The design and optimization of re-entry spacecraft or its subsystems is a multidisciplinary or multiobjective optimization problem by nature. Multidisciplinary design optimization (MDO) focuses on using numerical optimization in designing systems with several subsystems or disciplines that have interactions and independent actions. In the present paper, the system-level optimizer, trajectory, geometry and shape, aerodynamics, and aerothermodynamics differential equations, are converted to algebraic equations using the Radau pseudospectral method (RPM) since a spacecraft is a nonlinear, extensive, and sparse system. The solution to the problem with the help of MDO is reached by iterating all the disciplines together; one can simultaneously enhance the design, decrease the time and cost of the entire design cycle, and minimize the structural mass of a re-entry spacecraft. Considering various methods presented in earlier research works, a combined and innovative all-at-once (AAO), RPM-based MDO method, including the key subsystems in the design process of a re-entry capsule-shape spacecraft with a low lift-to-drag ratio (L/D), is presented. Considering the applicable state and control variables, various constraints, and parameters applied to several geometric shapes of a blunt capsule and using Apollo’s aerodynamic and aerothermodynamic coefficients, the optimized dimensions for a re-entry spacecraft are presented. The introduced optimization scheme led to a 17% mass reduction compared to the original mass of the Apollo vehicle. Fast computing and simplified models are used together in this method to analyze a wide range of vehicle shapes and entry types during conceptual design.
{"title":"Multidisciplinary Design Optimization of a Re-Entry Spacecraft via Radau Pseudospectral Method","authors":"Masoud Kabganian, S. M. Hashemi, J. Roshanian","doi":"10.3390/applmech3040067","DOIUrl":"https://doi.org/10.3390/applmech3040067","url":null,"abstract":"The design and optimization of re-entry spacecraft or its subsystems is a multidisciplinary or multiobjective optimization problem by nature. Multidisciplinary design optimization (MDO) focuses on using numerical optimization in designing systems with several subsystems or disciplines that have interactions and independent actions. In the present paper, the system-level optimizer, trajectory, geometry and shape, aerodynamics, and aerothermodynamics differential equations, are converted to algebraic equations using the Radau pseudospectral method (RPM) since a spacecraft is a nonlinear, extensive, and sparse system. The solution to the problem with the help of MDO is reached by iterating all the disciplines together; one can simultaneously enhance the design, decrease the time and cost of the entire design cycle, and minimize the structural mass of a re-entry spacecraft. Considering various methods presented in earlier research works, a combined and innovative all-at-once (AAO), RPM-based MDO method, including the key subsystems in the design process of a re-entry capsule-shape spacecraft with a low lift-to-drag ratio (L/D), is presented. Considering the applicable state and control variables, various constraints, and parameters applied to several geometric shapes of a blunt capsule and using Apollo’s aerodynamic and aerothermodynamic coefficients, the optimized dimensions for a re-entry spacecraft are presented. The introduced optimization scheme led to a 17% mass reduction compared to the original mass of the Apollo vehicle. Fast computing and simplified models are used together in this method to analyze a wide range of vehicle shapes and entry types during conceptual design.","PeriodicalId":8048,"journal":{"name":"Applied Mechanics Reviews","volume":null,"pages":null},"PeriodicalIF":14.3,"publicationDate":"2022-09-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77154725","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Multiwall polycarbonate sheets are applied as construction elements. Modelling and analysis of thermal processes that occur in this material demand the knowledge of solar transmittance. Values of this parameter determined in laboratory conditions are given in the technical specification of the product. However, the parameter is in practice a complex function depending on the number of factors. This paper presents theoretical and experimental research results for total solar transmittance (TST) for a polycarbonate sheet with twin wall rectangular structure. Theoretical TST is calculated as a product of transmissivity after accounting for light absorption in polycarbonate and of transmissivity after accounting for multiple reflections of solar rays from walls of a channel. The first kind of transmissivity is insignificant and can be neglected. The second one depends on the number of reflection layers, season, and time of day. Experimental TST is determined as the ratio of irradiance under and above the polycarbonate sheet measured by pyranometers. Experimental TST is also a function of time of day and season. Both kinds of TST have an approximately constant value in the time about noon. The theoretical values of TST (0.74) are approximately equal to experimental values of TST (0.75) for the selected summer day. The value of TST in catalogue is equal to 0.82.
