Search Results

Multigrade automotive lubricants contain polymeric viscosity modifiers which enable the oil to provide adequate hydrodynamic lubrication at high temperatures and good starting/pumping performance at low temperatures. Under operating conditions in engines, transmissions and gear boxes, polymeric additives undergo both temporary and permanent viscosity loss. The former is caused by flow orientation and the latter by molecular chain scission. Whatever the mechanism, original equipment manufacturers are interested in maintaining a minimum level of hydrodynamic viscosity from oil change to oil change. This is often expressed as a “stay-in-grade” requirement. Commercial viscosity modifiers (VM) span a wide range of chemistries and molecular architectures.

Laboratory testing is an essential part of product development. However, it usually only reflects a small portion of the experience that a lubricant may see in actual service conditions. Many laboratory tests are designed to only address one or two facets of what is deemed to be critical performance areas. Since it is difficult to cover all of the critical performance conditions problems sometimes arise in service that were not anticipated by the laboratory test. Or, conversely, some above average performance evolves during service that was not observed in a specific laboratory test. This paper highlights the overall performance of four manual transmission fluids approved or accepted by the manufacturer for this application. The evaluations were conducted in a city bus fleet with the test buses assigned to the same route for approximately 300,000 km over 30 months.

City transit buses are a severe environment for an automatic transmission fluid. The fluid must endure very high operating temperatures because of the use of brake retarders, frequent stop-and-go driving, and numerous shifts. There is an increasing trend toward the use of extended-drain, synthetic-based ATFs for such severe service applications. This paper documents a field trial with both synthetic and petroleum-based ATFs at a large municipal bus fleet in Southern California. Three different commercial ATFs, made with either API Group 2, 3, or 4 base oils, respectively, were compared after roughly 80,000 km. and one year of operation. Because of different additive packages in each fluid, not all of the results can be explained by base oil effects alone. However, the base oil is certainly a dominant contributor to the finished fluid performance. The following four variables were monitored by used oil analysis: iron wear, copper wear, viscosity change, and acid number change.

Component bench fatigue testing is a cost-effective way to evaluate the durability of exhaust catalytic converters. A successful bench fatigue test depends on the development of a test specification. The test specification should represent the actual customer duty cycle that the component is exposed to. Based on the concept of equivalent fatigue damage, a systematic approach is presented to obtain the test specification from the acquired road load data. A method based on damage analysis is proposed to determine the effective notch factor, and an empirical relationship is presented to account for the thermal effect on the test specification. The principles and procedures of multiple block testing and constant amplitude testing are also presented.

The Sequence IIIG is a newly developed 100 hour test used to evaluate the performance of crankcase engine oils in the areas of high temperature viscosity increase, wear, deposits, pumpability, and ring sticking for the North American GF-4 standard. Data from the ASTM Precision Matrix, completed in the spring of 2003, along with early reference data from the Lubricant Test Monitoring System (LTMS) showed unexpected test results for selected oils and indicated that percent viscosity increase and pumpability were highly correlated with oil consumption. This correlation led to an intensive study of the factors that influence oil consumption and an attempt to compensate for non-oil related oil consumption through a model based adjustment of the results. The study and scrutiny of the IIIG data has led to more uniform oil consumption in the test and improved test precision, and has eliminated the need for a correction equation based on non-oil related oil consumption.

The effects of lubricating oil on friction and wear were investigated using light-duty 2.2L compression ignition direct injection (CIDI) engine components for bench testing. A matrix of test oils varying in viscosity, friction modifier level and chemistry, and base stock chemistry (mineral and synthetic) was investigated. Among all engine oils used for bench tests, the engine oil containing MoDTC friction modifier showed the lowest friction compared with the engine oils with organic friction modifier or the other engine oils without any friction modifier. Mineral-based engine oils of the same viscosity grade and oil formulation had slightly lower friction than synthetic-based engine oils.

