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1

Effect of low cycle fatigue on subsequent high cycle fatigue life of 316L stainless steel  

International Nuclear Information System (INIS)

The effect of low cycle fatigue (LCF) on the subsequent high cycle fatigue (HCF) life of a 316L steel was investigated. A spectacular increase of HCF life following a certain number of LCF cycles is reported. A further increase in the number of LCF cycles leads to a drop in HCF life. (orig.)

1998-10-15

2

A method for calculation of finite fatigue life under multiaxial loading in high-cycle domain  

Directory of Open Access Journals (Sweden)

Full Text Available A method for fatigue life assessment in high-cycle domain under multiaxial loading is presented in this paper. This approach allows fatigue assessment under any kind of load history, without limitations. The methodology lies on the construction - at a macroscopic level - of an “indicator” in the form of a set of cycles, representing plasticity that can arise at mesoscopic level throughout fatigue process. During the advancement of the loading history new cycles are created and a continuous evaluation of the damage is made.

M. Malnati

2014-04-01

3

The Effect of Drive Signal Limiting on High Cycle Fatigue Life Analysis  

Science.gov (United States)

It is common practice to assume a Gaussian distribution of both the input acceleration and the response when modeling random vibration tests. In the laboratory, however, shaker controllers often limit the drive signal to prevent high amplitude peaks. The high amplitudes may either be truncated at a given level (socalled brick wall limiting or abrupt clipping), or compressed (soft limiting), resulting in drive signals which are no longer Gaussian. The paper first introduces several methods for limiting a drive signal, including brick wall limiting and compression. The limited signal is then passed through a linear time-invariant system representing a device under test. High cycle fatigue life predictions are subsequently made using spectral fatigue and rainflow cycle counting schemes. The life predictions are compared with those obtained from unclipped input signals. Some guidelines are provided to help the test engineer decide how clipping should be applied under different test scenarios.

Kihm, Frederic; Rizzi, Stephen A.

2014-01-01

4

Microstructural effects on high cycle fatigue  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Mechanical components subjected to cyclic loadings below the ultimate strength of the material often fail due to a phenomenon known as fatigue. Fatigue failures occur in three stages; crack initiation, crack propagation, and final catastrophic failure. For high cycle fatigue the crack initiation component of the total life usually dominates. Crack initiation in high cycle fatigue originates at the microstructural level often occurring at initial material imperfections or at plastic slip bands...

2010-01-01

5

Fretting Fatigue Strength and Life Estimation in Ultra High Cycle Region Considering the Fretting Wear Process  

Science.gov (United States)

In this paper we present the estimation methods of fretting wear process and fretting fatigue life using this wear process. Firstly the fretting-wear process was estimated using contact pressure and relative slippage. And then the stress intensity factor for cracking due to fretting fatigue was calculated by using contact pressure and frictional stress distributions, which were analyzed by the finite element method. The S-N curves of fretting fatigue were predicted by using the relationship between the calculated stress intensity factor range (?K) with the threshold stress intensity factor range (?Kth) and the crack propagation rate (da/dN) obtained using CT specimens of the material. Finaly fretting fatigue tests were conducted on Ni-Mo-V steel specimens. The S-N curves of our experimental results were in good agreement with the analytical results obtained by considering fretting wear process. Using these estimation methods we can explain many fretting troubles in industrial fields.

Hattori, Toshio; Yamashita, Minoru; Nishimura, Naoya

6

High cycle fatigue of fretting induced cracks  

Science.gov (United States)

The objective of this study was to quantify the effect of fretting fatigue stress histories on fatigue crack growth and the fatigue crack growth thresholds due to High Cycle Fatigue (HCF) loading. The approach used to meet this objective consists of both experimental and analytical studies with the experimental results helping to verify the analysis. Test pieces from Ti-6Al-4V fretting fatigue experiments were examined and fatigue tested. The first type of experiment involved interruption of the fretting fatigue experiment prior to failure followed by continued fatigue testing of the specimen under remote loading without fretting. The crack growth and coalescence of the fretting cracks located at the edge of contact was recorded and compared to fracture mechanics analysis. The analysis conservatively predicted the growth to failure in these specimens. For the second type of experiment a unique fatigue specimen was designed from the fretting pad used in the fretting fatigue experiments. This fretting pad was subject to high local contact stresses that could initiate cracks, but they would not propagate to failure due to the lack of a bulk cyclic tension. The fatigue crack growth thresholds of these fretting cracks were measured by step testing. The cracks were measured from the fracture surface after failure with the aid of heat tinting. The measured fatigue crack growth thresholds of these cracks were consistent with a small crack threshold model. Many of the specimens were stress relieved prior to testing to eliminate load history effects and ultimately no fretting load history effect on the threshold was conclusively observed. Crack initiation, propagation, and threshold models were applied to the results of the experiments conducted for this research with mixed success. These models were then applied to the fretting fatigue experiments performed by other researchers. Stress life and constant life diagrams were created and compared well with the experimental data. The affect of various fretting load parameters on the fatigue life and threshold predictions was investigated.

Golden, Patrick John

7

A PROBABILISTIC TWO-SCALE MODEL FOR HIGH CYCLE FATIGUE LIFE PREDICTIONS  

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It is proposed to develop and identify a probabilistic two-scale model for HCF that accounts for the failure of samples but also for the thermal effects during cyclic loadings in a unified framework. The probabilistic model is based on a Poisson point process. Within the weakest link theory, the model corresponds to a Weibull law for the fatigue limits. The thermal effects can be described if one considers the same hypotheses apart from the weakest link assumption. A method of identification ...

Doudard, Ce?dric; Calloch, Sylvain; Cugy, Philippe; Galtier, Andre?; Hild, Franc?ois

2005-01-01

8

Effects of mean tensile stresses on high-cycle fatigue life and strain accumulation in some reactor materials  

International Nuclear Information System (INIS)

An assessment has been made of the effects of mean tensile stresses on the high-cycle fatigue behavior of solution-treated Type 304 stainless steel, normalized and tempered 21/4Cr-1Mo steel, Incoloy-800H, and low-carbon Incoloy-800. Mean stresses are usually detrimental to fatigue strength, especially at high temperatures and stress levels, where significant creep can occur during fatigue cycling. Depending on the magnitudes of the alternating and mean stresses, failure may be creep or fatigue controlled. Strain accumulation is also affected by these stress levels and possibly, also, by the cyclic work-hardening characteristics of the material. It is shown that the Goodman Law for estimating mean stress effects is inadequate, since it does not account for time-dependent deformation. An alternative expression not having such a limitation was, therefore, derived and this relates the alternating and mean stresses to the time to failure. Based on limited metallographic observations of fatigue striations in the 21/4Cr-1Mo steel an estimate was made of the crack propagation rate. It was found that a crack of critical size could, under certain conditions, propagate through most of the specimen diameter in a matter of seconds. This presents a more significant safety problem than the case for a crack extending under low-cycle conditions since preventative measures probably could not be implemented before the crack had grown to a large size

1977-01-01

9

High cycle fatigue properties of inconel 690  

International Nuclear Information System (INIS)

Inconel 690 is presently used as sleeve material and a replacement alloy in degraded steam generators, as well as the material for new steam generators. But Inconel 690 has low thermal conductivity which are 3-8% less than that of Inconel 600 at operating temperature. For the same power output, conduction area must be increased. As a result, more fluid induced vibration can cause a fatigue damage of Inconel 690. High cycle fatigue ruptures occurred in the U-bend regions of North Anna Unit 1 and Mihama Unit 2 steam generators. At this study, the effect of temperature on fatigue crack growth rate in Inconel 690 steam generator tube was investigated at various temperature in air environment. With increasing temperature, fatigue crack growth rate increased and grain size effect decreased. Chromium carbides which have large size and semi-continuous distribution in the grain boundaries decreased fatigue crack growth rate

1997-10-01

10

High Cycle Thermal Fatigue in French PWR  

International Nuclear Information System (INIS)

Different fatigue-related incidents which occurred in the world on the auxiliary lines of the reactor coolant system (SIS, RHR, CVC) have led EDF to search solutions in order to avoid or to limit consequences of thermodynamic phenomenal (Farley-Tihange, free convection loop and stratification, independent thermal cycling). Studies are performed on mock-up and compared with instrumentation on nuclear power stations. At the present time, studies allow EDF to carry out pipe modifications and to prepare specifications and recommendations for next generation of nuclear power plants. In 1998, a new phenomenal appeared on RHR system in Civaux. A crack was discovered in an area where hot and cold fluids (temperature difference of 140 deg. C) were mixed. Metallurgic studies concluded that this crack was caused by high cycle thermal fatigue. Since 1998, EDF is making an inventory of all mixing areas in French PWR on basis of criteria. For all identified areas, a method was developed to improve the first classifying and to keep back only potential damage pipes. Presently, studies are performing on the charging line nozzle connected to the reactor pressure vessel. In order to evaluate the load history, a mock-up has been developed and mechanical calculations are realised on this nozzle. The paper will make an overview of EDF conclusions on these different points: - dead legs and vortex in a no flow connected line; - stratification; - mixing tees with high ?T. (authors)

2002-04-14

11

High cycle fatigue of austenitic stainless steels  

International Nuclear Information System (INIS)

This study concerns the evaluation of material data to be used in LMFBR design codes. High cycle fatigue properties of three austenitic stainless steels are evaluated: type AISI 316 (UKAEA tests), type AISI 316L (CEA tests) and type AISI 304 (Interatom tests). The data on these steels comprised some 550 data points from 14 casts. This data set covered a wide range of testing parameters: temperature from 20-6250C, frequency from 1-20 000 Hz, constant amplitude and random fatigue loading, with and without mean stress, etc. However, the testing conditions chosen by the three partners differed considerably because they had been fixed independently and not harmonized prior to the tests. This created considerable difficulties for the evaluations. Experimental procedures and statistical treatments used for the three subsets of data are described and discussed. Results are presented in tables and graphs. Although it is often difficult to single out the influence of each parameter due to the different testing conditions, several interesting conclusions can be drawn: The HCF properties of the three steels are consistent with the 0.2% proof stress, the fatigue limit being larger than the latter at temperatures above 5500C. The type 304 steel has lower tensile properties than the two other steels and hence also lower HCF properties. Parameters which clearly have a significant effect of HCF behaviour are mean stress or R-ratio (less in the non-endurance region than in the endurance region), temperature, cast or product. Other parameters have probably a weak or no effect but it is difficult to conclude due to insufficient data: environment, specimen orientation, frequency, specimen geometry

1990-01-01

12

High cycle fatigue properties of stainless martensitic chromium steel springs  

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For many materials and components like in high speed trains and airplanes fatigue failures occur in the range of over 107 load cycles which is called the high cycle fatigue range. A modern version of the springs was invented which are applied in a certain application. Ultrasonic fatigue testing (20 kHz machine) was conducted for evaluating the steel of the springs. This research explores the fundamental understanding of high cycle fatigue testing of strip steel and assesses a stainless marten...

Pirouznia, Pouyan

2012-01-01

13

High cycle fatigue of austenitic stainless steels under random loading  

Energy Technology Data Exchange (ETDEWEB)

The effect of high cycle random loading at 330deg C and at 550deg C on the fatigue resistance of austenitic stainless steels Type 316NL has been investigated. The aim was to improve the predictions of the consequences of thermal fluctuations occurring in some reactor components. The experimental means used for this purpose was a minicomputer, which generated random stationary Gaussian load sequences in a Markov matrix, and several servo-hydraulic fatigue testing machines. This method has the advantage of taking into account the mean load for each cycle. The specimens tested were taken from two plates which were at two different heats, one 45 mm thick and slightly cold worked, the other 26.5 mm thick. Random fatigue tests were mainly performed in the endurance region of the fatigue curve, using the stair-case method to determine the scatter. The experimental data were analyzed in terms of the test temperature and the irregularity factor, with the aim of establishing design curves for reactor components. The results obtained have shown that the random loading is more damaging than the constant amplitude loading when compared on the basis of the mean square root conventional fatigue limit. They have also shown that the linear damage accumulation, according to the Miner's rule, yields conservative results at least when used in conjunction with the probability density function of peaks for a case when the irregularity factor is near 100%. Based on these observations a method is proposed for predicting the fatigue life from the design curves, which includes random loading effects with the irregularity factor as the indexing parameter. (orig.).

Gauthier, J.P.; Petrequin, P. (CEA Centre d' Etudes Nucleaires de Saclay, 91 - Gif-sur-Yvette (France))

1989-09-01

14

Estimation of the Plain High-Cycle Fatigue Propagation Resistance in Steels  

Directory of Open Access Journals (Sweden)

Full Text Available In this work a method to estimate the high cyclic fatigue propagation life of steel specimens under constant loading is presented. This method is based in experimental evidence that the fatigue limit represents the threshold stress for the propagation of nucleated cracks, so that both the fatigue limit and the fatigue resistance depend on the effective resistance of the microstructural barriers that have to be overcome by the nucleated cracks. It is proposed also, that in those cases where the number of cycles that is necessary for the nucleation of the cracks can be neglected, the fatigue crack propagation life can be taken as an estimation of the total fatigue life. The high cycle fatigue propagation life of a structural steel of the type JIS 10C is estimated.

Chapetti Mirco D.

2002-01-01

15

Fatigue behavior of Alloy 690 and Alloy 800 SG tubing at temperatures up to 330oC in very high cycle fatigue regime  

International Nuclear Information System (INIS)

During the service in nuclear power plants, steam generator (SG) tubing will suffer from a vibration with a frequency from 30-40 Hz. This means that SG tubing will undergo a very high cycle fatigue process during the design life time (25 years=about 3x1010cycles). The material degradation and the very high cycle fatigue life of SG tubing materials due to the vibration are therefore of concern. In this investigation, the fatigue properties of Alloy 690 and Alloy 800 SG tubing in the very high cycle fatigue regime (higher than 107 cycles) and strain controlled fatigue at temperatures up to 330oC have been investigated. The fatigue properties of SG tubing of Alloy 690 are comparable to that of wrought material. The strain controlled fatigue properties of Alloy 690 and Alloy 800 are slightly better at 288oC than at room temperature (RT). At the stress near the fatigue endurance, the influence of temperature on the high cycle fatigue properties of Alloy 690 is small. The fatigue properties of Alloy 800 are comparable to that of Alloy 690. The strain controlled fatigue properties of Alloy 690 and Alloy 800 are higher than the Argonne design curve and the ASME design curve. The high cycle fatigue properties in the very high cycle fatigue regime are comparable to that of Alloy 600. (author)

2007-08-19

16

High cycle fatigue of 2.25Cr-1Mo steel at elevated temperatures  

International Nuclear Information System (INIS)

Information on the elevated temperature, long life (> 10"5 cycles to failure) fatigue resistance of pressure vessel and piping alloys is needed to properly design structural components subjected to low amplitude cyclic loadings at high temperatures. The high cycle fatigue resistance of annealed 2 1/4 Cr-1Mo steel has been evaluated in air at temperatures up to 538"0C. A design fatigue curve has been developed for temperatures = 4 x 10"-"3 sec"-"1, more long life fatigue data are needed for applications at lower strain rates. The effect of tensile mean stress on fatigue life has been evaluated. Design fatigue curve corrections for maximum effect of mean stress appear to be adequate at <= 427"0C, but they may not be satisfactory at higher temperatures. The present experimental work was limited to constant amplitude cycling and a crack initiation failure criterion. (author)

1980-05-23

17

Evaluation of high-cycle fatigue behavior of 316FR at high temperature  

International Nuclear Information System (INIS)

High-cycle fatigue data which are necessary in evaluating integrity of upper sore structures of FBR plants were collected for 316FR steel. Fatigue data up to 10 million cycles were obtained and the following observations were made: (1) Influence of loading frequency on deformation and failure life was small. (2) Forging material showed lower life than plate material at low strain range. (3) Best-fit fatigue strength equation can be applied to forging material but modification was proposed for plate material to correct nonconservative tendency at low strain ranges. (author)

2002-04-01

18

High cycle fatigue failure analysis of Monju SHTS thermowell  

Energy Technology Data Exchange (ETDEWEB)

It has been clarified that the Monju sodium leak accident was caused by high cycle fatigue failure of a thermowell due to in-line flow induced vibration, which has been reported in the PNC Technical Report No.99. In this report described are the results of further study. First, regarding the point `why only this particular thermowell failed?`, it was inferred that the bent sheath increased the vibration response of the thermowell by reducing its damping factor. Secondly, some important points in fatigue analysis, e.g., fatigue curve, strain concentration factor, growth of a short crack, and so on, were discussed to make a full assessment of the fatigue failure process. (author)

Morishita, Masaki; Aoto, Kazumi; Wada, Yusaku; Ichimiya, Masakazu [Power Reactor and Nuclear Fuel Development Corp., Oarai, Ibaraki (Japan). Oarai Engineering Center; Yokota, Toshio

1997-03-01

19

Plasticity-damage based micromechanical modelling in high cycle fatigue  

Science.gov (United States)

A micro-macro approach of multiaxial fatigue in unlimited endurance is proposed. It allows one to take into account plasticity and damage mechanisms which occur at the scale of Persistent Slip Bands (PSB). The proposed macroscopic fatigue criterion, which corresponds to microcracks nucleation at the PSB-matrix interface, is derived for different homogenization schemes (Sachs, Lin-Taylor and Kröner). The role of a mean stress and of the hydrostatic pressure in high cycle fatigue is shown; in particular, in the case of Lin-Taylor scheme and linear isotropic hardening rule at microscale, one recovers the linear dependance in pressure postulated by K. Dang Van for the macroscopic fatigue criterion. This dependence is related here to the damage micro-mechanism. Finally, the particular case of affine loading is presented as an illustration. To cite this article: V. Monchiet et al., C. R. Mecanique 334 (2006).

Monchiet, Vincent; Charkaluk, Eric; Kondo, Djimedo

2006-02-01

20

High cycle fatigue testing of glass fibre reinforced polyester and welded structural details  

Energy Technology Data Exchange (ETDEWEB)

In order to allow a safe and economic design of wind turbines it is necessary to determine the high cycle fatigue properties of materials and substructures used in rotor blades. High cycle fatigue properties were determined with coupon specimens from glass fibre reinforced polyester plates, produced under industrial conditions. For two stress ratios (R = 0.1 and R = {minus}1) and for two failure criteria (fracture and 10% stiffness reduction), constant amplitude fatigue curves ({epsilon}-n) are obtained. The results indicate that a fatigue limit will only exist in the very high cycle range (approx. 10{sup 9}). An experimental program to investigate the effect of pre-cycling (high-low step tests) on the constant amplitude (c.a.) fatigue performance of glass fibre polyester coupons was performed. Subsequently, fatigue tests were carried out with a reference load sequence, WISPER, on glass fibre/polyester coupons and welded structural details. The results of the high-low step tests show, contrary to the expectation, not the detrimental effect on the c.a. fatigue life at R = 0.1. However, at R = {minus}1, the c.a. fatigue life is reduced in the higher stress range, probably due to an additional damage mechanism (micro-buckling). The WISPER tests on the glass fibre reinforced polyester coupons show that the fatigue life can be predicted within the usual scatter by a linear damage accumulation calculation based on a modified Mandell type of {epsilon}-n curve. From the results of the WISPER tests on two welded structural details it is concluded that a Dutch standard for fatigue is conservative, although the margin becomes small in the higher stress range. 24 figs., 18 refs., 8 tabs., 3 apps.

Bach, P.W.

1991-03-01

 
 
 
 
21

Effects of HTGR helium on the high cycle fatigue of structural materials  

International Nuclear Information System (INIS)

High cycle fatigue tests have been conducted on Incoloy 800H and Hastelloy X in air and in HTGR helium environments containing low and high levels of moisture. For the helium environments, a higher mositure level usually gives a lower fatigue strength. For air, however, the strength is usually much lower than those for helium. For long test times at higher test temperatures, the fatigue strengths for Incoloy 800H often show a large decrease, and the fatigue limits are much lower than those anticipated from low cycle tests. Optical and scanning electron microscope observations were made to correlate fatigue life with surface and bulk microstructural changes in the material during test. Oxide scale cracking and spallation, surface recrystallization and intergranular attack appear to contribute to losses in fatigue strength

1982-06-02

22

Characterization of high cycle fatigue behavior of a new generation aluminum lithium alloy  

Energy Technology Data Exchange (ETDEWEB)

Highlights: {yields} Effect of microstructure on fatigue fracture of an advanced Al-Li alloy was studied in detail. {yields} Preferential crack propagation in T3 state at specific orientations was analyzed. {yields} Fatigue crack propagation difference between T3 and T8 tempers and friction stir welded condition was rationalized. {yields} The effect of grain size on fatigue life for T3 and T8 tempers was justified based on current theories. {yields} Delamination in T3 and T8 tempers was rationalized using microstructural analysis and FEA simulation. - Abstract: The high cycle fatigue life characteristics of an Al-Li alloy were studied as a function of microstructure. While for the parent microstructure fatigue life decreased as grain size increased, no such effect was noted at high stresses. This decrease in fatigue life was correlated with lower crack initiation life due to small crack effect. Under multiaxial stress conditions, the alloy exhibited intergranular cracking. The cross-linking of intergranular cracks (in the T8 condition) caused a further deterioration in fatigue life. Additionally, planar slip movements (in the T3 condition) in stage I crack propagation were observed. Slip planarity depended on both the sample texture and the nature of the precipitates. Fractographic and textural evidence is presented.

De, P.S. [Center for Friction Stir Processing, Department of Materials Science and Engineering, Missouri University of Science and Technology, Rolla, MO 65409 (United States); Mishra, R.S., E-mail: rsmishra@mst.edu [Center for Friction Stir Processing, Department of Materials Science and Engineering, Missouri University of Science and Technology, Rolla, MO 65409 (United States); Baumann, J.A. [Boeing Company, St. Louis, MO 631666 (United States)

2011-09-15

23

Characterization of high cycle fatigue behavior of a new generation aluminum lithium alloy  

International Nuclear Information System (INIS)

Highlights: ? Effect of microstructure on fatigue fracture of an advanced Al-Li alloy was studied in detail. ? Preferential crack propagation in T3 state at specific orientations was analyzed. ? Fatigue crack propagation difference between T3 and T8 tempers and friction stir welded condition was rationalized. ? The effect of grain size on fatigue life for T3 and T8 tempers was justified based on current theories. ? Delamination in T3 and T8 tempers was rationalized using microstructural analysis and FEA simulation. - Abstract: The high cycle fatigue life characteristics of an Al-Li alloy were studied as a function of microstructure. While for the parent microstructure fatigue life decreased as grain size increased, no such effect was noted at high stresses. This decrease in fatigue life was correlated with lower crack initiation life due to small crack effect. Under multiaxial stress conditions, the alloy exhibited intergranular cracking. The cross-linking of intergranular cracks (in the T8 condition) caused a further deterioration in fatigue life. Additionally, planar slip movements (in the T3 condition) in stage I crack propagation were observed. Slip planarity depended on both the sample texture and the nature of the precipitates. Fractographic and textural evidence is presented.

2011-09-01

24

High cycle fatigue damage analysis of KALIMER UIS bottom plate  

International Nuclear Information System (INIS)

The KALIMER Upper Internal Structure(UIS) bottom region is subjected to a high cycle thermal striping load during steady state operation due to the mixing of the sodium jets from different core assemblies with various velocities and temperatures. In this paper, a simple procedure for UIS striping analysis was proposed and the Inconel 718 liner plate was introduced to protect the UIS bottom plate from severe thermal striping load. The proposed simple procedure for the calculation of high cycle fatigue damage has been confirmed reasonably by an axisymmetric analysis of the UIS bottom structure. The analysis results of this study indicated that the conceptually designed UIS by attaching the Inconel 718 liner plate under the UIS bottom plate could be protected against severe thermal striping load by attaching

1999-05-01

25

Torsional fatigue behaviour and damage mechanisms in the very high cycle regime  

Directory of Open Access Journals (Sweden)

Full Text Available Purpose: of this paper: Many engineering components operate under combined torsion and axial cyclic loading conditions, which can result in fatigue fracture after a very long life regime of fatigue. This fatigue regime were carried out beyond 109 loading cycles called very high cycle fatigue (VHCF to understand the fatigue properties and damage mechanisms of materials.Design/methodology/approach: Torsional fatigue tests were conducted using a 20 kHz frequency ultrasonic fatigue testing device. The results obtained were compared to those of the conventional torsional fatigue test machine operated at 35 Hz to observe any discrepancy in results due to frequency effects between two experiments.Findings: All the fatigue tests were done up to 1010 cycles at room temperature. Damage mechanisms in torsional fatigues such as crack initiation and propagation in different modes were studied by imaging the samples in a Scanning Electron Microscope (SEM. The results of the two kinds of material show that the stress vs. number of cycle curves (S-N curves display a considerable decrease in fatigue strength beyond 107 cycles.Research limitations/implications: Each test, the strain of specimen in the gage length must be calibrated with a strain gage bonded to the gage section. This is a critical point of this study. The results are very sensitive to the calibration system. Control of the displacement and the output of the power supply are made continuously by computer and recorded the magnitude of the strain in the specimen.Practical implications: torsional fatigue tests has been investigated in the very high cycle fatigue (VHCF range for two kinds of alloys used very largely in automotive engine components. Based on the test results and analyses presented in this paper, practical applications are being actually carried out in the automotive industry essentially in France.Originality/value: Ultrasonic fatigue damage (VHCF >109 in VHCF is originally different from classical fatigue (up to 106 by typical internal fish eye formation. Additionally, fatigue crack of all the fractured specimens for the 2-AS5U3G-Y35 specimens initiated at the surface of the specimens. Fatigue fracture surfaces of AISI52100 steel specimens show a typical “scorpion-shaped” formation, which was considerably different from the fatigue fracture specimen subjected to axial cyclic loading, which exhibited the “fish-eye” formation.

E. Bayraktar

2010-06-01

26

Surface finish effects on the high-cycle fatigue of Alloy 718  

International Nuclear Information System (INIS)

Load control high-cycle fatigue tests at 427 and 649"0C were conducted on Alloy 718 specimens given various surface finishes. The standard surface preparation for fatigue specimens involves a low-stress grind to minimize the residual surface stresses. A low-stress grind surface was used for generating baseline data; various other surfaces that could be considered feasible for large components fabricated in commercial shops were produced on test specimens, and the high-cycle fatigue strength of each was compared. Surface finishes produced by belt sanding, grit blasting, fine machining, and electropolishing were examined. Surface roughness measurements were taken on typical specimens with each surface finish, and residual stress profiles were measured on three of the surface types. Results show little or no difference in fatigue life for the various surfaces and indicate that residual stress profile and grain size are more important factors than surface roughness in determining high-cycle fatigue strength. 12 figures, 5 tables

1981-05-11

27

High-cycle fatigue behavior of ultrafine-grained austenitic stainless and TWIP steels  

Energy Technology Data Exchange (ETDEWEB)

High-cycle fatigue behavior of ultrafine-grained (UFG) 17Cr-7Ni Type 301LN austenitic stainless and high-Mn Fe-22Mn-0.6C TWIP steels were investigated in a reversed plane bending fatigue and compared to the behavior of steels with conventional coarse grain (CG) size. Optical, scanning and transmission electron microscopy were used to examine fatigue damage mechanisms. Testing showed that the fatigue limits leading to fatigue life beyond 4 x 10{sup 6} cycles were about 630 MPa for 301LN while being 560 MPa for TWIP steel, and being 0.59 and 0.5 of the tensile strength respectively. The CG counterparts were measured to have the fatigue limits of 350 and 400 MPa. The primary damage caused by fatigue took place by grain boundary cracking in UFG 301LN, while slip band cracking occurred in CG 301LN. However, in the case of TWIP steel, the fatigue damage mechanism is similar in spite of the grain size. In the course of cycling neither the formation of a martensite structure nor mechanical twinning occurs, but intense slip bands are created with extrusions and intrusions. Fatigue crack initiates preferentially on grain and twin boundaries, and especially in the intersection sites of slip bands and boundaries.

Hamada, A.S. [Materials Engineering Laboratory (4KOMT), Box 4200, University of Oulu, 90014 Oulu (Finland); Metallurgical and Materials Engineering Department, Faculty of Petroleum and Mining Engineering, Suez Canal University, Box 43721, Suez (Egypt); Karjalainen, L.P., E-mail: pentti.karjalainen@oulu.fi [Materials Engineering Laboratory (4KOMT), Box 4200, University of Oulu, 90014 Oulu (Finland)

2010-08-20

28

High-cycle fatigue behavior of ultrafine-grained austenitic stainless and TWIP steels  

International Nuclear Information System (INIS)

High-cycle fatigue behavior of ultrafine-grained (UFG) 17Cr-7Ni Type 301LN austenitic stainless and high-Mn Fe-22Mn-0.6C TWIP steels were investigated in a reversed plane bending fatigue and compared to the behavior of steels with conventional coarse grain (CG) size. Optical, scanning and transmission electron microscopy were used to examine fatigue damage mechanisms. Testing showed that the fatigue limits leading to fatigue life beyond 4 x 106 cycles were about 630 MPa for 301LN while being 560 MPa for TWIP steel, and being 0.59 and 0.5 of the tensile strength respectively. The CG counterparts were measured to have the fatigue limits of 350 and 400 MPa. The primary damage caused by fatigue took place by grain boundary cracking in UFG 301LN, while slip band cracking occurred in CG 301LN. However, in the case of TWIP steel, the fatigue damage mechanism is similar in spite of the grain size. In the course of cycling neither the formation of a martensite structure nor mechanical twinning occurs, but intense slip bands are created with extrusions and intrusions. Fatigue crack initiates preferentially on grain and twin boundaries, and especially in the intersection sites of slip bands and boundaries.

2010-08-20

29

High cycle fatigue property of Ti-600 alloy at ambient temperature  

Energy Technology Data Exchange (ETDEWEB)

Research highlights: Ti-600, developed by Northwest Institute for Nonferrous Metal Research (NIN) in China, is a near alpha titanium alloy designed for components used in turbine engines up to 600 deg. C. Mechanical behavior of the alloy at ambient temperature and its service temperature has widely been studied, the fatigue property for the alloy has never been systematically discussed. Smooth axial fatigue tests were taken for solutioned plus aged alloy, and the fractographies were observed. In order to get the damage mechanism, OM and TEM microstructures were also investigated. - Abstract: Smooth axial fatigue tests were carried out at ambient temperature on one kind of near alpha titanium alloy named after Ti-600 at a frequency of 120-130 Hz and with two kinds of load ratios. The high cycle fatigue (HCF) strength for the solutioned and aged alloy is found to be 475 MPa fatigued with a load ratio R of 0.1, and which is 315 MPa with a load ratio R of -1. The observed high HCF strength for the samples fatigued with a load ratio R of 0.1 is attributed to its overlapping fine and thin plate like {alpha} + {beta} phase microstructure. During the crack propagation region, at the same stress of 600 MPa, the sample with a fatigue life of 1.78 x 10{sup 6} cycles has a better fatigue resistance than that of the sample with a fatigue life of 8.61 x 10{sup 5} cycles, because of its smaller striation distance, its well-developed secondary cracks, more wider and coarsened {alpha} lathes precipitated at grain boundaries, and the heavily arranged interlacing transformed {beta} microsructures. The average grain size of rare earth phases varies from several micrometers to 0.2 {mu}m, no cracks corresponding to rare earth particles can be initiated.

Zeng Liying, E-mail: ZENG-ly@163.com [School of Metallurgical Engineering, Xi' an University of Architecture and Technology, Xi' an 710055 (China) and Northwest Institute for Nonferrous Metal Research, Xi' an 710016 (China); Zhao Yongqing, E-mail: trc@c-nin.com [Northwest Institute for Nonferrous Metal Research, Xi' an 710016 (China); Hong Quan [Northwest Institute for Nonferrous Metal Research, Xi' an 710016 (China); Yang Guanjun [School of Metallurgical Engineering, Xi' an University of Architecture and Technology, Xi' an 710055 (China)

2011-02-03

30

Low cycle fatigue: high cycle fatigue damage accumulation in a 304L austenitic stainless steel  

International Nuclear Information System (INIS)

The aim of this study was to evaluate the consequences of a Low Cycle Fatigue pre-damage on the subsequent fatigue limit of a 304L stainless steel. The effects of hardening and severe roughness (grinding) have also been investigated. In a first set of tests, the evolution of the surface damage induced by the different LCF pre-cycling was characterized. This has permitted to identify mechanisms and kinetics of damage in the plastic domain for different surface conditions. Then, pre-damaged samples were tested in the High Cycle Fatigue domain in order to establish the fatigue limits associated with each level of pre-damage. Results evidence that, in the case of polished samples, an important number of cycles is required to initiate surface cracks ant then to affect the fatigue limit of the material but, in the case of ground samples, a few number of cycles is sufficient to initiate cracks and to critically decrease the fatigue limit. The fatigue limit of pre-damaged samples can be estimated using the stress intensity factor threshold. Moreover, this detrimental effect of severe surface conditions is enhanced when fatigue tests are performed under a positive mean stress (author)

2007-01-01

31

Fatigue Strength and Crack Initiation Mechanism of Very-High-Cycle Fatigue for Low Alloy Steels  

Science.gov (United States)

The fatigue strength and crack initiation mechanisms of very-high-cycle fatigue (VHCF) for two low alloy steels were investigated. Rotary bending tests at 52.5 Hz with hour-glass type specimens were carried out to obtain the fatigue propensity of the test steels, for which the failure occurred up to the VHCF regime of 108 cycles with the S-N curves of stepwise tendency. Fractography observations show that the crack initiation of VHCF is at subsurface inclusion with "fish-eye" pattern. The fish-eye is of equiaxed shape and tends to tangent the specimen surface. The size of the fish-eye becomes large with the increasing depth of related inclusion from the surface. The fish-eye crack grows faster outward to the specimen surface than inward. The values of the stress intensity factor ( K I ) at different regions of fracture surface were calculated, indicating that the K I value of fish-eye crack is close to the value of relevant fatigue threshold (? K th ). A new parameter was proposed to interpret the competition mechanism of fatigue crack initiation at the specimen surface or at the subsurface. The simulation results indicate that large inclusion size, small grain size, and high strength of material will promote fatigue crack initiation at the specimen subsurface, which are in agreement with experimental observations.

Hong, Youshi; Zhao, Aiguo; Qian, Guian; Zhou, Chengen

2012-08-01

32

The high-cycle fatigue and fracture behavior of a copper-niobium microcomposite  

Energy Technology Data Exchange (ETDEWEB)

Niobium particle-reinforced dispersion strengthened copper composite has shown the promise of being the candidate material for applications requiring high strength, high thermal and electrical conductivities and resistance to softening at elevated temperatures. In this paper, the results of a study on the high-cycle fatigue and final fracture behavior of a microcomposite based on an oxide dispersion strengthened copper matrix is presented and discussed. Specimens of both the composite and the unreinforced counterpart were cyclically deformed, over a range of stress amplitudes, at both ambient and elevated temperatures. Increase in test temperature was found to have a detrimental influence on the cyclic fatigue life of the copper-niobium microcomposite. Temperature was found to have little influence on the cyclic fatigue life of the unreinforced dispersion strengthened microstructure. For both the unreinforced and reinforced materials macroscopic fracture was reminiscent of brittle fracture over the entire range of stress amplitudes. However, on a microscopic scale cyclic fracture revealed features reminiscent of locally brittle and ductile mechanisms. The cyclic fatigue and final fracture behavior of the composite are discussed in light of the mutually interactive influences of intrinsic composite microstructural effects, stress amplitude and test temperature.

Srivatsan, T.S.; Singh, K.P.D. [Univ. of Akron, OH (United States). Dept. of Mechanical Engineering; Troxell, J.D. [OGM Americas, Research Triangle Park, NC (United States)

1997-12-31

33

Interaction of high-cycle and low-cycle fatigue of Haynes 188 alloy at 1400 F deg  

Science.gov (United States)

The interaction of low-cycle fatigue (LCF) and high-cycle fatigue (HCF) was evaluated at the NASA Lewis Research Center on Haynes 188 alloy at 1400 F. Completely reversed, axial-load, strain-controlled fatigue tests were performed to determine the baseline data for this study. Additional specimens for interaction tests were cycled first at a high strain range for various small portions of expected LCF life followed by a step change to a low strain range to failure in HCF. Failure was defined as complete specimen separation. The resultant lives varied between 10 and 5000 cycles for the low-cycle fatigue tests and between 4500 and 3 million for the high-cycle fatigue tests. For the interaction tests the low-cycle-life portion ranged from 30 and 1000 applied cycles while the high-frequency life ranged from 300 and 300,000 cycles to failure. The step change results showed a significant nonlinear interaction in expected life. Application of a small part of the LCF life drastically decreased the available HCF life as compared with what would have been expected by the classical linear damage rule (LDR).

Bizon, P. T.; Thoma, D. J.; Halford, G. R.

1985-01-01

34

Effects of high mean stress on the high-cycle fatigue behavior of PWA 1480  

International Nuclear Information System (INIS)

PWA 1480 is a potential candidate material for use in the high-pressure fuel turbine blade of the Space Shuttle Main Engine. As an engine material it will be subjected to high-cycle fatigue loading superimposed on a high mean stress due to combined centrifugal and thermal loadings. This paper describes results obtained in an ongoing program to determine the effects of a high mean stress on the high-cycle fatigue behavior of this material

1985-06-04

35

Development of a high cycle vibration fatigue diagnostic system with non-contact vibration sensing  

International Nuclear Information System (INIS)

Nuclear power plants have a large number of pipes. Of these small-diameter pipe branches in particular are often damaged due to high-cycle fatigue. In order to ensure the reliability of a plant it is important to detect the fatigues in pipe branches at an early stage and to develop the technology to predict and diagnose the advancement of fatigue. Further, in order to carry out the diagnosis of the piping system effectively during operation, non-contact evaluation is useful. Hence, we have developed a 'high-cycle fatigue diagnostic system with non-contact vibration sensing', where the vibration of the pipe branch is measured using a non-contact sensor. Since the contents of the developed sensor technology has already been reported, this paper mainly describes the newly developed high-cycle fatigue diagnostic system. (authors)

2001-04-08

36

Characterization of the temperature evolution during high-cycle fatigue of the ULTIMET superalloy: Experiment and theoretical modeling  

Science.gov (United States)

High-speed, high-resolution infrared thermography, as a noncontact, full-field, and nondestructive technique, was used to study the temperature variations of a cobalt-based ULTIMET alloy subjected to high-cycle fatigue. During each fatigue cycle, the temperature oscillations, which were due to the thermal-elastic-plastic effects, were observed and related to stress-strain analyses. A constitutive model was developed for predicting the thermal and mechanical responses of the ULTIMET alloy subjected to cyclic deformation. The model was constructed in light of internal-state variables, which were developed to characterize the inelastic strain of the material during cyclic loading. The predicted stress-strain and temperature responses were found to be in good agreement with the experimental results. In addition, the change of temperature during fatigue was employed to reveal the accumulation of fatigue damage, and the measured temperature was utilized as an index for fatigue-life prediction.

Jiang, L.; Wang, H.; Liaw, P. K.; Brooks, C. R.; Klarstrom, D. L.

2001-09-01

37

High cycle fatigue properties of type 316 stainless steel  

International Nuclear Information System (INIS)

Strain-controlled fatigue tests using a flexural resonant vibration were performed on the miniature specimens of the solution treated 316 stainless steel up to 12 x 10"-"4 in the total strain amplitude, ?_t, between 293 K and 573 K. From the investigations of in situ changes in the resonant period, P, and in the drive force, DF, applied to the specimens during the fatigue tests, the following are obtained. (1) Overlapped on general changes in P and DF, small and step-like changes in P and DF were observed for ?_t above the fatigue limit and were considered to be associated with a proceeding of fatigue damages. (2) The general change of P observed in the middle stage during the fatigue tests showed a tendency of stableness or increase (softening) at T = 333 K but a strong decrease (hardening) at T = 573 K. From the detailed investigation into the above mentioned phenomena, it was concluded that the fatigue test with ?_t above the fatigue limit itself induced an age hardening at T = 573 K but not at T = 333 K. The age hardening became to be revealed above T = 473 K and increased in magnitude with increasing ?_t. (author)

1985-01-01

38

High cycle fatigue properties of type 316 stainless steel  

International Nuclear Information System (INIS)

Strain-controlled fatigue tests using a flexural resonant vibration were performed on miniature specimens of the solution treated 316 stainless steel with the total strain amplitude ?_t ? 12 x 10"-"4 at temperatures between 293 K and 573 K. From the investigations of in situ changes in the resonant period, P, and in the drive force, DF, applied to the specimens during the fatigue tests, the following results were obtained. (1) Overlapped on general changes in P and DF, small and step-like changes in P and DF were observed for ?_t larger than the fatigue limit and were considered to be associated with the proceeding of fatigue damages. (2) General changes of P at the middle stage during the fatigue tests were a slight increase (softening) at T = 333 K but a strong decrease (hardening) at T = 573 K. From the detailed study of the above mentioned phenomena, it was concluded that the fatigue test with ?_t above the fatigue limit induced an age hardening at T = 573 K. The age hardening became to be revealed above T = 473 K and increased in magnitude with increasing ?_t. (author)

1986-01-01

39

Effects of ?-ferrite and welding structure on high-cycle fatigue properties of austenitic stainless steels weld metals  

International Nuclear Information System (INIS)

We studied the effects of ?-ferrite and welding structure on high-cycle fatigue properties for austenitic stainless steel weld metals at cryogenic temperatures. SUS304L and SUS316L weld metals contained 0% ?-ferrite (0% material) and 10% ?-ferrite (10% material) were prepared. High-cycle fatigue tests were carried out at 293, 77 and 4 K. The S-N curves of those weld metals shifted towards higher stress levels, i.e., the longer life side, with decreasing test temperature. The ratios of 106-cycles fatigue strength (FS) to tensile strength (TS) of 0% material decreased from 0.8 to 0.45 and those of 10% material decreased between 0.35 to 0.65 with decreasing test temperature. Fatigue crack initiation sites of SUS304L 10% material were almost at blowholes, and those of SUS316L 10% material were at weld pass interface boundaries. On the other hand, those of 0% materials were considered to be due to the interface of the solidification structure. Although ?-ferrite reduces toughness at cryogenic temperatures in austenitic stainless steel weld metals, the effects of ?-ferrite on high-cycle fatigue properties are not significant

2002-05-15

40

Very high cycle fatigue crack initiation in electroplated Ni films under extreme stress gradients  

International Nuclear Information System (INIS)

A characterization technique based on kilohertz micro-resonators is presented to investigate the very high cycle fatigue behavior of 20 ?m thick electroplated Ni films with a columnar microstructure (grain diameter less than 2 ?m). The films exhibit superior fatigue resistance due to the extreme stress gradients at the surface. The effects of stress amplitude and environment on the formation of fatigue extrusions and micro-cracks are discussed based on scanning electron microscopy and the tracking of the specimens’ resonant frequency.

2012-07-01

 
 
 
 
41

High cycle fatigue of austenitic stainless steels under random loading  

International Nuclear Information System (INIS)

To investigate reactor components, load control random fatigue tests were performed at 3000C and 5500C, on specimens from austenitic stainless steels plates in the transverse orientation. Random solicitations are produced on closed loop servo-hydraulic machines by a mini computer which generates random load sequence by the use of reduced Markovian matrix. The method has the advantage of taking into account the mean load for each cycle. The solicitations generated are those of a stationary gaussian process. Fatigue tests have been mainly performed in the endurance region of fatigue curve, with scattering determination using stair case method. Experimental results have been analysed aiming at determining design curves for components calculations, depending on irregularity factor and temperature. Analysis in term of mean square root fatigue limit calculation, shows that random loading gives more damage than constant amplitude loading. Damage calculations following Miner rule have been made using the probability density function for the case where the irregularity factor is nearest to 100 %. The Miner rule is too conservative for our results. A method using design curves including random loading effects with irregularity factor as an indexing parameter is proposed

1987-08-24

42

The influence of growth rate and temperature on high cycle fatigue of Al-Al3Ni  

Science.gov (United States)

High-cycle fatigue tests have been conducted on specimens of an Al-Al3Ni eutectic alloy, unidirectionally solidified at selected rates from 0.000139 to 0.3 cm/sec. Tests were conducted in air at 298, 458 and 683 K. Room temperature fatigue lives were independent of growth rate at low solidification rates but were markedly improved in samples grown at 0.3 cm/sec. Materials grown at 0.00833 cm/sec exhibited fatigue lives similar to those of the lower growth rates, despite gross misalignment due to cellular growth. The dependence of fatigue life on growth rate at elevated temperatures appears to be due primarily to differences in cyclic creep rates as a result of varying interfiber spacings. Crack initiation and propagation mechanisms were established by metallographic and fractographic examination. Dislocation substructure-fiber interactions were studied by transmission electron microscopy.

Maurer, G. E.; Duquette, D. J.; Stoloff, N. S.

1976-01-01

43

High cycle fatigue of AA6082 and AA6063 aluminum extrusions  

Science.gov (United States)

The high cycle fatigue behavior of hollow extruded AA6082 and AA6063 aluminum extrusions has been studied. Hollow extruded aluminum profiles can be processed into intricate shapes, and may be suitable replacements for fatigue critical automotive applications requiring reduced weight. There are several features inherent in hollow aluminum extrusions, such as seam welds, charge welds, microstructural variations and die lines. The effects of such extrusion variables on high cycle fatigue properties were studied by taking specimens from an actual car bumper extrusion. It appears that extrusion die lines create large anisotropy differences in fatigue properties, while welds themselves have little effect on fatigue lives. Removal of die lines greatly increased fatigue properties of AA6082 specimens taken transverse to the extrusion direction. Without die lines, anisotropy in fatigue properties between AA6082 specimens taken longitudinal and transverse to the extrusion direction, was significantly reduced, and properties associated with the orientation of the microstructure appears to be isotropic. A fibrous microstructure for AA6082 specimens showed great improvements in fatigue behavior. The effects of elevated temperatures and exposure of specimens to NaCl solutions was also studied. Exposure to the salt solution greatly reduced the fatigue lives of specimens, while elevated temperatures showed more moderate reductions in fatigue lives.

Nanninga, Nicholas E.

44

High cycle fatigue properties of irradiated and unirradiated stainless steel DIN 1.4948 plate at 823 K  

International Nuclear Information System (INIS)

High cycle fatigue experiments have been carried out on stainless steel DIN X 6 CrNi 1811 (Werkst. 1.4948, similar to AISI 304) in irradiated and reference condition. Specimens were irradiated at 823 K up to a fast fluence (E > 0.1 MeV) of 5x10"2"4n.m"-"2 and a thermal fluence of 1.6x10"2"4n.m"-"2. The nominal test temperature was 823 K; deviations from this nominal value were kept smaller than 3 K by avoiding too high test frequencies. The results indicate a slight increase of the fatigue limit after irradiation from 152.5 MPa to 162.5 MPa. For both conditions the fatigue curve has a horizontal part for Nsub(f) > 8x10"4 cycles. Striation counts indicate that a major part of the fatigue life is consumed by initiation. As a consequence fatigue life and possibly the fatigue limit are dependent on factors which influence the initiation stage of fatigue, like surface roughness, residual stresses and defects

45

Resistance Spot Welding Characteristics and High Cycle Fatigue Behavior of DP 780 Steel Sheet  

Science.gov (United States)

Resistance spot welding characteristics of DP 780 steel was investigated using peel test, microhardness test, tensile shear test, and fatigue test. Tensile shear test provides better spot weld quality than conventional peel test and hardness is not a good indicator of the susceptibility to interfacial fracture. The results of high-cycle fatigue behavior of spot welded DP 780 steel under two different parameters show that at high load low cycle range a significant difference in the S- N curve and almost similar fatigue behavior of spot welds at low load high cycle range are obtained. However, when applied load was converted to stress intensity factor, the difference in the fatigue behavior between welds diminished. Furthermore, a transition in fracture mode, i.e., interfacial and plug and hole-type at about 50% of yield load is observed.

Pal, Tapan Kumar; Bhowmick, Kaushik

2012-02-01

46

The role of high cycle fatigue (HCF) onset in Francis runner reliability  

International Nuclear Information System (INIS)

High Cycle Fatigue (HCF) plays an important role in Francis runner reliability. This paper presents a model in which reliability is defined as the probability of not exceeding a threshold above which HCF contributes to crack propagation. In the context of combined Low Cycle Fatigue (LCF) and HCF loading, the Kitagawa diagram is used as the limit state threshold for reliability. The reliability problem is solved using First-Order Reliability Methods (FORM). A study case is proposed using in situ measured strains and operational data. All the parameters of the reliability problem are based either on observed data or on typical design specifications. From the results obtained, we observed that the uncertainty around the defect size and the HCF stress range play an important role in reliability. At the same time, we observed that expected values for the LCF stress range and the number of LCF cycles have a significant influence on life assessment, but the uncertainty around these values could be neglected in the reliability assessment.

