Finite Element Analysis of Vehicle Load Effect on Harvesting Energy Properties of a Piezoelectric Unit

To realize the goal of harvesting energy from pavement vibration on a large scale, a new type of piezoelectric harvesting units as the energy transducer has been proposed. The piezoelectric harvesting units are paved 40 mm below the asphalt, which is the same as thickness of the top layer of typical asphalt pavement in China. The spacing distance is 2200 mm, which is the same as the one between two tires of a normal vehicle. A mathematical model of the unit is deduced on Meda empirical formula and Hamilton principle and piezoelectric equations. Effects of the external vehicle load on its harvesting energy properties and pavement deformation and stress are analyzed with the finite element method. The results show that the excited voltage is linearly variation with contact pressure while the harvested electrical energy exponential varies with contact pressure. The more the contact pressure is, the larger the harvested electrical energy and the deformation and stress are. The harvested electrical energy also increases with the load frequency. At least 100 mJ of electrical energy can be collected with the proposed piezoelectric harvesting unit. It shows that the technology application of the piezoelectric harvesting energy from pavement is promising.

Simulation of fluid-structure interaction in a microchannel using the lattice Boltzmann method and size-dependent beam element on a graphics processing unit

Fluid-structure interaction （FSI） problems in microchannels play a prominent role in many engineering applications. The present study is an effort toward the simulation of flow in microchannel considering FSI. The bottom boundary of the microchannel is simulated by size-dependent beam elements for the finite element method （FEM） based on a modified cou- ple stress theory. The lattice Boltzmann method （LBM） using the D2Q13 LB model is coupled to the FEM in order to solve the fluid part of the FSI problem. Because of the fact that the LBM generally needs only nearest neighbor information, the algorithm is an ideal candidate for parallel computing. The simulations are carried out on graphics processing units （GPUs） using computed unified device architecture （CUDA）. In the present study, the governing equations are non-dimensionalized and the set of dimensionless groups is exhibited to show their effects on micro-beam displacement. The numerical results show that the displacements of the micro-beam predicted by the size-dependent beam element are smaller than those by the classical beam element.

超高温高压油气井完井封隔器研制与应用

随着深井深层油气田的勘探开发,超高温高压腐蚀性的特殊油气田日益增多,对完井封隔器提出了更高要求,国内现有封隔器不能完全满足工况需求。开发了一种耐高温、高压、腐蚀的新型特种氟橡胶材料和多材料复合密封单元结构,研制了温压指标232℃/103.4 MPa超高温高压油气井完井封隔器。研制中进行了仿真分析和室内测试,并在现场作业中进行了应用。结果表明,在232℃/103.4 MPa测试条件下,密封单元密封完好,封隔器整机满足API-11D1 V0等级的测试要求。在超高温高压环境累计14井次应用过程中,完井封隔器密封良好,无泄漏或失效情况发生,满足油田生产需求,具有现场应用推广价值。

轮毂轴承单元密封结构优化设计及试验验证

针对轮毂轴承单元密封结构产生的摩擦力矩占比过大的问题,提出了将密封材料由氟橡胶改进为丁腈橡胶,密封结构减少一个接触唇的改进措施,并通过优化得到最优密封中间唇参数为唇倾斜角65°、唇厚0.6 mm、唇长3.8 mm、过盈量0.35 mm。将密封改进后的轮毂轴承单元进行了密封圈应力、漏脂试验、泥浆试验的仿真分析并通过试验进行验证,结果表明,优化后的轴承应力均满足材料许用应力要求,未出现漏脂现象,油脂含水量增加小于3%,启动、动态摩擦力矩分别降低了24.3%,22.1%,证明了优化后密封结构的可靠性。

新型弯管机关键机构设计及相关工艺的开发

针对新型弯管机组在生产弯管的过程中,由于管材弯曲变形的特殊性和复杂性,使得弯管的成形过程中容易产生管壁失稳起皱、减薄拉裂、横截面畸变等各种缺陷等重要问题,以外径60.3mm、壁厚3.05mm规格的不锈钢管材为对象,在机械设计理论的基础上,对其管状毛坯的定位机构进行了设计并通过有限元分析实现管状毛坯两端倾角,管状毛坯上下端长度以及管状毛坯的中心长度变形率的确定。使新型弯管机的弯管成形机构、管状毛坯和液压推杆的中轴线保持在同一水平高度上面,以保证管状毛坯在液压推杆的推动下能够准确地进入成形模具之中。可以代替原本的设备,提高弯管的成形质量,提高生产效率,具有进一步推广应用的价值。

