed and compared, respectively.
Interfacial shear behavior of composite flanged concrete beams
Directory of Open Access Journals (Sweden)
Moataz Awry Mahmoud
2014-08-01
Full Text Available Composite concrete decks are commonly used in the construction of highway bridges due to their rapid constructability. The interfacial shear transfer between the top slab and the supporting beams is of great significance to the overall deck load carrying capacity and performance. Interfacial shear capacity is directly influenced by the distribution and the percentage of shear connectors. Research and design guidelines suggest the use of two different approaches to quantify the required interfacial shear strength, namely based on the maximum compressive forces in the flange at mid span or the maximum shear flow at the supports. This paper investigates the performance of flanged reinforced concrete composite beams with different shear connector’s distribution and reinforcing ratios. The study incorporated both experimental and analytical programs for beams. Key experimental findings suggest that concentrating the connectors at the vicinity of the supports enhances the ductility of the beam. The paper proposes a simple and straight forward approach to estimate the interfacial shear capacity that was proven to give good correlation with the experimental results and selected code provisions. The paper presents a method to predict the horizontal shear force between precast beams and cast in-situ slabs.
Shear Capacity and Failure Behavior of Steel-Reinforced High Ductile Concrete Beams
Directory of Open Access Journals (Sweden)
Mingke Deng
2015-01-01
Full Text Available The shear behavior of six high ductile fiber reinforced concrete (HDC beams is studied to investigate the influence of shear-span ratio and HDC mechanical property on the improvement of the shear failure mode and shear capacity of short beams. Four steel-reinforced high ductile concrete beams (SHDC beams with different shear span ratios are tested under concentrated load at midspan. To study the effect of stirrups and steel on the shear capacity of short beams, two additional specimens without steel but one including stirrups are investigated. The main aspects of SHDC beams are discussed in detail, such as failure mode, deformability, and shear capacity. Test results show that the SHDC short beams keep high residual bearing capacity and great integrity when suffering from large deformation. It is revealed that HDC increased the shear ductility and improved the shear failure mode of short beams. A comparison with the shear equations of Chinese YB9082-2006 shows that the Chinese Code equation provides conservative estimation for HDC beams. This study proposes modifications to the equation for predicting the shear capacity of HDC beams.
Shear Deformation Behaviors of Sn3.5Ag Lead-free Solder Samples
Institute of Scientific and Technical Information of China (English)
Jing Han; Hongtao Chen; Mingyu Li; Chunqing Wang
2013-01-01
In this study,shear tests have been performed on the as-reflowed Sn3.5Ag solder bumps and joints to investigate the deformation behavior of Sn3.5Ag lead-free solder samples.Scanning electron microscopy (SEM) was employed to characterize the microstructures of the samples and orientation imaging microscopy (OIM) with electron backscattered diffraction (EBSD) in SEM was used to obtain crystallographic orientation of grains to provide a detailed characterization of the deformation behavior in Sn3.5Ag solder samples after shear tests.The deformation behavior in solder samples under shear stress was discussed.The experimental results suggest that the dynamic recrystallization could occur under shear stress at room temperature and recrystallized grains should evolve from subgrains by rotation.Compared with that of non-recrystallized and as-reflowed microstructures,the microhardness of the recrystallized microstructure decreased after shear tests.
Energy Technology Data Exchange (ETDEWEB)
Kiani, Keivan, E-mail: k_kiani@kntu.ac.ir
2014-09-15
Useful nonlocal discrete and continuous models are developed to explain free vibration of two-dimensional (2D) ensembles of single-walled carbon nanotubes (SWCNTs) in bending. For this purpose, the models are constructed based on the nonlocal Rayleigh, Timoshenko, and higher-order beam theories. In contrast to an individual SWCNT exhibits identical bending behavior in different directions, for 2D ensemble networks of SWCNTs, it is shown that such a fact is completely dissimilar. Such an important issue leads to the definition of in-plane and out-of-plane flexural behaviors for such nanostructures. Subsequently, their corresponding fundamental frequencies are evaluated based on the proposed nonlocal models. The capabilities of the proposed nonlocal continuous models in predicting flexural frequencies of SWCNTs' ensembles with different numbers of SWCNTs as well as various levels of slenderness ratios are then explained. Such investigations confirm the high efficiency of the proposed continuous models. This matter would be of great importance in vibration analysis of highly populated ensembles of SWCNTs in which the discrete models may suffer from the size of the governing equations. The roles of the number of SWCNTs, slenderness ratio, intertube distance, small-scale parameter, and radius of the SWCNT on both in-plane and out-of-plane fundamental frequencies are addressed.
Mohamed, Omar Ahmed; Masood, Syed Hasan; Bhowmik, Jahar Lal
2017-03-01
The resistance of polymeric materials to time-dependent plastic deformation is an important requirement of the fused deposition modeling (FDM) design process, its processed products, and their application for long-term loading, durability, and reliability. The creep performance of the material and part processed by FDM is the fundamental criterion for many applications with strict dimensional stability requirements, including medical implants, electrical and electronic products, and various automotive applications. Herein, the effect of FDM fabrication conditions on the flexural creep stiffness behavior of polycarbonate-acrylonitrile-butadiene-styrene processed parts was investigated. A relatively new class of experimental design called "definitive screening design" was adopted for this investigation. The effects of process variables on flexural creep stiffness behavior were monitored, and the best suited quadratic polynomial model with high coefficient of determination ( R 2) value was developed. This study highlights the value of response surface definitive screening design in optimizing properties for the products and materials, and it demonstrates its role and potential application in material processing and additive manufacturing.
Mohamed, Omar Ahmed; Masood, Syed Hasan; Bhowmik, Jahar Lal
2016-12-01
The resistance of polymeric materials to time-dependent plastic deformation is an important requirement of the fused deposition modeling (FDM) design process, its processed products, and their application for long-term loading, durability, and reliability. The creep performance of the material and part processed by FDM is the fundamental criterion for many applications with strict dimensional stability requirements, including medical implants, electrical and electronic products, and various automotive applications. Herein, the effect of FDM fabrication conditions on the flexural creep stiffness behavior of polycarbonate-acrylonitrile-butadiene-styrene processed parts was investigated. A relatively new class of experimental design called "definitive screening design" was adopted for this investigation. The effects of process variables on flexural creep stiffness behavior were monitored, and the best suited quadratic polynomial model with high coefficient of determination (R 2) value was developed. This study highlights the value of response surface definitive screening design in optimizing properties for the products and materials, and it demonstrates its role and potential application in material processing and additive manufacturing.
Zhou, Guangming; Liu, Chang; Cai, Deng'an; Li, Wenlong; Wang, Xiaopei
2016-11-01
An experimental, theoretical and numerical investigation on the shear behavior of 3D woven hollow integrated sandwich composites was presented in this paper. The microstructure of the composites was studied, then the shear modulus and load-deflection curves were obtained by double lap shear tests on the specimens in two principal directions of the sandwich panels, called warp and weft. The experimental results showed that the shear modulus of the warp was higher than that of the weft and the failure occurred in the roots of piles. A finite element model was established to predict the shear behavior of the composites. The simulated results agreed well with the experimental data. Simultaneously, a theoretical method was developed to predict the shear modulus. By comparing with the experimental data, the accuracy of the theoretical method was verified. The influence of structural parameters on shear modulus was also discussed. The higher yarn number, yarn density and dip angle of the piles could all improve the shear modulus of 3D woven hollow integrated sandwich composites at different levels, while the increasing height would decrease the shear modulus.
FRP-RC Beam in Shear: Mechanical Model and Assessment Procedure for Pseudo-Ductile Behavior
Directory of Open Access Journals (Sweden)
Floriana Petrone
2014-07-01
Full Text Available This work deals with the development of a mechanics-based shear model for reinforced concrete (RC elements strengthened in shear with fiber-reinforced polymer (FRP and a design/assessment procedure capable of predicting the failure sequence of resisting elements: the yielding of existing transverse steel ties and the debonding of FRP sheets/strips, while checking the corresponding compressive stress in concrete. The research aims at the definition of an accurate capacity equation, consistent with the requirement of the pseudo-ductile shear behavior of structural elements, that is, transverse steel ties yield before FRP debonding and concrete crushing. For the purpose of validating the proposed model, an extended parametric study and a comparison against experimental results have been conducted: it is proven that the common accepted rule of assuming the shear capacity of RC members strengthened in shear with FRP as the sum of the maximum contribution of both FRP and stirrups can lead to an unsafe overestimation of the shear capacity. This issue has been pointed out by some authors, when comparing experimental shear capacity values with the theoretical ones, but without giving a convincing explanation of that. In this sense, the proposed model represents also a valid instrument to better understand the mechanical behavior of FRP-RC beams in shear and to calculate their actual shear capacity.
Strength and behavior in shear of reinforced concrete deep beams under dynamic loading conditions
Energy Technology Data Exchange (ETDEWEB)
Adhikary, Satadru Das [School of Civil and Environmental Engineering, Nanyang Technological University, 639798 (Singapore); Li, Bing, E-mail: cbli@ntu.edu.sg [School of Civil and Environmental Engineering, Nanyang Technological University, 639798 (Singapore); Fujikake, Kazunori [Department of Civil and Environmental Engineering, National Defense Academy, Yokosuka 239 8686 (Japan)
2013-06-15
Highlights: ► Effects of wider range of loading rates on dynamic shear behavior of RC deep beams. ► Experimental investigation of RC deep beam with and without shear reinforcements. ► Verification of experimental results with truss model and FE simulation results. ► Empirical equations are proposed to predict the dynamic increase factor of maximum resistance. -- Abstract: Research on reinforced concrete (RC) deep beams has seen considerable headway over the past three decades; however, information on the dynamic shear strength and behavior of RC deep beams under varying rates of loads remains limited. This paper describes the experimental results of 24 RC deep beams with and without shear reinforcements under varying rates of concentrated loading. Results obtained serve as useful data on shear resistance, failure patterns and strain rates corresponding to varying loading rates. An analytical truss model approach proves its efficacy in predicting the dynamic shear resistance under varying loading rates. Furthermore, three-dimensional nonlinear finite element (FE) model is described and the simulation results are verified with the experimental results. A parametric study is then conducted to investigate the influence of longitudinal reinforcement ratio, transverse reinforcement ratio and shear span to effective depth ratio on shear behavior. Subsequently, two empirical equations were proposed by integrating the various parameters to assess the dynamic increase factor (DIF) of maximum resistance under varying rates of concentrated loading.
Institute of Scientific and Technical Information of China (English)
侯和涛; 马克峰; 李国强; 陈璐
2011-01-01
Energy-saving composite sandwich panels were composed of two wythes of concrete and a core layer of thermal insulation, which were connected to each other by truss shear connectors. Because of their advantages, such as the superior flexural resistance and stiffness, light weight and excellent thermal insulation, sandwich composite panels were widely employed in steel residential houses. In order to investigate how the arrangements of truss shear connectors affect the flexural behavior and dynamic response of the panels, two full-scale sandwich composite panels were built and tested. One specimen was a composite panel with the plane truss shear connectors, and the other was a CL ( composite light-weight) panel with the spatial truss shear connectors. Test results showed that the panels with the plane truss shear connectors had a higher ultimate flexural strength and higher-order mode damping ratios than the CL panel, but with a similar crack loads. The influence of the truss shear connector on the flexural strength and mode damping ratios of sandwich composite panel could be significant.%节能复合墙板是由两块钢筋混凝土面板和聚苯板芯层通过斜向钢丝可靠连接而成的复合板,具有抗弯刚度大、承载力高、自重轻和节能保温等特点,广泛应用于钢结构住宅.为研究斜向钢丝的布置对复合墙板抗弯承载力和振动模态的影响,本文分别对足尺平面钢丝桁架复合墙板和CL(composite light-weight)空间网架墙板进行了抗弯承载力和振动特性的试验研究,结果得出平面钢丝桁架复合墙板的极限抗弯承载力和一阶以上的阻尼比均高于CL墙板,而开裂荷载基本相同,表明斜向钢丝布置对复合墙板的抗弯承载力和阻尼比影响较大.
Shear behavior of coarse aggregates for dam construction under varied stress paths
Institute of Scientific and Technical Information of China (English)
Liu Hanlong; Deng An; Shen Yang
2008-01-01
Coarse aggregates are the major infrastructure materials of concrete-faced rock-fill dams and are consolidated to bear upper and lateral loads. With the increase of dam height, high confining pressure and complex stress states complicate the shear behavfor of coarse aggregates, and thus impede the high dam's proper construction, operation and maintenance. An experimental program was conducted to study the shear behavior of dam coarse aggregates using a large-scale triaxial shear apparatus. Through triaxial shear tests, the strain-stress behaviors of aggregates were observed under constant confining pressures: 300 kPa, 600 kPa, 900 kPa and 1200 kPa. Shear strengths and aggregate breakage characteristics associated with high pressure shear processes are discussed. Stress path tests were conducted to observe and analyze coarse aggregate response under complex stress states. In triaxial shear tests, it was found that peak deviator stresses increase along with confining pressures, whereas the peak principal stress ratios decrease as confining pressures increase. With increasing confining pressures, the dilation decreases and the contraction eventually prevails. Initial strength parameters (Poisson's ratio and tangent modulus) show a nonlinear relationship with confining pressures when the pressures are relatively low. Shear strength parameters decrease with increasing confining pressures. The failure envelope lines are convex curves, with clear curvature under low confining pressures. Under moderate confining pressures, dilation is offset by particle breakage. Under high confining pressures, dilation disappears.
Al-Rousan, R. Z.
2015-09-01
The main objective of this study was to assess the effect of the number and schemes of carbon-fiber-reinforced polymer (CFRP) sheets on the capacity of bending moment, the ultimate displacement, the ultimate tensile strain of CFRP, the yielding moment, concrete compression strain, and the energy absorption of RC beams and to provide useful relationships that can be effectively utilized to determine the required number of CFRP sheets for a necessary increase in the flexural strength of the beams without a major loss in their ductility. To accomplish this, various RC beams, identical in their geometric and reinforcement details and having different number and configurations of CFRP sheets, are modeled and analyzed using the ANSYS software and a nonlinear finite-element analysis.
Shear-banding phenomena and dynamical behavior in a Laponite suspension
Ianni, F.; di Leonardo, R.; Gentilini, S.; Ruocco, G.
2008-03-01
Shear localization in an aqueous clay suspension of Laponite is investigated through dynamic light scattering, which provides access both to the dynamics of the system (homodyne mode) and to the local velocity profile (heterodyne mode). When shear bands form, a relaxation of the dynamics typical of a gel phase is observed in both bands soon after the flow stops. Periodic oscillations of the flow behavior, typical of a stick-slip phenomenon, are also observed when shear localization occurs. Both results are discussed in the light of various theoretical models for soft glassy gels.
Nonlinear response of plain concrete shear walls with elastic-damaging behavior
Energy Technology Data Exchange (ETDEWEB)
Yazdani, S.; Schreyer, H.L.
1997-02-01
This report summarizes the theoretical and computational efforts on the modeling of small scale shear walls. Small scale shear walls are used extensively in the study of shear wall behavior because the construction and testing of full size walls are rather expensive. A finite element code is developed which incorporates nonlinear constitutive relations of damage mechanics. The program is used to obtain nonlinear load-deformation curves and to address the initial loss of stiffness due to shrinkage cracking. The program can also be used to monitor the continuous degradation of the fundamental frequency due to progressive damage.
Institute of Scientific and Technical Information of China (English)
车轶; 郑新丰; 王金金; 宋玉普
2012-01-01
Reinforced high-strength concrete beams subjected to bending were tested to investigate the effect of depth on flexural behavior of beams.The geometry of specimens varied in cross sections with the depth-width ratios of the cross sections,the shear span ratios and longitudinal reinforcement ratios of specimens being constant.C70 concrete was used to cast the specimens and HRB 400 steel bars were used for the longitudinal reinforcement.The influence of beam depth on the nominal cracking moment,nominal yield moment,nominal ultimate flexural moment,ductility,and plastic rotation capacity of high-strength concrete beams was investigated.It is shown that there is no apparent size effect on nominal cracking moment,nominal yield moment and nominal ultimate moment of reinforced high-strength concrete beams.But the displacement ductility ratio and plastic rotation capacity show significant size effect.The displacement ductility factor and the rotational capacity of high-strength concrete beam decrease with the increasing of cross section.%进行了不同截面尺寸高强混凝土梁的弯曲试验,研究了梁高对其受弯性能的影响。试件采用C70高强混凝土,纵向受力钢筋采用HRB400级钢筋。试件截面尺寸不同,截面长宽比、剪跨比和配筋率等参数保持一致。分析了不同截面尺寸对高强混凝土梁的名义开裂弯矩、名义屈服弯矩、名义极限弯矩、延性以及塑性转动能力的影响。研究结果表明,高强混凝土梁的名义开裂弯矩、名义屈服弯矩和名义极限弯矩无明显尺寸效应,而试件的位移延性系数和塑性铰区的塑性转动能力则表现出明显的尺寸效应,随截面尺寸的增大梁的位移延性系数和塑性铰区塑性转动能力有所降低。
Seismic Behavior of Vertical Shear Links made of Easy-Going Steel
Directory of Open Access Journals (Sweden)
Amir S. Daryan
2008-01-01
Full Text Available Problem Statement: Since the time that steel was first used as a construction material, engineers have attempted to increase strength, reduce weight and produce more economical structures by using elegant member sections. However, the increase in steel strength and the decrease in cross section area are not always useful and in some cases it is necessary to reduce the strength to allow the structure to behave in a specific manner. This issue is seen in systems designed to withstand lateral loads, such as wind and earthquake loads. Approach: To improve the seismic behavior of braced frames, the V-EBF system with shear panels made of easy-going steel is presented. Using the finite element method, braced frames with shear panels made of easy-going steel were analyzed and compared to the behavior of the same frame with shear panels made of construction steel. The influence of shear panel systems made of easy-going steel is investigated by inserting this system in 4, 8 and 12-storey frames and analyzing them under earthquake loads. Results: The results indicate that contrary to shear panels made of construction steel no local buckling occurs in shear panels made of easy-going steel and the energy dissipation and ductility are increased considerably. Consequently, frames with shear panels made of easy-going steel exhibit better performance and energy absorption. Conclusion: In this research, it is attempted to improve the behavior of V-EBF frames by using a new type of steel, EGS, which has a lower yield stress than construction steel. The study shows that if EGS is used in a shear panel, seismic behavior of these frames improves noticeably.
A DEM investigation on simple shear behavior of dense granular assemblies
Institute of Scientific and Technical Information of China (English)
史旦达; 薛剑峰; 赵振营; 史跻宇
2015-01-01
A micromechanical investigation on simple shear behavior of dense granular assemblies was carried out by discrete element method. Three series of numerical tests were performed to examine the effects of initial porosity, vertical stress and particle shape on simple shear behavior of the samples, respectively. It was found that during simple shear the directions of principal stress and principal strain increment rotate differently with shear strain level. The non-coaxiality between the two directions decreases with strain level and may greatly affect the shear behavior of the assemblies, especially their peak friction angles. The numerical modelling also reveals that the rotation of the principal direction of fabric anisotropy lags behind that of the major principal stress direction during simple shear, which is described as fabric hyteresis effect. The degrees of fabric and interparticle contact force anisotropies increase as particle angularity increases, whereas the orientations of these anisotropies have not been significantly influenced by particle shape. An extended stress–dilatancy relationship based on ROWE-DAVIS framework was proposed to consider the non-coaxiality effect under principal stress rotation. The model was validated by present numerical results as well as some published physical test and numerical modelled data.
BEHAVIOR OF ELASTIC TOWING CABLES IN SHEAR CURRENTS
Institute of Scientific and Technical Information of China (English)
HOU Guo-xiang; LI Hong-bin; ZHANG Sheng-jun; YANG Yun-tao; XU Shi-hua; XIE Wei
2005-01-01
The formulation and solution of governing equations that can be used to analyse the three-dimensional behaviour of elastic towing cables subjected to arbitrary sheared currents were presented in this paper. The elastic cable geometry was described in terms of two angles, elevation and azimuth, which are related to Cartesian co-ordinates by geometry compatibility relations. These relations were combined with the cable equilibrium equations to obtain a system of non-linear differential equations. In the end, results for cable tension, angles, geometry and elongation are presented for example cases.
Oscillatory shearing behavior of rocket leaves powder incorporated dough
Almusallam, Abdulwahab Salem; Ahmed, Jasim; Nahar, Shamsun; Chacko, Siby
2016-05-01
Dough blended with rocket leaves powder was subjected to small and large amplitude oscillatory shears. Small amplitude oscillatory shear data were fitted to a discrete relaxation model of elastic solids and to a critical gel model. The small amplitude relaxation spectrum was thereafter used to calculate the LAOS predictions of various large deformation models. The LAOS theoretical calculations using the Phan-Thien model showed good agreement with the first harmonic stress data, and only qualitative agreement with the third and the fifth harmonic stress values. Lissajous curves showed dissimilarity in shape between the experimental data and Phan-Thien model. The network model of Sim et al. (2003). Did not have the butterfly shape displayed in the Phan-Thien model, but it provided a worse fit to stress harmonics than the Phan-Thien model. An improved damage function was proposed, where time effect on network damage was taken into consideration, and fits to stress harmonics and to Lissajous stress-strain curves were significantly improved.
A simple higher order shear deformation theory for mechanical behavior of laminated composite plates
Adim, Belkacem; Daouadji, Tahar Hassaine; Rabahi, Aberezak
2016-06-01
In the present study, the static, buckling, and free vibration of laminated composite plates is examined using a refined shear deformation theory and developed for a bending analysis of orthotropic laminated composite plates. These models take into account the parabolic distribution of transverse shear stresses and satisfy the condition of zero shear stresses on the top and bottom surfaces of the plates. The most interesting feature of this theory is that it allows for parabolic distributions of transverse shear stresses across the plate thickness and satisfies the conditions of zero shear stresses at the top and bottom surfaces of the plate without using shear correction factors. The number of independent unknowns in the present theory is four, as against five in other shear deformation theories. In the analysis, the equation of motion for simply supported thick laminated rectangular plates is obtained through the use of Hamilton's principle. The accuracy of the analysis presented is demonstrated by comparing the results with solutions derived from other higher order models and with data found in the literature. It can be concluded that the proposed theory is accurate and simple in solving the static, the buckling, and free vibration behaviors of laminated composite plates.
Fracture Behavior of Dielectric Elastomer under Pure Shear Loading
Ahmad, D.; Patra, K.
2017-09-01
Dielectric elastomer has become a very important material for many emerging applications areas like optics, micro fluidics, sensors, actuators and energy harvesting. However, these elastomer components are prone to fracture or catastrophic failure because of defects likes notches, flaws, and fatigue crack, impurities which occur during production or during service. To make better use of this material, it is important to investigate fracture characteristics under different operating conditions. This study experimentally investigated the effects of notch length and strain rate on the fracture toughness, failure stretch and failure stress of acrylic elastomer under pure shear deformation mode. It is observed that failure stretch depends on notch length and independent of strain rate, but failure stress decreases with increasing notch length and increases with increasing strain rate. It is also found that fracture toughness is independent of notch lengths. However, fracture toughness is found to increase with strain rate.
A modified model of a single rock joint shear behavior in limestone specimens
Dindarloo, Saeid R
2016-01-01
The shear behavior of a single rock joint in limestone specimens, under a constant normal load (CNL), was analyzed in this study. Test specimens with different asperity roughness were prepared and tested. The Goodman model of a rock joint shear behavior, under CNL, was modified to render a better representation of the data obtained. The model applicability was validated. The proposed model shows better correlation with experimental data. It also, requires fewer variables. The steps to calculate all the necessary variables for the model are discussed.
Clauss, D. B.; Reuter, R. C., Jr.
1983-02-01
A simplified theory for the bending behavior of a thin flat bilamina panel was developed which includes the effects of shear deformation in the central adhesive layer. Static equilibrium equations for elastic thermomechanical cylindrical bending of a thin plate are used. A solution form is proposed which greatly facilitates application of this theory to structural panels with numerous discrete property changes in the variable direction. The influence of adhesive shear stiffness parameters upon overall laminate behavior is characterized through numerical examples typifying various thermal and mechanical loading conditions.
Shear effects on crystallization behaviors and structure transitions of isotactic poly-1-butene
DEFF Research Database (Denmark)
Li, Jingqing; Guan, Peipei; Zhang, Yao;
2014-01-01
Different melt pre-shear conditions were applied to isotactic poly-1-butene (iP-1-B) and the effect on the crystallization behaviors and the crystalline structure transitions of iP-1-B were investigated. The polarized optical microscope observations during isothermal crystallization process...... crystalline structures. With the melt pre-shear rate increasing, the lattice spaces of the crystallites decreased and the long period, L, and the amorphous layer thickness, La, along the equator direction increased slightly, but L and La along the meridian direction was not affected by melt pre-shear flow....... Though the orientated crystalline structures existed in the iP-1-B samples, no accelerating effect on crystal transition from II to I was found. Importantly, the final crystalline structures of iP-1-B in form I was found tunable under different melt pre-shear conditions, even though...
Ductility of Reinforced Concrete Structures in Flexure
DEFF Research Database (Denmark)
Hestbech, Lars
2013-01-01
In this thesis, a rotational capacity model for flexural reinforced concrete elements is presented. The model is based on the general assumption, that any other failure mode than bending is prevented by proper design. This includes failure due to shear, anchorage, concentrated loads etc. Likewise......, beams governed by failure described by Kani’s Valley are not covered by the presented model. Hence, the model is delimited to shear reinforced elements failing in flexure. The rotational capacity model is divided into the following calculation procedures. 1. A cross sectional analysis of the critical...... are not necessarily so. An example shows the applicability of the model and a parametric study shows the advantages of the model compared with code provisions. Finally, improvements of the compression zone modelling is performed in order to include a better performance when concrete crushing is the failure criterion...
Investigation of the Behavior of Steel Shear Walls Using Finite Elements Analysis
Directory of Open Access Journals (Sweden)
K. Abubakri
2016-10-01
Full Text Available Currently, steel shear walls are considered by engineers as an economic method against lateral loads imposed by wind and earthquake in tall structures. Accordingly, there is a growing need to develop accurate methods alongside approximation methods to estimate the behavior of these structural elements. The finite element technique is one of the strongest numerical methods in analysis of solid mechanics problems. Finite element analysis however requires high technical knowledge of the behavioral models of materials. Therefore, it is less used by designers for certain structural elements such as steel shear walls. This study examines the failure mechanism of steel shear walls using finite elements analysis and validates this modeling by comparing the results with experimental studies.
Short Communication: Flexure delicacies
Directory of Open Access Journals (Sweden)
S. Henein
2012-01-01
Full Text Available Flexures are nowadays enjoying a new boom in numerous high-precision and extreme-environment applications. The paper presents some delicate issues concerning stiffness compensation, large reduction ratios, as well as rectilinear and circular movements in compliant mechanisms. Novel concrete technical solutions to these well-known issues are described, giving a glimpse into the vast and still largely unexploited potential of flexure mechanisms manufactured by wire-electrical-discharge machining.
Directory of Open Access Journals (Sweden)
Philipp-M. Hilgendorff
2014-01-01
Full Text Available The monitored resonant behavior of fatigue specimens of metastable austenitic stainless steel (AISI304 is correlated with its damage accumulation in the very high cycle fatigue (VHCF regime. The resonant behavior is studied experimentally and shows a distinct transient characteristic. Microscopic examinations indicate that during VHCF a localized plastic deformation in shear bands arises on the specimen surface. Hence, this work focuses on the effect of damage accumulation in shear bands on the resonant behavior of AISI304 in the VHCF regime. A microstructural simulation model is proposed that takes into account specific mechanisms in shear bands proven by experimental results. The simulation model is solved numerically using the two-dimensional boundary element method and the resonant behavior is characterized by evaluating the force-displacement hysteresis loop. Simulation of shear bands agrees well with microscopic examinations and plastic deformation in shear bands influences the transient characteristic of the resonant behavior.
DEFF Research Database (Denmark)
Luo, Baojing; Li, Hongfei; Zhang, Yao
2014-01-01
Shearing is unavoidable during the polymer process, and isotactic polypropylene (iPP) is one of the most used commercial polymers. iPP mixed with beta-nucleating agent TMB-5 was isothermally crystallized at 135 degrees C from melts under various shear conditions and investigated via synchrotron r......-iPP are in direct proportion to the orientation degree rather than shear rate especially at high shear rate, which proves that wall slip should not be neglected when taking shear effect or rheological behavior into consideration....
Institute of Scientific and Technical Information of China (English)
YiWu; Xian-yuan Liang; Rui-fen Chen; Yong-gang Shangguan; Qiang Zheng
2012-01-01
The influences of shearing conducted by a Brabender rheometer on phase morphology,thermal and rheological behavior of a commercial impact polypropylene copolymer (IPC) were studied.The crystallization and melting traces show that short-time annealing at 210℃ is unable to completely erase the influence of shearing on the samples.When the samples which were treated at a rotation speed of 80 r/min crystallize at a cooling rate of 10 K/min,their Tcs and corresponding Tms obviously rise with the increase of shearing time.Furthermore,the POM results reveal that the shearing can lead to the formation of shish-kebab and the shish-kebab amount is proportional to shearing time.The rheological measurement results show that the treated samples exhibit different G'～ω dependences.The ‘second plateau’ appears when the sample is treated at a rotation speed of 60 r/min or 80 r/min for 10 min,and linear G'～ω dependence is observed at other rotation speeds.In addition,it is found that the appearance of the ‘second plateau’ depends on the sheafing time when the rotation speed is fixed.According to SEM observations,it is proposed that the ‘second plateau’ of IPC samples should be ascribed to the aggregation of dispersion particles.
Energy Technology Data Exchange (ETDEWEB)
Zhong, Lirong; Oostrom, Martinus; Truex, Michael J.; Vermeul, Vincent R.; Szecsody, James E.
2013-01-15
Xanthan gum, a biopolymer, forms shear thinning fluids which can be used as delivery media to improve the distribution of remedial amendments injected into heterogeneous subsurface environments. The rheological behavior of the shear thinning solution needs to be known to develop an appropriate design for field injection. In this study, the rheological properties of xanthan gum solutions were obtained under various chemical and environmental conditions relevant to delivery of remedial amendments to groundwater. Higher xanthan concentration raised the absolute solution viscosity and increased the degree of shear thinning. Addition of remedial amendments (e.g., phosphate, sodium lactate, ethyl lactate) caused the dynamic viscosity of xanthan gum to decrease, but the solutions maintained shear-thinning properties. Use of simple salt (e.g. Na+, Ca2+) to increase the solution ionic strength also decreased the dynamic viscosity of xanthan and the degree of shear thinning, although the effect is a function of xanthan gum concentration and diminished as the xanthan gum concentration was increased. At high xanthan concentration, addition of salt to the solution increased dynamic viscosity. In the absence of sediments, xanthan gum solutions maintain their viscosity properties for months. However, xanthan gum solutions were shown to lose dynamic viscosity over a period of days to weeks when contacted with saturated site sediment. Loss of viscosity is attributed to physical and biodegradation processes.
A Conceptual Model for Shear-Induced Phase Behavior in Crystallizing Cocoa Butter
Energy Technology Data Exchange (ETDEWEB)
Mazzanti,G.; Guthrie, S.; Marangoni, A.; Idziak, S.
2007-01-01
We propose a conceptual model to explain the quantitative data from synchrotron X-ray diffraction experiments on the shear-induced phase behavior of cocoa butter, the main structural component of chocolate. We captured two-dimensional diffraction patterns from cocoa butter at crystallization temperatures of 17.5, 20.0, and 22.5 {sup o}C under shear rates from 45 to 1440 s{sup -1} and under static conditions. From the simultaneous analysis of the integrated intensity, correlation length, lamellar thickness, and crystalline orientation, we postulate a conceptual model to provide an explanation for the distribution of phases II, IV, V, and X and the kinetics of the process. As previously proposed in the literature, we assume that the crystallites grow layer upon layer of slightly different composition. The shear rate and temperature applied define these compositions. Simultaneously, the shear and temperature define the crystalline interface area available for secondary nucleation by promoting segregation and affecting the size distribution of the crystallites. The combination of these factors (composition, area, and size distribution) favors dramatically the early onset of phase V under shear and determines the proportions of phases II, IV, V, and X after the transition. The experimental observations, the methodology used, and the proposed explanation are of fundamental and industrial interest, since the structural properties of crystalline networks are determined by their microstructure and polymorphic crystalline state. Different proportions of the phases will thus result in different characteristics of the final material.
Seismic behavior of outrigger truss-wall shear connections using multiple steel angles
Li, Xian; Wang, Wei; Lü, Henglin; Zhang, Guangchang
2016-06-01
An experimental investigation on the seismic behavior of a type of outrigger truss-reinforced concrete wall shear connection using multiple steel angles is presented. Six large-scale shear connection models, which involved a portion of reinforced concrete wall and a shear tab welded onto a steel endplate with three steel angles, were constructed and tested under combined actions of cyclic axial load and eccentric shear. The effects of embedment lengths of steel angles, wall boundary elements, types of anchor plates, and thicknesses of endplates were investigated. The test results indicate that properly detailed connections exhibit desirable seismic behavior and fail due to the ductile fracture of steel angles. Wall boundary elements provide beneficial confinement to the concrete surrounding steel angles and thus increase the strength and stiffness of connections. Connections using whole anchor plates are prone to suffer concrete pry-out failure while connections with thin endplates have a relatively low strength and fail due to large inelastic deformations of the endplates. The current design equations proposed by Chinese Standard 04G362 and Code GB50011 significantly underestimate the capacities of the connection models. A revised design method to account for the influence of previously mentioned test parameters was developed.
Patrício, P; Almeida, P L; Portela, R; Sobral, R G; Grilo, I R; Cidade, T; Leal, C R
2014-08-01
The activity of growing living bacteria was investigated using real-time and in situ rheology-in stationary and oscillatory shear. Two different strains of the human pathogen Staphylococcus aureus-strain COL and its isogenic cell wall autolysis mutant, RUSAL9-were considered in this work. For low bacteria density, strain COL forms small clusters, while the mutant, presenting deficient cell separation, forms irregular larger aggregates. In the early stages of growth, when subjected to a stationary shear, the viscosity of the cultures of both strains increases with the population of cells. As the bacteria reach the exponential phase of growth, the viscosity of the cultures of the two strains follows different and rich behaviors, with no counterpart in the optical density or in the population's colony-forming units measurements. While the viscosity of strain COL culture keeps increasing during the exponential phase and returns close to its initial value for the late phase of growth, where the population stabilizes, the viscosity of the mutant strain culture decreases steeply, still in the exponential phase, remains constant for some time, and increases again, reaching a constant plateau at a maximum value for the late phase of growth. These complex viscoelastic behaviors, which were observed to be shear-stress-dependent, are a consequence of two coupled effects: the cell density continuous increase and its changing interacting properties. The viscous and elastic moduli of strain COL culture, obtained with oscillatory shear, exhibit power-law behaviors whose exponents are dependent on the bacteria growth stage. The viscous and elastic moduli of the mutant culture have complex behaviors, emerging from the different relaxation times that are associated with the large molecules of the medium and the self-organized structures of bacteria. Nevertheless, these behaviors reflect the bacteria growth stage.
Longtime behavior of one-dimensional biofilm models with shear dependent detachment rates.
Abbas, Fazal; Sudarsan, Rangarajan; Eberl, Hermann J
2012-04-01
We investigate the role of non shear stress and shear stressed based detachment rate functions for the longterm behavior of one-dimensional biofilm models. We find that the particular choice of a detachment rate function can affect the model prediction of persistence or washout of the biofilm. Moreover, by comparing biofilms in three settings: (i) Couette flow reactors, (ii) Poiseuille flow with fixed flow rate and (iii) Poiseuille flow with fixed pressure drop, we find that not only the bulk flow Reynolds number but also the particular mechanism driving the flow can play a crucial role for longterm behavior. We treat primarily the single species-case that can be analyzed with elementary ODE techniques. But we show also how the results, to some extent, can be carried over to multi-species biofilm models, and to biofilm models that are embedded in reactor mass balances.
Flexural eczema versus atopic dermatitis
DEFF Research Database (Denmark)
Jacob, Sharon E; Goldenberg, Alina; Nedorost, Susan
2015-01-01
Flexural eczema and atopic dermatitis are frequently synonymized. As respiratory atopy is rarely tested for and found in these patients, systematically equating a flexural distribution of dermatitis with atopic dermatitis may too frequently result in misclassified diagnoses and potentially missed...
Effect of stress ratio on long life fatigue behavior of Ti-Al alloy under flexural loading
Institute of Scientific and Technical Information of China (English)
XUE Hong-qian; TAO Hua; SHAO Ren-ping; B.CLAUDE
2008-01-01
A new ultrasonic three-point bending fatigue test device was introduced to investigate fatigue life ranging up to 1010 cycles and associated fracture behavior of Ti-Al alloy. Tests were performed at a frequency of 20kHz with stress ratio R=0.5 and R=0.7 at ambient temperature in air. Three groups of specimens with different surface roughness were applied to investigate the effect of surface roughness on fatigue life. Furthermore, optical microscopy (OM) and scanning electron microscopy (SEM) were used for microstructure characteristic and fracture surface analysis. The S-N curves obtained show that fatigue failure occurs in the range of 105-1010 cycles, and the asymptote of S-N curve inclines slightly in very high cycle regime, but is not horizontal for R=0.5. Fatigue limit appears after 108 cycles for R=0.7. Surface roughness (the maximum roughness is no more than 3μm) has no influence on the fatigue properties in the high cycle regime. A detailed investigation on fatigue fracture surface shows that the Ti-Al alloy studied here is a binary alloy in the microstructure composed of α2-Ti3Al and γ-Ti-Al with fully lamellar microstructure. Fractography shows that fatigue failures are mostly initiated on the surface of specimens, also, in very high cycle regime, subsurface fatigue crack initiation can be found. Interlamellar fatigue crack initiation is predominant in the Ti-Al alloy with fully lamellar structure. Fatigue crack growth is mainly in transgranular mode.
Analytical study of building height effects over Steel Plate Shear Wall Behavior
Directory of Open Access Journals (Sweden)
Benyamin Kioumarsi
2016-09-01
Full Text Available In the latest three decades, the steel plate shear walls (SPSW system has emerged as a promising lateral load resisting system for both construction new buildings and retrofit of existing buildings. This system has acceptable stiffness for control of structure displacement, ductile failure mechanism and high energy absorption. This paper will quantify the effect of increasing the height over analytical behavior of SPSW (height effect. Considering abundant emergence of high-rise buildings all over the world in recent years and their need for strengthening, the importance of the studies presented in this paper cannot be overemphasized for optimum height usage of SPSW lateral resisting system. The study was performed through design of four models of dual system with special moment frames capable of resisting at least 25% of prescribed seismic forces. In this article, structure buildings consisting of 5, 10, 15 and 20 stories have been modelled. Results consisting of story shear absorption, support reaction forces, lateral story displacement and drift index have investigated for different cases. Results show that SPSW absorbs more shears at the lower stories than top stories. Furthermore, axial reaction of edge supports experience decreasing rate corresponding to increase in the story numbers. Drift magnitude of steel plate shear wall with the 5 stories has the maximum value at the top story while the systems with the 10 and the 15 stories have maximum drift at lower stories.
Influence of Particle Morphology on 3D Kinematic Behavior and Strain Localization of Sheared Sand
Energy Technology Data Exchange (ETDEWEB)
Alshibli, Khalid A.; Jarrar, Maha F.; Druckrey, Andrew M.; Al-Raoush, Riyadh I.
2017-02-01
The constitutive behavior of sheared sand is highly influenced by particle morphology, gradation, mineralogy, specimen density, loading condition, stress path, and boundary conditions. The current literature lacks a three-dimensional (3D) systematic experimental study that investigates the influence of particle morphology, confining pressure, and specimen density on the failure mode of sheared sand. In this paper, surface texture, roundness, and sphericity of three uniform sands and glass beads with similar grain size were quantified by using 3D images of particles. In situ nondestructive 3D synchrotron microcomputed tomography (SMT) was used to monitor the deformation of medium-dense and very dense dry sand specimens that were tested under axisymmetric triaxial loading condition at 15 and 400 kPa confining pressures. The particles were identified and tracked in 3D as shearing progressed within the specimens, and maps of incremental particle translation and rotation were developed and used to uncover the relationship between particle morphology, specimen density, and confining pressure on the deformation and failure mode of sheared sand. This paper discusses the relationship between the failure mode and particle morphology, specimen density, and confining pressure.
Institute of Scientific and Technical Information of China (English)
高剑平; 温群昊; 罗丹; 罗民; 林杨
2011-01-01
为了充分利用CFRP材料高强的优势,抑制加固梁早期剥离破坏,本文提出一种附加锚固措施:内锁锚固系统,并进行了6根CFRP布加固钢筋混凝土梁抗弯性能试验研究,以验证这种内锁锚固系统对早期剥离破坏的抑制效果,同时研究控制参数对加固效果(破坏特征、承载力、刚度、裂缝开展等)的影响规律.试验结果表明:这种锚固方法能阻止CFRP布的剥离向端部发展,将弯剪裂缝引起的剥离限制在局部区域内,抑制其产生滑移；可提高极限荷载10％ ～ 20％,提高抗弯刚度7％～34％,有效降低梁的裂缝宽度.通过对比,发现减小开槽间距对梁的受弯影响不大,适当增加开槽宽度可提高梁的抗弯刚度.%To take full advantage of high strength advantage of carbon Fiber Reinforced Plastic(CFRP) , and resolve the problem of the debonding failure of concrete beams strengthened with CERP, a new anchor system which CERP strips is proposed in this paper. Six reinforced concrete ( RC) beams strengthened with CFRP sheets are tested to evaluate the flexural behavior. The effect of anchor system on avoiding the debonding failure is validated. Furthermore, the influence of control parameters on reinforcement effect is investigated, including failure characteristics, bearing capacity, stiffness, crack developing and so on. The results show that the anchor system can prevent the debonding of CFRP from expanding to the end of CFRP due to the crack of bend and shear loads. It means the debonding of CFRP is restricted to the local area and slippage is inhibited. Besides, the ultimate load can be increased by 10% to 20% , and bending rigidity can be increased by 7% to 34% . The crack width of beams is decreased effectively. It is found that reducing the space of grooves has little influence on bearing capacity, and bending rigidity would be properly raised due to the increase of the width of grooves.
Armwood, Catherine K.
In this project, 26 fiber-reinforced mortar (FRM) mixtures are evaluated for their workability and strength characteristics. The specimens tested include two control mixtures and 24 FRMs. The mixtures were made of two types of binders; Type N Portland cement lime (Type N-PCL) and Natural Hydrated Lime 5 (NHL5); and 6 fiber types (5 synthetic fibers and one organic). When tested in flexure, the results indicate that majority of the synthetic fiber mixtures enhanced the performance of the mortar and the nano-nylon and horse hair fibers were the least effective in improving the mortar's modulus of rupture, ductility, and energy absorption. Four FRMs that improved the mortar's mechanical properties most during the flexural strength test were then used to conduct additional experiments. The FRM's compressive strength, as well as flexural and shear bond strength with clay and concrete masonry units were determined. Those four mixtures included Type N-PCL as the binder and 4 synthetic fibers. They were evaluated at a standard laboratory flow rate of 110% +/- 5% and a practical field flow rate of 130% +/- 5%. Results indicate that the use of fibers decreases the compressive strength of the mortar most of the time. However, the bond strength test results were promising: 81% of the FRM mixtures increased the flexural bond strength of the prism. The mixtures at 110 +/- 5% flow rate bonded better with concrete bricks and those ate 130+/-5% flow rate bonded better with clay bricks. The results of the shear bond strength show 50% of the FRM mixtures improved the shear bond strength. The FRM mixtures at 110+/-5% flow rate bonded with clay units provided the most improvement in shear bond strength compared to control specimen results. Along with detailed discussions and derived conclusions of these experiments, this dissertation includes recommendations for the most feasible FRM for different applications.
Energy Technology Data Exchange (ETDEWEB)
Gupta, S.A.; Cochran, H.D.; Cummings, P.T. [Department of Chemical Engineering, University of Tennessee, Knoxville, Tennessee 37996-2200 (United States)]|[Chemical Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6268 (United States)
1997-12-01
In this three part study, nonequilibrium molecular dynamics simulation of the rheology of confined films is used to explore the microscopic properties and response of model lubricants under shear. The rheological behavior of two alkanes that differ in molecular structural complexity is examined: tetracosane (C{sub 24}H{sub 50}), which is a linear alkane, and squalane (C{sub 30}H{sub 62}), which has six symmetrically placed methyl branches along a 24 carbon backbone. The model lubricants are confined between model walls that have short chains tethered to them, thus screening the wall details. Shear flow is generated by moving the walls at constant velocity, and various properties are calculated after attainment of steady state. Heat generated by viscous dissipation is removed by thermostatting the first two atoms of the tethered molecules at 300 K, which allows a temperature profile to develop across the width of the lubricant layer. This paper details the molecular model and simulation method, and examines interfacial slip at the interface between the tethered chains and the fluid alkane. The effects of various parameters on the slip behavior are presented. Two subsequent papers respectively address the structural features of these liquid alkanes under shear flow and compare the viscosities from independent calculations of the bulk and confined fluids. {copyright} {ital 1997 American Institute of Physics.}
Experimental research of mechanical behavior of porcine brain tissue under rotational shear stress.
Li, Gang; Zhang, Jianhua; Wang, Kan; Wang, Mingyu; Gao, Changqing; Ma, Chao
2016-04-01
The objective of this paper is to investigate mechanical behavior of porcine brain tissue with a series of rotational shear stress control experiments. To this end, several experiments including stress sweep tests, frequency sweep tests and quasi-static creep tests were designed and conducted with a standard rheometer (HAAKE RheoStress6000). The effects of the loading stress rates to mechanical properties of brain tissue were also studied in stress sweep tests. The results of stress sweep tests performed on the same brain showed that brain tissue had an obvious regional inhomogeneity and the mechanical damage occurred at the rotational shear stress of 10-15Pa. The experimental data from three different loading stress rates demonstrated that the mechanical behavior of porcine brain tissue was loading stress rate dependent. With the decrease of loading stress rate, a stiffer mechanical characteristic of brain tissue was observed and the occurrence of mechanical damage can be delayed to a higher stress. From the results of frequency sweep tests we found that brain tissue had almost completely elastic properties at high frequency area. The nonlinear creep response under the rotational shear stress of 1, 3, 5, 7 and 9Pa was shown in results of creep tests. A new nonlinear viscoelastic solid model was proposed for creep tests and matched well with the test data. Considering the regional differences, loading stress rates and test conditions effects, loss tangent tan δ in porcine brain tissue showed a high uniformity of 0.25-0.45.
STUDY ON INTERMITTENT SHEAR FLOW AND RELAXATION BEHAVIOR OF THERMOTROPIC LIQUID CRYSTALLINE POLYMER
Institute of Scientific and Technical Information of China (English)
Ruo-Bing Yu; Chi-Xing Zhou; Wei Yu
2005-01-01
Intermittent shear flow including start-up flow and small oscillatory amplitude time sweep or stress relaxation after cessation of shear flow was used to study the rheological behavior and internal structure of thermotropic liquid crystalline polymer (TLCP). There are two kinds of intermittent shear flow: all start-up flows are in the same direction (intermittent flow forward: IFF) and start-up flows change their directions alternately (intermittent flow reversal: IFR). The results show that the stress of start-up flow of IFF and IFR in the test process is not superposed, indicating different changes of internal structure of thermotropic LCP (TLCP). Two main factors affect structure changes in the experimental time scale. One relates to long-term texture relaxation process, the other is an interchain reaction that becomes important after 30 min. The two factors raise the stress of IFF, but express complex effects for the stress of IFR. The latter factor becomes very important at long time annealing process. The relaxation behavior was also studied by the application of wide range relaxation spectrum calculated from the combined dynamic modulus, which gave three characteristic relaxation times (0.3, 10 and 600 s)ascribable to the relaxations of less-phase orientation, domain orientation, and domain deformation, respectively. The result also shows that the domain coalescence (texture relaxation), a long relaxation time, is a much slow process and lasts beyond 2400 s of the test time.
Analysis of flexural wave cloaks
Directory of Open Access Journals (Sweden)
Alfonso Climente
2016-12-01
Full Text Available This work presents a comprehensive study of the cloak for bending waves theoretically proposed by Farhat et al. [see Phys. Rev. Lett. 103, 024301 (2009] and later on experimentally realized by Stenger et al. [see Phys. Rev. Lett. 108, 014301 (2012]. This study uses a semi-analytical approach, the multilayer scattering method, which is based in the Kirchoff-Love wave equation for flexural waves in thin plates. Our approach was unable to reproduce the predicted behavior of the theoretically proposed cloak. This disagreement is here explained in terms of the simplified wave equation employed in the cloak design, which employed unusual boundary conditions for the cloaking shell. However, our approach reproduces fairly well the measured displacement maps for the fabricated cloak, indicating the validity of our approach. Also, the cloak quality has been here analyzed using the so called averaged visibility and the scattering cross section. The results obtained from both analysis let us to conclude that there is room for further improvements of this type of flexural wave cloak by using better design procedures.
Analysis of flexural wave cloaks
Climente, Alfonso; Torrent, Daniel; Sánchez-Dehesa, José
2016-12-01
This work presents a comprehensive study of the cloak for bending waves theoretically proposed by Farhat et al. [see Phys. Rev. Lett. 103, 024301 (2009)] and later on experimentally realized by Stenger et al. [see Phys. Rev. Lett. 108, 014301 (2012)]. This study uses a semi-analytical approach, the multilayer scattering method, which is based in the Kirchoff-Love wave equation for flexural waves in thin plates. Our approach was unable to reproduce the predicted behavior of the theoretically proposed cloak. This disagreement is here explained in terms of the simplified wave equation employed in the cloak design, which employed unusual boundary conditions for the cloaking shell. However, our approach reproduces fairly well the measured displacement maps for the fabricated cloak, indicating the validity of our approach. Also, the cloak quality has been here analyzed using the so called averaged visibility and the scattering cross section. The results obtained from both analysis let us to conclude that there is room for further improvements of this type of flexural wave cloak by using better design procedures.
Optical measurement on dynamic buckling behavior of stiffened composite panels under in-plane shear
Lei, Zhenkun; Bai, Ruixiang; Tao, Wang; Wei, Xiao; Leng, Ruijiao
2016-12-01
The buckling behavior and failure mode of a composite panel stiffened by I-shaped stringers under in-plane shear is studied using digital fringe projection profilometry. The basic principles of the dynamic phase-shifting technique, multi-frequency phase-unwrapping technique and inverse-phase technique for nonlinear error compensation are introduced. Multi-frequency fringe projection profilometry was used to monitor and measure the change in the morphology of a discontinuous surface of the stiffened composite panel during in-plane shearing. Meanwhile, the strain history of multiple points on the skin was obtained using strain rosettes. The buckling mode and deflection of the panel at different moments were analyzed and compared with those obtained using the finite element method. The experimental results validated the FEM analysis.
Performance evaluation of HSC beams with low flexural reinforcement
Directory of Open Access Journals (Sweden)
T.M. Elrakib
2013-04-01
Full Text Available The main objective of the current research is to establish experimental data for minimum flexural reinforcement, ρmin, of high strength concrete (HSC rectangular beams. Nine full-scale singly reinforced beams with flexural reinforcement ratios varying from 50% to 100% of the minimum limit specified by the ACI 363R-35were tested in flexure. Concrete compressive strengths of 52, 73 and 96.5 MPa were used. The test results including crack patterns, deflections and strains in the tensile flexural steel bars show that a 25% reduction of the ACI 363R-35 limit for the ρmin would result in a satisfactory flexural beam behavior with a reserve flexural parameter (Py,/Pcr ⩾ 1.29 and a displacement ductility index λΔ > 5 for all concrete grades which may lead to good savings in the amount of the flexural reinforcement. Also, it was noted that the displacement ductility index λΔ increased as the concrete compressive strength increased for the same ratio (ρ/ρmin up to 75 MPa and then decreases as fcu increases. For the same concrete compressive strength with low values of flexural reinforcement ratio, ρ, the displacement ductility index λΔ increased as ρ increased. The experimental results of this study were compared with the limits specified by available codes and researches.
Discrete element modeling of sand behavior in a biaxial shear test
Institute of Scientific and Technical Information of China (English)
Zhi-yi HUANG; Zhong-xuan YANG; Zhen-yu WANG
2008-01-01
The mechanical behavior of sand is very complex,and depends on factors including confining pressure,density,and drainage condition.A soil mass Call be contractive or dilative when subjected to shear loading,and eventually reaches an ultimate state,referred to as the critical state in soil mechanics.Conventional approach to explore the mechanical behavior of sand mainly relies on the experimental tests in laboratory.This paper gives an alternative view to this subject using discrete element method (DEM),which has attracted much attention in recent years.The implementation of the DEM is carried out by a series of numerical tests on granular assemblies with varying initial densities and confining pressures,under different test configurations.The results demonstrate that such numerical simulations can produce correct responses of the sand behavior in general,including the critical state response,as compared to experimental observations.In addition,the DEM can further provide details of the microstructure evolutions during shearing processes,and the resulting induced anisotropy can be fully captured and quantified in the particle scale.
