Punch Speed Research Articles

An analysis of the forming speed variation with relation to deep drawing depth of steel DP 600 sheets

Stamping is a metal forming process which aims to manufacture shaped parts from flat sheets. The automotive industry has used this manufacturing process in large scale, thereby requiring development of numerical tools with objective of time and cost reduction. Use of ever thinner sheets has prompt study of forming mechanisms, in special ductile failure. This work is inserted within this framework, in which a numerical methodology to study ductile failure in stamping processes is proposed. Emphasis is placed on a strategy to determine an optimum forming speed based on assessment of failure onset. The technique was applied to a dual phase DP 600 steel. Strain paths in predefined directions were adopted to approach ductile failure onset and evolution. A forming limit curve determined experimentally in a previous work was used as failure criterion. The results indicate an optimum punch speed which allows maximum speed without failure onset.

The influence of warm forming conditions on the natural aging and springback of a 6016-T4 aluminum alloy

Heat treatable aluminum alloys are very attractive materials to replace traditional steels in automotive body-in-white construction. However, their reduced formability and high springback limits their application in sheet metal forming operations. Moreover, these alloys are prone to natural aging that causes variability in forming operations and increases the amount of scrap. Warm forming can be a very interesting solution to improve formability and reduce springback. However, depending on the processing time, precipitation hardening may occur during the warm forming of these heat treatable alloys. Thus, punch speed has a major influence on the success of sheet metal forming operations. The present study addresses the influence of natural aging and punch speed in the warm forming of an Al-Mg-Si alloy: EN AW 6016-T4. The thermo-mechanical behavior was studied in function of temperature (from 22 to 300 °C), punch speed (from 0.1 to 10 mm·s−1) and storage time (from 1 to 18 months), using uniaxial tensile tests, cylindrical cup tests, and split ring (springback) tests. Warm temperatures between 200 and 250 °C reduce the flow stress, minimizing the effects of natural aging on the variability of the mechanical properties. A high punch speed is advantageous since it minimizes the occurrence of precipitation hardening which contributes to increase the springback. Thus, warm conditions at high punch speed can be used as an effective solution to minimize the variability caused by the natural aging in forming operations of heat treatable aluminum alloys.

Importance of hole punching conditions during Hole Expansion test

There is an increasing interest in the steelmaking and automotive industries to evaluate the edge cracking sensitivity of Advanced High Strength Steel sheets used in car body manufacturing. Currently, the Hole Expansion test is the only test procedure that is defined by norms (JFS and ISO). This test is increasingly used to assess the formability of cut-edges on punched sheets because it is relatively simple. However, it has been already shown that there can be large differences in Hole Expansion Ratio (HER) values generated by different testing facilities. Among the main sources of variability: punched hole quality and hole expansion termination point. Hole punching operation has a detrimental effect on cut-edge quality and HER values. However, current standards do not give any recommendation. No technical specification is given for the tooling, quality control system and punching speed. It has been stated that the press speed difference in the hole punching operation are significantly different from one laboratory to another one and some steel microstructures sensitive to it. However, very few papers and data are available. As a result, an experimental study was conducted to examine this important issue. A specific 4-post assembly tool was designed to guarantee the best punched hole quality. Different punching speeds, from 0.2mm/s to 367mm/s were tested on different steel sheets (mild steel, AHSS including TWIP and 3rd Gen steel) to emphasize or not the influence on final HER values.

The Effect of Functional Force Trainings on the Physical Efficiency, Force and Speed of Straight Punches Performance for Boxing Beginners

The research was designed to study the effect of functional force trainings on the physical efficiency, force and speed of straight punches for boxing beginners. The researcher used the method using experimental design for one group by pre and post measurements due to its appropriateness to the nature of the research. The sample is consisted of (20) boxers, 12 boxers were selected intentionally and the exploratory is (8) boxers for conducting scientific transactions, and the researcher used the physical efficiency test (LHARD FARD), Attachment (5 /a) and device of punch performance force measurement PFM. ) and device of punch performance speed measurement PSM Attachment (7 / a). The most important results are that the rates of improvement of post measurement are more than the pre measurement through the application of functional force trainings in the physical efficiency, force and speed of punch straight for boxing beginners. The researcher recommends to use the trainings of the functional force for boxers because of having a positive and effective impact on the improvement and increase physical efficiency, force and speed of punch during the matches, and the interest in design training programs using functional force trainings according to the scientific foundations of the different age groups of boxing players.

