Rolling Direction Of Sheet Research Articles

Efficient isogeometric shell element with through-thickness stretch: application to incremental sheet forming

An isogeometric shell element with through-thickness stretch is applied to a two-point incremental forming problem. The shell element supports full three-dimensional constitutive laws and therefore does not make the plane stress assumption. An anisotropic material model is implemented to account for the sheet rolling direction. Automatically adjusting penalty stiffness is proposed for modeling the contact between the stylus tool and the sheet, whereas the die contact algorithm uses traditional constant penalty stiffness. A comparison is made between experimental results as well as results from a conventional shell formulation.

Influence of fiber type on the impact response of titanium-based fiber-metal laminates

This investigation examines the influence of fiber type on the failure of titanium-based fiber metal laminates (FMLs). Two types of FMLs, comprising fiber-based composite layers, sandwiched between titanium sheets, were subjected to impact by a 12 mm steel sphere at various velocities ranging from 100–400 m/s. The first FML incorporated carbon fiber reinforced plastic (CFRP) layers, whereas the second had hot-pressed ultra-high-molecular-weight polyethylene fiber (UHMWPE, Dyneema®HB50) layers as the sandwiched component. FML specimens were clamped between annular plates, which exposed a circular target, and impacted at the center by spherical projectiles. Optical images of the deformation and failure induced in the two types of FMLs were captured by a high-speed camera, and the respective responses compared; the ballistic limit and energy absorbed were also determined. The results indicate that the ballistic performance of the Ti/HB50 system is superior to the Ti/CFRP combination, in terms of ballistic limit and energy absorption. However, this difference diminishes when the impact velocity exceeds 1.5 times the ballistic limit. The rolling direction of the titanium sheet plays a significant role in the amount of energy absorbed, through its influence on the deformation/failure mode of the FMLs.

Metallographic Analysis of Filiform Corrosion

The surface line type defects on the can twist-off lids from lacquered tinplate material have been analyzed. The analyzed defects manifested themselves like the lines bulged above the surrounding surface. They were aligned roughly perpendicular to the lid circumference; they were mostly arranged on the lower part of lid circumference edge. The defects surface was fully covered by lacquer layer. After lacquer layer removal it was visible in the defective area that tin layer was damaged on some defect areas. The defect presented itself like filiform corrosion which occurred in conditions slightly above room temperature and high humidity under the originally continuous covering layer. According to the findings, corrosion occurred on the hidden sheet cut edges and then propagated first perpendicular to the circumference into the sheet. Then sometimes its direction changed into the sheet rolling direction along the lines with less but still suitable tin layer thickness. This defect can be controlled by special protecting of lid cut edge against corrosion or decreasing of the temperature and the humidity conditions in the stores.

Effect of Computational Parameters on Springback Prediction by Numerical Simulation

Elastic recovery of the material, called springback, is one of the problems in sheet metal forming of drawpieces, especially with a complex shape. The springback can be influenced by various technological, geometrical, and material parameters. In this paper the results of experimental testing and numerical study are presented. The experiments are conducted on DC04 steel sheets, commonly used in the automotive industry. The numerical analysis of V-die air bending tests is carried out with the finite element method (FEM)-based ABAQUS/Standard 2016 program. A quadratic Hill anisotropic yield criterion is compared with an isotropic material described by the von Mises yield criterion. The effect of a number of integration points and integration rules on the springback amount and computation time is also considered. Two integration rules available in ABAQUS: the Gauss’ integration rule and Simpson’s integration rule are considered. The effect of sample orientation according to the sheet rolling direction and friction contact behaviour on the prediction of springback is also analysed. It is observed that the width of the sample bend in the V-bending test influences the stress-state in the cross-section of the sample. Different stress-states in the sample bend of the V-shaped die cause that the sheet undergoes springback in different planes. Friction contact phenomena slightly influences the springback behaviour.

