气动载荷在等参形函数表达方式下的合力理论解

民用飞机常使用等参形函数表达气压载荷,但是现有算法对等参形函数没有进行深入研究,导致求解过程繁琐、耗时。文章对等参形函数进行了深入的理论推导,给出了部分计算的理论解,相比先前的求解方法,求解速度可大幅提高。

Optimization of AZ80 magnesium alloy squeeze cast process parameters using morphological matrix

The squeeze cast process parameters of AZ80 magnesium alloy were optimized by morphological matrix. Experiments were conducted by varying squeeze pressure, die pre-heat temperature and pressure duration using L9（33） orthogonal array of Taguchi method. In Taguchi method, a 3-level orthogonal array was used to determine the signal/noise ratio. Analysis of variance was used to determine the most significant process parameters affecting the mechanical properties. Mechanical properties such as ultimate tensile strength, elongation and hardness of the components were ascertained using multi variable linear regression analysis. Optimal squeeze cast process parameters were obtained.

Effect of hot deformation conditions on grain structure and properties of 7085 aluminum alloy

The influences of deformation conditions on grain structure and properties of 7085 aluminum alloy were investigated by optical microscopy and transmission electron microscopy in combination with tensile and fracture toughness tests. The results show that the volume fraction of dynamic recrystallization increased with the decrease of Zener-Hollomon （Z） parameter, and the volume fraction of static recrystallization increased with the increasing of Z parameter. The strength and fracture toughness of the alloy after solution and aging treatment first increased and then decreased with the increase of Z parameter. The microstructure map was established on the basis of microstructure evolution during deformation and solution heat treatment. The optimization deformation conditions were acquired under Z parameters of 1.2×10^10-9.1×10^12.

Hot deformation behavior of extruded AZ80 magnesium alloy

The hot deformation behavior of extruded AZ80 magnesium alloy was studied through hot compression tests performed at temperatures ranging from 250 to 450 ~C with strain rates varying from 0.001 to 10 s-1. The flow stress was corrected due to the deformation heating. The Zener-Hollomon parameter （Z parameter） and processing map were established to describe the hot deformation behavior. The results indicate that the applicable deformation should be conducted at the strain rate of 0.1 s-~ and the temperature range of 350-400 ~C. Besides, the relationship between the microstructure evolution and Z parameter was also discussed. High temperature and low strain rate result in a low Z parameter, which leads to full dynamic recrystallization （DRX） and large DRX grain size in the microstructure. Considering processing map and microstructure, the hot deformation should be carried out at the temperature of 400 ~C and the strain rate of 0.1 s 1.

太子参蛋白提取工艺优化及SDS-PAGE分析

【目的】研究太子参的最佳蛋白提取工艺和不同参形太子参蛋白条带差异。【方法】选取3种蛋白提取方法(Tris-HCl法、TCA-丙酮法、饱和酚法)对贵州施秉县牛大场太子参种植基地的3种参形太子参进行蛋白提取及SDSPAGE分析,利用响应面分析法对筛选出的最佳蛋白提取方法的提取工艺进行优化。【结果】3种蛋白提取方法中Tris-HCl法提取的蛋白含量较高,经SDS-PAGE分析,太子参蛋白条带大致分布在10 k Da^90 k Da之间,15 k Da处一等参的蛋白表达量明显高于二等参和统货。利用响应面优化法获得提取太子参蛋白的最佳工艺。【结论】获得太子参蛋白的最佳提取工艺:料液比1∶1.32、提取温度25℃、pH值7.47、提取时间1.5 h,还发现不同参形太子参蛋白在15 k Da处的表达量存在明显差异,这可为今后利用蛋白质组学技术进一步揭示不同参形太子参形成的分子机制提供理论依据。

Effect of geometrical parameters on forming quality of high-strength TA18 titanium alloy tube in numerical control bending

The forming quality of high-strength TA18 titanium alloy tube during numerical control bending in changing bending angle β, relative bending radius R/D and tube sizes such as diameter D and wall thickness t was clarified by finite element simulation. The results show that the distribution of wall thickness change ratio Δt and cross section deformation ratio ΔD are very similar under different β; the Δt and ΔD decrease with the increase of R/D, and to obtain the qualified bent tube, the R/D must be greater than 2.0; the wall thinning ratio Δto slightly increases with larger D and t, while the wall thickening ratio Δti and ΔD increase with the larger D and smaller t; the Δto and ΔD firstly decrease and then increase, while the Δti increases, for the same D/t with the increase of D and t.

