On the Fatigue Strength of Large Size Roller Chains for Power Transmission

Fatigue test results on the large size roller chains for power transmission (Tsubakimoto RS 0206) was reported in this paper. The test results were discussed on the fatigue strength of large size roller chains and compared with those obtained on the small size roller chains reported in the provious issue. For fatigue testing two kinds of Losenhausen oil pressure type fatigue testing machines were used, that is, UHS type (capacity, static load 35ton, dynamic load 20ton) and UHP type (capacity, static load 20ton, dynamic load 10ton). The former was used for repeated load over 10ton, and the latter for under 9ton. Also fatigue tests on steel plates for chain links were carried out by Haighs fatigue testing machine (capacity 1.5ton) for comparison's sake. The driving speed of the testing machines was 800cycle/min at Losenhausen machine and 1800cycle/min at Haigh machine. The results obtained are as follows: 1. The critical part of the chains applied to tests was the cross section of roller links perpendicular to longitudinal direction, where bushes were press-fitted. 2. The endurance ratio of the large size roller chains is about 1/4. This value is larger than that for small size roller chains which was about 1/7, as previously reported. The reason is considered to be due to the fact that the endurance ratio of roller link plate materials for large size roller chains was larger than that for smaller ones. 3. The effective stress concentration factor for the large size roller chain was 3.4 at 107, and 2.2 at 105. 4. Eliminating the effect of fitting pressure, the value of the effective stress concentration factor was calculated to be 4.8 at 107, which is nearly equal to the value of the stress concentration factor for the eye end plate loaded by a pin with clearance.