Tahir Altinbalik

Effect of die inlet geometry on extrusion of clover sections through curved dies: Upper bound analysis and experimental verification

The effect of die inlet and transition geometry on the extrusion loads and material flow for extrusion of clover sections were investigated and presented both theoretically and experimentally. For this purpose, four different die geometries including straight tapered and cosine transition profile and each of them having round and clover inlet geometries were chosen. In the experimental study, commercially pure lead was used because of its hot forming characteristic at room temperature. A newly kinematical admissible velocity field to analyze different profiles of extrusion dies of clover section from round bars was proposed by upper bound analysis. It is clear that the extrusion loads obtained from the theoretical analysis for various die inlet-die transition geometry combinations are in good agreement with the experimental results. Axis deviations of the parts which define the dimensional quality of the products were also investigated.

Redesigning and Manufacturing of a Land Levelling Shovel by Assembly Structural Stress Analysis

The aim was to redesign and manufacture of a shovel for a pull-type land levelling machine, which, in its present condition, is used to get easily damaged even under low loads. Firstly, the maximum pulling load affecting the levelling shovel was experimentally determined. Then, stable-shovel system with the bolt connection was replaced with a bearing-shaft connection system. In this way, the new shovel has gained a capability of making oscillation motion so that it can operate on sloped grounds. CATIA program was used in the design studies. The shovel system was investigated by assembly structural stress analyses. This new construction enabled the system to operate 3 times more securely at maximum stress conditions without changing the levelling shovel material. Thus, it is managed to prevent any possible damages that might occur due to maximum loading conditions of the system. Besides, displacements that occur on the shovel decreased at the rate of 90%.