Pub Date : 2019-08-01DOI: 10.3389/fmech.2019.00048
A. Gambarotta, V. Papetti, P. Dimopoulos Eggenschwiler
Today restrictions on pollutant emissions require the use of catalyst-based after-treatment systems as a standard both in SI and in Diesel engines. The application of monolith cores with a honeycomb structure is an established practice: however, to overcome drawbacks such as weak mass transfer from the bulk flow to the catalytic walls as well as poor flow homogenization, the use of ceramic foams has been recently investigated as an alternative showing better conversion efficiencies (even accepting higher flow through losses). The scope of this paper is to analyse the effects of foam substrates characteristics on engine performance. To this purpose a 0D “crank-angle” real-time mathematical model of an I.C.Engine developed by the Authors has been enhanced improving the heat exchange model of the exhaust manifold to take account of thermal transients and adding an original 0D model of the catalytic converter to describe mass flows and thermal processes. The model has been used to simulate a 1.6l turbocharged Diesel engine during a driving cycle (EUDC). Effects of honeycomb and foam substrates on fuel consumption and on variations of catalyst temperatures and pressures are compared in the paper.
{"title":"Analysis of the Effects of Catalytic Converter on Automotive Engines Performance Through Real-Time Simulation Models","authors":"A. Gambarotta, V. Papetti, P. Dimopoulos Eggenschwiler","doi":"10.3389/fmech.2019.00048","DOIUrl":"https://doi.org/10.3389/fmech.2019.00048","url":null,"abstract":"Today restrictions on pollutant emissions require the use of catalyst-based after-treatment systems as a standard both in SI and in Diesel engines. The application of monolith cores with a honeycomb structure is an established practice: however, to overcome drawbacks such as weak mass transfer from the bulk flow to the catalytic walls as well as poor flow homogenization, the use of ceramic foams has been recently investigated as an alternative showing better conversion efficiencies (even accepting higher flow through losses). The scope of this paper is to analyse the effects of foam substrates characteristics on engine performance. To this purpose a 0D “crank-angle” real-time mathematical model of an I.C.Engine developed by the Authors has been enhanced improving the heat exchange model of the exhaust manifold to take account of thermal transients and adding an original 0D model of the catalytic converter to describe mass flows and thermal processes. The model has been used to simulate a 1.6l turbocharged Diesel engine during a driving cycle (EUDC). Effects of honeycomb and foam substrates on fuel consumption and on variations of catalyst temperatures and pressures are compared in the paper.","PeriodicalId":53220,"journal":{"name":"Frontiers in Mechanical Engineering","volume":"1 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2019-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90396724","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-07-31DOI: 10.3389/fmech.2019.00045
Konstantin Weller, S. Lipp, Martin Röck, C. Matzer, Andreas Bittermann, S. Hausberger
Real world emission and energy consumption behavior from vehicles is a key element for meeting air quality and greenhouse gas (GHG) targets for any country. While CO2 fleet targets for vehicles are defined on basis of standardized test procedures, in real driving conditions manifold parameters show large variabilities. Main differences are Driving cycle Vehicle loading and driving resistances Ambient temperature levels, start conditions and trip length Gear shift behavior of the drivers Power demand from auxiliaries Fuel quality For the upcoming update of the Handbook Emission Factors for Road Transport (HBEFA 4.1) we have performed analysis, measurements and simulations to elaborate real world energy consumption values for 2-wheelers, passenger cars (PC), light commercial vehicles (LCVs) and heavy duty vehicles (HDVs), so called emission factors (EF). EFs show fuel consumption or emission level in [g/km] and [#/km] for fuel, gaseous exhaust gas components and also for the particle number (PN). EFs are provided for a lot of different traffic situations covering stop & go up to highway for different road gradient categories. EFs are different for each vehicle category and for each powertrain technology and emission standard (from EURO 0 gasoline PC to EURO VI HDV with CNG engine). To produce the EFs, vehicle tests from chassis dyno and from on-board measurements were collected in all European labs to set up models for all vehicle segments in the passenger cars and heavy duty emission model (PHEM). The models for PC and LCVs were based on weight and road load data available from the type approval test, the worldwide harmonized light vehicles test procedure (WLTP), and then calibrated in a stepwise approach to consider all influences in real world driving. Finally, the results for new vehicle fleet fuel consumption values were compared with data from the fuel consumption monitoring data base. For HDVs, the models are based on data from the development of the HDV CO2 determination method (Regulation (EU) 2017/2400, “VECTO”). The methods and also the results in terms of differences between real world and type approval for loading, road load, energy consumption and emission levels are described in this paper.
