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This paper contributes to the Committee on Commonized Aerodynamics Automotive Testing Standards (CAATS) initiative, established by the late Gary Elfstrom. It is collaboratively compiled by automotive wind tunnel users and operators within the Subsonic Aerodynamic Testing Association (SATA). Its specific focus lies in automotive wind tunnel test techniques, encompassing both those relevant to passenger car and race car development. It is part of the comprehensive CAATS series, which addresses not only test techniques but also wind tunnel calibration, uncertainty analysis, and wind tunnel correction methods. The core objective of this paper is to furnish comprehensive guidelines for wind tunnel testing and associated techniques. It begins by elucidating the initial wind tunnel setup and vehicle arrangement within it.

Efficient thermal management is essential in high power density electric drive units (EDUs) due to limited space and working environment. Major heat sources in EDUs are from the inverter, motor and gearbox. System level thermal response prediction models comprising various components within the EDU are of interest from both product performance and software controls standpoint. A system level physics-based lumped parameter thermal network (LPTN) model is built in a one-dimensional (1D) framework using inputs from empirical, electromagnetic, three-dimensional conjugate fluid/heat transfer analysis and test data to predict the component temperature within the EDU. Empirical models were used to calculate heating due to efficiency loss from the gearbox. The thermal loses from the motor are estimated as outputs from electromagnetic simulations.

Electronically locking differentials that have dog-clutches may not always have a smooth engagement. The duration of the engagements needs to be quantified, and the different types of engagement need to be qualified. The engagement time is dictated by both the mechanical and electrical sub-systems of the differential. Three different analytical methods were developed to simulate engagement. The first method uses Simulink to co-simulate the electromagnetic behavior of the actuator in ANSYS Maxwell, and the multibody dynamic behavior of the differential in MSC ADAMS. The second method simulates the mechanics of the differential in AMESim, where an equation for the electromagnetic force inside the actuator is integrated into the model. The third method leverages the former two methods by combining the MSC ADAMS multibody dynamic behavior with integrated equation for the electromagnetic force inside the actuator.

Over the years, requirements for an electric drive for traction applications have increased substantially in terms of efficiency, power density, packaging space and cost. Manufacturers have employed various strategies to achieve high efficiency and power dense solutions. One such strategy is to use a synergistic approach by combining typical EDU sub-components such as an inverter, a motor and a gearbox with a differential to form a fully integrated 3-in-1 solution. Electrical and thermal losses from such a system can be quite significant as it includes losses from the inverter, the motor and the gearbox. As a result, thermal performance is often a limiting factor in improving the packaging space and power density. To address thermal issues, an effective liquid cooling system must be employed that ensures sufficient heat dissipation from all of the EDU subcomponents and helps to reduce packaging space.

Automotive electric drive unit designs are often limited by installation space and the related environmental conditions. Electrical losses in various components of the motor such as stator, rotor and coils can be significant and as a result, the thermal design can become a bottle neck to improve power and torque density. In order to mitigate the thermal issue, an effective liquid cooling system is often employed that ensures sufficient heat dissipation from the motor and helps to reduce packaging size. Although both stator and rotor are cooled in a typical motor, this paper discusses a multiphase oil-air mixture analysis on a spinning hollow rotor and rotor shaft subjected to forced oil cooling. Three-dimensional computational fluid dynamics (CFD) conjugate heat transfer (CHT) simulations were carried out to investigate flow and heat transfer. The effect of centrifugal force, shaft RPM, density gradients and secondary flows were investigated.

The Environmental Protection Agency (EPA) requirement for 54.5mpg by 2025 to reduce greenhouse gases has pushed the industry to look for alternative fuels to run vehicles. Electricity is of those green energies that can help auto industry to achieve those strict requirements. However, the electric or hybrid-electric vehicles brought new challenges into science and engineering world including the Noise and Vibration issues which are usually tied up with both airborne and structural noises. The electromagnetic force plays a significant role in acoustic noise radiation in the electric motor which is an air-gap radial Maxwell force. This paper describes an innovative approach to model the physics of noise radiated by the electric motor.