An Investigation on Square Tube Forming using a Reuleaux triangle

Currently the standard for forming tube is to use a variety of shaped mandrels and hydrostatic pressures. Tube forming is the expansion of a circular cross-sectional area into a variety of different shapes. This paper is focused on square tube forming. Traditionally to create a tube with a square cross-section area, a square mandrel must pass through the circular tube in small increments until the circular cross-sectional is completely transformed into a square cross-section. A novel process named Reuleaux forming to flare the tube in to a square section is introduced and the results were compared with conventional forming. In this new process, a triangular shaped bit flares circular cross-sectional tubes to square tube. While experimenting with the Reuleaux triangular bit, the force required to form the tube, profile generated and thickness distribution were analyzed. Furthermore, the effect of friction and punch speed on deformation was studied. It was found that much lower forces were required to form the shape using the Reuleaux triangle as compared to conventional forming. It was also observed that the friction and speed does not affect much during the new process.

Effect of Temperature and Deformation Speed on Formability of IN718 Sheets: Experimentation and Modelling

The objective of present work is to get insight into the formability behavior of mill annealed 1mm thick Inconel 718 (IN718) sheets under different elevated temperatures and deformation speeds. The preliminary study consisted of uniaxial tensile testing within a temperature range of 500°C – 700°C at an interval of 50°C and crosshead velocities of 0.03,0.3, 3, and 30mm/s. It was observed that the total elongation improved by approximately 18% with the increase in temperature from 500°C to 700°C. However, a considerable reduction in total elongation with increase in flow stress was found with the increase in deformation speed at elevated temperatures. Based on the true stress-strain responses, the Johnson-Cook (JC) constitutive equation was developed to capture the material flow behavior. The correlation coefficient (R), average absolute error ( Δ ) and standard deviation (SDA) were found to be 0.97, 10.8 and 6.8 respectively. Further, stretch forming behavior at isothermal elevated temperatures of 500°C and 650°C were analyzed by performing laboratory scale limiting dome height (LDH) tests. A 20mm width Hasek specimen was deformed at punch speeds of 0.3mm/s and 30mm/s using a sub-sized hemispherical punch of ϕ50 mm. The LDH was found to be higher at 650°C, and the maximum LDH was achieved at lower punch speed of 0.3mm/s. The higher deformation speed decreased the LDH by 7.4% and 12% at 500°C and 650°C respectively. The thermo-mechanical finite element modeling of isothermal LDH tests was developed successfully by incorporating JC model. The predicted punch load, thickness and surface strain distributions were validated with experimental data. It was established that the predicted peak loads were within nominal 8.6% error highlighting the suitability of JC constitutive equation in FE model.

Experimental investigations on forming limit diagram of ultra thin SS 304 steel: effect of circular grid size, sheet orientation, punch size and deformation speed

ABSTRACTIn the present work, SS 304 sheet of 200 μm thickness was used to experimentally evaluate the forming limit diagram (FLD). In this context, a sub-size limiting dome height (LDH) test setup was developed to deform rectangular specimens of different widths using a 30 mm hemispherical punch. Further, effect of various parameters such as change in circular grid size, stretching direction with respect to rolling direction of the sheet, punch size and deformation speed on limiting strains was investigated. It was observed that there was marginal change in limiting strains due to the change of punch diameter from 30 mm to 50 mm. The FLD0 level changed approximately 7.5% and 6.8% with the change in punch diameter and stretching direction respectively. It was also found that the FLD0 value increased by 15% with change in circular grid diameter from 2.5 mm to 2.0 mm. However, a negligible change in the limiting strains was noted when the grid diameter was further reduced to 1.0 mm. There was negligible change in the FLD0 level with increase in punch speed from 4 mm/min to 100 mm/min, but approximately 13% decrease was found when the punch speed was further increased to 400 mm/min. Moreover, the LDH, strain distribution and failure strains were also analyzed in context of formability.

Temperature analysis during the drawing of an aluminum cylindrical cup

Both the plastic deformation and the friction forces generate heat in sheet metal forming processes. This yields a temperature rise on the blank and tools, which is mainly dictated by the blank properties and the press speed. Although modest values of temperature rise yield negligible changes in the mechanical behavior of metals, the lubricant properties are rather influenced by the temperature. Thus, the deep drawing of an aluminum cylindrical cup was selected to evaluate, experimentally and numerically, the temperature variation of the forming tools and blank at room temperature. Different values of punch speed are compared to evaluate the impact of the heat losses to the environment. The experimental results show that the temperature rise on the die surface is higher than 9°C when the punch speed is 10 mm/s. The temperature is underestimated by the finite element model due to the isothermal conditions imposed on the forming tools.

