A Amirat | Badji Mokhtar - Annaba University (original) (raw)

Papers by A Amirat

Journal of Failure Analysis and Prevention

Abstract To investigate the effect of the slide diamond burnishing process on the mechanical prop... more Abstract To investigate the effect of the slide diamond burnishing process on the mechanical properties of GCR15 steel, an experimental study was carried out. For this purpose, burnished and unburnished specimens have been prepared and compared in fatigue performance, surface roughness, microhardness, and SEM analysis. The burnishing process was carried out at a speed of 560 rpm, a burnishing force of 10 Kgf, a feed rate of 0.074 mm/rev and several passes of 3. Rotary bending fatigue tests were performed on the burnished and unburnished specimens, S–N curves were plotted from a maximum load representing 66% of tensile strength. The findings indicate that the fatigue strength was increased by up to 36% because of slide diamond burnishing compared to the non-burnished case. At lower stress levels, the improvement in fatigue strength is clearly observed. The fatigue curves reveal a slight reduction in the fatigue strength results compared to those reported in the literature, which can be attributed to the specimen’s small shoulder fillet value.

The present work is a fulfilment study on previous contribution presented by Mokas et al (2018) t... more The present work is a fulfilment study on previous contribution presented by Mokas et al (2018) through investigation on the effect of chisel wear on the machinability of hardened C22 steel under drilling operations using twist high-speed steel (HSS) grade drill bits. Therefore, the evolution of wear in twist drill bits with respect to both flank and chisel edges has been reconsidered in order to sort out the most dominant wear rate in drill edges. Experimental investigation has been conducted on annealed and hardened C22 steel according to the planning experience methodology (L8). The input parameters are cutting regime elements, cutting speed, feed rate, and drill diameter; meanwhile, the output parameter is the chisel wear related to tool life. Results show that eventually, drilling annealed material generates much better tool life. Relatively to flank wear, chisel wear has great effect in some cutting conditions. In the annealing condition, flank wear is still most dominant and ...

The present work is a contribution to the improvement of the hydrodynamic method proposed by Si L... more The present work is a contribution to the improvement of the hydrodynamic method proposed by Si Li et al [2016] used to predict the pressures and the rolling speeds during hot rolling of aluminum strips. The hydrodynamic model gives good prediction however it is based on empirical coefficients that must be identified for each rolling case. Therefore, a critical analysis of the method has been first made and then a methodology for improving it has been presented. The improvement consists in coming out of the empiric coefficients and considering the variation of viscosity as a function of pressures. Results are much better in good agreement with the experimental data. The validated model can then be admitted as an improved hydrodynamic model for predicting pressures and velocities during hot rolling of thin strips.

Advances in materials research, 2020

The objective of the present work is to investigate the effect of cutting parameters (Vc, fz and ... more The objective of the present work is to investigate the effect of cutting parameters (Vc, fz and ap) on tool life and the level of vibrations velocity in the machined part during face milling operation of hardened AISI 52100 steel. Dry-face milling has been achieved in the annealed (28 HRc) and quenched (55 HRc) conditions using multi-layer coating micro-grain carbide inserts. Statistical analysis based on the Response surface methodology (RSM) and ANOVA analysis have been conducted through a plan of experiments methodology using a reduced Taguchi table (L9) in order to obtain engineering models for tool life and vibration velocity in the workpiece for both heat treatment conditions. The results show that the cutting speed has a dominant influence on tool life for both soft and hard part. Cutting speed and feed per tooth is the most significant parameters for vibration levels. Comparing the experimental values with those predicted by the developed engineering models of tool life and...