Hypoid gears transmission error (TE) is a metric that is usually used to evaluate their NVH performance in component level. The test is usually done at nominal position as well as out of positions where the pinion and gear are moved along their own axis and also along offset direction to evaluate sensitivity of the measured TE to positional errors. Such practice is crucial in practical applications where the gear sets are inevitably exposed to off position conditions due to a) housing machining and building errors, b) deflections of housing, bearings, etc. under load and c) thermal expansions or contractions of housing due to ambient temperature variations. From initial design to development stage, efforts should be made to design the gear sets to be robust enough to all combinations of misalignments emanated from all three mentioned categories.

An SBAR system for H2O and CO2 removal from spacecraft cabin air was studied both experimentally and theoretically. An emphasis was placed on its purgeless, deep vacuum regeneration step. Three evacuation steps were studied: 1) single ended depressurization (SED) through the feed end of the bed; 2) simultaneous dual ended depressurization (DED) through both ends of the bed; and 3) simultaneous triple ended depressurization (TED) through both ends of the bed and a port located at some axial position. TED resulted in a lower average bed pressure at the end of evacuation compared to DED, which, in turn caused more CO2 to be removed. An optimal third port location also existed. The use of TED should allow the SBAR bed size to be reduced.

In the powertrain development of an automobile, the accurate prediction and understanding of the fuel supply and injection system behavior is necessary to achieve the targeted vehicle performance. With stronger demand from the customers for quieter vehicles, complementary functional objectives have to be met such as packaging, component or material change, or the modification of the fuel supply system layout. Understand the possible sources of noise and vibration from the fuel supply and delivery system requires having an analytical model of a complete fuel system, from the fuel pump assembly to the injectors. One has to note that adequate level of component details is required for the modeling and validation. In this study, the lumped-parameter model approach of the fluid dynamics on the fuel supply and delivery system has been developed and validated with the test results.

Static and dynamic strength tests were performed on spot welded specimens made of dual-phase (DP) 780 and mild steels (DQSK). Lap-shear (LS) and cross-tension (CT) as well as a new mixed mode specimen were studied using MTS hydraulic universal testing machine for static tests and drop weight tower for dynamic tests. Three weld nugget sizes were made for each steel and CT and LS. DP780 with one weld size was also tested in mixed mode. Load and displacement as functions of time and fracture mode of the spot welds were recorded. Representative data are reported in this paper.

Efforts by vehicle manufacturers to reduce road testing have resulted in an increased reliance on the simulation methods for loads measurement and validation, including increased emphasis on methods to characterize and digitally represent test road inputs. Accurate terrain models are especially important in the case of large dynamic road inputs, and for evaluation of vehicle suspension loads and durability. In contrast to direct terrain topology measurement, methods to estimate test road input using only vehicle suspension measurements and a tire dynamic model will be presented. Applications of terrain models for generic simulation and testing will also be discussed.

Competitive pressures, globalization of markets, and integration of new materials and technologies into heavy vehicle suspension systems have increased demand for durability validation of new designs. Traditional Proving Ground and on-road testing for suspension development have the limitations of extremely long test times, poor repeatability and the corresponding difficultly in getting good engineering level data on failures. This test approach requires a complete vehicle driven continuously over severe Proving Ground events for extended periods. Such tests are not only time consuming but also costly in terms of equipment, maintenance, personnel, and fuel. Ideally multiple samples must be tested to accumulate equivalent millions of kilometers of operation in highly damaging environments.

With increasingly stringent emissions regulations and concurrent requirements for enhanced engine thermal efficiency, a comprehensive characterization of the automotive gasoline fuel spray has become essential. The acquisition of accurate and repeatable spray data is even more critical when a combustion strategy such as gasoline direct injection is to be utilized. Without industry-wide standardization of testing procedures, large variablilities have been experienced in attempts to verify the claimed spray performance values for the Sauter mean diameter, Dv90, tip penetration and cone angle of many types of fuel sprays. A new SAE Recommended Practice document, J2715, has been developed by the SAE Gasoline Fuel Injection Standards Committee (GFISC) and is now available for the measurement and characterization of the fuel sprays from both gasoline direct injection and port fuel injection injectors.

The problem of predicting the quality of weld is critical to manufacturing. A great deal of data is collected under multiple conditions to predict the quality. The data generated at Daimler Chrysler has been used to develop a model based on grammatical evolution. Grammatical Evolution Technique is based on Genetic Algorithms and generates rules from the data which fit the data. This paper describes the development of a software tool that enables the user to choose input variables such as the metal types of top and bottom layers and their thickness, intensity and speed of laser beam, to generate a three dimensional map showing weld quality. A 3D weld quality surface can be generated in response to any of the two input variables picked from the set of defining input parameters. This tool will enable the user to pick the right set of input conditions to get an optimal weld quality. The tool is developed in Matlab with Graphical User Interface for the ease of operation.