{"title":"Real World Fuel Consumption and Emissions From LDVs and HDVs","authors":"Konstantin Weller, S. Lipp, Martin Röck, C. Matzer, Andreas Bittermann, S. Hausberger","doi":"10.3389/fmech.2019.00045","DOIUrl":"https://doi.org/10.3389/fmech.2019.00045","url":null,"abstract":"Real world emission and energy consumption behavior from vehicles is a key element for meeting air quality and greenhouse gas (GHG) targets for any country. While CO2 fleet targets for vehicles are defined on basis of standardized test procedures, in real driving conditions manifold parameters show large variabilities. Main differences are Driving cycle Vehicle loading and driving resistances Ambient temperature levels, start conditions and trip length Gear shift behavior of the drivers Power demand from auxiliaries Fuel quality For the upcoming update of the Handbook Emission Factors for Road Transport (HBEFA 4.1) we have performed analysis, measurements and simulations to elaborate real world energy consumption values for 2-wheelers, passenger cars (PC), light commercial vehicles (LCVs) and heavy duty vehicles (HDVs), so called emission factors (EF). EFs show fuel consumption or emission level in [g/km] and [#/km] for fuel, gaseous exhaust gas components and also for the particle number (PN). EFs are provided for a lot of different traffic situations covering stop & go up to highway for different road gradient categories. EFs are different for each vehicle category and for each powertrain technology and emission standard (from EURO 0 gasoline PC to EURO VI HDV with CNG engine). To produce the EFs, vehicle tests from chassis dyno and from on-board measurements were collected in all European labs to set up models for all vehicle segments in the passenger cars and heavy duty emission model (PHEM). The models for PC and LCVs were based on weight and road load data available from the type approval test, the worldwide harmonized light vehicles test procedure (WLTP), and then calibrated in a stepwise approach to consider all influences in real world driving. Finally, the results for new vehicle fleet fuel consumption values were compared with data from the fuel consumption monitoring data base. For HDVs, the models are based on data from the development of the HDV CO2 determination method (Regulation (EU) 2017/2400, “VECTO”). The methods and also the results in terms of differences between real world and type approval for loading, road load, energy consumption and emission levels are described in this paper.","PeriodicalId":53220,"journal":{"name":"Frontiers in Mechanical Engineering","volume":"7 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2019-07-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78591049","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-07-19DOI: 10.3389/fmech.2019.00044
Minoru Takagi, Kazunari Yoshida, H. Hoshino, R. Tadakuma, Yoshiyuki Suzuri, H. Furukawa
Soft-matter robotics, which is named for robots made from soft materials, will possibly conquer the limit of conventional rigid body dynamics of hard robots made from hard materials. For example, a snake-like robot, of which body is made from soft materials, will walk in various environments including narrow space like drain pipes with complicated structure. Here we developed a walking robot with the friction control of double-network hydrogel (DN gel) on its feet, as the first model based on the concept of the soft-matter robotics. It is found that with appropriate control of the friction of DN gel, the inchworm walking robot has realized its high enough velocity for pipe inspection. We discussed the physical principle of the walking motion of the inchworm search robot and its actual mechanism to provide thrust for its walking motion.
