Analysis and Technology in Metal Forming

1989 ◽  
Author(s):  
Shiro Kobayashi ◽  
Soo-Ik Oh ◽  
Taylan Altan
Keyword(s):  
Heat Transfer ◽  
Plastic Deformation ◽  
Flow Stress ◽  
Velocity Field ◽  
Metal Forming ◽  
Metal Flow ◽  
Die Design ◽  
Flow Forming ◽  
Part Geometry ◽  
Formed Part

The design, control, and optimization of forming processes require (1) analytical knowledge regarding metal flow, stresses, and heat transfer, as well as (2) technological information related to lubrication, heating and cooling techniques, material handling, die design and manufacture, and forming equipment. The purpose of using analysis in metal forming is to investigate the mechanics of plastic deformation processes, with the following major objectives. • Establishing the kinematic relationships (shape, velocities, strain-rates, and strains) between the undeformed part (billet, blank, or preform) and the deformed part (product); i.e., predicting metal flow during the forming operation. This objective includes the prediction of temperatures and heat transfer, since these variables greatly influence local metal-flow conditions. • Establishing the limits of formability or producibility; i.e., determining whether it is possible to perform the forming operation without causing any surface or internal defects (cracks or folds) in the deforming material. • Predicting the stresses, the forces, and the energy necessary to carry out the forming operation. This information is necessary for tool design and for selecting the appropriate equipment, with adequate force and energy capabilities, to perform the forming operation. Thus, the mechanics of deformation provides the means for determining how the metal flows, how the desired geometry can be obtained by plastic deformation, and what the expected mechanical properties of the produced part are. For understanding the variables of a metal-forming process, it is best to consider the process as a system, as illustrated in Fig. 2.1 in Chap. 2. The interaction of most significant variables in metal forming are shown, in a simplified manner, in Fig. 3.1. It is seen that for a given billet or blank material and part geometry, the speed of deformation influences strain-rate and flow stress. Deformation speed, part geometry, and die temperature influence the temperature distribution in the formed part. Finally, flow stress, friction, and part geometry determine metal flow, forming load, and forming energy. In steady-state flow (kinematically), the velocity field remains unchanged, as is the case in the extrusion process; in nonsteadystate flow, the velocity field changes continuously with time, as is the case in upset forging.

Theoretical Justification of the Longitudinal Rolling Method of the Thick Sheets by the Severe Shear Deformation

2020 ◽  
Vol 299 ◽  
pp. 617-621
Author(s):  
Danis Nukhov ◽  
Andrey O. Tolkushkin
Keyword(s):  
Plastic Deformation ◽  
Grain Size ◽  
Metal Forming ◽  
Large Strain ◽  
Metal Flow ◽  
Coarse Grained ◽  
Theoretical Justification ◽  
Longitudinal Rolling ◽  
Steel Sheets ◽  
Rolling Method

Severe plastic deformation (SPD) methods are based on obtaining materials with a grain size of about 100 nm by means of large strain. The SPD processes provide conditions for non-monotonic deformation of the billetsб due to the redistribution of metal macro-flows during shear or alternating strain. Numerous studies have proved the possibility of obtaining high total strain degree for a single SPD cycle. Traditional metal forming processes, such as rolling, implement monotonic deformation behaviorб due to one directional metal flow. In the process of longitudinal rolling, a banded coarse-grained structure with uneven distribution of properties in the volume of the processed metal is observed. The idea of ensuring the SPD in the process of longitudinal rolling of steel sheets is promising. The idea can be realized by the development of deformation tools and modes, which provide redistribution of metal macro-flows not only in the longitudinal but also in the transverse directions of the deformation zone.

Development of Advanced Technologies for the Production of Innovative Materials with a Submicrocrystalline Structure by Methods of Severe Plastic Deformation

2021 ◽  
Vol 410 ◽  
pp. 191-196
Author(s):  
Danis Sh. Nukhov ◽  
Andrey O. Tolkushkin
Keyword(s):  
Plastic Deformation ◽  
Metal Forming ◽  
Metal Flow ◽  
Continuous Rolling ◽  
Axial Zone ◽  
Entire Cross Section ◽  
Product Size ◽  
Advanced Technologies ◽  
Innovative Materials ◽  
Rolling Method

A promising direction for the development of steel and alloy processing processes is the intensification of plastic deformation by creating zones of localization of shear strains not only in the longitudinal but also in the transverse directions of the deformed metal flow. Intensification of alternating deformations along the entire cross-section and, especially, in the axial zone of the billet by creating new deformation schemes is an effective way to increase the physical, mechanical and functional properties of the metal with the maximum approximation of the finished product size to the original billet size. The paper shows that a promising idea is the development of new technological schemes that implement severe alternating deformation in existing metal forming processes. A continuous rolling method of wide strips is proposed, which provides severe alternating deformation with minor changes in the size of the billet. Based on this method, a scheme of continuous rolling of the strip with the intensification of plastic deformation of the metal is designed. The results of computer simulation showed that the new rolling method increases the strain uniformity in height and the value of the strain degree in the plane of symmetry of the billet.

