Acceptable Mechanical Performance Research Articles

Gas tungsten arc welding of a multiphase CoCuxFeMnNi (x=20,30) high entropy alloy system: Microstructural differences and their consequences on mechanical performance

With the current advancements in materials science, the development of high entropy alloys (HEAs) is progressively increasing. Hence, research on their processability is essential to make them competitive alternatives to common engineering alloys that are widely used in structural applications. One manufacturing technique commonly employed in this sector is gas tungsten arc welding (GTAW). This technique allows to obtain single monolithic parts from separate components, often at the cost of local microstructural and mechanical properties variation across the joint. As such, GTAW processing is capable of supplying relevant knowledge regarding the feasibility of joining new materials and their potential industry uptake. In this study, we present a comparative analysis on the use of GTAW on two distinct multiphase high entropy alloys: CoCu20FeMnNi and the CoCu30FeMnNi. Firstly, microstructural observations coupled with CalPhaD-based calculations and synchrotron X-ray diffraction analysis, allowed to delve, and compare, the microstructural evolution across both welds. It was possible to observe the dual phase nature of the microstructure throughout the welded joint alongside the nucleation of a B2 BCC phase in the heat affected zone (HAZ) of both HEAs. Considering the mechanical properties of the welded materials, results evidenced a poorer, yet still acceptable mechanical performance. The observed decrease in mechanical strength is attributed to the residual stress conditions and large grain size that developed owing to the process thermal cycle, which contrasted deeply with the microstructure of each base material.

Healable and Recyclable Polyurea‐Urethane Elastomer with High Mechanical Robustness, Superhigh Elastic Restorability, and Exceptional Crack Tolerance

AbstractDeveloping the elastomer materials with high mechanical robustness through simple and environmentally friendly methods poses significant challenges. In this research, a simple solvent‐free polymerization method is reported to synthesize a transparent polyurea‐urethane elastomer using polycaprolactone (PCL) as soft segment and adjusting various hard segments. The target elastomer successfully combine acceptable mechanical performance and exceptional crack tolerance, whereby the notched samples can readily lift 25000 times (a rarely reported value) its weight. Moreover, the superhigh elastic restorability allow target elastomer recover to its original dimension from elongation over 5 times or to fracture. These results are attained due to the presence of densely and uniformly distributed hard microdomains within the elastomer, leading to effective energy dissipation. Furthermore, owing to the linear structure of the molecular chains and the reversible hydrogen‐bonding interactions between the chains, target elastomer can be conveniently healed and recycled under heating conditions. This research can provide a general and feasible strategy for the construction of elastomer materials with exceptional comprehensive properties, and the elastomers are expected to be applied in emerging fields such as protective elements and flexible electronics.

Performance of carbon fiber (CF)/Ceiba petandra fiber (CPF) reinforced hybrid polymer composites for lightweight high-performance applications

Natural and synthetic fibers have their own advantages and disadvantages. For this reason, hybridization was performed to combine the two fibers to get composite reinforcement with high mechanical properties. It is used to synergize the two fibers aiming to create a higher performance than that of natural fiber-reinforced composites. This study used carbon fiber and natural fiber namely Ceiba petandra fiber (CPF). Compared to hybrid and CPF reinforced composites, carbon fiber (CF)-reinforced composites had superior mechanical properties, especially in terms of tensile and flexural characteristics. However, it is more brittle and expensive. In contrast, CPF composite has the lowest tensile strength, flexural quality, and abundance. The optimal value was shown in CF/CPF reinforced hybrid composites with a composition of 15 % CF and 15 % CPF, with tensile and flexural strength reaching 130.16 ± 17.37 MPa and 98.53 ± 12.2 MPa. Hybrid composite improves the thermal stability of the composite. Findings showed that incorporating natural and synthetic fibers produced composite materials with acceptable and ideal mechanical performance.

