scholarly journals Effects of the Rock Bridge Ligament on Fracture and Energy Evolution of Preflawed Granite Exposed to Dynamic Loads

2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Kaihua Sun ◽  
Xiong Wu ◽  
Xuefeng Yi ◽  
Yu Wang
Keyword(s):  
Strain Rate ◽  
Impact Load ◽  
Rock Fracture ◽  
Slope Instability ◽  
Peak Strain ◽  
Energy Evolution ◽  
Dynamic Rupture ◽  
Dissipation Energy ◽  
Rock Bridge ◽  
The Impact

This paper aims to reveal the mechanical properties, energy evolution characteristics, and dynamic rupture process of preflawed granite under impact loading with different rock bridge angles and strain rates. A series of dynamic impact experiments were conducted along with the separate Hopkinson press bar (SHPB) testing system to analyze and study the overall rock fracture process. Under the impact load, the peak stress of granite increases with the increase of rock bridge angle and strain rate, but the increase gradually decreases. The peak strain also increases gradually with the increase of rock bridge angle, but there is an upper limit value; the total input strain energy increases with the increase of strain rate and rock bridge angle. It is shown that the higher the strain rate, the higher the unit dissipation energy, and the greater the degree of rock fragmentation. For rock under impact loads, the crack first initiates from the wing end of the prefabricated flaw, the preflaw closes gradually, and finally the crack propagates at the locking section leading to the coalescence of rock bridge. With the increase of strain rate, the fragmentation degree of the specimen increases asymptotically, and the average fragmentation size of the specimen decreases with the increase of strain rate. It is suggested that the stability of large rocked slopes is controlled by the locked section, and understanding the fracture evolution of the rock bridge is the key to slope instability prediction.

Effect of the Fine Recycled Aggregates on the Dynamic Compressive Behavior of Recycled Mortar

2020 ◽  
Vol 991 ◽  
pp. 62-69
Author(s):  
Sallehan Ismail ◽  
Mohamad Asri Abd Hamid ◽  
Zaiton Yaacob
Keyword(s):  
Compressive Strength ◽  
Strain Rate ◽  
Energy Absorption ◽  
Specific Energy ◽  
Split Hopkinson Pressure Bar ◽  
Recycled Aggregates ◽  
Fine Aggregate ◽  
Peak Strain ◽  
Specific Energy Absorption ◽  
The Impact

This study aims to investigate the dynamic behavior of recycled mortar under impact loading using a split Hopkinson pressure bar (SHPB). Several mortar mixtures were produced by adding various fine recycled aggregates (FRA) to the mixture in replacement percentages of 0%, 25%, 50%, 75%, and 100% of the natural fine aggregate (NFA). The effects of strain rate on compressive strength and specific energy absorption were obtained. Results show that the dynamic compressive strength and specific energy absorption of recycled mortar are highly strain rate dependent; specifically, they increase nearly linearly with the increase in peak strain rate. However, the compressive strength and specific energy absorption of recycled mortar are generally lower than those of NFA mortar (reference samples) under similar high strain rates. The findings of this research can help researchers and construction practitioners to ascertain the appropriate mix design procedure to optimize the impact strength properties of recycled mortar for protective structural application.

scholarly journals Study on Strain Rate Effect and Size Effect of Dynamic Response Characteristics of Granite

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Zhihang Hu ◽  
Yuying Ning ◽  
Jiuyang Zhang ◽  
Jianyu Zhao
Keyword(s):  
Aspect Ratio ◽  
Strain Rate ◽  
Split Hopkinson Pressure Bar ◽  
Impact Load ◽  
Hopkinson Pressure Bar ◽  
Aspect Ratios ◽  
Rate Of Increase ◽  
Density Index ◽  
The Impact ◽  
Time Density

Under impact load, the dynamic mechanical properties of rock are complex and changeable. The Split Hopkinson Pressure Bar (SHPB) system was used to change the impact load to carry out different strain rate loading tests on granite with different aspect ratios, and to analyze the influence of strain rate and aspect ratio on the dynamic energy consumption of granite crushing. The results show that at an impact velocity of 14 m/s, the granite with an aspect ratio of 1.4 appears to be strip-shaped fragments after being broken; the granite with an aspect ratio of 1.0 uniform square fragments after being broken; the granite with an aspect ratio of 0.6 appears to be a large number of flat fragments after being broken. When the load strain rate of the granite with an aspect ratio of 0.6 increases from 50 s-1 to 150 s-1, the energy-time density index increases significantly; when the load strain rate exceeds 150 s-1, the energy-time density index decreases. When the strain rate of granite with an aspect ratio of 1.0 exceeds 80 s-1, the energy-time density increases significantly. When the strain rate of the granite with an aspect ratio of 1.4 exceeds 60 s-1, the rate of increase of the energy-time density of the rock increases significantly.