Shear behavior of squalane and tetracosane under extreme confinement. II. Confined film structure
Energy Technology Data Exchange (ETDEWEB)
Gupta, S.A.; Cochran, H.D.; Cummings, P.T. [Department of Chemical Engineering, University of Tennessee, Knoxville, Tennessee 37996-2200 (United States)]|[Chemical Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6268 (United States)
1997-12-01
This paper focuses on the structural characteristics of confined squalane and tetracosane under shear flow conditions. Nonequilibrium molecular dynamics simulation is used to explore the rheology of these model lubricants. A preceding paper describes the molecular model and the simulation method, and examines interfacial slip. The lubricants are confined between model walls that have short chains tethered to them, thus screening the wall details. In this paper we examine the density profiles and chain conformations of the alkanes under shear flow conditions. Our results indicate a profound influence of the walls on the fluid structure. In particular, when the wall spacing is close to an integral multiple of the molecular diameter, tetracosane shows the formation of distinct layers with the molecules being in a fully extended state. This behavior is not observed for squalane. Under shear flow conditions the molecules tend to orient parallel to the walls, as would be expected, with a greater degree of orientation (a) close to the walls, (b) at the positions of local density maxima, and (c) at higher strain rates. {copyright} {ital 1997 American Institute of Physics.}
Zhong, C; Zhang, H; Cao, Q P; Wang, X D; Zhang, D X; Ramamurty, U; Jiang, J Z
2016-08-02
Molecular dynamics simulations were employed to investigate the plastic deformation within the shear bands in three different metallic glasses (MGs). To mimic shear bands, MG specimens were first deformed until flow localization occurs, and then the volume of the material within the localized regions was extracted and replicated. Homogeneous deformation that is independent of the size of the specimen was observed in specimens with shear band like structure, even at a temperature that is far below the glass transition temperature. Structural relaxation and rapid cooling were employed to examine the effect of free volume content on the deformation behavior. This was followed by detailed atomic structure analyses, employing the concepts of Voronoi polyhedra and "liquid-like" regions that contain high fraction of sub-atomic size open volumes. Results suggest that the total fraction of atoms in liquid-like regions is a key parameter that controls the plastic deformation in MGs. These are discussed in the context of reported experimental results and possible strategies for synthesizing monolithic amorphous materials that can accommodate large tensile plasticity are suggested.
Behavior of R/C Cylindrical Panel Subjected to Combined Axial and Shear Loadings
Hara, Takashi
2009-01-01
p. 1722-1730 Reinforced concrete (R/C) cylindrical panels have been applied to the roof or the underground structures. Also, in constructing a high rise building, an R/C wall is often used to improve the lateral rigidity of the building comparing with beam column systems under wind or seismic loading. In this paper, the behavior of R/C cylindrical shell under combined axial and lateral shear loadings is analyzed numerically. R/C cylindrical shells are often adopted for the core wa...
Kinugasa, Ryuta; Oda, Toshiaki; Komatsu, Toshihiko; Edgerton, V Reggie; Sinha, Shantanu
2013-11-01
Muscle fascicles insert into a sheet-like aponeurosis. Adjacent aponeuroses are structurally in contact with each other, and ultimately merge into a common tendon. Consequently, fascicle shortening in planes of tissue layers in adjacent compartments must cause sliding between aponeuroses parallel to the acting forces. In this study, we used velocity-encoded, phase-contrast, and water-saturated spin-lattice relaxation time-weighted imaging to identify and track fascicle and aponeurosis behaviors of human medial gastrocnemius (MG) and soleus (Sol) during 15° dorsiflexion to 30° plantarflexion contractions of the ankle. Interaponeurosis shear strain, which was defined as the relative displacement of the aponeurosis at the fascicle end points (insertion) of the MG and Sol, was an average of 1.35 ± 0.27% (range 1.12 ∼ 1.87%), indicating that the strain is greater in the aponeurosis of MG fascicle insertion than the Sol. The myotendinous junction (MTJ) displacement increased significantly with decreasing interaponeurosis shear strain (P < 0.05). The magnitude of interaponeurosis shear strain had significant correlation with the temporal difference between the time at which the peak aponeurosis displacement of the MG and Sol occurred (P < 0.05). Our model also indicated that theoretical MTJ displacement varies in relation to temporal difference: no temporal difference caused the largest MTJ displacement and presence of temporal differences indicated a reduction in MTJ displacement. Therefore, we concluded that interaponeurosis shear strain is a mechanism enabling individual muscle contraction and thus specific loading of the tendon and joint.
Dong, Hongying; Cao, Wanlin; Wu, Haipeng; Qiao, Qiyun; Yu, Chuanpeng
2015-03-01
In this paper, a steel-concrete multi-energy dissipation composite shear wall, comprised of steel-reinforced concrete (SRC) columns, steel plate (SP) deep beams, a concrete wall and energy dissipation strips, is proposed. In order to study the multi-energy dissipation behavior and restorability after an earthquake, two stages of low cyclic loading tests were carried out on ten test specimens. In the first stage, test on five specimens with different number of SP deep beams was carried out, and the test lasted until the displacement drift reached 2%. In the second stage, thin SPs were welded to both sides of the five specimens tested in the first stage, and the same test was carried out on the repaired specimens (designated as new specimens). The load-bearing capacity, stiffness, ductility, hysteretic behavior and failure characteristics were analyzed for both stages and the results are discussed herein. Extrapolating from these results, strength calculation models and formulas are proposed herein and simulations using ABAQUS carried out; they show good agreement with the test results. The study demonstrates that SRC columns, SP deep beams, concrete wall and energy dissipation strips cooperate well and play an important role in energy dissipation. In addition, this study shows that the shear wall has good recoverability after an earthquake, and that the welding of thin SP's to repair a deformed wall is a practicable technique.
Directory of Open Access Journals (Sweden)
M. A. Algorafi
2011-07-01
Full Text Available Externally Prestressed Segmented (EPS concrete beams are generally used in the construction of bridge structures. External Prestressed technique uses tendons that are placed completely outside the concrete section and attached to the concrete at anchorages and deviators only. Segmented bridge is a bridge built in short sections. Segmented bridge applies smart technique that is a part of an engineering management. EPS bridges are affected by combined stresses i.e., bending, shear, normal, and torsion stresses especially at the segments interface joints. Previous studies on EPS bridges did not include the effect of torsion in the load carrying capacity and other structural behavior. This paper presents an experimental investigation of the structural behavior of EPS bridged under combined bending, shear, normal, and torsion stresses. The aim of this paper is to improve the existing equation to include the effect of torsion in estimating the failure load of EPS bridge. A parametric study was carried out to investigate the effect of different external tendon layouts and different levels of torsion.
Directory of Open Access Journals (Sweden)
Heidenreich, Sebastian
2008-02-01
Full Text Available Shear thickening, i.e. the increase of the viscosity with increasing shear rate as it occurs in dense colloidal dispersions and polymeric fluids is an intriguing phenomenon with a considerable potential for technical applications. The theoretical description of this phenomenon is patterned after the thermodynamic and mesoscopic modeling of the orientational dynamics and the flow behavior of liquid crystals in the isotropic and nematic phases, where the theoretical basis is well-established. Even there the solutions of the relevant equations recently yielded surprises: not only stable flow alignment and a periodic behavior (tumbling are found as response to an imposed stationary shear flow but also irregular and chaotic dynamics occurs for certain parameter ranges. To treat shear-thickening fluids, a non-linear Maxwell model equation for the symmetric traceless part of the stress tensor has been proposed in analogy to the equations obeyed by the alignment tensor of nematics. The fluid-solid transition is formally analogous to the isotropic-nematic transition. In addition to shear-thickening and shear-thinning fluids, substances with yield stress can be modeled. Furthermore, periodic stick-slip-like motions and also chaotic behavior are found. In the latter cases, the instantaneous entropy production is not always positive. Yet it is comforting that its long-time average is in accord with the second law.
双向纤维腹板增强夹层结构的弯曲性能%Flexural Behavior of Two-way Fiber Reinforced Sandwich Structure
Institute of Scientific and Technical Information of China (English)
刘子建; 刘伟庆; 万里; 方海; 陆伟东
2012-01-01
设计并制备了双向纤维腹板增强复合材料夹层梁,对其受弯性能进行了四点弯曲试验研究,开展单、双向格构夹层梁性能对比分析,研究不同腹板高度、厚度对夹层梁受弯性能的影响,基于经典夹层梁理论及简支梁受弯基本理论,研究夹层梁破坏模式和机理。试验结果表明：双向格构腹板增强形式能有效提高该夹层结构的极限变形能力与受弯极限承载力,且随着试件厚度加大提高作用更明显;保持夹层梁基本参数不变,增加试件高度有利于提高刚度,增强夹层梁极限承载力;单一增加腹板厚度有益于提高该夹层梁的极限变形能力,但不能明显提高其极限承载力。理论分析表明：采用铁木辛柯梁理论求得的挠度理论值与实验值吻合较好。%Two-way fiber reinforced sandwich beam was designed and fabricated by vacuum infusion molding process(VIMP).Flexural behavior of the beam was experimentally analyzed by the four-point bending test.Comparative analysis was made between the one-and two-way sandwich beams,and then the failure mode were observed from the test species with different webs height and web thickness.Based on the classic sandwich beam theory and the bending theory of simply supported beam,the ultimate bearing capacity and the failure mode of the sandwich composites beam were studied.It is concluded that the extreme deformation ability and the ultimate bearing capacity could be improved by the two-way lattice webs,while the improvement would become obvious with increasing sample thickness.Besides,both the stiffness and ultimate bearing capacity could also be effectively enhanced by increasing web height.Moreover,the extreme deformation could be improved by increasing web thickness,while the improvement of ultimate bearing capacity could hardly be observed.In addition,theoretical analysis indicates that deflection calculated by Timoshenko Beam Theory is in good accordance with the
Directory of Open Access Journals (Sweden)
M. Said
2013-12-01
Full Text Available The shear behavior of reinforced concrete wide beams was investigated. The experimental program consisted of nine beams of 29 MPa concrete strength tested with a shear span-depth ratio equal to 3.0. One of the tested beams had no web reinforcement as a control specimen. The flexure mode of failure was secured for all of the specimens to allow for shear mode of failure. The key parameters covered in this investigation are the effect of the existence, spacing, amount and yield stress of the vertical stirrups on the shear capacity and ductility of the tested wide beams. The study shows that the contribution of web reinforcement to the shear capacity is significant and directly proportional to the amount and spacing of the shear reinforcement. The increase in the shear capacity ranged from 32% to 132% for the range of the tested beams compared with the control beam. High grade steel was more effective in the contribution of the shear strength of wide beams. Also, test results demonstrate that the shear reinforcement significantly enhances the ductility of the wide beams. In addition, shear resistances at failure recorded in this study are compared to the analytical strengths calculated according to the current Egyptian Code and the available international codes. The current study highlights the need to include the contribution of shear reinforcement in the Egyptian Code requirements for shear capacity of wide beams.
Lemarchand, Claire A.; Bailey, Nicholas P.; Todd, Billy D.; Daivis, Peter J.; Hansen, Jesper S.
2015-06-01
The rheology and molecular structure of a model bitumen (Cooee bitumen) under shear are investigated in the non-Newtonian regime using non-equilibrium molecular dynamics simulations. The shear viscosity, normal stress differences, and pressure of the bitumen mixture are computed at different shear rates and different temperatures. The model bitumen is shown to be a shear-thinning fluid at all temperatures. In addition, the Cooee model is able to reproduce experimental results showing the formation of nanoaggregates composed of stacks of flat aromatic molecules in bitumen. These nanoaggregates are immersed in a solvent of saturated hydrocarbon molecules. At a fixed temperature, the shear-shinning behavior is related not only to the inter- and intramolecular alignments of the solvent molecules but also to the decrease of the average size of the nanoaggregates at high shear rates. The variation of the viscosity with temperature at different shear rates is also related to the size and relative composition of the nanoaggregates. The slight anisotropy of the whole sample due to the nanoaggregates is considered and quantified. Finally, the position of bitumen mixtures in the broad literature of complex systems such as colloidal suspensions, polymer solutions, and associating polymer networks is discussed.
Gaudino, D.; Pasquino, R.; Kriegs, H.; Szekely, N.; Pyckhout-Hintzen, W.; Lettinga, M. P.; Grizzuti, N.
2017-03-01
The shear flow dynamics of linear and branched wormlike micellar systems based on cetylpyridinium chloride and sodium salicylate in brine solution is investigated through rheometric and scattering techniques. In particular, the flow and the structural flow response are explored via velocimetry measurements and rheological and rheometric small-angle neutron scattering (SANS) experiments, respectively. Although all micellar solutions display a similar shear thinning behavior in the nonlinear regime, the experimental results show that shear banding sets in only when the micelle contour length L ¯ is sufficiently long, independent of the nature of the micellar connections (either linear or branched micelles). Using rheometric SANS, we observe that the shear banding systems both show very similar orientational ordering as a function of Weissenberg number, while the short branched micelles manifest an unexpected increase of ordering at very low Weissenberg numbers. This suggests the presence of an additional flow-induced relaxation process that is peculiar for branched systems.
Flexure fatigue testing of 90 deg graphite/epoxy composites
Peck, Ann Nancy W.
1995-01-01
A great deal of research has been performed characterizing the in-plane fiber-dominated properties, under both static and fatigue loading, of advanced composite materials. To the author's knowledge, no study has been performed to date investigating fatigue characteristics in the transverse direction. This information is important in the design of bonded composite airframe structure where repeated, cyclic out-of-plane bending may occur. Recent tests characterizing skin/stringer debond failures in reinforced composite panels where the dominant loading in the skin is flexure along the edge of the frame indicate failure initiated either in the skin or else the flange, near the flange tip. When failure initiated in the skin, transverse matrix cracks formed in the surface skin ply closest to the flange and either initiated delaminations or created matrix cracks in the next lower ply, which in turn initiated delaminations. When failure initiated in the flanges, transverse cracks formed in the flange angle ply closest to the skin and initiated delamination. In no configuration did failure propagate through the adhesive bond layer. For the examined skin/flange configurations, the maximum transverse tension stress at failure correlates very well with the transverse tension strength of the composites. Transverse tension strength (static) data of graphite epoxy composites have been shown to vary with the volume of material stressed. As the volume of material stressed increased, the strength decreased. A volumetric scaling law based on Weibull statistics can be used to predict the transverse strength measurements. The volume dependence reflects the presence of inherent flaws in the microstructure of the lamina. A similar approach may be taken to determine a volume scale effect on the transverse tension fatigue behavior of graphite/epoxy composites. The objective of this work is to generate transverse tension strength and fatigue S-N characteristics for composite materials using
Shear-thickening behavior of modified silica nanoparticles in polyethylene glycol
Energy Technology Data Exchange (ETDEWEB)
Yu Kejing; Cao Haijian, E-mail: caohaijian20010@163.com; Qian Kun; Sha Xiaofei; Chen Yanping [Jiangnan University, Key Laboratory of Eco-textiles, Ministry of Education (China)
2012-03-15
The surface of silica nanoparticles with an average diameter of 650 nm was modified by ball milling and chemical treatment with ethylene glycol (EG). The Fourier-transform infrared spectra and particle size analysis methods were used to characterize the modified silica nanoparticles. The morphologies of the silica nanoparticles before and after the different surface treatments were examined by transmission electron microscope, scanning electron microscope. The rheological behaviors of modified silica suspensions in polyethylene glycol were studied by using Anton-paar 301 stress-controlled rheometer. The results of rheological tests indicated that the surface treatments had a great effect on increasing the maximum weight fraction of silica nanoparticles in Shear-thickening fluids, especially treated by the chemical method with EG.
THE NONLINEAR BEHAVIOR OF INTERFACE BETWEEN TWO-PHASE SHEAR FLOW WITH LARGE DENSITY RATIOS
Institute of Scientific and Technical Information of China (English)
DONG Yu-hong
2006-01-01
The Navier-Stokes equations for the two-dimensional incompressible flow are used to investigate the effects of the Reynolds number and the Weber number on the behavior of interface between liquid-gas shear flow.In the present study, the density ratios are fixed at approximately 100-103.The interface between the two phases is resolved using the level-set approach.The Reynolds number and the Weber number, based on the gas, are selected as 400-10000 and 40-5000, respectively.In the past, simulations reappeared the amplitude of interface growth predicted by viscous Orr-Sommerfeld linear theory, verifying the applicability and accuracy of the numerical method over a wide range of density and viscosity ratios; now, the simulations show that the nonlinear development of ligament elongated structures and resulted in the subsequent breakup of the heavier fluid into drops.
Shear wave dispersion behaviors of soft, vascularized tissues from the microchannel flow model.
Parker, K J; Ormachea, J; McAleavey, S A; Wood, R W; Carroll-Nellenback, J J; Miller, R K
2016-07-07
The frequency dependent behavior of tissue stiffness and the dispersion of shear waves in tissue can be measured in a number of ways, using integrated imaging systems. The microchannel flow model, which considers the effects of fluid flow in the branching vasculature and microchannels of soft tissues, makes specific predictions about the nature of dispersion. In this paper we introduce a more general form of the 4 parameter equation for stress relaxation based on the microchannel flow model, and then derive the general frequency domain equation for the complex modulus. Dispersion measurements in liver (ex vivo) and whole perfused placenta (post-delivery) correspond to the predictions from theory, guided by independent stress relaxation measurements and consideration of the vascular tree structure.
Meier, R.; Kirdar, C.; Rudolph, N.; Zaremba, S.; Drechsler, K.
2014-05-01
Efficient production and consumption of energy are of greatest importance for contemporary industries and their products. This has led to an increasing application of lightweight materials in general and of Carbon Fiber Reinforced Plastics (CFRP) in particular. However, broader application of CFRP is often limited by high costs and manual labor production processes. These constraints are addressed by Liquid Composite Molding (LCM) processes. In LCM a dry fibrous preform is placed into a cavity and infiltrated mostly by thermoset resins; epoxy resins are wide spread in CFRP applications. One crucial parameter for a fast mold filling is the viscosity of the resin, which is affected by the applied shear rates as well as temperature and curing time. The work presented focuses on the characterization of the shear thinning behavior of epoxy resins. Furthermore, the correlation with the conditions in vibration assisted LCM processes, where additional shear rates are created during manufacture, is discussed. Higher shear rates result from high frequencies and/or high amplitudes of the vibration motions which are created by a vibration engine mounted on the mold. In rheological investigations the shear thinning behavior of a representative epoxy resin is studied by means of rotational and oscillatory experiments. Moreover, possible effects of shear rates on the chemical curing reaction are studied. Here, the time for gelation is measured for different levels of shear rates in a pre-shearing phase. Based on the rheological studies, the beneficial effect of vibration assistance in LCM processes with respect to mold filling can further be predicted and utilized.
A coupled damage-plasticity model for the cyclic behavior of shear-loaded interfaces
Carrara, P.; De Lorenzis, L.
2015-12-01
The present work proposes a novel thermodynamically consistent model for the behavior of interfaces under shear (i.e. mode-II) cyclic loading conditions. The interface behavior is defined coupling damage and plasticity. The admissible states' domain is formulated restricting the tangential interface stress to non-negative values, which makes the model suitable e.g. for interfaces with thin adherends. Linear softening is assumed so as to reproduce, under monotonic conditions, a bilinear mode-II interface law. Two damage variables govern respectively the loss of strength and of stiffness of the interface. The proposed model needs the evaluation of only four independent parameters, i.e. three defining the monotonic mode-II interface law, and one ruling the fatigue behavior. This limited number of parameters and their clear physical meaning facilitate experimental calibration. Model predictions are compared with experimental results on fiber reinforced polymer sheets externally bonded to concrete involving different load histories, and an excellent agreement is obtained.
Directory of Open Access Journals (Sweden)
Yurisman
2010-11-01
Full Text Available This paper presents results of numerical and experimental study of shear link behavior, utilizing diagonal stiffener on web of steel profile to increase shear link performance in an eccentric braced frame (EBF of a steel structure system. The specimen is to examine the behavior of shear link by using diagonal stiffener on web part under static monotonic and cyclic load. The cyclic loading pattern conducted in the experiment is adjusted according to AISC loading standards 2005. Analysis was carried out using non-linear finite element method using MSC/NASTRAN software. Link was modeled as CQUAD shell element. Along the boundary of the loading area the nodal are constraint to produce only one direction loading. The length of the link in this analysis is 400mm of the steel profile of WF 200.100. Important parameters considered to effect significantly to the performance of shear link have been analyzed, namely flange and web thicknesses, , thickness and length of web stiffener, thickness of diagonal stiffener and geometric of diagonal stiffener. The behavior of shear link with diagonal web stiffener was compared with the behavior of standard link designed based on AISC 2005 criteria. Analysis results show that diagonal web stiffener is capable to increase shear link performance in terms of stiffness, strength and energy dissipation in supporting lateral load. However, differences in displacement ductility’s between shear links with diagonal stiffener and shear links based on AISC standards have not shown to be significant. Analysis results also show thickness of diagonal stiffener and geometric model of stiffener to have a significant influence on the performance of shear links. To perform validation of the numerical study, the research is followed by experimental work conducted in Structural Mechanic Laboratory Center for Industrial Engineering ITB. The Structures and Mechanics Lab rotary PAU-ITB. The experiments were carried out using three test
Flexural creep behaviour of jute polypropylene composites
Chandekar, Harichandra; Chaudhari, Vikas
2016-09-01
Present study is about the flexural creep behaviour of jute fabric reinforced polypropylene (Jute-PP) composites. The PP sheet and alkali treated jute fabric is stacked alternately and hot pressed in compression molding machine to get Jute-PP composite laminate. The flexural creep study is carried out on dynamic mechanical analyzer. The creep behaviour of the composite is modeled using four-parameter Burgers model. Short-term accelerated creep testing is conducted which is later used to predict long term creep behaviour. The feasibility of the construction of a master curve using the time-temperature superposition (TTS) principle to predict long term creep behavior of unreinforced PP and Jute-PP composite is investigated.
Yousefi, Ali R; Eivazlou, Razieh; Razavi, Seyed M A
2016-10-01
The rheological properties of food hydrocolloids are remarkably influenced by the quality of solvent/cosolutes in a food system. In this work, the steady shear flow behavior of sage seed gum (SSG, 0.5% w/w) at the presence of different levels of salts (KCl & MgCl2, 0-100mM) and sugars (sucrose, lactose & glucose, 0-6% w/w) was studied. It was found that the rheological properties of SSG were affected by the type of sugars and salts and their concentrations as well. Synergistic interaction was observed between SSG and sugars which enhanced the viscosity of gum solutions, while salts addition diminished the viscosity. SSG solutions exhibited a shear thinning behavior at all conditions tested. Various time-independent rheological models were used to fit the shear stress-shear rate data, although the Herschel-Bulkley (R(2)=0.994-0.999) and Sisko (R(2)=0.995-0.999) models showed the best results to describe the flow behavior of SSG. In the presence of salts, the yield stress (τ0), consistency coefficient (k), and flow behavior index (n) values decreased. The k and τ0 values enhanced and the n value lowered in the presence of sugars. Divalent cations of Mg(2+) and sucrose roughly showed more effect on rheological parameters than others.
Institute of Scientific and Technical Information of China (English)
司炳君; 孙治国; 杜修力; 王东升; 黄照南
2011-01-01
Quasi-static tests were conducted to study the seismic flexural-shear damage mechanisms and rapid repair techniques for earthquake damaged bridge piers.Six original pier specimens of circular cross sections were severely damaged under cyclic lateral force and constant axial load,and the damaged specimens were subsequently repaired using high-fluidity concrete with high early-strength and Carbon Fiber-Reinforced Polymer（CFRP）,and then put into test again within a week.The failure pattern,strength,ductility and dissipated energy parameters and stiffness degradation of the repaired specimens were compared with the original ones.It is founded that the ultimate performance of bridge piers designed according to current seismic design codes of JTG/T B02-01—2008 and Caltrans with minimum confining reinforcement ratios may be dominated by shear failure in the plastic hinge zones.The repaired specimens show lower initial stiffness and larger yield displacement as a result of the pre-existing damage.But the failure for all of the repaired specimens was due to flexure,with higher strength,larger or the same ductility and dissipated energy parameters and recovered stiffness,which demonstrated the effectiveness of the proposed repair techniques.%为研究钢筋混凝土桥墩的地震弯剪破坏机理与震后快速修复技术,首先进行了6个圆形截面桥墩试件的拟静力试验,试件均发生严重弯剪破坏,然后利用高流动性早强混凝土和CFRP布对其进行快速修复并在1周内重新进行加载试验,将原桥墩与修复后试件的破坏形态、承载力、延性与耗能能力、刚度退化等进行了对比分析。研究表明：塑性铰区配箍满足我国《公路桥梁抗震设计细则》（JTG/T B02-01—2008）及美国Caltrans规范要求的钢筋混凝土桥墩试件,最终仍有可能因塑性铰区抗剪强度不足发生弯剪破坏。由于初始损伤的存在,震后修复
Epackachi, Siamak
The seismic performance of rectangular steel-plate concrete (SC) composite shear walls is assessed for application to buildings and mission-critical infrastructure. The SC walls considered in this study were composed of two steel faceplates and infill concrete. The steel faceplates were connected together and to the infill concrete using tie rods and headed studs, respectively. The research focused on the in-plane behavior of flexure- and flexure-shear-critical SC walls. An experimental program was executed in the NEES laboratory at the University at Buffalo and was followed by numerical and analytical studies. In the experimental program, four large-size specimens were tested under displacement-controlled cyclic loading. The design variables considered in the testing program included wall thickness, reinforcement ratio, and slenderness ratio. The aspect ratio (height-to-length) of the four walls was 1.0. Each SC wall was installed on top of a re-usable foundation block. A bolted baseplate to RC foundation connection was used for all four walls. The walls were identified to be flexure- and flexure-shear critical. The progression of damage in the four walls was identical, namely, cracking and crushing of the infill concrete at the toes of the walls, outward buckling and yielding of the steel faceplates near the base of the wall, and tearing of the faceplates at their junctions with the baseplate. A robust finite element model was developed in LS-DYNA for nonlinear cyclic analysis of the flexure- and flexure-shear-critical SC walls. The DYNA model was validated using the results of the cyclic tests of the four SC walls. The validated and benchmarked models were then used to conduct a parametric study, which investigated the effects of wall aspect ratio, reinforcement ratio, wall thickness, and uniaxial concrete compressive strength on the in-plane response of SC walls. Simplified analytical models, suitable for preliminary analysis and design of SC walls, were
Hydrodynamic behavior in the outer shear layer of partly obstructed open channels
Ben Meftah, Mouldi; De Serio, Francesca; Mossa, Michele
2014-06-01
Despite the many studies on flow in partly obstructed open channels, this issue remains of fundamental importance in order to better understand the interaction between flow behavior and the canopy structure. In the first part of this study we suggest a new theoretical approach able to model the flow pattern within the shear layer in the unobstructed domain, adjacent to the canopy area. Differently from previous studies, the new analytical solution of flow momentum equations takes into account the transversal velocity component of the flow, which is modelled as a linear function of the streamwise velocity. The proposed theoretical model is validated by different experiments carried out on a physical model of a very large rectangular channel by the research group of the Department of Civil, Environmental, Building Engineering and Chemistry of the Technical University of Bari. An array of vertical, rigid, and circular steel cylinders was partially mounted on the bottom in the central part of the flume, leaving two lateral areas of free flow circulation near the walls. The three-dimensional flow velocity components were measured using a 3D Acoustic Doppler Velocimeter. A comparison of the measured and predicted data of the present study with those obtained in other previous studies, carried out with different canopy density, show a non-dependence of this analytical solution on the array density and the Reynolds number. In the second part of the paper, detailed observations of turbulent intensities and spanwise Reynolds stresses in the unobstructed flow are analyzed and discussed. Differently from some earlier studies, it was observed that the peak of the turbulence intensity and that of the spanwise Reynolds stress are significantly shifted toward the center of the shear layer.
Flexural eczema versus atopic dermatitis.
Jacob, Sharon E; Goldenberg, Alina; Nedorost, Susan; Thyssen, Jacob P; Fonacier, Luz; Spiewak, Radoslaw
2015-01-01
Flexural eczema and atopic dermatitis are frequently synonymized. As respiratory atopy is rarely tested for and found in these patients, systematically equating a flexural distribution of dermatitis with atopic dermatitis may too frequently result in misclassified diagnoses and potentially missed opportunity for intervention toward improving patients' symptoms and quality of life. We present a critical review of the available evidence for the atopic dermatitis diagnosis and discuss the similarities between atopic dermatitis and allergic contact dermatitis. Because neither flexural predilection nor atopy is specific for atopic dermatitis, we conclude that the term atopic dermatitis is a misnomer and propose an etymologic reclassification of atopic dermatitis to "atopy-related" dermatitis. Allergic contact dermatitis can induce an atopic dermatitis-like phenotype, and thus, flexural dermatitis cannot be assumed as atopic without further testing. Patch testing should at least be considered in cases of chronic or recurrent eczema regardless of the working diagnosis.
Smith, Stuart T.; Badami, Vivek G.; Dale, Jami S.; Xu, Ying
1997-03-01
This paper presents closed form equations based on a modification of those originally derived by Paros and Weisbord in 1965, for the mechanical compliance of a simple monolithic flexure hinge of elliptic cross section, the geometry of which is determined by the ratio ɛ of the major and minor axes. It is shown that these equations converge at ɛ=1 to the Paros and Weisbord equations for a hinge of circular section and at ɛ ⇒∞ to the equations predicted from simple beam bending theory for the compliance of a cantilever beam. These equations are then assessed by comparison with results from finite element analysis over a range of geometries typical of many hinge designs. Based on the finite element analysis, stress concentration factors for the elliptical hinge are also presented. As a further verification of these equations, a number of elliptical hinges were manufactured on a CNC milling machine. Experimental data were produced by applying a bending moment using dead weight loading and measuring subsequent angular deflections with a laser interferometer. In general, it was found that predictions for the compliance of elliptical hinges are likely to be within 12% for a range of geometries with the ratio βx(=t/2ax) between 0.06 and 0.2 and for values of ɛ between 1 and 10.
Pravin*, Jeyapratha
2016-01-01
This paper ambit to evaluate the flexural strength of glass fiber sandwich panels with varying z-pins pitches. Failure of sandwich panel are delamination and core shear, to minimize the crack propagation, pins are inserted in z-direction, by varying pitches through its thickness. During the insertion of pin, may cause the material some damage. Despite the damage, flexural property does not affected due interpolation of pins. Although the experiment were pull out with a phenomenal results of z...
Punching Shear Behavior of Continuous Bubbled Reinforced Reactive Powder Concrete Slab
Directory of Open Access Journals (Sweden)
Mohammad Redha K. Mahmood
2017-03-01
Full Text Available This paper presents an experimental investigation on punching shear behavior of continuous bubbled reinforced Reactive Powder Concrete (RPC slabs. Bubbled slab is one of the various types of voided slabs. It consists of bubbles placed inside a concrete slab which will reduce the self-weight of the structure by about 35% (Tina Lai 2009. On the other hand, using RPC make it possible for structural member to have smaller dimensions due to the great strength of this type of concrete. In this study, these two method to increase the building spaces dimensions by reducing self-weigh of the structure by using bubbled slabs and to decrease the structural members' dimensions by using RPC have been investigated together. To study the punching shear behavior of continuous bubbled flat slabs such as the ultimate load carrying capacity, central deflection and slabs crack pattern at the ultimate load, nine different types of slabs were tested. The parameters of the study were type of concrete (RPC and Normal Concrete (NC, bubbles diameter to slab thickness ratio (D/t of (0.6 and 0.7, bubbles location (at all slab area, started from distance D and 1.5D from the center slab and solid slab. The test results show that the crack pattern and ultimate load capacity as well as maximum deflection depends on all of the mentioned parameters, were by increasing (D/t ratio the ultimate load capacity increases about (6.49 and 9.58% for slabs with bubbles started at distance 2D and 3D, respectively. But in the slabs with bubbles at all slab area the ultimate load and the maximum deflection decreases about (6.63 and 9.47% and (7.96 and 6.84% for RPC and NC slabs, respectively. Also, the solid slab increases the ultimate load about (5.28% compare to bubbled slab at all area. It was found that by removing bubbles from center of the slab at distance 2D and 3D the ultimate load will increase about (14.72 and 8.76%, respectively for slabs with (D/t = 0.6 compare to slabs with
Dong, Xia; Liu, Xianggui; Liu, Wei; Han, Charles C.; Wang, Dujin
2015-03-01
The morphology evolution and rheological response of a near-critical composition polybutadiene /polyisoprene blend and solution-polymerized styrene-butadiene rubber/polyisoprene/silica ternary composites after various shear flow were in situ studied with the rheological and rheo-optical techniques. The relationship between the morphology of the blend during the relaxation after the cessation of steady shear with different shear rates and their corresponding rheological properties was successfully established. It was found that the different shear-induced morphologies under steady shear would relax to the equilibrium states via varied mechanisms after the shear cessation. The storage modulus G' increased significantly in the breakup process of the string-like phase. In long time scale, silica slowed down the succeeding breakup of the string-phase domains and simultaneous coalescence of broken droplets, and then effectively reduced the droplets size and stabilized the morphology. The authors thank the financial support from National Natural Science Foundation of China (No. 51173195).
Non-Newtonian behavior and molecular structure of Cooee bitumen under shear flow
DEFF Research Database (Denmark)
Lemarchand, Claire; Bailey, Nicholas; Daivis, Peter
2015-01-01
The rheology and molecular structure of a model bitumen (Cooee bitumen) under shear are investigated in the non-Newtonian regime using non-equilibrium molecular dynamics simulations. The shear viscosity, normal stress differences, and pressure of the bitumen mixture are computed at different shear...... rates and different temperatures. The model bitumen is shown to be a shear-thinning fluid at all temperatures. In addition, the Cooee model is able to reproduce experimental results showing the formation of nanoaggregates composed of stacks of flat aromatic molecules in bitumen. These nanoaggregates...
Experimental Validation of the Transverse Shear Behavior of a Nomex Core for Sandwich Panels
Farooqi, M. I.; Nasir, M. A.; Ali, H. M.; Ali, Y.
2017-05-01
This work deals with determination of the transverse shear moduli of a Nomex® honeycomb core of sandwich panels. Their out-of-plane shear characteristics depend on the transverse shear moduli of the honeycomb core. These moduli were determined experimentally, numerically, and analytically. Numerical simulations were performed by using a unit cell model and three analytical approaches. Analytical calculations showed that two of the approaches provided reasonable predictions for the transverse shear modulus as compared with experimental results. However, the approach based upon the classical lamination theory showed large deviations from experimental data. Numerical simulations also showed a trend similar to that resulting from the analytical models.
Wrinkle-crease interaction behavior simulation of a rectangular membrane under shearing
Institute of Scientific and Technical Information of China (English)
C.G.Wang; H.-F.Tan; X.-D.He
2011-01-01
Wrinkling analysis of a rectangular membrane with a single crease under shearing is performed to understand the wrinkle-crease interaction behaviors. The crease is considered by introducing the residual stresses from creasing and the effective modulus into the baseline configuration with assumed circular cross-sectional crease geometry.The wrinkling analysis of the creased membrane is then performed by using the direct perturb-force(DP) simulation technique which is based on our modified displacement components(MDC) method. Results reveal that the crease may influence the stress transfer path in the membrane and further change the wrinkling direction. The crease appears to improve the bending stiffness of the membrane which has an effective resistance on the wrinkling evolution. The effects of the crease orientation on wrinkle-crease interaction are studied toward the end of this paper. The results show that the wrinkling amplitude,wavelength,and direction increase as the crease orientation increases,and the wrinkling number decreases with the increasing crease orientation. These resuits will be of great benefit to the analysis and the control of the wrinkles in the membrane structures.
Directory of Open Access Journals (Sweden)
Chitta Sai Sandeep
2017-03-01
Full Text Available The micromechanical behavior at grain contacts subjected to tangential and normal forces is of major importance in geotechnical engineering research and practice. The development of the discrete element method (DEM over the past three decades necessitated a more systematic study on the experimental grain contact behavior of real soil grains as DEM simulations use as input tangential and normal load–displacement relationships at grain contacts. In this study, experimental results conducted at the City University of Hong Kong are presented exploring the tangential load–displacement behavior of geological materials. The focus of the study is to explore the possible effect of repeating the shearing test to the same grains on the inter-particle coefficient of friction accounting for the level of the applied normal load. Additionally, the study reports on the frictional behavior of different geological materials including quartz sand grains, denoted as Leighton Buzzard sand (LBS in the study and completely decomposed volcanic granules denoted as CDV. Quartz grains may find applications as proppant in petroleum engineering, whilst the CDV granules consisted of a material taken from a recent landslide in Hong Kong, whose applications are related to debris flow. Through the micromechanical sliding experiments, the inter-particle coefficient of friction was quantified following shearing paths of about 60 to 200 microns. While at the smallest vertical load of 1 N, there was not observed a notable effect of the repeating shearing for the LBS grains, it was noticed that for small to medium vertical loads, between 2 and 5 N, the repeating shearing reduced the friction at the contacts of the LBS grains. This trend was clear between the first and second shearing, but additional cycles did not further alter the frictional response. However, at greater vertical loads, between 7 and 10 N, the results showed a continuous increase in the dynamic inter
Institute of Scientific and Technical Information of China (English)
杨春艳; 王朝进; 董凤波; 胡敏
2014-01-01
本文采用自由落锤抗弯冲击装置研究了改性煤沥青碳纤维混凝土的抗弯冲击性能。随着纤维掺量的增加，混凝土冲击性能显著提高。纤维体积掺量为0.076%时，改性煤沥青碳纤维混凝土的初裂冲击次数、破坏冲击次数分别比素混凝土提高1458％、1462％，当掺量大于0.076%时，冲击韧性不再明显提高。%Flexural impact behavior of reinforced concrete with modified coal tar pitch carbon fiber was studied by free drop hammer device in this paper. The results showed that impact behavior of concrete was improved significantly with increase of fiber volume content. When it was 0.076%, first crack impact and fracture impact times of carbon fiber reinforced concrete were increased 1458%and 1462%than that of plain concrete. However, when more than 0.076%, impact behavior of fiber concrete was no longer improved.
Tensile and Flexural Properties of Ultra High Toughness Cemontious Composite
Institute of Scientific and Technical Information of China (English)
LI Hedong; XU Shilang; Christopher K Y Leung
2009-01-01
The tensile and flexural properties of polyvinyl alcohol(PVA)fiber reinforced ultra high toughness cementitious composite(UHTCC)were investigated.The composite,tested at the age of 14 d,28 d and 56 d,shows extremely remarkable pseudo strain hardening behavior,saturated mul-tiple cracking and ultra high ultimate strain capacity above 4%under uniaxial loading.Also,the cor-responding crack widths are controlled under 50 μm even at 56 days age.In the third point bending tests on thin plate specimens,the composite shows ultra high flexural ductility and multiple cracking on the tension surface.The high ultimate flexural strength/first tensile strength ratio of about 5 verifies the pseudo strain hardening behavior of UHTCC.SEM observation on fracture surfaces provides in-direct evidence of optimal design for the composite.
Cooperative effects of matrix stiffness and fluid shear stress on endothelial cell behavior.
Kohn, Julie C; Zhou, Dennis W; Bordeleau, François; Zhou, Allen L; Mason, Brooke N; Mitchell, Michael J; King, Michael R; Reinhart-King, Cynthia A
2015-02-03
Arterial hemodynamic shear stress and blood vessel stiffening both significantly influence the arterial endothelial cell (EC) phenotype and atherosclerosis progression, and both have been shown to signal through cell-matrix adhesions. However, the cooperative effects of fluid shear stress and matrix stiffness on ECs remain unknown. To investigate these cooperative effects, we cultured bovine aortic ECs on hydrogels matching the elasticity of the intima of compliant, young, or stiff, aging arteries. The cells were then exposed to laminar fluid shear stress of 12 dyn/cm(2). Cells grown on more compliant matrices displayed increased elongation and tighter EC-cell junctions. Notably, cells cultured on more compliant substrates also showed decreased RhoA activation under laminar shear stress. Additionally, endothelial nitric oxide synthase and extracellular signal-regulated kinase phosphorylation in response to fluid shear stress occurred more rapidly in ECs cultured on more compliant substrates, and nitric oxide production was enhanced. Together, our results demonstrate that a signaling cross talk between stiffness and fluid shear stress exists within the vascular microenvironment, and, importantly, matrices mimicking young and healthy blood vessels can promote and augment the atheroprotective signals induced by fluid shear stress. These data suggest that targeting intimal stiffening and/or the EC response to intima stiffening clinically may improve vascular health.
Institute of Scientific and Technical Information of China (English)
于天来; 张(王乐)元; 耿立伟
2011-01-01
Based on the static experiment of 13 concrete beams strengthened by external prestressing Carbon Fiber-Reinforced Polymer(CFRP) tendons ,this study attempts to analyzes the flexural behavior of strengthened beams with external CFPR tendon, including damage model, crack, deformation, concrete strain, steel bar strain and CFRP tendon strain.Moreover,it comparatively analyzes the effect of various factors on ultimate load of strengthened concrete beams, and discusses the simplified algorithm of flexural capacity.The test results demonstrate that the average strain of concrete beam with CFRP tendons also conforms to the plane section assumption.When the bending angle of external CFRP tendons is more than 10 ° ,it was disadvantageous to fiexural capacity of concrete beams.Besides, with the increase of concrete strength, flexural capacity of reinforced concrete beams increase was not obvious.Therefore, in the reinforcement design process, the load level of the original beams should be considered.What is more, after ignoring the quadratic effects of the external prestressing CFRP tendons reinforcement system, the flexural capacity calculation could be simplified, and the simplified calculation results are in good agreement with the measured results.%目的 研究体外CFRP筋加固钢筋混凝土简支梁的抗弯性能,探讨体外预应力CFRP筋加固混凝土梁抗弯承载力的计算方法.方法 通过对13根体外CFRP筋加固试验梁的静载试验,分析加固梁的破坏形态、裂缝开展、挠度、混凝土应变、体内受拉钢筋和体外CFRP筋应变的变化情况,对比分析各种因素对加固梁极限荷载的影响.结果 加载过程中,跨中截面混凝土的平均应变沿梁高基本呈直线分布;当体外CFRP筋弯折角度大于10°时,对梁体抗弯性能不利;随着混凝土强度的提高,加固梁抗弯承载力的提高不明显.对于体内受拉钢筋配筋率较大的梁,采用体外预应力CFRP筋加
High accuracy flexural hinge development
Santos, I.; Ortiz de Zárate, I.; Migliorero, G.
2005-07-01
This document provides a synthesis of the technical results obtained in the frame of the HAFHA (High Accuracy Flexural Hinge Assembly) development performed by SENER (in charge of design, development, manufacturing and testing at component and mechanism levels) with EADS Astrium as subcontractor (in charge of doing an inventory of candidate applications among existing and emerging projects, establishing the requirements and perform system level testing) under ESA contract. The purpose of this project has been to develop a competitive technology for a flexural pivot, usuable in highly accurate and dynamic pointing/scanning mechanisms. Compared with other solutions (e.g. magnetic or ball bearing technologies) flexural hinges are the appropriate technology for guiding with accuracy a mobile payload over a limited angular ranges around one rotation axes.
Broadband cloaking for flexural waves
Zareei, Ahmad
2016-01-01
The governing equation for elastic waves in flexural plates is not form invariant, and hence designing a cloak for such waves faces a major challenge. Here, we present the design of a perfect broadband cloak for flexural waves through the use of a nonlinear transformation, and by matching term-by-term the original and transformed equations. For a readily achievable flexural cloak in a physical setting, we further present an approximate adoption of our perfect cloak under more restrictive physical constraints. Through direct simulation of the governing equations, we show that this cloak, as well, maintains a consistently high cloaking efficiency over a broad range of frequencies. The methodology developed here may be used for steering waves and designing cloaks in other physical systems with non form-invariant governing equations.
Large shear rate behavior for the Hébraud-Lequeux model
Institute of Scientific and Technical Information of China (English)
OLIVIER; Julien
2012-01-01
The Hébraud-Lequeux model is a model describing the flow of soft glassy material in a simple shear flow configuration.It is given by a kinetic/Fokker-Planck-type equation whose coefficients depend on the shear rate of the experiment.In this paper we want to study what happens to the stationary solutions of this model when the shear rate is asymptotically large.In order to do that,we expand the solution of the equation using singular perturbation tools.In the end,we rigorously prove the estimate of Hébraud and Lequeux that the material asymptotically behaves as a Newtonian fluid.
Wafai, Husam
2016-09-20
Fiber-reinforced composites with improved dissipation of energy during impact loading have recently been developed based on a polypropylene copolymer commonly called impact polypropylene (IPP). Composites made of IPP reinforced with glass fibers (GF) are particularly attractive to the automotive industry due to their low cost and good impact resistance. In such composites, the cooling rate varies depending on processing techniques and manufacturing choices. Here, we study the effects of the cooling rate of GF-IPP composites on shear behavior, which is critical in impact applications, using [±45]s monotonic and cyclic (load/unload) tensile specimens. The specimens were manufactured under a wide range of cooling rates (3 °C/min, 22 °C/min, 500–1000 °C/min). Mainly dominated by the properties of the matrix, the global shear behavior of GF-IPP composites differed considerably with respect to the cooling rate. However, the performance of the fiber-matrix interface (chemically modified) appeared to be unaffected by the range of cooling rates used in this study. We found that the cooling rate has a minor effect on the rate of damage accumulation, while it strongly modifies the shear-activated rate-dependant viscoelastic behavior. © 2016 Elsevier Ltd
Flexural vibrations of finite composite poroelastic cylinders
Indian Academy of Sciences (India)
Sandhya Rani Bandari; Srisailam Aleti; Malla Reddy Perati
2015-04-01
This paper deals with the flexural vibrations of composite poroelastic solid cylinder consisting of two cylinders that are bonded end to end. Poroelastic materials of the two cylinders are different. The frequency equations for pervious and impervious surfaces are obtained in the framework of Biot’s theory of wave propagation in poroelastic solids. The gauge invariance property is used to eliminate one arbitrary constant in the solution of the problem. This would lower the number of boundary conditions actually required. If the wavelength is infinite, frequency equations are degenerated as product of two determinants pertaining to extensional vibrations and shear vibrations. In this case, it is seen that the nature of the surface does not have any influence over shear vibrations unlike in the case of extensional vibrations. For illustration purpose, three composite cylinders are considered and then discussed. Of the three, two are sandstone cylinders and the third one is resulted when a cylindrical bone is implanted with Titanium. In either case, phase velocity is computed against aspect ratios.
Morphology Evolution and Dynamic Viscoelastic Behavior of Ternary Elastomer Blends under Shear
Dong, Xia; Liu, Xianggui; Han, Charles C.; Wang, Dujin
The influence of nanoparticle geometry, such as size and shape, on the phase morphology of partially miscible binary polymer blends under and after shear has been examined by rheological and rheo-optical techniques. The phase morphologies of the solution-polymerized styrene-butadiene rubber and low vinyl content polyisoprene (SSBR/LPI) blend systems were affected by the dispersion status of fillers which were determined by filler shapes and shear strength. Under weak shear flow, the domain morphology of the OMMT filled blend was much thinner than that of the SiO2 filled blend. Under strong shear flow, the string-like phase interface of the OMMT filled blend was much blurred compared with that of the SiO2 filled blend. After shear cessation, the orientation status of OMMT sheets determined the orientation of newborn domains. Combined morphology observation and rheological analysis showed that the anisotropic structure and the unfavorable bending energy of OMMT sheets played important roles on phase morphology and its evolution process during or after shear. The authors thank the financial support from National Natural Science Foundation of China (No.51173195).
Directory of Open Access Journals (Sweden)
Şevket Murat ŞENEL
2002-02-01
Full Text Available Computer program which investigates the effectiveness of confinement regions of shear walls was developed.Specimens which have unique web reinforcement and different confinement regions were analyzed by using this computer program. Data needed for theoratical computations were obtained by tensile testing of steel rods and by concrete specimen tests. Mander Method was applied to reflect confined concrete behavior. Strain hardening behavior of steel was included in computations. Effect of stirrup spacing and hook reinforcement was introduced together and seperately to understand the moment-curvature response of specimens.
Static deformation modeling and analysis of flexure hinges made of a shape memory alloy
Du, Zhijiang; Yang, Miao; Dong, Wei; Zhang, Dan
2016-11-01
The flexure hinge is a key element in compliant mechanisms to achieve continuous motion; however the motion range of a flexure hinge is severely restricted by the material’s allowable strain. Due to the superelasticity effect, shape memory alloys (SMAs) can undergo much larger strain than other metals; this means that they are excellent candidates for the fabrication of flexure hinges with a large motion range. In this paper, a simple static deformation modeling approach is proposed for a flexure hinge made of a SMA. The superelastic behavior of the SMA is described by Brinson’s constitutive model. The flexure hinge is considered as a non-prismatic cantilever beam associated with geometrical and material nonlinearities. Govern equations of the flexure hinge are derived and solved numerically by applying the nonlinear bending theory of the Euler-Bernoulli beam. Experimental tests show that the proposed modeling approach can predict the deformation of the flexure hinge precisely; the maximum relative error is less than 6.5%. Based on the static deformation model, the motion capacity, the stiffness characteristic and the rotational error of the flexure hinge are also investigated. The results reveal that the flexure hinge made of a SMA has great potential to construct compliant mechanisms with a large motion range.
An experimental study on flexural strength enhancement of concrete by means of small steel fibers
Directory of Open Access Journals (Sweden)
Abdoullah Namdar
2013-10-01
Full Text Available Cost effective improvement of the mechanical performances of structural materials is an important goal in construction industry. To improve the flexural strength of plain concrete so as to reduce construction costs, the addition of fibers to the concrete mixture can be adopted. The addition of small steel fibers with different lengths and proportion have experimentally been analyzed in terms of concrete flexural strength enhancement. The main objectives of the present study are related to the evaluation of the influence of steel fibers design on the increase of concrete flexural characteristics and on the mode of failure. Two types of beams have been investigated. The force level, deflection and time to failure of beams have been measured. The shear crack, flexural crack and intermediate shear-flexural crack have been studied. The steel fiber content controlled crack morphology. Flexural strength and time to failure of fiber reinforce concrete could be further enhanced if, instead of smooth steel fibers, corrugated fibers were used.
Characterization of flexure hinges for the French watt balance experiment
Directory of Open Access Journals (Sweden)
Pinot Patrick
2014-01-01
Full Text Available In the French watt balance experiment, the translation and rotation functions must have no backlash, no friction, nor the need for lubricants. In addition errors in position and movement must be below 100 nm. Flexure hinges can meet all of these criteria. Different materials, profile shapes and machining techniques have been studied. The flexure pivots have been characterized using three techniques: 1 an optical microscope and, if necessary, a SEM to observe the surface inhomogeneities; 2 a mass comparator to determine the bending stiffness of unloaded pivots; 3 a loaded beam oscillating freely under vacuum to study the dynamic behavior of loaded pivots.
Characterization of flexure hinges for the French watt balance experiment
Pinot, Patrick; Genevès, Gérard
2014-08-01
In the French watt balance experiment, the translation and rotation functions must have no backlash, no friction, nor the need for lubricants. In addition errors in position and movement must be below 100 nm. Flexure hinges can meet all of these criteria. Different materials, profile shapes and machining techniques have been studied. The flexure pivots have been characterized using three techniques: 1) an optical microscope and, if necessary, a SEM to observe the surface inhomogeneities; 2) a mass comparator to determine the bending stiffness of unloaded pivots; 3) a loaded beam oscillating freely under vacuum to study the dynamic behavior of loaded pivots.
Institute of Scientific and Technical Information of China (English)
方志; 刘明; 郑辉
2015-01-01
In order to study the mechanical behavior of prestressed reactive powder concrete (RPC) box girders ,the flexural behavior tests of two prestressed RPC box girders were carried out .T he force characteristic of RPC box girders and the influence of transverse prestressing force to its flexural performance were studied .The results show that the prestressed RPC box girders display a good deformation capacity ,with a maximal deflection of 1/50 of its span .The crack width and the short‐time stiffness of the RPC box girders can be calculated according to the formula in Technical Specif ication for Fiber Reinforced Concrete Structures (CECS 38 :2004) , with a coefficient of 0 .4 and 0 .2 considering influence from steel fiber , respectively . The transverse prestressing force in the top plate of RPC box girders has little influence on the flexural bearing capacity , but the force can make a more uniform strain distribution of the compressive concrete so as to reduce the shear‐lag effect and increase the ductility of the specimen .By applying a transverse prestressing force of 2 .95 M Pa (only 3 .1% of the RPC prism compressive strength of 94 MPa) at the top plate ,the effective distribution width of box girder increases by 10% ,and ductility index of specimen increases by 3% .The calculated formula to evaluate the cracking moment and the ultimate moment of a prestressed RPC box girders is proposed and verified by the experimental results .%为研究预应力活性粉末混凝土（RPC ）箱梁的正截面受力性能，进行了2片预应力RPC箱梁的抗弯性能试验，研究了RPC箱梁的受力变形特征以及顶板横向预应力对其抗弯性能的影响。结果表明：预应力RPC箱梁具有良好的变形能力，其极限变形可超过跨径的1／50；RPC箱梁正常使用阶段的裂缝宽度和短期刚度可参照《纤维混凝土结构技术规程》（CECS 38：2004）的相应公式计算，其中的钢纤维影响系数可分别取为0
Pengaruh Penggunaan Serat Baja Terhadap Flexural Toughness Reactive Powder Concrete
Directory of Open Access Journals (Sweden)
Widodo Kushartomo
2016-08-01
Full Text Available This research present flexural toughness behavior of local steel fiber reinforced reactive powder concrete produced with different steel fibers volume fraction and aspect ratio. Prismatic concrete specimens of 100 x 100 x 350 mm were prepared with and without steel fiber. Steel fiber was used of 0% (control, 1,0%, 1,5%, and 2,0% by volume and 75, 100 and 125 as aspect ratio. Specimens were de-molded after 24 hours and cured in water until 3 days, after that the speciments were cure by steam curing for 8 hours at 90°C. Flexural toughness of the prisms has been defined at 28 day old. The result show that the effects of fibre volume and aspec ratio on flexural toughness of reactive powder concrete are very significant.
