| 1. |
- Vieira, Tiago, 1984-, et al.
(författare)
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Evaluation of uncertainty on Shore hardness measurements of tyre treads and implications to tyre/road noise measurements with the Close Proximity method
- 2020
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Ingår i: Measurement. - : Elsevier. - 0263-2241 .- 1873-412X. ; 162
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Tidskriftsartikel (refereegranskat)abstract
- Shore hardness measurements subject rubber bodies to standardized indentations. While easily performed, the measurements are subject to uncertainties. Although typical variances for Shore hardness are found in standards, operator and instrument effects are not well described, requiring statistically designed experiments to estimate effects and variance components. This paper focuses on uncertainty in Shore A hardness measurements of tyre tread elements and quantifies operator and instrument effects. Evaluation of uncertainty of Shore A measurements were performed on tyres under controlled conditions using three instruments, two tyres and five operators. Results show that the operator variance component and instrument effects are larger than the reference variance contribution in ISO 11819-3:2017. The interaction between operator and instrument is estimated to be the largest source of variation, while operator and instrument main effects are of similar size as the error component. Recommendations to reduce uncertainties include ignoring instantaneous values and requiring an instrument stand.
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| 2. |
- Finnsgård, Christian, 1974, et al.
(författare)
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Swedish shippers’ strategies for coping with slow-steaming in deep sea container shipping
- 2018
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Ingår i: Journal of Shipping and Trade. - : Springer Singapore. - 2364-4575. ; 3:8
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Tidskriftsartikel (refereegranskat)abstract
- When container shipping lines experience over-capacity and high fuel costs, they typically respond by decreasing sailing speeds and, consequently, increasing transport time. Most of the literature on this phenomenon, often referred to as slow-steaming, takes the perspective of the shipping lines addressing technical, operational and financial effects, or a society perspective focusing on lower emissions and energy use. Few studies investigate the effects on the demand side of the market for container liner shipping. Hence, the aim of this study is to elaborate on the logistics consequences of slow-steaming, particularly the strategies that Swedish shippers purchasing deep sea container transport services employ to mitigate the effects of slow-steaming. Workshops and semi-structured interviews revealed that shippers felt they had little or no impact on sailing schedules and were more or less subject to container shipping lines’ decisions. The effects of slow-steaming were obviously most severe for firms with complex supply chains, where intermediate products are sent back and forth between production stages on different continents. The shippers developed a set of strategies to cope with the low punctuality of containerised shipping, and these were categorised in the domains of transfer-the-problem, transport, sourcing and distribution, logistics and manufacturing, and product design. All firms applied changes in the transport domain, although the lack of service segmentation limited the effects of the strategy. Most measures were applied by two firms, whereas only one firm changed the product design.
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| 3. |
- Romano, Luigi, 1994, et al.
(författare)
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Brush tyre models for large camber angles and steering speeds
- 2022
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Ingår i: Vehicle System Dynamics. - : Informa UK Limited. - 1744-5159 .- 0042-3114. ; 60:4, s. 1341 -13492
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we discuss three improved brush models. The first one deals with the coupling between the slip and spin parameters and is valid for relatively high steering speed and small camber angles; the second one is more complex and considers the presence of a two-dimensional velocity field inside the contact patch due to large camber angles; the third one is more general and combines both the previous formulations. For the last two models, the investigation is conducted with respect to a rectangular contact patch, for which we show that three different regions can be identified, each of them corresponding to a different steady-state solution for the deflection of the bristle. Furthermore, from the transient analysis it emerges that each region can be in turn separated into an area in which steady-state conditions reign and another one in which the transient solution takes place. An asymptotic analysis is carried out for the three models and it is shown that the solutions are equivalent to the ones predicted by the standard brush theory for small values of the spin ratio and camber angle. Finally, a comparison is performed amongst the models to highlight the differences in the predicted tyre characteristics.
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| 4. |
- Thomson, Robert William, et al.
(författare)
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EDR Pre-Crash Data : Potential For Applications In Active Safety Testing
- 2013
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Ingår i: Proceedings of the 23rd International Technical Conference on the Enhanced Safety of Vehicles, May 2013, Seoul.
