Testing Machine Research Articles

Biomechanical Performance of 4-Leg Sustained Dynamic Compression Staples in First Tarsometatarsal Arthrodesis.

This study investigates the biomechanical efficacy of new 4-leg Sustained Dynamic Compression (SDC) NiTiNOL staples, hypothesized to offer superior stability and resilience to loading before fusion completion, compared with conventional hardware. Twenty sawbones left full foot models were divided into 4 treatment groups: (1) 4-leg Inline Staple, (2) 4-leg Inline Staple + 2-leg Staple, (3) 4-leg Inline Staple + Screw, and (4) Plate + Screw. An osteotomy was performed to simulate a Lapidus procedure, and the respective fixation methods were applied. Mechanical testing was conducted using a servo-hydraulic testing machine to evaluate constructs' load, contact force, contact area, and plantar gap. The 4-leg Inline Staple + Screw group demonstrated significantly increased joint contact force, joint contact area, and decreased plantar gap compared with the Plate + Screw group, both before and after cyclic testing. All SDC-containing constructs exhibited post-cyclic joint contact areas that were 2.36×, 3.87×, and 5.49× greater than the post-cyclic plate + screw group. Most notably, the 4-leg Inline Staple + Screw group maintained a plantar gap of less than 3 mm throughout the testing, unlike other groups. The 4-leg Inline SDC Staple, particularly when combined with a static screw, demonstrated biomechanical superiority over traditional plate and screw constructs in Lapidus procedures. These findings suggest a promising avenue for enhanced post-operative stability, which could translate into quicker patient recovery, improved fusion rates, and potentially lower non-union rates. Further clinical trials are warranted to validate these biomechanical advantages in patient outcomes. Therapeutic, Level V: Bench Testing.

First lattice QCD calculation of J/ψ semileptonic decay containing D and Ds particles

We perform the first lattice calculation on the semileptonic decay of J/ψ using the (2+1)-flavor Wilson-clover gauge ensembles generated by CLQCD collaboration. Three gauge ensembles with different lattice spacings, from 0.0519 to 0.1053 fm, and pion masses, mπ∼300 MeV, are utilized. After a naive continuum extrapolation using three lattice spacings, we obtain Br(J/ψ→Dseνe)=1.90(6)(5)Vcs×10−10 and Br(J/ψ→Deνe)=1.21(6)(9)Vcd×10−11, where the first errors are statistical, and the second come from the uncertainties of Cabibbo-Kobayashi-Maskawa matrix element Vcs(d). The ratios of the branching fractions between lepton μ and e are also calculated as RJ/ψ(Ds)=0.97002(8) and RJ/ψ(D)=0.97423(15) after performing a continuum limit including only a2 term. The ratios provide necessary theoretical support for the future experimental test of lepton flavor universality. Published by the American Physical Society 2024

Chitosan solutions and films properties obtained using electromagnetic-activated water

Purpose of research: to obtain chitosan films with improved performance properties by using water activated by an electromagnetic field of the radio frequency range as a solvent. Objects of research: water activated by an electromagnetic field of the radio frequency range (90-200 MHz), as well as chitosan solutions and films obtained using it. Methods of research: conductometry, potentiometry, densitometry, viscometry, turbidimetry, gravimetry, IR spectroscopy are used in the work. To determine the deformation and strength characteristics of the films, a universal testing machine with an electromechanical drive УТС-110M was used. Main results of research: The effect of pretreatment of water with an electromagnetic field of various frequencies on the properties of acetic acid (2 %) chitosan solutions in the concentration range of 0.1-2.0% has been studied. A decrease in surface tension by 2.0–5.2 % was found, as well as an increase in light transmission by 10-30 % and viscosity of solutions by 24-37 % at a chitosan concentration of 1.0-2.0 %. These effects are most pronounced for frequencies of 70, 90, 110 and 130 MHz. Films were prepared from 2 % chitosan solutions and their deformation-strength and sorption characteristics with respect to water vapor were determined. The greatest increase in tensile strength was found for chitosan films obtained from solutions prepared on water activated by an electromagnetic field with frequencies of 70 and 110 MHz (38 and 23 %, respectively). A decrease in the hygroscopicity of films and an increase in the intensity of bands in the IR spectra of films obtained using activated water were found.

Design of novel test rig for prosthetic finger distal interphalangeal and phalanx strengths.

