The Effect of Geometrical and Material Parameters on the Stress Distribution in Dies Compressed for Extrusion

The paper contains the results of stress analysis in dies pre-stressed with one ring. The tests included a die with a steel insert and a sintered carbide insert. Three die design solutions were adopted. With a constant tool diameter, three different values of the ratio of the die insert wall thickness (g_m) to the compression ring wall thickness (g_p) were introduced, and the following values of g_m/g_p = (0.57; 1 and 1.75) were adopted. The tests were carried out for three values of assembly interference equal to 0.004; 0.008; 0.016) mm. The aim of the research was to check the influence of the type of insert material and the ratio of the insert wall thickness to the thickness of the compression ring on the value of assembly and working stresses. The influence of the interference between the insert and the compression ring on the value this stresses in the die was also studied. After the research, the influence of the tested parameters on the distribution and level of circumferential stresses in the die compressed with one ring using both inserts was analyzed. The investigations showed the significant influence of all tested parameters (i.e. the size of the mounting interference, the type of die insert material and the ratio of g_m/g_p) on the level of circumferential stresses in the die both during assembly and working during extrusion. It was found that the size of the interference fit and the quotient (g_m/g_p) had the greatest impact on the reduction of the working stresses in the die insert, while the type of die insert material had the smallest effect. Moreover, it has been demonstrated that the geometric configuration of the die, expressed by the gm/gp ratio, has a very positive effect on the value of circumferential stresses in the die insert. As the value of this parameter decreases, the favourable stresses in the insert increase. In the studied range, the most favorable gm/gp ratio was 0.57.