Eccentric Mechanisms Research Articles

Loading modes control for testing tracked tractor transmission

BACKGROUND: Confirmation of the operability of agricultural tractor transmission units is obtained by machinery manufacturers on the basis of bench tests. The development of technical solutions for test rigs for transmissions and load control systems with an approximation to operational modes is a relevant technical task.
 AIMS: Development of technical solutions of test rigs for testing transmissions of tracked tractors and load management systems based on the analysis of operational loading of transmissions.
 METHODS: An analysis of the operational loading of the transmissions of the DT and VT series tracked agricultural tractors was performed, based on the results of which the technical solutions for loading devices of test rigs were developed that allow reproducing loading modes with parameters statistically equivalent to the operational loading modes on the tested transmissions.
 RESULTS: A technical solution is proposed for a test rig with a hydro-closed power circuit, in which a hydraulic loader with a rotating spool, by lifting and relieving the pressure of the working fluid in the pressure lines, forms a load on the parts of the tested transmission in accordance with the operational loading mode obtained as a result of preliminary analysis. A technical solution for a test rig with eccentric loaders is also proposed, in which a constant level of load on the tested transmission is created by hydraulic loaders acting on the track chains, and variable loads are formed by eccentric mechanisms and disturbances from the track chains rewinding.
 CONCLUSIONS: The practical value of the study lies in the possibility of using the proposed technical solutions of test rigs to conduct tests of tracked tractor transmissions with an increase in the degree of reliability of their results due to the approximation of the transmission loading conditions on the test rigs to the operational ones.

Estimation of durability of carrier shafts in eccentric mechanisms

This paper has suggested a procedure to analyze durability of supporting shafts in eccentric mechanisms based on finite-element modeling. When conducting the analysis, the steady movement of the mechanism is investigated. The analysis of durability is based on the model of additive accumulation of damage. The shaft stress assessment is carried out based on the finite-element modeling of the mechanism that operates under a steady mode at working frequencies that are closest to the critical ones. Following the detection of stress concentrators and the most stressed shaft regions, an analysis of the characteristic cycle of loading is performed. After reducing a loading cycle to a series of symmetric cycles, the shaft damage assessment at each cycle is performed and its resource is estimated. Based on the proposed method, we have analyzed durability of a carrier shaft in the centrifugal-gyratory ore mill of link type. A simplified estimated model has been built based on the mechanical model in order to improve efficiency and performance of the finite-element calculation. The model of ore movement in grinding chambers under a steady motion mode has been proposed. We have built the Campbell’s diagrams for oscillations of the system and have established that the mill’s mechanism is not part of the resonance at the working frequency of excitation. The region of mechanical stresses concentration and the region of maximal mechanical stresses in the mill shaft have been identified. The shaft operating conditions have been analyzed and a value for the shaft material’s endurance limit in the zone of greatest stresses has been calculated. We have built a characteristic cycle of the mill shaft loading under a steady mode of operation, which consists of 16 sections. Each section has been reduced to a symmetric cycle, which has made it possible to calculate shaft damage at each section of the cycle and over the entire load cycle in general. Application of the additive damage accumulation procedure has made it possible to estimate the resource of a mill shaft. The proposed methodology for estimating durability of the carrier shaft could be used to analyze the resource of various mining and processing mechanisms, light industry equipment, and vibration generators

On a stake-out: Mycobacterial small RNA identification and regulation.

Persistence of mycobacteria in the hostile environment of human macrophage is pivotal for its successful pathogenesis. Rapid adaptation to diverse stresses is the key aspect for their survival in the host cells. A range of heterogeneous mechanisms operate in bacteria to retaliate stress conditions. Small RNAs (sRNA) have been implicated in many of those mechanisms in either a single or multiple regulatory networks to post-transcriptionally modulate bacterial gene expression. Although small RNA profiling in mycobacteria by advanced technologies like deep sequencing, tilling microarray etc. have identified hundreds of sRNA, however, a handful of those small RNAs have been unearthed with precise regulatory mechanism. Extensive investigations on sRNA-mediated gene regulations in eubacteria like Escherichia coli revealed the existence of a plethora of distinctive sRNA mechanisms e.g. base pairing, protein sequestration, RNA decoy etc. Increasing studies on mycobacterial sRNA also discovered several eccentric mechanisms where sRNAs act at the posttranscriptional stage to either activate or repress target gene expression that lead to promote mycobacterial survival in stresses. Several intrinsic features like high GC content, absence of any homologue of abundant RNA chaperones, Hfq and ProQ, isolate sRNA mechanisms of mycobacteria from that of other bacteria. An insightful approach has been taken in this review to describe sRNA identification and its regulations in mycobacterial species especially in Mycobacterium tuberculosis.

Research of working capacity of pulsed variable-speed drives

The paper presents the results of experimental researches of the basic working capacity characteristics of pulsed variable-speed drives - gear ratio, efficiency factor, and reliability of the eccentric free-wheel mechanisms When conducting research, the main working capacity parameters of the pulsed variable-speed drive (independent factors) changed according to the design of experiment in the range: the load applied to the output shaft was from 250 to 2.750 N·m; adjustable gear ratio - from 20 to 180. It was established that the reliability of the eccentric free-wheel mechanisms is guaranteed when making mechanisms of 100Cr6 steel with hardness not lower than HRCЭ 58…62 with a module of at least 0.75 mm. It was shown that the yield surface, which characterizes the change in the gear ratio of the pulsed variable-speed drive, can be described by a model using first-order polynomials. It was established that with increasing load, a slight increase (at 1.0...9.9%) occurs in the adjusted gear ratio, which has a character close to linear. It was concluded that with an increase in load, the increase in efficiency factor is non-linear and equals 1.8...2.6 times, an increase in the gear ratio causes its linear decrease by 1.13...1.64 times in the dependence close to a linear one. Empirical dependences are obtained to determine the magnitude of the gear ratio and efficiency factor.

