Fatigue life prediction is one of the most critical engineering disciplines in the automotive industry, affecting both car safety and potential warranty issues. Further, accurate fatigue life predictions support the work to reduce the weight of the car. In the past automotive manufacturers invested billions in the creation of multiple prototypes and physical testing. As technology advanced and computer-aided design and engineering tools became more robust, the car development process shifted from physical to virtual testing. This has led to lower development costs, shorter lead times, and, because more design variants can be examined in the same time frame, higher-quality cars. Key to this paradigm change in the development process is the comprehensive use of the right CAE tools early in the design process, long before the first physical prototype. A good example of successful fatigue simulation usage in the automotive development process is Volvo Car Group (Volvo Cars). Volvo Cars’ CAE teams apply technologies such as nCode DesignLife to predict the fatigue life performance of new cars.
When a new car is developed, all components and assemblies have to be tested for fatigue life, first virtually and later through physical testing, to be approved for production.
At Volvo Cars, the CAE analysis teams work closely with testing and design teams to keep required development iterations to a minimum.
Sällström sums up the advantages of this virtual approach, saying, “With nCode DesignLife and today’s development process, we have our answers much faster than in the past, and they are more accurate. We get better designs faster, and can reduce the overall development time for the car. In addition, nCode DesignLife enables the repeatability of the process, which is very important when identifying critical areas.”
In production since 1927, Volvo is one of the most well-known and respected car brands in the world with car sales in around 100 countries. Volvo Cars has been under the ownership of the Zhejiang Geely Holding of China since 2010. As of December 2015, Volvo Cars had almost 29,000 employees worldwide. The company’s main office including product development, marketing, and administration functions are located in Göteborg, Sweden. A technology center is also established in Shanghai, China. The company’s main production plants are located in Göteborg, Ghent (Belgium), and Chengdu and Daqing (China), while engines are manufactured in Skövde (Sweden) and Zhangjiakou (China), and body components in Olofström (Sweden).
When a new car is developed, all components and assemblies have to be tested for fatigue life, first virtually and later through physical testing, to be approved for production. At Volvo Cars, the CAE analysis teams work closely with testing and design teams to keep required development iterations to a minimum.
“The most complex fatigue analysis we have is the body rig test,” says Sällström. “To physically test the body structure a complete car is taken to the test track and driven a few laps to measure accelerations and wheel forces. The car is then brought to the test rig. The loads applied in the rig are iterated until they give the same accelerations and forces as on the test track. The load cycles are then repeated to correspond to a specified number of laps on the test track.”
Time load history data from the test track is used to mimic the same loads on the test rig.
If the fatigue analysis indicates a place where a crack might occur, the CAE engineers give this input to the design teams. Together, design and CAE engineers discuss how to improve the body design by changing the geometry or just a radius, adding or moving spot welds, or using a different material or material thickness. If the fatigue analysis indicates very long fatigue life, this information can be used to reduce the weight of the car. nCode DesignLife offers sophisticated spot weld and seam weld analysis capabilities, which are widely used by the fatigue engineers at Volvo Cars, together with the strain life and stress life modules.
Depending on whether a new car is created on an entirely new car platform, or if an existing platform is used, the engineers might simulate hundreds of runs of the body rig during the full car development project.
This will bring together HBM, Brüel & Kjær, nCode, ReliaSoft, and Discom brands, helping you innovate faster for a cleaner, healthier, and more productive world.
This will bring together HBM, Brüel & Kjær, nCode, ReliaSoft, and Discom brands, helping you innovate faster for a cleaner, healthier, and more productive world.
This will bring together HBM, Brüel & Kjær, nCode, ReliaSoft, and Discom brands, helping you innovate faster for a cleaner, healthier, and more productive world.
This will bring together HBM, Brüel & Kjær, nCode, ReliaSoft, and Discom brands, helping you innovate faster for a cleaner, healthier, and more productive world.
This will bring together HBM, Brüel & Kjær, nCode, ReliaSoft, and Discom brands, helping you innovate faster for a cleaner, healthier, and more productive world.
