The unique properties of Terahertz (THz) radiation include among others the ability to penetrate through electrical insulators such as ceramics, plastics, or plastic composites. Because of that, it is possible to non-destructively and contact free analyze the materials with internal cavities both in transmission and reflection configuration. The commercially available low-power sources provide results which quality is still beyond expectations. As a result, efforts are being made to resolve the studies' focused on optimizing the experimental setup. In the presented work the comparison between two experimental setups operated at the frequencies of 100 GHz and 300 GHz was described. The studies were performed in transmission mode on selected composite material. They were next compared to the results obtained using common pulsed thermography. Some practical application in non-destructive testing and possible improvements of described methods are discussed.
With regards to composites, the need for non-destructive evaluation (NDE) of their inner structure, or constructions they form continuously rises. Nowadays, a great deal of attention has been paid to methods based on the use of Terahertz radiation (THz). It is related to the exceptional properties of THz radiation which allows for contactless, safe, and fast inspection of non-conductive materials. In the frame of this work the results of the use of the Terahertz imaging method, operated at the frequency of 300 GHz, are presented. The selected aramid fiber-reinforced composites with intentionally introduced defects were monitored. A thorough structural materials inspection was carried out in transmission mode. The obtained images were preprocessed and enhanced. Overall, the phenomenon of noninvasive monitoring using Terahertz radiation and the tremendous advances in this field were presented.
With regards to composite materials, the need for noninvasive evaluation of their structures, components, or systems they form continues to rise. It relates to the fact that composites, due to their two-phased (at least) composition, are vulnerable to different damages arising during their manufacturing or their use. Thus, there is a need to non-destructively monitor such materials especially when they are used in safety applications such as e.g., bulletproof vests and their damage may pose a real threat. In the frame of this work, the use of the newly developed non-destructive testing (NDT) method based on the application of Terahertz (THz) radiation was presented. For this purpose, the series of samples without defects and with a defect in their interior was investigated. The samples were prepared as the soft insert of a bulletproof vest and one of them had intentionally introduced defect in the form of aramid fibers textile soaked in salty water. The results obtained using the THz imaging method were compared to the ones obtained using the conventional X-ray method. Overall, the potential of THz transmission measurements was demonstrated and a selected application using THz-based system was presented.
In the case of weapons, the inner surface of the barrel bore, due to difficult operating conditions, such as high pressure, high temperature and chemically aggressive products of propellant combustion, are exposed to wear and damage. The paper presents an analysis using both a numerical simulation and experimental tests, conducted in order to check capability of non-destructive testing of gun barrels using eddy current thermography. The obtained results have confirmed the capability of detecting defects on the barrel bore surface by means of this method.
SPARTAN is a multimedia shooting training system that uses optoelectronic solutions such as simulated firing with a laser technology, infrared detection of the points of impact projectiles of training and live ammunition, the use of adapted nightvision and thermal sights for shooting. It is designed to teach, monitor and evaluate the targeting of small arms and to prepare soldiers for firing the live ammunition at open ranges for combat targets and silhouettes. It is also intended for the preparation of soldiers for detection, classification and engagement of real targets upon different terrains, weather conditions and periods during the day. The aim of the paper is to assess the impact of the system on the soldiers training process as well as the economic aspects of its application. This system in the Polish Armed Forces, in various configurations, has been used for several years, so it is possible its preliminary analysis.
Aramid composites very often occur in the form of laminates, resulting from the combination of layers of aramid fabric joined by various resin types. The most effective methods in the testing of composites reinforced with fibres are active methods of infrared thermography. In non-destructive thermographic testing, defect detection is carried out by means of image (thermogram) analysis. During tests, a sequence of thermograms consisting mainly of several hundred or more individual images is recorded. An effective analysis of such a large number of images without the use of appropriate algorithms is practically impossible. In order to improve the visual representation of defect occurrence in the thermograms, special image processing methods are utilised, such as Principal Component Analysis. . Selected results from these analyses are presented.
Part of basic training for every soldier is firearms training, during which soldiers learn to master the principles of firearm operation, proper posture, and correct use of weapons including constructing and servicing the weapon. The main objective of this training is to improve their skills with small arms using different targets in different weather conditions. A particularly difficult part of this training is shooting at night. In night conditions, shooting is carried out using optoelectronic sights: night vision and thermovision. The principle of operation of a night vision sight is based on the reinforcement of residual visible light. Thermovision sights for imaging need infrared radiation in two basic so-called 3-5 μm and 8-14 μm windows. Therefore, targets used for daytime shooting, visible in the normal visible range, can’t be seen at night using these sights. Of course, these targets could be lit with reflectors of visible light and would then be visible without the use of night sights, but clearly these are not conditions that occur during real military operations. A variety of heated targets are used, but it is easy to damage (cut) them while shooting, especially the power cables used in their construction. As a result, the target immediately stops working. A consortium consisting of MIAT and OPTIMUM undertook the development of new target solutions, whose utility parameters will be much better than previously used targets. As a result of this project, three types of non-heated targets for both night and daytime shooting, and a heated target were developed. This paper presents both the concept of these targets and testing results of their models.