Micro-structure and Air-tightness of Squeeze Casting Motor housing for New Energy Vehicle

In order to improve the performance of automobile parts, the influence of squeeze casting process parameters on casting defects, material structure and air-tightness of aluminum alloy motor housing for new energy vehicle was studied. The results show that the density of the castings increases with the increase in pressure and mold temperature. With increase in pouring temperature, it increases first and then decreases. Pressure has the greatest influence on the density of the castings. Under a certain pressure, with moderate increase in casting temperature and mold temperature, the grain growth begins to increase; the dendrites become less, the new α - Al grains are spherical and granular, the micro-structure is uniform. Also, with increase in pressure, this effect is more pronounced, the air-tightness of castings improve. In conclusion, when the pressure is 110MPa, pouring temperature is 680° C, mold temperature is 280° C, pressure holding for 30s, and punch speed of 0.1m/s, there is no clear shrinkage in the casting, the structure is uniform, the qualified rate of air-tightness of production reaches 86%, and the performance is excellent.

Dynamic frictional contact problems involving elastic coatings

Abstract This paper presents a general theory of dynamic frictional contact of elastic coatings pressed against by a rigid punch moving with a constant speed. Governing equations of elastodynamics are solved by applying Galilean and Fourier transformations. The contact problem is then reduced to a singular integral equation, which is solved numerically. Developed procedures are verified through comparisons made to the available computational and analytical results. Parametric analyses illustrate the influences of punch speed, material and geometric parameters, and friction on contact stresses. Especially at higher punch speeds, the difference between contact stress magnitudes obtained through elastostatic and elastodynamic solutions is rather significant. A formulation based on the elastodynamic theory is required to compute contact stresses generated in such problems.

Finite element simulation on investigations, modeling, and multiobjective optimization for clinch joining process design accounting for process parameters and design constraints

Clinch joining is a complexed mechanical behavior influenced by both process parameters and geometry parameters. The present clinch joining optimizations are more dedicated on geometry parameters, and except some property objectives of optimization, the other design properties of clinching process are not considered as constrained conditions. Therefore, the multiobjective optimization in the paper takes clinching process parameters such as punch speed, bottom thickness, and blank holder force into consideration besides geometry parameters, and then sets two thinning rates as constrained conditions. In the paper, a sufficient and systemic procedure for high-quality clinched joint based on FEA (finite element analysis), PS (parameter study), RSM (response surface methodology), and NSGA-II (non-dominated sorting genetic algorithm-II) is developed. Parameter study is conducted to choose significant parameters from both process and geometric parameters for neck, interlock, and tensile force. Then, mathematical models of nine selected parameters with responses are built based on RSM, and the interactions on interlock and tensile force are clearly identified by the model. Finally, three objectives neck, interlock, and tensile force and two constraints thinning rates of side face of joint are applied on multiobjective optimization using NSGA-II, which could obtain comprehensive high-quality joint, and the Pareto sets reveal negative relations of both tensile force to neck and interlock to neck, as well as the positive relation between interlock and tensile force. The result shows that the presented procedure performs well in optimization of clinch joining process and the use of finite element simulation model is valuable for complex optimization design.

Concurrent Validity and Reliability of a Linear Positional Transducer and an Accelerometer to Measure Punch Characteristics

Lambert, C, Beck, BR, and Weeks, BK. Concurrent validity and reliability of a linear positional transducer and an accelerometer to measure punch characteristics. J Strength Cond Res 32(3): 675-680, 2018-Punch speed is an important factor in the sport of boxing, and its measurement has important implications for monitoring training progression and outcomes. The aim of the current study was to establish the concurrent validity and reliability of a linear positional transducer and an accelerometer for the quantification of punch characteristics in untrained adults. Men and women aged 18-30 years with no previous boxing experience and no upper-limb musculoskeletal injuries were recruited. Participants performed 6 straight right punches; 3 at a self-determined 50% effort; and 3 at maximum effort. An accelerometer (Crossbow) and a linear positional transducer (GymAware) were used to examine peak velocity and acceleration of each punch. Validity was examined using Pearson's correlation analyses and by calculating mean bias and limits of agreement between measures from each device, whereas reliability was established using intraclass correlation coefficients (ICCs). Forty-four healthy young adults (28M and 16F; age 22.2 ± 2.9 years) participated. Moderate-to-strong positive associations were observed for both devices at 50% effort for velocity (r = 0.572-0.696) and acceleration (r = 0.867-0.921) and at maximum effort for velocity (r = 0.748-0.781) and acceleration (r = 0.897-0.946). High levels of reliability were observed with maximum punches for both devices (ICC = 0.922-0.981). Overall, moderate-strong measurement validity and reliability for punch speed was observed between the accelerometer and GymAware. Thus, the GymAware linear positional transducer is an acceptable measurement tool for the quantification of punch speed for straight punches in untrained adults.

