Italian Group Fracture (IGF): E-Journals / Gruppo Italiano Frattura
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Numerical Investigation of the Seismic Behavior of Unanchored Steel Tanks with an emphasis on the Uplift Phenomenon
Get PDFGround steel storage tanks are widely used in different industries. Regarding the significance of these structures, ensuring the proper performance of such structures in earthquakes needs evaluating their seismic performance. The present study examines the seismic behavior of an unanchored fluid storage system via ABAQUS after validation using an experimental model. Next, the uplift of the bottom sheet is studied using the accelerogram records of the 1940 El Centro and 1994 Northridge earthquakes. The overturning moment time history of the fluid storage system and the maximum overturning moments were obtained to identify their behavior. The results indicated that not bracing storage tanks leads to the uplift phenomenon. Finally, the maximum axial stress of the storage tank shell was compared with the values recommended in the design codes to control the buckling
Physical Parameters of Polymer Composite Materials Created on the Basis of Low and High Molecular Weight Rubbers
Get PDFABSTRACT. The theoretical foundations of the structural and mechanical behavior of filled three-dimensional cross-linked elastomers are supplemented. Numerical experiments are carried out, based on the data of numerical experiments, three dimensional cross linked, filled with dispersed particles frost-resistant elastomers based on low and high molecular weight rubbers are developed. Theoretical and experimental data are compared and their good convergence is shown. Comparison of the physical parameters of the composites created by the authors on the basis of low and high molecular weight rubbers showed that the deformation characteristics of the composite based on high molecular weight rubbers are many times superior to composites based on low molecular weight, as well as their glass transition temperature is also very different. The created composites are recommended as a structural material in relation to the engineering problem of creating wear-resistant parts and components of road and air transport operated in a wide temperature range, including the Far North and the Arctic.
 
Improvement of Fatigue Properties of AZ31B Extruded Magnesium Alloy through Forging
Get PDFAxial monotonic and load-controlled fatigue tests were performed to investigate the influence of forging at various temperatures and different deformation rates, on both the microstructural and mechanical behaviour of extruded AZ31B magnesium alloy. The obtained microstructural analysis showed that the extruded AZ31B magnesium alloy possesses a bimodal grain structure with strong basal texture. In contrast, once forged, the material showed refined grains and a modified texture. A monotonic yield and ultimate tensile strength of about 223 MPa and 278 MPa were observed for the forged samples showing an increase of 18%, from the as-extruded material. The optimum forging condition was determined to be the coldest of the investigated temperatures, based on the improvement in both monotonic and cyclic properties vs. the as-extruded material. The fractographic analysis of the failure surfaces showed that ductile type fractures occurred in both as-extruded and forged samples. However, more dimples and plastic deformation were identified in the fracture surfaces of the forged specimens. A significant improvement of fatigue life was also observed for all of the forged samples, in particular those forged at 400°C and 39 mm/min. Forging improved the fatigue life via a combination of grain refinement and texture modification resulting in improved strength and ductility
Evaluating Properties of Asphalt Mixtures Containing polymers of Styrene Butadiene Rubber (SBR) and recycled Polyethylene Terephthalate (rPET) against Failures Caused by Rutting, Moisture and Fatigue
Get PDFProperties of asphalt mixture play a vital role in structural integrity and performance of flexible pavements structure. In flexible pavements asphalt concrete surface layer consists of asphalt binder, aggregates and in some cased additives.
In this research study styrene butadiene rubber (SBR) and recycled polyethylene terephthalate (rPET) used to evacuate their individual and also their combination effects upon moisture susceptibly, rutting and low temperature cracking of asphalt concrete mixture.
