Structural Materials Research Articles

Technological and Mechanical Studies on Additively Manufactured Cellular Structures Made of the Ultrafuse 316L Composite Filament

Regular cellular materials produced using additive manufacturing (AM) techniques represent a significant development trend in modern engineering materials. Depending on the applied elementary unit cell of topology, it is possible to define the course of the structure deformation process in order to obtain the highest possible energy absorption effectiveness. This feature makes regular cellular structural materials particularly attractive for a number of industrial branches. This paper presents the results of technological trials and the results of experimental studies on the mechanical properties of regular cellular structures made using 3D printing technology under compression test loading conditions. The material used for their production was the Ultrafuse 316L filament and the fused filament fabrication (FFF) technique. The proposed material is a polymer-metal composite with a manufacturing process similar to metal injection moulding (MIM). The adopted research methodology included a feasibility study aimed at achieving material homogeneity and compression tests of the developed and manufactured regular cellular structures under quasi-static loading conditions. Several structural topologies were analysed. Experimental results indicated that regular cellular structures made from 316L steel exhibit high mechanical strength and extensive plastic deformation capabilities. The utilized in this work manufacturing technology used combines the advantages of 3D printing process with the potential of powder metallurgy. The proposed technique of structure manufacturing process is much cheaper than other based on melting metallic powders.

THERMAL TECHNOLOGICAL CONDITION OF IVG.1M RESEARCH REACTOR CORE UNDER VARIOUS OPERATING MODES

The relevance of the study is related to the determination of the thermal characteristics of the IVG.1M research reactor core with the low enriched uranium fuel under the nominal and design operating modes. The thermal technological condition of the IVG.1M research reactor during the start-up are determined by the readings of the temperature, pressure and coolant flow sensors of the information and measuring system. The indirect methods including the computer simulating ones are used to determine the temperature of the core structural materials and the distribution of the coolant temperature by the height of the fuel assembly. The research has been carried out using the method of the finite element analysis using the ANSYS Fluent software package. The study goal was to verify the adequacy of the calculation methodology and obtain the calculated data on the temperature distribution in the fuel assembly in the reactor power range from the nominal to design one. The article presents a description of the IVG.1M reactor, the research methodology, computer model, simulation results and the comparison of the calculated data with the experimental ones. The study scientific novelty consists in determining the temperature conditions of the fuel rods during the reactor operation at various levels of the design capacity with a conservative approach to the cooling conditions. The significance of the research results lies in the fact that a computer model can be used to determine the characteristics of the IVG.1M reactor core under the reactor various operating modes and to analyze the thermohydraulic processes in the fuel assembly.

Analysis of culvert design methods as methods of ensuring reliability at the design stage

This analysis focuses on the factors and methods for ensuring the reliability of metal culverts, which are essential for the trouble-free operation of motorways. Special attention is paid to the calculation methods for structures with annular cross-sections. The results of the work are conclusions about the necessity of their annular cross-section. They also conclude the importance of developing these structures to enhance culverts’ durability and failure-free operation. This involves considering the stochastic nature of load parameters, structural materials, and operating conditions. Addressing this issue is possible through the assessment of reliability indicators for culverts using simulation modeling methods.

Systematization of the application of polymer composite materials in the design of bridge structures

Background. This study systematizes the principles of using polymer composite materials in bridge structure design, outlining the fundamental principles for calculating load-bearing structures of bridge spans featuring these materials. Aim. The goal is to enhance the strength and durability of bridge spans during construction and maintenance, while optimizing costs through the use of polymer composite materials. Materials and Methods. The research employs a modern approach to bridge structure design, utilizing mathematical statistics for experimental data analysis and numerical methods for calculating bridge structures using nonlinear deformation models of anisotropic materials. Results. Developed principles for designing bridge spans with polymer composite elements include methods for strengthening and reinforcing concrete bridge structures. These methods account for operational factors such as long-term constant and temporary loads, low and elevated temperatures, as well as methods for designing all-composite spans pedestrian and road bridges Conclusion. The principles of designing bridge spans with elements made of polymer composite materials have been introduced into the practice of transport construction in the Russian Federation. The technical and economic efficiency of using polymer composite materials in bridge structures of transport infrastructure has been confirmed.

