Experimental study of the dynamically induced rockburst of a rock wall with double free faces

2018 ◽  
Vol 28 (4) ◽  
pp. 611-637 ◽  
Author(s):  
Guoshao Su ◽  
Zhiyong Chen ◽  
J Woody Ju ◽  
Bin Zhao ◽  
Sizhou Yan ◽  
...  
Keyword(s):  
Cyclic Loading ◽  
Dynamic Loading ◽  
Elastic Strain Energy ◽  
Strain Energy Release ◽  
The Self ◽  
Rockburst Hazard ◽  
Dynamic Disturbance ◽  
Rock Wall ◽  
Free Face ◽  
Rock Structure

Dynamic disturbance is regarded as one of the most significant factors that induce rockburst around the boundary of underground excavation, particularly in high confining pressure conditions. In the present study, three types of dynamic loading tests are conducted to investigate the dynamically triggered rockburst behavior of a rock wall with double free faces. The three types of dynamic loading considered are the large stress single-pulse loading (mild-disturbance), the middle stress low-frequency cyclic loading (modest-disturbance), and the small stress high-frequency cyclic loading (weak-disturbance). The experimental results are analyzed and the damage evolution process during the dynamic disturbances is described. The tests reveal that the failure strain (i.e., the strain at unstable failure) of the dynamically triggered rockburst is greater than that of the self-initiated rockburst. The intensity of rockburst depends not only on the initial static stress level but also on the dynamic disturbance type. The rockburst induced by the mild-disturbance is mainly related to large amounts of disturbance energy imported. The rockburst caused by the modest-disturbance is contributed by the disturbance degradation of ultimate energy-storage capacity of specimen. The rockburst in a weak-disturbance specimen is primarily due to the disturbance aggravation of the damage in specimen and the elastic strain energy release. In particular, the rockburst hazard from the double free faces is more likely to be triggered and its result more serious than that of the rock structure with only one free face because the increasing free face decreases the rock strength. The fragmentation of the dynamically induced rockburst is larger than that of the self-initiated rockburst. With increasing time of dynamic loading, the damage induced by the modest-disturbance and the weak-disturbance first increases continually, subsequently increases steadily, and finally increases drastically. By contrast, the damage of the specimen under the mild-disturbance condition has a linearly increasing trend.

scholarly journals Stationary Self-Heating of the Circular and Annular Composite Plates Hinged on the Boundary under Axisymmetric Cyclic Loading

2011 ◽  
Vol 20 (5) ◽  
pp. 096369351102000 ◽  
Author(s):  
Andrzej Katunin
Keyword(s):  
Heat Transfer ◽  
Cyclic Loading ◽  
Transfer Equation ◽  
Heating Temperature ◽  
Composite Plates ◽  
The Self ◽  
Heat Transfer Equation ◽  
Dissipation Energy ◽  
Self Heating ◽  
Parametric Analyses

The present study is focused on the analytical modelling of the stationary self-heating caused by the hysteretic behaviour of the polymeric laminated circular and annular plates hinged on the boundary under axisymmetric transverse cyclic loading. The investigation was based on the complex parameters concept. The coupled thermoviscoelasticity problem was solved by substitution of the dissipation energy function to the heat transfer equation as a source function. The self-heating temperature distributions formulas were obtained by solving the heat transfer equation with appropriate thermal boundary conditions using trigonometric Fourier series. Numerous parametric analyses were presented. It was shown, that omitting the influence of the self-heating effect may results in the incorrect description of the behaviour of polymeric composites under cyclic loading.

scholarly journals Subloading Surface Model and Experimental Study of Coal Failure under Cyclic Loading

2019 ◽  
Vol 2019 ◽  
pp. 1-13 ◽  
Author(s):  
Si-fei Liu ◽  
Zhi-jun Wan ◽  
Jing-chao Wang ◽  
Shuai-feng Lu ◽  
Tong-huan Li
Keyword(s):  
Cyclic Loading ◽  
Mechanical Response ◽  
Surface Model ◽  
Deformation Characteristics ◽  
Response Characteristics ◽  
Rock Structure ◽  
Specific Strain ◽  
Damage Process ◽  
The Stability ◽  
Number Of Cycles

The fatigue damage of rock is an important factor affecting the stability of rock structure. In this paper, the mechanical response of coal under cyclic loading was studied. In order to accurately describe the deformation characteristics of coal under cyclic loading, an elastic-plastic model of coal based on the theory of subloading surface was established and verified by experiments. The model can well reflect the Mancin effect and ratcheting effect of coal samples, which is basically consistent with the actual deformation characteristics of coal, and the theoretical value and experimental value are in good agreement. At the same time, the cyclic response characteristics of specimens under strain load disturbance were analyzed. The results show that the specific strain disturbance can only cause a certain damage to coal and the area of hysteresis loop decreases first, then stabilizes, and then increases as the number of cycles increases. In addition, the damage factor Dn in the model was analyzed in this paper. Dn, which can accurately describe the damage process of coal, accurately locate the time point of disturbance load change, and has greater sensitivity to coal failure, is helpful to improve the accuracy of the stability judgment of coal structure and ensure the safety of engineering. The above results are of great significance for strengthening the understanding of coal mass instability process and mode under cyclic loading.

