Full Calibration Procedure Research Articles

Modeling of Fatigue Cracking in Asphalt Materials Based on the Paris Law with an Initialization Term—Calibration from Notched and Unnotched Specimens

Abstract This article aims at presenting a thermo-mechanical model dedicated to fatigue cracking in bituminous material. The model calibration based on two-point bending (2PB) fatigue tests performed on specimens of bitumen-bound sand is also detailed. In the model, crack growth is handled by the Paris law considering the initialization term Nini. This parameter represents the number of loading cycles required to initiate a short macrocrack of length a0 from which the Paris law can be applied. The tests utilized for calibration and comparison with the numerical simulations are performed on notched and unnotched trapezoidal samples, for different levels of imposed displacement amplitude. The parameters of the Paris law are determined using the notched specimens (a0 being assimilated to the notch depth) except for Nini, which is deduced from the difference in lifetime duration between the tests carried out on notched and unnotched specimens. The full calibration procedure described thereafter has the advantage to not depend on the choice of a0. It is shown that the simulations run for the calibrated model are globally in good agreement with the test results obtained for both types of samples and for all the imposed displacement amplitudes. Finally, the model is used to predict the response of four-point bending tests carried out on the same bitumen-bound sand, considering the input parameters determined from the 2PB tests. The intrinsic nature of the model is evaluated through its ability to simulate both types of tests using the same set of material parameters.

First full dynamic range calibration of the JUNGFRAU photon detector

The JUNGFRAU detector is a charge integrating hybrid silicon pixel detector developed at the Paul Scherrer Institut for photon science applications, in particular for the upcoming free electron laser SwissFEL. With a high dynamic range, analogue readout, low noise and three automatically switching gains, JUNGFRAU promises excellent performance not only at XFELs but also at synchrotrons in areas such as protein crystallography, ptychography, pump-probe and time resolved measurements. To achieve its full potential, the detector must be calibrated on a pixel-by-pixel basis. This contribution presents the current status of the JUNGFRAU calibration project, in which a variety of input charge sources are used to parametrise the energy response of the detector across four orders of magnitude of dynamic range. Building on preliminary studies, the first full calibration procedure of a JUNGFRAU 0.5 Mpixel module is described. The calibration is validated using alternative sources of charge deposition, including laboratory experiments and measurements at ESRF and LCLS. The findings from these measurements are presented. Calibrated modules have already been used in proof-of-principle style protein crystallography experiments at the SLS. A first look at selected results is shown. Aspects such as the conversion of charge to number of photons, treatment of multi-size pixels and the origin of non-linear response are also discussed.

Calibration of a large water-Cherenkov detector at the Sierra Negra site of LAGO

The Latin American Giant Observatory (LAGO) is an international network of water-Cherenkov detectors (WCD) set in different sites across Latin America. On top of the Sierra Negra volcano in Mexico at an altitude of 4530m, LAGO has completed its first out of three instrumented detector. It consists of a cylindrical water tank with a diameter of 7.3m and a height of 1m and a total detection area of 40m2 that is sectioned in four equal slices. In this work we present the full calibration procedure of this detector and the initial measurements of stability in rate. We also derive the effective area to gamma-ray bursts for the complete array using the LAGO simulation chain, based on CORSIKA and GEANT4.

Method for independent strain and temperature measurement in polymeric tensile test specimen using embedded FBG sensors

A novel method to obtain independent strain and temperature measurements using embedded Fibre Bragg Grating (FBG) in polymeric tensile test specimens is presented in this paper. The FBG strain and temperature cross-sensitivity was decoupled using two single mode FBG sensors, which were embedded in the specimen material with a certain angle between them. It is demonstrated that, during temperature variation, both FBG sensors show the same signal response. However, for any applied load the signal response is different, which is caused by the different levels of strain acting in each sensor. Equations to calculate independently the strain and temperature are presented in the article, together with a measurement resolution study.This multi-parameter measurement method was applied to an epoxy tensile specimen, tested in a unidirectional tensile test machine with a temperature controlled cabinet. A full calibration procedure (temperature and strain) was performed to this material-sensor pair, where a calibration error < 1% was achieved. This was followed by a strain-temperature test case, where multiple two loading/strain stages of ε = 0.30% and ε = 0.50% were applied during a continuous variation of temperature, from 40 °C to –10 °C.The consistency of the expected theoretical results with the calibration procedure and the experimental validation shows that this proposed method is applicable to measure accurate strain and temperature in polymers during static or fatigue tensile testing. Two different calibration protocols are presented and analysed.