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Konferensbidrag (refereegranskat)abstract
- Passive safety testing has been based on accident research where objective physical evidence can be compiled and analysed when establishing technical test requirements. Active safety tests pose new challenges because objective data is more difficult to obtain. Until pre-crash variables became available in Event Data Recorders (EDR), the only sources of pre-crash vehicle motions were tire marks or witness statements. Both data sources have limitations since they may not always be available and require interpretation by the analyst. The pre-crash EDR data variables provide an objective source of data to active safety test development. However, the suitability of the data has not been thoroughly investigated in the published literature.The review of existing data shows that the variables identified in the new EDR requirement in FMVSS 563 are useful but incomplete for a comprehensive analysis of vehicle dynamics manoeuvres prior to a crash. In particular, the absence of vehicle yaw rate reduces the positioning accuracy of the vehicle in reconstructions. The objective data in the limited cases were used to compile the frequency of pre-crash braking and steering, and when possible, the magnitude of these driver inputs. Active Safety test development will benefit with more EDR analysis but the older data that does not conform to Part 563 has limited application.
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| 5. |
- Sharifzadeh, Seyed Mojtaba, 1988, et al.
(författare)
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An effective tyre to road friction estimation applied to heavy vehicles
- 2024
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Ingår i: Proceedings of the Institution of mechanical engineers. Part D, journal of automobile engineering. - : SAGE PUBLICATIONS LTD. - 0954-4070 .- 2041-2991.
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Tidskriftsartikel (refereegranskat)abstract
- Knowledge about the tyre to road friction is central to many vehicle functions as well as the overall performance of the vehicle. In this paper, a new real-time algorithm is presented for estimating the coefficient of friction using available on-board sensor information. A computationally efficient algorithm is presented, that reduces resources usage compared to previously published approaches. Issues connected to heavy vehicles and friction estimation is addressed, such as wind up of hub assembly and vehicle speed sensing. The performance of the algorithm is illustrated on data sets acquired from the test track recordings in winter conditions.
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| 6. |
- Li, Xin, 1985, et al.
(författare)
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Simulation of wheel–rail impact load and sleeper–ballast contact pressure in railway crossings using a Green's function approach
- 2019
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Ingår i: Journal of Sound and Vibration. - : Elsevier BV. - 1095-8568 .- 0022-460X. ; 463
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Tidskriftsartikel (refereegranskat)abstract
- A method for the simulation of dynamic vehicle–track interaction and evaluation of measures to improve the design of railway crossings is presented. To accurately represent the high-frequency dynamics and non-linear contact conditions of the vehicle–track system, the vertical interaction between a wheelset and the crossing is simulated in the time domain using a Green's function approach based on extensive finite element models of track and wheelset in combination with an implementation of Kalker's variational method to solve the non-Hertzian, and potentially multiple, wheel–rail contact. Both wheels of the wheelset in simultaneous contact with the crossing rail and the outer rail are considered. Rigid and flexible wheelset models are compared. The sampled contact geometry of the crossing, including the discrete irregularity between the wing rail and the crossing nose, is used to determine a three-dimensional surface geometry between each pair of adjacent rail cross-sections. A parameter study is performed to investigate the influence of crossing design on the maximum vertical wheel–rail contact force and the contact pressure generated at the sleeper–ballast interface. It is concluded that a design with a combination of increased sleeper width, softer rail pads and implementation of under sleeper pads (USP) will reduce the track stiffness gradients in the crossing panel and mitigate the risk of differential track settlement by lowering the sleeper–ballast contact pressure.
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| 7. |
- Nielsen, Jens, 1963, et al.
