The regressive updating technique is illustrated on updating a finite element model from output-only transmissibility measurements. The output-only results is compared with the results of a traditional input-output modal analysis procedure.
A way of applying stochastic updating is done by taking into account the uncertainty on the measurements. If various sets of measurement data are available, weighting of the modal data can be applied, based on the mean value and standard deviation of the estimated resonance frequencies.
This information can be taken into account whereby relatively higher weights are assigned to the measured resonance frequencies that are more reliable. This effect on the updating results is examined in. Until now, the subject of regressive model updating is introduced. On the other hand, the regressive technique also be used for generalized optimization cases concerning multiple parameters. Similar to model updating, structural design optimization can be divided into deterministic and stochastic optimization. Deterministic optimization considers the situation where optimal or desired target values need to be achieved for certain FE output properties by optimizing the input parameter values.
Two application cases on deterministic and topology design optimization is considered, making use of the regressive technique to minimize the process bias between the actual and optimal value to be achieved. A computationally efficient strategy for optimization of structures, described by a finite element model, is presented. The method makes use of transmissibility functions and takes into consideration realistic external loading types that are often defined statistically by means of their power spectral density.
The transmissibility optimization is performed by making use of the regressive technique and the updating results and calculation time will be compared with respect to the results when making use of existing optimization techniques. Complementary to the research performed in the field of deterministic optimization, an indication is given to quantify the uncertainty on the FE model output with respect to the uncertainty on the input design parameters.
An important part of this thesis aims to characterize the variability in structural response due to system uncertainties in combination with mean and variance response surface modelling techniques. Modelling these uncertainties provides a format for the efficient description of the randomness in a system and forms the basis for the prediction of the structural response. The suggested robust optimization approach is extended and applied on an application case considering parameter uncertainty.
A comparison of different optimal, robust and generalized optimization approaches is investigated and applied on a slat track finite element model, making use of mean and variance response functions to model the uncertainty on the finite element displacement values. Different response surface modelling techniques will be applied and compared on the level of accuracy and calculation time.
The Fourth China-Japan-Korea Joint Symposium on Optimization of Structural and Mechanical Systems
On the other hand, robust design optimization is considered, suggesting a generalized mean squared error approach in order to minimize variance as well as considering target objectives on the FE output. Overslaan en naar de algemene inhoud gaan. Voor studenten Lessenroosters Flexibel studeren Studiebegeleidingscentrum Academische kalender. Follow us on. Doctoreren Doctoreren, iets voor jou? Personeel VUB-personeelsleden Oud-werknemers.
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This is true for manufactured structures as well as geomechanical applications. Temperature-dependent materials are explored in this model. A fast temperature transient top can lead to high stresses bottom. A circular pipe, made from an elastoplastic material, is squeezed between two plates to illustrate an analysis of large plastic deformation and contact. The introduction of heat to a mechanical structure leads to expansion and deformation. If this structure expansion is hindered, or the heat transfer occurs very rapidly, there is a build-up of thermal stresses within the structure. Cooling the structure can prevent the damage before it becomes permanent.
Yet, sometimes thermal stresses are unavoidable during the manufacture of a component or part, and they should be analyzed and understood before connecting it to a structure or assembly. Many real-life mechanisms consist of multiple components or bodies that are connected through a variety of joints.
Rather than solving for an assembly with contact between the different components, you can apply a multibody dynamics technique, where standard constraints simulate the behavior of different types of joints. A multibody dynamics analysis allows you to assume that some of the bodies are rigid, while others may undergo elastic or plastic deformations. The results can be also be evaluated with respect to fatigue.
Helicopter flight control is achieved through the operation of a swashplate mechanism where, in this example, the rotor blades are analyzed as flexible bodies, and all other components are assumed to be rigid. The stresses generated through operating a three-cylinder reciprocating engine are investigated in this multibody dynamics analysis. Acoustics is an area of mechanical design where analysis helps you understand and produce the components that either create, measure, harness, or muffle acoustic waves. Acoustic pressure wave propagation in solids, porous media, and fluids is dependent on the medium that the waves are passing through, as well as the size, structure, and damping properties of the component.
To obtain an accurate description of your system's acoustic properties, you will have to consider all of these contributions as well as other participating physics, such as thermoacoustics or fluid flow. An analysis of the acoustics behavior of a loudspeaker is shown being built from scratch in this video. Considered are how this behaviour is affected by the electromagnetic and structural mechanical characteristics of the loudspeaker. See how you can simulate acoustic waves and related phenomena by visiting the: Acoustics Module.
Structures can be subjected to repetitive loads which do not compromise structural integrity in the static sense, yet still fail after a large number of cycles. This is due to the phenomenon known as fatigue and should be understood and factored into situations where repetitive load application occurs. Minimizing the risk of fatigue damage early in the design process through analysis provides multiple advantages. A virtual fatigue analysis can predict whether your component will fail or not, and even determine the number of load cycles it can withstand.
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The solder joints in a ball grid array between the chip and the printed circuit board are subjected to thermal strain cycling when the heat generation in the chip varies over time. This example shows a fatigue analysis based on the Darveaux energy-based model. In this example with a bracket geometry, the S-N curve is used to compute the number of load cycles to failure. The product lifecycle for mechanical systems requires simultaneously working on your CAD and analysis models to provide the details for accurate and efficient manufacturing.
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An effective and seamless integration between the two allows for more effective optimization of your design and its manufacturing process — and shortens your product lifecycle and time-to-market. The Optimization Module is used in this example to minimize the mass of a bracket given limits on the maximum stress and minimum natural frequency. This is achieved by changing the size and position of various objects in the bracket geometry. This video tutorial shows how geometric parameters can be modified and updated between a simulation and CAD software in order to run a parametric sweep.
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