Numerical Simulation of Sheet Metal Forming Using Non-Associated Flow Rule and Mixed Isotropic-Nonlinear Kinematic Hardening Model

This dissertation consists of three major parts. In the first section, the springback simulation of Numisheet&\u2705 Benchmark#3 was investigated with different material models (Hill\u27s 1948 yield with pure isotropic and mixed isotropic-nonlinear kinematic hardening) using the commercial finite element code ABAQUS. Different theoretical and experimental parameters affecting springback were discussed. In the second section, a new anisotropic material model based on non-associated flow rule (NAFR) and mixed isotropic-nonlinear kinematic hardening was developed and implemented into ABAQUS as a user-defined subroutine. Also, a new direct stress integration formulation applicable to quadratic yield and potential functions (e.g., Hill&\u27s 1948 anisotropic function) was developed based on the return mapping algorithm. This model is able to consider different aspects of anisotropy and cyclic hardening while maintaining both theoretical and computational simplicity. The model was validated by comparing numerical predictions of material behaviour under different loading conditions (equibiaxial tension, monotonic and cyclic shear) and of mechanical properties (uniaxial yield stresses, r-values) with experimental data. The model was used to simulate cup drawing and plane-strain channel drawing with drawbeads. The results showed that this non-associated, mixed hardening model significantly improves the prediction of earing and springback, even when a rather simple quadratic constitutive model is used. In the third section, two different anisotropic models for sheet materials were compared: (i) the quadratic NAFR model; (ii) a non-quadratic associated model, so-called Yld2000-2d, proposed by Barlat et al. (2003). A new general stress integration scheme applicable to all types of yield and potential functions (quadratic or non-quadratic) and flow rules (associated or non- associated) with mixed hardening, based on the multi-stage backward-Euler return mapping algorithm was developed. Both models were implemented into ABAQUS (for both isotropic and mixed hardening) and used to simulate cup drawing and springback of a plane-strain channel section formed with drawbeads. Cyclic tension-compression tests were performed to determine the mixed hardening parameters. The simulation results predicted with each model were compared and it was shown that both models are able to describe the springback and anisotropic behaviour of sheet materials quite accurately. However, the quadratic NAFR model required significantly less computation time

Розробка методу визначення деформацій при виготовленні обода колеса транспортного засобу

