The evolution of stress-strain state and the distribution of temperature and relative density throughout a porous workpiece subjected to hot extrusion forging to produce axisymmetric parts with an ...axial hole was studied by computer simulation. The hot forging process was modeled using the finite element method employing the DEFORM 2D/3D software package. Analysis of the simulation results showed that the region of strains, stresses, and relative densities formed under the conical protrusions of the punches in the initial stages of the process, and these parameters decreased radially from the center of the workpiece to its periphery. As the axial strain increased with further deformation, the region of elevated stresses and densities extended deeper into the material, spreading from the center of the workpiece to its periphery. In the final stage, after the die cavity was filled with the forged material, the relative densities and stress intensities averaged over the workpiece, while the strain intensity noticeably decreased in the radial direction from the center to the periphery following additional compaction. This was explained by the deformation that occurred in the final stage when the forged material filled the pore volume in the additional compaction process after the die cavity was filled. The forging force increased sharply when the die cavity was filled fully and the material underwent additional compaction but increased monotonically in the initial stages of the process.
Stainless steel is an excellent material that has properties such as heat and corrosion resistance. Thus, stainless steel is used as a material in steam turbine blades. Steam turbine blades are ...mainly manufactured using two methods. One is the cutting of unforged metal ingots. Another is the cutting of forged parts. Small blades are made by cutting metal ingots. Large blades are made by cutting forged parts. The mechanical characteristics of a metal ingot and a forged part, such as hardness and toughness, are almost the same. There were not researches related to a relationship between “an unforged ingot and a forged part of stainless steel” and “the differences of the tool wear and the finished surface by high-speed milling”.In this study, the high-speed milling of stainless steel was attempted for high-efficiency cutting of a steam turbine blade. The differences of the tool wear and the finished surface in the cuttings of an unforged ingot and a forged part were investigated. In the experiment, the cutting tool was a TiAlN coating radius solid end mill made of cemented carbide. The diameter of the end mill was 5 mm, and the corner radius was 0.2 mm. The cutting speed were 100 m/min-600 m/min. The workpieces used were a metal ingot and a forged part of stainless steel. In the results, it was found that the differences of the tool wear and the finished surface in the cuttings of an unforged ingot and a forged part. In the case of the unforged ingot, the flank wear became large with increasing cutting speed. On the other hand, in the case of forged part, the flank wear rapidly increased at a cutting speed of 100 m/min. In addition, the flank wear became smaller than the cutting speed 100 m/min at the cutting speed 200 m/min. Further, the flank wear became large with increasing cutting speed at cutting speeds higher than 200 m/min. That is, the flank wear was at a minimum at a cutting speed of 200 m/min. Although it could not be confirmed the characteristic of high speed milling at an unforged ingot, it has been identified at a forged part.
The article showed procedure of forging technological flow design modification of real component “fork”, with using of computer simulation. By using of the primary technological process at production ...was produced failure forgings, checking simulation showed incorrect material flow in filling of die cavity, and therefore it was needed to raw part design modifications. These modifications were suggested on base results obtained from simulation, the results were abolition of defects, resolution of problem and correctness verification of final forging technological flow.
The work’s purpose is to increase the forging ingot’s quality. A crystallization mechanism of shortened ingots has been investigated. The shortened ingots allow changing a direction of the metal ...solidification. The rational geometry of the ingot (a ratio of height to diameter and a value of taper) needs to be determined. The special technique of the theoretical and experimental investigations has been developed. The theoretical investigations have been carried out by finite element method. An adequacy test of the theoretical results has been carried out by experimental investigations on transparent and metallic models (pure aluminum) of the ingots. The macrostructure investigations of the shortened ingots with directional solidification have been produced. A hardness distribution on the longitudinal section has been investigated. It was found that for the ingot with the ratio of
H
/
D
= 1.1 the most part of the ingot’s body (60–70%) has a dense, homogeneous and small-grained structure. The small grain, which provides a dense structure, forms at the bottom and in the corners from the bottom side. The distribution of the grain dimensions along the ingot radius at different height levels allows to conclude that the bottom and middle parts along the height have the same small-grained structure. The high and uniform hardness values are characteristic for the ingot with
H
/
D
= 1.1. The middle and hot-top layers of the ingot have commensurate hardness, which have a difference from the bottom part maximum on the 5%. The ingot with the reverse taper of 7% allows to make a most dense and homogeneous structure. Thus, the improvement in the large forged quality ingots is possible by providing the directional solidification and reverse taper.
