Preparation of MIM213 turbine wheel with hollow internal structure

Turbine wheels fabricated by conventional ingot metallurgy suffer casting defects and compositional segregation problems, and their mechanical properties can't be fully developed. This article presents the preparation of MIM213 turbine wheels through metal injection molding in conjunction with hot isostatic pressing. The filling stages of the turbine wheel were investigated by simulation and experimental short shots, and the microstructure and mechanical properties of MIM213 superalloy were examined. It is shown that MIM is suitable for the near-net shape forming of turbine wheel with hollow internal structure and complex blade geometry. Compared with the turbine wheel with solid core structure, the turbine wheel with hollow internal structure has relatively smaller proportion of high temperature region during injection molding, resulting in smaller shrinkage stress and the elimination of shrinkage voids. The relative density of MIM213 superalloy sintered in Ar atmosphere reaches 96.6%. A high volume fraction (31%) of spherical γ′ phase with average particle size of 124 nm, discrete secondary grain boundary borides and internally precipitated MC carbides are formed in austenite matrix. The tensile properties of MIM213 superalloy are higher than that of the equivalent cast K213 superalloy.     

飞机轮速信号测试方法研究

为解决某飞机轮速信号测试中出现的数据缺失、曲线阶梯状不平滑及数据回零问题,分析轮速信号测试原理及测试系统结构,结合待测轮速信号特性,提出轮速信号测试优化方法,包括备份设计、直流隔离、周期测试及指标优化等。并针对轮速信号地面状态特性,设计一种信号测试链路检测方案。试飞测试验证结果表明,备份数据误差低于0.5%,数据曲线平滑,可消除数据回零现象,设计的轮速信号测试链路检测方案可行,有助于试飞航前检查。     

卧轮式分级机转子临界转速的计算

为避免卧轮式分级机在运转过程中产生共振,以卧轮式分级机实验机和工业样机转子为研究对象,采用传递矩阵法和基于ANSYS Workbench 16.0的有限元法对其临界转速进行计算,将计算结果与试验测试结果进行比较。结果表明,对于实验机,传递矩阵法与试验测试结果偏差为11.9%,有限元法与试验测试结果偏差为4.1%;对于工业样机,传递矩阵法与试验测试结果偏差为10.5%,有限元法与试验测试结果偏差为3.5%,说明有限元法计算结果准确性更高,认为对于卧轮式分级机转子临界转速的计算,更适合采用有限元法。     

High speed preprocessing system

In systems employing tracking, the area of interest is recognized using a high resolution camera and is handed over to the low resolution receiver. The images seen by the low resolution receiver and by the operator through the high resolution camera are different in spatial resolution. In order to establish the correlation between these two images, the high-resolution camera image needs to be preprocessed and made similar to the low-resolution receiver image. This paper discusses the implementation of a suitable preprocessing technique, emphasis being given to develop a system both in hardware and software to reduce processing time. By applying different software/hardware techniques, the execution time has been brought down from a few seconds to a few milli-seconds for a typical set of conditions. The hardware is designed around i486 processors and software is developed in PL/M. The system is tested to match the images obtained by two different sensors of the same scene. The hardware and software have been evaluated with different sets of images.     

风力机复合材料柔性叶片的颤振分析

将风力机叶片简化为薄壁复合材料封闭截面弯扭耦合变形梁,基于Hamilton原理并结合变分渐进法（VAM）,建立风力机叶片的气动弹性力学模型。结构模型包括材料各向异性,截面翘曲,离心载荷,科里奥利加速度,以及预锥角和预扭转角的影响。气动载荷采用叶素动量理论和准定常气动力理论进行描述。将位移按广义坐标进行模态展开,采用Galerkin法导出系统的质量、刚度和阻尼矩阵,采用特征值技术进行叶片颤振性能的数值求解。针对周向反对称刚度配置（CAS）叶片进行数值近似计算,揭示了入流比、预扭转角和纤维铺层角等参数对风力机叶片颤振性能的影响。     

Structural design of a carbon fiber-reinforced polymer wheel for ultra-high speed grinding

Ultra-high speed grinding (UHSG) is receiving considerable attention owing to its ability to achieve high machining accuracy and productivity. The materials and design of the grinding wheels play a significant role in this technology. Wheels with steel bodies are currently widely used, but have deficiencies such as a large mass loading imposing on the spindle, along with high power consumption, large stress and deformation, and limited practical grinding wheel speed. Wheel bodies made of carbon fiber-reinforced polymer (CFRP) show promise for use in UHSG because of the low density and high specific strength of this material. The main aim of this paper is to carry out a structural design of a CFRP grinding wheel for UHSG. Comparisons of stress and deformation, dynamic characteristics, thermal deformation, and power consumption between steel and CFRP wheel bodies reveal the superior performance characteristics of CFRP. The design of the laminate structure of the CFRP is then optimized, considering various laminate processes. The abrasive layers are designed with regard to the number and thickness of segments. Finally, a CFRP wheel for UHSG is developed based on the design proposal.     

Evaluation of shear flow in composite wind turbine blades

The present work addresses the evaluation of the shear flow as an extension of the Jourawski’s formula. This idea is developed here for the case of a multi-celled composite thin-walled section. Firstly, the explicit formulation of the shear flow due to shear forces and torsion is derived, noting the simplificative hypothesis adopted. Then, the implemented model is verified by means of a benchmark problem with a known analytical solution. Finally, this model is utilized to evaluate the shear flow on an actual blade configuration, comparing the results obtained with those of a Finite Element model of the same blade, with a similar discretization.     

