Evaluation of Shape of Graphite Particles in Cast Irons by a Shape Factor

Vaško, Alan

doi:10.1016/j.matpr.2016.03.006

Cited by 16 publications

(9 citation statements)

References 3 publications

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“…Although cast iron has various superior characteristics as mentioned above, the presence of graphite causes some undesirable affection to various mechanical properties due to the decrease of the effective sectional area of matrix and producing internal notch effect [4] [5] [6], therefore, cast iron is regarded as a material with a less anti-impact characteristic than that of steel. On the other hand, cast iron is also regarded as a material which is less sensitive against outer-notch than steel [7], but this characteristic has not been systematically investigated so far [8].…”

Section: Introductionmentioning

confidence: 99%

Impact Properties of Austempered Spheroidal Graphite Cast Irons

Nobuki¹,

Hatate²,

Shiota³

2017

MSA

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This study aims to clarify the influence of external notch on impact characteristics of high toughness ductile cast irons prepared by austempering heat treatment. We produced ductile cast irons samples with various matrix microstructure tested by Charpy impact within five kinds of external notches whose stress concentration factors (α), with values taken from 1.0 (Unnotched) to 4.8. In addition, to clarify the initiation process of impact characteristics, we observed the evolution of microstructure surface during bending tests with a slow loading speed for the un-notched and the notched impact samples. The results showed that the impact fracture energy decreases strongly in the range of α from 1 to 2.3 but decreases slightly for α larger than 3.Moreover, the impact value of samples with austempered microstructure is sensitive to the external notch shape. The impact transition temperature increases with increasing the stress concentration factor. The fracture energy is decreasing with the external notch from the impact test since the crack initiation energy is directly affected by this later. This work contributes to get a better understanding in the basic theories of external notch effect on impact characteristics of austempered spheroidal graphite cast irons (ADI).

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Section: Introductionmentioning

confidence: 99%

Impact Properties of Austempered Spheroidal Graphite Cast Irons

Nobuki¹,

Hatate²,

Shiota³

2017

MSA

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“…Especially, 65-45-12 sample composed of imperfect graphite spherulites with separated sectors. Advanced segmentation methods like active contour method [20] and shape factors that are sensitive to surface irregularities [21] can be utilized in order to quantify the effect of perimeter morphology. Figure 7a compares graphite, pearlite and ferrite percentages in all samples.…”

Section: Resultsmentioning

confidence: 99%

Assessing the Volume Fractions of the Phases, Nodularity and Nodule Count of Spheroidal Graphite Cast Iron Using Imagej Software

Toraman

Cosgun

Alkan

et al. 2019

Mugla Journal of Science and Technology

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In this study, a simple method for assessing the microstructure of ductile cast iron by using a freeware digital image processing software is described. The method is applied to three different ductile iron grades to assess their ferrite, pearlite and graphite volume fractions as well as graphite nodularity, nodule count, nodule size. All specimens were found to show good nodularity (~ 88 % by area) with different graphite average size and perimeter morphology. The amount of graphite was also found to be similar (11±2 % by area) in all specimens. On the other hand, ferrite percentages were found as 85. 8, 57.1, and 52.5 % respectively for ASTM A536 grades 60-40-18, 65-45-12, and 80-55-06. It was also found that among these three grades, the higher the pearlite content, the higher the hardness. The agreement with the standards confirms that quantitative metallography through image processing is a powerful tool in order to estimate the mechanical properties of cast irons. ÖzetBu çalışmada, küresel grafitli dökme demirlerin mikro yapılarını nicel olarak tanımlamak için ücretsiz dijital görüntü işleme yazılımının kullanıldığı basit bir yöntem açıklanmıştır. Yöntem üç farklı küresel grafitli dökme demir türüne uygulanarak, bunların içyapılarındaki ferrit, perlit ve grafit faz oranları, grafit nodülerliği, nodül sayısı, nodül büyüklüğünü değerlendirilmiştir. Örneklerin iyi derecede nodülerlik (alana göre ~ % 88) gösterdiği, farklı grafit ortalama büyüklüğüne ve çevre morfolojisine sahip oldukları bulunmuştur. Tüm örneklerde grafit miktarının da benzer olduğu (alana göre % 11 ± 2) bulunmuştur. Öte yandan, ASTM A536 sınıfları 60-40-18, 65-45-12 ve 80-55-06 için ferrit yüzdeleri sırasıyla % 85.8, 57.1 ve% 52.5 olarak hesaplanmıştır. Ayrıca, bu üç sınıf arasında, perlit içeriği arttıkça sertliğin arttığı gösterilmiştir. Sonuçların standartlar ile uyumlu olması, görüntü işleme yoluyla kantitatif metalografinin dökme demirlerin mekanik özelliklerini tahmin etmek için güçlü bir araç olduğunu göstermiştir.

