Ultrasonic Testing Method Research Articles

Impact fatigue behaviour of GFRP mesh reinforced engineered cementitious composites for runway pavement

Concrete runway pavement faces a long term issue of cracking resulting in reduced durability and increased maintenance cost. This paper proposes a new type of runway pavement using engineered cementitious composites (ECC) with glass fiber reinforced polymer (GFRP) mesh reinforcements. This paper investigates the impact fatigue behaviour of the GFRP mesh reinforced ECC pavement through a series of cyclic impact tests. Five impact pressures were adopted considering the impacts induced by various types of airplanes. The number of impacts when the first crack appeared (N0) and at the failure (NC) were reported. The experimental results show that N0 of GFRP mesh reinforced ECC is increased by a maximum of 800 times comparing to that of concrete pavement. The GFRP mesh reinforced ECC could sustain 30,000 impacts without failure. Finally, a non-destructive health monitoring algorithm was proposed based on the ultrasonic testing method and validated using the experimental results. This method is able to assess the damage status, and predict the remaining impact fatigue life of the GFRP mesh reinforced ECC pavement.

The Effect of Phased Array Parameters on the Detecting Accuracy of Welding Discontinuities and 3D Measurement

The reliable detection of defects is one of the most important tasks in nondestructive tests, mainly in the radiography test (RT) and ultrasonic test (UT). Non-Destructive Testing (NDT) is the most efficient as internal and external discontinuities are inspected while maintaining the target’s original structure (form and function). Therefore, in this paper, the Phased Array Ultrasonic Testing (PAUT) method was applied to propose inspection method that can address certain key PAUT Parameters and image processing to enhance the precision of discontinuities and the reliability of calculations of discontinuity size and characterization and also transfer 2D S-Scan images into 3D images (volumetric scan) which is more reliable and easily interpretation.

Small strain moduli of compacted silt by ultrasonic pulse velocity measurements

This study reported the investigation on the small strain modulus of compacted low plastic Mississippi River Valley silt under varying moisture contents and dry densities through ultrasonic pulse velocity testing method. Detailed procedures on filtering the ultrasonic pulse velocity signals and determining the wave arrival times were established. The variation of the small strain elastic moduli with bulk density, dry density as well as water content was also studied. The elastic properties of the compacted Mississippi River Valley silt were found to remain relatively constant with increasing moisture content and bulk density up to a point then decrease rapidly as moisture content increases wet of optimum water content and bulk density increases from around 2000 kg/m3 (bilinear model). The investigation of how pulse wave velocities and moduli vary with density, moisture content, and saturation was found to provide alternative tool for assessing soil characteristics, and based on the trends observed in this study, ultrasonic pulse velocity testing could provide insight on the stability of partially saturated compacted soils.

Experimental determination of freeze-thaw resistance in self-compacting concretes

The paper describes the determination of freeze-thaw resistance in self-compacting concretes and compares several test methods used for this purpose. The basic principle of testing freeze-thaw resistance is the observation of changes, in this case the loss of certain properties, in concrete attacked by freeze-thaw cycles. This paper documents measurements of tensile strength, tensile splitting strength, and dynamic Young’s modulus measured by the ultrasonic pulse velocity test and resonance method. The outcome of the experiment is an evaluation of how suitable each test is for determining the freeze-thaw resistance of self-compacting concrete.

DETERMINATION OF THE POLYMERIZATION DEGREE OF THE MATRIX OF POLYMER COMPOSITE MATERIAL USING ULTRASONIC METHOD

The results of studying the efficiency of the laser-acoustic method of ultrasonic testing in determination of the degree of polymerization of the matrix of polymer composite material (PCM) are presented. We have studied the PCM samples used for manufacturing integrated structures. It is shown that excessive degree of polymerization of the preformed blanks leads to a decrease in the strength of connection of the structural elements and precludes obtaining the desired shape and geometric dimensions of the product. We developed fundamentally new diagnostic parameters, which are characterized by high reliability and accuracy of determination. To forecast sample curing regimes with given values of the degree of transformation, the reaction kinetics was analyzed using differential scanning calorimetry Experimental results used for calculation of the kinetic parameters were obtained on a thermoanalytical complex DSC 1 (Switzerland). The kinetic parameters of polymerization and degree of binder curing in plastics were determined by the thermal effect of the reaction. It is shown that when determining the degree of polymerization of a PCM matrix by an ultrasonic method (laser-acoustic method of exciting ultrasonic vibrations), the product of attenuation of the bottom signal of longitudinal ultrasonic vibrations by the signal round-trip time and energy of the structural noise (thus taking into account the porosity of the material), can be used as reliable parameters of diagnostics. The proposed method provides higher accuracy compared to other methods used for control of the degree of polymerization.

