Results Of Non-destructive Tests Research Articles

Automated image-based geometric modelling of thick laminates with three-dimensional ply wrinkles

Ply wrinkles are commonly induced during thermal–mechanical manufacturing process of laminated composite structures or components. Fibre misalignment due to ply wrinkles compromises the structural integrity of a composite structure. The damage criticality can be assessed numerically based on non-destructive testing results. Geometric modelling is usually required and it is time-consuming if complex wrinkles have to be incorporated into the finite element model. This study presents an automated image-based three-dimensional geometric reconstruction method for thick laminates with complex ply wrinkles. The geometry of a thick laminate is reconstructed based on the limited inspection images from the sides of laminates. The two-dimensional geometric reconstruction of the detected wrinkled plies is done using a multiple Gaussian functions model or linear interpolation, while the intermediate plies are defined by distance-based interpolation. Based on the reconstructed two-dimensional geometries, the three-dimensional ply wrinkles are modelled via an inverse distance weighting interpolation method. To verify the proposed method, a thick glass fibre laminate with artificially induced wrinkles is manufactured and the cross-sectional geometries of the reconstructed model are compared well with and the realistic inspection data. Progressive failure analysis of a two-dimensional and a three-dimensional reconstructed model are compared in terms of damage progression and load versus nominal strain response to highlight the relevance of modelling three-dimensional wrinkles to obtain more accurate and efficient damage criticality assessments.

Investigation of the Mechanical and Microstructural Properties of Masonry Mortar Made with Seashell Particles.

In order to study the mechanical and microstructural properties of masonry mortar, combined particles of cockle and scallop seashell wastes were incorporated and analysed through destructive and non-destructive tests. River sand was replaced with the combined seashell particles (SPs) at seven mixes, viz., 0, 5, 10, 15, 20, 25, and 30% with a 0.5 constant water-to-cement ratio (W/C). A mortar mix design of M4-type of BS EN 1996-1-1 was adopted with a target compressive strength of 5.17 MPa at 28 days. The physical, chemical and mineralogy properties of the SPs were analysed through BS standard sieving, X-ray fluorescence (XRF), scanning electron microscopy (SEM), and X-ray diffraction (XRD) methods. The hardened SP-based mortars were subjected to direct compressive strength, rebound hammer, ultrasonic pulse velocity tests, and nonevaporable degree of hydration analysis. The XRF, SEM, and XRD analysis results of the SPs showed over 86% calcium oxide content, irregular and needle-like particles, and hydroxyapatite/calcium silicates, respectively. The direct compressive strength and the non-destructive test results revealed that up to 30% sand replacement with SP in masonry mortar, an improvement of 45% compressive strength could be attained over the control sample. The nonevaporable water method of the degree of hydration analysis showed that after 28 days, hydration increased considerably for the SP-blended mortars over the control, especially the SPM-30 with 30% sand replacement. Therefore, the study concludes that the investigated SPs in blended masonry mortar could benefit an eco-friendly environment and conservation of natural resources.

PV Defects Identification through a Synergistic Set of Non-Destructive Testing (NDT) Techniques

A synergistic set of NDT techniques, including I-V analysis, UVF imaging, IR thermography, and EL imaging, supports a diagnostics methodology developed in this work to qualitatively and quantitatively identify a wide range of PV defects. The methodology is based on (a) the deviation of the module electrical parameters at STC from their nominal values, for which a set of mathematical expressions was developed that provide an insight into potential defects and their quantitative impact on the module electrical parameters, and (b) the variation analysis of EL images captured at a sequence of bias voltages for a qualitative investigation on the spatial distribution and strength of the defects. The synergy of these two pillars, supported by UVF imaging, IR thermography, and I-V analysis cross-correlating their findings, makes the diagnostics methodology effective and reliable. It was applied on c-Si and pc-Si modules operating from 0-24 years, exhibiting a diversity of defects of varying severity, either pre-existing or formed by natural ageing or externally induced degradation. Defects such as EVA degradation, browning, corrosion in the busbar/interconnect ribbons, EVA/cell-interface delamination, pn-junction damage, e-+hole recombination regions, breaks, microcracks, finger interruptions, and passivation issues are detected. Degradation factors triggering a cascade of internal degradation processes through cause and effect are analysed and additional models are proposed for the temperature pattern under current mismatch and corrosion along the busbar, further empowering the cross-correlation of NDT results. Power degradation was determined from 1.2% in 2 years of operation to more than 50% in modules with film deposition.

