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Tension test principal stresses

In a recent attempt to bring an engineering approach to multiaxial failure in solid propellants, Siron and Duerr (92) tested two composite double-base formulations under nine distinct states of stress. The tests included triaxial poker chip, biaxial strip, uniaxial extension, shear, diametral compression, uniaxial compression, and pressurized uniaxial extension at several temperatures and strain rates. The data were reduced in terms of an empirically defined constraint parameter which ranged from —1.0 (hydrostatic compression) to +1.0 (hydrostatic tension). The parameter () is defined in terms of principal stresses and indicates the tensile or compressive nature of the stress field at any point in a structure —i.e.,... [Pg.234]

According to the maximum principal stress theory, failure occurs when one of the three principal stresses reaches a stress value of elastic limit as determined from a uniaxial tension test. This theory is meaningful for brittle fracture situations. [Pg.28]

According to the maximum shear stress theory, the maximum shear equals the shear stress at the elastic limit as determined from the uniaxial tension test. Here the maximum shear stress is one half the difference between the largest (say principal stresses. This is also known as the Tresca criterion, which states that pelding takes place when... [Pg.28]

The concept of shear failure in thick sections of brittle material such as concrete is obscure and in many instances it could be misleading. One clear concept is that concrete failure can easily be put to the test if it is assumed that it is governed by the principal tensile and compressive stress caused by the so-called shear . The problem with this simple concept is the limitation on these stresses. In the prestressed concrete reactor vessels due to variations in loading conditions these principal stresses at any time at any point may vary from biaxial and triaxial compression to compression—tension—tension in any combination. These instant changes can bring about any kind of failure. For example, it may be pure flexural-cumnominal shear failure or principal tensile or compressive failure or by the so-called shear compression failure or in any combination of these. It must be borne in mind that the type of failure is directly related to the vessel overall layout. Before discussing the individual sample examples, it is necessary to know what the above-mentioned terms are and what effect they have on the prestressed concrete vessels. [Pg.319]

Since in a simple tension test, the lateral surfaces of the specimen are supposed to be unloaded, the principal stresses corresponding to the directions 2 and 3 vanish. For deformation (59) the strain invariants become ... [Pg.236]

Of the many theories developed to predict elastic failure, the three most commonly used are the maximum principal stress theory, the maximum shear stress theory, and the distortion energy theory. The maximum (principal) stress theory considers failure to occur when any one of the three principal stresses has reached a stress equal to the elastic limit as determined from a uniaxial tension or compression test. The maximum shear stress theory (also called the Tresca criterion) considers failure to occur when the maximum shear stress equals the shear stress at the elastic limit as determined from a pure shear test. The maximum shear stress is defined as one-half the algebraic difference between the largest and smallest of the three principal stresses. The distortion energy theory (also called the maximum strain energy theory, the octahedral shear theory, and the von Mises criterion) considers failure to have occurred when the distortion energy accumulated in the part under stress reaches the elastic limit as determined by the distortion energy in a uniaxial tension or compression test. [Pg.26]

The stress distribution given by Eq. 15.1 is shown in Fig. 15.1 for a vessel with r /fj = 2.2, The maximum stress is in the hoop direction and is at the inner surface where r = r. As the pressure is increased, the stresses increase until they reach a maximum limiting stress where failure is assumed to occur. For thin vessels the ASME Code assumes that failure occurs when the yield point is reached. This failure criterion is convenient and is called the maximum principal stress theory. In thick vessels the criterion usually applied for ductile materials is the energy of distention theory. This theory states that the inelastic action at any point in a body under any combination of stresses begins only when the strain energy of distortion per unit volume absorbed at the point is equal to die strain energy of distortion absorbed per unit volume at any point in a bar stressed to the elastic limit under a state of uniaxial stress as occurs in a simple tension test. The equation that expresses this theory is given by... [Pg.283]

For each of the failure criteria, we will generate biaxial stresses by off-axis loading of a unidirectionally reinforced lamina. That is, the uniaxial off-axis stress at 0 to the fibers is transformed into biaxial stresses in the principal material coordinates as shown in Figure 2-35. From the stress-transformation equations in Figure 2-35, a uniaxial loading obviously cannot produce a state of mixed tension and compression in principal material coordinates. Thus, some other loading state must be applied to test any failure criterion against a condition of mixed tension and compression. [Pg.105]

Determination of the fourth-rank tensor term F. 2 remains. Basically, F.,2 cannot be found from any uniaxial test in the principal material directions. Instead, a biaxial test must be used. This fact should not be surprising because F-,2 is the coefficient of the product of a. and 02 in the failure criterion. Equation (2.140). Thus, for example, we can impose a state of biaxial tension described by a, = C2 = c and all other stresses are zero. Accordingly, from Equation (2.140),... [Pg.116]

Figure 16 illustrates several test specimens which have been used (46) in the multiaxial characterization of solid propellants. The arrows indicate the direction of load application. The strip tension or strip biaxial test has been used extensively in failure studies. It can be seen that the propellant is constrained by the long bonded edge so that lateral contraction is prevented and tension is produced in two axes simultaneously. The sample is free to contract normal to these axes. The ratio of the two principal tensile stresses may be varied from 0 to 0.5 by varying the bonded length of incompressible materials. [Pg.213]

For polymers, the torsion test is often the test of choice because, as discussed in Chapter 2, the time dependent (viscoelastic) behavior of polymers is principally due to the deviatoric (shear or shape change) stress components rather than the dilatoric (volume change) stress components. Typically, constant strain rate tests are often used for either tension, compression or torsion as discussed in Chapter 3. If the material is linear elastic, the stress rate is proportional to the strain rate as the modulus is time independent. That is. [Pg.159]

If a load is static or changes relatively slowly with time and is applied uniformly over a cross section or surface of a member, the mechanical behavior may be ascertained by a simple stress-strain test these are most commonly conducted for metals at room temperature. There are three principal ways in which a load may be applied namely, tension, compression, and shear (Figures 6.1a, b, c). In engineering practice many loads are torsional rather than pure shear this type of loading is illustrated in Figure 6.Id. [Pg.170]


See other pages where Tension test principal stresses is mentioned: [Pg.34]    [Pg.369]    [Pg.3892]    [Pg.178]    [Pg.191]    [Pg.580]    [Pg.47]    [Pg.595]    [Pg.89]    [Pg.75]    [Pg.147]    [Pg.216]    [Pg.405]    [Pg.241]    [Pg.139]    [Pg.367]    [Pg.203]   
See also in sourсe #XX -- [ Pg.27 , Pg.28 , Pg.29 ]




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