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In this paper, responses from a vehicle's suspension, chassis and body, are used to demonstrate a methodology to optimize physical test results. It is well known that there is a variability effect due to an increase of wheel unsprung mass (due to loads measurement fixturing), tire pressure, speed, etc. This paper quantifies loading variability due to Wheel Force Transducer (WFT) unsprung mass by using a rainflow cycle counting domain. Also, presents a proving ground-to-test correlation study and the data reduction techniques that are used in road simulation test development to identify the most nominal road load measurement. Fundamental technical information and analytical methodology useful in overall vehicle durability testing are discussed. Durability testing in a laboratory is designed to correlate fatigue damage rig to road. A Proving Ground (PG) loading history is often acquired by running an instrumented vehicle over one or more PG events with various drivers.

In this paper, loads acting on driveline components during an entire proving ground (PG) durability schedule are used to demonstrate the methodology of optimizing driveline performance reliability using both physical and computational methods. It is well known that there is an effect of driver variability on the driveline component loads. Yet, this effect has not been quantified in the past for lack of experimental data from multiple drivers and reliable data analysis methods. This paper presents the data reduction techniques that are used to identify the extreme driver performance and to extrapolate the short-term measurement to long-term data for driveline performance reliability. The driveline loading variability is made evident in the rotating moment histogram domain. This paper also introduces the concept for a simulation model to predict the driveline component loads based on a complete proving grounds schedule. A model-to-test correlation is also performed in this paper.

The performance of a large-volume production torque converter is slightly different from those of development prototype due to the core leakage flow. The sealing gap between the stator crown and pump or turbine core of the production converter is usually larger than that of prototypes because of fabrication method and tolerances. In this work, the core leakage flow of torque converter was investigated using CFD. The core region was modeled and coupled together with other three major components of a converter. Studies show that for a particular converter the core leakage flow could result in a 3.6% stall torque ratio reduction and a 2% peak efficiency decrease. The effects of sealing gap dimensions were also studied. Computational investigations in this work indicated that the variation of input K factor with input torque level observed in dyno tests is due to the cavitation in the torque converter.

To improve vehicle launch feeling, the powertrain torque output needs to be largely increased. Compared with modifications to engine, transmission, and axle, one of the most inexpensive ways of achieving this goal is to modify the torque converter to get a higher stall torque ratio. In other applications, in order to lower engine speed for better fuel economy, and to match with a higher output engine, a converter with higher torque capacity (lower K factor) is also often desired. In some case of small-volume production, the torque converter modifications are limited to the stator only in order to reduce the manufacturing cost. In the present study, the engineering CFD simulations were used to develop new stators for stall torque ratio and K factor improvement. The flow fields of both baseline and modified torque converters were simulated. The overall performances of the converter were calculated from the flow field data, and correlated with the dyno test data.

Hot Isostatic Pressing (HIP) has been routinely used to densify castings for aerospace and medical applications for over 30 years. While HIP is widely known to improve the toughness and fatigue life of castings through the healing of internal porosity, it has been perceived as too expensive for most cast aluminum alloys for automotive applications. Recent developments suggest that the cost effectiveness of certain special HIP processes should be revisited due to reductions in process cost and improvements in throughput. This paper will evaluate the Densal® II process applied to a front aluminum steering knuckle. Two casting processes representing differing levels of relative cost and quality were evaluated. The first was Alcoa's VRC/PRC process, a metal mold process with bottom fill, evacuation before fill and pressurization after fill. This is considered to be a premium quality, but higher cost casting process that is already qualified for this application.

Traditionally, high-strength low-alloy (HSLA) steel is used for automotive vehicle weight reduction in the North American automotive industry. Dual phase (DP) high strength steel has gained great attention because it provides a combination of high strength and good formability. The main advantage of DP steel is the high ratio of tensile strength to yield strength, which provides more flexibility in stamping and higher energy absorption in a component crush event. This study compares the performances of DP and HSLA steel grades in stamping processes and component crush events, as shown in a typical automotive unibody inner rail. Simulation results show that DP steel offers more uniform strain distribution, improved formability, and better crush performance than conventional HSLA steel.

