An Optimization Technique for Inverse Crack Detection

Any attempts to apply techniques that are based on indirect measurements of parameters that are believed to correlate to any material properties (or state) in an in-line situation must by necessity identify a mathematical model of this relationship. The most conventional approach is to use some empirically based model. If the analysis instead is based on an analytical model of a physical explanation, this trainee period can be minimized and the system is more dynamic and less sensitive to changes within the chain of production. A numerical solution to the inverse problem of ultrasonic crack detection is in this case investigated. This solution is achieved by applying optimization techniques to a realistic model of the ultrasonic defect detection situation. This model includes a general model of an ultrasonic contact probe working as transmitter and/or receiver and its interaction with the defect. The inverse problem is reduced to minimization of a nonlinear least squares problem and is performed with a quasi-Newton algorithm consisting of a locally convergent SVD-Newton method combined with a backtracking line search algorithm. The set of synthetic data the model is fitted with are generated both by numerical integration and with the two-dimensional stationary-phase method while the forward solver in the optimization procedure is based on the latter. In both these cases, the convergence, in terms of numbers of iterations, is sufficient when the initial guess is reasonably Close

Recent survey and application of the simSUNDT software

The simSUNDT software is based on a previous developed program (SUNDT). The latest version has been customized in order to generate realistic synthetic data (including a grain noise model), compatible with a number of off-line analysis software. The software consists of a Windows®-based preprocessor and postprocessor together with a mathematical kernel (UTDefect), dealing with the actual mathematical modeling. The model employs various integral transforms and integral equation and enables simulations of the entire ultrasonic testing situation. The model is completely three-dimensional though the simulated component is two-dimensional, bounded by the scanning surface and a planar back surface as an option. It is of great importance that inspection methods that are applied are proper validated and that their capability of detection of cracks and defects are quantified. In order to achieve this, statistical methods such as Probability of Detection (POD) often are applied, with the ambition to estimate the detectability as a function of defect size. Despite the fact that the proposed procedure with the utilization of test pieces is very expensive, it also tends to introduce a number of possible misalignments between the actual NDT situation that is to be performed and the proposed experimental simulation. The presentation will describe the developed model that will enable simulation of a phased array NDT inspection and the ambition to use this simulation software to generate POD information. The paper also includes the most recent developments of the model including some initial experimental validation of the phased array probe model. © 2010 American Institute of Physics

Estimation of Grain Orientation in an Anisotropic Weld by Using a Model of Ultrasonic Propagation in an Inverse Scheme

The initial step towards a nondestructive technique that estimates grain orientation in an anisotropic weld is presented in this paper. The purpose is to aid future forward simulations of ultrasonic NDT of this kind of weld to achieve a better result. A forward model that consists of a weld model, a transmitter model, a receiver model, and a 2D ray tracing algorithm is introduced. An inversion based on a multiobjective genetic algorithm is also presented. Experiments are conducted for both P and SV waves in order to collect enough data used in the inversion. Calculation is conducted to fulfill the estimation with both the synthetic data and the experimental data. Concluding remarks are presented at the end of the paper

POD GENERATED BY MONTE CARLO SIMULATION USING A META-MODEL BASED ON THE simSUNDT SOFTWARE

A recent developed numerical procedure for simulation of POD is used to identify the most influential parameters and test the effect of their interaction and variability with different statistical distributions. With a multi-parameter prediction model, based on the NDT simulation software simSUNDT, a qualified ultrasonic procedure of personnel within Swedish nuclear power plants is investigated. The stochastical computations are compared to experimentally based POD and conclusions are drawn for both fatigue and stress corrosion cracks

X-ray modeling of realistic synthetic radiographs of thin titanium welds

This paper describes the addition and benefits of an improved detector model and a radiographic noise model to a previously developed mathematical model of a specific radiographic system. The model intentions are to simulate realistic synthetic radiographs of thin laser welded titanium welds and to act as an X-ray projection kernel in an image analysis algorithm. Both these objectives put high demands on low calculation time and to accomplish this a number of simplifications have been done. An evaluation of the tradeoff when using the simplifications is essential and simulations of specific geometries and the radiographic inspection procedure are used for this purpose. As verification the simulated radiographs are compared to real digital radiographs relevant for the proposed applications

Experimental verification of phased array annular probe in ultrasonic immersion setting : Papers of the ECNDT 2023

With the ongoing development of materials and manufacturing techniques, new product design opportunities manifest themselves. However, care must be taken when applying techniques and material where there is less inherent knowledge about different parameters’ effect on the integrity of the final component. In conjunction with destructive testing of components, non-destructive evaluation (NDE) provides valuable insight into the manufacturing process reliability, as well as the possibility for subsequent future in-service inspection. Phased array ultrasonic testing (PAUT) facilitates the inspection of complex geometries on a wide set of material. Mathematical modelling of ultrasonic signal facilitates the optimization of inspection procedures by e.g., maximizing the probability of detection (POD) of specific defect types. In this paper, the response from an immersion annular phased array probe is experimentally validated to the output of the simulation software simSUNDT. In order to only validate the probe model (as both transmitter and receiver) a set of well-defined defects are used. The validity of the simulated amplitude response from side-drilled holes at a depth range of 20-115 mm is investigated. A total of 14 SDH holes in one test piece of is used as cases for validation. The results show a good correspondence between simulated and experimental data for the case where the probe is normal to the component surface. CC BY 4.0</p

Estimation of Grain Orientation in an Anisotropic Weld by Using a Model of Ultrasonic Propagation in an Inverse Scheme

The initial step towards a nondestructive technique that estimates grain orientation in an anisotropic weld is presented in this paper. The purpose is to aid future forward simulations of ultrasonic NDT of this kind of weld to achieve a better result. A forward model that consists of a weld model, a transmitter model, a receiver model, and a 2D ray tracing algorithm is introduced. An inversion based on a multiobjective genetic algorithm is also presented. Experiments are conducted for both P and SV waves in order to collect enough data used in the inversion. Calculation is conducted to fulfill the estimation with both the synthetic data and the experimental data. Concluding remarks are presented at the end of the paper

Radiographic sensitivity improved by optimized high resolution X-ray detector design

A compact imaging detector, based on scintillation fiber optics, has been used for high resolution industrial radiography since 1996. This type of imaging detectors have proven to give superior performance compared to fine grained industrial x-ray film in terms of detection efficiency and spatial resolution. The objective of this paper is to show that the radiographic sensitivity can be improved even further. First, the detection process has been studied by Monte-Carlo simulations and the result shows that the radiation is detected in a very narrow range from the axis of the primary beam. Secondary, Monte-Carlo simulations shows that a bent fiber optic image conduit can eliminate radiation induced noise in the CCD almost completely and reduce the depth of the detector to less then 100 mm