Strain Gauge Blog Let’s understand STRAIN Whenever an external force is applied on a body, some changes occur in the dimension of the body. The ratio of this change of dimension in the body to its actual length is called Strain. It is a key parameter to identify the changes occurring in the internal structure of any material on load application. Types of STRAIN 1 Tensile Strain Produced by tensile force & results elongation of length & decrement in cross-sectional area. 2 Compressive Strain Produced by compressive force & results in decrease of dimensions of the body. 3 Volumetric Strain Produced by external forces & results in change in volume of the body. 4 Shear Strain Produced by shear forces & may result in change of shape of the …show more content…
This force creates a stress within a body that balance and react to the loads applied to it. The stress distribution may or may not be uniform, depending on the load application. Stress is directly proportional to strain within the elastic limit of the material known as Hook’s Law. Until this point, elastic deformation occurs as the material can come back to its original shape. Till this point, the applied stresses are lower than a critical stress known as yield strength. If a material is loaded beyond elastic limit, the material will remain in a deformed condition even after the load is removed. This is called plastic deformation. Measuring STRAIN Strain is measured using a gauge know as strain gauge. It is a sensor which is made of metal of specific resistance. An external force produces a change in the resistance of the sensor which can then be measured. Generally, strain gauges use copper-nickel or nickel-chrome alloy as the resistive element. If the original resistance is R & change in resistance is ∆R, the following relation is developed- Where, GF = Gauge Factor represents strain gauge sensitivity. The value is approximately 2 for above mentioned alloys. Types of Strain …show more content…
Strain Gauge Checking A number of methods are used for checking the strain gauge pasting & working. Visual Inspection Air bubbles are checked with the help of a magnifier. Poor bonding at edges are checked by pasting a gauge tape over the gauge and peeling it off again & again. Drift Check A ±3 micro strain drift is acceptable. If the drift is more, connection needs to be checked again. Electrical Check Check for the gauge resistance value as per the bridge configuration. After all the checking is done, apply M-Coat over the gauge to cover it from any environmental dust & other damaging conditions. Strain Gauge Measurement To measure the changes in resistance, different strain gauge configuration based on the concept of wheatstone bridge is used. A simple explanation of the wheatstone bridge is given here. Wheatstone Bridge The Wheatstone bridge is an electric circuit suitable for determining small resistance changes. It is therefore used to measure resistance changes of a strain gauge. The bridge is configured by combining four resistors. In Wheatstone bridge, R1 = R2 = R3 = R4 or R1 x R3 = R2 x R4 The output voltage of the bridge is equal to Vo
Elastic strain region at small and big end of connecting rod is shown in figure no. 10. The maximum and minimum equivalent strain values are 0.00033975 and 2.1407e-10 respectively. Due to applied pressure there will be change in original dimensions of the connecting rod and hence strain developed can be
Rigid body motion does not change the length of a vector joining the pair of points inside the body and has no concern with the strain analysis. When external forces are applied on an elastic body, the body undergoes deformation. Due to the elasticity of the body, there comes into play a force which resists the deformation. This force is called stress force. Clearly, the deformation of the body is accompanied by the stress force. In other words, stress and strain occur together in inelastic body. There are two types of elastic deformation: (i) Dilatation and (ii) Shear strain set up in the body in such a way that there is a change only in volume but no change in shape, is called dilatation. In the shear deformation, there is a change in the shape of the body without a change in its volume. Dilatations are further categorized into two kinds: compression, in which volume is reduced; and rarefaction, in which the volume is
...). Effect of Cold Drawing on Microstructure and Corrosion Performance of HighStrength. Mechanics of TimeDependent , 307-319.
US Army Correspondence. (2000). METAL PROPERTIES, CHARACTERISTICS,. US ARMY REPAIR SHOP TECHNICIAN WARRANT. Retrieved from www.hnsa.org/doc/pdf/metal-properties
First is contractility, the ability to contract or shorten in length. This causes increased tension between the ends of the muscle. Because of contractility, the length of muscles can decrease, increase, or stay the same. Next is extensibility, meaning that muscles have the ability to stretch when pulled. They are able to react positively to a force. Muscles also respond to stimuli like nerve impulses, a characteristic is known as excitability. Stimuli, whether external or internal cause muscles to contract. Last is elasticity. Muscles are said to have elasticity because they return to original size and shape after being extended or
as the “r-value” and “r” can be any value between -1 and +1. It can be
A strain is an injury of a muscle and/or tendon. Tendons are fibrous cords of tissue that attach muscles to bone.
The objective of this lab is to illustrated the procedures required to perform tensile tests. Using data obtained from the test will enable the student to determine various material characteristics that affect the design process. Some findings/interpretations are the stress vs strain curve will help us show how the metal reacted to the forces applied, and the point of failure is very important as it is the ultimate strength.
Strain – When muscle fibres stretch or tear it’s strain injury which is caused by muscle being stretched beyond its limits or forced to contract (shorten) too quickly. Muscle strains legs and back, such as hamstring strains and lumbar (lower back) strains.
It is the force which has to act on stock material in order to cut out the blank or slug. It determines the capacity of the press to be used for the particular tool.
• For this particular experiment the gain of the output for the strain gauges are set to 1 as 0 to 8 degrees slip angle is been measured. If smaller angles are measured a larger gain may be required.
The notch depth and tip radius is very important as some materials are more sensitive toward notches. Notches in the materials serve as stress concentration zones.
Yield strength (y) (0.2%) is found by drawing a parallel line to the elastic region and the point at which this line intersects with the stress-strain curve is set as the yielding point. The following figure shows the tensile tester that is used to test the samples. Figure 1: Tensile testers. Objective Tension test is carried out to obtain the stress-strain diagram, to determine the tensile properties and hence to get valuable information about the mechanical behaviour and the engineering performance of the material.
Law of elasticity is known as Hooke’s law, showing the relationship between the forces applied to a spring and its elasticity, which states that relationship between small deformation of the object and the displacement or size are directly proportional to loading and the deforming force. According to Hooke’s law, elastic behaviour of solids could explain by the fact that in component ions, molecules, or atoms from normal positions, which is small deformation, are also proportional to the force that causes the displacement. The deforming force might be applied to a solid by squeezing, compressing, stretching twisting, or bending. Accordingly, spring will return to its primary size and shape upon discharge of the load (Tega, 2010).