{"title":"Theoretical and Experimental Comparisons of Total Solar Transmittance for Polycarbonate Sheet with Twin Wall Rectangular Structure","authors":"Z. Zapałowicz, Agnieszka Garnysz-Rachtan","doi":"10.3390/applmech3040066","DOIUrl":"https://doi.org/10.3390/applmech3040066","url":null,"abstract":"Multiwall polycarbonate sheets are applied as construction elements. Modelling and analysis of thermal processes that occur in this material demand the knowledge of solar transmittance. Values of this parameter determined in laboratory conditions are given in the technical specification of the product. However, the parameter is in practice a complex function depending on the number of factors. This paper presents theoretical and experimental research results for total solar transmittance (TST) for a polycarbonate sheet with twin wall rectangular structure. Theoretical TST is calculated as a product of transmissivity after accounting for light absorption in polycarbonate and of transmissivity after accounting for multiple reflections of solar rays from walls of a channel. The first kind of transmissivity is insignificant and can be neglected. The second one depends on the number of reflection layers, season, and time of day. Experimental TST is determined as the ratio of irradiance under and above the polycarbonate sheet measured by pyranometers. Experimental TST is also a function of time of day and season. Both kinds of TST have an approximately constant value in the time about noon. The theoretical values of TST (0.74) are approximately equal to experimental values of TST (0.75) for the selected summer day. The value of TST in catalogue is equal to 0.82.","PeriodicalId":8048,"journal":{"name":"Applied Mechanics Reviews","volume":null,"pages":null},"PeriodicalIF":14.3,"publicationDate":"2022-09-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78170019","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
E. Ananiadis, Alexander Efstathios Karantzali, D. Exarchos, T. Matikas
New particle reinforced aluminum matrix composites with the addition of refractory High Entropy Alloy, MoTaNbVW, fabricated via powder metallurgy process were assessed for their properties. Basic mechanical properties (modulus of elasticity, hardness) for the aluminum matrix, the pure aluminum and the reinforcement phase were assessed by means of dynamic nano-indentation technique. Nano-indentation based creep response was also evaluated in these three areas of interest. Hardness shows an increase with the addition of the particulates and so does the elastic moduli and the ratio of the energy absorbed in the elastic region. The creep response was approached in terms of dislocation mobility and critical volume for their nucleation. The produced Al–HEA composites were also studied for their sliding wear behavior and showed that with the increase in percentage of RHEA particulates the wear resistance increases. Microstructural considerations, wear track morphologies, and debris characteristics were used for the assessment of the involved wear mechanisms.
{"title":"Al-RHEA Particulates MMCs by PM Route: Mechanical Properties and Sliding Wear Response","authors":"E. Ananiadis, Alexander Efstathios Karantzali, D. Exarchos, T. Matikas","doi":"10.3390/applmech3030065","DOIUrl":"https://doi.org/10.3390/applmech3030065","url":null,"abstract":"New particle reinforced aluminum matrix composites with the addition of refractory High Entropy Alloy, MoTaNbVW, fabricated via powder metallurgy process were assessed for their properties. Basic mechanical properties (modulus of elasticity, hardness) for the aluminum matrix, the pure aluminum and the reinforcement phase were assessed by means of dynamic nano-indentation technique. Nano-indentation based creep response was also evaluated in these three areas of interest. Hardness shows an increase with the addition of the particulates and so does the elastic moduli and the ratio of the energy absorbed in the elastic region. The creep response was approached in terms of dislocation mobility and critical volume for their nucleation. The produced Al–HEA composites were also studied for their sliding wear behavior and showed that with the increase in percentage of RHEA particulates the wear resistance increases. Microstructural considerations, wear track morphologies, and debris characteristics were used for the assessment of the involved wear mechanisms.","PeriodicalId":8048,"journal":{"name":"Applied Mechanics Reviews","volume":null,"pages":null},"PeriodicalIF":14.3,"publicationDate":"2022-09-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87111084","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A. Sudasinghe, Padmassun Rajakareyar, E. Matida, Hamza abo el Ella, M. ElSayed
