L.6 - Strain

Question 1

What is croissants ratio?

Answer 1

the ratio of transverse contraction strain to longitudinal expansion strain in the direction of the applied force / v=lateral strain/axial strain

Question 2

What is a strain gauge?

Answer 2

it is a transducer that undergoes a physical change in resistance due to applied displacement, force, or pressure

Question 3

if a strain gauge senses tension, would the resistance increase or decrease?

Answer 3

resistance would increase and vice versa

Question 4

How do metal strain gauges work?

Answer 4

a metal strain gauge is made up of a thin metal, bonded to the material surface and when the material undergoes strain, resistance in strain gauge changes

Question 5

What is strain sensitivity?

Answer 5

it is the ratio of the relative change in electrical resistance of a conductor to the relative applied change in conductor length

Question 6

When is a Wheatstone Bridge used? and how does it work?

Answer 6

• used to measure very small resistance changes
• it is an arrangement of resistors with similar values that produce voltage when one of the resistor values slightly changes

Question 7

What are some issues with using a Wheatstone Quarter Bridge?

Answer 7

1) because the resistance in the wire changes with temperature, that can negatively affect the accuracy of the strain measurement

2) when inserting a strain gauge, current flow causes power dissipation and self-heating, thus raising temp. and affect measurements

INSTEAD A WHEATSTONE HALF BRIDGE CIRCUIT CAN BE USED (MORE SENSITIVE AND BETTER THAN 1/2 WAVE)

Question 8

List some strain gauge applications:

Answer 8

1) Weighing scales

2) Electronic scales

3) Bicycle power meters

4) To measure strain placed on components of buildings