Stress and Strain Lecture Notes Flashcards

Flashcards covering key concepts and definitions from the Stress and Strain lecture notes.

What is normal stress?

The force intensity on a section cut perpendicular to the member axis of an axially loaded member.

Define stress (σ).

The internal resistance force per unit area acting on a material or intensity of the forces distributed over a given section.

What is the formula for stress?

σ = P/A, where P is the force in Newton and A is the original area in square meters.

Define Tensile Stress (σt).

Stress is tensile when σ > 0, causing the component to elongate due to the external force.

Define Compressive Stress (σc).

Stress is compressive when σ < 0, causing the component to shorten due to the external force.

Define Shear Stress (τ).

The stresses developed in a plane parallel to the applied force, acting parallel to the plane of interest.

What is the formula for average shear stress (τ)?

τ = P/Area, where P is the applied force and Area is the area of the plane parallel to the force.

Define Strain (ε).

The displacement per unit length (dimensionless).

Define Tensile Strain (εt).

The elongation per unit length. εt = ∆L/Lo

Define Compressive Strain (εc).

The reduction of length per unit length when the applied force is compressive. εc = (-∆L)/Lo

Define Shear Strain (γ).

The lateral displacement of the upper face of an element relative to the lower face divided by the distance between these faces. γ = δ/L

Define True Stress.

The ratio of the load to the cross-section area at any instant.

What is the relationship between true strain (εT) and engineering strain (ε)?

εT = ln(1 + ε)

What is Hooke's Law?

Stress is directly proportional to strain (σ = Eε and τ = Gγ).

Define Modulus of Elasticity (E).

The coefficient representing a material's resistance to elastic strain.

Define Shear Modulus of Elasticity (G).

The coefficient representing a material's resistance to shear strain.

Define Volumetric Strain (εv).

The change in volume divided by the original volume: εv = ∆V/V0

What is Dilation?

Area or volume changes due to the hydrostatic component of total stress.

Define Bulk Modulus (K).

A measure of a substance's resistance to compression. K = Δp / (ΔV/V)

What is the relationship between E, G, K, and μ for a linearly elastic, isotropic, and homogeneous material?

E = 2G(1+μ) = 3K(1-2μ) = 9KG / (3K+G)

Define Poisson's Ratio (μ).

The ratio of transverse strain to longitudinal strain (μ = -εy / εx)

What is the impact of Self Weight on a body?

Elongation of a uniform rod of length L due to its own weight W: δ = WL / 2AE

Define Thermal Stress.

Stress induced in a material due to temperature changes when expansion or contraction is restrained. (σt = αE(ΔT))

Define Creep.

Slow, permanent deformation of a material under constant load over a long period, especially at elevated temperatures.

Describe the three stages of a typical Creep curve.

Primary creep (decreasing creep rate), secondary creep (constant creep rate), and tertiary creep (rapidly increasing creep rate leading to rupture).

What is Yield Strength?

The stress required to produce a small specific amount of deformation (offset yield strength).

What is Tensile Strength or Ultimate Tensile Strength (UTS)?

The maximum load divided by the original cross-sectional area of the specimen.

Define Elasticity.

The property of a material to regain its original shape after deformation when external forces are removed.

Define Plasticity.

The state where deformation will not be fully removed. Under plastic conditions materials ideally deform without any increase in stress.

Define Strain Hardening.

Reloading from point C will follow the previous unloading path. The material will follow the same path as that of a virgin material and fails on reaching the ultimate strength which remains unaltered due to the intermediate loading and unloading process.

What is Resilience (Strain Energy)?

The energy stored within a material when work has been done on the material, assuming the material remains elastic.