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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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Identification of constitutive model parameters for nickel aluminum bronze in machining

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Transactions of Nonferrous Metals Society of China 2016年第4期26卷 1105-1111页

作者：付中涛杨文玉曾思琪郭步鹏胡树兵华中科技大学机械科学与工程学院数字制造装备与技术国家重点实验室武汉430074 华中科技大学材料科学与工程学院武汉430074

The material of nickel aluminum bronze (NAB) presents superior properties such as high strength, excellent wear resistance and stress corrosion resistance and is extensively used for marine propellers. In order to establish the constitutive relation of NAB under high strain rate condition, a new methodology was proposed to accurately identify the constitutive parameters of Johnson?Cook model in machining, combining SHPB tests, predictive cutting force model and orthogonal cutting experiment. Firstly, SHPB tests were carried out to obtain the true stress?strain curves at various temperatures and strain rates. Then, an objective function of the predictive and experimental flow stresses was set up, which put the identified parameters of SHPB tests as the initial value, and utilized the PSO algorithm to identify the constitutive parameters of NAB in machining. Finally, the identified parameters were verified to be sufficiently accurate by comparing the values of cutting forces calculated from the predictive model and FEM simulation.

关键词： nickel aluminum bronze constitutive parameter Johnson-Cook model identification method

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维普期刊数据库

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Statistical condition assessment of existing structures using virtual work error estimator

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Journal of Southeast University(English Edition) 2007年第4期23卷 577-582页

作者：蔡晶吴智深南京工业大学土木工程学院南京210009 东南大学土木工程学院

A statistical damage detection and condition assessment scheme for existing structures is developed. First a virtual work error estimator is defined to express the discrepancy between a real structure and its analytical model, with which a system identification algorithm is derived by using the improved Newton method. In order to investigate its properties in the face of measurement errors, the Monte Carlo method is introduced to simulate the measured data. Based on the identified results, their statistical distributions can be assumed, the status of an existing structure can be statistically evaluated by hypothesis tests. A 5-story, two-bay steel frame is used to carry out numerical simulation studies in detail, and the proposed scheme is proved to be effective.

关键词： virtual work constitutive parameter parameter estimation hypothesis test

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