infrared thermography in civil engianeering
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INFRARED THERMOGRAPHY IN CIVIL ENGINEEERING
Presented byAkash Padole B.Tech. Final Year Civil Engineering.GuideProf. P. S. Lande
GOVERNMENT COLLEGE OF ENGINEERING, AMRAVATI(An Autonomous Institute of Government of Maharashtra)DEPARTMENT OF CIVIL ENGINEERING & APPLIED MECHANICS 2013-2014
TABLE OF CONTENTSINTRODUCTIONMETHODS OF THERMOGRAPHY MECHANISM OF IR THRMOGRAPHY APPLICATIONS CASE STUDIES CONCLUSION REFERENCES
INTRODUCTIONThermography is nothing but the temperature profiling of a surface or point.As the name suggests, infrared thermography is based on infrared (IR) technique.The principle underlying this technique is that every object emits certain amount of IR energy and the intensity of this IR radiation is a function of temperature.Infrared thermography is one of the non-destructive thermal methods which is becoming even more popular in nondestructive testing of materials and structures as well.
HISTORY OF THERMOGRAPHY
Thermography has a long history, although its use has increased dramatically with the commercial and industrial applications of the past fifty years. Sir William Herschel, an astronomer, discovered infrared in 1800. He found that the heat radiation coming out from an object is beyond red light, The radiation causing this heating was not visible.He termed this invisible radiation "calorific rays".Today, we know it as infrared ray.
the technology advance allowed the development of the first quantum detectors, based on the interaction between radiation and matter now there is a direct conversion of radiation into electrical signalsWith this type of detector the response time was reduced considerably and measurement accuracy is increased.Then, The first commercial infrared cameras appeared in the end '90s.Recent innovations, particularly detector technology, the incorporation of built-in visual imaging, automatic functionality, and infrared software development, deliver more cost-effective thermal analysis solutions than ever before.
METHODS OF THERMOGRAPHYThere are two methods which is based on thermal radiation emission of the object or specimen on which thermographic image are obtain :
Passive thermography Active thermography
PASSIVE THERMOGRAPHYIt is a method in which there is no need of external source or light (or sunlight) and radiation is requiredThe thermo graphic image can directly generated as the object itself emitted the radiation and the camera captured these radiations and produces the image By using the passive thermography, defects in the construction elements that are not exposed to direct sunlight cannot be located
Setup for Passive thermography
ACTIVE THERMOGRAPHYIf a thermal gradient between the scene and the object of interest exist, the target can be inspected using the passive approach However, when the object or feature of interest is in equilibrium with the rest of the scene, it is possible to create a thermal contrast on the surface using a thermal source; this is known as the active thermography In this method, Energy brought to the object of interest will cause the change of thermal gradient, thus witnessing the presence of subsurface defects.
Setup for active thermography
METHOD OF THERMOGRAPHYAreas of specimens were 205 x 205 mm2Total thickness 2.5 mmA hot air blower with 2.5 kW output power was used as heat source The specimens were located at a distance of 30 cm from heat source while camera at 70cm
The shape of the high temperature region reflects the delamination shape under the surface due to the temperature differenceDue to the surface heating by active thermography, heat propagates from the surface to the rear side.
INFRARED Image of Specimen
TYPICAL INFRARED THERMOGRAPH CAMERA
FLIR ThermaCam P640 infrared camera
Other models of infrared thermograhic cameraFlir E40KIT15 Compact Infrared Thermal Imaging CameraFlir i3 Compact Infrared Thermal Imaging Camera
APPLICATIONSLocation of Voids In Concrete
Concrete test specimen including polystyrene cuboids with different sizes at different depths (photo before concreting)
Structural infrared Surveying of CMU Walls
Visual and infrared image of a CMU wall showing a bond beam (horizontal reinforcing) incomplete on the left side of the man door.
Quality Assurance of the Thermal Envelope
Visual and infrared image of a new residential building with air leakage and missing insulation.
