High Strength Applications Research Articles

Elasticity study of SLA Additively Manufactured Composites

This study investigates the mechanical properties of ceramic and photopolymer composites created using stereolithography (SLA) 3D printing. It aims to evaluate and compare the performance of two SLA materials: Liqcreate Composite-X and Phrozen's Water-Washable Resin, using dynamic flexural vibration tests to determine Young's modulus. Liqcreate Composite-X, a photopolymer resin with excellent mechanical properties, including high tensile and flexural strength, showed a first resonance frequency of 318 Hz and a Young's modulus of 0.93 x 1010 Pa. Phrozen's Water-Washable Resin, designed for easy post-processing, had a first resonance frequency of 210 Hz and a Young's modulus of 0.30 x 1010 Pa. In conclusion, Liqcreate Composite-X demonstrates superior mechanical performance, making it suitable for high-strength applications, while Phrozen's Water-Washable Resin, with lower mechanical properties, is more suited for less demanding uses. This study enhances the understanding and application of SLA-based ceramic composites in various engineering domains.

Influence of HEA reinforcement on pulse electric current sintered Aluminium Composites: Microstructure, Density, and nanomechanical properties

This study investigates how different compositions of high-entropy alloys (HEAs), known for their strength and thermal stability, affect the microstructure, density, and nanomechanical properties of aluminium matrix composites produced by pulse electric current sintering (PECS). Commercial aluminium was reinforced with 5%, 7%, and 10% HEA and sintered using PECS. Microstructural analysis showed improved particle bonding and dispersion, resulting in enhanced mechanical properties. Although relative density slightly decreased with higher HEA content, there was a significant enhancement in nanohardness and elastic modulus. The composites exhibited improved resistance to plastic deformation and increased stiffness, thus, highlighting the effectiveness of HEA reinforcement in optimizing aluminium composites for high-strength, lightweight, and advanced engineering applications. These findings offer valuable insights for developing next-generation materials suited to demanding engineering environments.

Investigation on the microstructure and compressive behavior of open-cell copper- Al2O3 composite foams

The objective of this study is to evaluate the mechanical behavior and energy absorption characteristics of open-cell copper- Al2O3 composite foams fabricated using polyurethane foam with an average pore size of 1.2 mm and a combination of electroless and electrodeposition methods. During electroplating process, the composite foams were fabricated with varying amounts of Al2O3 particles (0.1, 0.6, 0.8, and 1 g/l) in electrolyte solution. To assess mechanical properties of the fabricated foams, uniaxial compression test was conducted to determine the maximum compressive strength, energy absorption density, efficiency, and specific energy absorption. The content of Al2O3 in the fabricated composite foams was evaluated using energy dispersive X-ray (EDX) analysis, and the microstructure was examined using scanning electron microscopy (SEM). The results indicate that the incorporation of Al2O3 particles significantly improves the mechanical properties of the copper-Al2O3 composite foam. Specifically, in the composite foam with 9.34 vol% of Al2O3 particles, the maximum compressive strength, total energy absorption, specific energy absorption, and energy absorption efficiency reach 1.03 MPa, 6.48 MJ m−3, 1.9 J g−1, and 75%, respectively. This amount of alumina particles enhances the maximum compressive strength and total energy absorption of open-cell copper foam by approximately 30% and 100%, respectively. However, the mentioned parameters slightly decreased with an increasing amount of Al2O3 particles up to 16.32 vol%. These significant improvements in the mechanical properties of these foams make them well-suited for high-strength applications.

