Abstract
Traditionally, ultimate tensile strength (UTS) is used as the main property for the characterization of lamellar graphite iron (LGI) alloys under static loads. The main models found in the literature for predicting UTS of pearlitic lamellar graphite iron are based on either regression analysis on experimental data or on modified Griffith or Hall-Petch equation.In pearlitic lamellar graphite iron the primary austenite dendritic network, transformed to pearlite, reinforces the bulk material while the distance between those pearlite grains, defines the maximum continuous defect size in the bulk material. Recently the novel parameter of the Diameter of Interdendritic Space has been used to express the flow length in a modified Griffith equation for the prediction of the UTS in LGI. Nevertheless this model neglects the strengthening effect of the pearlite lamellar spacing within the perlite grains. A model based on modified Hall-Petch equation was developed in this work. The model considers the effect of both microstructure parameters and covers a broad spectrum of microstructure sizes typical for complex shape castings with various wall thicknesses.
Highlights
Environmental regulations, economy, high performance and fuel consumption are the main parameters that drive the development of heavy truck engines
Cylinder blocks and cylinder heads are the primary components of these engines and the majority of them are made of lamellar graphite iron (LGI) alloy
In a recent work [7] it has been found that the coarseness and the amount of the eutectic phase, as it is expressed by the novel develop parameter of the Hydraulic Diameter of the Inter-dendritic Phase (DIPHyd), can be used in the Griffith equation, instead of the graphite length, for the more accurate prediction of the ultimate tensile strength (UTS) in LGI alloys, see Eq 3
Summary
Environmental regulations, economy, high performance and fuel consumption are the main parameters that drive the development of heavy truck engines. The maximum strength of LGI is an essential factor that determines the performance and the fuel consumption of those engines. The dependence between different microstructural parameters and the ultimate tensile strength (UTS) of LGI has been thoughtfully investigated in the past [1-7 and 9] and shows that the UTS can be predicted either by using the Griffith relation [1, 3, 6 and 7] or a modified Hall-Petch equation [9]. Where c is the flaw length and kt is the stress intensity factor of the metallic matrix. Previous research works [1, 3, 6] considered that the graphite flakes, dispersed in the metal matrix, behave as Griffith cracks in a brittle type solid and they used the maximum graphite length as the flaw parameter (c) in the Eq 1. In a recent work [7] it has been found that the coarseness and the amount of the eutectic phase, as it is expressed by the novel develop parameter of the Hydraulic Diameter of the Inter-dendritic Phase (DIPHyd), can be used in the Griffith equation, instead of the graphite length, for the more accurate prediction of the UTS in LGI alloys, see Eq 3
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