Search Results

Typical automotive body structures use resistance spot welding for most joining purposes. New materials, such as Advanced High Strength Steels (AHSS) are increasingly used in the construction of automotive body structures to meet increasingly higher structural performance requirements while maintaining or reducing weight of the vehicle. One of the challenges for implementation of new AHSS materials is weldability assessment. Weld engineers and vehicle program teams spend significant efforts and resources in testing weldability of new sheet metal stack-ups. In this paper, we present a methodology to determine the weldability of sheet metal stack-ups using an Artificial Neural Network-based tool that learns from historical data. The paper concludes by reviewing weldability results predicted by using this tool and comparing with actual test results.

A laboratory wear test is used to evaluate the wear protection properties of new and used engine oils formulated for FFV service. Laboratory-blended mixtures of these oils with methanol and water have also been tested. The test consists of a steel ball rotating against three polished cast iron discs. Oil samples are obtained at periodic intervals from a fleet of 3.0L Taurus vehicles operating under controlled go-stop conditions. To account for the effects of fuel dilution, some oils are tested before and after a stripping procedure to eliminate gasoline, methanol and other volatile components. In addition to TAN and TBN measurements, a capillary electrophoresis technique is used to evaluate the formate content in the oils. The results suggest that wear properties of used FFV lubricants change significantly with their degree of usage.

This paper explores the extent to which standard dilution tunnel measurements of motor vehicle exhaust particulate matter modify particle number and size. Steady state size distributions made directly at the tailpipe, using an ejector pump, are compared to dilution tunnel measurements for three configurations of transfer hose used to transport exhaust from the vehicle tailpipe to the dilution tunnel. For gasoline vehicles run at a steady 50 - 70 mph, ejector pump and dilution tunnel measurements give consistent results of particle size and number when using an uninsulated stainless steel transfer hose. Both methods show particles in the 10 - 100 nm range at tailpipe concentrations of the order of 104 particles/cm3.

Because it is common to attach plastic parts to other plastic, metal, or ceramic assemblies with mechanical fasteners that are often stronger and stiffer than the plastic with which they are mated, it is important to be able to predict the retention of the fastener in the polymeric component. The ability to predict this information allows engineers to more accurately estimate length of part service life. A study was initiated to understand the behavior of threaded fasteners in bosses molded from engineering thermoplastic resins. The study examined fastening dynamics during and after insertion of the fastener and the effects of friction on the subsequent performance of the resin. Tests were conducted at ambient temperatures over a range of torques and loads using several fixtures that were specially designed for the study. Materials evaluated include modified-polyphenylene ether (M-PPE), polyetherimide (PEI), polybutylene terephthalate (PBT), and polycarbonate (PC).

Present models and methods for simulations of sheet metal forming processes are reviewed in this paper. Because of rapid progress of computer hardware, complex computations, formerly impossible to perform due to high computational cost, are now feasible. Therefore, more realistic and computational intensive models are suggested for finite elements, materials, and frictional forces. Also, simulation methods suitable for sheet metal forming processes are recommended. Four numerical examples at the end of the paper are presented to support the recommendations.

Edge stretchability reduction induced by mechanical trimming is a critical issue in advanced high strength steel applications. In this study, the tooling effects on the trimmed edge damage were evaluated by the specially designed in-plane hole expansion test with the consideration of three punch geometries (flat, conical, and rooftop), three cutting clearances (6%, 14%, and 20%) and two materials grades (DP980 and DP1180). Two distinct fracture initiation modes were identified with different testing configurations, and the occurrence of each fracture mode depends on the tooling configurations and materials grades. Digital Image Correlations (DIC) measurements indicate the materials are subject to different deformation modes and the various stress conditions, which result in different fracture initiation locations.

The change in the resistance of titanium dioxide with oxygen partial pressure is utilized to obtain an air-to-fuel ratio sensor. TiO2 material properties, sensor components and performance characteristics are discussed. Some results of engine dynamometer and vehicle tests of sensor performance and durability are presented.

