Cantilevers are elements typically used in the design of various structures such as factory halls or cantilever cranes. Traditionally, such elements are made of standard profiles or, in the case of ...large loads, by welding from standard sheets. Often, due to stationary conditions of exploitation, no attention is paid to mass reduction. Increasingly stringent requirements on reducing costs, but also on reducing environmental impact through reducing energy consumption necessary for the production, processing, and transport of materials, facilitate the application of optimization to obtain a construction solution with minimal mass. However, doing so requires advanced high-cost computer tools and increases the required competencies of designers. In this paper, a series of optimizations have been carried out for typical reach and load values of cantilevers aiming to create a database that will facilitate algorithms for selecting cross-sectional dimensions suitable for production using either additive technologies or traditional methods.
Electropolishing at high current densities without agitation of the electrolyte results in a pitting phenomenon that produces dimple-like surface features. Although pitting is unfavorable in the ...electropolishing process, its effect on surface modification, such as surface texturing, has not been thoroughly investigated. Surface topography and chemical composition analyses of electropolished steel revealed surface pits and an oxide surface layer, indicating the presence of surface texture and coating. The resulting surface is characterized by negative skewness and high kurtosis values. The tribological behavior of the electropolished steel-bronze pair is investigated by evaluating coefficients of friction and bronze wear using sliding tests conducted in mixed and boundary lubrication regimes. The results are compared to those of the ground steel-bronze pair. In the mixed and upper range of the boundary lubrication regime, coefficients of friction reduction up to 30% and shorter running-in phases are observed for electropolished steel (electropolished steel μavg = 0.019 vs. ground steel μavg = 0.028). In contrast, the coefficient of friction increased in the lower range of boundary lubrication regime by 50% (electropolished steel μavg = 0.098 vs. ground steel μavg = 0.065). Electropolishing, as a cost- and time-effective method applicable to complex geometries, presents an alternative method for achieving surface modifications aimed at friction reduction and improved tribological behavior for non-conformal contacts in the boundary and mixed lubrication regimes.
•A review of available studies on gear pair optimisation was carried out.•The studies concerned with both micro- and macro-geometry were covered.•The optimisation process was formalised and its steps ...covered in detail.•Guidelines for carrying out gear optimisation studies were provided.•Based on the literature, rough gear design guidelines were given.
Gear pairs effectively transmit power and movement over short distances. Their design is well-defined in the technical literature, including standards and handbooks. However, the resulting transmission performance will still mostly depend on the designer's skill and experience. Thus, by including the optimisation in the transmission design process, it is possible to increase its value through enhanced operational characteristics. In addition to providing an overview of studies on gear optimisation, this review article aims to summarise results obtained by other researchers and to formalise gear optimisation process. The paper is focused on the macro-geometry optimisation, while also providing some details on micro-geometry, aiming to present a comprehensive optimisation procedure. Based on the reviewed literature, recommendations for carrying out the gear pair optimisation process were given, including the design variable selection, selection of objective functions, and formulation of constraints. Finally, rough macro-geometry design guidelines based on the findings reported by other researchers were provided.
•Multi-objective optimization of gear pair parameters was conducted.•Main goal was reducing the transmission volume and power losses.•Five optimization variables were used; z1, b, m, x1, and ...x2.•Solutions have shown that the trade-off between volume and efficiency is obligatory.•Combination of the lower gear module, the lower face width, and the higher profile shift coefficients yield good results.
Besides satisfying the essential strength requirements, gearbox design should ensure additional desirable properties in order to be competitive. For example, a gearbox should be efficient, durable, quiet, compact, and light. Nowadays, as a consequence of rising environmental concerns, high efficiency is a rather desirable feature. In this article, a genetic algorithm was used for conducting a multi-objective optimization of gear pair parameters with a goal of reducing the transmission volume and power losses. Gearing efficiency primarily depends on the normal load, sliding velocities, and the friction coefficient. Gearing efficiency was calculated analytically, using the approximate load distribution formulae and efficiency formulation developed by Schlenk. The resulting formula was included in the genetic algorithm as an objective. To verify it, results were compared to the ones obtained by other authors. Optimization variables consisted of the gear module, the face width, the pinion and wheel profile shift coefficients and the number of teeth of the pinion. Solutions have shown that the trade-off between volume and efficiency is obligatory and a combination of the lower gear module, the lower face width, the higher profile shift coefficients and the higher number of teeth of the pinion yield good results regarding both objectives.
•Influence of profile shift on the spur gear pair optimization was investigated.•A genetic algorithm with profile shift coefficients as variables was used.•Profile shifted spur gear pairs were ...compared with pairs without profile shift.•The objective was to minimize volume, while meeting the ISO 6336 requirements.•The authors propose including the profile shifts as optimization variables.
