| 1. |
- Alemani, Mattia, et al.
(författare)
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A study on emission of airborne wear particles from car brake friction pairs
- 2015
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Ingår i: SAE International Journal of Materials & Manufacturing. - : SAE International. - 1946-3979 .- 1946-3987. ; 9:1, s. 147-157
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Tidskriftsartikel (refereegranskat)abstract
- The emission of airborne wear particles from friction material / cast iron pairs used in car brakes was investigated, paying special attention to the influence of temperature. Five low-metallic materials and one non-asbestos organic material were tested using a pin-on-disc machine. The machine was placed in a sealed chamber to allow airborne particle collection. The concentration and size distribution of 0.0056 to 10 μm particles were obtained by a fast mobility particle sizer and an optical particle sizer. The temperature was measured by a thermocouple installed in the disc. The experiments show that as the temperature increases from 100 to 300 °C the emission of ultrafine particles intensifies while that of coarse particles decreases. There is a critical temperature at which the ultrafine particle emission rate rises stepwise by 4 to 6 orders of magnitude. For the friction pairs investigated, the critical temperature was found to be between 165 and 190 °C. Below the critical temperature, fine particles outnumber coarse and ultrafine particles, although coarse particles make up the bulk of the particulate matter mass. The friction pairs differ in the ultrafine particle emission rate by 1 to 2 orders of magnitude. Above the critical temperature, ultrafine particles constitute almost 100% of the total particle number and their relative mass contribution can exceed 50%. Analysis of the particle size distributions revealed peaks at 0.19-0.29, 0.9 and 1.7 μm. Above the critical temperature, one more peak appears in the ultrafine particle range at 0.011-0.034 μm.
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| 2. |
- Biteus, Jonas, et al.
(författare)
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Planning Flexible Maintenance for Heavy Trucks using Machine Learning Models, Constraint Programming, and Route Optimization
- 2017
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Ingår i: SAE International Journal of Materials & Manufacturing. - : SAE International. - 1946-3979 .- 1946-3987. ; 10:3, s. 306-315
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Tidskriftsartikel (refereegranskat)abstract
- Maintenance planning of trucks at Scania have previously been done using static cyclic plans with fixed sets of maintenance tasks, determined by mileage, calendar time, and some data driven physical models. Flexible maintenance have improved the maintenance program with the addition of general data driven expert rules and the ability to move sub-sets of maintenance tasks between maintenance occasions. Meanwhile, successful modelling with machine learning on big data, automatic planning using constraint programming, and route optimization are hinting on the ability to achieve even higher fleet utilization by further improvements of the flexible maintenance. The maintenance program have therefore been partitioned into its smallest parts and formulated as individual constraint rules. The overall goal is to maximize the utilization of a fleet, i.e. maximize the ability to perform transport assignments, with respect to maintenance. A sub-goal is to minimize costs for vehicle break downs and the costs for maintenance actions. The maintenance planner takes as input customer preferences and maintenance task deadlines where the existing expert rule for the component has been replaced by a predictive model. Using machine learning, operational data have been used to train a predictive random forest model that can estimate the probability that a vehicle will have a breakdown given its operational data as input. The route optimization takes predicted vehicle health into consideration when optimizing routes and assignment allocations. The random forest model satisfactory predicts failures, the maintenance planner successfully computes consistent and good maintenance plans, and the route optimizer give optimal routes within tens of seconds of operation time. The model, the maintenance planner, and the route optimizer have been integrated into a demonstrator able to highlight the usability and feasibility of the suggested approach.
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| 3. |
- Björnsson, Andreas, 1981-, et al.
