This paper briefly introduces the mechanism of gear failure, the main vibration modes and frequency characteristics of gear vibration signals, and analyzes the time-frequency characteristics of gear failure vibration signals. The ensemble empirical mode decomposition(EEMD) and cyclic auto-correlation function(CAF) are used to extract the fault features of gears and SVM-HMM model is used to diagnose the faults of gears. The experimental results show that both the EEMD and CAF signal processing methods can be used to extract the fault feature signals of gears. In comparison, CAF based method has a higher recognition rate between tooth surface wear and pitting, between broken tooth and root crack.

According to the rationale of resonance demodulation of vibration signals of rolling bearing faults, the paper probes into aperiodic vibration signals of rolling bearing faults with variable speed, and the changing rotation rate-related resonance frequency of rolling bearing. An experimental scheme is designed for vibration signals of rolling bearing with variable speed. A rolling bearing fault model is created where frequency conversion is the modulation signal and the frequency conversion resonance attenuation signal is the carrier. A variable speed rolling bearing fault diagnostic method is proposed basing on EHMM (as the fault feature extraction method) and CHMM (as the fault mode recognition method). The feasibility of the method is verified by experiments.

A new model of improved friction is proposed considering the bearing oil film force and nonlinear rubbing force and based on dual - span rotor system. The nonlinear dynamic equations of the two-span rotor system under the influence of nonlinear oil film force and rubbing force are established. The dynamic characteristics of the double-disk rub-impact fault of the double-span rotor system were analyzed by numerical simulation method. Through the contrast analysis of the linear friction model and the improved model of the impact force, it is found that the dynamic response of the improved model is more complex and more realistic to reflect the rubbing fault.

It is difficult to diagnose the faults of diesel engines with traditional method, to address this issue, a high precision diesel engine fault diagnosis system based on the embedded ARM platform was designed. An improved artificial bee colony algorithm (ABC) was proposed, which was used to optimize the training fault samples with back propagation (BP) artificial neural networks algorithm for obtaining a set of fault model parameters with high diagnosis precision. The fault type was obtained by making calculations with these parameters on the ARM platform. Experiment results show that the improved ABC algorithm can overcome the shortcoming of easily falling into local optimum of the basic ABC algorithm, helping to increase the accuracy of fault diagnosis results.

Faced with fierce competition and various customer demands in marketplaces, manufacturers need to determine the appropriate settings of statistical quality control criterion for dynamic batches composed of similar products with different customer preferences so that the best customer satisfaction and minimized production cost can be obtained. To achieve this, functional models of dynamic batch generating and customer preferences related to quality control criterion need to be developed. In this paper, a dynamic statistical quality control model considering customer preferences is suggested to solve such statistical quality control problems. Production batches with appropriate quality control criterion are formed regarding various customer preferences, and the small sample capacity for applying SPC is considered. Our application results in special steel product process quality designs which involves various customer preferences is presented to demonstrate the effectiveness of the proposed method. Introduction.

为改善某型驱动桥半轴的售后故障率,对现有产品进行台架试验验证.计算分析半轴的应力情况,按照锻钢的S-N曲线经验公式,预估半轴扭转的疲劳极限,进行半轴改进的设计校核.将改进后的半轴再次进行台架试验验证,改进效果满足预期要求,并使用试验结果修正半轴扭转的S-N曲线使之更加精确.

By taking the rotor test-bed as the research object, the new comprehensive models of multi-rotor-bearing-coupling system with looseness fault are built in consideration of the factors of nonlinear oil-film force, shaft coupling, looseness in different pedestals, et al. The dynamic equations of the rotor system and it with looseness in different pedestals is deduced and presented. The dynamic responses and fault characteristics of the systems are analyzed by numerical method. It provides a basic foundation for numerical simulation and further research on the nonlinear vibration characteristics of the system.

The dynamic model of nonlinear stiffness rotor-bearing system with pedestal looseness fault was set up, taking the linearity and cube item as the physics nonlinear factors. The periodic solution of system was analyzed by continuation-shooting algorithm for periodic solution of nonlinear non-autonomous system, and the stability of system periodic motion and unsteady law are discussed by Floquet theory. The unstable form of it is Hopf bifurcation. In the region of critical rotate speed, the main motion of the system is periodic-4; and it of ultra critical rotate speed, the main motion of the system is periodic-3 and chaotic motion. The conclusions provide theoretic basis reference for the fault diagnosis of the rotor-bearing system.

Based on the coupling model of nonlinear oil-film force and nonlinear seal fluid force, a nonlinear dynamic model of rotor system with rub-impact fault is set up. The dynamic characteristics of the system were studied with numerical simulation and the effects of airflow excited force, rubbing gap and stiffness parameters on movement characteristics of the rotor were analyzed. The results indicate that the airflow excited force can significantly restrain the stability and amplitude of rubbing rotor. The less rubbing gap and larger rubbing stiffness are in favor of the stability of the system.

