Elastic Constants - Strength of Materials [Book]
PDF | Brazilian disk compression has been proposed as an alternative for KeywordsBrazilian disk-Elastic constants-Failure-Digital image correlation- Optical technique . plane strain, and the stress ﬁeld does not depend on the elastic constants of View. Show abstract However, it worth noting that the tensile elastic. These results have given rise to the view that pressure and temperature derivatives of wave . 6, is an expression of the temperature behavior of the elastic constants. .. which are derived by assuming either stress continuity or strain (dis-. Elastic constants are very important quantities to describe the . and deriving the elastic constants from the strain–stress relationship .
If the deformation is sinusoidal in time, Poisson's ratio may depend on frequency, and may have an associated phase angle. Specifically, the transverse strain may be out of phase with the longitudinal strain in a viscoelastic solid. Get pdf of a research article on this. Poisson's ratio and phase transformations Poisson's ratio can vary substantially in the vicinity of a phase transformation.
Typically the bulk modulus softens near a phase transformation but the shear modulus does not change much. The Poisson's ratio then decreases in the vicinity of a phase transformation and can attain negative values. Phase transformations are discussed further on the linked page.
Young's modulus - Wikipedia
Poisson's ratio, waves and deformation The Poisson's ratio of a material influences the speed of propagation and reflection of stress waves. In geological applications, the ratio of compressional to shear wave speed is important in inferring the nature of the rock deep in the Earth.Stress, strain and elastic constants
This wave speed ratio depends on Poisson's ratio. Poisson's ratio also affects the decay of stress with distance according to Saint Venant's principle, and the distribution of stress around holes and cracks. Analysis of effect of Poisson's ratio on compression of a layer. What about the effect of Poisson's ratio on constrained compression in the 1 or x direction? Constrained compression means that the Poisson effect is restrained from occurring.
This could be done by side walls in an experiment. Also, compression of a thin layer by stiff surfaces is effectively constrained. Moreover, in ultrasonic testing, the wavelength of the ultrasound is usually much less than the specimen dimensions.
The Poisson effect is restrained from occurring in this case as well. In Hooke's law with the elastic modulus tensor as Cijkl we sum over k and l, but, due to the constraint, the only strain component which is non-zero is e Let us find the physical significance of that tensor element in terms of engineering constants.
One may also work with the elementary isotropic form for Hooke's law. There is stress in only one direction but there can be strain in three directions.
So Young's modulus E is the stiffness for simple tension, with the Poisson effect free to occur. The physical meaning of Cis the stiffness for tension or compression in the x or 1 direction, when strain in the y and z directions is constrained to be zero.
The reason is that for such a constraint the sum in the tensorial equation for Hooke's law collapses into a single term containing only C For example, as the linear theory implies reversibilityit would be absurd to use the linear theory to describe the failure of a steel bridge under a high load; although steel is a linear material for most applications, it is not in such a case of catastrophic failure.
In solid mechanicsthe slope of the stress—strain curve at any point is called the tangent modulus. It can be experimentally determined from the slope of a stress—strain curve created during tensile tests conducted on a sample of the material. Directional materials[ edit ] Young's modulus is not always the same in all orientations of a material. Most metals and ceramics, along with many other materials, are isotropicand their mechanical properties are the same in all orientations.
However, metals and ceramics can be treated with certain impurities, and metals can be mechanically worked to make their grain structures directional.
These materials then become anisotropicand Young's modulus will change depending on the direction of the force vector. Anisotropy can be seen in many composites as well. Among the binary materials are solid solutions and compounds, the latter often being ordered intermetallic compounds.
One challenge associated with using published experimental data for elastic moduli is that the spread in the reported values for a given system can be quite large, depending on the details of the experimental conditions and techniques employed.
What is Poisson's ratio?
Efforts aimed at developing databases of elastic moduli from first-principles computational methods have been undertaken in previous work e. Such a computational approach provides an advantage that all of the data can be derived in a consistent manner, facilitating comparisons across materials chemistries.
In the present work we expand on this approach. Specifically, we present here the to-date largest database of calculated elastic properties of crystalline inorganic compounds, ranging from metals and metallic compounds to semiconductors and insulators.
Strength of Materials by V. Ramasamy, P. Purushothama Raj
These calculations are part of a high-throughput HT effort 36undertaken within the framework of the Materials Project MP www. The database of elastic tensors currently consists of over 1, materials and is being updated regularly. The elastic properties are obtained using first-principles quantum-mechanical calculations based on Density Functional Theory DFT.
The remainder of the paper is organized as follows. We then give an overview of the structure of the data, followed by a description of our results. Finally, we describe the verification and validation tests to assess the precision and accuracy of the chosen density functional and the HT algorithms employed in the calculations.
Methods Generation of elasticity data In this launch of the elastic constant database we tabulate results for a subset of 1, compounds chosen from those present in the current MP database.