Before starting the measurement, the equipment is calibrated for a specific measurement volume through the use of a calibration body. The item to be tested is prepared by application of a random or regular high-contrast pattern to the surface. The pictures from the cameras are analysed using what is known as correlation analysis. The method provides a means of visual description of deformations and strains on the surface of the object, and permits 'virtual' sensors to be positioned at specific points.
SP Building Technology and Mechanics has six calibration objects for the equipment, covering measurement volumes from
25 x 25 x 5 mm3 to 550 x 550 c 550 mm3. The system can measure displacements and strains with a spatial resolution of about 0,1 mm for the smallest volumes, up to a few mm for the larger volumes. Strains from about 0,01 % to more than 200 % can be measured with an accuracy of up to 0,01 %.
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The system provides a means of enhanced analyses, and is therefore a valuable tool for SP's work of providing advanced services in the fields of materials testing, product development, method development and verification. In particular, the ability to combine this advanced method of measurement with calculations based on finite element analysis has a major potential. The equipment is also a valuable tool in the research projects that SP participates in. |
The measurement technique is used in such field as:
· Materials testing and characterisation
· Design and analysis of products and components
· Identification of non-linear relationships
· Characterisation of creep and ageing processes
· Determination of forming limit curves
· Fracture mechanics
· Verification of FEM calculations