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Technical Paper

A Statistical Method to Substructure Crash Simulation Model

2021-12-03
2021-01-5107
This work presents a statistical method to use a portion of a full finite element vehicle model on a crash analysis event. The substructure model is linked to the full model by recording the interface boundary history. The lateral moving deformable barrier (MDB) test by the Insurance Institute for Highway Safety (IIHS) is used to demonstrate this substructure method: Substructure portion is identified by energy absorption distribution, and noise elements are filtered out by density-based spatial clustering of applications with noise (DBSCAN), a nonsupervised machine learning method. Crashworthiness simulation is performed in LS-DYNA software, and results between substructure vehicle model, full vehicle model, and physical vehicle test results are compared. It shows the result from the substructure model is more effective without accuracy compromise.
Technical Paper

Grid Independence Validation and Numerical Simulation of an Opposed-Piston Free-Piston Engine

2021-11-23
2021-01-5104
To evaluate the grid independence of the in-cylinder numerical simulation, the combustion chamber model of an opposed-piston free-piston engine was divided into three styles: structured, unstructured, and hybrid meshes. Furthermore, the grid independence of the hybrid mesh was analyzed using different grid resolutions. In order to avoid the influence of subjective judgments, the grid resolution is introduced to characterize the degree of grid refinement, combined with the grid convergence index (GCI) to assess the convergence of simulation. The results show that there are differences in the flow fields for the different grid styles. In addition, the hybrid mesh captured more small-scale swirls around the intake and exhaust ports. When the resolution reached 12, the GCI was less than 6%, indicating that the numerical simulation was impervious to the grid resolution. Moreover, the mixing distribution hardly changed when the resolution reached 12.
Research Report

Unsettled Aspects of the Digital Thread in Additive Manufacturing

2021-11-15
EPR2021026
Additive manufacturing (AM), also known as “3D printing,” now provides the ability to have an almost fully digital chain from part design through manufacture and service. This “digital thread” can bring great benefits in improving designs, processes, materials, operations, and the ability to predict failure in a way that maximizes safety and minimizes cost and downtime. Unsettled Aspects of the Digital Thread in Additive Manufacturing discusses what the interplay between AM and a digital thread in the mobility industry would look like, the potential benefits and costs, the hurdles that need to be overcome for the combination to be useful, and how an organization can answer these questions to scope and benefit from the combination. Click here to access the full SAE EDGETM Research Report portfolio.
Technical Paper

Seat Belts: A Review of Technological Milestones, Regulatory Advancements, and Anticipated Future Trajectories

2021-10-21
2021-01-5097
Decades after their introduction, seat belts remain the most important safety innovation in automotive history. Seat belt usage remains the single most effective way to minimize the risk of injury or death in severe crash events. Despite having matured, seat belts continue to evolve and improve and are expected to play an equally critical role in future passenger vehicles as increasing automation leads to changes in occupant compartment design and occupant-to-vehicle interaction. In this paper, an overview of major technical milestones in the development of seat belts is presented, ranging from the earliest lap belts to today’s systems that seamlessly synthesize and integrate information from a variety of sensors to prepare the restraints for an imminent crash. A brief overview of contemporary regulatory events is also provided, illustrating how regulatory actions have followed and occasionally driven the development and proliferation of various aspects of occupant restraints.
Technical Paper

The Behavior of Fuel Droplets on a Heated Substrate

2021-10-15
2021-01-5099
The processes of surface wetting and film evaporation play a major role in any application using liquid fuels. Since the behavior of entire multi-liquid films is influenced by many simultaneously occurring physical processes, exact modeling is not yet possible. In order to reduce the complexity and to determine the basic effects in the spreading and evaporation of multi-component films, this study was carried out by placing single 5 μl droplets on a heated metal surface. Various alkanes, ethanol, and mixtures, as well as real gasoline, were studied at surface temperatures between 69°C and 140°C. To describe the processes qualitatively and determine the time-dependent wetted surface area, the droplets were visualized using cameras. With the results, it was possible to determine the course of the wetted surface over time and to compare different liquids under varying surface temperatures.
Technical Paper

