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A study of the influence of vertical tyre force on rolling resistance coefficient and lateral slip stiffness coefficient using truck tyre model
(2021) Govardhan Raju, Bharath; Nobeling, Nicholas; Rajopadhye, Chirag; Tota, Pranay Damodhar; Chalmers tekniska högskola // Institutionen för mekanik och maritima vetenskaper; Sjöblom, Jonas; Jacobson, Bengt; Bruzelius, Fredrik; Fröjd, Niklas; Romano, Luigi
Tyres are an important component that affect the energy consumption and performance of all vehicles, including trucks. The vital properties of the tyre realising these phenomena are the rolling resistance and lateral slip stiffness, respectively. This project aims to investigate and understand the influence of vertical load on the rolling resistance coefficient and lateral slip stiffness and based on these investigations, evaluate the possibility of creating simple and physically interpretable yet tune-able tyre models. The lateral slip stiffness investigation involves modelling a physical tire model based on the brush model with parabolic pressure distribution and a curve-fit model based on the ’openPBS’ tool non-linear tyre model. These models are tuned to match the data extracted from the VTI experiments of test performed with a truck tyre on the tyre testing facility. The lateral slip stiffness generated using both models is compared with the experimental test data, and found that the curve-fit model presents a better approximation of the test data. However, dense measurement data in terms of more data sets for varying vertical loads as well as more number of measured lateral force vs. slip points for each vertical load data set will be required to confirm this conclusion. The variation of RRC with lifted and non-lifted axles is studied using test data availed from a report by Lennart Cider, discussing the rollout tests of two different trucks with lifted and non-lifted axles. A proposition of load independent wheel bearing torque loss is considered as an alternate explanation for the varying rolling resistance and a study conducted for the same shows that the friction losses in the wheel bearings could approximately account for around only 13.5% of the estimated change in rolling resistance. Hence this cause solely is an unlikely explanation of the difference in rolling resistance. A finite element study of the tyre contact patch and the vertical load offset could aid the understanding of this phenomena better.
Advanced Combustion Analysis: The development of an advanced combustion analysis tool
(2021) Ahmed, Aijaz; Edholm, Oskar; Lutimath, Ajanish; Raj, Avanish; Tagesson, Filip; Chalmers tekniska högskola // Institutionen för mekanik och maritima vetenskaper; Sjöblom, Jonas; Sjöblom, Jonas; Koopmans, Lucien; Ahmed, Ahfaz
The main purpose of this project is to study and investigate advanced combustion analysis in compression-ignited (CI) and spark-ignited (SI) engines. A MATLAB code will be developed as the major deliverable, which will calculate the (apparent and real) rate of heat release with the provision of different, effective intake valve closing, heat transfer models, blow-by loss and gas properties with automatic polytropic coefficient detection. This code will also be used to compare and validate the different zero level corrections with commercial data acquisition software by Dewesoft (stakeholder for this project). For the study a 6-cylinder CI engine and am SI engine at Chalmers is used to record the in-cylinder pressure. Measurements of the in-cylinder pressure accurately plays an important role in pressure trace analysis. In this project, the experimental data like raw cylinder pressure and crank angle degree is recorded with the Dewesoft data acquisition system. Along with the recorded data, data from other test cells were also collected which was further analyzed and processed through the MATLAB code developed. After the investigation, the common assumption of constant values of certain parameters, such as IVC effective, constant polytropic coefficient, temperature at IVC, wall temperature, heat transfer loss and blow-by loss was found to skew the data significantly, thus giving incorrect results. Further, in-depth analysis for each of the above parameters is done and function scripts were developed and integrated into the main MATLAB program. The major findings are that the commercial combustion analyzer software’s usually considers a constant polytropic coefficient and also performs an apparent rate of heat release, thus neglecting the heat transfer and blow-by losses. But in reality, the polytropic coefficient varies and the heat transfer and blow-by loss do contribute and affect the amount of heat energy liberated during combustion. The results from the analysis of the data’s influence on the heat release is presented in the report.
