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Abstract An investigation into the capability of passive porosity to reduce the drag of a bluff-body is presented. This initial work involves integrating varying degrees of porosity into the side and back faces of a small-scale model to determine optimum conditions for maximum drag reduction. Both force and pressure measurements at differing degrees of model yaw are presented, with the conditions for optimum performance, identified. At a length-based Reynolds number of 2.3 × 106, results showed a maximum drag reduction of 12% at zero yaw when the ratio of the open area on the back face relative to the side faces was between two and four. For all non-zero yaw angles tested, this ratio reduced to approximately two, with the drag benefit reducing to 6% at 10.5 degrees. From a supplementary theoretical analysis, calculated optimum bleed rate into the base for maximum drag reduction, also showed reasonable agreement to other results reported previously.

Laminated steel body panels are used in different applications in vehicles, such as dash panels and wheel wells. A part made out of laminated steel has the potential to provide structure-borne noise reduction and also improve the airborne noise reduction of the part compared to a monolithic part. The use of laminated steel has been more critical when there are deep draws on the part as the deep draws cause localized resonances which degrade the acoustic performance significantly. However, due to lightweighting demands, hybrid laminated panels, commonly known as acoustic patch laminates have become very attractive. This paper discusses the damping and sound transmission loss performances of a dash panel part with monolithic, laminated, and acoustic patch panels.

Automotive manufacturers are being challenged to come up with radical solutions to achieve substantial (30-35%) vehicle weight reductions without compromising Safety, Durability, Handling, Aero-thermal or Noise, Vibration and Harshness (NVH) performance. Developing light weight vehicle enablers have assumed foremost priority amongst vehicle engineering teams in order to address the stringent Fuel Economy Performance (FEP) targets while facilitating lower CO2 emissions, downsizing of engines, lower battery capacities etc. Body sheet metal panels have become prime targets for weight reductions via gage reduction, high strength steel replacement, lighter material applications, lightening holes etc. Many of these panel weight reduction solutions are in sharp conflict with NVH performance requirements.

Vehicle cabin comfort emphasizes a specific image of a brand and its product quality. Low frequency powertrain induced noise and vibration levels are a major contributor affecting comfort inside passenger cabin. Thus, using hydraulic mount is a natural choice. Introduction of lighter body panels coupled with cost effective hydraulic mounts has resulted in some additional noises on rough road surfaces which are challenging to identify during design phase. This paper presents a novel approach to identify two such noises i.e. Cavitation noise and Mount membrane hitting noise based on component level testing which are validated at vehicle experimentally. These noises are encountered at 20~30kmph on undulated road surfaces. Sound quality aspect of such noises is also studied to evaluate the solution effectiveness.

The scope of this SAE Recommended Practice is restricted to the testing of original equipment on passenger vehicles and to provide for a uniform industry test procedure.

The scope of this SAE Recommended Practice is restricted to the testing of original equipment on passenger vehicles and to provide for a uniform industry test procedure.

This study concerns a dissimilar materials joining technique for aluminum (Al) alloys and steel for the purpose of reducing the vehicle body weight. The tough oxide layer on the Al alloy surface and the ability to control the Fe-Al intermetallic compound (IMC) thickness are issues that have so far complicated the joining of Al alloys and steel. Removing the oxide layer has required a high heat input, resulting in the formation of a thick Fe-Al IMC layer at the joint interface, making it impossible to obtain satisfactory joint strength. To avoid that problem, we propose a unique joining concept that removes the oxide layer at low temperature by using the eutectic reaction between Al in the Al alloy and zinc (Zn) in the coating on galvanized steel (GI) and galvannealed steel (GA). This makes it possible to form a thin, uniform Fe-Al IMC layer at the joint interface. Welded joints of dissimilar materials require anticorrosion performance against electrochemical corrosion.

