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An evaluation methodology has been developed for assessing the suitability of R-1234yf in vehicles. This relates primarily to evaluating the flammability of R-1234yf in the engine compartment during a frontal collision. This paper will discuss the process followed in the methodology, the technical rationale for this process, and the results of the analysis. The specific types of analysis included in the methodology are: exhaust-system thermal characterization, computer simulated crash tests, actual crash tests, teardown and examination of crashed parts, and releases of refrigerant onto hot exhaust manifolds. Each type of analysis was logically ordered and combined to produce a comprehensive evaluation methodology. This methodology has been applied and demonstrates that R-1234yf is difficult to ignite when factors that occur in frontal crashes are simultaneously considered.

This investigation utilizes a DFSS analysis approach to determine automatic transmission gear content required to minimize fuel consumption for various powertrain - vehicle systems. L18 and L27 inner arrays with automatic transmission design and shift pattern constraint parameters were varied to determine their relative influence on fuel consumption. An outer noise array consisting of two vehicles with various engines, final drive ratios and legislated emissions test cycles was used to make a robust transmission selection based on minimizing fuel consumption. The full details of the DFSS analysis method and assumptions are presented along with a detailed examination of the results. With respect to transmission design parameters, parasitic spinloss and gear mesh efficiency were found to be most important followed by the number of gears. The DFSS analysis further revealed that unique transmission design formulations are potentially required for widely varying engines.

A GT-Power Fast Run Model simplified from detail model for HIL is verified with a bench test using the dSPACE Simulator. Firstly, the conversion process from a detailed model to FRM model is briefly described. Then, the spark timing, fuel pulse with control for FAR, and torque level control are developed for proof of concept. Moreover a series of FRM/Simulink co-simulation and HIL tests are conducted. In the summary, the test results are presented and compared with GT detailed model simulations. The test results show that the FRM/dSPACE HIL stays consistent in most variables of interest under 0.7-0.9 real-time factor condition between 1000 - 5000 RPM. The same steady-state can be reached by RCP controllers or with GT-Power internal controllers. The transient states are close using different control algorithm. The main purpose of HIL application is achieved, despite inconsistencies in performance data like fuel consumption.

Diesel particulate filter (DPF) is a widely used emission control device on diesel vehicles. The DPF captures the particulate matter coming from the engine exhaust and periodically burns the collected soot via the regeneration process. There are various trigger mechanisms for this regeneration, such as distance, time, fuel and simulation. Another method widely used in the industry is the pressure drop across the filter. During calibration, relation between the pressure sensor reading and soot mass in the filter is established. This methodology is highly effective in successful DPF operation as pressure sensor is a live signal that can account for any changes in engine performance over time or any unforeseen hardware failures. On the other hand, any erroneous feedback from the sensor can lead to inaccurate soot mass prediction causing unnecessary regenerations or even needless DPF plugging concerns.

A dog clutch, if successfully implemented in an automatic transmission, provides better packaging and the potential for improved fuel economy. The technical requirements for this concept are examined through modeling and simulation. As a first step, a physics-based component level model is developed that provides an understanding of the basic contact and impact dynamics. The model is compared to a built-in AMESim block to establish confidence. This component level model is then integrated into a powertrain system model within the AMESim environment. As a test bed, the powertrain model is exercised to simulate a friction plate to dog clutch shift in a 6-speed automatic transmission. The analysis helps to define the slip speed target at the onset of the dog clutch engagement while ensuring shift requirements are met. Finally, the model is validated by comparing the simulated results with measured dynamometer data.

This investigation utilizes energy analysis and statistical methods to optimize step gear automatic transmissions gear selection for fuel consumption. A full factorial matrix of simulations using energy analysis was performed to determine the optimal number of gears and gear ratios that provide the best fuel consumption performance for a particular vehicle - engine application. The full factorial matrix setup as a design of experiment (DOE) was applied to five vehicle applications, each with two engines to examine the potential differences that variations in road load and engine characteristics might have on optimal transmission gearing selection. The transmission gearing options considered in the DOE were number of gears, launch gear ratio and top gear ratio. Final drive ratio was also included due to its global influence on vehicle performance and powertrain operating speeds and torque.

The automotive industry is under great pressure to reduce vehicle mass for both cost and fuel economy gains. A significant contributor to body and suspension structure mass is peak vertical loads, primarily entering the body structure through the jounce bumper to body interface. This paper focuses on the successful development of “Loads Management Striker Caps” for the 2013 Cadillac ATS front and rear suspension. Component design and development of the striker caps was executed using explicit finite element analysis tools. Multi-body dynamics vehicle models were used to set component requirements and confirm striker cap performance for the vehicle during peak vertical events. The “Loads Management Striker Caps” ultimately reduced peak strut/shock tower loads by 40% in the front suspension and 25% in the rear suspension. This resulted in significant body and chassis mass savings, contributing to the Cadillac ATS's class leading curb weight.

