scholarly journals Investigation of Changes in Fatigue Damage Caused by Mean Load under Block Loading Conditions

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 2738
Author(s):  
Roland Pawliczek ◽  
Tadeusz Lagoda
Keyword(s):  
Fatigue Life ◽  
Fatigue Damage ◽  
Strain Curve ◽  
Mean Value ◽  
Fatigue Properties ◽  
Stress Strain ◽  
Reference Case ◽  
Block Loading ◽  
The Mean ◽  
Mean Strain

The literature in the area of material fatigue indicates that the fatigue properties may change with the number of cycles. Researchers recommend taking this into account in fatigue life calculation algorithms. The results of simulation research presented in this paper relate to an algorithm for estimating the fatigue life of specimens subjected to block loading with a nonzero mean value. The problem of block loads using a novel calculation model is presented in this paper. The model takes into account the change in stress–strain curve parameters caused by mean strain. Simulation tests were performed for generated triangular waveforms of strains, where load blocks with changed mean strain values were applied. During the analysis, the degree of fatigue damage was compared. The results of calculations obtained for standard values of stress–strain parameters (for symmetric loads) and those determined, taking into account changes in the curve parameters, are compared and presented in this paper. It is shown that by neglecting the effect of the mean strain value on the K′ and n′ parameters and by considering only the parameters of the cyclic deformation curve for εm = 0 (symmetric loads), the ratio of the total degree of fatigue damage varies from 10% for εa = 0.2% to 3.5% for εa = 0.6%. The largest differences in the calculation for ratios of the partial degrees of fatigue damage were observed in relation to the reference case for the sequence of block n3, where εm = 0.4%. The simulation results show that higher mean strains change the properties of the material, and in such cases, it is necessary to take into account the influence of the mean value on the material response under block loads.

The Characteristics of the Fatigue Life of the SAE 1541 Carbon Steel Based on the Strain-Life Approach

2021 ◽  
Vol 872 ◽  
pp. 73-77
Author(s):  
Akmal Rauzatul ◽  
. Husaini ◽  
Edisah Putra Teuku
Keyword(s):  
Fatigue Life ◽  
Carbon Steel ◽  
Fatigue Damage ◽  
Strain Effect ◽  
Mean Values ◽  
Significant Difference ◽  
Strain Data ◽  
The Mean ◽  
Mean Strain

The aim of this study was to characterize the fatigue life of the SAE 1541 carbon steel. The fatigue life was predicted based on the strain-life approach through the application of constant and variable strain data with negative, zero, and positive mean values. Each strain data was developed at amplitude range of 200 με, 400 με, 600 με, 800 με, 1,000 με, 1,200 με, 1,400 με, 1,600 με, 1,800 με, and 2,000 με. The results showed there was no significant difference in the fatigue life for negative, zero, and positive mean strain amplitudes using the Coffin-Manson model. This is due to the non-consideration of the mean strain effect by the Coffin-Manson model. However, according to the Morrow and SWT models, negative mean strain data gave a longer fatigue life while positive mean strain data gave a shorter life. In addition, variable strain data gave a longer fatigue life since they contain low and high amplitudes, with the low amplitudes contributing to minimum fatigue damage.

scholarly journals Infarcted Left Ventricles Have Stiffer Material Properties and Lower Stiffness Variation: Three-Dimensional Echo-Based Modeling to Quantify In Vivo Ventricle Material Properties

2015 ◽  
Vol 137 (8) ◽  
Author(s):  
Longling Fan ◽  
Jing Yao ◽  
Chun Yang ◽  
Dalin Tang ◽  
Di Xu
Keyword(s):  
Wall Thickness ◽  
Material Properties ◽  
Strain Curve ◽  
Stress And Strain ◽  
Stress Strain ◽  
Material Stiffness ◽  
The Mean ◽  
Lv Volume ◽  
Parameter Values

