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Technical Paper

Fatigue Life Prediction Method for Self-Piercing Rivets Considering Crack Propagation

2019-04-02
2019-01-0531
This paper describes a numerical prediction method for fatigue strength of Self Piercing Rivets (SPRs) using fracture mechanics. Recently, high strength steels and non-ferrous metals have been adopted to light weight automotive bodies. Various types of joining are proposed for multi-material bodies. It is important to predict the fatigue life of these joints using numerical simulation. However, the fatigue strength of these joints is related to sheet thickness, base materials, and loading conditions. Therefore, a large number of coupon tests are necessary to determine the S-N curve for the fatigue life prediction of joints in the automotive body. To reduce the amount of coupon testing, numerical simulation will be an efficient method in obtaining the S-N curve of these joints. The fatigue fracture process consists of two stages, crack initiation and crack growth. There are many studies about crack growth estimation methods using stress intensity factor.
Technical Paper

A Target Cascading Method Using Model Based Simulation in Early Stage of Vehicle Development

2019-04-02
2019-01-0836
In the early stages of vehicle development, it is important for decision makers to understand a feasible constraint region that satisfies all system level requirements. The purpose of this paper is to propose a target cascading method to solve for a feasible design region which satisfies all constraints of the system based on model based simulation. In this method, the feasible design region is explored by using both global optimization methods and active learning techniques. In optimization problems, the inverse problem for understanding feasibility for specific designs is defined and solved. To determine the objective functions of the inverse problem, an index representing the achievement level of constraints from system requirements is introduced. To predict feasible regions in the specific design space, a surrogate model of minimized values of the index is trained by using a kriging model.
Technical Paper

Reference PMHS Sled Tests to Assess Submarining of the Small Female

2018-11-12
2018-22-0003
In the last decade, extensive efforts have been made to understand the physics of submarining and its consequences in terms of abdominal injuries. For that purpose, 27 Post Mortem Human Subject (PMHS) tests were performed in well controlled conditions on a sled and response corridors were provided to assess the biofidelity of dummies or human body models. All these efforts were based on the 50th percentile male. In parallel, efforts were initiated to transfer the understanding of submarining and the prediction criteria to the THOR dummies. Both the biofidelity targets and the criteria were scaled down from the 50th percentile male to the 5th percentile THOR female. The objective of this project was to run a set of reference PMHS tests in order to check the biofidelity of the THOR F05 in terms of submarining. Three series of tests were performed on nine PMHS, the first one was designed to avoid submarining, the second and third ones were designed to result in submarining.
Technical Paper

Development of CFD Inverse Analysis Technology Targeting Heat or Concentration Performance Using the Adjoint Method and Its Application to Actual Components

2018-04-03
2018-01-1033
To resolve two major problems of conventional CFD-based shape optimization technology: (1) dependence of the outcome on the selection of design parameters, and (2) high computational costs, two types of innovative inverse analysis technologies based on a mathematical theory called the Adjoint Method were developed in previous studies for maximizing an arbitrary hydrodynamic performance aspect as the cost function: surface geometry deformation sensitivity analysis to identify the locations to be modified, and topology optimization to generate an optimal shape. Furthermore, these technologies were extended to transient flows by the application of the transient Adjoint Method theory. However, there are many cases around flow path shapes in vehicles where performance with respect to heat or concentration, such as the total amount of heat transfer or the flow rate of a specific gas component, is very important.
Technical Paper

New 2.0L I4 Gasoline Direct Injection Engine with Toyota New Global Architecture Concept

2018-04-03
2018-01-0370
Toyota Motor Corporation has developed a new 2.0L Inline 4- Cylinder (I4) Gasoline Direct Injection Engine, the second Naturally Aspirated (NA) engine of the Toyota New Global Architecture (TNGA) engine series, to meet our customers’ expectations for drivability, performance, and fuel economy. The high speed combustion technologies adopted previously in our 2.5 L NA conventional and Hybrid Vehicle (HV) engines for the 2018 Toyota Camry are necessary for high engine power and thermal efficiency. To adopt our high speed combustion technology on engines with different displacements, the turbulence intensity has been defined as the target index of combustion speed. The basic engine structure has been revised by using Computational Fluid Dynamics (CFD) analysis to achieve the combustion target.
Technical Paper

