Impact damage in brittle materials in the elastic-plastic response régime

Abstract

The impact fracture created in the elastic-plastic response régime has been characterized in terms of its surface extension and penetration. A numerical dynamic analysis has been performed of a typical impact within this régime to indicate some of the principal characteristics of the contact behaviour and the stress field. The damage has then been analysed, by using simplified postulates based on key features of the impact dynamics and basic fracture mechanics concepts. This has enabled the primary material and target parameters affecting the impact fracture to be identified. Thereafter, some implications for strength degradation and erosion have been discussed.

Solid particle erosion mechanisms of protective coatings for aerospace applications

“…Although the use of equation 2.8 for the lateral crack system has no theoretical justification [65], Evans et al [66] found that the radial and lateral crack lengths where proportional to each other. Therefore, Evans [66], and then Wiederhorn et al [67], used equation 2.8 to calculate the lateral crack length c l , and evaluate the cylindrical volume loss during a single sharp particle impact using,…”

“…Therefore, Evans [66], and then Wiederhorn et al [67], used equation 2.8 to calculate the lateral crack length c l , and evaluate the cylindrical volume loss during a single sharp particle impact using,…”

“…For small angular particles, the damage will strongly depend on the particle's kinetic energy (KE) and will progress from plastic cutting or ploughing of the surface for low energies to radial/median cracking at higher energies. This can result in lateral fracture removing significant amounts of matter [66,67,198]. In one of his important articles, Hutchings [31] properties.…”

“…Based on the work by Marshall, Lawn and Evans [20,21,197,201], several indentation-based analytical models have been developed for the SPE by lateral fracture, among which both Evans [66] and Wiederhorn et al [202] proposed interpretations based on elasto-plastic indentation. The former adopted a dynamic approach for the calculation of the particle penetration depth and the maximum applied load while the latter used a quasi-static approach where the particle's KE is transferred to the target by the work of indentation.…”

“…The surfaces to be protected are generally metallic (stainless steel or titanium alloys), and they erode in a predominantly plastic mode of material removal through micro-cutting or ploughing mechanisms [51,52,196]. However, the protective coatings, applied to impede erosion, are generally composed of much harder ceramic materials such as titanium nitride-based compounds, and they erode in a brittle manner through crack initiation and propagation [51,66,67,69,[197][198][199].…”