Using NX Advanced Motion and NX Advanced Simulation to analyze suspensions, Fiat Abarth attains the ideal combination of excellent flexibility and total data reliability
Specializing in rally vehicles and bulk vehicle production
Abarth & C. SpA, now part of the Fiat family, was founded in 1949 by the brilliant Austrian entrepreneur Karl Abarth, who was also an engineer and driver at the time he founded the company. Across the decades the Abarth brand has produced and exported wellknown models such as the 1100-103 and the 207A. Fiat Abarth specializes in rally vehicles and bulk vehicle production. The distinctive style and high performance of Fiat Abarth vehicles, many designed in collaboration with Alfa, Lancia and Pininfarina, have always attracted worldwide interest.
In a recent restructuring, Fiat Abarth moved to a new location to consolidate its manufacturing, design and management departments as well as the resources of the racing team. More than 100 employees work at the new facility, which covers nearly 250,000 square feet (23,000 square meters) and integrates all the activities of the brand.
“We have been using NX from Siemens PLM Software as our design solution since 2002,” says Manuela Coalova, wheeled chassis design manager at Fiat Abarth. “After the technical office was expanded in 2007 we also implemented a CAE solution from Siemens.” With the goal of creating an engineering team capable of designing high-end vehicles, such as those used in rally racing, Abarth brought in Francesco Latini, a vehicle kinematics and dynamics engineer, and Giuseppe Fedele, a design and structural calculation engineer, to join Coalova’s department.
Integrating design and engineering
After years of using a standalone solution for structural analysis, Abarth wanted a solution that offered greater flexibility.“Structural calculation is crucial for us in designing our vehicles because we must find the best balance between minimum weight and maximum resistance to stress,” says Coalova.“We really needed to expand our use of this technology as well as speed up the process.”
The previous software presented certain problems in various applications, but worse, it was not integrated with the CAD software. The NX™ Advanced Simulation solution from Siemens solved these problems.“All the geometries remain in the structural analysis software,” says Coalova. “There is no need to export them or re-mesh them.”
Abarth uses NX Motion to analyze suspensions. The first project with NX Motion proved that multibody models of the suspension (front and rear) yielded completely reliable results. NX Motion proved to be easy to use, very fast and tightly integrated with the solid modeling software.
“It is possible to import geometry and edit it without converting it to another format,” Latini says.“In the future, we plan to take the mathematical model, connect it into the frame and proceed with motion analysis to assess the space requirements and the interferences directly with the CAD geometry.
“In our design activity, suspension simulation is used mainly to leverage the existing suspension,” he adds.“If, for example, we have to move the rolling center, the hard points are edited, the typical suspension curves are extracted, and from there it is possible to rebuild the geometry to reassess the space requirements and the positioning of the suspension in the vehicle.We used this procedure last summer for the rear suspension with excellent results, which were verified on road.”
Since NX Motion is a general multibody software, the system analyst must personally model the joints as correctly as possible to reflect the actual behavior of the suspension.“This apparent limit actually offers a substantial advantage,” explains Coalova.“Since he does not have any predefined settings that he must follow, the designer may model the joint in a very precise way and, once having verified that it works correctly, it is possible to save it as a template that can be used again. This way, we have the utmost confidence in the results because the designer knows exactly what he is doing. For example, with NX Motion, the contact point between the wheel and the road is simulated exactly, without approximation or customizations.”
Abarth’s first project using NX analysis software involved the Abarth Grande Punto Super2000, which has a MacPherson-type scheme for both the front and rear suspensions. To perform the kinematics analysis, Abarth designers imported the CAD model of the MacPherson frame (a multibody model), using a bottomup method starting with typical suspension points to create a wireframe model. This procedure simplified the analysis and made the results available quickly.
The multibody model was completely parametric and associative with the CAD model. This made it possible to quickly change the suspension geometry simply by changing a value in an Excel spreadsheet file.“By connecting the various hard points, it was possible to achieve a very light, flexible diagram and perform a simulation in very little time,” says Latini.“From this model, by means of macros generated by NX Motion, it was possible to create the data, which is managed in Excel, for plotting the diagrams. Charts such as converging, camber and rolling center allow us to interpret the kinematics behavior of the vehicle.”
Now Abarth is ready to integrate the entire design and engineering process, including geometries, templates, diagrams and space requirements for the vehicle. The final goal is to model the entire system in such a way that, simply by entering data for a new vehicle, the software performs a defined and tested calculation process.
“This stage is currently being tested to verify that the calculations of NX Motion match the conditions found on the actual vehicle,” adds Coalova.“And we are doing the same to verify the structural calculations.We are also planning to implement computational fluid dynamics (CFD) analysis. Aerodynamics is not a critical consideration for rally vehicles, but it is influential. For example, a preliminary analysis of how the vehicle behaves with a rear balancing flap is useful and allows us to reduce the amount of wind tunnel testing we do. By bringing these capabilities in-house, we save the cost of outside services and reduce the design time required for our vehicles.”