Edge Of Punch Research Articles

Optimization of Motor Rotor Punch Wear Parameters Based on Response Surface Method

To reduce the wear of the motor rotor punching punch and ensure the efficiency is the highest in actual production, the finite element analysis software Deform-3Dv11 is used to simulate the punch wear based on the Archard model theory. With punch wear as the response target and punch speed, punch clearance, and punch edge fillet as the main factors, 17 groups of response surface Box–Behnken test designs are established, as well as a quadratic polynomial regression model between the main factors and the response. The results revealed that: the influence of various parameters on punch wear is in the order of punch edge fillet C > punch clearance B > punch speed A; the order of the interactive influence of various factors is as follows: punch speed and punch edge fillet AC > punch speed and punch clearance AB > punch clearance and punch edge fillet BC. The optimal blanking process combination obtained by using Design-Expert13 software is as follows: blanking speed 50 mm/s, blanking clearance 0.036 mm, and die cutting edge rounded corner 0.076 mm; the predicted response surface value is 6.95 × 10−12 mm. Through simulation verification, the actual optimized simulation value is 6.93 × 10−12 mm, with an absolute relative error of 2.5% for the predicted response value. Moreover, the optimized simulation value is reduced by 30.4% compared to the one before optimization, effectively reducing the punch wear of the motor rotor punching forming and providing a theoretical foundation for further wear optimization.

Fine Blanking of Austenitic Stainless Steel Gears Using Carbon-Supersaturated High-Speed Steel Tools

Austenitic stainless steel gears were fabricated via the fine blanking process that can be used for mass production. A carbon-supersaturated (CS)-matrix high-speed steel punch was prepared to minimize the adhesive and abrasive wear damage. Its edge profile was tailored and finished to control the local metal flow around the punch edges and edge corners. This CS punch was utilized in fine blanking the AISI304 austenitic stainless steel gears. Ball-on-disc (BOD) testing was first employed to describe the frictional behavior of the CS tool steel disc against the AISI304 stainless steel balls. SEM-EDX analysis on the wear track revealed that a free-carbon tribofilm was formed in situ in the wear track to prevent adhesive wear via galling on the tool steel disc. No significant adhesive or abrasive wear was detected on the punch edges and punch edge corners after continuously fine blanking with 50 strokes. AISI304 gears were produced to have fully burnished surfaces. Their pitches, widths and circles were measured to evaluate their gear-grade balancing during the fine blanking process. The stabilized gear-grade balancing in JIS-9 to JIS-10 grades was attained for these as-blanked AISI304 gears without finishing processes.

Prediction of Hole Expansion Ratio for Advanced High-Strength Steel with Image Feature Analysis of Sheared Edge

The punching process of AHSS induces edge cracks in successive process, limiting the application of AHSS for vehicle bodies. Controlling and predicting edge quality is substantially difficult due to the large variation in edge quality, die wear induced by high strength, and the complex effect of phase distribution. To overcome this challenge, a quality prediction model that considers the variation of the entire edge should be developed. In this study, the image of the entire edge was analyzed to provide a comprehensive evaluation of its quality. Statistical features were extracted from the edge images to represent the edge quality of DP780, DP980, and MART1500 steels. Combined with punching monitoring signals, a prediction model for hole expansion ratio was developed under punch conditions of varying clearance, punch angle, and punch edge radius. It was found that the features of grayscale variation are affected by the punching conditions and are related to the double burnish and uneven burr, which degrades the edge quality. Prediction of HER was possible based on only edge image and monitoring signals, with the same performance as the prediction based solely on punching parameters and material properties. The prediction performance improved when using all the features.

An adhesive detachment paradox: Does the substrate thickness matter?

A normal adhesive contact between a flat-ended cylindrical punch with elliptical cross-section and the surface of an elastic substrate, which can be regarded as an elastic layer of finite thickness, is considered. The experimental evidence published elsewhere indicates that the initiation of detachment can occur at the ends of the minor axis of the elliptical contact area, which eventually comes into contradiction with the surface energy theory developed so far. This paradox of adhesive detachment is examined in the framework of the JKR-type model formulated in terms of the stress intensity factor (SIF) of the contact normal stress. Based on the asymptotic model for a relatively thick elastic layer, the contact SIFs at the ends of the minor axis are shown to grow with decreasing the relative layer thickness faster than those at the ends of the major axis of the initial contact area. A plausible explanation for the observed inconsistency between experiment and state-of-the-art theory is found in the effect of the nonuniform elastic deformations on the square root singularity of the contact pressure at the punch edge.

