| Vibroseis is a kind of signal excitation equipment for seismic exploration.Compared with traditional explosion source,it has characteristics like controllable output seismic wave,environment protecting and high efficiency,which has become the preferred signal excitation source.As the core component of vibroseis,the vibrator's structure and properties have fatal effect on exploration precision and security during field work site.The field failure statistic data show that the failure rate of heavy hammer seal is 34.30%,which has significant impact on vibrator's working performance.Moreover,the field construction can't satisfy dismounting technologies that replacement of maintenance need.So there is no choice but depot repair, which seriously reduce the exploration efficiency.Therefore,on the basis of plenty of engineering data and the existent study about vibrator system,combined with development requirements of oil and gas resources exploration,this work make failure analysis on vibrator system.Meanwhile,it adopt probability statistics to study the reliability analysis of vibrator system for life predication and structural development.The study results have significance on prolonging the service life and improve the efficiency and stability of oil and gas exploration.The main research contents and achievements are as follows:(1)On the basis of vibroseis vibrator system design status and working principle and plentiful field engineering data,it makes failure analysis on vibrator system.The results show that the common failure modes of vibrator system are wear-out failure,fatigue failure and fracture failure.And the heavy hammer seal leakage and electro-hydraulic servo valve cavitation are the main factors that affect the system stability.It also researches the homologous failure mechanism.(2)Due to the vibrator has complex structure and plenty of components,the applying of fault tree analysis method can effectively establish vibrator system's fault-tree model and calculate the failure probability and probability importance,then obtain the vibrator system reliability.Through contrasting the probability importance and combining the specific field working condition,it confirms that the key factor influent vibrator system failure is hammer seal.(3)Through the uniaxial tensile test for sealing material,the properties are measured under three temperature gradients and obtain the stress-strain relations.Then the MATLAB linear regression is applied to carry on data fitting.It adopts mean value method to ensure sealing material's Mooney-Rivlin constants in order to describe the mechanical behavior.(4)According to large plastic deformation theory and Hertz classical contact mechanics theory,the finite element algorithm is used to calculate the seal structure under periodic pressure and grasp the stress response regularity of seal ring.The results show that along with the increasing of working frequency the fluctuation of seal ring peak stress will be more severe and lead to the seal failure.Otherwise,the Von mises stress is decreased first then increased along with the increase of compression ratio,nonlinear increase with the increase of notch radius,changing little with the increase of friction coefficient.(5)Analyzing the stress distribution of O-ring under periodic pressure to find out the dangerous section and improve the structure.By Contrasting the seal ring before and after improvement,the equivalent stress method is used to calculate strain energy.Then through setting the strain energy release rate as damage parameter and applying fracture mechanics method to predict the life of dangerous section node of O-ring.It turns out that the life after improvement has increased averagely by 7.93%,which has significant meaning to improve the vibrator's working properties and vibroseis's efficiency and safety. |
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