Conventional Testing Techniques Research Articles

Detecting Multi-Scale Defects in Material Extrusion Additive Manufacturing of Fiber-Reinforced Thermoplastic Composites: A Review of Challenges and Advanced Non-Destructive Testing Techniques.

Additive manufacturing (AM) defects present significant challenges in fiber-reinforced thermoplastic composites (FRTPCs), directly impacting both their structural and non-structural performance. In structures produced through material extrusion-based AM, specifically fused filament fabrication (FFF), the layer-by-layer deposition can introduce defects such as porosity (up to 10-15% in some cases), delamination, voids, fiber misalignment, and incomplete fusion between layers. These defects compromise mechanical properties, leading to reduction of up to 30% in tensile strength and, in some cases, up to 20% in fatigue life, severely diminishing the composite's overall performance and structural integrity. Conventional non-destructive testing (NDT) techniques often struggle to detect such multi-scale defects efficiently, especially when resolution, penetration depth, or material heterogeneity pose challenges. This review critically examines manufacturing defects in FRTPCs, classifying FFF-induced defects based on morphology, location, and size. Advanced NDT techniques, such as micro-computed tomography (micro-CT), which is capable of detecting voids smaller than 10 µm, and structural health monitoring (SHM) systems integrated with self-sensing fibers, are discussed. The role of machine-learning (ML) algorithms in enhancing the sensitivity and reliability of NDT methods is also highlighted, showing that ML integration can improve defect detection by up to 25-30% compared to traditional NDT techniques. Finally, the potential of self-reporting FRTPCs, equipped with continuous fibers for real-time defect detection and in situ SHM, is investigated. By integrating ML-enhanced NDT with self-reporting FRTPCs, the accuracy and efficiency of defect detection can be significantly improved, fostering broader adoption of AM in aerospace applications by enabling the production of more reliable, defect-minimized FRTPC components.

Emerging Trends of Immunosensors Development for Detection of Food Toxins

The present study highlights the ongoing threat of foodborne illnesses to public health, primarily caused by bacterial pathogens. Despite advancements in conventional microbiological testing techniques, which are sensitive but time-consuming, challenges remain in ensuring timely detection of contaminants throughout the food supply chain. The Hazard Analysis Critical Control Point (HACCP) system is recognized as a more effective approach to ensuring food safety, emphasizing proactive identification and control of hazards at critical points in production. Emerging technologies like quantitative polymerase chain reaction (PCR) and biosensors offer faster and more accurate detection methods, although with certain limitations. Biosensors such as ELISA, SPR, and electrochemical immunosensors, in particular, show promise due to their high sensitivity and specificity, enabling rapid detection of a wide range of contaminants. This paper underscores the importance of integrating advanced technologies with established food safety protocols to enhance the safety and quality of food products, benefiting consumers, producers, and regulatory agencies alike.

Temporal-Logic-Based Testing Tool Architecture for Dual-Programming Model Systems

Today, various applications in different domains increasingly rely on high-performance computing (HPC) to accomplish computations swiftly. Integrating one or more programming models alongside the used programming language enhances system parallelism, thereby improving its performance. However, this integration can introduce runtime errors such as race conditions, deadlocks, or livelocks. Some of these errors may go undetected using conventional testing techniques, necessitating the exploration of additional methods for enhanced reliability. Formal methods, such as temporal logic, can be useful for detecting runtime errors since they have been widely used in real-time systems. Additionally, many software systems must adhere to temporal properties to ensure correct functionality. Temporal logics indeed serve as a formal frame that takes into account the temporal aspect when describing changes in elements or states over time. This paper proposes a temporal-logic-based testing tool utilizing instrumentation techniques designed for a dual-level programming model, namely, Message Passing Interface (MPI) and Open Multi-Processing (OpenMP), integrated with the C++ programming language. After a comprehensive study of temporal logic types, we found and proved that linear temporal logic is well suited as the foundation for our tool. Notably, while the tool is currently in development, our approach is poised to effectively address the highlighted examples of runtime errors by the proposed solution. This paper thoroughly explores various types and operators of temporal logic to inform the design of the testing tool based on temporal properties, aiming for a robust and reliable system.