Due to the established load capacity calculations and extensive literature, gearbox design process is rather simple. In order to gain a competitive edge, transmission designers and manufacturers are forced to constantly improve the design process and the product quality. The gearbox design process can be improved by using genetic algorithm to determine the optimal values of gear pair parameters. In this paper, besides the frequently used gear optimization variables, i.e. the module, the face width, and the number of teeth, profile shift coefficients of both gears are included to create a five-variable process. Since the profile shift influences the form, zone and stress factors, as well as the transversal and face load factors, it affects the optimization results significantly. The gear pair volume served as a fitness function, while the tooth root bending strength and the contact pressure calculations were used as constraints. Optimization results of the pair without profile shift and the arbitrary profile shifted pair were compared. The genetic algorithm solution is found for three data sets; the solution is verified using commercial gear optimization software.
In this article, the authors have experimentally determined the friction coefficient in the polyoxymethylene gear pairs lubricated by a dry film lubricant. The obtained expression increases the ...precision of the frictional power loss calculation, which is essential when the frictional power loss is used as the optimization criterion. The friction coefficient was characterized for three influencing parameters: radius of relative curvature, sliding velocity, and normal load. The full factorial organization was used for the experiment design; five curvature radii levels, four sliding velocity levels, and three load levels were used. Each of the runs was recorded three times, which resulted in a total of 180 experimental runs. The resulting expression for the friction coefficient is valid for the gear modules between 1 and 4.5 mm and sliding speeds of up to 2.7 m/s. The normal load was found to have the greatest influence on the friction coefficient, while the sliding velocity influenced only the specimens running under lower load levels. A further increase in the values of radii of relative curvature above 5 mm had no effect on the friction coefficient. The experimental data is provided in full.
Walking mechanisms are a solution for cases in which wheels are not applicable, such as uneven or stepped surfaces and surfaces withobstacles. Furthermore, it is possible to tailor mechanism ...footpaths to expected working conditions through optimization. Thus, in this paper, a mechanism optimization process was proposed, focusing on single-leg performance. Numerical Simulink calculations were used to determine objective function values, which were then input to a non-dominated sorting genetic algorithm (NSGA-II) for optimization. In each following generation, NSGA-II provided a new set of units for evaluation. The procedure was applied to the single leg of the Chebyshev lambda mechanism to better illustrate it, enabling a comprehensive analysis of candidates. Four objective functions (i.e., length in the x-direction, trajectory height variation, maximum foot acceleration, and foot speed fluctuation) were used to carry out a multi-objective optimization. The calculation time was approximately 2 s/unit.
Abstract
This study compares empirical and topology optimization methods for reducing gear body mass. Specimens produced via empirical guidelines and topology optimization were compared to referent ...full-disc gear, focusing on stresses and deformations. Values were determined numerically (Ansys was used) and the calculation method was verified using ISO 6336. The empirical approach exhibited substantial increases in stress and deformation while topology optimization method had promising outcomes. While decreasing mass, it also diminished tooth root stress on the tensile side by 17.1%.
This study aims to present a procedure for optimisation of polymer gear pairs, along with the rough design guidelines. Multi-objective optimisation of polymer spur gear pairs was carried out. The ...gear pair module, face width, pinion number of teeth, and profile shift coefficients of both gears served as design variables. Two objective functions were used to rate the designs—volume and frictional power losses. Compared with well-researched steel gear pair optimisation, additional boundary conditions were necessary: tooth flank and root temperatures, abrasion wear, and tooth addendum displacement. Two arbitrary datasets were used as examples, each made of polyoxymethylene. For each of the sets, a Pareto optimal solution was manufactured to enable the experimental validation. For this purpose, an open-circuit experimental rig was designed. As no literature was found on the polymer gear pair optimisation, results were compared with ones for steel gear pairs. The results have shown that changes in macro-geometry affect polymer gears significantly different. The lower volume pairs made of polymer had greater face widths, while the opposite was observed in steel gears. The differences between the analytical and experimental results were up to 21%.
With the increase in material and labour costs, the optimization of welded steel structures is gradually becoming a necessity. Precise cost calculation methods are a prerequisite for the optimization ...process; they enable the designers to differentiate between product variations and select the best one. However, while the calculation of the material cost is simple, the calculation of fabrication costs, which include the costs of cutting, handling, welding, and surface preparation, is harder to define. Thus, in this paper, two available cost calculation methods are compared by observing two specific welded structures: a welded I beam and a gearbox housing. Both the total and the partial costs were compared. Based on the results, it was concluded that the methods are in agreement considering the total cost values and that both methods can differentiate between the design variations comparably. On the other hand, partial costs of process segments differed, mostly due to variations in the pre-defined scope of each process (e.g., one method included handling in the material costs, while the other included it in the welding costs).
