基于深度学习特征匹配的铸件微小缺陷自动定位方法

针对射线实时成像检测中精密铸件微小缺陷自动定位的需要,提出一种基于深度学习特征匹配的铸件缺陷三维定位方法。模拟选择注意机制的中央-周边差算法,提出以视觉显著度为尺度,从射线图像复杂背景中检测出微小缺陷及其区域,以定义的区域中央点为待匹配点;然后,提出构造深度卷积神经网络自动提取微小缺陷区域的深度学习特征,通过深度学习特征矢量的相似度,实现在不同视角下投影图像中的同一微小缺陷点的自动匹配;最后,基于平移视差测距原理计算缺陷匹配点的三维空间坐标。实验表明,基于深度学习特征匹配的方法能够正确搜索平移前后投影图像中的同一缺陷点,以此为基础,利用视差测距原理实现了微小缺陷匹配点的自动准确定位,深度定位误差小于5.52%,能够满足对精密铸件微小缺陷智能评判的需要。     

采用内模控制理论的双馈感应风机鲁棒控制器设计

针对工程中双馈感应电机转子电流控制器参数整定的问题,提出一种利用内模控制理论设计转子电流控制器的鲁棒控制方法。首先定义内模控制的灵敏度函数和互补灵敏度函数,并推导双馈感应电机转子电流控制系统传递函数,建立了转子电流内环的内模数学模型。IMC控制器的设计以平方积分误差值和鲁棒稳定M值为准则,并与传统比例积分控制器进行比较。通过对1.5 MW双馈感应电机的MATLAB/SIMULINK仿真表明,本文方法稳态跟踪精度高、动态响应快、对模型误差和外界干扰具有较好的鲁棒性。最后在11 k W的双馈风机实验平台上验证了所提方法的有效性。     

Constitutive analysis of 6013 aluminum alloy in hot plane strain compression process considering deformation heating integrated with heat transfer

Hot plane strain compression tests of 6013 aluminum alloy were conducted at temperatures ranging from 613 to 773 K and strain rates ranging from 10^-3 to 10 s^-1. A novel model is developed to describe the temperature rise considering deformation heating integrated with heat transfer in tests. The experimental flow stress data are corrected by the proposed novel model. Based on the corrected flow stress, the modified power function constitutive model is developed considering the coupled effects of deformation temperature and strain rate on flow stress. Meanwhile, another two widely used models, temperature-compensated power function and straincompensated hyperbolic sine constitutive model, are also established for the studied 6013 aluminum alloy. Finally, the three constitutive models are compared from the aspects of accuracy, stability and efficiency. It is found that the experimental flow stress is significantly affected by the temperature rise. Furthermore, the influence of heat transfer on temperature rise cannot be ignored. When the constitutive model is established, the coupled effects of deformation temperature and strain rate on flow stress should be considered. The modified power function constitutive model is the best one in describing the flow behavior among the three models.     

Characterizing the Effects of Washing by Different Detergents on the Wavelength-Scale Microstructures of Silk Samples Using Mueller Matrix Polarimetry

Silk fibers suffer from microstructural changes due to various external environmental conditions including daily washings. In this paper, we take the backscattering Mueller matrix images of silk samples for non-destructive and real-time quantitative characterization of the wavelength-scale microstructure and examination of the effects of washing by different detergents. The 2D images of the 16 Mueller matrix elements are reduced to the frequency distribution histograms (FDHs) whose central moments reveal the dominant structural features of the silk fibers. A group of new parameters are also proposed to characterize the wavelength-scale microstructural changes of the silk samples during the washing processes. Monte Carlo (MC) simulations are carried out to better understand how the Mueller matrix parameters are related to the wavelength-scale microstructure of silk fibers. The good agreement between experiments and simulations indicates that the Mueller matrix polarimetry and FDH based parameters can be used to quantitatively detect the wavelength-scale microstructural features of silk fibers. Mueller matrix polarimetry may be used as a powerful tool for non-destructive and in situ characterization of the wavelength-scale microstructures of silk based materials.     

