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How does Creep happen?
Creep usually occurs as a result of thermal and physical stress overcoming the elasticity of the metal preventing it from returning to its original shape after the stress is removed.
When a material is loaded within elastic limit the what is proportional to the what produced by the stress?
The displacement is proportional to the strain. This does not factor for creep and time.
What is scope creep in project management?
Scope creep refers to scope changes applied without processing them though the change control process. The role of the Project Manager is to ensure that Scope Creep does not happen in their project. As per the PMBoK guide, the Control Scope process is used to control the projects scope.
When a project scope has a tendency to increase - known as?
Scope creep
Ultimate strength of steel in tension and shear?
Static and Dynamic Yield Stress: What's the difference and which should I use?The most commonly used method for obtaining a yield stress value is to shear the sample over a range of shear rates, plot the shear stress as a function of shear rate and fit a curve (various models are available) through the data points (see fig 1).The intersection on the stress axis is then taken as the yield stress, the assumption being that any stress below this is insufficient to cause the sample to flow. Rheologists call this a dynamic yield stress; we are looking at the sample in motion (i.e. under shear) and extrapolating from this how it behaves when not in motion.However, there's more than one way to skin a cat! Another approach is to start with the sample in its at-rest state (zero shear) and incrementally increase the stress until we identify at value at which it starts to flow i.e. we record non-zero shear rate (see fig 2)We call this value a static yield stress - the stress at which we initiate flow - and it is usually considerably higher than its dynamic counterpart for any given product. In reality the sample is undergoing creep flow below this stress but we can assume for many practical purposes that it is static. This test can be performed with a quick (non-equilibrium) stress ramp on a controlled stress rheometer or a constant rate test on a vane-based tester.So which yield stress should you use?Well it depends on what you need to know. A good starting point is to match the test type to the flow process of interest: If you are interested in how a fluid stops flowing after shear (such as screen printing, dip coating, enrobing or slumping) then the dynamic yield stress is a key determinant. On the other hand if you are interested in how hard you need to push to get the fluid moving in the first place (spreadability of butters, texture of tubs of cream, mixer and pump start-up etc) then the product's static yield stress will prove a major factor.
