Test Material Research Articles

A contact-based constitutive model for the numerical analysis of masonry structures using the distinct element method

This study presents a robust contact constitutive model in the distinct element method (DEM) framework for simulating the mechanical behavior of masonry structures. The model is developed within the block-based modeling strategy, where the masonry unit is modeled as deformable blocks with potential crack surfaces in the middle of the bricks, while the mortar joints are defined as zero-thickness interfaces. The modeling strategy implements multi-surface plasticity with damage mechanics, including a tension cut-off, Coulomb failure criterion, and an elliptical compressive cap for the damage in tension, shear, and compression, respectively. Two new features are introduced in this contact model: a piecewise linear softening function for strength degradation in tension and shear and a hardening/softening function to phenomenologically define the compressive damage of masonry composite into the unit-mortar interface. The constitutive model is implemented in commercial DEM software using the small displacement configuration and validated against material and experimental tests on masonry walls subjected to constant pre-compression and monotonically increasing in-plane load. The experimental and numerical results regarding the force-displacement relationship and damage pattern produced by the proposed constitutive model are compared and critically discussed, demonstrating the capability of DEM coupled with the suitable constitutive law in simulating the behavior of masonry structures.

Novel low-temperature and high-flux hydrogen plasma source for extreme-ultraviolet lithography applications

Inside extreme-ultraviolet (EUV) lithography machines, a hydrogen plasma is generated by ionization of the background gas by EUV photons. This plasma is essential for preventing carbon build-up on the optics, but it might affect functional performance and the lifetime of other elements inside the machine. The interaction of scanner materials and components with hydrogen plasma is investigated in controlled experiments using laboratory (off-line) setups, where the properties of EUV-generated plasmas are mimicked. Here, we present a novel experimental setup at TNO, where a low-temperature hydrogen plasma is generated by means of electron-impact ionization using a high-current, high-pressure electron beam (e-beam) gun. We show that the produced ion flux, peak ion energies, and radical-to-ion ratio are similar to that of the EUV-generated plasma. Since the e-gun has the option of operating the e-gun in the pulsed mode, it is possible to reproduce the time-dependent behavior of the scanner plasma as well. Moreover, as shown by Luo et al. [RSC Adv. 10, 8385 (2020)], electrons that impinge on surfaces mimic EUV photons in the generation of secondary electrons, which often drive radiation-induced processes (e.g., surface oxidation, reduction, and growth of carbon). We conclude that e-beam generated hydrogen plasma is a very promising technology for cost-effective lifetime testing of materials and optics, as compared to setups with EUV sources.

An Investigation of Tensile, Fatigue, and Fracture Behavior of 3D-Printed Polymers

Abstract The progression of manufacturing technology has significantly benefited from the adoption of 3D printing techniques, which enable the production of parts with intricate geometries. However, it is important to acknowledge that components fabricated through this additive manufacturing method frequently manifest defects and are prone to failure under severe conditions. Therefore, a thorough examination of the mechanical properties of these parts is essential to effectively reduce the failure. This study aimed to explore the mechanical properties of two prevalently used 3D-printed polymers, specifically Onyx and acrylonitrile butadiene styrene (ABS), by integrating computational and experimental analyses. The experimental study utilized a material testing system and digital image correlation (DIC) technology, while the computational analysis covered the finite element (FE) modeling of the 3D-printed samples. The research focused on evaluating the tensile strength and fatigue resistance of the specimens printed in various orientations, alongside a detailed investigation of their fracture behavior. The crack propagation analysis was carried out using the DIC system and the separating morphing and adaptive re-meshing technology (SMART) scheme in ansys. It was observed that upright build orientation produced the weakest samples for axial loading and specimens with notches failed earlier than those without. Moreover, Onyx was found to have a higher resistance to fracture or failure compared to ABS. The FE modeling results demonstrated strong agreement with the experimental results, validating their accuracy and reliability in characterizing the critical mechanical response of 3D-printed parts rapidly and cost effectively.

Genome-wide association study of the loci and candidate genes associated with agronomic traits in Amomum villosum Lour.

