Punch Load Research Articles

Experimental and Finite Element Studies of Stretch Forming Process for ASS 316L at Elevated Temperature

Austenitic stainless steel 316 L grade is a material having extraordinary mechanical properties, low cost and easily available. This is the reason it was used in various industrial and nuclear applications. In the present work, ASS 316L nakazima specimens are stretched under hot forming conditions (750°C, 825°C and 900°C) at a constant strain rate (0.1s-1) along with three different orientations. These six types of nakazima specimens were used to know the formability behaviour of the material with the help of forming limit diagrams (FLD) obtained by the stretch forming process. A smaller change in Punch load and an increase in displacement were observed, which indicates the formability improvement of ASS 316L sheet metal with the increase in temperature. In addition, ABAQUS 6.13 computer code was applied for the prediction of formability from 750°C to 900°C.To improve the accuracy of the simulation, a number of integration points were accrued within the thickness direction, limiting dome height (LDH).The ductile fracture was observed from SEM images for all the temperatures. A close agreement was found between experimental and simulated results.

The Deep Drawing of a Flanged Square Hole in Thin Stainless Steel Sheet

To manufacture metal products of accurate size and shape by deep drawing requires the precise control of a number of variables. The problem of spring-back after the load has to be avoided, and the prevention of cracks in the product requires careful control of the punch load. In this study, where drawing experiments and simulations were carried out on thin sheets of SUS304 stainless steel, the influence of the scale effect on the thin sheets also needed consideration. This was accomplished by the use of an updated Lagrangian formulation and finite element analysis. Material behavior was simulated using a micro-elastoplastic material model, the performance of which was compared with that of models involving conventional materials. The Dynaform LS-DYNA solver was used for simulation analysis, and pre and postprocessing were carried out to obtain material deformation history as well as to determine thickness change, distribution and material stress, and prepare strain distribution maps. Scaling was necessary to account for the effect of the thickness of the sheet and the relationship between punch load and stroke, the distribution of thickness, stress and strain, and the maximum size (d) of the flanged hole and the maximum height of the flange. The simulation results were compared with experimental results to confirm the accuracy of the three-dimensional finite element analysis of the elastoplastic deformation. The results showed that the size of the fillet radius of the hole (Br) had an effect on the punch load, which increased with an increase in Br. However, the minimum thickness of the formed flange decreased with an increase in Br. The maximum principal stress/strain and height of the flange also increased with an increase in Br. The punch fillet radius (Rp) also had an impact on the process. The punch load decreased with the increase in Rp, while the minimum thickness increased slightly. The average values of the minimum thickness for three models were 0.148, 0.0775, and 0.0374 mm. The forming ratio also had an influence on the process. When the forming limit of the square hole flange was FLR = 0.84, cracking occurred in the corners of the flange, and wrinkles formed over the undrawn area of the sheet. These findings can serve as a valuable reference for the design of deep drawing processes.

Performance Analysis of Indentation Punch on High Energy Lithium Pouch Cells and Simulated Model Improvement.

In this research, the aim relates to the material characterization of high-energy lithium-ion pouch cells. The development of appropriate model cell behavior is intended to simulate two scenarios: the first is mechanical deformation during a crash and the second is an internal short circuit in lithium-ion cells during the actual effect scenarios. The punch test has been used as a benchmark to analyze the effects of different state of charge conditions on high-energy lithium-ion battery cells. This article explores the impact of three separate factors on the outcomes of mechanical punch indentation experiments. The first parameter analyzed was the degree of prediction brought about by experiments on high-energy cells with two different states of charge (greater and lesser), with four different sizes of indentation punch, from the cell’s reaction during the indentation effects on electrolyte. Second, the results of the loading position, middle versus side, are measured at quasi-static speeds. The third parameter was the effect on an electrolyte with a different state of charge. The repeatability of the experiments on punch loading was the last test function analyzed. The test results of a greater than 10% state of charge and less than 10% state of charge were compared to further refine and validate this modeling method. The different loading scenarios analyzed in this study also showed great predictability in the load-displacement reaction and the onset short circuit. A theoretical model of the cell was modified for use in comprehensive mechanical deformation. The overall conclusion found that the loading initiating the cell’s electrical short circuit is not instantaneously instigated and it is subsequently used to process the development of a precise and practical computational model that will reduce the chances of the internal short course during the crash.

