Mechanical Engineering: Creep Failure and Design Against Creep

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What is the main purpose of a creep test?

To apply a constant tensile stress to a specimen at a constant temperature and measure strain over time

What is one of the mechanisms of creep mentioned in the text?

Vacancies migrating within the material

Why are materials with high melting temperatures often selected for turbine engine blades?

To reduce the susceptibility to creep deformation at high temperatures

What is a characteristic of ceramics that provides resistance to deformation by creep?

<p>High melting temperatures</p> Signup and view all the answers

What is an example application where components experience creep phenomenon?

<p>Gas turbine engines</p> Signup and view all the answers

What type of stress do power plant pipes and turbine engine blades experience?

<p>Centrifugal stresses and high pressure steam lines</p> Signup and view all the answers

Why is it important to know the operating conditions of the system when selecting materials for an application?

<p>Materials experience thermally activated creep at different temperatures</p> Signup and view all the answers

Which temperature range can polymers or tin-lead solder be susceptible to creep?

<p>$30˚C$</p> Signup and view all the answers

What factor determines the rupture lifetime in a creep test?

<p>The slope of the strain vs. time curve</p> Signup and view all the answers

What is being measured in a typical creep test?

<p>Strain as a function of time at a constant stress and temperature</p> Signup and view all the answers

What is creep in the context of materials science?

<p>Time-dependent deformation of a material under constant stress</p> Signup and view all the answers

At what temperature does creep become significant for a material?

<p>0.4 Tm</p> Signup and view all the answers

What is one possible consequence of creep failure?

<p>Fracture known as stress rupture</p> Signup and view all the answers

How does creep occur in the context of creep mechanisms?

<p>Via atomic diffusion and elongation of grains</p> Signup and view all the answers

What renders a material useless in performing its intended function in the context of creep failure?

<p>Dimensional change</p> Signup and view all the answers

When does creep failure occur?

<p>When stress is less than the yield stress</p> Signup and view all the answers

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