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Ti-6Al-4V 합금의 고온 성형시 미세조직 예측에 관한 연구
이유환,신태진,박노광,심인옥,황상무,이종수,Lee You Hwan,Shin Tae Jin,Park No Kwang,Shim In Ok,Hwang Sang Moo,Lee Chong Soo 한국군사과학기술학회 2004 한국군사과학기술학회지 Vol.7 No.4
A study has been made to investigate the high temperature deformation behavior of Ti-6Al-4V alloyand to predict the final microstructure under given forming conditions. Equiaxed and $Widmanst\ddot{a}tten$ microstructures of Ti-6Al-4V alloys were prepared as initial microstructures. By performing the compression tests at high temperatures$(700\~1100^{\circ}C)$ and at a wide range of strain rates$(10^{-4}\~10^2/s)$, various parameters such as strain rate sensitivity(m) and activation energy(Q) were calculated and used to establish constitutive equations. When the specimens were deformed up to strain 0.6, equiaxed microstructure did not show any significant changes in microstructure, while $Widmanst\ddot{a}tten$ microstructure revealed considerable flow softening, which was attributed to the globularization of a platelet at the temperature range of $800\~970^{\circ}C$ and at the strain rate range of $10^{-4}\~10^{-2}/s$. To predict the final microstructure after forming, finite element analysis was performed considering the microstructural evolution during the deformation. The grain size and the volume fraction of second phase of deformed body were predicted and compared with the experimental results.
Ti-6Al-4V합금의 열간 후방압출에 대한 성형 안정성 평가모델의 고찰
염종택,박노광,이유환,신태진,황상무,홍성석,심인옥,이종수,Yeom Jong-Taek,Park Nho-Kwang,Lee You-Hwan,Shin Tae-Jin,Hwang Sang-Mu,Hong Sung-Suk,Shim In-Ok,Lee Chong-Soo 한국군사과학기술학회 2004 한국군사과학기술학회지 Vol.7 No.3
The metal forming behavior of Ti-6Al-4V tube during hot backward extrusion was investigated with various forming stabilities or instabilities criteria. that is, Ziegler's instability criterion, dynamic materials model(DMM) stability criteria and Rao's instability criterion. These approaches also were coupled to the internal variables generated from FE simulation. In order to validate the reliabilities of three criteria, hot backward extrusions for Ti-6Al-4V tube making were carried out with different backward extrusion designs. The useful model for predicting the forming defects was suggested through the comparison between experimental observations and simulation results.
신태진,이유환,염종택,홍성석,박노광,심인옥,이종수,황상무,Shin Tae-Jin,Lee You-Hwan,Yeum Jong-Taek,Hong Sung-Suk,Park No-Kwang,Shim In-Ok,Lee Chong-Soo,Hwang Sang-Moo 한국군사과학기술학회 2004 한국군사과학기술학회지 Vol.7 No.2
Titanium alloys are vital elements for developing advanced structural components, especially in aerospace applications. However, process design for successful forming of titanium alloys is a difficult task, which has to be achieved within a very narrow range of process parameters. In this paper is a finite element based optimal design technique is presented and applied to volume fraction optimization process design in backward extrusion of titanium alloys.
김홍규 ( Hong Kyu Kim ),홍성석 ( Sung Suk Hong ),심인옥 ( In Ok Shim ) 한국복합재료학회 2011 Composites research Vol.24 No.2
이 논문은 전투차량의 주 장갑재료로 사용되는 금속장갑재료의 개발현황 및 방탄성능에 영향을 마치는 조직학적 요인들을 중심으로 방탄성 향상을 위한 요소기술을 살펴보고, 향후 급속장갑재의 발전전망에 대하여 서술하였다. 금속장갑재는 요구되는 방호특성에 따라 사용되는 합금계가 다르지만 강도와 인성을 최적화하여 위협 단에 대한 관통저항성 및 취성파단에 대한 저항성을 극대화하는 것이 필요하며, 이를 위해서는 금속재료의 방탄조건에서 특징적으로 나타나는 단열전단현상을 이해하고 적절히 제어하는 기술이 요구된다. This paper describes the state of the art for the development of metallic armor materials which are mainly used as armor plates of the combat vehicles. Several important micro-structural features affecting ballistic properties of the metallic armor are discussed. Optimization of the strength and toughness balance of the metallic armor is necessary for the improvement of the ballistic performance resulting from maximizing the resistance to the penetration of the bullet and also to brittle failure of the plates. Understanding and control of the adiabatic shearing phenomenon developed remarkably during high strain rate deformation is needed to prevent brittle failure of the metallic armor materials.
