Formability Criteria Research Articles

Production Optimization of Premium Food Can with Distortion Printing under Waving Requirement

This research aims to propose a novel approach for evaluating and minimizing scraps in an industrial production of premium food cans with distortion printing. Beyond conventional formability criteria, a waving requirement is introduced to ensure aesthetic quality of the printed graphics. The research focuses on real production conditions, specifically involving double-cold-reduced (DR) low-carbon steel sheets and chromium-coated tin-free steel with a thickness of 0.16 mm. The sheets are laminated on both sides with a plastic film prior to undergoing distortion printing on the exterior. Subsequently, a blank is subjected to a drawing-redrawing process to form a food can. To address challenges associated with characterizing these thin sheets, a material parameter identification method is proposed and demonstrated. The thickness profile and flange length are identified as key criteria for this identification process. Measurements of thickness distribution and flange length are obtained using digital image correlation (DIC) and microscopy techniques. Within the manufacturing system, uncertainties related to material properties and forming processes can result in scraps or defects. To analyze these processes, finite element analysis (FEA) is employed and validated through experiments. For the evaluation of scrap rates, uncertainty propagation is conducted using a metamodeling technique, specifically employing radial basis function (RBF) neural networks. The study concludes by offering process optimization recommendations aimed at reducing the scrap rate.

Forming limit diagrams and mechanical properties of AA1050/Ti CP2 multilayered composite produced by the accumulative roll bonding technique

In this study, the AA1050/Ti CP2 metallic multilayered composite was produced by accumulative roll bonding (ARB) using AA 1050 and commercially pure titanium Ti (CP-Ti ASTM grade 2) for three cycles at ambient temperature. The microstructure evolution was investigated by scanning electron microscopy (SEM) equipped with an energy dispersive spectrometer (EDS) and X-ray diffraction (XRD). Also, the tensile test and Vickers microhardness measurement were conducted to evaluate mechanical properties. The forming limit diagrams (FLD) were obtained for a metallic multilayered composite for the first time by the Nakazima test. It was observed that a continuous and well-bonded composite was fabricated after the first cycle. For the subsequent two cycles, necking and fracture of Ti reinforcement occurred in the Al matrix. The maximum tensile strength was reached after two cycles with almost a 98% increase compared to the annealed aluminum sample. However, the tensile strength was reduced after the third cycle. The uniform elongation considerably decreased after the first cycle and was maintained for the subsequent two cycles. The microhardness improved by 124% and 47% for Al and Ti, respectively, in the whole process of ARB in comparison with annealed Al and Ti. As a formability criterion, the level of forming limit curve (FLC) was reduced sharply after the first ARB cycle. For subsequent cycles, this reduction was neglectable. The Al/Ti composite fracture surfaces were a combination of shear ductile and brittle after the third pass.

Why are Double Perovskite Iodides so Rare?

Following on the heels of the remarkable lead halide perovskite optoelectronic materials, interest in lead-free halide perovskites has grown rapidly in the past decade. Double perovskite halides with the general formula A₂MᴵMᴵᴵᴵX₆ (where A is a large monovalent cation in the perovskite A site, Mᴵ is a univalent metal, Mᴵᴵᴵ is a trivalent metal, and X is a halide) represent one of the promising classes of such materials, and of these, the iodides are particularly interesting since their band gaps are expected to be similar to those found in the iconic lead-containing phases, APbI₃. However, the successful synthesis of A₂MᴵMᴵᴵᴵI₆ iodides appears to have been elusive. In this work, we examine the likelihood that double perovskite halides will form using a combination of the Goldschmidt tolerance factor and the radius ratio of the trivalent metals, Mᴵᴵᴵ, and rationalize the rarity of double perovskite iodides in terms of these descriptors. Using this model as the formability criterion, we predict the possible existence of more than 300 hitherto unknown double perovskite iodides with organic and inorganic cations in the A site.

Effect of feed and step depth in hole flanging using single point incremental forming

Single Point Incremental Forming can be used to form hole flanges in automobile and aerospace applications. In hole flanging using single point incremental forming, a study on effect of feed and step depth on formability has been carried out. Hole flange thickness is taken as formability criterion. Moreover, effect of those parameters on surface roughness has also been studied to understand effect of Single Point Incremental Forming. The results obtained by experimental work were analyzed and are presented here.

Study on the influence of the springback on the hole expansion ratio characterization

Material formability has become one of the main problems, together with the springback, when stamping high added-value components for the automotive industry. The pursuit of weight reduction has led to higher strength alloys which show a lower formability. Among the different formability criteria (e.g. necking, edge strain, fracture and radius cracks) the edge strain is starting to be a critical aspect on the process planning stage. In order to characterise this criteria, the hole expansion ratio (HER) is conducted under the ISO 16630 standard. In the last years, multiple authors have analysed the HER of different alloys and its dependency on different process variables i.e. cutting method, test speed, material strength. However, the influence of the springback phenomenon on the test result has not been previously analysed. In this work, the influence of the springback on the HER values has been analysed for a mild steel DX54D and a third generation steel Fortiform1050 with a novel measuring technique. From the obtained results, it can be stated that the springback has a critical influence on the characterised HER value, mainly for the third generation steel, leading to differences of about 40% on the HER limits.

