Génie mécanique
Study of the effect burnishing on superficial hardness and hardeningof S355JR steel using experimental planning
Surface hardness plays an important role in lifetime of a mechanical piece subjected to friction and wear. Indeed, thehardness can be improved by superficial plastic deformation processes (SDP), such as mechanical surface treatment"MST", in particular the ball burnishing. However, the treatment result of is conditioned by mastery of operationthus ensuring treated piece good mechanical and geometric properties. Experimental work was carried out byapplying the ball burnishing process on steel tensile specimens S355JR, in order to observe the influence oftreatment parameters regime on surface hardness 'Hv' and the effect of latter on tensile behavior of this steel. Twoparameters of regime were considered namely: burnishing force "Py" and number of passes "i". The relationshipbetween these parameters and microhardness measured at "Hv" surface has been highlighting using factorial plans22. Moreover a mathematical model has been obtained allowing prediction of response (Hv) as well as optimizationof parameters of treatment regime. The experimental results showed that for surface hardness Hv it is possible toreach a 45% improvement rate for a burnishing force py = 20 Kgf and a number of passages i = 3 for this material.Regarding behavior of material during tensile test, for a low burnishing force (py = 10N) and a number of passes (i= 5), the section further weakening (S = 4.14), proof than ductility of material has decreased. Voir les détails
Mots clés : Surface hardness, factorial designs, ball burnishing, Mathematical model, tensile behaviour
Effects of work hardening on mechanical metalproperties—experimental analysis and simulation by experiments
The aim of the present work is to improve the materials’ performances, particularly their elastic property based on an optimalexploitation of surface work-hardening phenomenon, using surface plastic deformation treatment (DPS). The surface of amechanical piece is considered as the most vulnerable zone that determines its mechanical performances. To improve thesurface physico-mechanical properties, the surface plastic deformation treatment (DPS) is often used. The (DPS) acts by acombined action of: surface hardening, structural modification, and the generation of the compression residual stresses, thefactors that will create a heterogeneous plastic deformation. Knowing that during operation the mechanical pieces have to besubjected to a stress smaller than the elastic limit (taking into account the safety margins), where the material behavior isreversible, and to reach the maximum allowable stresses, we have to increase the material’s elastic limits. This objective canbe realized through an optimal use of work hardening phenomenon for the treated surface by the DPS. The work hardening ischaracterized by the increase of the yield strength (Re), the surface hardness (Hv), and consequently the increase of thebrittleness. Depending on the considered metals, when the piece has a defect variation: cavity, inclusion (precipitate), orzones of different hardness, it can create a stress concentration which generates a local hardening. This phenomenon is one ofthe main causes of crack generation. In our study, we consider the influence of work hardening on the elastic behavior ofXC38 steel and aluminum alloy. Voir les détails
Mots clés : Work hardening . Hardening of materials . Mechanical surface treatment (TMS) . Burnishing
Endurance and Damage in Fatigue of Symmetrical Configuration 2P-2V-2P Perlon-Glass-Acrylic Composite Laminates of Orthopaedic Use
In this paper, an experimental characterization of fatigue behaviour on prismatic specimens of a symmetrical laminated composite material perlon- glass- acrylique 2P-2V-2P for orthopaedic use is conducted. Cyclic repeated solicitation is employed corresponding to applied minimum stress σmin equal zero. The various loading levels imposed on the specimens are 80%, 70%, 60%, 55%, 45%, 35% and 25% of the value of the static failure strength measured in flexure. A significant scatter characterizes the results of material fatigue lifetime. That is the consequence of the heterogeneity of the material structure. The scattered phenomenon prevents any prediction of the lifetime with a good probability using Wohler equation. This enables defining a constant degradation rate by 10% cycle decade. The microstructure morphology study through microscopic observations is also discussed and analyzed. The damage state in fatigue is characterized by a combination of density and orientation of micro-cracks. This damage is mainly due to mechanisms complexity of matrix micro-cracking, inter facial exfoliation, debonding and delamination. The damage evolution stages in the case of cyclic loading have the same nature than those found in static loading but have different chronology and scale Voir les détails
Mots clés : perlon, acrylic, Orthopaedic, fatigue, Scatter
