In mechanical testing and analysis, one needs to know how an object responds to various forces. The strain is the quantity of deformation which a material gets because of an applied force. The strain is the ratio change in length of something to the original. It can be tensile (positive) because of elongation, or compressive (negative), due to contraction. The quality load cells from Tacuna are able to withstand all types of stress and strain. When an object is compressed to one direction, it expands perpendicular to the force in the other two directions, which is known as a Poisson effect.
Types of strain
There are four kinds of pressures. These are bending, torsional, axial and shear. Bending and Axial are common.
- A stretch onto a side of a material and the opposite side contraction because of linear force applied to the vertical direction is bending strain.
- Torsional strain considers circular force with components in horizontal and vertical directions.
- When a material compresses or stretches because of a linear force to the flat side, it is known as axial strain.
- Shear stress measures deformation amounts which take place from a direct force with vertical and horizontal direction components.
How to measure strain
Pressure can be measured using many methods though the most common one is by use of a strain gage. Electrical resistance in a strain gage varies about the size of pressure in the device. Bonded metallic is the most used strain gage. It consists of a fragile wire or, more traditional; grid pattern arranged metallic foil. The grid pattern increases the size of foil or metallic wire subject to strain in parallel directions. A thin backing known as the carrier bonds the network and is attached directly to the specimen of the test. Thus, the experienced strain from the test sample is moved directly into the strain gage and responds with an electrical resistance with a linear change.
A core parameter of the gage is its strain sensitivity to strain, which is expressed in quantity, as the gage factor (GF). Gage factor fractional change ratio in electrical resistance to the fractional length chain or stain. The GF is usually around 2 for metallic strain gauges. Sensor documentation or sensor vendor gives the real gage factor. Strain measurement in practice, rarely has quantities bigger than some few millistrain (e x 103).
Types of strain gages
There are three types of pressure configuration gages. These are full, half and quarter bridge, determined by some active elements on the Whitestone Bridge, the strain type being measured and the strain gages orientation.