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从自由镦粗变形程度基本定义式 ,推导出了自由镦粗成形工艺的顶镦变形次数n和各次变形程度εhn,这两个自由镦粗变形基本工艺参数的设计计算公式 ,并举例说明了其应用方法 相似文献
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本文利用上限法研究了圆柱体镦粗变形过程的计算机模拟,提出了一种以实验研究结果为依据的变形流动模式和动可容速度场,以及绘制各步增量变形后镦粗坯料外形的简易尺寸变换法。然后,将计算所得数学模型编制成步进模拟用的ALP1D程序,在IBMPC/XT微机及配置的绘图系统上运行,获得了圆柱体镦粗过程自由表面的外形变化、力——行程曲线和速度矢量分布图。模拟结果与实测数据很一致。 相似文献
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局部镦粗是标准紧固件行业生产中普遍应用的方法之一,而局部镦粗的长径比(L/d)则是影响镦锻头部质量的关键参数。长径比越大镦锻的头部质量越难保证。但究竟影响头部质量的长径比界限是多少,目前尚无冷镦局部镦粗标准。目前用于冷镦局部镦粗工艺的初冲、光冲设计及长径比确定等,主要是结合冷锻生产实 相似文献
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引入相对高度系数m,用平衡微分方程与塑性条件联立建立了圆柱体粗糙平板不均匀镦粗的应力场,求解出了圆柱体镦粗时的鼓形方程和镦粗变形压力数学解析式,并对变形体内应力分布特点及纵向裂纹成因进行了理论探讨. 相似文献
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通过分析粗糙平板间平面镦粗时金属的流动规律,用数学解析法和计算机辅助设计相结合.确定该塑性变形体内各点最大剪应力的轨迹.即建立滑移线场. 相似文献
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分析了硬铝合金方头柱塞件的冷挤镦工艺 ,设计了方头柱塞冷挤镦件图 ,计算及选用了毛坯形状及尺寸 ,验算了许可变形程度 ,选择了冷成形用的设备 ,拟制了冷挤镦工艺前的毛坯处理并设计了方头柱塞冷挤镦模具结构。 相似文献
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着重研究了六角凸缘螺栓冷切挤工艺及其与热墩工艺的比较 ,并介绍了在多工位冷墩机上的模具设计方案。 相似文献
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利用道南膜技术(DMT)研究土壤中重金属自由离子浓度 总被引:10,自引:3,他引:7
采用近年新发展起来的一种研究重金属自由离子浓度的方法———道南膜技术,研究了采自我国不同地区的11种耕层土壤中Cd、Zn、Pb和Cu的自由离子浓度.结果表明,道南膜技术测定的Cd、Zn自由态浓度与WinHumicV模型计算结果吻合较好,测定的Pb和Cu自由态浓度稍高于WinHumicV模型计算结果.同时,采用Sauv啨提出的吸附腜投匀芙馓妥杂商闹亟鹗艚蟹治?结果表明,溶解态Zn、Cu和Pb以及自由态的Zn、Cu受土壤的污染程度(重金属总量)、土壤pH和溶液中溶解性有机碳控制. 相似文献
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Chemodynamics of heavy metals in long-term contaminated soils:Metal speciation in soil solution 总被引:4,自引:2,他引:2
The concentration and speciation of heavy metals in soil solution isolated from long-term contaminated soils were investigated. The
soil solution was extracted at 70% maximum water holding capacity (MWHC) after equilibration for 24 h. The free metal concentrations
(Cd2+, Cu2+, Pb2+, and Zn2+) in soil solution were determined using the Donnan membrane technique (DMT). Initially the DMT was
validated using artificial solutions where the percentage of free metal ions were significantly correlated with the percentages predicted
using MINTEQA2. However, there was a significant difference between the absolute free ion concentrations predicted by MINTEQA2
and the values determined by the DMT. This was due to the significant metal adsorption onto the cation exchange membrane used in
the DMT with 20%, 28%, 44%, and 8% mass loss of the initial total concentration of Cd, Cu, Pb, and Zn in solution, respectively.
This could result in a significant error in the determination of free metal ions when using DMT if no allowance for membrane cation
adsorption was made. Relative to the total soluble metal concentrations the amounts of free Cd2+ (3%–52%) and Zn2+ (11%–72%) in
soil solutions were generally higher than those of Cu2+ (0.2%–30%) and Pb2+ (0.6%–10%). Among the key soil solution properties,
dissolved heavy metal concentrations were the most significant factor governing free metal ion concentrations. Soil solution pH showed
only a weak relationship with free metal ion partitioning coefficients (Kp) and dissolved organic carbon did not show any significant
influence on Kp. 相似文献
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目的研究舱室间壁板不同约束条件及不同敷设方式对隔声量的影响。方法用VA One建立两个舱室的统计能量分析(Statistical Energy Analysis,SEA)模型,对约束阻尼结构和自由阻尼结构的隔声性能进行分析。针对约束阻尼结构,讨论其两侧金属层厚度差对整个壁板的隔声性能的影响;对自由阻尼结构,分析金属层与阻尼层之间的相对位置对其隔声性能影响。结果约束阻尼结构隔声量A计权声压级比自由阻尼结构高。结论阻尼层厚度和壁板总厚度一定时,自由阻尼结构金属层与阻尼层之间的相对位置对实际的隔声性能并没有影响;约束阻尼结构,两侧金属层等厚敷设时,其隔声效果最优,且两侧厚度差越大隔声量越小。 相似文献
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根据高压气瓶的特殊形状及尺寸 ,通过塑性工艺分析及许多次工艺试验 ,文中提出了一种多次缩口顶镦工艺方法 ,从而解决了实际生产的关键技术问题。 相似文献
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Activated sludge was immobilized into Ca-alginate beads via entrapment, and biosorption of three heavy metal ions, copper(Ⅱ), zinc(Ⅱ), and chromimum(Ⅱ), from aqueous solution in the concentration range of 10-100 mg/L was studied by using both entrapped activated sludge and inactivated free biomass at pH≤5. A biphasic metal adsorption pattern was observed in all immobilized biomass experiments. The biosorption of metal ions by the biosorbents increased with the initial concentration increased in the medium. The adsorption rate of immobilized pre-treated activated sludge(PAS) was much lower than that of free PAS due to the increase in mass transfer resistance resulting from the polymeric matrix. Biosorption equilibrium of beads was established in about 20 h and the adsorbed heavy metal ions did not change further with time. No significant effect of temperature was observed in the test for free biomass while immobilized PAS appeared to be strong temperature dependent in the test range of 10 and 40℃.Besides, the content of activated sludge in the calcium alginate bead has an influence on the uptake of heavy metals. The sorption equilibrium was well modeled by Langmuir isotherm, implying monomolecular adsorption mechanism. Carboxyl group in cell wall played an important role in surface adsorption of heavy metal ions on PAS. 相似文献