Creep Behavior in Interlaminar Shear of a SiC/SiC Ceramic Composite with a Self-healing Matrix
Ruggles-Wrenn, M. B.; Pope, M. T.
2014-02-01
Creep behavior in interlaminar shear of a non-oxide ceramic composite with a multilayered matrix was investigated at 1,200 °C in laboratory air and in steam environment. The composite was produced via chemical vapor infiltration (CVI). The composite had an oxidation inhibited matrix, which consisted of alternating layers of silicon carbide and boron carbide and was reinforced with laminated Hi-Nicalon™ fibers woven in a five-harness-satin weave. Fiber preforms had pyrolytic carbon fiber coating with boron carbide overlay applied. The interlaminar shear properties were measured. The creep behavior was examined for interlaminar shear stresses in the 16-22 MPa range. Primary and secondary creep regimes were observed in all tests conducted in air and in steam. In air and in steam, creep run-out defined as 100 h at creep stress was achieved at 16 MPa. Larger creep strains were accumulated in steam. However, creep strain rates and creep lifetimes were only moderately affected by the presence of steam. The retained properties of all specimens that achieved run-out were characterized. Composite microstructure, as well as damage and failure mechanisms were investigated.
Flexural Vibration Characteristics of Initially Stressed Composite Plates
Directory of Open Access Journals (Sweden)
Rupesh Daripa
2010-01-01
Full Text Available The influence of localised in-plane load on the flexural vibration characteristics of isotropic and composite plates have been studied using a four-noded shear flexible high precision plate bending finite element. First, the critical buckling loads of such plates subjected to partial or concentrated compressive loads were calculated, then the linear and nonlinear flexural vibration frequencies were obtained. Limited parametric study was carried out to study the influences of location and distribution of tensile or compressive in-plane load on the vibration frequencies of such plates.Defence Science Journal, 2010, 60(1, pp.106-111, DOI:http://dx.doi.org/10.14429/dsj.60.117
Seismic behavior and mechanism analysis of innovative precast shear wall involving vertical joints
Institute of Scientific and Technical Information of China (English)
孙建; 邱洪兴
2015-01-01
To study the seismic performance and load-transferring mechanism of an innovative precast shear wall (IPSW) involving vertical joints, an experimental investigation and theoretical analysis were successively conducted on two test walls. The test results confirm the feasibility of the novel joints as well as the favorable seismic performance of the walls, even though certain optimization measures should be taken to improve the ductility. The load-transferring mechanism subsequently is theoretically investigated based on the experimental study. The theoretical results show the load-transferring route of the novel joints is concise and definite. During the elastic stage, the vertical shear stress in the connecting steel frame (CSF) distributes uniformly;and each high-strength bolt (HSB) primarily delivers vertical shear force. However, the stress in the CSF redistributes when the walls develop into the elastic-plastic stage. At the ultimate state, the vertical shear stress and horizontal normal stress in the CSF distribute linearly;and the HSBs at both ends of the CSF transfer the maximum shear forces.
Alexander, C. S.; Ding, J. L.; Asay, J. R.
2016-03-01
Magnetically applied pressure-shear (MAPS) is a new experimental technique that provides a platform for direct measurement of material strength at extreme pressures. The technique employs an imposed quasi-static magnetic field and a pulsed power generator that produces an intense current on a planar driver panel, which in turn generates high amplitude magnetically induced longitudinal compression and transverse shear waves into a planar sample mounted on the drive panel. In order to apply sufficiently high shear traction to the test sample, a high strength material must be used for the drive panel. Molybdenum is a potential driver material for the MAPS experiment because of its high yield strength and sufficient electrical conductivity. To properly interpret the results and gain useful information from the experiments, it is critical to have a good understanding and a predictive capability of the mechanical response of the driver. In this work, the inelastic behavior of molybdenum under uniaxial compression and biaxial compression-shear ramp loading conditions is experimentally characterized. It is observed that an imposed uniaxial magnetic field ramped to approximately 10 T through a period of approximately 2500 μs and held near the peak for about 250 μs before being tested appears to anneal the molybdenum panel. In order to provide a physical basis for model development, a general theoretical framework that incorporates electromagnetic loading and the coupling between the imposed field and the inelasticity of molybdenum was developed. Based on this framework, a multi-axial continuum model for molybdenum under electromagnetic loading is presented. The model reasonably captures all of the material characteristics displayed by the experimental data obtained from various experimental configurations. In addition, data generated from shear loading provide invaluable information not only for validating but also for guiding the development of the material model for
Energy Technology Data Exchange (ETDEWEB)
Gupta, S.A.; Cochran, H.D.; Cummings, P.T. [Department of Chemical Engineering, University of Tennessee, Knoxville, Tennessee 37996-2200 (United States)]|[Chemical Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6268 (United States)
1997-12-01
This study uses nonequilibrium molecular dynamics simulation to explore the rheology of confined liquid alkanes. Two alkanes that differ in molecular structural complexity are examined: tetracosane (C{sub 24}H{sub 50}), which is a linear alkane, and squalane (C{sub 30}H{sub 62}), which has six symmetrically placed methyl branches along a 24 carbon backbone. These model lubricants are confined between model walls that have short chains tethered to them, thus screening the wall details. This paper, the third of a three part series, compares the viscosities of the confined fluids to those of the bulk fluids. The alkanes are described by a well-documented potential model that has been shown to reproduce bulk experimental viscosity and phase equilibria measurements. Details of the simulation method, and structural information can be found in the preceding two papers of this series. The measured strain rates in these simulations range between 10{sup 8} and 10{sup 11} s{sup {minus}1}, which is typical of a number of practical applications. The confined fluids undergo extensive shear thinning, showing a power-law behavior. Comparison of results for the confined fluid to those for the bulk fluid reveal that, for the conditions examined, there is no difference between the bulk and confined viscosities for these alkanes. This observation is in contrast to experimental results at much lower strain rates (10{endash}10{sup 5} s{sup {minus}1}), which indicate the viscosities of the confined fluid to be much larger than the bulk viscosities. In making the comparison, we have carefully accounted for slip at the wall and have performed simulations of the bulk fluid at the same conditions of strain rate, temperature, and pressure as for the corresponding confined fluid. The viscosity is found to be independent of the wall spacing. The calculated power-law exponents are similar to experimentally observed values. We also note that the exponent increases with increasing density of the
Effect of boundary vibration on the frictional behavior of a dense sheared granular layer
Ferdowsi, B; Guyer, R A; Johnson, P A; Carmeliet, J
2014-01-01
We report results of 3D Discrete Element Method (DEM) simulations aiming at investigating the role of the boundary vibration in inducing frictional weakening in sheared granular layers. We study the role of different vibration amplitudes applied at various shear stress levels, for a granular layer in the stick-slip regime and in the steady-sliding regime. Results are reported in terms of friction drops and kinetic energy release associated with frictional weakening events. We find that larger vibration amplitude induces larger frictional weakening events. The results show evidence of a threshold below which no induced frictional weakening takes place. Friction drop size is found to be dependent on the shear stress at the time of vibration. A significant increase in the ratio between the number of slipping contacts to the number of sticking contacts in the granular layer is observed for large vibration amplitudes. These vibration-induced contact rearrangements enhance particle mobilization and induces a fricti...
Snijkers, F.
2016-03-31
We report upon the characterization of the steady-state shear stresses and first normal stress differences as a function of shear rate using mechanical rheometry (both with a standard cone and plate and with a cone partitioned plate) and optical rheometry (with a flow-birefringence setup) of an entangled solution of asymmetric exact combs. The combs are polybutadienes (1,4-addition) consisting of an H-skeleton with an additional off-center branch on the backbone. We chose to investigate a solution in order to obtain reliable nonlinear shear data in overlapping dynamic regions with the two different techniques. The transient measurements obtained by cone partitioned plate indicated the appearance of overshoots in both the shear stress and the first normal stress difference during start-up shear flow. Interestingly, the overshoots in the start-up normal stress difference started to occur only at rates above the inverse stretch time of the backbone, when the stretch time of the backbone was estimated in analogy with linear chains including the effects of dynamic dilution of the branches but neglecting the effects of branch point friction, in excellent agreement with the situation for linear polymers. Flow-birefringence measurements were performed in a Couette geometry, and the extracted steady-state shear and first normal stress differences were found to agree well with the mechanical data, but were limited to relatively low rates below the inverse stretch time of the backbone. Finally, the steady-state properties were found to be in good agreement with model predictions based on a nonlinear multimode tube model developed for linear polymers when the branches are treated as solvent.
FLEXURAL TOUGHNESS OF STEEL FIBER REINFORCED CONCRETE
Directory of Open Access Journals (Sweden)
Fehmi ÇİVİCİ
2006-02-01
Full Text Available Fiber concrete is a composite material which has mechanical and physical characteristics unlike plain concrete. One of the important mechanical characteristics of fiber concrete is its energy absorbing capability. This characteristics which is also called toughness, is defined as the total area under the load-deflection curve. A number of composite characteristics such as crack resistance, ductility and impact resistance are related to the energy absorbtion capacity. According to ASTM C 1018 and JSCE SF-4 the calculation of toughness is determined by uniaxial flexural testing. Fiber concrete is often used in plates such as bridge decks, airport pavements, parking areas, subjected to cavitation and erosion. In this paper, toughness has been determined according to ASTM C 1018 and JSCE SF-4 methods by testing beam specimens. Energy absorbing capacities of plain and steel fiber reinforced concrete has been compared by evaluating the results of two methods. Also plain and steel fiber reinforced plate specimens behaviors subjected to biaxial flexure are compared by the loaddeflection curves of each specimen.
Derivation of a poroelastic flexural shell model
Mikelic, Andro
2015-01-01
In this paper we investigate the limit behavior of the solution to quasi-static Biot's equations in thin poroelastic flexural shells as the thickness of the shell tends to zero and extend the results obtained for the poroelastic plate by Marciniak-Czochra and Mikeli\\'c. We choose Terzaghi's time corresponding to the shell thickness and obtain the strong convergence of the three-dimensional solid displacement, fluid pressure and total poroelastic stress to the solution of the new class of shell equations. The derived bending equation is coupled with the pressure equation and it contains the bending moment due to the variation in pore pressure across the shell thickness. The effective pressure equation is parabolic only in the normal direction. As additional terms it contains the time derivative of the middle-surface flexural strain. Derivation of the model presents an extension of the results on the derivation of classical linear elastic shells by Ciarlet and collaborators to the poroelastic shells case. The n...
Shear and Rapeseed Oil Addition Affect the Crystal Polymorphic Behavior of Milk Fat
DEFF Research Database (Denmark)
Kaufmann, Niels; Kirkensgaard, Jacob Judas Kain; Andersen, Ulf;
2013-01-01
The effect of shear on the crystallization kinetics of anhydrous milk fat (AMF) and blends with 20 and 30 % w/w added rapeseed oil (RO) was studied. Pulse 1H NMR was used to follow the a to b0 polymorphic transition. The NMR method was confirmed and supported by SAXS/WAXS experiments. Samples wer...
Predicting the shear–flexural strength of slender reinforced concrete T and I shaped beams
Cladera Bohigas, Antoni; Marí Bernat, Antonio Ricardo; Ribas González, Carlos Rodrigo; Bairán García, Jesús Miguel; Oller Ibars, Eva
2015-01-01
A mechanical model previously developed by the authors for the prediction of the shear flexural strength of slender reinforced concrete beams with rectangular cross-section with or without stirrups has been extended to beams with T and I cross-sections. The effects of the section shape on each shear transfer action have been identified and incorporated into the corresponding equations. General expressions for strength verification and transverse reinforcement design have been derived. The con...
Li, Wangnan; Cai, Hongneng; Li, Chao
2014-11-01
This paper deals with the characterization of the strength of the constituents of carbon fiber reinforced plastic laminate (CFRP), and a prediction of the static compressive strength of open-hole structure of polymer composites. The approach combined with non-linear analysis in macro-level and a linear elastic micromechanical failure analysis in microlevel (non-linear MMF) is proposed to improve the prediction accuracy. A face-centered cubic micromechanics model is constructed to analyze the stresses in fiber and matrix in microlevel. Non-interactive failure criteria are proposed to characterize the strength of fiber and matrix. The non-linear shear behavior of the laminate is studied experimentally, and a novel approach of cubic spline interpolation is used to capture significant non-linear shear behavior of laminate. The user-defined material subroutine UMAT for the non-linear share behavior is developed and combined in the mechanics analysis in the macro-level using the Abaqus Python codes. The failure mechanism and static strength of open-hole compressive (OHC) structure of polymer composites is studied based on non-linear MMF. The UTS50/E51 CFRP is used to demonstrate the application of theory of non-linear MMF.
Energy Technology Data Exchange (ETDEWEB)
Chono, S.; Tsuji, T. [Kochi Institute of Technology, Kochi (Japan)
1999-11-25
The Doi equations have been directly computed for shear and extensional flow without closure approximations. An extension is imposed on the shear flow plane. It is well-known that for simple shear flow there are three orientation regimes, depending on the magnitude of shear rate; rotational (tumbling), oscillatory (wagging), and stationary (aligning) orientation behaviors. When we add an extension to simple shear flow, the time period of tumbling is increased, while the order parameter in the regime is almost unchanged. In the wagging regime, however, both the time period and the order parameter are increased. Transitions from the tumbling and wagging regimes to the aligning regime are induced when more than a certain magnitude of extension is imposed on a system. An extension has also an effect to make the first normal stress difference positive. Furthermore, motion of individual molecules has been analyzed by integrating the Langevin equation. It is found that the aligning state in shear and extensional flow is due to an approximately stationary behavior of individual molecules, while the aligning state in simple shear flow is an apparently stationary behavior of a group of many rotational molecules. (author)
Effects of mode coupling on the admittance of an AT-cut quartz thickness-shear resonator
Institute of Scientific and Technical Information of China (English)
He Hui-Jing; Yang Jia-Shi; Zhang Wei-Ping; Wang Ji
2013-01-01
We study the effects of couplings to flexure and face-shear modes on the admittance of an AT-cut quartz plate thickness-shear mode resonator.Mindlin's two-dimensional equations for piezoelectric plates are employed.Electrically forced vibration solutions are obtained for three cases:pure thickness-shear mode alone; two coupled modes of thickness shear and flexure; and three coupled modes of thickness shear,flexure,and face shear.Admittance is calculated and its dependence on the driving frequency and the length/thickness ratio of the resonator is examined.Results show that near the thickness-shear resonance,admittance assumes maxima,and that for certain values of the length/thickness ratio,the coupling to flexure causes severe admittance drops,while the coupling to the face-shear mode causes additional admittance changes that were previously unknown and hence are not considered in current resonator design practice.
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AHMER ALI
2013-02-01
Full Text Available In recent years steel-concrete composite shear walls have been widely used in enormous high-rise buildings. Due to high strength and ductility, enhanced stiffness, stable cycle characteristics and large energy absorption, such walls can be adopted in the auxiliary building; surrounding the reactor containment structure of nuclear power plants to resist lateral forces induced by heavy winds and severe earthquakes. This paper demonstrates a set of nonlinear numerical studies on I-shaped composite steel-concrete shear walls of the nuclear power plants subjected to reverse cyclic loading. A three-dimensional finite element model is developed using ABAQUS by emphasizing on constitutive material modeling and element type to represent the real physical behavior of complex shear wall structures. The analysis escalates with parametric variation in steel thickness sandwiching the stipulated amount of concrete panels. Modeling details of structural components, contact conditions between steel and concrete, associated boundary conditions and constitutive relationships for the cyclic loading are explained. Later, the load versus displacement curves, peak load and ultimate strength values, hysteretic characteristics and deflection profiles are verified with experimental data. The convergence of the numerical outcomes has been discussed to conclude the remarks.
Institute of Scientific and Technical Information of China (English)
Sun Yuguo; Zhou Zhengong
2005-01-01
In this paper, the behavior of two collinear cracks in magneto-electro-elastic composite material under anti-plane shear stress loading is studied by the Schmidt method for permeable electric boundary conditions. By using the Fourier transform, the problem can be solved with a set of triple integral equations in which the unknown variable is the jump of displacements across the crack surfaces. In solving the triple integral equations, the unknown variable is expanded in a series of Jacobi polynomials. Numerical solutions are obtained. It is shown that the stress field is independent of the electric field and the magnetic flux.
Institute of Scientific and Technical Information of China (English)
SUN Yu-guo; WU Lin-zhi
2005-01-01
The dynamic behavior of two collinear cracks in magneto-electro-elastic composites under harmonic anti-plane shear waves is studied using the Schmidt method for the permeable crack surface conditions. By using the Fourier transform, the problem can be solved with a set of triple integral equations in which the unknown variable is the jump of the displacements across the crack surfaces. In solving the triple integral equations, the jump of the displacements across the crack surface is expanded in a series of Jacobi polynomials. It can be obtained that the stress field is independent of the electric field and the magnetic flux.
EFFECT OF FILLER LOADING ON PHYSICAL AND FLEXURAL PROPERTIES OF RAPESEED STEM/PP COMPOSITES
Directory of Open Access Journals (Sweden)
Seyed Majid Zabihzadeh
2011-03-01
Full Text Available The objective of the study is to develop a new filler for the production of natural filler thermoplastic composites using the waste rapeseed stalks. The long-term water absorption and thickness swelling behaviors and flexural properties of rapeseed filled polypropylene (PP composites were investigated. Three different contents of filler were tested: 30, 45, and 60 wt%. Results of long-term hygroscopic tests indicated that by the increase in filler content from 30% to 60%, water diffusion absorption and thickness swelling rate parameter increased. A swelling model developed by Shi and Gardner can be used to quantify the swelling rate. The increasing of filler content reduced the flexural strength of the rapeseed/PP composites significantly. In contrast to the flexural strength, the flexural modulus improved with increasing the filler content. The flexural properties of these composites were decreased after the water uptake, due to the effect of the water molecules.
Institute of Scientific and Technical Information of China (English)
杨晓辉; 卢锦花; 李克智; 张守阳; 杨茜; 曾燮榕
2012-01-01
The thermal expansion behavior of 2D-C/C composites and the effect of fatigue loading conditions on the thermal expansion of the composites were studied. The flexural fatigue experiment was made under the stress level of 70% and 90% , cycling times of 104 , 5 X 104 , 1 X 105 and 1.5x10 , and then the thermal behavior was investigated. The results show that fatigue loading didn't change the variation law that thermal expansion behavior is improved with the increased temperature. However, compared with the thermal expansion behavior of 2D-C/C composites at different fatigue loading conditions, the thermal expansion behavior of the samples after fatigue loading drops with increasing of the stress level and cycling times, which is due to the all kinds of fatigue damages generated during the fatigue loading.%研究了2D-C/C复合材料的热膨胀性能以及疲劳加载条件对其热膨胀性能的影响规律,分别进行了应力水平为70％、90％及循环周次为104、5×104、1×105和1.5×105次的弯-弯疲劳试验,并随后测试其热膨胀性能.结果表明,疲劳加载并没有改变其热膨胀性能随温度升高而增大的变化规律,但对比不同疲劳加载条件下2D-C/C复合材料的热膨胀性能,可发现疲劳加载后试样的热膨胀性能随着应力水平和循环周次的增大有降低趋势.经分析认为,这主要是由于疲劳加载过程中产生的各种疲劳损伤所致.
Lai, Wei-Jen
The mechanical behaviors of LiFePO4 battery cell and module specimens under in-plane constrained compression were investigated for simulations of battery cells, modules and packs under crush conditions. The experimental stress-strain curves were correlated to the deformation patterns of battery cell and module specimens. Analytical solutions were developed to estimate the buckling stresses and to provide a theoretical basis for future design of representative volume element cell and module specimens. A physical kinematics model for formation of kinks and shear bands in battery cells was developed to explain the deformation mechanism for layered battery cells under in-plane constrained compression. A small-scale module constrained punch indentation test was also conducted to benchmark the computational results. The computational results indicate that macro homogenized material models can be used to simulate battery modules under crush conditions. Fatigue behavior and failure modes of ultrasonic spot welds in lap-shear specimens of magnesium and steel sheets with and without adhesive were investigated. For ultrasonic spot welded lap-shear specimens, the failure mode changes from the partial nugget pullout mode under low-cycle loading conditions to the kinked crack failure mode under high-cycle loading conditions. For adhesive-bonded and weld-bonded lap-shear specimens, the test results show the near interface cohesive failure mode and the kinked crack failure mode under low-cycle and high-cycle loading conditions, respectively. Next, the analytical effective stress intensity factor solutions for main cracks in lap-shear specimens of three dissimilar sheets under plane strain conditions were developed and the solutions agreed well with the computational results. The analytical effective stress intensity factor solutions for kinked cracks were compared with the computational results at small kink lengths. The results indicate that the computational results approach to
Regulation of shear stress on rolling behaviors of HL-60 cells on P-selectin
Ling, YingChen; Fang, Ying; Yang, XiaoFang; Li, QuHuan; Lin, QinYong; Wu, JianHua
2014-10-01
Circulating leukocytes in trafficking to the inflammatory sites, will be first tether to, and then roll on the vascular surface. This event is mediated through specific interaction of P-selectin and P-selectin glycoprotein ligand-1 (PSGL-1), and regulated by hemodynamics. Poor data were reported in understanding P-selectin-mediated rolling. With the flow chamber technique, we herein observed HL-60 cell rolling on P-selectin with or without 3% Ficoll at various wall shear stresses from 0.05 to 0.4 dyn/cm2. The results demonstrated that force rather than transport regulated the rolling, similar to rolling on L- and E-selectin. The rolling was accelerated quickly by an increasing force below the optimal shear threshold of 0.15 dyn/cm2 first and then followed by a slowly decelerating phase starting at the optimum, showing a catch-slip transition and serving as a mechanism for the rolling. The catch-slip transition was completely reflected to the tether lifetime and other rolling parameters, such as the mean and fractional stop time. The narrow catch bond regime stabilized the rolling quickly, through steeply increasing fractional stop time to a plateau of about 0.85. Data presented here suggest that the low shear stress threshold serves as a mechanism for most cell rolling events through P-selectin.
Study the Effectiveof Seismic load on Behavior of Shear Wall in Frame Structure
Directory of Open Access Journals (Sweden)
Dr.Hadi Hosseini
2014-11-01
Full Text Available Structural walls, or shear walls, are elements used to resist lateral loads, such as those generated by wind and earthquakes. Structural walls are considerably deeper than typical beams or columns. This attribute gives structural walls considerable in-plane stiffness which makes structural walls a natural choice for resisting lateral loads. In addition to considerable strength, structural walls can dissipate a great deal of energy if detailed properly. Walls are an invaluable structural element when protecting buildings from seismic events. Buildings often rely on structural walls as the main lateral force resisting system. Shear walls are required to perform in multiple ways. Shear walls can then be designed to limit building damage to the specified degree. The load-deformation response of the structural walls must be accurately predicted and related to structural damage in order to achieve these performance goals under loading events of various magnitudes. The applied load is generally transferred to the wall by a diaphragm or collector or drag member. The performance of the framed buildings depends on the structural system adopted for the structure The term structural system or structural frame in structural engineering refers to load-resisting sub-system of a structure. The structural system transfers loads through interconnected structural components or members. These structural systems need to be chosen based on its height and loads and need to be carried out, etc. The selection of appropriate structural systems for building must satisfy both strength and stiffness requirements. The structural system must be adequate to resist lateral and gravity loads that cause horizontal shear deformation and overturning deformation. The efficiency of a structural system is measured in terms of their ability to resist lateral load, which increases with the height of the frame. A building can be considered as tall when the effect of lateral loads is
Study Effective of Wind Load on Behavior of ShearWall in Frame Structure
Directory of Open Access Journals (Sweden)
Mahdi Hosseini
2014-11-01
Full Text Available Wind load is really the result of wind pressures acting on the building surfaces during a wind event. This wind pressure is primarily a function of the wind speed because the pressure or load increases with the square of the wind velocity.Structural walls, or shear walls, are elements used to resist lateral loads, such as those generated by wind and earthquakes. Structural walls are considerably deeper than typical beams or columns. This attribute gives structural walls considerable in-plane stiffness which makes structural walls a natural choice for resisting lateral loads. In addition to considerable strength, structural walls can dissipate a great deal of energy if detailed properly. Walls are an invaluable structural element when protecting buildings from seismic events. Buildings often rely on structural walls as the main lateral force resisting system. Shear walls are required to perform in multiple ways. Shear walls can then be designed to limit building damage to the specified degree. The loaddeformation response of the structural walls must be accurately predicted and related to structural damage in order to achieve these performance goals under loading events of various magnitudes. The applied load is generally transferred to the wall by a diaphragm or collector or drag member. The performance of the framed buildings depends on the structural system adopted for the structure The term structural system or structural frame in structural engineering refers to load-resisting sub-system of a structure. The structural system transfers loads through interconnected structural components or members. These structural systems need to be chosen based on its height and loads and need to be carried out, etc. The selection of appropriate structural systems for building must satisfy both strength and stiffness requirements. The structural system must be adequate to resist lateral and gravity loads that cause horizontal shear deformation and
Directory of Open Access Journals (Sweden)
Abu-Bakre Abdelmoneim Elamin Mohamad
2016-08-01
Full Text Available The developed study aimed at investigating the mechanical behavior of a new type of self-insulating concrete masonry unit (SCMU. A total of 12 full-grouted wall assemblages were prepared and tested for compression and shear strength. In addition, different axial stress ratios were used in shear tests. Furthermore, numerical models were developed to predict the behavior of grouted specimens using simplified micro-modeling technique. The mortar joints were modeled with zero thickness and their behavior was applied using the traction–separation model of the cohesive element. The experimental results revealed that the shear resistance increases as the level of precompression increases. A good agreement between the experimental results and numerical models was observed. It was concluded that the proposed models can be used to deduct the general behavior of grouted specimens.
Flexural modulus identification of thin polymer sheets
Gluhihs, S.; Kovalovs, A.; Tishkunovs, A.; Chate, A.
2011-06-01
The method of determination of the flexural Young's modulus is based on a solution to the problem of compression of a thin-walled cylindrical specimen by two parallel planes (TWCS method). This method was employed to calculate the flexural modulus for PET polymer compositions. The flexural modules received by TWCS method were verified by comparing the experimentally measured eigenfrequencies by Polytec vibrometer with numerical results from ANSYS program.
Flexural modulus identification of thin polymer sheets
Energy Technology Data Exchange (ETDEWEB)
Gluhihs, S; Kovalovs, A; Tishkunovs, A; Chate, A, E-mail: s_gluhih@inbox.lv [Riga Technical University, Institute of Materials and Structures, Azenes 16/22, LV-1048, Riga (Latvia)
2011-06-23
The method of determination of the flexural Young's modulus is based on a solution to the problem of compression of a thin-walled cylindrical specimen by two parallel planes (TWCS method). This method was employed to calculate the flexural modulus for PET polymer compositions. The flexural modules received by TWCS method were verified by comparing the experimentally measured eigenfrequencies by Polytec vibrometer with numerical results from ANSYS program.
An experimental investigation of the seismic behavior of semi-supported steel shear walls
DEFF Research Database (Denmark)
Jahanpour, Alireza; Jönsson, Jeppe; Moharrami, H.
2010-01-01
A semi-supported steel shear wall (SSSW) has been developed in the recent decade, the steel wall is connected to secondary columns that do not carry vertical loads and are used to enable the plate to enter into the post buckling region and develop a tension field. Theoretical research...... on this system has been performed and an algorithmic method has been developed, which enables the determination of the ultimate capacity of the wall. In this paper results from an experimental investigation of this type of system including two half scale models under cyclic quasi static loading will be presented...
Institute of Scientific and Technical Information of China (English)
张兴刚; 张用兵
2013-01-01
树脂基复合材料具有粘弹性，长期在外力作用下会发生蠕变现象，导致复合材料的刚度和强度都发生衰退，致使复合材料结构失去继续承载能力。由于复合材料蠕变研究多集中在拉伸状况下，缺少足够的弯曲蠕变数据，难以进行复合材料结构的可靠性设计。针对玻纤增强乙烯基树脂复合材料进行了弯曲蠕变测试，分析了弯曲蠕变后复合材料试样的力学性能及翘曲变形，并根据时间-挠度曲线探讨了蠕变极限。结果显示，该复合材料在20天左右基本可以达到蠕变平衡，且其蠕变性能优异。%As the viscoelastic nature of fiber reinforced plastic, creep may occur under long term ex-ternal force, then the stiffness and strength of composite structures decrease gradually, and the whole structural system will fail at last. For many years, creep study on fiber reinforced plastic is mainly concerned with tensile behavior, but less research is done on the flexural creep behavior. Because of the insufifciency of storage data, it is dififcult to study the reliability of composites structures in long-term use of lfexure loadings. In this paper, by means of testing lfexural lfexibility change at different times, the lfexural creep behavior by three-point loading of glass if-ber reinforced vinyl ester resins composites is studied. The results show that lfexural delfection changes obviously at the beginning stage of applying lfexural loading, and the change of lfexural delfection is decreased with the prolong of time.
Evaluation of Steel Shear Walls Behavior with Sinusoidal and Trapezoidal Corrugated Plates
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Emad Hosseinpour
2015-01-01
Full Text Available Reinforcement of structures aims to control the input energy of unnatural and natural forces. In the past four decades, steel shear walls are utilized in huge constructions in some seismic countries such as Japan, United States, and Canada to lessen the risk of destructive forces. The steel shear walls are divided into two types: unstiffened and stiffened. In the former, a series of plates (sinusoidal and trapezoidal corrugated with light thickness are used that have the postbuckling field property under overall buckling. In the latter, steel profile belt series are employed as stiffeners with different arrangement: horizontal, vertical, or diagonal in one side or both sides of wall. In the unstiffened walls, increasing the thickness causes an increase in the wall capacity under large forces in tall structures. In the stiffened walls, joining the stiffeners to the wall is costly and time consuming. The ANSYS software was used to analyze the different models of unstiffened one-story steel walls with sinusoidal and trapezoidal corrugated plates under lateral load. The obtained results demonstrated that, in the walls with the same dimensions, the trapezoidal corrugated plates showed higher ductility and ultimate bearing compared to the sinusoidal corrugated plates.
Rheological Investigation on the Effect of Shear and Time Dependent Behavior of Waxy Crude Oil
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Japper-Jaafar A.
2014-07-01
Full Text Available Rheological measurements are essential in transporting crude oil, especially for waxy crude oil. Several rheological measurements have been conducted to determine various rheological properties of waxy crude oil including the viscosity, yield strength, wax appearance temperature (WAT, wax disappearance temperature (WDT, storage modulus and loss modulus, amongst others, by using controlled stress rheometers. However, a procedure to determine the correct parameters for rheological measurements is still unavailable in the literature. The paper aims to investigate the effect of shear and time dependent behaviours of waxy crude oil during rheological measurements. It is expected that the preliminary work could lead toward a proper rheological measurement guideline for reliable rheological measurement of waxy crude oil.
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Ramazan-Ali Jafari-Talookolaei
2015-09-01
Full Text Available A finite element (FE model is developed to study the free vibration of a rotating laminated composite beam with a single delamination. The rotary inertia and shear deformation effects, as well as the bending–extension, bending–twist and extension–twist coupling terms are taken into account in the FE model. Comparison between the numerical results of the present model and the results published in the literature verifies the validity of the present model. Furthermore, the effects of various parameters, such as delamination size and location, fiber orientation, hub radius, material anisotropy and rotating speed, on the vibration of the beam are studied in detail. These results provide useful information in the study of the free vibration of rotating delaminated composite beams.
Bodaghi, M.; Damanpack, A. R.; Liao, W. H.
2016-07-01
The aim of this article is to develop a robust macroscopic bi-axial model to capture self-accommodation, martensitic transformation/orientation/reorientation, normal-shear deformation coupling and asymmetric/anisotropic strain generation in polycrystalline shape memory alloys. By considering the volume fraction of martensite and its preferred direction as scalar and directional internal variables, constitutive relations are derived to describe basic mechanisms of accommodation, transformation and orientation/reorientation of martensite variants. A new definition is introduced for maximum recoverable strain, which allows the model to capture the effects of tension-compression asymmetry and transformation anisotropy. Furthermore, the coupling effects between normal and shear deformation modes are considered by merging inelastic strain components together. By introducing a calibration approach, material and kinetic parameters of the model are recast in terms of common quantities that characterize a uniaxial phase kinetic diagram. The solution algorithm of the model is presented based on an elastic-predictor inelastic-corrector return mapping process. In order to explore and demonstrate capabilities of the proposed model, theoretical predictions are first compared with existing experimental results on uniaxial tension, compression, torsion and combined tension-torsion tests. Afterwards, experimental results of uniaxial tension, compression, pure bending and buckling tests on {{NiTi}} rods and tubes are replicated by implementing a finite element method along with the Newton-Raphson and Riks techniques to trace non-linear equilibrium path. A good qualitative and quantitative correlation is observed between numerical and experimental results, which verifies the accuracy of the model and the solution procedure.
Shear and anchorage behaviour of fire exposed hollow core slabs
Fellinger, J.H.H.; Stark, J.; Walraven, J.C.
2005-01-01
The fire resistance of hollow core slabs is currently assessed considering flexural failure only. However, fire tests showed that shear or anchorage failure can also govern the load bearing behaviour. As the shear and anchorage capacity of these slabs rely on the tensile strength of the concrete, th
Shear and Anchorage Behaviour of Fire Exposed Hollow Core Slabs
Fellinger, J.H.H.
2004-01-01
Hollow core (HC) slabs are made of precast concrete with pretensioned strands. These slabs are popular as floor structures in offices and housing. At ambient conditions, the load bearing capacity can be dominated by four different failure modes, i.e. flexure, anchorage, shear compression and shear t
Shear and Anchorage Behaviour of Fire Exposed Hollow Core Slabs
Fellinger, J.H.H.
2004-01-01
Hollow core (HC) slabs are made of precast concrete with pretensioned strands. These slabs are popular as floor structures in offices and housing. At ambient conditions, the load bearing capacity can be dominated by four different failure modes, i.e. flexure, anchorage, shear compression and shear
Shear and Anchorage Behaviour of Fire Exposed Hollow Core Slabs
Fellinger, J.H.H.
2004-01-01
Hollow core (HC) slabs are made of precast concrete with pretensioned strands. These slabs are popular as floor structures in offices and housing. At ambient conditions, the load bearing capacity can be dominated by four different failure modes, i.e. flexure, anchorage, shear compression and shear t
Modeling and analysis of circular flexural-vibration-mode piezoelectric transformer.
Huang, Yihua; Huang, Wei
2010-12-01
We propose a circular flexural-vibration-mode piezoelectric transformer and perform a theoretical analysis of the transformer. An equivalent circuit is derived from the equations of piezoelectricity and the Hamilton's principle. With this equivalent circuit, the voltage gain ratio, input impedance, and the efficiency of the circular flexural-vibration-mode piezoelectric transformer can be determined. The basic behavior of the transformer is shown by numerical results.
Institute of Scientific and Technical Information of China (English)
无
2007-01-01
The behavior of two parallel symmetry permeable cracks in functionally graded piezoelectric materials subjected to an anti-plane shear loading was investigated. To make the analysis tractable, it was assumed that the material properties varied exponentially with coordinate vertical to the crack. By using the Fourier transform, the problem could be solved with the help of two pairs of dual integral equations, in which the unknown variables were the jumps of the displacements across the crack surfaces. To solve the dual integral equations, the displacement on the crack surfaces expanded in a series of Jacobi polynomials. The normalized stress and electrical displacement intensity factors were determined for different geometric and property parameters for permeable electric boundary conditions. Numerical examples were provided to show the effect of the geometry of the interacting cracks and the functionally graded material parameter upon the stress intensity factors of cracks.
Directory of Open Access Journals (Sweden)
Pedro Henrique Santos
Full Text Available Summary The aim of this study was to evaluate the rheological behavior of malay apple, a traditional Amazonian fruit with high bioactive properties, at different temperatures and soluble solids concentrations. The experiments were carried out in a Brookfield R/S Plus rheometer with concentric cylinders geometry. Power Law, Herschel-Bulkley, Mizrahi-Berk, and Sisko rheological models were fitted to the experimental data. The malay apple juice (pulp and skin showed a pseudoplastic behavior for all temperatures and concentrations with flow behavior indexes lower than 1. The temperature effect on the samples’ apparent viscosity was analyzed by the Arrhenius equation. The activation energy increased with a decrease in the soluble solids concentration, showing that the lower the concentration, the greater the temperature influence on the apparent viscosity. The soluble solids effect was described by the exponential equation. The exponential factor increased with the temperature increasing, showing that the higher the temperature, the greater the effect of the soluble solids concentration on samples’ apparent viscosity. Finally, a triparametric mathematical model combining temperature, concentration, and shear rate was proposed aiming to evaluate its effects on the samples’ apparent viscosity and has accurately adjusted to the data with high correlation index R2.
DEFF Research Database (Denmark)
Mirzaev, S. Z.; Behrends, R.; Heimburg, Thomas Rainer
2006-01-01
2,6-dimethylpyridine-water, specific heat, dynamic light scattering, shear viscosity Udgivelsesdato: 14 April......2,6-dimethylpyridine-water, specific heat, dynamic light scattering, shear viscosity Udgivelsesdato: 14 April...
The Effect of Soil Particle Arrangement on Shear Strength Behavior of Silty Sand
Directory of Open Access Journals (Sweden)
Nik Norsyahariati Nik Daud
2016-01-01
Full Text Available The presence of fines in sandy soil is recognized as a problem in geotechnical engineering. It is often assumed that the strength and liquefaction potential of a soil decreases with increasing fines content. Sand with a significant amount of fines is always encountered in geotechnical engineering projects. The main interest of this paper is to study the effect of particles arrangement and stress behaviour on sand and silty sand sample. The objectives are to determine the basic properties as well as the morphological and mineralogical properties and the relationship of those properties to the stress behaviour of the soils. Sand-silt mixtures with fines contents of 20% and 40% were prepared and a series of testing was carried out to determine their basic properties, morphological and thin section properties, and mechanical properties by using direct shear box equipment. Results show that the basic properties and morphological properties of soil affect the mechanical behaviour of soil. Shape of the soil particle can influence the packing of the soil, hence altering the mechanical behaviour of the soil. From the thin section, the soil is observed to be well graded and have a dense packing while the minerals observed were mainly quartz and rutile.
Numerical Investigation of the Seismic Behavior of Corrugated Steel Shear Wall by ABAQUS software
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Ali Banazadeh
2016-09-01
Full Text Available Advantages of using steel shear walls in supplying the requirements of regulations relating to the peripheral loadings including winds and earthquake have caused that the use develops in constructs. High capacity of the system inenergy dissipation, significant primary stiffness, and profitability are among main advantages of this system. However, it has some weaknesses such as elastic buckling of the filler plate before its flow which this issue sometimes causes the increase in the need to out-of-plate stiffness of columns. One of the methods of coping with this phenomenon is the use ofcorrugated plates instead ofbed plates. Different studies indicate that this group of plates enjoy relatively better capacity of absorbing energy and reduce in-plate instability of the system as well. The present study is to investigate and model numerically this type of plate using ABAQUS software and by gauging the verification of numerical model outputs, develop the use of it on plates with different angular position. The results indicate that in spite of the reduction in theultimate bearing capacity of corrugated plates compared to bed plates, the degree of absorbing energy and formability of the system increases significantly.
Institute of Scientific and Technical Information of China (English)
无
2008-01-01
Four exterior joints with special-shaped columns which have different lengths of limbs are tested under low cyclic loading. Special-shaped columns adopted are L- and T-shaped in section. It can be concluded that crack pattern, failure mode and shear strength of joints are affected by the length of limb, and that shear strength and ductility increase with the length of limb; the joints with the flexural failure of the beam have better seismic behavior than those with the shear failure of the joint core.
Failure behavior for composite single-bolted joints in double shear tension
Tang, Zhanwen; Liu, Hanyang; Yang, Zhiyong; Shi, Hanqiao; Sun, Baogang
2016-05-01
In order to improve the reliability and load carrying capacity of composite laminates structures which were lap jointed by bolt, in this paper, the failure strength and failure mode of laminated composite pinned-joints is investigated. To determine the effects of joint geometry and stacking sequence on the bearing strength and damage mode, the multi-scale numerical model combining with the Generalized Method of Cells (GMC) and considering the failure and the damage of constituent materials was created based on the ABAQUS and its user subroutine (USDFLD). A three-dimensional finite element technique was used for the stress analysis. Based on the three-dimensional state of stress of each element, different failure modes were detected by the failure theories of constituent materials, all of which are applied at the fiber, matrix and fiber-matrix interface constituent level. Numerical simulations have been carried out by which edge distance-to-hole diameter ratio, and plate width-to-hole diameter ratio are varied, The composite laminated plates are stacked with the following four different orientations: [+45/-45]2s, [90/+45/-45]s, and [0/90/0]s, the results show that failure mode and bearing strength are closely related to by stacking sequence of plates and geometrical parameters. Finally, the ultimate strength and failure modes of composite bolted joints in static tension double-shear loading conditions are predicted by using the progressive damage method established and the effects of layup and dimension of laminates on the properties of the connection structure were researched in this paper. An excellent agreement is found between data obtained from this study and the experiment.
Energy Technology Data Exchange (ETDEWEB)
Chono, S.; Tsuji, T.; Taniguchi, A. [Fukui University, Fukui (Japan). Faculty of Engineering
1996-02-25
Finite difference solutions to the Doi equation without closure approximations in shear flow are obtained. The Maier-Saupe potential is used to model the mean-held potential which induces the nematic state. Under equilibrium conditions, an isotropic phase is stable when the nematic potential intensity U is less than 4.49 and the lowest value of U for which a nematic phase is stable is 5. In the presence of shear flow, three different types of rheological behavior exist depending on the magnitude of shear rate: aligning, wagging and tumbling. With increasing shear rate, in the aligning regime, the preferred angle has a maximum and the order parameter shows a monotonic increase. For U=6, the transitions from tumbling to wagging and wagging to aligning occur at shear rates of approximately 16 and 32, respectively. The first normal stress difference has a negative value in moderate shear rates which include the whole regime of wagging and a part of the tumbling and aligning regimes. 20 refs., 8 figs.
Lemarchand, Claire A; Todd, Billy D; Daivis, Peter J; Hansen, Jesper S
2015-01-01
The rheology and molecular structure of a model bitumen (Cooee bitumen) under shear is investigated in the non-Newtonian regime using non-equilibrium molecular dynamics simulations. The shear viscosity and normal stress differences of the bitumen mixture are computed at different shear rates and different temperatures. The model bitumen is shown to be a shear-thinning fluid. The corresponding molecular structure is studied at the same shear rates and temperatures. The Cooee bitumen is able to reproduce experimental results showing the formation of nanoaggregates composed of stacks of flat aromatic molecules. These nanoaggregates are immersed in a solvent of saturated hydrocarbon molecules. The nanoaggregates are shown to break up at very high shear rates, leading only to a minor effect on the viscosity of the mixture. At low shear rates, bitumen can be seen as a colloidal suspension of nanoaggregates in a solvent. The slight anisotropy of the whole sample due to the nanoaggregates is considered and quantified...
Shear bond strength of veneering porcelain to porous zirconia.
Nakamura, Takashi; Sugano, Tsuyoshi; Usami, Hirofumi; Wakabayashi, Kazumichi; Ohnishi, Hiroshi; Sekino, Tohru; Yatani, Hirofumi
2014-01-01
In this study, two types of porous zirconia and dense zirconia were used. The flexural strength of non-layered zirconia specimens and those of the layered zirconia specimens with veneering porcelain were examined. Furthermore, the shear bond strength of veneering porcelain to zirconia was examined. The flexural strength of the non-layered specimens was 1,220 MPa for dense zirconia and 220 to 306 MPa for porous zirconia. The flexural strength of the layered specimens was 360 MPa for dense zirconia and 132 to 156 MPa for porous zirconia, when a load was applied to the porcelain side. The shear bond strength of porcelain veneered to dense zirconia was 27.4 MPa and that of porcelain veneered to porous zirconia was 33.6 to 35.1 MPa. This suggests that the veneering porcelain bonded strongly to porous zirconia although porous zirconia has a lower flexural strength than dense zirconia.
Adeli, Mostafa; Samavati, Vahid
2015-01-01
The extraction of water-soluble polysaccharide from Ziziphus lotus fruit (WPZL) was performed by ultrasonic-assisted extraction method. A Box-Behnken design (BBD) was applied to evaluate the effects of three independent variables (ultrasonic power (X1: 70-100 W), extraction time (X2: 10-30 min), extraction temperature (X3: 55-95 °C), and water to raw material ratio (X4: 5-25)) on the extraction yield of APH. The effect of temperature and concentration on flow behavior of gum solution was studied. WPZL solutions exhibited shear-thinning non-Newtonian flow behavior for concentrations above 0.5% (w/v). The viscosity of fully hydrated gum solutions decreased as temperature increase. The correlation analysis of the mathematical-regression model indicated that quadratic polynomial model could be employed to optimize the extraction of WPZL. The optimal conditions to obtain the highest extraction of WPZL (13.398 ± 0.019%) were as follows: ultrasonic power, 88.77 W; extraction time, 29.96 min, extraction temperature, 77.73 °C and water to raw material ratio 24.44 mL/g. Copyright © 2014 Elsevier B.V. All rights reserved.
Institute of Scientific and Technical Information of China (English)
纪晓东; 蒋飞明; 钱稼茹; 杨懿; 施正捷
2013-01-01
提出一种适用于超高层建筑底部楼层的钢管-双层钢板-混凝土组合剪力墙,通过5个剪跨比为2.5的一字形截面组合剪力墙试件的拟静力试验,研究组合剪力墙的抗震性能.试验结果表明:试件的破坏形态为压弯破坏,墙底部边缘构件矩形钢管管壁和钢板鼓曲、钢管断裂、混凝土压溃；矩形钢管混凝土约束边缘构件沿墙肢长度显著影响试件的变形能力和耗能能力；钢板含钢率基本不影响试件的变形能力；矩形钢管混凝土边缘构件内设置圆钢管可提高试件承载力,但对其变形能力影响不大.矩形钢管混凝土约束边缘构件沿墙肢长度为0.2倍墙截面高度、设计轴压比为0.45时,组合墙试件的屈服位移角不小于0.005 rad、极限位移角可达0.030 rad.提出组合墙正截面承载力的计算式,计算结果与试验值吻合较好,误差小于10％.%This paper proposed an innovative composite wall,named the steel tube-double plate-concrete composite shear wall,which is suited for use in the lower stories of super high-rise buildings.The seismic behavior of the composite walls was examined through results of an experimental research program where five rectangle-shaped wall specimens with a shear span ratio of 2.5 were tested.The test results indicate that the specimens fail in a flexural mode,characterized by local buckling of boundary steel tubes and steel plates,fracture of steel tubes,and compressive crushing of concrete at the wall base.The extent of concrete filled steel tubular (CFST) boundary elements significantly affects the deformation and energy dissipation capacities of the composite walls.The area ratio of steel plate has a minimal effect on the deformation capacity of the wall specimens.The addition of circular steel tubes embedded in the CFST boundary elements leads to an increase in the lateral load-carrying capacity of the composite walls,but it does not increase the wall' s deformation
Directory of Open Access Journals (Sweden)
Yi Yang
2017-07-01
Full Text Available In order to reveal the differences and conversion relations between the tensile, compressive and flexural moduli of cement stabilized macadam, in this paper, we develop a new test method for measuring three moduli simultaneously. By using the materials testing system, we test three moduli of the cement stabilized macadam under different loading rates, propose a flexural modulus calculation formula which considers the shearing effect, reveal the change rules of the tensile, compression and flexural moduli with the loading rate and establish the conversion relationships between the three moduli. The results indicate that: three moduli become larger with the increase of the loading rate, showing a power function pattern; with the shear effect considered, the flexural modulus is increased by 47% approximately over that in the current test method; the tensile and compression moduli of cement stabilized macadam are significantly different. Therefore, if only the compression modulus is used as the structural design parameter of asphalt pavement, there will be a great deviation in the analysis of the load response. In order to achieve scientific design and calculation, the appropriate design parameters should be chosen based on the actual stress state at each point inside the pavement structure.
Flexure-based nanomagnetic actuators
Vasquez, Daniel James
Nanometer-scale actuators powered through applied-magnetic fields have been designed, fabricated, and tested. These actuators consist of one or more ferromagnetic elements attached to a mechanical flexure. Two types of flexures were studied including a cantilever beam that is fixed on one end, and free on the other. The free end of the cantilever is attached to a, ferromagnetic element allowing a bending torque to be applied by a magnetic field. The second type of actuator design uses a set of torsion beams that are each anchored on one end, and attached to the magnetic element on the other end. The torsion beams are designed such that the application of a magnetic field will result in a twist along the long axis of the beam with little to no bending. The smallest fabricated and tested device is a cantilever-based ferromagnetic actuator that consists of a single 1.5-mum-long, 338-nm-wide, and 50-nm-thick nickel element, and a 2.2-mum-long, 110-nm-wide, and 30-nm-thick gold cantilever beam. A deflection of over 17° was measured for this actuator, while a similar one with a 10.1-mum long cantilever beam experienced measured deflections up to 57°. Torsion-based ferromagnetic actuators have been fabricated and tested with 110-nm-wide, and 50-rim-thick magnetic elements. Such magnetic elements contain only a single saturated magnetic domain. The ultimate scalability of ferromagnetic actuation is limited by the ability of thermal noise to affect the temporal stability of a nanometer-scale magnet. Theory to describe thermal noise and ultimate scalability of the ferromagnetic actuators has been developed. The size of the ferromagnetic actuators studied in this manuscript are smaller than most plant and animal cells. This enables the possibility of such actuators to manipulate a, living cell on an intracellular level. Other potential applications of such small actuators include MHz, to GHz frequency resonators, and tunable optical filters.
Garai, Ashesh; Nandi, Arun K
2008-04-01
The melt rheology of polyaniline (PANI)-dinonylnaphthalenedisulfonic acid (DNNDSA) gel nanocomposites (GNCs) with organically modified (modified with cetyl trimethylammonium bromide)-montmorillonite (om-MMT) clay has been studied for three different clay concentrations at the temperature range 120-160 degrees C. Field emission scanning electron microscopy (FE-SEM), wide angle X-ray scattering (WAXS), differential scanning calorimetry (DSC) and dc-conductivity data (approximately 10(-3) S/cm) indicate that the PANI-DNNDSA melt is in sol state and it is not de-doped at that condition. The WAXS data indicate that in GNC-1 sol clay tactoids are in exfoliated state but in the other sols they are in intercalated state. The zero shear viscosity (eta0), storage modulus (G') and loss modulus (G") increase than that of pure gel in the GNCs. The pure sol and the sols of gel nanocomposites (GNCs) exhibit Newtonian behavior for low shear rate (solid at higher frequency where G' and loss modulus (G") show a crossover point in the frequency sweep experiment at a fixed temperature. The crossover frequency decreases with increase in clay concentration and it increases with increase in temperature for GNC sols. The pseudo-solid behavior has been explained from jamming or network formation of clay tactoids under shear. A probable explanation of the two apparently contradictory phenomena of shear thinning versus pseudo-solid behavior of the nanocomposite sols is discussed.
Flexural Strength of Functionally Graded Nanotube Reinforced Sandwich Spherical Panel
Mahapatra, Trupti R.; Mehar, Kulmani; Panda, Subrata K.; Dewangan, S.; Dash, Sushmita
2017-02-01
The flexural behaviour of the functionally graded sandwich spherical panel under uniform thermal environment has been investigated in the present work. The face sheets of the sandwich structure are made by the functionally graded carbon nanotube reinforced material and the core face is made by the isotropic and homogeneous material. The material properties of both the fiber and matrix are assumed to be temperature dependent. The sandwich panel model is developed in the framework of the first order shear deformation theory and the governing equation of motion is derived using the variational principle. For the discretization purpose a suitable shell element has been employed from the ANSYS library and the responses are computed using a parametric design language (APDL) coding. The performance and accuracy of the developed model has been established through the convergence and validation by comparing the obtained results with previously published results. Finally, the influence of different geometrical parameters and material properties on the flexural behaviour of the sandwich spherical panel in thermal environment has been investigated through various numerical illustrations and discussed in details.
