Построение дисперсионной зависимости корректирующего коэффициента при контроле компактных изделий квадратного сечения импакт-эхометодом

2021 ◽  
pp. 3-14
Author(s):  
В.К. Качанов ◽  
И.В. Соколов ◽  
А.А. Самокрутов ◽  
В.Г. Шевалдыкин ◽  
С.А. Федоренко ◽  
...  
Keyword(s):  
Dispersion Curve ◽  
Longitudinal Wave ◽  
Correction Factor ◽  
Lamb Wave ◽  
Geometric Correction ◽  
Wide Range

This paper presents results of calculation of the geometric correction factor β of the compact square-sectioned samples. It is shown by simulation that in compact samples thickness resonance type changes from longitudinal wave to Lamb wave. Furthermore, the geometric correction factor varies over a wide range and nonlinear in compact samples. The dispersion curve of the geometric correction factor β for compact square-sectioned samples is built.

scholarly journals An Efficient Time Reversal Method for Lamb Wave-Based Baseline-Free Damage Detection in Composite Laminates

2018 ◽  
Vol 9 (1) ◽  
pp. 11 ◽  
Author(s):  
Liping Huang ◽  
Junmin Du ◽  
Feiyu Chen ◽  
Liang Zeng
Keyword(s):  
Damage Detection ◽  
Time Reversal ◽  
Lamb Wave ◽  
Composite Laminates ◽  
Narrow Band ◽  
Great Influence ◽  
Time Intervals ◽  
Wide Range ◽  
Reconstructed Signal ◽  
Short Time

Time reversal (TR) concept is widely used for Lamb wave-based damage detection. However, the time reversal process (TRP) faces the challenge that it requires two actuating-sensing steps and requires the extraction of re-emitted and reconstructed waveforms. In this study, the effects of the two extracted components on the performance of TRP are studied experimentally. The results show that the two time intervals, in which the waveforms are extracted, have great influence on the accuracy of damage detection of the time reversal method (TRM). What is more, it requires a large number of experiments to determine these two time intervals. Therefore, this paper proposed an efficient time reversal method (ETRM). Firstly, a broadband excitation is applied to obtain response at a wide range of frequencies, and ridge reconstruction based on inverse short-time Fourier transform is applied to extract desired mode components from the broadband response. Subsequently, deconvolution is used to extract narrow-band reconstructed signal. In this method, the reconstructed signal can be easily obtained without determining the two time intervals. Besides, the reconstructed signals related to a series of different excitations could be obtained through only one actuating-sensing step. Finally, the effectiveness of the ETRM for damage detection in composite laminates is verified through experiments.

scholarly journals Adaptation of the Integrated Nitrogen Model for Catchments (INCA) to seasonally snow-covered catchments

2004 ◽  
Vol 8 (4) ◽  
pp. 695-705 ◽  
Author(s):  
K. Rankinen ◽  
Ø. Kaste ◽  
D. Butterfield
Keyword(s):  
Correction Factor ◽  
Snow Accumulation ◽  
Scale Model ◽  
Snow Pack ◽  
Climate Effect ◽  
N Transformation ◽  
Nitrogen Model ◽  
Degree Day ◽  
Wide Range ◽  
Soil Temperatures

Abstract. Testing of the Integrated Nitrogen model for Catchments (INCA) in a wide range of ecosystem types across Europe has shown that the model underestimates N transformation processes to a large extent in northern catchments of Finland and Norway in winter and spring. It is found, and generally assumed, that microbial activity in soils proceeds at low rates at northern latitudes during winter, even at sub-zero temperatures. The INCA model was modified to improve the simulation of N transformation rates in northern catchments, characterised by cold climates and extensive snow accumulation and insulation in winter, by introducing an empirical function to simulate soil temperatures below the seasonal snow pack, and a degree-day model to calculate the depth of the snow pack. The proposed snow-correction factor improved the simulation of soil temperatures at Finnish and Norwegian field sites in winter, although soil temperature was still underestimated during periods with a thin snow cover. Finally, a comparison between the modified INCA version (v.1.7) and the former version (v.1.6) was made at the Simojoki river basin in northern Finland and at Dalelva Brook in northern Norway. The new modules did not imply any significant changes in simulated NO3- concentration levels in the streams but improved the timing of simulated higher concentrations. The inclusion of a modified temperature response function and an empirical snow-correction factor improved the flexibility and applicability of the model for climate effect studies. Keywords: inorganic N leaching, degree-day snow model, snow pack, catchment scale model

A Method for the Routine Determination of Corn Sirup in Prepared Meat Products

1964 ◽  
Vol 47 (5) ◽  
pp. 903-909
Author(s):  
Lester Hankin ◽  
Alphonse F Wickroski
Keyword(s):  
Statistical Analysis ◽  
Quantitative Determination ◽  
Correction Factor ◽  
Meat Products ◽  
Processed Meat ◽  
Average Amount ◽  
Wide Range ◽  
The Difference

Abstract A method has been devised for the determination of corn sirup added to processed meat products. The method is based on the quantitative determination of dextrin added to corn sirup. The dextrins are enzymatically hydrolyzed by α-amylase and β-amylase, and maltose is calculated as the difference in CuO2 found by copper reduction between a treated and an untreated aliquot. A correction factor was devised to determine the average amount of dextrin in corn sirup by testing a number of commercial sirups for their dextrin content and subjecting the data to statistical analysis. With this equation the method is applicable to a wide range of sirups. The method also permits the estimation of dextrose added to meats in excess of that included as one of the components of corn sirup.

