http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
압전 구동기를 이용한 인코넬 690 튜브의 프레팅 마멸시험
정일섭(Ilsup Chung),이명호(Myungho Lee),박기홍(Kihong Park),이정훈(Junghoon Lee),권재도(Jaedo Kwon) Korean Society for Precision Engineering 2009 한국정밀공학회지 Vol.26 No.2
A fretting wear test rig for dry ambient condition, which employs a piezoelectric actuator, has been developed. It is driven and loaded in a very simple manner with acceptable experimental accuracy By using the rig, Inconel 690 tube has been tested under the normal load of 10 and 15N with sliding amplitude of less than 100j..lm during 106cycles. The wear resistance of the material has been characterized in terms of the wear coefficient based on the work rate model. SEM micrographs show the complex structures of the scars, which consist of risen peaks, plate-type thin layers and locally exposed bare surfaces. The cracks spread over the layers give clue to the fretting wear mechanism of the material.
정일섭(Ilsup Chung) Korean Society for Precision Engineering 2004 한국정밀공학회지 Vol.21 No.1
Structural analysis for materials containing regularly spaced in-homogeneities is usually executed by using averaged material properties. For the homogenization process, a unit cell is defined and loaded somehow, and its response is investigated to evaluate the properties. The imposed loading conditions should accord to the behavior of unit cell immersed in the macroscopic structure in order to guarantee the accuracy of the effective properties. Each unit cell shows periodic variation of strain if the material is loaded uniformly, and in this study, direct implementation of this characteristic behavior is attempted on FE models of unit cell. Conventional finite element analysis tool can be used without any modification, and the boundary of unit cell is constrained in a way that the periodicity is satisfied. The proposed method is applicable to skew arrayed in-homogeneity problems. The flexibility matrix relating tensorial stress and strain components in skewed rectilinear coordinate system is transformed so that the required engineering constants can be evaluated. Effective properties are computed for the materials with square and skew arrayed circular holes, and its accuracy is examined.
정일섭(Ilsup Chung) Korean Society for Precision Engineering 2005 한국정밀공학회지 Vol.22 No.7
Analysis of structures which are composed of numerous repeated unit structures can be simplified by using homogenized properties. If the unit structure is repeated in one direction, the whole structure may be regarded as a beam. Once the effective stiffness is obtained from the analysis of the unit structure in a proper way, the effort for the detail modeling of the global structure is not required, and the real structure can be replaced simply with a beam. This study proposes a kinematical periodicity constraint to be imposed on the FE model of the unit structure, which improves the accuracy of the effective stiffness. The method is employed to a one dimensionally arrayed 3D structure containing periodically repeated un-symmetric holes. It is demonstrated that the deformation behavior of the homogenized beam agrees well with that of the real structure.
정일섭(Ilsup Chung) Korean Society for Precision Engineering 2005 한국정밀공학회지 Vol.22 No.2
Evaluating the effective properties of materials containing various types of in-homogeneities is an important issue in the analysis of structures composed of those materials. A simple and effective method for the purpose is to impose the periodic displacement boundary conditions on the finite element model of a unit cell. Their theoretical background is explained based on the purely kinematical relations in the regularly spaced in-homogeneity problems, and the strategies to implement them into the analysis and to evaluate the homogenized material constants are introduced. The creep behavior of a thin sheet with square arrayed rectangular voids is characterized, where the orthotropy is induced by the presence of the voids. The homogenization method is validated through the comparison of the analysis of detailed model with that of the simplified one with the effective parameters.
인코넬 690 튜브의 상온 프레팅 마멸 특성에 대한 연구
정일섭(Ilsup Chung),이명호(Myungho Lee),채영석(Youngsuck Chai) 대한기계학회 2009 大韓機械學會論文集A Vol.33 No.4
A fretting wear test rig for cross contacting tube specimens, which employs a piezoelectric actuator, has been developed. Along with the simple loading scheme using dead weights, the rig is very simple to be used also. The accuracy was found acceptable. Inconel 690 tubes were tested in room temperature and ambient condition. Normal load and sliding amplitude range up to 35N and 100㎛, respectively. The sizes of wear scar and the wear volumes were measured, and wear coefficients have been calculated based on those. A study on the fretting wear mechanism of the tubes has been attempted via microscopic observation. Rugged wear surfaces are induced by the separation and adhesion of particles and formation and subsequent fracture of surface layers. Lapped specimens were also tested and abrasive wear seems to be playing a dominant role.