基于声音信号的汽车安全带卷收器质量检测方法研究

为提高汽车安全带生产现场质量检测效率,根据《QC/T987—2014汽车安全带卷收器性能要求和试验方法》搭建实验平台,采集卷收器合格品与次品工作过程中的声音信号,将卷积注意力模块(CBAM)嵌入残差网络(ResNet-18)残差块之前,设计CBAM-ResNet-18“Before Blocks”模型,对采集到的卷收器声音信号进行分类。与不加注意力机制的ResNet-18模型、在残差块后加注意力机制的CBAM-ResNet-18“Within Blocks”模型、传统分类模型支持向量机和随机森林相比,模型在卷收器声音信号分类任务中的混淆矩阵、准确率、精确率、召回率和F 1值等方面均表现良好。实验结果表明:所设计的模型对于基于声音信号的汽车安全带卷收器质量检测十分有效。

求解多目标柔性作业车间调度问题的两层遗传算法

多目标柔性作业车间调度是复杂加工系统中一类重要的调度问题。针对大多数算法求解多目标柔性作业车间调度问题所存在的稳定性差、搜索深度不够、无法对多目标中单一目标进行深入搜索的问题,对传统遗传算法作出改进,设计了一套新的交叉策略,并舍去选择算子,在此基础上提出了一种求解多目标问题的双层遗传算法。引入了信息熵的概念对所提算法优化后的种群进行了分析,并从最大完工时间、最大机器负载、机器总负载三个方面对经典案例进行测试。与其他同类算法相比,该双层遗传算法共获得了31个可支配其他算法所求解的非支配解,和96个新的支配解。实验结果表明,所提算法在保留种群多样性的同时,仍拥有较好的深度搜索能力和跳出局部最优的能力,体现了算法的可靠性。

304不锈钢TIG焊接工艺及数值模拟

采用TIG焊对304不锈钢进行平板焊接试验,并从微观组织、力学性能方面对试验结果进行分析,选出最佳工艺参数为:焊接电流310 A、焊接速度13 mm/s。通过金相组织表征、X射线荧光衍射和电子背散射衍射等分析方法得出焊接接头的焊缝组织奥氏体和铁素体组成。采用大型通用有限元模拟软件Abaqus,选用双椭球热源模型对TIG焊接过程进行模拟。将模拟获得的焊缝截面形貌与试验获得的焊缝截面形貌进行对比,并根据对比结果优化模拟模型,为实现工艺参数优化提供参考。

融合Powell搜索法的遗传算法求解柔性车间调度问题

针对柔性车间调度问题,提出一种融合Powell搜索法的(改进)遗传算法(GA-Powell)。该算法分别以最大完工时间、机器总载荷和最大机器载荷为优化目标。考虑到柔性车间调度遗传算法中染色体编码方案的特殊性,对传统的Powell搜索法进行改进,以免在进化过程中产生不可行解。利用文献中的测试实例和Brandimarte测试实例测试GAPowell,验证了GA-Powell的可行性和有效性。