Research on the performance of high-strength explosive ink and application of direct writing technology in micro-explosive network

With the widespread application of 3D direct writing technology in the field of energetic materials, it has become a current research topic to design an explosive ink with excellent micro-size detonation performance and high-strength mechanical properties and combining it with explosion network technology to improve detonation synchronization has become a research hotspot. This article uses FEVE-F2311 and PF as the composite bonding system, submicron CL-20 as the main explosive, and adds an appropriate amount of TDI as the curing agent to prepare an explosive ink with excellent micro-size detonation performance and high-strength mechanical properties. Research shows that the explosive ink has a detonation velocity of 7322 m·s−1 at a charge density of 1.621 g·cm−3, a critical propagation size of 0.3×0.3 mm, a critical propagation thickness of 1×0.040 mm, and a maximum detonation Corners can reach 160°. The error of detonation synchronization in the "one in and six out" micro-explosion network is within 150 ns, showing excellent detonation synchronization. The nano-indentation test shows that the average elastic modulus of CL-20-based explosive ink is 6.991 GPa and the average hardness is 0.200 GPa, showing excellent mechanical properties; the compressive stress-strain curve shows that its average compressive stress is 7.62 MPa, showing excellent Compressive strength. It not only greatly improves the mechanical properties of explosive ink, but also provides a method to improve the synchronization performance of micro-explosive networks.

Overview on aluminium alloys as sinks for end-of-life vehicle scrap

Abstract A fundamental principle in metallurgy is that the higher the purity of metals and alloys, the more favourable their properties will be. However, as the recycling of materials in production becomes increasingly significant, the levels of impurities are also on the rise. In the case of aluminium, the consequences can be detrimental due to the low solubility of most elements in this metal, which leads to the formation of brittle intermetallic phases (IMPs). Moreover, once impurities have entered aluminium, it is difficult to remove them. In 2017, almost 100 million cars were produced worldwide. Historically, vehicle design prioritised performance, resulting in a multi-material mix to utilise the best materials for each application. This included over 40 different wrought and cast aluminium alloys, Cu-based materials for electrics, and steels for high-strength applications. In the recycling of end-of-life vehicles (ELVs), high purity wrought Al alloys are today down-cycled to low purity cast engine blocks. However, recent advancements show that the drawback of increase IMP-fractions can be turned into benefits through the strategic design of heterostructured alloys. A first successful alloy example from this approach enables interesting forming properties, previously only found in 5xxx series wrought aluminium alloys, in combination with a matrix composition and age-hardening potential known from 6xxx series wrought aluminium alloys. A second examples reviews compositions directly resulting from ELV scrap. By manipulating IMPs it is feasible to create heterostructures with an interesting balance of strength and ductility. These approaches challenge traditional views, allowing for a greater volume fraction of intermetallic phases. Understanding the formation and role of intermetallic particles is crucial. This work gives an overview to the current problem and the state of the art and addressed the potential of upcycled aluminium alloys that tolerate high impurity levels by using intermetallic phases as impurity sinks.

Impact of lattice structure on compressive performance and strength to weight ratio in continuous stereolithography

Lattice structures have emerged as a creative solution in additive manufacturing to achieve lightweight structures. Lattices offer the capability to reduce material usage, production costs, and weight while maintaining the structural integrity of a part. Due to its rise in popularity and excellent properties, lattice structures have been used in many applications, including but not limited to aerospace, bioengineering, and acoustics. This study aimed to explore the performance of different types of lattices on 3D additive manufactured parts by varying the type of unit cell. The three unit cells that were compared are body-centered cubic (BCC), face-centered cubic (FCC), and Fluorite. The lattice’s strength-to-weight ratio of different lattice unit cells when subjected to compression forces was evaluated. BCC and FCC have had considerable research while Fluorite has had far less research. This study aims to contribute new knowledge on the less studied Fluorite unit cell. The selected lattice structures were printed using continuous stereolithography (CSLA). This 3D printing process utilizes a photopolymerization reaction to solidify liquid resin layer by layer. Through this study, Fluorite demonstrated the highest strength-to-weight ratio among the three lattice structures examined, averaging 19,377 Nm/kg over five samples. Its potential for applications requiring high strength requirements is highlighted by this finding. Alternatively, BCC lattice structures had the weakest strength-to-weight ratio but exhibited remarkable structural resilience to deformation. The BCC lattice structures showed a more significant deformation before failure. Fluorite lattice structures are more suitable for high-strength applications, while BCC lattice structures can be used where high strength is not a primary parameter. This research aimed to determine the optimal lattice unit cell to implement in future choices in additive manufacturing applications.

