Causes & Prevention Of Material Failure Flashcards
What are three stable forms of substances?
Oxides
Hydroxides
Sulphides
When does stress corrosion occur?
When (due to weather) a material repeatedly expands & shrinks in hot and cold temperatures
When does crevice corrosion occur?
In holes (crevices) where oxygen is restricted
What is galvanic corrosion?
When 2 different metals in contact are immersed in a common electrolyte (i.e. salt water)
The more active metal in the galvanic couple (anode) corrodes faster than the noble metal (cathode)
When does intergranular corrosion occur?
When impurities are present at grain boundaries
What is SCC (Stress Corrosion Cracking)?
The growth of cracks due to both stress and a reactive environment
When does chemical corrosion occur?
When a metal’s surface is destroyed due to reacting with substances in its external environment (i.e. acid rain)
What causes erosion corrosion caused by?
Rapid flow of turbulent fluid on a metal surface
What are the four methods of corrosion prevention?
Protective coating
Metal alloy
Corrosion inhibitors
Electrochemical control measures
What is deformation?
Material failure due to the change of shape/size caused by applied forced or change of temperature
What forces cause deformation?
Tensile (pulling)
Compressive (pushing)
Shear
Bending
Torsion (twisting)
What are types of deformation?
Elastic deformation
Plastic deformation
Metal fatigue
Compressive failure
What is fracture?
Cause of failure due to separation of material into 2 or more pieces under applied stress
What are the two types of fracture?
Ductile fracture
Brittle fracture
What is creep failure?
Time dependant & permanent deformation of a material under constant stress
