scholarly journals Characterising Fatigue Behaviour of Nodular Cast Iron Using Micromechanical Simulations

2019 ◽  
Vol 300 ◽  
pp. 13002
Author(s):  
Mehul Lukhi ◽  
Meinhard Kuna ◽  
Geralf Hütter
Keyword(s):  
Finite Element ◽  
Cast Iron ◽  
Volume Fraction ◽  
Cell Model ◽  
Kinematic Hardening ◽  
Nodular Cast Iron ◽  
Fatigue Behaviour ◽  
Cyclic Stress ◽  
Finite Element Simulations ◽  
Final Failure

Elastic-plastic porous materials experience an increase in the mean void volume fraction when they are subjected to cyclic loading. This behavior is known both from the experiments and simulations in the literature. The authors have first time used this mechanism for the evaluation of the fatigue life in nodular cast iron. In this contribution, the stress-life approach is presented for the characterization of fatigue failure. For this purpose, micromechanical finite-element simulations are carried out using the axisymmetric cell model. The cell model having isotropic/non-linear kinematic hardening behavior is subjected to fully reversed cyclic stress controlled loading. The finite element simulations are carried out cycle by cycle until the final failure of the cell model. The numbers of cycles to failure are extracted from the simulations. The stress-life curves are shown for spherical and elliptical graphite particle cell models. The results of the micromechanical simulations are in qualitative agreement with the typical experimental stress-life curves.

Determination of the relationship between microstructure and constitutive behaviour of nodular cast iron with a unit cell model

2005 ◽  
Vol 40 (2) ◽  
pp. 107-116 ◽  
Author(s):  
L Collini ◽  
G Nicoletto
Keyword(s):  
Cast Iron ◽  
Mechanical Performance ◽  
Volume Fraction ◽  
Cell Model ◽  
Nodular Cast Iron ◽  
Unit Cell ◽  
Constitutive Law ◽  
Cast Irons ◽  
Present Contribution ◽  
The Matrix

Unit cell models have been proposed to predict the constitutive law and failure of ductile materials with complex microstructures, such as ferritic nodular cast iron and particulate metal matrix composites (PMMCs). The present contribution aims to extend this modelling approach to the prediction of the constitutive response of nodular cast iron with a mixed ferritic/pearlitic matrix. The finite element method is used within the framework of continuum mechanics to carry out the calculations. The effect of some microstructural features, such as graphite volume fraction and ferrite-pearlite ratio of the matrix, on the mechanical performance is determined. The computational results are compared to results obtained in a previous experimental activity on nodular cast irons.

Direct Diode Laser Surface Melting of Nodular Cast Iron

2015 ◽  
Vol 809-810 ◽  
pp. 423-428 ◽  
Author(s):  
Damian Janicki
Keyword(s):  
Cast Iron ◽  
Diode Laser ◽  
Heat Input ◽  
Volume Fraction ◽  
Residual Austenite ◽  
Nodular Cast Iron ◽  
Surface Melting ◽  
Laser Surface ◽  
Test Method ◽  
Laser Surface Melting

A nodular cast iron (NCI) has been surface melted using the high power direct diode laser (HPDDL) with a quasi-rectangular laser beam spot and the uniform distribution of power. The effect of a heat input and a shielding gas on the quality of surface melted layers (SMLs) has been investigated. The microstructure of the SMLs has been assessed by optical microscopy, scanning electron microscopy and X-ray diffraction (XRD). Comparative erosion tests between the SMLs and as-received NCI have been performed following the ASTM G 76 standard test method. The HPDD laser surface melting of the NCI enables to produce non-porous layers having a hardness up to 1000 HV. It has been determined that the hardness of SMLs depends on the amount of cementite and residual austenite in the fusion zone. The SMLs produced in an argon atmosphere contain higher volume fraction of austenite, than those produced in nitrogen, and consequently have the lower hardness. With increasing heat input the hardness increases, as the result of more complete dissolution of graphite and the higher amount of cementite. The SMLs exhibited significantly higher erosion resistance than the as-received NCI for erodent impact angle of 3<em>0°, and slightly lower at 90°.</em><em></em>

A Constitutive Model for the Simulation of the Deformation Behavior of TWIP Steels

2015 ◽  
Vol 639 ◽  
pp. 411-418
Author(s):  
André Haufe ◽  
Andrea Erhart ◽  
Alexander Butz
Keyword(s):  
Finite Element ◽  
Constitutive Model ◽  
Volume Fraction ◽  
Kinematic Hardening ◽  
Flow Behavior ◽  
Three Dimensional ◽  
High Strength ◽  
Engineering System ◽  
Twip Steels ◽  
User Friendly

Due to their high strength (tensile strength > 1GPa) in combination with an extreme ductility (failure strain 30-50%) TWinning Induced Plasticity–steels (TWIP-steels) can be considered as promising materials for the production of lightweight automotive components. The industrial application of TWIP-steels requires a fundamental experimental validation of the mechanical behavior as basis for an user-friendly but at the same time accurate constitutive framework and its implementation into commercial Finite Element codes. Related investigations and implementations in order to allow for the simulation of TWIP-steel forming processes are currently conducted within the research project “TWIP4EU”, executed as a cooperation of Fraunhofer - Institut für Werkstoffmechanik IWM in Freiburg (Germany), Salzgitter Mannesmann Forschung GmbH (Germany), Swerea KIMAB (Sweden), Faurecia Autositze GmbH (Germany / France), DYNAmore GmbH (Germany) and ESI GmbH Engineering System (Germany / France).The monotonic one-dimensional hardening behavior of TWIP-steels as a function of the twin volume fraction and dislocation density has been described by Bouaziz et al. (2008), Bouaziz et al. (2011). This model has been proven to be adequate for the description of the flow behavior of TWIP-steels and serves as basis for the constitutive model, presented here. This Bouaziz-model has been extended to a three-dimensional elasto-plastic formulation, including the influence of different loading conditions, anisotropy and kinematic hardening. The present paper deals with the implementation for solids and shells in the commercial Finite Element Code LS-DYNA®and appropriate validation simulations will be presented.

