Criteria for evaluating the surface strain-hardening of machine parts

Yatsenko, V. K.; Kostenko, N. A.

doi:10.1007/bf01755915

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“…However, in the practice of engineering calculations, both processes are considered equivalent. However, at a hardness identical and constant across the thickness of the specimen (steel 12Kh2N3A, C 0.09-0.15%, Ni 3.25-3.65%, Cr 1.25-1.65%, Si 0.17-0.37%, Mn 0.3-0.6%), the σ e+ of the samples subjected to nitrocarburizing is 10-12% higher than cemented ones [36,37], which, in the absence of data on the corresponding increase in σ e− allowed, in the first approximation, take at the hardness level 850H HV the values of the ductility parameter χ = 0.6 (cementation of nickel-free steels) and χ = 0.68-0.7 (cementation of nickel-containing steels and nitrocarburizing). In the absence of additional information, the change in the plasticity parameter in the interval 400-850H HV was assumed linear:…”

Section: Lebedev-pisarenko Criterionmentioning

confidence: 97%

Deep Contact Strength of Surface Hardened Gears

Beskopylny

Meskhi

Onishkov

et al. 2020

Metals

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This article is devoted to the analysis methods for assessing the load capacity of gears hardened by surface chemical-thermal treatment (CTT), which are characterized by structural and chemical heterogeneity. The leading type of failure is determined by several factors, the main of which are the surface and deep layer properties of the material, which fundamentally differ in the energy and structural state. Intercrystalline fracture mechanisms predominate in the surface layers and transcrystalline in the core. For these cases, the classical failure criteria of Mohr, Tresca, and Mises lead to significant errors. Therefore, the bearing capacity of the layer component is investigated by the generalized criterion of the limit state of the Pisarenko-Lebedev structurally inhomogeneous material, considering changes in its plastic properties due to surface hardening. The reliability of predicting the level of bearing capacity of surface hardened steel parts, such as gears, was significantly improved. The influence of the plasticity parameter on the level of bearing capacity for various types of CTT is estimated. Calculations using the presented model show that for alloy steels with a Ni content up to 1%, the safety coefficient can be limited to 1.2, which will increase the bearing capacity by 25–27%.

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Section: Lebedev-pisarenko Criterionmentioning

confidence: 97%