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Plasticity and fatigue damage modeling of severely loaded tubing
=s transferred to the uncracked layer as the crack grows. This reduces the stress intensity and slows the crack-growth rate The model ~s used to analyse tests performed on a section of a wing spanw=se lap Joint (7075 AI) The crack was initiated at a rivet and grown under constant-amphtude cyclic loads Both experimentally observed crack-growth rates and the analysJs show the retardation that occurs as a result of load transfer between layers A good correlation ts obtained between predicted and observed crack-growth rates for the fully developed throughthickness crack
On t h e prediction o f t h e f a t i g u e propagation of semi-elliptical defects.
Soboyejo, W.O. Proc. Conf. Advances in Fatigue Lifetime Predictive Techniques, San Francisco, California, USA, 24 Apr. 1990 4 3 5 - 4 4 8 The ~mphcatmns of the results of recent experimental and numerical investigations of the propagation of single and muittpie configurations of semf-e)hptlca) cracks (in QIN steel) are assessed for the predict=on of fatigue hfe tn structures and components in service. Simphfied methodologies for the assessment of the effects of crack closure and stress state on the propagation charactensttcs of seml-ellipt~cel cracks are proposed, and numerrcal techmques for the analys~s of coplanar and noncopianar configurations of seml-elhptmal cracks are also presented. These include the results of fimte element and simplified fracture mechanics analyses m which crack growth was computed on a step-by-step basis from the Pans equation
Life prediction o f c i r c u m f e r e n t i a l l y grooved components under l o w cycle fatigue. Hatanaka, K., Fu/imitsu, T., Omori, J. and Shiraishi, S.
Proc, Conf. Advances in Fatigue Lifetime Predictive Techniques, San Francisco, California, USA, 24 Apr. 1990 402-421 Stress-strata response was analysed m the cross-section of circumferentlally notched components by the finite element method. Then, the cyclic J-integral range, J, was estimated for the semi-elliptical surface crack and for the cprcumferential crack. The growth rate of the surface crack was successfully plotted against the estimated, JintegraJ range under low-cycle fatigue loading Furthermore, the transition from the seml-elhptlcal surface crack to the mrcumferentiaf crack, which Occurred in the fatigue crack growth process in the acutety notched cylindrical component, was reasonably analysed in terms of elastic-plastic fracture mechanics. Finally, the lowcycle fatigue hves of the dully and acutely notched cyhndrtcal components were satlsfactordy eva~uated through the analysis of the growth of the surface and circumferenttal cracks (for $35C steel)
Nonproportional fatigue of w e l d e d structures. Siljander, A , Kurath, P and Lawrence, F.V. Jr. Proc. Conf. Advances m Fatigue Lifetime Predictive Techniques, San Francisco, California, USA, 24 Apr. 1990 3 1 9 - 3 3 8 Rending and shearing stresses in many structures are out of phase, A typical example is the evaluation of a fixed positron m a bridge beam as a moving load crosses tt. Tradttlonal fattgue design approaches for welded structural details are generally based on in-phase laboratory data Thus the effect of non-proportional stress histories on the fatigue life of welded structural details is usually not considered. Stress-reheved tube-to-plate (A519 to A36) weldments were subjected to multlaxlal in-phase and out-of-phase stress states using combinations of bending and torsmn. The fatigue test results were evaluated using three local stress-damage criteria modified for multlaxlal loading. Finite element techniques were used to calculate the local stresses and stratus The local shear-stress-based approach of Ftndley provided the best correlatpon of all test data for the loading paths considered. The unique aspects of non-proportional loading are reflected by the Fmdley model fatigue damage calculations, and the test data were correlated to within a factor of two Since the scatter in the experimental data was also a factor of two for identical tests, further improvements m predmtive abihty are not possible. Also, the predicted direction of fatigue damage for the Findley model comctded with surface cracking characteristics Failure modes in a Type 316 stainless steel u n d e r biaxial strain cycling.
