1、-1-CharacteristicsCharacteristicsCharacteristicsCharacteristics ofofofof StampingStampingStampingStamping andandandand PropertiesPropertiesPropertiesProperties ofofofofSheetSheetSheetSheet MetalMetalMetalMetal FormingFormingFormingFormingStamping is a kind of plastic forming process in which a part
2、is produced by means of theplastic forming of the material under the action of a die.Stamping is usually carried out undercold state,so it is also called cold stamping.Heat stamping is used only when the blankthickness is greater than 8100mm.The blank material for stamping is usually in the form ofs
3、heet or strip,and therefore it is also called sheet metal forming.Some non-metal sheets(suchas plywood,mica sheet,asbestos，leather)can also be formed by stamping.Stamping is widely used in various fields of the metalworking industry,and it plays acrucial role in the industries for manufacturing auto
4、mobiles,instruments,instruments,military parts and household electrical appliances,etc.The process,equipment and die are the three foundational problems that needed to bestudied in stamping.The characteristics of the sheet metal forming are as follows:(1)High material utilization.(2)Capacity to prod
5、uce thin-walled parts of complex shape.(3)Good interchangeability between stamping parts due to precision in shape anddimension.(4)Parts with lightweight,high-strength and fine rigidity can be obtained.(5)Highproductivity,easytooperateandtorealizemechanizationandautoimmunization.The manufacture of t
6、he stamping die is costly,and therefore it only fits to massproduction.For the manufacture of products in small batch and rich variety,the simplestamping die and the new equipment such as a stamping machining center,are usuallyadopted to meet the market demands.The materials for sheet metal stamping
7、 include mild steel,copper,aluminum,magnesiumalloy and high-plasticity alloy-steel,etc.Stamping equipment includes plate shear and punching press.The former shears plate-2-into strips with a definite width,which would be pressed later.The later can be used both inshearing and forming.1.11.11.11.1Cha
8、racteristicsCharacteristicsCharacteristicsCharacteristics ofofofof stampingstampingstampingstamping formingformingformingformingThere are various processes of stamping forming with different working patterns andnames.But these processes are similar to each other in plastic deformation.There arefollo
9、wing conspicuous characteristics in stamping:(1)The force per unit area perpendicular to the blank surface is not large but is enoughto cause the material plastic deformation.It is much less than the inner stresses on the plateplane directions.In most cases stamping forming can be treated approximat
10、ely as that of theplane stress state to simply vastly the theoretical analysis and the calculation of the processparameters.(2)Due to the small relative thickness,the anti-instability capability of the blank is weakunder compressive stress.As a result,the stamping process is difficult to proceed suc
11、cessfullywithout using the anti-instability device(such as blank holder).Therefore the varieties of thestamping processes dominated by tensile stress are more than those dominated bycompressive stress.(3)During stamping forming,the inner stress of the blank is equal to or sometimes lessthan the yiel
12、d stress of the material.In this point,the stamping is different from the bulkforming.During stamping forming the influence of the hydrostatic pressure of the stress statein the deformation zone to the forming limit and the deformation resistance is not soimportant as to the bulk forming.In some cir
13、cumstances,such influence may be neglected.Even in the case when this influence should be considerer,the treating method is alsodifferent from that of bulk forming.(4)In stamping forming,the restrain action of the die to the blank is not severe as in thecase of the bulk forming(such as die forging).
14、In bulk forming,the constraint forming isproceeded by the die with exactly the same shape of the part.Whereas in stamping,in mostcase，the blank has a certain degree of freedom,only one surface of the blank contacts withthe die.In some extra case,such as the forming of the suspended region of sphere
15、of cone,and curling at the end of tube,neither sides of the blank on the deforming zone contact with-3-die.The deformation in these regions are caused and controlled by the die applying anexternal force to its adjacent area.Due to the characteristics of stamping deformation and mechanics mentioned a
16、bove,thestamping technique is different from the bulk metal forming:(1)The importance of the strength and rigidity of the die in stamping forming is lessthan that in bulk forming because the blank can be formed without applying large pressure perunit area on its surface.Instead,the techniques of the simple die and the pneumatic andhydraulic forming are developed.(2)Due to the plane stress or simple strain state in comparison with bulk forming,moreresearch on deformation or force and power parame
