FE analysis on Deformation and Temperature Nonuniformity in Forming of AISI-5140 Triple Valve by Multi-Way Loading

Abstract

In triple valve forming process by multi-way loading severely nonuniform deformation and temperature distributions are prone to occur, which may lead to poor forming quality and macro-micro defects. A 3D coupled thermo-mechanical rigid-viscoplastic finite element (FE) model for multi-way loading forming of AISI-5140 steel equal diameter triple valve was developed based on DEFORM-3D. Through comprehensive simulation and analysis, the influences of main process parameters on the forming process and nonuniformity of deformation and temperature were studied. The results showed that: (1) the degree of deformation nonuniformity decreased with the increase of the punch loading speed, initial temperature of billet, or the decrease of the friction factor; (2) the average temperature of forming body increased as the punch loading speed, initial temperature of billet and the friction increased, while the degree of temperature nonuniformity decreased with the increase of punch loading speed or decrease of initial billet temperature.

Appendices

Appendix 1: Materials Properties of AISI-5140 and AISI-H13

See Table 2, Fig. 9, and 10.

Table 2 Materials properties of AISI-5140 and AISI-H13

Fig. 9

Stress-strain curves of AISI-5140

Fig. 10

Stress-strain curves of AISI-H13

Appendix 2: The Previous Work of FE Model and Model Validation in Ref 6-8

Based on FE soft environment of DFEORM-3D, a reliable coupled thermal-mechanical 3D-FE model of multi-way loading forming process of multi-ported valve body is established using rigid-viscoplastic FE method. The material properties of the billet and die come from the material library in DEFORM-3D. In the model, the die is treated as a rigid body, while the billet as a rigid-plastic material. In the simulation, the metal yields based on the Von Mises yielding criteria. The shear friction model is employed to describe the friction at die-billet interface. The frictions between male dies and female die are ignored.

$$ f_{\text{s}} = mK $$

(1)

where f _s is the frictional stress; K is the shear yield stress of the metal; and m is the friction factor.

The multi-way loading process of multi-ported valve adopts a closed forging without flash. In the process, upper and lower (z axis) female dies close firstly, then the male dies in the plane (x and y axis) are loaded at the same time or in sequential time. The geometric models of billet and dies are built in CAD software. Then, the geometric models are inputted into DEFORM-3D by means of STL format, which are assembled under DEFORM.

According to the geometrical and boundary conditions of multi-way loading to manufacture the tee valve, it is possible to model 1 s of the problem. Furthermore, structures of dies are also simplified, such as (1) grip blocks of male dies are omitted, thus the male die is composed of punch and die block; (2) the thickness of die block of male die is reduced; (3) the thickness and lengths in x and y axis of female die are reduced. Four-node tetrahedron elements are generated for the billet and the dies, shown in Fig. 11. The initial meshes in dies are not homogeneous, being coarser beyond the die-billet interface. Automatic remeshing technology is used to avoid mesh distortion.

Fig. 11

3D-FE model of tee valve forming process under multi-way loading; 1—billet, 2—x axial male die, 3—y axial male die, 4—female die, and 5—die block of male die

In order to validate the 3D-FE model, simulations for two multi-way loading processes have been carried out, respectively, based on forming the forging in the literature (Ref 3). The shapes and dimensions of the forgings are shown in Fig. 12.

Fig. 12

Shapes and dimensions of forging

The loading conditions are the same for forging in the literature (Ref 3), and are as follows: (1) at the first loading stage, two horizontal (x axial) male dies are loaded until two horizontal cavities are formed, then the male dies are held on that position; (2) at the second loading stage, vertical (y axial) male die is loaded until vertical cavity is formed; (3) finally three male dies could be unloaded. Above loading conditions and parameters listed in Table 3 are used to simulate forming process of forging A.

Table 3 Basic parameters used by literature (Ref 3)

The comparison of shapes of forging A between numerical simulation results and the experimental results is shown in Fig. 13. It can be seen from Fig. 13 that the shapes of forging A in numerical simulation show a good agreement with that obtained by experiment in the literature (Ref 3). So, it indicates that the established 3D-FE model is reasonable.

Fig. 13

Shapes of forging at the chosen stages. (a) Experimental results (Ref 3) and (b) FEM results