Journal of Natural Gas Science and Engineering, 2022

Considering corrosion rate during the remaining life assessment of aging pipelines is fundamental... more Considering corrosion rate during the remaining life assessment of aging pipelines is fundamental to calculate the interval between two consecutive inspections. A total of 798 internal and external corrosion defects have been detected, using the Magnetic Flux Leakage intelligent inspection tool, over 48 km of a pipeline length located in the west region of Algeria. The statistical analysis has shown that there is a strong correlation between the corrosion defect length and the corrosion defect circumferential width, with a significant correlation coefficient equal to 82.87%. A probabilistic methodology is presented for the assessment of the remaining life of a corroded pipeline transporting gas, and a finite element method (FEM) was used to assess the pipeline failure pressure. The numerical FEM modeling results were compared with the commonly used codes-models for calculating limit pressure to establish a more realistic and accurate engineering model. The reliability analysis of an API 5L X60 steel made Algerian natural gas pipeline, in service for thirty years, and exposed to active corrosion attack, is presented. The sensitivity analysis of the basic random variables within the nonlinear limit state function was carried out to bring out the relative contribution of each variable affecting the remaining life of corroded pipelines. The reliability analysis is carried out by using Breitung's formula, based on the second-order reliability method (SORM). The reliability assessment of the corroded pipeline is based on the usage of the notched failure assessment diagram (NFAD), different codes for the calculation of the failure pressure, and the numerical results using the finite element analyses (FEA) software ANSYS.

L'importance de l'engrenage, comme element mecanique necessaire et ideal, est demontree p... more L'importance de l'engrenage, comme element mecanique necessaire et ideal, est demontree par la vaste gamme qu'on trouve dans toutes les industries. La performance des engrenages en plastiques telles que le polyoxymethylene (POM) et le polyamide (PA) est liee a leur capacite a resister l’usure. Les polyamides sont utilises comme materiaux pour engrenages en plastique moule par injection. Les engrenages en plastique ont plusieurs avantages en comparaison avec les engrenages en metal, telles que le poids leger, le bruit reduit, et le degre de liberte eleve dans la geometrie des engrenages. L’objectif de ce travail etant d’etudier l’usure des roues dentees en polyamide « PA66 », l’investigation concerne la determination de l’evolution de cette usure dans un contact sec, lubrifie a l’eau, lubrifie a un melange d’eau et de detergent a base de phosphate. L’influence de l’environnement d’essai sur le comportement d’usure des engrenages, indique que l’air (usure a sec) provoque u...

The present work proposes new engineering models for determining corrosion initiation time in con... more The present work proposes new engineering models for determining corrosion initiation time in concrete reinforcing steels in marine environment. The models are based on Fick\'s second law that is commonly used for chloride diffusion. The latter is based on deterministic analyses involving the most influencing parameters such as distance of the concrete structure from the seaside, depth of steel concrete cover, ambient temperature, relative humidity and the water-cement ratio. However, a realistic corrosion initiation time cannot be estimated because of the uncertainties associated to the different parameters of the models. Therefore a reliability approach using FORM/SORM method has been applied to develop the proposed engineering models integrating a limit state function and a reliability index B. As a result, the corrosion initiation time is expressed by new exponential engineering models where the uncertainties are associated to the model parameters. The main emerging result i...

Wear investigation has been conducted on mixed ceramic cutting tool (70% Al2O3 + 30% TiC) when ma... more Wear investigation has been conducted on mixed ceramic cutting tool (70% Al2O3 + 30% TiC) when machining hardened AISI 52100 steel (66 HRC). Experimental planning method has been used to assess the relationship between radial cutting vibrations and surface roughness as a function of the machining conditions. First, wear results show that when the cutting speed is increased 3.78 times, tool life drops of 8.75 times. When increasing the feed rate by a factor of 2.75 tool life decreases by a factor of 1.4. Then, the effect of cutting parameters (speed, feed and depth) on one hand surface roughness (Ra) and in the other hand radial tool vibrations has been determined using the multiple regression models with a coefficient of determination R2 equal to respectively 95.5% and 89.3%. With regards to surface roughness, ANOVA analyses reveal that feed rate contributes of about 84% in the surface roughness. Meanwhile, looking at the vibration phenomena, the cutting speed has the most significa...

Generalement, les causes de la deterioration des pipelines de transport d'hydrocarbures sont ... more Generalement, les causes de la deterioration des pipelines de transport d'hydrocarbures sont liees a la presence de defauts apparents (piqures, fissures, corrosion, etc.). Les methodes mecano-fiabilistes sont necessaires a developper en se basant sur des methodes probabilistes. L’objectif de ce travail est l’evaluation probabiliste de la fiabilite des pipelines avec des defauts localises. Le modele mecanique de degradation utiliser est base sur la mecanique de la rupture, pour evaluer la probabilite de defaillance a travers les dimensions des defauts par la methode FORM/SORM. L’etude parametrique a pour but de selectionner les variables les plus significatives, ce qui permet de mieux les maitriser selon leur role par rapport au comportement mecanique ou a la fiabilite. Les parametres les plus dominants sont l’epaisseur et le diametre du tube.

