scholarly journals Simulation Research on the Time-Varying Meshing Stiffness and Vibration Response of Micro-Cracks in Gears under Variable Tooth Shape Parameters

2019 ◽  
Vol 9 (7) ◽  
pp. 1512 ◽  
Author(s):  
Jianfeng Ma ◽  
Tongtong Liu ◽  
Chunqing Zha ◽  
Liuyang Song
Keyword(s):  
Vibration Response ◽  
System Stability ◽  
Time Varying ◽  
Shape Parameters ◽  
Dynamic Simulations ◽  
Tooth Shape ◽  
Meshing Stiffness ◽  
Pressure Angle ◽  
Micro Cracks ◽  
Almost All

The gear is one of the important parts of a rotary gearbox. Once catastrophic gear failure occurs, it will cause a great threat to production and life safety. The crack is an important failure factor causing changes in time-varying stiffness and vibration response. It is difficult to effectively identify the vibration response and meshing stiffness changes when there is a fine crack in the gear. Therefore, it is of great importance to improve the accuracy of meshing stiffness calculation and dynamic simulations under micro-cracks. Investigations of meshing stiffness and the vibration response of a gearbox is almost all about fixed gear shape parameters. However, the actual production process of gear system needs to change gear shape parameters. In this paper, the meshing stiffness and vibration response of the dynamic simulation signals of gear teeth with different crack depths at different tooth shape parameters (the pressure angle, the modulus, and the tooth number) were calculated, respectively. The influence of cracks on the vibration response was investigated by the fault detection indicators, the Root Mean Square (RMS), the kurtosis, and the crest factor. The result shows that when the pressure angle and modulus change, the vibration response changes erratically. However, when the tooth numbers change, the vibration response changes regularly. The results could be a guide for choosing gears in different shape parameters when system stability is the aim.

Shape Parameters Measurement of Profile-Shifted Spur and Helical Gears

2005 ◽  
Author(s):  
Ah-Der Lin ◽  
Jao-Hwa Kuang
Keyword(s):  
Calculated Data ◽  
Measurement Methods ◽  
Shape Parameters ◽  
Tooth Shape ◽  
Helical Gears ◽  
Ball Size ◽  
Pressure Angle ◽  
Tooth Form ◽  
Parameters Measurement ◽  
Good Agreement

Various measurement methods have been proposed to measure the tooth shape parameters of profile-shifted spur and helical gears. This study proposes an over-balls measurement technique based on the tooth form equations of the profile-shifted spur and helical gears. The relations between the over-ball distance and the tooth parameters, i.e. the profile-shifted factor and the pressure angle, are derived for the two gears. The effect of the ball size on the accuracy of the measurements is investigated. An algorithm is proposed to extract the profile-shifted factor and the pressure angle from the measured over-ball chordal lengths. A good agreement is found between the calculated data and the measured results. Hence, the proposed inverse measurement method provides a feasible approach for obtaining highly accurate estimates of the tooth shape parameters of profile-shifted spur and helical gears.

scholarly journals Vibration Response of the Planetary Gears with a Float Sun Gear and Influences of the Dynamic Parameters

2020 ◽  
Vol 2020 ◽  
pp. 1-17
Author(s):  
Yinghui Liu ◽  
Dong Zhen ◽  
Huibo Zhang ◽  
Hao Zhang ◽  
Zhanqun Shi ◽  
...  
Keyword(s):  
Phase Modulation ◽  
Vibration Response ◽  
Operating Conditions ◽  
Mechanical Transmission ◽  
Time Varying ◽  
The Sun ◽  
Dynamic Parameters ◽  
Planetary Gearbox ◽  
Pressure Angle ◽  
Overlap Ratio

Planetary gearboxes are widely used in mechanical transmission systems due to their large transmission ratio and high transmission efficiency. In a planetary gearbox, the sun gear is usually set to float to balance the sharing of loads among planet gears. However, this floating set will result in the variation of pressure angle, overlap ratio, and meshing phase in the meshing progress and when gear faults occur, the variation will be enlarged. In the previous studies, these parameters were reduced to constant. To study the influence of the dynamic parameters on the vibration response of planetary gearboxes under different operating conditions, a new lumped-parameter model containing the time-varying pressure angle (TVPA), time-varying overlap ratio (TVOR), and time-varying meshing phase (TVMP) is established. Based on this model, the vibration response mechanism of the sun gear is analyzed. Moreover, the comparison with the previous model is made and the rule of phase modulation caused by these dynamic parameters is revealed. By comparing the dynamic responses under different loads and rotation speeds, the phase modulation is studied in detail. Finally, the sun gear fault is introduced, and the phase modulation is analyzed in different fault degrees. This study can provide theoretical reference for the condition monitoring and fault diagnosis of planetary gearbox based on vibration analysis.