Testing is one of the most significant phases of any engineering process, the last process followed by conceptualization, designing, and fabricating. If the testing outcomes are not genealogy sensible measurables, then eventually it calls for a redesign overhaul. Existing testing equipment to analyze the load and failures are conventional digital universal testing machines with minimum jigs and fixtures. In addition, the existing fixtures cannot be adapted to the anatomy of a human finger. Consequently, the present work explores the best possible design of a jig for testing the naturally articulated movement of a human finger (prosthetic wear-on). Furthermore, the present jig design checks a wide range of parameters such as freedom of motion, a path along with curvature, load, failures, and intermittent positions of applied load, which is adaptable to existing universal testing machines available for broader applications.

Mechanical and tribological properties of FeS/Cu–Bi self-lubricating materials reinforced with copper-plated steel fibers

Purpose This study aims to investigate the effect of steel fibers on the mechanical and tribological properties of FeS/Cu–Bi self-lubricating materials. Design/methodology/approach The microstructure of the material was characterized by scanning electron microscopy. Tests on the crushing strength, impact toughness and tribological properties of materials were conducted using a universal electronic testing machine, a 300 J pendulum impact testing machine and an M200 ring-block sliding tribometer, respectively. Findings The mechanical properties of the material initially increased and then stabilized with increased copper-plated steel-fiber length. When the length of the copper-plated steel fiber was 7 mm, the mechanical properties of the material reached stability. Compared with the material without a copper-plated steel fiber, its crushing strength and impact toughness increased by 32.6% and 53%, respectively. A copper-plated steel fiber with a length of 7 mm lay flat in a copper matrix can strengthen the friction interface and enrich the lubricant. Accordingly, the antifriction and wear resistance of the materials increased by 17.6% and 55%, respectively. Originality/value The effects of copper-plated steel fibers on the properties of FeS/Cu–Bi self-lubricating materials were clarified. This work can serve as a reference for improving material performance and its engineering applications.

Global fit to b→cτν anomalies as of Spring 2024

Recently, several new experimental results of the test of lepton flavor universality (LFU) in B→D(*) semileptonic decays were announced: the first result of RD from the LHCb run 1 data, the first results of RD and RD* from the LHCb run 2 data, and the first result of RD* from the Belle II collaboration. Including these new data, a global analysis still prefers the violation of the LFU between the tau and light leptons. A new world average of the data from the , LHCb, Belle, and Belle II collaborations is RD=0.342±0.026 and RD*=0.287±0.012. Including this new data, we update a circumstance of the b→cτν¯ measurements and their implications for new physics (NP). Incorporating recent developments for the B→D(*) form factors in the Standard Model, we observe a 4.4σ deviation from the Standard Model prediction. Our updates also include model-independent NP formulas for the related observables and the global fittings of parameters for leptoquark scenarios as well as single NP operator scenarios. Furthermore, we show future potential to indirectly distinguish different NP scenarios with the use of the precise measurements of the polarization observables in B→D(*)τν¯ at the Belle II and the high-pT flavored-tail searches at the LHC. We also discuss an impact on the LFU violation in ϒ→l+l−. Published by the American Physical Society 2024

Fatigue reliability analysis methodology based on fatigue life and failure mechanism for carburized gear

Gears are one of the important components in mechanical products, and their fatigue reliability determines the safety performance of mechanical products. In this paper, the fatigue characteristics of carburized gears under different torque and constant rotational speed conditions are investigated by using a gear contact fatigue testing machine, and combined with the dynamic maximum contact stress distribution on the subsurface of the meshing gears, the very-high cycle fatigue P-S-N curves of carburized gears under a stress ratio of −1 is established. Local stress concentration in the surface or subsurface of carburized gears causes grain dislocation movement under the combined influence of maximum contact and residual stresses, and then causes dislocation pileup and transcrystalline rupture after being hindered by grain boundaries, ultimately leading to pitting and fatigue failure of gears. Based on the dislocation energy method and combined with the fatigue failure mechanism of gears, a life prediction model of gears with good prediction results is established by considering the interaction of factors such as dynamic load, grain size, initial crack length, residual stress, slip band length and width. A fatigue reliability analysis method of gears is established based on the life state equation of gears considering the life prediction model. Further analyses of the influence of rotational speed, grain size, residual stress, slip band width, slip band length and initial crack size on the fatigue life reliability index of the gears resulted in the conclusion that the fatigue reliability of the gears not only decreases with the increase of the above-mentioned parameters, but also shows decreasing trend with the increase of time. This is of significance for evaluating the fatigue reliability of gears under very-high cycle fatigue conditions.

