Search Results

The application of high-strength steel sheets to car bodies is expanding to improve the crashworthiness and achieve weight reduction [1, 2]. Conversely, in recent years, the occurrence of liquid metal embrittlement (LME) cracks has been discussed in resistance spot welding using a Zn-based coated high-strength steel [3-5]. This study examined the factors causing LME cracks and identified the locations of LME cracks found in resistance spot welds using a Zn-coated high-strength steel sheet. Furthermore, through an analytical approach using a scanning electron microscopy (SEM) and transmission electron microscopy (TEM), for a joint with an LME crack, it was found that (1) grain boundary fracture occurred at LME crack portion and its fracture surface was covered with Zn, (2) Zn penetrated into prior-austenite grain boundaries near the LME crack, and (3) Zn concentration decreased toward the tip of the Zn-penetrated site.

Gasoline engines have the trace-knock phenomena induced by the fast combustion which happens a few times during 100 cycles. And that constrains the thermal efficiency improvement due to limiting the ignition timing advance. So the authors have been dedicating a trace-knock simulation so that we could obtain any pieces of information associated with trace-knock characteristics. This simulation consists of a turbulent combustion model, a cycle-by-cycle variation model and a chemical calculation subprogram. In the combustion model, a combustion zone is considered in order to obtain proper turbulent combustion speed through wide range of engine speed. From a cycle-by-cycle variation analysis of an actual gasoline engine, some trace-knock features were detected, and they were involved in the cycle-by-cycle variation model. And a reduced elementary reaction model of gasoline PRF (primary reference fuel) was customized to the knocking prediction, and it was used in the chemical calculation.

The automotive refrigerant system can occasionally exhibit an excessive noise out of air-conditioner (A/C) vents during vehicle’s developments. If the vehicle has been parked for long hours in summer and the A/C system is turned on, sometimes hissing noise is induced by the refrigerant flow. In order to understand the mechanism, a lot of bench and vehicle tests were conducted. However, there is still not enough to understand the physical behavior in detail. Therefore, for the first step, the visualization method to capture the behavior of multi-phased refrigerant flow jet inside the pipe was proposed with a high-speed camera, some light devices and acrylic test piece. In addition, image analysis to quantify the flow regime from a series of observed snapshots. Using proposed method, the correlation study between flow and noise was performed at A/C bench test. As a result, different flow features such as the velocity can be observed in the occurrence of the noise or not.

Improving fuel efficiency often affects NVH performance. Modifying a vehicle’s design in the latter stages of development to improve NVH performance is often costly. Therefore, to optimize the cost performance, a Multi-Attribute Balancing (MAB) approach should be employed in the early design phases. This paper proposes a solution based on a unified 1D system simulation model across different vehicle performance areas. In the scope of this paper the following attributes are studied: Fuel economy, Booming, Idle, Engine start and Drivability. The challenges to be solved by 1D simulation are the vehicle performance predictions, taking into account the computation time and accuracy. Early phase studies require a large number of scenarios to evaluate multiple possible parameter combinations employing a multi-attribute approach with a systematic tool to ease setup and evaluation according to the determined performance metrics.

Without engine noise, the cabin of an electric vehicle is quiet, but on the other hand, it becomes easy to perceive refrigerant-induced noise in the automotive air-conditioning (A/C) system. When determining the A/C system at the design stage, it is crucial to verify whether refrigerant-induced noise occurs in the system or not before the real A/C systems are made. If refrigerant-induced noise almost never occurs during the design stage, it is difficult to evaluate by vehicle testing at the development stage. This paper presents a 1D modeling methodology for the assessment of refrigerant-induced noise such as self-excitation noise generated by pressure pulsation through the thermal expansion valve (TXV). The GT-SUITE commercial code was used to develop a refrigerant cycle model consisting of a compressor, condenser, evaporator, TXV and the connecting pipe network.

Recently, the evaluation of the thermal environment of an engine compartment has become more difficult because of the increased employment and installation of turbochargers. This paper proposes a new prediction model of the momentum source for the turbine of a turbocharger, which is applicable to three-dimensional thermal fluid analyses of vehicle exhaust systems during the actual vehicle development phase. Taking the computational cost into account, the fluid force given by the turbine blades is imitated by adding an external source term to the Navier-Stokes equations corresponding to the optional domain without the computational grids of the actual blades. The mass flow rate through the turbine, blade angle, and number of blade revolutions are used as input data, and then the source is calculated to satisfy the law of the conservation of angular momentum.

