Dynamic stiffness matrix of thin-walled composite I-beam with symmetric and arbitrary laminations
Kim, Nam-Il; Shin, Dong Ku; Park, Young-Suk
2008-11-01
For the spatially coupled free vibration analysis of thin-walled composite I-beam with symmetric and arbitrary laminations, the exact dynamic stiffness matrix based on the solution of the simultaneous ordinary differential equations is presented. For this, a general theory for the vibration analysis of composite beam with arbitrary lamination including the restrained warping torsion is developed by introducing Vlasov's assumption. Next, the equations of motion and force-displacement relationships are derived from the energy principle and the first order of transformed simultaneous differential equations are constructed by using the displacement state vector consisting of 14 displacement parameters. Then explicit expressions for displacement parameters are derived and the exact dynamic stiffness matrix is determined using force-displacement relationships. In addition, the finite-element (FE) procedure based on Hermitian interpolation polynomials is developed. To verify the validity and the accuracy of this study, the numerical solutions are presented and compared with analytical solutions, the results from available references and the FE analysis using the thin-walled Hermitian beam elements. Particular emphasis is given in showing the phenomenon of vibrational mode change, the effects of increase of the modulus and the bending-twisting coupling stiffness for beams with various boundary conditions.
Free vibrations of thin-walled semicircular graphite-epoxy composite frames
Noor, Ahmed K.; Carden, Huey D.; Peters, Jeanne M.
1991-01-01
A detailed study is made of the effects of variations in lamination and material parameters of thin-walled composite frames on their vibrational characteristics. The structures considered are semicircular thin-walled frames with I and J sections. The flanges and webs of the frames are modeled by using two-dimensional shell and plate finite elements. A mixed formulation is used with the fundamental unknowns consisting of both the generalized displacements and stress resultants in the frame. The frequencies and modes predicted by the two-dimensional finite-element model are compared with those obtained from experiments, as well as with the predictions of a one-dimensional, thin-walled-beam, finite-element model. A detailed study is made of the sensitivity of the vibrational response to variations in the fiber orientation, material properties of the individual layers, and boundary conditions.
Thermal postbuckling of thin-walled composite stiffeners
Noor, Ahmed K.; Peters, J. M.
1991-01-01
A study is made of the thermal postbuckling response of composite stiffeners subjected to prescribed edge displacement and a temperature rise. The flanges and web of the stiffeners are modeled by using two-dimensional plate finite elements. A mixed formulation is used with the fundamental unknowns consisting of the generalized displacements and the stress resultants of the plate. A reduction method is used in conjunction with mixed finite element models for determining the postbuckling response of the stiffeners. Sensitivity derivatives are evaluated and used to study the effects of variations in the different lamination and material parameters of the stiffeners on their postbuckling response characteristics. Numerical studies are presented for anisotropic stiffeners with Zee and channel sections.
Vibration and Stability of Variable Cross Section Thin-Walled Composite Shafts with Transverse Shear
Directory of Open Access Journals (Sweden)
Ma Jing-min
2015-01-01
Full Text Available A dynamic model of composite shaft with variable cross section is presented. Free vibration equations of the variable cross section thin-walled composite shaft considering the effect of shear deformation are established based on a refined variational asymptotic method and Hamilton’s principle. The numerical results calculated by Galerkin method are analyzed to indicate the effects of ply angle, taper ratio, and transverse shear deformation on the first natural frequency and critical rotating speed. The results are compared with those obtained by using finite element package ANSYS and available in the literature using other models.
Computation of macro-fiber composite integrated thin-walled smart structures
Zhang, S. Q.; Zhang, S. Y.; Chen, M.; Bai, J.; Li, J.
2016-07-01
Due to high flexibility, reliability, and strong actuation forces, piezo fiber based composite smart material, macro-fiber composite (MFC), is increasingly applied in various fields for vibration suppression, shape control, and health monitoring. The complexity arrangement of MFC materials makes them difficult in numerical simulations. This paper develops a linear electro-mechanically coupled finite element (FE) model for composite laminated thin-walled smart structures bonded with MFC patches considering arbitrary piezo fiber orientation. Two types of MFCs are considered, namely, MFC-d31 in which the d 31 effect dominates the actuation forces, and MFC-d33 which mainly uses the d 33 effect. The proposed FE model is validated by static analysis of an MFC bonded smart plate.
Defect Characterization in a Thin Walled Composite RP-1 Tank: A Case Study
Langsing, Matthew D.; Walker, James L., II; Russell, Samual S.
2000-01-01
A full scale thin walled composite tank, designed and fabricated for the storage of pressurized RP- I rocket fuel, was fully inspected with digital infrared thermography (IR) during assembly and prior to proof testing. The tank featured a "pill capsule" design with the equatorial bondline being overwrapped on both the inner and outer surfaces. A composite skirt was bonded to the aft dome of the tank to serve as a structural support when the tank was stood on end in service. Numerous anomalies were detected and mapped prior to proof testing, some along bondlines and some scattered throughout the acreage. After the tank was intentionally burst, coupons were cut from the regions including thermographic anomalies. These coupons were again inspected thermographically to document the growth of any indications due to proof testing. Ultrasonic inspections (UT) were also performed on the coupons for comparison to thermography. Several coupons were dissected and micrographed. Relationships between IR and UT indications and the physical nature of the dissected material are presented.
Institute of Scientific and Technical Information of China (English)
诸德超; 邓忠民; 王荇卫
2001-01-01
In the present paper, a series of hierarchical warping functions is developed to analyze the static and dynamic problems of thin walled composite laminated helicopter rotors composed of several layers with single closed cell. This ethod is the development and extension of the traditional constrained warping theory of thin walled metallic beams, which had been proved very successful since 1940s. The warping distribution along the perimeter of each layer is expanded into a series of successively corrective warping functions with the traditional warping function caused by free torsion or free bending as the first term, and is assumed to be piecewise linear along the thickness direction of layers. The governing equations are derived based upon the variational principle of minimum potential energy for static analysis and Rayleigh Quotient for free vibration analysis. Then the hierarchical finite element method is introduced to form a numerical algorithm. Both static and natural vibration problems of sample box beams are analyzed with the present method to show the main mechanical behavior of the thin walled composite laminated helicopter rotor.
Na, Sungsoo
1997-01-01
A dual approach integrating structural tailoring and adaptive materials technology and designed to control the dynamic response of cantilever beams subjected to external excitations is addressed. The cantilevered structure is modeled as a thin-walled beam of arbitrary cross-section and incorporates a number of non-classical effects such as transverse shear, warping restraint, anisotropy of constituent materials and heterogeneity of the construction. Whereas structura...
Directory of Open Access Journals (Sweden)
Yongsheng Ren
2015-03-01
Full Text Available The structural model of the thin-walled laminated beams with integral shape memory alloy active fibers and accounting for geometrically nonlinear is presented in this article. The structural modeling is split into two parts: a two-dimensional analysis over the cross section and a geometrically nonlinear analysis of a beam along the beam span. The variational asymptotic method is used to formulate the force–deformation relationship equations taking into account the presence of active shape memory alloy fibers distributed along the cross section of the beam. The geometrically nonlinear governing equations are derived using variational principle and based on the von Kármán-type nonlinear strain–displacement relations. The equations are then solved using Galerkin’s method and an incremental Newton–Raphson method. The validation for the proposed model has been carried out by comparison of the present results with those available in the literature. The results show that significant extension, bending, and twisting coupled nonlinear deflections occur during the phase transformation due to shape memory alloy actuation. The effects of the volume fraction of the shape memory alloy fiber and ply angle are also addressed.
Directory of Open Access Journals (Sweden)
XIE Jiang
2017-04-01
Full Text Available To study the crushing energy-absorbing characteristics and failure mode, the multi-shells finite element model of composite thin-walled C-channel specimen was established based on the quasi-static crushing test results. The simulation results show that the delamination failure, local buckling and beam bending failure of C-channel specimen can be simulated with the multi-shells finite element model. The load-displacement curve well fits the test results, and the deviation of initial peak load (Fmax, specific energy absorption (Es and crushing mean load (Fmean is small compared with the test results. The initial peak load of C-channel specimen is larger and the load efficiency is lower, so it is necessary to further reduce the initial peak load by the design optimization.
Institute of Scientific and Technical Information of China (English)
Bai Jiangbo; Xiong Junjiang
2014-01-01
This paper seeks to outline the temperature effect on the buckling properties of ultra-thin-walled lenticular collapsible composite tube (LCCT) subjected to axial compression. The buckling tests of the LCCT specimens subjected to axial compression were carried out on INSTRON-500N servo-hydraulic machine in dry state and at the temperatures of 25 ?C, 100 ?C and ?80 ?C. The load-displacement curves and buckling initiation loads were measured and the buckling initiation mechanism was discussed from experimental observations. Experiments show that the buckling initiation load, on average, is only about 2.2% greater at the low temperature of ?80 ?C than at the room temperature of 25 ?C due to the material hardening, demonstrating an insignificant increase in the buckling initiation load, whereas it is about 19.5%lower at the high temperature of 100 ?C than at the room temperature owing to the material softening, implying a significant decrease in the buckling initiation load. The failure mode of the LCCT in axial compres-sion tests at three different temperatures can be reckoned to be characteristic of the buckling initi-ation and propagation around the central region until rupture. The finite element (FE) model is presented to simulate the buckling initiation mechanism based on the eigenvalue-based methodol-ogy. Good correlation between experimental and numerical results is achieved.
Thin-walled composite tubes using fillers subjected to quasistatic axial compression
AL-Qrimli, Haidar F.; Mahdi, Fadhil A.; Ismail, Firas B.; Alzorqi, Ibrahim S.
2015-04-01
It has been demonstrated that composites are lightweight, fatigue resistant and easily melded, a seemingly attractive alternative to metals. However, there has been no widespread switch from metals to composites in the automotive sector. This is because there are a number of technical issues relating to the use of composite materials that still need to be resolved including accurate material characterization, manufacturing and joining process. The total of 36 specimens have been fabricated using the fibre-glass and resin (epoxy) with a two different geometries (circular and corrugated) each one will be filled with five types of filler (Rice Husk, Wood Chips, Aluminium Chips, Coconut Fibre, Palm Oil Fibre) all these type will be compared with empty Tubes for circular and corrugated in order to comprehend the crashworthiness parameters (initial failure load, average load, maximum crushing load, load ratio, energy absorption, specific energy absorption, volumetric energy absorption, crushing force efficiency and crush strain relation) which are considered very sufficient parameters in the design of automotive industry parts. All the tests have been done using the “INSTRON Universal machine” which is computerized in order to simply give a high precision to the collection of the results, along with the use of quasi-static load to test and observe the behaviour of the fabricated specimens.
Institute of Scientific and Technical Information of China (English)
王明海; 孙越; 孙国强
2013-01-01
In the traditional simulation method for twisted thin-walled part of blades,the cutting load does not follow the actual tool path,which leads to a large error between simulation and actual deformation,and the deformation area is not accurate.To solve these problems,the simulation method for twisted thin-walled part of blades based on the tool path generated by NC program is proposed.In the case of a full-scale structural 3-D model of certain engine installed leaves,the milling process simulations under three different milling modes including flank milling,turnover milling and helical milling are accomplished.The stress distribution and deformation condition in three different milling modes,and the region and the amount of bending and twisting elastic deformation of the part are determined.Finally,combined with the milling experiment,the correctness and effectiveness of the simulation method are verified.%为了解决叶片类扭曲薄壁件铣削加工的传统仿真方法中不按实际走刀轨迹进行载荷加载而导致模拟变形量与实际变形量之间误差较大且变形区域不准确等问题,提出了一种基于数控程序生成的刀具轨迹对叶片类扭曲曲面薄壁件铣削加工进行有限元模拟的方法.以某型发动机装机叶片的全尺寸三维结构模型为例,结合数控刀具轨迹进行了侧铣、翻面铣、螺旋铣3种加工方式下的铣削过程仿真模拟.获得了该类零件在3种铣削方式下的应力分布和变形情况,确定了发生弯扭弹性变形的区域和变形量.最后,结合相关铣削实验,验证了该仿真分析方法的正确性及有效性.
Song, O; Jeong, N H; Librescu, L
2001-03-01
Problems related with the implications of conservative and gyroscopic forces on vibration and the stability of a circular cylindrical shaft modeled as a thin-walled composite beam and spinning with constant angular speed about its longitudinal axis are addressed. Taking into account the directionality property of fiber reinforced composite materials, it is shown that for a shaft featuring flapwise-chordwise-bending coupling, a dramatic enhancement of both the vibrational and stability behavior can be reached. In addition, the effects played in the same context by transverse shear, rotatory inertias as well as by the various boundary conditions are discussed and pertinent conclusions are outlined.
Energy Technology Data Exchange (ETDEWEB)
J.F. Cuttino; D.M. Stefanescu; T.S. Piwonka
2001-10-31
Results of an investigation made to develop methods of making iron castings having wall thicknesses as small as 2.5 mm in green sand molds are presented. It was found that thin wall ductile and compacted graphite iron castings can be made and have properties consistent with heavier castings. Green sand molding variables that affect casting dimensions were also identified.
Dynamic stiffness for thin-walled structures by power series
Institute of Scientific and Technical Information of China (English)
ZHU Bin; LEUNG A.Y.T.
2006-01-01
The dynamic stiffness method is introduced to analyze thin-walled structures including thin-walled straight beams and spatial twisted helix beam. A dynamic stiffness matrix is formed by using frequency dependent shape functions which are exact solutions of the governing differential equations. With the obtained thin-walled beam dynamic stiffness matrices, the thin-walled frame dynamic stiffness matrix can also be formulated by satisfying the required displacements compatibility and forces equilibrium, a method which is similar to the finite element method (FEM). Then the thin-walled structure natural frequencies can be found by equating the determinant of the system dynamic stiffness matrix to zero. By this way, just one element and several elements can exactly predict many modes of a thin-walled beam and a spatial thin-walled frame, respectively. Several cases are studied and the results are compared with the existing solutions of other methods. The natural frequencies and buckling loads of these thin-walled structures are computed.
Mahadev, Sthanu
Continued research and development efforts devoted in recent years have generated novel avenues towards the advancement of efficient and effective, slender laminated fiber-reinforced composite members. Numerous studies have focused on the modeling and response characterization of composite structures with particular relevance to thin-walled cylindrical composite shells. This class of shell configurations is being actively explored to fully determine their mechanical efficacy as primary aerospace structural members. The proposed research is targeted towards formulating a composite shell theory based prognosis methodology that entails an elaborate analysis and investigation of thin-walled cylindrical shell type laminated composite configurations that are highly desirable in increasing number of mechanical and aerospace applications. The prime motivation to adopt this theory arises from its superior ability to generate simple yet viable closed-form analytical solution procedure to numerous geometrically intense, inherent curvature possessing composite structures. This analytical evaluative routine offers to acquire a first-hand insight on the primary mechanical characteristics that essentially govern the behavior of slender composite shells under typical static loading conditions. Current work exposes the robustness of this mathematical framework via demonstrating its potential towards the prediction of structural properties such as axial stiffness and bending stiffness respectively. Longitudinal ply-stress computations are investigated upon deriving the global stiffness matrix model for composite cylindrical tubes with circular cross-sections. Additionally, this work employs a finite element based numerical technique to substantiate the analytical results reported for cylindrically shaped circular composite tubes. Furthermore, this concept development is extended to the study of thin-walled, open cross-sectioned, curved laminated shells that are geometrically
Thin Wall Austempered Ductile Iron (TWADI
Directory of Open Access Journals (Sweden)
M. Górny
2009-07-01
Full Text Available In this paper the analysis of thin walled castings made of ductile iron is considered. It is shown that thin wall austempered ductile iron can be obtained by means of short-term heat treatment of thin wall castings without addition of alloying elements. Metallographic examinations of 2 mm thin walled castings along with casting with thicker wall thickness (20x28 mm after different austempring conditions are presented. It has been proved that short-term heat treatment amounted 20 minutes of austenitizing at 880 oC followed by holding at 400 oC for 5 minutes causes ausferrite matrix in 2 mm wall thickness castings, while casting with thicker wall thickness remain untransformed and martensite is still present in a matrix. Finally there are shown that thin wall ductile iron is an excellent base material for austempering heat treatments. As a result high mechanical properties received in thin wall plates made of austempered ductile iron.
Free vibration of a rotating composite thin-walled beam with large deformation%旋转几何非线性复合材料薄壁梁的自由振动分析
Institute of Scientific and Technical Information of China (English)
任勇生; 代其义; 孙丙磊; 张纯金
2013-01-01
A rotating composite thin-walled beam is a class of typical structure used in study on vibration control of advanced helicopter blades and wind turbine blades.The dynamic behavior investigation of this structure is of significance in theory and practice.However,so far the dynamic behavior study on the above-mentioned structure is limited only for rotating composite beams with small elastic deformation.The free vibration of a rotating composite thin-walled beam with large deformation was studied here.The governing nonlinear equations of motion for the rotating composite thin-walled beam were derived using Hamilton's energy principle and the variational-asymptotical method (VAM) on the basis of von Karman's assumption.The nonlinear free vibration of the beam was studied using Galerkin method and the harmonic balance method.The large amplitude of free vibration of the beam could be expressed as a nonlinear eigenvalue problem and solved using an iterative solution procedure.Numerical results were obtained for a laminated composite configuration thin-walled beam with circumferentially uniform stiffness (CUS).The results showed the effect of fiber orientation and rotating speed on the relation between nonlinear natural frequency and amplitude.The developed model could be capable of describing nonlinear free vibration behaviors of a rotating composite thin-walled beam with large deformation.%研究具有几何非线性的旋转复合材料薄壁梁的自由振动.梁的变形引入了Von Kármán几何非线性,基于Hamilton原理和变分渐进法(Variational-Asymptotical Method-VMA),导出旋转复合材料薄壁梁的非线性振动偏微分方程组.采用Galerkin法将振动方程离散化为常微分方程组.借助于谐波平衡法(Harmonic Balance Method-HBM)建立自由振动的振幅-非线性固有频率关系方程.将上述方程化为非线性特征值问题,采用迭代算法进行求解.将所建立的旋转复合材料薄壁梁非线性自由振动分
Khouli, F.; Langlois, R. G.; Afagh, F. F.
2007-02-01
An asymptotically correct theory for multi-cell thin-wall anisotropic slender beams that includes the shell bending strain measures is extended to include embedded active fibre composites (AFCs). A closed-form solution of the asymptotically correct cross-sectional actuation force and moments is obtained. Active thin-wall beam theories found in the literature neglect the shell bending strains, which lead to incorrect predictions for certain cross-sections, while the theory presented is shown to overcome this shortcoming. The theory is implemented and verified against single-cell examples that were solved using the University of Michigan/Variational Beam Sectional Analysis (UM/VABS) software. The stiffness constants and the actuation vector are obtained for two-cell and three-cell active cross-sections. The theory is argued to be reliable for efficient initial design analysis and interdisciplinary parametric or optimization studies of thin-wall closed cross-section slender beams with no initial twist or obliqueness.
Thin Wall Austempered Ductile Iron (TWADI)
M. Górny; E. Fraś
2009-01-01
In this paper the analysis of thin walled castings made of ductile iron is considered. It is shown that thin wall austempered ductile iron can be obtained by means of short-term heat treatment of thin wall castings without addition of alloying elements. Metallographic examinations of 2 mm thin walled castings along with casting with thicker wall thickness (20x28 mm) after different austempring conditions are presented. It has been proved that short-term heat treatment amounted 20 minutes of a...
Extension-twist coupling optimization in composite rotor blades
Ozbay, Serkan
2005-07-01
For optimal rotor performance in a tiltrotor aircraft the difference in the inflow and the rotor speeds between the hover and cruise flight modes suggests different blade twist and chord distributions. The blade twist rates in current tiltrotor applications are defined based upon a compromise between the figure of merit in hover and propeller efficiency in airplane mode. However, when each operation mode is considered separately the optimum blade distributions are found to be considerably different. Passive blade twist control, which uses the inherent variation in centrifugal forces on a rotor blade to achieve optimum blade twist distributions in each flight mode through the use of extension-twist coupled composite rotor blades, has been considered for performance improvement of tiltrotor aircraft over the last two decades. The challenge for this concept is to achieve the desired twisting deformations in the rotor blade without altering the aeroelastic characteristics of the vehicle. A concept referred to as the sliding mass concept is proposed in this work in order to increase the twist change with rotor speed for a closed-cell composite rotor blade cross-section to practical levels for performance improvement in a tiltrotor aircraft. The concept is based on load path changes for the centrifugal forces by utilizing non-structural masses readily available on a conventional blade, such as the leading edge balancing mass. A multilevel optimization technique based on the simulated annealing method is applied to improve the performance of the XV15 tiltrotor aircraft. A cross-sectional analysis tool, VABS together with a multibody dynamics code, DYMORE are integrated into the optimization process. The optimization results revealed significant improvements in the power requirement in hover while preserving cruise efficiency. It is also shown that about 21% of the improvement is provided through the sliding mass concept pointing to the additional flexibility the concept
Statics of Thin-Walled Pretwisted Beams
DEFF Research Database (Denmark)
Krenk, Steen; Gunneskov, O.
1981-01-01
The displacement and strain fields of thin-walled pretwisted beams are prescribed in terms of generalized displacements for extension, bending, torsion and warping. Differential equations and boundary conditions are obtained from the elastic potential energy functional without assuming coincidenc...
Fillability of Thin-Wall Steel Castings
Energy Technology Data Exchange (ETDEWEB)
Robert C. Voigt; Joseph Bertoletti; Andrew Kaley; Sandi Ricotta; Travis Sunday
2002-07-30
The use of steel components is being challenged by lighter nonferrous or cast iron components. The development of techniques for enhancing and ensuring the filability of thin-wall mold cavities is most critical for thinner wall cast steel production. The purpose of this research was to develop thin-wall casting techniques that can be used to reliably produce thin-wall castings from traditional gravity poured sand casting processes. The focus of the research was to enhance the filling behavior to prevent misrunds. Experiments were conducted to investigate the influence of various foundry variables on the filling of thin section steel castings. These variables include casting design, heat transfer, gating design, and metal fluidity. Wall thickness and pouring temperature have the greatest effect on casting fill. As wall thickness increases the volume to surface area of the casting increases, which increases the solidification time, allowing the metal to flow further in thicker sect ions. Pouring time is another significant variable affecting casting fill. Increases or decreases of 20% in the pouring time were found to have a significant effect on the filling of thin-wall production castings. Gating variables, including venting, pouring head height, and mold tilting also significantly affected thin-wall casting fill. Filters offer less turbulent, steadier flow, which is appropriate for thicker castings, but they do not enhance thin-wall casting fill.
Thin-walled reinforcement lattice structure for hollow CMC buckets
Energy Technology Data Exchange (ETDEWEB)
de Diego, Peter
2017-06-27
A hollow ceramic matrix composite (CMC) turbine bucket with an internal reinforcement lattice structure has improved vibration properties and stiffness. The lattice structure is formed of thin-walled plies made of CMC. The wall structures are arranged and located according to high stress areas within the hollow bucket. After the melt infiltration process, the mandrels melt away, leaving the wall structure to become the internal lattice reinforcement structure of the bucket.
Institute of Scientific and Technical Information of China (English)
赵卫锋; 张武东; 周靖; 曹勇龙; 龙志林
2014-01-01
研究方形薄壁型钢管/多层竹胶板组合空芯柱（Square, thin-walled steel tube/multi-layered bamboo plywood composite hollow column，SBCC）的轴心抗压性能，揭示其受力破坏机理，为其工程应用提供试验和理论基础。考虑试件的截面尺寸、空心率及长细比对SBCC抗压承载力的影响，设计制作了15根轴心抗压试件，通过SBCC的抗压性能测试，考察测试过程中的破坏形态和变形特征，分析各因素对试件轴心抗压力学性能的影响规律。试验结果表明：SBCC轴心抗压失效主要有竹胶合板材料破坏、基体胶结面开胶破坏以及整体失稳破坏3种形态，总体上胶结面间的胶粘强度及长细比是决定破坏模式的主要因素。SBCC的轴心抗压承载力随组合柱竹净截面面积、空心率的增大而显著提高，随长细比的增大而降低。通过试验数据的非线性回归分析，建立了SBCC的轴心抗压承载力计算公式，公式估算结果与试验测试结果的误差在20%以内。该研究结果表明SBCC是一种轴心抗压性能较优异的钢/竹组合结构单元，可实现“以竹代木”，作为工程结构用材的应用前景广阔。%The development of laminated-bamboo has broadened the application range of bamboo material in the field of structural engineering. A new type of steel/laminated bamboo composite column was developed based on the existing bamboo composite element for constructing multi-story, pre-fabricated, column-supported, and bamboo-framed buildings, and named as square thin-walled steel tube/multi-layered bamboo plywood composite hollow column (SBCC). The core of the SBCC is a square thin-walled steel tube, and the exterior column consists of several high-strength bamboo plywood pieces (such as bamboo mat plywood) that are bonded together using a structural adhesive to form a composite hollow column. SBCCs are a new type of steel/bamboo composite with excellent physical and
Analysis and Parametric Investigation of Active Open Cross Section Thin Wall Beams
Griffiths, James
The static behaviour of active Open Cross Section Thin Wall Beams (OCSTWB) with embedded Active/Macro Fibre Composites (AFCs/MFCs) has been investigated for the purpose of advancing the fundamental theory needed in the development of advanced smart structures. An efficient code that can analyze active OCSTWB using analytical equations has been studied. Various beam examples have been investigated in order to verify this recently developed analytical active OCSTWB analysis tool. The cross sectional stiffness constants and induced force, moments and bimoment predicted by this analytical code have been compared with those predicted by the 2-D finite element beam cross section analysis codes called the Variational Asymptotic Beam Sectional (VABS) analysis and the University of Michigan VABS (UM/VABS). Good agreement was observed between the results obtained from the analytical tool and VABS. The calculated cross sectional stiffness constants and induced force/moments, the constitutive relation and the six intrinstic static equilibrium equations for OCSTWB were all used together in a first-order accurate forward difference scheme in order to determine the average twist and deflections along the beam span. In order to further verify the analytical code, the static behaviour of a number of beam examples was investigated using 3-D Finite Element Analysis (FEA). For a particular cross section, the rigid body twist and displacements were minimized with the displacements of all the nodes in the 3-D FEA model that compose the cross section. This was done for a number of cross sections along the beam span in order to recover the global beam twist and displacement profiles from the 3-D FEA results. The global twist and deflections predicted by the analytical code agreed closely with those predicted by UM/VABS and 3-D FEA. The study was completed by a parametric investigation to determine the boundary conditions and the composite ply lay-ups of the active and passive plies that
Thin wall ductile and austempered iron castings
Directory of Open Access Journals (Sweden)
E. Fraś
2010-07-01
Full Text Available It has been shown that it is possible to produce thin wall castings made of ductile iron with wall thickness in the range of 1.2 to 2.9 mm(without chills, cold laps and misruns. Thin wall ductile iron castings can be lighter (380 g than their substitutes made of aluminium alloys (580g. The kinetics of austenitising transformation was studied in unalloyed ductile iron. The advance of transformations during austenitising was monitored by measurement the fraction of martensite and also by dilatometic studies. It has been shown that in thin wall ductile iron castings austenitising at 880 oC for 20 minutes is adequate to obtain the austenite matrix at the end of the first stage of austempering heat treatment cycle.
Inflated Sporopollenin Exine Capsules Obtained from Thin-Walled Pollen
Park, Jae Hyeon; Seo, Jeongeun; Jackman, Joshua A.; Cho, Nam-Joon
2016-06-01
Sporopollenin is a physically robust and chemically resilient biopolymer that comprises the outermost layer of pollen walls and is the first line of defense against harsh environmental conditions. The unique physicochemical properties of sporopollenin increasingly motivate the extraction of sporopollenin exine capsules (SECs) from pollen walls as a renewable source of organic microcapsules for encapsulation applications. Despite the wide range of different pollen species with varying sizes and wall thicknesses, faithful extraction of pollen-mimetic SECs has been limited to thick-walled pollen capsules with rigid mechanical properties. There is an unmet need to develop methods for producing SECs from thin-walled pollen capsules which constitute a large fraction of all pollen species and have attractive materials properties such as greater aerosol dispersion. Herein, we report the first successful extraction of inflated SEC microcapsules from a thin-walled pollen species (Zea mays), thereby overcoming traditional challenges with mechanical stability and loss of microstructure. Morphological and compositional characterization of the SECs obtained by the newly developed extraction protocol confirms successful protein removal along with preservation of nanoscale architectural features. Looking forward, there is excellent potential to apply similar strategies across a wide range of unexplored thin-walled pollen species.
Thin wall ductile and austempered iron castings
E. Fraś; M. Górny
2010-01-01
It has been shown that it is possible to produce thin wall castings made of ductile iron with wall thickness in the range of 1.2 to 2.9 mm(without chills, cold laps and misruns). Thin wall ductile iron castings can be lighter (380 g) than their substitutes made of aluminium alloys (580g). The kinetics of austenitising transformation was studied in unalloyed ductile iron. The advance of transformations during austenitising was monitored by measurement the fraction of martensite and also by dil...
Vibrations in High Speed Milling of Thin-walled Components
Institute of Scientific and Technical Information of China (English)
WANG Tongyue; HE Ning; LI Liang
2006-01-01
Thin-walled structures have been widely used in the aerospace industry. The dynamic interaction between the milling cutter and thin-walled workpiece can easily lead to vibration. This paper investigates the vibration caused during milling the thin-walled workpiece on the NC machining center, presents a theoretical milling vibration model of thin-walled beam. The model was verified by using milling experiments and numerical simulations. Some valuable conclusions are derived, this will be references to scientific research and guides to the vibration-free milling of thin-walled structures at different cutting speeds.
Distortional Modes of Thin-Walled Beams
DEFF Research Database (Denmark)
Jönsson, Jeppe; Andreassen, Michael Joachim
2009-01-01
The classic thin-walled beam theory for open and closed cross-sections can be generalized by including distortional displacement modes. The introduction of additional displacement modes leads to coupled differential equations, which seems to have prohibited the use of exact shape functions...... in the modelling of coupled torsion and distortion. However, if the distortional displacement modes are chosen as those which decouple the differential equations as in non proportionally damped modal dynamic analysis then it may be possible to use exact shape functions and perform analysis on a reduced problem...
Seismic Behavior of Thin-Walled C Steel-Bamboo Plywood Composite Column%薄壁C型钢—竹胶板组合箱型柱抗震性能试验
Institute of Scientific and Technical Information of China (English)
蒋天元; 李玉顺; 单炜; 张王丽
2011-01-01
提出了一种新型的组合柱—以两块薄壁C型钢为基本骨架口对口拼接,在型钢腹板及翼缘处用结构胶黏剂黏结4块竹帘胶合板,形成截面形式为箱型的薄壁C型钢—竹胶板组合柱.以钢板厚度、长细比、轴压比等为基本参数,对5根组合柱进行了拟静力加载试验,观察组合柱在不同参数设置下的钢板、竹胶板的应变变化和荷载—位移滞回曲线,得到了组合柱的承载力指标和耗能系数、延性系数等抗震性能指标,在此基础上进行了组合柱的承载力计算方法分析.结果表明,长细比和钢板厚度对钢—竹组合柱加载初期的受力性能影响不明显,但影响柱子的后期极限承载力和刚度,而轴压比对组合柱的极限承载力和延性性能起着决定作用.根据钢—竹组合柱在弹性阶段的轴压力大小和应力—应变关系,提出了组合柱的力学简化模型及屈服承载力计算方法,其计算结果与试验值吻合较好.%The paper presents a new type of composite column composed by gluing four pieces of bamboo plywood on the surface of box columns and two pieces of thin-walled C steel spliced mouth to mouth in the core. Pseudo-static tests on a total of 5 composite columns were conducted in terms of steel sheet thickness, slenderness ratio and axial compression ratio of the columns. The bearing capacity, dissipative coefficient, ductility, and other indexes about seismic performance were ac quired by analyzing the changes of strain in the steel sheets and bamboo plates and the load-displacement hysteretic curves under different parameters. Result shows that slenderness ratio and steel sheet thickness have little effect on the mechanical behaviors of initial load, but have effect on ultimate strength and stiffness under load imposed in the late period. Axial compression ratio makes a great dif ?rence in bearing capability and ductility performances of these columns. Based on the measurement of
Institute of Scientific and Technical Information of China (English)
DU Baisong; GE Yaojun; ZHOU Zheng
2007-01-01
In this paper,an analytical method is proposed for calculating torsional constants for complicated thin-walled cross-sections with arbitrary closed or open rib stiffeners.This method uses the free torsional theory and the principle of virtual work to build goveming equilibrium equations involving unknown shear flows and twisting rate.After changing the form of the equations and combining these two unknowns into one,torsional function,which is a function of shear flow,shear modulus,and twisting rate,is included in the governing equations as only one of the unknowns.All the torsional functions can be easily obtained from these homogeneous linear equations,and torsional constants can be easily obtained from the torsional functions.The advantage of this method is that we can easily and directly obtain torsional constants from the torsional functions,rather than the more sophisticated shear flow and twisting rate calculations.Finally,a complicated thin-walled cross-section is given as a valid numerical example to verify the analytical method,which is much more accurate and simpler than the traditional finite element method.
Thermo-Insulating Moulding Sand for thin Walled Castings
Directory of Open Access Journals (Sweden)
Cholewa M.
2014-10-01
Full Text Available In paper the selection of the composition and determination of main properties of novel moulding sand was described. The mail goal was to create moulding sand characterized by high thermal insulating properties in relations with low specific weight. This type of moulding sand will find application in thin walled castings with complex geometry, in particular for cores of the skeleton castings. In this work the results of the compressive strength, permeability and friability was presented. It was noted that aluminosilicate microspheres are suitable as moulding sand matrix. Influence of the polyglicol addition on quality and properties of the moulding sand was described. The use of the aluminosilicate microspheres allowed to obtain the moulding sand characterized by high insulation rate, low specific weight and good mechanical properties.
Institute of Scientific and Technical Information of China (English)
谢紫龙; 尚柏林; 常飞; 杨哲; 尹俊杰
2013-01-01
Delamination damage was prefabricated on composite thin-wall stiffened panels used in advanced aircraft by impact test,and then the buckling,post-buckling carrying capacity and failure modes of the samples with and without damage at shear load were studied by shear tests.The result show that the delamination damage could reduce the stiffness of the composite thin-wall stiffned panel and change its failure mode,and cause the obvious local buckling appearing during shear process,and thus greatly reduced bucking,post-bucking and damage loads.%利用冲击试验对先进飞机上常用的复合材料薄壁加筋板预制分层损伤,通过剪切试验研究了完好试样和损伤试样在剪切载荷下的屈曲、后屈曲承载能力及破坏形式.结果表明:分层损伤会降低复合材料薄壁加筋板的刚度,并改变其破坏形式,使其在剪切过程中出现明显的局部屈曲,进而大大降低其屈曲失稳载荷、后屈曲承载载荷和破坏载荷.
Institute of Scientific and Technical Information of China (English)
Luo Yong; Cui Xiaorong; Lu Hua
2008-01-01
Based on blasting demolition of high thin-wall hyperbolic reinforced concrete cool tower,by virtue of engi-neering practice of blasting the tube concrete structures,the analysis and research were made on the mechanism of cool tower collapse through selecting blasting parameters and selecting gap form,gap size and gap angle.The cool tower was twisted,collapsed directionally and broken weU according to the design requirements.The expected results and purpo-ses of blasting were obtained with no back blow,total blasted pile approximates to 4 ～ 5 m,no occurrence of flying stones and no damage to fixed buildings and equipment,the large-sized hyperbolic thin-wall reinforced concrete cool towers are twisted during blasting and it collapses well with good breaking.The test and measurement of blasting vibra-ting velocity was carried out during blasting and the measuring results are much less than critical values specified by Safety Regulations for Blasting.The study shows that gap form,gap size and gap angle are the key factors to cool tower collapse and will give beneficial references to related theoretical study and field application.
Concept modeling of tapered thin-walled tubes
Institute of Scientific and Technical Information of China (English)
Yu-cheng LIU; Michael L.DAY
2009-01-01
This paper presents a method to create concept models for the tapered thin-walled tubes using beam elements and spring elements. Developed concept tapered beam models with different taper angles and cross sections are compared with those detailed models through impact analyses. Important crash results are recorded and compared, and the relatively good agreement is achieved between these analyses. Concept modeling steps are illustrated in detail, and a general concept modeling method for such thin-walled tubes is summarized and presented.
Active stabilization of thin-wall structures under compressive loading
Welham, Jared; Calius, Emilio P.; Chase, J. Geoffrey
2003-08-01
The active suppression of elastic buckling instability has the potential to significantly increase the effective strength of thin-wall structures. Despite all the interest in smart structures, the active suppression of buckling has received comparatively little attention. This paper addresses the effects of embedded actuation on the compression buckling strength of laminated composite plates through analysis and simulation. Numerical models are formulated that include the influence of essential features such as sensor uncertainty and noise, actuator saturation and control architecture on the buckling process. Silicon-based strain sensors and diffuse laser distance sensors are both considered for use in the detection of incipient buckling behavior due to their increased sensitivity. Actuation is provided by paired distributions of piezo-electric material incorporated into both sides of the laminate. Optimal controllers are designed to command the structure to deform in ways that interfere with the development of buckling mode shapes. Commercial software packages are used to solve the resulting non-linear equations, and some of the tradeoffs are enumerated. Overall, the results show that active buckling control can considerably enhance resistance to instability under compressive loads. These buckling load predictions demonstrate the viability of optimal control and piezo-electric actuation for implementing active buckling control. Due to the importance of early detection, the relative effectiveness of active buckling control is shown to be strongly dependent on the performance of the sensing scheme, as well as on the characteristics of the structure.
Finite element based investigation of buckling and vibration behaviour of thin walled box beams
Directory of Open Access Journals (Sweden)
Ramkumar K.
2013-12-01
Full Text Available Thin-walled box type conventional and composite structures are having wide applications for building the structural system which are used in advanced ships, aerospace, civil, construction equipment and etc. Often these structures are subjected to vibration and buckling due to the environmental effect such as mechanical, thermal, electrical, magnetic, and acoustic or a combination of these. Also dampingmaterial and structural stiffness plays an important role for the improvement of vibration, noise control, fatigue and bulking resistance of these structures. So it is important to know the dynamic and buckling characteristics of these structures. Pre-stress in a structure affects the stiffness, which modifies the dynamic and stability characteristics of the structure. So it is also important to know the influence of pre-stress on the vibration and buckling character. In this paper, buckling and dynamic characteristics of the thin-walled box type structures are analyzed using finite element software ANSYS.
A distortional semi-discretized thin-walled beam element
DEFF Research Database (Denmark)
Andreassen, Michael Joachim; Jönsson, Jeppe
2013-01-01
Due to the increased consumption of thin-walled structural elements there has been increasing focus and need for more detailed calculations as well as development of new approaches. In this paper a thin-walled beam element including distortion of the cross section is formulated. The formulation...... is based on a generalized beam theory (GBT), in which the classic Vlasov beam theory for analysis of open and closed thin-walled cross sections is generalized by including distortional displacements. The beam element formulation utilizes a semi-discretization approach in which the cross section...... is discretized into wall elements and the analytical solutions of the related GBT beam equations are used as displacement functions in the axial direction. Thus the beam element contains the semi-analytical solutions. In three related papers the authors have recently presented the semi-discretization approach...
Simulation of Welding of Thin-Walled Pipe
Directory of Open Access Journals (Sweden)
Marek GEBAUER
2013-12-01
Full Text Available The presented paper deals with the residual stress after a welding operation performed by using the TIG method. It was necessary to determine whether or not tension plays a major role in the distortion of the geometry of a thin-walled pipe, or in other words, whether the drawing dimension of the ovality exceeds the specified tolerance. The result of this simulation will help to determine whether or not designers will have to find another technological solution to complete parts. The assembly consists of three parts: the weld bead, thin-walled pipe, and hoop, which are connected by welds as a final product.
Institute of Scientific and Technical Information of China (English)
陈明; 芦文文; 刘凯
2014-01-01
According to the composite column of double cold-formed thin-walled C steel back to back connected with gusset plate, the test and finite element analysis were carried out to study the stability bearing capacity and failure modes of the specimen under eccentric loading.The elements such as slenderness ratio, gusset plate thickness and gusset plate spacing were discussed , which produced the impacts to composite column ’ s bearing capacity, the relationship between stiffness and axial loading, and the curves of M-φof eccentricity.The results revealed that before the overall instability the local-buckling was occurred, the failure modes were belonging to the in-plane-flexural buckling.The major factors are slenderness ratio, eccentricity and gusset plate spacing which effected the mechanical behavior, while the gusset plate thickness has no obvious impact.In the end, the calculation method of the bearing capacity of the cold-formed thin-walled column was compared with that in“Technical Code of Cold-Formed Thin-Walled Section Steel Structures” ( GB 50018-2002 ) , some suggestions based on the type of composite section column calculation were put forward , and the bearing capacity correction coefficient of the steel composite columns was given .%针对带垫板的双肢背靠背C型钢组合柱，通过试验和有限元模拟分析，研究该类型组合柱在偏心荷载作用下的受力特性，就偏心距、长细比、垫板厚度和间距等参数对组合柱承载力、刚度与轴向荷载的关系和M-φ曲线的影响进行讨论。结果表明：C型钢腹板和受压翼缘在整体失稳之前出现了严重的局部屈曲，组合柱的破坏模式均为弯矩作用平面内的弯曲失稳。长细比、偏心距和垫板间距是影响组合柱受力性能的主要因素，垫板厚度的影响有限。最后与规范GB 50018-2002《冷弯薄壁型钢结构技术规范》规定的柱承载力的计算方法进行对比，对该类组合柱的
Soft composites with the twisted plywood microstructure, a lesson from nature
Kim, Yongjin; Crosby, Alfred; Crosby Research Group Team
The twisted plywood microstructure, consisting of rigid structural units within a continuous matrix, is known to be prevalent in many natural materials, including exoskeletons of crustacean, scales of fish, and even bones of mammals. Although it is yet to be resolved whether this structure is a product of evolution or an inevitable consequence of chirality of building blocks, nature utilizes the structure extensively to create various components. Previous studies have focused on fabricating and characterizing synthetic composites with similar structures; however, these composites have been based on a rigid matrix, e.g. an epoxy resin, and hard fibers, e.g. carbon fibers. For this combination of materials, it has been difficult to deconvolute the specific roles of each component. For a better understanding of the advantage of the structure, we have developed flexible composites, comprising a soft matrix and hard fiber bundles at two different size scales. Macroscopic engineered samples were created by combining elastomer and hard fibers, while sub-micron composites are fabricated from self-assembled nanoparticle ribbons and hydrogel matrices. The advantageous mechanical response of these flexible twisted plywood composites is characterized and presented. This material is based upon work supported by, or in part by, the U. S. Army Research Laboratory and the U. S. Army Research Office under Contract/Grant Number W911NF-15-1-0358.
The Dynamic Similitude Design Method of Thin Walled Structures and Experimental Validation
Directory of Open Access Journals (Sweden)
Zhong Luo
2016-01-01
Full Text Available For the applicability of dynamic similitude models of thin walled structures, such as engine blades, turbine discs, and cylindrical shells, the dynamic similitude design of typical thin walled structures is investigated. The governing equation of typical thin walled structures is firstly unified, which guides to establishing dynamic scaling laws of typical thin walled structures. Based on the governing equation, geometrically complete scaling law of the typical thin walled structure is derived. In order to determine accurate distorted scaling laws of typical thin walled structures, three principles are proposed and theoretically proved by combining the sensitivity analysis and governing equation. Taking the thin walled annular plate as an example, geometrically complete and distorted scaling laws can be obtained based on the principles of determining dynamic scaling laws. Furthermore, the previous five orders’ accurate distorted scaling laws of thin walled annular plates are presented and numerically validated. Finally, the effectiveness of the similitude design method is validated by experimental annular plates.
Standard surface grinder for precision machining of thin-wall tubing
Jones, A.; Kotora, J., Jr.; Rein, J.; Smith, S. V.; Strack, D.; Stuckey, D.
1967-01-01
Standard surface grinder performs precision machining of thin-wall stainless steel tubing by electrical discharge grinding. A related adaptation, a traveling wire electrode fixture, is used for machining slots in thin-walled tubing.
Drag-based composite super-twisting sliding mode control law design for Mars entry guidance
Zhao, Zhenhua; Yang, Jun; Li, Shihua; Guo, Lei
2016-06-01
In this paper, the drag-based trajectory tracking guidance problem is investigated for Mars entry vehicle subject to uncertainties. A composite super twisting sliding mode control method based on finite-time disturbance observer is proposed for guidance law design. The proposed controller not only eliminates the effects of matched and mismatched disturbances due to uncertainties of atmospheric models and vehicle aerodynamics but also guarantees the continuity of control action. Numerical simulations are carried out on the basis of Mars Science Laboratory mission, where the results show that the proposed methods can improve the Mars entry guidance precision as compared with some existing guidance methods including PID and ADRC.
Ayad, Mohamed F; Bahannan, Salma A; Rosenstiel, Stephen F
2011-01-01
Thin-walled root canals always present a challenge to dentists to select a restorative treatment that does not further weaken the thin tooth structure. The prognosis of dowel and core restorations can be unpredictable. This clinical report describes the treatment of a patient with extensive caries extending into the root canal of an endodontically treated maxillary central incisor. The use of a flowable composite resin in combination with a quartz fiber reinforced post is described, resulting in the rehabilitation of a structurally compromised root canal with satisfactory esthetic and functional outcomes.
Assumption tests regarding the ‘narrow’ rectangles dimensions of the open thin wall sections
Oanta, E.; Panait, C.; Sabau, A.; Barhalescu, M.; Dascalescu, A. E.
2016-08-01
Computer based analytic models that use the strength of materials theory are inheriting the accuracy given by the basic simplifying hypotheses. The according assumptions were rationally conceived hundreds of years ago in an age when there was no computing instrument, therefore the minimization of the necessary volume of calculi was an important requirement. An initial study was an attempt to evaluate how ‘thin’ may be the walls of an open section in order to have accurate results using the analytic calculus method. In this initial study there was compared the calculus of the rectangular sections loaded by twisting moments vs. a narrow section under the same load. Being compared analytic methods applied for a simple shape section, a more thorough study was required. In this way, we consider a thin wall open section loaded by a twisting moment, section which is discretized in ‘narrow’ rectangles. The ratio of the sides of the ‘narrow’ rectangles is the variable of the study. We compare the results of the finite element analysis to the results of the analytic method. The conclusions are important for the development of computer based analytic models which use parametrized sections for which different sets of calculus relations may be used.
Distortional eigenmodes and solutions for thin-walled beams
DEFF Research Database (Denmark)
Andreassen, Michael Joachim; Jönsson, Jeppe
2011-01-01
This paper presents a generalization of the classic theory for thin-walled beams by including distortional displacements. A condensed presentation of the novel finite-elementbased displacement approach in [1,2] is given, where specific distortional displacement fields, which decouple the differen......This paper presents a generalization of the classic theory for thin-walled beams by including distortional displacements. A condensed presentation of the novel finite-elementbased displacement approach in [1,2] is given, where specific distortional displacement fields, which decouple...... found for the homogeneous system the final uncoupled set of distortional differential equations including the load terms are presented and the full solution is given, including an illustrative example. This new approach is an alternative to the traditional first order GBT method....
Static and dynamic buckling of thin-walled plate structures
Kubiak, Tomasz
2013-01-01
This monograph deals with buckling and postbuckling behavior of thin plates and thin-walled structures with flat wall subjected to static and dynamic load. The investigations are carried out in elastic range. The basic assumption here is the thin plate theory. This method is used to determination the buckling load and postbuckling analysis of thin-walled structures subjected to static and dynamic load. The book introduces two methods for static and dynamic buckling investigation which allow for a wider understanding of the phenomenon. Two different methods also can allow uncoupling of the phenomena occurring at the same time and attempt to estimate their impact on the final result. A general mathematical model, adopted in proposed analytical-numerical method, enables the consideration of all types of stability loss i.e.local, global and interactive forms of buckling. The applied numerical-numerical method includes adjacent of walls, shear-lag phenomenon and a deplanation of cross-sections.
Manufacturing of thin walled near net shape iron castings
DEFF Research Database (Denmark)
Larsen, Per Leif
2003-01-01
The demand for near net shape thin walled iron castings is growing. This has several reasons, the main one is the need for lowering the fuel consumption of cars; the easiest way to do that is to lower the weight of the cars. The best way to do this was for a period of time believed...... to be substituting iron casings with aluminum castings. Substituting iron castings with aluminum castings is not as easy as first believed, and hence the substitution is very slow. This combined with the lack of fully exploiting the potential in iron castings, makes research in iron castings interesting. The 60.......000.000 cars produced world wide each year consumes enormous amounts of cast parts ! The aim of the project is to develop the green sand molding method on DISAMATIC to be able to deal with the new demands for thin walled near net shape castings in iron....
On milling of thin-wall conical and tubular workpieces
Tsai, Mu-Ping; Tsai, Nan-Chyuan; Yeh, Cheng-Wei
2016-05-01
Thin-wall tubular-geometry workpieces have been widely applied in aircraft and medical industries. However, due to the special geometry of this kind of workpieces and induced poor machinability, the desired accuracy of machining tends to be greatly degraded, no matter what type of metal-cutting task such as milling, drilling or turning is undertaken. Though numerous research reports are available that the tool path can be planned on the basis of preset surface profile before actual milling operation is performed, it is still difficult to predict the real-time surface profile errors for peripheral milling of thin-wall tubular workpieces. Instead of relying on tool path planning, this research is focused on how to real-time formulate the appropriate applied cutting torque via feedback of spindle motor current. On the other hand, a few suitable cutting conditions which are able to prevent potential break/crack of thin-wall workpieces and enhance productivity but almost retain the same cutting quality is proposed in this research. To achieve this goal, estimated surface profile error on machined parts due to deflections caused by both tool and workpiece is studied at first. Traditionally, by adjusting cutting parameters such as feed rate or cut depth, the deflection of tool or workpiece can be expected not to exceed the specified limit. Instead, an effective feedback control loop is proposed by this work for applying real-time appropriate applied cutting torque to prevent potential break/crack of the thin-wall conical workpieces. The torque estimation approach by spindle motor current feedback and the corresponding fuzzy logic controller are employed. Compared with constant cutting torque during milling operation in tradition manner, it is observed that the time consumption of milling cycle by aid of the aforesaid fuzzy logic controller is greatly shortened while the resulted cutting accuracy upon finish of workpiece can be almost retained.
Institute of Scientific and Technical Information of China (English)
王静峰; 余波; 朱旭峰; 董传明
2013-01-01
为揭示地震作用下开洞类型和开洞率对冷弯薄壁管桁架组合墙体的抗震性能影响,进行六榀足尺冷弯薄壁管桁架组合墙体的水平低周反复荷载试验,了解其抗震性能和破坏模式,深入研究墙体的水平荷载-水平位移滞回曲线和骨架曲线、强度和刚度退化规律、耗能能力等.结合现有规范,对新型墙体的延性进行评价.试验表明,冷弯薄壁管桁架结构组合墙体具有良好的滞回性能、延性和耗能能力,其中延性系数μ=3.78 ～6.54,极限状态能量耗散系数E =0.55 ～0.68;开洞类型、开洞率和蒙皮效应对此类墙体的抗震性能影响较大,在设计中应合理考虑这些因素.双面OSB板对冷弯薄壁骨架结构起到较好的蒙皮效应；墙体开洞会削弱墙体的承载力和刚度,当开洞面积较小时增加四肢柱数量和加强洞口两侧构造可明显提高其受力性能和抗震性能.%To investigate the influence of opening type and opening rate on seismic behavior of composite walls with cold-formed thin-walled steel tube truss, an experimental program on six full-scale specimens under horizontal cyclic loading was conducted. The seismic behavior and failure modes of the composite walls were investigated. The load-displacement hysteresis curves and envelope curves, degeneration regulation of strength and stiffness, and energy dissipation were also analyzed. The test results show that the proposed composite wall has good hysteretic behavior, ductility and energy dissipation, for which ductility coefficient μ = 3 . 78 ~ 6. 54 and energy dissipation coefficient E -0. 55 ~ 0. 68. It is found that the opening type, the opening rate and the skin diagram action may affect the seismic behavior of the composite walls, and hence these parameters should be considered effectively in the structural design. The double-side OSB plates have good skin diaphragm effects on the cold-formed thin-walled steel framework. The strength
Isogeometric analysis for thin-walled composite structures
Guo, Y.
2016-01-01
The conceptual ideas behind isogeometric analysis (IGA) are aimed at unifying computer aided design (CAD) and finite element analysis (FEA). Isogeometric analysis employs the non-uniform rational B-spline functions (NURBS) used for the geometric description of a structure to approximate its physical
Structure of ductile iron in thin walled castings
Directory of Open Access Journals (Sweden)
M. Górny
2007-12-01
Full Text Available It this work it has been shown that it is possible to produce thin wall ductile iron (TWDI castings with considerably length using Archimedes spiral with wall thickness of 1, 2 and 3 mm. Inmould technique was used to produce TWDI. It has been estimated castability and metallographic investigations were made using different moulding materials. From castability measurements result that it is possible to obtain thin wall ductile iron castings with wall thickness down to 1 mm with castability of 200 mm. Using mould with small ability to absorb heat castability increases twice. At wall thickness equal 3 mm castability reaches 1000 mm and using LDASC sand its value increases to over 1500 mm. Structure parameters for different wall thickness and moulding materials (graphite nodule count, ferrite and cementite fraction are plotted versus distance from the beginning of spiral. It is shown strong influence of LDASC sand (material with small ability to absorb heat on structure parameters (NF, Vf i VC revealing gradient character of TWDI.
Linear motion feed through with thin wall rubber sealing element
Mikhailov, V. P.; Deulin, E. A.
2017-07-01
The patented linear motion feedthrough is based on elastic thin rubber walls usage being reinforced with analeptic string fixed in the middle part of the walls. The pneumatic or hydro actuators create linear movement of stock. The length of this movement is two times more the rubber wall length. This flexible wall is a sealing element of feedthrough. The main advantage of device is negligible resistance force that is less then mentioned one in sealing bellows that leads to positioning error decreasing. Nevertheless, the thin wall rubber sealing element (TRE) of the feedthrough is the main unreliable element that was the reason of this element longevity research. The theory and experimental results help to create equation for TRE longevity calculation under vacuum or extra high pressure difference action. The equation was used for TRE longevity determination for hydraulic or vacuum equipment realization also as it helps for gas flow being leaking through the cracks in thin walls of rubber sealing element of linear motion feedthrough calculation.
Institute of Scientific and Technical Information of China (English)
张家亮; 李玉顺; 翟家磊; 黄帅
2016-01-01
It was presented the heat transfer behavior of a new form of energy saving composite walls composed of bamboo plywood and cold-formed thin-walled C steel.Two bamboo plywood laths were glued and cold-formed thin-walled steel channel as wall keel, and two pieces of bamboo plywoods on the upper and lower side of the wall keel, and then filled insulation materials were filled inside and posted outside.It was studied the heat transfer behavior of 13 specimens experimentally through changing the thickness of specimens, different insulation materials and setting the exterior insulation system.It was also observed the thermal bridge at the location of keel and the temperature variation on the surface, and analyzed the effect of different thickness of composite wall, different types of filled insulation materials and extruded polystyrene board exterior insulation system on the heat insulation of the walls.On this basis, it was also analyzed and compared the experimental and theoretical values of heat transfer behavior of the composite walls. The results showed that the composite walls filled with glass wool or polyurethane foam had good thermal insulation properties, whose thermal conductivity was between 0.145 ~0.387 W/( m2·℃), and the polyurethane foam wall performance was better than that of glass wool wall.The extruded polystyrene board exterior insulation system could reduce the heat loss of composite walls and weaken the thermal bridge effect at the location of keel, thus improving the thermal insulation properties of composite walls.Using the guarded hot plate method, the thermal conductivities of main materials were measured, and the transfer coefficient of specimens was calculated.The average error between the calculated values and the experimental ones was about 5%, so they were in good agreement.Which showed that a reliable heat transfer behavior evaluation of bamboo-steel composite walls could be got through theoretical analysis.%以冷弯薄壁C型钢与其
Impact of Thin-Walled Projectiles with Concrete Targets
Directory of Open Access Journals (Sweden)
Rayment E. Moxley
1995-01-01
Full Text Available An experimental program to determine the response of thin-walled steel projectiles to the impact with concrete targets was recently conducted. The projectiles were fired against 41-MPa concrete targets at an impact velocity of 290 m/s. This article contains an outline of the experimental program, an examination of the results of a typical test, and predictions of projectile deformation by classical shell theory and computational simulation. Classical shell analysis of the projectile indicated that the predicted impact loads would result in circumferential buckling. A computational simulation of a test was conducted with an impact/penetration model created by linking a rigid-body penetration trajectory code with a general-purpose finite element code. Scientific visualization of the resulting data revealed that circumferential buckling was induced by the impact conditions considered.
Castability of ductile iron in thin walled castings (TWDI
Directory of Open Access Journals (Sweden)
M. Górny
2008-10-01
Full Text Available In work it has been presented results of influence of pouring temperature (Tp and carbon equivalent (CE on castability of ductile iron in thin walled castings with wall thickness of 1, 2 and 3 mm, respectively. Analysis was done on ductile iron with carbon equivalent ranging from 4.30 to 5.00 and pouring temperature varied from 1400 to 1500 oC. It has been shown that a statistical liner relationship exists between wall thickness and castability. Influence of CE and Tp on castability of cast iron flowing through channel with wall thickness of 2 and 3 mm can be presented by means of correlation equations (L = f(CE, Tp. Statistical analysis shows that pouring temperature has much higher influence on castability in comparison with influence of carbon equivalent.
