CMAC神经网络在应力盘光学加工中的应用研究

计算机数控应力盘光学加工技术有其突出的优势，但应力盘形变却难以有效控制，是实现计算机数控应力盘光学加工中的难题。对此，本文分析了应力盘形变控制系统的特点，引入了CMAC神经网络实现应力盘形变控制的模型。提出了将CMAC神经网络应用于应力盘逆变形智能控制的创意和实现方法，以应力盘面形参数和对应的驱动器电压参数作为样本训练CMAC神经网络，将训练成功的CMAC神经网络作为控制器控制应力盘变形，取得了误差小于5％的计算机仿真结果。     

计算机数控应力盘面形研究

简要讨论了计算机控制应力盘抛光大口径高陡度非球面的基本原理,用Zernike多项式拟合的数学方法研究应力盘工作过程中的面形动态变化,对这一方法所能达到的精度进行了分析,给出了计算结果.     

微尺度CSP焊点弯振耦合应力应变分析与优化

建立了微尺度芯片尺寸封装(chip scale package, CSP)焊点三维有限元模型,对其进行了弯振复合加载应力应变仿真分析。分析了焊点材料、焊点直径、焊点高度和焊盘直径对微尺度CSP焊点弯振耦合应力应变的影响;选取焊点直径、焊点高度和焊盘直径为设计变量,设计了17组不同水平组合的焊点模型并获取了相应焊点最大弯振耦合应力,采用响应曲面法建立了焊点弯振耦合应力与焊点结构参数的回归方程,结合粒子群算法对焊点结构参数进行了优化。结果表明:焊点材料为SAC387时弯振耦合应力最大,最大弯振耦合应力应变随焊点高度和焊盘直径增大而减小、随焊点直径增大而增大;最优焊点结构参数水平组合为焊点直径0.18 mm、焊点高度0.16 mm和焊盘直径0.15 mm;优化后CSP焊点最大弯振耦合应力下降了8.49%。     

计算机控制抛光大口径高陡度非球面技术研究

报告了计算机控制应力变形抛光盘加工大口径高陡度非球面技术的发展精况,讨论了这一方法的理论基础;给出了应力变形抛光盘的数学力学原理与结构特点;研究了机床的整体机械设计与电学系统设计原则;探讨了应力变形盘与抛光磨头轴的连接方式;最后讨论了发展这项新技术的若干初步考虑。     

制造喷气式发动机渦轮盘用的钢及合金

涡轮盘是喷气式发动机上的一个非常重要的零件。因此选择涡轮盘的合适材料及其制造的工艺是特别重要的。 涡轮盘在工作中受热是不均匀的。在涡轮盘的周边(轮边)上温度达700℃而在同一时间其中心部分(轮毂)的温度约为300℃。这种温度的差别引起了附加的拉伸热应力,这种应力有时为整个应力的50％左右。     

镍基高温合金微型涡轮盘热塑性成形工艺

目的 研究GH4698微型涡轮盘热塑性成形工艺。方法 采用有限元软件Deform-3D对镍基高温合金微型涡轮盘模锻过程进行数值模拟分析,研究坯料不同高径比、不同模锻温度下涡轮盘成形的最大载荷值、等效应力、等效应变、速度场的变化规律。结果 微型涡轮盘模锻过程载荷最大值随模锻温度升高而降低,温度和高径比对涡轮盘的凸台、直榫等部位的等效应力、等效应变影响有明显的差异。在涡轮盘路径1上,随着温度的升高,等效应力逐渐降低,变形更加均匀;随着高径比的增加,变形不均匀程度增大,高径比为1时等效应力的极大值最小;温度和高径比对速度场的影响较小。结论 温度和高径比对GH4698微型涡轮盘锻造变形行为有显著的影响,选择合适的模锻工艺参数可以有效降低成形载荷,并获得使用性能较好的微型涡轮盘。     

热等静压技术制造的核主泵屏蔽电机推力盘的性能分析

采用热等静压技术制造的推力盘,其表面层硬度值高于50HRC且分布均匀,表面质量良好,表面残余应力为压应力,结合界面实现了良好的冶金结合。     

基于Simufact的割草盘控制杆焊接成形质量控制研究

目的 保证割草机割草盘控制杆焊后的装配精度和尺寸稳定性.方法 采用Simufact Welding软件对割草盘控制杆焊接过程进行模拟仿真.通过建立合适的热源模型,得到焊后变形和焊接应力分布情况.结果 椭圆板焊缝处为焊接变形最大的区域,最大总变形量为0.73 mm;焊后最大等效应力为395.59 MPa,且沿焊缝两侧向外扩展,等效应力呈递减趋势.结论 通过工装优化方案,实现了焊后残余变形控制,最大变形量由0.73 mm降低到0.41 mm,且未引起焊接残余应力的上升,但焊后残余应力仍处于较高的水平,可通过焊后退火消除残余应力.     

失调叶片盘的振动特性

本文采用了一种非常接近于真实失调叶片盘的物理模型,借子结构模态综合法建立系统的运动方程,分析了调谐及失调叶片盘的固有振动,以及它们在几种力函数及不同激振频率下的强迫振动;研究了失调分布规律对强迫振动时失调叶片盘中最大应力幅值的影响.得到的结论可能对指导实际叶片盘的装配及排振有重要的参考价值.     

