Small Volume Of Material Research Articles

Analysis of the Creep Mechanism of Low-Alloy Steel in Terms of Plastic Deformation

AbstractAs the proportion of renewable energy sources within the energy grid increases, boiler operations increasingly rely on managing disparities in energy supply. This condition substantially curtails their operational lifespan due to frequent switching cycles. Materials exposed to prolonged stress at high temperatures in harsh environments gradually degrade and eventually fail catastrophically. Thus, understanding processes like creep is essential for accurately evaluating the condition of operational components under new operational standards in power plants. In this regard, this paper introduces an innovative methodological framework for analyzing the creep mechanism, focusing on the plastic deformation of a crucial pipeline segment, specifically an elbow composed of 14MoV6-3 steel, both before and after extensive usage periods (164,000 and 302,000 h). The study explored the development of microstrain from the material's surface employing the electron backscattered diffraction method. This analysis assessed how operational durations influence dislocation structural changes, as examined by synchrotron radiation techniques, across a material depth from 0 to 1.5 mm. Based on these observations, the extent of deformation over time was demonstrated. Furthermore, the evolution of precipitation processes was investigated through transmission electron microscopy. These tests allowed to obtain and compare information on the dislocation structure of the tested steel after service in creep conditions, of small and large volumes of material.

Tensile testing of S690QL1 HSS welded joint heterogeneous zones using small scale specimens and indentation methods

Abstract The welded joints are structures with significant heterogeneity, indicated by their fundamental segmentation into base metal (BM), heat affected zone (HAZ), and weld metal (WM). The heat affected zone, having width in millimeter scale for fusion welding processes, is further segmented into several characteristic regions, having differences in grain structure and size. The microstructural heterogeneity results in significant differences in mechanical properties of individual welded joint zones. Mechanical testing of such small material volumes is inconvenient, or even impossible, using the standard size specimens proposed in testing standards. Requirement to precisely position the specimens, even ones with subsize dimensions, and investigate mechanical properties of specific narrow HAZ regions presents certain challenge. This work investigates the X welded joint of S690QL1 grade high strength steel (HSS), welded with slightly overmatching filler metal. The material tensile properties are tested, using small scale specimens and indentation methods. Small scale specimens are ASTM E8 round tensile subsize and flat sheet mini tensile specimens (MTS). The indentation methods include hardness testing and profilometry-based indentation plastometry (PIP) method, to gain additional insights into material stress–strain behavior. Finally, paper evaluates the testing methods, comparatively processes the collected experimental data, and provides guidelines for heterogeneous structures testing.

Dynamic loading platforms coupled to ultra-high speed X-ray imaging at beamline ID19 of the European Synchrotron ESRF

ABSTRACT The intersection of dynamic compression, high-rate material response and X-ray science has seen rapid growth, leading to the establishment of specialized end-stations at international facilities such as Linac Coherent Light Source LCLS (Matter at Extreme Conditions – MEC) and Advanced Photon Source APS (Dynamic Compression Sector – DCS), both USA. Although these facilities excel in working with X-rays tailored for small material volumes (i.e. < 1 mm 3 ), it needs a different approach to delve into subsequent processes. This is particularly the case in the transition from the micro- to mesoscale: here the ESRF distinguishes itself. The large beam size (several cm2) of the ID19 beamline, in conjunction with a strong high energy component, source flux density, and outstanding imaging sensitivity, enables sub-surface visualization of engineering-scale structures as well as natural systems in representative volume, under high rate and shock. This is particularly valuable when studying materials with complex mesostructures and heterogeneities on relevant volumetric scales, which often dominate the dynamic material response. The study of the behavior of materials under dynamic loading presents a unique challenge due to inherently spanning over multiple lengths- and timescales. The evolution of sudden (thermo)mechanical excitation, starting from the lattice scale and progressing through grains, phase domains, and ultimately to structures, exhibits a spectrum of responses spanning from the microscopic to bulk length scales. Consequently, a diverse range of diagnostics as well as driver instrumentation is required to identify, study, and characterize this material response spectrum. This article shall introduce platforms available at beamline ID19 and underline their potential by selected showcase applications. Community access proposals such as the beamtime Block Allocation Group (BAG) allow for access in a routine manner.

