R.K. Pandey

Performance of Lubricated Rolling/Sliding Concentrated Contacts With Surface Textures: A Review

Benefits of surface textures for improving the performance behaviors of tribo-contacts are being explored and established by the investigators across the globe. But the consolidated information of findings of such explorations are spread. Therefore, the objective of this paper is to summarize the information available related to the preparation of surface textures and performance outcomes in the presence of surface textures at the concentrated contacts. Mainly, recent research findings and practices followed for the study of friction, wear, lubrication, contact fatigue, vibration, and noise at the generic concentrated contacts in presence of surface textures are reviewed for current status of research in the area and outlining the future prospects.

Tribological Studies of Lubricated Laser-Textured Point Contacts in Rolling/Sliding Reciprocating Motion with Investigations of Wettability and Nanohardness

The friction and wear behaviors of concentrated point contacts formed between lapped bearing steel balls and lapped/laser-textured flat bearing steel surfaces were studied in the boundary/mixed lubrication regimes under reciprocating rolling and sliding motions. Nanohardness variation in the vicinity of the dimples of the textured surface along with lubricants wettability of the lapped and textured flat surfaces were measured to understand the tribological behaviors at the concentrated contacts. Moreover, the morphologies of wear debris collected from the contacts were investigated using analytical ferrography and scanning electron microscopy (SEM). It has been observed based on the experimental studies under the adopted operating parameters that the friction coefficient reduces to 33 and 27% at the rolling velocity (0.12 m/s) and sliding velocity (0.16 m/s), respectively, at the heavy load (PH > 0.7 GPa) at the textured point contacts in comparison with lapped point contacts. However, at the light load (PH ≤ 0.7 GPa), the friction coefficient increases or remains the same with respect to the lapped point contact in rolling motion. The specific wear rates of the balls of the contact (formed between the ball/textured surface) found more (varying in the range 9–69%) in comparison with the balls of the ball/lapped surface contact for all sliding velocities adopted in the investigation.

Fracture characteristics of Al/zircon particulate composites

Abstract A study has been made of the effects of volume fraction and size of zircon particulates on fracture toughness and micromechanisms of fracture in Al/zircon particulate composites. The composites are prepared by a liquid metallurgy technique using volume fractions of zircon in the range 0·06–0·18 and particulate sizes between 75 and 250 μm. The study was conducted on composites in the cast and the forged conditions. The experimental programme included a particle size distribution study, tensile tests, fracture mechanics tests leading to J 1c and crack tip opening displacement evaluation, fractographic investigations, etc. The process zone size at the crack tip was evaluated from crack tip stresses and strains, and compared with the interparticle spacing and particle diameter in order to understand the micromechanics of cracking. The Al/zircon composites were compared with Al/graphite composites in terms of strength and fracture toughness as a function of volume fraction of the filler phase, and regions of optimum performance were identified.