发动机前端附件带轮旋压成形仿真

通过金属材料拉伸实验,得到了旋压带轮板材的力学特性参数;分析了旋压成形仿真过程中的网格划分、求解器选择、质量放大等技术;通过系统能量法,对所建模型的合理性进行验证并得到最佳质量放大系数1×107。同时,以一发动机附件的带轮为研究对象,仿真分析其旋压成形过程、成形过程中毛坯材料的应变分布和材料流速,以及对比分析仿真轮齿的几何形状与实际加工轮齿的几何形状。基于建立的有限元模型,分析毛坯截面形状和旋轮进给量对旋压成形的影响。

湿法烟气脱硫装置用阀门的选择

概述了湿法烟气脱硫工艺的特点及腐蚀机理,介绍了湿法烟气脱硫装置几种适用阀门的特点及其所适用的场合,阐述了湿法烟气脱硫工艺选择阀门应考虑的几个问题及阀门材料的选择。

解决整体车门内板窗框起皱的工艺优化方案

针对整体车门内板的窗框角部起皱问题,传统工艺补充方式容易产生型面褶皱及生产过程不稳定的问题。通过工艺思路的改变,拉伸补充的调整和优化,改变了材料成形过程中的流动状态,解决了车门内板窗框角部位置的型面不平整和轻微起皱状态;调整后的工艺状态,冲压生产稳定,制造成本有一定降低。

FE analysis of extrusion defect and optimization of metal flow in porthole die for complex hollow aluminium profile

To solve the defects of bottom concave appearing in the extrusion experiments of complex hollow aluminium profiles,a 3D finite element model for simulating steady-state porthole die extrusion process was established based on HyperXtrude software using Arbitrary Lagrangian–Eulerian(ALE)algorithm.The velocity distribution on the cross-section of the extrudate at the die exit and pressure distribution at different heights in the welding chamber were quantitatively analyzed.To obtain an uniformity of metal flow velocity at the die exit,the porthole die structure was optimized by adding baffle plates.After optimization,maximum displacement in the Y direction at the bottom of profile decreases from 1.1 to 0.15 mm,and the concave defects are remarkably improved.The research method provides an effective guidance for improving extrusion defects and optimizing the metal flow of complex hollow aluminium profiles during porthole die extrusion.

High-Throughput Multi-Plume Pulsed-Laser Deposition for Materials Exploration and Optimization

A high-throughput multi-plume pulsed-laser deposition （MPPLD） system has been demonstrated and compared to previous techniques. Whereas most combinatorial pulsedlaser deposition （PLD） systems have focused on achieving thickness uniformity using sequential multilayer deposition and masking followed by post-deposition annealing, MPPLD directly deposits a compositionally varied library of compounds using the directionality of PLD plumes and the resulting spatial variations of deposition rate. This system is more suitable for high-throughput compound thin-film fabrication.

Slope Debris Flows in the Wenchuan Earthquake Area

Avalanches and landslides,induced by the Wenchuan Earthquake on May 12,2008,resulted in a lot of disaggregated,solid material on slopes that could be readily mobilized as source material for debris flows.Rainstorms triggered numerous slope debris flows with great damage to highways and rivers over the subsequent two years.Slope debris flows(as opposed to channelized debris flows) are defined as phenomena in which high-concentration mixtures of debris and water flow down slopes for short distances to highways and river banks.Based on field investigations and measurements of 19 slope debris flows,their main characteristics and potential mitigation strategies were studied.High rainfall intensity is the main triggering factor.Critical rainfall intensities for simultaneous occurrence of single,several and numerous slope debris flow events were 20 mm/day,30mm/day,and 90 mm/day,respectively.Field investigations also revealed that slope debris flows consist of high concentrations of cobbles,boulders and gravel.They are two-phase debris flows.The liquid phase plays the role of lubrication instead of transporting medium.Solid particles collide with each other and consume a lot of energy.The velocities of slope debris flows are very low,and their transport distances are only several tens of meters.Slope debris flows may be controlled by construction of drainage systems and by reforestation.

Dynamic recrystallization behavior and kinetics of high strength steel

The dynamic recrystallization behavior of high strength steel during hot deformation was investigated.The hot compression test was conducted in the temperature range of 950-1150 °C under strain rates of 0.1,1 and 5 s-1.It is observed that dynamic recrystallization(DRX) is the main flow softening mechanism and the flow stress increases with decreasing temperature and increasing strain rate.The relationship between material constants(Q,n,α and ln A) and strain is identified by the sixth order polynomial fit.The constitutive model is developed to predict the flow stress of the material incorporating the strain softening effect and verified.Moreover,the critical characteristics of DRX are extracted from the stress-strain curves under different deformation conditions by linear regression.The dynamic recrystallization volume fraction decreases with increasing strain rate at a constant temperature or decreasing deformation temperature under a constant strain rate.The kinetics of DRX increases with increasing deformation temperature or strain rate.

大型带筋薄壁圆管铝型材挤压成形数值模拟

以某大型带筋薄壁圆管铝型材为研究对象,建立了大型带筋薄壁圆管铝型材穿孔针挤压成形有限元数值模型。基于数值模拟结果,开展了导流室轮廓和工作带长度优化。研究结果表明,大型带筋薄壁圆管铝型材存在材料流速、断面温度极不均匀的问题,型材筋部的材料流速极快,最高达到了724 mm·s^(-1),而型材圆弧部分的流速很慢,最低仅为3.079 mm·s^(-1)。导流室轮廓经过优化后,材料流速的控制范围为20.40~59.23 mm·s^(-1),断面的温度范围为500.8~518.3℃,显著地改善了材料流速和温度分布的效果。工作带长度经过优化后,材料流速和断面温度均匀性得到了进一步的提高,材料流速控制范围为25.76~44.40 mm·s^(-1),断面的温度范围为504.5~517.5℃,获得了较为理想的材料流速与温度分布均匀性。