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비파괴적 인장물성 평가를 위한 Advanced Indentation System의 응용 연구
장재일(Jae-il Jang),최열(Yeol Choi),권동일(Dongil Kwon),박주승(Joo Seung Park) 대한기계학회 2001 대한기계학회 춘추학술대회 Vol.2001 No.3
Until now, the tensile properties of materials can be obtained just in accordance with conventional tensile testing methods which are described in several standards such as ASTM (American Society for Testing and Materials) standard and BS (British Standard). For some cases including on-service facility materials, however, the standard testing methods cannot be applicable due to the destructive testing procedure and specimen size requirement. Therefore, simple, non-destructive and advanced indentation technique was proposed. This test measures indentation load-depth curve during indentation and analyzes the mechanical properties related to deformation and fracture. In this paper, the research trend of non-destructive evaluation of tensile properties using AIS (advanced indentation system) and its application fields are reviewed and discussed.
비파괴 신기술을 이용한 석유화학설비 경년손상의 새로운 평가변수 고찰
장재일(Jae-il Jang),최열(Yeol Choi),손동일(Dongil Son),이윤희(Yun-Hee Lee),권동일(Dongil Kwon),김정태(Jeoung Tae Kim) 대한기계학회 2001 대한기계학회 춘추학술대회 Vol.2001 No.8
Newly developed continuous indentation technique has made nondestructive assessment of tensile properties possible. The present study was undertaken to determine new parameters for indicating time-dependent material degradation of petro-chemical plant. Continuous indentation tests were performed at Cr-Ni steel and Cr-Mo steel which are widely used as facilities of petro-chemical plant. From the results, it was found that yield strength and tensile strength cannot be used as general degradation parameters because the change tendencies of the strengths with aging time are variable. On the other hand, work hardening exponent and yield ratio showed consistent tendency with increasing aging time. Therefore, main attention of this work was paid on them as new degradation parameters, and the in-field applicability of the parameters was evaluated and discussed.
나노 압입곡선의 이론적 분석을 통한 박막의 잔류응력 평가
이윤희,장재일,권동일,Lee, Yun-Hee,Jang, Jae-Il,Kwon, Dong-Il 대한기계학회 2002 大韓機械學會論文集A Vol.26 No.7
Residual stress is a dominant obstacle to efficient production and safe usage of device by deteriorating the mechanical strength and failure properties. Therefore, we proposed a new thin film stress-analyzing technique using a nanoindentation method. For this aim, the shape change in the indentation load-depth curve during the stress-relief in film was theoretically modeled. The change in indentation depth by load-controlled stress relaxation process was related to the increase or decrease in the applied load using the elastic flat punch theory. Finally, the residual stress in thin film was calculated from the changed applied load based on the equivalent stress interaction model. The evaluated stresses for diamond-like carbon films from this nanoindentation analysis were consistent with the results from the conventional curvature method.
LNG 저장탱크 내조용 9% Ni강의 SAW 용접열영향부내 파괴인성 변화 평가
장재일,이정석,이백우,주장복,권동일,김우식,Jang, Jae-Il,Lee, Jeong-Seok,Lee, Baek-U,Ju, Jang-Bok,Gwon, Dong-Il,Kim, U-Sik 대한기계학회 2002 大韓機械學會論文集A Vol.26 No.3
As one step for the safety performance of LNG storage tank, the change in fracture toughness within the X-grooved weld heat-affected zone (HAZ) of newly developed 9% Ni steel, which was submerged arc (SA)-welded, was investigated. Both crack initiation fracture toughness and crack arrest fracture toughness were evaluated by the crack tip opening displacement (CTOD) tests and compact crack arrest (CCA) tests. As the evaluated region approached the fusion line, each test result shorted different tendency, that is, crack initiation toughness decreased while crack arrest toughness increased. The results were discussed through the observation of the microstructural change.