The nonlinear dynamic model of rotor-bearing-seal system with crack in shaft is set up based on the coupling model of nonlinear oil-film force and Muszyska's nonlinear seal fluid force. The dynamic vibration characteristics of the rotor-bearing-seal system and the effects of physical and structural parameters of labyrinth seal and crack fault on movement character of the rotor were analyzed. The increases of seal length, seal pressure differential, seal radius and axial velocity are in favor of the stability of the system, and it of seal gap and crack depth are not in favor of the stability of the system. Copyright © 2014 IFSA Publishing, S. L.

The model of three-span rotor-bearing system with three cracks in shaft supporting on the six sliding bearings was set up. The influences of crack faults to the responses of the rotor system were studied on numerical simulation. Along with the increase of the crack depth in first span, the main influence to the dynamic characteristics of the system is in the first span. Along with the increase of the crack depth in second span, the main influences to the response of first and third spans are in the region of critical rotate speed, and it to the second span is in the regions of critical and supercritical rotate speed. Along with the increase of the crack depth in third span, the main influences to the response of the three spans are in the region of critical rotate speed.

The model of nonlinear stiffness rotor-bearing system with crack fault was set up, and the nonlinear dynamic characteristics of the system were analyzed by numerical method. In critical rotational speed range, there are frequency division motions when the crack depth is sallow and chaotic motion when the crack is deep. In supercritical rotational speed range, the main motions are periodical frequency divisions. The numbers increase along with the depth of crack. In ultra-supercritical rotational speed range, there are quasi-periodic motion decreasing when the crack depth is sallow and periodical-3 motion when the crack is deep. The conclusions provide a theoretic basis reference for the failure diagnosis to the nonlinear stiffness rotor-bearing systems with crack fault.

Due to the feature and the forms of motion of the gears, the vibration signal of the gear is mainly the frequency modulation, amplitude modulation, or hybrid modulation signal corresponding to the gear-mesh frequency and its double frequency signal. When faults arise on the gears, the number and shape of the modulation sideband will be changed. The structures and forms of the FM composition differ according to the type of faults. According to the above mentioned characteristic, this essay raises a method to disassemble the gear vibrate signal, points out the formulas to build up characteristic vector, on that basis, the essay raised a gear fault diagnosis method based on EMD and Hidden Markov Model (HMM), this method can identify the working condition of the normal gears, snaggletooth gears, and pitting gears.

This paper compares the existing speed measurement methods, discusses a speed measurement based on microcontroller used in non-constant speed bearing fault diagnosis that has the wide measuring range, high precision, good real-time performance.

The wear and tear allowances (displacements) of axial thrust bearing in air compressor was diagnosed and predicted, applying the model of artificial neural network (ANN), and compared with the traditional method of diagnosis and prediction. It showed that the results of diagnosis and prediction are more precise than that of traditional method. It can diagnosis and predicts the wear and tear allowances of axial thrust bearing better.

The test rig of two-span rotor-bearing system with rub-impact and crack faults was constructed. The vibration of the rotor-bearing system was observed for different conditions, such as single rub-impact fault, double rub-impact faults and coupling faults of rubbing and crack. The 3D-waterfall spectrum of rotor system was used to analyze the dynamic characteristics of the system during faults. The results indicate there appears 6-superharmonic frequency component on double rub-impact faults. The amplitudes of subharmonic frequencies decrease obviously and it of superharmonic frequencies increases on coupling faults of rubbing and crack, and the superharmonic frequency components are different obviously in different span.

The RBF network was applied in the rotor system to realize the fault diagnosis aiming the mapping complexity between fault symptoms and fault patterns. It can overcome the problems of low learning rates of convergence and falling easily into part minimums in BP algorithm, and improve the precision of diagnosis. The normalized values of seven frequency ranges in amplitude spectrum were used as the fault characteristic quantity, the RBF network was trained to diagnose the faults of rotor system. The results show that RBF neural network is a valid method of diagnosis of mechanical failure.

The dynamic model of the three-span rotor-bearing system with rub-impact fault was set up. The influence to nonlinear dynamics behaviors of the rotor-bearing system that induced by rub-impact of one disc, two discs and three discs were numerically studied. The main influence of the rotor system response by the rub-impact faults are in the supercritical rotate speed. There are mutations of amplitudes in the responses of second and third spans in supercritical rotate speed when rub-impact with one disc, and there are chaotic windows in the response of first span, and jumping changes in second and third spans when rub-impact with two or three discs.

The nonlinear dynamic model of two-span rotor-bearing system with two cracks in shafts is set up, and the effects of two cracks in shafts on dynamic characteristics of the rotor-bearing system are analyzed. Along with the increase of the crack depth in first span, the chaotic and periodic motions increase, and the quasi-periodic motion decrease in the supercritical rotate speed. There are harmonic elements of 1/4, 1/2 and 3/4 frequency division within the sub-critical speed range at different crack depths. There appears the frequency doubling resonance obviously when the crack depths are larger. Along with the increase of the crack depth in second span, the main influences to the responses of system are in the second span. The chaotic regions increase and then decrease and the periodic motions region increase in the sub-critical rotate speed range.