Thick-wire GMAW for fusion welding of high-strength steels

The paper describes a high-current Gas Metal Arc Welding (GMAW) process using wire electrodes with diameters up to 4.0 mm for single-pass full penetration butt joint welding of 20 mm thick steel plates. Fundamental research aims to develop thick-wire GMAW into a high-efficiency method by identifying the limits of welding performance and achievable deposition rates. Current gaps in understanding include equipment requirements, process properties, application fields, and weld quality. The research project addresses these gaps through systematic investigations of basic technological analyses, application sample welding, and quality evaluations. The objective was to create a robust, cost-efficient gas-shielded high-performance welding technology with deposition rates comparable to Submerged Arc Welding. The fully mechanized, automatic welding setup included two parallel-connected welding power sources, one wire feeder and one high-power welding torch. Welding parameters and conditions were evaluated with the aim of achieving a high-quality weld. Optimal parameters were identified for one-sided single-pass welding on 20 mm thick plates. Validation of thick-wire GMAW for 20 mm thick high-strength steels was conducted via two-sided single-pass welding on S690Q grade plates. Testing of the weld joint included static tensile strength test (3x tensile specimen), a Charpy impact test at −40 °C (6x Charpy V-notch specimens respectively with notch position in weld metal, base material and heat-affected zone (HAZ)), microstructure examination and a hardness test. The lowest recorded impact energy was observed to be 50 J within the weld metal, in combination with hardness peaks in the HAZ reaching 415 HV1, and all tensile specimens failing outside the HAZ within the base material. The process achieved reliable, reproducible, and economical joint welding, meeting necessary mechanical-technological quality standards. The paper enhances the understanding of selected welding techniques tor thick plate joining and offers valuable industrial insights, demonstrating the technique's applicability and feasibility for high-strength applications.

Development of sustainable HPC using rubber powder and waste wire: carbon footprint analysis, mechanical and microstructural properties

This research advances the development of eco-friendly high-performance concrete (HPC) by integrating tire rubber powder and waste wire, focusing on both enhanced mechanical properties and reduced environmental impact. Substituting up to 40% of silica sand with rubber powder helps maintain the compressive strength necessary for high-strength concrete applications. The addition of waste wire is designed to improve ductility. A comprehensive evaluation includes mechanical and microstructural analyses, such as compressive, splitting tensile, and flexural strength assessments, in addition to Scanning Electron Microscopy (SEM) and Differential Thermal Analysis (DTA). Environmental implications are assessed by measuring the embodied carbon footprint. Findings indicate that the absence of rubber powder allows for a compressive strength peak of 95 MPa, while 50% rubber content leads to a decrease to 25 MPa, establishing a 40% rubber threshold for optimal strength. Conversely, 3% waste wire reinforcement enhances the strength to 106 MPa. Microstructural investigations reveal that increased rubber content adversely affects compressive strength by weakening the cement matrix, and reducing calcium-silicate-hydrate (C-S-H) formation. Significantly, the study reveals that replacing silica sand with rubber powder, along with waste wire reinforcement, substantially reduces the carbon footprint of the material, contributing to more sustainable construction methodologies.

Hot extrusion of SiCp/Al-Cu composites: optimizing mechanical properties through microstructural control

