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ABSTRACT In recent years the heavy-duty Class 8 truck market has become very focused on weight and cost reduction. This represents a major challenge for design engineers since these vehicles are used in a wide variety of vocations from highway line haul to logging in severe off-road environments.50672
The challenge is to meet the weight and cost reduction goals without sacrificing durability and performance. This paper discusses the integration of computer aided design and engineering software codes (Pro/Engineer,ADAMS, and ANSYS) to simulate the effect of design changes to the truck frame .In particular, this paper discuses the development of an ADAMS multi-body dynamics model of a full truck and trailer to simulate vehicle handling, roll stability, ride performance, and durability loading. The model includes a flexible frame model using a component mode synthesis approach with modes imported from a finite element analysis program. The link between the multi-body simulation and the finite element code is also used to transfer loads back to the finite element model for stress analysis. Tight links between all the codes ensures that new design iterations can be quickly evaluated for concurrent design and analysis. A detailed case study showing how this technology has been used is also included.
INTRODUCTION
Recently the heavy truck industry has experienced a large push to develop vehicles with reduced cost and weight. Thishas been a major challenge for truck manufacturers as they look for ways to optimize their vehicle designs without sacrificing durability or performance. Since the truck frame is a major component in the vehicle system, it is often identified for refinement. This paper outlines a computer aided engineering (CAE) procedure for analyzing changes to the truck frame and how these changes affect vehicle performance .The frame of a heavy truck is the backbone of the vehicle and integrates the main truck component systems such as the axles, suspension, power train, cab, and trailer. The typical frame is a ladder structure consisting of two C channel rails connected by cross-members. The frame rails vary greatly in length and cross-sectional dimensions depending on the truck application. Likewise, the cross-members vary in design, weight, complexity, and cost. These variations will depend upon the cross-member purpose and location. Refer to Figure 1 for an illustration of a truck frame. However, the effects of changes to the frame and cross-members are not well understood.
For example, if the torsional stiffness of a suspension cross-member is lowered, what is the effect on the vehicle’s roll stability, handling, ride, and durability? Design engineers require answers to these types of questions to guide them in their work. In particular, a concurrent design and analysis procedure is required so that new designs can be quickly evaluated.
Figure 1. Class 8 Heavy-Duty Truck Frame
COMPUTER AIDED ENGINEERING
In the last twenty years there has been an enormous growth in the development of CAE tools for automotive design. Much of this technology has been adopted by the truck industry as truck manufacturers look to improve their designs in a rapidly growing market. Today structural design is typically performed using two CAE tools: finite element analysis (FEA), and multi-body system simulation (MSS). These are combined with computer aided design (CAD) software to improve design and analysis communication.
CAD – In the last fifteen years CAD systems have replaced drawing boards as the method of choice for design. They enable designers and engineers to quickly create realistic models of truck components, vehicle assemblies, and design drawings for manufacturing. Advanced CAD systems are rich in features such as parametric solid model and large assembly management. They have evolved to become major databases for engineering information. In particular , CAD systems provide important data for downstream CAE applications. FEA – Finite element analysis is usually used by engineers to study the strength of structural components.