禽蛋裂纹检测敲击装置力学分析与结构优化

为了增强敲击响应信号对禽蛋蛋壳裂纹信息的感知能力,提高禽蛋裂纹检测的准确性,分析了敲击装置的力学模型,并以此为依据优化设计激励棒的结构参数和检测条件。力学分析发现,禽蛋的激振力脉冲形态与激励棒质量、棒头刚度和敲击速度有关;优化后的激励棒质量应小于5.6 g,棒头采用尼龙材质;建立了冲击力能量与激励棒质量和敲击速度之间的相互关系,并建立了瞬态冲击过程的数学模型。试验结果表明,优化后激励棒对完好蛋激振力脉冲的稳定性较好,与所建立数学模型的相关系数均达到0.92以上;产生的力信号频带能覆盖禽蛋固有频率且具有足够的激振能量,有利于提高完好蛋与裂纹蛋的可区分性和响应信号的信噪比。

Mechanical Analysis and Structural Optimization of Knocking Device for Eggshell Crack Detection

In order to enhance the ability of response signal to reflect eggshell crack information and improve the accuracy of eggshell crack detection, structural parameters and detection conditions of the excitation stick were optimally designed by dynamic experiments based on mechanical model of the knocking device. The shape of pulse produced by excitation stick was related to the weight of stick, stiffness coefficient and percussion speed according to mechanics analysis results. The spectrum of excitation pulse was analyzed. The results showed that the sensitivity of response signals for eggshell creak information can be improved by reducing the pulse width and increasing the pulse peak. The excitation pulse signal was collected by a quartz force sensor, which was analyzed to optimize the excitation stick by using force spectrum method. In order to ensure that the main lobe band of the excitation force pulse covered the natural frequency of eggs, the weight of the optimized excitation stick with nylon striking end was less than 5.6g. The relationship model between the pulse peak and the stick percussion speed was established, which would offer a reference to select the appropriate percussion speed for different varieties of eggs. The mathematical model of the transient impulse process was established to provide the basis for the later finite element simulation. The experiment results showed that the excitation pulse produced by the optimized excitation stick had the advantage of good stability, and the correlation coefficients between the pulse of intact eggs and mathematical model were more than 0.92. Frequency band of the pulse could cover the natural frequency of eggs and the pulse had sufficient excitation energy, which were of great help to distinguish between intact eggs and crack eggs and increase the signal to noise ratio (SNR) of response signal.