Temperature Distribution and Scuffing of Tapered Roller Bearing

In the field of aerospace, high-speed trains and automobile, etc, analysis of temperature filed and scuffing failure of tapered roller bearings are more important than ever, and the scuffing failure of elements of such rolling bearings under heavy load and high speed still cannot be effectively predicted yet. A simplified model of tapered roller bearings consisted of one inner raceway, one outer raceway and a tapered roller was established, in which the interaction of several heat sources is ignored. The contact mechanics model, temperature model and model of scuffing failure are synthesized, and the corresponding computer programs are developed to analyze the effects of bearings parameters, different material and operational conditions on thermal performance of bearings, and temperature distribution and the possibility of surface scuffing are obtained. The results show that load, speed, thermal conductivity and tapered roller materials influence temperature rise and scuffing failure of bearings. Ceramic material of tapered roller results in the decrease of scuffing possibility of bearings to a high extent than the conventional rolling bearing steel. Compared with bulk temperature, flash temperature on the surfaces of bearing elements has a little influence on maximum temperature rise of bearing elements. For the rolling bearings operated under high speed and heavy load, this paper proposes a method which can accurately calculate the possibility of scuffing failure of rolling bearings.

TEMPERATURE FIELD THERMOGRAPHY ON FRICTION FACING OF CERTAIN WEAR-RESISTANT ALLOYS

The change of temperature field on the friction facing during contact wearing for 3 wear-resistant alloys.Co-Cr-Ni-Si,Co-Cr-Mo and Co-Cr-W has been monitored by the infrared sensing thermography.Their flash temperature of the wearing area was measured.

TEMPERATURE FIELD THERMOGRAPHY ON FRICTION FACING OF CERTAIN WEAR-RESISTANT ALLOYS

The change of temperature field on the friction facing during contact wearing for 3 wear-resistant alloys:Co-Cr-Ni-Si,Co-Cr-Mo and Co-Cr-W has been monitored by the infrared sensing thermography.Their flash temperature of the wearing area was measured.

Reduction in thermal conductivity of monolayer WS_(2) caused by substrate effect

Understanding the substrate and temperature effect on thermal transport properties of transition metal dichalcogenides(TMDs)monolayers are crucial for their future applications.Herein,a dual-wavelength flash Raman(DF-Raman)method is used to measure the thermal conductivity of monolayer WS_(2) at a temperature range of 200–400 K.High measurement accuracy can be guaranteed in this method since the influence of both the laser absorption coefficient and temperature-Raman coefficient can be eliminated through normalization.The room-temperature thermal conductivity of suspended and supported WS_(2) are 28.5±2.1(30.3±2.0)and 15.4±1.9(16.9±2.1)W/(m·K),respectively,with a~50%reduction due to substrate effect.Molecular dynamics(MD)simulations reveal that the suppression of acoustic phonons is mainly responsible for the striking reduction.The behaviors of optical phonons are also unambiguously investigated using Raman spectroscopy,and the in-plane optical mode,E(Γ),is surprisingly found to be slightly enhanced while out-of-plane mode,A1g(Γ),is suppressed due to substrate interaction,mutually verified with MD results.Our study provides a solid understanding of the phonon transport behavior of WS_(2) with substrate interaction,which provides guidance for TMDs-based nanodevices.