2012-11-26

47

Very High Cycle Fatigue for single phase ductile materials : slip band appearance criterion  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The DISFAT project is a French project financially supported by the French National Agency for Research (ANR). It aims at a deeper understanding of mechanisms leading to crack initiation in metals and alloys under Very High Cycle Fatigue loading (VHCF). The VHCF regime is associated with stress magnitudes lower than the conventional fatigue limit and as a result, numbers of cycles higher than 109. Tests were carried out using an ultrasonic technique at loading frequency of 20 kHz. In the case...

Phung, Ngoc-lam; Marti, Nicolas; Blanche, Antoine; Ranc, Nicolas; Favier, Ve?ronique; Chrysochoos, Andre?; Saintier, Nicolas; Gre?gori, Fabienne; Bacroix, Brigitte; Thoquenne, Guillaume

2013-01-01

48

High-Cycle Fatigue Properties at Cryogenic Temperatures in INCONEL 718  

Science.gov (United States)

High-cycle fatigue properties at 4 K, 20 K, 77 K and 293 K were investigated in forged-INCONEL 718 nickel-based superalloy with a mean gamma (?) grain size of 25 ?m. In the present material, plate-like delta phase precipitated at ? grain boundaries and niobium (Nb)-enriched MC type carbides precipitated coarsely throughout the specimens. The 0.2% proof stress and the tensile strength of this alloy increased with decreasing temperature, without decreasing elongation or reduction of area. High-cycle fatigue strengths also increased with decreasing temperature although the fatigue limit at each temperature didn't appear even around 107 cycles. Fatigue cracks initiated near the specimen surface and formed faceted structures around crack initiation sites. Fatigue cracks predominantly initiated from coarse Nb-enriched carbides and faceted structures mainly corresponded to these carbides. In lower stress amplitude tests, however, facets were formed through transgranular crack initiation and growth. These kinds of distinctive crack initiation behavior seem to lower the high-cycle fatigue strength below room temperature in the present material.

Ono, Y.; Yuri, T.; Sumiyoshi, H.; Takeuchi, E.; Matsuoka, S.; Ogata, T.

2006-03-01

49

High-Cycle Fatigue Properties at Cryogenic Temperatures in INCONEL 718  

International Nuclear Information System (INIS)

High-cycle fatigue properties at 4 K, 20 K, 77 K and 293 K were investigated in forged-INCONEL 718 nickel-based superalloy with a mean gamma (?) grain size of 25 ?m. In the present material, plate-like delta phase precipitated at ? grain boundaries and niobium (Nb)-enriched MC type carbides precipitated coarsely throughout the specimens. The 0.2% proof stress and the tensile strength of this alloy increased with decreasing temperature, without decreasing elongation or reduction of area. High-cycle fatigue strengths also increased with decreasing temperature although the fatigue limit at each temperature didn't appear even around 107 cycles. Fatigue cracks initiated near the specimen surface and formed faceted structures around crack initiation sites. Fatigue cracks predominantly initiated from coarse Nb-enriched carbides and faceted structures mainly corresponded to these carbides. In lower stress amplitude tests, however, facets were formed through transgranular crack initiation and growth. These kinds of distinctive crack initiation behavior seem to lower the high-cycle fatigue strength below room temperature in the present material

2006-03-31

50

Infrared temperature mapping of ULTIMET alloy during high-cycle fatigue tests  

Energy Technology Data Exchange (ETDEWEB)

Fatigue analysis is an important aspect of understanding mechanical properties of metals and alloys. It is well known that the temperature of a specimen during cyclic fatigue testing increases as a result of internal friction. The temperature changes of a specimen are usually obtained using a thermocouple, but such measurements only provide temperature readings at a specific location. On the other hand, a detailed temperature distribution map of the specimen obtained during fatigue tests could be used as a new dynamic method of monitoring crack initiation and propagation behavior. Temperature changes during fatigue tests are expected to be local and in the form of thermal transients. Capturing thermal signatures associated with fatigue cracks requires a high-speed, high-sensitivity infrared imaging system. Relevant studies using a scanning infrared camera (IR) with temperature resolution of 0.1 K at 293 K can be found in the literature. In the present study, a state-of-the-art IR camera was employed to monitor temperature changes of ULTIMET* alloy during high-cycle fatigue tests. Using the snap-shot and the sequence modes of the IR camera, temperature distribution maps of the specimen as a function of time (cycles) have been obtained. This work reports temperature changes during high-cycle fatigue tests and infrared imaging of fatigue cracks as a heat source before the final failure.

Wang, H.; Jiang, L.; Liaw, P.K.; Brooks, C.R.; Klarstrom, D.L.

2000-04-01

51

Infrared temperature mapping of ULTIMET alloy during high-cycle fatigue tests  

International Nuclear Information System (INIS)

Fatigue analysis is an important aspect of understanding mechanical properties of metals and alloys. It is well known that the temperature of a specimen during cyclic fatigue testing increases as a result of internal friction. The temperature changes of a specimen are usually obtained using a thermocouple, but such measurements only provide temperature readings at a specific location. On the other hand, a detailed temperature distribution map of the specimen obtained during fatigue tests could be used as a new dynamic method of monitoring crack initiation and propagation behavior. Temperature changes during fatigue tests are expected to be local and in the form of thermal transients. Capturing thermal signatures associated with fatigue cracks requires a high-speed, high-sensitivity infrared imaging system. Relevant studies using a scanning infrared camera (IR) with temperature resolution of 0.1 K at 293 K can be found in the literature. In the present study, a state-of-the-art IR camera was employed to monitor temperature changes of ULTIMET* alloy during high-cycle fatigue tests. Using the snap-shot and the sequence modes of the IR camera, temperature distribution maps of the specimen as a function of time (cycles) have been obtained. This work reports temperature changes during high-cycle fatigue tests and infrared imaging of fatigue cracks as a heat source before the final failure

2000-04-01

52

Statistical Analysis of High-Cycle Fatigue Behavior of Friction Stir Welded AA5083-H321.  

Science.gov (United States)

A review of the literature revealed that high-cycle fatigue data associated with friction stir-welded (FSW) joints of AA5083-H321 (a solid-solution-strengthened and strain-hardened/stabilized Al-Mg-Mn alloy) are characterized by a relatively large statist...

A. Hariharan B. Pandurangan C. Yen G. Arakere M. Grujicic

2011-01-01

53

Biaxial high cycle fatigue: experimental investigation and two-scale damage model  

International Nuclear Information System (INIS)

This research thesis first describes the multi-axial fatigue phenomenon in the cases of mechanical and complex loadings, discusses multi-axial fatigue criteria, and presents the approach of fatigue by incremental damage mechanics. Then, it reports an experimental investigation of fatigue crack initiation under biaxial polycyclic fatigue in 304L austenitic stainless steel and in titanium alloy. The author presents a probabilistic two-scale damage model, and then reports the assessment of multi-axial fatigue life by means of this model

2009-01-01

54

Robust high-cycle fatigue stress threshold optimization under uncertain loadings  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in english This paper proposes a strategy to achieve robust optimization of structures against high-cycle fatigue when a potentially large number of uncertain load cases are considered. The strategy is heavily based on a convexity property of some of the most commonly used high-cycle design criteria. The conve [...] xity property is rigorously proven for the Crossland fatigue criterion. The proof uses a perturbation technique and involves the principal stress components and analytical expressions for the applicable fatigue criteria. The multiplicity of load cases is treated using load ratios which are bounded but are otherwise free to vary within certain limits. The strategy is applied to a notched plate subject to traditional normal and shear loadings that possess uncertain or unspecified components.

Faria, Alfredo R. de; Frota Jr., Roberto T. C..

55

Effects of load ratio, R, and test temperature on high cycle fatigue behavior of nano-structured Al-4Y-4Ni-X alloy composites  

Energy Technology Data Exchange (ETDEWEB)

Nanostructured Al-4Y-4Ni-X composites created by extruding atomized amorphous powders at different extrusion ratios were tested under high cycle bending fatigue at load ratios, R=0.1, 0.33 and -1 at room temperature, 149 Degree-Sign C and 260 Degree-Sign C. Increasing the extrusion ratio generally improved the fatigue life and the fatigue limits were well in excess of that obtained on conventional aluminum alloys at all temperatures tested. The fatigue limits obtained in this work were also compared to previously reported values for a nanostructured composite Al-Gd-Ni-Fe alloy produced via similar means.

El-Shabasy, Adel B., E-mail: ashabasy@hotmail.com [Department of Design and Production Engineering, Faculty of Engineering, Ain Shams University, Cairo 11517 (Egypt); Hassan, Hala A. [Department of Design and Production Engineering, Faculty of Engineering, Ain Shams University, Cairo 11517 (Egypt); Lewandowski, John J. [Department of Material' s Science and Engineering, Case Western Reserve University, Cleveland, OH 44106 (United States)

2012-12-15

56

New challenges for thermo-mechanical fatigue. 4. High cycle thermal fatigue induced by fluid temperature fluctuation  

International Nuclear Information System (INIS)

Some examples of troubles occurred recently at the pipes used in the light water reactors and the fast breeder reactors in Japan and abroad mostly depend on high-cycle thermal-fatigue by fluid temperature fluctuation. The pipes always are located at the position of flow together with cold and hot water. The initiation mechanism of the high-cycle thermal-fatigue was reviewed based on the IAEA international joint study with participation of specialists in thermal hydraulics and structural design from the world. As measures against the fatigue, the evaluation guideline formulated by the Japan Society of Mechanical Engineers (JSME) was reported. In the guideline, the effect of temperature fluctuation due to the interflow was emphasized. The integration analysis of thermal hydraulics and structure, evaluation methods of crack initiation and stress intensity factor were also introduced and discussed. (author)

2007-04-01

57

Effects of Laser Peening Treatment on High Cycle Fatigue and Crack Propagation Behaviors in Austenitic Stainless Steel  

Science.gov (United States)

Laser peening without protective coating (LPwC) treatment is one of surface enhancement techniques using an impact wave of high pressure plasma induced by laser pulse irradiation. High compressive residual stress was induced by the LPwC treatment on the surface of low-carbon type austenitic stainless steel SUS316L. The affected depth reached about 1mm from the surface. High cycle fatigue tests with four-points rotating bending loading were carried out to confirm the effects of the LPwC treatment on fatigue strength and surface fatigue crack propagation behaviors. The fatigue strength was remarkably improved by the LPwC treatment over the whole regime of fatigue life up to 108 cycles. Specimens with a pre-crack from a small artificial hole due to fatigue loading were used for the quantitative study on the effect of the LPwC treatment. The fracture mechanics investigation on the pre-cracked specimens showed that the LPwC treatment restrained the further propagation of the pre-crack if the stress intensity factor range ?K on the crack tip was less than 7.6 MPa?m. Surface cracks preferentially propagated into the depth direction as predicted through ?K analysis on the crack by taking account of the compressive residual stresses due to the LPwC treatment.

Masaki, Kiyotaka; Ochi, Yasuo; Matsumura, Takashi; Ikarashi, Takaaki; Sano, Yuji

58

Effects of laser peening treatment on high cycle fatigue and crack propagation behaviors in austenitic stainless steel  

International Nuclear Information System (INIS)

Laser peening without protective coating (LPwC) treatment is one of surface enhancement techniques using an impact wave of high pressure plasma induced by laser pulse irradiation. High compressive residual stress was induced by the LPwC treatment on the surface of low-carbon type austenitic stainless steel SUS316L. The affected depth reached about 1mm from the surface. High cycle fatigue tests with four-points rotating bending loading were carried out to confirm the effects of the LPwC treatment on fatigue strength and surface fatigue crack propagation behaviors. The fatigue strength was remarkably improved by the LPwC treatment over the whole regime of fatigue life up to 108 cycles. Specimens with a pre-crack from a small artificial hole due to fatigue loading were used for the quantitative study on the effect of the LPwC treatment. The fracture mechanics investigation on the pre-cracked specimens showed that the LPwC treatment restrained the further propagation of the pre-crack if the stress intensity factor range ?K on the crack tip was less than 7.6 MPa?m. Surface cracks preferentially propagated into the depth direction as predicted through ?K analysis on the crack by taking account of the compressive residual stresses due to the LPwC treatment. (author)

2010-02-01

59

The effect of low cycle fatigue cracks and loading history on high cycle fatigue threshold  

Science.gov (United States)

High cycle fatigue (HCF) has been of great concern of late in light of the many HCF gas turbine engine failures experienced by the U.S. Air Force. Due to the high frequency, failures occur rapidly when components sustain damage from other sources. Low cycle fatigue (LCF) can initiate cracks that produce such damage. This study investigates the HCF threshold of Ti-6A1-4V when naturally initiated small surface cracks (2a = 25 mum--600 mum) are present. Small surface cracks are initiated in notched specimens using two different LCF loading histories at room temperature and 10 Hz. Direct current potential difference (DCPD) is used to detect crack initiation. Surface crack measurements are made using a scanning electron microscope prior to HCF testing. Heat tinting prior to HCF testing is used to mark the crack front to allow for post fracture crack measurements. HCF thresholds at R = 0.1 and R = 0.5 are determined for each specimen using step loading at room temperature and 600 Hz. Additionally, the HCF threshold is measured at R = 0.1 for specimens with small cracks that have been stress relief annealed to eliminate residual stresses and load history. Long crack thresholds are determined using a similar step loading procedure at R = 0.1 and R = 0.5 for specimens which have been precracked using a range of Kmax. Long crack threshold measurements are also determined for specimens which have been precracked using a range of Kmax, but stress relief annealed prior to testing. Comparisons show that HCF threshold measurements, when naturally initiated small cracks are present, are dependent on the load histories that are used to initiate the cracks. Further comparisons show that the measured small crack thresholds follow similar trends for load history effects which occur in the long crack threshold data. Additionally, it is found that thresholds can be measured free of load history effects by using a stress relief annealing process after the precracking and prior to the threshold testing.

Moshier, Monty Allen

60

Microstructural Effects on High Cycle Fatigue of Ni-AI-Mo Aligned Eutectics  

Science.gov (United States)

Two nickel-base aligned eutectics, AG15 (Ni-8.1 wt pct Al-26.4 wt pct Mo) and AG34 (Ni-6.3 wt pct Al-31.2 wt pct Mo), have been tested in high cycle fatigue at room temperature. Experimental variables were test environment and post-solidification heat treatment. The fatigue lives of both alloys and the crack propagation resistance of AG15 improved substantially in tests performed in vacuum vs those performed in air. AG34 had a higher fatigue limit than AGI5; both alloys showed surface initiation and stage I crack propagation. Post-solidification heat treatment had a beneficial effect on the S-N lives of AG34 specimens. Fatigue resistance of both alloys is compared with that of other nickel or cobalt base eutectics strengthened with brittle fibers.

Tartaglia, J. M.; Stoloff, N. S.

1981-06-01

 
 
 
 
61

Avoiding thermal striping damage: Experimentally-based design procedures for high-cycle thermal fatigue  

International Nuclear Information System (INIS)

In the coolant circuits of a liquid metal cooled reactor (LMR), where there is turbulent mixing of coolant streams at different temperatures, there are temperature fluctuations in the fluid. If an item of the reactor structure is immersed in this fluid it will, because of the good heat transfer from the flowing liquid metal, experience surface temperature fluctuations which will induce dynamic surface strains. It is necessary to design the reactor so that these temperature fluctuations do not, over the life of the plant, cause damage. The purpose of this paper is to describe design procedures to prevent damage of this type. Two such procedures are given, one to prevent the initiation of defects in a nominally defect-free structure or to allow initiation only at the end of the component life, and the other to prevent significant growth of undetectable pre-existing defects of the order of 0.2 to 0.4 mm in depth. Experimental validation of these procedures is described, and the way they can be applied in practice is indicated. To set the scene the paper starts with a brief summary of cases in which damage of this type, or the need to avoid such damage, have had important effects on reactor operation. Structural damage caused by high-cycle thermal fatigue has had a significant adverse influence on the operation of LMRs on several occasions. It is necessary to eliminate the risk of such damage at the design stage. In the absence of detailed knowledge of the temperature history to which it will be subject, an LMR structure can be designed so that, if it is initially free of defects more than 0.1 mm deep, no such defects will be initiated by high-cycle fatigue. This can be done by ensuring that the maximum source temperature difference in the liquid metal is less than a limiting value, which depends on temperature. The limit is very low, however, and likely to be restrictive. This method, by virtue of its safety margin, takes into account pre-existing surface crack-like defects up to 0.1 mm deep. If the surface temperature-time history for points on the component is known, the procedure allows the calculation of allowable surface temperature amplitudes such that crack initiation will not occur before the end of the component life. This imposes a less restrictive limit, but it still might be 65 K for a life of 300,000 hours. It is also dependent on the nature of the surface temperature fluctuations, in particular the infrequent large fluctuations. In practice it is difficult to ensure that a structure as built is free from defects greater than 0.1 mm deep, and it has to be recognised that such defects may grow under the imposed thermal loading. A procedure based on limited crack growth and arrest at a depth of about 0.5 mm has been developed. It requires a knowledge of the maximum surface temperature amplitude and the frequency spectrum if the fluctuations, as well as the stress state of the component and the postulated crack shape. For a nominally unstressed structure this procedure is less restrictive and can give allowable amplitudes (though a design safety factor is not included). Detailed information on the temperature fluctuations can in principle be obtained from measurements on the plant or in a liquid metal rig, but it has been shown that if the modelling is correct an air model can provide reliable and conservative information, and can provide it more quickly and economically

1994-11-22

62

Effects of In-Situ Proton-Irradiation and Thermal-Pulse on the High-Cycle Fatigue Properties of Low Carbon 316 Stainless Steels  

Digital Repository Infrastructure Vision for European Research (DRIVER)

For the modifîed 316L stainless steel in which the dislocation interaction governs the fatigue hardening process, the high-cycle fatigue tests were carried out between 300 and 403 K. The in situ irradiation tests and the in situ thermal-pulse tests indicate that dislocation rearrangements due to thermal-pulse give rise to an increase in the areal density of persistent slip bands (PSBs), resulting in elongation of the fatigue life Nf, and an introduction of obstacles to dislocation motions, i...

1996-01-01

63

An Investigation of High-Cycle Fatigue Models for Metallic Structures Exhibiting Snap-Through Response  

Science.gov (United States)

A study is undertaken to develop a methodology for determining the suitability of various high-cycle fatigue models for metallic structures subjected to combined thermal-acoustic loadings. Two features of this problem differentiate it from the fatigue of structures subject to acoustic loading alone. Potentially large mean stresses associated with the thermally pre- and post-buckled states require models capable of handling those conditions. Snap-through motion between multiple post-buckled equilibrium positions introduces very high alternating stress. The thermal-acoustic time history response of a clamped aluminum beam structure with geometric and material nonlinearities is determined via numerical simulation. A cumulative damage model is employed using a rainflow cycle counting scheme and fatigue estimates are made for 2024-T3 aluminum using various non-zero mean fatigue models, including Walker, Morrow, Morrow with true fracture strength, and MMPDS. A baseline zero-mean model is additionally considered. It is shown that for this material, the Walker model produces the most conservative fatigue estimates when the stress response has a tensile mean introduced by geometric nonlinearity, but remains in the linear elastic range. However, when the loading level is sufficiently high to produce plasticity, the response becomes more fully reversed and the baseline, Morrow, and Morrow with true fracture strength models produce the most conservative fatigue estimates.

Przekop, Adam; Rizzi, Stephen A.; Sweitzer, Karl A.

2007-01-01

64

High-cycle fatigue properties of the ODS-alloy MA 6000 at 850 °C  

Science.gov (United States)

The high cycle fatigue (HCF) and cyclic crack growth rate (CCGR) properties of the dispersion strengthened ODS-alloy MA 6000 were investigated with smooth bars and with fracture mechanics samples at 850 °C. The material was very coarse grained with the grains elongated in the rolling direction. Fatigue crack initiation and crack propagation were studied parallel and perpendicular to the rolling direction and a pronounced influence of orientation was found. The fatigue limit of sam-ples cut parallel to the grain elongation direction (p-samples) was almost a factor of 2 higher than the one of samples cut transverse to the elongation direction (t-samples). Inclusions were found to be responsible for crack initiation. For p-samples a reasonable agreement between particle size, fatigue limit, and crack growth behavior was found. For t-type samples such an agreement also exists provided differences in the crack growth behavior of short cracks and long cracks are taken into consideration. The low fatigue strength of t-samples could be linked with low Young's modulus in this direction. The crack propagation rate of long cracks is lower in t-samples than in p-samples due to crack branching along the grain boundaries. HCF-strength of MA 6000 is high compared to conventional cast alloys mainly because of reduced size of crack nucleation sites and higher fatigue threshold stress intensity range ?Kth, as a result of higher Young's modulus.

Hoffelner, W.; Singer, R. F.

1985-03-01

65

High cycle fatigue test and regression methods of S-N curve  

International Nuclear Information System (INIS)

The fatigue design curve in the ASME Boiler and Pressure Vessel Code Section III are based on the assumption that fatigue life is infinite after 106 cycles. This is because standard fatigue testing equipment prior to the past decades was limited in speed to less than 200 cycles per second. Traditional servo-hydraulic machines work at frequency of 50 Hz. Servo-hydraulic machines working at 1000 Hz have been developed after 1997. This machines allow high frequency and displacement of up to ±0.1 mm and dynamic load of ±20 kN are guaranteed. The frequency of resonant fatigue test machine is 50-250 Hz. Various forced vibration-based system works at 500 Hz or 1.8 kHz. Rotating bending machines allow testing frequency at 0.1-200 Hz. The main advantage of ultrasonic fatigue testing at 20 kHz is performing Although S-N curve is determined by experiment, the fatigue strength corresponding to a given fatigue life should be determined by statistical method considering the scatter of fatigue properties. In this report, the statistical methods for evaluation of fatigue test data is investigated

2011-01-01

66

Aspects of high-cycle fatigue performance in a Ti-6Al-4V alloy  

Energy Technology Data Exchange (ETDEWEB)

Determination of critical levels of microstructural damage that can lead to fatigue crack propagation under high-cycle fatigue loading conditions is a major concern for the aircraft industry regarding structural integrity of turbine engine components. The cyclic frequencies characteristic of service loading spectra are extremely high and appear to require a damage-tolerant design approach. One idea for such an approach is to attempt to define a practical, appropriate crack-propagation threshold, {Delta}K{sub TH}. The present study identifies a practical lower-bound large-crack threshold under high-cycle fatigue conditions in a Ti-6 Al-4V blade alloy (with {approximately}60% primary {alpha} in a matrix of lamellar {alpha}+{beta}). The authors suggest that lower-bound thresholds can be determined by modifying standard large-crack propagation tests to simulate small-crack behavior. Modification techniques include high load-ratio testing under both constant-R and constant-K{sub max} conditions, performed at cyclic loading frequencies up to 1 kHz and R ratios up to 0.95. The results of these tests are compared to the near-threshold behavior of naturally-initiated small cracks, and to the crack initiation and early growth behavior of small cracks emanating from sites of simulated foreign object damage.

Boyce, B.L.; Campbell, J.P.; Roder, O.; Thompson, A.W.; Ritchie, R.O.

1999-07-01

67

Thermally Induced Ultra High Cycle Fatigue of Copper Alloys of the High Gradient Accelerating Structures  

CERN Document Server

In order to keep the overall length of the compact linear collider (CLIC), currently being studied at the European Organization for Nuclear Research (CERN), within reasonable limits, i.e. less than 50 km, an accelerating gradient above 100 MV/m is required. This imposes considerable demands on the materials of the accelerating structures. The internal surfaces of these core components of a linear accelerator are exposed to pulsed radio frequency (RF) currents resulting in cyclic thermal stresses expected to cause surface damage by fatigue. The designed lifetime of CLIC is 20 years, which results in a number of thermal stress cycles of the order of 2.33•1010. Since no fatigue data existed in the literature for CLIC parameter space, a set of three complementary experiments were initiated: ultra high cycle mechanical fatigue by ultrasound, low cycle fatigue by pulsed laser irradiation and low cycle thermal fatigue by high power microwaves, each test representing a subset of the original problem. High conductiv...

Heikkinen, Samuli; Wuensch, Walter

2010-01-01

68

High-cycle fatigue properties of the ODS-alloy MA 6000 at 850 C  

Energy Technology Data Exchange (ETDEWEB)

The high cycle fatigue (HCF) and cyclic crack growth rate (CCGR) properties of the dispersion strengthened ODS-alloy MA 6000 were investigated with smooth bars and with fracture mechanics samples at 850 C. The material was very coarse-grained with the grains elongated in the rolling direction. The fatigue limit of samples cut parallel to the grain elongation direction (p-samples) was almost a factor of 2 higher than the one of samples cut transverse to the elongation direction (t-samples). Inclusions were found to be responsible for crack initiation. For p-samples a reasonable agreement between particle size, fatigue limit, and crack growth behavior was found. For t-type samples such an agreement also exists, provided differences in the crack growth behavior of short cracks and long cracks are taken into consideration. The low fatigue strength of t-samples could be linked with low Young's modulus in this direction. The crack propagation rate of long cracks is lower in t-samples than in p-samples due to crack branching along the grain boundaries. HCF-strength of MA 6000 is high compared to conventional cast alloys mainly because of reduced size of crack nucleation sites and higher fatigue threshold stress intensity range, as a result of higher Young's modulus. 15 references.

Hoffelner, W.; Singer, R.F.

1985-03-01

69

High-cycle fatigue characteristics of weldable steel for light-water reactors  

International Nuclear Information System (INIS)

Czechoslovak and Soviet 15Kh2NMFA steel was used for running fatigue tests at temperatures of 20, 350 and 400 degC in the high-cycle range with various loading regimes. The results show that at the given temperatures in this type of steel a cyclic softening occurs. The fatigue characteristics were measured with great dispersion of results, but within this dispersion they are almost identical for various steels at the same temperature. Increased temperature results in the decrease in the amplitude of cyclic deformation stress and in the increase in the amplitude of plastic deformation. The diversity in the values of cyclic plasticity and stress response measured in the given mode may be explained by the lower level of softening and the non-homogeneous cyclic plastic deformation of material under the given constant conditions. (J.B.)

1982-01-01

70

High cycle fatigue of a die cast AZ91E-T4 magnesium alloy  

International Nuclear Information System (INIS)

This study reveals the micro-mechanisms of fatigue crack nucleation and growth in a commercial high-pressure die cast automotive AZ91E-T4 Mg component. Mechanical fatigue tests were conducted under R=-1 conditions on specimens machined at different locations in the casting at total strain amplitudes ranging from 0.02% to 0.5%. Fracture surfaces of specimens that failed in the high cycle fatigue regime with lives spanning two orders of magnitude were examined using a scanning electron microscope. The difference in lives for the Mg specimens was primarily attributed to a drastic difference in nucleation site sizes, which ranged from several hundred ?m's to several mm's. A secondary effect may include the influence of average secondary dendrite arm spacing and average grain size. At low crack tip driving forces (Kmaxmax>3.5 MPa ? m fractured particles and boundary decohesion created weak paths for fatigue crack propagation, and consequently the cracks followed the interdendritic regions, leaving serrated markings as the crack progressed through this heterogeneous region. The ramifications of the results on future modeling efforts are discussed in detail

2004-03-08

71

Device for carrying out environmental very high cycle fatigue tests with ultrasonic excitation in asymmetric push-pull mode  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The increasing lifetime of many engineering components leads to a growing demand for accelerated testing methods. Fatigue failure of components submitted to cyclic loading at stress levels below the endurance limit occurs even beyond 10(7) cycles which has been the traditional limit for fatigue testing in most laboratories. Test programs covering this range of cycles on servo-hydraulic or resonance machines are very time consuming. Therefore methods for very high cycle fatigue (VHCF) testing ...

Bruchhausen, M.; Haehner, P.; Fischer, B.; Cornu, D.

2013-01-01

72

Very high cycle regime fatigue of thin walled tubes made from austenitic stainless steel  

DEFF Research Database (Denmark)

Fatigue life data of cold worked tubes (diameter 4 mm, wall thicknesses 0.25 and 0.30 mm) of an austenitic stainless steel, AISI 904 L, were measured in the regime ranging from 2 Ã? 105 to 1010 cycles to failure. The influence of the loading frequency was investigated as data were obtained in conventional rotating bending at 160 and 200 Hz and in ultrasonic axial loading at 20 kHz. Above 5 Ã? 106 cycles the fatigue lifetimes found with both methods were comparable. The results show that the slope of the Sâ??N curve significantly decreases beyond 108 cycles. Fracture surfaces were examined using scanning electron microscopy. Fatigue cracks initiate at the surface and no significant influence from frequency or from loading modes on fatigue crack initiation and growth is visible.

Carstensen, J.V.; Mayer, H.

2002-01-01

73

Hydrogen induced surface cracking in an 8090 Al-Li alloy during high cycle fatigue  

Energy Technology Data Exchange (ETDEWEB)

In recent years, there has been an increasing interest in understanding the effects of aggressive or moist environments on the properties of Al-Li alloys. However, most of the existing work has been focused on their stress corrosion cracking resistance. Consequently, only a few reports are available on the environmental fatigue strength of these alloys. Upon exposure to aggressive environments, the fatigue crack propagation resistance can be detrimentally affected. R. Piascik and R. Gangloff found enhanced cyclic crack growth rates in an Al-Li-Cu alloy when a critical water vapor pressure was exceeded. Thermodynamically, at atmospheric pressures, strong interactions between hydrogen and lithium are expected to give rise to stable lithium hydrides. Evidence for the development of hydride phases in Al-Li alloys exposed to hydrogen environments has been reported by various workers. Thus, it is likely that HE via hydride formation can be the relevant mechanisms in Al-Li alloys that have been in contact with hydrogen. Since lithium hydrides are stable up to temperatures of 773 K, previous hydrogen exposure can lead to an irreversible mode of embrittlement. Thus, it was the objective of the present work to investigate the effects of hydrogen during aging on the ensuing high cycle fatigue (HCF) performance of an 8090 Al-Li alloy.

Laffin, C.; Raghunath, C.R.; Lopez, H.F. (Univ. of Wisconsin, Milwaukee, WI (United States). Materials Dept.)

1993-10-01

74

Microstructure-sensitive weighted probability approach for modeling surface to bulk transition of high cycle fatigue failures dominated by primary inclusions  

Science.gov (United States)

The mechanical alloying and casting processes used to make polycrystalline metallic materials often introduce undesirable non-metallic inclusions and pores. These are often the dominant sites of fatigue failure origination at the low stress amplitudes that correspond to the high cycle fatigue (HCF) and very high cycle fatigue (VHCF) regimes, in which the number of cycles to crack initiation is more than 106. HCF and VHCF experiments on some advanced metallic alloys, such as powder metallurgy Ni-base superalloys, titanium alloys, and high-strength steels have shown that the critical inclusions and pores can appear on the surface as well as in the bulk of the specimen. Fatigue lives have been much higher for specimens that fail from a bulk site. The relative number of bulk initiations increases as the stress amplitude decreases such that just below the traditional HCF limit, fatigue life data appears to be evenly scattered between two datasets corresponding to surface and bulk initiations. This is often referred to as surface to bulk transition in the VHCF regime. Below this transition stress, the likelihood of surface versus bulk initiation significantly impacts the low failure probability estimate of fatigue life. Under these circumstances, a large number of very costly experiments need to be conducted to obtain a statistically representative distribution of fatigue life and to predict the surface versus bulk initiation probability. In this thesis, we pursue a simulation-based approach whereby microstructure-sensitive finite element simulations are performed within a statistical construct to examine the VHCF life variability and assess the surface initiation probability. The methodology introduced in this thesis lends itself as a cost-effective platform for development of microstructure-property relations to support design of new or modified alloys, or to more efficiently predict the properties of existing alloys.

Salajegheh, Nima

75

Mean stress effects on high-cycle fatigue of Alloy 718  

International Nuclear Information System (INIS)

This report covers an investigation of the effects of tensile mean stress on the high-cycle fatigue properties of Alloy 718. Three test temperatures (24, 427, and 649 degree C) were employed, and there were tests in both strain and load control. Results were compared with three different models: linear Modified-Goodman, Peterson cubic, and stress-strain parameter. The linear Modified-Goodman model gave good correlation with actual test data for low and moderate mean stress values, but the stress-strain parameter showed excellent correlation over the entire range of possible mean stresses and therefore is recommended for predicting mean stress effects of Alloy 718. 13 refs., 12 figs

1980-01-01

76

The Effect of a Non-Gaussian Random Loading on High-Cycle Fatigue of a Thermally Post-Buckled Structure  

Science.gov (United States)

High-cycle fatigue of an elastic-plastic beam structure under the combined action of thermal and high-intensity non-Gaussian acoustic loadings is considered. Such loadings can be highly damaging when snap-through motion occurs between thermally post-buckled equilibria. The simulated non-Gaussian loadings investigated have a range of skewness and kurtosis typical of turbulent boundary layer pressure fluctuations in the vicinity of forward facing steps. Further, the duration and steadiness of high excursion peaks is comparable to that found in such turbulent boundary layer data. Response and fatigue life estimates are found to be insensitive to the loading distribution, with the minor exception of cases involving plastic deformation. In contrast, the fatigue life estimate was found to be highly affected by a different type of non-Gaussian loading having bursts of high excursion peaks.

Rizzi, Stephen A.; Behnke, marlana N.; Przekop, Adam

2010-01-01

77

Study of the influence of microstructure on fatigue crack propagation in the high cycle fatigue regime in 316L steel  

International Nuclear Information System (INIS)

Full text of publication follows: In the High cycle fatigue regime, about 80 percent of the fatigue live of austenitic stainless steel specimens consists in the propagation of short cracks whose length is comparable to the size of few grains. This high sensitivity of crack propagation to microstructure can explain partly the dispersion that is observed in this regime. At very low load level close to the fatigue limit, this dispersion can reach a factor 100 which complicates predictions of fatigue lives of large structures in service. As a consequence, to assess and predict this dispersion, it is necessary to understand better how microstructure influences locally crack propagation, i.e., the development of cyclic plasticity at the crack tip. In this aim, we propose to describe the influence of crystallographic orientation on the cyclic behavior of the grains of 316L stainless steel using crystal plasticity theory. In a first step, the stress strain response of the 316L grains is simulated using elastic-plastic constitutive equations that have been implemented in the three dimensional finite element code Cast3m of the CEA. The evolution of the resolved shear stress on each slip system is described with a non linear kinematics hardening law. This law is identified using cyclic stress strain curves obtained on austenitic stainless steel monocrystal. In a second step, the crack tip opening displacement (CTOD) will be calculated for different crystallographic orientation in order to quantify the influence of the crystallographic orientation of the grain at the crack tip on crack propagation. A statistic treatment of the CTOD values obtained from the finite element simulations performed at the local scale of the grain can help to understand the dispersion observed at the macroscopic scale. (authors)

2007-12-10

78

Study of the influence of microstructure on fatigue crack propagation in the high cycle fatigue regime in 316L steel  

Energy Technology Data Exchange (ETDEWEB)

Full text of publication follows: In the High cycle fatigue regime, about 80 percent of the fatigue live of austenitic stainless steel specimens consists in the propagation of short cracks whose length is comparable to the size of few grains. This high sensitivity of crack propagation to microstructure can explain partly the dispersion that is observed in this regime. At very low load level close to the fatigue limit, this dispersion can reach a factor 100 which complicates predictions of fatigue lives of large structures in service. As a consequence, to assess and predict this dispersion, it is necessary to understand better how microstructure influences locally crack propagation, i.e., the development of cyclic plasticity at the crack tip. In this aim, we propose to describe the influence of crystallographic orientation on the cyclic behavior of the grains of 316L stainless steel using crystal plasticity theory. In a first step, the stress strain response of the 316L grains is simulated using elastic-plastic constitutive equations that have been implemented in the three dimensional finite element code Cast3m of the CEA. The evolution of the resolved shear stress on each slip system is described with a non linear kinematics hardening law. This law is identified using cyclic stress strain curves obtained on austenitic stainless steel monocrystal. In a second step, the crack tip opening displacement (CTOD) will be calculated for different crystallographic orientation in order to quantify the influence of the crystallographic orientation of the grain at the crack tip on crack propagation. A statistic treatment of the CTOD values obtained from the finite element simulations performed at the local scale of the grain can help to understand the dispersion observed at the macroscopic scale. (authors)

Ferrie, E. [CEA Saclay, Dir. de l' Energie Nucleaire (DEN/SRMA), 91 - Gif sur Yvette (France); Sauzay, M. [CEA Saclay (DEN/DANS/DMN/SRMA/LC2M), 91 - Gif-sur-Yvette (France)

2007-07-01

79

Comparison of the very high cycle fatigue behaviors of INCONEL 718 with different loading frequencies  

Science.gov (United States)

In order to clarify the differences of very high cycle fatigue (VHCF) behavior of nickel based superalloy IN718 with different loading frequencies, stress-controlled fatigue tests were carried out by using ultrasonic testing method (20 KHz) and rotary bending testing method (52.5 Hz), both at room temperatures, to establish stress versus cycles to failure (S-N) relationships. Results disclosed that cycles to failure at a given stress level increased with an increase of the applied frequency, i.e., the higher frequency produced an upper shift of the S-N curves. Fractographic analysis suggested that crack initiation and propagation behaviors had large differences: cracks in low-frequency tests preferentially initiated from multiple sources on the specimen surface, while in high-frequency tests, cracks mostly originated from a unique source of subsurface inclusions. Subsequently, frequency-involved modeling was proposed, based on the damage accumulation theory, which could well illustrate qualitatively those comparisons due to different loading frequencies.

Zhang, YangYang; Duan, Zheng; Shi, HuiJi

2013-03-01

80

Additive manufactured AlSi10Mg samples using Selective Laser Melting (SLM): Microstructure, high cycle fatigue, and fracture behavior  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In order to produce serial parts via additive layer manufacturing, the fatigue performance can be a critical attribute. In this paper, the microstructure, high cycle fatigue (HCF), and fracture behavior of additive manufactured AlSi10Mg samples are investigated. The samples were manufactured by a particular powder-bed process called Selective Laser Melting (SLM) and machined afterwards. 91 samples were manufactured without (30°C) and with heating (300°C) of the building platform and in diff...

Brandl, E.; Heckenberger, U.; Holzinger, V.; Buchbinder, D.

2012-01-01

 
 
 
 
81

Laser High-Cycle Thermal Fatigue of Pulse Detonation Engine Combustor Materials Tested  

Science.gov (United States)

Pulse detonation engines (PDE's) have received increasing attention for future aerospace propulsion applications. Because the PDE is designed for a high-frequency, intermittent detonation combustion process, extremely high gas temperatures and pressures can be realized under the nearly constant-volume combustion environment. The PDE's can potentially achieve higher thermodynamic cycle efficiency and thrust density in comparison to traditional constant-pressure combustion gas turbine engines (ref. 1). However, the development of these engines requires robust design of the engine components that must endure harsh detonation environments. In particular, the detonation combustor chamber, which is designed to sustain and confine the detonation combustion process, will experience high pressure and temperature pulses with very short durations (refs. 2 and 3). Therefore, it is of great importance to evaluate PDE combustor materials and components under simulated engine temperatures and stress conditions in the laboratory. In this study, a high-cycle thermal fatigue test rig was established at the NASA Glenn Research Center using a 1.5-kW CO2 laser. The high-power laser, operating in the pulsed mode, can be controlled at various pulse energy levels and waveform distributions. The enhanced laser pulses can be used to mimic the time-dependent temperature and pressure waves encountered in a pulsed detonation engine. Under the enhanced laser pulse condition, a maximum 7.5-kW peak power with a duration of approximately 0.1 to 0.2 msec (a spike) can be achieved, followed by a plateau region that has about one-fifth of the maximum power level with several milliseconds duration. The laser thermal fatigue rig has also been developed to adopt flat and rotating tubular specimen configurations for the simulated engine tests. More sophisticated laser optic systems can be used to simulate the spatial distributions of the temperature and shock waves in the engine. Pulse laser high-cycle thermal fatigue behavior has been investigated on a flat Haynes 188 alloy specimen, under the test condition of 30-Hz cycle frequency (33-msec pulse period and 10-msec pulse width including a 0.2-msec pulse spike; ref. 4). Temperature distributions were calculated with one-dimensional finite difference models. The calculations show that that the 0.2-msec pulse spike can cause an additional 40 C temperature fluctuation with an interaction depth of 0.08 mm near the specimen surface region. This temperature swing will be superimposed onto the temperature swing of 80 C that is induced by the 10-msec laser pulse near the 0.53-mm-deep surface interaction region.

Zhu, Dong-Ming; Fox, Dennis S.; Miller, Robert A.

2001-01-01

82

Influence of HVOF sprayed WC/Co coatings on the high-cycle fatigue strength of mild steel  

International Nuclear Information System (INIS)

HVOF thermally sprayed WC/Co coatings are applied onto components which are exposed to wear caused by abrasion, erosion, fretting and sliding. Beside wear attacks and static stresses in lots of cases alternating mechanical stresses caused by dynamic loads occur additionally. Therefore, the fatigue resistance of WC/Co 88/12 and WC/Co 83/17 coated specimens was investigated by high-cycle fatigue tests (HCF). The results of the fatigue tests were documented in statistically ascertained Woehler-diagrams (S-N-curves). Furthermore, the mechanisms of failure are discussed

1995-09-11

83

Probabilistic material strength degradation model for Inconel 718 components subjected to high temperature, high-cycle and low-cycle mechanical fatigue, creep and thermal fatigue effects  

Science.gov (United States)

The development of methodology for a probabilistic material strength degradation is described. The probabilistic model, in the form of a postulated randomized multifactor equation, provides for quantification of uncertainty in the lifetime material strength of aerospace propulsion system components subjected to a number of diverse random effects. This model is embodied in the computer program entitled PROMISS, which can include up to eighteen different effects. Presently, the model includes five effects that typically reduce lifetime strength: high temperature, high-cycle mechanical fatigue, low-cycle mechanical fatigue, creep and thermal fatigue. Results, in the form of cumulative distribution functions, illustrated the sensitivity of lifetime strength to any current value of an effect. In addition, verification studies comparing predictions of high-cycle mechanical fatigue and high temperature effects with experiments are presented. Results from this limited verification study strongly supported that material degradation can be represented by randomized multifactor interaction models.

Bast, Callie C.; Boyce, Lola

1995-11-01

84

Probabilistic Material Strength Degradation Model for Inconel 718 Components Subjected to High Temperature, High-Cycle and Low-Cycle Mechanical Fatigue, Creep and Thermal Fatigue Effects  

Science.gov (United States)

The development of methodology for a probabilistic material strength degradation is described. The probabilistic model, in the form of a postulated randomized multifactor equation, provides for quantification of uncertainty in the lifetime material strength of aerospace propulsion system components subjected to a number of diverse random effects. This model is embodied in the computer program entitled PROMISS, which can include up to eighteen different effects. Presently, the model includes five effects that typically reduce lifetime strength: high temperature, high-cycle mechanical fatigue, low-cycle mechanical fatigue, creep and thermal fatigue. Results, in the form of cumulative distribution functions, illustrated the sensitivity of lifetime strength to any current value of an effect. In addition, verification studies comparing predictions of high-cycle mechanical fatigue and high temperature effects with experiments are presented. Results from this limited verification study strongly supported that material degradation can be represented by randomized multifactor interaction models.

Bast, Callie C.; Boyce, Lola

1995-01-01

85

Application of in situ thermography for evaluating the high-cycle and very high-cycle fatigue behaviour of cast aluminium alloy AlSi7Mg (T6).  

Science.gov (United States)

The present paper illustrates the application of infrared thermal measurements for the investigation of crack initiation point and crack propagation in the high-cycle and the very high-cycle fatigue range of cast AlSi7Mg alloy (A356). The influence of casting defects, their location, size and amount was studied both by fractography and thermography. Besides internal and surface fatigue crack initiation as a further crack initiation type multiple fatigue crack initiation was observed via in situ thermography which can be well correlated with the results from fractography obtained by SEM investigations. In addition, crack propagation was studied by the development of the temperature measured via thermography. Moreover, the frequency influence on high-cycle fatigue behaviour was investigated. The presented results demonstrate well that the combination of fractography and thermography can give a significant contribution to the knowledge of crack initiation and propagation in the VHCF regime. PMID:23541962

Krewerth, D; Weidner, A; Biermann, H

2013-12-01

86

A study on fatigue crack growth in the high cycle domain assuming sinusoidal thermal loading  

Energy Technology Data Exchange (ETDEWEB)

The assessment of fatigue crack growth due to turbulent mixing of hot and cold coolants presents significant challenges, in particular to determine the thermal loading spectrum and the associated crack growth. The sinusoidal method is a simplified approach for addressing this problem, in which the entire spectrum is replaced by a sine-wave variation of the temperature at the inner pipe surface. The loading frequency is taken as that which gives the shortest crack initiation and growth life. Such estimates are intended to be conservative but not un-realistic. Several practical issues which arise with this approach have been studied using newly-developed analytical solutions for the temperature and stress fields in hollow cylinders, in particular the assumptions made concerning the crack orientation, dimensions and aspect ratio. The application of the proposed method is illustrated for the pipe geometry and loadings conditions reported for the Civaux 1 case where through wall thermal fatigue cracks developed in a short time, but the problem is relevant also for fast reactor components.

Radu, V., E-mail: vasile.radu@nuclear.r [Institute for Nuclear Research, 1st Campului Street, 115400 Mioveni, Arges POB 78, Pitesti (Romania); Paffumi, E. [European Commission, Joint Research Centre, Institute for Energy, Petten (Netherlands); Taylor, N. [European Commission, Joint Research Centre, Institute for Energy, Ispra (Italy); Nilsson, K.-F. [European Commission, Joint Research Centre, Institute for Energy, Petten (Netherlands)

2009-12-15

87

Ultrasonic evaluation of the effects of compressive residual stresses on aircraft engine turbine blades subjected to high cycle fatigue  

International Nuclear Information System (INIS)

Experiments conducted on titanium (Ti-64) turbine blades with the LCR ultrasonic wave at 20 MHz showed significant differences in untreated blades and blades treated to increase the subsurface compressive residual stress. Group 1 showed significant differences in the treated and untreated areas, the top and bottom of the blades, high cycle fatigue and cracked and uncracked conditions. Group 2 blades showed significant difference between untreated and treated travel-times at probes located at the blade leading edge

2002-05-25

88

Simulation of Delamination Propagation in Composites Under High-Cycle Fatigue by Means of Cohesive-Zone Models  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A damage model for the simulation of delamination propagation under high-cycle fatigue loading is proposed. The basis for the formulation is a cohesive law that links fracture and damage mechanics to establish the evolution of the damage variable in terms of the crack growth rate dA/dN. The damage state is obtained as a function of the loading conditions as well as the experimentally-determined coefficients of the Paris Law crack propagation rates for the material. It is shown that by using t...

Turon Travesa, Albert; Costa I Balanzat, Josep; Camanho, Pedro P.; Da?vila, Carlos G.

2006-01-01

89

High cycle thermal fatigue: benchmark at a Te junction piping system of the nuclear power plant Phenix  

International Nuclear Information System (INIS)

This paper presents the studies of the benchmark concerning a high cycle thermal fatigue problem. This benchmark is based on an industrial case, a Te junction piping system of the french FBR Phenix. The main objectives were the comparison of the different methods used by the participants and the analysis of the damage evaluation methods capacity compared to the observed phenomena. This study took place in an international framework with the United Kingdom, Italy, Japan, Korea, Russia, India and France. (A.L.B.)

2000-11-23

90

Simulation of Delamination Propagation in Composites Under High-Cycle Fatigue by Means of Cohesive-Zone Models  

Science.gov (United States)

A damage model for the simulation of delamination propagation under high-cycle fatigue loading is proposed. The basis for the formulation is a cohesive law that links fracture and damage mechanics to establish the evolution of the damage variable in terms of the crack growth rate dA/dN. The damage state is obtained as a function of the loading conditions as well as the experimentally-determined coefficients of the Paris Law crack propagation rates for the material. It is shown that by using the constitutive fatigue damage model in a structural analysis, experimental results can be reproduced without the need of additional model-specific curve-fitting parameters.

Turon, Albert; Costa, Josep; Camanho, Pedro P.; Davila, Carlos G.