An improved analysis of small punch deformation for evaluating tensile properties

Small punch (SP) method is a promising technique for evaluating tensile properties using small volumes of test material, yet its applicability is bound by large errors in estimation of tensile yield strength (YS) using the yield force (FY) determined by the existing two tangent, offset or bilinear function fitting methods. In this study, a yield force (FY) based on the occurrence of yielding across the specimen thickness is identified through finite element analysis and a methodology is formulated for determination of FY from experimental data, supported with acoustic emission (AE) technique. The YS-FY correlation for various structural steels, Inconel and Aluminium exhibit excellent linearity and standard errors within ±7 %. Based on the onset of plastic instability in SP deformation at an inflection point (Fs, us) of force-deflection curve, the specimen deflection us is shown to correlate with tensile uniform strain better than parameter um (deflection at peak load). The tensile properties of neutron irradiated SS 316 evaluated from SP tests using the methodologies and SP-tensile correlations formulated in this work, are found to be within 6–8 % of the uniaxial tensile test results.

Influence of different heat treatments on fracture behavior of rolling element bearing steels

Rolling element bearings (REB), one of the critical components of mechanical power transmissions, operate under high contact loads concentrated over small volumes of material. The damage caused by fatigue to REBs happens in two stages: the initiation of cracks and the propagation of cracks from areas of stress concentration. To select bearing steels for different applications, it is important to have knowledge about the material’s ability to resist fracture. This study presents results from an experimental investigation of bearing steels manufactured using different heat treatments. Steels were induction-hardened, carburized, and through-hardened, generating varying microstructures. Fracture mechanics tests were conducted using ASTM standards. The data generated is useful for predicting crack initiation and growth behavior under different loading conditions. Microscopic-level investigations are also presented to discern the fracture mechanisms associated with different microstructures.

Изучение условий получения прекурсоров из жаропрочного сплава на основе NiAl, предназначенных для 3D технологий

This article is the second in a series of articles devoted to studying the possibilities of preparing high-quality powder materials from heat-resistant light alloys based on refractory monoaluminides of nickel (β-NiAl), ruthenium (β-RuAl) and the FeCrAl system (fechrals) for the production of compact samples/products of complex shapes using additive technologies with minimal final machining. Additive technologies are based on the use of spherical precursor micropowders with a regulated granulometric composition, good fluidity and an oxide-free surface. In the first article, the possibilities of obtaining precursors from RuAl-based alloys by plasma spheroidization of powders obtained by crushing mixtures from scrap samples of RuAl-based alloys with various additives were considered. This article examines the possibility of obtaining precursors from NiAl-based alloys by plasma spheroidization of powders obtained by crushing mixtures from scrap samples of NiAl-based alloys with various additives. It has been shown that grinding and subsequent grinding of scrap powders in an attritor makes it possible to obtain precursors using the “attrition + plasma spheroidization” scheme with characteristics that make them suitable for additive manufacturing (perfectly round shape, surface almost free of oxides, phase composition – solid solution grains on based on NiAl with thin layers of Ni3Al of nano-sized thickness). The non-uniform distribution of alloying elements in NiAl grains is caused by the short duration (5 hours) of grinding the initial powders of scrap ingots of various compositions obtained using foundry technology. This can be corrected by increasing the grinding duration to 15 hours, which will require the use of the “attrition + granulation + plasma spheroidization” scheme, since the proportion of dispersed powders that must be included in circulation will increase. It has been shown that preliminary reaction alloying in the liquid phase (vacuum arc melting), including the use of recycled materials (scrap alloy samples) as starting materials, allows one to vary the alloy compositions over a wide range, using small volumes of material, and does not require specialized equipment.

In Vivo Evaluation of Bone Regenerative Capacity of the Novel Nanobiomaterial: β-Tricalcium Phosphate Polylactic Acid-co-Glycolide (β-TCP/PLLA/PGA) for Use in Maxillofacial Bone Defects.