Toyota’s New Driveline for FR Passenger Vehicles

2017-03-28
2017-01-1130
The renewed platform of the upcoming flagship front-engine, rear-wheel drive (FR) vehicles demands high levels of driving performance, fuel efficiency and noise-vibration performance. The newly developed driveline system must balance these conflicting performance attributes by adopting new technologies. This article focuses on several technologies that were needed in order to meet the demand for noise-vibration performance and fuel efficiency. For noise-vibration performance, this article will focus on propeller shaft low frequency noise (booming noise). This noise level is determined by the propeller shaft’s excitation force and the sensitivity of differential mounting system. In regards to the propeller shaft’s excitation force, the contribution of the axial excitation force was clarified. This excitation force was decreased by adopting a double offset joint (DOJ) as the propeller shaft’s second joint and low stiffness rubber couplings as the first and third joints.
Journal Article

A CFD Analysis Method for Prediction of Vehicle Exterior Wind Noise

2017-03-28
2017-01-1539
High frequency wind noise caused by turbulent flow around the front pillars of a vehicle is an important factor for customer perception of ride comfort. In order to reduce undesirable interior wind noise during vehicle development process, a calculation and visualization method for exterior wind noise with an acceptable computational cost and adequate accuracy is required. In this paper an index for prediction of the strength of exterior wind noise, referred to as Exterior Noise Power (ENP), is developed based on an assumption that the acoustic power of exterior wind noise can be approximated by the far field acoustic power radiated from vehicle surface. Using the well-known Curle’s equation, ENP can be represented as a surface integral of an acoustic intensity distribution, referred to as Exterior Noise Power Distribution (ENPD). ENPD is estimated from turbulent surface pressure fluctuation and mean convective velocity in the vicinity of the vehicle surface.
Technical Paper

Synchrotron X-Ray Visualization and Simulation for Operating Fuel Cell Diffusion Layers

2017-03-28
2017-01-1188
The key challenge in designing a high power density fuel cell is to reduce oxygen transport loss due to liquid water. However, liquid water transport from catalyst layers to channels under operating conditions is not completely understood. Toyota developed a high resolution space and time liquid water visualization technique using synchrotron x-ray (Spring-8) radiography. In addition, a simulation method was created based on computational fluid dynamics (CFD) to identify the cell performance relationship to water distribution. The relationship among gas diffusion layer (GDL) parameters, water distribution, and fuel cell performance was clarified by combining the techniques Toyota developed.
Journal Article

An Application of a Model-Prediction-Based Reference Modification Algorithm to Engine Air Path Control

2017-03-28
2017-01-0586
In real-world automotive control, there are many constraints to be considered. In order to explicitly treat the constraints, we introduce a model-prediction-based algorithm called a reference governor (RG). The RG generates modified references so that predicted future variables in a closed-loop system satisfy their constraints. One merit of introducing the RG is that effort required in control development and calibration would be reduced. In the preceding research work by Nakada et al., only a single reference case was considered. However, it is difficult to extend the previous work to more complicated systems with multiple references such as the air path control of a diesel engine due to interference between the boosting and exhaust gas recirculation (EGR) systems. Moreover, in the air path control, multiple constraints need to be considered to ensure hardware limits. Hence, it is quite beneficial to cultivate RG methodologies to deal with multiple references and constraints.
Technical Paper

Internal Thrust Force Analysis of CVT Push Belt

2016-10-17
2016-01-2353
A CVT belt is composed of multiple elements and layered rings. Each of these component parts generates loss, including relative slippage caused by the geometrical relationship between the elements and innermost ring layer. An effective way of increasing CVT efficiency is to reduce this slippage. However, since the relative slippage also controls whether the rings transmit constant torque at all times, reducing the slippage will also have an effect on the torque transmission performance of the rings. Therefore, to improve CVT efficiency by reducing the relative slippage, it is first necessary to analyze the changes to torque transmission. However, this slippage is a phenomenon of the inner portion of the belt and it is extremely difficult to identify the internal thrust force when actual load is applied. This paper describes experiments carried out to analyze the changes in each torque transmission ratio when the relative slippage between the elements and innermost ring layer changes.
Technical Paper

