Search results

This paper uses numerical methods to investigate the collision and skidding of rolling elements in a cageless ball bearing. This paper aims to analyse the effects of the rotational speed and number of rolling elements on the rolling element collision and skidding.

Based on Hertzian theory and tribological theory, the collision contact model of the rolling element was established. Based on the proposed model, the differential equations of motion of the two degrees of freedom rolling element were constructed. The fourth-order Adams algorithm solved the collision contact force between the rolling elements. The sliding velocity between the rolling element and the inner and outer races was calculated.

The collision frequency and slip of rolling elements can be reduced by increasing the rotational speed appropriately and reducing the number of rolling elements by one.

The developed model can reveal the collision and slip characteristics of the rolling elements for cageless bearings. This study can provide theoretical guidance for the design and manufacture of cageless ball bearings.

The purpose of this paper is to discuss the asymptotic models of different parts with a pitting fault in rolling bearings.

For rolling bearings with a pitting fault, the displacement deviation between raceways and rolling elements is usually considered to vary instantaneously. However, the deviation should change gradually. Based on this shortcoming, the variation rule and calculation method of the displacement deviation are explored. Asymptotic models of different parts with a pitting fault are discussed, respectively. Besides, rolling bearing systems have prominent fractional characteristics unconsidered in the traditional models. Therefore, fractional calculus is introduced into the modeling of rolling bearings. New dynamic asymptotic models of different parts with a pitting fault are proposed based on fractional damping. The numerical simulation is performed based on the proposed model, and the dynamic characteristics are analyzed through the bifurcation diagrams, trajectory diagrams and frequency spectrograms.

Compared with the model based on integral calculus, the proposed model can better reflect the periodic characteristics and fault characteristics of rolling bearings. Finally, the proposed model is verified by the experiment. The dynamic characteristics of rolling bearings at different rotating speeds are analyzed. The experimental results are consistent with the simulation results. Therefore, the proposed model is effective.

(1) The above models are idealized, i.e. the local pitting fault is treated as a rectangle. When a component comes into contact with the fault, the displacement deviation between the component and the fault component immediately releases if the component enters the fault area and restores if the component leaves. However, the displacement deviation should change gradually. Only when the component touches the fault bottom, the displacement deviation reaches the maximum. (2) Due to the material's memory and fluid viscoelasticity, rolling bearing systems exhibit significant fractional characteristics. However, the above models are all proposed based on integral calculus. Integral calculus has some local characteristics and is not suitable for describing historical dependent processes. Fractional calculus can better describe the essential characteristics of the system.

The efficient and economical use of natural resources is a big issue. Machine elements with a rolling contact are highly relevant because of their wide application in technical systems and a large production quantity. Innovative hard machining can reduce the friction and increase the fatigue strength of rolling element bearings. The purpose of this study is to focus on the surface properties of such parts.

A new model to predict bearing fatigue life is presented which takes compressive residual stresses in the bearing subsurface area into consideration. The investigated bearings were machined by the processes of hard turning, hard turning with subsequent deep rolling and a combination of hard turning and deep rolling (turn-rolling) in one process step. Changes in the residual stress state during bearing fatigue tests were investigated and the influence of residual stresses on the bearings fatigue life was researched.

Both combinations including the deep rolling process decrease the surface roughness and induce compressive residual stresses. As a result, the L₁₀ fatigue life of roller bearings was increased by the factor of 2.5. Owing to the developed models, this effect can be considered within the design process.

In the context of the research program “Resource efficient Machine Elements (SPP1551),” machining processes of bearings were investigated regarding the bearing fatigue life. By inducing beneficial residual stresses on the bearings’ subsurface area, the fatigue life could be increased. Thus higher resource efficiency was achieved. To increase the productivity, a combination of hard turning and deep rolling was evaluated.

ROLLING‐element bearings for aircraft turbine engine mainshaft applications are generally specified to be made of AISI M‐50 steel. Current aircraft turbine engine manufacturers' material specifications require a double vacuum melted (VIM‐VAR, for vacuum induction melt, vacuum arc smelt) AISI M‐50 steel for mainshaft bearings. With this material, ball bearing fatigue lives of nearly 100 times AFBMA predicted life have been obtained. Reduction in inclusion content, trace elements, and interstitial gas content is considered responsible for a major portion of this life advancement. AISI M‐50 also has the hot hardness and hardness retention ability for long‐life rolling‐element bearing operation at temperatures up to 588 K (600°F).

This paper sets out to develop a reliable analysis method based upon a low‐cost procedure to monitor the wear condition of low‐speed and heavily loaded rolling element bearing.

Special solvents for grease are invented and new test methods, including spectroscopy and ferrography of used grease, are developed to monitor the wear condition of a deferred bearing of ladle turret in continuous casting.

According to the analytical results, the service life of the ladle turret bearing in No. 1 continuous casting machine is extended to 14 years and significant expense is saved, which proved that it is feasible for grease analysis to be used in the condition monitoring of low speed and heavily loaded rolling element bearing, especially those deferrable bearings.

The fault mechanism of the huge bearing is not estimated.

One useful analysis method to monitor the wear condition of low speed and heavily loaded rolling element bearing is reported, and it can be used in other industrial fields.

This paper provides a way of studying condition monitoring of low‐speed and heavily loaded rolling element bearings.

The purpose of this study was to examine the effect of the magnetic field to the friction coefficient in the rolling element bearings which exists in electric motors.