Nonlinear behaviour and stability of thin-walled shells
Obodan, Natalia I; Gromov, Vasilii A
2013-01-01
This book focuses on the nonlinear behaviour of thin-wall shells (single- and multilayered with delamination areas) under various uniform and non-uniform loadings. The dependence of critical (buckling) load upon load variability is revealed to be highly non-monotonous, showing minima when load variability is close to the eigenmode variabilities of solution branching points of the respective nonlinear boundary problem. A novel numerical approach is employed to analyze branching points and to build primary, secondary, and tertiary bifurcation paths of the nonlinear boundary problem for the case of uniform loading. The load levels of singular points belonging to the paths are considered to be critical load estimates for the case of non-uniform loadings.
Magnetic properties of a long, thin-walled ferromagnetic nanotube
Energy Technology Data Exchange (ETDEWEB)
Sun, Chen, E-mail: chen.sun@physics.tamu.edu [Department of Physics and Astronomy, Texas A and M University, College Station, TX 77843-4242 (United States); Pokrovsky, Valery L. [Department of Physics and Astronomy, Texas A and M University, College Station, TX 77843-4242 (United States); Landau Institute for Theoretical Physics, Chernogolovka, Moscow District, 142432 (Russian Federation)
2014-04-15
We consider magnetic properties of a long, thin-walled ferromagnetic nanotube. We assume that the tube consists of isotropic homogeneous magnet whose spins interact via the exchange energy, the dipole–dipole interaction energy, and also interact with an external field via Zeeman energy. Possible stable states are the parallel state with the magnetization along the axis of the tube, and the vortex state with the magnetization along azimuthal direction. For a given material, which of them has lower energy depends on the value γ=R{sup 2}d/(Lλ{sub x}{sup 2}), where R is the radius of the tube, d is its thickness, L is its length and λ{sub x} is an intrinsic scale of length characterizing the ratio of exchange and dipolar interaction. At γ<1, the parallel state wins, otherwise the vortex state is stable. A domain wall in the middle of the tube is always energy unfavorable, but it can exist as a metastable structure. Near the ends of a tube magnetized parallel to the axis a half-domain structure transforming gradually the parallel magnetization to a vortex just at the edge of the tube is energy favorable. We also consider the equilibrium magnetization textures in an external magnetic field either parallel or perpendicular to the tube. Finally, magnetic field produced by a nanotube and an array of tubes is analyzed. - Highlights: • We obtain a simple criterion for stable state of a long, thin-walled magnetic tube. • A domain wall in the middle is always energy unfavorable, but can be metastable. • In external field different states show different hystereses. • Field produced by a tube and an array of tubes is calculated.
Mechanical testing of thin-walled zirconia abutments
Directory of Open Access Journals (Sweden)
Luigi CANULLO
2013-01-01
Full Text Available Although the use of zirconia abutments for implant-supported restorations has gained momentum with the increasing demand for esthetics, little informed design rationale has been developed to characterize their fatigue behavior under different clinical scenarios. However, to prevent the zirconia from fracturing, the use of a titanium connection in bi-component aesthetic abutments has been suggested. Objective Mechanical testing of customized thin-walled titanium-zirconia abutments at the connection with the implant was performed in order to characterize the fatigue behavior and the failure modes for straight and angled abutments. Material and Methods Twenty custom-made bi-component abutments were tested according to ISO 14801:2007 either at a straight or a 25° angle inclination (n=10 each group. Fatigue was conducted at 15 Hz for 5 million cycles in dry conditions at 20°C±5°C. Mean values and standard deviations were calculated for each group. All comparisons were performed by t-tests assuming unequal variances. The level of statistical significance was set at p≤0.05. Failed samples were inspected in a polarized-light and then in a scanning electron microscope. Results Straight and angled abutments mean maximum load was 296.7 N and 1,145 N, the dynamic loading mean Fmax was 237.4 N and 240.7 N, respectively. No significant differences resulted between the straight and angled bi-component abutments in both static (p=0.253 and dynamic testing (p=0.135. A significant difference in the bending moment required for fracture was detected between the groups (p=0.01. Fractures in the angled group occurred mainly at the point of load application, whereas in the straight abutments, fractures were located coronally and close to the thinly designed areas at the cervical region. Conclusion Angled or straight thin-walled zirconia abutments presented similar Fmax under fatigue testing despite the different bending moments required for fracture. The main
Institute of Scientific and Technical Information of China (English)
史艳莉; 王文达; 靳垚
2012-01-01
低层冷弯薄壁型钢结构住宅体系的抗震性能是进行该类结构推广应用的关键。该文基于ANSYS软件建立了该类结构体系的数值模型，在考虑冷弯薄型钢构件及门窗洞口加强与否、考虑组合墙体作用与否等情况下，分别进行了设防烈度为7度时常遇地震下的静力分析和弹性时程分析和设防烈度分别为7度、8度和9度时罕遇地震下的弹塑性时程分析。结果表明：常遇地震作用时结构弹性层间位移由风荷载控制，罕遇地震作用下结构弹塑性层问侧移则由地震作用控制；是否考虑组合墙体及墙面板材料特性对结构承载力、变形及抗震性能影响显著。在设防烈度分别为7度、8度和9度时的罕遇地震作用下，考虑组合墙体时结构最大弹塑性层间位移角可满足现行抗震规范（GB50011-2010）要求，双面OSB墙面板且角柱进行加强时抗震性能最好。该文结果可为进一步进行此类结构体系的抗震性能研究及应用提供参考。%The seismic behavior of the cold-formed thin-walled steel framing system of low-rise residential buildings is essential for their wide application. A numerical model was developed to simulate the performance of this type of structures using ANSYS. The steel members and the holes at doors or windows with or without the stiffened ribs, and the frames with or without composite walls were considered. Static and elastic dynamic time history analysis were performed under frequent earthquake based on the design earthquake intensity 7, and elastic-plastic dynamic time history analysis was performed under rare earthquake based on the design earthquake intensity 7, 8 and 9, respectively. It is shown that the elastic story-drift of the structure was determined by the wind loads mainly under the loading combination with frequent earthquake action, and the elastic-plastic story-drift was determined by the loading combination with rare
Thermal analysis of ductile iron in thin walled casting
Directory of Open Access Journals (Sweden)
M. Górny
2007-12-01
Full Text Available Hypereutectic ductile iron was cast in self hardening moulding sand to produce castings with the shape of Archimedes spirals and with wall thickness of 1, 2 and 3 mm. Inmould technique was used to produce thin wall ductile iron (TWDI. In this work it has been carried out thermal analysis in spiral with 3 mm wall thickness. The present work provides results of thermal analysis, that are initial temperature of metal in mould cavity, velocity of metal stream as well as solidification time. Measurement of temperature shows that there is essential its drop during filling of mould cavity and amounts 230 oC for distance 700 mm from the beginning of spiral. On the basic on first derivative of temperature versus time characteristic solidification points were distinguish, namely solidification of primary graphite, austenite dendrite and eutectic. Experimental measurements of temperature drop during filling of mould cavity along with microscopic examinations of castings structure can be used to verify computer modeling and simulation of fluid flow and thermal field in TWDI.
Springback of thin-walled tube NC precision bending and its numerical simulation
Institute of Scientific and Technical Information of China (English)
GU Rui-jie; YANG He; ZHAN Mei; LI Heng
2006-01-01
The springback is one of the key factors which affect the forming quality of thin-walled tube NC precision bending. The elastic-plastic finite element method was proposed to study the springback process of thin-walled tube NC precision bending and the combination of dynamic explicit algorithm and the static implicit algorithm was proposed to solve the whole process of thin-walled tube NC precision bending. Then,the 3D elastic-plastic finite element model was established based on the DYNAFORM platform,and the model was verified to be reasonable. At last,the springback rule of thin-walled tube NC precision bending and the effect of geometry and material parameters on the springback rule of thin-walled tube NC precision bending were studied,which is useful to controlling the springback of thin-walled tube NC precision bending,and the numerical simulation method can be used to study other effect of parameters on the forming quality of thin-walled tube NC precision bending.
Energy absorption of aluminum alloy thin-walled tubes under axial impact
Energy Technology Data Exchange (ETDEWEB)
Sun, Hongtu; Wang, Jian [Ludong University, Yantai (China); Shen, Guozhe; Hu, Ping [Dalian University of Technology, Dalian (China)
2016-07-15
Aluminum alloys are important technological materials for achieving the lightweight design of automotive structures. Many works have reported on the deformation and energy absorption of thin-walled tubes. Multicorner tubes with extra concave corners in the cross section were presented in this study to improve the energy absorption efficiency of aluminum alloy thin-walled tubes. The axial crushing of square and multicorner thin-walled tubes was simulated with the same cross-sectional perimeter. The method of folding element was applied to predict the crushing behavior of the thin-walled tubes under axial impact. The corners on the cross section were discussed to determine their effect on the energy absorption performance of thin-walled tubes. Results showed that the increasing performance of energy absorption of aluminum alloy thin-walled tubes was caused by the increasing number of corners on the cross section of multicorner tubes. Both the number and size of corners had an important effect on the crushing force efficiency of multicorner tubes. The maximum crushing force efficiency of multicorner tubes was 11.6% higher than that of square tubes with the same material consumption of thin-walled tubes. The multicorner tubes with 12 corners showed better energy absorption performance than the tubes with more than 12 corners; this high number of corners could lead to the small size of corners or unstable deformations. The high energy absorption performance of multicorner tubes prefers increasing the corner number and corner size of adjacent sides at the same time.
Institute of Scientific and Technical Information of China (English)
邓勇军; 姚勇; 刘欢; 陈代果; 徐刚
2014-01-01
保持砂卵石压实系数在大于87．7％的范围，对两组6根薄壁方钢管-砂卵石短柱的轴压静力性能进行了试验研究，分析了试件的破坏形态、极限承载力、轴向荷载-位移曲线以及轴向荷载-应变曲线等数据。试验结果表明：（1）薄壁方钢管-砂卵石短柱的破坏模式均为局部失稳破坏，且破坏后砂卵石随钢管变形而变形；（2）薄壁方钢管-砂卵石短柱轴向荷载-位移曲线根据钢管与砂卵石分担荷载情况大致可以分为钢管主要受力阶段、砂卵石压实阶段、砂卵石主要受力阶段、破坏阶段4个阶段；（3）增加壁厚能增强薄壁钢管与砂卵石的相互作用。%Under keeping the compaction factor of sandy pebble is greater than the suggestion of the range of 87 .7%, take static experimental study on the axis pressure mechanical property of two groups of six sandy -pebble-filled thin-walled square steel tubular short columns .The failure characteristics , the ultimate bearing capacity , the load-strain curves and the load -compression displacement curves of dif-ferent test specimens were comparatively analyzed .The experimental results indicate that ( 1 ) thin -walled square steel tube -sandy pebble short column failure mode are local buckling failure , the de-struction of the sand and gravel with deformed steel deformation ;(2) Thin-walled square steel tube -sandy pebble short column axial load -displacement curve according to the steel tube and sandy pebble all share the load situation can be divided into four stages: main stress on steel stage , compaction on sandy pebble stage , main stress on sandy pebble stage , failure stage;( 3 ) Increasing the wall thickness can significantly enhance the interaction of thin -walled steel pipe with sandy pebble .
Optimum design of the carbon fiber thin-walled baffle for the space-based camera
Yan, Yong; Song, Gu; Yuan, An; Jin, Guang
2011-08-01
The thin-walled baffle design of the space-based camera is an important job in the lightweight space camera research task for its stringent quality requirement and harsh mechanical environment especially for the thin-walled baffle of the carbon fiber design. In the paper, an especially thin-walled baffle of the carbon fiber design process was described and it is sound significant during the other thin-walled baffle design of the space camera. The designer obtained the design margin of the thin-walled baffle that structural stiffness and strength can tolerated belong to its development requirements through the appropriate use of the finite element analysis of the walled parameters influence sensitivity to its structural stiffness and strength. And the designer can determine the better optimization criterion of thin-walled baffle during the geometric parameter optimization process in such guiding principle. It sounds significant during the optimum design of the thin-walled baffle of the space camera. For structural stiffness and strength of the carbon fibers structure which can been designed, the effect of the optimization will be more remarkable though the optional design of the parameters chose. Combination of manufacture process and design requirements the paper completed the thin-walled baffle structure scheme selection and optimized the specific carbon fiber fabrication technology though the FEM optimization, and the processing cost and process cycle are retrenchment/saved effectively in the method. Meanwhile, the weight of the thin-walled baffle reduced significantly in meet the design requirements under the premise of the structure. The engineering prediction had been adopted, and the related result shows that the thin-walled baffle satisfied the space-based camera engineering practical needs very well, its quality reduced about 20%, the final assessment index of the thin-walled baffle were superior to the overall design requirements significantly. The design
DEFF Research Database (Denmark)
Pedersen, Karl Martin; Tiedje, Niels Skat
2008-01-01
Temperature measurement using thermocouples (TC’s) influence solidification of the casting, especially in thin wall castings. The problems regarding acquisition of detailed cooling curves from thin walled castings is discussed. Experiments were conducted where custom made TC’s were used to acquire...... cooing curves in thin wall ductile iron castings. The experiments show how TC’s of different design interact with the melt and how TC design and surface quality affect the results of the data acquisition. It is discussed which precautions should be taken to ensure reliable acquisition of cooling curves...
Investigation of solidification of thin walled ductile cast iron using temperature measurement
DEFF Research Database (Denmark)
Pedersen, Karl Martin; Tiedje, Niels
2005-01-01
Investigation of solidification of thin walled ductile cast iron can be improved using temperature measurement. This article includes some background of the precautions that have to be taken when measuring temperatures in thin walled castings. The aim is to minimize influence of temperature...... measurement on castings and to get sufficient response time of thermocouples. Investigation of thin wall ductile iron has been performed with temperature measurement in plates with thickness between 2,8 and 8mm. The cooling curves achieved are combined with examination of the microstructure in order to reveal...
NUMERICAL ANALYSIS OF THE CRITICAL STATE OF THIN-WALLED STRUCTURE WITH Z-PROFILE CROSS SECTION
Directory of Open Access Journals (Sweden)
Patryk Różyło
2017-03-01
Full Text Available The object of the study was the thin-walled profile with Z-shaped cross section made of the carbon-epoxy composite. Material model was prepared based on the implemented orthotropic properties. The purpose of study was to determine the value of the critical load at which buckling occurs, the form of buckling and operating characteristics in critical condition. In order to achieve this numerical analysis were carried out. Additionally, the effects of the modification in arrangement of layers of the laminate to the stability and strength of thin-walled composite structures was presented. Numerical studies were carried out using commercial simulation software - ABAQUS®. Within the FEM research, both forms of buckling and the associated critical load, dependent on the configuration the layers of the composite were achieved. Analysis of the obtained results, allowed the evaluation of the structure's work in relation to the level of energy consumption or rigidity estimation. In the paper only numerical simulations of the critical state were conducted.
Rohde, Sean E.
This document outlines the research performed on the design, manufacturing, modeling, and experimental testing of composite shafts possessing bend-twist coupling. A novel design for achieving this bend-twist coupling is presented. Closed form solutions modeling the behavior are derived for predicting the deformations of both tapered and non-tapered shafts possessing this novel design. The design and manufacturing of these shafts are detailed along with solutions to common problems faced. An experimental technique for quantifying the bend-twist coupling present in these shafts, using digital image correlation, is detailed. To understand how the shaft deforms under thermal changes, three separate analytical models are derived from three separate sets of assumptions. These are then compared to finite element analysis. Torsion experiments are performed on these shafts to determine the torsional strength and study how failure occurs. Micrographs were taken of these fractured shafts to observe the locations and manner of fracture. The design of these shafts is optimized as a function of performance objectives. Recommendations are then made for directions of future work.
De Luca, Gino; Rey, Alejandro D
2004-01-01
Biological fibrous composites commonly exhibit an architecture known as twisted plywood, which is similar to that of the cholesteric liquid-crystalline mesophases. The explanation for the structural similarity is that biological fibrous composites adopt a lyotropic cholesteric liquid-crystalline phase during their formation process. In this work, a mathematical model based on the Landau-de Gennes theory of liquid crystals has been developed to reproduce the process by which long chiral fibrous molecules form the twisted plywood structures observed in biological composites. The dynamics of the process was then further investigated by analytically solving a simplified version of the governing equations. Results obtained from the model are in good qualitative agreement with the theory of Neville [Biology of Fibrous Composites (Cambridge University Press, Cambridge, England, 1993)] who hypothesized the necessity of a constraining layer to lock the direction of the helical axis of the plywood in order to create a monodomain structure. Computational results indicate that the plywood architecture is obtained by a chiral front propagation process with a fully relaxed wake. The effects of chirality and concentration on the formation process kinetics are characterized.
PHYSICAL BASES OF SYSTEMS CREATION FOR MAGNETIC-IMPULSIVE ATTRACTION OF THIN-WALLED SHEET METALS
Directory of Open Access Journals (Sweden)
Y. Batygin
2009-01-01
Full Text Available The work is dedicated to the physical base of systems creating for the thin-walled sheet metals magnetic pulse attraction. Some practical realization models of the author’s suggestions are represented.
The precision cutting control research of automotive stainless steel thin wall pipe
Directory of Open Access Journals (Sweden)
Jin Lihong
2015-01-01
Full Text Available Stainless steel thin-walled tube are widely used in automobile industry at present, but as a result of thin wall pipe is poor strength and poor rigidity,which lead to deformation, shaped differencer and other problems in the process, it is hard to ensure the processing quality of parts. This paper proposes a method of thin stainless steel thin wall pipe cutting process in vehicle, greatly improved the problems and technical difficulties in the traditional process, the main research is about the cutting system and the hydraulic fixture design, obtained under low cost circumstances, it can realize high precision stainless steel pipes, high degree of automation to automatic cutting,simplified operation steps at the same time, increased the applicability of the system, provided a kind of advanced stainless steel thin wall pipe cutting device for the small and medium-sized enterprises.
Identification of cracks in thin-walled structures by means of wavenumber filtering
Kudela, Paweł; Radzieński, Maciej; Ostachowicz, Wiesław
2015-01-01
This research is related to a signal processing of full wavefield data as an effective tool for detection, localization and visualization of a crack growth in thin-walled structures. Full wavefield data of propagating Lamb waves in structures such as plates and shells made out of metallic alloys and composite laminates contain a wealth of information about wave pattern anomalies due to occurrence of a damage. The aim is to demonstrate a method for enhancing damage visualization in structures such that estimation of the length and orientation of the crack can be easily obtained. The proposed signal processing involves application of discrete fast Fourier transform, wavenumber domain filtering and inverse discrete Fourier transform. The method is further enhanced by a technique for compensation of the wave attenuation so that the effects of structural damage have the same influence regardless of the location. The concept is first illustrated on numerically simulated data, and then tested on experimental results. In the experiments, full wavefield measurements are obtained using a scanning laser Doppler vibrometer, which allows the measurement of displacements and/or velocities along three axes over a user-defined grid. In the proposed method only out-of-plane velocities are used. Tests performed on simple aluminum and composite plates with artificially introduced longitudinal cracks confirm the effectiveness of the method and its potential for application to the inspection of a variety of structural components.
A study of thin-walled Taylor column under the influence of rotation
Lai, Kuan-Ruei; Chu, Chin-Chou; Chang, Chien-Cheng
2016-11-01
An extended study of thin-walled Taylor column under the influence of rotating cylinder is presented with very consistent results in numerical simulations and laboratory experiments. In the previous set-up, the Taylor column effect is produced under the influence of protruded cylinder from the top lid, and the thin-walled Taylor column is formed by draining of the fluid at the bottom. The primary interest of this study is to investigate the influence to thin-walled Taylor column when the cylinder is exerted with a relative rotation rate under very small Rossby number (Ro = U / fR) and Ekman number (Ek = ν / fR2) . The flow patterns are performed with different cylinder height ratios (h/ H) along with varying relative rotation ratio of cylinder to the background α = ω / Ω . Steady-state solutions being solved numerically in the rotating frame are shown to have good agreements with experimental flow visualizations on the resulting appearance of deformed thin-walled Taylor columns. As a result, the thin-walled Taylor column is observed to strengthen up with increasing α, and weakens with decreasing α. In addition, the weakening thin-walled Taylor column is observed to experience a break through transition near the bottom, which penetration diverged the recirculating region into two portions. Supported by the Ministry of Science and Technology, TAIWAN ROC, Contract No's 103-2221-E002-099-MY3; 105-2221-E002-097-MY3.
CSIR Research Space (South Africa)
Forbes, A
2010-12-01
Full Text Available Research at the Mathematical Optics Group uses "twisted" light to study new quatum-based information security systems. In order to understand the structure of "twisted" light, it is useful to start with an ordinary light beam with zero twist, namely...
Thin-walled aluminum alloy tube NC precision bending based on finite element simulation
Institute of Scientific and Technical Information of China (English)
GU Rui-jie; YANG He; ZHAN Mei; LI Heng
2006-01-01
Elongation and springback are the bottleneck problems of thin-walled aluminum alloy tube NC precision bending. So thin-walled aluminum alloy tube NC precision bending based on finite element simulation is put forward. The finite element model of thin-walled aluminum alloy tube NC bending is established based on the DYNAFORM platform. The process of thin-walled aluminum alloy tube NC precision bending is simulated with the model and the elongation and springback of tube bending can be is put forward and the computing equations of bending angle, bending radius, blanking length and initial bending section based on elongation and springback angle are derived. The bending angle, bending radius, blanking length and initial bending section of tube bending can be gained with these equations based on the elongation and springback angle from the simulation. The study can be used to control the quality of thin-walled aluminum alloy tube NC bending so that precision bending without redundance can be realized.
Crack propagation analysis of welded thin-walled joints using boundary element method
Mashiri, F. R.; Zhao, Xiao-Ling; Grundy, P.
Tube-to-plate nodal joints under cyclic bending are widely used in the road transport and agricultural industry. The square hollow sections (SHS) used in these constructions are thin-walled and cold formed, and they have thicknesses of less than 4mm. Some fatigue failures have been observed. The weld undercut may affect the fatigue life of welded tubular joints especially for thin-walled sections. The undercut dimensions were measured using the silicon imprint technique. Modelling of thin-walled cruciform joints, as a simplification of welded tubular joints, is described in this paper to determine the effect of weld undercut on fatigue propagation life. The Boundary Element Analysis System Software (BEASY) is used. The results of the effect of weld toe undercut from this analysis are compared with results from previous research to determine the comparative reduction in fatigue life between thin-walled joints (T=3mm) and those made of thicker sections (T=20mm). The loss in fatigue strength of the thin-walled joints is found to be relatively more than that for thicker walled joints. A 3D model of a tube to plate T-joint is also modelled using the boundary element software, BEASY. The nodal joint consists of a square hollow section, 50×50×3 SHS, fillet welded to a 10-mm thick plate, and subjected to cyclic bending stress. Fatigue analyses are carried out and the results are compared with the only available S-N design curve.
Stability analysis of large diameter thin-walled tube beam-columns
Institute of Scientific and Technical Information of China (English)
2008-01-01
Based on a blind spot in the current design standard of steel structures,the large diameter thin-walled tube beam-columns are analyzed using nonlinear finite element method in this paper.The influence of several factors on stability capacity of the large diameter thinwalled tube beam-columns is taken into account.Thus,according to the correlative design standard of steel structures,and on the basis of the numerical analytical results by the finite element methods,the calculation formulas of the stability bearing capacity are presented for beam-column members of the large diameter thin-walled tubes.Three tests of thin-walled steel tube beam-columns were reported.Test results for deformations and ultimate strength are found to be in a good agreement with the corresponding values predicted by the calculation formulas,and the proposed methods can be used in design practice.
Newly developed vacuum differential pressure casting of thin-walled complicated Al-alloy castings
Institute of Scientific and Technical Information of China (English)
无
2005-01-01
The newly designed vacuum differential pressure casting (VDPC) unit was introduced, by which the capability of the VDPC process to produce thin-walled complicated Al-alloy castings, that are free from oxides, gas pore and shrinkage cavity and thus enhance overall part quality, was studied. Experimental results were compared with those of traditional gravity pouring and vacuum suction casting. The first series of experiments were focused on investigating the castability of thin section Al-alloy casting. In the second series of experiments the metallographic evidence, casting strength and soundness were examined. Finally, case studies of very interesting thin walled complicated casting applications were described. The advantages of the described technique have made possible to produce thin walled complicated Al-alloy casting (up to a section thickness of 1 mm), which is not practical for gravity pouring and vacuum suction casting.
Free torsion of thin-walled structural members of open- and closed-sections
Institute of Scientific and Technical Information of China (English)
Long-yuan LI; D. EASTERBROOK
2014-01-01
Free torsion of thin-walled structures of open- and closed-sections is a classical elastic mechanics problem, which, in literature, is often solved by the method of membrane analogy. The method of membrane analogy, however, can be only applied to structures of a single material. If the structure consists of both open-and closed-sections, the method of membrane analogy is difficult to be applied. In this paper, a new method is presented for solving the free torsion of thin-walled structures of open- and/or closed-sections with multiple materials. By utilizing a simple statically indeterminate concept, torsional equations are derived based on the equilibrium and compatibility conditions. The method presented here not only is very simple and easy to understand but also can be applied to thin-walled structures of combined open-and closed-sections with multiple materials.
Isogeometric Analysis of Deformation, Inelasticity and Fracture In Thin-Walled Structures
de Borst, René
2016-08-01
The basic idea of isogeometric analysis (IGA) is to use splines, which are the functions commonly used in computer-aided design (CAD) to describe the geometry, as the basis function for the analysis as well. A main advantage is that a sometimes elaborate meshing process is by-passed. Another benefit is that spline basis-functions possess a higher-order degree of continuity, which enables a more accurate representation of the stress. Further, the order of continuity of the basis-functions can be reduced locally by knot insertion. This feature can be used to model interfaces and cracks as discontinuities in the displacement field. In order to study failure-mechanisms in thin-walled composite materials, an accurate representation of the full three-dimensional stress field is mandatory. A continuum shell formulation is an obvious choice. Continuum shell elements can be developed based on the isogeometric concept. They exploit NURBS basis functions to construct the mid-surface of the shell. In combination with a higher-order B-spline basis function in the thickness direction a complete three-dimensional representation of the shell is obtained. This isogeometric shell formulation can be implemented in a standard finite element code using Bézier extraction. Weak and strong discontinuities can be introduced in the B-spline function using knot-insertion to model material interfaces and delaminations rigorously as discontinuities in the displacement field. The exact representation of material interfaces vastly improves the accuracy of the through-the- thickness stress field. The ability to provide a double knot insertion enables a straightforward analysis of delamination growth in layered composite shells. Illustrative examples will be given.
Iron melt flow in thin-walled sections using vertically parted moulds
DEFF Research Database (Denmark)
Larsen, Per; Tiedje, Niels
2004-01-01
Reducing the fuel consumption of vehicles can be done in many ways. A general way of doing it, is to reduce the weight as it is applicable together with all other means of saving fuel. Even though iron castings have been used in cars from the first car ever build, a big potential still exist...... for optimizing iron cast parts. To do so thin walled parts have to be used. I.e. flow in thin walled sections becomes important. Flow in plates with thicknesses from 2 to 4 mm have been investigated. It is shown that the main flow path can be changed even in such small thicknesses and that when conventional...
Cast-in-place concrete thin-wall pipe pile as barrier for vibration isolation
Institute of Scientific and Technical Information of China (English)
张富有; 陈灿寿; 魏良甲; 张霆
2008-01-01
Three dimensional analysis was performed by regarding vibration isolation performance cast-in-place concrete thin-wall pipe pile (PCC) and using the finite element analysis software ANSYS. The ground vertical amplitude was analyzed behind the single row cast-in-place concrete thin-wall pipe pile after the source vibration, and the influencing factors were also studied. The results indicate that in the one time of wavelength before the barrier, the oscillation amplitude is weakened; meanwhile the range which covers 4 times wavelength behind the barrier has a good vibration isolation effect, when the distance is larger than the barrier latter 4 times wavelength vibration isolation expiration.
Study on Numerical Simulation for Control of Winding Process of Thin Wall Spiral Tube
Institute of Scientific and Technical Information of China (English)
ZHENG Jing; MA Guang; WANG Yi; LI Yin'e; JIA Zhihua; LI Jin
2012-01-01
Being aimed at the inside wall wrinkling and sinking phenomenon of palladium-yttrium alloy thin wall spiral tube used for preparation of high purity hydrogen,extraction of hydrogen isotope,and purification and separation of hydrogen in the winding process,this article analyzed the reasons for above phenomena,established a numerical simulation model of winding process of above tube,using elastic-plastic Finite Element method analyzed the max.tensile stress and max.compression stress and their locations,thereby provides a theory base for the control of working forming course of thin wall spiral tube.
DEFF Research Database (Denmark)
Pedersen, Karl Martin; Tiedje, Niels Skat
2008-01-01
Temperature measurements in castings are carried out with thermocouples (TC’s), which are inserted in the melt. The TC influence solidification of the casting, especially in thin wall castings where the heat content of the melt is small compared to the cooling power of the TC. A numerical analysis...... of factors influencing temperature measurement in thin walled castings was carried out. The calculations are based on and compared with experiments presented in part 1 of this paper. The analysis shows that the presence of the TC has only a minor influence on the microstructure of the casting. The influence...
Method of fabricating thin-walled articles of tungsten-nickel-iron alloy
Hovis, V.M. Jr.; Northcutt, W.G. Jr.
The present invention relates to a method for fabricating thin-walled high-density structures of tungsten-nickel-iron alloys. A powdered blend of the selected alloy constituents is plasma sprayed onto a mandrel having the desired article configuration. The sprayed deposit is removed from the mandrel and subjected to liquid phase sintering to provide the alloyed structure. The formation of the thin-walled structure by plasma spraying significantly reduces shrinkage, and cracking while increasing physical properties of the structure over that obtainable by employing previously known powder metallurgical procedures.
Prediction of Microporosity in Complex Thin-Wall Castings with the Dimensionless Niyama Criterion
Kang, Maodong; Gao, Haiyan; Wang, Jun; Ling, Lishibao; Sun, Baode
2013-01-01
The dimensionless Niyama criterion was used to predict the formation of microporosity in nickel-based superalloy casting, which extended the model application from a simple plate casting to complex thin-wall superalloy casting. The physical characteristics of the superalloy were calculated by JMatPro software. The relation between the volume percentage of microporosity and the dimensionless Niyama values were constructed. Quantitative metallographic measurements of the microporosity of the practical thin-wall casting were carried out. The prediction agreed well with the experiment in general, except for some thick-wall sites in the casting. PMID:28809243
Giurgiutiu, Victor
2004-02-01
Piezoelectric wafer active sensors (PWAS) are inexpensive, non-intrusive, unobtrusive devices that can be surface-mounted on existing structures or inserted between the layers of new composite structures. The PWAS can be used in both active and passive modes. PWAS generate and detect Lamb waves and enable the development of embedded NDE concepts. This paper will present two embedded NDE concepts based on the PWAS technology and Lamb waves approach. The first concept utilizes traveling Lamb waves and could be described as embedded ultrasonics. It is shown that embedded PWAS are able to reproduce most of the conventional ultrasonic techniques, such as pitch-catch, pulse-echo, and phased array. Several experiments using Lamb waves traveling in thin-wall structures are presented.
Thin-Wall Aluminum Die-Casting Technology for Development of Notebook Computer Housing
Institute of Scientific and Technical Information of China (English)
无
2008-01-01
Silicon-based aluminum casting alloys are known to be one of the most widely used alloy systems mainly due to their superior casting characteristics and unique combination of mechanical and physical properties.However, manufacturing of thin-walled aluminum die-casting components, less than 1.0 mm in thickness, is generally known to be very difficult task to achieve aluminum casting alloys with high fluidity. Therefore, in this study, the optimal die-casting conditions for producing 297 mm×210 mm×0.7 mm thin-walled aluminum component was examined experimentally by using 2 different gating systems, tangential and split type, and vent design. Furthermore, computational solidification simulation was also conducted. The results showed that split type gating system was preferable gating design than tangential type gating system at the point of view of soundness of casting and distortion generated after solidification. It was also found that proper vent design was one of the most important factors for producing thin-wall casting components because it was important for the fulfillment of the thin-wall cavity and the minimization of the casting distortion.
Plastic wrinkling prediction in thin-walled part forming process:A review
Institute of Scientific and Technical Information of China (English)
Liu Nan; Yang He; Li Heng; Yan Siliang
2016-01-01
The precision forming of thin-walled components has been urgently needed in aviation and aerospace field. However, the wrinkling induced by the compressive instability is one of the major defects in thin-walled part forming. The initiation and growth of the wrinkles are interac-tively affected by many factors such as stress states, mechanical properties of the material, geometry of the workpiece and boundary conditions. Especially when the forming process involves compli-cated boundary conditions such as multi-dies constrains, the perturbation of clearances between workpiece and dies and the contact conditions changing in time and space, etc., the predication of the wrinkling is further complicated. In this paper, the current prediction methods were summa-rized including the static equilibrium method, the energy method, the initial imperfection method, the eigenvalue buckling analysis method, the static-implicit finite element method and the dynamic-explicit finite element method. Then, a systematical comparison and summary of these methods in terms of their advantages and limitations are presented. By using a combination of explicit FE method, initial imperfection and energy conservation, a hybrid method is recommended to predict plastic wrinkling in thin-walled part forming. Finally, considering the urgent requirements of com-plex thin-walled structures’ part in aviation and aerospace field, the trends and challenges in wrin-kling prediction under complicated boundary conditions are presented.
Dynamic response of thin-walled structures by variable kinematic one-dimensional models
Carrera, E.; Varello, A.
2012-11-01
This paper investigates the accuracy capabilities of using variable kinematic modeling in compact and thin-walled beam-like structures with dynamic loadings. Carrera Unified Formulation (CUF) is employed to introduce refined one-dimensional (1D) models with a variable order of expansion for the displacement unknowns over the beam cross-section. Classical Euler-Bernoulli and Timoshenko beam theories are obtained as particular cases of these variable kinematic models while a higher order expansion permits the detection of in-plane cross-section deformation, since it leads to shell-like solutions. Finite element (FE) method is used to provide numerical results and the Newmark method is implemented as a time integration scheme. Some assessments with closed form solutions are discussed and comparisons with shell-type results obtained with commercial FE software are made. Further analyses address both compact and thin-walled cross-sections. In particular, the case of a deformable thin-walled cylinder loaded by time-dependent internal forces is discussed. The results clearly show that finite elements which are formulated in the CUF framework do not introduce additional numerical problems with respect to classical beam theories. Comparisons with elasticity solutions prove that the present 1D CUF model offers an accuracy in analyzing thin-walled structures which is typical of shell or three-dimensional models with a remarkable reduction in the computational cost required.
Investigation of solidification of thin walled ductile cast iron using temperature measurement
DEFF Research Database (Denmark)
Pedersen, Karl Martin; Tiedje, Niels
2005-01-01
measurement on castings and to get sufficient response time of thermocouples. Investigation of thin wall ductile iron has been performed with temperature measurement in plates with thickness between 2,8 and 8mm. The cooling curves achieved are combined with examination of the microstructure in order to reveal...
Institute of Scientific and Technical Information of China (English)
Xianfang Yue; Li Wang; Feng Zhou
2008-01-01
The human skuU,composed of tabula externa,tabula interna,and a porous diploe sandwiched in between,is deformed with changing intracranial pressure (ICP).Because the human skull's thickness is only 6 mm,it is simplified as a thin-walled shell. The objective of this article is to analyze the strain of the thin-walled shell by the stress-strain calculation of a human skull with changing ICP.Under the same loading conditions,using finite element analysis (FEA),the strains of the human skull were calculated and the results were compared with the measurements of the simulative experiment in vitro.It is demonstrated that the strain of the thin-walled shell is totally measured by pasting the one-way strain foils on the exterior surface of the shell with suitable amendment for data.The amendment scope of the measured strain values of the thin-walled shell is from 13.04% to 22.22%.
Computation Analysis of Buckling Loads of Thin-Walled Members with Open Sections
Directory of Open Access Journals (Sweden)
Lihua Huang
2016-01-01
Full Text Available The computational methods for solving buckling loads of thin-walled members with open sections are not unique when different concerns are emphasized. In this paper, the buckling loads of thin-walled members in linear-elastic, geometrically nonlinear-elastic, and nonlinear-inelastic behaviors are investigated from the views of mathematical formulation, experiment, and numerical solution. The differential equations and their solutions of linear-elastic and geometrically nonlinear-elastic buckling of thin-walled members with various constraints are derived. Taking structural angle as an example, numerical analysis of elastic and inelastic buckling is carried out via ANSYS. Elastic analyses for linearized buckling and nonlinear buckling are realized using finite elements of beam and shell and are compared with the theoretical results. The effect of modeling of constraints on numerical results is studied when shell element is applied. The factors that influence the inelastic buckling load in numerical solution, such as modeling of constraint, loading pattern, adding rib, scale factor of initial defect, and yield strength of material, are studied. The noteworthy problems and their solutions in numerically buckling analysis of thin-walled member with open section are pointed out.
Computationally efficient analysis and optimisation of stiffened thin-walled panels in shear
CSIR Research Space (South Africa)
Viljoen, A
2005-05-01
Full Text Available nonlinear finite element analysis, which makes it attractive for use during initial design iterations, even though global collapse of a structure cannot be predicted. As an illustration of the optimal design of buckled, stiffened thin-walled structures...
A NEW HIGH-ORDER MULTI-JOINT FINITE ELEMENT FOR THIN-WALLED BAR
Institute of Scientific and Technical Information of China (English)
李正良; 白绍良; 谢炜
2002-01-01
A new high-order multi-joint finite element for thin-walled bar was derived from the Hermite interpolation polynomial and minimum potential energy principle. This element's characteristics are that it is of high accuracy and can be used in finite method analysis of bridge, tall mega-structure building.
Nonlinear Collapse of General Thin-Walled Cross-Sections Under Pure Bending
DEFF Research Database (Denmark)
Couturier, Philippe; Krenk, Steen
2016-01-01
Thin-walled beams exhibit a nonlinear response to bending moments due to the progressive flattening of the crosssection, a behavior commonly referred to as the Brazier effect. Most approaches to model this effect are limited to either circular cross-sections or to cross-sections made of isotropic...
Numerical modelling of thin-walled hypereutectic ductile cast iron parts
DEFF Research Database (Denmark)
Pedersen, Karl Martin; Hattel, Jesper Henri; Tiedje, Niels Skat
2006-01-01
Solidification of hypereutectic thin-walled ductile cast iron has been modelled in one dimension taking into account the precipitation of off-eutectic austenite dendrites during solidification. The simulations have been compared with casting experiments on plate geometries with plate thicknesses...
Nucleation and solidification of thin walled ductile iron - Experiments and numerical simulation
DEFF Research Database (Denmark)
Pedersen, Karl Martin; Tiedje, Niels Skat
2005-01-01
Investigation of solidification of thin walled ductile cast iron has been performed based on experiments and numerical simulation. The experiments were based on temperature and microstructure examination. Results of the experiments have been compared with a 1-D numerical solidification model...
Zhao, Liuxian; Semperlotti, Fabio
2017-02-01
We explore the use of structure-embedded Acoustic Black Holes (ABH) to design thin-walled structural components exhibiting broadband vibration attenuation characteristics. The ABH is a geometric taper with a power-law profile fully integrated into the structural component and able to induce a smooth and progressive decrease of both the velocity and the wavelength of flexural waves. Previous studies have shown these characteristics to be critical to enable highly efficient vibration attenuation systems. The performance of ABH thin-walled structures is numerically and experimentally evaluated under both transient and steady state excitation conditions. Both numerical and experimental results suggest that the proposed approach enables highly efficient and broadband vibration attenuation performance.
Analysis on Forced Vibration of Thin-Wall Cylindrical Shell with Nonlinear Boundary Condition
Directory of Open Access Journals (Sweden)
Qiansheng Tang
2016-01-01
Full Text Available Forced vibration of thin-wall cylindrical shell under nonlinear boundary condition was discussed in this paper. The nonlinear boundary was modeled as supported clearance in one end of shell and the restraint was assumed as linearly elastic in the radial direction. Based on Sanders’ shell theory, Lagrange equation was utilized to derive the nonlinear governing equations of cylindrical shell. The displacements in three directions were represented by beam functions and trigonometric functions. In the study of nonlinear dynamic responses of thin-wall cylindrical shell with supported clearance under external loads, the Newmark method is used to obtain time history, frequency spectrum plot, phase portraits, Poincare section, bifurcation diagrams, and three-dimensional spectrum plot with different parameters. The effects of external loads, supported clearance, and support stiffness on nonlinear dynamics behaviors of cylindrical shell with nonlinear boundary condition were discussed.
Rapid precision casting for complex thin-walled aluminum alloy parts
Directory of Open Access Journals (Sweden)
Xuanpu DONG
2004-11-01
Full Text Available Based on Vacuum Differential Pressure Casting (VDPC precision forming technology and the Selective Laser Sintering (SLS Rapid Prototyping (RP technology, a rapid manufacturing method called Rapid Precision Casting (RPC process from computer three-dimensional solid models to metallic parts was investigated. The experimental results showed that the main advantage of RPC was not only its ability to cast higher internal quality and more accurate complex thin-walled aluminum alloy parts, but also the greatly-reduced lead time cycle from Selective Laser Sintering(SLS plastic prototyping to metallic parts. The key forming technology of RPC for complex thin-walled metallic parts has been developed for new casting production and Rapid Tooling (RT, and it is possible to rapidly manufacture high-quality and accurate metallic parts by means of RP in foundry industry.
Fabrication technology for a series of cylindrical thin-wall cavity targets
Zheng Yong; Sun Zu Oke; Wang Ming Da; Zhou La; Zhou Zhi Yun
2002-01-01
Cylindrical thin-wall cavity targets have been fabricated to study the behavior of superthermal electrons and their effects on inertial confinement fusion (ICF). Self-supporting cavity targets having adjustable, uniform wall thickness, and low surface roughness were required. This required production of high-quality mandrels, coating them by sputtering or electroplating, developing techniques for measurement of wall thickness and other cavity parameters, improving the uniformity of rotation of the mandrels, and preventing damage to the targets during removal from the mandrels. Details of the fabrication process are presented. Experimental results from the use of these targets are presented. These results, in good agreement with simulations, indicate that the use of thin-wall cavity targets is an effective method for studying superthermal electrons in ICF.
Multi-pass spinning of thin-walled tubular part with longitudinal inner ribs
Institute of Scientific and Technical Information of China (English)
JIANG Shu-yong; ZHENG Yu-feng; REN Zheng-yi; LI Chun-feng
2009-01-01
Based on the process experiments, micrography analysis was dedicated to advancing the understanding of plastic flow of the metal in backward ball spinning of thin-walled tubular part with longitudinal inner ribs. Micrography analysis reveals that severe plastic deformation leads to grain refinement, grain orientation and grain flow line of the spun part. Based on rigid-plastic finite element method, DEFORME3D finite element code was used to simulate and analyze multi-pass backward ball spinning of thin-walled tubular part with longitudinal inner ribs. Finite element simulation results involve the distributions of the strain, the shape variation of the inner ribs as well as the prediction of the spinning loading.
Solidified structure of thin-walled titanium parts by vertical centrifugal casting
Directory of Open Access Journals (Sweden)
Wu Shiping
2011-05-01
Full Text Available The solidified structure of the thin-walled and complicated Ti-6Al-4V castings produced by the vertical centrifugal casting process was studied in the present work. The results show that the wall thickness of the section is featured with homogeneously distributed fine equiaxial grains, compared with the microstructure of the thick-walled section. The grain size of the castings has a tendency to decrease gradually with the increasing of the centrifugal radius. The inter-lamellar space in thick-walled casting parts is bigger than that of the thin-walled parts, and the profile of inter-lamellar space is not susceptible to the centrifugal radius.
Electroless-plating technique for fabricating thin-wall convective heat-transfer models
Avery, D. E.; Ballard, G. K.; Wilson, M. L.
1984-01-01
A technique for fabricating uniform thin-wall metallic heat-transfer models and which simulates a Shuttle thermal protection system tile is described. Two 6- by 6- by 2.5-in. tiles were fabricated to obtain local heat transfer rates. The fabrication process is not limited to any particular geometry and results in a seamless thin-wall heat-transfer model which uses a one-wire thermocouple to obtain local cold-wall heat-transfer rates. The tile is relatively fragile because of the brittle nature of the material and the structural weakness of the flat-sided configuration; however, a method was developed and used for repairing a cracked tile.
Research on Cutting Force of Turn-Milling Based on Thin-Walled Blade
Directory of Open Access Journals (Sweden)
Lida Zhu
2016-01-01
Full Text Available Turn-milling is regarded as the milling of a curved surface while rotating the workpiece around its center point, which combines effectively the advantages of both turning and milling, wherein it allows for good metal removal with the difficult-to-cut thin-walled workpieces in aviation. The objective of the present work is to study cutting force by turn-milling in cutting condition. Aiming at the deformation properties of thin-walled blade, the predicted models of rigid cutting force and flexible cutting force with ball cutter are provided, respectively, in turn-milling process. The deformation values of blade and cutter are calculated, respectively, based on the engaged trajectory by using the iterative algorithm. The rigid and flexible cutting forces are compared and the influence degrees of cutting parameters on cutting forces are analyzed. These conclusions provide theoretical foundation and reference for turn-milling mechanism research.
Study On The External Gas-Assisted Mold Temperature Control For Thin Wall Injection Molding
Directory of Open Access Journals (Sweden)
ThanhTrung Do
2017-03-01
Full Text Available Dynamic mold surface temperature control (DMTC has many advantages in micro-injection molding as well as thin-wall molding product. In this paper, DMTC will be applied for the thin-wall molding part with the observation of the weldline appearance and the weldline strength. The heating step of DMTC will be achieved by the hot air flow directly to the weldline area. The results show that the heating rate could be reached to 4.5C/s, which could raising the mold surface from 30C to over 120C within 15 s. The melt filling was operated with high temperature at the weldline area; therefore, the weldline appearance was eliminated. In addition, the weldline strength was also improved. The results show that the thinner part had the higher strength of the weldline
Mixed finite element models for free vibrations of thin-walled beams
Noor, Ahmed K.; Peters, Jeanne M.; Min, Byung-Jin
1989-01-01
Simple, mixed finite element models are developed for the free vibration analysis of curved thin-walled beams with arbitrary open cross section. The analytical formulation is based on a Vlasov's type thin-walled beam theory with the effects of flexural-torsional coupling, transverse shear deformation and rotary inertia included. The fundamental unknowns consist of seven internal forces and seven generalized displacements of the beam. The element characteristic arrays are obtained by using a perturbed Lagrangian-mixed variational principle. Only C(sup o) continuity is required for the generalized displacements. The internal forces and the Lagrange multiplier are allowed to be discontinuous at interelement boundaries. Numerical results are presented to demonstrate the high accuracy and effectiveness of the elements developed. The standard of comparison is taken to be the solutions obtained by using 2-D plate/shell models for the beams.
Directory of Open Access Journals (Sweden)
Lang Lihui
2015-01-01
Full Text Available The explosively forming projectile (EFP had been traditional adopted for the aluminum thin-walled corrugated sheet, whose deformation range is large but the formability is poor, and this process usually has problems of poor surface quality, long manufacturing cycle and high cost. The active hydroforming process was suggested to solve these issues during EFP. A new technology named as blank bulging by turning the upside down active hydroforming technology was proposed to overcome difficulties in non-uniform thickness distribution and cracking failure of corrugated sheet during the conventional hydroforming process. Both numerical simulations and experiments were conducted for this new technology. The result show that the deformation capacity of aluminum alloys can be improved effectively, and the more uniform distribution of wall thickness was obtained by this new method. It is conducted that the new method is universal for thin-walled, shallow drawing parts with complex section.
Minimum Normal Force Principle Based Quantitive Optimizationof Clamping Forces for Thin Walled Part
Institute of Scientific and Technical Information of China (English)
ZHANG Fa-ping; SUN Hou-fang; SHAHID I.Butt
2008-01-01
Based on the stability criteria of workpiece-fixture system, quantitative optimization of clamping forces during precise machining process for thin walled part is studied considering the contact condition between wokpiece and locator, the contact mechanical model is achieved ,which is further been used to calculate the entire passive forces acting on the statically undetermined workpiece by means of the force screw theory as well as minimum norm force principle. Furthermore, a new methodology to optimize clamping forces is put forward, on the criteria of keeping the stability of workpiece during cutting process. By this way, the intensity of clamping forces is decreased dramatically, which will be most beneficial for improving the machining quality of thin-walled parts. Finally, a case study is used to support and validate the proposed model.
Development of a Thin-Wall Magnesium side door Inner Panel for Automobiles
Energy Technology Data Exchange (ETDEWEB)
Jekl, J.; Auld, J.; Sweet, C.; Carter, Jon; Resch, Steve; Klarner, A.; Brevick, J.; Luo, A.
2015-05-17
Cast magnesium side door inner panels can provide a good combination of weight, functional, manufacturing and economical requirements. However, several challenges exist including casting technology for thin-wall part design, multi-material incompatibility and relatively low strength vs steel. A project has been initiated, supported by the US Department of Energy, to design and develop a lightweight frame-under-glass door having a thin-wall, full die-cast, magnesium inner panel. This development project is the first of its kind within North America. Phase I of the project is now complete and the 2.0mm magnesium design, through casting process enablers, has met or exceeded all stiffness requirements, with significant mass reduction and part consolidation. In addition, a corrosion mitigation strategy has been established using industry-accepted galvanic isolation methods and coating technologies.
Interfacial double layer mediated electrochemical growth of thin-walled platinum nanotubes
Zhang, Liqiu; Kim, Sang Min; Cho, Sanghyun; Jang, Hee-Jeong; Liu, Lichun; Park, Sungho
2017-01-01
This work demonstrates that thin-walled platinum nanotubes can be readily synthesized by controlling the interfacial double layer in alumina nanochannels. The gradient distribution of ions in nanochannels enables the creation of Pt nanotubes with walls as thin as 5 nm at the top end when using a solution containing polyvinylpyrrolidone (PVP) and chloroplatinic acid (H2PtCl6) under the influence of an electric potential in nanochannels. The highly efficient formation of thin-walled Pt nanotubes is a result of the concentration gradient of {{{{PtCl}}}6}2- and a thick double layer, which was caused by the low concentration of Pt precursors and the enhanced surface charge density induced by protonated PVP steric adsorption. This well-controlled synthesis reveals that the interfacial double layer is a useful tool to tailor the structure of nanomaterials in a nanoscale space, and holds promise in the construction of more complex functional nanostructures.
Numerical modelling of solidification of thin walled hypereutectic ductile cast iron
DEFF Research Database (Denmark)
Pedersen, Karl Martin; Hattel, Jesper; Tiedje, Niels
2006-01-01
Numerical simulation of solidification of ductile cast iron is normally based on a model where graphite nodules are surrounded by an austenite shell. The two phases are then growing as two concentric spheres governed by diffusion of carbon through the austenite shell. Experiments have however shown...... simulation of thin-walled ductile iron castings. Simulations have been performed with a 1-D numerical solidi¬fication model that includes the precipitation of non-eutectic austenite during the eutectic stage. Results from the simulations have been compared with experimental castings with wall thick...... the presence of austenite dendrites even in hypereutectic castings. In thin-walled castings the presence of austenite dendrites is even more pronounced, which increases the risk of shrinkage porosities. This off-eutectic austenite is therefore an important part that should be taken into account during...
Role of Titanium in Thin Wall Vermicular Graphite Iron Castings Production
Directory of Open Access Journals (Sweden)
M. Górny
2013-04-01
Full Text Available In this paper the effects of titanium addition in an amount up to 0.13 wt.% have been investigated to determine their effect on the microstructure and mechanical properties of Thin Wall Vermicular Graphite Iron Castings (TWVGI. The study was performed for thinwalled iron castings with 3-5 mm wall thickness and for the reference casting with 13 mm. Microstructural changes were evaluated by analyzing quantitative data sets obtained by image analyzer and also using scanning electron microscope (SEM. Metallographic examinations show that in thin-walled castings there is a significant impact of titanium addition to vermicular graphite formation. Thinwalled castings with vermicular graphite have a homogeneous structure, free of chills, and good mechanical properties. It may predispose them as a potential use as substitutes for aluminum alloy castings in diverse applications.
Graphite nodule count and size distribution in thin-walled ductile cast iron
DEFF Research Database (Denmark)
Pedersen, Karl Martin; Tiedje, Niels Skat
2008-01-01
Graphite nodule count and size distribution have been analysed in thin walled ductile cast iron. The 2D nodule counts have been converted into 3D nodule count by using Finite Difference Method (FDM). Particles having a diameter smaller than 5 µm should be neglected in the nodule count...... as these are inclusions and micro porosities that do not influence the solidification morphology. If there are many small graphite nodules as in thin walled castings only 3D nodule count calculated by FDM will give reliable results. 2D nodule count and 3D nodule count calculated by simple equations will give too low...... results. The 3D size distribution showed presence of primary graphite nodules in hypereutectic castings. In thin plates the nodule count is similar in eutectic and hypereutectic plates. In thicker plates the hypereutectic casting has the highest nodule count....
The FEM simulation of the thin walled aircraft engine corpus deformation during milling
Matras, A.; Plaza, M.
2016-09-01
This paper discusses the results of the experimental research performed with the support of finite element method. The deformation of the thin walled aircraft engine corpus was analyzed based on a geometric model. Then, the boundary of the outer side of the part was loaded by the components of a cutting force during milling. The material model of the part was also defined in the simulation software. The analysis allowed to optimize feed rate in order to decrease the deformation of the part.
Cold drawing of 316L stainless steel thin-walled tubes: experiments and finite element analysis
Palengat, Muriel; Chagnon, Grégory; Favier, Denis; Louche, Hervé; Linardon, Camille; Plaideau, Christel
2013-01-01
International audience; Drawing process of thin walled tubes used to fabricate catheters and stents for medical applications was studied. Medical use needs accurate dimensions and a smooth finish of the inner and outer surfaces. This paper deals with 316L stainless steel tubes which are manufactured by means of cold drawing with or without inner plug (mandrel drawing and hollow sinking, respectively). To improve the quality of the finish of the tubes, numerical modelling can be used. In this ...
Collapse behavior evaluation of hybrid thin-walled member by stacking condition
Institute of Scientific and Technical Information of China (English)
Kil-Sung LEE; Hyeon-Kyeong SEO; Yong-June YANG; Woo-Chae HWANG; Kwang-Hee IM; In-Young YANG
2011-01-01
The recent trend of vehicle design aims at crash safety and environmentally-friendly aspect. For the crash safety aspect,the energy absorbing members should absorb collision energy sufficiently but for the environmentally-friendly aspect, the vehicle structure must be light weight in order to improve the fuel efficiency and reduce the tail gas emission. Therefore, the light weight of vehicle must be achieved in a securing safety status of crash. An aluminum or carbon fiber reinforced plastics (CFRP) is representative one of the light-weight materials. Based on the respective collapse behavior of aluminum and CFRP member, the collapse behavior of hybrid thin-walled member was evaluated. The hybrid members were manufactured by wrapping CFRP prepreg sheets outside the aluminum hollow members in the autoclave. Because the CFRP is an anisotropic material whose mechanical properties, such as strength and elasticity, change with its stacking condition, the effects of the stacking condition on the collapse behavior evaluation of the hybrid thin-walled member were tested. The collapse mode and energy absorption capability of the hybrid thin-walled member were analyzed with the change of the fiber orientation angle and interface number.
Die Casting Mold Design of the Thin-walled Aluminum Case by Computational Solidification Simulation
Institute of Scientific and Technical Information of China (English)
Young-Chan Kim; Chang-Seog Kang; Jae-Ik Cho; Chang-Yeol Jeong; Se-Weon Choi; Sung-Kil Hong
2008-01-01
Recently, demand for the lightweight alloy in electric/electronic housings has been greatly increased. However, among the lightweight alloys, aluminum alloy thin-walled die casting is problematic because it is quite difficult to achieve sufficient fluidity and feedability to fill the thin cavity as the wall thickness becomes less than 1 mm. Therefore, in this study, thin-walled die casting of aluminum (Al-Si-Cu alloy: ALDC 12) in size of notebook computer housing and thickness of 0.8 mm was investigated by solidification simulation (MAGMA soft) and actual casting experiment (Buhler Evolution B 53D). Three different types of gating design, finger, tangential and split type with 6 vertical runners, were simulated and the results showed that sound thin-walled die casting was possible with tangential and split type gating design because those gates allowed aluminum melt to flow into the thin cavity uniformly and split type gating system was preferable gating design comparing to tangential type gating system at the point of view of soundness of casting and distortion generated after solidification. Also, the solidification simulation agreed well with the actual die-casting and the casting showed no casting defects and distortion.