A single‐sided 1H NMR study of the self‐drying properties of a ternary self‐levelling underlayment

AbstractSelf‐leveling underlayments (SLU) are used for smoothing and levelling sub‐floors before any flexible flooring is applied. Though being comparatively simple in its requirements, commercial SLUs have become one of the most complex cementitious mixtures in dry‐mortar technology. By using ternary binders, most SLUs are designed to be self‐drying, binding most of the mixing water in crystalline cementitious phases, allowing a fast work progress. In this study, the simultaneous hydration and drying of a commercial SLU are monitored with single‐sided 1H nuclear magnetic resonance (NMR). This technique allows the quantification of chemically bound water and water in different pore environments with superior time and depth resolution. The technique is combined with conventional testing techniques enabling a more comprehensive view on the processes at hand. Results allow quantification of hydration and self‐drying, superimposed by physical drying effects over time. Additionally, the drying of a PVC adhesive through water absorption into a well‐dried SLU are visualized with this technique. The results are discussed in the context of moisture transport processes and floor‐laying readiness of the material.

Locating cracks in isotropic plates using nonlinear guided waves

Guided waves are gaining popularity in the NDT (Nondestructive Testing) industry due to their potential for cost and time savings when inspecting structures and their high sensitivity in detecting micro-defects over large areas. Cracks caused by various issues are one of the most common causes of material failure, severely affecting the structure’s durability and serviceability. The significance of small cracks may vary across different applications. As a result, detecting and classifying damages is a challenging process limited by the current detection techniques. This makes the damage detection process challenging and sets the limit on the range of damage detection techniques that can be used. This study uses experimental and numerical approaches for detecting and locating cracks in isotropic plates using the second harmonic of the symmetric guided wave (S0) induced by cracks. This article analyzes a range of numerical models with varying orientations and dimensions. The second harmonic of the (S0) guided wave is used for detecting and locating the crack. The results show that the second harmonic of the (S0) guided wave induced by crack can detect and locate cracks in plates. The proposed technique is accurate, reliable, and does not require baseline data, providing an advantage over conventional ultrasonic testing techniques.

A bioprinted 3D gut model with crypt-villus structures to mimic the intestinal epithelial-stromal microenvironment

The intestine is a complex tissue with a characteristic three-dimensional (3D) crypt-villus architecture, which plays a key role in the intestinal function. This function is also regulated by the intestinal stroma that actively supports the intestinal epithelium, maintaining the homeostasis of the tissue. Efforts to account for the 3D complex structure of the intestinal tissue have been focused mainly in mimicking the epithelial barrier, while solutions to include the stromal compartment are scarce and unpractical to be used in routine experiments. Here we demonstrate that by employing an optimized bioink formulation and the suitable printing parameters it is possible to produce fibroblast-laden crypt-villus structures by means of digital light projection stereolithography (DLP-SLA). This process provides excellent cell viability, accurate spatial resolution, and high printing throughput, resulting in a robust biofabrication approach that yields functional gut mucosa tissues compatible with conventional testing techniques.

A Simple Method to Calculate the Void Ratio of Very Loose Silts and Silty Sands in Torsional Shear Hollow Cylinder Testing

Abstract The determination of the critical state locus (CSL) via triaxial testing has become a key input to the current state of practice to characterize the liquefaction susceptibility of tailings. However, an accurate estimate of void ratio is required to infer the CSL and allow correlation of the expected in situ state to element laboratory testing. This is an issue of particular importance for the loose moist tamped specimens generally used for CSL testing, which undergo significant volumetric collapse during saturation—a volume change that is difficult to measure using conventional test techniques. The torsional shear hollow cylinder (TSHC) device has been adopted in the past to investigate the effect of cross-anisotropy on the strength of soils, although studies on tailings in the TSHC are limited. The void ratio in previous TSHC testing programs appear to have been based on initial dimension measurements, with or without the adoption of internal instrumentation. However, as silty sands and sandy silts prepared in a loose state experience collapse during saturation, this may introduce an unquantifiable error in void ratio if the initial dimensions method is adopted and volumetric change due to saturation is not properly considered. A procedure is proposed in this paper that provides simple steps and calculations to enable the determination of void ratio in the TSHC apparatus in specimens that undergo significant volumetric collapse on saturation. This method is potentially more accurate than methods based on initial dimensions measurements to infer void ratio and does not require costly internal instrumentation.

