core 4 - p4 Flashcards
(25 cards)
What are smart materials? Provide two examples.
Materials that respond to external stimuli (e.g., temperature, stress, light). Examples:
-Shape-memory alloys (e.g., Nitinol).
-Piezoelectric materials (e.g., quartz).
Define nanomaterials and their unique properties.
Materials with structures at the nanoscale (1–100 nm). Properties: High strength-to-weight ratio, enhanced reactivity, and unique electrical/optical behaviors.
What is sustainability in materials engineering? Name two eco-friendly materials.
Designing materials to minimize environmental impact. Examples:
–Bioplastics (e.g., PLA).
-Recycled composites (e.g., reclaimed fiberglass).
What is LCA (Life Cycle Assessment)?
A method to evaluate environmental impacts of a material/product from extraction to disposal.
Explain fatigue failure and its causes
Failure due to cyclic loading below ultimate strength. Causes: Repeated stress, microcrack propagation, and material defects.
What is creep in materials? Where is it critical?
Slow, permanent deformation under constant stress at high temperatures. Critical in turbines, pipelines, and aerospace components
Define thermal expansion coefficient and its formula.
Measures dimensional change with temperature. Formula:
α = ΔL / (L0 / ΔT)
(ΔL: length change; L0: original length; ΔT: temp change).
What is Fick’s Law?
Describes diffusion rate:
J = − D (∂C / ∂x)
(J: flux; D: diffusivity; ∂C/∂x: concentration gradient).
What are dislocations in metals? How do they affect properties?
Line defects in crystal lattices. They enable plastic deformation but reduce strength (unless pinned by alloys).
What is grain boundary strengthening?
Increasing material strength by reducing grain size (Hall-Petch relationship), which hinders dislocation movement.
Define electrochemical corrosion and its prevention methods.
Corrosion via redox reactions (e.g., rusting). Prevention: Coatings, cathodic protection, or alloying (e.g., stainless steel).
What is NDT (Non-Destructive Testing)? Name two methods.
Inspecting materials without damage. Methods:
-Ultrasonic testing (sound waves).
-Radiography (X-rays).
What is composite laminate design?
Layering fibrous composites (e.g., CFRP) in specific orientations to optimize strength and stiffness.
Explain anisotropy vs. isotropy in material
-Anisotropic: Properties vary with direction (e.g., wood).
-Isotropic: Properties uniform in all directions (e.g., glass).
What is resilience in material science?
Energy absorbed elastically before plastic deformation (area under elastic region of stress-strain curve).
Define Poisson’s ratio (ν).
Ratio of transverse strain to axial strain:
ν = − (ε transverse / ε axial)
What is stress concentration? How is it mitigated?
Localized stress increase at defects (e.g., cracks). Mitigation: Smoothing edges, adding fillets, or using ductile materials.
What is case hardening?
Surface hardening of steel by diffusing carbon/nitrogen (e.g., carburizing), enhancing wear resistance.
What are superalloys? Give an application.
High-performance alloys resistant to heat/corrosion (e.g., Inconel). Used in jet engines and nuclear reactors.
Define biocompatibility and its importance.
Material’s ability to function in the body without adverse effects. Critical for implants (e.g., titanium hips).
What is additive manufacturing? Name a material used
3D printing layer-by-layer. Materials: Polymers (e.g., ABS), metals (e.g., titanium powder), or ceramics.
What is the Ashby chart?
A tool for material selection by plotting properties (e.g., strength vs. density) to compare material performance.
What is thermal conductivity? Provide its formula.
Ability to conduct heat. Formula:
q = − k (ΔT/ d)
(q: heat flux; k: conductivity; ΔT: temp difference; d: thickness).
What is brittle fracture? How does it differ from ductile fracture?
Sudden failure with little plastic deformation (e.g., glass). Ductile fracture involves significant deformation (e.g., copper).