Advances in materials research, 2018

The present paper is an investigation on the effect of slide diamond burnishing on the fatigue en... more The present paper is an investigation on the effect of slide diamond burnishing on the fatigue endurance of a component made of AISI52100 steel. Burnishing operation has been performed on cylindrical specimens using optimal parameters statistically selected such as burnishing force, burnishing feed and number of tool passes. Bending fatigue tests in air at R= -1 and S-N curves have been plotted by incrementing the applied stress from a maximum stress level of about 66% of the ultimate tensile stress to a stress value below which fatigue does not occur. Results show that slide diamond burnishing has increased the fatigue resistance comparing to unburnished specimens. The fatigue endurance is respectively 222 MPa and 190 MPa. At high stress levels, the fatigue resistance improvement is clearly observed and the fatigue trends are in good agreement with those reported in literature. However, the present results are slightly lower and that is attributed to the shoulder fillet value of th...

The International Journal of Advanced Manufacturing Technology, 2020

The present work is a contribution to developing a strategy for rapid analysis of the behaviour o... more The present work is a contribution to developing a strategy for rapid analysis of the behaviour of surface roughness and tool wear during machining hardened steel with carbide cemented cutting tools on conventional cutting machines. In agreement with dies and mould manufacturers in East Algeria, the strategy is based on the machining potential of the manufacturers, cutting tools manufacturer’s guidelines and recommendations from literature. The agreement suggested to focus on up and down shoulder finish milling of hardened AISI D3 tool steel using GC1030 insert on a conventional vertical milling machine. The strategy has been developed within five successive steps starting from the analyses of the performance of a machine tool to the definition of an experimental plan to respect. As expected, results show that down shoulder milling is the most suitable process rather than up shoulder milling which must be avoided whatever the hardening condition. In addition, the best performance of down shoulder milling is obtained when machining unhardened steel. In the as-received condition (31.6 HRc) when using down milling the cutting speed can be increased up to the maximum value of 113 m/min, however, the tool life obtained for this value is three times lower than that at Vc = 59 m/min. In 49 HRc hardening condition, milling at Vc = 59 m/min resulted in the good surface finish but with a tool life 6.5 times lower than the tool life when milling in the as-received condition. Vibration measurements provide a time referential data on the evolution of surface roughness together with corresponding tool wear. A time referential data on the evolution of displacement together with the corresponding tool life has been proposed as useful information to meet the needs of dies and moulds manufacturers when milling hardened steels.

Lecture Notes in Mechanical Engineering, 2019

This paper presents a probabilistic study to estimate the remaining lifespan of cracked steel pip... more 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.

The International Journal of Advanced Manufacturing Technology, 2018

The reliability of high-density polyethylene (HDPE) pipes remains a central issue for gas transpo... more The reliability of high-density polyethylene (HDPE) pipes remains a central issue for gas transportation and distribution networks. The objective of this study is to investigate the estimation of reliability index (β) for a plastic pipe using the critical stress intensity factor (K IC) as the maximum limit for safe operating conditions. Simulations are performed as a function of operating pressure, crack length, and standard dimension ratio (SDR) for three fracture toughness levels (low, moderate, and high). In addition, the study compares results from three hoop stress calculations methods (thin, thick, and ISO plastic pipe equation). Based on design recommendation for reliability index, it is found that both operating pressure and crack length show comparable behaviors. However, the thick wall pipe results overestimate (β) for every K IC level. In all cases, it is found that the higher the critical stress intensity factor, the better the reliability index. Results obtained with the standard ISO pipe formula are more realistic, as they are usually around the design recommendation, i.e., SDR basis indicates that it is a true conservative design approach incorporating both upper and lower thickness limits. The importance of all variables (thickness, diameter, crack length, pressure, and fracture toughness) is also discussed.

