Ultrasonic C-scan Research Articles

Development of gantry radial arm robotic system for corrosion inspection on wall of reactor tank TRIGA

This paper focuses on the design upgrade of existing scanner of gantry radial arm robotic system for corrosion inspection on wall reactor of a TRIGA tank. The scanner design will be used for under water inspection environment verification. This inspection can be performed by using ultrasonic C-scan that will be designed in this project. This gantry radial arm system is a modular design that allows upgrading, easy dimensional matching and, specifications related to kinematic and technique. The gantry radial arm system is expected to be user-friendly. SolidWorks software was used to design the prototype of the gantry radial arm. Most of the components are made from Aluminium which is much sturdy and low cost. Meanwhile for the rod holder system, spring mechanism was used to prevent rod from bending when it moves down into the water. The test results show that the system designed is safe to be used, as it has been proved by simulation and calculation.

Effect of toughened polyamide-coated carbon fiber fabric on the mechanical performance and fracture toughness of CFRP

In this study, carbon/epoxy composites were manufactured by coating with a polyamide at different weight percentages (5 wt.%, 10 wt.%, 15 wt.%, and 20 wt.%) to improve their impact resistance and fracture toughness. The chemical reaction between the polyamide and epoxy resin were examined by fourier transform infrared spectroscopy, differential scanning calorimetry and X-ray photoelectron spectroscopy. The mechanical properties and fracture toughness of the carbon/epoxy composites were analyzed. The mechanical properties of the carbon/epoxy composites, such as transverse flexural tests, longitudinal flexural tests, and impact tests, were investigated. After the impact tests, an ultrasonic C-scan was performed to reveal the internal damage area. The interlaminar fracture toughness of the carbon/epoxy composites was measured using a mode I test. The critical energy release rates were increased by 77% compared to the virgin carbon/epoxy composites. The surface morphology of the fractured surface was observed. The toughening mechanism of the carbon/epoxy composites was suggested based on the confirmed experimental data.

Numerical simulation of thermal cycle and void closing during friction stir spot welding of AA-2524 at different rotational speeds

A three dimensional and Coupled Eulerian–Lagrangian (CEL) model for the refill friction stir spot welding (RFSSW) of 2524-T3 aluminum alloy was developed based on the ABAQUS/Explicit. The distribution of stress and temperature field at the joint area, at five different rotational speeds, were simulated and verified using experimental studies. The simulation results showed that with increasing rotational speed, heat production by friction and plastic deformation was enhanced, while the stress was reduced. Moreover, internal voids, the typical defect, were found on the bottom edge of the stir zone, and the propensity for the voids were the lowest at the rotational speed of 2800 rpm (rpm); this was verified using the immersion ultrasonic C-scan test (IUCT) test results. Based on the simulation results, isothermal compression test results and electron backscatter diffraction (EBSD) analysis results of the joint, the relationship between grain size and the Zener–Hollman parameter at the stir zone (SZ) was also established, thereby providing an in-depth understanding and detailed rationalization of the RFSSW processes.

Detection of Cracks in Aerospace Turbine Disks Using an Ultrasonic Phased Array C-scan Device

Crack detection in an aerospace turbine disk is essential for aircraft- quality detection. With the unique circular stepped structure and superalloy material properties of aerospace turbine disk, it is difficult for the tradi... | Find, read and cite all the research you need on Tech Science Press

Multi-mode ultrasonic visualization of porosity in composites using a focused transducer with high sensitivity and near-surface resolution

Porosity ranging from 0.15% to 2.33% in carbon fiber-reinforced polymer composites (CFRPs) is detected and characterized by multi-mode visualizations including ultrasonic A-Scan, B-Scan, C-Scan and Tomography-Scan using a focused ultrasonic transducer. Three-dimensional visualizations are also reconstituted from the ultrasonic tomography scan images. The result shows: UT using the focused transducer possesses high sensitivity, near-surface resolution and depth estimation for porosity in composites. Using this transducer, multi-mode visualizations can characterize porosity feature and fiber orientations through the entire volume. The amplitude and transit time of A-Scan waveforms have correlations with porosity size and depth. B-Scan imaging characterizes porosity distribution with depth estimation up to one-ply thickness, which is approximate 0.18 mm. C-Scan imaging characterizes porosity size and distribution in the integral composite bulk. Tomography scan can give detailed information about porosity feature and fiber orientations ply by ply, with detection sensitivity of no more than 1.0 mm and excellent near-surface resolution of one ply.