Laboratory Investigation of the Strength Degradation against Ultraviolet Radiation of Geonets for Slope Protection.

Sufficient light and high UV intensity pose significant challenges to the long-term performance of polymeric geonet materials for slope-protection structures. This study investigates strength degradation under the effect of UV radiation; five different types of geonets were selected, which can be categorized as polyamide (PA), polypropylene (PP), and polyethylene (PE) materials. A comprehensive experimental investigation was performed, including tension strength, peer strength, artificially accelerated aging, and SEM tests, to further establish a service life prediction method used for slope-protection design. The results showed that the tension strength, percentage of breaking elongation, and peer strength all depict a descending trend with aging-elapsed time, especially in the early 600 h. The decreasing tendency of these mechanical properties' magnitude differed in the diversity of direction and material type. Significant changes have been generated on the geonet surface after aging; materials with smooth surfaces exhibit a strong ability against strength degradation. Fitting results affirmed the predictive technique as a useful engineering tool for tension strength assessments, offering guidelines for using and designing of geonets for slope-protection structures.

The effect of post heat treatment on microstructural evolution and mechanical properties of Ti2AlNb intermetallic alloy prepared by point-forging and laser-deposition

Ti2AlNb-based intermetallic alloy is considered to be the latest class of light-weight structural material severing in the range of 600∼750 °C. Hybrid interlayer point-forging with laser-deposition (PF-LD) provides a new idea to produce near-net-shape Ti2AlNb part with promising mechanical performance. The present work mainly investigated the effect of post heat-treatment on microstructural evolution and tensile mechanical properties of PF-LDed Ti2AlNb alloy. The experimental results demonstrated that solution-treated at 940 °C–1020 °C followed by aging at 840 °C was effective to regulate phase morphology and tensile mechanical properties. With the consecutive increase of solution temperature, more fine-lamellar O-phase was reprecipitated within parent B2/β matrix during secondary aging treatment. The ultimate tensile strength was enhanced significantly from 1055.5 MPa to 1148.1 MPa with the help of precipitation hardening effect. In the meantime, stronger stress accumulation introduced by fine-lamella also exerted a detrimental impact on tensile strain capability, and the elongation after failure decreased from 10.9 % to 7.4 % with increasing solution temperature. Considering above results, this study provides a basic research for exploring the heat treatment of PF-LDed Ti2AlNb-alloy, and it is feasible to obtain high-strength and high-ductility properties by tailoring phase morphology.

Promoting the ordering of L10-FeNi phase via chemical interactions with substrate: A molecular dynamics simulation study

The L10-type FeNi intermetallic phase is an important rare-earth-free magnetic material. However, its fabrication remains challenging. In this paper, we propose a chemical-interaction-enhanced ordering mechanism in vapor deposition processes, which is supported by molecular dynamics deposition simulations. Additionally, we describe guidelines for the fabrication of further ordered intermetallic thin films. Thus, we present not only the fabrication of an L10-type FeNi intermetallic magnet but also guidelines for developing diverse structural and functional layer-ordered intermetallic materials.

Bayesian Inference for the Calibration of Progressive Damage Model of Dovetail Specimens from Laminated Composite Fan Blade

Abstract Composite fan blades are the preferred alternative for the fan stage of most advanced high bypass ratio turbofan engines. The ability of the dovetail to safely bear this load is one of the key points of the multi-level “test pyramid” approach of compliance demonstration for special airworthiness regulation. Debonding between adjacent layers is the main damage mode of laminated composite fan blades. However, there is difficulty in measuring the as manufactured interlaminar mechanical properties used in finite element models. In this study, tensile loading was applied to simulate the interacting centrifugal force and capture mixed mode damage evolution. Structural responses and material damages were calibrated with measured tensile loads through Bayesian inversion. Posterior probability distributions of maximum interface tractions and contact stresses were solved using Markov chain Monte Carlo sampler. Results indicated the two bilinear cohesive material models had a capacity of predicting empirical means of longitudinal reaction forces as that in test considering additional discrepancy term (0.035 kN and 0.96 kN respectively), while they made an significant impact on the prediction of tensile load history especially when two delamination cracks initiated and propagated. Interface elements provided a higher matching quality in predicting loading history and capturing damage mechanism in association with in-plane progressive damage analysis. This calibrated parameter set could be functioned as benchmark in numerically determining the ultimate tensile load of dovetail elements and reducing the necessary number of physical tests at elemental length level.

