A generic hybrid model for bulk elastodynamics, with application to ultrasonic nondestructive evaluation

Abstract

Practical ultrasonic inspection requires modeling tools that enable rapid and accurate visualisation; due to the increasing sophistication of practical inspection it is becoming increasingly difficult to use a single modelling method to represent an entire inspection process. Hybrid models that utilize different or interacting numerical schemes in different regions, to use their relative advantages to maximal effect, are attractive in this context, but are usually custommade for bespoke applications or sets of modelling methods. The limitation of hybrid schemes to particular modelling techniques is shown here to be related to their fundamental formulation. As a result it becomes clear that a formalism to generalize hybrid schemes can be developed: an example of how such a generic hybrid modelling interface is constructed is illustrated for the abstraction of bulk ultrasonic wave phenomena, common in practical inspection problems. This interface is then adapted to work within a prototype hybrid model consisting of two smaller Finite Element model-domains, and explicitly demonstrated for bulk ultrasonic wave propagation and scattering examples.Sources of error and ways of improving the accuracy of the interface are also discussed.

A time-domain finite element boundary integration method for ultrasonic nondestructive evaluation

“…The modeling procedure in this paper makes use of the concept from hybrid methods such as [13] and in particular as developed and implemented recently in [14]. The general hybrid concept as generated in [14] to model a complete ultrasonic inspection is illustrated in Figure 1.…”

“…The general hybrid concept as generated in [14] to model a complete ultrasonic inspection is illustrated in Figure 1. T1 represents the transducer sending waves to the defect and T2…”

“…We broadly follow [14] by dividing into three steps as well, but with major modifications taking advantage of boundary integrals. In the first step as shown in Fig.…”

“…To reduce the computation effort while handling a complete inspection problem, different hybrid methods have been developed [10]- [14] in the NDE field to combine numerical and analytical results. The main idea of these methods is to model the near field scattering behaviour of the defect in a small local region, and then project the monitored values to observation points as a post-processing procedure.…”

“…Also, in the time domain, simulated waveforms including surface reflections, tip diffractions, and surface waves can be visualized and benefit real inspection techniques, such as time-of-flight diffraction. A more generic time domain hybrid method has been developed recently to calculate the complete time domain signals [14] with implementation of an existing commercial FE time explicit solver. Similar with [13], a rectangular (2D) or cubic (3D) monitoring box is placed around the defect to monitor the scattered displacements and stresses which are used for field computation.…”