共查询到14条相似文献,搜索用时 187 毫秒
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在假设无限小波叠加在各向同性变形弹性体基础上,推导了超声波法应力测量的理论基础声弹性方程,特殊条件下简化出临界折射纵波声弹性方程.建立了超声波法焊接残余应力测量系统,选用对应力敏感的临界折射纵波作为测量波形,对20 mm厚X坡口双丝焊对接2219铝合金平板纵向残余应力场梯度进行了测量,获取了纵向残余应力场引起的声时差信号分布,用MARC软件计算了铝合金残余应力场纵向应力的分布,与声时差信号的趋势进行了对比,趋势符合.为超声波法重建焊接残余应力场作了准备. 相似文献
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基于临界折射纵波声弹性理论对激光熔覆层应力的评价方法进行研究.结果表明,激光熔覆层各向异性组织及层间界面是导致其临界折射纵波信号信噪比低、波形畸变程度大的主要因素,弹性极限内随应力的增大,临界折射纵波信号间时间差基本呈线性规律增大,当应力达到658 MPa时,再随应力的增大,时间差呈跳跃趋势变化,激光熔覆层各向异性组织引起的熔覆层不均匀塑性变形是导致上述结果的主要因素,且随应力的增大该影响程度亦逐渐增大.应力验证结果最大相对误差为4.5%,因而认为采用临界折射纵波法可实现激光熔覆层应力的无损评价. 相似文献
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高速列车车体采用铝合金焊接结构,高速列车起动快和制动,交会对接和出入隧道,车体承受应力复杂,车体残余应力分布迫切需要关注.基于声弹性效应,超声波可以无损检测出结构内部应力.开发了超声波法焊接残余应力测量系统,克服了传统应力测量方法费时耗力、破坏、体积庞大等缺点.对高速列车车体侧墙部位的焊接残余应力进行了实时快速无损测量,为服役状态下高速列车车体结构安全评估和疲劳寿命预测奠定了基础.提出了焊接结构安全评定虚拟样机的工程应用设想. 相似文献
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利用有限元法对5A06铝合金薄板拉伸过程进行数值模拟,以模拟结果为依据设计平面双向应力加载试件。基于声弹性理论,在单、双向加载的条件下,采用临界折射纵波法(LCR)对铝合金薄板进行单、双向应力检测试验研究,得到平面应力下单向和双向应力曲线。对比分析单向加载条件和双向加载条件下的应力曲线及应力系数,结果说明:LCR波在试件中的传播声时是由平行与垂直方向的应力共同决定的,垂直方向应力的作用约为平行方向应力的33%,垂直方向的应力对应力系数的影响不可忽略。 相似文献
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Ultrasonic travel times obtained with the LcR wave are able to distinguish between stress relieved and non-stress relieved 13 mm (1/2 in) thick, steel plates. Two 1.22 m (48 in) square plates were patch welded in the centre to create a residual stress field, and one of the plates was stress relieved. The LcR ultrasonic technique sends a critically refracted longitudinal wave travelling beneath the plate surface, and the stresses in the plate affect the travel times through the acoustoelastic relationship. The LCR travel-time measurements not only distinguished between residual stress states in the plate, but also gave some information on their distribution and magnitude. Neither texture nor localized residual stresses affect the results. These findings demonstrate the potential usefulness of the technique for evaluating the state of post-weld heat treatment in structural steels. 相似文献
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Qimeng Zhu Jia Chen Guoqing Gou Hui Chen Peng Li W. Gao 《Journal of Materials Engineering and Performance》2016,25(10):4181-4189
Residual stress measurement and control are highly important for the safety of structures of high-speed trains, which is critical for the structure design. The longitudinal critically refracted wave technology is the most widely used method in measuring residual stress with ultrasonic method, but its accuracy is strongly related to the test parameters, namely the flight time at the free-stress condition (t 0), stress coefficient (K), and initial stress (σ0) of the measured materials. The difference of microstructure in the weld zone, heat affected zone, and base metal (BM) results in the divergence of experimental parameters. However, the majority of researchers use the BM parameters to determine the residual stress in other zones and ignore the initial stress (σ0) in calibration samples. Therefore, the measured residual stress in different zones is often high in errors and may result in the miscalculation of the safe design of important structures. A serious problem in the ultrasonic estimation of residual stresses requires separation between the microstructure and the acoustoelastic effects. In this paper, the effects of initial stress and microstructure on stress coefficient K and flight time t 0 at free-stress conditions have been studied. The residual stress with or without different corrections was investigated. The results indicated that the residual stresses obtained with correction are more accurate for structure design. 相似文献