As a result of the lower backing weld efficiency, the applying of automatic welding is seriously limited. So a kind of special automatic welder is designed and manufactured for backing weld. This paper introduces the ...As a result of the lower backing weld efficiency, the applying of automatic welding is seriously limited. So a kind of special automatic welder is designed and manufactured for backing weld. This paper introduces the character of the assembled pulse CO2 arc welding machine which has strong penetrability. It specifies the technology of controlling the parameters of all position automatic welding by computer and multi-axis controller. Moreover typical welding procedure parameters are provided. It is proved by examination that the economical and practical equipment and technology are suitable for the long-distance transmission pipeline, and it has a good foreground of spreading and applying.展开更多
A new kind of inertial piezoelectric actuator for a micro in-pipe robot is proposed and studied. The actuator is composed of a body, corresponding to a mass rod, and four elastic legs. Each leg is a composite piezoele...A new kind of inertial piezoelectric actuator for a micro in-pipe robot is proposed and studied. The actuator is composed of a body, corresponding to a mass rod, and four elastic legs. Each leg is a composite piezoelectric bimorph beam, made up of a middle metal element, an upper and lower piezoelectric elements. The mechanism is driven by an asymmetric waveform voltage, such as saw-toothed waveform, and utilizes the dynamic relationship between the maximum static friction force and the inertial force. To study the actuator, firstly, the constituent equation of a composite piezoelectric bimorph under both applied voltage and external force was inferred by thermodynamics. Secondly, the dvnamic model of the actuator was established analyzing the relationship between the locomotive states, viz. displacement and velocity, and design parameters, such as piezoelectric strain constant, elastic modulus,length, width and thickness of the piezoelectric element, actuator mass, and driving vohage. At last, the dynamic equation was solved and the theoretical calculation of the inherent frequency was more consistent with the experimental data, which proved the rationality of the model. All these lay a theoretical foundation of the micro actuator parameter optimization and more research on a micro robot.展开更多
Many engineering components, such as power-plant steam pipes, aero-engine turbine discs, etc., operate under severe loading/temperature conditions. As a result, cracks can initiate and subsequently propagate over time...Many engineering components, such as power-plant steam pipes, aero-engine turbine discs, etc., operate under severe loading/temperature conditions. As a result, cracks can initiate and subsequently propagate over time due to creep. The Liu and Murakami＇s model has proven to be a useful tool for the prediction of creep crack growth under such conditions. Previously, experimental conditions used in obtaining the constant ofmultiaxiality, a, have not reflected the multiaxial severity of the stress state ahead of a crack tip. Therefore, the present study presents a novel method for interpolating crack growth data to obtain a.展开更多
The centrifugal air compressor outlet pipeline vibration was not decreased after barrel viscous dampers were installed in a petrochemical plant in Tianjin.A pipeline-damper experiment apparatus was built for studying ...The centrifugal air compressor outlet pipeline vibration was not decreased after barrel viscous dampers were installed in a petrochemical plant in Tianjin.A pipeline-damper experiment apparatus was built for studying the influence factors of the barrel viscous damper and pipe hoop in pipeline vibration reduction.The performance of the damper under different frequency and amplitude was researched respectively,the results showed that damping effect dependsed mainly on frequency and was not related to amplitude.Damper will fail when its vibration frequency exceeds its limit working frequency which was 40 Hz in test.The mechanical properties and energy dissipation were analyzed by using the Maxwell model,which explains experimental results well.According to damping effect and calculation of stiffness with ANSYS in different hoop width,hoop stiffness should match pipe stiffness and keep uniform along transfer path.Damping effect will get worse when local stiffness is too small or too large.Finally,the outlet pipeline vibration was decreased by 70%after using appropriate pipe hoop width and replacing the original damping liquid.展开更多
The modal analysis of piping system in air conditioner (AC) outdoor unit is essential to investigate the vibration properties of the system. In view of the growing significance of numerical finite element (FE) model f...The modal analysis of piping system in air conditioner (AC) outdoor unit is essential to investigate the vibration properties of the system. In view of the growing significance of numerical finite element (FE) model for vibration behaviour prediction, the AC piping elastic end support characterization has been explored. The axial and radial stiffness variables (ka, kr1, kr2) of the compressor-piping mounting are obtained and represented by dynamic stiffness of compressor grommet. They are obtained from dynamic load deflection test based on compressor operating condition such as excitation frequency and amplitude. The unknown stiffness variables of the other tube end (chassis-piping mounting) are determined by parameter fine tuning. An experimental modal analysis using impact hammer test has also been employed to determine the vibration properties such as natural frequencies, mode shapes and damping ratio of the piping structures. The modal parameters acquisition using SCADAS mobile acquisition system and LMS Impact Testing software is compared with the corresponding simulated modal properties using Abaqus. Most of the simulated natural frequencies achieve good correlation with the measured frequencies and it is reasonably a good prediction model to predict vibration behaviour of AC piping structures.展开更多
Flow measurement is important in the fluid process and transmission system. For the need of accuracy measure- ment of fluid, stable flow is acquired. However, the elbows and devices as valves and rotary machines may p...Flow measurement is important in the fluid process and transmission system. For the need of accuracy measure- ment of fluid, stable flow is acquired. However, the elbows and devices as valves and rotary machines may pro- duce swirling flow in the natural gas pipeline networks system and many other industry fields. In order to reveal the influence of upstream swirling flow on internal flow fields and the metrological characteristics, numerical si- mulations are carried out on the swirl meter. Using RNG k-e turbulent model and SIMPLE algorithm, the flow field is numerically simulated under swirling flows generated from co-swirl and counter-swirl flow. Simulation results show fluctuation is enhanced or weakened depending on the rotating direction of swirling flow. A coun- ter-swift flow increases the entropy production rate at the inlet and outlet of the swirler, the junction region between throat and divergent section, and then the pressure loss is increased. The vortex precession dominates the static pressure distributions on the solid walls and in the channel, especially at the end region of the throat.展开更多
文摘As a result of the lower backing weld efficiency, the applying of automatic welding is seriously limited. So a kind of special automatic welder is designed and manufactured for backing weld. This paper introduces the character of the assembled pulse CO2 arc welding machine which has strong penetrability. It specifies the technology of controlling the parameters of all position automatic welding by computer and multi-axis controller. Moreover typical welding procedure parameters are provided. It is proved by examination that the economical and practical equipment and technology are suitable for the long-distance transmission pipeline, and it has a good foreground of spreading and applying.