Engineering Properties of Green and Ecofriendly Grouting Materials with Different Sand Filling Ratios.

With the active development of offshore wind power worldwide, the development of a green and ecofriendly grouting material (GEGM) has garnered global attention. Such a material must also be developed in Taiwan. Therefore, in this study, a series of environmentally friendly recycled materials were mixed in different proportions to develop a GEGM which can be implemented in the future construction of offshore wind turbines. To evaluate the mechanical properties of the GEGM, low water-to-binder (W/B) ratios (i.e., 0.21, 0.27, and 0.35) were used; cement was replaced with fixed amounts (20%) of ground granulated blast-furnace slag and fly ash; 2%, 2.5%, and 3% superplasticizers (SPs) were added; and two levels of sand content (60% and 70%) were used. The setting time of the GEGM was used to evaluate its workability; its compressive strength and flexural strength were used to evaluate its mechanical properties; and its sulfate resistance, length changes, and four-terminal resistance were used to evaluate its durability. The relationship between the durability and drying shrinkage of the GEGM was subsequently evaluated, and the ratio of final to initial setting times (F/I value) was calculated to determine the effects of the amount of SP added on workability. The highest F/I value (7.7) was achieved when 2 wt.% modified lignin sulfonate (MLS) was added because of the high viscosity of MLS, which compromised the workability of the concrete. The optimal compressive strength (83.62 MPa) was achieved when a W/B ratio of 0.21 was used, when the sand content was 70%, and when a 2% polycarboxylate superplasticizer (PCE) was added, whereas the optimal flexural strength (20.86 MPa) was achieved when 2.5% PCE was added. According to the nondestructive test results and the R2 value (>0.7) obtained from regression analyses of mechanical properties, the study results are reliable and may serve as a reference for future construction projects.

Nano-modified epoxy coatings: An effective method for sustainable construction

Corrosion in reinforced concrete (RC) structures is an increasingly prevalent issue in the construction industry. Thus, reducing corrosion and strengthening concrete structure would help sustain the environment. This study is centred around the development of epoxy coatings modified with nano-clay and graphene derivatives including multi-walled CNT (Graphene Oxide (GO), and reduced Graphene Oxide (rGO)). Prepared coatings matrix applied on mild steel bar and embedded in concrete specimen for testing for accelerated corrosion. The study evaluated the effectiveness of epoxy coatings modified with nanoparticles using various non-destructive methods, including visual inspection, impressed current corrosion testing, and ultrasonic-guided wave measurements. The non-destructive testing results were further supported by the findings from destructive testing. Ultrasonic studies showed that nano-clay coating is 1.5 times better than PE, however GO/CNT showed no corrosion onset after 60 days of corrosion testing. PE coatings lost 2–3% more mass than nano-clay coatings, while GO/CNT coatings lost 98% less mass as represents in destructive testing. Nano-clay coatings minimize tensile strength loss by 9% than PE coatings, whereas GO/CNT coatings lower it by 98–99%. Overall, graphene-based coatings are more effective in corrosion inhibition than nano-clay coatings. Suggested modification increase infrastructure life by several factors and reduces maintenance, promoting sustainable construction.