Torque profile control is one of required technologies for propulsion engines. A smaller parametric model is more preferable for control algorithm design and evaluation. Mean value engine torque can be obtained from throttle opening change using a transfer function. A transfer function for a turbocharged engine was investigated with thermo-dynamic equations for a turbine and a compressor and test data. A small turbocharged engine was tested to model the air transfer process. Turbine speed was measured with temperatures, pressures and air mass flow. Turbine speed response is like a first order system to air mass flow into a combustion chamber. The pressure ratio at the compressor is approximated by a curve proportional to the turbine speed square. Based on those findings, a reduced order model for describing dynamic air transfer process with a turbocharger was constructed. The proposed model is compact and suitable for engine torque control design and controller implementation.

To research the mechanism of automobile aerodynamic noise which transmits to the inside of a cabin, flow structure and sound field have been investigated by applying experimental measurements at the wind tunnel and computational fluid dynamics (CFD) based on lattice Boltzmann method (LBM). In this research, transmitted noise at a front side window glass is focused. Pressure fluctuations on the side window glass contain both hydrodynamic pressure fluctuations induced by convection of flow field and acoustic pressure fluctuations propagated from noise sources. But it was found that acoustic pressure fluctuations have large contributions on the side window glass at the high frequency range by considering of the experimental transmission loss. On the other hand, at the low frequency range, hydrodynamic pressure fluctuations are dominant, however their effects to transmitted noise are not so influential for high fluctuation levels.

Accuracy of numerical simulation has to be evaluated through the actual phenomenon such as experiment or measurement and then it can be employed to design the air-conditioning system of car cabin at the development phase. Scaled model of vehicle cabin was created by the Society of Automotive Engineers of Japan (JSAE) and the experiment was performed to obtain the detailed information of heat transfer characteristics inside the cabin under the non-isothermal condition. The sheet heaters were put to the inner surface of the acrylic cabin and they supplied certain amount of heat. The temperatures of inner and outer surface and air were measured to evaluate the thermal environment of the cabin. The results lead to enhancement of the data of the standard model of the cabin.

Automotive fenders is one such example where specialized thermoplastic material Noryl GTX* (blend of Polyphenyleneoxide (PPO) + Polyamide (PA)) has successfully replaced metal by meeting functional requirements. The evolution of a fender design to fulfill these requirements is often obtained through a combination of unique material properties and predictive engineering backed design process that accounts for fender behavior during the various phases of its lifecycle. This paper gives an overview of the collaborative design process between Mitsubishi Motors Corporation and SABIC Innovative Plastics and the role of predictive engineering in the evolution of a thermoplastic fender design of Mitsubishi Motors Corporation's compact SUV RVR fender launched recently. While significant predictive work was done on manufacturing and use stage design aspects, the focus of this paper is the design work related to identifying support configuration during the paint bake cycle.

OBD (On Board Diagnosis) has been applied to detect malfunctions in powertrains. OBD requirements have been extended to detect various failures for ensuring the vehicle emission control system being normal. That causes further costs for additional sensors and software works. Two layers diagnosis system is proposed for a passenger car gearbox system to detect changes from normal behavior. Conventional physical constraints based diagnosis is placed on the base layer. Model based diagnosis and specific symptom finding diagnosis are built on the second layer. Conventional physical constraints based diagnosis is direct and effective way to detect the failure of system if the detected signals exceed their normal ranges. However under the case of system failure with related signals still remain in normal ranges, the conventional detection measures can not work normally. Under this case, Model based diagnosis is proposed to enhance the functionality of diagnosis system.

This paper proposes a rolling machine that forms fine corrugated section patterns for thin sheets. A prototype of the machine was made and the performance of the machine was tested. As compared with press forming, rolling has the advantages of the high forming limit, the low forming reaction force, the easy control of the thin sheet's curve and high productivity. We confirmed these four advantages by using finite element analyses and the prototype rolling machine. Stainless steel sheets and titanium sheets, which were one of the materials with a low forming limit, were used. Firstly, the rolling showed a 1.3-times higher forming limit than the press forming in the case that a fine corrugated section pattern was formed in a stainless steel sheet of 22-mm square sizes. Secondly, the forming reaction force of the rolling was about one-twentieth of the press forming without coining, and the experimental results agreed with the finite element simulation.

Rapid Controller Prototyping (RCP) is an efficient method for design & development of ECU (Electronic Controller Unit) at early stage. Usually, RCP requires firstly performing Software-in-the-loop simulation and then connecting universal controller (e.g. MicroAutoBox) to real controlled system for testing of controller functionality. During this process, it is likely that some problems related to signal configuration and real time characteristics occur and consequently give rise to unexpected results, e.g., sensor signals or controlling signals produce large deviation and possibly damage components of real system under severe condition. On the other hand, it cannot make sure that the real time characteristics of designed controller are suitable just after applying Software-in-the-loop simulation.

