Italian Group Fracture (IGF): E-Journals / Gruppo Italiano Frattura
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Damage identification in steel plate using FRF and inverse analysis
Get PDFMetaheuristic algorithms have known vast development in recent years. And their applicability in engineering projects is constantly growing; however, their deferent exploration and exploitation techniques cause the engineering problems to favor some algorithms over others. This paper studies damage identification in steel plates using Frequency Response Function (FRF) damage indicator to detect and localize the healthy and damaged structure. The study is formulated as an inverse analysis, investigating the performance of three new metaheuristic algorithms of Wild Horse Optimizer (WHO), Harris Hawks Optimization (HHO), and Arithmetic Optimization Algorithm (AOA). The objective function is based on measured and calculated FRF damage indicators. The results showed that the case of four damages with different damage severity levels presented a good challenge where the HWO algorithm was shown to have the best performance. Both in convergence speed and CPU time
Influence of 3d-printing parameters on the mechanical properties of 17-4PH stainless steel produced through Selective Laser Melting
Get PDFAdditive Manufacturing (AM) is a technological process in which elements are fruitfully built up adding materials layer by layer. AM had a massive development in recent times, thanks to its intrinsic advantages, especially if compared with conventional processes (i.e. subtractive manufacturing methods), in terms of free-form design, high customization of products, a significant reduction in raw materials consumption, low request of postprocessing and heat treatments, use of pure materials and reduced time for final products to be marketed. In order to give an innovative contribution to the knowledge in the field of metal AM materials, this paper reports the main outcomes of an experimental campaign focused on the influence of several specific printing parameters on the mechanical features of the 17-4PH stainless steel, which is one of the most used metal for the Selective Laser Melting (SLM) technology. The influence of different printing directions and sample inclinations on the material mechanical behavior is assessed, with the aim of considering an innovative use in the field of structural engineering. Moreover, the effects due to scanning and recoating times are studied. In addition, the consequences of heat treatment (annealing) on both the residual stresses and the amount of residual austenite are appraised
Numerical study of TRIP transformation in 35NCD16 steel-effects of plate orientation and some criteria
Get PDFThis study aims to analyze the effect of thermo mechanical coupling damage in the presence of a phase change (austenite/martensite) in 35NCD16 steel. The impact of increasing mechanical traction load, accompanied by a martensitic transformation on the scale of a single grain with boundary has been studied. The prediction transformation of induced plasticity (TRIP) was evaluated by taking into account the following parameters: twenty shear directions of the martensitic plates, two values of the shear deformation of the martensitic plates, energetic and thermodynamics criteria for getting in order the transformation of the martensitic plates, elastoplastic behavior of the two areas in the first case (martensitic plate and grain boundary) and elastic behavior for the grain boundary in the second case. The numerical calculation is carried out using the finite element method (FEM), implemented in the Zebulon calculation code. The developed approach is validated using the available experimental results reported in the literature. The numerical results showed that the estimation of TRIP given by the energetics criteria with the values of the shear deformation (γ0 = 0.16) are closer to the experiment results
Optimization of High-Performance-Concrete properties containing fine recycled aggregates using mixture design modeling
Get PDFThis investigation means to predict and modeling the fresh and hardened concrete behavior containing fine aggregates from concrete and brick wastes, for different recycled aggregates substitution rates.
To succeed this, the design of experiments DOE method was used. It is observed that slump of recycled concrete is significantly influenced by the content in recycled concrete aggregates (RCA), natural sand (NS) and recycled brick aggregates (RBA), respectively.The compressive strength (CS) reaches a maximum value of 83.48 MPa with factors values of 25% RBA, and 75% RCA. And HPC’s based on RBA sand presented greater values of flexural strength at 7 days than HPC’s based on RCA sand, it was revealed that this is due to the RBA fines pozzolanic reaction and the production of new CSHs, which leads to better cement matrix densification.Under optimal conditions, themaximum desirability is 0.65, who has given HPC no added natural sand, by mixing recycled sands RBA (9.5%) with RCA (90.5%).The statistical terms result show that the expected models are very well correlated with the experimental data and have shown good accuracy
Fragility analysis of concrete elevated water tanks under seismic loads
Get PDFThe design of concrete elevated water tanks involves several kinds of uncertainties. Traditionally, the design of these structures is based on a deterministic analysis. Partial safety factors prescribed in design codes are applied to take into account these uncertainties and to ensure sufficiently safe design. However, this approach does not allow rational evaluation of the risk related to the structural failure and consequently its reliability. In fact, the partial safety factors can lead to over-designed structures; or to under designed structural components leading to a lack of structural robustness. In this study, a probabilistic approach based on Monte Carlo simulations is used to analyze the reliability of elevated water tanks submitted to hazard seismic loading. This reliability approach, takes into account mainly two parameters. Firstly, the hydraulic charge in the tank container which is a function of time, and secondly, the hazard seismic loading through the Peak Ground Acceleration is considered as a random variable. Fragility curves depending on seismic zones and soil types are obtained by using the probabilistic approach, where they demonstrate the dominant failure modes that can cause the structural failure with respect to different seismic levels, soil types and water height level in the tank container
Behavior of Structural Concrete Frames with Hybrid Reinforcement under Cyclic Loading
Get PDFA substantial amount of work was carried out on the use of fiber-reinforced polymer (FRP) in reinforcing concrete structural elements, which demonstrated considerable inelasticity or deformity through monotonous and fatigue loads. Even so, the action of FRP bars in FRP-RC columns and frame structures has not yet been studied during reversed cyclic loading.
