Design of a Novel Integrated Ultrasonic Tool Holder for Friction Stir Welding

Ultrasonic vibration used in friction stir welding (FSW) has shown advantages in reducing welding defects and improving welding quality. How to design an ultrasonic tool holder is a challenge because the holder is rotating in a confined space. In this study, we design a 20 kHz integrated ultrasonic tool holder in FSW. This novel configuration can be applied in general machining equipment. The elastic modulus is measured by non-destructive acoustic testing to attain the precise frequency. Three FSW transducers with alloy steel are designed by the modal analysis and the transducer prototypes are fabricated. The effect of pre-tightening force on transducer frequency is investigated, where the prestress of the piezoelectric stack instead of the torque is tested to achieve an optimal working frequency. The vibration of the transducers is measured by a Doppler Vibrometer System. It proved that the resonant frequencies are well consistent between simulation model and the experiment by the elastic modulus testing and the pre-tightening optimization. Moreover, the experiment demonstrates that the vibration amplitude is significantly different, even in a slight difference of steel material properties are adopted. The dynamic performance of the designed transducers is acceptable by the vibration measurement.

Blade Serial Number Identification Based on Blade Tip Clearance without OPR Sensor

Blade serial number identification is one of the key issues in blade tip-timing vibration measurement without once-per-revolution (OPR) sensor. In order to overcome the shortcomings of the existing blade serial number identification methods without OPR sensor, a new identification method of blade serial number based on blade tip clearance is proposed in this paper. The relationship between blade tip-timing data and blade serial number can be identified by the matching relationship between blade tip clearance under static state and dynamic state. According to the finite element simulation and experimental data, the accuracy of the blade serial number identification method based on blade tip clearance is verified by using the OPR sensor method. The results show that in the nonresonant rotation speed region, the method can identify the blade serial number, and the identification result is consistent with the result of the OPR sensor method. In the resonance rotation speed region, when the blade tip clearance change caused by the blade circumferential bending vibration is less than the dispersion of initial blade tip clearance, the method in this paper can accurately identify the blade serial number. Otherwise, the inference method can be used. It provides theoretical support and technical basis for the engineering application of blade tip-timing vibration measurement technology without OPR sensor.

Advanced High Frequency In-Bit Vibration Measurement Including Independent, Spatially Separated Sensors for Proper Resolution of Vibration Components Including Lateral, Radial, and Tangential Acceleration

Vibration measurement has become ubiquitous in drilling. Focus of drilling enhancement has expanded from traditional lateral and stick slip assessment to include torsional oscillations on motors, and high-frequency torsional oscillations (HFTO). Recent publications have highlighted the importance of these higher frequency measurements to analyze drilling dynamics and diagnose dysfunctions which can cause tool failures. A new vibration recorder will be presented which is capable of sampling at 2 kHz and higher to analyze non-linear transient dysfunctions. Most in-bit vibration measurement options utilize a single unsynchronized triaxial accelerometer and low speed gyro. This design practice inherits specific challenges to the measurement and prevents the ability to decouple lateral from angular acceleration. Use of two sets of symmetrically placed (180 degree opposing) accelerometers has been in practice, but design constraints limit this approach to larger bits. Utilization of a new, outer diameter (OD) mounted vibration recorder for slim hole bits/BHAs with multiple spatially separated triaxial accelerometers, and a high-speed precision gyro will be described and evaluated with a comparison to other commercially available options. Downhole vibration recorders have existed for over 20 years providing conventional drilling dynamics evaluation. These devices suffered from hardware limitations which constrained the customer to spaced out snapshots of time rather than continuous observation and required separate research modules to cover high frequency needs. This paper presents case studies utilizing a new vibration recorder which can cover these two customer needs in one device. Drilling Engineers desire a rapid turnaround macro view of synchronized downhole and surface data for offset well parameter optimization while research engineers desire a micro view with kilohertz range sample rate for a comprehensive understanding of all possible dysfunctions including HFTO, and high frequency shock, along with the capacity to research geology prediction techniques including fracture identification. Use of an advanced cloud-based software suite will be illustrated for a rapid high-level view of the full run with benchmarking capability of offset wells. Case study observations include stick slip identification covering 0 to above 600 rpm using a single gyroscope, and HFTO identification with accurate decoupling of tangential acceleration vs radial and lateral. Having the ability to satisfy both objectives with one device is new to the industry and presents a step change in capability. A new, advanced vibration recorder is detailed which includes synchronized, spatially separated triaxial accelerometers, a triaxial shock sensor, a highspeed triaxial gyroscope, and temperature sensors. With 5 gigabytes of high temperature flash memory, more than 2 kHz sample rate for burst data and 1s period for downhole processed data, logged downhole recordings can cover greater than 200 hrs of drilling and may be available for analysis within minutes from drilling completion.

Measurement and Analysis of Downhole Drill String Vibration Signal

Downhole drill string vibration data can provide an effective reference for research drill string vibration during drilling. In this paper, the research group used a storage-type downhole vibration measurement equipment equipped with an orthogonal, three-axis accelerometer to measure and collect drill string vibration signals during drilling in an oil well. Based on the installation characteristics of the sensor, the relationship between the acceleration measurement value of the sensor and the center acceleration value of the drill string is obtained. Then the time-domain signals representative of the vibration in igneous rock drilling is analyzed. It can be found that the occurrence of stick-slip vibration can be judged by the regular wave packets in the time-domain signal, while the time-domain signal of whirl is disorderly. The main frequency of stick-slip vibration in the low-frequency band is 0.1221 Hz and the period of stick-slip vibration is very close to 10 s through Fast Fourier (FFT) and Short-time Fourier transform (DTFT) methods. In the process of whirling, two frequencies, respectively, 0.05341 Hz and 155.5 Hz, play a major role. The frequency 0.05341 Hz is very close to the reciprocal of the period of 20 s when the peak energy spectrum density appears, indicating that the occurrence of whirl is very likely to be related to the natural frequency of the drilling tool. Through further time-frequency analysis, it also can be found that the occurrence of whirl and stick-slip is greatly related to the use of torsional impactors and jars.