Effect of artificial aging and different surface finishing protocols on the flexural strength and surface hardness of a photopolymer for manufacturing monolithic polychromatic complete dentures using PolyJet 3D printing.

This study evaluated the effect of thermocycling and three different surface finishing protocols on the flexural strength and surface hardness of a novel photopolymer intended for manufacturing monolithic polychromatic dental prostheses using PolyJet 3D printing. A total of 90 specimens were manufactured using a photopolymer for 3D printing monolithic polychromatic dental prostheses using PolyJet technology (TrueDent; Stratasys USA). The specimens were divided into three groups (n=30) according to the surface finishing protocol used: The control group Pumice+Moldent (Pumice), Pumice+Optiglaze (Optiglaze), and Polycril+Moldent (Polycril). Half of the specimens of each group (n=15) were subjected to 5000 thermocycles (Thermocycling Unit OMC350TSX; Odeme Dental Research, Santa Catarina, Brazil), The other half was stored in distilled water at room temperature for 7 days before testing. The flexural strength of the specimens was assessed in a universal testing machine (MTS Sintech ReNew; MTS Systems Corp, Aiden Prairie, MN), and the Vicker's surface hardness was evaluated with a microhardness tester (Micro indentation Hardness Tester LM247AT; Leco Instruments Ltd, Ontario, Canada). The resulting data was analyzed using two-way ANOVA tests, and Fisher's protected least significant differences (α=0.05) in a professional statistical analysis computer program (SAS v9.4, SAS Institute, Cary, NC) RESULTS: The two-way ANOVA tests suggested a statistically significant effect of thermocycling and the surface finishing protocol on the flexural strength (p=0.01) but without significant interaction between both independent variables (p=0.18). The post hoc analysis revealed no significant differences in the flexural strength between groups without thermocycling (p>0.05). Thermocycling decreased the flexural strength of all groups (p<0.05), and the Optiglaze group exhibited significantly higher flexural strength than the Polycril and Pumice groups after thermocycling (p<0.01). Regarding the surface hardness, the two-way ANOVA indicated a significant 2-way interaction between thermocycling and the surface of the finishing protocol (p=0.01). The post hoc analysis showed that the Optiglaze group had significantly higher hardness than the other groups, both before and after thermocycling (p<0.01) After thermocycling, a significant decrease in surface hardness was observed in the Polycril and Pumice groups (p<0.01). Surface finishing protocols and artificial aging can affect the surface hardness and flexural strength of the dental prostheses manufactured using the photopolymer studied. Careful polishing and surface finishing are required to ensure favorable clinical performance. Coating with a photopolymerizable glaze material seems to be a favorable surface treatment for monolithic polychromatic complete dentures fabricated using PolyJet 3D printing.

Performance of Recycled Opaque PET Modified by Reactive Extrusion

A comparative study of the structural integrity of an opaque recycled poly(ethylene terephthalate) (rPET-O) has been carried out with two types of modified rPET-O by applying reactive extrusion techniques, namely (a) using a multi-epoxide reactive agent (REx-rPET-O) and (b) a 90/10 (wt/wt) rPET-O/polycarbonate (PC) blend. The chemical modifications introduced during reactive extrusion were confirmed using differential scanning calorimetry (DSC) and rheological dynamic analysis (RDA). For the quantification of the fracture parameters, an instrumented pendulum impact testing machine was used using specimens in SENB configuration. The structural modifications generated during reactive extrusion promote an increase of between 16 (REx-rPET-O) and 20% (rPET-O/PC) in the stress-intensity factor (KQ) compared to unmodified rPET-O. The most significant differences between both modifications are registered in the “specific work of fracture” (wf) (alternative parameter to the standardized impact strength), where an increase of 61% is reached for the case of rPET-O/PC and only 11% for REx-rPET-O. This trend can be attributed to the type of reactive modification that is generated, namely chain branching (REx-rPET-O) vs. the generation of a random copolymer “in situ” (rPET-O/PC). This copolymer decreases the crystallization capacity and degree of crystalline perfection of rPET-O, promoting an increase in the critical hydrostatic stress conditions for the generation of crazing and crack propagation.

