Papers by Keyword: Roller Bearing

Abstract: This paper presents a new method, called data fitting method based on numerical results, to calculate the contact deformation between logarithmical crowned roller and raceway of rolling bearings. First, the contact deformations between logarithmically crowned roller and raceway are analyzed and numerically calculated according to influence coefficient method, and then a fitting formula based on the calculated contact deformations is obtained by means of multiple linear regression method. The formula includes the dimensions and logarithmic crowned parameters of bearing together with the load parameter, and can be used for fast calculation of contact deformation between logarithmical crowned roller and raceway in low and medium load conditions, so that the formula is suitable to efficiently analyze the dynamics characteristics of arbitrary logarithmic crowned rolling bearing.

Abstract: This paper studies the roller bearing fault diagnosis method with harmonic wavelet packet and Decision Tree-Support Vector Machine (DT-SVM). The harmonic wavelet packet possesses better performances for its box-shaped spectrum and unlimited subdivision compared with the conventional time-frequency feature exaction method. Firstly, the proposed method decomposes the roller bearing vibration signal with harmonic wavelet packet and extracts the feature energy with coefficients of each spectrum. After the feature energy is normalized, feature vector are available. Based on multi-level binary tree, this paper designs the multi-classification SVM model due to its superior nonlinear mapping capability. Three two-classifications are incorporated to diagnosis the roller bearing faults. Finally, the proposed method is illustrated with the vibration data from the roller bearing stand of electric engineering lab in case western reserve university. Experimental results illustrate the higher accuracy of the proposed method compared with conventional method.

Abstract: The life time of roller bearings can be increased by inducing compressive residual stresses in the subsurface region of the raceway. These stresses can be induced by overloading in the first numbers of revolution. It would be much more useful to create the surface integrity within the manufacturing process. In this paper a method is presented to improve the process chain from grinding and honing to hard turning and deep rolling. As a result the surface finish is comparable to ground bearings. Due to the deep rolling process the maximum compressive stresses can be induced to higher values and depth. For the evaluation of the surface roughness in hard turning process and the maximum compressive stresses in deep rolling empirical models based on D-optimal experimental design are used.

Abstract: In view of the characteristics of the non-stationary and multi-component AM-FM signals of vibration signals in the rolling element bearing, the generalized demodulation time-frequency analysis method is used for its fault diagnosis, overcoming the problem that the maximal overlap discrete wavelet packet transform (MODWPT) has no adaptability. First of all, the original vibration signal is took preprocessing by generalized Fourier; Then, using MODWPT to decompose signals after pretreatment and obtaining weights; Once again, the weights are carried out the inverse generalized Fourier transform to get the weights of the original signal; Finally, reconstructing principal component of the original signal to get the Hilbert instantaneous energy spectrum, roller bearing fault diagnoses based on the Hilbert instantaneous energy spectrum. The experimental results show that the method can effectively diagnose rolling bearing fault.

Abstract: This paper presents analysis of the influence of the laser hardening bearing 100CrMnSi6-4 steel on the selected properties: hardness and microstructure. The best process parameters were selected by: radiation impulse length λ = 1064 nm, different radiation power density and repetition frequency, as well as different variants of geometric surface texture. The process was carried out in a air environment, mainly in the field of ablation texturing with "thermal effect." As a result of laser hardening, the obtained martensitic microcrystalline microstructure in the superficial zone and in the middle of the hardened zone, and martensitic - bainite and bainite in the transition zone. The microstructures with high microhardness in the range of 580 850 HV0.01 are resulting from ultrafast phase transformation occurring during the crystallization of the Fe-C-Cr-Mn-Si alloy from the liquid phase. The microstructures are in the area directly adjacent to the lubricant microchannels produced during laser texturing. It was clearly noticeable on highly fragmented microstructure and confirmed by increased microhardness. There were no micro-cracks on the surface layer, what promises great technological opportunities. The results are promising and may have a significant impact on improving the tribological associations friction pair: roller - large-size track roller bearing.

Abstract: This paper presents a fault diagnosis method of roller bearings based on intrinsic mode function (IMF) kurtosis and support vector machine (SVM). In order to improve the performance of kurtosis under strong levels of background noise, the empirical mode decomposition (EMD) method is used to decompose the bearing vibration signals into a number of IMFs. The IMF kurtosis is then calculated because of its sensitivity of impulses caused by faults. Subsequently, the IMF kurtosis values are treated as fault feature vectors and input into SVM for fault classification. The experimental results show the effectiveness of the proposed approach in roller bearing fault diagnosis.

Abstract: Hilbert-Huang transform (HHT) is a very effective time-frequency analysis method, but it has some disadvantages. For example, the dense modal signal cannot be decomposed completely, and redundancy intrinsic mode functions (IMFs) are easy emerging at low frequency, which will cause the distortion of the processing results. In view of the above questions, this study applies the wavelet packet transform for denoising before HHT for improving the dense modal problem, and applies the correlation coefficient method to eliminate the redundancy IMF. The fault diagnostic case of roller bearing shows the effectiveness of the proposed method.

Abstract: In roller bearing reformation of a medium scale mill, the micro-dimensional theory of mill is adopted. A new space self-alignment roll system is developed, including a divided base. This ensures the statically determinate of the mill under both light duty and heavy duty conditions. So the load distribution of roller bearing can be improved, and the bearing will have a long life. Since the new roll system began to run, it is in a fine motion until now. The roller bearing has exceeded its specified life. The design aim of service longevity is realized.

Abstract: Causes are investigated on earlier failures of the bearings for China railway freight cars with tilting bogie. Through dissembling failure objects, checking manufacturing qualities and calculating rolling contact fatigue (RCF) stresses, it reveals that RCF plays a key role to the bearing failures. Design mismatch of the RCF stresses between outer and inner rings is main cause of the earlier failures of bearings. It is further verified that the present earlier failures of the bearings on the cars with tilting bogie than others on cars without tilting bogie is a reasonable phenomenon, because the wheelsets on the cars with the tilting are subjected to more severe loads. In addition, material manufacturing flaws, inhomogeneous force transferring circumstances, and seal leak may play an aided role to speed up the bearings failures.

Abstract: Causes are investigated on the earlier failures of the bearings for China railway freight cars with radial bogie. Through observing failure objects, checking manufacturing quality, and calculating rolling contact fatigue (RCF) stresses, it reveals that poor manufacturing quality of bearing outer ring plays a key role to the earlier failures and, in addition, mismatch design of RCF stresses between the outer ring and the inner ring acts as an aid actor. Checks verify that surface and core of the outer ring have lower hardness values than requirements; seldom micro-structures, i.e. black-white bands with thickness of around 0.6 to 1.3 mm, appear in the carburized layer of the bearing outer ring; the white part is needle like martensites with higher hardness values, while the black part is pearlites with lower hardness values; and more contingently, crack like manufacturing flaws may appear in the carburized layer with equiaxed grains of ferrites having lower hardness values are around the flaws. RCF values of the outer ring are much larger than that of the inner ring. But the equivalent RCF stress on the present car with radial bogie is lower than that on other cars. This indicates that main cases of the present earlier failures are due the bearings themselves other than the cars.