Development of CFD Method for Spray Shape Estimation

2016-10-17
2016-01-2198
Computational fluid dynamic (CFD) is widely used to develop engine combustion. Especially the in-cylinder spray calculation is important in order to resolve the issues of direct injection gasoline engines (e.g., particulate matter (PM) and oil dilution caused by fuel wetting on the cylinder walls). Conventional spray calculation methods require fitting based on measurements of spray characteristics such as penetration and droplet diameter (i.e., the Sauter mean diameter (SMD)). Particularly in the case of slit nozzle shapes that widen from the inlet to the outlet to form a fan-shaped spray, fitting the shape of spray is a complex procedure because the flow inside the nozzle is not uniform. In response, a new calculation method has been developed that eliminates the need for spray shape fitting by combining calculations of the Eulerian multiphase and the Lagrangian multiphase.
Journal Article

Low-viscosity Gear Oil Technology to Improve Wear at Tapered Roller Bearings in Differential Gear Unit

2016-10-17
2016-01-2204
Torque loss reduction at differential gear unit is important to improve the fuel economy of automobiles. One effective way is to decrease the viscosity of lubricants as it results in less churning loss. However, this option creates a higher potential for thin oil films, which could damage the mechanical parts. At tapered roller bearings, in particular, wear at the large end face of rollers and its counterpart, known as bearing bottom wear is one of major failure modes. To understand the wear mechanism, wear at the rolling contact surface of rollers and its counterpart, known as bearing side wear, was also observed to confirm the wear impact on the tapered roller bearings. Because gear oils are also required to avoid seizure under extreme pressure, the combination of a phosphorus anti-wear agent and a sulfurous extreme pressure agent are formulated.
Technical Paper

Ball Behavior Analysis of Rzeppa Constant Velocity Joint

2016-04-05
2016-01-1135
Driveshafts are composed of a transmission side joint, wheel side joint, and shaft which connect the two joints. The Rzeppa type constant velocity joint (CVJ) is usually selected as the wheel side joint of a drive shaft for front wheel drive automobiles. Due to recent needs of fuel efficiency and lighter weight for vehicles, it is necessary to reduce the joint size and improve the efficiency of a CVJ. In order to reduce the weight, solving tribology details for long life under high contact pressure is an important issue for developing a CVJ. It is difficult to understand the characteristics of a contact surface, such as relative slip velocity or spin behavior, because the outer race, inner race, cage, and balls, act complicatedly and exchange loads at many points. Meanwhile, after joint endurance tests, ball spalling marks at pole of the ball are sometimes observed.
Technical Paper

Analysis for Vibration Caused by Starter Shaft Resonance

2016-04-05
2016-01-1319
It is important for vehicle concept planning to estimate fuel economy and the influence of vehicle vibration using virtual engine specifications and a virtual vehicle frame. In our former study, we showed the 1D physical power plant model with electrical starter, battery that can predict combustion transient torque, combustion heat energy and fuel efficiency. The simulation result agreed with measured data. For idling stop system, the noise and vibration during start up is important factor for salability of the vehicle. In this paper, as an application of the 1D physical power plant model (engine model), we will show the result of analysis that is starter shaft resonance and the effect on the engine mount vibration of restarting from idle stop. First, an engine model for 3.5L 6cyl NA engine was developed by energy-based model using VHDL-AMS. Here, VHDL-AMS is modeling language registered in IEC international standard (IEC61691-6) to realize multi physics on 1D simulation.
Technical Paper

Solar Module Laminated Constitution for Automobiles

2016-04-05
2016-01-0351
Replacing the metal car roof with conventional solar modules results in the increase of total car weight and change of center of mass, which is not preferable for car designing. Therefore, weight reduction is required for solar modules to be equipped on vehicles. Exchanging glass to plastic for the cover plate of solar module is one of the major approaches to reduce weight; however, load bearing property, impact resistance, thermal deformation, and weatherability become new challenges. In this paper a new solar module structure that weighs as light as conventional steel car roofs, resolving these challenges is proposed.
Technical Paper

Improvement of Adhesion Properties between Epoxy Resin and Primer and between Primer and Ni Plating in Hybrid Vehicle Power Semiconductor Module under High Temperature Conditions