Large and thick-walled aluminium forgings exhibit shape distortions induced by residual stresses. To restore the nominal geometry, a series of highly manual and time-consuming reshaping operations ...need to be carried out. In this paper, we are concerned with the development of efficient computer simulation tools to assist operators in bending straightening, which is one of the most common reshaping operations. Our approach is based on the computation of reshaping diagrams, a tool that allows selecting a nearly optimal bending load to be applied in order to minimize distortion. Most importantly, we show that the reshaping diagram needs not to account for the residual stress field, as its only effect is to shift of the reshaping diagram by some offset. That is, the overall behaviour including a realistic 3D residual stress field in a forged part can be retrieved by shifting the
residual stress free
reshaping diagram by the appropriate offset. Finally, we propose a strategy in order to identify the offset on-the-fly during the reshaping operation using simple force-displacement measures.
The purpose of this work is a study of strain distribution in a workpiece body during billet profiling with convex wedge dies with different angles and degrees of reduction followed by a drawing ...operation with flat and cut dies. This development of a new forging process was focused on an increase in quality of large forged parts. A conceptual design of this process for working of large workpieces without an upsetting operation has been proposed. The proposed process leads to the accumulation of a high level of strain in the workpiece without significant reduction of the cross-sectional area. It has been found that an increase in convex dies angle and an increase in deformation depth lead to a linear growth of strain in the forging’s body. It was shown that the following drawing of the profiled workpiece with a concave cross-section by flat dies causes a decrease in deformation force by 2–3 times in comparison with drawing by cut dies. An optimal die shape for the achievement of a uniform strain distribution has been established. It was found that the die wedge angle must be in the range of 150°–165°. The necessary parameters for deformation without upsetting operation have been determined. The degree of billet reduction by the convex dies must be in the range of 20–30%. The drawing after profiling must be carried out with flat dies. The orientation of the workpiece in the flat dies must be “edgewise”. The strain state in the workpiece body has been investigated using FEM and a combined theoretical/experimental method of coordinate gridlines. The prime novelty and originality of the present research are the establishment of an optimal convex die geometry for profiling and die configuration for the follow-on drawing process, as well as the determination of the mechanical deformation required for obtaining a uniform strain distribution in the forged workpiece. A forging process for pressure working of large workpieces by convex wedge dies without using upsetting has been introduced. This novel forging process results in an increase in productivity of 17–25%. The heat energy loss was decreased from 6 to 4. The derived results have confirmed the feasibility of eliminating the upsetting process previously required. The forging process time has been decreased by 20%. Energy consumption required for deformation was reduced by 15%. Practical recommendations, derived from the present investigation, have been implemented at the Public Joint Stock Company “Novokramatorsky Mashinostroitelny Zavod”.
New steel grades for forged components are designed to meet the requirements of the automotive industry in order to obtain excellent strength and toughness behavior as well as a high endurance limit. ...Beside precipitation hardened ferritic-pearlitic steels, bainitic steels have gained more and more importance. Basic considerations on the alloy design (C-, Si-, Cr-; B-content) are done using JMatPro-Calculations and by some experimental trials. Using the thermomechanical testing system Gleeble 3800, various cooling strategies have been applied and the kinetics of the bainite formation has been measured at different holding temperatures and times. A detailed microstructural characterization has been done with relation to the mechanical properties. The isothermal tests are compared to continuous cooling situations. Finally, forging trials are performed to find out the most suitable and robust production schedule to be used in practice. The actual findings support the increasing use of bainitic steels for forged parts, especially regarding material saving, independence of cross section and good fatigue performance.
This work concerns knowledge integration from manufacturing activities in design in order to make full use of the advantages provided by “net-shape” forging processes, by setting up tools and using ...specific competencies. The main objectives are improvements in product quality, together with a time reduction required for the design and manufacturing cycle. The specific aspects of this work are to be found in the identification of the pertinent data, information, and knowledge in a context of redesigning industrial products in relation to evolutions in the manufacturing processes. The approach described here is based on analysis of the stages in the product life cycle. This approach is illustrated by the example of forged pinions used in automotive vehicle differentials, and it shows the improvements obtained mainly through design activities. A feature approach is mentioned in perspective in order to make it easier to formalize and capitalize on pertinent information through its integration in a product data management (PDM) system.
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