Suspension systems influence the overall performance of the vehicle by receiving the loads create... more Suspension systems influence the overall performance of the vehicle by receiving the loads created by the road excitation. These loads are transmitted through the tires and the wheels ensuring that vibrations are isolated and not perceived by the passengers. Depending on the aspect of interest regarding the design of a suspension system, the focus of the studies is turned on the ride comfort or the road holding of the vehicle being the basic needs for a good suspension system. Ride comfort is related to the passenger’s perception of the moving vehicle’s environment, while road holding is the degree to which a car maintains contact with the road surface in various types of directional changes. Keeping the tires in contact with the ground constantly is of vital importance for the friction between the vehicle and the road affecting the vehicle’s ability to steer, brake and accelerate. Time domain statistics, such as mean suspension deflection, maximum and RMS values of suspension accel...
Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering, 2019
A seat that provides good vibration isolation is of prime importance for passenger’s safety and h... more A seat that provides good vibration isolation is of prime importance for passenger’s safety and health. The main conflict in seat suspensions implies that the increasing initial deformation of the system (increase in “static discomfort”) leads to better isolation of accelerations (increase in “dynamic comfort”). Many researchers have focused on overcoming or at least suppressing this conflict between load support capacity and vibration isolation by modeling new suspension systems, such as the so-called negative suspension systems. However, apart from the modeling of new suspension systems, optimization is an important part in designing a seat and finding the best compromise between these two objectives. Thus, in this work, four types of seat suspension systems with embedded negative stiffness elements are implemented and optimized in order to be benchmarked. Three of them have already been tested either in passenger or in an off-road vehicle seat. All the vibration isolators are opt...
The actual wind loads which are applied on the various wind turbine parts and components are vary... more The actual wind loads which are applied on the various wind turbine parts and components are varying in amplitude and direction. Due to the stochastic nature of the wind force, this variation is stochastic too. Calculating these stochastic loads is not easy and many techniques have been proposed by researchers. In areas where wind turbines are installed, statistical data regarding the wind behavior are obtained using proper equipment and data recorders. These data usually are further processed using modern statistical tools in order to find the characteristics of the wind forces and their trend. The two parameter Weibull distribution and the Rayleigh distribution seem to fit with the actual data. Using time series analysis, the aim is to identify the distribution parameters and its ‘shape factor’. In this work, we perform an analysis of these stochastic loads on wind turbines and we propose a method for assigning an equivalent dynamic load on the main parts of the wind turbine in or...
Various vibration isolators using negative stiffness elements have been proposed in order to impr... more Various vibration isolators using negative stiffness elements have been proposed in order to improve ride comfort of passengers in vehicles. In this paper, five different ones are compared. Four of them have been already propped, while the fifth one is novel, based on the KDamping concept, which has proven efficient in other applications. After optimising each one with respect to static and dynamic factors of ride comfort, three types of analysis are performed. In the first type, the models are simulated for the optimum solutions, for two more excitations which correspond to the response of the vehicle's body while driving over road profiles of Class B and C. In the second type, the models are simulated for different seated passengers. While in the third type, based on the Pareto theory, three solutions are finally selected for each model, and their transmissibility from seat to head (STHT) is compared. The main conclusion is that the isolator using the KDamping concept has proven its adaptability and universality for different excitations corresponding to different road classes and for different seated passengers, minimising the resonance frequency around 0.56 Hz and providing the most compact and comfortable optimum design solutions among all the other models.
Dynamic tyre forces are thought to be a cause of increased damage to roads caused by heavy vehicl... more Dynamic tyre forces are thought to be a cause of increased damage to roads caused by heavy vehicles. For many years, research into “vehicle-highway interaction” involved measuring or simulating the dynamic tyre forces generated by heavy vehicles, without reference to the response of the road surface. As a consequence, there is a considerable literature concerning dynamic tyre forces generated by trucks. A variety of techniques can use for measuring the dynamic tyre forces generated by heavy vehicles. In our laboratory a combination of accelerometers and strain gauges had been used to determine the wheel forces through measuring the shear and bending strains, and the accelerations of the wheels. Our research focused on the comparison of these methods and especially on the understanding of the dynamic behavior of the forces applied on the two wheels. A variety of road tests were conducted in order to evaluate the methods in depth during cornering, accelerating, and other cases.
Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering, 2021
In this work, a novel distribution-based control strategy of semi-active vehicle suspensions is t... more In this work, a novel distribution-based control strategy of semi-active vehicle suspensions is tested under different conditions. The novelty lies in the use of an appropriate threshold in the operational condition of the control algorithm, with which the operational conditions severity is quantified and the state of the damper is controlled according to the magnitude of the operational conditions and not their sign. The value of the threshold depends on the vibrations induced to the sprung mass by the road profile. In order to be evaluated, the operational conditions of the algorithm are fitted to a t-student distribution. The cumulative distribution function of this distribution is used in order to decrease the fraction of the sample operating with the damper’s stiff state. The strategy is applied to traditional SH control algorithms and is tested using a quarter car model excited by different road excitations. A sensitivity analysis for various threshold values is performed, inv...
Engineering Science and Technology, an International Journal, 2019
This paper investigates the optimization of semi-active suspension systems operating with various... more This paper investigates the optimization of semi-active suspension systems operating with various skyhook (SH) control algorithms. In addition, a novel distribution-based control strategy (CDF) is applied. In contrast to existing works that focus mainly on ride comfort and road holding, in this work we investigate the design of semi-active suspensions with respect to more performance aspects. More specifically, apart from ride comfort and road holding, the trade-off between the dissipated energy and the vibration control performance is considered. Furthermore, the chatter in the response of the vehicle is used as a design criterion. However, in order to consider all these objectives without costing computational time in the optimization procedure, an approach based on KEMOGA algorithm is applied. Firstly, the vehicle model is optimized with respect to ride comfort and road holding using a multi-objective genetic algorithm (MOGA). Each of these two objectives is represented by a single performance index. Then, a sorting algorithm (KE) is applied so as to seek the optimum solution among the alternatives from MOGA considering extra objectives. These extra objectives are introduced in the sorting algorithm (KE) in order to either enhance the two main criteria, being supplementary to them, or because of their importance in the suspension design. Conclusions regarding the optimum design solutions are extracted in addition with the benchmark of them in terms of objectives' values and their design variables.
Tank vehicles are widely used for the road transportation of dangerous goods and especially flamm... more Tank vehicles are widely used for the road transportation of dangerous goods and especially flammable liquid fuels. Existing gross weight limitations, in such transportations, render the self-weight of the tank structure a crucial parameter of the design. For the design and the construction of metallic tank vehicles carrying dangerous goods, the European Standard EN13094:2015 is applied. This Standard poses a minimum thickness for the shell thickness for the tank construction according to the mechanical properties of the construction material. In the present paper, primarily, the proposed design was investigated and a weight minimization of such a tank vehicle with respect to its structural integrity was performed. As test case, a tank vehicle with a box-shaped cross-section and low gross weight was considered. For the evaluation of the structural integrity of the tank construction, the mechanical analysis software ANSYS ® 2019R1 was used. The boundary values and the suitable comput...
In this paper the techniques of evolutionary system identification are implemented in the paramet... more In this paper the techniques of evolutionary system identification are implemented in the parametric, time domain identification of a flexible robotic arm. More specifically, the (μ+λ) Evolution Strategy (ES) is used for the estimation of both ARMA and ARMAX models, by means of Prediction-Error method (PEM), capable to describe system’s dynamics in the absence or existence of an input data set, respectively. The performance of (μ+λ)-ES within the framework of PEM is monitored throughout the estimation process and evaluated by the corresponding fitness to data of its resulted models and also by the ability to produce valid modal characteristics (natural frequencies, damping ratios). Key-Words: System Identification, Evolutionary Algorithms, Modal Analysis.