Near net shape casting process for producing high strength 6xxx aluminum alloy automobile suspension parts

The automobile suspension parts of a high strength 6xxx aluminum alloy were produced using a novel technique known as near net shape casting for forging stock preparation. Based on the outline dimension of the forging stock, the shape of the ingot was designed as the near net shape and its casting process was studied by the numerical simulation and experimental investigation. The results show that the shrinkage of the ingot was highly correlated to its shape parameters and could be successfully forecast by the stimulation model. The casting parameters of the near net shape ingot were optimized and the near net shape 6xxx aluminum alloy ingots free of defects were cast in the laboratory. In order to obtain high performance forged suspension parts, the hot compression tests of the ingot were carried out. The results show that the subgrain fraction of the forged ingot was strongly affected by Zener-Hollomon parameters （Z parameters）. The intermediate Z parameters, 1.09×10^16 s^-1, will contribute to the larger number fraction of subgrains inside the forged ingot, which contributes to the high performance of the forged products.

Establishment of size-dependant constitutive model of micro-sheet metal materials

The inherent mechanism of size effect in micro-sheet material behavior of plastic forming was explained by the surface layer model and theory of metal crystal plasticity. A size-dependant constitutive model based on the surface layer model was established by introducing the scale parameters and modifying the classical Hall-Petch equation. The influence of the geometric dimensions and the grain size on the flow behavior of the material was discussed using the new material constitutive model. The results show that, the flow stress decreases while the sheet metal thickness decreases when the grain size keeps constant, and the micro-sheet metal with a larger grain size is more easily to be influenced by the size effects. The material constitutive model established is validated by the stress-strain curve of the micro-sheet metal with different thicknesses derived from the tensile experiments. The rationality of the material model is verified by the fact that the calculation results are consistent with the experimental results.

Identification of material parameters from punch stretch test

To accurately describe the mechanical properties of aluminium alloy sheet during deformation, an inverse identification was presented to deal with material parameters from the popular punch stretch test. In the identification procedure, the optimization strategy combines finite element method （FEM）, Latin hypercube sampling （LHS）, Kriging model and multi-island genetic algorithm （MIGA）. The proposed approach is used on material parameter identification of aluminium alloy sheet 2D12. The anisotropic yield criterion Hill’90 is discussed. The results show that the Hill’90 anisotropic yield criterion with identified anisotropic material parameters has a good potential in describing the anisotropic behaviours. It provides a way to obtain the material parameters for FE simulations of sheet metal forming.

文登四叶参种植与管理技术

四叶参原为昆嵛山区的野生品种,现经过驯化由野生转为大田种植。四叶参俗名山戎萝卜,又称狗头参、乳薯,学名轮叶党参,入药也可食用,具有强身壮体,养阴清肺,止咳化痰,增加乳汁之功效,是我国出口美国、日本、韩国的山菜之王。四叶参经济价值与外皮的颜色有关,颜色越深价值越低,价格相差一倍,同时参形越好价值越高,侧根越多价值越低。

DETERMINATION OF MATERIAL PARAMETERS FOR COMPUTER SIMULATION OF SUPERPLASTIC FORMING PROCESSES

In order to analyze and simulate the complex super-plastic forming process by computer, a method of equal height bulging for determining material parameters m and K of the superplastic alloy is presented. The formulae related to the method are deduced in this paper. The accuracy of the method is available for evaluating the examples used in simulating the superplastic sheet-metal bulging processes.

Bézier curves with shape parameter

In this paper, Bézier basis with shape parameter is constructed by an integral approach. Based on this basis, we define the Bézier curves with shape parameter. The Bézier basis curves with shape parameter have most properties of Bernstein basis and the Bézier curves. Moreover the shape parameter can adjust the curves’ shape with the same control polygon. As the increase of the shape parameter, the Bézier curves with shape parameter approximate to the control polygon. In the last, the Bézier surface with shape parameter is also constructed and it has most properties of Bézier surface.

