A row between the mainland's railway authorities and an inspection company over alleged cracks in the driving axles of high-speed trains can be solved simply, according to one expert in metal fatigue: just cut the shafts and have a look.
Dr Zhao Jiaxi, a researcher with the fatigue and fracture division of the National Laboratory for Material Sciences in Shenyang, Liaoning, said yesterday that the debate could be settled once and for all by cutting the suspect axles apart and examining the structure inside.
According to a report by Caixin Century magazine on Sunday, ultrasonic inspections since June of high-speed trains in Jinan, Shandong, discovered fractures in the driving axles of one of the newest models of high-speed trains operating between Beijing and Shanghai. It suggested that the recall of 54 trains by China CNR this month was linked to the discovery of the cracks.
The Ministry of Railways said it had been a false alarm and, after internal discussion, ruled that the German ultrasonic detector used was too sensitive. But Beijing Sheenline Technology, which supplied the detector, insisted that there had been no problem with it and that the factures did exist, according to the Caixin report.
China CNR, the manufacturer of the trains, told the Beijing Daily yesterday that the ministry had solved the problem by resetting the parameters of the detector. There had been no more alerts and the suspect axles were still is use.
Zhao said an ultrasonic detector worked like radar. The detector collected the pulses of sound waves reflected by the internal structure of a sample to determine whether there was a crack inside. But just as radar could not always tell the difference between, say, a flock of birds and an aeroplane, the detector would sometimes falsely alarm.
'The most authoritative method is to cut open the sample to see what is inside,' he said. 'Truth can only side with one party. We must respect truth rather than make judgments on various possibilities based on experience. We cannot simply make a conclusion with reasoning.