A comprehensive analysis of extrusion behavior, microstructural evolution, and mechanical properties of 6063 Al–B4C composites produced by semisolid stir casting

In this study, composites of aluminum alloy 6063 reinforced with 10 wt% boron carbide microparticles were successfully fabricated by a combination of spark plasma sintering and stir casting methods, followed by hot extrusion. A systematic study on the relationship between extrusion process variables (i.e. extrusion ratio, temperature, and punch speed) and porosity, particle refinement, particle distribution and consequently tensile properties and fracture behavior of the composites was performed. Extensive electron microscopy analysis and tensile testing of the composites revealed a multifactoral interdependency of microstructural evolution and mechanical properties on the extrusion process variables. For example, while increasing the extrusion ratio at higher temperatures led to moderate particle refinement, better densification of the composites, and improvement in mechanical properties, concurrent particle fragmentation and microvoid formation around the particles at lower temperatures had opposing effects on the mechanical behavior. We show that the dependency of mechanical properties on all such microstructural factors makes it difficult to predict optimum extrusion conditions in aluminum matrix composites. That is, unlike the common approach, extruding the composites at higher temperatures and achieving more reduction in area may not necessarily lead to the most favorable mechanical properties.

Finite Element Modelling of Functionally Graded Cemented Tungsten Carbide Compaction with Flow Stress Estimation

Preparation of functionally graded material (FGM) is a challenging task for researchers in regard to the development of effective gradient having tuneable properties such as density, hardness, strength, etc. Although a number of the methods are available but powder metallurgy (PM) is an effective amongst them for creating defect free gradient. In the present work, PM route is adopted for the preparation of WC-Co FGM where strength is directly correlated with density. The prepared FGM performance is significantly influenced by the different parameters such as the size of powder particles, compaction pressure, punch speed and method of compaction, therefore compaction process is crucial for the prepared FGM quality. Punch speed, a method of compaction (single action and double action compaction) are considered as variables for simulation. The finite element method is implemented for simulation of compaction to know the deformation nature of powder. This deformation nature is helpful for prediction of final compact density. Flow stress is the major input parameter to model deformation behaviour of material and is estimated by “Johnson-Cook model”. The predicted results are in well accord with the work done by Favrot et al. It is observed that with an increasing punch speed density increases simultaneously. In addition to this under same experimentation condition, double action compaction produces more density compare to single action compaction. These results will be helpful to assess the influence of punch speed and compaction method on the density of compacted powder for the research community.

Six Sigma Framework Methodology for Deep Drawing Process Improvement

Deep drawing is one of the common sheet metal forming processes, its products are suffering from many defects, where avoiding such defects can be achieved by many methods. The objective of this work is to provide a framework methodology of using Six Sigma approach to avoid deep drawing defects and improve the process. The product under consideration is an aluminium cooker suffers from five types of defects; flange wrinkling, wall wrinkling, tearing, earing, and scratches. Six Sigma project is used for random data to reduce the defective rate through the DMAIC procedures. Product and its defects are defined in the define phase. The current situation is measured in the measure phase. Four factors are considered to construct a design of experiment in the analysis phase, there factors are: holding force, lubricant, punch speed, and clearness. Improvement procedure is suggested by adopting the best factorial level that is found in the analysis phase. Finally, a set of procedures is suggested to maintain the improved conditions in the control phase.

Effect of die width on spring back of electrogalvanized CR4 steel during air bending

This study is an attempt for analyzing the effect on spring back due to changes in the die width during air bending of electro-galvanized CR4 steel. A universal testing machine, enabling recording of bending force and controlling of punch travel was used for conducting the experiments. A flexible die set with die width Wd = 40mm, Wd = 60mm and Wd = 80mm was used whose die width can be changed by simply changing a distance block. Die radius, punch radius and punch speed were kept constant. Galvanizing was done by electrodeposition method using alkaline non-cyanide baths. Different thickness of electro-galvanizing, Tg = 0 µm, 4 µm, 7 µm, and 10 µm were achieved by changing the timing of electrodeposition. An approach to vary one factor at a time was employed. Angles were measured by using optical profile projector and graphics. The Graphical method was used for analyzing the spring back. It has been witnessed that spring back increases with the increase in width of die for every punch travel and for non-galvanized as well as galvanized steels of different galvanizing thicknesses. An increase in spring back was observed when the galvanizing thickness was increased. The results are important for the tool engineers and process shop engineers for tool design and process control.

