RATCHETING EVALUATION OF BIOLOGICAL TISSUES OVER ASYMMETRIC LOADING CYCLES

2021 ◽  
pp. 2150054
Author(s):  
M. S. HASHEMI ◽  
A. VARVANI-FARAHANI
Keyword(s):  
Close Agreement ◽  
Biological Tissues ◽  
Mean Stress ◽  
Asymmetric Loading ◽  
Testing Frequency ◽  
Nonzero Mean ◽  
Stress Cycles ◽  
Stress Ratios ◽  
Influential Parameters ◽  
Skin Samples

This study intends to evaluate the ratcheting response of biological samples prepared from bovine and porcine trabecular bone, articular cartilage, meniscus, and skin tissues and tested under asymmetric (nonzero mean stress) cycles. Meniscus and skin samples were tested with stress ratios of [Formula: see text] and [Formula: see text], respectively, while other tissues were tested at [Formula: see text]. Experimental ratcheting data and related influential parameters including stress level, stress rate, and testing frequency were discussed. A parametric ratcheting equation was further calibrated to estimate the ratcheting response of tissues. The predicted ratcheting data were found to be in close agreement with the reported experimental data.

A New Failure Criterion for Woven-Roving Fibrous Composites Subjected to Tension-Compression Local Plane Stresses With Different Stress Ratios

2005 ◽  
Vol 127 (1) ◽  
pp. 130-135
Author(s):  
M. Nasr ◽  
M. N. Abouelwafa ◽  
A. Gomaa ◽  
A. Hamdy ◽  
E. Morsi
Keyword(s):  
Mean Amplitude ◽  
Failure Criteria ◽  
Fatigue Tests ◽  
Static Strength ◽  
Static Stress ◽  
Mean Stress ◽  
Amplitude Component ◽  
The Mean ◽  
Stress Ratios ◽  
Local Plane

Thin-walled tubular specimens, made from woven-roving glass fiber-reinforced polyester (GFRP) with two fiber orientations, [±45°]2s and [0,90°]2s, were tested under torsional fatigue tests at negative stress ratios R,R=−1,−0.75,−0.5,−0.25, 0. The mean-amplitude diagram of the [0,90°]2s specimens was found to be divided into two regions; region (1) in which the mean stress is ineffective and region (2) in which the mean stress has a detrimental effect on the amplitude component. All examined failure criteria were found to be valid for the [0,90°]2s specimens, without any modifications; using the amplitude component and the corresponding fatigue strength in region (1), and the equivalent static stress with the corresponding static strength in region (2). For the [±45]2s specimens, having the mean stress being effective in the whole mean-amplitude diagram, the equivalent static stress was used with the corresponding static strength in different failure criteria. None of the available criteria succeeded in predicting failure for the studied case; consequently, was introduced, which a new modifying term SWT2/F1sF1f was introduced, which made Norris-Distortional, Tsai-Hahn, and Tsai-Hill criteria suitable for this case.

Ratchetting Behavior of Primary Heat Transport (PHT) Piping Material SA-333 Carbon Steel Subjected to Cyclic Loads at Room Temperature

2004 ◽  
Author(s):  
Sandeep Kulkarni ◽  
Y. M. Desai ◽  
T. Kant ◽  
G. R. Reddy ◽  
C. Gupta ◽  
...  
Keyword(s):  
Carbon Steel ◽  
Heat Transport ◽  
Biaxial Loading ◽  
Experimental Results ◽  
Biaxial Stress ◽  
Mean Stress ◽  
Bending Load ◽  
Chaboche Model ◽  
Stress Ratios ◽  
Uniaxial And Biaxial Loading

