Mechanical properties of materials

The Institute has many-year experience of investigations and developments in the field of NDT. These are, mainly, developments which allowed creation of a series of eddy current flaw detectors for various applications. The Institute has traditionally studied the physico-mechanical properties of materials, their stressed-strained state, fracture mechanics and developed on this basis the procedures and instruments which measure the properties and predict the behaviour of materials. Quite important are also developments of technologies and equipment for control of thickness and adhesion of thin protective coatings on various bases, corrosion control of underground pipelines by indirect method, acoustic emission control of hydrogen and corrosion cracking in structural materials, etc. 

M. M. Eisenstadt, Introduction to Mechanical Properties of Materials, The Macmillan Co., New York, 1971. 

Karnes, C.H., The Plate Impact Configuration for Determining Mechanical Properties of Materials at High Strain Rates, in Mechanical Behavior of Materials Under Dynamic Loads (edited by Lindholm, U.S.), Springer-Verlag, New York, 1968, pp. 270-293. 

While evaluating the mechanical properties of materials, attention must also be given to availability. Sometimes an alloy of attractive properties is not commercially available. It may be possible to obtain special heats for large parts such as appreciable quantities of plate, large forgings, and so forth, but it may be difficult to contain smaller quantities required for incidental pieces. 

For many years hydrogen was considered as a deleterious impurity which deteriorates mechanical properties of materials. This is clearly illustrated by hydrogen embrittlement of ferrous metals and alloys. The main effort of the research was aimed therefore at the study of hydrogen embrittlement and at the ways to avoid it. ... 

Table 2.23 Selected mechanical properties of materials used in total joint replacement ...

Since the early 1980s, the study of mechanical properties of materials on the nanometre scale has received much attention, as these properties are size dependent. The nanoindentation and nanoscratch are the important techniques for probing mechanical properties of materials in small volumes. Indentation load-displacement data contain a wealth of information. From the load-displacement data, many mechanical properties such as hardness and elastic modulus can be determined. The nanoindenter has also been used to measure the fracture toughness and fatigue properties of ul-... 

It is useful to get preliminary learning on the mechanical properties of materials under simple static tension. Members of engineering structures are often subjected to steady axial loads in tension. Moreover, the response of materials subjected to other types of loading also can often be explained or predicted on the basis of knowledge of their behaviour under simple tension. In addition, such behaviour is usually quite easy to study experimentally. 

Chemists clearly contribute to both synthesis and analysis of materials, less so in the physical and mechanical properties of materials and their applications in systems. 

Creep tests give extremely important practical information and at the same time give useful data on those interested in the theory of the mechanical properties of materials. As illustrated in Figure 1, in creep tests one mea-... 

The mechanical properties of materials, though not often studied in detail, can have a profound effect on solids processing. Clearly, tableting properties are influenced by the elastic and plastic deformation properties as well as the viscoelastic properties of a material. As we have pointed out, the powder flow properties are also affected, as well as the tendency of materials to set up on storage. Because of the importance of mechanical properties, it is important to be able to... 

One of the more recently exploited forms of thermal analysis is the group of techniques known as thermomechanical analysis (TMA). These techniques are based on the measurement of mechanical properties such as expansion, contraction, extension or penetration of materials as a function of temperature. TMA curves obtained in this way are characteristic of the sample. The technique has obvious practical value in the study and assessment of the mechanical properties of materials. Measurements over the temperature range - 100°C to 1000°C may be made. Figure 11.19 shows a study of a polymeric material based upon linear expansion measurements. 

Surface mechanical properties (nanoindentation). Nanoindentation technique has an important role in the characterisation of mechanical properties of materials... 

Most of the adsorbents used in the adsorption process are also useful to catalysis, because they can act as solid catalysts or their supports. The basic function of catalyst supports, usually porous adsorbents, is to keep the catalytically active phase in a highly dispersed state. It is obvious that the methods of preparation and characterization of adsorbents and catalysts are very similar or identical. The physical structure of catalysts is investigated by means of both adsorption methods and various instrumental techniques derived for estimating their porosity and surface area. Factors such as surface area, distribution of pore volumes, pore sizes, stability, and mechanical properties of materials used are also very important in both processes—adsorption and catalysis. Activated carbons, silica, and alumina species as well as natural amorphous aluminosilicates and zeolites are widely used as either catalyst supports or heterogeneous catalysts. From the above, the following conclusions can be easily drawn (Dabrowski, 2001) ... 

Anelasticity therefore affects the mechanical properties of materials. As seen below, its study yields unique information about a number of kinetic processes in materials, such as diffusion coefficients, especially at relatively low temperatures. 

These findings are of singular importance in the light of the steady widening of the application range of man-made crystals, whose purity or stimulated modifications allow control of the mechanical properties of materials. 

The mechanical properties of materials are of enormous influence on the way these can be processed. After a molten metal has cooled to a solid, the solid metal is mechanically moulded into the desired form. The way of cooling and the final shape to a large extent determine the properties of the product. By means of a heat treatment it is possible to alter the properties of some metals. In this process the polycrystalline material is converted to a less polycrystalline form and eventually a state is reached which comes close the the ideal state, i.e. the metal is nearlv monocrvstalline (figure 10.10). 

The development of composite structural materials based on ordered nanostructures in a matrix material has been surprisingly difficult to accomplish, and has only proved successful in a few cases165. Part of the difficulty is that the surface chemistry of the nanostructures must be controlled carefully so that the structure truly is a composite and that the nanostructured phase in the matrix is ordered. Given the importance of nano-scale heterogeneity in determining the mechanical properties of materials, this area is one of great theoretical and practical interest. 

Mechanical and viscoelastic behaviour of materials can be determined by different kind of instrumental techniques. Broadband viscoelastic spectroscopy (BVS) and resonant ultrasound spectroscopy (RUS) are more commonly used to test viscoelastic behavior because they can be used above and below room temperatures and are more specific to testing viscoelasticity. These two instruments employ a damping mechanism at various frequencies and time ranges with no appeal to time-temperature superposition. Using BVS and RUS to study the mechanical properties of materials is important to understanding how a material exhibiting viscoelasticity will perform. 

Budanov A.V., Kustov A.I., Migel I.A. (2004) The Study of Changes of Physical - Mechanical Properties of Materials in a Condensed State under Hydrogen influence using Fault Detection Acoustic Microscopy Methods. // Hydrogen materials science..., Science Series, II. Mathematics, Physics..., v. 72, 203-215. 

The mechanical properties of materials involve various concepts such as hardness, shear and bulk modulus. The group III nitrides are now mostly used as fihns or layers grown by metal organic vapour phase epitaxy (MOVPE) or molecular beam epitaxy (MBE) on sapphire, GaAs or SiC. The lattice parameters of the substrate do not generally match those of the deposited layer, and therefore, stresses appear at the interface and in the layer and modify its physical properties. Hence, it is necessary to have a good knowledge of these properties. 

In general it appears that the electrical properties of organic materials practically do not change, as long as the mechanical properties of materials withstand the action of radiation. 

The materials community has made significant advances in predicting mechanical properties of materials and initiation of defects using hybrid multiscale simulation. This is one of the application areas where multiscale simulation has advanced the most. Several nice reviews and perspectives have already been published (Maroudas, 2000, 2003 Miller and Tadmor, 2002 Rudd and Broughton, 2000). Therefore, it suffices to give only a brief account of the evolution of multiscale simulation in this area here. One of the earlier and... 

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