Magnetic Measurements Applied to Energy Storage

AbstractHow to increase energy storage capability is one of the fundamental questions, it requires a deep understanding of the electronic structure, redox processes, and structural evolution of electrode materials. These thorny problems now usually involve spin–orbit, spin‐related electron configuration, etc., which cannot be probed using conventional testing techniques. Considering the intimate connection between spin and magnetic properties, using electron spin as a probe, magnetic measurements make it possible to analyze energy storage processes from the perspective of spin and magnetism. Owing to the capability of characterizing spin properties and high compatibility with the energy storage field, magnetic measurements are proven to be powerful tools for contributing to the progress of energy storage. In this review, several typical applications of magnetic measurements in alkali metal ion batteries research to emphasize the intimate connection between the magnetic properties and electronic structure, which is associated with the electrochemical performance of the electrode materials, are presented. Finally, the current challenges of magnetic measurements and the prospects for enhanced analysis of energy storage systems are discussed.

Nondestructive thermographic detection of internal defects using pixel-pattern based laser excitation and photothermal super resolution reconstruction

In this work, we present a novel approach to photothermal super resolution based thermographic resolution of internal defects using two-dimensional pixel pattern-based active photothermal laser heating in conjunction with subsequent numerical reconstruction to achieve a high-resolution reconstruction of internal defect structures. With the proposed adoption of pixelated patterns generated using laser coupled high-power DLP projector technology the complexity for achieving true two-dimensional super resolution can be dramatically reduced taking a crucial step forward towards widespread practical viability. Furthermore, based on the latest developments in high-power DLP projectors, we present their first application for structured pulsed thermographic inspection of macroscopic metal samples. In addition, a forward solution to the underlying inverse problem is proposed along with an appropriate heuristic to find the regularization parameters necessary for the numerical inversion in a laboratory setting. This allows the generation of synthetic measurement data, opening the door for the application of machine learning based methods for future improvements towards full automation of the method. Finally, the proposed method is experimentally validated and shown to outperform several established conventional thermographic testing techniques while conservatively improving the required measurement times by a factor of 8 compared to currently available photothermal super resolution techniques.

Assessment of adaptability and fruit quality in new apple cultivars for intensive orchards

Background. Competitive early-fruiting apple cultivars with high commercial and consumer qualities, resistant to unfavorable stressors, are required for successful horticulture development.Materials and methods. The study included apple cultivars developed by innovative methods using scab resistance donors (Rvi6) and diploid gamete donors. Foreign cultivars commercialized in the region were also used. Conventional variety testing techniques were applied. Fifteen cultivars released by the Institute of Fruit Crop Breeding (VNIISPK), 6 foreign cultivars, and one reference (‘Antonovka obyknovennaya’) were assessed.Results. Simulating damaging factors helped to identify good resistance of tissues and buds of domestically bred apple cultivars to early winter frosts. These cultivars survived a temperature decrease to –30°C without damage in early winter and without significant damage (no more than 2.0 pts) at –40°C in midwinter, including the scab-immune (Rvi6) cultivars ‘Ivanovskoye’ and ‘Pamyat Hitrovo’, and immune triploids (3×) ‘Aleksandr Boyko’, ‘Akademik Saveliev’ and ‘Vavilovskoye’. Bud damage in ‘Gala’ and ‘Ligol’ was stronger (2.5 pts) and increased to 3.0 pts under simulated temperatures down to –38°C and –40°C. ‘Gala’ showed the lowest resistance in midwinter. Early-fruiting cvs. ‘Blagodat’, ‘Ivanovskoye’, ‘Pamyat Hitrovo’ and ‘Rozhdestvenskoye’ were identified. On average, triploids ‘Blagodat’ and ‘Patriot’, scab-immune ‘Afrodita’, ‘Ivanovskoye’ and ‘Start’, and scab-immune triploid ‘Rozhdestvenskoye’ significantly exceeded ‘Antonovka’ and other cultivars in yield. Conclusion. The new innovative winter cultivars developed at VNIISPK matched foreign cultivars in marketability and consumer qualities, while in scab resistance and adaptability they significantly exceeded most of them. ‘Akademik Saveliev’, ‘Aleksandr Boyko’, ‘Afrodita’, ‘Vavilovskoye’, ‘Ivanovskoye’, ‘Prazdnichnoye’ and ‘Rozhdestvenskoye’ were recommended for intensive-type orchards.