Amomum villosum Lour. (A. villosum) is a valuable herbaceous plant that produces the famous traditional Chinese medicine Amori Fructus. Identifying molecular markers associated with the growth of A. villosum can facilitate molecular marker-assisted breeding of the plant. This study employed 75 A. villosum accessions as the test material and utilized 71 pairs of polymorphic simple sequence repeat (SSR) molecular markers to genotype the population. The study analyzed the association between SSR markers and phenotypic traits through the linkage imbalance and population structure analysis. Candidate genes associated with the molecular markers were also identified. The results showed that the phenotypic diversity index range of the 12 agronomic traits was 4.081-4.312 and conformed to a normal distribution. Moreover, 293 allelic variations were detected in the 75 accessions, with an average of 5.32 amplified alleles per loci, ranging from 3 to 8. The maximum number of amplified alleles for AVL12 was 8. The population structure and cluster analysis indicated that the accessions could be divided into two subgroups. Using the mixed linear model (MLM) model of population structure (Q)+kinship matrix (K) for association analysis, three SSR molecular markers significantly associated with the agronomic traits were detected. Fluorescence quantification was used to analyze the expression levels of six candidate genes, and it was found that three of the genes were differentially expressed in phenotypically different accessions. This study is the first to use SSR markers for genome-wide association study (GWAS) mapping and identification of the associated agronomic traits in A. villosum. The results of this study provide a basis for identifying genetic markers for growth traits for marker-assisted breeding in A. villosum.

Dynamic thermal runaway evolution of Li-ion battery during nail penetration

The nail penetration test is widely adopted to evaluate the safety of lithium-ion batteries by triggering the internal short circuit. This work compares the phenomena, temperature rise rate, surface temperature, and mass loss under the penetration test for different nail materials, nail diameters, and cell SOCs. The thermal runaway behaviour and characteristics of these test cells are studied in depth. The results show that the maximum temperature and temperature rise rate of the cell increase with the increase of SOC. The maximum temperature and the temperature rise rate of the cell decrease with the increase of the nail diameter. Under high SOC conditions (greater than 75 % SOC), the more conductive nail increases the release of Joule heat generation inside the battery, which leads to a more intense thermal runaway behaviour. At low SOC (less than 50 % SOC), the more conductive nail promote cooling, which reduces the intensity of thermal runaway. However, non-conductive nails show the exact opposite effect. This dual effect of different nail materials was elucidated by a simplified heat transfer analysis. By calculating the heat production and heat dissipation during the thermal runaway process, the effects of the nail material and the cell SOCs on the thermal runaway behaviour of the battery can be summarized. This work deepens the understanding of the safety of batteries under external shocks and provides new scientific insights into battery design and its safety testing.

90-day oral toxicity study in rats of a protein-rich powder derived from Xanthobacter sp. SoF1.

Xanthobacter sp. SoF1 (SoF1) is an autotrophic hydrogen-oxidizing bacteria that produces protein-rich biomass and has potential to be an alternative protein source that is more environmentally sustainable than animal and plant derived proteins. A protein-rich powder derived from SoF1 was the test material in a 90-day repeated-dose oral toxicity study to explore major toxic effects, demonstrate target organs, and provide an estimate of a no-observed-adverse-effect level (NOAEL). Daily doses of 0 (vehicle only), 375, 750, and 1500 mg/kg bw/day of the test material were administered by gavage to 10 Han:WIST rats/sex/group. An additional group was administered 1290 mg/kg bw/day whey protein concentrate as positive control. No treatment-related adverse effects were observed, and no target organs were determined after 90/91 days of consecutive administration of the test item. A NOAEL of 1500 mg/kg bw/day was determined.

Developing an optimised method for accurate wear testing of dental materials using the ‘Rub&Roll’ device

Dental materials are challenged by wear processes in the oral environment and should be evaluated in laboratory tests prior to clinical use. Many laboratory wear-testing devices are high-cost investments and not available for cross-centre comparisons. The ‘Rub&Roll’ wear machine enables controlled application of force, chemical and mechanical loading, but the initial design was not able to test against rigid antagonist materials. The current study aimed to probe the sensitivity of a new ‘Rub&Roll’ set-up by evaluating the effect of force and test solution parameters (deionized water; water + abrasive medium; acid + abrasive medium) on the wear behaviour of direct and indirect dental resin-based composites (RBCs) compared with human molars against 3D-printed rod antagonists. Molars exhibited greater height loss than RBCs in all test groups, with the largest differences recorded with acidic solutions. Direct RBCs showed significantly greater wear than indirect RBCs in the groups containing abrasive media. The acidic + abrasive medium did not result in increased wear of RBC materials. The developed method using the ‘Rub&Roll’ wear machine in the current investigation has provided a sensitive wear test method to allow initial screening of resin-based composite materials compared with extracted human molars under the influence of different mechanical and erosive challenges.