The growth of the airline industry has highlighted the need for more environmentally conscious aviation, leading to the conceptualization of more fuel-efficient aircraft. One concept that has received significant attention and has been associated with improved fuel efficiency is the boundary layer ingesting (BLI) propulsion system, which refers to the ingesting of the aircraft wake by the propulsors. Although BLI has theoretically been proven to reduce fuel burn, this can potentially be offset by the reduced efficiency and stability experienced by the propulsor in the presence of distorted inflow. Therefore, engine intakes must be optimized in order to mitigate the effects of BLI on the propulsion system. In this work, the shape optimization of a BLI intake is investigated using a free-form deformation technique in combination with a multi-objective genetic algorithm, in order to minimize pressure losses and distortion at the engine inlet. The optimization is performed on an S-duct intake at a cruise altitude of approximately 37,000 feet and a free stream Mach number of 0.7. An optimization strategy was developed for the task which was able to produce a Pareto optimal set of designs with improved pressure recovery and distortion. The general trend of the optimal designs shows that to reduce distortion the optimizer accelerates the flow to reduce the size of the low total pressure region and increase the dynamic pressure at the engine inlet. In contrast, the pressure recovery was increased by reducing velocity as well as shifting the maximum velocity region to the outlet, which reduces the viscous dissipation losses within the intake. The final result is a fully autonomous optimization strategy resulting in reduced pressure losses and reduced distortion leading to higher efficiency BLI S-duct intake designs.
{"title":"Aerodynamic Shape Optimization of an Aircraft Propulsor Air Intake with Boundary Layer Ingestion","authors":"A. Sudasinghe, Padmassun Rajakareyar, E. Matida, Hamza abo el Ella, M. ElSayed","doi":"10.3390/applmech3030064","DOIUrl":"https://doi.org/10.3390/applmech3030064","url":null,"abstract":"The growth of the airline industry has highlighted the need for more environmentally conscious aviation, leading to the conceptualization of more fuel-efficient aircraft. One concept that has received significant attention and has been associated with improved fuel efficiency is the boundary layer ingesting (BLI) propulsion system, which refers to the ingesting of the aircraft wake by the propulsors. Although BLI has theoretically been proven to reduce fuel burn, this can potentially be offset by the reduced efficiency and stability experienced by the propulsor in the presence of distorted inflow. Therefore, engine intakes must be optimized in order to mitigate the effects of BLI on the propulsion system. In this work, the shape optimization of a BLI intake is investigated using a free-form deformation technique in combination with a multi-objective genetic algorithm, in order to minimize pressure losses and distortion at the engine inlet. The optimization is performed on an S-duct intake at a cruise altitude of approximately 37,000 feet and a free stream Mach number of 0.7. An optimization strategy was developed for the task which was able to produce a Pareto optimal set of designs with improved pressure recovery and distortion. The general trend of the optimal designs shows that to reduce distortion the optimizer accelerates the flow to reduce the size of the low total pressure region and increase the dynamic pressure at the engine inlet. In contrast, the pressure recovery was increased by reducing velocity as well as shifting the maximum velocity region to the outlet, which reduces the viscous dissipation losses within the intake. The final result is a fully autonomous optimization strategy resulting in reduced pressure losses and reduced distortion leading to higher efficiency BLI S-duct intake designs.","PeriodicalId":8048,"journal":{"name":"Applied Mechanics Reviews","volume":null,"pages":null},"PeriodicalIF":14.3,"publicationDate":"2022-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78117409","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper presents a new dynamic tensile test based on the Taylor impact technique for application on metallic materials. The Taylor impact test is a well-known technique to characterize the behavior of metallic materials in compression because it allows us to reach very high strain rates (105s−1). In this dynamic tensile test, we launch a projectile with an initial velocity into a specially designed target in order to generate tensile deformation in its central area. In this paper, the geometry of a tensile target previously published in our laboratory was modified and optimized to achieve higher plastic strains and strain rates without reaching the critical state of target failure. Numerical simulations and experimental tests validate the new geometry. Experimental tests have been performed with this new geometry to show the gains allowed. Numerical simulations by finite elements on Abaqus show the equivalent plastic deformations and elongation of the two versions of the targets and the correlation of these results with the tests.