The solid-state processing and utilization of light-metal-based composites align with green policies by reducing the weight of components and employing lower processing temperatures compared to traditional metallurgical methods. This study explores the incorporation of SiC particles at concentrations of 5 and 10 wt.% into an Al4Cu matrix through powder mixing, compaction at 235 MPa, hot extrusion, and sintering at 600 °C in a nitrogen atmosphere. The resulting microstructure, hardness, compressive strength, and flexural strength of the composites were evaluated. During extrusion, the composite underwent plastic deformation, leading to cracking and fragmentation of the SiC particles within the matrix. Therefore, evenly distributed reinforcing particles with a diameter much smaller than the originally introduced ceramic particles were observed. Recrystallization also occurred, with Al2Cu precipitates forming on grain boundaries and nanosized Al2O3 oxides observed in porous areas and at matrix-reinforcement interphase boundaries. The composite containing 5 wt.% SiC exhibited the highest compressive strength of 305 MPa, while the composite with 10 wt.% SiC achieved the highest flexural strength of 889 MPa. However, non-deformable SiC particles crack before reaching maximum strength due to stress concentration at their sharp edges, initiating microcracks in the matrix. Microstructural analysis further revealed that SiC particles tend to crack during hot extrusion, reducing their effectiveness in stress transfer. The hardness remained constant at 78 HV1, irrespective of SiC content. These findings demonstrate that the addition of SiC particles significantly enhances the mechanical properties of Al4Cu composites, making them promising materials for lightweight and high-strength applications.

Enhanced morphological and thermal properties of epoxy composites reinforced with Palm and Prosopis Juliflora fibers

Abstract This study investigates the fabrication and characterization of a hybrid epoxy matrix composite reinforced with Palm and Prosopis Juliflora fibers fabricated using the hand layup technique. Three composite samples were prepared with varying weight percentages of palm and Prosopis Juliflora fiber reinforcements: 5% (Sample A), 10% (Sample B), and 15% (Sample C). Sample B having 10 weight percentage each of Palm fiber and Prosopis Juliflora fiber and 80 weight percentage of Epoxy matrix, exhibited superior performance with a tensile strength of 45.5 MPa and a hardness of 86.5 Shore D. Thermal analysis revealed Sample B’s exceptional thermal stability, with distinct decomposition stages observed through Thermogravimetric Analysis (TGA) and Differential Thermal Analysis (DTA). Void content analysis indicated Sample C had the lowest void content at 4.5%. Energy Dispersive x-ray (EDX) Analysis confirmed homogeneous fiber distribution and strong fiber-matrix adhesion, supported by carbon and oxygen peaks. Fourier-transform infrared spectroscopy (FTIR) spectra showed interactions between functional groups, including alcohols, carboxylic acids, and carbonyl compounds. These findings underscore the composite’s potential for high strength, toughness, and thermal stability applications.

Effect of Pouring Temperature Variation on Cooling Rate, Hardness and Microstructure of Al-Zn in Aircraft Structures

Al-Zn alloys are widely utilized in industries such as automotive, aircraft manufacturing, and advanced military equipment due to their exceptional strength-to-weight ratio. Among various fabrication methods, metal casting is a commonly used technique for producing structural components from these alloys. However, a significant challenge with metal casting is the reduction in mechanical properties compared to the base material before melting. This reduction highlights the need for research to identify the optimal casting conditions, particularly the casting temperature, which plays a crucial role in maintaining and potentially enhancing the material's mechanical properties. Aluminum alloy 7075, known for its high strength, was selected for investigation. According to the Al-Zn phase diagram, the melting point of aluminum alloy 7075, based on the weight percentage specified by the Standard Aluminum Association, is approximately 660°C. Experiments were conducted by varying the pouring temperature during casting in 30°C increments above this melting point. Specifically, the alloy was melted and cast at three different temperatures: 690°C, 720°C, and 750°C. The mold temperature was consistently maintained at 220°C to isolate the effects of the pouring temperature. Results indicate that increasing the casting temperature significantly affects the alloy's microstructure and mechanical properties. As the casting temperature increases, the cooling rate decreases, leading to a finer grain structure. This finer grain size directly contributes to an increase in hardness, suggesting that higher casting temperatures can enhance the mechanical properties of Al-Zn alloys. These findings emphasize the importance of precise control over casting temperatures to optimize the performance characteristics of aluminum alloy 7075 in high-strength applications.

