Fracture dependencies

This illness is mainly characterized by an age-related bone loss. The detection of osteocalcin in bone was the starting point for a series of studies on the role of vitamin K-dependent proteins in bone development and maintenance and on possible supplemantation therapies. Epidemiologic studies found differences in the risk of hip fractures depending on the dietary vitamin K... 

The manner in which a particle fractures depends on (i) the nature of the particle and (ii) the manner in which the fracture force is applied. A number of terms have been used to describe the different mechanisms of single particle fracture. The different terms considered here are abrasion, cleavage, shatter, and chipping. It may be pointed out that in practice these events do not occur in isolation. Real breakage involves a combination of these processes, with the proportions changing, depending on the equipment, and on the manner each particle is stressed within it. 

The conditions under which CO gas bubbles form and the reaction scale fractures depend on the relative permeabilities of CO and oxygen through the reaction scale, which typically consists of a three-phase mixture of mullite, alumina, and an aluminosilicate glass. If the CO permeability is greater than... 

The influence of hydrogen on fracture depends on hydrogen concentration, C, in the sites where localized material damage might occur. The accumulation of hydrogen in these zones proceeds by diffusion from external or internal sources, i.e., local fracture event takes place when and where hydrogen concentration reaches some critical value, Cor, which is conditioned by the stress-strain state in material [1], This is expressed by the following equation... 

Figure 8.32 shows the effect of filler type and concentration on the mode of fracture. Several factors are responsible for the behavior. CaT (calcium terephthalate) fillers have good adhesion to the matrix and have an elongated shape. CaCOs (1) and (2) are both untreated fillers of smaller particle sizes (2.2 and 4.1 (dm, respectively). CaCO (3) is a stearate coated filler (better dispersion, but poor adhesion to matrix) with a particle size of 6.1 im. The mode of fracture depends on filler concentration, the degree of adhesion to the matrix, and particle size. 

Another consequence of stress relaxation is that, for a higher stress applied to a material, it takes a shorter time before a high strain is attained and a shorter time before failure occurs (i.e., yielding or fracture, depending on the material). This is illustrated in Figure 17.6b. 

Thus, these two concepts are equivalent. In the classical failure context, fracture depends on some critical combination of stress at the crack tip and the tip radius, neither of which are precisely defined (or definable) or accessible to measurement. For experimental accuracy and practical apphcation, it is more appropriate to use the accessible quantities o and a to determine the fracture toughness of the material. It is to be recognized that the quantities involving a a and a represent the crackdriving force, and 2y, in the Griffith sense, represents the material s resistance to crack growth, or its fracture toughness. 

Tensile Strength - The maximum tensile stress that a specimen can sustain in a test carried to failure. Note The maximum stress can be measured at or after the failure or reached before the fracture, depending on the viscoelastic behavior of the material. Also called ultimate tensile strength, tensile ultimate strength, tensile strength at break. 

A number of phenomena, such as extradate swell and melt fracture, depend on blend composition and, in turn, affect the process. Melt fracture obviously puts limitations to the production rate. Swelhng of fibers at the exit from spinneret holes was reported to be a non-linear function of the blend composition for a number of systems [Han and Yu, 1972]. 

Mechanical Strength Stress measurements can be conducted using SEM and TEM. A report on the mechanical properties of polyethylene under deformation and fracture was presented [41]. Three types of fractures depending on the molecular weight and linearity, namely, crazing, elongation, and the interfacial splitting of spherulites were described. 

Higher pan speed creates more physical stress for particles/tablets, which could contribute to attrition and fracture depending on particle/tablet integrity. 

Figure 5.17 provides the key to understanding the effects of test conditions and materials structure upon the fracture behaviour of polymers. All materials contain small defects of some kind, but whether they are large enough to cause brittle fracture depends upon the relative positions of the yield and fracture lines on the diagram, and therefore upon rr and Kiq. 

There is great diversity in the way in which fibres fracture, depending on the fibre type and the mode of application of stress. The subject can be studied at three levels the macroscopic applied forces the microscopic level, which shows the path of fibre breakage and the response of the molecules. Attempts at theoretical interpretations of the gross experimental observations in terms of molecular effects can be misleading, because abstract statements about the forces involved are related to abstract views of imperfectly understood structures. The intermediate level, for which the scanning electron microscope (SEM) provides concrete evidence, must be taken into account in order to understand the mechanisms of failure. 

Ductile fracture dok-Cl [MF L, MF, fr. ductilis, from ducere] (14c) (ductile rupture) adj. The breaking or tearing, most commonly in tension, of a test specimen or part after considerable unrecoverable stretching (plastic strain) has occurred. Since the mode of fracture depends on conditions as well as material, the distinction between ductile and brittle fracture, which latter occurs after relatively little, recoverable strain, is not always clear. Low temperatures, especially below the glass transition (Tg), and high rates of strain favor brittle behavior, while the opposites favor ductile behavior. 

The growth of cracks eventually leads to intergranular fractures or transgranular fractures, depending on the nature of the crack. Sometimes, mixed fractures are observed that partly follow the grain boundaries, partly traverse the grains. Figure... 

Figure 1.1 Scheme of correlations between polymerization, molecular structure, morphology, processing conditions, and micro- or nanomechanical mechanisms of deformation and fracture depending on loading conditions, all of which determine the ultimate mechanical properties... 

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