Material Science_Mechanical Properties

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Questions and Answers

What is the purpose of selecting a material with a large elastic modulus?

To increase toughness

To reduce ductility

To increase plastic behavior

To minimize deformation (correct)

What type of deformation occurs when the tensile stress reaches sy?

Torsional deformation

Elastic behavior

Ductility

Plastic behavior (correct)

What is the unit of measurement for toughness?

N/m

J/m^3 (correct)

MPa

What is the relationship between stress and strain in elastic behavior?

Linear Signup and view all the answers

What is the definition of ductility?

The plastic strain at failure Signup and view all the answers

What is the value of the tensile strength (TS) of the given 1045 plain carbon steel?

565 MPa Signup and view all the answers

What is the condition for bi-axial tension in a stress state?

sx > 0 and sz > 0 Signup and view all the answers

What is the formula for engineering strain in the case of tensile strain?

e = d / Lo Signup and view all the answers

What is the unit of strain?

dimensionless Signup and view all the answers

What is the purpose of an extensometer in a stress-strain testing machine?

To measure the deformation of the specimen Signup and view all the answers

What is the type of strain that occurs when a specimen is subjected to a torque?

Shear strain Signup and view all the answers

What is the condition for hydrostatic compression in a stress state?

sx < 0 and sz < 0 Signup and view all the answers

What is the formula for shear strain in terms of the angle of deformation?

g = tan q Signup and view all the answers

What is the purpose of a stress-strain testing machine?

To determine the stress-strain relationship of a material Signup and view all the answers

What are the units of stress?

N/m2 or lbf/in2 Signup and view all the answers

What type of stress occurs when a force is applied tangentially to the surface of a material?

Shear stress Signup and view all the answers

What is the formula for calculating tensile stress in a material?

s = F/Ao Signup and view all the answers

What type of deformation occurs when a material is subjected to a stress that exceeds its elastic limit?

Plastic deformation Signup and view all the answers

What is the formula for calculating shear stress in a material?

t = M/AcR Signup and view all the answers

What type of stress occurs when a material is subjected to a compressive force?

Compressive stress Signup and view all the answers

What is the relationship between stress and strain in a material?

Stress is directly proportional to strain Signup and view all the answers

What type of deformation occurs when a material is subjected to a twisting force?

Torsional deformation Signup and view all the answers

Study Notes

Types of Stress

Bi-axial tension: occurs in pressurized tanks, where both sq and sz are greater than 0
Hydrostatic compression: occurs in fish under water, where sh is less than 0

Engineering Strain

Tensile strain: e = ΔL / Lo, where e is the strain, ΔL is the change in length, and Lo is the original length
Lateral strain: eL = -ΔL / Lo
Shear strain: γ = Δx / y = tan(90° - q), where γ is the shear strain, Δx is the change in distance, and y is the original distance

Stress-Strain Testing

Typical tensile test machine: consists of an extensometer and a specimen
Typical tensile specimen: has a working load of 220,000 N, a yield strength of 310 MPa, and an ultimate tensile strength of 565 MPa

Stress and Strain

Stress and strain are size-independent measures of load and displacement
Elastic behavior: reversible behavior often shows a linear relation between stress and strain
Plastic behavior: permanent deformation occurs when the tensile (or compressive) uniaxial stress reaches the yield strength (sy)

Material Properties

Toughness: the energy needed to break a unit volume of material
Ductility: the plastic strain at failure

Types of Stress and Strain

Tensile stress: s = Ft / Ao, where s is the tensile stress, Ft is the force, and Ao is the original area
Shear stress: t = Ft / Ao, where t is the shear stress, Ft is the force, and Ao is the original area
Linear elastic behavior: occurs when stress is proportional to strain
Plastic behavior: occurs when the stress-strain curve is non-linear

Common States of Stress

Simple tension: occurs in cables, where F is the force and Ao is the cross-sectional area
Torsion (a form of shear): occurs in drive shafts, where M is the moment, Ac is the cross-sectional area, and R is the radius
Simple compression: occurs in structures, where F is the force and Ao is the cross-sectional area

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Description

This quiz covers other common stress states, including bi-axial tension and hydrostatic compression, with examples of pressurized tanks and fish under water. It also touches on engineering strain and tensile strain.