Aerodynamic investigations of a bus under high side wind conditions conditions
(2020) Hellsten, Oskar; Pettersson, Oskar; Minár, Matús; Gefors, Hugo; Forsström, Birk; Ravindra, Nithin Bharadwaj; Chalmers tekniska högskola // Institutionen för mekanik och maritima vetenskaper; Sjöblom, Jonas; Sebben, Simone; Vdovin, Alexey
The Norwegian Public Roads Administration (NPRA) is looking for different solutions on how to shorten the travel time for road vehicles between Bergen and Trondheim. The main reason for the long traveling time is due to the amount of fjords that needs to be crossed by ferries when traveling by the coast. Because of this several alternatives to ferries are explored and one of these alternatives is using floating bridges. Since side winds affect the stability of the floating bridge coverage of the sides will be minimal and therefore all vehicles will be fully exposed to side winds. Larger vehicles like buses and trucks are the main concern in regards to sudden instability or a rollover. To prevent accidents it has been decided that a vehicle dynamic model will be made to evaluate the wind speed threshold for when the bridge should be closed or the vehicle speed should be limited. The magnitude of the side forces on long vehicles during high wind conditions is needed as an input to create this vehicle dynamic model. By using CFD together with wind tunnel testing with a scale model an investigation of these forces has been performed. A scale model of the Volvo 9700 series coach bus was 3D printed to be used for wind tunnel testing. Because of a predetermined available mounting area as well as with regards to wind tunnel blockage ratio a scale of 1:18 was chosen. The model was then printed in 9 different parts excluding the wheels because of print volume limitations. To be able to try different design configurations the model was made modular. The front and rear were attached using neodymium magnets while the other parts were either permanently attached using epoxy based glue or screws together with threaded inserts that were melted in to fuse with the plastic. To get a good surface finish for added accuracy in the wind tunnel the model was covered with body filler, sanded, then covered in spray filler and lastly painted black. The wind tunnel testing of yaw angles covered a complete 360 sweep with increments of 5 up to 90 and then increments of 10 for the rest. The results were mainly used as reference to the CFD results since the wind tunnel setup did not include rotating wheels and boundary layer suction. Visualization of the airflow around the bus was achieved by using tufts, smoke and thermal camera. A steady state incompressible RANS equations(Reynolds Averaged Navier Stokes) are numerically solved in StarCCM+ to determine forces and moments. These forces were determined by running simulations for a changing yaw angle from 0 to 90 in 5 steps. Non-dimensional co-efficients of drag force, lift force, side force, yaw moment, roll moment and pitch moment are calculated to compare the data from wind tunnel. This is done as the wind tunnel testing is obtained for a scaled model and in CFD the actual size of the bus is used. Results show that the trends observed in CFD follow the trends from wind tunnel test data. It was observed that coefficient of side force and roll moment increases with the increasing yaw angle and reaches a maximum value at 90 yaw. This shows the importance of the effect of cross winds on vehicles with large side area. This data can be further used in a vehicle dynamic model to evaluate the impact on vehicle stability.
Aerodynamic investigations of a simplified truck under high yaw wind conditions
(2021) Dineff, Athanasia; Upadhyaya, Avaneesh; Nagaraja Rao, Kaushik; van Hoorn, Philip; Gudihal, Vinay; Chalmers tekniska högskola // Institutionen för mekanik och maritima vetenskaper; Sjöblom, Jonas; Sebben, Simone; Vdovin, Alexey
The Norwegian Public Roads Administration (NPRA) are investigating the impact of side winds on vehicles travelling over a floating bridge that they wish to construct to shorten travel time. To mitigate the movement of the floating bridge due to high crosswinds, the bridge will be designed in a way that it does not obstruct the wind as much; resulting in high wind impacts on the commuting vehicles. The tractor-trailer combination is a large bluff body and experiences large side wind forces. Due to these forces, it may affect its lateral stability and might result in rollover at high crosswind speeds. This automotive engineering project aims to investigate the forces and moments acting on the truck during strong side winds and design a generic modular model for research use in the road vehicle aerodynamics course. The force investigations were performed numerically using STAR-CCM+ and experimentally through the closed-loop wind tunnel test facility at the Chalmers University of Technology. SOLIDWORKS was used to design a simplified model of a truck that can be used for research purposes. To accommodate the option of add-ons and to increase the ease of add-ons interchangeability during the wind tunnel testing, the truck design was made modular. The customization could be, for example, the addition of roof fairing, boat tailing or even an American-nose. The down-scaled model was printed and then sanded down and spray-painted for a smoother surface finish and better aesthetics. Assembly of the parts was done using epoxy, super glue and magnets. This model was tested in the wind tunnel, where a sweeping study was performed at a constant wind speed of 30 m/s for varying yaw angles between 0 and 90 . The modular design made it easy to test different configurations, such as different gap sizes between tractor and trailer, and the addition of a roof fairing. Multiple computational fluid dynamics (CFD) simulations were performed on the 1:1 model to mimic open road conditions and cross-validate the wind tunnel test. STAR-CCM+ software was used to mesh, analyze and post-process the CFD data. A steady-state approach and the k-e turbulence model were used to solve the Reynolds- Averaged Navier-Stokes (RANS) equations. A mesh independence study was performed to ensure the validity of the mesh used for the sweep study. The sweep study tested different relative wind directions between 0 and 90 for the same domain and mesh. A simulation is said to have converged when the force coefficients averaged over 750 iterations lie within 2 drag counts for 750 iterations. A comparison between the CFD and wind tunnel results validate the results as the forces and moments acting on the models follow a similar trend for varying yaw angles. The slight discrepancies in the comparison occurred due to the absence of a moving ground, varying boundary conditions and the mounting struts that act as a flow obstruction
Brake load characterization of heavy-duty vehicles
(2024) Achmad Munthahar, Sayid; Dhamane, Bhumika; Randby, David; Suresh, Nandu; Wurzinger, Jakob; Chalmers tekniska högskola // Institutionen för mekanik och maritima vetenskaper; Chalmers University of Technology / Department of Mechanics and Maritime Sciences; Sjöblom, Jonas; Srivastava, Suraj; Petersson, Martin
In the fast-changing automotive world, more vehicles have zero tail-pipe emissions due to electrification. Global and local air quality has increased in recent times due to the implementation of legislation regarding tail-pipe emissions. Regulators are now looking at other sources of emissions, like particulate matter from brakes and tires, which have severe health effects. The particulate matter can enter the airways and if it is small enough, it can travel down to the lungs and even further into the bloodstream. The particle sizes can be divided into PM10, PM2.5, and Ultra-fine particles. Legislation for PM10 will be implemented regarding brake wear in the new Euro 7 legislation for light-duty vehicles in 2025 and something similar to this is expected for heavy-duty vehicles. The stakeholder for this project is Volvo Group, which has been involved during the whole project. This project mainly focuses on the emissions caused by disc brakes on Volvo’s Internal Combustion Engine (ICE) and Battery Electric Vehicle (BEV) heavy-duty vehicles. Field-test datasets from several ICE and BEV trucks, along with Volvo’s brake test rig data are used to estimate brake wear based on brake temperature and braking energy. Data analysis was performed on the dataset and brake wear estimation was done to characterize the braking behaviors of ICE and BEV trucks and determine which affects the brake wear the most. An in-depth analysis was performed by doing a multivariate analysis. The in-depth analysis resulted in the identification of four different clusters that were characterized by their unique driving behavior. From this exploration, it becomes evident that several factors influence brake wear, with temperature emerging as a prominent indicator linked to driving behavior.