A comparison of welding techniques was performed to determine the most effective method for producing aluminum tailor-welded blanks for high volume automotive applications. Aluminum sheet was joined with an emphasis on post weld formability, surface quality and weld speed. Comparative results from several laser based welding techniques along with friction stir welding are presented. The results of this study demonstrate a quantitative comparison of weld methodologies in preparing tailor-welded aluminum stampings for high volume production in the automotive industry. Evaluation of nearly a dozen welding variations ultimately led to down selecting a single process based on post-weld quality and performance.

GM has developed an all-new gasoline-electric hybrid powertrain for the model year 2016 Chevrolet Malibu Hybrid vehicle, which was designed to achieve excellent fuel economy, performance, and drive quality. The powertrain shares the transmission architecture with the 2016 Chevrolet Volt extended range electric vehicle, but includes changes to optimize the system for engine driven charge sustaining operation in the range of conditions represented by the US EPA 5 cycle fuel economy tests. In this paper, we describe the Malibu Hybrid propulsion system features and components, including the battery pack, transaxle, electric motors and power electronics, engine, and thermal system. The modifications between the Volt and Malibu Hybrid propulsion systems are discussed and explained as resulting from the differences between the primarily electric and gasoline powered applications.

This paper describes the development of a semi-automated end-of-line driveline system balance tester for an automotive assembly plant. The overall objective was to provide final quality assurance for acceptable driveline noise and vibration refinement in a rear wheel drive vehicle. The problem to be solved was how to measure the driveline system unbalance within assembly plant constraints including cycle time, operator capability, and integration with a pre-existing vehicle roll test machine. Several challenging aspects of the tester design and development are presented and solutions to these challenges are addressed. Major design aspects addressed included non-contacting vibration sensing, data acquisition/processing system and vehicle position feedback. Development challenges addressed included interaction of engine and driveline vibration orders, flexible driveline coupling effects, tachometer positional reference error, and vehicle-to-vehicle variation of influence coefficients.

Future diesel combustion systems may operate with significantly higher levels of boost and EGR than used with present systems. The potential benefits of higher boost and EGR were studied experimentally in a single-cylinder diesel engine with capability to adjust these parameters independently. The objective was to study the intake and exhaust conditions with a more optimum combustion phasing to minimize fuel consumption while maintaining proper constraints on emissions and combustion noise. The engine was tested at four part-load operating points using a Design of Experiments (DOE) approach. Two of the operating points correspond to low-speed and low-load conditions relevant for the New European Driving Cycle (NEDC). The other two points focus on medium load conditions representative of the World-wide harmonized Light-duty Test Procedures (WLTP).

AZ31B Mg sheet is being considered for automotive applications. This study investigates the effect of pre-treatments, such as heat-treatments and surface treatments, on the corrosion performance of AZ31B sheet, with a goal of learning which pre-treatment can improve corrosion resistance of the sheet material in production. It is found that the heat-treatment and oxidation during a warm and hot forming (WHF) process will not deteriorate the corrosion performance of the AZ31B sheet; polishing and acid etching can clean the surface and significantly increase the corrosion resistance, but corrosion can be accelerated by sandblasting which contaminates the surface. The change in corrosion performance can be associated with surface cleaning or contamination of the sheet by these pre-treatments. Furthermore, the influence of a pre-treatment on the uncoated AZ31B sheet may affect its corrosion behavior after coating.

Impact toughness (or resistance to fracture) is a key material property for press hardened steel used in construction of the safety-critical elements of automotive body structures. Prior austenite grain size, as primarily controlled by the incoming microstructure and austenitization process, is a key microstructural feature that influences the impact toughness of press hardened steel. In this paper, a special Charpy V-notch impact test is developed to quantify the impact toughness of press hardened steel sheets with various prior austenite grain sizes, by stacking a number of thin sheets via mechanical riveting. Both the ductile-to-brittle transition temperature and upper shelf energy are analyzed in an effort to establish a correlation between impact toughness and prior austenite grain size. Within tested conditions, impact performance shows only a slight decrease as the prior austenitic grain size increases from 18 to 38 microns.