Modular sandwich panel system for non-loadbearing walls – Experimental mechanical, fire and acoustic testing

Investment in the construction industry has increased over the last years and conventional construction materials, techniques, solutions and practices cannot meet the current needs. Resources are not being used to their full potential and there is a lack of manpower. It is vital to evolve encouraging sustainable and quality cost-effective materials, techniques, solutions and practices, therefore also enhancing the construction workers’ quality of life. This work proposes a new modular sandwich panel system for interior walls partition applications. The modular sandwich panel is made of an extruded polystyrene boards (XPS) core and has three options as facesheets: gypsum plasterboard (PGC), fire resistant gypsum plasterboard (PGF) and magnesium oxide board (MGO). This is an alternative solution for partition walls based on five main factors: it has the potential to be reused; its modules are self-supported (they do not need vertical metal studs from floor to ceiling); it is easy to install (on-site) by only two people; it is quick to install; and it provides easy local access to the interior of sanitary facilities. This work also includes experimental research for evaluation of proposed the wall solution in terms of mechanical resistance and stability, fire safety and airborne sound insulation between adjacent rooms. Mechanical resistance testing includes impact resistance tests, simple compression load tests, sanitary appliance load tests and endurance cycle load tests. Fire resistance testing allows to assess the integrity and maintenance of the panel wall under fire conditions. Acoustic experiments aim to determine the weighted standardised sound level difference (DnT,w) between adjacent compartments separated by the proposed panel wall system. Mechanical resistance tests indicate that the panel wall system has acceptable mechanical performance, including the connections between the panel wall modules. Results indicate that fire resistance and sound insulation characteristics of the panel wall can be enhanced.

Synergetic effects of boron nitride with waste zirconia: Evaluation of instantaneous fingerprint detection and mechanical properties for biomedical applications

Herein, present study mainly focuses on the synthesis and characterizations of boron nitride reinforced waste zirconia (wZrO2) with different concentrations. Composites were prepared via a scalable solid-state reaction method. Various physical parameters such as density, ionic concentration, polaron radius, and field strength were evaluated. XRD results reveal crystalline nature with a major phase of tetragonal zirconia and as boron nitride is reinforced, the tetragonal transforms into a monoclinic zirconia. Interconnected spherical grains and nanosheets were observed using FESEM. Mechanical characterizations revealed the highest compressive strength of 266 MPa. The latent fingerprints were visualized using a composite on different surfaces, implementing the powder dusting and solution techniques. MTT assay was performed and revealed good biocompatible nature. These results reveal that composite is suitable for fabrication of bioceramics with acceptable mechanical and biological performances. The composite can also be utilized for latent fingerprint detection in forensic science.

Performance evaluation on bond, durability, micro-structure, cost effectiveness and environmental impacts of fly ash cenosphere based structural lightweight concrete

The production of huge fly ash waste from thermal power plants and gradual depletion of natural aggregates due to their high consumption in concrete making are two major threats to the sustainability of the environment. The strategic utilization of this waste as a replacement of natural aggregate in production of concrete can solve both the problems simultaneously. Hence, this study aims to evaluate the performance of structural lightweight concrete (LWC) containing fly ash cenosphere (FAC), a by-product of fly ash, in order to check its suitability for construction. In this study, one control concrete mix, i.e., without FAC, and other ten concrete mixes utilizing FAC as the replacement of natural fine aggregate (NFA) at the increment of 20% and with/without superplasticizer (SP) are prepared. The Mechanical properties (compressive and bond strength), durability aspects (sulphuric acid, magnesium sulphate and sodium chloride resistance) and the microstructural characteristics from X-ray diffraction and scanning electron microscope analyses of these mixes are evaluated. Moreover, the environmental impact assessment and cost-effective analysis are also conducted. From this investigation, it is found that the structural LWC can be produced by utilizing high volume FAC with/without SP with the acceptable mechanical and durability performances. Further, the concrete with 80% FAC and SP is found to be optimum having compressive strength of 32.59 MPa, which satisfies M25 grade concrete as per IS 456 (2000), meets ACI 213 (2014) requirements of structural LWC and has also acceptable durability properties. The microstructure studies have also supported the strength and durability results of these mixes. Moreover, these mixes are found to be cost effective and environmentally friendly. Hence, structural LWC prepared with a high volume of FAC and SP can be recommended for construction, which reduces the cost and environmental impacts significantly and preserves natural resources for the future generations.

