Topic
Fracture toughness
About: Fracture toughness is a research topic. Over the lifetime, 39642 publications have been published within this topic receiving 854338 citations.
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TL;DR: In this article, a two parameter fracture model is proposed to include this nonlinear slow crack growth and the critical effective crack extension is dictated by the elastic critical crack tip opening displacement, CTODc.
Abstract: Attempts to apply linear elastic fracture mechanics (LEFM) to concrete have been made for several years. Several investigators have reported that when fracture toughness, Klc, is evaluated from notched specimens using conventional LEFM (measured peak load and initial notch length) a significant size effect is observed. This size effect has been attributed to nonlinear slow crack growth occurring prior to the peak load. A two parameter fracture model is proposed to include this nonlinear slow crack growth. Critical stress intensity factor, KIcS, is calculated at the tip of the effective crack. The critical effective crack extension is dictated by the elastic critical crack tip opening displacement, CTODc. Tests on notched beam specimens showed that the proposed fracture criteria to be size independent. The proposed model can be used to calculate the maximum load (for Mode I failure) of a structure of an arbitrary geometry. The validity of the model is demonstrated by an accurate simulation of the experimen...
786 citations
TL;DR: A review of the development and the state of the art in dynamic testing techniques and dynamic mechanical behaviour of rock materials can be found in this article, where a detailed description of various dynamic mechanical properties (e.g., uniaxial and triaxial compressive strength, tensile strength, shear strength and fracture toughness) and corresponding fracture behaviour are discussed.
Abstract: The purpose of this review is to discuss the development and the state of the art in dynamic testing techniques and dynamic mechanical behaviour of rock materials. The review begins by briefly introducing the history of rock dynamics and explaining the significance of studying these issues. Loading techniques commonly used for both intermediate and high strain rate tests and measurement techniques for dynamic stress and deformation are critically assessed in Sects. 2 and 3. In Sect. 4, methods of dynamic testing and estimation to obtain stress–strain curves at high strain rate are summarized, followed by an in-depth description of various dynamic mechanical properties (e.g. uniaxial and triaxial compressive strength, tensile strength, shear strength and fracture toughness) and corresponding fracture behaviour. Some influencing rock structural features (i.e. microstructure, size and shape) and testing conditions (i.e. confining pressure, temperature and water saturation) are considered, ending with some popular semi-empirical rate-dependent equations for the enhancement of dynamic mechanical properties. Section 5 discusses physical mechanisms of strain rate effects. Section 6 describes phenomenological and mechanically based rate-dependent constitutive models established from the knowledge of the stress–strain behaviour and physical mechanisms. Section 7 presents dynamic fracture criteria for quasi-brittle materials. Finally, a brief summary and some aspects of prospective research are presented.
781 citations
TL;DR: In this paper, an epoxy resin, cured with an anhydride, has been modified by the addition of silica nanoparticles, and the measured modulus was compared to theoretical models, and good agreement was found.
777 citations
TL;DR: In this paper, the growth of cracks in photoelastic material and glass under compression is studied as part of an investigation of brittle fracture of rock, where the most severely stressed crack is inclined at about 30° to the axis of compression.
Abstract: The growth of cracks in photoelastic material and glass under compression is being studied as part of an investigation of brittle fracture of rock. In compression the most severely stressed crack is inclined at about 30° to the axis of compression. Such cracks, when either isolated or placed in an array, grow along a curved path which becomes parallel with the direction of compression. When this direction is attained, growth stops, unless applied compression is increased considerably. Cracks in certain en echelon arrays start to grow at much smaller applied stress than that required to enlarge an isolated crack.
771 citations
TL;DR: In this paper, an approximate stress analysis has indicated the importance of both the impression radius and the ratio of the hardness to the fracture toughness in the development of the observed fractures, which has been used to examine several important consequences of indentation fracture.
771 citations