Ultrasonic Measurement Model Research Articles

Data fusion of multi-view plane wave imaging for nozzle weld inspection

Ultrasonic non-destructive testing of nozzle-to-pipe welds has always been a challenge due to the complex saddle-shaped geometry of this junction. Inspection from the nozzle side can minimize geometry effects, however, conventional ultrasonic phased array methods suffer from artifacts and inadequate resolution. This paper proposes a novel nozzle-side inspection method based on the data fusion of multi-view plane wave imaging (PWI). A semi-analytic ultrasonic measurement model is derived, and a sensitivity mapping algorithm is presented for optimizing the inspection setup and enabling data fusion. Experiments were conducted on reference blocks and a nozzle specimen containing three embedded defects. Results demonstrate the capability of sensitivity mappings to not only optimize the inspection configuration, but also serve as filters to fuse multi-view images. Nozzle sidewalls were positioned in fusion images, evidencing the ability to deduce probe position around nozzle circumference without encoder feedback. A 10 dB amplitude difference was observed between the tip diffraction and specular reflection, enabling the defect characterization along with position and sizing accuracy within 0.59 mm and angle deviation below 9°. Slag, crack and lack of penetration were also characterized in the nozzle specimen, validating the proposed method.

Determination of the coefficient of thermal expansion of ultra-low-expansion glass using anultrasonic immersion testing method.

The coefficient of thermal expansion (CTE) of ultra-low-expansion (ULE) glass is critical to the development of precision optical systems. Herein, an ultrasonic immersion pulse-reflection method is proposed to characterize the CTE of ULE glass. The ultrasonic longitudinal wave velocity of ULE-glass samples with significantly different CTE values was measured using a correlation algorithm combined with moving-average filtering, which can achieve 0.2m/s precision with a contribution to the ultrasonic CTE measurement uncertainty of 0.47ppb/°C. Furthermore, the established ultrasonic CTE measurement model predicted the 5°C-35°C mean CTE with a root-mean-square error of 0.9ppb/°C. Notably, a complete uncertainty analysis methodology was established in this paper, which can provide directional guidance for the subsequent development of higher-performance measurement devices and the improvement of relevant signal processing procedures.

Interaction effects from the elastodynamic scattering by two symmetric spherical cavities

The scattering of harmonic waves has been studied extensively for problems in quantum mechanics, acoustics, electromagnetics, and elasticity. Solutions to elastodynamic problems are the basis for ultrasonic non-destructive evaluation measurement models. Therefore, in this study, we investigate the use of the boundary element method (BEM) in the frequency domain using an off-boundary technique in which the observation points are taken inside the scattering object. This methodology removes both non-integrable singularities from the domain of integration along with avoiding ill-conditioning effects that occur at fictitious eigenfrequencies of which both require using special computationally demanding procedures to obtain solutions. Additionally, we employ both free and half-space fundamental solutions (Green’s displacement tensors) to investigate the elastodynamic scattering of an incident, plane, time-harmonic longitudinal wave in the frequency domain of a homogeneous, isotropic, and linear elastic solid with one or two spherical cavities. The half-space fundamental solution reduces the number of required boundary elements in half, which significantly reduces computational resource requirements. We only consider spherical cavities in this paper to illustrate the full and half-space off-boundary BEM and analyze the interaction effects associated with the elastodynamic scattering by two symmetric spherical cavities. To verify the validity of the free and half-space off-boundary BEM formulations, surface displacement results are compared with existing surface displacement results and show good agreement. Finally, the half-space off-boundary BEM is used to illustrate the interaction effects of the back and forward scattered displacement fields as a function of the distance from the spherical cavities.

Research on ultrasonic testing method of rotating component based on a 6-DOF robot

Some rotating components have the structural characteristics of variable thickness and variable curvature. The conventional ultrasonic testing is inappropriate for these components because of bad coupling and too many uncertainties. In order to meet the testing requirements of high-volume, high-efficiency and high-precision, the corresponding ultrasonic automatic detection program is proposed. A 6-DOF industrial robot is used to realize the precise control of the transducer position and posture, and combines the independent turntable to complete the spiral fast scan of the specimen. Based on the multi-Gaussian beam model and the internal flat-bottom hole flaw scattering model of specimen, the flaw ultrasonic measurement model is established. The system parameters, component material parameters and component surface parameters are all introduced to the ultrasonic measurement model to generate a series of flaw-sizing curves. An accurate flaw sizing method based on DGS(Distance-Gain-Size)curve predicted by regular reflector is proposed. The scanning experiment results of the reference specimen show that the minimum Ø 0.8mm artificial flat-bottom-hole flaw in the workpiece can be detected effectively, and the sizing error is less than Ø 0.3mm equivalent.