合成丙烯酸催化剂研究进展

对用于合成丙烯酸催化剂进行分类总结,综述丙烯氧化制丙烯酸催化剂和丙烷氧化制丙烯酸催化剂研究进展。丙烯两步氧化法制丙烯酸催化剂应用广泛,催化剂主要为Mo-Bi系和Mo-V系复合氧化物。提出扩大丙烯酸下游产品领域对调节产能扩张的重要性,提高国产丙烯酸催化剂性能、增强工业应用能力、降低生产成本、减少污染物排放和开发新型丙烯酸催化剂及其生产技术是下一步的研究重点。     

超声喷丸对工业纯Zr疲劳裂纹扩展行为的影响

对厚度为2.0 mm的工业纯锆板材进行双面超声喷丸（USSP）处理,研究了超声喷丸（USSP）对微观组织演变和疲劳裂纹扩展（FCG）行为的影响。通过光学显微镜、激光共聚焦显微镜、背散射电子衍射仪、透射电子显微镜和X射线衍射仪分别对微观结构演变进行表征。采用紧凑拉伸试样进行FCG试验,对断口形貌和裂纹扩展路径进行分析。结果表明,USSP处理后形成了具有约250 μm深度残余压应力的表面梯度结构,USSP试样比原始试样表现出更高的强度和表面粗糙度。值得注意的是,USSP-8 min和USSP-12 min试样的疲劳裂纹扩展寿命比原始试样分别提高了28.1%和50.9%。USSP处理有助于提高疲劳裂纹扩展抗力,进而在一定程度上降低疲劳裂纹的扩展速率。FCG性能的提高可归因于残余压应力和晶粒细化的共同作用,残余压应力增强了裂纹闭合效应,降低了有效应力比。同时,晶粒细化使晶界比例增加,循环塑性区尺寸减小,从而有利于抵抗裂纹扩展。     

改性纳米SiO2对再生沥青胶结料性能的影响

为提高再生沥青的再生效果,文中采用RA-F0110型再生剂作为A型再生剂和OP-900型再生剂作为B型再生剂对旧沥青进行再生;采用硅烷偶联剂KH-550和KH-570对纳米SiO2进行有机化表面改性;对比不同速率、不同搅拌时间、不同静置时间下纳米再生沥青的PG高温分级温度,确定纳米再生沥青的制备方法;对比添加不同种类不同掺量再生剂后再生沥青的PG连续分级确定再生剂的种类和掺量;对比不同纳米SiO2掺量下纳米再生沥青的PG连续分级确定纳米材料的掺量。试验表明：纳米SiO2在表面改性后团聚现象减少。纳米粒子被包覆,所以纳米粒子尺寸增大导致单个粒子的比表面积明显减小,纳米SiO2在沥青中更加稳定,采用KH-550表面改性剂的效果优于KH-570。选用A型再生剂的再生沥青的再生效果优于选用B型再生剂的再生沥青。在相同再生剂掺量下,添加一定比例的纳米SiO2,纳米再生沥青PG连续分级的高低温服务范围更宽广。当纳米材料的掺量为5%,A型再生剂掺量为15%时,纳米再生沥青胶结料的性能指标达到最佳。     

微量Y(0.2 wt.%)对铸造Mg-Sn合金热变形行为影响

采用MTS-CMT5105电子万能试验机,在温度为250~400℃、初始应变速率为10_-4~10_-1s_-1,最大变形量为40%的条件下,对铸态Mg-2.5Sn(wt.%)和Mg-2.5Sn-0.2Y(wt.%)合金进行压缩变形。结合真应力-应变曲线、峰值应力、显微组织、本构方程、DMM加工图,研究了微量Y(0.2 wt.%)对铸造Mg-Sn合金热变形行为的影响。结果表明：微量Y的添加,在较低应变速率时,会使Mg-Sn合金热压缩峰值应力增加30%以上;但在较高应变速率时,却对其影响不大。会改变合金塑性变形机制的控制方式,即由扩散控制变为位错的滑移和攀移。会抑制动态再结晶。会降低功率耗散系数,扩大加工失稳区。     

松散破碎围岩锚注在返修巷道中的研究应用

通过对锚注支护机理的阐述,研究锚注支护修复巷道的可行性。结合丁集矿典型返修巷道变形与破坏形式特征,设计该返修巷道锚注支护方案,并完成了现场监测分析与评价。实践表明,该技术是解决深井高应力软岩返修巷道支护的有效途径,具有较高的推广应用价值。