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SS 41材의 疲勞크랙 傳播速度에 미치는 熔接殘留應力의 影響에 관한 硏究
정석주,한병기,정강,Chung, Suk-Choo,Han, Byeong-Kee,Chung, Kang 대한기계학회 1988 대한기계학회논문집 Vol.12 No.3
본 연구에서는 용접잔유응력의 영향을 보다 정확하게 규명할 목적으로 용접잔 유응력의 피로반복 사이클 수에 따른 이완량을 측정하고, 모재의 실험 결과에 중첩의 개념을 도입함으로써 용접잔유응력이 피로크랙 전파에 미치는 영향을 규명할 수 있는 방법을 제시한다. 하나의 예로서 SS41재를 선택하여 서브머지드아크 용접을 한 후, 본 논문의 방법을 작용함으로써 용접잔유응력의 영향에 대하여 분석하였다. In this study, a method that can realize the effect of residual stresses on fatigue crack propagation has been proposed. This method requires that the relaxation quantities of residual stresses are measured by experimental method according to fatigue cycles and are employed to the experimental results of base materials by introducing the concept of superposition. SS41 material has been analyzed as an example. The results show that the relaxation factor of residual stresses for fatigue cycles is .alpha.$_{i}$= 1/0.6903+0.0380 $a_{I}$ the effective stress ratio for fatigue crack propagation length is ( $R_{eff}$)$_{i}$ = 1/1.1274+0.0118$_{I}$ and the fatigue crack propagation rate for relaxation quantities of residual stresses is (da/dN)$_{t}$ = 0.5 $K_{cf}$ - .DELTA.K/{1-1/1.1274+0.0118$_{ai}$ } $K_{cf}$ - .DELTA. K(da/dN), for stress ratio /R=0.5.io /R=0.5.5.
축대칭 경계적분법에 의한 항공기 가스터빈 로터디스크 구조해석에 관한 연구
공창덕,정석주,Kong, Chang-Duk,Chung, Suk-Choo 대한기계학회 1996 大韓機械學會論文集A Vol.20 No.8
A design process and an axisymmetric boundary integral equation method for precise structural analysis of the aircraft gas turbine rotor disk were developed. This axisymmetric boundary integral equation method for stress and steady-state thermal analysis was improved in solution accuracy by appling an implicit technique for Cauchy principal value evaluation, a subelement technique for weak singular integral evaluation and a double exponentical integral technoque for internal point solution near boundary surfaces. Stresses, temperatures, low cycle fatigue lifes and critical speeds for the turbine rotor disk of the thrust 1421 N class turbojet engine were analysed in a pratical calculation model problem.
현가장치용 코일스프링의 피로특성에 미치는 온간쇼트피닝 가공의 영향
김기전,정석주,Kim, Ki-Jeon,Chung, Suk-Choo 대한기계학회 2002 大韓機械學會論文集A Vol.26 No.6
The requirements of coil spring fer higher fatigue strength have been increased to achieve the weight reduction of a vehicle. As the possible increase in fatigue strength by using the conventional shot peening treatment is found to be limited, it is necessary to modify the shot peening treatment. The warm shot peening is a shot peening treatment carried out within warm temperature range. The aim of this paper is to analyze some experimental results concerned with the effect of warm shot peening and to discuss the mechanism of warm shot peening in detail. By the results of rotating bending fatigue test, the fatigue strength of test specimen increases up to 23.8% in the production condition of warm shot peening at 200$\^{C}$ compared with conventional shot peening. The major reason why the warm shot peening is effective to the improvement of fatigue strength is the increase of a compressive residual stress distribution, which can be caused by more effective deformation under the condition of warm temperature.
정석주 서울産業大學校 1993 논문집 Vol.38 No.1
This paper derives the generalized mass to find dynamic characteristics and its derivatives of a continuos system. And a new sensitivity analysis method is presented by using the amount of change of generalized mass and vibrational mode caused by the variation of lumped and distributed mass. In this paper, to get or detect appropriate results, cantilever beam and stepped beam are used. Deviations of sensitivity coefficient, natural frequency, vibrational mode and transfer function are calculated as result, and compared with the theoretical exact values.
鄭錫柱 서울産業大學校 1988 논문집 Vol.28 No.1
本 硏究는 韓國 朝鮮朝 梵鐘의 音響效果를 考慮한 動的特性을 理論 및 實驗的으로 解析하였다. 固有振動數 및 모우드形狀에 依한 數値解는 四邊形과 三角形 판-셀 要素를 使用하는 有限要素法인 NASTRAN프로그램을 利用함으로써 얻었다. 實驗用鐘은 韓國 朝鮮朝 梵鐘가운데, 公州에 있는 甲寺鐘파 유사한 A 및 B 形으로서 원래의 梵鐘크기와 다른 크기로 製作되었다. 이러한 實驗用鐘의 크기를 變化시킴으로써, 動的 反應에 미치는 影響을 考慮하여 벽두께,下端部의 두께, 그리고非對稱 撞座等의 變化에 따라 解析하였다. 實驗的 動的反應의 解析은 衡擊 햄머법과 F. F. T. 分析裝置(Fast courier Trans-formation Analyzer)를 利用하였으며 그 結果는 數値解析結果와 잘 一致하였다.
鄭錫柱 서울産業大學校 1984 논문집 Vol.20 No.1
本 硏究는 兩端이 自由로운 경우에 半徑方向으로 集中衝擊荷重을 非對稱的으로 円筒셸의 動的特性을 Donnell 方程式을 利用하여 解析하였다. 實計算例로서 靑銅으로 制作된 円筒셸을 解析하였고, 그 結果를 Rayleigh Mode 와 比較하였다. 그 結果가 잘 一致하였으며, 適用 荷重과 經界條件을 달리 하는 셸의 動的特性에 應用이 可能하다.
鄭錫柱 서울産業大學校 1980 논문집 Vol.13 No.1
Stress of a thin uniform cylindrical shell with free ends is investigated by the experimental method. The experimental results agree well with the computed results that are obtained by an approximate theory of Love and Warburton. Also the stress levels of three kinds of cylindrical shells are experimentally investigated The results obtained were as follows: 1) In this paper, it is given the distributions of the stresses and the natural frequencies at the specified point (by the angle) on the Cylindrical shell. And also we plotted the results obtained from the experimental data. 2) Experiments show that the response of the decreasing of the stress level as increasing the cylinder's length and diameter ratio. 3) The natural frequencies of cylinders are decreased as increasing the cylinder's length ratio, 510(C/S) in l/d=1.0, 485(C/S) in l/d=1.4. 4) We also find the influence of the axial stresses have the value of stress of 1/15∼1/10 Compared with the tangential stress.