Modelling of ultrasonic method for measuring gas holdup of Oil-Gas-Water three phase flows

In oil–gas-water three-phase flow, the presence of two physically distinct dispersed phases leads to complex interfacial effects and relative velocities between the phases, which poses a significant challenges for gas holdup measurements. In this paper, a novel gas holdup measurement based on flow structure detection is realized. Firstly, the effect of gas bubble diameter on ultrasonic attenuation was studied, and a gas bubble diameter-based ultrasonic gas holdup measurement model was proposed. According to the model's specifications, a combined measurement system consisting of pulse transmission ultrasonic sensor and bi-optical fiber probe sensor was built. The dynamic experiment of oil–gas-water three-phase flow was conducted on a simulated well installation to measure the gas holdup using the combined measurement system. The results suggest that the proposed ultrasonic-optical measurement system can attain a high level of measuring precision.

Ultrasonic measurement model-based non-destructive detection method for curved components using an immersion spherically focused transducer

ABSTRACT The ultrasonic measurement model (UMM) has been theoretically studied over the past few decades, but there is little published work on its practical application for guiding defect detection. In this work, we present a model-based ultrasonic method to detect flaws in curved components using immersion of spherically focused transducers. The UMM of focused transducers is further investigated theoretically and verified experimentally, and some key issues in the model with focused transducers are addressed, including the necessity of correctly using effective geometrical parameters and the corresponding transfer function. The UMM is employed to guide the inspection of a magnesium alloy shell component which consists of several curved surfaces. The alignment between the transducer and the shell is conducted by comparing the measured and theoretically predicted interface-echo signals, the water path is selected by simulating the effective detection region, and the system gain is set by quantitatively analysing the amplitudes of flaw signals and noises. When the inspection conditions are determined, a variable threshold based on the predicted flaw signals is introduced to distinguish noise and flaw signals. The ultrasonic C-scan images of the shell are compared with the digital radiography (DR) images, and the comparison shows that the flaws of interest can be detected in the C-scan images, which verifies the effectiveness of the UMM-based detection method.

Measuring the Wall Thickness of a Trailing Arm Using Ultrasonic Measurement Model

Trailing arms are widely used in the automobiles’ suspension system, and effective detection of their wall thickness is essential to ensure their mechanical properties and to evaluate the casting process. In this work, an ultrasonic measurement model (UMM) is firstly established with consideration of the curvature and thickness of the trailing arm, then the UMM is introduced to predict the theoretical ultrasonic waveforms with different hypothetical thicknesses of the trailing arm. Next, the experimental ultrasonic waveforms are collected and matched with the predicted theoretical waveforms by using the correlation matching algorithm. The hypothetical thickness with the best match is regarded as the wall thickness of the trailing arm. Finally, an automatic ultrasonic experiment was conducted on a trailing arm with a 5-degrees of freedom (DOF) manipulator, in which the ultrasonic beam can radiate into a trailing arm at normal incidence. The results are compared with those determined by the micrometer and microscope, showing that their relative errors are controlled within 0.08 mm, which reveals the effectiveness of the present method. The method can also work for wall thickness measurements of curved components with CAD models.

Defects identification using the improved ultrasonic measurement model and support vector machines

With a combination of the improved ultrasonic measurement model (IUMM) and support vector machines (SVM), a novel method to identify inclusions and cavities in metallic materials using scanning acoustic microscopy is proposed. In the IUMM, a hybrid model of Born approximation and Kirchhoff approximation is developed to calculate the far-field scattering amplitude of cavities, which improves the accuracy in phase and amplitude of the predicted pulse-echo signals of defects. The SVM classifier, with the amplitude and peak frequency of the predicted echo signals as major features, is applied to distinguish inclusions and cavities. The experimental result shows that the echo signals predicted by the proposed IUMM are more accurate than conventional UMM in amplitude and frequency. The SVM classifier, with the predicted signals as the training set, enables the identification of inclusions and cavities in metallic materials successfully. This work improves the performance of SAM in the identification of internal defects in metallic materials and realizes the intelligent analysis of ultrasonic signals.

