CIEG213 Final Vocab

Plastic region

past yield; permanent deformation occurs

Ultimate strength

the peak stress on the curve (highest point)

Necking

the curve drops after ultimate strength as the specimen starts to narrow locally before fracture

Fracture point

where the specimen breaks

Modulus of Elasticity (E)

the slope of the linear portion of the curve (elastic region). It's a material property that measures stiffness

What "mechanical behavior of a material" means

how a material responds (deforms) under loads.

Axis for stress strain curve

X-axis = strain, Y-axis = stress (not the other way around)

Proportional Limit (PL)

the point where the curve stops being perfectly linear

Yield Limit (YL)

where the material begins permanent (plastic) deformation

Elastic region

below yield; material returns to original shape when load is removed

The Charpy test

measures a material's toughness, defined as the energy absorbed before failure.

Energy chain

Potential Energy (PE) → Kinetic Energy (KE) → absorbed as toughness energy in the material

Toughness ≠ Strength

A strong material is NOT necessarily tough. Toughness is about energy absorption capacity.

Ductile materials

absorb a lot of energy, deform significantly before breaking (high toughness)

Brittle materials

absorb little energy, break suddenly without much deformation (low toughness)

Static loads

applied slowly and steadily (like a typical tension test)

Dynamic loads

applied suddenly/rapidly (like an impact). The Charpy test is a dynamic load test. This distinction matters because materials behave differently under each type.

Three(3) point bending

single load at midspan; shear is constant on each half, moment peaks at the center

Four point bending

two loads applied symmetrically; the region between the two loads has zero shear and constant moment — this is called "pure bending" and it's significant because it eliminates shear's influence in that zone, giving clean bending data

Why we draw V&M diagrams

to find the maximum shear and maximum moment, because those locations are most likely to fail

A strain gage

sensor bonded to the surface of a material that measures strain (deformation) at that point by detecting tiny changes in electrical resistance. From measured strain, stress can be calculated.

Concrete ingredients

Cement, water, fine aggregate, coarse aggregate, and admixtures.

Admixture

Ingredient added to modify a specific concrete property (e.g., plasticizer improves workability).

Hydration

Exothermic chemical reaction between water and cement that causes hardening.

Exothermic reaction

Reaction that releases heat — hydration of cement produces heat as concrete cures.

Slump test

Measures fresh concrete workability; higher slump = more workable.

Workability

How easily fresh concrete can be placed and compacted.

Water/cementitious (w/c) ratio

Lower w/c = higher strength; higher w/c = more workable but weaker.

Cementitious material

Cement-like material (e.g., fly ash) that releases less CO₂ than Portland cement.

Why potable water is required

Chlorides in non-potable water corrode steel rebars inside concrete.

Why test concrete at 28 days

Concrete reaches ~99% of its design strength after 28 days of curing.

Compression test (concrete)

Cylinder is crushed; strength calculated using σ = F/A.

σ = F/A

Stress = force divided by cross-sectional area.

Failure mode

The crack pattern of a concrete cylinder during compression — varies by mix design.

Flexure test (concrete)

Bending test on a concrete beam; unreinforced fails suddenly in tension.

Why concrete needs rebar in tension

Concrete is ~10x weaker in tension than compression; steel rebar carries the tensile forces.

Reinforced vs. metal beam stress

In reinforced concrete: concrete takes compression, rebar takes tension. In metal: stress distributes through the whole section.

Isotropic material

Same properties in all directions (e.g., steel, aluminum).

Orthotropic material

Different properties in different directions — wood is orthotropic due to its grain structure.

Why wood is orthotropic

Straw-like fibers grow along the trunk to carry gravity and wind loads, making it direction-dependent.

Axial direction (wood)

Parallel to the grain; the strongest direction.

Radial direction (wood)

Perpendicular to grain, pointing toward the tree's center.

Tangential direction (wood)

Perpendicular to grain, running tangent to the growth rings.

Cantilevered beam

Fixed at one end, free at the other — a tree is a natural example.

Wood grading and stamping

Lumber is evaluated for quality at the mill and stamped with a structural rating.