August 14, 2012, Accutek Engineering Team
By: Ross Frischmuth, Project Engineer
“Without materials, there is no engineering.”
This is something I often heard while working on my Materials Science and Engineering degree. And now, having worked in an engineering test lab, I have come to realize the importance of material selection through every part of a product or components life cycle: from product development to process control to service environment to (hopefully not) a failure analysis.
Validate Material Selection
During new product design, there is plenty of literature available with basic mechanical properties (tensile strength, hardness, toughness, etc.) for a design engineer to reference. However, on many occasions the particular application for which the designer is considering a material requires information about that material that is not publicly available, such as S/N fatigue curves, low temperature impact strength, or elevated temperature tensile strength. A good FEA model is invaluable in product design, but the model is only as good as the material property inputs, so physical testing is a necessary part of determining if a material is truly suitable for the application in question.
Verify what you “think” you know
Once a product has reached manufacturing stage, it is important that the raw material purchased has the properties that you think it does (or that the supplier certification says it does). Suppliers issue material specs with tensile strength, hardness, and chemistry of each heat lot, but it is prudent to occasionally confirm their accuracy, particularly when using a new supplier. Most metals are certified to an ASTM, SAE, AISI, or some other internationally recognized body.
Since many of these aforementioned tests are destructive, for a final quality check there are nondestructive tests available as well. A hardness reading in a discreet, noncritical location can be correlated with tensile strength to ensure proper heat treat. Metallographic replication allows a grain structure analysis to be performed on a finished part without requiring a cross section. All that’s required is a small area to be polished to a metallographic finish.
Achieve understanding through failure analysis
Finally, in the event that a part has broken, a failure analysis can help determine if the cause was a material, manufacturing, or design deficiency. Having a clear understanding of why the failure occurred allows the engineer charged with determining and fixing the problem to focus his/her attention on the root cause of the failure.
As technology advances, increased demands have led to increased mechanical properties performance of materials. No matter how good the design, without the right materials, your idea will never move from the drawing board to the reality.