Computer application of the kinematics control system for a virtual stretch-tightening press RO-630-11

A computer application of the control system for the virtual display of a real stretch-tightening press RO-630-11, taking into account its kinematic features, has been developed. The focus is on the research carried out by the finite element method in modeling the processes of shaping a sheet blank by a tightening punch, with a surface oriented relative to the curvature lines and placed on the table of a virtual stretch-tightening press RO-630-11.

Material Characteristics Evaluation for DC04-Welded Tube Hydroforming

Tube hydroforming (THF) technology is widely applied, especially in the automotive and aircraft industries. Material characteristics of tubular workpieces should be evaluated in terms of bending and THF processes. A mathematical model, which combines the assumption of elliptical contour of a bulged wall and the prediction equation of wall thickness, is provided to analyze the THF process and to obtain the strain-stress relationship of tubes. Material characteristics of a DC04-welded tube is obtained by using a self-designed THF test machine. Considering the effects of pre-work hardening, we discuss the material strain-stress relationships of the tube and original sheet blank. An approximate determination method is proposed to obtain the stress-strain curve of the tube by using the curve of the original sheet blank and the hardness of the tube and sheet blank. A suitable constitutive equation with pre-work hardening is applied to the DC04-welded tubes through simulation and experimental methods.

A Study on the Effect of Process and Material Variables on the Hot Stamping Formability of Automotive Body Parts

Hot stamping is a method capable of manufacturing high-strength automotive body parts by inducing a martensitic phase transformation through forming and die quenching after heating a metal sheet into a high temperature austenite phase. However, it is not easy to solve various formability problems occurring in the hot stamping process due to the complexity of the process and material behavior during high temperature forming. In this study, fracture-related forming limits and martensite phase ratio were selected as criteria for evaluating hot stamping formability. First, a hot stamping test was performed on a T-type part that simplified the B-pillar, an automotive body part, and the fracture behavior according to the temperature and thickness of the sheet blank was investigated. Additionally, forming analysis was performed on the hot stamping process of mass-produced B-pillar parts by varying the temperature of the sheet blank, the thickness of the sheet blank, the die-blank friction coefficient, and the strain-rate sensitivity of material among various process and material variables. Based on the analysis results, the effect of each process and material variable on the hot stamping formability of B-pillar parts was quantitatively analyzed. By utilizing the results of this study, it will be possible to solve the formability problem that occurs in the mass-production hot stamping process for automotive body parts and improve the quality of parts in the future.

Determination of cutting force of roll-formed section in shaped dies-knife guillotine

The change in cutting force in the cutting process of roll-formed section in shaped dies-knife guillotine is studied. It is established that to calculate the cutting force in shaped guillotine, one can use formulas to determine the cutting force of sheet blank on conventional straight knives guillotine.

The System of Informational Choice of the Kinematic Scheme for the Formation of Shells of a Complex Spatial Form

Three kinematic schemes are studied, which differ from one another in the route of technological operations. Each of these kinematic schemes has its own set of power stages of shaping and stages of free bending or bending of the ends of the sheet blank. In addition, the quantitative values of the angular parameters of a particular kinematic scheme are determined. Numerical experiments have been carried out, which give complete information about the distribution of the shell thickness as discrete values in one or another element. The result is statistical processing of this information, the scope of the predicted values and comparison with the tolerance on the thickness of the peel used in aviation enterprises.

Analysis of non-equal-channel angular pressing scheme applied for obtaining magnesium sheet in cold state

Deformation patterns of rolling, equal-channel angular pressing and non-equal-channel angular pressing were evaluated. It is noted that when rolling, it is difficult to transfer a circular section preform into a rectangular section with a small thickness. This problem cannot be solved using equal-channel angular pressing. In connection with this, it is proposed to use a non-equal-channel angular pressing pattern to study the cast structure of magnesium. An experimental procedure based on cold extrusion of cylinders with a diameter of 42 mm and a height of 40 mm is described. The strip at the outlet was 40 mm in width and 1 mm in thickness. The percentage reduction of the preform material determined by the ratio of areas was 96 % with a draw ratio of 17. The specific pressures on the punch at the beginning ofthe extrusion process were 1200—1300 MPa, and extrusion force was 1670—1800 kN. The preform was cut into lengths that were rolled at a room temperature into 50 and 10 pm thick foils without intermediate annealing. Rolling was carried out on the Duo mill with a percentage reduction of 12—20 % at an average speed of 0,1 m/s. 20 passes were performed with a total relative reduction of 95 % to make the 50 pm thick foil. The results of computer simulation by the finite element method demonstrated that the constant value of the deformation degree is achieved at a rather considerable distance from the front end estimated as 50 times the thickness of the strip. The deformation rate field was calculated to determine the configuration of the deformation center. Energy costs were estimated. As a result of the completed set of calculated and experimental work, it was possible to establish the following — it is possible to produce a thin sheet preform from a cylindrical cast magnesium blank in one operation at a room temperature. The sheet blank has a level of ductility sufficient for subsequent sheet rolling. The sheet blank obtained in the proposed process has a high level of plastic deformation elaboration created due to the forming pattern with the high level of elongation and shear deformation. Despite the high level of pressure that must be applied to create a comprehensive compression scheme taking into account the lack of the need to heat the preform, energy costs are no higher than in traditional treatment processes.