Applied Mechanics and Materials Vols. 34-35

Abstract: Failure of drill pipe is very severe in gas drilling. Based on the erosion theory and field condition, the erosion of drill pipe is investigated by using numerical simulation. The agreement between the simulation result and experimental data is very good, this agreement indicates that the numerical model is realistic in this paper. The erosion wear of drill pipe is investigated in gas drilling and mud drilling by using this model. According to study result of drill pipe erosion between gas drilling and mud drilling, the erosion rate of drill pipe in gas drilling is greater than that of in mud drilling. The result shows that the local erosion rate of joint is more severe than that of the drill pipe body in gas drilling, and also the local erosion of drill pipe body is severe. There are many eroded pits on drill pipe body in gas drilling. This study will reveal the failure mechanism of drill pipe in gas drilling, and also have some guiding significance to reduce the failure of drill pipe.

Abstract: In order to clarify the abnormal failure mechanism for the spring of the water injection pump, the velocity and the pressure are simulated for hydraulic unit in different driven angle. The eccentric load is found in the ansys, which is the main factor for leading to the exceptional failure of the spring. The improvement method is presented by using Computational Fluid Dynamics (CFD) technology. Flow field of the improved hydraulic unit is more uniform after the numerical simulation. The effect of eccentric load is greatly reduced for the suction spring. At the same time without changing the rate of flow, section surface of the suction valve and the discharge valve is appropriately reduced to bring down the load of the spring. The fluid dynamics analysis and optimization of the hydraulic unit has been completed in this paper. This study has great significance in perfecting the working theory of the water injection pump and raising the robustness of the pump’s motion.

Abstract: Based on the elasticoplasticity contact analysis theory, a mechanical model for the whole process of the slip holding fast to the drilling pipe is established and a complete method is proposed to assess the performance of slip dog's structural parameters. For drilling pipe systems of different specifications, the coupling effect among tooth anterior corner, posterior corner, tooth height, tooth spacing of slip dog and the effect of the parameter variation on both the drilling pipe and itself after the slips hold fast to the drilling pipe are analyzed, and the slip dog's plastic damage law on the drilling pipe under different parameter combinations is obtained. Using this law to instruct field slip dog design, it is discovered that this slip dog significantly reduces the drilling pipe's plastic damage by both laboratory and field experiments, which has proved the universality and applicability of this method, effectively reduced the drilling operational risk and drilling costs. The technology has been put into use in Sichuan and Chongqing region and acquired good technical assessment.

Abstract: Rotary kin shell is welded by cylindrical steel plates. Crack propagation of weld toes near supporting rollers until final fracture is the main failure form. Based on fracture mechanics, an overall intensity factor with regard to circumferential stress, concentrated stress, residual stress, and temperature stress is used to asses the crack growth. Under complex overloading conditions, the major factor, namely, circumferential stress across shell, is calculated by using finite element (FE) code ANSYS. Concentrated stress, residual stress, and temperature stress play a major role in the fatigue growth behavior, thus their effects are considered in a theoretical analysis to be included in the overall intensity factor. A certain extent good lifetime results are obtained compared with practical observation. This paper presents a reasonable procedure to evaluate propagation lifetime of weld shell, and the results are quit significant for equipment daily maintenance of rotary kiln.

Abstract: This paper mainly introduces the concepts and brief development history of profile connection, brief discusses its design theory and manufacturing techniques and finally some application prospect are put forward.

Abstract: The paper designs an image security system. It includes four parts: keys generation, permutation, diffusion and decryption. Using six decimal numbers as the key, it can get three new keys: key1, key2 and key3 from the origin key in keys generation. The permutation used a new chaotic map to shuffles the image pixels by key1 and key2. The diffusion used the logistic map to flat the histogram of the ciphered image. The key3 is the parameters of the logistic map. The results of simulation show the validity of security system. Analysis shows that it can be used in real-time image encryption applications with high speed.

Abstract: The paper designed a multi-channel data acquisition system based on PXI 6281. It used DAQmx technology in LabVIEW for synchronous analog channel data acquisition. It realized multi-channel real-time data acquisition, processing, display and data auto-saving. Data acquisition system consists of three major modules: the pressure measurement module, the motor speed measurement modules and real-time temperature measurement module. It has advantage of short cycle of technological upgrading, development and low maintenance costs. It has some reference value for other data acquisitions.

Abstract: The paper proposed a training mode for undergraduates of creativity and innovation in engineering education. It includes three elements: Precise and professional personnel training, application-oriented teaching mode and strict quality supervision. Only trinity, it can train good engineering talent. The paper proposed a practical method. It is proved by the practice of engineering education in years.

Abstract: Tool wear monitoring plays an important role in the automatic machining processes. Therefore, a reliable method is necessary for practical application. In this paper, a new method based on cointegration theory was introduced to extract features from the cutting force signal in the milling process. Cointegration relationship between cutting forces of different directions could be found and the corresponding cointegration vector could also be calculated. In order to improve the reliability of pattern recognition, the cointegration vectors combined with the energy of the high-frequency components of the acoustic emission signals were used as features. Once all the features are extracted, they were trained and tested through a support vector machine model. Experiments were performed to verify this method and the results showed that it could efficiently recognize the tool wear status.

Abstract: A forced van der Pol system with two time-delays is studied. The central aim is analyzing primary resonance of this system. Perturbation method is used to obtain the average equation and bifurcation equation with time-delays. Based on the average equation, the stable region of this system is discussed. Based on the bifurcation equation, the multivalued property of response amplitude is studied. The result indicates that this system can be well controlled with time delays.