Punch Temperature Research Articles

Microstructure and mechanical properties of thixoforged complex box-type component of 2A12 aluminum alloy

Complex box-type components of 2A12 aluminum alloy were thixoforged successfully, and their microstructures and mechanical properties were studied. Full filling status without surface defects was acquired by thixoforging a trapezoidal semisolid billet at the female die temperature of 420 °C and punch temperature of 340 °C. The maximum yield strength, ultimate tensile strength and elongation of the thixoforged component under optimized T4 treatment condition were 263.4 MPa, 414.2 MPa and 36.0%, respectively. Liquid segregation phenomenon happened at the upper edge of the component due to liquid flow and flow of liquid incorporating solid particles. Liquid fraction at the bottom part of the component was little, therefore severe plastic deformation mechanism of solid particles along with dynamic recrystallization was dominant. Dislocations, dislocation loops and dislocation bands of thixoforged 2A12 product were observed through transmission electron microscope (TEM). Deformation textures (Brass, Goss and S), recrystallization textures (Cube and R) and shear texture (rotated Cube) existed at the bottom region. Dispersoids Al20Cu2Mn3, Al7Cu2Fe particles and intermetallic phase S (Al2CuMg) were speculated in the microstructure of thixoforged 2A12 component with T4 heat treatment. Dislocations strengthening, refinement strengthening and strengthening of the second phase codetermined the final mechanical properties.

Weight losses estimation of industrial punch tools

Many studies have been conducted on the estimation of weight losses of industrial tools; however, these investigations are very rare. And there is no prediction study on the weight loss of industrial punches. An artificial neural network model (ANN) was proposed in order to establish relationships with the field data including input parameters as punch diameter, punch stroke, stroke noise, and punch temperature and output parameter as weight loss of punch. Effect of each parameter on the weight loss of industrial punch was analyzed with the developed model. An empirical formula was also obtained with the generalization capabilities of the ANN system. Analysis results showed that the estimation results are in good agreement with the field data. And these numerical results with high efficiency can make it possible to use the neural designs for real-life industrial punch estimation applications.

The effects of lubricants on temperature distribution of 6063 aluminium alloy during backward cup extrusion process

Backward extrusion has received several applications in the production and manufacturing sectors, most importantly in the bulk forming processes and various researchers have carried out several studies about backward extrusion processes in the time past varying from experimental, theoretical, empirical, analytical to numerical methods in order to analyze and optimize it. In this present investigation, backward cup extrusion of AA6063 was successfully carried out experimentally and theoretically using tropical coconut oil and castor oil as lubricants. The experiment was also carried out without lubrication. With the different lubricating conditions, the strain rate was varied at 1.5×10−3s−1, 2.0×10−3s−1, 2.5×10−3s−1 and 3.0×10−3s−1 respectively. A numerical analysis using DEFORM 3D software for backward cup extrusion at strain rates of 2.0×10−3s−1 and 2.5×10−3s−1 were then performed to determine optimum lubricated condition and temperature distribution during the deformation. It was found that the temperature increased with increasing strain rates. At a higher strain rate, the temperature of both punch and lower die also increased. The highest temperature was observed when lubricated with tropical coconut oil at a strain rate of 3.0×10−3s−1 which was observed to be above 33°C when compared to other lubricants. The punch temperature showed a higher temperature compared to the lower die temperature in all cases. The extrusion load–stroke curve of the simulation result was consistent with the experimental results.

Considerations for the accreditation of small punch creep testing

Efforts to extend a pre-existing European Code of Practice (CoP) covering small punch creep and tensile testing into a full International standard procedure are progressing. Swansea Materials Research & Testing Ltd, in collaboration with the academic team based at Swansea University, have been proactive in anticipating some of the key recommendations from the ECISS TC 1010/WG 1 with a view to gaining accreditation for an extensive suite of small punch test equipment. Here, comparisons between the miniaturised form of small punch creep testing will be made to the expectations for calibration and measurement laid down by existing standards for creep testing of conventional scale specimens. In particular, the calibration requirements relating to load, displacement, alignment and temperature measurement will be addressed. With test reproducibility at the forefront of our attention, recent modifications to test rigs to control load application and validation exercises to define small punch temperature distribution will be described. Ultimately, the need to develop an uncertainty budget for small punch creep testing will be highlighted.