Multimedia shooting training systems are increasingly being used in the training of security staff and uniformed services. An advanced practicing–training system SPARTAN for simulation of small arms shooting has been designed and manufactured by Autocomp Management Ltd. and Military Institute of Armament Technology for the Polish Ministry of National Defence.
SPARTAN is a stationary device designed to teach, monitor and evaluate the targeting of small arms and to prepare soldiers for:
• firing the live ammunition at open ranges for combat targets and silhouettes
• detection, classification and engagement of real targets upon different terrains, weather conditions and periods during the day
• team work as a squad during the mission by using different types of arms
• suitable reactions in untypical scenarios.
Placed in any room the training set consists of:
• the projection system that generates realistic 3D imaging of the battlefield (such as combat shooting range) in high-resolution
• system that tracks weapons aiming points
• sound system which delivers realistic mapping of acoustic surroundings
• operator station with which the training is conducted and controlled
• central processing unit based on PC computers equipped with specialist software realizing individual system functions
• units of smart weapons equipped with radio communication modules, injection laser diodes and pneumatic reloading system.
The system make possible training by firing in dynamic scenarios, using combat weapons and live ammunition against visible targets moving on a screen. The use of infrared camera for detecting the position of impact of a projectile.
In military applications, laminates reinforced with aramid, carbon, and glass fibers are used for the construction of protection products against light ballistics. Material layers can be very different by their physical properties. Therefore, such materials represent a difficult inspection task for many traditional techniques of non-destructive testing (NDT). Defects which can appear in this type of many-layered composite materials usually are inaccuracies in gluing composite layers and stratifications or delaminations occurring under hits of fragments and bullets. IR thermographic NDT is considered as a candidate technique to detect such defects. One of the active IR thermography methods used in nondestructive testing is vibrothermography. The term vibrothermography was created in the 1990s to determine the thermal test procedures designed to assess the hidden heterogeneity of structural materials based on surface temperature fields at cyclical mechanical loads. A similar procedure can be done with sound and ultrasonic stimulation of the material, because the cause of an increase in temperature is internal friction between the wall defect and the stimulation mechanical waves. If the cyclic loading does not exceed the flexibility of the material and the rate of change is not large, the heat loss due to thermal conductivity is small, and the test object returns to its original shape and temperature. The most commonly used method is ultrasonic stimulation, and the testing technique is ultrasonic infrared thermography. Ultrasonic IR thermography is based on two basic phenomena. First, the elastic properties of defects differ from the surroundings, and acoustic damping and heating are always larger in the damaged regions than in the undamaged or homogeneous areas. Second, the heat transfer in the sample is dependent on its thermal properties. In this paper, both modelling and experimental results which illustrate the advantages and limitations of ultrasonic IR thermography in inspecting multi-layered aramide composite materials will be presented.
Eddy current thermography is a new NDT-technique for the detection of cracks in electro conductive materials. It combines the well-established inspection techniques of eddy current testing and thermography. The technique uses induced eddy currents to heat the sample being tested and defect detection is based on the changes of induced eddy currents flows revealed by thermal visualization captured by an infrared camera. The advantage of this method is to use the high performance of eddy current testing that eliminates the known problem of the edge effect. Especially for components of complex geometry this is an important factor which may overcome the increased expense for inspection set-up. The paper presents the possibility of applying eddy current thermography method for detecting defects in ballistic covers made of carbon fiber reinforced composites used in the construction of military vehicles.
Thermography is one of many techniques used for nondestructive testing for which both passive and active approach
could be taken. The passive approach is effective for materials and structures which are naturally at a different
temperature than the environment. The active approach requires an external heating source to stimulate the materials
or structures to be tested. These methods can be also applied to detect mines hidden in the ground. Passive approach
is used when natural heating of soil by sun radiation is exploited. In the case of active approach it is used an external
heating source for example a microwave source to provide thermal stimulation. In this paper the results of our
experiments with both methods carried out in the laboratory set-up and in the outdoor measuring field are presented.
The main disadvantage of applying the IRT method is presence of plenty false indications in thermograms. A simple
use of IRT equipment with better temperature resolution would not help in distinguishing the mines, since noise
comes not from a camera, but from soil surface. Recognizing the role of moisture and density of sand and
possibilities to express it quantitatively plays an important role. In our model of thermal properties of the soil the
volumetric unit of the soil consists of mineral and organic particles, as well as water and air. All needed parameters
can be calculated. Calculations of thermal signatures of the underground objects were made basing on 3D-heat
equation for the sinus type heating of 3D model and cooling by convection. Measurements were made for field and
laboratory stand-ups, using methodologies typical for "single-shot" measurements as well as analyses of transient
processes based on sequence of thermograms. Results of simulations and measurements confirm expectation tha that
high level of "radiant noises" is caused mainly by differences in the moisture and sand density levels.