Study of the effect burnishing on superficial hardness and hardening of S355JR steel using experimental planning
Surface hardness plays an important role in lifetime of a mechanical piece subjected to friction and wear. Indeed, the hardness can be improved by superficial plastic deformation processes (SDP), such as mechanical surface treatment "MST", in particular the ball burnishing. However, the treatment result of is conditioned by mastery of operation thus ensuring treated piece good mechanical and geometric properties. Experimental work was carried out by applying the ball burnishing process on steel tensile specimens S355JR, in order to observe the influence of treatment parameters regime on surface hardness ‘Hv’ and the effect of latter on tensile behavior of this steel. Two parameters of regime were considered namely: burnishing force "Py" and number of passes "i". The relationship between these parameters and microhardness measured at "Hv" surface has been highlighting using factorial plans 22. Moreover a mathematical model has been obtained allowing prediction of response (Hv) as well as optimization of parameters of treatment regime. The experimental results showed that for surface hardness Hv it is possible to reach a 45% improvement rate for a burnishing force py = 20 Kgf and a number of passages i = 3 for this material. Regarding behavior of material during tensile test, for a low burnishing force (py = 10N) and a number of passes (i = 5), the section further weakening (S = 4.14), proof than ductility of material has decreased. Voir les détails
Mots clés : Surface hardness, factorial designs, ball burnishing, Mathematical model, tensile behaviour
Remaining Life Estimation of the High Strength Low Alloy Steel Pipelines by Using Response Surface Methodology
This paper presents a probabilistic study to estimate the remaining lifespan of cracked steel pipeline by using the response surface technique. The purpose is to assess the reliability index of the high strength low alloy steel (HSLA) pipelines for a limit state function without closed-form. The implicit objective function is approximated by a polynomial representing a quadratic response surface and the assessment of the failure probability is obtained using Second order reliability method (SORM). The presence of a semi-elliptical crack defect in the longitudinal direction of the pipe steel will intensify the stress field at the crack tip and will decrease the limit state function. Exhaustive and costly tensile and Charpy V notch tests prepared from the longitudinal direction of the parent tube were achieved in order to study the mechanical behavior of API X70 steel grade and integrating the uncertainties of the engineering model parameters through their probabilistic densities. The assessment of the stress intensity factor is conducted by using the finite element methods. The estimation of the reliability index and the probability of failure are carried out by coupling the mechanical model, and the finite element method based on the commercial code ABAQUS. This coupling based on the response surface methodology, could be used as a decision making support for any repair or replacement of the damaged pipeline. Voir les détails
Mots clés : Reliability, Elliptical crack, Response surface, Uncertainties
Inspections, statistical and reliability assessment study of corroded pipeline
The purpose of this work is to examine some points of views on the burst pressure standards assessment for a pipeline with internal and/or external corrosion defects. The proposed work contains three major parts. First, we used several analytical and numerical methods with the use of Ansys Software. The goal is presenting different aspects concerning burst pressure standards computation of real burst test. The second part shows an experimental study in order to check the inspections standards using an intelligent pig tool over a 48?km of a pipeline located in Algeria. All detected defects in the corroded pipeline are statistically analyzed. The final part, the reliability index β of the corroded pipeline subjected to internal pressure is estimated by using the SORM reliability approach. Voir les détails
Mots clés : Corroded pipeline burst test, Probability of failure, Failure assessment diagram, Finite Element Analysis
Experimental study of chemically aged HDPE pipe material in toluene-methanol mixture and distilled water
