This paper deals with free vibrations of the axially functionally graded (AFG) horseshoe arch. The modulus of elasticity and the mass density of AFG material of arch are chosen as a univariate quadratic function. The differential equations with the boundary conditions that govern the free vibration of such arch are derived and numerically solved to calculate natural frequencies and mode shapes. Natural frequencies of this study agree well with those of the finite element ADINA. Parametric studies of the geometrical and mechanical properties of the arch on frequencies and mode shapes are performed and extensively discussed.

Failure of composite materials due to poor anticipations of damages occur very frequently. Damages in composite materials may exist as visible or non-visible with different configurations and identities. Thus, investigation of damages existence in composite materials has to have prior attention to avoid the failure of structures. The current work investigates the damping response offered by a damaged fiber-reinforced polymer plate. The plate is put under three different conditions regarding the damage existence. The focus is to measure the loss factor in all cases and determine whether there is a difference among them to prove damage presence in the composite part. The loss factor is experimentally measured by measuring the reverberation time RT60. The resulting data of loss factors show a well-distinguished difference that might lead to predicted damages and to do a more expanded analysis of this issue.

The influence of loading type on tensile and tearing fracture resistance of ballast rock was assessed using edge-notched diametrically compressed disc (ENDC) and edge-notched disc bend (ENDB) test geometries. The geometry of these two specimens was similar; however, their loading type (i.e., three-point bend and diametral compressive) was different affecting the geometry factors. The obtained pure tensile fracture toughness (KIc) using the ENDB test was higher than the ENDC test. In contrast to tensile fracture toughness, the pure tearing fracture toughness (KIIIc) in the ENDC test was higher than the ENDB fracture test. The obtained experimental data were explained in terms of crack propagation path, since two distinct trajectories were observed for both configurations under tearing deformation.

With the increase of construction activities in Ghana, there is an increasing demand in building materials leading to the shortage of the conventional materials. The informal sector is gradually seeing the introduction of quarry dust as a substitute of sand in block production. This paper focuses on a comparative analysis of the quality of sandcrete blocks and quarry dust cement blocks. Block samples were gathered from various suppliers around the Prampram and Dawhenya areas and through various laboratory tests were tested for their dimension tolerance, water absorption and compressive strengths. Aggregate samples were also taken from suppliers for sieve analyses. The study revealed that the quarry dust cement blocks contained relatively higher percentages of coarse grade particles compared to the sandcrete blocks. The total average water absorption of sandcrete blocks was found to be 3.90% while quarry dust showed an improved value of 3.28%. Sandcrete blocks were averagely found to be of a higher compressive strength of 4.31N/mm2, with quarry dust at 3.0N/mm2. The study suggested the likelihood of a lesser use of cement in the production of quarry dust cement blocks due to the similarities in colour between the quarry dust and cement, hence, negatively affecting its compressive strength.

Multi-purpose forest fire fighting vehicles should carry a set of firefighting equipment such as high-pressure water pumps, tree cutters to create a fire isolation corridor, vacuum, and blowing machine high-speed wind sandblasting devices etc. The bumpy road and velocity of moving vehicles can affect the vibration response of these vehicles. Hence, in this research the vibration analysis of a Multi-purpose forest fire fighting vehicle mounted on a URAL4320 active three-wheel drive vehicle is simulated and analyzed. The effect of road bumping and speed of vehicle on the vibration parameters are studied via building mathematical models with 19 degree of freedom for simulating the suspension system of the investigated vehicle.

The basic aim of this study was to find a relationship between heat input and mechanical properties of high strength low alloy steel (HSLA) welded joints and also elaborate its effect on microstructure. The combined effect of welding current, voltage and speed i.e. Heat Input on mechanical properties of High Strength Low Alloy Steel (ASTM A242 type-II) weldments have been studied in the present work. HSLA steel work pieces were welded by Gas metal arc welding (GMAW) process under varying welding current, arc voltage, and welding speed. Total nine samples were prepared at different heat input level i.e. 1.872 kJ/mm, 1.9333 kJ/mm, 2.0114 kJ/mm, 2.1 kJ/mm, 2.1956 kJ/mm, 2.296 kJ/mm, 2.4 kJ/mm, 2.5067 kJ/mm and 2.6154 kJ/mm It was observed that as heat input increases the ultimate tensile strength and microhardness of weldment decreased while impact strength increased and it was also observed that on increasing the heat input grain size of microstructure tends to coarsening it is only due to decreasing in cooling rate.

