The shear machine (European patent EP 0687899) is a new concept testing machine that has been developed and validated within the framework of the Brite – EuRam Programme of the European Commission. On this machine, a pair of antisymmetric forces F₁ is exerted in the outer pinholes of a specially designed specimen and as a result an opposite pair of forces is developed in the two inner pinholes by reaction. Due to the antisymmetrical loading, at the middle of the specimen (gauge area) bending moment is zero and the shear force reaches a maximum, therefore pure shear conditions arise. The uniformity in shear stress distribution over the gauge area and the avoidance of stress concentration is assured by the smooth U-groove geometry in the shearing plane of the specimen and the smooth waist profile in the vertical (out-of-plane) direction.

The unique design of the shear machine enables:

§   The development of a uniform shear stress field in a 3-D specimen region

§   Controlled creep and fatigue testing at room and elevated temperature

§   Easy calculation of the nominal shear stress based on the applied forces without resorting to any constitutive relation for the material

§   Easy and reliable measurement of the shear strain field for small and large deformations by the use of a strain gauge rosette or a special extensometer

§   Shear testing along joint zones between similar and dissimilar materials (metal – ceramic joints) or along welds

§   Measurement of the constitutive parameters G_ij and strength in the three spatial directions.

§   Crack growth measurements at high temperature in real-time using either optical microscopy or a specially modified potential drop technique.