유한요소법을 이용한 복합조직강의 경도비 변화에 따른 응력-변형거동에 관한연구

吳澤烈,張現貴 慶熙大學校 材料科學技術硏究所 1992 材料科學技術硏究論集 Vol.5 No.-

Mechanical properties of dual phase steel are affected by the microstructural factor, such as, martensite volume fraction, grain size of ferrite, hardeness ratio of ferrite-martensite, connectivity and chemical properties. In this study, the tensile test was carried out to analyze the tensile characteristic of the Ferrite-Martensite dual phase steel with the Hardeness Ratio of four kinds. The result obtained could be summarized as follow ; The calculated Stress-Strain curves for four hardeness ratios were compared with their corresponding experimental curves, and in general, good agreements were found. After tensile tests were done at various tempering temperatures, we had a result that the tensile strength at 200℃ was the largest. It was found that for a given hardeness ratio, the calculated stress-strain curve was higher than experimental curve. The more reduce the hardeness ratio, the more narrow the gaps between the experimental curve and the calculated curve. It is related with the plastic constraint factor K.

1998학년도 신입생 실태조사

오택열,지은림 경희대학교 수원캠퍼스 학생생활센터 1999 학생생활연구 Vol.3 No.-

레이저를 이용한 Tailored Blank 용접 판재의 피로거동

오택열,권윤기,이종재,곽대순 韓國工作機械學會 2000 한국생산제조학회지 Vol.9 No.4

For the Tailor Welded Blank sheet used for automobile body panel, the characteristics of fatigue strength and crack propagation behavior were studied. The thickness of specimen was joined to be same (0.9mm+0.9mm) and different (0.9mm+2.0mm). As a base test, mechanical properties around weld zone were examined. The results indicated that there were no significant decreases in mechanical properties, but hardness around weld bead was 2.3 times greater than base material. The fatigue strength was the highest when the loading direction was parallel to the welding direction, which was about 85% of tensile strength of base metal. It was decreased by 8.5% when the thickness of specimen and base metal was different, and it was increased by 25% when pre-strain was applied. The crack propagation rate was noticeably decreased around weld line and rapidly increased as it passed through weld line. Reviewing the shape of the crack propagation, crack width around weld line was wide around the weld zone due to retardation of crack growth, but it became narrow passing weld line due to decreased toughness.

1997학년도 신입생 실태조사

오택열,지은림,송소원 경희대학교 수원캠퍼스 학생생활센터 1998 학생생활연구 Vol.2 No.-

複合組織鋼의 引張强度特性에 관한 硏究

吳澤烈 慶熙大學校 1986 論文集 Vol.15 No.-

A study has made of the tensile characteristics of dual phase(martensite plus ferrite) steels produced when a low carbon steel is quenched from either the austenite of austenite plus ferrite phase fields. The results can be summarized as follows; 1. The hardness ratio of second phase martensite to ferrite phase and reduction of area are decreased with increasing the martensite volume fraction when dual phase structures are made of a steel having the same composition. 2. Ductile fracture decreases when the intercritical temperature is increased and martensite hardness is decreased, because of the composite hardness increasing with increasing the intercritical temperature. 3. Tensile and yield strength of dual phase steel are function of martensite volume fraction, and the yield ratio showed relative low values. 4. The morphology of martensite in a low carbon steel through the step quenching is a lath type, and the true uniform strain is decreased according to the increase of martensite volume fraction, but it is higher than HSLA steel in the same strength level.

Dual phase steel의 衝擊破壞特性에 關한 硏究

吳澤烈 慶熙大學校 1982 論文集 Vol.11 No.-

In this report strength, ductility, formability, energy absorption and deformed angle of dual phage being accompanied martensite volume fraction under the dynamic Impact bending load, is present. The reciprocal relations of thess factor which are studied in connection with variation impact velocity are as follows. (1) Impact maximum load is increased linearly in proportion to Martensite volume fraction increase rate. (2) Imapat maximum load is rapidly increased until fraction on the other hand, is slowly increased after fraction. (3) Loading time is nearly decreased linearly because ferrite volume decrease rate is constant. (4) Due to ferrite volume, energy absorption is decreased in proportion to martensite volume increase rate. (5) Reformed angle condition is similar until impact velocity reach 2.71 m/sec.

