DESCRIPTION

Technical Description

Stress hypotheses are applied in the science of the strength of materials when calculating comparative stresses where unequal stresses are combined.

The following stress hypotheses, taking into account material properties, have been tried and proven in practice: Rankine yield criterion (direct stress hypothesis), von Mises yield criterion (change of shape hypothesis) and Tresca yield criterion (shear stress hypothesis).

The experimental unit WP 130 is used to verify these comparative stress hypotheses on test specimens made of various metals. For the purpose, a multi-axial stress state is produced at a point on the specimen and the resulting deformation is measured.

The specimen is clamped on one end to the fixed frame. A loading plate is clamped to the specimen on the other end. A load is attached on the outer circumference of the plate. A balance load compensates for the dead-load of the plate and the load. As a result only direct and shearing stress occur at a point on the test specimen and shear forces are avoided.

The loading plate has a graduation grid enabling loads to be attached at 15° increments. This permits purely bending moment and tor as well as combined load moments to be achieved. Diametrically opposite the load, measurement points are provided on the loading plate to measure the deformation. This enables the deformation at the point of maximum deflection to be measured.

The various elements of the experiment are clearly laid-out and housed securely in a storage system.

The well-structured instructional material sets out the fundamentals and provides a step-by-step guide through the experiments. 

Learning Objectives / Experiments

- generation of multi-axial loads on test samples made of ductile metals: 
  * steel, copper, brass, aluminium
- generation of various load moments
  * purely bending moment
  * pure torque
  * combined bending moment and torque
- determination of the yield point
- verification of the Rankine yield criterion 
- verification of the Tresca yield criterion 
- representation in Mohr’s Circle of stresses and strains