This paper introduces a hybrid optimization algorithm, followed by a corresponding estimation tec... more This paper introduces a hybrid optimization algorithm, followed by a corresponding estimation technique, for the estimation of ARMAX models. The hybrid algorithm consists of a stochastic component and a deterministic counterpart and aims at combining high convergence rate together with reliability in the search for global optimum. The estimation procedure is slit in two phases, due to the mixed linear-nonlinear relationship between the residuals and the parameter vector, and results in stable and invertible models. The proposed methodology is implemented in the estimation of a half-car suspension model of a road vehicle, using noise-corrupted observations, and the results yield very stable performance of the hybrid algorithm, reduced computational cost, in comparison to conventional stochastic optimization algorithms, and ability to describe satisfactory system’s dynamics.
Volume 3: Dynamic Systems and Controls, Symposium on Design and Analysis of Advanced Structures, and Tribology, 2006
The assessment of vertical dynamics in modern ground vehicles is a difficult task with crucial im... more The assessment of vertical dynamics in modern ground vehicles is a difficult task with crucial importance, as it appears to be possessed by a number of conflicting objectives, such as ride comfort and stability. Thus, the effective use of possible control units is depended by the successful description of the vertical performance. The aim of this study is to provide a closed description of vehicles’ vertical dynamics using VARMA models, which are estimated by means of a novel, hybrid optimization algorithm and a corresponding estimation procedure. The hybrid algorithm interconnects the diverse characteristics of its deterministic and stochastic counterparts, while the estimation procedure assures the stability and invertibility requirements in the resulted models. For the practical implementation of the above, a five dimensional VARMA model is used for the description of a passenger vehicle, through the acquisition of noise–corrupted vertical acceleration measurements.
... Statistics and Spectral Analysis Vasilis K. Dertimanis and Dimitris V. Koulocheris National T... more ... Statistics and Spectral Analysis Vasilis K. Dertimanis and Dimitris V. Koulocheris National Technical University of Athens, Mechanical Design & Automatic Control Department Iroon Politechniou 9, 157 80, Athens, Greece Abstract. ... Ξ[t] = ∞ ∑ k=0 Fk·N[t − k] (13) ...
New Technologies, Development and Application II, 2019
A vehicle collision can be divided in three distinct time phases, the pre-collision, the collisio... more A vehicle collision can be divided in three distinct time phases, the pre-collision, the collision and the post-collision phase. Usually during a traffic accident reconstruction the collision and post-collision phases are investigated in order for the accident reconstructionist to draw conclusions concerning the causes and the events that lead to the vehicle collision. The investigation of both phases is usually a repetitive procedure which terminates when the investigation results match the physical evidence drawn from the accident scene. The objective of the analysis of the collision phase is the determination of the velocities of both vehicles prior and post collision. For the computational simulation of the collision phase two main approaches exist in the literature, the energy-based approach, developed by McHenry, and the momentum based one, developed by Brach, both in the late 1970s. The objective of the analysis of the post collision phase is the reconstruction of the trajectories of both vehicles from the point of collision to the point of rest. For the computational simulation of the vehicle trajectories different approaches exist, such as their approximation using geometric curves and the application of the equations of motion for each vehicle after collision. In the present paper two algorithms for vehicle collision reconstruction have been set up in Matlab. Each one utilizes a different approach for both the collision and the post collision phase. In more details the momentum-based approach has been coupled with geometric approximation of the trajectories while the energy-based approach has been coupled with the equations of motion for the post-collision phase. Both algorithms incorporate a suitable optimization method in order to provide optimized results in terms of collision geometry, collision physics and post-collisional trajectories of the vehicles. In order to evaluate the performance of both algorithms, the vehicle collisions described in details in the RICSAC database have been used. The results of each algorithm are compared with each other as well as with the measured quantities existing in RICSAC database.
Proceedings of the 6th International Conference on Informatics in Control, Automation and Robotics, 2009
The interrelation of stochastic and deterministic optimization algorithms, as well as the exploit... more The interrelation of stochastic and deterministic optimization algorithms, as well as the exploitation of the advantages that each counterpart presents simultaneously, is studied in this paper. To this, a hybrid optimization algorithm is developed, which consists of a conventional Evolution Strategy that maintains its recombination and selection phases unaltered, while its mutation operator is replaced by well-known deterministic methods, such as line-search and/or trust-region. The alteration results in superior performance of the novel algorithm, compared to other instances of Evolutionary Algorithms, as exploited out in tests using Griewangk and Rastrigin functions. The proposed algorithm is further examined through its implementation to the structural optimization problem of a full-car suspension model, with satisfying results.
