# STRENGTH OF MATERIALS LAB VIVA QUESTIONS AND ANSWERS

I’m happy to help you prepare for your Strength of Materials lab viva! Here are some potential questions and answers:

## Q: What is the purpose of a tensile test?

A: The purpose of a tensile test is to measure the tensile strength and other mechanical properties of a material under tension.

## Q: What are the steps involved in a tensile test?

A: The steps involved in a tensile test are: preparing the specimen, clamping the specimen into the testing machine, applying a slowly increasing load to the specimen, recording the load and corresponding deformation, and analyzing the data.

## Q: What is the difference between stress and strain?

A: Stress is the force per unit area that a material experiences when subjected to an external load, while strain is the resulting deformation of the material.

## Q: What is the yield strength of a material?

A: The yield strength of a material is the stress at which it begins to deform plastically, or permanently, without any additional increase in stress.

## Q: What is the difference between brittle and ductile materials?

A: Brittle materials have a low tolerance for deformation and fracture easily, while ductile materials can undergo significant deformation before fracturing.

## Q: What is the purpose of a shear test?

A: The purpose of a shear test is to measure the shear strength and other mechanical properties of a material under shear stress.

## Q: What is Poisson’s ratio?

A: Poisson’s ratio is the ratio of the transverse strain to the longitudinal strain in a material that is being subjected to tension or compression.

## Q: What is the difference between elastic and plastic deformation?

A: Elastic deformation is a temporary deformation of a material that disappears when the external load is removed, while plastic deformation is a permanent deformation that remains even after the external load is removed.

## Q: What is Hooke’s Law?

A: Hooke’s Law states that the strain of an elastic material is proportional to the stress applied to it, as long as the material remains within its elastic limit.

## Q: What is the difference between ultimate strength and yield strength?

A: Ultimate strength is the maximum stress a material can withstand before it fails, while yield strength is the stress at which a material begins to deform plastically.

## Q: What is the modulus of elasticity?

A: The modulus of elasticity is a measure of a material’s stiffness or resistance to deformation under an applied load.

## Q: What is the difference between axial and bending loads?

A: Axial loads are applied parallel to the longitudinal axis of a member, while bending loads are applied perpendicular to the longitudinal axis of a member.

## Q: What is the purpose of a compression test?

A: The purpose of a compression test is to measure the compressive strength and other mechanical properties of a material under compression.

## Q: What is the difference between tension and compression?

A: Tension is a stretching force that causes a material to elongate, while compression is a compressive force that causes a material to shorten.

## Q: What is the purpose of a hardness test?

A: The purpose of a hardness test is to measure the resistance of a material to indentation or scratching.

## Q: What is the difference between static and dynamic loads?

A: Static loads are loads that remain constant over time, while dynamic loads are loads that change over time, such as those caused by vibrations or impacts.

## Q: What is the purpose of a fatigue test?

A: The purpose of a fatigue test is to measure a material’s resistance to cyclic loading, which can cause failure over time even if the maximum stress is below the ultimate strength.

## Q: What is the difference between shear stress and shear strain?

A: Shear stress is the force per unit area that a material experiences when subjected to a shear load, while shear strain is the angular deformation of the material due to the shear load.

## Q: What is the purpose of a torsion test?

A: The purpose of a torsion test is to measure a material’s resistance to torsion or twisting.

## Q: What is the difference between a beam and a column?

A: A beam is a horizontal or inclined structural member that supports loads by bending, while a column is a vertical structural member that supports loads primarily by compression.

## Q: What is the difference between a statically determinate and statically indeterminate structure?

A: A statically determinate structure is one where the internal forces and reactions can be determined solely by applying the equations of statics, while a statically indeterminate structure is one where the internal forces and reactions cannot be determined by statics alone.

## Q: What is the purpose of a buckling test?

A: The purpose of a buckling test is to measure a material’s resistance to buckling or instability under compressive loads.

## Q: What is the difference between a truss and a frame?

A: A truss is a structure composed of members connected by joints, typically designed to carry axial loads, while a frame is a structure composed of beams and columns, typically designed to carry bending loads.

