DEMM | Engineering and Manufacturing magazine NZ

The combination of experimental stress measurement with
analytical techniques provides a powerful method of solving engineering problems.

For example, repeated tiebar failures on an injection moulding machine indicated that the loads were not being shared equally between the tiebars, with overloading as a result.

Strain gauges were attached to the four tiebars to measure individual loads. The loads were then equalised between the bars. The total load was also measured and compared with the normal machine settings.

In another example, a large industrial gearbox had suffered several shaft failures. Suspected causes were either a higher torque than the original design value, or superimposed vibrations. Strain gauges were attached to the shaft to measure the torque and a small radio telemetry unit mounted on the shaft to amplify the signal and transmit it to an adjacent receiver. Vibration was eliminated as the cause, but high cyclic loads and shaft stresses were measured and subsequent calculations showed agreement with the observed fatigue failures.

Optimech has a range of services including:

• Static and dynamic strain measurement using electrical
resistance strain gauges.

• Stress analysis and fatigue analysis.

• Measurement of loads, torque and displacement.

• Failure investigation.

• Vibration analysis.

• Temperature measurement.

• Mechanical and aeronautical engineering design and
consultancy.

Typical work includes checking for chassis cracking on logging trucks, aircraft propeller vibration testing, strain measurement on the Auckland Harbour Bridge, tensioning work on roof trusses, torque and power measurements on a ship’s propeller shafts, and much more.