Maxillofacial bone defects are treated by autografting or filling with synthetic materials in various forms and shapes. Electrospun nanobiomaterials are becoming popular due to their easy placement and handling; combining ideal biomaterials extrapolates better outcomes. We used a novel electrospun cotton-like fiber made from two time-tested bioresorbable materials, β-TCP and PLLA/PGA, to check the feasibility of its application to maxillofacial bone defects through an in vivo rat mandibular bone defect model. Novel β-TCP/PLLA/PGA and pure β-TCP blocks were evaluated for new bone regeneration through assessment of bone volume, inner defect diameter reduction, and bone mineral density. Bioactive/osteoconductivity was checked by scoring the levels of Runt-related transcription factor x, Leptin Receptor, Osteocalcin, and Periostin biomarkers. Bone regeneration in both β-TCP/PLLA/PGA and β-TCP was comparable at initial timepoints. Osteogenic cell accumulation was greater in β-TCP/PLLA/PGA than in β-TCP at initial as well as late phases. Periostin expression was more marked in β-TCP/PLLA/PGA. This study demonstrated comparable results between β-TCP/PLLA/PGA and β-TCP in terms of bone regeneration and bioactivity, even with a small material volume of β-TCP/PLLA/PGA and a decreased percentage of β-TCP. Electrospun β-TCP/PLLA/PGA is an ideal nanobiomaterial for inducing bone regeneration through osteoconductivity and bioresorbability in bony defects of the maxillofacial region.

Microstructural evolution in shear-punch tests: A comparative study of pure Cu and Cu-Cr alloy

Understanding the mechanisms behind microstructural evolution during shear deformation has been a long-standing area of interest. However, establishing a connection between microstructure, mechanical properties, and the extent of shear deformation is challenging and requires refined experimental approaches. Shear-punch testing (SPT) provides a controlled method to introduce shear into small volumes of material that later can be subjected to detailed microstructural characterization. In this study, we utilize an SPT device to induce shear deformation to pure copper (Cu) and a binary copper-chromium (Cu-Cr) alloy. Electron backscatter diffraction and transmission electron microscopy were used to study the mechanisms of plastic deformation after SPT. Our results indicate that shear deformation of pure Cu produces a dense network of intercepting microshear bands upon sustained deformation. Twin boundaries in annealed Cu undergo transformation into high-angle grain boundaries due to simultaneous deviation from the axis-angle pair condition of 60° misorientation on [111] direction. The presence of 50 vol% Cr particles in the soft Cu matrix altered the shear deformation mechanism. Preferential deformation of the Cu matrix in Cu-Cr alloy led to accelerated shear-induced formation of low and high-angle grain boundaries and subsequent grain refinement. Comparatively, insignificant grain refinement occurred in pure Cu samples even at a strain ∼10 times larger (ε = 4.73) than that of the Cu-Cr case (ε = 0.42). This study sheds light on the microstructural evolution of Cu during shear deformation and highlights the significant influence of a hard second phase in modifying the microstructural response mechanisms of a softer matrix.

Semi-analytical model for predicting mechanical properties of metals using flat truncated cone indenter and its application

Based on the energy density equivalence method, a semi-analytical model describing the relationship between the material parameters of Hollomon’s law, load, displacement, and indenter geometry under flat truncated cone indentation (FTCI) was proposed. For a specific indenter, the model parameters were determined by presetting a small volume of material in finite element analysis (FEA). An FTCI test method to obtain the strain hardening coefficient and strain hardening exponent of the material from the load–displacement curve was proposed, and a damage factor (β) model was developed to predict the elastic modulus of the material by using multi-stage loading and unloading tests. Indentation tests were conducted on ten types of steel material using two types of flat truncated cone indenters with 15° and 30° angles. The results showed that the errors between the Young’s modulus measured via the indentation and uniaxial tensile tests were less than 5%; the relative errors between the indentation tensile strength and yield strength by the 30° flat truncated cone indenter and the uniaxial tensile test were less than 6%. For the 30° flat truncated cone indenter, the goodness-of-fit between the stress–strain relationship measured via the indentation and the uniaxial tensile tests was more than 0.95, and 80% of the goodness-of-fit was more than 0.97.

