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22대 대한민국 국회 국회정보길라잡이 국회의원검색
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Abstract 7

I. 서론 8

II. 재료 및 평가방법 9

1. 평가시험편 9

2. 과대응력으로 무한 수명이 가능한 균열 크기 평가 10

2.3. 미소균열의 피로균열 진전평가 12

III. 결과 및 고찰 13

IV. 결론 23

References 24

표목차

Table 1. Characteristic values of each material used for evaluation 9

Table 2. Crack length to satisfy infinite life under different overstress. 14

Table 3. Maximum crack size to satisfy infinite life under each overstress depending on design stress in case of Al6061-T6. 17

Table 4. Maximum crack size to satisfy infinite life under each overstress depending on design stress in case of SCM440. 21

Table 5. Maximum crack size to satisfy infinite life under each overstress depending on design stress in case of STS316L. 21

Table 6. Maximum crack size to satisfy infinite life under each overstress depending on design stress in case of SUP9A. 22

그림목차

Fig. 1. Model of specimen for analysis. 9

Fig. 2. Schematic of a finite plate containing a semielliptical crack. 10

Fig. 3. Relationship of △K versus crack size(a, c) depending on different overstress. 14

Fig. 4. Evaluation of crack size to satisfy infinite life under each overstress depending on design stress in case of Al6061-T6. (a) As＝1.0, (b) As＝0.6, (c) As＝0.3, (d) As＝0.1 17

Fig. 5. Evaluation of crack size to satisfy infinite life under each overstress depending on design stress in case of SCM440. (a) As＝1.0, (b) As＝0.6, (c) As＝0.3, (d) As＝0.1 18

Fig. 6. Evaluation of crack size to satisfy infinite life under each overstress depending on design stres s in case of STS316L. (a) As＝1.0, (b) As＝0.6, (c) As＝0.3, (d) As＝0.1 19

Fig. 7. Evaluation of crack size to satisfy infinite life under each overstress depending on design stress in case of SUP9A. (a) As＝1.0, (b) As＝0.6, (c) As＝0.3, (d) As＝0.1 20

초록보기

Many studies have reported the retardation in crack growth on the structural members and its principle. Until now, much research has been studied the change in the rate of crack growth by overstress. However, there are no studies on the fatigue life of machines and structures considering the size of the plastic zone due to overstress. Therefore, this study assumed semi-elliptical surface cracks with different aspect ratios (As) to evaluate the infinite life of four types of structural member due to overstress. As a result of the evaluation, infinite life is possible in most cases with appropriate overstress. The crack growth pattern according to the AS is determined by the surface crack (c) for the infinite life of As＝1.0. In the case of As＝0.6 and 0.3, it was determined from surface cracks and (c) and crack depth (a), but there were some differences depending on the material. When As＝ 0.1, it was determined only by the crack depth (a). The infinite life of fatigue cracks due to overstress is mostly affected by the crack size, design stress, and As, but crack size (a, c) has the greatest effect. Therefore, it is necessary to accurately measure the crack size (a, c) for the infinite life of the structure due to overstress.

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