Thermal debonding of inclusions in compacted graphite iron: Effect of matrix phases

Palkanoglou, Evangelia Nektaria; Baxevanakis, Konstantinos P.; Silberschmidt, Vadim V.

doi:10.1016/j.engfailanal.2022.106476

Cited by 8 publications

(6 citation statements)

References 38 publications

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“…Accordingly, the thermal analysis in cast iron was mainly focused on spherical graphite iron [21]. There is insufficient research into the mechanism of thermal damage in CGI under pure thermal loading at the microscale [46]. Under high-temperature conditions, CGI is vulnerable due to the mismatch of thermal expansion between graphite inclusions and its metallic matrix.…”

Section: Introductionmentioning

confidence: 99%

Effect of Graphite Morphology on the Thermomechanical Performance of Compacted Graphite Iron

Cao

Baxevanakis

Silberschmidt

2023

Metals

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Compacted graphite iron (CGI) has gained significant attention in automotive industry applications thanks to its superior thermomechanical properties and competitive price. Its main fracture mechanism at the microscale—interfacial damage and debonding between graphite inclusions and a metallic matrix—can happen under high-temperature service conditions as a result of a mismatch in the coefficients of thermal expansion between the two phases of CGI. Macroscopic fracture in cast iron components can be initiated by interfacial damage at the microscale under thermomechanical load. This phenomenon was investigated in various composites but still lacks information for CGI, with its complex morphology of graphite inclusions. This research focuses on the effect of this morphology on the thermomechanical performance of CGI under high temperatures. A set of three-dimensional finite-element models was created, with a unit cell containing a single graphite inclusion embedded in a cubic domain of the metallic matrix. Elastoplastic behaviour was assumed for both phases in numerical simulations. The effect of graphite morphology on the thermomechanical performance of CGI was investigated for pure thermal loading, focusing on a high-temperature response of its constituents. The results can provide a deeper understanding of the correlation between graphite morphology and CGI fracture mechanisms under high temperatures.

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Section: Introductionmentioning

confidence: 99%

Effect of Graphite Morphology on the Thermomechanical Performance of Compacted Graphite Iron

Cao

Baxevanakis

Silberschmidt

2023

Metals

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“…Tables 2 and 3 list the constitutive parameters for these two domains, respectively. Mechanical tests were used to derive the constitutive values for the metallic matrix, as described in [11]. The behaviour of a material can be significantly influenced by microstructural features.…”

Section: Constitutive Relationsmentioning

confidence: 99%

“…In the work of Muhond et al [8], some trace elements (S, B, Se) were observed to stabilise the flake or nodular growth morphology of graphite, while F, O, N, P failed to do so. In general, there are two main approaches used for modelling the mechanical behaviour of CGI: representative volume element (RVE) and unit cell [9][10][11][12]. To the best of the author's knowledge, these two approaches are widely used in the field of computational mechanics to simulate the fracture behaviours of heterogeneous materials.…”

Section: Introductionmentioning

confidence: 99%

“…Besides, XFEM is usually used to predict the stress-strain behaviour without a predefined crack [9,10]. With its need for additional degrees of freedom, XFEM may require more computational resources, while In general, there are two main approaches used for modelling the mechanical behaviour of CGI: representative volume element (RVE) and unit cell [9][10][11][12]. To the best of the author's knowledge, these two approaches are widely used in the field of computational mechanics to simulate the fracture behaviours of heterogeneous materials.…”

Section: Introductionmentioning

confidence: 99%

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Microstructure-Based CZE Model for Crack Initiation and Growth in CGI: Effects of Graphite-Particle Morphology and Spacing

Luo,

Baxevanakis,

Silberschmidt

2024

Solids

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Compacted graphite iron (CGI) is an engineering material with the potential to fill the application gap between flake- and spheroidal-graphite irons thanks to its unique microstructure and competitive price. Despite its wide use and considerable past research, its complex microstructure often leads researchers to focus on models based on representative volume elements with multiple particles, frequently overlooking the impact of individual particle shapes and interactions between the neighbouring particles on crack initiation and propagation. This study focuses on the effects of graphite morphology and spacing between inclusions on the mechanical and fracture behaviours of CGI at the microscale. In this work, 2D cohesive-zone-element-based models with different graphite morphologies and spacings were developed to investigate the mechanical behaviour as well as crack initiation and propagation. ImageJ and scanning electron microscopy were used to characterise and analyse the microstructure of CGI. In simulations, both graphite particles and metallic matrix were assumed isotropic and ductile. Cohesive zone elements (CZEs) were employed in the whole domain studied. It was found that graphite morphology had a negligible effect on interface debonding but nodular inclusions can notably enhance the stiffness of the material and effectively impede the propagation of cracks within the matrix. Besides, a small distance between graphite particles accelerates the crack growth. These results can be used to design and manufacture better metal-matrix composites.

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“…This contradictory relationship between the thermal and mechanical properties of CGI is also one of the reasons limiting the application of CGI brake discs. Ralkanoglou et al [18] studied the primary fracture mechanism of CGI in thermal cycling conditions using a numerical approach. They developed a 2D model to investigate the effects of ellipse graphite decohesion and matrix plasticization on microcracking.…”

Section: Introductionmentioning

confidence: 99%

Thermal Cracking and Friction Performance of Two Kinds of Compacted Graphite Iron Brake Discs under Intensive Braking Conditions

Xu,

Wang,

2024

Metals

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The limited thermal conductivity of compacted graphite iron constrains its application in brake discs. The matrix plays a crucial role in balancing the thermal conductivity and mechanical performance of compacted graphite iron. Therefore, two kinds of compacted graphite brake discs with different ferrite proportions were utilized to investigate their thermal cracking and friction performance under intensive braking conditions based on inertia friction tests. The variations in peak temperature, pressure load and friction coefficient stability were also analyzed. The brake disc with a higher ferrite proportion exhibited a lower peak temperature, attributed to increased thermal conductivity. Moreover, the elevated content of soft ferrite resulted in a greater furrow height on the worn surface, contributing to an increase in friction force and stability. As a result, both the input pressure and mechanical stress decreased. It was observed that the compacted graphite iron brake disc with a higher ferrite proportion exhibited fewer thermal cracks without compromising wear resistance. Furthermore, the results suggest that lowering the disc temperature to 210 °C–250 °C can mitigate fatigue wear and matrix oxidation, hindering the propagation of thermal cracks.

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Thermal debonding of inclusions in compacted graphite iron: Effect of matrix phases

Cited by 8 publications

References 38 publications

Effect of Graphite Morphology on the Thermomechanical Performance of Compacted Graphite Iron

Effect of Graphite Morphology on the Thermomechanical Performance of Compacted Graphite Iron

Microstructure-Based CZE Model for Crack Initiation and Growth in CGI: Effects of Graphite-Particle Morphology and Spacing

Thermal Cracking and Friction Performance of Two Kinds of Compacted Graphite Iron Brake Discs under Intensive Braking Conditions

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