Effect of curing temperature on hydration characteristics of GGBFS-based cementless high-strength concrete

This research examines how curing temperature affects in the development of CaO-activated cementless GGBFS high-strength concrete. Compressive strength tests were conducted on samples cured at 50 °C, 70 °C, and 90 °C for 12 h, with additional evaluation after 3 and 28 days of water curing. TGA, FT–IR, NMR, MIP, and BET analyses further investigated the microstructural evolution. Findings show that higher temperatures significantly enhance pozzolanic reactions, leading to initial strengths of up to 95.6 MPa and maintaining high levels after 28 days. Elevated temperatures enhances the formation of denser and more stable hydration products, predominantly C–S–H, confirmed by spectroscopic analysis which relates with increased binder reactivity to enhanced compressive strength. Additionally, improved porosity refinement at higher temperatures correlates with increased strength. This research highlights the dual benefit of using cementless high-strength concrete: achieving substantial strength and reducing CO2 emissions, supporting its potential for high-strength applications with reduced environmental impact.

Preparation and characterization of ox bone powder and bamboo fibers reinforced hybrid epoxy composites

Composite materials are one of the fastest growing when compared with metal, ceramic, and polymer due to their high specific strength, stiffness, and versatile application in various fields. This study aimed to develop an ox bone powder and bamboo fiber-reinforced hybrid epoxy composite for stock and bumper applications and investigate the effect of the reinforcements on the composite’s mechanical properties. The reinforcements used in this work were random orientations of animal bone (ox) powder of 75 microns and bamboo fiber. The matrix used for this work was epoxy resin. Composite materials were prepared using the hand layup method with a 40% weight fraction of reinforcement (bone powder and bamboo fiber) and a 60% weight fraction of epoxy resin matrix. Five different combinations of bone powder and bamboo fiber with a fixed amount of epoxy resin were used for this work. The combinations of bamboo fiber and bone powder were: 40% bamboo fiber with 0% bone powder; 30% bamboo fiber with 10% bone powder; 20% bamboo fiber with 20% bone powder; and 0% bamboo fiber with 40% bone powder. The mechanical properties studied were compressive strength, impact strength, and flexural strength. In addition, water absorption was studied for all combinations. The maximum results of the flexural and impact strengths were 278.91 MPa and 7.5 J/m, respectively, at a 0:40 (bone powder: bamboo fiber) composite. The maximum compressive strength and the lowest absorption obtained were 283.3 MPa and 1.05%, respectively, at the 40:0 (bone powder: bamboo fiber) composite. For the hybrid composite case, optimal flexural and impact strengths were 236.72 MPa and 6.66 J/m, respectively, and water absorption was 1.52% at 10:30 (bone powder: bamboo fiber). Since reasonable flexural strength, impact strength, and water absorption were obtained with the hybrid composite of 10:30 (bone powder: bamboo fiber), this combination of the hybrid composite is recommended for stock and bumper applications.

Uncertainty Analysis of Tensile Strength of Scarf Adhesive Joints using Numerical Method and Validation through Experimentation

Adhesive joints represent a significant advancement in material bonding technology, offering benefits such as reduced weight and uniform stress distribution, which distinguish them from conventional joining methods. Among the various adhesive joints, the scarf adhesive joint stands out due to its mechanical advantages and potential for high-strength applications. This research investigates the impact of key parameters on the strength of scarf adhesive joints, including scarf angle, surface roughness, adhesive type, and adhesive layer thickness. By systematically varying these parameters and employing a design of experimentation (DOE) methodology, we aim to identify the optimal conditions that maximize joint strength. A series of scarf adhesive joint specimens with diverse parameter combinations will be fabricated and tested to evaluate the resultant joint strength. Statistical analysis of the experimental data will facilitate the understanding of how each parameter influences joint performance and contribute to the development of optimized adhesive joint designs. The findings of this study are expected to advance the application of scarf adhesive joints in various high-performance engineering fields, providing insights into the critical factors that govern their strength and reliability. Key Words: Scarf Adhesive Joint, Adherend Material, SS 304 Stainless Steel, Finite Element Analysis (FEA), Tensile Strength, Max von Mises Stress, Scarf Angle, Design of Experiments (DOE), Adhesive Properties, Surface Roughness.