外加辅助条件搅拌摩擦焊技术研究进展

搅拌摩擦焊(FSW)是一种应用广泛的固相连接技术,但仍存在部分材料焊接难度较大、接头晶粒较粗、异种材料FSW接头内金属间化合物(IMC)难以调控和接头力学性能有待进一步提高等问题,严重阻碍了FSW技术的发展。在传统FSW基础上添加辅助条件能有效克服传统FSW的不足,提高FSW接头的质量。传统FSW过程产热量有限,导致部分材料在焊接时搅拌头磨损严重且轴向力大,焊接效率低,甚至无法进行有效焊接。在焊接前添加预热措施或焊接时加入超声波辅助,可增加焊接材料的软化程度,有效降低焊接过程中搅拌头的磨损,减小焊接时的轴向力,提升焊接效率。针对传统FSW接头晶粒粗大的问题,利用超声波的机械振动作用破碎接头中已形成的再结晶晶粒,同时超声波提供的能量能够增大接头内位错密度,有效地抑制晶粒粗化;外加冷却辅助能够迅速带走焊接过程中产生的热量,使接头快速冷却,缩短晶粒生长时间,抑制晶粒长大。对于异种材料FSW,接头内生成的IMC大部分为脆硬相,是接头断裂的裂纹源和裂纹扩展路径,添加超声波辅助将已形成的IMC破碎并抑制IMC生成;外加冷却方式提高了接头的冷却速率,抑制IMC生长。为了进一步拓展FSW的应用领域,在传统FSW基础上添加了焊前预热、超声波和冷却条件等辅助手段,这对提高接头性能有一定作用,外加辅助条件能软化焊接材料,减小材料流动阻力,改善材料的流动性,避免焊缝缺陷的产生,获得良好的连接界面,有效地提升接头性能。本文从外加辅助条件的有益效果角度对外加辅助条件FSW技术进行了总结,综述了不同辅助条件下FSW在焊接过程、晶粒细化、IMC控制和性能提升方面的国内外最新研究进展,分析了不同辅助方式起到有益效果的基本原理,以期为FSW技术的研究者提供参考。

基于纳秒激光加工技术的表面织构工艺参数研究

研究了脉冲激光输出功率、扫描间距和扫描速度对材料表面性能的影响,使用扫描电子显微镜、表面能测量仪对材料表面形貌、润湿性及表面能进行测量表征。结果表明,在一定范围内,激光功率对材料的性能影响较大,但由于等离子屏蔽效应影响,高功率范围内材料性能随输出功率变化不大。扫描间距和扫描速度对材料的影响效果相似,过低的扫描间距和扫描速度会抑制表面织构的效果,影响表面润湿性和表面能,同时会诱发大量微裂纹;过高的扫描间距和速度会降低织构密度,减小材料的表面润湿性能。

铝合金盒体的搅拌摩擦焊封装

对航空电子元件盒的搅拌摩擦连接封装技术展开应用研究。使用改造后的4轴搅拌摩擦焊接机床成功实现了大倾角下的盒盖、盒身的矩形轨迹封装焊接。各试验组焊缝均表面形貌良好,无宏观缺陷,且满足现有气密性标准。各组盒体的高度最大变形量范围为1.47~2.53 mm;随着焊接速度的增加,盒体的最大高度变形量呈单调减小规律;随着搅拌头旋转速度的升高,最大高度变形量呈现先减小,后增大的规律。焊接热输入较小的两组盒体耐压极限较低,其内部气压达到0.5~0.6 MPa时,封装轨迹的第一拐角后出现了撕裂状开口。开口截面位置位于搅拌针后退侧侧面。在焊接热输入,转角焊缝轨迹,搅拌针形状等因素影响下,焊接封装接头上会存在微小的孔洞、隧道等缺陷。这些缺陷在应力加压情况下的扩张、发展是泄漏的成因。

非严格递增作业速度的斗链装配线自平衡特性

为解决标准斗链模型中约束条件"员工作业速度严格递增排列"在实际生产中难以实现的问题,释放标准斗链模型的约束条件,对作业速度非严格递增的斗链装配线进行了建模分析及数值仿真研究;分析了其平衡点特性及向自平衡状态收敛的能力,提出非严格递增作业速度斗链装配线的平衡点存在定理;在此基础上给出同质员工斗链装配线的运行规则,并通过对生产实例的Witness仿真验证了其有效性。

改进Faster R-CNN网络的航拍小目标检测研究

针对航拍图像中目标尺度变化大和小目标难以检测的问题,基于Faster R-CNN算法提出一种多尺度航拍目标检测算法网络MS-R-CNN。MS-R-CNN选用Res2Net特征提取网络替换VGG网络,在更有效提取特征的同时降低了模型参数量,改进后的特征提取网络与特征金字塔网络融合,将高分辨率、语义弱的特征和低分辨率、语义强的特征相结合,提高对小目标的检测精度。通过分析数据集并调整锚框的大小及数量,使网络适应多尺度目标的检测。通过测试数据集进行分析实验,结果表明,MS-R-CNN算法的平均精度达到了66.2%,较Faster R-CNN算法精度提升了16.1%。

