# SOLID MECHANICS INTERVIEW QUESTIONS AND ANSWERS

## What is the difference between stress and strain?

Stress is defined as the force per unit area that a material experiences when subjected to an external force or load, while strain is the amount of deformation or change in shape experienced by a material in response to that stress.

## What is Poisson’s ratio?

Poisson’s ratio is a measure of the transverse contraction that occurs when a material is stretched in one direction. It is defined as the ratio of the lateral strain to the axial strain.

## What is Hooke’s Law?

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

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

Elastic deformation is temporary and reversible, meaning that the material will return to its original shape once the external force is removed. Plastic deformation, on the other hand, is permanent and irreversible, meaning that the material will not return to its original shape once the external force is removed.

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

Tensile stress occurs when a material is pulled apart or stretched, while compressive stress occurs when a material is pushed together or compressed.

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

A beam is a structural element that is designed to support loads perpendicular to its longitudinal axis, while a column is a vertical structural element that is designed to support loads primarily in the axial direction.

## What is the difference between buckling and yielding?

Buckling occurs when a slender structural element fails due to compression, while yielding occurs when a material begins to deform plastically due to excessive stress.

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

A statically determinate structure is one in which the reactions and internal forces can be calculated using only the equations of static equilibrium, while a statically indeterminate structure is one in which the reactions and internal forces cannot be calculated using only the equations of static equilibrium.

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

A stress concentration factor is a measure of the increase in stress that occurs at a point where there is a change in the geometry of a structural element, while a fatigue factor is a measure of the decrease in the fatigue life of a material due to cyclic loading.

## What is the difference between a bolt and a screw?

A bolt is a threaded fastener that is designed to be used with a nut to hold two or more objects together, while a screw is a threaded fastener that is designed to be inserted into a threaded hole to hold one object to another.

## What is the difference between shear stress and normal stress?

Shear stress is the stress that acts parallel to a plane, while normal stress is the stress that acts perpendicular to a plane.

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

Modulus of elasticity, also known as Young’s modulus, is a measure of a material’s ability to resist deformation in response to an applied stress, while modulus of rigidity, also known as shear modulus, is a measure of a material’s ability to resist deformation in response to an applied shear stress.

## What is the difference between a statically determinate beam and a statically indeterminate beam?

A statically determinate beam is one in which the external loads and reactions can be determined by using the equations of static equilibrium, while a statically indeterminate beam is one in which the external loads and reactions cannot be determined by using the equations of static equilibrium alone.

## What is the difference between ultimate stress and yield stress?

Ultimate stress, also known as the tensile strength, is the maximum stress that a material can withstand before breaking, while yield stress is the stress at which a material begins to deform plastically.

## What is the difference between fatigue failure and fracture failure?

Fatigue failure occurs when a material fails due to repeated cyclic loading, while fracture failure occurs when a material fails due to a single overload or impact.

## What is the difference between axial load and eccentric load?

Axial load is a load that is applied in line with the longitudinal axis of a structural element, while eccentric load is a load that is applied off-center with respect to the longitudinal axis of a structural element.

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

A truss is a structural element that consists of interconnected triangles and is designed to support loads primarily in tension and compression, while a frame is a structural element that is designed to support loads primarily in bending.

## What is the difference between a fixed support and a simply supported beam?

A fixed support is a support that prevents both translation and rotation of a structural element, while a simply supported beam is a beam that is supported at two points that allow for both translation and rotation.

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

A stress-strain curve for a brittle material shows a sharp drop in stress after reaching the elastic limit, while a stress-strain curve for a ductile material shows a gradual decrease in stress after reaching the yield point.

## What is the difference between a linear and nonlinear stress-strain curve?

A linear stress-strain curve shows a constant slope throughout the elastic range, while a nonlinear stress-strain curve shows a changing slope throughout the elastic range.

## What is the difference between an isotropic and an anisotropic material?

An isotropic material has the same properties in all directions, while an anisotropic material has different properties in different directions.

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

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 two points that allow for both translation and rotation.

## What is the difference between a composite and a homogeneous material?

A composite material is made up of two or more different materials that are combined to create a new material with improved properties, while a homogeneous material is made up of only one material.

## What is the difference between a concentrated load and a distributed load?

A concentrated load is a load that is applied at a single point, while a distributed load is a load that is applied over a certain length or area.

## What is the difference between strain and deformation?

Strain is a measure of the amount of deformation that occurs in a material under an applied stress, while deformation is a general term that refers to any change in shape or size of a material.

## What is the difference between a shear force and a bending moment?

A shear force is a force that acts parallel to the cross-section of a structural element, while a bending moment is a moment that causes a structural element to bend or deform.

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

A beam is a structural element that is designed to support loads primarily in bending, while a column is a vertical structural element that is designed to support compressive loads.