Experimental investigation of mechanical properties of bamboo/carbon fiber reinforced hybrid polymer matrix composites

Natural fiber composites are gaining popularity in various fields such as aerospace, automotive, and interior design due to their biodegradability, cost-effectiveness, and wide availability. Hybrid composites, which utilize both natural and synthetic fibers as reinforcement, are becoming more prevalent due to the desirable properties of each. Natural fibers possess strong damping properties and are biodegradable, while synthetic fibers have good elastic modulus. This research aimed to investigate the mechanical properties of bamboo and carbon fiber reinforced hybrid composites through tensile, flexural, and Izod tests. Hybrid composites exhibited 74.53% higher tensile strengths, 41.47% higher flexural strengths, and 182.24% higher impact strength than bamboo fiber reinforced composites. Carbon fiber reinforced composites had superior mechanical properties compared to hybrid and bamboo fiber reinforced composites, especially in terms of tensile and flexural characteristics. The study concludes that combining natural and synthetic fibers leads to composite materials with acceptable mechanical performance.

Physics‐Based Machine‐Learning Approach for Modeling the Temperature‐Dependent Yield Strength of Superalloys

In the pursuit of developing high‐temperature alloys with improved properties for meeting the performance requirements of next‐generation energy and aerospace demands, integrated computational materials engineering has played a crucial role. Herein, a machine learning approach is presented, capable of predicting the temperature‐dependent yield strengths of superalloys utilizing a bilinear log model. Importantly, the model introduces the parameter break temperature, Tbreak, which serves as an upper boundary for operating conditions, ensuring acceptable mechanical performance. In contrast to conventional black‐box approaches, our model is based on the underlying fundamental physics built directly into the model. A technique of global optimization, one allowing the concurrent optimization of model parameters over the low‐ and high‐temperature regimes, is presented. The results presented extend previous work on high‐entropy alloys (HEAs) and offer further support for the bilinear log model and its applicability for modeling the temperature‐dependent strength behavior of superalloys as well as HEAs.

Focus on the crucial deformation region to adjust the comprehensive performance of poly (L-lactic acid) stent

The fully biodegradable polymer stent is considered as the fourth-generation vascular implant with good biocompatibility and long-term therapeutic potential. It has attracted much attention because it overcomes the disadvantage of the permanently implanted metal stent. However, compared with the metal stent, its mechanical properties are slightly inferior, which is an urgent problem. Based on previous studies, fully biodegradable polymer stents are prone to experience cracks and damage in large deformation region during the crimping and expansion process. The large deformation region is mainly located at the ring bend of the stent. We supposed that these damages are the leading causes of weakening the mechanical performance of polymer stents and are mainly affected by the crucial deformation region. For this purpose, this work studies the relationship between different crucial deformation regions and the mechanical performance of the polymer stent. Firstly, the volume of the crucial deformation region is improved by increasing the ring width. Although the radial strength of the stent is enhanced with the increase in ring width, the radial stiffness also increases, and correspondingly, the flexibility of the stent decreases. To obtain acceptable comprehensive mechanical performance, two types of slotting design in critical deformation region were proposed. The proposed slotted stent with a bulge has sufficient radial strength and low radial stiffness, having a good radial support capacity and flexibility. In other words, the proposed stent has improved the radial support without sacrificing flexibility. Overall, different crucial deformation regions cause different degrees of damage to the stent during crimping and expansion, which affects the mechanical properties of the stent. Reasonable structural design of the crucial deformation region is the key to adjust the comprehensive performance of the stent.

Design of concrete incorporating microencapsulated phase change materials for clean energy: A ternary machine learning approach based on generative adversarial networks

The inclusion of microencapsulated phase change materials (MPCM) in construction materials is a promising solution for increasing the energy efficiency of buildings and reducing their carbon emissions. Although MPCMs provide thermal energy storage capability in concrete, they typically decrease its compressive strength. A unified framework for the mixture design of concrete incorporating MPCM is yet to be developed to facilitate practical applications. This study proposes a mix design procedure using a novel ternary machine learning (ML) paradigm. For this purpose, the tabular generative adversarial network (TGAN) was utilized to generate large synthetic mixture design data based on the limited available experimental observations. The synthetic data is then employed to construct robust predictive ML models. The gradient boosting regressor (GBR) model trained with synthetic data outperformed the model trained with real data, achieving a testing coefficient of determination (R2) of 0.963 and mean absolute error (MAE) of 2.085 MPa. The TGAN-GBR model was ultimately integrated with the particle swarm optimization (PSO) algorithm to construct a powerful recommendation system for optimizing the mixture design of concrete and mortar incorporating different types of MPCMs. Extensive parametric analyses along with the employed optimization procedure accomplished the mixture design of latent heat thermal energy storage concrete with maximum MPCM inclusion and minimum cement content for various compressive strength classes. The proposed framework enables energy conservation technology in the design of eco-friendly building materials with acceptable mechanical performance.

