Flow in a branched channel is studied experimentally using the PIV technique. The presented study is concentrated on clarifying the dynamical behaviour in individual branches. The 11 branches issuing from the main channel perpendicularly, all channels are of rectangular cross-section. First, the time-mean flow-field is shown, then the flow dynamics is investigated using the OPD method. Flow patterns and frequencies are evaluated in three selected branches. The separated flow in branches exhibits highly dynamical behaviour, which differs substantially in the branches close to the inflow, in the main channel middle and close to its end. The typical topologies and frequencies of the detected quasi-periodical structures in the channel braches are shown in the study. Mostly, the flow-fields are populated by trains of vortices with alternating orientation and saddle-like structures. The flow-field close to the channel walls affects heat transfer process between the wall and fluid.
{"title":"Dynamics of flow in a branching channel","authors":"V. Uruba, P. Procházka, V. Skála","doi":"10.1051/MECA/2021014","DOIUrl":"https://doi.org/10.1051/MECA/2021014","url":null,"abstract":"Flow in a branched channel is studied experimentally using the PIV technique. The presented study is concentrated on clarifying the dynamical behaviour in individual branches. The 11 branches issuing from the main channel perpendicularly, all channels are of rectangular cross-section. First, the time-mean flow-field is shown, then the flow dynamics is investigated using the OPD method. Flow patterns and frequencies are evaluated in three selected branches. The separated flow in branches exhibits highly dynamical behaviour, which differs substantially in the branches close to the inflow, in the main channel middle and close to its end. The typical topologies and frequencies of the detected quasi-periodical structures in the channel braches are shown in the study. Mostly, the flow-fields are populated by trains of vortices with alternating orientation and saddle-like structures. The flow-field close to the channel walls affects heat transfer process between the wall and fluid.","PeriodicalId":49018,"journal":{"name":"Mechanics & Industry","volume":"37 1","pages":""},"PeriodicalIF":1.2,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83980529","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Martial Crozet, Y. Berthier, A. Saulot, David Jones, B. Bou-Saïd
Within diesel engines, the valve-seat contact is one of the few non-lubricated contacts which is subjected to significant degradation. This degradation is put in evidence by material removal at the intake valve. The material pull out is promoted by the replication of combustion cycles (500 million) and severe operating conditions (pressure 18 MPa). The wear can lead to gas leakage and engine failure. The target of this work was to identify the main parameters affecting this wear. Our approach was based on the tribological triplet and material flows within the contact involving both numerical and experimental approaches. A dynamic model and a valvetrain test bench showed that the wear flows could be activated by the architecture of the valve opening system. Consequently, the limitation of these flows can be obtained by controlling the “global” geometry of the system and therefore without modifying the properties of the materials. In the same way, a finite element model of the local response of the seat-valve contact highlighted the impact of the “local” geometry of the contact. The change of this geometry is a lever to limit the shearing forces which reduces the tearing of the particles and therefore wear. Finally, tests carried out on the engine and on a specifically adapted test bench completed the understanding of degradation mechanisms (source flow, wear flow, etc.). Morphological interpretations of worn surfaces in terms of material flows allowed the understanding of the build-up stages of a protective layer. One solution to promote this internal flow is the use of pollutants from combustion. For example, the burned oil in contact, which is a priori harmful, becomes an opportunity here. In addition, un-burned hydrocarbons from the combustion of biodiesel help to protect the contact.
