T. Bulzak

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.

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 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.

A Rotary Compression Process for Producing Titanium Alloy Ti6Al4V Shafts

The paper reports selected results of the research on a rotary compression method for producing a hollow driving shaft used in a helicopter’s rear gear. The tests were performed on two types of material: steel grade 42CrMo4 (Polish Standard: 40 HM) and titanium alloy Ti6Al4V. The first part of the research involved performing a numerical analysis by the finite element method to determine an optimal range of parameters of the rotary compression process. The numerical results were then verified in experimental tests using a machine designed by the authors of this paper. The preliminary experimental results confirm that hollow parts made of steel and titanium alloys can be formed by rotary compression. The results also offer prospects for further research on this problem.

NUMERICAL MODELING OF SKEW ROLLING PROCESS OF TWIST DRILLS

This paper presents the results of numerical modeling of skew rolling process of twist drills in four-segments configuration. On the basis of the conducted numerical simulation the results were obtained in a form of distributions: stress intensity, strain intensity, temperature and damage. The energetic parameters of the process were also given on the example of a drill Ø10 mm from high-speed steel HS6-5-2. The conducted numerical simulation confirmed the usefulness of the graphic method based on envelope theory in tools designing for skew rolling of twist drills.

Theoretical and experimental analysis of rotary compression of ball pins hollow forgings

This paper presents the chosen results of ball pins hollow forgings forming by means of rotary compression. Theoretical research was based on numerical simulations, conducted using finite element method. The software Simufact was applied for calculations needs. During simulations, kinematics of material flow, strain intensity distribution, damage criterion according to Cockroft-Latham and temperature distributions were determined. Force parameters in the process were also determined and limiting phenomena were identified. Results from FEM modeling were verified in laboratory conditions. Ball pins hollow forgings forming tests were performed in a special forge aggregate. The obtained results fully confirmed the possibility of ball pins hollow forgings manufacturing by means of rotary compression.

Innovative Metal Forming Techniques Developed at the Lublin University of Technology

This study presents innovative metal forming techniques that have been developed at the Lublin University of Technology in Lublin, Poland, including rotary compression, cross wedge rolling and roll forging. Dozens of Polish patents and several European patents have been granted for inventions based on the use of the above forming techniques. This study gives an overview of applications of these innovative techniques for producing stepped axes and shafts (including hollow and gear shafts) that are made of steel and light metal alloys (aluminium, titanium). It also presents prototype machines for forming metals and metal alloys.