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

在工业实践中，对移动式起重机(DIN EN 13000，有限元分析5.004)和装载机起重机(EN 12999)进行了准静态计算。一般情况下，起重机传动的加速度载荷由刚体动力学模型确定或基于经验确定。在荷载效应的计算中，采用动力系数来考虑弹性效应。在前面的研究项目中，通过动态有限元计算确定了格构式臂架起重机在起升、变幅和回转过程中的最大动应力。与按规范进行的准静力设计相比，两种计算形式存在较大的偏差。由于系统的相似性，本课题的研究结果也适用于装载机起重机。为了避免按标准计算设计载荷的错误，起重机设计时可根据起重机标准EN 13001-1进行动态有限元计算。然而，这种方法在工业应用中几乎不可行，因为这将增加计算时间。因此，建立能反映准静态载荷下的最大动应力的振动模型是非常必要的。前面的研究项目表明，基于单质量振子的振动模型可以很好地估计简单悬臂系统的动力因素。在此基础上，建立了基于振型叠加的振动模型。它适用于任何复杂的悬臂系统的分析。在一个示例应用程序中，很好地描述了起重机的回转。此振动模型应在所要求的移交项目中进行系统检查。它的工业应用由一家移动起重机制造商和一家装载机起重机制造商进行测试。所有需要的算法都由主席FML编程，然后集成到公司的计算环境中。为了验证可实现的精度，座椅FML将基于振动模型的动态有限元计算结果与准静态计算结果进行了比较。调查了所有常见的设置和起重臂长度。这些公司根据其实际适用性对振动模型进行评估，并计算出与以前计算方法的差异。为了在实验的基础上验证结果，这些公司对选定的业务进行了测量。该研究项目的成功完成将提供一种工业级、符合标准的设计方法，将动态有限元计算的准确性与准静态分析的有效性相结合。

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.