Exp.4: Rubber in Shear Apparatus

1. Exp.4: Rubber in Shear Apparatus Eng. Ahmed Y Manama Eng. Saeed A Shurab Eng. Ahmed Al Afeefy

2. Objectives • Measure the shear deformation of the block. • Determine of modulus of rigidity.

3. Introduction • Rubber blocks in shear force are often used on engine and in equipment mounting to isolate vibrations. They do this by absorbing shock energy by deforming. This deformation leads to a decrease in cross-section as the block lengthens, an effect described by Poisson's Ratio.

4. Introduction Shear Stress and Strain

5. Introduction • The force F acting at angle theta with respect to the horizontal , the force resolved to it’s component ( perpendicular and parallel to the surface area). • The perpendicular component will produce an Axial Stress The parallel component will effect the rod by producing a Shear Stress. • The units of both Axial and Shear Stress will normally be lb/in2 or N/m2

6. Introduction • Shear StrainThe shear stress produces a displacement of the rod which produces a shear strain. The edge of the rod is displaced a horizontal distance, from its initial position ,this displacement (or horizontal deformation) divided by the length of the rod L is equal to the Shear Strain.

7. Introduction

8. Introduction Tan γ = γ = δ / L Where : δ is the deformation γ shear strain L original length The shear strain is dimensionless.

9. Shear Modulus (Modulus of Rigidity) • The modulus of rigidity ( shear modulus) (denoted by G or sometimes S or μ,) is concerned with the deformation of a solid when it experiences a force parallel to one of its surfaces while its opposite face experiences an opposing force (such as friction). • Shear modulus is usually measured in GPaor ksi (thousands of pounds per square.

10. Shear Modulus (Modulus of Rigidity) • It’s defined as the ratio of shear stress to the shear strain: • where • Fis the force which acts • A is the area on which the force acts • Δxis the transverse displacement • I is the initial length

11. Equipment • A rubber block 150 x 75 x 25mm is bonded to two aluminum alloy plates.

12. Results