共查询到20条相似文献,搜索用时 15 毫秒
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基于 Biot 固结原理和达西定律 , 建立了二维树脂流动与纤维密实模型 , 采用有限元方法实现了 L 形层板热压成型过程树脂压力分布、 层板变形的预测。通过对 AS4 炭纤维/环氧 350126 等厚层板厚度变化的模拟结果与实验数据的对比分析 , 证明了数学模型和有限元程序的可靠性。以阳模成型 90° 铺层 S22玻璃纤维/环氧 648L 形层板为例 , 对工艺过程层板厚度变化进行了分析。模拟结果表明 : 剪切模量对拐角以及拐角与平板过渡区域的变形影响较大 ; 平板长度对拐角区域变形影响较明显 , 对平板区的变形影响较小。采用热压罐制备了 90° 铺层S22玻璃纤维/环氧 648阳模成型 L 形层板 , 实验数据表明 , 固化后层板呈现拐角区厚、 平板区薄的厚度不均现象 , 并且平板长度对拐角区厚度变化影响较显著 , 这与数值预测结果具有较好的一致性。 相似文献
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采用LS-DYNA非线性有限元软件对Ti/Al3Ti金属间化合物基层状(MIL)复合材料靶板的弹道侵彻过程进行了数值模拟。考察了等厚度下Ti体积分数、层数和材料梯度分布对复合材料抗侵彻性能的影响。结果表明,Ti体积分数约为20%时,靶板的抗侵彻性能最好。随着层数的增加,复合材料靶板的抗侵彻性能逐渐增强;但超过25层后,靶板的抗侵彻性能逐渐趋于稳定。不同铺层结构功能梯度板的抗侵彻性能相差较大,正向铺层梯度板的抗侵彻性能明显优于等厚均质复合材料靶板。 相似文献
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基于ANSYS环境的平面编织层合板拉伸破坏数值仿真 总被引:3,自引:1,他引:2
以ANSYS为平台编制了具有可移植性的APDL程序, 建立了损伤累积模型, 对平面编织层合板的损伤破坏行为进行了数值仿真。该模型对适合于单向铺层的Hanshin判据和Reddy刚度衰减方法进行了相应的修正。为验证模型的有效性, 对G803/5224平面编织光滑板、 孔板进行了相应的试验研究。结果表明, 该模型仿真结果与试验结果吻合, 并且比较简单直观, 为平面编织层合板的损伤扩展与破坏的研究提供了便于工程应用的数字化手段。 相似文献
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用自编的动态有限元分析程序APIC 对含缺陷的复合材料层合板的冲击损伤问题进行了模拟计算。该程序采用三维20 节点超单元分析了复合材料层合板内的应力分布, 通过修正后的C. T. Sun 的接触定律建立了冲击物和层合板的运动状态与冲击接触力之间的关系, 采用Wilson-θ法求解层合板和冲击物的运动微分方程。在处理层间分层缺陷问题时, 采用拉格朗日乘子法使预制分层缺陷界面上满足不可互相贯穿条件。对本文中的计算结果和试验结果进行比较表明: 模拟计算结果与试验结果有良好的一致性。相对于无缺陷层合板, 含预制分层缺陷的复合材料层合板在分层部位遭受冲击时, 分层缺陷对冲击损伤扩展有一定的抑制作用。 相似文献
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建立了一个三维真空热处理炉的非线性有限元模型,该模型的热源是电流通过加热体产生的焦耳热,传热途径主要考虑了加热体与内屏蔽层间、各屏蔽层之间的非线性辐射传热.利用有限元软件ANSYS对真空热处理炉加热过程中的瞬态温度场进行了模拟计算,得到了热电偶温度随时间的变化曲线,并与实验结果进行了比较,讨论了进一步提高计算准确性的途径. 相似文献
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Two numerical methods have been developed for the prediction of gas/vapour transmission rates in multilayer laminate films consisting of different polymers with extensive variations in relative thicknesses. The methods developed allow the use of different spatial step lengths for the different layers. The methods have been applied to experimental oxygen transmission rates through laminates based on low‐density polyethylene and poly(ethylene terephthalate) and it was found that the predictions agreed with the experimental results within the experimental error limits. The methods were also used to predict the water vapour transmission rates for a three‐layer laminate of low‐density polyethylene and polyamide‐6. Since water vapour diffusivity in polyamide‐6 is a function of the water concentration, different and sometimes complex results were obtained depending on the location of the polyamide‐6 layer in the laminate. Calculations showed that the only way to predict the optimum positions of different layers, in order to minimize the penetrant transmission rate through a laminate when the penetrant interacts with the material, is by rigorous simulations using these or similar methods. Copyright © 1999 John Wiley & Sons, Ltd. 相似文献
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V V Ranade 《Sadhana》1992,17(2):237-273
This paper reviews the available information on numerical simulation of dispersed gas-liquid flows. Emphasis is on informing the reader about various aspects of constructing simulation models rather than giving an exhaustive literature review. The information is organised in a way so as to provide answers to the following questions: how to formulate model equations? how to select suitable algorithms and numerical techniques to solve these model equations? how to translate these into workable computer codes? how to use such codes for simulating flows in industrial equipment? Though greater emphasis is given to dispersed gas-liquid flows, the methodology can be applied to any multi-phase problem. Special features of multi-phase flow simulation over single-phase simulation are highlighted. A case of gas-liquid flow in a bubble column is presented as an illustration for the general methodology. The simulated mean flow field agrees reasonably with the experimental data. Properly validatedcfd codes thus can serve as a useful tool for design engineers of multi-phase systems. Some of the common pitfalls in using simulation codes for design are also discussed. This review is expected to give an overall idea about the present state-of-art of two-phase simulation in industrial equipment. 相似文献