An Investigation of Punch Radius and Clearance Effects on the Sheet Metal Blanking Process

In this study, the effects of punch edge radius and blanking clearance on product quality and blanking process in blanking of AISI 304 stainless steel sheet were investigated by using the fi-nite element analysis method. The blanking analyzes were performed at four different punch tip radii (0.01, 0.25, 0.5, 1 mm) and three different blanking clearance (1 %, 5%, 10%). As a result of the analysis, rollover, burr length increased, smooth sheared / fractured surface ratio and blanking force decreased with the increase in blanking clearance. Depending on the increase in the amount of punch tip radius, the blanking force, and burr length also increased, and the smooth sheared / fractured surface ratio decreased compared to the blanking process with flat punches.

Effect of small corner radius in cold punching of 22MnB5 die-quenched boron steel sheets

The effect of small corner radius in punching process of ultra-high strength category of steel i.e. 22MnB5 die-quenched boron steel was investigated. Although the die-quenched steel sheet can reach superior strength of above 1500 MPa, the ductility of the steel sheet is low, making punching process totally challenging. Punching of hole at 22MnB5 boron steel commonly carried out in hot condition prior to die-quenching and usually needed for complex tools for preheating, punching, transferring, and cooling the part. Inaccurate of hole dimension after quenching is inevitable due to the change of grain structure during cooling. In this study, a pre-hardened 22MnB5 boron steel sheet is punched under a small clearance in a normal cold condition. The small corner radius disperses the stress concentration at the punch edge and thus increases the material flow during initial stage of the punch penetration. The action of small clearance between punch and die reduce the tensile stress and therefore, the initiation of crack is delayed. The quality of the sheared edge surface was improved with the high percentage of area cover with the burnished surface.

Effect of Die Edge Roundness on Crack Initiation near Punch Edge in Blanking

In this study, the effect of die edge radius on crack initiation was discussed in finish blanking. Experiments were carried out using die with rounded cutting edge. As a result, it was confirmed that crack initiation near the punch edge occurred earlier than that near the die edge. It was also confirmed that the burnished surface increased with an increase in the die edge radius. Finite element method was carried out from the initial stage of shearing and until the punch penetration depth was achieved just before the occurrence of the cracks to investigate the distribution of the mean stress. As a result, it was confirmed that the punch stroke, where the mean stress began to increase rapidly to a positive value, increased with an increase in the die edge radius, and the punch stroke at which the mean stress increased rapidly also increased.

Quantitative Characterization of the Affected Zones in a Single Crystal Fe-6Si Steel Sheet by Fine Piercing.

An iron loss in the motor core was often enhanced by formation of plastically affected zones in piercing the electrical steel sheets. A platform methodology to carry out quantitative evaluation of these affected zones in the pierced electrical steel sheets was proposed to search for the way to minimize the affected zone widths. A coarse-grained electrical steel sheet was employed as a work material for a fine piercing experiment under the narrowed clearance between the plasma-nitrided SKD11 punch and core-die. The shearing behavior by the applied loading for piercing was described by in situ measurement of the load-stroke relationship. The plastic straining in the single-crystal electrical steel sheet was characterized by SEM (scanning electron microscopy) and EBSD (electron back-scattering diffraction) to define the affected zone size and to analyze the rotation of crystallographic orientations by the induced plastic distortion during piercing. Integral and differentiation of spin rotation measured the affected zones. The effect of punch edge sharpness on these spin-rotation measures was also discussed using the nitrided and ion-milled SKD11 punch and core-die.

