Failure locus

PMDA-ODA on Al 0,. A minor improvement is noticed in the peel force of PMDA-ODA on Al20, when APS is applied to the surface. From the surface analysis results one can see that the APS was not retained on the IPA cleaned sapphire surface to any detectable level, which is likely the cause for no significant improvement in the peel force. The minor improvement in the results may have to do with a possible surface cleaning effect of the sapphire surface with APS solution. The data in Table 3 show that the failure locus has not changed significantly by the APS or T H exposure, being essentially in the polyimide film close to the polyimide/ceramic interface. 

The locus of failure in all PMDA-ODA/MgO cases is consistently a mixed mode type leaving ceramic on the polyimide failure surface, and leaving polyimide on the ceramic failure surface. APS application prior to polyimide coating does not change the failure locus or the peel strength behavior of these interfaces. 

Figure 5. Polarized transmitted light photomicrograph at x 70 of a typical fiber break for a water-sized E-glass fiber embedded in a coupon of DER 383/DACH epoxy matrix at greater strain. The matrix crack, while still evident, has noi extended appreciably and evidence of interfacial debonding can be seen. The failure locus changes from matrix to matrix/interfacial because of the arresting of the matrix crack by the bulk matrix away from the fiber surface.

Figure II. Photographs of 0° epoxy-sized E-glass fiber laminates tested in flexure showing the edge ci the specimen. The failure locus extends through the sample thickness as well as by propagating delaminations along the tensile surface of the specimen.

Fig. 23. Critical stresses

Since is a real number, it alone cannot fully characterize the crack tip field. In order to specify K, which has two real components, the phase angle ip defined by Eq. (5) is also required. Using this definition, a point in the (( , ip) plane is uniquely related to a point in the (JCj, Ku ) plane. Following the concept of failure locus introduced by Rice [20] for a given phase angle ip, the interface crack will... 

Figure 2.12. Failure locus in terms of stress versus crack length separated into three regions (A, B, and C) of response.

SE images of a matched pair of tensile failed PET fibers are shown in Fig. 4.30. A classical slow fracture zone, or mirror, is seen adjacent to the locus of failure. A typical ridged or hackle morphology is exhibited as the crack propagates and accelerates away from the failure locus. In this study, an inorganic residue from the polymer process was shown to be the cause of failure [295]. The value of such a fractography is that... 

The conversion of the analytical simple shear model for the Jenike failure locus into principal stress space and implication of the model for hopper design... 

The mechanistic equation for the Jenike failure locus is converted into equations of principal stress and the relationship to each other is shown graphically. The basic form of the parametric failure function equations are developed from the bulk property coefficients of the Jenike failure locus equation. It is shown how different forms of failure function are created by the type of dependency of the bulk property coefficients on the equilibrium stress and how these different forms have implications for the design of the outlet size of hoppers. 

Converting (3) into principal stress equations can only be achieved parametrically using the slope of the failure locus, which is obtained by differentiation, where tan(i )) is the instantaneous slope of the locus. 

Birks, M.S.A. Bradley, R.J. Famish, The Conversion of The Analytical Simple Shear Model For The Jenike Failure Locus Into Principal Stress Space and the Implication of The Model for Hopper Design, 3rd. Israeli Conference for handling and Conveying of Particulate Solids, The Dead Sea, 29 May, 2000. 

Failure locus described by normal and tangential maximum stresses bars show 1 standard deviation (From Goglio and Rossetto [2008], copyright Elsevier)... 

For the U-form hybrid structures, a comparison for the performance of both uncoated and coated inserts has been done. Figure 8. A valuable improvement in both stiffness and strength has been found with all of the metal inserts studied. An increase in the maximum torque value of about 30% has been achieved. A failure locus in both cases has been detected on the side contact between metal profile edges and the over-molded thermoplastic dne to the formation of shear stress over the contact area. Another failure has taken place at the intersection points of the ribs due to the high tensile and eompression stresses along both rib directions. 

---