Experimental and numerical analysis of the wear mechanism in spring coil forming die and the effects of die geometry on wear

The present work aimed at understanding the wear mechanism of spring coil forming die and the effects of die geometry on wear. The wear morphology was analyzed by scanning electron microscopy and energy dispersive spectrometer. The main wear mechanism was found to be adhesive wear, and a variant of the Archard wear model was established. The wear distribution in spring coil forming die was numerically analyzed in DEFORM software, and the effects of die geometry parameters on wear were discussed. Numerical results revealed that the wear distribution in the die was uneven and the wear mainly occurred at the sides of the die cavity. The wear depth was greatly affected by the width and angle of the die cavity, whereas the length of the die cavity had little effect. A small cavity width or angle led to severe wear, while a large cavity width reduced the forming quality of the spring coil. Moreover, a simple and effective life prediction method was proposed based on wear results. The findings of this research will be helpful for the effective design of spring coil forming die and the prediction of wear.

Influence of Die Threading and Finishing Length in the Thread-Rolling Process Using Flat Dies: A Numerical Analysis

In this paper, a numerical analysis of the cold thread-rolling process using flat dies is presented as a function of the die geometry design. Five die geometries with different threading and finishing ratios were modelled to induce different screw deformation rates. An analytical method was proposed by the authors to design die geometries as a function of screw roll rotation. Screw geometry accuracy, induced stress, and die wear were selected to compare the tested geometries. The results showed that three screw rotations in the threading step were sufficient to guarantee good geometry accuracy. Moreover, the results highlighted that die wear is the most affected parameter among all the tested geometries. Finally, a new solution was proposed by the authors to obtain uniform wear and reduce the die length.

The influences of the variable speed and internal die geometry on the performance of two commercial soluble oils in the drawing process of pure copper fine wire

The cold wiredrawing process constitutes a classical-tribological system in which a stationary tribe-element (die) is in contact with a tribe-element in relative motion (wire) and both interacting with the interfacial tribe-element (lubricant). This condition is reflected in the effect of friction as a function of the drawing speed and temperature, and directly affects the wearing of the surface into the die and the final quality on the drawn wire. The aim of this work has been to determine the best conditions to process ETP-copper using two different types of oil/water emulsion lubricants. For this purpose, six different die geometries have been proposed and a set of tests have been carried out at different speeds (between 1 and 21 m/s) to determine those combinations that give a lower value in the required drawing force (Fd). The experiments allowed to know the friction coefficient (µ), the temperature profile inside the drawing die and in the lubricant and also the mean roughness (Ra) in the drawn product. The results have shown that drawing speeds above 10 m/s significantly decrease the drawing force and, as a consequence, the friction effect on the interface. The best results have been achieved in the combinations of the lower die angle (2β = 14°) with drawing speeds between 17 and 18 m/s with both types of lubricants used, obtaining the lower values of the friction coefficient between µ = 0.10–0.15 with the lubricant type D (Agip S234-60 oil at 7% concentration). It has been found that those tests carried out with dies with a smaller approach angle have generally made it possible to obtain better qualities in the final product. Additionally, FEM simulations have been done to analyse those cases with the lower values of µ, throwing values of Fd that are consistent with those measured in the experimental setting and allowing to better understand the behavior of the material as it passes through the die.

Increasing the Durability of Trimming Dies Used to Clean Anodes in the Aluminum Industry

Increasing the durability of trimming dies used to clean anodes is a very important goal in order to reduce the costs involved in obtaining aluminum. The research focused both on choosing an optimal material for the execution of trimming dies and on the application of technologies for plating active areas and, at the same time, on optimizing the geometric shape of the active area of the trimming die. In order to choose an optimal material from which to make the trimming dies, it was taken into account that they are usually made of X210Cr12 steel. In the stage of choosing an optimal material for the execution of the trimming dies, five steels were taken into account, namely: K105, K107, K110, K360, and K460. Analyses of the metallographic structure of the passage area were performed between the metal deposited by welding and the base material, demonstrating the fact that hot welding plating allows obtaining a more homogeneous metallographic structure compared to cold welding plating. The choice of new material was not a solution to increase the durability of the trimming die. Change in the trimming die geometry determined a reduction in deformations of about 13.8 times and of the equivalent stresses of about 7 times compared to those obtained in the case of the old trimming die. In addition, the durability of the trimming die with the new construction shape increases approximately three times compared to the trimming die with the old geometric shape. This demonstrates that the solution to increasing the durability of the trimming die is to adopt an optimal geometry of the active part at the expense of choosing an optimal material.

