Forming Limit Diagrams of Perforated St12 Steel Sheets

One of the unique characteristics of sheet metals is their formability, which is determined by the forming limit diagrams. These diagrams specify the maximum deformation limit before part’s failure. For several applications of metal sheets, they have to be in the perforated format. Existence of holes in the perforated sheets may adversely deteriorate the forming limit of metal sheets. In this study, the effect of perforated sheets’ hole size and hole layout on their formability are investigated. Several specimens of St12 steel with 0.6 mm thickness, different widths, two various hole sizes of 2 and 4 mm, and two layouts of triangular and square were prepared. The specimens were tested using Nakajima test (stretch with a hemispherical punch) to generate the forming limit diagrams. It was observed that both the diameter and layout of the punched holes have a significant effect on the formability of the perforated sheets. The perforated sheets with triangular hole layout showed higher forming limits due to their larger ligament ratios.

Forming Limit Diagrams of Perforated St12 Steel Sheets

One of the unique characteristics of sheet metals is their formability, which is determined by the forming limit diagrams. These diagrams specify the maximum deformation limit before part’s failure. For several applications of metal sheets, they have to be in the perforated format. Existence of holes in the perforated sheets may adversely deteriorate the forming limit of metal sheets. In this study, the effect of perforated sheets’ hole size and hole layout on their formability are investigated. Several specimens of St12 steel with 0.6 mm thickness, different widths, two various hole sizes of 2 and 4 mm, and two layouts of triangular and square were prepared. The specimens were tested using Nakajima test (stretch with a hemispherical punch) to generate the forming limit diagrams. It was observed that both the diameter and layout of the punched holes have a significant effect on the formability of the perforated sheets. The perforated sheets with triangular hole layout showed higher forming limits due to their larger ligament ratios.

Analysis and Optimization of Springback during the V-bending of Hot-Rolled High Strength Steels (JSH440)

Influences of thickness, width, bend angle, applied load and holding time are evaluated over the springback in hot-rolled, high-tensile strength sheet-metals (JSH-440). Blanks' thickness, width and bend angles are considered the geometric parameters, whereas applied load and holding time are the process parameters considered in the research. Analysis of variance (ANOVA) and sensitivity analysis are applied to evaluate the significance of the factors over the springback magnitude. Analytical models are developed to predict the springback in the sheet metals for the desired geometric and process parameters. Simplified analytical models are also developed for different geometries of sheet metals. Finally, the Genetic Algorithm has also been applied to determine the optimal process parameters for the minimum springback with varying geometries of the sheet metals. Finally, the influence of parameters and optimized results are discussed in detail.

Optimization of the technology of cutting heavy-gage sheet metal by thermal method

The analysis of the influence of various technological solutions used in the thermal cutting of heavy-gage sheet metals to reduce the deformations of the resulting piece parts is given. It has been suggested to use a gas-oxygen cutting technology with packing sequence without localization of heat build-up. The effect of improving the efficiency and quality of production using the developed cutting technology is shown.

A Versatile Punch Stroke Correction Model for Trial V-Bending of Sheet Metals Based on Data-Driven Method

During air bending of sheet metals, the correction of punch stroke for springback control is always implemented through repeated trial bending until achieving the forming accuracy of bending parts. In this study, a modelling method for correction of punch stroke is presented for guiding trial bending based on a data-driven technique. Firstly, the big data for the model are mainly generated from a large number of finite element simulations, considering many variables, e.g., material parameters, dimensions of V-dies and blanks, and processing parameters. Based on the big data, two punch stroke correction models are developed via neural network and dimensional analysis, respectively. The analytic comparison shows that the neural network model is more suitable for guiding trial bending of sheet metals than the dimensional analysis model, which has mechanical significance. The actual trial bending tests prove that the neural-network-based punch stroke correction model presents great versatility and accuracy in the guidance of trial bending, leading to a reduction in the number of trial bends and an improvement in the production efficiency of air bending.