Thermal Nondestructive Testing Research Articles

A novel reference-free technique for processing one-sided thermal NDT results in the time domain

In this study, simple analytical and numerical solutions were used to introduce a novel technique of processing thermal nondestructive testing (TNDT) results using a one-sided test procedure to determine material apparent diffusivity and represent TNDT results in the time domain without identifying non-defect areas. The technique is based on establishing dimensionless levels in the temperature decay functions that describe the cooling profile of a test sample after pulsed heating. The times when such levels cross the front-surface response curves may serve as specific heat transit times and may reduce the temperature-related noise. The corresponding level images are not associated with any reference point and allow determining apparent diffusivity thus providing more contrast representation of defect indications than raw infrared images.

Parametric study of anomaly detection models for defect detection in infrared thermography

In the current NDT 4.0 revolution, machine learning and artificial intelligence have emerged as the major enablers for non-destructive testing and evaluation (NDT&E) of industrial components. However, recent developments in active thermal NDT (TNDT) support its use as a practical method for checking a range of industrial components. Additionally, recent post-processing research in TNDT has developed several machine learning models to replace human interaction and offer automatic defect detection. However, the smaller area of the flaws and their related few thermal profiles than the wide sound area, leading to imbalanced datasets, make it difficult to train a supervised deep neural. Recently added to TNDT are anomaly detection models and one-class classifiers, both of which are commonly applied machine learning models to real-world issues. The accuracy and other important metrics in autonomous defect detection are influenced by the hyper-parameters of these models, such as contamination factor, volume of training data, and initialization parameter of the relevant model. The current paper investigates how initialization parameters affect these models’ TNDT capabilities for automated flaw detection. Using quadratic frequency modulated thermal wave imaging (QFMTWI), a carbon fiber-reinforced polymer specimen with variously sized artificially produced back-holes at different depths is examined. A good hyper-parameter for automatic flaw identification is chosen after qualitatively comparing testing accuracy, precision, recall, F-score, and probability.

Detecting and evaluating water ingress in horizontally oriented aviation honeycomb panels by using automated thermal nondestructive testing

Results of applying active thermal nondestructive testing for the detection of water ingress in horizontally oriented aviation honeycomb panels and quantitative evaluation of water content are presented. Unlike ultrasonic inspection, thermal testing allows detecting water and evaluating its quantity in the presence of air gaps between water and inspected honeycomb skin. The proposed algorithm based on using an artificial neural network has enabled estimating water content with errors under 15 % in the cases where water contacts with a honeycomb skin, as well as in presence of air gaps between skin and water.

Thermal testing of corundum ceramic plates

A review of the methods of production of corundum ceramics with specified characteristics is carried out and possible causes of hidden defects are indicated. Ceramic samples for research were obtained by the method of slip casting and their physical properties were determined. The possibility of diagnosing the integrity of corundum ceramic plates was investigated by the method of active thermal non-destructive testing. Various testing schemes and sources of thermal stimulation of the studied samples were applied. As a reference method, X-ray inspection was used, which confirmed the characteristics of the defect detected by the thermal method in the control sample.

DETECTION OF HAZARDOUS STATES AND FAULT CONTROL
 IN STRETCHED STEEL ELEMENTS BY THERMAL METHOD

The article discusses the areas of effective application, the features of heat generation and the main possibilities
 of the passive method of thermal non-destructive testing of steel elements and products. The basic requirements
 for passive thermal control equipment are formulated. The mechanism of heat generation in steel is described and
 the structure of the formula for changing its temperature during deformation is substantiated. It is shown that
 the diagnostics of steel elements in the passive mode should be carried out with the functioning of heat sources in them,
 arising as a result of force effects on structures. The features of determining the stress state in steel elements by
 the passive thermal method are considered.
 
 It is shown that the passive method of thermal non-destructive testing of steel structures, loaded with
 continuously increasing or decreasing forces in time, under the influence of which internal deformation heat sources
 and surface temperature fields function in potentially dangerous zones of elements, makes it possible to control the
 operability in elastic, elastic-plastic stages of steel operation, the origin and development of destruction. The power
 of thermal deformation sources, the places of their occurrence and the kinetics of development depend on the conditions
 of force loading, external temperature influences, material and structural shape of the elements.

Efficiency of using different types of infrared imagers in active thermal nondestructive testing of delaminations in non-metals

Six types of infrared imagers characterized by different technical performance (arrays from 160×120 to 640×512 and temperature sensitivity from 25 до 110 mK) and cost were used in active thermal nondestructive testing of delaminations with size from от 5×5 to 45×45 mm located at the depth of 3,1 mm in a reference sample made of polymethylmetacrilat. The efficiency of TNDT was evaluated by 9 thermographers to demonstrate that reasonable inspection results can be achieved by using IR imagers and modules of an economic cost segment.

