Erichsen Test Research Articles

Control of Microstructure and Texture for Mechanical Properties of Mg-Al-Zn Alloys

In Mg-Al-Zn alloy sheets, the grains were refined from 30 mm to 2 mm during the process of differential speed rolling at 473 K, having approximately the same size dominate at a high thickness reduction rate of 60 %. In addition to these microstructural changes, the rolled sheets showed a weaker texture characterized by pole than those of commercial sheets. The DSR sheets have equal value of elongation at 0, 45, and 90 degrees from the rolling direction. With the mechanical properties, the results of Erichsen test indicate that DSR process remarkably enhanced ductility of the present Mg alloy sheets at room temperature.

Formability of ultrafine-grained interstitial-free steel fabricated by accumulative roll-bonding and subsequent annealing

The miniaturized Erichsen test was successfully developed for evaluating the stretch formability of the ARB and annealed IF steel sheets. The Erichsen value tends to decrease as the average grain size becomes small. However, it should be emphasized that even in the specimen with ultrafine grain, a high Erichsen value is obtained. This result indicates that the ultrafine grained IF steel sheet could be highly deformed under multiaxial stress.

金属冷間加工用低環境負荷潤滑剤の開発と評価

In plastic metalworking, a lubricant is usually applied between the metal surface and the tool surface to reduce friction. The reduction in friction prevents seizing, improves the forming limit and decreases the energy that the process requires. Therefore the use of a lubricant is extremely important. Oil-based lubricants and phosphate coatings which have a high environmental load have mainly been used as conventional lubricants before and after the working process. However with the recent trend in environmental protection lubricants should be pollution-free materials. In this project we aim to develop and evaluate new lubricants based soap and detergents. These materials are good lubricants and have little environmental load. The performance of the new lubricants was evaluated by the Erichsen test and cold bar drawing. The results of the experiments and elastic-plastic FEA were compared to determine the coefficient of Coulomb friction. It was clarified that an appropriate mixture of soap and a mild detergent is superior to lubricants on the market. In particular, the soap-based lubricant mixed with washing powder shows excellent performance. In addition, these lubricants are easily removed by water. Guidelines for the development of environmentally friendly lubricants and the application of such lubricants to metalworking were obtained.

Effects of Ca on Tensile Properties and Stretch Formability at Room Temperature in Mg-Zn and Mg-Al Alloys

The tensile tests and the Erichsen tests at room temperature have been performed on seven kinds of Mg alloys: Mg-1.5Zn, Mg-1.5Zn0.1Ca, Mg-3Zn, Mg-3Zn-0.1Ca, Mg-3Al, Mg-3Al-0.1Ca and Mg-1Al-1Zn-0.1Ca-0.5Mn alloys. In the Mg-Zn alloys, the 0.2% proof stress at 90 � , which was the angle between the tensile direction and the RD, was decreased by addition of Ca, while the 0.2% proof stress at 0 � was increased by addition of Ca. Also, an increase in elongation to failure by addition of Ca at 90 � was larger than that at 0 � . However, such variations in tensile properties by addition of Ca were not found in the Mg-Al alloy. The stretch formability for the Mg-Zn alloys was significantly enhanced by addition of Ca, while the stretch formability of the Mg-Al alloy was not enhanced by addition of Ca. These results by the mechanical testing are ascribed to the variations in basal texture by addition of Ca. [doi:10.2320/matertrans.M2011048]

Deep-Drawing and Fatigue Properties of Advanced Steel Sheet Stripes

Analysis of the deep drawing and fatigue properties is given in this contribution for two advanced micro alloyed sheet steel grades with Yield strength values Re 246 and 382 MPa, respectively. The 2 mm thick steel sheets were hot dip zinc coated. The deep drawing properties were evaluated by tensile testing and by the Erichsen test at different strain rates. For fatigue testing the symmetric bending test was applied. Results showed favorable deep drawing properties of these steel sheets assigned for heavy duty parts in automotive industry. Steel grade with Re 246 MPa had elongation A80 32%, n 0.21, Erichsen number IE 12.5 mm and the steel with Re 382 MPa had A80 24 %, n 0.17 and IE 12.4 mm. The tested values showed some growth in dependence on the strain rate up to the press tool velocity about 0.1 m.s1 and at higher strain rates they decreased. The fatigue limit in bending was about 0.6.Re . The zinc coating on the sheet surface remains complete up to the final fracture of the test piece.

