Failure behavior

Other strength criteria are described by Sendeckyj [2-28]. Tennyson, MacDonald, and Nanyaro addressed the next logical step in a curve-fitting procedure, namely a third-order polynomial fit to failure data [2-29], However, the added complexity of their criterion has limited its use even though they identified some loading conditions under which their criterion is necessary to properly describe the actual failure behavior. 

Fracture mechanic The fracture mechanics theory developed for metals is also adaptable for use with plastics. The basic concepts remain the same, but since metals and plastics are different they require different techniques to describe their fatigue-failure behaviors. Some of the comments made about crack and fracture influences on fatigue performance relate to the theory of fracture mechanics. The fracture mechanics theory method, along with readily... 

The composition, density, thermal properties mechanical properties (elastic, viscoelastic failure behavior) of these mock explosives are given in Ref 7... 

An important consideration in all failure studies is the influence of material variability. Statistical distributions of failure incidence must be known and properly accounted for if reliability limits are to be set. Wiegand and co-workers (14, 113) have discussed propellant sample and batch variability, and its effect on failure behavior, in numerous reports. These studies point out the statistical nature of failure and the fact that knowledge of the distributions is required to set conservative design values for motor stress and strain capability. Statistical distributions permit the prediction of the probability of failure, but mission considerations dictate the allowable failure frequencies. 

Uniaxial tensile criteria can lead to gross inaccuracies when applied to situations where combined stresses lead to failure in multiaxial stress fields. Often one assumes that combined stresses have no influence and that the maximum principal stress governs the failure behavior. An improved approach applied to biaxial tension conditions relies upon a pragmatic biaxial correction factor which is applied to uniaxial data,... 

Majerus (61, 62) has approached the failure behavior of highly filled polymers by a thermodynamic treatment in which the ability to resist rupture is related to the propellant s ability to absorb and dissipate energy at a certain rate. An energy criterion which requires failure to be a function of both stress and strain was originally stated by Griffith (36) for brittle materials and later adapted to polymers by Rivlin and Thomas (80). Williams (115) has applied an energy criterion to viscoelastic materials such as solid propellants where appropriate terms are included for viscous energy dissipation. 

Fig. li. The change in failure at the single-fiber level as shown by the embedded single-fiber test is mirrored by the failure behavior at the macroscopic level. The increase in adhesion also tracks the same between the ITS results and 0° flexure data. 

Meschke, F., Alves-Riccardo, P., Schneider, G.A. and Claussen, N. Failure behavior of alumina and alumina/silicon carbide composites with natural and artificial flaws , J. Mat. Res. 12 (1997) 3307-3315. 

Blugan, G., Dobedoe, R., Gee, I., Orlovskaya, N., Kuebler, J., Failure behavior of high toughness multilayer Si3N4 and Si3N4-TiN based laminates, Key Eng. Mater., submitted, 2005. 

As in a continuous flow process downstream apparatus is directly linked to upstream devices, the complete production line is interrupted in case of a failure upstream. It will be examined if this failure behavior can be corrected either by the design of several parallel lines or by supplying buffer tanks, additional spare pumps, machines,... 

Generally, when testing materials with a nonlinear stress-strain behavior, the tests should be conducted under uniform stress fields, such that the associated damage evolution is also uniform over the gauge section where the material s response is measured. Because the stress field varies with distance from the neutral axis in bending tests, uniaxial tension or compression tests are preferred when characterizing the strength and failure behavior of fiber-reinforced composites. 

An essential step in developing an interactive reliability model requires formulating a deterministic failure criterion that reflects the limit state behavior of the material. Miki et al.,21 and de Roo and Paluch22 have adopted this approach in computing the reliability of unidirectional composites. In both articles, the Tsai-Wu failure criterion is adopted, where different failure behavior is allowed in tension and compression, both in the fiber direction and... 

Two representative failure criteria formulated by Wiliam and Warnke,23 and Ottosen24 satisfy the requisite failure behavior of reduced tensile strength, and sensitivity to hydrostatic stress. For the sake of brevity, the discussion here is limited to the Willam-Warnke criterion. The Willam-Wamke criterion can be expressed as... 

The effects of morphology (i.e., crystallization rate) (6,7, 8) on the mechanical properties of semicrystalline polymers has been studied without observation of a transition from ductile to brittle failure behavior in unoriented samples of similar crystallinity. Often variations in ductlity are observed as spherulite size is varied, but this is normally confounded with sizable changes in percent crystallinity. This report demonstrates that a semicrystalline polymer, poly(hexamethylene sebacate) (HMS) may exhibit either ductile or brittle behavior dependent upon thermal history in a manner not directly related to volume relaxation or percent crystallinity. 

Figure 15.14 Different failure behaviors depending on relative values of fiber and matrix failure strains and fiber volume fraction.

The sudden introduction of a crack in a pressurized pipe or vessel can result in two widely different failure behaviors with widely different consequences. If the crack does not... 

In order to examine the creep failure behavior of filled rubbers, a carbon filled SBR was examined. The distribution of tg in this case becomes a unimodal distribution as shown in Figure 7. The exponential distribution obtained from pure SBR is also shown in the same figure in order to compare the change in the type of distribution from exponential to unimodal type. 

The purpose of the research introduced here is to approach closely to the failure mechanism of rubbery polymers from a phenomenological view. Many of excellent observations on the time dependent failure behavior of rubbery polymers have been done by those scientists, T. L. Smith (5> 6, 7) F- Bueche (8),... 

Finally, the concept of linear additivity of damage serves as a useful framework for analyzing the failure behavior of polymeric materials. Examining the deviations of the experimental data from linear additivity behavior should provide a basis for expanding the concept to a more general damage law in which the... 

The failure behavior of composite propellants, which are filled elastomers, is complicated by the presence of filler particles. Under loading, phenomena such as cavitation and debonding can arise at or near the filler-matrix interface. (1, 2) Identification of a practical failure criterion for such... 

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