Question

Question 2 (20 pts): Charpy V-notch test was performed for different steel specimens. Please answer the following questions briefly. a) (3) As the temperature becomes lower, the metals usually experience a transition from ductile fracture to brittle fracture at a certain temperature. This temperature is called: b) (6) The graph below shows the test results for annealed 1018 steel and annealed 1045 steel. Please label the curves with relevant steel (1018 or 1045) and briefly explain your reason. 1018 AND 1045 Impact Energy (1) 300 250 200 156 100 50 -300 -200 0 -100 0 TEMPERATURE (°C) 100 200 c) (4) The appearance of the fractured surface for a material with low Charpy impact energy is: i. Dull and fibrous surface ii. Shiny surface iii. Plastically deformed iv. Not deformed, cleavage failure Provide a sketch of the fractured cross-section appearance. d) (4) The appearance of the fractured surface for a material with high Charpy impact energy is: i. Dull and fibrous surface ii. Shiny surface iii. Plastically deformed iv. Not deformed, cleavage failure Provide a sketch of the fractured cross-section appearance. e) (3) If we are selecting a material for a hull of a ship that will operate at temperatures as cold as 0°C, which carbon content would provide the safest steel for our design.

Answer 1

a) 3. Ductile to Brittle Transition Temperature DBTT

b) 6. The blue curve is 1018 steel and red curve is 1045 steel.

b 1018 steel Impact LA 1045 steed. Energy. Temperature CS Scanned with CamScanner

c) 4. ii) Shiny surface

iv) Not deformed, cleavage failure.

d) 4. i) Dull and fibrous surface.

iii) Plastically deformed.

e) Carbon percentage of 0.14 to 0.2%C would provide safest steel for design.