Simulation of Cracks in Fiber Reinforced Composite Plate

2011 ◽  
Vol 471-472 ◽  
pp. 892-897 ◽  
Author(s):  
Pramod Kumar ◽  
Ashish Kakyal
Keyword(s):  
Cyclic Loading ◽  
Crack Propagation ◽  
Crack Growth ◽  
Fem Analysis ◽  
Strain Energy Release ◽  
Crack Propagation Rate ◽  
Propagation Rate ◽  
Fiber Reinforced ◽  
Automotive Parts ◽  
Mechanical Approach

Material flaws, pre-cracks and crack initiation due to cyclic loading often lead to undetected crack propagation in commercial structures like aircraft components, automotive parts and computer motherboard. Cyclic loading can make the crack grow large into any shape with an arbitrary orientation, depending on the structure geometry, boundary and loading conditions. Since crack propagation in many cases may lead to catastrophic failure with human and monetary loss as a result, it is important to enable crack growth prediction at all stages of development and during maintenance in order to prevent such scenarios. Micro mechanical approach is used for modelling the crack in composite materials. Crack propagation in a single edge crack plate is carried out by using FEM analysis. 2D model is analysed to determine the crack growth. The crack propagation rate, stress intensity factor and strain energy release rate are predicted by varying the crack length in fiber reinforced epoxy composite using NISA/ENDURE.

Fatigue accumulated damage in notched quasi-isotropic composites under high-temperature conditions: A discussion on the influence of matrix nature on the stress energy release rate

2017 ◽  
Vol 52 (17) ◽  
pp. 2397-2412 ◽  
Author(s):  
B Vieille
Keyword(s):  
Cyclic Loading ◽  
Energy Release Rate ◽  
Energy Release ◽  
Release Rate ◽  
Strain Energy ◽  
Strain Energy Release Rate ◽  
Strain Energy Release ◽  
Fatigue Behaviour ◽  
Polyphenylene Sulfide ◽  
Plastic Deformations

In order to investigate the contribution of matrix nature to the fatigue behaviour, the purpose of the present work is to establish the correlation between material toughness and macroscopic damage accumulation during tensile cyclic loading in the brittle (C/epoxy) and ductile (C/Polyphenylene sulfide) matrix systems. More specifically, this article presents a fracture mechanics-based approach to compute the strain energy release rate during fracture along with the macroscopic transverse crack growth in fatigue. The knowledge of energy-absorbing processes is important as they are responsible for the toughness of the composite. Woven-ply laminates are characterised by matrix-rich regions which may stop or slow down the growth of fatigue cracks by absorbing the mechanical energy through local plastic deformations at the cracks tip depending on matrix nature. With respect to C/epoxy laminates, the local plastic deformations at the cracks tip are prominent in highly ductile composite systems (e.g. C/Polyphenylene sulfide), and ultimately results in fatigue behaviour virtually independent of the applied stress level under high temperatures T > Tg. To evaluate the influence of matrix ductility and toughness on fatigue damage, a damage variable d based on the measurement of longitudinal stiffness at each cycle was used. A model derived from a Paris law and a fracture mechanics criterion were combined to: (i) evaluate the fatigue crack growth – (ii) compare the changes in the strain energy release rate G and the macroscopic damage d during cyclic loading. Macroscopic damage appears to be well correlated with the strain energy released during fracture.

scholarly journals In vitro evaluation of self-etch bonding in orthodontics using cyclic fatigue

2011 ◽  
Vol 81 (5) ◽  
pp. 783-787 ◽  
Author(s):  
Ameerah Yousef Mansour ◽  
James L. Drummond ◽  
Carla A. Evans ◽  
Zuhair Bakhsh
Keyword(s):  
Cyclic Loading ◽  
Bond Strength ◽  
Cyclic Fatigue ◽  
The Self ◽  
Shear Testing ◽  
Cyclic Shear ◽  
Bonding System ◽  
Bonding Failure ◽  
Bond Strengths ◽  
Self Etch

