Engineering Materials Flashcards: Plastics, Metals and Processing

Question 1

Engineering stress in a tensile test: force divided by what?

Accepted Answer

Original specimen cross-sectional area.

Question 2

Engineering strain in a tensile test: extension divided by what?

Accepted Answer

Original gauge length. Strain is dimensionless.

Question 3

Elastic deformation: what happens after unloading?

Accepted Answer

The deformation recovers.

Question 4

Young’s modulus describes which material behaviour?

Accepted Answer

Resistance to elastic tensile or compressive strain, in the linear elastic region.

Question 5

Yield strength marks the onset of what?

Accepted Answer

Significant permanent deformation, using the specified yield or proof criterion.

Question 6

Ultimate tensile strength: which point on an engineering stress–strain curve?

Accepted Answer

The maximum engineering tensile stress.

Question 7

Ductility describes what happens before tensile fracture?

Accepted Answer

How much plastic deformation the material can undergo.

Question 8

Indentation hardness measures resistance to what?

Accepted Answer

Localized permanent penetration by an indenter.

Question 9

Tensile toughness: what does the area under the stress–strain curve to fracture represent?

Accepted Answer

Energy absorbed per unit volume up to fracture under those test conditions.

Question 10

Density relates which two quantities?

Accepted Answer

Mass per unit volume.

Question 11

Thermal conductivity describes which ability?

Accepted Answer

Transferring heat through a material under a temperature gradient.

Question 12

Electrical conductivity describes which ability?

Accepted Answer

Carrying electric current under an electric field.

Question 13

Creep: what changes under a sustained load over time?

Accepted Answer

Deformation increases with time; temperature and stress affect the rate.

Question 14

Fatigue damage is associated with what loading pattern?

Accepted Answer

Repeated or fluctuating loading that can initiate and grow cracks.

Question 15

Brittle fracture: how much plastic deformation precedes it?

Accepted Answer

Little plastic deformation compared with ductile fracture under the same test conditions.

Question 16

A bracket bends too far but recovers fully. Which property should you examine first?

Accepted Answer

Elastic stiffness: material modulus together with the bracket’s geometry.

Question 17

A metal clip stays bent after one overload. Which threshold was exceeded locally?

Accepted Answer

Its yield threshold; permanent deformation occurred.

Question 18

A housing must absorb a drop without fracture. Which evidence matters beyond tensile strength?

Accepted Answer

Impact-test performance under relevant temperature, notch and geometry conditions.

Question 19

Two materials have equal yield strength. Must their tensile toughness be equal?

Accepted Answer

No. Different ductility can produce different energy absorption before fracture.

Question 20

A plastic clamp slowly loosens at fixed deflection. Which time-dependent effect is this?

Accepted Answer

Stress relaxation: the stress decreases while the imposed deformation is held.

Question 21

Does a higher hardness alone prove a part will resist every wear mechanism?

Accepted Answer

No. Wear also depends on contact, loading, lubrication and the wear mechanism.

Question 22

Why compare impact results only with matching test conditions?

Accepted Answer

Specimen geometry, notches, temperature and test method affect measured impact behaviour.

Question 23

Can a generic family property range serve as a finished-part design allowable?

Accepted Answer

No. Select a grade, condition and relevant design data before qualifying the part.

Question 24

A lighter material is proposed for the same-size part. Which property predicts its mass change?

Accepted Answer

Density, provided the volume remains the same.

Question 25

Ferrous versus nonferrous metals: what is the defining distinction?

Accepted Answer

Whether iron is the main constituent. Nonferrous does not mean completely iron-free.

Question 26

Steel belongs to which basic alloy family?

Accepted Answer

Iron-based alloys containing carbon, often with other alloying elements.

Question 27

Why specify a steel grade and heat treatment rather than just “steel”?

Accepted Answer

Composition and processing change its microstructure and mechanical properties.

Question 28

What is a grain in a polycrystalline metal?

Accepted Answer

A crystalline region with a particular lattice orientation.

Question 29

What separates neighbouring metal grains with different orientations?

Accepted Answer

A grain boundary.

Question 30

Which crystal defect commonly moves during plastic deformation of metals?

Accepted Answer

A dislocation.

Question 31

Cold working usually trades increased strength for what?

Accepted Answer

Reduced ductility, as plastic deformation impedes further dislocation motion.

Question 32

What is a common purpose of annealing a cold-worked metal?

Accepted Answer

Restore ductility and reduce hardness through a controlled heat treatment.

Question 33

Quenching in metal heat treatment means what cooling step?

Accepted Answer

Rapid cooling using a specified medium; the appropriate regime depends on the alloy and intended result.

Question 34

What gives stainless steel much of its corrosion resistance?

Accepted Answer

A thin chromium-rich passive surface film.