## What is the difference between stress concentration and stress relaxation?

Stress concentration occurs when there is a localized increase in stress within a material, while stress relaxation occurs when a material’s stress decreases over time under a constant load.

## What is the difference between a plastic and an elastic deformation?

A plastic deformation is a permanent deformation that occurs in a material when it is subjected to a stress beyond its yield point, while an elastic deformation is a temporary deformation that occurs in a material when it is subjected to a stress within its elastic limit.

## What is the difference between a load and a force?

A load is a type of force that is applied to a structural element, while force is a general term that refers to any influence that can cause a change in motion or deformation of a material.

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

A torque is a force that causes a rotational motion, while a moment is a force that causes a bending or twisting motion.

## What is the difference between a material’s ultimate tensile strength and ultimate compressive strength?

A material’s ultimate tensile strength is the maximum stress that it can withstand before breaking under a tensile load, while ultimate compressive strength is the maximum stress that it can withstand before breaking under a compressive load.

## What is the difference between a beam and a truss?

A beam is a structural element that is designed to support loads primarily in bending, while a truss is a structural element that consists of interconnected triangles and is designed to support loads primarily in tension and compression.

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

A statically determinate structure is one that can be analyzed using the equations of static equilibrium alone, while a statically indeterminate structure requires additional equations or techniques to analyze.

## What is the difference between a stress and a strain?

Stress is the internal force that resists an external load, while strain is the amount of deformation that occurs in a material under an applied stress.

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

A principal stress is a stress that acts in a direction that is perpendicular to a plane of maximum shear stress, while shear stress is a stress that acts parallel to a plane.

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

A simply supported beam is a beam that is supported at two points that allow for both translation and rotation, while a cantilever beam is a beam that is fixed at one end and free at the other end.

## What is the difference between a tensile stress and a compressive stress?

A tensile stress is a stress that causes a material to elongate or stretch, while a compressive stress is a stress that causes a material to shorten or compress.

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

A truss is a type of structural element that consists of interconnected triangles and is designed to support loads primarily in tension and compression, while a frame is a type of structural element that consists of interconnected beams and columns and is designed to support loads primarily in bending and shear.

## What is the difference between a failure and a fracture?

A failure is any type of material or structural breakdown, while a fracture specifically refers to a break or separation of a material due to stress.

## What is the difference between a linear and nonlinear material?

A linear material exhibits a linear relationship between stress and strain within its elastic limit, while a nonlinear material does not exhibit a linear relationship between stress and strain.

## What is the difference between a cross-section and a longitudinal section?

A cross-section is a view of a structural element that shows the shape and size of its cross-sectional area, while a longitudinal section is a view that shows the shape and size of the element along its length.

## What is the difference between a concentrated load and a distributed load?

A concentrated load is a load that is applied at a specific point or area, while a distributed load is a load that is applied over an area or length.

## What is the difference between a moment of inertia and a polar moment of inertia?

A moment of inertia is a measure of an object’s resistance to rotational motion around an axis, while a polar moment of inertia is a measure of an object’s resistance to torsional motion around its longitudinal axis.

## What is the difference between a shaft and a beam?

A shaft is a cylindrical structural element that is designed to transmit torque, while a beam is a structural element that is designed to support loads primarily in bending.

## What is the difference between a creep and a fatigue failure?

Creep failure occurs when a material deforms over time under a constant load, while fatigue failure occurs when a material fails due to repeated loading and unloading.

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

A ductile material is one that can undergo significant plastic deformation before failure, while a brittle material is one that exhibits little or no plastic deformation before failure.

## What is the difference between a yield strength and a tensile strength?

A yield strength is the stress at which a material begins to deform plastically, while a tensile strength is the maximum stress that a material can withstand before breaking under a tensile load.

## What is the difference between an elastic modulus and a shear modulus?

An elastic modulus is a measure of a material’s resistance to deformation under an applied stress, while a shear modulus is a measure of a material’s resistance to deformation under a shear stress.

## What is the difference between a bar and a rod?

A bar is a long, thin structural element that is typically round or rectangular in cross-section, while a rod is a long, thin structural element that is typically cylindrical in shape.

## What is the difference between a buckling and a crippling failure?

A buckling failure occurs when a material fails due to buckling, or instability under compressive loads, while a crippling failure occurs when a material fails due to plastic deformation under compressive loads.

## What is the difference between a beam and a girder?

A beam is a structural element that is designed to support loads primarily in bending, while a girder is a larger beam that is used to support other beams or structural elements.

## What is the difference between an axial load and a bending load?

An axial load is a load that is applied along the axis of a structural element, while a bending load is a load that is applied perpendicular to the axis of a structural element, causing it to bend.

## What is the difference between an underdamped and overdamped system?

An underdamped system is one in which the response of the system oscillates before settling to its steady-state value, while an overdamped system is one in which the response of the system does not oscillate and settles to its steady-state value more slowly.