Study on the influence of the springback on the hole expansion ratio characterization

Material formability has become one of the main problems, together with the springback, when stamping high added-value components for the automotive industry. The pursuit of weight reduction has led to higher strength alloys which show a lower formability. Among the different formability criteria (e.g. necking, edge strain, fracture and radius cracks) the edge strain is starting to be a critical aspect on the process planning stage. In order to characterise this criteria, the hole expansion ratio (HER) is conducted under the ISO 16630 standard. In the last years, multiple authors have analysed the HER of different alloys and its dependency on different process variables i.e. cutting method, test speed, material strength. However, the influence of the springback phenomenon on the test result has not been previously analysed. In this work, the influence of the springback on the HER values has been analysed for a mild steel DX54D and a third generation steel Fortiform1050 with a novel measuring technique. From the obtained results, it can be stated that the springback has a critical influence on the characterised HER value, mainly for the third generation steel, leading to differences of about 40% on the HER limits.

Forming limit diagram prediction of 6061 aluminum by GTN damage model

Forming limit diagram (FLD) is one of the formability criteria which is a plot of major strain versus minor strain. In the present study, Gurson-Tvergaard-Needleman (GTN) model is used for FLD prediction of aluminum alloy 6061. Whereas correct selection of GTN parameters’ is effective in the accuracy of this model, anti-inference method and numerical simulation of the uniaxial tensile test is used for identification of GTN parameters. Proper parameters of GTN model is imported to the finite element analysis of Nakazima test for FLD prediction. Whereas FLD is dependent on forming history and strain path, forming limit stress diagram (FLSD) based on the GTN damage model is also used for forming limit prediction in the numerical method. Numerical results for FLD, FLSD and punch’s load-displacement are compared with experimental results. Results show that there is a good agreement between the numerical and experimental results. The main drawback of numerical results for prediction of the right-hand side of FLD which was concluded in other researchers’ studies was solved in the present study by using GTN damage model.

On the benefits of a stress criterion for the simulation of cup drawing process

Experimental and numerical cup drawing process has been investigated on 0.65 mm zinc sheets. The cup exhibits anisotropic earrings due to the material microstructure. The material formability is studied through elliptical bulge tests in the rolling, diagonal and transverse direction. High anisotropy of the formability is observed. The numerical simulation of cup drawing is then made and demonstrates the correct fitting with experimental results. A stress formability criterion developed by Jansen et al. [14] is then implemented into a finite element method software and applied to predict the material rupture observed for some process conditions. The risk zone of the cup is subjected to some strain path changes according to the simulation whereas the strain value does not explain the rupture according to the experimental formability measured by the bulge tests. It has been shown that the rupture is due to some critical stresses, which are reached in the risk zone of the cup. The use of the stress criterion and its non-dependence on the strain path change allows the fracture prediction. Finally, the numerical fracture propagation by the “kill element method”, as briefly discussed by Bouchard et al. [4], is used and shows a good similarity with the experience.

Evaluation of Formability of Thin Sheet Metal from Mechanical Properties

The evaluation of formability for sheet metals by means of different tests such as hole-expansion and forming limit tests is widely used in industry. The experimental efforts for these tests and the scatter of the results are much higher than those for the identification of the mechanical properties of various material charges for the same material grade in tensile test. Difficulties in accurate formability evaluation for new steel grades, such as AHSS, have necessitated a review of the existing prediction methods. Consequently, a new formability criterion was developed from the statistical relations of parameters for approximately fifty steel grades in various thickness ranges. The criterion considers the combination of mechanical properties from the tensile testing as the yield strength, tensile strength and total elongation and plastic deformation energy in a single value. The quality ranking of different charges and coils was made by using of the criterion as well as, for comparison, other well-known criteria which are currently used in the industry. The results obtained involving the new formability criterion seems to be accurate for a wide range of material grades and thicknesses, from the viewpoint of automotive design requirements.

Anisotropic mechanical behavior and formability criterion for zinc sheets

The mechanical behavior of zinc has been studied and linked to the formability of sheets. An anisotropic elastic–viscoplastic behavior law has been developed to take into account the anisotropy of the material. Anisotropy is induced by crystallographic and morphological textures, and possibly by the spatial distribution of intermetallics. The temperature dependence is introduced through a Zener–Hollomon type term. The resulting anisotropic formability of sheets implies a new approach by adapting the forming limit diagram with a stress based criterion. This approach is confronted and validated by considering the industrial forming of a head clip.