{"title":"Sliding Walk With Friction Control of Double-Network Gel on Feet of Inchworm Robot","authors":"Minoru Takagi, Kazunari Yoshida, H. Hoshino, R. Tadakuma, Yoshiyuki Suzuri, H. Furukawa","doi":"10.3389/fmech.2019.00044","DOIUrl":"https://doi.org/10.3389/fmech.2019.00044","url":null,"abstract":"Soft-matter robotics, which is named for robots made from soft materials, will possibly conquer the limit of conventional rigid body dynamics of hard robots made from hard materials. For example, a snake-like robot, of which body is made from soft materials, will walk in various environments including narrow space like drain pipes with complicated structure. Here we developed a walking robot with the friction control of double-network hydrogel (DN gel) on its feet, as the first model based on the concept of the soft-matter robotics. It is found that with appropriate control of the friction of DN gel, the inchworm walking robot has realized its high enough velocity for pipe inspection. We discussed the physical principle of the walking motion of the inchworm search robot and its actual mechanism to provide thrust for its walking motion.","PeriodicalId":53220,"journal":{"name":"Frontiers in Mechanical Engineering","volume":"2 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2019-07-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81529100","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-07-16DOI: 10.3389/fmech.2019.00042
K. Chumak, R. Martynyak
This paper presents a study on the combined thermal and mechanical effect of interstitial gas on thermal rectification between a periodically grooved surface and a flat one. To evaluate the interstitial medium influence, the analytico-numerical solution to the corresponding thermoelastic contact problem is constructed taking into account the effect of thermal strains on gap deformation. The results are provided for the Stainless Steel AISI 304 – Aluminum Alloy A380 pair in the presence of air or krypton in the interface gaps. The effects of the gas thermal conductivity and pressure, the imposed pressure and heat flux, and the maximum groove height on the effective thermal contact resistance and the level of thermal rectification are analyzed. It is revealed that taking into account the mechanical effect of the gap filler leads to lower values of thermal rectification level. Also, the change of the gap filler thermal conductivity has more pronounced effect that the change of its pressure.
{"title":"The Combined Thermal and Mechanical Effect of an Interstitial Gas on Thermal Rectification Between Periodically Grooved Surfaces","authors":"K. Chumak, R. Martynyak","doi":"10.3389/fmech.2019.00042","DOIUrl":"https://doi.org/10.3389/fmech.2019.00042","url":null,"abstract":"This paper presents a study on the combined thermal and mechanical effect of interstitial gas on thermal rectification between a periodically grooved surface and a flat one. To evaluate the interstitial medium influence, the analytico-numerical solution to the corresponding thermoelastic contact problem is constructed taking into account the effect of thermal strains on gap deformation. The results are provided for the Stainless Steel AISI 304 – Aluminum Alloy A380 pair in the presence of air or krypton in the interface gaps. The effects of the gas thermal conductivity and pressure, the imposed pressure and heat flux, and the maximum groove height on the effective thermal contact resistance and the level of thermal rectification are analyzed. It is revealed that taking into account the mechanical effect of the gap filler leads to lower values of thermal rectification level. Also, the change of the gap filler thermal conductivity has more pronounced effect that the change of its pressure.","PeriodicalId":53220,"journal":{"name":"Frontiers in Mechanical Engineering","volume":"25 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2019-07-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81729857","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-07-12DOI: 10.3389/fmech.2019.00043
F. Hedayati, Babak Bahrani, Aixi Zhou, S. Quarles, Daniel J. Gorham
Generation of firebrands from various fuels has been well studied in the past decade. Limited details have been released about the methodology for characterizing firebrands such as the proper sample size and the measurement process. This study focuses on (1) finding the minimum required sample size to represents the characteristics of the population, and (2) proposes a framework to facilitate the tedious measurement process. To achieve these goals, several firebrand generation tests were conducted at a boundary layer wind tunnel with realistic gusty wind traces. Firebrands were generated from burning structural fuels and collected in 46 strategically located water pans. The statistical analysis showed that the minimum required sample size based on the chosen statistical parameters (standard deviation, confidence interval, and margin of error) is 1400 for each test. To facilitate characterizing such a large sample of firebrands, an automated image processing algorithm to measure the projected area of the firebrands was developed, which can automatically detect the edges of the background sheet, rotate the photo if its tilted before cropping, detect edges of firebrands, remove erroneous particles (e.g. ash) and finally measures the projected area. To facilitate the weighing process, a Gaussian process regression was performed to predict the mass based on projected area, traveling distance and wind speed. The model can predict the firebrand mass within 5% error compared to the measurement. This framework and model can provide a probabilistic range of firebrand characteristics over the continuous range of the collection region.
