• Transactions of Materials Processing
• /
• v.8 no.1
• /
• pp.57-64
• /
• 1999

The press formability analysis of welding parts was studied in the current work by the tailor welded blank. As the body panel is used in the press forming of welding parts by a weld method of the tailor welded blank, the following conditions are demanded: 1) The strength of welding parts must be the higher than base metals. 2) After the welding, severe welding deformatins must be avoided. 3) The press formability of welding parts is similar to that of many base metals. 4) The productibility of a welding has to be higher. There are many welding methods satisfying these conditions, but the purpose of this study is to inbestigate the upset weldability and formability of the material (SPCC). SPCC steel sheet showed good weldability and formability under some welding conditions. The experimental results were discussed by the evaluation of the results obtained from tensile tests, hardness tests, micro-structures and Erichsen cup test was a little lower than that of parent material.

• Transactions of the Korean Society of Machine Tool Engineers
• /
• v.15 no.1
• /
• pp.102-107
• /
• 2006

This study investigates the properties as the difference friction welding area on SM25C steel rod. The tensile and bending strength and of welded joints, the hardness distribution of welds, the microstructure of welds and the tensile fracture surfaces were mainly investigated through this experiment. The fixed friction welding conditions were revolution 2000rpm, friction pressure 70Mpa, friction time 1.5sec, upset pressure 100Mpa, upset time 2.0sec, upset length 2.8mm and changeable friction welding parameter was friction welding area.

• Proceedings of the Korean Nuclear Society Conference
• /
• 1996.05c
• /
• pp.353-358
• /
• 1996

Hot cell에서의 활용을 전제로 한 용접기술 개발을 목적으로 가용한 용접방식의 적용 타당성 및 용접부 특성에 대해 조사, 분석하였다. 적용한 용접방식은 Upset butt저항용접, GTAW, LBW이었다. 각 용접방식에 따른 기계적 시험에 있어서 공히 용접부가 아닌 피복관 파괴로 연료봉 봉단용 접부의 품질요건을 만족하였으며, 용접부 형상 및 미세경도 분석에 있어서는 열영향부가 GTAW, Upset butt저항용접, LBW의 순으로 작게 나타났다. 또, 미세조직상으로는 거의 유사한 조직의 martensitic $\alpha$'와 Widmanstatten조직이 혼합되어 있었다. 따라서 Upset butt 저항용접, GTAW, LBW 방식을 적용한 Zr-4 핵연료 피복관의 봉단용접은 가능했으며, Hot cell 적용을 고려시 LBW 용접방식이 적절하였다.

• Journal of Welding and Joining
• /
• v.8 no.4
• /
• pp.20-26
• /
• 1990

In this study, to make research on its optimum condition in friction weld when the heating pressure is change during 1.6 to 3.0 $kgf/mm^2$, the experiment was performed with metal bearing under various condition; 1600 r.p.m spindile speed, 0.6 $kgf/mm^2$ preheating pressure, upset pressure 2.6 $kgf/mm^2$, 0.5 seconds preheating time, 1.7 seconds heating time, water and air was ejected 6 $kgf/mm^2$ into the bushing. On the basis of the experimental results, the following conclusion are drawn; 1) At the area of weld interface, the heardness is shown the maximum value and heat-affected zone about 0.5mm both sides. 2) Bending strength is shown the optimum heating pressure 2.4 kgf/mm. 3) With the approach of the flash, Sn is increased only 2 mm in A-alloy structure.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2004.10a
• /
• pp.325-328
• /
• 2004

This paper deals with void crushing behavior by ingot forging process which consists of sequential operations of upset forging and bloom forging. The predicted results of void crushing behavior by the simplified global-local method using F.E. analysis showed that the inherent void at the top region of the ingots remains incompletely crushed even after several forging operations. From the results of the hot upset forging test using the billets with drilled voids, it was found that the bonding efficiency of the void after forging process increases with an increase in deformation, and a decrease of initial diameter of voids.

