Crack Closure Effect and Energy Dissipation Model for Rocks under Uniaxial Compression

2019 ◽  
Vol 38 (1) ◽  
pp. 621-629
Author(s):  
Yan Chen ◽  
Baohua Guo
Symmetry ◽  
2020 ◽  
Vol 12 (8) ◽  
pp. 1283
Author(s):  
Feng Jiang ◽  
Zheyu Ding ◽  
Yiwan Wu ◽  
Hongbai Bai ◽  
Yichuan Shao ◽  
...  

In this paper, a symmetrically coated damping structure for entangled metallic wire materials (EMWM) of pipelines was designed to reduce the vibration of high temperature (300 °C) pipeline. A series of energy dissipation tests were carried out on the symmetrically coated damping structure at 20–300 °C. Based on the energy dissipation test results, the hysteresis loop was drawn. The effects of temperature, vibration amplitude, frequency, and density of EMWM on the energy dissipation characteristics of coated damping structures were investigated. A nonlinear energy dissipation model of the symmetrically coated damping structure with temperature parameters was established through the accurate decomposition of the hysteresis loop. The parameters of the nonlinear model were identified by the least square method. The energy dissipation test results show that the symmetrically coated damping structure for EMWM of pipelines had excellent and stable damping properties, and the established model could well describe the changing law of the restoring force and displacement of the symmetrically coated damping structure with amplitude, frequency, density, and ambient temperature. It is possible to reduce the vibration of pipelines in a wider temperature range by replacing different metal wires.


Author(s):  
Masanori Kikuchi ◽  
Yoshitaka Wada ◽  
Maigefeireti Maitireyimu ◽  
Hirotaka Sano

Crack closure effect on interaction of two surface crack growth processes by fatigue is studied. At first, change of C value in Paris’ law along crack front of single surface crack is measured experimentally. It is shown that C value decreases near specimen surface. Crack closure effect is studied numerically for a surface crack by elastic-plastic cyclic analyses. It is found that closure effect appears more strongly near specimen surface than the maximum-depth point. By determining effective stress intensity factor including closure effect, it is shown that change of C value is equal to the change of closure effect along crack front. Using new C value considering closure effect, fatigue crack growth is predicted using S-FEM. It is shown that fatigue life and crack configuration agree well with experimental ones. Finally, interaction of two surface cracks is evaluated numerically, and it is shown that crack closure plays important role on the interaction of two cracks.


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