In engineering applications, analysis of crack growth life is useful in situations where an unexpected crack has been found in a component of a machine, vehicle, or structure. The objective of this research is to investigate the correlation curve of magnetic flux leakage, Hp(y) signals by evaluating their critical value point with respect to step size. Moreover, the relation of fatigue crack growth rate, da/dN toward the stress intensity range, ΔK and Hp(y) in metal components is also discussed in this paper. The tension-tension fatigue test was conducted with the metal magnetic memory scanning device and crack opening displacement (COD) gauges in 10 Hz (testing frequency) by applying a load for 3.0-5.0 kN respectively. As a result, the correlation curve of Hp(y) was built with the R-Squared values in the range of 0.99 and one mathematical model has been developed for estimation analysis. The sigmoidal shape curve was plotted on the graph of da/dN versus ΔK and also with Hp(y). Thus, for validation, the linear relation is represented between ΔK and Hp(y) that present a good approach for magnetic parameter to be developed in the fatigue crack growth analysis. Therefore, the magnetic method has greater capability to analyze the fatigue crack propagation life in a real application.

In engineering applications, analysis of crack growth life is useful in situations where an unexpected crack has been found in a component of a machine, vehicle, or structure. The objectives of this research are to investigate the correlation curve of magnetic flux leakage, Hp(y) signals by evaluating their critical value point with respect to step size. Moreover, the relation of the fatigue crack growth rate, da/dN with the stress intensity range, ΔK and Hp(y) in metal components is also discussed in this paper. The tensiontension fatigue test was conducted with the metal magnetic memory (MMM) scanning device and crack opening displacement (COD) gauges at 10 Hz (testing frequency) by applying a load of 3.0-5.0 kN. As a result, the correlation curve of Hp(y) was built with the R-squared values in the range of 0.99 and a mathematical model was developed for estimation analysis. The sigmoidal shape curve was plotted on the graph of da/dN versus ΔK and also with Hp(y). Thus, for validation, the linear relation is represented between ΔK and Hp(y) and presents a good approach for magnetic parameters to be developed for fatigue crack growth analysis. Therefore, the magnetic method has a greater capability to analyse the fatigue crack propagation life in a real application.

In this paper, metal magnetic memory (MMM) method is used to detect the micro-crack position on the ferromagnetic material due to the fatigue process by determining to the stress concentration zones in the metal surfaces. The MMM method was carried out on mild steel using Instron 8874 universal tensile testing machine with different values of the ultimate tensile strength (UTS) varies from 75%, 80% and 85% until the specimens fails. An equipment of stress concentration indicator was used to measure the magnetic flux leakage, Hp patterns in the specimens. The results indicated that the position of a crack on the specimen that failed due to fatigue test was correlated with the scanning interval from the magnetic flux leakage signals. Therefore, the MMM method provides the potential possibility to detect the position of fatigue damage or defect in the metal components.

This work presents a modelling strategy for ductile fracture materials by implementing the Rousselier damage model with the extended finite element method (XFEM). The implicit integration scheme and consistent tangent modulus (CTM) based on a radial return mapping algorithm for this constitutive model are developed by the user-defined material subroutine UMAT in ABAQUS/ Standard. To enhance the modelling of the crack development in the materials, the XFEM is used that allows modelling of arbitrary discontinuities, where the mesh does not have to be aligned with the boundaries of material interfaces. This modelling strategy, so-called Rousselier-UMAT-XFEM (RuX) model is proposed to connect both concepts, which gives an advantage in predicting the material behaviour of ductile material in terms of voids and crack relation. This is the first contribution where XFEM is used in ductile fracture analysis for micromechanical damage problems. The results indicate that the RuX model is a promising technique for predicting the void volume fraction damage and crack extension in ductile material, which shows a good agreement in terms of stress-strain and force-displacement relationships.

This paper presents a numerical strategy for the characterisation of the creep behaviour model of the copper alloy, which is widely used in aircraft applications under creep conditions. The high possibility of the material failing, while operating under load at an elevated temperature, has led to the important study of the creep lifetime prediction analysis, by presenting the Norton's rule based on the Power-law model to describe the secondary creep behaviour of the material. In order to demonstrate the nature of the creep formulation, the SOL 400 modules from MSC Nastran 2014 are implemented in order to conduct the uniaxial tensile test in 2000 N of applied load and 473 K of temperature condition. As a result, the exponential curve is formed from the relationship of the creep strain rate and stress, with a 5.1% error based on the value of the stress exponent, n, between the simulation and experimental results and this was still be acceptable because it was relatively small due to the formulation in the simulation. Consequently, a relation of the creep rate curve can then be plotted with respect to the load steps and the variation patterns due to the stress factor also being discussed. Therefore, the results show a good agreement, which indicates the capability of this model to give an accurate and precise estimation of the secondary creep behaviour of the materials.