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Case Studies - LCVP Strain Gauging

Imes were involved in a project to evaluate the suitability of the existing Landing Craft Vehicle and Personnel (LCVP) mills gear. The craft was load tested using Water Weights and monitored using strain gauging and Acoustic Emission (AE) provided by Imes field engineers.

Imes were asked to:

  • Investigate whether the deck of the boat carried load when involved in lifting operations.
  • Determine whether the supporting struts on the Forward gear carry load when involved in lifting operations
  • Investigate the structural integrity of both sets of Mills gear, Forward and Aft and particularly the connection of the Mills gear to the keel plate on both batch types 1 and 2.
  • To determine what stresses are experienced on the Mills gear under a load test to 210% of rated SWL.

Initially two lab based destruction tests were completed upon specimens of the material used within the keel-plate to determine if this material was suitable for AE testing, the type of AE signals that could be detected and the level of warning that could be expected prior to yielding.

Using Water Weights it was possible to accurately control the load applied to the vessel and have it evenly distributed. This allowed the test to more accurately simulate in-service conditions than would be possible with conventional loading techniques. A total of 32 AE sensors and 25 strain gauges were deployed to assess the stresses experienced by the vessels during the load tests, and two separate vessels were tested.

From the data collected it was possible to determine that there was yielding in the aluminium keel plate during the proof testing.