Strain-based failure models

Concrete structures typically contain steel reinforcement. Steel reinforcement exhibits rate effects and yields in a ductile manner until it breaks at an ultimate strain greater than approximately 20 percent. The reinforcement model plays an important role in modeling reinforced concrete behavior (Holomek Bajer 2012, Jiang et al. 2012). Our approach is to explicitly model the reinforcement (beam elements) separately from the concrete (hex elements) using an elasto-plastic material model with yielding, hardening, rate effects, and plastic strain-based failure. 

Maximum-stress-and-strain-based failure criteria were used by Harris and Adams (1984) to predict the failure of single lap joints. A nonlinear finite element analysis with an elasto-plastic material model for the adhesive and adherends was carried out. The selection of stressor strain-based failure criterion was based on the results of uniaxial tensile test results. For an un-toughened adhesive, a brittle failure was observed and a maximum stress criterion was used, while for a toughened adhesive, failure was ductile and a maximum-strain-based criteria was used. However, these criteria are difficult to implement when highly localized stress concentrations or stress singularities exist in an adhesive joint. 

As mentioned above, for a creep stress exponent, n<3, the crack tip stress field for a continuously growing crack is the applied A -field. For this case, based on the model of Purushothaman and Tien48 the crack growth rate is, for strain-controlled failure,... 

A thorough understanding of the mechanics of UHMWPE is important for efforts to improve the performance of orthopedic components. Elastic properties, resistance to plastic deformation, stress and strain at failure, fatigue behavior, and wear resistance of UHMWPE are believed to play roles in the life expectancy of an UHMWPE bearing. There exists a fundamental relationship between a material s intrinsic mechanical properties, akin to state variables, and how a structure made of the material will respond under mechanical stimuli. This material-specific fundamental relationship is referred to as a constitutive model. A validated constitutive model is a required input to a finite element (FE)-based simulahon of a structure made of the material in question. 

The development of the WPCs for load-bearing structural applications necessitates the characterization of their strain rate-dependent mechanical properties. In this regard, the effect of strain rate on flexural properties of WPG was addressed by Tamrakar and Lopez [49]. The strain at failure was not significantly influenced by the strain rate variation. A prediction model for the effects on strain rate on the modulus of elasticity (MOE) of WPG material was demonstrated based on the viscoelastic standard solid model. Yu et al. [50] analyzed the variability of the dynamic young s modulus of WPG, which was measured by different non-destructive test (NDT) methods. They also estimated the correlativity between the dynamic Young s modulus and the static MOE of WPG. 

As shown in Sect. 2, the fracture envelope of polymer fibres can be explained not only by assuming a critical shear stress as a failure criterion, but also by a critical shear strain. In this section, a simple model for the creep failure is presented that is based on the logarithmic creep curve and on a critical shear strain as the failure criterion. In order to investigate the temperature dependence of the strength, a kinetic model for the formation and rupture of secondary bonds during the extension of the fibre is proposed. This so-called Eyring reduced time (ERT) model yields a relationship between the strength and the load rate as well as an improved lifetime equation. 

Mechanical models based on elastic assumptions are not generally applicable to high-strain deformation where specific failure mechanisms should be... 

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