Thermal nondestructive testing: traditional approaches and novel trends (review)

In the last years, thermal testing has shown up as a quickly growing nondestructive evaluation technique. This is explained by wide implementation of composite materials in many industrial spheres, first of all, aviation and aerospace. Inspection of composites by means of traditional nondestructive testing (NDT) methods encounters some difficulties, which can successfully be overcome by using thermal NDT. Moreover, an overwhelming progress in development and commercialization of infrared imagers also took place in the last two decades. On the basis of earlier reviews in the field of thermal NDT, the author has attempted to summarize recent achievements in this field, including inspection methodologies and data processing, as well as development of thermal NDT equipment and applications of this technique. The review describes both national achievements and international approaches, which have been lately proposed in thermal NDT thus making this technique a very promising in NDT of some classes of materials and constructions.

Effect of internal defects on the thermal conductivity of fiber-reinforced polymer (FRP): A numerical study based on micro-CT based computational modeling

Use of fiber-reinforced polymer (FRP) composite in structural and aerospace fields is often restricted in a heated service condition. The thermal-induced degradation of FRP can be complicated by the internal defects with geometrical irregularities. This highlights the need for new characterization methods capable of revealing the thermal conduction process of FRP with different types of defects. To this end, the present study establishes a state-of-the-art methodology, namely micro computed tomography based finite element analysis (μCT-based FEA), for evaluating the influence of internal defects on the thermal conductivity of FRP. The modelling work through μCT gains an insight into the actual three-dimensional (3D) meso-scale structures for various species of defects (void, needle-like cavity, air pocket/unfilled bug hole, and delamination) in FRP. From the numerical ‘virtual’ experiments, the simulated through-thickness thermal conductivities range from 0.2196 to 0.2270 W/(m·K), which are comparable with the experimental data from literature. The investigation also discovers that the unfilled bug hole and delamination decrease the effective thermal conductivity of FRP, while these defects can cause sub-surface heat concentration. In contrast, the needle-like cavity has negligible effect on the through-thickness thermal conductivity. Increasing the water saturation degree of defects leads to an exponential increase in the thermal conductivity of FRP, especially when a large air cavity or delamination is incorporated into the composite. Based on transient analysis, the relationship among temperature, heat flux intensity and exposure time is numerically determined. The research findings can motivate the applications of μCT-based FEA in quality inspection/control of manufactured polymer composite products and even in improving the thermal non-destructive testing methods for defect detection of field composite structures.

Thermal Nondestructive Testing: Development of Conventional Directions and New Trends (A Review)

Thermal Nondestructive Testing: Development of Conventional Directions and New Trends (A Review)

INCREASING THE ACCURACY OF DEFECTOSCOPY BY THE METHOD OF ACTIVE THERMOGRAPHY OF PRODUCTS MADE OF NON-METALLIC HETEROGENEOUS MATERIALS AND USED IN ENGINEERING

Nowadays, non-metallic heterogeneous materials are widely used in mechanical engineering, which is primarily due to their unique properties, such as strength, light weight, corrosion resistance, and high vibration, sound, and heat insulation characteristics. At the same time, non-destructive control methods that would allow to obtain the most complete picture of the defective state of products made of such materials are of great importance. The main task of the work is the development of optimal algorithms for determining each defect of a product made of non-metallic heterogeneous material with the establishment of its exact location, including the depth of occurrence, as well as its geometric parameters. The method of thermal non-destructive testing is considered promising. Studies of the accuracy of determining the parameters of defects in non-metallic heterogeneous materials by the specified method have been carried out.

The novel procedure of active thermal ndt: combining heating and forced cooling

A novel technique of active thermal nondestructive testing is proposed. It involves consecutive heating and forced cooling of the surface of test objects. The results of numerical modeling and experiments have demonstrated efficiency of this technique in case of test materials, which are characterized by a high level of emission/absorption noise. Optimization of such test procedure requires correctly choosing power and turn-on time of forced cooling to stimulate increase of temperature contrast over defects at particular times. An additional advantage of forced cooling is decrease of a thermal load on test materials that may be important in case of composites.

Detection of hidden defects of thermal protection of buildings and determination of some thermal properties of structural building materials by Non-destructive Thermal Imaging method

