Microstructural Dependence of Tensile and Fatigue Properties of Compacted Graphite Iron in Diesel Engine Components

Ghodrat, Sepideh; Kestens, Léo

doi:10.1002/srin.201500219

Cited by 12 publications

(21 citation statements)

References 20 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…It appears that the crack path morphology is affected by these particles. A similar phenomenon was observed in a previous study of cast iron with the graphite particles embedded in a pearlitic metal matrix during thermo-mechanical fatigue (TMF) testing [16]. Similar to the cast iron case, in the current material under investigation, the crack deviates towards the particles that exhibit a characteristic stress field.…”

Section: Resultssupporting

confidence: 60%

Measuring Plasticity with Orientation Contrast Microscopy in Aluminium 6061-T4

Ghodrat

Riemslag

Kestens

2017

Metals

Self Cite

View full text Add to dashboard Cite

Orientation contrast microscopy (i.e., electron backscattered diffraction, EBSD) was employed to monitor the plastic strain in loaded tensile samples of aluminium alloy Al6061 in T4 condition. The kernel average misorientation (KAM) is known to be an appropriate parameter in orientation contrast microscopy which has the potential to characterise the plastic strain by monitoring the local misorientations. This technique was applied here to gauge the extent of the plastic zone around a fatigue crack. To establish the magnitude of strain (which can be identified by the KAM parameter), a series of tensile samples were strained in the range of 1% to 25%. KAM maps were compared, and the average misorientations were related to the tensile strain values. The KAM distribution functions for all the strained samples were derived from a large scanned area. In addition, Vickers microhardness tests were conducted for these series of samples. This allowed the comparison of the mesoscopic plastic strain measured by Vickers microhardness with the micro plastic strain locally obtained by KAM. Noise was observed in the average KAM values up to a plastic strain of 1.5%. For the plastic strain exceeding 1.5%, noise no longer dominates the KAM map, and a positive-though not linear-correspondence between plastic strain and KAM was observed. The observed plastic zone at the tip of the fatigue crack by micro-Vickers hardness measurements was about an order of magnitude higher than the plastic zone observed on the KAM maps. In view of the calibration of KAM values on the tensile samples, it could be concluded that in the larger area of the plastic zone, the strain did not exceed the critical value of 1.5%.

show abstract

Section: Resultssupporting

confidence: 60%

Measuring Plasticity with Orientation Contrast Microscopy in Aluminium 6061-T4

Ghodrat

Riemslag

Kestens

2017

Metals

Self Cite

View full text Add to dashboard Cite

show abstract

“…In the presence of an external notch, the notch depth can be considered as the initial crack length. The mechanical graphite/matrix interaction of CGI is demonstrated by Ghodrat and Kestens [6], showing a weak mechanical bonding. This was confirmed by a recent work [7], studying the mechanical behavior of the graphite/matrix interface for cycling load conditions at room temperature, for three types of cast iron, including spheroidal cast iron.…”

Section: Of 21mentioning

confidence: 97%

“…Fatigue-crack initiation and growth in graphitic cast irons is largely affected by the presence of graphite particles. Because of the likely fast initiation of TMF cracks in cast irons as a result of delamination at the graphite-metal interface, Ghodrat et al [3][4][5] evaluated TMF lifetime using a crack-growth model, and they proved that, in tension, the graphite particles can be considered as internal notches or defects, from which TMF cracks start to grow during the very first TMF cycles. In the presence of an external notch, the notch depth can be considered as the initial crack length.…”

Section: Of 21mentioning

confidence: 99%

“…A TMF test set-up, capable of independently imposing temperature and strain profiles on the specimen, was employed for TMF testing identical to the set-up that was as used by Ghodrat et al For a detailed description of the TMF test set-up, the reader is referred to this previous work [3,4]. Geometry of thermo-mechanical fatigue (TMF) dog-bone specimen for (a) the case of unnotched (smooth) specimens, and (b) for circumferentially notched specimens with notch depth of 0.2 mm (as example) and a 0.04-mm notch-tip radius (dimensions are given in mm).…”

Section: Experimental Set-upmentioning

confidence: 99%

See 1 more Smart Citation

Thermo-Mechanical Fatigue Lifetime Assessment of Spheroidal Cast Iron at Different Thermal Constraint Levels

