Abstract
Abstract Nondestructive evaluation (NDE) is an effective technology that has been used for many decades to assess wood properties. However, NDE has not been well developed for in-service assessment of railroad ties of various wood species, grades, and boundary conditions. Acoustic velocity (AV) of railroad ties in free (on ballast) and fixed (packed with ballast and under static weight) boundary conditions was investigated herein. Overall, 60 new on-grade, 40 new off-grade, and 55 Grade-one (1) legacy ties were investigated. Ties were either oak/hickory or mixed hardwood. All ties were first measured in the free boundary condition and then packed with ballast, weighted, and measured in the fixed boundary condition. Ties were placed on ballast with approximately 10- to 11-cm (4- to 4.5-in.)-wide gaps between each. The AV that was measured after each tie was placed on the ballast (AVfree). Next, the ties were packed with ballast. Then a static weight, mimicking the load of rails, was placed on each tie and the AV was measured (AVfixed) with a Hitman HM220. All data were analyzed using three-way analysis of variance. The AV was higher for new on-grade versus new off-grade and legacy ties. The AV was higher for fixed versus free boundary condition. These results indicate that AV could be used to separate on-versus off-grade ties during production and that laboratory-scale AV technology could develop into an in-service technique.
Published Version
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