Owing to their large and curved shape, blade castings, a key component for heavy hydro turbines, are susceptible to deformation during casting and heat treatment. In the present paper, the stress analysis of a blade casting during both casting and heat treatment is performed. The coupled thermo-stress and thermo-phase transformation stress models are used for casting and heat treatment respectively. Machining allowance distribution is used as the deformation criterion and an algorithm of inverse deformation determination is presented. The mechanical properties of the martensitic stainless steel ZG 0 Cr 13 Ni 4 Mo (13Cr–5Ni–1Mo) at different temperatures are measured under as cast and heat treated status. Finally, the inverse deformation of the blade during both casting and heat treatment processes is obtained, and a series of sections of the blade casting with inverse deformation design are given for pattern making. The calculated deformation results are compared to the measured one, and they are basically in agreement.
The parameters obtained in the study of single layer of laser cladding forming are not suitable for the forming of actual structures. The cooling condition varies with the height of clad layers, which result in instability and then failure of cladding. Therefore, the stability of laser cladding forming is of significance. In this paper, melt pool depth is used as a criteria for stability. And the effect of processing parameters such as laser power and laser velocity on melt pool depth, are investigated by numerical simulation method. The results unveil that there is a transition zone from the beginning to stable stage during laser cladding forming. In the transition zone, laser power should be decreased or laser velocity should be increased to maintain the constant melt pool depth and to ensure the former clad layer would not be remelt. The optimized processing parameters are obtained for stable processing for a thin flat wall and a cylindrical wall, which successfully guide the manufacturing of the real structures.
The (TiVCr)x-(TaW)1-x binary system thin films were deposited by a magnetron sputtering system with two intermediate alloy targets. The elemental composition were adjusted by tuning the currents of the two targets, and the value of x in the (TiVCr)x-(TaW)1-x binary system changes from 25 to 90 with the current changes. The surface morphology, roughness, element composition and phase structure of the coatings were studied. With increasing the value of x, the film changes from body-centered-cubic (BCC) to BCC + amorphous structures, and the surface morphology and roughness also show a certain correlation with the phase-structure transition. The research focuses on the mechanical properties and radiation response of the film. The nanoindentation method is used to analyze the hardness and modulus of the material, and the wear resistance of the material is analyzed through reciprocating abrasion experiments. The influence of the 70Kev He+ ions implantation on the structure and microstructure was investigated. The results show that at x=0.51, the film exhibits the best mechanical properties under the action of various strengthening mechanisms. On the other hand, forming a BCC polycrystalline structure and an amorphous mixed structure can improve the radiation resistance of the material.
Ultrasonic treatment is a hot research topic in the treatment of the melt of metals. Numerical simulation is a useful method to unveil the principles of ultrasonic treatment. In this paper, the Novier-Stoke equations and the cavitation model are coupled to simulate the cavitation during ultrasonic treatment by using Fluent. It is found that as the nucleation site volume fraction increases to a certain degree, there will be a bubble layer surrounding the amplitude transformer, which insulates the effect of ultrasound beyond the bubble blanket. Experiment was carried out, and the simulated results were validated. And the effect of nucleation site volume fraction in water is investigated. The nucleation site volume fraction should be controlled into a certain range to realize uniform cavitation.
To deal with the shortage of 3 He gas, which is widely used in thermal neutron detection, the boron coated straw-tubes have been developing to replace the 3 He proportional counters. We present in this paper the realization process of a straw tube with 1 m long and the diameter is 4 mm, with 1 μm B 4 C layer coated on the inner surface to convert neutrons to charged particles. [1] The parameters, high voltage, working gas and the diameter of the anode wire, are researched to realize the best performance of the straw tube. 7.27 mm, the average position resolution of a single tube, is achieved with the straw tube with 15 μm-diameter karma anode wire (1.33μΩ · m at 20°C), with 1atm pure argon as working gas and working under the voltage of 730 V in the tentative experimental research. The linearity of positions measured by charged division read out and the real positions can achieve 99.992%.
