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세라믹/금속접합재의 고온피로에 따른 접합계면의 응력분포
박영철(Young-Chul Park),허선철(Sun-Chul Hue),김현수(Hyun-Su Kim),윤두표(Doo-Pyo Yun),김광영(Kwang-Young Kim) 한국해양공학회 1996 韓國海洋工學會誌 Vol.10 No.2
The ceramic has various high mechanical properties such as heat, abrasion, corrosion resistance and high temperature strength compared with metal. It also has low specific weight, low thermal expansibility, low thermal conductivity. However, it could not be used as structural material since it is brittle and difficult for the machining. Therefore, there have been many researches to attempt to join ceramic with metal which is full of ductility in order to compensate the weakness of ceramic.<br/> The problem is that residual stress develops around the joint area while the ceramic/metal joint material is cooled from high joining temperature to room temperature due to remarkable difference of thermal expansion coefficients between ceramic and metal. Especially, the residual stress at both edges of the specimen reduces the strength of joint to a large amount by forming a singular stress field.<br/> In this study, two dimensional finite element method is attempted for the thermal elastic analysis. The joint residual stress of ceramic/metal developed in the cooling process is investigated and the change of joint residual stress resulted from the repetitive heat cycle is also examined.<br/> In addition, it is attempted to clarify the joint stress distribution of the case of tensile load and of the case of superposition of residual stress and actual loading stress.
허선철(Sun-Chul Huh),박영철(Young-Chul Park),윤두표(Doo-Pyo Yun) 한국해양공학회 1998 韓國海洋工學會誌 Vol.12 No.4
Since the ceramic and metal are joined at high temperature, the residual stress will develop when it is cooled from bonding temperature due to remarkable difference of thermal expansion coefficient between ceramic and metal. Moreover, the edge of jointed interface makes singular stress field and this singular sσess field influences on the strength of joints. In this study. The effects of residual stress, mechanical load and repeat thermal cycle were estimated in the ceramic/metal joints. The change of singular stress field due to these effectswas analyzed. The results are as follow : 1) Strength of jcints was evaluated by the sσess singularity index λ and the intensity K of singular stress field. 2) The stress singularity index λ and the intensity K of singular stress field also increase as temperature of thermal cycle and its number of cycle increase. 3) In the case of mechanical load, the effect of residual stress reduces since the difference(Δλ) of stress singular index between existence and inexistence of residual stress decreases in proportion to the increasing of tensile load.
TiNi 섬유가 강화된 형상기억복합재료에 있어서의 응력해석
윤두표,김광영,박영철 東亞大學校 大學院 1998 大學院論文集 Vol.23 No.-
The shape momery alloy material is producted by the powder metallugy with TiNi alloy, before its mechanic properties are resulted by the stress analysis. Because the result of the stress analysis and that of the tensile test is similar, we would properly design the volume fracton and the strength of the shape memory alloy material.
Squeeze casting에 의한 TiNi/A1 6061 복합재료의 특성에 관한 연구
박영철,윤두표 동아대학교 공과대학부설 생산기술연구소 1998 生産技術硏究所硏究論文集 Vol.3 No.1
In this paper, it is attempted to reconfirm the "Intelligent" material properties using both the TiNi/Al6061 matrix composite made by sqeeze casting method. It is necessary to remove a tensile residual stress to increase the strength of composits. On the contrary, when compressive residual stress resides in matrix of composite in stread of tensile residual stress the strength of composite increase. This paper introduces the development of a high strength composite by using compressive residual stress. By using these specimens, shape memory strengthening effect in tensile strength above inverse transformation temperature of TiNi fiber was investigated. We occurs the pre-strain and volume fraction to discuss the effects of a composite strength.
최영호,윤두표,김광영,최병오 한국공작기계학회 2001 한국공작기계학회 춘계학술대회논문집 Vol.2001 No.-
In this paper, We have studied on the critical vibration limits of spindle unit for the high speed ball pen tip processing machine. The vibration of bearing can be measured by FFT, and the influence of vibration amplitude due to the Unbalance, bearing deflect, bite and timing belts tension are analyzed. So, the critical vibration limits of spindle is determined by the X, Z directional vibration of spindle Unit.