Search Results

A stress durability test method that incorporates exposure to a corrosive environment has been used to evaluate the performance of adhesively bonded steel joints. For the systems examined, corrosion exposure is more damaging than exposure to humidity alone. The combination of load and corrosion exposure is substantially more severe than either alone. A method for analysis of the data and comparison of the test results for the evaluation of adhesive bond durability is proposed. The dependence of lifetime on load is defined as , where f is the ratio of applied load to initial, unexposed failure load. The exponent n provides a measure of the degree of acceleration of the interfacial degradation processes by load.

Many foams exhibit significant strain rate dependency in their mechanical responses. To characterize these foams, a strain rate dependent constitutive model is formulated and implemented in an explicit dynamic finite element code developed at FORD. The constitutive model is developed in conjunction with a Lagrangian eight node solid element with twenty four degrees of freedom. The constitutive model has been used to model foams in a number crash analysis problems. Results obtained from the analyses are compared to the experimental data. Evidently, numerical results show excellent agreement with the experimental data.

Increased use of powder-forged connecting rods in the automotive industry prompted an investigation into the suitability of powders from different suppliers for this application. Specifications developed by North American users call for ultra clean powders to enhance machinability and fatigue life. Powders from four manufacturers were each blended with graphite and lubricant, then pressed, sintered and forged to full density. Metallographic samples were prepared and evaluated for inclusion content. In addition, the powders were mixed to the composition of connecting rods, (C - 0.5%, Cu - 2% and MnS - 0.3%), and were similarly pressed, sintered and forged. Test bars were machined from the forged discs. Uniaxial fatigue tests were performed in the tension-compression mode and strain-life curves were developed. It was determined that all powders examined were very clean and were comparable in their inclusion content.

OEMs are racing to develop lightweight vehicles as government regulations now mandate automakers to nearly double the average fuel economy of new cars and trucks by 2025. Lightweight materials such as aluminum, magnesium and carbon fiber composites are being used as structural members in vehicle body and suspension components. The reduction in weight in structural panels increases noise transmission into the passenger compartment. This poses a great challenge in vehicle sound package development since simply increasing weight in sound package components to reduce interior noise is no longer an option [1]. This paper discusses weight saving approaches to reduce noise level at the sources, noise transmission paths, and transmitted noise into the passenger compartment. Lightweight sound package materials are introduced to treat and reduce airborne noise transmission into multi-material lightweight body structure.

A new in-line small diameter, tube and fin aluminum heat exchanger has been developed for automobile air conditioning condenser use. This condenser, while maintaining heat transfer performance, reduces weight, package volume, air flow resistance, and manufacturing complexity.

Current trends in the auto industry requiring tighter dimensional specifications combined with the use of lightweight materials, such as aluminum, are a challenge for the traditional manufacturing processes. The hemming process, a sheet metal bending operation used in the manufacturing of car doors and hoods, poses problems meeting tighter dimensional tolerances. Hemming is the final operation that is used to fasten the outer panel with the inner panel by folding the outer panel over the inner panel. Roll in/out is one of the main quality concerns with hemming, and keeping it under tolerance is a high priority issue for the auto manufacturers. Current hemming process technology, given the mechanical properties of current materials, has reached its saturation limit to deliver consistent dimensional quality to satisfy customers and at the same time meet government standards.

The performance of an organic Rankine cycle (ORC) that recovers heat from the exhaust of a heavy-duty diesel engine was simulated. The work was an extension of a prior study that simulated the performance of an experimental ORC system developed and tested at Oak Ridge National laboratory (ORNL). The experimental data were used to set model parameters and validate the results of that simulation. For the current study the model was adapted to consider a 15 liter turbocharged engine versus the original 1.9 liter light-duty automotive turbodiesel studied by ORNL. Exhaust flow rate and temperature data for the heavy-duty engine were obtained from Southwest Research Institute (SwRI) for a range of steady-state engine speeds and loads without EGR. Because of the considerably higher exhaust gas flow rates of the heavy-duty engine, relative to the engine tested by ORNL, a different heat exchanger type was considered in order to keep exhaust pressure drop within practical bounds.

Motivated by a combination of increasing consumer demand for fuel efficient vehicles, more stringent greenhouse gas, and anticipated future Corporate Average Fuel Economy (CAFE) standards, automotive manufacturers are working to innovate in all areas of vehicle design to improve fuel efficiency. In addition to improving aerodynamics, enhancing internal combustion engines and transmission technologies, and developing alternative fuel vehicles, reducing vehicle weight by using lighter materials and/or higher strength materials has been identified as one of the strategies in future vehicle development. Weight reduction in vehicle components, subsystems and systems not only reduces the energy needed to overcome inertia forces but also triggers additional mass reduction elsewhere and enables mass reduction in full vehicle levels.

AMONG the many outstanding advantages of the shell molding process of casting crankshafts, as described here, are the following: 1. Manner in which entire process responds to a high degree of automation. 2. Close tolerances that can be maintained from casting to casting. 3. Raw sand requirements are reduced from 125 lb (previous method) to 20 lb. 4. Results in 70% reduction in weight of chips produced. 5. Resulting crankshafts have highest wear resistance and exceptional endurance. 6. Gives additional design leeway: Allowing the most efficient distribution of weight. Contributing to engine compactness by varying the casting contour to prevent potential interferences.

PROPER protection of metal parts operating as bearing surfaces, or in contact under relatively heavy loads, during the break-in period often means the difference between successful operation and failure. Various surface coatings have been investigated to discover which ones will give this protection. The authors discuss here three types of surface treatment for cast-iron and steel that do give superior wear and scuff resistance.

