Material Strength: Testing, Properties, and Hardness

Why are trials? 1) Identify properties of materials and determine their possible use 2) Quality control in manufacturing processes 3) Determine previous history and composition of materials 4) Establishing the causes of failure of the material in service 5) Study of new types of materials

Uniaxial tensile test: Performed with a standard specimen, a constant-load vellocidad and is a destructive test.

Hooke's law (elastic): ? _n = ? _n E · [MPa = 10 ⁶ N / m ² = kg / mm ^2]

E _{ceramic>metal} E> E _Polymer E ? ? ? ? ? Tfusion F _bond

Poisson's ratio: v =-? _lateral / _longitudinal ?

Yield strength: ? _and ? = 0.2 -> Polymers (? ? Max + min) / 2

Tensile strength (Rt): max. Rated voltage that supports the tensile specimen

Resistance to fracture: tension which supports the material in the break point

Ductility: the degree of plastic deformation that can be supported by a material before rupture

Deformation% total = 100 · (long end brands - long ini) / long ini -> Quality of material, ? If there are defects or pores.

% Reduc. Area (necking) = 100 · (ini Area - Area fin) / Area ini

Tenacity: ability to absorb energy until failure in elastic and plastic deformation (Area: + area = ductile and - area = fragile)

Resilience (Ur): Ability of a material to absorb _elastic when E is deformed. Ur = 0.5 · (? _y)² / E

Deformations true:

_real ? = Ln (1 +? _n) = Ln (A ₀ / A) = 2 Ln (D ₀ / D)

_real ? = ? _{N •} (1 + ? _n) = ? _n · (A ₀ / A) = ? _n · (L ₀ / L)

Hardening: Strain -> increased resistance when the material has been plastically deformed. For solid solution -> improve the prop. Mechanical and yet the ductility, _corrosion and electrical conductivity R. Tb by precipitation and by reduction of grain size.

Prop. Ceramic mechanical: high melting temperatures, hard, fragile, porous. (MOR-> elastic until rupture zone only) work better compression than traction, low Weibull modulus.

Mechanical Prop. Polymers: If ? Vel. Deformation fragility ? ?, ? Def. Percentage of breakage, ? Dificutal unwind. If T ? ? ? Modules of elasticity, _rupture ? R, ? Of. Percentage at break

Brinell hardness (HBW): WC ball, diameter D

HBW = P / ? · D · 0.5 (D - root (D ² - Di ²⁾⁾_{load factor} Q = P / D ²

Rockwell Hardness (HRX) steel ball (B, F, G) or diamond cone (A, C, D)

HR = N - (h / S) -> N and S to scale h Increm. In the penetration

Vickers hardness (HV): 136 º diamond pyramid to face

HV = 1854 F / d ²

Knoop microhardness: similar to Vickers but performed with microscopy, measurement scale necessary