Micromechanical Method to Predict Fatigue Life of Solder

1990 ◽  
Vol 112 (2) ◽  
pp. 179-182 ◽  
Author(s):  
A. Zubelewicz ◽  
Q. Guo ◽  
E. C. Cutiongco ◽  
M. E. Fine ◽  
L. M. Keer
Keyword(s):  
Fatigue Life ◽  
Constitutive Equations ◽  
Cyclic Hardening ◽  
Cyclic Softening ◽  
Stress And Strain ◽  
Fatigue Lifetime ◽  
Eutectic Solder ◽  
Tension Tests ◽  
Physical Phenomena ◽  
High Lead

Fatigue lifetimes of low-tin high-lead and tin-lead eutectic solders under total strain controlled tension-tension tests were studied in this paper. Based on the stress and strain micro-macro correlations, a modified Coffin-Manson law is obtained. The modified lifetime prediction formulas which had been used to predict the fatigue lifetime for low-tin high-lead solder, exhibiting cyclic hardening and then saturation, was found to apply to the eutectic solder, where substantial cyclic softening has been observed. This micromechanically based approach allows one to model the known physical phenomena in solders by modifying the appropriate parameters in the predictive micromechanically based constitutive equations.

Modelling of Cyclic Plasticity With Unified Constitutive Equations: Improvements in Simulating Normal and Anomalous Bauschinger Effects

1980 ◽  
Vol 102 (2) ◽  
pp. 215-222 ◽  
Author(s):  
A. K. Miller
Keyword(s):  
Constitutive Equations ◽  
Work Hardening ◽  
Hysteresis Loops ◽  
Experimental Tests ◽  
Cyclic Hardening ◽  
Back Stress ◽  
Cyclic Softening ◽  
Cyclic Plasticity ◽  
Dislocation Loops ◽  
Work Hardening Coefficient

In simulating cyclic plasticity with several existing “unified” constitutive equations, the predicted hysteresis loops are “oversquare” with respect to experimentally-observed behavior. To eliminate this shortcoming in the constitutive equations developed by the present author, the work-hardening coefficient in the equation controlling the back stress (R) has been made a function of the back stress itself and the sign of the effective modulus-compensated stress σ/E – R. This improvement results in simulated hysteresis loops whose curvature closely resembles that in experimental tests. The improvement preserves all of the previously demonstrated capabilities such as cyclic hardening, cyclic hardening, cyclic softening, etc. The same equations can also simulate some unusual experimentally-observed Bauschinger effects involving local reversals in curvature. The curvature reversals in the simulations result from strain softening of the isotropic work-hardening variable in the equations. The physical significance of the behavior of the constitutive equations is discussed in terms of annihilation of previously-generated dislocation loops by reversing dislocations and experimentally-observed decreases in dislocation density and dissolution of cell walls upon stress reversal.

Multiaxial Fatigue of 6061-T6 Aluminum Alloy under Corrosive Environment

2016 ◽  
Vol 853 ◽  
pp. 77-82
Author(s):  
Xu Chen ◽  
Rui Si Xing ◽  
Xiao Peng Liu
Keyword(s):  
Aluminum Alloy ◽  
Fatigue Life ◽  
Stress Amplitude ◽  
Low Cycle Fatigue ◽  
Cyclic Hardening ◽  
Cyclic Softening ◽  
Fatigue Tests ◽  
Plastic Strain Amplitude ◽  
Multiaxial Fatigue ◽  
Corrosive Environment

Aluminium alloys are widely used in the fields of automobile, machinery and naval construction. To investigate the effect of non-proportional loadings and corrosive environment on the fatigue resistance of 6061-T6 aluminum alloy, a set of uniaxial and multiaxial low cycle fatigue tests were carried out. Firstly, the results of uniaxial tests showed that the alloy exhibited cyclic hardening then cyclic softening. With the increase of stress amplitude the cyclic softening became pronounced. The increasing of plastic deformation was basically cyclically stable with small plastic strain amplitude accumulation when the stress amplitude was lower than 200MPa ,while it was increasing rapidly when the stress amplitude was higher than 220MPa. Secondly, it was observed that non-proportional cycle additional hardening of 6061-T6 aluminum alloy was little. While the fatigue life was badly affected by the loading paths. Thirdly ,the fatigue corrosion interactions were also talked about in details by performing the tests under the same loading conditions with corrosive environment. The experiment proved that the seawater corrosion has huge impact on fatigue life under pH 3. Finally, a multi-axial fatigue life prediction model was used to predict the fatigue life with or without the corrosive environment which showed a good agreement with experimental data.

