SDNews : October 2024
News Summary:
???[Conference] ISMA 2024 feedback
??[Project] Milling robot modal analysis using spindle-driven unbalanced excitation in context of its response nonlinearity
??[Expertise] Connections to shells in 3D models.
??? [Conference] ISMA 2024 feedback
Etienne Balmes attended the #ISMA24 (Conference on Noise and Vibration Engineering) organized by 比利时荷语天主教鲁汶大学 . This biannual conference is the occasion to meet specialists in our core domain and follow new research trends. There were many interesting communications on non-linear vibrations and acoustics. AI is of course getting momentum in the field and some pragmatic applications were also presented.
More specifically Etienne Balmes chaired the JOINT1 session, interested in the dynamics of joints. Focusing on bolted joints, the presentations discussed non-linear joint dynamics identification for connection modeling, and superharmonic coupling simulations where higher order modes get excited by non-linear forces harmonics.
SDTools was involved in three communications detailed below:
??? Hybrid FEM/test twin building, an electric engine case history (MU session: Updating)
Discussion about hybrid FEM/test twin building challenges when it comes to an electric drive application?. Keeping a rational parametrized reduced order modelling approach based on component mode synthesis, a fast model is built integrating a full FEM with refined geometry and sensors for experimental state estimation and prediction.
??Read the full post ? https://www.sdtools.com/isma-2024-hybrid-fem-test-twin-building-an-electric-engine-case-history/
??? Non-linear viscoelastic damping: designing tests needed for transient simulation of a rail track (D session: Damping).
For transient rail/wheel contact simulations a proper model of the non-linear viscoelastic pads fitted under the sleepers is required. A modelling approach associated to an experimental characterization strategy is presented.
??Read the full post ? https://www.sdtools.com/non-linear-viscoelastic-damping-designing-tests-needed-for-transient-simulation-of-a-rail-track/
??? Milling robot modal analysis using spindle-driven unbalanced excitation in context of its response nonlinearity (Poster session : POS4)
This last communication presented by Grigorii Altshul is detailed in the following topic.
??[Project] Milling robot modal analysis using spindle-driven unbalanced excitation in context of its response nonlinearity
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How to perform modal analysis of milling robot using a spindle-driven unbalanced excitation ?
?? SDTools is a partner in a research project aiming to characterize the dynamic properties of a machining robot.
? Experimental modal analysis based on impact hammer testing would be a classical method, but it does not consider the influence of spindle rotation or cutting forces on system dynamics. For this, an operational modal analysis could be performed, but it would require extensive instrumentation.
This project proposes an intermediate method:
?? Excitation using eccentric masses that generate force with spindle rotation
?? Excitation frequency sweep by slowly increasing the rotation frequency
?? Estimation of transfers : output sensors responses to input force
?? Highlighting of non-linearities with several masses generating different levels of excitation
?? SDT was used to estimate transfers using a recently developed method where an HBV (Harmonic Balanced Vector) signal model is estimated using demodulation.
We will come back to the principle of this method in a later post !
??? The initial results of this project were the subject of a conference paper at ISMA2024.
?? Summary:
“This article presents a novel modal analysis method for investigating the dynamic behavior of milling robots. The proposed method utilizes inertial forces generated by an unbalanced tool rotating on the spindle to excite vibrations, and the frequency response function (FRF) is obtained through demodulation of the recorded vibrations. The study demonstrates the evolution of the robot’s FRF with varying levels of unbalance, showing that the modes exhibit softening behavior and increased damping as the unbalance increases. The method offers a balance between simplicity and precision, requiring less instrumentation than operational modal analysis (OMA) methods while allowing for controlled excitation levels. The importance of precise spindle rotation speed data is highlighted, suggesting the benefits of using spindles with encoders for better results. This method can be applied for characterization of robots in different poses, addressing non-linear behavior significant for the robot’s role in milling processes.”
?? Authors: Grigorii Altshul, Mikhail Guskov , Etienne Balmes and Philippe Lorong
??[Expertise] Connections to shells in 3D models.
As part of our expertise post series dealing with model quality and coupling, this month’s posts focused on 3D shell connection. Slender structures are common in applications and are better modelled by simplifying the small dimensions, that avoids meshing challenges while using larger mesh characteristic lengths. However, when dealing with connections in assemblies, the simplified dimension must be accounted for, and the mesh length may not suit the fastener scale. Three aspects have been discussed this month
??Read the full post ? https://www.sdtools.com/connections-to-shells-in-3d-models/
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