The effect of elasticity in powder metal gears on tooth loading and mean coefficient of friction

Abstract

Powder metal gears have a lower density than conventional steel gears due to their intrinsic porosity from the manufacturing process. This also results in a lower elasticity leading to larger deformations and lower contact pressure in a gear contact. By using different modelling tools (namely FEA and available commercial software), the load behavior along the line of action is studied to compare the influence of lower elasticity with standard wrought steel elasticity for FZG-C type gears. A further step is taken analyzing this effect on the mean coefficient of friction through the recalculation of the gear mesh power loss factor. Conclusions observed are differences in load distribution and marginal differences in the gear mesh power loss factor when comparing sintered and wrought steel FZG-C type gears. Sintered steel showed a marginally longer line of action and simultaneously a decrease of the single tooth contact length when compared to wrought steel, while differences in the gear mesh power loss factor proved non-essential due to the spread in previously measured experimental data.

Tooth Root Bending Fatigue Strength of High-Density Sintered Small-Module Spur Gears: The Effect of Porosity and Microstructure

“…While the first stage of fatigue damage consists of multiple crack initiation and coalescence to form the main crack, the cracks not involved in this process, such as those shown in Figure 10 stop growing and become non-propagating. This observation agrees with those reported elsewhere in the technical literature [5,8,12,13].…”

“…This clearly impacts on the stiffness, tensile, fatigue and wear properties of such components [2][3][4]. In the context of P/M gears, (i) the lower stiffness is detrimental to the mesh precision and mesh power loss factor [5], (ii) inferior fatigue properties negatively affect tooth root bending fatigue strength [6] and pitting resistance [7], and (iii) sintered tooth flanks have higher wear rates [8]. To combat these adverse effects, many treatments have been devised so far, such as shot peening [9], surface rolling [10], sinter-forging [11], and the double press double Metals 2019, 9,599; doi:10.3390/met9050599 www.mdpi.com/journal/metals Metals 2019, 9,599 2 of 14 sinter process [12].…”

Influence of gear surface roughness on the pitting and micropitting life

“…A previous study by Lindholm et al. 8 compared the contact pressure calculations in KISSsoft with FEM calculations and found the results comparable. In Figures 7 and 8, the calculated contact stress can be found for LS 7 to 10.…”

A calculation method of sliding friction coefficient on tooth surface for helical gear pair based on loaded tooth contact analysis and elastohydrodynamic lubrication theory

“…When loads on all contact lines are calculated, the load distribution on the tooth surface can be obtained (Figure 9). The load per unit contact line can be obtained by dividing the load on contact line by the length of contact line, which is described in equation (2).…”

“…Accurate calculation of sliding friction coefficient on tooth surface is of great significance to reduce the power loss, increase the load capacity of tooth and improve the transmission performance of gear system. [1][2][3] The calculation method of sliding friction coefficient on tooth surface includes: (1) the sliding friction coefficient on tooth surface is replaced with the average sliding friction coefficient. 4,5 The method is relatively simple but imprecise because the sliding friction coefficient on tooth surface is related to the relative sliding velocity, entrainment velocity, lubricant viscosity, load, curvature radius and surface roughness of the meshing point on tooth surface; (2) the sliding friction coefficient on tooth surface comes from the test formula, which is obviously more accurate than the first one, 6,7 but these formulas are all taken from the specific test environment, such as lubrication type, temperature, velocity, load and surface roughness, which may be different from the actual calculation environment of the user; (3) the sliding friction coefficient on tooth surface is to improve the experimental formula, 8,9 so that it can be used more widely.…”