Question 35

Why distinguish grey cast iron from ductile cast iron during selection?

Accepted Answer

Graphite form and resulting mechanical behaviour differ; “cast iron” is not one property set.

Question 36

Why are aluminium alloys often screened for lightweight structures?

Accepted Answer

Their relatively low density can help reduce mass; stiffness, strength and geometry still need checking.

Question 37

Why is copper often screened for electrical conductors?

Accepted Answer

High electrical conductivity; cost, strength and connection design also matter.

Question 38

Brass is principally an alloy of copper with which element?

Accepted Answer

Zinc.

Question 39

Traditional tin bronze is principally an alloy of which two elements?

Accepted Answer

Copper and tin. Other bronze families use different alloying additions.

Question 40

Does “stainless” mean immune to chloride corrosion?

Accepted Answer

No. Grade, environment and surface condition still govern corrosion resistance.

Question 41

Two dissimilar metals touch in salty water. Which corrosion mechanism should be checked?

Accepted Answer

Galvanic corrosion, because electrical contact and an electrolyte can form a galvanic couple.

Question 42

Can you rank aluminium and steel parts by stiffness using only their material names?

Accepted Answer

No. Compare the actual moduli and part geometries for the required loading.

Question 43

A copper alloy is stronger than pure copper. Must it conduct electricity equally well?

Accepted Answer

No. Alloying changes conductivity as well as mechanical properties; check that alloy’s data.

Question 44

A steel sheet cracks during forming after extensive cold work. What processing step may restore formability?

Accepted Answer

An appropriate anneal before further forming; confirm the alloy-specific procedure.

Question 45

What is a common purpose of tempering a quench-hardened steel?

Accepted Answer

Improve toughness and ductility, usually with some reduction in hardness.

Question 46

How can an insulating washer help a dissimilar-metal joint resist galvanic corrosion?

Accepted Answer

By interrupting the electrical connection, if the whole joint is electrically isolated.

Question 47

Before approving a welded metal component, which material region besides the weld metal needs consideration?

Accepted Answer

The heat-affected zone, whose thermal cycle can change properties without melting it.

Question 48

What is the key processing–structure–property lesson for metal selection?

Accepted Answer

A chemical composition alone does not determine performance; processing changes microstructure.

Question 49

A polymer is built from what kind of molecular structure?

Accepted Answer

Large molecules containing many linked repeating units.

Question 50

Which polymer class can usually be reheated and reshaped: thermoplastics or cured thermosets?

Accepted Answer

Thermoplastics. Cross-links in a cured thermoset prevent ordinary melt reshaping.

Question 51

What deformation behaviour distinguishes an elastomer?

Accepted Answer

It can undergo substantial deformation and recover toward its original shape when the load is removed, within its working range.

Question 52

What does “semi-crystalline polymer” mean?

Accepted Answer

Ordered crystalline regions coexist with amorphous regions.

Question 53

Which polymer regions undergo glass transition: amorphous or crystalline?

Accepted Answer

Amorphous regions. Around the glass transition, motion of chain segments becomes much easier.

Question 54

What structural feature prevents a cured thermoset from flowing like a thermoplastic melt?

Accepted Answer

A covalently cross-linked network.

Question 55

Why are plasticizers added to some polymer formulations?

Accepted Answer

To increase flexibility; the amount and compatibility affect the final properties.

Question 56

Why add UV stabilizers to a polymer intended for outdoor exposure?

Accepted Answer

To reduce degradation caused by ultraviolet exposure; the formulation and exposure still need verification.

Question 57

Why can adding glass fibres make moulded polymer properties direction-dependent?

Accepted Answer

Fibres become oriented during flow, so reinforcement differs with direction.

Question 58

What structural change separates glass transition from crystalline melting in a polymer?

Accepted Answer

Glass transition increases chain-segment mobility in amorphous regions; melting breaks down the ordered crystalline regions.

Question 59

ABS is an abbreviation for which polymer name?

Accepted Answer

Acrylonitrile butadiene styrene.

Question 60

PA6 is another name for which polyamide?

Accepted Answer

Polyamide 6, also called nylon 6.

Question 61

Why distinguish “dry” from “conditioned” polyamide property data?

Accepted Answer

Moisture conditioning changes the material state and can change mechanical behaviour.

Question 62

Does one grade’s ABS datasheet establish the properties of every ABS grade?

Accepted Answer

No. Formulation, grade, test method and conditions must match the claim.

Question 63

INEOS Terluran GP-22 is specified for which main shaping process?

Accepted Answer

Injection moulding; it is a general-purpose ABS grade.

Question 64

BASF Ultramid B3S is supplied for which main shaping process?

Accepted Answer

Injection moulding; BASF describes this PA6 grade as easy-flowing and finely crystalline.

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