Engineering Failure Analysis, 2017

Despite the various engineering models existing for lifetime investigation of hydrocarbon steel p... more Despite the various engineering models existing for lifetime investigation of hydrocarbon steel pipelines under localized corrosion and crack defects there is still a lack of information about the correlation between the two main parameters characterizing the geometrical defect model, depth and length. So the aim of the present work is a contribution in evaluating the remaining life of the pipeline using reliability analysis in order to correlate the two parameters through one common parameter, the reliability index. As a first step, the investigation is carried out on four standard and well established engineering models; Irwin, SINTAP, ASME B31G and Modified ASME B31G methods, aiming to coordinate results given by each of the four models. The potential defect depth and length correlation through a reliability index can be used as a decision-making tool to give realistic answers for replacing and/or repairing a tube subjected to internal pressure and on which flaws of different depths and lengths have been detected from inspection of a pipeline after few years of service.

The International Journal of Advanced Manufacturing Technology, 2016

The probabilistic approach is the best way to give realistic answers for design and maintenance a... more The probabilistic approach is the best way to give realistic answers for design and maintenance and it is considered as a powerful decision-making tool. In the present paper, assessment of the failure probability of corroded pipeline subjected to internal pressure is estimated by using the first order reliability method (FORM). Measurements of defect dimensions have been achieved changed into collected by using ultra sound inspection probe through a 75-km pipeline portion on one of the main Algerian high pressure gas transportation that has been in service for 30 years. The sensitivity analyses have been carried out on random variables to identify the importance of the parameters within the reliability mechanical model. The modified B31G code has been coupled as a mechanical model, with Rackwitz optimization algorithm by using PHIMECA Software. The limit state function resumes the difference between the pipeline burst pressure and the pipeline operating pressure. The aim of the present work is to make in evidence the competitive importance of pressure service, wall thickness and the defect depth with regards to defect length and to determine the influence of the coefficients of variation on the failure probability and the remaining life of the pipeline. A diagram based on the reliability index results is proposed to predict the pipeline degradation and it can be used as a decision tool for maintenance program.

The International Journal of Advanced Manufacturing Technology, 2017

The present work proposes a new numerical approach based on the derivation method of Bridgman to ... more The present work proposes a new numerical approach based on the derivation method of Bridgman to determine (K IC) of galvanized steel sheets. The method relies on a fracture analysis numerical code "Franc2D," which permits to simulating the initiation and propagation of a crack on grooved tensile specimens. First, the stress intensity factor is obtained while the crack is propagating and then (K IC) is determined from the fitting curves of the stress intensity factor (K I) to crack length (a) plot through mathematical transformations. The results are validated by comparing them to those obtained through the experimental approach using Vickers hardness based IEF engineering models. The relative values of (K IC) are admissible and acceptable with a coefficient of variation of 14% for a large range of groove radius. Hence, the present numerical simulation can be fairly used in order to reduce time consuming and avoid costly experimental mechanical tests.

The International Journal of Advanced Manufacturing Technology, 2017

The present paper is a contribution in developing an engineering model expressing the evolution o... more The present paper is a contribution in developing an engineering model expressing the evolution of tooth flank wear in polyamide spur gears as a function of number of cycles. The method is based on first observing the behavior of wear on tooth flanks in real test conditions. Then progressive flank wear profiles are plotted in order to sort out the corresponding fitting curves together with the associated mathematical equations. The general engineering model controlling the evolution of wear profile is found of the form of quadratic equation where the variable is the circular thickness of a tooth at a given depth from the top land of the tooth. The respective parameters of the engineering wear equation are determined as a function of number of revolutions of the spur gear. A wear correction parameter kw is added in order to catch up the measuring errors when plotting the wear profile curves using the proposed engineering wear model for spur gears. The data are in good agreement with that obtained from experimental measurements.

The International Journal of Advanced Manufacturing Technology, 2016

The International Journal of Advanced Manufacturing Technology, 2016

This paper focuses on an approach of implementing traceability of machined parts for subsets used... more This paper focuses on an approach of implementing traceability of machined parts for subsets used in automotive products. The objective is to recover the memory of a given part that has been shaped by removing material from a blank to the finished part in order to fulfil a required function. The approach includes describing the process plan of a given part to be machined, analysing the reliability of the production system, introducing the notion of points of data traceability recording (PDTR) and identifying the machined part by a well-established codification number within the machining workshop. The present approach is illustrated through a case study of implementing internal traceability on batches of parts of hubs for wheelchairs that are manufactured at the Cyclomotor company CYCMA, Guelma in Algeria. Recalls and defective parts can be significantly identified towards the raw material, the process plan, the cutting tool and operators.

