Intermediate stress relieve

ISR (Intermediate Stress Relieve) This is a heat treatment procedure used during the fabrication cycle prior to allowing the material temperature to cool below the preheat temperature. Done at 1150°F. Must be done in... 

Fibrous structures represent a grain refinement of columnar structure. Stress-relieving additives, eg, saccharin or coumarin, promote such refinement, as do high deposition rates. These may be considered intermediate in properties between columnar and fine-grained structures. 

The chlorine headers popular in Europe are dual laminate headers, which are preferred over FRP for environmental reasons. The dual laminate has an inner ring of less brittle PVC-C of 5-mm thickness for corrosion protection and an outer layer of 10-15 mm thickness of FRP for structural strength, the intermediate layer being 5 mm of resin-rich FRP 5 ION or 197-3. The outer layer contains a flame retardant and is added after the dual laminate is stress relieved. The chlorinated PVC (CPVC)/FRP dual laminate header is fabricated from CPVC tubing up to 60 cm in diameter. The dual laminate headers have a life of 8-10 years vs the 6-12 years of life of FRP, at a comparable cost. 

At low viscosities, glass forming melts usually behave as Newtonian liquids which immediately relax to relieve an applied stress. At extremely high viscosities, however, these liquids respond to the rapid application of a stress as if they were actually elastic materials. It follows that there must exist an intermediate range of viscosities where the response of these melts to application of a stress is intermediate between the behavior of a pure liquid and that of an elastic solid. Since this behavior has aspects of both viscous flow and elastic response, it is known as viscoelasticity, or viscoelastic behavior. 

Finally, consider the case where the viscosity of the liquid has an intermediate value. Since flow requires time, the instantaneous response of the element to the displacement will be the same as that for a purely elastic material. The application of the force to the piston, however, will result in flow of the liquid to relieve the strain in the spring and the piston will rise in the dashpot. Eventually, the force will decrease to zero as the spring recovers to its original length and the displacement of the bottom of the element to point B will be permanent. If we calculate the stress as a function of time, we find that ... 

Subsequent recombination produces a secondary ozonide (or just ozonide). In small olefins, ozonide formation is generally a facile process. In stretched rubber, however, ozonide formation is more difficult, since the cleaved intermediates may be forcefully separated to relieve the stress. Interestingly, both crosslinking and chain scission products may form during rubber ozonation. Rubbers containing trisubstituted double bonds (e.g., polyisoprene, IR, and butyl rubber, IIR) are more prone to yield chain scission products. Several pathways can lead to chain scission. 

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