Separation of Pd from Pt and Rh by solvent extraction method from waste solution

The paper investigated the possibility of extractive separation of palladium from platinum and rhodium with ionic liquid Cyphos IL 101. A technological solution obtained by dissolving waste materials was used as the test material. Based on the experiments performed, it was found that a 10% (v/v) solution of the Cyphos IL 101 ionic liquid in toluene allows the extraction of both Pd and Pt with an efficiency of 99% from the initial solution when extraction is carried out at the pH 0.5, vorg:vaq phase ratio 1:1 and contact time of 15 min. Moreover, the research proved that it is possible to separate Pd from Pt at the stripping stage using a 0.1 mol/dm3 thiourea solution while maintaining a high selectivity coefficient.

High resolution X-ray phase contrast imaging for non-destructive testing of composite materials

X-ray imaging is widely used in non-destructive testing dedicated to industry, medical or security domain. In aircraft production, the aerospace industry increasingly integrates carbon fibre reinforced polymers (CFRP), which may develop defects from operational wear, like lightning strikes. To robustly characterize density changes resulting from induced lightning damage in CFRP, multilateral shearing interferometry (MLSI) – a phase imaging technique – have been incorporated on a X-ray laboratory bench. Indeed, such method provides higher contrasts than X-ray attenuation imaging for composite materials and brings complementary information of the imaged sample. However, extracting the phase signal requires conditions of the imaging system and algorithmic strategies, which can lead to the emergence of artifacts in phase images. This thesis work involved the characterisation of these artifacts in the context of MLSI applied to X-ray phase imaging, as well as the development of tracking methods and corrective strategies.

Studying the effect of Cr content on microstructure and deformation behavior of (NiCo)88-xCrxAl10Ta2 medium-entropy alloy through L-DED gradient material

Optimization of Cr content is crucial for γ'-strengthened NiCoCr-based medium entropy alloys, influencing the stacking fault energy, deformation behavior and the precipitation of brittle σ phase. In this study, (NiCo)88-xCrxAl10Ta2 gradient materials were prepared by L-DED, and the influence of Cr content on the phase precipitation and tensile deformation behavior was investigated. As the Cr content decreases from 24.1at.% to 13.9at.%, the aging time for σ phase precipitation at the grain boundaries at 750°C increases from 100hours to 215hours. Meanwhile, the coarsening rate of γ' phase at 750°C are found to be 7.84×10-28 m3/s and 13.6×10-28 m3/s for the Cr content of 24.1at.% and 18.7at.%, respectively. It suggests that the reduction in Cr content notably suppresses the precipitation of σ phase, and accelerates the coarsening rate of γ' phase. Tensile testing of the gradient material reveals that the lower Cr content region exhibits fewer and shorter stacking faults during tensile deformation due to its higher stacking fault energy, leading to the rapid development of local strain, subsequent necking, and eventual fracture. Taking into account the evolution of microstructure, hardness, and deformation substructure with varying Cr content, the appropriate Cr content in (NiCo)88-xCrxAl10Ta2 medium entropy alloy is 17-24 at%.

Fatigue failure analysis of grey cast iron water pipes accounting for fatigue strength variation

Fatigue cracking is thought to be a critical failure mode for Grey Cast Iron (GCI) water pipes; however, this failure mechanism is poorly understood. Using a novel approach to sourcing GCI pipe material for testing, the variation in fatigue strength between pipes from the same batch was experimentally quantified. These results were used to assess the impact of fatigue strength variation on a hypothetical but realistic GCI water pipe years-to-failure scenario. Full-pipe sections were used during fatigue testing and the observed failure mode gave physical meaning to the years-to-fatigue-failure predictions for the first time. The accumulation of fatigue damage was predicted to represent a terminal and very small part of a GCI pipe’s life, so the loads applied to a GCI pipe early in its life are likely to have a limited impact on its remaining life and so do not need to be included in predictive modelling. For the scenario considered here, the predicted variation in lifetime was an 8.6-year range about an average of 59.4 years. GCI pipes in the UK are all > 50 years old, so this is a significant variation for asset and investment planners to account for as these pipes approach the end of their lives.

Preparation of Self-Assembled Graphene Materials with Assisted Multi-structured TiO2: Internal Three-phase Heterojunction Built by Doping with Al3+

Conductive coatings provide electromagnetic shielding against interference and radiation from electromagnetic waves. This is critical for electronic devices, communications equipment, medical instruments, and other industries. In this paper, XRD and Raman proved that Al3+ doped anatase, rutile, and brookite coexisting mixed crystalline phase TiO2, which evolved into highly conductive powder materials after ultrasonically compounding graphene, are prepared by simply controlling the calcination temperature. Tauc spectra proved the three-phase heterojunction shortens the distance between the conduction and valence bands, and electron jumping becomes easy. XPS proves that with low-price Al3+, the high-price Ti4+ in the lattice will be replaced, forming oxygen vacancies. A fast charge transfer pathway (Al-O-C) is established between Al3+ and graphene, and the synergistic effect of the two greatly reduces the resistivity. Four-probe test material resistance learned the resistivity of TAl-G is 57% lower than that of T-G. At the same time, the excellent electrical conductivity of the TAl-G composite makes it suitable for practical applications in antistatic coatings, while the significantly shorter bandgap gives it great potential for photoelectrocatalysis.