ANALYSIS OF MECHANICS IN BALL SPINNING OF THIN-WALLED TUBE
Institute of Scientific and Technical Information of China (English)
JIANG Shuyong; REN Zhengyi
2008-01-01
Ball spinning is applied to manufacturing thin-walled tube with high precision and high mechanical properties. On the basis of plastic mechanics, by simplifying ball spinning of thin-walled tube as plane strain problem, slab method is used for the purpose of calculating the contact deformation pressure. The spinning force components, the torsional moment, the deformation power and the deformation work are calculated further as well. The influence of the two important process parameters such as the feed ratio and the ball diameter on the spinning force components is analyzed in order to further control the spinning force components by regulating the two process variables during the ball spinning process. The stress and strain state in deformable zone as well as mechanics boundary conditions in ball spinning are obtained. The effect of the three spinning force components on the formability of the spun part is analyzed and validated through the ball spinning experiments. The theoretical and experimental results show that the radial spinning component plays a significant role in ball spinning of thin-walled tube, and the mechanics situation in backward ball spinning contributes to enhancing the plasticity of the metal material, but that in forward ball spinning contributes to advancing the axial flow of the metal material.
Numerical study on injection parameters optimization of thin wall and biodegradable polymers parts
Santos, C.; Mendes, A.; Carreira, P.; Mateus, A.; Malça, C.
2017-07-01
Nowadays, the molds industry searches new markets, with diversified and added value products. The concept associated to the production of thin walled and biodegradable parts mostly manufactured by injection process has assumed a relevant importance due to environmental and economic factors. The growth of a global consciousness about the harmful effects of the conventional polymers in our life quality associated with the legislation imposed, become key factors for the choice of a particular product by the consumer. The target of this work is to provide an integrated solution for the injection of parts with thin walls and manufactured using biodegradable materials. This integrated solution includes the design and manufacture processes of the mold as well as to find the optimum values for the injection parameters in order to become the process effective and competitive. For this, the Moldflow software was used. It was demonstrated that this computational tool provides an effective responsiveness and it can constitute an important tool in supporting the injection molding of thin-walled and biodegradable parts.
Viscous Inner and Outer Pressure Forming Method of Thin-walled Tube and Its Application
Institute of Scientific and Technical Information of China (English)
GAO Tiejun; LIU Yang; WANG Zhongjin
2015-01-01
Aiming at overcoming the difficulties in integral forming of thin-walled tubes with complex shapes, a novel forming method by inner and outer pressure through viscous was proposed. In this method, by dividing large deformation of the part into inner and outer pressure forming deformations, the limit deformation of tube part can be increased by several times. Meanwhile, the principle of viscous inner and outer pressure forming was provided, and key problems during the forming process such as reduction of the wall-thickness and instability wrinkling were analyzed. Thereby, the complex curved surface super-alloy GH3044 thin-walled tube with varying diameter ratio of 1.35 (the ratio between the maximum and minimum diameters of the part) can be integrally formed by this method. The experimental surface of the formed part is superior in quality and the wall-thickness distribution is uniform. The results show that the viscous inner and outer pressure forming can provide a new approach for integral forming of thin-walled tubes with complex shapes.
Redesigned Surface Based Machining Strategy and Method in Peripheral Milling of Thin-walled Parts
Institute of Scientific and Technical Information of China (English)
JIA Zhenyuan; GUO Qiang; SUN Yuwen; GUO Dongming
2010-01-01
Currently, simultaneously ensuring the machining accuracy and efficiency of thin-walled structures especially high performance parts still remains a challenge. Existing compensating methods are mainly focusing on 3-aixs machining, which sometimes only take one given point as the compensative point at each given cutter location. This paper presents a redesigned surface based machining strategy for peripheral milling of thin-walled parts. Based on an improved cutting force/heat model and finite element method(FEM) simulation environment, a deflection error prediction model, which takes sequence of cutter contact lines as compensation targets, is established. And an iterative algorithm is presented to determine feasible cutter axis positions. The final redesigned surface is subsequently generated by skinning all discrete cutter axis vectors after compensating by using the proposed algorithm. The proposed machining strategy incorporates the thermo-mechanical coupled effect in deflection prediction, and is also validated with flank milling experiment by using five-axis machine tool. At the same time, the deformation error is detected by using three-coordinate measuring machine. Error prediction values and experimental results indicate that they have a good consistency and the proposed approach is able to significantly reduce the dimension error under the same machining conditions compared with conventional methods. The proposed machining strategy has potential in high-efficiency precision machining of thin-walled parts.
Method in calculating own vibration frequencies of open sections bars with thin walls
Mihuț, N.
2016-08-01
Dynamic stability of thin-walled bars of open sections, as well as the stability of elastic systems dynamics in general, is studying closely with their vibrations. This, because, areas of dynamics instability is around twice the frequency of free vibration of the bar or elastic system in all cases excitation parametric, on the one hand, and on the other hand matrices involved in the matrix equation of free vibration are matrices of matrix equation of dynamic stability. In this paper we settled differential equations of parametric vibrations of thin-walled straight bars open sections constant as a system with a triple infinity of second order differential equations, linear coefficients homogeneous and periodicals. In the end of work, by customizing differential equations of forced vibration parameters have been obtained differential equations of own vibration of bars with thin wall and open sections as a system with a triple infinity of differential equations of second order, linear, homogeneous with constant coefficients and, using it, the algebraic equation of own vibrations pulsations.
Dullin, Holger R
2015-01-01
A complete description of twisting somersaults is given using a reduction to a time-dependent Euler equation for non-rigid body dynamics. The central idea is that after reduction the twisting motion is apparent in a body frame, while the somersaulting (rotation about the fixed angular momentum vector in space) is recovered by a combination of dynamic and geometric phase. In the simplest "kick-model" the number of somersaults $m$ and the number of twists $n$ are obtained through a rational rotation number $W = m/n$ of a (rigid) Euler top. This rotation number is obtained by a slight modification of Montgomery's formula [9] for how much the rigid body has rotated. Using the full model with shape changes that take a realistic time we then derive the master twisting-somersault formula: An exact formula that relates the airborne time of the diver, the time spent in various stages of the dive, the numbers $m$ and $n$, the energy in the stages, and the angular momentum by extending a geometric phase formula due to C...
Dickens, Charles
2005-01-01
Oliver Twist is one of Dickens's most popular novels, with many famous film, television and musical adaptations. It is a classic story of good against evil, packed with humour and pathos, drama and suspense, in which the orphaned Oliver is brought up in a harsh workhouse, and then taken in and
Dickens, Charles
2005-01-01
Oliver Twist is one of Dickens's most popular novels, with many famous film, television and musical adaptations. It is a classic story of good against evil, packed with humour and pathos, drama and suspense, in which the orphaned Oliver is brought up in a harsh workhouse, and then taken in and explo
Isaev, A.; Grechishnikov, V.; Kozochkin, M.; Volosova, M.; Petuhov, Yu; Peretyagin, P.
2016-04-01
The present study aims at study of structure and properties of raw and thermal treated titanium-based powder material used to produce the thin-walled components by electron beam melting technology. Producing the end product means also studying the finishing cutting process. Examining the quality of end product in terms of geometric tolerance and thin walls thickness stability consists of control the surface roughness is also included in this study.
Hermann, Keith; Pratumyot, Yaowalak; Polen, Shane; Hardin, Alex M; Dalkilic, Erdin; Dastan, Arif; Badjić, Jovica D
2015-02-23
A preparative procedure for obtaining a pair of twisted molecular baskets, each comprising a chiral framework with either right ((P)-1syn) or left ((M)-1syn) sense of twist and six ester groups at the rim has been developed and optimized. The racemic (P/M)-1syn can be obtained in three synthetic steps from accessible starting materials. The resolution of (P/M)-1syn is accomplished by its transesterification with (1R,2S,5R)-(-)-menthol in the presence of a Ti(IV) catalyst to give diastereomeric 8(P) and 8(M). It was found that dendritic-like cavitands 8(P) and 8(M), in CD2Cl2, undergo self-inclusion ((1)H NMR spectroscopy) with a menthol moiety occupying the cavity of each host. Importantly, the degree of inclusion of the menthol group was ((1)H NMR spectroscopy) found to be greater in the case of 8(P) than 8(M). Accordingly, it is suggested that different folding characteristic of 8(P) and 8(M) ought to affect the physicochemical characteristics of the hosts to permit their effective separation by column chromatography. The absolute configuration of 8(P)/8(M), encompassing right- and left-handed "cups", was determined with the exciton chirality method and also verified in silico (DFT: B3LYP/TZVP). Finally, the twisted baskets are strongly fluorescent due to three naphthalene chromophores, having a high fluorescence quantum yield within the rigid framework of 8(P)/8(M).
Inspection of thin-walled pipe welds using mechanized ultrasonic techniques
Energy Technology Data Exchange (ETDEWEB)
Lozev, M.; Spencer, R. [Edison Welding Inst., Columbus, OH (United States); Hodgkinson, D. [TransCanada PipeLines Ltd., Calgary, AB (Canada)
2004-07-01
This paper investigated applications of high-frequency single/multiprobe techniques and phased-array (PA) technology for the inspection of thin-walled pipes welds. Ultrasonic testing (UT), modeling and simulation was used as an effective way of determining that the desired calibration reflectors and flaws in thin-walled pipes can be accurately sized. A laboratory experiment was conducted in which simple or complex flaws were virtually split on several segments. Beam profile monitoring and automated ultrasonic testing was performed for non-focused 5, 10 and 15 MHz single elements, a variety of focused MHz elements, and a 10 MHz 32 element linear PA probe. A Mephisto model was used to examine the various echo-formation mechanisms. Beam interactions and connected planar flaws were examined. Two calibration targets were used: (1) a 1.5 mm diameter side-drilled hole; and (2) a 4 per cent deep notch. A thin-walled pipe sample was designed for the validation of modeling results. A commercially available PA system and computer software program was used to create focal laws, as well as to steer the beam, collect data, and perform the analysis. Results of the notch tilt models showed that inspection angles of approximately 58 to 68 degrees were the least sensitive to tilt. Signal amplitude losses of less than 10 decibels were observed when compared with the reference notch. The PA model for complex flaws showed that signal loss arising from tilt and skew stabilized at approximately 10 degrees due to a loss of amplitude. Larger sound beams resulted in a greater echo-dynamic that increased masking effects. It was concluded that the most accurate UT simulations were achieved using a 10 MHz, 32-element linear PA technology. 4 refs., 2 tabs., 8 figs.
Distortional eigenmodes and homogeneous solutions for semi-discretized thin-walled beams
DEFF Research Database (Denmark)
Jönsson, Jeppe; Andreassen, Michael Joachim
2011-01-01
-element-based displacement approach in combination with a weak formulation of the shear constraints and constrained wall widths. The weak formulation of the shear constraints enables analysis of both open and closed cell cross-sections by allowing constant shear flow. We use variational analysis to establish and clearly......The classical Vlasov theory for torsional analysis of thin-walled beams with open and closed cross-sections can be generalized by including distortional displacement fields. We show that the determination of adequate distortional displacement fields for generalized beam theory (GBT) can be found...
Analysis of moderately thin-walled beam cross-sections by cubic isoparametric elements
DEFF Research Database (Denmark)
Høgsberg, Jan Becker; Krenk, Steen
2014-01-01
numerically by introducing a cubic-linear two-dimensional isoparametric element. The cubic interpolation of this element accurately represents quadratic shear stress variations along cross-section walls, and thus moderately thin-walled cross-sections are effectively discretized by these elements. The ability......In technical beam theory the six equilibrium states associated with homogeneous tension, bending, shear and torsion are treated as individual load cases. This enables the formulation of weak form equations governing the warping from shear and torsion. These weak form equations are solved...... of this element to represent curved geometries, and to accurately determine cross-section parameters and shear stress distributions is demonstrated....
DEFF Research Database (Denmark)
Hodicky, Kamil; Hulin, Thomas; Schmidt, Jacob Wittrup
2013-01-01
This paper presents a new thin-walled concrete sandwich panel system reinforced with basalt fiber-reinforced plastic (BFRP) with optimum structural performances and a high thermal resistance developed by Connovate and Technical University of Denmark. The shear connecting system made of a BFRP grid...... is described and provides information on the structural design with its advantages. Experimental and numerical investigations of the BFRP connecting systems were performed. The experimental program included testing of small scale specimens by applying shear (push-off) loading and semi-full scale specimens...
Extensional and Flexural Waves in a Thin-Walled Graphite/Epoxy Tube
Prosser, William H.; Gorman, Michael R.; Dorighi, John
1992-01-01
Simulated acoustic emission signals were induced in a thin-walled graphite/epoxy tube by means of lead breaks (Hsu-Neilsen source). The tube is of similar material and layup to be used by NASA in fabricating the struts of Space Station Freedom. The resulting waveforms were detected by broad band ultrasonic transducers and digitized. Measurements of the velocities of the extensional and flexural modes were made for propagation directions along the tube axis (0 degrees), around the tube circumference (90 degrees) and at an angle of 45 degrees. These velocities were found to be in agreement with classical plate theory.
Lateral static and dynamic characteristics of thin-walled box girder
Institute of Scientific and Technical Information of China (English)
CAN Yan-an; ZHOU Guang-chun
2009-01-01
To analyze the static and dynamic behaviors of the thin-walled box girder in its lateral webs in consideration of shear lag effect and shear deformation, an approach based on the minimum potential principle is introduced in this paper. Both static and dynamic response equations as well as the corresponding natural boundary conditions of the box girder are deduced. Meanwhile, three generalized displacement functions:w(x), U(x) and 0(x) are employed and their differences in the calculus of variation are quantitatively investigated. The comparison of finite shell element results with analytical results of calculation examples validates the feasibility of the proposed approach.
Improved concept models for straight thin-walled columns with box cross section
Institute of Scientific and Technical Information of China (English)
Yu-cheng LIU
2008-01-01
This paper focuses on developing improved concept models for straight thin-walled box sectional columns which can better predict the peak crushing force that occurs during crashworthiness analyses.We develop a nonlinear translational spring based on previous research and apply such a spring element to build the enhanced concept models.The work presented in this article is developed on the basis of the publication of the author(Liu and Day,2006b)and has been applied in a crashworthiness design issue,which is presented by the author in another paper(Liu,2008).
Experimental validation of error in temperature measurements in thin walled ductile iron castings
DEFF Research Database (Denmark)
Pedersen, Karl Martin; Tiedje, Niels Skat
2007-01-01
An experimental analysis has been performed to validate the measurement error of cooling curves measured in thin walled ductile cast iron. Specially designed thermocouples with Ø0.2 mm thermocouple wire in Ø1.6 mm ceramic tube was used for the experiments. Temperatures were measured in plates...... to a level about 20C lower than the actual temperature in the casting. Factors affecting the measurement error (oxide layer on the thermocouple wire, penetration into the ceramic tube and variation in placement of thermocouple) are discussed. Finally, it is shown how useful cooling curve may be obtained...
Reduction of Injection Pressure for Thin Walled Molding using the Laser Metal Sintered Mold
米山, 猛; 内藤, 圭亮; 阿部, 諭; 宮丸, 充
2010-01-01
Using milling combined laser metal sintering, porous surface has been fabricated on the thin walled cavity closed by the surrounded thick cavity in the injection mold. Resin flows into the cavity of 2mm thick at first around the thin part and then flows into the thin cavity of 0.2mm thick with 11mm square by packing pressure. The packing pressure for filling the thin part was compared among laser metal sintered mold with or without porous surface, steel mold with or without porous block. The ...
Spatial resolution of thin-walled high-pressure drift tubes
Davkov, V I; Tikhomirov, V O; Smirnov, S Y; Gregor, I; Senger, P; Naumann, L; Myalkovskiy, V V; Mouraviev, S V; Peshekhonov, V D; Russakovich, N A; Rufanov, I A; Rembser, C
2011-01-01
A small prototype detector based on high pressure thin-walled tubes (straws) has been developed and its parameters have been studied on a bench at JINR, Dubna, and SPS at CERN. The inner diameter of the straws is 9.53 mm. The pressure of the active gas mixture Ar/CO(2) (80/20) was varied from 1 to 5 bar. The best spatial resolution achieved in this pressure range is similar to 40 mu m. Both the high efficiency and high rate capability are retained. (C) 2011 Published by Elsevier B.V.
A prototype coordinate detector based on granulated thin-walled drift tubes
Bazylev, S N; Tikhomirov, V O; Davkov, K I; Gregor, I; Smirnov, S Y; Senger, P; Shutov, A V; Slepnev, I V; Myalkovskiy, V V; Naumann, L; Mouraviev, S V; Zhukov, I A; Peshekhonov, V D; Russakovich, N A; Rufanov, I A; Rembser, C
2011-01-01
A prototype detector based on thin-walled segmented tubes has been developed and its parameters have been studied. The detector contains 360 registration channels with a straw diameter of 4 mm. The prototype' granularity is 4 cm(2) and the length of insensitive region due to straw internal elements is less than 5\\% of its full sensitive area. Deterioration of the spatial resolution near these elements is observed for 1.0\\% of the detector sensitive area. The time and spatial parameters of the detector do not differ from those of conventional tracking detectors based on drift tubes. (C) 2011 Published by Elsevier B.V.
Spatial Finite Element Analysis for Dynamic Response of Curved Thin-Walled Box Girder Bridges
Directory of Open Access Journals (Sweden)
Yinhui Wang
2016-01-01
Full Text Available According to the flexural and torsional characteristics of curved thin-walled box girder with the effect of initial curvature, 7 basic displacements of curved box girder are determined. And then the strain-displacement calculation correlations were established. Under the curvilinear coordinate system, a three-noded curved girder finite element which has 7 degrees of freedom per node for the vibration characteristic and dynamic response analysis of curved box girder is constructed. The shape functions are used as the interpolation functions of variable curvature and variable height to accommodate to the variation of curvature and section height. A MATLAB numerical analysis program has been implemented.
Large structural, thin-wall castings made of metals subject to hot tearing, and their fabrication
Smashey, Russell W. (Inventor)
2001-01-01
An article, such as a gas turbine engine mixer, is made by providing a mold structure defining a thin-walled, hollow article, and a base metal that is subject to hot tear cracking when cast in a generally equiaxed polycrystalline form, such as Rene' 108 and Mar-M247. The article is fabricated by introducing the molten base metal into the mold structure, and directionally solidifying the base metal in the mold structure to form a directionally oriented structure. The directionally oriented structure may be formed of a single grain or oriented multiple grains.
Directory of Open Access Journals (Sweden)
Jairo A. Paredes
2016-04-01
Full Text Available Ferrocement thin walls are the structural elements that comprise the earthquake resistant system of dwellings built with this material. This article presents the results drawn from an experimental campaign carried out over full-scale precast ferrocement thin walls that were assessed under lateral static loading conditions. The tests allowed the identification of structural parameters and the evaluation of the performance of the walls under static loading conditions. Additionally, an isotropic damage model for modelling the mortar was applied, as well as the classic elasto-plastic theory for modelling the meshes and reinforcing bars. The ferrocement is considered as a composite material, thus the serial/parallel mix theory is used for modelling its mechanical behavior. In this work a methodology for the numerical analysis that allows modeling the nonlinear behavior exhibited by ferrocement walls under static loading conditions, as well as their potential use in earthquake resistant design, is proposed.
Dynamic Analysis of Horizontally Curved Thin-Walled Box-Girder Bridge due to Moving Vehicle
Directory of Open Access Journals (Sweden)
K. Nallasivam
2007-01-01
Full Text Available The impact on curved box-girder bridges due to vehicle moving across rough bridge deck have been analyzed using bridge-vehicle coupled dynamics. The bridge deck unevenness has been assumed to be a homogeneous random process in space specified by a PSD function. The analysis incorporates the effect of centrifugal forces due to vehicle moving on curved bridge. The curved box-girder bridge has been numerically modeled using computationally efficient thin-walled box-beam finite elements which take into account the torsional warping, distortion and distortional warping, that are important features of thin-walled box girders. Rigid vehicle with longitudinal and transverse input to the wheels giving rise to heave-pitch-roll degrees of freedom has been considered. The theoretical bridge model used in simulation study has been validated by a free vibration experiment using impact excitation. The impact factors for several response parameters such as bending moment, shear force, torsional moment, torsional bi-moment, distortional moment, distortional bi-moment and vertical deflections have been obtained for various bridge-vehicle parameters. Both constant velocity and forward acceleration of the vehicle have been considered to examine impact factor. The results highlighted that the impact factors of a curved box girder bridge corresponding to torsion, distortion and their corresponding bimoments have been observed to be generally very high, while those of the other responses are also relatively higher than that of corresponding straight box girder bridge.
Anti-impact and energy-absorption of metal and compound thin-wall cylindrical tubes
Institute of Scientific and Technical Information of China (English)
CHEN Yong-tao; SHEN Zhi-chun; ZHENG Gang-tie
2008-01-01
The paper presents an energy iterative method to determine the second critical velocity by comparing the time histories of the kinetic energy and the buckling deformation based on the finite element model of the impact system. To design anti-impact structures of the thin-wall cylindrical tubes with this new method, the cost of the experiment can be considerably reduced. The feasibility and validity of this method are demonstrated by a dropping hammer experiment. In addition, this paper deals with the influence of constrained damping layers on the anti-impact capability and energy-absorption of thin-wall cylindrical tubes. Results show that the constrained damping layers make the energy-absorption and the anti-impact capability increased comparing with the naked tubes; the thickness of the damping layer should be restricted in a range, or else the anti-impact capability will decrease with the increase of the damping layer thickness; for the constrained layer, the anti-impact capability will increase with the augment of its thickness.
A thin-walled Taylor column surrounding a bathtub vortex in rotating tank.
Chu, Chin-Chou; Lai, Kuan-Ruei; Chen, Yin-Chung; Chang, Chien-Cheng; Vortex Dynamics Team
2015-11-01
Numerical simulations and laboratory experiments were jointly conducted to investigate a bathtub vortex under the influence of a protruding cylinder in a rotating tank. The flow pattern depends on Rossby number (Ro = U /fR), Ekman number (Ek = ν /fR2) , and height ratio, h/ H, where R is the radius of the cylinder, f the Coriolis parameter, ν the kinematic viscosity of the fluid, h the vertical length of the cylinder and H the height of the tank. Steady-state solutions obtained by numerically solving the Navier-Stokes equations in the rotating frame are shown to have good agreements with flow visualizations measurements. The bathtub vortex exhibits an interesting two-celled structure with an inner Ekman pumping and an outer up-drafting motion. The two regions of up-drafting motion are separated by a notable finite-thickness structure, identified as thin-walled Taylor column. The Taylor column sets a barrier to the fluid flow that flows into the inner region only through the narrow gaps, one above the Taylor column and one beneath it. Moreover, the dependence of thickness and height of the thin-walled Taylor column on angular velocity ratio of cylinder to background rotation (ω/ Ω) , ranging from -8/3 to 8/3 are also discussed. Supported by Ministry of Science and Technology, TAIWAN ROC, under contract no's 102-2221-E-002-068-MY3 & 103C-4514-1.
Forming characteristics of thin-walled tube bending process with small bending radius
Institute of Scientific and Technical Information of China (English)
LI Heng; YANG He; ZHAN Mei; GU Rui-Jie
2006-01-01
Currently requirements of thin-walled tube with small bending radius cause the defects such as wrinkling,overthinning and cross-section distortion more prone to occur in bending process. Based on the analysis of the forming characteristics by analytical and experimental methods,a complete 3D elastic-plastic FEM model of the process was developed using ABAQUS/Explicit code,including bending process,balls retracting and unloading process,and thus the plastic deformation characteristics with small bending radius were investigated. The main results show that: 1) The utmost deformation feature of the NC bending process is its continuous progressive deformation. 2) The occurring conditions of the defects such as wrinkling and tension instability in the process are obtained. The wrinkling is traditional on the double compressive stresses state and the tension instability is on the double tension stresses state. 3) The enhanced non-uniform deformation in thin-walled tube with small bending radius is demonstrated by comparing the stress/ strains distributions under the 1.5D and 1D bending conditions. 4) For 1D small bending process,a new method-"stepped mandrel retraction" is proposed to improve the bending quality in experiment according to the FE simulation. The simulation results are verified by experiment.
Magnetic moment jumps in flat and nanopatterned Nb thin-walled cylinders
Energy Technology Data Exchange (ETDEWEB)
Tsindlekht, M.I., E-mail: mtsindl@vms.huji.ac.il [The Racah Institute of Physics, The Hebrew University of Jerusalem, 91904 Jerusalem (Israel); Genkin, V.M.; Felner, I.; Zeides, F.; Katz, N. [The Racah Institute of Physics, The Hebrew University of Jerusalem, 91904 Jerusalem (Israel); Gazi, Š.; Chromik, Š. [The Institute of Electrical Engineering SAS, Dúbravská cesta 9, 84104 Bratislava (Slovakia); Dobrovolskiy, O.V. [Physikalisches Institut, Goethe University, 60438 Frankfurt am Main (Germany); Physics Department, V. Karazin Kharkiv National University, 61077 Kharkiv (Ukraine); Sachser, R.; Huth, M. [Physikalisches Institut, Goethe University, 60438 Frankfurt am Main (Germany)
2017-02-15
Highlights: • Magnetization curves of as-prepared and patterned thin-walled cylinders were measured in magnetic fields applied parallel to cylinders axis. • Magnetic moment jumps were observed in magnetic fields lower and above Hc1. • Critical current density in isthmus between two antidots is higher than in a film itself. - Abstract: Penetration of magnetic flux into hollow superconducting cylinders is investigated by magnetic moment measurements. The magnetization curves of a flat and a nanopatterned thin-walled superconducting Nb cylinders with a rectangular cross section are reported for the axial field geometry. In the nanopatterned sample, a row of micron-sized antidots (holes) was milled in the film along the cylinder axis. Magnetic moment jumps are observed for both samples at low temperatures for magnetic fields not only above H{sub c1}, but also in fields lower than H{sub c1}, i. e., in the vortex-free regime. The positions of the jumps are not reproducible and they change from one experiment to another, resembling vortex lattice instabilities usually observed for magnetic fields larger than H{sub c1}. At temperatures above 0.66T{sub c} and 0.78T{sub c} the magnetization curves become smooth for the patterned and the as-prepared sample, respectively. The magnetization curve of a reference flat Nb film in the parallel field geometry does not exhibit jumps in the entire range of accessible temperatures.
Laser bending of pre-stressed thin-walled nickel micro-tubes
Che Jamil, M. S.; Imam Fauzi, E. R.; Juinn, C. S.; Sheikh, M. A.
2015-10-01
Laser forming is an innovative technique of producing bending, spatial forming and alignment of both metallic and non-metallic parts by introducing thermal stresses into a work piece with a laser beam. It involves a complex interaction of process parameters to mechanical and thermal characteristics of materials. This paper presents a comprehensive experimental and numerical study of laser bending process of thin-walled micro-tubes. The effect of input parameters, namely laser power, pulse length and pre-stress constraint, on the process and the final product characteristics are investigated. Results of the analysis show that the bending angle of the tube increases considerably when a constraint is imposed at the tube's free end during the heating period. The introduction of compressive pre-stresses (from mechanical bending) in the irradiated region increases the final deformation which varies almost linearly with the amount of pre-stress. Due to high thermal conductivity and thin-walled structure of the tube, the heat dissipates quickly from the irradiated region to its surrounding material. Therefore, a combination of short pulse duration and high power is preferable to generate a higher thermal gradient and induce plastic strain. Design of experiment and regression analysis are implemented to develop an empirical model based on simulation results. Sensitivity analysis is also performed to determine the influence of independent variables on output response. It is evident that initial displacement and pulse length have a stronger positive effect on the output response as compared to laser power.
Effect of frictions on cross section quality of thin-walled tube NC bending
Institute of Scientific and Technical Information of China (English)
YANG He; GU Rui-jie; ZHAN Mei; LI Heng
2006-01-01
The effect of frictions between dies and tube on the cross section quality of thin-walled tube numerical controlled(NC) bending was studied by numerical simulation method, combined with theoretical analysis and experiment. The results show that the frictions between mandrel, wiper, pressure die, bending die and tube have a significant and complicate effect on the section quality of thin-walled tube NC bending. To improve the section quality, frictions between mandrel, wiper and tube should be decreased, but the frictions between the pressure die, bending die and tube increase. The effect on the section distortion is more significant from mandrel, wiper, pressure die to bending die and the effect on the wall thinning more significant from mandrel, pressure die, wiper, to bending die. The effects of frictions between all dies and tube on wall thinning are smaller than their effects on section distortion.Mandrel and wiper should be lubricated well and drawing oil is used to lubricate them in actual production. The frictions between pressure die, bending die and tube should be increased and the dry friction is used between pressure die, bending die and tube in actual production.
Effect of Different Molding Materials on the Thin-Walled Compacted Graphite Iron Castings
Górny, Marcin; Dańko, Rafał; Lelito, Janusz; Kawalec, Magdalena; Sikora, Gabriela
2016-10-01
This article addresses the effects of six mold materials used for obtaining thin-walled compacted graphite iron castings with a wall thickness of 3 mm. During this research, the following materials were analyzed: fine silica sand, coarse silica sand, cerabeads, molohite and also insulated materials in the shape of microspheres, including low-density alumina/silica ceramic sand. Granulometric and SEM observations indicate that the sand matrix used in these studies differs in terms of size, homogeneity and shape. This study shows that molds made with insulating sands (microspheres) possess both: thermal conductivity and material mold ability to absorb heat, on average to be more than five times lower compared to those of silica sand. In addition to that, the resultant peak of heat transfer coefficient at the mold/metal interface for microspheres is more than four times lower in comparison with fine silica sand. This is accompanied by a significant decrease in the cooling rate of metal in the mold cavity which promotes the development of compacted graphite in thin-walled castings as well as ferrite fractions in their microstructure.
Thin-Walled CFST Columns for Enhancing Seismic Collapse Performance of High-Rise Steel Frames
Directory of Open Access Journals (Sweden)
Yongtao Bai
2017-01-01
Full Text Available This paper numerically studied the collapse capacity of high-rise steel moment-resisting frames (SMRFs using various width-to-thickness members subjected to successive earthquakes. It was found that the long-period component of earthquakes obviously correlates with the first-mode period of high-rises controlled by the total number of stories. A higher building tends to produce more significant component deterioration to enlarge the maximum story drift angle at lower stories. The width-to-thickness ratio of beam and column components overtly affects the collapse capacity when the plastic deformation extensively develops. The ratio of residual to maximum story drift angle is significantly sensitive to the collapse capacity of various building models. A thin-walled concrete filled steel tubular (CFST column is proposed as one efficient alternative to enhance the overall stiffness and deformation capacity of the high-rise SMRFs with fragile collapse performance. With the equivalent flexural stiffness, CFST-MRF buildings with thin-walled members demonstrate higher capacity to avoid collapse, and the greater collapse margin indicates that CFST-MRFs are a reasonable system for high-rises in seismic prone regions.
Joshi, Shrikrishna Nandkishor; Bolar, Gururaj
2017-06-01
Control of part deflection and deformation during machining of low rigidity thin-wall components is an important aspect in the manufacture of desired quality products. This paper presents a comparative study on the effect of geometry constraints on the product quality during machining of thin-wall components made of an aerospace alloy aluminum 2024-T351. Three-dimensional nonlinear finite element (FE) based simulations of machining of thin-wall parts were carried out by considering three variations in the wall constraint viz. free wall, wall constrained at one end, and wall with constraints at both the ends. Lagrangian formulation based transient FE model has been developed to simulate the interaction between the workpiece and helical milling cutter. Johnson-Cook material and damage model were adopted to account for material behavior during machining process; damage initiation and chip separation. A modified Coulomb friction model was employed to define the contact between the cutting tool and the workpiece. The numerical model was validated with experimental results and found to be in good agreement. Based on the simulation results it was noted that deflection and deformation were maximum in the thin-wall constrained at one end in comparison with those obtained in other cases. It was noted that three dimensional finite element simulations help in a better way to predict the product quality during precision manufacturing of thin-wall components.
Institute of Scientific and Technical Information of China (English)
LI Cheng; YANG He; ZHAN Mei; XU Xu-dong; LI Guang-jun
2009-01-01
Numerical control(NC) bending experiments with different process parameters were carried out for 5052O aluminum alloy tubes with outer diameter of 70 mm, wall thickness of 1.5 mm, and centerline bending radius of 105 mm. And the effects of process parameters on tube wall thinning and cross section distortion were investigated. Meanwhile, acceptable bending of the 5052O aluminum tubes was accomplished based on the above experiments. The results show that the effects of process parameters on bending process for large diameter thin-walled aluminum alloy tubes are similar to those for small diameter thin-walled tubes, but the forming quality of the large diameter thin-walled aluminum alloy tubes is much more sensitive to the process parameters and thus it is more difficult to form.
On deformation of thin-walled parts while turning on the lathes
Directory of Open Access Journals (Sweden)
E. V. Arbuzov
2014-01-01
Full Text Available In a number of industries such as aviation engineering, instrumentation engineering, etc. the nonrigid thin-walled parts are a widespread sort of products. For their turning on the lathes the specially designed arrangements are necessary to prevent parts from deformation caused by the action of cutting force and retaining pressure. To create and use the arrangements extra costs are needed, and it, as a consequence, leads to the growth of production price. Potentially, there is another approach. It is to machine using the standard arrangements under special "soft" cutting operation conditions, which are characterized by reduced forces to act on the part, thus decreasing process deformations to the appropriate level. It may be a priori expected that such approach is economically more preferable. Unfortunately, it is difficult to conduct a comparative assessment of these two alternatives to choose a preferable version because of limited data on studies and implementation of the second alternative. Thereupon, to learn the thin-walled deformations versus their treatment conditions is of interest.The aim of the paper is to have general information on topology and elastic deformation value of thin-walled parts, machined on the lathes. The objective is to assess a perspective for further potentially possible activities to develop a concept of machining the thin-walled parts with controlled deformation due to selecting the "soft" cutting operation conditions.The paper studies the thin-walled steel parts of class "Tube" and "Disk" in the role of force action with their dimensions within the range of 5-200 mm for the length, 60-250 mm for diameter, and 4-25 mm for the wall thickness. It considers a chucked work-holding scheme and two machining types, namely external turning cut (for parts of class "Tube" and cross butt turning (for parts of class "Disk". Three stages of machining have been simulated for each type of machining, namely rough (Ra 12.5; IT10
Thin wall ductile iron casting as a substitute for aluminum alloy casting in automotive industry
Directory of Open Access Journals (Sweden)
M. Górny
2009-01-01
Full Text Available In paper it is presented thin wall ductile iron casting (TWDI as a substitute of aluminium alloy casting. Upper control arm made of ductile iron with wall thickness ranging from 2 – 3.7 mm was produced by inmold process. Structure, mechanical properties and computer simulations were investigated. Structural analysis of TWDI shows pearlitic-ferritic matrix free from chills and porosity. Mechanical testing disclose superior ultimate tensile strength (Rm, yield strength (Rp0,2 and slightly lower elongation (E of TWDI in comparison with forged control arm made of aluminium alloy (6061-T6. Moreover results of computer simulation of static loading for tested control arms are presented. Analysis show that the light-weight ductile iron casting can be loaded to similar working conditions as the forged Al alloy without any potential failures.
Finite element modeling of power spinning of thin-walled shell with hoop inner rib
Institute of Scientific and Technical Information of China (English)
BAI Qian; YANG He; ZHAN Mei
2008-01-01
A 3D elasto-plastic finite element(FE) model of power spinning of thin-walled aluminum alloy shell with hoop inner rib was established under software ABAQUS. Key technologies were dealt with reasonably. The reliability of the FE model was verified theoretically and experimentally. The forming process was simulated and studied. The distribution of the thickness and stress, and the variations of spinning force were obtained. The workpiece springback was analyzed with ABAQUS/Standard. The results show that the FE model considering elastic deformation can not only be used to analyze the workpiece springback in the complex spinning process, but also serve as a significant guide to study the local deformation mechanism and choose the reasonable parameters.
Distortional buckling modes of semi-discretized thin-walled columns
DEFF Research Database (Denmark)
Andreassen, Michael Joachim; Jönsson, Jeppe
2012-01-01
eigenvalue problem. This gives the buckling mode shapes and the associated eigenvalues corresponding to the bifurcation load factors. Thus the buckling modes are found directly by the analytical solution of the coupled GBT-equations without modal decomposition. Illustrative examples showing global column......This paper presents distorting buckling solutions for semi-discretized thin-walled columns using the coupled differential equations of a generalized beam theory (GBT). In two related papers recently published by the authors a novel semi-discretization approach to GBT has been presented. The cross...... section is discretized and analytical solutions are sought for the variation along the beam. With this new approach the general GBT equations for identification of a full set of deformation modes corresponding to both homogeneous and non-homogenous equations are formulated and solved. Thereby giving...
Optimal Shakedown of the Thin-Wall Metal Structures Under Strength and Stiffness Constraints
Directory of Open Access Journals (Sweden)
Alawdin Piotr
2017-06-01
Full Text Available Classical optimization problems of metal structures confined mainly with 1st class cross-sections. But in practice it is common to use the cross-sections of higher classes. In this paper, a new mathematical model for described shakedown optimization problem for metal structures, which elements are designed from 1st to 4th class cross-sections, under variable quasi-static loads is presented. The features of limited plastic redistribution of forces in the structure with thin-walled elements there are taken into account. Authors assume the elastic-plastic flexural buckling in one plane without lateral torsional buckling behavior of members. Design formulae for Methods 1 and 2 for members are analyzed. Structures stiffness constrains are also incorporated in order to satisfy the limit serviceability state requirements. With the help of mathematical programming theory and extreme principles the structure optimization algorithm is developed and justified with the numerical experiment for the metal plane frames.
Institute of Scientific and Technical Information of China (English)
AI Yuan-fang; MEI Chi; JIANG Shao-jian; HUANG Guo-dong; CHEN Hong-rong
2006-01-01
The heat transfer characteristic of honeycomb ceramic regenerator was optimized by the perturbation analytical-numerical method. The results show that there is a temperature efficiency peak and the corresponding optimal switch time. The decrease of air oxygen concentration leads to the decrease of maximum temperature efficiency. Optimal switch time is directly proportional to the matrix thickness. The solid heat conduction along the flow direction and the regenerator heat storage capacity of the unit volume have no impact on maximum temperature efficiency and optimal switch time. The temperature efficiency tendency based on the semi-analysis is the same as dispersion combustion tests with low oxygen concentration, and optimal switch time of 2 - 4 s agrees well with that of 4 s in high-temperature gasification tests. The possibility of design, operate and control a thin-walled regenerator with high efficiency by means of the perturbation method is proved.
Large rotation FE transient analysis of piezolaminated thin-walled smart structures
Zhang, S. Q.; Schmidt, R.
2013-10-01
A geometrically nonlinear large rotation shell theory is proposed for dynamic finite element (FE) analysis of piezoelectric integrated thin-walled smart structures. The large rotation theory, which has six independent kinematic parameters but expressed by five nodal degrees of freedom (DOFs), is based on first-order shear deformation (FOSD) hypothesis. The two-dimensional (2D) FE model is constructed using eight-node quadrilateral shell elements with five mechanical DOFs per node and one electrical DOF per piezoelectric material layer with linear constitutive equations. The linear and nonlinear dynamic responses are determined by the central difference algorithm (CDA) and the Newmark method. The results are compared with those obtained by simplified nonlinear theories, as well as those reported in the literature. It is shown that the present large rotation theory yields considerable improvement if the structures undergo large displacements and rotations.
Cost optimization of load carrying thin-walled precast high performance concrete sandwich panels
DEFF Research Database (Denmark)
Hodicky, Kamil; Hansen, Sanne; Hulin, Thomas
2015-01-01
and HPCSP’s geometrical parameters as well as on material cost function in the HPCSP design. Cost functions are presented for High Performance Concrete (HPC), insulation layer, reinforcement and include labour-related costs. The present study reports the economic data corresponding to specific manufacturing......The paper describes a procedure to find the structurally and thermally efficient design of load-carrying thin-walled precast High Performance Concrete Sandwich Panels (HPCSP) with an optimal economical solution. A systematic optimization approach is based on the selection of material’s performances....... The solution of the optimization problem is performed in the computer package software Matlab® with SQPlab package and integrates the processes of HPCSP design, quantity take-off and cost estimation. The proposed optimization process outcomes in complex HPCSP design proposals to achieve minimum cost of HPCSP....
THIN-WALLED CROSS SECTION SHAPE INFLUENCE ON STEEL MEMBER RESISTANCE
Directory of Open Access Journals (Sweden)
Elżbieta Urbańska-Galewska
2016-03-01
Full Text Available This work describes why trending thin-walled technology is achieving popularity in steel construction sector. A purpose of this article is to present the influence of the cold-formed element cross-section shape on an axial compression and a bending moment resistance. The authors have considered four different shapes assuming constant section area and thickness. Calculations were based on three different steel grades taking into account local, distortional and overall buckling. The results are presented in a tabular and a graphical way and clearly confirm that cross-section forming distinctly impact the cold-formed member resistance. The authors choose these cross-sections that work better in compression state and the other (those slender and high that function more efficiently are subjected to bending.
Nonlinear mechanics of thin-walled structures asymptotics, direct approach and numerical analysis
Vetyukov, Yury
2014-01-01
This book presents a hybrid approach to the mechanics of thin bodies. Classical theories of rods, plates and shells with constrained shear are based on asymptotic splitting of the equations and boundary conditions of three-dimensional elasticity. The asymptotic solutions become accurate as the thickness decreases, and the three-dimensional fields of stresses and displacements can be determined. The analysis includes practically important effects of electromechanical coupling and material inhomogeneity. The extension to the geometrically nonlinear range uses the direct approach based on the principle of virtual work. Vibrations and buckling of pre-stressed structures are studied with the help of linearized incremental formulations, and direct tensor calculus rounds out the list of analytical techniques used throughout the book. A novel theory of thin-walled rods of open profile is subsequently developed from the models of rods and shells, and traditionally applied equations are proven to be asymptotically exa...
Directory of Open Access Journals (Sweden)
V. Santhosh kumar
2016-03-01
Full Text Available Energy absorbing characteristics (EAC of thin wall tube during the impact are important in the automobile and aerospace industries. In this paper, energy absorbing characteristics such as mean force, peak force, energy absorption and crash force efficiency (CFE of three different cross-sections (square, rectangular and circular at three different thicknesses (2 mm, 2.5 mm and 4 mm were analyzed. The analysis was accomplished using ABAQUS/EXPLICIT, and aluminum alloy (AA6063 was used as a shell material. The result of impact (or crash-worthiness against axial load indicates that the circular cross section of 2.5 mm thickness is optimum. During the oblique (15°, 30°, 45° impact, increasing the angle leads to less energy absorption. Also, Multilinear regression analysis was carried out to predict the energy absorption characteristics at 90°.
Cellular automaton modeling of ductile iron microstructure in the thin wall
Directory of Open Access Journals (Sweden)
A.A. Burbelko
2011-10-01
Full Text Available The mathematical model of the globular eutectic solidification in 2D was designed. Proposed model is based on the Cellular Automaton Finite Differences (CA-FD calculation method. Model has been used for studies of the primary austenite and of globular eutectic grains growth during the solidification of the ductile iron with different carbon equivalent in the thin wall casting. Model takes into account, among other things, non-uniform temperature distribution in the casting wall cross-section, kinetics of the austenite and graphite grains nucleation, and non-equilibrium nature of the interphase boundary migration. Solidification of the DI with different carbon equivalents was analyzed. Obtained results were compared with the solidification path calculated by CALPHAD method.
Optimization process for thin-walled high performance concrete sandwich panels
DEFF Research Database (Denmark)
Hodicky, Kamil; Hulin, Thomas; Schmidt, Jacob Wittrup
2014-01-01
with the specifications of the design constrains and variables. The tool integrates the processes of HPCSP design, quantity take-off and cost estimation into a single system that would provide different costs for different HPCSP designs. The proposed multi-objective optimisation scheme results into derivation of basic......A Nearly zero energy buildings are to become a requirement as part of the European energy policy. There are many ways of designing nearly zero energy buildings, but there is a lack of knowledge on optimization processes in the sense of structurally and thermally efficient design with an optimal...... economical solution. The present paper aims to provide multi-objective optimisation procedure addressed to structural precast thin-walled High Performance Concrete Sandwich Panels (HPCSP). The research aim is concerned with developing a tool that considers the cost of HPCSP materials along...
Optimization process for thin-walled High Performance Concrete sandwich panels
DEFF Research Database (Denmark)
Hodicky, Kamil; Hulin, Thomas; Schmidt, Jacob Wittrup
2013-01-01
with the specifications of the design con-strains and variables. The tool integrates the processes of HPCSP design, quantity take-off and cost estimation into a single system that would provide different costs for different HPCSP designs. The proposed multi-objective optimisation scheme results into derivation of basic......A Nearly zero energy buildings are to become a requirement as part of the European energy pol-icy. There are many ways of designing nearly zero energy buildings, but there is a lack of knowledge on opti-mization processes in the sense of structurally and thermally efficient design with an optimal...... economical solu-tion. The present paper aims to provide multi-objective optimisation procedure addressed to structural precast thin-walled High Performance Concrete Sandwich Panels (HPCSP). The research aim is concerned with de-veloping a tool that considers the cost of HPCSP materials along...
Institute of Scientific and Technical Information of China (English)
Zi-qian ZHANG
2016-01-01
Cross-sectional ovalization of thin-walled circular steel tube because of large plastic bending,also known as the Brazier effect,usually occurs during the initial stage of tube′s continuous rotary straightening process.The amount of ovalization,defined as maximal cross section flattening,is an important technical parameter in tube′s straightening process to control tube′s bending deformation and prevent buckling.However,for the lack of special analytical model,the maximal section flattening was determined in accordance with the specified charts developed by experienced operators on the basis of experimental data;thus,it was inevitable that the localized buckling might oc-cur during some actual straightening operations.New normal strain component formulas were derived based on the thin shell theory.Then,strain energy of thin-walled tube (per unit length)was obtained using the elastic-plastic the-ory.A rational model for predicting the maximal section flattening of the thin-walled circular steel tube under its straightening process was presented by the principle of minimum potential energy.The new model was validated by experiments and numerical simulations.The results show that the new model agrees well with the experiments and the numerical simulations with error of less than 10%.This new model was expected to find its potential application in thin-walled steel tube straightening machine design.
Multiple, thin-walled cysts are one of the HRCT features of airspace enlargement with fibrosis
Energy Technology Data Exchange (ETDEWEB)
Watanabe, Yasutaka, E-mail: yasuyasu@omiya.jichi.ac.jp [Division of Diagnostic Pathology, Saitama Prefectural Cardiovascular and Respiratory Center, 1696 Itai, Kumagaya City, Saitama 360-0105 (Japan); Division of Pulmonary Medicine, Clinical Department of Internal Medicine, Jichi Medical University, Saitama Medical Center, Amanuma-cho, Omiya City, Saitama 330-8503 (Japan); Kawabata, Yoshinori [Division of Diagnostic Pathology, Saitama Prefectural Cardiovascular and Respiratory Center, 1696 Itai, Kumagaya City, Saitama 360-0105 (Japan); Kanauchi, Tetsu [Department of Radiology, Saitama Prefectural Cardiovascular and Respiratory Center, 1696 Itai, Kumagaya City, Saitama 360-0105 (Japan); Hoshi, Eishin [Department of Thoracic Surgery, Saitama Prefectural Cardiovascular and Respiratory Center, 1696 Itai, Kumagaya City, Saitama 360-0105 (Japan); Kurashima, Kazuyoshi [Department of Pulmonary Medicine, Saitama Prefectural Cardiovascular and Respiratory Center, 1696 Itai, Kumagaya City, Saitama 360-0105 (Japan); Koyama, Shinichiro [Division of Pulmonary Medicine, Clinical Department of Internal Medicine, Jichi Medical University, Saitama Medical Center, Amanuma-cho, Omiya City, Saitama 330-8503 (Japan); Colby, Thomas V. [Department of Laboratory Medicine and Pathology, Mayo Clinic Scottsdale, Scottsdale, AZ 85259 (United States)
2015-05-15
Highlights: • High resolution computed tomography (HRCT) findings of airspace enlargement with fibrosis (AEF), recently identified as a smoking related change. • Investigation was in 35 smokers. • They underwent lobectomy for lung cancer with pathological confirmation of AEF. • Multiple, thin-walled cysts are one of the HRCT features of AEF. - Abstract: Purpose: Airspace enlargement with fibrosis (AEF) has been identified pathologically as a smoking related change. We sought to identify the HRCT findings of AEF and search for distinguishing features from honeycombing. Materials and methods: 50 patients (47 males; mean age 69) were evaluated. All had undergone lobectomy for lung cancer and had confirmed AEF and/or usual interstitial pneumonia (UIP) by pathological evaluation. HRCT findings were first evaluated preresection for resected lobes, and then correlated with the subsequent pathological findings in the resection specimens. Three groups were devised: one with AEF alone to determine the HRCT findings of AEF, a second with AEF and UIP and third with UIP alone. HRCT features of AEF and honeycombing were compared. Results: There were 11 patients (10 male; mean age 69) with AEF alone, 24 patients (22 male; mean age 69) with AEF and UIP, and 15 patients (15 male; mean age 68) with UIP alone. The HRCT on the AEF alone showed subpleural (but not abutting the pleura) multiple thin-walled cysts (MTWCs) in 7 and reticular opacities in 3. The HRCT in AEF and UIP showed MTWCs in 10, reticular opacities in 17; and honeycombing in 5. Among these 35 patients with the pathological finding of AEF (with or without UIP), 17 showed MTWCs. The maximum cyst wall thickness of MTWCs (mean 0.81 mm) was significantly thinner than that of honeycombing (mean 1.56 mm). MTWCs did not locate in lung base and was distant from the pleura. HRCT findings correlated with gross findings on both cysts and honeycombing. No MTWCs were seen in the 15 patients with UIP, 8 of 15 had
Institute of Scientific and Technical Information of China (English)
田宗若; 田宗漱
2001-01-01
用张量分析及微分几何对旋转曲面上的测地线微分方程及斜驶线微分方程进行了研讨。纤维缠绕除满足短程线的环向缠绕(周向缠绕)，并考虑到对纤维缠绕结构，提高其层间剪切强度是提高纤维缠叠层构件整体破坏强度的主要途径，而对纤维缠绕构件，采用横跨交叉编织是提高层间剪切强度的一种方法。根据这种计算的思路，对某叶环复合材料环壳的缠绕方式采用环形周向缠绕加环跨交叉缠绕的方法，优于美国采用的单纯环向缠绕方法。 建议的环形周向缠绕和环跨交叉缠绕均是在满足短程线方程的前提下进行的。叶环缠绕完全可按环跨交叉缠绕及周向缠绕相结合的程序进行重叠缠绕。本文还证明了旋转柱面上的测地线方程、螺旋线方程以及斜驶线方程三者的一致性。%The differential equation of geodesic and the differential equation of inclined path of revolutionary curved surface have been studied by using tensor analysis and differential geometry. For fibre circumferential shell twist, besides satisfying the toroidal twist (circumferential twist)of the shortest path, and also considering the fibre twisting structure, increasing the interlayer shear strength is the main method for increasing the global breaking strength of the layered component twisted with fibre. But for fibre twisting component using cross twist is an alternative method to increase interlayer shear strength. Based on this idea the combination of toroidal twisting and cross twisting for the composite shell twisting is a better method than the simple toroidal twisting method used in the United States of America. The precondition for the toroidal twisting and cross twisting suggested above is to satisfy the shortest path equation. The present parper has also proved the consistence of geodesic equation, solenoidal equation and inclined path equation on the revolutionary cylinder
Optimal Design for Thin-Walled Box Beam Based on Material Strength Reliability
Institute of Scientific and Technical Information of China (English)
无
2003-01-01
According to the reliability of material strength,the optimal design for the cross sectional size of thin-walled box beam was studied.Firstly the cross sectional size as design random variable was determined,then its stochastic nature was researched,with which the objective function is to seek the maximum reliability of the beam under given constraint conditions.This way is not the same as the conventional optimal design for the minimum weight of the material.With establishing the optimal objective,the reliability of the material under conditions of static and fatigue was considered.The corresponding calculated expressions are given.Normally the cross section sizes are fitted to the normal distribution,for the simplification of the design variable,the variation of the section size is assumed as a dependent variable proportional to the mean of the size.The way is different not only with the conventional optimal design but also with the common reliability design.The maximum reliability of material is obtained,meanwhile the area of the cross section is reduced,i.e.,the weight of the material is decreased.
Impact of assembly on signal detection from thin-wall rotors of micro-gyroscopes
Directory of Open Access Journals (Sweden)
Hai Li
2014-03-01
Full Text Available The assembly of sealed hollow rotors, a key component in achieving liquid-levitated micro-gyroscopes, represents a significant challenge. The rotor is a thin-wall cylinder composed of materials that are only 100-μm thick. Furnace soldering and hand soldering are used to join the work pieces, but produce defects evident from deformations and surface roughness. Modeling and experiments show that the deformation is related to the temperature during assembly and the mode by which heat is applied to the components. Temperature affects the deformation through thermal stress and air pressure on the rotor, but the mode of heating creates a big difference. Surface deformation of the rotor alters the detecting capacitance and introduces uncertainty in detection sensitivity of the gyroscope. Experiments show that at 220°C, furnace soldering of rotors causes a great decrease in detection sensitivity, leading to a relative uncertainty of nearly 40%. In contrast, hand soldering leads to a relative uncertainty of about 5%. Spot heating of the rotor during assembly is much better than total heating as less thermal stress is generated and the air pressure difference is almost eliminated. Lowering the temperature is helpful to as long as the connection is sufficiently strengthened.
Wang, Kai Yu
2009-04-01
To develop high-flux and high-rejection forward osmosis (FO) membranes for water reuses and seawater desalination, we have fabricated polybenzimidazole (PBI) nanofiltration (NF) hollow fiber membranes with a thin wall and a desired pore size via non-solvent induced phase inversion and chemically cross-linking modification. The cross-linking by p-xylylene dichloride can finely tune the mean pore size and enhance the salt selectivity. High water permeation flux and improved salt selectivity for water reuses were achieved by using the 2-h modified PBI NF membrane which has a narrow pore size distribution. Cross-linking at a longer time produces even a lower salt permeation flux potentially suitable for desalination but at the expense of permeation flux due to tightened pore sizes. It is found that draw solution concentration and membrane orientations are main factors determining the water permeation flux. In addition, effects of membrane morphology and operation conditions on water and salt transport through membrane have been investigated. © 2008 Elsevier Ltd. All rights reserved.
Plastic Mechanisms for Thin-Walled Cold-Formed Steel Members in Eccentric Compression
Directory of Open Access Journals (Sweden)
Ungureanu Viorel
2016-03-01
Full Text Available The Eurocode 3 concerning thin-walled steel members divides members subjected to compression into four classes, considering their ductility. The representatives of the class C4 are short bars, for which the load-capacity corresponds to the maximum compression stresses less than the yield stress. There are bars prone to local buckling in the elastic range and they do not have a real post-elastic capacity. The failure at ultimate stage of such members, either in compression or bending, always occurs by forming a local plastic mechanism. This fact suggests the possibility to use the local plastic mechanism to characterise the ultimate strength of such members. The present paper is based on previous studies and some latest investigations of the authors, as well as the literature collected data. It represents an attempt to study the plastic mechanisms for members in eccentric compression about minor axis and the evolution of plastic mechanisms, considering several types of lipped channel sections.
Institute of Scientific and Technical Information of China (English)
江树勇; 薛克敏; 宗影影; 喻林
2004-01-01
As a successively and locally plastic deformation process, ball backward spinning is applied for the purpose of producing thin-walled tubular parts with longitudinal inner ribs. By simplifying ball backward spinning as forward extrusion mechanics model, slab method is used in order to solve spinning force. Based on plastic mechanics, the influence of the process parameters involved on formability of inner ribs as well as the quality defects of spun parts is analyzed so as to present an approach to acquire the desired parts. The quality of inner ribs is one of the critical tasks in obtaining the desired spun workpieces and the height of inner rib depends greatly on spinning material,ball diameter, feed ratio, and wall thickness of tubular blank. The knowledge of the influence of process variables such as ball diameter, feed ratio, and wall thickness of tubular blank on the spinning process is essential to prevent the quality defects of the spun parts and obtain the desired spun parts.
Numerical simulation of mold-filling capability for a thin- walled aluminum die casting
Sun, L.; Subasic, E.; Jakumeit, J.
2015-06-01
Mold-filling capability is an important property of casting materials. Especially in thin-walled die casting, fast cooling of the melt by contact to the die makes complete filling difficult to ensure. Simulation is an important tool enabling investigation of filling problems, even before the die is manufactured. However, the prediction of misruns is challenging. Flow and solidification have to be computed as closely coupled. The effects of surface tension, the wetting angle and reduced melt flow due to solidification must be modeled with high precision. To meet these requirements, a finite-volume method using arbitrary polyhedral control volumes is used to solve flow and solidification as closely coupled. The Volume-of-Fluid approach is used to capture the phase separation between gas, melt and solid in connection with a High-Resolution Interface-Capturing scheme to obtain sharp interfaces between phases. To model the resistance of the dendrite network to the melt flow, an additional source term in the momentum equation was implemented. The Bolt test was performed for A356 alloys at a range of different casting temperatures. Numerical prediction of incomplete filling in the bottleneck regions agreed well with experimental findings using 3D camera scanning. The simulation enables derivation of the dependence of critical wall-thickness, i.e. the thickness which is fillable, on casting temperature and metallostatic pressure. This could prove useful in predicting filling problems ahead of casting.