{"title":"A Framework to Facilitate Firebrand Characterization","authors":"F. Hedayati, Babak Bahrani, Aixi Zhou, S. Quarles, Daniel J. Gorham","doi":"10.3389/fmech.2019.00043","DOIUrl":"https://doi.org/10.3389/fmech.2019.00043","url":null,"abstract":"Generation of firebrands from various fuels has been well studied in the past decade. Limited details have been released about the methodology for characterizing firebrands such as the proper sample size and the measurement process. This study focuses on (1) finding the minimum required sample size to represents the characteristics of the population, and (2) proposes a framework to facilitate the tedious measurement process. To achieve these goals, several firebrand generation tests were conducted at a boundary layer wind tunnel with realistic gusty wind traces. Firebrands were generated from burning structural fuels and collected in 46 strategically located water pans. The statistical analysis showed that the minimum required sample size based on the chosen statistical parameters (standard deviation, confidence interval, and margin of error) is 1400 for each test. To facilitate characterizing such a large sample of firebrands, an automated image processing algorithm to measure the projected area of the firebrands was developed, which can automatically detect the edges of the background sheet, rotate the photo if its tilted before cropping, detect edges of firebrands, remove erroneous particles (e.g. ash) and finally measures the projected area. To facilitate the weighing process, a Gaussian process regression was performed to predict the mass based on projected area, traveling distance and wind speed. The model can predict the firebrand mass within 5% error compared to the measurement. This framework and model can provide a probabilistic range of firebrand characteristics over the continuous range of the collection region.","PeriodicalId":53220,"journal":{"name":"Frontiers in Mechanical Engineering","volume":"23 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2019-07-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82812343","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-07-09DOI: 10.3389/fmech.2019.00040
J. Glusman, Kyle E. Niemeyer, Amanda S. Makowiecki, N. Wimer, C. Lapointe, G. Rieker, P. Hamlington, J. Daily
New skeletal chemical kinetic models have been obtained by reducing a detailed model for the gas-phase combustion of Douglas Fir pyrolysis products. The skeletal models are intended to reduce the cost of high-resolution wildland fire simulations, without substantially affecting accuracy. The reduction begins from a 137 species, 4533 reaction detailed model for combustion of gas-phase biomass pyrolysis products, and is performed using the directed relation graph with error propagation and sensitivity analysis method, followed by further reaction elimination. The reduction process tracks errors in the ignition delay time and peak temperature for combustion of gas-phase products resulting from the pyrolysis of Douglas Fir. Three skeletal models are produced as a result of this process, corresponding to a larger 71 species, 1179 reaction model with less than 1% error in ignition delay time compared to the detailed model, an intermediate 54 species, 637 reaction model with 24% error, and a smaller 54 species, 204 reaction model with 80% error. Using the skeletal models, peak temperature, volumetric heat release rate, premixed laminar flame speed, and diffusion flame extinction temperatures are compared with the detailed model, revealing an average maximum error in these metrics across all conditions considered of less than 1% for the larger skeletal model, 10% for the intermediate model, and 24% for the smaller model. All three skeletal models are thus sufficiently accurate and computationally efficient for implementation in high-resolution wildland fire simulations, where other model errors and parametric uncertainties are likely to be greater than the errors introduced by the reduced kinetic models presented here.