Fabrication of highly durable functional textile through microencapsulation of organic citronella oil

The use of organic and eco-friendly plant-based materials has shown an increasing interest for researchers over recent years. This study describes the preparation of microcapsules from a natural citronella oil and its treatment on polyester-cotton blended (PC) fabric. The citronella oil is an essential oil obtained from the leaves and stems of various species of Cymbopogon. Microcapsules containing citronella oil as core material were produced by a complex coacervation technology and applied to fabric using the pad-dry-cure method. The morphology of the solution of microcapsules was investigated by optical microscope and the dried microcapsules were examined by scanning electron microscope (SEM). Furthermore, the microcapsules were also characterized for particle size distribution and zeta potential. SEM was also used to investigate the surface morphology of fabric surfaces after the treatment of microcapsules. A conventional test technique (cage test) was used to evaluate the medicated fabric's ability to keep mosquitoes away and comfort properties of fabric like air permeability and water absorbency were also studied. The fabric sample finished with 15% (solid in water) citronella oil microcapsules at zero wash exhibited 90% mosquito repellency, and after 30 washes the fabric possessed 80% mosquito repellency committing the durability of as prepared finished fabric. The medicated PC fabric revealed good air permeabilities and water absorbencies. Hence, this report presented an eco-friendly approach for the development of highly durable functional mosquito repellent textiles. • The successful synthesis of microcapsules using organic oils as core material. • Application of microcapsules on a polyester cotton blended fabric using the pad-dry-cure method. • Characterization of the prepared microcapsules by optical microscope, SEM, DLS, and zeta potential. • Establishing the mosquito repellent property of the prepared textile fabric in cage test. • Investigation of the durability under rigorous washing cycles.

Nondestructive Testing Technologies for Rail Inspection: A Review

Alongside the development of high-speed rail, rail flaw detection is of great importance to ensure railway safety, especially for improving the speed and load of the train. Several conventional inspection methods such as visual, acoustic, and electromagnetic inspection have been introduced in the past. However, these methods have several challenges in terms of detection speed and accuracy. Combined inspection methods have emerged as a promising approach to overcome these limitations. Nondestructive testing (NDT) techniques in conjunction with artificial intelligence approaches have tremendous potential and viability because it is highly possible to improve the detection accuracy which has been proven in various conventional nondestructive testing techniques. With the development of information technology, communication technology, and sensor technology, rail health monitoring systems have been evolving, and have become equally significant and challenging because they can achieve real-time detection and give a risk warning forecast. This paper provides an in-depth review of traditional nondestructive techniques for rail inspection as well as the development of using machine learning approaches, combined nondestructive techniques, and rail health monitoring systems.

Measurement of the anisotropic thermal conductivity of carbon-fiber/epoxy composites based on laser-induced temperature field: Experimental investigation and numerical analysis

In this paper, the authors proposed an inverse analysis using an in–house three-dimensional finite element method for the extraction of thermal conductivity tensor components of carbon-fiber/epoxy composite, based on the recorded thermographic data in the form of laser-induced temperature field. The core of the computational algorithm used for determining the thermal conductivity values (tensor components) consists of finite element solver, which operates in a hybrid mode with an analytical model. The presented method evaluates the thermal conductivity values by matching the calculated spatial and temporal temperature fields to the experimental data. Due to the specific nature of the measurement process and computational algorithm, the proposed technique is very efficient and allows for relatively rapid obtainment of the thermal conductivity values. For considered in this work composite material with 34% fiber volume fraction the experimental thermal conductivity values in transverse and parallel to the fiber directions were equal to 0.32 W/mK and 6.80 W/mK, respectively. Additionally, in order to verify the reliability of the presented methodology, the selected isotropic reference material was investigated, using the same testing procedure. The results obtained by using this novel approach are in good agreement with data measured using the conventional testing techniques.

