Search Results

For incorporating titanium components onto a vehicle in place of existing iron/steel components, there is a need for a methodical procedure to ensure successful and efficient integration. This involves a refinement over standard lightweight engineering procedures. In this paper, a suitable procedure is developed for replacing a structural component with titanium and the method realized. Design and manufacturing issues associated with integrating titanium are identified and addressed. The importance of justifying component replacement in terms of life-cycle costs rather than purely by the manufacturing cost alone is also emphasized.

This paper deals with stability of motion and its criteria for tracking control of intelligent vehicle systems. It deals with general control structure and specification of an optimum range of predefined control parameters for accurate tracking of these vehicle systems. A two degree of freedom (DOF) nonlinear dynamic model is developed to represent their plane motion. This model is further utilized in deriving a linear model that is used to do this stability analysis. Path tracking of the vehicle is attained by controlling the position and orientation errors about a predefined trajectory, which is accomplished by modifying the steering input signal on the basis of error feedbacks to the controller.

The general manufacturing objective during the fabrication of automotive components, particularly through machining, can be stated as the striving to achieve predefined product quality characteristics within equipment, cost and time constraints. The current state of the economy and the consequent market pressure has forced vehicle manufacturers to simultaneously reduce operating expenses along with further improving product quality. This paper examines the achievability of surface roughness specifications within efforts to reduce automotive component manufacture cycle time, particularly by changing cutting feeds. First, the background and attractiveness of aluminum as a lightweight automotive material is discussed. Following this, the methodologies employed for the prediction of surface roughness in machining are presented. The factors affecting surface roughness as well as practical techniques for its improvement through optimizing machining parameters are discussed next.

Due to titanium's excellent strength-to-weight ratio and high corrosion resistance, titanium and its alloys have great potential to reduce energy usage in vehicles through a reduction in vehicle mass. The mass of a road vehicle is directly related to its energy consumption through inertial requirements and tire rolling resistance losses. However, when considering the manufacture of titanium automotive components, the machinability is poor, thus increasing processing cost through a trade-off between extended cycle time (labor cost) or increased tool wear (tooling cost). This fact has classified titanium as a “difficult-to-machine” material and consequently, titanium has been traditionally used for application areas having a comparatively higher end product cost such as in aerospace applications, the automotive racing segment, etc., as opposed to the consumer automotive segment.

Current vehicle manufacturers must meet economic demands and design/manufacture more fuel efficient vehicles with increasingly better performance. As a result, they are turning to the use of more non-traditional lightweight materials in their products. One favorable material due to its excellent strength-to-weight ratio and high corrosion resistance is titanium. However, to warrant the replacement of traditional materials with titanium alloys there must be the benefit of reduced vehicle mass as well as performance enhancement gains from the substitution at a justifiable cost. In this work, an unsprung suspension component is selected and redesigned from the standpoint of (i) a direct material substitution and (ii) a material and requirements consideration based substitution. In addition, for the redesign of the component in titanium, the manufacturing procedure and process plan is integrated into the design phase for the component.

To warrant the substitution of traditionally used structural automotive materials with titanium alloys, the material substitutional and redesign advantages must be attainable at a justifiable cost. Typically, during material replacement with such ‘exotic’ aerospace alloys, the initial raw material cost is high; therefore, cost justification will need to be realized from a life-cycle cost standpoint. Part I of this paper highlighted the redesign, fabrication, and validation of an automotive component. Part II details the particulars of constructing the total life-cycle cost model for both prototypes (P1, P2). Considerations in the model include adaptation to a high volume production scenario, availability of near-net size plate/bar stock, etc. Further, response surfaces of fuel costs savings and consequent life-cycle costs (state-variables) are generated against life-cycle duration and unit fuel price (design-variables) to identify profitable operating conditions.