Compressive measurement

It is known that mechanical and physical properties of the amorphous and crystalline phases differ significantly [80T01]. For this reason, it is anticipated that properties of the mechanically and electrically treated film will depend explicitly on its history. Shock-compression measurements such as those carried out on amorphous materials in a thick form [80M01] will not prove characteristic of thin, treated films. 

Curran [61C01] has pointed out that under certain unusual conditions the second-order phase transition might cause a cusp in the stress-volume relation resulting in a multiple wave structure, as is the case for a first-order transition. His shock-wave compression measurements on Invar (36-wt% Ni-Fe) showed large compressibilities in the low stress region but no distinct transition. 

The work on iron-nickel alloys has described shock-compression measurements of the compressibility of fee 28.5-at. % Ni Fe that show a well defined, pressure-induced, second-order ferromagnetic to paramagnetic transition. From these measurements, a complete description is obtained of the thermodynamic variables that change at the transition. The results provide a more complete description of the thermodynamic effects of the change in the magnetic interactions with pressure than has been previously available. The work demonstrates how shock compression can be used as an explicit, quantitative tool for the study of pressure sensitive magnetic interactions. 

Interesting deviations from Gaussian stress-strain behaviour in compression have been observed which related to the Me of the networks formed, rather than their degrees of swelling during compression measurements. 

The experimental data to be considered are shown in Figure 1. They refer to previously published data on hexamethylene diisocyanate(HDI) reacting with polyoxypropylene(POP) triols and tetrols in bulk and in nitrobenzene(5-7,12) that is, to RA2 + RBj polymerisations. is the molar mass of chains between elastically effective junction points. A/Mj. has been determined directly from small-strain compression measurements on swollen and dry networks using the equations... 

This is known as the Born-Lande equation the values of Fq and n can be obtained from X-ray crystallography and from compressibility measurements, respectively. The other terms in the equation are well-known constants, and when values for these are substituted, we get ... 

H2.1 General Compressive Measurements H2.2 Textural Measurements with Special Fixtures H2.3 Texture Profile Analysis... 

Chapter H2 describes the measurement of textural properties of solid-like foods. The first unit in that chapter, unit H2.i, describes a general procedure commonly used to evaluate the texture of solid foods. This method involves the compression of the food material between two parallel plates. There are a number of empirical textural parameters which can be evaluated with this technique. Simple compressive measurements do not provide a complete textural picture of some foods untthi.i presents variations to the parallel plate compression method with the use of special fixtures. For example the use of a puncture probe or a wire cutting device provide data that may relate more directly to the consumer s evaluation of texture for products like apples and cheese, unit m.3 describes a general protocol for the evaluation of a number of sensory texture parameters. This protocol is... 

Aspect ratios of certain types of prepared specimens vary from author to author. In addition, no standardized deformation rates have been established for many of the food specimens subjected to compressive measurements. Thus, comparison of results between different laboratories is difficult if test conditions vary. As a result, valid comparisons of data may only be possible internally. 

Compressive measurements provide a means to determine specimen stiffness, Young s modulus of elasticity, strength at failure, stress at yield, and strain at yield. These measurements can be performed on samples such as soy milk gels (Kampf and Nussi-novitch, 1997) and apples (Lurie and Nussi-novitch, 1996). In the case of convex bodies, where Poisson s ratio is known, the Hertz model should be applied to the data in order to determine Young s modulus of elasticity (Mohsenin, 1970). It should also be noted that for biological materials, Young s modulus or the apparent elastic modulus is dependent on the rate at which a specimen is deformed. 

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