Papers by Keyword: Non-Destructive Evaluation

Abstract: This research integrates experimental testing and Machine Learning (ML) techniques to predict the weld quality of Tungsten Inert Gas (TIG) and Shielded Metal Arc Welding (SMAW). A balanced dataset comprising weld parameters and mechanical test results including tensile strength, impact energy, and bend test outcomes was compiled for mild steel and stainless steel specimens with thickness ranging from 6mm to 10mm. Experimental results revealed that TIG welding produced superior tensile strength (up to 572 MPa) and impact energy (up to 58J) compared to SMAW. A Random Forest classifier achieved 100% accuracy in classifying weld quality as Good or Defect, while linear Regression produced tensile strength with an R2 of 0.68, Mean Absolute Error (MAE) of 17.5 MPa, and Root Mean Squared Error (RMSE) of 20.27 MPa. These results confirm the viability of ML techniques as non-destructive tools for weld quality prediction and mechanical property estimation. The framework developed in this research contributes to intelligent welding process control and supports the transition toward efficient, data driven manufacturing.

Abstract: The study investigates LVI testing on woven carbon fiber-reinforced composite laminates at three different energy levels and assesses the specimens for their compressive strengths. X-ray CT scans are used to study the damaged envelopes, which allows better insights into the damage progression and failure mechanisms of the composite. The study investigates how post-impact damage propagation is influenced by alterations in impact energy and stacking orientation. The findings demonstrated that several variables, such as the characteristics of the constituent materials, the stacking order, laminate thickness, and ply orientations, had an impact on the CAI strength of the composite laminate. These findings highlight the importance of considering multiple factors when designing composite materials that can withstand impact loading and maintain their structural integrity. Even in specimens showing barely perceptible surface damage, a considerable drop in compressive strength is seen after the LVI testing. When specimens are struck with 25 J of energy, the compressive strength reduction reached a maximum value of 15.68%. In CAI testing, it is typical for sub-laminates to buckle near the impact-induced damage zone, resulting in failure. The magnitude of impact damage area can significantly affect the CAI strength, as the damaged area may create a stress concentration that can lead to buckling or other types of failure. Therefore, it is important to consider the impact energy and damage size when evaluating the CAI strength of composite materials.

Abstract: Tetra-Boron Carbide (B4C) are an excellent material for industrial applications in the nuclear, aerospace, and military. It is an excellent neutron absorber for use as a radiation shield. Using B4C as thermal barrier coating reduces the metal surface temperature, shields the substrate metal alloy from excessive heat, and increases system efficiency. In this degraded has been evaluated using non- destructive techniques that are appropriate for the predicament. To track the thermal barrier coating’s integrity over time, a microwave non-destructive technique was used to predict the porosity of the topcoat. Network analyzer (ENA5701C) in X-band (12–18 GHz) was utilized for this investigation. Detection was based on the changes in the electromagnetic properties, such as permittivity . A set of samples contained varied filler ranging of 5, 10, 15, 20 percent particle reinforcement. Most tested samples shows that porosities have maximum permittivity in the range of 15.4 – 16.7 GHz where some resonance occurred when real primitivity represent the capability of B4C to store and dissipate energy. This study suggesting that the proposed methodology could be a valuable aid technique for evaluating degraded on composite material systems in a non-destructive and accurate manner with complex pore morphology

Abstract: Non-destructive evaluation of structures is a key procedure in operation of aircraft structures, necessary to maintain their quality and integrity. Numerous non-destructive testing (NDT) techniques have been adapted to inspect aircraft structures and are currently used according to appropriate protocols. However, many of them provide only qualitative results, such as the D-Sight optical NDT technique used for inspections in aviation. In this study, a concept of improvement of the D-Sight technique is proposed by means of appropriate experimental program and processing procedures applied to the resulting images from inspection. It was demonstrated that appropriately selected processing methods may allow assessing damage quantitatively and improve the overall sensitivity and applicability of a given NDT technique.

