scholarly journals Mechanical Response and Shear-Induced Initiation Properties of PTFE/Al/MoO3 Reactive Composites

Materials ◽  
2018 ◽  
Vol 11 (7) ◽  
pp. 1200 ◽  
Author(s):  
Junyi Huang ◽  
Xiang Fang ◽  
Shuangzhang Wu ◽  
Li Yang ◽  
Zhongshen Yu ◽  
...  
Keyword(s):  
Strain Rate ◽  
Yield Stress ◽  
Mechanical Response ◽  
Dynamic Compression ◽  
Volume Ratio ◽  
Outer Edge ◽  
Reaction Products ◽  
Initiation Mechanism ◽  
Static Compression ◽  
Drop Weight

Polytetrafluoroethylene/aluminum/molybdenum oxide (PTFE/Al/MoO3) reactive composites of a volume ratio of 60:16:24 were studied in this research. Quasi-static compression, dynamic compression and drop-weight experiments were performed to explore the mechanical response and the shear-induced initiation properties of the composites. Mesoscale images of the specimens after sintering demonstrate that PTFE, Al and MoO3 powders were evenly mixed and no chemical reaction occurred after the materials were stirred, pressed and sintered. The yield stress and compressive strength of PTFE/Al/MoO3 specimens are sensitive to strain rate within the range of 10−3~3 × 103 s−1, and the yield stress shows a bilinear dependence on the logarithm values of strain rate. The established Johnson-Cook constitutive model based on the experimental data can describe the mechanical response of PTFE/Al/MoO3 material well. Drop-weight tests show that the PTFE/Al/MoO3 specimens can react violently when impacted, with the characteristic drop height (H50) calculated as 51.57 cm. The recovered specimens show that the reaction started from the outer edge of the specimen with the largest shear force and the most concentrated shear deformation, indicating a shear-induced initiation mechanism. The reaction products of PTFE/Al/MoO3 specimens were AlF3, Al2O3, Mo and C, demonstrating that redox reaction occurred between PTFE and Al, and between Al and MoO3.

Analysis of Twinning Behavior of Ti-2V Alloy Compressed at High Strain Rate

2017 ◽  
Vol 898 ◽  
pp. 231-235
Author(s):  
Qiao Chu Wang ◽  
Rui Liu ◽  
Wen Jun Ye ◽  
Yang Yu ◽  
Xiao Yun Song ◽  
...  
Keyword(s):  
Strain Rate ◽  
Mechanical Response ◽  
Dynamic Compression ◽  
Orientation Imaging Microscopy ◽  
Optical Microscope ◽  
Dynamic Mechanical Properties ◽  
Hopkinson Pressure Bar ◽  
Deformation Degree ◽  
Ebsd Technique ◽  
Pressure Bar

The spilt Hopkinson pressure bar was employed to study dynamic compression mechanical response of Ti-2V alloy. The dynamic compression experiment was carried at a strain rate of 3000s-1. The microstructure of deformed specimen with ε=0.05, 0.18, 0.26 was observed by optical microscope. Electron Back-Scattered Diffraction (EBSD) technique was applied to confirm the types of twinning. Through analyzing mechanical response and microstructure evolution rule, the effect of element vanadium and deformation degree on dynamic mechanical properties and twinning deformation behavior was revealed. The results indicate that twinning is the prime dynamic deformation mechanism in Ti-2V alloy and the twinning fraction is increasingly raised during the deformation process. The twinning types, confirmed by Orientation Imaging Microscopy software, are namely {102}, {112} and {111} twinning. And the number of {111} twinning is far less than the other two types of twinning.

Strain-Rate Dependence of Compressive Yield Strength of Titanium Grade 4 with Coarse-Grained and Ultrafine-Grained Structures: Experimental Results and Theoretical Calculation

2018 ◽  
Vol 1145 ◽  
pp. 100-105
Author(s):  
Ivan V. Smirnov ◽  
Alexander Y. Konstantinov
Keyword(s):  
Yield Strength ◽  
Strain Rate ◽  
Yield Stress ◽  
Split Hopkinson Pressure Bar ◽  
Dynamic Compression ◽  
Pure Titanium ◽  
Coarse Grained ◽  
Strain Rates ◽  
Ultrafine Grained ◽  
Titanium Grade

The nanocrystalline (NC) and ultrafine-grained (UFG) structures of metallic materials can lead to their extraordinary high strength. However, most of the papers on this topic consider deformation parameters of NC and UFG materials only for the case of quasi-static tensile tests. Characteristics of dynamic strength and fracture of such materials remain unexplored. This paper presents a study of the mechanical behavior of pure titanium Grade 4 with a coarse-grained (CG) and UFG structure under uniaxial compression with different strain rates. The UFG structure was provided using the method of equal-channel angular pressing. The dynamic compression was carried out on a setup with the Split-Hopkinson pressure bar. It is found that in the observed range of strain rates 10–3-3×103 s–1, the yield stress of the CG titanium increases by 20%, and does not exceed the yield stress of the UFG titanium. However, the yield stress of the UFG titanium remains close to a quasi-static value. It is shown that these strain-rate dependencies of the yield strength can be predicted by the incubation time approach. The calculated curves show that at strain rates above 104 s–1 the yield stress of the CG titanium becomes higher than the yield strength of the UFG titanium.

