For brick-concrete buildings which are easily damaged by mining activities, this study conducted measurements using a terrestrial laser scanning and adopted the wall length as a deformation monitoring index. First, the point cloud data of the individual walls are extracted by segmenting the building-point cloud data and redistributing the wall-point cloud data. Second, after individual walls were rotated, the boundary points of all the wall-point clouds were estimated. Third, based on boundary points, the top boundary lines are fitted using the weighted iterative least squares method by applying the constraint that two adjacent (top) boundary lines intersect at a common point. Fourth, multiple regions of interest were constructed by performing downward translations on each wall, and the length of the wall was calculated at these regions. Finally, for a brick-concrete building in the coal mining area, the difference between the wall lengths of two consecutive measurements at the same interest-region was estimated to obtain the deformation information about the building. The results show that the deformation estimated using the proposed method is consistent with the actual deformation of the building as reflected by the wall fractures. The method exhibits millimeter-level accuracy in determining the wall length, with an absolute error in the range – 6 to 6 mm.
TC4 (Ti-6Al-4V) is a comprehensive metal material with excellent ductility, low density, high specific strength, and a series of advantages such as excellent toughness and weldability, so it is widely used in the aerospace industry. Due to defects such as porosity in the welding process and exposure to alternating loads, welded components of titanium alloys in the aerospace industry become the most vulnerable parts and are extremely susceptible to failure and fracture. In this paper, a single-sided sequential laser impact strengthening process is used to treating the laser welds of TC4 titanium alloy cold rolled parts to investigating the tensile properties of the laser welded welds before and after the process. By observing the tensile fracture by SEM, measuring the microhardness by Vickers hardness tester, and measuring the physical phase by XRD diffractometer, the results of these data were combined to analyze the strengthening mechanism of this laser shock peening process on the laser welds of TC4 titanium alloy. The experimental results show that after the surface strengthening process, the tensile strength and surface hardness of TC4 laser welds are improved compared with those before 1the treatment. The analysis shows that the high residual compressive stress layer and grain refinement caused by laser shock peening are the reasons for the improvement of mechanical properties of materials.
为提高锂电池温度在线监测能力,通过双路解调方案构建分布式拉曼光纤温度测试系统,采用外部触发方式,实现相互协调的工作状态.温度测试结果表明,常温状态下系统各通道距离10 m范围的温度精度达到±1℃.经过8次测试后温度值误差均在0.17℃内,表明系统常温条件下可以保持良好的稳定性,满足设计条件.该系统能够满足锂电池的测温要求,能够对锂电池局部温度异常情况进行准确反馈,有效预防锂电池各类事故.10 m传感距离内行程误差最大值只有2 m,符合锂电池测温要求.模拟试验测试结果表明,该系统能够对故障进行准确辨别与定位,表明系统具备优异的分布式测试性能.DTS系统可以达到±1 m的分辨能力,可以快速响应锂电池故障引起的温度变化.
激光冲击成形是利用激光冲击波和凹模的限制作用实现膜材微纳结构制备的有效方法,近20年来得到学术界的广泛关注.目前广泛使用的激光冲击成形工艺中,激光光斑跨越数个微结构特征并且所使用的激光重复频率小于1000 Hz,这一方面使激光束所覆盖的各个结构受到的冲击波作用不均匀,另一方面低重复频率激光限制了激光冲击成形速度.为此,提出高脉冲重复频率小光斑激光扫描冲击渐进成形工艺用于微结构成形制造.采用脉冲重复频率为40 kHz、光斑直径为50pm的高脉冲重复频率小光斑激光冲击成形宽度为200 μm、长度为6 mm的微槽结构,分析成形微结构的高度和微结构的截面形状随激光扫描范围的波动情况.结果表明,在激光扫描范围变动的情况下,成形微结构的高度较为稳定;在微结构的起始阶段和终止阶段,成形微结构的高度具有一定的过渡范围,终止阶段的过渡长度远大于起始阶段的过渡长度;所成形的微结构截面能够采用圆弧进行拟合.
中频波前均方根(PSD1)是用来评价光学元件中频段波前质量的关键参数,在对其进行数值计算之前,需要对波前数据进行频率域滤波.滤波后的数据易导致待测区域内、外的数据截断,引入较大的边缘高频误差与吉布斯噪声,从而严重影响了计算准确度.为了减小数据截断带来的影响,通过对边缘截断的数据做趋优填充,减少截断区域内外的空间频率突变.通过对现有的空域预处理方法进行对比,提出了一种四向扩展平均算法.经试验验证,所提出的方法可以较好地还原光学元件的中频段面形,显著提高PSD1测量准确度,试验表明所提出的方法较标准值的误差平均值小于5％.
