Correlation between the accuracy of a SHPB test and the stress uniformity based on numerical experiments

2003 ◽  
Vol 28 (5) ◽  
pp. 537-555 ◽  
Author(s):  
H. Meng ◽  
Q.M. Li
Keyword(s):  
Numerical Experiments ◽  
Shpb Test ◽  
Stress Uniformity

Stress uniformity process of specimens in SHPB test under different loading conditions of rectangular and half-sine input waves

2008 ◽  
Vol 14 (6) ◽  
pp. 450-456 ◽  
Author(s):  
Liang Hong ◽  
Xibing Li ◽  
Xiling Liu ◽  
Zilong Zhou ◽  
Zhouyuan Ye ◽  
...  
Keyword(s):  
Loading Conditions ◽  
Shpb Test ◽  
Stress Uniformity

scholarly journals Experimental Study on Stress Uniformity and Deformation Behavior of Coals with Different Length-to-Diameter Ratios under Dynamic Compression

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Qiupeng Yuan ◽  
Guangxiang Xie ◽  
Lei Wang ◽  
Zhenhua Jiao ◽  
Peng Zou ◽  
...  
Keyword(s):  
Deformation Behavior ◽  
Dynamic Compression ◽  
Test System ◽  
Peak Strain ◽  
Test Protocol ◽  
Impact Compression ◽  
Stress Equilibrium ◽  
Shpb Test ◽  
Stress Uniformity ◽  
Elastic Stage

In this study, a uniaxial impact compression test was performed on coal samples with length-to-diameter L / D ratios of 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, and 1 using a Φ 50 mm split Hopkinson pressure bar (SHPB) test system. This study researched the stress uniformity and deformation behavior of coal samples with different L / D ratios during dynamic compression, defined the stress equilibrium coefficient ξ , proposed a new method for determining whether a sample meets the stress uniformity hypothesis, and obtained the critical L / D ratio of 0.6 and the optimal L / D ratio of 0.3 or 0.4 for coal samples to obtain the stress equilibrium. The experimental results showed that the dynamic stress-strain curve of coal had an elastic stage, a plastic stage, and a failure stage. As the L / D ratio increased, the proportion of the elastic stage to the prepeak curve of the samples declined progressively; with an increase in the L / D ratio, the peak part of the curve also changed from “sharp” to “stagnated,” while an increase in the plasticity led to strain softening. As the L / D ratio of the samples increased, the average strain rate decreased approximately as a power function, and the decreasing trend was gradually reduced from 296.49 s−1 ( L / D =0.3) to 102.85 s−1 ( L / D =1), with a reduction of approximately 65.31%. With an increase in the L / D ratio, the peak strain gradually decreased exponentially. This study concluded that the SHPB test protocol design is of a certain reference value for low-density, low-strength, heterogeneous brittle materials, such as coal.

Numerical Simulation the Stress Uniformity in Split Hopkinson Pressure Bar Testing

2013 ◽  
Vol 634-638 ◽  
pp. 2861-2864
Author(s):  
Hong Bin Jin
Keyword(s):  
Numerical Simulation ◽  
Wave Propagation ◽  
Split Hopkinson Pressure Bar ◽  
Hopkinson Pressure Bar ◽  
Large Area ◽  
Test Technique ◽  
Split Hopkinson ◽  
Shpb Test ◽  
Pressure Bar ◽  
Stress Uniformity

The assumption of uniform stress in a test specimen is fundamental to SHPB test technique. In the present paper, a numerical simulation of wave propagation in SHPB is performed to validate the assumption. A one-dimensional model based on CSPM is firstly developed. Then the wave propagations in SHPB with various area ratios of bar/specimen are simulated. The results show that the condition of stress uniformity is not satisfied, especially at the beginning of wave propagation. For the large area specimen, the stress tends to be uniform. While for the small area specimen, the non-uniformity of stress is more apparent.

Controllable Compliance Joint For Human Oriented Robots

2013 ◽  
Vol 43 (1) ◽  
pp. 47-60
Author(s):  
Mihail Tsveov ◽  
Dimitar Chakarov
Keyword(s):  
Numerical Experiments ◽  
Position Control ◽  
Joint Stiffness ◽  
Joint Motion ◽  
Compliance Control ◽  
Leaf Springs ◽  
Antagonistic Actuation

Abstract In the paper, different approaches for compliance control for human oriented robots are revealed. The approaches based on the non- antagonistic and antagonistic actuation are compared. In addition, an approach is investigated in this work for the compliance and the position control in the joint by means of antagonistic actuation. It is based on the capability of the joint with torsion leaf springs to adjust its stiffness. Models of joint stiffness are presented in this paper with antagonistic and non-antagonistic influence of the spring forces on the joint motion. The stiffness and the position control possibilities are investigated and the opportunity for their decoupling as well. Some results of numerical experiments are presented in the paper too.

Improved Burn-In Stress Methodology for Stress Uniformity

2018 ◽  
Author(s):  
Jungsuk Ko ◽  
Hoonchang yang ◽  
Hyungchae Jeon ◽  
Gyuyoung Nam ◽  
Youngseok Ryu ◽  
...  
Keyword(s):  
Temperature Stress ◽  
Stress Condition ◽  
Temperature Deviation ◽  
Stress Effects ◽  
Hot Temperature ◽  
Production Environments ◽  
Stress Environment ◽  
The Stability ◽  
Stress Uniformity ◽  
Stress Voltage

Abstract The necessity of hot temperature stress is widely recognized as the initial stress methodology to maintain the stability of products from infant defects in device [1, 2]. However, hot temperature stress has a disadvantage in terms of stress uniformity because temperature variation according to stress environment such as chamber, board, and tester accelerates different stress effects per chips. In addition, this stress condition can cause serious reliability problem in the mass production environments. Therefore, the stress temperature should be lowered to minimize the temperature deviation due to the production environments. The reduction of stress temperature cause the lack of stress amount, so optimized stress voltage and time to maintain the stress condition is required. In this study, various stress voltage and time with decreasing temperature were evaluated in consideration of lifetime that unit elements such transistors and capacitors did not degrade by any stress conditions. In addition, it was confirmed that stress uniformity can be improved in the stress condition obtained by the evaluation. Furthermore, the enhanced initial failure screen ability was proven with mass evaluations.

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