SMT2Test: From SMT Formulas to Effective Test Cases

One of the primary challenges in software testing is generating high-quality test inputs and obtaining corresponding test oracles. This paper introduces a novel methodology to mitigate this challenge in testing program verifiers by employing SMT (Satisfiability Modulo Theories) formulas as a universal test case generator. The key idea is to transform SMT formulas into programs and link the satisfiability of the formulas with the safety property of the programs, allowing the satisfiability of the formulas to act as a test oracle for program verifiers. This method was implemented as a framework named SMT2Test, which enables the transformation of SMT formulas into Dafny and C programs. An intermediate representation was designed to augment the flexibility of this framework, streamlining the transformation for other programming languages and fostering modular transformation strategies. We evaluated the effectiveness of SMT2Test by finding defects in two program verifiers: the Dafny verifier and CPAchecker. Utilizing the SMT2Test framework with the SMT formulas from the SMT competition and SMT solver fuzzers, we discovered and reported a total of 14 previously unknown defects in these program verifiers that were not found by previous methods. After reporting, all of them have been confirmed, and 6 defects have been fixed. These findings show the effectiveness of our method and imply its potential application in testing other programming language infrastructures.

Impact of Eccentric Loading on the Structural Performance of Reinforced Concrete Pad Footings: An Experimental Study

Setting out of building footings are usually carried out using profile board. This method is usually not accurate in locating the position of columns. Hence, columns that are designed as a concentric columns to their respective footings ends up being columns having eccentricities to the pad footings that supports them. Since the stress distribution under pad footing with concentric column is different from that of pad footing with eccentric column, there is need to study the effect of these eccentricity on the load carrying capacity of the pad footing. In carrying out this work, four pad footings and a typical foundation were used. The pad footings were of sizes 230 mm x 230 mm x 150 mm, with columns of 150 mm x 150 mm cross-section. The first pad footing P1SH was pad footing with short column and zero eccentricity, the second pad footing P2SL was pad footing with slender column and zero eccentricity, the third pad footing P3SL was footing with slender column with 40 mm eccentricity, while the forth pad footing P4SL was footing with slender column with 80 mm eccentricity. The foundation comprises of sand which was contained in a sandbox. The sandbox was made of steel plate of dimensions 0.3 m × 0.3 m × 0.2 m of 4 mm thickness, was used to provide support for the foundation. The foundation was produced by compacting loose sand in three layers with 20 blows per layer in the steel box and with density of about 735 kg/m3. The pad footings were placed on top of the foundation contained in the sandbox, and together were placed on the loading plate of Universal Testing Machine (UTM). Compressive load was applied on each of the pad footings through the columns till failure occurred, using UTM. It was found out that pad footing P1SH have the highest load capacity of 261.25 kN, P2SL pad footing with load capacity of 124.24 kN, P3SL pad footing with load capacity of 39.34 kN, while P4SL pad footing with load capacity of 23.30 kN.

Effect of the synergistic interaction of zinc adipate, hydrotalcite and ethylene propylene rubber on the performances of polypropylene

Polypropylene (PP) is widely used in a range of areas due to its excellent physical and chemical properties, but its low-temperature brittleness and low-impact resistance largely limits its application. Hence, this study investigated the changes in mechanical and thermal properties of isotactic polypropylene (iPP) modified by the addition of the β-nucleating agent zinc adipate (ZnAA), the inorganic rigid particle hydrotalcite (HT), and the rubber elastomer bipropylene rubber (EPR). The structure and properties of modified PP were investigated by Fourier transform infrared (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), electronic universal material testing machine, and simple-beam impact testing machine. At last, the non-isothermal crystallization kinetics of iPP was investigated by the Caze method. It was found that with the addition of EPR reached 30 wt%, the notched impact strength of iPP was 34.74 kJ/m2, which was 542.43 % higher than that of pure iPP, and more than twice as high as that of ZnAA and HT modification, and the relative crystallinity ( K β) value of the β-crystalline form reached 79.66 % when 10 wt% EPR was added to the iPP. The addition of ZnAA, HT and EPR could significantly increase the crystallisation peak temperature ( T c), shorten the half-crystallisation time ( t 1/2) and increase the crystallisation activation energy ( ΔE) of iPP.