Investigations of Fatigue Damage in a Nitriding Low-Carbon Bainitic Steel for High-Performance Crankshaft

In the automotive environment, the need to increase the performance of materials requires extra engineering efforts. The possibility of developing new materials is strategically important. Indeed, alternative solutions in terms of material choice allow designers to optimise their projects and keep competitive production costs. Traditional quenched and tempered steels are usually used for highly stressed components, and possible alternatives could be important competitive opportunities. One possible substitute is using bainitic steels to exploit their economic advantages while maintaining acceptable mechanical performances. This paper explores the fatigue life behaviour of a new low-carbon bainitic steel for applications requiring case hardening treatment obtained by the nitriding process. A high-cycle fatigue (HCF) strength assessment is conducted through a test campaign to compare treated and untreated material. The improvement in fatigue strength is evaluated as well as the study of fracture surfaces, residual stress, and microhardness profiles to assess in detail the effectiveness of the nitriding process. It is found that the nitriding leads to an improvement in fatigue life but not as much as expected because of the low ductile behaviour of this steel, the high speed of stress application added, and the embrittlement of the nitriding treatment, as confirmed through fracture surface analysis.

Kinetics of Bainite Transformation in Multiphase High Carbon Low-Silicon Steel with and without Pre-Existing Martensite

In the present study, the isothermal decomposition of austenite to bainite in 1.0 wt% carbon, 0.21% silicon steel during the partitioning step of a quenching and partitioning (Q&P) heat treatment has been investigated in a dilatometer in the temperature range of 200 to 350 °C and compared to conventional austempering heat treatment. The bainite transformation was shortened by about 75% in the presence of pre-existing martensite (QP). The kinetics of bainite transformation is described by the well-known Avrami equation. The calculated parameter ‘n’ in the Avrami equation shows that bainite forms in the absence of pre-existing martensite (TT) at a constant nucleate rate, while in the presence of pre-existing martensite, nucleation is interface controlled. The overall bainite transformation activation energy, calculated by the Avrami equation, ranges from 64 to 110 kJ/mol. The outcomes of this investigation provide guidelines for the development of multiphase microstructures, including pre-existing martensite and bainite in high-carbon low-silicon steel, within an industrially acceptable time scale and mechanical performance.

Fabrication, in vitro and in vivo properties of β-TCP/Zn composites

In recent years, biodegradable Zn-based materials became a hopeful approach for new generation biomedical implants due to their acceptable mechanical performance, moderate biodegradation rate, and good biocompatibility. In this study, the combination of high-energy planetary milling and spark plasma sintering process were employed to fabricate n vol% β-TCP (n = 0, 0.5, 1, 3, 5, 10)/Zn composites with uniform microstructure and high relative density. The microstructure investigation, mechanical performance, degradation behavior, in vitro and in vivo properties of the composites were systematically investigated. As a result, β-TCP nanoparticles were homogeneously dispersed in the whole composites and possessed a good bonding interface with the Zn matrix. The degradation of pure Zn and β-TCP/Zn composites in vitro and vivo is a uniform corrosion process. Enhanced corrosion resistance attributed to the addition of β-TCP with a optimized content. The evaluation of osteogenic differentiation process showed that the addition of β-TCP induced the up-regulated expression of osteogesis-related genes (ALP) in mouse preosteoblasts, thus improving the osteogenic ability. As revealed by animal experiments, six months after implantation of pure Zn and 3TCP/Zn components, the blood biochemical parameters of rats showed no obvious tissue inflammation, indicating excellent in vivo biocompatibility of experimental materials. Histological investigation showed that with prolonged implantation time, the 3TCP/Zn components were more effective than pure Zn in promoting new bone formation. In summary, 3TCP/Zn matrix components developed in the present study should be useful for orthopedic implants.