Apple-like Shape of Freezing Paraffin Wax Droplets and Its Origin.

Paraffin wax stores energy in the form of latent heat at a nearly constant temperature during melting and releases this energy during solidification. This effect is used in industrial energy storage. At the same time, the possible deformation of even small volumes of material as a result of phase change is insufficiently studied. In this paper, the physical nature of such deformation, probably for the first time, is studied on the example of a droplet of paraffin wax. An unusual change in the shape of a melted droplet of paraffin wax placed on a relatively cold glass plate was observed in the laboratory experiments. As the droplet solidifies, its upper surface becomes nearly flat, and a dimple is formed in the center of this surface, making the droplet look like a fruit (pumpkins are more commonly shaped like this, but the authors prefer apples). A series of experiments, as well as physical and numerical modeling of the droplet's thermal state, taking into account the formation of a mushy zone between liquidus and solidus, made it possible to understand the role of gravity and gradual increase in viscosity and density of paraffin wax on changing the droplet shape and, in particular, to clarify the mechanism of formation of the dimple on its upper. It was shown that the mushy zone between the liquidus and solidus of the paraffin wax is responsible for the dimple formation.

Solid-State Power Combining for Heating Small Volumes of Mixed Waste Materials

Microwave heating of waste results in chemical breakdown that can lead to conversion of mixed waste materials to fuel. Heating waste mixtures with microwave energy rather than incineration results in faster breakdown and can therefore be more efficient. Here we address heating of small volumes of mixed food waste materials with widely differing and temperature-dependent electrical properties. Uniform heating is accomplished with mode mixing within a loaded cavity and by spatial power combining of solid-state power amplifiers (SSPAs). We present a heating comparison of two circuit-combined and spatially-combined 2.45 GHz 70-W 65% efficient GaN SSPAs with controlled relative phase. The heating efficacy is shown to improve by volumetric combining inside the waste loading. The temperature changes in several locations and for several common waste materials and mixtures are investigated and compared to FEM electromagnetic simulations, as well as FDTD multi-physics simulations that incorporate thermal dependence of material properties. The approach is scalable in volume and power, demonstrated by a simulation comparison of the 1.4 L small cavity to a 5.2 L volume.

Fluid inclusions in minerals: from geosciences to the physics of water and back

Natural mineral samples often contain small volumes of trapped fluid material. They carry information about the history of the host mineral and its environment, and for this reason are used by geoscientists. Physicists and physico-chemists have successfully harnessed water inclusions in quartz to bring liquid water to a metastable state, at a pressure well below its equilibrium pressure with vapor. The pressure can reach negative values as large as -140 MPa, which exceeds by far the limits of other techniques, and approaches the theoretical threshold for spontaneous nucleation of a vapor bubble. This has enabled a deeper understanding of nucleation and of the anomalies of water. In turn, the optical techniques developed to study water’s properties have recently found a new application in the reconstruction of palaeotemperatures in surface processes. I review here some aspects of fluid inclusions, these fascinating objects at the crossroads between disciplines.

A microfluidics-assisted photopolymerization method for high-resolution multimaterial 3D printing

