Cracks are one of the main causes of structural failure and they develop in the structures due to various reasons such as fatigue, temperature variation, excessive load, cyclic load, environmental effects, impact loading etc. Thus, structural health monitoring is necessary to avoid risks, damages and failures. So, in order to avoid an extensive failure or accident, the early prognosis of crack in structures is necessary. Visual inspection and some non-destructive testing (NDT) methods for detection of crack are difficult as it requires time, expenses and are quite inefficient. So the alternative methods are motivated to be developed. In this study, vibration analysis, finite element analysis (FEA) and an alternative way which is artificial neural network (ANN) is used to predict, detect and identify the damages in structures. It is found that the theoretical, experimental, finite element analysis and artificial neural network have good accuracy in predicting the crack characteristics.

This paper studies the bending behavior of honeycomb structures by varying their weight through the introduction of glass microspheres. For this purpose, four different types of syntactic foam specimens were manufactured, varying the percentage by volume of glass microspheres between 20%, 30% and 40%. Afterwards, three-point bending tests were performed on each of these groups of specimens based on ASTM D7264/D7264M-15, thus obtaining data that allowed determining mechanical behavior and comparing it with material without glass microspheres. The optimum positive influence of microspheres over specific flexural strength was found at 30% of addition of glass bubbles. Additionally, results of the structures under impact gravity test confirm that 30% is a good proportion for these structures.

The purpose of the study is to improve the performance characteristics of powder pseudo-alloy materials using surface heat treatment. Such materials have unique properties, for example, self-lubrication under dry friction conditions, high thermal conductivity coefficient, and high electroerosion resistance. The disadvantage of powder pseudo-alloys is their relatively low strength. The paper considers the method of surface hardening by high-energy treatment - laser radiation. The paper describes the method of experimental research, describes the method of obtaining powder material, its chemical composition, shows the equipment used. The results of studies of the microstructure and microhardness of the surface layer of steel-copper powder pseudo-alloy after laser heat treatment (LHT) of a continuous-wave fiber laser with a maximum power of 1 kW are given, LHT modes are indicated, the influence of LHT parameters on the characteristics of the hardened layer is evaluated. It is revealed that the partial melting region in which melting occurs in the volumes of the fusible component (copper) in the initial structure and contacting segments of steel matrix is formed in the material in addition to the total melting zone. Then the quenching zone from the solid state follows, in which the maximal hardness up to 1000 HV is attained for best samples in the volume of martensite, which is formed in perlite colonies of the initial steel–copper material.

In this research, acheiving submicrocrystalline structure in commercially pure Al is investigated using severe plastic deformation (SPD) method named constrained groove pressing (CGP). In order to find a procedure that acts more effective in grain refinement and mechanical properties enhancement, three experimental procedures were defined and carried out. The procedures were defined by variables of die groove angle (45° and 50°) and using Cu covering sheets at top and down of the specimens instead of rigid die surface as a lubricant. Grain refinement during CGP process was investigated by William-hall analysis on X-Ray diffraction pattern and scanning electron microscopy (SEM). The results show that CGP process in all three procedures can severely refine the microstructure to an ultra-fine grained (UFG) structure with less than 1 micron grain size. Although grain refinement rate in die with 50° groove angle is higher but because of facility of applying extra CGP passes in 45° groove angle die with covering sheets (procedure 2), final grain size in procedure B is lesser. Mechanical properties of CGPed samples was investigated by tensile and hardness tests and the results show that at primary passes in all procedures strength-related properties increases significantly through a decrease in elongation, but at subsequent passes this behaviuor is diffentent for each procedure.

This paper presents an experimental programme designed to investigate the failure mode and ultimate capacity of pultruded glass fibre reinforced polymer (GFRP) cellular profiles subject to transverse loading. Presented in this study are the results of the characterisation of twenty six GFRP 152 × 76 × 6.4 mm I stub beams, 300 mm long. The beam specimens were categorised as plain for the control tests and those with circular or rectangular openings, centrally positioned. The specimens were subject to different loading configurations, noted as End Bearing with solid ground (EB), Interior Two Flange (ITF), Interior Bearing with solid base (IB) and End Two Flange (ETF) Results indicate a reduction in load-carrying capacity of the specimens with the opening when compared to the control specimens. The reduction was up to 20% for the specimens with circular openings and up to 25% for specimens with rectangular openings. The study revealed that loading configuration IB and ITF exhibit larger nonlinear behaviour and deformability than loading configurations EB and ETF. Various research has been conducted on its mechanical properties, connections, pultrusion techniques and web crippling behaviour of thin-walled GFRP section. Limited research can be found in the literature on the behaviour of pultruded GFRP beams with large perforation, subject to transverse static loadings.

