تاثير بهبود رفتار سايشي چرخهاي فولادي بر ايمني سير قطار : مطالعه موردي واگن مسافري مسير تهران ميانه

Enhancing wheel wear behaviour and coach safety using B5T grade steel

سامانه بين شهري حمل ونقل ريلي مسافري ايران به منظور افزايش طول عمر چر خهاي فولادي خود، در دو سال گذشته براي اولين بار اقدام به استفاده از فولاد گريد B5T نموده است. در اين مقاله رفتار سايشي اين چر خها با استفاده از اندازه گيري ميداني مورد مطالعه قرار گرفته و تاثير آن بر تداوم سير ايمن قطار بررسي شده است. به اين منظور يك واگن مسافري در سال 1387 پس از آماده سازي در مسير تهران- ميانه به سير فرستاده شد. واگن مزبور در مدت سير پنج ماهه خود تحت نظارت بوده و پروفيل ( نيمرخ) چر خهاي آن به طور متناوب در ايستگاه تهران اندازه گيري شد. نتايج اندازه گير يها نشان داد كه در مقايسه با گريد فولاد B2Nكه در سال1382 در همين مسير مورد مطالعه قرار گرفته بود، گريد فولاد B5T در يك مسافت برابر داراي ميزان سايش كمتر (%40) متقارن ( با تفاضل 25 % در يك محور) و در نتيجه ايمني سير بيشتر است

Steel wheels are affected during coach operation on the rail due to high normal and tangential stresses. The wheel profile is then varied, which could be resulted in an unexpected derailment when wheel wear is focused on within the flange region. This dangerous situation should be prevented, using various solutions including the deployment of higher grades of steel wheels. A field test was planned and conducted within 2007-2008 period to find out the influence of B5T grade steel on the wheel wear magnitude and pattern, which could lead to safe operation of a passenger coach. The test coach wheels were measured frequently at Tehran station for a 5-month time interval. It was found that B5T grade has a better strength to resist against wheel failure mechanisms, i.e., wear as well as rolling contact fatigue (rcf) in comparison with B2N grade which was tested during 2003-2004 period in the same route, that was Tehran-Mianeh track. The wear pattern was gained more symmetric within each wheelset (about 25%) than the previously used wheelsets within field test results. Consequently, this coach likely operated longer life (40%), as well as, safer than the earlier test coach which had been equipped with B2N grade steel wheels. To justify the higher wear rate at the initiation of coach operation, it could be explained when the running-in period of wheels was finished, a harder material raised to the wheel surface resulted in a balanced material removal condition in terms of wear. As a result, the wear rate of the wheels was gradually decreased.