Optimization of Die design to abolish surface defect on Telescopic Front Fork (TFF) Tube

Background: The telescopic fork is mainly used for suspension purposes in the different devices to absorb the vibration and disturbances from the road or mechanical devices. Factors such as die angle, drawing velocity, lubrication, and area reduction per pass significantly affect the drawing loads and residual stresses formed in the drawn tube during the tube marking process. Objective: Instantaneous transverse crack was found on the pipe's outer surface during the drawing process in the current work, and the key challenges were to reduce the percentage of pipe rejection. Methodology: In this work, optimum drawing die designs were proposed by using the finite element method (FEM). A FEM solving tool called Abaqus has been used for simulating and solving the cold-rolled process. The FEM model of the cold drawing process is generated in Abaqus with the same boundary condition (Axial load and constrain) as using on the actual wire drawing machine. Result: There was a substantial reduction in the area; axial stress (Tensile) along the die side is 672 MPa which is 23 % lower than the current die axial stress value of 877 MPa. A 48 % plastic strain was found along the purposed die side, which was 17 % lower than the existing strain of 64%. Finally, reduced the area by changing the die geometry from ~52% to 35 to 40 %. Conclusion: It was possible to abolish transverse crack on the pipe's outer surface to reduce the area reduction (35 to 40 %) in the output tube and strain (17 %). As part of the optimization of the FEM work process, this work gives us encouraging results. Further research will be considered for future positions.

INFLUENCE OF THE PRESSURE DIE GEOMETRY ON THE BENT TUBE OVALITY

The paper deal with analysis and optimization of the pressure bar geometry in the case of the tube bending. The bending process is realized on Wafios RBV 60 ST CNC bending machine using rotary draw bending system. The processed semi-finished product is a tube, which is made of 24MnB5 steel. Currently, after tube bending by an angle of 120°, an unacceptable ovality occurs on its body. Therefore, the article presents the optimization of the pressure bar geometry, which helps to prevent the occurrence of the mentioned defect. Due to the least possible intervention in the bending process, only the change in the pressure bar geometry is tested. For this reason, a numerical simulation in ANSYS software is performed. Before the actual optimization, an accuracy of the simulation is verified by comparing the real initial state with simulation results.

Effect of graphite die geometry on energy consumption during spark plasma sintering of zirconium diboride

The present work aims to investigate the geometrical parameters of the graphite die on energy consumption needed for sintering of a ZrB2 sample. The Maxwell and electrical charge conservation equations are solved to obtain the electrical potential and current of the system. The governing equations are discretized by the Galerkin method and solved using the finite element method. The electric current distribution is obtained at each geometry and the temperature contours are obtained. The results showed that the height of die has a direct effect on power consumption. This can be attributed to the increased electric resistance and consequent increased Joule heating. On the other hand, increasing the die height resulted in more uniform temperature distribution through the sintered sample.

Adjusting the Residual Stress State in Wire Drawing Products via In-Process Modification of Tool Geometries

After conventional forming processes, the residual stress distribution in wires is frequently unfavorable for subsequent processes, such as bending operations. High tensile residual stresses typically occur near the wire surface and normally limit further processability of the material. Additional heat treatment operations or shot peening are often used to influence the residual stress distribution in the material after conventional manufacturing, which is time- and energy-consuming. This paper presents an approach for influencing the residual stress distribution by modifying the forming process, especially regarding die geometry. The aim is to reduce the resulting tensile stress levels near the surface. Specific forming elements are integrated into the dies to achieve this residual stress reduction. These modifications in the forming zone have a significant influence on process properties, such as plastic strain and deformation direction, but typically do not influence product geometry. This paper describes the theoretical approach and model setup, the FE simulation, and the results of the experimental tests. The characterization of the residual stress states in the specimen was carried out through X-ray diffraction using the sin2Ψ method.

Numerical investigations on the influence of the weld surface and die geometry on the resulting tensile stresses in the joining zone during an extrusion process

Bulk metal components are often used in areas which are subjected to very high loads. For most technical components, a distinction between structural and functional areas can be made. These areas usually have very different loading profiles, sometimes with contradictory requirements. Nevertheless, nowadays almost only monomaterials are used for the production of bulk metal components. With increasing requirements towards more and more efficient products with lower weight, compact design and extended functionality, these materials are reaching their material-specific limits. A significant increase of product quality and economic efficiency can be expected exclusively with locally adapted properties by combining different materials within one component. In this regard, the focus of this contribution is the production of a hybrid pinion shaft made of the material combination steel (37CrS4) and aluminium (AW6082). The tool concept for extrusion of the hybrid preform, the simulation-based design of the forming process as well as the material characterisation are presented. With the help of the FE-simulation, different serially arranged semi-finished component geometries were investigated in order to minimise the occurring tensile stresses in the component during the extrusion process to prevent failure during forming.