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Experimental analysis and computational modelling of damage and fracture

Crack tip and notch tip plastic zone size measurement by the laser speckle technique

Crack initiation studies using a speckle technique

This paper presents an integrated peak spectral intensity method for the measurement of plastic deformation in metallic materials. The method employs a laser speckle technique and a computer based image processing system. Test results on aluminium, brass and copper sheets subjected to bi-axial stretching using the hydroforming process shows a correlation between the integrated peak spectral intensity coefficient Hi and the equivalent strain. In addition, the use of the parameter Hi requires less computation and enables measurement of plastic strains of up to 30%.

Plastic strain determination using peak speckle pattern intensity

A method for measuring plastic strain using laser speckle pattern has been presented. Unlike previous techniques, the method is based on the intensity level of the speckle image, thus enabling analysis to be carried out on a PC based system. The simplicity of the method and the results obtained indicate the potential of developing a non-contacting and in-situ measurement technique for the assessment of plastic deformation.

A pc‐based laser vision system for plastic strain determination

This paper presents an integrated autocorrelation method for the measurement of plastic deformation in metallic materials. The method employs a laser beam to illuminate the test objects. The diffracted images are digitised, recorded and processed on a computer based image processing system. The subsequent speckle pattern correlation analysis yields information on the surface deformation of the test objects. The technique is applied to brass tensile specimens and it is found that the integrated autocorrelation coefficient is linearly proportional to the plastic shear strain. For the range of plastic strain measured the error involved would be less than 10%.

C.J. Tay

Papers

Inegrated autocorrelation method for plastic strain determination

Plastic strain determination using peak speckle pattern intensity