미소원공을 갖는 SF50A재의 피로크랙전파거동에 관한 연구

정재강,김건호,방웅주 조선대학교 생산기술연구소 1994 生産技術硏究 Vol.16 No.2

In this paper, the fatigue crack propagation behaviors are investigated experimentally for the material SF50A forged steel with small circular defects. The summerized results are as follows; 1. The relation between ratio of life N/N_(f) and crack length 2a was straight line aproximately in plot, the material constant m was 0.90-1.66. 2. In the relation to d(2a)/dN and 2a, the unstable propagation region in crack propagation rate appeared at crack initial point. The inclination of these relations in stable region was 1 approximately. 3. The crack propagation rate predition used d(2a)/dN=△K proposed by Paris did not apply because reliability of stress at the more large defect and the high stress was the more large. 4. Mechanical variables proposed by Nisitani, d(2a)/dN = Aσ_(α)^(n)α^(p) was capable of applicaition as a formula to crack propagation rate pγedition because the reliability of stress disappeared.

Al5083-O 알루미늄합금의 보호가스 혼합비율 및 입열량에 따른 GMA용접 특성에 관한 연구

정재강,양훈승,이동길 대한용접접합학회 2002 대한용접·접합학회지 Vol.20 No.2

This study was to evaluate GMA welding characteristics of the A15083-O aluminum alloy according to the shield gas mixing ratio and heat input change. The GMA welding of the base metal was carried out with flour different shield gas mixing ratios(Ar100%+He0%, Ar67%+He33%, Ar50%+He50%, and Ar33%+He67%). Regarding the if1uence on the bead shape of the shield gas mixing ratio and heat input, the bead width was greatest in Ar100%+He0% mixture. But the penetration depth and area were greatest in Ar33%+He67% mixture considering that the lower Ax gas ratio, the higher bead depth and area. Also, dilution was also best in the shield gas mixing ratio. The size and number of deflects were least in Ar33%+He67% mixture. Higher He gas ratio resulted in less deflects detected by the radiographic inspection.

旋削工具에 發生하는 Chatter 振動의 實驗的 解析

鄭在康,曺圭宰 조선대학교 동력자원연구소 1984 動力資源硏究所誌 Vol.6 No.1

A mechanism and energy of the self-excited tool chatter vibration is experimentally investigated in this paper. The results obtained are as follows ; 1. The tool vibration of the primary chatter vibration where the exciting energy is supplied by contact of the flank surface with the workmaterial due to the bending of the tool shank. 2. Exciting energy of the tool chatter vibration is supplied during the tool moves to lower direction and consumed in the next half cycle to upper direction. 3. The frequency of tool chatter vibration is related with cutting speed

SS41강 용접부의 동적균열개시인성 평가

정재강,김건호 대한용접접합학회 1994 대한용접·접합학회지 Vol.12 No.2

In the present study, the dynamic crack initiation toughness and total absorbed energy behavior of Heat Affected Zone(HAZ) was experimentally evaluated for SS41 steel welding. The materials were submerged arc-welded SS41 steel plate with thickness 19mm. The test temperature range was from $20^{\circ}C$(room temperature) to $-70^{\circ}C$ The HAZ of welding were divided into three sub-zones for analysis; H1, H2, H3, according to the distance from the fushion line. From the experimental studies, the reference value of dynamic crack initiation toughness $(J_{Id(R)})$ can be use to estimate dynamic fracture toughness characteristics of steel welding.

보호가스 혼합비율에 따른 Al5083-O 용접부의 저온 인성에 관한 연구

정재강,양훈승,이동길 대한용접접합학회 2002 대한용접·접합학회지 Vol.20 No.6

In this study, the low temperature toughness was evaluated by using the instrumented Charpy impact testing procedures for A15083-O aluminum alloy used in the LNG carrying and storage tank. The specimens were GMA(Gas Metal Arc) welded with four different mixing shield gas ratios (Ar100%+He0%, Ar67%+He33%, Ar50%, and Ar33%+He67%), and tested at four different temperatures(+25, -30, -85, and $-196^{\circ}C$) in order to investigate the influence of the mixing shielding gas ratio and the low temperature. The specimens were divided into base metal, weld metal, fusion line, and HAZ specimen according to the notch position. From experiment the maximum load and displacement were shown the highest and He lowest at $-196^{\circ}C$ than the other test temperatures. The absorption energy of weld metal notched specimens was not nearly depends on test temperature and mixing shield gas ratio because the casting structure was formed in weld metal zone by melting welding wire. On the other hand, the others specimens was shown that the lower temperature, the higher absorption energy slightly up to $-85^{\circ}C$ but the energy was decreased so mush at $-196^{\circ}C$.

