scholarly journals Bedding Effect of Carbonaceous Slate Failure Behavior at Direct Shear Tests

2021 ◽  
Author(s):  
Han Wang ◽  
Fuqiang Ren ◽  
Yuan Chang
Keyword(s):  
Energy Release Rate ◽  
Energy Release ◽  
Release Rate ◽  
Bedding Plane ◽  
Dissipated Energy ◽  
Direct Shear ◽  
Shear Tests ◽  
Main Frequency ◽  
Direct Shear Tests ◽  
Fracture Topography

Abstract In this study, the carbonaceous slate of Muzhailing tunnel was selected to explore the deformation and failure mechanism of tunnel layered slate under direct shear conditions. Five sets of direct shear tests were carried out on slate with different bedding dip angles (β: 0°, 30°, 45°, 60°, and 90°). The strength parameters, failure mode, fracture topography, dissipated energy, and acoustic emission (AE) characteristics were analyzed in detail to study the bedding effect of slate failure. The results show that the cohesion and internal friction angle of slate increases and decreases linearly with β from 0° to 90°, respectively, and the shear strength of bedding plane is lower than that of matrix. Additionally, the relative roughness (δ) of gray-scale image was defined, and the linear relationship between δ and root-mean-square height (Sq) was established to improve the efficiency of evolution of fracture topography. Furthermore, the shear energy consumption per unit area (us) was calculated, less sensitive to the variation of β. Moreover, a larger AE count and energy release rate were observed when the shear stress decreased, and a relative quiet period was observed before the peak loading. Additionally, both the count and energy release rate linearly decreased with the increase in β, and the proportion of tensile microcracks for vertical bedding is slightly higher than that for horizontal bedding. The main frequency of vertical bedding slate is smaller than that of horizontal bedding, i.e., the size of microcracks of slate with β of 90° is relatively larger. Generally, the frequency bandwidth of slate became narrower when β was varied from 30° to 60°, and the main frequency increased, indicating that the degree of shear failure of matrix is weakened. In contrast, the degree of cracking along the bedding plane increased.

Calculating Energy Release Rate as a Function of Crack Length Using a Multiple-Step Crack Closure Technique in Tire Finite Element Models

2018 ◽  
Vol 46 (3) ◽  
pp. 130-152
Author(s):  
Dennis S. Kelliher
Keyword(s):  
Finite Element ◽  
Energy Release Rate ◽  
Crack Length ◽  
Energy Release ◽  
Crack Closure ◽  
Release Rate ◽  
Fatigue Behavior ◽  
Three Dimensions ◽  
Quantitative Prediction ◽  
Closure Technique

ABSTRACT When performing predictive durability analyses on tires using finite element methods, it is generally recognized that energy release rate (ERR) is the best measure by which to characterize the fatigue behavior of rubber. By addressing actual cracks in a simulation geometry, ERR provides a more appropriate durability criterion than the strain energy density (SED) of geometries without cracks. If determined as a function of crack length and loading history, and augmented with material crack growth properties, ERR allows for a quantitative prediction of fatigue life. Complications arise, however, from extra steps required to implement the calculation of ERR within the analysis process. This article presents an overview and some details of a method to perform such analyses. The method involves a preprocessing step that automates the creation of a ribbon crack within an axisymmetric-geometry finite element model at a predetermined location. After inflating and expanding to three dimensions to fully load the tire against a surface, full ribbon sections of the crack are then incrementally closed through multiple solution steps, finally achieving complete closure. A postprocessing step is developed to determine ERR as a function of crack length from this enforced crack closure technique. This includes an innovative approach to calculating ERR as the crack length approaches zero.

scholarly journals Sand- and Clay-Photocured-Geomembrane Interface Shear Characteristics Using Direct Shear Test

2021 ◽  
Vol 13 (15) ◽  
pp. 8201
Author(s):  
Lihua Li ◽  
Han Yan ◽  
Henglin Xiao ◽  
Wentao Li ◽  
Zhangshuai Geng
Keyword(s):  
Soil Surface ◽  
Friction Angle ◽  
Direct Shear ◽  
Tensile Crack ◽  
Shear Tests ◽  
Interface Shear ◽  
Direct Shear Tests ◽  
Carbon Black Powder ◽  
Shear Characteristics ◽  
Impermeable Layer

