• 한국압력기기공학회 논문집
• /
• 제11권1호
• /
• pp.12-19
• /
• 2015

As a measure of improving the mechanical properties of a diffusion bonded joint of a ferritic/martensitic steel (FMS), the post-bonding heat treatment (PBHT) is applied. In the temperature range of normalizing condition ($950-1,050^{\circ}C$), diffusion bonding is employed with compressive stress (6 MPa). Due to the martensite structure distributed in the matrix, Vicker's hardness values of the as-bonded are much higher than those of the as-received. Through the PBHT for 1 h at $720^{\circ}C$, hardness values are recovered to as low as those of the as-received condition. Also, tensile properties of PBHT are similar to those of the as-received at up to the test temperature of $550^{\circ}C$, when the diffusion bonding is carried out over $1,000^{\circ}C$. Based on the creep-rupture testing performed at $650^{\circ}C$ in air environment, the joint efficiency of the PBHTed specimens is about 80% in, which is higher than that of the as-bonded specimens.

• 한국동물생명공학회지
• /
• 제36권4호
• /
• pp.194-202
• /
• 2021

In this study the effect of vitamin C administration on pregnancy rates during summer heat stress in dairy cows was examined. A total of 80 Holstein-Friesian cows were divided into control and treatment groups (n = 40 each). Control group animals were given 10 mL isotonic normal saline, and treatment group, Vitamin C (4 mg/kg) on artificial insemination day (day 0) and 4^th, 8^th and 12^th day post insemination. Pregnancy diagnosis was performed on 30^th day post insemination by ultrasonography. Blood samples were randomly taken from 11 animals from each group. Serum P₄, GSH, MDA and plasma 8-OHdG levels were determined by using ELISA method. Results showed that 8-OHdG levels were lower in treatment group on day 4, 8 and 12 (p < 0.05) compared with the control group. Similarly, pregnancy rate was higher in treatment group (32.5%) than control (22.5%), respectively. However, MDA, P₄ and GSH levels were similar in both groups at 4^th, 8^th and 12^th day. A gradual increase in P₄, and MDA levels, and a strong positive correlation between 0, 4^th (r = 0.54), 4, 8^th (r = 0.59) and 8, 12^th (r = 0.51) day was found. Similarly, GSH levels also showed positive correlation at days 0, 4^th (r = 0.47) and 4, 8^th (r = 0.56). However, a strong negative correlation (r = -0.56) between MDA day 0, and GSH day 8 was found. In conclusion, vitamin C application during insemination period in postpartum cows increases pregnancy rate, and reduces oxidative stress metabolite 8-OHdG levels.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2003년도 춘계학술대회
• /
• pp.334-339
• /
• 2003

The welding residual stress has on important effect on welding deformation, fatigue fracture, buckling strength, brittle fracture, etc. For the purpose of relaxation of welding residual stress, post welding heat treatment is widely used. In this paper, residual stresses were calculated by two dimensional thermal elasto-plastic analysis using finite element method. Heat transfer analysis are performed by transient analysis. Also structure analysis are carried out by of thermal-mechanical coupled analysis. Numerical analysis are used by ANSYS 5.7.

• 한국산업융합학회 논문집
• /
• 제24권5호
• /
• pp.517-523
• /
• 2021

In this study, in the selection of materials for the elements of a small plant, those with high resistance to corrosion are selected and the material properties of coatings for corrosion prevention are evaluated. In addition, corrosion characteristics and material analysis were performed on the welded part, and the hardness characteristics of the welded part, heat-affected part, and the base metal were evaluated. In the case of the post-weld-heat-treated(PWHT) specimen, the corrosion resistance of STS 316 was lower than that of the specimen without the PWHT due to the formation of intergranular carbide. As a result of evaluating the distribution of the hardness of the weld before and after the PWHT, the hardness of the specimen after the PWHT increased by about 20 Hv. As a result of the corrosion test on the welded specimen, the weight loss tended to increase as the time increased. In the case of the PWHT specimen, the corrosion resistance tended to be significantly lower than that of the specimen without PWHT due to the formation of intergranular carbide.

• 한국응용곤충학회지
• /
• 제54권1호
• /
• pp.17-23
• /
• 2015

국내 사과를 외국으로 수출하기 위해서는 수입국의 검역 대상 해충을 완전히 제거하는 것이 필수적이다. 이를 위한 수확 후 해충 사멸 기술로서 환경조절열처리(controlled atmosphere and temperature treatment system: CATTS) 기술이 개발되고 있다. 본 연구는 상이한 가해 습성으로 사과 과실에 피해를 주는 두 해충에 대해 CATTS의 사멸조건을 결정하였다. 사과애모무늬잎말이나방(Adoxophyes paraorana)은 사과 과실 표면을 가해하는 해충인 반면 복숭아명나방(Dichocrocis punctiferalis)은 과실의 내부를 가해한다. 여러 가해 발육태 가운데 두 곤충 모두 5령 유충이 열에 대한 내성이 가장 높았다. 고농도(15%)의 이산화탄소, 저농도(1%) 산소 및 $46^{\circ}C$ 온도 조건에서 1 시간 동안 처리하는 CATTS 처리조건은 사과애모무늬잎말이나방 5령 유충을 100% 사멸시켰다. 그러나 동일한 CATTS 조건에서 복숭아명나방 5령 유충은 88%의 사멸 효과를 보였으며, 100% 사멸 효과를 나타내기 위해서는 2 시간의 열처리를 요구했다. 이를 바탕으로 사과를 가해하고 있는 두 종의 5령 유충 3,000 마리 이상에 대해서 각각 CATTS 처리 효과를 확증하였다. 본 연구는 완전 사멸을 위해서는 심식충이 비심식충에 비해 장기간 CATTS 처리가 요구 된다는 것을 보여 주었다.

