Hot Forging Process Design and Initial Billet Size Optimization for Manufacturing of the Talar Body Prosthesis by Finite Element Modeling

In hot forging industry, the process design and the billet size determination are very crucial steps because those steps directly influence both the product quality and material utilization. The purpose of this paper was to propose a technique used to design the hot forging process for the manufacturing of the talar body prosthesis. The talar body prosthesis is one of the artificial bones, which its geometry is a free form shape. In this study, the Finite Element Modeling (FEM) was used as a tool to verify the proposed design before implementation in a production line. In addition, an initial billet was determined the optimum size in the FEM by varying the mass ratio factor, the diameter, and the length. It was found that the mass ratio factor is a very useful guideline since the optimum size is quite close to the provided size from the guideline. The FEM results showed that the dimensions of the initial billet significantly affect the complete metal filling in the die cavity. Moreover, the optimum size between the diameter and length can reduce the material waste in the hot forging process of the talar body prosthesis. Finally, the experimental results of the hot forging process showed that the proposed process design with the optimum size of the initial billet is achieved in order to manufacture the talar body prosthesis and the material utilization of the new proposed process is improved from the traditional process by 2.6 times.

The Limits of Applicability of the Method of Discontinuous Solutions in the Study of Pipe Drawing Processes

Introduction. Non-contact deformation of the workpiece material, which occurs along the boundaries of the deformation zone, is one of the main factors determining the energy-power parameters of pipe reduction processes. The most widespread practice in the design of metal forming processes is the method of discontinuous solutions, which makes it quite simple to take into account non-contact deformation in numerical simulation of processes. However, for most processes in the technical literature there are no systematic practical recommendations on the application of this method, which inevitably leads to a mismatch of theoretical principles and practice. The aim of the work is to determine the limits of applicability of the method of discontinuous solutions for processes of faultless drawing of pipes through a conical die, depending on the geometric parameters of the workpiece, tool, as well as the degree of deformation and hardening of the processed material. Research Methods. The model of the deformation zone for the process of flawless drawing is considered in two versions: by the method of discontinuous solutions and taking into account non-contact bends of the pipe wall. From the condition of the balance of the shear forces acting on the conditional shear surface and the bending moments caused by the bending of the pipe wall, under various deformation conditions, the boundary values of the thickness parameter are determined, at which it is advisable to carry out numerical simulation of the drawing processes using the discontinuous solution method. In this case, the calculations are performed separately for two sections of the deformation zone corresponding to the bending of the pipe wall at the entrance to and exit from the die. Results and discussions. The numerical implementation of the obtained dependences showed that at the entrance to the deformation zone, the boundary value of the thickness parameter increases with an increase in the taper angle of the die and the hood for the transition, but decreases with an increase in the anti-tension stress and the thickness parameter of the initial workpiece. At the exit from the deformation zone, the boundary value of the thick-walled parameter increases with an increase in the taper angle of the die and decreases with an increase in the stretch coefficient for the transition and the thick-walled parameter of the initial billet. If the parameter of the thickness of the initial billet exceeds the boundary value, then in numerical modeling it is advisable to use the method of discontinuous solutions. If it does not exceed, then other methods and models should be used. The results of a theoretical study can be used in the design of pipe drawing processes.

Development of rational deformation mode of tube billet in continuous roll forming

Universal formula is proposed for calculating the optimal strip width and tube-billet perimeter at each stage of bending in the production of electrowelded low- and medium-diameter straight-seam tube and pipe of round and complex cross section. This formula determines the conditions of tube deformation in machines of different type and allows the increase in tube-billet perimeter in group of stands with open gauge profi le to be taken into account for different forming behavior. For the tube and pipe range produced, the reduction at the tube-billet perimeter in group of stands with closed gauge profi le should be no more than 0.6 %. That decreases the steel consumption by decreasing the width of the initial billet, without loss of pipe quality, and increases the product yield by eliminating edge buckling in the course of forming.

Development of self-protective powder wire with diameter of 1.6 mm for automatic welding of pipe-lines joints root

The results of self-protective powder wire with diameter of 1.6 mm are presented. The working purpose is to create small-section powder wire and its manufacturing technology, designed for automatic welding of the root layer of the seam of non-rotating joints of main pipe-lines transporting oil and gas with admixture of hydrogen sulfi de, and providing increase of at least 1.5 times the productivity of pipe welding. The forming rollers for the initial billet with diameter of 2.4 mm of two-bend powder wire are developed. The composition of the charge fl uxcored wire, providing the requirements of product development: reliable penetration of the root layer of the seam fi xed joints of pipe-lines with tensile strength of the weld metal at 490 MPa. Recommendations on the production technology of self-protective powder wire of two-bend design are developed.

