Micro-gravity experiment of a space robotic arm using parabolic flight

We conducted a micro-gravity flight experiment on a space robotic arm, which is a part of the Reconfigurable Brachiating space Robot (RBR) unit arm developed by the authors. We used a 4-d.o.f. arm and an end-effector in the experiment. The airplane (MU-300) generates the micro-gravity environment for approximately 20 s in parabolic flight operation. After the flight, we conducted the corresponding ground experiments, and obtained the data of the motor current, servo control characteristics and manipulation performances, which were compared with the flight experiment data. Then, we conducted the numerical analysis of the 4-d.o.f. RBR arm based on the experiment results. In the analysis, we investigated feasibility of simulation model and identified model parameters. In this paper, we report the results of the flight experiments and numerical analysis.     

Heat transfer analysis of blast furnace cast steel cooling stave

Abstract

Cast steel blast furnace (BF) cooling staves are widely used in the Chinese steel industry. A heat transfer mathematical model of a BF cast steel cooling stave has been developed and verified by thermal state experiments. Calculation of a cooling stave working under steady state has been carried out based on the model. Effects of two factors, thickness of scale on the cooling water pipes and gas clearance between the pipes and main body, which are difficult for experimental measurement but determined mathematically, on the temperature field of the stave body are discussed. The results indicate that much importance should be attached to the two factors during manufacturing of cooling staves as they highly influence cooling capability of cooling stave and hence BF operation.     

Measurement of ladle slag oxygen activity using electrochemical sensor

Abstract

The oxygen activity of the ladle slag may be measured in situ with an electrochemical sensor. The measurement principle of this sensor needs further clarification. An experimental and computational study has been carried out of the contribution of specific components to the oxygen activity of the slag and of the factors that influence oxygen activity measurement with the sensor. Experiments on an industrial and on a laboratory scale show that FeO_x, SiO₂ and MnO exert a measurable influence on the results. The measurements also show a marked influence of the dissolved oxygen content in the steel. The oxygen activity of the slags has been calculated thermodynamically and compared with the sensor measurements. A systematic difference is observed. A hypothesis on the working principle of the sensor and on the cause of occasional problematic measurement values is proposed.     

Experimental and operational thermal studies on blast furnace cast steel staves

Abstract

The operating conditions of cast steel staves at Masteel blast furnace have been simulated to generate the temperature distribution under different operating conditions. The influence of the temperature and velocity of cooling water as well as the gas temperature of blast furnace on the temperature distribution of the cast steel stave was obtained. The main cause of stave damage is discussed. The result shows that cast steel staves possess better heat transfer ability and a lower temperature distribution field than nodular cast iron staves, but their performance is much less satisfactory than that of copper staves.     

Hatfield Memorial Lecture 2007 Railways and materials: synergetic progress

Abstract

Railways were originally uniquely identified with the material of their initial construction and now are technically identified by the characteristic contact of 'steel wheel on steel rail'. Over 160 years ago failures of iron railway axles led to research into what we now know as metal fatigue. Accidents throughout the ages have acted as catalysts for research and improvements: this lecture will identify some key incidents. The change from iron to steel, following Bessemer's discovery of a method of bulk production and its implementation in Sheffield, resulted in fewer materials failures and enabled greater loads to be carried at greater speeds. Today's railways rely on a wide variety of materials from all the major classes of materials. The requirements of cost, weight, reliability, crashworthiness, maintainability and inspection are often in conflict as the service loadings imposed by the modern railway on materials have become more severe. It is not therefore surprising that despite our advances in knowledge and capabilities, costly failures still occasionally occur. Nevertheless, railways have benefited from, and contributed to, advances in material engineering way beyond the initial emphasis on iron.     

Measurement of the intrinsic strength and intrinsic and total fracture resistances of stainless steel/E-glass composite joints

Parameters that characterize joint fracture are defined and procedures to measure them discussed. The interface strength σ _o is measured by using a novel laser spallation experiment, which uses a laser-induced stress wave to separate the interface. The intrinsic (G _ir) and total (G _or) fracture resistances are measured using double cantilever beam experiments by carrying out these at cryogenic and ambient temperatures, respectively. These experiments are used to obtain hitherto unreported relationships between G _or and G _ir, and between σ _o and G _ir, for joints between stainless steel and E-glass composite sections. The durability of the joints under moisture exposure was also studied and was used as a means to alter σ _o and G _ir. Joint chemistries, including use of silane layers on the steel substrate, are disclosed which optimize the joint performance, with and without the preconditioning treatment of moisture exposure. In such optimized joints, the fracture is always cohesive within the composite adherend. The paper provides quantitative values for G _ir, G _or and σ _o which are useful to a designer to set up the local failure condition in design simulations of ship structures in which such joints are considered as a part.     

Development of a functional model for a master–slave combined manipulator for laparoscopic surgery

Minimally invasive surgery helps patients by accelerating postoperative recovery. However, its application is impeded because it is necessary for the surgeons performing such surgery to possess surgical skills of a high order. Therefore, a master-slave combined manipulator (MCM) has been proposed as a robotic tool that enhances the surgeon's skill in laparoscopic surgery. The master grip and the slave hand are combined through the manipulator body, and a surgeon can operate the tool near the patient. The slave hand is controlled electrically by the master grip and its position is directly controlled by the surgeon. A prototype model of the MCM has been developed. The functions of the MCM have been verified by basic evaluation tests and the MCM has been used in a preliminary animal experiment. This paper describes the concept, the basic performance and the validation of the MCM.     

SIMULATION AND EXPERIMENT OF BUBBLY FLOW INSIDE THROTTLING GROOVE

The relationship between pressure distribution and cavitation (noise) inside throttling groove is investigated by numerical simulation and experimental method. A valve pocket with several transducers is performed to detect the pressure distributions inside the valve chamber, and the results fit quite well with the computational fluid dynamics(CFD) analysis. High-speed imaging techniques are employed to investigate the cavitation mechanisms, in particular bubble inception and cluster formation near the throttling groove. A spectrum analyzer is used to measure the sound pressure level of noise generated by the bubble flow. It is found that the pressure distributions inside the groove are sensitive to the valve port configuration and back pressure. The pressure distribution determines the bubble size and number passing through the valve grooves and the sound pressure level of noise induced by collapsing bubbles. The inlet pressure mainly affects the saturation degree of bubbly flow inside the groove and the intensity of sound pressure level accordingly.