Insight into the Influence of Punch Velocity and Thickness on Forming Limit Diagrams of AA 6061 Sheets—Numerical and Experimental Analyses

In this article, the forming limit diagram (FLD) for aluminum 6061 sheets of thicknesses of 1 mm and 3 mm was determined numerically and experimentally, considering different punch velocities. The punch velocity was adjusted in the range of 20 mm/min to 200 mm/min during the Nakazima test. A finite element (FE) simulation was carried out by applying the Johnson–Cook material model into the ABAQUSTM FE software. In addition, a comparison between the simulation and the experimental results was made. It was observed that by increasing the punch velocity, the FLD also increased for both thicknesses, but the degree of the improvement was different. Based on these results, we found a good agreement between numerical and experimental analyses (about 10% error). Moreover, by increasing the punch velocity from 20 mm/min to 100 mm/min in 1 mm-thick specimens, the corresponding FLD increased by 3.8%, while for 3 mm-thick specimens, this increase was 5.2%; by increasing the punch velocity from 20 mm/min to 200 mm/min in the 3 mm-thick sheets, the corresponding FLD increased by 9.3%.

Application of a Validated Innovative Smart Wearable for Performance Analysis by Experienced and Non-Experienced Athletes in Boxing

An athlete’s sporting performance depends to a large extent on the technical execution of the athletic motion in order to achieve maximum effectiveness in physical performance. Performance analysis provides an important means of classifying and quantifying athletic prowess in terms of the significant performance aspects of the sport to provide objective feedback. This study aimed to analyze technical execution in terms of punch trajectory, force, velocity and time, considering the expert-novice paradigm by investigating the technical execution of 31 experienced and non-experienced athletes for the four main punching techniques of the cross, jab, uppercut and hook strike. The kinetic and kinematic data were collected by means of a boxing monitoring system developed and validated for in-field use. The research revealed significant correlation for executed punching trajectory and punch force in intragroup comparison and significant differences in intergroup comparison. No significant differences were detected for punch velocity in either inter- or intra-group paradigms. This study, through use of the sensor system, aligns with the results of existing publications conducted in laboratory conditions, in the assessment of punch force, punch speed and punch time and thus extends the state of research by use of a smart wearable in field method.

Investigation of Thickness Distribution Variation in Deep Drawing of Conical Steel Products

This study investigates the thickness variation behavior of deep drawing conical products under the effect of different forming parameters such as die wall inclination angle, punch velocity, sheet thickness, and sheet metal type. Two types of sheet metal were used, low carbon (AISI 1008) and galvanized steel sheets, of 110 mm diameters circular blanks at 0.9 and 1.2mm thickness formed by tooling set (punch, die, and blank holder). The conical dies inclination angles were at 70ᵒ, 72ᵒ, and 74ᵒ where, the punch velocity was 100, 150, and 200 mm/min. Numerical simulation was conducted using ABAQUS 6.14 where a dynamic explicit solver was used to perform forming of conical products. The results show that maximum thinning occurs at punch nose radius region and maximum thickening in sidewall region and thinning are increased with the increasing of die sidewall angle and sheet thickness. In regard to sheet type, the Lankford coefficients r-value shows a great role in thinning behavior with respect to rolling (r-values direction). The results have shown a good agreement between experimental and numerical work with a maximum discrepancy of 5%.

Optimization of Process Parameters on Microstructure and Mechanical Properties of ADC12 Alloy Aptomat Contact Fabricated by Thixoextrusion

The mechanical properties of thixoextrusion components can be improved by controllable processing parameters such as the solid fraction of alloy, holding time, punch velocity, heat treatment and die temperature. In this study, the effects of thixoforming parameters on the microstructures and mechanical properties of thixoextrusion ADC12 alloy Aptomat Contact are studied. ADC12 has excellent castability with high fluidity and low shrinkage rate, so it is widely used in industry, especially in automotive and motorcycle engine part casting. It is a near eutectic alloy with high strength and low ductility (1%). The optimization parameters mechanical properties were investigated by changing the punch velocity, specimen temperature and holding time. The results also indicated optimal value at punch velocity (15 mm/s), specimen temperature (560 °C) and holding time (5 min) which was changed microstructure from eutectic dendrite to globular grain, increasing the ductility (3.3%) of this alloy during the semi-solid forming process while the remaining mechanical properties lead to an increase in the quality of finished parts.

