A New Approach to the Evaluation of Fatigue Under Multiaxial Loadings

1981 ◽  
Vol 103 (2) ◽  
pp. 118-125 ◽  
Author(s):  
Y. S. Garud
Keyword(s):  
Fatigue Life ◽  
Constitutive Relations ◽  
Cyclic Stress ◽  
Fatigue Tests ◽  
Plastic Work ◽  
Strain Response ◽  
New Approach ◽  
Hardening Rule ◽  
Multiaxial Loadings ◽  
Good Agreement

A critical review of the methods for evaluating fatigue of metals under simple (proportional) and complex (nonproportional) loadings indicates that most of the criteria are expressed in terms of either stresses or strains. In this paper a new approach to the evaluation of fatigue under these loadings is proposed. This approach is based upon the idea of relating fatigue life to the plastic work during a cycle of the loading. A procedure is outlined for the calculation of plastic work which involves explicit considerations of the material constitutive relations. It is based on the structure of modern plasticity theories and a new “hardening rule.” Validity of the constitutive relations to predict the cyclic stress-strain response is demonstrated for out-of-phase multiaxial loadings. Available experimental results of fatigue tests under out-of-phase loadings are shown to be in good agreement with the predictions using the new approach.

scholarly journals Fatigue behaviour of selected materials under multiaxial asynchronous loadings

2019 ◽  
Vol 300 ◽  
pp. 15006 ◽  
Author(s):  
Łukasz Pejkowski ◽  
Dariusz Skibicki ◽  
Jan Seyda
Keyword(s):  
Fatigue Life ◽  
Aluminium Alloy ◽  
Significant Influence ◽  
Fatigue Behaviour ◽  
Cyclic Stress ◽  
Strain Response ◽  
Strain Components ◽  
Thin Walled ◽  
The Difference ◽  
Multiaxial Loadings

Four types of materials: PA38 aluminium alloy, E235 steel, E355 steel and 1.4301 austenitic steel were subjected to low-cycle multiaxial loadings. All tests were strain-controlled and typical, thin-walled, hollow specimens were used. Various synchronous and asynchronous loadings were applied. The analysis of experimental results involved: cyclic stress-strain response, fatigue life and observation of microcracks behaviour on the surfaces of fatigued specimens. Obtained results indicate that the difference in the strain components frequency of the asynchronous loadings has a significant influence on the fatigue behaviour of the materials.

Novel Methods for High-Cycle Fatigue Life Determination

2019 ◽  
Vol 810 ◽  
pp. 40-45
Author(s):  
Pavel Konopík ◽  
Radek Procházka ◽  
Martin Rund ◽  
Jan Džugan
Keyword(s):  
Fatigue Life ◽  
High Cycle Fatigue ◽  
Fatigue Tests ◽  
Cycle Fatigue ◽  
Testing Methods ◽  
Destructive Testing ◽  
New Approach ◽  
Constant Loading ◽  
Thermographic Analysis ◽  
Novel Methods

In the present paper, two novel methods for determining the fatigue limit are presented. Despite the fact that these methods are different in principle, both represent a new approach to testing where the main benefit is reduced consumption of material. The first method is based on small round specimens and can be considered as one of semi-destructive testing methods. The second method is based on infrared thermographic analysis and requires only one specimen. Results obtained with these techniques were compared with those obtained from standard high-cycle force-controlled fatigue tests under constant loading until failure.

Temperature and Frequency Modified Fatigue Initiation Life of Solder Alloys Predicted by Endochronic Cyclic Damage-Coupled Viscoplasticity

2011 ◽  
Vol 27 (2) ◽  
pp. 267-277 ◽  
Author(s):  
C. F. Lee ◽  
S. I. Jeng ◽  
M. T. Liu
Keyword(s):  
Solder Alloy ◽  
Cyclic Stress ◽  
Fatigue Tests ◽  
Least Square ◽  
Strain Response ◽  
Stress Strain ◽  
Life Data ◽  
Form Equation ◽  
Fatigue Initiation ◽  
Cyclic Damage

ABSTRACTIn this paper, an evolution equation of cyclically internal damage in the intrinsic damage time scale after the threshold cycles N0 was extended by employing its damage parameters proposed to be dependent of frequency (v) and temperature (T) under cyclic fatigue loading. The resulting damage-coupled endochronic viscoplasticity can drive v and T modified power form equations of cyclic damage and its fatigue initiation life = N1 + N0. Under fatigue tests with T effect and N0 = 0, the power form equation of N1(T)/(Th), named as T-LCM (T modified Lee Coffin-Manson) equation for fatigue initiation life can bederived. The T modified factor (Th) depends on the T dependent material elastic modulus, the cyclicstress-strain response and the damage parameters. Theoretical predictions in the life data ofSn/3.8Ag/0.7Cu solder alloy under cyclic strain test with Tϵ [298,393] K were very well.Also under fatigue tests with v effect only, the power form equation of /v-LCM (v modified Lee-Coffin-Manson) equation for fatigue initiation life can be derived. The v modified parameter depends on the v dependent cyclic stress-strain response and the damage parameters. Theoreticalpredictions in the life data of 96.5Sn/3.5Ag solder alloy with surface cracking effect i.e. N0 ≠ 0 during cyclicstrain tests with v ϵ [0.001,1] Hz were quite well.Obviously, the values of power exponents C in the T-LCM and the v-LCM equations can not be determinedsimply by the least square method as in the Coffin-Manson empirical formulae. Also, they must bejustified by constrains imposed in the material parameters defining in the cyclic stress-strain response andthe accumulation behavior of cyclic damage.The resultant equations derived here and the Δ-LCM equation derived under Δ angle proportional cyclicstrain tests can be combined together to form a T-v-ΔLCM equation for fatigue life studies in the solderalloys using bulk specimens or BGA solider joint specimens.

