Crack initiation design

Typically, ozone cracking initiates at sites of high stress (flaws) on the mbber surface. Thus, in general, mbber articles should be designed to rninirnize potential sites of high elongation such as raised lettering. Similarly, the use of clean molds helps to reduce the incidence of surface flaws. 

A bolt fails when it can no longer provide the support it is designed for. Fracture is the separation of a solid body into two or more parts under the action of stress. It consists of crack initiation and propagation. 

Although steam cracking was initially designed for ethylene manufacture, it is only economically justified if tbe different hydrocarbons which it produces are properiy upgraded as petrochemical intennediates. Hence although ethane only produces ethylene as an upgradable product, in the case of propane an attempt is made to profit from the sale of ethylene and propylene, and, in the case of the liquid petroleum fractions (naphtha... 

Extensive design and testing conducted on the DAVINCH vessels monitoring of fatigue damage and crack initiation remote operation using robotic arm to transport munition into vessel very heavy dual-walled construction of vessel and door. 

Design can also be made to minimize locations with stress concentration, which can act as crack initiation sites and locations where coatings can crack. The design... 

A circular hole in a region of a product that is under tensile stress can lead to crack initiation. Contrast the mechanisms in a brittle plastic like polystyrene and a ductile plastic like polycarbonate (when the hole diameter is much less than the part thickness). How can the design of the polystyrene part be modified to avoid such crack initiation ... 

Weldments are the preferential sites of crack initiation in elevated temperature structures. In the RCC-MR code ( 8.5.2.1), when the design is based on an elastic analysis this behaviour is taken into account by use of admissible stresses specific to the joints. These admissible stresses of welded joints depend on the quality of the weld and its mechanical characteristics. They are obtained by multiplying the allowable stresses in the weld by an efficiency coefficient which takes account of the extent of the non-destructive examination performed. The allowable stresses for the weld are deduced... 

All corners in reinforced PPS parts should have a radius of 60% of the wall thickness. This will eliminate stress concentration points and potential sites for crack initiation, and it will also help to create smoother flow patterns during filling to reduce the potential for molded-in stresses and void formation. Reinforced PPS is a particularly notch-sensitive semicrystalline thermoplastic, so sharp inside corners create crack initiation points and must he avoided in part designs. 

Effect of design and operating temperature on time to crack initiation in nozzle weldments. 

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