Three combination of SBR and rPET along with water were vulcanized to from thermoplastic elastomer polymers as bitumen modifier. Then conventional bitumen tests including penetration grade, softening point and rotational viscosity (RV) as well as asphalt mixture tests including resilient modulus, dynamic creep, IDT fatigue and moisture susceptibility tests were performed on binders and asphalt mixture specimens. The test results indicated that SBR and rPET increase viscosity and softening point and stiffen the binders by reducing their penetration grade. Test results of spearmens prepared with modified binders showed higher tensile strength and higher rutting resistance than that of control specimen within the contest of this study it is conclude that modification of bitumen with SBR reduces low temperature stiffness of binder and hence reduces failure of thermal cracking and modification with rPET increases rutting resistance of the mixture at high temperatures
Comparative study of the repair of cracked plates with two different composite patches
Get PDFThe purpose of this study is to analyze the behavior of a crack with and without reinforcement by a composite patch of an aluminum plate in mode I using the finite element method. The repair patch is boron / epoxy and Carbon / epoxy, which are used with great success by many researchers
For the distribution of the stresses according to the various loadings, we can conclude that the effect of repair by patch in composite is very distinct, considering the intensities of stresses which decrease for each repair corresponding to the plate not repaired, therefore, the patch in composite dampens the stress field induced at the crack tip and causes a reduction in stresses. The repair with the Bore / epoxy composite patch is more effective than the Carbon/Epoxy patch, this is due to the mechanical properties and the various characteristics specific to boron/Epoxy which gives very significant and very effective results for the repai
Mechanical characterization of different epoxy resins enhanced with carbon nanofibers
Get PDFEpoxy with carbon nanofibers (CNFs) are effective nano enhanced materials that can be prepared by easy and low-cost method. The present paper compares the improvements, in terms of flexural and viscoelastic properties, of two epoxy resins reinforced with different weight percentages (wt.%) of CNFs. These epoxy resins have different viscosities, and weight contents between 0% and 1% of CNFs were used to achieve the maximum mechanical properties. Subsequently, for the best configurations obtained, the sensitivity to the strain rate and the viscoelastic behaviour (stress relaxation and creep) were analysed based on international standards. It was possible to conclude that, for both resins, carbon CNFs promote significant improvements in all the studied mechanical properties, even for different contents by weight.
 
Experimental characterization of a new sustainable sand concrete in an aggressive environment
Get PDFThe scarcity of building materials and the shortage of coarse aggregates which represents the main component of concrete is a problem in the most third world countries, especially in the vast desert areas in Algeria. In desert conditions where the environment suffers from the phenomenon of rising water and aggressive soil; the evaluation of existing abundant Sand Dune and its compensation for naturel Sand could be a very good economic solution. Several researches at the local and the global levels confirm that Sand Dune can be exploited in concrete after a granular correction. In this paper, a new Sand resource (Oued El-Ratm, El Oued-Algeria) is proposed as an alternative of natural Sand to perform a Sand Concrete. The findings of this experimental study show that the Sand Concrete based on this new resource of sand dune of the Algerian desert has a good resistance when used in the ambient Saharan aggressive conditions
Experimental analysis of the state of stress in a steel – titanium perforated plate loaded with concentrated force
Get PDFThe paper presents an experimental analysis of the state of stress, free supported on the edge of a steel – titanium circular perforated plate loaded with a centrally concentrated force, created in the technological process of explosion welding. For this purpose, a special test stand was designed and a methodology for testing the perforated plate was developed. Resistance strain gauges were used to measure the state of strain. The load was applied in the center of the plate to a pressure stamp. As a result of the research, the values of radial, circumferential and equivalent von Mises stress were obtained as a function of the radius of the plate perforation circle and its load. The stress distribution topography revealed the zones of maximum stress of the steel – titanium perforated plate. The proposed method of experimental research can be used by engineers to verify the state of stress, e.g. in the designed tube sheet walls of reactors for ammonia synthesis
Shear behaviour of reinforced concrete beams under impact loads by the lumped damage framework
Get PDFImpact loadings such as vehicle collisions or falling rocks on a structure could lead it to collapse and, eventually, to fatal victims. Among possible alternatives to analyse this issue, Lumped Damage Mechanics is an interesting option due to its formulation and easiness for practical application. Therefore, this paper presents a simplified lumped damage model to evaluate reinforced concrete structures under impact loads with shear failure mode. In the proposed approach, the damage variable is considered as an output parameter. Such damage variable takes values between zero and one that quantifies the concrete cracking due to impact loading. The proposed formulation was applied in experiments of reinforced concrete beams under impact loads that presents shear collapse. The obtained results showed good accuracy between the proposed model and the actual structural behaviour. Moreover, a possible flowchart for practical applications is also presented. Since the model parameters are easily associated to inelastic phenomena, the proposed formulation might become accessible to engineers in practice
Prediction of the burst pressure for defective pipelines using different semi-empirical models
Get PDFThe main aim of this work is to predict the theoretical burst pressure of defective pipelines using different semi-empirical models and compare them with the results of the hydrostatic tests. A methodology was formulated with accounting for a minimum thickness (weakest section of the pipe) over the length of the pipe to predict the most conservative burst pressure. With a simple analytical expression, a reasonable accuracy and more conservative burst pressure can be obtained for any arbitrary defect shapes. A variation of burst pressure was found between theoretical prediction and hydrostatic burst test results with respect to the different semi-empirical models even for the same corroded defects. Different defect geometry shapes and pipe material conditions are the possible causes for variation in the burst pressure between the semi-empirical models, so a careful selection of these parameters is necessary. The proposed methodology predicted a more conservative burst pressure for all arbitrary defects shapes and can predict reasonably accurate values if it accounts for the axial stress