scholarly journals Strength and Failure Characteristics of Natural and Water-Saturated Coal Specimens under Static and Dynamic Loads

2018 ◽  
Vol 2018 ◽  
pp. 1-15 ◽  
Author(s):  
Wen Wang ◽  
Heng Wang ◽  
Dongyin Li ◽  
Huamin Li ◽  
Zhumeng Liu
Keyword(s):  
Dynamic Loading ◽  
Split Hopkinson Pressure Bar ◽  
Three Dimensional ◽  
Dynamic Strength ◽  
Hopkinson Pressure Bar ◽  
Static Compression ◽  
One Dimensional ◽  
Before And After ◽  
Loading Tests ◽  
Water Saturated

Rock bursts occur frequently in coal mines, and the mechanical properties of saturated coal specimens under coupled static-dynamic loading need to be studied in detail. Comparative tests of coal specimens having different water content under static and static-dynamic loading are conducted using the split Hopkinson pressure bar (SHPB) and RMT-150C test systems. The results demonstrate that the natural specimen strength is greater than that of seven-day (7D) saturated specimens under both uniaxial compression and triaxial static compression loading; however, the dynamic strength of 7D saturated specimens is lower than that of natural specimens under one-dimensional static-dynamic loading. The particle size of the 7D saturated specimens is relatively small under uniaxial static compression and one-dimensional static-dynamic loading, and the specimen particle sizes before and after static triaxial loading tests and three-dimensional static-dynamic loading tests do not exhibit an obvious difference.

scholarly journals Dynamic Characteristics of Deep Dolomite Under One-Dimensional Static and Dynamic Loads

2019 ◽  
Vol 101 (1) ◽  
pp. 49-56 ◽  
Author(s):  
Jianguo Wang ◽  
Yang Liu ◽  
Kegang Li
Keyword(s):  
Strain Rate ◽  
Axial Compression ◽  
Split Hopkinson Pressure Bar ◽  
Dynamic Strength ◽  
Strong Positive Correlation ◽  
Hopkinson Pressure Bar ◽  
Irreversible Damage ◽  
One Dimensional ◽  
Rock Structure ◽  
The Impact

AbstractThe failure characteristics of rock subjected to impact disturbance under one-dimensional static axial compression are helpful for studying the problems of pillar instability and rock burst in deep, high geostress surrounding rock under blasting disturbances. Improved split Hopkinson pressure bar equipment was used for one-dimensional dynamic–static combined impact tests of deep-seated dolomite specimens under axial compression levels of 0, 12, 24, and 36 MPa. The experimental results demonstrate that the dolomite specimens exhibit strong brittleness. The dynamic strength always maintains a strong positive correlation with the strain rate when the axial compression is fixed; when the strain rate is close, the dynamic elasticity modulus and peak strength of the specimens first increase and then decrease with the increase in axial compression, and the peak value appears at 24 MPa. The impact resistance of specimens can be enhanced when the axial compression is 12 or 24 MPa, but when it increases to 36 MPa, the damage inside the specimen begins to cause damage to the dynamic rock strength. Prior to the rock macroscopic failure, the axial static load changes the rock structure state, and it can store strain energy or cause irreversible damage.

Study on dynamic strength of sandstone based on SHPB numerical experimentation

2020 ◽  
Author(s):  
Wengang Zhang ◽  
Fansheng Meng ◽  
Qi Wang
Keyword(s):  
Rock Mass ◽  
Dynamic Loading ◽  
Split Hopkinson Pressure Bar ◽  
Axial Loading ◽  
Dynamic Strength ◽  
Experimental Sample ◽  
Hopkinson Pressure Bar ◽  
Rock Engineering ◽  
Static Tests ◽  
Numerical Experimentation

