Italian Group Fracture (IGF): E-Journals / Gruppo Italiano Frattura
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Performance of Reinforced Concrete Flat Slabs Having GFRP Gratings
Get PDFA thorough study of the literature indicated that there is not much relevant research on the application of GFRP gratings. Otherwise, extensive study has been done on FRP bars, laminates, sheets, strips, and rods. This study proposes a novel approach to improve the punching shear resistance of flat slab column connections by inserting GFRP gratings across the slab thickness. The results of seven specimens tested under vertical static loading are presented, considering the influence of the grating’s characteristics. All specimens were tested as simply supported slabs under one point of static loading. Experimental results, including crack patterns, slab deflection, concrete compressive strain, tensile steel strain, GFRP grating strain, and failure load, were recorded using extensive electric instrumentation. Test results revealed an enhancement in the failure load ranging between 9.03% and 27.67% for the specimens provided with the GFRP grating. In addition, a nonlinear finite element numerical model analysis was carried out using the ANSYS 15 program. Correlational studies based on the load-deflection response and crack patterns were utilized, resulting in a good agreement between numerical simulations and experimental results with differences ranging from 1.0% to 8.0%.
 
Longitudinal elastic nonlinearity of composite material
Get PDFIt is known that the initial waviness of the fiber affects the stiffness characteristics and strength of the polymer composite material. The article presents a continuum model taking into account the nonlinearity of the longitudinal stiffness of the unidirectional composite. In this study, a finite element experiment was conducted to investigate the variations in the longitudinal stiffness of the composite material subjected to uniaxial compression. The experiment considered a range of different degree of fiber’s waviness to comprehensively examine the impact on the material's stiffness. Obtained results explain the difference in stiffness observed in fiber composites in the longitudinal direction under uniaxial tension and compression. Special constitutive relations proposed to model compressive stiffness reduction in longitudinal direction.  
Structural Health Evaluation of Arch Bridge by Field Test and Optimized BPNN Algorithm
Get PDFArch bridges play an important role in rural roads in China. Due to insufficient funds and a lack of management techniques, many rural arch bridges are in a state of disrepair, unable to meet the increasing transportation needs. Thus, it is of great significance to develop a set of rapid and economic damage identification procedures for the management and maintenance of old arch bridges. Sanliushui Bridge, located in Chenggu County, Hanzhong, is selected as a model case. Field tests and numerical simulations were carried out to identify the damage states of Sanliushui Bridge. The sum square of wavelet packet energy change rate, a damage identification index based on wavelet packet analysis method was implemented to process the measured data of the load test and the simulated data of the numerical calculation model with assumed damage. BPNN, GA-BPNN, PSO-BPNN and test data analysis are adopted to compare the measured data with the simulated data to quantitatively identify the damage degree of the selected bridge. By comparing the results of the two methods mentioned above, it is found that the proposed damage identification approach realized a precise damage identification of the selected arch bridges
Crashworthiness performance of the designed concave hexagonal structures as filler element in cylindrical shell in multiple load cases
Get PDFSafety Impact resistance is defined as the ability of a material to absorb impact energy through controlled failure mechanism. The greater the energy absorption by the crash safety structure, the greater the safety in preventing deformation of the main structure due to impact. In this study, numerical validation, mesh convergence studies and multiple load case studies were performed to investigate crash resistance under axial loading. Numerical validation results show that the similarity between this study and the reference reaches 95%. A deviation of 5% occurs due to different input material properties. The results show that the concave hexagons as filling elements have greater energy absorption capacity than conventional hollow tubes, and the more concave hexagonal structures, the better the energy absorption. Oblique compression was performed in this study and as a result the sample has good impact resistance at low angles and no effect at high angles like 20°
Investigation into effective mechanical properties of porous material produced by the additive manufacturing method
Get PDFPorous materials are defined as materials that contain holes, voids, or spaces in their structures, which can be interconnected or isolated. In the most complex forms of these materials, the holes can have irregular shapes with a random distribution in size, location, and direction, making studying their properties a challenging problem. Additive manufacturing techniques offer opportunities to create complex structures, and in this paper, we investigate the effective mechanical properties of porous material produced by the Fused Displacement Modeling (FDM) technique. We also propose an algorithm for generating a porous body containing irregularly shaped holes with arbitrary distributions in size and location while maintaining specific porosity. Due to the orthotropic properties of bodies created by the FDM technique, Reinforced Isotropic Solid Modeling (RISM) is combined with existing theories that calculate the effective properties of isotropic materials. For the experiments, some modified standard specimen with a porosity of 0.05 to 0.40 has been fabricated, and the elastic modulus and ultimate stress have been calculated using the tensile test. Finally, the results are compared with experimental data
High carbon steel/Inconel 718 bimetallic parts produced via Fused Filament Fabrication and Sintering
Get PDFThe possibility of producing high carbon steel/Inconel 718 bimetallic parts via Fused Filament Fabrication and Sintering is explored. Compatibility of the two alloys with particular attention to elements interdiffusion through the interface as well as the effect of the deposition strategy were analyzed. Microstructural features, relative density and parts shrinkage were investigated, as well. Although first-tentative process parameters values were not sufficient to reach an acceptable material densification, a good bonding between Inconel 718 and carbon steel was observed, suggesting the potential to obtain sound bimetallic parts with a great range of material properties. Due to a difference in densification kinetics, sintering temperature was revealed to be the most critical process parameter to optimize to minimize porosity
Fractography and Tensile studies on the effect of different carbon fillers reinforced hybrid nanocomposites
Get PDFThe use of elastomers has become increasingly important in a variety of industries, including automotive, medical, and food packaging. The adaptability of elastomers to different mechanical stresses has made them a popular choice for these applications. However, the mechanical properties of elastomers can be further enhanced by adding suitable fillers. In this study, the effects of different carbon fillers, namely carbon black, carbon graphite, and carbon nanotubes, on the tensile strength of elastomeric materials were investigated. Different combinations of plain silicone with varying concentrations of CB, CG, and CNT fillers were prepared using a solution casting method. The concentrations of the fillers ranged from 5% to 15% with an interval of 5%. The tensile strength of each combination was measured, and the results showed that the maximum tensile strength was achieved with the combination of CNT at 15% loading. The results of this study highlight the importance of filler selection in enhancing the mechanical properties of elastomers. Carbon fillers, particularly CNTs, have shown to be effective in improving the tensile strength of elastomeric materials. This has important implications for various industries, particularly in the development of new materials for applications in the automotive and medical fields.
