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张春 《拖拉机与农用运输车》1985,(2)
<正> 495A柴油机齿轮罩原设计用ZL12铸造铝合金,由于铸造中产生缩孔等缺陷,废品率较高。因此,我们改用了冷冲件,经过一年多生产实践,取得了良好效果。 1.零件结构和工艺过程 零件结构如图1、2。改进前工艺较简单,铸造后进行切削加工。改进后采用1.5毫米厚的08钢板,经落料、拉延成形、整形、切边、冲孔、翻边等六个冲压工序,最后镀锌。其中较关键的工序是拉延成形(图3)。拉延 相似文献
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基于LS-DYNA显隐式算法,采用真实拉延筋模型和各向异性硬化准则,应用新的模拟方法对复杂汽车覆盖件进行回弹模拟,详细介绍了压边、拉延成形、切边和回弹模拟过程。由于压边圈的接触面是凹凸不平的空间曲线,采用压边使板料和压边圈形状相吻合,使压边力能顺利施加到压边圈上,以此提高板料成形质量,进而提高回弹精度。 相似文献
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根据汽车覆盖件模具设计的工艺,在UG平台上将标准件技术和参数化方法应用于汽车覆盖件模具的设计中,能够大大地缩短传统覆盖件模具设计的周期,达到快速响应制造。本文以汽车后地板前加强梁左/右连接板为例介绍了汽车覆盖件拉延模具设计,经过实践应用,证明该方法简化了设计过程,提高了设计效率。 相似文献
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针对汽车外覆盖件的A级表面,设计并制造了4种不同试验模具,在试验模具中包含了在汽车外覆盖件容易产生破裂的典型的反拉延特征.通过冲压试验,观察到表面破裂缺陷的产生,并搜集产生表面破裂缺陷处的应变及位移的历程及在破裂区域的接触压力的数据.同时,以自主开发的商品化冲压成形CAE软件KMAS/UFT模块为平台,针对冲压过程中破裂缺陷进行精确预示,并以CAE数值模拟软件LS-DYNA3D对比,模拟计算结果与冲压试验结果基本一致.依据广义成形理论,提出针对破裂控制方案的实施建议,为进一步修正冲压模具奠定基础. 相似文献
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铝合金车身覆盖件冲压成形回弹仿真方法研究 总被引:1,自引:0,他引:1
王强 《农业装备与车辆工程》2012,50(4):50-53
研究铝合金车身覆盖件冲压成形回弹的仿真方法能够降低研发成本、缩短开发周期、提高设计质量.阐述了铝合金车身覆盖件冲压成形回弹仿真的流程,首先是几何建模,即在专业软件中建立零件的几何模型后再导入到有限元仿真软件中,然后进行有限元建模及仿真,主要包括覆盖件网格划分、冲压方向和方式的确定、模具工艺补充的建立、压料面的建立和凹模的生成、板料模型的建立、拉延筋的处理、凸模的生成、仿真模型的装配等.总结提出了铝合金覆盖件冲压成形回弹仿真的关键技术,包括隐式回弹分析方法、节点约束、适合于铝合金成形的材料模型和单元类型等,最后对某车型前翼子板进行了回弹仿真. 相似文献
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1.发达国家设施农业的现状
目前,大多数发达国家的设施农业都以塑料温室为主,而荷兰等西欧国家由于气候的原因则以玻璃温室为主.其温室骨架大都为钢骨架,屋顶则选用铝合金.其覆盖材料一般分两层,即外覆盖材料和内覆盖材料,外覆盖材料多用各种塑料薄膜、玻璃、玻璃纤维加强聚酯板和聚酸酯板;内覆盖材料有保温帘(用于冬季或夜间提高保温性能)、遮阳网或各种降温、降湿材料(用于夏季降低温室内的温度和湿度). 相似文献
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《Journal of Agricultural Engineering Research》1998,69(3):249-254
A model to represent the discolouration of dried powder of carrots as a function of temperature was developed. Two types of carrots, Asian and European, containing large amount of lycopene and β-carotene, respectively, were tested. The dried powder was stored under an atmosphere with O2and at three different temperatures, 5,20 and 35°C. The surface colour of the powder was monitored during storage by a Hunter colour ratioa/b. In the proposed model, the rate of oxidation was assumed to be represented by the product of the fraction of concentration of oxidized pigment at arbitrary time and a specific rate of oxidation of pigment. The rate parameters in the proposed model were calculated by fitting the experimental data with smooth curves by trial and error at the end of the induction period but before discolouration took place. The frequency constant and activation energy, expressing the temperature dependence of the rate parameters, were expressed by the Arrhenius relation. The simulation results of a Hunter colour ratioa/bof dried powder at 25°C showed good agreement with the experimental data, suggesting that the proposed model was effective for the prediction of discolouration of dried powder of both types of carrot. The use of the induction period in the manner described may enable the shelf life of dried powder to be predicted. 相似文献
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感官检验棉花的品级,这是农村常见的一种检测手段.它的一个主要特点就是存在不确定性.这是由于检验员的品级检验水平存在一定的差异,其中有很多因素制约着检验的结果.文章对影响感官检验结果的因素进行了系统的分析. 相似文献
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The fractional outflow rate of water from the rumen, measured as the rate of disappearance of the chromium complex of ethylenediamine tetra-acetic acid, was related to a number of dietary factors. A multiple regression equation was derived which expressed fractional outflow rate as a function of the intakes of dry matter, ash, acid-detergent fibre and crude protein.The data analysed consisted of 243 observations for sheep on 59 diets, including forage, concentrate and mixed diets. The ranges covered by the data were: fractional outflow rate 0.7–3.6 day?1; dry matter intake 560–1400g/day; ash 4–30%, acid-detergent fibre 7–41%, crude protein 5–26 % of dry matter; there were no observations for sheep of less than 34 kg liveweight.The equation accounted for 56·3 % of the total variance. Between-sheep variance could not be calculated for the whole of the data but was undoubtedly substantial since, for a sixth of the data, it was known to account for 38 % of the total variance. 相似文献
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从灾害经济学的角度探讨了城镇供水优化调度的必要性和可能性,认为在缺水不可避免的情况下,对供水进行优化调度可以减小缺水带来的损失,产生较好的减灾效益,特别是可以大大减小严重干旱的灾害效应。并根据水资源的特性,提出了缺水损失的计算模式以及优化调度的原则和方法。 相似文献