박종수 ( Jong Soo Park ),송영범 ( Young Beum Song ),임태홍 ( Tae Hong Lim ),홍성석 ( Sung Suk Hong ),이흥렬 ( Hung Reyl Lee ),심인옥 ( In Ok Shim ) 대한금속재료학회 ( 구 대한금속학회 ) 2006 재료마당 Vol.19 No.5
앞에서 언급되어진 Titanium 합금 빌렛에서의 결함종류, 원인 분석 및 해결방안을 표2에 요약하였다.
열분석법에 의한 Cu 를 함유한 HSLA 강의 시효 거동에 관한 연구
박태원,김영우,심인옥,강창윤 대한금속재료학회(대한금속학회) 1995 대한금속·재료학회지 Vol.33 No.1
The aging behavior of Cu-bearing HSLA steels was studied by using differential scanning calorimetry (DSC), transmission electron microscopy and hardness tester. Two heat evolution peaks were observed during DSC scans over the temperature range of 25∼590℃ at a heating rate of 5℃/min. The peaks appeared in low(241∼319℃ : HSLA-A, 224∼310℃ : HSLA-B) and high temperature (514℃∼ 590℃ : HSLA-A, 451∼558℃ : HSLA-B) are attributed to the formation of coherent Cu-clusters and noncoherent ε-Cu phase, respectively. And at a rapid heating rate over 7.5℃/min, another peak between these two peaks was observed in the temperature range of 300∼370℃. This peak is conjectured to be due to the formation of 9R martensite structures proposed by Othen et al. It will be necessary further research to identify this peak clearly. It was confirmed that as aging proceeds, the coherent bcc Cu-clusters transform to noncoherent fcc ε-Cu phase. In the case of the aging to peak hardness at 300℃ and 400℃, the coherent Cu-clusters contributed to the hardening. As aging time and temperature increase over peak hardness, noncoherent ε-Cu are formed and hardness decreases. The activation energy due to the formation of coherent bcc Cu-clusters in HSLA-B steel is 55㎉/mole. And those due to the formation of nonchorent ε-Cu phase in HSLA-A and HSLA-B steels are 59㎉/mole and 51㎉/mole, respectively. These are similiar to the activation energy(58㎉/mole) for the solute diffusion of Cu in α-Fe.
정전위 SSRT법에 의한 해양구조물용 Cu함유 고장력저합금강의 수소취성한계전위 규명에 관한 연구
김성종,박태원,심인옥,김종호,김영식,문경만 한국해양대학교 해양과학기술연구소 2001 硏究論文集 Vol.10 No.1
A marine structural material was well known to have high tensile strength, good weldability and proper corrosion resistance . Cu-containing high strength low alloy (HSLA) steel was recently developed for their purposes mentioned above, And the steel is free about preheating for welding, therefore it is reported that shipbuilding cost by using it can be saved more or less. However the marine structural materials like Cu-containing HSLA steel are being generally adopted with cathodic protection method in severe corrosive environment like natural sea water but the high strength steel may give rise to Hydrogen Embrittlement due to over protection at high cathodic current density for cathodic protection. In this study, Cu-containing HSLA steel using well for marine atructure was investigated about the susceptibility of Hydrogen Embrittlement as functions of tensile strength, strain ratio, fracture time, and fracture mode, etc. and an optimum cathodic protection potential by slow strain rate test(SSRT) method as well as corrosion properties in natural sea water. And its corrosion resistance was superior to SS400 steel , but Hydrogen Embrittlement susceptibility of Cu-containing HSLA steel was hider than that of SS400 steel. However Hydrogen Embrittlement of its steel by SSRT method was showed with pheonomena such as decreasing of fracture time. strain ratio and fracture mode of QC (quasi-cleavage) Eventually it is suggested that an optimum cathodic protection potential not presenting Hydrogen Embrittlement of Cu-containing of HSLA steel by SSRT method was from-770mV(SCE) to - 900mV(SCE) under natural sea water. (Received September 21, 2000)