September 25, 2012, Accutek Engineering Team
By: Ryan Castells, PE
Accutek’s Engineering Team offers insight into the five key metals used in structural engineering.
Aluminum: Aluminum is a common engineering material. Structural aluminum is most frequently seen in alloy form, with common alloying elements such as silicon, iron, titanium and magnesium. Aluminum and aluminum alloys are characterized by their low density and high strength (relative to weight). In addition, Aluminum also exhibits good corrosion resistance. However, one consideration with Aluminum alloys is their low Modulus of Elasticity relative to steel, so care must be taken when trying to replace a steel part with an aluminum part. Another drawback to aluminum is that it does not exhibit an endurance limit. Overall, aluminum alloys are very desirable and widely used in the aerospace and transportation industries.
Steel: No discussion of structural materials can be complete without a mention of steel. Steel is an alloy of iron and carbon. Other alloying elements such as molybdenum, chromium or vanadium are frequently added to create the desired mechanical properties. Steel can be alloyed and heat treated in an almost endless variety to produce a very wide range of mechanical properties. For example, steel can be alloyed to produce exceptional corrosion resistance, very high hardness and yield strength, high fracture toughness or any combination of these properties. For these reasons, the most important structural engineering material is steel, which is also desirable for a wide range of industries. Its use and material properties are well understood and documented making it an ideal choice for a designer.
Titanium: Titanium is an advanced material that is widely used in the aerospace and medical device industries. It is characterized by the fact that it has the highest strength to weight ratio of any metal. It is a difficult material to machine, form and weld; so its utilization must be carefully considered before being implemented. Titanium has high fracture toughness and good resistance to fatigue cracks so it is a good choice when long fatigue life is needed. Titanium is also bio-compatible, hence widely used in the orthopedic implant industry.
Magnesium: Magnesium alloys are considered the lightest of the useful metals. Magnesium alloys offer strength similar to aluminum, but with an even lower density. Magnesium is usually alloyed with aluminum, manganese or zinc to produce useful structural alloys. Magnesium alloys are typically more brittle than aluminum alloys. Magnesium alloy is an ideal choice when a light, thick component must be designed with little importance on the strength of the component. Magnesium alloys are most commonly used in the aerospace, exotic automotive and electronics industries.
Nickel Based Super Alloys: A super alloy is a modern, exotic material that is designed to have high strength, high toughness, high creep resistance or excellent corrosion resistance at extremely high temperatures. These alloys are usually nickel-based and contain alloying elements such as chromium, molybdenum, manganese, titanium or aluminum. Some trade names of common super alloys are Inconel, Waspaloy and Hastelloy. Super alloys are typically used in gas turbine engines where extreme temperatures are necessary for high efficiency.
If you have a question about how to determine the right material for your design/application, Accutek has extensive experience testing many different materials serving a wide variety of industries. Material testing can be used to validate FEA models, validate designs/manufacturing processes or verify performance of new materials.