Search Results (70)

The use of sustainable building materials is becoming increasingly important in order to reduce their environmental impact. This article draws attention to the lack of life cycle assessment (LCA) of building façades, which would take into account national conditions. The aim of the work is to assess the environmental impact of various building façade solutions. The analysis concerned a ventilated façade on an aluminum substructure with a fiber cement board and external thermal insulation composite system (ETICS) with expanded polystyrene (EPS). The assessed façades differed with regard to the used insulation materials. The study aims to select more ecological façades, while at the same time taking into account national conditions, which is important at the stage of designing a building. The study also aims to fill a gap in the existing literature by providing information concerning the environmental analysis of building façades based on real data. Based on a comparative analysis, it was shown that ETICSs with EPS have higher façade-damage category indicators in all impact categories except for eutrophication, human toxicity (carcinogenic and non-carcinogenic), and resource use related to minerals and metals, for which the ventilated façade shows higher values. Additionally, hot-spots for the analyzed façades were also presented. In the case of a ventilated façade, the determinant is the used insulating material, which is mineral wool. In the case of ETICS, it is the finish coat. For the first time in Poland, the LCA of a ventilated façade and ETICS was presented based on real data. The results of this study can be used as the first step of a full cradle-to-grave LCA for buildings. Full article

Preparation of metallic materials via laser powder bed fusion has gained high popularity primarily due to the versatility of the processed materials and the complexity of the available component geometries. However, the prepared components feature characteristic shortcomings. Among the ways to successfully reduce/eliminate printing issues and homogenize the properties within additively prepared materials is optimized post-processing. In this study, we present the positive effects of deformation post-processing at ambient (room) temperature on the microstructure and mechanical properties of AISI 316L stainless steel prepared by laser powder bed fusion. The post-processing was performed by the industrially applicable method of rotary swaging, for which varying swaging degrees were applied. The selected swaging degree influenced primarily the interactions between the dynamic strengthening and softening processes and consequently the strength/plasticity ratio, although all the applied swaging degrees successfully eliminated the residual porosity and imparted (sub)structure development and grain refinement. The ultimate tensile strength (UTS) for the original workpiece was 282 MPa, and it increased up to more than 1400 MPa after the final swaging while maintaining favorable plasticity (elongation to failure over 30%). The study thus proposes a way to successfully enhance the performance of additively manufactured AISI 316L steel with the use of a commercially applicable plastic deformation technology. Full article

This study addresses the fundamental problem of representing the rheological properties of heterostructured materials composed of metals that differ significantly in their crystal structure, stacking fault energy, and related characteristics. The necessity of accounting for essential strengthening mechanisms is highlighted. The study is based on experimental results related to the fabrication of a multilayer, heterogeneous system via multistage wire drawing, supported by microstructural analysis, microhardness measurements, and numerical simulations employing various flow-stress models. A discussion is presented regarding the effectiveness of these models in representing the deformation behavior of the investigated materials. The primary materials examined were a multilayer system composed of microalloyed steel and titanium. The obtained results indicate that, in addition to incorporating strengthening mechanisms, it is necessary to consider significant microstructural changes affecting microstructure evolution—particularly grain refinement induced by continuous recrystallization and the effects of strain hardening. Moreover, the findings point to the potential intensification of strengthening associated with pile-up mechanisms, linked to the development of dislocation substructures and the possible fragmentation of the hard phase in the vicinity of the more ductile microalloyed steel phase. In conclusion, the discussion integrates measurements of rheological properties obtained through tensile tests, supported by microstructural analysis, digital image correlation (DIC), and microhardness measurements, which collectively demonstrate the effectiveness of the adopted analytical approach. Full article

