Validation setup for the investigation of aeroacoustic and vibroacoustic sound emission of confined turbulent flows

Confined flows induce sound at certain flow conditions, which can be annoying in electric vehicles due to the absence of combustion noise. Noise in internal flow may occur due to unfavorable flow-guiding geometries caused by the complex packaging required in engine compartments of modern vehicles. The flow-induced sound is emitted at duct openings (e.g., ventilation inside the passenger cabin). It also originates from the vibroacoustic emissions of the flow-guiding structure excited by the flow. We propose a modular validation procedure for aeroacoustic simulations of confined flows. The experimental setup includes the vibroacoustic emission of the involved flow-guiding structure. The test rig consists of a sensor system, a high-pressure blower, modular pipe sections, and absorbers, which decouple the system from blower noise and avoid acoustic reflections at the pipe exit. A sufficiently long straight inlet section ensures fully developed flow conditions entering the investigated region. For capturing the vibroacoustic sound radiation of the flow-guiding structure, the measurement object and the surrounding microphones are encapsulated in a wooden box, lined with micro-perforated plates. Measurement results of a straight pipe and a pipe with a half-moon-shaped orifice are presented. Additionally, the sound generation is reproduced by Lighthill's aeroacoustic analogy applying a hybrid approach.

Analysis of the random measurement error of areal 3D coordinate measurements exclusively based on measurement repetitions

The measurement uncertainty characteristics of a measurement system are an important parameter when evaluating the suitability of a certain measurement system for a specific measurement task. The measurement uncertainty can be calculated from observed measurement errors, which consist of both systematic and random components. While the unfavourable influence of systematic components can be compensated by calibration, random components are inherently not correctable. There are various measurement principles which are affected by different measurement error characteristics depending on specific properties of the measurement task, e. g. the optical surface properties of the measurement object when using fringe projection or the material properties when using industrial X-ray computed tomography. Thus, it can be helpful in certain scenarios if the spatial distribution of the acquisition quality as well as uncertainty characteristics on the captured surface of a certain measurement task can be found out. This article demonstrates a methodology to determine the random measurement error solely from a series of measurement repetitions without the need of additional information, e. g. a reference measurement or the nominal geometry of the examined part.

Investigation of Temperature-Induced Errors in XCT Metrology

The presented research shows the time dependent temperature distribution and thermal time constant within a typical industrial X-ray computed tomography (XCT) system used for dimensional metrology. Temperature effects can significantly affect measurement results of XCT scans either by directly changing the dimensions of the measurement object, or by indirectly changing the geometry of XCT scanner. In either case, the effect is not known well enough to be used for correction of measurement results or estimation of measurement uncertainty. In order to determine these effects, traceable temperature measurements were performed with a custom measurement system designed for this application. The influence of temperature fluctuations on length errors was determined by correlation of the measured temperature fluctuations with measurement deviations of a reference standard in repeated CT scans at different X-ray power levels. After experimental determination of X-ray focal spot displacement due to thermal expansion, a simple mathematical model of X-ray source displacement as a function of its temperature was developed and validated for a selected X-ray power level.

Non-Contact Damage Detection under Operational Conditions with Multipoint Laservibrometry

Scanning laser–Doppler vibrometry (SLDV) can localize and visualize damages in mechanical structures. In order to enable scanning, it is necessary to repeat the vibration. Therefore, this technique is not suited to detect emerging hazards in working machinery that change the vibration behavior. A common technique for such cases is monitoring the vibration excited by machine operation with accelerometers. This technique requires mechanical coupling between sensors and the measurement object, which influences the high-frequency vibration responses. However, in the low-frequency range, local damages do not shift resonances or distort operational deflection shapes (ODS) significantly. These alterations in the vibration behavior are tiny and hard to detect. This paper shows that multipoint laservibrometry (MPV) with laser excitation can measure these effects efficiently, and it further demonstrates that damages influence ODSs at frequencies above 20 kHz much stronger than at frequencies below 20 kHz. In addition, ODS-based damage indices are discussed; these are highly sensitive to minute visible changes of the ODSs. In order to enhance the sensitivity of hazard detection, the response vector assurance criterion value is computed and evaluated during operation. The capabilities and limitations of the methodology on the example of a cantilever with manually emerging damage are demonstrated.