Shudder vibration of a hydraulic power steering system during parking maneuver was studied with numerical and experimental methods. To quantify vibration performance of the system and recognize important stimuli for drivers, a shudder metric was derived by correlation between objective measurements and subjective ratings. A CAE model for steering wheel vibration analysis was developed and compared with measured data. In order to describe steering input dependency of shudder, a new dynamic friction modeling method, in which the magnitude of effective damping is determined by average velocity, was proposed. The developed model was validated using the measured steering wheel acceleration and the pressure change at inlet of the steering gear box. It was shown that the developed model successfully describes major modes by comparing the calculated FRF of the hydraulic system with measured one from the hydraulic excitation test.

Validation and simulations of a real-time dynamic cabin model were conducted on the sorbent-based atmosphere revitalization system for Orion. The dynamic cabin model, which updates the concentration of H2O and CO2 every second during the simulation, was able to predict the steady state model values for H2O and CO2 for long periods of steady metabolic production for a 4-person crew. It also showed similar trends for the exercise periods, where there were quick changes in production rates. Once validated, the cabin model was used to determine the effects of feed flow rate, cabin volume and column volume. A higher feed flow rate reduced the cabin concentrations only slightly over the base case, a larger cabin volume was able to reduce the cabin concentrations even further, and the lower column volume led to much higher cabin concentrations. Finally, the cabin model was used to determine the effect of the amount of silica gel in the column.

Determination of an engine's inertial properties is critical during vehicle dynamic analysis and the early stages of engine mounting system design. Traditionally, the inertia tensor can be determined by torsional pendulum method with a reasonable precision, while the center of gravity can be determined by placing it in a stable position on three scales with less accuracy. Other common experimental approaches include the use of frequency response functions. The difficulty of this method is to align the directions of the transducers mounted on various positions on the engine. In this paper, an experimental method to estimate an engine's inertia tensor and center of gravity is presented. The method utilizes the traditional torsional pendulum method, but with additional measurement data. With this method, the inertia tensor and center of gravity are estimated in a least squares sense.

Low frequency torsional vibrations can be a significant source of objectionable vehicle vibrations and in-vehicle boom, especially with changes in engine operation required for improved fuel economy. These changes include lower torque converter lock-up speeds and cylinder deactivation. This paper has two objectives: 1) Examine the effect of increased torsional vibrations on vehicle NVH performance and ways to improve this performance early in the program using test and simulation techniques. The important design parameters affecting vehicle NVH performance will be identified, and the trade-offs required to produce an optimized design will be examined. Also, the relationship between torsional vibrations and mount excursions, will be examined. 2) Investigate the ability of simulation techniques to predict and improve torsional vibration NVH performance. Evaluate the accuracy of the analytical models by comparison to test results.

This paper describes the process used to develop an experimental model with forward prediction capabilities for passenger vehicle axle whine performance, focusing initially on beam axle design modifications. This process explains how experimental Transfer Path Analysis (TPA), Running Modes Analysis (RMA) and Modal Analysis were used along with an experimental FRF-Based Substructuring (FBS) model. The objective of FBS techniques is to predict the dynamic behavior of complex structures based on the dynamic properties of each component of the structure. The FBS model was created with two substructures, the body/suspension and the empty rear beam axle housing. Each step in the creation of the baseline FBS model was correlated, and the forward predictive capability was verified utilizing an experimental modification to the beam axle structure.

This paper summarizes a study on axle balance measurement and balancing strategies. Seven types of axles were investigated. Test samples were randomly selected from products. Two significant development questions were set out to be answered: 1) What is the minimum rotational speed possible in order to yield measured imbalance readings which correlated to in-vehicle imbalance-related vibration. What is the relationship between the measured imbalance and rotational speed. To this end, the imbalance level of each axle was measured using a test rig with different speeds from 800 to 4000 rpm with 200 rpm increments. 2) Is it feasible to balance axle sub-assemblies only and still result in a full-assembly that satisfies the assembled axle specification? To this end, the sub-assemblies were balanced on a balance machine to a specified level. Then with these balanced sub-assemblies, the full assemblies were completed and audited on the same balance test rig in the same way.