Emerging terminals, such as smartwatches, true wireless earphones, in-vehicle computers, etc., are complementing our portals to ubiquitous information services. However, the current ecology of information services, encapsulated into millions of mobile apps, is largely restricted to smartphones; accommodating them to new devices requires tremendous and almost unbearable engineering efforts. Interaction Proxy, firstly proposed as an accessible technique, is a potential solution to mitigate this problem. Rather than re-building an entire application, Interaction Proxy constructs an alternative user interface that intercepts and translates interaction events and states between users and the original app's interface. However, in such a system, one key challenge is how to robustly and efficiently "communicate" with the original interface given the instability and dynamicity of mobile apps (e.g., dynamic application status and unstable layout). To handle this, we first define UI-Independent Application Description (UIAD), a reverse-engineered semantic model of mobile services, and then propose Interaction Proxy Manager (IPManager), which is responsible for synchronizing and managing the original apps' interface, and providing a concise programming interface that exposes information and method entries of the concerned mobile services. In this way, developers can build alternative interfaces without dealing with the complexity of communicating with the original app's interfaces. In this paper, we elaborate the design and implementation of our IPManager, and demonstrate its effectiveness by developing three typical proxies, mobile-smartwatch, mobile-vehicle and mobile-voice. We conclude by discussing the value of our approach to promote ubiquitous computing, as well as its limitations.
Using voice commands to automate smartphone tasks (e.g., making a video call) can effectively augment the interactivity of numerous mobile apps. However, creating voice command interfaces requires a tremendous amount of effort in labeling and compiling the graphical user interface (GUI) and the utterance data. In this paper, we propose AutoVCI, a novel approach to automatically generate voice command interface (VCI) from smartphone operation sequences. The generated voice command interface has two distinct features. First, it automatically maps a voice command to GUI operations and fills in parameters accordingly, leveraging the GUI data instead of corpus or hand-written rules. Second, it launches a complementary Q&A dialogue to confirm the intention in case of ambiguity. In addition, the generated voice command interface can learn and evolve from user interactions. It accumulates the history command understanding results to annotate the user’s input and improve its semantic understanding ability. We implemented this approach on Android devices and conducted a two-phase user study with 16 and 67 participants in each phase. Experimental results of the study demonstrated the practical feasibility of AutoVCI.
Hydraulic turbine band castings are susceptible to deformation in heat treatment process if their cooling is not well controlled. The coupled analysis of forced air flow and heat transfer in normalizing process of a heavy turbine band runner casting with outer diameter of 8000 mm was carried out by using ANSYS software. The band undergoes significant deformation because of uneven cooling resulted by uneven air flow around it during normalizing. The forced air flow pattern is a key factor which influences the cooling uniformity and efficiency. It is optimized by adjusting the cooling fans’ orientation relative to the casting to form cyclone around it. Consequently, cooling uniformity is improved to avoid deformation.
In order to reduce the internal cracks and control the quality of the steel strand in continuous casting, a thermal-mechanical model considering the movement of the strand, real roll arrangement and caster structure, has been established with the elasto-viscoplastic constitution to predict the three dimensional temperature distribution and bulging deformation of the strand. Using the sequentially coupled finite element method the model is solved numerically, and is validated by the comparisons of the simulation results and measured data. The model is suitable for future research on the whole strand bulging deformation to help improve the strand quality in continuous casting.
Multi-track laser cladding is necessary in the forming of parts. The overlap between neighbor tracks plays an important role, which determines the quality and surface smoothness of the clad layer. In this paper, numerical simulation of the multi-track laser cladding process is studied. The heat source of laser spot is applied by updating the profile of clad region and the location of the moving laser spot. The clad profile of overlapped track was obtained, from which the surface roughness was analyzed by the variation of overlap ratio. Meanwhile, experiments were carried out to evaluate the effect of overlap ratio. The simulated and the experimental results are in good agreement; both show that there is an optimal overlap ratio to achieve best surface roughness.
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