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Single-point incremental forming (SPIF) has emerged as a cost-effective and rapid manufacturing method, especially suitable for small-batch production due to its minimal reliance on molds, swift production, and affordability. Nonetheless, SPIF’s effectiveness is closely tied to the specific characteristics of the employed sheet materials and the intricacies of the desired shapes. Immediate experimentation with SPIF often leads to numerous product defects. Therefore, the pre-emptive use of numerical simulations to predict these defects is of paramount importance. In this study, we focus on the critical role of the forming limit curve (FLC) in SPIF simulations, specifically in anticipating product fractures. To facilitate this, we first construct the forming limit curve for Al1050 sheet material, leveraging the modified maximum force criterion (MMFC). This criterion, well-established in the field, derives FLCs based on the theory of hardening laws in sheet metal yield curves. In conjunction with the MMFC, we introduce a graphical approach that simplifies the prediction of forming limit curves at fracture (FLCF). Within the context of the SPIF method, FLCF is established through both uniaxial tensile deformation (U.T) and simultaneous uniform tensile deformation in bi-axial tensile (B.T). Subsequently, the FLCF predictions are applied in simulations and experiments focused on forming truncated cone parts. Notably, a substantial deviation in fracture height, amounting to 15.97%, is observed between simulated and experimental samples. To enhance FLCF prediction accuracy in SPIF, we propose a novel method based on simulations of truncated cone parts with variable tool radii. A FLCF is then constructed by determining major/minor strains in simulated samples. To ascertain the validity of this enhanced FLCF model, our study includes simulations and tests of truncated cone samples with varying wall angles, revealing a substantial alignment in fracture height between corresponding samples. This research contributes to the advancement of SPIF by enhancing our ability to predict and mitigate product defects, ultimately expanding the applicability of SPIF in diverse industrial contexts.

The increase in the efficiency of the RGU-P350 corrugating machine as part of a process line to produce corrugated sheet material by modernizing the control system of the corrugation unit is considered. The modernization includes synchronization of the speed of the feed shafts and synchronization of the corrugation shafts by angular position using a programmable logic controller for more accurate synchronization of servo drives. The proposed solutions will increase the productivity and reliability of the process line.

Auxiliary cutting paths are always manually added to guarantee the quality of sheet material, which is time-consuming and costly. In this paper, a novel and systematic method for automatic generation of auxiliary cutting path based on the semantic information of reserved and discard areas of raw sheet material is proposed. The semantic information of raw sheet material is extracted from the given layout result using the proposed method. The cut-in and cut-out auxiliary paths are automatically inserted to each contour on the discard area. Collision detection and necessary adjustment are then performed to ensure that the auxiliary cutting paths are completely positioned within the discard area. The experiments with various layout results are conducted to verify the proposed method. The experimental results show that the proposed method can correctly obtain semantic information and effectively generate conflict-free auxiliary cutting paths automatically.

A procedure for evaluating the in-plane anisotropy of a sheet material used in structural elements with their integrity maintained during hardness tests is proposed. An innovative procedure performs anisotropy assessment not by hardness values, but by Vickers and Brinell indentation parameters, as well as by the structural parameters of the material. This procedure can be used to determine an anisotropy level from Vickers hardness, from structural material condition through statistical processing of indentation results, as well as to define the anisotropy of rolled plates, in particular high-strength low-alloy steels as-received, from Brinell imprints. The procedure is also useful in estimating the anisotropy of sheets and even high-strength steel plates whose material exhibits a slightly pronounced anisotropy, when it cannot be determined from imprint measurements, or its correctness controlled by statistical processing of imprint sizes. It is focused on the labor input reduction in determining the in-plane anisotropy of sheet materials as-received with their integrity maintained, on the higher efficiency of research and reliability of anisotropy measurements for high-strength plates with a slightly pronounced anisotropy. The procedure can be instructive in controlling the anisotropy data of sheet materials by indentation parameters.

Purpose The last stage of the cold rolling process is skin-pass rolling and one of its most significant goals is to obtain appropriate topography on the surface of the sheet steel used extensively such as in automotive industry. The purpose of this paper is to investigate the effect of thickness change and various reduction ratios on roughness transfer of DC04 grade sheet material. Design/methodology/approach DC04 grade sheet materials with different reduction ratios and several thicknesses were subjected to skin-pass rolling process in the rolling equipment with a two-high roll. Some roughness parameters were determined as a result of roughness measurements from the surfaces of roughened sheet materials. Findings While the roughness transfer is higher in 1-mm thick material in reduction ratios up to 430 micrometers; in reduction ratios above 430 micrometers, it is higher for 1.5-mm thick materials. As the reduction ratio increases in DC04 grade sheet materials, the homogeneity of the roughness distribution in 1-mm thickness sheet material deteriorates, while the roughness distribution in 1.5-mm thickness sheet material is more homogeneous. Originality/value This paper demonstrates how material thickness and reduction ratio affect the roughness transfer in skin-pass rolling. The results obtained can be used by optimizing in manufacturing processes.