Zamrik, S.Y., Davis, D.C. and Kulowitch, P.J. Proc. Conf. Advances in Fatigue Lifetime Predictive Techniques, San Francisco, California, USA, 24 Apr. 1990 2 9 9 - 3 1 8 Discussed are the failure modes observed m a Type 316 stemless steel under biaxlal high-temperature low-cycle fatigue (HTLCF) and creep-fattgue strain cycling. All tests were carned OUt in air at 621 °C using thin-walled tubular type specimens specially designed for axial, torsional, and combined axial-torsmnal (btaxisl) cyclic Ioadlngs Results from HTLCF and creep-fatigue tests at six different blaxiahW ratios (~ - ~xy/~xx), 0 0, 1 0, 2 0, 2.5, 3.6, and infinity, are g~ven. At these b=axiality ratios, crack initiation in HTLCF is a shear process and crack propagation occurs mainly in a normal mode. With the introduction of creep through a comb=ned inphase tensile-torsional hold-time imposed on the blaxlal HTLCF cycle, the direction of the crack propagation was found to be dominated by the axial creep-fatigue component These results are compared with some multlaxral fatigue strain-based failure criteria S m a l l crack growth in m u l t i a x i a l fatigue. Reddy, S.C. and Fatemi, A.
Electric-potential-drop studies of fatigue crack development in tensileshear s p o t w e l d s . Swellam, M.H., Kurath, P. and Lawrence, F.V. Proc. Conf. Advances in Fatigue Lifetime Predictive Techniques, San Francisco, California, USA, 24 Apr. 1990 383-401 The development of fatigue cracks m galvamzed Iow-cerbon and high-strength-lowalloy steel, tensile-shear-spot weldments was mvestigated using a d.c. electricalpotential-drop techmque which sensed the depth of fatigue cracks as they propagated through the thtckness of the specimens. These reststlVlW changes were correlated with the actual crack depths measured on sectioned specimens. This correlation was used to tdentify hves at which certain crack depths were achieved: the duration of Stage I (initiation) corresponded to a crack depth of approx 18% of the sheet thtckness (approx 0 16-0.48 ram), and the duratton of Stage II (through-thickness propagation) corresponded to a crack depth equal to the sheet thickness (0.89-2 72 ram) The final fatlure of the specimen determined the conclusion of Stage HI (cross-width crack propagatmn) The effects of sheet thickness, specimen width, and nugget diameter were studied. Sheet thtckness was found to have the largest effect on fatigue life, whde the nugget diameter had the least. The fatigue life of the galvanized h~gh-strength-low-alloy specimens was found to be dominated by through-thickness propagation {Stage II), whde the fatigue life of the galvanized low-carbon specimens was dominated by Stage I. The fatigue life of all specimens tested at a given R ratto could be correlated with the initial value of stress intensity factor for the comb=ned effects of Mode I and II loading condittons
Plasticity and f a t i g u e d a m a g e m o d e l i n g o f severely loaded tubing.
Tipton, S,M. and Newburn, D.A. Proc. Conf. Advances in Fatigue Lifetime Predictive Techniques, San Francisco, California, USA, 24 Apr. 1990 3 6 9 - 3 8 2 The deformation and fatigue behavtour of a tubular component (A606) under repeated flexural bending and static internal pressure are investigated. The bending strains reduced in the component results in gross cyclic plasticity and fatigue lives of the order of a few hundred cycles. Result from a case study are presented that describe considerations in measuring dynamic, high elongation strains using a variety of experimental techniques during full-scale component testing. Measured strains are used with an incremental plasticity model to compute corresponding tube stresses and utilized in an algorithm to predict tube fatigue behaviour. A number of local strata-based multiaxial fatigue theories are investigated, including several critical plane aproaches, an extension of Sines methodology, an approach which considers hydrostatic stress effect and plastic work. Several of the theories make reasonable life estimates for tests involving negligible internal pressure but do not reflect the damage imposed by higher values of internal pressure. Non-hnear damage summation may be required to correlate fatigue lives.