{"title":"Reduced Gas-Phase Kinetic Models for Burning of Douglas Fir","authors":"J. Glusman, Kyle E. Niemeyer, Amanda S. Makowiecki, N. Wimer, C. Lapointe, G. Rieker, P. Hamlington, J. Daily","doi":"10.3389/fmech.2019.00040","DOIUrl":"https://doi.org/10.3389/fmech.2019.00040","url":null,"abstract":"New skeletal chemical kinetic models have been obtained by reducing a detailed model for the gas-phase combustion of Douglas Fir pyrolysis products. The skeletal models are intended to reduce the cost of high-resolution wildland fire simulations, without substantially affecting accuracy. The reduction begins from a 137 species, 4533 reaction detailed model for combustion of gas-phase biomass pyrolysis products, and is performed using the directed relation graph with error propagation and sensitivity analysis method, followed by further reaction elimination. The reduction process tracks errors in the ignition delay time and peak temperature for combustion of gas-phase products resulting from the pyrolysis of Douglas Fir. Three skeletal models are produced as a result of this process, corresponding to a larger 71 species, 1179 reaction model with less than 1% error in ignition delay time compared to the detailed model, an intermediate 54 species, 637 reaction model with 24% error, and a smaller 54 species, 204 reaction model with 80% error. Using the skeletal models, peak temperature, volumetric heat release rate, premixed laminar flame speed, and diffusion flame extinction temperatures are compared with the detailed model, revealing an average maximum error in these metrics across all conditions considered of less than 1% for the larger skeletal model, 10% for the intermediate model, and 24% for the smaller model. All three skeletal models are thus sufficiently accurate and computationally efficient for implementation in high-resolution wildland fire simulations, where other model errors and parametric uncertainties are likely to be greater than the errors introduced by the reduced kinetic models presented here.","PeriodicalId":53220,"journal":{"name":"Frontiers in Mechanical Engineering","volume":"73 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2019-07-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90594632","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-07-05DOI: 10.3389/fmech.2019.00041
A. Rodrigues, Carlos Ribeiro, J. Raposo, D. Viegas, J. André
In this paper the problem related with a fire front propagating laterally on a slope with a nearby canyon is presented. The presence of the canyon can modify the intensity of the fire and create a difficult situation for elements involved in fire suppression. When a fire propagating laterally in a slope enters in the canyon, a rapid increase in the fire’s rate of spread occurs and a strong convective activity is generated due to the burning inside the canyon. The convective flow generated will then induce a change in the propagation of the fire in the slope. In certain conditions the rate of spread and the intensity of the fire will be strongly increased. This type of extreme fire behaviour is referred to as eruptive fire behaviour (or blow-up) and usually happens over slopes or in canyon configurations. In this study, we analysed the results of laboratory-scale experiments that model a fire spreading latterly over a slope and then enter a canyon that is embedded in the slope. Three configuration parameters were used in the experiments. The first is the inclination of the slope, the second is the orientation of the axis of the canyon and the third is the angle of the ignition line. The fire spread is very complex and dynamic resulting in situations in which very high values of the ROS can be reached for several configurations, creating dangerous situations for firefighters.
{"title":"Effect of Canyons on a Fire Propagating Laterally Over Slopes","authors":"A. Rodrigues, Carlos Ribeiro, J. Raposo, D. Viegas, J. André","doi":"10.3389/fmech.2019.00041","DOIUrl":"https://doi.org/10.3389/fmech.2019.00041","url":null,"abstract":"In this paper the problem related with a fire front propagating laterally on a slope with a nearby canyon is presented. The presence of the canyon can modify the intensity of the fire and create a difficult situation for elements involved in fire suppression. When a fire propagating laterally in a slope enters in the canyon, a rapid increase in the fire’s rate of spread occurs and a strong convective activity is generated due to the burning inside the canyon. The convective flow generated will then induce a change in the propagation of the fire in the slope. In certain conditions the rate of spread and the intensity of the fire will be strongly increased. This type of extreme fire behaviour is referred to as eruptive fire behaviour (or blow-up) and usually happens over slopes or in canyon configurations. In this study, we analysed the results of laboratory-scale experiments that model a fire spreading latterly over a slope and then enter a canyon that is embedded in the slope. Three configuration parameters were used in the experiments. The first is the inclination of the slope, the second is the orientation of the axis of the canyon and the third is the angle of the ignition line. The fire spread is very complex and dynamic resulting in situations in which very high values of the ROS can be reached for several configurations, creating dangerous situations for firefighters.","PeriodicalId":53220,"journal":{"name":"Frontiers in Mechanical Engineering","volume":"5 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2019-07-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74374607","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-07-03DOI: 10.3389/fmech.2019.00037
Conor G. Harris, Nicholas J. S. Jursik, Willie E. Rochefort, T. Walker
The adhesion in 3D-printed composites between dissimilar layers was investigated in response to demand for multimaterial prints. Previously, we reported on the thermal properties for printability of thermoplastic polyurethane (TPU) blends~cite{harris001}. Here, we report the qualitative and quantitative adhesion properties between commonly-printed materials, acrylonitrile butadiene styrene (ABS) or acrylonitrile styrene acrylate (ASA), and flexible TPU. ASTM D1002/D3164 lap shear adhesion tests were performed to measure the adhesion strength between the acrylonitrile plastics and TPU, finding values of $4.7~mathrm{MPa}$ between ABS and TPU and $6.4~mathrm{MPa}$ between ASA and TPU. These values are on the same order of magnitude of reported commercial adhesives, suggesting that multimaterial 3D printing can provide an automated, industrially-relevant alternative to handmade fabrication. SEM images are reported to show the quality of adhesion between materials in the composites. These images expose qualitative differences in the interlayer adhesion between materials in the composites that depend on the textit{order of printing}. Thermal (DSC and TGA) and rheological characterizations were performed to investigate the processing conditions of the extruded plastics while they are in their melt states. The role of viscosity is shown to have major implications on the adhesion, as materials with lower viscosities displayed improved filling of the interlayer voids and increased strength of adhesion.