CFD investigation of a generic vehicle side-view mirror
(2020) Ibáñez, Cristóbal; Palm, Richard; Rahani, Ramin; Shao, Xinyuan; Chalmers tekniska högskola // Institutionen för mekanik och maritima vetenskaper; Johansson, Håkan
Electric automobiles are becoming more common in today’s society. Since interior car noise can have negative mental health effects for the driver and passengers, it becomes relevant to find out how it is being generated. One important source of noise is the surface pressure fluctuations caused by shear layer impingement and turbulence from the flow around a side-view mirror. Even though many studies about the flow past a side-view mirror have been done, there is not sufficient research for lower speed cases at which electric cars drive at. The purpose of this project is therefore to study the flow around a generic side-view mirror and investigate how it generates noise for some of these cases. The computational fluid dynamics (CFD) software STAR-CCM+, running both steady and unsteady Reynolds-Averaged Navier Stokes (RANS) simulation models is used. Three cases at different freestream speeds of 20, 30 and 40 m/s are simulated. To ensure accurate results, a mesh independence study is carried out for the 40 m/s case with steady RANS simulation. The final mesh is then used to simulate the 20 and 30 m/s cases as well. The steady flow fields were obtained using the realizable k −" model and later used as initialization fields for the unsteady cases, were SST k − ! model is used. Pressure fluctuations data series of specific sensors placed on the surfaces of the mirror and window where analyzed for their power spectral density (PSD) in the frequency domain. For sensors placed in the back of the mirror and on the window inside the recirculation region, noticeable peaks at 500-1300 Hz in the signal’s power were observed. Comparison of the PSD’s against the Strouhal number revealed that the power peaks are due to coherent structures in the free shear layer developed from the mirror edges. Those PSD peaks will generate tonal noise which is of 500-1300 Hz. Measures should be taken to prevent drivers and passengers from hearing this kind of noise. The present study is also a fundamental step to provide hydrodynamic pressure fluctuation data for a future acoustic wave simulations.
Deformations and Stresses in Welded Panels: Development and analysis of a simulation procedure for two-pass fillet welding of a stiffener to a plate
(2021) Boominathan, Thangam; Pujari, Aditya; Sjödin, Wilhelm; Stoyanova, Monika; Chalmers tekniska högskola // Institutionen för mekanik och maritima vetenskaper; Johansson, Håkan; Josefson, Lennart; McDill, Moyra
This project is a part of the Masters programme Applied Mechanics at Chalmers and will also be a contribution to a benchmark exercise in a Specialist Committee, V.3 Material and Fabrication Technology for the International Ship and Offshore Structures Congress (ISSC) 2022 Conference. The goal of this project is to further develop and analyse an existing simulation procedure for two-pass fillet welding of a stiffener to a plate with the aim to find what simplifications that can be made in the modelling. The results from finite element simulations (FE-simulations) are then compared to analytical solutions and experimental data for validation. The FE-simulations are carried out with the commercial FEA-software ABAQUS using forward-coupled thermal-mechanical FE-simulations with geometrical and material nonlinearities included. The analysis is first performed on a shorter plate (200 mm) to draw faster conclusions by saving computational time. Once the analysis for the shorter plate has been conducted, a longer plate (1000 mm) representing the benchmark geometry is analysed. To verify that a simplified model of the heat input can be used, FE-simulations on the short plate are used to calculate the cooling time between 800˚C and 500˚C at a node on the weld. This data is then used to compare with analytical solutions for the cooling time in this interval, valid for the weld parameters specific to this benchmark project. By adapting the weld speed and maximum temperature of the weld, the optimal cooling time, and parameters for the heat input, are found. The simplified heat source model then gives the same behaviour as a real weld. With the thermal simulation settings validated by analytical solutions, the results from the mechanical part of the FE-simulations are analysed for the short plate. Here different sequences of releasing mechanical boundary conditions are studied, and how they affect the residual deformations after the two-pass fillet welding. This is achieved in ABAQUS by changing simulation steps and compiling the deformation fields for different configurations. Furthermore, different methods for preventing rigid body motion (RBM) are analysed and their influence on the residual deformations. Mechanical contact between a table beneath the plate is modelled using Lagrange multipliers creating a hard contact. The effect of this contact modelling on the residual deformations is also investigated, whether it is necessary or not since a removal of contact conditions will reduce computational cost considerably. One conclusion that can be drawn is that the release of mechanical boundary conditions is mainly elastic, and thus they can be modelled as removed at the same time. Furthermore, it is seen that the mechanical contact modelling is necessary to obtain reasonable results for some methods of preventing RBM. The long plate is then studied, where the complete benchmark geometry is modelled. Using Chalmers Centre for Computation Science and Engineering (C3SE) one complete simulation is run in a reasonable time of 12 hours on 24 CPUs. The residual stresses and deformations are then extracted and compared to experimental data on angular distortion and deformations. It is found that the simplified modelling approach used can give good agreement for the residual stresses and for the shape of the residual deformations. The magnitudes of the residual deformations, though, are harder to predict.
