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SB41鋼 潛弧熔接部의 平滑 및 側面홈에 관한 疲勞크랙 傳播特性 : 大氣雰圍氣下에서의 擧動 at Room Temperature in Air
吳世旭,金在喆,李祥源 동아대학교 공과대학 부설 한국자원개발연구소 1986 硏究報告 Vol.10 No.2
Fatigue test was conducted on the smooth and side-grooved specimens fabricated from submerged are welded plate of SB41 steel. Test conditions were constant-loan-amplitude fatigue crack growth test with stress ratio 0.1, loading frequency 5㎐, sinusoidal waveform at room temperature in air. The results are summarized as follows: 1) Fatigue crack growth rate of weld metal is slightly lower than that of base metal. 2) Due to the effect of plastic constraint, side-grooved specimen shows somewhat faster fatigue crack growth rate than smooth specimen. 3) Welding residual stress affects fatigue crack growth rate.
單一試驗片의 安定히스테리시스 曲線에서 金屬의 硬化指數 推定에 관한 硏究
吳世旭,金在喆 동아대학교 공과대학 부설 한국자원개발연구소 1986 硏究報告 Vol.10 No.1
Fully reversed pull-push low cycle fatigue test under triangle cyclic waveform mode of constant strain control were conducted for SM15C and copper at the room temperature in air. Cyclic strain hardening exponent, n' was obtained from the cyclic δ-ε curve defined as the locus of tips of the stable hysteresis loops. Equivalent cyclic strain hardening exponent, n'_(eq), was obtained from the outer trace of a single stable hysteresis loop. Modified equivalent cyclic strain hardening exponent, n'_(eqm) , was obtained from the outer trace of a single stable hysteresis loop in the modified coordinate system. The relationship between n'_(eq), n'_(eqm), and n' was investigated with the test results. Equivalent cyclic strain hardening exponent n'_(eq) is considerable dependent upon the controlled strain range Δ^(ε) and decrease with increase of Δ^(ε). If Modified equivalent cyclic strain hardening exponent n'_(eqm) is calculated from the stable hysteresis loop at the modified coordinate system translated along the elastic slope, it closely approach to cyclic strain hardening exponent n'.
複合組織鋼의 回轉굽힘 疲勞크랙發生 및 傳播에 미치는 母相粒徑의 影響
吳世旭,金雄執 동아대학교 공과대학 부설 한국자원개발연구소 1984 硏究報告 Vol.8 No.1
The weight reduction and reliability of various steel used in industrial machinery have become a great importance as industry developes. For this reason a study on dual phase steel has been consisted different size of ferrite grain which has approximatly the constant plastic constraint effect and internal stress through heat treatments. They were prepared to able to apply the stress intensity factor equation K=σ√πℓ to the hollow shaft as assuming infinite plane without residual stress. Especially, it is possible to reduce the weight in hollow shaft and this hollow shaft is largely expected contribution in the machines operated with high speed or design manufacturing of aeronautical eguipments. Therefore, the fatigue crack behavior and fractography on the high-low stress level of M.E.F dual phase steel by rotary bending fatigue test were discussed. The results of the experiment are as follows. 1. The fatigue durability of the M.E.F dual phase steel is 1.6~1.8times greater than mild steel. 2. The initiation fatigue crack of the M.E.F dual phase steel and mild steel was created within 21~23%, 9% of fracture number of revolutions. 3. The smaller ferrite grain size is increased to m, decreased to C and located to high K range in M.E.F dual phase steel. 4. The fatigue and tensile fracture surface formed dimple facet and river pattern in M.E.F dual phase steel.
精密鑄造法의 硏究 : on the Shell Molding Process Shell Molding Process에 關하여
吳世旭 東亞大學校 1964 東亞論叢 Vol.2 No.2
The mass production and the progress of accurate castings are more asked for recently, and especially the superhard refractory alloy is more widely used according to the modern industrial development,but the casting and its machining have become very harden to be worked. And so nowadays we need the higher accuracy of casting practice. Shell molding process has been held very important as a new technical development of every foundry in the world for recent years,because the process is high-accurate,high-efficient and very regular and also it admit the capability of mass production of castings. The author has experimentally studied in this process energentically and continuously since May 1959, and he is quite sure that it is possible to industrialize the process in Korea. Of course we have still many problems not to be solved about the shell molding process even in the extreme of casting skill. Howeven we must not be backward in the advanced foreign casting skills and we must reform and develop our casting skill in Korea by developing more the method of the shell molding process. Shell mold casting is the process that uses a relatively thin-wall mold made by bonding silica or zircon sand with a thermosetting phenolic or urea resin. It has gained wide spread use because these castings offer many advantage over con-ventional sand casting. Shell mold casting is a practical and economical way to meet the demand for weight reduction, thinner sections, and closer toerances. The same materials can be cast by the Shell molding process as are cast in green sand molds. Use of the shell mold casting process provides following advantage; (1) High production rates and fewer finishing operations result in a lower unit cost for applicable parts. (2) Shell castings are made to closer tolerances than sand castings. (3) Shell molding provides an improved surface when compared with sand casting. (4) The greater precision of shell molding reduces and, in many cases, eliminates machining or grinding operations. (5) The insulating properties of the molds produce casting surface free of chil and with a more unifom grain structure. Although a shell mold is more expensive than a green sand mold, the possi-bility of reducing weight, minimizing machining and eliminating cores often results in savings sufficient to offset the mold cost.
SUS 316 강의 온도의존성 결정입경이 크리이프 거동에 미치는 영향
오세욱,강욱,Oh, Sae-Wook,Kang, Oug 대한용접접합학회 1983 대한용접·접합학회지 Vol.1 No.2
Austenitic stainless steel has been investigated widely for creep strength of heat resistant material and effects of grain sizes due to various solution treatment time under constant temperature. It was studied that effects of grain sizes subject to solution treatment temperature 1100.deg. C, 1125.deg. C, 1175.deg. C, 1250.deg C, and 1300.deg. C respectively on the creep strength, fracture behaviour and fractography of SUS 316 stainless steel. The experimental results obtained were as follows. 1. The optimum grain size for the maximum creep strength did not vary with creep testing temperatures and stress levels. 2. Among various grain sizes due to different solution treatment temperature, the optimum grain size for the creep strength was found 0.044mm. Also the size showed the minimum initial strain regardless creep temperature. 3. Garofalo's equation of creep rupture life was applied well to SUS 316 stainless steel. 4. The fractography of optimum size was ductile intergranular fracture of dimple type and showed along with the increase of grain size intergranular fracture of w type.