欧洲美国日本药典药用辅料元素杂质检查的变革

目的通过分析欧洲药典(EP)、美国药典(USP)和日本药典(JP)中药用辅料品种正文中重金属及特定元素检查项的收载历史及现状,探讨其设置的特点,为《中国药典》药用辅料品种中元素杂质检查的收载策略提供参考,为行业加强药品和药用辅料元素杂质控制提供借鉴。方法梳理EP、USP和JP中药用辅料品种及其重金属和特定元素检查项的收载及修订过程,主要从品种数目、重金属设置比例、专业类别、处理情况等方面与《中国药典》进行对比分析,探讨其差异的原因及未来可能的发展方向。结果USP收载的药用辅料品种最多,EP对药用辅料元素杂质评估进度最快,JP药用辅料中湿化学方法比例最多。结论可借鉴EP、USP和JP的处理方式制定《中国药典》药用辅料元素杂质收载策略,按照药用辅料类别进行风险等级分类,对于风险较低的品种可以考虑直接删除重金属,风险较高的矿物类药用辅料逐一进行元素杂质风险评估,特定元素杂质的检查项按类别进行风险评估,根据风险评估结果确定药典中特定元素的收载形式,必要时按类或按品种制定元素杂质单独限度或方法。

Inversion of the Main Mineral Compositions and Subdivision of Tectonic Units on Lunar LQ-4 based on Chang'e Data

Spectra are sensitive in detecting main minerals on the lunar surface from visible light to infrared light. Since spectral characteristics of minerals are closely related to their compositions and the maturity level of soil on the Moon, studying the compositions and distribution of elements and minerals on the lunar surface can help to understand the evolution of the Moon through remote sensing technology. The correlation between the spectral characteristics of Chang＇e-1 interference imaging spectrometry（IIM） reflectance images and the mineral contents of LSCC（Lunar Soil Characterization Consortium） lunar surface mineral samples was discussed and the spatial distributions of Fe O and Al_2O_3 contained in both pyroxene and plagioclase on LQ-4 were studied using the improved angle parameter method, MNF, and band ratio statistics. A comparison of the mapping results of the optical models by Lucey, Shkuractov and other researchers on Clementine and the gamma ray spectrometry data shows that the content error is within 0.6% for lunar mare areas and close to 1% for the highland areas. The tectonic framework on the lunar surface was also investigated. And based on integrated analysis of previous findings on topography of the lunar surface, Chang＇e LAM, CCD and LOLA images and the gravity anomalies data（Clementine GLGM-2）, the tectonic unit subdivision was established for LQ-4, the idea of subdividing the lunar tectonic units was proposed, and this will provide a good foundation for studying the lunar tectonic evolution.

A PRECISE SINGULAR FINITE ELEMENT FOR CRACK ANALYSIS

The multi-variable finite element algorithm based on the generalized Gulerkin's method is more flexible to establish a finite element model in the continuum mechanics. By using this algorithm and numerical tests a new singular finite element for elasto-plastic fracture analysis has been formulated. The results of numerical tests show that the new element possesses high accuracy and good performance. Some rules for formulating a multi-variable singular finite element are also discussed in this paper.

Stream Surface Strip Element Method and Simulation of Three-Dimensional Deformation of Continuous Hot Rolled Strip

A new method,the stream surface strip element method,for simulating the three-dimensional deformation of plate and strip rolling process was proposed.The rolling deformation zone was divided into a number of stream surface(curved surface)strip elements along metal flow traces,and the stream surface strip elements were mapped into the corresponding plane strip elements for analysis and computation.The longitudinal distributions of the lateral displacement and the altitudinal displacement of metal were respectively constructed to be a quartic curve and a quadratic curve,of which the lateral distributions were expressed as the third-power spline function,and the altitudinal distributions were fitted in the quadratic curve.From the flow theory of plastic mechanics,the mathematical models of the three-dimensional deformations and stresses of the deformation zone were constructed.Compared with the streamline strip element method proposed by the first author of this paper,the stream surface strip element method takes into account the uneven distributions of stresses and deformations along altitudinal direction,and realizes the precise three-dimensional analysis and computation.The simulation example of continuous hot rolled strip indicates that the method and the model accord with facts and provide a new reliable engineering-computation method for the three-dimensional mechanics simulation of plate and strip rolling process.

