Papers by Author: Wei Fu Fan

Abstract: The fine-blanking procedure for AISI-1045 and AISI-1020 under the condition of various blanking allowance has been simulated by the DEFORM-2D software, and a large number of fine-blanking experiments have been made. Some key factors, like blanking allowance affecting upon the ejector force, the perfect ratio of fracture and the fracture procedure, are discussed, and the principles for choosing value of blanking allowance are given. In order to reduce ejector force, increase the perfect ratio of fracture and separate scrap from sheet metal easily, a smaller value C of blanking allowance should be adopted whenever possible. The value C of blanking allowance should be chosen according to the mechanism capability. For some types of steels which have good plasticity, a larger value C of blanking allowance should be chosen, so that the work-piece without blanking edge could be obtained. For some types of steels which have poor plasticity, a smaller value C of blanking allowance should be chosen to obtain blanking work-piece with higher quality. Generally speaking, the optimized value of blanking allowance should be from 0.15mm to 0.35mm, and the largest value must be less than 0.5mm.The research result has instructive significance and reference value to improve the quality of work pieces and the perfect ratio of sheared band.

Abstract: The different separation mechanism of fine-blanking with negative clearance and conventional blanking under different blanking process are analyzed through fine-blanking with negative clearance and conventional blanking processing experiments on AISI-1045 steel. The fractography photographs in the different deformation regions, such as rollover zone, shearing band, fracture zone and burr zone are scanned by scanning electron microscope (SEM-JSM-6360LV). The place of fracture of fine-blanking with negative clearance has emerged into the middle of work piece not the undermost of workpiece, and the width of fracture band is as tiny as 50-100 micron. The smooth surface formed by the uniform plastic flow in the process fine-blanking with negative clearance, and the full course of finally toughness fracture have been analyzed in the final phase of ejecting in fine-blanking with negative clearance. From the perspective of material meso-damage, the fracture mechanism of special blanking process with negative clearance has been illustrated in details.

Abstract: This paper carries through pure shearing fine-blanking processing experiment with negative clearance for the AISI-1020、AISI-1045 steel and the relations curves of the blanking force and the blanking stroke is obtained. The micro hardness of the sheared surface for the blanked work pieces in breadthways and lengthways direction is measured by Vickers-micro hardness instrument (MH-6), thereby the relations curves of punch stroke and the micro-hardness of the blanking work pieces are gained. The relation between work hardening degree and blanking clearance for the negative blanking is obtained too. This paper focuses on formation mechanism of work hardening for the negative blanking and analyzes the work hardening capability of blanked work piece. The work hardening degree is compared to the materials which possess different hardening index. The research shows that the work hardening degree of the blanking work pieces is strengthened evidently by the fine-blanking with negative clearance and the hardening layer of blanking fracture could enhance structure intensity and wear resistance of blanking work piece evidently. Therefore, it could enhance fatigue strength exceedingly and extend the working life of work piece greatly.

Abstract: This paper obtained work piece of fine blanking with negative clearance by experiment. The microstructure and fractography photograph in regions like rollover zone, shearing band, under sheared surface and fracture band were scanned by instrument of scanning electron microscope (SEM-JSM-6360LV). The fine-blanking with negative clearance makes the metal deformation regions into a state of triaxial stress precise and it causes an intense metallic stream that brings about inter-dislocation and distortion of metallic crystal product under the action of stronger force, so the metallic crystal is reset and the isometric metallic crystal of shearing zone is staved, sloped and pulled and it appears as dense lined and strip crystal. The paper analyzes the full course of producing and development of micro crack in the ejecting stage in the fine-blanking processing of negative clearance. And the course of final rupture is also analyzed. The relationship curve of blanking stroke and micro hardness is measured by Vickers Hardness instrument (MH-6). The deforming principle of fine blanking deformation with negative clearance is analyzed by means of microstructure, metallographic photograph and micro hardness.