Key Engineering Materials Vols. 622-623

Abstract: 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.

Abstract: Springback and limited forming limits of modern high strength steels are a big challenge in manufacturing engineering. Both aspects are crucial in sheet metal bending processes. Different modifications of the air bending process have already been developed in order to reduce springback and also to increase the forming limits of materials. A new method (the incremental stress superposition on air bending) has been developed. Studies of this new process alternative show a positive effect on the springback behavior. In order to investigate the potential of this process a comparison with other already established bending processes have been carried out. A possible process control to extend the forming limits has also been investigated.

Abstract: Scar formation in fine blanking was investigated by means of a particularly developed fine blanking tool and experimental evidence about significant the process parameters chamfer size of the blanking tools, V-Ring usage and clearance is given. Furthermore, a special purpose Finite Element code using the Arbitrary-Lagrange-Eulerian method with a process specific mesh generation is demonstrated and used for the determination of relevant parameters for prediction crack formation in 3D fine blanking simulations. The simulations shown, that a commonly used description of fracture strain as a function of stress and deformation state is not sufficient. In order to simulate scar occurrence on the blanking surface, the significant increase of fracture strain due to temperature rise because of plastic heat generation has to be taken into account. A possible way of measuring the temperature effect was shown in torsion tests at different initial temperature levels.

Abstract: Titanium alloy (Ti6Al4V) is the most widely used alloy grade of titanium in the aerospace industry because of its excellent properties. Laser beam forming is a highly flexible rapid prototyping and low-volume manufacturing process that employs laser-induced thermal distortion to shape sheet metal parts without hard tooling or external forces. The resulting formed shape and the curvature are determined by the beam power and size, scanning velocity, number of scan irradiations and the effect of cooling, all these form part of the process parameters that have to be optimised in order to achieve the desired shape and properties in formed components. Hence, a good control of the process parameters is inevitable to achieve these desired properties. Controlling a single process parameter in a process may be considered easy to manage than a system of multiple parameter process such as a laser beam forming process. This study investigates the effect of the scan velocity, laser power and cooling effect on the developed curvature with the aim of achieving good structural integrity.

Abstract: This paper proposes an experimental and numerical investigation of the quasi-static mechanical behavior of TA6V at room temperature. Different loading conditions (tension, compression, plane strain and simple shear) were applied on a 0.6 mm thick sheet in several in-plane directions. Based on the experimental results, several identifications are performed to determine the parameters involved in the CPB06 yield criterion and its extensions. The error/time computation ratio for the different identifications is next analyzed to fix the choice of the yield criterion. The latter is finally associated with an isotropic hardening law on the one side and a formulation taking into account the evolution of the yield locus on the other side in order to describe the material. The ability of the proposed formulations to predict the TA6V response is studied in the case of a deep-drawing process.

Abstract: Recently, to construct an airframe 2-layer composite materials consisting of carbon fiber reinforced plastic (CFRP) laminates and TiAl6V4 still need to be machined, whereby drill holes are frequently machined. Special attention has to be paid to the machining quality, which implies hole dimensional accuracy, defect free peripheral zone, edge quality at inlet and outlet of hole and so on. Machining defects often occur as a consequence of excessive mechanical and thermal loads, which are often caused by wrong process conditions or by the wrong choice of machining process itself. With respect to widely used state-of-the-art machine tools providing high performance and equipped with potent control unit, for the comparatively large drill hole, circular milling gains interest as an alternative to the drilling operation [1, 2]. In this research, in order to select suitable machining conditions for 2-layer composite materials consisting of CFRP laminates and TiAl6V4 a large number of circular milling tests of 6 mm diameter are executed by using a high performance vertical milling machine. Hole diameter deviation from 6 mm and inner surface roughness in relation to number of hole machined are measured and evaluated for CFRP laminates and TiAl6V4. Moreover, from observations of cutting edges in relation to number of hole machined it is confirmed that under wrong machining conditions the difference of heat conductivity between CFRP laminates and TiAl6V4 induces for chips of TiAl6V4 to be deposited on the end cutting edges of endmill used. In this case tool life shortens extremely.

Abstract: This paper presents results of numerical calculations of rolling extrusion process of a toothed shaft made from titanium alloy Ti6Al4V. FEM analysis was conducted applying the software DEFORM 3D for the process chosen technological parameters. The kinematics of metal flow in the area of the formed teeth was analyzed. Distributions of stresses, strains and temperatures during teeth forming were determined. Calculated values of axial and radial forces and moments acting on rotating roll tools allow for designing of tools for experimental verification of the designed forming process.

Abstract: Cold flowforming is a chipless forming process that deforms tubular parts by reducing theirouter diameter and thickness while increasing their length. It consists of a rotating mandrel and oneor more rollers that are translated along the tube axis, thus plastically deforming it. Flowforming ofTi-6Al-4V (also known as Ti64) is of great interest for improving the mechanical properties of thematerial, such as yield stress and fatigue strength. However this alloy is known to have poor ductilityat room temperature. Therefore, flowforming of Ti64 without failure or crack is a great challenge. Inthis present paper, the authors have attempted to predict the different failure modes occurring duringflowforming. An experimental machine has been built at the Center forMaterial Forming (CEMEF) inorder to monitor the force on the single roller, the torque on the mandrel and the actual rotation speedof the roller as well. Numerous flowforming tests have been performed using different processingparameters, such as working depth, roller feed and initial geometry, in order to investigate the criticalvalues which lead to the failure of the flowformed tube. In addition, numerical simulations of theprocess have been performed using the FORGE FEM solver. The results of the simulations have beenused to evaluate the relevance of usual failure criteria (Crockford-Latham, Rice-Tracey and Oyane).

Abstract: The paper presents selected results of a numerical investigation of the orbital forging process for producing a hollow part. This part is a jaw coupling sleeve made of titanium alloy, widely used in the agricultural industry. The FEM simulation was performed based on the following assumptions: (i) the orbital forging process is conducted under hot conditions using an industrial press of MCOF type and (ii) the final part is formed from a special hollow preform. The preform shape was selected such to ensure optimal conditions of the orbital forging process. The aim of the investigation was to identify phenomena which occur during the orbital forging process. The results obtained are thoroughly examined and described.