High Strain Rate Behavior of Carbon Nanotubes Reinforced Aluminum Foams

2017 ◽  
Vol 140 (1) ◽  
Author(s):  
Abdelhakim Aldoshan ◽  
D. P. Mondal ◽  
Sanjeev Khanna
Keyword(s):  
Carbon Nanotubes ◽  
Strain Rate ◽  
Aluminum Foam ◽  
High Strain ◽  
Split Hopkinson Pressure Bar ◽  
Dynamic Compression ◽  
Strain Rates ◽  
Aluminum Foams ◽  
Static Compression ◽  
Closed Cell

The mechanical behavior of closed-cell aluminum foam composites under different compressive loadings has been investigated. Closed-cell aluminum foam composites made using the liquid metallurgy route were reinforced with multiwalled carbon nanotubes (CNTs) with different concentrations, namely, 1%, 2%, and 3% by weight. The reinforced foams were experimentally tested under dynamic compression using the split Hopkinson pressure bar (SHPB) system over a range of strain rates (up to 2200 s−1). For comparison, aluminum foams were also tested under quasi-static compression. It was observed that closed-cell aluminum foam composites are strain rate sensitive. The mechanical properties of CNT reinforced Al-foams, namely, yield stress, plateau stress, and energy absorption capacity are significantly higher than that of monolithic Al-foam under both low and high strain rates.

On Computer Aided Impact Experiments - A Case of Drop Weight Experiment -

2006 ◽  
Vol 326-328 ◽  
pp. 1547-1550
Author(s):  
Yasuhisa Sato ◽  
Keiou Nishimura
Keyword(s):  
Strain Rate ◽  
Personal Computer ◽  
Dynamic Compression ◽  
Equations Of Motion ◽  
Dynamic Force ◽  
Runge Kutta Method ◽  
Drop Weight ◽  
Measured Strain ◽  
Force Time ◽  
Spring Coefficient

Stress-strain curves of some kinds of materials at high strain-rate conditions were able to be determined by a drop weight experiment system which has only to measure the force-time relation using a load-cell but not to measure directly the deformation or deformation-rate of specimen. To evaluate the strain-rate or the strain of the specimen it had been necessary to measure the motion, i.e. the velocity or the displacement of tup and anvil so far. In this new method the velocity and the displacement of the tup and the anvil which contacted the both end surfaces of specimen were calculated using a personal computer on the basis of the equations of motion for the tup and the anvil, respectively. The differential equations, in which the measured dynamic-force versus time characteristics were contained, were integrated by Runge-Kutta method using the personal computer. In the differential equation of motion of the anvil, a spring coefficient K for the rubber cushion beneath the anvil is used. For the first approximation of the coefficient K is assumed to be the value determined by the oscillation method of cantilever beam. The spring coefficient K with high accuracy is determined when the computed strain of the specimen on the basis of the method described above is almost equal to the measured strain of it by using a micrometer caliper after the dynamic compression. The coefficient K with the higher accuracy can be obtained the incremental compression experiment using some kinds of hard stop ring in the prescribed height.

scholarly journals Compressive Properties and Constitutive Model of Semicrystalline Polyethylene

Polymers ◽  
2021 ◽  
Vol 13 (17) ◽  
pp. 2895
Author(s):  
Kebin Zhang ◽  
Wenbin Li ◽  
Yu Zheng ◽  
Wenjin Yao ◽  
Changfang Zhao
Keyword(s):  
Constitutive Model ◽  
Strain Rate ◽  
Yield Stress ◽  
Dynamic Compression ◽  
Molecular Structures ◽  
Strengthening Effect ◽  
Compression Tests ◽  
Compression Process ◽  
Softening Effect ◽  
Constitutive Parameters

