Strength Against Fracture of End Hemispherical Cavity Roller Under Static Loading: Experimental and Simulation Investigation

Abstract

Enhancement in fatigue life of rolling element bearing has been captivating since years. The hollow concept had been triggered years back, however it could not catch widespread applications due to catastrophic failure. Thus, any novel concept of rolling element must be assessed for its strength against catastrophic failure before competing for better fatigue life on-field with other alternatives. This paper commences with the outcomes of comparative assessment of the experimental evaluation of strength against fracture under static loads for layered and hollow rollers with solid rollers, which devise the requirements for new concepts. The EHC (End Hemispherical Cavity) roller concept, being a proper geometrical blending of solidity and hollowness, prospects to overcome the strength concern along with considerable reduction in contact stresses. Thus, experimental investigation was conducted with full-bearing fracture tests and individual roller specimens fracture tests for five variants: EHC, solid, layered, 61H and 37H (Hollow rollers with 61% and 37% hollowness respectively). The simulations were carried out to support the outcomes of experimental trials. The experimental results with full-bearing samples and individual roller specimens demonstrated ranking as: EHC, 37H, layered and 61H. The EHC roller concept was substantiated to be stronger than hollow and layered rollers besides prompting appreciable reduction in contact stresses compared to solid roller. The simulation results agreed well with experimental results of fracture tests and the recommendations from findings of failure theories (Maximum Normal Stress, Distortion Energy and Maximum Shear Stress) adopted for estimating fracture load for rollers have been discussed.

Relative contact width evaluation of end hemispherical cavities rollers as an indication of Hertzian contact pressure

“…As in the preceding investigation about the mentioned novel roller concept, the EHC roller exhibited better strength against fracture 15 than the hollow roller variant, and in another simulation study, 16 the EHC roller concept showed better prospects in the fatigue life estimation analysis than the flat cylindrical solid roller variant; therefore, the present investigation was undertaken to explore the EHC roller concept further with the aim of evaluating contact widths of the EHC roller comparatively with the solid roller to indirectly appraise the contact pressure behavior because the contact stresses are mainly responsible for the fatigue life of rolling element bearings in case of "good" material properties (regarding inclusions, roughness etc.) and "optimum" operating conditions (viscosity ratio κ >2-4, good cleanliness).…”

“…Since the results of preceding investigations 15 about a recent roller concept (EHC roller) were encouraging, it necessitated to push the exploration about the EHC roller concept further. Moreover, a simulation study 16 showed the prospects of higher fatigue life of the EHC roller than the solid roller as well.…”

“…Since the preceding investigation for the assessment of strength against fracture 15 revealed that two roller variants, namely, layered and 61H fractured and could not withstand the load equivalent to the static load rating of the chosen thrust cylindrical roller bearing, that is, 81,209; therefore, the present investigation focused to gauge the performance of only the remaining qualifier roller concepts, namely, EHC and 37H, with respect to the solid roller. Thus, in the present investigation, three roller variants (solid, 37H, and EHC) have been discussed.…”

“…Otherwise, its applications will be limited like hollow (annular) rollers. To this end, an experimental investigation was conducted to gauge the strength against fracture of such a novel concept named the “end hemispherical cavities (EHC) roller” 15 in which different cylindrical roller variants (Layered, 61H, 37H, and EHC) were examined experimentally, along with simulation analysis, and the results of full-bearing sample tests, individual roller-on-plate tests, and simulation analysis concluded that the EHC roller has better strength against fracture among other competitive roller variants (Layered, 61H and 37H) and thus it will not show flexural fractures like hollow rollers at relatively lower load ranges as per the static/dynamic load rating of solid roller bearings. Furthermore, as one of the important objectives of research in rolling bearings is the enhancement of fatigue life of bearings, the performance of the EHC roller from the fatigue life aspect was comparatively assessed through a simulation study 16 in which again, the performance of five cylindrical roller variants (solid, layered, 61H, 37H, and EHC) were compared through the simulation results, and it was observed that in 61H and layered rollers (cylindrical roller variants with relatively thin walls), the stressed volume elements existed near the inner bore surfaces, whereas in the EHC roller, no such stressed volume elements near the inner bore cavity were spotted and furthermore, the collective influence of decisive stress and volume of the stressed element was inspected in which the EHC roller demonstrated highest relative fatigue life estimations (with respect to solid roller) among other contestant roller variants (layered, 61H and 37H).…”

“…Otherwise, its applications will be limited like hollow (annular) rollers. To this end, an experimental investigation was conducted to gauge the strength against fracture of such a novel concept named the "end hemispherical cavities (EHC) roller" 15 in which different cylindrical roller variants (Layered, 61H, 37H, and EHC) were examined experimentally, along with simulation analysis, and the results of full-bearing sample tests, individual roller-on-plate tests, and simulation analysis concluded that the EHC roller has better strength against fracture among other competitive roller variants (Layered, 61H and 37H) and thus it will not show flexural fractures like hollow rollers at relatively lower load ranges as per the static/dynamic load rating of solid roller bearings.…”