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Evaluation on Fatigue Characteristics of Tire Sidewall Rubber according to Aging Temperature
( Namgyu Jun ),( Byungwoo Moon ),( Yongseok Kim ),( Jae-mean Koo ),( Chang-sung Seok ),( Ui Seok Hong ),( Min Kyeong Oh ),( Seong Rae Kim ) 한국고무학회 2017 엘라스토머 및 콤포지트 Vol.52 No.3
Ultra-high performance (UHP) tires, for which demand has recently surged, are subject to severe strain conditions due to the low aspect ratio of their sidewalls. It is important to ensure sidewall material durability, since a sudden tire sidewall breakage during vehicle operation is likely to cause a major accident. In the automotive application of rubber parts, cracking is defined as a failure because when cracks occur, the mechanical properties of rubber change. According to Mars<sup>(8)</sup>, Andre<sup>(11)</sup> et al., strain and strain energy density (SED) are mainly used as a failure parameters and the SED is generally used as a fatigue damage parameter. In this study, the fatigue life curves of sidewall rubber of tires were determined by using the SED as fatigue damage parameter while the effect of aging on fatigue life was evaluated after obtaining the SED-Nf curves according to aging condition.
DC Potential Drop Method for Evaluating Material Degradation
Chang-Sung Seok,Bong-Kook Bae,Jae-Mean Koo 대한기계학회 2004 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.18 No.8
The remaining life estimation for the aged components in power plants as well as chemical plants are very important because mechanical properties of the components are degraded with in-service exposure time in high temperatures. Since it is difficult to take specimens from the operating components to evaluate mechanical properties of components, nondestructive techare needed to evaluate the degradation. In this study, test materials with several different degradation levels were prepared by isothermal aging heat treatment at 630℃. The DC potential drop method and destructive methods such as tensile and fracture toughness were used in order to evaluate the degradation of 1 Cr-l Mo-0.25V steels. In this result, we can see that tensile strength and fracture toughness can be calculated from resistivity and it is possible to evaluate material degradation using DC potential drop method, non-destructive method.
Evaluation of Material Degradation of 1Cr-1Mo-0.25V steel using Ball Indentation Method
Chang-Sung Seok,Jeong-Pyo Kim,Jae-Mean Koo 대한기계학회 2004 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.18 No.10
The BI (Ball Indentation) method has the potential to assess the mechanical properties and to replace conventional fracture tests. In this study, the effect of aging on mechanical behavior of 1Cr-1Mo-0.25V steels procured by isothermal aging heat-treatment at four different aging times in the range of 0~1820 hours at 630℃, were investigated using BI system.
잔류응력으로 인한 응력비 변화를 고려한 U자형 구조의 피로특성 평가
김상영(Sang Young Kim),구재민(Jae Mean Koo),석창성(Chang Sung Seok),모진용(Jin Yong Mo) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.11
Mechanical structures with power sources experience repeated force produced by motors. As a result, the life of the pipes reduces and ultimately, the pipes collapse. In most cases, the U-shape pipe is made from a straight pipe by complicated bending work. During this work process, plastic deformation of the pipe produces residual stress in the pipe. This residual stress significantly affects the fracture behavior of the pipe and induces the change of the stress ratio (min. stress/Max. stress = R). For this reason, residual stress has to be evaluated. In this paper, the residual stress of a U-shaped pipe was evaluated by FEM analysis. In addition, fatigue tests of the U-shaped pipe were performed by using a uniaxial fatigue testing machine. The results of the fatigue test were modified with the results of FEM (Finite Element Method) analysis for residual stress. The modified fatigue test results of the U-shaped pipe were compared with those of a straight pipe.
석창성,구재민,김동중,안하늘,박은수 한국산업안전학회 2000 한국안전학회지 Vol.15 No.4
The remaining life estimation for the aged components in power plants as well as chemical plants are very important because mechanical properties of the components are degraded with time of service exposure in the high temperature. Since it is difficult to take specimens from the operating components to evaluate mechanical properties of components, accelerated aging technique are needed to estimate and analyse the material degradation. In the this study, test materials with 4 different degradation levels were prepared by isothermal aging heat treatment at 630℃. And tensile test, K_(IC) test, hardness test and Scanning Electron Microscope analysis were performed in order to evaluate the degradation of 1Cr-1Mo-0.25V steels.
〈학술논문 or 기술논문〉 저속 충격손상을 받은 평직 CFRP 복합재료의 잔류강도 평가
석창성(Chang-Sung Seok),최정훈(Jung-Hun Choi),강민성(Min-Sung Kang),신인환(In-Hwan Shin),구재민(Jae-Mean Koo) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.11
Composite materials have a higher specific strength and modulus than traditional metallic materials. Additionally, these materials offer new design flexibilities, corrosion and wear resistance, low thermal conductivity and increased fatigue life. These, however, are susceptible to impact damage due to their lack of through-thickness reinforcement and it causes large drops in the load-carrying capacity of a structure. Therefore, the impact damage behavior and subsequently load-carrying capacity of impacted composite materials deserve careful investigation. In this study, the residual strength and impact characteristics of plain-woven CFRP composites with impact damage are investigated under axial tensile test.
홀 노치를 포함한 평직 CFRP 복합재료의 파괴기준 연구
김상영(Sang Young Kim),금진화(Jin Hwa Geum),구재민(Jae Mean Koo),석창성(Chang Sung Seok) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.11
Recently, CFRP (Carbon Fiber Reinforced Plastic) is more and more using in the various fields because of a higher specific modulus, chemical property and so on. Most products using CFRP composite are manufactured by construction of components. Various independent components are joined with those by bolts and pins. Holes for bolts and pins are decreasing strength of components, because those act as notch in structures. In this paper, the fracture behavior of CFRP plain-woven composite plates containing circular holes is experimentally investigated to examine the effects of hole-size and specimen width on notched tensile strength. It is shown in this paper that the characteristic length according to the point stress criterion depends on the hole-size and specimen width. Notched tensile strength and characteristic length are shown a certain relation. Fracture criterion is redefined by this relation.
항공기용 복합재료의 충격후 잔류강도 예측 모델에 관한 연구
석창성(Chang-Sung Seok),최정훈(Jung-Hun Choi),박홍선(Hong-Sun Park),강민성(Min-Sung Kang),구재민(Jae-Mean Koo) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.11
Damage induced by low velocity impact loading in aircraft composite is the form of failure which is occurred in aircraft. As the consequences of impact loading in composite laminates, matrix cracking, delamination and eventually fiber breakage for higher impact energies can be occurred. Even when no visible impact damage is observed, damage can exist inside of composite laminates and carrying load of the composite laminates is considerably reduced. The reduction of strength by impact occurs various loading during the flight. The objective of this study is to evaluate residual strength behavior of composite laminates by impact loading and to predict residual strength of impacted composite laminates. Impact and Tensile test was carried out on composite laminates made of woven CFRP.