Tensile strength defined

We obtain the specific tensile strength, defined by 0 s = o-b/Ps, where ps is the specific gravity. We know that 0 s is a useful index for comparison with different materials, for example, 0 s = 220 MPa for (L) is several times larger than that for the usual steel used for the bodies of cars, Os(car) = 40-80 MPa [46]. Thus, the NOCs show specific strength 2-5 times higher than common steel with the same mass. 

Although the USP defines the knot-pull tensile strength test in terms of a surgeon s knot, most surgeons use a variety of other knots depending on... 

F Distribution In reference to the tensile-strength table, the successive pairs of daily standard deviations could be ratioed and squared. These ratios of variance would represent a sample from a distribution called the F distribution or F ratio. In general, the F ratio is defined by the identity... 

Only a small amount of work has been done up to now concerning the prediction of bond strengths and other properties based on the results of the analysis of the resin. Ferg et al. [59] worked out correlation equations evaluating the chemical structures in various UF-resins with different F/U molar ratios and different types of preparation on the one hand and the achievable internal bond as well as the subsequent formaldehyde emission on the other hand. These equations are valid only for well defined series of resins. The basic aim of such experiments is the prediction of the properties of the wood-based panels based on the composition and the properties of the resins used. For this purpose various structural components are determined by means of - C NMR and their ratios related to board results. Various papers in the chemical literature describe examples of such correlations, in particular for UF, MF, MUF and PF resins [59-62]. For example one type of equation correlating the dry internal bond (IB) strength (tensile strength perpendicular to the plane of the panel) of a particleboard bonded with PF adhesive resins is as follows [17]... 

The maximum value of it will occur when (tensile strength of the fibre, Ofu, and this is defined as the critical fibre length, Ic... 

As for the tenacity, which describes the fiber s resistance to the action of the tensile force, the quantitative index assumed most often is the tensile strength (crj (cN/tex). For the quantitative assessment of tenacity an index of mechanical long life (t) is used, proposed by Zurkow and Abasow [46,47]. This index defines the time after which, when applying a definite tensile strength and a definite temperature, the fiber breaks. 

The melt flow index describes the viscosity of a solid plastic. It is the weight in grams of a polymer extruded through a defined orifice at a specified time. The melt viscosity and the melt flow index can measure the extent of polymerization. A polymer with a high melt flow index has a low melt viscosity, a lower molecular weight, and usually a lower impact tensile strength. 

The generalized stress-strain curve for plastic shown in Fig. 2-7 serves to define several useful qualities that include the tensile strength, modulus (modulus of elasticity) or stiffness (initial straight line slope of... 

The next step is to determine an allowable working stress. This is done by using a safety factor usually of IV2 to 2V2 on the yield strength or tensile strength. If the type of stress is clearly defined, the IV2 factor is adequate otherwise, it should be higher (Chapter 2, Safety Factor). 

The ultimate tensile strength (UTS) of a material refers to the maximum nominal stress that can be sustained by it and corresponds to the maximum load in a tension test. It is given by the stress associated with the highest point in a nominal stress-nominal stress plot. The ultimate tensile strengths of a ductile and of a brittle material are schematically illustrated in Figure 1.11. In the case of the ductile material the nominal stress decreases after reaching its maximum value because of necking. For such materials the UTS defines the onset of plastic instability. 

How do we determine the tensile modulus, tensile yield point, elongation at break and tensile strength of a polymer What characteristics of the polymer define these properties ... 

The tensile test is performed by placing a specially shaped specimen in the heads of the testing machine. The specimen is pulled apart through a hydraulic or mechanical loading system (Figure 15.33). Most ordinary tensile tests are conducted at room temperature and the tensile load is applied slowly. The unit measure of tensile strength is the pascal (Pa), or newtons per square meter (N-nf2), and is defined by the following equation ... 

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