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Short period variations in monsoon rainfall are caused by the westward passage of low pressure systems (depressions) from
the northern sector of the Bay of Bengal. A primitive equation model was used to predict the movement of one such depression
(20 August 1977). Four research ships from the USSR, which formed a part of the recently concluded Monsoon Experiment, provided
additional meteorological data within the field of this depression. This enabled us to fix the depression’s initial position
with greater accuracy than would have been possible without the ships’ data.
The model used a co-ordinate system in which the lower boundary coincided with the earth’s surface, while the upper boundary
was placed at 200 mb. It resembled a three-dimensional channel with side walls at 0° and 140°E, and northern and southern
boundaries at 60°N and the equator. The grid spacing was 250 km. Numerical integration was performed upto 5 days of model
time. Gravity waves and other forms of ‘noise’ were filtered out every 24 hr by a process of adjustment referred to as ‘initialisation’.
Initialisation after every 24 hr was necessary because the boundary conditions in this regional model did not permit sufficiently
rapid dispersal of gravity waves.
In the first experiment only orographic features were included, but the second experiment considered the main features of
atmospheric radiation in addition to orography. The paper presents a statement of deviations between the predicted and actual
movement of the depression, and discusses reasons for such deviations. 相似文献
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Plasticized polysaccharide coatings on polypropylene (PP) film were prepared to evaluate the optical and tensile properties of the resulting coated films, as affected by biopolymer and plasticizer types, in order to develop a novel film structure of biopolymer coatings on common plastics intended for food packaging applications. Composite structures of PP film coated with several kinds of polysaccharides (MC, HPMC, chitosan, κ ‐carrageenan, dextrin) and plasticizers (PG, glycerol, PEG, sucrose, sorbitol) were obtained through a simple casting method. High glossy surfaces were observed on the coated films with chitosan and κ ‐carrageenan, with the sucrose‐plasticized chitosan coating giving the highest gloss of 142.7 GU. Biopolymers, but no plasticizers, exerted noticeable influence on the colour of the coated films. Chitosan‐ and κ ‐carrageenan‐coated PP films also showed greater transparency, tensile strength and elongation than the other coated films. Nisin‐incorporated κ ‐carrageenan coatings on PP film exhibited significant bacterial growth inhibition against Lactobacillus plantarum . The results suggest that coatings based on chitosan and κ ‐carrageenan with proper plasticizers possess excellent visual and mechanical characteristics and have great potential for acting efficiently as antimicrobial agent carriers in active packaging systems. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
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冷藏展示柜柜内温度场的数值模拟及实验 总被引:1,自引:0,他引:1
