The development of a material model for cast iron that can be used for brake system analysis

Abstract

This paper describes the methodology and reports the results of detailed thermomechanical nite element analyses of cast iron brake discs under repeated high g braking conditions. The thermal analysis allows for heat loss from the vanes in a back-ventilated disc design as well as heat transfer to other parts of the brake assembly. The cast iron material properties required for the non-linear structural analysis are generated by mechanical tests on samples cut from the brake disc. The material model developed by the authors allows for the variation of ow stress with temperature and for the diVerent yield properties of cast iron in tension and compression. The nite element results, derived from a preliminary investigation, indicate regions of high plastic strain accumulation which may lead to disc crazing and/or cracking and enable comparisons to be made between back-and front-vented rotor designs.

Overview of disc brakes and related phenomena - a review

“…In all of these, cooling air enters at the inner periphery and leaves the disc at outer periphery. One disadvantage with these configurations is that high stresses develop near the inner periphery primarily due to the inlets [8,9]. This could be a problem when a disc is used in a demanding situation.…”

“…So the deformations can appear in different forms in different discs. Some of the most commonly observed thermal deformations are coning and buckling as shown in figure 25 [77,85,9,86,76]. Generally, disc coning occurs due to the different thermal expansions of the outboard and inboard cheeks as the outboard cheek is integrally connected to the mounting bell which represents a constraint for its expansion as shown in figure 26 [8].…”

Finite Element Modeling of Contact Problems

“…Another material model which considers different yield behaviors in tension and compression, and employs the von Mises yield criterion both in tension and compression, is reported in [13] and [9]. In the latter model, the numerical results were much closer to the measured experimental data.…”

“…Due to different geometries of discs, each disc has different geometrical constraints to the thermal expansion and so the deformations can appear in different forms in different discs. Some of the most commonly observed thermal deformations are coning and buckling [7,8,9,10,11]. Such geometrical deviations could be avoided or reduced if the thermal loading and disc geometry are symmetric about the midplane of the disc [12,13], and the friction ring is decoupled from the mounting bell so that it has relatively more freedom to expand in the radial direction [14].…”

“…Another approach to simplify the model for a ventilated disc is to consider only a small sector of a disc by taking rotational symmetry into account, see e.g. [9,10]. Again the assumption has to be made about the smearing of the pad, implying that circumferential variations of temperature and contact pressure cannot be predicted satisfactorily.…”