On the estimation of tensile yield stress for polymer materials based on punch tests

The Small Punch Test (SPT) has been widely used for the high throughput evaluation of mechanical properties of metallic materials. However, all the correlations between characteristic punch loads and mechanical properties measured from tensile tests thus far have been developed based on the variation of specimen thickness. This paper introduce a new approach to the estimation of tensile yield stress from punch test measured load-displacement curves based on the variation of punch indenter diameter. Mechanical properties of high density polyethylene (HDPE) are first characterized using both monotonic tensile and punch tests at various loading speeds. Linear correlations between the maximum punch load and the square indenter diameter or the indenter diameter are established, based on which the tensile yield stress could be expressed as a function of maximum punch load and the square indenter diameter or indenter diameter. The yield stress estimated using the proposed correlations is compared with those measured from tensile tests and the results indicate that the correlation based on the variation of indenter diameter yields better prediction results than the correlation based on the variation of square indenter diameter. Good agreement has been achieved between the predicted results using correlation based on the variation of indenter diameter and the yield stress measured from tensile tests, suggesting the proposed approach is applicable for the estimation of mechanical properties for HDPE materials based on punch test.

Investigation of Punch Shape and Loading Path Design in Hydro-Flanging Processes of Aluminum Alloy Tubes

Hydro-joining is composed of hydro-piercing, hole flanging and nut-inlaying processes. In this study, a new hydro-flanging process combining hydro-piercing and hydro-flanging is proposed. An internal pressured fluid is used as the supporting medium instead of a rigid die. Three kinds of punch head shapes are designed to explore the thickness distribution of the flanged tube and the fluid leakage effects between the punch head and the flanged tube in the hydro-flanging process. A finite element code DEFORM 3D is used to simulate the tube material deformation behavior and to investigate the formability of the hydro-flanging processes of aluminum alloy tubes. The effects of various forming parameters, such as punch shapes, internal pressure, die hole diameter, etc., on the hydro-flanged tube thickness distributions are discussed. Hydro-flanging experiments are also carried out. The die hole radius is designed to make the maximum internal forming pressure needed smaller than 70 MPa, so that a general hydraulic power unit can be used to implement the proposed hole flanging experiments. The flanged thickness distributions are compared with simulation results to verify the validity of the proposed models and the designed punch head shapes.

EXPERIMENTAL INVESTIGATION OF SPRINGBACK OF LOCALLY HEATED ADVANCED-HIGH STRENGTH STEELS

Sheet metal bending is one of the important metals forming processes at ambient temperature. The usage of high-strength steel is one of the stronger materials for the construction of components in the automotive industries. However, for complex shapes, cold forming is not always sufficient, and heating the workpiece plays a major role in manufacturing these shapes. Bendability may increase with increasing forming temperature and currently, hot forming of advanced high strength steels (AHSS) is becoming more attractive. While hot forming of AHSS is beneficial for high formability, subsequent quenching is required to maintain final strength. This procedure extends the production time. In this study, temperature gradients, bending loads, and springback after V-bending were investigated. The experimental study was carried out on a 2 mm thick Docol 1500M steel at various temperatures by using a speed-controlled servo press machine. The bending regions of the specimens were locally heated to 200, 300, 400, 500, and 600oC by using a high-frequency induction heating device. The results show that; punch loads were significantly lowered with increasing the local heating temperature during bending. There were no cracks observed on the specimens. The amount of spring back is decreasing with the bending temperature and around 500oC almost no springback was measured. Negative spring back was observed for the bending temperatures higher than 500oC

Experimental investigation on the energy absorption characteristics of sandwich panels with layering of foam core under quasi-static punch loading

Quasi-static full penetration tests were investigated on sandwich panels with graded polyurethane foam core and aluminum face-sheets. Results showed that the panels with decreasing foam core density (HL) create more contact force and its amount is 1.5 times the force required to penetrate into panels with increasing foam core density (LH). Also, the indenter needs the highest energy to penetrate into sandwich panel with decreasing foam core density (HL), and its value is 1.32 times the energy required to penetrate into panel with increasing foam core density (LH).

Analytical, numerical and experimental analysis of double collar collet chuck holder by combined extrusion and forging processes

The present paper confers about design and analysis of double collar collet chuck holder (DCCCH) by combined extrusion and forging (CEF) process. The current work addresses the problem to estimate the parameters such as metal flow, heat transfer, friction, punch load and ram speed during the CEF process. It should be noted that complexity of shape and volume of the material are two major constitutes which ensign motivation for the present work. In this context, framework of the present in-situ focus on estimation of aforementioned parameters which enables us to develop complex shapes with minimal material wastage using CEF process. Henceforth followed by analytical and numerical solutions have been developed adjacent to the experimental procedure.