A task group within the SAE Automotive Corrosion and Protection (ACAP) Committee continues to pursue the goal of establishing a standard test method for in-laboratory cosmetic corrosion evaluations of finished aluminum auto body panels. The program is a cooperative effort with OEM, supplier, and consultant participation and is supported in part by USAMP (AMD 309) and the U.S. Department of Energy. Numerous laboratory corrosion test environments have been used to evaluate the performance of painted aluminum closure panels, but correlations between laboratory test results and in-service performance have not been established. The primary objective of this project is to identify an accelerated laboratory test method that correlates with in-service performance. In this paper the type, extent, and chemical nature of cosmetic corrosion observed in the on-vehicle exposures are compared with those from some of the commonly used laboratory tests

Aluminum consumption in automotive applications has maintained consistent growth in the past 30 years and is expected to continue to climb to meet the growing demand for more energy-efficient vehicles. Recycling post-consumer aluminum to build new vehicles will further reduce manufacturing life-cycle energy consumption and emissions leading to significantly lower production costs. To take full advantage of recycling automotive aluminum alloys, a guideline for the recycling practice and design of recycle-friendly alloys such as cost benefits is needed, while meeting the property requirements. Formability is one of critical properties for aluminum vehicle body panels and strongly depends on alloy composition and processing. The forming limit curve (FLC) offers the opportunity to determine process limitations in sheet metal forming and is used in the estimation of the stamping characteristics of sheet metal materials.

Three different acoustic finite element models of an automobile passenger compartment are developed and experimentally assessed. The three different models are a traditional model, an improved model, and an optimized model. The traditional model represents the passenger and trunk compartment cavities and the coupling between them through the rear seat cavity. The improved model includes traditional acoustic models of the passenger and trunk compartments, as well as equivalent-acoustic finite element models of the front and rear seats, parcel shelf, door volumes, instrument panel, and trunk wheel well volume. An optimized version of the improved acoustic model is developed by modifying the equivalent-acoustic properties. Modal analysis tests of a vehicle were conducted using loudspeaker excitation to identify the compartment cavity modes and sound pressure response to 500 Hz to assess the accuracy of the acoustic models.

Typically, in the automotive industry, the design of the body damping treatment package with respect to NVH targets is carried out in such a way to achieve panel mobility targets, within given weight and cost constraints. Vibration mobility reduction can be efficiently achieved thanks to dedicated CAE FE tools, which can take into account the properties of damping composites, and also, which can provide their optimal location on the body structure, for a minimal added mass and a maximized efficiency. This need has led to the development of different numerical design and optimization strategies, all based on the modeling of the damping composites by mean of equivalent shell representations, which is a versatile solution for the full vehicle simulation with various damping layouts.

Automobile manufacturers have experienced increasing consumer and regulatory pressure to improve fuel efficiency and crashworthiness while simultaneously decreasing overall vehicle body weight. As such, the use of advanced high strength steels (AHSS) in body panels and other structural elements is becoming more and more prevalent because these advanced materials present an economical and elegant solution to the problem. To ensure the quality and safety of AHSS components, residual stress (RS) specifications (among others) have been introduced with the intent to minimize failures experienced both in the field and during production. Moreover, when welding processes are applied to AHSS components, the localized loss of ductility in combination with tensile RS can result in localized cracking, distortion, and/or failures.

The machining of sculptured surfaces with the numerically controlled (NC) machines is a common practice in recent auto industry. Manufacturing of dies for the automotive body panels requires many complex surfaces to be machined within a given tolerance. Although various methods have been proposed by many authors, the basic concepts of current machining algorithms can be divided into two distinct categories, i.e., the surface-based method and the point-based method. While the former uses the parametric surface equations to get the machining tool path, the latter, on the other hand, discretizes the surface information into point data, and then calculates the tool path based on the resulting discretized point information. In this paper, the theoretical backgrounds of the two different approaches are presented.