Damage and failure analysis of composite stiffened panels under low-velocity impact and compression after impact

Impact resistance and damage tolerance after impact are important performance reference indices in the structural design of composite stiffened panels. The damage evolution and failure mechanism of composite panels with foam-filled hat-stiffeners under low-velocity impact and compression after impact (CAI) at different positions and different energies were studied by experimental and numerical simulation methods. The delamination damage caused by low-velocity impact was captured by ultrasonic phased array C-scan, and a fringe projection profile (FPP) measurement system was employed to measure the full-field buckling deformation and mode evolution of the stiffened composite panel during CAI. A damage model based on the Hashin failure criterion was established to study the complex damage and failure mechanisms, and the interface cohesion behavior embedded in ABAQUS/ Explicit was used to define the interlaminar damage model for characterizing delamination. The interlaminar delamination damage and intralaminar damage behavior in the process of impact and CAI were considered. The results obtained from the numerical simulation and the experimental results were combined to analyze the damage modes of the composite stiffened panel under different impact positions and impact energies and their effects on the damage development and failure during compression.

Laser ultrasonic imaging for defect detection on metal additive manufacturing components with rough surfaces.

Defects or discontinuities are inevitable during the melting and consolidation process of metal additive manufacturing. Online inspection of microdefects during the processing of layer-by-layer fusion is urgently needed for quality control. In this study, the laser ultrasonic C-scan imaging system is established to detect the surface defects of selective laser melting (SLM) samples that have a different surface roughness. An autosizing method based on the maximum correlation coefficient and lag time is proposed to accurately measure the defect length. The influences of the surface roughness on the laser ultrasound signal-to-noise ratio distribution and defect sizing accuracy are also studied. The results indicate that the proposed system can detect notches with a depth of 50 µm and holes with a diameter of 50 µm, comparable in size to raw powder particles. The average error for the length measurement can reach 1.5% if the notch is larger than 2 mm. Meanwhile, the sizing error of a 1 mm length notch is about 9%. In addition, there is no need to remove the rough surface of the as-built SLM samples during the detection process. Hence, we propose that the laser ultrasonic imaging system is a potential method for online inspection of metal additive manufacturing.

Study on Dynamic Response Characteristics of Bird Impact Glass Fiber Laminate

Composite structures are often subjected to bird impact loads during service, which causes visually invisible damage inside the structure. Such damage often weakens the mechanical properties of the laminated plate structure, resulting in a significant reduction in the bearing capacity and service life of the structure. Therefore, it is important to evaluate the impact resistance of composite structures and predict the corresponding impact damage characteristics for safety. Experimental research using real birds is costly and unrepeatable, so gelatin bird projectile was often used instead of real birds. In this study, gelatin projectile was prepared to meet the requirements of the experiment and impacted the glass fiber laminated at different speeds. The strain variation trend at each point was recorded and analyzed, Simultaneously capturing the test process with a high-speed camera. In order to understand the bird strike damage characteristics of fiberglass laminates, ultrasonic C-scans were performed on the test specimens after the experiment. The results show that the strain at the impact point is the largest during the impact process. When the impact speed is doubled, the strain at each point does not increase exponentially, but only slightly. In the test, point C is inner concave due to the affected of the impact, and the nearby area is outer convex, and then spread to the surrounding area in the form of "water wave". The gelatine pellets of 2bl did not cause lamination damage at the impact velocities of 44.4m/s, 66.6m/s, 88.8m/s and 111m/s, but plastic deformation will occur to varying degrees.

Experimental investigation on damage mechanisms and buckling behaviors of thin composite laminates in compression after impact

This paper presented an experimental investigation on the damage mechanisms and buckling behaviors of thin composite laminates under low-velocity impact and compression-after-impact (CAI) loading conditions. Barely visible impact damage was introduced into the laminates through drop-weight impact tests. The CAI tests were performed with a non-standard device in order to suppress the global buckling of plates. Three different stacking sequences were compared in this paper. A stage loading method in conjunction with ultrasonic C-scan was adopted to observe the process of delamination propagation and located the position of initial propagation. The 3D digital image correlation technique was employed to monitor the evolution of the out-of-plane displacement of the specimens. The effects of stacking sequences on delamination morphology, the compression damage propagation mode of thin laminates and the influence factors on local buckling were then discussed.