3D printing and bioprinting are recognized as key technologies for the construction of complex micro-devices, micro-environments, and culture models. Thanks to their potential to produce precisely heterogeneous and 3D architectures, multimaterial printing methods, which enable the production of functional 3D structures integrating multiple materials, have attracted specific attention. Nevertheless, combining multimaterial and high-resolution printing is still a major challenge, and the available technologies do not provide simultaneously the resolution and multiplexing capabilities required to create heterogeneous 3D environments. In this work, we introduce the 3D-FlowPrint concept, which involves an opto-microfluidic printhead immersed in a liquid and moved above a surface. This technology combines the convenience of microfluidics in terms of the handling and delivery of small volumes of materials with the resolution provided by laser lithography. Delivered materials are hydrodynamically confined under the printhead owing to controlled aspiration of the injected material, ensuring a continuous supply of material and avoiding cross-contamination issues. Combining microfluidics with photo-polymerization provides unique advantages as it separates the polymerization process from the material delivery, permitting high-resolution polymerization (down to 10 μm) and multimaterial handling (switching time below 60 s). We present a first proof-of-concept using poly(ethylene glycol) diacrylate (PEGDA)-based hydrogels as a photosensitive material model, along with a detailed investigation of the influence of exposure parameters, printhead velocity, and hydrodynamic parameters on the fabrication of 2D and 3D heterogeneous structures. 3D-FlowPrint allows the creation of sub-millimetric to millimetric scale objects with multimaterial designs. A first validation was performed to show the potential of the approach in biology for the creation of engineered microenvironments for cell culture.

First Asia-Pacific experience of trans-bronchial core biopsy with a Franseen needle.

Endobronchial ultrasound guided transbronchial needle aspiration (EBUS-TBNA) is the standard for evaluating mediastinal and hilar lesions. EBUS-TBNA is limited by small volume of material obtained for immunohistochemistry (IHC) and ancillary studies important for oncological therapies. The Franseen AcquireTM needle is designed for EBUS-transbronchial needle core biopsy (TBNB) allowing larger core sizes with evidence in gastroenterology literature but little in pulmonology. This study reports the first Asia-Pacific experience of EBUS-TBNB and adequacy of samples for diagnosis and ancillary studies. A retrospective cohort study of EBUS-TBNB at the Royal Adelaide Hospital was conducted between December 2019 and May 2021. Diagnostic rate, adequacy for ancillary studies and complications were evaluated. Samples were flushed into formalin for histological processing with no rapid on-site cytological evaluation (ROSE). For suspected lymphoma, samples were flushed into HANKS for flow cytometry. Cases performed with the Olympus VizishotTM during the same 18-month were similarly analysed. One hundred and eighty-nine patients were sampled with the AcquireTM needle. Diagnostic rate was 174/189 (92.1%). Where reported [146/189 (77.2%)], average core aggregate sample size was 13.4 mm × 10.7 mm × 1.7 mm. For non-small cell lung cancer (NSCLC) cases, 45/49 (91.8%) had adequate tissue for programmed cell death-ligand 1 (PD-L1). 32/35 (91.4%) adenocarcinoma cases had sufficient tissue for ancillary studies. There was one false negative malignant lymph node at the first AcquireTM procedure. There were no major complications. One hundred and one patients were sampled with the VizishotTM needle. Diagnostic rate was 86/101 (85.1%) with only 25/101 (24.8%) having reported tissue cores (P<0.0001 of VizishotTM) with the remaining samples processed via cell block. AcquireTM EBUS-TBNB diagnostic rate is comparable to historical data with >90% of cases having sufficient core material for ancillary studies. There appears to be a role for the AcquireTM alongside the standard of care for the work up of lymphadenopathy and particularly for lung cancer.

Feasibility analysis of damage assessment with the CRT method

The feasibility of damage assessment by CRT (creep-relaxation test) method was investigated. Four samples with different damage states were selected from creep data. ZD and ZCRT were proposed to describe the deviation caused by damage in creep and CRT respectively and their linear relationship shows that CRT is practicable and has the same effect as creep in damage assessment. PCRT and Pmin are the parameters obtained by normalizing the CRT data and creep data by the ε˙-T parameter method, respectively. PCRT-C represents PCRT under the same damage state and stress as Pmin according to the regression curves. The linear relationship between the minimum creep rate ε˙min and the CRT’ s creep rate ε˙CRT was obtained from the relationship between Pmin and PCRT-C, so that the creep rupture life can be predicted. Thus, the CRT model can save a lot of samples in damage assessment and life prediction with high accuracy, so it can reduce damage to the original components, making it more suitable for sampling small volumes of materials. Furthermore, different damage states have the same mechanism of dislocation motion during stress relaxation and creep according to activation energies and volumes, and thus the CRT method and creep exhibit similar responses to differences in material damage states due to the consistency of dislocation thermal activation motion.