2006-01-01

91

High-cycle fatigue tests as a method for rapid determination of materials endurance  

International Nuclear Information System (INIS)

It is suggested, that high-frequency cyclic loading should be used for accelerated determination of the metal fatigue characteristics. Data on the dependence of the endurance limit of some materials (1Kh2M, I5 steel, VT22M, VT20Y alloys) on the frequency of symmetric extension-compression within 10-20000 Hz range are presented. Perspectiveness of high-frequency cyclic loading methods is noted for comparative fatigue tests with minimum expenditures of time and facilities

1980-10-01

92

Thermal mixing in T-junction piping system concerned with high-cycle thermal fatigue in structure  

International Nuclear Information System (INIS)

In Japan Atomic Energy Agency (JAEA), a numerical simulation code 'MUGTHES' has been developed to investigate thermal striping phenomena caused by turbulence mixing of fluids in different temperature and to provide transient data for an evaluation method of high-cycle thermal fatigue. MUGTHES adopts Large Eddy Simulation (LES) approach to predict unsteady phenomena in thermal mixing and employs boundary fitted coordinate system to be applied to complex geometry in a power reactor. Numerical simulation of thermal striping phenomena in a T-junction piping system (T-pipe) is conducted. Boundary condition for the simulation is chosen from an existing water experiment in JAEA, named as WATLON experiment. In the numerical simulation, standard Smagorinsky model is employed as eddy viscosity model with the model coefficient of 0.14 (=Cs). Numerical results of MUGTHES are verified by the comparisons with experimental results of velocity and temperature. Through the numerical simulation in the T-pipe, applicability of MUGTHES to the thermal striping phenomena is confirmed and the characteristic large-scale eddy structure which dominates thermal mixing and may cause high-cycle thermal fatigue is revealed. (author)

2008-11-24

93

Some regularities of austenite steel structure phase state evolution at high-cycle fatigue  

International Nuclear Information System (INIS)

A study is made into the evolution of grain structure, structural and phase states and defect substructure of austenitic steel type 08Kh18N10T on fatigue testing at frequency of load alternations of 20 Hz and applied stress of 20 MPa. It is shown that under fatigue test conditions the transformation of dislocation structure occurs that is related not only with the process of material deformation but also with dynamic recrystallization. The latter results in the formation of gradient structure characterized by variations of mean longitudinal and lateral grain size, a coefficient of their anisotropy and a texture vector scattering angle as the distance to a fracture surface increases

2006-06-01

94

On crack closure and S-N fatigue life  

International Nuclear Information System (INIS)

The influence of crack closure on the fatigue life of common pressure vessel steels is investigated. In particular, experimental failure data used as the basis for the ASME Boiler and Pressure Vessel Code fatigue design criterion is evaluated. Generally, crack closure may influence crack propagation rates and thus the number of cycles-to-failure in fatigue specimens as well as in structural components. However, unlike the specimens, inservice components are subjected to assorted loadings, varying in both magnitude and type, as well as residual stresses, applied mean stresses and miscellaneous geometric constraints, all of which may influence crack closure. A bound on crack closure effects is established by estimating the cycles-to-failure of standard fatigue specimens assuming no crack closure occurs. Results indicate that fatigue life is significantly affected by an absence of crack closure and that mean stresses previously thought to be important only in the high cycle regime may be influential over the entire range of applied stresses or strains. Further work is continuing to quantify these effects for the general conditions important in designing components

1994-06-19

95

The Effect of Ballistic Impacts on the High Cycle Fatigue Properties of Ti-48Al-2Nb-2Cr (at.%)  

Science.gov (United States)

The ability of gamma - TiAl to withstand potential foreign and/or domestic object damage is a technical risk to the implementation of gamma - TiAl in low pressure turbine (LPT) blade applications. The overall purpose of the present study was to determine the influence of ballistic impact damage on the high cycle fatigue strength of gamma - TiAl simulated LPT blades. Impact and specimen variables included ballistic impact energy, projectile hardness, impact temperature, impact location, and leading edge thickness. The level of damage induced by the ballistic impacting was studied and quantified on both the impact (front) and backside of the specimens. Multiple linear regression was used to model the cracking and fatigue response as a function of the impact variables. Of the impact variables studied, impact energy had the largest influence on the response of gamma - TiAl to ballistic impacting. Backside crack length was the best predictor of remnant fatigue strength for low energy impacts (GE90 engine, a Ti-48Al-2Nb-2Cr LPT blade would survive an impact of normal service conditions.

Draper, S. L.; Lerch, B. A.; Pereira, J. M.; Nathal, M. V.; Austin, C. M.; Erdman, O.

2000-01-01

96

High Cycle Fatigue of Al and Cu Thin Films by a Novel High-Throughput Method  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In the last two decades, the reliability of small electronic devices used in automotive or consumer electronics gained researchers attention. Thus, there is the need to understand the fatigue properties and damage mechanisms of thin films. In this thesis a novel high-throughput testing method for thin films on Si substrate is presented. The specialty of this method is to test one sample at different strain amplitudes at the same time and measure an entire lifetime curve with only one experiment.

Burger, Sofie

2013-01-01

97

Influence of Microstructural Inhomogeneity and Residual Stress on Very High Cycle Fatigue Property of Clean Spring Steel  

Science.gov (United States)

The present study investigated the very high cycle fatigue (VHCF) properties of a spring steel SUP7-T386 under the conditions of surface grinding and electro-polishing by performing the axial loading test at a stress ratio of -1. The influence of the microstructural inhomogeneity (MI) generated in the process of heat treatment and the residual stress induced by surface grinding on the VHCF properties was discussed. This steel with surface grinding exhibits the continuously descending S-N characteristics, corresponding to the surface flaw-induced failure at high stress level and the interior flaw-induced failure at low stress level. Otherwise, with surface electro-polishing, it exhibits continuously descending S-N characteristics with lower fatigue strength, but only corresponding to the surface flaw-induced failure even at low stress level. Compared with the evaluated maximum inclusion size of about 11.5 ?m, the larger MI size and the compressive residual stress play a key role in determining fatigue failure mechanism of this steel under axial loading in the VHCF regime. From the viewpoint of fracture mechanics, MI-induced crack growth behavior belongs to the category of small crack growth, and threshold stress intensity factors controlling surface and interior crack growth are evaluated to be 2.85 and 2.51 MPa m1/2, respectively. The predicted maximum MI size of about 27.6 ?m can be well used to evaluate surface and interior fatigue limit of this steel under axial loading in the VHCF regime, combined with the correction of residual stress.

Li, Wei; Sakai, Tatsuo; Wang, Ping

2013-09-01

98

Coating pre-cracking effect on the LCF fatigue life of superalloys for gas turbine blades  

Energy Technology Data Exchange (ETDEWEB)

Low cycle fatigue (LCF) strain controlled experimental fatigue tests were conducted on the nickel superalloy MAR-M002 used in the construction of gas turbine blades. The aim of the study was to compare dwell times and high cycle fatigue (HCF) and LCF combined cycle fatigue test conditions. The study focused on investigating the potentially detrimental effect of coating cracking. A fatigue test system was equipped with an induction furnace and a high temperature extensometer. A procedure was developed to generate controlled cracking in the coating prior to fatigue testing. Loading modes used in the tests were representative of loads experienced by the superalloy turbine blades when in operation. HCF amplitudes were superimposed on major LCF cycles. It was concluded that coating cracks do not significantly impact the LCF fatigue life of aluminized investment casting nickel superalloy MAR-M002. 7 refs., 1 tab., 12 figs.

Filippini, M.; Foletti, S. [Politecnico di Milano, Milan (Italy); Pasquero, G. [AVIO SpA, Rivalta di Torino (Italy)

2009-07-01

99

Effects of alloying and heat treatment on the endurance limit of molybdenum in high cycle fatigue tests  

International Nuclear Information System (INIS)

The endurance limit (?sigmasub(w)) of molybdenum was investigated on four different materials in push-pull type high cycle fatigue tests at room temperature. The ?sigmasub(w) of recrystallized (AN) specimens was determined as 780 MN/cm2 in stress range, independent of materials, while that of stress relieved (SR) specimens was larger for TZM alloy than for other materials. The fracture toughness was estimated as 22.5 and 11.5 MN/msup(3/2) for SR and AN specimens, respectively. Intergranular fracture of AN specimens indicated that the ?sigmasub(w) can be governed by the decohesion strength of grain boundaries which is not affected by alloying. (orig.)

1984-05-01

100

Mechanism of fatigue crack initiation and propagation in the very high cycle fatigue regime of high-strength steels  

International Nuclear Information System (INIS)

Fatigue fracture surfaces of high-strength steels generated by a very high number of cycles to failure show so-called fine granular areas, for which the crack initiation and propagation mechanism is not fully understood. To clarify this mechanism of crack growth, scanning electron/ion microscopy, focused ion beam and transmission electron microscopy investigations were carried out at fracture surfaces showing this special crack part. On the basis of the results a mechanism for the formation of this area is proposed.

2012-11-01

 
 
 
 
101

High Cycle Thermal Fatigue Analysis for a Mixing Tee in Safety Injection and Shutdown Cooling System of SKN Unit 3 and 4 Power Plant  

International Nuclear Information System (INIS)

Safety Injection and Shutdown Cooling system (SISC) in a nuclear power plant has an important role of core cooling during plant shutdown and on emergency conditions. A heat exchanger on the SISC removes the heat energy generated in the reactor core during shutdown cooling event. Mixing tee placed on downstream of the heat exchanger designates a Tshaped branch connection where the hot flow passed through the by-pass line mixes with the flow passed through the heat exchanger, and due to the characteristics of fluid with bad heat conductivity, the flow develops a mixing zone in a distance from the mixing tee. The pipe wall in the mixing zone experiences the thermal oscillation of high cycle, and therefore is in a state of the high cycle thermal fatigue loadings. In this work, performed is the high cycle thermal fatigue analysis for a mixing tee under the prescribed thermal loadings in a mixing zone. Using the evaluation guide established by JSME, JSME S017- 2003 which has evaluation procedure composing of the four steps, we evaluate the fatigue integrity of the mixing tee of which the results show that the mixing tee satisfies the fatigue integrity in the last step (fourth) of four steps of evaluation procedure where the fatigue usage factor, U was calculated and then compared with the well known criterion, U<1. Representative results of the fatigue analysis are also discussed

2011-05-01

102

High Cycle Thermal Fatigue Analysis for a Mixing Tee in Safety Injection and Shutdown Cooling System of SKN Unit 3 and 4 Power Plant  

Energy Technology Data Exchange (ETDEWEB)

Safety Injection and Shutdown Cooling system (SISC) in a nuclear power plant has an important role of core cooling during plant shutdown and on emergency conditions. A heat exchanger on the SISC removes the heat energy generated in the reactor core during shutdown cooling event. Mixing tee placed on downstream of the heat exchanger designates a Tshaped branch connection where the hot flow passed through the by-pass line mixes with the flow passed through the heat exchanger, and due to the characteristics of fluid with bad heat conductivity, the flow develops a mixing zone in a distance from the mixing tee. The pipe wall in the mixing zone experiences the thermal oscillation of high cycle, and therefore is in a state of the high cycle thermal fatigue loadings. In this work, performed is the high cycle thermal fatigue analysis for a mixing tee under the prescribed thermal loadings in a mixing zone. Using the evaluation guide established by JSME, JSME S017- 2003 which has evaluation procedure composing of the four steps, we evaluate the fatigue integrity of the mixing tee of which the results show that the mixing tee satisfies the fatigue integrity in the last step (fourth) of four steps of evaluation procedure where the fatigue usage factor, U was calculated and then compared with the well known criterion, U<1. Representative results of the fatigue analysis are also discussed

Yang, Kyeong Jin; Lee, Dong Jae; Kim, Dae Soo; Huh, Man Gil [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

2011-05-15

103

Low cycle fatigue: high cycle fatigue damage accumulation in a 304L austenitic stainless steel; Endommagement et cumul de dommage en fatigue dans le domaine de l'endurance limitee d'un acier inoxydable austenitique 304L  

Energy Technology Data Exchange (ETDEWEB)

The aim of this study was to evaluate the consequences of a Low Cycle Fatigue pre-damage on the subsequent fatigue limit of a 304L stainless steel. The effects of hardening and severe roughness (grinding) have also been investigated. In a first set of tests, the evolution of the surface damage induced by the different LCF pre-cycling was characterized. This has permitted to identify mechanisms and kinetics of damage in the plastic domain for different surface conditions. Then, pre-damaged samples were tested in the High Cycle Fatigue domain in order to establish the fatigue limits associated with each level of pre-damage. Results evidence that, in the case of polished samples, an important number of cycles is required to initiate surface cracks ant then to affect the fatigue limit of the material but, in the case of ground samples, a few number of cycles is sufficient to initiate cracks and to critically decrease the fatigue limit. The fatigue limit of pre-damaged samples can be estimated using the stress intensity factor threshold. Moreover, this detrimental effect of severe surface conditions is enhanced when fatigue tests are performed under a positive mean stress (author)

Lehericy, Y

2007-05-15

104

Crack Growth Behavior in the Threshold Region for High Cycle Fatigue Loading  

Science.gov (United States)

This paper describes the results of a research program conducted to improve the understanding of fatigue crack growth rate behavior in the threshold growth rate region and to answer a question on the validity of threshold region test data. The validity question relates to the view held by some experimentalists that using the ASTM load shedding test method does not produce valid threshold test results and material properties. The question involves the fanning behavior observed in threshold region of da/dN plots for some materials in which the low R-ratio data fans out from the high R-ratio data. This fanning behavior or elevation of threshold values in the low R-ratio tests is generally assumed to be caused by an increase in crack closure in the low R-ratio tests. Also, the increase in crack closure is assumed by some experimentalists to result from using the ASTM load shedding test procedure. The belief is that this procedure induces load history effects which cause remote closure from plasticity and/or roughness changes in the surface morphology. However, experimental studies performed by the authors have shown that the increase in crack closure is a result of extensive crack tip bifurcations that can occur in some materials, particularly in aluminum alloys, when the crack tip cyclic yield zone size becomes less than the grain size of the alloy. This behavior is related to the high stacking fault energy (SFE) property of aluminum alloys which results in easier slip characteristics. Therefore, the fanning behavior which occurs in aluminum alloys is a function of intrinsic dislocation property of the alloy, and therefore, the fanned data does represent the true threshold properties of the material. However, for the corrosion sensitive steel alloys tested in laboratory air, the occurrence of fanning results from fretting corrosion at the crack tips, and these results should not be considered to be representative of valid threshold properties because the fanning is eliminated when testing is performed in dry air.

Forman, R. G.; Zanganeh, M.

2014-01-01

105

Fretting fatigue of carbon steels in the high cycle fatigue regime. A variation of the grain size and of the ferrite/pearlite morphologies of steels allows a detailed understanding of fretting fatigue behaviour  

Energy Technology Data Exchange (ETDEWEB)

Fretting fatigue can be a serious problem for many engineering applications. Relative motions between components in contact can generate surface and subsurface damage, which leads to failure of the component. Hence, it is very reasonable that the microstructural condition strongly influences the so-called fretting fatigue behaviour. Nevertheless, the microstructural influence on the fretting fatigue behaviour has not been very well investigated up to now. To investigate systematically the influence of specific microstructural parameters on the fretting fatigue behaviour, a broad variety of different iron-base materials were selected for this study. Based on a variation of the grain size and of the ferrite/pearlite morphologies, a detailed understanding of microstructural, effects on the fretting fatigue behaviour can be derived. In general, a reduction of the fatigue life compared to uniaxial fatigue tests by up to 50%, depending on the respective microstructure, normal load and strain amplitude, was observed. (orig.)

Neuner, F.C.; Nuetzel, R.; Hoeppel, H.W. [Erlangen-Nuernberg Univ., Erlangen (Germany). Inst. 1 - General Materials Properties

2004-07-01

106

Generation of stationary Gaussian processes and extreme value distributions for high-cycle fatigue models - application to tidal stream Turbines  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in english The operating environment of tidal stream turbines is random due to the variability of the sea flow (turbulence, wake, tide, streams, among others). This yields complex time-varying random loadings, making it necessary to deal with high cycle multiaxial fatigue when designing such structures. It is [...] thus required to apprehend extreme value distributions of stress states, assuming they are stationary multivariate Gaussian processes. This work focus on such distributions, addressing their numerical simulation with an analytical description. For that, we first focused on generating one-dimensional Gaussian processes, considering a band-limited white noise in both the narrow-band and the wide-band cases. We then fitted the resulting extreme value distributions with GEV distributions. We secondly extended the generation method to the correlated two-dimensional case, in which the joint extreme value distribution can be obtained from the associated margins. Finally, an example of application related to tidal stream turbines introduces a Bretschneider spectrum, whose shape is commonly encountered in the field of hydrology. Comparing the empirical calculations with the GEV fits for the extreme value distributions shows a very well agreement between the results.

Suptille, M.; Pagnacco, E.; Khalij, L.; Cursi, J. E. Souza de; Brossard, J..

107

Predicting fatigue life of metal bellows  

Science.gov (United States)

Classical method of presenting fatigue data in plots of alternating stress vs number of deflection cycles is applied to bellows formed of various metals, including corrosion-resistant steel, nickel alloys, and aluminum alloys. The expected life of a new bellows design can then be determined before fabrication and testing.

Daniels, C. M.

1968-01-01

108

Effect of different distribution condition of fatigue loads on fatigue life  

International Nuclear Information System (INIS)

In this article, 3 distribution styles, i.e, normal distribution, log-normal distribution and Gamma distribution, are used to simulate the variety of fatigue loads S. Same average value of fatigue loads variety S and different coefficient of variation C are adopted in every distribution style, and corresponding fatigue life Nrand and the average fatigue life Navg in the condition of S=S are calculated. By comparing the fatigue life Nrand and Navg, a rule can be found that when the average value of fatigue loads variety is small, the fatigue life will first increase and decrease later with the increasing of the coefficient of variation, and when the average value of the fatigue loads variety is large, the fatigue life will always decrease while the coefficient of variation increases. (authors)

2009-10-01

109

Fatigue, Creep-Fatigue, and Thermomechanical Fatigue Life Testing of Alloys  

Science.gov (United States)

The fatigue crack initiation resistance of an alloy is determined by conducting a series of tests over a range of values of stress amplitude or strain range. The observed number of cycles to failure is plotted against the stress amplitude or strain range to obtain a fatigue curve. The fatigue properties quoted for an alloy are typically the constants used in the equation(s) that describe the fatigue curve. Fatigue lives of interest may be as low as 10(exp 2) or higher than 10(exp 9) cycles. Because of the enormous scatter associated with fatigue, dozens of tests may be needed to confidently establish a fatigue curve, and the cost may run into several thousands of dollars. To further establish the effects on fatigue life of the test temperature, environment, alloy condition, mean stress effects, creep-fatigue effects, thermomechanical cycling, etc. requires an extraordinarily large and usually very costly test matrix. The total effort required to establish the fatigue resistance of an alloy should not be taken lightly. Fatigue crack initiation tests are conducted on relatively small and presumed to be initially crack-free, samples of an alloy that are intended to be representative of the alloy's metallurgical and physical condition. Generally, samples are smooth and have uniformly polished surfaces within the test section. Some may have intentionally machined notches of well-controlled geometry, but the surface at the root of the notch is usually not polished. The purpose of polishing is to attain a reproducible surface finish. This is to eliminate surface finish as an uncontrolled variable. Representative test specimen geometries will be discussed later. Test specimens are cyclically loaded until macroscopically observable cracks initiate and eventually grow to failure. Normally, the fatigue failure life of a specimen is defined as the number of cycles to separation of the specimen into two pieces. Alternative definitions are becoming more common, particularly for low-cycle fatigue testing, wherein some prescribed indication of impending failure due to cracking is adopted. Specific criteria will be described later. As a rule, cracks that develop during testing are not measured nor are the test parameters intentionally altered owing to the presence of cracking.

Halford, Gary R.; Lerch, Bradley A.; McGaw, Michael A.

2000-01-01

110

Probabilistic material strength degradation model for Inconel 718 components subjected to high temperature, high-cycle and low-cycle mechanical fatigue, creep and thermal fatigue effects. Final technical report, June 1992-January 1995  

Energy Technology Data Exchange (ETDEWEB)

This report presents the results of both the fifth and sixth year effort of a research program conducted for NASA-LeRC by The University of Texas at San Antonio (UTSA). The research included on-going development of methodology for a probabilistic material strength degradation model. The probabilistic model, in the form of a postulated randomized multifactor equation, provides for quantification of uncertainty in the lifetime material strength of aerospace propulsion system components subjected to a number of diverse random effects. This model is embodied in the computer program entitled PROMISS, which can include up to eighteen different effects. Presently, the model includes five effects that typically reduce lifetime strength: high temperature, high-cycle mechanical fatigue, low-cycle mechanical fatigue, creep and thermal fatigue. Statistical analysis was conducted on experimental Inconel 718 data obtained from the open literature. This analysis provided regression parameters for use as the model`s empirical material constants, thus calibrating the model specifically for Inconel 718. Model calibration was carried out for five variables, namely, high temperature, high-cycle and low-cycle mechanical fatigue, creep and thermal fatigue. Methodology to estimate standard deviations of these material constants for input into the probabilistic material strength model was developed. Using an updated version of PROMISS, entitled PROMISS93, a sensitivity study for the combined effects of high-cycle mechanical fatigue, creep and thermal fatigue was performed. Then using the current version of PROMISS, entitled PROMISS94, a second sensitivity study including the effect of low-cycle mechanical fatigue, as well as, the three previous effects was performed. Results, in the form of cumulative distribution functions, illustrated the sensitivity of lifetime strength to any current value of an effect.

Bast, C.C.; Boyce, L.

1995-01-01

111

Multiaxial fatigue life and strength criteria for non-proportional loading  

Energy Technology Data Exchange (ETDEWEB)

In the article a proposal of loading non-proportionality measure H for sinusoidal biaxial loading has been presented. On the basis of non-proportionality measure, there has been proposed a bending and torsional fatigue strength, with a phase shift of components and the mean value has been proposed. Moreover, a high-cycle fatigue life criterion based on the same non-proportionality measure has been proposed. The predictive capability of both criteria were demonstrated by analysing experimental results from the literature. The predicted results are generally in good agreement with the experimental ones.

Skibicki, D. [Bydgoszcz Univ. (Poland)

2006-07-01

112

Fatigue life prediction of stainless steel using acoustic emission  

International Nuclear Information System (INIS)

The feasibility of the acoustic emission technique in predicting the residual fatigue life of STS304 stainless steel is presented. Acoustic emission was continuously monitored during the fatigue tests. Considerable acoustic emission occurred during the first few cycles. Acoustic emission increased rapidly at about 90% of the fatigue life, clear and ample warning of impending fatigue failure was observed. Fatigue damage accumulation was evaluated in terms of an AE cumulative counts. The AE cumulative counts may be taken as an indicator of fatigue cumulative damage. Fatigue damages corresponding to 20, 40, 60 and 80% of the total life were induced at cyclic stress amplitude. The specimens with and without fatigue damage were subjected to tensile tests. In tensile tests, the total cumulative counts were reduced with increasing fatigue damage. It was observed that the residual tensile strength of material did not change significantly with prior cyclic loading damages

2001-06-27

113

A study on the role of grain boundary engineering in promoting high-cycle fatigue resistance and improving reliability in nickel base superalloys for propulsion systems  

Science.gov (United States)

High-cycle fatigue, involving the premature initiation and/or rapid propagation of small cracks to failure due to high-frequency (vibratory) loading, remains the principal cause of failures in military gas-turbine propulsion systems. The objective of this study is to examine whether the resistance to high-cycle fatigue failures can be enhanced by grain-boundary engineering, i.e., through the modification of the spatial distribution and topology of the grain boundaries in the microstructure. While grain boundary engineering has been used to obtain significant improvements in intergranular corrosion and cracking, creep and cavitation behavior, toughness and plasticity, cold-work embrittlement, and weldability, only very limited, but positive, results exist for fatigue. Accordingly, using a commercial polycrystalline nickel base gamma/gamma' superalloy, ME3, as a typical engine disk material, sequential thermomechanical processing, involving alternate cycles of strain and annealing, is used to (i) modify the proportion of special grain boundaries, and (ii) interrupt the connectivity of the random boundaries in the grain boundary network. The processed microstructures are then subjected to fracture-mechanics based high cycle fatigue testing to evaluate how the crack initiation and small- and large-crack growth properties are affected and to examine how the altered grain boundary population and connectivity can influence growth rates and overall lifetimes. The effect of such grain-boundary engineering on the fatigue-crack-propagation behavior of large (˜8 to 20 mm), through-thickness cracks at 25, 700, and 800°C was examined. Although there was little influence of an increased special boundary fraction at ambient temperatures, the resistance to near-threshold crack growth was definitively improved at elevated temperatures, with fatigue threshold-stress intensities some 10 to 20% higher than at 25°C, concomitant with a lower proportion (˜20%) of intergranular cracking. This work demonstrated that for cracks large compared to the scale of the microstructure, the principal role of an increased fraction of "special" grain boundaries is to enhance resistance only to intergranular cracking. Microstructurally small fatigue cracks exhibit considerably scattered growth rates at ambient temperatures and there is little discernible overall effect of an increased fraction of special boundaries on the growth rates of small cracks due to scattering. Crystallographic cracking shows deflection at grain boundaries, preferably along {111}. The analysis on the crack growth perturbation and crack deflection indicates that grain boundaries with higher misorientation angles, particularly twin boundaries (Sigma3), may be more effective in locally retarding small crack propagation.

Gao, Yong

114

A predictive fatigue life model for anodized 7050 aluminium alloy  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The objective of this study is to predict fatigue life of anodized 7050 aluminum alloy specimens. In the case of anodized 7050-T7451 alloy, fractographic observations of fatigue tested specimens showed that pickling pits were the predominant sites for crack nucleation and subsequent failure. It has been shown that fatigue failure was favored by the presence of multiple cracks. From these experimental results, a fatigue life predictive model has been developed including multi-site crack consid...

Chaussumier, Michel; Mabru, Catherine; Shahzad, Majid; Chieragatti, Re?my; Rezai?-aria, Farhad

2013-01-01

115

Fatigue life prediction of shot peened components  

Scientific Electronic Library Online (English)

Full Text Available SciELO Portugal | Language: English Abstract in portuguese A grenalhagem é um dos tratamentos mais eficientes na prevenção da iniciação de fendas por fadiga e na fase inicial de propagação. Grande parte dos estudos sobre o feito da grenalhagem no comportamento à fadiga são experimentais. Praticamente não existem trabalhos publicados relativos ao estudo de p [...] revisão do comportamento da grenalhagem. Neste trabalho são usados modelos tradicionais, de determinação da vida à fadiga, em componentes grenalhados. O método dos elementos finitos é usado para determinar a tensão, extensão e energia de deformação de provetes grenalhados que foram testados experimentalmente. Estes resultados são usados em modelos de previsão da vida total à fadiga. É apresentada uma discussão sobre a capacidade dos modelos usados na previsão de vida à fadiga de provetes que foram testados experimentalmente. Abstract in english Shot peening is one of the most effective surface treatments in order to prevent crack initiation and early crack propagation. Part of the studies to determine the fatigue performance of shot peening are based on experimental tests. Almost no work is published related with the prediction of shot pee [...] ning behaviour. The present paper evaluates the ability of the current methodologies, used to predict fatigue life, on components treated with shot peening. The Finite Element Method was used to determine the stress, strain and strain energy due to shot peening of some specimens tested experimentally. These results were used to apply methods to predict the total fatigue life. A final discussion is presented about the ability of the methods used, to predict the fatigue life of the specimens tested experimentally.

R.A., Cláudio; J.M., Silva; C.M., Branco; J., Byrne.

116

Effect of strain-induced martensitic transformation on high cycle fatigue behavior in cyclically-prestrained type 304  

International Nuclear Information System (INIS)

The effects of the cyclic prestrain on the fatigue behavior in type 304 austenitic stainless steel were investigated. Rotating bending fatigue tests have been performed in laboratory air using the specimens subjected to ±5% cyclic prestrain at room temperature (R.T.) and -5°C. Martensitic phase volume fraction of the prestrained specimen at -5°C was 48% and larger than 3.8% at R.T. The prestrained specimens exhibited higher fatigue strengths than the as-received ones, and larger volume fraction of martensitic phase resulted in the higher fatigue limit. EBSD analysis revealed that the martensitic phases were more uniformly distributed in the austenitic matrix in the cyclically-prestrained specimens than in the monotonically-prestrained ones. Fatigue crack initiation from inclusion was observed only in the cyclically-prestrained specimens at -5°C. High volume fraction and uniform distribution of martensitic phase induced the transition of crack initiation mechanism and led to the higher fatigue limit. In type 304 stainless steel with high volume fraction of strain-induced martensitic phase, the prediction of fatigue limit based on Vickers hardness could give unconservative results. (author)

2013-12-01

117

Effect of Corrosion on the High Cycle Fatigue Strength of Martensitic Stainless Steel X12CrNiMoV12-3  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This paper addresses the effects of corrosion on the high cycle fatigue (HCF) strength of a high mechanical strength martensitic stainless steel (X12CrNiMoV12-3) that is used in aeronautic applications. HCF tests (between 105 and 107 cycles) were carried out in two environments: (i) in air and (ii) in an aqueous solution (pH = 6) of 0.1 M NaCl + 0.044 M Na2SO4 at a loading frequency of 120 Hz. Surface crack initiation is observed in air, whereas in solution, the crack initiated at corrosion d...

El May, Mohamed; Palin-luc, Thierry; Saintier, Nicolas; Devos, Olivier

2012-01-01

118

High-cycle fatigue behavior of Incoloy alloy 800H in a simulated HTGR helium environment containing high moisture levels  

International Nuclear Information System (INIS)

A study has been carried out to evaluate the highcycle fatigue strength of Incoloy alloy 800H in a high-temperature gas-cooled reactor helium environment containing significant quantities of moisture. As-heat-treated and thermally aged materials were tested to determine the effects of long-term oxidation in the helium test gas. Results from these tests were compared to those for a standard air environment. It was found that the mechanisms of fatigue failure were complex and involved recovery/recrystallization of the surface-ground layer on the specimens, sensitization, work hardening, oxide scale integrity, and oxidation at the tips of propagating cracks. For certain situations, a corrosion-fatigue process seems to be important. However, for the helium environment studied, the fatigue strength was nearly always higher than that for air

1984-01-01

119

Fatigue life of automotive rubber jounce bumper  

Energy Technology Data Exchange (ETDEWEB)

It is evident that most rubber components in the automotive industry are subjected to repetitive loading. Vigorous research is needed towards improving the safety and reliability of the components. The study was done on an automotive rubber jounce bumper with a rubber hardness of 60 IRHD. The test was conducted in displacement-controlled environment under compressive load. The existing models by Kim, Harbour, Woo and Li were adopted to predict the fatigue life. The experimental results show strong similarities with the predicted models.

Sidhu, R S [Automotive Engineering Unit, Institute of Advanced Technology, University Putra Malaysia, 43400, UPM Serdang, Selangor (Malaysia); Ali, Aidy, E-mail: aidy@eng.upm.edu.my [Department of Mechanical and Manufacturing Engineering, Faculty of Engineering, Universiti Putra Malaysia, 43400 UPM, Serdang Selangor (Malaysia)

2010-05-15

120

Fatigue life of automotive rubber jounce bumper  

International Nuclear Information System (INIS)

It is evident that most rubber components in the automotive industry are subjected to repetitive loading. Vigorous research is needed towards improving the safety and reliability of the components. The study was done on an automotive rubber jounce bumper with a rubber hardness of 60 IRHD. The test was conducted in displacement-controlled environment under compressive load. The existing models by Kim, Harbour, Woo and Li were adopted to predict the fatigue life. The experimental results show strong similarities with the predicted models.

2010-05-01

 
 
 
 
121

Fatigue Life Investigation of PZT Ceramics by MSP Method  

Directory of Open Access Journals (Sweden)

Full Text Available The cycle fatigue of PZT ceramic under different stress was investigated by modified small punch (MSP tests. The research results show that residual strength and piezoelectric constant decrease with increasing cycle stress, which is attributed to crack propagation during cyclic stress process. The value of fatigue crack propagation (n is calculated to be 395 according to the relationship between maximum stress and fatigue life. The fatigue life under series cycle maximum stress can be induce by fatigue crack propagation. Below the maximum strength of 79.1 MPa, the PZT ceramics can be used over 5 years.

DENG Qi-Huang, WANG Lian-Jun, XU Hong-Jie, WANG Hong-Zhi, JIANG Wan

2012-10-01

122

Rolling-element fatigue life of AMS 5900 balls  

Science.gov (United States)

The rolling-element fatigue life of AMS 5900 12.7-mm (1/2-in.) dia was determined in five-ball fatigue testers. The 10% life with the warm headed AMS 5900 balls was equivalent to that of AMS 5749 and over eight times that of AISI M-50. The AMS balls fabricated by cold heading had small surface cracks which initiated fatigue spalls where these cracks were crossed by running tracks. The cold-headed AMS 5900 balls had a 10% fatigue life an order of magnitude less than that of the warm headed balls even when failures on the cold headed balls at visible surface cracks were omitted.

Parker, R. J.

1983-01-01

123

Calculation of the fatigue life distribution of a composite laminate  

Energy Technology Data Exchange (ETDEWEB)

A method based on a probabilistic interpretation of the Hashin criterion is proposed for calculating the fatigue life distributions of a unidirectional composite under conditions of a plane stressed state from test results obtained for simple loading schemes. By using the linear damage accumulation law, an estimate is obtained of the scatter of the composite fatigue life related to the scatter of the material fatigue strength. A procedure is then presented for estimating the fatigue life distribution of a composite laminate in the plane stressed state based on layer-by-layer fracture analysis using the linear damage summation law and the determining layer concept. 26 refs.

Anderson, IA.A.; Limonov, V.A. (AN LSSR, Institut Mekhaniki Polimerov, Riga, Latvian (USSR))

1991-02-01

124

Experimental study on prevention of high cycle thermal fatigue in a compact reactor vessel of advanced sodium cooled reactor. Thermal striping phenomena at bottom of upper internal structure  

International Nuclear Information System (INIS)

Japan sodium-cooled fast reactor, JSFR, has been investigated in the frame work of Fast Reactor Cycle Technology Development Project (FaCT). As the temperature difference between the control rod channels and the core fuel subassemblies is around 100degC, temperature fluctuation due to the fluid mixing at the core outlet may cause high cycle thermal fatigue at the bottom of Upper Internal Structure (UIS). Then, a water experiment was conducted using a 1/3 scale 60 degree sector model. Temperature and its fluctuation intensity distributions around the control rod were measured and an effect of the improved structure against the thermal fatigue was examined. The objectives of the experiment are as follows; (1) to grasp the flow pattern around the control rod(CR) channel outlet, (2) to grasp the amplitude and the frequency characteristics of the temperature fluctuation, (3) to confirm the effect of a countermeasure for the high cycle thermal fatigue. As a result, thermal striping phenomena in the region between the fuel subassembly outlet and the bottom of the UIS were grasped. The geometry of the UIS bottom and the handling head of the primary CR channel was modified so as to suppress the cold jets exiting from the CR channels. The comparison of measured temperature fluctuations around the CR channels revealed that the modified geometry was effective to decrease the temperature fluctuation intensity and amplitude in the sensitive frequency band to the stress in the structures. Temperature fluctuation intensity distributions at the boundary between blanket subassemblies and core fuel subassemblies were also grasped. (author)

2012-01-01

125

Effect of surface irregularities on bellows fatigue life  

Science.gov (United States)

Report presents test data on the bending fatigue life of notched sheet specimens. The influence of a surface irregularity on the fatigue life of a metal bellows is evaluated, with emphasis on accidental defects in ducting bellows which are impossible to avoid short of completely eliminating human contact.

Schmidt, E. H.; Sheaffer, E. F.; Turner, J. D.; Zeimer, R. L.

1968-01-01

126

Development of a procedure for estimating the high cycle fatigue strength of some high temperature structural alloys  

International Nuclear Information System (INIS)

The generation of strain controlled fatigue data, for the standard strain rate of 4 x 10-3 sec-1, presents a problem when the cycles to failure exceed 105 because of the prohibitively long test times involved. In an attempt to circumvent this difficulty an evaluation has been made of a test procedure involving a fast cycling rate (40 Hz) and load controlled conditions. The validity of this procedure for extending current fatigue curves from 105 to 108 cycles and beyond, hinges upon the selection of an appropriate effective strain value, since the strain usually changes rapidly during the early stage of fatigue. Results from annealed 2 1/4 Cr-1 Mo, type 304 stainless steel, Incoloy 800H and Hastelloy X, tested over a wide range of temperatures, show that the strain measured N/sub f/2 is a reasonable estimate since it gives an excellent correlation between the strain and load controlled tests in the 105 cycle range where the data overlap. It seems clear that the differences in cycling rate and early stress-strain history for the two tests do not significantly affect the correlation. It may, therefore, be concluded that such load control test procedures may be used as a valid fast way for extending currently available fatigue curves from 105 to 108 cycles, and beyond

1979-12-07

127

Development of a procedure for estimating the high cycle fatigue strength of some high temperature structural alloys  

Energy Technology Data Exchange (ETDEWEB)

The generation of strain controlled fatigue data, for the standard strain rate of 4 x 10/sup -3/ sec/sup -1/, presents a problem when the cycles to failure exceed 10/sup 5/ because of the prohibitively long test times involved. In an attempt to circumvent this difficulty an evaluation has been made of a test procedure involving a fast cycling rate (40 Hz) and load controlled conditions. The validity of this procedure for extending current fatigue curves from 10/sup 5/ to 10/sup 8/ cycles and beyond, hinges upon the selection of an appropriate effective strain value, since the strain usually changes rapidly during the early stage of fatigue. Results from annealed 2 1/4 Cr-1 Mo, type 304 stainless steel, Incoloy 800H and Hastelloy X, tested over a wide range of temperatures, show that the strain measured N/sub f/2 is a reasonable estimate since it gives an excellent correlation between the strain and load controlled tests in the 10/sup 5/ cycle range where the data overlap. It seems clear that the differences in cycling rate and early stress-strain history for the two tests do not significantly affect the correlation. It may, therefore, be concluded that such load control test procedures may be used as a valid fast way for extending currently available fatigue curves from 10/sup 5/ to 10/sup 8/ cycles, and beyond.

Soo, P.; Chow, J.G.Y.

1979-01-01

128

Effect of inclusion size on the high cycle fatigue strength and failure mode of a high V alloyed powder metallurgy tool steel  

Science.gov (United States)

The fatigue strength of a high V alloyed powder metallurgy tool steel with two different inclusion size levels, tempered at different temperatures, was investigated by a series of high cycle fatigue tests. It was shown that brittle inclusions with large sizes above 30 ?m prompted the occurrence of subsurface crack initiation and the reduction in fatigue strength. The fracture toughness and the stress amplitude both exerted a significant influence on the fish-eye size. A larger fish-eye area would form in the sample with a higher fracture toughness subjected to a lower stress amplitude. The stress intensity factor of the inclusion was found to lie above a typical value of the threshold stress intensity factor of 4 MPa·m1/2. The fracture toughness of the sample with a hardness above HRC 56 could be estimated by the mean value of the stress intensity factor of the fish-eye. According to fractographic evaluation, the critical inclusion size can be calculated by linear fracture mechanics.

Yao, Jun; Qu, Xuan-hui; He, Xin-bo; Zhang, Lin

2012-07-01

129

Biaxial High Cycle Fatigue of a type 304L stainless steel: Cyclic strains and crack initiation detection by digital image correlation  

International Nuclear Information System (INIS)

A series of biaxial High Cycle Fatigue tests at room temperature is performed to build up an extensive and well-documented database. The testing specimen is a maltese cross thinned in its centre with non-homogeneous strain/stress fields. The experimental protocol uses exclusively full-field strain measurements. The strains (cyclic and residual) as well as the crack initiation detection are obtained by use of Digital Image Correlation (DIC) techniques combined with a multi-scale stroboscopic image acquisition in-situ set-up. Nine cruciform specimens made of type 304L austenitic stainless steel are loaded by a multiaxial testing machine. Two kinds of loading paths are presented: equi-biaxial with a load ratio of 0.1, non-proportional with a cyclic load in one direction and a constant load in the other. The experimental results are given (strain amplitude, residual strain, number of cycles to crack initiation) for each loading path. The time history of local strain amplitudes and residual strains are recorded and plotted. Total strain vs. number of cycles fatigue curves show the different trends associated with each loading path. For instance, non-proportional loadings are found very damaging and leading to strong ratchetting effects. The tested material is briefly introduced, followed by an in-depth description of the experimental set-up. The fatigue test campaign results are then presented, with a final discussion. (authors)

2010-01-01

130

A Question of Location - Life with Fatigue after Stroke  

DEFF Research Database (Denmark)

This thesis treats the experiences of fatigue after stroke. Based on a qualitative fieldwork conducted among people who have had a stroke, it explores how they experience fatigue. This is done by way of an ethnological examination of how the informants locate fatigue in their everyday lives. By approaching their location as both place and practice, it is illustrated how a stroke may dislocate and relocate the experience of fatigue and how a new location of fatigue calls for new meaningful contexts in everyday life.

Andersen, Michael

2014-01-01

131

Fatigue life characterization for piezoelectric macrofiber composites  

International Nuclear Information System (INIS)

In an effort to aid the investigation into lightweight and reliable materials for actuator design, a study was developed to characterize the temperature-dependent lifetime performance of a piezoelectric macrofiber composite (MFC). MFCs are thin rectangular patches of polyimide film, epoxy and a single layer of rectangular lead zirconium titanate (PZT) fibers. In this study, the useful life of the MFC is characterized to determine the effect of temperature on the performance of the composite as it is fatigued by cyclic piezoelectric excitation. The test specimen consists of the MFC laminated to a cantilevered stainless steel beam. Beam strain and tip displacement measurements are used as a basis for determining the performance of the MFC as it is cyclically actuated under various operating temperatures. The temperature of the beam laminate is held constant and then cycled to failure, or 250 million cycles, in order to determine the useful life of the MFC over a temperature range from ? 15 to 145?°C. The results of the experiments show a strong temperature dependence of the operational life for the MFC. Damage inside the composite was identified through in situ visual inspection and during post-test microstructural observation; however, no degradation in operational performance was identified as it was cyclically actuated up to the point of failure, regardless of temperature or actuation cycle number. (paper)

2012-10-01

132

Life prediction of creep fatigue at very high temperatures  

International Nuclear Information System (INIS)

Life prediction methods of creep fatigue were investigated to consider applications to Hastelloy XRs at very high temperatures where materials would be damaged severely by creep deformation. The ductility exhaustion rule, coupled with a creep constitutive equation consisting of primary and secondary stages, showed a good prediction of creep-fatigue life as well as the damage-rate equations. The strain range partitioning method was also discussed regarding its possibility for life prediction. The results of these methods were compared with the time fraction rule in conjunction with the Miner's rule. In these experiments, creep tests were done under constant stress condition in air, and low-cycle fatigue tests were carried out with and without a dwell period in vacuum. Creep-fatigue damage was evaluated in the life of low-cycle fatigue tests with a dwell period. All specimens were fabricated from the same hot-rolled plates to reduce scatter in different heat treatments. (author)

1993-01-01

133

Improving a bridge fatigue life prediction by monitoring  

Digital Repository Infrastructure Vision for European Research (DRIVER)

For steel railway bridges, fatigue is the main reason for a limited service life. An initial prediction of the fatigue life is usually performed using loads and conservative assumptions stated in the governing standards. The result is used for decisions of further actions. Even if the result is an insufficient residual life, some bridges are not easy to strengthen or replace without causing large traffic disturbance. In this licentiate thesis, the real load effect is studied by monitoring a b...

Leander, John

2010-01-01

134

Leakage from CVCS pipe of regenerative heat exchanger induced by high-cycle thermal fatigue at Tsuruga Nuclear Power Station Unit 2  

International Nuclear Information System (INIS)

On July 12, 1999 while Tsuruga-2, PWR 4-loop plant, was operating at full power (1,160 MWe), unidentified leakage inside the primary containment vessel was detected. As the leakage was identified, the plant promptly started to proceed to cold shutdown. Visual inspection after an isolation of the CVCS (Chemical and Volume Control System) revealed that the leakage was from a connecting pipe between the middle and lower stages in the CVCS regenerative heat exchanger. The CVCS regenerative heat exchanger has three shells, i.e. the upper shell, the middle shell and the lower shell. Each heat exchanger shell has an inner cylinder containing a heat exchanger tube bundle. Reactor coolant is cooled inside the inner cylinder, however, the temperature of the coolant which flows outside the inner cylinder keeps high. These two coolant flows are mixed around the outlet of the inner cylinder. Thermal hydraulic mock-up tests simulating internal flows in the heat exchanger were conducted along with thermal and structural analyses to investigate a high-cycle thermal fatigue mechanism. As a result of the investigation, the cause of the leakage from the connecting pipe was considered to be as follows; (1) Flow out of the lower temperature bypass flow region occurred repeatedly at the lower part of the shell which yielded a cyclic deformation of the shell due to thermal expansion and shrinkage. (2) This cyclic deformation caused a cyclic change of the gap between the inner cylinder support ring and shell, and consequently the cyclic change of the flow pattern at the region where the bypass flow and main flow mixed. (3) Superposition of lower frequent temperature change due to the change of flow pattern and higher frequent temperature fluctuation due the mixture of the bypass flow and main flow caused high-cycle thermal fatigue cracking. (author)

2000-10-01

135

Prediction of residual fatigue life using nonlinear ultrasound  

International Nuclear Information System (INIS)

Prediction of fatigue life of components during service is an on-going and unsolved challenge for the NDT and structural health monitoring community. It has been demonstrated by a number of researchers that nonlinear guided waves or the acoustic nonlinear signature of fatigued cracked material provides clear signs of the progressive fatigue damage in the material, unlike linear guided waves. However, even with nonlinear acoustic-ultrasound methods there is a necessity to compare the current nonlinear feature to a previously measured cracked material state to assess the absolute residual fatigue life. In this paper, a new procedure based on the measurement of the second-order acoustic nonlinearity is presented which is able to assess the fatigue life of a metallic component without the need of a baseline. The Nazarov–Sutin crack nonlinearity equation and the Paris law are combined in order to obtain an analytical solution able to evaluate the theoretical second-order quadratic nonlinear parameters as a function of the crack growth and fatigue life that evolve during cyclic loading in metals. The model makes the assumption that the crack surface topology has variable geometrical parameters. The method was tested on aluminum alloy specimens AA2024-T351, containing fatigue fracture of different sizes, and excellent correlation was obtained between the theoretical and measured second-order nonlinear parameter. Then, it was demonstrated clearly that by measuring the nonlinear parameters it is possible to estimate crack size and fatigue life. Finally, advantages and limitations of the procedure are discussed. (paper)

2012-04-01

136

Prediction of residual fatigue life using nonlinear ultrasound  

Science.gov (United States)

Prediction of fatigue life of components during service is an on-going and unsolved challenge for the NDT and structural health monitoring community. It has been demonstrated by a number of researchers that nonlinear guided waves or the acoustic nonlinear signature of fatigued cracked material provides clear signs of the progressive fatigue damage in the material, unlike linear guided waves. However, even with nonlinear acoustic-ultrasound methods there is a necessity to compare the current nonlinear feature to a previously measured cracked material state to assess the absolute residual fatigue life. In this paper, a new procedure based on the measurement of the second-order acoustic nonlinearity is presented which is able to assess the fatigue life of a metallic component without the need of a baseline. The Nazarov-Sutin crack nonlinearity equation and the Paris law are combined in order to obtain an analytical solution able to evaluate the theoretical second-order quadratic nonlinear parameters as a function of the crack growth and fatigue life that evolve during cyclic loading in metals. The model makes the assumption that the crack surface topology has variable geometrical parameters. The method was tested on aluminum alloy specimens AA2024-T351, containing fatigue fracture of different sizes, and excellent correlation was obtained between the theoretical and measured second-order nonlinear parameter. Then, it was demonstrated clearly that by measuring the nonlinear parameters it is possible to estimate crack size and fatigue life. Finally, advantages and limitations of the procedure are discussed.

Amura, Mikael; Meo, Michele

2012-04-01

137

Fatigue life estimation of shot peened metal using accelerated life testing  

International Nuclear Information System (INIS)

Shot peening process is used as one of the various kinds of techniques to improve the fatigue properties. However, to obtain fatigue properties of metal materials, many efforts and time are needed. Because the fatigue life of shot peened metals increases highly. In this paper, fatigue properties of shot peened Al 7075-T6 are estimated using the fundamental of accelerated life test to reduce the experimental. Experimental results show that the estimated life data almost agree with actual rotary bending fatigue test data within 7% error

2004-11-03

138

On line fatigue life monitoring methodology for power plant components  

Energy Technology Data Exchange (ETDEWEB)

Fatigue is one of the most important ageing effects of power plant components. Information about fatigue helps in assessing structural degradation of the components and so assists in planning in-service inspection and maintenance. It may also support the future life extension programme of a power plant. In the present paper, the development of a methodology for on line fatigue life monitoring using available plant instrumentation is presented. The Green's function technique is used to convert plant data to stress-time data. Using a rainflow cycle counting method, stress-time data are analysed and the fatigue usage factor is computed from the material fatigue curve. Various codes are developed to generate Green's functions, to convert plant data to stress-time data, to find the fatigue usage factor and to display fatigue information. Using the developed codes, information about the fatigue life of various components of a power plant can be updated, stored and displayed interactively by plant operators. Three different case studies are reported in the present paper. These are the fatigue analyses of a thick pipe, of a nozzle connected to a pressure vessel and of a reducer connecting a heat exchanger to its piping system. (Author).

