scholarly journals Effects of Varying Mean Stress and Stress Amplitude on the Fatigue of Polysilicon

2003 ◽  
Vol 795 ◽  
Author(s):  
H. Kahn ◽  
R. Ballarini ◽  
A. H. Heuer
Keyword(s):  
Cyclic Loading ◽  
Polycrystalline Silicon ◽  
Stress Amplitude ◽  
Fatigue Behavior ◽  
Monotonic Loading ◽  
Mean Stress ◽  
Bend Strength ◽  
Electrostatic Actuator ◽  
Single Edge ◽  
Physical Mechanisms

ABSTRACTPolycrystalline silicon (polysilicon) single edge-notched fatigue specimens with micrometer-sized dimensions were macromachined and subjected to cyclic loading using an integrated electrostatic actuator. The effects of fatigue were determined by comparing the monotonic bend strength measured after cyclic loading to the monotonic bend strength of specimens that received no cycling. Both strengthening and weakening were observed, depending on the levels of mean stress and fatigue stress amplitude during the cyclic loading. Monotonic loading with similar stress levels prior to bend strength measurements had no effect on measured bend strength. Possible physical mechanisms responsible for this fatigue behavior are discussed.

Comparative study of the effective parameters on residual stress relaxation in welded aluminum plates under cyclic loading

2020 ◽  
Vol 21 (5) ◽  
pp. 505
Author(s):  
Yousef Ghaderi Dehkordi ◽  
Ali Pourkamali Anaraki ◽  
Amir Reza Shahani
Keyword(s):  
Residual Stress ◽  
Cyclic Loading ◽  
Stress Relaxation ◽  
Stress Amplitude ◽  
Cyclic Plasticity ◽  
Mean Stress ◽  
Effective Parameters ◽  
Perfect Plasticity ◽  
Residual Stress Relaxation ◽  
Aluminum Plates

The prediction of residual stress relaxation is essential to assess the safety of welded components. This paper aims to study the influence of various effective parameters on residual stress relaxation under cyclic loading. In this regard, a 3D finite element modeling is performed to determine the residual stress in welded aluminum plates. The accuracy of this analysis is verified through experiment. To study the plasticity effect on stress relaxation, two plasticity models are implemented: perfect plasticity and combined isotropic-kinematic hardening. Hence, cyclic plasticity characterization of the material is specified by low cycle fatigue tests. It is found that the perfect plasticity leads to greater stress relaxation. In order to propose an accurate model to compute the residual stress relaxation, the Taguchi L18 array with four 3-level factors and one 6-level is employed. Using statistical analysis, the order of factors based on their effect on stress relaxation is determined as mean stress, stress amplitude, initial residual stress, and number of cycles. In addition, the stress relaxation increases with an increase in mean stress and stress amplitude.

scholarly journals The influence of stress level on the ratcheting magnitude and progress rate in steel alloys under uniaxial loading conditions

2021 ◽  
Author(s):  
Prasanth Chandrasekar
Keyword(s):  
Cyclic Loading ◽  
Plastic Strain ◽  
Strain Rate ◽  
Loading Condition ◽  
Stress Amplitude ◽  
Fatigue Loading ◽  
Mean Stress ◽  
Cyclic Loading Condition ◽  
Ratcheting Strain ◽  
Cyclic Damage

Engineering materials in their service life undergo symmetric or asymmetric fatigue loading, which leads to fatigue damage in the material. Ratcheting damage is due to the application of mean stress under cyclic loading condition. From deformation behavior perspective, application of mean stress under stress-controlled fatigue loading gives rise to accumulation of plastic strain in the material. Ratcheting strain increases with an increase in applied mean stress and stress amplitude. In addition, ratcheting behavior will increase in cyclic damage with the rise in strain accumulation and it can be illustrated by a shift in the hysteresis loop towards large plastic strain amplitudes. This study focuses on the ratcheting behavior of different steel materials under uniaxial cyclic loading condition and suggests a suitable method to arrest ratcheting by loading the materials at zero ratcheting strain rate condition with specified mean stress and stress amplitudes. The three dimensional surface is created with stress amplitude, mean stress and ratcheting strain rate for different steel materials. This represents a graphical surface zone to study the ratcheting strain rates for various mean stress and stress amplitude combinations.