• Journal of Welding and Joining
• /
• v.17 no.5
• /
• pp.69-76
• /
• 1999

A copper-tungsten sintered alloy(Cu-W) has been friction welded to a tough pitch copper in order to investigate the effect of upset pressure on friction weldability. Under the condition of friction time 0.8sec, upset pressure 150MPa, the tensile strength and Charpy impact value of the friction welded joint were 336MPa, $400KJ/m^2$ respectively. And highest temperature of the weld measured was below $800^{circ}K$ which is very lower than melting point of Cu($1356^{circ}K$). Under the same conditions, W grains picked up in Cu matrix from Cu-W profitably affected on these mechanical fracture, and were dispersed in Cu by plastic flow during brake time.

• Journal of Magnetics
• /
• v.20 no.1
• /
• pp.21-25
• /
• 2015

Fine Nd-Fe-B-type particles were prepared by ball milling of different types of Nd-Fe-B precursor materials, such as die-upset magnet, HDDR-treated material, and sintered magnets. Coercivity dependence on the grain and particle size of the powder was investigated. Coercivity of the milled particles was reduced as the particle size decreased, and the extent of coercivity loss was dependent upon the precursor material. Coercivity loss in the finely milled particles was attributed to the surface oxidation. The extent of coercivity loss in the fine particles was closely linked to grain size of the precursor materials. Coercivity loss was more profound for the fine particles with larger grain size. Contrary to the fine particles from the sintered magnets with larger grain size the fine particles (~10 um) from the die-upset magnet and HDDR-treated material with much finer grain size still retained high coercivity (> 10 kOe for die-upset magnet, > 4 kOe for HDDR-treated material).

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.26 no.11
• /
• pp.1747-1750
• /
• 2022

As shrinking the semiconductor process into the deep sub-micron to achieve high-density, low power and high performance integrated circuits, MBU (multiple bit upset) by soft errors is one of the major challenge of on-chip memory systems. To address the MBU, single error correction, double error detection and double adjacent error correction (SEC-DED-DAEC) codes have been recently proposed. But these codes do not resolve mis-correction. We propose the SEC-DED-DAEC-TAED(triple adjacent error detection) code without mis-corrections. The generated H-matrix by the proposed heuristic algorithm to accomplish the proposed code is implemented as hardware and verified. The results show that there is no mis-correction in the proposed codes and the 2-stage pipelined decoder can be employed on-chip memory system.

• Nuclear Engineering and Technology
• /
• v.23 no.1
• /
• pp.1-11
• /
• 1991

The objective of this study is to investigate the effect of weld line on the mechanical strengths and the process of weld line elimination in the Zircaloy-4 resistance upset welding for the fabrication of heavy water reactor fuel rods. The weld current and the amount of upset increased linearly with the main heat, in which two relations between them were derived. It was found that the threshold to obtain sound weld was 50% of main heat in terms of weld upset size, mechanical strengths and weld line elimination. The weld microstructure of resistance upset welds of Zircaloy-4 comprsied basketweave, Widmanstatten and martensite respectively by changing the main heats. Dimples on uniaxially fractured surface at weld line in the Zr-4 welds were larger and deeper compared with those on biaxially fractured surface. It was also found that the process of the weld line elimination in the resistance upset weld of Zircaloy-4 could be divided into three stages in terms of the presence of many pores, their shrinkage and elimination, and the shrinkage of the original weld interface with increasing weld currents.

• Journal of Ocean Engineering and Technology
• /
• v.16 no.6
• /
• pp.49-54
• /
• 2002

The Finite Element Method is applied to the determination of the deformed bulge profile and strain distribution during upset forming of cylindrical billets. From the results of simulation, the bulging along the z-axis becomes more severe with increasing eight reduction, and with increasing friction at the die-material interface. The present method can be used for the simple prediction of the deformed shape and strain distribution in upset forging of cylindrical billets with dissimilar fictional conditions at the die-material interfaces.