Abstract: As a non-destructive evaluation method for friction stir welded joints, this research aims to develop and corroborate a method for material flow analysis and defect detection based on X-ray computed tomography (X-ray CT). Using a cylindrical FSW tool with a broad shoulder, joints of dissimilar materials AA6061-T6/AZ31b are friction welded employing tool rotary speed ranging from 1000 to 1500 RPM and tool feed from 125 to 400 mm/min. The welded joints are scanned via X-Ray CT with an image bit depth of 16-bit then segmented based on the Hounsfield Units scale (HU) and the global Otsu thresholding method. This segmentation divides the DICOM images into masks for each different material, from which 3D renderings are generated to record volumetric data. For analyzing elemental mixing, measurements of material penetration and transfer are carried out. Corroborating these results was accomplished using destructive cross-sectioning and Energy Dispersive X-ray Spectroscopy (EDX). The results show that this method can detect internal defects and characterize the material mixing with results comparable to that of destructive EDX analysis. The effect of improving scan resolution on reconstructed images was shown to slightly improve the accuracy of the thresholding method while reducing the standard deviation of segmented material ranges.

Abstract: Having a robust non-destructive evaluation (NDE) technique for friction stir welded (FSWed) joints is of interest to the processing community. Such a technique has to be sensitive to the different types and shapes of internal weld defects and has to be applicable for both similar and dissimilar material FSW joints. Investigated was the ability of ultrasonic guided waves to detect and assess the quality of FSW joints. The fundamental anti-symmetric (A₀) mode was selected to detect the flaws in FSW joints. Guided waves were excited (using PZT wafers) and received (using a laser Doppler vibrometer, LDV). Implemented was the frequency-wavenumber filtering technique to separate forward propagating wave from any back propagating reflected wave due to the welded joint. Identified was the reflection of the A₀ mode caused by the presence of the interface and/or defects within the joint. The findings indicate little sensitivity to the presence of material interface suggesting this technique to have a promising potential among guided-wave-based techniques in the qualitative and quantitative assessment of FSW joints.

Abstract: Maximum Length Sequence has great potential as testing signal in non-destructive testing. Because its autocorrelation is almost a delta function, the sequence can be used for speed of sound assessment. Resulting Impulse response contains very similar data as Impact-echo. Unlike Impact-echo, where strike energy is limited by nonlinear effects, Maximum Length Sequence can deliver virtually unlimited energy over time. Length of the sequence and also signal generation rate is a curtail choice in order to achieve the best results.

Abstract: Ultrasonic non-destructive testing methods such as Impact-echo are often conducted under different conditions. Such results might be distorted by ambient temperature or by water content of the tested sample. Tested mortar sample displayed shift of the fundamental frequency by 3.7 %. This article confirms necessity of standardized conditions during ultrasonic testing for both laboratory and in-situ testing.

Abstract: In this paper, the experimental modal identification analysis of the public building “San Giacomo” in Corfu (Greece) is illustrated. It represents the unique example of a structure built utilising carves stones inside the city of Corfu. The building has a rectangular plan shape with dimensions 24.75 x 14 m, and height 9 m; all the floors are made by wood. The monitoring system consists of several elements properly connected: the units of acquisitions or piezoelectric accelerometers (in total 18 installed on the different walls) with a sensitivity of 1000 mV/g; the data acquisition system or DAQs positioned at each monitored level; the laptop with an acquisition software; the cables that connect all elements to each other. The paper describes the phases of the investigations, the technical details of the performed in-situ tests, the first identified frequencies of the building by means of the classical methods of Operational Modal Analysis (OMA) and the comments about the acquired data.

Abstract: This study discusses the applicability of eddy current testing to the non-destructive evaluation of the depth of a flaw. Three-dimensional finite element simulations are carried out to calculate eddy current signals due to a flaw, and subsequent calculations correlate the difference between signals due to two flaws with the difference between the depths of the flaws. Standard deviation of the difference between the depths of the flaws is used to discuss the ill-posedness of the problem. A flaw is modeled as a sufficiently long rectangular region with a constant width and uniform electrical conductivity; an absolute pancake probe is considered. This study reveals that lift-off and coil diameter do not have a large effect on the ill-posedness, which supports that it is reasonable to decide parameters in actual inspections so that signal-to-noise ratio is maximized. The results obtained also indicate the difficulty in evaluating the depth of a flaw deeper than 1 mm using the signals obtained using an absolute pancake probe.