scholarly journals Effect of fatigue loading-confining stress unloading rate on marble mechanical behaviors: An insight into fracture evolution analyses

2020 ◽  
Vol 12 (6) ◽  
pp. 1249-1262 ◽  
Author(s):  
Yu Wang ◽  
Dongqiao Liu ◽  
Jianqiang Han ◽  
Changhong Li ◽  
Hao Liu
2005 ◽  
Vol 898 ◽  
Author(s):  
David H. Kohn ◽  
Nadder D. Sahar ◽  
Sun Ig Hong ◽  
Kurtulus Golcuk ◽  
Michael D. Morris

AbstractSkeletal fractures represent a significant medical and economic burden for society. It is generally thought that a high incidence of musculoskeletal fatigue loading results in damage accumulation at too high of a rate to be efficiently remodeled, leading to skeletal fracture. The state of damage in bone at a given time is therefore the net result of damage and repair processes, and is dependent upon extrinsic factors such as mechanical history, but also upon intrinsic factors, such as composition of bone mineral and matrix. In this invited paper, we review investigations on the coupling of Raman spectroscopy with mechanical loading of bone, providing insight into mechanisms of ultrastructural deformation in bone at smaller scales than previously understood. We also present new data showing that in-vivo mechanical loading results in increased resistance to fatigue damage, coupled with an increase in phosphate to amide I ratio and decrease in carbonate to phosphate ratio. Taken together, the data demonstrates the ability to modulate the mechanical and chemical properties of bone via exogenous mechanical stimulation.


Sensors ◽  
2019 ◽  
Vol 19 (19) ◽  
pp. 4195 ◽  
Author(s):  
Xingwang Sheng ◽  
Weiqi Zheng ◽  
Zhihui Zhu

In this paper, we present a new attempt to lay ballastless tracks on long-span cable-stayed bridges on high-speed railways. The arrangements of ballastless tracks laid on cable-stayed bridges can be divided into two conditions: (i) across the cable suspension-point cross-section or (ii) in discontinuity at the cable suspension-point cross-section. At present, there is a lack of in-depth research on ballastless tracks laid on long-span cable-stayed bridges, especially on the mechanical behaviors and fatigue performances of the ballastless tracks with different arrangements. For this paper, a segmental model of a long-span cable-stayed bridge was designed and built, on which full-scale ballastless tracks with two different arrangements were arranged. A series of fatigue tests and post-fatigue loading tests were carried out based on the two selected full-scale ballastless tracks. Some conclusions were drawn as follows. For the longitudinal end of the ballastless track, which is far from the loading positions, the interlayers of the ballastless tracks tend to warp up relatively, and the compressive pressures at the interlayers are also unloaded. However, there is no void or gap formed at the interlayers of the longitudinal end of the track slab due to the precompression of the rubber isolation layer. For the center of the track slab, which is close to the loading positions, the compressive deformations occur at the interlayers, and the pressures at interlayers are also increased. The maximum compressive deformation is less than 0.5 mm under the standard train axle load (170 kN), and it cannot affect the high-speed trains’ operation. With the increase of the post-fatigue loading, the load-displacement curves and the load-pressure variation curves of the ballastless tracks show apparent nonlinearity. Moreover, with the increase of the fatigue loading cycles, the compressive stiffness enhancement or degradation of the ballastless tracks are not noticeable. That is to say, the ballastless tracks laid on the long-span cable-stayed bridges with different arrangements have good mechanical behaviors, and their fatigue performances can also be guaranteed after bearing repeated loadings.


Nanomaterials ◽  
2018 ◽  
Vol 8 (10) ◽  
pp. 758
Author(s):  
Lili Li ◽  
Rui Sun ◽  
Jie Yang

Regular black phosphorus (BP) sheets possess strongly anisotropic properties due to the unique puckered atomistic configuration, making such BP mechanically very weak in the armchair direction. The present work aims to address this issue by proposing an angle-ply double-layer black phosphorus (DLBP) structure in which two individual atomic layers with different orientation angles are stacked up. The molecular dynamics simulations based on Stillinger-Weber potential show that the in-plane mechanical properties of such a DLBP structure, e.g., Young’s modulus and tensile strength are significantly influenced by the stacking angle of each layer. The property anisotropy of DLBP decreases as the stacking angle difference δ between two layers increases and becomes isotropic when δ = 90°. This work also shed insight into mechanisms of angle-ply layers underlying the mechanical behaviors of DLBP at the nanoscale, suggesting that the anisotropic material properties can be effectively controlled and tuned through the appropriately selected stacking angles.


2017 ◽  
Vol 29 (5) ◽  
pp. 924-937 ◽  
Author(s):  
Mohammad Parhizkar Yaghoobi ◽  
Iman Ghaffari ◽  
Mehdi Ghannad

The purpose of this article is to investigate the active control behavior and stress analysis of functionally graded piezoelectric material circular hollow cylinder and disk under electro-thermo-mechanical loading. Also, this research presents a new compact formula for analysis of cylinder and disk that could be useful for engineers and designers to get insight into behavioral change of structures by geometry. The exact solutions of the functionally graded piezoelectric material structures could be found based on Lame’s solution. For a radially polarized cylinder and disk with continuously graded properties, it is assumed that material properties are varied by a power-law function, and inner surface and outer surface of these structures are considered to be sensor and actuator, respectively. Based on the exact solution, extensive numerical analyses are carried out to provide an insight into the effect of non-homogeneity constant and control factor on electro-thermo-mechanical behaviors and active control analysis of structures. The results show how the electro-thermo-mechanical behaviors change by non-homogeneity and control factor.


Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-15
Author(s):  
H. J. Meng ◽  
Y. Wang ◽  
B. Zhang ◽  
S. H. Gao

This study is aimed at revealing the effect of dynamic loading frequency on the fracture evolution behavior in preflawed rock samples under multistage cyclic loading conditions. The fracture evolution characteristics were investigated using stress-strain descriptions and in situ acoustic emission techniques. It is shown that rock strength, deformation, AE pattern, and fatigue life are strongly affected by the applied dynamic loading frequency. Rock fatigue strength and lifetime increase with the increase of dynamic loading frequency. The AE count and energy output both increase with the increase of the applied loading frequency. Six kinds of cracking modes were revealed by AE spectral frequency analysis. It is shown that large-scaled cracks are easy to be formed for rock subjected to high-frequency loads, reflected as the deceasing of AE signals with high-frequency–high-amplitude signal feature. It is suggested that applied dynamic loading frequency has obvious impact on the crack coalescence at the rock bridge segment. The testing results are helpful to enhance the cognitive of the influence of dynamic frequency on the crack communication behavior and can be expected to predict the stability of rock mass structures where rock mass is subjected to fatigue loading.


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