Crack behavior

T. Hoshide. Simulation of microstructural effects on cracking behavior in biaxial fatigue. Mater Sci Res Int 5 119, 1997. 

In a recent study, Saintier et al. ° investigated the multiaxial effects on fatigue crack nucleation and growth in natural mbber. They found that the same mechanisms of decohesion and cavitation of inclusions that cause crack nucleation and crack growth in uniaxial experiments were responsible for the crack behavior in multiaxial experiments. They studied crack orientations for nonproportional multiaxial fatigue loadings and found them to be related to the direction of the maximum first principal stress of a cycle when material plane rotations are taken into account. This method accounts for material rotations in the analysis due to the displacement of planes associated with large strain conditions. 

FIGURE 5.6 Evaluation of seal wetting and cracking behavior on a zirconia substrate. 

Hydrothermal Stability and Cracking Behavior of Silicoaluminophosphate Molecular Sieve-37 with Different Silicon Contents... 

The large value of Kj for naphthalene shows that the presence of one hydrocarbon may greatly influence the rate of reaction of another hydrocarbon on the catalyst. Thus, the cracking behavior of a mixture of hydrocarbons need not be given by a simple sum of their pure cracking rates weighted according to their individual partial pressures. 

J.C. Newman A review of modeling small-crack behavior and fatigue-life predictions for aluminum alloys. J. Fatigue Fract. Eng. Mat. Struct. 17, 429-439 (1994)... 

Ishiyama C, Sakuma T, Shimojo M, Higo Y (2002) Effects of humidity on environmental stress cracking behavior in poly(methyl methacrylate). J Polym Sci Part B Polym Phys 40(1) 1—9... 

Li J, Arnold JC, Isaac DH (1994) Environmental stress cracking behavior of urethane methacrylate based resins - I. Environmental crazing and cracking under bending conditions. J Mater Sci 29(12) 3095—3101... 

In summary, short cracks form epsilon CTPZ development, whereas long cracks usually lack the required shear components to generate the shear-band pair, niis creates the anomalous short crack behavior. When epsilon CTPZs form, the shear bands stabilize the crack, thus allowing the DCG process to continue to much higher apparent AK, values, further differentiating from the non-epsilon CTPZ DCG crack growth behavior. 

Nuclear Regulatory Commission and the Electric Power Research Institute to understand and develop tools for managing rapid crack propagation and crack arrest [2,3]. In this effort, methods such as optical caustics and dynamic photoelasticity were used to measure directly the instantaneous stress intensity at the tip of a rapidly propagating and arresting crack. The relationship between crack tip stress intensity and crack velocity (Figure 1) was established as the material property governing crack behavior in a structure. This relationship was later confirmed by Zehnder and Rosakis [4]. 

The results shown in Figure 8 provide the required data for computing the dynamic crack behavior how fast md what distance the crack runs and when and where it arrests. However, the measurements of dynamic stress intensity require special expertise and are costly and time consuming. When different batches of material need to be routinely evaluated, such as polyethylene material for piping, such tests are impractical. A way was sought to simplify the procedure. 

Last is that the mechanism of compact failure also depends on strain rate. Figure 21-118 illustrates schematically the crack behavior observed in compacts as a function of capillary number. At low Ca, compacts fail by brittle fracture with macroscopic crack propagation, whereas at high Ca, compacts fail by plastic flow, which is more desirable to promote growth. 

Stress Cracking Behavior of HDPE Geomembranes and Its Prevention U.S. Environmental Protection Agency. 1993, EPA/600/SR-93/092. 

There are a number of considerations that must be addressed when formulating quantitative 13c NMR procedures - these include solvent effects, spectral overlap, line widths, dynamic and nuclear Overhauser effects and detailed assignments. The steps required to develop sound quantitative methods will be the subject of this chapter. It is imperative that excellent quantitative methods be established so that NMR can be utilized in studies of polymer structure-property relationships. Polymer molecular structure needs to be related to the incipient solid state structure and ultimately to observed solid state physical properties such as density, flexural moduli, environmental stress cracking behavior, to name a few. 

Now assume that in the example of interest here, preliminary analysis of the motor case shows that at the most likely points of debonding. Mode I loading dominates adhesive crack behavior. Two test methods that could appropriately be used to determine Ya Mode I are the blister test and the double cantilever beam (26). If one assumes that the first is chosen, then a layer of the adhesive (the solid propellant) is cast on a plate of the material from which the motor case is made. This plate contains a hole that has been fitted with a pressure connection. This connection is used to pressurize (with air, inert gases, fluids, etc.) the region between the plate and propellant, arid thereby produces a blister. The value of Ya can be determined from measurement of the pressure at which this blister grows as a function of its diameter (26). In our case, let us assume a series of tests yields a "least value" for Ya of J/m2. 

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