本文討論材料在受力時，裂縫附近之材料缺陷對其塑性反應的影響；藉由改變應力強度因子(Stress Intensity Factor)K，觀察Mode-I裂縫前端的塑性區變化。吾人在位於裂縫前端改變缺陷的距離、半徑、孔洞圓心與裂縫之夾角（孔洞上移），以便探討當缺陷的分布位置對裂縫之影響。
吾人以材料為不鏽鋼(stainless steel 316L)建構非線彈性(nonlinear inelastic)之雙線性隨動硬化(bilinear kinematic hardening)平板。並以工程分析軟體ANSYS來分析問題，藉由改變K值來探討塑性區形狀之變化。分析結果顯示，在同樣負載下，越靠近裂縫尖端之缺陷所造成裂縫尖端之應力、應變值會與之增大;若缺陷孔洞圓心至裂縫尖端距離與負載保持不變，則孔洞半徑越大，也會造成相同的結果。而當半徑縮至很小時，對裂縫尖端的影響已不大，此時，孔洞的存在與否，已不是這麼的重要。另外，在孔洞圓心至裂縫尖端距離不變下，將孔洞圓心上移，此時圓心至裂縫尖端之連線與水平軸夾45°。研究發現對裂縫前方應力值的影響較不敏感，其受力後變形由圓形變為近似橢圓，其主軸恆指向裂縫尖端。

Abstract
This article discuss when the material is in force, the effect about plastic zone to the defect of the material near the crack tip. By changing Stress Intensity Factor(SIF),K, to confer the plastic zone range in Mode-I. On the other hand, I change the distance between the crack tip and the center of a circle, the radius of the circle of defect and the included angle between the line which is the center of a circle to the crack tip and horizontal line, to concern the effect to the distribution of the defect.
In this paper I try to model the nonlinear inelastic plane that has bilinear kinematic hardening property by ANSYS and the material is stainless steel 316L.It is found that in the same loads the near defect around crack tip, the stress and strain is bigger. If in the same condition the bigger radius cause the same result. when radius is smaller the effect to the crack tip is not sensitivity. If keep the distance between the defect center and crack tip and elevate the defect center to make the the angle between the level line and the line with the center and crack tip to be 45°
,it is found that the holes are actually pulled towards the crack tip and change their shape to approximately elliptical with the major axis radial to the crack..

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