This paper presents the results of experimental tests and numerical analyses of the behaviour of brackets used in substructures of ventilated facades. Two representative solutions were compared: a traditional aluminium bracket and an innovative passive bracket with a composite interlayer. The aim was to assess their load-bearing capacity, deformation and failure mechanisms, and the suitability of the calculation methods used. Laboratory tests were carried out at ITB’s accredited Laboratory of Building Elements in accordance with the European Assessment Document (EAD 090034-00-0404). The aluminium bracket was tested under standard environmental conditions. In parallel, finite element (FE) analyses were performed, including elastic–plastic modelling for metallic systems and material and geometric nonlinear analyses for the passive bracket. The results revealed fundamental differences in the behaviour of the two solutions. The aluminium bracket exhibited a predictable plasticisation mechanism, the ability to redistribute stresses, and a gradual loss of capacity. Linear analyses proved sufficient in this case and were consistent with the tests. The passive bracket, by contrast, showed quasi-brittle behaviour, strong temperature sensitivity, and no plastic reserve, resulting in a sudden failure mechanism. For this case, the use of classical linear models leads to unsafe simplifications and underestimated results. The study demonstrates that the development of passive facade bracket technology requires a nonlinear approach and extended long-term testing covering the rheology of composite materials and environmental effects. The findings also reveal a normative gap: current design guidelines and EAD documents focus on metallic solutions while overlooking the specific behaviour of passive brackets. The results constitute an important contribution to knowledge on the safety and durability of ventilated facades and may serve as a basis for developing dedicated design procedures and for updating normative documents. Full article

Difficult, extreme operating conditions of parabolic antennas under precipitation and sub-zero temperatures require the creation of effective heating systems. The purpose of the research is to develop a multilayer coating containing two metal-ceramic layers, epoxy composite layers, carbon fabric, and an outer layer of basalt fabric, which allows for effective heating of the antenna, and to study the properties of this coating. The multilayer coating was formed on an aluminum base that was subjected to abrasive jet processing. The first and second metal-ceramic layers, Al₂O₃ + 5% Al, which were applied by high-speed multi-chamber cumulative detonation spraying (CDS), respectively, provide maximum adhesion strength to the aluminum base and high adhesion strength to the third layer of the epoxy composite containing Al₂O₃. On this not-yet-polymerized layer of epoxy composite containing Al₂O₃, a layer of carbon fabric (impregnated with epoxy resin) was formed, which serves as a resistive heating element. On top of this carbon fabric, a layer of epoxy composite containing Cr₂O₃ and SiO₂ was applied. Next, basalt fabric was applied to this still-not-yet-polymerized layer. Then, the resulting layered coating was compacted and dried. To study this multilayer coating, X-ray analysis, light and raster scanning microscopy, and transmission electron microscopy were used. The thickness of the coating layers and microhardness were measured on transverse microsections. The adhesion strength of the metal-ceramic coating layers to the aluminum base was determined by both bending testing and peeling using the adhesive method. It was established that CDS provides the formation of metal-ceramic layers with a maximum fraction of lamellae and a microhardness of 7900–10,520 MPa. In these metal-ceramic layers, a dispersed subgrain structure, a uniform distribution of nanoparticles, and a gradient-free level of dislocation density are observed. Such a structure prevents the formation of local concentrators of internal stresses, thereby increasing the level of dispersion and substructural strengthening of the metal-ceramic layers’ material. The formation of materials with a nanostructure increases their strength and crack resistance. The effectiveness of using aluminum, chromium, and silicon oxides as nanofillers in epoxy composite layers was demonstrated. The presence of structures near the surface of these nanofillers, which differ from the properties of the epoxy matrix in the coating, was established. Such zones, specifically the outer surface layers (OSL), significantly affect the properties of the epoxy composite. The results of industrial tests showed the high performance of the multilayer coating during antenna heating. Full article

This contribution compares various theories dealing with the assessment of dislocation density in metals subjected to different straining levels. The paper examines both substructure development and the evolution of dislocation densities in 1xxx, 5xxx, and 6xxx Al alloys. Barlat’s dislocation model, Kocks–Mecking–Estrin (K-M-E) theory, and Kubin–Estrin (K-E) type modeling approaches were analyzed. The dislocation model parameters were determined from the microindentation profiles for the rolled Al alloys. It was shown that a strong correlation exists between the K-E and K-M-E models, confirming their reliability in describing the relationship between strain, stress, and dislocation density. These numerical approaches effectively capture the evolution of dislocation density with strain, making them suitable for the analysis of the accumulation of stored energy during deformation. The development of substructure during straining was inferred from the microindentation experiments, and the resulting dependencies tended to align with the characteristic curve observed in various metals. Full article