Quality Assurance of the Moisture Envelope
Visual and infrared image of moisture in the outside ceiling of a residence
Roof moisture inspections
INFRARED image of RCC Roof
MERITS OF INFRARED THERMOGRAPHY
Reduces energy cost fast inspection rate Prevents electrical firesIt is a non-contact type technique. Fast, reliable & accurate output. A large surface area can be scanned in no time.Presented in visual & digital form.Software back-up for image processing and analysis.Requires very little skill for monitoring.It can be used to measure or observe in areas inaccessible or hazardous for other methodsIt can be used to detect objects in dark areas.
DEARITS OF INFRARED THERMOGRAPHY Quality cameras often have a high price range (often US$ 3,000 or more), cheaper are only 40x40 up to 120x120 pixelsCondition of work, depending of the case, can be drastic: 10C of difference between internal/external, 10km/h of wind maximum, no direct sun, no recent rainUnable to detect the inside temperature if the medium is separated by glass/ polythenematerial etcEffects of thermal losses (convective, radiative, conductive) perturbing thermal contrasts
CASE STUDY 1For actively heating the surface of structures to be investigated, different kinds of heating units including radiant and fan heaters, flash and halogen lamps can be appliedThe thermal heating unit contains of up to three INFRARED radiators having a power of 2400 WThe heating procedure is usually done dynamically by moving the radiators under computer control to obtain the best possible homogeneous heating
Left: Manual heating of the surface with an infrared radiator. Right: Recording of surface temperature with an infrared camera during cooling down
The presented case studies clearly show that active thermography can be applied for the investigation of cracks, delaminations and masonry structure behind plaster Recording thermal images with additional INFRARED radiation gives the best contrast for the detection of rising moisture at the surface
CASE STUDY 2 (North Middleton Bridge, Scottish Borders)The masonry arch bridge chosen was a twin span arch with each arch spanning 3.7 m, the width of the bridge 7.7 m and the height of the bridge 9 m.The types of defects that are theoretically expected to be detected by an infrared survey are areas where water is present, areas of delamination, cracks and voids
Figure showing the east side of the North Middleton BridgeInfrared image
Running vertically down the image is the drain pipe; this is warmer than the bridge because it is made of metal.Just below this feature is a very warm line running approximately a third of the way along the bridge on the right of the image. This is the metal reinforcing bracesLamppost, this can be seen as the sign on the lamppost is relatively warm
CONCLUSIONInfrared thermography is a modern non-destructive measuring method for the examination of redeveloped and non-renovated buildings. Infrared cameras provide a means for temperature measurement in building constructions from the inside as well as from the outside.It has been shown that infrared thermography is applicable for insulation inspection, identifying air leakage and heat losses sourcesThermography allowed studying the wetting and drying process of building materialsThermographic testing non-destructive technique has the main purpose to provide information by analyzing the real characteristics of the existing buildings in order to determine surface anomalies (cracks, voids, etc.)
REFERENCESTiano, P., Pardini, C. (eds.) (2008) "In situ monitoring of Monumental surfaces",Proceedings of the International Workshop SMW08, 27-29 October 2008, Florence, ItalyNondestructive Testing Handbook, Volume 3, Third Edition, Infrared and ThermalTesting, ASTM 2001, Chapter 11, Techniques of Infrared ThermographyBalaras C.A., Argiriou A.A., Infrared Thermography for Building Diagnostics. Elsevier Energy a. Buildings, 34, 171-183 (2002).V M Malhotra, N J Carino, 'Handbook on Nondestructive testing of Concrete', Second Edition, CRC Press, 2004.Biennial Quantitative Infrared Thermography (QUIRT) conference; 1992 2010
Binda L., Cantini L., Cucchi M., Thermovision: Applications in Conservation Field to Detect Hidden Characteristics of Building Structures. 11th North Amer. Masonry Conf., Minneapolis, USA, 2011Gamidi S. H., Non-Destructive Testing of Structures. Indian Inst. of Technology., Bombay, Nov. 20-23, 2009Barreira E., de Freitas P.V., Evaluation of Building Materials Using Infrared Thermography. Elsevier Construction and Building Materials, 21, 218-224 (2007).