Shear in Rubber Apparatus Exp 3 Introduction Rubber

Shear in Rubber Apparatus Exp. 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.

Shear Modulus (Modulus of Rigidity) • The shear modulus is the elastic modulus we use for the deformation which takes place when a force is applied parallel to one face of the object while the opposite face is held fixed by another equal force. • The bigger the shear modulus the more rigid is the material since for the same change in horizontal distance (strain) you will need a bigger force (stress). This is why the shear modulus is sometimes called the modulus of rigidity.

Objective • Measure the shear deformation of the block. • Determination of modulus of rigidity.

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

Shear Modulus (Modulus of Rigidity)

Results Load (N) 0 10 20 30 40 50 60 70 80 90 100 110 120 Dial Gauge (mm) Deflection (mm)

Questions • Plot the load against deflection • Draw the "best fit" straight lines through each set of points and determine the gradients. Then compute the modulus of rigidity (G). • Where the results are linear? • Would greater or lesser deflection improve linearity?