Resveratrol/epoxidized soybean oil bio-based non-isocyanate polyurethane: High strength, recyclability and adhesive applications

Advancing bio-based non-isocyanate polyurethanes (NIPUs) is vital for fostering sustainable development. This study, inspired by the concept of "rigid and flexible" successfully utilized resveratrol, epoxidized soybean oil, and carbon dioxide (CO2) to produce a novel type of NIPUs (CRSOP) with outstanding mechanical properties, recyclability, and adhesive properties. Test results reveal that CRSOP demonstrates a tensile strength of 20.85 MPa and an elongation at break surpassing 160 %. The synthesized CRSOP shows excellent recyclability, with a recycling efficiency of over 80 % even after three cycles. Additionally, the rich polar groups in CRSOP contribute to its exceptional adhesion on diverse substrates such as copper (5.29 MPa), steel (7.48 MPa), aluminum (6.12 MPa), glass (4.71 MPa), and polytetrafluoroethylene (1.75 MPa). Even after prolonged immersion in organic solvents, CRSOP maintains a lap shear strength comparable to the initial value, demonstrating outstanding environmental tolerance. This paper showcases a superior-performing NIPUs derived from renewable resources and simultaneously expands its extensive application in the adhesive field.

Structural Positive Electrodes Engineered for Multifunctionality.

Multifunctional structural batteries are of high and emerging interest in a wide variety of high-strength and lightweight applications. Structural batteries typically use pristine carbon fiber as the negative electrode, functionalized carbon fiber as the positive electrode, and a mechanically robust lithium-ion transporting electrolyte. However, electrochemical cycling of carbon fibre-based positive electrodes is still limited to tests in liquid electrolytes, which does not allow for to introduction of multifunctionality in real terms. To overcome these limitations, structural batteries with a structural battery electrolyte (SBE) are developed. This approach offers massless energy storage. The electrodes are manufactured using economically friendly, abundant, cheap, and non-toxic iron-based materials like olivine LiFePO4. Reduced graphene oxide, renowned for its high surface area and electrical conductivity, is incorporated to enhance the ion transport mechanism. Furthermore, a vacuum-infused solid-liquid electrolyte is cured to bolster the mechanical strength of the carbon fibers and provide a medium for lithium-ion migration. Electrophoretic deposition is selected as a green process to manufacture the structural positive electrodes with homogeneous mass loading. A specific capacity of 112mAhg-1 can be reached at C/20, allowing the smooth transport of Li-ion in the presence of SBE. The modulus of positive electrodes exceeded 80GPa. Structural battery-positive half-cells are demonstrated across various mass-loadings, enabling them to be tailored for a diverse array of applications in consumer technology, electric vehicles, and aerospace sectors.

Selective localization of carbonized polymer dots in amorphous phase towards high breakdown strength and energy density of PVDF-based dielectric composites

In a general way, there is a contradictory between dielectric constant (εr) and breakdown strength (Eb) in dielectric materials, and improving the discharge energy density (Ud) of dielectric polymers has become a great challenge. The semicrystalline ferroelectric polymer polyvinylidene fluoride (PVDF) is favored for its high εr, but its relatively weak Eb in amorphous regions makes it still difficult to obtain appreciable Ud. In response to the fact that the current method of introducing rigid chain amorphous polymers into the amorphous regions of PVDF has limited capability to enhance its Eb, in this work, due to the crystallization induced phase separation, carbonated polymer dots (CPDs) as well as PMMA were introduced into the amorphous region of PVDF, and CPDs/PVDF/PMMA composites were prepared towards high Eb and Ud. It is confirmed that, CPDs significantly increase the entanglement density of molecular chains in amorphous regions of PVDF; in addition, CPDs rely on their inorganic carbon cores with unique electrical properties to resist carrier migration in amorphous regions of PVDF under high electric fields. In brief, CPDs are used as a reinforcing agent for the amorphous region of PVDF to further enhance its Eb and Ud. The composite loaded with 0.1 wt% CPDs exhibits the superior Ud of 12.4 J/cm3 at the Eb of 652.0 MV/m. This work provides new understanding on the dielectric response of ultrasmall-sized CPDs on polymer dielectrics, which could help us design new dielectric polymer composites with suppressed segmental motions for high breakdown strength and high energy density applications.