This project investigated the effect of carburizing carbon-potential and thermal history on the bending fatigue performance of carburized SAE 4320 gear steel. Modified-Brugger cantilever bending fatigue specimens were carburized at carbon potentials of 0.60, 0.85, 1.05, and 1.25 wt. pct. carbon, and were either quenched and tempered or quenched, tempered, reheated, quenched, and tempered. The reheat treatment was designed to lower the solute carbon content in the case through the formation of transition carbides and refine the prior austenite grain size. Specimens were fatigue tested in a tension/tension cycle with a minimum to maximum stress ratio of 0.1. The bending fatigue results were correlated with case and core microstructures, hardness profiles, residual stress profiles, retained austenite profiles, and component distortion.

A serpentine flow channel is one of the most common and practical channel layouts for a PEM fuel cell since it ensures the removal of water produced in a cell. While the reactant flows along the flow channel, it can also leak or cross to neighboring channels via the porous gas diffusion layer due to a high pressure gradient. Such a cross flow leads to effective water removal in a gas diffusion layer thus enlarging the active area for reaction although this cross flow has largely been ignored in previous studies. In this study, neutron radiography is applied to investigate the liquid water accumulation and its effect on the performance of a PEM fuel cell. Liquid water tends to accumulate in the gas diffusion layer adjacent to the flow channel area while the liquid water formed in the gas diffusion layer next to the channel land area seems to be effectively removed by the cross leakage flow between the adjacent flow channels.

In this report, the DCX Stress Lab and the Tool Development & Test Support groups investigated automating a resonant bending crankshaft fatigue test. Fatigue testing, in general, is a laborious process since many samples are needed for analysis. This makes development cost and speed dependant on the component test efficiency. In the case of crankshaft resonant bending testing, both cost and speed are influenced by the manual feedback operation needed to run the current procedure. In order to increase the efficiency of this process, this project sought to automate the following tasks: maintaining the load on the part, reacting to resonance changes in the part, mapping resonance changes, logging the number of cycles, and discerning resonance frequency shift failure modes objectively.

The use of composite materials in the automotive industry has become increasingly widespread. With this increase in use, techniques for non-destructive testing (NDT) have become more and more important. Various optical NDT inspective methods such as holography, moiré techniques, and shearography have been used for material testing. Among these methods, shearography appears to be most practical. Shearography has a simple optical setup due to its “self-referencing” system, and it is relatively insensitive against rigid-body motions. Measurements of displacement derivatives, and thus strain directly, rather than the displacement itself is achieved through this method. Therefore shearography detects defects in objects by correlating anomalies of strain which are usually easier than correlating the anomalies of the displacement itself, as in holography. To date shearography has shown potential as a NDT tool for identifying defects in small structures.

This paper addresses the critical parameters required for development of automotive thermal protection plans. The test conditions should consider the ambient air temperature, exhaust gas temperature, vehicle speed and engine speed. The choice of test conditions is critical in determining potential thermal issues during the development phase. Appropriate design alternatives can then be implemented.

Light metal alloys based on magnesium and aluminum are increasingly being pursued for various vehicle interior applications because of distinct advantages such as weight savings and potential parts consolidation. One such application of light metal alloys is the steering wheel, which is an important component of a safety system that is comprised of the driver-side airbag, steering wheel, the steering column and its attachment bracketry to the instrument panel and the vehicle body structure. For the airbag to function effectively as a restraint during a frontal crash, the steering wheel has to provide adequate support. In addition to the steering column which is designed to absorb energy, the wheel can also function as an energy absorber if so designed. One way of achieving this energy absorption is through plastic deformation of the wheel. Adverse material characteristics, however, make the energy absorbing steering wheel design, using light metal alloys, a sizeable challenge.

Multifunctional or universal lubricating oils which service both gasoline and diesel engines have gained widespread commercial acceptance. Since 1970, numerous changes and additions have altered the performance tests and specifications which define the quality of these lubricants. New parameters include single cylinder and multicylinder diesel engine testing, valve train wear protection, clutch plate friction retention, extended drain interval and lubricant related fuel economy. In response to these requirements, new additive systems were developed. This paper discusses observed base oil-additive-engine test interactions and compares the performance of one of these additive systems to that of the old.