Investigation on Zener-Hollomon parameter in the warm-hot deformation behavior of 20CrMnTi

The warm-hot deformation behavior of 20CrMnTi steel was studied with hot compression tests at temperature range of 1123-1273 K and strain rate of 0.1-20 s^-1. The activation energy for warm-hot deformation is 426.064 KJ/mol. The influences of Zener-Hollomon parameter, strain and grain size imposing on the flow stress were analyzed in the temperature range of warm-hot forging. Creep theory and mathematical theory of statistics were used to obtain mathematical models of flow stress. The research and results provide scientific basis for controlling microstructure of forging process through Zener-Hollomon parameter.

Spherical parametrization of genus-zero meshes by minimizing discrete harmonic energy

The problem of spherical parametrization is that of mapping a genus-zero mesh onto a spherical surface. For a given mesh, different parametrizations can be obtained by different methods. And for a certain application, some parametrization results might behave better than others. In this paper, we will propose a method to parametrize a genus-zero mesh so that a surface fitting algorithm with PHT-splines can generate good result. Here the parametrization results are obtained by minimizing discrete har- monic energy subject to spherical constraints. Then some applications are given to illustrate the advantages of our results. Based on PHT-splines, parametric surfaces can be constructed efficiently and adaptively to fit genus-zero meshes after their spherical parametrization has been obtained.

Estimation of the van Genuchten Soil Water Retention Properties from Soil Textural Data

The van Genuchten (vG) function is often used to describe the soil water retention curve (SWRC) of unsaturated soils and fractured rock. The objective of this study was to develop a method to determine the vG model parameter m from the fractal dimension. We compared two approaches previously proposed by van Genuchten and Lenhard et al. for estimating m from the pore size distribution index of the Brooks and Corey (BC) model. In both approaches we used a relationship between the pore size distribution index of the BC model and the fractal dimension of the SWRC. A dataset containing 75 samples from the UNSODA unsaturated soil hydraulic database was used to evaluate the two approaches. The statistical parameters showed that the approach by Lenhard et al. provided better estimates of the parameter m. Another dataset containing 72 samples from the literature was used to validate Lenhard's approach in which the SWRC fractal dimension was estimated from the clay content. The estimated SWRC of the second dataset was compared with those obtained with the Rosetta model using sand, silt, and clay contents. Root mean square error values of the proposed fractal approach and Rosetta were 0.081 and 0.136, respectively, indicating that the proposed fractal approach performed better than the Rosetta model.

Mechanical properties and microstructure evolution in incremental forming of AA5754 and AA6061 aluminum alloys

This study performs single point incremental forming(SPIF)on two aluminum alloys(i.e.AA5754 and AA6061),and analyzes their post forming mechanical properties and microstructure evolution.The forming parameters namely wall angle(35°-55°),feed rate(1-4 m/min),spindle rotational speed(50-1000 r/min),and lubricant(grease and hydraulic oil)are varied to probe detailed processing effects.The pre-and post-SPIF mechanical properties and microstructures are characterized by conducting tensile tests and optical microscopy,respectively.It is shown that an increase in the wall angle,feed rate and rotational speed causes microscopic variations in the alloys such that the grains of AA5754 and the second phase particles of AA6061 elongate.As a result,the ultimate tensile strength of the formed parts is increased by 10%for AA5754 and by 8%for AA6061.And,the ductility of AA5754 is decreased from 22.9%to 12%and that of AA6061 is decreased from 16%to 10.7%.Regarding the lubricant effect,it is shown that the mechanical properties remain insensitive to the type of lubricant employed.These results indicate that SPIF processing modifies the microstructure of Al alloys in a way to enhance the strength at the cost of ductility.

