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目的 研究冲压胀形工艺与渐进成形工艺成形半球形零件的区别。方法 使用两种热处理状态的硬铝合金,AA2024-O和AA2024-T4,分别用冲压胀形工艺和渐进成形工艺成形半球形零件。结果 相比较渐进成形零件而言,使用冲压胀形工艺得出的半球形零件的壁厚相对均匀,变形程度可以达到更大;在相同的试验条件下,AA2024-O的成形性能远高于AA2024-T4的成形性能;在本实验所研究的参数范围内,下压量越小,成形高度越大,对AA2024-O进给速率越快,成形高度越大;而对AA2024-T4进给速率越慢,成形高度越大;对于胀形零件,材料在胀形过程中处于双向拉伸应变状态,而渐进成形零件在成形过程中处于平面应变状态;胀形零件的最大应变和最大减薄处是半球的中心,而渐进成形零件的最大应变和最大减薄处是半球的边缘。结论 胀形零件的危险截面在半球的中心,渐进成形零件的危险截面在半球的边缘。 相似文献
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目的 研究在金属双极板脉冲电流辅助冲压工艺中,将脉冲电流单独作用于保压阶段、冲压阶段以及作用于整个冲压过程(冲压阶段+保压阶段)3种通电方式对极板流道深度及壁厚分布的影响。方法 以316L不锈钢薄板作为实验材料,调节流经样品的电流参数,分别为0、10、20、30 A,分析脉冲电流参数和通电方式对极板流道深度及壁厚分布的影响规律。结果 在高电参数下,当采用在冲压阶段通电、在保压阶段断电的方式2时,在保压阶段可促进应力松弛,具有最佳的回弹抑制效果,其成形深度回弹可减小73.88%。在不同电参数下,3种成形方式对双极板流道壁厚分布具有相似的影响。槽顶和槽底的壁厚减薄相对较小,减薄量为原板材厚度的2%~6%;流道直壁壁厚减薄为原板厚度的9%~15%;而外圆角和内圆角区域的壁厚减薄较大,达到27%~30%。结论 在金属双极板脉冲电流辅助冲压工艺中,以不同方式施加脉冲电流,均可以显著提升流道深度,对壁厚影响并无明显差别。特别地,采用在冲压阶段通电、在保压阶段断电的方式2可以显著提升对流道回弹的抑制效果。 相似文献
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以正反向超塑成形厚度均匀的TC4钛合金深筒形件为背景(厚度精度要求1.6mm±0.2mm),设计了多种预成形模形状,采用MSC.MARC有限元模拟研究了不同形状的预成形模对深筒形件侧壁厚度分布的影响, 并分析了预成形模和终成形模的表面摩擦系数分别对成形件壁厚分布的影响,提出了模具型面变摩擦控制厚度分布的方法.结果表明:预成形模对压边部分环形带区域和筒形件底部区域的局部预减薄,对最终侧壁的厚度分布有非常大的改善.同时,合理地增大预成形模的表面摩擦能显著增加预成形的局部减薄作用,对于提高工件最终壁厚分布均匀性有利.减小终成形模的摩擦,可以使板料整体变形均匀化,壁厚分布趋于均匀.根据有限元分析结果,对模具表面进行处理,并通过正反向超塑成形实验制得TC4钛合金深筒形件,其厚度分布满足1.6mm±0.2mm. 相似文献
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目的解决球形件传统成形工艺冗余、困难的问题。方法提出了3种液压胀形成形方案,并利用有限元软件Dynaform,对每种方案进行了数值模拟。结果通过模拟分析,确定了各方案最佳模拟结果,获得了各方案壁厚分布情况,明确了成形缺陷形式以及产生的原因。最小壁厚位于球心横截面处,是危险区;当合模补料130 mm时,模拟结果显示最大壁厚减薄率最小,为16.5%。结论利用液压胀形可以成功成形球形件;补料方式对成形结果有很大的影响,合模补料成形质量最优,端头补料次之,无补料最差。 相似文献
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目的 研究软模成形过程中塑性应变比r值对双极板成形深度及壁厚的影响,探究不同工艺参数对双极板尺寸的影响规律。方法 通过单向拉伸实验得到纯钛极薄带的力学性能参数,然后采用橡胶软模成形方法制备纯钛燃料电池双极板,利用光学显微镜对制备的双极板尺寸及壁厚进行测量并深入分析。结果 TD取向的r值最大为2.56,沿该方向成形时,纯钛极薄带在载荷为300 kN、软模硬度为77HA条件下得到的双极板深度最大,为0.293 mm;同时,其壁厚减薄较小,在减薄最严重的位置壁厚减薄率仅为13.52%。结论 较大的载荷与适宜的软模硬度能得到较好的双极板深度,对双极板周期无影响;双极板深度、壁厚与r值有关,r值越大,纯钛极薄带抵抗壁厚减薄的能力越强,成形深度越大。 相似文献
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《International journal for numerical methods in engineering》2018,113(9):1488-1506
In this paper, we present a new method for inserting several triangulated surfaces into an existing tetrahedral mesh generated by the meccano method. The result is a conformal mesh where each inserted surface is approximated by a set of faces of the final tetrahedral mesh. First, the tetrahedral mesh is refined around the inserted surfaces to capture their geometric features. Second, each immersed surface is approximated by a set of faces from the tetrahedral mesh. Third, following a novel approach, the nodes of the approximated surfaces are mapped to the corresponding immersed surface. Fourth, we untangle and smooth the mesh by optimizing a regularized shape distortion measure for tetrahedral elements in which we move all the nodes of the mesh, restricting the movement of the edge and surface nodes along the corresponding entity they belong to. The refining process allows approximating the immersed surface for any initial meccano tetrahedral mesh. Moreover, the proposed projection method avoids computational expensive geometric projections. Finally, the applied simultaneous untangling and smoothing process delivers a high‐quality mesh and ensures that the immersed surfaces are interpolated. Several examples are presented to assess the properties of the proposed method. 相似文献
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Standards are the basis for production enterprises to organize production ex-factory inspection trade 《中国标准化(英文版)》2008,25(1):24-25
Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.…… 相似文献
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A flow calorimeter for enthalpy increment measurements on condensed gases is presented. A better knowledge of the properties of the liquefied natural gas is needed, and therefore a liquid loop has been designed for our flow calorimeter. The fluid loop in the calorimeter is designed in order to avoid the two-phase region, since two phases would give compositional disturbances in the measurements. The avoidance of the two-phase region is made possible by increasing the pressure of the test fluid after the measurement section, then heating the fluid at super-critical pressure past the critical point. Finally, the fluid is throttled to the low-pressure gas state at the inlet condition of the compressor that circulates the fluid. To perform the pressure increase, a new cryogenic pump has been designed. To evaluate the new equipment, measurements were taken on liquid ethane over the temperature range 146–256 K at pressure between 0.9 and 5.1 MPa. 相似文献
