排序方式: 共有16条查询结果,搜索用时 15 毫秒
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岩石直接拉伸破坏中的能量耗散及损伤特征 总被引:4,自引:3,他引:4
采用新近发展起来的拉伸式Hopkinson冲击装置(SHTB),成功地实现了对岩石试样的动态直接拉伸加载。利用圆柱形拉伸强度试样和切口圆柱拉伸断裂试样,并结合静态拉伸实验设备MTS材料试验机,进行了岩石的动态拉伸强度、动态拉伸断裂、静态拉伸强度、静态拉伸断裂共4种情况下的拉伸破坏实验,并将这4种实验条件下的拉伸破坏试样沿其纵剖面剖开,利用光学显微镜观察岩石在其纵剖面上的破坏特征。观察表明,岩石拉伸破坏所消耗的能量与岩石破坏时所形成的内部损伤有着十分密切的联系。 相似文献
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《Science & Technology of Welding & Joining》2013,18(6):486-490
AbstractWith an increase in the use of advanced high strength steels in vehicle architectures, materials joining issues have become increasingly important. Among the various joining methods, adhesive bonding is increasingly used in automobile manufacturing. Successful implementation of adhesive bonding to improve structural crashworthiness and reduce vehicle weight requires the knowledge of issues related not only to processing but also to joint performance. In this study, the impact strength of adhesive bonded high strength steel joints is evaluated with the split Hopkinson tension bar (SHTB) technique. The influences of loading speed and thickness of the steels on the shear strength of the joints were examined. Comparative quasi-static lap shear tests were also conducted on a tensile testing machine. Test results showed that strength and energy absorption of bonded steel joints increase with loading speed, and is greatly affected by the thickness of the steels. As the loading rates are increased to 1100 s–1 (i.e. 20 m s–1), bonded 0·75 mm thick DP600 steel shows a 152% increase in strength and an 83% increase in energy absorption when compared to its quasi-static values. Examination of the impact tested specimens showed the failure mode changes from coarse cohesive mode to fine cohesive mode with increasing loading speed. The results from this study will provide the information for a better understanding of impact failure mechanisms of adhesive bonded high strength steels. 相似文献
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《Journal of Adhesion Science and Technology》2013,27(2):291-304
This paper reported an experimental technique on the shear strength of adhesively bonded single lap joints subjected to impact loads by means of a split Hopkinson tensile bar. The experiments were conducted at two velocities (V = 20 m/s, 7 m/s) and testing temperatures ranging from ?40°C to 80°C. The results indicated that the shear strength of the specimen decreased with the increase of temperature and increased with the increase of velocity. The strength degradation from room temperature to high temperature was more severe than that from low temperature to room temperature. The effects of the pins, thermal stress and peel stress were also examined and found to have limited effects on the determination of the shear strength of the joints. It was concluded that the shear strength of the adhesively bonded single lap joints under impact loads can be determined by this experimental technique. 相似文献
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采用自制的Hopkinson拉杆装置,在20^-10^3s^-1应变速率范围内了近全片层组织Ti-47Al-2Mn-2Nb-0.8TiB2合金的拉伸力学性能。发现动态强度明显高于静态强度,前者与应变速度之间遵循线性关系,后者遵循半对数线性关系;室温塑性随应变速率变化而波动,变化范围不大。 相似文献
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为获得一种碳纤维二维正交平纹机织布增强树脂基复合材料准静态和动态下的层间拉伸力学性能,对垂直于碳布平面方向 ( 横向),分别利用Instron试验机和SHTB实验技术,进行了准静态拉伸和动态拉伸实验。得到了从低应变率 (10-3/s) 到较高应变率 (约3×102/s) 下的拉伸应力-应变曲线和拉伸强度。通过分析发现,拉伸破坏总是发生在相邻铺层的层间界面处,层间拉伸模量和拉伸强度都具有一定的应变率强化效应,但是层间拉伸破坏应变几乎不存在应变率效应。 相似文献
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《Science & Technology of Welding & Joining》2013,18(5):405-411
AbstractIn the development of vehicle structures, the proper selection of adhesives to bond the steels is important for safety of operation. In this study, toughened epoxy was tested for the ability to bond steels developed for low temperature use. Lap shear bonded DP600 and DP780 steel joints were prepared and tested in open air at ambient temperature and inside an environmental chamber at ?40°C respectively using a split Hopkinson tensile bar machine. The impact properties of bulk adhesive at ?40°C were also measured. It was found that the exposure of joints to a ?40°C environment had little influence on impact strength and energy absorption. Scanning electron microscopy of fracture surfaces indicates differences in fracture paths and interfacial regions for the ?40°C exposed specimens. Changes in the interphase region caused by low temperature exposure may contribute to an increased susceptibility of the adhesive joint to bond degradation. 相似文献
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采用常规拉伸和Hopkinson拉杆技术,研究具有近全片层组织形变Ti-47Al-2Mn-2Nb合金180K下静态和动态拉伸性能及其受硼的影响。发现Ti-47Al-2Mn-2Nb和Ti-47Al-2Mn-2Nb-1B合金180K下的拉伸强度均比室温度。 相似文献