To achieve this, the test rig was modified to adjust the density of the magnetic flux applied to the rolling ball element bearing. Experiments were carried out in the magnetic field from 0 to 7.5 mTesla at magnetic flux density range from 15, 40 and 65 N constant loads. Also, its rotary speed selected as 100, 200, 400, 800 to 1200 rpm, respectively.

In the majority of the experiments, it was observed that the magnetic field affected the friction coefficient. This influence reduced the friction coefficient in some experimental conditions and increased in some of them.

In the literature, there are very few studies on the effect of magnetic flux density to the friction coefficient in these rolling element bearings. It has become clear that more studies have been conducted on the effects of the magnetic field and/or electrical current on bearing damages and failures. This aspect is a study with specificity.

The purpose of this paper is to develop a mathematical model to determine optimum hollowness of a layered cylindrical hollow rolling element when it contacts with a flat plate.

In this work, finite element analysis (FEA) is carried out for different hollowness percentages ranging from 10 to 90 layered cylindrical hollow rolling elements corresponding to five standard NU 22 series bearings, i.e. 2206, 2210, 2215, 2220 and 2224. An experimental investigation is carried out for the NU 2206-layered cylindrical hollow roller bearing (LCHRB) at optimum hollowness under static loading condition.

Different parameters, such as bending stress (von Mises stress at the bore of the roller), von Mises stress, contact pressure and deflection in loaded contact are presented here.

The value of this research work is the development of a generalized solution that can be used to find the exact value of optimum hollowness for the layered cylindrical hollow rolling element, which is dependent on the yield strength of the material and the geometry of the roller under static loading condition. A static load test rig is designed to observe the load carrying capacity of the LCHRB as compared to the hollow cylindrical roller bearing.

The purpose of this paper is to contribute toward the modelling of the microscopic interaction between high‐frequency discharge bearing currents and rolling element bearings in the contact zone. It also aims to develop a reduced model that can serve as a starting point for further developments.

The complexity of an ideal comprehensive model is identified and analysed. Based thereon, a reduced model is developed.

The true system is highly complex and cannot be solved in a single‐step approach. The proposed reduced model allows the explanation of the melting of the bearing surfaces under the influence of the high‐frequency currents. It also provides a starting point for the development of an extended model.

The model excludes the dynamic rolling movement of the bearing. The development of the frosting and fluting observed on the bearing running surfaces can only be explained in parts.

The melting of the bearing race surface can be modelled and thereby explained. The proposed model forms a good basis for further work toward an extended model to explain the high‐frequency bearing current bearing damage mechanism.

The paper offers a method to model the microscopic interaction between high‐frequency discharge bearing currents and rolling element bearings in the contact zone. This phenomenon has not yet been modelled to this extent. Such a model – and the understanding brought forth from it – allows the reduction in the cost for safe operation of modern variable speed drive systems.

The objective of this paper is to provide a brief review of recent developments in the area of applications of ANN, Fuzzy Logic, and Wavelet Transform in fault diagnosis. The purpose of this work is to provide an approach for maintenance engineers for online fault diagnosis through the development of a machine condition‐monitoring system.

A detailed review of previous work carried out by several researchers and maintenance engineers in the area of machine‐fault signature‐analysis is performed. A hybrid expert system is developed using ANN, Fuzzy Logic and Wavelet Transform. A Knowledge Base (KB) is created with the help of fuzzy membership function. The triangular membership function is used for the generation of the knowledge base. The fuzzy‐BP approach is used successfully by using LR‐type fuzzy numbers of wavelet‐packet decomposition features.

The development of a hybrid system, with the use of LR‐type fuzzy numbers, ANN, Wavelets decomposition, and fuzzy logic is found. Results show that this approach can successfully diagnose the bearing condition and that accuracy is good compared with conventionally EBPNN‐based fault diagnosis.

The work presents a laboratory investigation carried out through an experimental set‐up for the study of mechanical faults, mainly related to the rolling element bearings.

The main contribution of the work has been the development of an expert system, which identifies the fault accurately online. The approaches can now be extended to the development of a fault diagnostics system for other mechanical faults such as gear fault, coupling fault, misalignment, looseness, and unbalance, etc.

The purpose of this article is to present a new application of pursuit‐based analysis for diagnosing rolling element bearing faults.

Intelligent diagnosis of rolling element bearing faults in rotating machinery involves the procedure of feature extraction using modern signal processing techniques and artificial intelligence technique‐based fault detection and identification. This paper presents a comparative study of both the basis and matching pursuits when applied to fault diagnosis of rolling element bearings using vibration analysis.

Fault features were extracted from vibration acceleration signals and subsequently fed to a feed forward neural network (FFNN) for classification. The classification rate and mean square error (MSE) were calculated to evaluate the performance of the intelligent diagnostic procedure. Results from the basis pursuit fault diagnosis procedure were compared with the classification result of a matching pursuit feature‐based diagnostic procedure. The comparison clearly illustrates that basis pursuit feature‐based fault diagnosis is significantly more accurate than matching pursuit feature‐based fault diagnosis in detecting these faults.

Intelligent diagnosis can reduce the reliance on experienced personnel to make expert judgements on the state of the integrity of machines. The proposed method has the potential to be extensively applied in various industrial scenarios, although this application concerned rolling element bearings only. The principles of the application are directly translatable to other parts of complex machinery.

This work presents a novel intelligent diagnosis strategy using pursuit features and feed forward neural networks. The value of the work is to ease the burden of making decisions on the integrity of plant through a manual program in condition monitoring and diagnostics particularly of complex pieces of plant.