Papers by Keyword: Dynamic Deformation

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Authors: L.A. Merzhievsky
Abstract: The main types (groups) of models of deformation and the fracture, used for the solution of problems of dynamic and shock wave deformation of materials, are considered. All models are divided into three main groups: macroscopic (models of mechanics of continuous medium), microstructural (based on the description of evolutions of ensemble of defects ) and atomistic (are used in calculations by methods of molecular dynamics and quantum mechanics). The short characteristic of models of the listed groups is given. Some approaches to development of the most perspective multilevel models are described. The simple test for applicability of models for the description of shock and wave processes are offered. Approaches to the description of destruction of materials and used at this criterion are considered. The perspective directions of development of models of dynamic deformation and fracture are suggested.
101
Authors: Han Liu, Peng Wan Chen, Bao Qiao Guo, Shao Long Zhang, Hai Bo Liu, Er Feng An
Abstract: In this paper, the dynamic deformation and rupture of pre-notched thin metal plates subjected to confined blast loading were investigated. The thin copper plates with cross-shape pre-notch were clamped on the end of a confined cylinder vessel by a cover flange. An explosive charge with a mass of 4g was detonated in the vessel center to generate blast load acting on the metal plates. The images of metal plates were recorded by two high-speed cameras. The displacement and strain fields during the deformation and rupture process were measured by using 3D digital image correlation (3D DIC). The effects of pre-notches on the dynamic deformation and rupture of thin metal plates were analyzed. The microstructure of fracture surface was examined The 3D DIC technique is proven to be an effective method to conduct dynamic full-field deformation measurement.
49
Authors: Zhen Yuan Jia, Jun Zou, Xiao Hong Lu, Zong Jin Ren
Abstract: Double loop cutters arrangement can settle the contradiction between rotational inertia of the tool magazine and the dimension limitation of the cutter head effectively, and increase the store of tools. Disc type tool magazine with double loop cutters arrangement is designed and researched. The spring steel 65Mn is used to manufacture elastic cutter fixture as the holding device for its inner and outer loop tools. The dynamic deformation of elastic cutter fixture is discussed. The entire geometric movement process of elastic cutter fixture from being opened by the tool holder to accomplishing the whole action is analyzed. The effect and trend of inner stress caused by geometric deformation are studied. Furthermore, the force condition in each part of tool fixture can be calculated, thus predicting the motion stability and reliability of the elastic cutter fixture, and providing theory references for the design of elastic cutter fixture.
341
Authors: Dong Geun Lee, Yang Gon Kim, Byoung Chul Hwang, Sung Hak Lee, Nack J. Kim
Abstract: Dynamic deformation and fracture behavior of Zr-based bulk metallic glass (BMG) and BMG composite containing dendritic β phases was investigated in this study. Dynamic compressive test results indicated that both maximum compressive stress and total strain of the BMG and BMG composite decreased with increasing test temperature because shear bands could propagate rapidly as the adiabatic heating effect was added at high temperatures. Above the glass transition temperature, total strain decreased more abruptly due to crystallization of amorphous phases. Maximum compressive stress and total strain of the BMG composite were higher than those of the BMG because β phases played a role in forming multiple shear bands. The BMG composite having more excellent dynamic properties than the BMG can be more reliably applied to the structures or parts requiring dynamic properties.
629
Authors: Hai Tao Hu, Feng Zhao, Ying Gang Miao, Tao Suo, Qiong Deng, Yu Long Li
Abstract: Equal channel angular pressing (ECAP) has been widely used for grain refinement in many alloys. In this article, the major emphasis was on the effect of grain size, temperature and strain rate on dynamic behavior of ECAPed AZ31. The dynamic mechanical properties of 6 pass and 8 pass ECAPed AZ31 were tested by split hopkinson pressing bar (SHPB) at wide temperatures range. At dynamic loading conditions, the ECAPed AZ31 shows strong strain hardening properties. The strain hardening rates decrease due to more slip systems’ opening with the increase of temperature. With the grain refinement, the fine-grain size and temperature show strong effect on the strain rate sensitivity.
104
Authors: Ouk Sub Lee, Jong Won Lee, Sung Hyun Kim
Abstract: This paper presents a modified Split Hopkinson Pressure Bar (SHPB) technique to obtain compressive stress-strain data for rubber materials. An experimental technique that modifies the conventional SHPB has been developed for measuring the dynamic compressive stress-strain responses of rubber materials with low mechanical impedance and low compressive strengths. This paper introduces an all-polymeric pressure bar set-up which achieves a closer impedance match between the pressure bar and the specimen materials. In addition, a pulse shaper is utilized to lengthen the rising time of the incident wave which helps the stress equilibrium and homogeneous deformation of rubber materials. It is found that the modified technique can determine the dynamic deformation behavior of NR and NBR rubber more accurately than those from the conventional SHPB technique.
172
Authors: Ouk Sub Lee, Sung Hyun Kim, Yong Hwan Han
Abstract: This paper presents a modified Split Hopkinson Pressure Bar(SHPB) technique to obtain compressive stress-strain data for a rubber material. An experimental technique with a modified the conventional SHPB has been developed for measuring the compressive stress strain responses of materials with low mechanical impedance and low compressive strengths such as a rubber. This paper uses an aluminum pressure bar to achieve a closer impedance match between the pressure bar and the specimen materials. In addition, a pulse shaper is utilized to lengthen the rising time of the incident pulse to ensure stress equilibrium and homogeneous deformation of a rubber. It is found that the modified technique can determine the dynamic deformation behavior of rubbers under various conditions such as high strain rate and low temperature effects.
1577
Authors: Lin Chong Huang, Cui Ying Zhou, Ye Cheng, Wei Ke Li
Abstract: Four models of the tunnel bedding structure were analyzed under the impact loads of the train by simulating the infrastructure under the track. In this study, we examined the relationship between the vertical dynamic coefficient and the train velocity, and also analyzed the damage sustained by the bedding structure under the static and dynamic loads. It is suggested that the damage in the concrete bedding is detected in the longitudinal direction, immediately below the two rails, and that this damage is likely to occur not from attaining an elastic limit under static loads but more likely from damage accumulation in fatigue due to repeated loadings. It is not advisable to improve the tunnel bedding structure by simply increasing the thickness of the concrete bedding board; however, the bending resistance of the tunnel bedding structure can be enhanced by adopting compact reinforced concrete structure.
1891
Authors: Tatsuhiko Aizawa, Toshiji Mukai, H. Kanahashi, Y. Suwa
13
Authors: Y.G. Ko, Y.G. Kim, S. Namgung, Dong Hyuk Shin, Sung Hak Lee
Abstract: In this study, dynamic deformation behavior of submicrocrystalline aluminum alloy was established with respect to equal-channel angular (ECA) pressing routes such as A, B, and C. After 8-pass ECA pressings, the deformed samples, regardless of the routes applied, were consisted of ultrafine grains together with high dislocation density near the boundaries. Microstructural observation revealed that the sample deformed via route B showed more diffused diffraction pattern than those deformed via route A and C, suggesting the fact that route B was most effective for a rapid evolution in the grain boundary orientation from low-angle to high-angle characteristics. In the torsion tests, the shear stress decreased once reaching the maximum point. This maximum was the highest in the sample deformed via route B, and decreased in the order of the route C and route A. The dynamic deformation was explained based on microstructural uniformity associated with ECA pressing routes.
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