Effects of polyvinylchloride (PVC) sheet thickness (t), feed speed (υ), spindle speed (ω), Z-axis feed rate (p) and tool head diameter (Φ) as well as their interactions during the single point incremental forming (SPIF) on forming performance of the PVC sheet material were studied through an orthogonal experimental test. In this experiment, the angle-variable cone was used and the maximum forming limiting angle was taken as the experimental index. Results showed that and ω×Φ influence forming performance of PVC sheet material significantly. υ is the main influencing factor of SPIF performance of PVC sheet material. Small υ is good for sheet material forming. p and Φ are proportional to forming performance of sheet material. Over ω will cause material wear-out. Effect of t could be neglected.

In this paper, an improved approach is proposed to determine the optimal profiles of two controllable process parameters (hydraulic pressure and blank holder force), which improve the forming condition and/or make better use of forming limits in hydromechanical deep drawing (HMD) process. A method based on adaptive finite element analysis coupled with fuzzy control algorithm (aFEA-FCA) was developed using LS-DYNA to determine the optimal loading profiles and thus to maximize the limiting drawing ratio (LDR). Maximum thickness reduction, maximum wrinkle height in the flange region of the sheet metal blank, and position of the nodes in the unsupported portion of the sheet metal blank between punch and die were used as criteria in the fuzzy control algorithm. Different rule-based matrices were compared by considering the maximum thinning occurred in the sheet metal blank, and thus, the most accurate matrices were determined for the control algorithm. The optimal loading profiles could be determined in a single FEA, thus reducing the computation time. The proposed approach enables determining the optimal loading profiles and also could be applied to complex parts easily. In addition, effects of initial blank diameter and coefficient of friction between the sheet-blank holder and sheet-die on the optimal loading profiles were investigated. An attainable LDR of 2.75 for AA 5754-O sheet material in hydromechanical deep drawing process was proven experimentally using the optimal loading profiles determined by adaptive FEA.

A sheet-type sinter-bonding material was developed to form thermally stable and highly heat-conductive joints suitable for wide-bandgap (WBG) semiconductor dies and high-heat-flux devices, and its bonding characteristics were investigated. To enhance the cost-competitiveness of the bonding material, Ag-coated Cu (Cu@Ag) particles were employed as fillers instead of conventional Ag particles. To facilitate accelerated sintering, a bimodal particle size distribution comprising several micron- and submicron-sized particles was adopted by synthesizing and mixing both size ranges. For sheet fabrication, a decomposable resin was used as the essential binder component, which could be removed during the bonding process via thermal decomposition. This approach enabled the formation of a sintered bond line composed entirely of Cu@Ag particles. Thermogravimetric and differential thermal analyses revealed that the decomposition of the resin in the sheet occurred within the temperature range of 290–340 °C. Consequently, sinter-bonding conducted at 350 °C and 370 °C exhibited significantly superior bondability compared to bonding at 330 °C. In particular, sinter-bonding at 350 °C for just 60 s resulted in a highly densified joint microstructure with a low porosity of 7.6% and high shear strength exceeding 25 MPa. The formation of the bond line was initiated by sintering between the outer Ag shells of the adjacent particles. However, with increasing bonding time or temperature, sintering driven by Cu diffusion from the particle cores to the outer Ag shells, particularly in the submicron-sized particles, was progressively enhanced. These results obtained from the fabricated sheet-type materials demonstrate that, even with the use of resin, rapid solid-state sintering between filler particles combined with the removal of resin through decomposition enables the formation of a metallic bond line with excellent thermal conductivity.

A multiscale FE simulation has been conducted for DP1000 sheet material with a thickness of 1.5 mm, which exhibits enhanced edge roughness due to laser-polishing. A smoother geometry and a new martensitic structure at the edge were observed during the laser-polishing process for the hole expansion sample. The effects of this new edge geometry are considered in the macroscopic simulation. The material characterization of the martensitic microstructure is performed based on the findings from heat treatment experiments. The coupled modified Bai-Wierzbicki (MBW) damage model is employed to predict damage behavior in the macroscopic simulation of the hole expansion test. In the microscopic simulation, the same material characterization resulting from heat treatment was applied, while local roughness was represented using actual measured roughness data. The macroscopic simulation’s damage criterion has been optimized by utilizing surface parameters. Bridging the roughness information from the microscopic simulation to the macroscopic simulation demonstrates that simulation results better agree with experimental outcomes.

Many sheet metal parts go through a bending operation during the manufacturing process. Compared to deep-drawing operations, failure in bending operations cannot be predicted accurately with a forming limit curve from the Nakajima or Marciniak experiment, especially in a pre-deformed state. Due to the small bending radii and the associated strong curvature, the failure only occurs with significantly higher strains for states without pre-deformation. Likewise, the failure is not caused by a localization, but by damage to the outer surface of the sample. The introduction of pre-deformation in the sheet material leads to development of texture and damage, where these mechanisms depend on the loading direction. If such pre-deformed sheet material is subsequently bent, the sample may fail unexpectedly early compared to the initial forming limit curve. The present experimental work aims at investigating the influence of pre-deformation and subsequent loading direction for different materials. Therefore, specimens have been pre-deformed in different orientations, followed by bending tests in different orientations. Different pre-deformation levels and loading directions combinations on three sheet materials were investigated. Based on the experimental results a so called bending forming limit curve (BFLC) can be derived enabling enhanced prediction of failure for bending processes after pre-deformation.