{"title":"Additive Manufacturing With Soft TPU – Adhesion Strength in Multimaterial Flexible Joints","authors":"Conor G. Harris, Nicholas J. S. Jursik, Willie E. Rochefort, T. Walker","doi":"10.3389/fmech.2019.00037","DOIUrl":"https://doi.org/10.3389/fmech.2019.00037","url":null,"abstract":"The adhesion in 3D-printed composites between dissimilar layers was investigated in response to demand for multimaterial prints. Previously, we reported on the thermal properties for printability of thermoplastic polyurethane (TPU) blends~cite{harris001}. Here, we report the qualitative and quantitative adhesion properties between commonly-printed materials, acrylonitrile butadiene styrene (ABS) or acrylonitrile styrene acrylate (ASA), and flexible TPU. ASTM D1002/D3164 lap shear adhesion tests were performed to measure the adhesion strength between the acrylonitrile plastics and TPU, finding values of $4.7~mathrm{MPa}$ between ABS and TPU and $6.4~mathrm{MPa}$ between ASA and TPU. These values are on the same order of magnitude of reported commercial adhesives, suggesting that multimaterial 3D printing can provide an automated, industrially-relevant alternative to handmade fabrication. SEM images are reported to show the quality of adhesion between materials in the composites. These images expose qualitative differences in the interlayer adhesion between materials in the composites that depend on the textit{order of printing}. Thermal (DSC and TGA) and rheological characterizations were performed to investigate the processing conditions of the extruded plastics while they are in their melt states. The role of viscosity is shown to have major implications on the adhesion, as materials with lower viscosities displayed improved filling of the interlayer voids and increased strength of adhesion.","PeriodicalId":53220,"journal":{"name":"Frontiers in Mechanical Engineering","volume":"5 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2019-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89102739","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-06-28DOI: 10.3389/fmech.2019.00035
Nazmul Khan, D. Sutherland, R. Wadhwani, K. Moinuddin
Australian building standard AS 3959 provides mandatory requirements for the construction of buildings in bushfire prone areas in order to improve the resilience of the building to radiant heat, flame contact, burning embers, and a combination of these three bushfire attack forms. The construction requirements are standardised based on the bushfire attack level (BAL). BAL is based on empirical models which account for radiation heat load on structure. The prediction of the heat load on structure is a challenging task due to many influencing factors: weather conditions, moisture content, vegetation types and fuel loads. Moreover, the fire characteristics change dramatically with wind velocity leading to buoyancy or wind dominated fires that have different dominant heat transfer processes driving the propagation of the fire. The AS 3959 standard is developed with respect to a quasi-steady state model for bushfire propagation assuming a long straight line fire. The fundamental assumptions of the standard are not always valid in a bushfire propagation. In this study, physics based large-eddy simulations were conducted to estimate the heat load on a model structure. The simulation results are compared to the AS 3959 model; there is agreement between the model and the simulation, however, due to computational restrictions the simulations were conducted in a much narrower domain. Further simulations were conducted where wind velocity, fuel load, and relative humidity are varied independently and the simulated radiant heat flux upon the structure was found to be significantly greater than predicted by the AS 3959 model. The effect of the mode of fire propagation, either buoyancy-driven or wind dominated fires, is also investigated. For buoyancy dominated fires the radiation heat load on the structure is enhanced compared to the wind dominated fires. Finally, the potential of using physics based simulation to evaluate individual designs is discussed.