Experimental study of an electromagnetic flow meter for liquid metals based on torque measurement during pumping process

This paper presents a detailed experimental study on an electromagnetic flow measurement technique to measure the flow rate of liquid metals. The experimental setup consists of a contactless electromagnetic pump with a torque sensor mounted on the pump shaft. The electromagnetic pump is composed of two rotating steel discs having embedded permanent magnets with alternating poles. The rotation of the discs creates a travelling sinusoidal magnetic field and eddy currents within the liquid metal. The metal is contained inside the duct located between the discs of the pump. The interaction of the magnetic field and the induced eddy currents generates an electromagnetic Lorentz force providing the pumping effect. The flow rate is proportional to this force. The torque sensor measures the moment of the discs due to the Lorentz force, which is converted to a flow rate value. We name the method Lorentz torque velocimetry (LTV). The full calibration procedure and experimental investigation of the LTV are described. The method can be used as a non-contact flow rate control technique for liquid metals.

Stability of Negative Resistance Coefficient Thermistors for Long-term Temperature Measurement

The NTC (negative temperature coefficient) thermistor precision is significantly increased by the calibration process. The full calibration procedure process itself is sophisticated as it requires a set of calibration points when using the Steinhart-Hart equation for the linearization of the T(R) (Temperature – Resistance) characteristics. Aging and degradation processes tend to distort the metrological characteristics of the NTC thermistors. The novel method of calibration for groups of thermistors produced by the same manufacturer using the same technology is proposed in this paper. The initial calibration data acquired from the calibration results or from the manufacturer is used for approximate computations. During the additional calibration, the approximate data for the group of thermistors is adjusted using linear transformations. The result analysis for five different types of thermistors (A, B, C, D and E) revealed that the temperature measurement errors in the temperature range from 20 0C to 80 0C can be reduced by up to 10 times using the proposed method. The aging and degradation processes were investigated using the thermocycling procedure implemented with steep transitions (100 0C ... 0 0C ... 100 0C). The thermistor R(T) characteristics were repeatedly measured after 1000, 2000 and 3000 thermocycles. The results revealed that statistically, the average error of the temperature measurement for the types C, D and E increased significantly after 3000 thermocycles, whereas the measurement error trend of the thermistors of types A and B was insignificant (p > 0.05). DOI: http://dx.doi.org/10.5755/j01.eee.20.6.7268

Magnetic Field Sensor Calibration for Attitude Determination

AbstractThe presented work aims to give an overview of different calibration methods for magnetic field sensors, which are used for attitude determination. These methods are applicable in the field without any additional equipment. However, sometimes they require simplification assumptions. The paper addresses the validity of these assumptions, the accuracy and efficiency of the methods and the influence of the calibration error on the orientation estimation. Both simulations and measurements are used for evaluation. The measurements are performed using a GNSS multi-antenna system, providing an orientation reference (roll, pitch, yaw) without unknown external magnetic disturbances and with a sufficient accuracy (about 0.5 degrees). It is shown in simulations, that a full calibration of the sensor (including soft and hard iron disturbances by nearby materials) is possible without any additional equipment. However, experiments show, that some parts of the full calibration procedure are sensitive to an accurate execution of the necessary movements, which may lead to calibration errors in the same order of magnitude as a simplified method, which ignores the presence of soft iron disturbances.

Microfabrication and calibration of a single-polarity piezoresistive three-dimensional stress sensing chip

A single-polarity (n-type) piezoresistive sensing chip for three-dimensional (3D) stress sensing has been microfabricated and fully calibrated. The sensing chip, which is capable of extracting the six stress components, is prototyped using bulk microfabrication techniques on a (1 1 1) crystalline silicon. A full calibration procedure employing uniaxial, thermal and hydrostatic loading has been conducted. The calibration results confirm the feasibility of our proposed technique of using single-polarity (n-type) sensing elements to develop 3D stress sensors. Preliminary testing results are presented to demonstrate the operation of our developed sensing chip.