The place of the social in psychiatry: from structural determinants to the ecology of mind.

Social psychiatry considers the ways in which mental disorders are shaped by particular social environments. This paper outlines a cultural-ecosocial approach that emphasizes the ways in which cultural meaning and practices mediate the effects of the social determinants of mental health on the mechanisms of illness, disorder, and disease. Selective review of literature and conceptual synthesis. "The social" in psychiatry stands for the structures and dynamics of groups of people interacting on multiple scales from the intimate sphere of couple and family to neighbourhoods, communities, societies, nations, and transnational or global networks. These interactions create social contexts, niches, forms of belonging, identities, institutions, and larger systems that influence the causes, expression, course, and outcome of mental disorders. Characterizing these systems requires theory that considers the ways in which social systems constitute dynamical systems that configure material, energetic, and informational flows that give rise to human experience. Unpacking the health consequences of these local and extended systems requires an interdisciplinary approach that considers: (1) the social psychological, psychophysiological, and sociophysiological processes that mediate the impact of the environment on body, mind, and person; (2) the interactional dynamics of social systems that give rise to structural adversity and inequity as well as resilience; and (3) the recursive effects of self-understanding, agency and subjectivity. In the cultural-ecosocial view, "the social" is shorthand for interactional processes that constitute material and symbolic structures that provide cultural affordances, constraints, and challenges as well as resources for healing, recovery, and adaptation.

Superior Hole Injection Material PEGDT/TPF/PVDF with p-Doping Capability for Highly Efficient Solution-Processed Organic Light-Emitting Diode.

The ability to charge injection is a key factor in determining the performance of the organic light-emitting diode (OLED) devices. Improving the work function of the anode surface via interface modification, thus lowering the hole injection barrier, stands as a crucial strategy for enhancing the performance of the OLED device. Herein, we propose an innovative p-doping hole injection material, namely, PEGDT/TPF/PVDF that exhibits excellent performance in OLED devices with the value of maximum current efficiency at 56.4 Cd A-1, maximum luminescence at 25,564 Cd m-2, and a high EQE of 19.8%. The results for PEGDT/TPF/PVDF showed good conductivity, excellent film-forming property, and high transmittance over 98% in the spectrum range of 500-700 nm. Changes in the hole-injection energy barriers observed from the surface of the anode suggest a modified anode with PEGDT/TPF/PVDF deepened the work function at a value of 0.2 eV, which dramatically improves the hole-injection properties. This work not only provides novel structural materials with exceptional hole-injection properties but also proposes a promising alternative to PEDOT/PSS.

Selective-Area Growth of InGaAs Nanowires on SOI and the Vertical Transistor Application

The gate-all-around (GAA) structure avoids the problems inherent in miniaturizing field-effect transistors (FETs), such as off-state leakage current and short-channel effects. Among GAA structures, vertical GAA (VGAA) structures are expected as promising building blocks for future three-dimensional integrated circuit applications. The vertical III-V nanowires (NWs) on Si are expected as the fast channel materials for the VGAA structures on Si platforms. Thus, the combination of the VGAA structure with III-V NWs on Si significantly enhances on-state current while maintaining good gate controllability under low supply voltage. In addition, III-V NWs/Si tunnel junctions, which are formed by the direct integration of vertical III-V NWs on Si, can be utilized as VGAA tunnel FETs (TFETs) for low-power switch. Here we report on direct integration of vertical InGaAs NWs on silicon-on-insulator (SOI) substrates by selective-area growth and demonstrations of InGaAs NW-channel VGAA transistors (FETs and TFETs) on SOI.