Effects of Cu Coating Addition on Mechanical Properties of Vacuum Brazed Joints

In this study, a copper brazing filler metal coating is fabricated on a 304 stainless steel (304SS) substrate using an electroplating technique. The effect of using electroplated copper brazing filler metal coatings compared to pure copper foil of the same thickness for vacuum brazing of stainless steel joints is investigated. The microstructure and microhardness of the brazed joints are characterized using X‐ray diffraction (XRD), scanning electron microscopy (SEM), and a Vickers hardness tester. The shear strength of the brazed joints is measured using an INSTRON 5869 universal testing machine. The results indicate that the electroplated Cu coating is dense, predominantly with a single cubic phase, with a few copper particles aggregating on the surface. Under electroplating conditions of 20 mA cm−2 for 1 h, the coating thickness was 56 μm. The shear strength of the brazed joint with this coating reached a maximum of 333.7 MPa, which is higher than that of a brazed joint with a 60 μm thick copper foil, which exhibits a shear strength of 303.2 MPa. The shear strength of the brazed joints shows an initial increase followed by a decrease as current density and electroplating time increase. This study provides significant technical support for brazing complex shapes or precision components. It suggests a method to simplify the brazing process, reduce production costs, and enhance the strength of brazed joints.

Deformation Heat in Tension of Steel Elements

The purpose of the work is an approximate computational and experimental assessment of the specific energy intensity and heat generation at various stages of the material’s operation when the sample is stretched. The paper discusses an approximate method for estimating the specific energy intensity and heat generation at four stages of tensile deformation of a steel sample. Finite element modeling of the work of the manufactured sample under elastic-plastic tension was performed in the ANSYS multifunctional software package. The load in the digital model of the sample was applied according to the full-scale test program. The experiment used flat samples in accordance with GOST 1497, a WAW-1000 testing machine with a 100T microcomputer, and a testo 875i thermal imager with a temperature sensitivity of 0.05 °C at 30 °C. We compared the obtained values on graphs of full-scale tests and a digital model of the samples, identifying critical points and deviation values. Phased loading revealed that the development of destruction occurs on the descending branches and is accompanied by the gradual development of local instability of plastic deformation in the form of a “neck”. It is shown that the heating temperature of the tensile metal can be calculated using the formulas proposed in the paper or by calculation using the ANSYS software package. The test results showed that the surface temperatures of the samples at each stage differ significantly. Four main areas were identified on the graph of changes in the sample surface temperature at a point. An analysis of the existing database of measuring instruments and the ability to obtain and process data was carried out. Experimental values of surface temperatures during continuous quasi-static deformation exceed their calculated values (up to 5 times). The kinetics of changes in the temperature field of the sample surface was carried out using thermographic instruments.

An investigation on tribology performance of Abutilon Indicum fibre reinforced polymer composites

This research work investigates the tribological characteristics of Abutilon Indicum Fiber (AIF) reinforced composites with epoxy as the binding agent. The Abutilon Indicum fiber reinforced composites were manufactured by compression molding technique. These composites were fabricated by varying the fiber volume fraction ranging from 5%, 10%, 15% and 20% respectively and considering the fiber length as a fixed factor due to its short length. This research paper illustrates the effects of different fiber volume fractions (5,10,15 and 20%) on the tribological properties such as Specific wear rate (SWR) and Coefficient of friction (µ) of Abutilon Indicum fiber reinforced composites. Sliding wear tests were carried out under dry environment conditions with pin-on-disc wear testing machine. The experiments were performed for each composite with different combinations of testing parameters, sliding loads (10, 20 and 30 N); sliding distances (1,2 and 3 km); sliding speeds (1,2 and 3 m/s). Shore D hardness of 78.22 is determined to be higher for 15% volume fraction of AIF composites. Results conclude that the addition of AIFs in these composites enhanced the tribological performance with good wear resistance in relation with the pure epoxy-based composites with 15% volume fraction of AIFs displaying best results with higher resistance to wear at various operating conditions. Composites produced with 20% volume fraction displays the effects of fiber agglomeration which in turn has an inverse effect on hardness; limits the wear resistance with higher friction and wear rate and such results agree well with the wear debris, pits and contact patches in micrographs. Optimal fiber volume fraction of 15% was suggested in fabrication of composites for usage of AIFs as friction material.

