Peltier Effect Applied to the Design and Realization of a New Mass Flow Sensor

The present paper deals with design and realization of a new mass flow sensor using the Peltier effect. The sensor, shaped as a bimetallic circuit includes two continuous parallel strips coated with a great deal of metal plated spots. In such a device, one track performs as a classical thermoelectrical circuitry whose both plated and uncoated parts provide the thermopile junctions. The other strip is subjected to electrical current so as to generate numerous small thermal gradients owing to the Peltier effect. Then, the resulting differences in temperature induce a Seebeck e.m.f. detected by the other strip acting as a receiver. The thermal coupling between transmitter and receiver tracks depends on many variation of the surrounding environment heat transfer coefficient. Therefore, such a device allows us to detect any shift in physical properties related to the apparent thermal conductivity. In special case of a steady state fluid, the induced e.m.f. in the receiving track hinges on the thermal conductivity. When the fluid is in relative motion along the sensor, the velocity can be read out as a funotion of voltage as an application, the sensor is placed into a tube conducting a fluid flow, in order to design a new mass flowmeter

Relaxable Damage in Hot-Carrier Stressing of n

A method for device characterization is experimented to qualify the relaxable damage in hot-carrier stressing of n-MOS transistors. The degradation of physical parameters of the body-drain junction of power HEXFETs is presented for applied stress condition Vg= Vd/2. Large decrease of the resistance series, of the ideality factor, and of the reverse recombination current are shown to be related to relaxation time, and are significant at Vg=–Vd. These effects are discussed and explained by the evolution of the interface states

Mapping Non-Destructive Testing Data on the 3D Geometry of Objects with Complex Shapes

Abstract This paper presents an approach for measuring the geometry of objects with complex shapes with a 3D camera and, at the same time, collecting surface and subsurface information that is then mapped onto the geometry in good spatial alignment. Subsurface information can be captured with infrared thermography or ultrasonic probes. The approach can thus allow non-destructive testing procedures to be used for detecting, locating and measuring the size, shape and depth of undersurface defects of an object and to map these defects, and potentially other information such as reflectance or color, onto the geometric model of the object. Motivation In a long-term monitoring context, the inspection of objects with complex geometries using non-destructive techniques such as thermal infrared imaging or phased array ultrasound sensing implies that the undersurface structure of the object to be observed is in good registration with the 3D object geometry. This paper presents an approach for measuring the geometry of objects with complex shapes using a handheld 3D scanner and for collecting subsurface information, in this case thermal images or ultrasonic recording, in registration with the captured object geometry. An important step leading to accurate registration of thermal and geometric data is the calibration of the intrinsic and extrinsic parameters of the pinhole camera model used to model the infrared camera. Intrinsic parameters describe "internal" properties of the camera such as focal length, principal point, radial/tangential distortion, etc. Extrinsic parameters describe the position and orientation (i.e. the pose) of the pinhole in a global reference frame (often called the "world" reference frame). Once calibration is complete, the "storage" of thermal data in the 3D map can be achieved with the help of a motion tracking system. The paper is organized as follows. The experimental setup and the various instruments used for the experiments are described in Section 2. Second, the model that was adopted for describing image formation by the thermal infrared camera is described briefly in Section 3. Then, the procedure for calibrating the pinhole modelling the infrared camera is described in detail and validation experiments are presented and discussed in Section 4. Section 5 explains the procedure that is adopted for acquiring and registering 3D and thermal data. Experimental results are presented. Section 6 presents an extension of the thermal mapping approach to the case of phased array ultrasound data. Finally, conclusion and perspectives of future work are given in Section 7. Experimental setup and description of the instruments The motion tracking system provides accurate estimates of the pose of the object and of the camera case in the world reference frame through frame transformation matrices TVB and TVC respectively. Transform TPH-B between the reference frame of the pinhole, OPH, and the reference frame of the calibration target, OB, is estimated according to the procedure described in Section 4. Transform TC-PH between the reference frame of the camera case (OC) and the reference of the pinhole (OPH) is computed from the other transforms. There is no need to estimate the frame transformation between the handheld scanner and the motion tracking system or the transform between the scanner and the object/scene since this is taken care of automatically by the scanner which positions itself with respect to the markers installed on the object/scene. The thermal camera used for the experiments is a Jenoptik IR-TCM 384 with the specifications listed i

Diode Parameter Determination Applied to LDD-MOSFETs for Device Characterization

The electrical properties of the drain-substrate diode of MOSFETs are shown to be related to the device geometrical structure. The two dimensional analysis takes into account the edge effects of the length and width of the gate. Intrinsic parameters are extracted from current-voltage characteristics and obtained dependent on these dimensions

Pulsed thermography in the evaluation of an aircraft composite using 3D thermal quadrupoles and mathematical perturbations

Abstract This paper is devoted to the characterization of a subsurface flaw within an anisotropic medium during a nondestructive evaluation test using stimulated infrared thermography. A typical illustration is a delamination within a stratified composite material. The originality of the current study consists of providing simple analytical solutions to evaluate the depth and the volume of the flaw in a three-dimensional heat transfer configuration. The volume of the flaw is defined as the product of its lateral extent by its thickness. If the thermal contact resistance of the flaw is known, its lateral extent can be derived from the volume expression. The method proposed here consists of applying first a Laplace transform on the time variable t, then a Fourier transform on the space variables, x and y. The numerical or semi-analytical true solution of integral equations generated by this problem may be very time-consuming, especially in a three-dimensional configuration. We therefore suggest a modelling reduction using the analytical perturbation method written only at its first order. It is however assumed that flaw thermal resistance is small compared to the whole thermal resistance of the material under investigation. The perturbation formalism leads to the construction of approximate analytical solutions that are very convenient for quantitative inversion. The validity of this method has been analysed through a real nondestructive test performed on a calibrated carbon-epoxy laminate of known characteristics

Experimental Investigation on the Reliability of Thermal Wave Interferometry in the Thermophysical Characterization of Plasma Sprayed Coatings

The main focus of this work is to compare thermal diffusivity and effusivity data resulting from thermal wave interferometry (TWI) experiments on tungsten coatings of different thicknesses with those obtained using reference techniques, namely, the laser flash method and scanning electron microscopy (SEM). The deviations between TWI and the latter techniques are discussed in terms of lack of data in the low frequency range. The investigation shows that the lack of data at low frequencies does not affect diffusivity measurements, while it has a strong effect on effusivity measurements for thermally thick coatings. The conclusions of this experimental study are in good agreement with theoretical predictions resulting from a sensitivity analysis reported in a previous study.Peer reviewed: YesNRC publication: Ye

Analytical simulation of a multi -dimensional temperature field produced by planar defects of any shape; application to non-destructive testing

Abstract Thermal interface resistances are associated with bad contact between two materials. In the case where this interface takes place between two rectangular slabs of the same material, a heat pulse experiment with recording of the slab surface temperature evolution, gives information about the space distribution of this resistance. The inverse problem is considered here, using an explicit analytical solution of the direct problem and a stochastic approach, in the case of a non uniform interface resistance distribution. Experimental inversion of frames produced by an infrared camera is implemented