Italian Group Fracture (IGF): E-Journals / Gruppo Italiano Frattura
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The influence of sustainable reinforcing particulates on the density, hardness and corrosion resistance of AA 6063 matrix composites
Get PDFThe need for the fabrication of sustainable aluminium matrix composites (AMCs) is being sought after as practical alternatives to conventional metals and their alloys. This study was undertaken to investigate the effect of sustainable materials on the mechanical, physical and corrosion resistant properties of AA 6063. The weight fraction of the hybrid reinforcements was varied at 2.5, 5.0, 7.5 and 10.0 wt.%. For each variation, the fly ash and eggshells were weighed equally. The fabrication route selected was stir casting. The analysis of the density showed that the property decreased with increasing weight fraction of the hybrid reinforcements. Evaluation of the microhardness revealed hardness values of 78.13, 81.19, 81.54, 82.14, and 86.71 HV for the base metal, 2.5, 5.0, 7.5 and 10.0 wt.% samples respectively. The corrosion resistant properties were studied in 3.5 wt.% NaCl medium. The investigation showed that the reinforced AMCs exhibited improved corrosion resistance compared to the base metal. However, the 7.5 wt.% sample exhibited the least corrosion rate of 8.649 X 10-5 g/h
Effect of composition and heat treatment on the mechanical properties of Fe Mn Al steels
Get PDFStarting from the research aimed at the development of substitute alloys for stainless steels, with the aim of replacing strategic metals such as chromium and nickel with the more available manganese, FeMnAlC alloys have been studied and developed for several years. These alloys exhibit an attractive strength/ductility combination, low density, and some of them show good oxidation behaviour at high temperatures. After a preliminary study, in this paper the effect of a solubilization treatment followed by aging in the temperature range 550 - 750 °C has been evaluated. The results of the investigation revealed that the steel characterized by the higher amount of Mn and Al shows, after heat treatment, the formation of phases that make the alloy very brittle. Considering the obtained results, it is evident that optimizing the alloy chemical composition is of paramount importance to guarantee a high fracture toughness if the steel works for limited time intervals at high temperature
Method for weak zones location at the coal-bed – host rock joint relative to the problem of sudden outbursts: theory and laboratory experiment
No full textWithin the framework of a geomechanical model that describes the deformation of a rock mass during the subhorizontal coal-bed extraction, the mechanism for the formation and implementation of a sudden outburst is substantiated: as working face gets close to the weak zone of coal-bed – host rock joint, areas of tensile stresses arise, which creates the prerequisites for face space spalling and coal loss with methane. The inverse problem of determining the conditions at the horizontal boundaries of a coal-bed is formulated and solved using tomography data (longitudinal wave velocity V distribution) and the empirical dependence of V on the mean normal stress σ.Lab tests results on stepwise compression of parallelepipeds made of artificial geomaterials are presented. Tomography of the specimens was performed by acoustic sounding data, and the distribution of velocities V* was found. Using the pre-established empirical dependence V(σ) for geomaterial, the distribution σ*=V-1(V*) in the specimen was calculated, which served as input data for inverse problem of determining the shear stresses σxy at the “specimen faces – press platens” joints. Lab data inversion confirmed the possibility of identifying weak zones of the boundaries where σxy=0. These zones are associated with probable nucleus of failure and sudden outbursts
FFS Master Software For Fitness-For-Service Assessment of Hydrogen Induced Cracking Equipment Based on API 579-1/ASME FFS-1
Get PDFOver time, industrial equipment, particularly in the oil, gas, and petrochemical industries, is subjected to various forms of degradation and damage that can affect its structural integrity. Most of the Codes and Standards pertaining to components do not address the issues of degradation and damage. As such, performing a Fitness For Service (FFS) assessment is recommended to make run-repair-replace decisions of an in-service component that may be flawed or damaged. In this study, FFS Master –Fitness For Service (FFS) evaluation software –was developed according to the 3rd Edition of the API579-1/ASME FFS-1. The software coding was written using C# programming language with SQL server database. This software is developed specifically for low strength ferritic steel pressurized components with hydrogen induced cracking (HIC), giving the user the ability to accurately assess if system components can continue to operate in their current service condition
Effect of reinforcement type on structural behavior of RC beams containing recycled aggregate
No full textConcrete containing wastes from the demolition of old deteriorated buildings are produced enormously. Concrete is a brittle matrix that is usually reinforced by ductile reinforcement such as steel bars. However, due to the susceptibility of steel to corrosion, fiber-reinforced polymers (FRP) bars are used as an alternative reinforcement. The main drawback of FRP bars is their brittleness. These two types of reinforcements, i.e. steel and glass FRP (GFRP) bars, have been used in the present work. The flexural behavior of twelve RC beams reinforced with different ratios of GFRP or steel areas containing recycled aggregate has been experimentally studied and compared with beams without recycled aggregate. The present results show that beams reinforced with GFRP and containing recycled aggregate exhibit a lower load-carrying capacity, lower first crack, and higher deflection than all beams. All GFRP RC beams exhibited brittle failure, i.e., concrete crushing in the compression zone, except one beam, with 2f16 bars and concrete without recycled aggregate, which showed catastrophic failure, i.e., the rupture in GFRP bars. However, the ductile failure mode is observed for all beams reinforced with steel bars, i.e., yielding in steel bars followed by concrete crushin