Verification of the Effect of Temperature and Duration of Stamina for Heat Treatment of Zinc Coating on the Formability of Procedural AHSS Steels

Subject of presented contribution is process formability parameters evaluation of both side coated TRIP and HSLA steels in basic state and after its annealing in order to Fe-Zn coating creation. The samples were annealed at 450, 500 and 550°C for 10 and 60 seconds in argon shielding gas. Obtained values are compared with each other in order to determine whether the influence of temperature and duration after annealing changed the original class inclusion on a scale to measure the quality of steel sheets for deep drawing according to the value of limit drawing ratio. Limit drawing ratio was used as a process formability criterion and were reached by modified Swift cupping test. HSLA steel H220PD and TRIP steel RAK40/70 were used as experimental materials.

Impact of intragranular microstructure development on ductility limits of multiphase steels

In this paper, the effects of microstructure and deformation mechanisms on the ductility of multiphase steels are investigated. To this end, a formability criterion based on loss of ellipticity of the boundary value problem is coupled with an advanced multiscale model accounting for intragranular microstructure development and evolution. The spatially heterogeneous distribution of dislocations inside the grain is represented by three types of local dislocation densities. The resulting large strain elastic–plastic single crystal constitutive law (based on crystal plasticity) is incorporated into a self-consistent scale-transition scheme. The present contribution focuses on the relationship between the intragranular microstructure of B.C.C. steels and their ductility. The model allows interesting comparisons in terms of formability limits for different dislocation networks, during monotonic loading tests applied to polycrystalline aggregates.

APPROXIMATE BOUNDARY FORMABILITY WITH VOLUME ACTUATION

We study the approximate formability of the boundary of a two-dimensional isotropic elastic medium with the use of uniform volume actuation in the interior of that medium. We show that care is required in the selection of formability criteria to ensure that formability corresponds with common sense notions of "shape control". Finally, we analyze what we define as approximate normal boundary formability in the case of a rectangular and a triangular region, showing that such formability does not obtain in the first instance but, with some smoothness assumptions, does obtain in the second.

A simplified approach for sheet forming processes design

A new approach is developed to improve sheet forming parts and sheet forming processes design. In order to apply classical optimization methods, an energetic characterization of the global transformation of an elasto-plastic structure is proposed. After a brief review of thermostatics in elastoplastic laws, an energetic criterion is defined. With a geometrical definition of sheet forming processes, it is shown how to use this criterion to find the optimal displacement path between a flat blank and the part shape. Then, the classical assumptions of rigid-plastic behaviour and of thin shell geometry are introduced. Eventually, the criterion is used to define a formability criterion, for use at the preliminary design stage of parts. This paper concludes with numerical applications of the approach and analysis of formability criterion applications.

Evaluation of formable light metal-alloy steel composites

Al-steel and Ti-steel and rod composites were fabricated by hot-pressing or roll-bonding techniques in line with previously developed formability criteria for the production of formable metal-metal composites. The composite materials produced were in the form of roll-bonded laminates, hot-pressed sheet and roll-bonded rod composites. Each of these composite systems was evaluated with respect to the optimum fabrication process developed, the bond strength produced between the matrix and reinforcement, and the resultant mechanical properties. Precipitation-hardened aluminium alloy reinforced with either stainless steel or maraging steel and Ti 318 alloy reinforced with an ausforming (hot-cold worked) steel produced promising composite materials. Both these materials provided a range of mechanical properties which could compete with the high strength light metals.

Fabrication of formable metal-metal composites

Composite fabrication techniques were developed for the reinforcement of a precipitation-hardening aluminium alloy (Duralumin) with stainless steel and maraging steel and for the reinforcement of titanium alloys with high strength steel using an in situ ausforming (hot-cold working) operation. Both sheet and rod composites were produced using roll-bonding and hot-pressing techniques. Maximum permissible levels of rolling deformation in the direction of reinforcement were determined for these composites during both their fabrication and the subsequent rolling sequences using the previously developed formability criteria. Owing to the large difference in flow strengths between the Duralumin and steel reinforcement under the conditions of fabrication and cold rolling there was an upper limit of deformation achievable in the Al-steel composites. No such limit was found on using continuous “hot-cold”-rolling techniques for Ti-steel composites between the steel austenitizing temperature and 400°C. However, cold rolling of the Ti-steel composites was not possible because of the large difference in flow strengths between the matrix and reinforcement and the poorly sustained work-hardening rate of the ausformed steel reinforcement. Nevertheless, Al-steel and Ti-steel composites were produced which are capable of competing with the high strength light metals in terms of their specific strength and, at the same time, are capable of undergoing a certain amount of rolling deformation in the direction of reinforcement alignment.