Failure of the tail rotor of the Mi-24 helicopter as a result of a long-term impact of spatial resonance coupling

The most important element that has an impact on the safety of flight includes the helicopter power plant and the transmission shaft assembly. Monitoring with the use of the traditional vibroacoustic techniques does not provide satisfactory results. It is especially difficult to detect spatial resonance couplings, which may result in dangerous and rapid breaking of elements. This article focuses on a specific mechanism for formation and deepening of resonance and effects of resonance couplings of two subassemblies. For their monitoring, the FAM-C method was applied. It uses an on-board generator as a sensor. This is a synchronous method, which enables one to detect the onset of spatial resonance.

Dynamics of Electromechanical Systems Containing Long Elastic Couplings and Safety of Their Operation

The electromechanical systems under analysis include electric drives, working machines that perform specific tasks in the technological process, and working mechanisms that transmit mechanical power between the electric drive and the working machine. The vast majority of electric motors included in drive systems require rotational speed control. This task is most often performed with the use of closed-loop control structures based on speed controllers. A step or overly rapid change in the speed reference causes a temporary lock of the speed controller due to the applied limitations at its output. Particularly, unfavorable effects of such a lock can be observed in drive systems in which there is a long elastic coupling (transmission shaft) between the electric motor and the working machine. As a consequence, shaft torsion and accompanying twisting moments of considerable amplitudes appear. This article proposes an uncomplicated active torque limiter structure, which enables the uninterrupted operation of the speed controller thanks to the automatic adaptation of the rate of the speed reference change to any moment of inertia of the rotor and attached rotating masses. The results of the investigations confirm the effectiveness of the proposed structure.

Design of a New Type of Torsional Impactor and Analysis of Its Impact Performance

In view of the stick-slip phenomenon in deep and hard rock drilling, a new type of torsional impactor that can provide torsional impact vibration was designed. According to the working principle and structural characteristics of the designed torsional impactor, this paper theoretically analyzes the influences of different structural parameters and motion parameters on the impact frequency, impact force, and impact torque of the torsional impactor. The results show that the impact frequency f is directly proportional to the rotational speed VZ of the transmission shaft and the installed number n of torsional impact generating devices. Additionally, the impact force F is directly proportional to sine value of the impact angle α (i.e., sinα), impact hammer mass m, impact hammer rotation speed VZ (i.e., transmission shaft rotation speed), and impact hammer rotation radius r and is inversely proportional to action time Δt of the impact hammer and impact anvil. Furthermore, the impact torque M is directly proportional to the impact force F and rotary radius r of the impact hammer. This article lays a foundation for further theoretical and experimental research of torsional impactors and provides a reference for the design and testing of torsional impactors.

JUSTIFICATION OF THE STRUCTURE OF THE CRANE WHEEL WITH ELASTIC INSERT

The article considers the modernized design of the crane running wheel with anelastic insert.The purpose of the study is to substantiate the rational design of the running wheel onthe basis of determining the dynamic forces that occur when moving the truck and the crane bridge.Crane equipment is of great importance for the mechanization of lifting and transportoperations in various industries. Bridge cranes perform various lifting and transport operations.Installation and dismantling of equipment and machines. Also take part in the technologicalprocess of the metallurgical industry.The costs associated with the replacement and restoration of the running wheels are 15-17%of the cost of repairing the entire crane. At the same time more than 90% of crane wheels fail due towear of flanges.The main tasks for the diagnosis of crane wheels and rail tracks are usually solved duringscheduled maintenance by visual inspection of the wheel and rail and identify their wear. But thisdiagnostic tool does not quite satisfy the modern conditions of the cranes, namely, the compatiblecondition of the wheels and rails is not assessed, and it is impossible to carry out such controlconstantly during operation.Mechanisms for moving bridge cranes have several designs. The mechanism for moving thetruck, as a rule, has one drive, which transmits motion to the two drive wheels. The mechanisms ofmovement of the crane can be with the central and separate drive. The mechanisms of movement with the central drive can be with a low-speed transmission shaft, with a high-speed transmissionshaft and with a medium-speed transmission shaft.With this design, the gearbox shafts are connected to the drive wheel shaft by means of aclutch and a transmission shaft. This impairs the operation of the entire mechanism, because thepresence of the transmission shaft increases the complexity of the manufacture of the crane and itsweight and requires a very precise installation.To overcome these shortcomings, a separate drive of the end beams of the bridge is used.If the load on one of the support beams of the bridge is less than on the other, the enginespeed on this support increases and the support begins to run forward relative to the more loadedsupport. But the first engine begins to receive increased load, which is transmitted through themetal structure of the bridge and unloads the engine of the second support, due to which the speedof the first engine decreases and the speed of the second engine increases until they are equalized.Thus, in the process of moving the crane with a separate drive is the redistribution of loadbetween the two engines. Although the scheme of the mechanism with separate drives requires twoengines, two brakes and two gearboxes, it is the cheapest, light weight and easy to manufacture.The design of running wheels of cranes and crane carts should exclude a possibility ofderailment of wheels. To do this, the running wheels have two side flanges - flanges, which serve toguide the running wheels on the rails.The dynamic forces that arise when moving the trucks of cranes are quite large and cannot beignored when designing cranes. Most of all, they are manifested by wear of wheels and rails duringthe occurrence of distortions on the cranes.Thus, improving the performance and operational reliability of crane running wheels is avery important task of modern crane construction.The research technique is based on analytical methods of research of dynamic efforts in themechanism of movement of the truck of the bridge crane. The decision of three mass dynamicschemes of movement of the cargo cart is received.The analysis of the received decisions showed that at application of a running wheel with anelastic insert, dynamic factors at movement of the truck decreases. Dependences for determinationof dynamic forces which arise at movement of a running crane wheel taking into account rigidity ofan elastic ring which is inserted into a running wheel are received. The design and a technique ofcalculation of a running crane wheel with the vulcanized ring are offered.

