The Combined Analysis About Deformation And Failure During Fine-blanking Process Around The Punch Corner

Fine-blanking,as a near net forming process,has been widely used in industrial field especially in the automotive industry since it has excellent quality.How to improve the service life of fine-blanking die is a common problem faced with industry.Several methods are chosen to increase the punch’s service life.However,there is still room for life improving.Chipping failure was investigated in this paper to figure out the main reason accused of chipping cracks initiation during fine-blanking process.Besides,the evolution of material properties and geometry around the cutting edge was tracked to propose several suggestions for further improving punch’s service life.In this paper,a QHZ thin-walled blanking die was taken as research subject for chipping evolution analysis by the way of finite element method simulation and scanning electron microscope observation.Plastic deformation is the main reason accused of cracks initiation.The chipping evolution around cutting edge mainly reflects in 2 aspects:material properties and geometry.Higher rigidity,larger toughness,better fatigue resistance,greater geometry of cutting edge should be considered as a further way to improve die life.From the aspect of material properties,coarsened grain,decline ofΣ3 GB and CO rotation,as well as decreased elastic modulus were observed as the number of blanking increases.It turns out that the deterioration of performances on the plane parallel to the punching direction is the main reason that affects the tool life.Highlight of this work is that it offers possible directions to enhance the performances of punch with longer service life.The simulation model for estimating the final shape of cutting edge was established in this paper,whose result including plastic deformation and wear can accord with the fact.It turns out that plastic deformation has a greater impact on the geometry evolution of cutting edge than wear.As the number of blanking increases,the blanking pressure,deformation and equivalent stress are all decreased gradually.Specially,the plastic deformation has a trend of in-diffusion from the corner to the inside of the punch.The middle part of the cutting edge has an inward trend,while each side of it expands outward and prefers to wear.The stable and final geometry of the cutting edge is similar to an 11°chamfer.Besides,an oval cutting edge was designed for lower stress,lower blanking press and less plastic deformation,which were decreased around 18.87%,23.21%and 65.77%respectively.It was found that the punch corner will be stable after the 5^th blanking simulation,which can bringing longer die life forward.