Crack propagation Rapid

Fig. 4. Typical P-d traces and fracture behaviour (a) post-yielding, (b) Sequential post-yielding and tearing, (c) Ductile instability, (d) Post-yielding and fibrillation, and (e) rapid crack propagation, (a) the plastic zone geometry (diamond shaped) used for JS determinations.

Previous work pursued the model analytically, for a linearly elastic [5] (or, later, non-linearly elastic [6]) material with constant thermal properties. The analytical model explained several measured fracture properties of thermoplastics the magnitude of impact fracture toughness and its dependence on impact speed [7] and the absolute magnitude of resistance to rapid crack propagation [8]. Recent results have shown that the impact fracture properties of some amorphous and crosslinked polymers show the same rate dependence [11],... 

LABORATORY TEST FOR MEASURING RESISTANCE TO RAPID CRACK PROPAGATION... 

Whether a pressurized structure will leak or burst when suddenly cracked depends on the material s resistance to rapid crack propagation and its ability to arrest a crack. Thus, the governing material property, namely the stress intensity-crack velocity relationship, is necessary input for designing pressurized pipes and vessels and establishing safe operating conditions. Unfortunately, this material property is not easily measured, and reliable data do not generally exist. 

Rapid crack propagation, dynamic fracture toughness, crack arrest, polyethylene pipes, pressure vessels... 

Nuclear Regulatory Commission and the Electric Power Research Institute to understand and develop tools for managing rapid crack propagation and crack arrest [2,3]. In this effort, methods such as optical caustics and dynamic photoelasticity were used to measure directly the instantaneous stress intensity at the tip of a rapidly propagating and arresting crack. The relationship between crack tip stress intensity and crack velocity (Figure 1) was established as the material property governing crack behavior in a structure. This relationship was later confirmed by Zehnder and Rosakis [4]. 

Laboratory Test for Measuring Resistance to Rapid Crack Propagation... 

Kanninen, M.F., et al., (1997). Design and Technical R erence to Mitigate Rapid Crack Propagation in Polyethylene Pipes for Gas Distribution. Southwest Research Institute Final Report (Contract 5088-271-1822) to the Gas Research Institute. 

High rate fracture parameters are important in the assessment of structural integrity, particularly in applications where there is a risk of rapid crack propagation. Linear elastic fracture mechanics provide a method for assessing fracture parameters under quasi-static conditions but under impact conditions various dynamic effects make both experimental measurement and analysis difficult. 

The full 3D fluid-structure-fracture (FSF) model has been first developed to simulate rapid crack propagation in plastic pipes [6], and is adopted in the present work. Apart from fluid-solid coupling issues described elsewhere [3,4,7], there are two main issues that require special care in order to develop predictive model of failures of plastic containers ... 

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