J. Tomczak

Cross-Wedge Rolling of Driving Shaft from Titanium Alloy Ti6Al4V

This paper deals with the issue of the helicopter SW4 rear gear driving shaft forming. It was assumed that this shaft will be made from titanium alloy Ti6Al4V and it will be formed by means of cross-wedge rolling technology (CWR). It was also assumed that rolling will be realized in double configuration, which will guarantee axial symmetry of forming forces. The conception of tools guaranteeing the CWR process realization and numerical analysis results verifying the assumed CWR process parameters of the subject shaft were presented. Tests of shaft rolling in laboratory conditions at Lublin University of Technology were made, in the result of which the possibility of forming by means of CWR of a driving shaft, manufactured from titanium alloy Ti6Al4V, of the helicopter SW4 rear gear was verified.

AN INNOVATIVE METHOD FOR FORMING BALLS FROM SCRAP RAIL HEADS

The paper describes a new method for forming grinding media balls from scrap rail heads. This forming method involves the following operations: cutting the rail head to the desired length combined with lateral pressing of the produced workpiece; flashless die forging and sizing of balls in a helical impression. The proposed method was verified by numerical simulation which involved the modeling of a forming process for producing 80 mm diameter balls. As a result of the modeling, it was possible to examine the changes in the workpiece shape during each forming operation, the variations in loads and torques, as well as the distribution of temperatures enabling performing another forming operation, i.e. quenching. The results confirm that the designed method can be used to produce balls.

Theoretical and Experimental Research on a Method for Producing a Triangular Rosette-Shaped Flange

The paper presents a new method for forming a hollow shaft with a triangular rosette-shaped flange on its end. The part being investigated is used as a propeller shaft in helicopters. The product must be monolithic, therefore it cannot be produced by methods which consist in joining a flange with a tube. Up till now, such shafts have been produced by machining from solid barstock, the process which generates material losses exceeding 90%. The application of the proposed flanging method results in a significant reduction in both material and labour consumption, which leads to lower production costs. Due to beneficial texture of the shaft flange, shafts produced by this method exhibit better strength properties than shafts produced by machining. The paper presents the results of a numerical analysis of the flanging process, performed using DEFORM-3D software. Also, experimental tests were conducted using a three-slide forging press. Theoretical and experimental results obtained confirm the effectiveness of the new method for forming this part.

Numerical Modeling as the Method to Determine the Parameters of Tube Bending with Local Induction Heating

The numerical analysis results of bending with local induction heating of 10CrMo9-10 steel tubes have been presented in the paper. The goal of conducted simulations was to determine the process parameters that allow to obtain tube bends with geometric features which meet requirements of relevant standards. The risks of wrinkling, excessive tube bend ovalization and cracking (according to Cockroft-Latham criterion) have been analysed. The obtained results prove that numerical modeling can be used to minimize the costs of tube bending technology implementation without the need of further process parameters corrections.

GEOMETRICAL PHENOMENA IN TUBE BENDING WITH LOCAL INDUCTION HEATING

A theoretical and experimental analysis of heat induction bending for tubes used in the power industry is performed. First, the design of the heat induction bending process for tubes is described and industrial application areas for this technology are presented. Next, the main methods for tube bending with local induction heating are discussed and the effect of the technology on geometrical parameters of bends formed is presented. Then, the heat induction bending process for tubes is modeled using numerical techniques (FEM). The simulations are performed in a three-dimensional strain state, where thermal phenomena are taken into account, using the commercial software package Simufact Forming v. 11.0. In the simulations, the changes in workpiece geometry in the region of the bend being made (cross section ovalization, darkening and thickening of walls, neutral axis position) are examined. Also, potential phenomena that could limit the stability of the bending process and cause shape defects are predicted. The results of the numerical modeling are then compared to those obtained under industrial conditions.

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. Results of the numerical modelling are discussed. They clearly demonstrate that the proposed method can be used to produce balls with large diameters. Rolling experiments were performed under laboratory conditions to produce 40 mm diameter balls, i.e., in the 1:2.5 scale. The experimental findings show a good qualitative agreement with the numerical results.

FEM Modelling of a Helical Wedge Rolling Process for Axisymmetric Parts

The paper reports the results of a numerical analysis of helical-wedge rolling (HWR), a new metal forming method developed at the Lublin University of Technology. The numerical analysis was performed for three axisymmetric parts: a rotary cutter body, a stepped shaft and a ball pin. The numerical modeling was performed using the commercial simulation software Forge NxT 1.0. The paper examines changes in workpiece shape as well as variations in effective strains, temperatures, damage function, force parameters (on the rolls and guides), and torques acting on the rolls. It has been found that due to its advantages (low material losses and high efficiency), the new helical-wedge rolling process can be used as an alternative to currently employed methods for producing axisymmetric products.

Fem Simulation of the Cross-Wedge Rolling Process for a Stepped Shaft

The paper presents the results of numerical modeling of a cross-wedge rolling process for producing a stepped shaft. The modeling was performed with commercial software Forge NxT 1.1 using the finite element method. The numerical analysis enabled the determination of changes in the shape of the workpiece, effective strain, damage function and temperature distributions, as well as variations in the forces and torque acting on the tool. The numerical results demonstrate that personal computers can today be used to model even the most difficult cases of the cross-wedge rolling process, in which complex shapes of the tools and thermal phenomena occurring during the forming process have to be taken into consideration.

A Theoretical and Experimental Analysis of Rotary Compression of Hollow Forgings Formed Over a Mandrel

The paper presents selected results of studies of the process of forming hollow stepped shaft forgings by rotary compression with rotary tools. The aim of the study was to determine whether rotary compression could be performed using an additional tool – a mandrel, which, when positioned in the cavity of the workpiece, could be used to shape the surface of the cavity. A theoretical analysis was based on finite element modeling using Simufact Forming software. During the simulations, distributions of deformation intensity, temperature, and the Cockroft–Latham fracture criterion were determined. Predictions were also made regarding phenomena such as slippage and deformation of forging pieces and material cracking, as potential impediments to the investigated process. Additionally, force parameters were determined during the forming of forgings. Numerical results were verified experimentally. Rotary compression tests for hollow forgings were carried out in a special forging machine designed by the present authors. The results were validated on the basis of the geometric parameters of formed forgings and the force parameters of the process. The results confirm that hollow stepped shaft forgings can be formed in the process of rotary compression using a mandrel. Forgings formed over a mandrel are characterized by greater precision and quality compared to freely formed blanks (without a mandrel).

Comparative Analysis of Forging Rolling and Cross-Wedge Rolling of Forgings from Titanium Alloy Ti6Al4V

Theoretical-experimental results of forging rolling and cross-wedge rolling of stepped shafts forgings from titanium alloy Ti6Al4V are presented in this paper. Theoretical assumptions were based on the results of numerical simulations conducted by means of finite element method with the application of software Simufact Forming. During numerical simulations optimal parameters of the rolling processes were determined in view to possibility of obtaining forgings of assumed quality and stable process course. Experimental verification was conducted in universal forging rolling mill of own design, which allows for realization of such processes as splitting without waste, forging rolling and cross as well as cross-wedge rolling processes. During conducted research influence of the way of rolling on the obtained parts quality and the process force parameters were determined. Complex analysis of the chosen rolling parameters impact on the rolling process course and quality of finished products was made. Conducted research showed that it is possible to roll axi-symmetrical forgings of stepped shafts both in transverse and longitudinal arrangement. However, forgings rolled crosswise are characterized by larger precision than in comparison with semi-finished products in longitudinal arrangement.