Childhood flexural comedones: a new entity.
Larralde, Margarita; Abad, María Eugenia; Muñoz, Andrea Santos; Luna, Paula
2007-07-01
Comedones are usually found in acne and involve the seborrheic areas of the skin. Disseminated comedones can be found in other skin disorders. Flexural comedones are characterized by double orifices connected by a thin layer of epidermis that reveals the comedo content below it. To the best of our knowledge, flexural comedones have not been previously described as an entity. Our objective was to characterize this disorder. A cross-sectional descriptive study was performed from April 2004 to July 2006. We included 40 pediatric and adolescent patients with flexural comedones; 21 were female (52%), and 19 were male (48%) (mean age, 6.2 years). In 29 cases the lesions were single (72%) and in 32 cases (80%) unilateral. The lesions were located in the axilla in 88% of the patients. We performed biopsies of skin samples in 6 cases. To our knowledge, flexural comedones have not been previously described as an entity, and we felt that they deserved attention owing to the relative frequency of cases in our clinical practice. Because of its clinical appearance, flexural localization, and age distribution, we named this disorder childhood flexural comedones. Further investigation and follow-up of a larger number of patients is needed.
Roberts, Gary D.; Ho, Barry Ping Hsiao; Wallace, John F.
1993-01-01
The effects of thermal and mechanical fatigue on the flexural strength of G40-600/PMR-15 cross-ply laminates with ply orientation of (0(2),90(2))2S and (90(2),0(2))2S are examined. The relative importance of shear and tensile stresses is examined by varying the span-to-depth ratios of flexural test specimens from 8 to 45. Acoustic emission signals are measured during the flexural tests in order to monitor the initiation and growth of damage. Optical microscopy is used to examine specimens for resin cracking, delamination, and fiber breaks after testing. Transverse matrix cracks and delaminations occur in all specimens, regardless of ply orientation, span-to-depth ratio, or previous exposure of specimens to thermal and mechanical fatigue. A small amount of fiber tensile fracture occurs in the outer 0 deg ply of specimens with high span-to-depth ratios. Because of the complex failure modes, the flexural test results represent the 'apparent' strengths rather than the true flexural or shear strengths for these cross-ply laminates. Thermal cycling of specimens prior to flexural testing does not reduce the apparent flexural strength or change the mode of failure. However, fewer acoustic events are recorded at all strains during flexural testing of specimens exposed to prior thermal cycling. High temperature thermal cycling (32 to 260 C, 100 cycles) causes a greater reduction in acoustic events than low temperature thermal cycling (-85 to +85 C, 500 cycles). Mechanical cycling (0 to 50 percent of the flexural strength, 100 cycles) has a similar effect, except that acoustic events are reduced only at strains less than the maximum strain applied during flexural fatigue.
Triaxial shear behavior of a cement-treated sand–gravel mixture
Directory of Open Access Journals (Sweden)
Younes Amini
2014-10-01
Full Text Available A number of parameters, e.g. cement content, cement type, relative density, and grain size distribution, can influence the mechanical behaviors of cemented soils. In the present study, a series of conventional triaxial compression tests were conducted on a cemented poorly graded sand–gravel mixture containing 30% gravel and 70% sand in both consolidated drained and undrained conditions. Portland cement used as the cementing agent was added to the soil at 0%, 1%, 2%, and 3% (dry weight of sand–gravel mixture. Samples were prepared at 70% relative density and tested at confining pressures of 50 kPa, 100 kPa, and 150 kPa. Comparison of the results with other studies on well graded gravely sands indicated more dilation or negative pore pressure in poorly graded samples. Undrained failure envelopes determined using zero Skempton's pore pressure coefficient (A¯=0 criterion were consistent with the drained ones. Energy absorption potential was higher in drained condition than undrained condition, suggesting that more energy was required to induce deformation in cemented soil under drained state. Energy absorption increased with increase in cement content under both drained and undrained conditions.
Flexural Properties of E Glass and TR50S Carbon Fiber Reinforced Epoxy Hybrid Composites
Dong, Chensong; Sudarisman; Davies, Ian J.
2013-01-01
A study on the flexural properties of E glass and TR50S carbon fiber reinforced hybrid composites is presented in this paper. Specimens were made by the hand lay-up process in an intra-ply configuration with varying degrees of glass fibers added to the surface of a carbon laminate. These specimens were then tested in the three-point bend configuration in accordance with ASTM D790-07 at three span-to-depth ratios: 16, 32, and 64. The failure modes were examined under an optical microscope. The flexural behavior was also simulated by finite element analysis, and the flexural modulus, flexural strength, and strain to failure were calculated. It is shown that although span-to-depth ratio shows an influence on the stress-strain relationship, it has no effect on the failure mode. The majority of specimens failed by either in-plane or out-of-plane local buckling followed by kinking and splitting at the compressive GFRP side and matrix cracking combined with fiber breakage at the CFRP tensile face. It is shown that positive hybrid effects exist for the flexural strengths of most of the hybrid configurations. The hybrid effect is noted to be more obvious when the hybrid ratio is small, which may be attributed to the relative position of the GFRP layer(s) with respect to the neutral plane. In contrast to this, flexural modulus seems to obey the rule of mixtures equation.
Isostasy, flexure, and dynamic topography
Gvirtzman, Zohar; Faccenna, Claudio; Becker, Thorsten W.
2016-06-01
A fundamental scientific question is, what controls the Earth's topography? Although the theoretical principles of isostasy, flexure, and dynamic topography are widely discussed, the parameters needed to apply these principles are frequently not available. Isostatic factors controlling lithospheric buoyancy are frequently uncertain and non-isostatic factors, such as lithospheric bending towards subduction zones and dynamic topography, are hard to distinguish. The question discussed here is whether a set of simple rules that relate topography to lithospheric structure in various tectonic environments can be deduced in a way that missing parameters can be approximated; or does each area behave differently, making generalizations problematic. We contribute to this issue analyzing the Asia-Africa-Arabia-Europe domain following a top-down strategy. We compile a new crustal thickness map and remove the contribution of the crust from the observed elevation. Then, the challenge is to interpret the residual topography in terms of mantle lithosphere buoyancy and dynamics. Based on systematic relationships between tectonic environments and factors controlling topography, we argue that crustal buoyancy and mantle lithospheric density can be approximated from available geological data and that regions near mantle upwelling or downwelling are easily identified by their extreme residual topography. Yet, even for other areas, calculating lithospheric thickness from residual topography is problematic, because distinguishing variations in mantle lithosphere thickness from sub-lithospheric dynamics is difficult. Fortunately, the area studied here provides an opportunity to examine this issue. Based on the conjunction between the Afar Plume and the mid-ocean ridge in the nearby Gulf of Aden and southern Red Sea, we constrain the maximal amplitude of dynamic topography to ~ 1 km. This estimate is based on a narrow definition of dynamic topography that only includes sub
Influence of helium atoms on the shear behavior of the fiber/matrix interphase of SiC/SiC composite
Jin, Enze; Du, Shiyu; Li, Mian; Liu, Chen; He, Shihong; He, Jian; He, Heming
2016-10-01
Silicon carbide has many attractive properties and the SiC/SiC composite has been considered as a promising candidate for nuclear structural materials. Up to now, a computational investigation on the properties of SiC/SiC composite varying in the presence of nuclear fission products is still missing. In this work, the influence of He atoms on the shear behavior of the SiC/SiC interphase is investigated via Molecular Dynamics simulation following our recent paper. Calculations are carried out on three dimensional models of graphite-like PyC/SiC interphase and amorphous PyC/SiC interphase with He atoms in different regions (the SiC region, the interface region and the PyC region). In the graphite-like PyC/SiC interphase, He atoms in the SiC region have little influence on the shear strength of the material, while both the shear strength and friction strength may be enhanced when they are in the PyC region. Low concentration of He atoms in the interface region of the graphite-like PyC/SiC interphase increases the shear strength, while there is a reduction of shear strength when the He concentration is high due to the switch of sliding plane. In the amorphous PyC/SiC interphase, He atoms can cause the reduction of the shear strength regardless of the regions that He atoms are located. The presence of He atoms may significantly alter the structure of SiC/SiC in the interface region. The influence of He atoms in the interface region is the most significant, leading to evident shear strength reduction of the amorphous PyC/SiC interphase with increasing He concentration. The behaviors of the interphases at different temperatures are studied as well. The dependence of the shear strengths of the two types of interphases on temperatures is studied as well. For the graphite-like PyC/SiC interphase, it is found strongly related to the regions He atoms are located. Combining these results with our previous study on pure SiC/SiC system, we expect this work may provide new insight
影响金属玻璃中剪切带行为的微观机制%MICROMECHANISM OF AFFECTING THE SHEAR BANDING BEHAVIORS IN METALLIC GLASSES
Institute of Scientific and Technical Information of China (English)
刘龙飞; 胡静; 蔡志鹏; 李会强; 郭世柏; 张光业
2012-01-01
Shear banding behaviors in metallic glasses(MGs) are studied in the present paper. Based on the band-like solution and the critical wavelength of shear banding instability, the critical free volume concentration of shear banding instability and the thickness of shear band in MGs are predicted. The results a-gree well with experimental observations and simulations. We also demonstrates that the prediction of shear band thickness,which is based on the critical wavelength,is only valid for a short time after shear instability and the diffusion of defects should be included in the mature shear band in MGs. The physical factors governing the thickness of shear bands are also illustrated. The results indicate that the thickness of shear bands is insensitive to the Poison's ratio and is governed by the features and evolution of the defects.%论文对金属玻璃发生剪切失稳形成剪切带的行为进行了分析,得到了其发生剪切失稳时的临界自由体积浓度,预测结果与实验观察和模拟结果吻合；利用两种方法对其剪切带厚度进行了预测,结果表明基于剪切失稳临界波长预测金属玻璃剪切带厚度的方法只在发生剪切失稳后极短的时间内有效,对成熟剪切带厚度的预测必须考虑自由体积的扩散效应；考察了金属玻璃的宏微观材料参数对其剪切带厚度的影响及其微观机制,发现金属玻璃剪切带厚度对其宏观材料参数(泊松比)不敏感,对与剪切相变区相关的微结构参数敏感.
Institute of Scientific and Technical Information of China (English)
车轶; 王金金; 郑新丰; 宋玉普
2013-01-01
Six reinforced high-strength concrete beam-type specimens of different sizes with stubs columns in the middle were fabricated,and tested under low-cycle reversed loading to investigate the effect of depths on flexural behavior of reinforced high-strength concrete beams.The parameters of specimens varied in depths and ratios of longitudinal reinforcement on the top of cross sections,while the depth-width ratios of cross sections,shear span-todepth ratios and ratios of longitudinal reinforcement on the bottom of cross sections and stirrups were constant.C70 concrete was used to cast the specimens and HRB 400 steel bars were used as longitudinal reinforcement.The influence of beam depths on nominal cracking moment,nominal yield moment,nominal ultimate moment,displacement ductility,plastic rotation capacity,stiffness degradation and energy dissipation capacity of high-strength concrete beams were investigated.It is shown that there is no apparent size effect observed on nominal cracking moment,nominal yield moment and nominal ultimate moment of reinforced high-strength concrete beams,and that all specimens subjected to cyclic loading clearly show similar stiffness degradation which is independent of beam depths,while the displacement ductility factors,rotational capacity as well as work index of specimens decrease with increasing of depths,showing significant size effect.%设计了6根不同几何尺寸的中部带有短柱的高强混凝土梁式试件,进行受弯性能低周反复荷载试验,研究试件截面高度对反复荷载作用下高强混凝土梁受弯性能的影响.试件截面高度和上部纵向钢筋配筋率不同,截面长宽比、剪跨比、底部纵向钢筋配筋率和配箍率等参数相同.采用C70高强混凝土,纵向受力钢筋采用HRB400级钢筋.分析了截面高度对高强混凝土梁名义开裂弯矩、名义屈服弯矩、名义极限弯矩、位移延性、塑性转动能力、刚度退化以及耗能能力的影响.研究
门式刚架蒙皮抗剪支撑作用的研究%Study on shear bracing behavior of stressed diaphragm for steel gabled frame
Institute of Scientific and Technical Information of China (English)
颜喜林
2011-01-01
通过分析受力蒙皮单元抗剪支撑作用,利用刚度等效原理把受力蒙皮单元等效成支撑,从而建立考虑蒙皮效应的门式刚架轻钢结构计算模型,提出蒙皮抗剪支撑作用的实用计算方法.%It is also study on shear bracing behavior of stressed diaphragm. Upon the principle of equivalent stiffness, the stressed-skin ofroofs and walls is simplified to the bracing bars, with which the model of building systems can be established in a convenience way. Thecalculate method of the shear bracing behavior of stressed diaphragm is suggested.
Institute of Scientific and Technical Information of China (English)
吴小军; 金广谦; 赵亚军; 张艺凡
2011-01-01
针对单一纤维的FRP筋延性较差的缺点,在采用碳/玻混杂纤维复合材料（C/G-HFRP）筋的同时,引进预应力技术。通过对2根预应力HFRP筋混凝土梁、1根普通钢筋混凝土梁和1根普通HFRP筋混凝土梁的受弯性能试验研究,分析预应力HFRP筋混凝土梁的受力过程、破坏形态、抗弯承载力和变形等,提出了等效抗弯刚度的计算模型,为HFRP筋的工程应用提供了依据。%Based on the defects of low ductility of simplex FRP bars,carbon/glass hybrid fiber reinforced plastic（C/G-HFRP） bars and prestressed technology were used.The stressing process,failure patterns,flexural capacity and deformation were studied through experiment on two prestressed concrete beams reinforced with HFRP bars,one concrete beam reinforced with steel bars and one concrete beam reinforced with HFRP bars.The calculation mode for flexural stiffness of prestressed concrete beams reinforced with HFRP bars was presented which provided an evidence for engineering application.
Punching shear of flat reinforced-concrete s labs under fire conditions
Smith, Holly Kate Mcleod
2016-01-01
This thesis examines punching shear response of reinforced-concrete flat slabs under fire conditions. The shear behaviour of concrete in fire is relatively poorly understood compared to its flexural response. Failures such as the Gretzenbach car park failure in Switzerland (2004) have prompted concerns over the punching shear capacity of flat slabs in fire. The shear behaviour of reinforced-concrete in fire depends on degradation of the individual material properties with te...
Component-Based Model for Single-Plate Shear Connections with Pretension and Pinched Hysteresis.
Weigand, Jonathan M
2017-02-01
Component-based connection models provide a natural framework for modeling the complex behaviors of connections under extreme loads by capturing both the individual behaviors of the connection components, such as the bolt, shear plate, and beam web, and the complex interactions between those components. Component-based models also provide automatic coupling between the in-plane flexural and axial connection behaviors, a feature that is essential for modeling the behavior of connections under column removal. This paper presents a new component-based model for single-plate shear connections that includes the effects of pre-tension in the bolts and provides the capability to model standard and slotted holes. The component-based models are exercised under component-level deformations calculated from the connection demands via a practical rigid-body displacement model, so that the results of the presented modeling approach remains hand-calculable. Validation cases are presented for connections subjected to both seismic and column removal loading. These validation cases show that the component-based model is capable of predicting the response of single-plate shear connections for both seismic and column removal loads.
Flexural performance of woven hybrid composites
Maslinda, A. B.; Majid, M. S. Abdul; Dan-mallam, Y.; Mazawati, M.
2016-07-01
This paper describes the experimental investigation of the flexural performance of natural fiber reinforced polymer composites. Hybrid composites consist of interwoven kenaf/jute and kenaf/hemp fibers was prepared by infusion process using epoxy as polymer matrix. Woven kenaf, jute and hemp composites were also prepared for comparison. Both woven and hybrid composites were subjected to three point flexural test. From the result, bending resistance of hybrid kenaf/jute and kenaf/hemp composites was higher compared to their individual fiber. Hybridization with high strength fiber such as kenaf enhanced the capability of jute and hemp fibers to withstand bending load. Interlocking between yarns in woven fabric make pull out fibers nearly impossible and increase the flexural performance of the hybrid composites.
Flexure and rheology of Pacific oceanic lithosphere
Hunter, Johnny; Watts, Tony
2016-04-01
The idea of a rigid lithosphere that supports loads through flexural isostasy was first postulated in the late 19th century. Since then, there has been much effort to investigate the spatial and temporal variation of the lithosphere's flexural rigidity, and to understand how these variations are linked to its rheology. We have used flexural modelling to first re-assess the variation in the rigidity of oceanic lithosphere with its age at the time of loading, and then to constrain mantle rheology by testing the predictions of laboratory-derived flow laws. A broken elastic plate model was used to model trench-normal, ensemble-averaged profiles of satellite-derived gravity at the trench-outer rise system of circum-Pacific subduction zones, where an inverse procedure was used to find the best-fit Te and loading conditions. The results show a first-order increase in Te with plate age, which is best fit by the depth to the 400 ± 35°C plate-cooling isotherm. Fits to the observed gravity are significantly improved by an elastic plate that weakens landward of the outer rise, which suggests that bending-induced plate weakening is a ubiquitous feature of circum-Pacific subduction zones. Two methods were used to constrain mantle rheology. In the first, the Te derived by modelling flexural observations was compared to the Te predicted by laboratory-derived yield strength envelopes. In the second, flexural observations were modelled using elastic-plastic plates with laboratory-derived, depth-dependent yield strength. The results show that flow laws for low-temperature plasticity of dry olivine provide a good fit to the observations at circum-Pacific subduction zones, but are much too strong to fit observations of flexure in the Hawaiian Islands region. We suggest that this discrepancy can be explained by differences in the timescale of loading combined with moderate thermal rejuvenation of the Hawaiian lithosphere.
Flexural performance of foam concrete containing pulverized bone as partial replacement of cement
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Efe Ikponmwosa
2014-01-01
Full Text Available This paper presents the results of a study conducted to investigate the flexural behaviour of foam concrete containing pulverised bone as partial replacement of cement. A total of sixty reinforced beams (150×150×750 mm were used to investigate the flexural behaviour of the specimens. For reinforcement of the beams, hot-rolled, deformed 10-mm-diameter bars with yield and ultimate stresses of 478.10 N/mm2 and 710.81 N/mm2 respectively were used. The cement constituent of the mix was partly replaced with up to 20% of pulverised bone. The flexural parameters investigated are crack formation and its pattern, failure mode, ul timate load, theoretical and experimental ultimate moments, deflection and stiffness. From the results of this investigation, it is concluded that the provision of the design standard in relation to shear and flexural design of beams can be considered as adequate for the design of reinforced foam concrete. It is further concluded that the stiffness is not affected by the inclusion of pulverised bone in the mix at up to 15% cement replacement level , and neither is the deflection pattern of the uncracked sections of the specimens affected by the inclusion of pulverised bone. The bending moments of the specimens,however, decreased with increase in pulverised bone.
Rotation flexure with temperature controlled modal frequency
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Salas, Theodore E.; Barney, Patrick S.; Ison, Aaron M.; Akau, Ronald L; Weir, Nathan
2017-09-12
A flexure bearing includes an inner race, an outer race, and a plurality of substantially planar radially extending blades coupled between the inner and outer race. The blades have a thickness that is thinner than a thickness of the inner and outer races. The inner race, outer race, and blades have substantially the same height. At least one heating element is coupled to the inner race and/or the outer race. The heating element is configured to apply heat to the race that it is coupled to in order to tune the flexure bearing.
Wu, Xianqian; Yin, Qiuyun; Huang, Chenguang
2015-11-01
The dynamic response of the 57 vol./vol. % dense spherical silica particle-polyethylene glycol suspension at high pressure was investigated through short pulsed laser induced shock experiments by measuring the back free surface velocities of aluminum-shear thickening fluid (STF)-aluminum assembled targets. The results showed that the attenuation behavior of shock wave in the STF was dependent on shock pressure, stress state, and test temperature. The measured back free particle velocities of the targets and shock wave velocities in the STF decreased with the decrease in shock pressure while shocked at the same stress state and the same test temperature. In addition, two types of dragging mechanisms in the STF were observed while shocked at different stress states. For a uniaxial strain state, the impact induced jamming behavior in the STF is the dragging mechanism for the attenuation of shock wave, and a critical shock pressure was required for the impact induced thickening behavior. However, while the shock wave transformed from a uniaxial strain state to a dilatation state after transmitted to a certain distance, beside the dragging effect of impact induced jamming behavior, a strong dragging effect, induced by shear induced thickening behavior, was also observed.
Shear Thinning of Noncolloidal Suspensions
Vázquez-Quesada, Adolfo; Tanner, Roger I.; Ellero, Marco
2016-09-01
Shear thinning—a reduction in suspension viscosity with increasing shear rates—is understood to arise in colloidal systems from a decrease in the relative contribution of entropic forces. The shear-thinning phenomenon has also been often reported in experiments with noncolloidal systems at high volume fractions. However its origin is an open theoretical question and the behavior is difficult to reproduce in numerical simulations where shear thickening is typically observed instead. In this letter we propose a non-Newtonian model of interparticle lubrication forces to explain shear thinning in noncolloidal suspensions. We show that hidden shear-thinning effects of the suspending medium, which occur at shear rates orders of magnitude larger than the range investigated experimentally, lead to significant shear thinning of the overall suspension at much smaller shear rates. At high particle volume fractions the local shear rates experienced by the fluid situated in the narrow gaps between particles are much larger than the averaged shear rate of the whole suspension. This allows the suspending medium to probe its high-shear non-Newtonian regime and it means that the matrix fluid rheology must be considered over a wide range of shear rates.
Institute of Scientific and Technical Information of China (English)
NIU Peng-zhi; HUANG Pei-yan; DENG Jun; HAN Qiang
2007-01-01
Extensive research has shown that externally bonded carbon fiber reinforced polymer (CFRP) laminates are particularly suitable for improving the fatigue behavior of reinforced concrete (RC) beams. This paper presents the research on flexural rigidity evolvement laws by testing 14 simple-supported RC beams strengthened with carbon fiber laminates (CFL) under cyclic load, and 2 under monotone load as a reference. The cyclic load tests revealed the peak load applied onto the surface of a supported RC beam strengthened with CFL is linear to the logarithm of its fatigue life, and the flexural rigidity evolvement undergoes three distinct phases: a rapid decrease from the start to about 5% of the fatigue life; an even development from 5% to about 99% of the fatigue life; and a succedent rapid decrease to failure. When the ratio of fatigue cycles to the fatigue life is within 0.05 to 0.99, the flexural rigidity varies linearly with the ratio. The peak load does not affect the flexural rigidity evolvement if it is not high enough to make the main reinforcements yield. The dependences of the flexural rigidity of specimens formed in the same group upon their fatigue cycles normalized by fatigue life are almost coincident. This implies the flexural rigidity may be a material parameter independent of the stress level. These relationships of flexural rigidity to fatigue cycles, and fatigue life may be able to provide some hints for fatigue design and fatigue life evaluation of RC member strengthened with CFL; nevertheless the findings still need verifying by more experiments.
Energy Technology Data Exchange (ETDEWEB)
Ruggles-Wrenn, M.B., E-mail: marina.ruggles-wrenn@afit.edu; Pope, M.T.; Zens, T.W.
2014-07-29
Creep behavior in interlaminar shear of a non-oxide ceramic composite with a multilayered matrix was investigated at 1200 °C in laboratory air and in steam environment. The composite was produced via chemical vapor infiltration (CVI). The composite had an oxidation inhibited matrix, which consisted of alternating layers of silicon carbide and boron carbide and was reinforced with laminated Hi-Nicalon™ fibers woven in a five-harness-satin weave. Fiber preforms had pyrolytic carbon fiber coating with boron carbon overlay applied. The interlaminar shear properties were measured. The creep behavior was examined for interlaminar shear stresses in the 16–22 MPa range. Primary and secondary creep regimes were observed in all tests conducted in air and in steam. In air and in steam, creep run-out defined as 100 h at creep stress was achieved at 16 MPa. Similar creep strains were accumulated in air and in steam. Furthermore, creep strain rates and creep lifetimes were only moderately affected by the presence of steam. The retained properties of all specimens that achieved run-out were characterized. Composite microstructure, as well as damage and failure mechanisms were investigated. The tested specimens were also examined using electron probe microanalysis (EPMA) with wavelength dispersive spectroscopy (WDS). Analysis of the fracture surfaces revealed significant surface oxidation, but only trace amounts of boron and carbon. Cross sectional analysis showed increasing boron concentration in the specimen interior.
Directory of Open Access Journals (Sweden)
Ruggles-Wrenn Marina
2015-01-01
Full Text Available Creep behavior in interlaminar shear of a non-oxide ceramic composite with a multilayered matrix was investigated at 1200∘C in laboratory air and in steam environment. The composite was produced via chemical vapor infiltration (CVI. The composite had an oxidation inhibited matrix, which consisted of alternating layers of silicon carbide and boron carbide and was reinforced with laminated Hi-NicalonTM fibers woven in a five-harness-satin weave. Fiber preforms had pyrolytic carbon fiber coating with boron carbon overlay applied. The interlaminar shear properties were measured. The creep behavior was examined for interlaminar shear stresses in the 16–22 MPa range. Primary and secondary creep regimes were observed in all tests conducted in air and in steam. In air and in steam, creep run-out defined as 100 h at creep stress was achieved at 16 MPa. Similar creep strains were accumulated in air and in steam. Furthermore, creep strain rates and creep lifetimes were only moderately affected by the presence of steam. The retained properties of all specimens that achieved run-out were characterized. Composite microstructure, as well as damage and failure mechanisms were investigated. The tested specimens were also examined using electron probe microanalysis (EPMA with wavelength dispersive spectroscopy (WDS. Analysis of the fracture surfaces revealed significant surface oxidation, but only trace amounts of boron and carbon. Cross sectional analysis showed increasing boron concentration in the specimen interior.
Reinhart, William; Gustavsen, Rick; Vogler, Tracy; Alexander, Scott; Thornhill, Tom; Clements, Brad; Bartram, Brian; SNL/LANL Collaboration
2013-06-01
HMX (cyclotetramethylene-tetranitramine) based explosive, PBX 9501, is a conventional high explosive formulation composed of 95% wt. of HMX and 5% binders. A series of experiments were performed to investigate one-dimensional combined pressure-shear waves in PBX-9501. This study is thought to be the first to estimate shear stress and strength in a plastic bonded high explosive. Experiments were conducted using Sandia National Laboratories oblique launcher at the Shock Thermodynamics Applied Research (STAR) facility. A projectile is keyed to a slot in the launcher barrel in order to prevent rotation. The projectile is faced with a titanium alloy plate inclined at 20 degrees to the launcher axis. The target consists of a 1 mm thick PBX 9501 disk sandwiched between two titanium alloy plates. Measurements of shear and longitudinal particle velocities were used to determine stresses and infer strength. Longitudinal stresses from 1.4 to 3.1 GPa were applied which presented corresponding shear stresses of 0.1 to 0.23 GPa at high shearing strain rates up to 0.4 x 105s-1. This experimental data now provides for the first time, relevant information for model development.
Flexural strength and ductility of reinforced concrete beams
Kwan, AKH; Ho, JCM; Pam, HJ
2002-01-01
In the design of reinforced concrete beams, especially those made of high-strength concrete and those in earthquake-resistant structures, both the flexural strength and ductility need to be considered. From the numerical results obtained in a previous study on the post-peak behaviour and flexural ductility of reinforced concrete beams, the interrelation between the flexural strength and the flexural ductility that could be simultaneously achieved was evaluated and plotted in the form of chart...
Flexural waves focusing through shunted piezoelectric patches
Yi, K.; Collet, M.; Ichchou, M.; Li, L.
2016-07-01
In this paper, we designed and analyzed a piezo-lens to focus flexural waves in thin plates. The piezo-lens is comprised of a host plate and piezoelectric arrays bonded on the surfaces of the plate. The piezoelectric patches are shunted with negative capacitance circuits. The effective refractive indexes inside the piezo-lens are designed to fit a hyperbolic secant distribution by tuning the negative capacitance values. A homogenized model of a piezo-mechanical system is adopted in the designing process of the piezo-lens. The wave focusing effect is studied by the finite element method. Numerical results show that the piezo-lens can focus flexural waves by bending their trajectories, and is effective in a large frequency band. The piezo-lens has the ability to focus flexural waves at different locations by tuning the shunting negative capacitance values. The piezo-lens is shown to be effective for flexural waves generated by different types of sources.
Flexural Properties of Eastern Hardwood Pallet Parts
John A. McLeod; Marshall S. White; Paul A. Ifju; Philip A. Araman
1991-01-01
Accurate estimates of the flexural properties of pallet parts are critical to the safe, yet efficient, design of wood pallets. To develop more accurate data for hardwood pallet parts, 840 stringers and 2,520 deckboards, representing 14 hardwood species, were sampled from 35 mills distributed throughout the Eastern United States. The parts were sorted by species,...
Psoriasis of the face and flexures.
Kerkhof, P.C.M. van de; Murphy, G.M.; Austad, J.; Ljungberg, A.; Cambazard, F.; Duvold, L.B.
2007-01-01
Facial and flexural psoriasis may impair the quality of life of psoriatic patients considerably. For the adequate management of psoriasis it is important to pay attention to lesions at these sensitive sites, which require an approach different to that for lesions on other sites in several respects.
Psoriasis of the face and flexures.
Kerkhof, P.C.M. van de; Murphy, G.M.; Austad, J.; Ljungberg, A.; Cambazard, F.; Duvold, L.B.
2007-01-01
Facial and flexural psoriasis may impair the quality of life of psoriatic patients considerably. For the adequate management of psoriasis it is important to pay attention to lesions at these sensitive sites, which require an approach different to that for lesions on other sites in several respects.
Flexural buckling of fire exposed aluminium columns
Maljaars, J.; Twilt, L.; Soetens, F.
2009-01-01
In order to study buckling of fire exposed aluminium columns, a finite element model is developed. The results of this model are verified with experiments. Based on a parametric study with the finite element model, it is concluded that the simple calculation model for flexural buckling of fire expos
Moore, Diane E.; Lockner, David A.
2013-01-01
The serpentinized ultramafic rocks found in many plate-tectonic settings commonly are juxtaposed against crustal rocks along faults, and the chemical contrast between the rock types potentially could influence the mechanical behavior of such faults. To investigate this possibility, we conducted triaxial experiments under hydrothermal conditions (200-350°C), shearing serpentinite gouge between forcing blocks of granite or quartzite. In an ultramafic chemical environment, the coefficient of friction, µ, of lizardite and antigorite serpentinite is 0.5-0.6, and µ increases with increasing temperature over the tested range. However, when either lizardite or antigorite serpentinite is sheared against granite or quartzite, strength is reduced to µ ~ 0.3, with the greatest strength reductions at the highest temperatures (temperature weakening) and slowest shearing rates (velocity strengthening). The weakening is attributed to a solution-transfer process that is promoted by the enhanced solubility of serpentine in pore fluids whose chemistry has been modified by interaction with the quartzose wall rocks. The operation of this process will promote aseismic slip (creep) along serpentinite-bearing crustal faults at otherwise seismogenic depths. During short-term experiments serpentine minerals reprecipitate in low-stress areas, whereas in longer experiments new Mg-rich phyllosilicates crystallize in response to metasomatic exchanges across the serpentinite-crustal rock contact. Long-term shear of serpentinite against crustal rocks will cause the metasomatic mineral assemblages, which may include extremely weak minerals such as saponite or talc, to play an increasingly important role in the mechanical behavior of the fault. Our results may explain the distribution of creep on faults in the San Andreas system.
Design and Performance Optimization of Large Stroke Spatial Flexures
Wiersma, D.H.; Boer, S.E.; Aarts, R.G.K.M.; Brouwer, D.M.
2013-01-01
Flexure hinges inherently lose stiffness in supporting directions when deflected. In this paper a method is presented for optimizing the geometry of flexure hinges, which aims at maximizing supporting stiffnesses. In addition, the new ∞ -flexure hinge design is presented. The considered hinges are
Cumulative Effect of Crumb Rubber and Steel Fiber on the Flexural Toughness of Concrete
Directory of Open Access Journals (Sweden)
B. H. Abu Bakar
2017-02-01
Full Text Available Concrete properties, such as toughness and ductility, are enhanced to resist different impacts or blast loads. Rubberized concrete, which could be considered a green material, is produced from recycled waste tires grinded into different crumb rubber particle sizes and mixed with concrete. In this study, the behavior of rubberized steel fiber-reinforced concrete is investigated. Flexural performance of concrete beams (400×100×100 mm manufactured from plain, steel fiber, crumb rubber and combination crumb rubber and steel fiber are also evaluated. Similarly, concrete slabs (500×500×50 mm are also tested under flexural loading. Flexural performance of the SFRRC mixtures was significantly enhanced. The toughness and maximum deflection of specimens with rubber were considerably improved. Steel fiber/crumb rubber-reinforced concrete can be used for practical application, which requires further studies.
Flexural fatigue characteristics of steel fiber reinforced recycled aggregate concrete (SFRRAC
Directory of Open Access Journals (Sweden)
Heeralal M.
2009-01-01
Full Text Available This research work is aimed at investigating the flexural fatigue behavior of Steel Fiber Reinforced Recycled Aggregate Concrete (SFRRAC. This study gains importance in view of the wide potential for demolished concrete to serve as a source of quality aggregate feed stock in a variety of structural and non-structural applications. This is a continuation of a series of investigations being conducted aimed at optimizing the utilization of recycled aggregate concrete in rigid pavements. A total of 72 standard flexure specimens of 100mm x 100mm x 450mm were cast and tested for flexure under both static and fatigue loading. The parameters of the investigation included the different replacements of recycled aggregate in natural aggregate, presence of steel fiber and different stress levels. The study showed that the recycled aggregates can be used in rigid pavements also and the inclusion of fibers can benefit the fatigue performance of recycled aggregate concrete.
Effect of fiber loading on flexural strength of hybrid sisal/hemp-HDPE composites
Aggarwal, Lakshya; Sinha, Shishir; Gupta, V. K.
2015-05-01
The continuing demand for sustainable materials and increasing environmental concerns have led to intense research in the field of natural fiber reinforced composites. Natural fibers are favored over synthetic fibers as reinforcement due to positive environmental benefits such as raw material utilization at source and easy disposable of the biodegradable fiber. In the present work, we have investigated flexural behavior of hybrid natural fiber reinforced HDPE composites. The matrix comprises of 50-50 ratio of virgin and recycled HDPE and the content of fibers (sisal and hemp) in the composite is varied from 10 to 30%. The natural fibers were mercerized with NaOH solution and chemically treated with maleic anhydride. The flexural specimens were prepared by injection moulding process and the testing was conducted in accordance to ASTM D790 standards. It is revealed that the flexural strength of the hybrid composite increases with the increase in fibers content when compared to specimen containing 100% HDPE.
Linear free flexural vibration of cracked functionally graded plates in thermal environment
Natarajan, S; Ganapathi, M; Kerfriden, P; Bordas, S; 10.1016/j.compstruc.2011.04.002
2011-01-01
In this paper, the linear free flexural vibrations of functionally graded material plates with a through center crack is studied using an 8-noded shear flexible element. The material properties are assumed to be temperature dependent and graded in the thickness direction. The effective material properties are estimated using the Mori-Tanaka homogenization scheme. The formulation is developed based on first-order shear deformation theory. The shear correction factors are evaluated employing the energy equivalence principle. The variation of the plates natural frequency is studied considering various parameters such as the crack length, plate aspect ratio, skew angle, temperature, thickness and boundary conditions. The results obtained here reveal that the natural frequency of the plate decreases with increase in temperature gradient, crack length and gradient index.
Institute of Scientific and Technical Information of China (English)
丁亚红; 马艳洁
2012-01-01
A technique for increasing the flexural properties of concrete beams strengthened with prestressed carbon fiber in sawed grooves in the concrete cover is studied. Ten beams under monotonic loads were tested. The stressing process, failure capacity, flexural capacity, displacement ductility and deformation were studied. The test shows that the strengthening technique using carbon fiber bonding in the concrete cover can enhance the first-crack load and steel- yielding load of beams compared with the ordinary beam. It is worth noticing that the prestressed carbon fiber can limit the crack width all the way up to failure and improve the service performance of the strengthened beams. It also reduces the deformation of reinforcement and increases yield loads. The high-strength performance of carbon fiber reinforcement can be fully used. With the reinforcement amount and the initial prestressing level increased, ductility will be reduced to some extent. The embedded strengthening method with prestressing carbon fiber reinforcement can effectively solve the problems of existing strengthening method, such as the inadequate use of materials and debonding failure. It is an effective strengthening method.%通过对内嵌预应力碳纤维加固混凝土梁的静力加载试验，对其受力过程、破坏形态、承载力、延性和变形情况进行了分析。试验结果表明：内嵌预应力碳纤维筋加固混凝土梁能大幅度提高被加固梁的开裂荷载和极限荷载，延迟裂缝开展，改善梁的正常使用状态；有效减小加固构件的变形，延缓筋材屈服，充分利用碳纤维筋的高强性能；且随着加固量及初始预应力水平的提高，被加固试件的延性有所降低。内嵌预应力碳纤维筋加固法能有效解决现有加固方法在材料利用不充分，粘结剥离破坏等方面的缺点，是一种行之有效的加固方法。
Shear and anchorage behaviour of fire exposed hollow core slabs
Fellinger, J.
2005-01-01
The fire resistance of hollow core slabs is currently assessed considering flexural failure only. However, fire tests show that shear or anchorage failure can also govern the load bearing behaviour. This paper is based on the dissertation by the author1 and discusses existing and new fire tests. It
Magnetohydrodynamic Shearing Waves
Johnson, B M
2006-01-01
I consider the nonaxisymmetric linear theory of an isothermal magnetohydrodynamic (MHD) shear flow. The analysis is performed in the shearing box, a local model appropriate for a thin disk geometry. Linear perturbations in this model can be decomposed in terms of shearing waves (shwaves), which appear spatially as plane waves in a frame comoving with the shear. The time dependence of these waves cannot in general be expressed in terms of a frequency eigenvalue as in a normal mode decomposition, and numerical integration of a set of first-order amplitude equations is required for a complete characterization of their behavior. Their generic time dependence, however, is oscillatory with slowly-varying frequency and amplitude, and one can construct accurate analytic solutions by applying the Wentzel-Kramers-Brillouin method to the full set of amplitude equations. For the bulk of wavenumber space, therefore, the shwaves are well-approximated as modes with time-dependent frequencies and amplitudes. The incompressiv...
Energy Technology Data Exchange (ETDEWEB)
Zheng, Zhong, E-mail: 11329038@zju.edu.cn; Song, Yihu, E-mail: s-yh0411@zju.edu.cn; Wang, Xiang, E-mail: 11229036@zju.edu.cn; Zheng, Qiang, E-mail: zhengqiang@zju.edu.cn [MOE Key Laboratory of Macromolecule Synthesis and Functionalization, Department of Polymer Science and Engineering, Zhejiang University, Hangzhou 310027 (China)
2015-07-15
Variation of colloidal and interfacial interactions leads to a microstructural diversity in fumed silica dispersions exhibiting absolutely different sol- or gel-like rheological responses. In this study, fumed silicas with different surface areas (200–400 m{sup 2}/g) and surface characteristics (hydrophilic or hydrophobic) are dispersed into moisture-cured polyurethane. The microstructures investigated using transmission electron microscope are associated perfectly with three different rheological behaviors: (i) Sols with well-dispersed silica aggregates, (ii) weak gels with agglomerate-linked networks, and (iii) strong gels with concentrated networks of large agglomerates. Though sols and gels are well distinguished by shear thickening or sustained thinning response through steady shear flow test, it is interesting that the sols and weak gels exhibit a uniform modulus plateau-softening-hardening-softening response with increasing dynamic strain at frequency 10 rad s{sup −1} while the strong gels show a sustained softening beyond the linear regime. Furthermore, the onset of softening and hardening can be normalized: The two softening are isoenergetic at mechanical energies of 0.3 J m{sup −3} and 10 kJ m{sup −3}. On the other hand, the hardening is initiated by a critical strain of 60%. The mechanisms involved in the generation of the sol- and the gel-like dispersions and their structural evolutions during shear are thoroughly clarified in relation to the polyols, the characteristic and content of silica and the curing catalysts.
Flexural Mie Resonances: Localized Surface Platonic Modes
Farhat, M; Chen, P Y; Salama, K N; Bagci, H
2016-01-01
Surface plasmons polaritons were thought to exist only in metals near their plasma frequencies. The concept of spoof plasmons extended the realms of plasmonics to domains such as radio frequencies, magnetism, or even acoustic waves. Here, we introduce the concept of localized surface platonic modes (SPMs). We demonstrate that they can be generated on a two-dimensional clamped (or stress-free) cylindrical surface, in a thin elastic plate, with subwavelength corrugations under excitation by an incident flexural plane wave. Our results show that the corrugated rigid surface is elastically equivalent to a cylindrical scatterer with negatively uniform and dispersive flexural rigidity. This, indeed, suggests that plasmonic-like platonic materials can be engineered with potential applications in various areas including earthquake sensing, or elastic imaging and cloaking.
Flexural Free Vibrations of Multistep Nonuniform Beams
Directory of Open Access Journals (Sweden)
Guojin Tan
2016-01-01
Full Text Available This paper presents an exact approach to investigate the flexural free vibrations of multistep nonuniform beams. Firstly, one-step beam with moment of inertia and mass per unit length varying as I(x=α11+βxr+4 and m(x=α21+βxr was studied. By using appropriate transformations, the differential equation for flexural free vibration of one-step beam with variable cross section is reduced to a four-order differential equation with constant coefficients. According to different types of roots for the characteristic equation of four-order differential equation with constant coefficients, two kinds of modal shape functions are obtained, and the general solutions for flexural free vibration of one-step beam with variable cross section are presented. An exact approach to solve the natural frequencies and modal shapes of multistep beam with variable cross section is presented by using transfer matrix method, the exact general solutions of one-step beam, and iterative method. Numerical examples reveal that the calculated frequencies and modal shapes are in good agreement with the finite element method (FEM, which demonstrates the solutions of present method are exact ones.
Tachykinin receptors in the equine pelvic flexure.
Sonea, I M; Wilson, D V; Bowker, R M; Robinson, N E
1997-07-01
Tachykinins, of which substance P (SP) is the prototype, are neuropeptides which are widely distributed in the nervous systems. In the equine gut, SP is present in enteric nerves and is a powerful constrictor of enteric muscle; in other species, SP is also known to have potent vasodilatory and pro-inflammatory effects. The specific effects of SP are determined by the subtype of receptor present in the target tissue. There are 3 known subtypes of tachykinin receptors, distinguished by their relative affinities for SP and other tachykinins. The distribution of SP binding sites in the equine pelvic flexure was determined using 125I-Bolton Hunter SP (I-BHSP) autoradiography. Most I-BHSP binding sites were determined to be saturable and specific, therefore presumably representing tachykinin receptors. The greatest degree of I-BHSP binding occurred over very small vessels, and over the muscularis mucosae; I-BHSP binding was also intense over the circular muscle of the muscularis externa and mucosa, and present, although less intense, over the longitudinal muscle of the muscularis externa. Competition of I-BHSP with specific receptor agonists for binding sites in the equine pelvic flexure were used to determine the subtypes of tachykinin receptors present. The neurokinin-1 receptor subtype predominated in the equine pelvic flexure, followed by the neurokinin-3 receptor subtype.
Shen, Hui-Shen
2010-06-01
Buckling and postbuckling analysis is presented for axially compressed microtubules (MTs) embedded in an elastic matrix of cytoplasm. The microtubule is modeled as a nonlocal shear deformable cylindrical shell which contains small scale effects. The surrounding elastic medium is modeled as a Pasternak foundation. The governing equations are based on higher order shear deformation shell theory with a von Kármán-Donnell-type of kinematic nonlinearity and include the extension-twist and flexural-twist couplings. The thermal effects are also included and the material properties are assumed to be temperature-dependent. The small scale parameter e (0) a is estimated by matching the buckling load from their vibrational behavior of MTs with the numerical results obtained from the nonlocal shear deformable shell model. The numerical results show that buckling load and postbuckling behavior of MTs are very sensitive to the small scale parameter e (0) a. The results reveal that the MTs under axial compressive loading condition have an unstable postbuckling path, and the lateral constraint has a significant effect on the postbuckling response of a microtubule when the foundation stiffness is sufficiently large.
Buckling and postbuckling of radially loaded microtubules by nonlocal shear deformable shell model.
Shen, Hui-Shen
2010-05-21
This paper presents an investigation on the buckling and postbuckling of microtubules (MTs) subjected to a uniform external radial pressure in thermal environments. The microtubule is modeled as a nonlocal shear deformable cylindrical shell which contains small scale effects. The governing equations are based on higher order shear deformation shell theory with a von Kármán-Donnell-type of kinematic nonlinearity and include the extension-twist and flexural-twist couplings. The thermal effects are also included and the material properties are assumed to be temperature-dependent. A singular perturbation technique is employed to determine the buckling pressure and postbuckling equilibrium paths. The small scale parameter e(0)a is estimated by matching the buckling pressure of MTs measured from the experiments with the numerical results obtained from the nonlocal shear deformable shell model. The numerical results show that buckling pressure and postbuckling behavior of MTs are very sensitive to the small scale parameter e(0)a. The results reveal that the 13_3 microtubule has a stable postbuckling path, whereas the 13_2 microtubule has an unstable postbuckling behavior due to the presence of skew angles.
Hu, Bin; Kieweg, Sarah
2011-11-01
Many complex fluids of interest exhibit viscoelastic hehavior. Polymeric drug delivery vehicles, such as anti-HIV topical microbicides, are among these fluids. For the optimal design of microbicides, the combined effect of shear-thinning and elastic behavior on the gravity-driven spreading of viscoelastic fluids is studied. We develop a 2D model to simulate the fluids spreading down an incline using ANSYS POLYFLOW software package. Arbitrary Lagrangian-Eulerian (ALE) method combined with Lagrangian remeshing is applied to track the moving free surface of fluids during spreading. Adaptive meshing method is used to generate high quality mesh for the remeshing process. Based on an elastic viscous split stress (EVSS) approach, several differential viscoelastic constitutive models are studied to investigate the combined effect of shear-thinning and elastic behavior. Mesh convergence test and constant volume check are studied to verify the new model. Moreover, the new model with zero elasticity is compared with previous studies of Newtonian and power-law fluids.
Energy Technology Data Exchange (ETDEWEB)
Jiang, Linhua, E-mail: hhulhjiang@gmail.com [College of Mechanics and Materials, Hohai University, 1 Xikang Rd., Nanjing, 210098 (China); Hydraulic Engineering Research Center for New Materials and Protection, Jiangsu Province, 1 Xikang Rd., Nanjing, 210098 (China); Liu, Hao; Wang, Yongliang; Zhang, Yan; Song, Zijian; Xu, Jinxia; Jin, Ming; Jiang, Peng; Xu, Yi; Gao, Hailang [College of Mechanics and Materials, Hohai University, 1 Xikang Rd., Nanjing, 210098 (China)
2015-08-15
The flexural fatigue was enforced on reinforced concrete beam with stress level of 0.6 and different fatigue life cycles. Steels removed from the beams were soaked in the saturated Ca(OH){sub 2} solution, which was used as a simulated concrete pore solution. The NaCl solution was chosen as the source of chloride ions. The Chloride Threshold Values (CTV) were detected by combining the open-circuit potentials (E{sub corr}) with the corrosion current densities (i{sub corr}), which were obtained by electrochemical impedance spectroscopy (EIS). The changes of microstructure caused by the flexural fatigue were observed by scanning electron microscopy (SEM). The results showed that as the fatigue cycle times increased, the CTV decreased under a certain stress level and range of fatigue life cycles. The grains became finer and cracks appeared on the surface of the steels. While the capacitive arcs under no flexural fatigue decreased gradually with the addition of chloride ions, the ones under flexural fatigue presented no regularity. Cracks at the surface were expanded because of sustaining flexural fatigue, which degenerated the later resistance to chloride ions of the steels. - Highlights: • The influence of flexural fatigue on chloride threshold value was examined. • The chloride threshold values vary with different fatigue life cycles. • The corrosion behavior depends on the surface integrity of the steels.
THE EFFECT OF FLY ASH ON FLEXURAL CAPACITY CONCRETE BEAMS
Directory of Open Access Journals (Sweden)
Amir Mohammad Amiri
2016-06-01
Full Text Available This paper presents the flexural response of Reinforced Geopolymer Concrete (RGPC beam. A commercial finite element (FE software ABAQUS has been used to perform a structural behavior of RGPC beam. Using parameters such: stress, strain, Young’s modulus, and Poisson’s ratio obtained from experimental results, a beam model has been simulated in ABAQUS. The results from experimental test and ABAQUS simulation were compared. Due to friction forces at the supports and loading rollers; slip occurring, the actual deflection of RGPC beam from experimental test results were slightly different from the results of ABAQUS. And there is good agreement between the crack patterns of fly-ash based geopolymer concrete generated by FE analysis using ABAQUS, and those in experimental data.
Zhao, X; Qian, Z H; Zhang, S; Liu, J X
2015-12-01
An analytical approach is taken to investigate shear horizontal wave (SH wave) propagation in layered cylinder with initial stress, where a piezomagnetic (PM) material thin layer is bonded to a piezoelectric (PE) cylinder. Two different material combinations are taken into account, and the phase velocities of the SH waves are numerically calculated for the magnetically open and short cases, respectively. It is found that the initial stress, the thickness ratio and the material performance have a great influence on the phase velocity. The results obtained in this paper can offer fundamental significance to the application of PE/PM composite media or structure for the acoustic wave and microwave technologies.
Institute of Scientific and Technical Information of China (English)
邓宗才; 薛会青
2011-01-01
Fiber reinforced high ductility cementitious composites(ECC) has high ductility and could effectively control micro-crack width. The experiment of direct shear behavior is researched for adhesion of ECC on existing concrete and provides records for retrofitting or strengthening concrete. Experimental results show that compressive and flexural strength of ECC are improved with increase of age; Interface shear strength of ECC bonding specimens is improved with increase of S/C, indicating the behavior of adhesion of ECC on existing concrete is improved with increase of S/C; The behavior of adhesion of ECC on existing concrete is much better than on self-compacting concrete and plain concrete. ECC is perfect material for retrofitting deck and pavement, strengthening reservoir and dam.%高韧性纤维增强水泥基复合材料(ECC)具备很好的延展性和微裂缝宽度控制能力,通过ECC与老混凝土之间的界面直剪试验,研究高韧性复合材料与普通混凝土之间的界面黏结性能,为混凝土工程的维修或加固提供试验数据.试验结果表明:随着龄期的增加,ECC抗压强度与抗折强度逐渐提高;随着砂灰比的增加,ECC黏结试件的界面抗剪强度逐渐提高,说明增加砂灰比可以提高ECC与老混凝土间的界面黏结性能;ECC与老混凝土间的界面黏结性能远优于自密实混凝土和普通混凝土,高韧性水泥基复合材料是修补桥面、路面和加固水库、大坝等混凝土工程的理想材料.
岩石剪切破坏全应力-应变性状%COMPLETE STRESS-STRAIN BEHAVIOR FOR SHEAR FAILURE OF ROCKS
Institute of Scientific and Technical Information of China (English)
无
2001-01-01
The investigation of complete stress-strain behavior andcompressive failure behavior of some Hong Kong rocks are carried out. A large number of tests have been conducted to study the deformation and failure features of rocks. Some interesting test results have been obtained. These results show that localized deformation and failure strongly affect the deformation and failure process of the specimens just prior to the peak stress and in the post-peak stage. The two types of failure modes, namely exfoliation and shear failure have been investigated in detail. For the exfoliation failure mode, an experiment method has been proposed to observe the exfoliating process. A proposed model has been used to explain the influence of exfoliation on the gross stress-strain curve. It is found that the exfoliation during loading may be one of the reasons that a granite specimen exhibits Class Ⅱ behavior. The influences of machine stiffness control modes, end constraints, loading rate and confining pressure on the test results have been discussed and investigated. A new classification method of rock failure has been proposed. Special attention has been devoted to the investigation of the localized deformation and failure process of intact rock in the shear failure mode. A test method is proposed to detect the process. It is found that the deformation of rock material may be divided into three stages: namely uniform stage, pre-peak bifurcation stage and post-peak bifurcation stage. This phenomenon has been explained by a proposed qualitative analysis. It is further found that this localized process will significantly influence the shape of stress-strain curves, that is, the localized deformation is one of reasons that rock displays the effect of length to diameter ratio. A constitutive model is proposed to simulate the localized deformation and failure process. It can simulate the strain softening, strain localization, effect of length to diameter(L/D) ratio， unloading
Maiti, Moumita; Vinutha, H. A.; Sastry, Srikanth; Heussinger, Claus
2015-10-01
Using an athermal quasistatic simulation protocol, we study the distribution of free volumes in sheared hard-particle packings close to, but below, the random-close packing threshold. We show that under shear, and independent of volume fraction, the free volumes develop features similar to close-packed systems — particles self-organize in a manner as to mimick the isotropically jammed state. We compare athermally sheared packings with thermalized packings and show that thermalization leads to an erasure of these structural features. The temporal evolution in particular the opening-up and the closing of free-volume patches is associated with the single-particle dynamics, showing a crossover from ballistic to diffusive behavior.