Journal of Failure Analysis and Prevention

Abstract To investigate the effect of the slide diamond burnishing process on the mechanical prop... more Abstract To investigate the effect of the slide diamond burnishing process on the mechanical properties of GCR15 steel, an experimental study was carried out. For this purpose, burnished and unburnished specimens have been prepared and compared in fatigue performance, surface roughness, microhardness, and SEM analysis. The burnishing process was carried out at a speed of 560 rpm, a burnishing force of 10 Kgf, a feed rate of 0.074 mm/rev and several passes of 3. Rotary bending fatigue tests were performed on the burnished and unburnished specimens, S–N curves were plotted from a maximum load representing 66% of tensile strength. The findings indicate that the fatigue strength was increased by up to 36% because of slide diamond burnishing compared to the non-burnished case. At lower stress levels, the improvement in fatigue strength is clearly observed. The fatigue curves reveal a slight reduction in the fatigue strength results compared to those reported in the literature, which can be attributed to the specimen’s small shoulder fillet value.

The present work is a fulfilment study on previous contribution presented by Mokas et al (2018) t... more The present work is a fulfilment study on previous contribution presented by Mokas et al (2018) through investigation on the effect of chisel wear on the machinability of hardened C22 steel under drilling operations using twist high-speed steel (HSS) grade drill bits. Therefore, the evolution of wear in twist drill bits with respect to both flank and chisel edges has been reconsidered in order to sort out the most dominant wear rate in drill edges. Experimental investigation has been conducted on annealed and hardened C22 steel according to the planning experience methodology (L8). The input parameters are cutting regime elements, cutting speed, feed rate, and drill diameter; meanwhile, the output parameter is the chisel wear related to tool life. Results show that eventually, drilling annealed material generates much better tool life. Relatively to flank wear, chisel wear has great effect in some cutting conditions. In the annealing condition, flank wear is still most dominant and ...

The present work is a contribution to the improvement of the hydrodynamic method proposed by Si L... more The present work is a contribution to the improvement of the hydrodynamic method proposed by Si Li et al [2016] used to predict the pressures and the rolling speeds during hot rolling of aluminum strips. The hydrodynamic model gives good prediction however it is based on empirical coefficients that must be identified for each rolling case. Therefore, a critical analysis of the method has been first made and then a methodology for improving it has been presented. The improvement consists in coming out of the empiric coefficients and considering the variation of viscosity as a function of pressures. Results are much better in good agreement with the experimental data. The validated model can then be admitted as an improved hydrodynamic model for predicting pressures and velocities during hot rolling of thin strips.

Advances in materials research, 2020

The objective of the present work is to investigate the effect of cutting parameters (Vc, fz and ... more The objective of the present work is to investigate the effect of cutting parameters (Vc, fz and ap) on tool life and the level of vibrations velocity in the machined part during face milling operation of hardened AISI 52100 steel. Dry-face milling has been achieved in the annealed (28 HRc) and quenched (55 HRc) conditions using multi-layer coating micro-grain carbide inserts. Statistical analysis based on the Response surface methodology (RSM) and ANOVA analysis have been conducted through a plan of experiments methodology using a reduced Taguchi table (L9) in order to obtain engineering models for tool life and vibration velocity in the workpiece for both heat treatment conditions. The results show that the cutting speed has a dominant influence on tool life for both soft and hard part. Cutting speed and feed per tooth is the most significant parameters for vibration levels. Comparing the experimental values with those predicted by the developed engineering models of tool life and...