Numerical investigations for the impacts of triple-moment and double-moment condensation schemes on the warm rain formation

The initiation and intensity of warm rain are processes dominated by the evolution of cloud droplet spectra.To treat the cloud condensation process properly is a fundamental step for the simulation of warm rain formation.Double-moment bulk schemes with a limited number of prognostic variables cannot simulate the evolution of droplet spectra properly.A triple-moment bulk scheme,however,should overcome the problem of spurious cloud droplet spectrum broadening induced by double-moment schemes.To compare the effects of a newly developed triplemoment scheme with double-moment schemes on warm rain formation,the authors conducted WRF-LES numerical simulations to investigate the impacts of the two types of condensation scheme on rain initiation and intensity.In the early stage of raindrop formation,the simulation with the triple-moment scheme delays the raindrop initiation and produces droplet spectra with smaller average radii than those with the double-moment scheme.In the developing stage,the triple-moment scheme reduces the raindrop water content at the precipitation center.However,the further triple-moment scheme for raindrop is needed to simulate the development of warm rain accurately.

Watershed Prioritization of Palar Sub-watershed Based on the Morphometric and Land Use Analysis

Morphometric analysis is an indispensable tool for hydrological investigation that involves the development and management of drainage basin. This study characterizes the micro watersheds in the Palar sub-watershed using morphometric analysis and assesses its risk by land use and land cover features in a particular micro watershed. Palar sub-watershed is divided into 6 micro watersheds for prioritization based on morphometric and land use analysis. Several morphometric parameters （linear, shape and relief） are determined from the drainage map; ranks are assigned based on their capacity to induce erodability and degradation. Final ranking is based on the composite index calculated from the sum of the ranks of each morphometric parameter. Morphometric analysis reveals micro watersheds 5 and 6 as most susceptible and 2 and 3 as low susceptible. Land use is mapped using IRS ID LISS III satellite data. The risk in terms of watershed degradation involved to each micro watershed is based on the ranks of each land use feature, obtained from a similar composite index as that of morphometric analysis. Land use analysis shows that micro watersheds 2 and 4 fall under high priority category while 5 and 6 under low priority category. Integration of the morphometric and land use analysis shows that only microwatershed 1 falls under the same category in both analyses. Control measures are suggested to contain degradation depending on its specific land use pattern and morphometric features. This study ean be used to prepare a comprehensive watershed plan for the development or for planning resource conservation strategies, by integrating land use features with the drainage characteristics of the region, in particular for a hill ecosystem as the prioritization is at micro level.

An adaptive waveform-detection threshold joint optimization method for target tracking

The joint optimization of detection threshold and waveform parameters for target tracking which comes from the idea of cognitive radar is investigated for the modified probabilistic data association(MPDA)filter.The transmitted waveforms and detection threshold are adaptively selected to enhance the tracking performance.The modified Riccati equation is adopted to predict the error covariance which is used as the criterion function,while the optimization problem is solved through the genetic algorithm(GA).The detection probability,false alarm probability and measurement noise covariance are all considered together,which significantly improves the tracking performance of the joint detection and tracking system.Simulation results show that the proposed adaptive waveform-detection threshold joint optimization method outperforms the adaptive threshold method and the fixed parameters method,which will reduce the tracking error.The average reduction of range error between the adaptive joint method and the fixed parameters method is about 0.6 m,while that between the adaptive joint method and the adaptive threshold only method is about 0.3 m.Similar error reduction occurs for the velocity error and acceleration error.

Morphological parameters of both surfaces of coupled joint

Twenty one joints were made with Brazilian tests and each surface was scanned by the Talysurf CLI 2000. Morphological characteristics of joint surface were quantified by statistical and textural parameters. By the contrast of these parameters between both sides of each coupled joint, the following conclusions are drawn. The upper and lower surfaces of coupled joints have approximately equal values of Sp（maximum height of joint surface）, Sa（arithmetic mean height of joint surface） and Sq（root mean square height of joint surface）, but the Ssk（skewness of the height distribution of joint surface） values of the two surfaces of a coupled joint are different, one is positive while the other is negative. The Saj（auto-correlation length） parameter values of both surfaces of each coupled joint are quite close, and the S^（texture aspect ratio） values have the same situation to the Sal parameter, but the same parameters of different surfaces have big differences which illustrates its own characteristics of each joint. The two surfaces of each coupled joint have similar values of θp （mean profile angle） which can be used to deduce the value of θp each other.