• Journal of Welding and Joining
• /
• 제5권2호
• /
• pp.9-16
• /
• 1987

Post weld heat treatment (PWHT) is carried out to increase the fracture toughness in heat affected zone(HAZ) and remove the residual stress. There occur some problems such as toughness decreement and stress relief cracking(SRC) in the coarse grained HAZ subjected to the effect of tempering treatment. Especially, embitterment of structure directly relates to the mode of fracture and is appeared as the difference of fracture surface, that is, grain boundary failure. Therefore, in this paper, PWHT was carried out under the stress of 0, 10, 20 and $30kg/cm^2$ to simulate residual stress in HAZ welded by heat input of 10, 30 and 40KJ/cm. Applied stress in weld HAZ during PWHT assisted precipitin of over saturated alloying element in the structure, and grain boundary failure according to welding heat input didn't almost appear at the heat input of 10 KJ/cm, but it appeared from being the applied stress of $30kg/cm^2$ at $30KJ/cm and 20kg/mm^2$ at 40KJ/cm.

• 동력기계공학회지
• /
• 제10권1호
• /
• pp.77-82
• /
• 2006

In this study, dissimilar friction welding were produced using 15mm diameter solid bar in chrome molybedenum steel(SCM440) to carbon steel(S45C) to investigate their mechanical properties and the relationship between the weld parameters and the nondestructive coefficients, such as AE counts and ultrasonic attenuation coefficient. The main friction welding parameters were selected to endure good quality welds on the basis of visual examination, tensile tests, Vickers hardness surveys of the bond of area and heat affected zone. The specimens were tested as-welded and post weld heat treated(PWHT). The tensile strength of the friction welded steel bars was increased up to 100％ of the S45C base metal under the condition of all heating time. The ductility of PWHT specimens is higher than as-welded.

• 열처리공학회지
• /
• 제37권1호
• /
• pp.1-8
• /
• 2024

Phase stability of tetragonal crystals in yttria-stabilized zirconia ceramics is dependent on the content of yttria and the heat-treatment condition, related with mechanical properties. In this study, we fabricated the 1.5 mol% yttria-stabilized zirconia (1.5Y-YSZ) ceramics by cold isostatic pressing (CIP) and post-sintering at temperature range of 1200 to 1350℃ for 2 hours and investigated the sintered properties and microstructural evolution. Sintered and microstructural parameters, i.e, apparent density, grain size and phase composition of 1.5Y-YSZ ceramics were mainly dependent on the sintering temperature. Maximum sintered density of 99.4 % and average grain size of 200-300 nm could be obtained from the heat-treatment condition above sintering temperature at 1300℃ for 2 hours, possessing the superior mechanical hardness with 1200 Hv. However, phase stability of tetragonal grains in 1.5 YSZ ceramics is very low, inducing the phase transformation to monoclinic crystals on specimen surface during cooling after heat-treatment.

• 한국염색가공학회지
• /
• 제30권3호
• /
• pp.216-226
• /
• 2018

The combination dyeing have been attempted to get the various color. The objective of this research was to study the color developing effects on cotton fabrics dyed with persimmon, catechu and combination of the both by heat treatment process. These dye were applied on bleached cotton fabrics for the dyeing before post mordanting with aluminium potassium sulfate, copper sulfate, and iron sulfate. The various color changes on cotton fabric were measured by color spectrophotometer. The heat treatment of temperature around $150^{\circ}C$ for an hour can reach the highest color developing. The dyed fabrics with mordanting were heated for specific time period, which was compared without the mordanting. The post mordanted fabrics showed that more various colors can be obtained using combination dyeing. K/S values of dyed fabrics with Al, Fe, and Cu mordants were higher than the cases without mordants. The Cu mordanted fabric showed very effective color developing by the heating process. The fabrics dyed with catechu lowered L* value with little changes in a* and b* values, while the a* and b* values became higher with heat treatment. The fabrics dyed with persimmon has the lowest L* value and more changes in a*, b* value with heating process. Therefore, K/S values can be increased effectively by the combination dyeing of persimmon and catechu. Colorfastness to washing in color change was grade 2-3 in non-mordanted fabric, and grade 3 in mordanted fabric. Lightfastness of the dyed fabrics was above grade 4.

• 한국화재소방학회논문지
• /
• 제16권1호
• /
• pp.77-83
• /
• 2002

본 연구의 목적은 UL(미국보험협회)에 규정된 암모니아 대기상태에서 측벽형 스프링클러 헤드 디플렉터의 응력부식균열을 막기 위한 방안을 제시하는 것이다. 성형 후처리로서 성형제품 그대로와 샌드블래스팅 처리한 것, 그리고 풀림 열처리를 한 것 등 3가지에 대하여 부식시험을 실시하였다. 금속현미경으로 시편을 관측한 결과 잔류응력이 부식균열을 일으키는 주요원인이며, 극심한 부식조건에서 발생할 수 있는 잔류응력을 적절한 열처리를 통해 제거하거나 감소시킬 수 있어 파손을 방지할 수 있다는 것을 확인 하였다.