Mukhopadhyay, N.K.; Dutta, B.K.; Kushwaha, H.S.; Mahajan, S.C.; Kakodkar, A. (Bhabha Atomic Research Centre, Bombay (India). Reactor Design and Development Group)

1994-01-01

139

On line fatigue life monitoring methodology for power plant components  

International Nuclear Information System (INIS)

Fatigue is one of the most important ageing effects of power plant components. Information about fatigue helps in assessing structural degradation of the components and so assists in planning in-service inspection and maintenance. It may also support the future life extension programme of a power plant. In the present paper, the development of a methodology for on line fatigue life monitoring using available plant instrumentation is presented. The Green's function technique is used to convert plant data to stress-time data. Using a rainflow cycle counting method, stress-time data are analysed and the fatigue usage factor is computed from the material fatigue curve. Various codes are developed to generate Green's functions, to convert plant data to stress-time data, to find the fatigue usage factor and to display fatigue information. Using the developed codes, information about the fatigue life of various components of a power plant can be updated, stored and displayed interactively by plant operators. Three different case studies are reported in the present paper. These are the fatigue analyses of a thick pipe, of a nozzle connected to a pressure vessel and of a reducer connecting a heat exchanger to its piping system. (Author)

1994-01-01

140

High cycle thermal fatigue: benchmark at a Te junction piping system of the nuclear power plant Phenix; Fatigue a grand nombre de cycles: benchmark d'un te de tuyauterie de la centrale Phenix  

Energy Technology Data Exchange (ETDEWEB)

This paper presents the studies of the benchmark concerning a high cycle thermal fatigue problem. This benchmark is based on an industrial case, a Te junction piping system of the french FBR Phenix. The main objectives were the comparison of the different methods used by the participants and the analysis of the damage evaluation methods capacity compared to the observed phenomena. This study took place in an international framework with the United Kingdom, Italy, Japan, Korea, Russia, India and France. (A.L.B.)

Gelineau, O.; Simoneau, J.P. [NOVATOME, a Div. of Framatome, 69 - Lyon (France); Roubin, P. [CEA Cadarache, DER, 13 - Saint-Paul-lez-Durance (France)

2001-07-01

 
 
 
 
141

Fatigue tests and life estimation of Incoloy alloy 908  

International Nuclear Information System (INIS)

Incoloy reg-sign alloy 908* is a candidate conduit material for Nb3Sn cable-in-conduit superconductors. The conduit is expected to experience cyclic loads at 4 K. Fatigue fracture of the conduit is one possible failure mode. So far, fatigue life has been estimated from fatigue crack growth data, which provide conservative results. The more traditional practice of life estimation using S-N curves has not been done for alloy 908 due to a lack of data at room and cryogenic temperatures. This paper presents a series of fatigue test results in response to this need. Tests were performed in reversed bending, rotating bending, and uniaxial fatigue machines. The test matrix included different heat treatments, two load ratios (R=-1 and 0.1), two temperatures (298 and 77 K), and two orientations (longitudinal and transverse). As expected, there is a semi-log linear relation between the applied stress and fatigue life above an applied stress (e.g., 310 MPa for tests at 298 K and R=-1). Below this stress the curves show an endurance limit. The aged and cold-worked materials have longer fatigue lives and higher endurance limits than the others. Different orientations have no apparent effect on life. Cryogenic temperature results in a much high fatigue life than room temperature. A higher tensile mean stress gives shorter fatigue life. It was also found that the fatigue lives of the reversed bending specimens were of the same order as those of the uniaxial test specimens, but were only half the lives of the rotating bending specimens for given stresses. A sample application of the S-N data is discussed

1995-07-17

142

On the ability of some cyclic plasticity models to predict the evolution of stored energy in a type 304L stainless steel submitted to high cycle fatigue  

International Nuclear Information System (INIS)

Fatigue analyses of materials are generally based on a so-called stabilized cycle, on which plastic strain amplitude, plastic energy, maximum shear stress and so on are determined. The part of plastic energy which is dissipated in heat cannot be used to accumulate damage and it should be worthwhile extracting only the part of plastic energy which is stored in material microstructure in order to build a consistent damage model. In this paper, some cyclic plasticity models including a polycrystalline model are reformulated in the thermodynamic framework in order to test their capacity to predict both the stress-strain behaviour and the partition of plastic energy for a high cycle fatigue test on a type 304L stainless steel. For an equivalent description of stress-strain loops, the number of kinematic hardening variables chosen in a model may qualitatively alter the prediction of plastic energy partition due to the modification of the isotropic hardening variable. Measurements of the specimen temperature increase due to plastic dissipation is therefore proposed as a convenient complementary experimental data to identify the constitutive equation of the isotropic hardening variable of a cyclic plasticity model. (author)

2008-01-01

143

The effects of scratches and shot peening on the high cycle fatigue crack growth of aluminum alloy 2024-T3  

Energy Technology Data Exchange (ETDEWEB)

An experimental study was performed to determine the crack growth rates of scratched-then-shot peened Aluminum alloy 2024-T4 under high cyclic fatigue conditions. Tests were conducted at a constant stress amplitude. As expected, the crack growth rate of a scratched specimen increased with increasing the scratch depth. However, glass shot peening significantly reduced crack growth rates. The rates of scratched-then-peened specimens were similar to those of as-received specimens at low and intermediate stress intensity factors` ranges. In addition, it was found that the scratch exhibited small crack growth behavior. This behavior is related to the crack`s path change occurring before propagates across the specimen. An analytic model for a stress intensity factor was developed for scratched samples.

Talia, M. [Univ. of Kansas, Lawrence, KS (United States). Mechanical Engineering Dept.; Talia, J.E. [Wichita State Univ., KS (United States). Mechanical Engineering Dept.

1997-12-31

144

Fatigue life estimation in welded joints under multiaxial loadings  

Directory of Open Access Journals (Sweden)

Full Text Available Welded joints are frequently locations for cracks initiation and propagation that may cause fatigue failure of engineering structures. Biaxial or triaxial stress-strain states are present in the vicinity of welded joints, due to local geometrical constraints, welding processes and/or multiaxial external loadings. Fatigue life evaluation of welded joints under multiaxial proportional (in-phase cyclic loading can be performed by using conventional hypotheses (e.g. see the von Mises criterion or the Tresca criterion on the basis of local approaches. On the contrary, the fatigue life predictions of welded joints under non-proportional (out-ofphase cyclic loading are generally unsafe if these conventional hypotheses are used. A criterion initially proposed by the authors for smooth and notched structural components has been extended to the fatigue assessment of welded joints. In more detail, fatigue life of welded joints under multiaxial stress states can be evaluated by considering a nonlinear combination of the shear stress amplitude (acting on the critical plane and the amplitude and the mean value of the normal stress (acting on the critical plane. In the present paper, fatigue lifetimes predicted through the proposed criterion are compared with experimental fatigue life data available in the literature, related to fatigue biaxial tests.

Sabrina Vantadori

2009-07-01

145

Application of multistage life prediction methods to fretting fatigue interactions  

International Nuclear Information System (INIS)

This paper reports the application field of the multistage prediction model extended to fretting- fatigue interaction. The model was used to achieve a preliminary evaluation of the reduction in fatigue life induced by fretting conditions in a case-hardening steel. Satisfactory agreement with experimental data was found without considering any effects on the propagation stage

1989-08-14

146

The effect of creep cavitation on the fatigue life under creep-fatigue interaction  

International Nuclear Information System (INIS)

Low cycle fatigue tests have been carried out with three different materials (1Cr-Mo-V steel, 12Cr-Mo-V steel and 304 stainless steel) for the investigation of the effect of surface roughness on the fatigue life. To see the effect systematically, we have chosen those materials which may or may not form grain boundary cavities.Test results show that the continuous fatigue life of 1Cr-Mo-V steel and aged 304 stainless steel with a rough surface is decreased compared with that of the specimens with a smooth surface. These two alloys are found to have no grain boundary cavities formed under creep-fatigue test conditions. On the contrary, the fatigue life of 12Cr-Mo-V steel and solutionized 304 stainless steel in which grain boundary cavities are formed under creep-fatigue test conditions is not influenced by the states of surface roughness.The characteristic test results strongly confirm that the fatigue life of the specimen under creep-fatigue interaction, during which creep cavities are forming, may be controlled by the cavity nucleation and growth processes rather than the process of surface crack initiation. ((orig.))

1995-01-01

147

Predicting mooring system fatigue life by probabilistic methods  

Energy Technology Data Exchange (ETDEWEB)

Failure of moored structures from accumulated fatigue damage in shackles, connecting links, chain and wire rope components is common. When systems will be deployed for long periods, it is especially important to determine at the design, inspection and maintenance stages the fatigue damage. Since slack moored structures behave in a highly nonlinear manner, commonly used fatigue analysis procedures are normally inadequate. This paper reviews present probablistic fatigue analysis methods, and provides a means for incorporating nonlinear mooring behavior into analysis and design to predict accumulated damage and remaining service life. The procedures presented are general, and they are also applicable to ship and buoy moorings, offshore terminals, and guyed and tension leg platforms.

Saders, D.R.; Dominguez, R.F.; Ho, K.C.; Lai, N.W.

1983-05-01

148

Behaviors of residual stress and high-temperature fatigue life in ceramic coatings produced by PVD  

Energy Technology Data Exchange (ETDEWEB)

To investigate the effect of ceramic coatings on fatigue characteristics at room and elevated temperatures, residual stress measurements using the X-ray diffraction (XRD) method and high cycle fatigue tests were performed. The fatigue test for the uncoated and TiAlN-coated specimens was carried out at room temperature, 400 and 538 deg. C, respectively, while the residual stress and hardness variation of the TiAlN-coated layer were measured according to the temperature of the stress relief (SR) treatment. As a result, high compressive residual stress was measured in the coating, which decreased relative to the SR temperature. The cracks in the fatigue test, at both room and elevated temperatures, started from inclusions in the substrate near the interface between the base material and the coated ceramic. There was no hardness degradation in the coatings relative to the SR conditions. Therefore, it was concluded that the improvement in the fatigue life for the coated specimens was mainly due to compressive residual stress rather than surface constraints due to the higher hardness of the layer.

Suh, C.-M.; Hwang, B.-W.; Murakami, R.-I

2003-02-25

149

Behaviors of residual stress and high-temperature fatigue life in ceramic coatings produced by PVD  

International Nuclear Information System (INIS)

To investigate the effect of ceramic coatings on fatigue characteristics at room and elevated temperatures, residual stress measurements using the X-ray diffraction (XRD) method and high cycle fatigue tests were performed. The fatigue test for the uncoated and TiAlN-coated specimens was carried out at room temperature, 400 and 538 deg. C, respectively, while the residual stress and hardness variation of the TiAlN-coated layer were measured according to the temperature of the stress relief (SR) treatment. As a result, high compressive residual stress was measured in the coating, which decreased relative to the SR temperature. The cracks in the fatigue test, at both room and elevated temperatures, started from inclusions in the substrate near the interface between the base material and the coated ceramic. There was no hardness degradation in the coatings relative to the SR conditions. Therefore, it was concluded that the improvement in the fatigue life for the coated specimens was mainly due to compressive residual stress rather than surface constraints due to the higher hardness of the layer

2003-02-25

150

Analysis of fatigue properties and failure mechanisms of Ti6Al4V in the very high cycle fatigue regime using ultrasonic technology and 3D laser scanning vibrometry.  

Science.gov (United States)

Accelerated fatigue tests with Ti6Al4V were carried out using a 20kHz ultrasonic testing facility to investigate the cyclic deformation behavior in the Very High Cycle Fatigue (VHCF) regime in detail. Beside parameters like the ultrasonic generator power and the displacement of the specimen, a 3D laser scanning vibrometer was used to characterize the oscillation and fatigue behavior of the Ti-alloy. The course of the S-N(f) curve at the stress ratio R=-1 shows a significant decrease of the bearable stress amplitude and a change from surface to subsurface failures in the VHCF regime for more than 10? cycles. Microscopic investigations of the distribution of the ?- and ?-phase of Ti6Al4V indicate that inhomogeneities in the phase distribution are reasons for the internal crack initiation. High resolution vibrometry was used to visualize the eigenmode of the designed VHCF-specimen at 20 kHz in the initial state and to indicate local changes in the eigenmodes as a result of progressing fatigue damage. Non-contact strain measurements were realized and used to determine the stress amplitude. The determined stress amplitudes were correlated with strain gauge measurements and finite element analysis. PMID:23545114

Heinz, Stefan; Balle, Frank; Wagner, Guntram; Eifler, Dietmar

2013-12-01

151

An investigation on fatigue life of borided AISI 1010 steel  

Directory of Open Access Journals (Sweden)

Full Text Available Purpose: This study aims to investigate the fatigue life of box borided AISI 1010 steel materials.Design/methodology/approach: Fatigue specimens firstly have been prepared according to ASTM E466-96 standard and normalized. Then their surfaces have been cleaned by polishing. Boriding heat treatment has been applied in solid media with the help of Ekabor2 powder. Specimens have been borided at 1173-1223-1273 and 1323 K temperatures for 2-4 and 6 hours respectively. Fatigue tests have been made in rotating-bend test device. Separate S-N diagram has been formed for each boriding condition and then their results were compared with the results of the specimens on which any heat treatment has not been made.Findings: As a result it has been seen that boriding has no positive effect on fatigue life of AISI 1010 steel materials. And also it has been determined that fatigue life of the materials on which boriding heat treatment applied, decreases in between 14 %-55 %.Research limitations/implications: It can be noted that the reasons of short fatigue life determination are the boride layer’s much higher hardness than the substrate material’s, and the micro cracks existed between boride phases formed onto the surface.Originality/value: The investigations on fatigue life of borided AISI 1010 steel were made.

O.N. Celik

2009-01-01

152

Probabilistic fatigue life prediction of metallic and composite materials  

Science.gov (United States)

Fatigue is one of the most common failure modes for engineering structures, such as aircrafts, rotorcrafts and aviation transports. Both metallic materials and composite materials are widely used and affected by fatigue damage. Huge uncertainties arise from material properties, measurement noise, imperfect models, future anticipated loads and environmental conditions. These uncertainties are critical issues for accurate remaining useful life (RUL) prediction for engineering structures in service. Probabilistic fatigue prognosis considering various uncertainties is of great importance for structural safety. The objective of this study is to develop probabilistic fatigue life prediction models for metallic materials and composite materials. A fatigue model based on crack growth analysis and equivalent initial flaw size concept is proposed for metallic materials. Following this, the developed model is extended to include structural geometry effects (notch effect), environmental effects (corroded specimens) and manufacturing effects (shot peening effects). Due to the inhomogeneity and anisotropy, the fatigue model suitable for metallic materials cannot be directly applied to composite materials. A composite fatigue model life prediction is proposed based on a mixed-mode delamination growth model and a stiffness degradation law. After the development of deterministic fatigue models of metallic and composite materials, a general probabilistic life prediction methodology is developed. The proposed methodology combines an efficient Inverse First-Order Reliability Method (IFORM) for the uncertainty propogation in fatigue life prediction. An equivalent stresstransformation has been developed to enhance the computational efficiency under realistic random amplitude loading. A systematical reliability-based maintenance optimization framework is proposed for fatigue risk management and mitigation of engineering structures.

Xiang, Yibing

153

Estimation of Fatigue Life of Laser Welded AISI304 Stainless Steel T-Joint Based on Experiments and Recommendations in Design Codes  

Directory of Open Access Journals (Sweden)

Full Text Available In this paper the fatigue behavior of laser welded T-joints of stainless steel AISI304 is investigated experimentally. In the fatigue experiments 36 specimens with a sheet thickness of 1 mm are exposed to one-dimensional cyclic loading. Three different types of specimens are adopted. Three groups of specimens are used, two of these are non-welded and the third is welded with a transverse welding (T-Joint. The 13 laser welded specimens are cut out with a milling cutter. The non-welded specimens are divided in 13 specimens cut out with a milling cutter and 10 specimens cut out by a plasma cutter. The non-welded specimens are used to study the influence of heat and surface effects on the fatigue life. The fatigue life from the experiments is compared to fatigue life calculated from the guidelines in the standards DNV-RP-C203 and EUROCODE 3 EN-1993-1-9. Insignificant differences in fatigue life of the welded and non-welded specimens are observed in the experiments and the largest difference is found in the High Cycle Fatigue (HCF area. The specimens show a lower fatigue life compared to DNV-RP-C203 and EUROCODE 3 EN-1993-1-9 when the specimens are exposed to less than 4.0 1E06 cycles. Therefore, we conclude that the fatigue life assessment according to the mentioned standards is not satisfactory and reliable.

Søren Heide Lambertsen

2013-06-01

154

Strain rate dependence of the growth rate of grain boundary cavities during the high cycle high temperature fatigue of copper  

Energy Technology Data Exchange (ETDEWEB)

High temperature fully reversed fatigue tests of high purity copper were made as a function of stress amplitude. A mean cavity volume V{sub p} and corresponding number density of cavities N{sub p} were determined from the total cavity volume fraction V{sub v} obtained from precision density measurements (PDM) and the total cavity surface area S{sub v} calculated from small angle neutron scattering (SANS) measurements. Under the range of stress amplitudes tested, the plastic strain rate d{epsilon}{sub p}/dt was found to cover three orders of magnitude. The results of these tests of the influence of stress amplitude on cavity growth were combined with previous results in which the frequency of cycling was varied. It was found that the cavity growth rate correlates well with the measured plastic strain and stress amplitude through the relation dV{sub p}/dt {proportional{underscore}to} (d{epsilon}{sub p}/dt){sup 0.45} {proportional{underscore}to} {Delta}{sigma}{sup 2}.

Barker, J.G.; Weertman, J.R.; Pedersen, J.S.

1999-07-01

155

Fatigue life prediction in woven carbon fabric polyester composites  

International Nuclear Information System (INIS)

An analytical model, based on stiffness degradation during fatigue loading, which has been used for fatigue life predictions in the Fiber Reinforced Plastics (FRP), is employed to examine its validity to the fatigue life predictions in the Woven Fabric Reinforced Plastics. The rate of stiffness degradation (dE/dN) has been obtained from the constant amplitude fatigue testing of 8-ply coupons made from prepreg plain-weave woven carbon-carbon fabric having a polyester resin as the matrix material. The test coupons had three different ply stacking sequences, namely, the unidirectional (0)8,and two off axis plied (0,0,+45,-45)s, and (+45,-45,0,0)s orientations. The estimated fatigue lives obtained from the damage rate function dD/dN, which in turn was a function of the stiffness degradation rate dE/dN, were compared with the experimentally observed fatigue life data. It is shown that the stiffness degradation model provides reasonably good correlation between the analytically determined fatigue lives and the experimentally observed fatigue for the plain-weave woven Carbon-Carbon Fabric Reinforced Plastic Composites. (author)

1999-01-01

156

Temperature evolution and life prediction in fatigue of superalloys  

Science.gov (United States)

Low-cycle fatigue behavior of two superalloys, ULTIMET® alloy, Co-26 pct Cr-9 pct Ni (wt pct), and HAYNES® HR-120® alloy, Ni-33 pct Fe-25 pct Cr, was studied at room temperature. An infrared thermography system was employed to monitor the temperature evolution of fatigue processes for both superalloys. Temperature changes during fatigue were related to the hysteresis effect, and were successfully predicted, based on the consideration of the hysteresis effect and heat conduction. The temperature increase of a specimen from the initial to the equilibrium stages was used as an index to predict the fatigue life of the two superalloys. It was found that the fatigue-life predictions using the present model were in good agreement with the experimental results.

Jiang, L.; Wang, H.; Liaw, P. K.; Brooks, C. R.; Chen, L.; Klarstrom, D. L.

2004-03-01

157

On the fatigue life of 3D woven composite  

Energy Technology Data Exchange (ETDEWEB)

Polymer composites with three-dimensional woven graphite fiber reinforcement (3D interlock weaves) have been tested in compression-compression fatigue under load control. As under monotonic loading, the principal mechanism of failure is kink band formation in the primary load bearing twos. Observations of kink bands and microcracking in sectioned specimens suggest that fatigue progresses by the accumulation of damage to the resin within individual tows. If it is assumed that resin damage accumulates at a rate proportional to some power of the local axial shear stress in a misaligned tow, then a simple formula follows for the cycles to kink band formation. Under load control, only a few kink bands are required for specimen failure. Then the formula is also the basis for estimates of fatigue life. Fatigue life data and measured misalignment angles, which determine the local axial shear stress, support the fatigue model.

Dadkhah, M.S.; Cox, B.N. [Rockwell International Science Center, Thousand Oaks, CA (United States)

1995-12-31

158

Research on the fatigue character of ERW pipe welded seam and fatigue life assessment method  

Energy Technology Data Exchange (ETDEWEB)

This paper studies the effects of fatigue on electric resistance weld (ERW) seams in API X65 grade line pipe steel subjected to 0.1 and 0.6 stress ratios. A compact tension specimen was subjected to repeated loading, and the propagation rate of the fatigue crack and the threshold of the pipe seam were tested with a high-frequency fatigue testing machine. Radiographic inspection revealed that the main weld defect in the ERW pipe is the crack caused by the cold welding. To predict fatigue remaining life, it is essential to determine the original flaw. Contrary to the common bonding technique, ERW involves melting down, pushing down and heating, which depend on extrusion force. If the extrusion force exceeds the acceptable limit, the weld is misaligned, which reduces the fracture toughness. This paper establishes a method to predict the fatigue remaining life by means of the Paris formula and the failure assessment diagram.

Zhang, Guangli; Luo, Jinheng; Zhao, Xinwei; Zhang, Hua; Zhang, Liang; Zhang, Yi [Tubular Goods Research Center of CNPC, XI' AN (China)

2010-07-01

159

FATIGUE LIFE EVALUATION OF SUSPENSION KNUCKLE USING MULTIBODY SIMULATION TECHNIQUE  

Directory of Open Access Journals (Sweden)

Full Text Available Suspension is part of automotive systems, providing both vehicle control and passenger comfort. The knuckle is an important part within the suspension system, constantly encountering the cyclic loads subjecting it to fatigue failure. This paper presents an evaluation of the fatigue characteristics of a knuckle using multibody simulation (MBS techniques. Load time history extracted from the MBS is used for stress analysis. An actual road profile of road bumps was used as the input to MBS. The stress fluctuations for fatigue simulations are considered with the road profile. The strain-life method is utilized to assess the fatigue life. The instantaneous stress distributions and maximum principal stress are used for fatigue life predictions. Mesh sensitivity analysis has been performed. The results show that the steering link in the knuckle is found to be the most susceptible region for fatigue failure. The number of times the knuckle can manage a road bump at 40 km/hr is determined to be approximately 371 times with a 50% certainty of survival. The proposed method of using the loading time history extracted from MBS simulation for fatigue life estimation is found to be very promising for the accurate evaluation of the performance of suspension system components.

A.G.A. Rahman

2012-12-01

160

Prestraining and its influence on subsequent fatigue life  

Science.gov (United States)

An experimental program was conducted to study the damaging effects of tensile and compressive prestrains on the fatigue life of nickel-base, Inconel 718 superalloy at room temperature. To establish baseline fatigue behavior, virgin specimens with a solid uniform gage section were fatigued to failure under fully-reversed strain-control. Additional specimens were prestrained to 2 percent, 5 percent, and 10 percent (engineering strains) in the tensile direction and to 2 percent (engineering strain) in the compressive direction under stroke-control, and were subsequently fatigued to failure under fully-reversed strain-control. Experimental results are compared with estimates of remaining fatigue lives (after prestraining) using three life prediction approaches: (1) the Linear Damage Rule; (2) the Linear Strain and Life Fraction Rule; and (3) the nonlinear Damage Curve Approach. The Smith-Watson-Topper parameter was used to estimate fatigue lives in the presence of mean stresses. Among the cumulative damage rules investigated, best remaining fatigue life predictions were obtained with the nonlinear Damage Curve Approach.

Halford, Gary R.; McGaw, Michael A.; Kalluri, Sreeramesh

1995-03-01

 
 
 
 
161

Thermomechanical fatigue life prediction of high temperature components  

Energy Technology Data Exchange (ETDEWEB)

The aim of the work described in this paper is to provide a computational method for fatigue life prediction of high temperature components, in which the time and temperature dependent fatigue crack growth is a relevant damage mechanism. The fatigue life prediction is based on a law for microcrack growth and a fracture mechanics estimate of the cyclic crack tip opening displacement. In addition, a powerful model for nonisothermal cyclic plasticity is employed, and an efficient laboratory test procedure is proposed for the determination of the model parameters. The models are efficiently implemented into finite element programs and are used to predict the fatigue life of a cast iron exhaust manifold and a notch in the perimeter of a turbine rotor made of a ferritic/martensitic 10%-chromium steel. (orig.)

Seifert, Thomas; Hartrott, Philipp von; Riedel, Hermann; Siegele, Dieter [Fraunhofer-Inst. fuer Werkstoffmechanik (IWM), Freiburg (Germany)

2009-07-01

162

APPLICATION OF MULTIBODY SIMULATION FOR FATIGUE LIFE ESTIMATION  

Directory of Open Access Journals (Sweden)

Full Text Available In automobile design, the safety of passengers is of prime concern to the manufacturers. Suspension is one of the safety-related automotive systems which is responsible for maintaining traction between the road and tires, and offers a comfortable ride experience to the passengers by absorbing disturbances. One of the critical components of the suspension system is the knuckle, which constantly faces cyclic loads subjecting it to fatigue failure. This paper presents an evaluation of the fatigue characteristics of a knuckle using a gravel road profile acquired using a data acquisition system and standard SAE profiles for the suspension (SAESUS, bracket (SAEBRAKT and transmission (SAETRN. The gravel road profile was applied as the input to a multi body simulation (MBS, and the load history for various mounting points of the knuckle is extracted. Fatigue life is predicted using the strain-life method. The instantaneous stress distributions and maximum principal stress are used for fatigue life predictions. From the results, the strut connection is found to be the critical region for fatigue failure. The fatigue life from loading extracted from gravel road MBS agreed well with the life prediction when standard SAE profiles were used. This close agreement shows the effectiveness of the load extraction technique from MBS. This method can also be effectively used for more complex loading conditions that occur during real driving environments.

M. Kamal

2013-06-01

163

Surface fatigue life of high temperature gear materials  

Energy Technology Data Exchange (ETDEWEB)

Three high temperature gear materials were evaluated using spur gear surface fatigue tests. These materials were, VASCO max 350, VASCO matrix 2, and nitralloy N and were evaluated for possible use in high temperature gear applications. The fatigue life of the three high temperature gear materials were compared with the life of the standard AISI 9310 aircraft gear material. Surface fatigue tests were conducted at a lubricant inlet temperature of 321 K (120 F), a lubricant outlet temperature of 350 K (170 F), a maximum Hertz stress of 1.71 GPa (248 ksi), a speed of 10,000 rpm, and with a synthetic paraffinic lubricant. The life of the nitralloy N was approximately the same as the AISI 9310, the life of the VASCO max 350 was much less than the AISI 9310 while the life of the VASCO matrix 2 was several times the life of the AISI 9310. The VASCO max 350 also showed very low fracture toughness with approximately half of the gears failed by tooth fracture through the fatigue spall. The VASCO matrix 2 had approximately 10-percent fracture failure through the fatigue spalls indicating moderate to good fracture toughness.

Townsend, D.P.

1994-04-01

164

Studies of Microtexture and Its Effect on Tensile and High-Cycle Fatigue Properties of Laser-Powder-Deposited INCONEL 718  

Science.gov (United States)

The current work studies the microstructure, texture, and mechanical properties of INCONEL 718 alloy (IN718) produced by laser direct metal deposition. The grain microstructure exhibits an alternative distribution of banded fine and coarse grain zones as a result of the rastering scanning pattern. The effects of the anisotropic crystallographic texture on the tensile and high-cycle fatigue (HCF) properties at room temperature are investigated. Tensile test results showed that the tensile strength of laser-deposited IN718 after direct aging or solution heat treatment is equivalent to the minimum-forged IN718 properties. The transverse direction (relative to the laser scanning direction) produces >10 pct stiffer modulus of elasticity but 3 to 6 pct less tensile strength compared to the longitudinal direction due to the preferential alignment of grains having and directions parallel to the tensile loading direction. Laser-deposited IN718 with good metallurgical integrity showed equivalent HCF properties compared to the direct-aged wrought IN718, which can be attributed to the banded grain size variation and cyclic change of inclining grain orientations resulted from alternating rastering deposition path.

Qi, Huan; Azer, Magdi; Deal, Andrew

2012-11-01

165

Thermomechanical fatigue, oxidation, and Creep: Part II. Life prediction  

Science.gov (United States)

A life prediction model is developed for crack nucleation and early crack growth based on fatigue, environment (oxidation), and creep damage. The model handles different strain-temperature phasings (i.e., in-phase and out-of-phase thermomechanical fatigue, isothermal fatigue, and others, including nonproportional phasings). Fatigue life predictions compare favorably with experiments in 1070 steel for a wide range of test conditions and strain-temperature phasings. An oxide growth (oxide damage) model is based on the repeated microrupture process of oxide observed from microscopic measurements. A creep damage expression, which is stress-based, is coupled with a unified constitutive equation. A set of interrupted tests was performed to provide valuable damage progression information. Tests were performed in air and in helium atmospheres to isolate creep damage from oxidation damage.

Neu, R. W.; Sehitoglu, Huseyin

1989-09-01

166

a Study on the Fretting Fatigue Life of Zircaloy Alloys  

Science.gov (United States)

Studies on the strength and fatigue life of machines and structures have been conducted in accordance with the development of modern industries. In particular, fine and repetitive cyclic damage occurring in contact regions has been known to have an impact on fretting fatigue fractures. The main component of zircaloy alloy is Zr, and it possesses good mechanical characteristics at high temperatures. This alloy is used in the fuel rod material of nuclear power plants because of its excellent resistance. In this paper, the effect of the fretting damage on the fatigue behavior of the zircaloy alloy is studied. Further, various types of mechanical tests such as tension and plain fatigue tests are performed. Fretting fatigue tests are performed with a flat-flat contact configuration using a bridge-type contact pad and plate-type specimen. Through these experiments, it is found that the fretting fatigue strength decreases by about 80% as compared to the plain fatigue strength. Oblique cracks are observed in the initial stage of the fretting fatigue, in which damaged areas are found. These results can be used as the basic data for the structural integrity evaluation of corrosion-resisting alloys considering the fretting damages.

Kwon, Jae-Do; Park, Dae-Kyu; Woo, Seung-Wan; Chai, Young-Suck

167

Cyclic calculations and life estimation in thermomechanical fatigue  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The present paper describes a new numerical procedure devoted to the calculation of aeronautic engines and to the fatigue life assessment evaluation. The original aspects consists (1) in a new method used to determine the mechanical steady state of a structure under thermomechanical loading, (2) in a short review of an advanced fatigue model which can reproduce the Woehler curve, including the influence of the mean stress.

Azzouz, Farida; Cailletaud, Georges; Chaboche, Jean Louis; Ostoja-kuczynski, Elisabeth; Quilici, Ste?phane

2010-01-01

168

Fatigue life assessment under multiaxial variable amplitude loading  

International Nuclear Information System (INIS)

A variable amplitude multiaxial fatigue life prediction method is presented in this paper. It is based on a stress as input data are the stress tensor histories which may be calculated by FEM analysis or measured directly on the structure during the service loading. The different steps of he method are first presented then its experimental validation is realized for log and finite fatigue lives through biaxial variable amplitude loading tests using cruciform steel samples. (authors). 9 refs., 7 figs

1996-01-01

169

Study the Effect of Cooling Rate on Fatigue Strength and Fatigue Life of Heated Carbon Steel Bars  

Directory of Open Access Journals (Sweden)

Full Text Available The fatigue failure is the reason of (90% of mechanical failures. This work tries improving the fatigue strength and increasing the fatigue life for steel bars that used in concrete reinforcing. Tensile test were done to find the mechanical properties of steel bar. The heating over critical temperature (AC3 and cooling by different cooling rates were done for steel bars, and tested this samples by tensile and fatigue tests. The tensile test results show increasing in yield and tensile strength for sample that cooled by oil (medium cooling rate.The  fatigue test results show increasing in the fatigue life for samples that cooled by oil.

Ali S. Yasir

2013-07-01

170

Fatigue Life and Cyclic Softening Behavior of JLF-1 Steel  

International Nuclear Information System (INIS)

Development of reactor materials and blankets is a critical issue for early realization of fusion energy. A reduced-activation ferritic/martensitic steel, JLF-1, is considered as one of the candidate alloys for the first wall application of fusion reactor. In this paper, the low cycle fatigue (LCF) properties of JLF-1 steel were studied from room temperature (RT) to 873 K in a vacuum condition using engineering size cylinder specimens with 8 mm in diameter. The fatigue life at elevated temperature was almost as same as that at RT when the life was plotted against the total strain range. But when the life was plotted against the plastic strain range, the fatigue life curves for RT, 673 K and 873 K of JLF-1 were on different lines. This phenomenon were also observed in F82H and modified 9Cr-1Mo. Cyclic softening was observed in fatigue test at elevated temperature. The cyclic stress-strain curve can be obtained from the fatigue stress-strain hysteresis curves around half life. The cyclic yield point was lower than the static one, especially at 873 K. That means the cyclic softening is a design issue at elevated temperature, which will reduce the design margin significantly.The experiments of thermal history simulating the LCF test (annealing) were performed at 673 K and 873 K in vacuum.The temperature and cyclic deformation effects on microstructure will be observed by TEM. (author)

2006-09-11

171

Multiaxial fatigue models for short glass fibre reinforced polyamide. Part II: Fatigue life estimation  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Components made of short fibre reinforced thermoplastics are increasingly used in the automotive industry, and more frequently subjected to fatigue loadings during their service life. The determination of a predictive fatigue criterion is therefore a serious issue for the designers, and requires the knowledge of the local mechanical response. As the cyclic behaviour of polymeric material is reckoned to be highly nonlinear, even at room temperature, an accurate constitutive model is a prelimin...

Launay, Antoine; Maitournam, M. H.; Marco, Yann; Raoult, Ida

2013-01-01

172

Fatigue life and initiation mechanisms in wrought Inconel 718 DA for different microstructures  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Wrought Inconel 718 DA superalloy disk zones present a wide range of behavior in fatigue life due to the variability of the microstructure. In order to link the effect of the forging conditions and achieved microstructure to the fatigue life, two microstructures have been tested in fatigue. Fatigue tests under strain control were performed at 450°C. Grain size distributions and phase distributions were characterized in the specimens and related to fatigue failure initiation modes. Fatigue cr...

Abikchi, Meriem; Billot, Thomas; Cre?pin, Je?rome; Longuet, Arnaud; Mary, Caroline; Morgeneyer, Thilo F.; Pineau, Andre?

2013-01-01

173

A methodology to evaluate the fatigue life of flexible pipes  

Energy Technology Data Exchange (ETDEWEB)

This paper focus on a methodology to perform the fatigue analysis of flexible pipes. This methodology employs functions that convert forces and moments obtained in global analyses into stresses. The stresses are then processed by well-known cycle counting methods, and S-N curves evaluate the damage at several points in the pipe cross-section. Palmgren-Miner linear damage hypothesis is assumed in order to calculate the accumulated fatigue damage. A parametric study on the fatigue life of a flexible pipe employing this methodology is presented. The main points addressed in the study are the influence of friction between layers in the results, the importance of evaluating the fatigue life in various points of the pipe cross-section and the effect of different mean stress levels. The obtained results suggest that the consideration of friction effects strongly influences the fatigue life of flexible risers and these effects have to be accounted both in the global and local analyses of the riser. Moreover, mean stress effects are also significant and at least 8 equally spaced wires in each analyzed section of the riser must be considered in fatigue analyses. (author)

Sousa, Fernando J.M. de; Sousa, Jose Renato M. de; Siqueira, Marcos Q. de; Sagrilo, Luis V.S. [Coordenacao dos Programas de Pos-graduacao em Engenharia (COPPE/UFRJ), Rio de Janeiro, RJ (Brazil); Lemos, Carlos Alberto D. de [Petroleo Brasileiro S.A. (PETROBRAS), Rio de Janeiro, RJ (Brazil)

2009-07-01

174

Fatigue-Life Computational Analysis for the Self-Expanding Endovascular Nitinol Stents  

Science.gov (United States)

Self-expanding endovascular stents made of Nitinol (a Ni-Ti intermetallic compound possessing superelastic and shape-memory properties) are being widely used to treat a common circulatory problem in which narrowed arteries, primarily due to fatty deposits, hamper blood flow to the extremities (the problem commonly referred to as "peripheral artery disease"). The stents of this type unfortunately occasionally fail structurally (and, in turn, functionally) rendering the stenting procedure ineffective. The failure is most often attributed to the fatigue-induced damage since over its expected ten-year life span, the stent will normally experience 370-400 million pulsating-blood flow-induced loading cycles. Redesign/redevelopment of the stents using the conventional make-and-test approaches is quite expensive and time consuming and therefore is being increasingly complemented by computational engineering methods and tools. In the present study, advanced structural and fluid-structure interaction finite element computational methods are combined with the advanced fatigue-based durability analysis techniques to further enhance the use of the computational engineering analysis tools in the development of vascular stents with improved high-cycle fatigue life.

Grujicic, M.; Pandurangan, B.; Arakere, A.; Snipes, J. S.

2012-11-01

175

Creep fatigue life prediction for engine hot section materials (isotropic)  

Science.gov (United States)

The first two years of a two-phase program aimed at improving the high temperature crack initiation life prediction technology for gas turbine hot section components are discussed. In Phase 1 (baseline) effort, low cycle fatigue (LCF) models, using a data base generated for a cast nickel base gas turbine hot section alloy (B1900+Hf), were evaluated for their ability to predict the crack initiation life for relevant creep-fatigue loading conditions and to define data required for determination of model constants. The variables included strain range and rate, mean strain, strain hold times and temperature. None of the models predicted all of the life trends within reasonable data requirements. A Cycle Damage Accumulation (CDA) was therefore developed which follows an exhaustion of material ductility approach. Material ductility is estimated based on observed similarities of deformation structure between fatigue, tensile and creep tests. The cycle damage function is based on total strain range, maximum stress and stress amplitude and includes both time independent and time dependent components. The CDA model accurately predicts all of the trends in creep-fatigue life with loading conditions. In addition, all of the CDA model constants are determinable from rapid cycle, fully reversed fatigue tests and monotonic tensile and/or creep data.

Moreno, Vito; Nissley, David; Lin, Li-Sen Jim

1985-01-01

176

Estimating fatigue life for pipeline integrity management  

Energy Technology Data Exchange (ETDEWEB)

Pipelines constructed from materials manufactured prior to 1980 are more likely to contain manufacturing or transportation-induced defects. This paper described a method of predicting the reassessment intervals needed to ensure that the defects do not become enlarged and fail as a result of pressure-cycle-induced fatigue crack growth. An analysis of previous pipeline defects was used to ascertain that factors with the greatest influence on fatigue failures occurred as a result of the presence or absence of relatively large, longitudinally-oriented defects; the aggressiveness of the pressure cycles at the locations of the defects; and the rate of crack growth inherent in the material in its environment. A Paris law approach was used to predict times to failure. An initial defect size was established. Pressure cycles were represented as stress-intensity factors. Raju-Newman equations were used to calculate the stress intensity factor. The flow stress of the material was divided by a Folias-based correction factor to obtain hoop stress levels. A small amount of eccentricity was used to account for radial bulging. Predictions of times to failure from pressure-cycle-induced fatigue were used to calculate crack-tool re-inspection internals and hydrostatic retest intervals, and were also used to assess pressure-cycle aggressiveness based on a set of benchmark cycle tests. Results of the study suggested that defects likely to lead to failures were relatively large and easy to detect using currently available crack-detection tools. Hook cracks and mismatched plate edges were shown to be associated with fatigue failures. It was concluded that the analysis technique accurately predicted times to failure for fatigue cracks. The use of current standards as a guide for crack growth analysis is likely to result in conservative predictions of time to failure when pressure cycles and crack growth rates are adequately represented. 8 refs., 2 tabs., 5 figs.

Kiefner, J.F.; Zelenak, P.A.; Kolovich, C.E.; Wahjudi, T. [Kiefner and Associates Inc., Worthington, OH (United States)

2004-07-01

177

Fatigue Life of High-Strength Steel Offshore Tubular Joints  

DEFF Research Database (Denmark)

In the present investigation, the fatigue life of tubular joints in offshore steel structures is studied. Two test series on full-scale tubular joints have been carried through. One series was on joints in conventional offshore structural steel, and the other series was on joints in high-strength steel with a yield stress of 820-830 MPa and with high weldability and toughness properties. The test specimens of both series had the same geometry. The present report concentrates on the results obtained in the investigation on the high-strength steel tubular joints.The test specimens were fabricated from Ã? 324-610 mm tubes, and the joints were loaded in in-plane bending. Both fatigue tests under constant amplitude loading and tests with a stochastic loading that is realistic in relation to offshore structures, are included in the investigation.A comparison between constant amplitude and variable amplitude fatigue test results showed shorter fatigue lives in variable amplitude loading than should be expected from the linear fatigue damage accumulation formula. Furthermore, the fatigue tests on high-strength steel tubular joints showed slightly longer fatigue lives than those obtained in corresponding tests on joints in conventional offshore structural steel.

Agerskov, Henning

1996-01-01

178

Multiaxial low cycle fatigue life under non-proportional loading  

International Nuclear Information System (INIS)

A simple and clear method of evaluating stress and strain ranges under non-proportional multiaxial loading where principal directions of stress and strain are changed during a cycle is needed for assessing multiaxial fatigue. This paper proposes a simple method of determining the principal stress and strain ranges and the severity of non-proportional loading with defining the rotation angles of the maximum principal stress and strain in a three dimensional stress and strain space. This study also discusses properties of multiaxial low cycle fatigue lives for various materials fatigued under non-proportional loadings and shows an applicability of a parameter proposed by author for multiaxial low cycle fatigue life evaluation

2013-10-01

179

Effects of pre-working and dynamic strain aging on high cycle fatigue fracture of a stainless steel SUS316NG at 300degC  

International Nuclear Information System (INIS)

In order to obtain information about relationships between fatigue strength of a SUS316NG austenitic stainless steel and hardening behavior due to dynamic strain aging during fatigue tests, rotating bending fatigue tests were carried out at 300degC for notched specimens for stress concentration factors being less than 2.0 and for burnished hourglass type specimens. As for the notched specimens, fatigue fracture occurred before the specimens hardened enough during fatigue tests and the fatigue strengths did not reach the expected values from fatigue strengths of notched specimens for stress concentration factor being greater than 2.0. As for the burnished specimens, the specimen surfaces hardened enough previously to fatigue test but the fatigue strength also did not reach the expected value. Internal fracture occurred for burnished specimens and fish-eye patterns were observed on the fracture surfaces. (author)

2011-08-01

180

Prediction of corrosion fatigue life using DCPD method  

International Nuclear Information System (INIS)

In order to develop a method of corrosion fatigue design and estimate reliability of TMCP steel using as the material of heavy industries and plants, its corrosion susceptibilities and corrosion fatigue life considering corrosion degradation were investigated. From the results, the corrosion characteristic of TMCP steel is very susceptible in 3.5wt.% NaCl solution. Its susceptibility was linearly increased with the solution temperature increase. The potential difference due to the crack growth behavior in 25 deg. C, 3.5wt.% NaCl solution is very susceptible. And it was found that stress amplitude has a linear relationship with the critical potential. Therefore, it is expected that the corrosion fatigue life of TMCP steel can be nondestructively predicted using the DCPD method

2003-04-23

 
 
 
 
181

Fatigue life of ablation-cast 6061-T6 components  

Energy Technology Data Exchange (ETDEWEB)

The fatigue life of 6061-T6 alloy, normally used in its wrought form, was investigated in this study in cast form from parts produced by the new ablation casting process. All specimens were excised from military castings. Unidirectional tensile test results yielded elongation values comparable to forgings and extrusions. A total of 39 fatigue specimens were tested by the rotating cantilever beam technique at five maximum stress levels. Moreover nine specimens excised from a forging were also tested for comparison. Results revealed that the fatigue life of ablation-cast 6061-T6 (i) follows a three-parameter Weibull distribution, and (ii) is comparable to data from the 6061 forging and is superior to conventionally cast Al-7% Si-Mg alloy castings published in the literature. Analysis of the fracture surfaces of ablation-cast 6061-T6 via scanning electron microscopy showed the existence of fracture surface facets and multiple cracks propagating in different directions.

Tiryakioglu, Murat, E-mail: m.tiryakioglu@unf.edu [School of Engineering. University of North Florida, Jacksonville, FL 32224 (United States); Eason, Paul D. [School of Engineering. University of North Florida, Jacksonville, FL 32224 (United States); Campbell, John [Department of Metallurgy and Materials, University of Birmingham, Edgbaston B15 2TT (United Kingdom)

2013-01-01

182

Study the Effect of Cooling Rate on Fatigue Strength and Fatigue Life of Heated Carbon Steel Bars  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The fatigue failure is the reason of (90%) of mechanical failures. This work tries improving the fatigue strength and increasing the fatigue life for steel bars that used in concrete reinforcing. Tensile test were done to find the mechanical properties of steel bar. The heating over critical temperature (AC3) and cooling by different cooling rates were done for steel bars, and tested this samples by tensile and fatigue tests. The tensile test results show increasing in yield and te...

2013-01-01

183

Mean Strain Effects on the Strain Life Fatigue Curve.  

Science.gov (United States)

Aluminum 7075-T6 was tested using a Fatigue Material Test System. After creating the monotonic and cyclic stress-strain curves to verify material properties, strain life test data were replicated twenty times each to obtain the statistical description of ...

B. L. Smith

1993-01-01

184

Fatigue life assessment of free spanning pipelines containing corrosion defects  

Energy Technology Data Exchange (ETDEWEB)

The free spanning pipelines assessment is a highlighted issue to be considered during the project and maintenance of the submarine pipelines. It is required to evaluate the fatigue life and the maximum stress due to VIV (Vortex Induced Vibration) as well as wave forces when applicable in case of shallow water. The code DNV-RP-F105 (2006) presents a methodology to calculate the fatigue life for free spanning pipelines. Such methodology however considers the pipe with no kind of defects. Nevertheless, sometimes corrosion defects are detected in periodic inspections and therefore their effects need to be taken into account in the fatigue life evaluation. The purpose of this paper thus is to present a procedure to assess the influence of the corrosion defects in the fatigue life of free spanning pipelines. Some FE analyses were performed to determine the stress concentrate factor (SCF) of the corrosion defects, which were used as input in the methodology presented in the code DNV-RP-F105 (2006). Curves of damage and so lifetime have been generated as function of the span length and water depth. As a practical application, this methodology was applied to a sub sea pipeline with several corrosion defects, localized in shallow water offshore Brazil. (author)

Lopes, Rita de Kassia D.; Campello, Georga C.; Matt, Cyntia G. da Costa; Benjamin, Adilson C.; Franciss, Ricardo [PETROBRAS S.A., Rio de Janeiro, RJ (Brazil). Centro de Pesquisas (CENPES)

2009-12-19

185

Effect of cyclic frequency on the fatigue life of ASME SA-106-B piping steel in PWR environments  

International Nuclear Information System (INIS)

The author describes fatigue life tests in pressurized water reactor (PWR) environments performed on smooth and sharply notched specimens of ASME SA-106-B piping steel at cyclic frequencies of 1.0 Hz, 0.1 Hz, and 0.017 Hz. On the basis of these tests, it was concluded that no effect of cyclic frequency existed for smooth specimens whereas a frequency of 0.017 Hz proved to have the most detrimental effect on the cyclic life of the notched specimens. However, a reduction in fatigue strength in the low cycle fatigue regime and a fatigue strength enhancement in the high cycle regime was observed in both 2880C (5500F) air environment tests and PWR environment tests. This is believed to be due to dynamic strain aging processes. As a result, the current ASME Section III design curve for carbon steels is nonconservative in its positioning, which may decrease the presumed safety factor against fatigue failures in carbon steel piping components having structural discontinuities

1988-01-01

186

Finite Element Analysis of the Fatigue Life for the Connecting Rod Remanufacturing  

Directory of Open Access Journals (Sweden)

Full Text Available One important technical issue is whether the residual fatigue life of products meeting the needs of its next life cycle.This study analyzes the failure mechanism of the connecting rod, establishes its three dimensional model, uses dynamic simulation software ADAMS to calculate its time-load spectrum of the connecting rod; uses finite element analysis software ANSYS to get local stress-strain distribution; uses the traditional anti-fatigue methods to calculate the condition limited fatigue strength and then based on Miner fatigue damage theory and the stress of the connecting rod to make analysis, finally, uses Goodman fatigue theory to get fatigue strength and to estimate its total fatigue life, combined with its historical service time to predict its residual fatigue life. Provide reliable data to support how to calculate the residual fatigue life of these parts.

