Microscale Analysis Research Articles

Micro-scale residual stress and deformation analysis in bimetal bronze-stainless steel samples produced by laser powder bed fusion technology

Additive manufacturing technologies attract significant interest as a route to fabricate structural elements with complex net shapes. 3D printing may offer the option of combining dissimilar materials within one build, like dissimilar metals in the case of laser powder bed fusion. The strength of bimetallic interfaces formed by immiscible metals such as stainless steel and copper alloys depends on the mechanism of bonding, the presence and nature of defects, and residual stresses, placing the focus of interest on the structure–mechanical performance relationship in the vicinity of the bimetallic interface. In this article, we report an investigation of laser powder bed fusion fabrication of thin plate bimetallic bronze-stainless steel samples. Sample characterization was performed using several techniques including surface topography and fractography, energy dispersive X-ray spectroscopy, electron backscatter diffraction, mechanical testing with digital image correlation mapping of strains during in situ tension inside scanning electron microscope. Spatially resolved evaluation of the local residual stress was carried out using the Korsunsky Focused Ion Beam micro-ring-core drilling method (FIB-DIC). Pure bronze and stainless steel samples fabricated separately possessed good strengths (ultimate tensile strengths of 150 MPa and 850 MPa, respectively) and significant amounts of ductility (local strains to failure of 0.8% and 1.2%, respectively), in spite of the presence of a relatively coarse and porous structure. Although the values for the bimetallic sample were somewhat reduced, they also demonstrated good mechanical properties, with the ultimate tensile strength of 105 MPa and 0.7% ductility. The fracture of bimetal takes place within the bronze at a distance of about 150 μm from the interface. The present report discusses the insights obtained, and charts the pathways towards further improvement of bimetal joint strengths through simple modifications of the laser powder bed fusion printing procedures.

Characterization of Phase Separated Planar Lipid Bilayer Membrane by Fluorescence Ratio Imaging and Scanning Probe Microscope

The lipid membrane forms nanodomains (rafts) and shows heterogeneous properties. These nanodomains relate to significant roles in various cell functions, and thus the analysis of the nanodomains in phase-separated lipid membranes is important to clarify the function and role of the nanodomains. However, the lipid membrane possesses small-sized nanodomains and shows a small height difference between the nanodomains and their surroundings at certain lipid compositions. In addition, nanodomain analysis sometimes requires highly sensitive and expensive apparatus, such as a two-photon microscope. These have prevented the analysis by the conventional fluorescence microscope and by the topography of the scanning probe microscope (SPM), even though these are promising methods in macroscale and microscale analysis, respectively. Therefore, this study aimed to overcome these problems in nanodomain analysis. We successfully demonstrated that solvatochromic dye, LipiORDER, could analyze the phase state of the lipid membrane at the macroscale with low magnification lenses. Furthermore, we could prove that the phase mode of SPM was effective in the visualization of specific nanodomains by properties difference as well as topographic images of SPM. Hence, this combination method successfully gave much information on the phase state at the micro/macro scale, and thus this would be applied to the analysis of heterogeneous lipid membranes.

Representative volume element for microscale analysis of additively manufactured composites

The development of additive manufacturing technologies has been followed by an increase in material variety, especially by the introduction of numerous types of reinforcements to enhance the mechanical performance of basic polymers. Since the microstructure of these novel composites may vary in types, sizes, shapes, and ratios of reinforcements, it is necessary to optimize these parameters before conducting experimental validation. Hence, a microscale analysis based on representative volume element modeled according to the statistically significant constituent’s data acquired from the microscopic analysis is proposed. Moreover, to account for the weak fiber/matrix bounding in comparison with the ideal bond assumption, cohesive behavior can be prescribed at these interfaces. According to the type of reinforcement, three variations of RVE-s have been modeled in the Abaqus CAE environment utilizing periodic boundary conditions, and each was tested for longitudinal, transverse, and shear loading cases. The validation has been conducted on two unidirectional [0] and [90], as well as one multidirectional [45/−45]4s carbon fiber reinforced composite specimens. The experimental tests have been performed quasistatically and monitored using a digital image correlation system. Experimental and numerical results have been systematically compared with the published data, proposing a guideline for the protocol applicability and the necessity for further improvements.

