World market leader for mobile cranes stems from simulation tasks with Ansys
Ansys simulations in crane development at Liebherr
Part 1 of the three-part series on simulation with Ansys and CADFEM in Liebherr-Werk deals with general aspects. It gives an insight into how and why simulations are used in the development of giant cranes, what Liebherr engineers achieve as a result and which applications come into play. Parts 2 and 3 take a closer look at structural mechanics and CFD.
Pioneer and world market leader from Ehingen
Anyone going to Ehingen on the Danube can see them towering into the sky from afar: the masts and booms of Liebherr mobile cranes. They look like gigantic giraffe necks in a technology zoo. Since its founding in 1969, the company has continued to develop and is now the world market leader for mobile and crawler cranes. A key success factor is the use of Ansys simulation technology in conjunction with application consulting by CADFEM.
The fascination of technology immediately grips you at the sight of a crane. The size and the effect of the forces when moving enormous loads inevitably captivates you. Since the first use of these ingenious lifting devices in ancient Greece, it has been impossible to imagine any major construction project without cranes. Since then, resourceful people have continued to refine the crane design.
R&D in focus
Liebherr-Werk Ehingen (LWE for short) specializes in mobile cranes. Hans Liebherr personally founded the site in 1969. To this day, all related competencies are combined there. Two main types of mobile cranes are developed and manufactured at LWE: “all-terrain cranes” and “lattice boom crawler cranes”.
- All-terrain cranes have tires, are all-terrain and are usually street legal.
- In the case of a lattice boom crawler crane, the crane assemblies are first assembled on the construction site before these giants move by means of a crawler drive.
The mobile and crawler cranes division is one of the top-selling in the group. More than 3,500 employees from research and development, production, and global sales and service focus on customer needs. The state-of-the-art telescopic and lattice boom cranes are mounted on mobile and crawler undercarriages. Ever since it was founded, Liebherr has attached great importance to a high technological standard combined with top quality. That is why research and development are heavily invested in.
Ever since it was founded, Liebherr has attached great importance to a high technological standard combined with top quality. That is why research and development are heavily invested in.
LWE’s extensive knowledge of movable support structures is recognized in the international professional world, which is why special projects are repeatedly carried out.
- For example, for the construction of the Kurushima suspension bridges in Japan, LWE designed the diesel-hydraulic heavy-duty winches for lifting the 30 m wide and 540 t heavy bridge segments.
- Another unusual project was the realization of 250 large-scale screens for the piazza of the Prophet's Mosque in Medina, Saudi Arabia. They form the largest retractable roof in the world.
- Cranes from LWE are also in demand when erecting gigantic wind turbines, such as the Holzhausen wind farm near Paderborn. The new LR 1700-1.0 erected the prefabricated 96-meter-high concrete tower for the plant with a hub height of 164 meters. The heaviest components were the machine housing and drive train with gross loads of 72 and 75 tons, respectively.
Simulation is vital
The use of simulation software is vital for the implementation of the various requirements. Prototypes and laboratory setups are much too time-consuming and expensive. LWE uses the computing power available today and the latest simulation software from Ansys for digital transformation in testing.
LWE is primarily concerned with two major areas of simulation: structural mechanics modeling (FEM) and fluid mechanics (CFD).In general, the goal in the development of a mobile crane is to combine the lowest possible transport weight with a high load capacity. This inevitably forces you to use lightweight design, because a large payload to deadweight ratio is the best selling point. For engines, operator cabs and hydraulics, the flow data are important for optimum performance and comfort.
Computational Engineer / Structural Engineering, Liebherr-Werk Ehingen GmbH
Simulation brings us huge savings potential in terms of costs, time and labor, and it does so at an early phase of product development.
Example cable pulley
A good example of the advantage of simulation in development is the cable pulley.
- During operation, a cable pulley is subject to high loads in connection with a high number of load changes. It must be ensured that it withstands this.
- Since the cable pulley is welded, a large number of complex and cost-intensive tests would be required to determine the optimum variant.
Niels Finkbeiner, computational engineer in the area of structural engineering at LWE, provided the fatigue strength verification according to the FKM guideline with an FE simulation in Ansys Workbench. The critical points were quickly determined, despite complex processes. The results showed that shear forces were loading the notch. A hint to the design department to change the angle of the circular blank and an adjustment of the sheet thickness was sufficient, even before anything had to appear physically.
CADFEM opens up simulation possibilities
The variety of products from Ansys and the wide range of applications require an experienced partner. LWE has relied on CADFEM for many years. Both in application consulting and in finding solutions and training, the specialists from Grafing near Munich are the first choice.
Joachim Henkel heads the structural engineering department and, in addition to the software delivery, appreciates the professional exchange.
“If we get stuck with a calculation, the next important pillar of our cooperation comes into play: support. This requires quick and competent assistance. We receive both from our Ansys partner CADFEM. Of course, our people must be trained in handling the software so that we can work as efficiently as possible. This is where CADFEM accommodates us with a Liebherr Learning Subscription for trainings. Liebherr has a long-term vision, and the strategic orientation and consistency of our partners is particularly important to us. We have been working together with Ansys and CADFEM for more than 35 years. For us, Ansys is the best solution in its software class. It has proven that many times over all these years.”
Computational Engineer and Head of Structural Engineering, Liebherr-Werk Ehingen GmbH
We have been working together with Ansys and CADFEM for more than 35 years. For us, Ansys is the best solution in its software class. It has proven that many times over the years.
Efficient infrastructure required
More extensive calculations, which occur more frequently at LWE, require appropriate computing power and simulation expertise. Thomas Lerner, Senior Simulation Engineer FE-Infrastructure, describes the demand:
“The increasing level of detail of today's models requires a high-performance simulation environment with a powerful infrastructure. The parallelization of processes (e.g., meshing or modeling) leads to considerable time savings. Simulation engineers can calculate more model variants in the same amount of time. A powerful and scalable computing cluster on a fail-safe basis was therefore installed at LWE and put into operation at an early stage.
For structural mechanical calculations, 144 cores are available for up to 12 parallel calculations. Moving the local workstations to the data center has further accelerated the process. For example, transfer times of computational models between workstation and computational cluster have been reduced by 30 to 50 percent,” saysThomas Lerner.
Technological progress in manufacturing and logistics allows the prefabrication of ever larger and heavier components of parts and machines in factory buildings. Afterwards, the transport “in one piece” to the place of use is on the agenda. Everyone is now familiar with heavy transports involving entire bridges or complete blades of wind turbines. The Liebherr plant in Ehingen meets this development with efficient simulation software from Ansys.
This is the only way to economically develop ever more powerful cranes capable of lifting the huge components on site for assembly.
Senior Simulation Engineer FE-Infrastructure, Liebherr-Werk Ehingen GmbH
The parallelization of processes leads to considerable time savings. Simulation engineers can calculate more model variants in the same amount of time.
Read in the second part how LWE manages to overcome apparent contradictions with structural-mechanical calculations. In the third and last part of our LWE series, learn how CFD simulation significantly shortens the time to market.
In the third part of our LWE series, read about where and how flow simulations significantly shorten the time to market.