{"title":"Physics-Based Simulation of Heat Load on Structures for Improving Construction Standards for Bushfire Prone Areas","authors":"Nazmul Khan, D. Sutherland, R. Wadhwani, K. Moinuddin","doi":"10.3389/fmech.2019.00035","DOIUrl":"https://doi.org/10.3389/fmech.2019.00035","url":null,"abstract":"Australian building standard AS 3959 provides mandatory requirements for the construction of buildings in bushfire prone areas in order to improve the resilience of the building to radiant heat, flame contact, burning embers, and a combination of these three bushfire attack forms. The construction requirements are standardised based on the bushfire attack level (BAL). BAL is based on empirical models which account for radiation heat load on structure. The prediction of the heat load on structure is a challenging task due to many influencing factors: weather conditions, moisture content, vegetation types and fuel loads. Moreover, the fire characteristics change dramatically with wind velocity leading to buoyancy or wind dominated fires that have different dominant heat transfer processes driving the propagation of the fire. The AS 3959 standard is developed with respect to a quasi-steady state model for bushfire propagation assuming a long straight line fire. The fundamental assumptions of the standard are not always valid in a bushfire propagation. In this study, physics based large-eddy simulations were conducted to estimate the heat load on a model structure. The simulation results are compared to the AS 3959 model; there is agreement between the model and the simulation, however, due to computational restrictions the simulations were conducted in a much narrower domain. Further simulations were conducted where wind velocity, fuel load, and relative humidity are varied independently and the simulated radiant heat flux upon the structure was found to be significantly greater than predicted by the AS 3959 model. The effect of the mode of fire propagation, either buoyancy-driven or wind dominated fires, is also investigated. For buoyancy dominated fires the radiation heat load on the structure is enhanced compared to the wind dominated fires. Finally, the potential of using physics based simulation to evaluate individual designs is discussed.","PeriodicalId":53220,"journal":{"name":"Frontiers in Mechanical Engineering","volume":"8 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2019-06-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81842712","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-06-25DOI: 10.3389/fmech.2019.00038
Elaheh Alizadeh-Birjandi, A. Alshehri, H. Kavehpour
Optimization of the efficiency of the condensers via different surface engineering techniques is a subject of interest due to its wide range of application in thermal management for aerospace vehicles, power generation systems, and etc., which will further result in considerable savings in annual investments and operating costs by millions of dollars. However, the current technologies are lacking either the necessary condensation enhancements or cost-effective, large-scale fabrication method. In this work, we present a new surface topography to enhance drop-wise condensation at low manufacturing costs. These surfaces consist of macro-scale hydrophobic patterns on hydrophilic structures. Due to their high wettability contrast, the biphilic surfaces enhance drop-wise condensation with long-term functionality, and more importantly, they can be easily manufactured in large-scale using conventional methods as no nano- or micro-features are needed.
{"title":"Condensation on Surfaces With Biphilic Topography: Experiment and Modeling","authors":"Elaheh Alizadeh-Birjandi, A. Alshehri, H. Kavehpour","doi":"10.3389/fmech.2019.00038","DOIUrl":"https://doi.org/10.3389/fmech.2019.00038","url":null,"abstract":"Optimization of the efficiency of the condensers via different surface engineering techniques is a subject of interest due to its wide range of application in thermal management for aerospace vehicles, power generation systems, and etc., which will further result in considerable savings in annual investments and operating costs by millions of dollars. However, the current technologies are lacking either the necessary condensation enhancements or cost-effective, large-scale fabrication method. In this work, we present a new surface topography to enhance drop-wise condensation at low manufacturing costs. These surfaces consist of macro-scale hydrophobic patterns on hydrophilic structures. Due to their high wettability contrast, the biphilic surfaces enhance drop-wise condensation with long-term functionality, and more importantly, they can be easily manufactured in large-scale using conventional methods as no nano- or micro-features are needed.","PeriodicalId":53220,"journal":{"name":"Frontiers in Mechanical Engineering","volume":"75 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2019-06-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86391359","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}