The desire to anticipate and predict quality of the manufactured products, its compliance with the technical requirements of the customer at the stage of technology design leads to the development of various methods for theoretical analysis of the processes of plastic deformation. The purpose of these methods is to establish explicit patterns in the processes implemented using the intuitively clear mathematical functions.We have formulated a method for determining relative deformations at a local change in the shape of a closed shell of rotation through radial-rotational profiling. It is shown that it is possible, based on the derived analytical dependences, to predict dimensions of a semi-finished product at the design stage of the technological process. Up to now, there have not been any analytical expressions that would estimate an unambiguous dependence of deformation on the rollers radii ratio, on a billet, and on the magnitude of feed. It is established that the magnitude of relative deformations in three mutually perpendicular directions depends on the ratio of diametrical dimensions of deforming rollers and initial diameter of a billet. Comparison of calculation results, obtained in this work, with experimental data and existing expressions allows us to argue that a given method of calculation demonstrates the accuracy acceptable for the industrial production. This contributes to the possibility to control a field of stresses and deformations in order to manufacture an equally strong wheel rim at the stage of production preparation and a technological process design. The practical application of a given method of calculation would enable technologists and designers to take into consideration the deformation strengthening after each run of profiling. As well as to determine the operational dimensions of semi-finished products and to predict thickness of a finished product in radius transitions of the profile, that is, to intensify the considered process.Стремление предусмотреть и прогнозировать качество изготовляемой продукции, ее соответствие техническим требованиям заказчика на стадии проектирования технологии приводит к разработке различных методов теоретического анализа процессов пластического деформирования. Целью данных методов является установление явных закономерностей процессов, реализуемых с помощью интуитивно понятных математических функций.Сформулирован метод определения относительных деформаций при локальном формоизменении замкнутой оболочки вращения способом радиально-ротационного профилирования. Показано, что на основании полученных аналитических зависимостей возможно прогнозирование размеров полуфабриката на стадии проектирования технологического процесса. В настоящее время аналитических выражений, которые оценивали бы однозначную зависимость деформаций от соотношения радиусов роликов, заготовки и величины подачи не существовало. Установлено, что величина относительных деформаций в трех взаимно перпендикулярных направлениях зависит от соотношения диаметральных размеров деформирующих роликов и начального диаметра заготовки. Сравнение результатов расчета, полученных в данной работе, с экспериментальными данными и существующими выражениями дает основание считать, что данный метод расчета обладает приемлемой для производства точностью. Это способствует возможности управлять полем напряжений и деформаций с целью изготовления равнопрочного обода колеса на стадии подготовки производства и проектирования технологического процесса. Применение на практике данного метода расчета позволит технологам и конструкторам учитывать деформационное упрочнение после каждого перехода профилирования. А также определять операционные размеры полуфабрикатов и прогнозировать толщину готового изделия в радиусных переходах профиля, то есть интенсифицировать рассмотренный процессПрагнення передбачити і прогнозувати якість виготовленої продукції, її відповідність технічним вимогам замовника на стадії проектування технології призводить до розробки різних методів теоретичного аналізу процесів пластичного деформування. Їх метою є встановлення явних закономірностей процесів, що реалізуються за допомогою інтуїтивно зрозумілих математичних функцій.Сформульовано метод визначення відносних деформацій при локальному формозміненні замкнутої оболонки обертання способом радіально-ротаційного профілювання. Показано, що на підставі отриманих аналітичних залежностей можливе прогнозування розмірів напівфабрикату на стадії проектування технологічного процесу. На даний час аналітичних виразів, які б оцінювали однозначну залежність деформацій від співвідношення радіусів роликів, заготовки та величини подачі, не існувало. Встановлено, що величина відносних деформацій в трьох взаємноперпендикулярних напрямках залежить від співвідношення діаметральних розмірів деформуючих роликів і початкового діаметра заготовки. Порівняння результатів розрахунку, отриманих в даній роботі, з експериментальними даними та існуючими виразами дає підставу вважати, що даний метод розрахунку володіє прийнятною для виробництва точністю. Це дає можливість керувати полем напружень і деформацій з метою виготовлення однаковоміцного обіду колеса на стадії підготовки виробництва і проектування технологічного процесу. Застосування на практиці даного методу розрахунку дозволить технологам і конструкторам враховувати деформаційне зміцнення після кожного переходу профілювання, визначати операційні розміри напівфабрикатів і прогнозувати товщину готового виробу в радіусних переходах профілю, тобто інтенсифікувати розглянутий проце

Electrohydraulic Forming of Near-Net Shape Automotive Panels

The objective of this project was to develop the electrohydraulic forming (EHF) process as a near-net shape automotive panel manufacturing technology that simultaneously reduces the energy embedded in vehicles and the energy consumed while producing automotive structures. Pulsed pressure is created via a shockwave generated by the discharge of high voltage capacitors through a pair of electrodes in a liquid-filled chamber. The shockwave in the liquid initiated by the expansion of the plasma channel formed between two electrodes propagates towards the blank and causes the blank to be deformed into a one-sided die cavity. The numerical model of the EHF process was validated experimentally and was successfully applied to the design of the electrode system and to a multi-electrode EHF chamber for full scale validation of the process. The numerical model was able to predict stresses in the dies during pulsed forming and was validated by the experimental study of the die insert failure mode for corner filling operations. The electrohydraulic forming process and its major subsystems, including durable electrodes, an EHF chamber, a water/air management system, a pulse generator and integrated process controls, were validated to be capable to operate in a fully automated, computer controlled mode for forming of a portion of a full-scale sheet metal component in laboratory conditions. Additionally, the novel processes of electrohydraulic trimming and electrohydraulic calibration were demonstrated at a reduced-scale component level. Furthermore, a hybrid process combining conventional stamping with EHF was demonstrated as a laboratory process for a full-scale automotive panel formed out of AHSS material. The economic feasibility of the developed EHF processes was defined by developing a cost model of the EHF process in comparison to the conventional stamping process

