Italian Group Fracture (IGF): E-Journals / Gruppo Italiano Frattura
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Exploring the elastocaloric effect of Shape Memory Alloys for innovative biomedical devices: a review
Full text linkThis paper discusses Shape Memory Alloys’ (SMA) elastocaloric effect (EC) and underscores its potential use in substituting conventional cooling systems, for future and innovative applications in the biomedical sector, where temperature has a significant influence on the structure and function of crucial macromolecules and cells. After an introduction on SMA’s EC and its relevance for medical and biomedical field, the authors examine the principles and mechanisms at the base of this particular property, with a focus on main keys essential to evaluate performances and the differences characterizing most used elastocaloric alloys, also exploring strategies currently in place to improve performances. Thereafter, the discussion moves on the current design and development of instruments exploiting this innovative behavior, introducing thermal microdevices made of elastocaloric materials in biomedical applications. It concludes by analyzing future directions of elastocaloric cooling and heating for biomedical applications, including possible upcoming medical and biomedical devices, evaluating challenges that researchers still need to address for the adoption of SMA’s EC in the biomedical field
The Epoxy-based composites with Size-Fractionated Waste Areca Sheath: An Experimental Investigation on the Macroscopic and Vibrational Properties
No full textThe use of Areca sheath in developing a newer composite material is proposed in this article. The Areca sheath particulates are extracted by pulverizing long sheaths into different sizes of particulates and are reinforced into the epoxy to process the composites. The study evaluated these composites' macroscopic and vibrational properties, revealing that those with coarse particulates demonstrated superior tensile and flexural strengths, impact strength, hardness, and natural frequency. Notably, the coarse epoxy composite with a 10% weight fraction of particulates exhibited tensile strength and modulus values of 24 MPa and 1050 MPa, respectively. These findings suggest that incorporating a 10% weight fraction of coarse Areca sheath particulates into epoxy resin significantly enhances the composite's macroscopic and vibrational properties, making it a promising material for various building applications like Partition panels, Ceiling Panels, and similar applications.
Numerical analysis of 3D printed joint of wooden structures regarding mechanical and fatigue behaviour
Full text linkThis paper presents numerical models of a 3D printed plastic joint applicable to the connection of wooden structures. The research presented provides a comparison of two alternative solutions for the geometry of the joint and results from several loading schemes and boundary conditions. Included are analyses evaluating the mechanical behaviour in a simple axial tensile test, a three-point bending test and, finally, a sensitivity analysis of the location susceptible to fatigue damage. The models include a 3D printed polycarbonate joint, wooden elements and steel shear pins. The combined model allows a deeper understanding of the interactions. Finite element method (FEM) software was used to develop the numerical models and suitably defined boundary conditions, and material properties of all parts were adopted. The simulation results show that the 3D joint exhibits a high resistance to tensile loading, while in the case of three-point bending, a higher susceptibility to fracture of the printed joint is observed. The sensitivity fatigue analysis identified critical areas on the 3D printed component that need to be improved before further development. These analyses provide important information for optimizing the design of 3D printed plastic joints intended for wooden structures
Ultrasonic fatigue testing of AISI 304 and 316 stainless steels under environmental and immersion conditions
Full text linkUltrasonic fatigue tests were carried out on stainless steel AISI 316 and 304, under two modalities: at room temperature and in immersion (water for 316 and antifreeze for 304 steels); all tests were carried out with a loading ratio R=-1. The results obtained in the tests at room temperature (without immersion), for both materials exhibited a significant increase in temperature, leaving heat marks on the narrow section of the specimens. This phenomenon occurred due to the low coefficient of thermal conductivity of these stainless steels (16.2 W/ (m °K)), and the recorded temperatures were around 200 °C, generating instantaneous failure of material. Analyzes of fracture surfaces on specimens tested at room temperature reveal that crack initiation was related to the high temperature, causing alteration at the granular scale of the material, followed by a typical behavior crack propagation and failure. For specimens tested under immersion conditions, it was possible to reduce the temperature below 100 °C, which solved the problem of failure due to thermal effect. The results for 316 stainless steel immersed in water showed a fatigue life of 1.188×1010 cycles at188 MPa of stress loading in the specimen; while specimens subjected to 263 MPa stress showed a fatigue life of around 7×106 cycles, representing a significant reduction with an approximate factor of 1700. On the other hand, specimens of 304 stainless steel immersed in antifreeze with the lowest loading values of 169 MPa, showing an infinite ultrasonic fatigue life; while tests subjected to 263 MPa loading stress attains 3.62×106 cycles of ultrasonic fatigue life. The scanning electron microscopy visualizations for both cases of immersion tests showed that the initiation and propagation of the crack occurred on the surface of the specimens, exhibiting the typical mechanical fracture behavior without any apparent thermal influence
