Strength,Fracture and Complexity

In the current research, the production of composites, characterization, mechanical and wear behavior of 5 and 10 wt.% of nano composites have been investigated by reinforcing the nano B₄C ceramic particulates into Al2024 alloy. The composites were prepared by using two stage stir casting technique containing Al2024 alloy as a matrix phase and nano B₄C particulates as reinforcement. After the composite preparation, the prepared composite material was examined by using various techniques such as SEM, EDS and XRD for characterizing the chemical elements and microstructures of reinforced and unreinforced material. Later, the mechanical properties and wear behavior of as cast Al2024 alloy and Al2024 −5 and 10 wt.% nano B₄C composites were studied. Different mechanical properties such as hardness, percentage elongation, ultimate and yield strength were evaluated as per the ASTM standards. The dry sliding wear tests were conducted by using pin on disc equipment. The experiments were conducted for the sliding distance of 3000 m by varying the sliding speed and load. It was found that due to the addition of nano B₄C ceramic particles in the Al2024 alloy matrix, the hardness, ultimate tensile strength and yield strength of the prepared composites were increased and the percentage elongation was decreased. Furthermore, there was an improvement in the volumetric wear loss with respect to the speed, load, and sliding distance for all the prepared composite materials. However, with the addition of nano B₄C ceramic particulates in the base Al2024 matrix, the volumetric wear loss was decreased. The scanning electron microscope was used to study and analyze the fractography and different wear mechanisms for various test conditions of different compositions, tensile fractured surfaces and worn surfaces.

In this paper, the problem of two unequal collinear semi-permeable cracks in a piezo-electromagnetic media is proposed and addressed mathematically using a complex variable technique. The problem is mathematically modeled as a non-homogeneous Riemann–Hilbert problem in terms of unknown complex potential functions. The solutions to the fracture parameters are obtained in explicit forms by solving the Hilbert problem. An illustrative numerical case study is presented for poled BaTiO₃-CoFe₂O₄ ceramic cracked plate to show the effect of volume fractions, prescribed loads and inter-crack distance on fracture parameters.

This paper focusses on deriving a general solution to the strain energy release rate for a longitudinal circular cylindrical crack in non-linear elastic inhomogeneous beams with circular cross-section. The radius of the cross-section changes continuously in the length direction of the beam. The solution to the strain energy release rate is derived assuming continuous (smooth) material inhomogeneity in radial direction. The solution holds for arbitrary law for continuous change of the radius of the cross-section along the length of the beam. The solution is valid for a longitudinal circular cylindrical crack located arbitrary in radial direction. The solution is applied to analyze the longitudinal fracture behaviour of a cantilever inhomogeneous beam configuration assuming that the radius of the cross-section changes continuously along the beam length in cotangent law. The longitudinal fracture behaviour of the cantilever beam is also analysed by considering the complementary strain energy in order to verify the solution to the strain energy release rate. The influence of the continuously changing radius of the cross-section along the beam length on the fracture behaviour is investigated. It is shown that the general solution to the strain energy release rate can also be used when the beams exhibit continuous material inhomogeneity in both radial and length directions.

One of the main reasons for mechanical failures in railway structures is attributed to the propagation of defects and cracks. Exact prediction of crack growth in rails and wheels may lead to solutions to reduce damages, improve efficiency and facilitate maintenance. In this paper, the driving force of surface cracks on the rail under contact forces caused by wheel movement on the rail is investigated. The contact problem of the rails and wheels is simulated by a 2D model in finite element software and the elastic–plastic material model is considered for the rail. In order to calculate the crack driving force, the configurational force method is used to accurately predict the crack behavior and rail damage in plastic dominated zones. The parametric results of load, slip, size, crack orientation and the influence of interaction of cracks are studied for the surface cracks in rail and crack growth path and driving forces are estimated for inclined and vertical cracks. It is shown that the inclined cracks are more prone to propagation than vertical cracks under the same contact loading of rails and wheels.