金屬材料於平面應變下裂縫前端之彈塑性分析

游智凱(Chih-Kai Yu)

指導教授 ： 蔣長榮

國立清華大學/工學院/動力機械工程學系/碩士(2006年)

摘要

探討含有裂縫之材料結構受力時，當裂縫尖端所受之應力超過其降伏應力後，便會產生塑性變形，其塑性區之形狀關係著材料結構的破裂行為。本文根據破裂力學的原理，撰寫成程式計算出模型的邊界條件，並利用ANSYS工程分析軟體建立模型。在小尺度塑性變形的條件下，模擬一均向性(Isotropic)材料平板處於Mode-I張開型的裂縫時，改變應力強度因子(Stress Intensity Factor) ，求得裂縫尖端之應力、應變與塑性區分佈。並探討改變不同材料之應變硬化率對其影響。基於材料特性故以雙線性(Bilinear)力學模型及隨動硬化規則(Kinematic Hardening)來進行模擬。
由文中結果可知，裂縫尖端產生塑性變形後，發生了尖端鈍化的現象，故其應力為有限值。且材料於不同應變硬化率時會對塑性區內應力及應變分佈有所改變，對於外圍彈性區則影響不大。

關鍵字

尖端裂縫 ； 塑性區 ； 平面應變 ； 應力強度因子 ； 有限元素

並列摘要

Crack tip plastic zone is a very important factor in the fracture behavior of metallic materials. To simulate the plastic deformation at the crack tip, the principle of fracture mechanics is implemented in finite element method (FEM) and ANSYS engineering analysis software. For a homogeneous and isotropic material under Mode-I loading and small scale yielding condition, we change its stress intensity factor (SIF) and material strain hardening rate (SHR) to obtain the stress-strain distribution of the crack tip. The material property depends on bilinear mechanics model and kinematics hardening rule.
From the result of this study, plastic deformation has occurred and led it to a blunt crack tip. So the stress value at the crack tip is a finite value. Also different material strain hardening rate has strongly influence to its stress-strain distribution in the plastic zone.

並列關鍵字

crack tip ； plastic zone ； plane strain ； stress intensity factor ； finite element

參考文獻

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