Fatigue life prediction and experimental verification for an automotive suspension component using dynamic simulation end f i n i t e e l e m e n t analysis. Baek, W.K. and Stephens, R.I. Proc. Conf. Advances in Fatigue Lifetime Predictive Techniques, San Francisco, California, USA, 24 Apr. 1990 3 5 4 - 3 6 8 An integrated fatigue hfe prediction methodology is presented using multi-body dynamic simulation, finite element analysis, and fatigue life predictton methods. This methodology was applied for predicting the finite life of an automotive suspensmn component (SAE 950X) Experimental verification of the predicted life ~s described The results indicate that thts integrated fatigue life prediction methodology can be used as a reliable tool to reduce expense and time of design iteration.
66
Proc Conf. Advances in Fatigue Lifetime Predictive Techniques, San Francisco, California, USA, 24 Apr. 1990 2 7 6 - 2 9 8 The small-crack problem tn multiaxlal fatigue is studied usmg avatlable crack-growth data from thin-walled tubular specimens made of Inconel 718 and 1045 HR steels. The Ioadmgs consist of axial, torsional, proportional and non-proportional axial-torsional with or without mean stress, and blaxial tension tests. An equivalent stram-based intensity factor range based on Irwin's energy release rate, and a proposed strain-based intensity factor range formulation based on the critical plane approach, are used to correlate the crack-growth data obtained from different loading conditions. The proposed formulation is an attempt to present a unified approach to crack ~nttlatlon and crack propagation, based on the physical mechanisms of the multiaxial fatigue damage process. Crack-growth rate correlations and smeltcrack effects with respect to the microstructure and different loading paths are discussed A m u l t i a x i a l f a t i g u e life e s t i m a t i o n technique. Bannantine, J.A. and
Socie, D.F. Proc. Conf. Advances in Fatigue Lifetime Predictive Techniques, San Francisco, California, USA, 24 Apr. 1990 2 4 9 - 2 7 6 A method to estimate the fatigue life of a component subjected to variable-amphtude multiaxial loading has been developed. The strata-life approach, which achieved success in correlating the fatigue lives of components subjected to umaxial variable amplitude loading, is used as the foundation of this approach. The method incorporates critical plane multiaxial damage models that relate fatigue damage to remote loading parameters. A computer model was developed to ~mplement the proposed method. Measured or estimated strain histories are used as input. Corresponding stress intensities are calculated using a non-proportional cyclic plasticity model. Damage is calculated using the stress and strain histories and multiaxial damage models. The plane experiencing the maximum damage is identified as the critical plane, and the fatigue life of the component is estimated from the damage calculations on this plane. Experimental test results were used to evaluate and verify the proposed method. The measured stress-strain response of thin-wall tubes loaded in combined tension and torsion was used to verify the nonproportional cychc plasticity model. Good correlation between predicted and measured responses was observed. Results from tests conducted on SAE 1045 steel components, loaded in bending, proportional bending and torsion, and nonproportional bending and torsion, were used to evaluate the overall method. Good correlation between predicted and actual fatigue hves was achieved.
A probebilistic fracture mechanics approach for structural reliability assessment o f space f l i g h t systems. Sutharshana, S., Ebbeler, D., Moore, N. and Creager, M. Proc. Conf. Advances in Fatigue Lifetime Predictive Techniques, San Francisco, California, USA, 24 Apr. 1990 2 3 4 - 2 4 6 A probabihstic fracture mechanics approach for predicting the failure life distribution due to subcriticel crack growth is presented. A state-of-the.art crack-propagation method is used in a Monte Carlo simulation to generate a distribution of failure lives. The crack-growth failure model expresses failure life as a function of stochastic parameters including environment, loads, material properties, geometry, and model specification errors. A stochastic crack-growth rate model that considers the uncertainties due to scatter in the data and model mis-specificetion is proposed. The rationale for choosing a particular type of probability distribution for each stochastic input parameter and for specifymg the distribution parameters is presented. The approach is demonstrated through a probabilist=c crack-growth failure analysis of a welded tube in the Space Shuttle main engme A dtscusslon of the results from this application of the methodology is given (for 316L).