Research on dynamic characteristics of gear system considering the influence of temperature on material performance

2021 ◽  
pp. 107754632110026
Author(s):  
Zhou Sun ◽  
Siyu Chen ◽  
Xuan Tao ◽  
Zehua Hu
Keyword(s):  
Elastic Modulus ◽  
Dynamic Characteristics ◽  
Poisson’S Ratio ◽  
Gear System ◽  
Poisson's Ratio ◽  
Effect Of Temperature ◽  
Time Varying ◽  
Influence Of Temperature ◽  
Meshing Stiffness ◽  
Influence Of Temperature On

Under high-speed and heavy-load conditions, the influence of temperature on the gear system is extremely important. Basically, the current work on the effect of temperature mostly considers the flash temperature or the overall temperature field to cause expansion at the meshing point and then affects nonlinear factors such as time-varying meshing stiffness, which lead to the deterioration of the dynamic transmission. This work considers the effect of temperature on the material’s elastic modulus and Poisson’s ratio and relates the temperature to the time-varying meshing stiffness. The effects of temperature on the elastic modulus and Poisson’s ratio are expressed as functions and brought into the improved energy method stiffness calculation formula. Then, the dynamic characteristics of the gear system are analyzed. With the bifurcation diagram, phase, Poincaré, and fast Fourier transform plots of the gear system, the influence of temperature on the nonlinear dynamics of the gear system is discussed. The numerical analysis results show that as the temperature increases, the dynamic response of the system in the middle-speed region gradually changes from periodic motion to chaos.

System stability with combined derivative constraints on time varying gains

Automatica ◽  
1978 ◽  
Vol 14 (1) ◽  
pp. 93-94 ◽  
Author(s):  
S. Ramarajan ◽  
K.L.P. Mishra
Keyword(s):  
System Stability ◽  
Time Varying

scholarly journals ANALYSIS OF SMES CREDIT RESTRUCTURING POLICY IN ECONOMIC RECOVERY DURING THE COVID-19 PANDEMIC

2021 ◽  
Vol 5 (2) ◽  
pp. 405
Author(s):  
Lussi Agustin ◽  
Moh. Yusron Solikin ◽  
Zunairoh .
Keyword(s):  
Financial Services ◽  
Global Economy ◽  
Empirical Studies ◽  
System Stability ◽  
Economic Recovery ◽  
Top Down ◽  
The Difference ◽  
Almost All ◽  
Industry Sectors ◽  
The Impact

Penelitian ini bertujuan untuk menganalisis seberapa maksimal proses kebijakan retrukturisasi Kredit UMKM dalam Pemulihan Ekonomi di Masa Pandemi Covid-19. Kondisi perekonomian global sedang mengalami goncangan hebat akibat mewabahnya Covid-19. Dampak dari pandemic ini sangat mempengaruhi segala aspek terutama pada kondisi Kesehatan dan perekonomian suatu negara, tidak terkecuali Indonesia. Secara keseluruhan, hampir semua sektor industry mengalami goncangan dan tidak terkecuali sektor UMKM. Maka dari itu dikeluarkanlah kebijakan retrukturisasi Kredit UMKM guna mendorong optimalisasi fungsi intermediasi pada perbankan dan menjaga stabilitas sistem keuangan serta mendukung pertumbuhan perekonomian. Program restrukturisasi kredit menjadi program dari OJK yang dapat diterapkan oleh perbankan kepada UMKM. Metode yang digunakan dalam penelitian ini adalah metode kualitatif dengan menggunakan studi empiris dari penelitian terdahulu serta peraturan-peraturan terkait dengan restrukturisasi kredit yang dikeluarkan oleh Otoritas Jasa Keuangan. Hasil penelitian ini menunjukkan bahwa implementasi kebijakan restrukturisai kredit bagi UMKM sudah berjalan dan digunakan oleh para pelaku UMKM. Kemudian berdasarkan implementasinya kebijakan ini merupakan kebijakan top-down dimana memerlukan banyak Lembaga untuk bekerja sama dan keputusan berasal dari Peraturan pemerintah baru di teruskan ke Lembaga-lembaga lain di bawahnya hingga informasinya sampai dan bisa dirasakan oleh para UMKM.  This research aims to analyze the policy of restructuring SMEs Credit in Economic Recovery during the Covid-19 Pandemic. The global economy is experiencing severe shocks due to the outbreak of Covid-19. The impact of this pandemic greatly affects all aspects, especially on the health and economic condition of a country, not least Indonesia. Overall, almost all industry sectors are experiencing shocks and are no exception to the SMEs sector. Therefore, the policy of restructuring SMEs Credit was issued to encourage optimization of intermediation function in banking and maintain the financial system stability and support economic growth. Credit restructuring program becomes a program from OJK that can be applied by banks to SMEs. The method used in this research is a qualitative method using empirical studies from previous research as well as regulations related to credit restructuring issued by the Financial Services Authority. The results of this research show that the implementation of credit restructuring policy for SMEs is already running and used by SMEs. Then based on the difference in implementation of this policy is a top-down policy that requires many Institutions to cooperate and decisions derived from the new government regulations are forwarded to other institutions under it until the information reaches and can be felt by SMEs.