The influence of heat treatment on properties of cold rolled alloyed steel and nickel superalloys sheets used in aircraft industry

Superalloys based on nickel and selected steels are widely used in the aerospace industry, because of their excellent mechanical properties, heat resistance and creep resistance. Metal sheets of these materials are plastically deformed and applied, inter alia, to critical components of aircraft engines. Due to their chemical composition these materials are hardly deformable. There are various methods to improve the formability of these materials, including plastic deformation at an elevated or high temperature, or a suitable heat treatment before forming process. The paper presents results of the metal sheets testing after heat treatment. For the research, sheets of two types of nickel superalloys type Inconel and of three types of steel were chosen. The materials were subjected to multivariate heat treatment at different temperature range and time. After this step, mechanical properties were examined according to the metal sheet rolling direction. The results were compared and the optimal type of pre-trial softening heat treatment for each of the materials was determined.

Improving channel depth of stainless steel bipolar plate in fuel cell using process parameters of stamping

This study is dedicated to overcome the poor formability problem of thin stainless steel sheets used as bipolar plates of proton exchange membrane fuel cells (PEMFCs). Different parameters such as the sheet type (SUS 304 and SUS 316), sheet direction (rolling and transverse), load condition (static and dynamic), and heat treatment can be varied to adjust the channel depth in the bipolar plate. The channel of a bipolar plate is formed using static and dynamic loads and along different directions (rolling and transverse). The depth of the formed channel is about 0.18 mm, and the difference in channel depth from static and dynamic loads is small regardless of the sheet direction. The forming limitations due to the stainless steel hardening during the process can be solved through heat treatment. The channel of a bipolar plate formed with a heat-treated sheet is more than twice as deep as the one formed from a sheet without heat treatment and is more uniform. The formed channel is deeper with a dynamic load than a static load and in the transverse to rolling direction than in the rolling direction of sheet.

Magnetic Field Analysis of Self-Propelled Rotary Actuator’s Stator in Consideration of the Rolling Direction of the Steel Sheet

In this paper, we consider the improvement of the stator structure of the self-propelled rotary actuator, whose rotational axis is parallel to the exciting magnetic field. The stator of the actuator is constructed from the grain-oriented electrical steel sheet. The relation between the rolling direction of the steel sheet and the direction of the exciting magnetic field is important for the starting torque and rotational stability of the actuator’s rotor. Therefore, we analyze the rotor in consideration of the rolling direction using the finite-element method that introduced the complex E&S model, which is able to express the 2-D vector magnetic properties. As a result, we estimate the suitable setting direction of the rolling direction in the steel sheet of the actuator’s stator by this analysis.

A study on the formability of aluminum tailor welded blanks produced by friction stir welding

Tailored welded blanks (TWBs) technology can give an important possibility to obtain components in automobile industry satisfying lightweight strategies as well as satisfying increased crashworthiness, corrosion resistance, and accuracy. Friction stir welding (FSW) is a joining process, which can be well fitted to obtaining aluminum tailored blanks when compared to other conventional joining processes. This paper presents an experimental study on TWBs produced by FSW with dissimilar aluminum alloy thin sheets. The formability performance is investigated by obtaining forming limit curves with Nakajima test using different blank widths. The properties of welded AA5182/AA6061 alloy pair, 1 mm thick, are studied and the corresponding formability is compared to base materials. Different weld line orientations are defined related to sheet rolling direction and corresponding forming limit curves are obtained in addition to load–displacement behavior. Results show a dependency of TWB formability on weld line orientation, as well as a decrease of welded pair alloy formability when compared to base materials.

