ME475 past test

T or F: Barreling in "Upsetting" is primarily caused by the frictional forces at the die-work piece interface that oppose the outward flow of material at these interfaces

True

T or F: In bending, failure from buckling to the inner fibers occur, when sections with high moment of inertia are used

false, buckling is not driven by inner fiber failure and high moments of inertia sections resist buckling

T or F: "Friction hill" is the pressure distribution curve drawn for a forging operation, showing the die pressure distribution along the length 'a' of a workpiece

True

T or F: Bulk plastic deformation is the processing of work pieces that have relatively large surface area to volume

False, it's for workpieces with a relatively small surface area to volume ratio

T or F: for a rigid-perfectly plastic material, the stress required to keep continuing the deformation is the yield stress Y of the material

true

In extrusion, as the die angle increases, the extrusion force required to overcome friction decreases

True

A material is said to be undergoing 'plane strain', when it is allowed to expand in all directions during a deformation process

False, plane strain is where all shape changes in a material occur on a single plane

In forging, sticking takes place, when, (mu)P - frictional stress and K - shear yield strength of the material, follow what relationship?

(mu)P = K

Pressure, in which of the following extrusion process is highest, because of frictional resistance in the chamber, as the billet moves towards the die? a) Hydrostatic extrusion, b) Direct extrusion, c) Indirect extrusion, d) All of these have the same frictional resistance, e) (b) and (c) have the same frictional resistance

direct extrusion

The max deformation theory (When a material is deformed plastically, the limiting deformation for fracture is equal to the true fracture strain in tension, (epsilon)ft, in the direction tensile strain is induced) is not valid for, a) Forging, b) Rolling, c) Upsetting, d) Stretching, e) Extrusion, f) Bending, g) None of these

Forging, Rolling, Upsetting, Extrusion, and Bending (unsure chat told me this is only valid for tension and stretching is the only process in tension and not compression)

Explain the 'Deep Drawing' process with a schematic and a few sentences

The deep drawing process is when a ram inputs force on a blank piece of steel and forms it to the shape of a die

Explain the Extrusion process

A billet is placed in a chamber, and force is applied to it by a ram through a die to create a piece with a desired size / shape. For example: a 10” rod is shaped into a 5” rod after being pushed through a die. The die may be round or of various shapes.

Explain the defects that could occur in an extrusion process

Internal cracking in the billet as well as surface cracks when there is discontinuity in the material or wear on the die plates