The Application of Finite Element Method for Analysis of Cross-Wedge Rolling Processes-A Review.

The aim of this article is to review the application of the finite element method (FEM) to cross-wedge rolling (CWR) modeling. CWR is a manufacturing process which is used to produce stepped axles and shafts as well as forged parts for further processing on forging presses. Although the concept of CWR was developed 140 years ago, it was not used in industry until after World War 2.

Forming Quality Research on the Variable-Diameter Section of the Hollow Axle in Three-Roll Skew Rolling.

The hollow axle is the key component of the high-speed train, and the realization of high-quality forming is the key to ensure the safety of train operation. In this paper, the specimen of the variable-diameter section of the hollow axle is taken as the research object, and the generation mechanism of surface spiral mark defects and the formula of spiral mark depth of variable-diameter section in the TRSR (three-roll skew rolling) process with variable roll spacing are explored. The external roundness error and the function C to measure the wall thickness uniformity of the cross-section were taken as the evaluation indexes and the single-factor simulation experiment was established and simulated in the software Simufact.

A Comparative Analysis of the Physical Modelling of Two Methods of Balls Separation.

The article presents the results of model tests with which a comparative analysis of two methods of ball separation during the skew rolling process was carried out. A verification of the results obtained in the physical modelling process with the results obtained in the real process of skew ball rolling was also carried out. During the physical modelling, the effect of changing the ball separation method on the quality of the products obtained, variations in maximum torque values and maximum radial forces were analyzed.

Determination of the Critical Value of Material Damage in a Cross Wedge Rolling Test.

This study investigates the problem of material fracture in cross wedge rolling (CWR). It was found that this problem could be analysed by means of well-known phenomenological criteria of fracture that are implemented in commercial FEM (Finite Element Method) simulation programs for forming processes. The accuracy of predicting material fracture depends on the critical damage value that is determined by calibration tests in which the modelled and real stresses must be in good agreement.

Skew Rolling of Bimetallic Rods.

The present article reports selected results of a preliminary study of the process of skew rolling of bimetallic rods. The experiments were conducted using a numerically controlled three-roller skew rolling mill. During the tests, bimetallic rods were rolled from billets whose cores and outer sleeves (bushings) were made of different types of steel.

Forging of Mg-Al-Zn Magnesium Alloys on Screw Press and Forging Hammer.

Magnesium alloys are highly strain rate sensitive and exhibit good workability in a narrow forging temperature range. Consequently, parts made of these materials are usually forged with low-speed hydraulic presses, using specially designed tool heating systems in order to ensure near-isothermal conditions. This study investigates whether popular magnesium alloys such as Mg-Al-Zn can be forged in forging machines equipped with high-speed forming tools.

A Rotary Compression Process for Producing Hollow Gear Shafts.

This paper presents selected numerical and experimental results of a study investigating the process of forming hollow stepped gear shafts from tubes by rotary compression. The objective of the study was to determine whether the rotary compression process is an effective method of producing hollow stepped gear shafts and to identify limitations of this manufacturing method. A theoretical analysis involved the numerical modeling of the proposed process by the finite element method (FEM).

Statistical Research of Stainless Austenitic Steel Grain Size Distribution after Screw Rolling.

Screw rolling of austenitic stainless-steel billets was conducted in two- and three-high mills. Statistical research results showed that, compared to heated but not rolled conditions, both screw rolling techniques provided a decrease of grain size, variance, grain size distribution asymmetry, and excess in the billet cross-section at the stationary stage of screw rolling. At that stage, grain size distribution after two-high screw rolling is closer to normal in terms of asymmetry and excess values compared to grain-size distribution after three-high screw rolling.

A Comparative Analysis of Forming Railway Axles in 3- and 4-Roll Rolling Mills.

The paper presents a comparative analysis of skew rolling in 3- and 4-roll CNC rolling mills. The analysis is performed using the FEM-based commercial simulation software Simufact.Forming.

Physical Modeling of Cross Wedge Rolling Limitations.

This article presents the results of model tests aiming to verify the possibility of applying commercial plasticine as a model material for modelling the limits to the cross-wedge rolling process. This study presents a comparison of the results of laboratory testing and physical modelling of cross-wedge rolling (CWR) processes. Commercial plasticine was the model material used in the research to model 50HS grade steel formed in 1150 ˚C.

Rotational Compression of Cylindrical Specimen as a New Calibrating Test for Damage Criteria.

The subject-matter of the article is the ductile fracture of materials-A phenomenon occurring in numerous metal forming processes. In order to prognosticate the possibility of a fracture, damage criteria are employed. Their effectiveness, however, depends on the accurate determination of the critical values of damage.

Skew Rolling of Rods from Scrap Rail Heads.

This paper presents the results of theoretical and experimental investigations of a new process of rolling rods from scrap rail heads. First, the industrial applications of scrap railway rails and methods of their recycling are discussed, and then the concept of two-stage rolling of rods from heads cut off from scrap rails is proposed. In the first stage of the process, a rail head preform was rolled in a hexagonal pass of a longitudinal rolling mill.

Limits of the Process of Rotational Compression of Hollow Stepped Shafts.

This article presents the results of theoretical-experimental testing of the process of rotational compression of hollow stepped shafts. The advantages of the technology and the potential area of its application were discussed. Further on, the limits of the rotational compression technology, preventing the manufacturing of high-quality products, were presented.

Effect of the Forming Zone Length on Helical Rolling Processes for Manufacturing Steel Balls.

This paper begins with a brief overview of the methods for producing balls. It then discusses the rolling processes for producing balls in helical passes. Next, a method for designing tools for helical rolling (HR) is described.

A Comparative Study of Helical and Cross-Wedge Rolling Processes for Producing Ball Studs.

This paper presents two rolling technologies: cross-wedge rolling (CWR) and helical-wedge rolling (HWR). The two rolling processes were compared using the example of rolling a ball stud forging. The technologies were modeled in the finite element model (FEM) environment.

Prediction of Crack Formation for Cross Wedge Rolling of Harrow Tooth Preform.

The article presents the issue of material fracture during the process of cross-wedge rolling (CWR). The object of the research was the process of forming a harrow tooth preform. In the conducted analysis nine damage criteria were applied.

Critical Damage Values of R200 and 100Cr6 Steels Obtained by Hot Tensile Testing.

The paper proposes a new method for determining critical damage values in hot forming processes. The method first involves performing tensile tests of axisymmetric samples and then simulating these tests numerically. Simulations are performed by the finite element method in a three-dimensional state of strain, including thermal phenomena occurring in the forming zone.

The Effect of Process Parameters in Helical Rolling of Balls on the Quality of Products and the Forming Process.

This paper presents selected numerical and experimental results of a skew rolling process for producing balls using helical tools. The study investigates the effect of the billet's initial temperature on the quality of produced balls and the rolling process itself. In addition, the effect of billet diameter on the quality of produced balls is investigated.

An Innovative Method for Forming Balls by Cross Rolling.

The paper describes an innovative cross rolling method that enables the production of six balls at the same time, each ball with a diameter of 100 mm. The principle of the proposed rolling technique is discussed and the tools used in this forming process are described. Two variations of the proposed method for producing balls were investigated, one performed with the use of flat tools and the other with the use of two rolls.