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“…As it can be seen in Figure 1c, some regions of the contour of the model are completely straight due to the contour that is computed at the pixel level; besides, other sections have corners with angles of 45 • and 90 • , which can produce stress concentrators in a FEA. Furthermore, these sections do not represent the geometric characteristics of graphite nodules, since a DCI is characterized by the semi-sphericity of its graphite nodules, as they have a CSF value of between 0.9 and 1 [15]. These geometric characteristics are a part of the errors that are produced by the discretization at the pixel level at the time of obtaining the contours through image processing.…”

Section: Discretization Error Due To Image Processingmentioning

confidence: 99%

“…While the pixels belonging to the contours are identified, their coordinates are stored and grouped into a set depending on the graphite nodule (gray level) to which each pixel corresponds. In this same step, it is obtained the perimeter and the total area corresponding to each graphite nodule, which are required to calculate the CSF dig [15]. Then, the coordinates of the points and the CSF dig values of the graphite nodules contours are written in a text file, which is used to carry out the next stage.…”

Section: Extraction Of the Graphite Nodule Contoursmentioning

confidence: 99%

“…At this point, the works that are mentioned above have only used geometric models where nodules are considered as holes or ideal spheres. To represent how spherical graphite nodules are within a DCI, there is an index called Circular Shape Factor (CSF), it has been shown that graphite nodules within a DCI have a CSF value that varies between 0.9 and 1 [15], where a value of 1 would represent a completely spherical nodule or in two dimensions a perfect circle. Therefore, all of the works that have used idealized models have considered their nodules or holes with a CSF value of 1, such consideration is impossible in the real morphologies, and also, as already mentioned, has significant effects on the mechanical behavior.…”

Section: Introductionmentioning

confidence: 99%

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Genetic Algorithm-Based Optimization Methodology of Bézier Curves to Generate a DCI Microscale-Model

et al. 2017

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Abstract:The aim of this article is to develop a methodology that is capable of generating micro-scale models of Ductile Cast Irons, which have the particular characteristic to preserve the smoothness of the graphite nodules contours that are lost by discretization errors when the contours are extracted using image processing. The proposed methodology uses image processing to extract the graphite nodule contours and a genetic algorithm-based optimization strategy to select the optimal degree of the Bézier curve that best approximate each graphite nodule contour. To validate the proposed methodology, a Finite Element Analysis (FEA) was carried out using models that were obtained through three methods: (a) using a fixed Bézier degree for all of the graphite nodule contours, (b) the present methodology, and (c) using a commercial software. The results were compared using the relative error of the equivalent stresses computed by the FEA, where the proposed methodology results were used as a reference. The present paper does not have the aim to define which models are the correct and which are not. However, in this paper, it has been shown that the errors generated in the discretization process should not be ignored when developing geometric models since they can produce relative errors of up to 35.9% when an estimation of the mechanical behavior is carried out.

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Evaluation of Shape of Graphite Particles in Cast Irons by a Shape Factor

Cited by 16 publications

References 3 publications

Impact Properties of Austempered Spheroidal Graphite Cast Irons

Impact Properties of Austempered Spheroidal Graphite Cast Irons

Assessing the Volume Fractions of the Phases, Nodularity and Nodule Count of Spheroidal Graphite Cast Iron Using Imagej Software

Genetic Algorithm-Based Optimization Methodology of Bézier Curves to Generate a DCI Microscale-Model

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