Reliability research of eccentric freewheel mechanisms of friction type

The article contains a research of the influence of design parameters (material, the jamming angle) on operation reliability of eccentric friction-type freewheel mechanisms using calculated and experimental techniques. As the investigated factor, the lower limit of the confidence interval for the time between failures is adopted It is shown that the necessary reliability of the eccentric freewheel mechanisms is ensured when jamming angles are 8–10° and when their elements are made of material 100Cr6. The reliability of such mechanisms is 1.7 times higher than of roller free-wheel mechanisms. The results of the research can be used when predicting the reliability of the mechanisms in the drives of machines.

Torsional rigidity of freewheel mechanisms in drives

The torsional rigidity of roller and eccentric frictional and nonfrictional freewheel mechanisms is compared.

Operational reliability of free-wheel mechanisms in a pulsed variable-speed drive

The operational reliability of eccentric free-wheel mechanisms (of both frictional and nonfrictional types) in a pulsed variable-speed drive is studied by calculation and experiment. The grades of steel ensuring the longest life of such mechanisms in pulsed loading are determined.

Синтез мелкомодульных храповых зубьев эксцентриковых механизмов свободного хода нефрикционного типа

Синтез мелкомодульных храповых зубьев эксцентриковых механизмов свободного хода нефрикционного типа

Assessment criteria of engineering level of free-wheel clutch mechanisms

Coefficients for the assessment of technical and economic properties of free-wheel clutch mechanisms for drives of agricultural machinery were suggested. Comparative evaluation of engineering level of non-frictional type eccentric mechanisms and mechanisms with sprags was carried out.

Influence of the geometric properties of an external housing on its stress-strain state

The strain and stress distributions in the external housing of free-running nonfrictional eccentric mechanisms are investigated by the finite-element method. Formulas describing the influence of the housing’s geometric parameters on its stress-strain state are derived.

Muskelverletzungen: Diagnostik und Behandlungen

Muscle injuries are common in sports. They are usually caused by either acute (mostly eccentric mechanisms) or chronic overloading with a lack of muscle coordination. They present in clinical practice as bruises and muscle sprains. Due to the rigours of a modern society and the high economic cost of time off work, an effective treatment needs to be employed. The key to an optimised therapy rests in the appropriate timing between immobilisation and mobilisation. The interval to muscle repair might be shortened by certain adjuvant therapies. In doing so, it is important that no physiological phases of wound healing are overlooked. Muscle healing can be accelerated by externally induced higher metabolic turnover. Surgical therapy is sometimes necessary in selected cases and in serious injuries.

Kinematic characteristics of pulsed speed regulators

Experimental kinematic characteristics are presented for pulsed speed regulators with eccentric free-wheel clutch mechanisms of different designs. Formulas have been obtained for the change in transmission ratios of pulsed speed regulators under load.

Design of integrated eccentric mechanisms and exact constraint fixtures for micron-level repeatability and accuracy

This paper introduces an eccentric ball–shaft kinematic fixture which is capable of six-axis alignment corrections and thereby improved fixture accuracy. A kinematic model for an eccentric ball–shaft fixture was developed and used to simulate the effect of: (1) tolerances, (2) actuation errors and (3) bearing run out on fixture accuracy. The kinematic model and these errors were used to determine when it is practical to use the technology to improve fixture accuracy. The kinematic model was used to design a prototype whose performance matched the kinematic model to within 10%. Diagnosis of experimental data indicates that differences between theory and data may be explained through statistical analysis of error sources. The stabilized 1 σ repeatability of the prototype was measured at better than 1.9 μm/3.6 μrad.

Nomograms for the correction of the adjustment tables of roll grinding lathes

Fig. i. Plan of the formation of a cut in the body profile by a thick abrasive wheel. Roll grinding lathes with eccentric mechanisms for profiling are widely used for grinding rolls for sheet rolling mills and calender roils for paper machines. Most commonly used are the models 3415E, 3415K, 3417V, KhSH5-08, and KhSH5-09 with a standard mechanism for profiling which is characterized by high accuracy and is standard. On these lathes it is possible to grind rolls with a body length up to 4500 mm and a diameter up to 1800 mm with parabolic, sinusoidal, and round profiles. At the same time the accuracy in the form of the profile is 0.02-0.03 mm.

応力波形の疲労強度に及ぼす影響

In this paper, the effects of forms of stress waves on the fatigue strength are investigated, using three low carbon steels. The forms of stress waves adopted are sinusoidal and nonsinusoidal ones.The fatigue tests were made in plane bending and torsion under completely and partly reversed stresses. The testing machines used were the Upton-Lewis plane bending fatigue testing machine and the Upton-Lewis torsion fatigue testing machine. The eccentric mechanisms of these machines were modified so that they might produce expected forms of stress waves. The driving speed was 100 to 200cpm.The test results were: (1) the fatigue lives at the cyclic nonsinusoidal waves, shown in Fig. 1, seem to be about the same as those at the cyclic sinusoidal waves, (2) the fatigue lives at the cyclic twin waves, shown in Fig. 2, are different from those at the cyclic sinusoidal waves, that is, the secondary wave in the twin wave has an effect on the fatigue life depending on the stress magnitude, and (3) the changes of the stress amplitude in the process of fatigue were similar for the all forms of cyclic stress waves under the constant strain amplitude.