3D FINITE ELEMENT ANALYSIS OF THE DAMAGE EFFECTS ON THE DENTAL COMPOSITE SUBJECT TO WATER SORPTION

The damage effects of water sorption on the mechanical properties of the hydroxyapatite particle reinforced Bis-GMA/TEGDMA copolymer （HA/Bis-GMA/TEGDMA） h-ave been predicted using 3D finite cell models. The plasticizer effect on the polymer matrix was considered as a variation of its Young＇s modulus. Three different cell models were used to determine the influence of varying particle contents, interphase strength and moisture concentration on the debonding damage. The stress distribution pattern has been examined and the stress transfer mode clarified. The Young＇s modulus and fracture strength of the Bis-GMA/TEGDMA composite were also predicted using the model with and without consideration of the damage. ine Iormer results with consideration of the debonding damage are in good agreement with existing literature experimental data. The shielding effect of our proposed model and an alternative approach were discussed. The FCC cell model has also been extended to predict the critical load for the damaged and the undamaged composite subject to the 3-point flexural test.

Eccentric Pumping Unit: Cost-effective and Reliable

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Elastic Predictions of 3D Orthogonal Woven Composites Using Micro/meso-scale Repeated Unit Cell Models

This presentation predicts the elastic properties of three-dimensional(3D)orthogonal woven composite(3DOWC)by finite element analysis based on micro/meso repeated unit cell(RUC)models.First,the properties of fiber yarn are obtained by analysis on a micro-scale RUC model assuming fibers in a hexagonal distribution pattern in the polymer matrix.Then a full thickness meso-scale RUC model including weft yarns,warp yarns,Z-yarns and pure resin zones is established and full stiffness matrix of the 3DOWC including the in-plane and flexural constants are predicted.For thick 3DOWC with large number of weft,warp layers,an alternative analysis method is proposed in which an inner meso-RUC and a surface meso-RUC are established,respectively.Then the properties of 3DOWC are deduced based on laminate theory and properties of the inner and surface layers.The predicted results by the above two alternative methods are in good experimental agreement.

STATISTIC MODELING OF THE CREEP BEHAVIOR OF METAL MATRIX COMPOSITES BASED ON FINITE ELEMENT ANALYSIS

The aim of the paper is to discover the general creep mechanisms for the short fiber reinforcement matrix composites (MMCs) under uniaxial stress states and to build a relationship between the macroscopic steady creep behavior and the material micro geometric parameters. The unit cell models were used to calculate the macroscopic creep behavior with different micro geometric parameters of fibers on different loading directions. The influence of the geometric parameters of the fibers and loading directions on the macroscopic creep behavior had been obtained, and described quantitatively. The matrix/fiber interface had been considered by a third layer, matrix/fiber interlayer, in the unit cells with different creep properties and thickness. Based on the numerical results of the unit cell models, a statistic model had been presented for the plane randomly-distributed-fiber MMCs. The fiber breakage had been taken into account in the statistic model for it starts experimentally early in the creep life. With the distribution of the geometric parameters of the fibers, the results of the statistic model agree well with the experiments. With the statistic model, the influence of the geometric parameters and the breakage of the fibers as well as the properties and thickness of, the interlayer on the macroscopic steady creep rate have been discussed.

Unit Cell Modelling of Auxetic Structure

Auxetic material structures exhibit a negative Poisson ratio. The structure expands in the axial and transverse directions under tensile loading and vice versa under compression loading. Many fabricated designs for auxetic materials exist such as re-entrant hexagonal, chiral, and arrowhead geometries. This paper studies the unit cell of the re-entrant hexagonal geometry to understand how changing the internal angle and fillet radius of the structure affects the Poisson’s ratio. The material chosen for this study is acrylonitrile butadiene styrene (ABS) due to its availability and frequent use in additive manufacturing. The study was based on finite element analysis. It is observed that the direction of load applied to the unit cell affects the unit cell strain, Poisson’s ratio, and maximum load capacity before failure responses. It is noticed that the re-entrant cell starts by showing a standard non-auxetic behavior until it reaches a specific axial strain value. A quadratic correlation is identified between axial and transverse strain. Designing an auxetic structure starts with understanding the behavior of a unit cell structure. The auxetic structure design is a complex process that requires a compromise between auxetic property to be achieved and load capacity via avoiding stress concentration zones.

Study on the particle breakage of ballast based on a GPU accelerated discrete element method

Breakage of particles will have greatly influence on mechanical behavior of granular material(GM)under external loads,such as ballast,rockfill and sand.The discrete element method(DEM)is one of the most popular methods for simulating GM as each particle is represented on its own.To study breakage mechanism of particle breakage,a cohesive contact mode is developed based on the GPU accelerated DEM code-Blaze-DEM.A database of the 3D geometry model of rock blocks is established based on the 3D scanning method.And an agglomerate describing the rock block with a series of non-overlapping spherical particles is used to build the DEM numerical model of a railway ballast sample,which is used to the DEM oedometric test to study the particles’breakage characteristics of the sample under external load.Furthermore,to obtain the meso-mechanical parameters used in DEM,a black-analysis method is used based on the laboratory tests of the rock sample.Based on the DEM numerical tests,the particle breakage process and mechanisms of the railway ballast are studied.All results show that the developed code can better used for large scale simulation of the particle breakage analysis of granular material.

