5. Use the data from the low carbon annealed steel to discuss the relationship between toughness (impact energy) and fra

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5 Use The Data From The Low Carbon Annealed Steel To Discuss The Relationship Between Toughness Impact Energy And Fra 1 (95.72 KiB) Viewed 38 times

5. Use the data from the low carbon annealed steel to discuss the relationship between toughness (impact energy) and fracture appearance (either %shear or %cleavage). How can this relationship explain the typical impact behavior of ductile and brittle materials? 6. The notch simulates a defect in the material (or poor design). How would the toughness be affected by a sharper notch (but not deeper)? Use the backward sample to prove your point. Summarize why a consistent sample geometry is critical in the Charpy test. 7. Given that the steel used in the T-2 tanker (Figure 1) had a transition temperature of 10°C, determine the three conditions that must have occurred to cause the brittle fracture. 8. Without changing the grade of steel used in the T-2 tanker, what could you do to the grain size to improve the transition temperature of the next ship's steel? Use your lab data to support your explanation. Why does changing the grain size improve toughness? 9. Calculate the impact toughness (convert to both ft-lb and Joules) for each of the following tests: o Hammer weight = 40 lb. (force) o Hammer mass = 20 kg Initial Height = 4.0 ft. Initial Height = 1.2 m Final Height = 0.5 ft. Final Height = 0.15 m
30J import Energy [J] * -35 - 280 NDT (~ 40°C) -to TemperTunics 20 ☆ Claray! - AISI 1020 A ✩ impact every [J] - A151 6820 A Best-fit- Cum for 1020 A impact- 35 Energy (0 40 9 1040 A 1020 N 10 20 CR A1 6061-T6 > Cleang < 106/ for
Results (Table 1; Use the steps on the previous page to graph this data) Test Temperature Sample (Alloy Condition) Toughness () % Shear (c) ALSI 1020A 30) AISI 1020 CR AISI 1020 N N A16061-T6 Backward Sample (do not include in graph) AISI 1040Q AISI 1040 A -50 -35 -20 -10 RT (21°c) +35 c 50 c -50 RT -50 RT -50 RT RT RT RT 40 ) 60) 205) 200) 272) 290) 245) 9 J 20) 60) 308) 23) 23 J jo) 55) 10% 20% 65% 90%. 95% 100% 100%. 50%. 20%. 40% 100% 90%- 90% N/A 0% 20% % Cleavage (100-%Shear) 95% 90% 80%. 35% 10 %. 5%. 0% 0% 50% 80% 60%- 0% 10%. 10% N/A 100% 80%
The significance of toughness was demonstrated many times during the Second World War. On January 16, 1942, the sea was calm and a T-2 tanker was sitting quietly at dock. As the shipbuilders were starting work on this cool morning (4°C), a tool was dropped (impact) near a square hatch (notch). Figure 1 shows the result of a crack that suddenly occurred in a brittle manner. The sound could be heard for over 2 km. Stress on the deck was below 10,000 psi and should not have caused failure. Analysis of this and other failures found that the crack initiated at the corner of the hatch and that the T15 of the steel was approximately 10°C. This analysis resulted in many design changes such as rounding the corners of all openings and selecting steels with a transition temperature (T15) below the expected operating temperature. RENT CTADY. Figure 1: Tanker that broke in a brittle manner at the dock. (See module 4 for details) Source: Rosenfield, A. (1947). The design and methods of construction of welded steel merchant vessels. Online. Last retrieved April 26, 2012 from: http://en.wikipedia.org/wiki/T2_tanker K₁ 1 2 3 00 1234 ABC 2.5 1.5 1.3 4 Surface Stamped Coarse Beveled Radius Double Sharp Ground Numbers surface Corner Corner Radius (Lathe) 1.8 90° 90° Corner Corner with inside 2.5 1.5 M Threaded High Streng Bolt Bolt with reduction