Erichsen Test Research Articles

Investigation of mechanical properties in FFF- produced PLA samples using the Erichsen test: application of definitive screening and RSM

Purpose This study aims to investigate how printing parameters affect the mechanical properties of specimens produced through fused filament fabrication, using the Erichsen test to assess deformation characteristics and material durability under stress. Design/methodology/approach Polylactic acid (PLA) specimens were printed and tested in accordance with the ISO 20482 standard. Definitive screening was conducted to identify the most influential process parameters. This study examined the effects of four key process parameters – number of layers, layer height, crossing angle and nozzle diameter – on force, distension, peak energy and energy to break. Each parameter was assessed at three levels and a large number of required experiments was managed by using response surface methodology (RSM). Findings This study revealed that the number of layers, layer height and crossing angle are the most significant factors that influence the mechanical properties of 3D-printed materials. The number of layers had the greatest impact on the peak force, contributing 44.25%, with thicker layers typically enhancing material strength. The layer height has a significant effect on energy absorption and deformation, with greater layer heights generally improving these properties. Nozzle diameter contributed only 1.10%, making it the least influential factor; however, its impact became more pronounced in interactions with other parameters. Originality/value This paper presents a comprehensive experimental investigation into the effects of process parameters on the crack strength and behavior of 3D-printed PLA specimens using the RSM method. The documented results can be used to develop optimization models aimed at achieving desired mechanical properties with reduced variation and uncertainty in the final product.

Formability and Failure Mechanisms of Continuous Glass Fiber-Reinforced Polypropylene Composite Laminates in Thermoforming Below the Melting Temperature.

In this study, the thermoforming formability of continuous glass fiber-reinforced polypropylene (CGFRPP) laminates below the melting temperature were investigated. The forming limits of CGFRPP laminates were explored using flexural tests, Erichsen tests and deep drawing tests. The failure mechanism of CGFRPP in thermoforming was investigated by observing typical failure specimens using a microscope. The results show that the flexural performance and Erichsen performance are optimal at 130 °C and 2 mm/min. At 160 °C and 100 mm/min, the deep drawing performance is optimal. The restriction of fibers by the matrix is affected by the deformation temperature, and the creation of defects is affected by the deformation rate. During forming, the CGFRPP laminates undergo shear and extrusion deformations, resulting in wrinkles, delamination, and fiber aggregation.

Effects of deformation-induced BCC martensitic transformation on uniaxial ductility and biaxial stretchability in metastable ferrous medium-entropy alloys

This study investigated the effects of deformation-induced martensitic transformation (DIMT) on the stretchability and fracture behavior of thin sheets made from ferrous medium-entropy alloys (MEAs). Analyses of punch load-stroke curves from Erichsen tests revealed that DIMT occurred in the 60 at% Fe MEA, 64 at% Fe MEA, and 304 stainless steel (60Fe, 64Fe, and 304SS alloys, respectively). This DIMT affects necking onset, uniform elongation, and the Erichsen index (EI) under diverse stress conditions. DIMT plays a significant role in strain hardening and mechanical instability during uniaxial tests, enhancing strain hardening through martensite formation and also initiating necking due to non-uniform deformation. Particularly in 64Fe, DIMT-induced early necking resulted in reduced uniform elongation. On the other hand, biaxial Erichsen test results demonstrated further strain hardening due to martensite-induced strain accommodation, leading to enhanced resistance to deformation during biaxial loading. The distinctive shapes of punch load-stroke curves in biaxial tests, compared to stress-strain curves from uniaxial tensile tests, are a result of the interaction between DIMT and stretching directions, as well as its alloy-dependent phase stability. In 60Fe, transformed martensite contributed to strain hardening and delayed necking initiation, while extensive martensite transformation in 64Fe enhanced strain hardening further. This understanding of the complex correlation between DIMT, strain hardening, and mechanical instability holds potential for alloy optimization and developing processing strategies, applicable to automotive manufacturing and structural engineering industries.