Silicon Carbide (SiC) based high temperature semiconductor gas sensors were tested for potential applications in the closed-loop control of NOx storage catalytic converters. The exhaust gas composition behind a storage catalyst was simulated by synthetic gas mixtures supplied from a gas blending manifold. In lean oxidizing ambients the sensors produced signals opposite in sign upon the appearance of NOx on the one hand and mixtures of HC and CO on the other hand. Transient gas measurements revealed response times ranging between several milliseconds for HC and several seconds for NOx. These features render SiC based sensors potentially useful for the control of NOx storage catalytic converters.

The staircase fatigue testing method is a recognized method for determining the fatigue limit of powertrain components. The purpose of this paper is to improve upon existing standards by adding common practices that will ensure a higher degree of statistical accuracy in the data. This includes specifying appropriate sample sizes, stress increments and initial load conditions, as well as making suggestions for appropriate methods of analyzing the data. Two methods (Dixon and Mood method and probit analysis method) are selected and compared in terms of relative percent difference on four parameters (mean, standard deviation, B10 fatigue strength and B50 fatigue strength). The staircase data are obtained by simulations from normal and lognormal fatigue limit distributions.

Historically, pump noise can be a contributor to customer dissatisfaction with automatic transmissions. In this paper, a Shainin experiment was conducted to identify all probable root causes for pump noise on a production RWD transmission. Sample transmissions were selected following subjective evaluations. Noise was objectively measured in the lab using a microphone and an accelerometer. The study was conducted following a systematic Shainin statistical engineering methodology, which included the following major steps: selection of the test measure using the isoplot technique, selection of Best of Best (BOB) and Worst of Worst (WOW) transmissions, assessment of assembly variation, component search, and pair-wise comparisons. The study successfully highlighted the key variables on the drive gear involute profile, which are now being tightly controlled for improved noise characteristics.

Sheet metal stamping involves a system of complex tribological (friction, lubrication, and wear), heat transfer, and material strain interactions. Accurate coefficient of friction, strain, and lubrication regime data is required to allow proper modeling of the various sheet stamping processes. In addition, non-intrusive means of monitoring the coefficient of friction in production stamping operations would be of assistance for efficiently maintaining proper stamping quality and to indicate when adjustments to the various stamping parameters, including maintenance, would be advantageous. One of the key sub-systems of the sheet metal stamping process is the draw bead. This paper presents an investigation of the tribology of the draw bead using a Draw Bead Simulator (DBS) Machine and automotive zinc-coated sheet steels. The investigation and findings include: 1) A new, non-intrusive method of measuring the surface temperature of the sheet steel as it passes through the draw bead.

At the initial accessory drive system design stage, a model was created using commercial CAE software to predict the dynamic response of the pulleys, tensioner motion and pulley slip. In a typical 6 cylinder automotive accessory drive systems, the first system torsional mode is near the engine idle speed. The combination of these two events could generate numerous undesirable noise and vibration effects in the system. Data acquisition on a firing engine with a powertrain dynamometer confirmed the computer model's results. Correlations are then developed and established based on results between the firing engine to the CAE model to increase confidence in the generated model. Further system optimization through design modifications are used to tune the system to minimize the overall system dynamics.

The homogeneous charge, compression-ignition (HCCI) combustion process has the potential to significantly reduce NOx and particulate emissions, while achieving high thermal efficiency and the capability of operating with a wide variety of fuels. This makes the HCCI engine an attractive technology that can ostensibly provide diesel-like fuel efficiency and very low emissions, which may allow emissions compliance to occur without relying on lean aftertreatment systems.

The recent trends of increasing driveline torque and use of traction control devices call for increasingly higher durability capacity from driveline components. Bench and vehicle durability tests are often used to validate designs, but they are not cost-effective and take months to complete. Traditional finite element analysis (FEA) procedures have been used effectively in the re-design of driveline components to reduce stress, and occasionally, to predict fatigue life. But in the case of certain rotating components, such as the Axle Differential Case, where the component sees large stress/strain fluctuations within the course of one complete rotation, even under constant input torque, historical fatigue analysis (when conducted) yields very conservative results. The axle differential case tends to be one of the weakest links in the rear axle assembly. Therefore, there is a crucial need for analytical methods to more accurately predict fatigue life to reduce testing time and cost.