{"title":"An Optimized Dynamic Tensile Impact Test for Characterizing the Behavior of Materials","authors":"O. Pantalé, L. Ming","doi":"10.3390/applmech3030063","DOIUrl":"https://doi.org/10.3390/applmech3030063","url":null,"abstract":"This paper presents a new dynamic tensile test based on the Taylor impact technique for application on metallic materials. The Taylor impact test is a well-known technique to characterize the behavior of metallic materials in compression because it allows us to reach very high strain rates (105s−1). In this dynamic tensile test, we launch a projectile with an initial velocity into a specially designed target in order to generate tensile deformation in its central area. In this paper, the geometry of a tensile target previously published in our laboratory was modified and optimized to achieve higher plastic strains and strain rates without reaching the critical state of target failure. Numerical simulations and experimental tests validate the new geometry. Experimental tests have been performed with this new geometry to show the gains allowed. Numerical simulations by finite elements on Abaqus show the equivalent plastic deformations and elongation of the two versions of the targets and the correlation of these results with the tests.","PeriodicalId":8048,"journal":{"name":"Applied Mechanics Reviews","volume":null,"pages":null},"PeriodicalIF":14.3,"publicationDate":"2022-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80328766","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Recent advances in drug delivery technology have led to renewed interest in shell structures with mixed kinematical constraints, one end clamped, another one free, the so-called sensitive shells. It is known that elliptic sensitive shell problems may not always satisfy the Shapiro–Lopatinsky conditions and hence are not necessarily well-posed. The new observation is that for shells of revolution if the profile function has regions of elliptic Gaussian curvature, that region will dictate the overall response of the structure under concentrated loading. Despite the monotonically increasing total energy as the thickness tends asymptotically to zero, these shells are not in a pure bending state. The numerical results have been verified using equivalent lower-dimensional solutions.
{"title":"On Computational Asymptotic Analysis of General Sensitive Shells of Revolution","authors":"H. Hakula","doi":"10.3390/applmech3030062","DOIUrl":"https://doi.org/10.3390/applmech3030062","url":null,"abstract":"Recent advances in drug delivery technology have led to renewed interest in shell structures with mixed kinematical constraints, one end clamped, another one free, the so-called sensitive shells. It is known that elliptic sensitive shell problems may not always satisfy the Shapiro–Lopatinsky conditions and hence are not necessarily well-posed. The new observation is that for shells of revolution if the profile function has regions of elliptic Gaussian curvature, that region will dictate the overall response of the structure under concentrated loading. Despite the monotonically increasing total energy as the thickness tends asymptotically to zero, these shells are not in a pure bending state. The numerical results have been verified using equivalent lower-dimensional solutions.","PeriodicalId":8048,"journal":{"name":"Applied Mechanics Reviews","volume":null,"pages":null},"PeriodicalIF":14.3,"publicationDate":"2022-08-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76608392","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Defects in crystalline solids play a crucial role in determining properties of materials at the nano, meso- and macroscales, such as the coalescence of vacancies at the nanoscale to form voids and prismatic dislocation loops or diffusion and segregation of solutes to nucleate precipitates, phase transitions in magnetic materials via disorder and doping. First principles Density Functional Theory (DFT) simulations can provide a detailed understanding of these phenomena. However, the number of atoms needed to correctly simulate these systems is often beyond the reach of many widely used DFT codes. The aim of this article is to discuss recent advances in first principles modeling of crystal defects using the spectral quadrature method. The spectral quadrature method is linear scaling with respect to the number of atoms, permits spatial coarse-graining, and is capable of simulating non-periodic systems embedded in a bulk environment, which allows the application of appropriate boundary conditions for simulations of crystalline defects. In this article, we discuss the state-of-the-art in ab-initio modeling of large metallic systems of the order of several thousand atoms that are suitable for utilizing exascale computing resourses.
