ACCURATE MEASUREMENT OF ROTARY MACHINE AXIS CENTER TRACE

Four methods aiming at measuring rotary machine axis center trace arediscussed in detail. The comparative analysis is made on some aspects such as measurement accuracy,on-machine characteristics, feasibility, practical operation convenience and the integrity ofmeasurement information. In order to simplify measurement, the axis profile error is ignored intraditional condition, while the measurement accuracy will be reduced. The 3-point method that theaxis profile error is firstly separated has better real time character, at the same time, not onlythe axis motion error but also the axis profile error can be measured. All of those information canbe used to diagnose the fault origin. The analysis result is proved to be correct by the experiment.

Fault Diagnosis of a Rotary Machine Based on Information Entropy and Rough Set

There exists some discord or contradiction of information during the process of fault diagnosis for rotary machine. But the traditional methods used in fault diagnosis can not dispose of the information. A model of fault diagnosis for a rotary machine based on information entropy theory and rough set theory is presented in this paper. The model has clear mathematical definition and can dispose both complete unification information and complete inconsistent information of vibration faults. By using the model, decision rules of six typical vibration faults of a steam turbine and electric generating set are deduced from experiment samples. Finally, the decision rules are validated by selected samples and good identification results are acquired.

Non-stationary signal analysis based on general parameterized time-frequency transform and its application in the feature extraction of a rotary machine

With the development of large rotary machines for faster and more integrated performance, the condition monitoring and fault diagnosis for them are becoming more challenging. Since the time-frequency （TF） pattem of the vibration signal from the rotary machine often contains condition information and fault feature, the methods based on TF analysis have been widely-used to solve these two problems in the industrial community. This article introduces an effective non-stationary signal analysis method based on the general parameterized tim^fre- quency transform （GPTFT）. The GPTFT is achieved by inserting a rotation operator and a shift operator in the short-time Fourier transform. This method can produce a high-concentrated TF pattern with a general kemel. A multi-component instantaneous frequency （IF） extraction method is proposed based on it. The estimation for the IF of every component is accomplished by defining a spectrum concentration index （SCI）. Moreover, such an IF estimation process is iteratively operated until all the components are extracted. The tests on three simulation examples and a real vibration signal demonstrate the effectiveness and superiority of our method.

Chatter stability of robotic rotary ultrasonic countersinking

In recent years,industrial robots have received extensive attention in manufacturing field due to their high flexibility and great workspace.However,the weak stiffness of industrial robots makes it extremely easy to arouse chatter,which affects machining quality inevitably and generates noise pollution in severe cases.Compared with drilling,the chatter mechanism of robotic countersinking is more complex.The external excitation changes with cutting width and depth in countersinking.This characteristic results in time-varying and nonlinearity of robotic countersinking dynamics.Thus,it is urgent to propose a new method of chatter suppression and provide an accurate stability analysis model.As a new special machining technology,rotary ultrasonic machining has been proved to improve robotic drilling and milling stability effectively.Based on this,robotic rotary ultrasonic countersinking(RRUC)is proposed to improve the robotic countersinking stability in this paper.A three-dimensional stability domain method of RRUC is established.First,the countersinking process was divided intoρparts.The dynamic model of every unit was constructed based on ultrasonic function angle(γ)and dynamic chip area.Then,the stability region of RRUC is obtained based on the semi-discrete method(SDM).Compared with the robotic conventional countersinking(RCC),RRUC improves the stability by 27%.Finally,the correctness and effectiveness of the stability region model are proved by robotic ultrasonic countersinking experiments.

Experimental study on rotary longitudinal-torsional ultrasonic machining of unidirectional CFRP

Addressing the challenges of high grinding temperature,poor hole quality,and tool rod blocking in core drilling of carbon fiber reinforced plastics(CFRP),this study investigates the material removal characteristic of rotary longitudinal-torsional ultrasonic machining(RLTUM)of CFRP based on the Hertz contact theory.The study also conducts relevant experiments to compare and analyze the grinding force,grinding temperature,hole wall quality,exit quality,and tool wear in ordinary core drilling(OCD),rotary ultrasonic machining(RUM),and RLTUM of CFRP.The results demonstrate that RLTUM significantly reduces the grinding force,grinding temperature,hole exit damage and improves the surface smoothness of the CFRP hole walls.By utilizing intermittent cutting in circumferential direction for torsional vibration,RLTUM enables automatic removal of rod chips while restraining tool chip adhesion and reducing heat generation as well as tool wear.Therefore,RLTUM shows great potential for enhancing the quality of holemaking in CFRP.

Experimental study and optimization of cutting parameters in machining of super alloy with hybrid ultrasonic method

Super alloys are intensively used in various industries, especially in the aerospace industry, because of their special characteristics. A number of holes are sometimes required to be drilled into super alloys for aircraft at their final stage assembly. In the present study, a hybrid ultrasonic machining method, called rotary ultrasonic machining （RUM）, was successfully used in super alloy drilling. The empirical modeling of the process parameters of RUM was performed for the super alloy （Inconel 718） using an experimental design approach, called response surface methodology （RSM）. Parameters, namely tool rotation, feed rate, ultrasonic power, and abrasive grit size, were selected as input variables. The others were kept constant. The performance was measured in terms of the machining rate and the surface roughness. The developed models were found to be reliable representatives of the experimental results with prediction errors less than 4-5%. Moreover, the feed rate for the quality and productivity aspect was found to be the most critical factor. The optimized values of the machining rate and the surface roughness achieved through a multi-response optimization were 0.9 825 mm3/s and 0.951 i.tm, respectively.

Modeling the optimal compensation capacitance of a giant magnetostrictive ultrasonic transducer with a loosely-coupled contactless power transfer system

The giant magnetostrictive rotary ultrasonic processing system(GMUPS)with a loosely-coupled contactless power transfer(LCCPT)has emerged as a high-performance technique for the processing of hard and brittle materials,owing to its high power density.A capacitive compensation is required to achieve the highest energy efficiency of GMUPS to provide sufficient vibration amplitude when it works in the resonance state.In this study,an accurate model of the optimal compensation capacitance is derived from a new electromechanical equivalent circuit model of the GMUPS with LCCPT,which consists of an equivalent mechanical circuit and an electrical circuit.The phase lag angle between the mechanical and electrical circuits is established,taking into account the non-negligible loss in energy conversion of giant magnetostrictive material at ultrasonic frequency.The change of system impedance characteristics and the effectiveness of the system compensation method under load are analyzed.Both idle vibration experiments and machining tests are conducted to verify the developed model.The results show that the GMUPS with optimal compensation capacitance can achieve the maximum idle vibration amplitude and smallest cutting force.In addition,the effects of magnetic conductive material and driving voltages on the phase lag angle are also evaluated.