绿色磨削加工技术研究进展

磨削液的使用在提高加工性能的同时也带来了经济、环境和健康问题。为解决磨削液的使用危害,国内外研究者提出了各种绿色磨削加工技术。在此基础上对目前先进的绿色磨削技术进行整理与分析,论述了干磨削技术、微量润滑技术、液氮冷却磨削、低温冷风磨削、固体润滑技术等的基本原理与主要研究成果。

基于声发射技术的搅拌摩擦焊接工具磨损监测

为在线监测搅拌摩擦焊接过程工具磨损状态,本文基于虚拟仪器技术设计了一套声发射在线监测系统,结合声发射传感器、数据采集卡及信号调理器实现了对搅拌摩擦焊接加工过程中声发射信号的采集。实验中采用带有螺纹的搅拌针工具来焊接7075铝合金,并利用自主开发的在线监测系统采集焊接过程中的声发射信号。然后对采集到的声发射信号进行小波包分解处理,计算分解后各频段能量所占百分比,并提取能量分布规律作为信号特征。研究表明:搅拌摩擦焊接工具在不同磨损情况下具有不同的声发射信号特征,小波包分解处理表明搅拌头磨损轻微时,低频段能量占比较高;相反,搅拌头磨损严重时,低频段能量占比较低。

基于多传感器技术的搅拌摩擦焊在线监测系统开发

搅拌摩擦焊连接是一个涉及多物理场的耦合过程,很有必要对这一过程中温度信号、声发射信号、振动信号进行采集与研究。详细地介绍了基于Lab VIEW虚拟仪器技术的搅拌摩擦焊在线监测系统的设计与开发。主要硬件有研华PCI-1714数据采集卡、红外线温度传感器、声发射传感器、加速度传感器及其相应的信号调理与放大电路。系统可实现多种信号数据的采集、数据处理、实时显示和数据保存,并且通过7022铝合金焊接实验验证了所开发系统的可靠性与精确度,为构建焊接加工预判系统提供了实验依据。

6061铝合金盒体的搅拌摩擦封装温度场研究

为明确航空电子元件盒搅拌摩擦封装过程中的温度场分布,建立了相应的温度数值模型,并在此基础上研究了不同加工参数下温度场的变化规律。结果表明:盒体上整体温度存在累积效果,焊缝峰值温度随时间增加;搅拌摩擦封装热影响区和作用范围远小于激光焊接,峰值温度更低;相比搅拌摩擦平板对接,盒体封装热源不对称性更加明显、侧壁前进侧温度更高、变化梯度更小。

Numerical Calculation and Experimental Research on Residual Stresses in Precipitation-hardening Layer of NAK80 Steel for Shot Peening

Shot peening can improve fatigue strength of materials by creating compressive residual stress field in their surface layers,and offers a protection against crack initiation and propagation,corrosion,etc.And fatigue fracture and stress corrosion cracking of NAK80 steel parts are improved effectively.Currently there lacks in-depth research in which the beneficial effect of the residual stress may be offset by the surface damage associated with shot peening,especially in terms of the research on the effective control of shot peening intensity.In order to obtain the surface residual stress field of NAK80 steel after shot peening,the samples are shot peened by pneumatic shot peening machine with different rules.The residual stress in the precipitation-hardening layer of NAK80 steel is measured before and after a shot peening treatment by X-ray diffraction method.In order to obtain true residual stress field,integral compensation method is used to correct results.By setting up analytical model of the residual stress in the process of shot peening,the surface residual stress is calculated after shot peening,and mentioning the reason of errors occurred between calculated and experimental residual stresses,which is mainly caused by the measurement error of the shoot arc height.At the same time,micro hardness,microstructure and roughness in the precipitation-hardening layer of NAK80 steel before and after shot peening were measured and surveyed in order to obtain the relation between shot peening strength and surface quality in the precipitation-hardening layer.The results show that the surface quality of NAK80 steel is significantly improved by shot peening process.The over peening effect is produced when the shot peening intensity is too high,it is disadvantageous to improve sample＇s surface integrity,and leading to reduce the fatigue life.When arc high value of optimal shot peening is 0.40 mm,the surface quality is the best,and the depth of residual stress in the precipitation-hardening layer reaches to about 450 μm.Numerical calculation is very useful to define the process parameters when a specific residual stress profile is intended,either to quantify the benefits on a specific property like fatigue life or to help on modeling a forming process like shot peen forming.In particular,the proposed parameter optimization in the progress of shot peening and effective control of the surface texture provide new rules for the quantitative evaluations of shot peening surface modification of NAK80 steel.