The recent development of TiAl-based alloys by the aerospace community has provided an excellent material alternative for hot components in automotive engines. The low density combined with an elevated temperature strength similar to that of Ni-base superalloys make TiAl-based alloys very attractive for exhaust valve applications. Lighter weight valvetrain components improve performance and permit the use of lower valve spring loads which reduce noise and friction and enhance fuel economy. However, difficult fabricability and a perception that TiAl alloys are high cost, low volume aerospace materials must be overcome in order to permit consideration for use in high-volume automotive applications. This paper provides a comparison of properties for several exhaust valve alternative materials. The density of TiAl alloys is lower than Ti alloys with creep and fatigue properties equivalent to IN-751, a current high performance exhaust valve material.

Semi-Permanent Mold (SPM) cast aluminum alloy cylinder heads are commonly used in gasoline and diesel internal combustion engines. The cast aluminum cylinder heads must withstand severe cyclic mechanical and thermal loads throughout their lifetime. The casting process is inherently prone to introducing casting defects and microstructural heterogeneity. Porosity, which is one of the most dominant volumetric defects in such castings, has a significant detrimental effect on the fatigue life of these components since it acts as a crack initiation site. A reliable analytical model for Thermo-Mechanical Fatigue (TMF) life prediction must take into account the presence of these defects. In previous publications, it has been shown that the mechanism-based TMF damage model (DTMF) is able to predict with good accuracy crack locations and the number of cycles to propagate an initial defect into a critical crack size in aluminum cylinder heads considering ageing effects.

Cast austenitic stainless steels, such as 1.4837Nb, are widely used for turbo housing and exhaust manifolds which are subjected to elevated temperatures. Due to assembly constraints, geometry limitation, and particularly high temperatures, thermomechanical fatigue (TMF) issue is commonly seen in the service of those components. Therefore, it is critical to understand the TMF behavior of the cast steels. In the present study, a series of fatigue tests including isothermal low cycle fatigue tests at elevated temperatures up to 1100°C, in-phase and out-of-phase TMF tests in the temperature ranges 100-800°C and 100-1000°C have been conducted. Both creep and oxidation are active in these conditions, and their contributions to the damage of the steel are discussed.

Measurements of oxygen storage capacity (OSC) and HC conversion efficiency for 17 catalysts were carried out in the laboratory. All catalysts with steady state HC efficiency below 90% were found to have roughly equivalent and very low capacities to store oxygen. However, catalyst oxygen storage capacity was seen to rise sharply with HC conversion efficiency in excess of 90 percent. These results parallel the trends which are observed between rear HEGO/EGO indexes for OBD-II catalyst monitoring and HC conversion efficiency. In addition, temperature programed reduction (TPR) was found to lend insight into the relationship between catalyst OSC and HC conversion efficiency by providing a qualitative understanding of the mechanisms by which OSC deteriorates. TPR profiles showed that most of the usable oxygen storage is derived from surface ceria which is interacted with precious metals.

The P2000S body structure was designed as part of an advanced research project to determine the feasibility of a high volume, lightweight sport utility vehicle (SUV) that would achieve performance targets of the newly emerging “City SUV” market by developing a unitized (no frame) SUV body structure fabricated principally of aluminum. In order to be viable, this body structure was required to meet all safety, durability, NVH and other functional attributes of a truck while having the ride characteristics of a sedan. This paper describes the P2000S body structure including the structural philosophy, project constraints on the design, manufacturing processes, supporting analyses, assembly processes and unique material and design concepts which resulted in the 50% body structure weight reduction in comparison to similar sized body-on-frame production steel sport utility vehicles.

The automotive industry is continuously striving to reduce vehicle mass by reducing the mass of components including wheel bearings. A typical wheel bearing assembly is mostly steel, including both the wheel and knuckle mounting flanges. Mass optimization of the wheel hub has traditionally been accomplished by reducing the cross-sectional thickness of these components. Recently bearing suppliers have also investigated the use of alternative materials. While bearing component performance is verified through analysis and testing by the supplier, additional effects from system integration and performance over time also need to be comprehended. In a recent new vehicle architecture, the wheel bearing hub flange was reduced to optimize it for low mass. In addition, holes were added for further mass reduction. The design met all the supplier and OEM component level specifications.