scholarly journals Effects of Microstructures on Fatigue Behavior of an Al-Mg-Sc Alloy at an Elevated Temperature

2012 ◽  
Vol 706-709 ◽  
pp. 426-430 ◽  
Author(s):  
Chihiro Watanabe ◽  
Ryoichi Monzen
Keyword(s):  
Fatigue Life ◽  
Fatigue Behavior ◽  
Cyclic Hardening ◽  
Cyclic Softening ◽  
Small Particles ◽  
Factors Affecting ◽  
Slip Bands ◽  
Large Particles ◽  
Fatigue Characteristics ◽  
The Relationship

Polycrystalline Al-1wt%Mg-0.27wt%Sc alloys bearing Al3Sc particles with different average sizes of 4 and 11nm in diameter have been cyclically deformed at 423K under various constant stress amplitudes, and the relationship between fatigue characteristics and microstructure of the alloy has been investigated. The specimen bearing 11 nm particles exhibited a cyclic hardening to saturation, while in specimens with the small particles a cyclic softening was observed after initial hardening. In the specimen with large particles, dislocations were uniformly distributed under all applied stress amplitudes, whereas the specimens bearing small particles, in which cyclic softening occurred exhibited clearly developed slip bands. The cyclic softening for the latter specimen was explained by particle shearing within the strongly strained slip bands. The width of precipitate free zones (PFZs) has been found to be one of the factors affecting the fatigue life of the specimens at 423K. The two-step aging decreases the width of PFZs, resulting in increase in the fatigue life.

A Discussion on the Performance of Continuum Plasticity Models for Fatigue Lifetime Assessment Based on the Local Strain Appraoch

2006 ◽  
Author(s):  
Abi´lio M. P. De Jesus ◽  
He´lder F. S. G. Pereira ◽  
Alfredo S. Ribeiro ◽  
Anto´nio A. Fernandes
Keyword(s):  
Fatigue Life ◽  
Kinematic Hardening ◽  
Local Strain ◽  
Cyclic Hardening ◽  
Mean Stress ◽  
Plasticity Model ◽  
Fatigue Lifetime ◽  
The Mean ◽  
Plate Connection ◽  
Mean Stresses

This paper presents a discussion on the performance of continuum plasticity models for fatigue lifetime assessment according to the local strain approach. Several cyclic plasticity phenomena such as the cyclic hardening/softening, ratchetting, cyclic mean stress relaxation and non-proportional cyclic hardening require, in general, specialized continuum plasticity models. Continuum plasticity models, available in commercial finite element codes (e.g. ANSYS®), with linear, multilinear and nonlinear kinematic hardening are identified using the experimental information available for a pressure vessel steel — the P355NL 1 steel. The potentialities of these plasticity models to describe the material cyclic behaviour are discussed, limiting the discussion to proportional loading. The plasticity models are applied to evaluate the strain ranges and mean stresses of a nozzle-to-plate connection. Two analysis strategies are applied to extract the strain ranges, namely the Twice Yield (TY) and the Cycle-by-Cycle (CBC) methods. The mean stress is only evaluated using the CBC method since the TY method has been proposed only for evaluation of the strain ranges. It is demonstrated that the TY and CBC methods gives similar results for the linear and multilinear kinematic hardening plasticity models. The plasticity model can have an important effect on the evaluation of the mean stresses and thus on predicted strain-life results, if mean stress effects are taken into account in the local strain approach. Finally, the calculated strain ranges and mean stresses are used in the evaluation of the fatigue life of the nozzle-to-plate connection using a local strain approach, and predictions are compared with available experimental results. The effect of the mean stress is important for long lives and is very dependent on the continuum plasticity model and on the number of cycles modelled in the CBC extraction method. Although differences are observed in the estimation of the strain ranges, using the several plasticity models, relatively small differences in fatigue life estimations were resulted.

Effect of Pre-Deformation on the Cyclic Behavior and Fatigue of 304L SS

2016 ◽  
Vol 703 ◽  
pp. 125-131 ◽  
Author(s):  
Lakhdar Taleb ◽  
Crescent Kpodekon
Keyword(s):  
Fatigue Life ◽  
Cyclic Strain ◽  
Cyclic Hardening ◽  
Cyclic Softening ◽  
Fatigue Tests ◽  
Cyclic Behavior ◽  
304L Stainless Steel ◽  
Strain Control ◽  
Hardening Process ◽  
Second Category

This study deals with the effect of the loading history on the cyclic behavior and the fatigue life of a 304L stainless steel at room temperature. The experiments have been performed using two specimens’ categories. The first one (virgin) has been submitted to only classical fatigue tests while in the second category, prior to the fatigue test; the specimen was subjected to a pre-hardening process under either monotonic or cyclic strain control. Cyclic softening followed by cyclic hardening are observed for the virgin specimens while only cyclic softening is exhibited by the pre-hardened specimens. The obtained results show that fatigue life is strongly influenced by the pre-hardening: the latter seems beneficial under stress control but detrimental under strain control, even in the presence of a compressive mean stress. The results are discussed regarding the cyclic evolution of the elastic modulus as well as the isotropic and kinematic parts of the strain hardening in different configurations: with or without pre-hardening, stress or strain control.