Deformations in welded panels
(2020) Selvaraj, Srikannan; Pamfil, Bogdan; Hård, Daniel; Gurram, Shivaprasad; Chalmers tekniska högskola // Institutionen för mekanik och maritima vetenskaper; Johansson, Håkan; Josefson, Lennart; McDill, Moyra
Welded panels are commonly used for ships hull manufacturing, and in order to lighten the hull the stiffened panel thickness tends to be reduced, thus increasing the distortion effects due to welding. This project will be part of Chalmers contribution to the benchmark exercise in a specialist committee, Material and Fabrication Technology, for the International Ship and Offshore Structures Congress (ISSC) 2021 conference. The project’s purpose is to compute the deformation for the ISSC2021v.3 benchmark [1] geometry of a stiffened welded panel which comprises of a stiffener 1000 x 100 x 5 mm DH36 plate which is initially tack welded on one side to a 1000 x 400 x 5 mm DH36. The welding procedure consists of a first weld fillet being deposited on one side of the stiffener, followed by a cooling time, and then another weld fillet being deposited on the other side and followed by a second cooling time before the welded panel is finally unclamped. To achieve that, both thermal and mechanical analyses are carried out by relying on the nonlinear Finite Element Analysis (FEA). The commercial FEA program ABAQUS is used for analyses in this project. Those simulations are however performed for a shorter plate and stiffener of length 200mm. The material properties were implemented in ABAQUS input file form, for both the weld and the plate and stiffener. Nonlinear thermal and mechanical properties were taken into account. The specific heat and thermal conductivity were implemented for the DH36 steel, however other properties such as thermal expansion coefficient, Poisson’s ratio etc., were implemented for a similar steel, S355. The weld material and the plate and stiffener are altogether modelled as being the same material except regarding the hardening modulus and the yield stress. When compared to the plate and stiffener material, the weld material itself has been modelled as having a higher yield stress and higher hardening modulus at room temperature. Two thermal models are considered with each having 1000 C as the heat source temperature of the weld. First, the fillet weld is activated simultaneously and in the second, the fillet weld material is activated sequentially by dividing the weld into segments. After each weld pass the model is allowed to cool down for 200 seconds so that the welded panel has cooled to around 50 C at the end of the simulation. The thermal simulations are coupled to mechanical simulations. In mechanical simulations, different clamping sequences are carried out. One with fully fixed and two with sliding clamps. In total six configurations are considered, since there are two thermal models and three clamping conditions for the mechanical simulations. Clamping is taken care of by taking the top and bottom nodes of the plate at designated locations. The same mesh model was used for both the thermal and mechanical simulations, and it consists of linear 8-node hexahedral and linear 4-node tetrahedral solid elements. The linear hexahedral elements are used to model the plate and stiffener and the welding joint is modelled by linear tetrahedral elements. Prior to choosing vi a final mesh a mesh convergence study was conducted by monitoring the temperature variation at a location close to the weld. The resulting mesh had 31200 nodes and elements with an aspect ratio lower than 10 to avoid complications with the mechanical simulations. The results of this project showed that the type of heating source and the clamping conditions have definite effects on the behaviour of the model. The displacements results for the mechanical simulations indicated that the sequential heating results were closer to the intended ones than for the simultaneous heating case. Also, the extent of clamping conditions, i.e., either fully clamped or sliding clamps, along with the methods used to prevent rigid body motions for a sliding clamp are all factors which have an effect on the behaviour of the model. And these differences in the thermal and mechanical loading configurations will be magnified when they are applied to the full length of 1000 mm for the plate and stiffener as per the ISSC2021v.3 benchmark.
