Using variable modulus to modify a rack cutter and generate a gear pair

In this paper, two normal imaginary helical rack cutters were first established. One of these cutters is a skewed-rack cutter with an asymmetrical straight edge. The other is a rack cutter with an asymmetric parabolic profile. Second, the gear’s tooth surface of the asymmetric parabolic rack cutter is modified to be barrel-shaped based on a variable modulus. The tooth thickness of the gear is gradually reduced along the face width of the tooth from the middle of the tooth surface. Then the coordinate relationship between the gears’ blanks and the imaginary helical rack cutters was established. Through the differential geometry, crowned and uncrowned helical gear pairs were generated. Because of human factors, when the gear pair is installed, it is easy to cause the gear pair edge contact. It is necessary to add artificial assembly error settings through the tooth contact analysis to investigate the kinematic errors and contact conditions of the crowned and uncrowned helical gear pair. The mathematical models and analysis methods proposed for the crowned imaginary rack cutter using variable modulus should be useful for the design and production of double crowned helical gears with asymmetric parabolic teeth.

Investigation of the width of the entry of an excavator when loading a mobile crushing plant in the conditions of the Angren coal mine of Uzbekistan

This article presents the results of studies to establish the optimal entry width for an excavator working in conjunction with mobile crushing plants in the development of overburden of the Angren open pit. According to the results of the research, an analytical relationship was established to determine the maximum productivity of the mining system “excavator-mobile crushing-reloading-conveyor complex” with cyclical-flow technology. A structural diagram has been developed that allows you to select the type and determine the main technological parameters of the equipment with the selected criteria for evaluating the effectiveness of the complexes. It has been established that the choice of equipment for conveyor lines should be carried out taking into account the mutual influence of adjacent technological links of the central heating systems, including the influence of the excavator-crushing and crushing-conveyor complexes on the efficiency of their mutual functioning within the framework of the adopted system as a whole. A functional graphical dependence of the excavator performance on the face width was obtained, taking into account the relationship of all technological parameters of the face. It has been established that the maximum excavator productivity of 1478.1 m3/hr is achieved with an excavator entry width of 17.4 m for the conditions of the Angren open pit. The resulting schedule makes it possible to assess the possibility of increasing the operational performance of single-bucket shovel excavators under various conditions of work, as well as to continue the optimization of excavation.

Cost optimization of two-stage helical gearboxes with second stage double gear-sets

In practice, the cost of a gearbox plays a very important role in the trade. Therefore, reducing the cost of gearboxes is an important task not only when manufacturing the gearboxes but also when designing them. In order to reduce the cost of a gearbox, there are many solutions in which determining the optimal partial gear ratios of a gearbox is an effective measure. This is because it not only the size, the mass but also the cost of a gearbox depends greatly on the partial gear ratios. This work presents a method for calculating the cost function of two-stage helical gearboxes with second-stage double gear-sets based on the mass of the components that construct the gearbox. The cost objective function is minimized to achieve the optimal transmission ratios. Furthermore, screening experiments are carried out with nine important input parameters that have significant effects on the optimum transmission ratio of the second stage. These parameters are the total gearbox ratio, the coefficient of wheel face width of the first stage, coefficient of wheel face width of the second stage, the allowable contact stress of the first stage, the allowable contact stress of the second stage, the output torque, the cost of gearbox housing, the cost of gears, and the shaft cost. The experimental results of were analysed by using the Analysis of Variance (ANOVA) method with the help of Minitab 19 software. The results demonstrate that the effective weight of the input parameters and their interactions on the output response was investigated. Also, a regression model for computing the optimal transmission ratio of the second stage was proposed. This brings significance not only in the design process but also in manufacturing since the gearbox cost can decrease

Gear Teeth Deflection Model for Spur Gears: Proposal of a 3D Nonlinear and Non-Hertzian Approach

In this paper, a three-dimensional model for the estimation of the deflections, load sharing attributes, and contact conditions will be presented for pairs of meshing teeth in a spur gear transmission. A nonlinear iterative approach based on a semi-analytical formulation for the deformation of the teeth under load will be employed to accurately determine the point of application of the load, its intensity, and the number of contacting pairs without a priori assumptions. At the end of this iterative cycle the obtained deflected shapes are then employed to compute the pressure distributions through a contact mechanics model with non-Hertzian features and a technique capable of obtaining correct results even at the free edges of the finite length contacting bodies. This approach is then applied to a test case with excellent agreement with its finite element counterpart. Finally, several results are shown to highlight the influence on the quasi-static behavior of spur gears of different kinds and amounts of flank and face-width profile modifications.