A New Method for the Determination of Amisulpride in a Small Volume (200 μL) of Human Saliva Using LC-DAD Supported by SPE

(1) Background: The concentration of amisulpride, an atypical antipsychotic drug, is most often determined in the blood, with many inconveniences. An alternative may be to use saliva as a diagnostic material for this purpose. The development of a method to determine amisulpride in saliva using a small volume of biological material could significantly improve patient comfort during Therapeutic Drug Monitoring (TDM). (2) Methods: Therefore, the aim of this study was to develop a method to determine amisulpride in 200 μL of saliva using solid-phase extraction for isolation and liquid chromatography with a diode array detector (LC-DAD) for quantitative analysis. (3) Results: The method was validated by determining its linearity in the concentration range 5–500 ng/mL (R2 &gt; 0.99), and the intra- and inter-day precision expressed as coefficient of variation (CV%) did not exceed 9%. (4) Conclusions: The developed method was used to determine the salivary concentration of amisulpride in patients treated with the studied compound, confirming its usefulness in TDM.

Can a bioactive interbody device reduce the cost burden of achieving lateral lumbar fusion?

Intervertebral devices are increasingly utilized for fusion in the lumbar spine, along with a variety of bone graft materials. These various grafting materials often have substantial cost burdens for the surgical procedure, although they are necessary to overcome the limitations in healing capacity for many traditional interbody devices. The use of bioactive interbody fusion devices, which have demonstrable stimulatory capacity for the surrounding osteoblasts and osteoprogenitor cells and allow for osseointegration, may reduce this heavy reliance on osteobiologics for achieving interbody fusion. The objective of this study was to evaluate the rate of successful interbody fusion with a bioactive lateral lumbar interbody titanium implant with limited volume and low-cost graft material. The authors conducted a retrospective study (May 2017 to October 2018) of consecutively performed lateral lumbar interbody fusions with a bioactive 3D-printed porous titanium interbody device. Each interbody device was filled with 2-3 cm3/cage of a commercially available ceramic bone extender (β-tricalcium phosphate-hydroxyapatite) and combined with posterior pedicle screw fixation. No other biological agents or grafts were utilized. Demographic, clinical, and radiographic variables were captured. Fusion success was the primary endpoint of the study, with graft subsidence, fixation failure, and patient-reported outcomes (Oswestry Disability Index [ODI] and visual analog scale [VAS]-back and -leg pain scores) collected as secondary endpoints. The authors utilized a CT-based fusion classification system that accounted for both intervertebral through-growth (bone bridging) and ingrowth (integration of bone at the endplate-implant interface). In total, 136 lumbar levels were treated in 90 patients. The mean age was 69 years, and 63% of the included patients were female. Half (50.0%) had undergone previous spinal surgery, and a third (33.7%) had undergone prior lumbar fusion. A third (33.7%) were treated at multiple levels (mean levels per patient 1.51). One year after surgery, the mean improvements in patient-reported outcomes (vs preoperative scores) were -17.8 for ODI (p < 0.0001), -3.1 for VAS-back pain (p < 0.0001), and -2.9 for VAS-leg pain (p < 0.0001). Bone bridging and/or appositional integrity was achieved in 99.3% of patients, including 97.8% who had complete bone bridging. No fixation loosening or implant failure was observed at any segment. Low-grade graft subsidence (Marchi grade ≤ I) occurred in 3 levels (2.2%), and intraoperative endplate violation occurred twice (1.5%). High-grade subsidence was not found. No implant failure or revision surgery for pseudarthrosis/subsidence was necessary. The use of bioactive titanium interbody devices with a large surface footprint appears to result in a very high rate of effective fusion, despite the use of a small volume of low-cost biological material. This potential change in the osteobiologics required to achieve high fusion rates may have a substantially beneficial impact on the economic burden inherent to spinal fusion.