(Keynote) Epitaxial Si/SiGe Multi-Stacks: From Stacked Nano-Sheet to Fork-Sheet and CFET Devices

After a short description of the evolution of metal-oxide-semiconductor (MOS) device architectures and the corresponding requirements on epitaxial growth processes, the manuscript describes the material properties of complicated Si/SiGe multi-layer stacks used for complementary field effect transistor (CFET) devices. They contain two different Ge concentrations and have been grown using conventional process gases. A relatively high growth temperature is used to obtain acceptable Si and SiGe growth rates. Still island growth has been suppressed for Ge concentrations up to 40%. Excellent structural and optical material properties of the Si/SiGe multi-layer stack will be reported, with up to 3 + 3 Si channels in the top and bottom part of the stack, respectively. The absence/presence of lattice defects has been verified by room temperature photoluminescence measurements. Photoluminescence measurements at low temperatures are used to study band-to-band luminescence from individual sub-layers and to illustrate the optical material quality of the CFET stack.

Determination of Dynamic Stresses and Displacements under the Action of an Impact Load on a Two-Layer Structure during the Indentation Process

Introduction. Numerous researchers of the reliability of building structures pay attention to hardness, an important characteristic of the structural material. It is determined by indentation — pressing the tip of the tool into the surface. The advantages of dynamic indentation methods and the distribution of stress intensity on the surface and inside the sample are investigated. However, the condition of layered materials on impact has been poorly studied. The objective of the presented work is to consider indentation for a two-layer sample and determine the sensitivity of the top layer to the strength of the substrate. This will allow us to identify significant characteristics of the strength properties of homogeneous and heterogeneous structures.Materials and Methods. An elastoplastic model of material behavior and a shock indentation scheme were used, which took into account the masses of the indenter and the striker coupled by linear springs. The surface of the indenter was conical, the opening angle was 120°. The impact was simulated in the MATLAB system. Finite element model in Ansys APDL was used to verify the data and analyze the results of the experiment. Traditional models of elasticity theory were used for calculations. The behavior of the material in the zone of plastic deformation was described using the options of multilinear isotropic hardening and the von Mises plasticity criterion.Results. The results of comparing three versions of varying the level of yield strength in the bottom layer are presented: when the yield strength in the bottom layer is half as high as the top one, equal to it, and twice as high. Displacements at different observation points for samples with a top layer of 2 mm and 1 mm were analyzed. In the first case, under horizontal shear, the displacement indices inside the sample did not change if the yield strength level was twice lower or higher than in the top one. If these indicators were equal, the difference became noticeable. In the second case (layer 1 mm), the difference in displacement was visible at all observation points. Thus, it can be reasonably concluded that a structure with a smaller top layer is more sensitive to impact. In the course of the research, it became known that vibrations associated with the transition to the plasticity zone occurred in the 2 mm zone, and elastic damping vibrations occurred below this zone. We solved the classification problem for the top layer of the material with changing characteristics of the base. The indicator for comparison was the Brinell hardness (HB) in the range of 200–600. The results were processed using a neural network and visualized in the form of graphs. The accuracy of its calculations was 98%.Discussion and Conclusion. To determine the strength properties of homogeneous structures, it is sufficient to characterize the speed of displacement inside the sample. For an inhomogeneous structure, additional parameters should be introduced — displacements on the surface and inside the sample at fixed observation points. An integrated approach to determining the strength properties of an inhomogeneous structure improves the accuracy of calculations, and the use of neural networks increases their speed.

Development and Evaluation of Insulation Materials for Deepwater Cementing.

