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Weld fatigue evaluation using the mesh-insensitive Battelle structural stress method has been applied to fusion welds, resistance spot welds and non-welded components. The effectiveness of the Battelle structural stress procedure has been demonstrated in a series of earlier publications for welded structures with different joint types, plate thicknesses, and loading modes. In this paper, a weld fatigue evaluation procedure using the Battelle structural stress method is proposed for friction stir welds currently being used in the automotive and aerospace industries. The applicability of the Battelle structural stress procedure is demonstrated by comparing fatigue life predictions for friction stir welded specimens to well-documented test data from the literature. Different specimen types, plate thicknesses and loading ratios were analyzed for several aluminum alloys.

The nodal force based Battelle structural stress method has shown its mesh insensitivity in the stress analysis of spot welds as well as fusion welds. In the conventional structural stress simulation procedure, the structural stress is calculated at the nodes along the nugget periphery. However, implementing a nugget into each spot weld is cumbersome and time consuming not only in preparing mesh for FE analysis but also in preparing a series of structural stress calculation after finishing the FE analysis. Therefore, the efficiency of the current Battelle structural stress practice for spot welds can be improved significantly for structures with a large number of spot welds. The simplified modeling procedure presented here delivers reliable structural stresses at spot welds and these stresses can then be utilized for fatigue life prediction using a master S-N Curve approach that is applicable to wide range of spot welding techniques.

Natural Gas engines are viewed as an alternative to diesel power in the quest to reduce heavy duty vehicle emissions in polluted urban areas. In particular, it is acknowledged that natural gas has the potential to reduce the inventory of particulate matter, and this has encouraged the use of natural gas engines in transit bus applications. Extensive data on natural gas and diesel bus emissions have been gathered using two Transportable Heavy Duty Vehicle Emissions Testing Laboratories, that employ chassis dynamometers to simulate bus inertia and road load. Most of the natural gas buses tested prior to 1997 were powered by Cummins L-10 engines, which were lean-burn and employed a mechanical mixer for fuel introduction. The Central Business District (CBD) cycle was used as the test schedule.

Homogeneous Charge Compression Ignition (HCCI) combustion has the potential to produce low NOx and low particulate matter (PM) emissions while providing high efficiency. In HCCI combustion, the start of auto-ignition of premixed fuel and air depends on temperature, pressure, concentration history during the compression stroke, and the unique reaction kinetics of the fuel/air mixture. For these reasons, the choice of fuel has a significant impact on both engine design and control strategies. In this paper, ten (10) gasoline-like testing fuels, statistically representative of blends of four blending streams that spanned the ranges of selected fuel properties, were tested in a single cylinder engine equipped with a hydraulic variable valve train (VVT) and gasoline direct injection (GDI) system.

In this study, an incrementally coupled finite element analysis procedure is used to analyze the electrical, thermal, and mechanical interaction during resistance spot welding processes. The results of the finite element analysis are validated by experimental measurements of the weld nugget sizes and dynamic resistance. The temperature results from the thermo-electric analysis are used as the input for the prediction of the microstructure evolution in the resistance spot welds of high strength steels. Consequently such welding parameters as welding current, electrode force, electrode designs, cooling water temperature and flow rate, and electrode holding time can be linked with the weld nugget size, microstructure and mechanical properties in spot welds, and eventually the residual stresses and performance of spot welded structures.

The effects of electrode wear on nugget development during resistance spot welding are major concerns in auto-body assembly and manufacturing. By considering detailed electrode-sheet interactions using advanced finite element modeling procedure, this paper presents a framework for detecting the electrode wear conditions and associated nugget development characteristics. Two important in-process parameters are studied in detail. They are the electrode movement and the dynamic resistance. It is found that the second-order derivative of the electrode movement and the first-order derivative of the dynamic resistance can be correlated in a fundamental form to identify the detailed nugget development process under various electrode wear conditions.