Microstructure and Oxidation Behaviors of Nano-particles Strengthened NiCoCrAlY Cladded Coatings on Superalloys

Nano-particles which can largely improve the microstructure and oxidation resistance of materials are often used as a strengthening component in metal matrix composites. However, few studies were reported on its application in the bond coat of duplex structure thermal barrier coating（TBC）. Three kinds of NiCoCrAlY coatings strengthened by different nano-particles with the same addition （1%, mass fraction） were prepared by the laser cladding technique on Ni-based superalloy substrates, aiming to study the effects of the nano-particles on microstructure and oxidation resistance of NiCoCrAlY coatings （the bond coat of the duplex structure thermal barrier coatings）. Scanning electron microscope （SEM）, X-ray diffractometer（XRD） and thermogravimetry were employed to investigate their morphologies, phases and cyclic oxidation behaviors in atmosphere at 1 050℃, compared with the coating without nano-particles. With the addition of nano-particles, the growth pattern of the grains at the interface changed from epitaxial growth to non-epitaxial growth or part-epitaxial growth; slender dendrites were broken and cellularized; cracks and pores were restrained; and the oxidation weight-gain and the stripping resistance of the oxide scale were improved as well. Among the three kinds of nano-particles, the SiC nano-particles showed the most improvement on microstructure, while the CeO2 nano-particles were insufficient, but its effects on the oxidation resistance are the same as those of the SiC nano-particles. Based on the discussions of the influence mechanism, it is believed that CeO2 nano-particles would show better improvement than SiC nano-particles if the proper amount is added and the proper preparation technique of micro-nanometer composite powders is adopted, with the synergistic action of nanometer effect and reactive element effect.

New Iron-based SiC Spherical Composite Magnetic Abrasive for Magnetic Abrasive Finishing

SiC magnetic abrasive is used to polish surfaces of precise, complex parts which are hard, brittle and highly corrosion-resistant in magnetic abrasive finishing（MAF）. Various techniques are employed to produce this magnetic abrasive, but few can meet production demands because they are usually time-consuming, complex with high cost, and the magnetic abrasives made by these techniques have irregular shape and low bonding strength that result in low processing efficiency and shorter service life. Therefore, an attempt is made by combining gas atomization and rapid solidification to fabricate a new iron-based SiC spherical composite magnetic abrasive. The experimental system to prepare this new magnetic abrasive is constructed according to the characteristics of gas atomization and rapid solidification process and the performance requirements of magnetic abrasive. The new iron-based SiC spherical composite magnetic abrasive is prepared successfully when the machining parameters and the composition proportion of the raw materials are controlled properly. Its morphology, microstructure, phase composition are characterized by scanning electron microscope（SEM） and X-ray diffraction（XRD） analysis. The MAF tests on plate of mold steel S136 are carried out without grinding lubricant to assess the finishing performance and service life of this new SiC magnetic abrasive. The surface roughness（Ra） of the plate worked is rapidly reduced to 0.051 μm from an initial value of 0.372 μm within 5 min. The MAF test is carried on to find that the service life of this new SiC magnetic abrasive reaches to 155 min. The results indicate that this process presented is feasible to prepare the new SiC magnetic abrasive; and compared with previous magnetic abrasives, the new SiC spherical composite magnetic abrasive has excellent finishing performance, high processing efficiency and longer service life. The presented method to fabricate magnetic abrasive through gas atomization and rapid solidification presented can significantly improve the finishing performance and service life of magnetic abrasive, and provide a more practical approach for large-scale industrial production of magnetic abrasive.

