Numerical Modelling of Bird Strike on Aerospace Structures by means of Coupling FE-SPH

This article offers a parametric mechanics investigation in defining the correlation between the parameters of a wing-body during a bird strike collision. A commercial software of LS-Dyna is used to compute the numerical modelling manifested in this research. In this study, it is an attempt to form a definitive work based on the Smoothed Particle Hydrodynamics (SPH) formulation by recognising the most critical influencing parameters in the bird-strike computation and verify the simulation with the experiment data. For instance, an idealised bird is modelled as a cylindrical shape with hemispherical ends to maintain the homogeneity and symmetry using SPH approach. Moreover, an aluminium alloy rigid flat plate is modelled as a shell element plate in the finite element model (FEM). Here, internal energy vs time for different plate thickness graph are plotted to observe the difference of absorbed energy during the impact. Such conditions are considered in this research from the sight of bird strike impact under multiple states (structural thickness) and constraints (bird size). The obtained computational results are in adjacent agreement with the experimental results published in another literature

Limit Cycle Oscillation (LCO) flutter of advanced high modulus graphite/epoxy composite oscillating supersonic wing

This paper presents an optimisation process of reducing the structural weight of the supersonic wing by constraining the structural durability due to limit cycle oscillation. The application of composite material in aeroelasticity contributes to the modification of the expected aeroelastic failure on flutter speed. The composite material such that Graphite/epoxy gives high modulus compared to the metallic material such as aluminium. The objective of this tailoring process is to optimise the wing weight while the flutter performance might be improved. As the optimisation process performed, the flutter speed and the plate manufacturing thickness become the restriction in the wing weight reduction. The study shows good agreement to the objective where the reduction of weight for the High Modulus (HM) Graphite/Epoxy wing skin for the skin weight, clean wing and total wing with missile launcher external stores are 75.82%, 61.96% and 22.09% respectively compared to the baseline aluminium wing model. For the tailoring process, it is found that the flutter Mach number increases more than 81% using the as the Graphite/epoxy composite replaced the aluminium as the skin

Study of mechanical and thermal properties for epoxy grouts subjected to seawater conditioning at elevated temperature: tensile test and compressive test

Pipelines and risers are major transportation of oil and gas. These components are often exposed to extreme marine environmental conditions that can cause pipelines to fail due to corrosion. Hence, epoxy grouts are used as a coating material on the surface of pipelines and risers for supporting the pipe structure and corrosion prevention. In this case, the efficiency of epoxy grout is important in pipeline rehabilitation. Research on the adaptation of seawater, temperature, and epoxy grouts is carried out to determine the changes in mechanical and thermal properties of the material. The preparation of epoxy grouts was prepared with a mixture of epoxy resins, epoxy hardeners, and aggregates. After the sample compounds have been flattened, the mixture will be put into the mold. The seawater aging process was performed for seven days before conducting laboratory experiments. After the seawater aging process, there were physical changes on the surface of the epoxy grouts which are the epoxy grout become harder and there were voids that can act as stress concentration points that may cause micro-crack on the specimen. Next, tensile (ASTM 638) experiments were performed at different temperatures of 27°C, 40°C, 52°C, 72°C, 80°C and 100°C while the result of compression experiment is based on the literature critique of past journals. Based on the result, the young modulus and ultimate tensile strength of the epoxy grouts are decreased with increasing temperature. The increment of temperature causes the epoxy grouts to become weaker due to the changes in the polymer matrix structure of the epoxy grouts which lead to the failure at low load and shortens the life of the material. In addition, epoxy grouts are amorphous materials where the glass transition temperature determine the mechanical and physical properties of epoxy grouts. Therefore, the results of the study found that the epoxy grouts changed its mechanical properties from brittle to ductile when the temperature is at 72°C. From the comparison between samples immersed and not immersed in seawater, there is a decrease in Young’s modulus, ultimate tensile stress and strain due to the effect of seawater reaction. In conclusion, the increment in temperature and seawater adaptation factors affect the strength and durability of epoxy grouts

Predictive Modelling of Creep Crack Initiation and Growth using Extended Finite Element Method (XFEM)