Ratchetting behavior of SA-333 Gr. 6 carbon steel used as primary heat transport (PHT) piping material has been investigated with three constitutive models proposed by Armstrong-Frederick, Chaboche and Ohno-Wang involving different hardening rules. Performance of the above mentioned models have been evaluated for a broad set of uniaxial and biaxial loading histories. The uniaxial ratchetting simulations have been performed for a range of stress ratios (R) by imposing different stress amplitudes and mean stress conditions. Numerical simulations indicated significant ratchetting and opening of hysteresis loop for negative stress ratio with constant mean stress. Application of cyclic stress without mean stress (R = −1.0) has been observed to produce negligible ratchet-strain accumulation in the material. Simulation under the biaxial stress condition was based on modeling of an internally pressurized thin walled pipe subjected to cyclic bending load. Numerical results have been validated with the experiments as per simulation conditions. All three models have been found to predict the observed accumulation of circumferential strain with increasing number of cycles. However, the Armstrong Frederick (A-F) model was found to be inadequate in simulating the ratchetting response for both uniaxial as well as biaxial loading cases. The A-F model actually overpredicted the ratchetting strain in comparison with the experimental strain values. On the other hand, results obtained with the Chaboche and the Ohno-Wang models for both the uniaxial as well as biaxial loading histories have been observed to closely simulate the experimental results. The Ohno-Wang model resulted in better simulation for the presents sets of experimental results in comparison with the Chaboche model. It can be concluded that the Ohno-Wang model suited well compared to the Chaboche model for above sets of uniaxial and biaxial loading histories.

scholarly journals Ratcheting response of biological tissues over asymmetric loading cycles

2021 ◽  
Author(s):  
Mahboubeh Sadat Hashemi
Keyword(s):  
Experimental Data ◽  
Strain Curve ◽  
Biological Tissues ◽  
Parametric Model ◽  
Stress Strain Curve ◽  
Stress Variation ◽  
Ratcheting Strain ◽  
Asymmetric Loading ◽  
Model Predictions ◽  
Failure Region

The purpose of this study is to examine the ratcheting phenomenon in a variety of biological tissues including the trabecular bone, meniscus, articular cartilage and skin, and propose a parametric model to predict the ratcheting strain of these tissues. Furthermore, utilizing experimental data, and the influence of different mechanical and biological parameters on the ratcheting strain are discussed. The dependency of ratcheting on frequency, stress rate, stress variation, physiological environment, and tissue sites is demonstrated. Besides, stiffness of the toe and linear regions in each cycle, and the modulus of the failure region of the stress-strain curve are computed. The energy dissipation in different cycles at two frequencies of 1 Hz and 10 Hz is discussed. A parametric model was employed to predict ratcheting behavior of the said biological tissues. The model predictions of the strain accumulation in tissues are found in agreement with the experimental data.

Spectral fatigue analysis for Al 2024-T3 with nonzero mean stress

2019 ◽  
Author(s):  
Pedro Henrique Alves Correa ◽  
Renner Egalon Pereira ◽  
Jorge Alberto Rodriguez Duran
Keyword(s):  
Fatigue Analysis ◽  
Mean Stress ◽  
Nonzero Mean ◽  
Al 2024

scholarly journals Study on the Elastic–Plastic Correlation of Low-Cycle Fatigue for Variable Asymmetric Loadings

Materials ◽  
2020 ◽  
Vol 13 (11) ◽  
pp. 2451 ◽  
Author(s):  
Junhong Zhang ◽  
Weidong Li ◽  
Huwei Dai ◽  
Nuohao Liu ◽  
Jiewei Lin
Keyword(s):  
Low Cycle Fatigue ◽  
Strain Ratio ◽  
Stress Effect ◽  
Mean Stress ◽  
Cycle Fatigue ◽  
Ratcheting Strain ◽  
Asymmetric Loading ◽  
Pressure Tubing ◽  
Proposed Model ◽  
The Mean

