Papers by Keyword: Infrared Thermography

Abstract: This paper provides an experimental investigation through infrared thermography of the steady-state temperature imbalance arising in parallel SiC MOSFETs. A switched-mode boost power converter based on two arrays of 4 parallel 1.2 kV MOSFETs is selected as a case-study. The analysis aims at proving that a proper device arrangement can minimize the thermal imbalance in the absence of circuit layout optimization.

Abstract: This study presents the results of visual and infrared (IR) inspection of photovoltaics (PV) technologies installed at the Qatar environment and energy research institute (QEERI) outdoor test facility (OTF) at Qatar Foundation (Doha, Qatar). Silicon based PV technologies which have been operational in the field since 2014, have been investigated for various failure modes. The visual inspections were carried out for all the PV modules from the backside however, the inspection from the front side was not possible for some modules due to heavy soiling. The visual defects which were identified during this study include, cracking of the back glass, yellowing of the encapsulant material, cracks formation in the back sheet, and pits formation in the back sheet. The visual inspection revealed that around 19 % of the total modules have back sheet cracking and discoloration, 8 % have yellowing of the encapsulant, and around 4 % were having pits in the back sheet. Moreover, one module was detected with back glass cracking. The IR inspection was also done both from front and backside for all the silicon PV modules to detect hot spots. The IR inspection has revealed that hot spots were generated at different locations of the PV modules. 39 % of the modules have hot spots at the location of junction boxes, around 6 % of the modules have hot spots in junction boxes and around 1 % have hot spots at the locations away from junction boxes. The visual and IR inspection has revealed that the dominant failure modes which have been observed for silicon-based technologies at OTF are the hot spots generation at junction boxes and the back sheet cracking, and its yellowing.

Abstract: Towards the growing trends in lightweight, flexible, and optical advantages, thin glasses become key components in numerous applications such as consumer electronics like foldable smartphones, or automotive interiors. Nonisothermal glass molding promises a viable technology for the cost-efficient production of precision glass components. In the existing production, the quality of the glass products can only be accessed at the end of the hot forming process. Due to high rates of product failures often appeared in the precision glass molding processes, the current quality control of the produced optical products suffers low process efficiency. This work introduces an enabling approach for monitoring the product quality in real-time using thermography and machine learning. Specifically, the acquisition of the temperature fields of the glass components during the hot forming stage enabled by an infrared thermographic camera allows machine learning to predict the final shape of the molded components at the end of the forming process. Several transfer learning models have been investigated to demonstrate the proposed method. To further enhance the prediction performance, self-built convolutional neural network models were developed using different types of image data. By incorporating the time-series image data as an input to the learning models, the prediction performance was achieved. The model built in the present work demonstrates an excellent prediction accuracy where the difference between the measured and predicted shapes of the glass products can be kept at low double-digit micrometers. Such accuracy achieved by our self-developed machine learning model promisingly satisfy the quality control in serial productions of numerous precision optical glass components in automotive and consumer electronics sectors.

Abstract: The uniaxial tensile test is often used to determine the mechanical properties of a material like its yield strength and elastic limit. However, some of the recent advances in imaging Non Destructive Evaluation (NDE) modalities offer experimental tools which, apart from determining the conventional properties, also make it possible to visualise and map the dynamic strain evolution during monotonic loading and correlate it with the micro mechanisms of deformation. Infrared thermal imaging (IRT) and digital image correlation (DIC) are two such advanced NDE methods which are being widely used in experimental mechanics. Infrared thermal imaging maps the thermal gradient including the dynamic thermal transients that may occur during the tensile testing and is based on the detection of infrared radiation. Digital image correlation, a non-contact optical method based on grey value correlation before and after deformation, maps the magnitude of deformation on the surface of the object under load. In this investigation, the global and local properties of a friction stir welded joint of 304 Austenitic Stainless steel through the simultaneous application of thermal imaging and digital image correlation. By characterising the various stages of tensile deformation, this study enabled correlation of the thermal and strain evolutions and to provide deeper insights into the micro-mechanisms of the associated deformation phenomenon.

