The establishment of stochastic grinding force and vibration model considering random grit distribution and ground surface roughness model with the effect of vibration

• Main Authors: Huang-cheng Chang, 張煌權
• Other Authors: J-J Junz Wang
• Format: Others
• Language: zh-TW
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/71470402662727090258

博士 === 國立成功大學 === 機械工程學系碩博士班 === 96 === Considering the random nature of grit distribution, this thesis establishes a grinding system, incorporating the stochastic grinding force, vibration and ground surface roughness model. First, a closed form expression for the stochastic grinding force as a function of the grinding conditions and grit distribution is presented. With the grinding force model, further analytical study can then be carried out to investigate the effects of wheel properties, machine dynamics and process parameters on the resulting grinding vibration, as well as in characterizing the effect of vibration on the ground surface topology. The stochastic grinding force model is formulated as the convolution of a single grit force and the grit density function in time domain, while the power spectrum density (PSD) of the total grinding force can be expressed as a product of the energy spectrum density of the single grit force and the PSD of the grit density function. A series of grinding experiments were performed and their results discussed to validate this model. Incorporating with the dynamics of the machine structure and the established force model, a closed loop grinding system was established. The system can be further simplified to an open loop system, thus the analytical expression for the PSD of grinding vibration can be derived. The effects of grinding conditions on the machine vibration can be analyzed based on the analytical expression machine vibration, and the results were verified by the experiments. By the variance analysis of kinematic grit and machine vibration profiles, an analytical ground surface roughness model representing their explicit effects on the ground surface was developed. The surface profile is treated as the superposition of the kinematic grit and vibration profiles. By the variance analysis of the two profiles, the root-mean-square ground surface roughness model can be derived. The transmitting factor, which defines the partition of power transmitted from spindle vibration to the ground surface, was derived from the dynamic grinding system and is related to the stiffness of the process, namely the workpiece cutting stiffness and wheel contact stiffness. An experimental procedure for identifying the stiffness in surface grinding was also developed. Discussions regarding the grinding conditions for the surface roughness based on experimental and model analysis results are presented. The model predictions and experimental results support the finding that a greater grinding depth and width increases the grinding force and hence deteriorates the ground surface.