{"title":"Valve-seat components in a diesel engine: a tribological approach to limit wear","authors":"Martial Crozet, Y. Berthier, A. Saulot, David Jones, B. Bou-Saïd","doi":"10.1051/meca/2021043","DOIUrl":"https://doi.org/10.1051/meca/2021043","url":null,"abstract":"Within diesel engines, the valve-seat contact is one of the few non-lubricated contacts which is subjected to significant degradation. This degradation is put in evidence by material removal at the intake valve. The material pull out is promoted by the replication of combustion cycles (500 million) and severe operating conditions (pressure 18 MPa). The wear can lead to gas leakage and engine failure. The target of this work was to identify the main parameters affecting this wear. Our approach was based on the tribological triplet and material flows within the contact involving both numerical and experimental approaches. A dynamic model and a valvetrain test bench showed that the wear flows could be activated by the architecture of the valve opening system. Consequently, the limitation of these flows can be obtained by controlling the “global” geometry of the system and therefore without modifying the properties of the materials. In the same way, a finite element model of the local response of the seat-valve contact highlighted the impact of the “local” geometry of the contact. The change of this geometry is a lever to limit the shearing forces which reduces the tearing of the particles and therefore wear. Finally, tests carried out on the engine and on a specifically adapted test bench completed the understanding of degradation mechanisms (source flow, wear flow, etc.). Morphological interpretations of worn surfaces in terms of material flows allowed the understanding of the build-up stages of a protective layer. One solution to promote this internal flow is the use of pollutants from combustion. For example, the burned oil in contact, which is a priori harmful, becomes an opportunity here. In addition, un-burned hydrocarbons from the combustion of biodiesel help to protect the contact.","PeriodicalId":49018,"journal":{"name":"Mechanics & Industry","volume":"70 1","pages":""},"PeriodicalIF":1.2,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90654392","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This research work presents a numerical study of the orthogonal cutting process employing a finite element approach to optimize dry machining of aluminium alloy 2024. The main objective of the research work is to perform three-dimensional finite element simulations for a better understanding of temperature distribution and residual stresses development in the workpiece and tool regions along depth of cut direction. While, two-dimensional models don't predict true picture of aforesaid parameters along cutting depth due to material's out of plane flow and deformation. In the present study, effects of tool rake angles (7°, 14°, 21°) and cutting speeds (200, 400, 800 m/min) upon variations in chip geometry at various sections along workpiece width (depth of cut) have been discussed at large. Furthermore, cutting forces and tool-workpiece temperature profiles are also in depth analysed. The findings will lead the manufacturers to better decide post machining processes like heat treatment, deburring, surface treatments, etc. The results showed that a combination of a rake angle of 14° at cutting velocity of 800 m/min produces serrated chip segments with relatively moderate cutting forces in comparison to other parametric combinations. The efficacy of the presented finite element model is verified by comparing the numerically obtained results with experimental ones.
{"title":"A three-dimensional finite element-approach to investigate the optimum cutting parameters in machining AA2024","authors":"H. Ijaz, M. Danish, M. Asad, S. Rubaiee","doi":"10.1051/meca/2020087","DOIUrl":"https://doi.org/10.1051/meca/2020087","url":null,"abstract":"This research work presents a numerical study of the orthogonal cutting process employing a finite element approach to optimize dry machining of aluminium alloy 2024. The main objective of the research work is to perform three-dimensional finite element simulations for a better understanding of temperature distribution and residual stresses development in the workpiece and tool regions along depth of cut direction. While, two-dimensional models don't predict true picture of aforesaid parameters along cutting depth due to material's out of plane flow and deformation. In the present study, effects of tool rake angles (7°, 14°, 21°) and cutting speeds (200, 400, 800 m/min) upon variations in chip geometry at various sections along workpiece width (depth of cut) have been discussed at large. Furthermore, cutting forces and tool-workpiece temperature profiles are also in depth analysed. The findings will lead the manufacturers to better decide post machining processes like heat treatment, deburring, surface treatments, etc. The results showed that a combination of a rake angle of 14° at cutting velocity of 800 m/min produces serrated chip segments with relatively moderate cutting forces in comparison to other parametric combinations. The efficacy of the presented finite element model is verified by comparing the numerically obtained results with experimental ones.","PeriodicalId":49018,"journal":{"name":"Mechanics & Industry","volume":"50 1","pages":""},"PeriodicalIF":1.2,"publicationDate":"2020-12-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87577639","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Machining of bio-medical Ti-6Al-4V ELI grade is categorized in difficult to cut metal alloys due to its lower thermal conductivity and highly reactive in nature at elevated temperature. However, to improve the machinability of this alloy, controlling the temperature during cutting action is a challenging task. On this context, current work introduced a novel cooling strategy named as pulsating minimum quantity lubrication technique to investigate the surface roughness, surface texture (surface topology, surface profile, amplitude distribution curve, Bearing area curve, and Power spectrum), tool-work temperature, and flank wear in high-speed CNC turning of Ti-6Al-4V ELI Alloy. Feed is the leading influencing term towards surface roughness, pulse time contributing the highest impact towards tool-work temperature while flank wear is largely influenced by cutting speed. Abrasion, notch wear, adhesion and diffusion mode of wear is found.
