The fracture of a wheel tire which had brought about the accident of Eschede clearly was caused by a fatigue crack at a relatively low mean stress level. The final fracture only occurred after the remaining cross-section had dropped to about 20%. The material corresponded to all specifications; no traces or pre-existing flaws which could have initiated a fatigue crack could be detected. Service loads had never been determined for this type of wheel, train and track. Before the wheel was commissioned there were performed strain measurements on a prototype of the wheel, fatigue tests on complete wheels and extended service tests on rail tracks. This procedure corresponded to the UIC-recommendations in force at that time. Seen from todays view-point facilities for design would be better. For this type of rubber-sprung wheel no individual UIC-guideline existed. After the accident fatigue tests have been carried out on whole wheels and on segments of tires which gave as result that a fatigue load of nearly four times the nominal wheel load would have been necessary to produce a fatigue crack without pre-existing flaw, which is practically impossible because the tire comes into contact with the wheel disc already at wheel loads of 2-2.5-times the nominal wheel load. When the segments were tested, a fatigue crack could be produced only with an initial flaw at least nearly 1 mm deep and a load 2.5-times the nominal load, without notch only at about 7 times the nominal load. Since no pre-existing flaw at all had been found at the crack origin, the fatigue crack must have started from other reasons.
The railway accident of Eschede - technical background
Engineering Failure Analysis ; 11 , 4 ; 515-535
2004
21 Seiten, 26 Bilder, 12 Tabellen, 9 Quellen
Article (Journal)
English
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