共查询到20条相似文献,搜索用时 187 毫秒
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介绍采用射线方法检测功率管芯片与基座之间的焊接质量。试验证明,选用合适的透照参数可使X射线照相和X射线实时成像对焊接部位的检测均得到较高的对比灵敏度,但X射线照相法成本低廉,一次可透照多个工件,效率高,为该功率管焊接质量的理想检测方法。 相似文献
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X射线实时成象是可代替常规X射线胶片照相探伤的一项新兴的无损检测技术.概述了X射线实时成象技术在液化石油气钢瓶焊缝探伤中的应用,包括X射线实时成象检测系统的设备、检测方法和检测结果评价. 相似文献
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Stress corrosion cracking of prestressing steels During the investigation of a post-tensioned bridge structure incipient cracks of the prestressing steels of the transverse prestressed members were observed. Defects related to non-injected ducts or the presence of corrosion inducing substances could not be detected. The prestressing steel used is a quenched and tempered steel, strength class St 140/160, which was produced in the former GDR. The cause for the cracks is the susceptibility of this type of steel to hydrogen-induced stress corrosion cracking as could be shown in laboratory tests. Under unfavourable conditions cracks can be initiated before grouting. Additional magnetic particle tests at selected areas of the longitudinal prestressed members did not indicate any signs for incipient cracks. 相似文献
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对直埋电缆、光缆对地绝缘电阻及土壤环境因素进行原位连续测试,研究电缆、光缆的绝缘性能随时间变化规律,探讨土壤环境因素变化对绝缘电阻的影响.研究表明,具有PVC护套的电缆对地绝缘电阻值随土壤温度、水分的升高而降低,而且随时间推移对地绝缘电阻值逐步上升. 相似文献
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重金属污染土防渗注浆材料的力学性能 总被引:1,自引:0,他引:1
采用水泥基复合注浆材料对有色金属矿区重金属污染土进行防渗隔离处理。水泥、粉煤灰和矿渣等主要材料分别以不同组分与水玻璃混合形成3种复合注浆材料。采用倒杯法试验、无侧限抗压强度试验等方法研究不同水玻璃掺量、波美度以及粉煤灰和矿渣掺量对复合注浆材料凝胶时间和抗压强度等力学性能的影响规律。此外,采用XRD和SEM等测试方法,从材料的物相组成及微观结构方面进一步分析了复合注浆材料的力学特性。研究结果表明:凝胶时间随着水玻璃掺量和波美度的增大而延长;粉煤灰可以显著延长凝胶时间,但使用矿渣代替部分粉煤灰会使凝胶时间略有减少。当水玻璃掺量在20%以下时,复合注浆材料抗压强度随着水玻璃掺量的增加而增加,当水玻璃掺量超过20%,抗压强度显著降低;抗压强度随波美度的增加而增大;粉煤灰和矿渣可提高复合注浆材料的抗压强度。 相似文献
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The elastic prestressed ultrasonic peen forming (UPF) was adopted in order to solve problems of insufficient bending deformation and large spherical deformation of plate during free UPF. The theoretical analysis of prestressed UPF and the influence of elastic prebending moment on deformation were analyzed. Spherical deformation coefficient was defined to quantificationally describe the spherical deformation. Experiments were conducted to compare the differences between free UPF and prestressed UPF processes and the effects of processing parameters on bending curvature and spherical deformation coefficient were studied. The results show that peening trajectory in chordwise direction is beneficial to enlarging spanwise bending deformation and decreasing spherical deformation coefficient. Large prebending curvature is helpful to increase spanwise bending deformation and decrease chordwise deformation, thereby obviously decreasing spherical deformation coefficient. Large spanwise deformation can be obtained under large firing pin velocity, small plate thickness and small offset distance. Large firing pin velocity plays a positive role in decreasing spherical deformation, while plate thickness and offset distance have little effect on it. Above all, prebending curvature and peening trajectory are the most important factors during prestressed UPF process. This study provides guidance for parameters optimization of prestressed UPF for wing plate with large thickness. 相似文献
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国产桥梁缆索用热镀锌钢丝的质量及应用状况 总被引:1,自引:1,他引:1
介绍了桥梁缆索用镀锌钢丝的种类及主要质量要求,重点叙述了国产钢丝与国际标准及进口实物质量的比较,认为目前国产斜拉索用镀锌钢丝的标准水平和实物水平已进入国际先进领域,1995年全国14座斜拉桥使用国产钢丝建造。 相似文献
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为了了解脉动灌浆系统的力学特性以及压力等参数的控制特性,通过对脉动灌浆系统组成和工作原理进行分析,基于AMESim仿真平台建立了脉动灌浆系统仿真模型。为了验证模型的正确性,将施工现场监测的输浆管道压力和流量数据与仿真模型的输出数据进行比较。结果表明:该仿真模型能够较为准确地模拟系统的动态曲线变化规律,压力及流量的平均相对误差分别为6.4%、7.6%,验证了模型的正确性。根据灌浆条件的变化,通过仿真模型分析,得到了不同的泵送频率、浆液黏度、管道长度等条件下的浆液管道内压力和流量特性的变化曲线。 相似文献
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分析一种索杆混合驱动并联机构的绳索拉力和刚度。考虑绳索单向受力和直线电机双向受力的特性,对机构动平台的位姿进行力学分析,得到关于绳索拉力与直线电机推力的关系式。通过规划动平台运动轨迹,得到绳索拉力与电机推力的分布曲线。结合刚度定义、机构结构参数和柔索拉力之间的关系,推导出并联机构的刚度矩阵模型;通过MATLAB仿真得到刚度评价指标,总结刚度在机构工作空间中的分布规律。 相似文献
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Since cable members are the major structural components of cable bridges, they should be properly inspected for surface damage and inside defects such as corrosion and/or breakage of wires. This study introduces an efficient image-based damage detection system that can automatically identify damages to the cable surface through image processing techniques and pattern recognition. The damage detection algorithm combines image enhancement techniques with principal component analysis (PCA) algorithm. Images from three cameras attached to a cable climbing robot are wirelessly transmitted to a server computer located on a stationary cable support. To improve the overall quality of the images, this study utilizes an image enhancement method together with a noise removal technique. Next the input images are projected into PCA sub-space, the Mahalanobis square distance is used to determine the distances between the input images and sample patterns. The smallest distance is found to be a match for an input image. The proposed damage detection algorithm was verified through laboratory tests on three types of cables. Results of the tests showed that the proposed system could be used to detect damage to bridge cables. 相似文献