scholarly journals FEM STABILITY ANALYSIS OF TAPERED BEAM‐COLUMNS

2005 ◽  
Vol 11 (3) ◽  
pp. 211-216
Author(s):  
Vaidotas Šapalas ◽  
Michail Samofalov ◽  
Viačeslavas Šaraškinas
Keyword(s):  
Correction Factor ◽  
Bending Moment ◽  
Critical Force ◽  
Cross Sectional ◽  
Beam Columns ◽  
Tapered Beam ◽  
Wide Range ◽  
Two Factors ◽  
Proper Values ◽  
Tapered Column

This paper deals with a theoretical and a numerical analysis of tapered beam‐columns subjected to a bending moment and an axial force. A standard FEM code COSMOS/M has been used for a numerical estimation of a critical load multiplier. It has been assumed that the critical force of an axially loaded tapered column could be calculated in an analogous way as for uniform member just with an additional correction factor αn. Similarly, a critical bending moment of the tapered column subjected to a pure bending could be determined by using a correction factor αm. A large number of simulations carried out within a wide range of the ratios of second moments of area allowed to determine the proper values of theses two factors. For practical engineers, solution of such kind of problems can be easier when an equivalent cross‐sectional height htr is used.

scholarly journals Ultrasound longitudinal-wave anisotropy estimation in muscle tissue

2021 ◽  
Author(s):  
Naiara Korta Martiartu ◽  
Saulė Simutė ◽  
Marga B. Rominger ◽  
Thomas Frauenfelder
Keyword(s):  
Longitudinal Wave ◽  
Orientation Angle ◽  
Transversely Isotropic ◽  
Parameter Estimates ◽  
Velocity Of Ultrasound ◽  
Wide Range ◽  
Linear Probe ◽  
First Arrival ◽  
The Relationship ◽  
Analytical Expressions

<p> The velocity of ultrasound longitudinal waves (speed of sound) is emerging as a valuable biomarker for a wide range of diseases, including musculoskeletal disorders. Muscles are fiber-rich tissues that exhibit anisotropic behavior, meaning that velocities vary with the wave-propagation direction. Quantifying anisotropy is therefore essential to improve velocity estimates while providing a new metric that relates to both muscle composition and architecture. This work presents a method to estimate longitudinal-wave anisotropy in transversely isotropic tissues. We assume elliptical anisotropy and consider an experimental setup that includes a flat reflector located in front of the linear probe. Moreover, we consider transducers operating multistatically. This setup allows us to measure first-arrival reflection traveltimes. Unknown muscle parameters are the orientation angle of the anisotropy symmetry axis and the velocities along and across this axis. We derive analytical expressions for the relationship between traveltimes and anisotropy parameters, accounting for reflector inclinations. To analyze the structure of this nonlinear forward problem, we formulate the inversion statistically using the Bayesian framework. Solutions are probability density functions useful for quantifying uncertainties in parameter estimates. Using numerical examples, we demonstrate that all parameters can be well constrained when traveltimes from different reflector inclinations are combined. Results from a wide range of acquisition and medium properties show that uncertainties in velocity estimates are substantially lower than expected velocity differences in muscle. Thus, our formulation could provide accurate muscle anisotropy estimates in future clinical applications.</p> p { margin-bottom: 0.25cm; line-height: 115%; background: transparent }

Dispersion curve analysis method for Lamb wave mode separation

2019 ◽  
Vol 19 (5) ◽  
pp. 1590-1601
Author(s):  
Yue Hu ◽  
Yanping Zhu ◽  
Xiaotong Tu ◽  
Jing Lu ◽  
Fucai Li
Keyword(s):  
Dispersion Curve ◽  
Lamb Wave ◽  
Hessian Matrix ◽  
Wave Mode ◽  
Curve Analysis ◽  
Energy Concentration ◽  
Time Frequency ◽  
Mode Separation ◽  
Multimodal Features ◽  
Wave Modes

The Lamb wave inspection has emerged as a promising method for structural health monitoring and nondestructive testing. However, because of the highly dispersive and multimodal features, the Lamb wave mode separation has become a challenging problem. Based on the dispersion curve analysis, a new signal processing method is proposed in this study to solve this problem. First, a novel function based on the Hessian matrix is constructed to enhance the energy concentration of the dispersion curve in the time–frequency representation to reduce the dispersion effect. Subsequently, the constrained penalty function algorithm is developed for detecting dispersion curves. Finally, a mode reconstruction algorithm is developed to recover Lamb wave modes. The proposed method can separate overlapping wave modes and detect the crack fault by enhancing the time–frequency feature of the Lamb wave signal. Two experiments are carried out to verify the effectiveness of the proposed method for Lamb wave mode separation.

The Application of Finite Element Simulation on Sheet Plate Modal Acoustic Emission Testing

2015 ◽  
Vol 713-715 ◽  
pp. 449-455
Author(s):  
Hao Du ◽  
Yan Liu
Keyword(s):  
Finite Element ◽  
Acoustic Emission ◽  
Dispersion Curve ◽  
Lamb Wave ◽  
Analog Signal ◽  
Signal Frequency ◽  
Finite Element Software ◽  
Emission Testing ◽  
Acoustic Emission Test ◽  
Lamb Wave Propagation

Based on mode acoustic emission theory, the paper uses dynamic finite element software ANSYS / LS-DYNA to simulate modal acoustic emission test, and obtains the Lamb wave propagation analog signal on sheet plate; By analyzing the analog signal, it determines the signal frequency and the Lamb wave arrival time of signal receiving point, then determines the guide wave group velocity at this frequency, and uses the method of time difference analysis to determine the dispersion curve. Comparing the simulation dispersion curve with the theoretical curve, the study has shown both curves are consistent and it is feasible to simulate modal acoustic emission signals with the finite element.

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