Cheng Gang

2013-01-01

187

Simulation work of fatigue life prediction of rubber automotive components  

International Nuclear Information System (INIS)

The usage of rubbers has always been so important, especially in automotive industries. Rubbers have a hyper elastic behaviour which is the ability to withstand very large strain without failure. The normal applications for rubbers are used for shock absorption, sound isolation and mounting. In this study, the predictions of fatigue life of an engine mount of rubber automotive components were presented. The finite element analysis was performed to predict the critical part and the strain output were incorporated into fatigue model for prediction. The predicted result shows agreement in term of failure location of rubber mount.

2010-05-01

188

Simulation work of fatigue life prediction of rubber automotive components  

Energy Technology Data Exchange (ETDEWEB)

The usage of rubbers has always been so important, especially in automotive industries. Rubbers have a hyper elastic behaviour which is the ability to withstand very large strain without failure. The normal applications for rubbers are used for shock absorption, sound isolation and mounting. In this study, the predictions of fatigue life of an engine mount of rubber automotive components were presented. The finite element analysis was performed to predict the critical part and the strain output were incorporated into fatigue model for prediction. The predicted result shows agreement in term of failure location of rubber mount.

Samad, M S A [Automotive Engineering Unit, Institute of Advanced Technology, University Putra Malaysia, 43400, UPM Serdang, Selangor (Malaysia); Ali, Aidy, E-mail: aidy@eng.upm.edu.my [Department of Mechanical and Manufacturing Engineering, Faculty of Engineering, Universiti Putra Malaysia, 43400 UPM, Serdang Selangor (Malaysia)

2010-05-15

189

Fatigue life prediction in wheel design  

Energy Technology Data Exchange (ETDEWEB)

In the fatigue components design is getting more and more consideration in the different design hypothesis of the whole load spectrum. As far as the commercial vehicles are concerned, in order to represent the load spectrum around 53 loading conditions, coupled to the relevant frequency are sufficient. Such a kind of load spectrum is usually used also in the project validation step, through 'Biaxial Machines' which indefinitely repeat the load program representing the mission profile. The design procedure developed is able not only to obtain the results relevant to the different loading conditions starting from the 3 main load cases, but also to synthesize the result in one scalar only, and namely the damage. (orig.)

Finzi, A.; Piazza, L. [GIANETTI RUOTE S.p.A., Ceriano Laghetto (Italy)

2000-07-01

190

Life prediction for bridged fatigue cracks  

Energy Technology Data Exchange (ETDEWEB)

One of the more promising classes of composites touted for high temperature applications, and certainly the most available, is that of relatively brittle matrices, either ceramic or intermetallic, reinforced by strong, aligned, continuous fibers. Under cyclic loading in the fiber direction, these materials develop matrix cracks that often run perpendicular to the fibers, while the fibers remain intact in the crack wake, supplying bridging tractions across the fracture surfaces. The bridging tractions shield the crack tip from the applied load, dramatically reducing the crack velocity from that expected in an unreinforced material subjected to the same value, {Delta}K{sub a}, of the cyclic applied stress intensity factor. An important issue in reliability is the prediction of the growth rates of the bridged cracks. The growth rates of matrix fatigue cracks bridged by sliding fibers are now commonly predicted by models based on the micromechanics of frictional interfaces. However, there exist many reasons, both theoretical and experimental, for suspecting that the most popular micromechanical models are probably wrong in detail in the context of fatigue cracks. Furthermore, a review of crack growth data reveals that the validity of the micromechanics-based predictive model has never been tested and may never be tested. In this paper, two alternative approaches are suggested to the engineering problem of predicting the growth rates of bridged cracks without explicit recourse to micromechanics. Instead, it is shown that the material properties required to analyze bridging effects can be deduced directly from crack growth data. Some experiments are proposed to test the validity of the proposals.

Cox, B.N.

1994-08-01

191

Fatigue Life Assessment of Selected Engineering Materials Based on Modified Low-Cycle Fatigue Test  

Directory of Open Access Journals (Sweden)

Full Text Available In this study, the mechanical tests were carried out on ductile iron of EN-GJS-600-3 grade and on grey cast iron of EN-GJL-250 grade.The fatigue life was evaluated in a modified low-cycle fatigue test (MLCF, which enables the determination of parameters resulting fromthe Manson-Coffin-Morrow relationship.The qualitative and quantitative metallographic studies conducted by light microscopy on selected samples of ductile iron with spheroidalgraphite and grey cast iron with lamellar graphite (showing only small variations in mechanical properties, confirmed also smallvariations in the geometrical parameters of graphite related with its content and morphological features.

M. Maj

2013-01-01

192

Relationship between fatigue life in the creep-fatigue region and stress-strain response  

Science.gov (United States)

On the basis of mechanical tests and metallographic studies, strainrange partitioned lives were predicted by introducing stress-strain materials parameters into the Universal Slopes Equation. This was the result of correlating fatigue damage mechanisms and deformation mechanisms operating at elevated temperatures on the basis of observed mechanical and microstructural behavior. Correlation between high temperature fatigue and stress strain properties for nickel base superalloys and stainless steel substantiated the method. Parameters which must be evaluated for PP- and CC- life are the maximum stress achievable under entirely plastic and creep conditions respectively and corresponding inelastic strains, and the two more pairs of stress strain parameters must be ascertained.

Berkovits, A.; Nadiv, S.

1988-01-01

193

Impact of Fatigue and Disability on Quality of Life in Multiple Sclerosis  

Directory of Open Access Journals (Sweden)

Full Text Available Purpose: To investigate the impact of fatigue and disability on the quality of life in 70 multiple sclerosis (MS patients. Material and Methods: Quality of Life was assessed using the Functional Assessment of MS (FAMS. Disability was assessed using the Kurtzke’s expanded disability status scale (EDSS and fatigue was quantified using the fatigue severity scale (FSS. Results: Fatigue groups (MSF had more impaired scores than nonfatigue groups (MSNF (p<0,05. Fatigue and disability were significantly associated with FAMS total and subgroups (p<0,05. Conclusion: Fatigue and disability have an effect on the quality of life.

Öztürk, A.

2005-01-01

194

Time-dependent fatigue--phenomenology and life prediction  

International Nuclear Information System (INIS)

The time-dependent fatigue behavior of materials used or considered for use in present and advanced systems for power generation is outlined. A picture is first presented to show how basic mechanisms and phenomenological information relate to the performance of the component under consideration through the so-called local strain approach. By this means life prediction criteria and design rules can be formulated utilizing laboratory test information which is directly translated to predicting the performance of a component. The body of phenomenological information relative to time-dependent fatigue is reviewed. Included are effects of strain range, strain rate and frequency, environment and wave shape, all of which are shown to be important in developing both an understanding and design base for time dependent fatigue. Using this information, some of the current methods being considered for the life prediction of components are reviewed. These include the current ASME code case, frequency-modified fatigue equations, strain range partitioning, the damage function method, frequency separation and damage rate equations. From this review, it is hoped that a better perspective on future directions for basic material science at high temperature can be achieved

1979-06-01

195

Fatigue Life Prediction of the Keel Structure of A Tsunami Buoy Using Spectral Fatigue Analysis Method  

Directory of Open Access Journals (Sweden)

Full Text Available One of the components of the Indonesia Tsunami Early Warning System (InaTEWS is a surface buoy. The surface buoy is exposed to dynamic and random loadings while operating at sea, particularly due to waves. Because of the cyclic nature of the wave load, this may result in a fatigue damage of the keel structure, which connects the mooringline with the buoy hull. The operating location of the buoy is off the Java South Coast at the coordinate (10.3998 S, 108.3417 E. To determine the stress transfer function, model tests were performed, measuring the buoy motions and the stress at the mooring line. A spectral fatigue analysis method is applied for the purpose of estimating the fatigue life of the keel structure. Utilizing the model-test results, the S-N curve obtained in a previous study and the wave data at the buoy location, it is found that the fatigue life of the keel structure is approximately 11 years.

Angga Yustiawan

2013-04-01

196

Fatigue life prediction and strength degradation of wind turbine rotor blade composites:  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Wind turbine rotor blades are subjected to a large number of highly variable loads, but life predictions are typically based on constant amplitude fatigue behaviour. Therefore, it is important to determine how service life under variable amplitude fatigue can be estimated from constant amplitude fatigue behaviour.

Nijssen, R. P. L.

2006-01-01

197

Effects of hydrogen on fatigue life of Ti-4Al-2V titanium alloy  

International Nuclear Information System (INIS)

Four hydrogen contents had been employed to investigate the effects of hydrogen on fatigue life of Ti-4Al-2V titanium alloy by means of section-varied samples. Results revealed that the fatigue life of hydrogen-charged materials is higher than that of natural hydrogen material provided that fatigue load ? ? is over 550 MPa. At higher ? ?, content of hydrogen has small effects on fatigue life within 116?280 ?g/g, but the fatigue life declines with the rise of hydrogen content in case of lower ? ?. Besides, amount of hydrogen tends to influence the crack initiation site. Explanation for the results is that interstitial hydrogen atoms and hydrides affecting the Persistent Slip Bands (PSB) become the cause of the decreasing in fatigue initiation life, and stress-induced precipitation of hydrides near crack tips for high hydrogen content seems being the reason of decrease in fatigue propagation life

2003-08-01

198

Cumulative fatigue damage behavior of MAR M-247  

Science.gov (United States)

The objective was to examine the room temperature fatigue and nonlinear cumulative fatigue damage behavior of the cast nickel-based superalloy, MAR M-247. The fatigue test matrix consisted of single-level, fully reversed fatigue experiments. Two series of tests were performed: one of the two baseline fatigue LCF (Low-Cycle Fatigue) life levels was used in the first loading block, and the HCF (High-Cycle Fatigue) baseline loading level was used in the second block in each series. For each series, duplicate tests were performed at each applied LCF life fraction.

McGaw, Michael A.; Halford, Gary R.; Kalluri, Sreeramesh

1991-05-01

199

A comparison of two total fatigue life prediction methods  

Energy Technology Data Exchange (ETDEWEB)

A 2-D analytical model which is termed the PICC-RICC model combines the effects of plasticity-induced crack closure (PICC) and roughness-induced crack closure (RICC). The PICC-RICC model handles naturally the gradual transition from RICC to PICC dominated crack growth. In this study, the PICC-RICC model is combined with a crack nucleation model to predict the total fatigue life of a notched component. This modified PICC-RICC model will be used to examine several controversial aspects of an earlier, computationally simpler total-life model known as the IP model.

Chen, N.; Lawrence, F.V.

1999-07-01

200

Life extension of components with high cumulative fatigue usage  

International Nuclear Information System (INIS)

The current ASME Boiler and Pressure Vessel Code fatigue design approach has significant margins of safety as evidenced by fatigue data from full-scale vessels. In order to extend the qualification (life) of components which have reached the Code design usage limit of unity, improved criteria are needed which address crack initiation and propagation separately such that safe operation of these components is assured. The fatigue crack initiation phase is composed of two processes: initial microcracking of internal particles or accumulation of local strain (cyclic slip) creating discontinuities which form microcracks, and the growth of the microcracks, and the growth of the microcracks in a noncontinuum manner. The microcracks which initiate will eventually grow to a size in which continuum mechanics apply, and fracture mechanics concepts can be employed. The later propagation to failure of a component is also composed of two parts, continuum crack growth in a stable manner and eventual unstable fracture of the remaining ligament of material. This paper reviews the current status of technology in assessing initiation and propagation relative to the current design Code and suggests areas of improvement to cover extended life of high usage factor components

1985-01-01

 
 
 
 
201

High cycles fatigue damage of CFRP plates clamped by bolts for axial coupling joint with off-set angle during rotation  

Science.gov (United States)

This study discussed the change of residual fracture torque and the fatigue damage process of thin CFRP plates clamped by bolts for axial coupling joint, in which flexible deformation was allowed in the direction of off-set angle by the deflection of the CFRP plates while effective stiffness was obtained in rotational direction. Mechanically laminated 4 layers of the CFRP plates were repeatedly deflected during the rotation of axial coupling, when two axes were jointed with 3 degree of off-set angle, in which number of revolution was 1,800 rpm (30Hz of loading frequency). At first, the fracture morphology of specimen and the residual fracture torque was investigated after 1.0×107 cycles of repeated revolutions. The reduction ratio of spring constant was also determined by simple bending test after the fatigue. The residual fracture torque of the joint was determined on the rotational test machine after 1.0×107 cycles of fatigue. After rotations of cyclic fatigue, fiber breaking and wear of matrix were observed around the fixed parts compressed by washers for setting bolts. The reduction of spring constant of the CFRP plates was caused by the initiation of cyclic fatigue damages around the fixed parts, when the axial coupling joint was rotated with off-set angle. It was found that residual fracture torque of the joint was related with the specific fatigue damage of the CFRP observed in this study.

Ooka, Kazuaki; Okubo, Kazuya; Fujii, Toru; Umeda, Shinichi; Fujii, Masayuki; Sugiyama, Tetsuya

2014-03-01

202

The Effect of Geometry on Fatigue Life for Bellows  

Science.gov (United States)

A bellows is a component installed in the automobile exhaust system to reduce or prevent the impact from engine. Generally, the specifications on the bellows are determined in the system design process of exhaust system and the component design is carried out to meet the specifications such as stiffness. Consideration of fatigue is generally an important aspect of design on metallic bellows expansion joints. These components are subject to displacement loading which frequently results in cyclic strains. This study has been investigated to analyze the effect of geometry on fatigue life for automotive bellows. 8 node shell element and non-linear method is employed for the analysis. The optimized shapes of the bellows are expected to give good guidelines to the practical designs.

Kim, Jinbong

203

Relationship between fatigue life in the creep-fatigue region and stress-strain response  

Science.gov (United States)

On the basis of mechanical tests and metallographic studies, strainrange partitioned lives were predicted by introducing stress-strain materials parameters into the Universal Slopes Equation. This was the result of correlating fatigue damage mechanisms and deformation mechanisms operating at elevated temperatures on the basis of observed mechanical and microstructural behavior. Correlation between high temperature fatigue and stress strain properties for nickel base superalloys and stainless steel substantiated the method. Parameters which must be evaluated for PP- and CC- life are the maximum stress achievable under entirely plastic and creep conditions respectively and corresponding inelastic strains, and the elastic modulus. For plasticity/creep interaction conditions (PC and CP) two more pairs of stress strain parameters must be ascertained.

Berkovits, A.; Nadiv, S.

1988-01-01

204

A review of the effects of coolant environments on the fatigue life of LWR structural materials  

International Nuclear Information System (INIS)

The American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code specifies design curves for the fatigue life of structural materials in nuclear power plants. However, the effects of light water reactor (LWR) coolant environments were not explicitly considered in the development of the design curves. The existing fatigue-strain-versus-life ((varepsilon)-N) data indicate potentially significant effects of LWR coolant environments on the fatigue resistance of pressure vessel and piping steels. Under certain environmental and loading conditions, fatigue lives in water relative to those in air can be a factor of 15 lower for austenitic stainless steels and a factor of ?30 lower for carbon and low-alloy steels. This paper reviews the current technical basis for the understanding of the fatigue of piping and pressure vessel steels in LWR environments. The existing fatigue (varepsilon)-N data have been evaluated to identify the various material, environmental, and loading parameters that influence fatigue crack initiation and to establish the effects of key parameters on the fatigue life of these steels. Statistical models are presented for estimating fatigue life as a function of material, loading, and environmental conditions. An environmental fatigue correction factor for incorporating the effects of LWR environments into ASME Code fatigue evaluations is described. This paper also presents a critical review of the ASME Code fatigue design margins of 2 on stress (or strain) and 20 on life and assesses the possible conservatism in the current choice of design margins.

2009-04-01

205

Fatigue life prediction for a cold worked T316 stainless steel  

International Nuclear Information System (INIS)

Permanent damage curves of initiation-life and propagation-life which predict the fatigue life of specimens of a cold-worked type 316 stainless steel under complex strain-range histories were generated by a limited test program. Analysis of the test data showed that fatigue damage is not linear throughout life and that propagation life is longer than initiation-life at high strain ranges but is shorter at low strain ranges. If permanent damage has been initiated by prior history and/or fabrication, propagation to a given life can occur at a lower strain range than that estimated from the fatigue curves for constant CSR. (author)

1983-12-01

206

Crack growth and high cycle fatigue behaviour of an aa6060 aluminium alloy after ecap combined with a subsequent heat treatment; Rissfortschritts- und Ermuedungsverhalten der Aluminiumlegierung EN AW-6060 nach ECAP und nachgelagerter Waermebehandlung  

Energy Technology Data Exchange (ETDEWEB)

Crack growth properties of the Al-Mg-Si alloy AA6060 as well as the high cycle fatigue behaviour have been investigated after equal-channel angular pressing (ECAP). In our study, experiments have been conducted on different stages of microstructural breakdown and strain hardening of the material as they were present after different numbers of ECAP passes. A bimodal condition, obtained after two pressings, and a homogeneously ultrafine-grained condition after eight repetitive pressings have been investigated. Furthermore, optimized conditions with an enhanced ductility, produced by ECAP processing combined with a following short-time aging treatment were included into the study. Crack growth experiments have been conducted in the near-threshold regime and the region of stable crack growth, covering a range of load ratios from R = 0.1 up to 0.7. It was found that the lowered fatigue threshold {delta}K{sub th} of the as-extruded material can be enhanced by the combination of ECAP and short-time aging, owing to the increased ductility and strain hardening capability of this material. By means of SEM investigations and tensile tests, the crack growth properties of the different conditions were related to microstructural and mechanical features. In fatigue tests, load reversals up to failure and the fatigue limit for an as-extruded condition and an optimized condition after two ECAP-passes have been compared to the coarse grained initial condition and a remarkable increase in fatigue strength was noted. (Abstract Copyright [2009], Wiley Periodicals, Inc.) [German] An der warmaushaertenden Aluminiumlegierung EN AW-6060 wurden Untersuchungen zum Rissfortschritt und zur Ermuedung nach hochgradig plastischer Verformung durch ECAP (Equal-Channel Angular Pressing) durchgefuehrt. Es wurden Zustaende in unterschiedlichen Stadien der Mikrostrukturfeinung und Verformungsverfestigung untersucht: ein bimodaler Zustand nach zwei sowie ein homogen ultrafeinkoerniger Zustand nach acht ECAP-Umformschritten. Zudem wurden zwei optimierte Zustaende mit verbesserter Duktilitaet, eingestellt durch eine Kombination aus ECAP mit einer nachfolgenden kurzen Auslagerungsbehandlung, in die Untersuchungen einbezogen. Rissfortschrittsversuche im Schwellwertbereich und dem stabilen Rissfortschrittsbereich bei Lastverhaeltnissen von R = 0,1 bis 0,7 ergaben fuer die optimierten Zustaende eine Verbesserung der Schwellwerte im Vergleich zu den ecapierten Zustaenden, was auf erhoehte Duktilitaet durch die Kombination von ECAP und einer Auslagerungsbehandlung zurueckgefuehrt wurde. Anhand von rasterelektronenmikroskopischen Analysen der Rissfortschrittsflaechen sowie den aus Zugversuchen ermittelten Festigkeits- und Zaehigkeitskennwerten konnte das Rissfortschrittsverhalten mit der Mikrostruktur und den mechanischen Eigenschaften in Verbindung gebracht werden. In Ermuedungsversuchen im Zeitfestigkeitsbereich (HCF ''high cycle fatigue'') wurden ein ecapierter sowie ein optimierter Zustand untersucht. Fuer beide Zustaende wurde eine deutliche Erhoehung der Ermuedungsfestigkeit im Vergleich zum Ausgangszustand festgestellt. (Abstract Copyright [2009], Wiley Periodicals, Inc.)

Hockauf, K.; Meyer, L.W.; Halle, T.; Hockauf, M. [Lehrstuhl Werkstoffe des Maschinenbaus, TU Chemnitz, 09107 Chemnitz (Germany)

2009-07-15

207

Fatigue life prediction of oil ducts under service loads  

Energy Technology Data Exchange (ETDEWEB)

A methodology to calculate the residual initiation and propagation lives of fatigue cracks in oil pipelines with corrosion-like defects is proposed and applied to predict the residual life of an old duct made of API 5L Gr. B steel, in service for more than 40 years. Since its inauguration, this pipeline has carried several heated products under variable temperatures and pressures. The calculated (nominal) service stresses are very high, due to thermal loads that induce significant bending in curved parts of the duct, with peaks close to the yield strength of the steel. The elastic- plastic fatigue damage at a notch or a corrosion pit root is calculated using the {epsilon}N method, and the effects of surface semi-elliptical cracks in its internal (or external) wall is studied considering appropriate stress intensity factor expressions and the actual service loads. In the presence of surface flaws associated to stress concentration factors of the order of three, a fatigue crack likely will initiate in the pipeline. However, if these surface cracks are small compared to the duct wall thickness, their predicted propagation rates are very low. (author)

Meggiolaro, Marco A.; Castro, Jaime T.P. [Pontificia Univ. Catolica do Rio de Janeiro, RJ (Brazil)

2003-07-01

208

Finite Element Based Fatigue Life Prediction of Cylinder Head for Two-Stroke Linear Engine Using Stress-Life Approach  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This study describes the finite element based fatigue life prediction of cylinder head for a two-stroke free piston linear engine subjected to variable amplitude loading, applicable to electric power generation. A set of aluminum alloys, cast iron and forged steel for cylinder head are considered in this study. The finite element modeling and analysis were performed utilizing the finite element analysis codes. The fatigue life analysis was carried out using finite element based fatigue ...

2008-01-01

209

Rolling-element fatigue life of AMS 5749 corrosion resistant, high temperature bearing steel  

Science.gov (United States)

The rolling element fatigue lives of AMS 5749 and AISI M-50 were compared in tests run in the five ball fatigue tester and the rolling contact fatigue tester. The effects of double vacuum melting and retained austenite on the life of AMS 5749 were determined in five ball fatigue tests. The double vacuum melting process consisted of induction vacuum melting followed by vacuum arc remelting (VIM-VAR). In the five ball tests, VIM-VAR AMS 5749 gave lives at least six times that of VIM-VAR AISI M-50. Similar tests in the rolling contact fatigue tester showed no significant difference in the lives of the two materials. The rolling element fatigue life of VIM-VAR AMS 5749 was at least 14 times that of vacuum induction melted AMS 5749. A trend toward increased rolling element fatigue life with decreased retained austenite is apparent, but the confidence that all experimental differences are significant is not great.

Parker, R. J.; Hodder, R. S.

1977-01-01

210

Theoretical modeling and experimental study on fatigue initiation life of 16MnR notched components  

International Nuclear Information System (INIS)

In order to investigate the effects of notch geometry and loading conditions on the fatigue initiation life and fatigue fracture life of 16MnR material, fatigue experiments were conducted for both smooth rod specimens and notched rod specimens. The detailed elastic-plastic stress and strain responses were computed by the finite element software (ABAQUS) incorporating a robust cyclic plasticity model via a user subroutine UMAT. The obtained stresses and strains were applied to the multiaxial fatigue damage criterion to compute the fatigue damage induced by a loading cycle on the critical material plane. The fatigue initiation life was then obtained by the proposed theoretical model. The well agreement between the predicted results and the experiment data indicated that the fatigue initiation of notched components in the multiaxial stress state related to all the nonzero stress and strain quantities. (authors)

2010-10-01

211

Fatigue and Quality of Life of Women Undergoing Chemotherapy or Radiotherapy for Breast Cancer  

Digital Repository Infrastructure Vision for European Research (DRIVER)

OBJECTIVE To examine fatigue and quality of life (QOL) in breast cancer patients undergoing chemotherapy or radiotherapy.METHODS A self-report survey derived from the Chinese version of Brief Fatigue Inventory, the Functional Assessment of Chronic Illness Therapy for Breast Cancer, and the Medical Outcomes Study Social Support Survey. Descriptive statistics was used to examine the intensity of fatigue and the prevalence of severe fatigue. Multivariate analysis of variance was used to de...

2009-01-01

212

Displacement measurement on specimens subjected to non-Gaussian random vibrations in fatigue life tests  

Science.gov (United States)

High-cycle fatigue life tests conducted using controlled random vibrations are commonly used to evaluate failure in components and structures. In most cases, a Gaussian distribution of both the input vibration and the stress response is assumed, while real-life loads may be non-Gaussian causing the response to be non-Gaussian as well. Generating non-Gaussian drive signals with high kurtosis and a given power spectral density, however, does not always guarantee that the stress response will actually be non-Gaussian, because this depends on the adherence of the tested system to the Central Limit Theorem. On the other side, suitable measurement methods need to be developed in order to estimate the stress amplitude response at critical failure locations, and therefore to evaluate and select input loads. In this paper, a simple test rig with a notched cantilevered specimen was developed to measure the response and examine the kurtosis values in the case of stationary Gaussian, stationary non-Gaussian, and non-stationary non-Gaussian excitation signals. The Laser Doppler Vibrometry (LDV) technique was used for the first time in this type of test, to estimate the specimen stress amplitude response in terms of differential displacement at the notch section ends. A method based on the use of accelerometers to correct for the occasional signal drops occurring during the experiment is described and the results are discussed with respect to the ability of the test procedure to evaluate the output signal.

Troncossi, M.; Di Sante, R.; Rivola, A.

2014-05-01

213

Determination of Turboprop Reduction Gearbox System Fatigue Life and Reliability  

Science.gov (United States)

Two computational models to determine the fatigue life and reliability of a commercial turboprop gearbox are compared with each other and with field data. These models are (1) Monte Carlo simulation of randomly selected lives of individual bearings and gears comprising the system and (2) two-parameter Weibull distribution function for bearings and gears comprising the system using strict-series system reliability to combine the calculated individual component lives in the gearbox. The Monte Carlo simulation included the virtual testing of 744,450 gearboxes. Two sets of field data were obtained from 64 gearboxes that were first-run to removal for cause, were refurbished and placed back in service, and then were second-run until removal for cause. A series of equations were empirically developed from the Monte Carlo simulation to determine the statistical variation in predicted life and Weibull slope as a function of the number of gearboxes failed. The resultant L(sub 10) life from the field data was 5,627 hr. From strict-series system reliability, the predicted L(sub 10) life was 774 hr. From the Monte Carlo simulation, the median value for the L(sub 10) gearbox lives equaled 757 hr. Half of the gearbox L(sub 10) lives will be less than this value and the other half more. The resultant L(sub 10) life of the second-run (refurbished) gearboxes was 1,334 hr. The apparent load-life exponent p for the roller bearings is 5.2. Were the bearing lives to be recalculated with a load-life exponent p equal to 5.2, the predicted L(sub 10) life of the gearbox would be equal to the actual life obtained in the field. The component failure distribution of the gearbox from the Monte Carlo simulation was nearly identical to that using the strict-series system reliability analysis, proving the compatibility of these methods.

Zaretsky, Erwin V.; Lewicki, David G.; Savage, Michael; Vlcek, Brian L.

2007-01-01

214

NASALIFE - Component Fatigue and Creep Life Prediction Program  

Science.gov (United States)

NASALIFE is a life prediction program for propulsion system components made of ceramic matrix composites (CMC) under cyclic thermo-mechanical loading and creep rupture conditions. Although the primary focus was for CMC components, the underlying methodologies are equally applicable to other material systems as well. The program references empirical data for low cycle fatigue (LCF), creep rupture, and static material properties as part of the life prediction process. Multiaxial stresses are accommodated by Von Mises based methods and a Walker model is used to address mean stress effects. Varying loads are reduced by the Rainflow counting method or a peak counting type method. Lastly, damage due to cyclic loading and creep is combined with Minor s Rule to determine damage due to cyclic loading, damage due to creep, and the total damage per mission and the number of potential missions the component can provide before failure.

Gyekenyesi, John Z.; Murthy, Pappu L. N.; Mital, Subodh K.

2005-01-01

215

Rainflow counting algorithm for the LIFE2 fatigue analysis code  

Energy Technology Data Exchange (ETDEWEB)

The LIFE2 computer code is a fatigue/fracture analysis code that is specialized to the analysis of wind turbine components. The numerical formulation of the code uses a series of cycle count matrices to describe the cyclic stress states imposed upon the turbine. In this formulation, each stress cycle is counted or binsed'' according to the magnitude of its mean stress and alternating stress components and by the operating condition of the turbine. This paper describes a set of numerical algorithms that have been incorporated into the LIFE2 code. These algorithms determine the cycle count matrices for a turbine component using stress-time histories of the imposed stress states. Example problems are used to illustrate the use of these algorithms. 4 refs., 4 figs.

Schluter, L.L.; Sutherland, H.J. (Sandia National Labs., Albuquerque, NM (USA))

1989-01-01

216

Residual life evaluation method for transmission line conductors subjected to fatigue damage  

Energy Technology Data Exchange (ETDEWEB)

The objective of this study was to develop a method for evaluating the status of electrical conductors subjected to fatigue damage and to estimate their residual life. The proposed method is based on the correlation between the loss of ductility of the material subjected to cyclic loading and the fatigue-consumed life fraction. The approach put forward to confirm this correlation comprises four consecutive steps: Determination of the tensile ductility of the conductor strands before the damage occurs; establishment of the fatigue curve of the strand; fatigue tests on the strands at different fractions of fatigue life; and determination of the residual tensile ductility of the tested strands. This paper presents the results of the study test program, performed on steel and aluminum strands of an ACSR 26/7 conductor. The end product of the study is a diagram containing all the necessary elements for estimating the residual life of conductors stressed by fatigue loading.

NONE

1995-12-31

217

An Analytical Model for Fatigue Life Prediction Based on Fracture Mechanics and Crack Closure  

DEFF Research Database (Denmark)

Fatigue in steel structures subjected to stochastic loading is studied. Of special interest is the problem of fatigue damage accumulation and in this connection, a comparison between experimental results and results obtained using fracture mechanics. Fatigue test results obtained for welded plate test specimens are compared with fatigue life predictions using a fracture mechanics approach. In the calculation of the fatigue life, the influence of the welding residual stresses and crack closure on the fatigue crack growth is considered. A description of the crack closure model for analytical determination of the fatigue life is included. Furthermore, the results obtained in studies of the various parameters that have an influence on the fatigue life, are given. A very good agreement between experimental and analytical results is obtained, when the crack closure model is used in determination of the analytical fatigue lives. Both the analytical and experimental results obtained show that the Miner rule may give quite unconservative predictions of the fatigue life for the types of stochastic loading studied.

Agerskov, Henning

1996-01-01

218

Finite Element Based Fatigue Life Prediction of a New Free Piston Engine Mounting  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This study presents the finite element based fatigue life prediction of a new free piston linear generator engine mounting. The objective of this research is to assess the critical fatigue locations on the component due to loading conditions. The effects of mean stress and probabilistic nature on the fatigue life are also investigated. Materials SAE 1045-450-QT and SAE 1045-595-QT are considered in this study. The finite element modeling and analysis was performed using computer-aided design ...

2008-01-01

219

An approach for long-term NSSS fatigue life assessment/validation  

International Nuclear Information System (INIS)

The prevention of metal fatigue due to mechanical and thermal loading cycles is an integral part of the design of nuclear power plants. Since fatigue is a cumulative process which increases with the number and severity of cycles experienced by plant components, metal fatigue should be addressed in plant life extension evaluations. The history of fatigue considerations for nuclear power plants is discussed. It is concluded that fatigue is generally not a concern at locations considered in the original plant design. Based on a number of considerations, an integrated program of fatigue monitoring focused inspection, and the associated technical justification is outlined as an approach for addressing the few fatigue-sensitive locations which should be included in nuclear plant life extension programs

1988-08-03

220

Use of Strain-life Models with Wavelet Bump Extraction (WBE fro Prediction Fatigue Damage  

Directory of Open Access Journals (Sweden)

Full Text Available This paper presents the use of strain-life fatigue damage models to observe the cycle sequence effects in the wavelet-based fatigue data editing algorithm. This algorithm is called Wavelet Bump Extraction (WBE, which was developed to produce a shortened signal by extracting fatigue damaging events from the original signal with the retention of the original cycle sequences. Current industrial practice uses the Plamgren-Miner linear damage rule to predict the fatigue life or fatigue damage under variable amplitude(VA loadings. Using VA loadings, however, this rule does not have load interaction accountability in the analysis. Thus, a more suitable approach has been identified for predicting fatigue damage od VA loadings, i.e. the Effective Strain Damage (ESD model. In this study, the cycle sequence effect observation was implemented in both analytical and experimental works using the WBE extracted VA loadings. The study includes the comparison between the experimental and the anlytical (using four strain-life fatigue damage models: Coffin-Manson, Morrow, Smith-Watson-Topper and ESD fatigue damage. The smallest average in the fatigue damage difference was found when using the ESD strain-life model, suggesting the suitability of the model for analysing VA fatigue technique.

John R. Yates

2008-08-01

 
 
 
 
221

Prediction of fatigue crack propagation life in notched members under variable amplitude loading  

Energy Technology Data Exchange (ETDEWEB)

One of the interesting phenomenon in the study of fatigue crack propagation under variable amplitude load cycling is the crack growth retardation that normally occurs due to the application of a periodic overload. Fatigue crack growth rate under simple variable amplitude loading sequence incorporating period overloads is studied using single edge notched specimens of AISI 304 stainless steel. Load interaction effects due to single and multiple overload have been addressed. Substantial retardation of fatigue crack growth rate is observed due to the introduction of periodic tensile overloads. Estimates of fatigue life have been obtained employing Wheeler model (using Paris and modified Paris equations) and Elber`s model. Analytical predictions are compared with experimental results. Results of these analytical fatigue life predictions show good agreement with the experimental results. Results of these analytical fatigue life predictions show good agreement with the experimental fatigue life data. Fatigue crack propagation rates also have been evaluated from the fractographic study of fatigue striations seen on the fracture surface. Good agreement was found between the experimentally observed crack growth rates and the fatigue crack growth rates determined by the fractographic studies.

Khan, Z.; Rauf, A.; Younas, M. [King Fahd Univ. of Petroleum and Minerals, Dhahran (Saudi Arabia). Mechanical Engineering Dept.

1997-06-01

222

The fatigue life prediction of aluminium alloy using genetic algorithm and neural network  

Science.gov (United States)

The behavior of the fatigue life of the industrial materials is very important. In many cases, the material with experiencing fatigue life cannot be avoided, however, there are many ways to control their behavior. Many investigations of the fatigue life phenomena of alloys have been done, but it is high cost and times consuming computation. This paper report the modeling and simulation approaches to predict the fatigue life behavior of Aluminum Alloys and resolves some problems of computation. First, the simulation using genetic algorithm was utilized to optimize the load to obtain the stress values. These results can be used to provide N-cycle fatigue life of the material. Furthermore, the experimental data was applied as input data in the neural network learning, while the samples data were applied for testing of the training data. Finally, the multilayer perceptron algorithm is applied to predict whether the given data sets in accordance with the fatigue life of the alloy. To achieve rapid convergence, the Levenberg-Marquardt algorithm was also employed. The simulations results shows that the fatigue behaviors of aluminum under pressure can be predicted. In addition, implementation of neural networks successfully identified a model for material fatigue life.

Susmikanti, Mike

2013-09-01

223

Development of a Composite Delamination Fatigue Life Prediction Methodology  

Science.gov (United States)

Delamination is one of the most significant and unique failure modes in composite structures. Because of a lack of understanding of the consequences of delamination and the inability to predict delamination onset and growth, many composite parts are unnecessarily rejected upon inspection, both immediately after manufacture and while in service. NASA Langley is leading the efforts in the U.S. to develop a fatigue life prediction methodology for composite delamination using fracture mechanics. Research being performed to this end will be reviewed. Emphasis will be placed on the development of test standards for delamination characterization, incorporation of approaches for modeling delamination in commercial finite element codes, and efforts to mature the technology for use in design handbooks and certification documents.

OBrien, Thomas K.

2009-01-01

224

Effects of laser shock processing on the fatigue life of 2024-T62 aluminium alloy  

Energy Technology Data Exchange (ETDEWEB)

Laser shock processing (LSP) is a new technology for strengthening the materials. The feasibility of using a high energy, pulsed laser beam to shock-harden the localized stress concentration zone, i.e., small holes in 2024-T62 aluminum alloy was investigated in this paper. Confining plasma technique was used in the study. In order to generate the pressure which is required to exceed the dynamic yield strength of 2024-T62 aluminum alloy, laser parameters were optimized. The fatigue life of specimens was studied before and after laser shocking. The fatigue tests showed that the fatigue life of 2024-T62 aluminum alloy treated by LSP had been improved significantly. With 95% confidence, the median fatigue life of shocked specimens was 1.9 to 2.5 times than that of unshocked ones. It is expected that LSP will be used as a good treatment for improving the fatigue life of aviation structures.

Zhang Hong; Lu Boliang; Zhang Shuren [Changchun Inst. of Optics and Fine Mechanics (China). Dept. of Mechanical Engineering; Tang Yaxin; Yu Chengye [Nanjing Univ. of Aeronautics and Astronautics (China). Dept. of Mechanical Engineering

1996-12-31

225

Probabilistic assessment of fatigue life including statistical uncertainties in the S-N curve  

International Nuclear Information System (INIS)

A probabilistic framework is set up to assess the fatigue life of components of nuclear power plants. It intends to incorporate all kinds of uncertainties such as those appearing in the specimen fatigue life, design sub-factor, mechanical model and applied loading. This paper details the first step, which corresponds to the statistical treatment of the fatigue specimen test data. The specimen fatigue life at stress amplitude S is represented by a lognormal random variable whose mean and standard deviation depend on S. This characterization is then used to compute the random fatigue life of a component submitted to a single kind of cycles. Precisely the mean and coefficient of variation of this quantity are studied, as well as the reliability associated with the (deterministic) design value. (author)

2003-08-17

226

Study on fatigue life evaluation of structural component based on crack growth criterion  

International Nuclear Information System (INIS)

As one of the practical application of fracture mechanics, fatigue life evaluation method based on crack growth criterion has been diffusing in various field of technology in order to determine the rational and reliable life of structural components. The fatigue life by this method is evaluated based on the fatigue crack growth analysis from defects, while many problems, such as the influence of residual stress on the crack growth behavior, the effect of overloading, and evaluation method for multiple surface cracks, are not sufficiently solved yet. In this paper, the above problems are treated, and based on some exprimental data some simple mehtods for fatigue life evaluation are proposed regarding the above problems. Verification of the proposed methods are shown in the paper by comparing with some experimental results, and the applicability of the proposed method is also examined by the fatigue test of pipes with cracks in the inner surface. (author)

1984-01-01

227

Test Population Selection from Weibull-Based, Monte Carlo Simulations of Fatigue Life  

Science.gov (United States)

Fatigue life is probabilistic and not deterministic. Experimentally establishing the fatigue life of materials, components, and systems is both time consuming and costly. As a result, conclusions regarding fatigue life are often inferred from a statistically insufficient number of physical tests. A proposed methodology for comparing life results as a function of variability due to Weibull parameters, variability between successive trials, and variability due to size of the experimental population is presented. Using Monte Carlo simulation of randomly selected lives from a large Weibull distribution, the variation in the L10 fatigue life of aluminum alloy AL6061 rotating rod fatigue tests was determined as a function of population size. These results were compared to the L10 fatigue lives of small (10 each) populations from AL2024, AL7075 and AL6061. For aluminum alloy AL6061, a simple algebraic relationship was established for the upper and lower L10 fatigue life limits as a function of the number of specimens failed. For most engineering applications where less than 30 percent variability can be tolerated in the maximum and minimum values, at least 30 to 35 test samples are necessary. The variability of test results based on small sample sizes can be greater than actual differences, if any, that exists between materials and can result in erroneous conclusions. The fatigue life of AL2024 is statistically longer than AL6061 and AL7075. However, there is no statistical difference between the fatigue lives of AL6061 and AL7075 even though AL7075 had a fatigue life 30 percent greater than AL6061.

Vlcek, Brian L.; Zaretsky, Erwin V.; Hendricks, Robert C.

2012-01-01

228

Fatigue Life Assessment for Metallic Structure: A Case Study of Shell Structure under Variable Amplitude Loading  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This study presents an analysis technique to asses the fatigue life of a shell structure under variable amplitude loadings (VAL). For this purpose, the finite element analysis technique was used for the simulation works. The life prediction results are useful for improving the component design methodology at the early developing stage especially for shell structures such as a pressure vessels or pipelines analysis. The fatigue life prediction was performed using the finite element based fatig...

2008-01-01

229

The Prediction of Fatigue Life Based on Four Point Bending Test:  

Digital Repository Infrastructure Vision for European Research (DRIVER)

To be able to devise optimum strategies for maintenance and rehabilitation, it is essential to formulate an accurate prediction of pavement life and its maintenance needs. One of the pavement life prediction methods is based on the pavement's capability to sustain fatigue. If it were possible to have a prediction that closely represent what is observed, we will come up with right decisions for pavement maintenance. The aim of this paper is to predict the fatigue life of gravel asphalt concret...

2013-01-01

230

Evaluation of Pressurization Fatigue Life of 1441 Al-li Fuselage Panel  

Science.gov (United States)

A study was conducted to evaluate the pressurization fatigue life of fuselage panels with skins fabricated from 1441 Al-Li, an attractive new Russian alloy. The study indicated that 1441 Al-Li has several advantages over conventional aluminum fuselage skin alloy with respect to fatigue behavior. Smooth 1441 Al-Li sheet specimens exhibited a fatigue endurance limit similar to that for 1163 Al (Russian version of 2024 Al) sheet. Notched 1441 Al-Li sheet specimens exhibited greater fatigue strength and longer fatigue life than 1163 Al. In addition, Tu-204 fuselage panels fabricated by Tupolev Design Bureau using Al-Li skin and ring frames with riveted 7000-series aluminum stiffeners had longer pressurization fatigue lives than did panels constructed from conventional aluminum alloys. Taking into account the lower density of this alloy, the results suggest that 1441 Al-Li has the potential to improve fuselage performance while decreasing structural weight.

Bird, R. Keith; Dicus, Dennis I.; Fridlyander, Joseph; Davydov, Valentin

1999-01-01

231

Development of a methodology for on line fatigue life monitoring of nuclear power plant components  

International Nuclear Information System (INIS)

A methodology has been developed for on line fatigue life monitoring of nuclear power plant components. Green's function technique is used to convert plant data to stress time data. Rainflow cycle counting method is used to compute the fatigue usage factor from stress time history by using material fatigue data. An interactive user friendly graphics code has been developed for updating the stored data and also for retrieving relevant informations by plant operators. (author)

1993-08-15

232

Effect of carbide distribution on rolling-element fatigue life of AMS 5749  

Science.gov (United States)

Endurance tests with ball bearings made of corrosion resistant bearing steel which resulted in fatigue lives much lower than were predicted are discussed. Metallurgical analysis revealed an undesirable carbide distribution in the races. It was shown in accelerated fatigue tests in the RC rig that large, banded carbides can reduce rolling element fatigue life by a factor of approximately four. The early spalling failures on the bearing raceways are attributed to the large carbide size and banded distribution.

Parker, R. J.; Bamberger, E. N.

1983-01-01

233

Fatigue Life of Titanium Alloys Fabricated by Additive Layer Manufacturing Techniques for Dental Implants  

Science.gov (United States)

Additive layer deposition techniques such as electron beam melting (EBM) and laser beam melting (LBM) have been utilized to fabricate rectangular plates of Ti-6Al-4V with extra low interstitial (ELI) contents. The layer-by-layer deposition techniques resulted in plates that have different surface finishes which can impact significantly on the fatigue life by providing potential sites for fatigue cracks to initiate. The fatigue life of Ti-6Al-4V ELI alloys fabricated by EBM and LBM deposition techniques was investigated by three-point testing of rectangular beams of as-fabricated and electro-discharge machined surfaces under stress-controlled conditions at 10 Hz until complete fracture. Fatigue life tests were also performed on rolled plates of Ti-6Al-4V ELI, regular Ti-6Al-4V, and CP Ti as controls. Fatigue surfaces were characterized by scanning electron microscopy to identify the crack initiation site in the various types of specimen surfaces. The fatigue life data were analyzed statistically using both analysis of variance techniques and the Kaplan-Meier survival analysis method with the Gehan-Breslow test. The results indicate that the LBM Ti-6Al-4V ELI material exhibits a longer fatigue life than the EBM counterpart and CP Ti, but a shorter fatigue life compared to rolled Ti-6Al-4V ELI. The difference in the fatigue life behavior may be largely attributed to the presence of rough surface features that act as fatigue crack initiation sites in the EBM material.

Chan, Kwai S.; Koike, Marie; Mason, Robert L.; Okabe, Toru

2013-02-01

234

Effect of hardening induced by cold expansion on damage fatigue accumulation and life assessment of Aluminum alloy 6082 T6  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Hole cold expansion (HCE) is an effective method to extend the fatigue life of mechanical structures. During cold expansion process compressive residual stresses around the expanded hole are generated. The enhancement of fatigue life and the crack initiation and growth behavior of a holed specimen were investigated by using the 6082 Aluminum alloy. The present study suggests a simple technical method for enhancement of fatigue life by a cold expansion hole of pre-cracked specimen. Fatigue dam...

2012-01-01

235

Surface characterization and influence of anodizing process on fatigue life of Al 7050 alloy  

International Nuclear Information System (INIS)

Highlights: ? We studied the effect of surface treatments on fatigue behaviour of 7050 alloy. ? Dissolution of constituent particles in pickling solution result in pits formation. ? Decrease is fatigue life caused by anodization is small. ? Multi-site cracks initiation has been observed for pickled and anodized specimens. -- Abstract: The present study investigates the influence of anodizing process on fatigue life of aluminium alloy 7050-T7451 by performing axial fatigue tests at stress ratio 'R' of 0.1. Effects of pre-treatments like degreasing and pickling employed prior to anodizing on fatigue life were studied. The post-exposure surface observations were made by scanning electron microscope (SEM) to characterize the effect of each treatment before fatigue testing. The surface observations have revealed that degreasing did not change the surface topography while pickling solution resulted in the formation of pits at the surface. Energy dispersive spectroscopy (EDS) was used to identify those constituent particles which were responsible for the pits formation. These pits are of primary concern with respect to accelerated fatigue crack initiation and subsequent anodic coating formation. The fatigue test results have shown that pickling process was detrimental in reducing the fatigue life significantly while less decrease has been observed for anodized specimens. Analyses of fracture surfaces of pickled specimens have revealed that the process completely changed the crack initiation mechanisms as compared to non-treated specimens and the crack initiation started at the pits. For most of the anodized specimens, fatigue cracks still initiated at the pits with very few cracks initiated from anodic coating. The decrease in fatigue life for pickled and anodized specimens as compared to bare condition has been attributed to decrease in initiation period and multi-site crack initiations. Multi-site crack initiation has resulted in rougher fractured surfaces for the pickled and anodized specimens as compare to bare specimens tested at same stress levels.

2011-06-01

236

Evaluation of Fatigue Life of CRM-Reinforced SMA and Its Relationship to Dynamic Stiffness  

Science.gov (United States)

Fatigue cracking is an essential problem of asphalt concrete that contributes to pavement damage. Although stone matrix asphalt (SMA) has significantly provided resistance to rutting failure, its resistance to fatigue failure is yet to be fully addressed. The aim of this study is to evaluate the effect of crumb rubber modifier (CRM) on stiffness and fatigue properties of SMA mixtures at optimum binder content, using four different modification levels, namely, 6%, 8%, 10%, and 12% CRM by weight of the bitumen. The testing undertaken on the asphalt mix comprises the dynamic stiffness (indirect tensile test), dynamic creep (repeated load creep), and fatigue test (indirect tensile fatigue test) at temperature of 25°C. The indirect tensile fatigue test was conducted at three different stress levels (200, 300, and 400?kPa). Experimental results indicate that CRM-reinforced SMA mixtures exhibit significantly higher fatigue life compared to the mixtures without CRM. Further, higher correlation coefficient was obtained between the fatigue life and resilient modulus as compared to permanent strain; thus resilient modulus might be a more reliable indicator in evaluating the fatigue life of asphalt mixture.