Mechanical and anisotropic behaviors of 7075 aluminum alloy sheets

Formability of 7075 aluminum alloy sheets was studied after annealing of 71% cold worked (CW) samples at different temperatures (270–450 °C). Uniaxial tensile test, deep drawing and Erichsen test were carried out at room temperature to evaluate formability parameters. Average plastic strain ratio, planar anisotropy, and work hardening exponent of samples were calculated from the tensile test data. The tensile properties and formability parameters were correlated with the limit drawing ratio (LDR) and Erichsen test. It was found that the sheets annealed at 400 °C possess good ductility, high average n-value and the normal anisotropy r-value so that, the formability of 7075 aluminum alloy can be improved by increasing annealing temperatures to the 350–400 °C.

Shielding gas influences on laser weldability of tailored blanks of advanced automotive steels

The effects of shielding gas types and flow rates on CO 2 laser weldability of DP600/TRIP700 steel sheets were studied in this work. The evaluated shielding gases were helium (He), argon (Ar) and different mixtures of He and Ar. Weld penetration, tensile strength and formability (Erichsen test) of laser welds were found to be strongly dependent upon the shielding gas types. The ability of shielding gas in removing plasma plume and thus increasing weld penetration is believed to be closely related to ionization potential and atomic weight which determine the period of plasma formation and disappearance. It was found that the higher helium shielding gas flow rate, the deeper weld penetration and the lower weld width.

Uni- and bi-axial deformation behavior of laser welded advanced high strength steel sheets

Bead-on-plate butt joints of 2.5 mm hot rolled DP600/DP600 and 1.2 mm cold rolled TRIP700/TRIP700 steel sheets were performed using 6 kW CO 2 laser beam welding. The welding speed ranged from 1.5 to 3.0 and from 2.1 to 3.9 m/min in DP/DP and TRIP/TRIP steel weldments respectively. A top surface helium gas was used as a shielding gas at a flow rate of 20 l/min. Metallographic examinations and transverse tensile testing (DIN EN 895: 1995) were carried out to characterize the weldments. The formability of base metals and weldments were investigated by standard Erichsen test (DIN EN ISO 20482). It was found that the uniaxial plastic behavior of both DP600 and TRIP700 base metals was in agreement with Swift and modified Mecking–Kocks models respectively. In a perpendicular tensile test to the weld line, all specimens were fractured at the base metal however the strengths were somewhat higher than those of base metal. There was a significant reduction in formability caused by welding of both DP/DP and TRIP/TRIP steel weldments and the formability has been improved with the increase of the welding speed.

On formability of tailor laser welded blanks of DP/TRIP steel sheets

This paper aims to evaluate the formability of tailor welded blanks of dual phase (DP600)/transformation induced plasticity (TRIP700) steel sheets. In this work, bead on plate butt joints of 2·5 mm DP600 and 1·2 mm TRIP700 steel sheets were performed using CO2 laser beam welding. Microhardness measurements and transverse tensile testing were carried out to characterise the welds. The formability of base metals and welds were investigated by standard Erichsen test. In a perpendicular tensile test to the weld line, all specimens were fractured at the TRIP base metal, and the strengths were somewhat higher than those of base metal. There was a significant reduction in formability caused by welding of the DP600/TRIP700 steel sheets, and the formability increased with increasing welding speed.

The study of 430Ti and 430LNb ferritic welding wires for application in the cold part of automotive exhaust systems

Ferritic stainless steels have been extensively used in automotive exhaust systems. Ferritic stainless steel wires have been recently introduced in the fabrication of these components to reduce costs (hot and cold parts) and improve the quality of hot part components, mainly thermo-mechanical fatigue resistance, and their use has been growing since. This study compares mechanical and metallurgical characteristics of fusion zones obtained with 430Ti and 430LNb welding wires. The influence of Ar 2%O2 and Ar 2%N2 3%CO2 shielding gases was also studied. Metallographic analysis was performed by optical and electronic microscopy, revealing the main characteristics of the fusion zone obtained with these welding wires and shielding gases. Welded joint ductility was measured using the Erichsen test. The results indicated that ferritic stainless steel wires could be used to produce welds with adequate ductility. However, this depends critically on the choice of the welding wire and the shielding gas to maximize mechanical and metallurgical properties and to avoid any future problems.