The Deposition by Raffaello Sanzio: New analytical insights on old cross sections for the characterisation of pictorial palette

In 2020, 500th anniversary of Raffaello Sanzio death, his Deposition (1507), -the altarpiece known also as the Pala Baglioni, today located at the Borghese Gallery in Rome-has been subjected to conservative revision and preventive conservation project. This included in-depth diagnostic campaigns through most modern non-invasive techniques, together with the analysis of old cross sections from the same Pala. These latters, prepared between 1966 and 1972, preserved in ICR laboratory of chemistry and testing materials archive, have been used to deepen the knowledge of Raffaello painting techniques. The use of such cross sections was fundamental to verify the original pictorial film and restoration re-paintings before the conservation intervention in the same years.In this paper, the results of analytical insights on Raffaello pictorial palette are presented. The information is obtained by the analysis of the old ICR stratigraphic sections, through the use of Scanning Electron Microscope with Energy Dispersive X-Ray analysis (SEM-EDX) and micro-Raman (632.8 nm), while Surface Enhanced Raman Scattering (SERS) analysis through colloidal paste has been tested for the identification of organic lake-pigments present in low concentration and for the successful recognition of copper resinate, whose SERS spectrum is here reported for the first time, according to our knowledge. This combined diagnostic approach has made it possible to recognize the pigments employed in the different pictorial layers, such species in traces and those from organic materials, responding to open questions arising previous non-invasive analyses and highlighting further aspects of the illustrious master refined painting technique.

Making the Cut: End Effects and the Benefits of Slicing

Cutting mechanics in soft solids have been a subject of study for several decades, an interest fuelled by the multitude of its applications, including material testing, manufacturing, and biomedical technology. Wire cutting is the simplest model system to analyse the cutting resistance of a soft material. However, even for this simple system, the complex failure mechanisms that underpin cutting are still not completely understood. Several models that connect the critical cutting force to the radius of the wire and the key mechanical properties of the cut material have been proposed. An almost ubiquitous simplifying assumption is a state of plane (and anti-plane) strain in the material. In this paper, we show that this assumption can lead to erroneous conclusions because even such a simple cutting problem is essentially three-dimensional. A planar approximation restricts the analysis to the stress distribution in the midplane. However, through finite element modelling, we reveal that the maximal tensile stress – and thus the likely location of cut initiation – is located in the front face. Friction reduces the magnitude of this stress, but this detrimental effect can be counteracted by large “slice-to-push” (shear-to-indentation) ratios. The introduction of these “end effects” helps reconcile a recent controversy around the role of friction in wire cutting, for it implies that slicing can indeed reduce required cutting forces, but only if the slice-push ratio and the friction coefficient are sufficiently large.

Bridging the gap between rate-dependent plasticity and stress wave dynamics: Calibrating a constitutive model for high-strength steel by inverse optimization

We present an approach for quantifying the flow stress of metals under dynamic loads, based on experiments that involve distinct but related physical phenomena. In modified Taylor tests, a stress-wave generated velocity-time signal is measured, which indirectly provides information on the plastic deformation behavior of the tested material at high strain rate. The Johnson-Cook plasticity model is calibrated for a high-strength steel on the basis of such measurements in combination with quasi-static and dynamic tensile test data. The plasticity model parameters are found with differential evolution through the inverse optimization of material test simulations. A consistent set of model parameters is identified that reproduces measurements from all types of tests. The obtained plasticity model features a small initial yield stress, which is compensated by large strain hardening so as to produce a realistic engineering yield stress. An independent calibration method is employed, by regression of the model on quasi-static and dynamic tensile test results, that confirms the validity of the plasticity model parameter values.