(författare)
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Low-cost Automation for Prepreg Handling - Two Cases from the Aerospace Industry
- 2015
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Ingår i: SAE International Journal of Materials & Manufacturing. - Warrendale, USA : SAE International. - 1946-3979 .- 1946-3987. ; 9:1, s. 68-74
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Tidskriftsartikel (refereegranskat)abstract
- With an increased use of composite materials within the aerospace industry follows a need for rational and cost-effective methods for composite manufacturing. Manual operations are still common for low to medium manufacturing volumes and complex products. Manual operations can for example be found in material handling, when picking prepreg plies from a cutter table and stacking them to form a plane laminate in preparation for a subsequent forming operation. Stacking operations of this kind often involves a great number of different ply geometries and removal of backing paper and other protecting materials like plastic. In this paper two different demonstrator cells for automated picking of prepreg plies and stacking of plane laminates are presented. One demonstrator is utilizing a standard industrial robot and an advanced end-effector to handle the ply variants. The other demonstrator is using a dual arm robot which allow for simpler end-effector design. In combination with a previously developed system for automated removal of backing papers both systems have shown to be capable of automatically picking prepreg plies from a plane surface and stack them to generate a flat multistack laminate. The dual arm approach has shown advantageous since it result in simpler end-effector design and a successive lay down sequence that result in good adhesion between the plies in the laminate. null.
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| 4. |
- Drignei, Dorin, et al.
(författare)
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A Variable-Size Local Domain Approach to Computer Model Validation in Design Optimization
- 2011
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Ingår i: SAE International Journal of Materials & Manufacturing. - : SAE International. - 1946-3979 .- 1946-3987. ; 4:1, s. 421-429
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Tidskriftsartikel (refereegranskat)abstract
- A common approach to the validation of simulation models focuses on validation throughout the entire design space. A more recent methodology validates designs as they are generated during a simulation-based optimization process. The latter method relies on validating the simulation model in a sequence of local domains. To improve its computational efficiency, this paper proposes an iterative process, where the size and shape of local domains at the current step are determined from a parametric bootstrap methodology involving maximum likelihood estimators of unknown model parameters from the previous step. Validation is carried out in the local domain at each step. The iterative process continues until the local domain does not change from iteration to iteration during the optimization process ensuring that a converged design optimum has been obtained. The proposed methodology is illustrated using a thermal, one-dimensional, linear heat conduction problem in a solid slab with heat flux boundary conditions
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| 5. |
- Farooqui, Maaz, et al.
(författare)
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Modeling and characterization of a porous metallic foam inside ducts
- 2015
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Ingår i: SAE International Journal of Materials & Manufacturing. - : SAE International. - 1946-3979 .- 1946-3987. ; 8:3, s. 937-945
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Tidskriftsartikel (refereegranskat)abstract
- A novel porous metallic foam has been studied in this work. This composite material is a mixture of resin and hollow spheres. It is lightweight, highly resistive to contamination and heat, and is capable of providing similar or better sound absorption compared to the conventional porous absorbers, but with a robust and less degradable properties. Several configurations of the material have been tested inside an expansion chamber with spatially periodic area changes. Bragg scattering was observed in some configurations with certain lattice constants. The acoustic properties of this material have been characterized from the measurement of the two-port matrix across a cylindrical sample. The complex density and speed of sound can be extracted from the transfer matrix using an optimization technique. Several models were developed to validate the effect of this metallic foam using Finite Elements and the Two-port Theory. There was a good agreement between both models and the measurement results.
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| 6. |
- Henriksson, Fredrik, et al.
(författare)
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Introduction of New Materials in the Automotive Industry : A Case Study-Based Framework
- 2021
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Ingår i: SAE International Journal of Materials & Manufacturing. - : SAE INT. - 1946-3979 .- 1946-3987. ; 14:1, s. 99-110
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Tidskriftsartikel (refereegranskat)abstract
- While new materials are introduced in the automotive industry regularly, there seems to be a lack of generalized frameworks for how to do this efficiently and effectively. Multiple studies have been published on material substitution in a specific component, but the applicability of these to other projects are unclear. Therefore, the authors propose a generalized framework for introduction of new materials in existing production systems in this article. In a study based on three cases in the Swedish automotive industry, the authors have found generalizable insights on challenges and opportunities when introducing new materials that could be converted into a framework for introduction of new materials in the automotive industry. This framework contains both organizational and technological aspects of new material introduction, and is built chronologically from the start of a material strategy framework formulation to the start of a material introduction project.