scholarly journals Frequency and Vibration Characteristics of High-Speed Gear-Rotor-Bearing System with Tooth Root Crack considering Compound Dynamic Backlash

2019 ◽  
Vol 2019 ◽  
pp. 1-19 ◽  
Author(s):  
Jie Liu ◽  
Weiqiang Zhao ◽  
Weiwei Liu
Keyword(s):  
Time Domain ◽  
Crack Depth ◽  
Transmission System ◽  
Gear System ◽  
Time Varying ◽  
Tooth Root ◽  
Meshing Stiffness ◽  
The Time Domain ◽  
Center Distance ◽  
Root Crack

Considering the microstructure of tooth surface and the dynamic characteristics of the vibration responses, a compound dynamic backlash model is employed for the gear transmission system. Based on the fractal theory and dynamic center distance, respectively, the dynamic backlash is presented, and the potential energy method is applied to compute the time-varying meshing stiffness, including the healthy gear system and the crack fault gear system. Then, a 16-DOF coupled lateral-torsional gear-rotor-bearing transmission system with the crack fault is established. The fault characteristics in the time-domain waveform and frequency response and statistics data are described. The effect of crack on the time-varying meshing stiffness is analyzed. The vibration response of three backlash models is compared. The dynamic response of the system is explored with the increase in crack depth in detail. The results show that the fault features of countershaft are more obvious. Obvious fluctuations are presented in the time-domain waveform, and sidebands can be found in the frequency domain responses when the tooth root crack appears. The effect of compound dynamic backlash on the system is more obvious than fixed backlash and backlash with changing center distance. The vibration displacement along meshing direction and dynamic meshing force increases with the increase in crack depth. Backlash and variation of center distance show different tendencies with increasing crack depth under different rotational speeds. Amplitude of the sidebands increases with crack depth increasing. The amplitude of multiplication frequency of rotational frequency has an obvious variation with growing crack depth. The sidebands of the multiplication frequency of meshing frequency show more details on the system with complex backlash and crack fault.

scholarly journals Mesh Phase Analysis of Encased Differential Gear Train for Coaxial Twin-Rotor Helicopter

2019 ◽  
Vol 2019 ◽  
pp. 1-9 ◽  
Author(s):  
Donglin Zhang ◽  
Rupeng Zhu ◽  
Bibo Fu ◽  
Wuzhong Tan
Keyword(s):  
Phase Difference ◽  
Gear Tooth ◽  
Phase Relations ◽  
Gear Train ◽  
Time Varying ◽  
Gear Pair ◽  
Meshing Stiffness ◽  
Differential Gear ◽  
Starting Point ◽  
Twin Rotor

Dynamic excitation caused by time-varying meshing stiffness is one of the most important excitation forms in gear meshing process. The mesh phase relations between each gear pair are an important factor affecting the meshing stiffness. In this paper, the mesh phase relations between gear pairs in an encased differential gear train widely used in coaxial twin-rotor helicopters are discussed. Taking the meshing starting point where the gear tooth enters contact as the reference point, the mesh phase difference between adjacent gear pairs is analyzed and calculated, the system reference gear pair is selected, and the mesh phase difference of each gear pair relative to the system reference gear pair is obtained. The derivation process takes into account the modification of the teeth, the processing, and assembly of the duplicate gears, which makes the calculation method and conclusion more versatile. This work lays a foundation for considering the time-varying meshing stiffness in the study of system dynamics, load distribution, and fault diagnosis of compound planetary gears.

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