Statics and Materials Exam Review

Flashcards about Statics and Materials Review

What are the steps for Truss analysis?

Draw FBD of whole structure to find reactions, Cut through members of interest and draw FBD, Apply equilibrium to the FBD

Member forces are __.

Always axial

What is the process for determining Internal Beam Forces using the Method of Sections?

Calculate reactions, Make a cut at the location you want to know the internal forces, Draw the FBD for one side of the cut, Apply equilibrium equations to the FBD, Take your moments of the CUT LOCATION, Answer will be relative to the internal force sign conventions

What prevents translation of two Free Body Diagrams(FBDs)?

Shear and axial force

What prevents rotation of the two FBDS?

The bending moment

According to Newton's Third Law, what is the relationship between internal forces on each FBD?

Equal in magnitude but opposite in direction

An internal hinge is a __.

Pin connection

M=0

What is the moment at a pinned connection?

What is a centroid?

Geometric centre of a body or shape

First moment of area = __

Area * Centroidal distance

zero

First moment of area about centroid axis is __.

What does Fracture Toughness (KIC) describe?

The material's resistance to crack propagation

Define fatigue.

Failure due to cyclic loading

What is Creep?

Time-dependent, gradual deformation of materials under constant stress, typically occurring at high temperatures or over prolonged periods.

What happens during Primary Creep (Stage I)?

Starts immediately upon applying stress and occurs at a decreasing rate

What happens during Secondary Creep (Stage II)?

The deformation rate stabilizes and becomes almost constant

What happens during Tertiary Creep (Stage III)?

Characterised by an accelerating strain rate leading to failure

List some methods of corrosion prevention

Material selection, Environmental alteration, Using inhibitors, Design changes, Coating, Cathodic protection

Stress = __

Load / Area

Strain = __

Increase of Length / Original Length

What does σy represent in a stress-strain diagram?

Yield Strength

What does UTS represent in a stress-strain diagram?

Ultimate Tensile Strength

What is σ*y?

The stress at which plastic deformation begins

What effects can occur by increasing stress or temperature with creep?

Increase in the instantaneous strain, Increase in the steady-state creep rate, Decrease in the rupture lifetime

What is observed with Stress when σ > σy?

Material doesn't obey Hooke's law

How can dislocations be reduced in materials?

Methods to reduce dislocations include Grain Size Control, solid solution strengthening and strain hardening

How does the distribution of shear force and bending moment change in a simply supported beam when subjected to a Uniformly Distributed Load (UDL) compared to a Linearly Varying Load?

Under UDL, shear force varies linearly and bending moment parabolically, whereas, with a linearly varying load, shear force varies parabolically and bending moment as a cubic curve, leading to different maximum locations.

What is a dislocation in materials science?

A dislocation is a crystallographic defect or irregularity within a crystal structure, characterized by the misalignment of atoms.

The two main types of dislocations are:

Edge dislocations

Screw dislocations

What are the two main types of dislocations?

Describe an edge dislocation.

An edge dislocation is created by an extra half-plane of atoms inserted into the crystal lattice. It's characterized by a Burgers vector that is perpendicular to the dislocation line.

Describe a screw dislocation.

A screw dislocation is visualized as a spiral ramp within the crystal structure, formed by a shear stress. Its Burgers vector is parallel to the dislocation line.

How do dislocations affect the mechanical properties of a material?

Dislocations significantly affect mechanical properties:

They facilitate plastic deformation by allowing atoms to move more easily than in a perfect lattice.

Dislocation movement is key to understanding material ductility and malleability.

the total length of dislocation lines per unit volume of a crystal. It increases with deformation, affecting material strength.

What is dislocation density?

Strain hardening is strengthening a material by plastic deformation. It increases dislocation density, which impedes further dislocation movement, thus increasing yield strength.

What is strain hardening (work hardening) in the context of dislocations?

How do dislocations interact with grain boundaries?

Grain boundaries impede dislocation movement because of the change in crystal orientation. Accumulation of dislocations at grain boundaries can lead to material strengthening.

crack initiation, crack propagation, and final failure

What are the stages of fatigue failure?

What are the types of stress cycles in fatigue?

Common stress cycles include:

• Fully Reversed Cycle: Stress varies symmetrically between tension and compression (mean stress is zero).

• Repeated Cycle: Stress varies from zero to a maximum value (either tension or compression), with a non-zero mean stress.

• Random Cycle: Stress varies irregularly with no fixed pattern, making prediction more complex.

What is dislocation motion?

Dislocation motion refers to the mechanism by which dislocations move through a crystal lattice under applied stress. This movement enables plastic deformation in materials.