Lining Property Characterizations for an Improved Integration Cascade

2021-10-11
2021-01-1272
New technologies, such as electrified powertrain and autonomous driving solutions, are transforming the automotive industry in such a way that achieving vehicle level performance requirements demands an increasingly intensive and detailed system integration exercise. Validation of the braking system, critical to any vehicle level project, must evolve so that the ever-increasing requirements cascade is answered in a way that ensures the highest level of safety and performance as the industry moves toward a new frontier of features. To support this evolution of integration methodology, critical-to-performance components, such as brake pads, must undergo a transformation in how performance metrics are characterized, communicated, and documented.
Technical Paper

Thermomechanical Instabilities in Metal-Free Friction Materials Using a Nonlinear Transient Simulation Approach

2021-10-11
2021-01-1286
The invention of metal-free friction materials is gaining popularity in the manufacturing of brake pads and clutch friction discs because of the negative factors associated with metals such as copper. To gain more insight into the failure mechanism of the recent invention during brake or clutch applications, a nonlinear transient thermomechanical model is established using Finite Element Code. The model is based on a two-dimensional configuration for an investigation on the onset of TMI (Thermo-Mechanical Instability) during sliding contact in such material. The model is validated by comparing the transient simulation results for a full-contact regime to the result from the existing eigenvalue method. A parametric study is carried out to examine how the thermal conductivities and the elastic moduli influence TMI. The simulation results show that the thermal conductivities in the transverse direction and elastic moduli in the longitudinal direction can stabilize the system.
Technical Paper

Development of a Simulation for a Shim Durability Test

2021-10-11
2021-01-1283
Shim durability is an important aspect of shim performance. During the brake operation, no mechanical failure of the shim is allowed. Typically, when releasing a shim into production, durability tests must be performed to ensure no failure occurs around the locator holes, and the shim does not walk over the locators. Since the durability test requires an actual pad and shim, the mechanical retention mechanism for the shim (locators) need to be designed, and backplates must be produced. If a failure is detected during these durability tests, either the shim needs to be changed or the retention locators have to be redesigned, which could negatively impact NVH performance and project timing/costs. In this paper, a finite element model is developed to simulate a stop in a shim durability test. The model can be used to predict stress levels at the shim’s locator holes and the failure mode of a shim during a durability test stop.
Technical Paper

Measurement of Particle Dynamics on the Real Vehicle in Different Driving Scenarios with Swarm Sensors

2021-10-11
2021-01-1299
Due to the increase in public attention in the analysis of non-exhaust emission sources because of the growing electrification of vehicles, measurements have been performed in recent years to develop a consistent test standard. In particular, the consideration of tyre and brake abrasion took a predominant position due to the small particle sizes. With measurements under controlled and laboratory-like athmosphere, for example for brakes on dynamometers, attempts have been made to create a uniform test standard according to the Worldwide harmonized Light vehicles Test Procedure (WLTP). However, a transfer to the real driving environment is not yet feasible because of many external disturbance variables, such as the wheel housing or atmospheric variables. Typical reference measurement sensors in the vehicle are only suitable to a limited extent for mobile operation due to their size and the necessary measurement infrastructure.
Technical Paper

Dynamic Brake Test Stand

2021-10-11
2021-01-1274
Nowadays, inertia dynamometers or roller dynamometers are used for the development and testing of vehicle brakes. However, these testing methods are either entirely unable to simulate dynamical conditions, close to real driving maneuvers, or they can do so approximately only at very high costs. This means that brakes, braking systems and brake-related assistance systems such as the ESC system can ultimately only be tested in a full prototype of the car, or before that on hardware-in-the-loop test stands. In the case of the ESC, these test stands have to simulate the behavior of the brake and the surrounding vehicle in real time, then stimulate the interfaces of the ESC sensors accordingly, and finally evaluate the reaction of the ESC system in different situations. The problem here, however, is that the braking system can only be approximated by simulations.
Technical Paper

Research on Trajectory Planning and Tracking Strategy of Lane-changing and Overtaking based on PI-MPC Dual Controllers