Forming and strain rate effects on crashworthiness of automotive body components were investigated in this study. Dynamic tensile tests were carried out to establish the stress-strain relationships at elevated strain rates. Dynamic tests of bending and axial crashing at various speeds were conducted using a stamped hat square column. The experimental results indicate that the absorbed energy of the hat square column decreased with the increase of material thinning in case of high strength steels. FEM analyses using material models with both strain rate sensitivity and forming effects were carried out to evaluate the computer prediction accuracy of crashworthiness.

The next generation of engine oil under development has been formulated to maintain beneficial oil lubrication properties at increased engine operating temperatures, increased drain-oil intervals, and with the recirculation of exhaust gas back through the engine (EGR). These conditions result in the formation of degradation products from decomposed fuel, additives, and base oil. Decomposition products containing reactive sulfur can result in the corrosion of copper alloys. Sulfur-containing compounds currently used in these formulations can include zinc dithiophosphates (ZDP), molydithiophosphates, molydithiocarbamates, and molybdic acid/amine complexes, along with sulfur containing detergents and antioxidants. Interactions among these components and others in the formulation often determine the propensity of these formulations for corrosion. This paper will discuss the results of corrosion bench tests used to screen oil formulations for copper corrosion.

Rapid wear out of a disk brake due to phenomena commonly known as hot spots is one of various problems faced by brake manufacturers. Hot spots are localized high temperature areas generated on the frictional surface of a disk brake during braking. The non-uniform surface expansion caused by hot spots on the disk surface may cause pedal pulsation or known as thermal judder. This effect in the long run will shorten a brake's life. Numerical simulation of a disk brake requires the use of nonlinear contact mechanics approach. The simulation is computationally very expensive and difficult to perform. A computer simulation technique has been developed at the DaimlerChrysler Brake Core Group to investigate the hot spot phenomena since 1997. The technique was implemented on 3-D finite element models to simulate frictional contacts between the disk and its pads. Computer code ABAQUS is used for these analyses and computations are performed in Silicon Graphics, Origin 2000 machines.

A new gas phase kinetic model using Westbrook's gas phase n-heptane model and Frenklach's soot model was constructed. This model was then used to predict the impact on PAH formation as an indices of soot formation on ethanol/diesel fuel blends. The results were then compared to soot levels measured by various researchers. The ignition delay characteristics of ethanol were validated against experimental results in the literature. In this paper the results of the model and the comparison with experimental results will be discussed along with implications on the method of incorporation of additives and alternative fuels.

Loads generated during assembly may cause significant stress levels in components. Under test conditions, these stresses alter the mean stress which in turn, alters the fatigue life and critical stress area of the components as well. This paper describes the Finite Element Analysis (FEA) procedure to evaluate behavior of a cast aluminum wheel subjected to the rotary fatigue test condition as specified in the SAE test procedure (SAE J328 JUN94). Fatigue life of the wheel is determined using the S-N approach for a constant reversed loading condition. In addition, fatigue life predictions with and without clamp loads are compared. It is concluded that the inclusion of clamp load is necessary for better prediction of the critical stress areas and fatigue life of the wheel.

The durability of fuel tank straps is essential for vehicle safety. Extensive physical tests are conducted to verify designs for durability. Due to the complexity of the loads and the fuel-to-tank interaction, computer-aided-engineering (CAE) simulation has had limited application in this area. This paper presents a CAE method for fuel tank strap durability prediction. It discusses the analytical loads, modeling of fuel-to-tank interaction, dynamic analysis methods, and fatigue analysis methods. Analysis results are compared to physical test results. This method can be used in either a fuel-tank-system model or a full vehicle model. It can give directional design guidance for fuel tank strap durability in the early stages of product development to reduce vehicle development costs.

Cavity reinforcement materials are used in the automotive industry to stiffen hollow cavities in vehicle body constructions. Typical areas of use include the engine rails, rocker panels, roof support or any other cavity in need of structural reinforcement. Use of these materials can allow for significant reductions in vehicle weight and increase structural stiffness with minimal impact to production tooling. Additional benefits can be gained by using the material as a physical barrier to the propagation of noise, water and dust. The objective of this paper is to describe a case study which implemented a new type of cavity reinforcing material to improve low frequency vehicle noise and vibration characteristics.