Blast loading of sandwich panels with thin-walled tube cores
Energy Technology Data Exchange (ETDEWEB)
Theobold, M.D.; Nurick, G.N. [Cape Town Univ., Cape Town (South Africa). Blast Impact and Survivability Research Unit
2007-07-01
This paper presented the results of an experimental and modelling study that investigated the responses to blast loading of a novel sandwich panel used in structural protection. The panel was comprised of thin-walled aluminium alloy square tubes with annealed steel outer plates. A split Hopkinson pressure bar was used to characterize the materials at quasi-static strain rates as well as at high strain rates. A series of blast tests was conducted with explosive charges that ranged from between 13 to 38 g with a blast tube mounted to a ballistic pendulum. Results of the experimental study showed that the panel had a large energy absorption capacity. The tube layout and the choice of materials had a significant influence on panel response. During larger blasts, progressive symmetric buckling was observed in core tubes, and core stability was compromised in lower impulse blasts. It was concluded that finite element analyses conducted on the panels showed good agreement with results obtained during the experimental studies.
Porter, Allison K.
The interaction of magnetic fields generated by large superconducting coils has multiple applications in space, including actuation of spacecraft or spacecraft components, wireless power transfer, and shielding of spacecraft from radiation and high energy particles. These applications require coils with major diameters as large as 20 meters and a thermal management system to maintain the superconducting material of the coil below its critical temperature. Since a rigid thermal management system, such as a heat pipe, is unsuitable for compact stowage inside a 5 meter payload fairing, a thin-walled thermal enclosure is proposed. A 1.85 meter diameter test article consisting of a bladder layer for containing chilled nitrogen vapor, a restraint layer, and multilayer insulation was tested in a custom toroidal vacuum chamber. The material properties found during laboratory testing are used to predict the performance of the test article in low Earth orbit. Deployment motion of the same test article was measured using a motion capture system and the results are used to predict the deployment in space. A 20 meter major diameter and coil current of 6.7 MA is selected as a point design case. This design point represents a single coil in a high energy particle shielding system. Sizing of the thermal and structural components of the enclosure is completed. The thermal and deployment performance is predicted.
Viability of thin wall tube forming of ATF FeCrAl
Energy Technology Data Exchange (ETDEWEB)
Maloy, Stuart Andrew [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Aydogan, Eda [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Anderoglu, Osman [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Lavender, Curt [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Yamamoto, Yukinori [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
2016-09-16
Fabrication of thin walled tubing of FeCrAl alloys is critical to its success as a candidate enhanced accident-tolerant fuel cladding material. Alloys that are being investigated are Generation I and Generation II FeCrAl alloys produced at ORNL and an ODS FeCrAl alloy, MA-956 produced by Special Metals. Gen I and Gen II FeCrAl alloys were provided by ORNL and MA-956 was provided by LANL (initially produced by Special Metals). Three tube development efforts were undertaken. ORNL led the FeCrAl Gen I and Gen II alloy development and tube processing studies through drawing tubes at Rhenium Corporation. LANL received alloys from ORNL and led tube processing studies through drawing tubes at Century Tubing. PNNL led the development of tube processing studies on MA-956 through pilger processing working with Sandvik Corporation. A summary of the recent progress on tube development is provided in the following report and a separate ORNL report: ORNL/TM-2015/478, “Development and Quality Assessments of Commercial Heat Production of ATF FeCrAl Tubes”.
Spinning Deformation Criteria of Thin-walled Tubular Part with Longitudinal Inner Ribs
Institute of Scientific and Technical Information of China (English)
JIANG Shuyong; XUE Kemin; LI Chunfeng; REN Zhengyi
2006-01-01
As a successive and local plastic delormation process, backward ball spinning was applied for the purpose of producing thin-walled tubular parts with longitudinal inner ribs. According to the local plastic deformation theory, the application of yield criterion to the spinning process and the influence of the radial spinning force component on the formability of inner ribs were analyzed. Based on yield criterion and plastic mechanics, the stable flow rude of metal material and forming criteria of the inner ribs were obtained and conformed to the experimental results so as to contribute greatly to improving the ball spinning process and optimizing the process variables, such as the diameter of ball, the reduction in a pass and the wall thickness of tubular blank, which have a significant influence on the formability of the inner ribs. The knowledge of the influence of the process variables such as the diameter of ball, the reduction in a pass and the wall thickness of tubular blank on the spinning process is essential to preventing the quality defects of the spun parts and obtaining the desired spun parts.
Bulging Behavior of Thin-walled Welded Low Carbon Steel Tubes
Directory of Open Access Journals (Sweden)
XIE Wen-cai
2017-01-01
Full Text Available In order to investigate the deformation behaviour of welded tubes during hydraulic bulging process,the hydraulic bulging tests of thin-walled welded low carbon steel tubes (STKM11A were conducted on the tube hydroformability testing unit.The thickness distribution,profiles of bulging area and the strain distribution were all obtained.Results show that the thickness reduction of weld zone is just 2.4%-5.5% while its effective strain is just 0.05-0.10,which is very small and negligible compared with the parent material and means that just the geometric position of weld zone is changed with the continuous bulging.The thinnest points are located on the both sides of weld seam symmetrically and the angle between the thinnest point and weld seam is about 30°,at which the necking has been occurred.When the length of bulging area increases,the fracture pressure,the thickness reduction and the ultimate expansion ratio all decrease,and the profile of the bulging area gradually steps away from the elliptical model which is powerless for the ratio of length to diameter up to 2.0.Moreover,the strain state of the tube is transformed from biaxial tension to plane strain state with the increasing length of bulging area,on the basis of this the forming limit diagram of welded STKM11A steel tubes can be established.
Viability of thin wall tube forming of ATF FeCrAl
Energy Technology Data Exchange (ETDEWEB)
Maloy, Stuart Andrew [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Aydogan, Eda [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Anderoglu, Osman [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Lavender, Curt [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Yamamoto, Yukinori [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
2016-09-16
Fabrication of thin walled tubing of FeCrAl alloys is critical to its success as a candidate enhanced accident tolerant fuel cladding material. Alloys that are being investigated are Generation I and Generation II FeCrAl alloys produced at ORNL and an ODS FeCrAl alloy, MA-956 produced by Special Metals. Gen I and Gen II FeCrAl alloys were provided by ORNL and MA-956 was provided by LANL (initially produced by Special Metals). Three tube development efforts were undertaken. ORNL led the FeCrAl Gen I and Gen II alloy development and tube processing studies through drawing tubes at Rhenium Corporation. LANL received alloys from ORNL and led tube processing studies through drawing tubes at Century Tubing. PNNL led the development of tube processing studies on MA-956 through pilger processing working with Sandvik Corporation. A summary of the recent progress on tube development is provided in the following report and a separate ORNL report: ORNL/TM-2015/478, “Development and Quality Assessments of Commercial Heat Production of ATF FeCrAl Tubes”.
Crack growth in the through-thickness direction of hydrided thin-wall Zircaloy sheet
Raynaud, Patrick A.; Koss, Donald A.; Motta, Arthur T.
2012-01-01
In a reactivity-initiated accident, cladding failure may occur by crack initiation within a defect such as a hydride rim or blister and subsequent crack propagation through the thickness of the thin-wall cladding. In such a circumstance, determining the cladding resistance to crack propagation in the through-thickness direction is crucial to predicting cladding failure. To address this issue, through-thickness crack propagation in hydrided Zircaloy-4 sheet was analyzed at 25 °C, 300 °C, and 375 °C. At 25 °C, the fracture toughness decreased with increasing hydrogen content and with an increasing fraction of radial hydrides. Hydride particles fractured ahead of the crack tip, creating a path for crack growth. At both 300 °C and 375 °C, the resistance to crack-growth initiation was sufficiently high that crack extension was often caused by crack-tip blunting. There was no evidence of hydride particles fracturing near the crack tip, and no significant effect of hydrogen content on fracture toughness was observed at these elevated temperatures.
Eikonal-based initiation of fibrillatory activity in thin-walled cardiac propagation models.
Herlin, Antoine; Jacquemet, Vincent
2011-12-01
Reentrant arrhythmias can be simulated in electrophysiological models of electrical impulse propagation governed by a reaction-diffusion system. To facilitate the initiation of a large number of independent episodes of simulated arrhythmias with controllable level of complexity, a new approach is proposed for thin-walled geometries in which depolarization wave dynamics is essentially two-dimensional. Points representing phase singularities are first randomly distributed over the epicardial surface and are assigned a topological charge (direction of rotation). A qualitatively-correct phase map is then reconstructed on the whole surface by interpolation. The eikonal-diffusion equation is used to iteratively regularize the phase map based on a priori information on wavefront propagation. An initial condition for the reaction-diffusion model is created from the resulting phase map with multiple functional/anatomical reentries. Results in an atrial model demonstrate the ability to generate statistical realizations of the same dynamics and to vary the level of complexity measured by the number of phase singularities. A library of 100 simulations with an average number of phase singularities ranging from 1 to 10 is created. An extension to volumetric patient-specific atrial models including fiber orientation and a fast conducting system is presented to illustrate possible applications.
Static analysis of reinforced thin-walled plates and shells by means of finite element models
Carrera, E.; Zappino, E.; Cavallo, T.
2016-03-01
In this paper, variable kinematic one-dimensional (1D) structural models have been used to analyze thin-walled structures with longitudinal stiffeners and static loads. These theories have hierarchical features and are based on the Carrera Unified Formulation (CUF). CUF describes the displacement field of a slender structure as the product of two function expansions, one over the cross-sectional coordinates, Taylor (TE) or Lagrange (LE) expansions were used here, and one along the beam axis. The results obtained using the refined 1D models have been compared with those from classical finite element analyses that make use of plates/shells and solids elements. The performances of classical and refined structural models have been compared in terms of accuracy and computational costs. The results show that the use of the LE over the cross-section allows the strain/stress fields to be evaluated accurately for all the structural components. The comparisons with the results obtained using the classical models highlight how, the use of 1D refined models, allows the number of degrees of freedom (DOF) to be reduced, meanwhile, the accuracy of the results can be preserved.
Directory of Open Access Journals (Sweden)
Yang Dongqing
2017-01-01
Full Text Available The deposition time for fabricating the thin-wall part as well as the peak temperature of the substrate during the process was analyzed in the double electrode gas metal arc welding (DE-GMAW based additive manufacturing (AM. The total deposition time and the interlayer idle time of the manufacturing process decreased with the increasing of the bypass current under the same interlayer temperature and the same deposition rate. The thermal cycling curves illustrated that the peak temperature of the substrate was lower in the DE-GMAW base AM under the same conditions. When depositing the thin-wall parts, the DE-GMAW based AM can reduce the heat input to the substrate and improve the fabrication efficiency, compared with the GMAW based AM.
Institute of Scientific and Technical Information of China (English)
LI Xin-lei; HAO Qi-tang; JIE Wan-qi; ZHOU Yu-chuan
2008-01-01
Counter gravity casting equipments(CGCE) were widely used to produce large thin-walled A357 aluminum alloy components. To improve the pressure control precision of CGCE to get high quality castings, a pressure control system based on fuzzy-PID hybrid control technology and the digital assembled valve was developed. The actual pressure tracking experiment results show that the special system by applying PID controller and fuzzy controller to varied phases, is not only able to inherit the small error and good static stability of classical PID control, but also has fuzzy control's advantage of fully adapting itself to the object. The pressure control error is less than 0.3 kPa. By using this pressure control system, large complex thin-walled A357 aluminum alloy castings with high quality was successfully produced.
Finite Element Simulation on the Spin-forming of the 3D Non-axisymmetric Thin-Walled Tubes
Institute of Scientific and Technical Information of China (English)
无
2006-01-01
The roller movement trace for the 3D non-axisymmetric thin-walled tubes is a complex space curve. Besides the roller rotation caused by contact with the blank, the roller rotates around the workpiece together with the main spindle, and also moves simultaneously along the direction of the revolution radius. The method to correctly establish the finite element (FE) models of the metal spinning is based on the MSC. MARC software was introduced. The calculation formulas considering both the revolution and rotation of the roller were obtained by the mathematical deduction. The saving calculation points m should be a multiple of 4 for one revolution of the roller around the workpiece to obtain the maximum forming force for the spinning of the 3D non-axisymmetric thin-walled tubes. The simulation results conform well to the experimental ones for several spinning methods; the maximum error is less than ±15%.
薄壁零件的工艺分析%Process Analysis of Ultra-thin Wall Parts
Institute of Scientific and Technical Information of China (English)
刘利民; 谭文凯; 黄新
2011-01-01
论述了在数控车床上加工薄壁零件时,如何针对零件特点优化加工工艺、制作专用的工装等工艺措施来提高产品合格率,并对工艺改进前后的零件质量进行比对分析.%It has been introduced that how to improve the rate of qualified products by optimizing the process, producing special tools and so on when the ultra-thin wall part is processed on CNC. The quality of the ultra-thin wall parts before and after proeess improvement was compared and analyzed.
Nonlinear Free Vibration Analysis of Thin-walled Curved Beam with Non-symmetric Open Cross Section
Institute of Scientific and Technical Information of China (English)
DUAN Hai-juan; SONG Zhen-sen
2008-01-01
A finite element formulation was presented for the nonlinear free vibration of thin-walled curved beams with non-symmetric open across section. The kinetic and potential energies were derived by the virtual principle. The energy function includes the effect of flexural-torsional coupling, the torsion warping and the shear centre location. For finite element analysis, cubic polynomials were utilized as the shape functions of the two nodal thin-walled curved elements. Each node possesses seven degrees freedom including the warping degree of freedom. The nonlinear eigenvalue problem was solved by the direct iteration technique. The results are compared with those for straight beams as available in the literature. The results for nonlinear free vibration analysis of curved beams for various radii and subtended angle are presented.
Shen, Qi; Trabia, Sarah; Stalbaum, Tyler; Palmre, Viljar; Kim, Kwang; Oh, Il-Kwon
2016-04-01
Development of biomimetic actuators has been an essential motivation in the study of smart materials. However, few materials are capable of controlling complex twisting and bending deformations simultaneously or separately using a dynamic control system. Here, we report an ionic polymer-metal composite actuator having multiple-shape memory effect, and is able to perform complex motion by two external inputs, electrical and thermal. Prior to the development of this type of actuator, this capability only could be realized with existing actuator technologies by using multiple actuators or another robotic system. This paper introduces a soft multiple-shape-memory polymer-metal composite (MSMPMC) actuator having multiple degrees-of-freedom that demonstrates high maneuverability when controlled by two external inputs, electrical and thermal. These multiple inputs allow for complex motions that are routine in nature, but that would be otherwise difficult to obtain with a single actuator. To the best of the authors’ knowledge, this MSMPMC actuator is the first solitary actuator capable of multiple-input control and the resulting deformability and maneuverability.
Directory of Open Access Journals (Sweden)
Dietmar Drummer
2014-01-01
Full Text Available In micro- and thin-wall injection moulding the process conditions affect the developed internal structures and thus the resulting part properties. This paper investigates exemplarily on polyamide 66 the interactions of different cooling conditions on the morphological and crystalline structures. The investigations reveal that a slow cooling rate of the melt results in a homogeneous morphology and a higher degree of crystallinity and also a favoured crystalline structure. Consequently, the dielectric behaviour and light transmitting part properties are affected.
A Study on 3D FE Simulation Method of NC Bending Process of Thin-walled Tube
Institute of Scientific and Technical Information of China (English)
无
2002-01-01
The numerical control (NC) precision bending process of thin-walled tube is on e of advanced plastic forming processes with high efficiency, forming precision, strength/weight ratio and low cost, thus it is playing more and more important role in manufacturing parts in aerospace and automobile industries. However, the determination of parameters crucial to make sure tube parts qualified is heavil y experience-based and involves repeated trial-and-errors in practice, which makes the production efficiency...
Institute of Scientific and Technical Information of China (English)
Ma Junjin; Zhang Dinghua; Wu Baohai; Luo Ming; Chen Bing
2016-01-01
Milling of the thin-walled workpiece in the aerospace industry is a critical process due to the high flexibility of the workpiece. In this paper, a flexible fixture based on the magnetorheological (MR) fluids is designed to investigate the regenerative chatter suppression during the machining. Based on the analysis of typical structural components in the aerospace industry, a general complex thin-walled workpiece with fixture and damping constraint can be equivalent as a rectangular can-tilever beam. On the basis of the equivalent models, natural frequency and mode shape function of the thin-walled workpiece is obtained according to the Euler–Bernoulli beam assumptions. Then, the displacement response function of the bending vibration of the beam is represented by the pro-duct of all the mode shape function and the generalized coordinate. Furthermore, a dynamic equa-tion of the workpiece-fixture system considering the external damping factor is proposed using the Lagrangian method in terms of all the mode shape function and the generalized coordinate, and the response of system under the dynamic cutting force is calculated to evaluate the stability of the milling process under damping control. Finally, the feasibility and effectiveness of the proposed approach are validated by the impact hammer experiments and several machining tests.
Institute of Scientific and Technical Information of China (English)
Jian Zhang; Chu-Wei Zhou; Jia-Shou Zhuo
2011-01-01
The FCSE controlling equation of pinned thinwalled curve box was derived and the indeterminate problem of continuous thin-walled curve box with diaphragm was solved based on flexibility theory. With Bayesian statistical theory, dynamic Bayesian error function of displacement parameters of indeterminate curve box was founded. The corresponding formulas of dynamic Bayesian expectation and variance were deduced. Combined with one-dimensional Fibonacci automatic search scheme of optimal step size,the Powell optimization theory was utilized to research the stochastic identification of displacement parameters of indeterminate thin-walled curve box. Then the identification steps were presented in detail and the corresponding calculation procedure was compiled. Through some classic examples, it is obtained that stochastic performances of systematic parameters and systematic responses are simultaneously deliberated in dynamic Bayesian error function. The one-dimensional optimization problem of the optimal step size is solved by adopting Fibonacci search method. And the Powell identification of displacement parameters of indeterminate thin-walled curve box has satisfied numerical stability and convergence, which demonstrates that the presented method and the compiled procedure are correct and reliable.The project was supported by the National Natural Science Foundation of China ( 10472045.10772078 and 11072108 and the Science Foundation of NUAA(S0851-013).During parameters' iterative processes, the Powell theory is irrelevant with the calculation of finite curve strip element (FCSE) partial differentiation, which proves high computation efficiency of the studied method.
Directory of Open Access Journals (Sweden)
Kołakowski Zbigniew
2016-06-01
Full Text Available A review of papers that investigate the static and dynamic coupled buckling and post-buckling behaviour of thin-walled structures is carried out. The problem of static coupled buckling is sufficiently well-recognized. The analysis of dynamic interactive buckling is limited in practice to columns, single plates and shells. The applications of finite element method (FEM or/and analytical-numerical method (ANM to solve interaction buckling problems are on-going. In Poland, the team of scientists from the Department of Strength of Materials, Lodz University of Technology and co-workers developed the analytical-numerical method. This method allows to determine static buckling stresses, natural frequencies, coefficients of the equation describing the post-buckling equilibrium path and dynamic response of the plate structure subjected to compression load and/or bending moment. Using the dynamic buckling criteria, it is possible to determine the dynamic critical load. They presented a lot of interesting results for problems of the static and dynamic coupled buckling of thin-walled plate structures with complex shapes of cross-sections, including an interaction of component plates. The most important advantage of presented analytical-numerical method is that it enables to describe all buckling modes and the post-buckling behaviours of thin-walled columns made of different materials. Thin isotropic, orthotropic or laminate structures were considered.
Thin-Walled Beam Theories and Their Applications in the Torsional Strength Analysis of Ship Hulls.
1987-01-01
numerous deep web frames and transverse bulkheads. The system has been utilized in a study of a frigate under an assumed torsional/flexural load, the...transverse bulkheads and r deep web frames. Figure 18 indicates that, despite the poor agreement in twist angle, the axial stress results compare quite...under torsional loads. This will be the case for a typical warship hull, because of the large number of deep web frames and transverse bulkheads. The
Status of Joining Thin Sheet and Thin Wall Tubes of 14YWT
Energy Technology Data Exchange (ETDEWEB)
Hoelzer, David T. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Unocic, Kinga A. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Tang, Wei [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Feng, Zhili [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
2015-09-18
Beginning this fiscal year, the FCRD research project initiated an investigation on joining thin sections of the advanced ODS 14YWT ferritic alloy. Friction stir welding (FSW) was investigated as a method to join thin plate and tubing of 14YWT since it is a solid state joining method that has been shown in past studies to be a promising method for joining plates of ODS alloys, such as 14YWT. However, this study will attempt to be the first to demonstrate if FSW can successfully join thin plates and thin wall tubing of 14YWT. In the first FSW attempt, a 1.06 cm thick plate of 14YWT (SM13 heat) was successfully rolled at 1000ºC to the target thickness of 0.1 cm with no edge cracking. This achievement is a highlight since previous attempts to roll 14YWT plates have resulted in extensive cracking. For the FSW run, a pin tool being developed by the ORNL FSW Process Development effort was used. The first FSW run successfully produced a bead-on-plate weld in the 0.1 cm thick plate. The quality of the weld zone appears very good with no evidence of large defects such as cavities. The microstructural characterization study of the bead-on-plate weld zone has been initiated to compare the results of the microstructure analysis with those obtained in the reference microstructural analysis of the 14YWT (SM13 heat) that showed ultra-fine grain size of 0.43 μm and a high number density of ~2-5 nm sizes oxygen-enriched nanoclusters.
Thin-walled Cystic Lung Cancer: An Analysis of 24 Cases and Review of Literatures
Directory of Open Access Journals (Sweden)
Juntang GUO
2014-07-01
Full Text Available Background and objective Lung cancer presenting as cystic lesions was first described by Anderson and Pierce in 1954. Lung cancer presenting as cysts is a rare entity in clinical practice. Differential diagnosis is difficult in the benign-like cyst. This study investigated the clinical characteristics, diagnosis and treatment of lung cancer presenting as cysts. Methods We conducted a retrospective analysis of the clinical records of 24 patients who underwent surgery for a primary lung cancer presenting as cysts in our department between 2007 and 2013. We defined a ‘Thin-walled cyst’ as a cavitary lesion with a wall thickness of 4 mm or less along at least 75% of the circumference of the lesion. The whole group underwent post-operative follow-up. Results The incidence of cystic lung cancer was 0.49% (24/4,897 of surgical cases. The subjects’ age ranged from 19 to 77 yr with a median age of 56.5 yr. Ten cases presented with respiratory symptoms while 14 showed abnormal shadows on a chest CT without symptoms. Histological analysis showed that 18 cases were of adenocarcinoma, three of squamous cell carcinoma, one of small cell carcinoma, one of adenosquamous carcinoma and one of large cell carcinoma. Three patients were dead, and the remaining 21 patients are alive and disease free at the end of follow-up. Conclusion Cystic lung cancer should be kept in mind during the differential diagnosis of focal benign cyst. Cystic lung cancer could achieve a good outcome if early diagnose can be obtained.
Hodges, Robert V.; Nixon, Mark W.; Rehfield, Lawrence W.
1987-01-01
A methodology was developed for the structural analysis of composite rotor blades. This coupled-beam analysis is relatively simple to use compared with alternative analysis techniques. The beam analysis was developed for thin-wall single-cell rotor structures and includes the effects of elastic coupling. This paper demonstrates the effectiveness of the new composite-beam analysis method through comparison of its results with those of an established baseline analysis technique. The baseline analysis is an MSC/NASTRAN finite-element model built up from anisotropic shell elements. Deformations are compared for three linear static load cases of centrifugal force at design rotor speed, applied torque, and lift for an ideal rotor in hover. A D-spar designed to twist under axial loading is the subject of the analysis. Results indicate the coupled-beam analysis is well within engineering accuracy.
Generalised twisted partition functions
Petkova, V B
2001-01-01
We consider the set of partition functions that result from the insertion of twist operators compatible with conformal invariance in a given 2D Conformal Field Theory (CFT). A consistency equation, which gives a classification of twists, is written and solved in particular cases. This generalises old results on twisted torus boundary conditions, gives a physical interpretation of Ocneanu's algebraic construction, and might offer a new route to the study of properties of CFT.
Casey, E. J.; Commadore, C. C.; Ingles, M. E.
1980-01-01
Long wire bundles twist into uniform spiral harnesses with help of simple apparatus. Wires pass through spacers and through hand-held tool with hole for each wire. Ends are attached to low speed bench motor. As motor turns, operator moves hand tool away forming smooth twists in wires between motor and tool. Technique produces harnesses that generate less radio-frequency interference than do irregularly twisted cables.
Twisted network programming essentials
Fettig, Abe
2005-01-01
Twisted Network Programming Essentials from O'Reilly is a task-oriented look at this new open source, Python-based technology. The book begins with recommendations for various plug-ins and add-ons to enhance the basic package as installed. It then details Twisted's collection simple network protocols, and helper utilities. The book also includes projects that let you try out the Twisted framework for yourself. For example, you'll find examples of using Twisted to build web services applications using the REST architecture, using XML-RPC, and using SOAP. Written for developers who want to s
Institute of Scientific and Technical Information of China (English)
无
2002-01-01
In the paper, the experimental researches were carr ie d out to discuss the roundness forming rule and the influence of cutting paramet ers on roundness by ultrasonic vibration cutting of the camera's guiding drawtu be with 47.75 mm diameter and 0.6～1.5 mm wall thickness. The research results s h ow that the roundness error of ultra-thin wall parts in ultrasonic vibration cu tting is only one third of that in common cutting. The relations between the rou ndness error and the cutting parameters behave as: (1...
The problems of calculating the load-bearing structures made of light steel thin-walled profiles
Directory of Open Access Journals (Sweden)
Roy Vera
2016-01-01
Full Text Available The article presents the results of a study of bearing capacity of thin-walled cold-formed steel beam of the guide profile. Such profiles have a small thickness and complex cross-sectional shape. Bending deformation develops in the cross-sectional plane under the influence of loads in beam. In addition, deformation of constrained torsion and warping arise. These deformations influence the stress distribution at the points of the cross-section of the beam and thereby determine its load-bearing capacity.
Overregularity in Oliver Twist
Institute of Scientific and Technical Information of China (English)
孔祥曼
2015-01-01
Oliver Twist is one of the earliest works of Charles Dickens. In this novel, the author uses many writing skills which impress the readers a lot. This paper gives a brief description of overregularity in Oliver Twist at the phonological and syntactical levels.
Sobouti, Farhad; Rakhshan, Vahid; Saravi, Mahdi Gholamrezaei; Zamanian, Ali
2016-01-01
Objective Traditional retainers (both metal and fiber-reinforced composite [FRC]) have limitations, and a retainer made from more flexible ligature wires might be advantageous. We aimed to compare an experimental design with two traditional retainers. Methods In this prospective preliminary clinical trial, 150 post-treatment patients were enrolled and randomly divided into three groups of 50 patients each to receive mandibular canine-to-canine retainers made of FRC, flexible spiral wire (FSW), and twisted wire (TW). The patients were monitored monthly. The time at which the first signs of breakage/debonding were detected was recorded. The success rates of the retainers were compared using chi-squared, Kaplan-Meier, and Cox proportional-hazard regression analyses (α = 0.05). Results In total, 42 patients in the FRC group, 41 in the FSW group, and 45 in the TW group completed the study. The 2-year failure rates were 35.7% in the FRC group, 26.8% in the FSW group, and 17.8% in the TW group. These rates differed insignificantly (chi-squared p = 0.167). According to the Kaplan-Meier analysis, failure occurred at 19.95 months in the FRC group, 21.37 months in the FSW group, and 22.36 months in the TW group. The differences between the survival rates in the three groups were not significant (Cox regression p = 0.146). Conclusions Although the failure rate of the experimental retainer was two times lower than that of the FRC retainer, the difference was not statistically significant. The experimental TW retainer was successful, and larger studies are warranted to verify these results. PMID:27019825
Nam-Il, Kim; Moon-Young, Kim
2005-06-01
An improved numerical method to exactly evaluate the dynamic element stiffness matrix is proposed for the spatially coupled free vibration analysis of non-symmetric thin-walled curved beams subjected to uniform axial force. For this purpose, firstly equations of motion, boundary conditions and force-deformation relations are rigorously derived from the total potential energy for a curved beam element. Next systems of linear algebraic equations with non-symmetric matrices are constructed by introducing 14 displacement parameters and transforming the fourth-order simultaneous differential equations into the first-order simultaneous equations. And then explicit expressions for displacement parameters are numerically evaluated via eigensolutions and the exact 14×14 element stiffness matrix is determined using force-deformation relations. In order to demonstrate the validity and the accuracy of this study, the spatially coupled natural frequencies of non-symmetric thin-walled curved beams subjected to uniform compressive and tensile forces are evaluated and compared with analytical and finite element solutions using Hermitian curved beam elements or ABAQUS's shell element. In addition, some results by the parametric study are reported.
Zsirka, Balázs; Horváth, Erzsébet; Szabó, Péter; Juzsakova, Tatjána; Szilágyi, Róbert K.; Fertig, Dávid; Makó, Éva; Varga, Tamás; Kónya, Zoltán; Kukovecz, Ákos; Kristóf, János
2017-03-01
Surface modification of the halloysite-10 Å mineral with tubular morphology can be achieved by slightly modified procedures developed for the delamination of kaolinite minerals. The resulting delaminated halloysite nanoparticles have unexpected surface/morphological properties that display, new potentials in catalyst development. In this work, a four-step intercalation/delamination procedure is described for the preparation of thin-walled nanoscrolls from the multi-layered hydrated halloysite mineral that consists of (1) intercalation of halloysite with potassium acetate, (2) replacement intercalation with ethylene glycol, (3) replacement intercalation with hexylamine, and (4) delamination with toluene. The intercalation steps were followed by X-ray diffraction, transmission electron microscopy, N2 adsorption-desorption, thermogravimetry, and infrared spectroscopy. Delamination eliminated the crystalline order and the crystallite size along the 'c'-axis, increased the specific surface area, greatly decreased the thickness of the mineral tubes to a monolayer, and shifted the pore diameter toward the micropore region. Unexpectedly, the removal of residual organics from intercalation steps adsorbed at the nanoscroll surface with a peroxide treatment resulted in partial recovery of crystallinity and increase of crystallite size along the 'c'-crystal direction. The d(001) value showed a diffuse pattern at 7.4-7.7 Å due to the rearrangement of the thin-walled nanoscrolls toward the initial tubular morphology of the dehydrated halloysite-7 Å mineral.
UBET analysis of process of extruding aluminum alloy ribbed thin-wall pipes through a porthole die
Institute of Scientific and Technical Information of China (English)
谢建新; 裴强; 刘静安
2002-01-01
Using the upper bound element technique (UBET), a numerical model was proposed for analyzing the metal deformation behavior in the extrusion process of ribbed thin-wall pipes through a porthole die. Optimization parameters were contained in the numerical model and determined through minimizing the total work of metal deformation. Taking the extrusion process of thin-wall pipe with one rib as an example, the calculated results using the proposed model are as follows: the extrusion pressure p is linearly related to the extrusion ratio R by p = a+bR 0.683, where a =14.13, b =0.911. When the length of the billet remaining in container is shorter than a quarter of the container diameter, the plastic region extends over the whole of the remained billet and the extrusion process reaches the state of funnel deformation. There exists an optimum depth of welding chamber in respect of the extrusion pressure, and to the calculated example the optimum depth is about 10% of the circumscribed diameter of portholes. To obtain more equitable metal flow in welding chamber, it is required to make the dividing planes in container to be consistent with corresponding welding planes in the chamber ( θ max i = θ′ max i ) through choosing different entering area for each of the portholes.
Tunneling from a Minkowski vacuum to an AdS vacuum: A new thin-wall regime
Masoumi, Ali; Weinberg, Erick J
2016-01-01
Using numerical and analytic methods, we study quantum tunneling from a Minkowski false vacuum to an anti-de Sitter true vacuum. Scanning the parameter space of theories with quartic and non-polynomial potentials, we find that for any given potential tunneling is completely quenched if gravitational effects are made sufficiently strong. For potentials where $\\epsilon$, the energy density difference between the vacua, is small compared to the barrier height, this occurs in the thin-wall regime studied by Coleman and De Luccia. However, we find that other potentials, possibly with $\\epsilon$ much greater than the barrier height, produce a new type of thin-wall bounce when gravitational effects become strong. We show that the critical curve that bounds the region in parameter space where the false vacuum is stable can be found by a computationally simple overshoot/undershoot argument. We discuss the treatment of boundary terms in the bounce calculation and show that, with proper regularization, one obtains an id...
Wang, Xinlin; Deng, Dewei; Qi, Meng; Zhang, Hongchao
2016-06-01
Direct laser fabrication (DLF) developed from laser cladding and rapid prototyping technique has been widely used to fabricate thin-walled parts exhibiting more functions without expending weight and size. Oblique thin-walled parts accompanied with inhomogeneous mechanical properties are common in application. In the present study, a series of AISI316L stainless steel oblique thin-walled parts are successfully produced by DLF, in addition, deposition strategies, microstructure, and mechanical property of the oblique thin-walled parts are investigated. The results show that parallel deposition way is more valuable to fabricate oblique thin-walled part than oblique deposition way, because of the more remarkable properties. The hardness of high side initially increases until the distance to the substrate reaches about 25 mm, and then decreases with the increase of the deposition height. Oblique angle has a positive effect on the tensile property but a negative effect on microstructure, hardness and elongation due to the more tempering time. The maximum average ultimate tensile strength (UTS) and elongation are presented 744.3 MPa and 13.5% when the angle between tensile loading direction and horizontal direction is 45° and 90°, respectively.
Twist decomposition of proton structure from BFKL and BK amplitudes
Motyka, Leszek
2014-01-01
An analysis of twist composition of Balitsky-Kovchegov (BK) amplitude is performed in the double logarithmic limit. In this limit the BK evolution of color dipole -- proton scattering is equivalent to BFKL evolution which follows from vanishing of the Bartels vertex in the collinear limit. We perform twist decomposition of the BFKL/BK amplitude for proton structure functions and find compact analytic expressions that provide accurate approximations for higher twist amplitudes. The BFKL/BK higher twist amplitudes are much smaller than those following from eikonal saturation models.
Freed, Daniel S
2012-01-01
We show how general principles of symmetry in quantum mechanics lead to twisted notions of a group representation. This framework generalizes both the classical 3-fold way of real/complex/quaternionic representations as well as a corresponding 10-fold way which has appeared in condensed matter and nuclear physics. We establish a foundation for discussing continuous families of quantum systems. Having done so, topological phases of quantum systems can be defined as deformation classes of continuous families of gapped Hamiltonians. For free particles there is an additional algebraic structure on the deformation classes leading naturally to notions of twisted equivariant K-theory. In systems with a lattice of translational symmetries we show that there is a canonical twisting of the equivariant K-theory of the Brillouin torus. We give precise mathematical definitions of two invariants of the topological phases which have played an important role in the study of topological insulators. Twisted equivariant K-theor...
Institute of Scientific and Technical Information of China (English)
MATHAI; Varghese
2010-01-01
We review the Reidemeister, Ray-Singer’s analytic torsion and the Cheeger-Mller theorem. We describe the analytic torsion of the de Rham complex twisted by a flux form introduced by the current authors and recall its properties. We define a new twisted analytic torsion for the complex of invariant differential forms on the total space of a principal circle bundle twisted by an invariant flux form. We show that when the dimension is even, such a torsion is invariant under certain deformation of the metric and the flux form. Under T-duality which exchanges the topology of the bundle and the flux form and the radius of the circular fiber with its inverse, the twisted torsion of invariant forms are inverse to each other for any dimension.
Mathai, Varghese
2009-01-01
We review the Reidemeister and Ray-Singer's analytic torsions and the Cheeger-M"uller theorem. We describe the analytic torsion of the de Rham complex twisted by a flux form introduced by the current authors and recall its properties. We define a new twisted analytic torsion for the complex of invariant differential forms on the total space of a principal circle bundle twisted by an invariant flux form. We show that when the dimension is even, such a torsion is invariant under certain deformation of the metric and the flux form. Under T-duality which exchanges the topology of the bundle and the flux form and the radius of the circular fiber with its inverse, the twisted torsions are inverse to each other for any dimensions.
薄壁防渗墙施工工艺%Construction technology of thin-walled anti-seepage wall
Institute of Scientific and Technical Information of China (English)
孟耀峰
2015-01-01
结合建造薄壁防渗墙工程实例，通过分析几种施工工艺的成墙原理和优缺点，合理选择薄壁防渗墙施工工艺。%Combined with the construction of thin-wall anti-seepage wall projects,based on analysis of principles of wall construction and advantages or disadvantages of construction technology ,selecting the construction technology of thin-wall anti-seepage wall.
Twisted radio waves and twisted thermodynamics.
Kish, Laszlo B; Nevels, Robert D
2013-01-01
We present and analyze a gedanken experiment and show that the assumption that an antenna operating at a single frequency can transmit more than two independent information channels to the far field violates the Second Law of Thermodynamics. Transmission of a large number of channels, each associated with an angular momenta 'twisted wave' mode, to the far field in free space is therefore not possible.
Directory of Open Access Journals (Sweden)
Zebbiche Toufik
2014-09-01
Full Text Available The presented work is to develop a numerical computation program to determine the distribution of the shear stress to shear in closed tubes with asymmetric single thin wall section with a constant thickness and applications to airfoils and therefore determining the position and value of the maximum stress. In the literature, there are exact analytical solutions only for some sections of simple geometries such as circular section. Hence our interest is focused on the search of approximate numerical solutions for more complex sections used in aeronautics. In the second stage the position of the shear center is determined so that the section does not undergo torsion. The analytic function of the boundary of the airfoil is obtained by using the cubic spline interpolation since it is given in the form of tabulated points.
Directory of Open Access Journals (Sweden)
Hetao Hou
2015-01-01
Full Text Available One steel grid and five thin-walled concrete-filled steel tubes (CTST used as the supports of tunnel were tested in site for investigating the mechanical behavior. The mechanical influences of thickness, node form, and concrete on CTST were gained and compared with the impacts on steel grid. It is indicated that high antideformation capacity of CTST improved the stability of surrounding rock in short time. The cementitious grouted sleeve connection exhibited superior flexibility when CTST was erected and built. Although the deformation of rock and soil in the tunnel was increasing, good compression resistance was observed by CTST with the new connection type. It was also seen that vault, tube foot, and connections were with larger absolute strain values. The finite element analysis (FEA was carried out using ABAQUS program. The results were validated by comparison with experimental results. The FE model could be referred by similar projects.
Garion, Cédric; Skoczen, Blazej
The present thesis is dedicated to the behaviour of austenitic stainless steels at cryogenic temperatures. The plastic strain induced martensitic transformation and ductile damage are taken into account in an elastic-plastic material modelling. The kinetic law of →’ transformation and the evolution laws of kinematic/isotropic mixed hardening are established. Damage issue is analysed by different ways: mesoscopic isotropic or orthotropic model and a microscopic approach. The material parameters are measured from 316L fine gauge sheet at three levels of temperature: 293 K, 77 K and 4.2 K. The model is applied to thin-walled corrugated shell, used in the LHC interconnections. The influence of the material properties on the stability is studied by a modal analysis. The reliability of the components, defined by the Weibull distribution law, is analysed from fatigue tests. The impact on reliability of geometrical imperfections and thermo-mechanical loads is also analysed.
Institute of Scientific and Technical Information of China (English)
无
2007-01-01
Backward ball spinning was applied for manufacturing thin-walled tubular parts with longitudinal inner ribs. Rigid-plastic finite element method(FEM) was used for simulating the backward ball spinning process in order to calculate the height of the inner ribs. With a view to guarantee a better simulation accuracy, it is essential to enhance and improve some general problems of FEM,such as generation of initial velocity field, choice of penalty factor, determination of boundary conditions, treatment of rigid region and description of convergence criteria. It is evident that whether the problems with respect to FEM are dealt with appropriately or not, they have a significant influence on the modeling accuracy and efficiency. By reasonable solving the general problems,rigid-plastic FEM can successfully simulate the height of the inner ribs and the calculated values are in good agreement with the measured values.
Directory of Open Access Journals (Sweden)
Minodora Maria PASĂRE
2010-10-01
Full Text Available In these paper, starting from the relations for the displacements and spinning the transversal section of a bar with thin walls of sections opened expressed by the corresponding influence functions and introducing the components of the exterior forces distributed and the moments of the exterior forces distributed due to the inertia forces, the exciting axial forces together with the following effect of these and of the reaction forces of the elastic environment for leaning it may reach to the system of the equations of parametric vibrations under the form of three integral equation These equations may serve for the study of vibrations of the bars, to study the static stability and to study the dynamic stability
Wang, Tao; Wang, Guilin; Zhu, Dengchao; Li, Shengyi
2015-02-01
In order to meet the requirement of aerodynamics, the infrared domes or windows with conformal and thin-wall structure becomes the development trend of high-speed aircrafts in the future. But these parts usually have low stiffness, the cutting force will change along with the axial position, and it is very difficult to meet the requirement of shape accuracy by single machining. Therefore, on-machine measurement and compensating turning are used to control the shape errors caused by the fluctuation of cutting force and the change of stiffness. In this paper, on the basis of ultra precision diamond lathe, a contact measuring system with five DOFs is developed to achieve on-machine measurement of conformal thin-wall parts with high accuracy. According to high gradient surface, the optimizing algorithm is designed on the distribution of measuring points by using the data screening method. The influence rule of sampling frequency is analyzed on measuring errors, the best sampling frequency is found out based on planning algorithm, the effect of environmental factors and the fitting errors are controlled within lower range, and the measuring accuracy of conformal dome is greatly improved in the process of on-machine measurement. According to MgF2 conformal dome with high gradient, the compensating turning is implemented by using the designed on-machine measuring algorithm. The shape error is less than PV 0.8μm, greatly superior compared with PV 3μm before compensating turning, which verifies the correctness of measuring algorithm.
Machinable, Thin-Walled, Gray and Ductile Iron Casting Production, Phase III
Energy Technology Data Exchange (ETDEWEB)
Charles Bates; Hanjun Li; Robin Griffin
2003-12-08
This report presents the results of research conducted to determine the effects of normal and abnormal processing and compositional variations on machinability (tool wear rate) of gray and ductile iron. The procedures developed allow precise tool wear measurements to be made and interpreted in terms of microstructures and compositions. Accurate data allows the most efficient ways for improving machinability to be determined without sacrificing properties of the irons.
Research on twisting of patterned ionic polymer metal composite%图案化电极的离子聚合物金属复合物扭转特性研究
Institute of Scientific and Technical Information of China (English)
赵扬; 徐兵; 郑高峰; 庄明凤; 黄伟伟; 关明杰
2014-01-01
Ionic polymer metal composite (IPMC)was a kind of ionic electroactive polymer,which can generate large deformation when applied low driving voltage.It will be widely used in bionic,medical biological and other fields.In this paper,the patterned IPMC was fabricated to accomplish twist motion.To get the twisting charac-teristic of patterned IPMC,the variation of structural dimension of patterned IPMC was studied.Meanwhile, the structural dimension of patterned IPMC which was pasted two IPMC together was also researched in this paper.The result of two kind of patterned IPMC was compared,which indicate the influencing factors of fabri-cating of patterned IPMC to realize twist motion.%离子聚合物金属复合物(ionic polymer met-al composite,IPMC)是一种新型离子型电致动聚合物,具有在低电压驱动下产生大变形的特点而有广阔的应用前景。通过在 IPMC 表面制作图案化电极,使其在电压驱动下实现扭转运动。针对图案化电极的结构尺寸对其扭转特性的影响进行研究,得到图案化电极IPMC的扭转特性规律。同时针对贴合方式 IPMC的结构尺寸变化对其扭转特性的影响进行研究,并比较两种IPMC的扭转运动效果,得出制备可实现扭转运动IPMC的影响因素。
Determination of Elastic Twist in Horizontal Axis Wind Turbines (HAWTs)
Energy Technology Data Exchange (ETDEWEB)
Stoddard, F.; Nelson, V.; Starcher, K.; Andrews, B.
2006-06-01
This report presents the results of a project at the Alternative Energy Institute (AEI) which measured and calculated the elastic twist of three representative composite horizontal-axis blades: Carter 300, Gougeon ESI 54, and UTRC 8 kW.
National Research Council Canada - National Science Library
Ahmed Elmarakbi; Niki Fielding; Homayoun Hadavinia
2011-01-01
... the explicit finite element code LS-DYNA. Results compare the absorbed energy and the deflection of each variable, and recommend best design for the tube structure which improved vehicle crashworthiness. KEYWORDS: Energy absorption; thin-walled structures; vehicle impact; finite element analysis; design optimization 1. Introduction Currently within the UK there ar...
Meek, MF; Robinson, PH; Stokroos, [No Value; Blaauw, EH; Kors, G; den Dunnen, WFA
2001-01-01
The aim of this study was to evaluate short-term peripheral nerve regeneration across a 15-mm gap in the sciatic nerve of the rat, using a thin-walled biodegradable poly(DL-lactide-epsilon -caprolactone) nerve guide filled with modified denatured muscle tissue (MDMT). The evaluation was performed us
Meek, MF; Robinson, PH; Stokroos, [No Value; Blaauw, EH; Kors, G; den Dunnen, WFA
2001-01-01
The aim of this study was to evaluate short-term peripheral nerve regeneration across a 15-mm gap in the sciatic nerve of the rat, using a thin-walled biodegradable poly(DL-lactide-epsilon -caprolactone) nerve guide filled with modified denatured muscle tissue (MDMT). The evaluation was performed us
Twisted derivations of Hopf algebras
Davydov, Alexei
2012-01-01
In the paper we introduce the notion of twisted derivation of a bialgebra. Twisted derivations appear as infinitesimal symmetries of the category of representations. More precisely they are infinitesimal versions of twisted automorphisms of bialgebras. Twisted derivations naturally form a Lie algebra (the tangent algebra of the group of twisted automorphisms). Moreover this Lie algebra fits into a crossed module (tangent to the crossed module of twisted automorphisms). Here we calculate this crossed module for universal enveloping algebras and for the Sweedler's Hopf algebra.
Effect of microstructure on mechanical properties of a thin-walled cast duplex steel
Energy Technology Data Exchange (ETDEWEB)
Petzold, L.; Kreschel, T.; Peisker, D. [TU Bergakademie Freiberg, Institut fuer Eisen- und Stahltechnologie, Freiberg (Germany); Minnich, D. [Evosteel GmbH, Leipzig (Germany)
2010-06-15
The paper investigates the microstructure and the resulting mechanical properties of a duplex steel cast in sand dead-moulds. The chemical composition and the cooling rate are the main parameters affecting the properties. The chemical composition influences the thermodynamics of the phase transformation, the cooling rate determines the kinetics of formation of the microstructure. The latter varies with changes in wall thickness (investigated from 2 to 7 mm) and the position of the material within the casting. Through heat treatment, the composition of the microstructural components can be changed selectively afterwards, thereby the properties are improved. The correlation between microstructure and mechanical properties is explained quantitatively. Additionally to the austenite-ferrite ratio, the dispersion of microstructure has a large influence on the mechanical properties. Ranges of chemical composition and heat treatment parameters are identified where third phases, such as carbides and {sigma}-phase tend to occur. These influence the properties very sensitively even in small amounts. Finally, structural parameters are recognized that will lead to optimal combinations of properties. With an appropriate heat treatment technique, in particular the ductility properties are further increased. (Abstract Copyright [2010], Wiley Periodicals, Inc.)
Energy Technology Data Exchange (ETDEWEB)
Zika-Beyerlein, B. [ElringKlinger (Germany). Geschaeftsbereich Abschirmtechnik
2004-09-01
Tightly packed engine compartments put special demands on thermal and acoustic shielding systems. With new material composites allowing for particularly thin-walled and light shielding parts, ElringKlinger is well equipped for the future. (orig.)
Ulmer, Melville
The project goal is to demonstrate that thin walled (price. Since the desired surface area for the next generation X-ray telescope is >10x that of Chandra, the >10x requirement is then for >200 m^2 of surface area with a surface finish of better than 0.5 nm. Therefore, replication of some sort is called for. Because no replication technology has been shown to achieve ≤1" angular resolution, post fabrication figure corrections are likely going to be necessary. Some have proposed to do this in orbit and others prelaunch including us. Our prelaunch approach is to apply in-plane stresses to the thin walled mirror shells via a magnetic field. The field will be held in by some magnetically hard material such as NiCo. By use of a so called magnetic smart material (MSM) such as Terfenol-D, we already shown that strong enough stresses can be generated. Preliminary work has also shown that the magnetic field can be held in well enough to apply the figure correcting stresses pre-launch. What we call "set-it and forget-it." However, what is unique about our approach is that at the cost of complexity and some areal coverage, our concept will also accommodate in-orbit adjustments. Furthermore, to the best of our knowledge ours is one of two known stress modification processes that are bi-axial. Our plan is first to validate set-it and forget-it first on cantilevers and then to expand this to working on 5 cm x 5 cm pieces. We will work both with NiCo and glass or Si coated with Terfenol-D. Except for the NiCo, substrates we will also coat the samples with NiCo in order to have a film that will hold in the magnetic field. As part of the coating process, we will control the stress of the film by varying the voltage bias while coating. The bias stress control can be used to apply films with minimal stress such as Terfenol-D and X-ray reflecting coatings such as Ir. Ir is a highly desirable coating for soft X-ray astronomy mirrors that can have significant built in stress unless
DEFF Research Database (Denmark)
Yiu, Man Lung; Jensen, Christian Søndergaard; Xuegang, Huang
2008-01-01
-based matching generally fall short in offering practical query accuracy guarantees. Our proposed framework, called SpaceTwist, rectifies these shortcomings for k nearest neighbor (kNN) queries. Starting with a location different from the user's actual location, nearest neighbors are retrieved incrementally...
Reweighting twisted boundary conditions
Bussone, Andrea; Hansen, Martin; Pica, Claudio
2015-01-01
Imposing twisted boundary conditions on the fermionic fields is a procedure extensively used when evaluating, for example, form factors on the lattice. Twisting is usually performed for one flavour and only in the valence, and this causes a breaking of unitarity. In this work we explore the possibility of restoring unitarity through the reweighting method. We first study some properties of the approach at tree level and then we stochastically evaluate ratios of fermionic determinants for different boundary conditions in order to include them in the gauge averages, avoiding in this way the expensive generation of new configurations for each choice of the twisting angle, $\\theta$. As expected the effect of reweighting is negligible in the case of large volumes but it is important when the volumes are small and the twisting angles are large. In particular we find a measurable effect for the plaquette and the pion correlation function in the case of $\\theta=\\pi/2$ in a volume $16\\times 8^3$, and we observe a syst...
Wang, Zuoqin
2007-01-01
The "twisted Mellin transform" is a slightly modified version of the usual classical Mellin transform on $L^2(\\mathbb R)$. In this short note we investigate some of its basic properties. From the point of views of combinatorics one of its most important interesting properties is that it intertwines the differential operator, $df/dx$, with its finite difference analogue, $\
Damage Detection on Thin-walled Structures Utilizing Laser Scanning and Standing Waves
Energy Technology Data Exchange (ETDEWEB)
Kang, Se Hyeok; Jeon, Jun Young; Kim, Du Hwan; Park, Gyuhae [Chonnam Nat’l Univ., Gwangju (Korea, Republic of); Kang, To; Han, Soon Woo [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)
2017-05-15
This paper describes wavenumber filtering for damage detection using single-frequency standing wave excitation and laser scanning sensing. An embedded piezoelectric sensor generates ultrasonic standing waves, and the responses are measured using a laser Doppler vibrometer and mirror tilting device. After scanning, newly developed damage detection techniques based on wavenumber filtering are applied to the full standing wave field. To demonstrate the performance of the proposed techniques, several experiments were performed on composite plates with delamination and aluminum plates with corrosion damage. The results demonstrated that the developed techniques could be applied to various structures to localize the damage, with the potential to improve the damage detection capability at a high interrogation speed.
Institute of Scientific and Technical Information of China (English)
Mei ZHAN; He YANG; Liang HUANG
2006-01-01
Springback is one of important factors influencing the forming quality of. numerical control(NC)bending of thin-walled tube. In this paper, a numerical-analytic method for springback angle prediction of the process was put forward. The method is based on springback angle model derived using analytic method and simulation results from three-dimensional(3D)rigid-plastic finite element method(FEM). The method is validated through comparison with experimental results. The features of the method are as follows:(1)The method is high in efficiency because it combines advantages of rigid-plastic FEM and analytic method.(2)The method is satisfactory in accuracy, since the field variables used in the model is resulting from 3D rigid-plastic FEM solution, and the effects both of axial force and strain neutral axis shift have been included.(3)Research on multi-factor effects can be carried out using the method due to its advantage inheriting from rigid-plastic FEM. The method described here is also of general significance to other bending processes.
3D FEM numerical simulation and experimental study on symmetric thin-wall tube neck-spinning
Institute of Scientific and Technical Information of China (English)
KUANG Wei-hua; XIA Qin-xiang; RUAN Feng
2006-01-01
A 3D FEM model for symmetric thin-wall tube neck-spinning is established. The spinning process is simulated by means of ANSYS software, and the dynamic boundary and contact problems in simulation are solved. The transient stress distribution of contact area, the transient strain distribution of nodes in typical section and the strain distribution of the whole part at last are attained, and the place and the cause of crack are analyzed. Simulation results show how the strain distribution of typical section, the thickness of some typical nodes, the Z coordinate in typical section and the spinning force of three rollers change with the time. According to study the variation curve, the material flow law along radial, tangential and axial direction is attained and the whole spinning process is studied. The experiment data reflect how the spinning force is influenced by different process parameters, such as feed rate, roundness radius and pass reduction. The simulation and the experiment results supply criteria for optimum design and reasonable parameter selection.
Long-Term Creep of a Thin-Walled Inconel 718 Stirling Power-Convertor Heater Head Assessed
Bowman, Randy R.
2002-01-01
The Department of Energy and NASA have identified Stirling power convertors as candidate power supply systems for long-duration, deep-space science missions. A key element for qualifying the flight hardware is a long-term durability assessment for critical hot section components of the power convertor. One such critical component is the power convertor heater head. The heater head is a high-temperature pressure vessel that transfers heat to the working gas medium of the convertor, which is typically helium. An efficient heater head design is the result of balancing the divergent requirements of thin walls for increased heat transfer versus thick walls to lower the wall stresses and thus improve creep resistance and durability. In the current design, the heater head is fabricated from the Ni-base superalloy Inconel 718 (IN 718, Inco Alloys International, Inc., Huntington, WV). Although IN 718 is a mature alloy system (patented in 1962), there is little long-term (>50,000-hr) creep data available for thin-specimen geometries. Since thin-section properties tend to be inferior to thicker samples, it is necessary to generate creep data using specimens with the same geometry as the actual flight hardware. Therefore, one facet of the overall durability assessment program involves generating relatively short-term creep data using thin specimens at the design temperature of 649 C (1200 F).
Directory of Open Access Journals (Sweden)
N.I. Vatin
2010-03-01
Full Text Available Insecurity of applied coatings and low service lives of St. Petersburg roofs generate the development of new technological solutions. Necessity of roof protection from the ice dams is a special factor in selecting technological solutions of the roof structure.The aim is selection of an optimal design solution for the roof and the device against the ice based on the parameters of efficiency and effectiveness. After completion of research as a design of the roof system was chosen light steel thin-walled structures (LSTC. As the device against the ice is proposed a constructive adaptation of drainage, which includes the transfer of the gutter from the roof edge closer to Snow barriers. Herewith downspouts must finish in the system and urban runoff.Efficiency of this method is confirmed by mathematical calculations and trial operation of such existing systems in the Nordic countries. The combination of the device against the ice with modern technology LSTC solve the problem of icicles, and generally can guarantee continuous and reliable operation of the roof.
Directory of Open Access Journals (Sweden)
Yoshihiko Hangai
2014-09-01
Full Text Available Aluminum foam has received considerable attention in various fields and is expected to be used as an engineering material owing to its high energy absorption properties and light weight. To improve the mechanical properties of aluminum foam, combining it with dense tubes, such as aluminum foam-filled tubes, was considered necessary. In this study, an aluminum foam-filled steel tube, which consisted of ADC12 aluminum foam and a thin-wall steel tube, was successfully fabricated by friction welding. It was shown that a diffusion bonding layer with a thickness of approximately 10 μm was formed, indicating that strong bonding between the aluminum foam and the steel tube was realized. By the X-ray computed tomography observation of pore structures, the fabrication of an aluminum foam-filled tube with almost uniform pore structures over the entire specimen was confirmed. In addition, it was confirmed that the aluminum foam-filled steel tube exhibited mechanical properties superior to those of the ADC12 aluminum foam and steel tube. This is considered to be attributed to the combination of the aluminum foam and steel tube, which particularly prevents the brittle fracture and collapse of the ADC12 foam by the steel tube, along with the strong metal bonding between the aluminum foam and the steel tube.
Directory of Open Access Journals (Sweden)
Mansour Borouni
2016-10-01
Full Text Available Internal defects are among the problems in gravity casting of aluminum parts. The main internal volumetric defects are gas and shrinkage defects which form during solidification of the melt and drastically reduce the quality of the produced parts. These defects adversely affect the mechanical properties of thin walled castings parts. In this study, ceramic nanoparticles coatings were applied on the sand mold and the effect of mold coatings on the reduction of defects were investigated. X-ray radiography was used to detect defects in sand molds with ceramic nanoparticles coatings. For comparison, this test was performed on molds with micro-ceramic and graffiti coatings and uncoated sand mold. The results showed that the maximum amount of gas and shrinkage defects was observed in casting parts from AL4-1 alloy in uncoated molds. On the other hand, the minimum defects were found in molds coated with ceramic nanoparticles. It seems that the reduced defects in casting parts in molds coated with ceramic nanoparticles may be due to high thermal and chemical stability and higher heat transfer rate of the coating. These results can facilitate the production of high quality aluminum alloys parts using nanotechnology.