{"title":"Pulsating minimum quantity lubrication assisted high speed turning on bio-medical Ti-6Al-4V ELI Alloy: An experimental investigation","authors":"Ramanuj Kumar, A. Sahoo","doi":"10.1051/MECA/2020097","DOIUrl":"https://doi.org/10.1051/MECA/2020097","url":null,"abstract":"Machining of bio-medical Ti-6Al-4V ELI grade is categorized in difficult to cut metal alloys due to its lower thermal conductivity and highly reactive in nature at elevated temperature. However, to improve the machinability of this alloy, controlling the temperature during cutting action is a challenging task. On this context, current work introduced a novel cooling strategy named as pulsating minimum quantity lubrication technique to investigate the surface roughness, surface texture (surface topology, surface profile, amplitude distribution curve, Bearing area curve, and Power spectrum), tool-work temperature, and flank wear in high-speed CNC turning of Ti-6Al-4V ELI Alloy. Feed is the leading influencing term towards surface roughness, pulse time contributing the highest impact towards tool-work temperature while flank wear is largely influenced by cutting speed. Abrasion, notch wear, adhesion and diffusion mode of wear is found.","PeriodicalId":49018,"journal":{"name":"Mechanics & Industry","volume":"38 1","pages":""},"PeriodicalIF":1.2,"publicationDate":"2020-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73607804","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The effect of the shape of the mirror of a heliostat is studied through wind tunnel tests in uniform smooth and turbulent flow conditions. Three shapes are investigated: square (reference case), octagonal and circular geometries. The forces and moments are measured on reduced scale models of heliostats in low, medium and strong turbulence wind conditions in a uniform wind profile. The turbulence intensity of the flow is adjusted in the wind tunnel test section by the adjunction of passive grids upstream the model. The experimental results are presented for several elevation and azimuth angles. The results showed that: in smooth flow conditions, the geometry of the mirror has very limited effect on the mean force coefficient, while impacting the fluctuating part of the aerodynamic loads. In turbulence flow conditions, the circular mirror/panel is advantageous for the aerodynamic design of the elevation drive and mirror support structure.
{"title":"Shape effects on aerodynamic loading of heliostats","authors":"H. Merarda, M. Aksas, T. Andrianne","doi":"10.1051/meca/2020086","DOIUrl":"https://doi.org/10.1051/meca/2020086","url":null,"abstract":"The effect of the shape of the mirror of a heliostat is studied through wind tunnel tests in uniform smooth and turbulent flow conditions. Three shapes are investigated: square (reference case), octagonal and circular geometries. The forces and moments are measured on reduced scale models of heliostats in low, medium and strong turbulence wind conditions in a uniform wind profile. The turbulence intensity of the flow is adjusted in the wind tunnel test section by the adjunction of passive grids upstream the model. The experimental results are presented for several elevation and azimuth angles. The results showed that: in smooth flow conditions, the geometry of the mirror has very limited effect on the mean force coefficient, while impacting the fluctuating part of the aerodynamic loads. In turbulence flow conditions, the circular mirror/panel is advantageous for the aerodynamic design of the elevation drive and mirror support structure.","PeriodicalId":49018,"journal":{"name":"Mechanics & Industry","volume":"32 1","pages":""},"PeriodicalIF":1.2,"publicationDate":"2020-11-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81578738","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Brake squeal is commonly defined at frequency upper than 1000 Hz and occurs if the system has a very high amplitude mechanical vibration with sound pressure level above 120 dB. Many studies are devoted to this problem and many of recent ones show that contact conditions and friction material behavior have a major influence on squeal occurrence. To investigate this aspect, an experimental set-up has been developed in this study. It is based on a simplified system in order to focus on the influence of the material in the one hand and surface conditions in the other hand. In this paper, the design of the pin-on-disc is described and an analytical model is also presented in order to understand the dynamic behavior of the system. Macroscopic aspects are investigated by varying the pin geometry. The results show clearly the influence of the variation of the contact length size on squeal occurrence. Comparison with the model shows good agreement and exhibit the necessity of considering an improved model of the friction material behavior. This study also gives information on the comprehension of squeal mechanisms.