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Steffen Müller-Probandt 《材料科学与工程:中英文B版...》2018,(4):161-177
We associate a variety of innovations with the term "Industry 4.0". The pioneer of many 4.0 modifications forms the basisfor the trend towards the integrated di... 相似文献
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On November 30, 2007, the China Association for Standardization (CAS) held a press conference at Beijing Diaoyutai State Guest House. Leaders from the China Household Electric Appliance Research Institute, the China Household Electric Appliance Association, and the China Consumers' Association attended and made speeches.…… 相似文献
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Janet Lang 《Materials and Manufacturing Processes》2017,32(7-8):857-866
ABSTRACTThe production of ferrous metal increased during the Roman Late Republican period, Principate and Empire. The direct bloomery process was used to extract the metal from its ores using slag-tapping and slag-pit furnaces. The fuel was charcoal and an air blast was introduced by bellows-operated tuyères. Iron formed as a bloom, often as a spongy mass of metal, which contained impurities from the smelting process, including unreacted ore, fuel, slag and fragments from the furnace walls, while the metal was often inhomogeneous with varied carbon contents. Blooms were either smithed directly into bars or ingots or they were broken up, which also allowed the removal of gross impurities and a selection of pieces with similar properties to be made. These could then be forge-welded together and formed into characteristically shaped ingots. Making steel in the furnace seems to have been achieved: it depended on the ore and the furnace and conditions within it. Surface carburization was also carried out. Iron and steel were used extensively in construction and for tools and weapons. Fire welding was often used to add pieces of steel to make the edges of tools and weapons, which could be heat-treated by quenching to harden them. 相似文献
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Zusammenfassung Bei der Gestaltung von Ernteprozessen — beispielsweise des Prozesses Mähdrusch, Körnertransport und -abnahme — als transportverbundene Fließarbeitsverfahren mit mindestens zwei verschiedenen Arbeitsmitteln gibt es einen großen Optimierungsspielraum. Solche Prozesse sind mehrstufige Bedienungsprozesse mit gemischter Anordnung der Bedienungseinrichtungen. Außerdem besitzen sie stark ausgeprägte räumliche Aspekte. Es wird vor allem gezeigt, welche Merkmale solcher Prozesse in Simulationsmodellen abgebildet sein müssen, welche Zielgrößen in Abhängigkeit von welchen Einflußgrößen unter Berücksichtigung welcher Prozeßbedingungen ermittelt werden sollten und wie der Bewertungsprozeß zur Ermittlung der gewünschten Informationen gestaltet werden muß. 相似文献
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C. Qihong W. Zhan‐Wen J. Yi J. Yehua L. Fei F. Hanguang 《Materialwissenschaft und Werkstofftechnik》2014,45(7):582-590
In the present study a high‐boron high speed steel (HSS) roll material was designed. Many expensive alloy elements have been substituted by cheap boron alloy, and high‐boron high speed steel roll has been manufactured by centrifugal casting method. The microstructures, mechanical properties and wear resistance of centrifugal casting high‐boron high speed steel roll have been investigated by optical microscopy (OM), scanning electron microscopy (SEM), and X‐ray diffraction (XRD) analysis, hardness test, impact test and wear test. The results indicated that the solidification microstructures of high‐boron high speed steel roll consisted of M2(B,C), (W,Mo)2(B,C), M3(B,C), M23(B,C)6 type borocarbides and martensite, a small amount of retained austenite. Borocarbides were continuously distributed over the grain boundary. After quenching from 1050 °C, local broken network appeared in partial borocarbides, and fine secondary borocarbide precipitated from the matrix. After tempering from 525 °C, the amount of precipitated borocarbide increased significantly. After heat treatment, the hardness of high‐boron high speed steel roll excelled 60 HRC, and its impact toughness excelled 8.0 J/cm2. The single groove steel rolling amount of high‐boron high speed steel rolls increases by 500% than that of bainite cast iron roll, when the rolls are used in K1 mill housing of bar mill. 相似文献
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Dimiter Hadjistamov 《材料科学与工程:中英文B版...》2019,(2):56-65
The definition of the thixotropy is a decrease in viscosity with time in shear and a subsequent recovery of viscosity after the shear deformation is removed.We ... 相似文献