Nishiguchi, H.; Evtoukhovitch, P.; Fujii, Y.; Hamada, E.; Mihara, S.; Moiseenko, A.; Noguchi, K.; Oishi, K.; Tanaka, S.; Tojo, J.; Tsamalaidze, Z.; Tsverava, N.; Ueno, K.; Volkov, A.
2017-02-01
The COMET experiment at J-PARC aims to search for a lepton-flavour violating process of muon to electron conversion in a muonic atom, μ-e conversion, with a branching-ratio sensitivity of better than 10-16, 4 orders of magnitude better than the present limit, in order to explore the parameter region predicted by most of well-motivated theoretical models beyond the Standard Model. The need for this sensitivity places several stringent requirements on the detector development. The experiment requires to detect the monochromatic electron of 105 MeV, the momentum resolution is primarily limited by the multiple scattering effect for this momentum region. Thus we need the very light material detector in order to achieve an excellent momentum resolution, better than 2%, for 100 MeV region. In order to fulfil such a requirement, the thin-wall straw-tube planar tracker has been developed by an extremely light material which is operational in vacuum. The COMET straw tracker consists of 9.8 mm diameter straw tube, longer than 1 m length, with 20-μm-thick Mylar foil and 70-nm-thick aluminium deposition. Currently even thinner and smaller, 12 μm thick and 5 mm diameter, straw is under development by the ultrasonic welding technique.
Directory of Open Access Journals (Sweden)
Laixiao Lu
2016-04-01
Full Text Available For studying the influence of a bilateral slid rolling process (BSRP on the surface integrity of a thin-walled aluminum alloy structure, and revealing the generation mechanism of residual stresses, a self-designed BSRP appliance was used to conduct rolling experiments. With the aid of a surface optical profiler, an X-ray stress analyzer, and a scanning electron microscope (SEM, the differences in surface integrity before and after BSRP were explored. The internal changing mechanism of physical as well as mechanical properties was probed. The results show that surface roughness (Ra is reduced by 23.7%, microhardness is increased by 21.6%, and the depth of the hardening layer is about 100 μm. Serious plastic deformation was observed within the subsurface of the rolled region. The residual stress distributions along the depth of the rolling surface and milling surface were tested respectively. Residual stresses with deep and high amplitudes were generated via the BSRP. Based on the analysis of the microstructure, the generation mechanism of the residual stresses was probed. The residual stress of the rolling area consisted of two sections: microscopic stresses caused by local plastic deformation and macroscopic stresses caused by overall non-uniform deformation.
dc and ac magnetic properties of thin-walled Nb cylinders with and without a row of antidots.
Tsindlekht, M I; Genkin, V M; Felner, I; Zeides, F; Katz, N; Gazi, Š; Chromik, Š; Dobrovolskiy, O V; Sachser, R; Huth, M
2016-06-01
dc and ac magnetic properties of two thin-walled superconducting Nb cylinders with a rectangular cross-section are reported. Magnetization curves and the ac response were studied on as-prepared and patterned samples in magnetic fields parallel to the cylinder axis. A row of micron-sized antidots (holes) was made in the film along the cylinder axis. Avalanche-like jumps of the magnetization are observed for both samples at low temperatures for magnetic fields not only above H c1, but in fields lower than H c1 in the vortex-free region. The positions of the jumps are not reproducible and they change from one experiment to another, resembling vortex lattice instabilities usually observed for magnetic fields larger than H c1. At temperatures above [Formula: see text] and [Formula: see text] the magnetization curves become smooth for the patterned and the as-prepared samples, respectively. The magnetization curve of a reference planar Nb film in the parallel field geometry does not exhibit jumps in the entire range of accessible temperatures. The ac response was measured in constant and swept dc magnetic field modes. Experiment shows that ac losses at low magnetic fields in a swept field mode are smaller for the patterned sample. For both samples the shapes of the field dependences of losses and the amplitude of the third harmonic are the same in constant and swept field near H c3. This similarity does not exist at low fields in a swept mode.
Directory of Open Access Journals (Sweden)
S.Mohammad Reza Mortazavi
2016-06-01
Full Text Available There have been some experimental tests on hollow curved-steel struts with thin-walled square sections, in order to investigate their general behavior, particularly their capacity for bearing differing loads. One set of square tubes are cold-formed into segments of circular arcs with curvature radii, equal to 4000 mm. Different lengths of curved struts are fabricated so as to cover a practical range of slenderness ratios. The struts tests were pin-ended and had slenderness ratios, based on the straight length between ends ranging from 31-126. The cold-forming operation induces initial inelastic behavior and associated residual stresses. There is, therefore, an interaction among material effects, such as the strain hardening capacity, the Bauschinger effect, strain aging, and residual stresses, together with the significant geometrical effect of the initial curvature, caused by the cold-forming operation. Eventually the results from three series of tests, which are taken on fully-aged and stress-relief-annealed square curved struts, are compared. The variations in load carrying response are discussed.
Institute of Scientific and Technical Information of China (English)
Li Yongchi; Huang Chengyi; Yuan Fuping; Jin Yongmei
2001-01-01
An in-depth analysis of propagation characteristics of elasto-plastic combined stress waves in circular thin-walled tubes has been made. In obtaining the simple-wave solution, however,most researches have ignored the influence of the circumferential stressrelated to the radial inertial effect in the tubes. In this paper the incremental elasto-plastic constitutive relations which are convenient for dynamic numerical analysis are adopted, and the finite-difference method is used to study the evolution and propagation of elasto-plastic combined stress waves in a thin-walled tube with the radial inertial effect of the tube considered. The calculation results are compared with those obtained when the radial inertial effect is not considered. The calculation results show that the radial inertial effect of a tube has a fairly great influence on the propagation of elasto-plastic combined stress waves.
Cui, Xiaoyan; Rohl, Andrew L; Shtukenberg, Alexander; Kahr, Bart
2013-03-06
Banded spherulites of aspirin have been crystallized from the melt in the presence of salicylic acid either generated from aspirin decomposition or added deliberately (2.6-35.9 mol %). Scanning electron microscopy, X-ray diffraction analysis, and optical polarimetry show that the spherulites are composed of helicoidal crystallites twisted along the growth directions. Mueller matrix imaging reveals radial oscillations in not only linear birefringence, but also circular birefringence, whose origin is explained through slight (∼1.3°) but systematic splaying of individual lamellae in the film. Strain associated with the replacement of aspirin molecules by salicylic acid molecules in the crystal structure is computed to be large enough to work as the driving force for the twisting of crystallites.
Twisted Ribbons: Theory, Experiment and Applications
Chopin, Julien; Davidovitch, Benjamin; Silva, Flavio A.; Toledo Filho, Romildo D.; Kudrolli, Arshad
2014-03-01
We investigate, experimentally and theoretically, the buckling and wrinkling instabilities of a pre-stretched ribbon upon twisting and propose strategies for the fabrication of structured yarns. Our experiment consists in a thin elastic sheet in the form of a ribbon which is initially stretched by a fixed load and then subjected to a twist by rotating the ends through a prescribed angle. We show that a wide variety of shapes and instabilities can be obtained by simply varying the applied twist and tension. The observed structures which include helicoids with and without longitudinal and transverse wrinkles, and spontaneous creases, can be organized in a phase diagram with the tension and twist angle as control parameters [J. Chopin and A. Kudrolli, PRL (2013)]. Using a far-from-threshold analysis and a slender body approximation, we provide a comprehensive understanding of the longitudinal and transverse instabilities and show that several regimes emerge depending on subtle combinations of loading and geometrical parameters. Further, we show that the wrinkling instabilities can be manipulated to fabricate structured yarns which may be used to encapsulate amorphous materials or serve as efficient reinforcements for cement-based composites. COPPETEC / CNPq - Science Without Border Program
FAKHIM, Y. G.; SHOWKATI, H.; K Abedi
2009-01-01
p. 2511-2522 The application of thin-walled cylindrical shells, as the essential structural members, has been known for engineers and functional duty of them is basic necessaries of modern industries. These structures are prone to fail by buckling under external pressure which could be happened during discharging or wind load. Although the buckling capacity of the shells depends principally on two geometric ratios of "length to radius" (L/R) and "radius to thickness" (R/t), but...
Study of a high-temperature and high-pressure FBG sensor with Al2O3 thin-wall tube substrate
Institute of Scientific and Technical Information of China (English)
ZHOU Hong; QIAO Xue-guang; WANG Hong-liang; FENG De-quan; WANG Wei
2008-01-01
A fiber Bragg grating (FBG) high-temperature and high pressure sensor has been designed and fabricated by using the Al2O3 thin-wall tube as a substrate. The test results show that the sensor can withstand a pressure range of 0-45 MPa and a temperature range of-10-300℃, and has a pressure sensitivity of 0.0426 nm/MPa and a temperature sensitivity of 0.0112nm/℃
Directory of Open Access Journals (Sweden)
Daijiro Fukuda
2004-01-01
Full Text Available Using diagrammatic pictures of tensor contractions, we consider a Hopf algebra (Aop⊗ℛλA** twisted by an element ℛλ∈A*⊗Aop corresponding to a Hopf algebra morphism λ:A→A. We show that this Hopf algebra is quasitriangular with the universal R-matrix coming from ℛλ when λ2=idA, generalizing the quantum double construction which corresponds to the case λ=idA.
Vranish, John M. (Inventor)
1996-01-01
A planetary gear system includes a sun gear coupled to an annular ring gear through a plurality of twist-planet gears, a speeder gear, and a ground structure having an internal ring gear. Each planet gear includes a solid gear having a first half portion in the form of a spur gear which includes vertical gear teeth and a second half portion in the form of a spur gear which includes helical gear teeth that are offset from the vertical gear teeth and which contact helical gear teeth on the speeder gear and helical gear teeth on the outer ring gear. One half of the twist planet gears are preloaded downward, while the other half are preloaded upwards, each one alternating with the other so that each one twists in a motion opposite to its neighbor when rotated until each planet gear seats against the sun gear, the outer ring gear, the speeder gear, and the inner ring gear. The resulting configuration is an improved stiff anti-backlash gear system.
Directory of Open Access Journals (Sweden)
Hu Qiang
2010-01-01
Full Text Available Abstract Thin-walled, open-ended, and well-aligned N-doped carbon nanotubes (CNTs on the quartz slides were synthesized by using acetonitrile as carbon sources. As-obtained products possess large thin-walled index (TWI, defined as the ratio of inner diameter and wall thickness of a CNT. The effect of temperature on the growth of CNTs using acetonitrile as the carbon source was also investigated. It is found that the diameter, the TWI of CNTs increase and the Fe encapsulation in CNTs decreases as the growth temperature rises in the range of 780–860°C. When the growth temperature is kept at 860°C, CNTs with TWI = 6.2 can be obtained. It was found that the filed-emission properties became better as CNT growth temperatures increased from 780 to 860°C. The lowest turn-on and threshold field was 0.27 and 0.49 V/μm, respectively. And the best field-enhancement factors reached 1.09 × 105, which is significantly improved about an order of magnitude compared with previous reports. In this study, about 30 × 50 mm2 free-standing film of thin-walled open-ended well-aligned N-doped carbon nanotubes was also prepared. The free-standing film can be transferred easily to other substrates, which would promote their applications in different fields.
Cui, Tongxiang; Lv, Ruitao; Kang, Feiyu; Hu, Qiang; Gu, Jialin; Wang, Kunlin; Wu, Dehai
2010-03-31
Thin-walled, open-ended, and well-aligned N-doped carbon nanotubes (CNTs) on the quartz slides were synthesized by using acetonitrile as carbon sources. As-obtained products possess large thin-walled index (TWI, defined as the ratio of inner diameter and wall thickness of a CNT). The effect of temperature on the growth of CNTs using acetonitrile as the carbon source was also investigated. It is found that the diameter, the TWI of CNTs increase and the Fe encapsulation in CNTs decreases as the growth temperature rises in the range of 780-860°C. When the growth temperature is kept at 860°C, CNTs with TWI = 6.2 can be obtained. It was found that the filed-emission properties became better as CNT growth temperatures increased from 780 to 860°C. The lowest turn-on and threshold field was 0.27 and 0.49 V/μm, respectively. And the best field-enhancement factors reached 1.09 × 105, which is significantly improved about an order of magnitude compared with previous reports. In this study, about 30 × 50 mm2 free-standing film of thin-walled open-ended well-aligned N-doped carbon nanotubes was also prepared. The free-standing film can be transferred easily to other substrates, which would promote their applications in different fields.
Institute of Scientific and Technical Information of China (English)
LI Heng; YANG He
2011-01-01
Thin-walled tube numerical control (NC) bending is a tri-nonlinear physical process with multi-defect and multi-die constraints. The clearance on each contact interface is the major factor to indicate the contact conditions. A three-dimensional-finite element (3D-FE) model is established to consider the realistic dynamic boundary conditions of multiple dies under ABAQUS/Explicit platform. Combined with experiment, numerical study on bending behavior and bendability under different clearance between tube and various dies is conducted in terms of wrinkling, wall thinning and cross section deformation. The results show that (1)with smaller clearance of tube-wiper die and tube-mandrel, the wrinkling can be restrained while the wall thinning It and cross-section deformation Id increase; while excessive small clearance blocks tube materials to flow past tangent point and causes piles up, the onset of wrinkling enhances It and Id. (2)Both It and Id decrease with smaller clearance of tube-pressure die; the wrinkling possibility rises with larger clearance on this interface if the mandrel's freedom along Y-axis is opened; smaller clearance of tube-bend die prevents wrinkling while increases It, and the clearance on this interface has little effect on Id. (3)A modified Yoshida buckling test (YBT) is used to address the wrinkling mechanisms under normal constraints in tube bending: the smaller clearance may restrain wrinkling efficiently; the smaller wall thickness, the less critical clearance needed; the critical clearance for tube bending 38 mm× 1 mm×57 mm (tube outer diameter×wall thickness×centerline bending radius) equals about 20％ of initial wall thickness.
Institute of Scientific and Technical Information of China (English)
无
2010-01-01
With increasing diameters of aluminum alloy thin-walled tubes (AATTs), the tube forming limits, i.e. the minimum bending factors, and their predictions under multi-index constraints including wrinkling, thinning and flattening have been being a key problem to be urgently solved for improving tube forming potential in numerical control (NC) bending processes of AATTs with large diameters. Thus in this paper, a search algorithm of the forming limits is put forward based on a 3D elastic-plastic finite element (FE) model and a wrinkling energy prediction model for the bending processes under axial compression loading (ACL) or not. This algorithm enables to be considered the effects of process parameter combinations including die, friction parameters on the multi-indices. Based on this algorithm, the forming limits of the different size tubes are obtained, and the roles of the process parameter combinations in enabling the limit bending processes are also revealed. The followings are found: the first, within the appropriate ranges of friction and clearances between the different dies and the tubes enabling the bending processes with smaller bending factors, the ACL enables the tube limit bending processes after a decrease of the mandrel ball thickness and diameters; then, without considering the effects of the tube geometry sizes on the tube constitutive equations, the forming limits will be decided by the limit thinning values for the tubes with diameters smaller than 80 mm, while the wrinkling for the tubes with diameters no less than 80 mm. The forming limits obtained from this algorithm are smaller than the analytical results, and reduced by 57.39%; the last, the roles of the process parameter combinations in enabling the limit bending processes are verified by experimental results.
Dhaneswara, Donanta; Suharno, Bambang; Nugroho, Janu Ageng; Ariobimo, Rianti Dewi S.; Sofyan, Nofrijon
2017-03-01
One of the problems in thin wall ductile iron (TWDI) fabrication is skin formation during the casting. The presence of this skin will decrease strength and strain of the TWDI. One of the ways to control this skin formation is to change the cooling rate during the process through a mold coating. In testing the effectiveness of skin prevention, the following variables were used for the mold coating i.e. (i) graphite: (ii) zirconium; and (iii) double layer of graphite-zirconium. After the process, the plates were characterized by non-etching, etching, tensile test, and SEM observation. The results showed that the average skin formation using graphite: 65 µm; zirconium: 13.04 µm; and double layer of graphite-zirconium: 33.25 µm. It seems that zirconium has the most effect on the skin prevention due to sulfur binding and magnesium locked, which then prevented rapid cooling resulting in less skin formation. The results also showed the number of nodules obtained in specimen with graphite: 703 nodules/mm2 with average diameter of 12.57 µm, zirconium: 798 nodules/mm2 with average diameter of 12.15 µm, and double layer of graphite-zirconium: 697 nodules/mm2 with average diameter of 11.9 µm and nodularity percentage of 82.58%, 84.53%, and 84.22%, respectively. Tensile test showed that the strength of the specimen with graphite is 301.1 MPa, with zirconium is 388.8 MPa, and with double layer of graphite-zirconium is 304 MPa. In overall, zirconium give the best performance on the skin formation prevention in TWDI fabrication.
Dhaneswara, D.; Suharno, B.; Nugraha, N. D.; Ariobimo, R. D. S.; Sofyan, N.
2017-02-01
Skin formation has become one of the problems in the thin wall ductile iron casting because it will reduce the mechanical properties of the materials. One of the solutions to reduce this skin formation is by using heat insulator to control the cooling rate. One of the insulators used for this purpose is ceramic fibre. In this research, the thickness of the ceramic fibre heat insulator used in the mould was varied, i.e. 50 mm on one side and 37.5 mm on the other side (A), no heat insulator (B), and 37.5 mm on both sides (C). After the casting process, the results were characterized in terms of metallography by using scanning electron microscope (SEM) and tensile test for mechanical properties. The results showed that the skin thickness formed in A is 34.21 μm, 23.38 μm in B, and 27.78 μm in C. The nodule count in A is 541.98 nodule/mm2 (84.7%) with an average diameter of 15.14 μm, 590 nodule/mm2 (86.7%) with an average diameter of 13.18 μm in B, and 549.73 nodule/mm2 (87.2%) with an average diameter of 13.95 μm in C. The average ultimate tensile strength for A was 399 MPa, B was 314 MPa, and C was 415 MPa. Microstructural examination under SEM showed that the materials have a ductile fracture with matrix full of ferrite.
The Gravitational Field of a Twisted Skyrmion
Hadi, Miftachul; Husein, Andri
2015-01-01
We study nonlinear sigma model, especially Skyrme model without twist and Skyrme model with twist: twisted Skyrme model. Twist term, $mkz$, is indicated in vortex solution. We are interested to construct a space-time containing a string with Lagrangian plus a twist. To add gravity, we replace $\\eta^{\\mu\
Properties of twisted ferromagnetic filaments
Energy Technology Data Exchange (ETDEWEB)
Belovs, Mihails; Cebers, Andrejs [University of Latvia, Zellu 8, LV-1002 (Latvia)], E-mail: aceb@tesla.sal.lv
2009-02-01
The full set of equations for twisted ferromagnetic filaments is derived. The linear stability analysis of twisted ferromagnetic filament is carried out. Two different types of the buckling instability are found - monotonous and oscillatory. The first in the limit of large twist leads to the shape of filament reminding pearls on the string, the second to spontaneous rotation of the filament, which may constitute the working of chiral microengine.
薄壁构件整体稳定性的有限元模拟%Finite element modelling of thin-walled members in overall stability analysis
Institute of Scientific and Technical Information of China (English)
张磊; 童根树
2011-01-01
In the overall stability analysis of thin-walled members employing the general purpose finite element (FE) softwares, the members are generally modelled using the thin-walled beam elements or the thin shell elements. The modelling details of these two FE models were presented, and a new thin shell element model, capable of prohibiting the local buckling modes in the overall buckling analysis, was proposed. The two types of FE models were then adopted into the buckling analysis of thin-walled members, including the beams and columns with doubly and singly symmetric sections, beam-columns, tapered beams. The comparisons of the results from FE analyses, analytical solutions and literature show that the proposed thin shell element model is superior to the existing models of this type; the thin-walled beam element of ANSYS is not applicable to the flexural-torsional buckling analysis of thin-walled beams and beam-columns of mono-symmetric section, and significant error may arise in buckling analysis of tapered beams using this element. The results from the presented shell element model can also be used as the benchmark results in verifying the buckling theory of thin-walled members. The outcome of this study may be helpful for modelling thin-walled members in overall stability analysis using general FE packages, not limited to ANSYS.%对薄壁构件整体稳定性分析中的薄壁梁单元和壳体单元两种有限元模型的特点进行了讨论,并提出一种新的适用于薄壁构件整体稳定分析的壳体单元模型,该模型可以有效消除各种局部屈曲模态的影响.采用通用有限元软件ANSYS,分别利用壳体单元模型和薄壁梁单元模型,分析了双轴对称截面梁、单轴对称截面梁、轴心受压构件、压弯构件和变截面梁的稳定性,通过与经典解或已有研究结果的比较对有限元模型的可靠性以及存在的问题进行了讨论.通过分析,发现ANSYS的薄壁梁单元模型不能用于分
Energy Technology Data Exchange (ETDEWEB)
Shindler, A. [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC
2007-07-15
I review the theoretical foundations, properties as well as the simulation results obtained so far of a variant of the Wilson lattice QCD formulation: Wilson twisted mass lattice QCD. Emphasis is put on the discretization errors and on the effects of these discretization errors on the phase structure for Wilson-like fermions in the chiral limit. The possibility to use in lattice simulations different lattice actions for sea and valence quarks to ease the renormalization patterns of phenomenologically relevant local operators, is also discussed. (orig.)
Twisting formula of epsilon factors
Indian Academy of Sciences (India)
SAZZAD ALI BISWAS
2017-09-01
For characters of a non-Archimedean local field we have explicit formula for epsilon factors. But in general, we do not have any generalized twisting formula of epsilon factors. In this paper, we give a generalized twisting formula of epsilon factorsvia local Jacobi sums.
Twisted supergravity and its quantization
Costello, Kevin
2016-01-01
Twisted supergravity is supergravity in a background where the bosonic ghost field takes a non-zero value. This is the supergravity counterpart of the familiar concept of twisting supersymmetric field theories. In this paper, we give conjectural descriptions of type IIA and IIB supergravity in $10$ dimensions. Our conjectural descriptions are in terms of the closed-string field theories associated to certain topological string theories, and we conjecture that these topological string theories are twists of the physical string theories. For type IIB, the results of arXiv:1505.6703 show that our candidate twisted supergravity theory admits a unique quantization in perturbation theory. This is despite the fact that the theories, like the original physical theories, are non-renormalizable. Although we do not prove our conjectures, we amass considerable evidence. We find that our candidates for the twisted supergravity theories contain the residual supersymmetry one would expect. We also prove (using heavily a res...
Twisted bialgebroids versus bialgebroids from a Drinfeld twist
Borowiec, Andrzej; Pachoł, Anna
2017-02-01
Bialgebroids (respectively Hopf algebroids) are bialgebras (Hopf algebras) over noncommutative rings. Drinfeld twist techniques are particularly useful in the (deformation) quantization of Lie algebras as well as the underlying module algebras (=quantum spaces). A smash product construction combines both of them into the new algebra which, in fact, does not depend on the twist. However, we can turn it into a bialgebroid in a twist-dependent way. Alternatively, one can use Drinfeld twist techniques in a category of bialgebroids. We show that both the techniques indicated in the title—the twisting of a bialgebroid or constructing a bialgebroid from the twisted bialgebra—give rise to the same result in the case of a normalized cocycle twist. This can be useful for the better description of a quantum deformed phase space. We argue that within this bialgebroid framework one can justify the use of deformed coordinates (i.e. spacetime noncommutativity), which are frequently postulated in order to explain quantum gravity effects.
Deformation Control of Thin-Walled Structure Welded by Electron Beam%柔性薄壁结构电子束焊接的变形控制
Institute of Scientific and Technical Information of China (English)
龚荣清; 杨锡龙
2015-01-01
Based on electron beam welding method, the deformation control method of vacuum elec-tron beam welding process of PTO flexible thin-walled structures is explored. The deformation control method combined with comprehensive application of the minimum weld heat input, reducing the overlap angle, reasonable welding assembly and heat radiation is proposed. The welding deformation is controlled effectively and the man-ufacturing of PTO lfexible thin-walled is achieved by using electron beam welding.%基于电子束焊接方法，探讨了功率分出轴柔性薄壁结构真空电子束焊接过程中的变形控制方法，提出了综合应用最小焊接热输入、减小焊接重叠角度和合理焊接装配及散热相结合的变形控制方法，有效地控制了焊接变形，实现了电子束焊接柔性薄壁结构的制造。
Directory of Open Access Journals (Sweden)
Ming Luo
2016-09-01
Full Text Available Thin-walled workpieces, such as aero-engine blisks and casings, are usually made of hard-to-cut materials. The wall thickness is very small and it is easy to deflect during milling process under dynamic cutting forces, leading to inaccurate workpiece dimensions and poor surface integrity. To understand the workpiece deflection behavior in a machining process, a new real-time nonintrusive method for deflection monitoring is presented, and a detailed analysis of workpiece deflection for different machining stages of the whole machining process is discussed. The thin-film polyvinylidene fluoride (PVDF sensor is attached to the non-machining surface of the workpiece to copy the deflection excited by the dynamic cutting force. The relationship between the input deflection and the output voltage of the monitoring system is calibrated by testing. Monitored workpiece deflection results show that the workpiece experiences obvious vibration during the cutter entering the workpiece stage, and vibration during the machining process can be easily tracked by monitoring the deflection of the workpiece. During the cutter exiting the workpiece stage, the workpiece experiences forced vibration firstly, and free vibration exists until the amplitude reduces to zero after the cutter exits the workpiece. Machining results confirmed the suitability of the deflection monitoring system for machining thin-walled workpieces with the application of PVDF sensors.
Luo, Ming; Liu, Dongsheng; Luo, Huan
2016-09-10
Thin-walled workpieces, such as aero-engine blisks and casings, are usually made of hard-to-cut materials. The wall thickness is very small and it is easy to deflect during milling process under dynamic cutting forces, leading to inaccurate workpiece dimensions and poor surface integrity. To understand the workpiece deflection behavior in a machining process, a new real-time nonintrusive method for deflection monitoring is presented, and a detailed analysis of workpiece deflection for different machining stages of the whole machining process is discussed. The thin-film polyvinylidene fluoride (PVDF) sensor is attached to the non-machining surface of the workpiece to copy the deflection excited by the dynamic cutting force. The relationship between the input deflection and the output voltage of the monitoring system is calibrated by testing. Monitored workpiece deflection results show that the workpiece experiences obvious vibration during the cutter entering the workpiece stage, and vibration during the machining process can be easily tracked by monitoring the deflection of the workpiece. During the cutter exiting the workpiece stage, the workpiece experiences forced vibration firstly, and free vibration exists until the amplitude reduces to zero after the cutter exits the workpiece. Machining results confirmed the suitability of the deflection monitoring system for machining thin-walled workpieces with the application of PVDF sensors.
Semantic Deviation in Oliver Twist
Institute of Scientific and Technical Information of China (English)
康艺凡
2016-01-01
Dickens, with his adeptness with language, applies semantic deviation skillfully in his realistic novel Oliver Twist. However, most studies and comments home and abroad on it mainly focus on such aspects as humanity, society, and characters. Therefore, this thesis will take a stylistic approach to Oliver Twist from the perspective of semantic deviation, which is achieved by the use of irony, hyperbole, and pun and analyze how the application of the technique makes the novel attractive.
Speziale, Simone
2013-01-01
We define and investigate a quantisation of null hypersurfaces in the context of loop quantum gravity on a fixed graph. The main tool we use is the parametrisation of the theory in terms of twistors, which has already proved useful in discussing the interpretation of spin networks as the quantization of twisted geometries. The classical formalism can be extended in a natural way to null hypersurfaces, with the Euclidean polyhedra replaced by null polyhedra with space-like faces, and SU(2) by the little group ISO(2). The main difference is that the simplicity constraints present in the formalims are all first class, and the symplectic reduction selects only the helicity subgroup of the little group. As a consequence, information on the shapes of the polyhedra is lost, and the result is a much simpler, abelian geometric picture. It can be described by an Euclidean singular structure on the 2-dimensional space-like surface defined by a foliation of space-time by null hypersurfaces. This geometric structure is na...
Design optimization for active twist rotor blades
Mok, Ji Won
This dissertation introduces the process of optimizing active twist rotor blades in the presence of embedded anisotropic piezo-composite actuators. Optimum design of active twist blades is a complex task, since it involves a rich design space with tightly coupled design variables. The study presents the development of an optimization framework for active helicopter rotor blade cross-sectional design. This optimization framework allows for exploring a rich and highly nonlinear design space in order to optimize the active twist rotor blades. Different analytical components are combined in the framework: cross-sectional analysis (UM/VABS), an automated mesh generator, a beam solver (DYMORE), a three-dimensional local strain recovery module, and a gradient based optimizer within MATLAB. Through the mathematical optimization problem, the static twist actuation performance of a blade is maximized while satisfying a series of blade constraints. These constraints are associated with locations of the center of gravity and elastic axis, blade mass per unit span, fundamental rotating blade frequencies, and the blade strength based on local three-dimensional strain fields under worst loading conditions. Through pre-processing, limitations of the proposed process have been studied. When limitations were detected, resolution strategies were proposed. These include mesh overlapping, element distortion, trailing edge tab modeling, electrode modeling and foam implementation of the mesh generator, and the initial point sensibility of the current optimization scheme. Examples demonstrate the effectiveness of this process. Optimization studies were performed on the NASA/Army/MIT ATR blade case. Even though that design was built and shown significant impact in vibration reduction, the proposed optimization process showed that the design could be improved significantly. The second example, based on a model scale of the AH-64D Apache blade, emphasized the capability of this framework to
Directory of Open Access Journals (Sweden)
Sathish Rao Udupi
2016-01-01
Full Text Available The previous research investigations informed that the tool wear of any machining operation could be minimized by controlling the machining factors such as speed, feed, geometry, and type of cutting tool. Hence the present research paper aims at controlling the process parameters to minimize the drill tool wear, during the machining of Glass Fiber Reinforced Polymer (GFRP composites. Experiments were carried out to find the tool wear rate and a wear mechanism map of uncoated High Speed Steel (HSS drill of 10 mm diameter was developed for the drilling of GFRP composite laminates. The surface micrograph images on the drill land surface displayed dominant wear mechanisms induced on HSS drill during machining of GFRP and they were found to be adhesive wear, adhesive and abrasive wear, abrasive wear, and diffusion and fatigue wear. A “safety wear zone” was identified on the wear mechanism map, where the minimum tool wear of the HSS drill occurs. From the safety zone boundaries, it was inferred that the drill spindle speed should be set between 1200 and 1590 rpm and feed rate must be set within a range of 0.10–0.16 mm/rev for GFRP work and HSS tool combination to enhance the service life of 10 mm HSS drills and to minimize the tool wear.
Performance of twist-coupled blades on variable speed rotors
Energy Technology Data Exchange (ETDEWEB)
Lobitz, D.W.; Veers, P.S.; Laino, D.J.
1999-12-07
The load mitigation and energy capture characteristics of twist-coupled HAWT blades that are mounted on a variable speed rotor are investigated in this paper. These blades are designed to twist toward feather as they bend with pretwist set to achieve a desirable twist distribution at rated power. For this investigation, the ADAMS-WT software has been modified to include blade models with bending-twist coupling. Using twist-coupled and uncoupled models, the ADAMS software is exercised for steady wind environments to generate C{sub p} curves at a number of operating speeds to compare the efficiencies of the two models. The ADAMS software is also used to generate the response of a twist-coupled variable speed rotor to a spectrum of stochastic wind time series. This spectrum contains time series with two mean wind speeds at two turbulence levels. Power control is achieved by imposing a reactive torque on the low speed shaft proportional to the RPM squared with the coefficient specified so that the rotor operates at peak efficiency in the linear aerodynamic range, and by limiting the maximum RPM to take advantage of the stall controlled nature of the rotor. Fatigue calculations are done for the generated load histories using a range of material exponents that represent materials from welded steel to aluminum to composites, and results are compared with the damage computed for the rotor without twist-coupling. Results indicate that significant reductions in damage are achieved across the spectrum of applied wind loading without any degradation in power production.
Template preparation of twisted nanoparticles of mesoporous silica
Institute of Scientific and Technical Information of China (English)
Kui Niu; Zhongbin Ni; Chengwu Fu; Tatsuo Kaneko; Mingqing Chen
2011-01-01
Optical isomers of N-lauroyl-L-(or-D-) alanine sodium salt {C12-L-(or-D-)AlaS} surfactants were used for the preparation of mesoporous silica nanoparticles with a twisted hexagonal rod-like morphology. Thermogravimetric analysis (TGA) was used to determine the temperature for template removal. Circular dichroism (CD) spectra of the surfactant solution with various compositions illustrated the formation and supramolecular assembly of protein-like molecular architecture leading to formation of twisted nanoparticles. Scanning electron microscopy (SEM),high-resolution transmission electron microscopy (HRTEM)and X-ray powder diffraction (XRD) patterns of these as-synthesized mesoporous silica confirmed that the twisted morphology of these nanoparticles was closely related to the supramolecular-assembled complex of amino acid surfactants.
Bend-twist coupling potential of wind turbine blades
DEFF Research Database (Denmark)
Fedorov, Vladimir; Berggreen, Christian
2014-01-01
In the present study an evaluation of the potential for bend-twist coupling effects in wind turbine blades is addressed. A method for evaluation of the coupling magnitude based on the results of finite element modeling and full-field displacement measurements obtained by experiments is developed...... and tested on small-scale coupled composite beams. In the proposed method the coupling coefficient for a generic beam is introduced based on the Euler-Bernoulli beam formulation. By applying the developed method for analysis of a commercial wind turbine blade structure it is demonstrated that a bend......-twist coupling magnitude of up to 0.2 is feasible to achieve in the baseline blade structure made of glass-fiber reinforced plastics. Further, by substituting the glass-fibers with carbon-fibers the coupling effect can be increased to 0.4. Additionally, the effect of introduction of bend-twist coupling...
薄壁塑料件注塑模具设计%PLASTIC MOULD DESIGN OF THIN-WALL PLASTIC PARTS
Institute of Scientific and Technical Information of China (English)
苏瞧忠
2011-01-01
The design process of thin-wall plastic was analyzed, gate style and position was choosen according to the mould structure, plastic injection molding process, plastic surface quality etc. Producing reliable and dimensinally stable product was realized by optimizing plastic wall thickness and the mould structure, and the product could meet the quality requirement. These plastic mould design essentials were summarized.%分析薄壁塑料件的设计过程,重点阐述根据模具结构、塑料件成型工艺、塑料件表面质量等来选择进胶方式和位置.通过优化塑料件壁厚和模具结构,实现生产可靠、尺寸稳定,质量满足要求,并总结此类塑料件的模具设计要点.
高架桥薄壁空心高墩施工%Construction Organizational Design for High Hollow Thin-wall Pier of Viaduct Bridge
Institute of Scientific and Technical Information of China (English)
冯世敏
2014-01-01
PJ-200 Cantilever formwork ( climbing formwork ) and big steel formwork lifted with tower crane ( turnover formwork construction) have been adopted for the construction of high hollow thin-wall pier of Hewei Bridge at Km:253+353 of Lechang-Guangzhou Expressway, which has achieved good economic benefits.%乐昌至广州高速公路K253+353河尾大桥薄壁空心高墩施工组织设计采用PJ-200悬臂模板(即爬模施工)和塔吊提升大块钢模的方法施工(即翻模施工)相结合的方式，取得了较好的经济效益。
Hangai, Yoshihiko; Nakano, Yukiko; Utsunomiya, Takao; Kuwazuru, Osamu; Yoshikawa, Nobuhiro
2017-02-01
In this study, Al-Si-Cu alloy ADC12 foam-filled thin-walled stainless steel pipes, which exhibit metal bonding between the ADC12 foam and steel pipe, were fabricated by friction stir back extrusion. Drop weight impact tests were conducted to investigate the deformation behavior and mechanical properties of the foam-filled pipes during dynamic compression tests, which were compared with the results of static compression tests. From x-ray computed tomography observation, it was confirmed that the fabricated foam-filled pipes had almost uniform porosity and pore size distributions. It was found that no scattering of the fragments of collapsed ADC12 foam occurred for the foam-filled pipes owing to the existence of the pipe surrounding the ADC12 foam. Preventing the scattering of the ADC12 foam decreases the drop in stress during dynamic compression tests and therefore improves the energy absorption properties of the foam.
Analysis of thin-walled parts CNC machining process quality improvement%薄壁零件数控加工工艺质量改进分析
Institute of Scientific and Technical Information of China (English)
李盼
2013-01-01
计算机技术和仿真技术的迅猛发展推动着薄壁零件数控加工工艺由不成熟的工艺发展蜕变为工程科学。在此过程中，薄壁零件数控加工技术研究由传统的经验研究转变为科学的“定量分析”。薄壁零件存在的问题是刚性差、结构较复杂，在数控加工中易变形且难以控制，加工质量得不到切实保障。对目前的加工系统而言，数据加工过程可以分为三大步：一是加工前的工艺设计和离线零件编程，二是在加工过程中的在线加工和监控，三是加工后的检验处理。只有将三大步骤紧密结合协调统一好，才能确保工艺加工质量。但是，在线加工工艺系统会受到诸多因素的干扰，比如刀具变形、受热变形等，这些外在因素会严重影响质量。薄壁零件数控加工工艺在工业中的应用越来越广泛，保障加工工艺质量是当前急需关注和强调的问题。本文通过分析加工工艺的影响因素，提出改进装夹方案、修改切削参数、修正刀具路径、局部调整进给量等几种策略，来对加工路径和方式进行分析和优化，达到改进加工工艺质量的目的。%The rapid development of computer technology and simulation technology are pushing the thin-walled parts CNC machining process by the process of transformation of immature development of Engineering science. In this process, the processing technology of the thin wall parts CNC experience traditional research into scientific quantitative analysis "". Thin wall parts there is the problem of poor rigidity, structure is complex, in NC machining deformation and difficult to control, the processing quality can not be guaranteed. The processing system at present, the data processing process can be divided into three steps: one is the processing of process design and the offline part programming, two is the online processing and monitoring in machining process, three is
Gavryushin, S. S.; Nikolaeva, A. S.
2016-05-01
The theoretical foundations, methods, and algorithms developed to analyze the stability and postbuckling behavior of thin elastic axisymmetric shells are discussed. The algorithm for numerically studying the processes of nonlinear deformation of thin-walled axisymmetric shells by the solution parametric continuation method is generalized to solving the practical problem of design of mechanical actuators of discrete action. The synthesis algorithm is based on the method of changing the subspace of control parameters, which is supplemented with the procedure of smooth transition in changing the subspaces. The efficiency of the proposed algorithm is illustrated by an example of synthesis of a thermobimetallic actuator of discrete action. The procedure of determining an isolated solution, whose existencewas predicted byV. I. Feodosiev, is considered in the framework of studying the process of nonlinear deformation of a corrugated membrane loaded by an external pressure.
Shao, Huifeng; Ke, Xiurong; Liu, An; Sun, Miao; He, Yong; Yang, Xianyan; Fu, Jianzhong; Liu, Yanming; Zhang, Lei; Yang, Guojing; Xu, Sanzhong; Gou, Zhongru
2017-03-13
Three-dimensional (3D) printing bioactive ceramics have demonstrated alternative approaches to bone tissue repair, but an optimized materials system for improving the recruitment of host osteogenic cells into the bone defect and enhancing targeted repair of the thin-wall craniomaxillofacial defects remains elusive. Herein we systematically evaluated the role of side-wall pore architecture in the direct-ink-writing bioceramic scaffolds on mechanical properties and osteogenic capacity in rabbit calvarial defects. The pure calcium silicate (CSi) and dilute Mg-doped CSi (CSi-Mg6) scaffolds with different layer thickness and macropore sizes were prepared by varying the layer deposition mode from single-layer printing (SLP) to double-layer printing (DLP) and then by undergoing one-, or two-step sintering. It was found that the dilute Mg doping and/or two-step sintering schedule was especially beneficial for improving the compressive strength (~25‒104 MPa) and flexural strength (~6‒18 MPa) of the Ca-silicate scaffolds. The histological analysis for the calvarial bone specimens in vivo revealed that the SLP scaffolds had a high osteoconduction at the early stage (4 weeks) but the DLP scaffolds displayed a higher osteogenic capacity for a long time stage (8~12 weeks). Although the DLP CSi scaffolds displayed somewhat higher osteogenic capacity at 8 and 12 weeks, the DLP CSi-Mg6 scaffolds with excellent fracture resistance also showed appreciable new bone tissue ingrowth. These findings demonstrate that the side-wall pore architecture in 3D printed bioceramic scaffolds is required to optimize for bone repair in calvarial bone defects, and especially the Mg doping wollastontie is promising for 3D printing thin-wall porous scaffolds for craniomaxillofacial bone defect treatment.
Polarization twist in perovskite ferrielectrics.
Kitanaka, Yuuki; Hirano, Kiyotaka; Ogino, Motohiro; Noguchi, Yuji; Miyayama, Masaru; Moriyoshi, Chikako; Kuroiwa, Yoshihiro
2016-09-02
Because the functions of polar materials are governed primarily by their polarization response to external stimuli, the majority of studies have focused on controlling polar lattice distortions. In some perovskite oxides, polar distortions coexist with nonpolar tilts and rotations of oxygen octahedra. The interplay between nonpolar and polar instabilities appears to play a crucial role, raising the question of how to design materials by exploiting their coupling. Here, we introduce the concept of 'polarization twist', which offers enhanced control over piezoelectric responses in polar materials. Our experimental and theoretical studies provide direct evidence that a ferrielectric perovskite exhibits a large piezoelectric response because of extended polar distortion, accompanied by nonpolar octahedral rotations, as if twisted polarization relaxes under electric fields. The concept underlying the polarization twist opens new possibilities for developing alternative materials in bulk and thin-film forms.
Drinfel'd basis of twisted Yangians
Belliard, Samuel
2014-01-01
We present a quantization of a Lie bi-ideal structure for twisted half-loop algebras of finite dimensional simple complex Lie algebras. We obtain Drinfel'd basis formalism and algebra closure relations of twisted Yangians for all symmetric pairs of simple Lie algebras and for simple twisted even half-loop Lie algebras. We also give an explicit form of twisted Yangians in Drinfel'd basis for the sl3 Lie algebra.
Meek, MF; Den Dunnen, WFA; Schakenraad, JM; Robinson, PH
1999-01-01
This study was performed to evaluate the long-term functional nerve recovery after reconstruction of a IO-mm gap in the sciatic nerve of the rat, with a thin-walled nerve guide, composed of a biodegradable copolymer of DL-lactide and epsilon-caprolactone [p(DLLA-epsilon-CL)]. To evaluate both motor
Properly twisted groups and their algebras
Bales, John W
2011-01-01
A twist property is developed which imparts certain properties on the twisted group algebra. These include an involution * satisfying (xy)*=y*x* and an inner product satisfying = and =. Examples of twisted group algebras having this property are the Cayley-Dickson algebras and Clifford algebras.
"Oliver Twist": A Teacher's Guide.
Cashion, Carol; Fischer, Diana
This teacher's guide for public television's 3-part adaptation of Charles Dickens's "Oliver Twist" provides information that will help enrich students' viewing of the series, whether or not they read the novel. The guide includes a wide range of discussion and activity ideas; there is also a series Web site and a list of Web resources.…
Helically twisted photonic crystal fibres.
Russell, P St J; Beravat, R; Wong, G K L
2017-02-28
Recent theoretical and experimental work on helically twisted photonic crystal fibres (PCFs) is reviewed. Helical Bloch theory is introduced, including a new formalism based on the tight-binding approximation. It is used to explore and explain a variety of unusual effects that appear in a range of different twisted PCFs, including fibres with a single core and fibres with N cores arranged in a ring around the fibre axis. We discuss a new kind of birefringence that causes the propagation constants of left- and right-spinning optical vortices to be non-degenerate for the same order of orbital angular momentum (OAM). Topological effects, arising from the twisted periodic 'space', cause light to spiral around the fibre axis, with fascinating consequences, including the appearance of dips in the transmission spectrum and low loss guidance in coreless PCF. Discussing twisted fibres with a single off-axis core, we report that optical activity in a PCF is opposite in sign to that seen in a step-index fibre. Fabrication techniques are briefly described and emerging applications reviewed. The analytical results of helical Bloch theory are verified by an extensive series of 'numerical experiments' based on finite-element solutions of Maxwell's equations in a helicoidal frame.This article is part of the themed issue 'Optical orbital angular momentum'. © 2017 The Authors.
Helically twisted photonic crystal fibres
Russell, P. St. J.; Beravat, R.; Wong, G. K. L.
2017-02-01
Recent theoretical and experimental work on helically twisted photonic crystal fibres (PCFs) is reviewed. Helical Bloch theory is introduced, including a new formalism based on the tight-binding approximation. It is used to explore and explain a variety of unusual effects that appear in a range of different twisted PCFs, including fibres with a single core and fibres with N cores arranged in a ring around the fibre axis. We discuss a new kind of birefringence that causes the propagation constants of left- and right-spinning optical vortices to be non-degenerate for the same order of orbital angular momentum (OAM). Topological effects, arising from the twisted periodic `space', cause light to spiral around the fibre axis, with fascinating consequences, including the appearance of dips in the transmission spectrum and low loss guidance in coreless PCF. Discussing twisted fibres with a single off-axis core, we report that optical activity in a PCF is opposite in sign to that seen in a step-index fibre. Fabrication techniques are briefly described and emerging applications reviewed. The analytical results of helical Bloch theory are verified by an extensive series of `numerical experiments' based on finite-element solutions of Maxwell's equations in a helicoidal frame. This article is part of the themed issue 'Optical orbital angular momentum'.
Helically twisted photonic crystal fibres
Beravat, R.; Wong, G. K. L.
2017-01-01
Recent theoretical and experimental work on helically twisted photonic crystal fibres (PCFs) is reviewed. Helical Bloch theory is introduced, including a new formalism based on the tight-binding approximation. It is used to explore and explain a variety of unusual effects that appear in a range of different twisted PCFs, including fibres with a single core and fibres with N cores arranged in a ring around the fibre axis. We discuss a new kind of birefringence that causes the propagation constants of left- and right-spinning optical vortices to be non-degenerate for the same order of orbital angular momentum (OAM). Topological effects, arising from the twisted periodic ‘space’, cause light to spiral around the fibre axis, with fascinating consequences, including the appearance of dips in the transmission spectrum and low loss guidance in coreless PCF. Discussing twisted fibres with a single off-axis core, we report that optical activity in a PCF is opposite in sign to that seen in a step-index fibre. Fabrication techniques are briefly described and emerging applications reviewed. The analytical results of helical Bloch theory are verified by an extensive series of ‘numerical experiments’ based on finite-element solutions of Maxwell's equations in a helicoidal frame. This article is part of the themed issue ‘Optical orbital angular momentum’. PMID:28069771
Institute of Scientific and Technical Information of China (English)
SHA Yun-dong; GUO Xiao-peng; LIAO Lian-fang; XIE Li-juan
2011-01-01
As to the sonic fatigue problem of an aero-engine combustor liner structure under the random acoustic loadings, an effective method for predicting the fatigue life of a structure under random loadings was studied. Firstly, the probability distribution of Von Mises stress of thin-walled structure under random loadings was studied, analysis suggested that probability density function of Von Mises stress process accord approximately with two-parameter Weibull distribution. The formula for calculating Weibull parameters were given. Based on the Miner linear theory, the method for predicting the random sonic fatigue life based on the stress probability density was developed, and the model for fatigue life prediction was constructed. As an example, an aero-engine combustor liner structure was considered. The power spectrum density (PSD) of the vibrational stress response was calculated by using the coupled FEM/BEM (finite element method/boundary element method) model, the fatigue life was estimated by using the constructed model. And considering the influence of the wide frequency band, the calculated results were modified. Comparetive analysis shows that the estimated results of sonic fatigue of the combustor liner structure by using Weibull distribution of Von Mises stress are more conservative than using Dirlik distribution to some extend. The results show that the methods presented in this paper are practical for the random fatigue life analysis of the aeronautical thin-walled structures.
Delamination and debonding failure of laminated composite T-joints
Cui, H.
2014-01-01
Composites are increasingly being used in aerospace, automotive and other industries. The T-joint (also named stringer stiffened skin) is a typical connection, broadly used in thin-walled structures, such as the wing and fuselage of aircraft. This thesis presents the analysis of the delamination and
DEFF Research Database (Denmark)
Henrichsen, Søren Randrup; Lindgaard, Esben; Lund, Erik
2015-01-01
Robust design of laminated composite structures is considered in this work. Because laminated composite structures are often thin walled, buckling failure can occur prior to material failure, making it desirable to maximize the buckling load. However, as a structure always contains imperfections...
Renormalization constants for 2-twist operators in twisted mass QCD
Alexandrou, C; Korzec, T; Panagopoulos, H; Stylianou, F
2010-01-01
Perturbative and non-perturbative results on the renormalization constants of the fermion field and the twist-2 fermion bilinears are presented with emphasis on the non-perturbative evaluation of the one-derivative twist-2 vector and axial vector operators. Non-perturbative results are obtained using the twisted mass Wilson fermion formulation employing two degenerate dynamical quarks and the tree-level Symanzik improved gluon action. The simulations have been performed for pion masses in the range of about 450-260 MeV and at three values of the lattice spacing $a$ corresponding to $\\beta=3.9, 4.05, 4.20$. Subtraction of ${\\cal O}(a^2)$ terms is carried out by performing the perturbative evaluation of these operators at 1-loop and up to ${\\cal O}(a^2)$. The renormalization conditions are defined in the RI$'$-MOM scheme, for both perturbative and non-perturbative results. The renormalization factors, obtained for different values of the renormalization scale, are evolved perturbatively to a reference scale set...
The twist box domain is required for Twist1-induced prostate cancer metastasis.
Gajula, Rajendra P; Chettiar, Sivarajan T; Williams, Russell D; Thiyagarajan, Saravanan; Kato, Yoshinori; Aziz, Khaled; Wang, Ruoqi; Gandhi, Nishant; Wild, Aaron T; Vesuna, Farhad; Ma, Jinfang; Salih, Tarek; Cades, Jessica; Fertig, Elana; Biswal, Shyam; Burns, Timothy F; Chung, Christine H; Rudin, Charles M; Herman, Joseph M; Hales, Russell K; Raman, Venu; An, Steven S; Tran, Phuoc T
2013-11-01
Twist1, a basic helix-loop-helix transcription factor, plays a key role during development and is a master regulator of the epithelial-mesenchymal transition (EMT) that promotes cancer metastasis. Structure-function relationships of Twist1 to cancer-related phenotypes are underappreciated, so we studied the requirement of the conserved Twist box domain for metastatic phenotypes in prostate cancer. Evidence suggests that Twist1 is overexpressed in clinical specimens and correlated with aggressive/metastatic disease. Therefore, we examined a transactivation mutant, Twist1-F191G, in prostate cancer cells using in vitro assays, which mimic various stages of metastasis. Twist1 overexpression led to elevated cytoskeletal stiffness and cell traction forces at the migratory edge of cells based on biophysical single-cell measurements. Twist1 conferred additional cellular properties associated with cancer cell metastasis including increased migration, invasion, anoikis resistance, and anchorage-independent growth. The Twist box mutant was defective for these Twist1 phenotypes in vitro. Importantly, we observed a high frequency of Twist1-induced metastatic lung tumors and extrathoracic metastases in vivo using the experimental lung metastasis assay. The Twist box was required for prostate cancer cells to colonize metastatic lung lesions and extrathoracic metastases. Comparative genomic profiling revealed transcriptional programs directed by the Twist box that were associated with cancer progression, such as Hoxa9. Mechanistically, Twist1 bound to the Hoxa9 promoter and positively regulated Hoxa9 expression in prostate cancer cells. Finally, Hoxa9 was important for Twist1-induced cellular phenotypes associated with metastasis. These data suggest that the Twist box domain is required for Twist1 transcriptional programs and prostate cancer metastasis. Targeting the Twist box domain of Twist1 may effectively limit prostate cancer metastatic potential. ©2013 AACR.
"Twisted" black holes are unphysical
Gray, Finnian; Schuster, Sebastian; Visser, Matt
2016-01-01
So-called "twisted" black holes have recently been proposed by Zhang (1609.09721 [gr-qc]), and further considered by Chen and Jing (1610.00886 [gr-qc]), and more recently by Ong (1610.05757 [gr-qc]). While these spacetimes are certainly Ricci-flat, and so mathematically satisfy the vacuum Einstein equations, they are also merely minor variants on Taub--NUT spacetimes. Consequently they exhibit several unphysical features that make them quite unreasonable as realistic astrophysical objects. Specifically, these "twisted" black holes are not (globally) asymptotically flat. Furthermore, they contain closed timelike curves that are not hidden behind any event horizon --- the most obvious of these closed timelike curves are small azimuthal circles around the rotation axis, but the effect is more general. The entire region outside the horizon is infested with closed timelike curves.
Polarization twist in perovskite ferrielectrics
Kitanaka, Yuuki; Hirano, Kiyotaka; Ogino, Motohiro; Noguchi, Yuji; Miyayama, Masaru; Moriyoshi, Chikako; Kuroiwa, Yoshihiro
2016-01-01
Because the functions of polar materials are governed primarily by their polarization response to external stimuli, the majority of studies have focused on controlling polar lattice distortions. In some perovskite oxides, polar distortions coexist with nonpolar tilts and rotations of oxygen octahedra. The interplay between nonpolar and polar instabilities appears to play a crucial role, raising the question of how to design materials by exploiting their coupling. Here, we introduce the concept of ‘polarization twist’, which offers enhanced control over piezoelectric responses in polar materials. Our experimental and theoretical studies provide direct evidence that a ferrielectric perovskite exhibits a large piezoelectric response because of extended polar distortion, accompanied by nonpolar octahedral rotations, as if twisted polarization relaxes under electric fields. The concept underlying the polarization twist opens new possibilities for developing alternative materials in bulk and thin-film forms. PMID:27586824
Polarization twist in perovskite ferrielectrics
Kitanaka, Yuuki; Hirano, Kiyotaka; Ogino, Motohiro; Noguchi, Yuji; Miyayama, Masaru; Moriyoshi, Chikako; Kuroiwa, Yoshihiro
2016-09-01
Because the functions of polar materials are governed primarily by their polarization response to external stimuli, the majority of studies have focused on controlling polar lattice distortions. In some perovskite oxides, polar distortions coexist with nonpolar tilts and rotations of oxygen octahedra. The interplay between nonpolar and polar instabilities appears to play a crucial role, raising the question of how to design materials by exploiting their coupling. Here, we introduce the concept of ‘polarization twist’, which offers enhanced control over piezoelectric responses in polar materials. Our experimental and theoretical studies provide direct evidence that a ferrielectric perovskite exhibits a large piezoelectric response because of extended polar distortion, accompanied by nonpolar octahedral rotations, as if twisted polarization relaxes under electric fields. The concept underlying the polarization twist opens new possibilities for developing alternative materials in bulk and thin-film forms.
Twist-related locomotion of a snake-like robot
Institute of Scientific and Technical Information of China (English)
Ye Changlong; Ma Shugen; Li Bin; Wang Yuechao; Jing Tao
2006-01-01
As a hyper-redundant robot, a 3D snake-like robot can perform many other configurations and types of locomotion adapted to environment except for mimicking the natural snake locomotion. The natural snake locomotion usually limits locomotion capability of the robot because of inadequacy in the mechanism and actuation to imitate characters of natural snake such as the too many DOFs and the characteristics of the muscle. In order to apply snake-like robots to the unstructured environment, the researchers have designed many gaits for increasing the adaptability to a variety of surroundings. The twist-related locomotion is an effective gait achieved by jointly driving the pitching-DOF and yawing-DOF, with which the snakelike robot can move on rough ground and even climb up some obstacles. In this paper, the twist-related locomotion function is firstly solved, and simplified to be expressible by sine or cosine function. The 2D locomotion such as V-shape and U-shape is achieved. Also by applying it to the serpentine locomotion or other types of locomotion, the snake-like robot can complete composite locomotion that combines the serpentine locomotion or others with twist-related locomotion. Then we extend the twist-related locomotion to 3D space. Finally, the experimental results are presented to validate all above analyses.
Design studies for twist-coupled wind turbine blades.
Energy Technology Data Exchange (ETDEWEB)
Valencia, Ulyses (Wichita State University, Wichita, KS); Locke, James (Wichita State University, Wichita, KS)
2004-06-01
This study presents results obtained for four hybrid designs of the Northern Power Systems (NPS) 9.2-meter prototype version of the ERS-100 wind turbine rotor blade. The ERS-100 wind turbine rotor blade was designed and developed by TPI composites. The baseline design uses e-glass unidirectional fibers in combination with {+-}45-degree and random mat layers for the skin and spar cap. This project involves developing structural finite element models of the baseline design and carbon hybrid designs with and without twist-bend coupling. All designs were evaluated for a unit load condition and two extreme wind conditions. The unit load condition was used to evaluate the static deflection, twist and twist-coupling parameter. Maximum deflections and strains were determined for the extreme wind conditions. Linear and nonlinear buckling loads were determined for a tip load condition. The results indicate that carbon fibers can be used to produce twist-coupled designs with comparable deflections, strains and buckling loads to the e-glass baseline.