Calibration of gamma-ray spectrometers coupled to Compton suppression and fast pneumatic systems for the k0-standardized NAA method

A new Compton suppression system (CSS) for the gamma-ray spectrometer portion of the neutron activation analysis (NAA) was set up at the RPI/ITN. The pneumatic transfer system, SIPRA, for short-lived nuclides and cyclic irradiations was improved. A full calibration procedure of the CSS and SIPRA systems was performed. Two certified reference materials, NIST-SRM-1572 (Citrus Leaves) and NIST-SRM-1633a (Coal Fly Ash) were analyzed using the calibration factors. The CSS was instrumental in lowering the detection limits of Cr, Fe, Hg, Rb, Sr, Th and Zn by reducing background and/or spectral interference considerably. The analytical results were evaluated by comparison to the NIST certified values with deviations ranging from 2% to 8% for the above mentioned elements, except Zn ranging from 10% to 15% for biological and environmental samples, respectively.

Determination of calibration function in thermal field flow fractionation under thermal field programming

A new procedure for determining the calibration function able to relate retention and operative parameters to molecular weight of the species in thermal field flow (ThFFF) under thermal field programming (TFP) conditions is presented. The procedure involves determining the average values of retention parameters under TFP and determining a numerical function related to the temperature variations that occur during TFP. The calibration parameters are obtained by a procedure fitting the retention and operative parameters that hold true at the beginning of the TFP. The procedure is closely related to the one previously developed to calibrate the retention time axis under TFP ThFFF and, together, they constitute a full calibration procedure. Experimental validation was performed with reference to polystyrene (PS)-decalin and PS-THF systems. The calibration functions here obtained were compared to those derived by the classical procedure at constant thermal field ThFFF to obtain the calibration function at variable cold wall temperatures. Excellent agreement was found in all cases proving "universality" of the ThFFF calibration concept, i.e. it is independent of the particular system on which it was determined and can thus be extended to ThFFF operating under TFP. The new procedure is simpler than the classical one since it requires less precision in setting the instrumentation and can be obtained with fewer experiments. The potential applications for the method are discussed.

Absolute calibration of a multilayer-based XUV diagnostic

A portable, universal narrowband XUV diagnostic suitable for calibration of various XUV light sources, was built, tested and fully calibrated. The diagnostic allows measurement of the absolute XUV energy and average power in two selected wavelength bands, at 11.4 and 13.4 nm. In addition, the pulse-to-pulse and long-term XUV stability of the source can be assessed, as well as the contamination of multilayer XUV optics exposed to the source. This paper describes the full calibration procedure: all optical elements were calibrated at the wavelength of operation by Physikalisch-Technische Bundesanstalt at the storage ring Bessy II, a full analysis of geometrical factors was done, and the influence of the spectral emissivity of the source on the calibration was analyzed in detail. The calibration was performed both for the centroid wavelength as for the full bandwidth of the diagnostic. The total uncertainty in the absolute calibration allowed measurement of source characteristics with an uncertainty of less than 5%, and a shot-to-shot repeatability to less than 2%. The uncertainty was mainly determined by external factors like background gas distribution and spectral source characteristics. Examples of application to a laser plasma and discharge plasma XUV source are given.

Assessment of the design and performance of the Sage syringe pump model 341A, with particular reference to its accuracy and stability.

Consideration of the timing circuitry employed in the Sage pump model 341A indicates that the pump's performance will be strongly affected by component tolerances, and our measurements have confirmed this impression. Thus, delivered flow rates may deviate considerably from those indicated on the calibration chart; our instrument was about 10% slow at all settings. For many applications it will be necessary to carry out a full calibration procedure, which should be repeated following any repairs to the electronic circuitry. The pump also suffered from drift at certain settings because an inappropriate component had been used in the timing circuitry. These findings will also apply to the Sage pump models 240A and 242A, which employ similar timing circuitry to the 341A. When precautions are taken to overcome these problems, the pump's performance is satisfactory for both clinical use and some laboratory applications.