【作者】 郑黎明；

【导师】 杨慎华；

【作者基本信息】 吉林大学 ， 材料加工工程， 2012， 博士

【摘要】 与传统的连杆体与连杆盖接合面的机械加工方式相比，裂解连杆采用了可控断裂方式完成连杆体与连杆盖接合面的加工，进而简化了接合面和螺栓孔的加工工艺。它具有产品质量好、生产成本低、加工效率高、节省加工设备投资、材料利用率高等优点。对于提高发动机性能、降低汽车制造成本、提高我国汽车产品竞争力具有重要意义。因此，它极具市场竞争力和发展潜力，已成为连杆制造行业的发展方向。裂解工艺的关键技术是连杆裂解新技术的核心，而精密高效的裂解装备则是连杆裂解新技术的应用基础。目前，国内外连杆裂解加工过程中的某些关键技术仍处于探索阶段，同时我国尚无具有自主知识产权的连杆裂解加工成套装备。因此进行连杆裂解加工关键技术研究、开发精密高效的连杆裂解加工成套装备具有重要的现实意义。本文得到了国家科技攻关项目“发动机连杆裂解技术装备研究开发”和博士点基金项目“剖分类零件断裂加工力学行为与缺陷控制”等项目的联合资助。论文以研究裂解加工关键技术，开发精密高效的连杆裂解加工装备，推动连杆裂解成套设备产业化为目标，着重对以下几个方面进行了研究：1.研究了机械拉削、线切割和脉冲激光三种裂解槽加工方法，进行了三种裂解槽加工试样的拉伸试验，确定脉冲激光加工裂解槽的低载荷和低缺口敏感度因子优势，并给出了脉冲激光裂解槽的加工工艺要求。在垂直切割条件下，对连杆典型材料C70S6脉冲激光切槽过程进行了数值模拟和物理切割实验，获得了不同激光加工参数下的裂解槽模拟形貌和真实形貌，给出了裂解槽的深度、宽度、张角、曲率半径、连续性随激光加工参数的变化规律。在真实裂解槽切割条件下（带有切割角度），进行物理切割正交优化试验，完成了裂解槽深度和裂解槽宽度两个试验指标的极差分析和方差分析。以裂解槽的切割深度为依据，给出适用于轿车连杆和卡车连杆裂解槽加工的两组工艺参数。数值分析及物理实验结果表明：激光加工参数对裂解槽宏观形貌影响显著，在小的负离焦量前提下，合理匹配激光加工参数可以获得理想的裂解槽宏观形貌。在影响槽深的因素中，影响因子排序为：峰值功率＞脉冲时间＞扫描速度；在影响裂解槽宽度的参数中，影响因子排序为：脉冲时间＞峰值功率＞扫描速度；在影响张角的因素中，影响因子排序为：离焦量＞峰值功率＞脉冲时间。扫描速度和脉冲频率是影响裂解槽连续性的主要因素，而导致烧蚀现象的主要因素是峰值功率、脉冲时间和扫描速度。2.对C70S6连杆坯料进行性能测试，获得了不同加载速率下C70S6的本构关系。建立了连杆裂解数值模型，通过数值分析方法，研究了应力强度因子随加载速率的变化规律，分析了不同加载速率下的应力与应变场的分布情况，从而探索了加载速率对连杆裂解加工质量的影响规律。研究结果表明：随着加载速度的增加，应力强度因子下降。当加载速度大于87mm/s时，断裂面塑性区宽度下降趋于平缓，能够保证连杆发生低应力脆性断裂，大头孔变形量在合理范围内。3.建立了定向裂解机床的液压系统数学模型，借助液压仿真分析，研究了液压元件参数对裂解加载速度的影响规律，确定了最优的液压与元件参数。构建了定向裂解机床的机电液耦合模型，在最优的液压与元件参数下，完成了恒定控制输入条件下和位移信号反馈的控制输入条件下的联合仿真分析，获取了以上两种条件下的机床加载速度特性。搭建了定向裂解机床的加载速度和工作压力检测系统，在最优的液压与元件参数下，获取了机床加载过程与空载过程的真实加载速度和工作压力特性。机电液联合仿真表明：恒定输入条件时，机床的加载速度约为118mm/s，裂解油缸工作压力约为12MPa。位移信号反馈的控制输入时，以椭圆曲线减速最为明显，能够有效降低裂解油缸末端速度的冲击对液压系统的损害，实际机床的加载速度可参照此曲线进行控制。检测试验表明：加载过程与空载过程的加载速度和工作压力曲线相同，机床裂解工作段的真实加载速度约为110mm/s，工作压力约为12MPa，检测结果与仿真结果相近，满足裂解加工的工艺要求。4.构建了连杆裂解成套装备的虚拟样机模型，对机械系统关键机构进行了动力学分析，获得了机构的性能指标，验证了设计方案的有效性，并进行了结构优化。动力学仿真结果表明：激光头摆动机构的最优工作压力为2.5MPa，节流阀流量系数为0.2，此时摆头动作精准可靠。对上螺栓与初拧紧工位进行了结构优化，优化后能够满足自动装配螺栓的基本要求。对连杆夹钳机构进行了结构优化，完成了夹具间隙的选择，优化后能够完成A型直连杆和B型斜连杆的整体传送和分体传送任务。5.对连杆裂解成套装备的总体开发方案进行了规划，并完成了装备的初始开发工作。初始开发内容涵盖成套装备性能指标规划，基本工位拟定，机械系统结构开发和工作流程规划。首次研制了连杆裂解成套装备的物理样机，为保证装备的加工精度和工作效率，对物理样机进行了多方面的试验工作，根据试验结果完成了裂解成套装备的改进工作。试验工作表明：对激光工位进行了轴向间隙补偿后，能够有效提高伺服轴的传动精度。在最优工作参数下，激光头摆动精准、可靠。进行了22Nm拧紧实验，实测扭矩值与设定值误差小于1%。物理样机各工位能够协调工作，工作节拍为22s左右。6.针对A型连杆，利用本文开发的连杆裂解成套装备物理样机进行了裂解加工试验，确定了裂解槽加工参数、裂解工序参数和螺栓装配工艺参数，完成了三大关键工序中的重要参数检测，并研究了常见裂解缺陷的产生机理。进行了批量生产考核工作，统计了产品质量信息。裂解加工试验表明：裂解槽槽深在0.46~0.55mm范围内，槽宽在0.19~0.21mm范围内，满足裂解槽的具体要求。大头孔变形量小于0.07mm，断裂线扩展误差小于±1mm，外轮廓缺损面积小于2×1mm~2，满足裂解工序具体要求。确定终拧紧工艺参数为20Nm+95°，螺栓轴向预紧力为30380±980N，并在可塑性区域内夹紧。批量生产考核表明：连杆的一次性成品率为98.8%，总成品率为99.78%，由夹渣导致的错口缺陷占废品比例75%，说明装备的除渣能力还有待加强。更多还原

【Abstract】 Different from the machining of composition plane between rod and cap for traditionalconnecting rod, fracture splitting (FS) connecting rod adopts controllable cracking to separatethe cap from the rod, which greatly simplifies the manufacturing procedures of the compositionplane and bolt holes. It has offered a list of remarkable merits in good product quality, lowmanufacturing cost, high production efficiency and material usage rate, saving equipmentinvestment, etc. It is of great significance for enhancing engine performance, reducingautomobile production cost and boosting our country automobile competitiveness. FSconnecting rod has high competitiveness and development potential. Consequently, it will be thedevelopment trend of connecting rod manufacturing industry.The key technologies are the core of FS technology, while the complete equipment withhigh efficiency and precision is application foundation of FS technology. Until now, some keytechnologies during FS processing of connecting rod are still in the exploring stage. Meanwhile,there still isn’t complete equipment for machining FS connecting rod with intellectual propertyrights in our country. Therefore, the research on key technologies and the development ofcomplete equipment have important realistic significance. This thesis is supported by nationalscience-technology tackling project and doctoral degree fund. This thesis aims to investigate theapplication of FS technology, to develop the complete equipment with high efficiency andprecision, and to accelerate the industrialization application of connecting rod FS equipment.The major researches are