•XIGA is utilized first time for the analysis of cracked FGMEE materials.•Generalized IFs are evaluated by combining XIGA with the interaction integral.•Asymptotic crack-tip fields of homogeneous MEE ...material are used in the interaction integral.•Effect of various parameters on the generalized IFs is investigated and discussed.
In this work, we present an extended isogeometric analysis (XIGA) for cracked functionally graded magneto-electro-elastic (FGMEE) material. The material properties inside the FGMEE domain vary exponentially. An electrically and magnetically impermeable crack in the FGMEE domain is modeled by adding appropriate enrichment functions into the isogeometric analysis (IGA) approximation. Heaviside function is utilized to model the displacement, electric, and magnetic potential along the crack face. In contrast, conventional four-field crack tip enrichment functions are used to mimic the crack tip singularity characteristics. The generalized intensity factors (IFs), i.e., the stress intensity factors (SIFs), electric displacement intensity factor (EDIF) and magnetic induction intensity factor (MIIF), are assessed using magneto-electro-mechanical interaction integral. A series of numerical studies over the cracked homogeneous and FGMEE material are presented. The accuracy of XIGA is examined by comparing the obtained results with the reference solutions. Various parameters such as volume fraction, crack length, loading combination parameter (both electrical and magnetic), material non-homogeneity parameter and crack orientation are taken to examine their effects on the generalized IFs.
In this study, high cycle fatigue behavior of friction stir welded aluminum 2024 alloy was investigated at different mean stresses. Complexity in the microstructure and tensile residual stress in the ...weld zone had a significant impact on the fatigue behavior of the welded joints. Apparent increase in mean stresses due to tensile residual stresses, decreased the fatigue lives of the welded joints. Increase in R-ratio from -1 to 0.1 resulted in significant depreciation of fatigue lives and endurance limit, while it was marginal when increased further to 0.5, thus suggesting the probable saturation of the detrimental mean stress effect. A shift in crack nucleation sites with a change in applied load amplitudes was observed. Hardening precipitates re-appeared across the weld section after heat-treatment of the welded joints thus hindering the movement of dislocations and stabilizes the grain boundary, thereby resulting in improvement of the fatigue lives. All these observations were attributed to the combined effect of mean stresses, residual stresses and the microstructural barriers, and are discussed.
•Combined effect of residual stress and mean stress on fatigue life was investigated.•Fatigue lives of welded joints reduced significantly as compared to tensile properties.•Crack nucleation sites in weld joints were controlled by applied stress amplitude.•PWHT resulted in uniformly distributed precipitates across the section.•PWHT improved tensile properties but the subsequent effect on fatigue lives was marginal.
•XIGA is firstly used for the analysis of cracked functionally graded piezoelectric materials.•The fracture parameters (SIFs and EDIF) are evaluated by combining XIGA with the electromechanical ...interaction integral.•Asymptotic crack-tip fields of homogeneous piezoelectric materials are used in the interaction integral.•Effect of various parameters on SIFs and EDIF are investigated and discussed.
In this paper, an extended isogeometric analysis (XIGA) is presented to model the crack in functionally graded piezoelectric materials (FGPMs). The material properties of functionally graded piezoelectric material (FGPM) vary in an exponential manner along the length of the domain. To model a crack in the FGPM, the isogeometric analysis (IGA) approximation is enriched with the Heaviside and crack tip enrichment functions. Conventional four-fold enrichment functions of isotropic materials are employed to capture the crack tip singularity. To determine the fracture parameters, the domain form of electromechanical interaction integral is used. The accuracy of the proposed XIGA approach is highlighted by validating the several cracked homogeneous and functionally graded piezoelectric material against the analytical/reference solution available in the literature. Several example problems of cracked FGPM domain are solved by XIGA. The influence of material non-homogeneity parameter, loading combination parameter and crack length are examined on the stress intensity factors (SIFs) and electrical displacement intensity factor (EDIF).
In this study, effect of post weld heat-treatment (PWHT) at two different aged temperatures was investigated on the microstructure and the material properties of the aluminum alloy 2024. The plates ...of AA2024 were welded using friction stir welding process, followed by PWHT at different aged conditions: 190°C for 10 hrs and 200°C for 10 hrs. Both tensile and cyclic properties were investigated. PWHT at 200°C–10 h resulted in significant changes in the microstructure and improvement in the mechanical properties of the welded joint. PWHT resulted in re-precipitation of the precipitates, specifically in the thermo-mechanically affected zone (TMAZ) & nugget zone (NZ) but no significant abnormal grain growth was observed in the nugget zone. A significant improvement in the ductility and the hardness of welded joint was observed for PWHT at 200°C–10 h. Long crack growth tests were conducted using sinusoidal loading of 10 Hz frequency and at a stress ratio of 0.1. The PWHT joint at 200-10 h resulted in higher threshold stress intensity factor range (ΔKth) as compared to as-welded joint and the PWHT joint at 190°C–10 h. The observations are explained based on microstructural changes in the FSW joint and are discussed in this work.