In the present research work using a backward cup extrusion (BCE) die profile, different lubricating conditions on aluminum alloy AA6063 have been experimentally and numerically investigated to predict the extrusion load. It was obvious that due to an increase in applications of the extrusion process, many researchers have worked on the extrusion process using different methods to achieve their aims. This experiment was conducted with three different lubricants namely: Castor oil, Palm Oil and tropical coconut oil; as well as without lubricants. Different lubricating conditions were employed of varying strain rates ranges from 1.5×10-3s-1, 2.0×10-3s-1, 2.5×10-3s-1, and 3.0×10-3s-1; Numerical analysis and simulation for dry and lubricated conditions during extrusion load were also performed using DEFORM 3D software. The results show that prediction extrusion load increases with increasing strain rates. The maximum extrusion load was found to be higher for extrusion without lubricants. In all cases of strain rate, palm oil showed a lower extrusion load compared to the other lubricants. Castor oil indicated the highest extrusion load when the experiment is carried out using lubrication. There was a consistent agreement between the result gotten from the experiment and simulation result of the extrusion load-strike curve.

Modeling of a crack propagating through a finite element mesh under mixed mode conditions is of prime importance in fracture mechanics. This paper presents an application of the finite element method to the analysis of crack growth problems in linear elastic fracture mechanics and the correlation of results with experimental data. In the present study, the crack growth simulation has been numerically simulated by using the finite element source code program using Visual FORTRAN language. This code includes the mesh generator based on the advancing front method as well as all the pre and post process for the crack growth simulation under linear elastic fracture mechanics theory. The maximum circumferential stress criterion has been used for prediction of the crack growth in isotropic materials under mixed-mode loading. Furthermore, the equivalent domain integral method has been used for calculating the stress intensity factors values during crack growth. The crack grows when the stress intensity factor exceeds the fracture toughness of the material in the case of static loading. Verification of the predicted crack path is validated with relevant experimental data and numerical results obtained by other researchers with a good agreement.

The paper is concerned with the cost reduction of the elements’ production according to the metal injection molding technology of metal powder mixtures (MIM), using the additive technologies (AT) for the production of the green part. This method allows obtaining high fidelity of the materials both in mass production and in one of a kind, and small-series production because it is not necessary to the production of expensive casting press mold of metal powder mixture on the injection molding machine. In his paper, the author showed the advantages and disadvantages of two AT technologies which directly use materials for MIM technology: the technology of fused filament fabrication (Fused Filament Fabrication – FFF) and the technology of Binder Jet (BJ). The author proposes to reduce costs reduction of manufacturing filament for 3D printing according to the FFF technology of green part using already existing feedstock as the basis. The manufacturing technology of the filament is shown by the example of the feedstock steel 316LW BASF. The specific character of the technology is a limited amount of polyoxymethylene (POM) and low-density polyethylene (LDPE) is introduced into the standard composition of the feedstock to increase its plasticity. The author presented the results of tensile testing of items manufactured by standard technology and using AT technologies. Some reduction in the strength characteristics of the items with the using AT technologies is primarily due to the printing modes. The optimization of print modes allows obtaining the properties of the items, not inferior items by standard technology.

The study of structures in engineering solid mechanics is very often requires the modeling of complexes structures composed of two parts of thin and thick structure elements. As examples is associated with the case of stiffener under a dome and the cooling tower of the nuclear power which is supported on massive supports. In the numerical analysis, this imposes the connection between two different types of finite elements, two dimensional element for thin structures and three-dimensional elements for solid structures. Knowing that solid finite elements contain only translational degrees of freedom, whereas the finite elements of thin shells includes nodal variables of rotations, and then the number of degrees of freedom are not compatible in the junction zone between these two types of structures. This obviously causes great difficulty in solving the problem numerically. The objective of this work is to present the development of a shell finite element with no degree of freedom of rotation that can be used for the modeling of these two different types of structures and can then easily solve the shell-solid junction problem. Validation tests of the developed element are presented and the results obtained are very encouraging.

This paper deals with buckling lengths of the heavy column with various end conditions, where both top and bottom ends are either free or hinged or clamped. Based on equilibrium equations of the buckled column element, the differential equation governing the buckled mode shape is derived. For solving the buckling length, the differential equation is integrated by the direct integration method and the buckling length is calculated by the determinant search method. The buckling lengths of this study agree well with those of references. The buckling lengths with various end conditions, buckled mode shapes and buckling stresses are presented.