Effect of Anisotropy, Temperature, Strain Rate on deep drawing using Conical Die

This paper covers the role of anisotropy, temperature, and strain rate on the flow behavior of the material when a conical die is used instead of conventional blank holder. The effect of anisotropy was investigated using Lankford’s coefficient (r) in three directions (0°, 45°, and 90°). The effect of working temperatures (Room temperature, 100°C - 300°C) on drawing stress and strain rate sensitivity on punch pressure were also investigated in detail. ANSYS APDL was used to investigate the effects of temperature, strain rate and anisotropy. The simulation results have confirmed that the strain variation in the direction of r0 and r45 are more than the variation of r90.

A novel design of a high-strength high-temperature graphite die

Graphite die is a critical component in material processing, especially at high temperature. However, its strength is a bottleneck. In this study, we propose a novel, efficient, and economical solution to remarkably enhance the strength of graphite dies by employing the pre-stressed carbon fiber winding technology. An engineering application of a graphite die for hot pressing at 1273 K demonstrated the reliability and practicality: the original graphite die breaks under a punch pressure of 70 MPa and the carbon fiber wound graphite dies work well under a punch pressure up to 100 MPa. The finite element simulations illustrate that the 1-mm-thick layer of carbon fiber is able to reduce the maximum principal stress of the graphite die effectively from 130 MPa to 30 MPa. This is the first application of the pre-stressed carbon fiber winding technique to high-temperature components.

Effect of Counter Punch Pressure on Springback of High Strength Steel Sheet

To reduce springback in U-bending the present paper proposes a new technique where the bottom of a U-bent part is clamped between a punch and a counter-punch during bending and it is pushed up with the counter punch at the final stage. The effect of counter punch pressure, both in sheet clamping and bottoming, was investigated by performing experiments on dual phase 590MPa and TRIP 780MPa HSS sheets. From the experiment, an appropriate combination of the clamping force and the final pushing-up force was found where springback was reduced to almost zero. To investigate the mechanism of the reduction of springback in the above three-step U-bending process, FE simulation of the bending with PAM-STAMP 2G was also conducted where the advanced kinematic hardening Yoshida-Uemori model was employed.

Cold Piercing of Cylindrical Aluminum Billet with Counter Punch Pressure

To make a hole with a high aspect ratio (depth/diameter) for lightweight structural components, piercing of cylindrical billet of aluminum alloy was carried out against a counter pressure on a servo-controlled double axis press. To obtain smooth shear surface of pierced hole, the counter pressure was applied to the billet by a counter punch from the opposite side of a piercing punch during piercing. Irrespective of amount of clearance of die–piercing punch, ratio of the length of shear surface/depth of pierced hole in the pierced billet reached about 0.9 by applying a counter punch pressure of 0.2 GPa. The maximum aspect ratio of the hole in the proposed piercing method was estimated to be approximately of 15 for the aluminum billet from viewpoints of buckling and strength of the punch.

Completely Inelastic Collision to Confirm Maximum Punch Pressure Force of Cold Pressure Welding

The maximum punch pressure force (TMPPF) of cold welding pressure affects not only the performance of the welding bonding but also the amount of the area of welding bonding. If punch force is more bigger, it may be take place cracks, stress concentration and welding concave pits, which affect application of materials and increase incidence of faults. The process that punch pressure of cold welding pressure applied on sheet materials to attain welding bonding is simplified beam in cold pressure welding. Under normal circumstances it is an important method to TMPPF by the manner of experiment, but the method to attain TMPPF is limited. In the paper completely inelastic collision theory is applied to explain the process of cold welding pressure, the theory of completely inelastic collision offers principle theory to attain TMPPF. In this paper, two supposes are put forward, on the basis of two supposes the critical velocity is attained. At the same time, critical kinetic momentum or critical kinetic energy will be attained. On the basis of the law of conservation of energy, energy balance equation is attained, which will drop in calculating difficulty of the non-linear process of cold pressure welding and decrease calculated amount. In this paper on the basis of the process of collision all phases are analyzed. Indeed elastic-plastic deformation phase is completely inelastic collision phase, and from point of view of collision to calculate energy loss. At the same time, to suppose other plate is utter stiff can attain critical velocity, thus, to achieve the equation of TMPPF.

A Study of the Lubrication Behavior of Solid Lubricants in the Upsetting Process

Four kinds of solid lubricants were tested in order to examine the frictional characteristics and the yield shear stress by the friction testing apparatus developed by the authors. The frictional shear stresses τf increased approximate linearly with the punch pressure p in every solid lubricant, and the friction coefficients μ were approximately constant. The yield shear stress k was also increased with the punch pressure p. In order to investigate lubrication behaviors of solid lubricants in upsetting processes, FEM simulations for upsetting of circular plates have been carried out. Some experimental upsetting tests of circular plate were tried using some kinds of solid lubricants. It has been confirmed that the solid lubricants can lubricate successfully without metal-to-metal contact when μD at the interface between tool and solid lubricant is relatively low and μM at the interface between work piece and solid lubricant is relatively high. On the other hand, metal-to-metal contact occurs easily at the peripheral regions of the work piece, when μD is relatively high and μM is relatively low. [S0742-4787(00)00804-3]

Impression creep behavior of SiC particle-MoSi2 composites

Using a cylindrical indenter (or punch), the impression creep behavior of MoSi2-SiC composites containing 0–40% SiC by volume, was characterized at 1000–1200 °C, 258–362 MPa punch pressure. Through finite element modeling, an equation that depends on the material stress exponent was derived that converts the stress distribution beneath the punch to an effective compressive stress. Using this relationship, direct comparisons were made between impression and compressive creep studies. Under certain conditions, compressive creep and impression creep measurements yield comparable results after correcting for effective stresses and strain rates beneath the punch. However, rate-controlling mechanisms may be quite different under the two stressing conditions, in which case impression creep data should not be used to predict compressive creep behavior. The addition of SiC affects the impression creep behavior of MoSi2 in a complex manner by pinning grain boundaries during pressing, thus leading to smaller MoSi2 grains and by obstructing or altering both dislocation motion and grain boundary sliding.

Backward Extrusion of Internally Shaped Tubes From Round Billets

An analytical method is proposed for estimating the steady-state punch pressure for three-dimensional backward extrusion (or piercing) of complicated internally shaped tubes from circular billets. A kinematically admissible velocity field is derived to formulate an upper-bound solution using velocity transformation and mapping function. The configuration of deforming boundary surfaces are determined by minimizing the extrusion power with respect to some chosen parameters. Experiments are carried out with commercially pure aluminum billets for internally shaped tubes at various reductions of area by using different sizes of shaped punches, such as square and regular hexagons. It is shown that the theoretical predictions for extrusion load are in good agreement with the experimental values.