On the use of the Theory of Critical Distances to estimate the dynamic strength of notched 6063-T5 aluminium alloy

Abstract

In this paper the so-called Theory of Critical Distances is reformulated to make it suitable for estimating the strength of notched metals subjected to dynamic loading. The TCD takes as its starting point the assumption that engineering materials' strength can accurately be predicted by directly post-processing the entire linear-elastic stress field acting on the material in the vicinity of the stress concentrator being assessed. In order to extend the used of the TCD to situations involving dynamic loading, the hypothesis is formed that the required critical distance (which is treated as a material property) varies as the loading rate increases. The accuracy and reliability of this novel reformulation of the TCD was checked against a number of experimental results generated by testing notched cylindrical bars of Al6063-T5. This validation exercise allowed us to prove that the TCD (applied in the form of the Point, Line, and Area Method) is capable of estimates falling within an error interval of ±20%. This result is very promising especially in light of the fact that such a design method can be used in situations of practical interest without the need for explicitly modelling the non-linear stress vs. strain dynamic behaviour of metals.

Dynamic Assessment of Induced Stresses and In-situ Stress Reorientation during Multi-Stage Hydraulic Fracturing in Unconventional Reservoirs

“…To quantify the critical radius, where a significant change in the state of field stress along propagating fracture occurs, the theory of critical distance (TCD) (Taylor, 2007) was applied and further extended in this study. The critical distances (TCD) found application in predicting fatigue and failure in a wide range of materials and components (Taylor, 2007;Yin et al, 2014;Louks et al, 2014). The TCD was also applied towards predicting fracture of rocks and minerals (Lajtai, 1971;Ito et al, 1991).…”

A comparison of the two approaches of the theory of critical distances based on linear-elastic and elasto-plastic analyses

“…It has also been proved that the TCD can be used to predict static fracture in ductile metallic materials containing various stress raisers and subjected to both uniaxial and multiaxial loading [8]. Moreover, in papers [9,10] was shown that Theory of Critical Distances is suitable for predicting the strength of notched metallic materials subjected to dynamic loading.…”

Evaluation of quasistatic and dynamic strength of components with stress concentrators based on the theory of critical distances

“…This fact requires the creation of adequate models and methods to predict the mechanical behavior of the materials in a wide range of the conditions of external effects, including intensive dynamic loads for materials having both direct and inverse strain rate sensitivity in view of the effect of the non-local destruction in the area of stress concentrators. To overcome this problem, we propose to use a theory of critical distance (TCD), whose effectiveness has already been shown for the prediction of the fracture of laboratory specimens of various materials and a complex geometry under quasistatic and dynamic loading [2,3]. …”