Material Properties & Characterization Flashcards

Which material property describes the ratio of stress to strain in the elastic region of a stress-strain curve?

Answer: Modulus of elasticity (Young's modulus)

Young's modulus defines the stiffness of a material as the slope of the linear elastic portion of the stress-strain curve.

In additive manufacturing, anisotropy of mechanical properties is most commonly caused by:

Answer: Layered build direction creating directional microstructure

The layer-by-layer deposition creates a directional microstructure, making properties stronger along certain axes than others.

Which test is used to measure the resistance of a material's surface to permanent indentation?

Answer: Hardness test

Hardness tests (Rockwell, Brinell, Vickers) measure resistance to surface indentation by a standardized indenter.

Porosity in metal AM parts is most problematic because it:

Answer: Acts as a stress concentrator that reduces fatigue life

Pores act as stress concentration points that initiate cracks under cyclic loading, significantly reducing fatigue life.

Which phenomenon occurs when a polymer AM material absorbs moisture from the environment, affecting print quality?

Answer: Hygroscopy

Hygroscopy is the tendency of certain materials to absorb moisture, which can cause bubbling and inconsistent extrusion in FDM printing.

The glass transition temperature (Tg) of a polymer is important in AM because it defines:

Answer: The temperature above which the material becomes rubbery and loses rigidity

Above Tg, amorphous polymers transition from a glassy rigid state to a rubbery state, which determines heat resistance of the finished part.

In powder bed fusion (PBF) of metals, the powder particle size distribution affects:

Answer: Powder flowability, packing density, and surface finish of the part

Particle size distribution controls how well powder flows and packs, directly influencing melt pool behavior and surface finish.