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The Right Stuff
Published in Sharon Ann Holgate, Understanding Solid State Physics, 2021
As we have already seen, elastic materials are materials that return to their original shape and size after being stretched. The elastic limit is the point up to which any stress applied to an elastic material will produce a strain that is proportional to that stress (and a strain that will disappear when the stress is removed). If stress continues to be applied to a material beyond its elastic limit, it will no longer return to its original shape. Elastic bands provide a good example of elastic behaviour when they are stretched by a moderate amount as Figure 4.8 shows. However, most of us will have discovered by playing with elastic bands as children that if they are stretched by a large amount, they become permanently stretched. All or part of them becomes much thinner, and if they continue to be stretched once they have reached this plastic stage, they will eventually break.
Plasticity
Published in G. Thomas Mase, Ronald E. Smelser, Jenn Stroud Rossmann, Continuum Mechanics for Engineers, 2020
G. Thomas Mase, Ronald E. Smelser, Jenn Stroud Rossmann
The uniaxial tensile test was introduced in Chapter 6 for elastic deformations. For plasticity, different aspects of the uniaxial tensile test are examined. Figure 10.1 shows an idealized stress-strain curve for a metal. As the load, F, is increased, the specimen undergoes elastic deformation. When the nominal stress, the Piola stress, reaches a level PY=FYA0, the elastic deformation gives way to permanent or plastic deformation. A0 is the original cross sectional area. This is termed the yield stress or the yield point and occurs at point Ⓐ in Figure 10.1, and the corresponding strain is the yield strain, eY.
Technology CAD Tools
Published in Chinmay K. Maiti, Introducing Technology Computer-Aided Design (TCAD), 2017
In addition, advanced packaging techniques have further resulted in proliferation of unwanted sources of mechanical stress, and the variations caused by mechanical stress effects have become comparable to those from lithography variations. Thus, it is important to consider the mechanical stress effects early in the design. Since we are mainly concerned with stress and strain, it is essential to understand the basics of engineering mechanics like stress, strain, and mechanical properties. Within the elastic limit, the property of a solid material to deform under the application of an external force and to regain its original shape after the force is removed is referred to as its elasticity. It is the law of Hooke, who described the elastic relation between the mechanical constraint and deformation which a material will undergo. The external force applied on a specified area is known as stress, while the amount of deformation is called the strain. In this section, the theory of stress, strain, and their interdependence is briefly discussed. Following the ATLAS manual, we describe sources of strain/stress and material parameters used for stress calculations in isotropic and anisotropic (crystalline) materials. Finally, we will discuss the simulation procedure and numerical methods used in VictoryStress.
An evaluation of 3D printable elastics for post stroke dynamic hand bracing: a pilot study
Published in Assistive Technology, 2023
Justin Huber, Stacey Slone, Babak Bazrgari
Additive manufacturing with 3D printable (3DP) materials offers rapid fabrication of complex geometries, cost-effective part customization, reduction of part counts, and decentralized manufacturing (Barrios-Muriel et al., 2020; S. Yang et al., 2015). Research on the clinical feasibility of 3DP hand devices has largely concentrated on rigid devices (Blaya et al., 2018; Fernandez-Vicente et al., 2017; Gabriele et al., 2016; Kim & Jeong, 2015; Paterson et al., 2015; Portnoy et al., 2020). Despite evidence in stroke literature supporting movement-based therapy (Kwakkel et al., 2015; Sawaki et al., 2008; Winstein et al., 2016; S. L. Wolf et al., 2008), the translation of 3DP techniques beyond rigid hand devices has been limited. Elastic materials can stretch and deform when subject to external forces, can passively store energy, and can return to their original shape when those forces are removed. The rise of 3DP elastic materials is a promising link to innovative 3DP devices that foster movement-based rehabilitation.
Investigating the free vibration of viscoelastic FGM Timoshenko nanobeams resting on viscoelastic foundations with the shear correction factor using finite element method
Published in Mechanics Based Design of Structures and Machines, 2022
Ghali Drici, Ismail Mechab, Hichem Abbad, Noureddine Elmeiche, Belaid Mechab
Viscoelasticity is generally defined as the property possessed by materials which exhibit both viscous and elastic characteristics when undergoing deformation. It should be noted that viscous materials resist shear flow and exhibit deformation that increases linearly with time when stress is applied to them (creep and relaxation). In addition, elastic materials deform when subjected to stresses, but quickly return to their original state once those stresses are removed. Moreover, in rheology a viscoelastic material presents an intermediate linear behavior between that of an ideal elastic solid that can be symbolized by a spring having a particular stiffness and that of a Newtonian viscous liquid that can be symbolized by a viscous damping coefficient. It is worth recalling that the viscosity of a material reflects its ability to dissipate energy. Different models can be used to describe the linear viscoelasticity of a material. One may mention Maxwell’s model which is well suited to viscoelastic liquids. The Kelvin–Voigt model is an elementary model that applies to viscoelastic solids. In addition, the models of Zener and Burgers, which fit the two previous cases equally well, are also worth mentioning (Maxwell 1867; Chen and Chen 2014; Chaillat and Bui 2007; Zou et al. 2021) .
A review on the application of particle finite element methods (PFEM) to cases of landslides
Published in International Journal of Geotechnical Engineering, 2022
Fhatuwani Sengani, François Mulenga
The most important feature defining the multiplicative approach is the introduction of an intermediate local configuration relative to which the elastic response of the material is characterized. The multiplicative decomposition has been widely reported on (Lee and Liu 1967; Lee, 1969; Kroner and Teodosiu 1972; Mandel 1964 &1974; Kratochvil 1973; Sidoroff 1974; Nemat–Nasser 1982; Agah–Tehrani et al. 1986; Lubliner 1984 &1986; Simo and Ortiz 1985; Simo, Kennedy, and Taylor 1988). And from a phenomenological standpoint, the total decomposition gradient F is split into the elastic and plastic components. Elastic refers to reversible deformation while plastic applies to an intermediate configuration of an irreversible deformation. The multiplicative decomposition can now be expressed as follows (Monforte et al., 2018a):