Flexible Shaft Couplings Research Articles

Vyladenie mechanickej sústavy pohonu piestového kompresora z hľadiska veľkosti torzného kmitania

One of possible ways to change the amount of compressed air delivered by a piston compressor is to change its operating speed. However, it can cause an improper tuning of the mechanical system of piston compressor drive in terms of torsional dynamics. In order to avoid excessive torsional vibration, a suitable pneumatic flexible shaft coupling can be used in the system. An optimum air pressure value in a pneumatic coupling was determined experimentally for three various operating modes of an experimental mechanical system of piston compressor drive.

Pneumatické pružné hriadeľové spojky v pohonoch mechanických sústav

The article presents a newly developed pneumatic flexible shaft coupling with hose flexible element usable, among other applications, in drives of mechanical systems. The presented coupling uses a hose-shaped flexible element winding between the supporting surfaces of coupling’s driving and driven hub. As the torque transfer is ensured with compressed air, the torsional stiffness of coupling can be adapted to actual operating parameters (rotational speed) with change or air pressure inside the flexible elements. This makes the presented coupling suitable for semi-active torsional vibration control. A patent was also granted for the presented coupling design. The design of hose-shaped element enables reliable sealing of compression volume and it is also easy to assembly and dismantle.

Novel Design of Variable Stiffness Pneumatic Flexible Shaft Coupling: Determining the Mathematical-Physical Model and Potential Benefits

Presently, mechanical system vibroisolation is becoming increasingly important. One of the new approaches is semi-active vibroisolation using elements capable of changing a selected mechanical property. These include, among others, pneumatic flexible shaft couplings capable of changing torsional stiffness during operation. The main goal of the article is to examine the potential advantages of a newly patented pneumatic coupling over a current type with the same pneumatic element arrangement. For comparison, parameters determinable from static load characteristics were selected. These parameters are maximum twist angle and torque, average torsional stiffness, and the percentage of torque transmitted by the bellows rubber shell. In all cases, the new coupling had better properties. Since the prototype of the new coupling has not yet been produced, its parameters were determined from its mathematical-physical model. The article contains a full procedure to obtain the static load characteristic of a new coupling type, beginning with the determination of air bellows force/height and volume/height characteristics, then optimum sizes of coupling with regards to the operating range of elements, the dependency of element height on the coupling’s twist angle, and finally the computation of the static load characteristic considering isothermal gas compression. The presented procedure can be applied to any pneumatic bellows where the force/height characteristics of different pressures are given.

Optimization and prediction of CBN tool life sustainability during AA1100 CNC turning by response surface methodology

The aluminium alloy (AA1100) was familiar with automotive flexible shaft coupling applications due to its high strength, good machinability, and superior thermal and resistance to corrosion characteristics. Machining tool life drives the prominent role for deciding the product quality (machining) act aims to productivity target with zero interruptions. The novelty of this present investigation is the focus on increasing tool life during the complexity of CNC turning operation for AA1100 alloy by using CBN coated insert tool with varied input parameters of spindle speed (SS), feed rate (f), and depth of cut (DOC). Design of experiment (L16), analysis of variance (ANOVA) statistical system adopted with response surface methodology (RSM) is implemented for experimental analysis. The turning input parameters of SS, f and DOC are considered as factors and its SS (900, 1100, 1300, and 1500 rpm), f (0.1, 0.15, 0.2, and 0.25), and DOC (0.1, 0.2, 0.3, and 0.4 mm) values are treated as levels. The investigational analysis was made with the ANOVA technique and the desirability of high tool life with input turning parameters was optimized by RSM, and sample no 11/16 was predicted as high tool life and performed with extended working hours compared to other samples. The RSM optimized best turning parameter combinations are 0.1 mm DOC, 0.2mm/rev to 0.25mm/rev f, and 1300 rpm–1500 rpm SS, facilitating a higher tool life of more than 20min.