Evaluation of Material Compatibility for Hydrogen Applications Using Performance Factors Obtained by In-Situ SP Test

Recently, a simple screening technique based on the quantitative evaluation of the hydrogen embrittlement (HE) sensitivity of the metallic materials using an in-situ small-punch (SP) test method was developed by the author group. The in-situ SP test can be easily carried out even under a high-pressure hydrogen gas environment. It makes possible to investigate the HE behaviors of metallic materials quantitatively adopting as a characterizing performance factor of the relative reduction of thickness (RRT) measured at the fractured parts of specimen after SP tests. In this paper, the application of the newly established in-situ SP test method for the hydrogen compatibility screening of austenitic stainless steels was performed at room and low temperatures. The influence of punch velocity on RRT of the HE sensitivity was examined for various austenitic stainless steels. Their HE sensitivities were evaluated quantitatively using RRT and checked by comparing to a factor, the relative reduction of area (RRA) obtained by SSRT tests.

SIMULATION AND EXPERIMENTAL INVESTIGATION OF WRINKLE DEFECT IN DEEP DRAWING PROCESS OF CARBON STEEL SPCC SHAPED CYLINDER FLANGE CUP

A Sheet Metal Forming (SMF) process, especially deep drawing, is one of the manufacturing processes that commonly used in the automotive industry. Compared with casting and forging, the SMF process has several advantages, including lesser weight materials and broader variations in shape that can be made. One of the problems in the SMF process is the wrinkling phenomenon, which can cause the size and appearance defects of sheet products. The wrinkle occurs because of the mechanical properties of the material, product geometry, and blank holder force (BHF). Several variations of BHF were applied in these simulations and experiments to eliminate the wrinkle defects of cylinder flange cup test products. The characteristic of the cylinder flange cup is from the cold-rolled coiled steel plate (SPCC) type of material with a thickness of 0.8 and 1.0 mm, the height of 10 mm, the inner diameter of 58 mm, and flange diameter of 76 mm. Simple simulations of the SMF process were carried out by using Solidworks with version 2017, and the experiment was carried out at a 600 kN press with a punch velocity of 40 strokes per minute and blank holder force variations from 0 to 21 kN. The experimental data performed with a single die on a flanged cup cylindrical test material shows that the higher the blank holder force (BHF) number, the smaller the wrinkle defect, and it can be eliminated starting from the BHF number of 15 kN.

THE EFFECT OF PUNCH GEOMETRY ON PUNCHING PROCESS IN TITANIUM SHEET

Reducing punch force, increasing the sheared surface, and improving the work hardening have been real challenges in developing a punching process, and the right selection of punch geometry can resolve these challenges. Selecting the appropriate geometry, however, has been difficult to do since the effect of punch geometry on the punching process is rarely studied, and therefore, this study aims to investigate the effect of punch force, sheared surface, and work hardening by using commercially pure titanium sheets. The punching process under the study employed three different punch geometries, namely flat (FLAT), single shear angle (SSA) and double shear angle (DSA) with a shear angle of 17°, while the Punch velocity used was 35mm/s and 70 mm/s. The results show that the punching process using SSA and DSA punch geometry with the punch velocity of 35 mm/s reduces the punch force by 18% and 13% consecutively compared to that of FLAT with the same velocity. However, the sheared surface quality seems to decline as the rollover height increases by about 48% and 32%. Moreover, the burnish height decreases by 34% and 7% and the resulted work hardening improves by 4.7% and 2.3% respectively. The study concludes that SSA and DSA punch geometry can be best used to reduce punch force and increase work hardening, but apparently fail in increasing the sheared surface quality.