# Lab 4 Memo

Topics: Temperature, Fracture, Fracture mechanics Pages: 2 (521 words) Published: January 9, 2013
SUBJECT: Temperature-dependent impact tests on AISI 1018 steel and 6061 Aluminum

Purpose
This lab was performed to fully comprehend the temperature dependency of the fracture toughness of the Aluminum and Steel. It was also executed to discover the ductile-brittle transition of each.

Summary
The experiment solidified the hypothesis that the 6061 aluminum has no ductile-to-brittle transition do to its FCC crystal structure. The 1018 steel has a ductile-to-brittle transition temperature of -31ºC due to its BCC crystal structure.

Results

Table 1: Test temperatures and average fracture energies with errors for Group 4 and entire class |CLASS | |6061 Aluminum |1018 Steel | |Temperature(°C) |Fracture Energy(J) |Temperature(°C) |Fracture Energy(J) | |Mean |

-28.5 |0.4 |5.2 |0.05 |-70.5 |0.2 |2.6 |0.03 | |-0.9 |0.7 |4.5 |0.05 |-35.2 |0.7 |14.5 |0.15 | |3.2 |0.5 |5.6 |0.06 |-15.3 |0.4 |17.1 |0.17 | |25.1 |0.05 |4.6 |0.05 |26 |0.05 |35.2 |0.35 | | [pic] Figure 1: Graph of fracture energy vs. temperature for entire class data

From Figure 1 one can determine that steel has a ductile-to-brittle transition temperature at -31ºC requiring a large increase in energy required to fracture over the temperature range. Also it can be determined that aluminum has no ductile to brittle transition due to the almost nonexistent change in fracture energy over the temperature range. Figure 2: Photos of the fracture of each specimen for each testing temperature

From the photos in Figure 2 one can see that the Aluminum...

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