2021-10-11
2021-01-1262
Aiming at the problem of poor robustness after the combination of lateral kinematics control and lateral dynamics control when an autonomous vehicle decelerates and changes lanes to overtake at a certain distance. This paper proposes a trajectory determination and tracking control method based on a PI-MPC dual algorithm controller. To describe the longitudinal deceleration that satisfies the lateral acceleration limit during a certain distance of lane change, firstly, a fifth-order polynomial and a uniform deceleration motion formula are established to express the lateral and longitudinal displacements, and a model prediction controller (MPC) is used to output the front wheel rotation angle. Through the dynamic formula and the speed proportional-integral (PI) controller to control and adjust the brake pressure.
Technical Paper

Application of Brake System Failed State Performance and Reliability Requirements to Brake System Architecting

2021-10-11
2021-01-1267
The modern braking system in the field today may be controlled by over a million lines of computer code and may feature several hundred moving parts. Although modern brake systems generally deliver performance, even with partial failures present in the system, that is well above regulatory minimums, they also have a level of complexity that extends well beyond what the authors of existing regulations had envisioned. Complexity in the braking system is poised for significant increases as advanced technologies such as self-driving vehicles are introduced, and as multiple systems are linked together to provide vehicle-level “features” to the driver such as deceleration (which can invoke service braking, regenerative braking, use of the parking brake, and engine braking). Rigorous safety-case analysis is critical to bring a new brake system concept to market but may be too tedious and rely on too many assumptions to be useful in the early architecting stages of new vehicle development.
Technical Paper

In-Depth Considerations for Electric Vehicle Braking Systems Operation with Steep Elevation Changes and Trailering

2021-10-11
2021-01-1263
As the automotive industry prepares to roll out an unprecedented range of fully electric propulsion vehicle models over the next few years - it really brings to a head for folks responsible for brakes what used to be the subject of hypothetical musings and are now pivotal questions for system design. How do we really go about designing brakes for electric vehicles, in particular, for the well-known limit condition of descending a steep grade? What is really an “optimal’ design for brakes considering the imperatives for the entire vehicle? What are the real “limit conditions” for usage that drive the fundamental design? Are there really electric charging stations planned for or even already existing in high elevations that can affect regenerative brake capacity on the way down? What should be communicated to drivers (if anything) about driving habits for electric vehicles in routes with significant elevation change?
Technical Paper

Investigations on the Deposition Behaviour of Brake Wear Particles on the Wheel Surface

2021-10-11
2021-01-1301
The deposition behavior of brake wear particles on the surface of a wheel and the mechanisms on it have not been fully understood. In addition, the proportion of brake wear particles deposited on the wheel surface compared to the total emitted particles is almost unknown. This information is necessary to evaluate the number- and mass-related emission factors measured on the inertia dynamometer and to compare them with on-road and vehicle-related emission behaviour. The aim of this study is to clarify the deposition behavior of brake particles on the wheel surface. First, the real deposition behaviour is determined in on-road tests. For particle sampling, collection pads are adapted at different positions of a front and rear axle wheel. In addition to a Real Driving Emissions (RDE)-compliant test cycle, tests are performed in urban, rural and motorway sections to evaluate speed-dependent influences.
Technical Paper

Research on High-efficiency Test Method of Vehicle AEB based on High-precision Detection of Radar Turntable Encoder

2021-10-11
2021-01-1273
With the increasingly complex traffic environment, the vehicle AEB system needs to go through a large number of testing processes, in order to drive more safely on the road. For speeding up the development process of AEB and solve the problems of long cycle, high cost and low efficiency in AEB testing, in this paper, a millimeter wave radar turntable is built, and a high-precision detection algorithm of turntable encoder is designed, at the same time, a test method of vehicle AEB based on the detection data of radar turntable encoder is designed. The verification results show that methods described in this paper can be used to develop the vehicle AEB test algorithm efficiently.
Technical Paper

