Thermal Nondestructive Testing Method Research Articles

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.

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.

Deep Learning Automated System for Thermal Defectometry of Multilayer Materials

Currently, along with growth in industrial production, the requirements for product quality testing are also increasing. In the tasks of defectoscopy and defectometry of multilayer materials, the use of thermal nondestructive testing method is promising. At the same time, interpretation of thermal testing data is complicated by a number of factors, which makes the use of traditional methods of data processing ineffective. Therefore, an urgent task is to search for new methods of thermal testing that will automate the diagnostic process and increase information content of obtained results. The purpose of article is to use the advances in deep learning for processing results of active thermal testing of products made of multilayer materials and development of an automated system for thermal defectoscopy and defectometry of such products. The proposed system consists of a heating source, an infrared camera for recording sequences of thermograms and a digital information processing unit. Three neural network modules are used for automated data processing, each of which performs one of the tasks: defects detection and classification, determination of the defect depth and thickness. The software algorithms and user interface for interacting with system are programmed in the NI LabVIEW development environment.Experimental studies on samples made of multilayer fiberglass have shown a significant advantage of the developed system over using traditional methods for analyzing thermal testing data. The defect classification (determining the type) error on the test dataset was 15.7 %. Developed system ensured determination of defect depth with a relative error of 3.2 %, as well as the defect thickness with a relative error of 3.5 %.

Ways to increase the production efficiency of hardwood blanks

The article presents the main results of experimental studies on the identification of the main grade defects of oak lumber by the thermal non-destructive testing method. Regressional dependences of wood defects temperature display from the main factors for the studied grade defects are proposed. Indicators of infrared radiation (temperature range) of the main visible oak grade defects obtained as a result of experimental studies are presented. A conceptual scheme for the line control methods of identification of the main grade defects in lumber are proposed.

Fault-tolerant nondestructive control of the stress-strain state of the load-bearing elements of pantograph lifts

This paper proposes a method of fault-tolerant nondestructive control of the stress-strain state of the load-bearing elements of lift and transportation machines, considered on the example of a prototype of pantograph-type lifts. The basic requirements for the load-bearing elements of lift and transportation machines are analyzed. An experimental research technique has been developed including tensometric and thermal nondestructive testing methods. A full-scale experiment of a prototype pantograph-type lifts is shown.

Intelligent screening of electrofusion-polyethylene joints based on a thermal NDT method

The combinations of infrared thermal images and artificial intelligence methods have opened new avenues for pushing the boundaries of available testing methods. Hence, in the current study, a novel thermal non-destructive testing method for polyethylene electrofusion joints was combined with k-means clustering algorithms as an intelligent screening tool. The experiments focused on ovality of pipes in the coupler, as well as misalignment of pipes-couplers in 25 mm diameter joints. The temperature responses of each joint to an internal heat pulse were recorded by an IR thermal camera, and further processed to identify the faulty joints. The results represented clustering accuracy of 92%, as well as more than 90% abnormality detection capabilities.

Nondestructive Testing of Materials Using Thermal Imaging

Nondestructive testing is helpful in preventing unintended failures in manufactured components. The research presented here examines a thermal nondestructive testing method that makes use of laser heating. Potential defects are found by using a thermal camera to examine the temperature response on the nonheated side of the object being tested. A mathematical model for the temperature response is generated using a two-dimensional numerical conduction solution in cylindrical coordinates. The presence of defects is difficult to detect by simply examining thermal images, but if the temperature response calculated by the mathematical model is subtracted from the measured temperature field, any defects in the material become much more obvious. In examining what is, essentially, the residual temperature field, which should ideally consist of measurement noise, any aberrations in measured temperature from material defects are effectively magnified. The sensitivity with which defects can be detected is strongly affected by the degree to which the physical heating process is correctly described by the mathematical model. Synthetic experiments are used to show the impact of the accuracy with which the thermal parameters are known on the effectiveness of the analysis method. Physical experiments are also examined to show practical applications of the method.

Applications of Barker coded infrared imaging method for characterisation of glass fibre reinforced plastic materials

Among various widely used thermal non-destructive testing methods, non-stationary thermal non-destructive testing modalities have proved to be an indispensable approach for the inspection and evaluation of various solid materials. These techniques facilitate the use of low peak power heat sources in a moderate time compared with the conventional widely used pulsed and sinusoidal modulated (lock-in) thermographic techniques. In this reported work, Barker non-stationary excitation followed by Hilbert transform-based matched filtering for the detection of subsurface features lying deep inside a glass fibre-reinforced plastic test sample is incorporated. Results obtained from this pulse compression approach are less affected by random noise generated inside the test sample during experimentation as well as the variations of surface emissivity over the test sample. A comparison has been carried out among the amplitude, time delay and phase images obtained for the experimentally matched filter data.

Numerical Modeling of the Thermal Behavior of Corrosion in Conduit in Transient Mode

The conduits in the buildings require a regular and permanent control, in order to avoid the risks of deterioration caused by corrosion. In this paper we present a thermal nondestructive testing method of concrete structures containing a conduit system, based on the analysis by infrared thermography principle and the numerical modeling in three dimensions. The aim is to study the detectability of these pipes in different situations versus time and to give a thermal characterization of the rust behavior in the transitory mode.

Thermal Nondestructive Testing of Buildings and Builded Constructions

A thermal nondestructive testing method ensuring the determination of characteristics of tested objects from an analysis of their temperature fields including the heat engineering characteristics of buildings and builded constructions with the use of the thermal imaging technique of recording the temperature fields is developed. The method is based on solving the inverse problem of time-dependent heat transfer in a multilayered three-dimensional domain. A method of simplification of solving the inverse problem, namely, the simplification of the total “plausibility functional” by separating the implicit dependence on a part of the parameters is proposed. A specific realization of the industrial testing of an object under full-scale environmental conditions is considered with reference to thermal nondestructive testing of envelope structures of an apartment house.

Study of Polymer Materials by Dielectric and Thermal NDT Methods

The application of Non-Destructive Testing (NDT) techniques (dielectric spectroscopy, thermal conductivity and thermal activity) to different polymers, including fibre reinforced materials with and without voids is described. The NDT results are shown to correlate well with the structural parameters of the polymers.

Study of Polymer Materials by Dielectric and Thermal NDT Methods

The application of Non-Destructive Testing (NDT) techniques (dielectric spectroscopy, thermal conductivity and thermal activity) to different polymers, including fibre reinforced materials with and without voids is described. The NDT results are shown to correlate well with the structural parameters of the polymers.

An infrared line scanning technique for detecting delaminations in carbon fibre tubes

A thermal nondestructive testing method based on an infrared line scanner for cylindrical specimens is presented. A seven-layered carbon-glass fibre tube with an artificial delamination was used as a test sample. A finite difference computational model of the heating of the tube was constructed in order to simulate the measurement and evaluate the capability of detecting delaminations. The numerical results show the temperature difference caused by the delamination to be well above the practical detection limit, which was verified by the actual measurements.