In-vitro comparison of fracture resistance of CAD/CAM porcelain restorations for endodontically treated molars

BackgroundThis study evaluates the fracture strength and patterns of feldspathic porcelain restorations made using CAD/CAM technology for lower first molars with extensive crown destruction. The restorations include post-core and full-contour crown, composite resin core and full-contour crown, and endocrown. This research provides insights into effective restorative options to address tooth fracture risk, supporting minimally invasive procedures and CAD/CAM integration in dental practices.MethodsThis study utilized 80 permanent mandibular first molars, which were divided into four groups: Group I (Post-Core-Full-contour crown), Group II (Core- Full-contour crown), Group III (Endocrown), and Group IV (Control). Root canal treatment was performed on all samples except for the control group. Following access cavity preparation, restorations for each tooth were fabricated using the CAD/CAM system and cemented with resin cement. The specimens were embedded in acrylic blocks. After undergoing thermomechanical aging, the samples were subjected to fracture resistance testing using a universal testing machine, which applied force until fracture occurred. The fracture patterns were subsequently analyzed, and the data were statistically evaluated using the Kruskal-Wallis and Chi-Square tests (p < 0.05).ResultsA significant difference in fracture values under axial forces was observed (p < 0.05). The control group had the highest fracture strength (1830 ± 277 N), while the Core- full-contour crown group showed the lowest (1532 ± 371 N). Failure types varied significantly among the groups (χ2 = 26.886, df = 9, p = 0.001). The most common failure type was Type-2 (33.75%), characterized by restorable fractures, while Type-3 fractures, unrestorable, were the least common (12.5%).ConclusionsThe findings underscore the significance of technological advancements in CAD/CAM for effectively restoring endodontically treated teeth with extensive crown damage. This study contributes valuable insights, emphasizing the clinical relevance of selecting appropriate restorative options to mitigate the risk of tooth fracture associated with coronal restoration failures.

Enhancing horticultural harvest efficiency: The role of moisture content in ultrasonic cutting of tomato stems

Ultrasonic vibration has notable benefits in the harvesting and processing of tomato stems, particularly in reducing cutting force and minimizing moisture loss. Given the anisotropic nature of biological materials, the moisture content of tomato stems significantly impacts their physical properties. This study investigates the influence of varying moisture content on temperature and cutting force during the ultrasonic cutting of tomato stems. Initially, the moisture content of tomato stems at different maturity stages was measured using a water activity meter. Mechanical properties were characterized using a universal testing machine, and thermal properties were analyzed with a differential scanning calorimeter (DSC). Regression models were established to correlate moisture content with these material properties. Additionally, a three-dimensional microscopic model of stem skeletons, interfaces, and fiber bundles was created to simulate the fracture mechanisms during ultrasonic cutting under different moisture levels. Single-factor and response surface optimization experiments were conducted using a custom experimental setup under varying maturity stages, excitation frequencies, and voltage variations. Results showed that after 24 h, the peak temperatures for tomato stems at different maturity stages were 97.84 °C, 80.59 °C, and 74.15 °C, with corresponding cutting forces of 0.492 N, 0.544 N, and 0.998 N, respectively. The discrepancy between experimental results and simulation data was within 10 %. Higher moisture content was found to enhance the thermal conductivity of fiber materials, aiding in the fracture of fiber bundles, thus reducing cutting time and force. This study provides a theoretical foundation for the application of ultrasonic technology in the efficient harvesting and processing of industrial crops, with significant implications for horticultural crop treatment and processing.

Multiaxial creep deformation investigation of miniature cruciform specimen for type 304 stainless steel at 923 K using non-contact displacement-measuring method

Abstract Multiaxial creep investigations at high temperatures are required to guarantee the integrity of structural materials such as boiler pipes for power generation and turbine blades for aviation and industrial applications. The multiaxial creep testing method using a cruciform specimen has several advantages, and the authors successfully downsized the specimen. The authors also developed a technique for the in situ observation of the specimen in an electric furnace and the non-contact displacement measurement in the development of a biaxial tensile creep testing machine for the miniature cruciform specimen. By observing the specimen at a target mark during the creep testing through an observation window installed at the bottom of the furnace, it was possible to visualize the specimen surface variations and obtain the axial strain from the locus of the target marks. The Mises-type equivalent strain was calculated from the axial strains obtained in the equi-biaxial tensile multiaxial creep testing and was compared with the strains obtained in the uniaxial creep testing. The Mises-type equivalent strain can be expressed using a unified method up to approximately 5% of the initial strain in the test, even in the multiaxial stress state.