The building sector significantly contributes to global energy consumption and carbon emissions, primarily due to the extensive use of carbon-intensive materials such as concrete and steel. Mass timber construction, particularly using cross-laminated timber (CLT), offers a promising low-carbon alternative. This study aims to calculate the embodied carbon emissions and biogenic carbon storage of a CLT-based affordable housing project, 340+ Dixwell in New Haven, Connecticut. This project was designed using a honeycomb structural system, where mass timber floors and roofs are supported by mass timber-bearing walls. The authors are not aware of a prior study that has evaluated the life cycle impacts of honeycomb mass timber construction while considering Timber Use Intensity (TUI). Unlike traditional post-and-beam systems, the honeycomb design uses nearly twice the amount of timber, resulting in higher carbon sequestration. This makes the study significant from a sustainability perspective. This study follows International Standard Organization (ISO) standards 14044, 21930, and 21931 and reports the results for both lifecycle stages A1–A3 and A1–A5. The analysis covers key building components, including the substructure, superstructure, and enclosure, with timber, concrete, metals, glass, and insulation as the materials assessed. Material quantities were extracted using Autodesk Revit^®, and the life cycle assessment (LCA) was evaluated using One Click LCA (2015)^®. The A1 to A3 stage results of this honeycomb building revealed that, compared to conventional mass timber housing structures such as Adohi Hall and Heartwood, it demonstrates the lowest embodiedf carbon emissions and the highest biogenic carbon storage per square foot. This outcome is largely influenced by its higher Timber Use Intensity (TUI). Similarly, the A1-A5 findings indicate that the embodied carbon emissions of this honeycomb construction are 40% lower than the median value for other multi-family residential buildings, as assessed using the Carbon Leadership Forum (CLF) Embodied Carbon Emissions Benchmark Study of various buildings. Moreover, the biogenic carbon storage per square foot of this building is 60% higher than the average biogenic carbon storage of reference mass timber construction types. Full article

In this study, we examine the evolution of dislocation substructures influenced by the fatigue behavior of SSM 6063 aluminum alloy processed through friction stir welding (FSW). The findings indicate that dislocation substructures have a significant impact on fatigue life. Cyclic loading induced recrystallization in the stir zone (SZ), the advancing-side thermomechanically affected zone (AS-TMAZ), and the retreating-side thermomechanically affected zone (RS-TMAZ). The transformation of the α-primary aluminum matrix phase into an S/S’ structure and the precipitation of Al₅FeSi intermetallic compounds into the T-phase were observed. Furthermore, the precipitation of Si and Mg, the primary alloying elements, was observed in the Guinier–Preston (GP) zone within the SZ. Transmission electron microscopy (TEM) analysis revealed small rod-like particles in the T-phase, measuring approximately 10–20 nm in width and 20–30 nm in length in the SZ. In the AS-TMAZ, these rod-like structures ranged from 10 to 120 nm in width and 20 to 180 nm in length, whereas in the RS-TMAZ, they varied between 10 and 70 nm in width and from 20 to 110 nm in length. The dislocation substructures influenced the stress amplitude, which was 42.46 MPa in the base metal (BM) and 33.12 MPa in the FSW-processed SSM 6063 aluminum alloy after undergoing more than 2 × 10⁶ loading cycles. The endurance limit was 42.50 MPa for BM and 32.40 MPa for FSW. Fractographic analysis of the FSW samples revealed distinct laminar crack zones and shear fracture surface zones, differing from those of other regions. Both brittle and ductile fracture characteristics were identified. Full article