Progress on the ultrasonic testing and laser thermography techniques for NDT of tokamak plasma-facing components

ABSTRACT During manufacturing and operation, different kinds of defects, e.g., delamination or surface cracks, may be generated in the plasma-facing components (PFCs) of a Tokamak device. To ensure the safety of the PFCs, various kinds of nondestructive testing (NDT) techniques are needed for different defect and failure mode. This paper gives a review of the recently developed ultrasonic testing (UT) and laser thermography methods for inspection of the delamination and surface cracks in PFCs. For monoblock W/Cu PFCs of divertor, the bonding quality at both W-Cu and Cu-CuCrZr interfaces was qualified by using UT with a focus probe during manufacturing. A noncontact, coupling-free and flexible ultrasonic scanning testing system with use of an electromagnetic acoustic transducer and a robotic inspection manipulator was introduced then for the in-vessel inspection of delamination defect in first wall (FW). A laser infrared thermography testing method is highlighted for the on-line inspection of delamination defect in FW through the vacuum vessel window of the Tokamak reactor. Finally, a new laser spot thermography method using laser spot array source was described for the online inspection of the surface cracks in FW.

Improving the Efficiency of Ultrasonic Testing Based on Additional Information on Defect Scattering Indicatrices

An ultrasonic testing (UST) method is proposed that allows one to classify internal defects in welded joints into planar and bulk ones by using defect scattering indicatrices. Dedicated angle twin-crystal transducers of the Duet type with probe angles of 29° and 61°, exciting a head wave in the test object, are employed as a transmitter and receiver for ultrasonic testing. Informative signs of defects based on using their scattering indicatrices are considered. These signs make it possible to improve the reliability of ultrasonic testing results. It is shown that due to the peculiarities of propagation of head waves, defect scattering indicatrices are most informative for the probe angle of 29° (a wedge angle close to the first critical value for the PMMA–aluminum-magnesium-alloy pair of materials) and the probe angle of 61° (the angle close to the value complementing the angle of 29° to 90°). The statistical significance of the results of calculating correlation and concordance coefficients were estimated for given significance levels $$\alpha = $$ 0.05 and $$\beta = $$ 0.05, where α and β are the probabilities of the errors of the first and second kind, respectively. Correlation matrices were compiled for the obtained defect scattering indicatrices. Additionally, the reliability of the results was verified by comparing the obtained data with a database of previously performed measurements and their results.

Plasticizing effect of oxidized biodiesel on polyethylene observed by nondestructive method

This paper explores the compatibility of biodiesel with different grades of polyethylene, specifically examining the extent of plasticization in order to gain a better understanding of the biofuel’s compatibility with this common polymer. Its bulk influences on polyethylene were investigated by gravimetric and mechanical testing, and by the application of a newly developed nondestructive ultrasonic testing method. Diffusion rates and the extent of plasticization by biodiesel were compared to results obtained with toluene, a known plasticizer for polyethylene. Mechanical and gravimetric analysis showed that biodiesel exhibited bulk attributes of a plasticizer for the tested polyethylenes with reduced moduli proportional to the amount of fuel uptake and that uptake was inversely proportional to crystalline content of the polymer. Based on uptake amounts, the efficiency of biodiesel as a plasticizer towards polyethylene was found to be more than double that of toluene. However, spectral analysis by ultrasonics showed that absorbed toluene and biodiesel influenced the microstructure of polyethylene differently. Notable differences in internal stresses were noted between the two fluids for the same amount absorbed. A subsequent study analyzed the impact that biodiesel degradation had on plasticization. Although the trend showed a slight change in diffusion rate with increasing oxidation of the medium, the mechanical and ultrasonic results did not show significant differences between fresh and degraded biodiesel within the 45 days span of the test. Combining the evidence observed in this study, a mechanism is proposed for biodiesel plasticization that can help with failure prevention and material selection.