Densification and microstructural evolution of spark plasma sintered NiTi shape memory alloy

The effect of particle size and sintering temperature on the densification and microstructural characteristics of nickel-titanium shape memory alloy (NiTi-SMA) has been investigated using spark plasma sintering (SPS) process. The Ni and Ti elements in different particle sizes were alloyed in the composition of Ni50.6Ti49.4. The milled NiTi powders were consolidated using SPS process in a temperature range of 700–900 °C. The densification was characterized by plotting temperature, current and relative displacement of punch as a function of holding time. The results showed that a maximum relative density of ∼98% can be achieved for NiTi-SMA with an average particle size of 10 µm at a sintering temperature of 900 °C. The microstructure of the sintered NiTi-SMA was examined using scanning electron microscope (SEM) and composition of NiTi alloy was analyzed using energy dispersive spectroscopy (EDS) analysis. The effect of sintering temperature on the microstructural evolution and transformation was also studied.

Improvement in Material Flow During Nonisothermal Warm Deep Drawing of Nonheat Treatable Aluminum Alloy Sheets

Automotive industries are very much interested in implementing warm forming technology for fabrication of light weight auto-body panels using aluminum alloys without localized thinning or splitting. A nonheat treatable and low formable AA5754-H22 aluminum alloy sheet was selected in the present work, and a laboratory scale warm deep drawing test set-up and process sequences were designed to improve material flow through independent heating of punch and dies. Significant enhancement in cup depth was observed when the temperature of punch and dies were set to 30 °C and 200 °C, respectively. Thermo-mechanical finite-element (FE) model of the nonisothermal deep drawing test was developed successfully to study the improvement in material flow incorporating Barlat-89 yield theory using temperature dependent anisotropy coefficients and Cowper–Symonds hardening model. It was found that a nonisothermal temperature gradient of approximately 93 °C was established within the blank from the center to flange at the start of deformation, and subsequent evolution of temperature gradient helped in improving material flow into the die cavity. The effect of temperature gradient on forming behavior in terms of cup height, ear profile, and thinning development across flange, cup wall, and blank center were predicted and validated with experimental results.

Analysis of Temperature and Stress in Differential Temperature Reverse Deep Drawing of 5A06 Aluminum Cup

The warm reverse deep drawing process is proposed to form cylindrical cups with greater drawing depths. Experimental and numerical investigations were conducted to analyze the effect of the temperature field on the drawing depth limit and the stress distribution during the warm reverse deep drawing process of a 5A06 aluminum plate. The effects of the punch temperature and initial flange temperature on the temperature gradient in the blank are discussed. The drawing depth limits for the different temperature gradients in the blank were determined. In addition, the effect of the temperature field on the radial stress distribution was analyzed. A 180°C temperature gradient occurs when the punch temperature is room temperature. When the temperature field generated in the blank is uniform, a fracture occurs, and the drawing depth limit (72 mm) is only 20% of the desired depth. When the temperature gradient is 100°C, the drawing depth limit increases by 400%. Fracture occurs for a uniform temperature field because the radial stresses at the inside corner are larger than those at the punch corner. As the temperature gradient increases, the radial stress at the inside corner is lower than that at the punch corner, which prevents fracture. A deep cup with a 375-mm drawing depth was produced when the temperature gradient exceeded 100°C.