Coupled Sequential Process-Performance Simulation and Multi-Attribute Optimization of Structural Components Considering Manufacturing Effects

Coupling of material, process, and performance models is an important step towards a fully integrated material-process-performance design of structural components. In this research, alternative approaches for introducing the effects of manufacturing and material microstructure in plasticity constitutive models are studied, and a cyberinfrastructure framework is developed for coupled process-performance simulation and optimization of energy absorbing components made of magnesium alloys. The resulting mixed boundary/initial value problem is solved using nonlinear finite element analysis whereas the optimization problem is decomposed into a hierarchical multilevel system and solved using the analytical target cascading methodology. The developed framework is demonstrated on process-performance optimization of a sheetormed, energy-absorbing component using both classical and microstructure-based plasticity models. Sheetorming responses such as springback, thinning, and rupture are modeled and used as manufacturing process attributes whereas weight, mean crush force, and maximum crush force are used as performance attributes. The simulation and optimization results show that the manufacturing effects can have a considerable impact on design of energy absorbing components as well as the optimum values of process and product design variables

Coupled Sequential Process-Performance Simulation and Multi-Attribute Optimization of Structural Components Considering Manufacturing Effects

Coupling of material, process, and performance models is an important step towards a fully integrated material-process-performance design of structural components. In this research, alternative approaches for introducing the effects of manufacturing and material microstructure in plasticity constitutive models are studied, and a cyberinfrastructure framework is developed for coupled process-performance simulation and optimization of energy absorbing components made of magnesium alloys. The resulting mixed boundary/initial value problem is solved using nonlinear finite element analysis whereas the optimization problem is decomposed into a hierarchical multilevel system and solved using the analytical target cascading methodology. The developed framework is demonstrated on process-performance optimization of a sheetormed, energy-absorbing component using both classical and microstructure-based plasticity models. Sheetorming responses such as springback, thinning, and rupture are modeled and used as manufacturing process attributes whereas weight, mean crush force, and maximum crush force are used as performance attributes. The simulation and optimization results show that the manufacturing effects can have a considerable impact on design of energy absorbing components as well as the optimum values of process and product design variables

Formability Characterization of a New Generation High Strength Steels

Advanced high strength steels (AHSS) are being progressively explored by the automotive industry all around the world for cost-effective solutions to accomplish vehicle lightweighting, improve fuel economy, and consequently reduce greenhouse emissions. Because of their inherent high strength, attractive crash energy management properties, and good formability, the effective use of AHSS such as Duel Phase and TRIP (Transformation Induced Plasticity) steels, will significantly contribute to vehicle lightweighting and fuel economy. To further the application of these steels in automotive body and structural parts, a good knowledge and experience base must be developed regarding the press formability of these materials. This project provides data on relevant intrinsic mechanical behavior, splitting limits, and springback behavior of several lots of mild steel, conventional high strength steel (HSS), advanced high strength steel (AHSS) and ultra-high strength steel (UHSS), supplied by the member companies of the Automotive Applications Committee (AAC) of the American Iron and Steel Institute (AISI). Two lots of TRIP600, which were supplied by ThyssenKrupp Stahl, were also included in the study. Since sheet metal forming encompasses a very diverse range of forming processes and deformation modes, a number of simulative tests were used to characterize the forming behavior of these steel grades. In general, it was found that formability, as determined by the different tests, decreased with increased tensile strength. Consistant with previous findings, the formability of TRIP600 was found to be exceptionally good for its tensile strength

Recent Advances and Applications of Machine Learning in Metal Forming Processes

Machine learning (ML) technologies are emerging in Mechanical Engineering, driven by the increasing availability of datasets, coupled with the exponential growth in computer performance. In fact, there has been a growing interest in evaluating the capabilities of ML algorithms to approach topics related to metal forming processes, such as: Classification, detection and prediction of forming defects; Material parameters identification; Material modelling; Process classification and selection; Process design and optimization. The purpose of this Special Issue is to disseminate state-of-the-art ML applications in metal forming processes, covering 10 papers about the abovementioned and related topics