Marine oil and gas resources are abundant in deepwater regions, where the shallow seabed harbors natural gas hydrate layers due to the cold temperature and high-pressure environment. Hydrates are prone to thermal decomposition, which can compromise the integrity of cement sealing and even lead to accidents like blowouts. While current low-hydrated heat cement systems mitigate hydrate decomposition from cement hydration heat during the waiting period for cementing, they do not address heat transfer from deep strata to shallow hydrate layers through fluid circulation in the tubing during deep oil and gas development. Rather than utilizing costly pipe insulation technology, adjusting the thermal conductivity of well cement emerges as a cost-effective approach to prevent heat loss in the wellbore to the hydrate layer and thus inhibit hydrate decomposition. The critical aspect lies in utilizing insulation functional materials. This study delves into the functional and structural design of insulation materials suitable for cement slurry systems in well cementing, outlining the preparation methods and processes for two insulation materials (SDBW and SDBW-II) tailored for deepwater well cementing. SDBW and SDBW-II are both nuclear shell structural materials. The core is made of high-strength hollow microspheres, produced by using a reverse suspension polymerization method to form spheres followed by high-temperature sintering. The shell consists of a wear-resistant BPA epoxy resin layer, with the surface of SDBW-II also containing highly reflective glass microspheres. Incorporating 20% of material SDBW into the cement reduces the thermal conductivity of the cement stone from 0.8 to 0.31 W·(m·K)-1 while achieving a compressive strength of 6 MPa after 24 h at 20 °C. Material SDBW-II offers both thermal resistance and reflection functions, increasing reflectivity (R) from 0.3 to 0.5. By adding 20% of this material to the cement, under the same conditions, although the compressive strength decreases to 4.2 MPa, the thermal conductivity can be reduced to 0.27 W·(m·K)-1. Furthermore, there is no significant change within 180 days, demonstrating long-term thermal insulation stability. These developed insulation materials can effectively improve the thermal insulation performance of the cement sheath, thereby maintaining the stability of the upper natural gas hydrate layer in the oil and gas production process of deepwater wells, providing an innovative solution for the long-term operation of deepwater oil and gas wells.

Machine learning guided prediction of dynamic energy release in high-entropy alloys

High-entropy alloy (HEA) type energetic structural materials (ESMs) offer exceptional strength, adequate ductility and reactivity upon dynamic loading, thus demonstrating great potentials in pyrotechnic applications. However, the main factors governing their energetic performance remain elusive, primarily attributable to the intricate mechanical-thermal-chemical coupling effects and the inherent challenges of HEA design. To address this, we propose a small-data machine learning framework designed to predict the energetic performance of HEA-type ESMs, employing support vector regression, leave-one-out cross-validation, and principal component analysis (PCA) to effectively manage a small, unevenly distributed, and highly dimensional dataset. Notably, the framework achieved a coefficient of determination (R2) of 0.854 while upholding robust performance, interpretability and computational efficiency. Fracture elongation (εt) and compressive yield strength (σcys) were identified as critical features, with σcys positively influencing performance while both εt and unit theoretical heat of combustion (UTHC) demonstrated negative effect. Guided by the framework, a series of novel Ti-V-Ta-Zr alloys with the comparable UTHC, velocity (v) and weight (m) but tailored εt and σcys were designed and tested. Ti30V30Ta30Zr10 alloy exhibited a commendable balance of mechanical properties and the smallest mean particle size, aligning with the model predictions and suggesting more thorough energy release during ballistic experiments.

A review of polymeric heart valves leaflet geometric configuration and structural optimization

Valvular heart disease (VHD) is a major cause of loss of physical function, quality of life and longevity, and its prevalence is growing worldwide due to increased survival rates and an aging population. The most common treatment for VHD is surgical heart valve replacement with mechanical heart valves (MHVs) and bioprosthetic heart valves (BHVs), but with different limitations. Polymeric heart valves (PHVs) exhibit promising material properties, valve dynamics and biocompatibility, representing the most feasible alternative to existing artificial heart valves. However, inadequate fatigue performance remains a critical obstacle to their clinical translation. In this case, geometry and material design are essential to obtain the best mechanical properties of the PHV. In this study, we summarized the effects of optimal design of PHVs from geometrical configuration optimization (valve height, thickness and design curve) and structural material optimization (anisotropy, fiber reinforcement, variable thickness, microstructure and asymmetric optimization), and selected the parameters including Effective Orifice Area (EOA), Regurgitant fraction (RF), and Stress Distribution to compare the performance of valves. It would provide the theoretical support for the optimal design of PHVs.

Adhesion of Meta-Aramid Coatings to Metal Substrates

The paper presents experimental investigations of the adhesive properties of meta-aramid coatings applied to metal substrates of different types. The increased adhesion ability of meta-aramid coatings to copper substrates was found in comparison with other metals and alloys used as structural materials. The dependence of the strength of the adhesive bond of the meta-aramid coating on the surface roughness at various concentrations of the polymer solution has been determined.