A developed energy-dependent model for studying thermal shock damage and phase transition of composite reinforced panel subjected to lightning strike

Lightning strikes generate large amounts of energy. Thus, composite structures subjected to lightning strikes undergo significant physicochemical changes. In this study, the thermal shock damage and three-phase transition of a composite reinforced panel were investigated through a numerical simulation, an experiment, and ultrasonic C-scanning. An anisotropic constitutive model and PUFF equation of state (EOS) were proposed to study the damage behaviors of composite materials. The dynamical damage behaviors and three-phase transition of the composite reinforced panel were simulated using the proposed constitutive model and PUFF EOS. Finally, a lightning experiment and ultrasonic C-scanning were conducted to validate the numerical results. Obvious fiber upwarping and swelling were observed in the numerical simulation. The melted and vaporized materials caused a reverse thermal shock effect, which led to concave pits, buckling and internal damages in the composite reinforced panel. The numerical results were compared with experimental results and scanning results to validate that the proposed constitutive model and modified PUFF EOS can be well used to simulate the dynamical damage behaviors of composite materials. The simulated damage behaviors of the composite reinforced panel agreed well with the behaviors observed in the experiment.

Investigation of damage to thick composite laminates under low-velocity impact and frequency-sweep vibration loading conditions

A detailed investigation of damage and failure mechanisms of composite laminates under low-velocity impact (LVI) by experimental tests and numerical modeling is presented. Five impact energy levels were investigated on composite laminates by drop-weight tests. Permanent indentations were measured, and delamination areas of each interface induced by each LVI event were captured using an ultrasonic C-scan. The 3D volume elements with a user-defined, material-based finite element model (FEM) has been applied to predict the LVI event considering damage modes, including intra-ply damage and inter-ply damage. The results of the FEM were found to agree well with experimental observations. Internal damage of the laminate during the impact process was analyzed. For thick laminates, the initiation of damage is observed at the first layer, and then spreads from the impact surface to the back, leading to a pine-type damage pattern as the thickness increases. Frequency-sweep vibration tests of composite laminates subjected to LVI events were studied under a “fixed ends” boundary condition. Our results show that it is reasonable to use frequency-sweep vibration experiments to evaluate the damage of laminates subjected to LVI events.

Electromagnetic-mechanical repair patch of radar-absorbing structure with electroless nickel–plated glass fabric damaged by lightning strike

This paper presents an electromagnetic-mechanical repair patch (EMRP) to restore the mechanical and electromagnetic (EM) wave absorption performance of a radar-absorbing structure (RAS) damaged by lightning strike. Several researchers have primarily focused on ensuring high repair efficiency, particularly in terms of the primary load-bearing properties of repaired fiber-reinforced plastics. However, no study has proposed a practical repair approach that considers the multi-functionality of the radar-absorbing structure. The EMRP method can be used to repair lightning strike damage in a radar-absorbing structure with electroless nickel-plated glass fabric, considering the need to maintain structural integrity and electrical continuity to achieve a high repair efficiency. Damage due to an artificial lightning strike was assessed in terms of area and depth of the damage using image processing, ultrasonic C-scan, and micro X-ray inspection. The EM characteristics of one-dimensional return loss scanning and the echo radar-cross-section level were measured to verify the stealth performance of the repaired radar absorber in the X-band. In addition, the tensile test results demonstrated that the repaired radar absorber had a high recovery rate of 93% compared to the pristine radar absorber. The experimental results obtained in this study validate the use of the proposed EMRP method in repairing radar-absorbing structures.