NEW DESIGNS OF VARIABLE STIFFNESS COUPLINGS

Flexible couplings are widely used in mechanical drives of transport and other machines. A fundamental function of flexible shaft couplings regarding torsional vibration is the optimum tuning of torsional oscillating mechanical systems. At the authors’ workplace, the focus is on the research and design of pneumatic couplings, where the torque is transmitted mainly by compressed gas (air) in their pneumatic flexible elements. The primary advantage of these couplings is that their mechanical properties can be quickly and effectively adjusted, especially the dynamic torsional stiffness, by air pressure change directly while the mechanical system is running. This allows us “to tune” the properties of the pneumatic coupling according to the current parameters of the machine drive to avoid resonance and minimize torsional vibration. Therefore, we tend to refer to them as “pneumatic tuners of torsional vibration”. This paper aims to present two new types of these “pneumatic tuners” that were recently granted patent protections, namely “Pneumatic flexible shaft coupling with hose flexible element” and “Drum pneumatic flexible shaft coupling”. Because these pneumatic tuners are not in practical use yet, this paper describes only their design and supposed benefits.

CONTINUOUS TUNING OF SHIP PROPULSION SYSTEM BY MEANS OF PNEUMATIC TUNER OF TORSIONAL OSCILLATION

Mechanical system drives consist of driving machines and gearing mechanisms interconnected by shafts and couplings. In terms of dynamics it is possible to say that every driving mechanism is able to oscillate. Especially piston devices can create excessive torsional oscillation, vibrations, as well as noise. Important task of a designer is to reduce torsional oscillation in mechanical systems. Presently this problem is mainly solved by the flexible shaft couplings that are selected with regard to the dynamic properties of the given system. It means that every torsional oscillating mechanical system needs to be suitably tuned. The aim of this paper is to present the possibilities of controlling of dangerous torsional oscillations of the mechanical systems by the means of new method, i.e. its optimal tuning by means of the pneumatic coupling with self-regulation, which were developed by us.

Dynamic Behavior Analysis of the Winding Rotor with Structural Coupling and Time-Frequency Varying Parameters: Simulation and Measurement

To satisfy the requirements of high speed, large capacity and constant winding, a textile winding rotor needs to work in a wide rotation speed range and frequently pass through critical speed points. Thus, the winding rotor adopts the flexible long shaft coupling structure and flexible support with rubber O-rings. This kind of rotor has a multi-coupling structure and frequency-dependent parameters characteristics, especially representative and universal in the dynamic analysis method of the high-speed rotor. In this paper, an approach was proposed to investigate the dynamic behavior of the winding rotor considering the flexible coupling and frequency-dependent supporting parameters. Firstly, a dynamic model of the winding rotor was established by using a Timoshenko beam element. Its dynamic behaviors were simulated by considering the time-varying rotation speed and the frequency-dependent parameters of flexible support. Secondly, a non-contact measuring device was developed for measuring the vibration displacement of the winding rotor in three different speed-up times. Finally, based on simulation and measurement data, how flexible support parameters and the speed-up time affect the winding rotor passing through the critical speed point of the rotor smoothly is revealed. The methods and findings reported here can be used for theoretical and experimental vibration analysis of other types of high-speed flexible rotors.

Electronic Constant Twist Angle Control System Suitable for Torsional Vibration Tuning of Propulsion Systems

Currently, great emphasis on reducing energy consumption and harmful emissions of internal combustion engines is placed. Current control technology allows us to customize the operating mode according to the currently required output parameters, while the tuning of mechanical systems in terms of torsional vibration is often ignored. This article deals with a semi-active torsional vibroisolation system using pneumatic flexible shaft coupling with constant twist angle control. This system is suitable, as it is specially designed, for the tuning of mechanical systems where the load torque has fan characteristics (fans, ship propellers, pumps). The main goal of this research is to verify the ability of an electronic control system developed by us to maintain the pre-set constant twist angle of the used pneumatic flexible shaft coupling during operation. The constant twist angle control function was tested on a laboratory torsional oscillating mechanical system. Presented results show that the proposed electronic control system meets the requirements for its function, namely that it can achieve, sufficiently accurately and quickly, the desired constant twist angle of the pneumatic flexible shaft coupling. It is possible to assume that the presented system will increase the technical level of the equipment where it will be applied.