Experimental and Numerical Analysis on the Formability of a Heat-Treated AA1100 Aluminum Alloy Sheet

The objective of this work is to experimentally and numerically determine the influence of plastic anisotropy on the forming limit curve (FLC) for a heat-treated (300 °C-1 h) AA1100 aluminum alloy sheet. The FLCs were obtained by the Nakajima test, where the anisotropy effect on the FLC was evaluated using hourglass-type samples taken at 0°, 45°, and 90° with respect to the sheet rolling direction. The effect of crystal orientations on the FLC is investigated using three micro-macro averaging schemes coupled to a Marciniak and Kuczynski (MK) analysis: the tangent viscoplastic self-consistent (VPSC), the tuned strength αVPSC, and the full-constraint Taylor model. The predicted limit strains in the left-hand side of the FLC agree well with experimental measurements along the three testing directions, while differences are found under biaxial stretching modes. Particularly, MK-VPSC predicts an unexpected limit strain profile in the right-hand side of the FLC for samples tested along the transverse direction. Only MK-αVPSC, with a tuning factor of 0.2, predicts satisfactorily the set of FLC measurements. Finally, the correlation of the predicted limit strains with the predicted yield surface by each model was also discussed.

One-sided laser beam welding of autogenous T-joints for 6013-T4 aluminium alloy

Autogenous T-joints for aluminium skin-stringer component performed by one-sided laser beam welding process was conducted using a high power Yb-fiber laser. The influence of the shielding gas, seam angle, beam focal position, and beam positioning relative to weld centerline were investigated regarding to weld microstructural features. The joint mechanical behavior was evaluated concerning to the sheet rolling directions. It was observed that a precise control of the process parameters enabled to obtain weld beads with acceptable dimensional and geometric characteristics and minimizing weld defects. Helium shielding gas produced higher aspect ratio welds than those with pure argon. Although, pores were observed in the fusion zone, they represented only about 5% of the weld bead area. The optimal beam positioning should remain up to 0.2mm relative to junction line, for seam angles between 10° and 15°. The weld mechanical behavior depended on the sheet rolling direction. Joint efficiency up to 85% were obtained after hoop tensile tests when the weld bead longitudinal-section was perpendicular to skin rolling direction and parallel to the stringer rolling direction.

Strain heterogeneities in the rolling direction of steel sheets submitted to the skin pass: A finite element analysis

Hot rolled, annealed or galvanized low carbon steel sheets display yield points in tensile testing. These are associated with deformation heterogeneities along the test specimen, known as Lüders bands, which cause an unacceptable surface appearance in steel sheet formed products. This problem is usually eliminated through a light cold rolling pass (“skin-pass”) in the material as a last step in its industrial manufacturing, imposing a reduction of thickness of about 1–2.0% on the sheet. Existing experimental results for these strain heterogeneities along the rolling direction are analyzed, as well as corresponding finite element analyses. The constitutive behavior of the material is described by a curve displaying an initial stress peak followed by the work hardening of the material. The FEAs led to distributions and shapes of Lüders bands in the sheets similar to the experimental ones. The bands nucleate intermitently and propagate from the surface of the sheets, at the initial contact region between the material and the rolls. For low and high friction between the material and the roll and for low sheet thickness reductions (0.5% and 1.0%), a limited influence of the roll diameter on the Lüders bands distribution was found. For sheet thickness reductions of 2.0% and higher, high friction between the roll and the material and large roll diameters, the distribution of LBs in the sheets was different from that obtained for small roll diameters and low friction between the rolls and the material. Increasing thickness reductions in the skin-pass led to changes in the Lüders bands distribution, involving an increasing homogeneity in the deformation. It is suggested that the critical thickness reduction in the skin-pass is associated to a minimum volume fraction of material deformed above a certain strain level.

Friction anisotropy of Aluminum 6111-T4 sheet with flat and laser-textured D2 tooling

Proper friction control during a sheet metal forming process can positively influences the quality of the final product. The effects of textured tooling surface and the rolling direction of the strip surface with respect to the sliding direction, the sliding velocity, and the contact pressure on friction coefficient were investigated in this study with Aluminum 6111-T4 sheet and D2 tool steel. A flat-on-cylindrical setup was used to measure the friction force by pulling a strip sample across a tooling sample. The tool steel has laser-textured micro wedge-shaped dimples. The results showed a reduction in friction coefficient by using a textured tool. In addition, in the tests, the relative motion direction parallel to the sheet rolling direction leads a lowest friction coefficient compared to other orientations.