Sizing Small Crack-like Flaws through Non-ideal Part Surface Using Ultrasonic Measurement Model

ABSTRACTTo accurately size small crack-like flaws in components with non-ideal surface conditions, such as curvature, roughness, and coating, we developed a flaw sizing method based on an ultrasonic measurement model. First, the effects of surface curvature on the sound beam profile, as well as the effects of surface coating and roughness on the wave energy are investigated theoretically and experimentally. Then, correction methods for curvature, roughness, and coating are introduced into the ultrasonic measurement model, and the flaw response in components with different surface conditions is predicted. Lastly, by accounting for the effects of surface conditions, a set of model-based flaw sizing curves is generated for predicting the equivalent size of crack-like flaws. These model-based curves can guide the setting of system parameters and improve the flaw sizing accuracy. Experiments are then conducted to verify the effectiveness of the proposed method. This work demonstrates the utility of the ultrasonic method for measuring the equivalent flaw size in practical applications.

DSmT-Based Ultrasonic Detection Model for Estimating Indoor Environment Contour

As for uncertainties of ranging and direction angle in the ultrasonic sensor measurement, an ultrasonic distance measurement model is first proposed for representing these uncertainties through analyzing the working principle of the ultrasonic sensor, which can be adopted to detect the contour of wall plan and cylinder. Moreover, the Dezert–Smarandache Theory (DSmT) method is employed to fuse the uncertainty data measured by using the ultrasonic sensor. Next, extended Hough transform (EHT) and least-squares method (LSM) are combined to identify the environmental contour. Then, the measurement uncertainty of the ultrasonic sensor is analyzed for setting the threshold Th used for distinguishing line and cylinder, and the detection range of the cylinder radius is estimated. Finally, we build an indoor environment and design the ultrasonic sensor hardware system to detect the indoor environment for experimental verification. The indoor environment contour obtained in the experimental results is consistent with the real environment, which illustrates the feasibility and effectiveness of the proposed method. The proposed method has certain reference value for research of simultaneous localization and mapping (SLAM) of the mobile robot.

Nondestructive testing method and application for internal defect of metal balls

ABSTRACTNondestructive testing for internal defects is necessary owing to the extensive application of metal balls in different industrial fields. The flat-bottom holes (FBHs) are used as the reference standards for the detection of internal defects. An ultrasonic measurement model with spherical-focused transducer based on multi-Gaussian beam is proposed to describe the detection of FBHs inside the metal ball. The comparison between the predicted signals and the pulse-echo responses of FBHs is given to certify the accuracy of the model. The distance-amplitude-correction (DAC) curves are provided to evaluate the equivalent size and depth magnitude of the defects inside the balls. The experimental results indicate that the model can predict and evaluate the internal defects accurately and efficiently. Finally, the method of spiral fully unfolding of ball surface based on orthogonal clamping is developed and successfully applied to the automatic ultrasonic testing system for internal defects of bearing balls combining with the model-based DAC curves.

Modeling Flaw Pulse-Echo Signals in Cylindrical Components Using an Ultrasonic Line-Focused Transducer with Consideration of Wave Mode Conversion.

Investigations on flaw responses can benefit the nondestructive testing of cylinders using line-focused transducers. In this work, the system function, the wave beam model, and a flaw scattering model are combined to develop an ultrasonic measurement model for line-focused transducers to predict flaw responses in cylindrical components. The system function is characterized using reference signals by developing an acoustic transfer function for line-focused transducers, which works at different distances for both planar and curved surfaces. The wave beams in cylindrical components are modeled using a multi-Gaussian beam model, where the effects of wave mode conversion and curvatures of cylinders are considered. Simulation results of wave beams are provided to analyze their propagation behaviors. The proposed ultrasonic measurement model is certified from good agreement between the experimental and predicted signals of side-drilled holes. This work provides guidance for evaluating the detection ability of line-focused transducers in cylindrical component testing applications.

