scholarly journals Permanent Deformation Characteristics of Coarse Grained Subgrade Soils under Train-Induced Repeated Load

2017 ◽  
Vol 2017 ◽  
pp. 1-15 ◽  
Author(s):  
Xianzhang Ling ◽  
Peng Li ◽  
Feng Zhang ◽  
Yingying Zhao ◽  
Yan Li ◽  
...  
Keyword(s):  
Initial Stress ◽  
Deformation Behavior ◽  
Stress Ratio ◽  
Stress Amplitude ◽  
Permanent Deformation ◽  
Cyclic Stress ◽  
Coarse Grained ◽  
Mean Stress ◽  
Axial Deformation ◽  
Repeated Load

This paper presents the results of a laboratory experiment that aimed to characterize the permanent deformation behavior of coarse grained soils. To evaluate the effects of the cyclic stress amplitude, initial mean stress, and initial stress ratio on the permanent axial deformation, six series of repeated load triaxial tests were performed. The results indicate that permanent deformation of coarse grained soils increased with increasing cyclic stress amplitude. In particular, for relative low cyclic stress levels, accumulation rate of permanent deformation decreased progressively with number of cycles and eventually reached an equilibrium state. The initial stress ratio was also found to obviously facilitate the buildup of axial deformation since it means higher deviatoric stress as the mean pressure kept constant. As the initial stress ratio was less than the slope of static failure line, the experimental results indicated that the increase of initial mean stress enhanced the capability of resisting deformation. A simplified mechanistic empirical prediction model was proposed, which predicted the permanent deformation as product of four independent functions about cyclic stress amplitude, initial mean stress, initial stress ratio, and number of load cycles. Satisfactory predictions of the permanent deformation behavior of coarse grained soils were obtained with the proposed model.

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.

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.

Asymmetric cyclic deformation behavior of SA 333 steel at elevated temperatures

2019 ◽  
Vol 16 (1) ◽  
pp. 78-86
Author(s):  
Girendra Kumar ◽  
Ashok Kumar ◽  
H.N. Bar
Keyword(s):  
Temperature Regime ◽  
Cyclic Deformation ◽  
Deformation Behavior ◽  
Stress Amplitude ◽  
Gauge Length ◽  
Stress Rate ◽  
Dynamic Strain ◽  
Mean Stress ◽  
Strain Accumulation ◽  
Content Type

Purpose The purpose of this paper is to study the effect of mean stress and stress amplitude on the asymmetric cyclic deformation behavior of SA333 Gr-6 C-Mn steel. Such type of loading may arise during the service period because of the load fluctuations, thermal gradients and sudden loading like seismic events. Tests were also carried out at different temperatures to understand the effect of it on sensitiveness of the materials deformation behavior. Design/methodology/approach Cylindrical specimen of 8-mm gauge diameter and 15-mm gauge length was fabricated from the pipe section along its axis. Stress controlled ratcheting tests were carried out by using triangular waveform for cyclic loading. The strain accumulations were measured using 12.5-mm gauge length extensometer. Ratcheting tests were carried out at fixed stress amplitude of 400 MPa and mean stress varying from 0 to 75 MPa, whereas at the fixed mean stress of 100 MPa and stress amplitude varies from 300 to 400 MPa at 300°C. To study the effect of temperature on ratcheting behavior, tests were carried out at a load of 100 MPa mean stress and 350 MPa stress amplitude, with a varying temperature between room temperature and 350°C. The stress rate of 115 MPas-1 was kept constant for all the tests. Findings Increase in mean stress and stress amplitude, ratcheting strain and plastic strain amplitude increases, whereas ratcheting life decreases. With an increase in temperature, ratcheting life increases and strain accumulation decreases up to 300°C, whereas on further increase in temperature, strain accumulation increases with reduction in ratcheting life. Minimum ratcheting rate was observed at 250°C and 300°C. The dynamic strain aging (DSA) phenomena lead to the hardening of the material. The investigated steel shows DSA temperature regime lies between 250°C and 300°C. The failure modes at 250°C and 300°C temperature was transgranular, whereas at 350°C complete ductile. Research limitations/implications The stress rate and loading condition may vary to study the ratcheting behavior. Practical implications From this study, the critical cyclic load may be determined. The DSA temperature regime of this material is determined at this stress rate. This could help to evaluate the cyclic deformation behavior of the material with temperature changes. Originality/value In this investigation, the DSA temperature regime has been determined where maximum ratcheting life, minimum strain accumulation and ratcheting rate were observed. The critical load where the minimum life of the material occurred at elevated temperature is 100 MPa mean stress and 400 MPa stress amplitude.