The aggressive reduction of future diesel engine NOx emission limits forces the heavy- and light-duty diesel engine manufacturers to develop means to comply with stringent legislation. As a result, different exhaust emission control technologies applicable to NOx have been the subject of many investigations. One of these systems is the NOx adsorber catalyst, which has shown high NOx conversion rates during previous investigations with acceptable fuel consumption penalties. In addition, the NOx adsorber catalyst does not require a secondary on-board reductant. However, the NOx adsorber catalyst also represents the most sulfur sensitive emissions control device currently under investigation for advanced NOx control. To remove the sulfur introduced into the system through the diesel fuel and stored on the catalyst sites during operation, specific regeneration strategies and boundary conditions were investigated and developed.

A gas chromatographic technique was used to determine the vapor pressures of blends of six candidate diesel fuel oxygenates with three diesel fuels at 0, 5, 10, 30, and 100 percent blend levels. Both the oxygenates and the diesel fuels were selected to represent a variety of chemical compositions. The vapor pressures were determined over a range of temperatures from -30 C to +30 C. In each case the fraction of the vapor pressure derived from the oxygenate and the fuel was identified. The vapor pressure results showed that there were significant deviations from ideality, leading to both higher and lower vapor pressures than would be predicted from Raoult's Law. These results are significant for fire safety and evaporative emissions as well as for a more basic understanding of the behavior of these blends. Data were also obtained on the heats of vaporization for each of the blends.

Miscibility, water tolerance, cloud point, and flash point data are presented for seven candidate diesel fuel oxygenates: dipentyl ether, dibutoxymethane, 2-ethoxyethyl ether, diethyl maleate, tripropylene glycol monomethyl ether, dibutyl maleate, and glycerol tributrate. These oxygenates were blended with three different diesel fuels: an oil sands diesel, an ultra-low sulfur diesel, and a Fischer-Tropsch diesel. Blend levels included 0, 5, 10, 30, and 100 % oxygenate. Properties were measured at temperatures of -30, -15, 0, 15, and 30 C.

Even under uniaxial loading, seemingly simple welded joint types can develop multi-axial stress states, which must be considered when evaluating both the fatigue strength and failure location. Based on the investigation of fatigue behavior for the multi-axial stress state, a procedure for fatigue behavior of welded joints with multi-axial stress states was proposed using an effective equivalent structural stress range parameter combined normal and in-plane shear equivalent structural stress ranges and the master S-N curve approach. In automotive structures, fatigue failure is often observed at weld end, which often show a complex stress state. Due to simplified weld end representation having a sharp right-angled weld corner, the fatigue failure prediction at the weld end tends to be overly conservative due to the excessive stress concentration at the right-angled weld termination.

An oxidizing catalytic converter was evaluated in the exhaust train of a 3.73 kW (5 hp) natural gas engine. The engine was developed for use in a gas engine-driven heat pump and is designed for operation at lean air/fuel ratios. The converter tested had a metallic substrate with a cell density of 31 cells/cm2. Converter tests measured emission performance as a function of the key engine variables: speed, load, spark advance and air/fuel ratio. As expected, CO conversion averaged well above 90 percent. Hydrocarbon conversion varied between 68.6 and 89.8 percent over a range of eight speed and load combinations selected to cover the normal operating range of the engine. Conversion of individual hydrocarbon species was examined also. Although the converter tests were not designed to isolate the key converter variables, a simple mathematical model allowed us to explore the effect of these variables on conversion.

Vehicle exhaust emissions measurements are reported for full-size panel vans operating on four alternative motor fuels and control gasoline. The emissions tests produced data on in-use vans. The vans were taken directly from commercial delivery service for testing as they accumulated mileage over a 24-month period. The alternative fuels tested were compressed natural gas, propane gas, California Phase 2 reformulated gasoline (RFG), and methanol (M-85 with 15 percent RFG). The control gasoline for the emissions tests was an industry average unleaded blend (RF-A). The vehicle technologies tested represent those options available in 1992 that were commercially available from Ford, Chrysler, and Chevrolet or which these manufacturers agreed to provide as test vans for daily use in commercial service by FedEx.

Research has shown that there are many factors that affect the long-term performance of nitrogen oxides (NOx) control systems used in diesel engine applications. However, if the NOx emissions can be accurately monitored, it might be possible to restore performance by making adjustments to the control systems. This paper presents results from a study that tested the durability of 25 NOx sensors exposed to heavy-duty diesel exhaust for 6,000 hours. The study, conducted by the Advanced Petroleum-Based Fuels - Diesel Emission Controls (APBF-DEC) project, tested the sensors at various locations in the exhaust stream.