Effect of Austenitization Temperature on Microstructure and Mechanical Properties of B1500HS Boron Steel in the Hot Stamping

In the paper, a typical part of B1500HS boron steel was formed using the hot stamping tools, and the effect of austenitization temperature on the microstructure and mechanical properties of B1500HS boron steel was studied. The results show that, the temperature of steel plate has a significant effect on the temperature of hot stamping tools, and the temperature of punch rises at a faster speed than that of die in the hot stamping process. The austenitization temperature has a significant effects on the size of martensite. The cooling rate of steel plate has a significant effect on the tensile strength when the austenitization temperature is 870 °C. The fracture of sample austenitized at 870 °C or 900 °C is the dimple, the fracture of sample austenitized at 930 °C or 960 °C is the mixture of quasicleavage and dimple.

Research on hot stamping for a typical part of B1500HS boron steel using experiment and numerical simulation methods

In the paper, a typical part of B1500HS boron steel was formed using the hot stamping tools, and the effect of austenitization temperature on the microstructure and mechanical properties of B1500HS steel was studied by the experiment and finite element methods. The results show that, the temperature of steel plate has a significant effect on the temperature of hot stamping tools, and the temperature of punch rises at a faster speed than that of die in the hot stamping process. The austenitization temperature and time both have significant effects on the size of martensite, but have not obvious effects on the hardness. The cooling rate of steel plate has a significant effect on the tensile strength when the austenitization temperature is 870 °C. The fracture of sample austenitized at 870 °C or 900 °C is the dimple, the fracture of sample austenitized at 930 °C or 960 °C is the mixture of quasicleavage and dimple.

Characterization of Tensile Properties, Limiting Strains, and Deep Drawing Behavior of AA5754-H22 Sheet at Elevated Temperature

Automotive industries are very much interested in characterization of formability improvement of aluminum alloys at elevated temperatures before designing tools, heating systems, and processing sequences for fabrication of auto-body panels by warm forming technology. In this study, tensile tests of AA5754-H22 aluminum alloy were carried out at five different temperatures and three different strain rates to investigate the deformation behavior correlating with Cowper-Symonds constitutive equation. Laboratory scale warm forming facilities were designed and fabricated to perform limiting dome height and deep drawing tests to evaluate forming limit strains and drawability of sheet metal at different tool temperatures. The forming limit strain and dome height improved significantly when both the die and punch were heated to 200 °C. Remarkable improvement in deep drawn cup depth was observed when die and punch temperatures were maintained at 200 and 30 °C, respectively, producing a non-isothermal temperature gradient of approximately 93 °C across the blank from flange to center. The forming behavior at different isothermal and non-isothermal conditions were predicted successfully using a thermo-mechanical FE model incorporating temperature-dependent properties in Barlat-89 yield criterion coupled with Cowper-Symonds hardening model, and the thinning/failure location in deformed cups were validated implementing the experimental limiting strains as damage model.

Study on temperature distribution of HSS in hot FLD test

In this paper, we study forming limit diagram (FLD) of high strength steel (HSS) under high temperature condition to simulate the hot stamping process. We investigate the sheet specimen temperature distribution in hot FLD test. First, we propose a simple model of heat transfer process in sheet specimen, in which the sheet specimen is separated into two sections due to different mechanism. In thermal radiation, the convection and thermal contact conductance are included in two partial differential equations (PDEs) to express the temperature distribution in these two sections (S1 and S2 sections). Second, hot FLD experiments (Nakazima test) are performed and temperature distributions of sheet specimen are investigated by thermal infrared imager. Furthermore, the experimental temperature distributions are compared with theoretical ones, and these two measurements make good agreement between each other. This conclusion validates the feasibility of proposed thermal model in hot stamping process. In addition, an uneven sheet temperature distribution is examined in expansion process experiment, we observe that the temperature of specimen increases from center to edge until it reaches the temperature of punch. The further theoretical analysis proves that this phenomenon is mainly caused by the punch through thermal contact conductance between punch and S1 section, which indicates that a hot punch is indispensable to sustain the temperature of the deforming sheet. Third, the theoretical temperature distribution on S1 section under different die height is calculated. The radiation heat flux of the sheet decreases as the die height is increasing, but the sheet temperature increment is small, which implies that the height of die affects the sheet temperature slightly.