Journal of Natural Gas Science and Engineering, 2022

Considering corrosion rate during the remaining life assessment of aging pipelines is fundamental... more Considering corrosion rate during the remaining life assessment of aging pipelines is fundamental to calculate the interval between two consecutive inspections. A total of 798 internal and external corrosion defects have been detected, using the Magnetic Flux Leakage intelligent inspection tool, over 48 km of a pipeline length located in the west region of Algeria. The statistical analysis has shown that there is a strong correlation between the corrosion defect length and the corrosion defect circumferential width, with a significant correlation coefficient equal to 82.87%. A probabilistic methodology is presented for the assessment of the remaining life of a corroded pipeline transporting gas, and a finite element method (FEM) was used to assess the pipeline failure pressure. The numerical FEM modeling results were compared with the commonly used codes-models for calculating limit pressure to establish a more realistic and accurate engineering model. The reliability analysis of an API 5L X60 steel made Algerian natural gas pipeline, in service for thirty years, and exposed to active corrosion attack, is presented. The sensitivity analysis of the basic random variables within the nonlinear limit state function was carried out to bring out the relative contribution of each variable affecting the remaining life of corroded pipelines. The reliability analysis is carried out by using Breitung's formula, based on the second-order reliability method (SORM). The reliability assessment of the corroded pipeline is based on the usage of the notched failure assessment diagram (NFAD), different codes for the calculation of the failure pressure, and the numerical results using the finite element analyses (FEA) software ANSYS.

L'importance de l'engrenage, comme element mecanique necessaire et ideal, est demontree p... more L'importance de l'engrenage, comme element mecanique necessaire et ideal, est demontree par la vaste gamme qu'on trouve dans toutes les industries. La performance des engrenages en plastiques telles que le polyoxymethylene (POM) et le polyamide (PA) est liee a leur capacite a resister l’usure. Les polyamides sont utilises comme materiaux pour engrenages en plastique moule par injection. Les engrenages en plastique ont plusieurs avantages en comparaison avec les engrenages en metal, telles que le poids leger, le bruit reduit, et le degre de liberte eleve dans la geometrie des engrenages. L’objectif de ce travail etant d’etudier l’usure des roues dentees en polyamide « PA66 », l’investigation concerne la determination de l’evolution de cette usure dans un contact sec, lubrifie a l’eau, lubrifie a un melange d’eau et de detergent a base de phosphate. L’influence de l’environnement d’essai sur le comportement d’usure des engrenages, indique que l’air (usure a sec) provoque u...

The present work proposes new engineering models for determining corrosion initiation time in con... more The present work proposes new engineering models for determining corrosion initiation time in concrete reinforcing steels in marine environment. The models are based on Fick\'s second law that is commonly used for chloride diffusion. The latter is based on deterministic analyses involving the most influencing parameters such as distance of the concrete structure from the seaside, depth of steel concrete cover, ambient temperature, relative humidity and the water-cement ratio. However, a realistic corrosion initiation time cannot be estimated because of the uncertainties associated to the different parameters of the models. Therefore a reliability approach using FORM/SORM method has been applied to develop the proposed engineering models integrating a limit state function and a reliability index B. As a result, the corrosion initiation time is expressed by new exponential engineering models where the uncertainties are associated to the model parameters. The main emerging result i...

Wear investigation has been conducted on mixed ceramic cutting tool (70% Al2O3 + 30% TiC) when ma... more Wear investigation has been conducted on mixed ceramic cutting tool (70% Al2O3 + 30% TiC) when machining hardened AISI 52100 steel (66 HRC). Experimental planning method has been used to assess the relationship between radial cutting vibrations and surface roughness as a function of the machining conditions. First, wear results show that when the cutting speed is increased 3.78 times, tool life drops of 8.75 times. When increasing the feed rate by a factor of 2.75 tool life decreases by a factor of 1.4. Then, the effect of cutting parameters (speed, feed and depth) on one hand surface roughness (Ra) and in the other hand radial tool vibrations has been determined using the multiple regression models with a coefficient of determination R2 equal to respectively 95.5% and 89.3%. With regards to surface roughness, ANOVA analyses reveal that feed rate contributes of about 84% in the surface roughness. Meanwhile, looking at the vibration phenomena, the cutting speed has the most significa...

Generalement, les causes de la deterioration des pipelines de transport d'hydrocarbures sont ... more Generalement, les causes de la deterioration des pipelines de transport d'hydrocarbures sont liees a la presence de defauts apparents (piqures, fissures, corrosion, etc.). Les methodes mecano-fiabilistes sont necessaires a developper en se basant sur des methodes probabilistes. L’objectif de ce travail est l’evaluation probabiliste de la fiabilite des pipelines avec des defauts localises. Le modele mecanique de degradation utiliser est base sur la mecanique de la rupture, pour evaluer la probabilite de defaillance a travers les dimensions des defauts par la methode FORM/SORM. L’etude parametrique a pour but de selectionner les variables les plus significatives, ce qui permet de mieux les maitriser selon leur role par rapport au comportement mecanique ou a la fiabilite. Les parametres les plus dominants sont l’epaisseur et le diametre du tube.