The mechanical properties of polyethylene (PE) materials are greatly influenced by their molecular structures, environmental temperature, and strain rate. In this study, static and dynamic compression tests were performed on two semicrystalline PE materials—ultrahigh molecular weight polyethylene (UHMWPE) and high-density polyethylene (HDPE). The stress–strain curves of HDPE and UHMWPE under uniaxial compression at temperatures of −40–120 °C and strain rates of 0.001–5500 s−1 were obtained. The research findings suggest that both the UHMWPE and HDPE showed significant strain rate-strengthening effect and temperature-softening effect. In particular, HDPE exhibited better compression resistance and high-temperature resistance. The relationships between the yield stress and temperature and between the yield stress and strain rate for both materials were fitted, and the Cowper–Symonds constitutive model was built while considering the temperature effect. The parameters of the constitutive model were obtained and input into LS-DYNA software to simulate the dynamic compression process of HDPE. The simulation result was consistent with the test result, validating the accuracy of the constitutive parameters.

scholarly journals Influence of strain rate on the mechanical response of nanostructured coppers elaborated by SPD and SPS

2021 ◽  
Vol 250 ◽  
pp. 03014
Author(s):  
Hervé Couque ◽  
Yuri Khoptiar ◽  
Frédéric Bernard ◽  
Itamar Gutman ◽  
Florian Bussiere ◽  
...  
Keyword(s):  
Strain Rate ◽  
Uniaxial Compression ◽  
Mechanical Response ◽  
Tensile Tests ◽  
Strain Rates ◽  
Static Compression ◽  
Plasma Sintering ◽  
History Of ◽  
Spark Plasma ◽  
Nanostructured Copper

The influence of strain rate on the mechanical response of two different nanostructured pure coppers was investigated under uniaxial compression. The first nanostructured copper was elaborated by powder metallurgy using the Spark Plasma Sintering (SPS) process. The second nanostructured copper was elaborated by Severe Plastic Deformation (SPD). Conventional characterizations were conducted with quasi-static compression and tensile tests, hardness tests and, with microstructure analysis. The effect of strain rate was evaluated under uniaxial compression at strain rates varying from 10-4 to 10+4 s-1. The high strain rate data were generated with a direct Hopkinson impact technique. The increase of strength with strain rates was analysed and discussed from the Scanning Electron Microscope observations and grain size distribution. The mechanical properties are consequently dependent on the metallurgical history of these samples prepared according to two different routes.

scholarly journals Dynamic Compression Characteristics and Failure Mechanism of Water-Saturated Granite

Water ◽  
2022 ◽  
Vol 14 (2) ◽  
pp. 216
Author(s):  
Ke Man ◽  
Xiaoli Liu ◽  
Zhifei Song ◽  
Zongxu Liu ◽  
Ruilin Liu ◽  
...  
Keyword(s):  
Strain Rate ◽  
Water Saturation ◽  
Dynamic Compression ◽  
Free Water ◽  
Dynamic Strength ◽  
Static Compression ◽  
Rate Condition ◽  
Static State ◽  
Medium Strain Rate ◽  
Water Saturated

For Fangshan granite in Beijing, the static compression and dynamic compression tests have been carried out separately under natural air drying and water saturation. It was found that the dynamic compressive strength of water-saturated granite is higher than that of air-dried granite, which is contrary to the result that the strength of water-saturated rock is lower than that of air-dried granite under static load. Furthermore, under the medium strain rate condition, when the strain rate is 85 s−1, the dynamic strength of natural air-dried granite could be increased by nearly 0.5 times compared with its static state. The dynamic strength of water-saturated granite could be increased by nearly 1–2 times compared with its static strength, which shows that water-saturated granite has stronger strain rate sensitivity than natural air-dried granite. Meanwhile, under impact loading, from the perspective of water-bearing granite the Bernoulli effect of fluid, the adhesion effect of free water and the Stefan effect of fluid in water-saturated granite were revealed, and found to be the essential reasons affecting the dynamic strength of water-saturated granite. The dynamic strength in different water-bearing states in the range of medium strain rate could then be analyzed in depth, providing a certain reference value for the strength design of water-bearing rock engineering.

scholarly journals Mechanical and Volumetric Fracturing Behaviour of Three-Dimensional Printing Rock-like Samples Under Dynamic Loading

2020 ◽  
Vol 53 (6) ◽  
pp. 2855-2864 ◽  
Author(s):  
Tao Zhou ◽  
Jianbo Zhu ◽  
Heping Xie
Keyword(s):  
Strain Rate ◽  
Dynamic Loading ◽  
Dynamic Compression ◽  
Three Dimensional ◽  
Peak Stress ◽  
Fracture Initiation ◽  
Static Compression ◽  
Three Dimensional Printing ◽  
Volumetric Fracturing ◽  
Dimensional Printing