Investigation on Brake Disc Deformation Under Asymmetric Mechanical Loads

2021-10-11
2021-01-1291
The mechanism of automobile brake hot spots is unclear, which is a problem in the brake industry. Complex coupling between friction, heat, contact, and structure is the main difficulty in revealing the mechanism of brake hot spots. This paper proposes a new way to study the mechanism of hot spots by analyzing the deformation behavior of brake discs under asymmetric mechanical loading. The actual brake is simplified into a brake disc and friction lining system, and a transient dynamic finite element model under asymmetric mechanical loads is established to analyze the deformation characteristics of the brake disc. The normal deformation of the brake disc under asymmetric mechanical loads consists of two parts: low-frequency bending deformation and high-frequency waviness deformation, which are caused by the squeezing effect of the asymmetric brake pressure on the brake disc and the constraint modal vibration of the brake disc.
Technical Paper

The Influence of Wheel Rotations to the Lateral Runout of a Hybrid Material or Dimensionally Reduced Wheel Bearing Flange

2021-10-11
2021-01-1298
The automotive industry is continuously striving to reduce vehicle mass by reducing the mass of components including wheel bearings. A typical wheel bearing assembly is mostly steel, including both the wheel and knuckle mounting flanges. Mass optimization of the wheel hub has traditionally been accomplished by reducing the cross-sectional thickness of these components. Recently bearing suppliers have also investigated the use of alternative materials. While bearing component performance is verified through analysis and testing by the supplier, additional effects from system integration and performance over time also need to be comprehended. In a recent new vehicle architecture, the wheel bearing hub flange was reduced to optimize it for low mass. In addition, holes were added for further mass reduction. The design met all the supplier and OEM component level specifications.
Technical Paper

Development of a Modeling Approach to Numerically Predict Filtration Efficiencies of Brake Dust Particle Filters

2021-10-11
2021-01-1285
According to the European Environment Agency, air pollution is the biggest environmental health risk in Europe. Since traffic is one of the main contributors of fine dust, technical solutions are necessary to reduce the particulate emission footprint of vehicles. Also, the Health Effects Institute hosted recently an international workshop on non-tailpipe emissions. Brake dust filtration concepts have proven to be a promising solution to significantly reduce fine dust emissions from brakes directly at the source. While CFD simulations for inner-ventilated brakes have become state-of-the-art, a holistic model from particle generation and emission to particle dynamics in the vicinity of the brake is not yet available. However, a good modeling approach of particle tracks is essential to predict filtration efficiencies of brake dust particle filters.
Technical Paper

Analysis of the Effect of the Wedged Type Brake Caliper Piston on Brake Drag

2021-10-11
2021-01-1293
Recently, there’s a massive flow of change in the automotive industry with the coming era of electric vehicles and self-driving (autonomous) vehicles. The automotive braking system field is not an exception for the change and there are not only lots of new systems being developed but also demands for researches for optimizations of conventional brake systems fitting to the newly appeared systems such as E-Booster and Electric Motor Brake (EMB) Caliper. Taking the Electric Motor Brake Caliper for example, it is considered as a very important and useful system for autonomous vehicles because the motor actuator of the caliper is much easier to control with ECUs compared to the conventional hydraulic pressure system. However, easy of control is not the only thing that excites brake system engineers.
Technical Paper

Design and Analysis of a Pneumatically Actuated Drag Reduction System

2021-10-05
2021-01-5080
The main goal of race car aerodynamics is to generate a desired intensity of downforce for the least possible amount of drag. Nonetheless, the balance of the forces under all circumstances due to speed and acceleration is equally important. The modeling was performed using SolidWorks, and the analysis was done both analytically and by means of computational fluid dynamics (CFD) using a flow simulation with STAR-CCM+. The aerodynamics package, which includes the rear wing, front wing, and undertray that help in faster cornering, is analyzed in the full-car analysis. The full-car analysis is done for pitch and yaw. The increase in cornering ability can come from two major aspects: an increase in the aerodynamic downforce and a decrease in the aerodynamic drag of the vehicle. In order to implement the desired aerodynamics package, an airfoil with a predefined profile was selected. The main factor that limits the selection of an airfoil is its effectiveness at low velocities.
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