## Q: What is the difference between ultimate stress and ultimate strain?

A: Ultimate stress is the maximum stress a material can withstand before it fails, while ultimate strain is the maximum strain a material can undergo before it fails.

## Q: What is the purpose of a creep test?

A: The purpose of a creep test is to measure a material’s tendency to deform over time under a constant load.

## Q: What is the difference between a cantilever beam and a simply supported beam?

A: A cantilever beam is a beam that is supported at one end and free at the other end, while a simply supported beam is a beam that is supported at both ends and free to rotate.

## Q: What is the purpose of a strain gauge?

A: The purpose of a strain gauge is to measure the strain or deformation of a material by converting the strain into an electrical signal.

## Q: What is the difference between stress concentration and stress distribution?

A: Stress concentration is the local increase in stress at a point or region in a material, while stress distribution is the pattern of stress throughout the material.

## Q: What is the purpose of a fatigue limit test?

A: The purpose of a fatigue limit test is to determine the maximum cyclic stress that a material can withstand without failure, even after an infinite number of loading cycles.

## Q: What is the difference between a principal stress and a maximum shear stress?

A: A principal stress is a normal stress that acts on a plane where there is no shear stress, while a maximum shear stress is the maximum shear stress that occurs on a plane.

## Q: What is the difference between a static and a dynamic strain measurement?

A: A static strain measurement is a measurement of strain under a constant load or stress, while a dynamic strain measurement is a measurement of strain under a changing load or stress.

## Q: What is the purpose of a hardness conversion test?

A: The purpose of a hardness conversion test is to convert the hardness value of one scale to another scale for comparison or standardization purposes.

## Q: What is the difference between a beam and a plate?

A: A beam is a one-dimensional structural element that is designed to resist bending loads, while a plate is a two-dimensional structural element that is designed to resist bending and shear loads.

## Q: What is the purpose of a hardness indentation test?

A: The purpose of a hardness indentation test is to measure the hardness of a material by indenting it with a hard object, such as a diamond or a tungsten carbide ball.

## Q: What is the difference between a ductile and a brittle material?

A: A ductile material can undergo large deformations before it fails, while a brittle material fails suddenly without significant deformation.

## Q: What is the purpose of a strain-hardening test?

A: The purpose of a strain-hardening test is to measure the increase in a material’s strength due to plastic deformation.

## Q: What is the difference between a stress-strain diagram for a ductile material and a brittle material?

A: The stress-strain diagram for a ductile material shows a gradual increase in stress with increasing strain, followed by a region of uniform plastic deformation and a final region of necking and failure, while the stress-strain diagram for a brittle material shows a rapid increase in stress with little or no plastic deformation before failure.

## Q: What is the difference between a stress concentration factor and a fatigue notch factor?

A: A stress concentration factor is a dimensionless parameter that relates the maximum stress at a stress concentration to the nominal stress in the absence of a stress concentration, while a fatigue notch factor is a dimensionless parameter that relates the fatigue strength of a notched specimen to the fatigue strength of a smooth specimen.

## Q: What is the purpose of a fracture toughness test?

A: The purpose of a fracture toughness test is to measure a material’s resistance to crack propagation and fracture under a static or dynamic load.

## Q: What is the difference between tensile stress and compressive stress?

A: Tensile stress is the stress that tends to pull a material apart, while compressive stress is the stress that tends to push a material together.

## Q: What is the purpose of a torsion test?

A: The purpose of a torsion test is to measure a material’s resistance to twisting or torsional deformation.

## Q: What is the difference between a uniform beam and a non-uniform beam?

A: A uniform beam has a constant cross-section along its length, while a non-uniform beam has a variable cross-section along its length.

## Q: What is the purpose of a creep test?

A: The purpose of a creep test is to measure a material’s resistance to deformation under a constant load or stress over a prolonged period of time.

## Q: What is the difference between elastic deformation and plastic deformation?

A: Elastic deformation is a temporary deformation that disappears when the load is removed, while plastic deformation is a permanent deformation that remains after the load is removed.

