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This paper presents the results of a study about the influence of the suspension manufacturing and assembly induced dimensional variation on the vehicle dynamic behavior for a compound crank rear suspension. A selection of representative vehicle dynamics metrics has been considered for this assessment and each individual dimensional variation has been categorized with respect to its overall effects on the selected metrics. By doing this, it is possible to identify the critical points where the dynamic behavior of the vehicle is more sensitive to the resulting dimensional variation, therefore creating a new criteria to define the appropriate tolerance control for the manufacturing and assembly of the related parts.

The Brazilian automotive market presents special characteristics: at the same time that it demands similar technologies applied in developed markets like USA and Europe for luxury cars, in the sub-compact entry-level segments (a segment where the profit margin is very tight) there are unique characteristics that justify the development of different cars. Taking into consideration the mini cars segment, there is no car developed specifically for the Brazilian market. While the mini cars development for the entry level segment is still rare, every new auto show presents new proposals and some of them are on the streets, but most are mainly focused in the luxury segment. These vehicles currently in the market are in a price range where it is not economically feasible for them to be acquired by someone who is coming from a motorcycle-based usage.

Analytical models are very useful to the vehicle dynamics project engineer in order to provide simple solutions that bring at the same time a deep understanding of the physical phenomena being studied. Due to their structure, the input of analytical models are only the variables of interest affecting the concerned handling metrics - this fact reduce the parameters quantity to build the same model, making them proper choices for advanced studies. Additionally, analytical models are more efficient in computational terms, aspect convenient for studies that involve large amounts of calculation iterations like numerical optimization processes. This paper presents analytical model results for the roll gradient, understeer gradient and steering sensitivity metrics and proposes enhancements in order to obtain results with accuracy compatible to the experimental measured variables.

The required hand wheel effort the driver inputs into the steering wheel during parking maneuvers is an important design factor for a vehicle, that has a strong influence on the customer's overall perception of steering performance. During the development of a new vehicle, the designer is faced by the challenge of achieving the desired level of steering effort without jeopardizing other handling characteristics, like steering sensitivity and on-center performance. The suspension and steering tuning to achieve the adequate trade-off between these different metrics is especially critical for manual steering systems, which is a very common configuration for emerging market vehicles. In addition, due to communization of architectures, it is common that a vehicle with a manual steering system must share common suspension components and geometric parameters with configurations that have power steering assistance, making this trade-off even more difficult.

The sheet metal joining through spot welding is the most widely used process for automotive body building, where an average vehicle has around 5,000 spot welding points in its structure. In this sense, the spot welding project is critical to the final product performance and it must be done in a way that can assure both quality and durability of the vehicle, already taking into consideration the fact that the spot weld mechanical properties related to fatigue and rupture resistance are much lower when compared to other available welding techniques like MIG welding for example. These properties have a direct impact in the fatigue durability and crashworthiness properties of the vehicle, as a significant part of the structural resistance goes through these spot welds. With this scenario, the correct application of FEA techniques is very important to assure that the projected joints and spot weld disposition meet the product targets in terms of safety and durability.

The vehicle design environment from a crashworthiness and safety perspective has become increasingly complex in recent years. New legal requirements imposed by the European Union (EU) and the United States National Highway Traffic Safety Administration (NHTSA) have created a design space of great complexity with many parameters that must be balanced to arrive at an overall design that performs adequately in all of these situations. The customer introduces further complexity through the addition of Consumer requirements in many markets that will influence a purchasing decision. In order to design to all of these conditions, an approach of using physical testing solely has problems associated with it. Due to the prohibitive nature of vehicle prototypes and limited availability during Engineering Development, other tools such a Computer Aided Engineering (CAE) have become popular.