Energy-Efficient Geopolymer Composites Containing Phase-Change Materials-Comparison of Different Contents and Types.

The purpose of this study was to analyze the effects of phase-change components on the properties of geopolymer foams. Geopolymer foams are lightweight foamed geopolymers that are characterized by a high degree of porosity. Phase change materials, on the other hand, are compounds that, when added to a material, allow it to absorb, store, and then release large amounts of energy. Three types of PCMs, i.e., MikroCaps, GR42, and PX25, were introduced at 15% by weight. Geopolymer materials were produced based on silica fly ash, and hydrogen peroxide H2O2 was used to foam the geopolymer structure. The PCM geopolymer composites were cured at 60 °C. The produced materials were tested for physical, chemical, and thermal properties. The tests included oxide and mineral composition analysis of the base material, PCM particle size analysis, apparent density and porosity tests on the foams, water leachability tests, thermal tests (λ, Cv, Cp, α), and structural and textural analysis. The most relevant tests to confirm the performance of the phase-change materials were thermal tests. With the introduction of PCMs, volumetric heat capacity increased by as much as 41% and specific heat by 45%, and thermal diffusivity decreased by 23%. The results confirm the great potential of geopolymer composites as modern insulation materials for buildings and structures.

Affective spaces of the rural: A praxeological analysis of the “spatial pioneers” of Upper Lusatia (Germany)

While many rural regions in Germany are facing a downward socio-structural spiral, there is a growing societal yearning for rurality and the practices associated with it. By creating a network for individuals who migrate from urban centers to a peripheral rural area, the self-proclaimed “spatial pioneer” movement of Upper Lusatia operates at the convergence of these realities. Through an ethnographic inquiry into this movement, we study the social practices of these spatial pioneers, particularly focusing on affective practices that evoke emotional responses within individuals. We identified five dimensions that shape the spatial pioneers' rural lifeworlds — nature, work, community, simplicity, and self-efficacy. From the perspective of the spatial pioneers, rural spaces are not necessarily ‘ideal’ via their discursive representations. However, rurality as a lifestyle (as a way of living) becomes desirable via the (affective) practices it enables. The singularity of structurally weak rural areas lies in the fact that they offer opportunities for living the ‘good life’ that, due to limiting material and cultural structures, are unavailable elsewhere (e.g., in urban settings). In applying the concept of affective spaces, we aim for a deeper understanding of the spatial pioneers' bodily-affective experience, perception, and practice-based production of space. By doing so, we provide insights into practice-based, affective (re-)productions of rurality and rural spaces.

Microstructure and energy release properties of W-Zr-Al energetic structural material fabricated by explosive consolidation

Multi-element intermetallic energetic structural materials (ESMs) as a new typical ESMs characterized by their high heat release properties and strength, which could be applied as reactive fragment, reactive shell and reactive shaped charge. Al-based ESMs had been extensively studied due to their excellent mechanical properties and high energy release characteristics. But, the low density of Al-based ESMs hindered its application. However, the need for higher density and energy release persists. In this work, the nearly fully dense W-Zr-Al ESMs with a molar ratio of 1.9:1:1 was fabricated successfully by explosive consolidation. The density reached 10.12 g/cm3 (97.5 % of the theoretical maximum density). Microstructure of the specimen was characterized by X-ray diffractometer (XRD), optical microscopy (OM), scanning electron microscope (SEM), energy dispersive spectrometry (EDS) and transmission electron microscope (TEM). The heat treatment was used to further improve the performance of the specimen and the mechanical properties of quasi-static compression was investigated before and after heat treatment. The reaction activity and process of W-Zr-Al ESMs was discussed by differential scanning calorimetry (DSC). Besides, the impact-induced energy release tests were carried out to evaluate the reactive characteristics of the W-Zr-Al ESMs. The results indicated that high-density, good-strength and high energy release unreacted W-Zr-Al energetic materials were fabricated successfully by explosive consolidation.