A Shear Fracture Criterion to Predict Limit Strains in Sheet Metal Forming

Present work examines a mathematical model to predict the onset of shear fracture in the industrial processes of sheet metal forming such as biaxial stretching. Historically, sheet metal formability has been assessed by simple testing such as the Erichsen test. Lately, the concept of experimental Forming Limit Curve, FLC, was developed to evaluate formability. The Forming Limit Diagram shows the FLC which is the plot of principal strains in the sheet metal surface, e1 and e2, occurring at critical points obtained in the laboratory formability tests or in the fabrication process. Two types of undesirable failure mechanisms can occur in sheet metal forming operations: local necking and shear fracture. Therefore, two kinds of limit strain curves can be plotted: the local necking limit curve FLC-N and the shear fracture limit curve FLC-S. The D-Bressan shear instability criterion model proposed for the theoretical prediction of forming limit strain curve owing to the onset of local necking, FLC-N, in sheet metal forming is reformulated to predict the shear fracture strain limit, FLC-S, of sheet metal forming operations. Shear fracture is anticipated to initiate in the direction of pure shear when the shear stress attains some critical value. The Barlat Yld2000-2d anisotropic yield function proposed by Barlat et al. is employed and the material is assumed to display both planar and normal anisotropy. The new approach investigate the influence of mechanical plastic properties such us the plastic anisotropy parameters, pre-strain and work hardening coefficient in sheet metal formability. Some experimental and theoretical results of forming limit curve for aluminium obtained from present model for two values of the power coefficients a = 5 and 6 are shown. The relevant issues related with the FLC-S is presented and discussed.

Plastic Localization Phenomena in a Mn-Alloyed Austenitic Steel

A 0.5 wt pct C, 22 wt pct Mn austenitic steel, recently proposed for fabricating automotive body structures by cold sheet forming, exhibits plastic localizations (PLs) during uniaxial tensile tests, yet showing a favorable overall strength and ductility. No localization happens during biaxial Erichsen cupping tests. Full-thickness tensile and Erichsen specimens, cut from as-produced steel sheets, were polished and tested at different strain rates. During the tensile tests, the PL phenomena consist first of macroscopic deformation bands traveling along the tensile axis, and then of a series of successive stationary deformation bands, each adjacent to the preceding ones; both types of bands involve the full specimen width and yield a macroscopically observable surface relief. No comparable surface relief was observed during the standard Erichsen tests. Because the stress state is known to influence PL phenomena, reduced-width Erichsen tests were performed on polished sheet specimens, in order to explore the transition from biaxial to uniaxial loading; surface relief lines were observed on a 20-mm-wide specimen, but not on wider ones.

Utilização do ensaio erichsen para a avaliação do desempenho de juntas soldadas

Para aprovação de uma junta soldada é comum a realização de testes mecânicos para avaliar seu desempenho em comparação com o metal base ou outra junta soldada. Entre os diversos ensaios que podem ser usados, o ensaio Erichsen tem sido utilizado para avaliar juntas em chapas de pequena espessura. A utilização deste ensaio nesta aplicação específica não está ainda bem estabelecida e a interpretação dos resultados obtidos muitas vezes gera controvérsia. Neste contexto, o presente trabalho compara os resultados de três tipos de ensaio mecânico (tração, dobramento e Erichsen) na avaliação de cordões de solda depositados em chapas de aço inoxidável ferrítico de 1,5 mm de espessura. Na primeira etapa deste trabalho, usando soldas obtidas com o processo de soldagem GTAW, foram selecionadas as condições para a realização do ensaio Erichsen. Para isto, foram comparados os resultados deste ensaio em diferentes condições e a distribuição de deformações na região de ensaio foi avaliada quantitativamente com um programa de computador específico. Na segunda etapa, juntas soldadas pelo processo GMAW foram avaliadas pelos ensaios de tração, dobramento e Erichsen e seus resultados comparados. Mostrou-se que o ensaio Erichsen foi mais efetivo para detectar uma menor ductilidade em juntas soldadas em condições para as quais se esperava um pior comportamento mecânico.

An Inverse Analysis of the Erichsen Test Applied for the Automatic Identification of Sheet Materials Behavior

Among the technological tests, the Erichsen drawing test gives a more appropriate material behavior, near the limit of the real manufactured process. In this paper an inverse finite element analysis of the Erichsen test is proposed. The new idea is to use a numerical simulation of the experimental test for the rheological identification of the constitutive equations available for sheet metals alloys. The inverse analysis is based on a robust optimization algorithm and uses simultaneously the experimental test data and the corresponding numerical one. A numerical inverse analysis software named OPTPAR was developed and improved for an automatically coupling with a commercial finite element code charged to simulate the experimental test. Results obtained for a virtual steel alloy will be analyzed numerically in order to validate the finite element model and the identification method. An application to an AA5182 aluminum alloy and a DC03 steel alloy will be presented.

An Inverse Analysis of the Erichsen Test Applied for the Automatic Identification of Sheet Materials Behavior

Among the technological tests, the Erichsen drawing test gives a more appropriate material behavior, near the limit of the real manufactured process. In this paper an inverse finite element analysis of the Erichsen test is proposed. The new idea is to use a numerical simulation of the experimental test for the rheological identification of the constitutive equations available for sheet metals alloys. The inverse analysis is based on a robust optimization algorithm and uses simultaneously the experimental test data and the corresponding numerical one. A numerical inverse analysis software named OPTPAR was developed and improved for an automatically coupling with a commercial finite element code charged to simulate the experimental test. Results obtained for a virtual steel alloy will be analyzed numerically in order to validate the finite element model and the identification method. An application to an AA5182 aluminum alloy and a DC03 steel alloy will be presented.