Corner inspection method for L-shaped composite structures using laser ultrasonic rotational scanning technique

Composite primary structures that can sustain high loads are used to reduce the weight of structures in various industries. Composite primary structures that are L-shaped or T-shaped have a right-angled corner, and phased-array ultrasonic inspection or water squirt robotic C-scan is mainly used for the corners. However, using a customized transducer has restrictions depending on the size and shape of the corner. In this paper, we propose a novel approach based on rotational laser ultrasonic inspection for even narrow corner sections regardless of size and angle. In the rotational scanning method, the target structure is rotated for inspection, which is different from conventional scanning methods in which transducers or a scanning head are moved along the inspection area. The rotational scanning method is designed to solve the problem of signal-to-noise ratio deterioration that occurs when the ultrasonic sensing laser scans a curved surface. The corner sections of two L-shaped specimens fabricated by autoclave curing and resin transfer molding were inspected using the rotational scanning method. Using the proposed method, all of the artificial defects inserted into the corner section of the specimens were clearly visualized. Then, the inspection results were compared with water squirt C-scan inspection results. The test results showed that the proposed method is highly reliable and useful for inspecting the corner sections.

Evaluation of damage evolution of impacted composite laminates under fatigue loadings by infrared thermography and ultrasonic methods

It is widely known that damage induced by low-velocity impact events will significantly affect the damage tolerance and integrity of composite structures. This study investigates the damage evolution and failure mechanism of impacted laminates under fatigue loadings using the infrared thermography and ultrasonic methods. Low-velocity impact damage was introduced by a drop weight with a hemispherical impactor, and compression-after-impact (CAI) tests were conducted to determine the residual compressive strength. Four stress levels were selected to conduct compression-compression fatigue tests with a stress ratio R = 10 based on the static CAI strength. During fatigue tests, the surface temperature variations were monitored online by an infrared camera, and the delamination damage evolution was observed using ultrasonic C-scan methods. The thermal images, delamination contours and stiffness degradation were analyzed. The maximum temperature increase and the stiffness degradation show the characteristic with three stages “rapid-slow-rapid”. For evolution of damage area, two stages were observed. The damage area extends from the impact indentation to two outer free edges in the perpendicular direction until the final collapse of the specimen.

Experimental Investigation of Impactor Diameter Effect on Low-Velocity Impact Response of CFRP Laminates in a Drop-Weight Impact Event.

The present study delved into the effect of impactor diameter on low velocity impact response and damage characteristics of CFRP. Moreover, the phased array ultrasonic technique (PAUT) was adopted to identify the impact damages based on double-sided scanning. Low-velocity impact tests were carried out using three hemispherical impactors with different diameters. The relationship of impact response and impactor diameters was analyzed by ultrasonic C-scans and S-scans, combined with impact response parameters. Subsequently, the damage characteristics were assessed in terms of dent depth, delamination area and extension shape via the thickness, and the relationships between absorbed energy, impactor displacement, dent depth and delamination area were elucidated. As revealed from experiment results, double-sided PAUT is capable of representing the internal damage characteristics more accurately. Moreover, the impactor diameter slightly affects the impact response under small impact energy, whereas it significantly affects the impact response under large impact energy.

Experimental investigations of electromagnetic punching process in CFRP laminate

ABSTRACT Electromagnetic punching is an efficient hole-machining process in order to satisfy structural or functional requirements. In this paper, the electromagnetic punching experiments were carried out to investigate hole-punching quality of carbon fiber reinforced plastic laminates with various punches. The quality evaluation such as macroscopic measurement, microstructure observation and delamination analysis was implemented. As a comparison, drilling experiments and corresponding quality tests were also accomplished. The results showed that the cutting tools had significant effects on the quality of the formed holes. For electromagnetic punched holes, the edged punch was superior to flat punch and hollow punch in term of the machining accuracy, microscopic morphology and delamination defect. Comparing with drilling process, the delamination factors of edged punched holes were lower than that of drilled holes on the basic of ultrasonic C-scan technology, implying that delamination of drilled hole was severer than edged punched holes.