Mashaan, Nuha Salim; Karim, Mohamed Rehan; Abdel Aziz, Mahrez; Ibrahim, Mohd Rasdan; Katman, Herda Yati

2014-01-01

237

Statistical analysis of fatigue strain-life data for carbon and low-alloy steels  

International Nuclear Information System (INIS)

The existing fatigue strain vs life (S-N) data, foreign and domestic, for carbon and low-alloy steels used in the construction of nuclear power plant components have been compiled and categorized according to material, loading, and environmental conditions. A statistical model has been developed for estimating the effects of the various test conditions on fatigue life. The results of a rigorous statistical analysis have been used to estimate the probability of initiating a fatigue crack. Data in the literature were reviewed to evaluate the effects of size, geometry, and surface finish of a component on its fatigue life. The fatigue S-N curves for components have been determined by applying design margins for size, geometry, and surface finish to crack initiation curves estimated from the model

1995-07-23

238

Finite Element Based Fatigue Life Prediction of Cylinder Head for Two-Stroke Linear Engine Using Stress-Life Approach  

Directory of Open Access Journals (Sweden)

Full Text Available This study describes the finite element based fatigue life prediction of cylinder head for a two-stroke free piston linear engine subjected to variable amplitude loading, applicable to electric power generation. A set of aluminum alloys, cast iron and forged steel for cylinder head are considered in this study. The finite element modeling and analysis were performed utilizing the finite element analysis codes. The fatigue life analysis was carried out using finite element based fatigue analysis commercial codes. Fatigue stress-life approach was used when the piston is subjected to variable amplitude at different loading conditions. The effects of mean stress and sensitivity analysis on fatigue life are discussed. From the results, it was shown that the Goodman mean stress correction method is predicted more conservative (minimum life results. It was found to differ significantly the compressive and tensile mean stresses. The compressive mean stress are beneficial however tensile mean stress detrimental to the fatigue life. The effect of materials and components S-N was also investigated and not found to give any large advantages, however the effect of certainty of survival was found to give noticeable advantages and it concluded that the 99.9% are fond to be design criteria. The proposed technique is capable of determining premature products failure phenomena.

M.M. Rahman

2008-01-01

239

Fatigue-life assessment methods and application to the model WTS-4 wind turbine. Final report  

Energy Technology Data Exchange (ETDEWEB)

An inexpensive method for estimating the fatigue life of wind turbine components from field measurements taken electronically over nine months of operation in 1984-1985 proved technically feasible. Further, in pinpointing the sources of fatigue damage, analysis of the data helped clarify the role of wind-induced structural loads in turbine lifetimes.

Murtha-Smith, S.

1985-10-01

240

Acoustic fatigue life prediction for nonlinear structures with multiple resonant modes  

Science.gov (United States)

This report documents an effort to develop practical and accurate methods for estimating the fatigue lives of complex aerospace structures subjected to intense random excitations. The emphasis of the current program is to construct analytical schemes for performing fatigue life estimates for structures that exhibit nonlinear vibration behavior and that have numerous resonant modes contributing to the response.

Miles, R. N.

1992-01-01

 
 
 
 
241

Methodology for on line fatigue life monitoring : rainflow cycle counting method.  

Science.gov (United States)

Green's function technique is used in on line fatigue life monitoring to convert plant data to stress versus time data. This technique converts plant data most efficiently to stress versus time data. To compute the fatigue usage factor the actual number o...

N. K. Mukhopadhyay B. K. Dutta H. S. Kushwaha

1992-01-01

242

Effects of LWR environments on fatigue life of carbon and low-alloy steels  

International Nuclear Information System (INIS)

SME Boiler and Pressure Vessel Code provides construction of nuclear power plant components. Figure I-90 Appendix I to Section III of the Code specifies fatigue design curves for structural materials. While effects of environments are not explicitly addressed by the design curves, test data suggest that the Code fatigue curves may not always be adequate in coolant environments. This paper reports the results of recent fatigue tests that examine the effects of steel type, strain rate, dissolved oxygen level, strain range, loading waveform, and surface morphology on the fatigue life of A 106-Gr B carbon steel and A533-Gr B low-alloy steel in water

1995-07-23

243

Predicted Effect of Dynamic Load on Pitting Fatigue Life for Low-Contact-Ratio Spur Gears.  

Science.gov (United States)

How dynamic load affects the surface pitting fatigue life of external spur gears was predicted by using NASA computer program TELSGE. Parametric studies were performed over a range of various gear parameters modeling low-contact-ratio involute spur gears....

D. G. Lewicki

1986-01-01

244

Residual Stress Effects at a Notch Root in A723 Steel to Extend Fatigue Life.  

Science.gov (United States)

Fatigue life tests were performed with notched bend specimens of ASTM A723 steel with three types of residual stress treatments and resulting residual stress: shot peening, bole swaging, and tensile overload. The three treatments produced widely different...

J. H. Underwood

1995-01-01

245

Fatigue, Physical Function and Quality of Life in Relation to Disease Activity in Established Rheumatoid Arthritis  

Directory of Open Access Journals (Sweden)

Full Text Available Objectives: This study was intended to find out therelationship of fatigue, functional disability and Health-Related Quality Of Life (HRQOL with disease activityin adult patients with active rheumatoid arthritis (RAand to observe the effect of rehabilitation programme onthese parameters.Material and Methods: 106 patients participated and 96completed the study. Disease Activity Score-28 (DAS-28, visual analogue scale for pain and fatigue,Multidimensional Assessment of Fatigue Scale (MAF,Health Assessment Questionnaire (HAQ, AmericanCollege of Rheumatology revised criteria for functionalstatus classification, World Health Organization QualityOf Life instrument (WHOQOL-BREF wereadministered. A comprehensive rehabilitation programmecomprising pharmacologic and non-pharmacologic therapywas continued for 6 months.Results: Mean VAS fatigue, DAS28 & HAQ scores were45.68, 5.14 and 1.16 respectively. Significant correlation(Pearson’s r =0.82, p<0.05; r=0.75, p<0.05; r=0.85,p=<0.05 between the disease activity and the value ofthe VAS Fatigue, Global Fatigue (MAF and HAQ scorerespectively and inverse co-relation between quality oflife (QOL domain scores and disease activity wereobserved. Similar results were also found in the final visit.Comprehensive rehabilitation reduced the disease activity,fatigue, functional disability and improved QOL.Conclusion: High fatigue level, disability, pain anddecreased QOL characterized RA disease activity.Reduction of DAS, Fatigue, HAQ scores with treatmentimproved QOL.

Barman A

2010-04-01

246

Impact of Radiotherapy Treatment on Jordanian Cancer Patients’ Quality of Life and Fatigue  

Directory of Open Access Journals (Sweden)

Full Text Available Background: The distressing treatment of cancer whether chemotherapy or radiotherapy is associated with fatigue and has negative impact on patient quality of life (QOL. Objectives: The purposes of this study were to examine the impact of radiotherapy treatment on Jordanian cancer patients’ QOL and fatigue, and to explore the relationship between fatigue and QOL. Methods: One group quasi-experimental correlational design was used with 82 patients who had been diagnosed with cancer and required radiotherapy treatment. QOL was measured using the Functional Assessment of Cancer Therapy-General (FACT-G. Fatigue was measured using Piper Fatigue Scale (PFS. Data were collected over a period of three months, and analyzed using Pearson Product Moment Correlation, descriptive statistics and paired-sample t-test. Results: Significant differences were found between pre- and post- radiotherapy QOL mean total scores (t=19.3, df=79, P<0.05, as well as physical, emotional, sexual, and functional wellbeing dimensions. Statistically significant differences were found between pre- and post- radiotherapy fatigue mean total scores (t=-8.95, df=79, P<0.05, as well as on behavioral, affective, sensory, and cognitive dimensions of PFS. Quality of life total scores correlated significantly and negatively with total fatigue scores (P<0.01. Conclusions: Exposure of cancer patient to radiotherapy treatment increased their fatigue level and decreased their QOL.  Nurses should assess cancer patients before, during, and after their treatment to design proper interventions to reduce fatigue and enhance QOL.

Kholoud Abu Obead

2013-11-01

247

Experimental Study of Crack Growth Behavior and Fatigue Life of Spot Weld Tensile-Shear Specimens  

Directory of Open Access Journals (Sweden)

Full Text Available In this study, the experimental behaviors of the fatigue crack growth are studied and the fatigue lives of tensile-shear (TS specimens are determined. To achieve this, many TS specimens are prepared by the welding mild steel sheets of 1 and 1.5 mm thickness and then tested under constant amplitude loading using a servo-hydraulic fatigue testing machine (INSTRON 8802. The fatigue crack growth and the crack length are measured simultaneously by an optical microscope with 100X magnification. The experimental results indicate that the fatigue life of specimens decreases with any increase in load level. Also the crack initiation and propagation firstly occurs in plate with less thickness. According to the experimental observations when a high level loading is applied to the spot weld joints, the nugget suddenly pull-out and cannot withstand the fatigue loading.

M. Shariati

2009-01-01

248

Fatigue Life and Short Crack Behavior in Ti-6Al-4V Alloy; Interactions of Foreign Object Damage, Stress, and Temperature  

Science.gov (United States)

High-cycle fatigue (HCF) failures associated with foreign object damage (FOD) in turbine engines of military aircrafts have been of major concern for the aeronautic industry in recent years. The present work is focused on characterizing the effects of FOD on crack initiation and small crack growth of a Ti-6Al-4V alloy at ambient and also elevated temperatures. Results show that the preferred crack initiation site depends on applied stress and temperature as maximum fractions of cracks emanating from the simulated damage site, and naturally initiated cracks are observed at 25 °C under the maximum stress of 700 MPa and at 300 °C under the maximum stress of 300 MPa. The fatigue crack growth rate is influenced by increasing temperature, and the FCG rate at 300 °C is higher than that at room temperature under the same ? K, whereas this effect for FOD-site initiated cracks is not so remarkable. This observation seems to be due to the effect of stress relaxation at 300 °C. Results also indicate that fatigue crack initiation life ( N i ) and fatigue life ( N f ) are expressed by three-parameter Weibull distribution function.

Majidi, Behzad

2008-04-01

249

Tensile, Fracture, Fatigue Life, and Fatigue Crack Growth Rate Behavior of Structural Materials for the ITER Magnets: The European Contribution  

International Nuclear Information System (INIS)

Fatigue crack growth rates (FCGR) are determined for R ratios between 0.1 - 0.7 at 7 K for three full-size Mock-up Models of the ITER Toroidal Field coil case produced by modified Type 316LN alloys. A representative forged block of Model 3 is additionally manufactured to determine its improved spatial tensile properties and compare it to former Model 3 data. From the new candidate jacket materials, developed for the ITER Central Solenoid coil, a batch is investigated to assess the fatigue life behavior at 7 K. Furthermore, the 4 K test facility, a 630 kN load capacity hydraulic machine has been used to allow fatigue life investigations under four point bending of the full-size jackets with artificial surface flaws. Cyclic life results have been assessed for the heat affected zone, weld, and base metal. The results are used in the fatigue analysis of the coil. Residual stresses resulting from jacket welding have been determined using two different techniques. First by distortion measurements of sliced pieces of the weld section and secondly by neutron diffraction measurements. In addition, tensile and fracture tests have been performed at 7 K with Al 7075, a candidate alloy for the pre-compression system of the CS coil

2004-06-28

250

Rolling-Element Fatigue Life of Silicon Nitride Balls.  

Science.gov (United States)

The five-ball fatigue tester was used to evaluate silicon nitride as a rolling-element bearing material. Results indicate that hot-pressed silicon nitride running against steel may be expected to yield fatigue lives comparable to or greater than those of ...

R. J. Parker E. V. Zaretsky

1974-01-01

251

The effects of sheet spacing on the fatigue life of spot­welded joints  

Digital Repository Infrastructure Vision for European Research (DRIVER)

While investigating the fatigue strength of spot-welded joints, the effects of sheet spacing or gap amounts between sheet joints may be considered as one of the most important parameters on the fatigue life duration of the joints. The main goal of the present work is to study the influence of sheet spacing on the fatigue life of 5083-O aluminium alloy spot welded tensile-shear joints. The amounts of sheet spacing are the average values over three measurements of photograph observation o...

Hassanifard S.; Zehsaz M.; Esmaeili F.

2010-01-01

252

Study on high-cycle fatigue evaluation for thermal striping in mixing tees with hot and cold water. 2. Type B; characteristics of temperature fluctuations and heat transfer in mixing tees with same pipe diameters  

International Nuclear Information System (INIS)

Thermal striping tests were conducted in mixing tees with the same pipe diameters in order to construct databases for an evaluation method for high-cycle thermal fatigue of piping systems. Hot and cold water with a temperature difference of 40 K were supplied to the mixing tee. Temperature fluctuations of the fluid and pipe wall were measured as the velocity ratio of the flow in the branch pipe to that in the main pipe was varied from 0.1 to 5. The power spectrum method was used to evaluate the heat transfer coefficient. The fluid temperature fluctuation characteristics were dependent on the velocity ratio, rather than on the absolute value of the flow velocity. Large fluid temperature fluctuations of more than 90% of the incoming flow temperature difference occurred near the mixing tee, and the fluctuation frequency was random. The ratios of the measured heat transfer coefficient to that evaluated by Dittus-Boelter's empirical equation were independent of the velocity ratio and Reynolds number. The ratios were within about two. (author)

2003-04-20

253

Low cycle fatigue life of two nickel-base casting alloys in a hydrogen environment  

International Nuclear Information System (INIS)

Results of low cycle fatigue tests on alloy Mar-M-246 and Inconel 713 are presented. Based on the limited data, it was concluded that the Mar-M-246 material had a cyclic life in hydrogen that averaged three times higher than the alloy 713LC material for similar strain ranges. The hydrogen environment reduced life for both materials. The life reduction was more than an order of magnitude for the 713LC material. Porosity content of the cast specimens was as expected and was an important factor governing low cycle fatigue life

1975-09-07

254

Fatigue Life of High Performance Grout in Dry and Wet Environment for Wind Turbine Grouted Connections  

DEFF Research Database (Denmark)

The cementitious material in grouted connections of offshore monopile wind turbine structures is subjected to very high oscillating service stresses. The fatigue capacity of the grout therefore becomes essential to the performance and service life of the grouted connection. In the present work the fatigue life of a high performance cement based grout was tested by dynamic compressive loading of cylindrical specimens at varying levels of cyclic frequency and load. The fatigue tests were performed in two series, one with the specimens tested in air and one with the specimens submerged in water during the test. The fatigue life of the grout, in terms of the number of cycles to failure, was found to be significantly shorter when tested in water than when tested in air, particularly at low frequency.

Sørensen, Eigil V.

2011-01-01

255

Low-Cycle Fatigue Life Prediction in GTD-111 Superalloy at Elevated Temperatures  

International Nuclear Information System (INIS)

The Ni-base super-heat-resistant alloy, GTD-111, is employed in gas turbines because of its high temperature strength and oxidation resistance. It is important to predict the fatigue life of this superalloy in order to improve the efficiency of gas turbines. In this study, low-cycle fatigue tests are performed as variables of total strain range and temperature. The relationship between the strain energy density and number of cycles to failure is examined in order to predict the low-cycle fatigue life of the GTD-111 superalloy. The fatigue life predicted by using the strain-energy methods is found to coincide with that obtained from the experimental data and from the Coffin-Manson method

2011-07-01

256

Study on durability of welded bellows. Fatigue life of bellows with crack in welded bead  

International Nuclear Information System (INIS)

Reports of study for welded bellows with cracks have apparently not been published to date. The purpose of this investigation is to understand the relationship between the state of stress of welded bellows with micro cracks and the fatigue life. Stresses of welded bellows with cracks were calculated for several different crack lengths by finite element method (FEM), and lives of bellows with cracks were examined by fatigue test. The fatigue life, i.e. the number of cycles to failure was arranged against the remaining wall thickness measured after test instead of the crack length. As a result, it was found that there is a regular relationship between the stress amplitude of peak stress calculated by FEM and the fatigue life of bellows. And then, it was shown that the life of bellows becomes longer than the life estimated using a theoretical S-N curve calculated by Manson's method. Stress intensity factor range (?K) and crack propagation rate (da/dN) were also calculated using the results of stress analysis by FEM and fatigue test. The relationship between ?K and da/dN obtained was almost coincident with the earlier result of fatigue crack growth test of Inconel 718 in the region of da/dN > 1.5x10-6 mm/cycle, and the propriety of the present results was confirmed. (author)

1994-11-01

257

A methodology for on line fatigue life monitoring : rainflow cycle counting method  

International Nuclear Information System (INIS)

Green's function technique is used in on line fatigue life monitoring to convert plant data to stress versus time data. This technique converts plant data most efficiently to stress versus time data. To compute the fatigue usage factor the actual number of cycles experienced by the component is to be found out from stress versus time data. Using material fatigue properties the fatigue usage factor is to be computed from the number of cycles. Generally the stress response is very irregular in nature. To convert an irregular stress history to stress frequency spectra rainflow cycle counting method is used. This method is proved to be superior to other counting methods and yields best fatigue estimates. A code has been developed which computes the number of cycles experienced by the component from stress time history using rainflow cycle counting method. This postprocessor also computes the accumulated fatigue usage factor from material fatigue properties. The present report describes the development of a code to compute fatigue usage factor using rainflow cycle counting technique and presents a real life case study. (author). 10 refs., 10 figs

1992-01-01

258

Consideration on corrosion fatigue crack life assessment; Fushoku hiro kiretsu hassei jumyo hyoka ni kansuru ichikosatsu  

Energy Technology Data Exchange (ETDEWEB)

Discussions were given on corrosion fatigue crack life by using corrosion fatigue crack initiation test and analysis. The test used 13Cr-based stainless steel as a test material, and aquamarine at 60{degree}C as a corrosion environment. The fatigue test was performed under a tension loading condition with a stress ratio of 0.1 and an iterative velocity of 1.7 Hz by using a 10-tonf fatigue testing machine. In the corrosion fatigue crack initiation test, a pit has been generated on a boundary of an exposed part and a painted part for masking, hence direct observation was impossible on pit growth behavior. Therefore, an intrinsic crack model was introduced from pit dimensions as observed from a fracture face, and analysis was made on corrosion fatigue crack growth by using the linear fracture dynamics, wherein clarification was made on a phenomenon occurring after the crack growth passes the pit growth until the test piece is fractured. A proposal was made to define the time when fatigue crack initiates and grows from the bottom of a pit as a result of surpassing the growth of corrosion pit as the corrosion fatigue crack life. 4 refs., 7 figs., 1 tab.

Yajima, H.; Yamamoto, M.; Saito, T. [Hiroshima University, Hiroshima (Japan). Faculty of Engineering; Morita, K. [Mitsubishi Heavy Industries, Ltd., Tokyo (Japan)

1996-10-01

259

Remaining fatigue life estimates for riveted railway bridges  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A large number of metallic railway bridges currently in use in the UK are of riveted construction and are close to 100 years old. A fatigue assessment methodology is needed for such bridges since these may be close to the end of their fatigue lives. Part of such a methodology is the global analysis of the bridge in order to identify the most fatigue critical details. The aim of this paper is to present results, in terms of Miner’s damage at the riveted connections of a typical riveted UK ra...

Imam, B.; Righiniotis, Td; Chryssanthopoulos, Mk

2005-01-01

260

Fatigue  

Science.gov (United States)

... disorders (such as McArdle’s and Tarui’s diseases) and mitochondrial diseases. But fatigue also can creep into the ... may become a factor. To make matters more complex, fatigue may set in if you simply don’ ...

 
 
 
 
261

Shear fatigue test and life prediction of composite laminates  

Energy Technology Data Exchange (ETDEWEB)

A cumulative damage model, which is able to consider the influence of in plane bi-axial stresses and mean stresses on the fatigue behavior of unidirectional laminates, was used to evaluate the fatigue lives of multidirectional laminates under cyclic shear loadings, with the least requirement for the S-N curves of unidirectional laminates corresponding to the three in-plane on-axis stress components separately. An Iosipescu-type of fixture, which had been previously used for the static shear strength tests of unidirectional laminates or metal materials, was proved useful for the shear fatigue tests of multidirectional laminates. Together with finite element stress analysis, cumulative damage modes and their distribution regions on T300/QY8911 shear fatigue specimens were reasonably simulated and the predicted lives agree well with the test results. (orig.)

Yazhi Li; Kaida Zhang; Boping Zhang [Northwestern Polytechnical Univ., Xi' an (China)

2003-07-01

262

Influence of surface finish on the high cycle fatigue behavior of a 304L austenitic stainless steel; Influence de l'etat de surface sur le comportement en fatigue a grand nombre de cycles de l'acier inoxydable austenitique 304L  

Energy Technology Data Exchange (ETDEWEB)

This work has dealt with the influence of surface finish on the high cycle fatigue behavior of a 304L. The role played by roughness, surface hardening and residual stresses has been particularly described. First part of this study has consisted of the production of several surface finishes. These latter were obtained by turning, grinding, mechanical polishing and sandblasting. The obtained surfaces were then characterised in terms of roughness, hardening, microstructure and residual stresses. Fatigue tests were finally conducted under various stress ratios or mean stresses at two temperatures (25 C and 300 C). Results clearly evidenced an effect of the surface integrity on the fatigue resistance of the 304L. This influence is nevertheless more pronounced at ambient temperature and for a positive mean stress. For all explored testing conditions, the lowest endurance limit was obtained for ground specimens whereas polished samples exhibited the best fatigue strength. Results also cleared out a detrimental influence of a positive mean stress in the case of specimens having surface defaults of a great acuity. The study of the relative effect of each of the surface parameter, under a positive stress ratio and at the ambient temperature, showed that roughness profile and surface hardening are the two more influential factors. The role of the residual stresses remains negligible due to their rapid relaxation during the application of the first cycles of fatigue. The estimation of the initiation and propagation periods showed that mechanisms differed as a function of the applied stress ratio. Crack propagation is governed by the parameter DK at a positive stress ratio and by Dep/2 in the case of tension-compression tests. (author)

Petitjean, S

2003-06-15

263

Design characteristics that improve the fatigue life of threaded pipe connections  

Directory of Open Access Journals (Sweden)

Full Text Available Threaded pipe connections are commonly used to connect risers, tendons, drill pipes and well casing strings. In these applications fatigue resistance plays an important role. A large variety of patented design features exist, all claiming to improve the connection’s fatigue life. However, patent documents only contain claims and numerical or experimental data about these connection’s performance is generally not published. This makes it hard to make a quantitative comparison between different designs. In this study anoverview is given of fatigue resistant threaded connections. Two major methods to improve the fatigue life of a connection were identified. First of all, local stress concentrations can be reduced by optimizing the geometry of the threads. Second the global shape of the connection can be optimized to obtain a more uniform load distribution.Using a parametric finite element model, different designs were compared. The connections were modelled by a 2D axisymmetric geometry with non-linear material properties and elaborate contact conditions.Selected designs have been subjected to experimental tests in a four-point bending fatigue setup. The experimental tests serve as a validation for the results of the numerical simulations. It was found that the multiaxial stress distribution at the thread roots is the defining factor for the fatigue life of the connection. Nevertheless, these stresses can be changed by the global geometry of the connection. It can be concluded that the fatigue life of threaded connections is determined by a combination of global and local aspects which should both be analysed for fatigue life calculations.

De Baets, Patrick

2011-10-01

264

Numerical fatigue life assessment of cardiovascular stents: A two-scale plasticity-damage model  

International Nuclear Information System (INIS)

Cardiovascular disease has become a major global health care problem in the last decades. To tackle this problem, the use of cardiovascular stents has been considered a promising and effective approach. Numerical simulations to evaluate the in vivo behavior of stents are becoming more and more important to assess potential failures. As the material failure of a stent device has been often associated with fatigue issues, numerical approaches for fatigue life assessment of stents have gained special interest in the engineering community. Numerical fatigue life predictions can be used to modify the design and prevent failure without making and testing numerous physical devices, thus preventing from undesired fatigue failures. We present a numerical fatigue life model for the analysis of cardiovascular balloon-expandable stainless steel stents that can hopefully provide useful information either to be used for product improvement or for clinicians to make life-saving decisions. This model incorporates a two-scale continuum damage mechanics model and the so-called Soderberg fatigue failure criterion. We provide numerical results for both Palmaz-Schatz and Cypher stent designs and demonstrate that a good agreement is found between the numerical and the available experimental results

2013-07-17

265

A numerical investigation of creep-fatigue life prediction utilizing hysteresis energy as a damage parameter  

International Nuclear Information System (INIS)

This paper explores the hypothesis that there exists an intrinsic material property, hysteresis damage energy at failure, which could be used as a creep-fatigue life prediction parameter. The connection between hysteresis energy and fatigue damage was introduced in the 1920's by Inglis, but the use of hysteresis energy as a measure of damage was first presented by Morrow and Halford. Hysteresis energy shows promise in bridging the gaps associated with life prediction when the combination of both creep and fatigue scenarios are present. Numerical simulations which replicate experimental test configurations with 9Cr-1Mo steel were performed from which the hysteresis energy failure density (HEFD) could be calculated for each experiment. Taking the average of the HEFD values calculated for all of the experimental data as the parameter for failure (EIntrinsic), creep-fatigue life predictions were made using a simplistic hysteresis energy based method as well as the time fraction/cycle fraction method endorsed by ASME Code and compared to experimental results. A good correlation with experimental results was obtained for life predictions using hysteresis energy density as a damage parameter. An investigation of the interaction between creep damage and fatigue damage based on the hysteresis energy method was also performed and compared with the damage interaction diagram utilized by the ASME and RCC-MR design codes. The hysteresis energy based method proved easy to implement and gave improved accuracy over the time fraction/cycle fraction method for low cycle creep-fatigue loading.

2011-04-01

266

Numerical fatigue life assessment of cardiovascular stents: A two-scale plasticity-damage model  

Science.gov (United States)

Cardiovascular disease has become a major global health care problem in the last decades. To tackle this problem, the use of cardiovascular stents has been considered a promising and effective approach. Numerical simulations to evaluate the in vivo behavior of stents are becoming more and more important to assess potential failures. As the material failure of a stent device has been often associated with fatigue issues, numerical approaches for fatigue life assessment of stents have gained special interest in the engineering community. Numerical fatigue life predictions can be used to modify the design and prevent failure without making and testing numerous physical devices, thus preventing from undesired fatigue failures. We present a numerical fatigue life model for the analysis of cardiovascular balloon-expandable stainless steel stents that can hopefully provide useful information either to be used for product improvement or for clinicians to make life-saving decisions. This model incorporates a two-scale continuum damage mechanics model and the so-called Soderberg fatigue failure criterion. We provide numerical results for both Palmaz-Schatz and Cypher stent designs and demonstrate that a good agreement is found between the numerical and the available experimental results.

Santos, H. A. F. A.; Auricchio, F.; Conti, M.

2013-07-01

267

Near-terminal creep damage does not substantially influence fatigue life under physiological loading.  

Science.gov (United States)

Cortical bone specimens were damaged using repeated blocks of tensile creep loading until a near-terminal amount of creep damage was generated (corresponding to a reduction in elastic modulus of 15%). One group of cortical bone specimens was submitted to the near-terminal damage protocol and subsequently underwent fatigue loading in tension with a maximum strain of 2000 ?? (Damage Fatigue, n=5). A second group was submitted to cyclic fatigue loading but was not pre-damaged (Control Fatigue, n=5). All but one specimen (a damaged specimen) reached run-out (10 million cycles, 7.7 days). No significant differences in microscopic cracks or other tissue damage were observed between the two groups or between either group and additional, completely unloaded specimens. Our results suggest that damage in cortical bone allograft that is not obvious or associated with a stress riser may not substantially affect its fatigue life under physiologic loading. PMID:21592481

Stern, Lorraine C; Brinkman, Jennifer G; Furmanski, Jevan; Rimnac, Clare M; Hernandez, Christopher J

2011-07-01

268

Quality of life in multiple sclerosis – association with clinical features, fatigue and depressive syndrome  

Directory of Open Access Journals (Sweden)

Full Text Available Introduction. The aim of the study was to assess the health related quality of life in patients suffering from multiple sclerosis (MS in association with clinical features, fatigue and depressive symptoms. Methods. The examined group consisted of 61 patients (45 women and 16 men in the mean age of 38.6±11.4. The mean duration of disease was 7.1±6.1 years. The control group consisted of 30 healthy volunteers. The following questionnaires were used: EuroQol (EQ5D with visual scale EuroQol-VAS, Modified Impact Fatigue Scale (MIFS and Beck Depression Inventory (BDI. Results. The quality of life in the examined group of MS patients was significantly lower in comparison to the control group. Results of EQ-5D and EQ-VAS were influenced by age, disease course, level of disability and carried treatment. Statistically significant association was also found between results of the questionnaires assessing quality of life and either fatigue or depressive symptoms. Conclusion. The used questionnaires confirmed that quality of life in patients with MS is significantly worse, especially in the older people with secondary progressive course of the disease, more disable and not treated. Presence of fatigue and depressive symptoms influenced the self-assessment of quality of life. Complex care of MS patient should consider diagnosis and treatment of fatigue and depression which could improve their quality of life.

?abuz-Roszak, Beata

2013-06-01

269

Evaluation of Fatigue Life of Semiconductor Power Device by Power Cycle Test and Thermal Cycle Test Using Finite Element Analysis  

Digital Repository Infrastructure Vision for European Research (DRIVER)

To accurately predict the fatigue life of a power device, a fatigue life evaluation method that is based on the power cycle is presented in terms of an algorithm based on a combination of electrical analysis, heat analysis, and stress analysis. In literature, the fatigue life of power devices has been evaluated on the basis of the thermal cycle. This cycle is alternately repeated within a range from a high temperature to a low temperature. In an actual operating environment, however, a power ...

Kazunori Shinohara; Qiang Yu

2010-01-01

270

An approach for determining an appropriate assumed distribution of fatigue life under limited data  

Energy Technology Data Exchange (ETDEWEB)

The case of limited data implies that some unknown uncertainties may be involved in fatigue reliability analysis. For the sake of statistical convenience, for consistency with the relevant physical arguments and, most importantly, to ensure the safety in design evaluation, an approach is developed to determine an appropriate distribution, from four possible assumed distributions--three-parameter Weibull, two-parameter Weibull, lognormal and extreme maximum-value distributions. The approach makes allowance for consistency with the fatigue physics and checking tail fit effects. An application to nine groups of fatigue life data of 16Mn steel (Chinese steel) welded plate specimens shows that the lognormal distribution and the extreme maximum-value distribution may be the appropriate distributions of the fatigue life under limited data.

Zhao, Y.-X.; Gao, Q.; Wang, J.-N

2000-01-01

271

Development of a low-cycle fatigue life curve for 80In15Pb5Ag  

Science.gov (United States)

The purpose of this study is to develop a methodology to predict the low-cycle (large strain—from 0.1 to 0.35 strain) fatigue life of solders subject to thermal cycling. Solders are commonly used in electronic assemblies. Using thermal fatigue data measured for 80In15Pb5Ag, a low-cycle fatigue curve for 80In15Pb5Ag solder subject to thermal cycling was developed. Specifically a Coffin-Manson relationship was derived for the solder, with a high degree of correlation (see Table I), for four different failure criteria, defined in the body of the paper. This relationship, together with calculated strains in the solder joint, allows the low-cycle fatigue life of the solder joint to be predicted.

Edwards, L. K.; Nixon, W. A.; Lakes, R. S.

2000-09-01

272

Fatigue Life Assessment for Metallic Structure: A Case Study of Shell Structure under Variable Amplitude Loading  

Directory of Open Access Journals (Sweden)

Full Text Available This study presents an analysis technique to asses the fatigue life of a shell structure under variable amplitude loadings (VAL. For this purpose, the finite element analysis technique was used for the simulation works. The life prediction results are useful for improving the component design methodology at the early developing stage especially for shell structures such as a pressure vessels or pipelines analysis. The fatigue life prediction was performed using the finite element based fatigue analysis codes. In addition the ability of stress-life (S-N and strain-life (?-N approaches to correlate and predict life are examined according to the different damage and failure rules. Numerical life prediction results (S-N and ?-N of shells under VAL, as well as Constant Amplitude Loading (CAL are presented and discussed. The effect of the mean stress, surface finish and the shell thickness are studied and discussed as apart of the interactions between geometries, loadings and materials. The simulation results showed that more studies on the shell structure need to be performed in order to obtain more accurate fatigue life.

S. Abdullah

2008-01-01

273

Effect Of Solidification Speed On Fatigue Properties  

Science.gov (United States)

Fast solidification increases fatigue life, but failure distribution becomes less predictable. Report describes effects of rate of solidification on nickel-based super-alloy MAR-M246(Hf) used in turbine blades. Based on experiments in which specimens directionally solidified at 5 cm/h and 30 cm/h, then tested for high cycle fatigue. Specimens also inspected by energy-dispersive x-ray (EDX) analysis and optical and electron microscopy.

Mccay, M. H.; Schmidt, D. D.; Hamilton, W. D.; Alter, W. S.; Parr, R. A.

1989-01-01

274

Self-reported fatigue and physical function in late mid-life  

DEFF Research Database (Denmark)

Objective: To determine the association between the 5 subscales of the Multidimensional Fatigue Inventory (MFI-20) and physical function in late mid-life. Design: Cross-sectional study. Subjects: A population-based sample of adults who participated in the Copenhagen Aging and Midlife Biobank population cohort (nâ??=â??4,964; age 49-63 years). Methods: Self-reported fatigue was measured using the MFI-20 comprising: general fatigue, physical fatigue, reduced activity, reduced motivation, and mental fatigue. Handgrip strength and chair rise tests were used as measures of physical function. Multiple logistic regression analyses were used to determine the associations between handgrip strength and the chair rise test with the MFI-20 subscales, adjusted for potential confounders. Results: After adjustments for potential confounders, handgrip strength was associated with physical fatigue (adjusted odds ratio (OR) 0.75 (95% confidence interval (CI) 0.66-0.86); pâ??â?¤â??0.001) and reduced motivation (adjusted OR 0.85 (95% CI 0.75-0.96); pâ??â?¤â??0.05), but not with the other subscales. After these adjustments, the chair rise test was associated with physical fatigue (adjusted OR 0.61 (0.53-0.69); pâ??â?¤â??0.001), general fatigue (adjusted OR 0.72 (0.62-0.84); pâ??â?¤â??0.001), reduced activity (adjusted OR 0.79 (0.70-0.90); pâ??â?¤â??0.001) and reduced motivation (adjusted OR 0.84 (0.74-0.95); pâ??â?¤â??0.01), but not with mental fatigue. Subgroup analyses for sex did not show statistically significant different associations between physical function and fatigue. Conclusion: The present study supports the physiological basis of 4 subscales of the MFI-20. The association between fatigue and function was independent of gender.

Mänty, Minna; Hansen, �se Marie

2014-01-01

275

The effects of fibre architecture on fatigue life-time of composite materials  

DEFF Research Database (Denmark)

Wind turbine rotor blades are among the largest composite structures manufactured of fibre reinforced polymer. During the service life of a wind turbine rotor blade, it is subjected to cyclic loading that potentially can lead to material failure, also known as fatigue. With reference to glass fibre reinforced composites used for the main laminate of a wind turbine rotor blade, the problem addressed in the present work is the effect of the fibre and fabric architecture on the fatigue life-time under tension-tension loading. Fatigue of composite materials has been a central research topic for the last decades; however, a clear answer to what causes the material to degrade, has not been given yet. Even for the simplest kind of fibre reinforced composites, the axially loaded unidirectional material, the fatigue failure modes are complex, and require advanced experimental techniques and characterisation methodologies in order to be assessed. Furthermore, numerical evaluation and predictions of the fatigue damage evolution are decisive in order to make future improvements. The present work is focused around two central themes: fibre architecture and fatigue failure. The fibre architecture is characterised using real material samples and numerical simulations. Experimental fatigue tests identify, quantify, and analyse the cause of failure. Different configurations of the fibre architecture are investigated in order to determine and understand the tension-tension fatigue failure mechanisms. A numerical study is used to examine the onset of fatigue failure. Topics treated include: experimental fatigue investigations, scanning electron microscopy, numerical simulations, advanced measurements techniques (micro computed tomography and thermovision), design of test specimens and preforms, and advanced materials characterisation. The results of the present work show that the fibre radii distribution has limited effect on the fibre architecture. This raises the question of which fibre radii distribution ensures optimum mechanical properties, damage tolerance, and fatigue performance. The experimental fatigue results and analyses identify and explain the onset of tension fatigue failure. It is documented that improvements of the fibre architecture and specimen design are needed in order to provide next generation of fatigue resistant composite materials for wind turbine rotor blades.

Hansen, Jens Zangenberg

2013-01-01

276

Fatigue life prediction of ZE41A magnesium alloy using Weibull distribution  

International Nuclear Information System (INIS)

In this investigation, the fatigue life prediction of ZE41A magnesium alloy has been statistically analyzed by Weibull distribution. The mechanical fatigue tests are conducted under R = 0.1 axial tension condition on specimen machined at as cast and welded materials. The micro structural investigations performed shows strong influence of precipitation on the fatigue failure of material. The curve for maximum stress and cycles to failure has been constructed for above stated materials. Using Weibull, the probability distribution according to which the material will fail is obtained. The fracture surface of the specimens is studied using scanning electron microscope

2008-01-01

277

Elliptical exercise improves fatigue ratings and quality of life in patients with multiple sclerosis  

Directory of Open Access Journals (Sweden)

Full Text Available Fatigue, reduced quality of life (QOL, and lower physical activity levels are commonly reported in patients with multiple sclerosis (MS. This study evaluated the effects of elliptical exercise on fatigue and QOL reports in patients with MS. Patients with MS (n = 26 completed the Fatigue Severity Scale (FSS, the Modified Fatigue Impact Scale (MFIS, and the Medical Outcomes Study 36-Item Short Form Health Survey (SF-36 before and after completing 15 elliptical exercise training sessions. Changes in fatigue and QOL were assessed based on any changes in the fatigue and SF-36 questionnaires, and correlations between changes in each of the scales were made to determine whether a relationship was present between the fatigue and QOL measures. Results showed significant improvement in FSS, MFIS, and five SF-36 subscales as a result of elliptical exercise. The change in FSS correlated with change in two of the SF-36 subscales. Elliptical exercise for patients with MS results in significant improvements in both fatigue and QOL. These findings indicate that regular elliptical exercise could be a part of inpatient and outpatient MS rehabilitation programs.

Jessie M. Huisinga, PhD

2011-08-01

278

Design characteristics that improve the fatigue life of threaded pipe connections  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Threaded pipe connections are commonly used to connect risers, tendons, drill pipes and well casing strings. In these applications fatigue resistance plays an important role. A large variety of patented design features exist, all claiming to improve the connection’s fatigue life. However, patent documents only contain claims and numerical or experimental data about these connection’s performance is generally not published. This makes it hard to make a quantitative comparison between diffe...

Wittenberghe, Jeroen; Baets, Patrick; Waele, Wim; Galle, Timothy; Bui, Tien Thanh; Roeck, Guido

2011-01-01

279

Assessment of existing steel structures. A guideline for estimation of the remaining fatigue life  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In many countries and regions, traffic infrastructure projects suffer from low funding. The budget is tight for new infrastructure building and, thus, the importance of inspection, maintenance and assessment of the existing traffic infrastructure increases. A new fatigue assessment guideline for the estimation of the remaining fatigue life of steel bridges has been written by technical committee 6 from ECCS. It will be a useful tool for the complementation of bridge management systems, used c...

Helmerich, Rosemarie; Ku?hn, Bertram; Nussbaumer, Alain

2007-01-01

280

Fatigue failure by in-line flow-induced vibration and fatigue life evaluation  

International Nuclear Information System (INIS)

The phenomenon of fatigue failure due to In-line flow-induced vibration has been investigated. In the experimental program an induced-vibration experimental set-up involving water flow was developed. This apparatus was used to produce fatigue failure resulting from In-line flow-induced vibration. The fatigue specimens were made of a medium carbon steel. A small hole was drilled into the specimen surface to localize the fatigue cracking process. A strain histogram recorder (Mini Rainflow Corder, MRC) was used to acquire the service strain histogram and also to detect any variations in natural frequency. The cumulative fatigue damage, D, as defined by the Modified Miner Rule, was determined by using the strain histogram of the early portion of the test record. The value of D was almost unity in the case of In-line vibration. In contrast, the value of D obtained in a previous investigation for the case of the Cross-flow vibration ranged approximately from 0.2 to 0.8. (author)

2005-04-01

 
 
 
 
281

Analysis of the Effects of Aggressive Shot Peening on Fatigue Life of 7075 ? T6 Aluminum Alloy  

Directory of Open Access Journals (Sweden)

Full Text Available For many years controlled shot peening was considered as a surface treatment. It is now clear that the performance of control shot peening in terms of fatigue depends on the balance between its beneficial (compressive residual stress and work hardening and beneficial effects (surface hardening.The overall aim of this paper is to study the effects of aggressive shot peening on fatigue life of 7075 ? T6 aluminum alloy. The fatigue life reduction factor (LRF due to the aggressive shot peening was established and empirical relations were proposed to describe the behavior of LRF, roughness and fatigue life. The benefits of shot peering in terms of fatigue life are dependent on the shot peening time (SPT. The higher SPT is the lower the benefit is. Higher roughness results in lower fatigue life.

Khairallah S. Jabur

2012-01-01

282

Effect of grinding conditions on the fatigue life of titanium 5Al-2.5Sn alloy  

Science.gov (United States)

An investigation into the effect of grinding conditions on the fatigue life of titanium 5Al-2.5Sn is presented. Damage to surface integrity and changes in the residual stresses distribution are studied to assess changes in fatigue life. A surface grinding machine, operating at speeds ranging from 2000 to 6000 fpm and using SiC wheels of grit sizes 60 and 120, was used to grind flat subsize specimens of 0.1-in. thickness. After grinding, the specimens were fatigued at a chosen stress and compared with the unadulterated material. A standard profilometer, a microhardness tester, and a scanning electron microscope were utilized to examine surface characteristics and measure roughness and hardness. Increased grinding speed in both wet and dry applications tended to decrease the fatigue life of the specimens. Fatigue life increased markedly at 2000 fpm under wet conditions, but then decreased at higher speeds. Grit size had no effect on the fatigue life.

Rangaswamy, P.; Terutung, H.; Jeelani, S.

1991-01-01

283

Fatigue life estimation for different notched specimens based on the volumetric approach  

Directory of Open Access Journals (Sweden)

Full Text Available In this paper, the effects of notch radius for different notched specimens has been studied on the values of stress concentration factor, notch strength reduction factor, and fatigue life duration of the specimens. The material which has been selected for this investigation is Al 2024T3 . Volumetric approach has been applied to obtain the values of notch strength reduction factor and results have been compared with those obtained from the Neuber and Peterson methods. Load controlled fatigue tests of mentioned specimens have been conducted on the 250kN servo-hydraulic Zwick/Amsler fatigue testing machine with the frequency of 10Hz. The fatigue lives of the specimens have also been predicted based on the available smooth S-N curve of Al2024-T3 and also the amounts of notch strength reduction factor which have been obtained from volumetric, Neuber and Peterson methods. The values of stress and strain around the notch roots are required to predict the fatigue life of notched specimens, so Ansys finite element code has been used and non-linear analyses have been performed to obtain the stress and strain distributions around the notches. The plastic deformations of the material have been simulated using multi-linear kinematic hardening and cyclic stress-strain relation. The work here shows that the volumetric approach does a very good job for predicting the fatigue life of the notched specimens.

Esmaeili F.

2010-06-01

284

Fatigue life estimation for different notched specimens based on the volumetric approach  

Science.gov (United States)

In this paper, the effects of notch radius for different notched specimens has been studied on the values of stress concentration factor, notch strength reduction factor, and fatigue life duration of the specimens. The material which has been selected for this investigation is Al 2024T3 . Volumetric approach has been applied to obtain the values of notch strength reduction factor and results have been compared with those obtained from the Neuber and Peterson methods. Load controlled fatigue tests of mentioned specimens have been conducted on the 250kN servo-hydraulic Zwick/Amsler fatigue testing machine with the frequency of 10Hz. The fatigue lives of the specimens have also been predicted based on the available smooth S-N curve of Al2024-T3 and also the amounts of notch strength reduction factor which have been obtained from volumetric, Neuber and Peterson methods. The values of stress and strain around the notch roots are required to predict the fatigue life of notched specimens, so Ansys finite element code has been used and non-linear analyses have been performed to obtain the stress and strain distributions around the notches. The plastic deformations of the material have been simulated using multi-linear kinematic hardening and cyclic stress-strain relation. The work here shows that the volumetric approach does a very good job for predicting the fatigue life of the notched specimens.

Zehsaz, M.; Hassanifard, S.; Esmaeili, F.

2010-06-01

285

Fatigue-life enhancement of nitrogen-implanted chromium steel  

International Nuclear Information System (INIS)

The effect of nitrogen implantation on the fatigue properties of chromium steel is investigated. A 30% enhancement of the endurance limit is achieved. The effect of sample heating during the implantation process and post-irradiation annealing on the fatigue properties are determined. Changes in nitrogen concentration profiles due to thermal diffusion are observed by means of the NRA method TEM analysis shows the presence of Fe_1_6N_2 precipitates in the implanted layer. The dimensions of these precipitates are temperature dependent. (author)

1986-06-16

286

Application of the strain energy for fatigue life prediction (LCF) of metals by the energy-based criterion  

International Nuclear Information System (INIS)

Full text: In this study, the plastic strain energy under multiaxial fatigue condition has been calculated in the cyclic plasticity models by the stress-strain hysteresis loops. Then, using the results of these models, the fatigue lives in energy-based fatigue model is predicted and compared to experimental data. Moreover, a weighting factor on shear plastic work is presented to decrease the life factors in the model fatigue. (author)

2009-11-03

287

Deformation history and load sequence effects on cumulative fatigue damage and life predictions  

Science.gov (United States)

Fatigue loading seldom involves constant amplitude loading. This is especially true in the cooling systems of nuclear power plants, typically made of stainless steel, where thermal fluctuations and water turbulent flow create variable amplitude loads, with presence of mean stresses and overloads. These complex loading sequences lead to the formation of networks of microcracks (crazing) that can propagate. As stainless steel is a material with strong deformation history effects and phase transformation resulting from plastic straining, such load sequence and variable amplitude loading effects are significant to its fatigue behavior and life predictions. The goal of this study was to investigate the effects of cyclic deformation on fatigue behavior of stainless steel 304L as a deformation history sensitive material and determine how to quantify and accumulate fatigue damage to enable life predictions under variable amplitude loading conditions for such materials. A comprehensive experimental program including testing under fully-reversed, as well as mean stress and/or mean strain conditions, with initial or periodic overloads, along with step testing and random loading histories was conducted on two grades of stainless steel 304L, under both strain-controlled and load-controlled conditions. To facilitate comparisons with a material without deformation history effects, similar tests were also carried out on aluminum 7075-T6. Experimental results are discussed, including peculiarities observed with stainless steel behavior, such as a phenomenon, referred to as secondary hardening characterized by a continuous increase in the stress response in a strain-controlled test and often leading to runout fatigue life. Possible mechanisms for secondary hardening observed in some tests are also discussed. The behavior of aluminum is shown not to be affected by preloading, whereas the behavior of stainless steel is greatly influenced by prior loading. Mean stress relaxation in strain control and ratcheting in load control and their influence on fatigue life are discussed. Some unusual mean strain test results are presented for stainless steel 304L, where in spite of mean stress relaxation fatigue lives were significantly longer than fully-reversed tests. Prestraining indicated no effect on either deformation or fatigue behavior of aluminum, while it induced considerable hardening in stainless steel 304L and led to different results on fatigue life, depending on the test control mode. In step tests for stainless steel 304L, strong hardening induced by the first step of a high-low sequence significantly affects the fatigue behavior, depending on the test control mode used. For periodic overload tests of stainless steel 340L, hardening due to the overloads was progressive throughout life and more significant than in high-low step tests. For aluminum, no effect on deformation behavior was observed due to periodic overloads. However, the direction of the overloads was found to affect fatigue life, as tensile overloads led to longer lives, while compressive overloads led to shorter lives. Deformation and fatigue behaviors under random loading conditions are also presented and discussed for the two materials. The applicability of a common cumulative damage rule, the linear damage rule, is assessed for the two types of material, and for various loading conditions. While the linear damage rule associated with a strain-life or stress-life curve is shown to be fairly accurate for life predictions for aluminum, it is shown to poorly represent the behavior of stainless steel, especially in prestrained and high-low step tests, in load control. In order to account for prior deformation effects and achieve accurate fatigue life predictions for stainless steel, parameters including both stress and strain terms are required. The Smith-Watson-Topper and Fatemi-Socie approaches, as such parameters, are shown to correlate most test data fairly accurately. For damage accumulation under variable amplitude loading, the linear damage rule associated with strain

Colin, Julie

288

The impact of hysteresis shape on failure mechanisms and the endurance fatigue life of ductile materials subject to high-temperature fatigue stressing  

International Nuclear Information System (INIS)

The paper discusses the various effects of load cycle shape and load cycle duration on the fatigue damage and thus on the endurance fatigue life of a material. The author illustrates his point by explaining experiments with two high-temperature alloys 800H and 617, which cannot be age-hardened or only slightly. (orig.)

