PDF《Combining KISSsoft&KISSsys with》

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8 Figure 3-2 Housing forces exported from KISSsys into text or Excel file Figure 3-3 Application of forces and moments on geometry model in pre-processor 4. Bearing support stiffness Import of bearing support stiffness (expressed through housing deformation compared to force applied) (see Figure 4-2) from FEM model (see Figure 4-1) into KISSsoft bearing/shaft calculation helps to improve the shaft deflection calculation as it is superimposed to the bearing stiffness calculation. The improved accuracy is relevant for the calculation of crowing/modifications to be applied in the gearing to improve the load sharing. Furthermore, any misalignment of the bearing supports calculated as bearing hole displacements may be directly added in the shaft calculation. Figure 4-1 Results of FEM analysis, housing deformation is also calculated. Calculate housing stiffness from load applied and displacement calculated. G:\KISSSYS\Application-Reports\app-014-combining-KISSsys-FEM.doc

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8 Figure 4-2 Left: Definition of support stiffness in bearing selection (lowest two fields). Right: symbols for bearing support offset and for bearing support stiffness. 5. Natural frequency analysis Comparison of meshing and bearing fault frequencies from KISSsoft/KISSsys with natural frequency calculation / eigenform calculation in FEM (see Figure 5-1) will show whether a given gearbox housing is prone to vibration. For this, using the FEM calculation, the natural frequencies need to be calculated. Using KISSsoft and KISSsys, the gear meshing frequencies are calculated based on shaft speeds and gear properties (see Figure 5-2). Furthermore, based on shaft speeds and bearing properties like number of rollers, bearing fault frequencies are calculated (see Figure 5-3). The natural frequency of an housing should then be different to the meshing frequencies present at the given operating speed. The bearing fault frequencies may be used for the set up of condition monitoring systems, measuring housing accelerations at the respective locations of the housing where large displacements occur in the eigenform. Figure 5-1 Eigenmode of a gearbox housing G:\KISSSYS\Application-Reports\app-014-combining-KISSsys-FEM.doc

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8 Figure 5-2 Meshing frequency analysis in KISSsys Figure 5-3 Output of bearing fault frequency calculation from KISSsys 6. Stress level assessment Figure 6-1 Left: Stress contour on housing, with various stress concentrations. Right: general describtion of a 3D stress state in a stress raiser. G:\KISSSYS\Application-Reports\app-014-combining-KISSsys-FEM.doc

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8 For the final strength verification of the housing, the stress state calculated (see Figure 6-1) needs to be compared with a permissible stress state and transformed into a safety number using the part S-N curve. The calculation of the utilisation (a comparison between safety factor required divided by safety factor achieved) for a required lifetime, considering material properties (see Figure 6-2), stress concentration, stress state (see figure Figure 6-1, right) and part properties is implemented in KISSsoft as per the FKM guideline (see Figure 6-3). Figure 6-2 Definition of material properties for S-N curve along FKM guideline Figure 6-3 Conversion of a given stress state for a 3D part as calculated in a stress concentration using FEM into an utilisation value. The analysis program delivers a complete, well documented proof of integrity for static and fatigue strength in a point of proof W. The proof is delivered along the local stress concept as described in the FKMguideline "Rechnerischer Festigkeitsnachweis für Maschinenbauteile". G:\KISSSYS\Application-Reports\app-014-combining-KISSsys-FEM.doc