Use of boudinaged rigid objects as a strain gauge: Insights from analogue and numerical models

The effect of blade frequency mistuning on the forced response of HPC-blisks is studied by means of experimental and numerical investigations applying discrete mechanical low degree of freedom models. Besides the mistuning resulting from manufacturing and inhomogeneous material also strain gauge (S/G) induced mistuning is considered. Blade by blade measurements supported by numerical calculations are used to determine mistuning distributions within an iterative approach. Due to the stiffness contribution of high temperature S/G, a significant increase of blade alone frequencies can be proved. It is shown within laser scanning measurements that this S/G induced mistuning can cause strongly localized mode shapes. Since S/G signals are used to monitor also non-instrumented blade resonances in engine-tests, it is reasonable to consider the S/G contribution within model-updates. The numerical models introduced in this paper are adjusted to experimentally determined blade alone frequency distributions. Within simulations of the forced response it is shown in principle, that the S/G-instrumentation also affects the response of non-instrumented blades which is important with regard to the S/G calibration process. Additional investigations are addressed to the consequences of small variations in measured mistuning distributions on the maximum forced response, i. e. resulting from a changing ambient temperature while measurement or a limited frequency resolution. In this context, a strong dependence on the engine order excited, the damping level and thus the flow conditions could be proved. As an example all investigations presented in this paper are carried out for two stages of a research compressor.

Download Full-text

Approaches to refinement of analytical models for stress-strain state assessments of structures based on the analysis of monitoring system data

TRANSACTIONS OF THE KRYLOV STATE RESEARCH CENTRE ◽

10.24937/2542-2324-2021-1-395-47-54 ◽

2021 ◽

Vol 1 (395) ◽

pp. 47-54

Author(s):

V. Korshunov ◽

◽

R. Mudrik ◽

D. Ponomarev ◽

A. Rodionov ◽

...

Keyword(s):

Numerical Simulation ◽

Monitoring System ◽

Strain Gauge ◽

Numerical Models ◽

Operation Time ◽

Material Behavior ◽

Strain Gauges ◽

Stress Strain ◽

Engineering Structures ◽

Strain Monitoring

Object and purpose of research. This paper discusses numerical simulation possibilities in terms of stress-strain monitoring for marine engineering structures. This approach can simulate the behavior of strain gauges for both elastic and plastic material behavior. Materials and methods. FEM-based simulation of strain gauge operation process taking into account geometric and physical non-linearity. Main results. Development of refined FE models for sensor installation area of stress-strain monitoring system. Numerical simulation of uniaxial and triaxial strain gauge operation. Time histories of strain gauge readings for linear and non-linear behavior of material. Sensitivity analysis of strain gauges in terms of various strain types. Update of strain gauge arrangement for the best description of structural strains. Conclusion. These results demonstrate and confirm a strong potential of numerical models in development of stress-strain monitoring systems for engineering structures. Simulating strain gauge operation, these models make it possible to determine global strained state of given structure as per strain gauging data for some of its areas.

Download Full-text

Dynamische Venenfunktionstests auf dem Prüfstand

Phlebologie ◽

10.1055/s-0037-1621393 ◽

2002 ◽

Vol 31 (04) ◽

pp. 85-90 ◽

Cited By ~ 2

Author(s):

H.-M. Häfner ◽

H. Bablich ◽

G. Rassner ◽

M. Jünger ◽

A. Steins

Keyword(s):

Strain Gauge ◽

Automatische Auswertung

Zusammenfassung Ziel: Überprüfung der Korrelation der photooptischen Venenfunktionstests Lichtreflexionsrheographie (LRR), digitale Photoplethysmographie (DPPG) und der Quecksilberdehnungsstreifen- Plethysmographie (Hg-strain gauge) mit der Phlebodynamometrie (PDM). Methode: Die simultane Messung von LRR, DPPG, Hg-strain gauge und PDM wurde an 34 Patienten mit chronischer venöser Insuffizienz in den klinischen Stadien I bis III nach Widmer an insgesamt 39 Unterschenkeln vorgenommen. Die Messungen erfolgten während Dorsalextension des Fußes in sitzender und während Plantarflexion des Fußes in stehender Position. Als Parameter für die Ermittlung des Korrelationskoeffizienten wurden die Wiederauffüllzeiten t0 und t1/2 sowie die venöse Abpumpleistung ermittelt. Ergebnisse: Unabhängig von Körperposition und Anlage von Tourniquets erreichten die Korrelationen für alle Messverfahren und Parameter Werte zwischen r = 0,76 (t0 LRR) und r = 0,05 (Abpumpleistung DPPG automatische Auswertung). Eine gute Korrelation von t0 wurde in stehender Körperposition unabhängig von der Anlage der Tourniquets beim Hg-strain gauge (r = 0,49) und LRR (r = 0,51) erreicht. Diese Korrelation verbesserte sich in sitzender Körperposition. Die schlechteste Korrelation wurde bei der DPPG ermittelt (r = 0,25 in stehender, r = 0,51 in sitzender Position). Eine Verbesserung der Korrelation wurde beim DPPG durch die manuelle Auswertung der Kurven erreicht. Schlussfolgerung: Sowohl die Wahl des Untersuchungsverfahrens wie auch das gewählte Belastungsprogramm können erhebliche Auswirkungen auf die Korrelation mit der PDM haben. Unsere Ergebnisse zeigen, dass bei der Bewertung der Wiederauffüllzeiten t0 und t1/2 der Hg-strain gauge und die LRR die höchste Korrelation bei Dorsalextension in sitzender Körperposition mit der PDM aufweisen.