Through-Thickness Strain and Texture Gradients of Al-Mg-Si-Cu Alloy Sheets Produced by Snake Rolling

The evolution of through-thickness strain gradients during snake rolling (SR), which introduces an horizontal offset between upper and lower rolls, of Al-Mg-Si-Cu sheets was investigated with the inscribed lines in side including rolling and normal direction of sheets. The complete pole figures were used to investigate the influence of such rolling on texture evolution. The results revealed that the SR rolled sheet developed a continuous through-thickness shear strain gradients and shear textures. The surface in contact with the slower roll (the lower roll) developed the largest shear strain and the strongest shear texture. While for the conventional symmetric rolling (CR), the sheet developed a small shear strain gradient which is symmetrical about the centerline of the sheet with nearly negligible shear strain and texture at the center of the sheet.

Effect of Loading Direction on the Bearing Capacity of Cold-Reduced Steel Sheets

AbstractThis study is concerned with double-shear bolted connections in cold-reduced steel sheets that undergo the pure bearing failure mode of the inside sheet. Compared to the published test results of bolted connections failing in the net section fracture, those involving the bearing failure mode had very wide scatter in the ultimate test loads of specimens having seemingly similar configurations. This technical note presents the laboratory test results of 51 specimens composed of G2 and G450 steel sheets, which have very different ductility properties. One new and significant finding is that the absolute bearing capacity can be considerably higher in the rolling direction of the cold-reduced steel sheet than in the perpendicular direction, even though the tensile strength has the opposite trend. Another result is that material ductility has a much greater effect on the bearing capacity than on the net section tension capacity. It was also found that snug tightening had little effect on the bearing cap...

An Experimental Study on Bending Process of AISI 304 Steel Sheets by using Diode Laser Forming

Laser bending is a promising technique utilised in order to deform metal sheets that offers the advantage of requiring no hard tooling and no external forces, thus reducing cost and increasing flexibility. Laser forming involves a complex interaction of many process parameters, ranging from those connected with the irradiation of the laser beam to those regarding the thermal and mechanical properties of the workpiece material. The present work is focused on the laser bending of AISI 304 steel sheets by using of a diode laser. The influence of process parameters, such as the power of laser beam and the scanning speed as well as the metal sheet thickness on the bending angle has been taken into account. The investigation has also analysed the effect of rolling direction of the metal sheets and the conditions of cooling on the bending process.

Texture Evolution of Columnar Grains in Electrical Steel During Hot Rolling

Columnar grains in cast slabs of electrical steel show strong anisotropy in grain orientation and morphology and thus influence the subsequent microstructure and texture after hot rolling significantly. The texture evolution of hot rolled sheets containing initial columnar grains with their <100> directions approximately parallel to the rolling direction (RD), transverse direction (TD) and normal direction (ND) of the hot rolled sheets was investigated by using EBSD technique. The results indicated that, whatever the initial texture of the columnar grains was, typical Goss, brass-type and copper-type shear texture component could develop in shear-deformed surface region. The copper-type texture formed under the maximum shearing force with the fine, sheared or dynamically recrystallized grains, and Goss grains were mainly elongated and deformed grains, while brass grains behaved between them. Additionally, the rotating relationship of the three types of shear textures was different due to the restriction of grain boundaries. In homogenously deformed center region, the RD sample contained more {112} <110> grains, and TD sample was covered by {100} textures such as {100}<011> and {100}<021> with coarse grains, while the ND sample developed many {100}<011> grains which were attributed to more {100} grains in the initial sample. Remarkable texture transition occurred on both sides of grain boundaries when {110} grains were adjacent to α-fiber texture grains. It was found that significant texture gradient and preferred distribution of rotating axis existed in the soft orientation grains on the α-fiber when the grains neighbored hard grains on γ-fiber.