Suspension systems influence the overall performance of the vehicle by receiving the loads create... more Suspension systems influence the overall performance of the vehicle by receiving the loads created by the road excitation. These loads are transmitted through the tires and the wheels ensuring that vibrations are isolated and not perceived by the passengers. Depending on the aspect of interest regarding the design of a suspension system, the focus of the studies is turned on the ride comfort or the road holding of the vehicle being the basic needs for a good suspension system. Ride comfort is related to the passenger’s perception of the moving vehicle’s environment, while road holding is the degree to which a car maintains contact with the road surface in various types of directional changes. Keeping the tires in contact with the ground constantly is of vital importance for the friction between the vehicle and the road affecting the vehicle’s ability to steer, brake and accelerate. Time domain statistics, such as mean suspension deflection, maximum and RMS values of suspension accel...
Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering, 2019
A seat that provides good vibration isolation is of prime importance for passenger’s safety and h... more A seat that provides good vibration isolation is of prime importance for passenger’s safety and health. The main conflict in seat suspensions implies that the increasing initial deformation of the system (increase in “static discomfort”) leads to better isolation of accelerations (increase in “dynamic comfort”). Many researchers have focused on overcoming or at least suppressing this conflict between load support capacity and vibration isolation by modeling new suspension systems, such as the so-called negative suspension systems. However, apart from the modeling of new suspension systems, optimization is an important part in designing a seat and finding the best compromise between these two objectives. Thus, in this work, four types of seat suspension systems with embedded negative stiffness elements are implemented and optimized in order to be benchmarked. Three of them have already been tested either in passenger or in an off-road vehicle seat. All the vibration isolators are opt...
The actual wind loads which are applied on the various wind turbine parts and components are vary... more The actual wind loads which are applied on the various wind turbine parts and components are varying in amplitude and direction. Due to the stochastic nature of the wind force, this variation is stochastic too. Calculating these stochastic loads is not easy and many techniques have been proposed by researchers. In areas where wind turbines are installed, statistical data regarding the wind behavior are obtained using proper equipment and data recorders. These data usually are further processed using modern statistical tools in order to find the characteristics of the wind forces and their trend. The two parameter Weibull distribution and the Rayleigh distribution seem to fit with the actual data. Using time series analysis, the aim is to identify the distribution parameters and its ‘shape factor’. In this work, we perform an analysis of these stochastic loads on wind turbines and we propose a method for assigning an equivalent dynamic load on the main parts of the wind turbine in or...
Various vibration isolators using negative stiffness elements have been proposed in order to impr... more Various vibration isolators using negative stiffness elements have been proposed in order to improve ride comfort of passengers in vehicles. In this paper, five different ones are compared. Four of them have been already propped, while the fifth one is novel, based on the KDamping concept, which has proven efficient in other applications. After optimising each one with respect to static and dynamic factors of ride comfort, three types of analysis are performed. In the first type, the models are simulated for the optimum solutions, for two more excitations which correspond to the response of the vehicle's body while driving over road profiles of Class B and C. In the second type, the models are simulated for different seated passengers. While in the third type, based on the Pareto theory, three solutions are finally selected for each model, and their transmissibility from seat to head (STHT) is compared. The main conclusion is that the isolator using the KDamping concept has proven its adaptability and universality for different excitations corresponding to different road classes and for different seated passengers, minimising the resonance frequency around 0.56 Hz and providing the most compact and comfortable optimum design solutions among all the other models.
Dynamic tyre forces are thought to be a cause of increased damage to roads caused by heavy vehicl... more Dynamic tyre forces are thought to be a cause of increased damage to roads caused by heavy vehicles. For many years, research into “vehicle-highway interaction” involved measuring or simulating the dynamic tyre forces generated by heavy vehicles, without reference to the response of the road surface. As a consequence, there is a considerable literature concerning dynamic tyre forces generated by trucks. A variety of techniques can use for measuring the dynamic tyre forces generated by heavy vehicles. In our laboratory a combination of accelerometers and strain gauges had been used to determine the wheel forces through measuring the shear and bending strains, and the accelerations of the wheels. Our research focused on the comparison of these methods and especially on the understanding of the dynamic behavior of the forces applied on the two wheels. A variety of road tests were conducted in order to evaluate the methods in depth during cornering, accelerating, and other cases.
Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering, 2021
In this work, a novel distribution-based control strategy of semi-active vehicle suspensions is t... more In this work, a novel distribution-based control strategy of semi-active vehicle suspensions is tested under different conditions. The novelty lies in the use of an appropriate threshold in the operational condition of the control algorithm, with which the operational conditions severity is quantified and the state of the damper is controlled according to the magnitude of the operational conditions and not their sign. The value of the threshold depends on the vibrations induced to the sprung mass by the road profile. In order to be evaluated, the operational conditions of the algorithm are fitted to a t-student distribution. The cumulative distribution function of this distribution is used in order to decrease the fraction of the sample operating with the damper’s stiff state. The strategy is applied to traditional SH control algorithms and is tested using a quarter car model excited by different road excitations. A sensitivity analysis for various threshold values is performed, inv...
Engineering Science and Technology, an International Journal, 2019
This paper investigates the optimization of semi-active suspension systems operating with various... more This paper investigates the optimization of semi-active suspension systems operating with various skyhook (SH) control algorithms. In addition, a novel distribution-based control strategy (CDF) is applied. In contrast to existing works that focus mainly on ride comfort and road holding, in this work we investigate the design of semi-active suspensions with respect to more performance aspects. More specifically, apart from ride comfort and road holding, the trade-off between the dissipated energy and the vibration control performance is considered. Furthermore, the chatter in the response of the vehicle is used as a design criterion. However, in order to consider all these objectives without costing computational time in the optimization procedure, an approach based on KEMOGA algorithm is applied. Firstly, the vehicle model is optimized with respect to ride comfort and road holding using a multi-objective genetic algorithm (MOGA). Each of these two objectives is represented by a single performance index. Then, a sorting algorithm (KE) is applied so as to seek the optimum solution among the alternatives from MOGA considering extra objectives. These extra objectives are introduced in the sorting algorithm (KE) in order to either enhance the two main criteria, being supplementary to them, or because of their importance in the suspension design. Conclusions regarding the optimum design solutions are extracted in addition with the benchmark of them in terms of objectives' values and their design variables.
Tank vehicles are widely used for the road transportation of dangerous goods and especially flamm... more Tank vehicles are widely used for the road transportation of dangerous goods and especially flammable liquid fuels. Existing gross weight limitations, in such transportations, render the self-weight of the tank structure a crucial parameter of the design. For the design and the construction of metallic tank vehicles carrying dangerous goods, the European Standard EN13094:2015 is applied. This Standard poses a minimum thickness for the shell thickness for the tank construction according to the mechanical properties of the construction material. In the present paper, primarily, the proposed design was investigated and a weight minimization of such a tank vehicle with respect to its structural integrity was performed. As test case, a tank vehicle with a box-shaped cross-section and low gross weight was considered. For the evaluation of the structural integrity of the tank construction, the mechanical analysis software ANSYS ® 2019R1 was used. The boundary values and the suitable comput...
In this paper the techniques of evolutionary system identification are implemented in the paramet... more In this paper the techniques of evolutionary system identification are implemented in the parametric, time domain identification of a flexible robotic arm. More specifically, the (μ+λ) Evolution Strategy (ES) is used for the estimation of both ARMA and ARMAX models, by means of Prediction-Error method (PEM), capable to describe system’s dynamics in the absence or existence of an input data set, respectively. The performance of (μ+λ)-ES within the framework of PEM is monitored throughout the estimation process and evaluated by the corresponding fitness to data of its resulted models and also by the ability to produce valid modal characteristics (natural frequencies, damping ratios). Key-Words: System Identification, Evolutionary Algorithms, Modal Analysis.