Dynamic Behavior of Acrylonitrile Butadiene Styrene Under Impact Loads

2015 ◽  
Author(s):  
Alex Peterson ◽  
Denzell Bolling ◽  
Adewale Olasumboye ◽  
Ed Habtour ◽  
Jaret C. Riddick ◽  
...  
Keyword(s):  
Strain Rate ◽  
Computer Aided Design ◽  
Fused Deposition Modeling ◽  
Split Hopkinson Pressure Bar ◽  
Impact Load ◽  
Acrylonitrile Butadiene Styrene ◽  
Fused Deposition ◽  
Computer Aided ◽  
The Impact ◽  
Butadiene Styrene

This paper is aimed at providing a better understanding of the potential energy absorption benefits of components fabricated using fused deposition modeling (FDM) additive manufacturing. Using FDM, it is possible to print three-dimensional (3-D) objects created through the use of computer-aided design and computer-aided manufacturing software coupled with computer codes that enable the layer-by-layer deposition of material to form the 3-D component. Also known as direct digital manufacturing or 3-D printing, AM offers the benefit of being able to rotate printing orientation during processing to manipulate the design build and ultimately control mechanical and structural properties when subjected to dynamic loads. In this work, tensile test specimens were first fabricated to characterize the general mechanical behavior of the of 3D-printed Acrylonitrile Butadiene Styrene (ABS) material to assess its potential strain rate dependency. The mechanical evaluation under the quasi-static load was also necessary to determine the properties necessary to characterize the dynamic evolution of ABS in compression at various strain rates. ABS specimens were subsequently subjected to high strain rate deformation through the use of the Split Hopkinson Pressure Bar. During compression a new phenomenon described as a multistage collapse in which the samples undergo multiple stages of contraction and expansion was observed as the impact load was applied.

Dynamic and Quasi-Static Compression Tests for Polylactic Acid Resin Foam

2012 ◽  
Vol 706-709 ◽  
pp. 745-750 ◽  
Author(s):  
Hidetoshi Kobayashi ◽  
Keitaro Horikawa ◽  
Keiko Watanabe ◽  
Kinya Ogawa ◽  
Kensuke Nozaki
Keyword(s):  
Strain Rate ◽  
Polylactic Acid ◽  
High Speed ◽  
Impact Load ◽  
Video Camera ◽  
Compression Tests ◽  
Rate Dependency ◽  
Static Compression ◽  
Acid Resin ◽  
The Impact

In this study, the effect of strain rate on the strength and the absorbed energy of polylactic acid resin foam (PLA-foam), which is generally known as one of carbon-neutral and environmentally-friendly polymers, were examined by a series of compression tests at various strain rates from 0.001 to 750 s-1. For the measurements of the impact load and the displacement of specimen, a special load cell and a high-speed video camera were used, respectively. The flow stress of the PLA-foam strongly depends upon not only strain rate but also density of specimens. Thus, a new technique to eliminate the effect of the difference in the specimen density was proposed and successfully applied. It was also found that the strain-rate dependency of PLA-foam can be expressed by a simple power law.

Multiaxial Impact Behavior and Modeling of ABS Polymer

2001 ◽  
Author(s):  
A. Saigal ◽  
R. Greif ◽  
Y. Duan ◽  
M. A. Zimmerman
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Strain Rate ◽  
Impact Load ◽  
Mechanical Test ◽  
Impact Behavior ◽  
Analysis Model ◽  
Element Analysis ◽  
The Finite Element Analysis ◽  
The Impact

Abstract The multiaxial impact behavior of CYCOLAC GPM5500 (ABS glassy polymer) is obtained as a function of impact velocity and temperature from the standard impact test as specified by ASTM D3763. Finite element analysis (FEA) and ABAQUS/Explicit are used to model the impact behavior of the polymer. The generalized “DSGZ” constitutive model, previously developed by the authors and calibrated using low strain rate uniaxial mechanical test data, is extended to the high strain rate regime and used in the finite element analysis. Load-displacement curves from the finite element analysis are compared with the experimental data and agree well up to the maximum impact load (failure). Therefore, the proposed finite element analysis model can be used to predict the multiaxial impact behaviors of polymers at different temperatures and impact velocities.