The Application of Micro-Scale Analysis Tools in Industrial Problem Solving

The Application of Micro-Scale Analysis Tools in Industrial Problem Solving

ANALYSIS OF LOW-COST UAV PHOTOGRAMMETRY SOLUTIONS FOR BEACH MODELLING AND MONITORING USING THE OPENSOURCE QUANTUM GIS

Abstract. Coastlines are fundamentally unique features. Their behavioural patterns are predominantly subjects of numerous environmental and engineering studies. With the magnitude of the effects of coastal flooding and erosion, there is a need for accurate techniques for data capture and data processing. With an emphasis on the zero-cost open source GIS software, there is no existing evaluative procedure for demonstrating the analytical capabilities of large-scale UAV-based outputs for microscale analysis for small changes on the beach such as sediment movement, erosion/accretion of individual features. There were four different drone surveys in the study area to determine microscale change over time. A three-stage analysis procedure helps in determining the overview of the coastline and highlights the region(s) of optimum change requiring further spatial analysis with micro-scale change detection. Results obtained show the analytical capabilities of large-scale UAV-based outputs for relatively small but detailed analysis using the open-source QGIS. Results obtained show that spatial analyses of the zoomed areas at different viewpoints and scales improve the confidence level of the hillshading and contour of that particular section on the coastline. The UAV photogrammetry and the three-stage analysis procedure can detect a 1cm change on the beach using the free and open-source QGIS software. It shows the profile modelling of the coastal inundations for both pre and post-flooding events at sub-centimetre intervals can be obtained from QGIS modelling, data computation, analysis, and visualization.

A mesoscale approach to simulate residual deformations in complex laser welding processes

Laser welding can be characterized by very small radii of beam, in the order of tenths of a millimeter, and very short high power inputs (more kW in few ms), and thus, it can be certainly classified as a microscale process with a high level of physical complexity. This is clearly incompatible, due to the high computational costs, with the analysis of macroscale processes related to large geometries and non-uniform welding patterns. In order to overcome this issue, a simplified finite element method (FEM)–based thermo-elastoplastic model is presented to simulate heat transfer and residual deformations due to thermal expansion and material plasticity. The idea is to substitute the microscale analysis with a mesoscale approach that renounces to describe in detail all the physical phenomena occurring in the heated zone and focuses attention on the correct prediction of the keyhole depth and weld pool size, that are the most important parameters to describe the mechanical characteristics of the welded joint. The concept of passive element, based on the numerical adjustment of the material properties in order to take into account the orthotropic behavior during the keyhole formation, is introduced. In particular, the new approach has been tested on the pulsed laser welding process of two overlapping DC04 steel plates with thickness of 0.5 mm (so-called sandwich) and validated through experimental tests involving different input parameters, such as power, pulse duration and frequency, speed, and geometrical pattern.

Direct observation of the microfiltration of yeast cells at the micro-scale: Characterization of cake properties

This study examines the accumulation of yeast cells at the membrane surface and the morphology of the formed cake through microscale monitoring and analysis of the microfiltration process. An original dead-end microfiltration device with a model membrane was designed and coupled with an optical imaging system to provide direct observation from the side, allowing in-situ real time study of the filtration operation (Valencia et al. 2020 [1]). Here, the deposition of yeast cells, monodispersed and polydispersed particles, in the same size range that yeast cells, was analyzed. Image processing was used to perform a quantitative characterization of cake morphological properties in terms of height, porosity, permeability, Kozeny coefficient and specific resistance. The cakes formed by monodispersed spherical and non-spherical rigid particles exhibit a similar incompressible behavior with higher porosity than yeast cakes, with mean porosity values of 0.38 for the rigid particles and 0.15 for the yeast at the end of the filtration run, respectively. The cake obtained by the microfiltration of a model suspension of polydispersed particles close to yeast size and shape is more compact (porosity of 0.29) and less permeable. However, polydispersity does not fully explain yeast cake properties, in particular its compressibility. Indeed, the yeast cake has a high compressibility index n = 1.1, which is reflected in a significant volume expansion of the yeast cake after transmembrane pressure was removed.