Gas carburized and quenched low alloy steels typically produce surface microstructures which contain martensite, retained austenite and often NMTP's (non-martensitic transformation products). The NMTP's are caused by a reduction of surface hardenability in the carburizing process from loss of alloying elements to oxidation. Gas carburized low alloy steels such as SAE 8620 with NMTP's on the surface have been shown to have inferior bending fatigue properties when compared to more highly alloyed steels which do not form NMTP's, such as SAE 4615M. One method of minimizing the formation of oxides and eliminating NMTP formation during carburizing and quenching is to use plasma carburizing instead of conventional gas carburizing. In this study the microstructures and bending fatigue performance of plasma carburized SAE 8620 and SAE 4615M is compared to the same alloys conventionally gas carburized and quenched.

The influence of calcium treatment on the mechanical properties of a plain carbon steel (SAE 1050) was investigated. The mechanical properties investigated were tensile and impact strength, fatigue crack growth rate, and the fatigue threshold. Impact testing was conducted at both room temperature and at -40°C. Several heats of both calcium and non-calcium treated steel (SAE 1050) were tested in both the as hot-rolled condition and in the quenched and tempered condition (with a hardness level of HRC = 45). The results of this investigation show no significant difference in the tensile properties or room temperature impact properties between the calcium treated and the non-calcium treated steels. However, the impact strengths of calcium treated steels were slightly higher than that of non-calcium treated steels at -40°C.

This paper discusses a motor vehicle noise source identification technique designed for use during the SAE J986a or similar drive-by test procedure. It provides, by application of the Fourier Transform, the capability to obtain a narrowband (9.8 Hz) frequency resolution over an extended frequency range (0-10,000 Hz) at the peak vehicle noise level, a particular RPM, or a particular vehicle location in the test zone. Other features include corrections for the Doppler shift, averaging of noise tests, and subtraction of spectra of two separate noise tests from a component disconnect/reconnect procedure. The above analysis, in conjunction with the noise source isolation resulting directly from the disconnect procedure, identifies the major vehicle noise contributors in terms of their respective amplitudes and frequencies.

A small-scale oxidation test for automatic transmission fluids has been developed. In the test air flow rates, temperature and catalytic activity can be closely controlled at desired levels. A test procedure for screening automatic transmission fluids is described. Data are presented illustrating the ability of the test to distinguish between different levels of oxidation resistance, the repeatability of the test, and the correlation achieved thus far with a presently used full-scale transmission oxidation test.

Erosion damage to automotive car bodies caused by stones and small sand particles and road debris significantly affects the appearance of paint. Painted engineering plastics as well as precoated sheet steel are affected by erosion phenomenon. Erosion of painted plastic substrates results in cosmetic concerns while that on metal substrates results in cosmetic to perforation corrosion. This work describes a laboratory simulation of erosion of painted plastic substrates by small particles on various paint and substrate types. Gloss loss was used to quantitatively evaluate erosion of painted surfaces. Wear behavior of painted plastic substrates to slag sand impact was evaluated as a function of several variables including paint type (one-component melamine crosslinked (1K) vs. two-component isocyanate crosslinked (2K)), thermal history, and coating modulus. The effect of slag sand type (particle size and chemical composition) was studied.

Vehicle emissions have been measured and the results statistically evaluated for a vehicle test fleet consisting of four Escorts and four Explorers using both a fully formulated durability fuel doped with methylcyclopentadienyl manganese tricarbonyl (MMT) at 1/32 gram Mn/gallon and the same fully formulated durability fuel without the MMT. The fleet was divided in half -- half with MMT and half without MMT doped fuel. This report covers emission measurement results at 5,000; 15,000; 50,000 and 100,000 miles of exposure to MMT doped fuel. A modified paired t-test is used to analyze the emission data obtained from all the fleet vehicles. The statistical evaluation of both feedgas and tailpipe emissions indicate that the use of MMT is detrimental to emissions of HC at the 15,000 mile; 50,000 mile and 100,000 mile levels of MMT exposure. As mileage is accumulated, the pronounced the effect on HC by the fuel additive MMT.

The effect of MMT on the OBD-II catalyst efficiency monitor has been investigated. The results conclusively show that manganese which is deposited onto the catalyst during the combustion of MMT- containing fuel provides for an increased level of catalyst oxygen storage capacity. This added oxygen storage was found to result in a reduced rear EGO sensor response and caused malfunctioning catalysts to be incorrectly diagnosed by the OBD-II catalyst efficiency monitor.