Experimental evaluation of cyclic stresses on axially loaded bolted joints

2016 ◽  
Vol 230 (15) ◽  
pp. 2611-2622 ◽  
Author(s):  
Sandro Griza ◽  
Marcio EG da Silva ◽  
Silvando V dos Santos ◽  
Telmo R Strohaecker
Keyword(s):  
Stress Amplitude ◽  
Fatigue Behavior ◽  
Joint Stiffness ◽  
Theoretical Models ◽  
Cyclic Stress ◽  
Bolted Joints ◽  
Mean Stress ◽  
Steel Members ◽  
Applied Torque ◽  
Wide Range

The bolted joints fatigue behavior was analyzed by using torque as tightening method and steel and aluminum as members’ material. The bolt used in the current study was the M6 class 8.8. The bolt preload value was calculated based on the bolts’ elongation in each applied torque. The fatigue limit increases as the torque increases up to the torque limit to fracture the bolt. This behavior was seen in both members’ material. Steel members support higher torque before bolt fracture. An analytical study also evaluated the relationship between the cyclic stress amplitude and the mean stress experienced by fatigue-tested bolts based on the available models for joint stiffness. The results were compared to the bolt fatigue diagram by Burguete and Patterson. The herein studied linear elastic theoretical models showed wide range in the correlation between stress amplitude and mean stress.

Test and Research on Ratchet Effect of 16 Mn Steel under Cyclic Loading

2015 ◽  
Vol 1095 ◽  
pp. 205-208
Author(s):  
Guang Hong Xiao ◽  
Yang Kai Xiang ◽  
Qiu Ling Zhang
Keyword(s):  
Control System ◽  
Cyclic Loading ◽  
Stress Amplitude ◽  
Mean Stress ◽  
Loading History ◽  
Ratchet Effect ◽  
Stress Control ◽  
Mn Steel ◽  
16Mn Steel

The uniaxial and multiaxial non-proportional cyclic experiments of 16Mn steel under stress-control were carried out using MTS809 Series machine and Teststar control system .The influence of stress amplitude, mean stress and their loading history on uniaxial and multiaxial ratcheting is studied.

scholarly journals The influence of stress level on the ratcheting magnitude and progress rate in steel alloys under uniaxial loading conditions

2021 ◽  
Author(s):  
Prasanth Chandrasekar
Keyword(s):  
Cyclic Loading ◽  
Plastic Strain ◽  
Strain Rate ◽  
Loading Condition ◽  
Stress Amplitude ◽  
Fatigue Loading ◽  
Mean Stress ◽  
Cyclic Loading Condition ◽  
Ratcheting Strain ◽  
Cyclic Damage

Engineering materials in their service life undergo symmetric or asymmetric fatigue loading, which leads to fatigue damage in the material. Ratcheting damage is due to the application of mean stress under cyclic loading condition. From deformation behavior perspective, application of mean stress under stress-controlled fatigue loading gives rise to accumulation of plastic strain in the material. Ratcheting strain increases with an increase in applied mean stress and stress amplitude. In addition, ratcheting behavior will increase in cyclic damage with the rise in strain accumulation and it can be illustrated by a shift in the hysteresis loop towards large plastic strain amplitudes. This study focuses on the ratcheting behavior of different steel materials under uniaxial cyclic loading condition and suggests a suitable method to arrest ratcheting by loading the materials at zero ratcheting strain rate condition with specified mean stress and stress amplitudes. The three dimensional surface is created with stress amplitude, mean stress and ratcheting strain rate for different steel materials. This represents a graphical surface zone to study the ratcheting strain rates for various mean stress and stress amplitude combinations.