Fatigue crack growth analysis of welded bridge details
Get PDFThe paper investigates the fatigue crack growth in typical bridge weldments by means of numerical analysis. The extended finite element (XFEM) method is coupled with the low-cycle fatigue (LCF) approach in ABAQUS, and parametric analyses are carried out in order to assess the influence of the main sample/testing features on the fatigue life of the investigated structures. The numerical results are found to be robust and reliable by performing comparisons with past experimental data and regulation design correlations
Investigation fatigue crack initiation and propagation cruciform welded joints by extended finite element method (XFEM) and implementation SED approach
Get PDFThis study has used the strain energy density (SED) approach to evaluate the stress intensity factor (SIF) of cracked cruciform welded joints in Hardox 450 steel. A microstructural analysis was made of Hardox 450 steel which is composed of refined and tempered low carbon martensite. The obtained results of simulation will be compared with those provided by J-integral methode for different enriched zones and contours based on the extended finite element method (XFEM) coupled with the level set technique (LST). Crack initiation and propagation under cyclic loading have been adopted for the modeling of cruciform welded joints
The use of frictional and bonded contact models in finite element analysis for internal fixation of tibia fracture
Get PDFTibia is one of the bones that often fracture, generally occurring due to a car accident, falling from high places, work accidents, and sports injuries. Internal fixation is one of the solutions to repair broken bones. In some cases, internal fixation also failed to carry out its function, so the healing process was disturbed and did not run according to the plan. Factors that might interfere with the process can be analyzed using FEM. The objective of this study is to study the effect of the contact model used to model the connection between broken bones of the tibia, to stress distribution that occurs on fixation plate for walking conditions. Analysis was carried out by using ANSYS software with fine-sized tetrahedrons mesh. Two contact models were used. Namely, friction and bonded. The load amount used is based on the average weight of Indonesian Adults, i.e. 63 kg. The results of the analysis show that, for the friction contact model, higher stress is found in the middle area plate, adjacent to the broken location on the bone. Different results are found in the bonded contact model, larger stress occurs in the upper-end area fixation plate
Predictive Modelling of Creep Crack Initiation and Growth using Extended Finite Element Method (XFEM)
Get PDFIn this study, a numerical strategy for predictive modelling of creep in tension tests for the rectangular plate with a single crack and CT-specimen based on the extended finite element method (XFEM) will be described in detail. A model of creep fracture initiation and creep crack growth (CCG) is developed, while the XFEM is employed to spots located inside the finite element for the purpose of predicting crack potential and propagation. In order to characterize the creep fracture initiation, identification of C(t)-integral formula is conducted. In addition, XFEM and analytical solutions are also analyzed to look at the connection of C(t)-integral with time for a rectangular plate with a single crack under plane stress conditions. An illustration showing the se-quence of stress distribution and displacement contour plots are also being presented. The stresses and displacements spread throughout the crack path have also been determined using CT-specimens. In addition, the creep cracks growth length with normalized time and the creep crack growth rate with the C(t)-integral are predicted to be related, indicating that the numerical results are in good accord with the experimental results
An experimental study and a proposed theoretical solution for the prediction of the ductile/brittle failure modes of reinforced concrete beams strengthened with external steel plates
Get PDFAn experimental study and a proposed theoretical solution are conducted in the present study to investigate the ductile/brittle failure mode of reinforced concrete beams strengthened with an external steel plate. The present experimental study has fabricated and tested six steel plate-strengthened RC beams and one non-strengthened RC beam under 4-point bending loads. The proposed theoretical model is then developed based on the observed experimental results to analyze the crack formation, to determine the distance between vertical cracks and to quantitatively predict the ductile/brittle failure mode of plate-strengthened RC beams. The experimental study shows that the failure mode is based on the sliding of concrete along with the external plate. This slip is limited between two vertical cracks, from which the maximum stress in the external steel is determined. Based on comparisons conducted in the present study, excellent agreements of the stresses/strains in soffit steel plates, crack distances, and system failure modes between the current theoretical solution and the previous and present experimental results are observed.