Material/Welding

Question 1

How to store welding rods?

Answer 1

A moisture free environment - moisture can enter the electrode flux and cause porosity and embrittlement, splatter

Sealing of opened packing to prevent moisture entering the electrodes
Ensure they are supported to prevent cracking of the flux coating

Question 2

Welding defects

Answer 2

Spatter - Caused by high welding current,
Porosity - caused by rust or oil on the surface
Overlap - improper technique, high current

Question 3

Edge preparation

Answer 3

Edge preparation ensures the surface is contaminant free such as rust and oil and also using the correct joint ensures a sufficient penetration and strong effective weld.

Question 4

What is yield stress?

Answer 4

Yield stress is the maximum stress the material can withstand before showing plastic deformation

Question 5

What is percentage elongation?

Answer 5

Its a measure of how much a material can stretch before failure. Represented as a percentage of its original length

Question 6

What is the modulus of elasticity?

Answer 6

The modulus of elasticity is the amount amount of resistance to elastic deformation a material has. Measured as the gradient of the slope

Question 7

What is the Ultimate tensile strength of a material?

Answer 7

The ultimate tensile strength is the peak amount of stress a material can withstand before failure

Question 8

What is creep in materials?

Answer 8

Creep is the plastic deformation of a material which is subjected to constant tensile stress over time primarily at elevated temperatures. The material can fail below its yield strength. Occurs in 3 stages.

Question 9

What is fatigue in materials?

Answer 9

Fatigue is the progressive structural damage of a material subjected to cyclic or fluctuating tensile loads. This can occur below the yield strength of the material. Failure is seen as fatigue cracking, initiation, growth, propagation and failure

Question 10

Hoop stress formula?

Answer 10

Hoop = PressureDiameter/2minimum thickness

Question 11

Use of aluminium? and why?

Answer 11

Turbocharger blades due to the

Question 12

Use of stainless steel