In this study, a numerical strategy for predictive modelling of creep in tension tests for the rectangular plate with a single crack and CT-specimen based on the extended finite element method (XFEM) will be described in detail. A model of creep fracture initiation and creep crack growth (CCG) is developed, while the XFEM is employed to spots located inside the finite element for the purpose of predicting crack potential and propagation. In order to characterize the creep fracture initiation, identification of C(t)-integral formula is conducted. In addition, XFEM and analytical solutions are also analyzed to look at the connection of C(t)-integral with time for a rectangular plate with a single crack under plane stress conditions. An illustration showing the se-quence of stress distribution and displacement contour plots are also being presented. The stresses and displacements spread throughout the crack path have also been determined using CT-specimens. In addition, the creep cracks growth length with normalized time and the creep crack growth rate with the C(t)-integral are predicted to be related, indicating that the numerical results are in good accord with the experimental results

Computational modelling of bird strike impact on an aluminium alloy plate via coupling of FE-SPH

This paper proposes a parametric mechanics study in determining the relationship between the parameters of the aerospace structure during a bird strike impact. A commercial software of LS-Dyna is used to compute the numerical modelling demonstrated in this research. Technically, an idealised bird is modelled as a cylindrical shape with hemispherical ends to maintain the homogeneity and symmetry using Smoothed Particle Hydrodynamics (SPH) approach. At the same time, an aluminium alloy plate is developed as a shell element plate in the finite element model. Such conditions are considered in this research from the view of bird strike impact under various conditions (structural thickness) and constraints (bird size). The obtained computational results are in close agreement with the experimental results published in another literature

Impak dari program mahasiswa ke masyarakat (M2M) kepada pelajar dan komuniti dalam penyebaran ilmu risiko ergonomik

Graduan yang berkualiti bukan sahaja berjaya dalam akademik, tetapi juga sahsiahnya, Sesuatu program universiti pada masa kini tidak hanya terarah kepada pencapaian akademik semata-mata. Hasil program dalam sesuatu program dalam masa sekarang juga menimbangkan atribut berkaitan komunikasi sama ada dengan ahli atau masyarakat dan juga kerja berkumpulan. Artikel ini mengkaji peranan mahasiswa dalam menyebarkan ilmu yang dipelajari di dalam kelas kepada masyarakat atau komuniti di luar. Masyarakat ketika ini bergelumang dengan pelbagai isu masalah kesihatan dan juga keselamatan bukan sahaja di luar rumah malahan juga di rumah sendiri. Oleh itu, pendekatan memperkasakan masyarakat melibatkan program kesedaran dalam penjagaan kesihatan dan keselamatan perlu dilakukan. Kajian ini melibatkan program perkongsian ilmu dari sebahagian mahasiswa Tahun Akhir Program Kejuruteraan Mekanikal kepada segelintir masyarakat dalam pelbagai peringkat berkenaan isu ergonomik. Kaedah temubual antara kumpulan pelajar dan komuniti merupakan kaedah utama dalam program ini. Hasil program ini menunjukkan, tahap kesedaran masyarakat bertambah baik melalui perkongsian ilmu risiko ergonomik. Selain itu, pemahaman pelajar juga bertambah baik melalui program ini. Kajian ini menunjukkan program yang berkaitan amalan merentasi pelbagai komuniti dapat membantu mahasiswa dalam memastikan pemahaman yang lebih baik dapat dicapai dalam sesuatu perkara

A review on modes of failure of rail tracks in railway transportation

The train is one of the main transportations to move or transfer loads, including people and goods from one place to another on wheeled vehicles running on a railways track. Since, the railways were exposed to extreme conditions, the purpose of the design structure for the railways is to overcome the circumstances. Furthermore, the same train running track was used year after year for nearly a decade. Mechanical failure will occur to the rail structure as the material will defect when subjected to constant and high impact load. The challenging part is how to detect this failure to avoid any catastrophic incident to the train. When a material fault can be recognised earlier, the maintenance work required, and the material's life prediction can be determined, harmful scenarios involving the train can be avoided in the future. In this paper, to better understand this matter, the mechanical failure on the railway running track will be reviewed. The mode of failure involved in the rail track structure includes fatigue failure, buckling effect, shear failure, and corrosion. The significance of this mechanical failure will be emphasised for the sake of this mode of transportation's safet