Development Progress of CRAFT SC Material Testing Facility

Development Progress of CRAFT SC Material Testing Facility

EIT probe based intraoperative tissue inspection for minimally invasive surgery

Abstract Electrical impedance tomography (EIT) has become an integral component in the repertoire of medical imaging techniques, particularly due to its non-invasive nature and real-time imaging capabilities. Despite its potential, the application of EIT in minimally invasive surgery (MIS) has been hindered by a lack of specialized electrode probes. Existing designs often compromise between invasiveness and spatial sensitivity: probes small enough for MIS often fail to provide detailed imaging, while those offering greater sensitivity are impractically large for use through a surgical trocar. Addressing this challenge, our study presents a breakthrough in EIT probe design. The open electrode probe we have developed features a line of 16 electrodes, thoughtfully arrayed to balance the spatial demands of MIS with the need for precise imaging. Employing an advanced EIT reconstruction algorithm, our probe not only captures images that reflect the electrical characteristics of the tissues but also ensures the homogeneity of the test material is accurately represented. The versatility of our probe is demonstrated by its capacity to generate high-resolution images of subsurface anatomical structures, a feature particularly valuable during MIS where direct visual access is limited. Surgeons can rely on intraoperative EIT imaging to inform their navigation of complex anatomical landscapes, enhancing both the safety and efficacy of their procedures. Through rigorous experimental validation using ex vivo tissue phantoms, we have established the probe’s proficiency. The experiments confirmed the system’s high sensitivity and precision, particularly in the critical tasks of subsurface tissue detection and surgical margin delineation. These capabilities manifest the potential of our probe to revolutionize the field of surgical imaging, providing a previously unattainable level of detail and assurance in MIS procedures.

Influence of Layer Thickness of 3D Printed Polyamide Against Temperature

Polyamide is one of the materials in 3D printing that can produce valuable products to meet the needs of the industry. Previous studies have proven that the layer thickness of the 3D printed material and the increase in temperature affect the mechanical and physical properties. However, only a few studies involve polyamide material as a test material, especially in analyzing the influence of the layer thickness of the printed material and the increase in temperature on the mechanical and physical properties of polyamide. Therefore, the bending properties of polyamide with different layer thicknesses at 0.1 mm, 0.2 mm and 0.3 mm and the tensile properties of the material at different temperatures at room temperature, 75˚C and 110˚C will be studied. This study will involve polyamide (PA) materials printed at three different layer heights using the Fused Deposition Modelling (FDM) process. Bending and tensile tests at different temperatures from 27˚C to 110˚C are conducted using the Instron Universal Testing Machine. The study results show that the layer height of 0.3 mm exhibits the highest flexural strength at an average rate of 11.05 MPa compared to 0.1 mm (6.7 MPa) and 0.2 mm (9.6 MPa). The tensile strength decreases when the temperature elevates, making the temperature of 110˚C have the lowest tensile value (1.591 MPa) compared to the temperature of 75˚C (1.6MPa) and 27˚C (2.1MPa). Several material characterizations such as SEM, TGA, DMA, DSC and density have been performed to study the microstructure and influence of tensile test temperature on the mechanical properties of polyamide.

Performance Validation of the NeoBase 2 Non-Derivatized MSMS Assay Kit and Cutoff Values Establishment of Term and Preterm Neonates

Objective NeoBase 2 Non-derivatized MSMS assay kit (NeoBase 2 kit) was used for newborn screening, the performance of the NeoBase 2 kit should be validated before its implementation in clinical diagnostic laboratories. Methods Leftover dried blood spot samples, quality control materials in the NeoBase 2 kit, and proficiency testing materials received from the NSQAP were used. Precision, accuracy, LOD, LLOQ, recovery, and stability were carried out to verify the performance of the Waters ACQUITY TQD MS/MS system with the NeoBase 2 kit for newborn screening. Cutoffs were determined and analytes requiring different cutoffs in preterm neonates were investigated. Results Within-run and between-run precisions ranged from 3.95% to 14.41%. The accuracy and stability were within 15%. All analytes demonstrated acceptable LOD, LLOQ, and recoveries. Cutoffs for term and preterm neonates were established. Conclusions The performance of the NeoBase 2 kit is acceptable and can be implemented in clinical diagnostic laboratories.

Mechanics of microblister tests in 2D materials accounting for frictional slippage

The blister test, in which a thin film adhered on a substrate is subject to a uniform transverse pressure from an underlying cavity, is increasingly utilized for the characterization of two-dimensional (2D) materials. Conventional theoretical models of the blister test often assume idealized interfacial conditions such as zero slippage or zero friction. However, experiments indicate that 2D materials can glide over the substrate with a finite interfacial slip resistance. In this study, a theoretical model of blister accounting for frictional slippage at the interface is developed. Subsequent proper normalization makes the model scale independent and serves as a bridge between the actual experiment and molecular dynamics (MD) simulations. On this basis, the inherent differences are revealed between the different interface hypotheses. And especially, to the best of our knowledge, elasticity-adhesion interaction is discussed in detail for the first time under the condition of frictional slippage, enabling a successful amendment to the measurement of interfacial adhesion. Finally, a simplified model is proposed for extracting mechanical properties of 2D materials based on the microblister test.