Creep temperature

Alloy Density p(Mg m- l Young s modulus E(GPa) Yield strength aJMPaj E/P E Vp E Vp- Oy/P" Creep temperature rc)... 

Not only are the creep compliance and the stress relaxation shear modulus related but in turn the shear modulus is related to the tensile modulus which itself is related to the stress relaxation time 0. It is therefore in theory possible to predict creep-temperature relationships from WLF data although in practice these are still best determined by experiment. 

The effect of heat, whether generated externally or by other mechanisms within the polymer itself, will be to raise the temperature. An increase in temperature will accelerate most of the degradation mechanisms listed, such as oxidation, chemical attack or mechanical creep. Temperature alone can cause thermal expansion, while at very high temperatures polymers will decompose, although this may be masked by the effects of oxidation. 

Cured Epoxy Requirements. In order to comply with multiple needs identified above, the epoxy pot should have a compressive yield strength of greater than 9000 psi. In addition, for brackish and seawater applications an arbitrary specification of zero creep at 50°C at 1000 psi under seawater for 3000 hours has been established. Applications at higher temperatures would obviously demand a higher zero creep temperature. 

Fig. 5.2 Comparison of creep behavior and time-dependent change in fiber and matrix stress predicted using a 1-D concentric cylinder model (ROM model) (solid lines) and a 2-D finite element analysis (dashed lines). In both approaches it was assumed that a unidirectional creep specimen was instantaneously loaded parallel to the fibers to a constant creep stress. The analyses, which assumed a creep temperature of 1200°C, were conducted assuming 40 vol.% SCS-6 SiC fibers in a hot-pressed SijN4 matrix. The constituents were assumed to undergo steady-state creep only, with perfect interfacial bonding. For the FEM analysis, Poisson s ratio was 0.17 for the fibers and 0.27 for the matrix, (a) Total composite strain (axial), (b) composite creep rate, and (c) transient redistribution in axial stress in the fibers and matrix (the initial loading transient has been ignored). Although the fibers and matrix were assumed to exhibit only steady-state creep behavior, the transient redistribution in stress gives rise to the transient creep response shown in parts (a) and (b). After Wu et al 1...

In the railroad industry, structures usually are designed by applying static load assumptions. In reality, however, cyclic loading, creep, temperature, and environmental influences occur which should be considered in adhesive joint design. Generic physical models taking into account all the possible effects are not applicable for a practical design concept. 

Fig. 6.6 Strain rate versus creeping time, creeping temperature a 1400 °C, b 1500 °C [84]. With kind permission of Dr. Nina Obradovic, Science of Sintering Editorial Board Secretariat...

For parts to be welded, including tank plates and structural steel, no bottom or side air or enriched air-blown converter steels should be used. Oxygen-blown converter steel may be used only below the creep temperature range. 

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