中鋼設備零件之破損分析研究－以解捲機心軸與除銹系統球型聯結器為例

本研究係利用設備故障破損件，以美國材料信息協會ASM Handbook材料破損目視特徵，來解析破裂起源以推斷損壞原因，並利用各種分析技術，如有限元素分析、掃描式電子顯微鏡、能量散佈光譜儀、背向散射電子影像等來作驗證，以強化推斷可靠度。研究之破損件有（1）解捲機心軸；（2）高壓除銹系統球形聯結器。其中破損件（1）以疲勞破斷特徵－海灘紋，研判破裂起始於心軸鍵槽底部的螺栓鎖固位置，推斷為螺栓代替鍵來傳遞扭力所致，經以有限元素分析破裂位置在上述狀況下會承受最大應力，且此應力值以古德曼圖來評估，亦也超過材料的疲勞安全限度，與破損狀況相符；破損件（2）以脆性破斷特徵-放射紋及裂紋生成原則-T字型法解析，研判破裂起始於破損件內壁具孔蝕特徵處，以掃描式電子顯微鏡、背向散射電子影像來觀察微裂紋走勢與蝕孔形貌，及利用能量散佈光譜儀作微區成份分析，得知孔蝕為氯離子所誘發。藉由上述兩不同損壞模式的分析，破損件以ASM目視特徵輔以裂紋走勢的解析，皆可準確判斷起始點，經進一步驗證可加增其可靠度。此巨觀裂紋走勢的解析在錯綜複雜的設備損壞原因下，能提供重要線索與診斷方向，在著重時效的工業應用上，可作為快速判斷破損件損壞原因的方法及作為後續設備改善的方向與客訴的依據。

關鍵字

破損分析；疲勞；孔蝕；有限元素分析

並列摘要

This paper utilizes ASM Handbook o f ASM International to identify the damage modes of the fracture parts. Examine the initial of rupture to infer the root cause of failure. Various analytical techniques, such as finite element analysis (FEA), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and backscattered electrons image (BSE), are applied to check the inference's trustworthiness. Analyses on two fracture parts were made in this paper. The first fracture part is the mandrel of pay-off-reel, and the second fracture part is ball coupling of high-pressure descaling system. The crack in the first fracture part initiated at the bolt hole in keyway. Characteristic beach mark due to fatigue damage was observed. The root cause verified by FEA is that the bolt exerted an abnormal load that result in high stress concentration at the bolt hole. The maximum stress exceeded the fatigue limit of the material was checked by Goodman Diagram. The fracture surface of second part was analyzed by rays mark and T-junction appearance, and was further observed by SEM and BSE. The crack was initiated from pitting corrosion at inner surface of the ball coupling. The pitting corrosion due to chloride ions was checked by EDS. According to the above two cases, the visual characteristics of ASM can be used to find the initial of rupture correctly. The inference can be verified by various analytical techniques to increase the reliability. Hence, visual examination of fracture parts can be used as a method to quickly determine the cause of damaged parts, provide important clues and diagnostic directions for troubleshooting. The verified root cause can also be a guidance to improve the equipment, and the evidence to negotiate with the supplier.