Practice Quiz

Explanation

Isotropic materials have the same properties in all directions, from Greek where “Iso” means “equal” and “tropos” means direction. Materials which are not isotropic are said to be anisotropic.

Explanation

As a material is plastically deformed, dislocations within the structure of the material move and become entangled. This causes the strength of the material to increase as the amount of plastic deformation is increased, which is called strain hardening, or work hardening.

Of the four engineering stress-strain curves shown, only Material A is exhibiting this behavior, as evidenced by the fact that the load required to deform the test piece increases with increasing strain.

Explanation

Mesh sensitivity studies are performed to identify the mesh density at which the solution becomes stable and further refinement produces minimal changes. This ensures that the solution is mesh-independent and gives confidence in the accuracy of the FEA results.

Explanation

The moments in this section of the beam must be in equilibrium. Taking moments about the right-hand side of the beam, we have the 21 Nm reaction moment and a moment equation to 18x, caused by the 18 N reaction force. Both of these moments act in the opposite direction to the bending moment M, so the correct equation must be M(x) = 21 + 18x.

Explanation

When a material is loaded beyond the elastic limit, there will be some permanent plastic deformation after the load has been removed. After the load is removed there will be the recovery of the elastic strain, so the material will unload along a curve which has a slope equal to Young's modulus, as shown in the image below. The permanent plastic strain after unloading is 1.0% in this case, which means that the 200 mm long bar has permanently increased in length by 2 mm.