The effect of forming strains on the fatigue behavior of an automotive mild steel, interstitial free steel, was studied after being prestrained by balanced biaxial stretch and plane strain. In the long life region, higher than 5×105 reversals, prestrain improves fatigue resistance. In the short life region, prestrain reduces fatigue resistance. At even shorter fatigue lives, the detrimental effect of prestrain diminishes. For plane strains, the fatigue behavior is anisotropic. In the direction perpendicular to the major strain, the steel exhibits much better fatigue resistance than in the direction parallel to the major strain.

In a vehicle NVH development and refinement phase, it is necessary to understand the source of the noise and vibration from various powertrain and drivetrain mechanisms. The noise and vibration generated by a drivetrain in a vehicle is a complicate but significant source of physical mechanism, which might become important issues in early or later phase of the vehicle development. For the diagnostic purpose of the drivetrain, a rear-wheel drive (RWD) vehicle in early development phase has been used to measure the bending and torsional vibration of the drivetrain, as well as the vehicle interior noise simultaneously, while the vehicle is running up and down under quasi-steady state on a chassis dynamometer. The lower frequency resonances of torsional and bending vibrations from the drivetrain are correlated with the vehicle interior boom or overall loudness.

Cylinder deactivation is a means of improving the fuel economy of gasoline engines. This paper covers the application of the technology to a V8 engine and implementation into vehicles. The description of the engine hardware and its operation are discussed. The engine and transmission control strategy are described, including an example of the compensation strategies to smooth the transition between the different modes of engine operation. The powertrain and chassis hardware changes required to address the noise vibration and harshness issues are discussed and examples of untuned systems are shown.

DKAD is an automated analysis tool for evaluating dynamic characteristics of accessory drives. Rotation response analysis predicts natural frequencies and effects of crankshaft excitation. Lateral response of each belt span shows the effect of pulley run-out and parametric excitation. DKAD systematically allows a user to define a design and its operating conditions and then performs a sequence of analysis to visualize the rotational and lateral responses. It also allows a user to quickly explore and assess alternative designs. Belt layout and associated parameters can be saved in templates for future reference.

Transfer Path Analysis (TPA) is a widely used methodology in Noise, Vibration and Harshness (NVH) analysis of motor vehicles. Either it is used to design a vehicle from scratch or it is applied to root cause an existing NVH problem, TPA can be a useful tool. TPA analysis is closely related to the concept of partial contribution. The very basic assumption in TPA is that the summation of all partial contributions from different paths constitutes the total response (which could be either tactile or acoustic). Another popular concept in NVH analysis of vehicles is the component sensitivity. Component sensitivity is a measure of how much the response changes due to a change in one of the components of the system, i.e., the thickness of a panel or elastic rate of an engine mount. Sensitivity rates are more popular among CAE/Simulation community, simply because they are reasonably easy to calculate using mathematical models.

Modern engines are designed to operate at highly rated engine speed and load, which brings up challenges to the lubrication design of main and connecting rod bearings. Damages could occur on rod bearings due to high-speed relative sliding motion. Expensive cross drillings are often seen in today's engineering practice to ensure adequate lubrication in rod bearings. The objective of this study is to establish a methodology for predicting lubrication flows in rod bearings and use it to guide the engineering design. The high-speed nature of the crankshaft makes it difficult to acquire experimental data during its normal operation for better understanding the flow inside rod bearings and oil circuits. In the present study, the commercial CFD code, FLUENT, has been used to evaluate the flow characteristics within the rod bearings and oil passages connecting main bearing to rod bearing.

Thixomolding (1) is a relatively new process in which the metallic slurry is injected into a die cavity tool at semi-solid or liquid temperatures to form near net-shape products from the solid feedstock. As part of on-going research into Thixomolding technology, this study continues the work of a previous study, that concentrated on magnesium alloys AZ91D and AM60B. The test samples were made with high, low and zero percent fraction solid. The test results of the thixomolded samples of the various percent fraction solid are compared to conventional high pressure die casting samples and there is a discussion of the why the Thixomolding process produces superior properties. In addition, a comprehensive corrosion resistance study was completed utilizing uncoated corrosion plates in an salt spray environment (ASTM B117).