Failure tensile

Madronero et al [52] give a diffusion model for the sword-in-sheath failure mode of VGCF. 

In the stress-strain curve of a VGCF, there is a toe-in corresponding to an apparent modulus increase of 28%, termed strain stiffening, which occurs due to the improvement of the orientation of the fiber s graphitic planes as the load is apphed. A mean value for E [51] of fibers under 10 pm diameter is 237 49 GPa. Ruland [53] pictured graphite fibers 

Weibull [54] introduced a model that used the weakest link principle, where the 

Integration of this equation gives the mean strength a  

The physical and mechanical properties of VGCF [55-57] and their use in composites [58,59] are given. 

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Romanchenko and Stepanov (1981) recognized that spall in an elastic-plastic material can involve plastic release to the tensile failure stress followed by elastic recovery as stress relaxation at the spall plane proceeds. Thus, the... 

The Burchell model s prediction of the tensile failure probability distribution for grade H-451 graphite, from the "SIFTING" code, is shown in Fig. 23. The predicted distribution (elosed cireles in Fig. 23) is a good representation of the experimental distribution (open cireles in Fig. 23)[19], especially at the mean strength (50% failure probability). Moreover, the predicted standard deviation of 1.1 MPa con ares favorably with the experimental distribution standard deviation of 1.6 MPa, indicating the predicted normal distribution has approximately the correct shape. 

Fig. 23. Predicted and experimental tensile failure probability distributions for grade H-451 graphite.

Fig. 24. The effect of particle size on the predicted tensile failure distribution of grade H-451 graphite.

Fig. 28. A comparison of experimental and predicted tensile failure probabilities for four graphites with widely different textures AGX, H-451, IG-110 and AXF-5Q.

As the second term is less than 1, a tensile failure in the 2-direction would be expected, (b) Maximum Strain Criterion From the data given... 

Dynamic tensile failure, called spall, is frequently encountered in shockloading events. Tension is created as compression waves reflect from stress-free surfaces and interact with other unloading waves or release-wave profiles. Spall has been widely studied by authors such as Curran, Ivanov, Dremin, and Davison and there is considerable data. As shown in Fig. 2.19, the wave profiles resulting from spall are characterized by an additional loading pulse after release of pressure. The late pulse is caused by wave reflection from the internal void of the tensile fracture. Analysis of such wave profiles yields appropriate spall stress values. 

The value of F,2 then depends on the various engineering strengths plus the biaxial tensile failure stress, a. Tsai and Wu also discuss the use of off-axis uniaxial tests to determine the interaction strengths such as F.,2 [2-26]. 

Figure 3-49 Rosen s Tensile Failure Model (After Rosen [3-27])...

B. Walter Rosen, Tensile Failure of Fibrous Composites, AIAA Journal, November 1964, pp. 1985-1991. 

The tensile failure strain of oxides grown on EN2 steel between 600°C and 900°C lies in the range 1 x 10 " to 2.5 x 10""" . Components in service may be stressed beyond these failure strains, leading to scale cracking. 

The design of the threads requires control, to prevent excessive shear, resulting in stripping the threads when torqued, and also to limit hoop stresses that can result in tensile failure. Although the mechanics of stress analysis for screw threads are readily available, the equations for them can be rather complicated. 

Strength can be measured in compression, in tension, in shear and transversely (flexural strength). However, if we exclude plastic flow as a means of failure, then materials can only fracture in one of two ways (1) by the pulling apart of planes of atoms, i.e. tensile failure, or (2) by the slippage of planes of atoms, i.e. shear failure. Strength is essentially a measure of fracture stress, which is the point of catastrophic and imcontrolled failure because the initiation of a crack takes place at excessive stress values. 

The tensile strength of compacts [30] also provides useful information. Excellent specimens of square compacts are necessary to conduct the tensile testing. For this reason, a split die [31 ] (Fig. 2) is used to make compacts that are not flawed. The split die permits triaxial decompression, which relieves the stresses in the compact more uniformly in three dimensions and minimizes cracking. These specimens are then compressed with platens 0.4 times the width of the square compacts in the tensile testing apparatus. (Fig. 3). Occasionally nylon platens and side supports are used to reduce the tendency to fail in shear rather than tension. The force necessary to cause tensile failure (tensile forces are a maximum... 

Blast loaded structures produce high reaction loads at column supports. This usually requires substantial base plates as well as high capacity anchor bolts. Achieving full anchorage of these bolts is of primary importance and will usually require headed bolts or plates at the embedded end of the bolts to prevent pullout. When anchor bolts are securely anchored into concrete, the failure mechanism is a ductile, tensile failure of the bolt steel. Insufficient edge distance or insufficient spacing between bolts results in a lower anchorage capacity and a brittle failure mode. 

Rosen, B.W. (1964). Tensile failure of fibrous composites. AlAA J. 2, 1985-1991. 

Zweben, C. (1968). Tensile failure of fiber composites. AIAA J. 6, 2325-2331. 

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