Shijian Yuan

The precision forming of pin parts by cold-drawing and rotary-forging

Abstract This paper introduces the cold-drawing and rotary-forging precision forming technology of pin parts used in locomotives and rail carriages. The determination of the drawing loads and the rotary forging loads, and the deformation mechanism and product quality are discussed. The deformation process is analyzed using the finite-element method. It has been shown by experiment and production that the pin parts manufactured by cold-drawing and rotary-forging can enhance the surface roughness in the relevant standard, and improve the mechanical properties to some degree. Therefore, it is an advanced precision forming technology for pin parts.

The development of integral hydro-bulge forming (IHBF) process and its numerical simulation

Abstract The integral hydro-bulge forming (IHBF) technology of spherical vessels has achieved an increasing application in a variety of fields. Recently IHBF has been extended into the forming of an ellipsoidal shell, the center part of a container head shell and a ring shell. In this paper, the process, application, development and numerical simulation of IHBF are discussed.

Experiment and numerical simulation of hydro-forming toroidal shells with different initial structure

In this paper, the effect of the initial structure on formation of toroidal shells is investigated for avoiding wrinkling in the hydro-forming process for manufacturing large elbows. The experimental results show that no wrinkling occurs on a toroidal shell with an octagonal cross-section. However, there are some tiny wrinkles on a toroidal shell with a hexagonal cross-section. The deformation process was simulated using an explicit dynamic finite element code LS-DYNA. The simulation results are basically in agreement with the experimental results. The reason for wrinkling is discussed. Research results show that wrinkling can be prevented by selecting an appropriate initial structure.

A new hydroforming process for large elbow pipes

Abstract A new hydroforming process for manufacturing elbow pipes is proposed to overcome the difficulties in manufacturing large elbow pipes with conventional technologies. The stresses in a toroidal shell are analyzed and the final hydroforming pressure is given. The displacement, strain distribution, wrinkling and cross-section profile variation of the toroidal shell during the hydroforming process are discussed. The dimensions of the formed toroidal shell are measured. It is shown experimentally that the manufacturing of elbow pipes with the integral hydroforming process is feasible.

Safety analysis of 200 m3 LPG spherical tank manufactured by the dieless hydro-bulging technology

Abstract This paper briefly introduces the design and manufacturing process of a 200 m3 LPG spherical tank manufactured by the dieless hydro-bulging technology, and then puts emphasis on its safety analysis. The results of measurements and experiments show that the geometrical tolerance and the mechanical properties can meet the requirements of the concerned codes, the wall thickness distributes evenly and there exist compressive residual stresses on the inside surface, which latter are favorable for preventing the hydro-bulged spherical tank from stress-corrosion cracking (SCC) and can improve the fatigue strength.

Numerical simulation of hydroforming a double conical tube

The hydroforming process of a double conical tube with the biggest difference of cross‐section 75 percent is studied by means of FE simulation in this paper. The effects of loading paths during hydroforming process on the wrinkle shape and failure modes are analyzed. Thickness distribution and strain path of position with the biggest expansion rate on FLD diagram of this workpiece are given. The simulation results show that the part can be formed successfully with the feeding pressure selected in the range from 20 to 25MPa. When the feeding pressure is 23MPa, the preform with desirable wrinkle distribution and plenty storage of materials can be obtained. The maximum of thinning rate by the simulation is about 18.29 percent, which is close to 19.54% that is obtained in experiment.

A study on the bending of a trough-shaped profile using a roller and PUR pad

In bending with PUR pad, profile with different curvature radius can be manufactured. Experiment of trough-shaped profile was carried out to investigate the effect of section shape, penetration depth, roller radius and PUR pad thickness. Results show that both the position of neutral surface and section moment of bending have significant effect on curvature radius. Profile with bigger section moment of bending is difficult to bend. Curvature radius of bent profile decrease sharply when penetration depth increase. Change of roller radius has similar effect as the position of neutral surface. PUR pad thickness has big effect under small penetration depth.

AN INVESTIGATION INTO THE PLASTIC FORMABILITY OF WELDED JOINTS

Abstract This paper deals with the plastic formability of welded joints simulating the dieless hydro-bulging process of spherical vessels using wide-plate specimens. The effect of welding factors such as weld strength, profile of the weld, toe etc., on the stress-and strain-distributions of the welded joints are analyzed by elasto-plastic FEM. The results show that the plasticity of the welded joints can satisfy the requirement of metal-forming processes, on condition that some technological measurements are adopted.