Simplified methods for the evaluation of mechanical properties of tuff masonry walls in Campania (Italy)

Conservation of heritage buildings still poses many challenges. Throughout the history, monuments have been exposed to catastrophic earthquakes. Assessment and retrofitting of this architectural heritage are effective measures to prevent heavy damage by future earthquakes. These operations require good knowledge of the material mechanical properties, it being one of the most important steps for a suitable seismic assessment. Mechanical characteristics may be determined through destructive, semi-destructive and non-destructive tests. As the application of destructive and semi-destructive testing on heritage buildings is often impossible, many attempts have been made to propose fully non-destructive methods for determining mechanical properties. One of the methods is called the Masonry Quality Index (MQI), only based on visual inspection. This method aims to develop a simple and systematic approach to the analysis of masonry constructions based on idealised typologies, different parameters and the mechanical properties of the constitutive materials (stone, brick, mortar, etc.). The aim of the present research is to propose a simplified approach to obtain mechanical properties of the historical masonry walls with lime mortar in Campania, by correlating the MQI, double flat jack and further non-destructive test results.

Need for structural health assessment of R.C.C. buildings

As civil engineering structures get older, there is a need to maintain, repair, retrofit and restore the structures once structural health of the structure is checked and found that it is deteriorating. The structural health is checked by performing various Non-Destructive Tests (NDT) or partially destructive tests on different structural members of the given structure and by calculating the service life and residual life of the structure. Sufficient service life remaining and good NDT results and conclusions allow for repair and retrofitting, of the deteriorating structure. The various Non Destructive Tests conducted are Rebound Hammer, Ultrasonic Pulse Velocity, Half Cell Potentiometer Test, Carbonation Test, Core Test, Cover Meter survey, Windsor Probe Test, Chloride Test, Sulphate Test, and Resistivity Measurements, Pull out tests, Radioactive Method of NDT. In the present study, two case studies of structural health monitoring and assessment of residual life of RCC buildings in Goa are undertaken and the need for retrofitting scheme is assessed. From the test results and analysis, it is observed that one structure can be retrofitted while the other structure cannot be retrofitted. Some of the retrofitting methods that will be used for the structure are Shotcrete, Fiber Wrap Technique, RCC Jacketing, and Plate Bonding.

Properties of cross-laminated oriented bamboo scrimber board (CL-OBSB)

Physical and mechanical properties were evaluated for cross-laminated oriented bamboo scrimber board (CL-OBSB). Results of non-destructive testing revealed a linear relationship of parallel grain content with ultrasonic-wave velocity, dynamic modulus of elasticity (DMOEu), tap-tone velocity, and DMOEt values. In terms of the ratio of parallel grain, CL-OBSB 80%(//) possessed the highest modulus of elasticity and modulus of rupture values along with the greatest strength. The high grain content compressed in a parallel direction contributed to superior strength performance. Regarding the perpendicular compressive (C┴) strength, because both the CL-OBSB 40%(//) configuration and CL-OBSB have a mid-layer consisting of 60% parallel grain, CL-OBSB 40%(//) holds the largest C┴ value. Furthermore, the shear bond strength (S) showed that the S// value was 1.03 times that of the S┴ value with a wood failure frequency of 97%. After the dimensional stability test, the water absorption and volumetric swelling of the four CL-OBSB types ranged between 15.3% and 17.7% and 9.5% to 10.6%, respectively. In conclusion, the orthogonal configuration of CL-OBSBs can improve balance expansion and contraction in different directions, thus increasing its dimensional stability.

Non-Destructive Testing of Magnetically Impelled Arc Butt Welding of Mild Steel Tubes

This paper presents the results of Non-Destructive Testing on Magnetically Impelled Arc Butt (MIAB) welded mild steel tubes of 27mm OD and 1.5mm thickness. As part of this work, the tests covered were radiography, liquid penetrant, and magnetic particle testing. The testing results indicate that porosity, penetration levels and the defects found are within acceptable limits as per standard. For this experimental work, the selection of parameters was based on trial and error adopted in preliminary trials. The irregularities found in the non-destructive testing samples have enabled the fine-tuning of process parameters. The optimum values of hydraulic pressure, weld time and weld current are assessed to be 30-35bar, 5.5s and 150 A, respectively 270 A for this dimension of tubes. This work focuses on the experimental observations of MIAB welding and Non-destructive testing results for MS tubes of the selected dimension, which have not been reported in the existing literature. The achieved input forms the database for the parametric study of this process. The optimum parametric ranges obtained from the results can be extrapolated to be used for joining tubes of different dimensions and can also form the inputs for reaching parameter and response dependency equations.

