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.

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.

Thermal cycling aging effects on the ratcheting behavior of anisotropic conductive film

2015 ◽  
Vol 27 (4) ◽  
pp. 185-194 ◽  
Author(s):  
Hong Gao ◽  
Jianhua Ma ◽  
Lilan Gao ◽  
Dunji Yu ◽  
Jinsheng Sun
Keyword(s):  
Thermal Cycling ◽  
Strain Rate ◽  
Loading Rate ◽  
Stress Amplitude ◽  
Mean Stress ◽  
Loading Conditions ◽  
Loading History ◽  
Adhesive Film ◽  
Content Type ◽  
Ratcheting Strain

Purpose – The purpose of this paper is to determine: how the thermal cycling aging affects the ratcheting behavior of anisotropic conductive adhesive film (ACF); how the loading conditions and loading history affect the ratcheting strain and strain rate of ACF with different thermal cycling aging histories. Design/methodology/approach – The ACF of CP6920F was cured at 190°C in an electro-thermal vacuum drying apparatus for 30 s. The cured specimens were put into the thermal cycling chamber (−40-150°C) for aging to 25, 50, 100, 200 and 500 cycles. A series of uniaxial ratcheting tests of aged ACF after different thermal cycles was carried out under stress control at 80°C. Findings – The ACF subjected to larger number of thermal aging cycles exhibits less ratcheting strain under the same loading conditions. The ACF with the same thermal cycling aging history shows more ratcheting strain and a higher ratcheting strain rate when loaded under a larger mean stress or stress amplitude or a lower loading rate. The ratcheting behavior of aged ACF is found to be more sensitive to the lower loading rate. The higher mean stress (or stress amplitude) enhances the deformation resistance and consequently restrains the ratcheting strain of subsequent cycling with a lower mean stress (or stress amplitude). The prior lower loading rate accelerates the plastic deformation more significantly than the higher one. Originality/value – The influencing trends of thermal cycling aging, loading condition and loading history on ratcheting behavior of ACF are obtained, which is important for the design and safety assessment of ACF joints.

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 On the Plastic Strain Accumulation in Notched Bars During High-Temperature Creep Dwell

2020 ◽  
Vol 36 (2) ◽  
pp. 167-176 ◽  
Author(s):  
Daniele Barbera ◽  
Haofeng Chen
Keyword(s):  
High Temperature ◽  
Cyclic Loading ◽  
Plastic Strain ◽  
Kinematic Hardening ◽  
High Temperature Creep ◽  
Strain Accumulation ◽  
Material Models ◽  
Cyclic Loading Condition ◽  
Hardening Material ◽  
Temperature Creep

ABSTRACTStructural integrity plays an important role in any industrial activity, due to its capability of assessing complex systems against sudden and unpredicted failures. The work here presented investigates an unexpected new mechanism occurring in structures subjected to monotonic and cyclic loading at high temperature creep condition. An unexpected accumulation of plastic strain is observed to occur, within the high-temperature creep dwell. This phenomenon has been observed during several full inelastic finite element analyses. In order to understand which parameters make possible such behaviour, an extensive numerical study has been undertaken on two different notched bars. The notched bar has been selected due to its capability of representing a multiaxial stress state, which is a practical situation in real components. Two numerical examples consisting of an axisymmetric v-notch bar and a semi-circular notched bar are considered, in order to investigate different notches severity. Two material models have been considered for the plastic response, which is modelled by both Elastic-Perfectly Plastic and Armstrong-Frederick kinematic hardening material models. The high-temperature creep behaviour is introduced using the time hardening law. To study the problem several results are presented, as the effect of the material model on the plastic strain accumulation, the effect of the notch severity and the mesh element type and sensitivity. All the findings further confirm that the phenomenon observed is not an artefact but a real mechanism, which needs to be considered when assessing off-design condition. Moreover, it might be extremely dangerous if the cyclic loading condition occurs at such a high loading level.

Uniaxial Ratcheting and Low-Cycle Fatigue Failure of U75V Rail Steel

2016 ◽  
Vol 853 ◽  
pp. 246-250 ◽  
Author(s):  
Tao Fang ◽  
Qian Hua Kan ◽  
Guo Zheng Kang ◽  
Wen Yi Yan
Keyword(s):  
Fatigue Life ◽  
Strain Amplitude ◽  
Stress Ratio ◽  
Stress Amplitude ◽  
Rail Steel ◽  
Low Cycle Fatigue ◽  
Mean Stress ◽  
Cycle Fatigue ◽  
Ratcheting Strain ◽  
Cyclic Straining

Experiments on U75V rail steel were carried out to investigate the cyclic feature, ratcheting behavior and low-cycle fatigue under both strain- and stress-controlled loadings at room temperature. It was found that U75V rail steel shows strain amplitude dependent cyclic softening feature, i.e., the responded stress amplitude under strain-controlled decreases with the increasing number of cycles and reaches a stable value after about 20th cycle. Ratcheting strain increases with an increasing stress amplitude and mean stress, except for stress ratio, and the ratcheting strain in failure also increases with an increasing stress amplitude, mean stress and stress ratio. The low-cycle fatigue lives under cyclic straining decrease linearly with an increasing strain amplitude, the fatigue lives under cyclic stressing decrease with an increasing mean stress except for zero mean stress, and decrease with an increasing stress amplitude. Ratcheting behavior with a high mean stress reduces fatigue life of rail steel by comparing fatigue lives under stress cycling with those under strain cycling. Research findings are helpful to evaluate fatigue life of U75V rail steel in the railways with passenger and freight traffic.

Bending Ratcheting Behavior of Zircaloy-4 Alloy at Room Temperature

2013 ◽  
Vol 690-693 ◽  
pp. 1713-1717 ◽  
Author(s):  
Hong Qiang Guo ◽  
Hua Li ◽  
Yi Chen Sun ◽  
Wei Wei Yu
Keyword(s):  
Room Temperature ◽  
Stress Amplitude ◽  
Experimental Results ◽  
Strain Level ◽  
Mean Stress ◽  
Cyclic Tests ◽  
Ratcheting Strain

In this paper, a series of bending cyclic tests under stress controlled were conducted at room temperature on Zircaloy-4 (Zr-4) to investigate its bending ratcheting behavior. The effects of mean stress and stress amplitude on the bending ratcheting behavior were experimentally studied, respectively. The experimental results show that the ratcheting strain of the material is very sensitive to mean stress and stress amplitude. It can be concluded that ratcheting strain level increases with increasing mean stress and stress amplitude.

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