Liu, Hongyi
2012-01-25
The MesoDyn method is used to investigate associative structures in aqueous solution of a nonionic triblock copolymer consisting of poly(propylene oxide) capped on both ends with poly(ethylene oxide) chains. The effect of adsorbing (hydrophobic) and nonadsorbing (hydrophilic) solid surfaces in contact with aqueous solutions of the polymer is elucidated. The macromolecules form self-assembled structures in solution. Confinement under shear forces is investigated in terms of interfacial behavior and association. The formation of micelles under confinement between hydrophilic surfaces occurs faster than in bulk aqueous solution while layered structures assemble when the polymers are confined between hydrophobic surfaces. Micelles are deformed under shear rates of 1 μs -1 and eventually break to form persistent, adsorbed layered structures. As a result, surface damage under frictional forces is prevented. Overall, this study indicates that aqueous triblock copolymers of poly(ethylene oxide) (PEO) and poly(propylene oxide) (PPO) (Pluronics, EO mPO nEO m) act as a boundary lubricant for hydrophobic surfaces but not for hydrophilic ones. © 2011 American Chemical Society.
Petit, Christophe; Canestrari, Francesco; Pannunzio, Valter; Virgili, Amadeo
2012-01-01
Synthetic waxes produced by standard and registered processes may be used to manufacture Warm Mix Asphalt (WMA), which is a modified asphalt concrete produced, applied and compacted at temperatures below those typically required. This feature leads to environmental benefits, such as reduced energy consumption, gas and fume emissions, as well as to economic/operational advantages, such as lower production costs and greater hauling distances for extended construction seasons with tighter schedules. The present article serves to compare the mechanical performance of a WMA produced by adding synthetic wax with a traditional Hot Mix Asphalt (HMA) specimen, in terms of shear fatigue response and both complex and stiffness moduli. The experimental results and related modeling work demonstrate that adding synthetic wax into the WMA composition does not hinder either the destructive or non-destructive performance of an HMA, and this finding is corroborated by respectively measuring fatigue life and stiffness.
Active Control of Shear Thickening in Suspensions
Lin, Neil Y C; Cates, Michael E; Sun, Jin; Cohen, Itai
2016-01-01
Shear thickening, an increase of viscosity with shear rate, is a ubiquitous phenomena in suspended materials that has implications for broad technological applications. Controlling this thickening behavior remains a major challenge and has led to empirical strategies ranging from altering the particle surfaces and shape to modifying the solvent properties. However, none of these methods allow for active control of flow properties during shear itself. Here, we demonstrate that by strategic imposition of a high-frequency and low-amplitude shear perturbation orthogonal to the primary shearing flow, we can largely eradicate shear thickening. The orthogonal shear effectively becomes a regulator for controlling thickening in the suspension, allowing the viscosity to be reduced by up to two decades on demand. In a separate setup, we show that such effects can be induced by simply agitating the sample transversely to the primary shear direction. Overall, the ability of in situ manipulation of shear thickening paves a...
Institute of Scientific and Technical Information of China (English)
周振功; 王彪
2003-01-01
The dynamic behavior of two collinear anti-plane shear cracks in a piezoelectriclayer bonded to two half spaces subjected to the harmonic waves is investigated by a newmethod. The cracks are parallel to the interfaces in the mid-plane of the piezoelectric layer.By using the Fourier transform, the problem can be solved with two pairs of triple integralequations. These equations are solved by using Schmidt's method. This process is quitedifferent from that adopted previously. Numerical examples are provided to show the effectof the geometry of cracks, the frequency of the incident wave, the thickness of thepiezoelectric layer and the constants of the materials upon the dynamic stress intensity factorof cracks.
Institute of Scientific and Technical Information of China (English)
周振功; 杜善义; 王彪
2003-01-01
In this paper, the non-local theory of elasticity is applied to obtain the behavior of a Griffith crack in the piezoelectric materials under anti-plane shear loading for permeable crack surface conditions. By means of the Fourier transform, the problem can be solved with the help of a pair of dual integral equations with the unknown variable being the jump of the displacement across the crack surfaces. These equations are solved by the Schmidt method. Numerical examples are provided.Unlike the classical elasticity solutions, it is found that no stress and electric displacement singularity is present at the crack tip. The non-local elastic solutions yield a finite hoop stress at the crack tip,thus allowing for a fracture criterion based on the maximum stress hypothesis. The finite hoop stress at the crack tip depends on the crack length and the lattice parameter of the materials, respectively.
Tensile and Flexural Properties of Cement Composites Reinforced with Flax Nonwoven Fabrics
Directory of Open Access Journals (Sweden)
Josep Claramunt
2017-02-01
Full Text Available The aim of this study is to develop a process to produce high-performance cement-based composites reinforced with flax nonwoven fabrics, analyzing the influence of the fabric structure—thickness and entanglement—on mechanical behavior under flexural and tensile loadings. For this purpose, composite with flax nonwoven fabrics with different thicknesses were first prepared and their cement infiltration was evaluated with backscattered electron (BSE images. The nonwoven fabrics with the optimized thickness were then subjected to a water treatment to improve their stability to humid environments and the fiber-matrix adhesion. For a fixed thickness, the effect of the nonwoven entanglement on the mechanical behavior was evaluated under flexural and direct tension tests. The obtained results indicate that the flax nonwoven fabric reinforcement leads to cement composites with substantial enhancement of ductility.
Tensile and Flexural Properties of Cement Composites Reinforced with Flax Nonwoven Fabrics
Claramunt, Josep; Ventura, Heura; Fernández-Carrasco, Lucía J; Ardanuy, Mònica
2017-01-01
The aim of this study is to develop a process to produce high-performance cement-based composites reinforced with flax nonwoven fabrics, analyzing the influence of the fabric structure—thickness and entanglement—on mechanical behavior under flexural and tensile loadings. For this purpose, composite with flax nonwoven fabrics with different thicknesses were first prepared and their cement infiltration was evaluated with backscattered electron (BSE) images. The nonwoven fabrics with the optimized thickness were then subjected to a water treatment to improve their stability to humid environments and the fiber-matrix adhesion. For a fixed thickness, the effect of the nonwoven entanglement on the mechanical behavior was evaluated under flexural and direct tension tests. The obtained results indicate that the flax nonwoven fabric reinforcement leads to cement composites with substantial enhancement of ductility. PMID:28772573
Flexure and isostasy of lunar mascons
Peters, S. T. M.; Foing, B. H.
2009-04-01
A mascon is a region of a planet's or moon's crust that contains an excess positive gravity anomaly, indicating the presence of additional mass in this area. Mascons on the Moon coincide with the locations of circular basins and hence a related origin for both is likely. The formation of a circular basin includes the excavation of the upper parts of the crust and subsequent upwelling of the lower parts as a result of isostatic compensation [1]. Afterwards, filling of the basins by mare basalts leads to concentrations of dense rocks and is hence suggested as the origin of the mascon. The present day presence of mascons indicates that there was no subsequent isostasy leading to downward migration of the moho and that they are hence supported by an elastic layer on the surface of the Moon. The interaction between mascons and this elastic shell is the main topic of our modeling. Since they were discovered by Muller and Sjogren (1968), the origin of mascons and their interaction with the crust became clearer. As we point out below, several questions have however remained unsolved. Our contribution includes the usage of recent gravity and topography models that have not been applied in mascon studies yet. Mascons act like a dense load on the lunar lithosphere and hence flexure it. Flexure profiles of circular basins have been made by previous authors [2], however, only a single-layered crust was considered until now. Our modeling includes the two-layered crustal model preferred by Wieczorek and Phillips (1997) which explains the gravity to topography ratios of the lunar highlands. On the hand of previously existing data it has been suggested that rings of negative gravity anomalies surround the mascons [3]. Whereas this observation was first questionable, prereleases of the high-resolution KAGUYA gravity measurements recently clearly confirmed the presence of these features. Part of our modeling focuses on the location and extent of the negative anomalies in respect to
Energy Technology Data Exchange (ETDEWEB)
Butler, B.D.; Hanley, H.J.M.; Straty, G.C. [National Institute of Standards and Technology, Boulder, CO (United States); Muzny, C.D. [Univ. of Colorado, Boulder, CO (United States)
1995-12-31
An experimental small angle neutron scattering (SANS) study of dense silica gels, prepared from suspensions of 24 nm colloidal silica particles at several volume fractions {theta} is discussed. Provided that {theta}{approx_lt}0.18, the scattered intensity at small wave vectors q increases as the gelation proceeds, and the structure factor S(q, t {yields} {infinity}) of the gel exhibits apparent power law behavior. Power law behavior is also observed, even for samples with {theta}>0.18, when the gel is formed under an applied shear. Shear also enhances the diffraction maximum corresponding to the inter-particle contact distance of the gel. Difficulties encountered when trying to interpret SANS data from these dense systems are outlined. Results of computer simulations intended to mimic gel formation, including computations of S(q, t), are discussed. Comments on a method to extract a fractal dimension characterizing the gel are included.
Lateral shear interferometry with holo shear lens
Joenathan, C.; Mohanty, R. K.; Sirohi, R. S.
1984-12-01
A simple method for obtaining lateral shear using holo shear lenses (HSL) has been discussed. This simple device which produces lateral shears in the orthogonal directions has been used for lens testing. The holo shear lens is placed at or near the focus of the lens to be tested. It has also been shown that HSL can be used in speckle shear interferometry as it performs both the functions of shearing and imaging.
LOADS INFLUENCE ANALYSIS ON NOVEL HIGH PRECISION FLEXURE PARALLEL POSITIONER
Institute of Scientific and Technical Information of China (English)
无
2006-01-01
A large workspace flexure parallel positioner system is developed, which can attain sub-micron scale accuracy over cubic centimeter motion range for utilizing novel wide-range flexure hinges instead of the conventional mechanism joints. Flexure hinges eliminate backlash and friction, but on the other hand their deformation caused by initial loads influences the positioning accuracy greatly, so discussions about loads' influence analysis on this flexure parallel positioner is very necessary. The stiffness model of the whole mechanism is presented via stiffness assembly method based on the stiffness model of individual flexure hinge. And the analysis results are validated by the finite element analysis (FEA) simulation and experiment tests, which provide essential data to the practical application of this positioner system.
1989-04-01
Nickel (Ni) content between the steels. As shown in Table 1, the Q&T steel had 5% Ni while the DQ steel had only 1% Ni. Nickel in alpha iron has been...Yield and Fracture Behavior of Alpha Iron ," Trans. Met. Soc. of AIME, Vol. 242, pp. 306 - 314, February, 1968 Kalthoff, J.F. and Winkler, S., "Fracture
Continuum Mechanics of Beam and Plate Flexure
DEFF Research Database (Denmark)
Jönsson, Jeppe
This text has been written and used during the spring of 1995 for a course on flexural mechanics of beams and plates at Aalborg University. The idea has been to concentrate on basic principles of the theories, which are of importance to the modern structural engineer. Today's structural engineer...... must be acquainted with the classic beam and plate theories, when reading manuals and using modern software tools such as the finite element method. Each chapter includes supplementary theory and derivations enabling consultation of the notes also at a later stage of study. A preliminary chapter...... analysis of beam structures is presented and includes both upper and lower-bound solution techniques. The remaining chapters are devoted to plates. The classic elastic plate theories are presented. The plastic yield line theory for plates is presented including both upper and lower-bound techniques...
Continuum Mechanics of Beam and Plate Flexure
DEFF Research Database (Denmark)
Jönsson, Jeppe
This text has been written and used during the spring of 1995 for a course on flexural mechanics of beams and plates at Aalborg University. The idea has been to concentrate on basic principles of the theories, which are of importance to the modern structural engineer. Today's structural engineer...... must be acquainted with the classic beam and plate theories, when reading manuals and using modern software tools such as the finite element method. Each chapter includes supplementary theory and derivations enabling consultation of the notes also at a later stage of study. A preliminary chapter...... introduces the modern notation used in textbooks and in research today. It further gives an introduction to three-dimensional continuum mechanics of elastic bodies and the related principles of virtual work. The ideas to give the students a basic understanding of the stresses and strains, the equilibrium...
Wang, Lu; Liu, Hongji; Li, Fanzhu; Shen, Jianxiang; Zheng, Zijian; Gao, Yangyang; Liu, Jun; Wu, Youping; Zhang, Liqun
2016-10-05
Although numerous research studies have been focused on studying the self-assembled morphologies of block-copolymers (BCPs) and their nanocomposites, little attention has been directed to explore the relation between their ordered structures and the resulting mechanical properties. We adopt coarse-grained molecular dynamics simulation to study the influence of the morphologies on the stress-strain behavior of pure block copolymers and block copolymers filled with uniform or Janus nanoparticles (NPs). At first, we examine the effect of the arrangement (di-block, tri-block, alternating-block) and the components of the pure block copolymers, and by varying the component ratio between A and B blocks, spherical, cylindrical and lamellar phases are all formed, showing that spherical domains bring the largest reinforcing effect. Then by studying BCPs filled with NPs, the Janus NPs induce stronger bond orientation of polymer chains and greater mechanical properties than the uniform NPs, when these two kinds of NPs are both located in the interface region. Meanwhile, some other anisotropic Janus NPs, such as Janus rods and Janus sheets, are incorporated to examine the effect on the morphology and the stress-strain behavior. These findings deepen our understanding of the morphology-mechanics relation of BCPs and their nanocomposites, opening up a vast number of approaches such as designing the arrangement and components of BCPs, positioning uniform or Janus NPs with different shapes and shear flow to tailor their stress-strain performance.
Research on Shearing Behavior of Domestic Epoxy Asphalt%国产环氧沥青混合料抗剪性能试验研究
Institute of Scientific and Technical Information of China (English)
钱振东; 陈磊磊; 尹祖超; 罗桑
2011-01-01
The 7610 type domestic epoxy asphalt was selected as the binder and the basalt with a nominal maximum aggregate size of 16 mm was selected as the aggregate, the epoxy asphalt mixtures with different gradations were formed using the gyratory compactor and tested through uniaxial penetration test.The shearing behaviors of asphalt mixture with different binders were compared according to the orthogonal test.The results show that the shearing performance of the thermosetting epoxy asphalt mixture is better than that of the normal asphalt mixtures, the asphalt content and the passing rate to 4.75 mm particle size are the major influencing factors.%选取国内研发的7610型环氧沥青为结合料,以最大公称粒径为16 mm的玄武岩为集料,利用单轴贯入试验对不同级配组成的环氧沥青混合料抗剪性能进行了试验研究,并采用正交试验法对不同沥青材料混合料的抗剪性能进行了对比.结果表明,环氧沥青混合料的抗剪性能远优于一般的沥青混合料,对其影响程度较大的因素主要是油石比和4.75 mm粒径通过率.
Energy Technology Data Exchange (ETDEWEB)
Al-Azizi, Ala A; Eryilmaz, Osman; Erdemir, Ali; Kim, Seong H.
2015-01-01
The oxidized layers at the surface of hydrogenated diamond-like carbon (H-DLC) were studied with X-ray photoelectron spectroscopy, near-edge X-ray absorption fine structure, and Raman spectroscopy. The structure of these layers was correlated with the friction and wear behavior observed on H-DLC. H-DLC is well-known for its ultralow friction in inert environments, but the steady superlubricious state is always preceded by a run-in period with a high friction. It was hypothesized that the run-in period is related to the surface oxide layer formed naturally upon exposure of the sample to air. To test this hypothesis, thermal oxide layers were grown, and their structures were analyzed and compared with the native oxide layer on a pristine sample. It was found that the Raman spectra of the surface oxide layers of H-DLC have higher D/G band ratio than the bulk, indicating a larger amount of aromatic clusters compared to the bulk film. Thick oxide layers grown at 300 °C showed a run-in friction behavior that resembled the friction of graphite. The run-in periods were found to become longer when the thickness of the oxide layers increased, indicating that the run-in behavior of H-DLC is attributed to the removal of the surface oxide layers.
Directory of Open Access Journals (Sweden)
Ling Xiao
2016-01-01
Full Text Available This study aims at investigating high flexural strength iron-OER soft magnetic composites (SMCs for active magnetic bearings (AMBs. Iron powders were firstly coated with oxide layer by the passivation process at room temperature. The effect of annealing methods on the static performance, magnetic properties, and flexural strength of SMCs was studied. The results showed that the significant improvements of permeability, magnetic loss, and flexural strength were presented by increasing the bonding number between iron surface and resin and using the two-step annealing method. In addition, the effect of pore shape and angle on the behavior of material fracture has been studied by FEM and the analysis was validated by experimental results.
Directory of Open Access Journals (Sweden)
Chengye Fan
2013-01-01
Full Text Available This paper introduces a new test, method, named internal-notched flexure (INF test, that is designed to measure the critical energy release rate of fibre-reinforced polymers for delamination growth in shear mode (mode II. The INF test generates stable delamination growth, with a monotonic increase of load and displacement in a nearly linear fashion. Values of the mode II delamination toughness were deduced using experimental compliance fitting method. Good repeatability of the results was obtained. Compared with the end-notched flexure (ENF test using the same material, the INF test yielded higher delamination resistance, possibly due to the bridging fibres found between fracture surfaces of the INF test specimens.
Energy Technology Data Exchange (ETDEWEB)
Kunz, S. C.
1980-01-01
The stiffness, strength and shear properties of three polyimide resins (NR-150B2, PMR-15 and CPI-2237) combined with three different moduli graphite fibers (C-6000, F-5A and GY-70) were determined at 20 to 371/sup 0/. Stiffness retention with increasing temperature is affected only by the thermal integrity of the polymide matrix. No loss in modulus occurs up to 316/sup 0/C for the PMR-15 and CPI-2237 based composites (T/sub g/ = 377/sup 0/C) or to 260/sup 0/C for the NR-150B2 based material (T/sub g/ approx. = 349/sup 0/C), with any of the three fibers. Both flexure and shear strengths show fiber dependent behavior with temperature. The higher modulus fiber composites (F-5A, GY-70) undergo little strength change up to 343/sup 0/C. Composite strengths of the lower modulus fibers (C-6000), however, degrade by as much as 50% over the same temperature range. Thermal-oxidative stability of the various graphite fibers, and its effect on interfacial strength degradation, are considered primary causes for the fiber-type dominated strength behavior. In general, strength retention appears directly related to degree of graphitization (modulus) of the fibers. The accumulated mechanical property data, some previously unknown, are correlated with microstructural features such as the fiber-matrix adhesion, porosity and processing defects. 11 figures.
Three-degree-of-freedom flexure-based manipulator for high-resolution spatial micromanipulation
Speich, John E.; Goldfarb, Michael
1998-10-01
Flexure-based compliant mechanism design enables the development of revolute joint manipulators without the backlash or Coulomb friction that impede precision position and especially force control. Additionally, due to scaling effects, the adverse consequences of Coulomb friction are exacerbated at small scales. Conventional approaches to compliant mechanism design impose several limitations, however, such as severely limited ranges of motion, poor kinematic behavior, and significant deformation under multi- axis loading. The authors have developed a new type of compliant mechanism that enables the implementation of spatially-loaded revolute joint manipulators with well- behaved kinematic characteristics and without the backlash and stick-slip behavior that would otherwise impede precision control. The primary innovation in the design is the split-tube flexure, a unique small-scale revolute joint that exhibits a considerably larger range of motion and significantly better multi-axis revolute joint characteristics than a conventional flexure. Specifically, the compliant manipulator has an approximately spherical workspace two centimeters in diameter, yet is structurally rigid along non-actuated axes. Data from the small-scale manipulator demonstrates that positioning resolution is limited by digital quantization and sensor noise, and not by more fundamental physical limitations, such as backlash or Coulomb friction.
Flexural and Thermal Properties of Novel Energy Conservation Slotted Reinforced Concrete Beams
Directory of Open Access Journals (Sweden)
Gao Ma
2016-01-01
Full Text Available Conventional solid reinforced concrete (RC beams were modified to slotted beams for consideration as thermal insulation structural components. The slotted beam consisted of an outer and an inner beam, respectively, with a slot located near the middle of the beam along its width direction for filling thermal insulation material. Flexural and thermal behavior of the slotted beams were investigated. Three RC reference solid beams and six slotted beams were fabricated and tested under four-point bending tests. The test results indicated that the failure mode of both slotted beams and the solid beams was flexural failure. However, the damage process of the slotted beams was different from that of the solid beams at the final loading stage. The moment curvature analysis indicated that the tensile reinforcement ratio of the outer and inner beams had an important effect on the flexural behavior, especially the ductility of the slotted beams. Thermal study indicated that the heat transfer coefficient of the slotted beam was greatly reduced and the thermal inertia factor increased a lot, compared with the solid beam. In addition, FE simulation results showed that a new frame structure using slotted beams exhibited obvious and attractive thermal insulation property.
Directory of Open Access Journals (Sweden)
Mehran Roohnia
2015-06-01
Full Text Available Studying the influence of defect on the dynamic behavior of wood in order to detect the local heterogeneities is of great importance in non-destructive testing of wood. The natural heterogeneities in wood are oriented in a volume. However, onedimensional models are still used in dynamic characterization of wooden beams. The aim of this study was to experimentally investigate the effects of the orientation and position of an artificial defect on the flexural vibration frequencies. Different batches of Fagus orientalis specimens were drilled in the radial direction at five positions along the specimen. Dynamic tests in free flexural vibration were performed on the specimens before and after drilling both in the longitudinal-radial (LR and longitudinal-tangential (LT bending plan. The behavior in free flexural vibration was found to be different depending on the position and orientation of heterogeneity. When the drilling axis lies in the bending plane (LR, the weakening of frequency was maximal at the location of an antinode of vibration. On the contrary, the frequency offset was maximal in the place of a vibration node when the drilling axis was orthogonal to the bending plane (LT.
Experimental investigation of laser surface processing of flexure silicon nitride ceramic
Institute of Scientific and Technical Information of China (English)
SUN Li; A. P. MALSHE; JIANG Wen-ping; P. H. MCCLUSKEY
2006-01-01
A continuous wave carbon dioxide (CO2) laser (λ=10.6μm) was employed to treat the surface of Si3N4 MOR (modulus of rupture) bars. The effects of the CO2 laser process on physical and mechanical properties of ground Si3N4 samples were investigated. Scanning electron microscopy (SEM) analysis shows that the area occupied by cavities and fracture is decreased by about 49.4% after laser treatments. Cross-sectional metallography results indicate that the secondary YSiAlON phase in the Si3N4 ceramic is softened/melted and flowed into the defects. Four-point bending tests show that the flexural strength of the treated samples is improved to 10.9%. Fractographic analysis show that the fracture origins move from the surface to subsurface. It is concluded that laser surface processing have significant effects on fracture behavior of flexure Si3N4 ceramic.
Flexural strength and microhardness of anterior composites after accelerated aging
Pala, Kanşad; Tuncer, Safa; Demirci, Mustafa; Öznurhan, Fatih; Serim, Merve
2017-01-01
Background This study aimed to evaluate the flexural strength and microhardness of three different anterior composites after 10 000 thermocycles. Material and Methods The mechanical properties of a nano-fill composite (Filtek Ultimate Universal Restorative (FUR) (Enamel)), a nano-hybrid composite (Clearfil Majesty ES2 (ES2) (Enamel)), and a micro-hybrid composite (G Aenial Anterior (GAA)) were investigated in this study. For the microhardness test, 8-mm diameter and 2-mm thickness composite discs were used (n = 10), and for the flexural strength test, 25x2x2 mm bar-shaped specimens were prepared (n = 13). The specimens were tested at 24 h and after 10 000 thermocycles. Data were analyzed using two-way analysis of variance and the post-hoc Tukey test (p .05). Pearson correlation analysis revealed that there was a negative relationship between the mean hardness and flexural strength values (correlation coefficient = -0.367, p = .043). After 10 000 thermocycles, microhardness values of each material and flexural strength of ES2 and GAA decreased significantly according to 24 h. Conclusions The nano-fill composite FUR displayed significantly higher microhardness values. However, each resin composite was statistically similar for flexural strength values. Ten thousand thermocycles significantly affected microhardness and flexural strength. Key words:Flexural strength, microhardness, anterior composites. PMID:28298986
Effect of electrospun nanofibers on flexural properties of fiberglass composites
White, Fatima T.
In the present study, sintered electrospun TEOS nanofibers were interleaved in S2 fiberglass woven fabric layers, and composite panels were fabricated using the heated vacuum assisted resin transfer molding (H-VARTM) process. Cured panels were water jet cut to obtain the flexural test coupons. Flexural coupons were then tested using ASTM D7264 standard. The mechanical properties such as flexural strength, ultimate flexural failure strains, flexural modulus, and fiber volume fraction were measured. The S-2 fiberglass composite with the sintered TEOS electrospun nanofibers displayed lower flexural stiffness and strength as compared to the composites that were fabricated using S-2 fiberglass composite without the TEOS electrospun nanofibers. The present study also indicated that the composites fabricated with sintered TEOS electrospun nanofibers have larger failure strains as compared to the ones that were fabricated without the presence of electrospun nanofibers. The study indicates that the nanoengineered composites have better energy absorbing mechanism under flexural loading as compared to conventional fiberglass composites without presence of nanofibers.
Directory of Open Access Journals (Sweden)
Oncu Serife
2016-01-01
Full Text Available Expansive soils in semi-arid climates must be mitigated to minimize potential structural damage to the overlying structures due to swell-shrink behavior caused by climatic changes. The expansive soil in this study was amended by sand which reduced the swell-shrink potential significantly. As a secondary additive, a waste by product of construction industry was selected, marble powder. Recycling this material would minimize its accumulation and covering a large space in landfill areas. In this study, waste material was assessed as a possible partial replacement for sand and due to its high calcite content, curing effect on its cementitious characteristic was also evaluated. It was observed that for mitigating the swell-shrink potential, 10% marble powder by dry mass was the optimum amount which was observed to gain improved characteristics with curing. The flexural strength, however, slightly reduced with marble powder addition, the soil mixture displayed a brittle behavior. Therefore the utilization of this material is recommended to be restricted to soils exposed to lower flexural loads, such as light traffic. The correlation between shrinkage strains and flexural strength parameters suggested herein, could be a potential empirical approach to predict the flexural strength based on shrinkage behavior.
Institute of Scientific and Technical Information of China (English)
蔡茂; 顾祥林; 华晶晶; 林峰
2011-01-01
Cyclic loading tests of 6 short columns were conducted.The shearing and bending responses were separated.Analysis results indicated that the shear stiffness of a shear critical column degraded rapidly following the development of shear cracking.The skeleton curve of the shearing response entered the descending branch as the peak shear force was reached.The shear hysteresis shows the characteristics of pinching effect and stiffness degradation.Before the peak shear force is reached,the bending response and the shearing response occur simultaneously.After the peak shear force,if the shear failure is detected,the bending response will not further develop while the shearing response will increase rapidly,and the vice versa for the two responses if the flexural failure occurs.For columns with lower shear strength than the flexural strength,shear failure will be detected as the shear force reached the initial shear strength.For columns with higher shear strength than the flexural strength,the shear strength of the column at plastic hinge zone will decrease with the development of bending deformation and the shear failure will be detected as the shear strength degrades to the value lower than the flexural bearing capacity.A shear spring representing the in-plane shear action was then introduced into the multi-spring model for the seismic analysis of reinforced concrete columns.The load-carrying mechanism of a column was decomposed into bending mechanism and shearing mechanism which were connected in series.Comparing the calculated results with the test results,it was found that the modified multi-spring model provided a good estimation of the seismic behavior of shear-critical columns under earthquakes.The multi-spring model ignoring the shear action overestimates the ductility,energy dissipation and shear strength of the shear critical columns and leads to unsafe evaluation results.%通过6根钢筋混凝土短柱的低周反复加载试验研究,分离了柱剪切反
A large workspace flexure hinge-based parallel manipulator system
Institute of Scientific and Technical Information of China (English)
Dong Wei; Du Zhijiang; Sun Lining
2005-01-01
Parallel manipulator systems as promising precision devices are used widely in current researches. A novel large workspace flexure parallel manipulator system utilizing wide-range flexure hinges as passive joints is proposed in this paper, which can attain sub-micron-scale precision over the cubic centimeter motion range. This paper introduces the mechanical system architecture based on the wide-range flexure hinges, analyzes the kinematics via stiffness matrices, presents the control system configuration and control strategy, and finally gives the system performance test results.
Thermoelastic dissipation in MEMS/NEMS flexural mode resonators.
Yan, Jize; Seshia, Ashwin A
2009-02-01
Understanding the energy dissipation mechanisms in single-crystal silicon MEMS/NEMS resonators are particularly important to maximizing an important figure of merit relevant for miniature sensor and signal processing applications: the Quality factor (Q) of resonance. This paper discusses thermoelastic dissipation (TED) as the dominant internal-friction mechanism in flexural mode MEMS/NEMS resonators. Criteria for optimizing the geometrical design of flexural mode MEMS/NEMS resonators are theoretically established with a view towards minimizing the TED for single-crystal silicon MEMS/NEMS flexural mode resonators.
Flexure bearing support, with particular application to stirling machines
Beckett, Carl D.; Lauhala, Victor C.; Neely, Ron; Penswick, Laurence B.; Ritter, Darren C.; Nelson, Richard L.; Wimer, Burnell P.
1996-01-01
The use of flexures in the form of flat spiral springs cut from sheet metal materials provides support for coaxial nonrotating linear reciprocating members in power conversion machinery, such as Stirling cycle engines or heat pumps. They permit operation with little or no rubbing contact or other wear mechanisms. The relatively movable members include one member having a hollow interior structure within which the flexures are located. The flexures permit limited axial movement between the interconnected members, but prevent adverse rotational movement and radial displacement from their desired coaxial positions.
Sensitivity Analysis of MEMS Flexure FET with Multiple Gates
Directory of Open Access Journals (Sweden)
K.Spandana
2016-02-01
Full Text Available This paper deals with the design and modelling of Flexure FET and the FETs are the one of the important fundamental devices in electronic devices.. In this paper we are going analyse one of the MEMS Flexure Gate Field Effect Transistors. Here we will design gate of the FLEXURE FET with different type of materials and with different structure and we made the comparison between all the structures. We apply pull-in voltage to the Gate with respect to the change in the gate voltage the respective displacement of the gate changes which reflect the change in the drain current and sensitivity.
Institute of Scientific and Technical Information of China (English)
陈大华; 吴博; 雷彩红
2011-01-01
The short term creep data of glass-fiber reinforced flame retardant poly (butylene terephthalate) (PBT-RG301) was studied under different stress using universal testing machine. The long term creep behavior was predicted based on time-stress superposition (TSS) principle, Burgers model and Findley power law. It was found that using TSS principle, the creep value up to 104 h could be predicted. Within experimental time of 4 000 s, the predicted results from Burgers model and Findley power law were in good agreement with the experimental results. The strain values under long time of 10 000h predicted based on Burgers model were far larger than those based on TSS principle and Findley power law, which was further proved by experimental results within 14 h.%采用万能电子拉力机测试了不同应力下玻纤增强阻燃PBT(PBT-RG301)的短期蠕变数据,并采用时间应力等效原理、Burgers模型以及Findley指数定律预测了长期蠕变行为.结果发现:依据时间应力等效原理可预测10000h后体系的蠕变数值,在4000s实验时间内Burgers模型和Findley指数定律均可很好的拟合实验结果,但Burgers模型预测的长期蠕变数据高于Findley指数定律和时间应力等效原理预测数值,实验时间14h的跟踪数据也证实了该结果.
Prediction of Buckling of Plain Knitted Fabric Sheets Subjected to Simple Shear in Wale Direction
Institute of Scientific and Technical Information of China (English)
ZHANG Yitong; AO Tao; XU Jiafu
2007-01-01
Knitted fabric is very different from woven fabric due to its more complicated knitting structures. The buckling of knitted fabric sheets subjected to simple shear in the wale direction is investigated analytically in consideration of the large deformation of fabric sheet in critical configuration. The theory on instability of finite deformation is applied to the analysis. All the stress boundary conditions of knitted fabric sheet are satisfied. An equation to determine the buckling direction angle is de-rived. It is shown that there are two possible buckling modes, flexural mode and barreling mode. The buckling condition equations for the flexural mode and barreling mode are also obtained respectively. Numerical illustrations reveal that only the flexural mode can actually occur and the barreling mode cannot, which agrees with the experimental observations. For a permitted buckling mode on margin boundaries, the critical value of shear amount and the buckling direction angle can be deter-mined.
Bowles, Kenneth J.
1993-01-01
To date, the effect of thermo-oxidative aging on unidirectional composite mechanical properties has been monitored by the measurement of interlaminar shear strength (ILSS) and either three or four point longitudinal flexural strength (LFS) of the composites being tested. Both results are affected by the fiber-to-matrix bonding, the former being dependent on the shear resistance of the interface and the latter on the degree of load sharing by the fibers through the fiber/matrix interface. Recently, fiber/matrix interfacial bond strengths have been monitored using a transverse flexural strength (TFS) test method. This test method was used to evaluate the effect of fiber surface treatment on the fiber/matrix.
Shear strengthening of reinforced concrete beams by means of vertical prestressed reinforcement
Santos Ferreira, Denise Carina; Bairán García, Jesús Miguel; Marí Bernat, Antonio Ricardo
2016-01-01
Strengthening reinforced concrete (RC) elements critical to shear with prestressed transversal reinforcement can be an efficient method to increase the shear resistance of structures, allowing the development of the full flexural capacity. However, research on the performance of this technique is very limited, and methods for designing the optimum amount of prestressed transversal reinforcement and assessing the retrofitted structure have not been produced yet. Nonlinear finite element models...
Analysis of flexural wave propagation in poroelastic composite ...
African Journals Online (AJOL)
DR OKE
of flexural vibrations of poroelastic composite hollow cylinder is obtained. ... The equations of motion of a homogeneous, isotropic poroelastic solid (Biot 1956) in the presence of dissipation b are: 2. 2. 11. 12. 2 ...... Vibration and Control, Vol.
predicting flexural strength river gravel using multi ravel using multi ...
African Journals Online (AJOL)
eobe
s building a multi-layer perception neural network model which uses expe layer perception neural ..... using flexural testing machine. 3.2.2 Regression Model ... Training the network (learning) could be supervised or unsupervised training.
Notch flexure hinges: An effective theory
Tseytlin, Yakov M.
2002-09-01
This article presents effective tractable equations for rotational compliance (stiffness) of a simple monolithic flexure hinge with circular (radius R and crosspiece thickness t), elliptical [at semiaxis ax, ay, elliptical ratio epsilon (=ax/ay)] and other cross sections. These equations and the method by inverse conformal mapping of circular approximating contour used to derive them are different from the known and widely used theoretical equations originally derived in 1965 by Paros and Weisbord for circular notch hinges. Later it was found that the circular hinge represents the worst case error between known theoretical and finite element models. The conformal mapping equations data presented in this article are likely to be much closer (within less than 10%) to the finite element analysis and experimental data than other theoretical equations. In particular this is the case for circular notch hinges at relative thickness beta(=t/2R) in the range 0.01 to 0.3 and for elliptical hinges at the elliptical ratio epsilon=1 to 10. The derived general equation is common for all types of notch hinges whose profiles can be approximated by two shifted contiguous circles and includes material parameters with Young's modulus and Poisson's ratio. The latter is totally omitted in known theoretical solutions by other authors. New tractable equations are derived from the general equation on the basis of trigonometric functions' simplified series expansion in certain ranges of hinge crosspiece relative thickness. The corresponding graphs are presented. Experimental data were received by holographic interference and autocollimator measurement.
Persano, Luana; Catellani, Alessandra; Dagdeviren, Canan; Ma, Yinji; Guo, Xiaogang; Huang, Yonggang; Calzolari, Arrigo; Pisignano, Dario
2016-09-01
The intrinsic flexible character of polymeric materials causes remarkable strain deformations along directions perpendicular to the applied stress. The biaxial response in the shear piezoelectricity of polyvinylidenefluoride copolymers is analyzed and their full piezoelectric tensors are provided. The microscopic shear is exploited in single suspended nanowires bent by localized loading to couple flexural deformation and transverse piezoelectric response.
Flexural testing of weld site and HVOF coating characteristics
Yilbas, Bekir Sami; Sahin, Ahmet
2014-01-01
This book provides fundamental understanding and practical application of characteristics of flexural motion in the assessment of the weld size and coating thickness. Some formulations of heat transfer and flexural motion are introduced while displacement and load correlation are used to estimate elastic modules and the size of the heat affected zone as well as the coating thickness. The case studies presented give a practical understanding of weld size and coating thickness characterizations.
Modeling the Flexural Carrying Capacity of Corroded RC Beam
Institute of Scientific and Technical Information of China (English)
WANG Xiao-hui; LIU Xi-la
2008-01-01
Considering the change of bond strength between corroded steel and concrete, flexural carrying ca-pacity of corroded reinforced concrete (RC) beam was calculated. On the basis of the condition of equilibriumof forces and compatibility of deformations for the whole beam, a model for the prediction of flexural carryingcapacity of the corroded RC beam was proposed. Comparison of the model's predictions with the experimentalresults published in the literature shows the practicality of the proposed method.
Thermal noise of a gram-scale cantilever flexure
Nguyen, Thanh T-H; Miller, John; Mow-Lowry, Conor M; Goßler, Stefan; Shaddock, Daniel A; McClelland, David E
2015-01-01
Measured thermal noise displacement spectra from low frequency to $3\\,$kHz of Niobium and Aluminium flexures are presented. With a simple thermal noise model dominated by structural and thermoelastic losses, the agreement between the theory and measurement has been robust. The thermal noise spectra were recorded up to an order of magnitude below and above the fundamental resonance, with the fundamental resonances for both Aluminium and Niobium flexures within the range of $50\\,$Hz to $300\\,$Hz
Hemmat Esfe, Mohammad; Rostamian, Hossein; Reza Sarlak, Mohammad; Rejvani, Mousa; Alirezaie, Ali
2017-10-01
In this article, rheological behavior of TiO2-MWCNT (45-55%)/10w40 hybrid nano-oil was studied experimentally. The nano- oils were tested at temperature ranges of 5-55 °C and in shear rates up to 11,997 s-1. With respect to viscosity, shear stress and shear rate variations it was cleared that either of the base oil and nano-oil were non-Newtonian fluids. New equations which were based on thickness of the fluid were presented for different temperature values, R-squared values were between 0.9221 and 0.9998 (the precise of correlation changes depend on temperature). Also to predict the nano-oil behavior, neural network method was utilized. an artificial neural network (MLP type) were used to predict the viscosity in terms of temperature, solid volume fraction and shear stress. to compare the prediction precise of neural network and correlation the results of these two were compared with together. ANN showed more accurate results in comparison with correlation results. R2 and (MSE) were 0.9979 and 0.000016 respectively for the ANN.
Methods to Analyze Flexural Buckling of the Consequent Slabbed Rock Slope under Top Loading
Directory of Open Access Journals (Sweden)
Hongyan Liu
2016-01-01
Full Text Available The consequent slabbed rock slope is prone to flexural buckling failure under its self-weight and top loading. However, nearly none of the existing studies consider the effect of the top loading on the slope flexural critical buckling height (CBH. Therefore, on the basis of Euler’s Method and the flexural buckling failure mode of the consequent slabbed rock slope, the calculation method of the CBH of the vertical slabbed rock slope under the self-weight is firstly proposed, and then it is extended to that of the consequent slabbed rock slope. The effect of slope dip angle, friction angle, and cohesion between the neighboring rock slabs and rock elastic modulus on the slope CBH is discussed. Secondly, the calculation method of the CBH of the consequent slabbed rock slope under its self-weight and top loading is proposed according to the superposition principle. Finally, on the basis of the hypothesis that the rock mechanical behavior obeys the statistical damage model, the effect of the rock mechanical parameters n and ε0 on the slope CBH is studied. The results show that the rock strength has much effect on the slope CBH. If the rock is supposed to be a linear elastic body without failure in Euler’s Method, the result from it is the maximum of the slope CBH.
Effect of flexural phonons on the hole states in single-layer black phosphorus
Brener, S.; Rudenko, A. N.; Katsnelson, M. I.
2017-01-01
Flexural thermal fluctuations in crystalline membranes affect the band structure of the carriers, which leads to an exponential density-of-states (DOS) tail beyond the unperturbed band edge. We present a theoretical description of this tail for a particular case of holes in single-layer black phosphorus, a material which exhibits an extremely anisotropic quasi-one-dimensional dispersion (my/mx≫1 ) and, as a result, an enhanced Van Hove singularity at the valence band top. The material parameters are determined by ab initio calculations and then are used for quantitative estimation of the effect of two-phonon (flexural) processes have on the charge carrier DOS. It is shown that unlike the isotropic case, the physics is determined by the phonons with wave vectors of the order of q*, where q* determines the crossover between harmonic and anharmonic behavior of the flexural phonons. The spectral density of the holes in single-layer black phosphorus at finite temperatures is calculated.
Time-domain flexural wave intensity estimation in orthotropic Kirchhoff plates
Halkyard, C. R.; Masson, P.
2016-04-01
In this paper, a method for estimating the vibrational energy flow associated with the flexural vibration of an orthotropic Kirchhoff plate, in the time-domain, is presented. The approach is based on the plane propagating wave solution to the equation of motion, and uses a Fourier series approximation of the wave field. The various linear and angular velocities, shear forces and moments that are needed to calculate the energy flow are estimated by digitally filtering and combining the outputs of an array of sensors. A similar approach is used to reconstruct the local wave field to provide an estimate of the wave propagation direction. The theoretical basis of the approach is described, and design considerations for the sensor array and for the filters used for parameter estimation are discussed. Simulations are presented for plane flexural waves and for transient transverse point force excitation of a range of orthotropic plates having different material properties, using a simulated array of velocity sensors. These simulations show that the method can provide accurate estimates of the magnitude and direction of the vibrational energy flow, as well as of the propagation direction of a single wave train or 'burst', provided that the sensor array is sufficiently distant from the excitation point. This is consistent with preliminary experimental measurements, also presented in this paper, performed on a composite orthotropic plate.
The flexural stiffness of superficial neuromasts in the zebrafish (Danio rerio) lateral line.
McHenry, Matthew J; van Netten, Sietse M
2007-12-01
Superficial neuromasts are structures that detect water flow on the surface of the body of fish and amphibians. As a component of the lateral line system, these receptors are distributed along the body, where they sense flow patterns that mediate a wide variety of behaviors. Their ability to detect flow is governed by their structural properties, yet the micromechanics of superficial neuromasts are not well understood. The aim of this study was to examine these mechanics in zebrafish (Danio rerio) larvae by measuring the flexural stiffness of individual neuromasts. Each neuromast possesses a gelatinous cupula that is anchored to hair cells by kinocilia. Using quasi-static bending tests of the proximal region of the cupula, we found that flexural stiffness is proportional to the number of hair cells, and consequently the number of kinocilia, within a neuromast. From this relationship, the flexural stiffness of an individual kinocilium was found to be 2.4 x 10(-20) N m2. Using this value, we estimate that the 11 kinocilia in an average cupula generate more than four-fifths of the total flexural stiffness in the proximal region. The relatively minor contribution of the cupular matrix may be attributed to its highly compliant material composition (Young's modulus of approximately 21 Pa). The distal tip of the cupula is entirely composed of this material and is consequently predicted to be at least an order of magnitude more flexible than the proximal region. These findings suggest that the transduction of flow by a superficial neuromast depends on structural dynamics that are dominated by the number and height of kinocilia.
Transformation cloaking and radial approximations for flexural waves in elastic plates
Brun, M; Jones, I S; Movchan, A B; Movchan, N V
2014-01-01
It is known that design of elastic cloaks is much more challenging than the design idea for acoustic cloaks, cloaks of electromagnetic waves or scalar problems of anti-plane shear. In this paper, we address fully the fourth-order problem and develop a model of a broadband invisibility cloak for channelling flexural waves in thin plates around finite inclusions. We also discuss an option to employ efficiently an elastic pre-stress and body forces to achieve such a result. An asymptotic derivation provides a rigorous link between the model in question and elastic wave propagation in thin solids. This is discussed in detail to show connection with non-symmetric formulations in vector elasticity studied in earlier work.
Directory of Open Access Journals (Sweden)
Xu Jiang
2016-08-01
Full Text Available Influence of moisture absorption/desorption on the flexural properties of Glass-fibre-reinforced polymer (GFRP laminates was experimentally investigated under hot/wet aging environments. To characterize mechanical degradation, three-point bending tests were performed following the ASTM test standard (ASTM D790-10A. The flexural properties of dry (0% Mt/M∞, moisture unsaturated (30% Mt/M∞ and 50% Mt/M∞ and moisture saturated (100% Mt/M∞ specimens at both 20 and 40 °C test temperatures were compared. One cycle of moisture absorption-desorption process was considered in this study to investigate the mechanical degradation scale and the permanent damage of GFRP laminates induced by moisture diffusion. Experimental results confirm that the combination of moisture and temperature effects sincerely deteriorates the flexural properties of GFRP laminates, on both strength and stiffness. Furthermore, the reducing percentage of flexural strength is found much larger than that of E-modulus. Unrecoverable losses of E-modulus (15.0% and flexural strength (16.4% for the GFRP laminates experiencing one cycle of moisture absorption/desorption process are evident at the test temperature of 40 °C, but not for the case of 20 °C test temperature. Moreover, a coupled hygro-mechanical Finite Element (FE model was developed to characterize the mechanical behaviors of GFRP laminates at different moisture absorption/desorption stages, and the modeling method was subsequently validated with flexural test results.
DEFF Research Database (Denmark)
Hansen, Christian Skodborg
-plane loaded walls and disks is however not included in any guidelines, and only a small fraction of scientists have initiated research within this topic. Furthermore, studies of the principal behavior and response of a strengthened disk has not yet been investigated satisfactorily, and this is the principal...... be altered to fit the surrounding boundary conditions. The effective cohesive law will then become a function of the investigated structural geometry. A simplified approach for the latter topic was used to predict the load capacity of concrete beams in shear. Results obtained were acceptable, but the model...
Failure mechanism of shear-wall dominant multi-story buildings
Yuksel, S.B.; Kalkan, E.
2008-01-01
The recent trend in the building industry of Turkey as well as in many European countries is towards utilizing the tunnel form (shear-wall dominant) construction system for development of multi-story residential units. The tunnel form buildings diverge from other conventional reinforced concrete (RC) buildings due to the lack of beams and columns in their structural integrity. The vertical load-carrying members of these buildings are the structural-walls only, and the floor system is a flat plate. Besides the constructive advantages, tunnel form buildings provide superior seismic performance compared to conventional RC frame and dual systems as observed during the recent devastating earthquakes in Turkey (1999 Mw 7.4 Kocaeli, Mw 7.2 Duzce, and 2004 Mw 6.5 Bingol). With its proven earthquake performance, the tunnel form system is becoming the primary construction technique in many seismically active regions. In this study, a series of nonlinear analyses were conducted using finite element (FE) models to augment our understanding on their failure mechanism under lateral forces. In order to represent the nonlinear behavior adequately, The FE models were verified with the results of experimental studies performed on three dimensional (3D) scaled tunnel form building specimens. The results of this study indicate that the structural walls of tunnel form buildings may exhibit brittle flexural failure under lateral loading, if they are not properly reinforced. The global tension/compression couple triggers this failure mechanism by creating pure axial tension in the outermost shear-walls.
Institute of Scientific and Technical Information of China (English)
张秀芳; 徐世烺; 侯利军
2009-01-01
Based on first-cracking criterion and steady-cracking criterion constructed from the micromechanical model, ultra-high toughness cementitious composites material, abbreviated as UHTCC, is tailored even in case of low fiber volume faction, typically 2% by volume. This material is characterized by the pseudo tension strain-hardening under direct tension, and has high ultimate tensile strain capacity up to 3%-5% , and narrow crack width of only 60-80 祄 at ultimate tension load. These advantages allow the transform of macro harmful crack into micro harmless crack and UHTCC therefore is considered to be a new promising solution to durable structures. The present paper investigated the flexural behavior of three groups of UHTCC/RC composited beams with three different reinforcement ratios, in which concrete in the region of tension zone of RC beam is partly replaced by UHTCC. The flexural load-carrying capacity, deformation ability, deformation compatibility between steel and UHTCC along with crack development in beam during the entire loading process are examined. For comparison, the ordinary reinforced concrete beams are tested as control reference, too. The experimental results reveal that, in case of the same reinforcement ratio, RC beam strengthened with UHTCC has high flexural capacity and can efficiently control crack width to obtain high durable structures in comparison with ordinary reinforced concrete beam. Moment-curvature curves and load-mid-span displacement curves of tested UHTCC/RC composited beams are calculated using the analytical formulae developed based on beam theory and compared with the experimental measurements. A good agreement between them is found.%基于微观力学建立的第一起裂应力准则和裂缝稳态开裂准则研发的超高韧性水泥基复合材料(英文缩写为UHTCC)在较小纤维掺量下(通常2%体积)拉应力应变曲线表现出明显的伪应变硬化特征,极限拉伸应变可高达3%～5%,极限荷载
Institute of Scientific and Technical Information of China (English)
彭凯; 朱俊高; 冯树荣; 蔡昌光; 朱晟
2013-01-01
The mechanical behaviors of the interface between coarse-grained soil and concrete are investigated by simple shear tests under conditions of cemented soil slurry (clay mixed with cement grout).The results show that the relation curve between shear stress and shear strain appears stress-strain softening and shear dilatation is significant.The point of peak strength and the position when the shear dilatation occurs are related to normal stress.In addition,shear dilatation occurs before the shear stress reaches peak value.In shear failure state,with the same height,the shear displacement increases as the normal stress increases.While with the same normal stress and at the same height,the shear displacement increases as the concrete content increases.A particle flow model of simple shear test between interface between coarse-grained soil and concrete is constructed by PFC (particle flow code).The disturbed height of the sample and the main influence factors are determined by analyzing the laws of particle motion at different heights inside the sample.The PFC results show disturbed height of the sample is related to maximum particle diameter of the soil,normal stress and roughness of the interface (with or without slurry) etc.In terms of the coarse-grained soil,the shear displacement is significant in the area which is close to the interface and about 3-4 times of the maximum particle diameter,and informed the obvious shear band.Further,the thickness of the interface can be regarded as the value.%采用大型单剪仪进行粗粒土与混凝土接触面在水泥土泥皮(粘土中掺入水泥)条件下的剪切试验,揭示泥皮条件下接触面的力学特性与机理.试验结果表明,峰值强度以及剪胀发生所对应的位置与法向应力大小有关,峰值强度所对应的剪应变滞后于产生剪胀的位置.剪切破坏时,在同一高度处,法向应力越大,切向位移也越大；同样的法向应力及高度处,切向位移随水泥含
Samant, Hrishikesh; Pundalik, Ashwin; D'souza, Joseph; Sheth, Hetu; Lobo, Keegan Carmo; D'souza, Kyle; Patel, Vanit
2017-02-01
The Panvel flexure is a 150-km long tectonic structure, comprising prominently seaward-dipping Deccan flood basalts, on the western Indian rifted margin. Given the active tectonic faulting beneath the Panvel flexure zone inferred from microseismicity, better structural understanding of the region is needed. The geology of Elephanta Island in the Mumbai harbour, famous for the ca. mid-6th century A.D. Hindu rock-cut caves in Deccan basalt (a UNESCO World Heritage site) is poorly known. We describe a previously unreported but well-exposed fault zone on Elephanta Island, consisting of two large faults dipping steeply east-southeast and producing easterly downthrows. Well-developed slickensides and structural measurements indicate oblique slip on both faults. The Elephanta Island fault zone may be the northern extension of the Alibag-Uran fault zone previously described. This and two other known regional faults (Nhava-Sheva and Belpada faults) indicate a progressively eastward step-faulted structure of the Panvel flexure, with the important result that the individual movements were not simply downdip but also oblique-slip and locally even rotational (as at Uran). An interesting problem is the normal faulting, block tectonics and rifting of this region of the crust for which seismological data indicate a normal thickness (up to 41.3 km). A model of asymmetric rifting by simple shear may explain this observation and the consistently landward dips of the rifted margin faults.
Effect of the Fiber Type and Axial Stiffness of FRCM on the Flexural Strengthening of RC Beams
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Abdulla Jabr
2017-01-01
Full Text Available The use of externally-bonded fiber-reinforced polymer (FRP sheets has been successfully used in the repair and strengthening of both the shear and flexural capacities of reinforced concrete (RC beams, slabs and columns since the 1990s. However, the externally-bonded FRP reinforcements still present many disadvantages, such as poor performance in elevated temperature and fire, lack of permeability and strength degradation when exposed to ultraviolet radiation. To remedy such drawbacks, the fiber-/fabric-reinforced cementitious matrix (FRCM has been recently introduced. The FRCM system consists of a fiber mesh or grid embedded in a cementitious bonding material. The present research investigates the flexural strengthening of reinforced concrete (RC beams with FRCM. The experimental testing included eight large-scale concrete beams, 150 mm × 250 mm × 2400 mm, internally reinforced with steel bars and strengthened in flexure with FRCM. The investigated parameters were the internal steel reinforcement ratio and the FRCM systems. Two steel reinforcement ratios of 0.18 and 0.36 of the balanced reinforcement ratio, as well as three FRCM systems using glass, carbon and PBO fibers were investigated. Test results are presented in terms of load-deflection, load-strain and load-crack width relationships. The test results indicated that the PBO FRCM significantly increased the ultimate capacity of the strengthened RC beams with both low and moderate internal reinforcement ratios compared to the glass and carbon FRCM.