Influence of Elastic Element Design Parameters on Buckling Effect for Different „Periflex“ Shaft Couplings

In the article has made research into the buckling resistance of flexible shaft coupling with toroidal elastic element. It is made a comparison between four different designs of “Periflex” coupling, the received data are preparing and systemizing. The obtained data show how the con-struction parameters of the elastic element influence to the critical buckling torque. The data ob-tained can be used to design a shaft coupler that will transmission a higher torque with used of smaller quantity of material.

Comparation of the impact of selected technical gases on properties of a pneumatic flexible coupling

An important part of the oscillating mechanical drives are flexible shaft couplings. The special use of the pneumatic flexible coupling is possibility to serve as mechanical drives tuners. Being examined in tuners mechanical drives there is also a research focus on the impact of industrial gases on the change of dynamic characteristics of pneumatic couplings. The paper investigates five different industrial gases, namely: air, helium (He-4.6), a mixture of propane and butane gas (C3H8+C4H10), argon (Ar) and nitrogen (N2) to see how these gases affect the dynamic characteristics of pneumatic flexible shaft coupling with marking 4-2/70 T-C.

Transient Torsional Analysis of a Belt Conveyor Drive with Pneumatic Flexible Shaft Coupling

Abstract Development and application of pneumatic flexible shaft couplings have been in the center of our department research activities for a long time. These couplings are able to change torsional stiffness by changing pressure in their flexible elements – air bellows. Until now we have dealt with the use of pneumatic flexible shaft couplings for tuning mechanical systems working with periodically alternating load torque at steady state. Some mechanical systems, however, operate with a static load torque at constant speed (e.g. hoists, elevators, etc.), where it is necessary to consider the suitability of shaft coupling in terms of load torque at transient conditions (run-up and braking). Therefore we decided to analyze the use of pneumatic flexible shaft couplings also in this type of mechanical systems on an example of conveyor belt drive.

Characteristics of Pneumatic Tuners of Torsional Oscillation as a Result of Patent Activity

Abstract Mechanical systems with combustion engines, compressors, pumps and fans, can be characterized as torsional oscillating mechanical systems (TOMS). It is therefore necessary to control their dangerous torsional vibrations. It was confirmed that dangerous torsional vibration can be reduced to acceptable level by an appropriate adjustment, respectively by tuning the TOMS. According to several authors, the most appropriate way of system tuning is application of suitable flexible element, which is flexible shaft coupling. It turned out that one of the types of shaft couplings, which are particularly suited to meeting this objective are pneumatic flexible shaft couplings, to act as so-called pneumatic tuners of torsional oscillations. The issue of research and development of pneumatic tuners of torsional oscillations, among other things is, long-term in the focus of the author. The existence of tuners creates the opportunity to develop new ways of tuning torsional oscillating mechanical systems. The author of the scientific article will focus on the characteristics of developed pneumatic tuners of torsional oscillation in terms of their design, construction, function, significance advantages and conditions imposed on pneumatic tuners based on the results of his patent activity. Simultaneously provides information about the characteristic properties of pneumatic tuners of torsional oscillations in the general design.

TORSIONAL NATURAL FREQUENCY TUNING BY MEANS OF PNEUMATIC FLEXIBLE SHAFT COUPLINGS

This article deals with the use of pneumatic flexible shaft couplings as device for tuning torsional natural frequencies of mechanical systems. These couplings are using air bellows as flexible elements. Their torsional stiffness can be changed by air pressure change, the natural frequencies of whole mechanical system may be adjusted on desired value.

The Measures for Reducing of Truck Bodybuilding Vibrations

This article is focused on finding the most appropriate solution for eliminating vibrations that pose harmful influences in mechanical systems. To find this solution, the kinetic equations were generated from dynamical model of truck bodybuilding. The block diagram for natural frequencies calculation was made up out of these equations. Two solutions were suggested – to place flexible shaft coupling between high pressure pump and Power Take off and to connect the pump and Power Take Off directly with shaft. It is important to note that vibrations emerging may be reduced more effectively by using of the former solution – flexible shaft coupling.