Research on the Mechanical Properties and Energy Consumption Transfer Law of Cement Tailings Backfill Under Impact Load

2021 ◽  
Vol 13 (5) ◽  
pp. 889-898
Author(s):  
Yong-Ye Mu ◽  
Xiang-Long Li ◽  
Jian-Guo Wang ◽  
Zhi-Gao Leng
Keyword(s):  
Mechanical Properties ◽  
Energy Transfer ◽  
Impact Load ◽  
Peak Stress ◽  
Peak Strain ◽  
Impact Compression ◽  
Average Strain Rate ◽  
Failure Morphology ◽  
The Stability ◽  
The Impact

The cemented tailings backfill (CTB), which plays a significant role in the stability of mine structure, is made of cement, tailings, and water in a certain proportion. When blasting and excavating an underground mine, the CTB will be disturbed by blasting. The impact load of blasting has an impact on the stability of the CTB, which is directly related to the safety of mine construction. The mechanical behaviour of CTB is generally affected by the cement-tailings ratio (C/T) and average strain rate (ASR). Therefore, a series of impact experiments were carried out on three CTB specimens with different C/T using a SHPB. Combined with the experimental results, this account reports studies on the effects of C/T and ASR on the mechanical properties of CTB, and on the energy transfer laws of CTB during impact compression. The research results show that when the ASR is less than 70 s−1, the peak stress and the peak strain have the same trend, and both of them continue to increase with the increase of ASR.When the ASR exceeds 70 s−1, as the ASR increases, the peak stress continues to increase, but the peak strain decreases gradually. Afterwards, the law of energy transfer of the CTB specimen was analyzed. It was found that as the incident energy increased, the energy reflection ratio of the CTB increased. Both the energy transmitted ratio and the energy dissipation ratio decreased. The volumetric energy showed a sharp increase first and then a trend Because of the slowly increasing trend. Finally, according to the failure morphology of the CTB, it is found that the ASR and the C/T together affect the failure of the CTB. The failure model of the CTB is mainly split failure and crush failure.

scholarly journals Dynamic Compressive Characteristics of Sandstone under Confining Pressure and Radial Gradient Stress with the SHPB Test

2018 ◽  
Vol 2018 ◽  
pp. 1-8 ◽  
Author(s):  
Shiming Wang ◽  
Yunsi Liu ◽  
Jian Zhou ◽  
Qiuhong Wu ◽  
Shuyi Ma ◽  
...  
Keyword(s):  
Elastic Modulus ◽  
Strain Rate ◽  
Split Hopkinson Pressure Bar ◽  
Large Diameter ◽  
Dynamic Strength ◽  
Confining Pressure ◽  
Peak Strain ◽  
Hopkinson Pressure Bar ◽  
Radial Gradient ◽  
The Impact

Research on the dynamic compressive characteristics of sandstone under radial gradient stress and confining pressure is conducive to understanding the characteristics of the surrounding rock, especially in an excavation operation for an underground mine roadway and tunnel. The present work aimed at studying the effects of radial gradient stress and confining pressure on the impact of compression of sandstone using a large-diameter split Hopkinson pressure bar. The results showed that the dynamic strength of sandstone under radial gradient stress increased with strain rate following a power function, and the dynamic strength of the sandstone under radial gradient stress was lower and more sensitive to strain rate. The increase in strain at peak stress (peak strain) was linearly correlated with the strain rate under different confining pressures. The sensitivity of the peak strain to confining pressure was lower for the sandstone with a hole, while the values of the elastic modulus were decreased. However, further increasing the stain rate would lead to an increase in the elastic modulus. Also, the ductility of the sandstone with a hole tested in this study was found to improve more significantly. Finally, with an increase in the incident energy, the absorbed energy per unit volume would increase, but would not be affected obviously by the radial gradient stress.

scholarly journals Effects of Different Strain Rates on the Impact Properties of Recycled Aggregate Concrete Modified With Nanosilica Solution and Polyvinyl Alcohol Fiber

2021 ◽  
Vol 8 ◽  
Author(s):  
Xingguo Wang ◽  
Maolin Jiang ◽  
Xianggang Zhang ◽  
Zhaoxia Cheng ◽  
Jian Gong ◽  
...  
Keyword(s):  
Polyvinyl Alcohol ◽  
Strain Rate ◽  
Peak Stress ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Peak Strain ◽  
Aggregate Concrete ◽  
Impact Properties ◽  
Pva Fiber ◽  
The Impact