Methods to quantify ventricle material properties noninvasively using in vivo data are of great important in clinical applications. An ultrasound echo-based computational modeling approach was proposed to quantify left ventricle (LV) material properties, curvature, and stress/strain conditions and find differences between normal LV and LV with infarct. Echo image data were acquired from five patients with myocardial infarction (I-Group) and five healthy volunteers as control (H-Group). Finite element models were constructed to obtain ventricle stress and strain conditions. Material stiffening and softening were used to model ventricle active contraction and relaxation. Systolic and diastolic material parameter values were obtained by adjusting the models to match echo volume data. Young's modulus (YM) value was obtained for each material stress–strain curve for easy comparison. LV wall thickness, circumferential and longitudinal curvatures (C- and L-curvature), material parameter values, and stress/strain values were recorded for analysis. Using the mean value of H-Group as the base value, at end-diastole, I-Group mean YM value for the fiber direction stress–strain curve was 54% stiffer than that of H-Group (136.24 kPa versus 88.68 kPa). At end-systole, the mean YM values from the two groups were similar (175.84 kPa versus 200.2 kPa). More interestingly, H-Group end-systole mean YM was 126% higher that its end-diastole value, while I-Group end-systole mean YM was only 29% higher that its end-diastole value. This indicated that H-Group had much greater systole–diastole material stiffness variations. At beginning-of-ejection (BE), LV ejection fraction (LVEF) showed positive correlation with C-curvature, stress, and strain, and negative correlation with LV volume, respectively. At beginning-of-filling (BF), LVEF showed positive correlation with C-curvature and strain, but negative correlation with stress and LV volume, respectively. Using averaged values of two groups at BE, I-Group stress, strain, and wall thickness were 32%, 29%, and 18% lower (thinner), respectively, compared to those of H-Group. L-curvature from I-Group was 61% higher than that from H-Group. Difference in C-curvature between the two groups was not statistically significant. Our results indicated that our modeling approach has the potential to determine in vivo ventricle material properties, which in turn could lead to methods to infer presence of infarct from LV contractibility and material stiffness variations. Quantitative differences in LV volume, curvatures, stress, strain, and wall thickness between the two groups were provided.

An Application of Incremental Plasticity Theory to Fatigue Life Prediction of Steels

1991 ◽  
Vol 113 (4) ◽  
pp. 404-410 ◽  
Author(s):  
W. R. Chen ◽  
L. M. Keer
Keyword(s):  
Fatigue Life ◽  
Life Prediction ◽  
Kinematic Hardening ◽  
Yield Condition ◽  
Strain Curve ◽  
Fatigue Life Prediction ◽  
304 Stainless Steel ◽  
Flow Rule ◽  
Stress Strain ◽  
Von Mises

An incremental plasticity model is proposed based on the von-Mises yield condition, associated flow rule, and nonlinear kinematic hardening rule. In the present model, fatigue life prediction requires only the uniaxial cycle stress-strain curve and the uniaxial fatigue test results on smooth specimens. Experimental data of 304 stainless steel and 1045 carbon steel were used to validate this analytical model. It is shown that a reasonable description of steady-state hysteresis stress-strain loops and prediction of fatigue lives under various combined axial-torsional loadings are given by this model

Effects of AP and AP-ethyl on the properties of PA6

2017 ◽  
Vol 31 (12) ◽  
pp. 1609-1618
Author(s):  
Long Lijuan ◽  
He Wentao ◽  
Li Juan ◽  
Xiang Yushu ◽  
Qin Shuhao ◽  
...  
Keyword(s):  
Tensile Strength ◽  
Fracture Surface ◽  
Thermal Degradation ◽  
Flame Retardant ◽  
Strain Curve ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Cone Calorimeter Test ◽  
Mean Size ◽  
The Mean