Indian Academy of Sciences (India)
Hrishikesh Samant; Ashwin Pundalik; Joseph D’souza; Hetu Sheth; Keegan Carmo Lobo; Kyle D’souza; Vanit Patel
2017-02-01
The Panvel flexure is a 150-km long tectonic structure, comprising prominently seaward-dipping Deccan flood basalts, on the western Indian rifted margin. Given the active tectonic faulting beneath the Panvel flexure zone inferred from microseismicity, better structural understanding of the region is needed. The geology of Elephanta Island in the Mumbai harbour, famous for the ca. mid-6th century A.D. Hindu rock-cut caves in Deccan basalt (a UNESCO World Heritage site) is poorly known. We describe a previously unreported but well-exposed fault zone on Elephanta Island, consisting of two large faults dippingsteeply east–southeast and producing easterly downthrows. Well-developed slickensides and structural measurements indicate oblique slip on both faults. The Elephanta Island fault zone may be the northern extension of the Alibag–Uran fault zone previously described. This and two other known regional faults (Nhava–Sheva and Belpada faults) indicate a progressively eastward step-faulted structure of the Panvel flexure, with the important result that the individual movements were not simply downdip but also oblique-slip and locally even rotational (as at Uran). An interesting problem is the normal faulting, block tectonics and rifting of this region of the crust for which seismological data indicate a normal thickness (up to 41.3 km). A model of asymmetric rifting by simple shear may explain this observation and the consistently landward dips of the rifted margin faults.
Experimental Evaluations for Failure Behavior of PCCV Wall-Base Juncture
Energy Technology Data Exchange (ETDEWEB)
Cho, Nam Soo; Jeong, Woon; Kim, Kyu Wang; Kim, Hyung Tae; Lee, Sung Hyung [Hyundai Institute of Construction Technology Development, Seoul (Korea, Republic of)
2005-02-15
KAERI research program has been gone on to examine the actual failure behavior at wall-base juncture of a prestressed concrete containment since 2005. As a part of the KAERI program, this study has been intended to simulate a nonlinear behavior and to predict a failure state based on experimental evaluation. Seismic tests in 2005 had been performed to investigate the shear failure mode of containment building subjected to earthquake, and shear-tension failure tests in 2006 was carried out to examine the mixed behavior of flexure-shear-tension at the wall-base juncture of containment. From these test results, the characteristic of shear failure at the wall-base juncture pointed out as secondary failure mode was experimentally evaluated, and then the structural integrities of containment were synthetically assessed along with the failure scenario on the basis of the results of the research project over the last 7 years. The results of the research project could make it possible to predict the failure behavior of a containment under ultimate state, and furthermore all test-verified data would be utilized to develop a nonlinear finite element software named as NuCAS.
Hamid Reza Ashrafi; Peyman Beiranvand; Kasra Shahbazian; Shaahin Bidmeshki; Somaye Yaghooti
2016-01-01
Steel moment frame systems, steel plate shear walls and also buckling restrained brace (BRB) are considered as the most widely used seismic resistant systems of the world. Firstly, in this research, in order to validate the finite element models, the tested sample of steel plate shear walls of 4 floors at the University of Alberta, Canada, and the tested sample of buckling restrained brace at the University of Berkeley California, with the software ABAQUS 6.10-1 were used. Then, the obtained ...
Institute of Scientific and Technical Information of China (English)
杜修力; 王作虎; 詹界东
2011-01-01
FRP筋是一种新型预应力筋材,具有轻质、高强、耐腐蚀、抗疲劳等优点,但是其横向剪切强度相对较低,这会影响预应力FRP筋混凝土梁的受剪承载力.通过27根混凝土梁的受剪试验,研究了预应力CFRP筋混凝土梁的剪切破坏形态,以及各种参数对其受剪承载力的影响,并与钢绞线预应力混凝土梁的受剪试验结果进行了比较.研究结果表明:预应力CFRP筋混凝上梁的剪切破坏形态有两种:斜压破坏和剪压破坏;剪跨比和配箍率是影响预应力CFRP筋混凝土梁受剪承载力的主要因素;有粘结预应力CFRP筋混凝土梁的受剪承载力比无粘结预应力CFRP筋混凝土梁要大15%左右;通过引入反映预应力筋种类和粘结条件的2个参数,提出了预应力FRP筋混凝土梁的简化受剪承载力计算式,计算结果与试验数据吻合较好.%As a new structural material, FRP (fiber reinforced plastics) features light weight, high strength, corrosion resistance, anti-fatigue, etc., and have a bright future when used as a new type of prestressing tendon in engineering structures.The horizontal shear strength of FRP tendon is low, which will affect the shear strength of concrete beams prestressed with FRP tendons.Based on experimental studies on 27 concrete beams prestressed with CFRP tendons, this paper studied the shear failure modes and a variety of parameters on shear strength, and compared the shear performance with concrete beams prestressed with steel strands.Studies show that there are two shear failure modes for concrete beams prestressed with FRP tendons, i.e.diagonal compression and shear-compression.Shear span ratio and stirrup rate are main factors influencing the shear behavior of concrete beams prestressed with CFRP tendons.The shear strength of concrete beams prestressed with bonded CFRP tendons is about 15％ larger than that of concrete beams prestressed with unbonded CFRP tendons.A simple formula for computing
Directory of Open Access Journals (Sweden)
Tara Sen
2013-01-01
Full Text Available Environmental awareness motivates researchers worldwide to perform studies of natural fibre reinforced polymer composites, as they come with many advantages and are primarily sustainable. The present study aims at evaluating the mechanical characteristics of natural woven jute fibre reinforced polymer (FRP composite subjected to three different pretreatments, alkali, benzyl chloride, and lastly heat treatment. It was concluded that heat treatment is one of the most suitable treatment methods for enhancing mechanical properties of jute FRP. Durability studies on Jute FRP pertaining to some common environmental conditions were also carried out such as effect of normal water and thermal aging on the tensile strength of jute FRP followed by fire flow test. The heat treated woven jute FRP composites were subsequently used for flexural strengthening of reinforced concrete beams in full and strip wrapping configurations. The study includes the effect of flexural strengthening provided by woven jute FRP, study of different failure modes, load deflection behavior, effect on the first crack load, and ultimate flexural strength of concrete beams strengthened using woven jute FRP subjected to bending loads. The study concludes that woven jute FRP is a suitable material which can be used for flexural upgradation of reinforced concrete beams.
Metal cap flexural transducers for air-coupled ultrasonics
Eriksson, T. J. R.; Dixon, S.; Ramadas, S. N.
2015-03-01
Ultrasonic generation and detection in fluids is inefficient due to the large difference in acoustic impedance between the piezoelectric element and the propagation medium, leading to large internal reflections and energy loss. One way of addressing the problem is to use a flexural transducer, which uses the bending modes in a thin plate or membrane. As the plate bends, it displaces the medium in front of it, hence producing sound waves. A piezoelectric flexural transducer can generate large amplitude displacements in fluid media for relatively low excitation voltages. Commercially available flexural transducers for air applications operate at 40 kHz, but there exists ultrasound applications that require significantly higher frequencies, e.g. flow measurements. Relatively little work has been done to date to understand the underlying physics of the flexural transducer, and hence how to design it to have specific properties suitable for particular applications. This paper investigates the potential of the flexural transducer and its operating principles. Two types of actuation methods are considerd: piezoelectric and electrodynamic. The piezoelectrically actuated transducer is more energy efficient and intrinsically safe, but the electrodynamic transducer has the advantage of being less sensitive to high temperature environments. The theory of vibrating plates is used to predict transducer frequency in addition to front face amplitude, which shows good correlation with experimental results.
Shear banding phenomena in a Laponite suspension
Ianni, F; Gentilini, S; Ruocco, G
2007-01-01
Shear localization in an aqueous clay suspension of Laponite is investigated through dynamic light scattering, which provides access both to the dynamics of the system (homodyne mode) and to the local velocity profile (heterodyne mode). When the shear bands form, a relaxation of the dynamics typical of a gel phase is observed in the unsheared band soon after flow stop, suggesting that an arrested dynamics is present during the shear localization regime. Periodic oscillations of the flow behavior, typical of a stick-slip phenomenon, are also observed when shear localization occurs. Both results are discussed in the light of various theoretical models for soft glassy materials.
Wassereau, Thibault; Ablitzer, Frédéric; Pézerat, Charles; Guyader, Jean-Louis
2017-07-01
This paper addresses the problem of estimating the local viscoelastic parameters of sandwich beams. An original procedure involving an inverse vibratory method (Force Analysis Technique) and the Timoshenko beam theory is detailed and applied experimentally on a sample presenting a honeycomb core. The major philosophy relies in considering multi-layer beams as equivalent homogeneous structures. This simplified approach is thought to be more representative of the global dynamic behaviour, in addition the reduction of degrees of freedom is obviously an improvement for modelling on Finite Element software. When compared to other usual approaches, the method developed in this paper shows a very good agreement between the experimental sandwich beam and the homogeneous model, which highlights interesting insights for applying it to industrial structures. The local aspect, the robustness and the self-regularization properties are verified on a wide frequency range, making the procedure possibly efficient for characterization of structures on a production line, flaw detection and Structural Health Monitoring.
Huang, Yihua; Huang, Wenjin; Wang, Qinglei; Su, Xujian
2013-07-01
The equivalent circuit model of a piezoelectric transformer is useful in designing and optimizing the related driving circuits. Based on previous work, an equivalent circuit model for a circular flexural-vibration-mode piezoelectric transformer with moderate thickness is proposed and validated by finite element analysis. The input impedance, voltage gain, and efficiency of the transformer are determined through computation. The basic behaviors of the transformer are shown by numerical results.
Energy Technology Data Exchange (ETDEWEB)
Kim, S. H.; Lee, J. I.; Rhee, K. Y. [Kyung Hee University, Yongin (Korea, Republic of); Choi, C. R. [ELSOLTEC Inc., Yongin (Korea, Republic of)
2015-05-15
Basalt fiber is widely used in various industries and several studies have been carried out to understand the mechanical behavior of basalt fiber reinforced composites. However, few studies have been made to specifically investigate the mechanical properties of basalt/carbon hybrid composites. In this study, the effect of stacking sequence on the flexural properties of carbon/basalt/epoxy hybrid composites was investigated in order to verify the reliability of this composite model. Two types of carbon/basalt/epoxy hybrid composites with a sandwich form were fabricated: basalt skin-carbon core (BSCC) composites and carbon skin-basalt core (CSBC) composites. After fabrication flexural tests and finite element method (FEM) were conducted. FEM results of flexural analysis are compared with experimental results. A FEA analysis model has been successfully developed in order to predict flexural behavior of basalt/carbon/epoxy hybrid composites. The simulation using the FEA model produces a similar flexural strength to that obtained from the experiment. Therefore, the developed FEA model in general will be highly useful for the prediction of stacking sequence of basalt/carbon/ epoxy hybrid composites for several industrial applications.
Pellegrino, C.; Modena, C.
2008-05-01
This paper deals with the shear strengthening of Reinforced Concrete (RC) flexural members with externally bonded Fiber-Reinforced Polymers (FRPs). The interaction between an external FRP and an internal transverse steel reinforcement is not considered in actual code recommendations, but it strongly influences the efficiency of the shear strengthening rehabilitation technique and, as a consequence, the computation of interacting contributions to the nominal shear strength of beams. This circumstance is also discussed on the basis of the results of an experimental investigation of rectangular RC beams strengthened in shear with "U-jacketed" carbon FRP sheets. Based on experimental results of the present and other investigations, a new analytical model for describing the shear capacity of RC beams strengthened according to the most common schemes (side-bonded and "U-jacketed"), taking into account the interaction between steel and FRP shear strength contributions, is proposed.
Directory of Open Access Journals (Sweden)
T.D. Jagannatha
2015-04-01
Full Text Available Hybrid composite materials are more attracted by the engineers because of their properties like stiffness and high specific strength which leads to the potential application in the area of aerospace, marine and automobile sectors. In the present investigation, the flexural strength and flexural modulus of carbon and glass fibers reinforced epoxy hybrid composites were studied. The vacuum bagging technique was adopted for the fabrication of polymer hybrid composite materials. The hardness, flexural strength and flexural modulus of the hybrid composites were determined as per ASTM standards. The hardness, flexural strength and flexural modulus were improved as the fiber reinforcement contents increased in the epoxy matrix material.
Microstructural description of shear-thickening suspensions
Directory of Open Access Journals (Sweden)
Singh Abhinendra
2017-01-01
Full Text Available Dynamic particle-scale numerical simulations are used to study the variation of microstructure with shear stress during shear thickening in dense non-Brownian suspensions. The microscale information is used to characterize the differences between the shear thickened (frictional and non-thickened (lubricated, frictionless states. Here, we focus on the force and contact networks and study the evolution of associated anisotropies with increase in shear stress. The force and contact networks are both more isotropic in the shear-thickened state than in non-thickened state. We also find that both force and structural anisotropies are rate independent for both low and high stress, while they are rate (or stress dependent for the intermediate stress range where the shear thickening occurs. This behavior is similar to the evolution of viscosity with increasing stress, showing a clear correlation between the microstructure and the macroscopic rheology.
Flexural and Impact Resistance of FRC/Bamboo Laminate
Institute of Scientific and Technical Information of China (English)
无
2002-01-01
The flexural and impact resistance of a newly developed FRC/bamboo laminate have been investigated. The laminate considered in this study was combined with reformed bamboo plate and extruded fiber reinforced cementitious (FRC)sheet. Innovated from the raw bamboo, reformed bamboo showed high tensile strength and high strength to weight ratio. It can not only remarkably strengthen the FRC sheet but also reduce the total weight of the laminate. Flexural and impact load, broken energy, deflection and duration were measured. Test results showed that the flexural strength value for the laminate can be improved to greater than 90 MPa, while the impact resistance is increased more than 10 times for the laminate when compared with the FRC sheet only.
Institute of Scientific and Technical Information of China (English)
周靖; 方小丹
2011-01-01
The shear-resistant behavior of concrete frame columns subjected to velocity pulse-like excitations was studied. The first floor columns of reinforced concrete frame structures were used to investigate the effects of vertical and horizontal velocity pulse-like excitations on shear-resistant behavior of concrete columns. Three equivalent sine velocity pulses were taken as earthquake import to execute nonlinear dynamic time history analysis. Combined effects of vertical-to-· horizontal peak acceleration ratio, import time difference of peak values between vertical and horizontal excitations, shear-span ratio, and fundamental period on shear-resistant demand and shear-resistant capacity were analyzed with the assessment of the effect of velocity pulse action. The results demonstrated that shear-resistant demand of concrete columns increases with increase in intensity of velocity pulse, and shear-resistant capacity decreases with increase in vertical-to-horizontal peak values ratio; import time difference between vertical and horizontal excitations has an important influence on the most unfavorable shear-resistant behavior of concrete frame columns; the higher the values of shear-span ratio, the more significant the influence of velocity pulse excitations; the nonlinear regression analysis for the above results is conducted, and an empirical approach considering different effect of these factors is proposed.%研究等效速度脉冲地震作用下混凝土框架柱最不利抗剪性能.以混凝土框架结构底层柱为分析对象,采用等效正弦速度脉冲激励作为地震动输入,通过非线性动力时程分析,研究竖直和水平向联合速度脉冲地震作用对框架柱抗剪性能的影响,分析速度脉冲地震作用与竖向和水平向加速度峰值比、峰值输入时差、剪跨比以及基本振动周期等对抗剪需求和抗剪承载力的交互影响规律.结果表明:脉冲速度强度增大,框架柱抗剪需求增大;竖向与
On the effect of shear coefficients in free vibration analysis of curved beams
Energy Technology Data Exchange (ETDEWEB)
Kim, Jin Gon; Lee, Jae Kon; Yoon, Hyun Joong [Catholic University of Daegu, Daegu (Korea, Republic of)
2014-08-15
We did a comparative study of shear coefficients in free vibration analysis of curved beams having circular and rectangular cross sections. Until recently, the shear coefficient k in Timoshenko beam theory has been studied by many researchers to include transverse shear deformation effect. To obtain more reliable numerical results, a higher-order hybrid-mixed curved beam element is formulated and programmed in MATLAB. The present numerical experiments show that k = 6(1+v){sup 2}/(7+12v+4v{sup 2}) is the best expression both for circular and rectangular cross-sections in the flexural vibration of curved beams.
Flexural-slip during visco-elastic buckle folding
Damasceno, Davi R.; Eckert, Andreas; Liu, Xiaolong
2017-07-01
Flexural-slip is considered as an important mechanism during folding and a general conceptual and qualitative understanding has been provided by various field studies. However, quantitative evidence of the importance of the flexural-slip mechanism during fold evolution is sparse due to the lack of suitable strain markers. In this study, 2D finite element analysis is used to overcome these disadvantages and to simulate flexural-slip during visco-elastic buckle folding. Variations of single and multilayer layer fold configurations are investigated, showing that flexural-slip is most likely to occur in effective single layer buckle folds, where slip occurs between contacts of competent layers. Based on effective single layer buckle folds, the influence of the number of slip surfaces, the degree of mechanical coupling (based on the friction coefficient), and layer thickness, on the resulting slip distribution are investigated. The results are in agreement with the conceptual flexural-slip model and show that slip is initiated sequentially during the deformation history and is maximum along the central slip surface of the fold limb. The cumulative amount of slip increases as the number of slip surfaces is increased. For a lower degree of mechanical coupling increased slip results in different fold shapes, such as box folds, during buckling. In comparison with laboratory experiments, geometrical relationships and field observations, the numerical modeling results show similar slip magnitudes. It is concluded that flexural-slip should represent a significant contribution during buckle folding, affecting the resulting fold shape for increased amounts of slip.
Flexural strength of acrylic resins polymerized by different cycles
Directory of Open Access Journals (Sweden)
Débora Barros Barbosa
2007-10-01
Full Text Available Despite the large number of studies addressing the effect of microwave polymerization on the properties of acrylic resin, this method has received limited clinical acceptance. This study evaluated the influence of microwave polymerization on the flexural strength of a denture base resin. A conventional heat-polymerized (Clássico, a microwave-polymerized (Onda-Cryl and a autopolymerizing acrylic (Jet resins were used. Five groups were established, according to polymerization cycles: A, B and C (Onda-Cryl, short cycle - 500W/3 min, long - 90W/13 min + 500W/90 sec, and manufacturing microwave cycle - 320W/3 min + 0W/3 min + 720W/3 min; T (Clássico, water bath cycle - 74ºC/9h and Q (Jet, press chamber cycle - 50ºC/15 min at 2 bar. Ten specimens (65 x 10 x 3.3mm were prepared for each cycle. The flexural strength of the five groups was measured using a three-point bending test at a cross-head speed of 5 mm/min. Flexural strength values were analyzed by one-way ANOVA and the Tukey's test was performed to identify the groups that were significantly different at 5% level. The microwave-polymerized groups showed the highest means (p<0.05 for flexural strength (MPa (A = 106.97 ± 5.31; B = 107.57 ± 3.99; C = 109.63 ± 5.19, and there were no significant differences among them. The heat-polymerized group (T showed the lowest flexural strength means (84.40 ± 1.68, and differ significantly from all groups. The specimens of a microwavable denture base resin could be polymerized by different microwave cycles without risk of decreasing the flexural strength.
Dubey, Ashish
One major problem associated with the testing of fiber reinforced concrete specimens under flexural loading is that the measured post-cracking response is severely affected by the stiffness of the testing machine. As a consequence, misleading results are obtained when such a flexural response is used for the characterization of composite toughness. An assessment of a new toughness characterization technique termed the Residual Strength Test Method (RSTM) has been made. In this technique, a stable narrow crack is first created in the specimen by applying a flexural load in parallel with a steel plate under controlled conditions. The plate is then removed, and the specimen is tested in a routine manner in flexure to obtain the post-crack load versus displacement response. Flexural response for a variety of fiber reinforced cementitious composites obtained using the Residual Strength Test Method has been found to correlate very well with those obtained with relatively stiffer test configurations such as closed-loop test machines. The Residual Strength Test Method is found to be effective in differentiating between different fiber types, fiber lengths, fiber configurations, fiber volume fractions, fiber geometries and fiber moduli. In particular, the technique has been found to be extremely useful for testing cement-based composites containing fibers at very low dosages (shear lag theory is introduced to study the problem of fiber pullout in fiber reinforced composites. The proposed model eliminates limitations of many earlier models and captures essential features of pullout process, including progressive interfacial debonding, Poisson's effect, and variation in interfacial properties during the fiber pullout process. Interfacial debonding is modeled using an interfacial shear strength criterion. Influence of normal contact stress at the fiber-matrix interface is considered using shrink-fit theory, and the interfacial frictional shear stress over the debonded
Flexural-Phonon Scattering Induced by Electrostatic Gating in Graphene
DEFF Research Database (Denmark)
Gunst, Tue; Kaasbjerg, Kristen; Brandbyge, Mads
2017-01-01
Graphene has an extremely high carrier mobility partly due to its planar mirror symmetry inhibiting scattering by the highly occupied acoustic flexural phonons. Electrostatic gating of a graphene device can break the planar mirror symmetry, yielding a coupling mechanism to the flexural phonons.......We examine the effect of the gate-induced one-phonon scattering on the mobility for several gate geometries and dielectric environments using first-principles calculations based on density functional theory and the Boltzmann equation. We demonstrate that this scattering mechanism can be a mobility...
Flexural waves induced by electro-impulse deicing forces
Gien, P. H.
1990-01-01
The generation, reflection and propagation of flexural waves created by electroimpulsive deicing forces are demonstrated both experimentally and analytically in a thin circular plate and a thin semicylindrical shell. Analytical prediction of these waves with finite element models shows good correlation with acceleration and displacement measurements at discrete points on the structures studied. However, sensitivity to spurious flexural waves resulting from the spatial discretization of the structures is shown to be significant. Consideration is also given to composite structures as an extension of these studies.
Directory of Open Access Journals (Sweden)
Hamid Reza Ashrafi
2016-03-01
Full Text Available Steel moment frame systems, steel plate shear walls and also buckling restrained brace (BRB are considered as the most widely used seismic resistant systems of the world. Firstly, in this research, in order to validate the finite element models, the tested sample of steel plate shear walls of 4 floors at the University of Alberta, Canada, and the tested sample of buckling restrained brace at the University of Berkeley California, with the software ABAQUS 6.10-1 were used. Then, the obtained results of the test and analysis have been compared. The confirmed models have been used for the analysis of two-dimensional frame of plain and perforated steel plate shear walls with a regular pattern of positing holes in the screen, buckling restrained brace and moment frame of 4 floors.
Walraven, J. C.; Reinhardt, H. W.
The mechanism or transmission of forces across cracks whose faces are subjected to shear displacements are investigated. This mechanism is achieved by interaction of several components: axial and transverse stiffness (dowel action) of the reinforcement and direct transfer of force between the rough concrete crack faces, generally denoted by the term 'aggregate interlock'. Experimental research and the derivation of a theoretical model gave insight into the phenomenon. Tests were carried out on precracked shear specimens. Variables in the tests were the type of reinforcement (embedded reinforcing bars, external restraint bars), the concrete strength, the type of the concrete (sand gravel concrete, lightweight concrete), the grading of the concrete (continuous discontinuous), the scale of the concrete, and the initial crack width. Measurements were carried for determining the shear force, the crack displacements and, for the specimens with external reinforcement, the force in the restraining bars.
Rodrigues, Sinval A; Ferracane, Jack L; Della Bona, Alvaro
2008-03-01
The aim of the present study was to evaluate the flexural strength and the Weibull modulus of a microhybrid and a nanofill composite by means of 3- and 4-point bending tests. Thirty specimens of Filtek Z250 (3M/ESPE) and Filtek Supreme (3M/ESPE) were prepared for each test according to the ISO 4049/2000 specification. After 24h in distilled water at 37 degrees C the specimens were submitted to 3- and 4-point bending tests using a universal testing machine DL2000 (EMIC) with a crosshead speed of 1 mm/min. Flexural strength data were calculated and submitted to Student's t-test (alpha=0.05) and Weibull statistics. The fractured surfaces were analyzed based on fractographic principles. The two composites had equivalent strength in both test methods. However, the test designs significantly affected the flexural strength of the microhybrid and the nanofill composites. Weibull modulus (m) of Supreme was similar with both tests, while for Z250, a higher m was observed with the 3-point bending test. Critical flaws were most often associated with the specimen's surface (up to 90%) and were characterized as surface scratches/grooves, non-uniform distribution of phases, inclusions and voids. Flexural strength as measured by the 3-point bending test is higher than by the 4-point bending test, due to the smaller flaw containing area involved in the former. Despite the large difference in average filler size between the composites, the volume fraction of the filler in both materials is similar, which was probably the reason for similar mean flexural strength values and fracture behavior.
Structural Behavior of Concrete Beams Reinforced with Basalt Fiber Reinforced Polymer (BFRP) Bars
Ovitigala, Thilan
The main challenge for civil engineers is to provide sustainable, environmentally friendly and financially feasible structures to the society. Finding new materials such as fiber reinforced polymer (FRP) material that can fulfill the above requirements is a must. FRP material was expensive and it was limited to niche markets such as space shuttles and air industry in the 1960s. Over the time, it became cheaper and spread to other industries such as sporting goods in the 1980-1990, and then towards the infrastructure industry. Design and construction guidelines are available for carbon fiber reinforced polymer (CFRP), aramid fiber reinforced polymer (AFRP) and glass fiber reinforced polymer (GFRP) and they are currently used in structural applications. Since FRP is linear elastic brittle material, design guidelines for the steel reinforcement are not valid for FRP materials. Corrosion of steel reinforcement affects the durability of the concrete structures. FRP reinforcement is identified as an alternative to steel reinforcement in corrosive environments. Although basalt fiber reinforced polymer (BFRP) has many advantages over other FRP materials, but limited studies have been done. These studies didn't include larger BFRP bar diameters that are mostly used in practice. Therefore, larger beam sizes with larger BFRP reinforcement bar diameters are needed to investigate the flexural and shear behavior of BFRP reinforced concrete beams. Also, shear behavior of BFRP reinforced concrete beams was not yet studied. Experimental testing of mechanical properties and bond strength of BFRP bars and flexural and shear behavior of BFRP reinforced concrete beams are needed to include BFRP reinforcement bars in the design codes. This study mainly focuses on the use of BFRP bars as internal reinforcement. The test results of the mechanical properties of BFRP reinforcement bars, the bond strength of BFRP reinforcement bars, and the flexural and shear behavior of concrete beams
Measurement of multiaxial ply strength by an off-axis flexure test
Crews, John H., Jr.; Naik, Rajiv A.
1992-01-01
An off-axis flexure (OAF) test was performed to measure ply strength under multiaxial stress states. This test involves unidirectional off-axis specimens loaded in bending, using an apparatus that allows these anisotropic specimens to twist as well as flex without the complications of a resisting torque. A 3D finite element stress analysis verified that simple beam theory could be used to compute the specimen bending stresses at failure. Unidirectional graphite/epoxy specimens with fiber angles ranging from 90 deg to 15 deg have combined normal and shear stresses on their failure planes that are typical of 45 deg plies in structural laminates. Tests for a range of stress states with AS4/3501-6 specimens showed that both normal and shear stresses on the failure plane influenced cracking resistance. This OAF test may prove to be useful for generating data needed to predict ply cracking in composite structures and may also provide an approach for studying fiber-matrix interface failures under stress states typical of structures.
Paimushin, V. N.; Firsov, V. A.; Gyunal, I.; Shishkin, V. M.
2016-11-01
A hardware and software system for studying the damping and elastic properties of soft materials in a low-frequency range of deformation up to 100 Hz, which most fully corresponds to the range of dynamic actions in actual service conditions of structures, is proposed. A novel identification method for evaluating the elastic and damping properties of soft materials in shear is developed. It employs the frequency and amplitude characteristics of the resonance flexural vibrations of three-layer test specimens with a soft inner layer. Identification of the elastic shear properties is based on a comparison of calculated and experimental frequencies of resonance vibrations of test specimens. To evaluate the shear damping properties of soft materials, the condition of minimum of an objective function containing experimental and calculated amplitudes of vibrations of the free end of a test specimen is used. The possibility of evaluating the properties mentioned from the experimental and calculated internal damping parameters of test specimens, which significantly reduces the laboriousness of the problem considered, is shown. Numerical calculations are carried out for identifying the elastic and damping characteristics of a technical rubber in shear based on an analysis of resonance flexural vibrations of seven test specimens with outer layers made of a D16AT aluminum alloy.
Influence of geometrical parameters on the flexural rigidity of the LHC dipole cold mass assembly
Bajko, M; Pardons, A
2002-01-01
In order to predict the mechanical behavior of the LHC dipole cold mass in situations such as handling, transport and cool down, a number of important structural parameters are required. The dipole's flexural rigidity determines entirely the mechanical elastic behavior of the cold mass. Therefore, models of a bent cold mass were created to calculate its rigidity. This paper presents a simplified parametric finite element model, created to study the deflection of the cold mass in different situations and supporting conditions. The sensitivity of the models to the supporting conditions is computed. To provide the finite element and the analytical models with input, the deflection of the cold mass under discrete loads in normal condition and then 90-degrees rotated were measured with a laser tracker. By comparing models with measurements, the vertical and transversal rigidity of the cold mass assembly are determined. Additionally, the paper reports on the plastic behavior of the cold mass assembly in the range o...
Institute of Scientific and Technical Information of China (English)
苏明周; 黄智光; 孙健; 齐岩; 申林
2011-01-01
为考察冷弯薄壁型钢组合墙体在循环荷载下的抗剪性能，进行10片足尺墙体试件水平低周反复加载试验，得到不同构造墙体的屈服荷载、最大荷载、破坏荷载、耗能系数和延性系数等性能指标。试验结果表明：组合墙体的耗能能力较好；墙体的抗剪承载力主要来源于墙板的蒙皮作用；斜撑对提高单柱墙体抗剪承载力起一定作用，但对双柱墙体的作用很小；当忽略墙体开洞部分的抗剪承载力后，单位长度开洞墙体的抗剪承载力比普通墙体稍高，表明墙体开洞部分承担了一定剪力；双柱墙体比单柱墙体的抗剪承载力显著提高；试验过程中各试件立柱的应变反应普遍较大、横撑%In order to study the shearing behavior of cold-formed steel wall panels, full scale model test was carried out for 10 pieces of wall panels under cyclic horizontal load. The shearing performance indexes of wall panels such as yield load, maximum load, failure load, energy dissipation coefficient, and ductility factor were calculated using the test results. Based on the analysis, the following conclusions are obtained. The wall panels had good energy dissipation capacity. The shear resistance of the wall panels mainly derived from skin action. The diagonal bracings were helpful to improve the shear resistance of single-column wall panel while nearly useless to double-column wall panel. The per unit shear resistance of wall panel with openings was higher than that of ordinary wall panel when the shear load carrying capacity of openings was ignored. The shear load carrying capacities of double-column wall panels were obviously higher than that of single-column ones. The strain response was largest for the column, smaller for the transverse bracing, and smallest for the diagonal bracing. The interface slip between the upper and lower wallboards was obvious, thus the seams between wallboards should be as small as possible
Silva, Clodoaldo J.; Daqaq, Mohammed F.
2017-02-01
Despite the shear amount of research studies on nonlinear flexural dynamics of cantilever beams, very few efforts address the practical geometry involving a constant thickness and linearly-varying width. This stems from the nature of the associated linear eigenvalue problem which cannot be easily solved in closed form. In this paper, we present a closed-form solution to this particular linear eigenvalue problem in the form of a general Meijer-G differential equation for which a solution is readily available in the shape of the Meijer-G functions. Using this approach, the exact linear modal frequencies and shapes are obtained and used in the discretization of the nonlinear partial-differential equation describing the dynamics of the system. The discretized system of ordinary-differential equations is then solved using the method of multiple scales to obtain an approximate analytical solution describing the primary resonance behavior of a given vibration mode. An analytical expression for the modal effective nonlinearity is obtained and used to analyze the influence of the beam's tapering on the nonlinear primary resonance behavior of the response (softening/hardening). Results are then compared to a finite element (FE) solution of the linear eigenvalue problem in which the modal shapes obtained using the FE method are fit into a set of orthogonal polynomial functions and used to discretize the nonlinear problem. It is shown that, while the modal frequencies obtained using the FE method approximate those obtained analytically with negligible error (less than 1%), there is a substantial error in the resulting estimates of the modal effective nonlinearity. This indicates that, even negligible errors in the approximate solution of the linear problem, can propagate to become significant when analyzing the nonlinear problem further reinforcing the importance of the exact solution.
Marshaline Seles, M.; Suryanarayanan, R.; Vivek, S. S.; Dhinakaran, G.
2017-07-01
The conventional concrete when used for structures having dense congested reinforcement, the problems such as external compaction and vibration needs special attention. In such case, the self compacting concrete (SCC) which has the properties like flow ability, passing and filling ability would be an obvious answer. All those SCC flow behavior was governed by EFNARC specifications. In present study, the combination type of SCC was prepared by replacing cement with silica fume (SF) and metakaolin (MK) along with optimum dosages of chemical admixtures. From the fresh property test, cube compressive strength and cylinder split tensile strength, optimum ternary mix was obtained. In order to study the flexural behavior, the optimum ternary mix was taken in which beam specimens of size 1200 mm x 100 mm x 200 mm was designed as singly reinforced section according to IS: 456-2000, Limit state method. Finally the comparative experimental analysis was made between conventional RCC and SCC beams of same grade in terms of flexural strength namely yield load & ultimate load, load- deflection curve, crack size and pattern respectively.
Mechanical behavior of carbon-carbon composites
Rozak, G. A.
1984-01-01
A general background, test plan, and some results of preliminary examinations of a carbon-carbon composite material are presented with emphasis on mechanical testing and inspection techniques. Experience with testing and evaluation was gained through tests of a low modulus carbon-carbon material, K-Karb C. The properties examined are the density - 1.55 g/cc; four point flexure strength in the warp - 137 MPa (19,800 psi) and the fill - 95.1 MPa (13,800 psi,) directions; and the warp interlaminar shear strength - 14.5 MPa (2100 psi). Radiographic evaluation revealed thickness variations and the thinner areas of the composite were scrapped. The ultrasonic C-scan showed attenuation variations, but these did not correspond to any of the physical and mechanical properties measured. Based on these initial tests and a survey of the literature, a plan has been devised to examine the effect of stress on the oxidation behavior, and the strength degradation of coated carbon-carbon composites. This plan will focus on static fatigue tests in the four point flexure mode in an elevated temperature, oxidizing environment.
Flexure of the Indian plate and intraplate earthquakes
Indian Academy of Sciences (India)
Roger Bilham; Rebecca Bendick; Kali Wallace
2003-09-01
The flexural bulge in central India resulting from India's collision with Tibet has a wavelength of approximately 670 km. It is manifest topographically and in the free-air gravity anomaly and the geoid. Calculations of the stress distribution within a flexed Indian plate reveal spatial variations throughout the depth of the plate and also a function of distance from the Himalaya. The wave- length (and therefore local gradient) of stress variation is a function of the effective elastic thickness of the plate, estimates of which have been proposed to lie in the range 40-120 km. The imposition of this stress field on the northward moving Indian plate appears fundamental to explaining the current distribution of intraplate earthquakes and their mechanisms. The current study highlights an outer trough south of the flexural bulge in central India where surface stresses are double the contiguous compressional stresses to the north and south. The Bhuj, Latur and Koyna earthquakes and numerous other recent reverse faulting events occurred in this compressional setting. The N/S spatial gradient of stress exceeds 2 bars/km near the flexural bulge. The overall flexural stress distribution provides a physical basis for earthquake hazard mapping and suggests that areas of central India where no historic earthquakes are recorded may yet be the locus of future damaging events.
Effect of silica coating on flexural strength of fiber posts
Valandro, LF; Ozcan, M; de Melo, RM; Galhano, GAP; Baldissara, P; Scotti, R; Bottino, MA
2006-01-01
Purpose: Fiber-reinforced composite (FRC) posts can be air-abraded to obtain good attachment to the resin cement. This study tested the effect of silica coating on the flexural strength of carbon, opaque, and translucent quartz FRC posts. Materials and Methods: Six experimental groups of FRC posts (
Substructural Identification of Flexural Rigidity for Beam-Like Structures
Directory of Open Access Journals (Sweden)
Ki-Young Koo
2015-01-01
Full Text Available This study proposes a novel substructural identification method based on the Bernoulli-Euler beam theory with a single variable optimization scheme to estimate the flexural rigidity of a beam-like structure such as a bridge deck, which is one of the major structural integrity indices of a structure. In ordinary bridges, the boundary condition of a superstructure can be significantly altered by aging and environmental variations, and the actual boundary conditions are generally unknown or difficult to be estimated correctly. To efficiently bypass the problems related to boundary conditions, a substructural identification method is proposed to evaluate the flexural rigidity regardless of the actual boundary conditions by isolating an identification region within the internal substructure. The proposed method is very simple and effective as it utilizes the single variable optimization based on the transfer function formulated utilizing Bernoulli Euler beam theory for the inverse analysis to obtain the flexural rigidity. This novel method is also rigorously investigated by applying it for estimating the flexural rigidity of a simply supported beam model with different boundary conditions, a concrete plate-girder bridge model with different length of an internal substructure, a cantilever-type wind turbine tower structure with different type of excitation, and a steel box-girder bridge model with internal structural damages.
Effect of Finger Joint on Flexural Strength of Teak Wood
Directory of Open Access Journals (Sweden)
Bharatesh A. Danawade
2014-01-01
Full Text Available This paper presents the flexural properties of rectangular Burma teak wood beam without finger joint and with finger joint. Finger joints enable full utilization of wood. Finger jointing technique is also used to eliminate wood defects which weaken the strength of wood. This paper considers finger joint as defined defect and its effect on the flexural strength is determined. Teakwood is hard and heavy, seasons rapidly and has good durability. The specimens were studied under three point bending test. Both edge wise and flat wise tests were carried out. It is observed that Burma teakwood beam without finger joint is stronger than beams with finger joints. Because of finger jointing the flexural strength reduces. It can be concluded that the strength loss can improved upon by selecting suitable geometry of finger joint and a suitable adhesive. It is recognized that further studies are necessary on jointing techniques of wood and type of adhesive so as to equal the flexural strength properties of clear teak wood beams.
Synthesis and Optimisation of Large Stroke Flexure Hinges
Grootens, Martijn; Aarts, Ronald; Brouwer, Dannis; Wenger, Philippe; Flores, Paulo
2016-01-01
Flexure hinges are advantageous for use in high-precision applications because of their lack of hysteresis, friction and backlash. However, their range of motion is limited due to increasing stresses and a decreasing support stiffness at large strokes. Currently available hinges are typically design
Strengthening of Steel Columns under Load: Torsional-Flexural Buckling
Directory of Open Access Journals (Sweden)
Martin Vild
2016-01-01
Full Text Available The paper presents experimental and numerical research into the strengthening of steel columns under load using welded plates. So far, the experimental research in this field has been limited mostly to flexural buckling of columns and the preload had low effect on the column load resistance. This paper focuses on the local buckling and torsional-flexural buckling of columns. Three sets of three columns each were tested. Two sets corresponding to the base section (D and strengthened section (E were tested without preloading and were used for comparison. Columns from set (F were first preloaded to the load corresponding to the half of the load resistance of the base section (D. Then the columns were strengthened and after they cooled, they were loaded to failure. The columns strengthened under load (F had similar average resistance as the columns welded without preloading (E, meaning the preload affects even members susceptible to local buckling and torsional-flexural buckling only slightly. This is the same behaviour as of the tested columns from previous research into flexural buckling. The study includes results gained from finite element models of the problem created in ANSYS software. The results obtained from the experiments and numerical simulations were compared.
On mechanical properties of planar flexure hinges of compliant mechanisms
Directory of Open Access Journals (Sweden)
F. Dirksen
2011-06-01
Full Text Available The synthesis of compliant mechanisms yield optimized topologies that combine several stiff parts with highly elastic flexure hinges. The hinges are often represented in finite element analysis by a single node (one-node hinge leaving doubts on the physical meaning as well as an uncertainty in the manufacturing process.
To overcome this one-node hinge problem of optimized compliant mechanisms' topologies, one-node hinges need to be replaced by real flexure hinges providing desired deflection range and the ability to bear internal loads without failure. Therefore, several common types of planar flexure hinges with different geometries are characterized and categorized in this work providing a comprehensive guide with explicit analytical expressions to replace one-node hinges effectively.
Analytical expressions on displacements, stresses, maximum elastic deformations, bending stiffness, center of rotation and first natural frequencies are derived in this work. Numerical simulations and experimental studies are performed validating the analytical results. More importance is given to practice-oriented flexure hinge types in terms of cost-saving manufacturability, i.e. circular notch type hinges and rectangular leaf type hinges.
Shear Reinforcement Requirements for High-Strength Concrete Bridge Girders
Ramirez, J. A.; Aguilar, Gerardo
2005-01-01
A research program was conducted on the shear strength of high-strength concrete members. The objective was to evaluate the shear behavior and strength of concrete bridge members with compressive strengths in the range of 10 000 to 15 000 psi. The goal was to determine if the current minimum amount of shear reinforcement together with maximum spacing limits in the 2004 AASHTO LRFD Specifications, and the upper limit on the nominal shear strength were applicable to concrete compressive strengt...
Institute of Scientific and Technical Information of China (English)
王文炜; 李果
2004-01-01
对9根玻璃纤维布加固的钢筋混凝土梁和3根对比梁进行了抗弯性能试验研究. 试验中考虑了配筋率、加固量、剪跨比与混凝土强度等级4个参数. 试验结果表明, 经玻璃纤维布加固的钢筋混凝土梁抗弯承载力有显著提高; 混凝土强度、配筋率、加固量对极限荷载有显著影响; 剪跨比对加固梁的破坏形态有影响. 根据不同的破坏模式, 提出了抗弯承载力计算方法.%Nine reinforced concrete (RC) beams strengthened with glass fiber reinforced polymer (GFRP) sheets and three control beams were tested. Four parameters considered in this experimental program included the concrete strength, the reinforcement ratio, the number of GFRP sheets, and the shear span ratio. It is shown that the application of GFRP sheets can increase the ultimate flexural capacity. The effect of the concrete strength, the reinforcement ratio and the number of GFRP sheets on load capacity is obvious. The shear span ratio can affect the failure mode of RC beams strengthened with GFRP sheets. A theoretical model for flexural behavior of the strengthened RC beam is also developed.
Flexural Performance of CFRP Wrapped Expansive Concrete Beams%CFRP 外包膨胀混凝土组合梁的抗弯性能
Institute of Scientific and Technical Information of China (English)
曹旗; 王晓峰; 王吉忠; 仲伟秋
2016-01-01
预应力混凝土结构在抗裂和抗渗方面都有着天然的优势，然而复杂的张拉工艺和严格的锚具制作制约了其在实际工程中的应用和发展。为研究出新型预应力结构，提出了CFRP外包膨胀混凝土组合梁技术，并对5根膨胀混凝土组合梁（SHCC ）和5根普通混凝土组合梁（PCC ）进行了抗弯性能试验研究。试验主要考虑了混凝土的种类、CFRP片材的层数和布置形式。试验结果表明，在CFRP增强方式相同的情况下，SHCC试件比PCC试件表现出了更好的延迟开裂、控制裂缝宽度和承受荷载的能力。组合梁的承载力随CFRP配筋率的增加而增大，然而过大的配筋率会使组合梁的破坏形态由弯曲破坏向弯剪破坏转变。在配筋率相同的条件下，相比CFRP对称布置，偏心布置CFRP组合梁试件表现出的抗弯性能更加优越。%Prestressed concrete structures has prominent advantages of cracking resistance and anti-permeability .However the complexity of streching-technique and strictness of anchorage has restricted their application and development in the practical engineering .In order to create an innovative prestressed concrete structure ,a hybrid FRP-wrapped expansive concrete beam structure was proposed .Five FRP-reinforced expansive concrete beams and five FRP-reinforced conven-tional concrete beams were tested to investigate their flexural behavior .The main parameters included in the tests are types of concrete ,layers and layout of CFRP sheets .The test results indicated that at the same layout of CFRP ,SHCC specimens have better performance than PCC on delaying cracking ,the control of crack width and the bearing capacity . The flexural capacity of the beam specimens increased with the increase of reinforcement ratio of CFRP ,However ,exces-sive reinforcement ratio made the failure modes transform from bending failure to shear failure .Under the condition of the same reinforcement
Origins of Shear Jamming for Frictional Grains
Wang, Dong; Zheng, Hu; Ren, Jie; Dijksman, Joshua; Bares, Jonathan; Behringer, Robert
2016-11-01
Granular systems have been shown to be able to behave like solids, under shear, even when their densities are below the critical packing fraction for frictionless isotropic jamming. To understand such a phenomena, called shear jamming, the question we address here is: how does shear bring a system from a unjammed state to a jammed state, where the coordination number, Z, is no less than 3, the isotropic jamming point for frictional grains? Since Z can be used to distinguish jammed states from unjammed ones, it is vital to understand how shear increases Z. We here propose a set of three particles in contact, denoted as a trimer, as the basic unit to characterize the deformation of the system. Trimers, stabilized by inter-grain friction, fail under a certain amount of shear and bend to make extra contacts to regain stability. By defining a projection operator of the opening angle of the trimer to the compression direction in the shear, O, we see a systematically linear decrease of this quantity with respect to shear strain, demonstrating the bending of trimers as expected. In addition, the average change of O from one shear step to the next shows a good collapse when plotted against Z, indicating a universal behavior in the process of shear jamming. We acknowledge support from NSF DMR1206351, NASA NNX15AD38G, the William M. Keck Foundation and a RT-MRSEC Fellowship.
Novel shear mechanism in nanolayered composites
Energy Technology Data Exchange (ETDEWEB)
Mara, Nathan [Los Alamos National Laboratory; Bhattacharyya, Dhriti [Los Alamos National Laboratory; Hirth, John P [Los Alamos National Laboratory; Dickerson, Patricia O [Los Alamos National Laboratory; Misra, Amit [Los Alamos National Laboratory
2009-01-01
Recent studies have shown that two-phase nanocomposite materials with semicoherent interfaces exhibit enhanced strength, deformability, and radiation damage resistance. The remarkable behavior exhibited by these materials has been attributed to the atomistic structure of the bi-metal interface that results in interfaces with low shear strength and hence, strong barriers for slip transmission due to dislocation core spreading along the weak interfaces. In this work, the low interfacial shear strength of Cu/Nb nanoscale multilayers dictates a new mechanism for shear banding and strain softening during micropillar compression. Previous work investigating shear band formation in nanocrystalline materials has shown a connection between insufficient strain hardening and the onset of shear banding in Fe and Fe-10% Cu, but has also shown that hardening does not necessarily offset shear banding in Pd nanomaterials. Therefore, the mechanisms behind shear localization in nanocrystalline materials are not completely understood. Our findings, supported by molecular dynamics simulations, provide insight on the design of nanocomposites with tailored interface structures and geometry to obtain a combination of high strength and deformability. High strength is derived from the ability of the interfaces to trap dislocations through relative ease of interfacial shear, while deformability can be maximized by controlling the effects of loading geometry on shear band formation.
Shear System Debugging and Shear Test
Institute of Scientific and Technical Information of China (English)
YANG; Dong-xue; JIAO; Hai-yang
2015-01-01
Shear system is the essential equipment of head-end processing in the spent fuel reprocessing process,with the aim of cutting spent fuels into appropriate lengths for dissolve,separatingspent fuel core from jacket.Shear system of CRARL is mainly set in 01Bhot cell,element rods will be cut into short lengths of 10-30mm
Klein, Fred W.
2016-04-01
Several lines of earthquake evidence indicate that the lithospheric plate is broken under the load of the island of Hawai`i, where the geometry of the lithosphere is circular with a central depression. The plate bends concave downward surrounding a stress-free hole, rather than bending concave upward as with past assumptions. Earthquake focal mechanisms show that the center of load stress and the weak hole is between the summits of Mauna Loa and Mauna Kea where the load is greatest. The earthquake gap at 21 km depth coincides with the predicted neutral plane of flexure where horizontal stress changes sign. Focal mechanism P axes below the neutral plane display a striking radial pattern pointing to the stress center. Earthquakes above the neutral plane in the north part of the island have opposite stress patterns; T axes tend to be radial. The M6.2 Honomu and M6.7 Kiholo main shocks (both at 39 km depth) are below the neutral plane and show radial compression, and the M6.0 Kiholo aftershock above the neutral plane has tangential compression. Earthquakes deeper than 20 km define a donut of seismicity around the stress center where flexural bending is a maximum. The hole is interpreted as the soft center where the lithospheric plate is broken. Kilauea's deep conduit is seismically active because it is in the ring of maximum bending. A simplified two-dimensional stress model for a bending slab with a load at one end yields stress orientations that agree with earthquake stress axes and radial P axes below the neutral plane. A previous inversion of deep Hawaiian focal mechanisms found a circular solution around the stress center that agrees with the model. For horizontal faults, the shear stress within the bending slab matches the slip in the deep Kilauea seismic zone and enhances outward slip of active flanks.
Flexural strength and fracture toughness of dental core ceramics.
Yilmaz, Handan; Aydin, Cemal; Gul, Basak E
2007-08-01
Many different strengthened all-ceramic core materials are available. In vitro study of their mechanical properties, such as flexural strength and fracture toughness, is necessary before they are used clinically. The purpose of this study was to evaluate and compare the mechanical properties of 6 commonly used all-ceramic core materials using biaxial flexural strength and indentation fracture toughness tests. Specimens of 6 ceramic core materials (Finesse, Cergo, IPS Empress, In-Ceram Alumina, In-Ceram Zirconia, and Cercon Zirconia) were fabricated (n=25) with a diameter of 15 mm and width of 1.2 +/- 0.2 mm. For each group, the specimens were tested to compare their biaxial flexural strength (piston on 3 balls) (n=15), Weibull modulus, and indentation fracture toughness (n=10) (IF method). The data were analyzed with 1-way ANOVA test (a=.05). The Tamhane multiple comparison test was used for post hoc analysis. Mean (SD) of biaxial flexural strength values (MPa) and Weibull modulus (m) results were: Finesse (F): 88.04 (31.61), m=3.17; Cergo (C): 94.97 (13.62), m=7.94; IPS Empress (E): 101.18 (13.49), m=10.13; In-Ceram Alumina (ICA): 341.80 (61.13), m=6.96; In-Ceram Zirconia (ICZ): 541.80 (61.10), m=10.17; and Cercon Zirconia (CZ): 1140.89 (121.33), m=13.26. The indentation fracture toughness results showed that there were significant differences between the tested ceramics. The highest fracture toughness values (MPa x m(0.5)) were obtained with the zirconia-based ceramic core materials. Significant differences were found in strength and toughness values of the materials evaluated. Cercon Zirconia core material showed high values of biaxial flexural strength and indentation fracture toughness when compared to the other ceramics studied.
考虑腹板剪切行为的波形钢腹板梁理论模型%Theory Model of Corrugated Steel Web Girder Considering Web Shear Behavior
Institute of Scientific and Technical Information of China (English)
聂建国; 李法雄
2011-01-01
为研究波形钢腹板剪切变形对波形钢腹板梁受力行为的影响,引入腹板剪切变形转角函数,将波形钢腹板梁的弯曲行为分解为桁架作用和弯曲作用,建立一个能够考虑波形钢腹板剪切变形的波形钢腹板梁理论模型。推导了端部无约束条件下简支波形钢腹板梁在均布荷载和端部约束条件下简支波形钢腹板梁在跨中集中荷载作用下的解析解,采用有限元方法验证了理论模型和解析解的正确性和适用性。研究结果表明：端部约束条件对主梁变形影响很小;波形钢腹板的剪切变形对主梁变形影响显著,在常见波形钢腹板梁桥尺寸范围内,由腹板剪切变形引起的主梁挠度占总挠度的10%～30%。%In order to study the influence of shear deformation of forcing behavior for corrugated steel web,shear rotation function of calculating shear deformation in the web was introduced,a theory model of corrugated steel web girder was presented.In the model,bending behavior of corrugated steel web girder could be divided into truss action and bending action between upper-flange and sub-flange.Then,analytical solutions for the cases of simply-supported corrugated steel web girder without end restraint sustaining under uniform distribution load and simply-supported corrugated steel web girder with end restraint under sustaining mid-span concentrated load were derived,validity and usability of the analytical solution and the model were well proved by finite element method.Results show that the end constraint conditions have little effect on the deformation of the main girder.However,the shear deformation of corrugated steel web has great impact on the deformation of main girder.In the common size ranges of bridge with corrugated steel web girders,the proportion of main girder deflection caused by shear deformation in the web may reach 10% to 30% of total deflection.
Energy Technology Data Exchange (ETDEWEB)
Dodelson, Scott; /Fermilab /Chicago U., Astron. Astrophys. Ctr. /Northwestern U.; Shapiro, Charles; /Chicago U. /KICP, Chicago; White, Martin J.; /UC, Berkeley, Astron.