Quick development of constructional composite materials application is caused by their good durability properties at low specific weight and resistance against corrosion. Requirements for prolonged service time generate the need for application of more efficient methods and diagnosis technics.
The main reason of defects in structures of composite materials is the variability of working charges in constructions during the process of using. Existed defects are complicated because of the effects like loss of continuity of reinforced fibres, binder cracks and loss of fibres adhesiveness to binders. Generally defects in composite material are usually more complicated than in metals. Diagnosis technics checked in metal constructions are little of use at composite construction research. At the present time an infrared diagnostics becomes more popular.
In the paper we present using of lock-in thermography for detection of destruction area in composite materials. Lock-in thermography is one of NDE methods providing phase images of thermal waves in a sample leading to receiving a distribution of internal defects and allowing for thermal properties evaluation. We used lock-in thermography in connection with modulated heat source synchronized with the IR image acquisition camera. We used a special lamp as the modulated heat source synchronized with the IR image acquisition camera. We used a special lamp as the modulated heat source. In this paper I present both simulated and measured results.
Values of thermal signature of a mine buried in soils, which ave different properties, were compared using mathematical- statistical modeling. There was applied a model of transport phenomena in the soil, which takes into consideration water and energy transfer. The energy transport is described using Fourier's equation. Liquid phase transport of water is calculated using Richard's model of water flow in porous medium. For the comparison, there were selected two soils: mineral and organic, which differs significantly in thermal and hydrological properties. The heat capacity of soil was estimated using de Vries model. The thermal conductivity was calculated using a statistical model, which incorprates fundamental soil physical properties. The model of soil thermal conductivity was built on the base of heat resistance, two Kirchhoff's laws and polynomial distribution. Soil hydrological properties were described using Mualem-van Genuchten model. The impact of thermal properties of the medium in which a mien had been placed on its thermal signature in the conditions of heat input was presented. The dependence was stated between observed thermal signature of a mine and thermal parameters of the medium.
The main disadvantage of applying IR thermal images for detection of buried mines, is the present of various false indications in thermograms together with strong influence of the environmental conditions for final results. A simple use of IRT equipment with better temperature resolution would not help in distinguishing mines, since noise does not come form camera but from the soil surface. The purpose of this paper is to present the phenomenology of the potential soil temperature gradients and distributions on the surface of the soil induced by both natural sources and buried mine. The aim of presented models is to help in recognizing the peculiarities of signal and noises depending on such parameters as: time and space variability of moisture and density of soil, buried mine and soil features and environmental conditions. Numerous examples of simulations and thermographic measurements are presented. Measurements were made for field and laboratory stand-ups, using methodologies typical for 'single-shot' measurements as well as analyses of transient processes based on sequence of thermograms. This paper shows chosen limitations of the thermal methodology efficiency.
In order to reduce a serious problem connected with the buried mines, various detection technologies are used. The main disadvantage of applying the IRT method is presence of plenty false indications in thermograms. A simple use of IRT equipment with better temperature resolution would not help in distinguishing the mines, since noise comes not from a camera, but from soil surface. Recognizing the role of time and space variability of moisture and density of sand and possibilities to express it quantitatively plays an important role. In our model of thermal properties of the soil the volumetric unit of the soil consists of mineral and organic particles, as well as water and air. All needed parameters can be calculated. Calculations of thermal signatures of the underground objects were made basing on 2D-heat equation for the sinus type heating of the three-layer model of cylindrical geometry and cooling by convection. Measurements were made for field and laboratory stand-ups, using methodologies typical for 'single- shot' measurements as well as analyses of transient processes based on sequence of thermograms. Results of simulations and measurements confirm expectation that high level of 'radiant noises' is caused mainly by differences in the moisture and sand density levels.
The main disadvantage of the IR thermography method for detection of buried mines is the presence of plentiful false indications in a thermogram. This often makes the level of false alarm too high. In a single and raw thermogram it was possible to identify mine with a naked eye only in rather rare and very carefully chosen, circumstances. We stated, that more attention should be directed on recognizing time evolution of detected signals, the same as recognizing usefulness of concepts and methodologies used in Dynamic Quantitative IR Thermography and active Thermal NDT. This paper presents the time dependent aspects of phenomenology potential detection mechanisms of buried mines, the same as selected methodologies developed for Thermal NDT and Dynamic Quantitative IR Thermography research and industrial applications. Results of the first trials in application software specialized for typical dynamic QIRT problems are shown, too.
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