Calculation of dynamic stresses of mobile cranes and truck loading cranes in quasi-static analysis

• Applicant: Professor Dr.-Ing. Willibald A. Günthner
• Subject Area: Engineering Design, Machine Elements, Product Development
• Term: from 2017 to 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 328105817

In industrial practice, stress analysis for mobile cranes (DIN EN 13000, FEM 5.004) and loader cranes (EN 12999) is carried out by quasi-static calculations. Generally, loads due to acceleration of the crane drives are determined by rigid body kinetic models or they are based on experience. During the calculation of the load effects, dynamic factors are used to take elastic effects into consideration. Within the preceding research project, maximum dynamic stresses of lattice boom cranes during the operations hoisting, luffing and slewing were determined by dynamic finite element calculations. A comparison with the quasi-static design according to the standards partially showed large deviations between the two calculation types. On account of the system similarity, the results of the research project are also valid for loader cranes. To avoid the mistakes of the design loads according to standard, dynamic finite element calculations for crane design can be used in accordance with the parent crane standard EN 13001-1. However, this approach is hardly feasible in industrial applications, since this would multiply computation time. Therefore it is desirable to develop vibration models which represent the maximum dynamic stresses by quasi-static loads. The preceding research project showed that vibration models based on a single-mass oscillator provide good estimations of the dynamic factors for simple boom systems. Based on these results, a vibration model using mode superposition has been developed. It is suitable for the analysis of boom systems of any complexity. In a sample application crane slewing was described very well. This vibration model shall be examined systematically in the requested transfer project. Its industrial application is tested both by a manufacturer of mobile cranes and a manufacturer of loader cranes. All required algorithms are programmed by the chair fml and are then integrated in the companies computing environments. In order to verify the achievable accuracy, the chair fml compares the results of dynamic finite element calculations with those of the quasi-static calculations based on the vibration model. All common set-ups and jib lengths are investigated. The companies assess the vibration model in terms of its practical applicability and work out differences to previous calculation methods. To verify the results on an experimental basis the companies carry out measurements for selected operations. The successful completion of the research project would provide an industrial-grade, standard-compliant design method that combines the accuracy of dynamic FE-calculations with the effectiveness of quasi-static analysis.

• DFG Programme: Research Grants (Transfer Project)
• Application Partner: Liebherr-Werk Ehingen GmbH; Palfinger Europe GmbH Köstendorf