Study of the mechanical, chemical, and surface behaviors of non-woven abrasive made from waste chemically modified tow fibers

This article aims to develop a non-woven abrasive material based on textile waste with suitable mechanical properties and surface conditions for the washing treatment of jeans. For this proposal, tow fibers mixed with cotton fibers were reinforced into a polyurethane resin and iron shavings using a coating technique. Abrasive morphology has been examined using MEB analysis. Their elemental composition was identified by EDX Test. The chemical characterization (FTIR) of iron grains was also mentioned. The influence of chemical fiber treatments (alkalinization and cationization) on the mechanical performance and surface properties of nonwovens has been analyzed. To examine fiber-matrix bonding and adhesion, a fiber pullout test was performed. The results showed that nonwoven created with cationized tow fibers improve interfacial properties compared to those made with untreated or alkalized fibers. While their mechanical qualities (Tear test, traction, etc.) were slightly reduced. The variation in the percentages of fibers (tow/cotton) has also an impact on the mechanical strength of the reinforcements. Using the Universal Surface Tester (UST), roughness measurements of nonwovens surface showed that the incorporation of Tow fibers led to significant improvement in the roughness. Cationization at 3% gives good interfacial adhesion and acceptable mechanical performance. This sample has been tried and validated by washing-out experts.

Observations of Polymer Foam Development during Rotational Moulding

Large scale buoyant structures typical of offshore wave energy generation devices may be produced using the rotational foam moulding process. Due to the challenging environmental conditions these parts experience during their lifetime at sea, it is important that the structures are optimised to ensure acceptable mechanical performance. Foams containing large cells suffer a reduction in mechanical properties; therefore, an optimal foam contains small, evenly sized, and well distributed bubbles in large numbers. Due to the lower pressures used in the process, this can be challenging to achieve. Careful selection of material and processing conditions is required to achieve an optimal structure. A unique bench-based rig was used to observe developing foam structures. A camera was used to record the foam height change at intervals. Foam height change was obtained using digital image analysis. Several parameters were studied such as the polymer particle size or the mould pressure for example. In addition to the foam height change, foam density were analysed. It is found that mould pressure, polymer particle size, chemical blowing agent concentration, and polymer rheology may be used to control the foamed structures.

Valorization of Posidonia-Oceanica leaves for the building insulation sector

A new bio-composite material appropriate for building thermal insulation is proposed. The hydrophilic, thermal, and mechanical properties of composites made with Posidonia-Oceanica leaves, are experimentally investigated. The effect of two different sizes of fibers (natural and crushed leaves) as well as the effect of the chemical treatment (1% sodium hydroxide) are studied. For this purpose, different parallelepipedic specimens of dimensions 270 × 270 × 30 mm3 (thermal properties tests) and 160 × 40 × 40 mm3 (mechanical properties tests) were prepared by varying densities of leaves (0, 5, 10, 15, 20, and 30% by volume). In comparison to the fiber size effect, the results reveal that fiber loading has a significant impact on the mechanical and thermal characteristics of composites. Alkali treatment can improve the compressive and flexural strength of bio-composites. The novel bio-composites have low thermal conductivity (0.09 W.m−1K−1 when 30% of reduced size Posidonia-Oceanica leaves were loaded into the reference mortar) and acceptable mechanical performances. Results also show (1) The addition of treated fiber improves the ductility of the material. (2) The fracture toughness is 75% greater than reference mortar. (3) The use of crushed fibers decreases the composite’s mechanical strengths. (4) The flexural strength decreases with the fibers content and increase after 1% sodium hydroxide treatment. It can be concluded that the proposed bio-composite can be employed as thermal insulation material.

Preparation and characterization of natural rubber–based new elastomers for high-damping base isolation systems