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| 7. |
- Karlsson, Mikael, et al.
(författare)
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A Note on the Applicability of Thermo-Acoustic Engines for Automotive Waste Heat Recovery
- 2016
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Ingår i: SAE International Journal of Materials & Manufacturing. - : SAE International. - 1946-3979 .- 1946-3987. ; 9:2, s. 286-293
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Tidskriftsartikel (refereegranskat)abstract
- A thermo-acoustic engine is a device converting thermal energy into high amplitude acoustic waves that can be harvested, for example, to obtain electricity. The core of the device is a stack/regenerator along which a temperature gradient is created using one hot and one cold heat exchanger. Correctly designed, the thermal interaction between the working fluid and the regenerator assists in amplifying incident acoustic waves. Previous studies have indicated good efficiency obtained with a system of low geometrical complexity. However, for the practical application of this technique it is vital to understand and identify critical design parameters and operating conditions. This is of special interest in automotive applications where the operating conditions vary significantly over a drive cycle. This works aims at providing a framework for studying the net power generation over a drive cycle. First, an engineering non-linear model for the efficiency of the thermo-acoustic engine is established. It is based on low-order acoustic networks that have the advantage of being computationally effective and allows for individual optimization of components. This model is then used to loop over a drive cycle of a typical commercial vehicle, while also accounting for pump losses given by the heat exchange processes. Although an engine not optimized for the present problem was used, promising performance, with a thermal efficiency of 7%, was found. Also the importance of adapting the engine to the varying operating conditions over the drive cycle was illustrated.
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| 8. |
- Molker, Henrik, 1979, et al.
(författare)
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Industrial framework for identification and verification of hot-spots in automotive composite structures
- 2019
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Ingår i: SAE International Journal of Materials and Manufacturing. - : SAE International. - 1946-3987 .- 1946-3979. ; 12:2, s. 17-120
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Tidskriftsartikel (refereegranskat)abstract
- In this article, a framework for efficient strength analysis of large and complex automotive composite structures is presented. This article focuses on processes and methods that are compliant with common practice in the automotive industry. The proposed framework uses efficient shell models for identification of hot spots, automated remodelling and analysis of found hot spots with high-fidelity models and finally an automated way of post-processing the detailed models. The process is developed to allow verification of a large number of load cases in large models and still consider all potential failure modes. The process is focused on laminated composite primary structures. This article highlights the challenges and tools for setting up this framework.
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| 9. |
- Öberg, Christian, et al.
(författare)
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Monotonic and Cyclic Creep of Cast Materials for Exhaust Manifolds
- 2019
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Ingår i: SAE International Journal of Materials & Manufacturing. - : SAE INT. - 1946-3979 .- 1946-3987. ; 12:2, s. 149-162
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Tidskriftsartikel (refereegranskat)abstract
- Cast materials are creep tested between 600 and 900 degrees C using three methods: (i) tensile testing at different strain rates, (ii) stress relaxation during thermal cycling and (iii) traditional creep tests at constant load. Comparisons are made between fast and slow methods and between monotonic and cyclic deformation modes. The tested materials, SiMo51, SiMo1000, Ni-resist D5S and HK30, are used for exhaust manifolds in heavy-duty diesel engines. The fast and cheap methods, (i) and (ii), were used on all materials, while the tedious and costly method, (iii), was used on SiMo51 only. The creep rates from monotonic tensile tests and stress relaxations during thermal cycling agree well. There is no difference between monotonic and cyclic creep rates, and cyclic rates are practically unchanged with the number of thermal cycles. No or small differences in creep rates are observed when comparing tension and compression, although three of the materials include large graphite nodules. At 700 degrees C, a Norton plot for SiMo51 shows coinciding results for tensile test and compressive stress relaxations, whereas the minimum creep rates from constant load tests fall one order of magnitude lower, but with the same slope. For all materials, the Norton creep parameters are evaluated with accurate reproduction of the experimental data. For HK30, two sets of parameters are needed because of deformation hardening.
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