Abstract: In this study, dynamic temperature field in a dissimilar steel joint specimen was numerically analyzed by means of three-dimensional explicit finite element analysis. Fully coupled thermal stress analysis was performed by using FE-code Abaqus/Explicit ver. 6.12. It was assumed that 90% of the plastic work was transferred to heat. Furthermore, dynamic loading tests were conducted with three-point bending specimen extracted from the dissimilar steel joint between a mild steel and a high tensile strength class steel. The specimen included a U-shape notch in the bonded interface. A high-speed infrared camera was used to measure the temperature field near the bonded interface. The temperature field was recorded at a frame rate of 200 Hz during the dynamic loading test. The numerically calculated temperature field near bonded interface showed reasonable agreement with the temperature field measured by the high-speed infrared thermography. The temperature in the soft steel particularly increased during the dynamic loading. On the other hand, the increase in temperature in the hard steel area was relatively few.

Abstract: The present work develops a learning methododology based on experiments related to the cutting temperature concept in turning processes. This proposal allows students to measure the temperature actually reached during a typical turning operation with a semi-automatic lathe. Temperature data are collected by a thermographic camera, which implies acquiring competences in this technique. The different tests involved in the practical experiment are defined for various cutting speeds and feed rates, and for a constant depth of cut. Two different materials are considered to point out the influence of turning parameters on cutting temperature.

Abstract: Bone Heating during Osteotomy for Dental Implant Placement is a High Risk Factor of Osteonecrosis. the Aim of this Study was to Investigate in Vitro the Temperature Changes Induced in Bone by Different Burs with External Cooling during the Surgical Step of Osteotomy. it was Used the Digital Infrared Camera FLIR SC640 (Flir Systems) that Allowed a Real-Time Infrared Thermographic Analysis of Thermal Images, Recorded 0.50 m Away from Osteotomy Site. there were Prepared 10 Osteotomy Sites with each MIS System Burs of Progressive Diameter (2 Mm ø, 2.8 Mm ø, and 3.2 Mm ø), at 2000 Rpm, on 30 Samples of Bovine Femoral Bone. the Thermographic Analysis Showed that the Mean Temperature Generated in Bone by Performing the Osteotomy was 46,5oC ± 0,48 for 2 Mm ø Bur, 59,5oC ± 1,62 for 2.8 Mm ø Bur, and 51,4oC ± 0,51 for 3.2 Mm ø Bur. Surprisingly the Maximal Temperatures were Recorded with Intermediatte 2.82 Mm ø Bur. the Infrared Thermography Proved to Be a High Accurate, Fast, and Efficient Non-Invasive Method of Bone Temperature Measurement Generated during Drilling for Placement of Dental Implants. while Drilling the Bone in a Progressive Sequence of Bur Diameters, the Temperature Raise is Non-Uniform because the Quantity of Removed Bone is Changing from One Bur to the other, and the Mechanical Friction of Following Burs in the Series is Reduced as Compared to the Pilot Bur.

Abstract: Honeycomb composite structures widely used in aviation are sturdy and light-weight but they may accumulate water from the atmosphere during aircraft operation. The presence of water in honeycomb cells leads to a higher airplane mass and excessive corrosion of aluminum cores, while the frozen water endangers panel integrity. This work describes the use of infrared thermography for detecting water trapped in aviation honeycomb cells.

Abstract: In the present work, the martensite formation during heat treatment of 1026 steel was studied in order to acquire process knowledge and reinforce the effectiveness of infrared thermography method to evaluate the temperature distributions. Several tests were carried out and monitored by an infrared camera and thermocouples. Martensite fraction was evaluated with the aid of the Koistinen-Marburger model and adequate parameters describing phase transformations were obtained for 1026 steel samples. This research revealed the need of model adjustment in order to accurately describe the martensite transformation kinetics according to experimental results.

Abstract: The paper presents a method which combines experimental and theoretical approach, to derive an expression for estimating the power of thermal source in a turning process. This method uses a finite element mesh overlapped on infrared images (obtained from the cutting process), in order to extract the nodal temperatures corresponding on. A reverse formulation for a finite element analysis is used, knowing the nodal temperatures and boundary conditions, and deriving the thermal load which produces the measured thermal distribution. This experiment has concentrated to allied steel.