Int J Fatigue January 1993
On t h e prediction o f t h e f a t i g u e propagation of semi-elliptical defects.
Soboyejo, W.O. Proc. Conf. Advances in Fatigue Lifetime Predictive Techniques, San Francisco, California, USA, 24 Apr. 1990 4 3 5 - 4 4 8 The ~mphcatmns of the results of recent experimental and numerical investigations of the propagation of single and muittpie configurations of semf-e)hptlca) cracks (in QIN steel) are assessed for the predict=on of fatigue hfe tn structures and components in service. Simphfied methodologies for the assessment of the effects of crack closure and stress state on the propagation charactensttcs of seml-ellipt~cel cracks are proposed, and numerrcal techmques for the analys~s of coplanar and noncopianar configurations of seml-elhptmal cracks are also presented. These include the results of fimte element and simplified fracture mechanics analyses m which crack growth was computed on a step-by-step basis from the Pans equation
Life prediction o f c i r c u m f e r e n t i a l l y grooved components under l o w cycle fatigue. Hatanaka, K., Fu/imitsu, T., Omori, J. and Shiraishi, S.
Proc, Conf. Advances in Fatigue Lifetime Predictive Techniques, San Francisco, California, USA, 24 Apr. 1990 402-421 Stress-strata response was analysed m the cross-section of circumferentlally notched components by the finite element method. Then, the cyclic J-integral range, J, was estimated for the semi-elliptical surface crack and for the cprcumferential crack. The growth rate of the surface crack was successfully plotted against the estimated, JintegraJ range under low-cycle fatigue loading Furthermore, the transition from the seml-elhptlcal surface crack to the mrcumferentiaf crack, which Occurred in the fatigue crack growth process in the acutety notched cylindrical component, was reasonably analysed in terms of elastic-plastic fracture mechanics. Finally, the lowcycle fatigue hves of the dully and acutely notched cyhndrtcal components were satlsfactordy eva~uated through the analysis of the growth of the surface and circumferenttal cracks (for $35C steel)
Nonproportional fatigue of w e l d e d structures. Siljander, A , Kurath, P and Lawrence, F.V. Jr. Proc. Conf. Advances m Fatigue Lifetime Predictive Techniques, San Francisco, California, USA, 24 Apr. 1990 3 1 9 - 3 3 8 Rending and shearing stresses in many structures are out of phase, A typical example is the evaluation of a fixed positron m a bridge beam as a moving load crosses tt. Tradttlonal fattgue design approaches for welded structural details are generally based on in-phase laboratory data Thus the effect of non-proportional stress histories on the fatigue life of welded structural details is usually not considered. Stress-reheved tube-to-plate (A519 to A36) weldments were subjected to multlaxlal in-phase and out-of-phase stress states using combinations of bending and torsmn. The fatigue test results were evaluated using three local stress-damage criteria modified for multlaxlal loading. Finite element techniques were used to calculate the local stresses and stratus The local shear-stress-based approach of Ftndley provided the best correlatpon of all test data for the loading paths considered. The unique aspects of non-proportional loading are reflected by the Fmdley model fatigue damage calculations, and the test data were correlated to within a factor of two Since the scatter in the experimental data was also a factor of two for identical tests, further improvements m predmtive abihty are not possible. Also, the predicted direction of fatigue damage for the Findley model comctded with surface cracking characteristics Failure modes in a Type 316 stainless steel u n d e r biaxial strain cycling.
