Number Of Tooth Pairs Research Articles

Modelling of contact and tribotechnical parameters of metal–polymer gears taking into account wear and correction of teeth

The estimation and the analysis of the arising contact pressures and tribotechnical parameters, that is, wear and durability, of metal-polymer spur gears using the author's computational method are presented in this study. Gears with a steel gear and pinion made of polyamide PA6 modified with dispersed carbon fibers (CF) or glass fibers (GF) whose content was 30%, PA6 + 30CF and PA6 + 30GF correspondingly, are studied. This took into account the parity of engagement, the effect of composite pinion teeth wear and gear correction. Quantitative and qualitative regularities of change of the specified parameters depending on composite type and gear correction type are established. It is found that the teeth wear of composite toothed wheels has a significant effect on reducing the values of the initial maximum contact pressures in the engagement. The distribution of linear wear along the teeth working profile and the localization of its maximum values, depending on the correction of engagement, are determined. The minimum durability of metal–polymer gears is calculated by simplified and improved methods. The optimal values of the correction coefficients at which the minimum durability is highest for both combination types of metal–polymer gears with height and angular teeth correction are established. The durability of metal–polymer gears with a driving pinion made of PA6 + 30CF composite calculated with the improved method is about seven times higher than the pinion made of PA6 + 30GF composite. In contrast to the methods of calculation of metal gears known from publications, the method presented in this study takes into account such practically significant factors as change of radii of tooth profile curvature owing to wear, their correction and number of teeth pairs at the engagement. In metal–polymer gears, there are no analytical calculation methods for modelling wear and tribological durability compared with that of the author's method.

Determination of Geometrical Parameters for Semi-Rolling Bevel Precessional Gears With Straight Teeth

The aim of this paper is to analyse the semi-rolling bevel precessional gear with straight teeth. The given method of cutting pinion and gear teeth significantly simplifies its manufacture technology. Authors have given a system of equations to study the analysis of generating pinion tooth surfaces and geometry of meshing for semi-rolling bevel precessional gear with straight teeth. A computer program was developed to enable implement formulas provided in the paper. By using this program authors obtained contact lines on the pinion tooth surface and number of tooth pairs in gears mesh.

Nutritional status of the older adult is associated with dentition status

Objective This study was designed to examine associations between the number of posterior occlusal pairs of teeth and the nutritional status of older adults participating in the third National Health and Nutrition Examination Survey (NHANES III) survey. Design Impaired dentition was assessed by number of posterior occluding pairs of teeth (grinding teeth, n=8 pairs) and complete denture status. Nutritional status was measured by nutrient intake, Healthy Eating Index (HEI) score, serum values, and body mass index (BMI). Subjects/setting Data from 5,958 participants in NHANES III ages 50 years and over with dental examination were included in the analysis. Statistical analyses performed Analysis of covariance and multivariate linear regression analyses were performed to examine associations between number of tooth pairs and nutritional status indicators controlled for potential confounders. Results Compared with individuals with five to eight posterior occluding pairs (HEI=68.2), those with impaired dentition (no posterior pairs, one to four pairs remaining, or full dentures) had consistently lower HEI scores (HEI=64.3, 66.5, and 66.5, respectively), consumed fewer servings of fruits, and had lower serum values of beta carotene and ascorbic acid. Participants with one to four posterior pairs also had a higher mean BMI (28.0) than those with five or more pairs (27.2). Participants in one or more groups with impaired dentition had lower dietary intake levels of vitamin A, carotene, folic acid, and vitamin C, and scored less well on diet variety, cholesterol, and sodium components of the HEI. Applications/conclusions Results show that dental health is closely associated with nutritional status and suggest that status of dentition should be considered in nutritional counseling and assessment of older adults. J Am Diet Assoc. 2003;103:61-66.