Metal-ceramic crowns and bridges provide a stable and aesthetic tooth reconstruction. Hot pressing of veneering ceramics to metal substructure minimizes the formation of pores. Within the oral cavity, prosthetic structures are exposed to thermal stress. The study examines the influence of temperature changes on the quality and durability of the metal-ceramic bond using thermocyclic loading. Prior to the ceramic pressing, 40 cylindrical alloy specimens (height: 15 mm, diameter: 7 mm) were treated with abrasive blasting using Al₂O₃ (250 µm) or SiC (250 µm). They were divided into four groups: two control groups (sandblasted with Al₂O₃ or SiC) and two groups subjected to thermocyclic simulation. The ceramic-to-metal bond strength was measured with a shear test before and after thermocyclic loading. A statistically significant reduction in the bond strength between the metal substructure and the pressed ceramic was found after thermocyclic exposure. The bond strength decreased by 57% for Al₂O₃ sandblasted specimens and 36% for those sandblasted with SiC, as against the control group. This indicates that thermocycling weakens the bond between the metal alloy and pressed ceramic. The SiC blasting of the cobalt-chromium alloy results in a higher shear bond strength of the material connection after thermocyclic stimulation than the abrasive blasting with Al₂O₃. Full article

The structural dynamics of a machine tool play a significant role in chatter occurrence, which significantly deteriorates the metal-cutting performance. The receptance coupling substructure analysis (RCSA) is known for eliminating the experimental dependency on repetitive impact hammer testing. However, the identified contact parameters between the holder and tool, which are necessary for RCSA, usually lose accuracy in predicting tool point dynamics when applied to other tool clamping lengths or to combinations with other tools. To this end, a new method based on conventional impact hammer testing and RCSA technique to identify these parameters is proposed. Two descriptions of the proposed method are presented for different tool combinations and different clamping lengths, respectively. This new method eliminates the need for specialized experimental setups. The predicted tool point dynamics, using the identified contact parameters from the proposed method, show deviations below 3% with one exception, indicating that the identifications are accurate for various clamping lengths. The new approach yields significant advancements in the predicted tool point dynamics and stability boundaries compared to a traditional identification method reported in the literature. Full article

A high-noble Au–Pt–Ge porcelain-fused-to-metal (PFM) dental alloy without the known adverse metallic elements and with the addition of germanium (Ge) was produced as a more cost-effective alternative to other precious alloying metals, with investigations for determining the functionality and clinical use of this alloy. The thermomechanical, biocompatibility, durability, workability and economic characteristics of the produced dental alloy were investigated. These properties were investigated with in vitro biocompatibility testing on human gingival fibroblasts (HGFs); static immersion testing for metal ion release; DSC analysis; hardness, tensile testing, density and coefficient of thermal expansion (CTE) measurements; metallographic and SEM/EDX microstructure investigations; and finally with the production of a test PFM dental bridge. The results of the thermomechanical testing showed alloy properties suitable for dental restorations and clinical use, with somewhat lower mechanical properties, making the alloy not suitable for extensive multiunit fixed restorations. The microstructure investigations showed segregations of Ge in the homogeneous alloy matrix, which reduce the alloy’s mechanical properties. The produced PFM dental bridge showed excellent workability of the alloy in a dental laboratory setting, as well as a high standard of the final dental restoration. The ion release was negligible, well below any harmful quantities, while the cell viability examination showed significantly higher viability ratings on polished alloy samples as compared to as-cast samples. The results showed that a dental substructure in direct contact with oral tissue and fluids should be highly polished. The performed investigations showed that the produced PFM dental alloy is suitable for clinical use in producing high-quality dental restorations with high biocompatibility for patients prone to metal allergies. Full article

Continuous dynamic recrystallization (CDRX) forms a new recrystallized microstructure through the progressive increase in low-angle boundary misorientations (LAGBs) during the hot forming of metallic materials with high stacking fault energy (SFE), such as aluminum alloys. The present work investigates the effect of deformation parameters on the evolution of the dynamic recrystallization microstructures of an AA1050 aluminum alloy during compression at elevated temperatures. The alloy microstructure is investigated at deformation temperatures and strain rates in the range of 300 °C to 500 °C and 0.001 to 0.8 s⁻¹. A well-defined substructure and subsequent DRX grains provide indication that recrystallization can proceed with continued strain under high-temperature compression. At a strain rate of 0.1 s⁻¹, the DRX fraction is observed to be 0.25 at a temperature of 300 °C. This fraction increases to 0.32 as the temperature rises to 400 °C. The recrystallization mechanism is identified by analyzing the flow stress, the evolution of the subgrain misorientation angle, and the distribution of recrystallized grains. The observations of discontinuous dynamic recrystallization (DDRX) and CDRX under various deformation parameters are discussed. Moreover, the main substructure evolution laws observed from the high-temperature compression of an AA1050 Al alloy are summarized. Full article