Impact of applied and preceding pressure on performance and reversible swelling of lithium-ion pouch cells with varying microporous separators

During the compression of battery cells in battery pack production, high forces occur temporarily due to the viscoelastic behavior of the cell components. The magnitude of these forces depends on the compression speed. Shortening the production time and, thus, increasing the compression speed is desirable for cost reduction. However, it must be ensured that the cells are not negatively affected by increased forces during production. The impact of these preceding forces, acting on the cell before operation, and the applied force during operation on the performance and the reversible swelling of 5Ah NMC811/graphite lithium-ion pouch cells are investigated in this study. To this end, a universal compression testing machine was adapted to enable high-precision thickness measurements under defined constant pressure and temperature conditions. In addition, the effects of different microporous separators manufactured via dry process and wet process in an otherwise identical cell configuration were investigated. In the test procedure, the pressure was incrementally increased from 0.01MPa to 2.5MPa. Each measurement was performed at the distinct constant pressure levels, followed by a subsequent measurement at a reference pressure of 0.2MPa to evaluate the impact of the preceding step. The results revealed that elevated preceding pressures on the cell can reduce the discharge rate capability on higher C-rates by up to 11%. The discharge rate capability of the cells with the wet-processed separator was more significantly influenced by increasing applied and preceding pressure than for those with the dry-processed separator. It was found that the reversible swelling of the cell was reduced by applying higher pressures, whereas elevated preceding pressure increased the reversible swelling. The results of this study suggest that cells should not be subjected to excessive forces before operation, for instance, during battery pack production, as this can negatively affect performance and swelling behavior. Furthermore, the mechanical stability of the separator during the pack production process should also be considered when designing a cell.

A realistic approach for evaluating antimicrobial surfaces for dry surface exposure scenarios.

The severe acute respiratory syndrome coronavirus 2 pandemic has raised public awareness about the importance of hygiene, leading to an increased demand for antimicrobial surfaces to minimize microbial contamination on high-touch surfaces. This is particularly relevant in public and private transportation settings, where surfaces frequently touched by individuals pose a significant, yet preventable, risk of infection transmission. Typically, the antimicrobial activity of surfaces is tested using test methods of the International Standards Organization, American Society for Testing and Materials, or Japanese Industrial Standards, which involve complete submersion in liquid, elevated temperature (37°C), and prolonged (24 h) contact periods. However, these conditions do not accurately represent real-world scenarios where surfaces are exposed to air. In this study, we propose a modified test method designed to better reflect real-life conditions in the intended end-use setting. The modifications included using deionized water instead of nutrient broth while preparing bacterial inoculum, applying a small test inoculum to the surface and allowing it to dry, maintaining ambient temperature and relative humidity throughout the contact period, and reducing the contact period to 4 h. With this modified approach, the antimicrobial activity of 20 samples was reassessed. This screening revealed that out of 20 samples, only 2 samples were effective against all species, while 8 samples demonstrated partial effectiveness against selected species, and 10 samples showed no significant effect. These findings highlight the inadequacy of the current test standard and emphasize the urgent necessity for revised and adapted testing method to ensure a reliable and accurate evaluation.IMPORTANCEThe recent severe acute respiratory syndrome coronavirus 2 pandemic has sparked increased demand for antimicrobial surfaces to mitigate the risk of fomites-transmitted infection in both indoors and confined spaces. Commonly, the antimicrobial activity of these surfaces is assessed using test standards established by national standards bodies, which do not distinguish between different application scenarios. While these test standards are suitable for surfaces intended for submerged application, they are inappropriate for antimicrobial surfaces designed for dry surface exposure. The usage of these standards can lead to an overestimation of antimicrobial efficacy. Thus, this study introduces a modified dry exposure test method aimed at better reflecting real-life conditions in the intended end-use setting. Our results revealed the subpar antimicrobial performance of numerous samples, highlighting the necessity to revise and tailor the universal test standard to real-world scenarios in order to ensure a reliable and accurate evaluation.