Hardwood timber has been the predominant material of choice for crossties since the establishment of the railroad industry in the US. Recently, several concerns, including higher speeds, heavier loads, durability and negative environmental effects associated with deforestation and wood-treating chemicals, have invoked the railroad industry's interest in alternative materials for crossties. Currently, several manufacturers offer alternative and sustainable solutions using different recycled plastic composite materials. Thousands of plastic crossties are currently in service in a wide variety of railroad applications. Several researchers have been studying and testing these new materials, specifically high-density polyethylene, however, their behavior when subjected to rail loading is not yet fully understood. Uncertainties in mechanical properties, failure modes and fracture render their performance and safety questionable. More research is required to properly characterize, describe and model the behavior of these materials as well as to assess the feasibility of implementing these materials in railway applications in terms of performance, safety, practicality and economy. Therefore, this study aimed to investigate the performance of plastic composite crossties through experimental testing and analytical modeling. A flexural testing program addressing two AREMA recommended tests for crossties; center and rail seat bending, was conducted. The behavior of the crosstie with the rail and fastening system installed was also investigated. An analytical finite element model, capable of simulating the flexural behavior of plastic crossties, was constructed using a material model that was calibrated using the experimental data. The plastic composite crossties demonstrated adequate performance throughout the experimental testing program. This paper also highlights the potential structural, social and economic benefits of implementing high-density polyethylene crossties in railroad applications.

Railroad spikes represent a vital component of the rail track system, as they fasten the rail to the supporting crossties. Thus, it is important to understand its behavior and effect on the fastening assembly to mitigate any local failure, which, in turn, could lead to system deterioration or damage. Currently, alternative solutions to the traditional hardwood timber crossties are increasing being adopted by the railroad industry in the USA, with recycled plastic composite crossties being among the available alternatives. Their sustainably, environmental benefits, durability and ease of installation render them an attractive and competitive solution. Several research programs have studied this material and its fastening system in the past; however, additional research is required to fully understand the behavior of these materials and their interactions with the fastening system components. This paper presents an investigation that aims to understand and assess the performance of typical railroad spikes used for recycled high-density-polyethylene crossties. The study encompassed a comprehensive experimental investigation and analytical finite element modeling. The testing program evaluated railroad spikes using static testing methods recommended by the American Railway Engineering and Maintenance-of-Way Association (AREMA) manual. These tests addressed the rail spike pullout and lateral restraint for both screw and cut spikes. Finite element models were constructed and calibrated using the data obtained from the experimental program in order to extrapolate on the experimental results and predict the behavior of full-scale systems beyond the scale of the laboratory. The results observed in this study showed great promise, surpassing all the AREMA recommendations, which highlights the potential of these materials if properly optimized and engineered. Screw spikes exhibited a very good performance, surpassing the minimum recommendations by a significant margin (up to more than 200%) and are thus are highly recommended for future implementation.

TC21 with a composition of Ti-6Al-3Mo-1.9Nb-2.2Sn-2.2Zr-1.5Cr is considered a new titanium alloy that is used in aerospace applications as a replacement for the famous Ti-6Al-4V alloy due to its high strength-to-weight ratio, high operating temperature and corrosion resistance. In this study, two different solution treatment techniques were applied on TC21 samples. Solution treatment was applied using two step heating at 1000/800 °C for 15 min each and then cooled using water quenching or air cooling to see the effect of cooling rate on microstructure as well as mechanical properties. The solution treated samples were divided into two groups; one was tested as solution treated samples without aging. While, the second group was aged at 575 °C for 4 hrs. Maximum hardness of 442 HV was observed for the water quenched and aged samples, while the minimum hardness of 340 HV was obtained for water quenched samples without aging. The lowest wear rate was obtained for water quenched and aged samples. However, the highest wear rate was reported for the samples solution treated and water quenched without aging.

Rail track longevity is a primary concern for the railroad industry in the US. Therefore, it is important to study the rail support system in detail. This includes understanding the interactions between the rail, the different fastening components, and the crosstie. Then evaluate the support system's long-term performance. Over the past several years, the railroad industry in the US has been leaning toward implementing alternative solutions to the traditional hardwood timber crossties. Recycled plastic composite crossties present an appealing and effective solution due to their sustainably, environmental benefits, durability, and ease of installation. Several US manufacturers are currently offering commercial crosstie solutions using different recycled plastic composite materials. Thousands of composite plastic crossties are currently in service in a wide variety of railroad tracks. Researchers have investigated this material in the past; however, additional research is still needed to fully understand the rail support system and its long-term behavior. This paper presents an experimental investigation aiming to understand and assess the performance of the full rail support system: the rail section, fastening assembly, and recycled high-density polyethylene crossties. The study encompassed a comprehensive experimental investigation using static and cyclic test methods recommended by the American Railway Engineering and Maintenance-of-Way Association manual. The static tests addressed the performance of the rail support system when subjected to uplift forces and longitudinal loading in the direction of the rail track, e.g. breaking and traction forces. The dynamic test evaluated the long-term behavior of the rail support system while being subjected to repeated loading for three million fatigue cycles. The outcomes of this study showed great results; the crossties survived the fatigue loading with normal wear and minimal degradation, which highlights the potential of these materials if properly optimized and engineered.

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