H9
Dynamics & Vibration 1

Back to overview

17:35
conference time (CEST, Berlin)
Combined 3D Cyclic Symmetry and 2D Axisymmetric Simulation for Turbine Engine Systems
26/10/2021 17:35 conference time (CEST, Berlin)
Room: H
M. Lamping (Siemens Digital Industries Software, USA); N. Kill (BEL); F. D'Ambrosio (BEL)
M. Lamping (Siemens Digital Industries Software, USA); N. Kill (BEL); F. D'Ambrosio (BEL)
Analysts have always used simplifications to turn the impossible into possible. Cyclic symmetry simulation is often used for efficient structural modeling of rotating systems such as fan, compressor, or turbine blades in engine systems. Such systems consist of multiple stages of blades and disks with each stage composed of multiple identical sectors about a cylindrical axis. A single stage can be simulated using cyclic symmetry constraints on one sector to give results over all sectors. In turbine engines, a 3D cyclic model of a blade and disk is used for computing detailed stress results needed for fatigue life prediction. Although a single stage is often modeled in isolation, all stages are closely connected and influence adjoining stages. An efficient way to account for the coupling between stages is to use a detailed 3D cyclic symmetric model of the blades at each stage, and then couple each blade to a 2D axisymmetric model of its disk and shaft of the turbine system. Basic techniques with standard FE simulation methods are typically used for coupling the 2D mesh with the 3D mesh for predicting response from static loads. They can also be used to predict the 0-order harmonic modes. However, these techniques have some limitations on accuracy and cannot be used to predict the higher order harmonic modes that are also needed for fatigue life predictions. A more accurate technique is to use a Fourier formulation for representing the 2D axisymmetric elements. Such a formulation can be used for static and multi-harmonic simulation. This paper will describe the Fourier formulation for 2D axisymmetric elements and its coupling with 3D cyclic symmetric models. The method will be demonstrated on an example turbine engine blade system and will be compared to the results obtained using basic 2D/3D coupling methods. Although the emphasis of the presentation will be on structural analysis, these methods are supported in a multiphysics thermal/structural environment too.
Turbine, Engine, Turbomachinery, Multiphysics, Thermal, Structural
17:55
conference time (CEST, Berlin)
Efficient Coupled Modal Vibro-acoustic Analysis for Structures With Heavy Fluids
26/10/2021 17:55 conference time (CEST, Berlin)
Room: H
A. Sohn (MSC Software, USA); S. Palfreyman, M. Robinson (Hexagon MSC, USA)
A. Sohn (MSC Software, USA); S. Palfreyman, M. Robinson (Hexagon MSC, USA)
Assemblies containing fluid filled reservoirs are present in space launch vehicles and their satellite payloads, automotive structures, ship containers and rail transportation to name just a few. When the reservoirs contain a liquid, or heavy fluid, they are strongly affected by the motion of the structure and the heavy fluid adds significant mass to that of the structure. Dynamic response analysis with the finite element method using direct solutions of the coupled fluid-structure assembly are expensive and provide no means to obtain the coupled modes of the fluid-structure assembly. A new real coupled modes capability was first introduced into MSC Nastran 2019 and has since been extended. The new method delivers the accuracy of direct methods with a significant gain in elapsed time allowing the engineer to perform fast and accurate design studies. Rigid body and constant pressure modes are handled correctly, and the modal basis is available for vibro-acoustic response analysis. Traditional damping models (modal, structural, wmodal, Rayleigh) may be used and the capability is available for interior and exterior acoustics with or without strong coupling (ACOWEAK) to the infinite domain. Excellent agreement is obtained when compared with the modal basis computed using a complex eigenvalue solution and dynamic responses computed using the direct method. In the later versions, external superelements may be generated that contain one or more heavy fluid cavities where the additional mass of the fluid, and the effects of the heavy fluid in the modal basis, are captured. This naturally also makes the capability available for Adams MNF, as well as AVL Excite, generation where the flexible body component may now contain heavy fluid filled reservoirs. In this talk you will learn from the core MSC Software development staff about the latest advancements with MSC Nastran's vibro-acoustic capabilities and how to apply that to your structures application.
FEA, Acoustics, Structures, Dynamics, Vibration, Rockets, Space
18:15
conference time (CEST, Berlin)
The Concept of Pseudo Damage When Using Acceleration Response Data
26/10/2021 18:15 conference time (CEST, Berlin)
Room: H
N. Bishop (MSC Software, USA); P. Murthy (Hexagon, FRA)
N. Bishop (MSC Software, USA); P. Murthy (Hexagon, FRA)
Very often analysts are faced with making design choices related to durability before adequate stresses can be obtained from the prototype. Sometimes, revisions to subsystems are needed when only Adams type MBDA models are available which do not, or cannot, include stress information from the flexible bodies within the system. In these circumstances, if the analyst wants to assess durability improvements, he or she, is forced to use tools like the Fatigue Damage Spectra (FDS) approach. The FDS approach is a highly simplified assessment of damage potential for a hypothetical system. The biggest limitation of the approach is that a “pretend” one degree of system is used to transform the input loading (e.g. acceleration) into stresses which can be used in a fatigue calculation. The resonant frequency of the 1 DOF system is swept through the required frequency range and the damage plotted as a function of frequency. In effect, the approach assumes zero knowledge about the real system. By far the best option in determining damage potential is to pass the loading through a real system, or a simplified version of it, in which case we have almost 100% knowledge about the system. The frequency domain approach offers the possibility to do this because of the separation of loads, system properties (transfer functions) and response (damage). In this paper, something in-between is proposed (which we call Pseudo Damage) where partial knowledge about the system is available via an Adams MBDA model. The MBDA model is used to generate a set of (acceleration) responses on the model. These acceleration responses are then transformed by switching the units into stress and scaling the magnitudes until the damage caused (for a specified material) is equal to 1.0. The scaling factors (different for each channel) are then stored as the “reference case for the model. Any proposed design changes can then be evaluated by seeing if the scale factors needed on the modified design go up, or down when compared to the reference case. This is the Pseudo Damage calculation. This approach is currently implemented in the time domain and results from a typical analysis will be shown. Further work to extend it into the frequency domain is ongoing.
Durability, MBDA, Fatigue, Dynamics
×

[TITLE]

[LISTING

[ABSTRACT]

[DATE]

[ROOM]

[KEYWORDS]