Numerical Analysis of Nd:YAG Pulsed Laser Polishing CVD Self-standing Diamond Film

Chemical vapor deposited （CVD） diamond film has broad application foreground in high-tech fields. But polycrystalline CVD self-standing diamond thick film has rough surface and non-uniform thickness that adversely affect its extensive applications. Laser polishing is a useful method to smooth self-standing diamond film. At present, attentions have been focused on experimental research on laser polishing, but the revealing of theoretical model and the forecast of polishing process are vacant. The paper presents a finite element model to simulate and analyze the mechanism of laser polishing diamond based on laser thermal conduction theory. The experimental investigation is also carried out on Nd：YAG pulsed laser smoothing diamond thick film. The simulation results have good accordance with the results of experimental results. The temperature and thermal stress fields are investigated at different incidence angles and parameters of Nd：YAG pulsed laser. The pyramidal-like roughness of diamond thick film leads to the non-homogeneous temperature fields. The temperature at the peak of diamond film is much higher than that in the valley, which leads to the smoothing of diamond thick film. The effect of laser parameters on the surface roughness and thickness of graphite transition layer is also carried out. The results show that high power density laser makes the diamond surface rapid heating, evaporation and sublimation after its graphitization. It is also found that the good polish quality of diamond thick film can be obtained by a combination of large incident angle, moderate laser pulsed energy, large repetition rate and moderate laser pulse width. The results obtained here provide the theoretical basis for laser polishing diamond film with high efficiency and high quality.

基于有限元分析的二维振动法应力释放装置设计

基于对二维振动系统的仿真分析研制了一种二维振动时效装置,通过振动特性检测验证了装置的可行性,并进行了二维振动法释放冷挤压孔周边应力实验。利用X射线衍射仪测量处理前后冷挤压孔周边的残余应力,通过对比发现二维振动法处理后孔边5 mm范围内应力平均消除率达到22.6%,最高可达32.2%;分析实验数据得出相位差是影响二维振动时效处理效果的最关键因素,其次是工件转速、激振时间、激振电压等。

梯形螺纹振动辅助冷挤压工艺参数影响分析

为深入研究梯形螺纹振动辅助冷挤压机床的加工过程,延长挤压丝锥寿命以及提高梯形内螺纹质量,本文建立了一套基于虚拟仪器的专用在线监测系统。研究了不同挤压工艺参数下加工过程中的振动、声发射、扭矩以及温度信号,并通过对信号的分析处理,揭示了不同工艺参数与加工过程信号之间的内在联系。研究结果表明,随着主轴转速和润滑油黏度系数的提高,振动、声发射信号的均方根值不断提高,振动、声发射信号频率由低频向高频移动,扭矩和温度也不断提高。激振频率的最优值在18 Hz左右。

Modeling and Validation of Indentation Depth of Abrasive Grain into Lithium Niobate Wafer by Fixed-Abrasive Lapping

The prediction of indentation depth of abrasive grain in hydrophilic fixed-abrasive(FA)lapping is crucial for controlling material removal rate and surface quality of the work-piece being machined.By applying the theory of contact mechanics,a theoretical model of the indentation depth of abrasive grain was developed and the relationships between indentation depth and properties of contact pairs and abrasive back-off were studied.Also,the average surface roughness(Ra)of lapped wafer was approximately calculated according to the obtained indentation depth.To verify the rationality of the proposed model,a series of lapping experiments on lithium niobate(LN)wafers were carried out,whose average surface roughness Ra was measured by atomic force microscope(AFM).The experimental results were coincided with the theoretical predictions,verifying the rationality of the proposed model.It is concluded that the indentation depth of the fixed abrasive was primarily affected by the applied load,wafer micro hardness and pad Young′s modulus and so on.Moreover,the larger the applied load,the more significant the back-off of the abrasive grain.The model established in this paper is helpful to the design of FA pad and its machining parameters,and the prediction of Ra as well.