Study on the normal contact stiffness of the fractal rough surface in mixed lubrication

In this paper, an elastic interface model is developed to theoretically analyze the contact stiffness of a mixed lubrication surface where the solid and the lubricant contacts have to-be-determined contributions to the whole contact stiffness. The interfacial contact stiffness is composed of the solid contact stiffness and the lubricant contact stiffness, in which the two components are associated with each other via the equivalent thickness of lubricant. Based on the combination of two widely acknowledged ultrasonic measurement models and the Taylor approximating equation, the derivation of the lubricant contact stiffness is mostly affected by the material properties and the equivalent thickness of lubricant, and the equivalent thickness is determined by the solid contact properties under the mixed lubrication condition. Results of the mathematical analysis show that the contact stiffness of the mixed lubrication surface is larger than that of the dry rough surface due to the presence of lubricant. The interfacial contact stiffness of the mixed lubrication is obviously affected by the surface topography and the lubricant property. The proportions of contact stiffness contributed from the solid part and the lubricant part are varying with the contact area and the surface topography. Model predictions are compared with experiment results to verify the accuracy of proposed model. The analysis of the interfacial contact stiffness involved in mixed lubrication provides a theoretical basis for the performance prediction of machine tools, and might be useful to elucidate the contact properties by ultrasonic pulse probing in real engineering applications.

Effects of the Oxide Coating Thickness on the Small Flaw Sizing Using an Ultrasonic Test Technique

When magnesium alloys are tested using ultrasonic techniques, their oxide coating will affect the transmitted ultrasonic energy and the accuracy of the flaw sizing. In this work, the effects of the coating thickness on the flaw sizing are investigated. An ultrasonic measurement model is employed to predict the flaw response signal, and the reflected and transmitted ultrasonic energy in the coated surface are corrected by modifying the reflection and transmission coefficients related to the effects of the coating thickness. The effectiveness of these coefficients and the ultrasonic measurement model are verified through experiments. With the correction of the coating thickness effects, the flaw-sizing curves predicted using the ultrasonic measurement model are provided. The flaws in magnesium alloy specimens with different coating thicknesses are tested, and the determined flaw sizes from these curves agree well with the actual sizes, which reveals the effectiveness of the proposed work. This work provides an effective tool to improve the flaw sizing performance using ultrasonic techniques in practical applications.

Prediction of flat-bottom hole signals received by a spherically focused transducer for an ultrasonic pulse echo immersion testing

The spherically focused transducer has been widely used for nondestructive evaluation of micrometer-scale inner defects in material and microelectronic devices due to its outstanding transverse resolution and high beam intensity. In this paper, by combining the beam model, the flaw scattering model and the system efficiency factor, an ultrasonic measurement model is developed for the spherically focused transducer in an ultrasonic pulse-echo immersion testing and is used to predict the ultrasonic flaw signal for flat bottom hole (FBH). The multi-Gaussian beam (MGB) model and the Gaussian beam equivalent point source (GBEPS) model are extended to evaluate the beam fields radiated by the spherically focused transducer in water and transmitted into solid through a planar interface. Results show that the MGB model is more excellent considering both the accuracy and efficiency. Experiments are performed to determine the system efficiency factor and the experimental measured flaw signal is compared with the model predictions to validate the accuracy of the proposed model. Effects of the depth and size of the FBH are further studied using the established model.

Numerical simulation of ultrasonic propagation and defect testing in laser cladding remanufacturing parts