Rate Dependent Constitutive Equations of Cyclic Softening

1985 ◽  
Vol 40 (7) ◽  
pp. 653-665
Author(s):  
J. S. Mshana ◽  
A. S. Krausz
Keyword(s):  
Stress Relaxation ◽  
Low Temperature ◽  
Constitutive Equations ◽  
Strain Softening ◽  
Structural Characteristics ◽  
High Stress ◽  
Cyclic Strain ◽  
Cyclic Stress ◽  
Cyclic Softening ◽  
Stress Softening

Constitutive equations of cyclic strain and stress softening for materials with low internal stress levels are derived from the rate theory. The study shows that over the high stress and low temperature range where the description of plastic flow in cyclic softening can be approximated with activation over a single energy barrier, cyclic strain softening is well related to stress relaxation process while cyclic stress softening is related to creep process. The material structural characteristics for cyclic strain softening, cyclic stress softening and stress relaxation are identical. Subsequently, it is shown that cyclic stress and strain softening within the high stress and low temperature range can be evaluated from the constitutive equations using the material structural characteristics measured from a simple stress relaxation test.

An Investigation of Cyclic Transient Behavior and Implications on Fatigue Life Estimates

1997 ◽  
Vol 119 (2) ◽  
pp. 161-170 ◽  
Author(s):  
Yanyao Jiang ◽  
Peter Kurath
Keyword(s):  
Stainless Steel ◽  
Fatigue Life ◽  
Cyclic Hardening ◽  
Transient Behavior ◽  
Fatigue Tests ◽  
304 Stainless Steel ◽  
Deformation History ◽  
Life Estimation ◽  
Fatigue Life Estimation ◽  
Track Deformation

Current research focuses on proportional cyclic hardening and non-Massing behaviors. The interaction of these two hardenings can result in the traditionally observed overall softening, hardening or mixed behavior exhibited for fully reversed strain controlled fatigue tests. Proportional experiments were conducted with five materials, 304 stainless steel, normalized 1070 and 1045 steels, and 7075-T6 and 6061-T6 aluminum alloys. All the materials display similar trends, but the 304 stainless steel shows the most pronounced transient behavior and will be discussed in detail. Existing algorithms for this behavior are evaluated in light of the recent experiments, and refinements to the Armstrong-Frederick class of incremental plasticity models are proposed. Modifications implemented are more extensive than the traditional variation of yield stress, and a traditional strain based memory surface is utilized to track deformation history. Implications of the deformation characteristics with regard to fatigue life estimation, especially variable amplitude loading, will be examined. The high-low step loading is utilized to illustrate the effect of transient deformation on fatigue life estimation procedures, and their relationship to the observed and modeled deformation.

Low-Cycle Fatigue Life of Continuously Cyclic-Hardening Material

2020 ◽  
Author(s):  
Zhong Zhang ◽  
Xijia Wu
Keyword(s):  
Fatigue Life ◽  
Plastic Strain ◽  
Root Mean Square ◽  
Low Cycle Fatigue ◽  
Cyclic Hardening ◽  
Mean Square ◽  
Cycle Fatigue ◽  
Fatigue Crack Nucleation ◽  
Hardening Material ◽  
Plastic Strain Range

Abstract A general fatigue life equation is derived by modifying the Tanaka-Mura-Wu dislocation pile-up model for variable strain-amplitude fatigue processes, where the fatigue crack nucleation life is expressed in terms of the root mean square of plastic strain range. Low-cycle fatigue tests were conducted on an austenitic stainless steel. at 400°C and 600°C, the material exhibits continuously cyclic-hardening behaviour. The root mean square of plastic strain ranges is evaluated from the experimental data for each test condition at strain rates ranging from 0.0002/s to 0.02/s. The variable-amplitude Tanaka-Mura-Wu model is found to be in good agreement with the LCF data, which effectively proves Miner’s rule on the stored plastic strain energy basis.

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