Farm Silage Facilities and Their Management for the Prevention of Anaerobic Bacteria Spore Contamination in Raw Milk

At feed-out, aerobic spoilage of silage enables an increase in anaerobic spore-forming bacteria (ANSB) that may enter the total mixed ration (TMR). The aim of our study was to understand whether in hot summers the silage structures and management may affect the level of ANSB in milk for long-ripening cheese production. A survey of silage facilities, management, and their relationships with silage, TMR, feces, and milk ANSB most probable number (MPN) content was conducted in the Po Valley during summer months. Silo type did not affect the mean ANSB, but only the wideness of their value distributions, with a narrow range for bags and a wider range for bunkers. The unloading equipment affected the ANSB count; the front-end loader with cutter was associated with a lower ANSB count—probably as a result of the reduced surface left after daily silage removal. Silo length and daily removed face width were the main factors affecting contamination of silage by spore-forming bacteria during summer, with longer silos and wider surface removal reducing ANSB contamination—probably as a consequence of reduced aerobic spoilage at the silage surface. The silage contamination by spore-forming bacteria within a log10 2 MPN g−1 allowed a low concentration of spore-forming bacteria at the farm bulk milk tank level. Fecal ANSB levels did not factor into the regression that explains the ANSB in farm milk. It has been found that silage facilities’ features and their management are an important first step to reduce the extent of ANSB contamination at the farm level.

Correlation of morphological parameters of donkey from Austria

The donkey, as a work animal, is gradually losing its value. Agriculture industrialization, mechanization of many processes on mountain and valley farms have lead to a reduction of donkey livestock. This reduction gives cause for concern, and is good reason to study all aspects of these domestic animals in order to revive its role, to restart livestock growth in its familiar habitats, and to introduce it into new environments. This study focuses on these aspects. The domestic donkey (Equus asinus) originated from Africa, and there are two kinds of African donkeys: Nubian and Somali. Their enormous, almost mystical, endurance is well known. There is no place in the world where a donkey is not able to perform the most difficult work, above all in transporting goods. A donkey has an amazing capability of stable movement through the most difficult places. For study sample consisted of 44 donkeys (28 males and 16 females) from Austria. The following morphometric parameters were analysed: height at the withers, height at the back, height of the croup, body length, chest depth, chest width, chest circumference anterior, chest circumference posterior, shin circumference, head length, skull length, face length, skull width, face width, length of ears. Measurements were performed using a ruler, tape measure and vernier callipers. The average height at the withers of males was 116.40 cm, ranging from 99.60 to 140.60 cm, while for females, the average was 102.38 cm, ranging from 90.50 to 125.70 cm. Body length of males was on average 121.85 cm with a standard deviation of 11.79, while the mean body length for females is 115.80 cm, with a range of 101.00 to 131.00 cm. Male head length ranged from 48.00 to 71.00 cm, with an average of 55.60 cm, while in females, head length was on average 50.06 cm, ranging from 43.00 to 56.00 cm. Using the Pearson correlation, a very significant or significant positive statistical correlation was observed between almost all parameters of males, while for females, Pearson correlation values had slightly different values than for males. There was no statistically significant correlation between chest width and anterior chest circumference with nearly any other parameters. For females, a negative correlation between the skull width and all other parameters was also observed.

Morphometric characteristics of skull and face parameters in fetuses and newborns

Modern science has a significant number of diagnostic methods: craniological, anatomical, ultrasound, radiological. The development of new research methods, such as ultrasound and X-ray methods (magnetic resonance imaging), forms the concept of ultrasound and X-ray norms at different stages of human development. Now it is important to study the anatomical variability of people, morphometric characteristics, relationships of organs, anatomical structures, their parts at all stages of human development. The purpose of the work is to establish normative morphometric parameters of the skull and face in fetuses and newborns, followed by construction of mathematical models. The study was performed on 57 preparations of human fetuses 4-10 months and 7 newborns using adequate anatomical methods: macropreparation, topographic anatomical sections, computed tomography, craniometry. The main parameters of the facial and cerebral skull were measured with the help of a centimeter tape, a thick, sliding compass and a caliper. Statistical analysis of the obtained data was performed using a licensed program RStudio. It is established that according to the graphs of the average values of the parameters of the skull and face, there are two periods of accelerated and two periods of slow development. For transverse skull length, face width and skull height, two periods of accelerated development from the 6th to the 8th month of fetal development and from the 9th month of fetal development to the neonatal period and two periods of delayed development from the 5th to the 6th months and from the 8th to the 9th month of fetal development were revealed. For the total height of the face – periods of accelerated development – from the 4th to the 6th month of fetal development and from the 7th to the 9th month of fetal development, periods of delayed development – from the 6th to the 7th month of fetal development and from the 9th month of fetal development to the neonatal period. On the basis of arithmetic mean data of transverse skull length, face width, skull height, total face height, models for predicting normative morphometric parameters in fetuses and newborns are constructed. The constructed models will serve as a norm for the subsequent determination of certain morphometric deviations to establish variants of the structure and malformations of the skull and face. Thus, our systematized data on the features of spatio-temporal transformations of morphometric parameters of transverse skull length, face width, skull height, total face height with subsequent construction of mathematical models will contribute to the individualization of the norm, improvement of early diagnosis methods and development of new methods for surgical correction of congenital defects of the skull and face.