2005-08-01
Measurements of ellipticities of background galaxies are sensitive to the reduced shear, the cosmic shear divided by (1-{kappa}) where {kappa} is the projected density field. They compute the difference between shear and reduced shear both analytically and with simulations. The difference becomes more important an smaller scales, and will impact cosmological parameter estimation from upcoming experiments. A simple recipe is presented to carry out the required correction.
Energy Technology Data Exchange (ETDEWEB)
Dodelson, Scott; /Fermilab /Chicago U., Astron. Astrophys. Ctr. /Northwestern U.; Shapiro, Charles; /Chicago U. /KICP, Chicago; White, Martin J.; /UC, Berkeley, Astron.
2005-08-01
Measurements of ellipticities of background galaxies are sensitive to the reduced shear, the cosmic shear divided by (1-{kappa}) where {kappa} is the projected density field. They compute the difference between shear and reduced shear both analytically and with simulations. The difference becomes more important an smaller scales, and will impact cosmological parameter estimation from upcoming experiments. A simple recipe is presented to carry out the required correction.
Institute of Scientific and Technical Information of China (English)
宁喜亮; 丁一宁
2015-01-01
Bending tests under four point loading were conducted on steel rebar-reinforced steel fiber-reinforced self-compacting concrete ( SFRSCC ) beams , and the corresponding loading-mid-span deflection curve , longitudinal reinforcement strain-longitudinal reinforcement strain curve and failure mode were obtained .The flexural bearing capacity of the beams and the hybrid effect of steel rebar and macro steel fibers were also examined .It is found that the addition of steel fibers can improve the flexural bearing capacity by 10%~42%.Moreover, by taking into ac-count the steel fiber distribution and its force transfer mechanism crossing the crack , a calculation formula is pro-posed to predict the flexural bearing capacity of the beams , and it is compared with the formulas of ACI 544 and CECS 38:2004.Calculation results show that the proposed formula has a better fit with the test results .Thus, it is suitable for the flexural analysis and design of SFRSCC beams .%通过四点弯曲试验得到钢筋－纤维自密实混凝土梁式构件的荷载－跨中挠度曲线、荷载－纵筋应变曲线和破坏形态，对梁式构件的受弯承载力及纤维与钢筋的混杂效应进行了分析。结果表明：钢纤维的加入使钢筋－纤维自密实混凝土梁式构件的抗弯承载力提高了10％～42％。考虑钢纤维跨越裂缝的传力机理及分布情况提出了钢筋－纤维混凝土梁式构件受弯承载力计算公式，并与ACI 544和CECS 38：2004的公式进行了对比，计算结果表明：文中建议公式计算的受弯承载力与试验结果最为接近，可用于钢筋－纤维自密实混凝土梁式构件的受弯分析与设计。
Theoretical research on the shear bearing capacity of exposed steel column foot
LIU, Xijin
2017-04-01
This paper makes an overview on the domestic research on the steel column shear capacity in detail. On such basis, in accordance with the 4th theory of strength and the flexural vibration of straight bar, it makes theoretical analysis on the shear-bearing capacity of the steel column foot with the shear key and without the shear key respectively. It proposes the methods for calculating the shear-bearing capacity of steel column foot under two situations. It suggests that Code for Design of Steel Structures should raise the separation point of exposed steel column foot, which would reduce the construction difficulty of the exposed steel column foot, shorten the construction period, improve the construction quality and provide certain theoretical references for the design and research on the steel column foot.
Time-Dependent Flexural Deformation Beneath the Emperor Seamounts
Wessel, P.; Watts, A. B.; Kim, S. S.
2014-12-01
The Hawaii-Emperor seamount chain stretches over 6000 km from the Big Island of Hawaii to the subduction cusp off Kamchatka and represents a near-continuous record of hotspot volcanism since the Late Cretaceous. The load of these seamounts and islands has caused the underlying lithosphere to deform, developing a flexural flanking moat that is now largely filled with volcanoclastic sediments. Because the age differences between the seafloor and the seamounts vary by an order of magnitude or more along the chain, the Hawaii-Emperor chain and surrounding area is considered a natural laboratory for lithospheric flexure and has been studied extensively in order to infer the rheology of the oceanic lithosphere. While most investigations have focused on the Hawaiian Islands and proximal seamounts (where data sets are more complete, including seismic reflection and refraction, swath bathymetry and even mapping and dating of drowned reef terraces), far fewer studies have examined the flexural deformation beneath the remote Emperor chain. Preliminary analysis of satellite altimetry data shows the flexural moats to be associated with very large negative gravity anomalies relative to the magnitudes of the positive anomalies over the loads, suggesting considerable viscous or viscoelastic relaxation since the loads were emplaced 50-80 Myr ago. In our study, we will attempt to model the Emperor seamount chain load as a superposition of individual elliptical Gaussian seamounts with separate loading histories. We use Optimal Robust Separation (ORS) techniques to extract the seamount load from the regional background bathymetry and partition the residual load into a set of individual volcanoes. The crustal age grid and available seamount dates are used to construct a temporal loading model and evaluate the flexural response of the lithosphere beneath the Emperor seamounts. We explore a variety of rheological models and loading scenarios that are compatible with the inferred load
A Single Mooring System with Sag-Extensibility and Flexural Rigidity Applied to Offshore Platform
Institute of Scientific and Technical Information of China (English)
M.-C.Tsai; Hsien Hua Lee; Jun-Yen Lee; S.-S.Hsiao
2013-01-01
Floating platform system has been extensively used in ocean exploitation,particularly for a tension-leg platform (TLP) system in deep water.Most of the TLPs are multi-mooring systems,where multi-joints are connected to the tension-legs so that the platform is not allowed to twist freely and may subject to enormous force induced by large incident waves in the weak-direction of the structure.This study aims to exploit a single moored offshore platform system that may attract less force and can be operated with less effort.In our analysis,in addition to mechanical properties of the tether,two important properties are also taken into consideration for the single mooring tether with expanded cross sectional dimension and utilization of stronger material,namely,the sag-extensibility and the flexural rigidity.Finally,the dynamic structural behavior produced by the mechanical effects on the new system is investigated and compared with that of traditional design while the wave-structure interactions of large body are also accounted for.Our study finds that the neglect of sag-extensibility or the flexural rigidity of large,strong mooring cable may result in a conservative but not necessarily safe design.
Force-Sensing Actuator with a Compliant Flexure-Type Joint for a Robotic Manipulator
Directory of Open Access Journals (Sweden)
Mathieu Grossard
2015-12-01
Full Text Available This paper deals with the mechatronic design of a novel self-sensing motor-to-joint transmission to be used for the actuation of robotic dexterous manipulators. Backdrivability, mechanical simplicity and efficient flexure joint structures are key concepts that have guided the mechanical design rationale to provide the actuator with force sensing capabilities. Indeed, a self-sensing characteristic is achieved by the specific design of high-resolution cable-driven actuators based on a DC motor, a ball-screw and a monolithic compliant anti-rotation system together with a novel flexure pivot providing a frictionless mechanical structure. That novel compliant pivot with a large angular range and a small center shift has been conceived of to provide the inter-phalangeal rotational degree of freedom of the fingers’ joints to be used for integration in a multi-fingered robotic gripper. Simultaneously, it helps to remove friction at the joint level of the mechanism. Experimental tests carried out on a prototype show an accurate matching between the model and the real behavior. Overall, this mechatronic design contributes to the improvement of the manipulation skills of robotic grippers, thanks to the combination of high performance mechanics, high sensitivity to external forces and compliance control capability.
Directory of Open Access Journals (Sweden)
Chan-Gi Park
2016-01-01
Full Text Available Hybrid glass/jute fiber reinforced polymer (HGJFRP composite bars were manufactured for concrete structures, and their interlaminar shear stress and tensile performance were evaluated. HGJFRP composite bars were manufactured using a combination of pultrusion and braiding processes. Jute fiber was surface-treated with a silane coupling agent. The mixing ratio of the fiber to the vinyl ester used in the HGJFRP composite bars was 7 : 3. Jute fiber was used to replace glass fiber in proportions of 0, 30, 50, 70, and 100%. The interlaminar shear stress decreased as the proportion of jute fiber increased. Fractures appeared due to delamination between the surface-treated component and the main part of the HGJFRP composite bar. Tensile load-strain curves with 50% jute fiber exhibited linear behavior. With a jute fiber volume fraction of 70%, some plastic deformation occurred. A jute fiber mixing ratio of 100% resulted in a display of linear elastic brittle behavior from the fiber; however, when the surface of the fiber was coated with poly(vinyl acetate, following failure, the jute fiber exhibited partial load resistance. The tensile strength decreased as the jute fiber content increased; however, the tensile strength did not vary linearly with jute fiber content.
Evaluating interfacial shear stresses in composite hollo
Directory of Open Access Journals (Sweden)
Aiham Adawi
2016-09-01
Full Text Available Analytical evaluation of the interfacial shear stresses for composite hollowcore slabs with concrete topping is rare in the literature. Adawi et al. (2014 estimated the interfacial shear stiffness coefficient (ks that governs the behavior of the interface between hollowcore slabs and the concrete topping using push-off tests. This parameter is utilized in this paper to provide closed form solutions for the differential equations governing the behavior of simply supported composite hollowcore slabs. An analytical solution based on the deformation compatibility of the composite section and elastic beam theory, is developed to evaluate the shear stresses along the interface. Linear finite element modeling of the full-scale tests presented in Adawi et al. (2015 is also conducted to validate the developed analytical solution. The proposed analytical solution was found to be adequate in estimating the magnitude of horizontal shear stress in the studied composite hollowcore slabs.
Shear crack propagation in MBC strengthened concrete beams”
DEFF Research Database (Denmark)
Täljsten, Björn; Blanksvärd, Thomas; Carolin, Anders
2008-01-01
study of MBC systems. Emphasis is placed on the cracking behavior of the MBC system used for shear strengthening of RC beams. Traditional foil strain gauges and photometric measurements have been used for monitoring of the cracking behavior. In this study it is shown that the use of mineral based shear...
Shear thickening of Laponite suspensions with poly (ethylene oxide)
Fall, A.; Bonn, D.
2012-01-01
We study the effect of addition of polyethylene oxide (PEO) on the rheological behavior of suspensions of Laponite. Experiments were performed on mixtures of PEO and Laponite at different concentrations. These mixtures can exhibit very strong shear thickening behavior: under shear, the suspension ca
Institute of Scientific and Technical Information of China (English)
薛建阳; 马辉
2013-01-01
In order to investigate the failure patterns and seismic performance of steel reinforced recycled concrete columns,four column specimens with different shear span ratio of steel reinforced recycled concrete were tested under low cyclic reversed loading.The failure process and patterns were observed.The mechanical behaviors,such as load-displacement hysteretic loops and skeleton curves,load carrying capacity,ductility,energy dissipation capacity and stiffness degradation of steel reinforced recycled concrete columns were analyzed.Test research results show that the shear diagonal compression failure,shear-bending failure and bending failure are the main patterns of steel reinforced recycled concrete columns.The load carrying capacity of specimens reduces with the increase of shearspan ratio,but the load-displacement hysteretic loops are plumper and the descending of load carrying capacity is relatively slow.It also shows the stiffness degradation rate is slower and the ductility or energy dissipation capacity is greater with the increase of shear span ratio.Overall,the steel reinforced recycled concrete columns with high shear-span ratio behave well in seismic performance.It can be used in the practical engineering.%为研究型钢再生混凝土柱的破坏形态和抗震性能,进行了4个不同剪跨比的型钢再生混凝土柱低周反复荷载试验,观察了其受力过程及破坏形态,分析了剪跨比对柱的滞回曲线、骨架曲线、承载力、延性、耗能及刚度退化等力学性能的影响.研究结果表明:根据剪跨比的不同,型钢再生混凝土柱的破坏形态主要为剪切斜压破坏、弯剪破坏以及弯曲破坏.随着剪跨比的增大,试件水平承载力降低,但滞回曲线愈加饱满,承载力下降越缓慢,刚度退化速率越慢,延性及耗能越好.总体上看,剪跨比较大试件的抗震性能较好,可以用于实际工程.
Localized surface plate modes via flexural Mie resonances
Farhat, M.
2017-05-11
Surface-plasmon polaritons are naturally generated upon excitation of metals with high-frequency electromagnetic waves. However, the concept of spoof plasmons has made it possible to generate plasmoniclike effects in microwave electrodynamics, magnetics, and even acoustics. Similarly, in this paper, the concept of localized surface plate modes (SPMs) is introduced. It is demonstrated that SPMs can be generated on a two-dimensional (clamped or stress-free) cylindrical surface with subwavelength corrugations, which resides on a thin elastic plate, under excitation by an incident flexural plane wave. Numerical characterization of this corrugated rigid structure shows that it is elastically equivalent to a cylindrical scatterer with dispersive but uniformly negative flexural rigidity. This, indeed, suggests that plasmoniclike elastic materials can be engineered with potential applications in various areas including earthquake sensing and elastic imaging and cloaking.
Enhanced flexural wave sensing by adaptive gradient-index metamaterials
Chen, Y. Y.; Zhu, R.; Barnhart, M. V.; Huang, G. L.
2016-10-01
Increasing sensitivity and signal to noise ratios of conventional wave sensors is an interesting topic in structural health monitoring, medical imaging, aerospace and nuclear instrumentation. Here, we report the concept of a gradient piezoelectric self-sensing system by integrating shunting circuitry into conventional sensors. By tuning circuit elements properly, both the quality and quantity of the flexural wave measurement data can be significantly increased for new adaptive sensing applications. Through analytical, numerical and experimental studies, we demonstrate that a metamaterial-based sensing system (MBSS) with gradient bending stiffness can be designed by connecting gradient negative capacitance circuits to an array of piezoelectric patches (sensors). Furthermore, we demonstrate that the proposed system can achieve more than two orders of magnitude amplification of flexural wave signals to overcome the detection limit. This research encompasses fundamental advancements in the MBSS with improved performance and functionalities, and will yield significant advances for a range of applications.
The LINC-NIRVANA fringe and flexure tracker: laboratory tests
Tremou, Evangelia; Eckart, Andreas; Horrobin, Matthew; Lindhorst, Bettina; Moser, Lydia; Rost, Steffen; Smajic, Semir; Straubmeier, Christian; Wank, Imke; Zuther, Jens; Bertram, Thomas
2010-07-01
LINC-NIRVANA is the NIR homothetic imaging camera for the Large Binocular Telescope (LBT). In close cooperation with the Adaptive Optics systems of LINC-NIRVANA the Fringe and Flexure Tracking System (FFTS) is a fundamental component to ensure a complete and time-stable wavefront correction at the position of the science detector in order to allow for long integration times at interferometric angular resolutions. In this contribution, we present the design and the realization of the ongoing FFTS laboratory tests, taking into account the system requirements. We have to sample the large Field of View and to follow the reference source during science observations to an accuracy of less than 2 microns. In particular, important tests such as cooling tests of cryogenic components and tip - tilt test (the repeatability and the precision under the different inclinations) are presented. The system parameters such as internal flexure and precision are discussed.
Flexural-Phonon Scattering Induced by Electrostatic Gating in Graphene
Gunst, Tue; Kaasbjerg, Kristen; Brandbyge, Mads
2017-01-01
Graphene has an extremely high carrier mobility partly due to its planar mirror symmetry inhibiting scattering by the highly occupied acoustic flexural phonons. Electrostatic gating of a graphene device can break the planar mirror symmetry, yielding a coupling mechanism to the flexural phonons. We examine the effect of the gate-induced one-phonon scattering on the mobility for several gate geometries and dielectric environments using first-principles calculations based on density functional theory and the Boltzmann equation. We demonstrate that this scattering mechanism can be a mobility-limiting factor, and show how the carrier density and temperature scaling of the mobility depends on the electrostatic environment. Our findings may explain the high deformation potential for in-plane acoustic phonons extracted from experiments and, furthermore, suggest a direct relation between device symmetry and resulting mobility.
Flexural analysis of palm fiber reinforced hybrid polymer matrix composite
Venkatachalam, G.; Gautham Shankar, A.; Raghav, Dasarath; Santhosh Kiran, R.; Mahesh, Bhargav; Kumar, Krishna
2015-07-01
Uncertainty in availability of fossil fuels in the future and global warming increased the need for more environment friendly materials. In this work, an attempt is made to fabricate a hybrid polymer matrix composite. The blend is a mixture of General Purpose Resin and Cashew Nut Shell Liquid, a natural resin extracted from cashew plant. Palm fiber, which has high strength, is used as reinforcement material. The fiber is treated with alkali (NaOH) solution to increase its strength and adhesiveness. Parametric study of flexure strength is carried out by varying alkali concentration, duration of alkali treatment and fiber volume. Taguchi L9 Orthogonal array is followed in the design of experiments procedure for simplification. With the help of ANOVA technique, regression equations are obtained which gives the level of influence of each parameter on the flexure strength of the composite.
Enhanced flexural wave sensing by adaptive gradient-index metamaterials
Chen, Y. Y.; Zhu, R.; Barnhart, M. V.; Huang, G. L.
2016-01-01
Increasing sensitivity and signal to noise ratios of conventional wave sensors is an interesting topic in structural health monitoring, medical imaging, aerospace and nuclear instrumentation. Here, we report the concept of a gradient piezoelectric self-sensing system by integrating shunting circuitry into conventional sensors. By tuning circuit elements properly, both the quality and quantity of the flexural wave measurement data can be significantly increased for new adaptive sensing applications. Through analytical, numerical and experimental studies, we demonstrate that a metamaterial-based sensing system (MBSS) with gradient bending stiffness can be designed by connecting gradient negative capacitance circuits to an array of piezoelectric patches (sensors). Furthermore, we demonstrate that the proposed system can achieve more than two orders of magnitude amplification of flexural wave signals to overcome the detection limit. This research encompasses fundamental advancements in the MBSS with improved performance and functionalities, and will yield significant advances for a range of applications. PMID:27748379
Controlling flexural waves in semi-infinite platonic crystals
Haslinger, Stewart G; Movchan, Alexander B; Jones, Ian S; Craster, Richard V
2016-01-01
We address the problem of scattering and transmission of a plane flexural wave through a semi-infinite array of point scatterers/resonators, which take a variety of physically interesting forms. The mathematical model accounts for several classes of point defects, including mass-spring resonators attached to the top surface of the flexural plate and their limiting case of concentrated point masses. We also analyse the special case of resonators attached to opposite faces of the plate. The problem is reduced to a functional equation of the Wiener-Hopf type, whose kernel varies with the type of scatterer considered. A novel approach, which stems from the direct connection between the kernel function of the semi-infinite system and the quasi-periodic Green's functions for corresponding infinite systems, is used to identify special frequency regimes. We thereby demonstrate dynamically anisotropic wave effects in semi-infinite platonic crystals, with particular attention paid to designing systems to exhibit dynami...
Novel parameter-based flexure bearing design method
Amoedo, Simon; Thebaud, Edouard; Gschwendtner, Michael; White, David
2016-06-01
A parameter study was carried out on the design variables of a flexure bearing to be used in a Stirling engine with a fixed axial displacement and a fixed outer diameter. A design method was developed in order to assist identification of the optimum bearing configuration. This was achieved through a parameter study of the bearing carried out with ANSYS®. The parameters varied were the number and the width of the arms, the thickness of the bearing, the eccentricity, the size of the starting and ending holes, and the turn angle of the spiral. Comparison was made between the different designs in terms of axial and radial stiffness, the natural frequency, and the maximum induced stresses. Moreover, the Finite Element Analysis (FEA) was compared to theoretical results for a given design. The results led to a graphical design method which assists the selection of flexure bearing geometrical parameters based on pre-determined geometric and material constraints.
DEFF Research Database (Denmark)
Jørgensen, Mads Koustrup; Pedersen, Malene Thostrup; Christensen, Morten Lykkegaard
2014-01-01
of shear stress and sludge concentration on the limiting flux. The model was developed by calculating the shear rate at laminar flow regime at different rotation speeds and radii on the membrane. Furthermore, through the shear rate and shear stress, the non-Newtonian behavior of MBR sludge was addressed...
Flexural Properties of WeftKnitted Fabric Reinforced Composites
Institute of Scientific and Technical Information of China (English)
龙海如; 冯勋伟
2001-01-01
Several different kinds of weft knitted fabrics from glass fiber yarns were used as reinforcement to make fabric/polyester composite laminates. Flexural tests were carried out to examine stress- deflection process and compare the mechanical properties in course and wale directions of these composites. The experimental results indicate that the numbers of load-bearing yarn in course and wale direction and the fabric density are the main factors influencing the ultimate tensile strength and initial elastic modulus of specimens.
Weakened Flexural Strength of Nanocrystalline Nanoporous Gold by Grain Refinement.
Gwak, Eun-Ji; Kim, Ju-Young
2016-04-13
High density of grain boundaries in solid materials generally leads to high strength because grain boundaries act as strong obstacles to dislocation activity. We find that the flexural strength of nanoporous gold of grain size 206 nm is 33.6% lower than that of grain size 238 μm. We prepared three gold-silver precursor alloys, well-annealed, prestrained, and high-energy ball-milled, from which nanoporous gold samples were obtained by the same free-corrosion dealloying process. Ligaments of the same size are formed regardless of precursor alloys, and microstructural aspects of precursor alloys such as crystallographic orientation and grain size is preserved in the dealloying process. While the nanoindentation hardness of three nanoporous golds is independent of microstructural variation, flexural strength of nanocrystalline nanoporous gold is significantly lower than that of nanoporous golds with much larger grain size. We investigate weakening mechanisms of grain boundaries in nanocrystalline nanoporous gold, leading to weakening of flexural strength.
Experimental Evaluation of Three Designs of Electrodynamic Flexural Transducers
Eriksson, Tobias J. R.; Laws, Michael; Kang, Lei; Fan, Yichao; Ramadas, Sivaram N.; Dixon, Steve
2016-01-01
Three designs for electrodynamic flexural transducers (EDFT) for air-coupled ultrasonics are presented and compared. An all-metal housing was used for robustness, which makes the designs more suitable for industrial applications. The housing is designed such that there is a thin metal plate at the front, with a fundamental flexural vibration mode at ∼50 kHz. By using a flexural resonance mode, good coupling to the load medium was achieved without the use of matching layers. The front radiating plate is actuated electrodynamically by a spiral coil inside the transducer, which produces an induced magnetic field when an AC current is applied to it. The transducers operate without the use of piezoelectric materials, which can simplify manufacturing and prolong the lifetime of the transducers, as well as open up possibilities for high-temperature applications. The results show that different designs perform best for the generation and reception of ultrasound. All three designs produced large acoustic pressure outputs, with a recorded sound pressure level (SPL) above 120 dB at a 40 cm distance from the highest output transducer. The sensitivity of the transducers was low, however, with single shot signal-to-noise ratio (SNR)≃15 dB in transmit–receive mode, with transmitter and receiver 40 cm apart. PMID:27571075
Asymmetric Flexural-gravity Lumps in Nonuniform Media
Liang, Yong
2014-01-01
Here we show that asymmetric fully-localized flexural-gravity lumps can propagate on the surface of an inviscid and irrotational fluid covered by a variable-thickness elastic material, provided that the thickness varies only in one direction and has a local minimum. We derive and present equations governing the evolution of the envelope of flexural-gravity wave packets allowing the flexing material to have small variations in the transverse (to propagation) direction. We show that the governing equation belongs to the general family of Davey-Stewartson equations, but with an extra term in the surface evolution equation that accounts for the variable thickness of the elastic cover. We then use an iterative Newton-Raphson scheme, with a numerical continuation procedure via Lagrange interpolation, in a search to find fully-localized solutions of this system of equations. We show that if the elastic sheet thickness has (at least) a local minimum, flexural-gravity lumps can propagate near the minimum thickness, an...
Edge chipping and flexural resistance of monolithic ceramics☆
Zhang, Yu; Lee, James J.-W.; Srikanth, Ramanathan; Lawn, Brian R.
2014-01-01
Objective Test the hypothesis that monolithic ceramics can be developed with combined esthetics and superior fracture resistance to circumvent processing and performance drawbacks of traditional all-ceramic crowns and fixed-dental-prostheses consisting of a hard and strong core with an esthetic porcelain veneer. Specifically, to demonstrate that monolithic prostheses can be produced with a much reduced susceptibility to fracture. Methods Protocols were applied for quantifying resistance to chipping as well as resistance to flexural failure in two classes of dental ceramic, microstructurally-modified zirconias and lithium disilicate glass–ceramics. A sharp indenter was used to induce chips near the edges of flat-layer specimens, and the results compared with predictions from a critical load equation. The critical loads required to produce cementation surface failure in monolithic specimens bonded to dentin were computed from established flexural strength relations and the predictions validated with experimental data. Results Monolithic zirconias have superior chipping and flexural fracture resistance relative to their veneered counterparts. While they have superior esthetics, glass–ceramics exhibit lower strength but higher chip fracture resistance relative to porcelain-veneered zirconias. Significance The study suggests a promising future for new and improved monolithic ceramic restorations, with combined durability and acceptable esthetics. PMID:24139756
Vidotti, Hugo A; Manso, Adriana P; Leung, Victor; do Valle, Accácio L; Ko, Frank; Carvalho, Ricardo M
2015-09-01
To evaluate the influence of different resin blends concentrations and nanofibers mass ratio on flexural properties of experimental Poliacrylonitrile (PAN) nanofibers reinforced composites. Poliacrylonitrile (PAN) nanofibers mats were produced by electrospinning and characterized by tensile testing and scanning electron microscopy (SEM). Experimental resin-fiber composite beams were manufactured by infiltrating PAN nanofiber mats with varied concentrations of BisGMA-TEGDMA resin blends (BisGMA/TEGDMA: 30/70, 50/50 and 70/30weight%). The mass ratio of fiber to resin varied from 0% to 8%. Beams were cured and stored in water at 37°C. Flexural strength (FS), flexural modulus (FM) and work of fracture (WF) were evaluated by three-point bending test after 24h storage. The tensile properties of the PAN nanofibers indicated an anisotropic behavior being always higher when tested in a direction perpendicular to the rotation of the collector drum. Except for WF, the other flexural properties (FS and FM) were always higher as the ratio of BisGMA to TEGDMA increased in the neat resin beams. The addition of different ratios of PAN fibers did not affect FS and FM of the composite beams as compared to neat resin beams (p>0.05). However, the addition of fibers significantly increased the WF of the composite beams, and this was more evident for the blends with higher TEGDMA ratios (presin blends did not negatively affect the properties of the composite and resulted in an increase in toughness that is a desirable property for a candidate material for prosthodontics application. Copyright © 2015 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.
Directory of Open Access Journals (Sweden)
D. A. Shcherbakova
2014-09-01
Full Text Available Supersonic shear wave imaging (SSI is a noninvasive, ultrasound-based technique to quantify the mechanical properties of bulk tissues by measuring the propagation speed of shear waves (SW induced in the tissue with an ultrasound transducer. The technique has been successfully validated in liver and breast (tumor diagnostics and is potentially useful for the assessment of the stiffness of arteries. However, SW propagation in arteries is subjected to different wave phenomena potentially affecting the measurement accuracy. Therefore, we assessed SSI in a less complex ex vivo setup, that is, a thick-walled and rectangular slab of an excised equine aorta. Dynamic uniaxial mechanical testing was performed during the SSI measurements, to dispose of a reference material assessment. An ultrasound probe was fixed in an angle position controller with respect to the tissue to investigate the effect of arterial anisotropy on SSI results. Results indicated that SSI was able to pick up stretch-induced stiffening of the aorta. SW velocities were significantly higher along the specimen's circumferential direction than in the axial direction, consistent with the circumferential orientation of collagen fibers. Hence, we established a first step in studying SW propagation in anisotropic tissues to gain more insight into the feasibility of SSI-based measurements in arteries.
Steel fiber reinforced concrete behavior, modelling and design
Singh, Harvinder
2017-01-01
This book discusses design aspects of steel fiber-reinforced concrete (SFRC) members, including the behavior of the SFRC and its modeling. It also examines the effect of various parameters governing the response of SFRC members in detail. Unlike other publications available in the form of guidelines, which mainly describe design methods based on experimental results, it describes the basic concepts and principles of designing structural members using SFRC as a structural material, predominantly subjected to flexure and shear. Although applications to special structures, such as bridges, retaining walls, tanks and silos are not specifically covered, the fundamental design concepts remain the same and can easily be extended to these elements. It introduces the principles and related theories for predicting the role of steel fibers in reinforcing concrete members concisely and logically, and presents various material models to predict the response of SFRC members in detail. These are then gradually extended to d...
Shearing stability of lubricants
Shiba, Y.; Gijyutsu, G.
1984-01-01
Shearing stabilities of lubricating oils containing a high mol. wt. polymer as a viscosity index improver were studied by use of ultrasound. The oils were degraded by cavitation and the degradation generally followed first order kinetics with the rate of degradation increasing with the intensity of the ultrasonic irradiation and the cumulative energy applied. The shear stability was mainly affected by the mol. wt. of the polymer additive and could be determined in a short time by mechanical shearing with ultrasound.
Shearing stability of lubricants
Energy Technology Data Exchange (ETDEWEB)
Shiba, Y.; Gijyutsu, G.
1984-03-01
Shearing stabilities of lubricating oils containing a high mol. wt. polymer as a viscosity index improver were studied by use of ultrasound. The oils were degraded by cavitation and the degradation generally followed first order kinetics with the rate of degradation increasing with the intensity of the ultrasonic irradiation and the cumulative energy applied. The shear stability was mainly affected by the mol. wt. of the polymer additive and could be determined in a short time by mechanical shearing with ultrasound.
Flexural Strength of Preheated Resin Composites and Bonding Properties to Glass-Ceramic and Dentin
Directory of Open Access Journals (Sweden)
Matthias Richard Kramer
2016-01-01
Full Text Available To test the impact of preheating (25, 37, 54, or 68 °C of TetricEvoCeram (TEC, FiltekSupremeXT (FSXT, and Venus (V on flexural strength (FS, shear bond strength (SBS and interfacial tension (IFT. FS was tested with TEC and FSXT. For SBS, glass-ceramic and human dentin substrate were fabricated and luted with the preheated resin composite (RC. SBSs of 1500 thermal cycled specimens were measured. For IFT, glass slides covered with the non-polymerized RC were prepared and contact angles were measured. Data were analyzed using 2/1-way ANOVA with Scheffé-test, and t-test (p < 0.05. Preheated TEC (37–68 °C showed higher FS compared to the control-group (25 °C (p < 0.001. FSXT presented higher FS than TEC (p < 0.001. For SBS to dentin higher values for FSXT than TEC were found. The preheating temperature showed no impact on SBS to dentin. SBS to glass-ceramic revealed a positive influence of temperature for TEC 25–68 °C (p = 0.015. TEC showed higher values than V and FSXT (p < 0.001. IFT values increased with the preheating temperature. A significant difference could be observed in every RC group between 25 and 68 °C (p < 0.001.
Strozzi, Matteo; Smirnov, Valeri V.; Manevitch, Leonid I.; Milani, Massimo; Pellicano, Francesco
2016-10-01
In this paper, the nonlinear vibrations and energy exchange of single-walled carbon nanotubes (SWNTs) are studied. The Sanders-Koiter theory is applied to model the nonlinear dynamics of the system in the case of finite amplitude of vibration. The SWNT deformation is described in terms of longitudinal, circumferential and radial displacement fields. Simply supported, clamped and free boundary conditions are considered. The circumferential flexural modes (CFMs) are investigated. Two different approaches based on numerical and analytical models are compared. In the numerical model, an energy method based on the Lagrange equations is used to reduce the nonlinear partial differential equations of motion to a set of nonlinear ordinary differential equations, which is solved by using the implicit Runge-Kutta numerical method. In the analytical model, a reduced form of the Sanders-Koiter theory assuming small circumferential and tangential shear deformations is used to get the nonlinear ordinary differential equations of motion, which are solved by using the multiple scales analytical method. The transition from energy beating to energy localization in the nonlinear field is studied. The effect of the aspect ratio on the analytical and numerical values of the nonlinear energy localization threshold for different boundary conditions is investigated. Time evolution of the total energy distribution along the axis of a simply supported SWNT
Coupling between flexural modes in free vibration of single-walled carbon nanotubes
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Rumeng Liu
2015-12-01
Full Text Available The nonlinear thermal vibration behavior of a single-walled carbon nanotube (SWCNT is investigated by molecular dynamics simulation and a nonlinear, nonplanar beam model. Whirling motion with energy transfer between flexural motions is found in the free vibration of the SWCNT excited by the thermal motion of atoms where the geometric nonlinearity is significant. A nonlinear, nonplanar beam model considering the coupling in two vertical vibrational directions is presented to explain the whirling motion of the SWCNT. Energy in different vibrational modes is not equal even over a time scale of tens of nanoseconds, which is much larger than the period of fundamental natural vibration of the SWCNT at equilibrium state. The energy of different modes becomes equal when the time scale increases to the microsecond range.
Coupling between flexural modes in free vibration of single-walled carbon nanotubes
Energy Technology Data Exchange (ETDEWEB)
Liu, Rumeng; Wang, Lifeng, E-mail: walfe@nuaa.edu.cn [State Key Laboratory of Mechanics and Control of Mechanical Structures, Nanjing University of Aeronautics and Astronautics, 210016 Nanjing (China)
2015-12-15
The nonlinear thermal vibration behavior of a single-walled carbon nanotube (SWCNT) is investigated by molecular dynamics simulation and a nonlinear, nonplanar beam model. Whirling motion with energy transfer between flexural motions is found in the free vibration of the SWCNT excited by the thermal motion of atoms where the geometric nonlinearity is significant. A nonlinear, nonplanar beam model considering the coupling in two vertical vibrational directions is presented to explain the whirling motion of the SWCNT. Energy in different vibrational modes is not equal even over a time scale of tens of nanoseconds, which is much larger than the period of fundamental natural vibration of the SWCNT at equilibrium state. The energy of different modes becomes equal when the time scale increases to the microsecond range.
Experimental Study on the Flexural Performance of Parallel Strand Bamboo Beams
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Aiping Zhou
2014-01-01
Full Text Available Searching for materials to provide proper housing with less emission and low energy becomes an urgent demand with the ever-growing population. Bamboo has gained a reputation as an ecofriendly, highly renewable source of material. Parallel Strand Bamboo (PSB is a new biocomposite made of bamboo strips which has superiority performances than wood products. It has attracted considerable interests as a sustainable alternative for more traditional building materials. But the mechanical performance study of PSB as construction materials is still inadequate. Also, the structural behavior of PSB is not quite understood as conventional construction materials, which results in the difficulties to predict the performances of PSB structural members. To achieve this purpose, 4-point bending experiments for PSB beams were carried out. The flexural performances, mode of failure in bending, and the damage mechanism of PSB beams were investigated in this paper.
Experimental study on the flexural performance of parallel strand bamboo beams.
Zhou, Aiping; Bian, Yuling
2014-01-01
Searching for materials to provide proper housing with less emission and low energy becomes an urgent demand with the ever-growing population. Bamboo has gained a reputation as an ecofriendly, highly renewable source of material. Parallel Strand Bamboo (PSB) is a new biocomposite made of bamboo strips which has superiority performances than wood products. It has attracted considerable interests as a sustainable alternative for more traditional building materials. But the mechanical performance study of PSB as construction materials is still inadequate. Also, the structural behavior of PSB is not quite understood as conventional construction materials, which results in the difficulties to predict the performances of PSB structural members. To achieve this purpose, 4-point bending experiments for PSB beams were carried out. The flexural performances, mode of failure in bending, and the damage mechanism of PSB beams were investigated in this paper.
Non-axisymmetric flexural vibrations of free-edge circular silicon wafers
Energy Technology Data Exchange (ETDEWEB)
Dmitriev, A.V., E-mail: dmitriev@hbar.phys.msu.ru; Gritsenko, D.S.; Mitrofanov, V.P., E-mail: mitr@hbar.phys.msu.ru
2014-02-07
Non-axisymmetric flexural vibrations of circular silicon (111) wafers are investigated. The modes with azimuthal index 2⩽k⩽30 are electrostatically excited and monitored by a capacitive sensor. The splitting of the mode frequencies associated with imperfection of the wafer is observed. The measured loss factors for the modes with 6≲k≲26 are close to those calculated according to the thermoelastic damping theory, while clamping losses likely dominate for k≲6, and surface losses at the level of inverse Q-factor Q{sup −1}≈4×10{sup −6} prevail for the modes with large k. The modes demonstrate nonlinear behavior of mainly geometrical origin at large amplitudes.
Energy Technology Data Exchange (ETDEWEB)
Franconetti, P.; Candel, J. J.; Vicente, A.; Amigo, V.
2013-07-01
Niobium and tantalum are added to titanium alloys to form new beta alloys with higher biocompatibility for biomedical applications. Both elements have a high melting point, that is the reason for their limited solid state diffusion. In this work samples of titanium with 3% at. niobium and tantalum have been manufactured by powder metallurgy. The effect of the compacting pressure, temperature and the sintering time on the strength, elasticity and ductility in bending has been studied. The results show that both elements behave similarly: flexural strength increases between 20-25%, elasticity between 0-10% and ductility over 150%. Therefore, the addition of these elements is beneficial to mechanical properties. Statistical analysis shows that the effect of temperature and pressure are important, while the effect of time is insignificant and even harmful in these alloys. (Author)
Shear failure of granular materials
Degiuli, Eric; Balmforth, Neil; McElwaine, Jim; Schoof, Christian; Hewitt, Ian
2012-02-01
Connecting the macroscopic behavior of granular materials with the microstructure remains a great challenge. Recent work connects these scales with a discrete calculus [1]. In this work we generalize this formalism from monodisperse packings of disks to 2D assemblies of arbitrarily shaped grains. In particular, we derive Airy's expression for a symmetric, divergence-free stress tensor. Using these tools, we derive, from first-principles and in a mean-field approximation, the entropy of frictional force configurations in the Force Network Ensemble. As a macroscopic consequence of the Coulomb friction condition at contacts, we predict shear failure at a critical shear stress, in accordance with the Mohr-Coulomb failure condition well known in engineering. Results are compared with numerical simulations, and the dependence on the microscopic geometric configuration is discussed. [4pt] [1] E. DeGiuli & J. McElwaine, PRE 2011. doi: 10.1103/PhysRevE.84.041310
Institute of Scientific and Technical Information of China (English)
LU Hai-jun; ZHANG Bao-yan; CHEN Xiang-bao
2005-01-01
To further investigate the influence of organic modifiers (primary amine with catalytic hydrogen and quaternary alkylammonium salt) on exfoliation behavior of clay tactoids, high-speed emulsifying and homogeneous mixing(HEHM) and ball milling were used to exert external shearing force on two organic clay tactoids (termed as MMTDDA and MMTDBDA, respectively), which were organically modified with DoDecyl Amine(DDA) and Dodecyl Benzyl Dimethyl Ammonium chloride(DBDA) ,respectively. The effects of external shearing force on microstructure and properties of both resultant nanocomposites were investigated by X-ray diffractometry(XRD), transmission electron microscopy(TEM) and thermogravimetric analysis(TGA). The results show that whether the clay tactoids are organically modified with catalytic primary amine or quaternary alkylammonium salt, the large agglomerates will not be finely dispersed or exfoliated by conventional mixing (magnetic stirring). After being vigorously sheared by HEHM or ball milling, the dispersion and exfoliation of clay tactoids are increasingly promoted for both MMTDDA and MMTDBDA, and the mechanical properties of the high-performance epoxy/clay nanocomposites are enhanced. For epoxy/MMTDDA nanocomposites, impact strength can be increased up to 44.5 kJ/m2 from 32.1 kJ/m2 , which is about 39% higher than that of pristine matrix, and the flexural strength is enhanced by about 4%. A similar enhancement for epoxy/MMTDBDA nanocomposites has also been achieved. Improvement on thermal stability of epoxy/clay nanocomposites is dependent on the exfoliation of clay layers and molecular structure of the modifiers. The onset temperature is increased with the clay loading decreasing from 5% or higher content to 3% (mass fraction), and the DBDA modifier with the heat-resistant benzyl may also improve the stability of epoxy/MMTDBDA nanocomposites.
Control of cracking in R.C. Structures: Numerical simulation of a squat shear wall
Damoni, C.; Belletti, B.; Lilliu, G.
2013-01-01
In this paper the behavior of a squat shear wall subjected to monotonic shear loading is investigated. The study fits into the experimental program driven by CEOS.fr on modeling of the behavior of the tested mocks-ups (monotonic and cycling loading-under prevented or free shrinkage). The shear wall
Mehrishal, Seyedahmad; Sharifzadeh, Mostafa; Shahriar, Korosh; Song, Jae-Jon
2017-04-01
In relation to the shearing of rock joints, the precise and continuous evaluation of asperity interlocking, dilation, and basic friction properties has been the most important task in the modeling of shear strength. In this paper, in order to investigate these controlling factors, two types of limestone joint samples were prepared and CNL direct shear tests were performed on these joints under various shear conditions. One set of samples were travertine and another were onyx marble with slickensided surfaces, surfaces ground to #80, and rough surfaces were tested. Direct shear experiments conducted on slickensided and ground surfaces of limestone indicated that by increasing the applied normal stress, under different shearing rates, the basic friction coefficient decreased. Moreover, in the shear tests under constant normal stress and shearing rate, the basic friction coefficient remained constant for the different contact sizes. The second series of direct shear experiments in this research was conducted on tension joint samples to evaluate the effect of surface roughness on the shear behavior of the rough joints. This paper deals with the dilation and roughness interlocking using a method that characterizes the surface roughness of the joint based on a fundamental combined surface roughness concept. The application of stress-dependent basic friction and quantitative roughness parameters in the continuous modeling of the shear behavior of rock joints is an important aspect of this research.
Effect of flexural crack on plain concrete beam failure mechanism A numerical simulation
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Abdoullah Namdar
2016-03-01
Full Text Available The flexural failure of plain concrete beam occurs along with development of flexural crack on beam. In this paper by using ABAQUS, mechanism failure of plain concrete beam under three steps have been simulated. The cracking moment has been analytically calculated and applied on the both sides of the fixed beam, and flexural crack has been simulated on beam. Displacement, von Mises, load reaction, displacementcrack length, von Mises-crack length and von Mises-displacement of beams have been graphical depicted. Results indicated that, the flexural crack governs beam mechanism failure and its effects on beam resistance failure. It has been found that the flexural crack in initial stage it developed slowly and changes to be fast at the final stage of collapsing beam due to reduction of the flexural resistance of beam. Increasing mechanical properties of concrete, collapse displacement is reduced.
The effect of nanoclay filler loading on the flexural strength of fiber-reinforced composites
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Vajihesadat Mortazavi
2012-01-01
Results: For groups with the same concentration of nanoparticles, PMMA-grafted filler-loaded group showed significantly higher flexural strength, except for 0.2% wt. For groups that contain PMMA-grafted nanoclay fillers, the 2% wt had the highest flexural strength value with significant difference to other subgroups. 1% wt and 2% wt showed significantly higher values compared to control (P 0.05. Flexural modulus of 2%, 5% wt PMMA-grafted and 0.5%, 1%, 2%, 5% wt unmodified nanoclay particles-loaded subgroups decreased significantly compared to control group (P < 0.05. Conclusions: PMMA-grafted nanoclay filler loading may enhance the flexural strength of FRCs. Addition of unmodified nanoparticles cannot significantly improve the flexural strength of FRCs. Addition of both unmodified and PMMA-grafted nanoclay particles in some concentrations decreased the flexural modulus.
A new look on blood shear thinning
Abkarian, Manouk; Lanotte, Luca; Fromental, Jean-Marc; Mendez, Simon; Fedosov, Dmitry; Gompper, Gerhard; Mauer, Johannes; Claveria, Viviana
2015-11-01
Blood is a shear-thinning fluid. At shear rates γ˙ blood cells (RBCs). For higher γ˙ in the range 10 - 1000 s-1 , where RBCs flow as single elements, studies demonstrated that RBCs suspended in a viscous fluid mimicking the viscosity of whole blood, deformed into ellipsoids aligned steadily in the direction of the flow, while their membrane rotated about their center of mass like a tank-tread. Such drop-like behavior seemed to explain shear-thinning. Here, using rheometers, microfluidics and simulations, we show that the dynamics of single RBCs in plasma-like fluids display a different sequence of deformation for increasing shear rates going from discocytes to successively, stomatocytes, folded stomatocytes, trilobes and tetralobes, but never ellipsoids. This result is also identical for physiological hematocrits. We correlate this shape diagram to the different regimes in blood rheology for high shear rates and propose a new-look on the interpretation of blood shear-thinning behavior.
A comparison between magnetic shear and flare shear in a well-observed M-class flare
Institute of Scientific and Technical Information of China (English)
Tuan-Hui Zhou; Hai-Sheng Ji
2009-01-01
We give an extensive multi-wavelength analysis of an eruptive M1.0/1N class solar flare, which occurred in the active region NOAA 10044 on 2002 July 26. Our empha-sis is on the relationship between magnetic shear and flare shear. Flare shear is defined as the angle formed between the line connecting the centroids of the two ribbons of the flare and the line perpendicular to the magnetic neutral line. The magnetic shear is computed from vector magnetograms observed at Big Bear Solar Observatory (BBSO), while the flare shear is computed from Transition Region and Coronal Explorer (TRACE) 1700A images. By a detailed comparison, we find that: 1) The magnetic shear and the flare shear of this event are basically consistent, as judged from the directions of the transverse mag-netic field and the line connecting the two ribbons' centroids. 2) During the period of the enhancement of magnetic shear, flare shear had a fast increase followed by a fluctuated decrease. 3) When the magnetic shear stopped its enhancement, the fluctuated decreasing behavior of the flare shear became very smooth. 4) Hard X-ray (HXR) spikes are well correlated with the unshearing peaks on the time profile of the rate of change of the flare shear. We give a discussion of the above phenomena.
沥青稳定类冷再生混合料抗剪特性研究%Study on Anti-shearing Behavior of Asphalt Stabilizing Type Cold Recycled Mixture
Institute of Scientific and Technical Information of China (English)
史永青
2016-01-01
Using emulsified asphalt and foamed asphalt as stabilizer of cold regenerated asphalt mixture, this paper studies 3 - axis shear behavior of cold regenerated asphalt mixture. Results show that the emulsified asphalt cold regenerated asphalt mixture has better anti -shearing behavior than that of the foamed asphalt cold regenerated asphalt mixture. Adding cement may obviously increase internal friction angle and cohesive strength of cold regenerated asphalt mixture; However, the cohesive strength has the trend of increase and reduce with the increasing of asphalt stabilizer, the internal friction angle reduces with the increment of asphalt, the major factor affect internal friction angle is composition of aggregate grains but not the types of asphalt stabilizer.%采用乳化沥青和泡沫沥青作为冷再生沥青混合料的稳定剂,研究冷再生混合料的三轴抗剪特性.研究表明:乳化沥青冷再生混合料比泡沫沥青冷再生混合料抗剪切强度略高;水泥的掺加能显著增加冷再生混合料的内摩擦角及粘聚力;而粘聚力随着沥青稳定剂用量的增大呈现先增大后减小的趋势,内摩擦角则随沥青用量增大而降低,且影响内摩擦角的主要因素为集料颗粒组成而非沥青稳定剂的类型.
Shear Strengthening of Reinforced Concrete Beams Using GFRP Wraps
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M. A. A. Saafan
2006-01-01
Full Text Available The objective of the experimental work described in this paper was to investigate the efficiency of GFRP composites in strengthening simply supported reinforced concrete beams designed with insufficient shear capacity. Using the hand lay-up technique, successive layers of a woven fiberglass fabric were bonded along the shear span to increase the shear capacity and to avoid catastrophic premature failure modes. The strengthened beams were fabricated with no web reinforcement to explore the efficiency of the proposed strengthening technique using the results of control beams with closed stirrups as a web reinforcement. The test results of 18 beams are reported, addressing the influence of different shear strengthening schemes and variable longitudinal reinforcement ratios on the structural behavior. The results indicated that significant increases in the shear strength and improvements in the overall structural behavior of beams with insufficient shear capacity could be achieved by proper application of GFRP wraps.
Design principle of high-precision flexure mechanisms based on parasitic-motion compensation
Li, Shouzhong; Yu, Jingjun
2014-07-01
In design of flexure mechanism, diminishing the parasitic-motion is a key point to improve the accuracy. However, most of existing topics concentrate on improving the accuracy of linear-motion flexure mechanisms via compensating the parasitic error, but few research the multi-dimensional flexure mechanisms. A general design principle and method for high-precision flexure mechanisms based on the parasitic-motion compensation is presented, and the proposed method can compensate the parasitic rotation in company with translation, or the parasitic translation in company with rotation, or both. The crucial step for the method is that the parasitic motion of a flexure mechanism is formulated and evaluated in terms of its compliance. The overall compliance matrix of a general flexure mechanism is formulated by using screw theory firstly, then the criteria for the parasitic motions is introduced by analyzing the characteristics of the resultant compliance matrix as well as with aid of the concept of instantaneous rotation center. Subsequently, a compliance-based compensation approach for reducing parasitic-motion is addressed as the most important part. The design principles and procedure are further discussed to help with improving the accuracy of flexure mechanisms, and case studies are provided to illustrate this method. Finally, an analytical verification is provided to demonstrate that the symmetry design philosophy widely used in flexure design can effectively improve accuracy in terms of the proposed method. The proposed compensation method can be well used to diminish the parasitic-motion of multi-dimensional flexure mechanisms.
Directory of Open Access Journals (Sweden)
K. Murali Mohan Rao
2009-10-01
Full Text Available The present investigation puts forward new natural fiber turmeric to be used in the preparation of turmeric fiber reinforced polyester (FRP composites. The dielectric strength of the composites shown decrease in trend with increase in volume fraction of fiber with appreciable reduction in their weight. There was clear fall in the density of the composites with increase in fiber volume fraction. The optimum value of dielectric strength was determined with flexural strength, flexural modulus and specific flexural strength, specific flexural modulus against percentage volume fraction of fiber from the graphs.
RING-TENSILE-STRENGTH AND FLEXURE-STRENGTH CORRELATIONS OF SEA ICE.
SEA ICE, MECHANICAL PROPERTIES), TENSILE PROPERTIES, SALINITY, TEMPERATURE, ICE, FLEXURAL STRENGTH , CORRELATION TECHNIQUES, ACCURACY, SAMPLING, THICKNESS, PREDICTIONS, ANTARCTIC REGIONS, LOADS(FORCES)
Reflection and refraction of flexural waves at geometric boundaries.
Evans, Arthur A; Levine, Alex J
2013-07-19
We present a theory of flexural wave propagation on elastic shells having nontrivial geometry and develop an analogy to geometric optics. The transport of momentum within the shell itself is anisotropic due to the curvature, and as such complex classical effects such as birefringence are generically found. We determine the equations of reflection and refraction of such waves at boundaries between different local geometries, showing that waves are totally internally reflected, especially at boundaries between regions of positive and negative Gaussian curvature. We verify these effects by using finite element simulations and discuss the ramifications of these effects for the statistical mechanics of thin curved materials.
Intrinsic embedded sensors for polymeric mechatronics: flexure and force sensing.
Jentoft, Leif P; Dollar, Aaron M; Wagner, Christopher R; Howe, Robert D
2014-02-25
While polymeric fabrication processes, including recent advances in additive manufacturing, have revolutionized manufacturing, little work has been done on effective sensing elements compatible with and embedded within polymeric structures. In this paper, we describe the development and evaluation of two important sensing modalities for embedding in polymeric mechatronic and robotic mechanisms: multi-axis flexure joint angle sensing utilizing IR phototransistors, and a small (12 mm), three-axis force sensing via embedded silicon strain gages with similar performance characteristics as an equally sized metal element based sensor.
Intrinsic Embedded Sensors for Polymeric Mechatronics: Flexure and Force Sensing
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Leif P. Jentoft
2014-02-01
Full Text Available While polymeric fabrication processes, including recent advances in additive manufacturing, have revolutionized manufacturing, little work has been done on effective sensing elements compatible with and embedded within polymeric structures. In this paper, we describe the development and evaluation of two important sensing modalities for embedding in polymeric mechatronic and robotic mechanisms: multi-axis flexure joint angle sensing utilizing IR phototransistors, and a small (12 mm, three-axis force sensing via embedded silicon strain gages with similar performance characteristics as an equally sized metal element based sensor.
Klein, Fred W.
2016-01-01
Several lines of earthquake evidence indicate that the lithospheric plate is broken under the load of the island of Hawai`i, where the geometry of the lithosphere is circular with a central depression. The plate bends concave downward surrounding a stress-free hole, rather than bending concave upward as with past assumptions. Earthquake focal mechanisms show that the center of load stress and the weak hole is between the summits of Mauna Loa and Mauna Kea where the load is greatest. The earthquake gap at 21 km depth coincides with the predicted neutral plane of flexure where horizontal stress changes sign. Focal mechanism P axes below the neutral plane display a striking radial pattern pointing to the stress center. Earthquakes above the neutral plane in the north part of the island have opposite stress patterns; T axes tend to be radial. The M6.2 Honomu and M6.7 Kiholo main shocks (both at 39 km depth) are below the neutral plane and show radial compression, and the M6.0 Kiholo aftershock above the neutral plane has tangential compression. Earthquakes deeper than 20 km define a donut of seismicity around the stress center where flexural bending is a maximum. The hole is interpreted as the soft center where the lithospheric plate is broken. Kilauea's deep conduit is seismically active because it is in the ring of maximum bending. A simplified two-dimensional stress model for a bending slab with a load at one end yields stress orientations that agree with earthquake stress axes and radial P axes below the neutral plane. A previous inversion of deep Hawaiian focal mechanisms found a circular solution around the stress center that agrees with the model. For horizontal faults, the shear stress within the bending slab matches the slip in the deep Kilauea seismic zone and enhances outward slip of active flanks.
