Strain ratio

Eor reinforcement, room temperature tensile strength and Young s modulus (stress—strain ratio) are both important. Typical values for refractory fibers are shown in Table 2. 

Plastic Stra.ln Ra.tlo. The plastic strain ratio is the ratio of strains measured in the width over the thickness directions in tensile tests. This ratio characterizes the abhity of materials to resist thinning during forming operations (13). In particular, it is a measure of the abhity of a sheet material to resist the thinning and failure at the base of a deep drawn cup. The plastic strain ratio is measured at 0°, 45°, and 90° relative to the rolling direction. These three plastic strain ratios Rq, R, and R q, are combined to obtain the average strain ratio, cahed the R or the R value, and its variation in strain ratio, cahed... 

The modulus term in this equation can be obtained in the same way as in the previous example. However, the difference in this case is the term V. For elastic materials this is called Poissons Ratio and is the ratio of the transverse strain to the axial strain (See Appendix C). For any particular metal this is a constant, generally in the range 0.28 to 0.35. For plastics V is not a constant. It is dependent on time, temperature, stress, etc and so it is often given the alternative names of Creep Contraction Ratio or Lateral Strain Ratio. There is very little published information on the creep contraction ratio for plastics but generally it varies from about 0.33 for hard plastics (such as acrylic) to almost 0.5 for elastomers. Some typical values are given in Table 2.1 but do remember that these may change in specific loading situations. 

Isotropic construction Identifies RPs having uniform properties in all directions. The measured properties of an isotropic material are independent on the axis of testing. The material will react consistently even if stress is applied in different directions stress-strain ratio is uniform throughout the flat plane of the material. 

FIGURE 34.22 Log (strain ratio) versus log (modulus) for field and oven-aged SUV/Minivan-A tires. Both sets are linear indicating oxidative aging, but the slopes are different indicating a change in composition of the wedge rubber. 

PLASTIC STRAIN RATIO, COPPER WROUGHT ALLOYS... 

Condensation polymers tend to exist below their Tg at room temperature. They typically form fairly ordered structures with lots of strong interactions between the various chains giving strong materials with some, but not much, elongation when stretched. They are normally used as fibers and plastics. They have high stress/strain ratios. 

Elasticity is nonlinear the secant modulus (the stress/strain ratio) decreases rapidly as strain increases. It can be reversible at very high strains, but this property can be rarely checked for in thermosets owing to their brittleness at T > Tg. 

The complex shear modulus, which is the complex stress to complex strain ratio ... 

For a given chain, the strain ratios 5 (q) fully determine the mean-square dimensions of the chain. In the following, they will be derived from free-energy self-consistent optimization. 

In the preceding, oc iq) (without the tilde) is the mean-square strain ratio of the q mode with respect to the unperturbed real chain with screened interactions (i.e., at r = 0), not with respect to the phantom chain accordingly, cco(q) s 1. In agreement with our assumption of a small solvent strength, will be proportional to T—, and we shall write... 

Strain Ratio of the change in length of a part to its original length (MIL). 

The crystal phases in the glass-ceramics were determined by XRD analysis. All instruments were precisely and identically set to ensure a high precision to obtain the integral peak area. The microstructure of the fresh fractured cross section of the glass-ceramics was observed by SEM. The thermal expansion coefficient (TEC) was calculated from room temperature to 500 °C at a heating rate of 5°C/min in the dilatometry analyser (NETZSCH, DIL402PC). The flexural strength was determined in a 3-point bend test at a constant strain ratio of 0.5mm/min. 

Conflicting data exist on the creep behavior of latex-modified mortar and concrete. The creep characteristics of SBR- and PAE-modified concretes reported by Ohamal l are represented in Fig. 4.40. Like ordinary cement concrete, the relationships between loading time (t) and creep strain (ec) or creep coefficient (< )) (i.e., creq) strain/elastic strain ratio) of the latex-modified concretes fit approximately the expression ... 

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