Application of the Point-Descriptor-Precedence representation for micro-scale traffic analysis at a non-signalized T-junction

ABSTRACT An intersection of two or more roads poses a risk for potential conflicts among vehicles. Often the reasons triggering such conflicts are not clear, as they might be too subtle for the human eye. The environment also plays a part in understanding where, when, and why a particular vehicle interaction has occurred in a certain way. Therefore, it is of paramount importance to dive deeper into the vehicle interaction at a micro-scale within the embedded geographical environment, particularly at the intersections. This would in turn assist in evaluating the association of vehicle interactions with conflict risks and near-miss accidents. Moreover, detection of such micro traffic interactions could also be used to improvise the complexity of the already established transport infrastructure. Conversely, traffic at intersections has been explored mainly for flow estimation, capacity and width measurements, and traffic congestion, etc., whereas the detection of micro-scale traffic interactions at intersections remains relatively under-explored. In this paper, we present a novel approach to retrieve and represent micro-scale traffic movement interactions at a non-signalized T-junction by extending a recently introduced qualitative spatiotemporal Point-Descriptor-Precedence (PDP) representation. We study how the PDP representation offers a fine solution to study the interaction of traffic flows at intersections. This permits tracking the micro-movement of vehicles in much finer detail, which is used later to retrieve movement patterns from a motion dataset. Unlike conventional approaches, we start our approach with the actual movements before modeling the static intersection environment. Additionally, with the aid of illustrative examples, we discuss how the length, width, and speed of the vehicles can be exploited in our approach to detect specific patterns more accurately. Additionally, we address the potential benefits of our approach for traffic safety assessment and how it can be extended to a network of intersections using different transport modes.

Testing the global significance of the sulfur isotope record of the ca. 2.0 Ga Zaonega Formation: A micro-scale S isotope investigation

The Paleoproterozoic metasedimentary rocks of the Zaonega Formation (Onega Basin, NW Russia) are important archives of inferred global environmental change following the initial oxygenation of the Earth’s atmosphere and oceans. However, the geochemical signals preserved in these exceptionally organic-and pyrite-rich metasedimentary rocks and their environmental meaning remain contested. In particular, the Zaonega Formation’s unusually high pyrite sulfur isotope ratios (δ34S) have been explained by either global or local forcings acting on sulfur cycling processes. We tested former interpretations of the Zaonega Formation’s sedimentary pyrite record by integrating bulk and micro-scale δ34S analysis to discriminate the isotopic signatures of different generations of pyrite and determine the underlying mechanisms contributing to δ34S variability. We show that the prolonged genesis of pyrite occurred via multiple stages and included precipitation from early diagenetic fluids, organic matter pyritization, and late-stage alteration fluids. Our results demonstrate that early-stage pyrite typically carries more variable and lower δ34S values than late-stage pyrite. Although the early pyrite captures pore water S isotope signatures least evolved from the seawater, their contribution to the bulk δ34S results can be dwarfed by the greater volume of late-stage coarse pyrite. Consequently, determining the sequence of pyrite precipitation and δ34S characteristics of individual generations in any given sample are fundamental to interpreting bulk δ34S records. Our micro-scale results suggest that previous estimates based on bulk pyrite data (ca. 6 to 18‰) should not be related to the original seawater sulfate’s isotopic composition. These results demonstrate that a thorough understanding of the geological context and mechanisms associated with S-cycling, and pyrite formation is necessary to interpret bulk δ34S records accurately.

Strain-rate based arclength model for nonlinear microscale analysis of unidirectional composites under off-axis loading

In this paper, a micromechanical framework for modeling the rate-dependent response of unidirectional composites subjected to off-axis loading is introduced. The model is intended for a thin slice representative volume element that is oriented perpendicular to the reinforcement of the composite material. The testing conditions from a uniaxial off-axis test are achieved by a dedicated strain-rate based arclength formulation. The constraint equation of the arclength model is constructed such that the deformation state of the micromodel, as imposed in its local coordinate system, corresponds to the strain-rate applied on the material in global frame of reference. The kinematic description allows for finite strains in the material, meaning that the micromodel changes orientation during the deformation process. This geometric nonlinear effect is also included in the evaluation of external loading, ensuring that the external forces are equivalent to the applied off-axis stress in global coordinate system. Several examples are considered in order to show that the model resolves rate-dependency of the material, accounts for different off-axis loading, and captures finite strains exactly. Additionally, a small strain version of the model is derived from the general nonlinear framework. Results obtained with this simplified approach are compared to results of the large deformation framework.