This paper introduces a hybrid optimization algorithm, followed by a corresponding estimation tec... more This paper introduces a hybrid optimization algorithm, followed by a corresponding estimation technique, for the estimation of ARMAX models. The hybrid algorithm consists of a stochastic component and a deterministic counterpart and aims at combining high convergence rate together with reliability in the search for global optimum. The estimation procedure is slit in two phases, due to the mixed linear-nonlinear relationship between the residuals and the parameter vector, and results in stable and invertible models. The proposed methodology is implemented in the estimation of a half-car suspension model of a road vehicle, using noise-corrupted observations, and the results yield very stable performance of the hybrid algorithm, reduced computational cost, in comparison to conventional stochastic optimization algorithms, and ability to describe satisfactory system’s dynamics.
Volume 3: Dynamic Systems and Controls, Symposium on Design and Analysis of Advanced Structures, and Tribology, 2006
The assessment of vertical dynamics in modern ground vehicles is a difficult task with crucial im... more The assessment of vertical dynamics in modern ground vehicles is a difficult task with crucial importance, as it appears to be possessed by a number of conflicting objectives, such as ride comfort and stability. Thus, the effective use of possible control units is depended by the successful description of the vertical performance. The aim of this study is to provide a closed description of vehicles’ vertical dynamics using VARMA models, which are estimated by means of a novel, hybrid optimization algorithm and a corresponding estimation procedure. The hybrid algorithm interconnects the diverse characteristics of its deterministic and stochastic counterparts, while the estimation procedure assures the stability and invertibility requirements in the resulted models. For the practical implementation of the above, a five dimensional VARMA model is used for the description of a passenger vehicle, through the acquisition of noise–corrupted vertical acceleration measurements.
... Statistics and Spectral Analysis Vasilis K. Dertimanis and Dimitris V. Koulocheris National T... more ... Statistics and Spectral Analysis Vasilis K. Dertimanis and Dimitris V. Koulocheris National Technical University of Athens, Mechanical Design & Automatic Control Department Iroon Politechniou 9, 157 80, Athens, Greece Abstract. ... Ξ[t] = ∞ ∑ k=0 Fk·N[t − k] (13) ...
New Technologies, Development and Application II, 2019
A vehicle collision can be divided in three distinct time phases, the pre-collision, the collisio... more A vehicle collision can be divided in three distinct time phases, the pre-collision, the collision and the post-collision phase. Usually during a traffic accident reconstruction the collision and post-collision phases are investigated in order for the accident reconstructionist to draw conclusions concerning the causes and the events that lead to the vehicle collision. The investigation of both phases is usually a repetitive procedure which terminates when the investigation results match the physical evidence drawn from the accident scene. The objective of the analysis of the collision phase is the determination of the velocities of both vehicles prior and post collision. For the computational simulation of the collision phase two main approaches exist in the literature, the energy-based approach, developed by McHenry, and the momentum based one, developed by Brach, both in the late 1970s. The objective of the analysis of the post collision phase is the reconstruction of the trajectories of both vehicles from the point of collision to the point of rest. For the computational simulation of the vehicle trajectories different approaches exist, such as their approximation using geometric curves and the application of the equations of motion for each vehicle after collision. In the present paper two algorithms for vehicle collision reconstruction have been set up in Matlab. Each one utilizes a different approach for both the collision and the post collision phase. In more details the momentum-based approach has been coupled with geometric approximation of the trajectories while the energy-based approach has been coupled with the equations of motion for the post-collision phase. Both algorithms incorporate a suitable optimization method in order to provide optimized results in terms of collision geometry, collision physics and post-collisional trajectories of the vehicles. In order to evaluate the performance of both algorithms, the vehicle collisions described in details in the RICSAC database have been used. The results of each algorithm are compared with each other as well as with the measured quantities existing in RICSAC database.
Proceedings of the 6th International Conference on Informatics in Control, Automation and Robotics, 2009
The interrelation of stochastic and deterministic optimization algorithms, as well as the exploit... more The interrelation of stochastic and deterministic optimization algorithms, as well as the exploitation of the advantages that each counterpart presents simultaneously, is studied in this paper. To this, a hybrid optimization algorithm is developed, which consists of a conventional Evolution Strategy that maintains its recombination and selection phases unaltered, while its mutation operator is replaced by well-known deterministic methods, such as line-search and/or trust-region. The alteration results in superior performance of the novel algorithm, compared to other instances of Evolutionary Algorithms, as exploited out in tests using Griewangk and Rastrigin functions. The proposed algorithm is further examined through its implementation to the structural optimization problem of a full-car suspension model, with satisfying results.