(författare)
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Wheel–Rail Impact Loads, Noise and Vibration: A Review of Excitation Mechanisms, Prediction Methods and Mitigation Measures
- 2021
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Ingår i: Notes on Numerical Fluid Mechanics and Multidisciplinary Design. - Cham : Springer International Publishing. - 1612-2909 .- 1860-0824. ; , s. 3-40, s. 3-40
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Railway noise and ground-borne vibration induced by wheel–rail impact loads are generated by discrete wheel/rail surface irregularities or local deviations in the nominal wheel–rail contact geometry. On the running surface of a rail, a discrete irregularity can be inherent to the railway design, for example at crossings or insulated joints. On the wheel or rail, the irregularity could also be the result of surface damage due to rolling contact fatigue cracking or a consequence of wheel sliding without rolling. This review describes the mechanisms of wheel–rail impact generated by wheel flats, rail joints and crossings. These can be a source of locally increased noise and vibration levels and increased annoyance, as well as of damage to vehicle and track components. The wheel–rail excitation at such irregularities, as indicated by the vertical wheel centre trajectory, leads to an abrupt change of momentum, potentially causing a momentary loss of wheel–rail contact followed by an impact on the rail. The resulting loading is a transient and often periodically repeated event exciting vibration in a wide frequency range with most of the energy concentrated below about 1 kHz. For the numerical prediction of high-magnitude transient loading and situations potentially leading to loss of contact, a non-linear wheel–rail contact model is required, implying that the simulation of contact force is carried out in the time domain. To avoid the need for large, computationally expensive models, a hybrid approach has been developed in which the time history of the contact force is transformed into an equivalent roughness spectrum; this is used as input to frequency-domain models for the prediction of noise and vibration. Since the excitation mechanism is similar to that for rolling noise, the same types of measures to mitigate wheel and track vibration can be applied. However, the main priority should be to control the irregularity by design and regular maintenance.
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| 8. |
- Carlberger, Andreas, 1992, et al.
(författare)
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An iterative methodology for the prediction of dynamic vehicle–track interaction and long-term periodic rail wear
- 2018
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Ingår i: Proceedings of the Institution of Mechanical Engineers, Part F: Journal of Rail and Rapid Transit. - : SAGE Publications. - 0954-4097 .- 2041-3017. ; 232:6, s. 1718-1730
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Tidskriftsartikel (refereegranskat)abstract
- In this study, a versatile numerical method for the prediction of long-term growth of rail roughness is presented and its functionality is demonstrated for the development of rail corrugation on small radius curves. The procedure includes two sub-modules: (1) a time-domain model for the simulation of dynamic vehicle–track interaction in a wide range of frequencies by using a commercial software for multibody dynamics and (2) a post-calculation of sliding wear based on the Archard’s model in combination with a non-Hertzian and transient wheel–rail contact model. The structural flexibility of the wheelset is accounted for by using the finite element method. The rail wear generated by a large number of passing trains is assessed by recurrently updating the rail surface based on the wear depth calculated in each post- processing step. The current work sets out from a previous study in which a model for the prediction of long-term growth of rail roughness on small radius curves was developed in a general-purpose programming language. By transfer- ring the model into a commercial software, the aim is to develop an engineering tool that is more applicable for different operational conditions, such as various vehicle and track designs and track alignments. The proposed method is verified by comparing the simulation results against those obtained with the pre-existing software. Conditions similar to a 120 m radius curve on the Stockholm metro exposed to corrugation growth on the low rail are considered. The corrugation is found to be generated by the leading wheelsets. The prevailing wavelength-fixing mechanisms are identified and discussed.
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| 9. |
- Genzel, Jonny, et al.
(författare)
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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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Ingår i: 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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Konferensbidrag (refereegranskat)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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| 10. |
- Torstensson, Peter, 1981, et al.
(författare)
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Rail Acceleration Induced by Train Pass-by—Field Measurements and Validation of a Simulation Model
- 2022
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Ingår i: Lecture Notes in Mechanical Engineering. - Cham : Springer International Publishing. - 2195-4356 .- 2195-4364. ; , s. 302-311, s. 302-311
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Konferensbidrag (refereegranskat)abstract
- The applicable frequency range of an existing code for simulation of vertical dynamic vehicle–track interaction is extended by implementation of a more advanced track model that includes the rail modelled by solid three-dimensional finite elements. In this paper, a previous validation of the software with respect to magnitudes of dynamic wheel–rail contact forces is supplemented by a comparison of measured and simulated rail accelerations at train pass-by. To this end, data collected as part of an extensive field measurement campaign related to the adaptation of the software CNOSSOS-EU to conditions on the Swedish railway infrastructure is used. In particular, the dataset includes measurements of track receptance, rail roughness, wheel out-of-roundness and pass-by rail acceleration. The results calculated when using a simplified two-dof mass-spring-damper wheelset model and a track model accounting for the rail by Rayleigh–Timoshenko beam elements show good agreement with those obtained for more advanced wheelset and track models deploying three-dimensional solid finite elements.
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