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Basis of Macro- and Microfracture Mechanics
Published in Yichun Zhou, Li Yang, Yongli Huang, Micro- and MacroMechanical Properties of Materials, 2013
Yichun Zhou, Li Yang, Yongli Huang
Damage mechanics involves the process from the presence of microdefects on the raw material or component to its growth into a macrocrack. Fracture mechanics involves the process from the macrocrack to the final fracture. Damage mechanics has gradually evolved. In 1958, Kachanov first introduced a theory that described the continuous performance variation in the material damage process using continuous variables [14]. Rabotnov, his student, later spread this theory and laid a firm foundation for damage mechanics [15]. In 1977, Janson and Hult came up with a new term "damage mechanics" [16]. At present, damage mechanics has become the frontier research area of solid mechanics, materials science, and condensed matter physics [17-22].
Damage Mechanics for Static and Fatigue Applications
Published in Raul D.S.G. Campilho, Strength Prediction of Adhesively-Bonded Joints, 2017
Ian A. Ashcroft, Aamir Mubashar
Damage mechanics is an approach to predicting failure in a material or structure by representing load induced damage through the deterioration of material properties in a constitutive equation. This can be seen in Fig. 9.1, where the material follows the abcd path, with deterioration of properties along path cd, as damage response of the material is included in the model. This can be compared with the conventional elastic-plastic response in the figure, illustrated by path abcd′ where there is no deterioration of the properties at point c, instead, strain hardening continues until failure at point d′.
Tensile strength estimation of paper sheets made from recycled wood and non-wood fibers using machine learning
Published in Cogent Engineering, 2023
Ming Li, Kaitang Hu, Suying Shao
Studies of the impact of fiber morphology on paper sheets have been carried out using various theories and equipment (Belle & Odermatt, 2016; Moral et al., 2010). Based on the theory of damage mechanics, damage will cause the ultra-structural disfigurement of fibers, which results in structure and property deterioration (Neagu et al., 2006). On the other hand, damage can be used to estimate the material property deterioration caused by changes in loading, ambient temperature, and so on. Since damage will unavoidably cause the deterioration of microstructures and macro properties during recycling, it is important to identify a damage index in the process where the damage is introduced. Thus, the changes in mechanical properties can be analyzed and described using the theory of damage mechanics of solid materials. The damage index should be a variable of interior states, which describes the irreversible changes in the structure of paper sheets (Keränen & Retulainen, 2016; Retulainen & Keränen, 2017). Hence, the damage index should be determined by some macro variables or micro parameters of paper sheets. It must also be measurable or obtainable easily.
A rock damage constitutive model and damage energy dissipation rate analysis for characterising the crack closure effect
Published in Geomechanics and Geoengineering, 2018
Tao Wen, Yourong Liu, Chenggang Yang, Xianlong Yi
Rock is a complex geological material with many complex minerals. There are many microdefects characterising with random distribution inside rocks, including microcracks, microvoids etc. The deformation and failure process of rock are accompanied by the formation, expansion and cut-through of various defects. The macro-mechanical effect can be represented by rock damage mechanics, including the development of microdefects and the process of rock failure. Kachanov (1992, 1994) first introduced the concept of damage when he was studying metal creep. On the basis of his research, damage mechanics has been developed into three blocks, the micro-damage mechanics, the macro-damage mechanics and quasi-macroscopic damage mechanics.
Continuum damage mechanics based failure prediction and damage assessment in laminated composite structures
Published in Mechanics Based Design of Structures and Machines, 2023
Gangadhara Rao T. Boyina, Vijaya Kumar Rayavarapu, Subba Rao V. V.
To exploit the potential of composites, appropriate constitutive material models (Jones 1999) are required to predict their response, especially when one attempts to obtain their mechanical properties empirically. Moreover, such models need to be suited for utilization in structural analysis to compute the behavior of laminated composite structures. The mechanics in which material damage and its mechanical effects are discussed (Janson and Hult 1977; Kachanov 1987; Krajcinovic and Lemaitre 1987) in the framework of continuum mechanics is referred to as continuum damage mechanics (CDM) or simply as damage mechanics. Namely, continuum damage mechanics is a branch of continuum mechanics used to describe the damage and fracture process ranging from the initiation of micro cavities or micro cracks to the final fracture in materials caused by the development of macro cracks. One of the most widely researched phenomena in terms of notched strength is the “hole size effect,” whereby the strength of a laminate decreases with increasing hole diameter for a constant stress concentration across the width of a specimen. Early work in the field of scaling of notched composites focused on developing semi-empirical analytical models for the prediction of notched strength. One of the earliest models was developed by Waddoups, Eisenmann, and Kaminski (1971), who applied a characteristic length to a fracture mechanics argument to predict notched strength with respect to notch size. Failure prediction of quasi-isotropic circular hole specimen configuration has been studied extensively both experimentally and computationally (Camanho, Maimí, and Dávila 2007; Green, Wisnom, and Hallett 2007; Hallett et al. 2009).