Formability behavior of friction stir processed dual phase steel

This study investigated the formability behavior of dual-phase (DP) steel subjected to friction stir process (FSP), using a miniaturized Erichsen test. The friction stir process yielded a refined microstructure, which consisted of lath martensite and fine ferrite, as a result of dynamic recrystallization (DRX) and phase transformation. Both yield and tensile strength were significantly increased via the grain refinement and increasing martensite fraction. Biaxial formability behavior of the friction stir processed sample exhibited a decline as the Erichsen index (EI) decreased from 2.7 mm to 2.2 mm. However, the required punch load (FEI) increased compatibly with the strength value after FSP. The grain refinement caused by FSP led to an improvement in the orange peel effect, defined as a negative effect of increased surface roughness after metal forming. The value of mean roughness in the free dome surface of the FSPed sample decreased from 4.90 μm to 2.62 μm. It can be concluded that the roughening with the orange peel effect on free surfaces of stretched metal can be eliminated by the friction stir process.

Influence of anisotropic yield criteria on simulation accuracy of the hole-expansion test

Prediction accuracy of the two well-known anisotropic yield criteria, namely, Hill’48 and Yld2004-18p, on plastic deformation of AA5052-O sheet aluminium alloy experiencing compound stress was profoundly examined and contrasted in this work. To obtain the flow behaviour and anisotropy of the test material in varying loading directions, both uniaxial tensile and balanced-biaxial tests were conducted in the corresponding directions. Furthermore, a disc-compression test was carried out to reveal the biaxial r-value. Those gained mechanical properties could therefore be used to determine the material constants required by each yield criterion. The standard conical-punch hole expansion test was chosen here to impose complex stress on the sheet specimen. Forming parameters such as the punch load, stroke paths, hole expansion ratio, sheet thickness profile around the hole circumference and flange height were all monitored and investigated. It was shown that the results from the Yld2004-18p model with an exponent of eight apparently better agreed with the experimental data than those from the Hill’48 one. A conclusion could be drawn here that the yield criterion significantly affected the accuracy of the predicted deformation behaviour of the investigated aluminium alloy grade AA5052-O nevertheless in dependence on the degree of material anisotropy.

Interaction between forming and joint quality of the friction-assisted clinching

In order to achieve the effective joining of aluminum and magnesium alloy sheets, a friction-assisted clinching is innovatively proposed to reduce material damage during the process and improve the joint quality. 2 mm thick Al5052 aluminum sheet and 2 mm thick AZ31 magnesium alloy sheet were selected as the research objects, the interaction between different forming parameters, i.e., die depth, rotational speed and rotation time, and the joint quality, i.e., the damage, neck and interlock were explored by DEFORM-3D. The influence of sheet temperature on damage and punch load is analysed, the rotational speed and rotation time have great influence on the forming joint, the die depth mainly affects the neck and interlock. Comparing the joint qualities under different forming parameter combinations, it is found that the joint quality is the best when the bottom die depth is 2.2 mm and the bottom punch is applied at 1000 rpm for 0.5 s. The research will provide a valuable reference for the realization of joining the aluminum and magnesium sheets.

An application of FEM in the determination of tensile properties for work-hardened carbon steel by means of small punch test

The determination of tensile properties from a small punch (SP) test by using a finite element method (FEM) has been studied. First, a finite element (FE) simulation of the SP test using true stress-strain curves including post-necking strain data of work-hardened SM490A carbon steel specimens was conducted. The simulation was validated with actual experimental results, which showed that the FE model can effectively reproduce the load-displacement curves without using a damage modeling technique. The FE model was then used to investigate an empirical correlation between the punch loads and the material parameters, including yield strength and ultimate tensile strength. The results indicated that the empirical constants are dependent on specimen thickness and may be valid for only a limited range of test configurations and materials. To expand the applicability of the SP test in the assessment of tensile properties, an inverse finite element method (iFEM) consisting of the iterative finite element calculation, bisection method, and Ludwik’s constitutive model was developed. Through the procedure, true stress-strain curves were constructed from the simulated load-displacement curves of hypothetical materials based on the SM490A steel specimens. Finally, yield strengths and ultimate tensile strengths of the carbon steel specimens were determined and found to be within 5.2% and 2.8% discrepancies, respectively, from the uniaxial tensile test results. iFEM provides consistent estimations of tensile properties with almost no influence of specimen thickness.

Deformation Behavior of Al/Cu Clad Composite During Twist Channel Angular Pressing.