Improvement of formability of Mg-2.2Gd-0.4Zr alloy by forming multi-type textures through the transverse gradient extrusion process

Mg-2.2Gd-0.4Zr sheets were prepared using transverse gradient extrusion (TGE) technology to improve their formability. The effects of different TGE processes (inclination angles of the die are 15°, 30°, 37°, 45° and 49°) on the microstructure, texture, mechanical properties, and formability of extruded sheets were researched. Furthermore, the flow behaviors of Mg-2.2Gd-0.4Zr sheets during extrusion were analyzed by the finite element simulation method. For comparison, Mg-2.2Gd-0.4Zr sheets were processed by conventional extrusion (CE) process. Results showed that the texture of TGE sheets was effectively altered. With the increase of the TGE dies tilt angle, the deviation of the basal pole in the center region of the extruded sheet towards the extrusion direction (ED) increased, while in the 1/4 edge region the basal pole deviated towards the transverse direction (TD) along the ED. The multi-type textures formed in TGE sheets are mainly attributed to the extra flow velocity along the TD and the flow gradient along the ED during extrusion. High elongation of 45.6% and low yield stress of 98.9 MPa are obtained for TGE-45 sheets. In addition, the Erichsen value (IE) of the TGE-45 sheet is 5.46 mm, which is about 47% higher than the 3.72 mm of the CE Mg-2.2Gd-0.4Zr sheet. The improved formability is due to the effective coordination of multi-directional strains during the Erichsen test for the TGE sheets.

Cold formability of friction stir processed 5754-H111 and 6082-T6 aluminum alloys: an experimental and numerical study

Aluminum has become increasingly important in the automotive sector due to its ability to reduce vehicle weight without compromising structural performance. However, joining different types of aluminum alloys can be challenging due to their different thermal and mechanical characteristics. Concurrently, friction stir processing (FSP) is a material processing technique that has garnered considerable attention for its versatility and industrial applicability, and it may represent a preliminary phase to correctly perform friction stir welding, which is a welding technology used to join different types of aluminum alloys. In this context, this study presents an extensive experimental campaign of FSP performed on 5754-H111 and 6082-T6 alloys, varying two rolling directions and four welding speeds. The processed materials were characterized, including cupping and tensile tests, microstructure analysis, and a correlation between welding parameters, microstructure, and mechanical resistance. In addition, a numerical method was proposed to simulate the Erichsen tests and predict the formability of the materials, before and after the FSP processes. The results showed that both alloys exhibited good formability after the FSP process, but with different behavior. AA6082 underwent internal decohesion and dynamic recrystallization, resulting in the absence of defects and an increase in ductility and cold formability. AA5754 experiences more difficulty with material flow during FSP and showed the presence of tunnel defects in all analyzed process conditions. However, the alloy 5754 did not undergo softening and had comparable mechanical behavior and cold formability to the base material. These results were validated by the numerical method proposed.

The Effect of Varnishing and Soaking on Formability of the AW-5052-H28 Aluminium Alloy Sheets in Erichsen Cupping Test

This article presents the results of experimental tests on the stretch-forming ability of 0.21-mm-thick AW-5052-H28 aluminium alloy sheets used in the production of pull-off cups. Erichsen test under various tribological conditions (dry friction, lubrication with graphite lubricant) was used to assess the sheet formability. Punches with a various diameter of the spherical end (8 and 20 mm) were used in the tests. The effect of soaking conditions and varnishing variants on the value of Erichsen indices IE and IE11 was investigated. The sheets were soaked for 13 minutes at various temperatures: 185°C, 190°C and 200°C. In test conditions without lubrication, the lowest value of the IE index = 3.3 mm was observed for sheets in as-received state and for samples after soaking. However, the highest values of the Erichsen index in tests without lubrication were measured for varnished samples and repeatedly soaked. The tests conducted under lubrication conditions with graphite grease revealed usually higher values of the IE index compared to testing conditions without the use of grease. The values of the IE11 index were approximately twice lower than the IE indices. Observation of the bulge surface revealed a smooth surface, which means that the material is characterised by a fine-grained microstructure.

Optimization of forming force and Erichsen index using Taguchi design of experiments: Mathematical models and experimental validation

Design of experiments is a statistical approach from which an optimized number of experiments is determined. Taguchi design of experiments, applied on Erichsen tests, is chosen to be considered in this paper. The most important parameters in this forming process, Erichsen index ( IE), and maximum generated force ( Fmax), are experimentally and theoretically determined. Three input factors are selected, at diverse levels, in order to study their influence on Erichsen output results. The considered input factors are sheet thickness, punch diameter, and friction coefficient. New mathematical models which take into account the effects of these factors and their interactions are developed. Moreover, the influence of Erichsen test on the S235 steel microstructural behavior is experimentally examined as function of the sheet thickness. A good agreement between experimental and theoretical findings proves that the proposed models provide a precise prediction and an exact estimation of the Erichsen output parameters ( IE and Fmax). The efficiency of the adopted design of experiments via Taguchi method is well confirmed.