Download Full-text

Diagnosis of Deep Vein Thrombosis by Combination of Doppler Ultrasound Flow Examination and Strain Gauge Plethysmography

Thrombosis and Haemostasis ◽

10.1055/s-0038-1657149 ◽

1982 ◽

Vol 47 (02) ◽

pp. 141-144 ◽

Cited By ~ 7

Author(s):

H Bounameaux ◽

B Krähenbühl ◽

S Vukanovic

Keyword(s):

Deep Vein Thrombosis ◽

Negative Predictive Value ◽

Doppler Ultrasound ◽

Strain Gauge ◽

Predictive Value ◽

Lower Limbs ◽

Vein Thrombosis ◽

Non Invasive ◽

Strain Gauge Plethysmography ◽

Deep Vein

SummaryDoppler ultrasound flow examination, strain gauge plethysmography and contrast venography were performed in 160 lower limbs of 80 in-patients. Deep vein thrombosis (DVT) was suspected in 87 limbs. Using measurement of venous stop-flow pressure, the Doppler method had an overall sensitivity of 83%. By combined use of Doppler and Plethysmography, sensitivity was increased to 96%. Specificity was 62% and 51%, respectively. With a positive and a negative predictive value of 80% and 73%, respectively, the combination of both non-invasive methods cannot reliably replace venography in the diagnosis of DTV, although all (40/40) thromboses proximal to or involving the popliteal segment were detected by either Doppler and Plethysmography or both.After exclusion of 14 patients (18%) suffering from conditions known to alter the results of these non-invasive methods, the positive predictive value of abnormal findings in both Doppler and Plethysmography was increased to 94% for suspected limbs, whilst negative predictive value of both negative Doppler and Plethysmography was 90%, allowing the avoidance of venography in these patients.

Download Full-text

An Adjustable Marine Fender System Programmed with the Aid of Numerical Models in Order to Minimize Berthing and Mooring Loads

Coastal Engineering 1986 ◽

10.1061/9780872626003.203 ◽

1987 ◽

Cited By ~ 2

Author(s):

Tj. J. Risselada ◽

C. Deelen

Keyword(s):

Numerical Models

Download Full-text

Supply Air Window PAZIAUD®: Comparison of Two Numerical Models for Integration in Thermal Building Simulation

Proceedings of the 2012 (3rd) International Conference on Engineering, Project, and Production Management ◽

10.32738/ceppm.201209.0028 ◽

2012 ◽

Author(s):

Gloriant F. ◽

◽

Tittelein P. ◽

Joulin A. ◽

Lassue S. ◽

...

Keyword(s):

Numerical Models ◽

Building Simulation

Download Full-text

Stochastic simulation of the spatio-temporal field of the average daily heat index in Southern Russia

Climate Research ◽

10.3354/cr01623 ◽

2020 ◽

Vol 82 ◽

pp. 149-160

Author(s):

N Kargapolova

Keyword(s):

Heat Waves ◽

Numerical Models ◽

Heat Index ◽

Real Field ◽

Gaussian Field ◽

The Real ◽

Southern Russia ◽

Weather Stations ◽

Spatio Temporal ◽

Temporal Field

Numerical models of the heat index time series and spatio-temporal fields can be used for a variety of purposes, from the study of the dynamics of heat waves to projections of the influence of future climate on humans. To conduct these studies one must have efficient numerical models that successfully reproduce key features of the real weather processes. In this study, 2 numerical stochastic models of the spatio-temporal non-Gaussian field of the average daily heat index (ADHI) are considered. The field is simulated on an irregular grid determined by the location of weather stations. The first model is based on the method of the inverse distribution function. The second model is constructed using the normalization method. Real data collected at weather stations located in southern Russia are used to both determine the input parameters and to verify the proposed models. It is shown that the first model reproduces the properties of the real field of the ADHI more precisely compared to the second one, but the numerical implementation of the first model is significantly more time consuming. In the future, it is intended to transform the models presented to a numerical model of the conditional spatio-temporal field of the ADHI defined on a dense spatio-temporal grid and to use the model constructed for the stochastic forecasting of the heat index.

Download Full-text