The role of dental education of 7–8 year’s children in the complex of preventive measures

The article is devoted to the study of the intensity, prevalence of dental caries and oral hygiene indices among younger schoolchildren, against the background of a complex of preventive measures and dental education, which was carried out on an individual and group level in the conditions of a school dental office, and health lessons in classes. The dental study involved 106 primary schoolchildren, including 54 boys (51%) and 52 girls (49%) aged 7–8 years, who were examined on the basis of the dental office of the school №176 of Nizhny Novgorod. The children were divided into 2 groups: 1 – prevention group and 2 – control group. In 1 group of children every three months during the year we carried out professional oral hygiene, then treatment of all teeth with a deep fluoridation and training in the standard method of brushing teeth on models in a dental office. In addition, for children of group 1, we organized health lessons with training in the standard method of brushing teeth in the classroom, the use of additional hygiene products for the oral cavity in children of this age and the demonstration of a cartoon about dental caries. In the control group a set of preventive measures was also carried out in the form of professional oral hygiene and application of all teeth with the drug Gluftored, training in the standard method of brushing teeth on models every three months during the year, but dental education in the form of health lessons in the classroom was not. According to the clinical examination of 7–8 year’s children, it was revealed that during regular preventive measures and dental education among younger schoolchildren, the development of caries for permanent teeth is not observed, oral hygiene is improved, and dental health is rising

Crack growth diagnostic of ball bearing using vibration analysis

It is known that supported ball bearings have great effects on the vibrations of the gear transmission system, above in all the presence of local faults as well as the crack growths. For this purpose, this paper focuses on shock and vibration crack growth diagnostic of ball bearing using vibration analysis. Our work is devoted first to a study the static behaviour of the ball bearing by determining the stress, strain and displacement, then its dynamic behaviour by determining the first four natural frequencies. Secondly, a dynamic analysis study of the bearing was carried with defects as a function of crack size and location. The obtained results clearly show that the natural frequencies decrease in a non-linear way with the growth of the length of the crack, on the other hand the stress increases with the presence of the singular points of the crack. Finally, this residual decrease in natural frequencies can be used as an indicator of the state of failure, as well as a parameter used for the diagnosis and screening, and to highlight the fatigue life of the bearing

Dynamic behavior to fatigue crack initiation of a glass/epoxy laminate

This paper based to study of the dynamic and fatigue behaviors with numerical and experimental parts of a composite material manufactured by stacking two layers of E-glass fiber in different angle orientations (0°/90°) immersed in polyester resin with total thickness 1.39mm. In Finite Element Analysis (FEA) using ABAQUS was used to evaluate the maximal (displacement, strain and stress) and the natural frequencies (mode shapes) of composite behavior under crack initiation condition. In the experimental part the laminate plate specimen with two layers is tested under one types of cyclic load in fully reversible tensile at (R=0), the fast fracture occur phenomenon and the fatigue life are presented, the fatigue testing exerted in INSTRON 8801 machine

An advanced dynamic repair of edge crack aluminum plate with a composite patch

In this work, repaired crack in 2024 T3 aluminium plate with composite patch is presented, the problem is handled in plane stress condition under tensile Mode I crack growth. In the numerical simulation, firstly we determine the displacement, strain and stress, also the first six mode shapes of the plate, secondly we compare the first results with result of a cracked plate, thirdly we repair the crack with composite patch for different materials (Glass, Boron, carbon) and for (2 layers, 4 layers). Finally the comparison of stress, strain, displacement and six first natural frequencies between uncracked, crack initiation and composite patch repair crack. The best offer operating according to the need is selecte