Corrosion inhibitors (CIs) have been used for years to protect the supply and distribution systems used for transportation of fuel from refineries. They are also used to buffer the potential organic acids present in an ethanol blended fuel to enhance storage stability. The impact of the types of inhibitors on spark-ignition engine fuel systems, specifically intake valve deposits, is known and presented in open literature. However, the relationship of the corrosion inhibitors to the powertrain intake valve deposit performance is not understood. This paper has two purposes: to present and discuss a survey of corrosion inhibitors and how they vary in concentration in the final blended fuel, specifically E85 (Ethanol Fuel Blends); and to show how variation in concentration of components of CIs and detergents impact intake valve deposit formation.

Traditional vehicle air conditioning systems are designed to cool the entire cabin to provide passenger comfort. Localized cooling, on the other hand, focuses on keeping the passenger comfortable by creating a micro climate around the passenger. Such a system also easily adapts to the number of passengers in the car and enables zonal control. The net impact of the localized cooling is that equivalent comfort can be achieved at reduced HVAC energy consumption rate. The present paper reports on a vehicle implementation of localized cooling using Thermoelectric Devices and the resulting energy saving.

The present paper reports on a study of the HVAC energy usage for an EREV (extended range electric vehicle) implementation of a localized cooling/heating system. Components in the localized system use thermoelectric (TE) devices to target the occupant's chest, face, lap and foot areas. A novel contact TE seat was integrated into the system. Human subject comfort rides and a thermal manikin in the tunnel were used to establish equivalent comfort for the baseline and localized system. The tunnel test results indicate that, with the localized system, HVAC energy savings of 37% are achieved for cooling conditions (ambient conditions greater than 10 °C) and 38% for heating conditions (ambient conditions less than 10 °C), respectively based on an annualized ambient and vehicle occupancy weighted method. The driving range extension for an electric vehicle was also estimated based on the HVAC energy saving.

Spot weld separation in vehicle development stage is one of the critical phenomena in structural analyses regarding quasi-static test condition, like roof strength or seat/belt pull. It directly reduces structural performance by losing connected load path and occasionally introduces tearing on surrounding sheet metals. Traditionally many efforts have been attempted to capture parent metal ductile fracture, but not applied to spot weld separations in automotive FEA simulations. [1,2,3] This paper introduces how to develop FFLD failure criteria from a series of parametric study on ultra high strength sheet steel and deals with failure criteria around spot weld and parent metal. Once the fracture strains for sheet steels are determined, those developed values were applied to traditional spot weld coupon FEA simulations and tests. Full vehicle level roof strength FEA simulations on a typical automotive body structure were performed and verified to the physical tests.

An experimental study was conducted to evaluate the variable amplitude fatigue behavior of a neat polymer (polypropylene impact co-polymer) and a polymer composite made of polybutylene terephthalate (PBT) with 30 wt% short glass fibers. Fatigue tests were conducted on un-notched and notched specimens at room temperatures. Plate-type specimens were prepared in the transverse direction with respect to the injection mold flow direction and a circular hole was drilled in the center of notched specimens. Two-step loadings (high-low and low-high) tests at two damage ratio of 0.2 and 0.5 at stress ratios of R = 0.1 and -1 were conducted to investigate load sequence effects and prediction accuracy of the linear damage rule. Different behaviors were observed for unreinforced and short glass fiber reinforced polymers under the two-step loading tests.

Friction stir linear welding (FSLW) is widely used in joining lightweight materials including aluminum alloys and magnesium alloys. However, fatigue life prediction method for FSLW is not well developed yet for vehicle structure applications. This paper is tried to use two different methods for the prediction of fatigue life of FSLW in vehicle structures. FSLW is represented with 2-D shell elements for the structural stress approach and is represented with TIE contact for the maximum principal stress approach in finite element (FE) models. S-N curves were developed from coupon specimen test results for both the approaches. These S-N curves were used to predict fatigue life of FSLW of a front shock tower structure that was constructed by joining AM60 to AZ31 and AM60 to AM30. The fatigue life prediction results were then correlated with test results of the front shock tower structures.

A new solution methodology for optimal spot-weld pattern design is presented. The objective of the optimization is to minimize the total number of welds in a structure while maintaining structural properties above a required level. Two approaches were developed, based on the representation of welds in a finite element model. In the approach ‘without ranking’ welds are represented in a traditional way, as rigid connections. In ‘with ranking’ approach welds are treated as elastic elements subjected to stresses and deformations under given loading conditions. The information on weld stress is utilized in the solution process to reduce the number of design variables and improve the quality of the solution. The applicability of the method to large automotive structures was demonstrated, as well as the capacity for optimization with respect to multiple load sets.