1989-01-01

289

Comparison of different damage laws for creep fatigue life assessment  

International Nuclear Information System (INIS)

The structures of fast breeder reactors are submitted to cyclic loading at high temperature. Consequently, they must be designed relatively to creep fatigue. Creep fatigue damage models already exist in the design codes, ASME and RCCMR propose models which provide separate estimation of fatigue damage and creep damage and then recombine them by means of an interaction diagram, with creep damage being assessed as a function of the stresses. The LASG procedure developed in Great Britain is similar in its principle but different as concerns the manner of assessing creep damage which is, in this case, based on the exhausting of the material's ductility. These models have already been widely used for the design of structures and have already formed the subject of benchmarch allowing their comparison with experimental results (reference 1). Other damage models have been developed, in France in particular, by ONERA and EMP (Ecole des Mines de Paris). These models are based on different considerations than those mentioned above. After presentation of the equations and principles of these models, the results of validations with respect to uniaxial fatigue relaxation tests are shown. Their utilization is then extended to the prediction of multiaxial tests on mock-ups tested in sodium

1993-08-15

290

Life-prediction methods for combined creep-fatigue endurance  

International Nuclear Information System (INIS)

The basis and current status of development of the various approaches to the prediction of the combined creep-fatigue endurance are reviewed. It is concluded that an inadequate materials data base makes it difficult to draw sensible conclusions about the prediction capabilities of each of the available methods. (author)

1981-01-01

291

Practical methodology to evaluate the fatigue life of seam welded joints  

Directory of Open Access Journals (Sweden)

Full Text Available Purpose: of this paper is to present a practical and robust methodology developed to evaluate the fatigue life of seam welded joints under combined cyclic loading.Design/methodology/approach: Fatigue analysis was conducted in virtual environment. The finite element stress results from each loading were imported to fatigue code FE-Fatigue and combined to perform the fatigue life prediction using the S x N (stress x life method. A tube-to-plate specimen was submitted to a combined cyclic loading (bending and torsion with constant amplitude. The virtual durability analysis result was calibrated based on these laboratory tests and design codes such as BS7608 and Eurocode 3. The feasibility and application of the proposed numerical-experimental methodology and contributions for the technical development are discussed. Major challenges associated with this modelling and improvement proposals are finally presented.Findings: The finite element model was validated due to laboratory results. The analytical stress result presented upper value due to the approach used that considered the fillet weld supported all work. The model presented a good representation of failure and load correlation.Research limitations/implications: The measurement or modelling of the residual stresses resulting from the welding process was not included in this work. However, the thermal and metallurgical effects, such as distortions and residual stresses, were considered indirectly with regard to the corrections performed in the fatigue curves obtained from the investigated samples.Practical implications: Integrating fatigue analysis and finite elements, it is possible to analyse several welded joint configurations in the design phase, providing development time and cost reduction, increasing the project reliability.Originality/value: This methodology will permit, in further studies, the modelling of both stresses, in-service and residual stresses, acting together, which seem like an advantage to engineers and researchers who work in design and evaluation of structural components against fatigue failures.

K.C.Goes

2011-11-01

292

Fatigue-life prediction for a copper alloy degraded by multiple flaws  

International Nuclear Information System (INIS)

A study to establish fatigue life prediction for alloy 155 copper degraded by multiple flaws is described. Twelve specimens with natural flaws were radiographically characterized and fatigue tested to failure in a manner which minimized data scatter. Disposition of defective alloy 155 copper plate stock and Doublet III B-coil machined center post components was based on radiographically determined flaw size. Along with the macroscopic vertical internal flaws detected by radiography, undetectable microscopic alloy segregations were present in the microstructure. Data scatter, including microscopic flaw distribution, was related to radiographically detectable flaw size, and the reliability of the radiographic method was evaluated. B-coil fatigue lives for various load conditions were predicted. B-coil life expended to date and useful life remaining are discussed

1981-01-01

293

Fatigue and depression in multiple sclerosis: Correlation with quality of life  

Directory of Open Access Journals (Sweden)

Full Text Available The aim of this work was to examine the relationship between fatigue and depression, common features of multiple sclerosis (MS, and the quality of life (QOL. The study was comprised of 120 patients with clinical manifestations of definite MS. Relapsing-remitting MS was present in 76.7% patients and secondary progressive MS was present in 23.3% patients. Mean disease duration was 8.1 ± 5.6 years and the mean Expanded Disability Status Score (EDSS was 3.5 ± 1.8 (range 1-8. Fatigue was measured with the Fatigue Severity Scale (FSS, depression was measured by the Beck Depression Inventory (BDI and QOL was assessed using the health-related quality of life questionnaire SF-36. We observed that the global FSS score was 4.6 ± 1.8 (range 1-7 and BDI was 10.7 ± 10.3 (range 0-39. The FSS significantly and positively correlated with the BDI scores (r = 0.572; p = 0.000. The severity of fatigue had a significant impact on the quality of life (r = -0.743; p = 0.000, in particular on mental health (r = -0.749; p = 0.000. We observed a significant correlation between the severity of depression and impaired quality of life (r = -0.684; p = 0.000. This study shows that fatigue and depression are associated with impaired QOL in MS.

Mileti? Svetlana

2011-01-01

294

Fatigue failure by in-line flow-induced vibration and fatigue life evaluation  

International Nuclear Information System (INIS)

The phenomenon of fatigue failure by the In-line flow-induced vibration was studied. A newly water-flow-induced vibration system was made and used to reproduce fatigue failure by flow-induced vibration. A medium carbon steel specimen was fixed to the experimental equipment. A small artificial hole was introduced onto the specimen surface. Fatigue crack initiated from the artificial hole. A small portable strain histogram recorder (Mini Rainflow Corder, MRC) developed in another project of the authors' team was used to acquire the service strain hisogram at a critical point of the specimen and to measure the variation of natural frequency. Cumulative fatigue damage D defined by the Modified Miner Rule was calculated by using the strain histogram at the initial stage of test. The value of D was almost unity in the case of In-line vibration, while the values of D in the case of the Cross-flow vibration ranged from 0.2 to 0.8. (author)

2004-02-01

295

Accelerated ultrasonic fatigue testing applications and research trends  

International Nuclear Information System (INIS)

Very high cycle fatigue (VHCF) behavior of aerospace components has emerged much attention due to their long service life. In this study, a piezoelectric ultrasonic fatigue testing (UFT) system has been developed by Mbrosiatec Co., Ltd. to study the high cycle fatigue (HCF) strength of Ti 6Al 4V alloy. Hourglass shaped specimens have been investigated in the range from 10'6' to 10'9' cycles at room temperature under completely reversed R=-1 loading conditions, Scanning electron microscopy (SEM) analysis revealed that failures occurred in the entire range up to the gigacycle regime, and the fractures have been found to be initiated from the surface, unlike in steels. However, it was found from the SEM microgprahs that microcracks transformed into intergranular fractures. Thus, it can be concluded from according to the results that this test method can be applicable to commercialized automotive and railroad parts that require high cycle fatigue strength

2012-06-01

296

Predicting the Fatigue Life in Steel and Glass Fiber Reinforced Plastics Using Damage Models  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Three cumulative damage models are examined for the case of cyclic loading of AISI 6150 steel, S2 glass fibre/epoxy and E glass fibre/epoxy composites. The Palmgren-Miner, Broutman-Sahu and Hashin-Rotem models are compared to determine which of the three gives the most accurate estimation of the fatigue life of the materials tested. In addition, comparison of the fatigue life of the materials shows the superiority of AISI 6150 steel and S2 glass fibre/epoxy at lower mean stresses, and that of...

Roselita Fragoudakis; Anil Saigal

2011-01-01

297

TBC bond coat-top coat interface roughness : influence on fatigue life and modelling aspects  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Thermal barrier coatings (TBCs), when used in gas turbines, may fail through thermal fatigue, causing the ceramic top coat to spall off the metallic bond coat. The life prediction of TBCs often involves finite element modelling of the stress field close to the bond coat/top coat interface and thus relies on accurate modelling of the interface. The present research studies the influence of bond coat/top coat interface roughness on the thermal fatigue life of plasma sprayed TBCs. By using diffe...

Eriksson, Robert; Sjo?stro?m, So?ren; Brodin, Ha?kan; Johansson, Sten; O?stergren, Lars; Li, Xin-hai

2013-01-01

298

Predicting the Fatigue Life in Steel and Glass Fiber Reinforced Plastics Using Damage Models  

Directory of Open Access Journals (Sweden)

Full Text Available Three cumulative damage models are examined for the case of cyclic loading of AISI 6150 steel, S2 glass fibre/epoxy and E glass fibre/epoxy composites. The Palmgren-Miner, Broutman-Sahu and Hashin-Rotem models are compared to determine which of the three gives the most accurate estimation of the fatigue life of the materials tested. In addition, comparison of the fatigue life of the materials shows the superiority of AISI 6150 steel and S2 glass fibre/epoxy at lower mean stresses, and that of steel to the composites at higher mean stresses.

Roselita Fragoudakis

2011-06-01

299

Quantitative description of the fatigue life with the four-parameter Weibull distribution  

International Nuclear Information System (INIS)

Frequently, statistical distributions of service life which are observed with ageing and fatigue processes do not obey to Weibull's distribution function. In those cases, the introduction of a third parameter into the distribution function permits to restore, quite phenomenologically, the straight line in the service life network that is advantageous for the evaluation. The article briefly discusses basic doubts about this approach. A procedure is described which avoids grave drawbacks of the three-parameter approach and is suitable for being used on a PC. The basic idea of this procedure is in unisson with recent results from research concerning the fatigue of metals. (orig.)

1993-07-01

300

Using artificial neural networks to predict the fatigue life of carbon and low-alloy steels  

International Nuclear Information System (INIS)

The ASME boiler and pressure vessel code contains rules for the construction of nuclear power plant components. Figures I-9.1 through I-9.6 of Appendix I to Section III of the Code specify fatigue design curves for structural materials. However, the effects of light water reactor (LWR) coolant environments are not explicitly addressed by the code design curves. Recent test data indicate significant decreases in the fatigue lives of carbon and low-alloy steels in LWR environments when five conditions are satisfied simultaneously. When applied strain range, temperature, dissolved oxygen in the water, and sulfur content of the steel are above a minimum threshold level, and the loading strain rate is below a threshold value, environmentally assisted fatigue occurs. For this study, a data base of 1036 fatigue tests was used to train an artificial neural network (ANN). Once the optimal ANN was designed, ANN were trained and used to predict fatigue life for specified sets of loading and environmental conditions. By finding patterns and trends in the data, the ANN can find the fatigue life for any set of conditions. Artificial neural networks show great potential for predicting environmentally assisted corrosion. Their main benefits are that the fit of the data is based purely on data and not on preconceptions and that the network can interpolate effects by learning trends and patterns when data are not available. (orig.)

2000-04-01

 
 
 
 
301

Effect of electric discharge machining on the fatigue life of Inconel 718  

Science.gov (United States)

The effect of electric discharge machining on the fatigue life of Inconel 718 alloy at room temperature was investigated. Data were generated in the uniaxial tension fatigue mode at ambient temperature using flat 3.175 mm thick specimens. The specimens were machined on a wire-cut electric discharge machine at cutting speeds ranging from 0.5 to 2 mm per minute. The specimens were fatigued at a selected stress, and the resulting fatigue lives compared with that of the virgin material. The surfaces of the fatigued specimens were examined under optical and scanning electron microscopes, and the roughness of the surfaces was measured using a standard profilometer. From the results of the investigation, it was concluded that the fatigue life of the specimens machined using EDM decreased slightly as compared with that of the virgin material, but remained unchanged as the cutting speed was changed. The results are explained using data produced employing microhardness measurements, profilometry, and optical and scanning microscopy.

Jeelani, S.; Collins, M. R.

1988-01-01

302

Analysis of the Effects of Aggressive Shot Peening on Fatigue Life of 7075 ? T6 Aluminum Alloy  

Digital Repository Infrastructure Vision for European Research (DRIVER)

For many years controlled shot peening was considered as a surface treatment. It is now clear that the performance of control shot peening in terms of fatigue depends on the balance between its beneficial (compressive residual stress and work hardening) and beneficial effects (surface hardening).The overall aim of this paper is to study the effects of aggressive shot peening on fatigue life of 7075 ? T6 aluminum alloy. The fatigue life reduction factor (LRF) due to the aggressive shot pe...

Jabur, Khairallah S.

2012-01-01

303

Creep, fatigue and creep-fatigue damage evaluation and estimation of remaining life of SUS 304 austenitic stainless steel at high temperature  

International Nuclear Information System (INIS)

Experimental study was made on the damage evaluation and estimation of remaining life of SUS 304 stainless steel in creep, low-cycle fatigue and creep-fatigue at 873 K in air. Creep, fatigue and creep-fatigue damage curves were drawn by the method proposed by D.A. Woodford and the relations between these damages and non-destructive parameters, i.e., microvickers hardness and quantities obtained from X-ray diffraction, were discussed. From these tests, the following conclusions were obtained. (1) Constant damage lines in the diagram of remaining lives in creep and fatigue could be drawn by changing load levels during the tests. Constant damage lines in creep-fatigue were also made by a linear damage rule using both static creep and fatigue damage curves, which agree well with the experimental data in creep-fatigue. (2) Microvickers hardness and half-value breadth in X-ray diffraction are appropriate parameters to evaluate creep damage but are not proper to evaluate fatigue damage. Particle size and microstrain obtained by X-ray profile analysis are good parameters to evaluate both creep and fatigue damages. (author)

1986-01-01

304

Experimental and modeling results of creep-fatigue life of Inconel 617 and Haynes 230 at 850 °C  

Science.gov (United States)

Creep-fatigue testing of Ni-based superalloy Inconel 617 and Haynes 230 were conducted in the air at 850 °C. Tests were performed with fully reversed axial strain control at a total strain range of 0.5%, 1.0% or 1.5% and hold time at maximum tensile strain for 3, 10 or 30 min. In addition, two creep-fatigue life prediction methods, i.e. linear damage summation and frequency-modified tensile hysteresis energy modeling, were evaluated and compared with experimental results. Under all creep-fatigue tests, Haynes 230 performed better than Inconel 617. Compared to the low cycle fatigue life, the cycles to failure for both materials decreased under creep-fatigue test conditions. Longer hold time at maximum tensile strain would cause a further reduction in both material creep-fatigue life. The linear damage summation could predict the creep-fatigue life of Inconel 617 for limited test conditions, but considerably underestimated the creep-fatigue life of Haynes 230. In contrast, frequency-modified tensile hysteresis energy modeling showed promising creep-fatigue life prediction results for both materials.

Chen, Xiang; Sokolov, Mikhail A.; Sham, Sam; Erdman, Donald L., III; Busby, Jeremy T.; Mo, Kun; Stubbins, James F.

2013-01-01

305

Experimental and modeling results of creep–fatigue life of Inconel 617 and Haynes 230 at 850 °C  

International Nuclear Information System (INIS)

Creep–fatigue testing of Ni-based superalloy Inconel 617 and Haynes 230 were conducted in the air at 850 °C. Tests were performed with fully reversed axial strain control at a total strain range of 0.5%, 1.0% or 1.5% and hold time at maximum tensile strain for 3, 10 or 30 min. In addition, two creep–fatigue life prediction methods, i.e. linear damage summation and frequency-modified tensile hysteresis energy modeling, were evaluated and compared with experimental results. Under all creep–fatigue tests, Haynes 230 performed better than Inconel 617. Compared to the low cycle fatigue life, the cycles to failure for both materials decreased under creep–fatigue test conditions. Longer hold time at maximum tensile strain would cause a further reduction in both material creep–fatigue life. The linear damage summation could predict the creep–fatigue life of Inconel 617 for limited test conditions, but considerably underestimated the creep–fatigue life of Haynes 230. In contrast, frequency-modified tensile hysteresis energy modeling showed promising creep–fatigue life prediction results for both materials.

2013-01-01

306

Creep fatigue life prediction for engine hot section materials (isotropic)  

Science.gov (United States)

A series of high temperature strain controlled fatigue tests have been completed to study the effects of thermomechanical fatigue, multiaxial loading, reactive environments, and imposed mean stresses. The baseline alloy used in these tests was cast B1900+Hf (with and without coatings); a small number of tests of wrought INCO 718 are also included. A strong path dependence was demonstrated during the thermomechanical fatigue testing, using in-phase, out-phase, and non-proportional (elliptical and 'dogleg') strain-temperature cycles. The multiaxial tests also demonstrated cycle path to be a significant variable, using both proportional and non-proportional tension-torsion loading. Environmental screening tests were conducted in moderate pressure oxygen and purified argon; the oxygen reduced the specimen lives by two, while the argon testing produced ambiguous data. Both NiCoCrAlY overlay and diffusion aluminide coatings were evaluated under isothermal and TMF conditions; in general, the lives of the coated specimens were higher that those of uncoated specimens. Controlled mean stress TMF tests showed that small mean stress changes could change initiation lives by orders of magnitude; these results are not conservatively predicted using traditional linear damage summation rules. Microstructures were evaluated using optical, SEM and TEM methods.

Nelson, R. S.; Levan, G. W.; Schoendorf, J. F.

1992-01-01

307

Fatigue Life Prediction of Multi Leaf Spring used in the Suspension System of Light Commercial Vehicle  

Directory of Open Access Journals (Sweden)

Full Text Available The Leaf spring is widely used in automobiles and one of the components of suspension system. It needs to have high fatigue life. As a general rule, the leaf spring is regarded as a safety component as failure could lead to severe accidents. The purpose of this paper is to predict the fatigue life of steel leaf spring along with analytical stress and deflection calculations. This present work describes static and fatigue analysis of a steel leaf spring of a light commercial vehicle (LCV. The dimensions of the leaf spring of a LCV are taken and are verified by design calculations. The non-linear static analysis of 2D model of the leaf spring is performed using NASTRAN solver and compared with analytical results. The preprocessing of the model is done by using HYPERMESH software. The stiffness of the leaf spring is studied by plotting load versus deflection curve for various load applications. The simulation results are compared with analytical results. The fatigue life of the leaf spring is predicted using MSC Fatigue software.

V.K.Aher

2012-06-01

308

Statistical analysis of fatigue strain-life data for carbon and low-alloy steels  

International Nuclear Information System (INIS)

The existing fatigue strain vs. life (S-N) data, foreign and domestic, for carbon and low-alloy steels used in the construction of nuclear power plant components have been compiled and categorized according to material, loading, and environmental conditions. A statistical model has been developed for estimating the effects of the various test conditions on fatigue life. The results of a rigorous statistical analysis have been used to estimate the probability of initiating a fatigue crack. Data in the literature were reviewed to evaluate the effects of size, geometry, and surface finish of a component on its fatigue life. The fatigue S-N curves for components have been determined by applying design margins for size, geometry, and surface finish to crack initiation curves estimated from the model. The significance of the effect of environment on the current Code design curve and on the proposed interim design curves for carbon and low-alloy steels presented in NUREG/CR-5999 is discussed

1994-01-01

309

A computational approach for thermomechanical fatigue life prediction of dissimilarly welded superheater tubes  

Energy Technology Data Exchange (ETDEWEB)

In this paper a computational approach for fatigue life prediction of dissimilarly welded superheater tubes is presented and applied to a dissimilar weld between tubes made of the nickel base alloy Alloy617 tube and the 12% chromium steel VM12. The approach comprises the calculation of the residual stresses in the welded tubes with a multi-pass dissimilar welding simulation, the relaxation of the residual stresses in a post weld heat treatment (PWHT) simulation and the fatigue life prediction using the remaining residual stresses as initial condition. A cyclic fiscoplasticity model is used to calculate the transient stresses and strains under thermocyclic service loadings. The fatigue life is predicted with a damage parameter which is based on fracture mechanics. The adjustable parameters of the model are determined based on LCF and TMF experiments. The simulations show, that the residual stresses that remain after PWHT further relax in the first loading cycles. The predicted fatigue lives depend on the residual stresses and, thus, on the choice of the loading cycle in which the damage parameter is evaluated. It the first loading cycle, where residual stresses are still present, is considered, lower fatigue lives are predicted compared to predictions considering loading cycles with relaxed residual stresses. (orig.)

Krishnasamy, Ram-Kumar; Seifert, Thomas; Siegele, Dieter [Fraunhofer-Institut fuer Werkstoffmechanik (IWM), Freiburg im Breisgau (Germany)

2010-07-01

310

Influence of cyclic thermal loading on residual fatigue life of materials damaged by simulated plasma disruption  

International Nuclear Information System (INIS)

Surface damage of type 304 stainless steel, which is one of the candidates for the first-wall structural material in a fusion reactor, at cyclic plasma disruption loadings is simulated by a high heat flux Neutron Beam Injection. Influences of the cyclic thermal loads on the residual fatigue life are studied. The results obtained are summarized as follows. (1) The maximum tensile residual stresses near the damaged surface increased with increasing thermal loading cycles from 1 to 5. (2) The fatigue strength and the fatigue limit of the specimen subjected to 5 cycles of thermal loading and those for 1 cycle are the same. (3) A critical crack length, 2be to vanish from sight caused by thermal loading is important for the evaluation of the residual fatigue life. If the defect length, 2be, residual life after the second thermal loading and that before thermal loading are the same. If 2b>2be, fatigue crack growth occurs due to the cyclic thermal load. (author)

1995-03-01

311

Effects of cellular growth on fatigue life of directionally solidified hypoeutectic Al-Fe Alloys  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in english Al-Fe hypoeutectic alloys are a family of casting alloys characterized by cell growth, low cost and appreciable formability. It is well known that fatigue strength is a requirement of prime importance considering the nature of load typically observed during operations involving the risers used in oi [...] l extraction. The aim of this study is to examine the influence of cell size and its intercellular phase distribution on the fatigue life (Nf) of the directionally solidified Al-0.5, 1.0 and 1.5wt% Fe alloys. A water-cooled vertical upward unidirectional solidification system was used to provide the castings. Microscopy light and SEM microscopy were used. It was found that fatigue life decreases as cell spacing (? c) increases. Smaller cell spacing allows a homogeneous distribution of Al-Fe fibers to happen within the intercellular regions, which tends to improve the mentioned fatigue property. Hall-Petch type correlations [Nf= Nf0+A(?c -1/2)-B(?c -1); where A and B are constants] seems to be able to encompass the fatigue life variation along the Al-Fe alloys.

Pryscilla Liberato, Ribeiro; Bismarck Luiz, Silva; Wanderson Santana da, Silva; José E, Spinelli.

312

Influence of the non-singular stress on the crack extension and fatigue life  

International Nuclear Information System (INIS)

Highlights: ? BEM is combined by characteristic analysis to calculate the singular stress field. ? A new method is proposed to evaluate the full stress field at crack tip region. ? Effect of non-singular stress on the propagation direction of the fatigue crack is analyzed. ? The influence of non-singular stress on the fatigue crack life is evaluated. - Abstract: The complete elasticity stress field at a crack tip region can be presented by the sum of the singular stress and several non-singular stress terms according to the Williams asymptotic expansion theory. The non-singular stress has a non-negligible influence on the prediction of the crack extension direction and crack growth rate under the fatigue loading. A novel method combining the boundary element method and the singularity characteristic analysis is proposed here to evaluate the complete stress field at a crack tip region. In this new method, any non-singular stress term in the Williams series expansion can be evaluated according to the computational accuracy requirement. Then, a modified Paris law is introduced to predict the crack propagation under the mixed-mode loading for exploring the influence of the non-singular stress on the fatigue life duration. By comparing with the existed experimental results, the predicted crack fatigue life when the non-singular stress is taken into consideration is more accurate than the predicted ones only considering the singular stress.

2012-07-01

313

Shape optimization considering fatigue life of pulley in power-steering pulley  

Energy Technology Data Exchange (ETDEWEB)

The pulley is one of core mechanical elements in the power steering system for vehicles. The pulley operates under both the compressive loading and the torque. Therefore, to assure the safety of the power steering system, it is very important to investigate the durability and the optimization of the pulley. In this study, the applied stress distribution of the pulley under high tension and torsion loads was obtained by using finite element analysis. Based on these results, the fatigue life of the pulley with the variation of the fatigue strength was evaluated by a durability analysis simulator. The results at 50% and 1% for the failure probability were compared with respect to the fatigue life. In addition to the optimum design for the fatigue life is obtained by the response surface method. The response function utilizes the function of the life and weight factors. Within range for design life condition, the minimization of the weight, one of the formulation, is obtained by the optimal design. Moreover, the optimum design by considering its durability and validity is verified by the durability test.

Shim, Hee Jin; Kim, Jung Kyu [Hanyang University, Seoul (Korea, Republic of)

2006-09-15

314

Fatigue life prediction of a stainless steel plate-fin structure using equivalent-homogeneous-solid method  

International Nuclear Information System (INIS)

Highlights: ? A fatigue life prediction method is established for 304 stainless steel plate-fin structure. ? The fatigue cracks initiate at the fillet and then propagate to the base metal of fin. ? The fatigue fracture in the filler metal shows brittle character. ? Typical dimple and striation are shown in the base metal. -- Abstract: Stainless steel plate-fin heat exchangers are key components in nuclear power stations and hydrogen production systems using High Temperature Gas-cooled Reactors (HTGR). Fatigue is the most failure mode for plate-fin structures because they operate under cyclic high pressures and high temperatures. This paper establishes a life prediction method of fatigue based on equivalent-homogeneous-solid method for a 304 stainless steel plate-fin structure. A finite element analysis (FEA) program of fatigue life has been developed, which has been verified by fatigue experiments. By using this method, both the local stress concentration and the fatigue life for the whole plate-fin structure can be predicted. The results show that the fatigue cracks initiate at the fillet and then propagate to the interface and eventually the base metal of fin. The fatigue fracture in the filler metal shows brittle character, while typical dimple and striation are shown in the base metal.

2011-12-01

315

Damage rate is a predictor of fatigue life and creep strain rate in tensile fatigue of human cortical bone samples.  

Science.gov (United States)

We present results on the growth of damage in 29 fatigue tests of human femoral cortical bone from four individuals, aged 53-79. In these tests we examine the interdependency of stress, cycles to failure, rate of creep strain, and rate of modulus loss. The behavior of creep rates has been reported recently for the same donors as an effect of stress and cycles. In the present paper we first examine how the evolution of damage (drop in modulus per cycle) is associated with the stress level or the "normalized stress" level (stress divided by specimen modulus), and results show the rate of modulus loss fits better as a function of normalized stress. However, we find here that even better correlations can be established between either the cycles to failure or creep rates versus rates of damage than any of these three measures versus normalized stress. The data indicate that damage rates can be excellent predictors of fatigue life and creep strain rates in tensile fatigue of human cortical bone for use in practical problems and computer simulations. PMID:15971698

Cotton, John R; Winwood, Keith; Zioupos, Peter; Taylor, Mark

2005-04-01

316

Fatigue life prediction of Ni-base thermal solar receiver tubes  

Energy Technology Data Exchange (ETDEWEB)

Solar receivers for tower type Solar Thermal Power Plants are subjected to complex thermo-mechanical loads including fast and severe thermo-mechanical cycles. The material temperatures can reach more than 800 C and fall to room temperature very quickly. In order to predict the fatigue life of a receiver design, receiver tubes made of Alloy 625 with a wall thickness of 0.5 mm were tested in isothermal and thermo-cyclic experiments. The number of cycles to failure was in the range of 100 to 100,000. A thermo-mechanical fatigue life prediction model was set up. The model is based on the cyclic deformation of the material and the damage caused by the growth of fatigue micro cracks. The model reasonably predicts the experimental results. (orig.)

Hartrott, Philipp von; Schlesinger, Michael [Fraunhofer-Institut fuer Werkstoffmechanik (IWM), Freiburg im Breisgau (Germany); Uhlig, Ralf; Jedamski, Jens [DLR Deutsches Zentrum fuer Luft- und Raumfahrt e.V., Stuttgart (Germany)

2010-07-01

317

An analytical method on evaluation of creep-fatigue life with long-time strain hold  

International Nuclear Information System (INIS)

Evaluation of creep-fatigue life with long-time strain hold is a very important problem for structural design of FBR. But, these creep-fatigue tests are very difficult because of test techniques and costs. Therefore, the life prediction for long-time must be based on analytical approach by which the extrapolation to the range of longer hold time effect can be evaluated and justified. In this paper, an analytical method is proposed, which is based on generalized relaxation analysis, creep damage analysis, total damage evaluation per cycle and the diagram of creep-fatigue interaction effect. By this method, it is expected that the prediction is simplified and the evaluation is conservative. (author)

1983-10-10

318

Evaluation of accuracy of fatigue-creep life preciction based on inelastic analysis  

International Nuclear Information System (INIS)

In our institute, the research on the improvement of solution accuracy of inelastic analysis is under way for the purpose of contribution to the rationalization in design of fast breeder reactors. In this research, the prediction accuracy of inelastic constitutive equations and creep-fatigue life estimation laws is evaluated based on a number of test results. In this report, we conduct the stress-strain analyses by elastic-plastic-creep equations and the failure life estimation by linear damage fraction rule. The results of them are compared with the experimental results. The following two types of tests, both of which are conducted at 550 deg C, are analyzed: (i) strain-hold type low-cycle fatigue tests (ii) slow strain-rate type low-cycle fatigue tests. The predicted failure lives for type (i) tests are smaller than the experimental values, whereas those for type (ii) tests tend to be larger than the test results. (author)

1986-01-01

319

The effect of different shot peening intensities on fatigue life of AW 7075 aluminium alloy  

Directory of Open Access Journals (Sweden)

Full Text Available In this study the effect of different shot peening intensities, from very light peening with ceramic beads to severe shot peening with high coverage, on the fatigue life of aircraft AW 7075 aluminium alloy was investigated. Results were discussed in means of surface roughness, character of deformed surface layer and residual stress profile measured by XRD methods. Light peening intensity creates high and shallow compression residual stress field in the subsurface layers of material and increases the fatigue life of studied alloy. Increasing the peening intensity increases the depth of residual stress field, however the surface damage created by impact of shots at high velocity causes significant surface damage and rapidly degrade the fatigue properties of AW 7075 aluminium alloy.

Libor Trško

2013-12-01

320

Implementation of on-line fatigue monitoring methodology in Heavy Water Plant, Kota for remnant life assessment programme  

International Nuclear Information System (INIS)

Fatigue, creep and creep-fatigue interaction phenomena are important in the design and operation of components used in nuclear industry, thermal power plant and chemical process plant. Extension of life of the existing plants is a major concern to plant management. Recently, a methodology has been developed to predict the aging degradation of various components subjected to severe fluctuating loading conditions. This methodology converts the plant transients to responses on the structure using Green's function technique. The stresses on the structure due to combined thermal and mechanical loading is transformed into stress frequency spectrum using Rainflow cycle counting algorithm. Using material fatigue data, fatigue usage factor is computed. There is a proposal to implement this on-line fatigue life monitoring system to estimate the fatigue degradation of components at Heavy Water Plant, Kota. This present paper describes the implementation of this methodology for remnant life assessment of components. (author). 3 refs., 3 figs

1996-08-01

 
 
 
 
321

Creep-fatigue, high-cycle fatigue and crack growth examinations in CoCr22Ni22W14 and NiCr22Co12Mo9 at selected temperatures; Ein- und Zweistufenermuedungs- sowie Rissausbreitungsuntersuchungen an CoCr22Ni22W14 und NiCr22Co12Mo9 in ausgewaehlten Temperaturbereichen  

Energy Technology Data Exchange (ETDEWEB)

The materials used for combustion chambers of modern aircraft engines or stationary gas turbines predominantly are high-chromium, solid-solution-hardened or carbide-hardened cobalt-base or nickel-base alloys, typical representatives being the alloys CoCr22Ni22W14 (Haynes 188), and NiCr22Co12Mo9 (Nicofer 5520 Co/Inconel 617). Whereas for the latter material, extensive experimental data are available on its isothermal, low-cycle high-temperature fatigue performance, the corresponding performance of the Haynes 188 alloy so far is less known. There also is an information gap with respect to the high-cycle deformation behaviour of combustion chamber materials at elevated temperatures. This is why studies have been carried out and data are presented on the total strain-controlled, cyclic deformation behaviour of the two materials at temperatures of 1 123 K {<=}T{<=} 1 473 K. Subsequent studies ecompass creep-fatigue experiments, high-cycle fatigue experiments at 1 123 K and 1 273 K, as well as crack propagation experiments in the temperature range of 295 K{<=}T{<=} 1473 K. (orig.) 140 figs., 8 tabs. [Deutsch] In modernen Flugtriebwerken und stationaeren Gasturbinen werden als Brennkammerwerkstoffe ueberwiegend mischkristall- und karbidverfestigte chromreiche Kobalt- und Nickelbasislegierungen eingesetzt, fuer die CoCr22Ni22W14 (Haynes 188) und NiCr22Co12Mo9 (Nicrofer 5520 Co/Inconel 617) typische Vertreter sind. Waehrend fuer NiCr22Co12Mo9 umfangreiche Untersuchungen zum isothermen einstufigen Hochtemperaturermuedungsverhalten existieren, gibt es dazu nur wenige fuer CoCr22Ni22W14. Ferner sind bisher nahezu keine Ergebnisse zum mehrstufigen zyklischen Verformungsverhalten von Brennkammerwerkstoffen bei hoeheren Temperaturen bekannt geworden. Deshalb werden zunaechst fuer beide Werkstoffe jeweils totaldehnungskontrollierte Wechselverformungsversuche im Temperaturbereich 1123 K{<=}T{<=}1473 K durchgefuehrt. Im Anschluss daran erfolgen Kriechermuedungsexperimente, Zweistufenermuedungsexperimente bei 1123 und 1273 K sowie Rissausbreitungsexperimente im Temperaturbereich 295 K{<=}T{<=}1473 K. (orig.)

Moendel, A.

1997-12-31

322

Fatigue life assessment of 316L stainless steel and DIN-1.4914 martensitic steel before and after TEXTOR exposure  

Science.gov (United States)

The effects of plasma exposure in the TEXTOR tokomak on elevated temperature fatigue lifetime and failure micromechanisms of 316L austenitic stainless steel and DIN 1.4914 martensitic steel (NET reference heats) have been evaluated. Fatigue tests were carried out in vacuum in the temperature range 150°-450°C and compared with data from reference specimens.Plasma-induced surface modifications lead to significant deterioration in fatigue life of 316L steel, whereas the lifetime of 1.4914 steel is unaffected. Fatigue in the 1.4914 steel is surface-initiated only at high stresses. At low stress amplitudes internal fatigue initiation at inclusions was observed.

Shakib, J. I.; Ullmaier, H.; Little, E. A.; Schmitz, W.; Faulkner, R. G.; Chung, T. E.

1992-09-01

323

Fatigue life assessment of 316L stainless steel and DIN-1.4914 martensitic steel before and after TEXTOR exposure  

International Nuclear Information System (INIS)

The effects of plasma exposure in the TEXTOR tokomak on elevated temperature fatigue lifetime and failure micromechanisms of 316L austenitic stainless steel and DIN 1.4914 martensitic steel (NET reference heats) have been evaluated. Fatigue tests were carried out in vacuum in the temperature range 150deg C-450deg C and compared with data from reference specimens. Plasma-induced surface modifications lead to significant deterioration in fatigue life of 316L steel, whereas the lifetime of 1.4914 steel is unaffected. Fatigue in the 1.4914 steel is surface-initiated only at high stresses. At low stress amplitudes internal fatigue initiation at inclusions was observed. (orig.)

1992-09-01

324

Fatigue, fracture, and life prediction criteria for composite materials in magnets  

Energy Technology Data Exchange (ETDEWEB)

An explosively-bonded copper/Inconel 718/copper laminate conductor was proposed to withstand the severe face compression stresses in the central core of the Alcator C-MOD tokamak toroidal field (TF) magnet. Due to the severe duty of the TF magnet, it is critical that an accurate estimate of useful life be determined. As part of the effort to formulate an appropriate life prediction, fatigue crack growth experiments were performed on the laminate as well as its components. Metallographic evaluation of the laminate interface revealed many shear bands in the Inconel 718. Shear bands and shear band cracks were produced in the Inconel 718 as a result of the explosion bonding process. These shear bands were shown to have a detrimental effect on the crack growth behavior of the laminate, by significantly reducing the load carrying capability of the reinforcement layer and providing for easy crack propagation paths. Fatigue crack growth rate was found not only to be dependent on temperature but also on orientation. Fatigue cracks grew faster in directions which contained shear bands in the plane of the propagating crack. Fractography showed crack advancement by fatigue cracking in the Inconel 718 and ductile tearing of the copper at the interface. However, further away from the interfaces, the copper exhibited fatigue striations indicating that cracks were now propagating by fatigue. Laminate life prediction results showed a strong dependence on shear band orientation, and exhibited little variation between room temperature and 77{degree}K. Predicted life of this laminate was lower when the crack propagation was along a shear band than when crack propagation was across the shear bands. Shear bands appear to have a dominating effect on crack growth behavior.

Wong, F.M.G.

1990-06-01

325

Effect of Creep and Oxidation on Reduced Creep-Fatigue life of Ni-based Alloy 617 at 850 C  

Energy Technology Data Exchange (ETDEWEB)

Low cycle fatigue (LCF) and creep fatigue testing of Ni-based alloy 617 was carried out at 850 C. Compared with its LCF life, the material s creep fatigue life decreases to different extents depending on test conditions. To elucidate the microstructure-fatigue property relationship for alloy 617 and the effect of creep and oxidation on its fatigue life, systematic microstructural investigations were carried out using scanning electron microscopy, energy-dispersive X-ray spectroscopy, and electron backscatter diffraction (EBSD). In LCF tests, as the total strain range increased, deformations concentrated near high angle grain boundaries (HAGBs). The strain hold period in the creep fatigue tests introduced additional creep damage to the material, which revealed the detrimental effect of the strain hold time on the material fatigue life in two ways. First, the strain hold time enhanced the localized deformation near HAGBs, resulting in the promotion of intergranular cracking of alloy 617. Second, the strain hold time encouraged grain boundary sliding, which resulted in interior intergranular cracking of the material. Oxidation accelerated the initiation of intergranular cracking in alloy 617. In the crack propagation stage, if oxidation was promoted and the cyclic oxidation damage was greater than the fatigue damage, oxidation-assisted intergranular crack growth resulted in a significant reduction in the material s fatigue life.

Chen, Xiang [ORNL; Yang, Zhiqing [ORNL; Sokolov, Mikhail A [ORNL; ERDMAN III, DONALD L [ORNL; Mo, Kun [ORNL; Stubbins, James [ORNL

2014-01-01

326

Effect of creep and oxidation on reduced fatigue life of Ni-based alloy 617 at 850 °C  

Science.gov (United States)

Low cycle fatigue (LCF) and creep-fatigue testing of Ni-based alloy 617 was carried out at 850 °C. Compared with its LCF life, the material's creep-fatigue life decreases to different extents depending on test conditions. To elucidate the microstructure-fatigue property relationship for alloy 617 and the effect of creep and oxidation on its fatigue life, systematic microstructural investigations were carried out using scanning electron microscopy, energy-dispersive X-ray spectroscopy, and electron backscatter diffraction (EBSD). In LCF tests, as the total strain range increased, deformations concentrated near high angle grain boundaries (HAGBs). The strain hold period in the creep-fatigue tests introduced additional creep damage to the material, which revealed the detrimental effect of the strain hold time on the material fatigue life in two ways. First, the strain hold time enhanced the localized deformation near HAGBs, resulting in the promotion of intergranular cracking of alloy 617. Second, the strain hold time encouraged grain boundary sliding, which resulted in interior intergranular cracking of the material. Oxidation accelerated the initiation of intergranular cracking in alloy 617. In the crack propagation stage, if oxidation was promoted and the cyclic oxidation damage was greater than the fatigue damage, oxidation-assisted intergranular crack growth resulted in a significant reduction in the material's fatigue life.

Chen, Xiang; Yang, Zhiqing; Sokolov, Mikhail A.; Erdman, Donald L.; Mo, Kun; Stubbins, James F.

2014-01-01

327

Fatigue life evaluation of connections between the HTGR thermal barrier attachment fixtures and the PCRV liner  

International Nuclear Information System (INIS)

The results of a development program to evaluate the fatigue life of the welded stud connections between the HTGR thermal barrier attachment fixtures and the prestressed concrete reactor vessel (PCRV) liner are presented. The corrective actions taken to remedy the problems disclosed by this program are also described

1977-01-01

328

Conductor fatigue life research: Eolian vibration of transmission lines: Final report  

Energy Technology Data Exchange (ETDEWEB)

Wind-induced vibration can cause premature failure of transmission lines through conductor fatigue. This research identifies design considerations to reduce this effect. It also suggests methods to treat minimally damaged conductors so that the transmission line can achieve its full design life without the need for expensive splicing or reconductoring.

Ramey, G.E.

1987-01-01

329

Effect of lubricant extreme-pressure additives on surface fatigue life of AISI 9310 spur gears  

Science.gov (United States)

Surface fatigue tests were conducted with AISI 9310 spur gears using a formulated synthetic tetraester oil (conforming to MIL-L-23699 specifications) as the lubricant containing either sulfur or phosphorus as the EP additive. Four groups of gears were tested. One group of gears tested without an additive in the lubricant acted as the reference oil. In the other three groups either a 0.1 wt % sulfur or phosphorus additive was added to the tetraester oil to enhance gear surface fatigue life. Test conditions included a gear temperature of 334 K (160 F), a maximum Hertz stress of 1.71 GPa (248 000 psi), and a speed of 10,000 rpm. The gears tested with a 0.1 wt % phosphorus additive showed pitting fatigue life 2.6 times the life of gears tested with the reference tetraester based oil. Although fatigue lives of two groups of gears tested with the sulfur additive in the oil showed improvement over the control group gear life, the results, unlike those obtained with the phosphorus oil, were not considered to be statistically significant.

Scibbe, H. W.; Townsend, D. P.; Aron, P. R.

1984-01-01

330

A method of calculating the safe fatigue life of compact, highly-stressed components  

Science.gov (United States)

This paper describes a method which has been developed for estimating the safe fatigue life of compact, highly-stressed and inaccessible components for aeroplanes and helicopters of the Royal Air Force. It is explained why the Design Requirements for British Military Aircraft do not favor the use of a damage-tolerance approach in these circumstances.

Cardick, Arthur W.; Pike, Vera J.

1994-01-01

331

Effects of contact pressure on fretting fatigue characteristics of Ti-4.5Al-3V-2Mo-2Fe with acicular alpha structure  

Energy Technology Data Exchange (ETDEWEB)

The effects of microstructure and contact pressure on fretting fatigue characteristics of Ti-4.5Al-3V-2Mo-2Fe conducted with annealing at 1123 K and 1223 K were investigated in this study. Fretting fatigue tests in low and high cycle fatigue life regions of the alloys with equiaxed {alpha} and acicular {alpha} structures were carried out at each contact pressure of 10, 15, 30, 45, 75, 105 and 153 MPa. In the alloy with equiaxed {alpha} structure, fretting fatigue strength tends to be very low at contact pressures of 10 MPa and 15 MPa in low and high cycle fatigue life regions, respectively. Furthermore, fretting fatigue strength tends to be nearly constant at the contact pressure over 45 MPa in each fatigue life region. On the other hand, in the alloy with acicular {alpha} structure, fretting fatigue strength tends to be very low at contact pressures of 15 MPa and 30 MPa in low and high cycle fatigue life regions, respectively. Furthermore, fretting fatigue strength tends to be nearly constant at contact pressures of 45 MPa and over 30 MPa in low and high fatigue life regions, respectively. (orig.)

Takeda, J.; Niinomi, M.; Akahori, T. [Dept. of Production Systems Engineering, Toyohashi Univ. of Technology, Tempaku-cho, Toyohashi (Japan)

2005-07-01

332

ARRANGING THICKNESSES AND SPANS OF ORTHOTROPIC DECK FOR DESIRED FATIGUE LIFE AND DESIGN CATEGORY  

Directory of Open Access Journals (Sweden)

Full Text Available Orthotropic steel highway bridges are subject to variable traffic loads, which differ in type and magnitude. Most of these bridges were built in 1960’s under design traffic load, which reflects the traffic conditions of those times. However, the number and weight of vehicles in traffic have increased since then too much in comparison to today. As a result these bridges are loaded more than their designed traffic loads and hence bridges' fatigue lives are shorten. As a remedy for this issue, thicknesses of fatigue sensitive structural parts of bridge shall be determined under today' s valid wheel loads and design category for desired fatigue life. In the scope of this study the traditional steel orthotropic highway bridge is analyzed using a FE- model, which encompasses bridge' s entire geometry. The traffic load is selected so conservatively, that it is composed of static wheel loads and wheel load area, which comply with the wheels of vehicles used today in traffic. Subsequently, fatigue lives of four fatigue sensitive structural parts of bridge are calculated. These are critical section in web of cross girder due to cut outs, weld connecting deck plate to trapezoidal rib, continuous longitudinal stringer and deck plate. Finally, required thicknesses and spans of these structural parts depending on their fatigue lives and design categories are given.

Abdullah Fettahoglu

2013-09-01

333

A study on fretting fatigue life in elevated temperature for Inconel 600 alloy  

Energy Technology Data Exchange (ETDEWEB)

The safety needs in the operation of nuclear power plant facilities have been increased due to the high temperature and pressure operation conditions within these facilities. Several reports exist on the fretting occurring in the materials of steam generator tubes used in nuclear power plants, which leads to a lower service life. The Inconel 600 alloy, used in steam generator tubes, is a type of nickel-chromium based heat resistant alloy. However, it is necessary to establish a systematic database to guarantee its integrity because there are few data indicating fretting fatigue behaviors at both room and high temperature conditions for the Inconel 600 alloy. Thus, this study analyzed the change in the fatigue characteristics of the Inconel 600 alloy under fretting fatigue by applying plain and fretting fatigue tests at 320 .deg. C, which is the room and actual operating temperature applied to the materials of steam generator tubes. In addition, this study measured the change in the friction force for repetitive cycles in fretting fatigue tests and analyzed the mechanism of fretting fatigue by observing the fracture surfaces.

Park, D. K. [Korea Textile Machinery Research Institute, Kyongsan (Korea, Republic of); Woo, S. W.; Yoon, D. H.; Jeung, H. K.; Chung, I. S.; Kwon, J. D. [Yeunganm University, Kyongsan (Korea, Republic of)

2009-07-01

334

A study on fretting fatigue life in elevated temperature for Inconel 600 alloy  

International Nuclear Information System (INIS)

The safety needs in the operation of nuclear power plant facilities have been increased due to the high temperature and pressure operation conditions within these facilities. Several reports exist on the fretting occurring in the materials of steam generator tubes used in nuclear power plants, which leads to a lower service life. The Inconel 600 alloy, used in steam generator tubes, is a type of nickel-chromium based heat resistant alloy. However, it is necessary to establish a systematic database to guarantee its integrity because there are few data indicating fretting fatigue behaviors at both room and high temperature conditions for the Inconel 600 alloy. Thus, this study analyzed the change in the fatigue characteristics of the Inconel 600 alloy under fretting fatigue by applying plain and fretting fatigue tests at 320 .deg. C, which is the room and actual operating temperature applied to the materials of steam generator tubes. In addition, this study measured the change in the friction force for repetitive cycles in fretting fatigue tests and analyzed the mechanism of fretting fatigue by observing the fracture surfaces.

2009-04-23

335

The effects of sheet spacing on the fatigue life of spot­welded joints  

Directory of Open Access Journals (Sweden)

Full Text Available While investigating the fatigue strength of spot-welded joints, the effects of sheet spacing or gap amounts between sheet joints may be considered as one of the most important parameters on the fatigue life duration of the joints. The main goal of the present work is to study the influence of sheet spacing on the fatigue life of 5083-O aluminium alloy spot welded tensile-shear joints. The amounts of sheet spacing are the average values over three measurements of photograph observation of the cut-off surfaces from the nugget centre of the spot-welded joints. The amounts of gap distances between spot weld sheet joints for three different electrode clamping force levels were 0.09mm, 0.11mm and 0.13mm, respectively. The values of notch strength reduction factors have been obtained at all levels of applied loads based on volumetric approach. The fatigue lives of spot welded joints have been obtained according to the volumetric method using the notch strength reduction factors and the available smooth S-N curve of 5083-O aluminium alloy sheets. The results based on the volumetric approach have been compared with the experimental fatigue test data and there is good agreement between numerical predictions and experimental results.