A horizontal punch on a layered and orthotropic composite system with negative Poisson’s ratio

This paper studies the problem of a layered and orthotropic material with a negative value of Poisson’s ratio under a horizontal punch through a rigid line. Full-field solutions near the edge of the rigid line are developed and expressed in terms of the relevant values of the stress intensity factor and energy release rate. The Influences of Poisson’s ratio, orthotropicity orientation and the difference between the properties of the layered materials on the stress field and energy absorption are identified. The results show that materials with a negative value of Poisson’s ratio have a great potential to reduce the stress concentration and to increase punch resistance. If the punch load is maintained constant, the punch edge stress will increase with the layer thickness. However, if the punch displacement is maintained, the punch edge stress will decrease with layer thickness.

Impression creep behavior of Babbitt alloy SnSb8Cu4

Abstract The creep behavior of the babbitt alloy SnSb8Cu4 was studied by impression under constant stress in the range of 15-30 MPa and at temperatures in the range of 333-393 K. OM, XRD, and SEM technologies were used to investigate the microstructural evolution of the material before and after creep. In conclusion, the stress exponent of SnSb8Cu4 in impression condition is 2.7. The creep activation energy is 46.7 kJ × mol-1, which reveals that the creep mechanism is based on dislocation glide controlled by dislocation pipe diffusion. With an increase in creep temperature and stress, the thermal vibration of the atom and atomic diffusion velocity increase. Moreover, Cu6Sn5 phase cannot effectively hinder dislocation glide and strengthen the material in a condition of high creep temperature and high stress, thus resulting in the decrease of creep resistance. After creep, the grains are elongated along the deformation flow direction both near the pressure punch edge and in the hemispherical zone beneath the pressure punch. The most severe deformation zone is near the pressure punch edge, whereas, no detectable deformation is found in other areas. It is concluded that impression creep is a localized phenomenon.

Continuous contact problem of thermoelectric layer pressed by rigid punch

In this study, the continuous contact problem of thermoelectric layer resting on a rigid substrate and loaded by a rigid punch is examined. Considering the body force of the thermoelectric layer, the model of stress distribution between thermoelectric layer and rigid layer is established. The general expressions for the stress between the thermoelectric layer and the substrate are given. Using the boundary conditions, the singular integral equation of the stress distribution is obtained and solved by Gauss-Chebyshev integral formula. The numerical results of the stress distribution between the rigid punch and the thermoelectric layer are obtained. It is found that the stress between the rigid punch and the thermoelectric layer exhibits singularity at the edge of the rigid punch. The influence of the parameters of the rigid punch and the thermoelectric layer on the critical load factor between the thermoelectric layer and the substrate is analyzed. The results show that the larger rigid punch width and the body force of the thermoelectric layer make it difficult to separate the thermoelectric layer from the rigid substrate. The results of this paper will provide a reference for studying the contact behavior of thermoelectric materials.

Local formability assessment of AHSS steels with shear cut tensile tests

As an alternative to the ISO16630 hole expansion test, the punched tensile test is increasingly popular for edge crack characterization of AHSS advanced high strength steels. In this investigation the reduction of area as well as thickness reduction at fracture in the vicinity of left/right sample edge fracture sides has been determined by means of light optical microscopy according to the Hance local formability test methodology for 10% to 40% cutting clearance in (both sided) sheared cut vs. spark eroded or milled edge conditions. An edge crack index has been defined based on the tensile sample fracture shape. Local formability tensile properties based on area reduction or average thickness reduction are more sensitive to edge condition than Axx fracture elongation values. The determination of the reduction of area at fracture is however challenging due to projection issues. The % thickness reduction at minimum thickness as well as at left/right thickness in cut edge vicinity may offer some additional information about edge crack initiation and final fracture. The shear punch edge quality (punch and die tool wear, target vs. actual clearance) should be closely monitored for accurate reproducible testing results.

Femtosecond Laser Trimming with Simultaneous Nanostructuring to Fine Piercing Punch to Electrical Amorphous Steel Sheets.