Two-scale Modeling of Composites damage with Voronoi cell finite element method for microscale computation

This paper develops an adaptive two-level computational model that includes macro and microscope analysis. Traditional displacement based finite element is used for macroscopic analysis, while Voronoi cell finite element model is used for computations of arbitrary heterogeneous domains. For an adaptive analysis, when local area may be destructive, VCFEM mesh is used instead of corresponding finite element for damage analysis. Because VCFEM model and finite element are all taken the nodal displacements as field variables, therefore, based on the idea of multigrid by the adaptive mesh adjustment, let finite element edge length and VCFEM edge length are basically the same, two kinds of elements were connected together through the use of shared nodes and use the order of the edge displacement interpolation. This formed a two-scale model of the coexistence of macro structure and micro structure. For microscale analysis, three Voronoi cell finite models (VCFEM) are build including perfect interface bonding model, interface debonding model and multiple matrix cracks model. Numerical example is executed for validating the effectiveness of the two-scale model method.

Electropolymerization of Pyrrole-Based Ionic Liquids on Selected Wireless Bipolar Electrodes.

This paper describes an electropolymerization-based on-chip valving system, accomplished by electrosynthesis of conductive polymeric ionic liquid (CPIL) films at selected points within an array of bipolar electrodes (BPEs), in which each of these wireless electrodes spans an IL-aqueous phase boundary. The low viscosity and high hydrophobicity of the CPIL precursor allow it to be patterned by established microfluidic methods. This advancement has the potential to impact microscale analysis because it allows on-demand creation of solid CPIL microstructures at locations specified by microfluidics, phase boundaries, and electrode potentials. To achieve this outcome, an imidazolium-based IL was functionalized with a pyrrole moiety, and the viscosity was tuned by choosing the appropriate counterion to form a CPIL with the desired viscosity, hydrophobicity, and oxidation potential. This monomer species was then introduced into a microfluidic device, which was prefilled with an aqueous buffer solution. The device comprised many parallel microchannels lined with nanoliter-scale chambers. BPEs interconnected the channels such that the BPE tips were each aligned to a chamber opening. The electrodes contacting the outermost channels were connected directly to a power supply and functioned as driving electrodes. The CPIL displaced the buffer in the channels and established a phase boundary at the opening of each chamber, thereby digitizing the aqueous phase. Finally, an alternating square waveform (under mode 1) was applied for 5 min to yield immobilized polymer films at a location defined by the BPE poles. In total, three modes were developed and three corresponding polymer film patterns were formed. Under mode 2, a DC power supply was used to achieve a dissymmetrical polymer film pattern, and, under mode 3, a regional polymer film pattern was formed under an AC potential with a DC offset. Our preliminary results demonstrate that the generated polymer films are immobile and sufficiently thick to seal the chambers at room temperature over the duration of our observation window (50 min), and this seal is maintained even at elevated temperatures that induce partial evaporation of the chamber contents. A key point is that this method is compatible with a preceding step─dielectrophoretic capture of single melanoma cells within the nanoliter-scale chambers.

How do time-bound practices initiate local sustainability pathways?

• Identifies need for micro-scale analysis of the emergence of transition pathways • Combines temporality and sustainability in theoretical terms • Draws on multi-actor analysis of district-level urban living lab • Presents how time-bound practices relate to persons, place, and permanence • Points out the analytical significance of reconfiguration This paper examines the micro-scale ignition of sustainability pathways in multi-actor collaboration in an urban living lab in Tampere, Finland, and aims to capture the reconfigurations that lead to urban sustainability. The conventional model of sustainability focusing on economic, environmental and social pillars does not correspond to the dynamic nature of urban sustainability. Thus, we utilise a sustainability framework that is more sensitive to urban conditions and compatible with a temporal typology of practices carried out by diverse actors in the living lab. The results show, first, that the emerging sustainability pathways are based on the coexistence of diverse actors and resources, develop through interconnected temporal phases of practices and are differently sensitised to place depending on the temporal phase. The sustainability pathways reach permanence when the actions of catalysing and revamping take the mode of routinisation. Second, we locate the generative moments of reconfigurations and address the cumulative nature of sustainability. In conclusion, this helps to recognise the incipient forms of sustainability pathways and their potential for local sustainability transitions.