보이드 생성기구에 의한 복합조직강의 연성 파괴거동에 관한 연구

吳澤烈,崔明振,楡龍錫,金松正 慶熙大學校 材料科學技術硏究所 1993 材料科學技術硏究論集 Vol.6 No.-

Ductile Fracture of Dual Pase Steel begins with void nucleation, at Martensite-Ferrite interface or deformed Martensite particle. In this study void nucleation, void growth, void volume fraction and void coalescence at given strain were studied in dual phase steel. Therefore, by means of the heat treatment of low corbon steel the study deal with void nucleation and void growth for ferrite grain sizeof dual phase steel. Void nucleaton and void growth with increasing strain are shown depend upon the ferrit grain size. The number of voids and volume fraction of voids generary increase as ferrite grain size decrease. At the close to fracture the void coalescence in the direction of the applied tensile stress, but near the fracture surface they linked in direction transverse to the tensile axis.

衝擊破壞擧動에 영향을 주는 連結度의 效果

吳澤烈 慶熙大學校 材料科學技術硏究所 1988 材料科學技術硏究論集 Vol.1 No.-

Mechanical properties of dual phase steel is affected by microstructural factors. Microstructural factors are composed of martensite volume fraction, grain size, hardness ratio, connectivity and chemical composition etc. In this study, connectivity of low Mn steel specimen on which other microstructural factors were made be constant has been changed by treatment process. This ferrite - Martensite dual phase specimen had given impact bending load, thereby impact strength, impact loading time and absorbed energy etc. of specimen was investigated. Some important results in this study can be summerized as follows. 1. The more connectivity increase, the more impact strength increase. Impact strength was increased according to the increase on impact velocity. 2. Based upon the velocity to cause fracture, impact load time curve shape devided into two.

塑性拘束에 의한 延性-脆性破壞擧動에 관한 硏究

吳澤烈 慶熙大學校 材料科學技術硏究所 1989 材料科學技術硏究論集 Vol.2 No.-

The problem on the dynamic ductile-brittle behavior is an important factor to the design of ferrite-martensite dual phase steel. The macroscopic fracture behavior of the dynamic ductile-brittle materials is related to the microscopic fracture behavior, which is explained by the micro slip together with crack initiation and propagation. Moreover, the mechanical properties of ferrite-martensite dual phase steel are affected by the microstructural factors, such as, martensite volume fraction, grain size of ferrite, strength ratio of ferrite-martensite, connectivity and chemical components etc. Therefore, this study investigated the rule of martensite on the microscope fracture behavior, the formation of micro crack and slip, the dunamic ductile-brittle fracture behavior, and plastic restraint of martensite on the plastic deformation.

有限要素法에 의한 複合組織鋼의 應力-變形曲線에 關한 硏究 : Martensite Volume Fraction을 中心으로

吳澤烈,白英男,金石煥 慶熙大學校 材料科學技術硏究所 1990 材料科學技術硏究論集 Vol.3 No.-

Mechanical properties of dual phase steel is affected by the microstructual factor, such as, martensite volume fraction, grain size of ferrite, strength ratio of ferrite-martensite, connectivity and chemical properties. In of that, martensite volume fraction affects mainly on mechanical properties of dual phase steel. In this study, the tensile test was carried out in order to analyze the tensile characteristic of the ferrite-martensite dual phase steel with the martensite volume fraction of four kinds. The calculations of stress-strain curve are compared with the experimental result and finite element method result by MSC/NASTRAN. The result obtained could be summerized as follow : It was found that for a given volume fraction, the calculated stress-strain curve was higher for experimental result than finite element method result. The calculated stress-strain curve for four different martensite volume fraction were compared with their corresponding experimental curves, and in general, good agreement was found. The maximum flow stress difference between the calculated and the experimental result occurs at the nearly begining of the plastic deformation, these are the maximum difference between the flow stresses of the calculated and experimental curve and a higher strain level, the differences are reduced.