Natural rubber (NR)–based vulcanizates have been used as base isolation materials for many years. Combining good damping properties, low cost, and availability with acceptable mechanical and aging performance, these materials have always been the first choice for base isolation applications. In this research, we try to formulate a natural rubber base recipe with increased damping properties, which can fulfill mechanical and aging requirements of base isolation systems. For this purpose, a series of blends have been formulated by incorporating chloroprene (CR) or butadiene (BR) and acrylonitrile butadiene rubber (NBR) into the natural rubber base. Filler content accelerator type and vulcanization system have been chosen to optimize damping while maintaining a reference point. All vulcanizates have been tested for their mechanical properties. Moving die rheometer (MDR) and rubber process analyzer (RPA) have been used to obtain general cure data as well as storage (G′) and loss modulus and loss angle (η). Crosslink densities have been calculated using RPA and Lee and Pawlowsky’s Coran approach. Dynamic material tests have been performed to obtain dynamic shear properties, equivalent damping ratio, and shear modulus. The results indicated that NR/NBR and NR/CR compounds with viscous damping values of 10.4% and 8.9% at frequency of .5 Hz can lay bases for formulating high-damping rubber (HDR) materials for base isolation systems due to their increased damping and rather good mechanical and relaxation performance.

The impact of thermal reprocessing of 3D printable polymers on their mechanical performance and airborne pollutant profiles

The alterations in volatile organic compound (VOC) and ultrafine particulate (UFP) matter emission profiles following thermal reprocessing of multiple materials were examined. Additionally, mechanical performance of the materials was studied. The VOCs were identified by collecting air samples with Tenax® TA tubes and analyzing them with a GC–MS system. UFP concentrations were monitored with a portable ultrafine particle counter. Total VOC emissions of all materials were reduced by 28–68% after 5 thermal cycles (TCs). However, slight accumulation of 1,4-dioxane was observed with poly(lactic acid) materials. UFP emissions were reduced by 45–88% for 3D printing grade materials over 5 TCs but increased by 62% in the case of a waste plastic material over 3 TCs. The mechanical performance of the materials was investigated by measuring their tensile strengths (TSs) and elastic moduli (EM) with an axial-torsion testing system. The reprocessed materials expressed fluctuations in their 3D printing qualities and mechanical performances. The mechanical performances were observed to reduce only slightly after 5 TCs, and the trend was observable only after the data was mass-normalized. The TSs of the samples were reduced by 10–24%, while the EM were reduced by 1–9% after 5 TCs. The TS and EM of one material were increased by 14 and 33%, respectively. In conclusion, recycled polymers are plausible 3D printing feedstock alternatives as they possess acceptable mechanical performance and low emittance according to this study. Furthermore, non-3D printing grade polymers may be applied in a 3D printer with caution.

Ti6Al4V alloy fabricated by gelcasting based on low-oxygen gel system using hydride-dehydride titanium alloy powders

Oxygen and carbon impurity residues and low density are the main issues for Ti gelcasting. To overcome these difficulties, this study develops a low-oxygen isoprene (Ip)/polyvinyl butyral (PVB) gel system to achieve Ti gelcasting using hydride-dihydride (HDH) Ti6Al4V powder. Slurries with 48 vol% solid loading content are employed to achieve moulding followed by cold isostatic pressing. During gelcasting, powder particles are held in place by the cross-linking of Ip monomer with PVB as adhesive to maintain shape. After sintering, nearly fully dense (4.38 g/cm3) Ti6Al4V alloys with low interstitial contamination (O: 0.356 wt%, C: 0.14 wt%) are successfully fabricated. The samples exhibit acceptable mechanical performance, with ultimate tensile strength of 1062 MPa, yield strength of 987 MPa, and elongation of 8.75%. Typical plastic fracture with river patterns is observed, which is distinctly different from that of HEMA based sample.

Topology Optimization of an aircraft engine gearbox

Topology Optimization (TO) is a mathematical method extensively employed to optimize material layout within the design space, for a given set of boundary conditions with the goal of maximizing the performance of the system. This process takes a three-dimensional design space and whittles material away within it to achieve the most efficient design. Currently, engineers use this mathematical approach at a concept level of a design process, leading to results which are often fine-tuned for manufacturability. In some cases, the optimized geometry can be directly manufactured using additive manufacturing, indeed, TO is a key part of design for additive manufacturing. This work aims to apply TO in order to minimize the mass of an engine gearbox while maintaining an acceptable mechanical performance when compared to the original design. Numerical simulations are carried out by means of CAD and FEM software in order to improve the design of an aircraft gearbox composed of four gears, therefore, irrelevant parts of material are removed in the design space to meet the goal of minimizing the mass of the gearbox. The application of TO allows to obtain a better, lighter, and more efficient design of the gearbox by keeping its mechanical performance unchanged.