Strain Gauge Measurements

Despite continued advancements in simulation modelling methods, strain gauge measurements remain important in determining actual strains developed in assets during testing and in-service operation.

The measurement of strain is a fundamentally simple, yet effective and accurate technique to record the strain that develops in components when loads are applied to them.

Strain gauges have application across almost any type of asset, with some examples being:

• Civil structures, such as bridges, overpass, steel and concrete buildings and various process building in mining, oil and gas.
• Product loading structures, such as ship loaders and container cranes.
• Shaft torsion measurements to determine both torque loads and torsional oscillations.
• Crushing plants
• Pipeline vibration
• Cranes and lifting equipment, an area in which ALS maintains LEEA (Lifting Equipment Engineers Association) developmental membership.

Advantages of Strain Gauges

The main advantages of testing via strain gauges include:

• Determining asset response under variable and unknown load conditions, such as materials bulk handling, excavation and mobile equipment.
• Determining loads applied, such as axial, bending or torsion.
• Providing high precision measurements.
• Strain gauges themselves are typically both small, inexpensive and their use does not damage the asset being tested.

The ALS Approach

To support our engineering investigations and our structural inspections, ALS maintains core capability in strain gauging.

By measuring strain in different directions and at different locations, the stress that a component is actually experiencing under load can be assessed. Through our technical experts, ALS can design effective strain gauge inspection programs that assess:

• Whether loads experienced by structures are as intended by design or whether load limits are being exceeded.
• Whether loads are changing under different operating scenarios.
• Whether or not fatigue cracking is likely to develop in structures.
• Determining the expected remaining life of the structure.
• The presence of any torsional resonance response in rotating shafts.
• Provide validation data for modelling.

Finite Element Analysis (FEA) is a computational analysis tool that allows stress in assets to be accurately estimated based on known engineering laws and principles. Existing designs with included defects can be assessed, as can expected modifications without having to rely on physical prototyping. However, the determination of realistic loads and restraints applied to such simulation models is often merely educated guesswork. Strain gauge measurements can greatly enhance the confidence in such models but providing calibration data to check against model predictions, plus provide actual load input information. The combination of strain gauging and finite element analysis gives ALS a massive advantage in understanding the stress conditions that assets encounter under operation.