As the cutting speed goes higher, the mechanism of chip deformation will be changed significantly, i.e., continuous chip in low cutting speed will shift to serrated chip with shear localization. For the shear localize...As the cutting speed goes higher, the mechanism of chip deformation will be changed significantly, i.e., continuous chip in low cutting speed will shift to serrated chip with shear localization. For the shear localized chip, the parameters used to assess the chip deformation for continuous chip, such as shorten coefficient ξ, shear angle φ and shear strain ε, can not describe the chip deformation correctly or comprehensively. This paper deals with the assessment of chip deformation of shear localization. There are two deformation regions in shear localized chip, one is the chip segment body with relative smaller plastic deformation, another one is the boundary between segments with shear localization, so called shear band. Considering the two distinct deformation regions, two parameters are used to define their deformation respectively. According to the analysis of chip formation process, the equations have been deduced to calculate the shear strains of shear band ε, shear strain of chip segment ε 1 and shear rate so that the shear localized chip deformation can be assessed correctly and comprehensively. By use of this assessment, the chip deformation in machining selenium treated stainless steel (STSS) and common stainless steel at various cutting conditions is investigated. The experiment results obtained by the machining of stainless steel prove that: (1) the shear strain and strain rate increase with the increasing of cutting speed; (2) the shear strain in shear band can be over 10 when cutting speed exceeding 200 m/min for both types of stainless steel, and it is much higher than the strain of chip segment. The difference will be enlarged as the cutting speed increasing; (3) As the comparison, the shear strain for the STSS is a little lower than that for JIS304; (4) The stain rate is extremely high (= 2.5×10 5 1/s ). In range of cutting speed less than 180 m/min, the strain rate for STSS is lower than that for JIS304. However, when the cutting speed is higher than 180 m/min, the strain rate for STSS is higher than that for JIS304.展开更多
Excellent quality of shearing edge implies that a s mo oth cutting edge without tearing will be observed on the whole edge surface. Thi s is one of the most significant features of the Fine-blanking process. To achi e...Excellent quality of shearing edge implies that a s mo oth cutting edge without tearing will be observed on the whole edge surface. Thi s is one of the most significant features of the Fine-blanking process. To achi eve such a superb blanking edge quality in fine-blanking, there actually involv es quite a large number of factors, such as blanking speed, processing material, product shape, lubrication and tool geometry, to be considered simultaneously d uring the operation. Nevertheless, the thorough investigations on different effe cts of those critical factors for different kinds of popular and applicable mate rial are rare and limited. Thus, the objective of this paper is mainly focused o n the study of the quality influence of tool geometry change in fine-blanking f or non-homogeneous materials. However, the most obvious change of the tool geo metry during the operation will be the essential variation of the nose radius of the punch. This is because the nose radius usually seriously deteriorates with the increasing service period in mass production which eventually causes the ent irely lose of the specific features of the fine-blanking process. Therefore, a tailor-made experimental study was carried out to investigate the relationship between the punch nose radius and the shearing edge quality, such as blanked edg e finish, burr height and die-roll height, during fine-blanking for different types of material. Five punches with each specified nose radius (Rp), 0.00 mm, 0.25 mm, 0.50 mm, 0.75 mm and 1.00 mm, and four kinds of blanking material ( Mil d steel SS400, Stainless steel AISI316L, Copper alloy UNSC16200 and Aluminium al loy AA6063 ) were employed throughout the study. Subsequently, features of the s heared edge surfaces and data of each experiment were observed and captured for further analysis in this research. Consequently, findings show that an increase of punch nose radius would produce a higher percentage of fracture of blanked ed ge and increase the amount of burr height. In overall comparison, it is found th at mild steel and copper alloy do provide better surface edge finish with higher percentage of sheared area and less burr height than that of stainless steel an d aluminium alloy.展开更多
文摘As the cutting speed goes higher, the mechanism of chip deformation will be changed significantly, i.e., continuous chip in low cutting speed will shift to serrated chip with shear localization. For the shear localized chip, the parameters used to assess the chip deformation for continuous chip, such as shorten coefficient ξ, shear angle φ and shear strain ε, can not describe the chip deformation correctly or comprehensively. This paper deals with the assessment of chip deformation of shear localization. There are two deformation regions in shear localized chip, one is the chip segment body with relative smaller plastic deformation, another one is the boundary between segments with shear localization, so called shear band. Considering the two distinct deformation regions, two parameters are used to define their deformation respectively. According to the analysis of chip formation process, the equations have been deduced to calculate the shear strains of shear band ε, shear strain of chip segment ε 1 and shear rate so that the shear localized chip deformation can be assessed correctly and comprehensively. By use of this assessment, the chip deformation in machining selenium treated stainless steel (STSS) and common stainless steel at various cutting conditions is investigated. The experiment results obtained by the machining of stainless steel prove that: (1) the shear strain and strain rate increase with the increasing of cutting speed; (2) the shear strain in shear band can be over 10 when cutting speed exceeding 200 m/min for both types of stainless steel, and it is much higher than the strain of chip segment. The difference will be enlarged as the cutting speed increasing; (3) As the comparison, the shear strain for the STSS is a little lower than that for JIS304; (4) The stain rate is extremely high (= 2.5×10 5 1/s ). In range of cutting speed less than 180 m/min, the strain rate for STSS is lower than that for JIS304. However, when the cutting speed is higher than 180 m/min, the strain rate for STSS is higher than that for JIS304.
文摘Excellent quality of shearing edge implies that a s mo oth cutting edge without tearing will be observed on the whole edge surface. Thi s is one of the most significant features of the Fine-blanking process. To achi eve such a superb blanking edge quality in fine-blanking, there actually involv es quite a large number of factors, such as blanking speed, processing material, product shape, lubrication and tool geometry, to be considered simultaneously d uring the operation. Nevertheless, the thorough investigations on different effe cts of those critical factors for different kinds of popular and applicable mate rial are rare and limited. Thus, the objective of this paper is mainly focused o n the study of the quality influence of tool geometry change in fine-blanking f or non-homogeneous materials. However, the most obvious change of the tool geo metry during the operation will be the essential variation of the nose radius of the punch. This is because the nose radius usually seriously deteriorates with the increasing service period in mass production which eventually causes the ent irely lose of the specific features of the fine-blanking process. Therefore, a tailor-made experimental study was carried out to investigate the relationship between the punch nose radius and the shearing edge quality, such as blanked edg e finish, burr height and die-roll height, during fine-blanking for different types of material. Five punches with each specified nose radius (Rp), 0.00 mm, 0.25 mm, 0.50 mm, 0.75 mm and 1.00 mm, and four kinds of blanking material ( Mil d steel SS400, Stainless steel AISI316L, Copper alloy UNSC16200 and Aluminium al loy AA6063 ) were employed throughout the study. Subsequently, features of the s heared edge surfaces and data of each experiment were observed and captured for further analysis in this research. Consequently, findings show that an increase of punch nose radius would produce a higher percentage of fracture of blanked ed ge and increase the amount of burr height. In overall comparison, it is found th at mild steel and copper alloy do provide better surface edge finish with higher percentage of sheared area and less burr height than that of stainless steel an d aluminium alloy.
