Rail Profile Grinding on High-Hardness Premium Rail at the Facility for Accelerated Service Testing. Research Results

摘要

Since 2003, Transportation Technology Center, Inc. (TTCI) has been evaluating the effects of rail grinding on the performance of high-hardness premium rail at the Facility for Accelerated Service Testing (FAST). A 6-degree test curve is divided into three test sections, representing two different grinding practices, as well as unground rail. There are three types of rail in each sectiontwo of approximately 395 Brinell hardness number (Bhn) and one approximately 370 Bhn. By the spring of 2007, 515 million gross tons (MGT) of traffic had accumulated on the rails. The following results, which are typical at FAST (revenue service conditions may differ), provide insights into the effects of wheel/rail contact conditions and rail mechanical properties on rail performance. State-of-the-art, high-hardness rail required little or no grinding. Unground rail developed only minor, isolated rolling contact fatigue (RCF), and had no internal railhead defects. Because wheels on the test train at FAST tend to wear to a shape conformal with the rail, and the gage face of the high rail and the top of the low rail are lubricated, contact stresses remained acceptable throughout the test. Compared to the unground rail, total metal loss in the preventive grinding zone was approximately 77-percent higher on the high rail and approximately 240-percent higher on the low rail. The metal removed by preventive grinding was the primary reason for the increase; wear rates were similar. The 370 Bhn rail wore and deformed more than the 395 Bhn rails. The difference in wear was approximately 15 percent on the high rail. A profile intended to produce higher contact stresses resulted in more RCF, but the RCF was not severe. There is much less RCF on the low rail of the lubricated 6-degree curve, than there is on the low rail of the unlubricated 5-degree curve at FAST. Unrelated to rail grinding tests, there were six rail breaks originating at base defects in the 395 Bhn test rails. No breaks were found in the 370 Bhn rail.