In this work, the effects of inorganic phosphinate flame retardant of aluminum hypophosphite (AP) and organic phosphinate flame retardant of ethyl substituted phosphinates (AP-ethyl) on the thermal degradation, flame performance, and mechanical properties of polyamide 6 (PA6) were investigated. Scanning electron micrograph showed AP with the shape of bulk and the mean size of 8 μm while AP-ethyl with irregular shape and the mean size of 30 μm. Thermal analysis indicated that the thermal degradation behavior of flame-retardant PA6 was different from pure PA6. Moreover, the cone calorimeter test results revealed that peak heat release rate (PHRR) of PA6/AP (85/15) and PA6/AP-ethyl (85/15) decreased by 51% and 64%, respectively, compared with pure PA6. Furthermore, pure PA6 showed ductile stress–strain curve with the tensile strength of 54.8 MPa. However, PA6/AP and PA6/AP-ethyl displayed brittle stress–strain curve and their tensile strength decreased to 52.3 and 47.1 MPa, respectively. In addition, pure PA6 showed a glossy and tough fracture surface morphology. The rough fracture surface morphologies for PA6/AP and PA6/AP-ethyl were observed, and the interface of PA6/AP was more obscure than that of PA6/AP-ethyl. Consequently, the small particle size of AP had a more uniform dispersion in PA6 matrix.

Assessment of Fatigue Life for High-Temperature Pipeline Welds Using X-Ray Diffraction Technique

2007 ◽  
Vol 353-358 ◽  
pp. 130-133
Author(s):  
Keun Bong Yoo ◽  
Jae Hoon Kim
Keyword(s):  
High Temperature ◽  
Fatigue Life ◽  
Fatigue Damage ◽  
Power Plants ◽  
Low Cycle Fatigue ◽  
Diffraction Method ◽  
Life Assessment ◽  
Fatigue Properties ◽  
X Ray Diffraction ◽  
X Ray

The objective of this study is to examine the feasibility of the X-ray diffraction method for the fatigue life assessment of high-temperature steel pipes used for main steam pipelines, re-heater pipelines and headers etc. in power plants. In this study, X-ray diffraction tests were performed on the specimens simulated for low cycle fatigue damage, in order to estimate fatigue properties at the various stages of fatigue life. As a result of X-ray diffraction tests, it was confirmed that the full width at the half maximum (FWHM) decreased with an increase in the fatigue life ratio, and that the FWHM and the residual stress due to fatigue damage were algebraically linearly related to the fatigue life ratio. From this relationship, a direct assessment of the remaining fatigue life was feasible.

Fatigue Properties of Superelastic Ti-Ni Filaments Used in Braided Cables for Bone Fixation

2008 ◽  
Vol 57 ◽  
pp. 235-240 ◽  
Author(s):  
Yannick Baril ◽  
Vladimir Brailovski ◽  
Patrick Terriault
Keyword(s):  
Fatigue Life ◽  
Strain Range ◽  
Fatigue Properties ◽  
Cyclic Testing ◽  
Testing Conditions ◽  
Bone Fixation ◽  
Ni Alloys ◽  
Strain Magnitude ◽  
The Impact ◽  
Mean Strain

Superelastic 0.1mm diameter Ti-Ni filaments are used to manufacture braided orthopedic cable for bone fixation. Biomechanical conditions for this application generally have a cyclic nature, and therefore it becomes important to evaluate the influence of the installation (mean) strain on the fatigue life of these filaments. Uniaxial tension cyclic testing of Ti-Ni filaments is performed in a water bath at 37°C with a 2Hz frequency of to 100 000 cycles. Strain-controlled testing conditions are as follows: alternating strain magnitude varies between 0.64 and 3.64% with mean strain range between 1.32 and 7.1%. Based on the premises that the minimum strain should be high enough to prevent any loss of tension in the tested specimen and that the maximum strain should not bring the specimen to failure during the first loading cycle, the total strain magnitude is encompassed between 0.68 and 8.94%. The results obtained provide a better understanding of the impact mean strain has on the fatigue life of superelastic Ti-Ni alloys.