{"title":"Towards Ab-Initio Simulations of Crystalline Defects at the Exascale Using Spectral Quadrature Density Functional Theory","authors":"Swarnava Ghosh","doi":"10.3390/applmech3030061","DOIUrl":"https://doi.org/10.3390/applmech3030061","url":null,"abstract":"Defects in crystalline solids play a crucial role in determining properties of materials at the nano, meso- and macroscales, such as the coalescence of vacancies at the nanoscale to form voids and prismatic dislocation loops or diffusion and segregation of solutes to nucleate precipitates, phase transitions in magnetic materials via disorder and doping. First principles Density Functional Theory (DFT) simulations can provide a detailed understanding of these phenomena. However, the number of atoms needed to correctly simulate these systems is often beyond the reach of many widely used DFT codes. The aim of this article is to discuss recent advances in first principles modeling of crystal defects using the spectral quadrature method. The spectral quadrature method is linear scaling with respect to the number of atoms, permits spatial coarse-graining, and is capable of simulating non-periodic systems embedded in a bulk environment, which allows the application of appropriate boundary conditions for simulations of crystalline defects. In this article, we discuss the state-of-the-art in ab-initio modeling of large metallic systems of the order of several thousand atoms that are suitable for utilizing exascale computing resourses.","PeriodicalId":8048,"journal":{"name":"Applied Mechanics Reviews","volume":null,"pages":null},"PeriodicalIF":14.3,"publicationDate":"2022-08-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72753842","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper presents an analytical method for determining the bending stresses and deformations in prismatic, noncircular profile shafts with trochoidal cross sections. The so-called higher trochoids can be used as form-fit shaft-hub connections. Hybrid (mixed) higher trochoids (M-profiles) were developed for the special application as a profile contour for the form-fit shaft and hub connections in an earlier work by the author. M-profiles combine the advantages of the two standardised polygonal and spline contours, which are used as shaft-hub connections for the transmission of high torques. In this study, the geometric and mechanical properties of the higher hybrid trochoids were investigated using complex functions to simplify the calculations. The pure bending stress and shaft deflection were determined for M-profiles using bending theory based on the theory of mathematical elasticity. The loading cases consisted of static and rotating bends. Analytical, numerical, and experimental results agreed well. The calculation formulas developed in this work enable reliable and low-cost dimensioning with regard to the stresses and elastic deformations of profile shafts subjected to bending loads.
{"title":"Bending Stresses and Deformations in Prismatic Profiled Shafts with Noncircular Contours Based on Higher Hybrid Trochoids","authors":"M. Ziaei","doi":"10.3390/applmech3030060","DOIUrl":"https://doi.org/10.3390/applmech3030060","url":null,"abstract":"This paper presents an analytical method for determining the bending stresses and deformations in prismatic, noncircular profile shafts with trochoidal cross sections. The so-called higher trochoids can be used as form-fit shaft-hub connections. Hybrid (mixed) higher trochoids (M-profiles) were developed for the special application as a profile contour for the form-fit shaft and hub connections in an earlier work by the author. M-profiles combine the advantages of the two standardised polygonal and spline contours, which are used as shaft-hub connections for the transmission of high torques. In this study, the geometric and mechanical properties of the higher hybrid trochoids were investigated using complex functions to simplify the calculations. The pure bending stress and shaft deflection were determined for M-profiles using bending theory based on the theory of mathematical elasticity. The loading cases consisted of static and rotating bends. Analytical, numerical, and experimental results agreed well. The calculation formulas developed in this work enable reliable and low-cost dimensioning with regard to the stresses and elastic deformations of profile shafts subjected to bending loads.","PeriodicalId":8048,"journal":{"name":"Applied Mechanics Reviews","volume":null,"pages":null},"PeriodicalIF":14.3,"publicationDate":"2022-08-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76348016","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Background: During a carving turn, vibrations are induced at the heel of the snowboard through edge friction when the heel slips sideways and subsequently travel through and along the board to the shovel, which vibrates and affects the edge control. The purpose of this study was to find a method for assessing the edge grip with a laser vibrometer. Method: Two boards, loaded and tilted at four different angles, were placed on a soft surface, with a shaker connected to the heel at the hindmost edge point. The shovel and particularly the frontmost edge point were scanned with a Polytec laser vibrometer. The frequency response functions of coherence, average shovel displacement, and displacement of the foremost edge point were recorded, and the latter was integrated for obtaining an edge mobility measure (EMM) to quantify the edge control. Results: Of the two boards compared, the shovel of board A was stiffer in the 1st and in the 3rd torsional mode, and the one of board B was stiffer in bending modes. The 2nd torsional mode was responsible for large edge vibrations and therefore for a diminished edge control. Shovel B had a smaller EMM at greater tilt angles, that is, less amplitude of the vibrations at the frontmost edge point, and therefore a better edge control. Shovel A, however, had a smaller EMM at smaller tilt angles. Conclusion: The method developed in this study provides a reliable test for assessment of edge control of a snowboard under standardized test conditions.
