Master Thesis at the Vehicle Analysis team at Volvo Group Truck Technology.
Description of thesis work
The durability lab at Volvo Groups Technology performs lab testing with shaker rigs as part of the verification process. Complete cabs and chassis components such as battery boxes and fuel tanks are mounted on a chassis frame which is excited with hydraulic actuators. The acceleration response on the test object is controlled and the goal is to reproduce the environment measured on a reference truck.
These test procedures are mainly intended to verify the structural integrity of components. However, there is lots to be gained if this test data could be used to verify CAE models as well. Battery electric trucks features new packaging solutions with heavy energy storage systems (ESS) mounted to the chassis frame. Some of these installations include soft bushings and other structural elements which are generally difficult to model. By performing correlation studies on shaker rig data one can identify modelling errors or detect possible problems with the test setup and related hardware at an early stage.
This thesis work will investigate different strategies to perform model correlation based on shake rig data. This is, in part, a continuation of a previous thesis work where a frame was tested and calibrated. For this work, a test setup with a chassis frame and a complete ESS installation will be used as a case study.
Methods based on transient simulations with measured load data will be examined, along with methods based on identifying structural mode shapes from test data. Initially, algorithm for Operational Modal Analysis (ODS/OMA) will be tested. These algorithms can identify underlying structural modes without direct input force measurements. As such, they can be appropriate for the shake rig since the input forces generated by the hydraulic actuator are typically not measured. The advantage with this approach is that raw data from the durability test can be reused for the correlation work and no additional test setup or equipment is needed.
The possibility to measure – or indirectly estimate - input forces will also be investigated throughout this study. Access to the input forces will simplify the correlation work since a classic Experimental Modal Analysis (EMA) method can be used to identify structural modes. Alternativity, the forces can be used for a transient analysis with the CAE model and correlation studies can be performed by comparing measured and simulated time histories.
The first part of this study will be carried out with simulation models. A finite element model of a shake rig for an ESS installation will be prepared in MSC Nastran. Virtual signals will be generated from the finite element model and the different strategies outline above will be tested. The most promising approach will then be selected and used on real shake rig data. If time is available, the finite element model will be calibrated based on the test data.
The ideal student will possess good communications skills in English (written and verbal), show a high level of initiative, be self-driven, have good analytical capabilities along with relevant courses related to finite-element modelling and structural dynamics. Experience with Matlab and/or Nastran is a merit.
Thesis Level: Master thesis.
Number of students: 1 student.
Andreas Josefsson, Lead Vehicle Analyst
Vehicle Analysis, Volvo GTT
+46 765 53 42 54
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