The purpose of this paper is to outline the current state of polyurethane bonding technology in the transportation industry. The paper focuses on the strengths and limitations of this technology and the reasons for its long-term success in the market place. Significant advances have been made in the range of end use applications for polyurethane structural adhesives. The introduction of the new General Motor's Lumina, Silhouette, and Transport mini vans has created the largest assembly line use of structural adhesive to bond SMC body panels to date. Molders and manufacturers of more traditional SMC assemblies have made noteworthy improvements in productivity with fast cure bonding cycles and simplified production processes using polyurethane technology. Auto makers have continued to capitalize on the cost and performance benefits of bonded composite body vehicles for specialty niche markets.

Sheet Molding Composite (SMC) technology has advanced significantly in the surface smoothness and appearance of compression molded automotive exterior body component parts over the past five years. An example of that new technology is the General Motors' APV Van Hood. As judged visually on vehicles and measured quantitatively in the laboratory, not only by the SMC molder and fabricator, but by other SMC molders and the automotive customer, this SMC hood sets a new SMC industry standard for surface appearance for thermoset composite exterior automotive body panels. The appearance of the GM APV Van Hood was the result of a total system approach to material and process optimization. Teamwork and partnership concepts contributed significantly and leveraged the application of technology.

In previous investigations, it has been shown that the dent resistance of an auto body panel depends upon the yield strength of the material. However, it is known that the yield strength of steel increases with prestrain due to strain hardening. Panel design and material selection based on the material properties obtained from unstrained sheet steels may lead to inaccurate prediction of the dent resistance of the formed panel. In this study, the effect of prestrain on the static dent resistance of auto body panels was investigated. Using existing empirical relationships between dent resistance and panel properties, it was found that the static dent resistance of an auto panel depends not only on the part geometry and material properties but also on the strain level in the panel. The improvement in dent resistance resulting from a material change from an AKDQ steel to a bake hardenable steel or a high strength steel was determined at different strain levels.

A simple and economical process has been developed that allows the recovery of scrap RIM thermoset polymer generated in the manufacturing of fascia, body panels and other parts. This process consists of a size reduction process of the thermoset polymer into a very fine powder and it's subsequent incorporation into virgin raw materials. Original polymer performance and surface quality are maintained. This “regrind” process provides positive environmental and economical effects to molders of RIM polymers.

With the Elan's launch, Lotus is moving into a new era of low-volume production. By the middle of the next decade, a maximum of 3000 a year will be produced at Hethel and it was these requirements, combined with a desire for more design freedom, that led Lotus to carefully examine its current VARI (Vacuum Assisted Resin Injection) process and develop a unique, flexible system for the Elan. It was decided to develop a manufacturing process to employ a larger number of separate panels to allow future design freedom. The aim was to jig assemble panels which would allow accurate and consistent control of the complete assembly. Evaluation of alternative materials and processes for body panel manufacturing began in 1987, leading to the conclusion that the Lotus patented VARI process was still the most cost effective for the new car.

In order to determine the best way to evaluate materials selection from an economic standpoint, a discussion of conventional cost estimation is given versus a more precise technique, Technical Cost Modeling. Automotive body panels are used as an application for the costing techniques; conclusions about fabrication costs and parts consolidation are drawn with regard to these parts.

Polyurea RRIM offers a proven technology for proposed vertical body panel programs. Applications to this point in time have involved non-standard assembly procedures, but polyurea RRIM is a viable candidate for programs involving an “E-coat” or “ELPO” step. The selection of a reinforcement is crucial to the overall performance of the composite. Physical properties are specified by the particular program, and they can be achieved by the correct selection of reinforcement level and type. The greater emphasis that has recently been placed on surface quality can also be satisfied through the proper reinforcement selection. Lastly, the interaction of the polyurea RRIM composite with an environment which leads to an absorption of moisture may be controlled by choosing a reinforcement that will allow a high diffusion rate and subsequently a higher maximum use temperature.