Saud Aldajah

Investigation of Top of Rail Lubrication and Laser Glazing for Improved Railroad Energy Efficiency

Two new technologies have recently been developed that can help to solve some of the wheel rail contact problems. The first is a method of top of rail lubrication (TOR) or friction modification (FM). The second is a technique of laser glazing of steel rails. Both technologies help in reducing the friction, wear, and energy consumption in the wheel rail contact. This paper introduces the two technologies and presents some specific aspects of both methods. A 1:12 scale wheel/rail simulator (LA 4000) was used to study the potential of these two new technologies on energy savings. In order to develop an efficient top of rail lubrication system, all parameters affecting FM consumption rates have been studied. These parameters include speed, angle of attack, load and lubricant quantity. LA 4000 friction/wear studies were conducted to evaluate the effect of laser glazing and TOR lubricant on the lateral slip forces between a simulated wheel/rail. Three conditions under dry and lubricated environments were studied: unglazed wheel and an unglazed rail, an unglazed wheel against a glazed rail, and a glazed wheel against a glazed rail. The results of the tests indicate that the use of TOR and laser glazing does indeed reduce the lateral forces, which are an indirect measure of the damage caused to the wheel, rail and track.

Effect of Laser Surface Modifications Tribological Performance of 1080 Carbon Steel

High-power laser surface treatments in the form of glazing, shock peening, cladding, and alloying can significantly affect material surface properties. In this paper, effects of laser glazing, laser shock peening, and their combination on the tribological behavior of 1080 carbon steel were investigated. Laser glazing is a process in which a high-power laser beam melts the top layer of the surface, followed by rapid cooling and resolidification. This results in a new surface layer microstructure and properties. Laser shock peening, on the other hand, is a mechanical process in which a laser generates pressure pulses on the surface of the metal, similar to shot peening. Five conditions were evaluated: untreated (baseline), laser shock peened only (PO), laser glazed only, laser glazed then shock peened last, and laser shock peened then glazed last (PFGL). In pin-on-disc testing, all laser-treated surfaces reduced dry friction when sliding against alumina, with the PFGL surface having maximum friction reduction of 43%, especially in the early stage of testing. Under lubricated conditions, all laser-treated surfaces except the PO sample lowered friction against alumina. Similarly, all glazed samples showed reduced wear by a factor of 2-3, whereas the peening alone did not change wear significantly. These tribological results are associated with changes in the near-surface microstructure and properties.

Role of nanofillers in low speed impact enhancement of composites

The current study investigates the impact characteristics of polymeric-based nanocomposites strengthened with carbon nanotubes, nanoclay, aluminum oxide and silicon carbide particles nanofillers. Different weight percentages of each nanofiller were prepared. A dead weight drop mechanism was utilized to compare the impact characteristics of different nanocomposite materials. An X-ray technique was utilized to characterize the formation of microstructural defects of the laminated composites post impact. The results showed that the nanoclay fillers were the best to enhance the impact and mechanical properties of the composite materials with 4.3 wt% of nanoclay being the optimum percentage.

Investigation of Scuffing Resistance and Tribological Performance of Laser Modified Surfaces

Latest development in high-power lasers made possible a wide variety of laser surface modifications. Such surface modifications include: glazing, shock peening, alloying, cladding and texturing. The main reason behind applying these treatments is to improve the tribological performance of the modified surfaces. In addition to reducing friction and wear, it is favorable to improve the scuffing resistance. Scuffing can be defined as a sudden catastrophic failure of a lubricated sliding surface characterized by a sudden rise in friction; resulting in severe surface damage through localized plastic flow. This paper investigates friction and scuffing performance of laser glazed 1080 steel and laser textured H13 stainless steel. Results showed that laser glazed surfaces reduced sliding friction under dry conditions by approximately 35% and improved wear resistance. In addition, laser glazed surfaces showed high resistance to scuffing compared to unglazed surfaces. Also, laser surface texturing technique reduced sliding friction under lubricated conditions and improved scuffing resistance.Copyright

FEM Modeling of Nanocomposites Low Speed Impact Behavior

A 2D finite element model using ABAQUS has been developed in order to understand the role of nanoclay in enhancing the low speed impact behavior of laminated woven kevlar nanocomposite. The model simulates an impactor as a shell rigid body while the composite samples were simulated in two dimensional model. ABAQUS/Explicit 6.8 was used to simulate the composite samples in this study. The FEM analysis focuses on the stress distribution in the impacted composite samples; the ability of the impactor to penetrate the samples; and the expected failure mode based on the Hashins theory damage initiation criteria for fiber- reinforced composites. The damage evolution was determined in terms of displacement and/or energy. In the displacement damage evolution, it is possible to define the damage as a function of the total or the plastic displacement after damage initiation. While as, in the energy evolution damage, it is defined in terms of the energy required for failure (fracture energy) after the initiation of damage. The theoretical and experimental results were in good agreement..

Scuffing Performance of Laser Modified Surfaces Under Lubricated Contacts

Latest development in high-power lasers made possible a wide variety of laser surface modifications. Such surface modifications include: glazing, shock peening, alloying, cladding and texturing. The main reason behind applying these treatments is to improve the tribological performance of the modified surfaces. In addition to reducing friction and wear, it is favorable to improve the scuffing resistance. Scuffing can be defined as a sudden catastrophic failure of a lubricated sliding surface characterized by a sudden rise in friction; resulting in severe surface damage through localized plastic flow. This paper investigates friction and scuffing performance of laser glazed 1080 steel and laser textured H13 stainless steel. Results showed that laser glazed surfaces reduced sliding friction under dry conditions by approximately 35% and improved wear resistance. In addition, laser glazed surfaces showed high resistance to scuffing compared to unglazed surfaces. Also, Laser surface texturing technique reduced sliding friction under lubricated conditions and improved scuffing resistance.Copyright