Look for cracks in axles, metal fatigue expert says
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.
'We must come up with real evidence that can make people believe and endure the test of time.'
A Beijing Sheenline Technology spokeswoman said yesterday that its technicians had been involved in the inspection and did not agree with the authorities' conclusion.
'The debate is still going on and we are waiting for a more authoritative verdict,' she said.
China CNR could not be reached for comment yesterday. The corporation said earlier that the trains had been recalled because of minor problems such as jittery sensors and the need for software upgrades.
Zhibo Lucchini Railway Equipment, the manufacturer of the suspect axles and the only supplier of high-speed train axles on the mainland, declined to comment. The company said on its website that its entire production line and technology were imported from Italy.
Professor Zhao Jian, an economist at Beijing Jiaotong University who is an expert on the development of the high-speed railway system, said the debate over the axle exposed a fatal weakness in the mainland's high-speed rail industry: with most of the technology and production lines imported from other countries, the authorities had no idea how to respond when problems rose.
'A German detector finds a crack in an Italian shaft; Chinese government buyers don't know how to deal with the problem,' he said. 'They will have to go back to their foreign partners and beg for solutions.'
Huang Yi, State Administration of Work Safety spokesman, told a Xinhua online forum yesterday that the central government had launched its biggest campaign for railway safety inspection since last month's fatal Wenzhou collision and would release a formal report next month. He did not respond to internet users' questions about the cracks.