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An inverse strategy to determine constitutive parameters of tubular materials for hydroforming processes

Chinese Journal of Aeronautics 2022年第6期35卷 379-390页

作者： Bin ZHANG Benny ENDELT Lihui LANG Yang ZHAO Shu YAN Karl Brian NIELSEN Department of Materials and Production Aalborg UniversityAalborg 9220Denmark School of Mechanical Engineering and Automation Beihang UniversityBeijing 100083China School of Materials Science and Engineering Northeastern UniversityShenyang 110819China Department of Mechanical and Production Engineering Aarhus UniversityAarhus 8000Denmark

This paper is to determine the flow stress curve of 5049-O aluminium alloy by a tube hydraulic bulging test with fixed end-conditions. During this test, several tubular specimens are bulged under different internal pressures before their bursting, and the corresponding bulging height and wall thickness at the pole are measured. An inverse strategy is developed to determine the constitutive parameters of tubular materials based on experimental data, which combines the finite element method with gradient-based optimization techniques. In this scheme, the objective function is formulated with the sum of least squares of the error between numerical and experimental data, and finite difference approximation is used to calculate the gradient. The tubular material behavior is assumed to meet the von Mises yield criterion and Hollomon exponential hardening law. Then, constitutive parameters identification is performed by minimization of the objective function. In order to validate the performance of this framework, identified parameters are compared with those obtained by two types of theoretical models, and tensile tests are performed on specimens cut from the same tubes. The comparison shows that this inverse framework is robust and can achieve a more accurate parameter identification by eliminating mechanical and geometrical assumptions in classical theoretical analysis.

关键词： Aluminum alloy Constitutive parameter Hydraulic bulging test inverse modelling Tubular material

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Information and knowledge behind data from underground rock grouting

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Journal of Rock Mechanics and Geotechnical Engineering 2021年第6期13卷 1326-1339页

作者： Fei Xiao Qian Liu Zhiye Zhao Department of Civil Engineering Nanjing University of Aeronautics and AstronauticsNanjing210016China School of Civil and Environmental Engineering Nanyang Technological University50 Nanyang Avenue639798Singapore

Data related to the pre-grouting work of a large underground project are systematically analyzed to reveal the mechanism behind,to shed some light on the execution of practical grouting,and to enrich the theory of engineering *** is generally taken as an effective way for controlling nonignorable water seepage during underground rock *** various models have been developed to guide grouting design or to specify criteria for grouting stop,it does not change the fact that grouting is still highly ***,explanation of the current situation due to grouting complexity is given through step-by-step data analysis,where the impact on grouting parameters from the geological and hydrogeological conditions is investigated,and the grouting features of two tunnels located at the same depth below the sea surface are compared and ***,the data from individual grout hole are used to construct the regional geological conditions via inverse *** is found that grouting of fractured rock masses is accompanied with great uncertainty,and field grouting data can contribute significantly to a better understanding of the regional geological conditions around an underground tunnel or rock cavern.

关键词： Field grouting data Water seepage Rock grouting inverse modelling Data analytics Geological conditions

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Simulation of inverse heat conduction problems in fusion welding with extended analytical heat source models

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Frontiers of Materials Science 2011年第2期5卷 119-125页

作者： V. A. KARKHIN A. PITTNER C. SCHWENK M. RETHMEIER St. Petersburg State Polytechnical University St. Petersburg 195251 Russia Federal Institute for Materials Research and Testing （BAM） Berlin Germany

The paper presents bounded volume heat sources and the corresponding functional-analytical expressions for the temperature field. The power density distributions considered here are normal, exponential and parabolic. The sources model real heat sources like the welding arc, laser beam, electron beam, etc., the convection in the weld pool as well as the latent heat due to fusion and solidification. The parameters of the heat source models are unknown a priori and have to be evaluated by solving an inverse heat conduction problem. The functional-analytical technique for calculating 3D temperature fields in butt welding is developed. The proposed technique makes it possible to reduce considerably the total time for data input and solution. It is demonstrated with an example of laser beam welding of steel plates.

关键词： laser beam welding volume heat source functional-analytical solution inverse modelling

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Simplified thermal and hygric building models： A literature review

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Frontiers of Architectural Research 2012年第4期1卷 318-325页

作者： Rick Kramer Jos van Schijndel Henk Schellen Deportment of the Built Environment Eindhoven University of Technology Eindhoven 5612 AZ The Netherlonds

This paper provides a systematic literature review on simplified building modelso Questions are answered like： What kind of modelling approaches are applied？ What are their （dis）advantages？ What are important modelling aspects？ The review showed that simplified building models can be classified into neural network models （black box）, linear parametric models （black box or grey box） and lumped capacitance models （white box）. Research has mainly dealt with network topology, but more research is needed on the influence of input parameters. The review showed that particularly the modelling of the influence of sun irradiation and thermal capacitance is not performed consistently amongst researchers. Furthermore, a model with physical meaning, dealing with both temperature and relative humidity, is still lacking. inverse modelling has been widely applied to determine models parameters. Different optimization algorithms have been used, but mainly the conventional Gaus-Newton and the newer genetic algorithms. However, the combination of algorithms to combine their strengths has not been researched. Despite all the attention for state of the art building performance simulation tools, simplified building models should not be forgotten since they have many useful applications. Further research is needed to develop a simplified hygric and thermal building model with physical meaning.

关键词： Literature review Building performancesimulation Simplified buildingmodels inverse modelling Climate change

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An Approach to Interpreting Critical Indoor Pollution Scenes of a Whole Building with Limited Sensor Outputs

An Approach to Interpreting Critical Indoor Pollution Scenes...

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The First International Conference on Building Energy and Environment

作者： Xiang Liu John Zhai Department of Civil Environmental and Architectural EngineeringUniversity of ColoradoUCB 428ECOT 441BoulderCO 80309-0428 USA

To maintain a healthful and secure indoor environment, it is critical to quickly identify contaminant source conditions (locations, strengths and release histories) so the source can be controlled and removed. This paper introduces a probability concept based inverse modelling method - the adjoint probability method - to identify potential indoor pollutant sources with limited pollutant sensor readings. The paper establishes the corresponding adjoint equations for both computational fluid dynamics (CFD) and multi-zone airflow models, which can be used to calculate the source location and travel time probabilities of an observed contamination. A two-stage integrated inverse modelling algorithm is proposed that can interpret critical indoor air quality (IAQ) scenes for a whole building with few sensor outputs. Preliminary research results for locating an indoor pollutant source in a residential building with different sensing conditions have been presented, which confirms the feasibility and accuracy of the developed method. The paper discusses the further research directions and applications.

关键词： Indoor air quality Source identification inverse modelling Adjoint probability method

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