主轴结构参数对静刚度贡献度的分析

为了研究主轴芯轴的结构参数对主轴径向静刚度的影响规律,以某型号主轴为研究对象,通过有限元模型静力学分析主轴径向静刚度。将主轴芯轴的结构参数简化为12个主要结构参数,采用单一变量法和相关性分析法分析结构参数和主轴径向静刚度的相关性,确定与主轴径向静刚度显著相关的结构参数。运用正交试验-方差分析法分析关键结构参数对主轴径向静刚度的贡献度。结果表明:主轴悬伸部分和轴承跨距之间的结构参数对主轴径向静刚度的贡献度分别为20.3%、69.8%,可以通过定向改变主轴芯轴结构参数控制主轴径向静刚度,提高主轴的刚度特性。

北京大院生活型街道边界要素对可步行性的影响--以玉渊潭南路、太平路、翠微路为例

文章以提升城市街道可步行性为目标,以北京大院生活型街道为例,对街道边界空间要素对可步行性的影响进行了研究。研究分析了3条北京大院生活型案例街道的边界要素构成及组合模式,并基于街景图像对街道可步行性进行评分,将要素与可步行性评分进行相关性研究,指出对可步行性影响高的边界要素及其作用,为大院生活型街道的更新设计提供参考。研究表明,要素的数量、感知边界要素的类型、要素的细部设计对街道可步行性有较高影响。此外,绿地要素的灵活运用能够显著提升街道的可步行性。

GNPs改性环氧3D编织复合材料导热特性研究

石墨烯纳米片(Graphene nanoplatelets,GNPs)改性3D编织复合材料将GNPs与编织物有机融合,有望协同提高材料导热特性。然而,3D编织复合材料内胞和表胞呈现出不同的导热特性,加之GNPs的协同改性作用,增加了材料导热特性研究难度。本文紧扣GNPs改性3D编织复合材料细观结构特征,以GNPs改性树脂等效热导率表征为基础,基于周期性温度边界条件,构建材料的多胞有限元热物理分析模型,详尽研究了GNPs含量、编织角和纤维体积分数等对各胞元热导率的影响规律。分析表明:随着GNPs含量增加,3D编织复合材料导热特性逐步提升。随着编织角增加,GNPs改性3D编织复合材料横向热导率迅速增加而纵向热导率下降;同时,GNPs改性3D编织复合材料热导率随纤维体积分数增加而提升。上述规律为GNPs改性3D编织复合材料导热性能设计提供了坚实的理论基础。

多层复合PVB夹层玻璃的低速冲击性能研究

采用ABAQUS有限元软件,构建落锤冲击聚乙烯醇缩丁醛酯(PVB)夹层玻璃板的1/4对称模型,在其网格单元间嵌入零厚度内聚力粘结单元,模拟冲击失效过程,在相同的总厚度条件下,分析了玻璃层数、PVB厚度对夹层玻璃抗冲击性能的影响。结果表明,总厚度不变的情况下,玻璃层数对夹层玻璃的冲击失效有明显的影响。玻璃厚度一定,当PVB厚度h≤1.9 mm时,适当减小PVB厚度能改善双层夹层玻璃的吸能效果;当PVB厚度h>1.9 mm时,适当增加PVB厚度能改善双层夹层玻璃的吸能效果。对于三层夹层玻璃,上层PVB厚度的变化对玻璃抗冲击性能的影响更加明显且适当减小上层PVB厚度能改善三层夹层玻璃的吸能效果。

C型钢缀板柱的有限元模拟方法研究

缀板柱以其制造简便、稳定性高且价格低廉的优势,在工程钢结构中得到了广泛应用,如何准确模拟缀板与立柱之间的连接情况,是工程结构有限元模拟时的重要问题。文章采用有限元软件ANSYS,研究C型钢缀板柱中缀板与立柱之间连接情况的有限元模拟问题,通过对比单元整体建模与节点耦合建模的模拟结果,分析了节点耦合连接方法的模拟原理并提出了使用时的注意事项。计算分析表明:整体建模模拟效果较好但不便于模型修改和精细化模拟,节点耦合便于修改但需要考虑耦合方法和连接面积。文章提出的简化统一耦合方法模拟效果好,适应性强,对于工程实践中的有限元模拟工作具有一定指导意义。