Deformation behavior and interface microstructure evolution of Al/Mg/Al multilayer composite sheets during deep drawing

Abstract The Al(5052)/Mg(AZ31)/Al(5052) multilayer composite sheets were fabricated via accumulative roll-bonding process at elevated temperatures. The present study aims to investigate the formability of the composite sheets by deep drawing test and orthogonal experimental design. The deep drawing parameters such as punch temperature, punch speed and die curvature radius have been optimized to maximize the limit drawing radio of the composite sheets at temperatures ranging from 150 °C to 230 °C. The limit drawing radio of the composite sheets obviously increased with the forming temperature, and the maximum drawing radio of 3.1 was obtained at 200 °C. After forming at 150 °C and 200 °C, the microstructure evolution of the intermetallic compound layers, consisting of Al 12 Mg 17 and Al 3 Mg 2 layers at the interface at different regions of the drawn cup in rolling direction (RD) and transverse direction (TD), was investigated. At the bottom region which was considered as less deformation, the microstructure of the intermetallic compound layers showed almost no changes both at 150 °C and 200 °C. However, the Al/Mg/Al multilayer composite sheets showed more satisfactory bonding properties when drawing at 200 °C with less cracks appearing at the wall region and corner region of the drawn cup than that at 150 °C.

Spring-back and spring-go behaviors in bending of thick plates of high-strength steel at elevated temperature

Recently, the usage of thick plate is being increased to replace the forged parts for reducing the weight, forming load as well as improving the tool life in the automotive industry. In this study, a numerical simulation was carried out to find the process conditions which affect the product quality by examining the U-channel shape and the forming capabilities for thick high-strength steel plates. The steel plate used was composed of Nb 0.05%–Ti 0.01%–V 0.07% micro-alloyed high-strength steel with a 580MPa strength at room temperature. The effect of forming temperature and corner radius of punch on spring-go behavior was investigated, and mechanism of spring-go based on through-thickness stress was found during the bending of thick plate at the elevated temperature. Based on the simulation results, a prediction model of spring-go was constructed, and compensation method of the tool to improve the dimensional accuracy of bent part was suggested.

New Methods for Quality Analysis of Deep-Drawn Packaging Components from Paperboard

Optimization of the quality of deep-drawn cups requires methods for precise measuring of quality criteria. This paper presents new objective methods to describe the quality of deep-drawn packaging components made of paperboard. The state of the art for quality analysis in three-dimensional paperboard forming is presented. Methods for the analysis of visual quality using image analysis and for the analysis of shape accuracy using surface scans are developed. Experimental results are used for the verification of the methods and for the investigation of influences of main process parameters. The new methods are found to be both precise and objective. A large blankholder force has been shown to cause an increasing number of wrinkles and has a negative influence on the shape accuracy. A high die temperature also increases the number of wrinkles but enhances the shape accuracy. The punch temperature has no effect on the number of wrinkles, but high punch temperature has a significant and positive effect on the shape accuracy. Copyright © 2014 John Wiley & Sons, Ltd.

Formability improvement with independent die and punch temperature control

A combined experimental and numerical study of the effects of die and punch temperature on the formability of a modified AA3003 aluminum alloy sheet for a case study sample is presented. Here, the non-isothermal deep drawing of a cup-like feature in a thin gauge aluminum automotive component is considered. An experimental forming setup that incorporates both heated dies and a cooled punch has been developed. A parametric study of the effects of die temperature, punch temperature, and blank holder force on the formability of the part is conducted. Numerical simulations of the warm forming process are performed using a coupled thermo-mechanical finite element model. The temperature-dependant material model combines the Bergstrom hardening rule with Barlat’s YLD2000 yield function and was implemented in LS-DYNA as a user-defined material model. Selected experimental cases were modelled numerically and compared to experiments. The FEA model was validated against experimental results by comparing measured and predicted punch force versus displacement as well as trends in the formability as a function of die temperature.