Developing a Solution to Utilize Vehicle Dynamics Simulation Tools with a Motion Driving Simulator
(2021) Madhava Prakash, Ajit Kumar; Garje Mohankumar, Anup; Misquith, Clive Rahul; Ganatra, Diler Paresh; Soudagar, Irfan Ahmed Khan; Johnsson, Jonas; Chalmers tekniska högskola // Institutionen för mekanik och maritima vetenskaper; Sjöblom, Jonas; Johansson, Ingemar; Jacobson, Bengt
The project develops a method to integrate a CAE software (IPG CarMaker) vehicle model into the CASTER driving simulator. The vehicle dynamics performance is assessed by comparing CarMaker (CM) simulation data against the driving simulator data. First, a baseline generic passenger SUV was modeled on CM with K&C parameters that resemble a real-world vehicle. Then, the driving scenarios and maneuvers such as steady state cornering [6] and double lane change [5] were modeled on CM. Alongside this, IPG Movie and CM for Simulink were used to create real driving scenarios with accurate driving views. Next, the baseline vehicle was simulated in CM and driven on the simulator for both maneuvers. Driver input signals from the driving simulator were fed into CM through CM for Simulink to run the physics of the vehicle model. The output signals computed by CM were fed to the driving simulator to provide motion, audio and visual cues. The integration tool was developed to introduce it in the early phase of vehicle development. The software simulation provides good objective data but no subjective assessment. The use of DIL-simulator is a good method to add subjective assessment in vehicle dynamics development. After every maneuver run, driver’s subjective assessment and rating was recorded. A statistical and graphical comparison of objective data between CM simulation and driving simulator drivers. Analysis of this data showed there is good correlation between results from CM simulations and the driving simulator. Then, vehicle parameter variations were made to understand the vehicle dynamics performance objectively and subjectively. For each model variation, a CM simulation and driving simulator test was carried out by multiple drivers. The vehicle specification variations were designed to produce changes in the steering feel and controllability. This indicates that the driving simulator is a viable supplement to prototype testing, however, further studies must be made to validate the preliminary conclusion. In reality, vehicle evaluations are performed by highly skilled test drivers with accurate subjective assessments. The project yields a tool to develop and evaluate the vehicle dynamics performance. In the hands of a professional driver, this will produce good subjective assessment that ties in with the objective metrics, thus validating it’s use as a cost effective and time efficient tool to develop vehicles.
Development of environments to test driver assist functions for reversing an A-double combination vehicle
(2021) Parshetti, Vikram; Keshava Reddy, Lohith Reddy; Prabhu, Anand; Ashok, Nrupathunga; Jain, Pratham; Srinivas, Akhil; Chalmers tekniska högskola // Institutionen för mekanik och maritima vetenskaper; Sjöblom, Jonas; Jonasson, Mats
transportation efficiency. These vehicles have multiple trailers pulled by a single tractor and the A-double is an example of such a vehicle. Although A-doubles improve transportation efficiency, they are extremely difficult to manoeuvre in the reverse direction. The work done in the project aims to develop a rapid prototype environment that reduces development time and cost of controllers used to assist drivers in reversing the A-double. The assist functions developed using these environments help improve loading and unloading time while also reducing the stress levels of the driver(s). The testing and validation of the controller is done in two tiers. The first tier is a virtual environment to test the basic functionality and the second tier is a scaled environment to test the robustness and performance of the controller. Two control strategies have been developed to validate the test environments and their performance has been discussed. The performance of the test environments and possible improvements have been discussed.
Drawbar Eye Identification and Guiding
(2024) Garg, Mahin; Winbo, Andreas; Liu, Biying; Qui, Shiyi; Renberg, Felix; Chalmers tekniska högskola // Institutionen för mekanik och maritima vetenskaper; Chalmers University of Technology / Department of Mechanics and Maritime Sciences; Vdovin, Alexey; Von Corswant, Fredrik; Johansson, Tobias
The purpose of this research project is to study if a machine learning algorithm can utilize a video feed from a camera mounted on the back of a truck to detect a drawbar eye under varying environmental, instrumental and lightning conditions. In order to achieve this, lab based and real world testing data was collected from a setup which simulated connecting a truck and a trailer. With these setup cases, different video feeds were collected and later, images were extracted from this feed, which were labeled for the machine learning algorithm. In order to train the algorithm, YOLOv8n (You Only Look Once Version 8) was used, which is a real time object detection algorithm to identify objects in an image. This was used to classify the drawbar eye and its position in real time. In order to better guide the driver, distance between camera and drawbar eye was calculated using the pinhole camera principle, and here the angle of the camera was introduced. From the calculation, we had the horizontal distance (X), vertical distance (Y) and distance in depth (Z). Two additional tests were done in order to verify the accuracy of distance and height calculation, and take the distortions of a fisheye camera into account while calculating the said distances. The final detection accuracy (ability to detect position of drawbar eye with 50-95 percent accuracy of the labeled position) of the model came at around 75.4 percent.