基金Sponsored by the National Natural Science Foundation of China(Grant No.69774020)the National Doctoral Foundation of China(Grant No.98014106).
文摘A new kind of inertial piezoelectric actuator for a micro in-pipe robot is proposed and studied. The actuator is composed of a body, corresponding to a mass rod, and four elastic legs. Each leg is a composite piezoelectric bimorph beam, made up of a middle metal element, an upper and lower piezoelectric elements. The mechanism is driven by an asymmetric waveform voltage, such as saw-toothed waveform, and utilizes the dynamic relationship between the maximum static friction force and the inertial force. To study the actuator, firstly, the constituent equation of a composite piezoelectric bimorph under both applied voltage and external force was inferred by thermodynamics. Secondly, the dvnamic model of the actuator was established analyzing the relationship between the locomotive states, viz. displacement and velocity, and design parameters, such as piezoelectric strain constant, elastic modulus,length, width and thickness of the piezoelectric element, actuator mass, and driving vohage. At last, the dynamic equation was solved and the theoretical calculation of the inherent frequency was more consistent with the experimental data, which proved the rationality of the model. All these lay a theoretical foundation of the micro actuator parameter optimization and more research on a micro robot.
文摘Many engineering components, such as power-plant steam pipes, aero-engine turbine discs, etc., operate under severe loading/temperature conditions. As a result, cracks can initiate and subsequently propagate over time due to creep. The Liu and Murakami＇s model has proven to be a useful tool for the prediction of creep crack growth under such conditions. Previously, experimental conditions used in obtaining the constant ofmultiaxiality, a, have not reflected the multiaxial severity of the stress state ahead of a crack tip. Therefore, the present study presents a novel method for interpolating crack growth data to obtain a.
基金Supported by the National Basic Research Program of China(No.2012CB026000)the Beijing Education Commission Special Fund andDoctoral Degree Fund(No.20110010110009)
文摘The centrifugal air compressor outlet pipeline vibration was not decreased after barrel viscous dampers were installed in a petrochemical plant in Tianjin.A pipeline-damper experiment apparatus was built for studying the influence factors of the barrel viscous damper and pipe hoop in pipeline vibration reduction.The performance of the damper under different frequency and amplitude was researched respectively,the results showed that damping effect dependsed mainly on frequency and was not related to amplitude.Damper will fail when its vibration frequency exceeds its limit working frequency which was 40 Hz in test.The mechanical properties and energy dissipation were analyzed by using the Maxwell model,which explains experimental results well.According to damping effect and calculation of stiffness with ANSYS in different hoop width,hoop stiffness should match pipe stiffness and keep uniform along transfer path.Damping effect will get worse when local stiffness is too small or too large.Finally,the outlet pipeline vibration was decreased by 70%after using appropriate pipe hoop width and replacing the original damping liquid.
文摘The modal analysis of piping system in air conditioner (AC) outdoor unit is essential to investigate the vibration properties of the system. In view of the growing significance of numerical finite element (FE) model for vibration behaviour prediction, the AC piping elastic end support characterization has been explored. The axial and radial stiffness variables (ka, kr1, kr2) of the compressor-piping mounting are obtained and represented by dynamic stiffness of compressor grommet. They are obtained from dynamic load deflection test based on compressor operating condition such as excitation frequency and amplitude. The unknown stiffness variables of the other tube end (chassis-piping mounting) are determined by parameter fine tuning. An experimental modal analysis using impact hammer test has also been employed to determine the vibration properties such as natural frequencies, mode shapes and damping ratio of the piping structures. The modal parameters acquisition using SCADAS mobile acquisition system and LMS Impact Testing software is compared with the corresponding simulated modal properties using Abaqus. Most of the simulated natural frequencies achieve good correlation with the measured frequencies and it is reasonably a good prediction model to predict vibration behaviour of AC piping structures.
基金supported by the National Natural Science Foundation of China(51579225)
文摘Flow measurement is important in the fluid process and transmission system. For the need of accuracy measure- ment of fluid, stable flow is acquired. However, the elbows and devices as valves and rotary machines may pro- duce swirling flow in the natural gas pipeline networks system and many other industry fields. In order to reveal the influence of upstream swirling flow on internal flow fields and the metrological characteristics, numerical si- mulations are carried out on the swirl meter. Using RNG k-e turbulent model and SIMPLE algorithm, the flow field is numerically simulated under swirling flows generated from co-swirl and counter-swirl flow. Simulation results show fluctuation is enhanced or weakened depending on the rotating direction of swirling flow. A coun- ter-swift flow increases the entropy production rate at the inlet and outlet of the swirler, the junction region between throat and divergent section, and then the pressure loss is increased. The vortex precession dominates the static pressure distributions on the solid walls and in the channel, especially at the end region of the throat.