{"title":"Experimental set-up and the associated model for squeal analysis","authors":"M. Duboc, V. Magnier, J. Brunel, P. Dufrénoy","doi":"10.1051/meca/2019083","DOIUrl":"https://doi.org/10.1051/meca/2019083","url":null,"abstract":"Brake squeal is commonly defined at frequency upper than 1000 Hz and occurs if the system has a very high amplitude mechanical vibration with sound pressure level above 120 dB. Many studies are devoted to this problem and many of recent ones show that contact conditions and friction material behavior have a major influence on squeal occurrence. To investigate this aspect, an experimental set-up has been developed in this study. It is based on a simplified system in order to focus on the influence of the material in the one hand and surface conditions in the other hand. In this paper, the design of the pin-on-disc is described and an analytical model is also presented in order to understand the dynamic behavior of the system. Macroscopic aspects are investigated by varying the pin geometry. The results show clearly the influence of the variation of the contact length size on squeal occurrence. Comparison with the model shows good agreement and exhibit the necessity of considering an improved model of the friction material behavior. This study also gives information on the comprehension of squeal mechanisms.","PeriodicalId":49018,"journal":{"name":"Mechanics & Industry","volume":"18 1","pages":""},"PeriodicalIF":1.2,"publicationDate":"2020-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79808928","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Anshuman J. Das, Sudhansu Ranjan Das, S. Patel, B. Biswal
Now-a-days due to growing demand of high precision components to attain high performances, hardened steels with hardness above 45HRC have numerous applications in automotive gear, machine tool and die industry because of their superior characteristics (high thermal stability, high indentation resistance, high abrasiveness, low ductility and high value of hardness to modulus of elasticity ratio). For this, higher tool life of cutting inserts cryogenic treatment is considered as the most prominent method but no substantial researches have been found concerning the impact of cryogenic treatment on cermet inserts, especially in turning of hardened steels. Therefore, in the present experimental investigation, the comparative assessment of various responses such as cutting force, flank wear, crater wear, chip morphology and surface roughness were carried out during machining of hardened steel with both untreated and cryo-treated cermet inserts under dry cutting condition. Lastly, the input variables were optimized using Response Surface Methodology (RSM) to evaluate the tool life for the economic analysis. The experimental result demonstrated that the uncoated deep cryo-treated with tempered cermet insert delivered better results in comparison to other cermet inserts. According to cost analysis, uncoated and deep cryo-treated with tempered cermet insert was found to be the most cost saving among other cermet inserts at the optimum cutting condition.
