Research On Dynamic Characteristics Of DTH Hammer Drill String System Of Rotary Drilling Rig

Down-the-hole(DTH)hammers of rotary drilling rigs are increasingly widely used in the field of drilling pile foundations.Research has been carried out on the vibration law of the drill string during the drilling process of the DTH hammer,and the optimization design,condition monitoring,status monitoring of the DTH hammer,and fault diagnosis and other forms of drilling equipment.Based on the system dynamics model,this thesis uses numerical simulation,finite element analysis and field experiments to study the characteristics of the vibration response signal of the DTH hammer drill string and the corresponding dynamic characteristics.The specific research work is as follows:Considering the support and fixing conditions of the rotary drilling rig on the drill string,the differential equation of vibration under the longitudinal vibration form of the hoisting wire rope-power head-vibration absorber-drill string-hammer head system is established through the domain decomposition method and the generalized variational principle.The Newmark-? method is used to solve the vibration dynamics equation,and the frequency change law of the longitudinal vibration response when the drilling conditions change and the boundary conditions change are analyzed at the same time.The increase in drill pipe length only affects the first-order natural frequency of the system,the change of hammerhead pressure/decompression conditions only affects the first two modal frequencies,and the higher-order frequencies remain basically unchanged.The evolution of the longitudinal vibration frequency distribution is in the vibration frequency spectrum.The identification of the natural frequency of the drill string provides a theoretical basis.Construct a wireless acquisition and test system for down-the-hole hammer drill string signals including vibration acceleration,vibration noise,air-supply flow rate and air pressure of the down-the-hole hammer.According to the site conditions,the signal acquisition scheme based on WIFI and wireless data transmission radio communication was selected to complete the development of the man-machine interface and module functions for data acquisition and analysis and processing;the wavelet filtering method was used to separate the low-frequency trend items in the vibration response and improve the vibration The accuracy of the calculation and analysis of the response signal;after field tests and cross-power spectrum analysis of vibration acceleration and noise,the bandwidth of the test signal and the main frequency components of the vibration are clarified,which provides for the study of the fault diagnosis of down-the-hole hammer impactor based on vibration and noise Theoretical support.The analysis method based on the second-order SOULTI damping wavelet transform is used to analyze and identify the time-frequency characteristics of drill string vibration during a single impact of the down-the-hole hammer.The simulation signal analysis based on zero damping and under damping verifies the superiority of the SOULTI damped wavelet transform analysis method compared with other time-frequency analysis methods.Through the time spectrum analysis of the vibration response of the drill string top during a single hammering under different formation conditions,it is proved that the coupling interference formed by the vibration of the power head transmission component on the longitudinal vibration of the drill string is negligible;the hardness of the rock formation increases,and the hammer head and the drill string The increase in the number of oscillations makes it easier to excite the natural frequency vibration components of the drill bit and drill string.Using the analysis technology of vibration reduction transmission rate based on harmonic wavelet frequency band energy decomposition,the working characteristics of the vibration absorber of two types of rotary drilling rigs are analyzed.The working frequency range of the two types of shock absorbers is determined by the cross-power spectrum analysis method.The application effect of the shock absorber is evaluated by the vibration drop and shock isolation coefficient.The spring-type shock absorber is analyzed through the analysis of the sub-band vibration damping transmission rate.The vibration isolation effect is better than the disc spring damping shock absorber;based on the vibration response analysis and application evaluation before and after the shock absorber,it provides a reference for the design and field application of the shock absorber.Under the condition that expert experience is widely used in field practice,a method of vibration and noise monitoring and fault diagnosis of large-aperture single DTH hammer based on convolutional neural network is proposed.Complete the modal frequency analysis of the hammer head and drill string through the finite element method,and verify the main natural frequency components that affect the longitudinal vibration through the hammer test of individual components,and then use the finite element analysis and calculation results to acquire the component response under actual working conditions The frequency characteristics of the hammer head and drill string are obtained.Through the comparative analysis of the vibration acceleration response and the noise signal in the hammer head test,the feasibility of the vibration and noise method is verified,and for the vibration and noise signal of the large sample of the DTH hammer,a DTH hammer impactor based on the convolutional neural network is proposed.In the fault identification method,the training accuracy of the convolutional neural network finally obtained is 99.22%,and the test accuracy is 98.91%,which provides a new idea for data-driven DTH fault diagnosis.There are 86 images,62 tables,and 108 references in this thesis.