Twisted Chern-Simons supergravity
Energy Technology Data Exchange (ETDEWEB)
Castellani, L. [Dipartimento di Scienze e Innovazione Tecnologica, Univ. del Piemonte Orientale, Alessandria (Italy); INFN Gruppo collegato di Alessandria (Italy)
2014-09-11
We present a noncommutative version of D = 5 Chern-Simons supergravity, where noncommutativity is encoded in a *-product associated to an abelian Drinfeld twist. The theory is invariant under diffeomorphisms, and under the *-gauge supergroup SU(2,2 vertical stroke 4), including Lorentz and N = 4 local supersymmetries. (Copyright copyright 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)
Counting Polyominoes on Twisted Cylinders
Barequet, Gill; Moffie, Micha; Ribó, Ares; Rote, Günter
2005-01-01
International audience; We improve the lower bounds on Klarner's constant, which describes the exponential growth rate of the number of polyominoes (connected subsets of grid squares) with a given number of squares. We achieve this by analyzing polyominoes on a different surface, a so-called $\\textit{twisted cylinder}$ by the transfer matrix method. A bijective representation of the "states'' of partial solutions is crucial for allowing a compact representation of the successive iteration vec...
Resummation of target mass corrections in two-photon processes twist-two sector
Belitsky, A V
2001-01-01
We develop a formalism for the resummation of target mass corrections in off-forward two-photon amplitudes given by a chronological product of electromagnetic currents, arising in e.g. deeply virtual Compton scattering. The method is based on a relation of composite operators with a definite twist to harmonic tensors, which form an irreducible representation of the Lorentz group. We give an application of the framework for the matrix elements of twist-two operators.
New twist on artificial muscles
Haines, Carter S.; Li, Na; Spinks, Geoffrey M.; Aliev, Ali E.; Di, Jiangtao; Baughman, Ray H.
2016-01-01
Lightweight artificial muscle fibers that can match the large tensile stroke of natural muscles have been elusive. In particular, low stroke, limited cycle life, and inefficient energy conversion have combined with high cost and hysteretic performance to restrict practical use. In recent years, a new class of artificial muscles, based on highly twisted fibers, has emerged that can deliver more than 2,000 J/kg of specific work during muscle contraction, compared with just 40 J/kg for natural muscle. Thermally actuated muscles made from ordinary polymer fibers can deliver long-life, hysteresis-free tensile strokes of more than 30% and torsional actuation capable of spinning a paddle at speeds of more than 100,000 rpm. In this perspective, we explore the mechanisms and potential applications of present twisted fiber muscles and the future opportunities and challenges for developing twisted muscles having improved cycle rates, efficiencies, and functionality. We also demonstrate artificial muscle sewing threads and textiles and coiled structures that exhibit nearly unlimited actuation strokes. In addition to robotics and prosthetics, future applications include smart textiles that change breathability in response to temperature and moisture and window shutters that automatically open and close to conserve energy. PMID:27671626
Institute of Scientific and Technical Information of China (English)
王鹏飞; 曹其新
2015-01-01
The thin-walled structural instability phenomenon was considered for the buckling analysis after the lightweight and the thin-wall design of the key component for the long-distance maintenance. A local buckling stress calculation model based on Rayleigh-Ritz variational method was proposed.A calculation model based on elastic buckling theory of thin-walled plate was presented simultaneously, which considers buckling half wave number,rectangular geometry dimension and boundary con-straint.The thin-walled rectangular cantilever beam was reduced to four thin-walled plate,which was loaded elastic rotational restraint along unloaded edge.A practical method of buckling analysis for rec-tangular cantilever beam was proposed.And the finite element simulation of cantilever beam composed by rectangular thin-walled plate was carried out.The effectiveness of the proposed methods was veri-fied by the finite element metod simulation result,which was consistent with the theoretical calculat-ing value.%针对远距离维护机器人关键结构件（矩形截面薄壁梁）轻量化、薄壁化设计后发生的屈曲问题，为避免薄壁结构件发生失稳现象，提出了基于瑞利-里兹能量变分法建立屈曲应力计算模型，以及基于弹性薄板理论构件容纳屈曲半波数、矩形几何尺寸和边界扭矩约束刚度等因素的数学模型的融合方法。将矩形薄壁梁简化为四个非载荷端承受弹性扭转约束的薄壁矩形板件，为矩形梁屈曲分析提供了一种实用方法。运用有限元方法对矩形薄板组成的悬臂梁进行仿真分析，所得结果与理论计算值具有一致性，验证了方法的正确性。
Institute of Scientific and Technical Information of China (English)
Tian Shan; Liu Yuli; Yang He
2013-01-01
Inner flange and side wrinkling often occur in rotary-draw bending process of rectangular aluminum alloy wave-guide tubes,and the distribution and magnitude of wrinkling is related to geometrical parameters of the tubes.In order to study the effects of geometrical parameters on wrinkling of rectangular wave-guide tubes,a 3D-FE model for rotary-draw bending processes of thin-walled rectangular aluminum alloy wave-guide tubes was built based on the platform of ABAQUS/Explicit,and its reliability was validated by experiments.Simulation and analysis of the influence laws of geometrical parameters on the wave heights of inner flange and side wrinkling were then carried out.The results show that inner flange wrinkling is the main wrinkling way to rectangular wave-guide tubes in rotary-draw bending processes,but side wrinkling cannot be neglected because side wrinkling is 2/3 of inner flange wrinkling when b and h are smaller.Inner flange and side wrinkling increase with increasing b and h; the influence of b on side wrinkling is larger than that of h,while both b and h affect inner flange wrinkling greatly.Inner flange and side wrinkling decrease with increasing R/h; the influence of h on inner flange and side wrinkling is larger than that of R.
Li, Heng; Yang, He; Zhan, Mei
2010-06-01
Thin-walled tube bending(TWTB) method of Al-alloy tube has attracted wide applications in aerospace, aviation and automobile,etc. While, under in-plane double tensile stress states at the extrados of bending tube, the over-thinning induced ductile fracture is one dominant defect in Al-alloy tube bending. The main objective of this study is to predict the critical wall-thinning of Al-alloy tube bending by coupling two ductile fracture criteria(DFCs) into FE simulation. The DFCs include Continuum Damage Mechanics(CDM)-based model and GTN porous model. Through the uniaxial tensile test of the curved specimen, the basic material properties of the Al-alloy 5052O tube is obtained; via the inverse problem solution, the damage parameters of both the two fracture criteria are interatively determined. Thus the application study of the above DFCs in the TWTB is performed, and the more reasonable one is selected to obtain the critical thinning of Al-alloy tube in bending. The virtual damage initiation and evolution (when and where the ductile fracture occurs) in TWTB are investigated, and the fracture mechanisms of the voided Al-alloy tube in tube bending are consequently discussed.
Energy Technology Data Exchange (ETDEWEB)
Fasoyinu, Yemi [CanmetMATERIALS; Griffin, John A. [University of Alabama - Birmingham
2014-03-31
With the increased emphasis on vehicle weight reduction, production of near-net shape components by lost foam casting will make significant inroad into the next-generation of engineering component designs. The lost foam casting process is a cost effective method for producing complex castings using an expandable polystyrene pattern and un-bonded sand. The use of un-bonded molding media in the lost foam process will impose less constraint on the solidifying casting, making hot tearing less prevalent. This is especially true in Al-Mg and Al-Cu alloy systems that are prone to hot tearing when poured in rigid molds partially due to their long freezing range. Some of the unique advantages of using the lost foam casting process are closer dimensional tolerance, higher casting yield, and the elimination of sand cores and binders. Most of the aluminum alloys poured using the lost foam process are based on the Al-Si system. Very limited research work has been performed with Al-Mg and Al-Cu type alloys. With the increased emphasis on vehicle weight reduction, and given the high-strength-to-weight-ratio of magnesium, significant weight savings can be achieved by casting thin-wall (≤ 3 mm) engineering components from both aluminum- and magnesium-base alloys.
Directory of Open Access Journals (Sweden)
Garrett J. Marshall
2016-06-01
Full Text Available An OPTOMEC Laser Engineered Net Shaping (LENS™ 750 system was retrofitted with a melt pool pyrometer and in-chamber infrared (IR camera for nondestructive thermal inspection of the blown-powder, direct laser deposition (DLD process. Data indicative of temperature and heat transfer within the melt pool and heat affected zone atop a thin-walled structure of Ti–6Al–4V during its additive manufacture are provided. Melt pool temperature data were collected via the dual-wavelength pyrometer while the dynamic, bulk part temperature distribution was collected using the IR camera. Such data are provided in Comma Separated Values (CSV file format, containing a 752×480 matrix and a 320×240 matrix of temperatures corresponding to individual pixels of the pyrometer and IR camera, respectively. The IR camera and pyrometer temperature data are provided in blackbody-calibrated, raw forms. Provided thermal data can aid in generating and refining process-property-performance relationships between laser manufacturing and its fabricated materials.
Nuclear reactor composite fuel assembly
Energy Technology Data Exchange (ETDEWEB)
Burgess, Donn M. (Richland, WA); Marr, Duane R. (West Richland, WA); Cappiello, Michael W. (Richland, WA); Omberg, Ronald P. (Richland, WA)
1980-01-01
A core and composite fuel assembly for a liquid-cooled breeder nuclear reactor including a plurality of elongated coextending driver and breeder fuel elements arranged to form a generally polygonal bundle within a thin-walled duct. The breeder elements are larger in cross section than the driver elements, and each breeder element is laterally bounded by a number of the driver elements. Each driver element further includes structure for spacing the driver elements from adjacent fuel elements and, where adjacent, the thin-walled duct. A core made up of the fuel elements can advantageously include fissile fuel of only one enrichment, while varying the effective enrichment of any given assembly or core region, merely by varying the relative number and size of the driver and breeder elements.
Noncommutative principal bundles through twist deformation
Aschieri, Paolo; Pagani, Chiara; Schenkel, Alexander
2016-01-01
We construct noncommutative principal bundles deforming principal bundles with a Drinfeld twist (2-cocycle). If the twist is associated with the structure group then we have a deformation of the fibers. If the twist is associated with the automorphism group of the principal bundle, then we obtain noncommutative deformations of the base space as well. Combining the two twist deformations we obtain noncommutative principal bundles with both noncommutative fibers and base space. More in general, the natural isomorphisms proving the equivalence of a closed monoidal category of modules and its twist related one are used to obtain new Hopf-Galois extensions as twists of Hopf-Galois extensions. A sheaf approach is also considered, and examples presented.
The Twist Limit for Bipolar Active Regions
Moore, Ron; Falconer, David; Gary, Allen
2008-01-01
We present new evidence that further supports the standard idea that active regions are emerged magnetic-flux-rope omega loops. When the axial magnetic twist of a cylindrical flux rope exceeds a critical amount, the flux rope becomes unstable to kinking, and the excess axial twist is converted into writhe twist by the kinking. This suggests that, if active regions are emerged omega loops, then (1) no active region should have magnetic twist much above the limit set by kinking, (2) active regions having twist near the limit should often arise from kinked omega loops, and (3) since active regions having large delta sunspots are outstandingly twisted, these arise from kinked omega loops and should have twist near the limit for kinking. From each of 36 vector magnetograms of bipolar active regions, we have measured (1) the total flux of the vertical field above 100 G, (2) the area covered by this flux, and (3) the net electric current that arches over the polarity inversion line. These three quantities yield an estimate of the axial magnetic twist in a simple model cylindrical flux rope that corresponds to the top of the active region s hypothetical omega loop prior to emergence. In all 36 cases, the estimated twist is below the critical limit for kinking. The 11 most twisted active regions (1) have estimated twist within a factor of approx.3 of the limit, and (2) include all of our 6 active regions having large delta sunspots. Thus, our observed twist limit for bipolar active regions is in good accord with active regions being emerged omega loops.
Fixture design of 3D laser cutting thin-walled stainless steel tube%薄壁不锈钢圆管三维激光切割夹具设计
Institute of Scientific and Technical Information of China (English)
王斌修; 田新国
2013-01-01
设计夹具解决了三维激光切割薄壁不锈钢圆管时,采用直接装夹方式产生装夹变形、翘曲变形及定位精度低的问题,而且还可以提高薄壁不锈钢圆管的切割质量和加工效率.%When the thin-walled stainless steel tube is cut with 3D laser cutting system, the fixture has been designed to solve the problems of clamping deformation, warping deformation and low position accuracy, which are caused by direct clamping method. The fixture can also improve the cutting quality and processing efficiency of thin-walled stainless steel tube.
DVCS amplitude with kinematical twist-3 terms
Radyushkin, A V
2000-01-01
We compute the amplitude of deeply virtual Compton scattering (DVCS) using the calculus of QCD string operators in coordinate representation. To restore the electromagnetic gauge invariance (transversality) of the twist-2 amplitude we include the operators of twist-3 which appear as total derivatives of twist-2 operators. Our results are equivalent to a Wandzura-Wilczek approximation for twist-3 skewed parton distributions. We find that this approximation gives a finite result for the amplitude of a longitudinally polarized virtual photon, while the amplitude for transverse polarization is divergent, i.e., factorization breaks down in this term.
Institute of Scientific and Technical Information of China (English)
吴享树
2012-01-01
高强薄壁箱体楼盖是一种与密肋楼盖在结构上很相似的新型空心楼盖,为研究这两种楼盖结构受力性能的异同,进行了这两种楼盖的有限元对比分析,研究表明,薄壁箱体楼盖的刚度比密肋楼盖大,薄壁箱体楼盖的弹性内力比密肋楼盖的弹性内力小,且薄壁箱体楼盖的极限承载力也比密肋楼盖大,证明了这种新型空心楼盖的优越性。%High strength thin-wall floor is a new kind of hollow floor which is similar to ribbed floor in structure.To study on the differences of the mechanical properties of the two floor structure.In this paper,the finite element analysis of the two floor systems was carried out.Research showed that,thin-wall box floor is of larger rigidity than ribbed floor,the elastic force of thin-wall box floor is smaller than that of ribbed floor,and the thin-wall box floor has a better ultimate bearing capacity than ribbed floor,which proved the superiority of this new type of hollow floor.
Institute of Scientific and Technical Information of China (English)
吴秀水; 辛克贵; 姜美兰
2001-01-01
根据位移变分原理，本文提出薄壁杆件稳定分析的有限杆元法。分析中考虑了杆壁中面剪应变的影响，能很好地描述剪力滞后现象。本方法采用线性函数作为横截面翘曲位移的插值函数，适用于任意横截面形状和任意边界条件的薄壁杆件。本文讨论了横向荷载作用下具有不同边界条件的工字型薄壁梁的屈曲荷载。数值算例结果表明了本方法灵活、有效、且有很好的精度。%Based on the principle of minimum potential energy, a generalmethod, called finite member element method, is developed for buckling analysis of thin-walled members with shear lag in the present paper. A linear function is used to express the warping displacements along the cross section of the thin-walled member. The present method is applicable to thin-walled members of any cross section with any boundary conditions. In order to evaluate this method, the critical loads of I-beams subjected to various loading conditions and different boundary conditions are studied. Numerical examples show that the present method is efficient and versatile. It offers more reliable and accurate results as compared to the classical theory of thin-walled members.
基于哈密顿理论的薄壁结构双向弯曲分析%Analysis for compound bending of thin-walled structure using hamiltonian theory
Institute of Scientific and Technical Information of China (English)
胡启平; 涂佳黄; 梁经群
2011-01-01
Based on the energy variation principle, dual variables are introduced by the Legendre's transformation.Hamiltonian dual systems are presented for the bending problems of thin-walled structure.Control differential equations of the thin-walled structure were transformed into Hamiltonian dual equations.Numerical calculation has good stability because the system matrix has characteristics of the symplectic matrix,then numerical solutions with high accuracy are often obtained with the precise integration method.The results of the example show that the method has higher precision and applicability.Moreover,it can be applied conveniently to calculating problem of non-uniform thin-walled structure.%从能量变分原理出发,由勒让德变换引入对偶变量,导出了薄壁结构双向弯曲问题的哈密顿对偶求解体系,将薄壁结构的控制微分方程转化为哈密顿对偶方程,其系统矩阵具有辛矩阵的特性,可用精细积分法求该体系的高精度数值解.算例计算结果表明,本方法具有较高的精度和适用性,并可方便地用于变截面薄壁结构的计算.
Twisted conjugacy in braid groups
González-Meneses, Juan
2011-01-01
In this note we solve the twisted conjugacy problem for braid groups, i.e. we propose an algorithm which, given two braids $u,v\\in B_n$ and an automorphism $\\phi \\in Aut (B_n)$, decides whether $v=(\\phi (x))^{-1}ux$ for some $x\\in B_n$. As a corollary, we deduce that each group of the form $B_n \\rtimes H$, a semidirect product of the braid group $B_n$ by a torsion-free hyperbolic group $H$, has solvable conjugacy problem.
A plant tendril mimic soft actuator with phototunable bending and chiral twisting motion modes
Wang, Meng; Lin, Bao-Ping; Yang, Hong
2016-12-01
In nature, plant tendrils can produce two fundamental motion modes, bending and chiral twisting (helical curling) distortions, under the stimuli of sunlight, humidity, wetting or other atmospheric conditions. To date, many artificial plant-like mechanical machines have been developed. Although some previously reported materials could realize bending or chiral twisting through tailoring the samples into various ribbons along different orientations, each single ribbon could execute only one deformation mode. The challenging task is how to endow one individual plant tendril mimic material with two different, fully tunable and reversible motion modes (bending and chiral twisting). Here we show a dual-layer, dual-composition polysiloxane-based liquid crystal soft actuator strategy to synthesize a plant tendril mimic material capable of performing two different three-dimensional reversible transformations (bending versus chiral twisting) through modulation of the wavelength band of light stimuli (ultraviolet versus near-infrared). This material has broad application prospects in biomimetic control devices.
带孔冷弯薄壁钢构件的屈曲研究%Buckling of Cold-Formed Thin-Walled Steel Members with Holes
Institute of Scientific and Technical Information of China (English)
陈骥
2012-01-01
Since the early 1940s,steel structural cold-formed members such as columns,beams and beam-columns with holes had been applied all over the world,since such cold-formed steel members can provide an economical design.In addition,unusual sectional forms can be easily made by the cold forming process.While during the last century,only individual compression or bending members are investigated.The analysis and design of steel cold-formed sections with holes are rather complex especially when the shape of holes and their arrangements are unusual.In this paper,the calculating methods for the flexural-torsional buckling and distortional buckling of cold-formed thin-walled members with and without holes are introduced with a few examples based on theoretical analysis and experimental data.%自20世纪40年代以来,带孔冷弯薄壁钢构件因为具有节省钢材且容易形成异型构件等优点而在全世界范围内得到广泛应用.但是早先的研究只局限于受压或受弯个别构件的弯曲屈曲研究.带孔冷弯薄壁构件的分析和设计相当复杂,尤其是当开孔形状及位置不规则时更是如此.从理论分析出发,并结合文献中给出的一系列试验资料,通过多个算例,介绍了带孔的和不带孔的冷弯薄壁钢构件弯扭屈曲和畸变屈曲的计算方法.
Directory of Open Access Journals (Sweden)
A. Bolchoun
2016-10-01
Full Text Available Fatigue life tests under constant and variable amplitude loadings were performed on the tube-tube thin-walled welded specimens made of magnesium (AZ31 and AZ61 alloys. The tests included pure axial, pure torsional and combined in-phase and out-of-phase loadings with the load ratio RR " ", " " 1 . For the tests with variable amplitude loads a Gaußdistributed loading spectrum with S L 4 5 10 cycles was used. Since magnesium welds show a fatigue life reduction under out-of-phase loads, a stress-based method, which takes this behavior into account, is proposed. The out-of-phase loading results in rotating shear stress vectors in the section planes, which are not orthogonal to the surface. This fact is used in order to provide an out-of-phase measure of the load. This measure is computed as an area covered by the shear stress vectors in all planes over a certain time interval, its computation involves the shear stress and the shear stress rate vectors in the individual planes. Fatigue life evaluation for the variable amplitudes loadings is performed using the Palmgren-Miner linear damage accumulation, whereas the total damage of every cycle is split up into two components: the amplitude component and the out-of-phase component. In order to compute the two components a modification of the rainflow counting method, which keeps track of the time intervals, where the cycles occur, must be used. The proposed method also takes into account different slopes of the pure axial and the pure torsional Wöhler-line by means of a Wöhler-line interpolation for combined loadings
Ketov, Sergei V.; Lechtenfeld, Olaf; Parkes, Andrew J.
1995-03-01
The most general homogeneous monodromy conditions in N=2 string theory are classified in terms of the conjugacy classes of the global symmetry group U(1,1)⊗openZ2. For classes which generate a discrete subgroup Γ, the corresponding target space backgrounds openC1,1/Γ include half spaces, complex orbifolds, and tori. We propose a generalization of the intercept formula to matrix-valued twists, but find massless physical states only for Γ=open1 (untwisted) and Γ=openZ2 (in the manner of Mathur and Mukhi), as well as for Γ being a parabolic element of U(1,1). In particular, the 16 openZ2-twisted sectors of the N=2 string are investigated, and the corresponding ground states are identified via bosonization and BRST cohomology. We find enough room for an extended multiplet of ``spacetime'' supersymmetry, with the number of supersymmetries being dependent on global ``spacetime'' topology. However, world-sheet locality for the chiral vertex operators does not permit interactions among all massless ``spacetime'' fermions.
Symmetry fractionalization and twist defects
Tarantino, Nicolas; Lindner, Netanel H.; Fidkowski, Lukasz
2016-03-01
Topological order in two-dimensions can be described in terms of deconfined quasiparticle excitations—anyons—and their braiding statistics. However, it has recently been realized that this data does not completely describe the situation in the presence of an unbroken global symmetry. In this case, there can be multiple distinct quantum phases with the same anyons and statistics, but with different patterns of symmetry fractionalization—termed symmetry enriched topological order. When the global symmetry group G, which we take to be discrete, does not change topological superselection sectors—i.e. does not change one type of anyon into a different type of anyon—one can imagine a local version of the action of G around each anyon. This leads to projective representations and a group cohomology description of symmetry fractionalization, with the second cohomology group {H}2(G,{{ A }}{{abelian}}) being the relevant group. In this paper, we treat the general case of a symmetry group G possibly permuting anyon types. We show that despite the lack of a local action of G, one can still make sense of a so-called twisted group cohomology description of symmetry fractionalization, and show how this data is encoded in the associativity of fusion rules of the extrinsic ‘twist’ defects of the symmetry. Furthermore, building on work of Hermele (2014 Phys. Rev. B 90 184418), we construct a wide class of exactly-solvable models which exhibit this twisted symmetry fractionalization, and connect them to our formal framework.
Multiple Twisted -Euler Numbers and Polynomials Associated with -Adic -Integrals
Directory of Open Access Journals (Sweden)
Jang Lee-Chae
2008-01-01
Full Text Available By using -adic -integrals on , we define multiple twisted -Euler numbers and polynomials. We also find Witt's type formula for multiple twisted -Euler numbers and discuss some characterizations of multiple twisted -Euler Zeta functions. In particular, we construct multiple twisted Barnes' type -Euler polynomials and multiple twisted Barnes' type -Euler Zeta functions. Finally, we define multiple twisted Dirichlet's type -Euler numbers and polynomials, and give Witt's type formula for them.
Large N reduction on a twisted torus
González-Arroyo, A; Neuberger, H
2005-01-01
We consider SU(N) lattice gauge theory at infinite N defined on a torus with a CP invariant twist. Massless fermions are incorporated in an elegant way, while keeping them quenched. We present some numerical results which suggest that twisting can make numerical simulations of planar QCD more efficient.
Stress effects in twisted highly birefringent fibers
Wolinski, Tomasz R.
1994-03-01
Hydrostatic pressure and uniaxial longitudinal strain effects in twisted highly birefringent optical fibers have been investigated from the point of the Marcuse mode-coupling theory. The problem is analyzed in terms of local normal modes of the ideal fiber and in the limit of weak twist, where large linear birefringence dominates over twist effect, and therefore twist coupling between local modes is not effective. The authors present the results of birefringence measurements in highly birefringent bow-tie fibers influenced simultaneously by hydrostatic pressure up to 100 MPa and twisting the result for highly birefringent elliptical-core fibers influenced by uniaxial longitudinal strain up to 4000 (mu) (epsilon) and twisting effect. The birefringence measurement method is based on twist-induced effects and has been successfully applied in a stress environment. The experiment was conducted with a specially designed stress generating device that makes it possible to simultaneously generate various mechanical perturbations such as hydrostatic and radial pressure, axial strain and twist, allowing study of their influence on mode propagation in optical fibers. A comparison with theoretical results as well as with pervious experimental data on stress influence on the beat length parameter in highly birefringent fibers is also provided.
Decay constants from twisted mass QCD
Dimopoulos, P; Michael, C; Simula, S; Urbach, C
2008-01-01
We present results for chiral extrapolations of the mass and decay constants of the rho meson. The data sets used are the nf=2 unquenched gauge configurations generated with twisted mass fermions by the European Twisted Mass Collaboration. We describe a calculation of three decay constants in charmonium and explain why they are required.
Twisting theory for weak Hopf algebras
Institute of Scientific and Technical Information of China (English)
CHEN Ju-zhen; ZHANG Yan; WANG Shuan-hong
2008-01-01
The main aim of this paper is to study the twisting theory of weak Hopf algebras and give an equivalence between the (braided) monoidal categories of weak Hopf bimodules over the original and the twisted weak Hopf algebra to generalize the result from Oeckl (2000).
Kato, J; Miyake, A; Kato, Junji; Kawamoto, Noboru; Miyake, Akiko
2005-01-01
We propose N=4 twisted superspace formalism in four dimensions by introducing Dirac-Kahler twist. In addition to the BRST charge as a scalar counter part of twisted supercharge we find vector and tensor twisted supercharges. By introducing twisted chiral superfield we explicitly construct off-shell twisted N=4 SUSY invariant action. We can propose variety of supergauge invariant actions by introducing twisted vector superfield. We may, however, need to find further constraints to identify twisted N=4 super Yang-Mills action. We propose a superconnection formalism of twisted superspace where constraints play a crucial role. It turns out that N=4 superalgebra of Dirac-Kahler twist can be decomposed into N=2 sectors. We can then construct twisted N=2 super Yang-Mills actions by the superconnection formalism of twisted superspace in two and four dimensions.
Institute of Scientific and Technical Information of China (English)
高剑平; 吴永根; 霍静思
2012-01-01
近年来,薄壁钢管混凝土柱由于其良好的力学性能和施工性能在各类建筑结构和桥梁上得到了广泛应用,但震害表明,普通薄壁钢管混凝土柱抗局部屈曲能力和屈曲后抗震性能较差.提出了一种薄壁波纹钢管混凝土柱,为了初步探索其抗震性能,以轴压比和截面形式为主要参数,进行了2根薄壁波纹钢管混凝土柱和2根普通薄壁钢管混凝土柱低周反复加载试验研究.主要结论如下:在轴压比相同的情况下,薄壁波纹钢管混凝土柱的滞回曲线明显要比其它两种截面形式的饱满；在相同位移时,薄壁波纹钢管混凝土柱的耗能能力明显好于方形和圆形的.三种截面形式的延性较接近且延性系数均超过3,且强度退化和刚度退化趋势和程度基本一致.综合分析,薄壁波纹钢管混凝土柱抗震性能较之圆、方形薄壁钢管混凝土柱的相当或稍好.研究结果可供城市高架桥的分析与设计参考.%In recent years, thin-walled concrete-filled steel tube column ha been widely used in many types of building structures and bridges, owing to its good mechanical properties and construction performance. However, the local buckling capacity and post-buckling seismic capacity of common thin-walled concrete-filled steel tube column are poor. A new-style thin-walled corrugated concrete-filled steel tube column was proposed. A low cyclic loading test was conducted to study its seismic performance with axial-compression ratio and section form as the main parameters. The main conclusions are as follows; the hysteresis loops of thin-walled corrugated steel concrete column are fuller than those of the other two section forms under the same axial-compression ratio. The dissipation energy capacity of thin-walled corrugated steel concrete column is better than that of square and circle under the same displacement condition. The ductility coefficients of the three section forms are close and all
Hidden Beauty in Twisted Viking Neck Rings
Olsen, Kasper
2010-01-01
Many hoards found in Ireland, Scotland, Orkney Islands, and Scandinavia demonstrate the vikings ability to fabricate beautiful arm and neck rings of twisted silver and gold rods. Characteristic for such rings is the uniform appearance of the twisted pattern along the length of the arm ring, as well as from one arm ring to another, also when found at distant geographical locations. How can the appearance of the twisted wires be so perfectly repetitive? We demonstrate that the answer is that the vikings utilized a self-forming motif: The pattern arises from a twisting of the wires to a maximally rotated configuration. That is why the twist patterns in these arm and neck rings are beautiful, repetitive, and universal.
Investigation of structural behaviour due to bend-twist couplings in wind turbine blades
DEFF Research Database (Denmark)
Fedorov, Vladimir; Dimitrov, Nikolay Krasimiroy; Berggreen, Christian;
2009-01-01
The structural behaviour of a composite wind turbine blade with implemented bend-twist coupling is examined in this paper. Several shell finite element models of the blade have been developed and validated against full-scale tests. All shell models performed well for flap-wise bending, but perfor......The structural behaviour of a composite wind turbine blade with implemented bend-twist coupling is examined in this paper. Several shell finite element models of the blade have been developed and validated against full-scale tests. All shell models performed well for flap-wise bending...
Twisted spacetime in Einstein gravity
Zhang, Hongsheng
2016-01-01
We find a vacuum stationary twisted solution in four-dimensional Einstein gravity. Its frame dragging angular velocities are antisymmetric with respect to the equatorial plane. It possesses a symmetry of joint inversion of time and parity with respect to the equatorial plane. Its Arnowitt-Deser-Misner (ADM) mass and angular momentum are zero. It is curved but regular all over the manifold. Its Komar mass and Komar angular momentum are also zero. Its infinite red-shift surface coincides with its event horizon, since the event horizon does not rotate. Furthermore we extend this solution to the massive case, and find some similar properties. This solution is a stationary axisymmetric solution, but not Kerr. It explicitly proves that pure Einstein gravity permits different rotational mode other than Kerr. Our results demonstrate that the Einstein theory may have much more rich structures than what we ever imagine.
Twisting cracks in Bouligand structures.
Suksangpanya, Nobphadon; Yaraghi, Nicholas A; Kisailus, David; Zavattieri, Pablo
2017-06-10
The Bouligand structure, which is found in many biological materials, is a hierarchical architecture that features uniaxial fiber layers assembled periodically into a helicoidal pattern. Many studies have highlighted the high damage-resistant performance of natural and biomimetic Bouligand structures. One particular species that utilizes the Bouligand structure to achieve outstanding mechanical performance is the smashing Mantis Shrimp, Odontodactylus Scyllarus (or stomatopod). The mantis shrimp generates high speed, high acceleration blows using its raptorial appendage to defeat highly armored preys. The load-bearing part of this appendage, the dactyl club, contains an interior region [16] that consists of a Bouligand structure. This region is capable of developing a significant amount of nested twisting microcracks without exhibiting catastrophic failure. The development and propagation of these microcracks are a source of energy dissipation and stress relaxation that ultimately contributes to the remarkable damage tolerance properties of the dactyl club. We develop a theoretical model to provide additional insights into the local stress intensity factors at the crack front of twisting cracks formed within the Bouligand structure. Our results reveal that changes in the local fracture mode at the crack front leads to a reduction of the local strain energy release rate, hence, increasing the necessary applied energy release rate to propagate the crack, which is quantified by the local toughening factor. Ancillary 3D simulations of the asymptotic crack front field were carried out using a J-integral to validate the theoretical values of the energy release rate and the local stress intensity factors. Copyright © 2017 Elsevier Ltd. All rights reserved.
Bend-twist coupling potential of wind turbine blades
Fedorov, V.; Berggreen, C.
2014-06-01
In the present study an evaluation of the potential for bend-twist coupling effects in wind turbine blades is addressed. A method for evaluation of the coupling magnitude based on the results of finite element modeling and full-field displacement measurements obtained by experiments is developed and tested on small-scale coupled composite beams. In the proposed method the coupling coefficient for a generic beam is introduced based on the Euler-Bernoulli beam formulation. By applying the developed method for analysis of a commercial wind turbine blade structure it is demonstrated that a bend-twist coupling magnitude of up to 0.2 is feasible to achieve in the baseline blade structure made of glass-fiber reinforced plastics. Further, by substituting the glass-fibers with carbon-fibers the coupling effect can be increased to 0.4. Additionally, the effect of introduction of bend-twist coupling into a blade on such important blade structural properties as bending and torsional stiffness is demonstrated.
Precision Turning of Aerospace Magnesium Alloy with Thin Wall%航天镁合金薄壁件的精密车削加工
Institute of Scientific and Technical Information of China (English)
罗成
2012-01-01
Uses the Deformfinite element analysis software for modeling the aerospace alloy thin-walled parts, simulating the changing rules of magnesium alloy cutting force resistance in the cutting process ,sum-mingup the impact of cutting speed,depth of cut and penetration of α cutting tool on cutting force resistance, and thus the main factors that impact the resistance are found,which can guide the production practice,select correctly the cutting parameters and effectively reduce the impact of cutting force resistance on bending deflection of the part,as much as possible reduce the different between the actual and theoretical penetration of a cutting tool and solve the problem of deformation impacting the dimensional accuracy existing for a long time.The practical tests verify that the thin magnesium alloy parts encountered frequently in practicing production shall be tested through the orthogonal test to measure the actual size of cylindrical part after each test,calculate the actualpenetrationof acuttingtool,andcompare with the analysis results made by finite element method%通过对航天镁合金薄壁零件运用Deform有限元软件进行建模分析,仿真出镁合金在切削过程中吃刀抗力的变化规律,总结出切削速度、进刀量、吃刀量对吃刀抗力的影响程度,最终找到影响吃刀抗力的主要因素,从而可以指导生产实践,正确选用切削参数,有效的减少吃刀抗力对零件弯曲变形的影响,尽可能的减少实际吃刀量与理论吃刀量的差值,解决长期以来零件让刀变形影响尺寸精度的难题.进行实践验证,通过对生产实践中经常遇到的薄壁镁合金零件进行正交试验,测量出零件在每次试验后外圆的实际尺寸,计算出零件的实际吃刀量,并与有限元分析的结果进行比较.
Wang, Xinlin; Deng, Dewei; Yi, Hongli; Xu, Haiyan; Yang, Shuhua; Zhang, Hongchao
2017-07-01
Laser material deposition (LMD) which combines laser cladding and rapid prototyping technique has been widely used to build full density metal parts directly without using modules or tools. There are many parameters affecting the quality and properties of the LMD parts through changing the energy distribution. Pulse laser provides the user an added degree of controlling over the energy distribution which seriously affects the solidification of molten pool and eventual part formation. In the present study, a series of AISI316L stainless steel thin-walled parts are successfully produced by LMD with different pulse laser parameters to investigate the effects of energy distribution on characteristics (microstructure, hardness, residual stress and tensile properties). The results show that the characteristics of LMD parts are obviously influenced by laser mode (pulse or continuous wave laser) and pulse laser parameters (T_pulse and T_pause). The microstructure of parts presents various grain sizes with the different pulse laser parameters. The different value (D-value) between the hardness of edge and central region varies considerably with the pulse laser parameters. The maximum D-value of hardness is presented in the part deposited by continuous wave laser. The maximum hardness is presented in item 4 (T_pulse=10 ms, T_pause=10 ms) and the minimum hardness is presented in part fabricated by continuous wave laser where the residual stress on Z-component presents tensile stress at the edge region and compress stress at the central region but opposite trend happens to the residual stress on Y-component. Tensile stress on Z-component at the edge region increases even presents compress tensile with the decrease of T_pulse. The stress on Y-component presents a periodic variation between tensile stress and compress stress in the Y-direction of the part fabricated by pulse laser. The ultimate tensile strength (UTS) of the part fabricated using pulse laser is higher than the
铝合金薄壁件的激光校形试验%Laser Correction of the Thin-Walled Aluminum Alloy Part
Institute of Scientific and Technical Information of China (English)
王秀凤; 郭晓丽; 彭青; 陈光南
2013-01-01
校形是保障板金属成形零件形状精度的重要手段.为改善校形效果、提高校形效率,提出了矫正其形状的新方法.该方法利用激光热源局部作用铝合金薄壁件待校形的区域,促使其弹性内能做塑性功并重新分布残余应力,达到提高校形效果和校形效率的目的.以航空用铝合金薄板进行三点弯曲试验得到待成形样件,激光热源沿其弯曲线进行扫描后,得到了一定的校形量,定量分析了校形效果,得出校形率的大小随试件的材质和厚度的不同而不同.试验结果表明了激光校形的可行性,为深入研究成形件的激光校形奠定了基础.%Shape correction is an important tool in ensuring the forming precision of sheet metal parts. In order to improve the correction effect and efficiency, a new method of laser correction of thin-walled aluminum alloy part is proposed. When laser beam irradiates the residual stress gathering area of the formed part, the elastic energy in this area is transformed into plastic work due to laser thermal effect, thus the forming error is corrected and the forming precision is improved. The formed part is produced by standard three-point bending test, and then laser beam scans it along the bending line, so that the actual correction values are obtained. The correction effect is discussed through the quantitative analysis of the experimental data. The actual correction rate varies with the choice of material and thickness of specimen. The feasibility of the laser correction technique is verified. Research foundation is laid for further application of laser correction in engineering.
DYNAMICS OF STRONGLY TWISTED RELATIVISTIC MAGNETOSPHERES
Energy Technology Data Exchange (ETDEWEB)
Parfrey, Kyle [Astronomy Department, Columbia University, 550 West 120th Street, New York, NY 10027 (United States); Beloborodov, Andrei M.; Hui, Lam, E-mail: parfrey@astro.princeton.edu [Physics Department and Columbia Astrophysics Laboratory, Columbia University, 538 West 120th Street, New York, NY 10027 (United States)
2013-09-10
Magnetar magnetospheres are believed to be strongly twisted due to shearing of the stellar crust by internal magnetic stresses. We present time-dependent axisymmetric simulations showing in detail the evolution of relativistic force-free magnetospheres subjected to slow twisting through large angles. When the twist amplitude is small, the magnetosphere moves quasi-statically through a sequence of equilibria of increasing free energy. At some twist amplitude the magnetosphere becomes tearing-mode unstable to forming a resistive current sheet, initiating large-scale magnetic reconnection in which a significant fraction of the magnetic free energy can be dissipated. This ''critical'' twist angle is insensitive to the resistive length scale. Rapid shearing temporarily stabilizes the magnetosphere beyond the critical angle, allowing the magnetosphere of a rapidly differentially rotating star to store and dissipate more free energy. In addition to these effects, shearing the surface of a rotating star increases the spindown torque applied to the star. If shearing is much slower than rotation, the resulting spikes in spindown rate can occur on timescales anywhere from the long twisting timescale to the stellar spin period or shorter, depending both on the stellar shear distribution and the existing distribution of magnetospheric twists. A model in which energy is stored in the magnetosphere and released by a magnetospheric instability therefore predicts large changes in the measured spindown rate before soft gamma repeater giant flares.
A smart soft actuator using a single shape memory alloy for twisting actuation
Shim, Jae-Eul; Quan, Ying-Jun; Wang, Wei; Rodrigue, Hugo; Song, Sung-Hyuk; Ahn, Sung-Hoon
2015-12-01
Recently, robots have become a topic of interest with regard to their functionality as they need to complete a large number of diverse tasks in a variety of environments. When using traditional mechanical components, many parts are needed to realize complex deformations, such as motors, hinges, and cranks. To produce complex deformations, this work introduces a smart soft composite torsional actuator using a single shape memory alloy (SMA) wire without any additional elements. The proposed twisting actuator is composed of a torsionally prestrained SMA wire embedded at the center of a polydimethylsiloxane matrix that twists by applying an electric current upon joule heating of the SMA wire. This report shows the actuator design, fabrication method, and results for the twisting angle and actuation moment. Results show that a higher electric current helps reach the maximum twisting angle faster, but that if the current is too low or too high, it will not be able to reach its maximum deformation. Also, both the twisting angle and the twisting moment increase with a large applied twisting prestrain, but this increase has an asymptotic behavior. However, results for both the width and the thickness of the actuator show that a larger width and thickness reduce the maximum actuation angle of the actuator. This paper also presents a new mechanism for an SMA-actuated active catheter using only two SMA wires with a total length of 170 mm to bend the tip of the catheter in multiple directions. The fabricated active catheter’s maximum twisting angle is 270°, and the maximum bending curvature is 0.02 mm-1.
Novel Properties of Twisted-Photon Absorption
Afanasev, Andrei; Mukherjee, Asmita
2014-01-01
We discuss novel features of twisted-photon absorption both by atoms and by micro-particles. First, we extend the treatment of atomic photoexcitation by twisted photons to include atomic recoil, derive generalized quantum selection rules and consider phenomena of forbidden atomic transitions. Second, we analyze the radiation pressure from twisted-photon beams on micro- and nano-sized particles and observe that for particular conditions the pressure is negative in a small area near the beam axis. A central part of the beam therefore acts as a "tractor beam".
Twisted spectral geometry for the standard model
Martinetti, Pierre
2015-07-01
In noncommutative geometry, the spectral triple of a manifold does not generate bosonic fields, for fluctuations of the Dirac operator vanish. A Connes-Moscovici twist forces the commutative algebra to be multiplied by matrices. Keeping the space of spinors untouched, twisted-fluctuations then yield perturbations of the spin connection. Applied to the spectral triple of the Standard Model, a similar twist yields the scalar field needed to stabilize the vacuum and to make the computation of the Higgs mass compatible with its experimental value.
Twist1 Is Essential for Tooth Morphogenesis and Odontoblast Differentiation.
Meng, Tian; Huang, Yanyu; Wang, Suzhen; Zhang, Hua; Dechow, Paul C; Wang, Xiaofang; Qin, Chunlin; Shi, Bing; D'Souza, Rena N; Lu, Yongbo
2015-12-04
Twist1 is a basic helix-loop-helix-containing transcription factor that is expressed in the dental mesenchyme during the early stages of tooth development. To better delineate its roles in tooth development, we generated Twist1 conditional knockout embryos (Twist2(Cre) (/+);Twist1(fl/fl)) by breeding Twist1 floxed mice (Twist1(fl/fl)) with Twist2-Cre recombinase knockin mice (Twist2(Cre) (/+)). The Twist2(Cre) (/+);Twist1(fl/fl) embryos formed smaller tooth germs and abnormal cusps during early tooth morphogenesis. Molecular and histological analyses showed that the developing molars of the Twist2(Cre) (/+);Twist1(fl/fl) embryos had reduced cell proliferation and expression of fibroblast growth factors 3, 4, 9, and 10 and FGF receptors 1 and 2 in the dental epithelium and mesenchyme. In addition, 3-week-old renal capsular transplants of embryonic day 18.5 Twist2(Cre) (/+);Twist1(fl/fl) molars showed malformed crowns and cusps with defective crown dentin and enamel. Immunohistochemical analyses revealed that the implanted mutant molars had defects in odontoblast differentiation and delayed ameloblast differentiation. Furthermore, in vitro ChIP assays demonstrated that Twist1 was able to bind to a specific region of the Fgf10 promoter. In conclusion, our findings suggest that Twist1 plays crucial roles in regulating tooth development and that it may exert its functions through the FGF signaling pathway. © 2015 by The American Society for Biochemistry and Molecular Biology, Inc.
Topological hypermultiplet on N=2 twisted superspace in four dimensions
Kato, J; Kato, Junji; Miyake, Akiko
2005-01-01
We propose a N=2 twisted superspace formalism with a central charge in four dimensions by introducing a Dirac-K\\"ahler twist. Using this formalism, we construct a twisted hypermultiplet action and find an explicit form of fermionic scalar, vector and tensor transformations. We construct a off-shell Donaldson-Witten theory coupled to the twisted hypermultiplet. We show that this action possesses N=4 twisted supersymmetry at on-shell level. It turns out that four-dimensional Dirac-K\\"ahler twist is equivalent to the Marcus's twist.
Institute of Scientific and Technical Information of China (English)
王明沧; 许正华
2011-01-01
Large thin-walled Al-Mg alloy housing for food machinery was usually produced by green sand casting or semi-permanent mold integrating with semi-green sand mold casting because of the easy occurrence of hot crack of Al-Mg alloy in permanent mold. A tilting gravity casting was presented to eliminate the problems in permanent mold casting. Considering mould design and adjusting the pouring parameters, large thin-walled Al-Mg alloy housing was produced successfully by permanent mold gravity casting. The practical production shows that the technology can be widely used to produce thin-walled parts or easily-hot crack alloy parts.%由于Al-Mg合金金属型铸造易产生热裂,在生产食品机械外壳大型薄壁铸件时,多以湿砂型或半金属型-半湿砂型方式生产.针对金属型工艺生产大型薄壁铸件比较困难的问题,提出一种倾转式重力铸造工艺,结合模具设计、浇注参数的调整,实现了全金属型大型Al-Mg台金薄壁铸件的生产.实践证明,本工艺可广泛应用于薄壁铸件或易产生热裂合金铸件的生产.
Institute of Scientific and Technical Information of China (English)
辛克贵; 姜美兰
2001-01-01
根据势能驻值原理，提出在横向荷载作用下薄壁杆件稳定分析的样条有限杆元法。方法采用转换B3样条函数模拟杆件横截面的翘曲位移场，并考虑了杆壁中面上剪切变形的影响，能很好地描述剪力滞后现象。适用于任意横截面形状和任意边界条件的薄壁杆件，为高层建筑和桥梁结构的稳定分析提供了可靠而有效的分析方法。文中讨论了横向荷载作用下具有不同边界条件的工字型薄壁梁的屈曲分析。数值算例的结果表明了方法的灵活性、精确性和有效性。%The displacement variational principle was used to develop thespline finite member element method for buckling analysis of thin-walled members with shear lag effect. A transformed B3 spline function was used to simulate the warping displacements along the cross section of the thin-walled members. The proposed method is applicable to thin-walled members of any cross section with any boundary condition. The method was evaluated by studying the elastic modes of I-beams subjected to various loading conditions and different boundary conditions. The versatility, accuracy and efficiency of the proposed method compares well with classical theory.
Nuclear reactor composite fuel assembly. [LMFBR
Energy Technology Data Exchange (ETDEWEB)
Burgess, D.M.; Cappiello, M.W.; Marr, D.R.; Omberg, R.P.
1980-11-25
A core and composite fuel assembly are described for a liquid-cooled breeder nuclear reactor including a plurality of elongated coextending driver and breeder fuel elements arranged to form a generally polygonal bundle within a thin-walled duct. The breeder elements are larger in cross section than the driver elements, and each breeder element is laterally bounded by a number of the driver elements. Each driver element further includes structure for spacing the driver elements from adjacent fuel elements and, where adjacent, the thin-walled duct. A core made up of the fuel elements can advantageously include fissile fuel of only one enrichment, while varying the effective enrichment of any given assembly or core region, merely by varying the relative number and size of the driver and breeder elements.
Transmission properties of cryogenic twisted pair filters
Energy Technology Data Exchange (ETDEWEB)
Song, Woon; Rehman, Mushtaq; Chong, Yonuk [Korea Research Institute of Standards and Science, Daejeon (Korea, Republic of); Ryu, Sangwan [Chonnam National University, Gwangju (Korea, Republic of)
2010-12-15
We fabricated a cryogenic low pass filter that consists of twisted pairs of manganin wires wrapped in copper tape and measured its transmission characteristics at frequencies up to 18 GHz. The dependence of the microwave transmission characteristics on the filter length was studied, which showed that a filter of length 1.0 m had a 70-dB attenuation at 1 GHz. We also studied the dependence of common- and differential-mode transmission on the number of twists per unit length and found that the number of twists per unit length affects differential-mode transmission but not common-mode transmission. Because the shielded twisted pair filter is more compact than a conventional copper powder filter, it can solve the space and thermal load issues when many cables are required for precision electronic transport experiments at low temperatures.
Mutations in the human TWIST gene.
Gripp, K W; Zackai, E H; Stolle, C A
2000-01-01
Saethre-Chotzen syndrome is a relatively common craniosynostosis disorder with autosomal dominant inheritance. Mutations in the TWIST gene have been identified in patients with Saethre-Chotzen syndrome. The TWIST gene product is a transcription factor with DNA binding and helix-loop-helix domains. Numerous missense and nonsense mutations cluster in the functional domains, without any apparent mutational hot spot. Two novel point mutations and one novel polymorphism are included in this review. Large deletions including the TWIST gene have been identified in some patients with learning disabilities or mental retardation, which are not typically part of the Saethre-Chotzen syndrome. Comprehensive studies in patients with the clinical diagnosis of Saethre-Chotzen syndrome have demonstrated a TWIST gene abnormality in about 80%, up to 37% of which may be large deletions [Johnson et al., 1998]. The gene deletions and numerous nonsense mutations are suggestive of haploinsufficiency as the disease-causing mechanism. No genotype phenotype correlation was apparent.
Observation of subluminal twisted light in vacuum
Bouchard, Frédéric; Mand, Harjaspreet; Boyd, Robert W; Karimi, Ebrahim
2015-01-01
Einstein's theory of relativity establishes the speed of light in vacuum, c, as a fundamental constant. However, the speed of light pulses can be altered significantly in dispersive materials. While significant control can be exerted over the speed of light in such media, no experimental demonstration of altered light speeds has hitherto been achieved in vacuum for ``twisted'' optical beams. We show that ``twisted'' light pulses exhibit subluminal velocities in vacuum, being slowed by 0.1\\% relative to c. This work does not challenge relativity theory, but experimentally supports a body of theoretical work on the counterintuitive vacuum group velocities of twisted pulses. These results are particularly important given recent interest in applications of twisted light to quantum information, communication and quantum key distribution.
Twisted Vector Bundles on Pointed Nodal Curves
Indian Academy of Sciences (India)
Ivan Kausz
2005-05-01
Motivated by the quest for a good compactification of the moduli space of -bundles on a nodal curve we establish a striking relationship between Abramovich’s and Vistoli’s twisted bundles and Gieseker vector bundles.
Gerbes and twisted orbifold quantum cohomology
Institute of Scientific and Technical Information of China (English)
2008-01-01
In this paper,we construct an orbifold quantum cohomology twisted by a flat gerbe. Then we compute these invariants in the case of a smooth manifold and a discrete torsion on a global quotient orbifold.
Deformed and twisted black holes with NUTs
Krtous, Pavel; Frolov, Valeri P; Kolar, Ivan
2015-01-01
We construct a new class of vacuum black hole solutions whose geometry is deformed and twisted by the presence of NUT charges. The solutions are obtained by `unspinning' the general Kerr-NUT-(A)dS spacetimes, effectively switching off some of their rotation parameters. The resulting geometry has a structure of warped space with the Kerr-like Lorentzian part warped to a Euclidean metric of deformed and/or twisted sphere, with the deformation and twist characterized by the `Euclidean NUT' parameters. In the absence of NUTs, the solution reduces to a well known Kerr-(A)dS black hole with several rotations switched off. New geometries inherit the original symmetry of the Kerr-NUT-(A)dS family, namely, they possess the full Killing tower of hidden and explicit symmetries. As expected, for vanishing NUT, twist, and deformation parameters, the symmetry is further enlarged.
Gerbes and twisted orbifold quantum cohomology
Institute of Scientific and Technical Information of China (English)
PAN JianZhong; RUAN YongBin; YIN XiaoQin
2008-01-01
In this paper, we construct an orbifold quantum cohomology twisted by a flat gerbe.Then we compute these invariants in the case of a smooth manifold and a discrete torsion on a global quotient orbifold.
Deformed and twisted black holes with NUTs
Krtouš, Pavel; Kubizňák, David; Frolov, Valeri P.; Kolář, Ivan
2016-06-01
We construct a new class of vacuum black hole solutions whose geometry is deformed and twisted by the presence of NUT charges. The solutions are obtained by ‘unspinning’ the general Kerr-NUT-(A)dS spacetimes, effectively switching off some of their rotation parameters. The resulting geometry has a structure of warped space with the Kerr-like Lorentzian part warped to a Euclidean metric of a deformed and/or twisted sphere, with the deformation and twist characterized by the ‘Euclidean NUT’ parameters. In the absence of NUTs, the solution reduces to a well known Kerr-(A)dS black hole with several rotations switched off. New geometries inherit the original symmetry of the Kerr-NUT-(A)dS family, namely, they possess the full Killing tower of hidden and explicit symmetries. As expected, for vanishing NUT, twist, and deformation parameters, the symmetry is further enlarged.
Institute of Scientific and Technical Information of China (English)
姚永红; 武振宇
2013-01-01
畸变屈曲是冷弯薄壁型钢构件的主要破坏模式之一,按翼缘模型计算其弹性畸变屈曲应力时需要确定腹板对翼缘的转动约束刚度.现有转动约束刚度计算公式较复杂,求解过程需要进行一次迭代.为了简化计算过程,提出了冷弯薄壁C形钢柱翼缘转动约束刚度简化计算方法.该方法在Lau和Hancock公式的基础上,结合我国《冷弯薄壁型钢结构技术规范》(GB50018-2002)中关于腹板和翼缘局部屈曲系数的规定而导出的,并根据Lau和Hancock公式计算结果对其进行了修正.与有限条分析值对比表明:该方法可以准确、方便地计算转动约束刚度,能够应用于冷弯薄壁型钢C形截面柱的设计计算.%The distortional buckling is one of the main failure modes for cold-formed thin-walled steel components. When the elastic distortional buckling stress of steel components is calculated with flange model, it is necessary to determine the rotational restraint stiffness provided by the web plate to the flange. However, the current calculation formula for the rotational restraint stiffness is complicated, and one iteration is required in the solution process. In order to simplify the calculation process, a simplified calculation method concerning the rotational restraint stiffness for the flange of cold-formed thin-walled C-shaped steel column was proposed. Based on Lau and Hancock' s formulas, the proposed method was derived in combination with the regulations concerning the local buckling coefficients of the web plate and flange in the Technical Code of Cold-Formed Thin-Walled Steel Structures (GB 50018-2002) in China, and it was then modified according to the results calculated by Lau and Hancock' s formulas. Compared with the finite strip analytical values, it is noted that the proposed method can calculate the rotational restraint stiffness accurately and conveniently, and can be used for the design and calculation of cold-formed thin-walled
Institute of Scientific and Technical Information of China (English)
肖海兵; 赵均海; 孙楚平; 彭宁; 孙珊珊
2012-01-01
Based on the unified strength theory, considering the effects of the intermediate principal stress and the differences of the multi-axial strength criterion for the lightweight aggregate concrete and common concrete, by introducing parameter αu and/βu, loop tensile stress σθ , longitudinal compressive stress σ, and radial compressiye stress σ of the thin- walled steel tube in ultimate bearing condition were obtained. Thus the calculation formula of ultimate bearing capacity of thin-walled steel tube short columns filled with lightweight aggregate concrete was deduced, and the influence complication was analyzed. Compared with the obtained solution and the test results in reference, good agreement can be found. The results indicate that the unified strength theory has the good applicability in the calculation of ultimate bearing capacity of thin-walled steel tube short columns filled with lightweight aggregate concrete. The results can provide theoretical foundation for the design of thin-walled steel tube filled with lightweight aggregate concrete.%运用统一强度理论,考虑中间主应力的影响,引入参数αu,βu确定薄壁钢管在极限荷载时的环向拉应力σθ、纵向压应力σz和径向压应力σr,并考虑轻骨料混凝土与普通混凝土多轴强度准则差异的影响,推导出薄壁钢管轻骨料混凝土轴压短柱的极限承载力公式,并对影响因素进行了分析。将本文计算结果与文献试验数据进行比较,结果吻合良好,表明将统一强度理论运用于薄壁钢管轻骨料混凝土轴压短柱承载力计算是可行的。该结果为薄壁钢管轻骨料混凝土的优化设计提供了一定的理论依据。
Genomic pathways modulated by Twist in breast cancer
Vesuna, Farhad; Bergman, Yehudit; Raman, Venu
2017-01-01
Background The basic helix-loop-helix transcription factor TWIST1 (Twist) is involved in embryonic cell lineage determination and mesodermal differentiation. There is evidence to indicate that Twist expression plays a role in breast tumor formation and metastasis, but the role of Twist in dysregulating pathways that drive the metastatic cascade is unclear. Moreover, many of the genes and pathways dysregulated by Twist in cell lines and mouse models have not been validated against data obtaine...
DDalphaAMG for Twisted Mass Fermions
Bacchio, Simone; Finkenrath, Jacob; Frommer, Andreas; Kahl, Karsten; Rottmann, Matthias
2016-01-01
We present the Adaptive Aggregation-based Domain Decomposition Multigrid method extended to the twisted mass fermion discretization action. We show comparisons of results as a function of tuning the parameters that enter the twisted mass version of the DDalphaAMG library (https://github.com/sbacchio/DDalphaAMG). Moreover, we linked the DDalphaAMG library to the tmLQCD software package and give details on the performance of the multigrid solver during HMC simulations at the physical point.
Twisted Covariant Noncommutative Self-dual Gravity
Estrada-Jimenez, S; Obregón, O; Ramírez, C
2008-01-01
A twisted covariant formulation of noncommutative self-dual gravity is presented. The recent formulation introduced by J. Wess and coworkers for constructing twisted Yang-Mills fields is used. It is shown that the noncommutative torsion is solved at any order of the $\\theta$-expansion in terms of the tetrad and the extra fields of the theory. In the process the first order expansion in $\\theta$ for the Pleba\\'nski action is explicitly obtained.
