Liqun Ruan

Characterization of Adhesive Strength of Phosphate Coatings in Cold Metal Forming

A test method is proposed to characterize adhesive strength of phosphate coatings based on the various deformation patterns at the tool-workpiece interface. The deformation patterns were induced by tools of different surface geometrical profiles, i.e., flat surface, sinusoidal surface, saw-tooth surface and multi-surface profiles, in a localized rod drawing technique. With change in the tool geometry, three deformation regimes were observed, i.e., full film lubrication regime, mixed regime, and seizure regimes, which were categorized by the level of friction coefficient attained, and the degree of galling observed on the surface of the drawn specimens. The full film lubrication regimes were noticed when flat dies were used. In this case, the friction coefficient was maintained at nearly μ = 0.065, irrespective of the change in the surface roughness of the tools and reduction. With sinusoidal surface and other non-flat dies, mixed regime and seizure regimes were observed, and the friction coefficient varied from μ = 0.1 to 0.3. To complement the friction data, surface analysis of the tool-workpiece interface was also conducted. The frictional range of μ = 0.065 to 0.3 obtained in this study, therefore, provides for a manageable characterization of phosphate coatings for cold metal forming of objects with intricate shapes.

Influence of die geometry on the workability of conversion coatings combined with soap lubricant in cold forming of steels

Abstract Tribological conditions pertaining to the plastic deformation of zinc-phosphate coated specimens under localized bar drawing experiments were investigated. Dies of different surface profiles namely; sinusoidal, saw-tooth, flat and multi-surface profiles were used to induce various deformation patterns at the tool workpiece interface. Significant changes in the interface friction with change in both the die geometry and the mean interface temperature were observed. In order to correlate the surface expansion behavior defined by the tool geometries with the distribution of lubricant film at the tool-workpiece interface, tool indentation simulations using Two Dimensional Rigid Viscoplastic Finite Element Method (2D-FEM) were also conducted.

Slide-bending Formation of Thin Metal Sheet by Using an Industrial Robot

In this paper we describes slide-bending formation of thin metal sheet by using an industrial robot which has five degrees of freedom. The reactive force were meadured by a force sensor mounted on the robot and the bending angle og the metal sheet was measured by a CCD camera. The trajectory of the robot was controlled so that the reactive force was kept constant. From the results of the experiment, it is shown that The trajectory of the robot was controlled so that the reactive force was kept constant. The bending angle of the sheet was measured by the CCD camera. From the results of the experiment, it is shown that the bending angle of the thin metal sheet can be controlled by the applied load.

Study of forming of magnesium alloy by explosive energy

Magnesium alloy is an attractive next generation material due to its high specific strength with low weight. However, magnesium alloys has few slip lines with close‐packed hexagonal lattice, and generally poor ductility at room temperature, therefore it is difficult to form this material by cold forging. It is well known that the speed of deformation of metallic materials rapidly changes at the high strain rate. For some metallic materials, it is reported that the ductility also increases at the high strain rate with this speed effect. In this study, a series of high speed impulsive compressive tests were carried. By using explosives for shock wave loading, the velocity in this experiment reached 100 m/s that can’t be easily obtained in normal experiment. In this paper, the possibility of forming the AZ31 extrusion magnesium alloy using explosive‐impulsive pressure is investigated. And improved ductility by the effect of high‐rate deformation is observed with this alloy.

308 Examination of Ductility Increase on Forming of Magnesium Alloy

The major problem for forging of magnesium alloy is the lack of process ductility at the low temperature. The Mg96Zn2Y2 is a high strength magnesium alloy material developed by Mr. Kawamura in Japan. Mg96Zn2Y2, a newly developed high strength magnesium alloy material is expected as forged parts of the automobile and materials for aerospace applications. It is necessary to clarify forging process characteristics of this material. The purpose of the present study is to examine increasing of ductility of forging process for the Mg96Zn2Y2 material. For this purpose, cylinder upsetting tests were performed by this method of two stages. In addition, the deformation resistance and ductility of the material were examined. The two stages forging process is effective for an increase of ductility of the material.