微尺度CSP焊点温振耦合应力应变有限元分析

建立了微尺度芯片尺寸封装(CSP)焊点三维有限元分析模型,对模型进行了热结构耦合分析和温振耦合分析,获得了微尺度CSP焊点应力应变分布结果;对比分析了微尺度CSP焊点与常规尺寸CSP焊点的应力应变分布;分析了不同焊料、焊盘直径和焊点体积对微尺度CSP焊点应力应变的影响。结果表明:温振耦合条件下,微尺度CSP焊点内应力应大于常规尺寸CSP焊点应力应变;在SAC305、SAC387、63Sn37Pb、62Sn36Pb2Ag四种焊点材料中采用SAC387的焊点最大应力最大;焊点最大直径由105μm减小至80μm时,微尺度CSP焊点内应力应变呈现出减小的趋势;焊盘直径由80μm减小至60μm时,微尺度焊点内应力应变呈现出增大的趋势。     

Finite element analysis simulation and experimental verification of the stressed lap's deformation accuracy

The deformation accuracy of the stressed lap is crucial to the fit between the lap and mirror in the production of large aspherics with stressed lap technology. As a preliminary work, we analyze a prototype model with the assistance of finite element analysis tools and build it out based on the analysis results in order to verify the accuracy of the deformation. Test results show that both the high-order residual error and repeatability of deformation of the lap are within 1?μm rms in an 80% diameter of the lap for common deformations, faithfully meeting the accuracy requirement in the polishing process.     

Experimental and analytical investigation of fatigue and fracture behaviors for scarfed lap riveted joints with different lap angle

Fastener load-transferred experiments and fatigue tests of the scarfed lap riveted joints with different lap angle were carried out. The fracture surfaces were observed by optical microscope (OM) in this paper. Both experimental and computational studies were described and compared when possible. Based on the qualitative finite element analysis (FEA), the multi-axial fatigue life of the scarfed lap riveted joints has been predicted by Smith–Watson–Topper (SWT) method and Wang–Brown (WB) method respectively. Both of the test results and predicted results show that fatigue life of scarfed lap riveted joints is remarkably increased after introducing lap angle into the faying surface. 8 mm-thick specimens with the lap angle of 1.68 °C exhibit the best fatigue performance, and 20 mm-thick with the lap angle of 3.37 °C do in the present study. Compared with the result of WB theory, the result of SWT theory is more conservative and reliable. For structures’ reliability designs, SWT theory and WB theory are all fallibility.     

基于遗传算法的碳纤维增强树脂复合材料层合板单搭胶接结构的多目标优化

基于遗传算法对碳纤维增强树脂复合材料(CFRP)层合板单搭胶接结构进行了多目标优化,以提高其结构性能。首先,通过三维Hashin准则和三角形内聚力模型建立三维有限元模型来预测CFRP层内损伤过程、层间失效和胶层损伤过程,并通过试验验证其有效性。其次,利用拉丁超立方抽样(LHS)方法和二次多项式响应面法(RSM),基于搭接长度、胶层厚度和被胶接件宽度等胶接参数建立以拉伸强度和剪切强度为目标函数的多目标优化代理模型。最后,基于遗传算法(GA)对拉伸强度和剪切强度代理模型进行优化,得出一组Pareto解集,并基于理想解排序方法(TOPSIS)对Pareto非劣解集进行折中处理,得到最好的胶接参数设计方案。结果表明:CFRP层合板单搭胶接结构的数值模拟结果与试验结果相比具有很高的吻合度,验证了有限元方法的可靠性;CFRP层合板单搭胶接结构的拉伸强度和剪切强度与搭接长度、胶层厚度和被胶接件宽度具有显著的关联性;二次响应面代理模型结果与数值模拟结果相比误差均小于2.3%;与常规的单搭胶接结构方案进行对比,搭接拉伸强度和剪切强度分别提高了2.65%和17.24%。      

铺层顺序对预成型体搭接复合材料拉伸性能影响的仿真与验证

使用有限元理论模拟分析了几种不同铺层顺序的预成型体搭接复合材料的拉伸性能,并且使用国产碳纤维与快速固化环氧树脂制备相应的单下陷搭接试样,测试其搭接接头的拉伸性能,对有限元计算结果进行了验证。结果表明,使用有限元计算与实验方法得到的结果基本相符。有限元模拟及实验验证发现不同铺层结构的预成型体搭接复合材料有两种不同的破坏损伤模式。搭接上层板的层间剥离强度与层板本身弯曲性能共同决定了搭接接头的破坏模式及拉伸性能,两者中强度较弱的先发生破坏,导致试样失效。在预成型体搭接接头中,0°铺层越靠近搭接面,对搭接性能的影响越明显,搭接强度越高。搭接界面处纤维层之间的相对角度不同,纤维铺层刚度不同,刚度差别越大,搭接强度就越低。     

Dissimilar joining of galvanized high-strength steel to aluminum alloy in a zero-gap lap joint configuration by two-pass laser welding

