A strain gauge is described as a sensor. This sensor measures electrical resistance that varies with changes in strain. It’s worth understanding how this strain is measured and what a strain measures itself.
As a technical term, ‘strain’ consists of tensile and compressive strain. This is distinguished by the use of a positive or negative sign. With that being said, strain gauges can be used to pick up expansion as well as contraction.
A strain is the deformation or displacement of a material that has resulted from applied stress. This stress is something that has been applied to the material with force and is divided by the material’s cross-sectional area. Load cells focus this stress through beam elements, and it’s here that the strain gauges are located. The strain gauges are responsible for converting the applied force, the pressure, and torque into what will be an electrical signal.
This electrical signal can then be measured. The force causes the strain and that is then measured with the strain gauge by changing the electrical resistance. That voltage measurement is then gathered using data acquisition.
Using Strain Gauge For Different Materials
It’s important to know how different materials behave in different ways and how strain gauge can be beneficial to use. Take a rubber band, for example, you cause stress by pulling it, and then once you release the stress, it returns to its previous shape. After removing stressing forces from materials, they’ve undergone elastic deformation. Many materials like rubber, some plastics, and metals, are surprisingly elastic when very small forces are used on them. However, when elastic materials reach a point where they can’t cope with the extra stress, they stretch permanently. This is what’s known as plastic deformation.
Stresses and strains are incredibly important to know about when it comes to being an engineer. There are going to be some hefty forces that will impact certain creations, and so it’s important to know how much force materials that you’re using can take and whether you might need something stronger.
Types of strain gauges
There are five main types of strain gauges worth knowing about. These are mechanical, hydraulic, electrical resistance, optimal, and piezoelectric.
A mechanical strain gauge is good for knowing how much time you have available on problems like a crack in the wall. It can help you notice how quickly the crack is forming and how long you have to fix it. A hydraulic is commonly used in Geology and works very much like a syringe. Connect a large piston to whatever’s producing the strain and a smaller piston to measure how much movement has occurred. Electrical resistance is usually done with long, thin strips of foil, and using a Wheatstone Bridge, you can measure resistance to calculate the strain. Optical helps for those materials that can shatter easily and uses polarized light onto it at an angle. The amount of reflected light helps measure the strain. Piezoelectric is often used for quartz crystals and ceramics.
It’s good to have an understanding of strain gauges and how they can help measure stresses and strains in various materials that you might work with.
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