The mean stress effect in fatigue life varies by material and loading conditions. Therefore, a classical low cycle fatigue (LCF) model based on mean stress correction shows limits in asymmetric loading cases in both accuracy and applicability. In this paper, the effect of strain ratio (R) on LCF life is analyzed and a strain ratio-based model is presented for asymmetric loading cases. Two correction factors are introduced to express correlations between strain ratio and fatigue strength coefficient and between strain ratio and fatigue ductility coefficient. Verifications are conducted through four materials under different strain ratios: high-pressure tubing steel (HPTS), 2124-T851 aluminum alloy, epoxy resin and AZ61A magnesium alloy. Compared with current widely used LCF models, the proposed model shows a better life prediction accuracy and higher potential in implementation in symmetric and asymmetric loading cases for different materials. It is also found that the strain ratio-based correction is able to consider the damage of ratcheting strain that the mean stress-based models cannot.

scholarly journals Study and modelling of anodized 2618 aluminum behavior subjected to multiaxial fatigue

2018 ◽  
Vol 165 ◽  
pp. 16010 ◽  
Author(s):  
Benaissa Malek ◽  
Catherine Mabru ◽  
Michel Chaussumier
Keyword(s):  
Fatigue Life ◽  
Fatigue Resistance ◽  
Detrimental Effect ◽  
Surface States ◽  
Tensile Loading ◽  
Multiaxial Fatigue ◽  
Uniaxial Tensile ◽  
Mean Stress ◽  
Stress Ratios ◽  
The Impact

Anodized Aluminum alloys are widely used in aeronautic construction due to their specific mechanical properties. However, anodization process often leads to a decrease of the fatigue resistance of the alloys. In order to identify and characterize the different mechanisms involved in the detrimental effect of anodization of 2618-T851 alloy on its fatigue life and to determine the impact of loading nature, several tests have been performed on specimens with different surface states at various stress ratios. It was found that roughness of machining has no effect unlike the stress ratio or mean stress in tensile tests. The tests on the pickled, anodized, impregnated and sealed specimens showed it was the anodic oxidation step which was the more detrimental for fatigue resistance under tensile loading comparing to the other steps. It has been also observed that no such detrimental effect occurred under torsion loading. Concerning the prediction of fatigue life, two critical plane-based analysis approaches have been used (Morel and Fatemi-Socie criteria) to make fatigue life prediction for uniaxial and multiaxial fatigue test. Comparisons showed that both criteria gives overestimated fatigue life for uniaxial tensile loading under compression mean stress and underestimated fatigue life for tensile-torsion in phase loading.

Stress anisotropy and wave propagation: a micromechanical view

1996 ◽  
Vol 33 (5) ◽  
pp. 770-782 ◽  
Author(s):  
J C Santamarina ◽  
G Cascante
Keyword(s):  
Wave Propagation ◽  
Polarization Plane ◽  
Mean Stress ◽  
Resonant Column ◽  
Measured Velocity ◽  
Stress Anisotropy ◽  
Mechanical Waves ◽  
The Mean ◽  
Stress Ratios ◽  
Deviatoric Stresses

Wave propagation is a constant-fabric macrophenomenon, suitable to microinterpretation. Both velocity and attenuation characterize state, including inherent and stress-induced anisotropy. The purpose of this research is to study the effect of isotropic and deviatoric stresses on wave propagation in particulate materials at low strains and to interpret results at the microlevel. A resonant-column device was midified to allow for the application of axial extension and axial compression deviatoric loading. The fixed-free boundary condition of the sample was maintained. Data for round, hard-grained sand show that shear wave velocity and attenuation are primarily dependent on the mean stress on the polarization plane, with minimal effect of the deviatoric component, in agreement with prior observations at stress ratios less than 2–3. Attenuation is strongly correlated with the mean stress in the polarization plane and the level of shear strain. Damping does not vanish at low strains, contrary to predictions based on hysteretic behaviour; hence, other loss mechanisms must take place at low strains. Low-strain wave parameters are adequately corrected for mid-strain using modified hyperbolic models. Measured velocity and damping trends during isotropic and anisotropic loading qualitatively agree with predictions based on regular arrays. Key words: mechanical waves, resonant column, damping, shear modulus, stress anisotropy, random vibration.

