’Weld unzipping has been mastered.’ Dennis Schut of the European Commission’s Directorate-General for Research made this bold assertion on September 7 at a conference on the crashworthiness of aluminium rail vehicles held at the UK’s National Railway Museum in York.
Noting that ’even now we are learning from analysing what remains of the wreckage’ of the head-on collision at Ladbroke Grove between a three-car aluminium-bodied Class 165 and an HST on October 5 1999, Schut sketched out the research work that has taken place in the intervening six years. Much of this has been carried out in response to Recommendation 57 of Lord Cullen’s inquiry into the accident. This called for investigation into alternatives to fusion welding, the use of grades of aluminium that are less susceptible to fusion weld weakening and further development of analytical techniques to increase confidence in the crashworthiness of bodyshell structures.
The Class 165 bodyshells have yielded a wealth of information to researchers, helping them formulate programmes of work that will ultimately improve bodyshell design. Structural investigations revealed that in some cases the welds under-matched the parent material in strength - the weld metal was of 4000 series whereas a 6000 series alloy was used as the parent material. In many cases the design of the welded joint was such that the weld cross-sectional area was less than that of the adjacent parent material, and in some areas manual welds had lack of fusion or penetration defects.
Accidents with other aluminium-bodied rolling stock in Europe, especially the ICE disaster at Eschede in Germany on June 2 1998 and a head-on collision involving a DMU at Årsta in Norway on January 4 2000, triggered considerable interest in the performance of aluminium welds. This and Recommendation 57 led to the establishment of a European consortium of experts in aluminium welding who drew up a detailed research programme known as Aljoin, which enjoyed financial support from the European Commission. Among the activities covered by Aljoin were:
