【作者】 刘广兴；

【导师】 李大勇；

【作者基本信息】 哈尔滨理工大学 ， 材料加工工程， 2008， 硕士

【摘要】 近年来,随着冶金、航空、造船、建筑等工业的发展,对一些受力复杂、工作条件苛刻的构件和零件提出了越来越高的要求。为保证产品质量、降低生产成本和确保工程安全,对落砂铸件进行缺陷在线检测具有非常重要的实际意义。本文基于音频检测原理构建了可实现铸件缺陷快速检测的音频检测系统。介绍了音频检测铸件缺陷的原理,对铸件缺陷与音频能量衰减和音频共振频率的关系进行了详细评述,在音频信号中提取共振频率与内耗作为铸件缺陷识别的主要参数。该系统具有测试装置简单、测试速度快和准确度高等特点。音频检测系统主要由脉冲激励装置、音频传感器、信号调理电路、数据采集卡和微型计算机等部分组成。采用具有固定势能的硬质小钢球向被测铸件提供脉冲激励,选用驻极体传声器作为音频传感器,利用计算机声卡作为音频信号的采集硬件。通过MATLAB提供的数据采集工具箱(Data Acquisition Tool)进行信号采集,并将音频信号数据存储到计算机中,利用信号处理工具箱对采集到的音频信号进行包括消除信号趋势项、平滑处理、数字滤波等处理,最终提取音频信号的特征参数,实现对铸件缺陷的快速识别。初步实验结果证明,本文设计的音频检测系统可用于铸件缺陷无损检测,具有方法简单、硬件成本低、识别准确等优点。更多还原

【Abstract】 In recent years, with the development of metallurgy, aviation, shipbuilding, architecture and other industries, higher requirements for components and spares which worked under complex loading conditions have arisen. To ensure the product quality, reduce the costs and guarantee the engineering safety, it has very important practical significance to online monitor the defects of castings.According to the resonant acoustic principle, a nondestructive inspection system of fast detecting the casting defects is constructed in this paper. On the basis of introducing the principle of the detecting the casting defects, the relations between acoustical energy attenuation, acoustic resonance frequency and the casting defects are described in detail, and thus resonant frequency and internal friction values of castings from acoustic signal are taken as the main parameters of identifiying the casting defects. The system has the merits of simple measurement device, fast measurement speed and high accuracy.The audio frequency inspection system is mainly composed of the impulse excitation device, acoustic sensor, signal conditioning circuits, data acquisition card and micro-computer and so on. Small hard steel spheres with fixed gravity potential energy are used as impulse exciter, the electrets condenser microphone is used as acoustic sensor, and computer sound card is used as the acoustic signal acquisition hardware. The data of acoustic signal are collected by the Data Acquisition Toolbox of Matlab, and the results are automatically stored by computer. After eliminating signal trend, smoothing signal curves and digital filter, characteristic parameters are got and thus the defects of the castings are fast indentified.The preliminary experimental results show the audio frequency inspection system can be used to nondestructive detect of the casting defects and the system has the advantages of simple opration, low-cost hardware and high accuracy.更多还原