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The purpose of this paper is to minimize the volume of straight bevel gear and to develop resistance towards scoring failure in the straight bevel gear. Two evolutionary and more advance optimization techniques were used for performing optimization of straight bevel gears, which will also save computational time and will be less computationally expensive compared to a previously used optimization for design optimization of straight bevel gear.

The following two different cases are considered for the study: the first mathematical model similar to that used earlier and without any modification to show efficiency of the optimization algorithm for straight bevel gear design optimization and the second mathematical model consist of constraints on scoring and contact ratio along with other generally used design constraints. Real coded genetic algorithm (RCGA) and accelerated particle swarm optimization (APSO) are used to optimize the straight bevel gear design. The effectiveness of the algorithms used has been validated by comparing the obtained results with previously published results.

It has been found that APSO and RCGA outperform other algorithms for straight bevel gear design. Optimized design values have reduced the scoring effect significantly. The values of the contact ratio obtained further enhances the meshing operation of the bevel gear drive by making it smoother and quieter.

Low volume is one of the essential requirements of gearing applications. Scoring is a critical gear failure aspect that leads to the broken tooth in both high speed and low-speed applications of gears. The occurrence of scoring is hard to detect early and analyse. Scoring failure and contact ratio have been introduced as design constraints in the mathematical model. So, the mathematical model demonstrated in this paper minimizes the volume of the straight bevel gear drive, which has been very less attempted in previous studies, with scoring and contact ratio as some of the important design constraints, which the objective function has been subjected to. Also, two advanced and evolutionary optimization algorithms have been used to implement the mathematical model to reduce the computational time required to attain the optimal solution.

The purpose of this article is to present a method for the analysis of the quality of the bevel gear at the development level.

A non-commercial aircraft bevel gear design support system was developed. The system utilises matrix and vector calculi to model the technological machining systems and to analyse the contact of the designed pair. Both the technological model and the design model offer the possibility of manipulating the calculated parameters. This enables independent selection of the pinion/gear engagement, making it possible to achieved the desired contact pattern (its shape, position and size) and/or minimise motion transmission deviation. This article presents an analysis of the meshing of the aircraft transmission designed in two variants.

The newly developed non-commercial transmission design support system offers the capability to freely adjust mesh quality indicators. The first step is to perform automated technological calculations for a specific geometry of gear members, on the basis of which gear and pinion flanks are developed. Then, numerical models of tooth flanks are configured in the designed pair, and tooth mesh quality is verified. Quality indicators are provided in the form of summary contact pattern and the motion graph. In the subsequent step, changes are made to basic geometry of pinion tooth flank. After satisfactory mesh indicators have been reached, the transmission is tested for assembly errors and additional corrections are made to the geometry of the pinion tooth surface, as required. The above methodology guarantees that the assumed quality indicators are achieved on the physically cut transmission.

Fast preparation of the technology with guaranteed high mesh quality is a significant factor in the competitiveness of an industrial plant which implements a new bevel gear in its manufacturing activities.

The visualisation of the results of the use of the application allows the user to easily interpret the analysed contact pattern and take appropriate decisions as to the necessity of making corrections.

The purpose of this paper is to study the main landing gear (MLG) mechanism configuration.

Mechanism kinematics and dynamics, stress analysis and sizing of the MLG structural members, and fatigue issues related with the mechanism operation. Spreadsheet solutions were incorporated to this survey to analyze the most conceivable loading situations, and important factors of the mechanism design for an initial evaluation of safety implications.

MLG design approach along with conservative fatigue design factors lies in the area of accepted limits in commercial aircraft industry.

MLG loading associated with landing as well as those associated with ground maneuvers (steering, braking and taxiing) contribute significantly to fatigue damage, along with the stresses induced by manufacturing processes and assembly. The application of FEA methods for the design of the landing gear does not always guarantee a successful approach to the problem solution, if precise analytical solutions are not available in advance.

From the investigation of this incident of fractured struts of the MLG it is confirmed that the reduction in Pintle Housing diameter on the upper part has contributed to the avoidance of damaging the fuel tank above the MLG that would lead to a catastrophic event. On the other hand, the airframe of the SKY-Jet was proved efficient for a belly landing with minor damages to the passengers and heavier damages for the aircraft.

On-line vibration monitoring sensors hooked up to the landing gear strut and Pintle House would greatly enhance safety, without relying in optical surveys in hard to access and inspect areas of the landing gears mechanisms housings.

Analytic methods were adopted and spreadsheet solutions were developed for the MLG main loading situations, along with design issues concerning mechanism kinematics and dynamics, stress analysis and sizing of the MLG structural members, as well as fatigue issues related with the mechanism operation. Spreadsheet solutions were incorporated to this survey to analyze the most conceivable loading situations, and important factors of the mechanism design for an initial evaluation of safety implications.