This study investigates the effect of different heat treatment procedures on tensile, hardness, and fatigue properties of additively manufactured AlSi10Mg. Tensile properties were evaluated for ...different material conditions, i.e., as-built (AB), direct aging (DA), solution treatment (ST), and T6 heat treatment. It was observed that the as-built samples had the highest yield and tensile strength with limited ductility while increasing the peak heat treatment temperature improves the ductility but at the cost of strength. The microhardness also followed a declining trend with an increase in peak heat treatment temperature. An empirical correlation, validated by experimental data, was established to predict the properties based on peak heat treatment temperatures. Based on the observed test results, four material conditions were selected for evaluating the high cycle fatigue (HCF) properties, i.e., AB, SR, DA, and T6. The as-built samples displayed superior fatigue resistance while that of T6 heat treated samples were most deteriorated. The heat treatment-induced microstructural transformation influences the tensile, hardness, and fatigue properties of the SLM AlSi10Mg, mainly due to the disintegration of continuous Al–Si cellular network and the subsequent formation of discrete Si-particles at high temperatures. The interaction between microstructurally-controlled mechanical properties, associated heat treatment process and the intrinsic damage mechanisms was investigated in detail and discussed later in this study.
•A crack opening model based on XFEM has been proposed to study the role of electrostatic tractions in cracked semipermeable piezoelectric material.•The electromechanical interaction integral ...approach is adopted to evaluate EDIF.•The EDIF obtained using the proposed model is found in excellent agreement with the analytical solution.•The effect of crack length, polarization angle, far-field loading, and electrostatic tractions is studied on EDIF.
In this work, a crack opening model is proposed to study the role of electrostatic tractions in a cracked semipermeable piezoelectric material. The extended finite element method (XFEM) is used in conjunction with six-fold electro-mechanical enrichment functions to capture the singularity and the discontinuous surface independent of the background mesh. The electric displacement intensity factor (EDIF) is evaluated using an electromechanical interaction integral approach in the presence of a dielectric medium inside the crack cavity. The accuracy of the proposed XFEM based approach is verified by comparing the numerical results with available analytical solutions. Further, a systematic numerical study is done to study the influence of electrostatic tractions on the EDIF using different crack configurations under far-field loading.
In the present work, effect of normalizing (950–1050 °C) and tempering (650–700 °C) has been investigated to study the microstructure and mechanical properties of modified 9Cr-1Mo steel (G91) at room ...temperature (RT) and 650 °C. To improve the high temperature mechanical properties, hot rolling has been done at optimized normalizing and tempering conditions. Microstructural observations show that an increase in tempering temperature leads to decrease in mechanical strength both at RT and 650 °C due to the growth of M23C6 particles, formation of sub-grain boundaries and recovery. G91 steel rolled at 550 °C and tempered at 650 °C is found to have best combination of strength and fracture toughness at RT, which may be attributed to large number of small size of precipitates and increase in dislocation density. However, specimen normalized at 1050 °C and tempered at 650 °C shows more than 70% improvement in tensile strength at 650 °C as compared to as-received condition, which shows that G91 steel is more amenable to precipitation hardening. A typical type of tensile fracture with radial cracks and axial splitting is noticed at RT and − 196 °C. The tendency and severity of such radial cracks and axial splitting are found to be affected by stress triaxiality and test temperature.
In this work, an extended isogeometric analysis (XIGA) is used for the analysis of through-thickness crack in a homogeneous and isotropic plate. In isogeometric analysis (IGA), non-uniform rational ...B-splines (NURBS) are used as a basis function. The plate kinematics is modelled by Reddy’s higher-order shear deformation theory (HSDT). The C1 continuity requirement of HSDT can be easily fulfilled by the NURBS basis functions. In order to obtain the plate fracture parameters (moment intensity factors), the expressions of crack-tip fields (auxiliary fields) are derived using separation of variables and Eigen-function approach. A new expression for moment intensity factors is developed using auxiliary fields solution (crack-tip fields) and interaction integral approach. Several cracked plate problems are solved by XIGA using HSDT. The results obtained by HSDT based XIGA (HSDT-XIGA) are compared with the FSDT based XIGA (FSDT-XIGA) and literature solutions.
•XIGA is implemented for the analysis of cracked plate using HSDT.•Near crack-tip fields solution is obtained for a homogeneous and isotropic plate.•Stress-resultants (Mrr, Mθθ, Mrθ, Prr, Pθθ and Prθ) exhibit inverse square root singularity near the crack tip.•A new interaction integral is derived for evaluation of moment intensity factors.•Results obtained using HSDT-XIGA are found in good agreement with available literature solution.
•A novel load-controlled iteration scheme is proposed within the XFEM framework for semipermeable piezoelectric material.•Interaction integral approach is used to evaluate the electric displacement ...intensity factor (EDIF).•Effect of polarization angle, crack length, loading parameter is investigated on the electric displacement intensity factor.•EDIF results show an excellent agreement with the results obtained from the iterative capacitor analogy (ICA).
In the present work, a novel load-controlled iteration scheme within the framework of extended finite element method (XFEM) is proposed to model the semipermeable crack in a piezoelectric material. To capture the stress and electric displacement singularity at the crack tip, the electromechanical 6-fold enrichment functions are used. The domain form of electromechanical interaction integral is employed to determine the generalized intensity factor. The accuracy of a proposed scheme based on XFEM is validated against the reference solutions derived from the iterative capacitor analogy (ICA) method. The effect of several crack configurations, polarization angle, far-field mechanical and electrical traction on electric displacement intensity factor (EDIF) are analyzed for cracked semipermeable piezoelectric material.
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