• Measurement of strain using strain gauges.
  • Application of Mohr’s Circle for stress and strain analysis, determination of the principal strains.
  • Determination of the principal stresses: Axial and circumferential stresses in magnitude and direction
    • on an open vessel (pipe)
    • on a closed vessel (boiler tank)
  • Comparison of open / closed vessels.
  • Determination of the Poisson’s ratio.
  • Investigation of correlations between strain, pressure and stress in the plane biaxial stress state.


  • Investigation of the stresses and strains in a thin-walled cylinder under internal pressure.
  • Cylinder usable as open pipe or as closed tank.
  • Strain gauge application on cylinder surface at various angles.
  • Hydraulic cylinder with spindle to generate pressure.
  • Hermetically sealed hydraulic system, maintenance-free.

A bench top mounted unit for studying the stress and strain in a thin walled cylinder under internal pressures. A pressure relief valve on the hand pump is factory set and tested. The main component of this bench top unit is a thin-walled aluminum cylinder. It is sealed on one side with a piston which can be repositioned with a hand wheel. This makes it possible to create either the dual-axis stress state of a sealed container or the single-axis stress state of a tube. The cylinder is filled with oil and is

sealed. The internal pressure is generated with a hand activated hydraulic pump and displayed on an easy-to-read pressure gauge. Five strain gauges are attached around the perimeter at angles of 0o, 30o, 45o, 60o and 90o to the cylinder axis to measure deformation. The unit is used in conjunction with the measuring amplifier.

The findings obtained from the experiments using thin wall cylinder demonstrate the calculation and design methods for pipes and pressure vessels commonly applied in practice. The principal stresses are key variables in calculating and designing steam tanks, pressure vessels and pipes.

The stresses and strains occurring in a vessel are not measured directly, but are determined by measuring the strains on the surface using strain Gauges. The apparatus is used to investigate stresses and strains in a thin-walled cylinder subjected to internal pressure. The oil-filled cylinder is closed at one end and a movable piston at the other end. This conveniently permits the unit to be either open or closed ended. A bolt with a threaded spindle is used to move the piston. Two load cases are represented: biaxial stress state of a closed cylinder, such as a boiler tank, and uniaxial stress state of an open vessel, such as a pipe.

Internal pressure is generated inside the cylinder by a hydraulic cylinder and a spindle. A pressure gauge indicates the internal pressure. Strain gauges are attached to the surface of the cylinder to record the strains. The measurement amplifier gives a direct readout of the measured strains. To assist and visualise evaluation of the experiment, the measurement data can be imported into the application software.

Mohr’s Circle for stress and strain analysis is used to represent the conversion of the strain graphically and determine the principal strains. The principal stresses are calculated from the principal strains by applying the appropriate equations of elasticity.