激光选区熔化成形TC4钛合金的电子束焊接气孔缺陷控制研究

激光选区熔化(SLM)增材制造技术常用于格栅、腔体结构、燃烧室组件等航空、航天、兵器领域复杂小型零件的制造.为了适应大尺寸零部件的制造,较为理想的方案是采用分段增材成形+拼焊连接的方案,针对SLM成形TC4钛合金进行了电子束焊接工艺验证研究,分析了SLM成形材料焊接气孔缺陷及其产生原因,探讨了不同焊接工艺对气孔缺陷的改...     

叉排扰流柱排列参数对旋转矩形通道对流换热特性的影响

本文用实验的方法研究了叉排扰流柱阵列的排列参数对旋转矩形通道对流换热特性的影响。实验共采用了6个模型,扰流柱的排列参数S_n/d的取值为5.0,6.5和8.0,S_p/S_n为1.2,1.6和2.0,其中d为扰流柱的直径,S_n为扰流柱横向间距,S_p为2倍的纵向间距。结果表明,在实验范围内,纵向排列参数S_p/S_n的取值介于1.2和1.6之间为好;扰流柱横向排列参数S_n/d=5,即最密时,最有利于换热,但应综合考虑其引起的流阻损失。      

带双扰流器喷雾装置的燃烧室出口温度场试验研究

本文采用装有3只小流量双径向扰流器混合杯式喷雾装置的二元矩形试验燃烧室,在常压和进口空气不加温条件下作燃烧试验,研究了不同的双扰喷雾装置对燃烧室的出口温度分布质量的影响。试验表明:正确设计的双扰喷雾装置相对于离心喷嘴将明显改善燃烧室出口温度分布质量;第一扰流器流量应小于第二扰流器流量;第二导流筒长度不应妨碍中心离心喷嘴油雾锥形成;相邻喷雾装置中气流旋向应相同。这对我国三大部件中短环形燃烧室研制有参考价值。     

Extension of continuous scanning laser Doppler vibrometry measurement for complex structures with curved surfaces

The continuous Scanning Laser Doppler Vibrometry (SLDV) developed on the base of the galvanometer scanner system has made it possible to quickly obtain the full field vibration responses within a rectangular area of the structure. In this paper, an arbitrary continuous scanning path generating method for Continuous Scanning Laser Doppler Vibometry (CSLDV) is further put forward in order to allow the CSLDV suitable for testing structures featured by complex shapes not just for regular areas. In the first step, the relationship between position of laser spot and the driving voltages of galvanometer scanner system has been described by a mathematical modeling. Then, a novel arbitrary scanning path generating strategy based on CSLDV is presented by deforming a normalization rectangular scanning path to an arbitrary continuous scanning path. The mapping relation between the normalization rectangular scanning path and arbitrary continuous scanning path is established using the reference points. In the second step, a compressor blade with curved surface was taken as an example for modal test using the proposed method. At the same time, a validated experiment was performed in SLDV. The results show the mode shapes derived from the extended CSLDV are in agreement with those from SLDV and the Modal Assurance Criterion (MAC) between the two are all greater than 0.96. They also demonstrate the feasibility and effectiveness of the proposed method for CSLDV test and show strong potential on further practical engineering applications.     

三星时差定位系统的有源校正算法

针对三星时差（TDOA）定位系统中，由星历误差和时间同步误差导致无法精确定位的问题，提出一种基于正交投影的两步迭代有源校正算法。该算法首先利用正交投影将时间同步误差从观测方程剔除，然后引入一个与辐射源位置和星历误差有关的中间变量，通过对中间变量的最优估计消除星历误差对定位精度的影响，最后利用中间变量求解出目标辐射源位置。仿真结果表明，所提算法定位性能的仿真值和理论值均可以达到克拉美-罗界（CRLB），当TDOA观测噪声较小且有3个以上参考源时，可以完全校正星历误差和时间同步误差对定位精度的影响。     

基于边缘与非边缘分开处理的印刷品缺陷检测

针对印刷品缺陷检测问题,通过对经典缺陷识别算法的研究,提出了一种边缘点与非边缘点分开处理的印刷品检测缺陷识别算法。算法以统计过程原理为出发点,根据边缘点和非边缘点不同的像素特征,对非边缘点采用统计阈值法处理,对边缘点采用邻域平均值与梯度值相结合的算法处理。该算法经过实验证明,能够有效地剔除伪疵点,提取出真正的缺陷。     

XP过程对软件缺陷影响分析

XP方法测试驱动和多版本发布的实践,决定了软件产品集成测试也是一个增量迭代的过程。用户使用测试对提高产品的可靠性有重要作用。本文探讨XP测试过程对软件缺陷的影响及其缺陷改正效率的度量。     

Comparative investigation on high-speed grinding of TiCp/Ti–6Al–4V particulate reinforced titanium matrix composites with single-layer electroplated and brazed CBN wheels

In order to develop the high-efficiency and precision machining technique of Ti Cp/Ti–6Al–4V particulate reinforced titanium matrix composites(PTMCs), high-speed grinding experiments were conducted using the single-layer electroplated cubic boron nitride(CBN) wheel and brazed CBN wheel, respectively. The comparative grinding performance was studied in terms of grinding force, grinding temperature, grinding-induced surface features and defects. The results display that the grinding forces and grinding temperature obtained with the brazed CBN wheel are always lower than those with the electroplated CBN wheel. Though the voids and microcracks are the dominant grinding-induced surface defects, the brazed CBN wheel produces less surface defects compared to the electroplated wheel according to the statistical analysis results. The maximum materials removal rate with the brazed CBN wheel is much higher than that with the electroplated one. All above indicate that the single-layer brazed CBN super-abrasive wheel is more suitable for high-speed grinding of PTMCs than the electroplated counterpart.     

矩形件排样的研究进展

从复合材料排样的需求出发,研究了矩形件排样问题.给出了矩形件排样的定义、分类，综述了国内外有关矩形件排样的各种算法，包括经典的近似算法、启发式算法及超级启发式算法和精确求解算法；并对各种算法的排样质量和效率进行比较,以期能为复合材料排样的研究提供帮助。     

LY12合金翼片等温模锻的缺陷分析

 简要叙述了大型薄腹板筋型翼片件,在5×10~4kN液压机上采用等温模锻工艺方案的可行性和等温模锻的变形温度、应变速率等工艺参数。分析了翼片等温模锻时产生穿筋、缩孔、折叠和裂纹等各种缺陷的原因。经试验确定了消除各种缺陷的实用方法,选择合理的模具结构设计和最佳的坯料外形、尺寸制备等。用CAD方法可得到较为理想的等效高度坯料和模具型槽中设计较为实用而又经济的工艺余料孔。