Abstract Objective: To evaluate the bond strength of a self-etch bonding system using static loading and cyclic fatigue with shear testing. This is a two-part evaluation; the first part will evaluate shear testing, the second part tensile testing. Materials and Methods: Bovine teeth (n  =  82) were randomly distributed to either a self-etch (Transbond Plus) or total-etch (37% phosphoric-acid + Transbond XT) group. The static shear (SSBS) and cyclic shear (CSBS) bond strengths were measured 24 hours after the bonding of mesh-based brackets. The adhesive remnant index (ARI) and failure sites were evaluated. Results: The mean SSBS was 34.25 ± 9.21 and 24.64 ± 9.42 MPa for the total- and self-etch groups, respectively. CSBS was 24.07 ± 0.65 MPa and 18.92 ± 1.08 MPa for the total- and self-etch groups, respectively. Cyclic loading produced lower bond strengths compared to static testing for both adhesives; the difference was only statistically significant for the total-etch system. Comparison of the two materials showed a statistically significant difference between the two techniques. The total-etch had higher bond strengths than the self-etch bonding system. The samples showed a predominance of ARI scored of 2 and 1, and their bonding failure sites were cohesive within the composite. Conclusion: Cyclic loading, simulating occlusal forces, reduces the bond strength of both bonding systems. Even though the self-etch bonding system had lower shear bond strength than the total-etch system, both were still clinically acceptable.

scholarly journals Fatigue and Thermal Failure of Polymeric Composites Subjected to Cyclic Loading

2012 ◽  
Vol 21 (3) ◽  
pp. 096369351202100 ◽  
Author(s):  
Andrzej Katunin ◽  
Marek Fidali
Keyword(s):  
Cyclic Loading ◽  
Heating Temperature ◽  
Qualitative Evaluation ◽  
Polymeric Composites ◽  
The Self ◽  
Heating Effect ◽  
Thermal Failure ◽  
Self Heating ◽  
Measurement Results ◽  
Parametric Dependencies

In the presented study the experimental results for the investigation of fatigue of polymeric composites subjected to intensive cyclic loading with presence of the self-heating effect were presented. Experiments were carried out on laboratory stand, which provides the synchronous measurement of loading force, displacements and temperature. It was observed, that the fatigue process during occurrence of the self-heating effect consists of three phases, which were analyzed and described. The characteristic self-heating temperature distributions and their evolution during the whole loading history were analyzed. The parametric analysis of influence of loading conditions on the self-heating temperature evolution and fatigue of polymeric composites was presented. Basing upon the measurement results the authors proposed empirical models, which give a qualitative evaluation of parametric dependencies.

Study on the Mechanical Behavior of Self-Centering Bridge under Horizontal Loading

2014 ◽  
Vol 1049-1050 ◽  
pp. 354-356
Author(s):  
Yuan Yuan Zhao ◽  
Xiao Bo Zhang ◽  
Yan Rong Wang
Keyword(s):  
Cyclic Loading ◽  
Mechanical Behavior ◽  
Rotation Curve ◽  
Mechanical Performance ◽  
The Self ◽  
Horizontal Load ◽  
Theoretical Derivation ◽  
Elastic Range ◽  
Curve Type ◽  
Horizontal Loading

This paper presents a self-centering bridge which is simplified as a deformation body ,while mechanical performance is still in the elastic range ,considering the influence of gravity pier ,the upper structure load ,prestressed tendons and dampers, the horizontal load vs. rotation curve of the self-centering bridge is obtained by theoretical derivation . The study for the self-centering bridge presented in this paper indicates that: under the cyclic loading hysteretic curve type is flag-shaped ,the prestressed tendons provide self-centering ability and dampers provide dissipating energy.

Effect of structure of laminated wood on bending strength after cyclic loading

2019 ◽  
Vol 105 ◽  
pp. 20-29
Author(s):  
JOZEF GÁBORÍK ◽  
JOZEF FEKIAČ
Keyword(s):  
Cyclic Loading ◽  
Flexural Strength ◽  
Dynamic Loading ◽  
Bending Strength ◽  
Flexural Modulus ◽  
Bending Properties ◽  
Cyclic Bending ◽  
Bending Radius ◽  
Number Of Cycles ◽  
Effect Of Structure

Effect of structure of laminated wood on bending strength after cyclic loading. Laminated wood is particularly suitable for the production of seating and bedding furniture, for its suitable properties. The work is focused on the changes of the bending properties of laminated wood from beech and poplar veneers after its dynamic loading by cyclic bending. As we increase the number of cycles, we notice a decrease in flexural strength, a slight increase in flexural modulus, and a decrease in the number of cycles. Also the increase in the minimum bending radius as well as the flexural coefficient.

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