Prediction of Geopolymer Concrete Compressive Strength Utilizing Artificial Neural Network and Nondestructive Testing

Abstract A promising substitute for regular concrete is geopolymer concrete. Engineering mechanical parameters of geopolymer concrete, including compressive strength, are frequently measured in the laboratory or in-situ via experimental destructive tests, which calls for a significant quantity of raw materials, a longer time to prepare the samples, and expensive machinery. Thus, to evaluate compressive strength, non-destructive testing is preferred. Therefore, the objective of this research is to develop an artificial neural network model based on the results of destructive and non-destructive tests to assess the compressive strength of geopolymer concrete without needing further destructive tests. According to the artificial neural network analysis developed in this study, the compressive strength of geopolymer concrete can be predicted rather accurately by combining the results of the non-destructive with R 2 of 0.9286.

Tri-level Framework for Realistic Estimation of Concrete Strength Using Bayesian Data Fusion of UPV and Guided Coring

Identification of in situ concrete characteristic strength (CCS) of deteriorating RC structures directly affects their rehabilitation. Contemporary practices lack the ability to yield CCS or at most produce an unrealistic estimate, because: (i) core tests are few due to technical and economic constraints and their positioning is random, inducing bias in the strength estimate, (ii) non-destructive tests (NDT) are themselves not good estimators of project specific strength, (iii) tests are only local indicators and most practising engineers are unaware of how to process the spatial variability. This paper overcomes these limitations with a novel and implementable framework, for an asset manager to make scientific estimates of CCS. This is a tri-level framework: (1) NDT are performed to capture the spatial variability of the investigated concrete; (2) core extractions are guided by the prior NDT information, to avoid bias in test location selection; (3) NDT and coring results are fused via Bayesian NDT test calibration and updating of the probability distribution of the concrete strength. The proposed framework is successfully implemented for the assessment and rehabilitation of a critical hospital complex in India.

A study on non-destructive testing of geometrical parameters of self-piercing riveting joints using an acoustic microscope with a scanning focusing converter

ABSTRACT A non-destructive technique was proposed for geometrical parameters’ measurement of self-piercing riveting (SPR) joints based on ultrasonic C-scan image. Firstly, in order to enhance the detection precision, the characteristics of the ultrasonic echo signal at the edge of internal structure were analysed, and a theoretical formula on its sound intensity distribution was established. Then, an image segmentation process for the detection of SPR expansion diameter was suggested. Results showed that taking the greyscale value at the ‘inflection point’ from the C-scan image as the threshold of the segmentation, the non-destructive test results can get good correlation with the metallographic cross section, which provides a new method on the quality evaluation of SPR by using non-destructive test.

Non-Destructive Detection of Real Defects in Polymer Composites by Ultrasonic Testing and Recurrence Analysis.

This paper presents results of ultrasonic non-destructive testing of carbon fibre-reinforced plastics (CFRPs) and glass-fibre reinforced plastics (GFRPs). First, ultrasonic C-scan analysis was used to detect real defects inside the composite materials. Next, the composite materials were subjected to drilling in the area of defect formation, and measured forces were used to analyse the drilling process using recurrence methods. Results have confirmed that recurrence methods can be used to detect defects formed inside a composite material during machining.