scholarly journals Nodular Cast Iron – Fatigue Crack Measurement and Simulation

2013 ◽  
Vol 577-578 ◽  
pp. 473-476
Author(s):  
Predrag Čanžar ◽  
Zdenko Tonković
Keyword(s):  
Numerical Simulation ◽  
Fatigue Crack ◽  
Cast Iron ◽  
Crack Initiation ◽  
Low Cycle Fatigue ◽  
Fatigue Crack Initiation ◽  
Nodular Cast Iron ◽  
Computational Procedure ◽  
Fatigue Behaviour ◽  
Cyclic Plasticity

Study presented in this paper is concerned with fatigue crack initiation detection, crack propagation observation and measurement as well as with numerical simulation of damage accumulation and propagation in the nodular cast iron grade EN-GJS-400-18-LT. Material properties of nodular cast iron are well elaborated in previous authors' papers. Crack initiation and its propagation observation as well as crack length measurement is performed on standardized specimens using ARAMIS 4M optical system. Based on the experimental results, a new three-dimensional constitutive model is proposed to simulate the low-cycle fatigue behaviour of considered material. An efficient algorithm for modelling cyclic plasticity is used for performing numerical simulation of crack initiation and growth on standardized specimens made from nodular cast iron. The computational procedure accuracy is verified by comparing the computed results with the real experimental data.

Strain Heterogeneity and Damage Localization in Nodular Cast Iron Microstructures

2005 ◽  
Vol 482 ◽  
pp. 255-258 ◽  
Author(s):  
Gianni Nicoletto ◽  
Luca Collini ◽  
Radomila Konečná ◽  
P. Bujnová
Keyword(s):  
Finite Element ◽  
Cast Iron ◽  
Mechanical Loading ◽  
Nodular Cast Iron ◽  
Fracture Mechanisms ◽  
Finite Element Models ◽  
Damage Localization ◽  
Matrix Microstructure ◽  
Heterogeneous Matrix

Fracture mechanisms of ferritic/pearlitic nodular cast iron are influenced by the heterogeneous matrix microstructure. This contribution is aimed at understanding the role of a heterogeneous matrix on the localization of damage due to mechanical loading. Therefore, bend specimens made of different nodular cast iron were plastically deformed and the degree of strain heterogeneity determined by comparison with a homogenized response. To address these observations elastic-plastic finite element models of local microstructures were developed. Computed strain maps are examined to understand the link between microstructural features and conditions for damage localization.

scholarly journals Effective Modulus Estimation Method of QT400-18 Cast Iron with Repair Welding

2019 ◽  
Vol 2019 ◽  
pp. 1-9
Author(s):  
Tao Wei ◽  
Wei Liu ◽  
Wenxuan Gou ◽  
Junqiang Kou
Keyword(s):  
Cast Iron ◽  
Volume Fraction ◽  
Estimation Method ◽  
Welding Process ◽  
Nodular Cast Iron ◽  
Effective Modulus ◽  
Uniaxial Tensile ◽  
Cross Sectional ◽  
Negative Exponential Function ◽  
Repair Welding

Repair welding is an important remediation process for castings with slight defects. In this paper, the tensile behaviors of the QT400-18 nodular cast iron with different repair welding sizes were experimentally analyzed. Specimens with different diameters of the filler region were prepared by the same welding process. The fracture initiated in the filler region under uniaxial tensile loading. The modulus, strength, and ductility decreased with the weld diameter increase. The postyield hardening phenomenon was not observed in the repaired specimen. The repair region ratio was defined as the proportion of the repair welding area to the cross-sectional area of the structure. The effective modulus of the repaired specimens decreased with the repair region ratio increase, and the relationship between them was fitted by a negative exponential function. The repair welding region was treated as an inclusion in the matrix of castings, and the volume fraction of inclusion was applied to characterize the repair welding size. Based on the theories of Eshelby tensor and Mori–Tanaka equivalent method, a method for estimating macroscopic effective modulus of repair welding castings was established. The theoretical solutions were in good agreement with the experimental results. The method will be helpful in estimating the safe service limit of repair welded castings.

Toughening Mechanisms in Al/Al-SiC Laminated Metal Composites

1996 ◽  
Vol 434 ◽  
Author(s):  
D. R. Lesuer ◽  
J. Wadsworth ◽  
R. A. Riddle ◽  
C. K. Syn ◽  
J. J. Lewandowski ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Finite Element ◽  
Aluminum Alloy ◽  
Metal Matrix Composite ◽  
Crack Growth ◽  
Matrix Composite ◽  
Metal Matrix ◽  
Volume Fraction ◽  
Finite Element Simulations ◽  
Metal Composites

AbstractThe fracture toughness of laminated metal composites consisting of alternating layers of a metal matrix composite (Al6090/SiC/25p) and a monolithic aluminum alloy (Al5182) has been studied as a function of the volume fraction of the component materials. Finite element simulations of the fracture toughness tests have been used to study the mechanisms of crack growth and extrinsic toughening. The mechanisms responsible for toughening in laminated metal composites are described.

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