summarized as follows:1. The processing methods of SN including mechanical broaching, wire cutting and pulselaser notching are investigated. The tension test with samples maded by the three methods iscarried out, and the lowest fracture load and notch sensitivity factor characteristics of pulse lasernotching are determined. At the condition of vertical cutting, the finite element (FE) simulationsand physical tests of laser notching process with typical material C70S6are achieved. Thesimulating morphology and experimental morphology of starting notch (SN) are obtained. Thechange laws of notch depth, notch width, continuity, opening angle and curvature radius of SNare investigated. At the condition with an actual cutting angle, the orthogonal tests are carriedout. Based on the experiment results, the sequence of importance of the processing parameterson SN dimension is determined. According to the requirements of notch depth for differentconnecting rod, optimum ranges of process parameters for car and truck connecting rod arepredicted.Some conclusions can be drawn from FE simulation and physical tests as follows: laserparameters show apparent influence on macro morphology of SN. At a small negativedefocusing amount, perfect macro morphology of SN can be obtained using rational laser parameters. Among the influence factors of notch depth, the sequence of importance is shown as:pulse power> pulse time> scanning speed. Among the influence factors of notch width, thesequence of importance is shown as: pulse time> pulse power> scanning speed. Among theinfluence factors of opening angle, the sequence of importance is shown as: defocusingamount> pulse power> pulse time. Scanning speed and pulse frequency are the main factors ofSN continuity. While ablation phenomena is mainly caused by pulse power, pulse width andscanning speed.2. In order to obtain the constitutive relations of C70S6steel, the material performancetests is carried out. The numerical model of con-rod fracture splitting is constructed. Based onthe numerical analysis method, the influence of loading speed on the stress relation isinvestigated, as well as the distribution of stress and strain under different loading speeds. Thus,the influence of loading speed on FS quality is studied. The numerical analysis results show thatstress intensity factors decrease with loading speed increasing. When loading speed is above87mm/s, plastic region width decreases slowly. At this time, Low-stress fracture likely occurs, andthe deformation of con-rod big end bore is within a reasonable range.3. After the mathematical model of FS circuit is constructed, some influencing factors onloading speed of FS cylinder are analyzed by using hydraulic simulations. Based on thesimulation results, the optimal hydraulic and component parameters are determined. The virtualprototype model of FS station is constructed. At the optimal hydraulic and componentparameters, the simulations with constant input and displacement feedback input are achieved,then the loading speed characteristic of FS station under the above two simulations are gained.The detection system of FS station is constructed. At the optimal hydraulic and componentparameters, the actual loading speed and working pressure characteristics of FS station aregained.Some conclusions can be drawn from the co-simulations as follows: In the simulation withthe constant input, the loading speed of FS cylinder is about118mm/s, and the working pressureis about12MPa. In the simulation with displacement feedback input, among the four designcurves, the elliptic curve input shows the most obvious deceleration characteristic during thestroke of FS cylinder, therefore the actual loading speed can be controlled referring this curve.The detecting experiment shows that the curves of load speed and working pressure duringloading process are the same as those during un-loading process. The actual loading speed of FScylinder is about110mm/s, and the actual superior vena pressure is about12MPa, which cansatisfy the basic requirements of connecting rod FS process. The trends of loading speed andworking pressure obtained by the detection system