建立了冷藏柜的物理数学模型,并用SIMPLE方法计算冷藏柜内空气的自然对流,得到柜内空气相应点的温度变化情况;同时对相应点的温度变化过程进行了实验研究。实验结果与理论计算结果能较好的吻合,模拟温度与实验温度的差值在1oC以内,从而验证了数学模型的正确性和计算程序的可靠性。 相似文献
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对溶液除湿器中传热传质过程进行热力学分析,根据除湿塔的结构及溶液与空气的流动方式,建立除湿器的热质交换物理和数学模型,模拟计算除湿器人口空气和溶液参数对除湿器出口空气参数的影响,得到各入口参数对出口空气温度和含湿量的影响曲线。结果表明:空气出口参数与空气人口含湿量、温度和流量、溶液人口温度和浓度几乎呈线性变化;当溶液入口流量达到2.5kg/s后,空气出口参数的变化趋于平缓。 相似文献
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热电偶是检测真空炉温度均匀性的常用计量器具,但目前热电偶的几何特性及发射率对炉温均匀性检测影响方面的研究较少.本文利用数值模拟方法研究了热电偶发射率和直径对真空炉温度均匀性检测的影响,结果表明直径和发射率对常用规格热电偶稳态温度影响量级相当.开展零维模型分析,结果表明热电偶温度对直径和发射率相对变化率的敏感性相等,验证... 相似文献
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Mikael Gllstedt Angela Brottman Mikael S. Hedenqvist 《Packaging Technology and Science》2005,18(4):161-170
The mechanical and gas‐barrier properties of paper and paperboard coated with chitosan–acetic acid salt (chitosan), whey protein isolate, whey protein concentrate and wheat gluten protein were studied. Paper sheets were solution‐coated using a hand applicator. In addition, bi‐layer composites of wheat gluten and paper or paperboard were produced by compression moulding, and the chitosan solution was also applied on paperboard using curtain coating. Young's modulus, fracture stress, fracture strain, tearing strength, air permeance and oxygen permeability were assessed. The mechanical and air permeance measurements of solution‐coated paper showed that chitosan was the most effective coating on a coat weight basis. This was due to its high viscosity, which limited the degree of penetration into the paper. The proteins, however, also enhanced the strength and toughness of the paper. Compression‐moulded wheat gluten/paper or paperboard, as well as curtain‐coated chitosan paperboard laminates, showed oxygen barrier properties comparable to those of paper and paperboard coated with commercial barrier materials. None of the composites could be delaminated without fibre rupture, indicating good adhesion between the coatings and the substrates. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
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矿井回风换热器数值模拟 总被引:3,自引:0,他引:3
为了提高矿井回风换热器对热能的利用率,改善矿区冬夏季室内环境的舒适度,利用热湿传递的基本原理以及计算流体力学的基本理论,并运用Ansys Fluent连续相与离散相耦合模型对矿井回风换热器夏季热湿传递进行数值模拟,分析结果显示换热器内部空气的温度、速度分布和水滴出口温度与实测数据较吻合。该研究为优化设计矿井回风换热器模型提供理论依据。 相似文献
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M. A. Del Nobile G. Mensitieri A. Aldi L. Nicolais 《Packaging Technology and Science》1999,12(6):261-269
Metallized polymeric films are amongst the most favoured candidates for replacing aluminum foil‐based multilayer films. The main advantages in using the former instead of the latter are: weight saving of about 40%; much less aluminum (320 time less in weight); improved recyclability; and the possibility of optimizing package barrier properties. It is generally assumed that metallization decreases the permeability of the polymeric substrate by reducing the total area available for permeation, even though the validity of such a hypothesis has never been proved experimentally. In the present paper an attempt has been made to elucidate the role of metal coating in reducing the permeation flux of polyolefine films. For this purpose, permeability tests were performed using oxygen, nitrogen and carbon dioxide at temperatures of 20–40°C. Permeation tests have been performed on two different metallized films, on their substrates alone and on two laminates. From the analysis of the experimental results, it has been concluded that, contrary to what generally thought, gas molecules can permeate through the metallized films investigated due to both the permeable porous structure of the deposited aluminum layer and the presence of pin‐holes uniformly dispersed on the metallized film surface. Copyright © 1999 John Wiley & Sons, Ltd. 相似文献