{"title":"Experimental investigation of various machining attributes and cost estimation during machining of hardened AISI 4340 steel with untreated and cryo treated cermet inserts","authors":"Anshuman J. Das, Sudhansu Ranjan Das, S. Patel, B. Biswal","doi":"10.1051/meca/2019082","DOIUrl":"https://doi.org/10.1051/meca/2019082","url":null,"abstract":"Now-a-days due to growing demand of high precision components to attain high performances, hardened steels with hardness above 45HRC have numerous applications in automotive gear, machine tool and die industry because of their superior characteristics (high thermal stability, high indentation resistance, high abrasiveness, low ductility and high value of hardness to modulus of elasticity ratio). For this, higher tool life of cutting inserts cryogenic treatment is considered as the most prominent method but no substantial researches have been found concerning the impact of cryogenic treatment on cermet inserts, especially in turning of hardened steels. Therefore, in the present experimental investigation, the comparative assessment of various responses such as cutting force, flank wear, crater wear, chip morphology and surface roughness were carried out during machining of hardened steel with both untreated and cryo-treated cermet inserts under dry cutting condition. Lastly, the input variables were optimized using Response Surface Methodology (RSM) to evaluate the tool life for the economic analysis. The experimental result demonstrated that the uncoated deep cryo-treated with tempered cermet insert delivered better results in comparison to other cermet inserts. According to cost analysis, uncoated and deep cryo-treated with tempered cermet insert was found to be the most cost saving among other cermet inserts at the optimum cutting condition.","PeriodicalId":49018,"journal":{"name":"Mechanics & Industry","volume":"7 1","pages":""},"PeriodicalIF":1.2,"publicationDate":"2020-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84289559","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The babbitt-steel bimetal sliding bearing material prepared by the MIG brazing has been applied in many fields. In the application, usually only the bonding force is tested, and the fatigue strength is not evaluated. For this reason, this study referred to the test method for the fatigue strength of bearing materials of internal combustion engines, used the sapphire test machine (Dana Glacier Vandervell Bearings, UK) to inspect the SnSb11Cu6 babbitt-steel bimetal material prepared by MIG brazing, and analyzed the test results in depth. The test results show that, the fatigue strength of the bimetal material is more than 40 MPa. In comparison, according to the same test method and conditions on the same sapphire test machine, the fatigue strength of the SnSb11Cu6 babbitt-steel bimetal bearing material obtained by the centrifugal casting method after optimizing process was usually around 35 MPa. Therefore, the MIG brazing could produce higher fatigue strength for SnSb11Cu6 babbitt-steel bimetal bearing material. In addition, in this study, the process of fatigue failure was usually that after the microcracks were generated on the surface, they expanded to the inside of the lining, thereby resulting in spalling. This study has guiding significance for engineering practice and scientific research.
{"title":"Study on fatigue strength of SnSb11Cu6 babbitt-steel bimetal sliding bearing material prepared by MIG brazing","authors":"Xinbo Wang, Z. Yin, Yonghong Chen","doi":"10.1051/meca/2019075","DOIUrl":"https://doi.org/10.1051/meca/2019075","url":null,"abstract":"The babbitt-steel bimetal sliding bearing material prepared by the MIG brazing has been applied in many fields. In the application, usually only the bonding force is tested, and the fatigue strength is not evaluated. For this reason, this study referred to the test method for the fatigue strength of bearing materials of internal combustion engines, used the sapphire test machine (Dana Glacier Vandervell Bearings, UK) to inspect the SnSb11Cu6 babbitt-steel bimetal material prepared by MIG brazing, and analyzed the test results in depth. The test results show that, the fatigue strength of the bimetal material is more than 40 MPa. In comparison, according to the same test method and conditions on the same sapphire test machine, the fatigue strength of the SnSb11Cu6 babbitt-steel bimetal bearing material obtained by the centrifugal casting method after optimizing process was usually around 35 MPa. Therefore, the MIG brazing could produce higher fatigue strength for SnSb11Cu6 babbitt-steel bimetal bearing material. In addition, in this study, the process of fatigue failure was usually that after the microcracks were generated on the surface, they expanded to the inside of the lining, thereby resulting in spalling. This study has guiding significance for engineering practice and scientific research.","PeriodicalId":49018,"journal":{"name":"Mechanics & Industry","volume":"74 1","pages":""},"PeriodicalIF":1.2,"publicationDate":"2020-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79269197","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
E. Lainé, J. Grandidier, Maxime Cruz, Anne-Laure Gorge, Claire Bouvy, G. Vaes
The aim of this paper is to study the damage mechanisms in a sandwich polymer structure that contains three layers: two polyolefin skins and the foam core (skin–foam–skin). Specific tests on structure associated with the acoustic emission (AE) technique and tomographic observations (RX) are used to identify the damage. Initially, a conventional tensile test was performed to correlate the acoustic emission with the initiation of plasticity and damage to a polyethylene sample. The results obtained are close to those observed in other studies and it is possible to separate the signal from cavitation and propagation of necking. The technique is then employed to capture the rupture of a polymer skin on a multilayer rotomoulded structure (bottle). Tests were carried out on this bottle under internal water pressure. Three tests are performed with more or less early interruptions in order to identify the first damage and understand their evolution. Different quantities (average frequency, RA value, etc.) are observed in order to quantify and understand the perceived damage. With the AE/RX correlation and mechanical behaviour, a scenario of structural damage is proposed.