Analyzing the long-term effects of e-glass mortar on sustainability and radiation shielding using ANOVA.

Significant investigations were performed on the use and impact on physical properties along with mechanical strength of the recycled and reused e-glass waste powder. However, it has been modeled how recycled display e-waste glass may affect the characteristics and qualities of dune sand mortar. This study investigates the long-term feasibility of using recycled display e-glass waste as a partial substitute for dune sand at varying percentages (5%, 10%, 15%, and 20%). The main focus is on evaluating its effectiveness in radiation shielding, strength properties, and durability for long-term development under the heating environmental process. Statistical analyses, including analysis of variance, are used to assess the significance of factors and their interactions on these characteristics. Additionally, a regression equation derived from the model offers insights into the quantitative relationship between the factors and properties. The results of the experiments led to the conclusion that the most effective proportion of e-glass waste to include in mortar is 20%, with the weight of dune sand. Including e-glass waste, they significantly increased the five characteristics of the mortar, making it suitable for high-strength mortar applications continue up to 68MPa. The ANOVA model used in this study was trained using the same experimental research design and was critical in predicting the properties of the mortar. The model produced an accurate result with an R2 value greater than 0.99. E-glass replacements exhibit remarkable radiation shielding, characterized by pozzolanic activity and superior internal bonding due to its compact texture, contributing to enhanced long-term strength.

Bolt load looseness detection for slip-critical blind bolt based on wavelet analysis and deep learning

Bolt preload is a crucial factor in high-strength bolt applications, particularly for the Slip-critical blind bolts (SCBBs). This study presents a novel nondestructive approach that leverages ultrasonic echo waves to accurately detect the state of bolt looseness, addressing a significant research gap in the field of blind bolt looseness detection. The proposed technique is uniquely suitable for blind bolted connections as it only necessitates access to a single side of the connection. Nine types of SCBBs were tested and obtained approximately 4000 ultrasonic echo signals with varying degrees of looseness. These signals have been transformed into image-based representations using wavelet analysis, and deep learning techniques were used to classify and predict the looseness level accurately. The performance of various damage assessment criteria, CNN models, and dataset sizes were evaluated and compared. The proposed method was validated by classifying 400 datasets with a validated accuracy of 97.30%.

Experimental studies on mechanical properties of Al-7075/TiO2 metal matrix composite and its tribological behaviour

This study explores the fabrication and characterization of an Al-7075/TiO2 metal matrix composites (MMCs) through stir casting, varying TiO2 contents from 2% to 10%. Various tests, including tensile, hardness, and elastic indentation modulus testing, dynamic mechanical analysis, microstructural evaluation, and XRD, were conducted. Tribological analysis involved tribo-pairs of an EN31 disc and a smooth MMCs pin, using a high-temperature Pin-on-disc setup. Microstructural analysis of Al-7075/TiO2 MMCs revealed uniform TiO2 distribution, grain refinement, and enhanced mechanical properties, with XRD confirming structural changes. Tensile tests showed improved ultimate force and stress with increasing TiO2 content, indicating potential for high-strength applications. Hardness assessments demonstrated progressive improvements in Martens, Elastic Indentation, and Vickers Hardness, highlighting the material's suitability for critical wear and tribology applications. The composites exhibited enhanced damping flexural characteristics, especially with 8% TiO2. Maximum and minimum modulus values are reported as 98.9 GPa at 25 °C and 77.3 GPa at 350 °C for 8% TiO2 mix MMC. Tribological performance was improved with lower COF values and wear rates. At elevated temperatures, the wear behavior varied with TiO2 content, influenced by factors such as heat generation and localized welding.