This work presents a stress-strain state analytical estimation of restored tooth hard tissues with consideration of their contact interactions with a monolithic filling or a dental onlay. The tooth with a defect is simulated as a continuous isotropic cylindrical body with a non-through hole, and the filling or onlay is simulated as an elastic deformable cylinder. The contact between the tooth and the fillings (onlay) is simulated as the ideal contact. The final strength estimation of the restored tooth is carried out according to the energy criterion. The authors suggest a linear index of tooth damage for practical application of the obtained results. This index can be easily obtained by direct measurement. The differential approach is developed to select a restoring method of the tooth with the defect to provide a reliable restoration of the anatomical crown of the tooth.

Composite materials show different mechanical properties in different directions which leads to complications in the prediction of their behavior. In addition to being inhomogeneous, behavior of composite materials is highly dependent on the curing process and many studies have tried to address these issues. Residual stress can induce high errors in prediction of composite material properties and leads to a difference between theoretical and experimental results. It has been observed that the humidity of environment and the chemical properties of composite materials are also important. Fewer studies have addressed thick layer composites and no damage theory has been developed for these materials. In this paper residual stress in thick layer composites have been studied. Using numerical analysis, the curing process has been modeled and mechanical properties of a thick layer composite are obtained and the induced residual stress in these composites has been assessed. Unlike thin layer composites, the stress in each layer is not specific and a tensile and compressive stress field can exist simultaneously in thick layer composites.

This study aims to understand the uncertainty about the optimum or best pin position (Dp) for friction stir lap welding (FSLW) of Al-Cu. Tensile shear testing is used to determine the Mechanical strength of FSL welds under static loading. Fracture strength (σLap) corresponding to the maximum load in a test over the sample width is used as the strength value. Interface microstructures differ depending on whether the tool pin penetrates the lapping interface. It has been found that σLap values of the defect free weld samples vary quite significantly and in general are significantly higher than those reported in the literature. When the pin penetration is close to zero no intermetallic layers were formed, hence the value of σLap was zero. When the pin penetration is 0.4mm, the commonly observed a thin Al–Cu interface layer forms and this layer does not grow beyond 3µm. It is shown that the thin interfacial layer can withstand a high tensile-shear load and thus the adjacent Al material shears to fracture. When the pin penetrates more than 0.4mm, the commonly observed mix stir zone (MSZ) forms and values of σLap are lower than that of 0.4mm pin penetration welds but remain quite high.

The concept of a deformable body point is taken in the form of a continuum point and an elementary volume connected with it. The continuum point determines the spatial position of the deformable body point, and the elementary volume is the carrier of its material properties and stress-strain state characteristics. Based on this representation, restrictions on the state parameters at the edge points (singular points) of an isotropic body are constructed. These restrictions become preset conditions in singular points. The study covers possible interactions of the edge-forming surfaces with the external environment. It is shown that the restrictions formed at the edge points are usually more numerous than the restrictions at the regular point on the surface of a deformable body. This circumstance leads to a non-classical formulation of the mechanics problem for bodies with singular points. The combinations of geometric and material parameters of a structural component are discovered that determine the singular stresses behavior in elementary volumes with edge points. The load restrictions ensuring the compatibility of parameters defined at singular points are formulated. The attained results will apply to studying stress concentration in the vicinity of 3D-edges of structural components.

This paper presents an investigation into the flexural behaviour of basalt FRP reinforced concrete beams through experimental and analytical methods. To achieve the research objectives, four concrete beams reinforced with steel and four identical concrete beams reinforced with BFRP bars were tested under four-point bending. The main parameters examined under the tests are the type of concrete (lightweight foam glass concrete and normal concrete) and the type of longitudinal reinforcement bars (BFRP and steel). Test results are presented in terms of failure modes; deformation crack pattern and the ultimate moment of resistance are presented. The experimental results are analysed and compared to predictive models proposed by ACI 440.1R, 2006 and BS EN 1992, Eurocode 2, for deformations and ultimate flexural capacities of the steel and BFRP reinforced concrete beams. The experimental results indicated that the flexural capacity decreased for the beams reinforced with BFRP bars compared to that of a corresponding beam reinforced with steel bars. Both types of beams failed in the modes predicted. The prediction models underestimated the flexural capacity of BFRP reinforced concrete beams. The increase in foam glass aggregate content was observed to reduce the cracking load by almost 10 - 40% and 25 - 50% for steel and BFRP reinforced concrete beams, respectively. The flexural capacities of BFRP reinforced beams were underestimated by using equations stipulated in ACI 440.1R and Eurocode 2 codes of practice.

