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/in 2 or N/m 2

6. Introduction  Shear Strain The 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. 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 GPa or 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  F is the force which acts  A is the area on which the force acts  Δx is 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 Load (N) Dial Gauge (mm) Deflection (mm) 0 10 20 30 40 50 60 70 80 90 100 110 120