Mechanical behavior of fiber-glass plastic with hole pattern using digital image correlation and acoustic emission methods
Full text linkIn this paper, tensile tests of specimens with a pattern of holes made of fiber-glass plastic based on combined epoxy and phenol-formaldehyde resins are carried out in order to study the processes of damage accumulation and tension fracture. The Vic-3D video system is used to evaluate damage development and inhomogeneity of strain localization during loading. Continuous recording of acoustic emission signals is carried out during the tests, resulting in obtaining data on fracture mechanisms in the material. Ranges of peak frequencies are identified. Surface analysis of specimens was carried out using a microscope. A significant reduction in strength occurs due to the presence of a circular hole in the material, although additional holes do not exacerbate this effect. Fracture patterns of specimens with a hole pattern have been analyzed, and different "paths" of fracture have been observed. The comparison of strain fields obtained on the basis of application of three-dimensional digital optical system with the configuration of strain fields constructed as a result of numerical modeling by the finite element method has been carried out. It is found that the strain fields for different open hole patterns are quantitatively and qualitatively similar and identical
The Impact of nanoparticles (B4C-Al2O3) on mechanical, wear, fracture behavior and machining properties of formwork grade Al7075 composites
No full textThis study explores how ageing temperature and the volume percentage of Al2O3+B4C nanoparticles influence the machinability and hardness of stir-cast Al-7075 Metal Matrix Composite (MMC). Using liquid metallurgy techniques, hybrid materials were created by reinforcing Al7075 metal matrix with varying weight percentages of nanosized B4C (1.5%, 3%, and 4.5%) and Al2O3 (1%, 1.5%, and 2%). After fabrication, the samples were subjected to five-hour ageing process at temperatures of 100, 120, and 140 degrees Celsius, followed by cooling to ambient temperature (27 degrees Celsius). Hybrid nano composites that had been heat treated were tested for wear, tensile strength, and hardness. Results shows that, the addition of nanoparticles and heat treatment considerably improves the tensile strength, hardness, and wear resistance of hybrid composites by 3%, 17%, and 10%, respectively, for samples reinforced with 4.5% B4C + 2% Al2O3. SEM analysis was used to investigate the type of wear and the tensile fracture mode of nano composite samples by analyzing the wornout surface and the surface where tensile fracture occurred. Machinability was assessed using L27 orthogonal array tests, focusing on three key process parameters: feed rate (0.1 mm/min), depth of cut (0.2 mm/min), and spindle speed (1000 rpm). Outcomes show that, increasing the wt. % of nano-Al2O3/B4C leads to higher machining force and surface roughness (Ra) of MMCs. Conversely, higher ageing temperatures result in decreased machining force and surface roughness. Optimal surface roughness and machining force were achieved with 1% Al2O3 + 1.5% B4C and an ageing temperature of 140°C. These findings offer valuable insights into the ease of machining of composite metal alloys, emphasizing the importance of parameter selection and optimization for desired machining outcomes
Modeling turning performance of Inconel 718 with hybrid nanofluid under MQL using ANN and ANFIS
Full text linkSoft computing techniques, with their self-learning capabilities, fuzzy principles, and evolutionary computational philosophy, are being increasingly utilized in modeling complex machining processes. This study develops artificial neural networks (ANN) and adaptive neuro-fuzzy inference system (ANFIS) models to predict cutting force, surface roughness, and tool life during Inconel 718 turning with a hybrid nanofluid under minimum quantity lubrication. The hybrid nanofluid was created by combining 50–50% multi-walled carbon nanotubes and aluminum oxide nanoparticles with vegetable-based palm oil. ANFIS and ANN models were constructed with data from well-designed machining trials. The ANFIS model predicted machining performance using fuzzy logic, whereas the ANN model employed a feedforward neural network design. The results showed that both models were able to accurately predict the machining performance. However, ANFIS outperforms ANN in terms of accuracy, with prediction errors of 4.47% and 10.97% for surface roughness, and 6.05% and 9.86% for tool life, respectively. However, the accuracy of cutting force prediction was slightly higher with the ANN. This shows that ANFIS could be a better option for forecasting the machining performance while turning Inconel 718. However, this study suggests further investigation into ANFIS modeling, with a focus on membership function parameter optimization through hybrid optimization techniques