The research and development of modern metallic materials goes hand in hand with increasing their lifetime via optimized deformation processing. The presented work deals with preparation of an Al/Cu clad composite with implemented reinforcing Cu wires by the method of twist channel angular pressing (TCAP). Single and double pass extrusion of the clad composite was simulated numerically and carried out experimentally. This work is unique as no such study has been presented so far. Detailed monitoring of the deformation behavior during both the passes was enabled by superimposed grids and sensors. Both the sets of results revealed that already the single pass imparted significant effective strain (higher than e.g., conventional equal channel angular pressing (ECAP)), especially to the Al matrix, and resulted in notable deformation strengthening of both the Al and Cu composite components, which was confirmed by the increased punch load and decreased plastic flow velocity (second pass compared to first pass). Processing via the second pass also resulted in homogenization of the imposed strain and residual stress across the composite cross-section. However, the investigated parameters featured slight variations in dependence on the monitored location across the cross-section.

Characterisation of deformation process and fracture mechanisms of P91 steel at 600 °C in small punch tensile testing

This paper investigates the microstructural evolution and fracture mechanism of the P91 steel during small punch tensile tests. Disc specimens, 8 mm in diameter and 0.5 mm in thickness, were tested in a small punch test rig at 600 °C using a constant displacement rate of 2 μm/s. Interrupted small punch tensile tests were performed to investigate the microstructural evolution in different deformation regimes. Deformed specimens were characterised by scanning electron microscopy and electron backscatter diffraction. Microstructure characterisation showed that block boundary alignment occurred in the plastic deformation direction, before achieving the maximum punch load. It was revealed that the martensitic structure was recovered when the tests progressed. The elongation of recovered grains occurred after achieving the maximum punch load. In addition, it was shown that the voids tended to nucleate along the recovered grain boundaries and became elongated to align with the plastic flow within the specimen.

Modelling of Sheet Metal Process using Finite Element Analysis 2DCAD Model to Find the Optimum Sheet Thickness

Deep drawing is popular sheet metal forming process. Complex axisymmetric geometries, and certain nonaxisymmetric geometries, can be produced in a few operations in small cycle time. Skill requirement of operator is relatively less. The basic theories governing the deep drawing are based on application of theory of plasticity to the deep drawing process. It is very difficult to apply these theories and arrive at a general solution which can handle any arbitrary geometry. Some simpler ‘mechanics models’ are more appropriate for such cases, though these do not incorporate all the aspects governing the process. Therefore, design in sheet metal forming, even after many years of practice, still remains more an art than science due to the large number of parameters involved in deep drawing and their interdependence. Design of tooling for deep drawing (die, blank holder and punch) has been largely based on trial and error resulting in loss of time and money and large development cycles. Using the finite element method one can simulate the process and study the effect of various parameters before finalizing the design. Several simulation tests were carried out to obtain the most appropriate value for some of the parameter. A computational experiment is made to explore the effect of process variables on stress distribution and punch load. An elastic-plastic finite element computational program is developed to simulate successive deep drawing process.

Analysis of Forming Complex Cup by Drawing Process

This paper aims to design and construct a deep drawing dies to produce a complex cup with eight vertices with the major diameter (41.5 mm) and the minor diameter (34.96 mm) and length (30 mm) using numerical simulation and experimental. Also, intended to study the influence of forming method on drawing load, distribution of thickness, and distribution of stress and strain along the wall of the cup were investigated. Two forming methods were used to accomplish this research. The first forming method, which is called the direct forming method in which the complex shape is performed by drawing the circular blank metal. The second forming method is called the converting method, in which the cylindrical cup is redrawn into a complex cup. The low carbon steel sheets (1008-AISI) of the thickness (0.7 mm) and diameter (80 mm) were utilized in this research. ANSYS Workbench 18.0 software in 3-D modeling was utilized to simulate the drawing processes. The results appear that the maximum punch load was with the first forming method (the complex cup is done by drawing the circular blank metal) and higher than the maximum punch load that occurred with the second forming method. The maximum thinning at cup curvature was subjected to the complex cup produced by the first method, especially in areas of convex and concave and more than the complex cups produced by the second forming method. The second forming method is the best method to produce a complex cup with the less thinning at cup curvature and more regular thickness, stress, and strains distribution.

