Experimental and fractography investigation of notch depth effect by instrumented instrumented impact pendulum in 7075 Aluminum alloy

In the present study, the Charpy impact test on the 7075 aluminum sample performed in full size 55×10×10 mm with different notch depth and the fracture energy is measured. The force-displacement curves for Charpy samples with different notch depth were drawn by instrumented impact pendulum. Then the energy connection of the Charpy fracture is determined as a function of the changes in the initial crack depth. Using this relationship can determine the amount of error in measuring the energy fracture of the tested aluminum by measuring the available geometric dimensions of the initial crack including the allowable tolerances specified in the standard. Also, the microstructure of the fracture surface of several samples with different notch depth was investigated. Fractography observations showed that different fracture mechanisms occurred by changing the notch depth of the specimens, including ductile-brittle fracture, quasi-brittle fracture, and brittle fracture. As the depth of the notch depth increases, the fracture becomes more brittle, which is due to increase cleavage and decrease dimple in the fracture surface. Also, as the notch depth increases, the fracture energy decreases based on the E = 22.857e-0.355a exponential relationship, Using this equation, the exact amount of Charpy fracture energy can be calculated for each desired notch in the 7075 aluminum tested.