Local twinning behavior of ZK61m magnesium alloy sheet under multiaxial stress during drawing-pressing with Erichsen test machine

In order to find a more effective method to preset twins and to explore the microstructure and twin evolution of magnesium alloy sheet under multi-axial stress state deformation, drawing-pressing deformation with Erichsen test machine is used as a sheet processing method to process ZK61m magnesium alloy sheet in this experiment. During repeated drawing-pressing deformation, the central area of the plate was subjected to annular tensile and compressive stress. In the process of deformation under unidirectional force, the slip direction of some grains is in hard orientation and it is difficult for the slip to operate, while the annular tensile and compressive stress state will provide the grains with multidirectional slipping options. Electron back-scattered diffraction (EBSD) technique was used to analyze the microstructure of magnesium alloy plates with different drawing-pressing times and different positions from local deformation center to edge. In this study, the complex circumferential force environment will weaken the anisotropy of deformation structure during repeated drawing-pressing, and the effect of prefabricated twins is more obvious. Based on the modified generalized Schmid factor (GSF) analysis, it is easier to show a variety of twin variation behaviors within a grain during Erichsen deformation. After the plate is deformed by Erichsen processing, the mechanical properties of magnesium alloy sheet have also been effectively improved.

Evaluation of forming limit diagram and bending stiffness of SS316L/polyurethane/SS316L sandwich sheets

Abstract In this study, SS316L/polyurethane/SS316L was produced by warm roll bonding and direct adhesion without using any adhesive. By changing the polymer core thickness in the sandwich sheet, its mechanical properties, such as tensile behavior and flexural bending strength, were investigated. Also, by performing the Erichsen test and getting the experimental forming limit diagram, the forming behavior of the sandwich sheets in various thicknesses was investigated and compared with that of the monolithic steel sheet. The experimental results showed that by increasing the thickness of the sandwich sheets with polymeric core thickness of 2 mm to 2.5 and 3 mm, the bending stiffness was raised by 111% and 288%; also, the displacement in the second region of the bending test diagram, indicating the bending ability without delamination, was increased from 100% to 109%. Forming limit diagrams of the sandwich sheets were higher than those of the steel sheet, which indicates that the forming behavior of them are higher than that of the monolithic steel sheet.

Testing of Lubricants for DIC Tests to Measure the Forming Limit Diagrams of Aluminum Thin Sheet Materials

We investigated lubricants and thin teflon foils that can be applied in the formability testing of the thin aluminum sheets used in the electronics and automotive industries. For the tests, thirteen different industrial lubricants (oils and greases) (i.e., L1–L13) and two Teflon films (i.e., 0.08 and 0.22 mm thick) were applied. The authors conducted an Erichsen test, and the thickness reduction of the discs was measured first. In forming-limit curve (FLC) tests, it is crucial that the stresses are localized in the central area of the specimen during forming and that biaxial deformation is maintained throughout, if possible. We aimed to achieve and fulfill this task. To perform this measurement, the GOM ARAMIS measuring system was utilized. It is an optical measuring system based on the digital image correlation (DIC) principle, capable of measuring both stresses and displacements in real time. A specific validation method was also developed to qualify the DIC system. We concluded that there was a 5% difference in Erichsen indentation (IE) number diagrams between the best (L12) and worst (L4) cases for the lubricants and oils tested, which is a significant difference for thin plates. We found that this value could be increased and improved by using Teflon discs. Furthermore, the localization of stress maxima, i.e., the centering of cracks in the specimen, could be achieved by combining Teflon discs and L12 lubricant (with appropriate layer order), which significantly aids in the recording of standard FLC diagrams. Using foils is also advantageous because they are readily available, have no expiry date, and are of less environmental concern.

Study on Press Formability and Properties of UV-Curable Polyurethane Acrylate Coatings with Different Reactive Diluents.

UV-curable coatings have numerous advantages, including environmental sustainability due to 100% solid content, economic feasibility attributable to relatively fast curing time, decent appearance, mechanical properties, chemical resistance, and abrasion resistance. However, UV-curable polyurethane acrylate coatings on metals apparently restrict their engineering applications owing to low mechanical properties and poor thermal stability, giving UV-curable coatings less flexibility and formability. In this study, we evaluated the property change of films according to the type of reactive diluents that lowers the viscosity of UV-curing coatings for pre-coated metal and has a substantial effect on the curing rate, viscoelastic properties, adhesive properties, and flexibility of the film. Moreover, there are many changes in the properties of coatings according to varied curing conditions in order to evaluate the oxygen inhibition phenomenon during the curing process in the atmosphere. In particular, to evaluate the effect of reactive diluents on forming formability, which is the most crucial property for the pre-coated metal, this study used conventional formability tests, such as t-bending or the Erichsen test. Moreover, a cross-die cup drawing mold with a similar form as failure and Safety Zone was utilized in order to obtain clearer information on its actual formability. The analysis on the effect of failure and safety zone on the material used in press forming was conducted by assessing limit punch height and forming a limit diagram of the manufactured film according to varied reactive diluents.