Forming feasibility of complex multi-cavity parts of 316LN steel by multi-direction loading: from aspect of geometric and process parameters

Multi-direction loading forming technology provides an effective way for green manufacturing of high-performance multi-cavity complex parts of 316LN steel, which are widely used in nuclear power pipelines. In this forming process, the material needs to undergo complex unequal deformation under a mixed stress state of tensile-shear, compression-shear and shear, flow and fill the cavity to obtain such complicated shape only from the simple cylindrical blank, thus forming defects are prone to occurring and restrict the forming feasibility, which is related to both process parameters and the geometric structures to be formed. In this paper, by considering the uniformity of deformation and temperature distribution, along with the forming load, the reasonable forming parameters were analyzed and obtained. The results showed that the deformation uniformity could be improved as the punch loading speed increased or the friction factor decreased. A lower forming load could be realized by reducing the loading speed of punches or raising the initial blank temperature. Then under the recommended process parameters, the reasonable range of geometric dimension of parts to be formed was acquired by investigating the velocity field, forming load, folding length, and damage distribution. When ratio of the branch pipe spacing to outer diameter of main pipe is Lm/D0 ≤ 0.5 or inner-outer diameter ratio of main pipe d0/D0 ≥ 0.8, the cracking would occur. When length of main pipe L0 = D0 or inner-outer diameter ratio of branch pipe is d1/D1 ≤ 0.6, both folding and cracking presented. Consequently, the acquired forming feasibility can provide guidance for the application of multi-direction loading forming process for multi-cavity complex parts.

Effects of the pre-hole geometry on the final shape of the countersunk hole

The main objective of this study is to characterize the effects of the pre-hole geometry on the countersinking process. The final shape of the countersunk hole and the punch load were investigated. A finite element model was developed using ABAQUS/Standard. A configuration with maintained blank-holder was used for this study. The adopted model was performed with an elastoplastic behavior and isotropic hardening rule for the workpiece. In this study, an approach based on the definitive screening design (DSD) was performed to perform a parametric study and a statistical analysis to investigate the effects of the geometrical parameters of the pre-hole and their interactions on the countersinking process. The evolution plot of the parameters of the final countersunk hole shape, during the process, was an additional tool to better understand the obtained results. It was concluded that the inner radius of the pre-hole had the most important impact on this final shape. In addition, it was found that the punch load was more affected by the fillet radius of the pre-hole than the other parameters. Concerning the thickness of the workpiece, it had the lowest influence on the process. The experiments were carried out and the obtained results were in good agreement with the numerical ones.

Numerical Modelling and Simulation of Vortex Extrusion as a Severe Plastic Deformation Technique Using Response Surface Methodology and Finite Element Analysis

Vortex extrusion (VE) as a severe plastic deformation method that imposes high values of strain with simultaneous torsion and extrusion of a workpiece was studied in this paper. Response surface methodology was used for investigation the relationship between reduction in area (RA), twist angle (φ), length of twist zone (L) and position of control points in Beziers’ formulation (C1) as input parameters, and efficient twisting of the material and punch load (steady state load) as output parameters using streamline proposed 6-indent VE die in different frictional conditions. Accuracy of the finite element analysis (FEA) results was evaluated with experimental data before of using FEA to obtain the responses. Analysis of variance was used to evaluate the effect of the parameters and their interaction on the responses and to develop a mathematical model for the responses. Results showed that, beside the effects of φ, RA, L on twisting of the materials in both frictionless and frictional conditions, interaction of φ and RA (φ × RA) is a significant parameter in the frictional condition. However, φ, RA and interaction of RA with RA (RA × RA) were considered as the significant parameters that affect the load of the process in both frictional conditions. Finally the proposed mathematical model for load of the process was evaluated with experimental data in similar conditions. It was concluded that the results of the modeling and experimental data are in a good agreement.

Three-point bending analysis with cohesive surface interaction for improved delamination prediction and application of carbon fibre reinforced plastics composites

Carbon fibre reinforced plastics laminates were loaded through to fracture in a three-point bending configuration, to gain understanding of the cohesive interaction between plies and validate mechanical properties and predictive capability of the FE model. The effect of mesh refinement, scaling techniques, failure models and cohesive surfaces were investigated. Fibre orientations investigated were parallel, 45° and perpendicular to the loading. Experimental results showed a larger radius punch promoted failure on the intended bottom side, tensile stresses region, allowing for the Aramis strain camera to record the failure. When the fibre orientation was perpendicular to the punch load, all failure models show similar rate of force increment with respect to displacement. No difference in failure prediction is observed for the different 0° models, except for a 4.18% under prediction by LaRC02 compared to the experiment. With fibre orientations at 45° and 90°, the Maximum Strain and LaRCO2 failure models were more suitable in terms of accuracy and convergence. Incorporating cohesive surfaces between instances improve nonlinearity prediction of 45° and 90° layups. Small span-to-thickness ratio analysis predicts interlaminar shear failure, delamination, versus large span-to-thickness ratio determine normal stresses to dominate failure in laminate. The model was setup in multi-fibre orientation and cross-ply layups for extended application and was shown to successfully predict material response described in literature.