Driver influence on vehicle track-ability on floating bridges
(2020) Balakrishna Bhat, Abhishek; Naik, Akshay; Adithya Reddy, Chintalapudi; Pishey, Kushaal; Manikanta, Venkatesh; Nishanth, Bharadwaj; Chalmers tekniska högskola // Institutionen för mekanik och maritima vetenskaper; Bengt, Jacobson; Sekulic, Dragan; Johansson, Ingemar
Thinking from a traveler’s perspective, it can be said that it is important to reduce travel time. The Norwegian Public Roads Administration (NPRA) is working on a long term project to extend the coastal highway route E39 as a continuous stretch of road between Kristiansand and Trondheim. The road has a number of ferry crossings over fjords. Due to the depth in the fjords, it is not possible to build conventional bridges. Thus, the objective is to reduce the travel time by implementing a series of connections (e.g.submerged floating tunnels, subsea road tunnels and floating bridges). One such fjord crossing is the Bjørnafjorden bridge which spans for a length of over 5000 m. The floating bridge will be exposed to a number of varied weather conditions of different intensities. It is important to assess the vehicle handling and how the driver is experiencing the moving road surface in these conditions. The bachelor thesis which was proposed on the same topic, established a method to simulate the weather conditions in the CASTER driving simulator at Chalmers. The Automotive Engineering project (AEP) aims at evaluating the driving comfort and handling, when driving over the bridge in different weather conditions. The main approach adopted is to simulate the driving conditions in CASTER driving simulator, using the weather data provided by NPRA. Further, driving trials are conducted for a combination of different weather conditions and vehicle speeds for car and bus models. The results obtained from the trials are analyzed both subjectively using the driver feedback and objectively using the data obtained from the driving simulator, to make suitable conclusions and recommendations regarding the safe operating conditions of the bridge. The project further concludes the correlation between the weather conditions and drivability through both subjective and objective data analysis. The weather conditions were varied from no wind condition to a 100-year storm condition. Also, the most frequently occurring 1-year storm condition was studied in detail with only wind on the vehicle, sea swell and wind due to the wave conditions. A total of 157 driving trials were conducted with different vehicle speeds (70 kmph, 90 kmph and 110kmph) and different maneuvers like lane change and overtaking were performed to analyze the handling and stability of the car and bus. Straight line driving is also simulated to determine the operating conditions of bridge, to check the safe speed limit and ability of the driver to stay in lane. Another deliverable of the project is to develop a driver model to perform a greater number driving trials to test more conditions. Due to the lack of time and complexity of the weather data, a basic driver model has been developed and a thorough literature survey has been done to make suitable suggestions for the existing basic driver model as a future scope of the project. To sum it up, the vertical and lateral dynamics of the vehicles driving over the bridge are assessed in a virtual environment. A detailed analysis is done with the help of the data obtained in order to make suitable recommendations for safe driving on the bridge at different weather conditions.
Finite element study of pressure distribution under tyre during low speed for explaining rolling resistance
(2021) Aalto, Robin; Johansson Sundblad, Lucas; Kareti, Priyatham Reddy; Olofsson, Nils; Subramanian, Vignesh; Chalmers tekniska högskola // Institutionen för mekanik och maritima vetenskaper; Johansson, Håkan; Jacobson, Bengt
Road transports are necessary as they are very flexible, and are essential for the logistics of today, though this requires sustainable solutions for environmentally stable transportation. Trucks are immense machines that are heavily affected by resistance, in both air and rolling resistance. In this report, the main focus will be to gain a better understanding of how the pressure distribution under a tyre influences the rolling resistance. In order to achieve a clearer perception of this phenomena, a 2D finite element model was defined. Two separate concepts were constructed, a more advanced model in ANSYS and a more simplified, yet more controllable, model in MATLAB. A hypothesis was formulated, wherein it is described that the pressure distribution is thought to be offset in the rolling direction. This would be the driving mechanism in creating rolling resistance, and the FE-models were made in order to try and capture this behaviour. The models were created with two layers, one for the sidewall and one for the belt. The boundary conditions were different between the models, in ANSYS the force was prescribed while in MATLAB, the deformation was prescribed. The simulations do show an offset for the pressure distribution beneath the tyre, which was thought to be the case. Though the simulation show that the offset would be in the other direction, something that was hard to explain. The two different model do however show a similar pattern, which was encouraging, though no unambiguous tendency was found. A varying vertical load, and the effects of that variation would be a desired factor to test, though since the project was short on time, this was not examined. Finally, there is more work to do in order to better understand the subject, which could be made by testing the model further or by developing a more complex model in either 2D or 3D.
Flow uniformity characterization in catalytic converters under turbulent inlet conditions
(2022) Tylén, Oskar; Larsson, Jacob; Murali, Aravind; Rangaswamy, Sunil; Peyvandi, Ehsan; Larsson, Axel; Chalmers tekniska högskola // Institutionen för mekanik och maritima vetenskaper; Johansson, Håkan; Ström, Henrik; Sjöblom, Jonas; Nagarajan, Pratheeba Chanda
In the sectors utilizing the combustion of fossil fuels, catalytic converters are commonly employed to reduce dangerous gases generated by combustion engines. For greater efficiency, it is critical to understand the exhaust flow homogeneity inside the converter. This work attempts to evaluate the added value of using Detached Eddy Simulation (DES) simulation over Reynolds-Averaged Navier-Stokes (RANS) simulation for analysis of turbulent flow inside catalytic converters. The meshing and simulation of the domain was carried out using ANSYS FLUENT and ANSYS Workbench. Initially a RANS simulation with k-ω SST turbulence model was carried out for a specific case to understand the behavior of the time averaged flow field with modeled turbulence and its effect on uniformity index. The results from the RANS simulation were, together with definitions of turbulent length scales, used to develop a mesh for DES simulation. In this process it was found that in order to resolve a sufficient amount of turbulence upstream of the monolith inlet, the DES simulation required a considerably finer grid than the RANS simulation. The DES simulation with k-ω SST model was used to simulate multiple retention times, attempting to achieve a quasi steady flow with resolved velocity fluctuations. However due to constraints on computational power, simulating until statistical convergence was not possible. The time averaged quantities were extracted from the DES simulation in order to make a fair comparison with RANS results. The uniformity indices of RANS and DES were then compared throughout the monolith of the catalytic converter. A difference of ∼1-1.5% in uniformity index was found from this comparison. Further more it was found that the resolved turbulence in the DES generates fluctuations of ∼3-6% in the uniformity index based on instantaneous quantities. The work concludes that for the exact case simulated, the possibility of increased accuracy when predicting uniformity index with DES instead of RANS does not outweigh the increased computational cost. However for different flow conditions, with larger mean velocity magnitude and less uniform flow, the measured difference between RANS and DES could make a larger difference for prediction of catalytic conversion efficiency. Hence in these cases it is possible that DES simulations are worth their computational cost. Whether this is the case or not would have to be examined through further research before coming to any definitive conclusions.