Development of double-sided friction stir welding of advanced high strength steel sheets

Double-sided friction stir welding (FSW), performed with a pair of rotation tools, was studied in an attempt to increase the joining speed when applied to welding of automotive advanced high-strength steels (AHSS). The experiments were performed on butt joint of 1.6-mm-thick 1180 MPa grade steel sheets, and sound welds were obtained when the travel speed was no more than 4 m/min, fairly comparable with laser beam welding (LBW), one of the conventional automotive welding processes. It was clarified by experimental and numerical analyses that the enhancement in travel speed was due to the unique material flow interactively developed by a pair of rotation tools. Double-sided FSW was performed at 3 m/min of joining speed on butt joint of dissimilar steel sheets in a combination of 1.5 GPa and 590 MPa grades. The mechanical properties of the welded joints were evaluated by tensile, V-bending and Erichsen tests comparing with LBW, which verified that double-sided FSW exhibited sufficient mechanical properties for the press-forming to produce automotive parts. A prototype automotive part was successfully fabricated using the tailor-welded blank welded with double-sided FSW, which demonstrates its applicability to automotive production.

Microstructure Evolution of ZK61m Magnesium Alloy Sheet during Erichsen Test

Microstructure Evolution of ZK61m Magnesium Alloy Sheet during Erichsen Test

Application of the DIC System to Build a Forming Limit Diagram (FLD) of Multilayer Materials

The extraordinary combination of strength and ductility of multilayered materials makes them attractive in the various applications and industries (military, aerospace, energy industry etc.). In the present work, the investigated materials were joined into multilayered sheet using the explosive welding method. The three-layer material was made of two titanium sheets and one Armco iron sheet in between. Materials produced by explosive welding can easily be used in a simple deformation process, but more complex processes that employ a more complex mechanical state are still not sufficiently studied. The presented study analyzes the possibilities of using Ti - Armco - Ti sheet for the deep drawing process. For this purpose, the forming limit diagram (FLD) has been constructed and verified. FLD is one of the most important tools in the analysis of sheet metal forming processes. In the presented work the non-standard method (Erichsen test) coupled with Digital Image Correlation analysis was used. The obtained results confirmed that the method of producing the tested sheet and the morphology of the microstructure created have a direct impact on the deformation mechanisms.

STUDY ON DEEP DRAWING BEHAVIOR OF THE INTERSTITIAL FREE STEEL IN CORRELATION WITH THE MICROSTRUCTURE

The objective of this paper was to present results obtained about the behaviour of the IF steel associated with high deformation. To evaluate the deep drawing aptitude, samples were subjected to tensile test, n and r values determination, hole expansion and Erichsen tests. The results were correlated with a microstructural study. Through thermodynamic simulation, the phase transformation temperature (Tg®a) and the precipitates formation were estimated. The Tg®a value was also determined by dilatometry test. The failure of the material during deep drawing or stamping process is evidenced through the formation of cracks in areas with critical angles changes. It was relevant to understand the mechanisms of fracture nucleation and propagation of the IF steel. A fractography study was carried out and was possible to verify the presence of cavitation mechanism as results of the superplastic flow at high deformation conditions, promoting necking and fracture after a high plastic deformation achieved.

Material and Damage Characterization of the Elastoplastic Response of the EK4 Deep Drawing Steel

Although EK4 drawing steel is nowadays widely used to manufacture a great variety of parts, it exhibits a marked normal and planar anisotropy that can make it difficult to control the process during its forming. In order to achieve an accurate description of the elastoplastic material response in sheet forming operations, this work presents a detailed material and damage characterization of EK4 deep drawing steel through a two-step methodology involving both experiments and finite element simulations. Firstly, tensile tests on sheet samples cut along the rolling, diagonal and transverse directions were carried out. The corresponding measurements were used to calibrate the material parameters related to the following modeling approaches adopted in the present study: the Hollomon hardening law, the non-associated Hill-48 phenomenological constitutive model and the anisotropic Hosford-Coulomb ductile fracture criterion. Secondly, this characterization was assessed and validated in the numerical simulation of the technological Erichsen test in which the material is mainly subjected to a biaxial stress state. The obtained predictions show a good agreement when compared with the corresponding experimental measurements of the punch load–displacement curve and thickness radial profile at the final fracture stage of the sample.

