simulated a bolt joint to investigate the CAN induced by bolt loosening.
Ansys 14 crack magnitude cracked#
also studied the CAN effect in a cracked pipe model where pulse-inversion technique was applied to maximise the second harmonic while minimising the other sources of nonlinearity. introduced a three-dimensional nonlinear elastic stress-strain into an aluminium plate model and defined the contact condition between crack surfaces to take into account the material nonlinearity and contact acoustic nonlinearity (CAN) due to the presence of crack. To further enhance the reliability of numerical simulation, 3D FEM was undertaken as well. defined a contact crack to a two-dimensional waveguide with changing crack length in each model to perform quantitative evaluation of crack using SHG. introduced nonlinear stress-strain constitutive relation to the model to study the plastic deformation in weld joint and Wang et al. developed a two-dimensional model with laser transient grating to detect closed surface crack on a steel plate using second harmonic generation (SHG). investigated the influence of crack orientation and localised multiple cracks in a 2D steel slab. The generation of higher harmonics has also been studied using 2D FEM. mimicked a disbonded single lap joint structure and identified the disbond based on subharmonic generation. simulated a cracked aluminium plate under various loading conditions to identify the damage by exploiting the nonlinear wave modulation technique. utilised FEM to examine the influence of damage depth and size on the generation of sidebands using vibro-acoustic modulation. FEM is one of widely employed approaches because of its advantages in analysing complex geometries and providing reliable insights into the generation of nonlinear characteristics as a result of the interaction between ultrasonic waves and defect. It could however be quite time consuming to carry out experiments to investigate all possible solutions.Īnalytical model, , local interaction simulation approach (LISA), finite difference method (FDM), and finite element method (FEM) are therefore adopted to simulate the wave propagation in waveguides for damage detection. On the other hand, guided waves are dispersive and have multiple modes existing concurrently at excitation frequencies, which produces certain challenge in application without careful design. Since nonlinear guided wave techniques have shown to be responsive to fatigue damage by monitoring the generation of nonlinear characteristics such as sidebands, ,, higher harmonics, ,, , and sub harmonics, due to the interaction between the ultrasonic wave and damage, it has a high prospect to be applied in SHM for damage detection in embryonic stage. For metallic structures, the failure modes are due to overload, corrosion, fatigue and creep where fatigue failure is common in mechanical structures. Structural health monitoring (SHM) is therefore of high importance to diagnose existing and potential defects, propose remediation work and estimate residual life. Given that the influence of crack orientation on contact acoustic nonlinearity (CAN) was taken into consideration, the developed advanced simulation could further enhance the capability of numerical modelling for simulating the interaction between nonlinear guided waves and fatigue crack, facilitating the fundamental investigation of CAN mechanism.Ī structure without regular inspection and routine maintenance not only reduces its life span but also presents a threat to the community. The results revealed that the nonlinearity in terms of the trend and magnitude with respect to crack length in the advanced simulation is closer to that in the experimental results than the common simulation approach where damage was modelled as a straight line crack. The simulated crack trajectory was first validated by experimental results in terms of crack initiation angle and number of fatigue cycles and was subsequently utilised for crack quantification based on second harmonic method. A numerical study including a fatigue crack trajectory simulation was undertaken by means of separating morphing and adaptive remeshing technology (SMART) Crack Growth in ANSYS, on the basis of which the simulations of nonlinear ultrasonic waves for fatigue damage detection using the precise fatigue crack trajectory was achieved.
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