In-plane strength and constitutive properties of composite materials is known as crucial problems. Although, several studies have been made for obtaining the in-plane mode II properties, the common test fixtures are blind in confrontation of shear zone. Furthermore, toughening mechanisms and consequently mode II fracture toughness cannot be evaluated, precisely. Also, proposing the convenient configuration of shear test fixture increase the accuracy of evaluation for the shear-zone energy dissipation, especially in orthotropic materials. Hence in the present research, a novel shear fixture configuration is proposed based on Iosipesque structural modification. Hereof, some arbitrary composite materials (e.g. graphite/epoxy and wood) were studies on the basis of DOE and E-691 ASTM. Furthermore, as the numerical method for indicating the comparison of the uniform and non-uniform shear stress distribution in the modified and common shear test fixture, a statistical procedure is used based on ASTM standard in addition to FEM analysis. The obtained results reveal that applying major amendments through the new scheme of the shear test fixture, would provide a remarkable precision and a reasonable estimation of the shear strength in comparison with the previous Iosipesque experiments.

In this study, the effects of alkaline accelerating admixture and its dosage on cementitious material’s behavior at early ages were evaluated through a series of ultrasound Pulse echo measurements. Thus, those measurements consist on following the evolution of frequency dependent attenuation coefficient during cementitious material age. Four stages can be identified on the attenuation coefficient vs. mortar age graphs, indicating that the development of the attenuation parameter is closely related to the setting and the hardening phenomena. Also, the ultrasound histograms, representing the evolution of the different echoes backscattered by the media of the container, filled with cementitious material’s samples, were characterized in order to assess the attenuative effect of alkaline accelerator and its dosage during the setting and the hardening period. Thus, the combined use of ultrasound P-wave measured density and young modulus parameters results in a comprehensive ultrasound method that gives a more effective picture of the void volume and resistivity of the accelerated cementitious materials. Ultrasound P-waves were generated using a 1 MHz central frequency immersion transducer and mortar samples were prepared with Portland composite cement CPJ 45.

This work investigated and predicted the fatigue life durability of Austenitic Stainless Steel 316L due to its importance in plant industries worldwide. Modelling and simulations were performed to clarify the fracture as well as stress distribution using integrated mechanism. Experimental fatigue validations were also carried out to demonstrate the effect of various fatigue life parameters. Various loading conditions with variable load amplitudes were validated utilizing a frequency of 5 Hz and a stress ratio of 0.1. The accuracy of the simulation results were also verified based on the experimental data. High consistencies between the predicted fatigue life and the experimental results were achieved which increases the validity of the built model.

The development of techniques that allow producing high-finish surfaces of geometrically-complex parts of difficult-to-machine materials by electrical discharge machining (EDM) is an emerging research area. The aim of this work is to study the application of electrolytic-plasma polishing technique for the high-quality surface finish of the parts obtained by EDM process. The structural alloy steel 38KH2N2MA (GOST 4543 – 71) was selected as the processing material. The morphology of the machined surface was examined using optical micrographs. It was observed that applying the electrolytic plasma polishing for the duration of 5 minutes results in reducing the surface roughness of the ED machined surface by a factor of 5. It is also concluded that the combined action of EDM with electrolytic plasma polishing method is suitable for attaining the desired surface finish.

In this work, novel cellulosic fibers are extracted from Washingtonia Filifera (WF) plant using an environment friendly technique. Morphological, physico-chemical, thermal and mechanical properties are reported in this paper. Micro graphical SEM shows the presence of cells in the fiber. FTIR and XRD experimental analyzes show a cristinality index of 48.88%, and the WF fibers are found to be thermally stable until 201°C by using TGA and DTG thermo graphic analyzes with an appropriate activation energy of 72.46 kJ/mol, where Young modulus and tensile strength of strain were determined using tensile tests of single fiber at 2.17 GPa, 134 MPa and 26.55%, respectively. Mechanical properties are analyzed using a statistical method.