3D Printing is increasingly considered a candidate method for the actual manufacturing of end-use... more 3D Printing is increasingly considered a candidate method for the actual manufacturing of end-use functional parts and components, to substitute former conventional methods and materials for many industrial sectors, including the automotive sector. It fundamentally differs from conventional production methods in many ways, such as in materials used, feasible external part geometries and non-solid internal structures that can be attributed to the parts produced. Proper selection and parameterization, as well as the basic influence of specific internal structures of 3D printed items on their strength, integrity and functional performance are multi-parametric issues, still not fully understood and investigated. This work attempts to estimate and-to a certain extent-verify basic influences of different internal structures on the structural integrity and expected mechanical performance of a typical automotive component (suspension arm) to be additively manufactured in polymer material via Fused Deposition Modeling (FDM). Design, FEM simulation & analysis and actual testing & verification of several, scaled-down 3D printed components of the examined component are addressed and combined in order to draw primary results, that could ultimately formulate a roadmap for the successful and efficient geometry selection and parameterization of typical 3D printed automotive components in the near future.
11th HSTAM International Congress on Mechanics, Athens Greece, 2016
The assessment of the static and dynamic properties of a tank vehicle is crucial and it is relate... more The assessment of the static and dynamic properties of a tank vehicle is crucial and it is related to the three motions, namely longitudinal (driving and braking), lateral (guidance and steering), and vertical (suspension and damping). Since tank vehicles are mainly used for the transportation of dangerous goods, European Standards specify the minimum requirements for their design and construction. In the present study the structural integrity of a wedge-shaped tank vehicle with a cyclical cross-section and three compartments designed to have maximum payload, has been investigated using the finite element (FE) software ANSYS®v.17.0. Different FE models of the tank vehicle have been set up to investigate the influence of the diameters of the front and the rear shell end, the angle of the wedge shaped compartment and the overall length, in the structural integrity of the tank vehicle. The constraints for the aforementioned geometrical variables, as well as the loading cases, have been defined considering the corresponding Standards and the restrictions posed by the manufacturing procedures of such a tank vehicle. The outcomes of this study provide, among others, the structural integrity of such a tank vehicle with marginal geometrical values, offering a useful insight for tank manufacturers.
The ECE R111 is the international regulation regarding the rollover stability of tank vehicles of... more The ECE R111 is the international regulation regarding the rollover stability of tank vehicles of category N2. The rollover stability of the vehicle shall be such that the point at which overturning occurs would not be passed if a lateral acceleration of 4 m/s 2 has not been reached. The calculation of the maximum lateral acceleration of a vehicle takes into consideration many factors which influence its rollover stability. Some of the most important are the height of the center of gravity, the suspension roll stiffness and the tires vertical rate. Based on experimental data of the laboratory, the correlation of these main factors is investigated in depth and curves illustrating their correlation will be presented.
9th Internatonal Conference on Engineering Computational Technology, Napoli Italy, 2014
The purpose of a control link in the suspension system of a vehicle is to control the movement of... more The purpose of a control link in the suspension system of a vehicle is to control the movement of the wheel without supporting the vehicle's weight. In the present paper, a commercial control link has been designed in Solidworks ® CAD software and its performance has been evaluated through static, modal and dynamic analysis in the Ansys Workbench ® CAE software. Additionally, optimization and design analysis tools, available in Ansys software, have been used in order investigate the robustness of the design and the material characteristics of this particular control link. More specifically the influence of its thickness along with different topologies and diameters of the holes that exist on its main body have been investigated in terms of achieving a more robust design. Finally, different material properties have been tested in the initial design in order to investigate the effect of different stiffness moduli to the static and the modal behaviour of the component.
Uploads
Papers by D. Koulocheris