Equivalent stress and strain distribution in helical compression springs subjected to bending

Stress and strain analyses of helical compression springs have long been an important factor in machine design. Designs routinely incorporate helical springs, either tensile or compressive, to transmit uniaxial loads. Recently, multiaxial loading has become more commonplace, with devices such as flexible shaft couplings. Through static mechanical experiments, coupled with finite element analysis, the equivalent stress distribution in uniformly deformed springs is developed based solely upon visual inspection of the bent helix. Equivalent strains are also approximated, with satisfactory correlation between predicted and observed strains. In situations that involve space constraints, stress monitoring equipment may be intrusive; as such, approximations have been based solely on visual inspection of the deformed helix.

Practical torsional analysis and coupling selection for multi-machine complex process rotating equipment trains

A multi-machine train consists of several complex shafts, rotors, or crankshafts and relatively flexible shaft extensions and couplings. It may also include gear unit, clutch, or flywheel. As connected machines function as spring systems in series, the potential exists for torsional resonance and torsional fatigue damage. Couplings are often modified to tune the overall system. Practical torsional analysis method, useful recommendations, and optimum coupling selection are addressed. Case studies for rigid connection (flange-to-flange connection without coupling), high torsional stiffness coupling, and flexible coupling are also investigated.

Optimal Tuning Method of Ships System by Means of Pneumatic Tuner of Torsional Oscillations

Drives of mechanical systems consist of driving machines and gearing mechanisms connected together by means of shafts and couplings. With regard to the dynamics it is possible to say that every driving mechanism is a system, which is able to oscillate. Especially piston machines are able to create dangerous and harmful torsional oscillations, vibrations, as well as noisiness.Important task of designer is reduction of torsional oscillations in mechanical system. Presently this problem is solved predominately with a suitable adjustment of dynamic properties of flexible shaft couplings with regard to the dynamic properties of given system. It means that every torsionally oscillating mechanical system needs to be tuned suitably. The main purpose of this paper is presentation of controlling possibilities of dangerous torsional oscillations of mechanical systems by means of a new method, i.e. its optimal tuning by means of pneumatic coupling with self-regulation, developed by us.

Shaft coupling model-based prognostics enhanced by vibration diagnostics

Flexible power transmission couplings are a vital part in the drive train of rotorcraft, conventional aircraft and other land, sea and marine propulsion systems. These components are generally subject to high torque, rotational speeds and temperatures, which result in high static and dynamic loads that make them susceptible to degradation and failure. Additionally, couplings can experience accelerated failures, mainly driven by high cyclic stresses induced by extreme shaft misalignment and secondary causes such as improper assembly, fastener damage and lubricant loss. Damage to other drive train components can also lead to increased vibration and misalignment which, in turn, induces coupling failure. As with many complex systems, the service life of a shaft is randomly distributed and can be modelled by a stochastic deterioration process that allows approximation of remaining useful life (RUL). However, in such an approach, knowledge of actual shaft damage (ie current crack size) is still required. In practical health monitoring applications, actual damage is estimated via inference, as it is nearly impossible to be measured directly. To address this critical need, a shaft and shaft coupling prognostics and health management (PHM) system was developed that integrates vibration diagnostics, finite element stress analysis and material fatigue modelling to predict RUL of helicopter drive shafts and flexible shaft couplings. This modelling and prediction approach was developed and validated against actual sub-scale failure testing that included the requisite measurement of the ‘ground truth’ damage level. Data from a scaled drive shaft/ coupling test stand was used to validate the approach. The results indicated a cumulative prognostic accuracy of 80% over the last 25 minutes of the coupling life. Vibration-based diagnostics helped to improve the accuracy to over 95% once a crack had initiated and been detected over the last five minutes of coupling life. The application of these technologies will establish an economical, safe and effective maintenance-scheduling regime for helicopter shafts and couplings by scheduling maintenance towards the end of actual component life, increasing availability by preventing unscheduled maintenance and reducing inspections.