{"title":"Acoustic emission description from a damage and failure scenario of rotomoulded polyolefin sandwich structure subjected to internal pressure for storage applications","authors":"E. Lainé, J. Grandidier, Maxime Cruz, Anne-Laure Gorge, Claire Bouvy, G. Vaes","doi":"10.1051/meca/2019077","DOIUrl":"https://doi.org/10.1051/meca/2019077","url":null,"abstract":"The aim of this paper is to study the damage mechanisms in a sandwich polymer structure that contains three layers: two polyolefin skins and the foam core (skin–foam–skin). Specific tests on structure associated with the acoustic emission (AE) technique and tomographic observations (RX) are used to identify the damage. Initially, a conventional tensile test was performed to correlate the acoustic emission with the initiation of plasticity and damage to a polyethylene sample. The results obtained are close to those observed in other studies and it is possible to separate the signal from cavitation and propagation of necking. The technique is then employed to capture the rupture of a polymer skin on a multilayer rotomoulded structure (bottle). Tests were carried out on this bottle under internal water pressure. Three tests are performed with more or less early interruptions in order to identify the first damage and understand their evolution. Different quantities (average frequency, RA value, etc.) are observed in order to quantify and understand the perceived damage. With the AE/RX correlation and mechanical behaviour, a scenario of structural damage is proposed.","PeriodicalId":49018,"journal":{"name":"Mechanics & Industry","volume":"170 1","pages":""},"PeriodicalIF":1.2,"publicationDate":"2020-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74881172","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Sharan Raj Rangasamy Mahendren, H. Welemane, O. Dalverny, A. Tongne
Material behaviour is often affected by the heterogeneities existing at the microscopic level. Especially the presence of cracks, voids, etc collectively known as defects, can play a major role in their overall response. Homogenization can be used to study the influence of these heterogeneities and also to estimate the effective properties of a given material. Several research works have been dedicated to determining the elastic behaviour of microcracked media. Yet, thermal properties are not investigated as much. Moreover, the question of unilateral effect (opening/closing of cracks) still remains an important issue. So, this paper aims to provide the effective thermal conductivity of 2D microcracked media with arbitrarily orientated cracks, either open or closed. With the help of Eshelby-like approach, homogenization schemes (dilute and Mori-Tanaka) and bounds (Ponte Castañeda-Willis) are developed to provide the closed-form expressions. In addition, these results are compared to numerical simulations performed based on finite element modelling.
{"title":"Steady-state heat transfer in microcracked media","authors":"Sharan Raj Rangasamy Mahendren, H. Welemane, O. Dalverny, A. Tongne","doi":"10.1051/meca/2020034","DOIUrl":"https://doi.org/10.1051/meca/2020034","url":null,"abstract":"Material behaviour is often affected by the heterogeneities existing at the microscopic level. Especially the presence of cracks, voids, etc collectively known as defects, can play a major role in their overall response. Homogenization can be used to study the influence of these heterogeneities and also to estimate the effective properties of a given material. Several research works have been dedicated to determining the elastic behaviour of microcracked media. Yet, thermal properties are not investigated as much. Moreover, the question of unilateral effect (opening/closing of cracks) still remains an important issue. So, this paper aims to provide the effective thermal conductivity of 2D microcracked media with arbitrarily orientated cracks, either open or closed. With the help of Eshelby-like approach, homogenization schemes (dilute and Mori-Tanaka) and bounds (Ponte Castañeda-Willis) are developed to provide the closed-form expressions. In addition, these results are compared to numerical simulations performed based on finite element modelling.","PeriodicalId":49018,"journal":{"name":"Mechanics & Industry","volume":"39 1","pages":""},"PeriodicalIF":1.2,"publicationDate":"2020-08-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79865586","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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