| 121. |
- Genzel, Jonny, et al.
(author)
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An Open-Source Finite Element Model of a Generic Car Seat: Development and Validation for Low-Severity Rear Impact Evaluations
- 2022
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In: Conference proceedings International Research Council on the Biomechanics of Injury, IRCOBI. - : IRCOBI. - 2235-3151. ; 2022-September, s. 229-242, s. 229-242
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Conference paper (peer-reviewed)abstract
- A Finite Element model of a generic Laboratory Seat was developed to replicate a physical counterpart used in rear-impact volunteer tests. The Laboratory Seat has a simplified design, developed to facilitate replication in computational models. The seat has a flat rigid base and the seatback consists of four horizontal panels attached to side posts by coil springs. The seat model was validated with results from component tests and sled tests, including the Anthropomorphic Test Device, BioRID II. An initial test series was carried out to generate data for component validation: the first set of tests to characterise the coil spring properties; and the second set comprising Impactor Tests on Head Restraint Foam to assess the head restraint material properties. For system level validation, sled tests were conducted both with the empty Laboratory Seat and with the BioRID II. The BioRID II tests were conducted in conjunction with an earlier volunteer test study. Both the component and the sled tests were reproduced in a virtual environment. Good agreement was achieved between the mechanical tests and the computational simulations. The seat model is freely available to use: https://openvt.eu/fem/open-access-laboratory-seat-model.
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| 122. |
- Korkmaz, Kadir Burak, et al.
(author)
-
CFD based form factor determination method
- 2021
-
In: Ocean Engineering. - : Elsevier Ltd. - 0029-8018 .- 1873-5258. ; 220
-
Journal article (peer-reviewed)abstract
- The 1978 ITTC Power Prediction method is used to predict the propulsive power of ships through towing tank testing. The form factor approach and its determination in this method have been questioned. This paper investigates the possibility to improve the power predictions by introducing Combined CFD/EFD Method where the experimental determination of form factor is replaced by double body RANS computations applied for open cases KVLCC2 and KCS, including first-time published towing tank tests of KVLCC2 at ballast condition including an experimental uncertainty analysis specifically derived for the form factor. Computations from nine organisations and seven CFD codes are compared to the experiments. The form factor predictions for both hulls in design loading condition compared well with the experimental results in general. For the KVLCC2 ballast condition, majority of the form factors were under-predicted while staying within the experimental uncertainty. Speed dependency is observed with the application of ITTC57 line but it is reduced with the Katsui line and nearly eliminated by numerical friction lines. Comparison of the full-scale viscous resistance predictions obtained by the extrapolations from model scale and direct full-scale computations show that the Combined CFD/EFD Method show significantly less scatter and may thus be a preferred approach.
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| 123. |
- Li, Mengtian, 1989, et al.
(author)
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Sealing System Analysis of Rotary Piston Pump
- 2019
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In: IOP Conference Series: Materials Science and Engineering. - 1757-8981 .- 1757-899X. ; 520:1
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Conference paper (peer-reviewed)abstract
- Rotary piston pump is designed by the Wankel engine. The structure, working feature and sealing system of rotary piston pump are introduced. The mathematical model of the internal cylinder profile and the theoretical flow are obtained by analysing the structural characteristics of the new pump. The axial seal and face seal of the rotary piston pump and their structures are analysed. The force analysis of the sealing strip is carried out in various cases. It can be concluded from the analysis that, for axial sealing, the key parameters that affect seal strip wear are working pressure, rotate speed of the crankshaft and the friction coefficient between sealing strip and inner wall of the cylinder. For axial sealing, the force of the spring under the curved sealing strips, the size of the sealing rings and curved sealing strips and material of them are the key design parameters.
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| 124. |
- Meyer, Knut Andreas, 1990, et al.
(author)
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Efficient 3d finite element modeling of cyclic elasto-plastic rolling contact
- 2021
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In: Tribology International. - : Elsevier BV. - 0301-679X. ; 161
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Journal article (peer-reviewed)abstract
- Railway rails accumulate large plastic deformations due to cyclic rolling contact loading. The plastic deformations alter the rail geometry, affect material behavior, and cause crack formation and growth. The complex interactions between these phenomena require high fidelity simulations to be understood. 3d finite element simulations are accurate, but their computational cost limits the possible number of simulated cycles. We propose a cyclic finite element simulation in which the wheel and rail remain in contact throughout the simulation. It uses periodic boundary conditions, shadow elements, and model reductions. Compared to previous work, it is 25 times faster. The method is available as an open-source plugin to Abaqus, enabling other researchers to study rolling contact loading coupled with large plastic deformations.
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| 125. |
- Mohammed, Omar D., et al.
(author)
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Robust multi-objective optimization of gear microgeometry design
- 2022
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In: Simulation Modelling Practice and Theory. - : Elsevier BV. - 1569-190X. ; 119
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Journal article (peer-reviewed)abstract
- Gear microgeometry is important as it can change the tooth flank contact pattern effectively. In gear design, it is important to minimize the peak-peak transmission error (PPTE) for lower Noise, Vibration and Harshness (NVH), and to minimize the generated stresses for higher durability that can help to avoid tooth failure. In the current article, a structured approach is developed that combines the advantages of applying meta-models and robust optimization. For the Design of Experiments (DOE), the LDP software tool was used to obtain the objective functions of PPTE, contact stress, and root stresses at all design points. Probability distribution and worst-case scenario measures were applied to weigh the objective functions and make them robust against torque. The generated data were used in MATLAB to build meta-models for each objective function using squared exponential Gaussian regression. The generated meta-models were then used in a multi-objective optimization algorithm to obtain a Pareto set of solutions. These solutions were examined and ranked from the highest to the lowest, based on the weights of the PPTE and stress safety factors. Using Rank 1 design, the gains of -25, -7, +3 and -5% for the PPTE, contact stress, gear 1 root stress and gear 2 root stress respectively were obtained. However, these gains can be different in other design cases because these gains were calculated using Rank 1 design as compared to the manually selected benchmarked design which mainly depends on the engineer's experience. The developed approach can save time and help to obtain a unique optimal design solution in a structured format.
