The Analysis of Deformability, Structure and Properties of AZ61 Cast Magnesium Alloy in a New Hammer Forging Process for Aircraft Mounts

This article presents the analysis of the deformability, structure and properties of the AZ61 cast magnesium alloy on the example of a new forging process of aircraft mount forgings. It was assumed that their production process would be based on drop forging on a die hammer. Two geometries of preforms, differing in forging degree, were used as the billet for the forging process. It was assumed that using a cast, unformed preform positively affects the deformability of hard-deformable magnesium alloys and flow kinematics during their forging and reduces the number of operations necessary to obtain the correct product. Numerical analysis of the proposed new technology was carried out using DEFORM 3D v.11, a commercial program dedicated to analyzing metal forming processes. The simulations were performed in the conditions of spatial strain, considering the full thermomechanical analysis. The obtained results of numerical tests confirmed the possibility of forming the forgings of aviation mounts from the AZ61 cast magnesium alloy with the proposed technology. They also allowed us to obtain information about the kinematics of the material flow during forming and process parameters, such as strain intensity distribution, temperatures, Cockcroft–Latham criterion and forming energy. The proposed forging process on a die hammer was verified in industrial conditions. The manufactured forgings of aircraft mounts made of AZ61 magnesium alloy were subjected to qualitative tests in terms of their structure, conductivity and mechanical properties.

Identification of the Cause of the Stem Neck Fracture in the Hip Joint Endoprosthesis

Endoprosthesis stem fractures are among the rarest complications that occur after hip joint arthroplasty. The aim of this paper is to evaluate the causes of the fractures of the Aura II stem neck, which is an element of an endoprosthesis implanted in a patient. In order to achieve it, a radiogram was evaluated, the FEM analysis was carried out for the hip joint replaced using the Aura II prosthesis and scanning tests as well as a chemical analysis were performed for the focus of fatigue. The tests performed indicate that the most probable causes leading to the fatigue fracture of the Aura II stem under examination were material defects in the process of casting and forging (forging the material with delamination and the presence of brittle oxides and carbides) that resulted in a significant reduction of strength and resistance to corrosion. In the light of an unprecedented stem neck fracture, this information should be an indication for non-destructive tests of ready-made stems aiming to discover the material and technological defects that may arise in the process of casting and drop forging.

The Rationalization of Production of Ring-Shaped Drop Forgings Using Computer Simulation of Closed-Die Forging Process

The rationalization of ring-shaped drop forgings production may be considered from different points of view. Important aspects of evaluation and selection of optimal production alternative are material and energy savings and issue of forging tool life. This contribution describes advanced technology of closed die forging without flash, which represents an effective method of manufacture of ring-shaped drop forging from steel alloy type 16MnCr5. This proposed method offers a cheaper possibility of production of mentioned forging piece resulting from saving of batch material. At present drop forgings with this shape are produced by an uneffective method, i.e. die forging with flash, which brings a considerable material loss. Simulation software determined for simulation of bulk forming processes have an important position at development of new advanced technologies of drop forgings production. A simulation program MSC.SuperForge described in this contribution was used in order to verify correct plastic flow of material in closed die cavity.