A CVD (Chemical Vapor Deposition) diamond coated tungsten carbide (WC) and cobalt (Co) sintered alloy punch was trimmed by the femtosecond laser machining to sharpen its edge with about 2 μm and to simultaneously make nanostructuring to its side surface. In addition to the sharpened edge, its edge profile was formed to be homogeneous enough to reduce the damage layer width by piercing the electrical amorphous steel sheet stack. Each brittle sheet in the stacked work was damaged to have three kinds of defects by piercing; e.g., the droop-like cracking in the thickness and at the vicinity of hole, the wrinkling in peak-to-valley with partial cracking on the peaks, and the circumferential cracking. When using the WC (Co) punch with the inhomogeneous edge profile in the sharpened edge width, these three damages were induced into each sheet and the maximum damage width exceeded 80 μm. When using the punch with the sharpened edge and homogeneous edge profile, the wrinkling mode was saved and the total affected layer width was significantly reduced to less than 20 μm. Through the precise embossing experiments, this effect of punch edge profile condition to the induced damages was discussed with a statement on the nanostructuring effect on the reduction of damaged width in electrical amorphous steel sheets. The developed tool with the sharpened edge and homogenous edge condition contributes to the realization of a low iron loss motor with a reduced affected layer width.

The Frictional Force between Slug and Die in Shear Cutting after Material Separation

Frictional forces in sheet metal blanking are central in different aspects, e.g. in wear prediction, validation of simulation models or in so called slug pulling. The latter is a phenomenon where the slug is pulled out of the die by the punch after the sheet metal is separated. This leads to process disturbances reaching from a blocked belt feeder up to severe tool damage caused by the simultaneous cutting of the slug and the sheet metal strip. A sufficiently high frictional force between the slug and the die prevents this effect. Despite its importance, this force and its causes have not yet been investigated in detail. A method was developed in this paper to measure the frictional force between slug and die. A shear cutting tool with an integrated piezoelectric load cell and an inductive position sensor was used on a stamping press to cut sheet metal made of CuSn6 (R350, thickness 1 mm). The die clearance, the punch edge radii and the lubrication conditions were varied. A larger die clearance resulted in a lower frictional force while a larger punch edge radius increased it significantly. Lubrication reduced the frictional force, especially for small die clearances. Finally, the cause of the frictional force was investigated by identifying the relevant springback modes of the slugs. This was carried out by correlating the slugs' deflection, oversize, and clean cut height with the frictional force. Especially the slug oversize, i.e. the difference between the slug's diameter and the die's inner diameter, revealed a strong correlation. Calculations showed that the deformation in radial direction is the main cause of the frictional force between slug and die. It suggests that the slug oversize is a good measure for the magnitude of the frictional force.

Using the artificial neural network to investigate the effect of parameters in square cup deep drawing of aluminum-steel laminated sheets

In this study, the effective parameters involved in the deep drawing of double-layer metal sheets in a die ofsquare cross-section were investigated through artificial neural network (ANN) modeling. For this purpose,first, the deep drawing of double-layer (Al1200 / ST14) sheets was carried out experimentally. Also, the finiteelement simulation of the process was performed, and the results validated through experimental tests. A setof 46 different experimental data were employed in this paper. The ANN was trained by using a mean squareerror of 10-4. The input parameters, i.e., punch radius, die radius, blank holder force, clearance, and the permutationlayers were set to the network. The surface response method (RSM); was employed to evaluate theresults of the ANN model, and the input parameters of the deep drawing process on the thinning of Al1200and ST14 composite layers were analyzed. The obtained results indicate that the punch edge radius has themost significant influence on the thinning of the Al1200 layer. Increasing the gap between the punch and dieto 1/4 of the sheet thickness, increased the cup wall layers thickness of the Al1200 and ST14 respectively by3.38% and 0.5%. The performance of the ANN model demonstrates that it can estimate the amount of thinningin the composite layers with satisfactory accuracy.

Simultaneous Nano-Texturing onto a CVD-Diamond Coated Piercing Punch with Femtosecond Laser Trimming

In this study, a CVD (Chemical Vapor Deposition)-diamond coated tungsten carbide cobalt (WC (Co)) punch was trimmed to adjust its surface roughness and to significantly reduce its edge curvature for fine piercing by femtosecond laser processing. Through this laser trimming, the surface quality of the diamond coating and the punch edge profile were improved to less than 0.5 μm at the maximum roughness and 2 μm in the edge width, respectively. In parallel with this improvement of surface quality, the side surface of the diamond coating was modified to include nano-textures via the LIPSS (Laser Induced Periodic Surface Structuring) process. Through the fine piercing process, this nanotexture was transcribed onto the pierced hole surface together with fine shearing of the hole by piercing. WLI (White-Light Interferometry) and SEM (Scanning Electron Microscopy) were utilized to describe this transcription of nanotextures during the piercing process. These semiregular nanotextures with an LIPSS period of 300 nm on the pierced hole surface induced a blue colored surface plasmon.