Reasons for formation of transverse cracks in longitudinal weld of a pipe of the main gas pipeline

Investigations of transverse cracks in a longitudinal weld of a main gas pipeline pipe are presented, and the reasons for the formation of defects are analyzed. A comparative analysis of the results of in-line diagnostics and additional non-destructive testing with the actual parameters of cracks in microsections was carried out. The microhardness of the weld metal was measured in the crack zone and at a distance of up to 20 mm from it in both directions, which showed the presence of residual stresses in the region of the crack tip. The methods of optical and electron scanning microscopy were used to study the crack zone with the determination of the chemical composition of the weld base metal and inclusions in the crack zone. The results obtained made it possible to classify defects as “cold cracks” that formed in the weld metal after a long period of operation and developed further according to the stress corrosion cracking mechanism.

Damage Occurrence in Welded Structures of the Bucket-Wheel Boom

Causes of damage occurrence in vital components of welded structures of the bucket-wheel excavator boom (DU1) at the coal landfill of the thermal power plant 'Nikola Tesla A' in Obrenovac (Serbia) are investigated. Bucket-wheel excavator was produced by French company 'Ameco' and it moves along the circular track. Taking into account lack of technical documentation, all tests and were carried out under the assumption that welded structures were made of structural steels S355 and S235. Investigation of causes of damage occurrence are based on results of non-destructive tests (NDT) and tensometric measurements.

Application of bird-strike verified analysis for the design of fast helicopter composite cowling

PurposeThe purpose of this paper is to describe the approach for the design of cowlings for a new fast helicopter from the perspective of airworthiness requirements regarding high-speed impact resistance.Design/methodology/approachValidated numerical simulation was applied to flat and simple curved test panels. High-speed camera measurement and non-destructive testing (NDT) results were used for verification of the numerical models. The final design was optimized and verified by validated numerical simulation.FindingsThe comparison between numerical simulation based on static material properties with experimental results of high-speed load shows no significant influence of strain rate effect in composite material.Research limitations/implicationsOwing to the sensitivity of the composite material on technology production, the results are limited by the material used and the production technology.Practical implicationsThe application of flat and simple curved test panels for the verification and calibration of numerical models allows the optimized final design of the cowling and reduces the risk of structural non-compliance during verification tests.Originality/valueNumerical models were verified for simulation of the real composite structure based on high-speed camera results and NDT inspection after impact. The proposed numerical model was simplified for application in a complex design and reduced calculation time.

Studying the Impact of Imposed Actual Loads on the Non-Destructive Test Results for Evaluating the Compressive Strength and Other Properties of Concrete

Among all the concrete characteristics, the compressive strength is known as the most important feature and therefore, it is often utilized to quantify the quality of concretes. The assessment of concretes strength in existing constructions is important during their service life. Thus, in addition to destructive evaluation of strength, many non-destructive techniques have been adopted to assess the concretes strength. Ultrasonic Pulse Velocity (UPV) is one of the non-destructive techniques that involve measuring the speed of ultrasonic wave through concretes to predict concretes strength. According to the Griffith’s theory, the strength of the material is greatly affected by the defects’ existence (for example, small cracks). These cracks can be current prior to the application of any loading or could create throughout the load application. The presence of micro-cracks in concretes that generate due to the applied load may affect the UPV test results in comparison with unloaded concretes. An experimental investigation is conducted in order to assess the impact of the applied of load (ultimate load) on the measured ultrasonic wave velocity and compared with the results of compressive strength from destructive test. A total of thirty (150 mm × 150mm) cube specimens have been utilized with water to cement ratios (0.45). These cubes have been examined in ultrasound without any loads and then they have been tested in the same way with applied ultimate load which is approximately equal to half of the required design load (failure load) and then inspected or tested in the normal way (destructive test). In order to assess the compressive strength of concretes using UPV, loading condition is considered in order to study the impact of the applying load. In addition, the water absorption has been examined for thirty concretes samples under the impact of the applied loads (20%, 40% and 60%). The results of non-destructive tests of concretes samples under the influence of imposed loads (60%) have showed to be less by compressive strength 5 MPa than the results obtained from testing of unloaded concretes samples through the resulting equation and comparing them to the equation from previous research. This is consistent with the water absorption test of the specimens under the imposed loads (60%) where Absorption values have been greater than concretes models without applied loads.