It is well known that geomembranes frequently and easily fail at the seams, which has been a ubiquitous problem in various applications. To avoid the failure of geomembrane at the seams, photocuring was carried out with 1~5% photoinitiator and 2% carbon black powder. This geomembrane can be sprayed and cured on the soil surface. The obtained geomembrane was then used as a barrier, separator, or reinforcement. In this study, the direct shear tests were carried out with the aim to investigate the interfacial characteristics of photocured geomembrane–clay/sand. The results show that a 2% photoinitiator has a significant effect on the impermeable layer for the photocured geomembrane–clay interface. As for the photocured geomembrane–sand interface, it is reasonable to choose a geomembrane made from a 4% photoinitiator at the boundary of the drainage layer and the impermeable layer in the landfill. In the cover system, it is reasonable to choose a 5% photoinitiator geomembrane. Moreover, as for the interface between the photocurable geomembrane and clay/sand, the friction coefficient increases initially and decreases afterward with the increase of normal stress. Furthermore, the friction angle of the interface between photocurable geomembrane and sand is larger than that of the photocurable geomembrane–clay interface. In other words, the interface between photocurable geomembrane and sand has better shear and tensile crack resistance.

scholarly journals Effect of the Characteristic Size and Content of Graphene on the Crack Propagation Path of Alumina/Graphene Composite Ceramics

Materials ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 611
Author(s):  
Benshuai Chen ◽  
Guangchun Xiao ◽  
Mingdong Yi ◽  
Jingjie Zhang ◽  
Tingting Zhou ◽  
...  
Keyword(s):  
Crack Propagation ◽  
Energy Release Rate ◽  
Energy Release ◽  
Release Rate ◽  
Volume Content ◽  
Phase Interface ◽  
Average Energy ◽  
Characteristic Size ◽  
Composite Ceramics ◽  
Graphene Composite

In this paper, the Voronoimosaic model and the cohesive element method were used to simulate crack propagation in the microstructure of alumina/graphene composite ceramic tool materials. The effects of graphene characteristic size and volume content on the crack propagation behavior of microstructure model of alumina/graphene composite ceramics under different interfacial bonding strength were studied. When the phase interface is weak, the average energy release rate is the highest as the short diameter of graphene is 10–50 nm and the long diameter is 1600–2000 nm. When the phase interface is strong, the average energy release rate is the highest as the short diameter of graphene is 50–100 nm and the long diameter is 800–1200 nm. When the volume content of graphene is 0.50 vol.%, the average energy release rate reaches the maximum. When the velocity load is 0.005 m s−1, the simulation result is convergent. It is proven that the simulation results are in good agreement with the experimental phenomena.

Modified Edge Lift-Off Test: Experimental Modifications for Multifilm Systems

1999 ◽  
Vol 594 ◽  
Author(s):  
J. C. Hay ◽  
E. G. Liniger ◽  
X-H Liu
Keyword(s):  
Energy Release Rate ◽  
Energy Release ◽  
Release Rate ◽  
Strain Energy ◽  
Plate Bending ◽  
Adhesion Test ◽  
Testing Method ◽  
Rate Calculation ◽  
Lift Off ◽  
Microelectronics Fabrication

AbstractIn developing an adhesion test for a microelectronics fabrication facility there are many criteria which must be met. Some of these include (i) sample prep must be simple, (ii) deformations should be elastic so the problem can be easily modeled, (iii) mechanics are ideally analytical, and (iv) the test end-point must be unambiguous and easy to obtain. A testing method in the literature which meets many of these criteria is the modified edge liftoff test (MELT). Delamination is induced through the release of strain energy stored in an elastic superlayer which results from a large mismatch in CTE between the film and substrate. In this work we consider details of the energy release rate calculation, effects of plate bending, and initial flaw size.

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