In this research, reversed cyclic loading was conducted on three beam-column joint models using the finite element method with ANSYS software. The first model was for a joint designed with steel rebar for both the longitudinal reinforcement and stirrups. Glass fiber reinforced polymer (GFRP) rebar was used to reinforced the second joint model for both longitudinal reinforcement and steel stirrups, and the third joint model was designed with hybrid steel/GFRP reinforcement for the longitudinal reinforcement and steel stirrups. The performance of the three models under reversed cyclic loading, such as load vs. story drift and energy dissipation capacity, were compared. The GFRP-reinforced model displayed a predominantly elastic activity up to failure. Although its energy dissipation was weak, its performance in terms of total storey drift demand was satisfactory
Impact response of different materials for sports mouthguards
Get PDFUp to this moment, there is no guideline regarding the materials to produce mouthguards. The most used is Ethylene-Vinyl Acetate (EVA). Studies indicate that laminating EVA sheets with rigid components could increase the protection capacities of the mouthguards whereas other studies suggest that only replacement of the material within it structure can increase energy absorption. The aim of this work is to evaluate the impact response of four different foils when compared to a 4 mm thickness EVA sheet. Five groups of different materials were subjected to impact tests with energies of 1.72 J, 2.85 J and 4.40 J. In this context was considered the following materials: EVA foils (G1), EVA foils with an EVA foam core (G2), EVA foils with an acetate core (G3), Foils of Erkoloc-pro (G4) and Foils of Ortho IBT resin (G5). Comparisons between the materials were made by qualitative analysis of the average energy-time and load-displacement curves, as well as by comparison of the peak load, maximum displacement, contact time and absorbed energy using the Kruskal-Wallis test. It was possible to conclude that statistically significant differences were found in the energy absorbed (p=0.001). Laminated foils with a soft core (G2) are a good option to produce mouthguards, while EVA foils with an acetate core (G3) and foils of Ortho IBT resin (G5) were declared unsuitable
Experimental study and modeling of the mechanical behavior of recycled aggregates-based high-strength concrete
Get PDFConcrete, a material of prime importance, is widely used in various works. Among the raw materials composing concrete, aggregates come first. It is widely acknowledged that the consumption of natural aggregates increases with the growth in the amount of concrete needed. It has recently emerged that concrete waste can be recycled and reused in civil engineering works after a series of treatments. Moreover, in order to protect the environment and based on the principles of sustainable development, it was considered urgent to produce a High Strength Concrete incorporating recycled materials in addition to silica fume and a high-efficiency superplasticizer. This would certainly help to establish a harmonious sustainable development that guaranties the ecological balance and environmental protection, and prevents the depletion of natural resources. This study is part of a larger research program that that seeks to recover, recycle and valorize construction and demolition wastes. The main objective sought in this article is firstly to use aggregates from demolition concrete in the manufacture of a new concrete with high mechanical and rheological performance, and secondly, to model the behavior of this type of concrete using the Finite Element Method. This modeling aims to evaluate the maximum compressive strengths and compare them with those obtained experimentally
Influence of the applied layer on the state of stress in a bimetallic perforated plate under two load variants
Get PDFThe paper presents the results of the analysis of the influence of the applied plate layer on the state of stress in the bimetallic perforated plate. The finite element method ANSYS program was used for numerical calculations. The paper presents the results of stress tests for a single-layer clad plate made of S355J2 steel and a bimetallic perforated plate consisting of layers made of S355J2 steel and titanium. In addition, the study presents the results of the research on the influence of the method of loading, i.e. the concentrated force P in the geometric center of the plate and the external pressure q on the entire surface of the plate, and the method of support, i.e. free support and fixed, on the location of stress concentration zones in the bimetallic circular perforated plate. It has been shown that the presence of a perforated layer in the plate reduces the value of the equivalent von Mises stress by a minimum of approximately 30% in the base (steel) layer
The effect of surface texturing in the sliding surface on tribological characteristics of alloy steel under wet condition
Get PDFSurface texturing plays a significant role on the tribological performance of contact surfaces. The tribological characteristics are mostly dependent upon the different pattern and methods of surface texturing. This research works investigates lubricated wear behaviour on circular dimples textured EN-31 alloy steel materials using DUCOM linear reciprocating tribometer. The surface dimples are fabricated by micro-EDM and micro-drilling CNC methods. Initially plane surfaces are tested under different lubricants ISO-68 and ISO-220 oil on a couple of EN31 plates with EN8 steel pin. At loading conditions the results clearly shows that the ISO 68 oil gives better performance than ISO-220 oil in terms of frictional force and COF. The operation during test under ISO-220 oil observed is very noisy and wear rate is also more. Then after experiments under different load conditions on textured surfaces were investigated using optimized ISO-68 oil. An experimental results on m-EDM provides superior frictional characteristics with respect to m-CNC. Surface texturing may act as wear debris trapper, lubricant reservoirs, hydrodynamic lift, and retarding the lubricant molecules flow in a particular path where potential exists. Here micro-dimples EDM surface textures can enhance mixed lubrication and in mixed lubrication the friction is least and this may leads to decrement of wear loss