Italian Group Fracture (IGF): E-Journals / Gruppo Italiano Frattura
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High Entropy Cantor Alloys (HEAs) modification induced by tungsten alligation, heat treatment and deep cold plastic deformation
Get PDFHigh Entropy Alloys (HEAs) is a unique class of materials that combine particular properties in a large-scale of temperatures, able to guarantee new unexplored materials and alloys with several potentially engineering applications (i.e. space and aerospace industries). As promising structural materials, HEAs consist of five or more principal elements. As a consequence of the monophasic microstructure which usually characterizes HEAs, these alloys offer an excellent combination of strength, strain hardening ability, good plasticity, ductility and fracture toughness especially at cryogenic temperatures better than the existing conventional metals and alloys. For the above reasons, the present work deals with Classic Cantor alloy, a well-known CoCrFeMnNi HEA, where mechanical properties were improved using low cost casting techniques and a combination of different metallurgical methodologies (heat treatment, cold working and adding alloying elements). A promising alloy element, tungsten, was used in the experimentation where mechanical and microstructural characterization were performed using different technique
The Stress Intensity Factor of convex embedded polygonal cracks
Get PDFIn the present work, a simple formula for the evaluation of the stress intensity factor (SIF) of convex embedded polygonal cracks has been proposed. This formula is structured as a correction factor of the Oore-Burns’ equation and is based on accurate three-dimensional FE analysis. Furthermore, a precise formula for a regular polygonal crack has been given
Microstructure and anisotropic tensile performance of 316L stainless steel manufactured by selective laser melting
Get PDFThe selective laser melting (SLM) technology is widely used to manufacture 316L stainless steel (SS) components for industrial applications. To understand the microstructure and the mechanical properties of additively manufactured 316L alloy, bulk materials were fabricated in longitudinal and transverse directions from which subset tensile specimens were then machine. Bulk materials were subjected to porosity detection with X-ray computed tomography and texture analysis with electron backscatter diffraction (EBSD). Microstructural investigations reveal that the SLM-built specimens had a porosity of 1.87%, and a preferential {110} orientation parallel to the build direction. The transverse specimens show significantly better properties in elastic modulus E (215.1±4.7GPa), yielding stress σy (548.2±8.3MPa) and ultimate tensile strength UTS (705.6±2.9MPa) than the longitudinal ones (E of 175.9±9.8GPa, σy of 495.3±15.5 and UTS of 608.8±3.6MPa). The anisotropic mechanical performance was attributed to the preferential {110} texture caused by thermal conditions during manufacturing and the embedded voids due to insufficient melting. A three-parameter Weibull distribution was adopted to further describe the mechanical anisotropy of SS316L based on stochastic experimental measurements. Fractography indicated the existence of manufacturing defects drive to premature failure of SS316L specimens—around half SS316L specimens failed of elongation less than 0.4
On the peak strength of 7050 aluminum alloy: mechanical and corrosion resistance
Get PDFThis work consists of an experimental study on the ageing response and resulting properties of AA7050 plate material. New heat treatments are investigated for achieving a peak-aged temper, as a T6 temper may be said to be, that achieves yield and tensile strengths superior to those of the documented T7 treatments. For this alloy, the Standard establishes T7X tempers which were developed to obtain a very good compromise between mechanical strength and corrosion resistance. Nevertheless, for all those applications in which the environment is not considered critical for corrosion behaviour, the peak strength condition could be beneficial. In this experimental work, the authors use standard hardness testing to investigate mechanical response as a function of ageing time at several ageing temperatures, all applied immediately after solution. Upon identifying specific times and temperatures of interest, specimens aged under the selected treatments were subjected to tensile testing and intergranular corrosion testing. The results show that a single-step ageing heat treatment is able to produce a significantly high both yield and ultimate tensile strength. Moreover, the corrosion test data indicates that this new heat treatment produces corrosion resistance similar to that of the T76 heat treatment
Use of combined CZM and XFEM techniques for the patch shape performance analysis on the behavior of a 2024-T3 aluminum structure reinforced with a composite patch
Get PDFThe presence of a geometric discontinuity such as a crack or a notch can cause the failure of a structure during its use. Under various mechanical or thermal stresses, a high concentration of stresses can take place at the level of these discontinuities, which in most cases will lead to the total failure of the structure. The service life of these structures can be improved with the use of the repair technique by bonding a composite patch. This technique is of significant interest in several fields, especially with the use of composite materials. This technique is widely used in aeronautics and ensures a long life of damaged structures. Current research aims to optimize the shape size and fiber's nature of this composite patch in order to ensure good load transfer by reducing the stresses in the damaged area. In this work, a finite element method is used to analysis the effect of the shape of the patch on the global response of a 2024-T3 aluminum structure in the presence of a central circular notch. The composite patch is of the carbon/epoxy type bonded through an A-140 Adekit type adhesive on the damaged part of the plate. The analysis consists in determining the force-displacement curves of the repaired structure by using the combination of the two techniques, XFEM for the damage of the aluminum plate 2024-T3 by the automatic creation of the crack and CZM for the analysis of the adhesive debonding. The analysis takes into account the damage in the plate and in the adhesive. However, for the composite patch, and since there will be no damage, we have just analyzed the effect of its shape and essentially the shape of its edges on the load transfer and consequently on the resistance of the structure under loading in tension. Two main patch shapes have been highlighted, namely the square and circular shape. The results show clearly that the shape of the patch’s edges has an impact on the stresses reduction in the plate and subsequently ensures good resistance in terms of force-displacement curve and consequently delays the peeling of the adhesive
Valorization and recycling of packaging belts and post-consumer PET bottles in the manufacture of sand concrete
Get PDFThe valorization of local by-products in the manufacture of a new range of sand concrete and the improvement of their properties, will lead to seek an arrangement between performance and cost in order to achieve a resistant material. Waste recycling affects two very important affect namely the environmental impact and the economic impact. The main objective of our work is to contribute to optimize the formulation of sand concrete as part of the recovery of waste, which is harmful to the environment given its bulky and unattractive nature, it is waste plastic. Most PET bottles become waste after use, causing environmental problems. To solve this problem, a method for recycling PET bottles as fibers to strengthen concrete is proposed.
