The assessment of the influence of the work-hardening of material on the optimum die profile and drawing force in rod drawing process is the main objective of the present paper. The upper bound solution, based on the assumption of perfect plasticity, has been extended to consider the work-hardening of the material during the rod drawing process through curved dies. Analytical results of drawing forces for rod drawing process through four different types of streamlined die profiles are compared with the finite element simulation data using the finite element code, DEFORM 2D. It is shown that as the work-hardening exponent increases, the optimum die length increases, the required drawing force decreases and maximum possible reduction in area increases. Based on this proposed modeling technique, drawing process of real materials through various curved dies can be optimized. Manuscript profile

Plane strain upsetting of round cross-section billets between the flat and V-shaped dies has been studied in this paper. A deformation model has been proposed and the geometry of the deformed billet cross-section is determined for a given displacement of the top flat die. To analyze the process, the slab method of analysis has been applied and for a given process conditions, the required forming load has been estimated. The process under consideration has been performed also with the finite-element method to predict the forming load and the material flow. The calculated forming load and the deformed billet cross-section geometry compare well with the FE simulations data. The effects of friction factor and the angle of the V-shaped bottom die on the forming load have been investigated. The theoretical results have been indicated that as the bottom die angle decreases the forming load decreases and the forming load is not influenced by friction in case of small bottom die angles. Manuscript profile

In this paper, an upper bound approach is used to analyze the tube extrusion process through rotating conical dies with large mandrel radius. The material under deformation in the die and inside the container is divided to four deformation zones. A velocity field for each deformation zone is developed to evaluate the internal powers and the powers dissipated on all frictional and velocity discontinuity surfaces. By minimization of the total power with respect to the slippage parameter between tube and the die and equating it with the required external power, the extrusion pressure is determined. The corresponding results for rotating conical dies are also determined by using the finite element code, ABAQUS. The analytical results show a good coincidence with the results by the finite element method with a slight overestimation. Finally, the effects of various process parameters such as mandrel radius, friction factor, etc., upon the relative extrusion pressure are studied. Manuscript profile

In this paper, a generalized expression for the flow field in axisymmetric extrusion process is suggested to be valid for any dies and the boundary shapes of the plastic deformation zone. The general power terms are derived and the extrusion force is calculated by applying upper bound technique for a streamlined die shape and exponential functions for shear boundaries. It is shown that assuming exponential boundaries for deformation zone yields a die shape with smaller extrusion force than that of by assuming spherical shape boundaries is in agreement with the results obtained by the finite element method. Manuscript profile

In this research, flat rolling process of bonded sandwich sheets is investigated by the method of upper bound. A kinematically admissible velocity field is developed for a single layer sheet and is extended into the rolling of the symmetrical sandwich sheets. The internal, shear and frictional power terms are derived and they are used in the upper bound model. Through the analysis, the rolling torque, the roll separating force and the thickness of each layer at the exit of deformation are determined. The validity of the proposed analytical method is discussed by comparing the theoretical predictions with the experimental data found in the literature and by the finite element method. It is shown that the accuracy of the newly developed analytical model is good. Manuscript profile

Metal tubes are widely used in various forms in engineering structures. Local deformation of the tube is required due to design considerations or the tube's location in the machine or structure to facilitate its installation. This paper investigates the process of locally laterally compressing aluminum tubes using experimental and numerical simulation methods. The tube is positioned horizontally on the fixed lower die and is subjected to compressive load by the upper die, which is connected to the movable ram of the press machine, resulting in plastic deformation. Both upper and lower dies are semi-cylindrical with equal radii, and their axes are perpendicular to the tube's axis. For the experimental and numerical analysis, two types of aluminum 6061-T6 tubes with the same outer diameter but different inner diameters were chosen, and three similar samples were created for each type. The true stress behavior, based on the true strain of the aluminum material, was determined from a simple tensile test. Subsequently, the geometric dimensions of the deformed area of the tubes were measured for various press strokes. The geometric shape of the deformation zone and the experimental forming load data were compared with the simulation results obtained using ABAQUS software. A comparison between the results from the two experimental and simulation methods demonstrated good agreement. Manuscript profile

این مقاله به تحلیل کرانه‌ی بالایی فرآیند اکستروژن مستقیم توخالی می‌پردازد. در این تحلیل که مرز تشکیل ناحیه‌ی فلز مرده به‌صورت منحنی سینوسی تخمین زده شده، ناحیه تغییرشکل به سه ناحیه‌ی تغییرشکل کوچک‌تر تقسیم شده است. با ارائه‌ی یک میدان سرعت جدید در دستگاه مختصات کروی، مقادیر نرخ کرنش‌ها در هر ناحیه‌ی تغییرشکل محاسبه شده‌اند. پس ار آن توان داخلی، توان برشی و توان اصطکاکی ماده به‌دست آمده‌اند. با بهینه‌سازی توان کل خارجی لازم نسبت به طول ناحیه‌ی فلز مرده، فشار نسبی اکستروژن محاسبه شده است. نتایج تحلیل با نتایج تحلیلی و آزمایش‌های انجام شده توسط سایر محققان مقایسه و نشان داده شده که نتایج تحلیل با نتایج آزمایش انطباق مناسبی دارند. در انتها نیز اثر کاهش سطح مقطع، شعاع سنبه و ضریب اصطکاک بر طول ناحیه‌ی فلز مرده بررسی شده‌اند. Manuscript profile