Exploring Urban Forms Vulnerable to Urban Heat Islands: A Multiscale Analysis

Understanding urban forms vulnerable to urban heat islands provides urban planning measures to improve urban heat islands and offering insight into different sustainable urban forms. The purpose of this study was to investigate the relationship between the urban heat island effect and urban forms, to explore which urban forms are vulnerable to this effect, and to present urban planning measures to alleviate urban heat islands. This study also conducted an analysis on two scales, the macro- and micro-dimensions, to develop policy suggestions for urban heat island mitigation. In the macro-scale analysis, the relationship between urban shape and urban heat islands was investigated through a statistical approach using a regression equation, and in the micro-scale analysis, a spatial analysis method using urban climate zones (LCZs) was used.

A framework for the assessment of electric bus charging station construction: A case study for Stockholm's inner city

Electromobility has gained momentum in the last years following the efforts to reduce transportation-related emissions. In this context, efficient charging infrastructure is vital to foster the expansion of electric vehicles. This paper presents a standardized framework for micro-scale analysis of potential charging locations for electric buses aiming at easing the analysis process and promoting the expansion of electric buses. The framework is tailor-made for the Municipality of Stockholm and tested in two city-centre public transport hubs, namely Odenplan and Slussen. However, the framework can be used in other locations by implementing minimum changes. Connecting charging stations to the power grid is identified as the main drawback in city-centre locations due to their high impact on the grid. Lack of available capacity at nearby connection points results in long distance connections, reaching up to 1 km in some cases. Such connections impact the overall cost of electrification directly, as they may account for up to 63% of the total cost. Although other issues regarding space availability and operational efficiency also need to be addressed, such as the lack of enough dwell time to charge the batteries, the framework proves the suitability of these inner-city locations as charging points.

Physicochemical Characterization of Asphaltenes Using Microfluidic Analysis.

Crude oils are complex mixtures of organic molecules, of which asphaltenes are the heaviest component. Asphaltene precipitation and deposition have been recognized to be a significant problem in oil production, transmission, and processing facilities. These macromolecular aromatics are challenging to characterize due to their heterogeneity and complex molecular structure. Microfluidic devices are able to capture key characteristics of reservoir rocks and provide new insights into the transport, reactions, and chemical interactions governing fluids used in the oil and gas industry. Understanding the microscale phenomena has led to better design of macroscale processes used by the industry. One area that has seen significant growth is in the area of chemical analysis under flowing conditions. Microfluidics and microscale analysis have advanced the understanding of complex mixtures by providing in situ imaging that can be combined with other chemical characterization methods to give details of how oil, water, and added chemicals interface with pore-scale detail. This review article aims to showcase how microfluidic devices offer new physical, chemical, and dynamic information on the behavior of asphaltenes. Specifically, asphaltene deposition and related flow assurance problems, interfacial properties and rheology, and evaluation of remediation strategies studied in microchannels and microfluidic porous media are presented. Examples of successful applications that address key asphaltene-related problems highlight the advances of microscale systems as a tool for advancing the physicochemical characterization of complex fluids for the oil and gas industry.