Enhanced mechanical properties and formability of hot-rolled Mg–Zn–Mn alloy by Ca and Sm alloying

In order to broaden the application of wrought Mg alloy sheets in the automotive industry, the influence of Ca and Sm alloying on the texture evolution, mechanical properties, and formability of a hot-rolled Mg–2Zn–0.2Mn alloy was investigated by OM, XRD, SEM, EBSD, tensile tests, and Erichsen test. The results showed that the average grain size and basal texture intensity of Mg–2Zn–0.2Mn alloys were remarkably decreased after Ca and Sm additions. 0.64 wt.% Ca or 0.48 wt.% Sm addition significantly increased the tensile strength, ductility and formability. Moreover, the synergetic addition of Sm and Ca improved the ductility and formability of Mg–2Zn–0.2Mn alloy, which was due to the change of Ca distribution and further reduction of the size of Ca-containing particles by Sm addition. The results provided a possibility of replacing RE elements with Ca and Sm in Mg alloys which bring about outstanding mechanical properties and formability.

Experimental and numerical investigation of sheet metal failure based on Johnson-Cook model and Erichsen test over a wide range of temperatures

The identification of Johnson-Cook parameters and the effect of different temperature gradients on A1050 sheet metal formability were performed. Tensile tests and modified Erichsen were carried out at different temperatures and also combined with numerical simulation to identify Johnson-Cook model parameters and the failure criterion. The obtained parameters were validated using the steam bulge test. A good correlation between numerical and experimental results was obtained in terms of failure behavior during the hot forming process. It was observed that hot forming improves the Erichsen index, and the thermal gradient strongly affects the failure zone position in the deformed specimens.

Overcoming the trade-off between stretch formability and heat resistance in magnesium via alloying dilute neodymium

This work aims to provide a reliable reference and a low-cost strategy for overcoming the trade-off between stretch formability and heat resistance in Mg alloys. A dilute Mg-0.8 wt%Nd alloy sheet was prepared for this purpose, and hot compression was conducted in order to regulate the microstructure and texture. For comparison, the samples with and without hot compression were labeled as fine-grained (FG) and coarse-grained (CG) samples respectively, corresponding to the occurrence of dynamic recrystallization. Tensile creep tests were carried out at 473 K and Erichsen tests were conducted at room temperature. Both the CG and the FG samples had higher stretch formability and stronger creep resistance than commercial Mg alloys tested for comparison. Especially, the FG sample performed the best in overcoming the trade-off. Pyramidal<c+a> slip dominated the creep behavior of the FG sample and enhanced the heat resistance, avoiding the deterioration caused by cross-slip, twinning and grain boundary sliding. High Schmid factors for basal slip of the fine grains enhanced the stretch formability of the FG sample, and compensated the adverse effect of the relatively low Schmid factors of the residual coarse grains. Thus, the dilute Mg-0.8 wt%Nd alloy successfully overcame the trade-off between stretch formability and heat resistance.

Comparison of room-temperature stretch formability of the as extruded Mg–Gd alloys with different double-peak pole spacing

This paper focused on the effect of angle α that the basal poles tilted from normal direction (ND) toward the extruded direction (ED) on the formability of as-extruded Mg-2Gd (wt.%) alloy sheets. The studied Mg-2Gd (wt%) alloy sheets with the angle α of 23°, 32° and 45°, respectively, were designed. The Erichsen test was carried out at the ambient temperature, in which the microstructure and texture evolution was characterized by the electron backscatter diffraction (EBSD) technique. The results showed that the strain coordination ability of the Mg-2Gd sheet along the thickness direction was enhanced with the increase of angle α, giving rise to a higher Index Erichsen (IE) value of 7.5 mm for the α of 45° due to a lower r-value. This superior high formability is not only closely associated with the lower r-value but also with the higher Schmid factors for basal slip (SF basal) in the large-angle α alloy sheets. Furthermore, the twinning induced a more random distribution along the transverse direction (TD) of basal texture in the early stage of the Erichsen test, which cancels out the SF basal reduction effect caused by the activation of basal slip. The TD-extended twinning texture provided a softer orientation for the TD strain during the Erichsen test, such that excellent formability was achieved in the alloy sheets with a larger angle α.