are similar to those obtained from the virtualsimulations, which illustrates that the models used in this thesis are feasible and reliable. Thesimulations can reflect the actual situation of hydraulic system approximately.4. The virtual prototype models of the equipment are constructed. The dynamic simulationsare achieved towards the mechanical system key components. Then the functionality andpracticability of the key components are gained, and the effectiveness of design plan is verified.The conclusions can be drawn from the simulations as follows: the laser cutting head asway mechanism works with stability, reliability and good cutting effect under the condition withappropriate process parameters (hydraulic pressure:2.5MPa, throttle valve’s dischargecoefficient:0.2). The initial assembling bolts station (IABS) after optimum structure cantransmit bolts from the feeding hopper into the bolt holes of connecting rods automatically. Thewhole transmission and split transmission of straight connecting rod and oblique connecting rodcan be accomplished through the straight pincer (SP) and oblique pincer (OP) after optimumstructure respectively, which illustrates that the structure design of these pincers are reasonable.5. The total design scheme of FS complete equipment is accomplished, the developingstrategy is investigated, and the initial design work is fulfilled. The basic content of initialdesign contains the planning of the equipment performance parameters, the determination ofworking stations, the structure design of mechanical system based on UG software, and theworking processes planning of the equipment. The physical prototype of the completeequipment is constructed for the first time. In order to guarantee the machining accuracy andwork efficiency of the prototype, some debugging experiments are done. Based on thedebugging results, some improvements are done, and it is expected that the product quality ofFS connecting rod and the stability of the equipment could be improved. Some conclusions canbe drawn from the debugging experiments as follows: after the compensation of backlash forlaser notching station (LNS), the transmission accuracy of servo-controlled axis has beenimproved. At the reasonable working parameters, the laser cutting head asway mechanismworks with stability and reliability. Tightening experiment at the parameter of22Nm isconducted, and the error of torque between the detection value and the set value is less than1%.The physical prototype of the complete equipment can work with coordination, and the workingtime is about22s.6. The FS processing experiment is achieved using the physical prototype towards type Acon-rod. The FS process parameters are determined, including the laser notching parameters,parameters of FS procedure and bolts assembling parameters. Then some important parametersduring the three core procedures are detected. The causes for some common defects areinvestigated, and the solving methods of the defects have been proposed. Mass production oftype A con-rod is carried out using the physical prototype, the information of product quality isobtained.Some conclusions can be drawn from the FS experiment as follows: the notch depth is inthe range of0.46~0.55mm, notch width is within the range from0.19mm to0.21mm, whichsatisfy the basic requirements of SN. The deformation value of big end bore is less than0.07mm, the extending oversize of FS line is within the range of±1mm, and the area of droppinggranule is less than2×1mm~2, which satisfy the requirements of FS procedure.20Nm+95°ischosen as the final tightening parameter, under this parameter, the axis pre-tightening force ofbolt is within the region of30380±980N, and the bolts work in the plastic range. Someconclusions can be drawn from the mass production as follows: The primary production yieldreaches98.8%, and the total quality rate reaches99.78%. Among all defects, the mismatchdefect takes75%. Mass production indicates that the complete equipment developed by this study can be competent enough to fulfill the FS processing task, but the deslagging ability of thecomplete equipment is in urgent need of strengthening.更多还原