Impact damage assessment in carbon fiber reinforced composite using vibration-based new damage index and ultrasonic C-scanning method

This paper presents a combination of the Vibration-based method and Non-destructive Ultrasonic C-scan method to identify, locate, and quantify the damage in impacted carbon composite fiber reinforced structure. The main objective of work consists of developing a new method to assessment of damage in carbon composite by using a different method to be applied to structural health monitoring. Experiments were carried out on laboratory specimens, which consists of carbon/epoxy laminates having three different stacking sequences ([0/0]s, [0/90]s, and [45/0–45/90]s) subjected to three different impact energies (7 J, 14 J, and 24 J) using conical shape impactor. Frequency Response Function (FRF) for intact and damaged specimens was obtained by using hammer and accelerometer sensors. FRFs are analysed using suitable metrics, including a new one, which is compared in terms of their capability for damage identification. Afterword, the ultrasonic C-scanning method is used to locate and quantify the damage in the specimen. The ultrasonic C-scanning works on the principle of ultrasonic reflection at the interface of impedance mismatch. In this method defects are based on the amplitude of ultrasonic high-speed waves; a qualitative approach is used to identifying the defects while measuring the amplitude of the signals. This technique has demonstrated great potential for damage localization and extension in carbon composites. Finally, the new method is proposed to identify and localization of damage in the impacted specimen using the Vibration-based method and Ultrasonic C-scanning methods.

Experimental assessment of Fully-Uncoupled Multi-Directional specimens for mode I delamination tests

This paper proposes an experimental study whose goal is to validate the concept of Fully-Uncoupled Multi-Directional (FUMD) specimens for delamination tests. In order to reduce the likelihood of delamination jump, a glass/epoxy UD-fabric composite was used to fabricate double cantilever beam specimens. Mode I tests were performed with standard UD specimens and with FUMD specimens having the following delamination interfaces: 0 °//0 °, 0°// 15°, 0 °//30 °, 0 °//45 ° and −45 °//45 °. Delamination fronts after the tests were observed by means of ultrasonic C-scans. By comparison with the UD specimens, it is shown that FUMD sequences are able to promote a fairly symmetric and flat delamination front. Analysis of the rotations of such specimens during the test confirms that they do exhibit an uncoupled mechanical behaviour. Critical energy release rate is found to be dependent on interface plies mismatch angle, but not on global stiffness of the specimens.

High Precision Detection Method for Delamination Defects in Carbon Fiber Composite Laminates Based on Ultrasonic Technique and Signal Correlation Algorithm.

This paper presents a method based on signal correlation to detect delamination defects of widely used carbon fiber reinforced plastic with high precision and a convenient process. The objective of it consists in distinguishing defect and non-defect signals and presenting the depth and size of defects by image. A necessary reference signal is generated from the non-defect area by using autocorrelation theory firstly. Through the correlation calculation results, the defect signal and non-defect signal are distinguished by using Euclidean distance. In order to get more accurate time-of-flight, cubic spline interpolation is introduced. In practical automatic ultrasonic A-scan signal processing, signal correlation provide a new way to avoid problems such as signal peak tracking and complex gate setting. Finally, the detection results of a carbon fiber laminate with artificial delamination through ultrasonic phased array C-scan acquired from Olympus OmniScan MX2 and this proposed algorithm are compared, which showing that this proposed algorithm performs well in defect shape presentation and location calculation. The experiment shows that the defect size error is less than 4%, the depth error less than 3%. Compared with ultrasonic C-scan method, this proposed method needs less inspector’s prior-knowledge, which can lead to advantages in automatic ultrasonic testing.

Effects of Impactor Geometry on the Low-Velocity Impact Behaviour of Fibre-Reinforced Composites: An Experimental and Theoretical Investigation

Carbon-fibre/epoxy-matrix composites used in aerospace and vehicle applications are often susceptible to critical loading conditions and one example is impact loading. The present paper describes a detailed experimental and numerical investigation on the relatively low-velocity (i.e. <10 m/s) impact behaviour of such composite laminates. In particular, the effects of the geometry of the impactor have been studied and two types of impactor were investigated: (a) a steel impactor with a hemispherical head and (b) a flat-ended steel impactor. They were employed to strike the composite specimens with an impact energy level of 15 J. After the impact experiments, all the composite laminates were inspected using ultrasonic C-scan tests to assess the damage that was induced by the two different types of impactor. A three-dimensional finite-element (FE) model, incorporating a newly developed elastic-plastic damage model which was implemented as a VUMAT subroutine, was employed to simulate the impact event and to investigate the effects of the geometry of the impactor. The numerical predictions, including those for the loading response and the damage maps, gave good agreement with the experimental results.