A welding procedure based on using two-pass laser scans is introduced for dissimilar joining of overlapped galvanized high-strength dual-phase (DP) steel DP590 to aluminum alloy (AA) 6061 sheets. The first pass is based on a defocused laser spot that scans across the top of the two overlapped sheets and heats the zinc coating at the faying surface to be melted and partially vaporized, while the second pass is executed with a focused laser spot in order to perform the welding. Completely defect-free galvanized steel to aluminum lap joints were obtained by using this two-pass laser welding procedure. An on-line machine vision system was applied to monitor the keyhole dynamics during the laser welding process. An energy-dispersive X-ray spectroscopy (EDS) was carried out to determine the atomic percent of zinc, aluminum, and iron in the galvanized steel to aluminum lap joints. Mechanical testing and micro-hardness test were conducted to evaluate the mechanical properties of the galvanized steel to aluminum lap joints. The experimental results showed that the lap joint of galvanized steel to aluminum obtained by the two-pass laser welding approach had a higher failure value than those joints obtained when the zinc at the faying surface was mechanically removed under the same welding speed and laser power.     

预腐蚀铝合金典型螺栓单搭接件疲劳寿命研究

模拟飞机服役环境,对航空LY12 铝合金板材典型螺栓单搭接试验件做了预腐蚀试验,然后通过疲劳试验得到了未腐蚀试验件和预腐蚀后试验件的疲劳寿命。通过对试验件分解检查,分析了腐蚀对航空LY12 铝合金典型螺栓单搭接件的影响。建立了考虑腐蚀影响的基于断裂力学的沉孔螺栓搭接件疲劳寿命计算模型,对预腐蚀搭接件的疲劳寿命进行了计算和分析。结果表明:螺栓孔附近和搭接面腐蚀较表面其他部位严重,腐蚀产物的膨胀作用下产生了“枕垫效应”;计算模型得到的疲劳寿命与试验寿命吻合较好,其中模型1 最大相对误差为36.7%,模型2 的最大相对误差为25.7%。搭接件不同的腐蚀程度要选择不同的计算模型才能得出精确的结果。在分析较严重的腐蚀对搭接件疲劳寿命影响时,应考虑搭接面的多腐蚀损伤。     

单晶硅镜面超光滑表面工艺技术研究

用古典的沥青盘抛光技术,通过对超光滑抛光时所使用磨料的选取、沥青抛光盘的软硬和 厚度的合理应用、抛光温度的控制等工艺参数的优化,以f220mm内的单晶硅进行了超光滑表面抛光工艺试验。试验结果,单晶硅表面粗糙度RMS值达0.37nm,平面面形误差PV小于l/15,且加工工艺技术稳定可靠。     

航空用Al-Li合金阳极氧化对粘接性能的影响

为研究Al-Li合金不同粘接工艺对粘接性能的影响,对其进行了磷酸阳极化处理,并选用不同的胶黏剂来考察Al-Li合金粘接副的拉剪强度。结果表明,阳极化处理使Al-Li合金试片表面产生了微观粗糙的多孔膜,实现了粘接界面上良好的机械啮合。经阳极化处理后,Al-Li合金粘接性能显著提高,当粘接副采用Lord 320/322胶粘接时拉剪强度提高了49%,当粘接副采用FM94胶粘接时拉剪强度提高了167%,破坏模式多为内聚破坏。     

Quantifying Surface Deformation With the Edge of Light-Enhanced Visual Inspection

Edge of light (EOL) is a rapid enhanced visual inspection technique developed by the Institute for Aerospace Research, National Research Council Canada. One application of interest is the inspection of aircraft lap joints for pillowing deformation caused by hidden corrosion. The EOL technique provides an intuitive result, which is a representation of surface topography. However, a quantitative interpretation of the inspection results is still a challenge. In this paper, the quantification of surface deformation is investigated by using a laser-displacement sensor as a calibration tool. A procedure that implements the reconstruction of the deformed surface from EOL scanning is proposed. Experimental results obtained from a pillowing simulator and a service-retired aircraft lap joint are presented in this paper to demonstrate the effectiveness of the proposed approach.     

Effect of the structural reinforcement of composite adherends on the mechanical strength of adhesive joints

This study proposes a novel method to strengthen fiber reinforced plastic (FRP) adherends in a single lap joint (SLJ) by using Kevlar threads. The adherend reinforcement procedure consists of applying a zigzag thread in the fiber glass layers that comprise the adherend in order to subsequently manufacture the adherends using the vacuum infusion method. For this study, three single lap joint configurations were used: Adherends without Kevlar reinforcement (SLJ₁), adherends with Kevlar reinforcement with a medium step zigzag (SLJ₂) and adherends with Kevlar reinforcement with a small step zigzag (SLJ₃). Mechanical tensile tests were carried out to determine the ultimate strength and displacement of the single lap joint configurations studied. Adherends reinforced by Kevlar threads increase the strength and displacement of the single lap joint. However, the influence of the step size of zigzag threads on the adherend does not significantly influence the strength, but significantly affects the maximum displacement of the single lap joint.