A continuous drive for lighter and better performing materials in the aerospace industry has led to progressive work regarding aluminum alloys.
Testing of the durability of the material through fatigue testing is absolutely essential to ensure the application of the material is suitable before moving through the expensive design process and further into product realization.
A fatigue fracture will have two distinct regions; One being smooth or burnished as a result of the rubbing of the bottom and top of the crack. The second is granular, due to the rapid failure of the material.
Striations are thought to be steps in crack propagation, were the distance depends on the stress range. Beachmarks on the other hand may contain thousands of striations.
Fatigue cracking is one of the primary damage mechanisms of structural components. Fatigue cracking results from cyclic stresses that are below the ultimate tensile stress, or even the yield stress of the material.
The fatigue life of a component can be expressed as the number of loading cycles required to initiate a fatigue crack and to propagate the crack to its critical size.
The fatigue behavior of a material is usually determined by conducting axial (tension and compression) and sometimes torsional fatigue experiments at the service temperature.
Between the temperatures of 150°C and 250°C the material strength decreases rapidly for almost all of the cast aluminum alloys as expected.
The engine block works under mechanical and thermal cyclic stresses in relative motion with other engine parts. High fatigue strength and good wear resistance are critical properties to engine block life.
Each specimen was tested under uniaxial cyclic loading using Instron 8032 system. To investigate the fatigue behavior of Al-Si-Mg alloy, specimens were exposed to different stress amplitudes from 115 to 185 MPa.
Aluminum alloys are progressively used in the automobile industry due to several advantages such as low specific weight, good formability, good corrosion resistance and a nice surface appearance. The standard production forming processes such as extrusion and forging, can give rise to large variations in the tensile, fatigue and fracture properties. In AlMgSi alloys (6061, 6062, 6060 and 6082), yield stress have been shown to have only a weak dependence on grain size. However, a large part of the variations in other properties can be traced back to differences in grain size.