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| 126. |
- Moraes Da Silva, Lucilene, 1987, et al.
(author)
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Analysis of Blade Aspect Ratio’s Influence on High-Speed Axial Compressor Performance
- 2024
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In: Aerospace. - 2226-4310. ; 11:4
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Journal article (peer-reviewed)abstract
- The ratio between blade height and chord, named the aspect ratio (AR), plays an important role in compressor aerodynamic design. Once selected, it influences stage performance, blade losses and the stage stability margin. The choice of the design AR involves both aerodynamic and mechanical considerations, and an aim is frequently to achieve the desired operating range while maximizing efficiency. For a fixed set of aerodynamic and geometric parameters, there will be an optimal choice of AR that achieves a maximum efficiency. However, for a state-of-the-art aero-engine design, optimality means multi-objective optimality, that is, reaching the highest possible efficiency for a number of operating points while achieving a sufficient stability margin. To this end, the influence of the AR on the performance of the first rotor row of a multistage, multi-objective, high-speed compressor design is analyzed. A careful setup of the high-speed aerodynamic design problem allows the effect of the AR to be isolated. Close to the optimal AR, only a modest efficiency variation is observed, but a considerable change in compressor stability margin (SM) is noted. Decreasing the AR allows for increasing efficiency, but at the expense of a reduced surge margin. This allows the designer to trade efficiency for stability. Increasing the AR, however, is shown to reduce both the surge margin and efficiency; hence, a distinct optimality in stability is observed for the analyzed rotor blade row. In this work, optimality in the surge margin with respect to the AR is observed, whereas there is a close to optimal efficiency. The predicted range from AR = 1.10 to AR = 1.64 is only indicative, considering that the definition of multi-objective optimality requires balancing efficiency and the surge margin and that the choice of balancing these two criteria requires making a design choice along a pareto optimal front.
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| 127. |
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| 128. |
- Pålsson, Björn, 1981
(author)
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A linear wheel–crossing interaction model
- 2018
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In: Proceedings of the Institution of Mechanical Engineers, Part F: Journal of Rail and Rapid Transit. - : SAGE Publications. - 0954-4097 .- 2041-3017. ; 232:10, s. 2431-2443
-
Journal article (peer-reviewed)abstract
- This paper presents the derivation of a linear model for wheel–rail interaction kinematics at railway crossings. The purpose of this model is to demonstrate the fundamental constraints imposed on a crossing geometry if it should be compatible with a given range of wheel profile shapes. In this model, the contact point locations on the wing rail and on the crossing nose are described using linear functions, and the wheel profiles are modelled as conical. Based on these assumptions, a method is developed to adjust the vertical position and longitudinal inclination of the wing rail and the crossing nose in order for the crossing geometry to be compatible with a given range of equivalent wheel profile cone angles. In particular, an expression is derived for the average impact angle. The derived relation highlights the potential of tailoring crossing geometries for a given spread in wheel profile shapes in traffic for minimized loading and damage. Further, the properties of the model are compared to the results of quasi-static multibody simulations for a range of wheel profiles.
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| 129. |
- Rehammar, Robert, 1980
(author)
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Load Optimization in Reverberation Chambers
- 2021
-
In: 15th European Conference on Antennas and Propagation, EuCAP 2021.
-
Conference paper (peer-reviewed)abstract
- Optimal loading conditions of a reverberation chamber were investigated. The relevant figure of merit is discussed and defined. Multiple loading configurations were tested and results are reported. A simple model of how loading affects measurement uncertainty was developed and used to find a loading configuration that vastly improve results with regards to the defined figure of merit compared to other configurations.
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| 130. |
- Saha, Ranjan, 1984-, et al.
(author)
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Aerodynamic Investigation of External Cooling and Applicability of Superposition
- 2015
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In: 11th EUROPEAN CONFERENCE ON TURBOMACHINERY FLUID DYNAMICS AND THERMODYNAMICS. - : EUROPEAN TURBOMACHINERY SOC-EUROTURBO.
-
Conference paper (other academic/artistic)abstract
- An experimental investigation of the overall external cooling on a cooled nozzle guide vanehas been conducted in a transonic annular sector cascade. The investigated vane is a typicaltransonic high pressure gas turbine vane, geometrically similar to a real engine component.The investigations are performed for various coolant-to-mainstream mass-flux ratios. Resultsindicate that the aerodynamic loss is influenced substantially with the change of the coolingflow. Area-averaged exit flow angles in midspan region are unaffected at moderate filmcoolant flows, for all cooling configurations except for trailing edge cooling. The trailing edgecooling decreases the turning in all investigated cases. Results lead to a conclusion that bothtrailing edge and suction side cooling have significant influence on the aerodynamic losswhereas the shower head cooling is less sensitive to the loss. Investigations with individualcooling features essentially lead to the applicability of the superposition technique regardingthe aerodynamic loss for film cooled vanes, which is this paper’s contribution to the researchfield. Results show that the superposition technique can be used for the profile loss but not forthe secondary loss.
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