순티타늄판의 Nd:YAG 레이저 용접성에 관한 연구(II) - 맞대기 용접 특성 -

Recently, as titanium and titanium alloys are being increasingly used in wide areas, there are on-going researches to obtain high quality weld zone. In particular, growing interest is being drawn to laser welding, which involves low heat input and large aspect ratio in various welding processes and can facilitate shield in atmospheric condition compared with electron beam welding. The first report covered the analysis of embrittlement by the bead color of weld zone through quantitative analysis of oxygen and nitrogen and measurement of hardness as basic experiment to apply laser welding to titanium. Results indicated that the element that affect embrittlement the most was nitrogen, and as embrittlement and oxygenation go on, bead color changed to silver, gold, brown, blue and gray. This study performed butt welding of pure titanium and STS304 by using 1kW CW Nd:YAG laser, and to find out basic physical properties, evaluated welding performance by laser output, welding speed, root gap and misalignment etc, and examined mechanical properties through tensile stress and Erichsen test. The reason particles of pure titanium welded metal and HAZ are greater than STS304 is because they are pure metal and do not include many impure elements that work as nuclei in case of resolidification, thus becoming coarse columnar crystals eventually. In addition, the reason STS304 requires more energy during welding than pure titanium is because the particle size of base metal is smaller.

Formability Evaluation of TRIP-aided Steel Sheets with Different Microstructures: Polygonal Ferrite and Bainitic Ferrite Matrix

Recently, application of TRIP-aided steel sheets has been developed due to their good balance of strength and formability. In this work, a comparative study was performed on the formability of two different microstructures of TRIP-aided steel with different retained austenite characteristics. Microstructures along with their specific retained austenite characteristics such as volume fraction, stability and morphology were achieved by annealing of cold rolled sheet at fully austenite and intercritical region during subsequent isothermal treatment in the range of 350–410°C. SEM and XRD measurements were used to evaluate retained austenite characteristics. Formability and mechanical properties of sheets were determined by Erichsen test and tensile test, respectively. Results indicate that steel sheets with polygonal ferrite (PF) matrix present better formability. However, at identical volume fraction of retained austenite, sheets with bainitic ferrite (BF) matrix show better stretch formability due to high retained austenite stability.

A study on sheet formability by a stretch-forming process using assumed strain FEM

The effects of sheet thickness and frictional condition between the punch and sheet on formability is predicted and compared with the experimental results of the Erichsen test as a stretch-forming process. The material and geometrical nonlinearity are considered. A hypoelastic–plastic model is used and strain-field stabilization is taken into account using the Assumed Strain Finite-Element Method. By considering the contact problem and applying the nonlinear finite-element method, the force and dome height for aluminum and steel sheets are computed and compared with the experimental results. The Oyane criterion is used to access the formability of the sheet. A good agreement was found between the experimental and predicted formability results of aluminum and steel sheets. The results show that for decreasing friction coefficient the position of tearing is moved from the rim to the pole. Also, by increasing the work-hardening exponent, formability is increased.

Enhancement of tensile ductility and stretch formability of magnesium by addition of 0.2 wt%(0.035 at%)Ce

Mg–0.2wt%(0.035at.%)Ce alloy was hot-rolled and its mechanical properties were investigated by conducting tensile and Erichsen tests at room temperature and 433K. The rolled Mg–Ce alloy exhibited greater elongation to failure and higher stretch formability than the rolled pure Mg. This was attributed to a reduction in basal texture intensity and the splitting of the basal plane by the addition of a small amount of Ce (0.2wt%). Also, the small amount of Ce strongly affected the recrystallization behavior during hot rolling. Microstructural observation revealed that the prismatic slip was activated in the Mg–Ce alloy. The enhancement of the non-basal slip by the addition of Ce was not attributed to a reduction in the c/a ratio. An increase in stacking fault energy due to the addition of Ce is suggested to play a vital role in the activation of the non-basal slip.

An inverse analysis approach of the Erichsen test starting from a finite element model

During the deep drawing process the deformation history is different as compared to the tensile one where the constitutive equation can be identified only for small values of the plastic strain. More accurate values of the constitutive parameters can be obtained using the Erichsen drawing test. In this work we propose to use the inverse analysis principle to identify the rheological parameters directly from the Erichsen test. Results obtained for classical steel will be analyzed using an identification numerical high board (OPTPAR) automatically coupled with a commercial finite element code charged to simulate numerically the experimental test. Application to a DC03 sheet steel alloy will be presented.