This paper reports the test results from the DPF (diesel particulate filter) portion of the DECSE (Diesel Emission Control - Sulfur Effects) Phase 1 test program. The DECSE program is a joint government and industry program to study the impact of diesel fuel sulfur level on aftertreatment devices. A systematic investigation was conducted to study the effects of diesel fuel sulfur level on (1) the emissions performance and (2) the regeneration behavior of a continuously regenerating diesel particulate filter and a catalyzed diesel particulate filter. The tests were conducted on a Caterpillar 3126 engine with nominal fuel sulfur levels of 3 parts per million (ppm), 30 ppm, 150 ppm and 350 ppm.

The Diesel Emission Control - Sulfur Effects (DECSE) program is a joint U.S. government/industry program that studies the impact of diesel sulfur levels on four types of emission control systems. One type of system, Diesel Particulate Filters (DPF), removes particulate matter (PM) from the exhaust stream by collection on a filter. The critical operating issue for DPF technology is the cleaning or regeneration of the control device (by oxidation of the collected PM) to prevent plugging. However, oxidation of sulfur in the exhaust forms sulfates, which are measured as PM. Two types of tests are conducted to evaluate the impacts of fuel sulfur on DPF performance: (1) emissions tests for PM components and gases, and (2) experiments to measure the effect of fuel sulfur on the regeneration temperature required by the filter devices.

Tailor-welded blanks (TWB) have been increasingly used in the automotive industry as an effective way to reduce weight and costs. Although some of the joining processes for TWB are relatively well known, little independent information exists regarding welding procedure effects on weld/HAZ properties, particularly their effects on form-ability and structural performance under various conditions. In this paper, advanced computational modeling techniques were used to investigate the effects of welding procedures on weld property evolution and its impact on the formability issues. Two case studies were presented. One is on TIG welding of 6000 series aluminum tailored blanks, where thermomechanical effects on weldability was analyzed. Its implication on weld performance during forming will be discussed. The other case is on laser-beam welding of high strength steel to mild steel with a non-linear weld. The detailed thermal history and residual stress development will be presented.

Welding induced residual stresses are an important factor to consider when evaluating fatigue design of welded automotive parts. Fortunately, design engineers have various residual stress mitigation technologies at their disposal for improving the fatigue performance of these parts. For this purpose, it is essential to understand the relationship between the residual stresses and fatigue performance quantitatively as well as qualitatively. It has been widely accepted that tensile residual stresses in welded structures are as high as the material yield strength level. Therefore, the fatigue strength of welded joints is governed predominantly by the applied stress range, regardless of the load ratio. However, in stress relieved components the tensile residual stress level is not as high, and the weld fatigue behavior is more influenced by the load ratio.

Lightweight, optimized vehicle designs are paramount in helping the automotive industry meet reduced emissions standards. Self-piercing rivets are a promising new technology that may play a role in optimizing vehicle designs, due to their superior fatigue resistance compared with spot welds and ability to join dissimilar materials. This paper presents a procedure for applying the mesh-insensitive Battelle Structural Stress Method to self-piercing riveted joints for fatigue life prediction. Additionally, this paper also examines the development of an interim fatigue design master S-N curve for self-piercing rivets. The interim fatigue design master S-N curve accounts for factors such as various combinations of similar and dissimilar metal sheets, various sheet thicknesses, stacking sequence, and load ratios. A large amount of published data was collapsed into a single interim S-N curve with reasonable data scattering.

As the automotive industry seeks to remove weight from vehicle chasses to meet increased fuel economy standards, it is increasingly turning to composites and aluminum. In spite of increasing demands for quality aluminum alloy spot welds that enable more fuel efficient automobiles, fatigue evaluation procedures for such welds are not well-established. This article discusses the results of an evaluation Battelle performed of the fatigue characteristics of aluminum alloy spot welds based on experimental data and observations from the literature. In comparison with spot welds in steel alloys, aluminum alloy spot welds exhibit several significant differences including a different hardness distribution at and around the weld, different fatigue failure modes, and more. The effectiveness and applicability of the Battelle structural stress-based simplified procedure for modeling and simulating automotive spot welds has previously been demonstrated by Battelle investigations.