Wear characteristics of die surface in deep drawing of stainless steel 304 by using finite element simulation

The characteristics of adhesive wear of TiN coating in drawing process by using finite element method were carried out to investigate the effects of drawing angles and sliding velocities of punch to explained wear index. Bending radius of die was used to increase the contact pressure between stainless sheet and TiN coating surface. Three sliding velocities (0.5, 1 and 5 mm/s) were studied each bending angle between (0O to 90O) by keeping the hardness of material coating to 24 GPa (HV.0.05). The results showed that the wear index were decreased with drawing angle but sliding speed of punch was not affected in slightly speed.

Deformation behavior and formability of gradient nano-grained AISI 304 stainless steel processed by ultrasonic impact treatment

The deformation behavior and formability of gradient nano-grained (GNG) AISI 304 stainless steel in uniaxial and biaxial states were investigated by means of tensile test and small punch test (SPT). The GNG top layer was fabricated on coarse grains (CG) AISI 304 by ultrasonic impact treatment. The results showed that the CG substrate could effectively suppress the strain localization of NC in GNG layer, and an approximate linear relationship existed between the thickness of substrate (h) and uniform true strain before necking (e unif). Grain growth of NC was observed at the stress state with high Stress triaxiality T, which led to better ductility of GNG/CG 304 in SPT, as well as similar true strain after the onset of necking (e neck) compared with coarse 304 in tensile test. Ei-values of GNG/CG 304 with different structures were nearly the same at different punch speeds, and good formability of GNG/CG 304 was demonstrated. However, punch speed and microstructure needed to be optimized to avoid much lost of membrane strain region in biaxial stress state.

A damage-coupled unified viscoplastic constitutive model for prediction of forming limits of 22MnB5 at high temperatures

Hot stamping of the boron steel 22MnB5 has been widely used to produce high strength parts in automobile industry. The forming limits of 22MnB5 sheets are governed by the damage evolution in hot stamping. The aim of this work is to formulate a constitutive model to predict the forming limits of 22MnB5 sheets under hot stamping condition according to continuum damage mechanics (CDM). The authors developed a set of damage-coupled viscoplastic constitutive equations to describe the thermal deformation behavior of 22MnB5 steel under uniaxial tensile state. The material constants of uniaxial constitutive equations were determined from the tensile testing data at a temperature range of 600–900 °C and a strain rate range of 0.01–10 s−1. The uniaxial damage-coupled constitutive equations were generalized to the plane stress state by introducing a multiaxial damage factor considering the effect of stress state on damage evolution. Hot Nakajima testing was conducted to get the forming limits of 22MnB5 sheets at different deformation temperatures and punch speeds. The material constants of multiaxial damage factor were calibrated and confirmed from the experimental data of Nakajima testing. The Nakajima test was numerically simulated by implementing the established constitutive equations via the user material subroutine VUMAT. The prediction by the numerical simulation agrees with the experimental results. Using the determined plane stress damage-coupled constitutive model, the forming limits of 22MnB5 sheets can be predicted under the hot stamping condition.

Stamping an AA5754 Train Window Panel with High Dent Resistance Using Locally Annealed Blanks

The warm stamping of an AA5754-H32 window panel for railway vehicles applications has been proposed in the present work. The adoption of increased working temperatures can be surely considered the most effective solution for this alloy to overcome the limited material formability at room temperature [Palumbo et al. “Warm Forming of an AA5754 Component for Railway Vehicle Applications”, Procedia Engineering, Vol. 183, 2017, Pages 351-356] but, in order to improve the overall dent resistance of the component, the initial wrought conditions have been chosen in the present work. The manufacturing of the window panel was thus subdivided into a preliminary local heat treatment (assumed to be performed by laser) to anneal the material and a subsequent warm stamping step using heated tools. The best combination of temperature and holding time able to produce the annealing of the investigated alloy was determined using the physical simulator Gleeble 3180. On the contrary, the warm forming step was designed by means of thermo-mechanical simulations: in order to model the AA5754-H32 blank with annealed regions, an extensive experimental campaign (tensile and formability tests) was conducted using specimens in the annealed (H111) and in the wrought (H32) conditions. Through the numerical approach it was thus possible define: (i) the extent of the annealed regions; (ii) the punch speed to get a sound component.