Anisotropic model for the numerical computation of magnetostriction in grain-oriented electrical steel sheets

Purpose – The modeling of magnetostrictive effects is a topic of intensive research. The authors' goal is the precise modeling and numerical simulation of the magnetic field and resulting mechanical vibrations caused by magnetostriction along the joint regions of electric transformers. Design/methodology/approach – The authors apply the finite element (FE) method to efficiently solve the arising coupled system of partial differential equations describing magnetostriction. Hereby, they fully take the anisotropic behavior of the material into account, both in the computation of the nonlinear electromagnetic field as well as the induced magnetostrictive strains. To support their material models, the authors measure the magnetic as well as the mechanical hysteresis curves of the grain-oriented electrical steel sheets with different orientations (w.r.t the rolling direction). From these curves they then extract for each orientation the corresponding commutation curve, so that the hysteretic behavior is simplified to a nonlinear one. Findings – The numerical simulations show strong differences both in the magnetic field as well as mechanical vibrations when comparing this newly developed anisotropic model to an isotropic one, which just uses measured curves in rolling direction of the steel sheets. Therefore, a realistic modeling of the magnetostrictive behavior, especially for grain-oriented electrical steel as used in transformers, needs to take into account the anisotropic material behavior. Originality/value – The authors have developed an enhanced material model for describing magnetostrictive effects along the joint regions of electric transformers, which fully considers the anisotropic material behavior. This model has been integrated into a FE scheme to numerically simulate the mechanical vibrations in transformer cores caused by magnetostriction.

Surface Roughness Analysis of Metal Spun Parts

The paper brings the results of roughness analysis of formed part produced by CNC multi-pass conventional metal spinning. The influence of the spindle speed, workpiece geometry and planar anisotropy of the blank on the formed part roughness was studied. For experiment design, an orthogonal array L27(313) was used and ANOVA (Analysis of Variance) was carried out. Based on the results it is determined that the higher spindle speed leads to rough surface finish. The surface roughness measured in different areas of experimental samples (corner R10, conical area, cylindrical area) indicates that the worst surface finish is in the conical area. Roughness in different directions refer to the sheet rolling direction shows minimal differences.

On the effect of the orientation of sheet rolling direction in shot peen forming

Peen forming is commonly used in the aerospace industry to shape large and thin panels, such as wing skins. This manufacturing process uses shot peening to introduce unbalanced compressive stresses near the surface of the component. These stresses tend to bend the panel and, when optimized, lead to the desired contour. Sheet materials often exhibit both elastic and plastic anisotropy, which can alter the development of curvatures. Since peen forming relies on compressive stresses to upset equilibrium, resulting curvatures may also be affected by initial stresses in the part. In this work, the influence of the rolling direction orientation with respect to the sample was investigated experimentally and numerically for the first time for aluminium alloy 2024-T3 specimens. Although maximum deflections were only slightly dependent on the rolling direction orientation, it was found that radii of curvature varied by as much as 10% with respect to this parameter. Finite element simulations allowed quantification of the individual effects of non-equibiaxial initial stresses and elastic orthotropy. It was found that these factors can significantly influence curvature development. Comparison of experimental and numerical results suggested that plastic anisotropy should also be taken into account in future studies. The tools developed in this study show promises for the accurate prediction of peen forming process for large scale components.

Correlation of morphological anisotropy and Lankford value of deep drawing sheets hot-rolled by compact strip production

Cold-rolled steel sheets in automotive applications require an excellent deep draw ability, which is characterized by the Lankford value (r-value). In this study, a correlation was identified between r-value and pancake-shaped grain flatness which is indicated as the ratio of grain diameter in the rolling direction (RD) and normal direction (ND) of sheets (dr/dn). A mathematical model \(\left( {r = e^{0.345\left( {d_n^{ - 1/2} - d_r^{ - 1/2} } \right)} } \right)\) was developed to calculate r-value by the microstructure of steel sheets hot-rolled by compact strip production (CSP). It is shown that the r-value is higher, if the microstructure of steel sheet is of pancake-shaped grains elongated in the rolling direction. The calculated r-value is confirmed to fit exactly to the measured one from the large-scale production.