Advances in materials research, 2018

The present paper is an investigation on the effect of slide diamond burnishing on the fatigue en... more The present paper is an investigation on the effect of slide diamond burnishing on the fatigue endurance of a component made of AISI52100 steel. Burnishing operation has been performed on cylindrical specimens using optimal parameters statistically selected such as burnishing force, burnishing feed and number of tool passes. Bending fatigue tests in air at R= -1 and S-N curves have been plotted by incrementing the applied stress from a maximum stress level of about 66% of the ultimate tensile stress to a stress value below which fatigue does not occur. Results show that slide diamond burnishing has increased the fatigue resistance comparing to unburnished specimens. The fatigue endurance is respectively 222 MPa and 190 MPa. At high stress levels, the fatigue resistance improvement is clearly observed and the fatigue trends are in good agreement with those reported in literature. However, the present results are slightly lower and that is attributed to the shoulder fillet value of th...

The International Journal of Advanced Manufacturing Technology, 2020

The present work is a contribution to developing a strategy for rapid analysis of the behaviour o... more The present work is a contribution to developing a strategy for rapid analysis of the behaviour of surface roughness and tool wear during machining hardened steel with carbide cemented cutting tools on conventional cutting machines. In agreement with dies and mould manufacturers in East Algeria, the strategy is based on the machining potential of the manufacturers, cutting tools manufacturer’s guidelines and recommendations from literature. The agreement suggested to focus on up and down shoulder finish milling of hardened AISI D3 tool steel using GC1030 insert on a conventional vertical milling machine. The strategy has been developed within five successive steps starting from the analyses of the performance of a machine tool to the definition of an experimental plan to respect. As expected, results show that down shoulder milling is the most suitable process rather than up shoulder milling which must be avoided whatever the hardening condition. In addition, the best performance of down shoulder milling is obtained when machining unhardened steel. In the as-received condition (31.6 HRc) when using down milling the cutting speed can be increased up to the maximum value of 113 m/min, however, the tool life obtained for this value is three times lower than that at Vc = 59 m/min. In 49 HRc hardening condition, milling at Vc = 59 m/min resulted in the good surface finish but with a tool life 6.5 times lower than the tool life when milling in the as-received condition. Vibration measurements provide a time referential data on the evolution of surface roughness together with corresponding tool wear. A time referential data on the evolution of displacement together with the corresponding tool life has been proposed as useful information to meet the needs of dies and moulds manufacturers when milling hardened steels.

Lecture Notes in Mechanical Engineering, 2019

This paper presents a probabilistic study to estimate the remaining lifespan of cracked steel pip... more 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.

The International Journal of Advanced Manufacturing Technology, 2018

The reliability of high-density polyethylene (HDPE) pipes remains a central issue for gas transpo... more The reliability of high-density polyethylene (HDPE) pipes remains a central issue for gas transportation and distribution networks. The objective of this study is to investigate the estimation of reliability index (β) for a plastic pipe using the critical stress intensity factor (K IC) as the maximum limit for safe operating conditions. Simulations are performed as a function of operating pressure, crack length, and standard dimension ratio (SDR) for three fracture toughness levels (low, moderate, and high). In addition, the study compares results from three hoop stress calculations methods (thin, thick, and ISO plastic pipe equation). Based on design recommendation for reliability index, it is found that both operating pressure and crack length show comparable behaviors. However, the thick wall pipe results overestimate (β) for every K IC level. In all cases, it is found that the higher the critical stress intensity factor, the better the reliability index. Results obtained with the standard ISO pipe formula are more realistic, as they are usually around the design recommendation, i.e., SDR basis indicates that it is a true conservative design approach incorporating both upper and lower thickness limits. The importance of all variables (thickness, diameter, crack length, pressure, and fracture toughness) is also discussed.