Why Is the Sun's Corona So Hot?

How does heat dissipating from the sun's core out beyond the surface to its corona abruptly punch temperatures up by a factor of 200 and more?

Stamping Formability of ZE10 Magnesium Alloy Sheets

Abstract ZE10 magnesium alloy sheets were prepared through ingot casting and the hot-rolling process. The mechanical properties, conical cup value ( CCV), bore expanding performance, and limit drawing ratio ( LDR) were investigated to examine the stamping formability of ZE10 alloy sheets, at temperatures ranging from 20 to 300 °C. The results showed that the tensile strength decreased, whereas, plasticity, drawing-bulging performance, bore expanding properties, and deep drawing performance increased markedly at elevated temperatures. The CCV specimens could be drawn into the conical die's underside cylindrical hole from the conical cliff, without cracking, and could have the minimum CCV at 200 and 250 °C. In the bore-expanding test, the bore (Φ10 mm) could be expanded to the dimension of the punch (Φ25 mm) and the maximum bore-expanding ratio could be achieved at above 150 °C. The limiting drawing ratio ( LDR) of 2.85 is acquired during the deep drawing test at 230 °C. with the punch temperature of 20 ∼ 50 °C, the punch velocity of 50 mm · min −1, and the mixture of graphite and cylinder grease as lubricant.

Approach of using a ductile fracture criterion in deep drawing of magnesium alloy cylindrical cups under non-isothermal condition

There have been many ductile fracture criteria published for predicting fractures in the isothermal metal-forming process, especially at room temperature. However, many materials, such as magnesium alloy and aluminium alloy, show an improved formability at elevated temperatures under non-isothermal conditions. It is significant to predict the occurrence of fracture in metal forming under these conditions since a forming limit diagram is almost powerless here. In the present work, an approach is proposed for extending the application of existent ductile fracture criteria in a non-isothermal metal-forming process. Using the new approach, combined with the finite element method (FEM), the deep drawing of magnesium alloy AZ31 cylindrical cups under non-isothermal condition is analysed. The fractures located in the punch radius region and in the cup wall close to the radius region of the female die resulting from the low and high punch temperatures, respectively, are predicted.

Press Forging of Magnesium Alloy AZ31 Sheets

Press forging of magnesium alloy AZ31 sheets was investigated in this paper. The typical component, a rectangular box with bosses at the bottom was formed. The experimental results show that the magnesium alloy sheets are suitable for press forging. The bosses and the rectangular box can be formed synchronously for 2 mm or 3 mm thick sheets when the punch temperature is 250 °C. By experimentation and numerical simulation, the effects of process parameters on material flow were analyzed, including the temperature, the die shape, the blank size, the lubrication manners and the friction condition.

An Experimental Investigation on Semi-Solid Forming of Micro/Meso-Scale Features

The potentials of semi-solid forming technology have generated much interest regarding its application in micromanufacturing. This study investigates the feasibility of using semi-solid forming technology to produce parts with micro/meso features. An experimental setup has been developed to study the effects of die/punch temperature, initial solid fraction, punch speed, and workpiece shape on the semi-solid forming process. A part has been produced for a microreactor application and has been analyzed with an optical measurement system for feature formation. The results indicated complex interaction among the process parameters and the material flow, which affected the final pin formation. The punch temperature and velocity had a significant effect on the overall die filling. The initial workpiece shape and solidification of the semi-solid material during forming influenced the micro/meso-feature formation sequence, affecting the final pin formation. Furthermore, grain deformation and distribution of the formed parts were investigated. The grains became larger due to induction heating and the forming process. Severely distorted grains were observed at the corner regions of the pins and the punch-workpiece interface.