Accuracy Assessment of Ultrasonic C-scan and X-ray Radiography Methods for Impact Damage Detection in Glass Fiber Reinforced Polyester Composites

The present study introduces two quantitative parameters to compare the accuracy of ultrasonic C-scan testing and X-ray radiography methods in the damaged area detection under low-velocity impact in polymer-based composites. For this purpose, the hand lay-up technique of composite processing was employed to prepare the composite specimen. A composite specimen consisting of the glass fiber reinforced with the unsaturated polyester resin was considered for this investigation. The impact tests at different energy levels were carried out to create three damaged areas in this composite specimen. Because the glass/polyester specimen had a transparent surface, a digital scanner was used to obtain an ideal image of specimen representing the region and edge of the impacted areas. Two image quality factors were introduced as quantitative parameters to compare the ultrasonic C-scan and X-ray radiography results with those of an ideal image. The results of this study showed that the ultrasonic C-scan is a more accurate method for inspection of the GFRP specimen.

Ultrasonic testing method for quality control of mold castings

The paper presents the review of one of the promising testing methods for quality control of mold castings that is ultrasonic inspection. Pulse-echo method, through transmission method and phased array technique are considered. The advantages and limitations for the analyzed methods are discussed. The produced by foreign and national companies aperture is reviewed.

Numerical Simulation of Propagation Process of Acoustic Emission Partial Discharge Signal in Medium Voltage Switch-Gears

The rapid and accurate detection of partial discharges (PD) ensures the safe operation of the power grid. It is important to improve the reliability of power supply. When a partial discharge (PD) occurs, acoustic wave will be produced. Usually the partial discharge (PD) produces an acoustic wave frequency of about a few kHz in the gas. This article will use the acoustic simulation module in the Comsol Multiphysics software to simulate the propagation of ultrasonic waves inside and outside the switchgear. Since the transmission of ultrasonic waves is affected by many factors, the geometry of the switchgear is the main factor affecting the propagation of ultrasonic waves. Therefore, this paper will simulate the transmission process of ultrasonic waves under different conditions. Exploring the impact of different monitoring locations on monitoring results through simulation. Through the analysis of the simulation results of the ultrasonic propagation process, we got the following conclusions. As the thickness of the switchgear cabinet increases, it only affects the amplitude of the signal. Opening a hole in the cabinet of the switchgear makes it easier to detect ultrasonic signals outside the cabinet. As the number of openings in the cabinet of the switch cabinet increases, the amplitude of the signal monitored outside the cabinet increases. Four monitoring points are placed on the front, back, upper and lower sides of the switchgear cabinet. Through the simulation of the ultrasonic transmission process, it can optimize ultrasonic testing method and provide guidance for the detection method of ultrasonic waves in production activities.

Assessment of four main representative flint facies as alternative storage materials for concentrated solar power plants

At present there is an intense research for developing alternative sensible heat storage materials, such as natural rocks and recycled ceramics, able to work in concentrated solar power plants at high temperatures. This work demonstrates the potential of flint rocks as an economic and efficient filler material to be used with air as heat transfer fluid in packed bed storage system. Four facies of flint rocks were collected from south of France. To predict the performance of the storage system, crystalline structure, thermo-physical and thermo-mechanical properties of the studied rocks have been identified. For this purpose, the candidate rocks were subjected to extensive experimental characterizations under a series of thermal cycles. XRD, SEM, DSC/TGA, pycnometer, LFA, dilatometer, high temperature ultrasonic testing and nano-indenter method have been used to analyze these samples. Consequently, the 400 °C was identified as ideal temperature for the heat treatment process of flint. The obtained results from the four analyzed samples have been compared together and with currently used storage materials. The results gathered from this paper prove the potential of flint in terms of high density, good specific heat capacity and good thermal stability up to 400 °C to be used as filler material in energy storage applications relevant for low and medium temperature solar power plants.