AbstractHeterogeneous rock contains numerous pre-existing three-dimensional (3D) cracks, which control its mechanical and fracturing properties. Considerable effort has been devoted to studying the volumetric fracturing behaviour of rock under static loading conditions. Although rock masses are often subject to dynamic impacts such as earthquakes and blasting, the mechanical and volumetric fracturing behaviour of rock under dynamic loading is still poorly understood. In this paper, dynamic laboratory tests were performed on 3D-printed artificial rock samples with 3D embedded flaws created during three-dimensional printing (3DP), with the aim of studying the volumetric fracturing and mechanical properties of these samples under impact with high strain rate. The results show that the dynamic compressive strength and the tangent modulus decrease with an increasing number of flaws, but have very limited effects on the ratio of the fracture initiation stress of the first crack to the peak stress of the sample, the maximum axial strain of the sample and the volumetric fracturing behaviour of the sample. The tensile failure of a sample is caused by the continuous extension of wing cracks from the outer flaw tips. The mechanical and volumetric fracturing behaviour of samples with 3D embedded flaws are strain rate dependent. The tangential modulus and the ratio of the fracture initiation stress of the crack to the peak stress increase significantly when the loading type changes from static compression to dynamic compression. Under dynamic compression, wing cracks can continuously extend to the sample ends, whereas under static compression, wing cracks can intermittently extend only a limited distance. Moreover, the fracturing behaviour of 3D flaw differs from that of 2D flaws under dynamic loading. Under high strain rate loading, wing cracks generated at 3D flaw tips lead to splitting failure of the sample, while shear cracks formed at 2D flaw tips result predominant shear failure of the sample. The findings in this paper could facilitate a better understanding of rock failure subjected to dynamic loading conditions.

scholarly journals Dynamic Response of Electro-Mechanical Properties of Cement-Based Piezoelectric Composites

2021 ◽  
Vol 11 (24) ◽  
pp. 11925
Author(s):  
Yi Li ◽  
Youwei Zhang ◽  
Haiwei Dong ◽  
Wenjie Cheng ◽  
Chaoming Shi ◽  
...  
Keyword(s):  
Strain Rate ◽  
Impact Loading ◽  
Mechanical Response ◽  
Dynamic State ◽  
Dynamic Impact ◽  
Piezoelectric Composites ◽  
Static Compression ◽  
Static State ◽  
Dynamic Impact Loading ◽  
Quasi Static Compression

By employing ordinary Portland cement as a matrix and PZT-5H piezoelectric ceramic as the functional body, 1-3 and 2-2 cement-based piezoelectric composites were prepared. Quasi-static compression tests were performed along with dynamic impact loading tests to study the electro-mechanical response characteristics of 1-3 and 2-2 cement-based piezoelectric composites. The research results show that both composites exhibit strain rate effects under quasi-static compression and dynamic impact loading since they are strain-rate sensitive materials. The sensitivity of the two composites has a non-linear mutation point: in the quasi-static state, the sensitivity of 1-3 and 2-2 composites is 157 and 169 pC/N, respectively; in the dynamic state, the respective sensitivity is 323 and 296 pC/N. Although the sensitivity difference is not significant, the linear range of the 2-2 composite is 24.8% and 61.3% larger than that of the 1-3 composite under quasi-static compression and dynamic impact loading, respectively. Accordingly, the 2-2 composite exhibits certain advantages as a sensor material, irrespective of whether it is subjected to quasi-static or dynamic loading.

Compressive Mechanical Property Analysis of Eva Foam: Its Buffering Effects at Different Impact Velocities

2016 ◽  
Vol 33 (4) ◽  
pp. 435-441
Author(s):  
D.-S. Liu ◽  
Z.-H. Chen ◽  
C.-Y. Tsai ◽  
R.-J. Ye ◽  
K.-T. Yu
Keyword(s):  
Strain Rate ◽  
High Speed ◽  
Mechanical Response ◽  
Numerical Models ◽  
Element Model ◽  
Strain Rates ◽  
Material Parameter Identification ◽  
Strain Rate Effects ◽  
Static Compression ◽  
Strain Behavior

AbstractEVA foams, like all other polymers, also exhibit strain-rate effects and hysteresis. However, currently available approaches for predicting the mechanical response of polymeric foam subjected to an arbitrarily imposed loading history and strain-rate effect are highly limited. Especially, the strain rates in the intermediate rate domain (between 100and 102s–1) are extremely difficult to study. The use of data generated through the drop tower technique for implementation in constitutive equations or numerical models has not been considered in past studies. In this study, an experiment including a quasi-static compression test and drop impact tests with a high speed camera was conducted. An inverse analysis technique combined with a finite element model for material parameter identification was developed to determine the stress–strain behavior of foam at different specific strain rates. It was used in this study to simulate multiple loading and unloading cycles on foam specimens, and the results were compared with experimental measurements.

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