OAM mode converter in twisted fibers
DEFF Research Database (Denmark)
Usuga Castaneda, Mario A.; Beltran-Mejia, Felipe; Cordeiro, Cristiano
2014-01-01
We analyze the case of an OAM mode converter based on a twisted fiber, through finite element simulations where we exploit an equivalence between geometric and material transformations. The obtained converter has potential applications in MDM. © 2014 OSA.......We analyze the case of an OAM mode converter based on a twisted fiber, through finite element simulations where we exploit an equivalence between geometric and material transformations. The obtained converter has potential applications in MDM. © 2014 OSA....
On Supermultiplet Twisting and Spin-Statistics
Hubsch, Tristan
2012-01-01
Twisting of off-shell supermultiplets in models with 1+1-dimensional spacetime has been discovered in 1984, and was shown to be a generic feature of off-shell representations in worldline supersymmetry two decades later. It is shown herein that in all supersymmetric models with spacetime of four or more dimensions, this type of twisting, if nontrivial, necessarily maps regular (non-ghost) supermultiplets to ghost supermultiplets.
On Supermultiplet Twisting and Spin-Statistics
Hubsch, Tristan
2012-01-01
Twisting of off-shell supermultiplets in models with 1+1-dimensional spacetime has been discovered in 1984, and was shown to be a generic feature of off-shell representations in worldline supersymmetry two decades later. It is shown herein that in all supersymmetric models with spacetime of four or more dimensions, this off-shell supermultiplet twisting, if non-trivial, necessarily maps regular (non-ghost) supermultiplets to ghost supermultiplets. This feature is shown to be ubiquitous in all...
The gradient flow in a twisted box
Energy Technology Data Exchange (ETDEWEB)
Ramos, Alberto [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC
2013-08-15
We study the perturbative behavior of the gradient flow in a twisted box. We apply this information to define a running coupling using the energy density of the flow field. We study the step-scaling function and the size of cutoff effects in SU(2) pure gauge theory. We conclude that the twisted gradient flow running coupling scheme is a valid strategy for step-scaling purposes due to the relatively mild cutoff effects and high precision.
Twisted Boundary Conditions in Lattice Simulations
Sachrajda, Christopher T C
2004-01-01
By imposing twisted boundary conditions on quark fields it is possible to access components of momenta other than integer multiples of 2pi/L on a lattice with spatial volume L^3. We use Chiral Perturbation Theory to study finite-volume effects with twisted boundary conditions for quantities without final-state interactions, such as meson masses, decay constants and semileptonic form factors, and confirm that they remain exponentially small with the volume. We show that this is also the case for "partially twisted" boundary conditions, in which (some of) the valence quarks satisfy twisted boundary conditions but the sea quarks satisfy periodic boundary conditions. This observation implies that it is not necessary to generate new gluon configurations for every choice of the twist angle, making the method much more practicable. For K->pipi decays we show that the breaking of isospin symmetry by the twisted boundary conditions implies that the amplitudes cannot be determined in general (on this point we disagree ...
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
Integral Twist Actuation of Helicopter Rotor Blades for Vibration Reduction
Shin, SangJoon; Cesnik, Carlos E. S.
2001-01-01
Active integral twist control for vibration reduction of helicopter rotors during forward flight is investigated. The twist deformation is obtained using embedded anisotropic piezocomposite actuators. An analytical framework is developed to examine integrally-twisted blades and their aeroelastic response during different flight conditions: frequency domain analysis for hover, and time domain analysis for forward flight. Both stem from the same three-dimensional electroelastic beam formulation with geometrical-exactness, and axe coupled with a finite-state dynamic inflow aerodynamics model. A prototype Active Twist Rotor blade was designed with this framework using Active Fiber Composites as the actuator. The ATR prototype blade was successfully tested under non-rotating conditions. Hover testing was conducted to evaluate structural integrity and dynamic response. In both conditions, a very good correlation was obtained against the analysis. Finally, a four-bladed ATR system is built and tested to demonstrate its concept in forward flight. This experiment was conducted at NASA Langley Tansonic Dynamics Tunnel and represents the first-of-a-kind Mach-scaled fully-active-twist rotor system to undergo forward flight test. In parallel, the impact upon the fixed- and rotating-system loads is estimated by the analysis. While discrepancies are found in the amplitude of the loads under actuation, the predicted trend of load variation with respect to its control phase correlates well. It was also shown, both experimentally and numerically, that the ATR blade design has the potential for hub vibratory load reduction of up to 90% using individual blade control actuation. Using the numerical framework, system identification is performed to estimate the harmonic transfer functions. The linear time-periodic system can be represented by a linear time-invariant system under the three modes of blade actuation: collective, longitudinal cyclic, and lateral cyclic. A vibration
Kumaraswamidhas, L. A.; Rajak, Dipen Kumar; Das, S.
2016-08-01
The objective of this research is to produce superior quality aluminum alloy foam with low relative density and higher resistance against compression deformation. This investigation has studied crash energy capacities of unfilled and filled aluminum alloy foams in mild steel tubes. The foam has been prepared by the melt route process with an addition of 5wt.% silicon carbide particles. The fabricated aluminum alloy foams were characterized by field emission scanning electron microscopy, x-ray diffraction, Fourier transform infrared spectroscopy, and Material Pro analyzer. It was observed that the foam-filled tubes could absorb more energy as compared to the unfilled tubes before reaching the complete densification point. Also, the aluminum alloy foams had better energy absorption capacity during the crash or impact loading. This article demonstrates the excellent ability of aluminum alloy foam application in the field where there is a need to absorb crash energy. It is to be noted that the amount of energy absorption will be greater for low-density foam filled in thin-wall rectangular section tubes. We have seen an increasing trend in the application of aluminum foams inside the thin-wall mild steel tubes for maximum energy absorption.
Institute of Scientific and Technical Information of China (English)
赵莹
2012-01-01
冷弯薄壁型钢节点通常采用拉铆钉或自攻螺钉作为连接方式,这种连接方式的缺点是承载力低,对构件的截面有削弱.本文采用试验方法对3种不同构造的冷弯薄壁型钢焊接节点进行研究和分析,并与相同构造的自贡螺钉连接节点的性能进行了对比分析,得到了关于冷弯薄壁型钢焊接节点的有益结论.%The cold -formed thin -walled steel node usually adopts pulling rivets or tapping screws as connection. The bearing capacity of this connection is low, the sections are weakened. This article got useful conclusions of cold - formed thin - walled steel welding joints through experimental research and contrast analysis.
Institute of Scientific and Technical Information of China (English)
郭小燕; 姚勇; 邓勇军
2012-01-01
结合某冷弯薄壁型钢结构住宅实例,采用大型通用有限元软件ANSYS建模,运用零阶法、一阶法对梁、柱构件截面进行优化分析.结果表明,与原设计相比,优化分析后工程的用钢量得到了大大的减少,这不仅有利于钢材的节约,带来可观的经济效益,而且有利于冷弯薄壁型钢结构住宅在我国的推广和应用.%Based on a cold-formed thin-walled steel structure example,using the universal finite element software ANSYS building model of actual engineering and using method of zero oider and first order to beam and column section for optimization design. Then we can obtain:Then we can obtain:Compared with the actual engineering steel quantity,which greatly reduces,saves steel quantity and brings considerable economic benefit. The high cost which block development is no longer a main factors. It's propitious to the development of cold-formed thin-walled steel structure housing in our country.
Institute of Scientific and Technical Information of China (English)
许永健
2014-01-01
电磁纯铁作为电磁材料，在充磁机、仪器仪表、开关、电磁锁、马达、电磁离合器等电子行业应用广泛，随着生产技术的发展，数控加工技术在电磁纯铁工件制造领域电磁机械制造领域得以应用发展，但经常遇到一些电磁纯铁薄壁工件的生产加工，文章从薄壁工件加工工艺来分析数控加工电磁纯铁特点。%As magnetic materials, the electromagnetism pure iron in the magnetizing apparatus, instruments and meters, switches, electromagnetic lock, motor, electromagnetic clutch, such as widely used in electronics industry and with the development of production technology, the nc machining technology in electromagnetic pure blacksmith manufacturing electromagnetic mechanical manufacturing to application development, but often encounter some electromagnetism pure iron production and processing of thin-walled workpiece, the article from the thin-walled workpiece processing technology for the analysis of nc machining characteristics of electromagnetism pure iron.
Kim, E; Kim, B G; Lim, Y J; Jeon, Y T; Hwang, J W; Kim, H C; Choi, Y H; Park, H P
2016-09-01
In clinical practice, both a thin-walled introducer needle and catheter-over-needle technique can be used to allow insertion of a guidewire during central venous catheterisation using the Seldinger technique. We compared the incidence of catheterisation-related complications (arterial puncture, haemothorax, pneumothorax, haematoma and catheter tip malposition) and insertion success rate for these two techniques in patients requiring right-sided subclavian central venous catheterisation. A total of 414 patients requiring infraclavicular subclavian venous catheterisation were randomly allocated to either a thin-walled introducer needle (needle group, n = 208) or catheter-over-needle technique (catheter group, n = 206). The catheterisation-related complication rate was lower in the needle group compared with the catheter group (5.8% vs. 15.5%; p = 0.001). Overall insertion success rates were similar (97.1% and 92.7% in the needle and catheter groups respectively; p = 0.046), although the first-pass success rate was higher in the needle group (62.0% vs. 35.4%; p technique for right-sided infraclavicular subclavian venous catheterisation.
一种液压夹套式平动离合器的设计和试验研究%The Design and Experiment of a Hydraulic Metal Thin-wall Clutch
Institute of Scientific and Technical Information of China (English)
韩旭; 马德森; 赵国平; 童军
2016-01-01
该文介绍一种液压夹套式平动离合器，该离合器利用液压夹套金属薄壁段受压应力变形和释放压力后金属薄壁回弹的性能实现离合功能，使用了液压油作为介质对薄壁均匀施压。经过初步结构设计及仿真设计了离合器产品。经过离合器的试验研究，考核了离合器性能，并通过试验研究的结果对仿真参数进行了修正。%This paper introduces a Hydraulic metal thin-wall clutch used in translational motion mechanism. The deformation and spring-back of the metal thin-wall is used for separation and reunion of the clutch. The clutch uses hydraulic oil to impose pressure in whole worked area. The clutch is designed after first structural design and simulation. Through experiment of the clutch, the function of the clutch is tested, and the results of the experiment improve the simulation.
Soft tissue twisting injuries of the knee
Energy Technology Data Exchange (ETDEWEB)
Magee, T.; Shapiro, M. [Neuroimaging Inst., Melbourne, FL (United States)
2001-08-01
Twisting injuries occur as a result of differential motion of different tissue types in injuries with some rotational force. These injuries are well described in brain injuries but, to our knowledge, have not been described in the musculoskeletal literature. We correlated the clinical examination and MR findings of 20 patients with twisting injuries of the soft tissues around the knee. Design and patients: We prospectively followed the clinical courses of 20 patients with knee injuries who had clinical histories and MR findings to suggest twisting injuries of the subcutaneous tissues. Patients with associated internal derangement of the knee (i.e., meniscal tears, ligamentous or bone injuries) were excluded from this study. MR findings to suggest twisting injuries included linear areas of abnormal dark signal on T1-weighted sequences and abnormal bright signal on T2-weighted or short tau inversion recovery (STIR) sequences and/or signal to suggest hemorrhage within the subcutaneous tissues. These MR criteria were adapted from those established for indirect musculotendinous junction injuries. Results: All 20 patients presented with considerable pain that suggested internal derangement on physical examination by the referring orthopedic surgeons. All presented with injuries associated with rotational force. The patients were placed on a course of protected weight-bearing of the affected extremity for 4 weeks. All patients had pain relief by clinical examination after this period of protected weight-bearing. Twisting injuries of the soft tissues can result in considerable pain that can be confused with internal derangement of the knee on physical examination. Soft tissue twisting injuries need to be recognized on MR examinations as they may be the cause of the patient's pain despite no MR evidence of internal derangement of the knee. The demonstration of soft tissue twisting injuries in a patient with severe knee pain but no documented internal derangement on MR
Noncommutative geometry in string and twisted Hopf algebra of diffeomorphism
Watamura, Satoshi
2011-09-01
We discuss the Hopf algebra structure in string theory and present the twist quantization as a unified formulation of the world sheet quantization of the string and the symmetry of the target spacetime. Applying it to the case with a nonzero B-field background, we explain a method to decompose the twist into two successive twists. There are two different possibilities of decomposition: The first is a natural decomposition from the viewpoint of the twist quantization, leading to a new type of twisted Poincaré symmetry. The second decomposition reveals the relation of our formulation to the twisted Poincaré symmetry on the Moyal type noncommutative space.
Twisted electron-acoustic waves in plasmas
Aman-ur-Rehman, Ali, S.; Khan, S. A.; Shahzad, K.
2016-08-01
In the paraxial limit, a twisted electron-acoustic (EA) wave is studied in a collisionless unmagnetized plasma, whose constituents are the dynamical cold electrons and Boltzmannian hot electrons in the background of static positive ions. The analytical and numerical solutions of the plasma kinetic equation suggest that EA waves with finite amount of orbital angular momentum exhibit a twist in its behavior. The twisted wave particle resonance is also taken into consideration that has been appeared through the effective wave number qeff accounting for Laguerre-Gaussian mode profiles attributed to helical phase structures. Consequently, the dispersion relation and the damping rate of the EA waves are significantly modified with the twisted parameter η, and for η → ∞, the results coincide with the straight propagating plane EA waves. Numerically, new features of twisted EA waves are identified by considering various regimes of wavelength and the results might be useful for transport and trapping of plasma particles in a two-electron component plasma.
Residual stress in composites with the thin-ring-slitting approach.
Park, J W; Ferracane, J L
2006-10-01
During polymerization, dental composites develop residual stresses that may compromise the marginal integrity and properties of the restorative. The objective of this study was to use the thin-walled ring-slitting method to measure and compare residual stresses. The hypotheses to be tested were that composites would generate different levels of residual stress based on their specific formulations and slitting times. Rings made from composites (Z100, Herculite, and Heliomolar) were cut at different times (10 min, 1 and 24 hrs) after being light-cured, and stress was measured. Residual stress was higher at the earlier cutting times, except for Heliomolar (alpha stress followed this order: Z100 > Herculite > Heliomolar. Early slitting was better to capture residual stress, and the thin-walled rings showed higher values than thick-walled rings and were better able to discriminate residual stress in composites.
Exotic twisted equivariant cohomology of loop spaces,twisted Bismut-Chern character and T-duality
Han, Fei
2014-01-01
We define completed periodic {\\em exotic twisted $\\mathbb{T}$-equivariant cohomology} for loop spaces of smooth manifolds. We then show that the twisted Bismut-Chern character, defined on the twisted K-theory of the smooth manifold, twisted by a gerbe with connection, takes values in the completed periodic exotic twisted $\\mathbb{T}$-equivariant cohomology of the loop space of the smooth manifold. We establish a localisation theorem for the completed periodic exotic twisted $\\mathbb{T}$-equivariant cohomology for loop spaces and apply it to establish T-duality in a background flux in type II String Theory from a loop space perspective.
Unraveling cellulose microfibrils: a twisted tale.
Hadden, Jodi A; French, Alfred D; Woods, Robert J
2013-10-01
Molecular dynamics (MD) simulations of cellulose microfibrils are pertinent to the paper, textile, and biofuels industries for their unique capacity to characterize dynamic behavior and atomic-level interactions with solvent molecules and cellulase enzymes. While high-resolution crystallographic data have established a solid basis for computational analysis of cellulose, previous work has demonstrated a tendency for modeled microfibrils to diverge from the linear experimental structure and adopt a twisted conformation. Here, we investigate the dependence of this twisting behavior on computational approximations and establish the theoretical basis for its occurrence. We examine the role of solvent, the effect of nonbonded force field parameters [partial charges and van der Waals (vdW) contributions], and the use of explicitly modeled oxygen lone pairs in both the solute and solvent. Findings suggest that microfibril twisting is favored by vdW interactions, and counteracted by both intrachain hydrogen bonds and solvent effects at the microfibril surface.
Analysis of gun barrel rifling twist
Sun, Jia; Chen, Guangsong; Qian, Linfang; Liu, Taisu
2017-05-01
Aiming at the problem of gun barrel rifling twist, the constraint relation between rifling and projectile is investigated. The constraint model of rifling and projectile is established and the geometric relation between the twist and the motion of projectile is analyzed. Based on the constraint model, according to the rotating band that is fired, the stress and the motion law of the rotating band in bore are analyzed. The effects to rotating band (double rotating band or wide driving band) caused by different rifling (rib rifling, increasing rifling and combined rifling) are also investigated. The model is demonstrated by several examples. The results of numerical examples and the constraint mode show that the uncertainty factors will be brought in the increasing rifling and combined rifling during the projectile move in the bore. According to the amplitude and the strength of the twist acting on rotating band, the steady property of rotational motion of the projectile, the rib rifling is a better choose.
Blind analysis results of the TWIST experiment
Hillairet, A; Bueno, J F; Davydov, Y I; Depommier, P; Faszer, W; Fujiwara, M C; Gagliardi, C A; Gaponenko, A; Grossheim, A; Gill, D R; Gumplinger, P; Hasinoff, M D; Henderson, R S; Hu, J; Koetke, D D; MacDonald, R P; Marshall, G M; Mathie, E W; Mischke, R E; Olchanski, K; Olin, A; Openshaw, R; Poutissou, J -M; Poutissou, R; Selivanov, V; Sheffer, G; Shin, B; Stanislaus, T D S; Tacik, R; Tribble, R E
2010-01-01
The TRIUMF Weak Interaction Symmetry Test (TWIST) experiment was designed to test the standard model at high precision in the purely leptonic decay of polarized muons. A general four-fermion interaction model is used to describe the muon decay. TWIST measures three of the four muon decay parameters of this model, $\\rho$, $\\delta$ and $P_{\\mu}^{\\pi} \\xi$, from the shape of the momentum-angle spectrum. The results of this model independent approach are compared to the standard model predictions and used to constrain new physics. Our collaboration has finalized the blind analysis of the final experimental data taken in 2006 and 2007. This analysis mostly reached our goal of a precision of an order of magnitude improvement over the pre-TWIST measurements.
Helicoids, wrinkles, and loops in twisted ribbons.
Chopin, Julien; Kudrolli, Arshad
2013-10-25
We investigate the instabilities of a flat elastic ribbon subject to twist under tension and develop an integrated phase diagram of the observed shapes and transitions. We find that the primary buckling mode switches from being localized longitudinally along the length of the ribbon to transverse above a triple point characterized by a crossover tension that scales with ribbon elasticity and aspect ratio. Far from threshold, the longitudinally buckled ribbon evolves continuously into a self-creased helicoid with focusing of the curvature along the triangular edges. Further twist causes an anomalous transition to loops compared with rods due to the self-rigidity induced by the creases. When the ribbon is twisted under high tension, transverse wrinkles are observed due to the development of compressive stresses with higher harmonics for greater width-to-length ratios. Our results can be used to develop functional structures using a wide range of elastic materials and length scales.
Dynamical Twisted Mass Fermions with Light Quarks
Boucaud, P; Farchioni, F; Frezzotti, R; Giménez, V; Herdoiza, G; Jansen, K; Lubicz, V; Martinelli, G; McNeile, C; Michael, C; Montvay, I; Palao, D; Papinutto, Mauro; Pickavance, J; Rossi, G C; Scorzato, L; Shindler, A; Simula, S; Urbach, C; Wenger, U; Boucaud, Ph.
2007-01-01
We present results of dynamical simulations with 2 flavours of degenerate Wilson twisted mass quarks at maximal twist in the range of pseudo scalar masses from 300 to 550 MeV. The simulations are performed at one value of the lattice spacing a \\lesssim 0.1 fm. In order to have O(a) improvement and aiming at small residual cutoff effects, the theory is tuned to maximal twist by requiring the vanishing of the untwisted quark mass. Precise results for the pseudo scalar decay constant and the pseudo scalar mass are confronted with chiral perturbation theory predictions and the low energy constants F, \\bar{l}_3 and \\bar{l}_4 are evaluated with small statistical errors.
Matrix theory compactifications on twisted tori
Chatzistavrakidis, Athanasios
2012-01-01
We study compactifications of Matrix theory on twisted tori and non-commutative versions of them. As a first step, we review the construction of multidimensional twisted tori realized as nilmanifolds based on certain nilpotent Lie algebras. Subsequently, matrix compactifications on tori are revisited and the previously known results are supplemented with a background of a non-commutative torus with non-constant non-commutativity and an underlying non-associative structure on its phase space. Next we turn our attention to 3- and 6-dimensional twisted tori and we describe consistent backgrounds of Matrix theory on them by stating and solving the conditions which describe the corresponding compactification. Both commutative and non-commutative solutions are found in all cases. Finally, we comment on the correspondence among the obtained solutions and flux compactifications of 11-dimensional supergravity, as well as on relations among themselves, such as Seiberg-Witten maps and T-duality.
On reweighting for twisted boundary conditions
Bussone, Andrea; Hansen, Martin; Pica, Claudio
2016-01-01
We consider the possibility of using reweighting techniques in order to correct for the breaking of unitarity when twisted boundary conditions are imposed on valence fermions in simulations of lattice gauge theories. We start by studying the properties of reweighting factors and their variances at tree-level. That leads us to the introduction of a factorization for the fermionic reweighting determinant. In the numerical, stochastic, implementation of the method, we find that the effect of reweighting is negligible in the case of large volumes but it is sizeable when the volumes are small and the twisting angles are large. More importantly, we find that for un-improved Wilson fermions, and in small volumes, the dependence of the critical quark mass on the twisting angle is quite pronounced and results in large violations of the continuum dispersion relation.
Local index formula and twisted spectral triples
Moscovici, Henri
2009-01-01
We prove a local index formula for a class of twisted spectral triples of type III modeled on the transverse geometry of conformal foliations with locally constant transverse conformal factor. Compared with the earlier proof of the untwisted case, the novel aspect resides in the fact that the twisted analogues of the JLO entire cocycle and of its retraction are no longer cocycles in their respective Connes bicomplexes. We show however that the passage to the infinite temperature limit, respectively the integration along the full temperature range against the Haar measure of the positive half-line, has the remarkable effect of curing in both cases the deviations from the cocycle identity.
On Supermultiplet Twisting and Spin-Statistics
Hübsch, T.
2013-10-01
Twisting of off-shell supermultiplets in models with (1+1)-dimensional spacetime has been discovered in 1984, and was shown to be a generic feature of off-shell representations in worldline supersymmetry two decades later. It is shown herein that in all supersymmetric models with spacetime of four or more dimensions, this off-shell supermultiplet twisting, if nontrivial, necessarily maps regular (non-ghost) supermultiplets to ghost supermultiplets. This feature is shown to be ubiquitous in all fully off-shell supersymmetric models with (BV/BRST-treated) constraints.
Multi-twist optical Mobius strips
Freund, Isaac
2009-01-01
Circularly polarized Gauss-Laguerre GL(0,0) and GL(0,1) laser beams that cross at their waists at a small angle are shown to generate a quasi-paraxial field that contains an axial line of circular polarization, a C line, surrounded by polarization ellipses whose major and minor axes generate multi-twist Mobius strips with twist numbers that increase with distance from the C point. These Mobius strips are interpreted in terms of Berry's phase for parallel transport of the ellipse axes around the C point.
Effects Of Twist On Ceramic Threads
Sawko, Paul M.; Tran, Huy Kim
1989-01-01
Report describes study of effects of yarn twist and other manufacturing parameters on strength of ceramic sewing threads. Three types of thread considered; silica, aluminoborosilicate (ABS) with 14 percent boria, and ABS with 2 percent boria. For silica thread, best twist found 300 turns per meter. Produced highest break strength at temperatures up to about 540 degree C. Overall strengths of both ABS threads higher than silica thread. Threads used to stitch insulating blankets for reusable spacraft; must resist high temperatures and high aerodynamic loads of reentry into atmosphere of Earth.
Spectral flows and twisted topological theories
Gato-Rivera, Beatriz; Gato-Rivera, Beatriz; Rosado, Jose Ignacio
1995-01-01
We analyze the action of the spectral flows on N=2 twisted topological theories. We show that they provide a useful mapping between the two twisted topological theories associated to a given N=2 superconformal theory. This mapping can also be viewed as a topological algebra automorphism. In particular null vectors are mapped into null vectors, considerably simplifying their computation. We give the level 2 results. Finally we discuss the spectral flow mapping in the case of the DDK and KM realizations of the topological algebra.
Institute of Scientific and Technical Information of China (English)
代军; 汤立民; 张以都; 吴琼
2011-01-01
Based on the model of helical ending milling force ,deformation of thin-wall part is calculated by FEM.The optimization parameters of cutting width are determined,then the surface accuracy of part is improved.According to analysis for the dynamic characteristic ,the displacement response curves are plotted.The cutting speed is chosen in stable states on the basis of the curve,which will grantee qualification of milling.Results of analysis for-shaped thin-wall part and the local thin-wall part of aircraft.Results show that they have the familiar dynamic characteristic.The locality of large and complex work pieces can be parameterized modeling and automatically analyzed.It will not only provide help for optimization of parameters in the milling but also improve the efficiency of analysis.%基于瞬态螺旋端面铣削力模型,应用有限元法求出加工过程中的薄壁件静态变形量,从而确定出优化的切宽参数,改善了表面精度.对薄壁件进行动态特性分析,绘制加工时薄壁件的动态振幅响应曲线,得到合理的铣削速度,保证铣削质量.将"一"字型薄壁件与复杂薄壁件的局部进行分析比较,结果表明:二者之间有相似的动态特性,则对于任意复杂的大型薄壁件,可实现局部参数化建模和动态特性分析,不仅为加工参数优化提供分析依据,而且缩短了分析的时间,提高了效率.
A non-commuting twist in the partition function
Govindarajan, Suresh
2012-01-01
We compute a twisted index for an orbifold theory when the twist generating group does not commute with the orbifold group. The twisted index requires the theory to be defined on moduli spaces that are compatible with the twist. This is carried out for CHL models at special points in the moduli space where they admit dihedral symmetries. The commutator subgroup of the dihedral groups are cyclic groups that are used to construct the CHL orbifolds. The residual reflection symmetry is chosen to act as a `twist' on the partition function. The reflection symmetries do not commute with the orbifolding group and hence we refer to this as a non-commuting twist. We count the degeneracy of half-BPS states using the twisted partition function and find that the contribution comes mainly from the untwisted sector. We show that the generating function for these twisted BPS states are related to the Mathieu group M_{24}.
On Twisting Real Spectral Triples by Algebra Automorphisms
Landi, Giovanni; Martinetti, Pierre
2016-11-01
We systematically investigate ways to twist a real spectral triple via an algebra automorphism and in particular, we naturally define a twisted partner for any real graded spectral triple. Among other things, we investigate consequences of the twisting on the fluctuations of the metric and possible applications to the spectral approach to the Standard Model of particle physics.
On Twisting Real Spectral Triples by Algebra Automorphisms
Landi, Giovanni; Martinetti, Pierre
2016-08-01
We systematically investigate ways to twist a real spectral triple via an algebra automorphism and in particular, we naturally define a twisted partner for any real graded spectral triple. Among other things, we investigate consequences of the twisting on the fluctuations of the metric and possible applications to the spectral approach to the Standard Model of particle physics.
Institute of Scientific and Technical Information of China (English)
王艳光; 彭晓东; 赵辉; 谢卫东; 魏群义
2011-01-01
The advantage and disadvantage as well as the development of sand casting, low tension casting, die casting, lost foam casting and centrifugal casting technologies for the production of large thin - wall precision magnesium alloy castings are discussed. According to the development of aerospace industry, the research and development direction of the magnesium alloy centrifugal casting are pointed out.%介绍了砂型、低压、压铸、消失模、离心铸造大型、薄壁、精密镁合金铸件的优势和缺点,以及这些铸造技术的最新发展情况.针对航天工业的发展指出离心铸造镁合金的研究与发展方向.
Institute of Scientific and Technical Information of China (English)
姚国荣
2015-01-01
The paper describes the craft features for the U-shaped cast-in-place reinforced concrete thin-wall hollow decoration columns,illus-trates the construction craft procedure and material requirements by combining with its construction craft principle,and researches the construc-tion quality,safety and environment protection control measures,so as to achieve better economic and social benefits.%描述了 U 型现浇配筋混凝土薄壁空心装饰柱施工的工艺特点，结合其施工工艺原理，阐述了施工工艺流程及材料要求，并对施工质量、安全、环保控制措施进行了研究，以取得良好的经济、社会效益。
Twisting singular solutions of Bethe's equations
Nepomechie, Rafael I
2014-01-01
The Bethe equations for the periodic XXX and XXZ spin chains admit singular solutions, for which the corresponding eigenvalues and eigenvectors are ill-defined. We use a twist regularization to derive conditions for such singular solutions to be physical, in which case they correspond to genuine eigenvalues and eigenvectors of the Hamiltonian.
Disconnected Loops with Twisted Mass Lattice QCD
Wilcox, W; Morgan, R; Lewis, R; Wilcox, Walter; Darnell, Dean; Morgan, Ron; Lewis, Randy
2005-01-01
We give a general introduction and discussion of the issues involved in using the twisted mass formulation of lattice fermions in the context of disconnected loop calculations, including a short orientation on the present experimental situation for nucleon strange quark form factors. A prototype calculation of the disconnected part of the nucleon scalar form factor is described.
Phase diagram of twisted mass lattice QCD
Sharpe, Stephen R.; Wu, Jackson M.
2004-11-01
We use the effective chiral Lagrangian to analyze the phase diagram of two-flavor twisted mass lattice QCD as a function of the normal and twisted masses, generalizing previous work for the untwisted theory. We first determine the chiral Lagrangian including discretization effects up to next-to-leading order (NLO) in a combined expansion in which m2π/(4πfπ)2˜aΛ (a being the lattice spacing, and Λ=ΛQCD). We then focus on the region where m2π/(4πfπ)2˜(aΛ)2, in which case competition between leading and NLO terms can lead to phase transitions. As for untwisted Wilson fermions, we find two possible phase diagrams, depending on the sign of a coefficient in the chiral Lagrangian. For one sign, there is an Aoki phase for pure Wilson fermions, with flavor and parity broken, but this is washed out into a crossover if the twisted mass is nonvanishing. For the other sign, there is a first order transition for pure Wilson fermions, and we find that this transition extends into the twisted mass plane, ending with two symmetrical second order points at which the mass of the neutral pion vanishes. We provide graphs of the condensate and pion masses for both scenarios, and note a simple mathematical relation between them. These results may be of importance to numerical simulations.
Gluon polarization and higher twist effects
Leader, Elliot; Stamenov, Dimiter
2008-01-01
We examine the influence of the recent CLAS and COMPASS experiments on our understanding of higher twist (HT) effects and the gluon polarization, and show how EIC could discriminate between negative and positive gluon polarizations. We comment on the issue of HT and the recent DSSV analysis.
HOMOCLINIC TWIST BIFURCATIONS WITH Z(2) SYMMETRY
ARONSON, DG; VANGILS, SA; KRUPA, M
1994-01-01
We analyze bifurcations occurring in the vicinity of a homoclinic twist point for a generic two-parameter family of Z2 equivariant ODEs in four dimensions. The results are compared with numerical results for a system of two coupled Josephson junctions with pure capacitive load.
Redefining B twisted topological sigma models
Jonghe, F. de; Termonia, P.; Troost, W.; Vandoren, S.
2007-01-01
The recently proposed procedure to perform the topological B-twist in rigid N = 2 models is applied to the case of the o model on a Kähler manifold. This leads to an alternative description of Witten’s topological o model, which allows for a proper BRST interpretation and ghost number assignement. W
Generalized Weyl modules for twisted current algebras
Makedonskyi, I. A.; Feigin, E. B.
2017-08-01
We introduce the notion of generalized Weyl modules for twisted current algebras. We study their representation-theoretic and combinatorial properties and also their connection with nonsymmetric Macdonald polynomials. As an application, we compute the dimension of the classical Weyl modules in the remaining unknown case.
Analysis of Cohesion inOliver Twist
Institute of Scientific and Technical Information of China (English)
程文文
2016-01-01
Cohesion is an important concept in the study of stylistics. This thesis aims to study the applications of cohesion in the Charles Dicken’ world-famous novelOliver Twist, including both the grammatical and lexical cohesive devices in the work.
Energy Release in Driven Twisted Coronal Loops
Bareford, M. R.; Gordovskyy, M.; Browning, P. K.; Hood, A. W.
2016-01-01
We investigate magnetic reconnection in twisted magnetic fluxtubes, representing coronal loops. The main goal is to establish the influence of the field geometry and various thermodynamic effects on the stability of twisted fluxtubes and on the size and distribution of heated regions. In particular, we aim to investigate to what extent the earlier idealised models, based on the initially cylindrically symmetric fluxtubes, are different from more realistic models, including the large-scale curvature, atmospheric stratification, thermal conduction and other effects. In addition, we compare the roles of Ohmic heating and shock heating in energy conversion during magnetic reconnection in twisted loops. The models with straight fluxtubes show similar distribution of heated plasma during the reconnection: it initially forms a helical shape, which subsequently becomes very fragmented. The heating in these models is rather uniformly distributed along fluxtubes. At the same time, the hot plasma regions in curved loops are asymmetric and concentrated close to the loop tops. Large-scale curvature has a destabilising influence: less twist is needed for instability. Footpoint convergence normally delays the instability slightly, although in some cases, converging fluxtubes can be less stable. Finally, introducing a stratified atmosphere gives rise to decaying wave propagation, which has a destabilising effect.
Institute of Scientific and Technical Information of China (English)
董宁娟; 赵洪金
2013-01-01
Applying the energy method and Hamilton principle, the differential equations for spatial dynamic stability analysis of a thin-walled circular arch with closed section subject to radial periodically-distributed load were established. Galerkin method was used to convert the partial differential equations into the ordinary differential Mathieu equations, so as to deduce the critical frequency equations of primary parameter resonance of deep arch. And then, the dynamic instability regions surrounded by periodic solutions were obtained. Spatial dynamic stability problems of parametric vibration of the thin-walled circular arch with closed section were discussed. The influences of dead load, radius of circle and central angle etc. on the dynamic stability were analyzed. This work provides some reference basis for dynamic analysis and design for engineering structures.% 通过能量法和Hamilton原理，建立径向均布周期荷载作用下闭口薄壁截面圆弧拱动力稳定偏微分方程，利用Galerkin方法将其转化为2阶常微分Mathieu-Hill型参数振动方程，求得周期解所包围的动力不稳定区域，探讨了闭口截面圆弧拱发生空间参数振动的动力稳定性问题，分析了恒载系数、圆弧半径以及圆心角等参数对空间动力不稳定区域的影响，为工程结构动力设计提供参考依据。
Institute of Scientific and Technical Information of China (English)
董宁娟; 赵洪金
2012-01-01
Spatial dynamic stability differential equation of thin-walled circular arch with open-section subject to under distributing radial periodic load is established through applying the energy method and Hamilton principle. Galerkin' s method is used to convert the partial differential equations into the ordinary differential Mathieu equations , so as to deduce the critical frequency equations of primary parameter resonance of deep arch, and then dynamic instability regions surrounded by periodic solutions are obtained. Spatial dynamic stability problems of parametric vibration is discussed about thin-walled circular arch with open section, through analyzing the influences of dead load, radius of circle and central angle etc. On the dynamic stabilities, which provides reference basis for dynamic analysis and design in structure engineering.%通过能量法和Hamilton原理,建立了径向均布周期荷载作用下开口薄壁截面圆弧拱动力稳定偏微分方程.利用Galerkin方法将其转化为二阶常微分Mathieu-Hill型参数振动方程.求得周期解所包围的动力不稳定区域.探讨了开口截面圆弧拱发生空间参数振动的动力稳定性问题.分析了恒载系数、圆弧半径以及圆心角等参数对空间动力不稳定区域的影响,为工程结构动力设计提供参考依据.
Institute of Scientific and Technical Information of China (English)
甘正红; 方晓东; 余国民; 余洋; 苏继权
2014-01-01
电阻焊管焊缝中易出现的缺陷有未熔合(冷焊)、裂纹、夹杂等，该类缺陷主要为沿焊缝延伸的面积型缺陷，采用超声检测。根据薄壁高频电阻焊管焊缝的缺陷特征，选用了超声爬波检测。阐述了超声爬波检测的原理、特点和工艺方法，设计了爬波检测专用探头和对比试块。实际检测结果表明，爬波检测是一种新型高效的检测方法，证明了爬波检测技术在薄壁电阻焊管焊缝检测中的可行性。%Some defects easily appear in weld of HFW pipe, such as incomplete fusion (cold welding), crack, inclusion etc. The above defects are mainly area type defects along weld extension. These defects can be detected by creeping wave testing according to defects characteristics of thin-walled high-frequency electric resistance welded pipe. In this article, it expatiated the detection principle, features and process method of the creeping wave testing method, designed the creeping wave testing special probe and the reference blocks. The practical detection results showed that the creeping wave testing is a new type of high efficient detection method, and the creeping wave detection technology feasibility in thin-walled high-frequency electric resistance welded pipe was proved.
ENERGY-VARIATIONAL METHOD OF STATIC ANALYSIS OF THIN-WALLED T-SHAPED BEAMS%T形梁静力学特性分析的能量变分法
Institute of Scientific and Technical Information of China (English)
吴发红; 崔传宗
2012-01-01
In consideration of shear lag and shear deformation effects, It was proposed an approach of analyzing the static characteristics of T-beams generally used in projects. A new warping displacement mode of T-beams was chosen to meet the axial self-equilibrium condition for corresponding stress, three generalized displacement functions were employed in analyzing static characteristics of the thin-walled T-beams with wide flanges by calculus of variations, the differential equations and the corresponding natural boundary conditions of the T-beams are induced based on the minimum potential principle. According to the fundamental differential equations and the corresponding natural boundary conditions, the static characteristics of thin-walled T-beams are discussed. The finite element solutions were compared with the analytical solutions and verified the validity of the proposed approach.%考虑了剪力滞后、剪滞翘曲应力自平衡条件和剪切变形等因素的影响,提出了一种对薄壁T形梁静力学特性的分析方法。以最小势能原理为基础,建立了T形梁静力学特性的控制微分方程和自然边界条件,据此对T形梁力学特性进行了研究。分析了剪滞翘曲应力自平衡条件、不同荷载形式和宽跨比等因素对T形梁静力学特性的影响,最后,通过解析解与有限元数值解进行了比较,说明了该分析方法的有效性。
Higher Twist Distribution Amplitudes of the Nucleon in QCD
Braun, V M; Mahnke, N; Stein, E
2000-01-01
We present the first systematic study of higher-twist light-cone distribution amplitudes of the nucleon in QCD. We find that the valence three-quark state is described at small transverse separations by eight independent distribution amplitudes. One of them is leading twist-3, three distributions are twist-4 and twist-5, respectively, and one is twist-6. A complete set of distribution amplitudes is constructed, which satisfies equations of motion and constraints that follow from conformal expansion. Nonperturbative input parameters are estimated from QCD sum rules.
Mechanical behaviors of multi-filament twist superconducting strand under tensile and cyclic loading
Wang, Xu; Li, Yingxu; Gao, Yuanwen
2016-01-01
The superconducting strand, serving as the basic unit cell of the cable-in-conduit-conductors (CICCs), is a typical multi-filament twist composite which is always subjected to a cyclic loading under the operating condition. Meanwhile, the superconducting material Nb3Sn in the strand is sensitive to strain frequently relating to the performance degradation of the superconductivity. Therefore, a comprehensive study on the mechanical behavior of the strand helps understanding the superconducting performance of the strained Nb3Sn strands. To address this issue, taking the LMI (internal tin) strand as an example, a three-dimensional structural finite element model, named as the Multi-filament twist model, of the strand with the real configuration of the LMI strand is built to study the influences of the plasticity of the component materials, the twist of the filament bundle, the initial thermal residual stress and the breakage and its evolution of the filaments on the mechanical behaviors of the strand. The effective properties of superconducting filament bundle with random filament breakage and its evolution versus strain are obtained based on the damage theory of fiber-reinforced composite materials proposed by Curtin and Zhou. From the calculation results of this model, we find that the occurrence of the hysteresis loop in the cyclic loading curve is determined by the reverse yielding of the elastic-plastic materials in the strand. Both the initial thermal residual stress in the strand and the pitch length of the filaments have significant impacts on the axial and hysteretic behaviors of the strand. The damage of the filaments also affects the axial mechanical behavior of the strand remarkably at large axial strain. The critical current of the strand is calculated by the scaling law with the results of the Multi-filament twist model. The predicted results of the Multi-filament twist model show an acceptable agreement with the experiment.
General relativistic neutron stars with twisted magnetosphere
Pili, A G; Del Zanna, L
2014-01-01
Soft Gamma-Ray Repeaters and Anomalous X-Ray Pulsars are extreme manifestations of the most magnetized neutron stars: magnetars. The phenomenology of their emission and spectral properties strongly support the idea that the magnetospheres of these astrophysical objects are tightly twisted in the vicinity of the star. Previous studies on equilibrium configurations have so far focused on either the internal or the external magnetic field configuration, without considering a real coupling between the two fields. Here we investigate numerical equilibrium models of magnetized neutron stars endowed with a confined twisted magnetosphere, solving the general relativistic Grad-Shafranov equation both in the interior and in the exterior of the compact object. A comprehensive study of the parameters space is provided to investigate the effects of different current distributions on the overall magnetic field structure.
Twisted black hole is Taub-NUT
Ong, Yen Chin
2017-01-01
Recently a purportedly novel solution of the vacuum Einstein field equations was discovered: it supposedly describes an asymptotically flat twisted black hole in 4-dimensions whose exterior spacetime rotates in a peculiar manner—the frame dragging in the northern hemisphere is opposite from that of the southern hemisphere, which results in a globally vanishing angular momentum. Furthermore it was shown that the spacetime has no curvature singularity. We show that the geometry of this black hole spacetime is nevertheless not free of pathological features. In particular, it harbors a rather drastic conical singularity along the axis of rotation. In addition, there exist closed timelike curves due to the fact that the constant r and constant t surfaces are not globally Riemannian. In fact, none of these are that surprising since the solution is just the Taub-NUT geometry. As such, despite the original claim that the twisted black hole might have observational consequences, it cannot be.
Twisted mass QCD at finite temperature
Energy Technology Data Exchange (ETDEWEB)
Ilgenfritz, E.M.; Mueller-Preussker, M.; Petschlies, M. [Humboldt-Universitaet, Berlin (Germany). Inst. fuer Physik; Jansen, K. [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany); Lombardo, M.P. [Istituto Nazionale di Fisica Nucleare, LNF, Frascati (Italy); Philipsen, O.; Zeidlewicz, L. [Muenster Univ. (Germany). Inst. fuer Theoretische Physik 1; Sternbeck, A. [Adelaide Univ. (Australia). CSSM School of Chemistry and Physics
2007-10-15
We discuss the use of Wilson fermions with twisted mass for simulations of QCD thermodynamics. As a prerequisite for a future analysis of the finite-temperature transition making use of automatic {partial_derivative} (a) improvement, we investigate the phase structure in the space spanned by the hopping parameter {kappa}, the coupling {beta}, and the twisted mass parameter {mu}. We present results for N{sub f}=2 degenerate quarks on a 16{sup 3} x 8 lattice, for which we investigate the possibility of an Aoki phase existing at strong coupling and vanishing {mu}, as well as of a thermal phase transition at moderate gauge couplings and non-vanishing {mu}. (orig.)
Magnetic Field Twisting by Intergranular Downdrafts
Taroyan, Youra; Williams, Thomas
2016-10-01
The interaction of an intergranular downdraft with an embedded vertical magnetic field is examined. It is demonstrated that the downdraft may couple to small magnetic twists leading to an instability. The descending plasma exponentially amplifies the magnetic twists when it decelerates with depth due to increasing density. Most efficient amplification is found in the vicinity of the level, where the kinetic energy density of the downdraft reaches equipartition with the magnetic energy density. Continual extraction of energy from the decelerating plasma and growth in the total azimuthal energy occurs as a consequence of the wave-flow coupling along the downdraft. The presented mechanism may drive vortices and torsional motions that have been detected between granules and in simulations of magnetoconvection.
Factorising the 3D Topologically Twisted Index
Cabo-Bizet, Alejandro
2016-01-01
In this work, path integral representations of the 3D topologically twisted index were studied. First, the index can be "factorised" into a couple of "blocks". The "blocks" being the partition functions of a type A semi-topological twisting of 3D N = 2 SYM placed on $\\mathbb{S}_2\\times (0, \\pi)$ and $\\mathbb{S}_2 \\times (\\pi, 2 \\pi)$ respectively. Second, as the path integral of the aforementioned theory over $\\mathbb{S}_2$ times $\\mathbb{S}_1$ with a point excluded. In this way we recover the sum over fluxes from integration over the real path and without sacrificing positive definiteness of the bosonic part of the localising action. We also reproduce the integration over the complex contour by using the localising term with positive definite bosonic part.
Tinkertoys for the Twisted D-Series
Chacaltana, Oscar; Trimm, Anderson
2013-01-01
We study 4D N=2 superconformal field theories that arise from the compactification of 6D N=(2,0) theories of type D_N on a Riemann surface, in the presence of punctures twisted by a Z_2 outer automorphism. Unlike the untwisted case, the family of SCFTs is in general parametrized, not by M_{g,n}, but by a branched cover thereof. The classification of these SCFTs is carried out explicitly in the case of the D_4 theory, in terms of three-punctured spheres and cylinders, and we provide tables of properties of twisted punctures for the D_5 and D_6 theories. We find realizations of Spin(8) and Spin(7) gauge theories with matter in all combinations of vector and spinor representations with vanishing beta-function, as well as Sp(3) gauge theories with matter in the 3-index traceless antisymmetric representation.
Valve-aided twisted Savonius rotor
Energy Technology Data Exchange (ETDEWEB)
Jaya Rajkumar, M.; Saha, U.K.
2006-05-15
Accessories, such as end plates, deflecting plates, shielding and guide vanes, may increase the power of a Savonius rotor, but make the system structurally complex. In such cases, the rotor can develop a relatively large torque at small rotational speeds and is cheap to build, however it harnesses only a small fraction of the incident wind energy. Another proposition for increasing specific output is to place non-return valves inside the concave side of the blades. Such methods have been studied experimentally with a twisted-blade Thus improving a Savonius rotor's energy capture. This new concept has been named as the 'Valve-Aided Twisted Savonius'rotor. Tests were conducted in a low-speed wind tunnel to evaluate performance. This mechanism is found to be independent of flow direction, and shows potential for large machines. [Author].
Overlap fermions on a twisted mass sea
Bär, O; Schäefer, S; Scorzato, L; Shindler, A
2006-01-01
We present first results of a mixed action project. We analyze gauge configurations generated with two flavors of dynamical twisted mass fermions. Neuberger's overlap Dirac operator is used for the valence sector. The various choices in the setup of the simulation are discussed. We employ chiral perturbation theory to describe the effects of using different actions in the sea and valence sector at non-zero lattice spacing.
Disconnected diagrams with twisted-mass fermions
Abdel-Rehim, Abdou; Constantinou, Martha; Finkenrath, Jacob; Hadjiyiannakou, Kyriakos; Jansen, Karl; Kallidonis, Christos; Koutsou, Giannis; Avilés-Casco, Alejandro Vaquero
2016-01-01
The latest results from the Twisted-Mass collaboration on disconnected diagrams at the physical value of the pion mass are presented. In particular, we focus on the sigma terms, the axial charges and the momentum fraction, all of them for the nucleon. A detailed error analysis for each observable follows, showing the strengths and weaknesses of the one-end trick. Alternatives are discussed.
DNA Packaging in Bacteriophage: Is Twist Important?
Spakowitz, Andrew James; Wang, Zhen-Gang
2005-01-01
We study the packaging of DNA into a bacteriophage capsid using computer simulation, specifically focusing on the potential impact of twist on the final packaged conformation. We perform two dynamic simulations of packaging a polymer chain into a spherical confinement: one where the chain end is rotated as it is fed, and one where the chain is fed without end rotation. The final packaged conformation exhibits distinct differences in these two cases: the packaged conformation from feeding with...
On rectangular HOMFLY for twist knots
Kononov, Ya
2016-01-01
As a new step in the study of rectangularly-colored knot polynomials, we reformulate the prescription of arXiv:1606.06015 for twist knots in the double-column representations $R=[rr]$ in terms of skew Schur polynomials. These, however, are mysteriously shifted from the standard topological locus, what makes further generalization to arbitrary $R=[r^s]$ not quite straightforward.
Ferromagnetic nanoparticles suspensions in twisted nematic
Cîrtoaje, Cristina; Petrescu, Emil; Stan, Cristina; Creangă, Dorina
2016-05-01
Ferromagnetic nanoparticles insertions in nematic liquid crystals (NLC) in twisted configuration are studied and a theoretical model is proposed to explain the results. Experimental observation revealed that nanoparticles tend to overcrowd in long strings parallel to the rubbing direction of the alignment substrate of the LC cell. Their behavior under external field was studied and their interaction with their nematic host is described using elastic continuum theory.
Twisted Radiation by Electrons in Spiral Motion
Katoh, M; Mirian, N S; Konomi, T; Taira, Y; Kaneyasu, T; Hosaka, M; Yamamoto, N; Mochihashi, A; Takashima, Y; Kuroda, K; Miyamoto, A; Miyamoto, K; Sasaki, S
2016-01-01
We theoretically show that a single free electron in circular/spiral motion radiates an electromagnetic wave possessing helical phase structure and carrying orbital angular momentum. We experimentally demonstrate it by double-slit diffraction on radiation from relativistic electrons in spiral motion. We show that twisted photons should be created naturally by cyclotron/synchrotron radiations or Compton scatterings in various situations in astrophysics. We propose promising laboratory vortex photon sources in various wavelengths ranging from radio wave to gamma-rays.
AN EXACT ANALYSIS OF FORCED THICKNESS-TWIST VIBRATIONS OF MULTI-LAYERED PIEZOELECTRIC PLATES
Institute of Scientific and Technical Information of China (English)
无
2007-01-01
This paper deals with the thickness-twist vibration of a multi-layered rectangular piezoelectric plate of crystals of 6 mm symmetry or polarized ceramics. An exact solution is obtained from the three-dimensional equations of linear piezoelectricity. The solution is useful to the understanding and design of composite piezoelectric devices. A piezoelectric resonator, a piezoelectric transformer, and a piezoelectric generator are analyzed as examples.
Twisted spectral geometry for the standard model
Martinetti, Pierre
2015-01-01
The Higgs field is a connection one-form as the other bosonic fields, provided one describes space no more as a manifold M but as a slightly non-commutative generalization of it. This is well encoded within the theory of spectral triples: all the bosonic fields of the standard model - including the Higgs - are obtained on the same footing, as fluctuations of a generalized Dirac operator by a matrix-value algebra of functions on M. In the commutative case, fluctuations of the usual free Dirac operator by the complex-value algebra A of smooth functions on M vanish, and so do not generate any bosonic field. We show that imposing a twist in the sense of Connes-Moscovici forces to double the algebra A, but does not require to modify the space of spinors on which it acts. This opens the way to twisted fluctuations of the free Dirac operator, that yield a perturbation of the spin connection. Applied to the standard model, a similar twist yields in addition the extra scalar field needed to stabilize the electroweak v...
Institute of Scientific and Technical Information of China (English)
邓福铭; 王博; 邓雯丽; 周小彦; 赵烨; 刘波; 张红林
2015-01-01
Service life and drilling efficiency are the important measurement indexes of the performance of diamond engineering thin-walled drill bit.Reinforced concrete drilling contrast experiments between engineering thin-walled drill bit manufactured by new tech-nique and a well known domestic product by conventional hot-pressing technique have been conducted.Result shows that the quantity of drill hole of the 1# drill bit manufac-tured by new technique is 94,and the abrasive resistance of it is 5 1.6% higher than that of the most durable procuct in China and their drill rate is similar.This drill bit can be categorized into the high abrasive resistance products;the average drill time of 3 # drill bit is 12.3min/hole and the dirll rate of it is 1 9.5mm/min which is similar to the domestic product of the highest drilling rate while the service life of it is 52% longer which makes is a high efficiency drilling product;the quantity of drill hole of the 2# drill bit is 72 with an average drill rate of 17.7mm/min,its abrasive resistance and drill rate are respectively 29~32% and 26 ~33% higher than those of the most advanced domestic products.The experiments have confirmed that the engineering thin-walled drill bit manufactured by new technique has a nature of high efficiency and long service life which has overcome the incompatibility of abrasive resistance and drill rate of the conventional product of hot-pressing sintering technique.%使用寿命长短以及钻切效率高低是衡量金刚石工程薄壁钻的使用性能优劣的重要指标。采用新工艺制备的金刚石工程薄壁钻与传统热压工艺生产的国内某著名厂家产品进行了钢筋混凝土台架钻切对比实验,结果表明,新工艺制备的1#钻头的钻孔数为94孔,其耐磨性比目前国内使用寿命最长的产品高51.6%,且钻速基本上与之相当,属于高耐磨型产品；3#钻头的平均钻进时间为12.3min/孔,钻速为19.5mm/min,与国内钻速最高的产品相
Institute of Scientific and Technical Information of China (English)
姚永红; 武振宇
2016-01-01
Cold-formed thin-walled steel has been used widely in building structures due to its many advantages.It has been found that the existing calculated values of distortional buckling bearing capacity of columns can' t reflect the experimental law well, and the calculation process of elastic distortional buckling stress is too cumbersome.The suggested direct strength method considering distortional and global interactive buckling and a rotational restraint calculation formula without iteration used for estimating the elastic distortional buckling stress was presented.The values of distortional buckling bearing capacity calculated by proposed method were safe compared with the experiment data, and decreased with the increasing of the column length, which was in accord with the experimental law.Which provided a reference for revision of Technical Code of Cold-Formed Thin-Walled Steel Structures in the future.%冷弯薄壁型钢构件由于自身的诸多优点,已广泛应用于建筑结构之中.分析发现现有柱试件畸变屈曲承载力计算值不能较好地反映试验规律,并且弹性畸变屈曲应力公式计算过程较繁琐.经过理论分析,提出考虑畸变与整体相关屈曲的直接强度法设计公式,给出无需迭代的转动约束刚度建议公式以用于弹性畸变屈曲应力的计算.通过与试验数据对比发现,所提出的建议公式可以较安全地计算柱试件的畸变屈曲承载力,其计算值随柱长增加而减小,符合试验规律,可为《冷弯薄壁型钢结构技术规范》的修订提供参考.
Institute of Scientific and Technical Information of China (English)
赵瑞斌
2015-01-01
Large complex thin-walled titanium alloy precision casting is the most advanced technologies in the world of military and civil aviation field.This paper introduces its process flow, technical features and the domestic and international research frontier achievements. Combined with the most popular international computer numerical simulation and 3D print and other new technology, summarizes the research trend and development direction of this technology in China: theory research strengthen of the investment casting process, research of titanium alloy design and exploration of large thin wall complex higher performance of casting titanium alloy, construction of model library, development of automatic coating machine slurry and sanding process, better quality management and control of the whole process, more emphasis on application of 3D printing technology in the fields of the manufacture and investment casting process of titanium alloy.%大型复杂薄壁钛合金精密铸造技术是当今世界军用与民用航空领域的尖端技术。介绍了熔模精密铸造技术的工艺流程、技术特点以及国内外研究现状。结合国际最流行的计算机数值模拟以及3D打印等新型技术，指出我国该项技术的研究趋势与发展方向是：①加强熔模铸造工艺的理论研究；②深化钛合金设计研究，探索性能更高的适合于大型复杂薄壁件铸造成形的钛合金；③深入研究纯净化技术，以及夹杂和铸造缺陷与性能之间的定量关系；④建立型壳模型库；⑤研发机器自动涂浸浆料与撒砂工艺；⑥加强全过程的质量管理与控制；⑦高度关注3D打印技术在钛合金制造领域的发展及其在钛合金熔模铸造领域的应用。
Expression of Twist Gene in Primary Liver Cancer
Institute of Scientific and Technical Information of China (English)
XU Jing; CHEN Xiaoping
2007-01-01
In order to investigate the possibility of overexpression of Twist in primary liver cancer (PLC), the Twist expression was detected by using immunohistochemical analysis and RT-PCR assay in 45 patients with PLC. Control tissues were obtained from 9 patients with liver hemangioma. It was found that in 36 (80.0%) out of 45 PLC patients, cancerous regions showed positive cytoplasm and nucleus staining for Twist with a diffuse pattern. In noncancerous adjacent areas and control liver tissues, the expression of Twist was 57.8% and 22.2% respectively. The results of RT-PCR assay re- vealed that the expression of Twist was stronger in the cancerous tissues than that in the noncancer- ous adjacent tissues. It was suggested that the expression of Twist was up-regulated in PLC, which play an important role in the progression of PLC.
Twisted exponential sums of polynomials in one variable
Institute of Scientific and Technical Information of China (English)
无
2010-01-01
The twisted T-adic exponential sums associated to a polynomial in one variable are studied.An explicit arithmetic polygon in terms of the highest two exponents of the polynomial is proved to be a lower bound of the Newton polygon of the C-function of the twisted T-adic exponential sums.This bound gives lower bounds for the Newton polygon of the L-function of twisted p-power order exponential sums.