Calibration of a Piezoelectric Transducer through Laser Measurements and Numerical Simulation

A piezoelectric transducer is an electromechanical sensor which converts electrical energy (voltage signal) to mechanical energy (displacement signal) and vice versa by taking advantage of the piezoelectric crystal. Depending on the physical combination of transducer parts, sensors may have a linear or non-linear response to the input signal. In seismic tests such as ultrasonic non-destructive testing (NDT) methods, analyzing stress wave propagation through the specimen gives an assessment of its condition. The signal attenuation is an important parameter to assess the condition of specimen which can be done by having the displacement signal as an output. However, instead of the displacement signal, the piezoelectric transducer provides the voltage signal as an output. Therefore, to get reliable and accurate results, it is essential to calibrate the transducers. An appropriate calibration results in a suitable Transfer Function (TF) which can be used to properly calculate the displacement signal. In this study, the output displacement of a 1 MHz piezoelectric transducer is measured using a laser vibrometer with a nanometer resolution. Measurements and calculated TF showed at frequencies of 0.1, 1, and 1.5 MHz, TF values are 0.8, 0.08, and 0.2 respectively which is a non-linear relation between displacement (absolute signal) and voltage (relative signal) as it was expected. Then, numerical simulation is implemented as part of this study to simulate all electrical and mechanical components of the piezoelectric transducer. The simulation was verified with the absolute displacement measurements result from the laser vibrometer.

NDT assessment of bonded assemblies - image optimization for weak bond characterization using ultrasonic array transducer

Compromised interface bonds in structural components can lead to premature loss of structural integrity. Such defects are very difficult to detect using traditional acoustic inspection techniques. We assess the ability of linear ultrasonic Non-Destructive Testing (NDT) methods to detect or differentiate between weak-kissing bonds from healthy ones, by using a set of contaminated and non-contaminated bonds. An Ultrasonic Array Transducer (UAT) enables increased informational content, hence they have been used to detect and differentiate compromised bonds. Considerable research has been made into detecting weak bonds, but a practical, cost effective and industrially applicable solution remains elusive. The key problem is the signal changes are small, therefore we have developed an iterative testing methodology, in which the experimental variation in each of the following steps is significantly reduced: Sample Preparation; Data Acquisition; Imaging[1, 2]; Feature Analysis[3, 4]; Characterization/Classification; Interpretation. Our research addresses the issues related to UAT measurement techniques, specifically Full Matrix Capture (FMC)[1, 2] and Total Focusing Method (TFM)[1, 2], Scattering Matrix(derived) [3, 4] extraction in time domain, and other related or derived methods. Here the optimization of bondline imaging, resulting in higher quality and coherence of the imaging, is presented and discussed.

Inspection of butt welds for complex surface parts using ultrasonic phased array

Detection of weld defects for complex surface parts has always been a difficult point in ultrasonic testing because the geometry complexity makes it difficult to arrange transducers and determine the propagation paths of acoustic beams. In this paper, the linear friction weld of the engine blade is taken as an example of the butt weld in complex surface parts, and the application of the ultrasonic array testing method is carried out. Firstly, the propagation properties of acoustic waves in the inspection area are analysed based on both the Snell's law and the acoustic pressure reciprocating transmittance (APRT). According to the inspection requirements, this study establishes a full-coverage inspection solution using multi-array transducers. Secondly, the whole inspection area is divided and the wedge parameters in each subarea are iteratively designed. Thirdly, based on the finite element method (FEM), a response simulation model of the ultrasonic array is established to testify the feasibility and validity of the inspection scheme. Lastly, experiments are conducted on the blade specimen welded by linear friction welding (LFW). The inspection results of different weld positions clearly identify the prefabricated crack defects, showing that the proposed method can fulfill the rapid and accurate inspection for the butt weld of complex surface parts.

Phased array ultrasonic test of vertical defect on butt-joint weld of CFETR vacuum vessel port stub

The CFETR vacuum vessel (VV) main-body and ports are connected via port stub. For the benefits of deep penetration and small deformation, electron beam welding (EBW) was selected for port stub butt-joint welding. Unacceptable defects such as vertical crack, non-fusion and non-penetration might appear in this kind of large depth-to-width ratio weld.In this paper, the phased array ultrasonic testing (PAUT) method was introduced. Reference blocks with artificial defects of different lengths and heights were fabricated, and then tested by 2.5 MHz 64el dual element matrix array probe and 2.25 MHz 64el single linear array probe. Detection sensitivity of 0.2 mm in width was achieved. In the end, the above probes were successfully applied on the detection of the EBW testing blocks with natural defects. The testing results of reference and testing blocks implied the full capability of the selected probes.