Handling increased need of maintenance to meet future freight demands: Deterioration and effective maintenance strategies for track system and rail vehicles
(2022) Mattsson, Klara; Lee, Jaseung; Ligmajer, Oskar; Chalmers tekniska högskola // Institutionen för mekanik och maritima vetenskaper; Kabo, Elena; Ekberg, Anders
This report addresses future increased demands of freight on the Swedish railways. To achieve an increase in total freight, different forms of operations can be utilized like increasing the axle load, speed, or frequency which are all scenarios that will be evaluated in the report. The impact caused by those measures will affect both deterioration and the need for efficient maintenance regarding rail vehicles and track systems. Different methods of maintenance, both currently used and newly developed methods are discussed in this report to be able to evaluate how it is possible to become more efficient. The deterioration that occurs during the operation of freight trains is described in the report since an understanding is needed to address the problems and possible solutions. What also plays a vital role in the maintenance plan is to detect faults efficiently. To get an idea about how all of these issues are handled in the industry, interviews have been held with professional staff at four large companies in Sweden. Together with literature studies, this forms the foundation of this report.
Increasing freight transport capacity
(2022) Carlsson, Johan; Edberg, Marcus; Gullberg, Viktor; Nieswand, Niklas; Chalmers tekniska högskola // Institutionen för mekanik och maritima vetenskaper; Kabo, Elena; Ekberg, Anders
The main objective of this report is to investigate how freight train capacity can be increased to enable transportation related to carbon capture and storage (CCS) on the Swedish railway system in order to achieve the carbon dioxide climate target. The increased need for sustainable transport will create a large demand on the existing railway network. To meet these demands, several measures need to be taken. To investigate this further, literature study, interviews, a case study and analysis of the current network were conducted. As the railway network is a complex system, a range of measures is suggested to counter a high capacity utilization within both shorter and longer time frames. In the report several line segments limiting the system capacity were identified. Several measures were suggested with regards to both railway infrastructure and train set-up. It is concluded that additional investments have to be made to handle ccs transportation.
Investigation of bus users’ motion comfort due to wind and bridge motion excitations
(2024) Blakqori, Albijon; Hermansson, Harald; Kotur, Mille; Ramesh, Shreekara; Tj¨arnlund Lepp¨am¨aki, Joakim; Chalmers tekniska högskola // Institutionen för mekanik och maritima vetenskaper; Chalmers University of Technology / Department of Mechanics and Maritime Sciences; Sedarsky, David; Sekulic, Dragan; Jacobson, Bengt J H; Vdovin, Alexey
This paper is based on a project in the 2023 ”Automotive Engineering Project” course atChalmers University of Technology. As a part of a large-scale project to reduce travel times,a floating bridge is planned to be built over Bjørnafjorden on the west coast of Norway. The planned floating bridge is prone to be sensitive to environmental factors (e.g. wind andwaves). Previous papers have studied the lateral stability of a bus riding over the bridge, and the Norwegian Public Roads Administration now sought an analysis of how riding over the bridge would affect bus passengers in terms of comfort and motion sickness. An existing 8 DOF bus model was extended to 13 DOF by adding a bus driver, and three passengers and also accounting for pitch motion. The model was simulated in Simulink. Accelerations from 8 axes for each bus occupant were retrieved and then weighted according to weighting filters from the ISO 2631-1. By using the mentioned ISO standard, bus users’ comfort could be assessed by comparison of bus occupants’ acceleration limits. Motion sickness was assessed numerically by the Motion Sickness Dose Value equation given in ISO 2631-1, however, it is a highly subjective illness. With the 1- and 2-year storm conditions and the bus model, ride comfort and motion sickness levels were assessed. According to the received results from the simulations, it could be seen that the key contributing factors to the ride comfort were vertical and lateral accelerations. It could also be concluded that the wind forces acting on the vehicle affected the ride comfort to a great extent. The seat position and the travelling speed were also big contributors to the ride comfort. Increasing speed and a seat position away from the bus’ centre of gravity had a negative impact on comfort. From a motion sickness perspective, the motions in the lower frequency range and accumulative travelling time were the main contributors. Travelling at a slower speed would negatively affect the Motion Sickness Dose Value, due to increased travelling time with motions at the low-frequency responses from the bus and bridge (e.g. wave load, current, wind excitations).