Terahertz Multiple Echoes Correction and Non-Destructive Testing Based on Improved Wavelet Multi-Scale Analysis

During terahertz (THz) non-destructive testing (NDT), multiple echoes from the sample interface reflection signals are mixed with the detection signals, resulting in signal distortion and affecting the accuracy of the THz NDT results. Combined with the frequency property of multiple echoes, an improved wavelet multi-scale analysis is put forth in this paper to correct multiple echoes, allowing the maximum retention of detailed signal information in contrast with the existing echo correction methods. The results showed that the improved wavelet multi-scale analysis enhanced the continuity and smoothness of the image at least twice in testing adhesive layer thickness, prevented missing judgments and misjudgments in identifying characteristic defects, and ensured accurate detection results. Hence, it is of great significance for evaluating the THz NDT results.

Prediction and analysis of properties of ramie fiber staple yarn reinforced unsaturated polyester composite based on fiber packing density

The limitation of plant fiber length can be overcome by using staple spinning to achieve continuity on short fibers. Ramie fiber staple yarn reinforced unsaturated polyester composites (RSYCs) were fabricated with ramie fiber and unsaturated polyester matrix. The unique fiber packing density of staple yarn must be tackled first to reflect the structure of RSYCs. The relationship between fiber packing density of staple yarn and fiber volume fraction of composite was evaluated to investigate the effect of fiber packing density on properties and predict the tensile strength of RSYCs using the rule of mixture. A scanning electron microscope illustrated fiber packing density of staple yarn. When the twist factor was 380 with the optimal yarn count of 80 tex, the fiber packing density was 19.9% higher than that at 260. Compared with the minimum tensile strength of RSYCs at 120 tex, the maximum of RSYCs at 380 was 399.2 MPa, improved by 238.6%. Measured by dynamic mechanical analysis, the viscoelastic rigidity and damping property of RSYCs was the best at 380, with the storage modulus of 31.9 GPa at 40 °C and the tan delta of 0.1226 at 80.59 °C. Compared with the neat resin and ramie fiber, the onset temperature of weight loss of RSYCs tested by thermogravimetric was reduced. The increasing fiber packing density significantly reduced the resin permeability of RSYCs, according to the contact angle and ultrasonic nondestructive testing results. There is no doubt that the obtained fiber packing density possessed great potential for promoting the development of RSYCs.

Fabrication and performance examination on explosively welded ODS-Cu / 316 L clad plate for CFETR divertor heat sink

Copper alloys are among the most promising candidate materials for divertor heat sinks owing to their remarkable advantages. However, it is challenging to use CuCrZr alloys as heat sink materials because of the harsh loading environment expected for plasma-facing components (PFCs) in future fusion reactors. Explosive welding is an effective method for manufacturing high-quality oxide dispersion strengthened copper (ODS-Cu) / 316 L stainless steel (SS) clad plates. Non-destructive testing results revealed a soundness bonding interface between ODS-Cu and 316 L without any detectable defects or cracks. In this study, optical microscopy and scanning electron microscope analysis revealed that the bonding interface did not contain any cavities and a typical wave-bonding morphology was observed. Moreover, the tensile stress of the bonding interface was higher than that of the ODS-Cu parent metal, and there was an increment in hardness on both sides near the bonding interface. The helium leak testing results indicate that the welded ODS-Cu / 316 L exhibits soundness without deformation or leakage at cyclic room and high temperatures. The results prove that the explosive welding method is a practical method for manufacturing high-quality ODS-Cu / 316 L clad plate that meet the design requirements and can provide critical references for the engineering design of the China Fusion Engineering Test Reactor (CFETR) divertor heat sink.