常溫에서 2段階應力을 받는 SM45C材의 疲勞强度에 관한 硏究

정재강,김건호,최종노 조선대학교 생산기술연구소 1993 生産技術硏究 Vol.15 No.2

The purpose of this thesis is to study the fatigue limit when the constant stress is applied to both notched and unnotched specimens, and investigate the effects to the constant stress level when the two level stress is applied to the same specimens at the room temperature. The specimen used for this test is SM45C, mechanical structural steel annealed. Also, experimental results is compared with the damage values obtained by theoretical Miner's rule.

旋削加工에서의 Burrs의 生成原因과 特性에 관한 硏究

鄭在康 조선대학교 생산기술연구소 1982 生産技術硏究 Vol.1982 No.-

The mechanisms causing machining burrs and two typical analistical models that predict burr properties are presented. The experimental study has been made to prevent the burrs produced on workpiece edges in turning operations. The effect and correlations between cutting conditions and burr sizes, and a mechanism of burr formation are discussed. The experimental results obtained are as follows; 1) The deformation of a workpiece edge by cutting force causes burrs. And there are two type of burrs, large size burrs and extremely small size burrs. 2) Small size burrs are produced at large depth of cut, small feed rate, large nose radius and small side cutting edge angle. 3) Brittle materials easily produce the small size burrs and ductile materials easily produce the large size burrs.

250 C에서 2段階應力을 받는 構造用鋼의 疲勞强度에 관한 硏究

정재강,김건호,최종노 조선대학교 생산기술연구소 1993 生産技術硏究 Vol.15 No.2

The purpose of this thesis is to study the fatigue limit when the constant stress is appiled to both notched and unnotched specimens, and investigate the effects to the constant stress level when the two level stress is applied to the same specimens at the 250℃. The specimen used for this test is SM45C, mechanical structural steel annealed. Also, experimental results is compared with the damage values obtained by theoretical Miner's rule.

미소원공을 갖는 선박 추진축재의 피로크랙 전파 거동에 관한 연구

정재강,김건호 한국마린엔지니어링학회 1995 한국마린엔지니어링학회지 Vol.19 No.2

In this paper, fatigue crack propagation behaviors were investigated experimentally for the materials, carbon steel forgings (SF45A, SF50A, SF60A) which are used in the marine propeller shaft. The results obtained are as follows: The number of cycles required to grow crack length 1.30mm from microcrack initiation was about 60% of the total fatigue life. Fatigue crack propagation rate was expressed by the equation d(2a)/dN_B 2a/$N_f$ and the result was agreed well with the experimented data. And the equation d(2a)/dN=$C{\sigma}_a^m(2a)^n$ was evaluated also. Obtained material property m and n are 3~5 and 1-1.5 respectably, and the result was reasonably agreed to the data obtained from experiments.

Submerged Arc 鎔接部의 動的破壤靭性 評價에 關한 硏究

鄭在康,洪錫柱 조선대학교 생산기술연구소 1991 生産技術硏究 Vol.13 No.1

In the present study, the dynamic fracrure behavior of steel weldments was experimentally evaluated with an instrumented Charpy impact test using pre-cracked Charpy V-notched specimens. The materials are submerged arc-weled plates of SM45C steel with a thickness of 19mm. The tested temperature renge was from +20℃(room temperature)to -160℃ The weldments were divided into the sub-zones for analysis : weld metal, grain coarsened HAZ, grain-refined HAZ, partially transformed HAZ and unchanged base metal. Empirical correlations were investigated between the dynamic fracture toughness (K_(Id)) and both the crack initiation energy(K_(Id)) and the total absorbed energy of fracture (Ei/A), and K_(Id) was estimated from the energy Ei/A or Et/A using the empirical equations determined.