This report presents results of experiments to determine the effect of elevated temperature exposures on the mechanical properties of aluminum alloy materials. The two alloys studied, 5754 and 6111, are of the types which would be used in a stamped automobile structure and exterior panels. Yield strength, tensile strength, and total elongation are reported for a variety of test conditions. The material temperature exposures simulated a broad range of conditions which might be experienced during manufacturing operations such as adhesive curing and vehicle paint bake cycles. In addition, tests were conducted at temperatures to resemble in-service under-hood and under body (near the exhaust system) conditions. Materials were prestrained various amounts prior to temperature exposure to simulate metal forming processes. Results show that both materials react to temperature and aging times differently.

Serious pitfalls exist in assuming that aluminum can be reliably resistance spot welded in the “as received” mill finish or even in the chemically cleaned condition. A commercially feasible surface abrading process was developed to promote reliability with existing tooling even 90 days afterwards. A weld reliability procedure was developed to evaluate process variables, various surface treatments, electrode materials and geometry. Comparative merits of AC and DC power were investigated. With the advent of abraded surfaces, aluminum can now be resistance spot welded with confidence and the dreaded fast electrode fauling condition associated with mill finish surfaces can be substantially alleviated.

There has been a substantial increase in the use of advanced high strength steel (AHSS) in automotive structures in the last few years. The usage of these materials is projected to grow significantly in the next 5-10 years with the introduction of new safety and fuel economy regulations. AHSS are gaining popularity due to their superior mechanical properties and use in parts for weight savings potential, as compared to mild steels. These new materials pose significant manufacturing challenges, particularly for welding and stamping. Proper understanding of the weldability of these materials is critical for successful application on future vehicle programs. Due to the high strength nature of AHSS materials, higher weld forces and longer weld times are often needed to weld these advanced strength steels.

This paper proposes an approach to use ABS wheel speed sensor signals together with other vehicle state information from a brake control module to detect an unbalanced tire or tires in real-time. The proposed approach consists of two-stage algorithms that mix a qualitative method using band-pass filtering with a quantitative parameter identification using conditional least squares. This two-stage approach can improve the robustness of tire imbalance or imbalances. The proposed approach is verified through vehicle testing and the test results show the effectiveness of the approach.

Structural system identification was applied to small sample problems and to large automotive structures. The technique combines mass and stiffness matrices from a finite element model with experimental mode shapes and natural frequencies to produce improved mass and stiffness matrices. In numerical experiments on small problems the procedure enabled us to identify regions of original finite element models where changes of model parameters were required to bring finite element predictions into better agreement with exact results. Also, node point displacements were calculated for small structures subjected to time-dependent sinusoidal loads, and it was found that predictions of displacements from “improved” models were more accurate than original finite element model predictions when forcing frequencies were within the range of experimental frequencies used with structural system identification calculations.

Under a new program of quality control in the field of powder metallurgy automotive parts called quality assurance, the supplier is made a closer partner with the buyer to get a more dependable part that consistently meets all requirements and specifications. The quality assurance program consists of review of potential suppliers, contract negotiations, initial quality assurance surveys, and routine quality assurance surveys.

The constant challenge for automotive engineers to design vehicles with greater reliability at lower cost has brought powder metallurgy (P/M) to the foreground. This technology provides parts to or near net shape and results in savings of material, energy, capital equipment and floor space. This paper is an extension of SAE reports 850458 and 870133 and describes automotive powder metal components not previously identified. It should help engineers find cost effective applications early in the design stage so that P/M technology can be efficiently adopted. In addition, recent important technological developments in the P/M field applicable to automotive parts are highlighted. In particular, increased reliability achieved through SPC is stressed. A novel blending process is described whereby the alloying ingredients are “glued” to iron powder particles resulting in an increase in P/M quality through improved homogeneity.

The trend to production of near net shape components in the automotive industry and the constant crusade for cost reduction has brought powder metallurgy technology to the foreground. Savings of material, energy, manufacturing cost and the avoidance of capital expenditure are some of the principal benefits of this process. This paper is an extension of the previously published report. SAE 850458, which describes P/M components in the automobile. It also includes a new family of parts recently identified by the authors, i.e., sensors used in conjunction with electronics and microcomputers. In addition, progress made in recent years in P/M technology is summarized. This article is written for automotive design engineers to show various new applications of P/M and allow them to take advantage of the potential savings this technology offers.

In line with the present trend to make structural parts at or near net shape, the powder metallurgy process is being studied more and more by automotive design and materials engineers who are finding an increased application for this energy and cost saving process. Many new applications, besides some older ones, of P/M by domestic and overseas automotive manufacturers are presented outlining material specifications and service conditions for engine, transmission and chassis parts. In addition to conventional porous P/M parts, examples of high tensile fully dense precision hot formed P/M parts are presented which give superior service life and lighter weight than conventional wrought steel. Despite the decreased size and weight of future automobiles, an increased number of applications of powder metal is likely to result in a greater usage of P/M materials per vehicle.

Creep-resistant magnesium alloys for automotive powertrain applications offer significant potential for vehicle weight reduction. In this study permanent mold casting, microstructure and creep behavior have been investigated for a series of ternary magnesium alloys (Mg-4Al-4X (X: Ca, Ce, La, Sr) wt%) and AXJ530 (Mg-5Al-3Ca-0.15Sr, wt%). A permanent mold was instrumented with twelve thermocouples and mold temperature was monitored during the casting process. Average mold temperature increased from 200°C to 400°C during a typical alloy casting series (fifteen to twenty castings). The cast microstructure for all alloys consists of primary α-Mg globular phase surrounded by eutectic structure which is composed of intermetallic(s) and α-Mg magnesium phases. The primary cell size of the AXJ530 increased from 18 to 24 μm with increasing mold temperature and a similar trend is expected for all alloys.