Computational mechanics stress

The pulsations can cause the use of excess horsepower when compared to the ideal or a system design that reduces pulsations and thereby improves cylinder performance and efficiency. The pulsation shaking forces in the suction and discharge dampeners (bottles) can be evaluated by computer analysis, and the magnitude and frequency in hertz can be reduced to an acceptable level by adjusting the dimensions (size) of the dampeners. The magnitude of the internal forces directly affects the mechanical stress on the nozzles of the cylinder and of the dampeners. Compressor... 

Molecular dynamics simulations have been used in a variety of ways. They can be used to compute mechanical moduli by studying the response of a model of the bulk polymer to a constant stress or strain, and to study the diffusion of molecules in membranes and polymers.There are numerous biomolecular applications. Structural, dynamic, and thermodynamic data from molecular dynamics have provided insights into the structure-function relationships, binding affinities, mobility, and stability of proteins, nucleic acids, and other macromolecules that cannot be obtained from static models. 

General physical laws often state that quantities like mass, energy, and momentum are conserved. In computational mechanics, the most important of these balance laws pertains to linear momentum (when reckoned per unit volume, linear momentum may be expressed as the material density p times velocity v). The balance equation for linear momentum may be considered as a generalization of Newton s second law, which states that mass times acceleration equals total force. As we saw in the previous section, stresses in a material produce tractions, which may be considered as internal forces. In addition, external forces such as gravity may contribute to the total force. These are commonly reckoned per unit mass and are usually referred to as body forces to distinguish them from tractions, which may be considered as surface forces. For a one-dimensional motion, balance of linear momentum requires that (37,38)... 

Liquid crystals have found an important place in modem life. Just look around we see them in our clocks, computer displays, TV screens, telephones and calculators, car dashboards, photo-cameras, etc. Other applications include slide projection systems, spatial light modulators, temperature sensors and even liquid crystal lasers. In all these technical innovations, which appeared over the life of only a single generation, liquid crystals occupy a key position. This is because they consume a barely perceptible amount of energy when they change their state under external influences such as temperature, electric field, mechanical stress or whatever. In addition, there are very important biological aspects of liquid crystals. 

The stresses obtained from the analyses—one example of this is demonstrated in Table 7.30—must be superimposed by the operational stresses of the component in question. Depending on the function and safety-related importance of the installation, other stress factors, like those resulting from accidents etc., can be superimposed as well. Stress assumptions are used to document the static stability and functionality of the technical installation. In general, this is achieved by the computation of stresses occurring in the supporting cross sections. For this purpose, simple methods are stated in the regulations and standards set up to the fields of construction and mechanical engineering. 

Sapountzakis, E.J. c Mokos, V.G. 2003. Warping Shear Stresses in Nonuniform Torsion by BEM, Computational Mechanics, 30(2) 131-142. 

For molecular liquids, Mishima et al. [24] found an amorphous-amorphous transition in water. The transition has recendy been studied in details [12]. Computer simulations also suggest the existence of LLT(s) in water [5,11,12,17,18]. Based on these findings, the connection of amorphous-amorphous transition and LLT in water was suggested and actively studied [11,12]. However, the LLT is hidden by crystallization in water, even if it exists. This makes an experimental study on the LLT extremely difficult especially for bulk water. It was also pointed out that the role of mechanical stress involved in amorphous-amorphous transition may complicate the connection [25]. 

Computed stresses are based on test thickness at test temperature. Since water pressure is a short-term condition, the allowable stresses for structural parts such as supports are frequently increased by a factor of 1.2. The upper limit of stress in the vessel shell during a hydrotest of pressure parts is not specified by the Code. However, it is a good engineering practice to limit the maximum membrane stress in any part of the vessel during a hydrotest to 80 percent of the yield strength. Thermal expansion stresses and local mechanical stresses will be absent and need not be considered. 

Th. Fett, D. Munz, Stress intensity factors and weight functions. Computational Mechanics Publ., Billerica, Massachusetts, 1997... 

In Chapter 12, Cemescu et al. present a reverse engineering application in the context of dental engineering. The aim is to efficiently and effectively assess the mechanical quality of manufactured complete dentures in terms of their behavior to mechanical stresses e.g. detect areas likely to underperform or crack in normal operation mode. The reverse engineering pipeline presented covers the steps of 3D model acquisition by means of scanning and surface reconstruction, creation of a finite element mesh suitable for numerical simulations, and the actual computation of stress and strain factors in presence of induced model defects. 

The DCB test, the blister test, and several other geometries are somewhat amenable to the analytical analyses needed for fracture mechanics. As a consequence, most early fracture mechanics analyses focused on such geometries. Modern computational methods, particularly finite element methods (FEM), have lifted this restriction. A brief outline of how FEM might be used for this purpose may be helpful. Inherent in fracture mechanies is the concept that natural cracks or other crack-like discontinuities exist in materials, and that failure of an object generally initiates at such points [13,16,17,23-25]. Assuming that a crack (or a debonded region) is situated in an adhesive bond line, modern computation techniques can be used to facilitate the computation of stresses and strains throughout a body, even where analytical solutions may not be convenient or even possible. 

Select a hoUow shaft, usually a standard pipe size, that meets the mechanical stress requirements [eqs. (21-7) and (21-8)]. Compute the critical speed... 

D. H. Chen (1994) General singular stress field in fracture mechanics, in Computational and Experimental Fracture Mechanics (Ed. H. Nisitani), Computational Mechanics Publications, Southhampton, UK, Boston, USA, p.213. 

Recently, computer simulation of a whole cell under mechanical stresses has received increasing attention because of the critical effects of stresses on battery life. This section introduces relevant schema used in two recent publications [55, 56]. 

When a complex joint is to be introduced in a structure, the ideal situation is to test that specific joint. However, this approach is very expensive. Before real joints or prototypes are built, the designer should first come up with a good prediction of the failure load based, among other things, on the basic mechanical properties of the adhesive. The basic properties can mean the elastic properties, such as the Young s modulus and the Poisson s ratio in case the analysis is linear elastic. However, for the more realistic theoretical methods that take into account the nonlinear behavior of the adhesive, the yield stress, the ultimate stress, and the failure strain are necessary. The stress-strain curve of adhesives is necessary for designing adhesive joints in order to compute the stress distribution and apply a suitable failure criterion based on continuum mechanics principles. 

Herrmann, K.P. and Ferber, F., Numerical and experimental investigations of branched thermal crack systems in self-stressed models of unidirectional ly reinforced fibrous composites. In Computational Mechanics 88, eds. S.N. Atiuri and G. Yagawa, Springer Verlag, Berlin/Heidelberg/New York, 1988, 8.V.1-8.V.4. 

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