Studying the aging phenomenon of plastic pipes presents simultaneously an economic achievement and a technical challenge for water and natural gas transportation systems. Ver y often, they are exposed to aggressive environmental agents such as UV rays, ambient oxygen, acids, bases and some other so lvents, altering the material microstructure, its physical and chemical properties. The high density polyethylene (HDPE) material degradation and loss of performance are usually the consequence of unwanted changes in mechanical behaviors leading to lower resistance. In this s tudy, we examine the effects of distilled water (DW) and a mixture of toluene-methanol (TM) in contact with an HDPE pipe. Morphological properties such as crystallinity and oxidation induction time (OIT) are in vestigated using DSC method. Tensile tests and thermal analysis show that the TM mixture is much more absorbed by the resin as compared to DW. An increase in crystallinity is observed as established from literature for other organic solutions. Finally, the study gives an idea about property variances and their evolution as a function of the pipe thickness which c an be used as an estimation of the structural heterogeneity of the product. Voir les détails
Mots clés : Pipe; HDPE; Aging; Distilled Water; Toluene-Methanol Mixture; Crystallinity; OIT
Study of The Reliability of A Composite Used In The Knee Prosthesis
In orthopedic surgery, the effectiveness of the implants used, such as hip and knee prostheses, depends mainly on their geometries and the type of loading to which they are subjected. In this work a probabilistic approach is chosen to study the reliability of a composite structure used in the manufacture of knee prostheses. The purpose of integrating reliability concepts is to consider uncertainty in several aspects including loading and material properties. The reliability index β is an excellent indication of durability and safety for given operating conditions. β is obtained using failure probability and a mechanical model. The critical stress intensity factor (Kc) is adopted as a criterion to the maximum limit of a numerically calculated KI. The results presented are discussed according to the length of the crack (a), and the limit load used. Voir les détails
Mots clés : Reliability analysis, critical stress intensity factor, crack length, load, reliability index
Investigation of the Effect of Aluminum Alloy Position on ResidualStresses in Dissimilar fsw Weld by Using the Ultrasonic Method
The main goal of this study is to show the effect of the advancing side (AD) and theretreating side (RT) position on the Residual stresses and local mechanical behaviour ofdissimilar friction stir welds of aluminum alloys AA2024-T3 and AA7075-T6. Different sampleswere produced by varying the rotational speed of the tool (1200 and 1400 rpm) and the alloyposition regarding the advancing side of the tool. Ultrasonic Method has been used to evaluateResidual Stresses. This method is based on the acoustoelastic effect, which measures the velocityvariation of the elastic waves according to the stress state of the material. This can be achievedthrough a calibration test, which permits the determination of the acoustoelastic coefficient (K).The results show a tensile stress in the Nugget (N), the heat affected zone (HAZ) and acompression stress in the base metal (BM). Increasing the rotational speed reduces the amplitudeof the longitudinal residual stresses with a high reduction in the case where AA7075 - T6 is inthe advancing side whit 1400 rpm. This has been directly associated to the increase in the heatinput and the reduction of the thermal mismatch between different areas of the weld. Themicrostructure effect of aluminum alloy position acts on the acoustoelastic constant K. Thechoice of t0 corrects the overestimated residual stresses in the (HAZ) and (N). Voir les détails
Mots clés : FSW, contraintes résiduelles, microstructure, comportement mécanique, corrélation d'image numérique
Numerical study of parameters affecting pressure drop of power-law fluid in horizontal annulus for laminar and turbulent flow
Efficient hydraulics program of oil and gas wells has a crucial role for the optimization of drilling process. In the presentpaper, a numerical study of power-law fluid flow through concentric (E = 0.0) and eccentric annulus (E = 0.3, E = 0.6 andE = 0.9) was performed for both laminar and turbulent flow regimes utilizing a finite volume method. The effects of innerpipe rotation, flow behavior index and diameter ratio on the pressure drop were studied; furthermore, the appearance anddevelopment of secondary flow as well as its impact on the pressure drop gradient were evaluated. Results indicated thatthe increment of the inner pipe rotation from 0 to 400 rpm is found to decrease pressure drop gradient for laminar flow inconcentric annulus while a negligible effect is observed for turbulent flow. The beginning of secondary flow formation in thewide region part of the eccentric annulus (E = 0.6) induces an increase of 9% and a slight increase in pressure drop gradientfor laminar and turbulent flow, respectively. On the other hand, the variation of the flow behavior index and diameter ratiofrom low to high values caused a dramatic increase in the pressure drop. Streamlines in the annulus showed that the secondary flow is mainly induced by eccentricity of the inner pipe where both high values of diameter ratio and low values of flowbehavior index tend to prevent the secondary flow to appear. Voir les détails
Mots clés : Computational fluid dynamics (CFD) · Power-law fluid · Pressure drop · Secondary flow