The Permeability Alternation of Shale Fractures due to Sc-CO2 Soaking: Implications for Sc-CO2 Fracturing and Deep CO2 Sequestration in Shale Reservoirs

The shale fracture permeability is critical in determining gas production and deep CO2 sequestration performance. Moreover, how shale fracture permeability evolves after interactions with supercritical carbon dioxide (Sc-CO2) should be understood to constrain the shale reservoir permeability and evaluate the long-term sealing ability of shale formations. In this research, we conducted soaking experiments with shale fractures and Sc-CO2 at various times and then measured the shale fracture permeability and hydraulic aperture evolution under different stress states. Additionally, we quantify the chemical compositions, pore characteristics, fracture surface roughness alternation through X-ray diffraction, nuclear magnetic resonance, scanning electron microscope, and optical profilometry techniques. Our results indicate that soaking with Sc-CO2 will dramatically increase the shale fracture permeability and aperture due to the calcite and dolomite dissolution. This free-face dissolution process will remove the mineral particles in the fracture surface, resulting in larger pores, peaks, and valleys in the fracture surfaces. This process may last for seven days, and after that, chemical reactions may terminate, and the rock-Sc-CO2 system turns stable. Our results explain how Sc-CO2 alters the shale fracture permeability through the chemical dissolution of specific minerals from a microscale analysis.

Various Images Versus the Stigma of Large Housing Estates: The Leipzig-Grünau Example

Large housing estates (LHEs) in eastern Germany are often stigmatised in media and public discourses. They are considered symbols of the state-socialist era. Furthermore, LHEs are usually presented as monotonous entities without inner variation, including in scientific literature. This poses the risk of a general and thoughtless stigmatisation of these estates. This paper focuses on the concept of territorial stigmatisation. Although stigmatised from the outside, in many cases the internal image contrasts with the external one. Previous literature indicates four main aspects that need more attention in scientific studies on LHEs and territorial stigmatisation: (1) a longterm perspective including the area’s historical development, (2) the analysis and evaluation of micro-scale data independent of common statistical boundaries, (3) the residents’ perceptions of their living environment, and (4) a more critical reflection in the academic discourse about one’s own role as a knowledge producer. By using the Leipzig-Grünau LHE as an example, we explore, first, how the internal image has changed over time, and second, whether micro-scale differences within the estate can be identified. We draw on findings of a long-term study investigating the development of the Leipzig-Grünau LHE since 1979. The results illustrate that the respective historical context has had a major influence on image generation over time. Furthermore, a micro-scale analysis reveals that even subspaces in immediate proximity differ with regard to socio-demographic characteristics, the housing and neighbourhood conditions and ownership. In particular, the residents perceive their living environment in a more nuanced way, which influences their image of the estate.

Comparative Study of Thermophysical Parameters of Different Types of Upholstery Wood and the Influence of Density on Combustion Parameters at Microscale

The fire behaviour of five types of wood was studied on a microscale. Some thermophysical parameters such as thermal conductivity, effusivity and diffusivity were also evaluated. The microscale analysis is based on the analysis of several parameters such as the assessment of heat released rates (HRR), peak heat released rates (pHRR), total heat released (THR), enthalpy variation (Δh) and residue rates with the combustion microcalorimeter (PCFC). The PF2C device was used to measure the conductivity, effusivity and diffusivity of wood, while the PCFC for the microscale study of wood behaviour in combustive situations. In terms of thermal conductivity, wood conducts heat with difficulty, while the other types, namely frake, bete, tek and red wood, more easily conduct heat and therefore cannot be considered as thermal insulators. For results, in terms of measuring effusivity, white wood has the smallest value, which means that it exchanges less thermal energy with its environment. Red and tek woods exchange much more energy with the environment compared to other types of wood. We observe that tek wood has the highest diffusivity, which means that it is the wood that reacts as quickly as possible to the change in temperature. White and frake woods have the same value of thermal diffusivity as red and bete wood which have the lowest thermal diffusivities. The fire behaviour of these materials is a very little variable on the microscale and we can conclude that at this level there is no major difference for our different types of wood. Hence, there is no influence of density on the microscale. We can say that for the white and tek wood the complete combustion begins at 700°C. By this same method of analysis, we come to the conclusion that the frake, bete and red woods tend towards a complete combustion at 675°C. At 675°C the bete and frake woods have the best combustive yields, to a lesser extent than the red and tek woods. The bete wood has the highest activation energy and the white wood the lowest.

Micro-Scale Residual Stress and Deformation Analysis in Bimetal Bronze-Stainless Steel Samples Produced by Laser Powder Bed Fusion Technology

Micro-Scale Residual Stress and Deformation Analysis in Bimetal Bronze-Stainless Steel Samples Produced by Laser Powder Bed Fusion Technology