【作者】 沈文众；

【导师】 艾长胜；

【作者基本信息】 济南大学 ， 机械电子工程， 2011， 硕士

【摘要】 冷镦作为钢球加工的第一道工序,其成形缺陷是主要的质量隐患和次品源头。国内钢球冷镦设备只执行机械式的往复动作,缺乏过程监测;传统的采用专用检测器具进行过程完成后的人工检测方式,量具易磨损,检测效率低,不能及时发现生产过程中的成形缺陷和故障,检测能力成为限制钢球冷镦工艺升级的瓶颈。国外对金属压力加工在线质量的监测开展了理论研究,通过对过程信号特征的在线分析实现过程实时监测,并将成形监测仪器的应用在塑性加工行业。首先分析了钢球冷镦的成形原理,并建立冷镦运动系统的数学模型。应用塑性加工专用的有限元软件DEFORM-3D针对钢球冷镦成形过程进行了数值模拟,通过改变冷镦棒料料长和模具同轴度两个指标,对正常工况及两类钢球墩制过程中常见的缺陷(环带缺陷和球形偏差)的成形过程进行有限元数值模拟。经过后处理运算,获得成球过程中,底模(静模)载荷曲线与常见成形质量缺陷的对应关系。分析模拟结果,不同环带大小主要体现在载荷曲线的峰值和时序两个特征上;相同料长情况下,球形偏心缺陷主要体现在冷镦初始阶段的载荷动态数值上。从而,采用载荷波形信号分析钢球毛坯成形质量状况是正确可行的,提出通过采集底模载荷信号监测钢球成形质量的信息特征:时序和局部峰值。波形的采集是实现质量分析的基础。针对底模载荷信号提取的特殊环境,分析比较力传感器的特点以及对钢球冷镦设备的影响;分析压电效应的原理和应用,提出应用压电传感器采集底模载荷信号。考虑钢球冷镦机的结构、刚度要求等因素选取压电材料,设计了PVDF薄膜式压电传感器,选取合适的安装位置,计算冷镦力大小对承载能力进行校核。针对压电传感器测量电路,从理论上分析了压电传感器的等效电路,对电荷和电压式前置放大电路进行了理论分析,提出应用高阻抗输入的电压放大器AD623作为前置放大器,并通过理论校核和实验,验证了电压放大器的可行性。在分析系统的功能要求和硬件架构的基础上,建立了硬件平台。设计了核心MCU模块、A/D转换单元、人机交互界面电路、系统时钟单元、键盘模块的电路等硬件模块。根据工厂实际状况,采取硬件抗干扰措施,设计了PCB电路板。分析系统软件的总体构架,通过模块化编程和调用,成功搭建了系统的软件运行平台。编写系统初始化模块、TFT显示模块、数据采集与分析模块、人机交互模块和系统时钟读写模块,供主程序和各子程序间有序的分时调用。实现了载荷信号离散化和鉴别算法,通过人机交互模块实现参数设定,通过系统时钟读写实现了质量和加工信息的可追溯性;最终实现了成形监测系统的研发。到工业现场采集3种成形缺陷的数据,编写了载荷信号学习与鉴别算法,利用MATLAB分析处理数据,验证了冷镦成形质量监测的有效性和准确性。更多还原

【Abstract】 As the first process for steel ball processing, the forming defects of cold heading are the main sources of quality problems and defects. Because of Lacking process monitoring, the domestic cold heading equipments only executive the reciprocating mechanical movement. Its traditional detection often use the special test apparatus for manual inspection after completion of the processing, which serious wear the measuring tools and has lower detection efficiency. More importantly, the forming defects and faults in the production process could not be found by the traditional detection method. The limited detecting ability has become the bottleneck that impedes the cold upsetting to upgrade. By analyzing the theory study and application of monitoring equipment for the on-line monitoring of metal forming process, a quality monitoring methods for cold heading are proposed by on-line collecting and analyzing the load signal.The forming principle of steel ball cold heading is analyzed in this paper to establish the mathematical model of motion system of cold forging machine. The steel ball cold heading process was simulated by Using the finite element software DEFORM-3D that populated in the special plastic forming field. The forming process in the normal condition and the two common forming defect conditions (burr defects and spherical eccentric defects) are numerical simulated respectively by changing two indicators (the length of Raw materials and Concentricity of two die). After post-processing operation, the load curves of the bottom die (static die) are obtained, which correspond common quality defects of forming. Analyzing Simulation results, different burr sizes are mainly reflected in the two characteristics of load curve, which are the peak value and sequence in time. In the case of same length of the bar materials,spherical eccentric defect is mainly reflected in dynamic load value in the initial stages of cold heading Thus, the Feasibility is theoretically proved by collecting the load curve in the axial Location to analysis the forming quality of steel ball blank.Waveform acquisition is the basis of analyzing quality. Considering the special condition for extracting the load signal in bottom die, this paper contrastive analysis the characteristics of force sensors and their effects to the steel ball cold heading and the principle and application of the piezoelectric effect. The piezoelectric sensor is used to obtain load signal in bottom die. Considering the structure of steel ball cold heading machine, stiffness and other required factors, the piezoelectric material is selected and design of the PVDF piezoelectric membrane sensor is designed. After that, the appropriate installation location is selected and the cold upsetting force is calculated to check the bearing capacity of the sensor. Equivalent circuits of piezoelectric sensor and the charge amplifier and voltage pre-amplifier are analyzed theoretically, the application of the voltage amplifier AD623 with high impedance input as a pre-amplifier is proposed, which feasibility is through theory and experimental verification.Based on the analysis of system functional requirements and hardware architecture, hardware platform of the system are established. We selected the appropriate the MCU, designed A/D conversion unit, interactive interface circuit, the system clock unit, keyboard and other hardware circuit. According to the realistic condition of the factory, PCB circuit boards are designed taking the hardware anti-jamming measures.Software operating system platform is successfully established based on Analysis of the overall system software architecture and modular programming. The software modules: system initialization module, TFT display module, data acquisition and analysis module, HMI module and clock reading and writing module are programmed, which are time-ordered called by the main program and the subprograms. The load signal is scattered and the identification algorithm is achieved. System parameters are adjusted by the human-computer interaction module, the quality and processing information is traced by reading and writing the system clock to achieve, and the forming monitoring system is successfully designed.The data of three kinds forming defects are obtained in the industrial field and the learning and discrimination algorithm for the load signal are programmed. Using MATLAB, the data are analysised and the effectiveness and accuracy of the cold heading quality monitoring system are verified.更多还原