Investigated on Fatigue Properties of Aluminum Ally 7050T7451 with Fastener Holes by Laser Shock Processing

2012 ◽  
Vol 460 ◽  
pp. 407-410
Author(s):  
Yin Fang Jiang ◽  
Xian Cong He ◽  
Yu Huang ◽  
Jian Wen Zhang ◽  
Zhi Fei Li
Keyword(s):  
Fatigue Life ◽  
Fatigue Properties ◽  
Hole Drilling ◽  
Mean Stress ◽  
Strengthening Effect ◽  
Laser Shock ◽  
Residual Stress Field ◽  
Laser Shock Processing ◽  
The Mean ◽  
Shock Processing

Based on the FEM code ABAQUS and MSC.Fatigue, the process of LSP before hole-drilling was adopted to study the residual stress field of aluminum alloy7050T7451 with Fastener Holes after Laser shock processing (LSP), and the fatigue life of the specimens by LSP was analyzed in this paper. The results indicate that multiple laser shock processing can improve the residual compressive stress and fatigue life to a certain degree, and with the increasing number of shot, the strengthening effect gradually decreases. The ratio of the fatigue life of specimens treated by LSP to the fatigue life of untreated specimens is gradually decreased as the mean stress σm increases, and when the σm is 67.3MPa, the fatigue life of specimens treated by LSP advances 719%, compared with that of untreated specimens.

Multiaxial Fatigue Life Assessment Method Based on the Mean Value of Modified Second Invariant of the Deviatoric Stress

2014 ◽  
Vol 224 ◽  
pp. 15-20
Author(s):  
Łukasz Pejkowski ◽  
Dariusz Skibicki
Keyword(s):  
Fatigue Life ◽  
Hydrostatic Stress ◽  
Assessment Method ◽  
Mean Value ◽  
Multiaxial Fatigue ◽  
Deviatoric Stress ◽  
Life Assessment ◽  
Fatigue Life Assessment ◽  
Fatigue Life Estimation ◽  
The Mean

Stress invariants approach to the multiaxial fatigue life estimation is generally based on the root mean square value of second invariant of the deviatoric stress amplitude and the value of hydrostatic stress. Such an approach omits a significant part of the information about multiaxial load history. It is particularly noticeable in case of non-proportional loadings, which lead to a reduction of fatigue life (i.e. [1–3]). In this work a new method based on the mean value of modified second invariant of the deviatoric stress has been presented.

Fatigue Life Prediction of Composite Laminate

2012 ◽  
Vol 472-475 ◽  
pp. 591-595 ◽  
Author(s):  
Jun Liu ◽  
Feng Peng Zhang
Keyword(s):  
Fatigue Life ◽  
Fatigue Damage ◽  
Composite Laminates ◽  
Life Prediction ◽  
Plate Theory ◽  
Damage Model ◽  
Prediction Method ◽  
Fatigue Life Prediction ◽  
Fatigue Properties ◽  
Adjacent Layer

Abstract. based on the accumulating fatigue damage model, with single ply plate theory and experiment data as the foundation, consider the interaction between adjacent layer and material degradation, a kind of fatigue life prediction method of fiber reinforced composite laminates is developed. The stiffness decline of each ply during cyclic loading is determined by the fatigue damage variable and the load amplitude and the fatigue life of any laminates can be predicted using the fatigue properties of single ply plate. Using this method a 3D Finite element model is established by ABAQUS software and the fatigue life and the fatigue damage evolution of a T300 / QY8911 laminats are analyzed, the results are more closer to the experimental results.

Fatigue Behavior of Ferritic-Pearlitic-Bainitic Steel – Effect of Positive Mean Stress

2009 ◽  
Vol 417-418 ◽  
pp. 577-580
Author(s):  
Jaroslav Polák ◽  
Martin Petrenec
Keyword(s):  
Fatigue Life ◽  
Plastic Strain ◽  
Strain Amplitude ◽  
Fatigue Behavior ◽  
Cyclic Creep ◽  
Plastic Strain Amplitude ◽  
Fatigue Properties ◽  
Mean Stress ◽  
Bainitic Steel ◽  
The Mean

The fatigue properties of ferritic-pearlitic-bainitic steel using specimens produced from massive forging were measured in stress controlled regime with positive mean stress. The cyclic creep curves and cyclic hardening/softening curves were evaluated. The fatigue life was plotted in dependence on the mean stress and on the plastic strain amplitude. The principal contribution to the drop of the fatigue life with the mean stress is due to the increase of the plastic strain amplitude in cycling with mean stress.

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