Incremental Formulation for the Prediction of Flow Stress and Microstructural Change in Hot Forming

1998 ◽  
Vol 120 (2) ◽  
pp. 316-322 ◽  
Author(s):  
J. Yanagimoto ◽  
K. Karhausen ◽  
A. J. Brand ◽  
R. Kopp
Keyword(s):  
Plastic Deformation ◽  
Flow Stress ◽  
Metal Forming ◽  
Mathematical Formulation ◽  
Microstructural Change ◽  
Hot Forming ◽  
Wide Range ◽  
Theoretical Predictions ◽  
Incremental Formulation ◽  
Formed Product

In metal forming, the workpieces are formed to the desired shapes or profiles. Especially in hot forming, the microstructure of workpiece changes during plastic deformation. Modern forming technologies allow to control the shape and the microstructure of formed product in a wide range and will gain increasing importance in future in the field of metal forming. In order to develop this forming technology which may be called “macroscopic microscopic materials processing”, theoretical predictions of plastic deformation as well as microstructural changes are indispensable. A new mathematical formulation to predict flow stress and microstructural change in hot forming will be presented in this paper. This model is based on an incremental formulation taking the dislocation density as a representative variable.

Influence of Flow Stress and Friction Upon Metal Flow in Upset Forging of Rings and Cylinders

1972 ◽  
Vol 94 (3) ◽  
pp. 775-782 ◽  
Author(s):  
C. H. Lee ◽  
T. Altan
Keyword(s):  
Flow Stress ◽  
Velocity Field ◽  
Strain Rate ◽  
Calibration Curve ◽  
Upper Bound ◽  
Metal Flow ◽  
Computer Programs ◽  
Ring Test ◽  
Stress Distributions ◽  
Upset Forging

An upper-bound velocity field that considers bulging has been applied to cylinder and ring upsetting. Computer programs have been developed to (a) determine strain, strain rate, velocity, and flow-stress distributions, and (b) predict load and bulge profile at various reductions by simulating the upsetting process. The calibration curve for a 6:3:2 ring, the load-displacement curves for ring and cylinder upsetting, and flow stress from the ring test have been predicted. The experimental results, with annealed 1100 Aluminum samples, agree well with theory at the lower and practical range of friction, but they show some disagreement at high friction.

Thermo-Viscoplastic Analysis

1989 ◽  
Author(s):  
Shiro Kobayashi ◽  
Soo-Ik Oh ◽  
Taylan Altan
Keyword(s):  
Heat Transfer ◽  
Plastic Deformation ◽  
Heat Generation ◽  
Metal Forming ◽  
Elevated Temperatures ◽  
Rate Sensitivity ◽  
Forming Process ◽  
Time Step ◽  
Plastic Materials ◽  
Metal Forming Process

The main concern here is the analysis of plastic deformation processes in the warm and hot forming regimes. When deformation takes place at high temperatures, material properties can vary considerably with temperature. Heat is generated during a metal-forming process, and if dies are at a considerably lower temperature than the workpiece, the heat loss by conduction to the dies and by radiation and convection to the environment can result in severe temperature gradients within the workpiece. Thus, the consideration of temperature effects in the analysis of metal-forming problems is very important. Furthermore, at elevated temperatures, plastic deformation can induce phase transformations and alterations in grain structures that, in turn, can modify the flow stress of the workpiece material as well as other mechanical properties. Since materials at elevated temperatures are usually rate-sensitive, a complete analysis of hot forming requires two considerations—the effect of the rate-sensitivity of materials and the coupling of the metal flow and heat transfer analyses. A material behavior that exhibits rate sensitivity is called viscoplastic. A theory that deals with viscoplasticity was described in Chap. 4. It was shown that the governing equations for deformation of viscoplastic materials are formally identical to those of plastic materials, except that the effective stress is a function of strain, strain-rate, and temperature. The application of the finite-element method to the analysis of metal-forming processes using rigid-plastic materials leads to a simple extension of the method to rigid-viscoplastic materials. The importance of temperature calculations during a metal-forming process has been recognized for a long time. Until recently, the majority of the work had been based on procedures that uncouple the problem of heat transfer from the metal deformation problem. Several researchers have used the following approach. They determined the flow velocity fields in the problem either experimentally or by calculations, and they then used these fields to calculate heat generation. Examples of this approach are the works of Johnson and Kudo on extrusion, and of Tay et al. on machining. Another approach uses Bishop’s numerical method in which heat generation and transportation are considered to occur instantaneously for each time-step with conduction taking place during the time-step.

Forming Limit Analysis of Molybdenum Reinforced Carbon Steels

2018 ◽  
Vol 777 ◽  
pp. 306-310 ◽  
Author(s):  
Ananthanarayanan Rajeshkannan ◽  
Sumesh Narayan
Keyword(s):  
Plastic Deformation ◽  
Free Surface ◽  
Powder Metallurgy ◽  
Ductile Fracture ◽  
Limit Analysis ◽  
Metal Forming ◽  
Carbon Steels ◽  
Die Design ◽  
Cold Forging ◽  
Forming Limit

The occurrence of ductile fracture during the plastic deformation of powder metallurgy materials is adverse and damaging and the prediction of fracture is very important in the early stages as early modifications will prevent failure. This will tend to save a lot of money and forming limit studies in many metal forming processes is up most important. Forming limit analysis on the cold forged molybdenum reinforced carbon steels were carried out in this work. In this study two key strain hardening parameters are used to study the formability characteristics. This analysis is effectively used for design of powder metallurgy parts and most importantly the die design as repressing needs to be employed before pores appear as cracks on the free surface. The cold forging was carried out on Fe-0.8%C, Fe-0.8%C-1%Mo, Fe-0.8%C-1.5%Mo and Fe-0.8%C-2.0%Mo and the formability behavior of the same is presented.

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