THREE-DIMENSIONAL PIEZOELECTRIC ACCELEROMETER FOR MEASURING DYNAMIC PARAMETERS OF MOVING OBJECTS

Analysis of structural construction of existing three-dimensional accelerometers is carried out, in which due to the opposite direction of sensitivity vectors and direction of measured inertial force, they allow to measure only linear inertia and accelerations varying in relatively small limits. On the other hand, due to the presence of elements in them that create electromagnetic fields, their construction is somewhat complicated. In addition, in known accel-erometers, due to the absence of a measurement object position sensor and an electronic control circuit, the func-tionality of the accelerometer is limited, Due to lack of integrator for acceleration integration, speed measurement is not provided, Due to rigid attachment of piezoelectric sensing elements through their bases, during measurement they generate interference signals, The amplitude of which exceeds the amplitude of the useful signal, which does not ensure reliability of the measured acceleration or speed and due to the presence of sensitive piezoelectric ele-ments, Having higher rigidity and requiring relatively large mechanical forces for generation of signals during mo-tion of acceleration and speed measurement object in automatic mode, which reduces sensitivity of accelerometer. Invention proposes new design and control scheme of three-dimensional piezoelectric accelerometer for measure-ment of dynamic parameters of moving objects in automatic mode. Wherein providing the position sensor of the moving measurement object with a three-axis signal detection unit to determine a direction of motion with meas-urement of acceleration or linear velocity when the measurement object moves along the coordinate axis; With the help of differential operational amplifiers through pulse generators and integrators, Speed measurement is provided by damping piezoelectric elements when the measurement object moves along one of the coordinate axes; Across the other two axes, the generated interference signals by amplitude are significantly reduced by their redemption; Having a piezoelectric element in the structure in the form of two-layer flat plates with an excitation section and a sensor section; Which generates signals at fast-changing acceleration and speed of moving object, amplitude of signal and sensitivity increases in 4-5 due to generation of signal by sensitive elements in vibration excitation mode created in accelerometer. Mathematical basis for accelerometer control circuits, mathematical model of its functioning is developed, applica-tion of which increases sensitivity of measurement of linear accelerations and speeds of moving objects and expands functional capabilities.

Inadequacy for mathematical models of measurement objects and risk calculations according to ISO/IEC 17025-2019

The problem of inadequacy of mathematical models of measurement objects is considered in connection with the problem of “definitional uncertainty of measurement” and the need for risk management in accordance with GOST ISO/IEC 17025-2019 “General requirements for the competence of testing and calibration laboratories”. The prehistory of the problem is described: from the formation of moment and compositional approaches to estimating accuracy to the introduction of a special term “inadequacy error for mathematical model of measurement object”. The negative impact of hopelessness of conceptual and terminological transformations in metrology and critical contradiction of the applicability estimates for “statistical methods” of GOST R ISO/IEC 31010-2011 “Risk management – Risk assessment techniques” and “Guide to the expression of uncertainty in measurement” is noted. It is shown that taking into account the inadequacy of probabilistic models in risk calculations is a necessary condition for results reliability.

METHODS AND MODELS OF CONSTRUCTION OF INFORMATION TECHNOLOGIES OF REMOTE MEASUREMENT OF NANOBRATION

Methods and models of systems for remote measurement and recording of vibrations with amplitude less than 10 nanometers are investigated on the basis of coherent laser sources. The mathematical model of the Doppler effect is analyzed. The basic characteristics of perspective measurement systems are determined. The modern tendencies of development of the direction of laser Doppler vibrometers and the scope of their application are revealed, as well as the expediency of further researches is substantiated. Observations of vibrations of various objects, their registration and analysis in the natural and applied sciences are one of the main methods on which the study of natural objects and phenomena, diagnostics in medicine and technology, the solution of special problems in military and law enforcement activities, ensuring information security at the objects of information activity, etc. In many cases, due to the specificity of the investigated objects, direct access to them is not possible or approaching the measurement object is unsafe for the researcher. The above determines the relevance of research into the problems and principles of building reliable information technologies for remote measurement of vibration, ensuring their high guaranteeability, including information security, resolution. Of particular interest in practical applications are technologies capable of distinguishing vibrations with an amplitude of less than 10 nanometers (hereinafter referred to as nanovibrations). Therefore, to select the essential parameters of designing a domestic product (laser vibrometer) and look for opportunities to increase the sensitivity of such products, the article elaborated and formed a set of qualitative and technical characteristics of existing devices for remote measurement of nanovibrations and provided comments on the solution of the sensitivity problem.

The Dilemma of Psychology: Objective without an Object?

Anyone who seeks the service of psychology (which translates to “science of the mind”) faces a persisting dilemma. One has to choose between two psychologies: “Subjective”, also called “qualitative”, psychologists believe that the focus on studying the internal structure of the human mind will provide important insights needed in therapy and education. Yet the human mind, they argue, can be studied only with subjective methods like clinical interview, not with standardized tests. In contrast, “objective” or “quantitative”, psychologists argue that if psychology wants to be recognized as a science, it must enlist only objective methods of measurement. Yet this excludes, they argue, the study of internal psychological factors of the human mind. While the subjective approach is based on psychological assumptions regarding the nature of the target measurement object, the objective approach is based on purely statis-tical theories. Must we really have to abandon psychological objects like intellectual and moral capaci-ties if we want our measurement to be objective? In this paper I show that both approaches are based on questionable theories about the relationship between visible behavior on the one side and psychological objects on the other. I also show that we can measure psychological traits objectively and validly if we use an experimental approach. Experimental Question-naires can be used in all fields of psychology in which testable theories about the nature of its object have been developed. We have successfully used this new approach, for example, for the construction and validation of the Moral Competence Test (MCT).