Tomasz Chady

Terahertz detection and identification of defects in layered polymer composites and composite coatings

Modern industry makes more and more extensive use of various composite materials. In this paper, for the purposes of various composite materials evaluation, the terahertz imaging method is presented. Basalt fibre-reinforced composites and polymeric anticorrosion coatings are considered. Basalt fibre composites are the innovative materials that are being increasingly used in modern industry. The paper also briefly introduces a specific type of complex coating of steel applied in the industry (e.g. oil or chemical). Two methods of defects detection in the mentioned structures are presented. The first method is based on a system identification, whereas the second one is on the estimation of time-domain signal parameters. Finally, the results achieved during terahertz inspection of coatings are compared with those obtained using active thermography.

Terahertz and Thermal Testing of Glass-Fiber Reinforced Composites with Impact Damages

The studies on glass-fiber reinforced composites, due to their growing popularity and high diversity of industrial applications, are becoming an increasingly popular branch of the nondestructive testing. Mentioned composites are used, among other applications, in wind turbine blades and are exposed to various kinds of damages. The equipment reliability requirements force the development of accurate methods of their health monitoring. In this paper we present the study of composite samples with impact damages, using three methods: terahertz time domain inspection, active thermography with convective excitation, and active thermography with microwave excitation. The results of discrete Fourier transform of obtained time sequences of signals will be presented as well as some image processing of resulting amplitude and phase images. Proposed experimental methods combined with harmonic analysis are efficient tool of defects detection and allowed to detect flaws in examined specimens. Reader may find it interesting that in spite of differences in nature of applied experimental methods, one technique of signal processing (harmonic analysis) gave adequate and comparable results in each case.

Electromagnetic system for nondestructive evaluation of train hollow axles

The structural integrity of train axles is one of the important factors for safety precautions in a railway industry. Most common techniques used nowadays in the railway industry for manual inspection are visual and magnetic particle techniques as well as ultrasound testing. In this paper, a novel system for electromagnetic inspection is proposed to meet the aforementioned requirements. The system consists of two subsystems and transducers dedicated for flux leakage and eddy current method. Results of measurements and evaluation of the transducers are provided.

Testing of glass-fiber reinforced composite materials using terahertz technique

Terahertz electromagnetic waves become a very useful tool for nondestructive testing of glass-fiber reinforced composite materials. In this paper we deal with detection abilities of defects which may arise in the mentioned structur es. Terahertz time domain measurements enable us to gain an information about interior part of multilayered materials. In o rder to flaws detectability evaluation finite element method simu lations were carried out. Numerical analysis was verified by measurements of multilayered reference structures.

Testing of composite materials using advanced NDT methods

Purpose – The purpose of this paper is to present capabilities of terahertz imaging technology in case of various composite materials and to propose a new defect detection algorithm.Design/methodology/approach – This paper first discusses an applicability of the terahertz technique in composite materials inspection. It then describes source of terahertz radiation (photoconductive antenna) and general structure of terahertz time domain imaging system. Next the terahertz imaging results of composite anticorrosion coating, glass‐ and carbon‐fiber‐reinforced laminates are presented. Then the signal processing and identification scheme based on time domain A‐scan signal equalization and C‐scan thresholding is presented. Data processed in this way are parameterized and defect identification database is prepared. The proposed procedure is verified using the exemplary inspection results of glass‐fiber laminate delamination. Finally, some comparison of terahertz time domain inspection with low energy digital radio...

Observation of Material Degradation under Fatigue and Static Loading Condition Using Selected Electromagnetic NDT Methods

The purpose of this paper is to present the results of observation of material degradation process in steel samples under combined conditions of static and cyclic dynamic loading, using selected electromagnetic NDT methods. To evaluate damages a Barkhausen noise observation, an AC magnetization, a magnetic flux leakage and eddy current method were used.

Eddy Current Transducer for Evaluation of Inhomogeneity in Titanium Billets

An effective method for inspection of billets made of titanium alloy is proposed. Two nondestructive testing (NDT) techniques were utilized: phase array ultrasonic testing (PA) and eddy current testing (ECT). In this paper, results obtained by ECT method will be shown and discussed. A dedicated transducer was introduced and optimized. The results of numerical simulations as well as measurements will be shown and discussed.

INTELLIGENT SYSTEM FOR RADIOGRAM ANALYSIS

In this paper we present a concept for an Intelligent System for Radiogram Analysis (ISAR) for welds quality inspection. Both, hardware and software solutions have been introduced in the system. The software operates with variety of scanner standards. It contains preliminary image processing (linear and nonlinear filtering algorithms) and some specialized functions, like Sauvola’s tresholding or IQI detection. The aim of the ISAR system is to support a radiologist in his work.

Numerical modelling of terahertz systems for nondestructive evaluation of dielectric materials

In this paper we deal with full-wave modelling of pulsed terahertz systems utilized in non-destructive testing. At the outset, some basic information on the terahertz NDT and next general remarks on its numerical modelling are presented. Frequency domain FEM and time domain FDTD analysis is carried out. Finally comparison of computed and measured signals is shown in order to prove numerical analysis correctness.

COMPARATIVE ANALYSIS OF SELECTED EDDY CURRENT TRANSDUCERS FOR TITANIUM ALLOY EVALUATION

Titanium alloy based details due to their mechanical properties continue to be in extensive use in various structures (mainly aerospace, automotive and petro‐chemical industrial applications). In this paper comparative study of various types of eddy current NDT transducers for testing titanium elements was done. Probes of absolute, differential and array configurations were constructed and analyzed. Two and three dimensional numerical analysis (FEM) were done in order to find the best type and configuration of the proposed transducers.