Chapter 6 materials Flashcards
What is density and its equation?
Density is mass per unit volume:
𝜌 = 𝑚/𝑉
What is Hooke’s Law?
The extension of a spring is proportional to the applied force, provided the limit of proportionality is not exceeded:
𝐹 = 𝑘𝑥
What is the spring constant (k)?
A measure of the stiffness of a spring — higher k means stiffer spring.
What is the elastic limit?
The point beyond which a material will not return to its original shape after the force is removed.
What is the limit of proportionality?
The point beyond which Hooke’s Law is no longer obeyed (force and extension are no longer proportional).
What is tensile stress?
Stress = Force / Cross-sectional area
𝜎 = 𝐹/𝐴
What is tensile strain?
Strain = Extension / Original length
𝜀 = Δ𝐿/𝐿
What is the Young modulus?
Young modulus = Stress / Strain
𝐸 = 𝜎/𝜀
What are the units of the Young modulus?
Pascals (Pa)
What is elastic deformation?
Reversible deformation — the material returns to its original shape when the load is removed.
What is plastic deformation?
Permanent deformation — the material does not return to its original shape after the load is removed.
How is energy stored in a stretched spring calculated?
𝐸 = 1/2 𝐹𝑥 = 1/2 𝑘𝑥²
What is ultimate tensile strength (UTS)?
The maximum stress a material can withstand before breaking.
What is breaking stress?
The stress at which a material physically breaks.
What does the area under a stress-strain graph represent?
The energy stored per unit volume of the material (strain energy density).
