Strain Gauges
T.C.D | Measurement of Strain using Electrical Resistance Strain Gauges | 3B3 - Mechanics of Solids | | Adam McCreevey | 3/15/2013 |
This is a laboratory to learn how to make measurements using a strain gauge by using different configurations, also to determine experimentally the axial and transverse stress at the surface of the beam and compare them to theoretical calculations |
Introduction
If a length of wire is subject to a stress within its elastic limits, the resulting elongation and change of diameter alters the resistance. The resulting principle is used in the resistance strain gauge, which consists of many turns of resistance wire, wound on an insulating former, the strain gauge wire is selected for the minimum temperature coefficient of resistivity. They may be used to measure extremely small displacements, of the order of nanometres. Strain gauges are classified as bonded or non-bonded. The bonded type has a wire mounted on a paper backing and the paper could be pasted to the surface of the body under strain. The unbonded type is simply wire mounted between two supports which move with respect to each other. For the purpose of this experiment, we use the bonded type of strain gauge. In order to convert variations in resistance into recordable electrical signals, the strain gauge is used as one arm of a wheatstone bridge. Each bridge produces a small differential voltage which is amplified, low-pass filtered and converted to a reading in microstrain. Because temperature errors may be encountered, the use of a single gauge element is uncommon.
Strain gauges can be configured in different ways to measure different aspects of strain. In this lab, we used 5 strain gauges. Two of the gauges were set up in a linear/ single configuration to measure the strain in one direction. The other three gauges were set up in a rosette configuration. This allows the measurement of the strain locally in all directions. The strain gauges in this
This is a laboratory to learn how to make measurements using a strain gauge by using different configurations, also to determine experimentally the axial and transverse stress at the surface of the beam and compare them to theoretical calculations |
Introduction
If a length of wire is subject to a stress within its elastic limits, the resulting elongation and change of diameter alters the resistance. The resulting principle is used in the resistance strain gauge, which consists of many turns of resistance wire, wound on an insulating former, the strain gauge wire is selected for the minimum temperature coefficient of resistivity. They may be used to measure extremely small displacements, of the order of nanometres. Strain gauges are classified as bonded or non-bonded. The bonded type has a wire mounted on a paper backing and the paper could be pasted to the surface of the body under strain. The unbonded type is simply wire mounted between two supports which move with respect to each other. For the purpose of this experiment, we use the bonded type of strain gauge. In order to convert variations in resistance into recordable electrical signals, the strain gauge is used as one arm of a wheatstone bridge. Each bridge produces a small differential voltage which is amplified, low-pass filtered and converted to a reading in microstrain. Because temperature errors may be encountered, the use of a single gauge element is uncommon.
Strain gauges can be configured in different ways to measure different aspects of strain. In this lab, we used 5 strain gauges. Two of the gauges were set up in a linear/ single configuration to measure the strain in one direction. The other three gauges were set up in a rosette configuration. This allows the measurement of the strain locally in all directions. The strain gauges in this