Mixed failure

Block polymer B differs substantially in its failure characteristics from BP A polycarbonate. For the block polymer a mixed failure mode predominates in three-point bend tests of notched specimens from —100°-90°C. In the mixed mode craze breakdown and plane strain fracture occur first inside the specimen subsequently shear failure occurs in the surface regions of the specimen. Shear lips (11) are formed as a result. Shear lips are also found on the notched Izod impact fracture surfaces of block polymer B, implying that the same mixed mode of failure occurs under high speed loading conditions. 

Fig. 18.9 Al peel strength as a function of pretreatment time and type of modification. Full symbols interfacial failure between Al and PTFE empty symbols interfacial failure between tape and Al half-filled symbols mixed failure.

Cost and downtime parameter values for a typical valve in the network were obtained subjectively from an expert. In order to maintain confidentiality, all costs are recorded relative to the cost of inspection. Thus the cost of inspection is the taken to be the unit cost. The time imit is also arbitrarily specified. Plausible values for the parameters of the mixed failure time distribution were a matter of debate. For the weak items, a small characteristic life might be explained by poor installation a larger value of characteristic life might reflect the use of a different component supplier. In the base case, we set the characteristic life of weak components jji = 2 and shape parameter = 2.5. For the strong components, we set the characteristic hfe jj2 = 18 and shape parameter 2=5. In this case, the hfetimes of the weak and strong are well separated in the mixture. The proportion of weak items is taken to be 0.10. A sensitivity ofthe results to the values ofthe mixture parameters is carried out. 

In this paper we propose a two-phase inspection policy for a single component preparedness system, in which the component itself may arise from a heterogeneous population. Criteria for the determination of optimal policy are presented. The work extends that of Vaurio (1999) who considered single phase polices for components from a homogeneous population. Reliability smdies of mixed failure distributions are well documented. Maintenance policy modelling when components in systems have mixed failure distributions is less well developed, and this paper makes a contribution to this area. 

T6/M11113 adhesive) where 1 cm of fresh surface was created. In Fig. 33, curve (a) represents the EE observed when the crack moved entirely along the interfaces leaving behind a relatively clean "metal surface. Curve (b), on the other hand involved large patches of cohesive failure with some interfacial failure. The differences in the peak emission during peeling and the decay curves reflect the enhanced emission one would expect from interfacial failure compared to "mixed failure. 

Mixed failure modes resulting from failure in more than one of the above regions are commonly observed. Clearly, with good design, option 1 should not occur with thick metal adherends however, this may be required in applications such as blister packaging when polymeric laminates of thin metal foils are used. 

Fig. 2. Failure surfaces of bonds between zinc and toughened epoxy resin (a) region of cohesive failure within the resin (b) region of apparently mixed failure. (Source as Fig. 1.)...

FIGURE 11.29 Potential failure surfaces that need to be studied in soil nail design (a) external failure, (b) internal failure, and (c) mixed failure. (After Cornforth, D., Landslides in Practice, Investigation, Analysis, and Remedial/ Preventative Options in Soils, Wiley, 2005.)... 

Canvas-canvas T-peel bonds. 2"/min. peel rate. A = adhesive failure at canvas C = cohesive failure A/C = mixed failure. Two coats of adhesive applied to each piece of canvas with 52 wire wound rod. 1/2 hour between coats. Green strength tested within 1 minute of joint assembly under indicated pressure. 

Low pressure assembly - 2 drawdown coats strengths in lbs./ inch/width A = adhesive failure at canvas C = cohesive failure C/A = mixed failure. 

More recent work with the PPQ in Eq. (3) has involved chromic acid and phosphoric acid anodized Ti surface treatments, which result in better moisture resistance but less thermal resistance than the surface from phosphate fluoride treatment. Chromic acid anodized Ti TSS provided strengths of 5000 psi at 25°C (cohesive failure), 2,000 psi at 232°C after 5,000 hours at 232°C in air (mixed failure) and low strengths at 232°C after 10,000 hours at 232°C in air (100% adhesive failure).An anodized Ti surface degrades when bonding temperatures approaching 370 C are employed. This may have been one of the factors which caused lower strengths at 232 C after aging. 

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