Stress and Materials
The department has carried out research looking at the fatigue and strength of complex materials and components for well over 30 years, working closely with industry and supported by the government.
Listed below are three current projects that show some of the diversity of the work undertaken.
Multiple flaw detection using artificial neural networks
The ability to detect damage automatically and at levels not perceivable by normal inspection has applications across a wide range of industrial sectors but particularly in fast processing environments such as the automotive industry. Many different techniques have been developed but difficulties still remain with regard to suitable experimental methods, signal processing and damage determination. In this work an artificial neural network based method has been developed to interpret ultrasonic A-scan signals that can indicate the presence, number, position and size of several flaws in steel components. The technique is being further developed to inspect components of more complex geometry and with multiple defects.
Strain distribution in superconducting coils
Knowledge of the strain distribution in superconducting coils is important as it affects the strength of the magnetic field and the amount of helium required to obtain the coil operating current. As the coil is energised any slight movements within the coil can create localised heating. This will make the coil non-superconducting which rapidly raises the temperature of the coil and boils off the liquid helium cooling agent. This means the coil needs to be re-cooled to start the energising process again, which is costly and time consuming.
A better understanding of the real strains developed within coil manufacture would help with understanding what causes more quenches (helium boil off) to occur within some coils over others. To obtain low temperature strain information an experimental apparatus is being developed using moiré interferometry. This will enable full field displacements to be measured across the coil surface.
Bearing versus bypass loading of composite joints
Bearing versus Bypass loading occurs in multi-fastened joints and is of special interest to the aircraft industry that uses these types of joints to join dissimilar materials. There is limited experimental data detailing the effect of hole clearance, laminate lay-up, washer contact size and clamping force value on the maximum bearing versus bypass loads obtainable.
In this work a special bearing versus bypass rig has been developed and a range of results have been obtained for a variety of composite layups. Numerical models have also been developed to better model bearing versus bypass failure. Future work is looking at the effect of fatigue loading.