2016-04-05
2016-01-0500
In this report, adhesion mechanism between epoxy resin and primer and between primer and Ni platting in Hybrid vehicle (HV) was investigated. Adhesion forces are thought to be a combination of mechanical bond forces (such as anchor effect), chemical bond forces and physical bond forces (such as hydrogen bonding and Van der Waals force). Currently there is insufficient understanding of the adhesion mechanism. In particular, the extent to which the three bond forces contribute to adhesion strength. So the adhesion mechanism of polyimide primers was analyzed using a number of different methods, including transmission electron microscope (TEM) and atomic force microscope (AFM) observation, to determine the contributions of the three bonding forces. Molecular simulation was also used to investigate the relationship between adhesion strength and the molecular structure of the primer.
Technical Paper

Development of Bicycle Carrier for Bicyclist Pre-Collision System Evaluation

2016-04-05
2016-01-1446
According to the U.S. National Highway Traffic Safety Administration, 743 pedal cyclists were killed and 48,000 were injured in motor vehicle crashes in 2013. As a novel active safety equipment to mitigate bicyclist crashes, bicyclist Pre-Collision Systems (PCSs) are being developed by many vehicle manufacturers. Therefore, developing equipment for evaluating bicyclist PCS is essential. This paper describes the development of a bicycle carrier for carrying the surrogate bicyclist in bicyclist PCS testing. An analysis on the United States national crash databases and videos from TASI 110 car naturalistic driving database was conducted to determine a set of most common crash scenarios, the motion speed and profile of bicycles. The bicycle carrier was designed to carry or pull the surrogate bicyclist for bicycle PCS evaluation. The carrier is a platform with a 4 wheel differential driving system.
Technical Paper

Pre-Collision System for Toyota Safety Sense

2016-04-05
2016-01-1458
Toyota Safety Sense is a safety system package developed to help drivers avoid accident types with a high frequency of occurrence. This paper deals with pre-collision system which forms the core of Toyota Safety Sense, especially Toyota Safety Sense P which uses a combined sensor configuration consisting of a monocular camera paired with millimeter wave radar, in order to achieve both high recognition performance and reliability. The use of a wide-angle monocular camera, millimeter wave radar integrated in the front grill emblem, and a collision determination algorithm for pedestrian targets enabled the development of a pre-collision system comprising detection capability of crossing pedestrians. Toyota has developed warning and pre-collision brake assist for driver to assist in avoiding a collision effectively; In addition, Pre-collision brake has achieved high level of performance for the drivers who cannot avoid a collision.
Journal Article

Development of CFD Inverse Analysis Technology Using the Transient Adjoint Method and Its Application to Engine In-Cylinder Flow

2016-04-05
2016-01-0607
Conventional CFD-based shape optimization technology that uses parametric shape modification and optimal solutions searching algorithms has the two problems: (1) outcome of optimized shapes depend on the selection of design parameters made by the designer, and (2) high computational costs. To resolve those problems, two innovative inverse analysis technologies based on the Adjoint Method were developed in previous study: surface geometry deformation sensitivity analysis to identify the locations to be modified, and topology optimization to generate an optimal shape for maximizing the cost function in the constrained design space. However, these technologies are only applicable to steady flows. Since most flows in a vehicle (such as engine in-cylinder flow) are transient, a practical technology for surface geometry sensitivity analysis has been developed based on the Transient Adjoint Method.
Journal Article

High Efficiency Electromagnetic Torque Converter for Hybrid Electric Vehicles

2016-04-05
2016-01-1162
A new concept of an electromagnetic torque converter for hybrid electric vehicles is proposed. The electromagnetic torque converter, which is an electric system comprised of a set of double rotors and a stator, works as a high-efficiency transmission in the driving conditions of low gear ratio including a vehicle moving-off and as a starting device for an internal combustion engine. Moreover, it can be used for an electric vehicle driving as well as for a regenerative braking. In this concept, a high-efficiency drivetrain system for hybrid electric vehicles is constructed by replacing a fluid-type torque converter with the electromagnetic torque converter in the automatic transmission of a conventional vehicle. In this paper, we present the newly developed electromagnetic torque converter with a compact structure that enables mounting on a vehicle, and we evaluate its transmission efficiency by experiment.
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