Revisiting classical concepts of Linear Elastic Fracture Mechanics - Part III: The stress field in a double-edge notched finite strip by means of the “stress-neutralization” technique
Full text linkThis is the third part of a short series of paper, revisiting some classical concepts of Linear Elastic Fracture Mechanics. Based on the solution for the single edge notched strip, discussed in Part-II, the present study deals with the stress field developed in a stretched finite strip, weakened by two symmetric edge notches. The notches are of parabolic shape, approximating the configuration of a rounded V-notch, varying from almost semicircular edge cavities to “mathematical” edge cracks of zero distance between their lips. The solution is obtained combining Muskhelishvili’s complex potentials technique with a procedure for “stress-neutralization” of specific areas of the loaded strip. To simplify the procedure, the notches are assumed to be “shallow” (short) so that they do not affect each other. Once the complex potentials are obtained, the stress field variations are plotted along strategic loci of the strip and along the periphery of the notches. Attention is paid to the stress field developed around the bases (tips or crowns) of the two notches, providing relatively simple formulae for the critical tensile stress. In addition, the respective stress concentration factor k is obtained for blunt notches, while in the case the edge discontinuities become “mathematical” cracks, a simple expression is given for the mode-I stress intensity factor KI at the tip of the crack. It is revealed that the assumption of “shallow” notches suffices a quite efficient solution for the overall stress field in finite strips
Rubberized reinforced concrete columns under axial and cyclic loading
Full text linkThe experimental study presented in this research was conducted to understand the performance of rubberized concrete columns under axial loads and numerically analyze the conduct of rubberized reinforced concrete (RRC) columns under cyclic loads. Twelve large-scale columns with square and circular cross sections were utilized to carry out experimental testing. Under axial loading, fine aggregate was replaced in percentages of 0%, 10%, and 15% with crumb rubber (CR). Square RRC columns were examined by a finite element program (ABAQUS) under cyclic loading. The experimental results indicated that the columns with crumb rubber had a lower load capacity than those without crumb rubber when exposed to axial loads. The numerical results were in good alignment with the experimental results, indicating that the simulated model may simulate the behavior of rubberized concrete columns under both axial and cyclic loads. According to the numerical analyses, the lateral displacement was significantly improved for rubberized reinforced concrete columns with 10% and 15% replacement of fine aggregates compared to columns without CR. Adding 10% and 15% of crump rubber to the fine aggregate in reinforced concrete columns increased the displacement ductility. The equivalent viscous damping ratio was enhanced by 33.67% when increasing crumb rubber (CR) from 0% to 10%, and when crumb rubber (CR) replacement became 15%, the damping ratio increased to 44.02%.The rubberized reinforced concrete columns showed a more ductile reaction than the traditional reinforced concrete columns, as evidenced by their softer post-peak response
Indentation Fracture Toughness of Aluminium-Graphite Composites: Influence of Nano-particles
Full text linkIn the field of composite materials, extensive research has been undertaken on aluminum-graphite composites. However, a research gap has been identified regarding the specific influence of nano-sized graphite particles on their fracture toughness. Previous studies have predominantly focused on larger graphite particles or different reinforcement materials, resulting in relatively unexplored effects of nano-graphite particles. This research is deemed critical as it has the potential to generate lightweight, high-strength materials, aligning with the demands of aerospace, automotive, and structural engineering. The primary objective of this study is to investigate how the inclusion of nano-sized graphite particles affects the fracture toughness of aluminum-graphite composites. To achieve this objective, systematic dispersion and incorporation of nano-sized graphite particles into an aluminum matrix will be carried out. Mechanical testing, including fracture toughness assessments, will be conducted to evaluate the performance of the composite materials. Factors such as particle size, distribution, volume fraction, and interfacial bonding will also be characterized within the study. It is anticipated that the presence of nano-sized graphite particles will lead to a significant enhancement of the fracture toughness of the aluminum-graphite nanocomposites. This enhancement is expected to be attributed to crack deflection, tortuosity, altered stress distribution, and increased plastic deformation around cracks