Numerous metals can be processed using the additive manufacturing process laser-based powder bed fusion of metals (PBF-LB/M, ISO/ASTM 52900). The main advantages of additive manufacturing technologies are the high degree of design freedom and the cost-effective implementation of lightweight structures. This could be profitable for gears with increased power density, combining reduced mass with considerable material strength. Current research on additively manufactured gears is focused on developing lightweight structures but is seldom accompanied by simulations and even less by mechanical testing. There has been very little research into the mechanical and material properties of additively manufactured gears. The purpose of this study is to investigate the behavior of lightweight structures in additively manufactured gears under static loads.

This research identifies the static load-carrying capacity of helical gears with different lightweight structures produced by PBF-LB/M with the case hardening steel 16MnCr5. A static gear loading test rig with a maximum torque at the pinion of T₁ = 1200 Nm is used. Further focus is set on analyzing material properties such as the relative density, microstructure, hardness depth profile and chemical composition.

All additively manufactured gear variants show no failure or plastic deformation at the maximum test load. The shaft hub connection, the lightweight hub designs and the gearing itself are stable and intact regarding their form and function. The identified material characteristics are comparable to conventionally manufactured gears (wrought and machined), but also some particularities were observed.

This research demonstrates the mechanical strength of lightweight structures in gears. Future research needs to consider the dynamic load-carrying capacity of additively manufactured gears.

The aim of this paper is to study the effect of pressure angle and helix angle on bending stress at the root of helical gear tooth under dynamic state. Gear design is a highly complex process. The consistent demand to build low-cost, quieter and efficient machinery has resulted in a gradual change in gear design. Gear parameters such as pressure angle, helix angle, etc. affect the load-carrying capacity of gear teeth. Adequate load-carrying capacity of a gear is a prime requirement. The failure at the critical section because of bending stress is an unavoidable phenomenon. Besides this fact, the extent of these failures can be reduced by a proper gear design. The stresses produced under dynamic loading conditions in machine member differ considerably from those produced under static loading.

The present work is intended to study the effect of pressure angle and helix angle on the bending stress at the root of helical gear tooth under dynamic state. The photostress method has been used as experimental methods. Theoretical analysis was carried out by velocity factor method and Spott’s equation. LS DYNA has been used for finite element (FE) analysis.

The results show that experimental method gives a bending stress value that is closer to the true value, and bending stress varies with pressure angle and helix angle. The photostress technique gives clear knowledge of stress pattern at root of tooth.

The outcomes of this work help the designer use optimum weight-to-torque ratio of gear; this is ultimately going to reduce the total bulk of the gear box.

The purpose of this paper is to present a novel retractable main landing gear for a light amphibious airplane, while the design, synthesis and analysis are given in details for constructing the main landing gear.

The constraint three-position synthesis has given the correct path of all linkages that suitably fit the landing gear into the compartment. The additional lock-link is introduced into the design to ensure the securement of the mechanism while landing. Having the telescopic gas-oil shock strut as a core element to absorb the impact load, it enhances the ability and efficiency to withstand higher impact than others type of light amphibious airplane.

By kinematics bifurcation analysis, the optimized value of the unlock spring stiffness at 90 N/m can be found to tremendously reduce the extended-retracted linear actuator force from 500 N to 150 N at the beginning of the retraction sequence. This could limit the size and weight of the landing gear actuator of the light amphibious airplane.

The drop test of the landing gear to comply with the ASTM f-2245 (Standard Specification for Design and Performance of a Light Sport Airplane) reveals that the novel landing gear can withstand the impact load at the drop height determined by the standard. The maximum impact loading 4.8 G occurs at the drop height of 300 mm, and there is no sign of any detrimental or failure of the landing gear or the structure of the light amphibious airplane. The impact settling time response reaches the 2% of steady-state value in approximately 1.2 s that ensure the safety and stability of the amphibious airplane if it subjects to an accidentally hard landing.

This paper presents unique applications of a retractable main landing gear of a light amphibious airplane. The proposed landing gear functions properly and complies with the drop test standard, ensuring the safety and reliability of the airplane and exploiting the airworthiness certification process.

This paper aims to present an analytical approach for the determination of helical gear tooth geometry and introduces the necessary parameters. Tooth geometry including tooth chamfer, involute curve, root fillet, helix as well as tooth microgeometry can be obtained using the presented approach.

The presented analytical approach involves deriving the equivalent equations at the transverse plane rather than the normal plane. Moreover, numerical evaluation of microgeometry modifications is presented for tooth profile, tooth lead and flank twist.

An analytical approach is presented and equations are derived and explained in detail for helical gear tooth geometry calculation, including tooth microgeometry. Method 1, which was presented by Lopez and Wheway (1986) for obtaining the root fillet, is examined and it is proven that it does not work accurately for helical gears, but rather it works perfectly in the case of spur gears. Changing the normal plane parameters in Method 1 to the transverse plane ones does not give correct results. Two alternative methods, namely, Methods 2 and 3, are developed in the current research for the calculation of the tooth root fillet of helical gears. The presented methods and also the numerical evaluation presented for microgeometry modification are examined against the geometry obtained from Windows LDP software. The results show very good agreement, and it is feasible to apply the approach using the presented equations.