<p>It is unavoidable that in rock engineering practices such as mining and tunnel constructions rocks are subjected to dynamic loading impacts including blasting, seismic loading, rock burst, and so on. The mechanical parameters for rock strength obtained via traditional static tests are not capable of characterizing the dynamic strength of rock mass. Therefore, the conventionally adopted tests cannot be further applied to guide the design of rock engineering subjected to dynamic loadings. Therefore the determination of the dynamic strength is essential for practical engineering. In this study, sandstone is chosen as the experimental sample for Split Hopkinson Pressure Bar (SHPB) numerical simulation by FLAC3D. The validation demonstrated that rocks are prone to fail under dynamic loading impacts. Extensive simulations are also carried out to investigate the development of rock dynamic strength and evolution process of energy accumulation and release in rock mass for samples of various sizes subjected to different levels of dynamic loading and axial loading. The simulation results may provide design guidance for the safety protection of rock engineering subjected to dynamic impacts.</p>

Rate-Dependent Constitutive Model Coupled with Temperature Softening for Open-Cell Aluminum Foam

2013 ◽  
Vol 470 ◽  
pp. 70-75
Author(s):  
Wei Zheng ◽  
Bao Jun Pang ◽  
Yong Chen
Keyword(s):  
Constitutive Model ◽  
Dynamic Loading ◽  
Aluminum Foam ◽  
Split Hopkinson Pressure Bar ◽  
Strain Curve ◽  
Hopkinson Pressure Bar ◽  
Element Analysis ◽  
Open Cell ◽  
Rate Dependent ◽  
Loading Tests

Both quasi-static compressive tests and dynamic loading tests on the open-cell aluminum foam made of 6061 aluminum alloy were firstly conducted. The Split Hopkinson Pressure Bar (SHPB) apparatus was used to perform the dynamic loading tests. The rate-dependent constitutive model for the open-cell aluminum foam was then studied. Based on the empirical constitutive model proposed by Sherwood for polyurethane foam, a new function was found to analyze the three-stage characteristic of quasi-static stress-strain curve of the aluminum foam. Moreover, the temperature softening was also modified. Thus a new strain rate hardening constitutive model coupled with temperature softening for the open-cell aluminum foam was obtained. Finally, both Taylor impact tests and finite element analysis (FEA) were conducted to verify the new constitutive model and the results show that the model was reliable.

An Experimental Study on Dynamic Constitutive Relationship of 7075-T651 Aluminum Alloy

2013 ◽  
Vol 816-817 ◽  
pp. 84-89
Author(s):  
Yong Gang Kang ◽  
Yuan Yang ◽  
Jie Huang ◽  
Jing Hang Zhu
Keyword(s):  
Aluminum Alloy ◽  
Constitutive Equation ◽  
Strain Rate ◽  
Split Hopkinson Pressure Bar ◽  
Flow Behavior ◽  
Constitutive Relationship ◽  
Hopkinson Pressure Bar ◽  
Experiment Data ◽  
Static Compression ◽  
Quasi Static Compression

7075-T651 aluminum alloy are widely used in aeronautical applications such as wing panels, but there is no corresponding constitutive model for it now. In this paper, the flow behavior of 7050-T651 aluminum alloy was investigated by Split Hopkinson Pressure Bar (SHPB) and quasi-static compression experiment system. The strain hardening parameters were obtained by quasi-static compression experiment data, and the strain rate hardening parameters at various strain rates (1000-3000s-1) and room temperature, and the thermal softening parameter at various temperatures (20-300°C) where strain rate is 3000s-1 were obtained by SHPB experiment data. Then the constitutive equation of 7075-T651 aluminum alloy is obtained based on Johnson-Cook constitutive equation model.

scholarly journals Stress-Induced Martensitic Phase Transformations in NiTi Shape Memory Alloys During Dynamic Loading

2000 ◽  
Author(s):  
David A. Miller ◽  
W. Richards Thissell ◽  
George T. Gray ◽  
Duncan A. S. Macdougall
Keyword(s):  
Shape Memory Alloys ◽  
Shape Memory ◽  
Dynamic Loading ◽  
Void Growth ◽  
Split Hopkinson Pressure Bar ◽  
Large Strain ◽  
Martensitic Phase ◽  
Hopkinson Pressure Bar ◽  
Martensitic Phase Transformations ◽  
Niti Shape Memory Alloys

