Dynamic Initiation and Propagation of Multiple Cracks in Brittle Materials.

Jie Li,Qiaoping Huang,Xiaodan Ren

doi:10.3390/ma6083241

Abstract

Brittle materials such as rock and ceramic usually exhibit apparent increases of strength and toughness when subjected to dynamic loading. The reasons for this phenomenon are not yet well understood, although a number of hypotheses have been proposed. Based on dynamic fracture mechanics, the present work offers an alternate insight into the dynamic behaviors of brittle materials. Firstly, a single crack subjected to stress wave excitations is investigated to obtain the dynamic crack-tip stress field and the dynamic stress intensity factor. Second, based on the analysis of dynamic stress intensity factor, the fracture initiation sizes and crack size distribution under different loading rates are obtained, and the power law with the exponent of −2/3 is derived to describe the fracture initiation size. Third, with the help of the energy balance concept, the dynamic increase of material strength is directly derived based on the proposed multiple crack evolving criterion. Finally, the model prediction is compared with the dynamic impact experiments, and the model results agree well with the experimentally measured dynamic increasing factor (DIF).

Highlights

Dynamic fracture of brittle materials is of special interest in the physics and materials community [1,2,3,4]
Mott [16] was the first to study the dynamic fragmentation in an analytical way
The fragmentation of brittle materials was formed by the competition between the dynamic stress loading and stress relief

Summary

Introduction

Dynamic fracture of brittle materials is of special interest in the physics and materials community [1,2,3,4]. In the work of Chen [24], the dynamic response of crack to various types of Heaviside loadings has been developed Based on this method, Kipp and his co-workers [25] explained the dynamic strength increase of oil shale under high strain rate. Based on this knowledge, and combined with the concept of energy balance in facture, a multiple crack propagation dynamic fracture model is proposed, and the dynamic increasing factor for brittle materials can be derived .

Fracture Initiation and Multiple Cracking

E 0 K 2IC 3

Multiple Dynamic Fracture model

Numerical Implementation and Results

Conclusions