Structural Assessment Techniques for In-Service Crossarms in Power Distribution Networks

Crossarms are widely used in power distribution and telecommunication sectors to support overhead cables. These structures are horizontally attached to the top of vertically erected utility poles and are essential elements in connecting overhead cables to the poles. Timber is the dominantly used material type for crossarms in the existing distribution networks. Nevertheless, there are alternative crossarms made from steel, composites, polymers, and even from concrete. This paper reviews the studies on the condition assessment of timber crossarms considering the aspects of decay identification and flexural strength assessment. The limitations and shortcomings of the conventional inspection techniques for crossarms are presented. Then, the studies on the developments of non-destructive test methods to address these issues are reviewed. Further, the results from the experimental work conducted to assess the structural capacity of in-service crossarms are presented and analysed. In addition, the possible future advancements of alternative crossarm types are also discussed, considering the mechanical strength, durability performance, and sustainability aspects. This paper aims to highlight the advantages and disadvantages of different condition assessment techniques for crossarms, indicating the importance of an integrated approach combining both the conventional and non-destructive testing techniques.

Particle image velocimetry and digital image correlation for determining the elasticity modulus in wood

Several non-destructive testing techniques have been improved and tested in recent years. The non-destructive testing techniques using particle image velocimetry (PIV) and digital image correlation (DIC) differ from conventional testing techniques, as they allow making measurements indirectly. In this study, the elastic modulus in wood beams of Eucalyptus grandis and Pinus oocarpa were determined using PIV and DIC. The application of PIV and DIC techniques occurred during the static bending tests, when the displacements were also measured by the conventional method. The applied load values allowed calculating the elasticity modulus. In all regions of analysis, the mean values of the elasticity modulus found by the DIC, PIV and conventional method are statistically equivalent. It is concluded that the PIV and DIC testing techniques can be used to determine mechanical properties of wood.

Deformation and fracture characteristics of zirconium plate produced via ultrasonic additive manufacturing

The microstructural evolution, deformation modes, and fracture mechanisms of zirconium plate produced using ultrasonic additive manufacturing (UAM) are presented. In addition to conventional tensile testing techniques, digital image correlation captured highly variable strain accumulation in specimens loaded perpendicular or parallel to the build height (Z). When tested in parallel to Z, delamination at prior foil/foil interfaces creates strain localization noticeable in strain rate maps, whereas specimens loaded perpendicular to Z illustrate conventional strain hardening until necking accelerates delamination. Although bond strengths are statistically and spatially variable, in situ electron backscattering diffraction tests illustrate the ability for grains near interfaces to accommodate strain with twinning and slip modes consistent with conventionally produced zirconium alloys. Finally, mixtures of ductile and delamination-induced fracture highlight the interface-driven failure modes of UAM zirconium plate in the as-built condition.Graphic abstract

Sporopollenin supported ionic liquids biosorbent for enhanced selective adsorption of 2,4-dinitrophenol from aqueous environment

This study attempts to bring about a facile approach to selectively adsorb 2,4-dinitrophenol (2,4-DNP) from an aqueous system using sporopollenin supported ionic liquid (SpIL) biosorbent, namely sporopollenin supported methylimidazolium (Sp-MIM). Sporopollenin acts as the host with the accessible chamber, while methylimidazolium acts as the active site that binds 2,4-DNP from the aqueous system. Methylimidazolium, being chemically immobilized onto sporopollenin, simultaneously ensures that the ionic liquid does not leach into the aqueous environment while providing increased affinity and selectivity towards 2,4-DNP. The solid samples were characterized using conventional solid-state testing techniques such as FTIR, 13C CP/MAS solid-state NMR, FESEM-EDX spectroscopy, TGA, and BET/BJH analysis. While UV-Visible spectroscopy was used to study the adsorption parameters. Based on the study, methylimidazolium's immobilization onto sporopollenin increased pore size distinctly from 5.06 nm to 44.94 nm, thereby reporting definitive mesoporous structure with a pronounced affinity towards 2,4-DNP, determined via a series of analyte screening. Adsorption parameter exploration revealed 15 mg of Sp-MIM was able to adsorb 84% of 2,4-DNP from 20 ppm concentrated aqueous solution within 15 min of contact under acidic condition (pH 4) and could be reused up to 5 cycles without any loss to adsorption percentage. The affinity of Sp-MIM towards 2,4-DNP was further explored employing computational calculations using molecular docking and quantum mechanics, both of which support the presence of π-π interaction and hydrogen bonding between Sp-MIM and 2,4-DNP.

