Question

i need a report (PowerPoint) about :

Strain-Measurement

Answer 1

Strain-Measurement:

1) Strain

• Strain is used to explain how the deformation of a material is measured. Due to the following factors, the material of a certain part or object can be elongated (tracted) or contracted (compressed), thereby experiencing strain: Impact of external force applied (Mechanical), The strength of heat and cold (Thermal), and Inside forces from non-uniform cooling, forging or welding of cast components (Residual).

2) Reason for measuring strain:

• Strain is most commonly measured to assess the level of stress on the material.
• The absolute value and direction of mechanical stress is defined by the measured strain and the material's established properties.
• Such calculations are based upon Law of Hooke.
• In its simplest form, Hooke's Law uses its elasticity or Young's modulus E [N/m2] to determine the relative proportionality of the strain $\varepsilon$ and the stress $\sigma$ [N/m2] of a certain material.
  0 = .
  

3) Strain-measurement:

• To understand how strain can be measured, the effects of strain on the material must first be understood. A non-strain specimen has a base/initial length of Li. If strain $\varepsilon$ is applied to the object, the length of the object will change by a certain quantity ($\Delta L$).

77 1

• 
  Change in Length Original Length ALL -L; LiL;
  
  • Where,
    • Lf - Final length;
    • Li - Initial length.
• Strain is a non-dimensional term, which describes a material's change in length relative to its initial length. Seeing that the length variations are typically very small, the SI system's regular fractional prefixes are used. In general micrometer per meter is used for pressure.

4)  Strain-measurement techniques:

• Photo-elasticity
• Strain gauges
• Brittle lacqures

5) Strain gauges:

• There are many different types of gages and sensors which can be used for strain measurements. Strain gauges are the most commonly used instruments.
• Mechanical strain gauges: They are used in applications requiring long gauge lengths and reliable instruments.
• Electrical strain gauges: Owing to the inherent advantages of electrical devices and the ability to calculate complex conditions at very high frequencies, mechanical strain gauges are replaced with electrical strain gauges.