Influence of Materials Hardenability Parameters on the Machine Parts Characteristics after Unloading

Abstract:

This paper studies the problem of the relative area changing on a decrease of the load applied to the joint of roughness surfaces. The penetration of a rigid rough sphere (indenter) into the elastic hardenable half-space is initially considered, then the elastic crater restoring by unloading is considered. To defining elastic-plastic material, Hollomon’s power law is used. To describe a contact of a rigid rough surface with an elastic plastic half-space, the discrete model of a rough surface is used. Microasperities are represented as a set of identical spherical segments, the height distribution of which corresponds to the bearing profile curve of the real surface. The dependence the dimensionless force elastic-geometric parameter F_q on a relative amount of indentation ε at loading and the dependence of analogous parameter F_qe on amount of ε-Dε at unloading are obtained. The relations of relative contact areas h and h_e on dimensionless loading F_q and F_qe at loading and unloading for different values of a hardening exponent n and parameter are given. The obtained results are of practical importance for the performance prediction of fixed machine elements’ joints at the design stage, in particular for tightness supply of flange couplings and high pressure vessels seals.

• Periodical: Key Engineering Materials (Volume 723)
• Pages: 369-375
• DOI: https://doi.org/10.4028/www.scientific.net/KEM.723.369
• Online since: December 2016
• Authors: Petr M. Ogar*, D.B. Gorokhov
• Keywords: Elastic Crater Restoring, Elastic-Plastic Half-Space, Hollomon’s Power Law, Relative Contact Area, Rough Surface, Unloading

References

[1] P. M. Ogar, D. B. Gorokhov, Rough surfaces contact: fractal approach. Bratsk: BrGU, (2007).

[2] P. M. Ogar, V. A. Tarasov, A. V. Turchenko, Contact geometry in the process of elastic-plastic indentation of a spherical asperity, Syst. Meth. Tech. 1 (2012) 9-16.

[3] P. M. Ogar, V. A. Tarasov, Kinetic indentation application to determine contact characteristics of sphere and elastoplastic half-space, Adv. Mater. Res. 664 (2013) 625-631.

DOI: 10.4028/www.scientific.net/amr.664.625

[4] S. V. Belokobil'skiy, P. M. Ogar, V. A. Tarasov, Optimal design of pipeline valves with sealing «metal-metal», Syst. Meth. Tech. 3 (2009) 9-15.

[5] S. I. Bulychev, V. P. Alekhin, Testing of materials by continuous depression of an indenter, Mashinostroenie, Moscow, 1990, p.224.

[6] A. P. Kovalev, Basic laws of the indentation of a spherical indenter and evaluation of physical and mechanical properties of the surface layer of machine elements, Strength. Tech. Coat. 1 (2007) 36-41.

[7] J. M. Collin, G. Mauvoisin, P. Pilvin, Materials characterization by instrumented indentation using two different approaches, Mater. Des. 31 (2010) 636 – 640.

DOI: 10.1016/j.matdes.2009.05.043

[8] X. Hernot, O. Bartier, Y. Bekouche, G. Mauvoisin, R. El Abdi, Influence of penetration depth and mechanical properties on contact radius determination for spherical indentation, Int. J. Solid. Struct. 43 (2006) 4136–4153.

DOI: 10.1016/j.ijsolstr.2005.06.007