The recycled aggregate (RA) was modified by 2% nanosilica solution, and the split Hopkinson pressure bar (SHPB) test device was used to study the dynamic impact properties of the modified recycled aggregate concrete (RAC) mixed with polyvinyl alcohol (PVA) fibers. The RA replacement percentage, the amount of PVA fiber, and the strain rate were variables. The failure pattern, the stress–strain curve of the nanosilica solution, and PVA fiber-modified RAC were shown under different strain rate conditions. Dynamic peak stress, peak strain, and dynamic increase factor (DIF) of the specimens are discussed. The results showed that the stress and dynamic peak strain value of the specimen increased with the increase of the strain rate; moreover, with the increase of the RA replacement percentage and the PVA fiber content, the dynamic peak stress of the specimen decreases, while the dynamic peak strain and the DIF value increase. The incorporation of nanosilica-modified RA is beneficial to the improvement of the impact performance of RAC, and the incorporation of an appropriate amount of the PVA fiber effectively improves the deformability of RAC.

scholarly journals Analysis of Energy Dissipation Characteristics of Damaged Sandstone under Impact Load

2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Feng Wang ◽  
Haibo Wang ◽  
Ying Xu ◽  
Bing Cheng ◽  
Qianqian Wang
Keyword(s):  
Rock Mass ◽  
Energy Dissipation ◽  
Cyclic Loading ◽  
Dynamic Load ◽  
Impact Load ◽  
Peak Strain ◽  
Dissipation Energy ◽  
Cyclic Loading And Unloading ◽  
Damage Degree ◽  
Loading And Unloading

Before rock burst, coal, and gas outburst dynamic load, rock mass in geotechnical engineering has been an indifferent degree of damage. The dissipation energy of rock mass under dynamic load reflects the difficulty of rock breaking. In view of the energy dissipation of damaged rock mass under dynamic load, the cyclic loading and unloading test is carried out to make sandstone in different damage states, and the damage degree of sandstone is characterized by the change of longitudinal wave velocity before and after cyclic loading and unloading. Then, the rock with different damage degrees is tested by adopting the split Hopkinson pressure bar (SHPB). Finally, the energy dissipation characteristics of damaged rock under impact load are analyzed. The results show that the damage factor of sandstone increases with the increase of the upper limit of stress after cyclic static loading. The dynamic strength and peak strain of damaged sandstone increase with the increase of impact pressure and decrease with the increase of damage degree. With the increase of damage degree of sandstone, the reflection energy and dissipation energy of sandstone increase, while the transmission energy decreases.

scholarly journals Experimental and Numerical Study on the Strain Behavior of Buried Pipelines Subjected to an Impact Load

2019 ◽  
Vol 9 (16) ◽  
pp. 3284 ◽  
Author(s):  
Feifei Dong ◽  
Xuemeng Bie ◽  
Jiangping Tian ◽  
Xiangdong Xie ◽  
GuoFeng Du
Keyword(s):  
Finite Element ◽  
Impact Load ◽  
Numerical Study ◽  
Scale Model ◽  
Peak Strain ◽  
Buried Pipeline ◽  
Buried Pipelines ◽  
Strain Behavior ◽  
Geological Conditions ◽  
The Impact

Long-distance oil and gas pipelines are inevitably impacted by rockfalls during geologic hazards such as mud-rock flow and landslides, which have a serious effect on the safe operation of pipelines. In view of this, an experimental and numerical study on the strain behavior of buried pipelines under the impact load of rockfall was developed. The impact load exerted on the soil, and the strains of buried pipeline caused by the impact load were theoretically derived. A scale model experiment was conducted using a self-designed soil-box to simulate the complex geological conditions of the buried pipeline. The simulation model of hammer–soil–pipeline was established to investigate the dynamic response of the buried pipeline. Based on the theoretical, experimental, and finite element analysis (FEA) results, the overall strain behavior of the buried pipeline was obtained and the effects of parameters on the strain developments of the pipelines were analyzed. Research results show that the theoretical calculation results of the impact load and the peak strain were in good agreement with the experimental and FEA results, which indicates that the mathematical formula and the finite element models are accurate for the prediction of pipeline response under the impact load. In addition, decreasing the diameter, as well as increasing the wall thickness of the pipeline and the buried depth above the pipeline, could improve the ability of the pipeline to resist the impact load. These results could provide a reference for seismic design of pipelines in engineering.

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