A review on modes of failure of rail track structure in railway transportation

The train is one of the main transportations to move or transfer loads, including people and goods from one place to another on wheeled vehicles running on a railways track. Since, the railways were exposed to extreme conditions, the purpose of the design structure for the railways is to overcome the circumstances. Furthermore, the same train running track was used year after year for nearly a decade. Mechanical failure will occur to the rail structure as the material will defect when subjected to constant and high impact load. The challenging part is how to detect this failure to avoid any catastrophic incident to the train. When a material fault can be recognised earlier, the maintenance work required, and the material's life prediction can be determined, harmful scenarios involving the train can be avoided in the future. In this paper, to better understand this matter, the mechanical failure on the railway running track will be reviewed. The mode of failure involved in the rail track structure includes fatigue failure, buckling effect, shear failure, and corrosion. The significance of this mechanical failure will be emphasised for the sake of this mode of transportation's safet

STRUCTURAL INTEGRITY OF DUCTILE MECHANICAL COMPONENTS SUBJECTED TO CREEP: DAMAGE AND FRACTURE MODELLING

This research is aimed at the computational assessment of the structural integrity in ductile mechanical components, subjected to creep based on damage and fracture analysis. In the present work, the implementation of constitutive damage model concerning the void damage and crack evolution in the material is performed. It leads to the development of a new model called Rousselier-UMAT-XFEM (RuX) model. To the author’s knowledge, this is the first attempt where the XFEM is formulated with the Rousselier model in ductile fracture analysis for micromechanical damage problems. The potential of the RuX model is tested in two-dimensional and three-dimensional problems, and the results are in good comparisons with the literature. The study is continued to investigate the creep failure behaviour of ductile material by simulating the predictive modelling of creep crack initiation and growth, and the results are being verified accordingly. Next, the development of the constitutive creep damage model is carried out where a new model called as Modified-Robinson-Rousselier (MRR) model is proposed. The MRR model is tested in tensile creep tests and showed good estimation results with the experimental data in terms of the void damage growth and creep strain curve. Furthermore, the extended analysis of MRR model is identified in which the XFEM technique is implemented to introduce the crack development in the analysis. As a result, a new model called as MRRX model is suggested to predict the creep damage behaviour due to void-crack growth mechanism. The results are compared with the literature and showed a worth comparison regarding the evolutions of crack growth and void formation. Therefore, this work is successfully implemented to enhance the predictive modelling tools for the application of fracture damage mechanics and computational approach in the structural engineering problems

Development of constitutive creep damage-based modified Robinson-Rousselier (MRR) model with XFEM for void-crack relation in ductile materials

In this work, we present the predictive modeling for ductile creep damage by implementing the modified Robinson–Rousselier constitutive relations and extended finite element method (XFEM) to treat creep rupture in the void-crack growth problem. We develop an attractive new model, called the modified Robinson–Rousselier (MRR) model, to predict the creep damage behavior in terms of micromechanical damage due to void growth in the ductile materials. The MRR model interface executes an implicit integration scheme in the UMAT subroutine of the Abaqus/Standard module. The radial return method is performed to integrate the viscoplastic constitutive equation in finite element formulation. The numerical models in 2D and 3D elements are implemented to identify the developed subroutines’ correctness, and the results are compared with the exact solution for verification. Furthermore, the tensile creep tests on the smooth bars specimen are modeled and tested at a constant temperature of 625 ◦C with different stress levels. The results show that the maximum values of stress, creep strain, and void damage are detected near the tensile specimen center, where the necking process is formed. Furthermore, the results are compared with the literature to verify and evaluate the developed model and show a reasonable agreement between both results. Then this analysis is extended by introducing crack development in the specimen based on the XFEM technique. As a result, a new model called the modified Robinson–Rousselier XFEM (MRRX) model is proposed, and the results are compared with the results found in the literature, which showed the evolutions of void growth in the crack path. Therefore the MRRX model solution is proven to have the potential to predict the creep damage behavior in terms of the void-crack growth in the ductile material structures