Objective. The purpose of the work is the practical approbation of a nondestructive thermal imaging method to identify hidden (invisible) defects and qualitative analysis of the thermal protection of a complex of construction objects in the city of Vologda, as well as the study of some physical (thermophysical) indicators (coefficients of thermal conductivity, thermal resistance (thermal insulation) and heat transfer) of structural building material in the form of silicate brick.Method. The fundamental laws of the theory of heat transfer, thermal nondestructive testing, infrared and technical diagnostics, the current domestic regulatory and technical and regulatory documentation, field experiments on real objects and laboratory samples.Result. The results of the practical determination of hidden defects in the thermal shells of the complex of civil and industrial buildings functioning in the urban environment, thermophysical properties (coefficients of thermal conductivity, thermal resistance (thermal insulation), heat transfer) of modern building materials by methods of thermal non-destructive testing are presented. The locations of identified invisible defects of thermal protection of the surveyed construction objects are determined and recommendations for their elimination are proposed. The obtained values of thermophysical characteristics for the studied structural building material are consistent with the data of current regulatory documents.Conclusion. The features of the nondestructive method of infrared thermography in determining the hidden defects of the heatshielding shells of operated buildings of various functional purposes and the complex of thermophysical parameters of modern structural building materials are shown. The demand for thermal imaging during energy and technical surveys of construction objects, their individual structural elements, life support engineering systems, as well as studies on the refinement, quantification and prediction of various thermal properties of building materials and products has been experimentally confirmed.

Perspective on pulse compression favorable infrared imaging techniques for non-destructive testing and evaluation of solids

Abstract Inspection reliability of sub-surface defects is imperative for safer functionality of critical components/materials/structures used in a wide variety of applications in various industries. The need for reliable, fast, remote, safe inspection and evaluation methods for detection of hidden defects increases in parallel with the demand for more sustainable solutions which helps in inherent modifications in design and manufacturing specifications. During in-service operation, the hidden defects are typically originated from various loading conditions leading to catastrophic failure. This perspective explores the best possible reliable, fast, remote, safe, and easy to implement for field inspection and evaluation experimental method and the associated post-processing approach using InfraRed Imaging (IRI) for Thermal Non-Destructive Testing and Evaluation (TNDT&E) of Glass Fibre Reinforced Polymer (GFRP) materials having delamination defects. This perspective further explores the state-of-the-art infrared imaging modalities used in TNDT&E by highlighting their advantages and limitations in terms of the detection sensitivity and depth resolvability to detect the subsurface defects located at interior of material. Most of the proposed experimental and post-processing techniques presented in the literature for TNDT&E, explore the observed spatial thermal contrast over the defective region of sample to provide the depth resolvability from the reconstructed thermograms even though it is obtained from the temporal data processing on the captured image sequence. This perspective provides an insight on the state-of-the-art research in the field of thermal/infrared non-destructive testing and evaluation and associated post-processing approaches to visualize the hidden subsurface defects not only resolved by spatial thermal gradients but also simultaneously provide temporal thermal gradients to locate defective regions.

ОПРЕДЕЛЕНИЕ ПОПЕРЕЧНЫХ РАЗМЕРОВ ДЕФЕКТОВ РАССЛОЕНИЯ БИМЕТАЛЛИЧЕСКОЙ ПЛАСТИНЫ ПРИ АКТИВНОМ ТЕПЛОВОМ НЕРАЗРУШАЮЩЕМ КОНТРОЛЕ

Various methods of nondestructive testing, including active infrared thermography, are used to detect latent subsurface defects in the contact of layers in multilayer products. One of the main difficulties using this method consists in processing and interpreting the thermal image data. The peculiarity of investigated defects of bimetal plate layers continuity violation is that the depth of defect location is known and the main task is to determine its size. Some methods are used for this purpose including analysis of spatial temperature profiles. Aim. To analyse the use of various approaches to determining the transverse dimensions of a delamination between metals in simulating active thermal non-destructive testing of steel-aluminium plates. Materials and methods. Mathematical and computer simulating methods, numerical differentiation are used. The delamination size is determined by projections of half the height of the amplitude signal and the extremum of the derivative of the temperature signal function. Calculations and graphical constructions are performed using the mathematical package GNU Octave. Results. Numerical simulation is carried out for different values of heat flow power, heating and cooling time. The temperature signal distribution over the surface of a multilayer bimetallic plate has been plotted. The values of the defect radius according to the projections of the characteristic points are determined. Conclusion. The results of simulation allow us to conclude that using the projection of the extremum of the temperature signal derivative function allows us to accurately estimate the defect size, while in the case of the point projection cor¬responding to half of the signal amplitude height, the result is underestimated. The obtained results can be used for further experimental studies of processes of active thermal non-destructive testing of products made of multilayer bimetallic materials.

Machine learning based models for defect detection in composites inspected by Barker coded thermography: A qualitative analysis

Machine learning and artificial intelligence have evolved as enablers for automation in various industrial applications. Barker-coded thermography is an active thermal non-destructive testing technique for examining subsurface features in industrial components. This article introduces supervised and unsupervised machine learning models for automatic defect detection in composite specimens inspected by the barker-coded stimulus. This work provides supervised and unsupervised machine learning methods to detect defects in composite specimens examined with a barker automatically coded stimulus. The suggested technology is tested using a carbon fiber-reinforced polymer sample with synthetically reproduced flat bottom hole flaws. The one-class Support vector machine is chosen for the unsupervised class of operation, whereas the supervised technique modifies the traditional Support Vector Machine (SVM). The qualitative comparison suggests that the unsupervised approach presents a less than 1% marginal difference in defect detection from its supervised counterpart.