3D Forging Simulation of a Multi-Partitioned Titanium Alloy Billet for a Medical Implant

The medical healthcare industry uses titanium and its alloys to manufacture structural implants such as hip and knee replacement joints, which require an interface with bone, as well biocompatibility with soft tissue. These components can be manufactured with a variety of processing routes; however, forging has been one of the traditionally used, successful methods. In order to enhance a medical implant component’s properties such as fracture toughness, strength, microstructure and biocompatibility, it is of interest to understand a capability to develop forging methods which can produce a finished component such that different initial partitions of the billet occupy specific locations. As such, a 3D finite element (FE) modelling framework was established to simulate the coupled thermal and mechanical processes experienced during the forging of a workpiece containing multiple titanium-alloy material partitions, using the commercial FE software, Deform. A series of four models were simulated which contained differing arrangements of partitioning the initial billet, with different titanium alloys assigned to partitions. The forging operation was simulated with the same nominal processing parameters. The locations of these partitions within the final forging have been predicted, with varying success. One partition combination gave a very unsuccessful filling of the die, whilst the other models all filled the die correctly, and had different partitions maintained at key component locations. Thus, allowing for a manufacturing methodology to be presented which can potentially target specific component locations for specific materials to enhance component performance.

Galling Generation Mechanism in Upsetting-Ball Ironing Test

An upsetting-ball ironing test has been developed to investigate the lubricating performance of coatings in multi-stage cold forging. By using this test, the lubricating performance of a zinc phosphate free coating called “dry in-place coating” was evaluated and improved, and now the dry in-place coating is used worldwide due to its high anti-galling ability and low environmental impact. In this study, galling generation mechanism in the upsetting-ball ironing test is investigated by using the point tracking function in FEM simulation. Scratches on ironed surface are generated at the starting point of ironing and the width and depth of scratches increase gradually with the increasing ironing stroke. It is revealed that all points on a scratch have been in contact with the same point of the ball. The lubrication coating on the billet surface peels off locally with the onset of ironing and some contamination particles enter the interface between the billet and the ball and thus cause scratches. Galling takes place at the ironing stroke of around 10 mm when the billet of 14 mm in diameter and 32 mm in height is upset to 45 percent reduction in height and then ironed by the ball of 10 mm in diameter. It is found that all points on the ironed surface at the starting position of galling are not on the initial billet surface but come from the inside of the billet. These points come out at the ironing stroke of 4 mm due to the dividing flow in the surface layer. It is concluded that galling in the upsetting-ball ironing test is generated by the extremely large surface expansion.

Finite Element Simulation of Hot Forging Process for KVBM Gear

In this study, the forging operations of gear has been modeled. This gear is a part which is manufactured with the help of hot forging industry for reduce the cost. The authors propose to reduce the initial billet volume of AISI 4340 steel for the forged through process optimization using the Finite Element (FE)method. The object of this research was to predict the effect of several parameters, such as effective stress, effective plastic strain, temperature and die contact, on the forming of the gear, utilizing computer simulation and experimental results. For this purpose, Solidworks CAD and Simufact Forming FE software were used for the modeling and analysis of the forging process. The billet volume and the preform design were predefined in order to reduce scrap by using preform type C. The experimental results showed that the initial billet volume was reduced at 32 %, which compared favorably with the simulation result of a 40 % reduction. The maximum preforming force of simulation result was diferent with the experiment result at 18 along with the maximum finishing force of simulation result was different with the experiment result at 11 %. It was also found that the effective stress decreased with increasing the temperature, and the press force decreased when the initial billet volume was decreased, which resulted in a decrease of effective plastic strain as well.

Temperature Field and Extrusion Load in Needle Piercing Extrusion Process Based on Ingot Billet for Large 7075 Aluminum Alloy Tube

The change rules of the billet temperature field and extrusion load are the significant basis for the optimal design of the needle piercing extrusion process based on ingot billet for the manufacture of large-diameter thick-walled tube. Taking the needle piercing extrusion process of a 7075 aluminum alloy tube with sizes of Φ500mmx400mm/6000mm as study object, we developed a precise FE model for the process under DEFORM-2D environment, then numerically revealed the distributions and evolution rules of the billet temperature field, and obtained the effects of the extrusion speed and initial billet temperature on the billet temperature filed and extrusion load. The results show that the peak extrusion load decreases linearly with the increase of initial billet temperature but is insensitive to the extrusion speed, and that the peak temperature rises with the increase of the extrusion speed and initial billet temperature, and always locates on the surface of the initially extruded tube close to the exit of the cavity die.