{"title":"Vibrations Affecting Stability and Edge Control of Snowboards","authors":"F. Fuss","doi":"10.3390/applmech3030059","DOIUrl":"https://doi.org/10.3390/applmech3030059","url":null,"abstract":"Background: During a carving turn, vibrations are induced at the heel of the snowboard through edge friction when the heel slips sideways and subsequently travel through and along the board to the shovel, which vibrates and affects the edge control. The purpose of this study was to find a method for assessing the edge grip with a laser vibrometer. Method: Two boards, loaded and tilted at four different angles, were placed on a soft surface, with a shaker connected to the heel at the hindmost edge point. The shovel and particularly the frontmost edge point were scanned with a Polytec laser vibrometer. The frequency response functions of coherence, average shovel displacement, and displacement of the foremost edge point were recorded, and the latter was integrated for obtaining an edge mobility measure (EMM) to quantify the edge control. Results: Of the two boards compared, the shovel of board A was stiffer in the 1st and in the 3rd torsional mode, and the one of board B was stiffer in bending modes. The 2nd torsional mode was responsible for large edge vibrations and therefore for a diminished edge control. Shovel B had a smaller EMM at greater tilt angles, that is, less amplitude of the vibrations at the frontmost edge point, and therefore a better edge control. Shovel A, however, had a smaller EMM at smaller tilt angles. Conclusion: The method developed in this study provides a reliable test for assessment of edge control of a snowboard under standardized test conditions.","PeriodicalId":8048,"journal":{"name":"Applied Mechanics Reviews","volume":null,"pages":null},"PeriodicalIF":14.3,"publicationDate":"2022-08-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75820450","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A new tilting delta tricycle is developed as a last-mile vehicle. This vehicle has a hinge between the front driver module and the rear cargo module to allow the driver to tilt while maneuvering. The driver module resembles a conventional bicycle without a rear wheel and the cargo module consists of a cargo area between two propelled rear wheels. The concept vehicle ensures proper handling qualities independent of the cargo. However, the driver module can still tip over when parked. Multiple solutions are being considered to improve the ergonomics of this vehicle. A metal-elastomer torsion spring with an integrated angle limit has the most advantages as this prevents the driver module from tipping over without requiring it to enable a mechanism while stepping off. Furthermore, the torsion system dampens vibrations while cycling and influences tilting while turning. These improvements are tested using the concept vehicle. The influence of this torsion system is calculated and validated with measurements. The influences of different torsion curves aimed to improve the low-speed stability are calculated.
{"title":"Effects of a Torsion Spring Used in a Flexible Delta Tricycle","authors":"J. D’hondt, P. Slaets, E. Demeester, M. Juwet","doi":"10.3390/applmech3030058","DOIUrl":"https://doi.org/10.3390/applmech3030058","url":null,"abstract":"A new tilting delta tricycle is developed as a last-mile vehicle. This vehicle has a hinge between the front driver module and the rear cargo module to allow the driver to tilt while maneuvering. The driver module resembles a conventional bicycle without a rear wheel and the cargo module consists of a cargo area between two propelled rear wheels. The concept vehicle ensures proper handling qualities independent of the cargo. However, the driver module can still tip over when parked. Multiple solutions are being considered to improve the ergonomics of this vehicle. A metal-elastomer torsion spring with an integrated angle limit has the most advantages as this prevents the driver module from tipping over without requiring it to enable a mechanism while stepping off. Furthermore, the torsion system dampens vibrations while cycling and influences tilting while turning. These improvements are tested using the concept vehicle. The influence of this torsion system is calculated and validated with measurements. The influences of different torsion curves aimed to improve the low-speed stability are calculated.","PeriodicalId":8048,"journal":{"name":"Applied Mechanics Reviews","volume":null,"pages":null},"PeriodicalIF":14.3,"publicationDate":"2022-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90887414","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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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