Calibration of fracture locus in scope of uncoupled elastic–plastic-ductile fracture material models

Wen

Fatigue Fract Eng Mat Struct

et al. 2019

The stress state is one of the most notable factors that dominates the initiation of ductile fracture. To examine the effects of the stress state on plasticity and ductile failure, a new tension‐shear specimen that can cover a wide range of stress triaxialities was designed. A fracture locus was constructed in the space of ductility and stress triaxiality for two typical steels based on a series of tests. It is observed that the equivalent plastic strain at failure exhibits a nonmonotonic variation with increasing the value of stress triaxiality. A simple damage model based on the ductility exhaustion concept was used to simulate the failure behaviour, and a good agreement is achieved between simulation results and experimental data. It is further shown that consideration of fracture locus covering a wide range of stress triaxialities is a key to an accurate prediction.

Section: Resultsmentioning

confidence: 99%

Effects of the stress state on plastic deformation and ductile failure: Experiment and numerical simulation using a newly designed tension‐shear specimen

Wen

Fatigue Fract Eng Mat Struct

et al. 2019

“…There are various factors having an impact on the quality of the measurement record, such as the measurement method, the test configuration, the quality of the sensors, the machine stiffness, the loading velocity and others. [1][2][3] In the present project, a rapid and effective datafitting procedure for various physical measurements was developed and implemented. Data fitting is in essence a fine tuning of the material-property data obtained with the mechanical tests.…”

Section: Preparation Of the Materials Modelsmentioning

confidence: 99%

“…2,3,5 In addition, these estimated parameters are used as the input parameters for the optimization script controlling the numerical simulation. The optimization script is iterative (Figure 2) (1)) depend on the boundary and initial conditions of the process (temperatures, strain rates) and their meanings are described below.…”

Section: Preparation Of the Materials Modelsmentioning

confidence: 99%

“…A typical example of a flat product with spatial features, such as a cylindrical recess, is shown in Figure 1. [1][2][3] Today's professional literature around the world describes various approaches to measuring material characteristics. They concern not only elastic-plastic materials, such as metal alloys, but also viscoelastic materials, such as rubber.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Effective preparation of non-linear material models using a programmed optimization script for a nurimerical simulation of sheet-metal processing

Urbánek¹,

Tikal²

2015

Mater. Tehnol.

Progressive methods and technologies are the key to the dynamic development of the automotive and electrical-engineering industries. The processes in sheet-metal processing have changed fundamentally since the end of the 1990s. Previously, the operations such as cutting, punching holes, etc., were carried out separately on different press machines. These operations can now be integrated into a single tool on one press machine due to the development of progressive tools and, especially, the fine-blanking technology. The result is an already completed component that can be used for the assembly. The development of progressive tools must be supported with the FEM simulations of sheet-metal processing that are dependent on their inputs. Therefore, only a correct material model can be expected to provide the right results. For the reasons described above, an experimental program dealing with measuring and fitting the data to the models with orthotropic material properties such as rolled sheets was designed and implemented. The aim is to obtain the material models of rolled sheets made of selected aluminum, copper and steel alloys. One of the objectives of the solution is to provide more efficient and more accurate data fitting because the more accurate the input material data are, the more accurate are the simulation results for sheet-metal processing. The optimization script using the simplex method was made for fitting. The main function of the optimization script is to specify the parameters of the material model iteratively and to compare the simulation results and the mechanical-test results. The script was programmed in the Python environment for the MSC.MARC/MENTAT software using the Johnson-Cook plasticity model. Fitting the data from the pressure tests by Rastegaev at different loading speeds is presented. The difference between the measured and simulated curves is less than 1 %. Keywords: FEM simulation, measurement, compression test, fitting, MSC.MARC, Python Napredne metode in tehnologije so klju~ne za dinami~en razvoj avtomobilske in elektro-industrije. Procesi preoblikovanja plo~evin so se bistveno spremenili od devetdesetih let zadnjega stoletja. Prej so se operacije, kot so rezanje, prebijanje lukenj in podobno, izvajale lo~eno na razli~nih strojih. Zaradi razvoja naprednih orodij in {e posebej tehnologije precizijskega {tancanja se te operacije lahko zdru`i v enem orodju na enem stroju. Rezultat je kompletna komponenta, ki je primerna za vgradnjo. Razvoj naprednih orodij mora biti podprt s FEM-simulacijami obdelave plo~evine, kar je odvisno od vhodnih veli~in. Zato samo pravilen model materiala lahko zagotavlja prave rezultate. Iz navedenih razlogov je bil postavljen in uporabljen eksperimentalni program, ki obravnava merjenje in ujemanje podatkov za modele z ortotropnimi lastnostmi materiala, kot je valjana plo~evina. Namen je dobiti modele materiala valjane plo~evine za izbrane aluminijeve in bakrove zlitine ter jekla. Eden od ciljev je zagotoviti bolj u~inkovito in bolj zanesljivo pridobivanje pod...

“…Kim et al [10], Gao et al [11], and Brünig et al [12] studied triaxiality and Lode angle. This has been followed up by many authors, including our laboratory, to develop testing procedures and the shape of the samples [13][14][15].The failure prediction procedure described in this paper consists of defining material behaviour for numerical simulation on the basis of several different tests and finding correlation between them and the accuracy and usability of the prediction. For this purpose, mechanical tests classified into three groups were performed.…”

mentioning

confidence: 99%

Using DEFORM Software for Determination of Parameters for Two Fracture Criteria on DIN 34CrNiMo6

Poláková¹,

Zemko²,

Rund³

et al. 2020

Metals

The aim of this study was to calibrate a material model with two fracture criteria that is available in the DEFORM software on DIN 34CrNiMo6. The purpose is to propose a type of simple test that will be sufficient for the determination of damage parameters. The influence of the quantity of mechanical tests on the accuracy of the fracture criterion was explored. This approach was validated using several tests and simulations of damage in a tube and a round bar. These tests are used in engineering applications for their ease of manufacturing and their strong ability to fracture. The prediction of the time and location of the failure was based on the parameters of the relevant damage model. Normalized Cockroft-Latham and Oyane criteria were explored. The validation involved comparing the results of numerical simulation against the test data. The accuracy of prediction of fracture for various stress states using the criteria was evaluated. Both fracture criteria showed good agreement in terms of the fracture locus, but the Oyane criterion proved more suitable for cases covering larger triaxiality ranges.