Crankshaft strength analysis methods have significantly developed since last 10 years. Modern numerical methods combine flexible multi-body dynamic simulation, Finite Element method and multiaxial fatigue criteria to predict local stresses under realistic boundary conditions very accurately. In parallel traditional, analytical methods and rules as Unified Requirement M53 are still used and have their place in large engine development due to their stability and reliability. Therefore they are also used by classification societies. Nevertheless, durability results between different methods can vary significantly due to their different approaches, representation of structures and loads, but also material data consideration and influence factors. Modern numerical methods also have the disadvantage that they can be considerably dependent on the tools involved and even the user, due to high number of required input and their deviation, as well as the complexity of the usage in general. Due to the necessity for high reliability, especially for large engine crankshafts, on one hand, but new demands in sense of efficiency and costs on the other hand, which can hardly be covered by traditional approaches, it is important to enhance the current rules to go closer to the limits and reach the new targets, but avoid loosing the stability of these methods. Therefore the relation between the methods and their results is of interest to be able to connect them or further develop the traditional ones. Within the current project different methods for crankshaft fillet strength are analyzed and compared. The present work is done within the CIMAC Working Group 4 and discusses a sequence of different approaches, starting from original UR M53 up to most complex approach using MBS, FEM-structures and multi-axial fatigue method. Each step is based on the previous one and differences in results are outlined to detect the specific influences of each approach. Focus is set on the local stresses and safety factors in pin and journal fillets of the specific crankshaft. The target crankshaft is a modern 20-cylinder 4-stroke ship engine crankshaft from Wärtsilä. The examined operating condition is 600 rpm with full load. Specific influences are investigated separately. Most important are stress concentration factors from analytical definition, via FEM based ones, up to direct evaluation of stresses, which avoids the usage of such factors, the load definition and the resultant local stresses. Loads are derived from analytically calculated bending moments in combination with torsional torque from separate torsional vibration analysis up to full 3-dimensional and transient coupled bending and torsional ones. Effects of phasing between loads and stress components as well as mean stress influence are worked out. Additional influences from material definition, influence factors and the usage of different fatigue methods are compared.


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    Titel :

    Comparison of crankshaft calculation methods with reference to classification societies' requirements


    Beteiligte:


    Erscheinungsdatum :

    2010


    Format / Umfang :

    10 Seiten, 12 Bilder, 2 Tabellen, 13 Quellen


    Medientyp :

    Aufsatz (Konferenz)


    Format :

    Datenträger


    Sprache :

    Englisch




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