Latent factors of the components of physical development in children and adolescents of the northern region with undifferentiated connective tissue displasion

In connection with the spread of undifferentiated forms of connective tissue dysplasia (UCTD) in unfavorable climatogeographic and environmental conditions, it seems relevant to assess the impact of organogenesis disorders on physical development in schoolchildren living in the northern region. Based on the foregoing, the purpose of this study was to study the relationships and interdependencies of the components of physical development and somatometric indicators in children of the northern region with phenotypic signs of connective tissue dysplasia. Anthropometric indicators were revealed that can be used for express diagnostics of the level of physical development in children with UCTD these are the length of the legs, the thickness of the skin-fat fold on the front surface of the shoulder and the interorbital-circumferential index. When assessing covariants such as age and sex, there is a correlation of clusters of long-length values with age, the relationship of the thickness of the skin-fat folds with the floor, and the parameters assessing changes in the cerebral and facial skull, such as: face width, head circumference and interorbital-circumferential index are associated with both sex and with age. The influence of posture disorders on the studied components of physical development is manifested by higher growth in children with flat and round-curved backs, a decrease in the thickness of skin-fat folds and head size with a round and round-curved back. Thus, for a comparative analysis of gender and age differences in the level of physical development in children with UCTD, it is necessary to take into account the dynamics of interdependent anthropometric indicators and indices, taking into account postural disorders.

Research on Optimization of a Solid Filling Mining Face Layout Based on a Combined Clamped Beam Model

Optimizing the mining scheme is an essential work for improving recovery efficiency of filling mining. An optimization equation of mining face width under a gangue mining condition is derived firstly. Then, analysis of the optimization equation of the mining face width is carried out based on the measure data of the F5001 mining face in the Tangshan Coal Mine. At last, the reasonable mining face width is determined combined with numerical simulation. Results show that mining face width and roof subsidence increase with the increase of unit weight and mining depth, but decrease with the increase of the elastic modulus of roof. The maximum width of the mining face is 105 m in Tangshan Coal Mine. When the mining width increases from 66 to 105 m, the increasing percentage of roof subsidence is 15–18%. Roof subsidence is controlled less than 30% of the mining height. The variation range of the maximum roof subsidence is small, which means the mining face width can be designed reasonably through the proposed equation.

Optimal weight design problem of spur gears

Gear is one of the most common and important components in machinery. Evaluation on durability of gears plays crucial role in the assessment of the whole system reliability and service life. For other parts like shafts, the gears also act as loads. Therefore, dimensions and weight of the gears should be reduced as much as possible, contributing the size and weight reduction of the whole systems, which is essential to be cost-effectiveness. The current research focuses on optimal weight design problem of spur gears, such that the weight is minimized under the constraints taken from working conditions. The weight is a function of six variables, i.e. face width, shaft diameter of pinion, shaft diameter of gear, number of teeth on pinion, module and hardness. Constraints are derived based on AGMA standard and engineering handbooks, including the bending strength, the surface fatigue strength, the interference condition, the condition for uniform load distribution, the torsional strength of shaft on pinion and gear, and the center distance. The set of optimum design variables is determined by the heuristic algorithm Grey Wolf Optimizer (GWO). The accuracy and efficiency of the GWO in the optimal weight design problem of spur gears are assessed based on comparison with other popular methods, such as Genetic Algorithm (GA), Particle Swarm Optimization (PSO) and Simulated Annealing (SA). It is noted that in previous works, some of the constraints are still violated. Therefore, a penalty term is taken into the objective function, such that any set of design variables that violates constraints will be considered as ``unfit'' by the algorithm. It is demonstrated that using the proposed approach by current work, the optimal weight and the corresponding set of design variable are very close to reference data. Yet the advantage of the proposed approach is exhibited in the fact that all of the constraints are satisfied.