A method for evaluation of weld overlays exposed to combined wear and very high cycle fatigue conditions

Key machinery components used for diminishing, transporting or processing massive volumes of material in heavy industries are severely exposed to combinations of different wear mechanisms, like abrasion and surface fatigue. The microstructure and wear properties of state of the art iron based welding alloys used as surface protection do not only depend on the nominal chemical composition of the welding consumables and their manufacturing route, but also on the base material, variations in process technology and applied welding parameters. Commonly used wear and hardness and test or microstructural investigations are either cost and time consuming or do not provide a complete understanding about the material behavior of surface coatings exposed to combined wear including fatigue. Thus the aim of this study was to prove the concept of using ultrasonic fatigue testing as new method to understand and predict the behavior of welded surface coatings in a fast and reproducible way. Two flux cored wires from different manufacturing lines, but of the same nominal chemical composition were compared applying identical welding parameters. As a result, the two wires could be distinguished clearly by applying the ultrasonic fatigue test method.

Mechanical Behavior of Cross-Laminated Timber Panels Made of Low-Added-Value Timber

Abstract The cross-laminated timber (CLT) construction system has recently emerged as an excellent alternative for civil construction. The objective of this work is to analyze the structural performance of CLT panels using plantation lumber, especially eucalyptus (Eucalyptus grandis) heartwood and pine (Pinus taeda). After visual grading, all boards were mechanically graded through the ultrasonic nondestructive testing method. Boards were organized to compose four types of three-layered CLT panels: 1) exclusively eucalyptus heartwood (EEE), 2) eucalyptus in the outer layers and pine in the central layer (EPE), 3) exclusively pine (PPP), and 4) pine in the outer layers and eucalyptus in the central layer (PEP). Three panels with graded timber were manufactured for each type, and one more panel was made out of ungraded timber, so each group had four panels altogether. Panels containing eucalyptus in the outer layers (EEE and EPE) were stiffer than the ones with pine in outer layers (PPP and PEP). However, the first two groups presented lower bending strength than the second ones. Modulus of elasticity and modulus of rupture results were compared to values observed in the literature and to the international standard that regulates CLT (American National Standards Institute/American Plywood Association PRG 320). From the four types studied, only panels containing mostly eucalyptus (EEE and EPE) could meet the PRG 320 E2 class. Panels containing mostly pine (PPP and PEP) did not reach the thresholds of any class in terms of stiffness although their resistance was much higher than that specified in the standard.

The mechanisms of cavitation erosion of raw and sintered basalt

The paper analyzes the morphology of cavitation damage of raw and sintered basalt samples. The experiment was conducted using the ultrasonic vibratory cavitation test method according to the ASTM G-32 standard. During the determination of the resistance to the effect of cavitation, a change in the mass of samples was observed in the function of the cavitation time of operation. The morphology of damage caused by the effect of cavitation was followed by scanning with an electron microscope, and the level of degradation of the surface of the samples was quantified using the image analysis. The results showed a significantly higher degree of resistance of sintered basalt, with a cavitation rate of 0.019 mg/min relative to raw basalt, with a cavitation rate of 0.738 mg/min. After 120 minutes of exposure to the cavitation effect, a smaller number of small pits on the surface of sintered basalt were observed, while a higher level of damage to the surface with the appearance of numerous pits was found in raw basalt, which can be connected in some places to larger and deeper pits in some places. The obtained results indicate the possibility of using sintered basalt for the production of parts that will be exposed to the effects of high cavitation loads.

Characterisation of self-healing efficiency of calcium nitrate microcapsules for concrete applications

This study presents characterisation of concrete samples containing 0.75% by cement weight of modified calcium nitrate self-healing microcapsules. The phased array ultrasonic testing method was used to investigate the healing efficiency of calcium nitrate microcapsules in concrete. The method is a novel non-destructive testing technique that is commonly used for detecting the defects in welding. Concrete beams were prepared from the control mix (without microcapsules) and mixes containing 0.75% by weight of cement of calcium nitrate microcapsules. After 28 days of moist curing, the phased array ultrasonic images of all beams were captured before loading, after applying 60% of the ultimate flexural load, and after 3 and 7 days of accelerated healing. Moreover, scanning electron microscopy images taken from fractured surfaces of the beams that were loaded up to failure before healing were compared to those of the beams that were healed for 7 days and loaded up to failure.