Esmaeili F.

2010-06-01

336

Quality of life in patients with multiple sclerosis: the impact of fatigue and depression.  

Science.gov (United States)

Quality of Life (QOL) is impaired in multiple sclerosis (MS) in part due to physical disability. MS-associated fatigue (MSF) and depression (MSD) are common and treatable features of MS, which could also impact on QOL, independent of physical disability. We prospectively studied 60 consecutive patients with MS. QOL was assessed using Multiple Sclerosis Quality of Life (MSQOL)-54. Group differences in QOL scores were assessed after adjusting for Expanded Disability Status Scale (EDSS), Fatigue Severity Scale (FSS) and Hamilton Depression Inventory scores. MS patients were grouped into relapsing-remitting (RR) or secondary-progressive (SP), MSF (FSS> or =5) or MS-nonfatigue (MSNF) (FSS< or =4), and MSD or MS-nondepression (MSND). After accounting for disability and depression, fatigue was associated with impaired QOL with respect to health perception (p=0.03) and limitations due to physical dysfunction (p=0.008). After accounting for disability and fatigue, depression was associated with lower QOL with respect to health perception (p=0.02), sexual dysfunction (p=0.03), health distress (p=0.03), mental health (p=0.006), overall QOL (p=0.006), emotional dysfunction (p=0.04), and limitations due to emotional dysfunction (p=0.03). This study demonstrates that fatigue and depression are independently associated with impaired QOL in MS, after accounting for physical disability, suggesting that their recognition and treatment can potentially improve QOL. PMID:12409184

Janardhan, Vallabh; Bakshi, Rohit

2002-12-15

337

Complex System Models used in the Automobile Clutch Release Bearing Fatigue Life Studies  

Directory of Open Access Journals (Sweden)

Full Text Available According to the system engineering point of view, any kind of technical product, regardless of the size and complexity of its structure are how a system should achieve the intended technical process and in this process relies on the input and output into contact with the outside world. Any mechanical system\\should be achieved economically task book the required technical capabilities and maintain the safety of people and the environment as part of its general goal to pursue. Regardless of economic feasibility, technical capabilities alone to achieve the target will lose mechanical practical value. In the automotive power transmission process, the role of the clutch release bearing by means of the axial displacement of the bearing to connect or disconnect the power transmission between the transmission and the engine, thus completing the smooth start the car, suspended and transform operations such gear. Automobile clutch release bearings are vital parts clutch parts of the merits of its performance, the car's handling performance vehicle has great influence. Release bearing fatigue life analysis is based on the bearing rings or rolling fatigue spalling began to appear, a phenomenon with exposure to cyclic stress related. Rolling elastic contact between components belong, the contact stress analysis methods used in the past experience or simple analytical method. In this study, bearing materials, lubricants, sealing structure, fatigue life test and simulate working conditions failure data processing methods have raised new research content, by establishing a new release bearing fatigue life model for complex systems, the introduction of the smelting process, the surface defect, roughness, residual stress, EHL oil film, environmental cleanliness, temperature, variable load characteristics And other factors that affect the fatigue life. The results showed that: release bearing new life prediction model is closer to the actual condition clutch for further study a new generation of high- speed heavy automobile clutch release bearings provide a theoretical support.

Guoliang Chen

2013-01-01

338

Defective pipeline fatigue-life prediction using failure assessment diagram technique  

Energy Technology Data Exchange (ETDEWEB)

Pipeline fatigue life prediction can be used to identify appropriate inspection, repair and replacement cycles for in-service pipelines. This paper described a failure assessment diagram (FAD) technique that was used to calculate toughness and load ratios. Full-scale pipe fatigue tests were conducted on an X60 pipeline in China. Clip extensimeter and galvanostat crack testers were calibrated to ensure crack measuring accuracy. Rounded grinder equipment was used to cut the outer surface of the test pipe along the axial direction. A knife was used to cut the bottom of the defect. A half-elliptical crack was then formed in the middle of the pipe. The test included measurements for depth-length ratios, maximum depth, surface length, loading frequency, loading waveform, stress rates, and environmental temperatures. Macroscopic fatigue fracture surfaces were then analyzed. Results showed that the crack grew along the crack depth orientation and remained unchanged along the crack length orientation. The crack propagated by increment of 3.7 mm in depth during the initial stages of the test. After 7700 cycles, crack growth accelerated. Leak failure occurred after 8000 cycles with an increment of 5.6 mm in depth. Results of the test were then used to create a finite element model (FEM). Paris crack fatigue growth expressions were used to predict the remaining fatigue life of the pipeline. Toughness ratios and load ratios were calculated repeatedly for every crack increment in the model. A comparison between results obtained during further testing showed that the FAD method is capable of predicting fatigue life. 5 refs., 6 figs.

Jinheng, L.; Xinwei, Z.; Qingren, X.; Chunyong, H. [Xi' an Jiaotong Univ., Xi' an (China). Key Laboratory for Mechanical and Environmental Behavior of Tubular Goods

2004-07-01

339

Creep-fatigue life assessment of cruciform weldments using the linear matching method  

International Nuclear Information System (INIS)

This paper presents a creep-fatigue life assessment of a cruciform weldment made of the steel AISI type 316N(L) and subjected to reversed bending and cyclic dwells at 550 °C using the Linear Matching Method (LMM) and considering different weld zones. The design limits are estimated by the shakedown analysis using the LMM and elastic-perfectly-plastic material model. The creep-fatigue analysis is implemented using the following material models: 1) Ramberg–Osgood model for plastic strains under saturated cyclic conditions; 2) power-law model in “time hardening” form for creep strains during primary creep stage. The number of cycles to failure N? under creep-fatigue interaction is defined by: a) relation for cycles to fatigue failure N? dependent on numerical total strain range ??tot for the fatigue damage ?f; b) long-term strength relation for the time to creep rupture t? dependent on numerical average stress ?¯ during dwell ?t for the creep damage ?cr; c) non-linear creep-fatigue interaction diagram for the total damage. Numerically estimated N? for different ?t and ??tot shows good quantitative agreement with experiments. A parametric study of different dwell times ?t is used to formulate the functions for N? and residual life L? dependent on ?t and normalised bending moment M-tilde , and the corresponding contour plot intended for design applications is created. -- Highlights: ? Ramberg–Osgood model is used for plastic strains under saturated cyclic conditions. ? Power-law model in time-hardening form is used for creep strains during dwells. ? Life assessment procedure is based on time fraction rule to evaluate creep damage. ? Function for cycles to failure is dependent on dwell period and normalised moment. ? Function for FSRF dependent on dwell period takes into account the effect of creep

2013-04-01

340

3-dimensional fatigue life evaluation for major components of nuclear power plant  

Energy Technology Data Exchange (ETDEWEB)

In general, major components of nuclear power plant have been evaluated based on 2-dimensional design codes conservatively. However, more exact assessment is necessary for continued operation beyond the design life. In this paper, 3-dimensional stress and fatigue analyses reflecting full geometry and monitored operating condition of reactor pressure vessel have been carried out. The analyses results showed that conservatism of current 2-dimensional evaluation based on design transient. Therefore, it is anticipated that the schemes developed from this research such as 3-dimensional finite element modeling, stress analysis and fatigue analysis related techniques can be utilized as fundamental tools for exact lifetime evaluation and license renewal of major nuclear components.

Ahn, Min Yong; Bae, Sung Ryul; Park, Young Jae; Chang, Yoon Suk; Choi, Jae Boong; Kim, Young Jin [Sungkyunkwan Univ., Suwon (Korea, Republic of); Jhung, Myung Jo; Choi, Young Hwan [KINS, Taejon (Korea, Republic of)

2004-07-01

 
 
 
 
341

Numerical Estimation of Fatigue Life of Wind Turbines due to Shadow Effect  

DEFF Research Database (Denmark)

The influence of tower design on damage accumulation in up-wind turbine blades during tower passage is discussed. The fatigue life of a blade is estimated for a tripod tower configuration and a standard mono-tower. The blade stresses are determined from a dynamic mechanical model with a delay effect included in the normal coefficient used to compute the transverse load. Furthermore, the rotational effect of the turbulence spectrum is included in the model. The proposed tripod configuration of the tower limits the damage accumulation in the turbine blades significantly when compared to the fatigue of a blade from a monotower wind turbine.

Thoft-Christensen, Palle; Pedersen, Ronnie

2009-01-01

342

Fatigue life prediction of a cable harness in an industrial robot using dynamic simulation  

Energy Technology Data Exchange (ETDEWEB)

The cable which transfers the signal and power in an industrial robot has a problem of fatigue fracture like steel components. Since the cable is very flexible compared to other components of the system, it is difficult to estimate its motion numerically. Some studies have been done on a large deformation problem, especially in a cable, and a few attempts have been made to apply the absolute nodal coordinate formulation (ANCF), which can simulate a large deformation. Only researches about the fatigue life of structural cables or comparative studies of FEM and ANCF simulations can be found. This paper presents a method to simulate the behavior of the cable harness using the ANCF and to predict the fatigue life while computing the strain time history of the point of interest. Rigid body dynamics is applied for the robot system, while ANCF is used for the cable harness. The simulation is performed by using the dynamic analysis process. The material property of the cable is obtained by a test. A simplified model is prepared. With these data, the behavior of the cable is simulated and the fatigue life is predicted

Yoon, Ji Won; Park, Tae Won [Ajou University, Suwon (Korea, Republic of); Yim, Hong Jae [Kookmin University, Seoul (Korea, Republic of)

2008-03-15

343

Microstructure-based fatigue life prediction for cast A356-T6 aluminum-silicon alloys  

Science.gov (United States)

Fatigue life prediction and optimization is becoming a critical issue affecting the structural applications of cast aluminum-silicon alloys in the aerospace and automobile industries. In this study, a range of microstructure and porosity populations in A356 alloy was created by controlling the casting conditions and by applying a subsequent hot isostatic pressing (“hipping”) treatment. The microstructure and defects introduced during the processing were then quantitatively characterized, and their effects on the fatigue performance were examined through both experiment and modeling. The results indicated that whenever a pore is present at or near the surface, it initiates fatigue failure. In the absence of large pores, a microcell consisting of ?-Al dendrites and associated Si particles was found to be responsible for crack initiation. Crack initiation life was quantitatively assessed using a local plastic strain accumulation model. Moreover, the subsequent crack growth from either a pore or a microcell was found to follow a small-crack propagation law. Based on experimental observation and finite-element analysis, a unified model incorporating both the initiation and small crack growth stages was developed to quantitatively predict the dependency of fatigue life on the microstructure and porosity. Good agreement was obtained between the model and experiment.

Yi, J. Z.; Gao, Y. X.; Lee, P. D.; Lindley, T. C.

2006-04-01

344

Thermal fatigue life prediction based on crack propagation behaviors in high-temperature materials for power plant components  

International Nuclear Information System (INIS)

For reducing an electric power supply cost, it is desired to extend the life of thermal power plant being still supplying the greater part of electric power in Japan. It is, therefore, becoming more and more important for the remaining life control of long-operated thermal power plants to exactly estimate the thermal fatigue damage accumulating in high temperature components. In this report, a discussion was made on thermal fatigue life laws derived from the crack propagation laws. As a result, the life laws were found to be effective for the evaluation of thermal fatigue life as well as isothermal fatigue life. Based on the concept of the life laws, the thermal and isothermal fatigue lives were also predicted as a propagation period of a crack with initial length equal to grain size from the characteristics of high temperature fatigue crack propagation. In addition to them, the rapid straining method was found to be required for more accurate estimation of creep strain in in-phase thermal fatigue. (author)

1986-01-01

345

The Study of Contact Pressure Analyses and Prediction of Dynamic Fatigue Life for Linear Guideways System  

Directory of Open Access Journals (Sweden)

Full Text Available The application of the linear guideways is very extensive, such as automation equipment, heavy-duty carry equipment, heavy-cut machining tool, CNC grinding machine, large-scale planning machine and machining center with the demand of high rigidity and heavy load. By means of the study of contact behavior between the roller/guideway and roller/slider, roller type linear guideways can improve the machining accuracy. The goal of this paper is to construct the fatigue life model of the linear guideway, with the help of the contact mechanics of rollers. In beginning, the analyses of the rigidity of a single roller compressed between guideway and slider was conducted. Then, the normal contact pressure of linear guideways was obtained by using the superposition method, and verified by the FEM software (ANSYS workbench. Finally, the bearing life theory proposed by Lundberg and Palmgren was used to describe the contact fatigue life.

Thin-Lin Horng

2013-05-01

346

Fatigue life prediction for wind turbines: A case study on loading spectra and parameter sensitivity  

Science.gov (United States)

Wind turbines are fatigue-critical machines used to produce electrical energy from the wind. These rotating machines are subjected to environmental loadings that are highly irregular in nature. Historical examples of fatigue problems in both research and commercial wind turbine development are presented. Some example data on wind turbine environments, loadings and material properties are also shown. Before a description of how the authors have chosen to attack the cumulative damage assessment, questions are presented for the reader's reflection. The solution technique used by the authors is then presented, followed by a case study applying the procedures to an actual wind turbine blade joint. The wind turbine is the 34-meter diameter vertical axis wind turbine (VAWT) erected by Sandia National Laboratories near Bushland, Texas. The case study examines parameter sensitivities for realistic uncertainties in inputs defining the turbine environment, stress response and material properties. The fatigue lifetimes are calculated using a fatigue analysis program, called LIFE2, which was developed at Sandia. The LIFE2 code, described in some detail in an appendix, is a PC-based, menu-driven package that leads the user through the steps required to characterize the loading and material properties, then uses Miner's rule or a linear crack propagation rule to numerically calculate the time to failure. Only S-n based cumulative damage applications are illustrated here. The LIFE2 code is available to educational institutions for use as a case study in describing complicated loading histories and for use by students in examining, hands on, parameter sensitivity of fatigue life analysis.

Sutherland, H. J.; Veers, P. S.; Ashwill, T. D.

347

Low cycle fatigue behaviors of type 316LN austenitic stainless steel in 310 deg. C deaerated water-fatigue life and dislocation structure development  

Energy Technology Data Exchange (ETDEWEB)

The low cycle fatigue tests for type 316LN stainless steel were performed in 310 deg. C deaerated water at various strain amplitudes and strain rates. The primary hardening was observed in all test conditions. It was found that the increase of bulk dislocation density and the interaction between mobile dislocations and atoms, which occur under the dynamic strain aging condition, were responsible for the primary hardening. On the other hand, the secondary hardening occurred distinctly for 0.4%/s and 0.4%. For that specific condition, the corduroy contrast resulted from pinned dislocations was observed at the crack tip. The secondary hardening may be associated with the corduroy contrast. The dislocation structure and fatigue surface revealed the characteristic feature of the hydrogen-induced cracking. Thus, we concluded the hydrogen-induced cracking contributed to the reduction in fatigue life and the enhancement of decreasing fatigue life with a decreasing strain rate in 310 deg. C deaerated water.

Cho, Hyunchul [Department of Nuclear and Quantum Engineering, Korea Advanced Institute of Science and Technology, 373-1 Guseong-dong, Yuseong-gu, Daejeon 305-701 (Korea, Republic of); Kim, Byoung Koo [Department of Nuclear and Quantum Engineering, Korea Advanced Institute of Science and Technology, 373-1 Guseong-dong, Yuseong-gu, Daejeon 305-701 (Korea, Republic of); Corporate R and D Institute, Doosan Heavy Industries and Construction Co. Ltd., 555 Gwigok-dong, Changweon, Gyeongnam 641-792 (Korea, Republic of); Kim, In Sup [Department of Nuclear and Quantum Engineering, Korea Advanced Institute of Science and Technology, 373-1 Guseong-dong, Yuseong-gu, Daejeon 305-701 (Korea, Republic of); Jang, Changheui [Department of Nuclear and Quantum Engineering, Korea Advanced Institute of Science and Technology, 373-1 Guseong-dong, Yuseong-gu, Daejeon 305-701 (Korea, Republic of)], E-mail: chjang@kaist.ac.kr

2008-03-15

348

Friction grip enclosure: a means for increasing the fatigue life of fuel rod end welds. LWBR Development Program  

International Nuclear Information System (INIS)

A friction grip enclosure was developed to increase the fatigue life of end welds in the LWBR fuel rods. This report describes the friction grip enclosure design concept and provides a sample analysis to illustrate the design application procedure. A cyclic proof test, performed to verify the fatigue performance of the friction grip enclosure, is also described. Adequate fatigue performance was demonstrated for the LWBR end welds when subjected to the maximum expected cyclic loads during LWBR operation

1983-01-01

349

Fatigue life prediction in a unidirectional glass-epoxy composite material subjected to off-axis cyclic loads  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Most of today s fatigue analysis and design methods for composite laminates were developed primarily on the basis of experience with homogeneous metals. Such methods are subject to serious drawbacks, however, because the failure the modes of failure observed in metals. A theoretical model for predicting the fatigue life of continuous glass-fibre/epoxy composite materials under general loading conditions has been developed on the basis of fundamental fatigue failure modes and local failure cri...

Revuelta, D.

2005-01-01

350

The Prevalence of Fatigue Following Deep Brain Stimulation Surgery in Parkinson's Disease and Association with Quality of Life  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Fatigue is a common and disabling nonmotor symptom seen in Parkinson's disease (PD). While deep brain stimulation surgery (DBS) improves motor symptoms, it has also been associated with non-motor side effects. To date no study has utilized standardized instruments to evaluate fatigue following DBS surgery. Our objective was to determine the prevalence of fatigue following DBS surgery in PD its impact on quality of life and explore predictive factors. We recruited 44 PD subjects. At least one ...

2012-01-01

351

Rolling-element fatigue life of AISI M-50 and 18-4-1 balls  

Science.gov (United States)

Rolling element fatigue studies were conducted with AISI M-50, EFR 18-4-1, and VAR 18-4-1. Groups of 12.7 mm (1/2-in) diameter balls of each material were tested in the five ball fatigue tester. Test conditions included a load of 1540 N (347 lbf) giving a maximum Hertz stress of 5520 MPa (800 000 psi), a shaft speed of 10,700 rpm, and a contact angle of 30 deg. Tests were run at a race temperature of 339 K (150 F) with a type 2 ester lubricant. The rolling element fatigue life of AISI M-50 was not significantly different from that of EFR 18-4-1 or VAR 18-4-1 based on a statistical comparison of the test results.

Parker, R. J.; Zaretsky, E. V.

1978-01-01

352

Creep-fatigue life property of FBR high-temperature structural materials under tension-torsion loading and life evaluation method  

International Nuclear Information System (INIS)

Creep-fatigue damage in high temperature structural components in a FBR progress under multiaxial stress condition depending on their operating conditions and configuration. Therefore, multiaxial stress effects on creep-fatigue damage evolution must be clarified to make precise creep-fatigue damage evaluation of these components. In this study, creep-fatigue tests in FBR high temperature materials such as SUS304, 316FR stainless steels and a modified 9Cr steel were conducted under biaxial stress subjecting tension-compression and torsion loading, in order to examine biaxial stress effects on failure mechanism and life property, and to discuss creep-fatigue life evaluation methods under biaxial stress. Main results obtained in this study are summarized as follows: 1. The main cracks under cyclic torsion loading propagated by shear mode in three materials. But intergranular failure was occurred in SUS304 and 316FR, and transgranular failure was observed in Mod.9Cr steel. 2. Nonlinear damage accumulation model proposed based on uniaxial creep-fatigue test results was extended to apply for creep-fatigue damage evaluation under biaxial stress state by considering the biaxial stress effects on fatigue and creep damage evolution. 3. It was confirmed that creep-fatigue life under biaxial stress could be predicted by the extended evaluation method with higher accuracy than existing methods. (author)

1994-04-01

353

Fatigue life prediction for high-heat-load components made of GlidCop by elastic-plastic analysis.  

Science.gov (United States)

A procedure to predict the fatigue fracture life of high-heat-load components made of GlidCop has been successfully established. This method is based upon the Manson-Coffin equation with a cumulative linear damage law. This prediction was achieved by consolidating the results of experiments and analyses, and considered the effects of environment and creep. A low-cycle-fatigue test for GlidCop was conducted so that environment-dependent Delta(t)-N(f) diagrams for any temperature could be prepared. A special test piece was designed to concentrate the strain in a central area locally, resulting in the low-cycle-fatigue fracture. The experiments were carried out by repeatedly irradiating a test piece with an electron beam. The results of the experiment confirmed that the observed fatigue life was within a factor of two when compared with the predicted fatigue life, yet located on the safer side. PMID:18296780

Takahashi, Sunao; Sano, Mutsumi; Mochizuki, Tetsuro; Watanabe, Atsuo; Kitamura, Hideo

2008-03-01

354

Fatigue life evaluation under out-of-phase push-pull and torsion. Iso sa wo yusuru hippari asshuku-nejiri no kumiawase oryoku ka ni okeru hiro jumyo hyoka ni tsuite  

Energy Technology Data Exchange (ETDEWEB)

Fatigue tests are performed on a low carbon steel under combined push-pull and completely reversed torsion at room temperature, and the stress based evaluation parameters for the life in comparatively wide intermediate to high cycle region including fatigue threshold are investigated basing on the result of the tests. Under combined loadings, fatigue life becomes longer with the increase in phase difference. The equivalent stress including out-of-phase loadings, which is an extended Gough{prime}s equation, is simple and can be applied if the time strength ratio for each single stress is given, but the life is slightly overestimated. The equivalent stress which is a modified Lee criterion can make a comparatively accurate evaluation of the life under combined stress. The equivalent stress which is a Bronw-Miller{prime}s theory extended to the out-of-phase case can standardize the result of this test for the entire region of life. 23 refs., 14 figs., 1 tab.

Okawa, I.; Takahashi, H. (Hosei Univ., Tokyo (Japan). Faculty of Engineering); Tomaru, T. (Hosei Univ., Tokyo (Japan). Graduate School); Misumi, M. (Seikei Univ., Tokyo (Japan). Faculty of Engineering)

1991-11-15

355

Fatigue life improvement of ?-titanium by novel ultrasonically assisted technique  

International Nuclear Information System (INIS)

A new rotating pin ultrasonic peening (RPUP) technique is introduced providing near surface severe plastic deformation via repetitive impactions with simultaneous compressive and shear modes of high rate strain. The basic concept of the RPUP is described with special attention to the possible nanocrystallization mechanism. The superior fatigue behavior of the commercially pure titanium samples observed after RPUP is shown to be attributable to a number of beneficial features such as (i) residual compressive stresses, (ii) surface nano-structure, (iii) enhanced surface hardness and (iv) reduced surface roughness. X-ray diffraction (XRD) is used to analyze the grain/cell size, the lattice microstrain and residual stresses in the top surface layer. The surface nanostructure observed in ?-titanium at a depth of about 30 ?m and its gradual increase in size down to depth of about 100 ?m are characterized by means of transmission electron microscopy (TEM). The peak-to-valley magnitude dependence on the correlation of the compressive and shear strain modes during single impaction with RPUP has been shown using a two-dimensional finite element analysis by modeling a rigid high-velocity pin impacting an elasto-plastic surface

2006-11-15

356

Effect of beam oscillation on fatigue life of Ti-6Al-4V electron beam weldments  

International Nuclear Information System (INIS)

The present study deals with the effect of beam oscillation technique using elliptical waveform on fatigue life of Ti-6Al-4V electron beam weldments. Autogenous full penetration bead-on-plate electron beam welds were made with and without beam oscillation. Some welds were subjected to post-weld heat treatment (PWHT) at two different temperatures (700 and 900 deg. C). Room temperature hardness, tensile properties and fatigue life of the weldments in the as-welded and PWHT conditions were studied and correlated with the microstructure. The beam oscillated weldments exhibited lower strength (hardness) compared to those made without beam oscillation. This was attributed to wider diffusional ? plates in the beam oscillated welds due to lower cooling rates. The beam oscillated weldments exhibited inferior fatigue lives compared with unoscillated weldments owing to the presence of wider ? platelets in the former. As the width of ? platelets in the weldments subjected to PWHT at 700 deg. C was smaller than that in the weldments subjected to PWHT at 900 deg. C, they exhibited longer fatigue lives

2007-12-15

357

A Nonlinear Reduced Order Method for Prediction of Acoustic Fatigue  

Science.gov (United States)

The goal of this investigation is to assess the quality of high-cycle-fatigue life estimation via a reduced order method, for structures undergoing geometrically nonlinear random vibrations. Modal reduction is performed with several different suites of basis functions. After numerically solving the reduced order system equations of motion, the physical displacement time history is obtained by an inverse transformation and stresses are recovered. Stress ranges obtained through the rainflow counting procedure are used in a linear damage accumulation method to yield fatigue estimates. Fatigue life estimates obtained using various basis functions in the reduced order method are compared with those obtained from numerical simulation in physical degrees-of-freedom.

Przekop, Adam; Rizzi, Stephen A.

2006-01-01

358

Fatigue life improvement factors obtained by weld reinforcement and toe grinding  

Energy Technology Data Exchange (ETDEWEB)

The potential of weld reinforcement and toe grinding techniques for improving the fatigue life of welded joints protected from seawater corrosion is quantified based on tests performed in air on welded plate specimens. Results are presented in terms of median fatigue life improvement factors and prediction intervals obtained by linear regression analysis. The significant improvements possible with weld reinforcement are shown to be caused partly by a slight alleviation of the stress concentration imposed by sharp angles at the weld toe. Variable improvements observed for toe ground welds are shown to be associated with the variable surface modifications which different tools impose on weld toes. Load and weld geometry are shown to be particulary important when bending stresses are applied to the weld toe, since reinforcement affects the bending moment at the toe section and toe grinding affects the conditions at the highly stressed outer fibers. 14 references.

Mullen, C.L.; Merwin, J.E.

1982-01-01

359

Fatigue properties of inconel 718 in long life region at elevated temperature  

Energy Technology Data Exchange (ETDEWEB)

The fatigue properties of Inconel 718 in long life region up to 10{sup 8} cycles were investigated under rotating bending at room temperature and 500 C. The early propagation of a crack was suppressed by oxide induced crack closure. Consequently, fatigue strength was higher at 500 C than at room temperature. Surface fracture occurred at high stress levels and internal fracture occurred in long life region beyond 10{sup 7} cycles at 500 C. Correspondingly, S-N curve at 500 C presented in a step-wise shape, compared to the conventional one-step shape at room temperature. Intergranular cracking was observed at the origins of internal fracture at 500 C. (orig.)

Yan, N.; Kawagoishi, N.; Chen, Q.; Kondo, E. [Faculty of Engineering, Kagoshima Univ., Kagoshima (Japan); Wang, Q.Y. [Dept. of Civil Engineering and Mechanics, Sichuan Univ., Chengdu (China); Nisitani, H. [Faculty of Engineering, Kyushu Sangyo Univ., Higashi-ku, Fukuoka (Japan)

2003-07-01

360

A new approach for estimating fatigue life in offshore steel structures  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Miner’s rule is generally accepted as the fatigue criteria for life estimation of existing offshore steel structures. Similarly, it has always been acknowledged as a simplification that is easy to use in design where detailed loading history is unknown. But in the case of existing structures where the detailed loading history is known, Miner’s rule might provide incorrect results because of its omission of load sequence effect. Recently, a new damage indicator-based sequential law has bee...

Kajolli, Redion

2013-01-01

 
 
 
 
361

Fatigue life estimation for different notched specimens based on the volumetric approach  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In this paper, the effects of notch radius for different notched specimens has been studied on the values of stress concentration factor, notch strength reduction factor, and fatigue life duration of the specimens. The material which has been selected for this investigation is Al 2024T3 . Volumetric approach has been applied to obtain the values of notch strength reduction factor and results have been compared with those obtained from the Neuber and Peterson methods. Load controlled fat...

Zehsaz M.; Hassanifard S.; Esmaeili F.

2010-01-01

362

Fatigue life evaluation of A356 aluminum alloy used for engine cylinder head  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The studied material is an A356 Al alloy, used to produce engine cylinder heads for the automotive industry by die casting process. The material displays a quite coarse dendritic microstructure in a eutectic matrix, with a mean grains size of 25 microns, intemetallic precipitates and porosities. The tensile properties are strongly affected by testing temperature, with a quite sensitive drop of the Young's modulus, the Yield stress as the temperature was raised. The isothermal fatigue life dro...

Angeloni, Mauricio

2011-01-01

363

Prediction of Contact Fatigue Life of Alloy Cast Steel Rolls Using Back-Propagation Neural Network  

Science.gov (United States)

In this study, an artificial neural network (ANN) was employed to predict the contact fatigue life of alloy cast steel rolls (ACSRs) as a function of alloy composition, heat treatment parameters, and contact stress by utilizing the back-propagation algorithm. The ANN was trained and tested using experimental data and a very good performance of the neural network was achieved. The well-trained neural network was then adopted to predict the contact fatigue life of chromium alloyed cast steel rolls with different alloy compositions and heat treatment processes. The prediction results showed that the maximum value of contact fatigue life was obtained with quenching at 960 °C, tempering at 520 °C, and under the contact stress of 2355 MPa. The optimal alloy composition was C-0.54, Si-0.66, Mn-0.67, Cr-4.74, Mo-0.46, V-0.13, Ni-0.34, and Fe-balance (wt.%). Some explanations of the predicted results from the metallurgical viewpoints are given. A convenient and powerful method of optimizing alloy composition and heat treatment parameters of ACSRs has been developed.

Jin, Huijin; Wu, Sujun; Peng, Yuncheng

2013-12-01

364

Prediction of inelastic behavior and creep-fatigue life of perforated plates  

International Nuclear Information System (INIS)

Prediction methods of macroscopic and local stress-strain behaviors of perforated plates in plastic and creep regime are proposed in this paper, and are applied to the creep-fatigue life prediction of perforated plates. Both equivalent-solid-plate properties corresponding to the macroscopic behavior and the stress-strain concentration around a hole were obtained by assuming the analogy between plasticity and creep and also by extending the authors' proposal in creep condition. The perforated plates which were made of Hastelloy XR were subjected to the strain-controlled cyclic test at 950degC in air in order to experimentally obtain the macroscopic behavior such as the cyclic stress-strain curve and creep-fatigue life around a hole. The results obtained are summarized as follows. (1) The macroscopic behavior of perforated plates including cyclic stress-strain behavior and relaxation is predictable by using the proposed method in this paper. (2) The creep-fatigue life around a hole can be predicted by using the proposed method for stress-strain concentration around a hole. (author)

1992-12-01

365

Effect of shot peening on surface fatigue life of carburized and hardened AISI 9310 spur gears  

Science.gov (United States)

Surface fatigue tests were conducted on two groups of AISI 9310 spur gears. Both groups were manufactured with standard ground tooth surfaces, with the second group subjected to an additional shot peening process on the gear tooth flanks. The gear pitch diameter was 8.89 cm (3.5 in.). Test conditions were a gear temperature of 350 K (170 F), a maximum Hertz stress of 1.71 billion N/sq m (248,000 psi), and a speed of 10,000 rpm. The shot peened gears exhibited pitting fatigue lives 1.6 times the life of standard gears without shot peening. Residual stress measurements and analysis indicate that the longer fatigue life is the result of the higher compressive stress produced by the shot peening. The life for the shot peened gear was calculated to be 1.5 times that for the plain gear by using the measured residual stress difference for the standard and shot peened gears. The measured residual stress for the shot peened gears was much higher than that for the standard gears.

Townsend, D. P.; Zaretsky, E. V.

1982-01-01

366

Fatigue life of AISI 316L stainless steel welded joints, obtained by GMAW  

International Nuclear Information System (INIS)

An investigation has been conducted in order to determine the effect of both the metallic transfer mode (pulsed arc or short circuit) and the O2 content in the Ar/O2 gas mixture, of the gas-metal arc welding process (GMAW), on the fatigue life under uniaxial conditions of welded joints of 316L stainless. it has been concluded that the mixture of the protective gases employed in the process could have an important influence on the fatigue life of the welded joints of such steel in two different ways. firstly, through the modification of the radius of curvature at the joint between the welding tow and the base metal and, secondly, through a more pronounced degree of oxidation of the alloying elements induced by a higher O2 content in the mixture. As far as the metallic transfer mode is concerned, it has been determined that the welded joints obtained under a pulsed arc mode show a greater fatigue life in comparison with the joints obtained under short circuit for both gas mixtures. (Author) 25 refs

2007-01-01

367

Magnitude of fatigue in cancer patients receiving radiotherapy and its short term effect on quality of life  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Background : Fatigue is one of the most common, ongoing symptoms reported by patients undergoing radiotherapy and has profound effects on the quality of life. Aims : This study attempts to identify the magnitude of fatigue and its implication on the quality of life during radiotherapy. Methods and Materials : A prospective study was conducted from March 2004 to September 2005, on 90 patients with histologically proven cancer, receiving radiotherapy. Pretreatment and w...

Janaki M; Kadam Amrit; Mukesh S; Nirmala S; Ponni Arul; Ramesh B; Rajeev A

2010-01-01

368

The impact of disability, fatigue and sleep quality on the quality of life in multiple sclerosis  

Directory of Open Access Journals (Sweden)

Full Text Available Background: Only few papers have investigated the impact of multiple sclerosis (MS, especially MS-related fatigue and the impact of the quality of sleep on the quality of life (QoL in MS patients. Objective: The objective of this study was to measure the quality of life in MS patients and the impact of disability, fatigue and sleep quality, using statistical modeling. Materials and Methods: A cross-sectional study was conducted and data was collected from 141 MS patients, who were referred to the Mottahari Clinic, Shiraz, Iran, in 2005. Data on health-related quality of life (MSQoL-54, fatigue severity scale (FSS, and Pittsburgh sleep quality Index (PSQI were obtained in the case of all the patients. Epidemiology data concerning MS type, MS functional system score, expanded disability status scale (EDSS etc. were also provided by a qualified neurologist. Spearman a coefficient, Mann-Whitney U test, and linear regression model were used to analyze the data. Results : The mean ±SD age of 141 MS patients was 32.6±9.6 year. Thirty five (24.8% of them were male and the others were female. Eighty two (58.1% of the patients had EDSS score of ? 2, 36 (25.5% between 2.5 and 4.5, and 23 (16.3% ? 5. As per PSQI scores, two (1.4% of the patients had good sleep, 16 (11.3% had moderate sleep and 123 (87.2% had poor sleep. There was a significant high positive correlation between the quality of mental and physical health composite scores (r = 0.791, P < 0.001. There was a significant negative correlation between the quality of physical score and age (r = -0.88, P < 0.001, fatigue score (r = -0.640, P < 0.001, EDSS score (r = -0.476, P < 0.001 and PSQI (sleep quality r = -0.514, P < 0.000. Linear regression analysis showed that PSQI score, EDSS, and fatigue score were predictors in the model between the quality of physical score and covariates ( P < 0.001. Linear regression model showed that fatigue score and PSQI were predictors in the model between the quality of mental score and covariates ( P < 0.001. Discussion and Conclusion: In conclusion, it may be said that MS patients had poor and moderate quality of mental and physical health. The quality of life was impaired as seen by PSQI, EDSS, and FSS. It is our suggestion that these patients require the attention of health care professionals, to be observed for the need of possible psychological support.

Ghaem Haleh

2008-01-01

369

Prediction of creep-fatigue life by use of creep rupture ductility  

International Nuclear Information System (INIS)

It was clarified that tension strain hold reduced creep-fatigue life of many engineering materials in different degrees depending on material, temperature and test duration. However the reduction in the life due to holding for various durations could be correlated to the fraction of intergranular facets on fracture surfaces which was considered to be an index of the damage introduced during strain hold. This fraction of intergranular facets by creep-fatigue failure exhibited a direct relation to the creep rupture ductility of the material tested at the same temperature and for the same creep-fatigue life-time. From these results an empirical equation has been derived as follow; (? sub(epsilonsub(i)))/Dsub(c).(N sub(h sup(?))) = C, where ? sub(epsilonsub(i)) is inelastic strain range, Dsub(c) is the creep rupture ductility for the same duration as creep-fatigue life time, Nsub(h) is the creep-fatigue life under tension strain hold conditions, and ? and C are constants depending on the material and testing temperature. From the equation the life prediction is possible for a given inelastic strain range ? sub(epsilonsub(i)) if the constants ? and C, and Dsub(c) are known. The value of ? was found to be 0.62 and 0.74 for various austenitic stainless steels and NCF800 at 600 "0C and 700 "0C, respectively, and 0.69 for 1 1/4Cr-1/2Mo steel at 600 "0C. The value of C was found to be 0.50 and 0.59 for various austenitic stainless steels and NCF800 at 600 "0C and 700 "0C, respectively, and 0.49 for 1 1/4Cr-1/2Mo steel at 600 "0C. The creep rupture ductility Dsub(c) is available in the NRIM Creep Data Sheets up to 10"5 h for multi-heats of many kinds of heat resistant alloys. (author)

1985-01-01

370

The impact of regular physical activity on fatigue, depression and quality of life in persons with multiple sclerosis  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract Background The purpose of this study was to compare fatigue, depression and quality of life scores in persons with multiple sclerosis who do (Exercisers and do not (Non-exercisers regularly participate in physical activity. Methods A cross-sectional questionnaire study of 121 patients with MS (age 25–65 yr living in Queensland, Australia was conducted. Physical activity level, depression, fatigue and quality of life were assessed using the International Physical Activity Questionnaire, Health Status Questionnaire Short Form 36, Becks Depression Inventory and Modified Fatigue Impact Scale. Results 52 participants performed at least two 30-min exercise sessions·wk-1 (Exercisers and 69 did not participate in regular physical activity (Non-exercisers. Exercisers reported favourable fatigue, depression and quality of life scores when compared to Non-exercisers. Significant weak correlations were found between both leisure-time and overall reported physical activity levels and some subscales of the quality of life and fatigue questionnaires. Additionally, some quality of life subscale scores indicated that regular physical activity had a greater benefit in subjects with moderate MS. Conclusion Favourable fatigue, depression and quality of life scores were reported by persons with MS who regularly participated in physical activity, when compared to persons with MS who were classified as Non-exercisers.

Minahan Clare L

2009-07-01

371

A Study on the Unified Damage Model for Creep-Fatigue Interacted Life Prediction of Nickel-base Superalloy  

International Nuclear Information System (INIS)

A methodology for creep-fatigue interacted life prediction of nickel-base superalloy at high temperature is presented enabling the experimentally measured life to be compared with the model predictions. Continuum damage mechanics has been employed to determine the accumulation of damage during the deformation by means of the unified damage model, which is coupled with the material behavior analysis. Several types of low cycle fatigue test at high temperature have been carried out, and thus the effect of plastic strain range together with the relaxed stress to the life can be investigated. Good agreements between the interacted model's predictions and experimental data of the life were obtained

2007-11-02

372

Effect of double vacuum melting and retained austenite on rolling-element fatigue life of AMS 5749 bearing steel  

Science.gov (United States)

AMS 5749 steel combines the tempering, hot hardness, and hardness retention characteristics of AISI M-50 steel with the corrosion and oxidation resistance of AISI 440C stainless steel. The five-ball fatigue tester was used to evaluate the rolling-element fatigue life of AMS 5749. Double vacuum melting (vacuum induction melting plus vacuum arc remelting, VIM-VAR) produced AMS 5749 material with a rolling-element fatigue life at least 14 times that of vacuum induction melting alone. The VIM-VAR AMS 5749 steel balls gave lives from 6 to 12 times greater than VIM-VAR AISI M-50 steel balls. The highest level of retained austenite, 14.6 percent, was significantly detrimental to rolling-element fatigue life relative to the intermediate level of 11.1 percent.

Parker, R. J.; Hodder, R. S.

1977-01-01

373

The surface fatigue life of contour induction hardened AISI 1552 gears  

Science.gov (United States)

Two groups of spur gears manufactured from two different materials and heat treatments were endurance tested for surface fatigue life. One group was manufactured from AISI 1552 and was finished ground to a 0.4 micron (16 micro-in.) rms surface finish and then dual frequency contour induction hardened. The second group was manufactured from CEVM AISI 9310 and was carburized, hardened, and ground to a 0.4 micron (16 micro-in.) rms surface finish. The gear pitch diameter was 8.89 cm (3.5 in.). Test conditions were a maximum Hertz stress of 1.71 GPa (248 ksi), a bulk gear temperature of approximately 350 K (170 F) and a speed of 10,000 rpm. The lubricant used for the tests was a synthetic paraffinic oil with an additive package. The test results showed that the 10 percent surface fatigue (pitting) life of the contour hardened AISI 1552 test gears was 1.7 times that of the carburized and hardened AISI 9310 test gears. Also there were two early failures of the AISI 1552 gears by bending fatigue.

Townsend, Dennis P.; Turza, Alan; Chaplin, Mike

1995-01-01

374

A generalized fitting technique for the LIFE2 fatigue analysis code  

Energy Technology Data Exchange (ETDEWEB)

The analysis of component fatigue lifetime for a wind energy conversion system (WECS) requires that the component load spectrum be formulated in terms of stress cycles. Typically, these stress cycles are obtained from time series data using a cycle identification scheme. As discussed by many authors, the matrix or matrices of cycle counts that describe the stresses on a turbine are constructed from relatively short, representative samples of time series data. The ability to correctly represent the long-term behavior of the distribution of stress cycles from these representative samples is critical to the analysis of service lifetimes. Several techniques are currently used to convert representative samples to the lifetime cyclic loads on the turbine. There has been recently developed a set of fitting algorithms that is particularly useful for matching the body of the distribution of fatigue stress cycles on a turbine component. Fitting techniques are now incorporated into the LIFE2 fatigue/fracture analysis code for wind turbines. In this paper, the authors provide an overview of the fitting algorithms and describe the pre- and post-count algorithms developed to permit their use in the LIFE2 code. Typical case studies are used to illustrate the use of the technique.

Sutherland, H.J. [Sandia National Labs., Albuquerque, NM (United States). Wind Energy Research Dept.; Wilson, T. [Univ. of New Mexico, Albuquerque, NM (United States). New Mexico Engineering Research Inst.

1996-08-01

375

Reduction factors for creep strength and fatigue life of modified 9Cr-1 Mo steel weldments  

International Nuclear Information System (INIS)

This paper reports on the provisions of ASME B and PV code Case N-47 currently include reduction factors for creep strength and fatigue life of weldments. To provide experimental confirmation of such factors for modified 9 Cr-1 Mo steel, tests of tubular specimens were conducted at 538 degrees C (1000 degrees F). Three creep-rupture specimens with longitudinal welds were tested in tension; and, of three with circumferential welds, two were tested in tension and one in torsion. In each specimen with a circumferential weld, a nonuniform axial distribution of strain was easily visible. The test results were compared to an existing empirical model of creep-rupture life. For the torsion test, the comparison was based on a definition of equivalent normal stress recently adopted in code Case N-47. some 27 fatigue specimens, with longitudinal, circumferential, or no welds, were tested under axial or torsional strain control. In specimens with welds, fatigue cracking initiated at fusion lines. In axial tests cracks grew in the circumferential direction, and in torsional tests cracks grew along fusion lines

1991-01-01

376

One-Year Longitudinal Study of Fatigue, Cognitive Functions, and Quality of Life After Adjuvant Radiotherapy for Breast Cancer  

International Nuclear Information System (INIS)

Purpose: Most patients with localized breast cancer (LBC) who take adjuvant chemotherapy (CT) complain of fatigue and a decrease in quality of life during or after radiotherapy (RT). The aim of this longitudinal study was to compare the impact of RT alone with that occurring after previous CT on quality of life. Methods and Materials: Fatigue (the main endpoint) and cognitive impairment were assessed in 161 CT-RT and 141 RT patients during RT and 1 year later. Fatigue was assessed with Functional Assessment of Cancer Therapy-General questionnaires, including breast and fatigue modules. Results: At baseline, 60% of the CT-RT patients expressed fatigue vs. 33% of the RT patients (p <0.001). Corresponding values at the end of RT were statistically similar (61% and 53%), and fatigue was still reported at 1 year by more than 40% of patients in both groups. Risk factors for long-term fatigue included depression (odds ratio [OR] = 6), which was less frequent in the RT group at baseline (16% vs. 28 %, respectively, p = 0.01) but reached a similar value at the end of RT (25% in both groups). Initial mild cognitive impairments were reported by RT (34 %) patients and CT-RT (24 %) patients and were persistent at 1 year for half of them. No biological disorders were associated with fatigue or cognitive impairment. Conclusions: Fatigue was the main symptom in LBC patients treated with RT, whether they received CT previously or not. The correlation of persistent fatigue with initial depressive status favors administering medical and psychological programs for LBC patients treated with CT and/or RT, to identify and manage this main quality-of-life-related symptom.

2011-11-01

377

Fatigue life predictions of friction stir welded joints by using fracture mechanics methods  

Energy Technology Data Exchange (ETDEWEB)

The deterioration of the airframe due to fatigue loading and corrosion attack should be monitored by scheduled periodic inspections to assure the appropriate detection of the damaged area. In the present investigation an exploratory test program has been carried out to improve the general understanding of the fatigue behaviour of undamaged and corrosion damaged joints. Also the sequence effects in FSW joints are studied. The aim is to offer a basis both for a better experimental documentation as well as for an evaluation of existing crack propagation prediction models. Moreover specifically existent fracture mechanics principles are applied to friction stir welded structures. The objective is to elaborate an easy, practical and reliable engineering approach to perform life predictions of friction stir welded structures under in-service loading and in the presence of corrosion attack.

Ghidini, T.

2006-07-01

378

Analysis of fretting fatigue in aircraft structures: Stresses, stress intensity factors, and life predictions  

Science.gov (United States)

Clamped contacts subjected to cyclic loading are prone to fretting fatigue, a mechanism of crack nucleation and propagation. In aircraft, fretting fatigue occurs at the rivet/hole interface on the fuselage skin and at the dovetail joint in engine hardware where disk and blade meet. The ability to predict the lives of such components would be a great aid in preventing failures. Finite element models appropriate for the calculation of fretting fatigue stresses and stress intensity factors are developed for two different contact geometries. In addition, several less computationally expensive numerical methods are also studied. Agreement between the various solutions is good. A severe increase in the mode I stress intensity factor near the surface is discovered in both geometries. Mode II stress intensity factors are also detailed, illustrating the complex non-proportional loading of fretting-induced cracks. A comparison is made between results obtained from actual surface profiles and those generated from prescribed surface profiles; the differences are significant. Equivalent initial flaw sizes are calculated for two different metals using an approach which ignores the effect of mode II stress intensity factors. Life predictions based on the equivalent initial flaw size approach are found to agree reasonably well with those measured in the laboratory for contact geometries similar to the rivet/hole interface. More data is needed before a judgment can be made about life correlations for the dovetail joint contact geometry. The analysis methods described throughout can be easily implemented and integrated into a system aimed at designing against fretting fatigue.

McVeigh, Pamela Alison

379

Utilization of fatigue life prediction by means of experimental stress analysis methods for the determination of exploitation of the portal gantry cranes  

Directory of Open Access Journals (Sweden)

Full Text Available The paper deals with assessment of fatigue life of heavy load-carrying steel structures of the portal gantry cranes by means of experimental stress analysis methods. Fatigue life prediction has an influence upon the determination of exploitation of the portal gantry cranes. The description of measuring methods and measuring chain are presented. There is demonstrated practical application of utilization of fatigue life calculations based on Nominal Stress Analysis (NSA.

Peter Sivak

2007-03-01

380

Fatigue Behavior of Inconel 718 TIG Welds  

Science.gov (United States)

Mechanical behavior of reference and TIG-welded Inconel 718 specimens was examined in the present work. Tensile, constant amplitude fatigue, and fracture toughness tests were performed in ambient temperature for both, reference and welded specimens. Microstructure revealed the presence of coarse and fine-grained heat-affected zones. It has been shown that without any post-weld heat treatment, welded specimens maintained their tensile strength properties while their ductility decreased by more than 40%. It was found that the welded specimens had lower fatigue life and this decrease was a function of the applied fatigue maximum stress. A 30% fatigue life decrease was noticed in the high cycle fatigue regime for the welded specimens while this decrease exceeded 50% in the low cycle fatigue regime. Cyclic stress-strain curves showed that Inconel 718 experiences a short period of hardening followed by softening for all fatigue lives. Cyclic fatigue response of welded specimens' exhibited cyclically stable behavior. Finally, a marginal decrease was noticed in the Mode I fracture toughness of the welded specimens.

Alexopoulos, Nikolaos D.; Argyriou, Nikolaos; Stergiou, Vasillis; Kourkoulis, Stavros K.

2014-05-01