Designing High Energy Density Batteries for Abuse Tolerance

Every month or so there is a news article announcing a recall of a product due to overheating and thermal runaway of the battery pack. This has occurred more frequently as the energy density of battery cells has increased. Here we present a method to greatly improve the tolerance of a cell to internal shorting and nail penetration that is uniquely enabled by Enovix LiB cells.A higher energy density results in less mass to absorb the energy released and less surface area to dissipate the heat. Frequently the failure has been identified as being initiated by an internal short between anode and cathode current collectors within a cell. These internal shorts have been associated with mechanical damage to the cell container, anode-separator-cathode alignment, and lithium dendrite breaches of the separator.External short circuits are most likely to be controlled by the battery management system before damage to the cell. In the event of an external short circuit that bypasses the BMS the power released uniformly heats the entire cell. A safe landing of the cell is reliant on the separator or electrolyte increasing resistance to the point that heat transfer from the surface of the cell can maintain the temperature below thermal run away.Shorts created by an internal short or mechanical penetration of a cell are more dangerous than external shorts. The short typically occurs at a point such that power is dissipated non-uniformly in a very small volume of material. This volume rapidly heats beyond thermal run away before the remaining cell increases significantly in temperature such that separator shutdown or electrolyte shutdown can not be relied upon to prevent thermal runaway. A thermal runaway event due to an internal short can be prevented by reducing the energy released at the point of the short.Internal shorts are difficult to create purposefully without modifying the cell. Frequently an internal short is simulated by mechanically penetrating the cell with a nail. The nail breaches the cell container and penetrates the current collector(s) and separator. Penetration of the cell is typically done perpendicular to the plane of the current collector which produces a parallel connection between all layers of anode and cathode current collectors with out much mixing of anode and cathode active materials. Penetration parallel to the current collectors tends to crush the separator and current collectors, mixes a larger volume of active materials, and connects few layers of the current collectors. The larger volume of active material mixing and fewer parallel short locations results in a more challenging test of the cell.Enovix battery architecture is designed for those systems that require a significant pressure between anode and cathode layers. A feature of this design is the segmentation of the cell into small area sub cells that are connected to a bus. Each sub cell bus connection can be designed to limit the current from the remainder of the cell in case of a short in the sub cell. We present abuse testing results of 3.4 AH cells with sub-cell protection that enable survival of nail penetration testing even when penetrated parallel to the current collector surface.

Estimation of UTS from small punch test using an improved method

Small punch test is a promising method for evaluating the tensile and fracture properties from small volumes of material especially for assessing material degradation of structural components in service. In this paper, the existing methods to determine ultimate tensile strength (UTS) from small punch test are revisited and an improved method is proposed and validated through finite element analysis and experiments. In the new method, the force corresponding to the inflection point in the slope of force-deflection curve in the membrane stretching regime is identified for UTS correlation. The onset of plastic instability during small punch deformation is associated with this inflection point. The UTS correlation determined from the slope based method exhibited stronger linearity with lower relative error compared to the existing methods for a wide range of material strength and ductility.

Homogenization of discrete diffusion models by asymptotic expansion

AbstractDiffusion behaviors of heterogeneous materials are of paramount importance in many engineering problems. Numerical models that take into account the internal structure of such materials are robust but computationally very expensive. This burden can be partially decreased by using discrete models, however even then the practical application is limited to relatively small material volumes. This paper formulates a homogenization scheme for discrete diffusion models. Asymptotic expansion homogenization is applied to distinguish between (i) the continuous macroscale description approximated by the standard finite element method and (ii) the fully resolved discrete mesoscale description in a local representative volume element (RVE) of material. Both transient and steady‐state variants with nonlinear constitutive relations are discussed. In all the cases, the resulting discrete RVE problem becomes a simple linear steady‐state problem that can be easily pre‐computed. The scale separation provides a significant reduction of computational time allowing the solution of practical problems with a negligible error introduced mainly by the finite element discretization at the macroscale.