Metal manufacturing processes based on deformation (forging, rolling) result in a fine grain structure with a complex dislocation substructure, which positively influence mechanical properties. Casting and additive manufacturing (powder- or wire-based) usually produce a coarse grain structure with a poorly developed dislocation substructure, which negatively affect mechanical properties. Heat treatment may alter phase balance and stimulate precipitation strengthening; however, precipitation kinetics depends on the dislocation substructure. In this paper, a comparative study of the microstructure and strength is presented for Monel K500 alloy containing 63 Ni, 30 Cu, 2.0 Mn, and 2.0 Fe (wt.%), and microalloyed with Al, Ti, and C hot-rolled to a round bar and deposited on a round surface using wire additive manufacturing (WAAM) technology. An increased dislocation density and number density of fine precipitates resulted in 8–25% higher hardness and 1.8–2.6 times higher compression yield stress in the hot-rolled alloy compared to these in the WAAM-produced alloy. However, due to a high work hardening rate, only 3–10% cold deformation was necessary to increase the strength of the WAAM alloy to this of the hot-rolled one. Age hardening heat treatment, through the intensification of the precipitation strengthening mechanism, reduced the value of cold deformation strain required to equalise the properties. Based on the obtained results, a new technology consisting of additive manufacturing, heat treatment, and cold deformation can be proposed. It can produce WAAM components with strength and hardness improved to the level of hot-rolled components, which is a significant development of additive manufacturing. Full article

The objective of this study is to investigate the formation of the structure and stress–strain state in the joints of AISI 304 stainless steel with a thickness of 2 mm and produced by welding with laser and plasma energy sources. It is established that the microhardness and parameters of the grain and subgrain structures of the welded joint material differ with respect to the dimensions of crystallites, grains, and subgrains according to the welding process. It is shown that, in terms of structure formation, including substructural features, the most favorable structures of 2 mm AISI 304 welded joints are formed by laser–plasma welding. It is predicted that the residual stressed state is less localized with the application of laser–plasma welding than laser welding, and it is characterized by a lower level of residual stresses compared to plasma welding. In all the cases, the maximal stress values are concentrated in the HAZ, and the value obtained using laser–plasma welding is in an intermediate position (431.7 MPa) between those of the laser (443 MPa) and plasma (413.7 MPa) processes. With laser–plasma and laser welding, displacements (deformations) are minimal and close to 0.2 mm. The method of electron speckle interferometry was used, and the results reveal that the error between the calculated and experimental values of equivalent stresses is no more than 6%, which is acceptable. The results of mechanical testing show that, under uniaxial tension, the strength of the welded joints made of AISI 304 steel using laser–plasma and laser welding is the highest and equal to 97% of that of the base metal. Full article

A strain isolation pad is a critical connection mechanism that enables deformation coordination between the rigid thermal insulation tile and the primary structure in the thermal protection system of a reusable hypersonic vehicle. An experimental investigation has been conducted to determine the static, loading–unloading, and high-cycle fatigue (HCF) responses of the SIP with 0.2 mm adhesive under through-thickness tension at room temperature. The contributions of the rigid thermal insulation tile and metallic substructure have not been considered so far. The results indicate that the tensile behavior of the SIP joint is highly nonlinear. The static and fatigue tensile failures both initiate from the corner close to the adhesive/SIP interface due to the stress concentration and the edge effect. The uniform breakage of the aramid fiber can be seen on the cross-section. A novel method is proposed to quantify the residual strain due to the short-time ratcheting effect of the SIP joint in the initial loading–unloading tensile response. As the number of fatigue cycles increases, the thickness of the SIP joint continues to increase until failure. An explicit expression associated with the growth of SIP joint thickness, fatigue cycle number, and peak cyclic stress is established. The turning point of the thickness growth rate with the fatigue cycle number is proposed as a new fatigue failure index for the SIP joint under tensile fatigue, and a fatigue life prediction model is developed. Full article