In the gear design process, it is important to model the correct gear tooth geometry and deliver all related dimensions and calculations accurately. However, the determination of helical gear tooth geometry has not been presented adequately by equations to facilitate gear modelling. The detailed helical gear tooth root has been enveloped using software tools that can simulate the cutter motion. Deriving those equations, presented in this article, provides gear design engineers and researchers with the possibility to model helical gears and perform design calculations in a structured, applicable and accurate method.

Actuators for human-interactive robot systems require transparency and guaranteed safety. An actuation system is called transparent when it is able to generate an actuation force as desired without any actuator dynamics. The requirements for the transparent actuation include high precision and large frequency bandwidth in actuation force generation, zero mechanical impedance and so on. In this paper, a compact rotary series elastic actuator (cRSEA) is designed considering the actuation transparency and the mechanical safety.

The mechanical parameters of a cRSEA are optimally selected for the controllability, the input and output torque transmissibility and the mechanical impedance by simulation study. A mechanical clutch that automatically disengages the transmission is devised such that the human is mechanically protected from an excessive actuation torque due to any possible controller malfunction or any external impact from a collision. The proposed cRSEA with a mechanical clutch is applied to develop a wearable robot for incomplete paraplegic patients. To verify torque tracking performance and disengagement of the mechanical clutch, experiments were conducted.

As the effects of the gear ratio, N1, on the four control performance indexes are conflicting, it should be carefully selected such that the controllability and the output torque transmissibility are maximized, while the disturbance torque transmissibility and the mechanical impedance are minimized. When the four control performance indexes were equally weighted, N1 was selected as 30. Experimental results showed that the designed cRSEA provided good control performances and the mechanical clutch worked properly.

It is important to design the actuator so as to maximize the control performance in accordance with its purpose. This paper presents the design guidelines for the SEA by introducing four control performance indexes and analyzing how the performance indexes vary according to the change of design parameter. From the viewpoint of practicality, a mechanical clutch design method that prevents excessive torque from being transmitted to the wearer and an analysis to solve the locking phenomenon when using a worm gear are presented, and a design method of SEA satisfying both control performance and practicality is presented.

The finite element method (FEM) has become the prevalent technique used for analyzing physical phenomena in the field of structural, solid and fluid mechanics. The output of scientific papers is fast growing and professionals are no longer able to be fully up‐to‐date with all the relevant information. The purpose of this paper is to provide a bibliographical review on the application of FEM in mechanical engineering, specifically for the analyses and simulations of gears and gear drives from the theoretical as well as practical points of view.

The following topics on gears and gear drives are handled from the computational points of view: gears in general, spur gears, helical gears, spiral bevel and hypoid gears, worm gears and other gear types and gear drives. The paper is organized into two parts. In the first one each topic is handled in a short text, relevant keywords are presented and current trends in applications of finite element techniques are briefly mentioned. The second part lists references of papers published for the period 1997‐2006.

This bibliography is intended to serve the needs of engineers and researchers as a comprehensive source of published papers on design, analysis and simulation of gears and gear drives.

The bibliography listed is by no means complete but it gives a comprehensive representation of different finite element applications on the subjects. It will save time for readers looking for information dealing with described subjects, not having an access to large databases or willingness to spend time with uncertain information retrieval.

The purpose of this paper is to present a cost‐effective design for a new rescue robot locomotion module using the principle of a continuous sliding membrane to achieve propulsion ratio (PR) near 1. Such high PR cannot be reached by other locomotion mechanisms that have been proposed.

The paper first introduces the PR as a reference parameter to assess locomotion effectiveness of snake‐ and worm‐like robots. The state‐of‐the‐art is reviewed. A direction to step beyond getting PR near 1 is indicated. The way is by realizing a continuous sliding membrane. Two solutions in this direction which have been recently proposed are recalled. It is shown that none of them can be practically implemented to realize functioning systems with today's available technology. A new design with membrane actuation has been identified and it is described in detail. A prototype has been realized and earliest results and evidence of functioning described.

Critical discussion of the concept of locomotion based on a sliding membrane was conducted. A new design for a robot locomotion module applying this concept was presented. Earliest evidence of functioning and effectiveness of the new system proposed was given.

A new locomotion principle is shown. The state‐of‐the‐art background is discussed. A design to realize the new system in a cost‐effective way is described. The research implications lie in the future development of new mobile robots with higher locomotion capability than today's available systems. Several future research and development directions are shown.

A new generation of more locomotion‐effective snake‐ and worm‐robots, especially for rescue application in rubble, is foreseen. The design proposed takes cost‐effectiveness and practical realizability into account.

The continuous sliding membrane concept had been already proposed but no reasonable realization and actuation solutions had been singled out. The design of the new locomotion system is totally new and contains several breakthrough ideas. A prototype is available proving worthy in concept and functioning. It is cost‐effective and this will allow shorter application to real robots.