Adjustable buttons for ACL graft cortical fixation partially fail with cyclic loading and unloading

2018 ◽  
Vol 27 (8) ◽  
pp. 2530-2536 ◽  
Author(s):  
J. Glasbrenner ◽  
C. Domnick ◽  
M. J. Raschke ◽  
T. Willinghöfer ◽  
C. Kittl ◽  
...  
Keyword(s):  
Cyclic Loading ◽  
Acl Graft ◽  
Cyclic Loading And Unloading ◽  
Loading And Unloading

Effects of Detwinning on the Inelasticity of AZ31B Sheets During Cyclic Loading and Unloading

2018 ◽  
Vol 10 (09) ◽  
pp. 1850095 ◽  
Author(s):  
H. Wang ◽  
D. Tang ◽  
D. Y. Li ◽  
Y. H. Peng ◽  
P. D. Wu
Keyword(s):  
Cyclic Loading ◽  
Magnesium Alloys ◽  
Plasticity Model ◽  
Inelastic Behavior ◽  
Deformation History ◽  
Cyclic Loading And Unloading ◽  
Polycrystal Plasticity ◽  
Self Consistent ◽  
Loading And Unloading ◽  
Previous Loading

Magnesium alloys exhibit significant inelastic behavior during unloading, especially when twinning and detwinning are involved. It is commonly accepted that noteworthy inelastic behavior will be observed during unloading if twinning occurs during previous loading. However, this phenomenon is not always observed for Mg sheets with strong rolled texture. Therefore, the inelasticity of AZ31B rolled sheets with different rolled textures during cyclic loading-unloading are investigated by elastic viscoplastic self-consistent polycrystal plasticity model. The incorporation of the twinning and detwinning model enables the treatment of detwinning, which plays an important role for inelastic behavior during unloading. The effects of texture, deformation history, and especially twinning and detwinning on the inelastic behaviors are carefully investigated and found to be remarkable. The simulated results are in agreement with the available experimental observations, which reveals that the inelastic behavior for strongly rolled sheets is very different than the extruded bars.

scholarly journals Damage and fractal evolution trends of sandstones under constant-amplitude and tiered cyclic loading and unloading based on acoustic emission

2019 ◽  
Vol 15 (7) ◽  
pp. 155014771986102
Author(s):  
Dongxu Liang ◽  
Nong Zhang ◽  
Lixiang Xie ◽  
Guangming Zhao ◽  
Deyu Qian
Keyword(s):  
Acoustic Emission ◽  
Cyclic Loading ◽  
Damage Evolution ◽  
Damage Accumulation ◽  
Fractal Dimensions ◽  
Damage Variable ◽  
Constant Amplitude ◽  
Kaiser Effect ◽  
Cyclic Loading And Unloading ◽  
Loading And Unloading

It is of significance to study the damage and destruction of rock under cyclic loading in geotechnical engineering. We determined the trends in damage evolution of sandstone under constant-amplitude and tiered cyclic loading and unloading under uniaxial compression. The results of the study show that (1) the variation of acoustic-emission events was consistent with the stress curves and 89% of all acoustic-emission events occurred during the cycling stages. The observed Kaiser effect was more notable in tiered cycling. (2) The damage variable increased sharply in the cycling stages and its increment was 0.07 higher for tiered cycling than constant-amplitude cycling. Sandstone exhibited greater damage under tiered cyclic loading and unloading. (3) Equations for the evolution of the damage variable under the two cycle modes were obtained by fitting of experimental data. (4) The fractal dimensions of the constant-amplitude cycle were larger than those of the tiered cycle. The process of damage and destruction presents a trend of reducing fractal dimension. The damage accumulation of sandstone under tiered cycling was faster than under constant-amplitude cycling. These results provide references for damage and early warning of rock under both constant-amplitude and tiered cyclic loading and unloading.

scholarly journals Research on the Mechanical Characteristics of Cyclic Loading and Unloading of Rock Based on Infrared Thermal Image Analysis

2021 ◽  
Vol 2021 ◽  
pp. 1-16
Author(s):  
Lewen Wu ◽  
Keping Zhou ◽  
Feng Gao ◽  
Zhongyuan Gu ◽  
Chun Yang
Keyword(s):  
Temperature Field ◽  
Cyclic Loading ◽  
Infrared Radiation ◽  
Energy Analysis ◽  
Heating Zone ◽  
Characteristic Analysis ◽  
Temperature Zone ◽  
Energy Accumulation ◽  
Cyclic Loading And Unloading ◽  
Loading And Unloading

In the operations of underground rock engineering, such as mining, the formation of goafs is often accompanied by unloading and energy effects. In this study, a cyclic loading and unloading stress test is carried out to analyze the strength characteristics of the loaded samples under different loading and unloading ranges as well as different numbers of cycles. The rock force is accompanied by substantial energy changes. To better fit the energy analysis under cyclic loading and unloading conditions, thermal infrared radiation characteristic analysis is performed during rock loading and unloading. An infrared radiation camera is adopted to detect the infrared characteristics of the rock force process after cyclic loading and unloading. Multiangle detection is implemented on the temperature, temperature field, and frequency histogram. The analysis shows that cyclic loading and unloading first strengthen and then weaken the rock. Moreover, the failure caused by the local stress concentration leads to a sharp increase in the temperature. There are significant temperature fluctuations before and after failure, and the temperature field after failure can be divided into three zones, namely, the normal temperature zone, heating zone, and mutational temperature zone, to comprehensively reflect that rock compression failure which is accompanied by the process of energy accumulation and release. On the basis of infrared energy analysis, the index of the energy release rate is introduced, and the loading and unloading analysis model is constructed. The research results reveal that rock failure is accompanied by the process of energy accumulation and release, which provides evidence for the analysis of the spatial stability of the rock mass under cyclic loading and unloading conditions and engineering excavation.

scholarly journals Study on Nonlinear Damage Creep Model for Rocks under Cyclic Loading and Unloading

2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Liangliang Zhang ◽  
Xiaojian Wang
Keyword(s):  
Cyclic Loading ◽  
Superposition Principle ◽  
Three Dimensional ◽  
Creep Model ◽  
Model Parameters ◽  
Nonlinear Creep ◽  
Cyclic Loading And Unloading ◽  
In Series ◽  
Loading And Unloading ◽  
Stress States

To determine the nonlinear creep characteristics of rocks under cyclic loading and unloading conditions, a nonlinear Kelvin model and damage viscoplastic model are proposed. The models are connected in series with a linear elastic body to establish a nonlinear damage creep model. The differential damage constitutive equations of the proposed creep model under one-dimensional and three-dimensional stress states are derived based on the creep mechanics and elasticity theory. The damage and unloading creep equations are then obtained based on the superposition principle, and a simple and feasible method for determining the model parameters is determined. Finally, the step cyclic loading and unloading creep test data for lherzolite and limestone are used to verify the rationality and feasibility of the nonlinear damage creep model. The results show that the theoretical creep curves of the nonlinear damage creep model are consistent with the experimental curves which indicates that the proposed model can not only determine the creep properties of lherzolite and limestone under cyclic loading and unloading but also determine the nonlinear characteristics of rocks in the transient and steady-state creep stages and particularly within the accelerating creep stage.

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