ПОВЫШЕНИЕ ЭФФЕКТИВНОСТИ ДЕЯТЕЛЬНОСТИ ПРОМЫШЛЕННЫХ ПРЕДПРИЯТИЙ, СВЯЗАННЫХ С ПРОИЗВОДСТВОМ И ИСПОЛЬЗОВАНИЕМ БИМЕТАЛЛИЧЕСКИХ ЛИСТОВЫХ МАТЕРИАЛОВ

Improving the efficiency of industrial enterprises is heavily reliant on the technologies employed in production and the practical application of the products and structures produced by the companies. The authors' research on quality control methods for manufacturing bimetallic sheet materials and technological equipment has revealed that non-destructive testing methods can significantly reduce production costs. The study identifies thermal testing as one of the most effective forms of non-destructive testing. Aim. The research aims to explore these testing methods and their cost-saving benefits within current technological procedures. Justifying the use of thermal non-destructive testing as a method for improving the quality control of bimetallic sheet materials during the manufacturing process and enhancing the efficiency of management in industrial enterprises of the relevant profile. Materials and methods. Analysis of researches in the field of technologies and methods of thermal non-destructive testing for enterprises. Results. The benefits and cost-effectiveness of using thermal non-destructive testing methods in manufacturing companies that produce products and use technological equipment with bimetallic sheet materials are demonstrated. Requirements are outlined and a quality control system structure for these materials is established based on the thermal non-destructive testing method. A mathematical model for determining the thermal state of a bimetallic plate is presented alongside the potential for its software implementation. Conclusion. The method of thermal nondestructive testing proves to be efficient and productive in modern conditions, enabling acceptable cost implementation of quality control systems in production and operation. The findings can be applied in industrial companies that work with multilayer bimetallic materials in their products and constructions.

Linear frequency modulation infrared thermal imaging detection technology for GFRP/PMI foam sandwich structure defects

As one of the important structures of composite materials, polymethacrylimide (PMI) foam sandwich structure is prone to debonding and delamination defects during manufacturing and service, which seriously affects the mechanical properties of materials. Therefore, it is necessary to detect the defects of foam sandwich structure. A linear frequency modulation infrared thermal wave nondestructive testing system was built to study the correlation between the geometric characteristics (diameter and depth) of the defect and the surface temperature signal and its influence on the detection effect. The image sequence is processed by principal component analysis, discrete Fourier transform, thermal wave signal reconstruction, and other algorithms. Studies have shown that the larger the defect diameter, the shallower the depth, easy to detect defects, detection effect is good. The detection system can effectively detect and identify debonding and de-lamination defects. The thermal wave signal reconstruction method is superior to the principal component analysis method and the discrete Fourier transform method in the signal-to-noise ratio index, which improves the quality of the image and is conducive to the effective identification of the image surface defect information.

МЕТОД ИНФРАКРАСНОЙ ТЕРМОГРАФИИ ДЛЯ ВЫЯВЛЕНИЯ ПОВРЕЖДЕНИЙ НА КОМПОЗИЦИОННЫХ МАТЕРИАЛАХ ПРИ УДАРНЫХ ВОЗДЕЙСТВИЯХ С МАЛОЙ ЭНЕРГИЕЙ

The use of thermal non-destructive testing of products made of polymer composite materials for impact damage is one of the promising directions. The paper presents a mobile monitoring approach that provides damage detection at low impact values. A feature of the developed method of impact damage detection is a comprehensive consideration of the presence of a coating on the surface of composite material, the type of a source of thermal loading, the technical excellence of the thermal imager and the capabilities of the temperature imaging software. In the post-processing of thermal imaging data, the method used monoframe-processing technology, which included a set of operations: visualization of imaging data in a monotone palette, contrast enhancement of the thermal image and sub-framing – narrowing the area of analysis of the original thermal image, with a scanning search.

The Quality Assessment of External Building Envelopes Using Thermal Non-Destructive Testing of Residential Buildings

The Quality Assessment of External Building Envelopes Using Thermal Non-Destructive Testing of Residential Buildings

Reducing the level of interference at thermal non-destructive testing considering the specific thermal physical and morphological characteristics of the object

The Paton Welding Journal, 2022, №12. International Scientific-Technical and Production Journal «The Paton Welding Journal» «The Paton Welding Journal» has been published monthly since 2000 in English, ISSN 0957-798X. «The Paton Welding Journal» is a cover-to-cover English translation of the «Avtomaticheskaya Svarka» (Automatic Welding) journal. The «Avtomaticheskaya Svarka» journal has been published monthly since 1948 in Russian, ISSN 005-111X.