An Energy-Based Fatigue and Creep-Fatigue Damage Parameter

1977 ◽  
Vol 99 (4) ◽  
pp. 524-533 ◽  
Author(s):  
B. N. Leis
Keyword(s):  
Damage Parameter ◽  
Mean Stress ◽  
Deformation Response ◽  
Mechanical Cycling ◽  
Creep Fatigue ◽  
General Parameter ◽  
Data Consolidation ◽  
Nonzero Mean ◽  
Fatigue Damage Parameter ◽  
High Degree

A general damage parameter for fatigue and creep-fatigue applications based on the hypothesis that damage is dependent on the internal total octahedral strain energy is derived. This general parameter is valid for isothermal mechanical cycling and inherently accounts for multiaxiality and mean stress for both nonviscous and viscous deformation response, including hold times. Forms of the parameter which correspond to laboratory test conditions under generalized states of stress and strain with nonzero mean stress are derived. The ability of these specific forms to affect data consolidation is examined using experimental fatigue and creep-fatigue life data for the corresponding conditions. It is shown that these specific forms of the general parameter affect a high degree of data consolidation.

The Effect of Mean Stress on Fatigue Crack Propagation in Plates Under Extension and Bending

1967 ◽  
Vol 89 (4) ◽  
pp. 885-892 ◽  
Author(s):  
R. Roberts ◽  
F. Erdogan
Keyword(s):  
Fatigue Crack ◽  
Crack Propagation ◽  
Fatigue Crack Propagation ◽  
Thin Plates ◽  
Mean Stress ◽  
Cylindrical Bending ◽  
Bending Loads ◽  
Nonzero Mean ◽  
Theoretical Considerations ◽  
Existing Data

An earlier study of fatigue crack propagation in thin plates under fluctuating plane extension and cylindrical bending is extended to include the effect of nonzero mean stress. The theoretical considerations are applied to existing data and to new data obtained from 2024-T3 bare and clad aluminum specimens subjected to fully reversed and nonsymmetric bending loads. For the ranges studied, the agreement between the data and the model developed seems to be very good.

The Effect of Mean Stress on the Fatigue Behavior of Woven-Roving Glass Fiber-Reinforced Polyester Subjected to Torsional Moments

2005 ◽  
Vol 127 (3) ◽  
pp. 301-309 ◽  
Author(s):  
Mohamed N. A. Nasr ◽  
M. N. Abouelwafa ◽  
A. Gomaa ◽  
A. Hamdy ◽  
E. Morsi
Keyword(s):  
Glass Fiber ◽  
Detrimental Effect ◽  
Fatigue Behavior ◽  
Local Stress ◽  
Mean Stress ◽  
Glass Fiber Reinforced ◽  
Stress Components ◽  
Amplitude Component ◽  
The Mean ◽  
Stress Ratios

The effect of torsional mean stress on the fatigue behavior of glass fiber-reinforced polyester (GFRP) is studied by testing thin-walled, woven-roving tubular specimens with two fiber orientations, [±45°]2s and [0,90°]2s, at negative stress ratios (R),R=−1,−0.75,−0.5,−0.25, 0. The [±45°]2s specimens were found to have higher fatigue strength than the [0,90°]2s specimens at all stress ratios. This is attributed to the difference in local stress components, the [±45°]2s specimens being subjected to tension-compression local stress components, while the [0,90°]2s specimens being subjected to pure local shear stress. For the studied stress ratios; the mean stress component had a detrimental effect on the amplitude component for the [±45°]2s specimens; while it was ineffective for the [0,90°]2s specimens in a certain region in the mean-amplitude diagram, region (1), then it had a detrimental effect in the rest of the diagram, region (2). The S–N curves for positive stress ratios were extrapolated from those for negative stress ratios, which were found experimentally, for the [0,90°]2s specimens. The positive stress ratio points, having the same local stress state as the negative ones, showed an acceptable behavior tending to decrease the amplitude component for the same life.

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