Test and Research on Ratchet Effect of 16 Mn Steel under Cyclic Loading

2012 ◽  
Vol 476-478 ◽  
pp. 965-968
Author(s):  
Guang Hong Xiao ◽  
Yang Kai Xiang ◽  
Xiao Lei Jia
Keyword(s):  
Control System ◽  
Cyclic Loading ◽  
Stress Amplitude ◽  
Mean Stress ◽  
Loading History ◽  
Ratchet Effect ◽  
Stress Control ◽  
Mn Steel ◽  
16Mn Steel

The uniaxial and multiaxial non-proportional cyclic experiments of 16Mn steel under stress-control were carried out using MTS809 Series machine and Teststar control system .The influence of stress amplitude, mean stress and their loading history on uniaxial and multiaxial ratcheting is studied.

Determinist-Probabilistic Concept in Modeling Fatigue Damage Through a Micromechanical Approach

2009 ◽  
Vol 132 (1) ◽  
Author(s):  
A. Abdul-Latif ◽  
M. Chadli
Keyword(s):  
Fatigue Life ◽  
Cyclic Loading ◽  
Elastic Strain ◽  
Low Cycle Fatigue ◽  
Fatigue Behavior ◽  
Damage Variable ◽  
Cyclic Behavior ◽  
Thermodynamic Force ◽  
Mean Stress ◽  
Loading Paths

Motivated by a micromechanical determinist-probabilistic model coupled with damage recently developed by the authors, a new generalization is proposed to describe the nonlinear elasto-inelastic cyclic strain-stress behavior of polycrystals notably under biaxial cyclic loading paths. In this context, this generalization considers a compressible and linear anisotropic granular elastic strain behavior coupled with damage. The model is expressed in the framework of the time dependent plasticity for a small strain assumption. It is assumed that a damage variable initiates at the mesoscopic (granular) level where the plastic strain localization phenomenon takes place. The associated thermodynamic force of the damage variable is determined using the concept of total granular energy (elastic and inelastic). The transition of the elastic strain from the single to the polycrystal is modified due to its explicit coupling with damage. Comparisons between predicted and experimental results are conducted describing the low-cycle fatigue behavior of the aluminum alloy 2024 under different complex cyclic loading paths. It is demonstrated that the model has a reasonable ability in describing the cyclic behavior of this alloy. Qualitatively, the model is tested under different cyclic loading paths with stress-controlled condition describing especially the ratcheting behavior of the alloy. In fact, the effects of the applied mean stress on the predicted overall elasto-inelastic behavior and on the fatigue life are carefully studied. It shows the dependence of the fatigue life on the mean stress value.

scholarly journals Experimental Observation on the Pure Torsional Ratchetting of Polycarbonate Polymer at Room Temperature

2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Fucong Lu ◽  
Bencheng Zhang ◽  
Bo Wu ◽  
Zhiwen Wu ◽  
Xiao Suo
Keyword(s):  
Cyclic Loading ◽  
Stress Level ◽  
Room Temperature ◽  
Stress Amplitude ◽  
Peak Stress ◽  
Stress Rate ◽  
Mean Stress ◽  
Loading History ◽  
Lower Stress ◽  
Lower Stress Level

The stress-controlled pure torsional cyclic tests are carried out to investigate the torsional ratchetting of polycarbonate (PC) polymer at room temperature. The effects of applied shear mean stress, stress amplitude, stress rate, peak stress hold, and stress history on the torsional ratchetting are discussed. The shear strain of tubular specimen is measured by a noncontact digital image correlation (DIC) apparatus. The results show that the torsional ratchetting of the polymer obviously depends on the applied shear stress level, stress rate, and peak stress hold; the shear ratchetting strain and its rate increase with the increasing mean stress, stress amplitude, and peak stress hold time and with the decreasing stress rate. Moreover, the torsional ratchetting depends on the stress history. A higher stress level cyclic loading history restrains the evolution of torsional ratchetting in the subsequent lower stress level cyclic loading, while the lower stress level cyclic loading history promotes the torsional ratchetting of the subsequent higher level cyclic loading.

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