Plastic Work Interaction Damage Rule Applied to Narrow-Band Gaussian Random Stress Situations

1988 ◽  
Vol 110 (1) ◽  
pp. 88-90 ◽  
Author(s):  
R. G. Lambert
Keyword(s):  
Fatigue Life ◽  
Narrow Band ◽  
Mathematical Expression ◽  
Fatigue Tests ◽  
Plastic Work ◽  
Wave Form ◽  
Work Interaction ◽  
Parameter Values ◽  
Life Parameter ◽  
Damage Rule

Fatigue life estimates that use a structural material’s constant amplitude stress life data values and a linear cumulative damage rule are always nonconservative for stress histories containing numerous subcycles and only a few large-amplitude cycles. Conservative fatigue life estimates were previously achieved by others with a plastic work interaction damage rule using the material’s overstrain fatigue life parameter values. Verification fatigue tests were run on laboratory specimens of 1020 steel using four selected variable amplitude stress wave form profiles. This paper extends the application of the plastic work interaction damage rule to narrowband Gaussian random stress situations. The derived stress life mathematical expression is of a power law form. The predicted fatigue life is more accurate than that predicted using a conventional linear damage rule.

Comparative Study of Microstructure and High Temperature Low Cycle Fatigue Behaviour of Nickel Base Superalloys Inconel 713LC and MAR-M247

2016 ◽  
Vol 713 ◽  
pp. 86-89 ◽  
Author(s):  
Ivo Šulák ◽  
Karel Obrtlík ◽  
Ladislav Čelko
Keyword(s):  
High Temperature ◽  
Fatigue Life ◽  
Low Cycle Fatigue ◽  
Strain Curve ◽  
Cyclic Stress ◽  
Fatigue Tests ◽  
Casting Defects ◽  
Cycle Fatigue ◽  
Stress Strain Curve ◽  
Nickel Base

The present work is focused on the study of microstructure and low cycle fatigue behavior of the first generation nickel-base superalloy IN 713LC (low carbon) and its promising second generation successor MAR-M247 HIP (hot isostatic pressing) at 900 °C. Microstructure of both alloys was studied by means of scanning electron microscopy (SEM). The microstructure of both materials is characterized by dendritic grains, carbides and casting defects. Size and morphology of precipitates and casting defects were evaluated. Fractographic observations have been made with the aim to reveal the fatigue crack initiation place and relation to the casting defects and material microstructure. Low cycle fatigue tests were conducted on cylindrical specimens in symmetrical push-pull cycle under strain control with constant total strain amplitude and strain rate at 900 °C in air. Hardening/softening curves, cyclic stress-strain curve and fatigue life data of both materials were obtained. Cyclic stress-strain curve of MAR M247 is shifted approximately to 120 MPa higher stress amplitudes in comparison with IN 713LC. Significantly higher fatigue life of MAR-M247 has been observed in Basquin representation. On the other hand IN 713LC shows prolonged lifetime compared with MAR-M247 in the Coffin-Manson representation. Results obtained from high temperature low cycle fatigue tests are discussed.

Predicting Fatigue Initiation Life of Sn/3.8Ag/0.7Cu Solder using Endochronic Cyclic Damage-Coupled Viscoplastic Theory

2008 ◽  
Vol 24 (4) ◽  
pp. 369-377 ◽  
Author(s):  
C. F. Lee ◽  
Z. H. Lee
Keyword(s):  
Strain Amplitude ◽  
Hysteresis Loops ◽  
Inelastic Strain ◽  
Cyclic Stress ◽  
Fatigue Tests ◽  
Cyclic Behavior ◽  
Dendritic Microstructure ◽  
Fatigue Initiation ◽  
Cyclic Damage ◽  
Good Agreement

AbstractThis paper studied cyclic behavior Sn/3.8Ag/0.7Cu solder with dendritic microstructure. A cyclic damage factor D under constant strain amplitude fatigue tests, was defined by using the reducing rate of maximum cyclic tensile stress σa. The critical cyclic damage DC and it's fatigue initiation life NI were determined very consistently by using separately the experimental σavs. N curves and the percolation theory. The endochronic cyclic damage-coupled viscoplastic theory proposed by the 1st author was used to simulate cyclic stress-strain hysteresis loops with damage under strain amplitude (εa) 0.8% at 298K. The results were in very good agreement with data. Combining the evolution equation of intrinsic damage and the computed cyclic stress-inelastic strain relation, a modified Coffin-Manson relationship was derived. By setting DC = 0.3, it predicted very effectively the NI data under σa from 0.2% to 1.0%.

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