## Q: What is the purpose of a strain rate test?

A: The purpose of a strain rate test is to measure a material’s response to deformation under different rates of loading, ranging from quasi-static to high-rate or dynamic loading.

## Q: What is the difference between a modulus of elasticity and a modulus of rigidity?

A: The modulus of elasticity is a measure of a material’s resistance to axial deformation or stretching, while the modulus of rigidity is a measure of a material’s resistance to shear deformation.

## Q: What is the difference between shear stress and bending stress?

A: Shear stress is the stress that tends to cause adjacent parts of a material to slide past each other in opposite directions, while bending stress is the stress that tends to cause a material to bend or deform under a bending moment.

## Q: What is the purpose of a fatigue test?

A: The purpose of a fatigue test is to measure a material’s endurance or resistance to failure under cyclic or repeated loading.

## Q: What is the difference between a cantilever beam and a simply supported beam?

A: A cantilever beam is a beam that is fixed at one end and free at the other end, while a simply supported beam is a beam that is supported at both ends and free to bend in the middle.

## Q: What is the difference between a static load and a dynamic load?

A: A static load is a load that remains constant over time, while a dynamic load is a load that varies with time, either periodically or randomly.

## Q: What is the purpose of a deflection test?

A: The purpose of a deflection test is to measure a beam’s deflection or deformation under a load, and to determine its stiffness or flexibility.

## Q: What is the difference between a tensile test and a compression test?

A: A tensile test is a test that measures a material’s response to pulling or stretching forces, while a compression test is a test that measures a material’s response to compressive or squeezing forces.

## Q: What is the difference between a strain gauge and an extensometer?

A: A strain gauge is a device that measures the strain or deformation of a material directly by measuring the change in electrical resistance of a wire or foil attached to the surface of the material, while an extensometer is a device that measures the change in length of a material directly by using a set of two or more mechanical arms or rods attached to the material.

## Q: What is the purpose of a impact test?

A: The purpose of an impact test is to measure a material’s resistance to fracture or failure under a sudden impact or shock load.

## Q: What is the difference between a moment of inertia and a section modulus?

A: The moment of inertia is a measure of a beam’s resistance to bending or deformation, while the section modulus is a measure of a beam’s ability to resist bending stresses.

## Q: What is the purpose of a hardness test?

A: The purpose of a hardness test is to measure a material’s resistance to indentation or scratching, and to determine its hardness or strength.

## Q: What is the purpose of a fracture test?

A: The purpose of a fracture test is to measure a material’s toughness or resistance to fracture or crack propagation under a tensile or impact load.

## Q: What is the difference between a moment and a torque?

A: A moment is a force multiplied by its distance from a reference point, while a torque is a force multiplied by its distance from an axis of rotation.

## Q: What is the difference between a stress-strain curve for a brittle material and a ductile material?

A: A stress-strain curve for a brittle material is a curve that shows a sudden drop in stress after reaching the maximum stress, while a stress-strain curve for a ductile material is a curve that shows a gradual decrease in stress after reaching the maximum stress.

## Q: What is the purpose of a beam deflection test?

A: The purpose of a beam deflection test is to measure a beam’s deflection or deformation under a load, and to determine its stiffness or flexibility.

## Q: What is the difference between an axial load and a transverse load?

A: An axial load is a load that is applied along the longitudinal axis of a member, while a transverse load is a load that is applied perpendicular to the longitudinal axis of a member.

## Q: What is the difference between a beam and a column?

A: A beam is a structural member that supports loads perpendicular to its longitudinal axis, while a column is a structural member that supports loads parallel to its longitudinal axis.

## Q: What is the purpose of a fracture toughness test?

A: The purpose of a fracture toughness test is to measure a material’s resistance to crack propagation or fracture under a tensile load, and to determine its ability to resist catastrophic failure.

## Q: What is the difference between a fixed support and a hinged support?

A: A fixed support is a support that prevents a member from rotating and translating, while a hinged support is a support that allows a member to rotate but prevents it from translating.

## Q: What is the purpose of a strain hardening test?

A: The purpose of a strain hardening test is to measure a material’s increase in hardness or strength due to plastic deformation, and to determine its ability to resist further deformation.