scholarly journals Effect of Cyclic Stress Level and Overconsolidation Ratio on Permanent Deformation Behaviour of Clayey Subsoil

2018 ◽  
Vol 4 (8) ◽  
pp. 1772 ◽  
Author(s):  
Lei Sun
Keyword(s):  
Stress Level ◽  
Stress Ratio ◽  
Deformation Behaviour ◽  
Permanent Deformation ◽  
Cyclic Stress ◽  
Test Results ◽  
Overconsolidation Ratio ◽  
Deviator Stress ◽  
Shakedown Limit

This paper presents the results of a series of one-way cyclic triaxial tests carried out to investigate the role of cyclic stress level and overconsolidation ratio (OCR) on the permanent deformation behaviour of saturated clayey subsoil during long-term cyclic loading. Based on the test results and shakedown concept, two cyclic threshold deviator stress ratios can be defined: the plastic shakedown limit cyclic deviator stress ratio CSRpt (0.46) and the plastic creep shakedown limit cyclic deviator stress ratio CSRpc (0.75). It was found that, below CSRpt, the soil experiences slight deformation and gradually achieves a long-term steady state response. Within the range of CSRpt<CSR<CSRpc, the plastic strain will accumulates substantially and becomes unstable. Once the CSRpc is exceeded significant deformation and failure may occur. In the practical engineering, CSRpt can be used for preliminary design of pavement foundation. In addition, based on the test results, a simplified permanent axial strain model that explicitly considers the effects of CSR and OCR is developed.

Effect of Vibrations on Lifetime of Ni Base Single Crystals Subjected to Tensile Stress

2007 ◽  
Vol 567-568 ◽  
pp. 293-296
Author(s):  
Ludvík Kunz ◽  
Petr Lukáš ◽  
Rastilav Mintách
Keyword(s):  
Fatigue Crack ◽  
Single Crystals ◽  
High Frequency ◽  
Detrimental Effect ◽  
Stress Amplitude ◽  
Stress Component ◽  
Cyclic Stress ◽  
Mean Stress ◽  
Initiation And Propagation ◽  
The Mean

The lifetime of superalloy single crystals CMSX-4 and CM186LC subjected to tensile mean stress with vibrations at high temperatures has been experimentally studied. Both beneficial and detrimental effect of cyclic stress component has been observed. An increase of lifetime due to superposition of cyclic component on the mean stress is explained by reduction of creep rate due to vibrations. The onset of decrease of lifetime with increasing stress amplitude is observed when the fatigue damage due to initiation and propagation of fatigue crack overbalances the beneficial influence of high frequency cycling.

Effect of variable confining pressure on cyclic behaviour of granular soil under triaxial tests

2017 ◽  
Vol 54 (6) ◽  
pp. 768-777 ◽  
Author(s):  
Qi Sun ◽  
Yuanqiang Cai ◽  
Jian Chu ◽  
Quanyang Dong ◽  
Jun Wang
Keyword(s):  
Initial Stress ◽  
Stress Ratio ◽  
Permanent Deformation ◽  
Confining Pressure ◽  
Stress Path ◽  
Average Stress ◽  
Triaxial Tests ◽  
Cyclic Behaviour ◽  
Different Strains ◽  
Variable Confining Pressure

Previous studies were performed to use combined cyclic deviatoric stress and confining pressure to simulate cyclic vertical and horizontal normal stresses under traffic loading. The effect of variable confining pressure (VCP) on the permanent deformation of soils was investigated. However, some studies concluded VCP could promote the development of permanent deformation compared to the tests with constant confining pressure (CCP), while others drew the opposite conclusions. In this study, three types of CCP and VCP tests with identical maximum stress, identical average stress, and identical initial stress were conducted. Test results showed VCP tests accumulated more permanent strains when CCP and VCP tests had identical maximum or average stress, and the permanent strains increased with the decrease in the inclinations of stress paths, while similar permanent strains were generated when CCP and VCP tests had identical initial stress. In addition, larger permanent strains were generated with the increase in stress ratio or length of stress path in both CCP and VCP tests. Considering that different strains were cumulated in CCP and VCP tests with the same stress ratio, it is recommended that both stress ratio and length of stress path be considered to assess the permanent deformation.

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