Zamrik, S.Y., Davis, D.C. and Kulowitch, P.J. Proc. Conf. Advances in Fatigue Lifetime Predictive Techniques, San Francisco, California, USA, 24 Apr. 1990 2 9 9 - 3 1 8 Discussed are the failure modes observed m a Type 316 stemless steel under biaxlal high-temperature low-cycle fatigue (HTLCF) and creep-fattgue strain cycling. All tests were carned OUt in air at 621 °C using thin-walled tubular type specimens specially designed for axial, torsional, and combined axial-torsmnal (btaxisl) cyclic Ioadlngs Results from HTLCF and creep-fatigue tests at six different blaxiahW ratios (~ - ~xy/~xx), 0 0, 1 0, 2 0, 2.5, 3.6, and infinity, are g~ven. At these b=axiality ratios, crack initiation in HTLCF is a shear process and crack propagation occurs mainly in a normal mode. With the introduction of creep through a comb=ned inphase tensile-torsional hold-time imposed on the blaxlal HTLCF cycle, the direction of the crack propagation was found to be dominated by the axial creep-fatigue component These results are compared with some multlaxral fatigue strain-based failure criteria S m a l l crack growth in m u l t i a x i a l fatigue. Reddy, S.C. and Fatemi, A.
Electric-potential-drop studies of fatigue crack development in tensileshear s p o t w e l d s . Swellam, M.H., Kurath, P. and Lawrence, F.V. Proc. Conf. Advances in Fatigue Lifetime Predictive Techniques, San Francisco, California, USA, 24 Apr. 1990 383-401 The development of fatigue cracks m galvamzed Iow-cerbon and high-strength-lowalloy steel, tensile-shear-spot weldments was mvestigated using a d.c. electricalpotential-drop techmque which sensed the depth of fatigue cracks as they propagated through the thtckness of the specimens. These reststlVlW changes were correlated with the actual crack depths measured on sectioned specimens. This correlation was used to tdentify hves at which certain crack depths were achieved: the duration of Stage I (initiation) corresponded to a crack depth of approx 18% of the sheet thtckness (approx 0 16-0.48 ram), and the duratton of Stage II (through-thickness propagation) corresponded to a crack depth equal to the sheet thickness (0.89-2 72 ram) The final fatlure of the specimen determined the conclusion of Stage HI (cross-width crack propagatmn) The effects of sheet thickness, specimen width, and nugget diameter were studied. Sheet thtckness was found to have the largest effect on fatigue life, whde the nugget diameter had the least. The fatigue life of the galvanized h~gh-strength-low-alloy specimens was found to be dominated by through-thickness propagation {Stage II), whde the fatigue life of the galvanized low-carbon specimens was dominated by Stage I. The fatigue life of all specimens tested at a given R ratto could be correlated with the initial value of stress intensity factor for the comb=ned effects of Mode I and II loading condittons
Plasticity and f a t i g u e d a m a g e m o d e l i n g o f severely loaded tubing.
Tipton, S,M. and Newburn, D.A. Proc. Conf. Advances in Fatigue Lifetime Predictive Techniques, San Francisco, California, USA, 24 Apr. 1990 3 6 9 - 3 8 2 The deformation and fatigue behavtour of a tubular component (A606) under repeated flexural bending and static internal pressure are investigated. The bending strains reduced in the component results in gross cyclic plasticity and fatigue lives of the order of a few hundred cycles. Result from a case study are presented that describe considerations in measuring dynamic, high elongation strains using a variety of experimental techniques during full-scale component testing. Measured strains are used with an incremental plasticity model to compute corresponding tube stresses and utilized in an algorithm to predict tube fatigue behaviour. A number of local strata-based multiaxial fatigue theories are investigated, including several critical plane aproaches, an extension of Sines methodology, an approach which considers hydrostatic stress effect and plastic work. Several of the theories make reasonable life estimates for tests involving negligible internal pressure but do not reflect the damage imposed by higher values of internal pressure. Non-hnear damage summation may be required to correlate fatigue lives.