## What is the difference between an isotropic and an anisotropic material?

An isotropic material exhibits the same mechanical properties in all directions, while an anisotropic material exhibits different mechanical properties in different directions.

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

A moment is a force that causes rotational motion around an axis, while a torque is a moment that is specifically applied to a rotating object.

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

A simply supported beam is supported at both ends and experiences bending due to loads applied to the middle, while a cantilever beam is fixed at one end and experiences bending due to loads applied to the free end.

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

A statically determinate structure is one in which all forces and displacements can be determined using only static equilibrium equations, while an indeterminate structure is one in which additional equations, such as compatibility equations, are required to determine all forces and displacements.

## What is the difference between a pre-stressed and a post-tensioned structure?

A pre-stressed structure is one in which the steel reinforcement is placed in tension before the concrete is poured, while a post-tensioned structure is one in which the steel reinforcement is placed in tension after the concrete has set.

## What is the difference between a limit load and an ultimate load?

A limit load is the maximum load that a structure can support without experiencing any permanent deformation, while an ultimate load is the load at which the structure will fail.

## What is the difference between a rigid and a flexible structure?

A rigid structure is one that is resistant to deformation, while a flexible structure is one that is capable of undergoing significant deformation without failure.

## What is the difference between a principal stress and a von Mises stress?

A principal stress is a normal stress that acts along one of the principal axes of a material, while a von Mises stress is a measure of the equivalent stress in a material due to all the stresses acting on it.

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

A beam is a structural element that is designed to support loads primarily in bending, while a column is a structural element that is designed to support loads primarily in compression.

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

A static load is a load that is applied slowly and remains constant over time, while a dynamic load is a load that changes in magnitude and/or direction over time.

## What is the difference between a tension and a compression member?

A tension member is a structural element that is designed to support loads primarily in tension, while a compression member is a structural element that is designed to support loads primarily in compression.

## What is the difference between a hinge and a roller support?

A hinge support is a support that allows rotation around a single axis, while a roller support is a support that allows translation in one direction and rotation around one axis.

## What is the difference between a trapezoidal load and a triangular load?

A trapezoidal load is a load that varies linearly from one end to the other, while a triangular load is a load that increases or decreases linearly from one end to the other, forming a triangle shape.

## What is the difference between axial and torsional loading?

Axial loading is loading that is applied parallel to the axis of a structure, while torsional loading is loading that is applied perpendicular to the axis of a structure and causes twisting.

## What is the difference between static and kinetic friction?

Static friction is the force that resists motion between two objects that are not moving relative to each other, while kinetic friction is the force that resists motion between two objects that are in motion relative to each other.

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

Ductile materials can deform plastically before they fracture, while brittle materials fracture without significant deformation.

## What is the difference between yield stress and ultimate stress?

Yield stress is the stress at which a material begins to deform plastically, while ultimate stress is the maximum stress that a material can withstand before failure.

## What is the difference between elastic and inelastic deformation?

Elastic deformation is deformation that is reversible and disappears when the load is removed, while inelastic deformation is deformation that is irreversible and remains even after the load is removed.

## What is the difference between a linear and nonlinear material?

A linear material exhibits a linear relationship between stress and strain, while a nonlinear material exhibits a nonlinear relationship between stress and strain.

## What is the difference between a force and a moment?

A force is a vector quantity that causes an object to accelerate, while a moment is a vector quantity that causes an object to rotate.

## What is the difference between a composite and homogeneous material?

A composite material is made up of two or more different materials with distinct properties, while a homogeneous material has uniform properties throughout.

## What is the difference between a beam and a truss?

A beam is a structural element that is designed to support loads primarily in bending, while a truss is a structure made up of interconnected triangular elements designed to support loads primarily in tension and compression.

## What is the difference between a stress concentration and a stress raiser?

A stress concentration is a localized area of high stress caused by a sudden change in geometry, while a stress raiser is a notch or crack that causes stress to be concentrated at that location.

## What is the difference between a moment of inertia and a polar moment of inertia?

A moment of inertia is a measure of an object’s resistance to rotational acceleration around a specific axis, while a polar moment of inertia is a measure of an object’s resistance to torsional deformation around a specific axis.

## What is the difference between a vibration and a resonance?

A vibration is a periodic motion that occurs in response to an external force, while a resonance is a phenomenon in which the amplitude of a vibration increases due to the natural frequency of the structure matching the frequency of the external force.

## What is the difference between a concentrated and a distributed load?

A concentrated load is a load that is applied at a single point, while a distributed load is a load that is applied over a distributed area.

## What is the difference between a compression and a tension test?

A compression test is a test to determine the compressive strength of a material, while a tension test is a test to determine the tensile strength of a material.

## What is the difference between a moment and a shear force?

A moment is a force that causes rotational motion around an axis, while a shear force is a force that acts parallel to the cross-section of a structure and causes deformation in the plane of the cross-section.