Ghodrat

Kalra

Kestens

et al. 2019

Metals

View full text Add to dashboard Cite

In previous work on the thermo-mechanical fatigue (TMF) of compacted graphite iron (CGI), lifetimes measured under total constraint were confirmed analytically by numerical integration of Paris’ crack-growth law. In current work, the results for CGI are further validated for spheroidal cast iron (SGI), while TMF tests at different constraint levels were additionally performed. The Paris crack-growth law is found to require a different CParis parameter value per distinct constraint level, indicating that Paris’ law does not capture all physical backgrounds of TMF crack growth, such as the effect of constraint level. An adapted version of Paris’ law is developed, designated as the local strain model. The new model considers cyclic plastic strains at the crack tip to control crack growth and is found to predict TMF lifetimes of SGI very well for all constraint levels with a single set of parameters. This includes not only full constraint but also over and partial constraint conditions, as encountered in diesel engine service conditions. The local strain model considers the crack tip to experience a distinct sharpening and blunting stage during each TMF cycle, with separate contributions to crack-tip plasticity, originating from cyclic bulk stresses in the sharpening stage and cyclic plastic bulk strains in the blunting stage.

show abstract

“…Qualquer variação nos aspectos microestruturais levará a uma variação de propriedades mecânicas, como resistência e tenacidade à fratura, mas também pode alterar propriedades físicas importantes como a condutividade térmica. [3] Alta capacidade de produção energética, baixo consumo de combustível, baixa emissão e redução do custo de manutenção estão entre as restrições que tornam o projeto de cabeçotes uma tarefa de alta complexidade. [4,5] Assim, análise detalhada e projeto bem executado são essenciais.…”

Section: Introductionunclassified

Previsão de vida em fadiga isotérmica e termomecânica em ferro fundido vermicular

Pina¹

View full text Add to dashboard Cite

With outstanding casting properties, good thermal conductivity and appropriate mechanical performance, compacted cast irons are widely used in the cylinder head of diesel engine. The engine usually works under transient operating conditions, such as starting, suddenly loading and unloading and shutting down. The processes usually leads to large temperature variation and serious fatigue damage. Therefore, the components are submitted during long periods to a large number of heating and cooling cycles, making thermo-mechanical fatigue (TMF) one of the most common failure mechanism. In the present work predictions of mechanical behavior of vermicular cast iron, 450 class, are made, using an elasto-plastic constitutive model of the commercial finite element software ABAQUS ®. The parameters of this model are identified from the cyclic increasing loading test, isothermal fatigue, and tensile tests. The parameters of the Wöhler curve in isothermal fatigue are characterized, and with these parameters, a characterization is proposed for the case of thermomechanical fatigue of the same curve. The results of the computational simulation present good results in the case of constant loading in isothermal fatigue while in thermomechanical fatigue the constitutive model cannot represent the stress relaxation effect of the material, thus lacking a more adequate model that reproduce the viscous effects. The prediction of life presents a reasonable result that depends on further statistical studies to prove its efficiency. The best input method to the plasticity model that fits the fatigue tests is using parameters and , because these parameters present better flexibility to describe the hardening curve compared to the Ramberg-Osgood equation. It was possible to obtain the fatigue life prediction under isothermal conditions using the Wöhler equation. While in the thermomechanical loads, it was possible to predict life using the modified Wöhler equations, which depend on the variation of the mechanical deformation and the use of parameters found from isothermal tests performed at the maximum temperature of the thermomechanical cycle.

show abstract

Microstructural Dependence of Tensile and Fatigue Properties of Compacted Graphite Iron in Diesel Engine Components

Cited by 12 publications

References 20 publications

Measuring Plasticity with Orientation Contrast Microscopy in Aluminium 6061-T4

Measuring Plasticity with Orientation Contrast Microscopy in Aluminium 6061-T4

Thermo-Mechanical Fatigue Lifetime Assessment of Spheroidal Cast Iron at Different Thermal Constraint Levels

Previsão de vida em fadiga isotérmica e termomecânica em ferro fundido vermicular

Contact Info

Product

Resources

About