Stresses and Fractures

Figure 8.11. Fragment size and fracture stress dependence on tensile loading strain rate for oil shale.

The dependence of the debonding stress on adhesion and particle size can be used to explain the observed yield and fracture stress in mineral particle filled polymer [29]. In the case of not treated precipitated CaC03 or Si02, the debonding stress ctd is higher than the local fracture... 

Creation of high strength states (increase of yield stress and fracture stress), based on new achievements of materials science and on application of the innovative technologies of material producing and processing increase of material stiffness (increase of its elastic moduli). 

FIGURE 17.4 Variation in textural properties, (a) Stress (o) versus strain (sh) curves and fracture points (X). (b) Relation between elastic shear modulus G and fracture stress (some types of gels of various concentrations of the networkforming material. (From approximate results by H. Kimura et al. J. Food Sci. 38 (1973) 668.)... 

The ore material is elasto-plastic with isotropic hardening mle. The plastic properties are described by yield stress Rp = 9.946 q MPa and fracture stress Rm = 12.661 MPa, which are given by bounded histograms, see Figures 6 and 7. 

Figure 7. Stochastic material properties of the ore (histograms for yield stress and fracture stress).

Zar] have shown non-monotonous temperature dependencies of dynamic yield and fracture stress of two refractory Ni based Co-Fe-Ni alloys (IN738LC and PWA 1483) for gas turbines measured under... 

Fig. 2.43 Critical flow stress (ffc) and fracture stress (

In Table I, some mechanical parameters of several crosslinked and noncrosslinked high polymers are listed. At 4.2 K, they have within 15% and 30% similar Young s modulus and fracture stress values. 

For polyurethanes. Quested et al. (148) found that A)3//Aa was greater than dTgIdP, except at pressures close to 1 bar. At high pressures, dTJdP reached a limiting value of 10.4°C/kbar. The effect of pressure has been studied for ultrasonic frequencies (149) and fracture stress differences (150). 

Fig. 85 Porcelain the creep rate spectrum (compression, a = 9 MPa), and fracture stress vs temperature dependence [331]...

In the Ref [49] the two deformation-strength characteristics prediction was carried out strain up to fracture and fracture stress 0. For the value theoretical estimation two methods can be used. The first from them does not include in the calculation of molecular characteristics and, hence, does not take into account their change, in any case, directly [51], This method is based on the cluster model of polymers amorphous state structure notions [ 14], taking into account the order availability, and the limiting draw ratio value in this case is given as follows [51] ... 

FIGURE 14.6 The dependences of elasticity modulus E ) and fracture stress (2) on extrusion draw ratio X for componors UHMPE - bauxite [44],... 

Tensile properties such as fracture stress and strain and Young s modulus of unidirectional ramie fiber/SPI and ramie fiber/MSPI composites tested in the longitudinal and transverse directions are presented in Table 12.6. As the data indicate, composites with stearic acid-modified resin showed significantly higher Young s modulus and fracture stress values as compared to the composites without stearic acid. These trends were similar to the results obtained for pure resins. In the case of composites, the fracture stress in the transverse direction also increased. Tensile properties of the unidirectional composites in the transverse direction are known to be a function of the resin and/or the interface properties. It is clear that interfacial property increased because tensile properties improve after stearic acid modification as indicated from data presented in Table 12.6. 

Figure 1.9 Effect of strain rate on the fracture of spherulitic iPP (a) Scanning electron micrographs of the fracture surface, in which fracture along interspherulite boundaries is seen at the three lowest strain rates, while intraspherulite fracture is seen at 10 m/s (b) yield stress and fracture stress versus strain rate (c) fraction of intraspherulite fracture versus strain rate. Sandt [39]. Reproduced with permission of...

For materials that are not suited for standard tensile testing, an alternative method for assessing the elastic modulus as well as yield and fracture stress is the three-point bend test. The sample in the form of a small bar d cm wide and b cm thick is supported on one side at two points spaced L cm apart while a force is applied at the midpoint on the opposite side. The elastic modulus as well as the )deld and fracture stress can be calculated from the force vs. bending data along with the geometry of the system. The flexure strength is given by... 

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