Study of Potential Correlation between Machining Damage of Al₂O₃ Surface and Grinding Acoustic Emission Signal

• Main Authors: Zhang,Yi-Yo, 張奕宥
• Other Authors: Chiu,Neng-Hsin
• Format: Others
• Language: zh-TW
• Published: 2018
• Online Access: http://ndltd.ncl.edu.tw/handle/nb5pqg

碩士 === 國立高雄第一科技大學 === 機械與自動化工程系碩士班 === 106 === ABSTRACT Ceramic materials have high strength, light weight, high temperature resistance, corrosion resistance, wear resistance and other characteristics that meet the requirements of engineering components. However, its resistance to collision and low fracture toughness make the difficulty in processing increase, which also limits its development and application. Despite advances in the technology of processing ceramic components, grinding with diamond wheels remains the preferred method of processing ceramic components. In the process of grinding ceramic workpieces, the action of the tool causes the surface of the material to be subjected to the normal force and the tangential force. When the brittle material is subjected to the normal force, plastic deformation, lateral cracks and radial cracks appear. The change in each grinding parameter is related to the occurrence of physical phenomena. When the grinding wheel is machined on the surface of the workpiece, radial cracks appear under the plastic deformation layer with the difference of the normal force, which also means the formation of subsurface damage. Subsurface damage is also different with different grinding parameters, and different subsurface damage has an effect on the quality of the workpiece. The subsurface damage can´t be directly observed by the naked eye. It must be indirectly observed through a special measuring instrument. It can´t be directly known at the processing site, but the cost of measuring the subsurface test piece is expensive, which also affects the progress of the on-site process. If the subsurface damage can be known by the sensing device, it will help the quality of the workpiece. This paper is aimed at the grinding process of alumina ceramics, and attempts to explore the correlation between grinding acoustic signal detection and alumina processing cracking. It is known through the literature that the normal stress is positively correlated with the subsurface damage, and the grinding sound signal is related to the normal stress. When grinding at the processing site, due to equipment limitations and cost considerations, the AE signal can only be obtained by the AE sensor, so it is expected to be released by diamond grinding when detecting ceramic workpieces. The AE signal is detected by the signal and the correlation with the normal stress is obtained. Then, by correlating the sound signal with the normal stress, it is analogous to grinding the subsurface damage of the AE signal. Based on the hypothesis of this paper, the grinding normal stress is positively correlated with the subsurface damage. According to the experimental results, there are at least four effective frequency clusters in the ceramic grinding acoustic signal, and the normal stress and the surface roughness and the effective frequency band settlement all contribute. Among them, the sound energy of the second frequency band (155K~275K) has a higher contribution to the normal stress of grinding, the sound energy of the second frequency band (155K~275K) and the third frequency band (275K~425K) It has a higher contribution to surface roughness. Through the above, it is known that the correlation between normal stress and subsurface damage ,Because this paper assumes that the normal stress is positively correlated with the subsurface damage.In other words, the correlation between grinding the AE signal and the normal stress is analogous to grinding the AE signal and subsurface damage.. Keyword: Al₂O₃ ceramic、acoustic emission of Frequency band signal、acoustic emission energy、Diamond grinding