Two types of plastic waste are added to sand concrete; the first concerns the recycling of post-consumer bottles in PET, in the form of polyester fiber supplied by the company RET-PLAST and the second type concerns the packaging belts made of polyethylene terephthalate (PET). The properties in the fresh state (workability and density) and in the hardened state (compressive strength, tensile strength and water absorption) of the various produced concretes are analyzed and compared against their respective controls. From the experimental results, it can be concluded that the reinforcement of the cement matrix with PET fibers with a rate of 1% improves the mechanical properties of sand concrete as well as a remarkable decrease in its water absorption capacity
Natural Frequency based delamination estimation in GFRP beams using RSM and ANN
Get PDFThe importance of delamination detection can be understood from aircraft components like Vertical Stabilizer, which is subjected to heavy vibration during the flight movement and it may lead to delamination and finally even flight crash can happen because of that. Any solid structure's vibration behaviour discloses specific dynamic characteristics and property parameters of that structure. This research investigates the detection of delamination in composites using a method based on vibration signals. The composite material's flexural stiffness and strength are reduced as a result of delaminations, and vibration properties such as natural frequency responses are altered. In inverse problems involving vibration response, the response signals such as natural frequencies are utilized to find the location and magnitude of delaminations. For different delaminated beams with varying position and size, inverse approaches such as Response Surface Methodology (RSM) and Artificial Neural Network (ANN) are utilized to address the inverse problem, which aids in the prediction of delamination size and location
The Mechanical properties and statistical analysis of the Charpy impact test using the Weibull distribution in jute-polyester and glass-polyester composites
No full textIn recent years, the use of natural fiber composites to provide a possible replacement for synthetic fiber composites for practical applications has been the subject of several studies. This study deals with the fabrication and investigation of jute-polyester composites and the comparison of it with glass-polyester composites. The static mechanical properties of the composites is obtained by testing the composite lamina for tensile and flexural strength. The dynamic mechanical properties of the composites is determined by using the Charpy impact test. By the Williams method based on the principle of linear elastic fracture mechanics, the impact toughness of the composites is deduced. The experimental results were statistically analyzed by using the Weibull theory to better understand the impact behavior of the composites. It is found that the glass-polyester composite has better properties than the jute-polyester composite
Influence of manufacturing shrinkage and microstructural features on the strength properties of carbon fibers/PEEK composite material
Get PDFThis research discusses the micromechanical modelling for thermoplastic composite material. Elastoplastic and damage model for PEEK matrix composite with the dependency of properties to stress state is presented. Plasticity initiation conditions and failure criterion are analyzed. The influence of manufacturing residual stresses is considered. All typical engineering experiments for neat PEEK under different stress state are good predicted by the model. Numerical experiment for macro-properties estimation based on micromechanical model is conducted and the results are compared with the test data
Fracture toughness of matrix cracked FRC and FGC beams using equivalent TPFM
Get PDFIn the present work, the fracture toughness (KIC) of full-depth (FD) fiber-reinforced concrete (FRC) and layered functionally graded concrete (FGC) matrix cracked (MC) beams has been determined by the equivalent relationships of the two-parameter fracture model (ETPFM). Forty-eight MC-FGC and MC-FD FRC beam specimens with span-depth ratios (L/d) equal 4, 5, and 6 were tested under the 3PB configuration. The MC length-depth ratio (ao/d) remained constant equal to one-third. All FRC beams have the same constitutes materials with hooked-end steel fiber volume fraction equals 1%. The FGC beams are composed of three equal layers, i.e., FRC in the bottom layer at the tension side, normal strength concrete (NSC) at the middle layer, and high strength concrete at the upper layer in the compression side. The results showed that the predicted values of KIC obtained from ETPFM are considered logic according to the maximum size of the non-damaged defect concept. The crack mouth opening displacement estimated from ETPFM showed acceptable values close to the present experimental results. The KIC values calculated within the presence of fibers in front of and through the MC for FRC beam specimens having 1% SFs is more than twice the value of NSC