The laser cladding remanufacturing parts show typical anisotropic behaviors, which is difficult for acoustic detection. Therefore, the propagation behaviors of ultrasonic beam in the laser cladding remanufactured parts should be investigated in-depth, which will provides an important theoretical basis for ultrasonic nondestructive evaluation of this kind of parts. An ultrasonic measurement model for the laser cladding remanufacturing parts was developed. The influence of anisotropic laser cladding coating on the propagation behaviors of ultrasonic beam was analyzed. The propagation behaviors of ultrasonic beam in the laser cladding Fe314 alloy coating were investigated with the help of Rayleigh integral combined with Pencil method. The simulation results show that the influence of anisotropic material on the incident field due to the value of slowness, the direction of beam steering is determined by the normal vector of slowness surface, the beam focusing and defocusing behavior is determined by the curvature of slowness surface. The radiated ultrasonic field maintains a uniform distribution relative to the axis of the incident beam, when the direction of incident beam is consistent with or perpendicular to the grain orientation of laser cladding coating, which the directivity of beam is preferably. The reason lies in the incident direction of ultrasonic wave is perpendicular to the isotropic plane of crystal. In the radiated field of transverse wave angle probe, the transverse wave splits and the beam steers, separates with the change of grain orientation. The fundamental reason that transverse wave splitting due to the anisotropy of the laser cladding coating. The reason that beam steering lies in that the direction of group velocity (the direction of normal vector of slowness surface) is inconsistent with that of phase velocity (the direction of transverse wave vector). The slowness surface of anisotropic laser cladding coating is irregular in shape, the beam will appear in other angles in addition to the main beam, when transverse wave refraction. An ultrasonic measurement model for the laser cladding remanufacturing parts was developed by combining the beam model with the scattering model based on Kirchhoff approximation and Born approximation theory. This model can be used to predict the testing signals from the flaws in laser cladding remanufacturing parts. The accuracy of the provided model was verified by comparisons of the simulation results with the experimental results, both the signal amplitude and phase were in good agreement. Numerical simulation results provide an important theoretical basis for rational design of the process scheme of ultrasonic testing for laser cladding remanufacturing parts.

Main Features of a Complete Ultrasonic Measurement Model: Formal Aspects of Modeling of Both Transducers Radiation and Ultrasonic Flaws Responses

This paper aims at describing the theoretical fundamentals of a reciprocity-based ultrasonic measurement model. This complete inspection simulation can be decomposed in two modeling steps, one dedicated to transducer radiation and one to flaw scattering and echo synthesis. The physical meaning of the input/output signals used in these two modeling tools is defined and the theoretical principles of both field calculation and echo computation models are then detailed. The influence on the modeling results of some changes in the simulated configuration (as the incident angle) or some input signal parameters (like the frequency) are studied: it is thus theoretically established that the simulated results can be compared between each other in terms of amplitude for numerous applications when changing some inspection parameters in the simulation but that a calibration for echo calculation is generally required.

Ultrasonic Measurement Models for Contact Testing with Bulk Waves, Surface Waves, and Plate Waves

A complete ultrasonic measurement model is obtained for contact testing, where all the electrical, electromechanical, and acoustic/elastic elements are explicitly described. Reciprocity principles are used to model those acoustic/elastic elements that cannot be measured directly in terms of an integral of the incident and scattered wave fields over the surface of the flaw. This general measurement model for contact testing is then reduced to new, highly modular forms that are applicable to contact tests involving bulk, surface, and plate waves. These modular forms are similar in structure to the measurement model previously developed by Thompson and Gray [7] for immersion bulk wave inspections.

Prediction of Side-Drilled Hole Signals Captured by a Dual Crystal Contact Probe

The dual crystal transducer plays an important role in many practical ultrasonic inspections due to its outstanding near surface resolution and signal-to-noise ratio. In order to get a deeper understanding on the characteristics of this kind inspection system, it is essential to develop an ultrasonic measurement model for dual crystal probes. To address such a need, by combining a multi-Gaussian beam model and a scattering model with the separation of variables method, we provide an efficient ultrasonic measurement model for the dual element transducer. This measurement model can be used to determine the system efficiency factor and predict the responses of a side-drilled hole. Furthermore, the comparisons of model predictions with experimental results are presented to certify the accuracy of this provided model.

Characterization of the system functions of ultrasonic linear phased array inspection systems

This work characterizes the electrical and electromechanical aspects of an ultrasonic linear phased array inspection system, using a matrix of system functions that are obtained from the measured response of individual array elements in a simple reference experiment. It is shown that for the arrays tested all these system functions are essentially identical, allowing one to use a single system function to characterize the entire array, as done for an ordinary single element transducer. The variation of this single system function with the number of elements firing in the array or with changes of the delay law used is examined. It is also demonstrated that once such a single system function is obtained for an array, it can be used in a complete ultrasonic measurement model to accurately predict the array response measured from a reference reflector in an immersion setup.