In the search for the solution to energy storage problems, this study investigates the interfacial energy interaction and temperature stability of the composites made of polypyrrole-graphene-borophene (PPy-Gr-Bon) by using molecular dynamics simulations. From the calculated thermodynamics and interfacial energies of the system, comparisons between the ternary and the binary-binary systems were made. The materials in the entity show a good degree of temperature stability to a dynamic process at 300, 350, 400, and 450 K. Moreso, at 300 K, the interaction energy of PPy-Gr, PPy-Bon, and PPy-Gr-Bon are: -5.621e3 kcal/mol, -26.094e3 kcal/mol, and -28.206e3 kcal/mol respectively. The temperature stability of the systems is in the order of: PPy-Gr-Bon > PPy-Bon > PPy-Gr. The effect of temperature on the interaction energy of the systems was also investigated. The ternary system showed higher stability as the temperature increased. In addition, the radial distribution function computed for the three systems revealed that there is a strong, but non-chemical bonding interaction between PPy-Gr-Bon, Bon-PPy, and Gr-PPy. By considering the excellent mechanical properties of PPy-Gr-Bon and the already established high electrical conductivity and chemical stability of Gr, Bon and PPy, their composite is therefore suggested to be considered for the manufacturing of electrochemical electrodes.

The forming steps by permanent deformation controlled by the tools generate a distribution of stresses inside the material which directly depends on the work hardening properties of the latter. The change in boundary conditions following the removal of the tools imposes the material to redistribute the stresses in the sections in a manner compatible with the new boundary conditions. This new distribution necessarily operates by local elastic deformations that result globally in a general change of shape called springback. This geometrical deviation can be minimized by the meticulous focus of the tools, but it cannot generally be completely annihilated due to the influence of several parameters. For this reason, the study of the influence of the different technological factors and physico-metallurgical parameters on the springback for the different metals is very important to design and properly realize forming tools. The main objective of this work is to find solutions to problems encountered in sheet metal forming such as the problem of springback. Our work has two essential purposes: the first is summarized in an experimental study based on theoretical analyses. To this end, much effort is made to add a new design of parts for a U-type stretch-bending device and adapt it to a tensile testing machine. This design has the advantage of modifying and assembling all parameters affecting springback at the same time and also of carrying out several forming processes on the same device. The second goal is the experimental and numerical prediction of springback, and the study of the effect of various stretch-bending process parameters such as punch velocity, the orientation of the sheet (anisotropy), hold time and punch-die clearance on springback behavior under heat treatment of aluminum alloy sheets with three different rolling directions (0°,45°,90°). A finite element (FE) model of stretch-bending has been established by utilizing ABAQUS/CAE software. From this analysis, it can be concluded that the springback is affected by the anisotropy of the sheet and the heat treatment in the stretch-bending process. The obtained experimental results were compared with the numerical simulations found in good agreement.

This work is devoted to development of optimum recipes of high-strength concretes based on filled binders with fine-milled anthropogenic mineral filler intended for earthquake resistant high-rise monolithic construction. The optimum recipes of concretes in this work have been developed on the basis of computations and experimental designing of cast concrete mixes with chemical additives and anthropogenic mineral fillers, as well as destructive inspection methods as the most precise for analysis of physicomechanical and deformation properties of concrete. The following raw materials have been used for production of high-strength concretes: natural quartz sands with the fineness modulus F.M. = 1.7-1.8; crushed limestone with the particles sizes of 5-20 mm; water reducing chemical additives and hardening retarder to control specifications of concrete mixes; plain Portland cement, grade PTs 500 D0; anthropogenic mineral additives (fillers) in the form of crushed concrete and ceramic bricks. Optimum recipes of monolithic concretes have been designed using anthropogenic raw materials including normal concrete grades with compressive strength of M30-M40 and high-strength concrete grades of M50-M80, characterized by high homogeneity of cement stone with significantly finer pores and lower shrinkage. Herewith, it has been established that fine-milled anthropogenic mineral filler in the form of crushed concrete and ceramic bricks at the ratio of 70:30, respectively, efficiently influences specifications of concrete mixes on their basis significantly increasing resistance of the mix against sedimentation and water gain. It has been established that the developed high-strength concretes based on filled binders with fine-milled anthropogenic mineral filler are characterized by high freeze–thaw resistance (from F400 to F600) and water tightness (W14 and higher), which is a solid base providing high lifecycle of such concretes.