Optimal design and experimental investigation of teeth connection joint on a filament wound composite transmission shaft

For limited weight reduction and avoidance of composite damage caused by the press mounting of the traditional metal teeth press-fit joint, a novel teeth connection joint technique of the fiber wound composite transmission shaft was investigated by theoretical analysis, finite element simulation, and experiment verification. Based on the mechanics of composite materials, the expressions of equilibrium torsional stiffness and static torsional strength were derived. According to the three-dimensional Chang-Chang failure criterion, its finite element model of progressive damage analysis was established through the user material subroutine. Applying the fast curing resin system, a typical sample of the structure was prepared through co-curing for the static torsional strength test, and its failure details of the fracture surface were observed by using a scanning electron microscope, which confirmed the validity of theoretical and numerical results. Based on this, the influence of the ply method and geometric characteristics on the failure strength was studied, and the optimal design of the joint was realized by the genetic algorithm. Compared with the press-fit joint, this structure reduces weight by 70 % under the same joint strength, which provides a new way for the connection of the composite transmission shaft.

Investigation of the Strength Parameters of Drilling Pumps during the Formation of Contact Stresses in Gears

The relevance of this research lies in the need to develop scientifically based methods for calculating and designing a transmission shaft with a hardened coating of increased strength and service life of a core drilling pump drive that can allow for a redistributing of resistance forces along the contact surfaces of the gear. This relevance is confirmed by the need to improve domestic methods for designing drive shafts of increased reliability which can ensure the development of frozen soils during deposits exploration. The purpose of the research is to increase the energy efficiency and service life of the high-loaded drive gear teeth of core drilling pump transmission shafts by justifying the critical loads and stresses in hardened gear coatings acting under intense wear of the contact surface with a broken contact symmetry. The criteria for the effective wear area with an uneven contact cross-section at the maximum bending moments of the transmission shaft of the drilling pump were justified and presented in the work. Additionally, the process of interaction of the transmission shaft gear teeth with the eccentric shaft gear at uneven axial torques was investigated. The effective power (Ng) of the gearing of the drive transmission shaft gear and the eccentric shaft gear, which characterizes the energy consumption of the drill bit depth stroke, was justified. This work also proposes a method of substantiating the technological and power parameters of the transmission shaft by using Legendre polynomials. A nomographic chart was developed for the determination of the dependence of the contact stress base cycles on the change in the load distribution factor and the contact spot deviation factor from the design axis λ.

Design and Development of Transmission and Braking Systems in Go-kart

We have completed this paper as per rulebook of kart racing competition. It involves 5 different departments which are Transmission, Roll cage, Brake, Steering, Wiring. This karting has no suspension and differential. It is generally recognized as small scale or economic way of motor sport. Transmission is the most important system in any vehicle. In go kart, there is no differential therefore we have to transmit power directly to shaft. Braking is a system which is used to stop transmitting power at instant. This involves stopping revolving transmission shaft by applying force on pedal.

Research on coupled vibrations of driveshaft–rear axle system based on nonlinear hybrid model

The transmission shaft–rear axle system is consisted of universal joint, hypoid gear pair, tapered roller bearing, and half shaft. In this article, as a combination of system dynamics and structure dynamics, a hybrid dynamic model of the bending–torsional–shaft vibration of the driveshaft main reducer was established to study its noise vibration harshness performance. Through dynamic frequency sweep analysis, it is found that the natural frequency of torsional vibration of the system is 53.96 Hz. Getting the natural frequency of the torsional vibration of the systems being 57 Hz by the bench tests and Adams simulations. The correctness of the nonlinear hybrid model of the driveshaft–rear axle system is proved. This research will be beneficial to the design, monitoring, and fault detection of the automobile transmission system.