Abstract This research explores the near-adiabatic, high strain rate stress-induced martensitic phase transformation in NiTi shape memory alloys using both a compressive and tensile Split Hopkinson Pressure Bar (SHPB). The results of the dynamic loading tests are presented with emphasis on the loading rate, stress-strain response, specimen temperature and post-test microstructural evaluation. In addition to the large strain rates, tensile specimens of various geometries are tested to large strain levels such that void growth and failure mechanisms are identified. The dynamically loaded specimens failed in a mixed mode, ductile void growth followed by transgranular failure. The void growth in incipient failure specimens showed ductile void growth throughout the specimen cross-section.

Quasi-Static and High Strain Rate Uniaxial Compressive Response of Recycled Polycarbonate from Industrial Waste

2020 ◽  
Vol 1012 ◽  
pp. 89-93
Author(s):  
Anderson Oliveira da Silva ◽  
Ricardo Pondé Weber ◽  
Sergio Neves Monteiro
Keyword(s):  
Industrial Waste ◽  
Split Hopkinson Pressure Bar ◽  
Dynamic Properties ◽  
Hopkinson Pressure Bar ◽  
Mechanical Recycling ◽  
Static Compression ◽  
Compressive Response ◽  
Split Hopkinson ◽  
Pressure Bar ◽  
Quasi Static Compression

This work evaluates the mechanical and dynamic behavior of recycled polycarbonate (rPC) from industrial waste. This study aims to verify whether the recycled process adopted for polycarbonate promotes both mechanical and dynamic properties values under compressive stress, similar to those found for virgin polycarbonate. The mechanical recycling of the rPC was carried out using the thermoforming technique in a thermal press. Two tests were carried out to evaluate the dynamic response of rPC. The quasi-static compression test was performed on a universal machine. The dynamic in a split Hopkinson pressure bar was performed with three different strain rates. The results showed that the mechanical and primary recycling adopted in this work promoted values of yield stress in compression (77 MPa) and dynamic (up to 118 MPa), close to or superior to those reported so far in the literature.

High Strain Rate Response of Rocks Under Dynamic Loading Using Split Hopkinson Pressure Bar

2017 ◽  
Vol 36 (1) ◽  
pp. 531-549 ◽  
Author(s):  
Sunita Mishra ◽  
Hemant Meena ◽  
Vedant Parashar ◽  
Anuradha Khetwal ◽  
Tanusree Chakraborty ◽  
...  
Keyword(s):  
High Strain Rate ◽  
Strain Rate ◽  
Dynamic Loading ◽  
High Strain ◽  
Split Hopkinson Pressure Bar ◽  
Hopkinson Pressure Bar ◽  
Split Hopkinson ◽  
Pressure Bar

Can a three-dimensional composite really provide better mechanical performance compared to two-dimensional composite under compressive loading?

2018 ◽  
Vol 38 (2) ◽  
pp. 49-61 ◽  
Author(s):  
M Tarfaoui ◽  
M Nachtane
Keyword(s):  
Mechanical Performance ◽  
Split Hopkinson Pressure Bar ◽  
Compressive Loading ◽  
Three Dimensional ◽  
Woven Composites ◽  
Two Dimensional ◽  
Hopkinson Pressure Bar ◽  
Out Of Plane ◽  
Split Hopkinson ◽  
Pressure Bar

A series of split Hopkinson pressure bar tests on two-dimensional and three-dimensional woven composites were presented in order to obtain a reliable comparison between the two types of composites and the effect of the z-yarns along the third direction. These tests were done along different configurations: in-plane and out-of-plane compression test. For the three-dimensional woven composite, two different configurations were studied: compression responses along to the stitched direction and orthogonal to the stitched direction. It was found that three-dimensional woven composites exhibit an increase in strength for both: in-plane and out-of-plane tests.

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