Railway Track & Structures - February 2008 - (Page 17) TTCI R&D Evaluation of grinding strategies to improve the performance of premium rail at FAST Different grinding practices are put to the test to find a strategy to reduce defects, extend rail life and improve safety. orth American railroads spend about two billion dollars each year purchasing and maintaining their rail. Extending its life can improve the economics and safety of railroad operations. This is a more difficult and important task when car weights are increased, as higher axle loads can affect the occurrence of surface and internal defects in rail. Rail profile grinding is one way of reducing the occurrence of defects, extending rail life and improving safety. Railroads are effectively using rail grinding to achieve these goals. N Grinding tests at FAST The most recent rail grinding tests at www.rtands.com the Facility for Accelerated Service Testing evaluated various grinding strategies, with metal removal amounts and grinding intervals recommended by railroad technical advisory groups. The test on highhardness premium rail started in spring 2003, evaluating the effects of various grinding practices on premium rail. The test curve was divided into three zones. Each zone represented one grinding practice and within each zone were three types of 141-pound rail: • Nippon Steel Corporation: Highcarbon Hypereutectoid (HE) 400, approximately 400 Bhn • Rocky Mountain Steel Mills: Onepercent Carbon Pearlite, approximately 395 Bhn • Rocky Mountain Steel Mills: Deep Head Hardened (DHH) 370, approximately 370 Bhn The grinding practices evaluated were: • Preventive grind: The rail was ground at approximately 30-mgt intervals. An Figure 1 shows the condition of unground rails after 515 mgt. Low rail, left; high rail, right. average of 0.011 square inches of metal was removed from the high rail and 0.016 square inches from the low rail with the goal of producing a two-point conformal profile on the high rail and an eight-inch crown radius on the low rail. Grinding also removed surface damage such as RCF cracks and spalls. • High-contact stress zone: The rail was ground to create a mismatch between the rail profile and the average worn wheel profile at FAST, causing high-contact stresses. WRTOL™ software was used to develop the rail profiles that led to poor wheel/rail interaction. WRTOL is a software package that assesses wheel/ rail contact conditions to predict RCF, wheel/rail wear and vehicle performance. Principal outputs are contact stress, wheel rolling radius difference and by Joseph LoPresti, TTCI February 2008 17 Railway Track & Structures http://www.aar.com http://www.rtands.com
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