Fatigue life prediction and experimental verification for an automotive suspension component using dynamic simulation end f i n i t e e l e m e n t analysis. Baek, W.K. and Stephens, R.I. Proc. Conf. Advances in Fatigue Lifetime Predictive Techniques, San Francisco, California, USA, 24 Apr. 1990 3 5 4 - 3 6 8 An integrated fatigue hfe prediction methodology is presented using multi-body dynamic simulation, finite element analysis, and fatigue life predictton methods. This methodology was applied for predicting the finite life of an automotive suspensmn component (SAE 950X) Experimental verification of the predicted life ~s described The results indicate that thts integrated fatigue life prediction methodology can be used as a reliable tool to reduce expense and time of design iteration.
66
Proc Conf. Advances in Fatigue Lifetime Predictive Techniques, San Francisco, California, USA, 24 Apr. 1990 2 7 6 - 2 9 8 The small-crack problem tn multiaxlal fatigue is studied usmg avatlable crack-growth data from thin-walled tubular specimens made of Inconel 718 and 1045 HR steels. The Ioadmgs consist of axial, torsional, proportional and non-proportional axial-torsional with or without mean stress, and blaxial tension tests. An equivalent stram-based intensity factor range based on Irwin's energy release rate, and a proposed strain-based intensity factor range formulation based on the critical plane approach, are used to correlate the crack-growth data obtained from different loading conditions. The proposed formulation is an attempt to present a unified approach to crack ~nttlatlon and crack propagation, based on the physical mechanisms of the multiaxial fatigue damage process. Crack-growth rate correlations and smeltcrack effects with respect to the microstructure and different loading paths are discussed A m u l t i a x i a l f a t i g u e life e s t i m a t i o n technique. Bannantine, J.A. and
Socie, D.F. Proc. Conf. Advances in Fatigue Lifetime Predictive Techniques, San Francisco, California, USA, 24 Apr. 1990 2 4 9 - 2 7 6 A method to estimate the fatigue life of a component subjected to variable-amphtude multiaxial loading has been developed. The strata-life approach, which achieved success in correlating the fatigue lives of components subjected to umaxial variable amplitude loading, is used as the foundation of this approach. The method incorporates critical plane multiaxial damage models that relate fatigue damage to remote loading parameters. A computer model was developed to ~mplement the proposed method. Measured or estimated strain histories are used as input. Corresponding stress intensities are calculated using a non-proportional cyclic plasticity model. Damage is calculated using the stress and strain histories and multiaxial damage models. The plane experiencing the maximum damage is identified as the critical plane, and the fatigue life of the component is estimated from the damage calculations on this plane. Experimental test results were used to evaluate and verify the proposed method. The measured stress-strain response of thin-wall tubes loaded in combined tension and torsion was used to verify the nonproportional cychc plasticity model. Good correlation between predicted and measured responses was observed. Results from tests conducted on SAE 1045 steel components, loaded in bending, proportional bending and torsion, and nonproportional bending and torsion, were used to evaluate the overall method. Good correlation between predicted and actual fatigue hves was achieved.
A probebilistic fracture mechanics approach for structural reliability assessment o f space f l i g h t systems. Sutharshana, S., Ebbeler, D., Moore, N. and Creager, M. Proc. Conf. Advances in Fatigue Lifetime Predictive Techniques, San Francisco, California, USA, 24 Apr. 1990 2 3 4 - 2 4 6 A probabihstic fracture mechanics approach for predicting the failure life distribution due to subcriticel crack growth is presented. A state-of-the.art crack-propagation method is used in a Monte Carlo simulation to generate a distribution of failure lives. The crack-growth failure model expresses failure life as a function of stochastic parameters including environment, loads, material properties, geometry, and model specification errors. A stochastic crack-growth rate model that considers the uncertainties due to scatter in the data and model mis-specificetion is proposed. The rationale for choosing a particular type of probability distribution for each stochastic input parameter and for specifymg the distribution parameters is presented. The approach is demonstrated through a probabilist=c crack-growth failure analysis of a welded tube in the Space Shuttle main engme A dtscusslon of the results from this application of the methodology is given (for 316L).
Int J Fatigue January 1993