Engineering Failure Analysis, 2017

Despite the various engineering models existing for lifetime investigation of hydrocarbon steel p... more Despite the various engineering models existing for lifetime investigation of hydrocarbon steel pipelines under localized corrosion and crack defects there is still a lack of information about the correlation between the two main parameters characterizing the geometrical defect model, depth and length. So the aim of the present work is a contribution in evaluating the remaining life of the pipeline using reliability analysis in order to correlate the two parameters through one common parameter, the reliability index. As a first step, the investigation is carried out on four standard and well established engineering models; Irwin, SINTAP, ASME B31G and Modified ASME B31G methods, aiming to coordinate results given by each of the four models. The potential defect depth and length correlation through a reliability index can be used as a decision-making tool to give realistic answers for replacing and/or repairing a tube subjected to internal pressure and on which flaws of different depths and lengths have been detected from inspection of a pipeline after few years of service.

The International Journal of Advanced Manufacturing Technology, 2016

The probabilistic approach is the best way to give realistic answers for design and maintenance a... more The probabilistic approach is the best way to give realistic answers for design and maintenance and it is considered as a powerful decision-making tool. In the present paper, assessment of the failure probability of corroded pipeline subjected to internal pressure is estimated by using the first order reliability method (FORM). Measurements of defect dimensions have been achieved changed into collected by using ultra sound inspection probe through a 75-km pipeline portion on one of the main Algerian high pressure gas transportation that has been in service for 30 years. The sensitivity analyses have been carried out on random variables to identify the importance of the parameters within the reliability mechanical model. The modified B31G code has been coupled as a mechanical model, with Rackwitz optimization algorithm by using PHIMECA Software. The limit state function resumes the difference between the pipeline burst pressure and the pipeline operating pressure. The aim of the present work is to make in evidence the competitive importance of pressure service, wall thickness and the defect depth with regards to defect length and to determine the influence of the coefficients of variation on the failure probability and the remaining life of the pipeline. A diagram based on the reliability index results is proposed to predict the pipeline degradation and it can be used as a decision tool for maintenance program.

The International Journal of Advanced Manufacturing Technology, 2017

The present work proposes a new numerical approach based on the derivation method of Bridgman to ... more The present work proposes a new numerical approach based on the derivation method of Bridgman to determine (K IC) of galvanized steel sheets. The method relies on a fracture analysis numerical code "Franc2D," which permits to simulating the initiation and propagation of a crack on grooved tensile specimens. First, the stress intensity factor is obtained while the crack is propagating and then (K IC) is determined from the fitting curves of the stress intensity factor (K I) to crack length (a) plot through mathematical transformations. The results are validated by comparing them to those obtained through the experimental approach using Vickers hardness based IEF engineering models. The relative values of (K IC) are admissible and acceptable with a coefficient of variation of 14% for a large range of groove radius. Hence, the present numerical simulation can be fairly used in order to reduce time consuming and avoid costly experimental mechanical tests.

The International Journal of Advanced Manufacturing Technology, 2017

The present paper is a contribution in developing an engineering model expressing the evolution o... more The present paper is a contribution in developing an engineering model expressing the evolution of tooth flank wear in polyamide spur gears as a function of number of cycles. The method is based on first observing the behavior of wear on tooth flanks in real test conditions. Then progressive flank wear profiles are plotted in order to sort out the corresponding fitting curves together with the associated mathematical equations. The general engineering model controlling the evolution of wear profile is found of the form of quadratic equation where the variable is the circular thickness of a tooth at a given depth from the top land of the tooth. The respective parameters of the engineering wear equation are determined as a function of number of revolutions of the spur gear. A wear correction parameter kw is added in order to catch up the measuring errors when plotting the wear profile curves using the proposed engineering wear model for spur gears. The data are in good agreement with that obtained from experimental measurements.

The International Journal of Advanced Manufacturing Technology, 2016

The International Journal of Advanced Manufacturing Technology, 2016

This paper focuses on an approach of implementing traceability of machined parts for subsets used... more This paper focuses on an approach of implementing traceability of machined parts for subsets used in automotive products. The objective is to recover the memory of a given part that has been shaped by removing material from a blank to the finished part in order to fulfil a required function. The approach includes describing the process plan of a given part to be machined, analysing the reliability of the production system, introducing the notion of points of data traceability recording (PDTR) and identifying the machined part by a well-established codification number within the machining workshop. The present approach is illustrated through a case study of implementing internal traceability on batches of parts of hubs for wheelchairs that are manufactured at the Cyclomotor company CYCMA, Guelma in Algeria. Recalls and defective parts can be significantly identified towards the raw material, the process plan, the cutting tool and operators.