Negative Regulatory Role of TWIST1 on SNAIL Gene Expression.
Forghanifard, Mohammad Mahdi; Ardalan Khales, Sima; Farshchian, Moein; Rad, Abolfazl; Homayouni-Tabrizi, Masoud; Abbaszadegan, Mohammad Reza
2017-01-01
Epithelial-mesenchymal transition (EMT) is crucial for specific morphogenetic movements during embryonic development as well as pathological processes of tumor cell invasion and metastasis. TWIST and SNAIL play vital roles in both developmental and pathological EMT. Our aim in this study was to investigate the functional correlation between TWIST1 and SNAIL in human ESCC cell line (KYSE-30). The packaging cell line GP293T was cotransfected with either control retroviral pruf-IRES-GFP plasmid or pruf-IRES-GFP-hTWIST1 and pGP plasmid. The KYSE-30 ESCC cells were transduced with produced viral particles and examined with inverted fluorescence microscope. DNA was extracted from transduced KYSE-30 cells and analyzed for copy number of integrated retroviral sequences in the target cell genome. The concentration of retroviral particles was determined by Real-time PCR. After RNA extraction and cDNA synthesis, the mRNA expression of TWIST1 and SNAIL was assessed by comparative real-time PCR amplification. Ectopic expression of TWIST1 in KYSE-30, dramatically reduces SNAIL expression. Retroviral transduction enforced TWIST1 overexpression in GFP-hTWIST1 nearly 9 folds in comparison with GFP control cells, and interestingly, this TWIST1 enforced expression caused a - 7 fold decrease of SNAIL mRNA expression in GFP-hTWIST1 compared to GFP control cells. Inverse correlation of TWIST1 and SNAIL mRNA levels may introduce novel molecular gene expression pathway controlling EMT process during ESCC aggressiveness and tumorigenesis. Consequently, these data extend the spectrum of biological activities of TWIST1 and propose that therapeutic repression of TWIST1 may be an effective strategy to inhibit cancer cell invasion and metastasis.
A twist tale of cancer metastasis and tumor angiogenesis.
Tseng, Jen-Chieh; Chen, Hsiao-Fan; Wu, Kou-Juey
2015-11-01
Twist1 is an evolutionally conserved transcription factor. Originally identified in Drosophila as a key regulator for mesoderm development, it was later implicated in many human diseases, including Saethre-Chotzen syndrome and cancer. Twist1's involvement in cancer has been well recognized. Driven by hypoxia-induced factor-1 (HIF-1), Twist1 has been considered as a proto-oncogene and its overexpression has been observed in a wide variety of human cancers. High expression level of Twist1 is closely related to tumor aggressiveness and metastatic potential. In cancer cells, Twist1 has been shown to function as a key regulator of epithelial-mesenchymal transition (EMT), a critical process for metastasis initiation. Twist1 has also been implicated in maintaining cancer stemness for self-renewal and chemoresistance. This review first summarizes the roles of Twist1 in embryo development and Saethre-Chotzen syndrome followed by a discussion of Twist1's critical functions in cancer. In particular, the review focuses on the recent discovery of Twist1's capability to promote endothelial transdifferentiation of cancer cells beyond EMT.
Twist1 activity thresholds define multiple functions in limb development
Krawchuk, Dayana; Weiner, Shoshana J; Chen, You-Tzung; Lu, Benson; Costantini, Frank; Behringer, Richard R.; Laufer, Ed
2010-01-01
The basic helix-loop-helix transcription factor Twist1 is essential for normal limb development. Twist1−/− embryos die at midgestation. However, studies on early limb buds found that Twist1−/− mutant limb mesenchyme has an impaired response to FGF signaling from the apical ectodermal ridge, which disrupts the feedback loop between the mesenchyme and AER, and reduces and shifts anteriorly Shh expression in the zone of polarizing activity. We have combined Twist1 null, hypomorph and conditional...
Nematic twist cell: Strong chirality induced at the surfaces
Lin, Tzu-Chieh; Nemitz, Ian R.; Pendery, Joel S.; Schubert, Christopher P. J.; Lemieux, Robert P.; Rosenblatt, Charles
2013-04-01
A nematic twist cell having a thickness gradient was filled with a mixture containing a configurationally achiral liquid crystal (LC) and chiral dopant. A chiral-based linear electrooptic effect was observed on application of an ac electric field. This "electroclinic effect" varied monotonically with d, changing sign at d =d0 where the chiral dopant exactly compensated the imposed twist. The results indicate that a significant chiral electrooptic effect always exists near the surfaces of a twist cell containing molecules that can be conformationally deracemized. Additionally, this approach can be used to measure the helical twisting power (HTP) of a chiral dopant in a liquid crystal.
Optical Möbius strips and twisted ribbon cloaks.
Freund, Isaac
2014-02-15
Optical Möbius strips that surround points of circular polarization, C points, in a generic three-dimensional optical field are cloaked by lines of twisted ribbons attached to the C points. When cloaking occurs, the observable signed twist index that counts the number of half-twists (one or three), and also measures the handedness (right or left), of a generic Möbius strip is determined by the twisted ribbon cloaks. Although some cloaks can be detached, they can never all be removed.
Twisted rudder for reducing fuel-oil consumption
Directory of Open Access Journals (Sweden)
Kim Jung-Hun
2014-09-01
Full Text Available Three twisted rudders fit for large container ships have been developed; 1 the Z-twisted rudder that is an asymmetry type taking into consideration incoming flow angles of the propeller slipstream, 2 the ZB-twisted rudder with a rudder bulb added onto the Z-twisted rudder, and 3 the ZB-F twisted rudder with a rudder fin attached to the ZB-twisted rudder. The twisted rudders have been designed computationally with the hydrodynamic characteristics in a self-propulsion condition in mind. The governing equation is the Navier-Stokes equations in an unsteady turbulent flow. The turbulence model applied is the Reynolds stress. The calculation was carried out in towing and self-propulsion conditions. The sliding mesh technique was employed to simulate the flow around the propeller. The speed performances of the ship with the twisted rudders were verified through model tests in a towing tank. The twisted versions showed greater performance driven by increased hull efficiency from less thrust deduction fraction and more effective wake fraction and decreased propeller rotating speed
Finite-dimensional representations of twisted hyper loop algebras
Bianchi, Angelo
2012-01-01
We investigate the category of finite-dimensional representations of twisted hyper loop algebras, i.e., the hyperalgebras associated to twisted loop algebras over finite-dimensional simple Lie algebras. The main results are the classification of the irreducible modules, the definition of the universal highest-weight modules, called the Weyl modules, and, under a certain mild restriction on the characteristic of the ground field, a proof that the simple modules and the Weyl modules for the twisted hyper loop algebras are isomorphic to appropriate simple and Weyl modules for the non-twisted hyper loop algebras, respectively, via restriction of the action.
Modelling of Nonthermal Microwave Emission From Twisted Magnetic Loops
Sharykin, I N
2016-01-01
Microwave gyrosynchrotron radio emission generated by nonthermal electrons in twisted magnetic loops is modelled using the recently developed simulation tool GX Simulator. We consider isotropic and anisotropic pitch-angle distributions. The main scope of the work is to understand impact of the magnetic field twisted topology on resulted radio emission maps. We have found that nonthermal electrons inside twisted magnetic loops produce gyrosynchrotron radio emission with peculiar polarization distribution. The polarization sign inversion line is inclined relatively to the axis of the loop. Radio emission source is more compact in the case of less twisted loop, considering anisotropic pitch-angle distribution of nonthermal electrons.
Institute of Scientific and Technical Information of China (English)
陈显福
2014-01-01
Variable cross-section hol ow thin-walled pier has the obvious superiority and good economy, and can use less material to obtain larger sectional resistance moment which is often used by mountain bridge engineering. Taking the Yujiagou1# bridge as the example, this article introduces the construction technology of variable cross-section hol ow thin-wal ed pier, and provides reference for similar engineering construction.%变截面空心薄壁方墩具有明显的优越性和较好的经济性，可以用较少的材料获取较大的截面抵抗矩，这种技术常常被山区、深沟建桥的工程所采用。本文以余家沟1号大桥为例，介绍了变截面空心薄壁方墩施工技术，可为类似工程施工提供借鉴。
Die-casting Process for High-performance Thin-wall Casting of Aluminum Alloy%高性能薄壁铝合金铸件的压铸
Institute of Scientific and Technical Information of China (English)
尹志鹏; 宋朝辉; 李义平
2016-01-01
采用本公司发明的专利技术制备了铝合金浆料。概述了高性能薄壁多抽芯铝合金铸件的半固态流变压铸生产过程。经半固态流变压铸生产的铝合金铸件的显微组织致密，无气孔、缩松和夹杂，T6热处理后的力学性能比普通压铸件提高了40%左右。%Aluminum alloy paste was fabricated with a patent technology invented by Cixi Alt Advanced Materials Co.. The semi-solid rheocasting process for high-performance multi-core thin-wall aluminum alloy castings was outlined. The aluminum alloy castings produced by the semi-solid rheologic die-casting technology exhibited dense structure in which there are not any pore, porosity and inclusion, and after being T6 treated its mechanical properties were 40% higher that of common die castings.
Directory of Open Access Journals (Sweden)
V. González Fernández
2000-03-01
Full Text Available Este trabajo está relacionado con el estudio del comportamiento de estructuras de paredes delgadas sometidas a presiónexterna, cuando aparecen imperfecciones geométricas, inherentes a los procesos de fabricación, que afectan los valores delas cargas críticas. En el mismo se describen comportamientos pos críticos típicos y su importancia en el estudio de losefectos de estas imperfecciones, así como formulaciones aproximadas, tomando en consideración la necesidad delconocimiento de las posibles trayectorias de equilibrio por parte del ingeniero en el análisis y toma de decisiones acerca deuna estructura.Palabras claves: Estructura, bóveda, estabilidad, fallas estructurales, trayectorias de equilibrio.________________________________________________________________________________AbstractThis work deals with the study of the behavior of thin walled structures external pressure, when in the same appear geometricimperfections that are inherent to the process of manufacturing and affect the values of critical loads. In the same, post criticaltypical behaviors and its importance in the study of the effects of the geometric imperfections are described, as well asapproximate formulations taking in consideration the possible trajectories of equilibrium in the structure analysis re.Key words: structures, shells, stability, structural failures, trajectories of equilibrium.
一種大直徑薄壁輸水管道敷設的計算方法%A Calculation Method of Laying Thin-walled Water Pipelines with Large Diameter
Institute of Scientific and Technical Information of China (English)
孟强; 吴云云
2014-01-01
大陆输水成为东南沿海诸岛屿供水主要途径，大直径薄壁跨海输水管道敷设成为主要技术难题。采用奇异摄动法，求含小参数微分方程的解析解，并给出了一种简洁的非线性方程组计算方法。以“舟山市大陆引水二期工程”为例，通过数值计算与现场陆上试验比对，验证了非线性方程计算方法的合理性。%Continental water has become a main way of water supply to southeast coastal islands .How to laying thin-walled cross-sea water pipelines with large diameter becomes a major technical problem .Using the singular perturbation method and obtaining the analytical solution of the differential equation containing small parameter , this paper gives a simple calculation method of nonlinear equations .Taking” Zhoushan continent diversion project II” as an example and comparing the numerical calculation with onshore test ,the rationality of the calculation method of nonlinear equations is verified in this paper .
Directory of Open Access Journals (Sweden)
Tao Zhijun
2017-01-01
Full Text Available Warm rotary draw bending (WRDB of large-diameter thin-walled (LDTW Ti–6Al–4V tube is a multi-nonlinear thermo-mechanical coupled process. Due to the high-cost, energy-wasting and long-term, the traditional physical experiments based on “trial and error” are no longer suitable for the WRBD process. Considering the non-uniform local heating and multi-tool constraints, a thermal–mechanical coupled 3D FE model of complete WRDB process for LDTW Ti–6Al–4V tube is established on ABAQUS as heating-bending-unloading three-stage. The FE models could predict the overall temperature distribution, describe thermo-mechanical bending deformation considering a modified Johnson–Cook model, and simulate the heating-bending-springback-cooling process. On that basis, the temperature distributions on both tube and dies under various heating schemes are compared, and the optimal heating scheme is determined on the basis of forming quality and efficiency. Combined with the experiments of WRDB, the optimal heating scheme and the established FE models are verified. In conclusion, the FE simulation provides a replacement of physical experiment and a convenient method of deformation prediction for WRDB of LDTW Ti–6Al–4V tube.
Institute of Scientific and Technical Information of China (English)
林勇; 罗育果; 汤立民
2012-01-01
The deformation of aeronautical component in CNC machining is a bottle-neck issue in aviation industry.Based on analysis of machining deformation principle ,a new machining deformation control methodology,which applies removing perpetual deformation,controlling machining stresses,loading preliminary stresses and rolling straightening synthetically,is proposed in it.The method has been applied in machining a thin-wall arc shaped in a large aircraft manufacturer of china,which result shows that this method is practical.%航空结构件在数控铣削加工过程中的加工变形问题是航空制造领域的共性难题.通过分析零件加工变形机理,综合运用塑性变形消除、加工应力控制、预应力装夹、滚碾校正,形成了一整套加工变形控制方法.该方法已在国内某大型航空企业航空薄壁弧形框数控加工中取得了良好的应用效果.
Institute of Scientific and Technical Information of China (English)
张登祥; 李占杰; B W Schafer
2012-01-01
In current cold-formed thin-walled steel design specifications,buckling information of all the three types,local-plate buckling,distortional buckling and global buckling(or Euler buckling),are desired.From the desire of practical design,the basic theory of constrained finite strip method(cFSM) was systematically introduced and new progress was presented.An emphasis had been put on the associated mechanic assumptions for defining the buckling modes.For these mechanic assumptions,a brand-new view in terms of the definition of buckling modes was illustrated via the static finite element analysis to verify its validity.%现有冷弯薄壁型钢设计规范中需要获知薄壁结构各个模态屈曲特性,如局部板件屈曲、畸变屈曲和整体屈曲。从工程设计需要出发,系统介绍约束有限元条分法的基础理论及进展,并着重阐述其在区分屈曲模态时的相关力学假设。对于由这些力学假设定义的模态是否正确,基于有限元静力分析从一个全新的角度验证其合理性。
Institute of Scientific and Technical Information of China (English)
杨彦芳; 卢献忠; 范晓明
2015-01-01
The heavy rail bearing of thin-walled tall steel castings were produced by the use of lost foam casting. But the problems such as 'vacant shell', collapse of sand and so on,which lead to the lower quality and yield of castings. By improving the casting process, using bottom pouring system to replace the ladder pouring system,using sprue and runner of refractory materials, reducing pouring temperature and degree of negative pressure, and adopting appropriate pouring speed, the quality and yield of heavy rail bearing steel castings were successfully improved. The experience of production is worth promoting.%利用消失模铸造工艺生产了薄壁高大铸钢重轨支座，出现了“空壳”、塌箱等问题，导致其质量和成品率较低。通过改进铸造工艺，改阶梯浇注为底部浇注，采用耐火材料直浇道和横浇道，降低浇注温度和负压度，并采用合适的浇注速度，成功提高了重轨支座铸钢件的质量和成品率，其生产经验值得推广。
Equilibrium shapes of twisted magnetic filaments
Energy Technology Data Exchange (ETDEWEB)
Belovs, Mihails; Cirulis, Teodors; Cebers, Andrejs [University of Latvia, Zellu 8, LV-1002 (Latvia)], E-mail: aceb@tesla.sal.lv
2009-06-12
It is shown that ferromagnetic filaments with free and unclamped ends undergo buckling instabilities under the action of twist. Solutions of nonlinear equations describing the buckled shapes are found, and it is shown that the transition to the buckled shape is subcritical if the magnetization is parallel to the field and supercritical when the magnetization of the straight filament is opposite to the external field. Solutions with the localized curvature distribution are found in the case of long filaments. The class of solutions corresponding to helices is described, and the behavior of coiled ferromagnetic and superparamagnetic filaments is compared.
Non-destructive identification of twisted light.
Li, Pengyun; Wang, Bo; Song, Xinbing; Zhang, Xiangdong
2016-04-01
The non-destructive identification of the orbital angular momentum (OAM) is essential to various applications in the optical information processing. Here, we propose and demonstrate experimentally an efficient method to identify non-destructively the OAM by using a modified Mach-Zehnder interferometer. Our schemes are applicable not only to the case with integer charges, but also to optical vortices with noninteger charges. Our Letter presents the first experimental demonstration of the non-destructive identification of twisted light with integer or noninteger topological charges, which has potential applications in the OAM-based data transmission for optical communications.
Instanton corrections to twist-two operators
Alday, Luis F
2016-01-01
We present the calculation of the leading instanton contribution to the scaling dimensions of twist-two operators with arbitrary spin and to their structure constants in the OPE of two half-BPS operators in $\\mathcal N=4$ SYM. For spin-two operators we verify that, in agreement with $\\mathcal N=4$ superconformal Ward identities, the obtained expressions coincide with those for the Konishi operator. For operators with high spin we find that the leading instanton correction vanishes. This arises as the result of a rather involved calculation and requires a better understanding.
Berry phase transition in twisted bilayer graphene
Rode, Johannes C.; Smirnov, Dmitri; Schmidt, Hennrik; Haug, Rolf J.
2016-09-01
The electronic dispersion of a graphene bilayer is highly dependent on rotational mismatch between layers and can be further manipulated by electrical gating. This allows for an unprecedented control over electronic properties and opens up the possibility of flexible band structure engineering. Here we present novel magnetotransport data in a twisted bilayer, crossing the energetic border between decoupled monolayers and coupled bilayer. In addition a transition in Berry phase between π and 2π is observed at intermediate magnetic fields. Analysis of Fermi velocities and gate induced charge carrier densities suggests an important role of strong layer asymmetry for the observed phenomena.
Quantum mass correction for the twisted kink
Pawellek, Michael
2008-01-01
We present an analytic result for the 1-loop quantum mass correction in semiclassical quantization for the twisted \\phi^4 kink on S^1 without explicit knowledge of the fluctuation spectrum. For this purpose we use the contour integral representation of the spectral zeta function. By solving the Bethe ansatz equations for the n=2 Lame equation we obtain an analytic expression for the corresponding spectral discriminant. We discuss the renormalization issues of this model. An energetically preferred size for the compact space is finally obtained.
DEFF Research Database (Denmark)
2014-01-01
Memory Pieces are open compositions to be realised solo by an improvising musicians. See more about my composition practise in the entry "Composition - General Introduction". Caution: streaming the sound files will in some cases only provide a few minutes' sample. Please DOWNLOAD them to hear them...
DEFF Research Database (Denmark)
Bergstrøm-Nielsen, Carl
2010-01-01
New Year is an open composition to be realised by improvising musicians. It is included in "From the Danish Seasons" (see under this title). See more about my composition practise in the entry "Composition - General Introduction". This work is licensed under a Creative Commons "by-nc" License. You...
DEFF Research Database (Denmark)
Bergstrøm-Nielsen, Carl
2011-01-01
Strategies are open compositions to be realised by improvising musicians. See more about my composition practise in the entry "Composition - General Introduction". Caution: streaming the sound files will in some cases only provide a few minutes' sample. Please DOWNLOAD them to hear them in full...
Effective cross-section distribution of anisotropic piezocomposite actuators for wing twist
Cesnik, Carlos E. S.; Park, Ryan S.; Palacios, Rafael
2003-08-01
The twist actuation of piezocomposite actuators embedded in a composite wing is numerically investigated. Parametric analysis of the actuation authority is conducted for wing cross sections with double and triple cells, considering different distributions of anisotropic piezocomposite actuators. The variational asymptotic beam cross-sectional (VABS) analysis is used to compute the airfoil stiffness, actuation force and mass properties. As a result, the regions with the highest specific actuation are determined and a cost-effective way of adding active material to the cross section is proposed. Results indicate that 50% of the maximum mass penalty associated with the addition of active plies is responsible for generating approximately 80% of the maximum available induced twist.
Needleless electrospinning with twisted wire spinneret.
Holopainen, Jani; Penttinen, Toni; Santala, Eero; Ritala, Mikko
2015-01-16
A needleless electrospinning setup named 'Needleless Twisted Wire Electrospinning' was developed. The polymer solution is electrospun from the surface of a twisted wire set to a high voltage and collected on a cylindrical collector around the wire. Multiple Taylor cones are simultaneously self-formed on the downward flowing solution. The system is robust and simple with no moving parts aside from the syringe pump used to transport the solution to the top of the wire. The structure and process parameters of the setup and the results on the preparation of polyvinyl pyrrolidone (PVP), hydroxyapatite (HA) and bioglass fibers with the setup are presented. PVP fiber sheets with areas of 40 × 120 cm(2) and masses up to 1.15 g were prepared. High production rates of 5.23 g h(-1) and 1.40 g h(-1) were achieved for PVP and HA respectively. The major limiting factor of the setup is drying of the polymer solution on the wire during the electrospinning process which will eventually force to interrupt the process for cleaning of the wire. Possible solutions to this problem and other ways to develop the setup are discussed. The presented system provides a simple way to increase the production rate and area of fiber sheet as compared with the conventional needle electrospinning.
Holographic generation of highly twisted electron beams
Grillo, Vincenzo; Mafakheri, Erfan; Frabboni, Stefano; Karimi, Ebrahim; Boyd, Robert W
2014-01-01
Free electrons can possess an intrinsic orbital angular momentum, similar to those in an electron cloud, upon free-space propagation. The wavefront corresponding to the electron's wavefunction forms a helical structure with a number of twists given by the \\emph{angular speed}. Beams with a high number of twists are of particular interest because they carry a high magnetic moment about the propagation axis. Among several different techniques, electron holography seems to be a promising approach to shape a \\emph{conventional} electron beam into a helical form with large values of angular momentum. Here, we propose and manufacture a nano-fabricated phase hologram for generating a beam of this kind with an orbital angular momentum up to 200$\\hbar$. Based on a novel technique the value of orbital angular momentum of the generated beam are measured, then compared with simulations. Our work, apart from the technological achievements, may lead to a way of generating electron beams with a high quanta of magnetic momen...
Twisting the [ital N]=2 string
Energy Technology Data Exchange (ETDEWEB)
Ketov, S.V.; Lechtenfeld, O. (Institut fuer Theoretische Physik, Universitaet Hannover, Appelstrasse 2, 30167 Hannover (Germany)); Parkes, A.J. (Department of Artificial Intelligence, 80 South Bridge, Edinburgh EH1 9HN (United Kingdom))
1995-03-15
The most general homogeneous monodromy conditions in [ital N]=2 string theory are classified in terms of the conjugacy classes of the global symmetry group U(1,1)[direct product][ital openZ][sub 2]. For classes which generate a discrete subgroup [Gamma], the corresponding target space backgrounds [ital openC][sup 1,1]/[Gamma] include half spaces, complex orbifolds, and tori. We propose a generalization of the intercept formula to matrix-valued twists, but find massless physical states only for [Gamma]=[ital open]1 (untwisted) and [Gamma]=[ital openZ][sub 2] (in the manner of Mathur and Mukhi), as well as for [Gamma] being a parabolic element of U(1,1). In particular, the 16 [ital openZ][sub 2]-twisted sectors of the [ital N]=2 string are investigated, and the corresponding ground states are identified via bosonization and BRST cohomology. We find enough room for an extended multiplet of spacetime'' supersymmetry, with the number of supersymmetries being dependent on global spacetime'' topology. However, world-sheet locality for the chiral vertex operators does not permit interactions among all massless spacetime'' fermions.
Twisting Fluorescence through Extrinsic Chiral Antennas.
Yan, Chen; Wang, Xiaolong; Raziman, T V; Martin, Olivier J F
2017-03-22
Plasmonic antennas and planar structures have been undergoing intensive developments in order to control the scattering and absorption of light. One specific class, extrinsic chiral surfaces, that does not possess 2-fold rotational symmetry exhibits strong asymmetric transmission for different circular polarizations under obliquely incident illumination. In this work, we show that the design of those surfaces can be optimized with complex multipolar resonances in order to twist the fluorescence emission from nearby molecules. While this emission is usually dipolar and linearly polarized, the interaction with these resonances twists it into a multipolar radiation pattern with opposite helicity in different directions. The proposed structure maximizes this effect and provides control over the polarization of light. Splitting of left- and right-handed circularly polarized light is experimentally obtained in the backward direction. These results highlight the intricate interplay between the near-field absorption and the far-field scattering of a plasmonic nanostructure and are further used for modifying the emission of incoherent quantum sources. Our finding can potentially lead to the development of polarization- and angle-resolved ultracompact optical devices.
Twisted Alexander polynomials of hyperbolic knots
Dunfield, Nathan M; Jackson, Nicholas
2011-01-01
We study a twisted Alexander polynomial naturally associated to a hyperbolic knot in an integer homology 3-sphere via a lift of the holonomy representation to SL(2, C). It is an unambiguous symmetric Laurent polynomial whose coefficients lie in the trace field of the knot. It contains information about genus, fibering, and chirality, and moreover is powerful enough to sometimes detect mutation. We calculated this invariant numerically for all 313,209 hyperbolic knots in S^3 with at most 15 crossings, and found that in all cases it gave a sharp bound on the genus of the knot and determined both fibering and chirality. We also study how such twisted Alexander polynomials vary as one moves around in an irreducible component X_0 of the SL(2, C)-character variety of the knot group. We show how to understand all of these polynomials at once in terms of a polynomial whose coefficients lie in the function field of X_0. We use this to help explain some of the patterns observed for knots in S^3, and explore a potential...
Twisted geometries, twistors and conformal transformations
Långvik, Miklos
2016-01-01
The twisted geometries of spin network states are described by simple twistors, isomorphic to null twistors with a time-like direction singled out. The isomorphism depends on the Immirzi parameter, and reduces to the identity when the parameter goes to infinity. Using this twistorial representation we study the action of the conformal group SU(2,2) on the classical phase space of loop quantum gravity, described by twisted geometry. The generators of translations and conformal boosts do not preserve the geometric structure, whereas the dilatation generator does. It corresponds to a 1-parameter family of embeddings of T*SL(2,C) in twistor space, and its action preserves the intrinsic geometry while changing the extrinsic one - that is the boosts among polyhedra. We discuss the implication of this action from a dynamical point of view, and compare it with a discretisation of the dilatation generator of the continuum phase space, given by the Lie derivative of the group character. At leading order in the continuu...
How the embryonic brain tube twists
Chen, Zi; Guo, Qiaohang; Forsch, Nickolas; Taber, Larry
2014-03-01
During early development, the tubular brain of the chick embryo undergoes a combination of progressive ventral bending and rightward torsion. This deformation is one of the major organ-level symmetry-breaking events in development. Available evidence suggests that bending is caused by differential growth, but the mechanism for torsion remains poorly understood. Since the heart almost always loops in the same direction that the brain twists, researchers have speculated that heart looping affects the direction of brain torsion. However, direct evidence is virtually nonexistent, nor is the mechanical origin of such torsion understood. In our study, experimental perturbations show that the bending and torsional deformations in the brain are coupled and that the vitelline membrane applies an external load necessary for torsion to occur. In addition, the asymmetry of the looping heart gives rise to the chirality of the twisted brain. A computational model is used to interpret these findings. Our work clarifies the mechanical origins of brain torsion and the associated left-right asymmetry, reminiscent of D'Arcy Thompson's view of biological form as ``diagram of forces''.
Structure of twisted and buckled bilayer graphene
Jain, Sandeep K.; Juričić, Vladimir; Barkema, Gerard T.
2017-03-01
We study the atomic structure of twisted bilayer graphene, with very small mismatch angles (θ ∼ {0.28}0), a topic of intense recent interest. We use simulations, in which we combine a recently presented semi-empirical potential for single-layer graphene, with a new term for out-of-plane deformations, (Jain et al 2015 J. Phys. Chem. C 119 9646) and an often-used interlayer potential (Kolmogorov et al 2005 Phys. Rev. B 71 235415). This combination of potentials is computationally cheap but accurate and precise at the same time, allowing us to study very large samples, which is necessary to reach very small mismatch angles in periodic samples. By performing large scale atomistic simulations, we show that the vortices appearing in the Moiré pattern in the twisted bilayer graphene samples converge to a constant size in the thermodynamic limit. Furthermore, the well known sinusoidal behavior of energy no longer persists once the misorientation angle becomes very small (θ \\lt {1}0). We also show that there is a significant buckling after the relaxation in the samples, with the buckling height proportional to the system size. These structural properties have direct consequences on the electronic and optical properties of bilayer graphene.
Cellularity of diagram algebras as twisted semigroup algebras
Wilcox, Stewart
2010-01-01
The Temperley-Lieb and Brauer algebras and their cyclotomic analogues, as well as the partition algebra, are all examples of twisted semigroup algebras. We prove a general theorem about the cellularity of twisted semigroup algebras of regular semigroups. This theorem, which generalises a recent result of East about semigroup algebras of inverse semigroups, allows us to easily reproduce the cellularity of these algebras.
Behaviour at infinity of solutions of twisted convolution equations
Energy Technology Data Exchange (ETDEWEB)
Volchkov, Valerii V; Volchkov, Vitaly V [Donetsk National University, Donetsk (Ukraine)
2012-02-28
We obtain a precise characterization of the minimal rate of growth at infinity of non-trivial solutions of twisted convolution equations in unbounded domains of C{sup n}. As an application, we obtain definitive versions of the two-radii theorem for twisted spherical means.
On the commutator length of a Dehn twist
Szepietowski, Blazej
2010-01-01
We show that on a nonorientable surface of genus at least 7 any power of a Dehn twist is equal to a single commutator in the mapping class group and the same is true, under additional assumptions, for the twist subgroup, and also for the extended mapping class group of an orientable surface of genus at least 3.
Quadratic Twists of Rigid Calabi–Yau Threefolds Over
DEFF Research Database (Denmark)
Gouvêa, Fernando Q.; Kiming, Ian; Yui, Noriko
2013-01-01
We consider rigid Calabi–Yau threefolds defined over Q and the question of whether they admit quadratic twists. We give a precise geometric definition of the notion of a quadratic twists in this setting. Every rigid Calabi–Yau threefold over Q is modular so there is attached to it a certain newfo...
Design optimization of a twist compliant mechanism with nonlinear stiffness
Tummala, Y.; Frecker, M. I.; Wissa, A. A.; Hubbard, J. E., Jr.
2014-10-01
A contact-aided compliant mechanism called a twist compliant mechanism (TCM) is presented in this paper. This mechanism has nonlinear stiffness when it is twisted in both directions along its axis. The inner core of the mechanism is primarily responsible for its flexibility in one twisting direction. The contact surfaces of the cross-members and compliant sectors are primarily responsible for its high stiffness in the opposite direction. A desired twist angle in a given direction can be achieved by tailoring the stiffness of a TCM. The stiffness of a compliant twist mechanism can be tailored by varying thickness of its cross-members, thickness of the core and thickness of its sectors. A multi-objective optimization problem with three objective functions is proposed in this paper, and used to design an optimal TCM with desired twist angle. The objective functions are to minimize the mass and maximum von-Mises stress observed, while minimizing or maximizing the twist angles under specific loading conditions. The multi-objective optimization problem proposed in this paper is solved for an ornithopter flight research platform as a case study, with the goal of using the TCM to achieve passive twisting of the wing during upstroke, while keeping the wing fully extended and rigid during the downstroke. Prototype TCMs have been fabricated using 3D printing and tested. Testing results are also presented in this paper.
Twisted tubular photobioreactor fluid dynamics evaluation for energy consumption minimization
Gómez-Pérez, C.A.; Espinosa Oviedo, J.J.; Montenegro Ruiz, L.C.; Boxtel, van A.J.B.
2017-01-01
This paper discusses a new tubular PhotoBioReactor (PBR) called twisted tubular PBR. The geometry of a twisted tubular PBR induces swirl mixing to guarantee good exposure of microalgae to Light-Dark (LD) cycles and to the nutrients and dissolved CO 2 . The paper analyses the energy uptake for fluid
Resonances and higher twist in polarized lepton-nucleon scattering
Edelmann, J; Kaiser, N; Weise, W
2000-01-01
We present a detailed analysis of resonance contributions in the context of higher twist effects in the moments of the proton spin structure function g_1. For each of these moments, it is found that there exists a characteristic Q^2 region in which (perturbative) higher twist corrections coexist with (non-perturbative) resonance contribution of comparable magnitude.
Twisted Fock representations of noncommutative Kähler manifolds
Sako, Akifumi; Umetsu, Hiroshi
2016-09-01
We introduce twisted Fock representations of noncommutative Kähler manifolds and give their explicit expressions. The twisted Fock representation is a representation of the Heisenberg like algebra whose states are constructed by applying creation operators to a vacuum state. "Twisted" means that creation operators are not Hermitian conjugate of annihilation operators in this representation. In deformation quantization of Kähler manifolds with separation of variables formulated by Karabegov, local complex coordinates and partial derivatives of the Kähler potential with respect to coordinates satisfy the commutation relations between the creation and annihilation operators. Based on these relations, we construct the twisted Fock representation of noncommutative Kähler manifolds and give a dictionary to translate between the twisted Fock representations and functions on noncommutative Kähler manifolds concretely.
Landau damping of Langmuir twisted waves with kappa distributed electrons
Energy Technology Data Exchange (ETDEWEB)
Arshad, Kashif, E-mail: kashif.arshad.butt@gmail.com; Aman-ur-Rehman [Pakistan Institute of Engineering and Applied Sciences, P. O. Nilore, Islamabad 45650 (Pakistan); Mahmood, Shahzad [Pakistan Institute of Engineering and Applied Sciences, P. O. Nilore, Islamabad 45650 (Pakistan); Theoretical Physics Division, PINSTECH, P.O. Nilore, Islamabad 44000 (Pakistan)
2015-11-15
The kinetic theory of Landau damping of Langmuir twisted modes is investigated in the presence of orbital angular momentum of the helical (twisted) electric field in plasmas with kappa distributed electrons. The perturbed distribution function and helical electric field are considered to be decomposed by Laguerre-Gaussian mode function defined in cylindrical geometry. The Vlasov-Poisson equation is obtained and solved analytically to obtain the weak damping rates of the Langmuir twisted waves in a nonthermal plasma. The strong damping effects of the Langmuir twisted waves at wavelengths approaching Debye length are also obtained by using an exact numerical method and are illustrated graphically. The damping rates of the planar Langmuir waves are found to be larger than the twisted Langmuir waves in plasmas which shows opposite behavior as depicted in Fig. 3 by J. T. Mendoça [Phys. Plasmas 19, 112113 (2012)].
Analysis list: Twist1 [Chip-atlas[Archive
Lifescience Database Archive (English)
Full Text Available Twist1 Embryo,Neural + mm9 http://dbarchive.biosciencedbc.jp/kyushu-u/mm9/target/Tw...ist1.1.tsv http://dbarchive.biosciencedbc.jp/kyushu-u/mm9/target/Twist1.5.tsv http://dbarchive.biosciencedbc....jp/kyushu-u/mm9/target/Twist1.10.tsv http://dbarchive.biosciencedbc.jp/kyushu-u/mm9/colo/Twist1.Embryo.tsv,http://dbarchive.bioscien...cedbc.jp/kyushu-u/mm9/colo/Twist1.Neural.tsv http://dbarchive.bioscience...dbc.jp/kyushu-u/mm9/colo/Embryo.gml,http://dbarchive.biosciencedbc.jp/kyushu-u/mm9/colo/Neural.gml ...
Twisted Fock Representations of Noncommutative K\\"ahler Manifolds
Sako, Akifumi
2016-01-01
We introduce twisted Fock representations of noncommutative K\\"ahler manifolds and give their explicit expressions. The twisted Fock representation is a representation of the Heisenberg like algebra whose states are constructed by acting creation operators on a vacuum state. "Twisted" means that creation operators are not hermitian conjugate of annihilation operators in this representation. In deformation quantization of K\\"ahler manifolds with separation of variables formulated by Karabegov, local complex coordinates and partial derivatives of the K\\"ahler potential with respect to coordinates satisfy the commutation relations between the creation and annihilation operators. Based on these relations, we construct the twisted Fock representation of noncommutative K\\"ahler manifolds and give a dictionary to translate between the twisted Fock representations and functions on noncommutative K\\"ahler manifolds concretely.
On the performance analysis of Savonius rotor with twisted blades
Energy Technology Data Exchange (ETDEWEB)
Saha, U.K.; Rajkumar, M. Jaya [Department of Mechanical Engineering, Indian Institute of Technology Guwahati, Guwahati-781 039 (India)
2006-09-15
The present investigation is aimed at exploring the feasibility of twisted bladed Savonius rotor for power generation. The twisted blade in a three-bladed rotor system has been tested in a low speed wind tunnel, and its performance has been compared with conventional semicircular blades (with twist angle of 0{sup o}). Performance analysis has been made on the basis of starting characteristics, static torque and rotational speed. Experimental evidence shows the potential of the twisted bladed rotor in terms of smooth running, higher efficiency and self-starting capability as compared to that of the conventional bladed rotor. Further experiments have been conducted in the same setup to optimize the twist angle. (author)
Institute of Scientific and Technical Information of China (English)
陆森强; 方有珍
2016-01-01
To study the hysteretic behavior of partially encased composite ( PEC) columns fabricated with thin-walled channel built-up section and steel beams median joint with welded split-tee and pretension through-out high strength bolted connections, one specimen was designed and fabricated by 1∶1.6 scale which represented the median joint. The pseudo-static test for the specimen was conducted and ABAQUS software was simulated the test and to verify the rationality of the FE model.By comparison of the hysteretic behaviors, energy-dissipation capacity and failure mode, the results showed that through-out bolts exhibited partial self-centering function and effectively realized the force-transfer mechanism of concrete equivalent strut in the panel zone;the failure mode primary induced by plastic hinge formed in the steel beam section near the end of split-tee web because of strengthening and the rotation angles of the joint all surpassed 0.02 rad.%为研究采用预拉对穿螺栓的薄钢板部分外包组合截面（ PEC）柱－钢梁中节点T形件焊接连接的滞回性能，按照1∶1.6缩尺设计制作了1个中节点试件，对其进行低周循环荷载试验，并采用有限元软件ABAQUS进行数值模拟验证，对比分析试件的滞回曲线、耗能能力和破坏模式。研究结果显示：预拉对穿螺栓具有部分自复位功效，且较好实现了混凝土斜压带传力机理；所有试件破坏模式均由于T形件对梁端加强而使梁截面塑性铰的出现位置向T形件腹板尾部附近梁截面转移，且所有试件达到破坏时，节点转角均超过了0.02 rad。
Twist1 activity thresholds define multiple functions in limb development.
Krawchuk, Dayana; Weiner, Shoshana J; Chen, You-Tzung; Lu, Benson C; Costantini, Frank; Behringer, Richard R; Laufer, Ed
2010-11-01
The basic helix-loop-helix transcription factor Twist1 is essential for normal limb development. Twist1(-/-) embryos die at midgestation. However, studies on early limb buds found that Twist1(-/-) mutant limb mesenchyme has an impaired response to FGF signaling from the apical ectodermal ridge, which disrupts the feedback loop between the mesenchyme and AER, and reduces and shifts anteriorly Shh expression in the zone of polarizing activity. We have combined Twist1 null, hypomorph and conditional alleles to generate a Twist1 allelic series that survives to birth. As Twist1 activity is reduced, limb skeletal defects progress from preaxial polydactyly to girdle reduction combined with hypoplasia, aplasia or mirror symmetry of all limb segments. With reduced Twist1 activity there is striking and progressive upregulation of ectopic Shh expression in the anterior of the limb, combined with an anterior shift in the posterior Shh domain, which is expressed at normal intensity, and loss of the posterior AER. Consequently limb outgrowth is initially impaired, before an ectopic anterior Shh domain expands the AER, promoting additional growth and repatterning. Reducing the dosage of FGF targets of the Etv gene family, which are known repressors of Shh expression in anterior limb mesenchyme, strongly enhances the anterior skeletal phenotype. Conversely this and other phenotypes are suppressed by reducing the dosage of the Twist1 antagonist Hand2. Our data support a model whereby multiple Twist1 activity thresholds contribute to early limb bud patterning, and suggest how particular combinations of skeletal defects result from differing amounts of Twist1 activity.
Aeromechanical Evaluation of Smart-Twisting Active Rotor
Lim, Joon W.; Boyd, D. Douglas, Jr.; Hoffman, Frauke; van der Wall, Berend G.; Kim, Do-Hyung; Jung, Sung N.; You, Young H.; Tanabe, Yasutada; Bailly, Joelle; Lienard, Caroline; Delrieux, Yves
2014-01-01
An investigation of Smart-Twisting Active Rotor (STAR) was made to assess potential benefits of the current active twist rotor concept for performance improvement, vibration reduction, and noise alleviation. The STAR rotor is a 40% Mach-scaled, Bo105 rotor with an articulated flap-lag hinge at 3.5%R and no pre-cone. The 0-5 per rev active twist harmonic inputs were applied for various flight conditions including hover, descent, moderate to high speed level flights, and slowed rotor high advance ratio. For the analysis, the STAR partners used multiple codes including CAMRAD II, S4, HOST, rFlow3D, elsA, and their associated software. At the high thrust level in hover, the 0 per rev active twist with 80% amplitude increased figure of merit (FM) by 0.01-0.02 relative to the baseline. In descent, the largest BVI noise reduction was on the order of 2 to 5 dB at the 3 per rev active twist. In the high speed case (mu = 0.35), the 2 per rev actuation was found to be the most effective in achieving a power reduction as well as a vibration reduction. At the 2 per rev active twist, total power was reduced by 0.65% at the 60 deg active twist phase, and vibration was reduced by 47.6% at the 45 deg active twist phase. The use of the 2 per rev active twist appears effective for vibration reduction. In the high advance ratio case (mu = 0.70), the 0 per rev actuation appeared to have negligible impact on performance improvement. In summary, computational simulations successfully demonstrated that the current active twist concept provided a significant reduction of the maximum BVI noise in descent, a significant reduction of the vibration in the high speed case, a small improvement on rotor performance in hover, and a negligible impact on rotor performance in forward flight.
Do twisted laser beams evoke nuclear hyperpolarization?
Schmidt, A. B.; Andrews, D. L.; Rohrbach, A.; Gohn-Kreuz, C.; Shatokhin, V. N.; Kiselev, V. G.; Hennig, J.; von Elverfeldt, D.; Hövener, J.-B.
2016-07-01
The hyperpolarization of nuclear spins promises great advances in chemical analysis and medical diagnosis by substantially increasing the sensitivity of nuclear magnetic resonance (NMR). Current methods to produce a hyperpolarized sample, however, are arduous, time-consuming or costly and require elaborate equipment. Recently, a much simpler approach was introduced that holds the potential, if harnessed appropriately, to revolutionize the production of hyperpolarized spins. It was reported that high levels of hyperpolarization in nuclear spins can be created by irradiation with a laser beam carrying orbital angular momentum (twisted light). Aside from these initial reports however, no further experimental verification has been presented. In addition, this effect has so far evaded a critical theoretical examination. In this contribution, we present the first independent attempt to reproduce the effect. We exposed a sample of immersion oil or a fluorocarbon liquid that was placed within a low-field NMR spectrometer to Laguerre-Gaussian and Bessel laser beams at a wavelength of 514.5 nm and various topological charges. We acquired 1H and 19F NMR free induction decay data, either during or alternating with the irradiation that was parallel to B0. We observed an irregular increase in NMR signal in experiments where the sample was exposed to beams with higher values of the topological charge. However, at no time did the effect reach statistical significance of 95%. Given the measured sensitivity of our setup, we estimate that a possible effect did not exceed a hyperpolarization (at 5 mT) of 0.14-6%, depending on the assumed hyperpolarized volume. It should be noted though, that there were some differences between our setup and the previous implementation of the experiment, which may have inhibited the full incidence of this effect. To approach a theoretical description of this effect, we considered the interaction of an electron with a plane wave, which is known to be
Twist-joints and double twist-joints in RNA structure.
Boutorine, Yury I; Steinberg, Sergey V
2012-12-01
Analysis of available RNA crystal structures has allowed us to identify a new family of RNA arrangements that we call double twist-joints, or DTJs. Each DTJ is composed of a double helix that contains two bulges incorporated into different strands and separated from each other by 2 or 3 bp. At each bulge, the double helix is over-twisted, while the unpaired nucleotides of both bulges form a complex network of stacking and hydrogen-bonding with nucleotides of helical regions. In total, we identified 14 DTJ cases, which can be combined in three groups based on common structural characteristics. One DTJ is found in a functional center of the ribosome, another DTJ mediates binding of the pre-tRNA to the RNase P, and two more DTJs form the sensing domains in the glycine riboswitch.
Investigation of Shielding Properties of Yarns, Twisted with Metal Wire
Directory of Open Access Journals (Sweden)
Sandra VARNAITĖ-ŽURAVLIOVA
2014-04-01
Full Text Available The development level of the modern techniques and information technologies creates diverse nature electromagnetic fields and electric field accumulations in the human environment. Electrically conductive textiles that protect against electromagnetic waves and electric charge accumulations can be usable as protective covers for work in computer equipment rooms, measuring stands, air and gas filters and so on. One of the methods used in increase of electrical conductivity in textiles is the development of their specific structures (including the development of threads with the metal component. In this paper, unlike the currently used in the world conductive material production method, where different metal fibres are used as an additives to the main fibre composition in order to create a variety of fibres and yarns, a spun yarn with metal wire was prototyped as samples for this research and the parameters of protective properties of these samples were investigated (such as surface resistivity, vertical resistance, etc.. The protective and shielding properties of woven network with prototyped twisted electro conductive thread with a wire (metal wire diameter of 15 microns were investigated. During the investigation the influence of the following factors, such as conductive fibre composition, electrically conductive thread distribution frequency of the longitudinal and transverse direction, on the protective shielding properties of conductive network were analyzed. The research enabled the assessment of influence of electrically conductive fibre yarn composition and its distribution in the woven mesh on protective shielding properties. DOI: http://dx.doi.org/10.5755/j01.ms.20.1.2492
Investigation of Shielding Properties of Yarns, Twisted with Metal Wire
Directory of Open Access Journals (Sweden)
Sandra VARNAITĖ-ŽURAVLIOVA
2014-04-01
Full Text Available The development level of the modern techniques and information technologies creates diverse nature electromagnetic fields and electric field accumulations in the human environment. Electrically conductive textiles that protect against electromagnetic waves and electric charge accumulations can be usable as protective covers for work in computer equipment rooms, measuring stands, air and gas filters and so on. One of the methods used in increase of electrical conductivity in textiles is the development of their specific structures (including the development of threads with the metal component. In this paper, unlike the currently used in the world conductive material production method, where different metal fibres are used as an additives to the main fibre composition in order to create a variety of fibres and yarns, a spun yarn with metal wire was prototyped as samples for this research and the parameters of protective properties of these samples were investigated (such as surface resistivity, vertical resistance, etc.. The protective and shielding properties of woven network with prototyped twisted electro conductive thread with a wire (metal wire diameter of 15 microns were investigated. During the investigation the influence of the following factors, such as conductive fibre composition, electrically conductive thread distribution frequency of the longitudinal and transverse direction, on the protective shielding properties of conductive network were analyzed. The research enabled the assessment of influence of electrically conductive fibre yarn composition and its distribution in the woven mesh on protective shielding properties. DOI: http://dx.doi.org/10.5755/j01.ms.20.1.2492
Institute of Scientific and Technical Information of China (English)
甘亚南; 周广春; 吴亚平
2011-01-01
以能量变分原理为基础,在曲线箱梁侧向综合考虑了剪力滞后和剪切变形效应的影响,建立了薄壁曲线箱梁的侧向弹性控制微分方程和自然边界条件,获得了相应广义位移的闭合解.论文提出了一种曲线箱梁侧向静力学特性分析的解析法,揭示了各参数之间的内在联系.算例中论文解析解与板壳有限元结果吻合较好,证明了本文方法的有效性,因而更具理论价值和工程实际意义.%Based on the energy variation principle, this paper proposes an approach of analyzing the effect of shear lag,shear deformation on the lateral static characteristic of curved thin-walled box girders generally applied in engineering. The minimum potential principle is applied to establish the lateral governing differential equations and the corresponding natural boundary conditions. The closed-form solutions of generalized displacements are obtained. The variations of shear lag effects of curved box girders,caused by the change of factors such as span-height ratio,types of loading and natural boundary conditions,are discussed. The results are compared with finite shell element solutions to verify the validity of the proposed approach.
Institute of Scientific and Technical Information of China (English)
李剑; 郝启堂; 李新雷; 陈云龙
2012-01-01
Filling capacity is an important factor affecting the forming of vacuum suction casting thin-walled castings. The filling capacity of vacuum suction casting was compared with the low-pressure casting by pouring sheet casting of aluminum alloys. Furthermore, the effects of vacuum level, filling speed and wall thickness on filling capacity in vacuum suction casting were researched. Due to the lower counter pressure in mold, the filling capacity of vacuum suction casting is the best among the investigated casting methods. In addition, the increase of vacuum and filling speed is helpful to increase the filling capacity of antigravity aluminum alloy casting, and the increase range is closely related to the wall thickness.%充型能力是影响真空吸铸薄壁铸件成形生产的重要因素.本研究通过铝合金薄板件的浇注试验,对比了真空吸铸和低压铸造的充型能力差异,研究了真空吸铸条件下真空度大小、充型速度及壁厚对充型能力的影响规律.结果表明:真空吸铸具有优良的充型能力,较低的型内反压是充型能力提高的主要原因；此外,真空度和充型速度的增大有助于提高反重力浇注铝合金薄壁件的充型能力,提高幅度与壁厚有密切关系.
等离子喷涂薄壁零件涂层中的残余应力%Residual Stresses of Plasma-Spraying Coating of Thin-Walled Part
Institute of Scientific and Technical Information of China (English)
牛丽萍; 张延安; 史冠勇; 豆志河
2011-01-01
A concept of thin-walled and thick-walled parts was proposed for plasma-spraying coating parts,and a mathematical model based on superposition principle established to calculate residual stresses.The results showed that both tensile stress and compressive stress may arise in the coating.The limit value of residual stress appears in the combination zone of substrate and coating.The relaxation of residual stress was effectively estimated with layer model and stress superposition method.The experimental results agree with the calculated results.The effect of thermal expansion coefficient,preheating temperature of substrate and coating thickness on residual stress is great.These results may provide a valuable reference for the design of plasma spraying coating.%以等离子喷涂零件为研究对象,提出了薄壁零件与厚壁零件的概念,并建立了一种基于叠加原理的残余应力计算模型.计算结果表明：在涂层中既可能产生拉应力,也可能产生压应力;喷涂零件残余应力极限值位于基体与涂层的结合区域;增层模型和应力叠加方法可有效估算残余应力的松弛;估算值与测量值吻合得较好;热膨胀系数、基体预热温度、涂层厚度对残余应力的影响较大.研究结果对等离子喷涂涂层的设计具有一定的参考价值.
Application of Ultrasonic Near-filed Guided Wave in Thin-walled Tube%超声近场导波在薄壁管检测中的应用
Institute of Scientific and Technical Information of China (English)
邢耀淇; 高佳楠; 陈以方
2016-01-01
To meet the testing requirements of AP1000 nuclear fuel cladding tube,based on ultrasonic near-field guided wave principle,this paper proposes a method to evaluate the quality of thin-walled tube.Defect information is shown in the form of ultrasonic feature image.The test system can detect the defects in the tube,such as cracks, gas porosity, inclusions, lamination and folding defects, thus completely avoiding the occurrence of leak or mistakenly testing.The applicable minimum defect equivalent can reach 3% of wall thickness.Besides that,we can get the location and equivalent of the defects with an accuracy of 0.2mm.In conclusion,ultrasonic guided wave is suitable for the nondestructive evaluation of high energy consumption cladding tube.%针对 AP1000核燃料包壳管的检测需求，基于超声近场导波的检测原理，提出了一种评价薄壁管质量的方法，并通过超声特征成像图对缺陷信息进行描述.构建的检测系统能对裂纹、气孔、夹杂、分层、折叠等缺陷进行检测，减少了漏检与误检，检测能力达到了壁厚3％的水平，定位定量误差均小于0．2 mm.结果表明，超声导波适用于高能耗包壳管的无损检测.
Institute of Scientific and Technical Information of China (English)
Hossein REZAEI; Ramli NAZIR; Ehsan MOMENI
2016-01-01
Thin-walled spread foundations are used in coastal projects where the soil strength is relatively low. Developing a predictive model of bearing capacity for this kind of foundation is of interest due to the fact that the famous bearing capacity equations are proposed for conventional footings. Many studies underlined the applicability of artificial neural networks (ANNs) in predicting the bearing capacity of foundations. However, the majority of these models are built using conventional ANNs, which suffer from slow rate of learning as well as getting trapped in local minima. Moreover, they are mainly developed for conventional footings. The prime objective of this study is to propose an improved ANN-based predictive model of bearing capacity for thin-walled shallow foundations. In this regard, a relatively large dataset comprising 145 recorded cases of related footing load tests was compiled from the literature. The dataset includes bearing capacity (Qu), friction angle, unit weight of sand, footing width, and thin-wall length to footing width ratio (Lw/B). Apart fromQu, other parameters were set as model inputs. To enhance the diversity of the data, four more related laboratory footing load tests were conducted on the Johor Bahru sand, and results were added to the dataset. Experimental findings suggest an almost 0.5 times increase in the bearing capacity in loose and dense sands whenLw/B is increased from 0.5 to 1.12. Overall, findings show the feasibility of the ANN-based predictive model improved with particle swarm optimization (PSO). The correlation coefficient was 0.98 for testing data, suggesting that the model serves as a reliable tool in predicting the bearing capacity.%目的：薄壁扩展式地基已被广泛应用于土壤强度相对较低的沿海工程。目前，已有很多学者对其进行了人工神经网络的适用性研究，希望用此对地基的承重能力进行预测。但是这些研究多数是基于传统的人工神经网络，
Optical Twist Induced by Plasmonic Resonance
Chen, Jun; Wang, Neng; Cui, Liyong; Li, Xiao; Lin, Zhifang; Ng, Jack
2016-06-01
Harvesting light for optical torque is of significant importance, owing to its ability to rotate nano- or micro-objects. Nevertheless, applying a strong optical torque remains a challenging task: angular momentum must conserve but light is limited. A simple argument shows the tendency for two objects with strong mutual scattering or light exchange to exhibit a conspicuously enhanced optical torque without large extinction or absorption cross section. The torque on each object is almost equal but opposite, which we called optical twist. The effect is quite significant for plasmonic particle cluster, but can also be observed in structures with other morphologies. Such approach exhibits an unprecedentedly large torque to light extinction or absorption ratio, enabling limited light to exert a relatively large torque without severe heating. Our work contributes to the understanding of optical torque and introduces a novel way to manipulate the internal degrees of freedom of a structured particle cluster.
Twisted Light Transmission over 143 kilometers
Krenn, Mario; Fink, Matthias; Fickler, Robert; Ursin, Rupert; Malik, Mehul; Zeilinger, Anton
2016-01-01
Spatial modes of light can potentially carry a vast amount of information, making them promising candidates for both classical and quantum communication. However, the distribution of such modes over large distances remains difficult. Intermodal coupling complicates their use with common fibers, while free-space transmission is thought to be strongly influenced by atmospheric turbulence. Here we show the transmission of orbital angular momentum modes of light over a distance of 143 kilometers between two Canary Islands, which is 50 times greater than the maximum distance achieved previously. As a demonstration of the transmission quality, we use superpositions of these modes to encode a short message. At the receiver, an artificial neural network is used for distinguishing between the different twisted light superpositions. The algorithm is able to identify different mode superpositions with an accuracy of more than 80% up to the third mode order, and decode the transmitted message with an error rate of 8.33%....
Twisted Polynomials and Forgery Attacks on GCM
DEFF Research Database (Denmark)
Abdelraheem, Mohamed Ahmed A. M. A.; Beelen, Peter; Bogdanov, Andrey;
2015-01-01
nonce misuse resistance, such as POET. The algebraic structure of polynomial hashing has given rise to security concerns: At CRYPTO 2008, Handschuh and Preneel describe key recovery attacks, and at FSE 2013, Procter and Cid provide a comprehensive framework for forgery attacks. Both approaches rely...... heavily on the ability to construct forgery polynomials having disjoint sets of roots, with many roots (“weak keys”) each. Constructing such polynomials beyond naïve approaches is crucial for these attacks, but still an open problem. In this paper, we comprehensively address this issue. We propose to use...... in an improved key recovery algorithm. As cryptanalytic applications of our twisted polynomials, we develop the first universal forgery attacks on GCM in the weak-key model that do not require nonce reuse. Moreover, we present universal weak-key forgeries for the nonce-misuse resistant AE scheme POET, which...
Obregón, O; Ryan, M P; Obregon, Octavio; Quevedo, Hernando; Ryan, Michael P.
2004-01-01
We construct a family of time and angular dependent, regular S-brane solutions which corresponds to a simple analytical continuation of the Zipoy-Voorhees 4-dimensional vacuum spacetime. The solutions are asymptotically flat and turn out to be free of singularities without requiring a twist in space. They can be considered as the simplest non-singular generalization of the singular S0-brane solution. We analyze the properties of a representative of this family of solutions and show that it resembles to some extent the asymptotic properties of the regular Kerr S-brane. The R-symmetry corresponds, however, to the general Lorentzian symmetry. Several generalizations of this regular solution are derived which include a charged S-brane and an additional dilatonic field.