Liquid Hydrogen Tanks for Low-Emission Aircraft
(2021) Sjöberg, Jacob; Smith, Joshua; Haglund Nilsson, Olle; Emanuelsson, Per; Otlu, Sena; Chalmers tekniska högskola // Institutionen för mekanik och maritima vetenskaper; Johansson, Håkan; Asp, Leif
Hydrogen power shows high potential in reducing emissions of greenhouse gases from aircraft, which has led to companies investing more of their resources into developing this technology. One of the main issues of this technique is the storing of the liquid hydrogen within the airplane without adding too much weight. This has lead to a demand for designing tanks in carbon bre reinforced plastics (CFRP). This project has therefore been structured as a pre-study to further increase the knowledge available on the design of liner-less composite pressure vessels. It was discovered that a liner-less pressure vessel made out of thin-ply composite material is a concept of great potential. The two sections of the proposed tank, the tube, and the two endcaps were constructed di erently. In terms of stress and strain, they both indicated potential complying to limits set on the material, both in terms of ultimate values and thermal fatigue. Connecting the two main parts through a single scarf joint, currently common within the aerospace industry, the overall weight of the tank was decreased with a factor of over 85% compared to a steel tank. In conclusion, the design of a liner-less composite tank shows great potential and it is of interest to conduct further research in this area.
Machine Learning-Based Optimization for Battery Pack Cooling
(2024) Abukar, Abubakar; John, Pedro; Boudagh, Francisco; Verde, Salvatore; Wendel, Gabriel; Chalmers tekniska högskola // Institutionen för mekanik och maritima vetenskaper; Chalmers University of Technology / Department of Mechanics and Maritime Sciences; Vdovin, Alexey; Vdovin, Alexey; Vivek, Anthony; Koutsimanis, Dimitrios; Alatalo, Viktor
The thermal management of electric vehicle (EV) batteries is a critical factor in safety, performance and durability. Traditional design methods for cooling channels rely on manual adjustments, trial and error processes and intensive topology optimizations leading to time con suming approaches and significant limitations in efficiency. This study introduces an innovative framework that combines machine learning (ML) and computational fluid dynamics (CFD) to optimize cooling channel designs that circumvent the challenges faced by traditional methods. These improvements are achieved by using two different components: The first component is a surrogate model. It is a machine learning model trained on a large dataset produced through CFD simulations using Star-CCM+. This model significantly reduces computational costs and time by predicting pressure drops and temperature distributions based on input geometries and system parameters. The second component is a genetic algorithm for geometry optimization. This component generates an optimal geometry by balancing pressure drop and an effective thermal regulation by using a Non-Dominated Sorting Genetic Algorithm (NSGA-II). This algorithm creates a number of random solutions and iteratively improves on them to find a Pareto front, which represents the optimal trade-offs between competing objectives: minimizing pressure drop and maximizing thermal regulation. The role of the surrogate model is to provide instant feedback on potential solutions throughout the algorithm, which is vital as the algorithm itself is inherently time consuming. By combining these two components, the framework accelerates the design process ensuring the creation of advanced cooling solutions. The results demonstrate the potential to reduce computational time while achieving superior performance. This work provides a framework for future advancements in the thermal management of EV batteries, highlighting the importance of combining CFD with ML in modern engineering solutions.
Method To Improve a Wheel Suspension Design Using VI-CarRealTime and Reinforcement Learning
(2024) Denneler, Manuel; Heilig, Christoph; Bangalore Venkatesh Prasad , Vinayanand; Madhuravasal Narasimhan, Vivekanandan; Kolekar, Abhishek Amit; Chalmers tekniska högskola // Institutionen för mekanik och maritima vetenskaper; Chalmers University of Technology / Department of Mechanics and Maritime Sciences; Sedarsky, David; Boerboom, Max; Ekström, Kenneth; Huang, Yansong; Jacobson, Bengt
The project focuses on the enhancement of wheel suspension design through the utilization of VI-CarRealTime and Reinforcement Learning techniques. The primary objective of the study is to improve vehicle dynamics and autonomous systems, thereby contributing to the advancement of automotive engineering. The development of vehicle suspension systems is a complex and iterative process, involving the adjustment of various parameters to meet quantitative and qualitative metrics. The report emphasizes the significance of simulating different suspension setups to achieve optimal design solutions. It highlights the essential collaboration between simulation engineers and design engineers to ensure the successful development of suspension systems. The project group aimed to use optimisation techniques and artificial intelligence to streamline the process of developing an optimal suspension in a time-saving manner. The use of the VI-CarRealTime simulation tool facilitated the analysis and synthesis loops in the suspension design development process and enabled the evaluation of kinematic properties and system requirements. Furthermore, this report deals with the application of machine learning theory, in particular with concepts of reinforcement learning. A comprehensive overview of reinforcement learning, its elements, workflows and classification is provided, highlighting its potential for suspension design optimisation. A detailed comparison of reinforcement learning with other optimisation methods is also presented, highlighting its benefits in the context of suspension development. The development and description of a MATLAB script for the project is presented, highlighting the technical aspects of implementing reinforcement learning techniques in the context of suspension design. This report concludes with a discussion of the potential impact of the research on the automotive industry, emphasising the importance of the results for the advancement of vehicle dynamics and automotive engineering as a whole. To summarise, the project represents a contribution to improving suspension design through the integration of VI-CarRealTime and reinforcement learning techniques. The findings and insights presented in this report have the potential to significantly impact the automotive industry by contributing to the development of more efficient and optimised vehicle suspension systems.

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