Post-buckling failure in multi-delaminated composite wind turbine blade materials

This study models the inter-laminar damage due to low velocity impacts on hybrid composite materials typical of those used in wind turbine blade structures. The effect of z-pinning using natural flax yarn on the critical buckling load and post-buckling behaviour of multi-delaminated composite beams was investigated. Laminated composite beams were pinned through their thickness using natural flax yarns to control delamination failure during the post-buckling process. A multiple delamination with a triangular shape was inserted into each of the beams to simulate the damage caused by a low velocity impact e.g. ice, on composite wind turbine blades. For a laminate design of [C₉₀/G₉₀]₄, global collapse caused no delamination failure during the post-buckling test while delamination failure occurred for a laminate design of [C₀/G₀]₄. In this case, z-pinning can significantly increase the failure resistance within a composite structure and it can then postpone the failure process. The buckling process of a multi-delaminated composite beam was also simulated by finite element software ANSYS and the results were substantially verified by relevant experimental results.     

Improving the response of a wheel speed sensor by using frequency-domain adaptive filtering

In this paper, a frequency-domain least-mean-square adaptive filter is used to cancel noise in a wheel speed sensor embedded in a car under performance tests. In this case the relevant signal is buried in a broad-band noise background, where we have little or no prior knowledge of the signal or noise characteristics. The results of the experiments show that the signal of interest and the noise (all forms of interference, deterministic, as well as stochastic) share the same frequency band and that the filter used significantly reduced the noise corrupting the information from the sensor while it left the true signal unchanged from a practical point of view. In this paper, a signal-to-noise ratio improvement higher than 40 dB is achieved. The results of the experiment show the importance of using digital signal processing when dealing with a signal corrupted by noise.     

High temperature materials in gas turbine engines

The current performance trends in civil, aero and industrial gas turbines are discussed. Future improvements in materials technology are needed for major components — aerofoils, discs and combustors — to achieve improved performances.     

High speed microcompression of paper coatings

A novel high speed microcompression platen tester was developed in order to measure the out-of-plane compressive modulus of thin materials. The instrument is capable of subjecting a sample of thickness 20 μm or greater to a transverse compressive pulse over a time interval ranging from approximately 2 ms to several seconds, and can therefore be used to collect data under conditions representative of those in a high speed calender nip. In this study, free layers of coating formulations normally used to coat paper were prepared and tested using the microcompression platen tester described above. Tests were conducted at high speeds, with a pulse duration of 2 ms during the compressive stroke, and at 23 °C to simulate room temperature calendering conditions. The compressive modulus of the coating did not correlate strongly with the modulus of its constituent latex. Latex content, however, strongly affected coating compressive modulus. A sharp increase in the compressive modulus was observed at the coating critical pigment volume concentration (CPVC)—essentially the latex concentration at which the coating layer porosity is reduced to zero. Pigment size distribution and pigment morphology also affected the compressive modulus of coating in a manner consistent with packing theory.     

Particle swarm-based structural optimization of laminated composite hydrokinetic turbine blades

Composite blade manufacturing for hydrokinetic turbine application is quite complex and requires extensive optimization studies in terms of material selection, number of layers, stacking sequence, ply thickness and orientation. To avoid a repetitive trial-and-error method process, hydrokinetic turbine blade structural optimization using particle swarm optimization was proposed to perform detailed composite lay-up optimization. Layer numbers, ply thickness and ply orientations were optimized using standard particle swarm optimization to minimize the weight of the composite blade while satisfying failure evaluation. To address the discrete combinatorial optimization problem of blade stacking sequence, a novel permutation discrete particle swarm optimization model was also developed to maximize the out-of-plane load-carrying capability of the composite blade. A composite blade design with significant material saving and satisfactory performance was presented. The proposed methodology offers an alternative and efficient design solution to composite structural optimization which involves complex loading and multiple discrete and combinatorial design parameters.     

陶瓷基复合材料涡轮叶盘设计、制备与考核验证

涡轮转子是燃气涡轮发动机的核心部件。针对SiC/SiC涡轮叶盘设计、制备与考核验证开展研究,采用蛛网仿形(SWS)SiC纤维预制体作为涡轮叶盘的增强体,预制体表面分别沉积BN界面相与SiC基体,通“在线加工”方式对SiC/SiC涡轮叶盘分别进行粗加工和精加工,采用大气等离子喷涂方法制备环境障碍涂层,形成满足设计要求的涡轮叶盘。采用CT对SiC/SiC涡轮叶盘进行无损检测,表征叶盘内部缺陷分布。针对制备的SiC/SiC涡轮叶盘开展性能评价、超转试验、台架试验等考核验证,研究表明：SiC/SiC涡轮叶盘最大破坏强度达到300 MPa;在室温超转试验中,当转速达到n=104 166 r/min时,叶片发生断裂,当转速达到n=108 072 r/min时,轮体发生破裂;在发动机台架试验中,累积完成了N=994次最高转速n_max=60 000 r/min的循环载荷及N=100次最高转速n_max=70 000 r/min的循环载荷试车考核。2022年1月1日,SiC/SiC涡轮叶盘在株洲成功完成了首次飞行试验验证,这也是国内陶瓷基复合材料转子首次配装平台...