應用超音波檢測殘留應力

Residual Stress Measured by the Ultrasonic Technique

彭聲澤(Sheng-Tse Peng)

指導教授 ： 何旭川

元智大學/工程學院/機械工程學系/碩士(2011年)

https://doi.org/10.6838/YZU.2011.00054

摘要

許多結構或材料在加工或成形過程如擠製、滾壓、緞造、固化等，均會產生殘留應力，因而降低強度減少使用壽命。藉由非破壞檢測方式，量測結構或材料殘留應力，不僅可預防結構破壞，更可做為評估加工或成形製程優劣之依據。超音波具有靈敏度高、穿透力強、成本低、檢測速度快、設備輕便、對人體無害等諸多優點，已被廣泛應用於各種非破壞檢測。本文應用超音波檢測304不鏽鋼材料殘留應力，首先以三點彎曲實驗量測304不鏽鋼超音波波速與彎曲應力之關係，求得材料三階彈性常數。再以高溫熱處理爐將焊錫熔解並與304不鏽鋼結合，製作鋼與錫之雙層樑試片。由於鋼與錫熱膨脹係數不同，使從高溫冷卻至室溫之雙層樑試片，內部產生殘留熱應力。藉由量測超音波在304不繡鋼之波速，結合材料三階彈性常數，量測雙層樑試片在304不繡鋼層之殘留熱應力，並與樑理論計算所得雙層樑殘留熱應力比較，驗證超音波量測殘留應力之準確性。

關鍵字

殘留應力 ； 超音波檢測 ； 材料三階彈性常數 ； 熱應力

並列摘要

The residual stresses can be generated inside the structures during the manufacturing processes such as extrusion, rolling, forging and solidification resulting in the decrease of the strength and serve life. In this study, the ultrasonic technique was employed to measure the residual stress in the 304 stainless steel. The relation ship between the ultrasonic velocity and stress for the 304 steel was determined by the three-point-bending test. Using the ultrasonic velocity and stress relation, the third order elastic constant of the 304 steel was evaluated. A bi-layered beam consisting of 304 steel and tin was fabricated at high temperature in a heat treatment furnace. Due to the difference of the thermal expansion coefficients between the 304 steel and tin, the thermal residual stress was generated as the bi-layered beam cooling down to the room temperature. The residual stress of the bi-layered beam measured by the ultrasonic technique was validated with the theoretical prediction basing on the beam theory.

並列關鍵字

residual stress ； ultrasonic technique ； thermal stress ； third order elastic constant

參考文獻

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