The use of elastomers in the automotive industry has become increasingly important due to their ability to absorb mechanical shocks and vibrations. Elastomeric materials have also found applications in the medical field, such as in the development of artificial skin, blood pumps, drug delivery systems, and implants. The use of elastomers in food packaging has also become popular due to their ability to provide a barrier against oxygen and moisture.
The use of carbon fillers in elastomeric materials has the potential to significantly enhance their mechanical properties, particularly their tensile strength. This study provides valuable insights into the effects of different carbon fillers on the tensile strength of elastomers, which can help in the development of new materials for various industrial applications
Analyzing Microstructural Features, Surface Topography, and Scratch Resistance of Innovative Nano-Composites Coated with High Velocity Air-Fuel Technology
Get PDFNew developments in thermal spraying processes may offer higher-quality alternatives to hard chrome plating and possibilities for hard chrome plating in a range of coating applications. These include spraying with high-velocity air fuel (HVAF) and new spray consumables. The low operating temperatures and accelerated particle velocity of the HVAF process enable investigation and development of a wide range of novel coating materials and applications. The High-velocity Air Fuel Process' quality and efficiency are primarily due to the broad combustion chamber and axial injection of the feedstock through it, as well as the relatively low combustion temperature of an air-fuel mixture and the low gas velocity that provides enough time for the mild heating of the powder particles. The current work discusses the inventive thermal spray procedure used for SAE 1008 carbon steel, a cost-effective substrate material. All of the compositions that were treated have undergone microstructure investigations. A scratch test is conducted in accordance with ASTM guidelines. Assessment of surface morphology clearly demonstrates the relationship between the evaluated parameters. According to the occurrence, scratch methods such as delamination, cracking, plastic deformation, and elastic deformation are highlighted. However, the findings of the scratch test showed that the samples' scratch resistance increased as the coating thickness rose. In comparison to samples with thinner coating, those with thicker coating demonstrated a stronger resistance to scratching. This is explained by the fact that coatings with a higher thickness and density can support the subsurface more effectively and stop cracks from scattering. This can retain the coating's integrity and stop more damage from occurring, improving scratch resistance. Better scratch resistance was displayed by the samples with denser microstructures and smoother surface morphologies.
The outcome is greater scratch resistance because a higher density covering can withstand deformation and fracture better than a lower density layer. This is due to the mechanism of deformation and fracture in the coating material. This improvement in scratch resistance can be due to the composites' increased HVAF coating's hardness and adherence. The findings imply that using an HVAF coating to increase the scratch resistance of new nanocomposites may constitute a successful strategy
Notch Sensitivity Study in U-notched Polymers Built by Additive Manufacturing (AM)
Get PDFOnyx ® is a new material composed of Polyamide 6 reinforced with short carbon fiber, used in the novel additive manufacturing composites technique. This paper aims to present the axial fatigue performance of this material with and without U-notches. The experimentally determined S-N fatigue curve was obtained under axial load with a load inversion ratio, R = 0.1, and compared to fatigue performance of U-notched samples ranging from 0.25 to 2 mm radius. In addition, the stress concentration factor was compared for static and alternative loading to obtain the notch sensitivity in terms of the U-notch radius, showing that there is indeed a difference in stress concentration between them. The advantage of the approach is that it permits using commonly used dimensioning methods for this AM material
Study on Micro-structure, Hardness and Optimization of Wear Characteristics of Al6061/TiB2/CeO2 Hotrolled MMCs using Taguchi Method
Get PDFAluminium composites are extensively used in several industrial applications. The production of Metal Matrix Composite (MMCs) with varying wt. % of reinforcement/s leads to enhancement of wear and mechanical behavior. In the present work, the varying wt. % of TiB2 and constant wt. % of CeO2 particulates were reinforced in Al6061 alloy to manufacture hybrid Al MMCs by Vortex (Stircasting) technique. Developed hybrid MMCs were hotrolled at 515°C of temperature. Hardness of hybrid MMCs was evaluated by using hardness test rig (Vickers). Result revealed that the hardness strength of developed hybrid MMCs increased with increase of the reinforcement content. The rate of wear of developed hybrid MMCs was evaluated by using Pin on Disc wear test. Test trials were conducted according to Taguchi technique. L27 array was implemented for evaluation of data. Effect of varying factors on the rate of wear and COF was analyzed by applying ANOVA (Analysis of Variance) method. ANOVA outcomes showed that the reinforcement content had a more significant impact on wear behavior and COF of the MMCs. Finally, L27 array outcomes were verified through confirmation experiments. A wear fractography outcome shows the internal fractured structure of a wear specimen which was studied using a SEM