Experimental investigation on shear responses of RUHTCC beams without stirrups%无腹筋RUHT CC梁抗剪性能试验研究
Institute of Scientific and Technical Information of China (English)
侯利军; 陈达; 徐世烺; 张秀芳
2014-01-01
In order to understand the shear behavior of ultrahigh toughness cementitious composite (UHTCC),the bending tests on six reinforced UHTCC (RUHTCC)beams and four reinforced con-crete (RC)comparison beams were performed under a concentrated loading at mid-span.The varied parameters were the shear-span ratio and the reinforcement ratio.The shear responses of the RU-HTCC beams and those of the RC beams were compared,including the diagonal crack pattern,the load-deflection curve,the shear cracking load,the ultimate shear capacity and the shear strength, etc.The experimental results indicate that with the increase in the reinforcement ratio and the de-crease in the shear-span ratio,the failure mode of the RUHTCC beams transforms from flexure-shear to shear-compression and the ultimate shear capacity rises gradually.The ultimate shear capacity of the RUHTCC beams is about twice that of the RC beams,and the average ultimate shear strength of the RUHTCC beams is about 0.86 times that of the ultimate tensile strength of the UHTCC.The RUHTCC beams present the stable propagation of multiple fine diagonal cracks,with the maximum crack width below 0.1 mm under the ultimate service condition.The minimum web reinforcement ratio is not required for the RUHTCC beams due to its large post-cracking reserve shear capacity and fine crack controlling capability.%为了探究超高韧性水泥基复合材料（UHTCC ）的抗剪性能，以配筋率和剪跨比为参数，对跨中荷载作用下的6根钢筋增强UHTCC（RUHTCC）梁和4根钢筋混凝土（RC）对比梁进行了受弯试验．对比研究了RUHTCC梁的抗剪性能，包括裂缝扩展形态、荷载挠度曲线、剪切开裂荷载、极限剪切能力以及剪切强度等．试验结果表明，随着配筋率的增大和剪跨比的减小，RUHTCC梁的破坏模式由弯剪破坏转变为剪压破坏，极限剪切承载能力逐渐增大．RUHTCC梁的极限剪切能力约为RC梁的2倍，平均抗剪
The brittle-viscous-plastic evolution of shear bands in the South Armorican Shear Zone
Bukovská, Zita; Jeřábek, Petr; Morales, Luiz F. G.; Lexa, Ondrej; Milke, Ralf
2014-05-01
microcracks and nearly absent in matrix grains in the well developed C bands. The chemical variation between primary and secondary new-formed micas was clearly identified by the Mg-Ti-Na content. The microstructural analysis documents a progressive decrease in quartz grain size and increasing interconnectivity of K-feldspar and white mica towards more mature shear bands. The contact-frequency analysis demonstrates that the phase distribution in shear bands tends to evolve from quartz aggregate distribution via randomization to K-feldspar aggregate distribution. The boundary preferred orientation is absent in quartz-quartz contacts either inside of outside the C bands, while it changes from random to parallel to the C band for the K-feldspar and and K-feldspar-quartz boundaries. The lack of crystallographic preferred orientation of the individual phases in the mixed matrix of the C planes suggests a dominant diffusion-assisted grain boundary sliding deformation mechanism. In the later stages of shear band development, the deformation is accommodated by crystal plasticity of white mica in micaceous bands. The crystallographic and microstructural data thus indicate two important switches in deformation mechanisms, from (i) brittle to Newtonian viscous behavior in the initial stages of shear band evolution and from (ii) Newtonian viscous to power law in the later evolutionary stages. The evolution of shear bands in the South Armorican Shear Zone thus document the interplay between deformation mechanisms and chemical reactions in deformed granitoids.
Haptic Edge Detection Through Shear
Platkiewicz, Jonathan; Lipson, Hod; Hayward, Vincent
2016-01-01
Most tactile sensors are based on the assumption that touch depends on measuring pressure. However, the pressure distribution at the surface of a tactile sensor cannot be acquired directly and must be inferred from the deformation field induced by the touched object in the sensor medium. Currently, there is no consensus as to which components of strain are most informative for tactile sensing. Here, we propose that shape-related tactile information is more suitably recovered from shear strain than normal strain. Based on a contact mechanics analysis, we demonstrate that the elastic behavior of a haptic probe provides a robust edge detection mechanism when shear strain is sensed. We used a jamming-based robot gripper as a tactile sensor to empirically validate that shear strain processing gives accurate edge information that is invariant to changes in pressure, as predicted by the contact mechanics study. This result has implications for the design of effective tactile sensors as well as for the understanding of the early somatosensory processing in mammals. PMID:27009331
Dilute rigid dumbbell suspensions in large-amplitude oscillatory shear flow: Shear stress response
Bird, R. B.; Giacomin, A. J.; Schmalzer, A. M.; Aumnate, C.
2014-02-01
We examine the simplest relevant molecular model for large-amplitude shear (LAOS) flow of a polymeric liquid: the suspension of rigid dumbbells in a Newtonian solvent. We find explicit analytical expressions for the shear rate amplitude and frequency dependences of the first and third harmonics of the alternating shear stress response. We include a detailed comparison of these predictions with the corresponding results for the simplest relevant continuum model: the corotational Maxwell model. We find that the responses of both models are qualitatively similar. The rigid dumbbell model relies entirely on the dumbbell orientation to explain the viscoelastic response of the polymeric liquid, including the higher harmonics in large-amplitude oscillatory shear flow. Our analysis employs the general method of Bird and Armstrong ["Time-dependent flows of dilute solutions of rodlike macromolecules," J. Chem. Phys. 56, 3680 (1972)] for analyzing the behavior of the rigid dumbbell model in any unsteady shear flow. We derive the first three terms of the deviation of the orientational distribution function from the equilibrium state. Then, after getting the "paren functions," we use these for evaluating the shear stress for LAOS flow. We find the shapes of the shear stress versus shear rate loops predicted to be reasonable.
Directory of Open Access Journals (Sweden)
V.R. Arun prakash
2017-02-01
Full Text Available In this present work siliconized e-glass fibre reinforced epoxy resin composite has been prepared and compared with acid and base treated e-glass fibre epoxy composites to know the significant advantage of silane treatment on fibre. The composites were fabricated by laying 20, 30 and 40vol% of e-glass fibre into epoxy resin matrix. The e-glass fibre woven mat was surface treated by an amine functional coupling agent 3-Aminopropyletrimethoxysilane (APTMS. The fibres were surface treated by aqueous solution method and thermo assisted to create silinol groups. Similarly for acid treatment H2SO4 and base treatment NaOH with 1N concentration was used for surface treating the fibres. Effectiveness of silane treatment on glass fibre was compared by inter laminar shear strength test according to ASTM D 2344. Drilling process with varying diameter drill bit and varying cutting speed was applied to check the composites for their delamination resistance while machining. Maximum improvement of 15%, 12.5% and 9% (20, 30 and 40vol % on ILSS was achieved for siliconized e-glass fibre reinforced epoxy composites. The scanning electron microscopy images revealed that no fibre pull out was present on fractured surfaces of composites which contains siliconized e-glass fibre. Similarly better dimensional accuracy was achieved on drilling process for composites contains siliconized e-glass fibre.
Flexure bearing compressor in the one watt linear (OWL) envelope
Rühlich, I.; Mai, M.; Wiedmann, Th.; Rosenhagen, C.
2007-04-01
For high performance IR detectors the split linear cooler is a preferred solution. High reliability, low induced vibration and low audible noise are major benefits of such coolers. Today, most linear coolers are qualified for MTTF of 8,000h or above. It is a strong customer desire to further reduce the maintenance costs on system level with significantly higher cooler lifetime. Increased cooler MTTF figures are also needed for IR applications with high lifetime requirements like missile warning applications, border surveillance or homeland security applications. AIM developed a Moving Magnet Flexure Bearing compressor to meet a MTTF of minimum 20,000h. The compressor has a full flexure bearing support on both sides of the driving mechanism. In the assembly process of the compressor an automated alignment process is used to achieve the necessary accuracy. Thus, side-forces on the pistons are minimized during operation, which significantly reduces the wear-out. In order to reduce the outgassing potential most of the internal junctions are welded and the use of all non-metallic components is minimized. The outline dimensions comply with the SADA2 requirements in length and diameter. Further, when operated with a 1/2" SADA type coldfinger, the cooler meets all specified performance data for SADA2. The compressor can be combined with different Stirling type coldfingers and also with the AIM Pulse Tube coldfinger, which gives increased lifetime potential up to 50,000h MTTF. Technical details and performance data of the new compressor are shown.
Fujii, Ayaka; Wakatsuki, Naoto; Mizutani, Koichi
2015-07-01
A loudspeaker for an auditory guiding system is proposed. This loudspeaker utilizes inclined sound transformed from a flexural wave in a honeycomb sandwich panel. We focused on the fact that the inclined sound propagates extensively with uniform level and direction. Furthermore, sound can be generated without group delay dispersion because the phase velocity of the flexural wave in the sandwich panel becomes constant with increasing frequency. These characteristics can be useful for an auditory guiding system in public spaces since voice-guiding navigation indicates the right direction regardless of position on a pathway. To design the proposed loudspeaker, the behavior of the sandwich panel is predicted using a theoretical equation in which the honeycomb core is assumed as an orthotropic continuum. We calculated the phase velocity dispersion of the flexural wave in the sandwich panel and compared the results obtained using the equation with those of a simulation based on the finite element method and an experiment in order to confirm the applicability of the theoretical equation. It was confirmed that the phase velocities obtained using the theoretical equation and by the simulation were in good agreement with that obtained experimentally. The obtained results suggest that the behavior of the sandwich panel can be predicted using the parameters of the panel. In addition, we designed an optimized honeycomb sandwich panel for radiating inclined sound by calculating the phase velocity characteristics of various panels that have different parameters of core height and cell size using the theoretical equation. Sound radiation from the optimized panel was simulated and compared with that of a homogeneous plate. It was clear that the variance of the radiation angle with varying frequency of the optimized panel was smaller than that of the homogeneous plate. This characteristic of sound radiation with a uniform angle is useful for indicating the destination direction. On
DEFF Research Database (Denmark)
Bay, Niels; Bjerregaard, Henrik; Petersen, Søren. B;
1994-01-01
The present paper describes an investigation of roll bonding an AlZn alloy to mild steel. Application of cross shear roll bonding, where the two equal sized rolls run with different peripheral speed, is shown to give better bond strength than conventional roll bonding. Improvements of up to 20......-23% in bond strength are found and full bond strength is obtained at a reduction of 50% whereas 65% is required in case of conventional roll bonding. Pseudo cross shear roll bonding, where the cross shear effect is obtained by running two equal sized rolls with different speed, gives the same results....
Ruda, Mitchell C [Tucson, AZ; Greynolds, Alan W [Tucson, AZ; Stuhlinger, Tilman W [Tucson, AZ
2009-07-14
One or more disc-shaped angular shear plates each include a region thereon having a thickness that varies with a nonlinear function. For the case of two such shear plates, they are positioned in a facing relationship and rotated relative to each other. Light passing through the variable thickness regions in the angular plates is refracted. By properly timing the relative rotation of the plates and by the use of an appropriate polynomial function for the thickness of the shear plate, light passing therethrough can be focused at variable positions.
Institute of Scientific and Technical Information of China (English)
周强; 刘伟庆; 方海
2011-01-01
Fiber reinforced sandwich composites with only one-way webs were fabricated by vacuum infusion molding process (VIMP). Test species with horizontal webs, different spaces between adjoining webs and web thicknesses were experimentally studied by four-point bending test. The failure mode and mechanism were observed and investigated. The flexural stiffness, ultimate bearing capacity and failure mode of sandwich composites were studied by classical sandwich beam theory and valid theoretical analysis model. Results of theoretical analysis are rather in agreement with the test results.%采用真空导入成型工艺,制备出单向纤维腹板增强复合材料夹层粱.对不同腹板间距、腹板厚度和增加横向腹板的试件进行了四点弯曲试验,研究其破坏模式和机理.基于经典夹层粱理论,采用有效的理论分析模型,预估了试件的抗弯刚度、破坏模式和受弯极限承载力,理论分析与试验结果较吻合.
Engelder, Terry; Peacock, David C. P.
2001-02-01
Alpine inversion in the Bristol Channel Basin includes reverse-reactivated normal faults with hanging wall buttress anticlines. At Lilstock Beach, joint sets in Lower Jurassic limestone beds cluster about the trend of the hinge of the Lilstock buttress anticline. In horizontal and gently north-dipping beds, J3 joints ( 295-285° strike) are rare, while other joint sets indicate an anticlockwise sequence of development. In the steeper south-dipping beds, J3 joints are the most frequent in the vicinity of the reverse-reactivated normal fault responsible for the anticline. The J3 joints strike parallel to the fold hinge, and their poles tilt to the south when bedding is restored to horizontal. This southward tilt aims at the direction of σ 1 for Alpine inversion. Finite-element analysis is used to explain the southward tilt of J3 joints that propagate under a local σ 3 in the direction of σ 1 for Alpine inversion. Tilted principal stresses are characteristic of limestone-shale sequences that are sheared during parallel (flexural-flow) folding. Shear tractions on the dipping beds generate a tensile stress in the stiffer limestone beds even when remote principal stresses are compressive. This situation favors the paradoxical opening of joints in the direction of the regional maximum horizontal stress. We conclude that J3 joints propagated during the Alpine compression caused the growth of the Lilstock buttress anticline.
Directory of Open Access Journals (Sweden)
Shinichi Shibata
2012-11-01
Full Text Available The effects of processing conditions such as pressure, temperature, and holding time on the flexural properties of bagasse and bamboo biodegradable composites were investigated. Each sample of bagasse or bamboo was mixed with a corn-starch-based biodegradable resin and fabricated by a hot press forming method. The cross-sectional structure of the bagasse fiber was found to be porous and compressible, while that of bamboo was found to be more solid. The relationship between flexural strength, flexural modulus, and pressure in bagasse fiber was apparently different from that of bamboo due to the differences in the cross-sectional structure. In bagasse, the flexural strength and flexural modulus increased with the increase in pressure, whereas in bamboo those properties decreased. In bagasse, an increase in pressure made the fibers into a more compressed structure, increasing their flexural properties. In rigid bamboo, an increase in pressure caused the resin to extrude between fibers, and this resulted in lower flexural properties. At temperatures above 170 oC, the resin depolymerized thermally and the degree of polymerization decreased. Thus, the flexural modulus and strength decreased gradually with increase in holding temperature in both bagasse and bamboo composites. Furthermore, a maximum fiber volume fraction existed for both bagasse and bamboo plastic composites in the approximate range of 75% to 80%.
A comparison of flexural strengths of polymer (SBR and PVA modified, roller compacted concrete
Directory of Open Access Journals (Sweden)
John N. Karadelis
2015-09-01
Full Text Available This brief article aims to reveal the flexural performance, including the equivalent flexural strength of PVA (Polyvinyl Alcohol modified concrete by comparing it primarily with that of SBR (Styrene Butadiene Rubber concrete. This data article is directly related to Karadelis and Lin [6].
A comparison of flexural strengths of polymer (SBR and PVA) modified, roller compacted concrete.
Karadelis, John N; Lin, Yougui
2015-09-01
This brief article aims to reveal the flexural performance, including the equivalent flexural strength of PVA (Polyvinyl Alcohol) modified concrete by comparing it primarily with that of SBR (Styrene Butadiene Rubber) concrete. This data article is directly related to Karadelis and Lin [6].
A comparison of flexural strengths of polymer (SBR and PVA) modified, roller compacted concrete
Karadelis, John N.; Lin, Yougui
2015-01-01
This brief article aims to reveal the flexural performance, including the equivalent flexural strength of PVA (Polyvinyl Alcohol) modified concrete by comparing it primarily with that of SBR (Styrene Butadiene Rubber) concrete. This data article is directly related to Karadelis and Lin [6].
The influence of resin flexural modulus on the magnitude of ceramic strengthening.
LENUS (Irish Health Repository)
Fleming, Garry J P
2012-07-01
The aim was to determine the magnitude of ceramic resin-strengthening with resin-based materials with varying flexural moduli using a regression technique to assess the theoretical strengthening at a \\'zero\\' resin-coating thickness. The hypothesis tested was that experimentally, increasing resin flexural modulus results in increased resin-strengthening observed at a theoretical \\'zero\\' resin-coating thickness.
A Symbolic Formulation for Analytical Compliance Analysis and Synthesis of Flexure Mechanisms.
Su, Hai-Jun; Shi, Hongliang; Yu, Jingjun
2012-05-01
This paper presents a symbolic formulation for analytical compliance analysis and synthesis of flexure mechanisms with serial, parallel, or hybrid topologies. Our approach is based on the screw theory that characterizes flexure deformations with motion twists and loadings with force wrenches. In this work, we first derive a symbolic formulation of the compliance and stiffness matrices for commonly used flexure elements, flexure joints, and simple chains. Elements of these matrices are all explicit functions of flexure parameters. To analyze a general flexure mechanism, we subdivide it into multiple structural modules, which we identify as serial, parallel, or hybrid chains. We then analyze each module with the known flexure structures in the library. At last, we use a bottom-up approach to obtain the compliance/stiffness matrix for the overall mechanism. This is done by taking appropriate coordinate transformation of twists and wrenches in space. Four practical examples are provided to demonstrate the approach. A numerical example is employed to compare analytical compliance models against a finite element model. The results show that the errors are sufficiently small (2%, compared with finite element (FE) model), if the range of motion is limited to linear deformations. This work provides a systematical approach for compliance analysis and synthesis of general flexure mechanisms. The symbolic formulation enables subsequent design tasks, such as compliance synthesis or sensitivity analysis.
Ultrasonic characterization of shear thickening suspensions
Johnson, Benjamin Lenihan
This dissertation describes the characterization of an inherently inhomogeneous medium capable of shear thickening. An aqueous suspension of cornstarch represents an important exemplar of such physical systems. The physics underlying the behavior of such shear thickening suspensions is incompletely understood. Characterization of these suspensions may provide valuable clues into the underlying mechanisms that result in shear thickening behavior. The goal of this thesis is to characterize the acoustic properties of suspensions of cornstarch in density-matched cesium chloride aqueous solutions. A review of the literature indicated that almost no information concerning the ultrasonic characteristics of suspensions of starches had been reported other than studies monitoring the gelatinization of starches not relevant to the shear stiffening of ungelatinized suspensions. Each chapter began with a discussion and validation of the specific experimental techniques and methods of analysis necessary for each type of measurement. Ultrasonic measurement of the group velocity, the frequency-dependent attenuation properties, the frequency-dependent phase velocity, and the frequency-dependent backscatter properties of the suspensions of cornstarch are reported. Initially counterintuitive results including negative (phase velocity) dispersion and a decrease in the measured backscatter coefficient with increasing particle concentration are understood in terms of widely accepted physical models. In sum, these studies represent an advancement of the understanding of the physics underlying the interaction between ultrasound and suspensions and lay the groundwork for future studies probing the physics of the shear thickening.
Direct Shear Tests with Evaluation of Variable Shearing Area
Directory of Open Access Journals (Sweden)
Šarūnas Skuodis
2014-12-01
Full Text Available Investigations of soil shear strength properties for Baltic Sea shore sand along Klaipėda city are presented. Investigated sand angle of internal friction (φ and cohesion (c is determined via two different direct shear tests procedures. First procedure is standard and ordinary in geotechnical practice, when direct shear test is provided using constant shearing area A0. Second test procedure is different because shearing area according to horizontal displacement each test second is recalculated. This recalculated shearing area author’s call corrected shearing area A. Obtained normal and tangential stresses’ difference via two different testing procedures was 10%.
Analytical large deformation shear strength for bolted rough discontinuous rock
Institute of Scientific and Technical Information of China (English)
LIU Bo(刘波); TAO Long-guang(陶龙光); YUE Zhong-qi(岳中琦)
2004-01-01
Presented a new analytical model for studying the shear-tensile large deformation behavior near the vicinity of joint interface for bolted rough discontinuous rock, and presented the formulation estimating global shear strength for bolted joints under shearing-tensile loads. The analytical strength curves of bolts contribution on reinforced discontinuous rocks as the function of joint displacements or deformation angle of a bolt at rock joints was obtained. Based on Barton's equation on JRC roughness profiles, the theoretical shearing strength of bolted rough joints was also established. Test results on bolted granite and marble specimen confirm the validity of the analytical approach.
Experimental and theoretical assessment of flexural properties of hybrid natural fibre composites
DEFF Research Database (Denmark)
Raghavalu Thirumalai, Durai Prabhakaran; Toftegaard, Helmuth Langmaack; Markussen, Christen Malte
2014-01-01
The concept of hybridization of natural fibre composites with synthetic fibres is attracting increasing scientific attention. The present study addresses the flexural properties of hybrid flax/glass/epoxy composites to demonstrate the potential benefits of hybridization. The study covers both...... experimental and theoretical assessments. Composite laminates with different hybrid fibre mixing ratios and different layer configurations were manufactured, and their volumetric composition and flexural properties were measured. The relationship between volume fractions in the composites is shown to be well...... predicted as a function of the hybrid fibre mixing ratio. The flexural modulus of the composites is theoretically assessed by using micromechanical models and laminate theory. The model predictions are compared with the experimentally determined flexural properties. Both approaches show that the flexural...
Mancini, Matthew L.
In most residential construction projects, laminated veneer lumber (LVL) beams are used to help support floor systems, and span doorways or garage door openings, amongst other applications. Because of its diverse application, it is not uncommon that openings are drilled through LVL beams to allow for the passage of utilities. This research evaluates the effects these openings have on long term deflection and flexural capacity, and looks to determine if current provisions for openings need to be amended. Two separate tests were conducted to analyze these behaviors. A long term flexural test was completed to determine the relative creep behavior, and an ultimate load test was conducted to determine the failure load under bending. A total of 26 beams (13 total samples) were tested in the long term test, which included beams with 5 different hole patterns loaded to either 50% or 75% of the allowable load set by the manufacturer. Each beam was loaded for over a year, and its midspan deflection and moisture content was monitored periodically. The environmental conditions such as relative humidity and temperature were also carefully monitored to determine if there was a correlation between relative humidity and long term deflection. Seven of the samples from the long term test were used in the ultimate load test, which included a control sample that was loaded to 60% of the predicted ultimate load so that it could continue being used as a control for the long term test. During the ultimate load test the midpsan and quarterspan deflections were recorded using LVDTs, and the total load was monitored via 4 load cells evenly spaced along the sample. This study found that 2" diameter openings placed in the middle third of the beam length and depth do not significantly affect the long term deflection or flexural capacity of LVL beams. However, as the 2" diameter openings are shifted away from the beam centroid, there is an evident decrease in overall performance in terms of
Rheometry-PIV of shear-thickening wormlike micelles.
Marín-Santibañez, Benjamín M; Pérez-Gonzalez, José; de Vargas, Lourdes; Rodríguez-Gonzalez, Francisco; Huelsz, Guadalupe
2006-04-25
The shear-thickening behavior of an equimolar semidilute aqueous solution of 40 mM/L cetylpyridinium chloride and sodium salicylate was studied in this work by using a combined method of rheometry and particle image velocimetry (PIV). Experiments were conducted at 27.5 degrees C with Couette, vane-bob, and capillary rheometers in order to explore a wide shear stress range as well as the effect of boundary conditions and time of flow on the creation and destruction of shear-induced structures (SIS). The use of the combined method of capillary rheometry with PIV allowed the detection of fast spatial and temporal variations in the flow kinematics, which are related to the shear-thickening behavior and the dynamics of the SIS but are not distinguished by pure rheometrical measurements. A rich-in-details flow curve was found for this solution, which includes five different regimes. Namely, at very low shear rates a Newtonian behavior was found, followed by a shear thinning one in the second regime. In the third, shear banding was observed, which served as a precursor of the SIS and shear-thickening. The fourth and fifth regimes in the flow curve were separated by a spurtlike behavior, and they clearly evidenced the existence of shear-thickening accompanied by stick-slip oscillations at the wall of the rheometer, which subsequently produced variations in the shear rate under shear stress controlled flow. Such a stick-slip phenomenon prevailed up to the highest shear stresses used in this work and was reflected in asymmetric velocity profiles with spatial and temporal variations linked to the dynamics of creation and breakage of the SIS. The presence of apparent slip at the wall of the rheometer provides an energy release mechanism which leads to breakage of the SIS, followed by their further reformation during the stick part of the cycles. In addition, PIV measurements allowed the detection of apparent slip at the wall, as well as mechanical failures in the bulk of the
Energy Technology Data Exchange (ETDEWEB)
Mütze, Annekathrin, E-mail: muetzea@ethz.ch; Heunemann, Peggy; Fischer, Peter [ETH Zürich, Institute of Food, Nutrition and Health, Schmelzbergstrasse 9, 8092 Zürich (Switzerland)
2014-11-01
Wormlike micellar salt/surfactant solutions (X-salicylate, cetylpyridinium chloride) are studied with respect to the applied shear stress, concentration, temperature, and composition of the counterions (X = lithium, sodium, potassium, magnesium, and calcium) of the salicylate salt solute to determine vorticity and gradient shear bands. A combination of rheological measurements, laser technique, video analysis, and rheo-small-angle neutron scattering allow for a detailed exploration of number and types of shear bands. Typical flow curves of the solutions show Newtonian, shear-thinning, and shear-thickening flow behavior. In the shear-thickening regime, the solutions show vorticity and gradient shear bands simultaneously, in which vorticity shear bands dominate the visual effect, while gradient shear bands always coexist and predominate the rheological response. It is shown that gradient shear bands change their phases (turbid, clear) with the same frequency as the shear rate oscillates, whereas vorticity shear bands change their phases with half the frequency of the shear rate. Furthermore, we show that with increasing molecular mass of the counterions the number of gradient shear bands increases, while the number of vorticity shear bands remains constant. The variation of temperature, shear stress, concentration, and counterions results in a predictable change in the rheological behavior and therefore allows adjustment of the number of vorticity shear bands in the shear band regime.
Design OF Flexure Bearing For Linear Compressor By Optimization Procedure Using FEA
Directory of Open Access Journals (Sweden)
Saurabh Malpani
2012-05-01
Full Text Available Bearing are used to allow the relative motion between two surfaces. A shaft has to rotate about its casing or a piston has to slide about the cylinder. Both requires relative motion to happened least rictional losses. The flexural bearing however ,offers a different approach in supporting the bearing surfaces. The elements of bearing surfaces are deformed on application of load to one of the surfaces, allowing the relative motion between the two surfaces on removal of the load ,the surfaces go back to their original position subjected tocondition that caused deformation of the bearing element due to pplied load is within the limit of elasticity. This eliminates the wear ,vibration and frictional losses. However ,the deformation has to be limited. The precision and micro machining applications and some medical applications very low relative motion. Hence, flexural bearing in this kind of application is a better. The present work is specific to the typical flexure bearing used in linear compressor. Since the flexural bearing designed procedure is not available, this paper proposes to the FEM as a tool to find the axial stiffness thatwould be offered by a typical flexure used in the linear compressor application for cryocooler. The cryocooler has a linear compressor use for compressing a gas with a typical displacement of 5 mm. The typical design has the flexural bearing with spiral cuts in the flexures. These spiral cuts allows each of the flexure to move itselfaxially on application of load in the axial direction. There are two states of flexures called stacks on either side of linear motor supporting a piston rod which moves the piston either side i.e. back and forth in gas displacer. As mentioned typical displacement of the piston is 5mm causing each of the flexure to get deformed by same amount. Since there is no any standard method available for alculating axial stiffness of bearing ,we haveconsider an example of disc.
Large-scale direct shear testing of geocell reinforced soil
Institute of Scientific and Technical Information of China (English)
无
2008-01-01
The tests on the shear property of geocell reinforced soils were carried out by using large-scale direct shear equipment with shear-box-dimensions of 500 mm×500 mm×400 mm (length×width×height).Three types of specimens,silty gravel soil,geoceli reinforced silty gravel soil and geoceli reinforood cement stabilizing silty gravel soil were used to investigate the shear stress-displacement behavior,the shear strength and the strengthening mechanism of geocell reinforced soils.The comparisons of large-scale shear test with triaxial compression test for the same type of soil were conducted to evaluate the influences of testing method on the shear strength as well.The test results show that the unreinforced soil and geocell reinforced soil give similar nonlinear features on the behavior of shear stress and displacement.The geocell reinforced cement stabilizing soil has a quasi-elastic characteristic in the case of normal stress coming up to 1.0 GPa.The tests with the reinforcement of geocell result in an increase of 244% in cohesion,and the tests with the geocell and the cement stabilization result in an increase of 10 times in cohesion compared with the unreinforced soil.The friction angle does not change markedly.The geocell reinforcement develops a large amount of cohesion on the shear strength of soils.
Source illusion devices for flexural Lamb waves using elastic metasurfaces
Liu, Yongquan; Liu, Fu; Diba, Owen; Lamb, Alistair; Li, Jensen
2016-01-01
Metamaterials with the transformation method has greatly promoted the development in achieving invisibility and illusion for various classical waves. However, the requirement of tailor-made bulk materials and extreme constitutive parameters associated to illusion designs hampers its further progress. Inspired by recent demonstrations of metasurfaces in achieving reduced versions of electromagnetic cloaks, we propose and experimentally demonstrate source illusion devices to manipulate flexural waves using metasurfaces. The approach is particularly useful for elastic waves due to the lack of form-invariance in usual transformation methods. We demonstrate metasurfaces for shifting, transforming and splitting a point source with "space-coiling" structures. The effects are found to be broadband and robust against a change of source position, with agreement from numerical simulations and Huygens-Fresnel theory. The proposed approach provides an avenue to generically manipulate guided elastic waves in solids, and is...
Ice-Shelf Tidal Flexure and Subglacial Pressure Variations
Walker, Ryan T.; Parizek, Byron R.; Alley, Richard B.; Anandakrishnan, Sridhar; Riverman, Kiya L.; Christianson, Knut
2013-01-01
We develop a model of an ice shelf-ice stream system as a viscoelastic beam partially supported by an elastic foundation. When bed rock near the grounding line acts as a fulcrum, leverage from the ice shelf dropping at low tide can cause significant (approx 1 cm) uplift in the first few kilometers of grounded ice.This uplift and the corresponding depression at high tide lead to basal pressure variations of sufficient magnitude to influence subglacial hydrology.Tidal flexure may thus affect basal lubrication, sediment flow, and till strength, all of which are significant factors in ice-stream dynamics and grounding-line stability. Under certain circumstances, our results suggest the possibility of seawater being drawn into the subglacial water system. The presence of sea water beneath grounded ice would significantly change the radar reflectivity of the grounding zone and complicate the interpretation of grounded versus floating ice based on ice-penetrating radar observations.
[Splenic flexure and irritable colon syndromes: conjugate conditions].
Osipenko, M F; Bikbulatova, E A; Mut-Gusaim, V I
2008-01-01
To investigate phenotypical and clinical characteristics in individuals with high fixation of the splenic angle (HFSA). The study group included 82 patients with HFSA, the comparison group--76 patients with irritable colon syndrome (ICS), control group--19 patients without colon pathology. the results of the following examinations were analysed: the disease history, detailed intestinal investigation, rectal sensitivity, constitution, connective tissue weakness, vegetative dysfunction and regulation. HFSA is encountered mainly in persons with hyperstenic constitution. Some HFSA patients have pain on the left side--splenic flexure syndrome (SFS). The pain corresponds most to clinical criteria of irritable colon syndrome diagnosis and is accompanied with reduced threshold of pain sensitivity to balloon extension. Provoking factors of the symptoms are stress situations in childhood. SFS can be considered as a variant of ICS arising in HFSA. The treatment should be based on the principles of ICS treatment.
The LINC-NIRVANA fringe and flexure tracker control system
Rost, Steffen; Eckart, Andreas; Horrobin, Matthew; Lindhorst, Bettina; Rauch, Christoph; Smajic, Semir; Straubmeier, Christian; Tremou, Evangelia; Wank, Imke; Zuther, Jens; Pott, Jörg-Uwe
2012-07-01
We present the latest status of the control system of the LN (LINC-NIRVANA) FFTS (Fringe and Flexure Tracker System) for the LBT. The software concept integrates the sensor data and control of the various subsystems and provides the interaction with the whole LN instrument. Varying conditions and multiple configurations for observations imply a flexible interconnection of the control loops for the hardware manipulators with respect to the time-critical data analysis of the fringe detection. In this contribution details of the implementation of the algorithms on a real-time Linux PC are given. By considering the results from simulations of the system dynamics, lab experiments, atmospheric simulations, and telescope characterization the optimal parameter setup for an observation can be chosen and basic techniques for adaption to changing conditions can be derived.
Free flexural vibration of functionally graded size-dependent nanoplates
Natarajan, S; Thangavel, M
2012-01-01
In this paper, the linear free flexural vibration behaviour of functionally graded (FG) size-dependent nanoplates are investigated using the finite element method. The field variables are approximated by non-uniform rational B-splines. The size-dependent FG nanoplate is investigated by using Eringen's differential form of nonlocal elasticity theory. The material properties are assumed to vary only in the thickness direction and the effective properties for FG nanoplate are computed using Mori-Tanaka homogenization scheme. The accuracy of the present formulation is tested considering the problems for which solutions are available. A detailed numerical study is carried out to examine the effect of material gradient index, the characteristic internal length, the plate thickness, the plate aspect ratio and the boundary conditions on the global response of FG nanoplate.
Shear rheology of lipid monolayers and insights on membrane fluidity
Espinosa, Gabriel; López-Montero, Iván; Monroy, Francisco; Langevin, Dominique
2011-01-01
The concept of membrane fluidity usually refers to a high molecular mobility inside the lipid bilayer which enables lateral diffusion of embedded proteins. Fluids have the ability to flow under an applied shear stress whereas solids resist shear deformations. Biological membranes require both properties for their function: high lateral fluidity and structural rigidity. Consequently, an adequate account must include, in addition to viscosity, the possibility for a nonzero shear modulus. This knowledge is still lacking as measurements of membrane shear properties have remained incomplete so far. In the present contribution we report a surface shear rheology study of different lipid monolayers that model distinct biologically relevant situations. The results evidence a large variety of mechanical behavior under lateral shear flow. PMID:21444777
Investigation into ferrofluid magnetoviscous effects under an oscillating shear flow
Energy Technology Data Exchange (ETDEWEB)
Pinho, M., E-mail: marcos.pinho.etu@univ-lemans.fr [LAUM - Laboratoire d' Acoustique de l' Universite du Maine UMR CNRS 6613 (France); Brouard, B.; Genevaux, J.M. [LAUM - Laboratoire d' Acoustique de l' Universite du Maine UMR CNRS 6613 (France); Dauchez, N. [LISMMA - Institut Superieur de Mecanique de Paris (SUPMECA), 93407 Saint Ouen (France); Volkova, O. [Centre de micro et nanorheometrie, Universite de Nice-Sophia Antipolis, Parc Valrose, 06108 Nice-cedex2 (France); Meziere, H.; Collas, P. [LAUM - Laboratoire d' Acoustique de l' Universite du Maine UMR CNRS 6613 (France)
2011-10-15
The use of ferrofluid seals in mechanical systems can lead to viscous damping that affects their dynamic behavior. This paper describes an investigation into local viscous properties in the case of an axial harmonic force. The influence of magnetic field level, shear stress amplitude and frequency are studied. Even for ferrofluid particles in a highly saturated magnetic field, it is shown that viscosity increases with magnetic intensity, decreases with the frequency of harmonic excitation and is not sensitive to shear rate amplitude. Viscosity is lower for oscillatory flows than for steady flows. - Highlights: > Extension of the magnetoviscous effect of ferrofluids to the oscillatory shear flow. > Influence of magnetic field level, shear stress amplitude and frequency is studied. > Ferrofluid viscosity is lower for oscillatory than for steady flow shearing. > Ferrofluid viscosity is not sensitive to shear rate amplitude. > Negative-viscosity effect occurs even for a null magnetic field.
Institute of Scientific and Technical Information of China (English)
无
2007-01-01
The free and forced vibration of large deformation composite plate embedded with shape memory alloy (SMA) fibers is investigated. A thermo-mechanical constitutive equation of SMA proposed by Brinson et al. is employed and the constitutive equations for evaluation of the properties of a hybrid SMA composite laminate are obtained. Based on the nonlinear theory of symmetrically laminated anisotropic plates, the governing equations of flexural vibration in terms of displacement and stress functions are derived. The Galerkin method has been used to convert the original partial differential equation into a nonlinear ordinary differential equation, which is then solved with harmonic balance method. The numerical results show that the relationship between nonlinear natural frequency ratio and temperature for the nonlinear plate has similar characteristics compared with that of the linear one, and the effects of temperature on forced response behavior during phase transformation from Martensite to Austenite are significant. The effects of the volume fraction of the SMA fiber, aspect ratio and free vibration amplitude on the dynamical behavior of the plate are also discussed.
Hayek, Sabih I.; Boisvert, Jeffrey E.
2003-11-01
This paper presents the derivation of the equations for nonaxisymmetric motion of prolate spheroidal shells of constant thickness. The equations include the effect of distributed mechanical surface forces and moments. The shell theory used in this derivation includes three displacements and two thickness shear rotations. Thus, the effects of membrane, bending, shear deformation, and rotatory inertia are included in this theory. The resulting five coupled partial differential equations are self-adjoint and positive definite. The frequency-wave-number spectrum has five branches, two acoustic and three optical branches representing flexural, extensional, torsional, and two thickness shear. For the case of axisymmetric motion, these were computed for various spheroidal shell eccentricities and thickness-to-length ratios for a large number of modes. The axisymmetric dynamic response for damped shells of various eccentricities and thicknesses under point and ring surface forces are presented.
CT Scan Mapping of Splenic Flexure in Relation to Spleen and its Clinical Implications.
Saber, Alan A; Dervishaj, Ornela; Aida, Samer S; Christos, Paul J; Dakhel, Mahmoud
2016-05-01
Splenic flexure mobilization is a challenging step during left colon resection. The maneuver places the spleen at risk for injury. To minimize this risk, we conducted this study for CT scan mapping of splenic flexure in relation to the spleen. One hundred and sixty CT scans of abdomen were reviewed. The level of the splenic flexure was determined in relation to hilum and lower pole of spleen. These levels were compared with patient demographics. Statistical analysis was performed using Fisher's exact test. The splenic flexure was above the hilum of the spleen in 95 patients (67.86%), at the splenic hilum level in 11 patents (7.88%), between the hilum and lower pole of the spleen in 12 (8.57%), at the lower pole of the spleen in 15 (10.7%) patients and 7 (5%) patients has a splenic flexure that lied below the lower pole of the spleen. Patient demographics showed no statistical significance in regard to splenic flexure location. Splenic flexure lies above the hilum of the spleen in majority of patients. This should be considered as part of operative strategies for left colon resection.
Comparative study of flexural strength test methods on CAD/CAM Y-TZP dental ceramics
Xu, Yongxiang; Han, Jianmin; Lin, Hong; An, Linan
2015-01-01
Clinically, fractures are the main cause of computer-aided design and computer-aided manufacturing (CAD/CAM) 3 mol%-yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) all-ceramic dental restorations failure because of repetitive occlusal loading. The goal of this work is to study the effect of test methods and specimen’s size on the flexural strength of five ceramic products. Both bi-axial flexure test (BI) and uni-axial flexure tests (UNI), including three-point flexure test (3PF) and four-point flexure test (4PF), are used in this study. For all five products, the flexural strength is as follows: BI > 3PF > 4PF. Furthermore, specimens with smaller size (3PF-s) have higher values than the bigger ones (3PF). The difference between BI and UNI resulted from the edge flaws in ceramic specimens. The relationship between different UNI (including 3PF-s, 3PF and 4PF) can be explained according to Weibull statistical fracture theory. BI is recommended to evaluate the flexural strength of CAD/CAM Y-TZP dental ceramics. PMID:26816646
Mixing through shear instabilities
Brüggen, M
2000-01-01
In this paper we present the results of numerical simulations of the Kelvin-Helmholtz instability in a stratified shear layer. This shear instability is believed to be responsible for extra mixing in differentially rotating stellar interiors and is the prime candidate to explain the abundance anomalies observed in many rotating stars. All mixing prescriptions currently in use are based on phenomenological and heuristic estimates whose validity is often unclear. Using three-dimensional numerical simulations, we study the mixing efficiency as a function of the Richardson number and compare our results with some semi-analytical formalisms of mixing.
Dynamics of Discontinuous Shear Thickening suspensions
Brown, Eric
2015-03-01
Concentrated suspensions of hard particles such as cornstarch in water exhibit Discontinuous Shear Thickening, in which an increasing shear rate drives a transition from liquid- to solid-like mechanical behavior. In steady-state shear this phenomena is a result of a dynamic version of jamming in which forces are transmitted along particle contact networks that span to system boundaries and repeatedly form and break up. Several dynamic phenomena observed in such suspensions have long been assumed to be a consequence of this shear thickening, but cannot be explained as a direct result of shear thickening; for example a uniquely strong impact response which allows a person to run on the fluid surface. We perform experiments in which a concentrated suspension is subjected to transient impact. We find that the strong impact response is due a short-lived jammed contact network spanning to the boundaries and a delay time required for this dynamically jammed region to propagate to the boundary. The resulting ability of this system-spanning solid-like region to support loads can explain the ability of a person to run on the surface of these fluids. This delay before a solid-like response may also explain several other dynamic phenomena observed in these fluids.
Viscoelasticity and shear thinning of nanoconfined water
Kapoor, Karan; Amandeep, Patil, Shivprasad
2014-01-01
Understanding flow properties and phase behavior of water confined to nanometer-sized pores and slits is central to a wide range of problems in science, such as percolation in geology, lubrication of future nano-machines, self-assembly and interactions of biomolecules, and transport through porous media in filtration processes. Experiments with different techniques in the past have reported that viscosity of nanoconfined water increases, decreases, or remains close to bulk water. Here we show that water confined to less than 20-nm-thick films exhibits both viscoelasticity and shear thinning. Typically viscoelasticity and shear thinning appear due to shearing of complex non-Newtonian mixtures possessing a slowly relaxing microstructure. The shear response of nanoconfined water in a range of shear frequencies (5 to 25 KHz) reveals that relaxation time diverges with reducing film thickness. It suggests that slow relaxation under confinement possibly arises due to existence of a critical point with respect to slit width. This criticality is similar to the capillary condensation in porous media.
NANO-BEARING: THE DESIGN OF A NEW TYPE OF AIR BEARING WITH FLEXURE STRUCTURE
Institute of Scientific and Technical Information of China (English)
KO Pui Hang; DU Ruxu
2007-01-01
A new type of air bearing with flexure structure is introduced. The new bearing is designed for precision mechanical engineering devices such as mechanical watch movement. The new design uses the flexure structure to provide 3D damping to absorb shocks from all directions. Two designs are presented: one has 12 T-shape slots in the radian direction while the other has 8 spiral slots in the radian direction. Both designs have flexure mountings on the axial directions. Based on the finite element analysis (FEA), the new bearing can reduce the vibration (displacement) by as much as 8.37% and hence, can better protect the shafts.
Controlling thermal and electrical properties of graphene by strain-engineering its flexural phonons
Conley, Hiram; Nicholl, Ryan; Bolotin, Kirill
2014-03-01
We explore the effects of flexural phonons on the thermal and electrical properties of graphene. To control the amplitude of flexural phonons, we developed a technique to engineer uniform mechanical strain between 0 and 1% in suspended graphene. We determine the level of strain, thermal conductivity and carrier mobility of graphene through a combination of mechanical resonance and electrical transport measurements. Depending on strain, we find significant changes in the thermal expansion coefficient, thermal conductivity, and carrier mobility of suspended graphene. These changes are consistent with the expected contribution of flexural phonons.
Geometrical design parameters for journal bearings with flexure pads and compliant liners
DEFF Research Database (Denmark)
Thomsen, Kim; Klit, Peder
2012-01-01
A hydrodynamic journal bearing utilizing flexure pads with a compliant liner is studied and its performance enhanced through a parametric study. The main geometrical dimensions are varied and the affect on pad performance is analyzed. This will put more knowledge into the design and function...... of flexure pads. uidelines are given to the design of the pads and are also covering the polymer liner. It is found that the use of flexure pads is an attractive alternative to pivoted pads. Pivot contact-related failure modes are eliminated and load capacity is not restricted by the force that can...
EFFECT OF NANOPOWDER ADDITION ON THE FLEXURAL STRENGTH OF ALUMINA CERAMIC - A WEIBULL MODEL ANALYSIS
Directory of Open Access Journals (Sweden)
Daidong Guo
2016-05-01
Full Text Available Alumina ceramics were prepared either with micrometer-sized alumina powder (MAP or with the addition of nanometer-sized alumina powder (NAP. The density, crystalline phase, flexural strength and the fracture surface of the two ceramics were measured and compared. Emphasis has been put on the influence of nanopowder addition on the flexural strength of Al₂O₃ ceramic. The analysis based on the Weibull distribution model suggests the distribution of the flexural strength of the NAP ceramic is more concentrated than that of the MAP ceramic. Therefore, the NAP ceramics will be more stable and reliable in real applications.
Detection of disbonds in foam composite assemblies using flexural waves and shearography
Lamboul, B.; Giraudo, O.; Osmont, D.
2015-03-01
This paper presents a method based on the generation of low frequency flexural waves for the detection of disbonds in foam composite assemblies. An imaging procedure based on the shearography technique is proposed for the fast generation of images suitable for nondestructive testing analysis. The method is assessed with calibrated disbond defects in a composite foam core sandwich. The role of local flexural resonances for obtaining clear defect signatures is studied and highlighted using complementary Laser vibrometry data. The minimum defect size for detection is associated with the conditions for exciting the first flexural mode in the defect region.
Design and analysis of a 2-degree-of-freedom flexure-based micro-motion stage
Directory of Open Access Journals (Sweden)
Yunsong Du
2016-03-01
Full Text Available This article presents the mechanical design, dimensional optimization, finite element analysis, and experimentation of a 2-degree-of-freedom flexure-based micro-motion stage. The stage is composed of four parallel limbs with symmetrical configuration, and each limb is composed of two serially connected prismatic joints. The divided parts of flexure hinge thickness constituting the two prismatic joints are selected as two. Based on analytical models established in stiffness and dynamic analysis, the dimensional optimization is carried out to maximize the first resonance frequency. Finite element analysis is then adapted to verify the stiffness, workspace, and dynamic behavior. Finally, a prototype of the stage is manufactured and an experimental platform is set up. The experimental results show that the stage has a workspace range of 19.53 µm × 19.07 µm with a frequency of 1987 Hz, and the cross-coupling ratio between two axes is less than 1%. For high-frequency cooperative tracking experiments, a proportional–integral controller is implemented to compensate for the tracking errors. Finally, good tracking performance at high frequency is obtained, which validates the effectiveness of the micro-motion stage.
Shafieyzadeh, M.
2015-12-01
In the flexural test, the theoretical maximum tensile stress at the bottom fiber of a test beam is known as the modulus of rupture or flexural strength. This work deals with the effects of Silica Fume and Styrene-Butadiene Latex (SBR) on flexural strength of concrete. An extensive experimentation was carried out to determine the effects of silica fume and SBR on flexural strength of concrete. Two water-binder ratios and several percentages of silica fume and SBR were considered. Abrams' Law, which was originally formulated for conventional concrete containing cement as the only cementations material, is used for prediction of flexural strength of these concretes. The aim of this work is to construct an empirical model to predict the flexural strength of silica fume-SBR concretes using concrete ingredients and time of curing in water. Also, the obtained results for flexural strength tests have been compared with predicted results.
DEFF Research Database (Denmark)
Hansen, Klaus
This report gives a summary of the present information on the behaviour of vertical keyed shear joints in large panel structures. An attemp is made to outline the implications which this information might have on the analysis and design of a complete wall. The publications also gives a short...
Indian Academy of Sciences (India)
Akira Onuki; Akira Furukawa; Akihiko Minami
2005-05-01
We present a time-dependent Ginzburg–Landau model of nonlinear elasticity in solid materials. We assume that the elastic energy density is a periodic function of the shear and tetragonal strains owing to the underlying lattice structure. With this new ingredient, solving the equations yields formation of dislocation dipoles or slips. In plastic flow high-density dislocations emerge at large strains to accumulate and grow into shear bands where the strains are localized. In addition to the elastic displacement, we also introduce the local free volume . For very small the defect structures are metastable and long-lived where the dislocations are pinned by the Peierls potential barrier. However, if the shear modulus decreases with increasing , accumulation of around dislocation cores eventually breaks the Peierls potential leading to slow relaxations in the stress and the free energy (aging). As another application of our scheme, we also study dislocation formation in two-phase alloys (coherency loss) under shear strains, where dislocations glide preferentially in the softer regions and are trapped at the interfaces.
Shear Banding of Soft Glassy Materials in Large Amplitude Oscillatory Shear
Radhakrishnan, Rangarajan; Fielding, Suzanne M.
2016-10-01
We study shear banding in soft glassy materials subject to a large amplitude oscillatory shear flow (LAOS). By numerical simulations of the widely used soft glassy rheology model, supplemented by more general physical arguments, we demonstrate strong banding over an extensive range of amplitudes and frequencies of the imposed shear rate γ ˙(t )=γ˙0cos (ω t ), even in materials that do not permit banding as their steady state response to a steadily imposed shear flow γ ˙=γ˙0=const. Highly counterintuitively, banding persists in LAOS even in the limit of zero frequency ω →0 , where one might a priori have expected a homogeneous flow response in a material that does not display banding under conditions of steadily imposed shear. We explain this finding in terms of an alternating competition within each cycle between glassy aging and flow rejuvenation. Our predictions have far-reaching implications for the flow behavior of aging yield stress fluids, suggesting a generic expectation of shear banding in flows of even arbitrarily slow time variation.
Shear strength of non-shear reinforced concrete elements
DEFF Research Database (Denmark)
Hoang, Cao linh
1997-01-01
The paper deals with the plastic shear strength of non shear reinforced T-beams.The influence of an un-reinforced flange on the shear capacity is investigated by considering a failure mechanism involving crack sliding in the web and a kind of membrane action over an effective width of the flange...
Rheological responses of fumed silica suspensions under steady and oscillatory shear
Institute of Scientific and Technical Information of China (English)
无
2009-01-01
Rheological experiments under steady and oscillatory shear were conducted for fumed silica suspen- sions in polyethylene glycol. Under steady shear the shear-thinning and thickening response were exhibited and the flow exponent N was determined. With the increase of concentration the flow exponent N showed a rapid increase, and it increased dramatically when the discontinuous shear-thickening took place. Oscillatory shear experiments were conducted at constant frequency and constant amplitude strain, respectively. The shear-thinning and the discontinuous shear-thickening behavior were observed under different constant frequencies from 10 to 80 rad/s. The correlation between complex modulus (G*) and sweep frequency (ω) was illuminated at γ =750%. It was found that the correlation between G* and ω could be fitted by equation: G*∝ωn. The indexes in shear-thinning region and shear-thickening were determined. The indexes were similar to some extent at shear-thinning region and increased dramati- cally to a much higher value when the shear-thickening occurred,especially at higher weight fractions. The behaviors can be qualitatively explained as follows: the shear-thinning owes to decrease of viscos- ity, which results from disruption of the aggregates; the cluster theory attributes the shear-thickening to the formation of metastable, flow induced clusters, which block the system.
Rheological responses of fumed silica suspensions under steady and oscillatory shear
Institute of Scientific and Technical Information of China (English)
YANG HaiLin; RUAN JianMing; ZOU JianPeng; WU QiuMei; ZHOU ZhongCheng; ZHOU ZhiHua
2009-01-01
Rheological experiments under steady and oscillatory shear were conducted for fumed silica suspensions in polyethylene glycol. Under steady shear the shear-thinning and thickening response were exhibited and the flow exponent Nwas determined. With the increase of concentration the flow exponent N showed a rapid increase, and it increased dramatically when the discontinuous shear-thickening took place. Oscillatory shear experiments were conducted at constant frequency and constant amplitude strain, respectively. The shear-thinning and the discontinuous shear-thickening behavior were observed under different constant frequencies from 10 to 80 rad/s. The correlation between complex modulus (G*)and sweep frequency (ω) was illuminated atγ=750%. It was found that the correlation between G* and ω could be fitted by equation: G*∝ωn. The indexes in shear-thinning region and shear-thickening were determined. The indexes were similar to some extent at shear-thinning region end increased dramatically to a much higher value when the shear-thickening occurred, especially at higher weight fractions. The behaviors can be qualitatively explained as follows: the shear-thinning owes to decrease of viscosity, which results from disruption of the aggregates; the cluster theory attributes the shear-thickening to the formation of metastable, flow induced clusters, which block the system.