The thermal or cold wake of the underwater vehicles will be formed at the sea surface in different region during sailing, then the underwater vehicles will be detected by airborne or space borne infrared detectors easily, which will imperil their security. A model between the detection probability and the Noise Equivalent Temperature Difference (NETD) of the detectors, and the temperature difference between the wake and the sea surface, etc., was established and the evaluation of detection probability in different discrimination levels and other parameters, such as time, location, atmosphere, sea, detector performance, wake temperature, etc., was realized, and a software named Wake Detection of Underwater Vehicle by Infrared (WDPUV-IR) was developed. The results showed that the detection probability to the wake with high detector performance or large temperature difference or short detection distance or low discrimination level was relatively high, but it was difficult to detect targets with small temperature difference and size when the atmospheric transmittance value was low.
A numerical method is proposed for the transport of infrared radiation in participating medium. The method is implemented using the Finite Volume Method (FVM) for solving the radiative transfer equation (RTE), and Mie theory for computing the absorption and scattering characteristics of the medium. The advantages of the method reflected in two aspects. On the one hand, the radiative characteristics is got from a data base established in advance using Mie theory, on the other hand, the scattering phase function is simplified by distinguishing the "forward average scattering" and "other directional average scattering". Both the two procedures yield significant computational savings with little loss in accuracy for predictions of spectral and total transmission.
As we all know, the temperature distributions reflected in the thermal images are the basis for detecting the information of subsurface defect in thermographic NDT. In the actual work of thermographic nondestructive inspection of the inner surface geometry of a plate-shaped structure, the cave defect in the inner heated surface usually results in a temperature rise of the outer inspection surface. However, on some specific conditions, an extension on the inner surface will also result in the same temperature rise of the inspection surface. Because the extension has no negative effect on the reliability of the plate or this extension is an originally designed functional structure, we may call this extension of the inner surface “fake defect”. In this paper, we will take a three-dimensional plate with a cylindrical extension as an example to discuss how this fake-defect phenomenon forms and when this phenomenon appears. This study is of meaning to both the inspection and quantitative identification of the inner-surface defect based on infrared thermographic temperature measurements of the outer plate surface.
The thermal wake would be formed owing to the cooling water or exhaust heat discharged by ship, and the cold wake could be formed by the cool water in the lower part of sea stirred up by the ship propeller or vortexes. Owing to the difference of surface temperature and emissivity between the ship wake and the surrounding ocean the ship wake will be easily detected by the infrared detecting system. The wave of wake also could be detected by the difference of reflected radiance between the background and the Kelvin wake of ship. In this paper the simulating models of infrared imaging of ship wake are developed based on the selfradiation of wake, the reflected radiance of the sky and sun and the transmitted radiance of atmosphere, and the infrared imaging signatures of ship wake are investigated. The results show that the infrared imaging signatures of ship wake can be really simulated by the models proposed in this paper. The effects of the detecting height, the angle of view, the NETD of detector and the temperature of wake on the infrared imaging signatures of ship wake are studied. The temperature difference between the ship wake and surrounding ocean is a main fact which effects on the detecting distance. The infrared imaging signatures of ship wake in 8-14μm wave band is stronger than that in 2-5μm wave band whenever the temperature of ship wake is warmer or cooler than the surrounding ocean. Further, the infrared imaging of thermal wake is investigated in the homogenous water and temperature stratified water at different speed of a ship and different flow rate and depth of the discharged water in a water tank. The spreading and decaying laws of infrared signature of ship wake are obtained experimentally. The results obtained in this paper have an important application in the infrared remote sensing of ship wake.
The dynamic simulation of infrared signature of the deep groove ball bearing (DGBB) was carried out based on ANSYS/LS-DYNA. A finite element model of the ball-raceway contact of the was established, and the slide friction between the ball and the raceway was considered as the main reason of heat generation, and the impacts of radial load, rotation speed and the coefficient of friction to the heat generation and the infrared characteristics of distribution were discussed in detail. The relative errors between the simulation results and the theoretical calculation value are less than 10%, which proves this simulation model is accurate and reliable.
Based on the theory of infrared radiation and of the infrared thermography, the mathematical correction model of the infrared radiation temperature measurement of semitransparent object is developed taking account by the effects of the atmosphere, surroundings, radiation of transmissivity and many other factors. The effects of the emissivity, transmissivity and measurement error are analysed on temperature measurement error of the infrared thermography. The measurement error of semitransparent object are compared with that of opaque object. The countermeasures to reduce the measurement error are also discussed.
KEYWORDS: Thermography, Infrared radiation, Control systems, Infrared imaging, Temperature metrology, Imaging systems, Linear filtering, Sensors, Chemical elements, Binary data
The components overheating inside an object, such as inside an electric control cabinet, a moving object, and a running
machine, can easily lead to equipment failure or fire accident. The infrared remote sensing method is used to inspect the
surface temperature of object to identify the overheating components inside the object in recent years. It has important
practical application of using infrared thermal imaging surface temperature measurement to identify the internal
overheating elements inside an electric control cabinet. In this paper, through the establishment of test bench of electric
control cabinet, the experimental study was conducted on the inverse identification technology of internal overheating
components inside an electric control cabinet using infrared thermal imaging. The heat transfer model of electric control
cabinet was built, and the temperature distribution of electric control cabinet with internal overheating element is
simulated using the finite volume method (FVM). The outer surface temperature of electric control cabinet was
measured using the infrared thermal imager. Combining the computer image processing technology and infrared
temperature measurement, the surface temperature distribution of electric control cabinet was extracted, and using the
identification algorithm of inverse heat transfer problem (IHTP) the position and temperature of internal overheating
element were identified. The results obtained show that for single element overheating inside the electric control cabinet
the identifying errors of the temperature and position were 2.11% and 5.32%. For multiple elements overheating inside
the electric control cabinet the identifying errors of the temperature and positions were 3.28% and 15.63%. The
feasibility and effectiveness of the method of IHTP and the correctness of identification algorithm of FVM were
validated.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.