Design and Analysis of Stage Progressive Die for a Sheet Metal Component

Stamping die industries had been a significant impact on research and development of new technology for bigger and advance. To sustain the stamping die industry under the current global situation, cost and time are most important factors that need to be focus. In this case study, the main problem of design and analysis of progressive die is cost spent for die fabrication is high, the number of station or stages is high that will affect the production time and lifespan of tool is short. This paper focused at the stages or station that will be redesign to reduce the cost for the die, station optimization to reduce time taken for stamping process and simulate the design of tools to calculate the life cycle of punch. The study is conducted through AutoCAD and Solidwork to redesign the die and strip layout optimization. Subsequently, the ABAQUS/CAE and e-fatigue are used to completed the analysis and life cycle results for punch with various design of punch edge. Theoretical analysis indicates that design of punch plays a vital role in life cycle analysis.

Investigation on wear-induced edge passivation of fine-blanking punch

Edge passivation of the punch is a common phenomenon that is induced by wear and which would affect tool life and part quality. To investigate the edge passivation of fine-blanking punch, a wear tester based on sheet metal extrusion was designed. The relevance of the designed tester in terms of the stress state to the fine-blanking process was analyzed via finite element methods. Meanwhile, material flow at the punch edge was studied with pad printing technology, and the effects of the punch geometry and extrusion stroke on the worn profile have been discussed. The results shows that reducing the length of straight lines and radius of arcs results in a large relative sliding distance of material at the punch edge, and for a punch with circular and linear edges, wear on the circular segment is more severe than that on the linear segment. In addition, from the viewpoint of simulation, adaption of the wear coefficient in different periods could lead to a more precise worn profile of the punch.

Finite element method-based modeling of bending under tension friction test of deep drawing quality steel sheets

Understanding of the effect of the friction on the sheet deformation is a key factor in design and realization of stamping process. Among others, bending under tension friction test simulates the frictional phenomena on rounded edge of punch in sheet metal forming operations. In this paper, change of friction coefficient with 1-mm-thick deep drawing quality steel sheet deformation was evaluated using a special tribological simulator which simulates the friction in rounded edge of punch. The results of experimental investigations have been used to verify the results of numerical modeling carried out inmSC. Marc 2014 program. The friction coefficient value and contact stresses have been determined numerically. The results show that the distribution of the normal and friction stresses is very non-uniform along the wrap angle of the cylindrical countersample and along the specimen width. It has been concluded that FEM-based investigations allow a fast and suitable selection of the punch edge profile ensuring an increase of maximum allowable sheet strains.

Analysis of formability in conventional hole flanging of AA7075-O sheets: punch edge radius effect and limitations of the FLC

Hole flanges are commonly manufactured in mass production by conventional press-working. In an industrial context, the process limits are usually evaluated by means of the Limiting Forming Ratio (LFR), which defines the maximum attainable diameter of the flange related to the initial pre-cut hole. Nevertheless, the LFR does not provide enough information about material deformation, thickness distribution or the expected onset and type of failure. In this sense, a systematic investigation using the Forming Limit Diagram (FLD) is needed. Under these circumstances, the aim of this work is to provide a better understanding of the deformation process in conventional hole flanging, analysing the effect of the punch edge radius as well as the influence of the strain distribution along the hole flange on formability. An experimental campaign on 1.6 mm thickness AA7075 annealed sheet was completed using cylindrical punches with different profile radii. In addition, numerical modelling of the process using finite elements was developed. The results allow better understanding of the physical mechanisms governing material deformation and process formability in very ductile materials. In this regard, this research work contributes to the current state of the art in conventional hole flanging by establishing the modes of failure that prevail in the process and the influence of the bending induced by the tool radius in the flange formability. In addition, the limitations of using conventional FLD for providing a limiting threshold for the strain states attained in the flanges deformed with different punch profiles are also identified.