In the present study, a model experiment is performed in order to clarify the ventilation characteristics of car cabin. This study also provides high precision data for benchmark test. As a first step, the ventilation mode is tested, which is one of the representative air-distribution modes. Part 1 describes the properties of the flow field in the cabin obtained by the experiment. Part 2 describes the ventilation efficiencies such as the age of air by using trace gas method. The properties of flow field are measured using particle image velocimetry (PIV). The mean velocity profiles, the standard deviation distribution, and the turbulence intensity distribution are discussed. The brief comparison between experiments and predictions of computational fluid dynamics (CFD) is also presented. In the comparison between experiment and CFD, the results showed similar flow field.

Flows around a forward facing step and a fence are simulated on structured grid to estimate aerodynamic noise by using direct simulation. Calculated results of sound pressure level show quantitatively good agreement with experimental results. To estimate aerodynamic noise from 3D complex geometry, a simplified side mirror model is also calculated. Averaged pressure distribution on the mirror surface as well as pressure fluctuations on the mirror surface and ground are simulated properly. However, calculated result of sound pressure level at a location is about 20dB higher than experiment due to insufficient spatial resolution. To capture the propagation of sound waves, more accuracy seems to be required.

The combination of 1D and 3D fluid flow models is achieved using a co-simulation methodology. This realizes that the internal flow in a component simulated in 3D is incorporated into a network (system) containing components represented in 1D. This methodology gives the details of the internal flow while conserving overall mass flow in the system, thus eliminating uncertainties in boundary conditions prescribed in the 3D model and reducing the overall simulation time. This paper shows numerical results for internal flow of water flow circuit of engine cooling system and availability and current problem of 1D/3D co-simulation method are discussed.

This paper investigates the potential of using FEA poro-elastic Biot elements for the modeling carpet-like trim systems in a simplified setup. A comparison between FEA computations and experiments is presented for two layer (mass-spring) trim systems placed on a test-rig consisting in a 510×354×1.6 mm flat steel plate clamped in a stiff frame excited at its base. Results are presented for a given heavy layer with two different poro-elastic materials: one foam and one fibrous material. The investigations included accelerometer measurements on the steel plate, laser-doppler vibrometer scans of the heavy layer surface, sound pressure measurements in free field at a distance of 1 meter above the plate, as well as sound pressure in a closed rectangular concrete-walled cavity (0.5×0.6×0.7 m) put on top of the test-rig. Computations were carried out using a commercial FEA software implementing the Biot theory for poro-elastic media.

In this study, with the purpose of applying to the metal catalyst substrates, we have examined the feasibility of improving the light-off performance of a catalytic converter by enhancing heat transfer in the cells with heat-transfer promoters. Experimental and CFD analyses have been conducted to estimate heat transfer rates and pressure losses of the model cells with hemispherical protrusions. The analyses show that, by enhancing heat transfer of the cells, the cell density can be reduced keeping the catalytic performance in the steady state at the same level as that of conventional ones. As a result, the thermal mass of the substrate can be also reduced effectively without an increase of the pressure loss, and consequently the light-off performance of the catalytic converter can be improved noticeably.

The Strategic Alliance for Steel Fuel Tanks (SASFT), an international group of steel producers and manufacturing companies, recently completed a major corrosion study of various steel ‘systems’ for automobile fuel tanks. The ten steel systems included low carbon steels (either pre-painted or post-painted with protective coatings) and stainless steels. The 2-year corrosion test program included testing in salt solutions to simulate road environments for the exterior of a fuel tank. Special test specimens were designed to represent a manufactured tank. The external tests used were the Neutral Salt Spray test (ASTM B117) with exposures up to 2000 hours and the Cyclic Corrosion test (SAE J2334) with exposures up to 120 and 160 cycles to represent vehicle lives of 15 years and 20 years, respectively. Additionally, the resistance to an aggressive ethanol-containing fuel (internal tank corrosion) was assessed by using uniquely designed drawn cups of the various steel systems.

A new single-brick Ba + alkali metals NOx-Trap catalyst has been developed to replace a two-brick NOx-Trap system containing a downstream three-way catalyst. Major development efforts include: 1) platinum group metals selection for higher HC oxidation with potassium-containing washcoat, 2) alumina and ceria selection, and Rh architecture design for more efficient NOx reduction and 3) NiO to suppress H2S odor. Mitsubishi Motors' 1.8L GDI™ with this Delphi new NOx-Trap catalyst with H2S control achieves J-LEV standard with less cost and lower backpressure compared to the previous model. It is further discovered that incorporation of NiO into the NOx-Trap washcoat is effective for H2S control during sulfur purge but has a negative impact on thermal durability and sulfur resistance. Further study to improve this trade-off has been made and preliminary results of an advanced washcoat design are presented in this paper. Details will be reported in a future publication.