• 소성∙가공
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• 제15권4호
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• pp.319-325
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• 2006

The laser forming process is a new flexible forming process without forming tools and external force, which is applied to various fields of industry. Especially, applications of the laser forming process focused on cutting, welding and marking process. In this paper, the laser bending process of sheet metal which is heated by laser beam and formed by internal stress is simulated by using thermo elastic-plastic analysis model. Based on the result of FE-analysis, the laser bending machine is made to obtain reliable data for sheet bending. Under the same condition as FE-analysis, the laser bending experiment has been performed to ver 펴 the result of FE-analysis and good agreement has been obtained between FE-analysis and experiments. Additional laser bending experiments have been performed to evaluate the laser bending machine.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2009년 추계학술발표대회
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• pp.22-22
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• 2009

Laser forming is a promising technology in manufacturing, such as in the shipbuilding, automobile, microelectronics, aerospace and other manufacturing industries. This process forms the sheet metal by utilization of laser-induced thermal stresses. Laser forming process has been studied extensively for rectangular shape geometry. This basic study presents the change in deformation behavior of sheet metal during transition from linear to curved geometries and irradiations as well. A series of experiments have been conducted on a wide range of specimen geometries such as quarter-circular and half circular plate. The reasons for this behavior have been analyzed. Results are compared and analyzed by simulations using ABAQUS. Influence of developed stresses on the bending has been investigated. This study provides the more understanding of forming mechanism influenced by geometry effect.

• 소성∙가공
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• 제21권6호
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• pp.378-383
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• 2012

Laser forming is an advanced process in sheet metal forming in which a laser heat source is used to shape the metal sheet. This is a new manufacturing technique that forms the metal sheet only by a thermal stress. Analyses of the temperature and stress fields are very important to identify the deformation mechanism in laser forming. In this paper, temperature distributions and deformation behaviors of DP980 steel sheets are investigated numerically and experimentally. FE simulations are first conducted to evaluate the response of a square sheet in bending. The effects of process parameters such as laser power and scanning speed are then analyzed numerically and experimentally. It is observed that experimental and numerical results are in good agreement. These results provide a relationship between the line energy and the angles for laser bending of DP980 steel sheets.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2005년도 춘계학술발표대회 개요집
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• pp.91-93
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• 2005

Forming sheet metal by laser-induced thermal stresses (laser forming) has been extensively studied, and the research has focused on two-dimensional geometries using a multi-pass straight line scan. Recently there came out some useful studies or three-dimensional laser forming which is applied to doubly curved shapes. The task of 3D laser forming sheet metal is to determine a set of process parameters such as laser scanning paths, laser power and scanning speed that will make a given shape. New method for laser forming of a doubly curved surface by using geometrical information was proposed and verified by experiments. This method shows good performance in the sense of calculation time and accuracy compared to the inherent strain method.

• 소성∙가공
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• 제26권1호
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• pp.35-40
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• 2017

Laser forming is an advanced process in sheet metal forming in which thermal stress originated from the laser heat source is used to shape the metal sheet. However, substantial waiting time is normally necessary for the workpiece to cool down between consecutive scans so that a steep temperature gradient can be reestablished in the next scan. In order to solve this drawback, laser bending characteristics are experimentally implemented in underwater condition. Laser forming effects under various conditions, including different laser power, scanning velocity, beam diameter, number of passes and material, are investigated. The results show that the underwater laser forming facilitates deliberate forming. The bending angle per respective laser scan is decreased with increasing the number of passes and scanning velocity.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1999년도 추계학술대회논문집
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• pp.14-17
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• 1999

The finite element formulation is developed for predicting strain distributions and weld line movements in the forming processes of laser welded blank. The welded zone(WZ) is modelled with several narrow finite elements whose material characteristics are analytically obtained from those of base metals based on the tensile tests. In order to show the reliability and effectiveness of weld element the forming process of hemispherical dome stretching and auto-body door inner panel stamping are simulated FEM predictions show good agreements with experimental observations.

• 대한기계학회논문집A
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• 제33권7호
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• pp.681-686
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• 2009

Direct laser metal forming technology was applied to restore the damaged mold surface. In order to estimate melting characteristics of the $20{\mu}m$ Fe-Cr-Ni powder, single layer experiments were performed at various levels of heat input. The process window of the $20{\mu}m$ Fe-Cr-Ni powder provided feasible process parameters for the smooth regular surface. The cross hatching scanning strategy on the multiple layer experiment was performed to reduce the thickness non-uniformity of edge portions compared with the one direction scanning. To estimate the coherence between the melted powder and the basematal, the tendency of hardness distribution has been observed. The hardness of the melted and the remelted zone was distributed from 400HV to 600HV. It is over 2 times compared of the hardness of the basemetal. Experimental results show that the mold restoring process using direct laser metal forming can be successfully applied in the mold repair industry.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2012년도 추계학술대회 논문집
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• pp.365-366
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• 2012

• 한국정밀공학회지
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• 제26권5호
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• pp.57-63
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• 2009

Interface friction in blanking dies, cold forging and extrusion of aluminum alloys is a major cause of inefficient process. This paper describes an investigation of femtosecond laser texturing for reduction of interface friction on sliding surfaces in forming process. Femtosecond direct writing technology was used to fabricate a laser micro-machined die and to create microgroove patterns with varying size and density on metal forming dies. A systematic approach to find the optimum parameters and computer simulation comparison of friction coefficients are provided to study the relation of friction coefficients and die profiles. In metal forming tests, the effectiveness of various laser-machined patterns for enhancing interface lubrication is determined.

• 소성∙가공
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• 제9권1호
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• pp.3-9
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• 2000

The new FLD of the laser welded blank, which includes FLCs of welded zone and base metals, is introduced. For the forming limits of welded zone, the hemispherical dome punch tests were performed with various widths of asymmetric specimen. The FLC0 as well as the dome height at fracture associated with various specimen widths in the same and different thickness combinations were found to see the formability depending on thickness combinations. In order to show the application of the new FLD, the measured strains of squared cup drawing and simulated strains of door inner panel stamping were compared with those of FLCs. The successful prediction of fracture in the applications reveals that the forming limits of welded zone and base metals should be separately found for more accurate evaluation of the formability and workability of the laser welded blank.