The precision of macroscale mechanical measurements is limited by the inherent structural heterogeneity of human stratum corneum

Biological tissues are structurally heterogenous mosaics at cellular and sub-cellular length scales. Some tissues, like the outermost layer of human skin, or stratum corneum (SC), also exhibit a rich topography of microchannels at larger mesoscopic length scales. Although this is well understood, modern studies continue to characterize the mechanical properties of biological tissues, including the SC, using macroscale techniques that assume these materials are homogenous in structure, thickness, and composition. Macroscale failure testing of SC is commonly associated with large sample to sample variability. We anticipate that microscale heterogeneities play an important role in defining the global mechanical response of the tissue. To evaluate the validity of the prevailing paradigm that macroscopic testing techniques can provide meaningful information about failure in soft heterogenous tissues, the macroscale work of fracture in isolated human SC samples is measured using conventional macroscale testing techniques and compared with the energy cost of creating new crack interfaces at the microscale, measured using a modified traction force microscopy technique. Results show that measured micro- and macroscale energy costs per unit crack path length are highly consistent. However, crack propagation is found to be guided by microscale topographical features in the tissue. This correlation reveals that macroscale mechanical sample to sample variability is caused by notable differences in crack propagation pathways. Statement of significanceAlthough designed to test homogeneous materials, macroscopic uniaxial tensometry is currently the gold standard for measuring the mechanical properties of biological tissues. All tissues, including human stratum corneum are structurally heterogeneous at the microscale and mechanical measurements are commonly highly variable, even for specimens from the same source. This study explores the fundamental causes of this disparity and evaluates the prevailing paradigm that macroscopic testing techniques can provide meaningful information about failure in soft heterogeneous tissues. Results conclude that the cause of large variability in mechanical work of fracture is due to inherent structural heterogeneities governing crack propagation pathways and altering the total crack length. Structural heterogeneities in tissue therefore limits the precision of macroscale biomechanical testing.

Visual test and evolutionary analysis of flow fields in cylinder of helical intake port diesel engine

The paper intends to overcome the difficulties associated with conventional PIV test techniques in measuring the flow fields near curved surfaces. So the paper combines the visual steady flow test and the CFD simulation method, to help observe the law of particle distribution near the cylinder wall directly, and reveal the law of steady/transient flow field movement and airflow evolution. The results show that the distribution of particle density and the gradient boundary lines of the tracer concentration correspond to those of the CFD simulation. Therefore, a visual test can display the characteristics of the movement of air in the cylinder near the wall. The swirl ratio of each radial section in the cylinder and the ω combustion chamber during the intake stroke is influenced by the intake airflow, while the swirl ratio during the compression stroke is determined by the piston movement. At the end of a compression stroke, the location of the highest swirl ratio directly influences the air-fuel mixture. As a result, analyzing the swirl ratio and evolutionary process of the flow fields near the wall of the cylinder and combustion chamber help improve the quality of the air-fuel mixture and the efficiency of combustion.

Comparative Study on Using Ultrasonic Array-Based Techniques for Detection of Flaws in Thick and Attenuating Materials

This paper reports the influence of thickness and material attenuation on volumetric inspection using conventional and advanced ultrasonic array-based techniques through suitable examples. The sensitivity achieved in conventional phased array ultrasonic testing technique with focusing at specific depth using delay laws and advanced array-based techniques for simultaneous focusing at all depths such as Full Matrix Capture-Total Focusing Method and plane wave imaging-TFM are compared in the present study. Finally, experimental results are discussed for advanced ultrasonic array-based techniques for detection and characterization of a 4 mm through wall dimension vertical planar defect (simulating a lack of side wall fusion in a thick narrow gap weld) in a nickel base alloy forging having fine and coarse grains. The sensitivities and signal-to-noise ratio achieved in the different techniques are discussed in detail.