弹体毛坯热收口成形工艺研究

目的设计弹体毛坯一次热收口成形工艺方案。方法将冲压成空心、变壁厚、桶状的毛坯,经过外皮粗车后进行收口变形,获得合理的弹体弧形部,生产出了合格毛坯。研究了弹体毛坯收口成形原理、温度控制、工装设计以及收口过程中的金属流动规律,根据体积不变原理,计算了收口前粗车毛坯尺寸。结果通过批量试制,根据收口过程中常见问题的控制措施,优化了收口工艺参数,实现了毛坯的一次热收口成形。结论通过收口原理分析、毛坯及工装设计,形成了毛坯一次收口设计规范,该弹体毛坯一次热收口工艺可行。     

某子母弹弹体毛坯加工工艺改进

为了提高弹体毛坯的材料利用率和降低生产成本,开展了钢管一次收口工艺改进.根据钢管收口过程的变形规律,改进已有工装、模具,最终实现了弹体毛坯由钢管一次收口成形.该工艺的难点是控制收口的形状,以及收口过程中模具润滑材料的选择.工艺改进后,简化了工序,减少了工模具及刀具的消耗,改善了工作环境,降低了操作工人的劳动强度,极大地提高了材料利用率,产品质量稳定,符合制造与验收规范要求.     

弹体毛坯热冲拔工艺

目的设计弹体毛坯热冲拔成形工艺方案。方法将冲子压入加热后的钢坯,使钢坯在压力作用下充满模腔,压成盂形,然后套在引伸冲子通过一串直径逐渐缩小的模圈,使弹体拉长、直径减小、壁厚减薄,获得合理的弹体毛坯尺寸,生产出合格毛坯。分析弹体毛坯冲拔成形原理、温度控制、工装设计及冲拔过程中的金属流动规律,根据体积不变原理,计算出冲拔毛坯尺寸。结果通过批量试制,根据冲拔过程中常见问题的控制措施,优化了冲拔工艺参数,实现了弹体毛坯热冲拔成形。结论通过冲拔原理分析、毛坯及工装设计,形成了热冲拔设计规范,该弹体毛坯热冲拔工艺可行。     

弹体成形工艺数字化设计系统的开发与实践

针对弹体成形工艺的特点,引入基于知识的工程技术,通过将成形工艺知识、数据及经验集成到知识库,研究开发了弹体成形工艺数字化设计系统。简要介绍了系统的技术原理和特点,并结合某型大口径弹体成形工艺,应用了该系统进行设计,达到了提高设计效率、降低开发成本的目的。     

钢管收口代替方钢热冲拔弹体毛坯加工工艺研究

重点介绍了炮弹新产品弹体毛坯由钢管收口代替传统的方钢热冲拔加工工艺,弹体一次收口工艺研究过程。确定的弹体生产工艺,工艺过程简单,产品质量得到大幅度提高,改善了工作环境,降低了劳动强度,在同行业处于领先水平,并为新型薄壁弹种的研发奠定了工艺基础。     

弹体热冲拔成形工艺数据库研究与开发

在充分总结弹体热冲拔成形知识的基础上,构建了弹体热冲拔成形工艺数据库,开发了数据库管理系统。应用在弹体热成形工艺与模具设计上,实现了工艺数据的积累、共享、重用,达到了优化工艺与模具设计,提高工艺设计水平与效率的目的。     

大口径、空心零件成形工艺

目的降低原材料的消耗,节约毛坯生产成本。方法改变成形方法,由原先的棒料锻造改为管料冲压成形,通过合理分配工序变形量,在小端收口的同时进行大端扩孔,经两次收口+一次扩口后冲压成形。结果不仅减少了原材料的消耗,而且减少了切屑工时。结论成功开创了大口径管材大扩孔量的先河,为今后成形更大直径的相似零件提供了强有力的技术支撑;同时采用了环形退料装置,优化了传统退料装置,消除了安全隐患,实现了半自动化卸料,可以同时满足大、中、小口径产品的退料要求,具有很好的推广和借鉴价值。     

AZ21B镁合金塑性成形工艺探究

针对镁是密排六方结构,室温下塑性差,很难进行塑性成形,及塑性成形工艺中加热效率、生产效率等问题,通过对镁合金材料性能、模具结构、加工条件等进行研究并做实验分析,探究其加热成形工艺（以AZ21B镁合金成形电池壳为载体）,进而获得较理想的塑性成形工艺方案及其模具。该工艺的主要创新在于设计并应用了一种镁合金加热送料通道,在保...     

无缝气瓶热旋压收口成形工艺数值模拟研究

本文采用有限元分析软件ABAQUS对无缝气瓶热旋压收口成形工艺进行模拟研究,分析了不同工艺参数对气瓶热旋压成形的影响。模拟结果表明,无缝气瓶热旋压收口成形过程中,随着旋压温度的升高和进给比的增加,起旋点处最小壁厚减薄,瓶肩最大壁厚处壁厚增加;随着旋压温度的升高,最大等效应力不断减小,最大等效应变不断增加;随着进给比增加最大等效应力应变都略有增加;旋压力随着温度的升高和进给比的减小而降低。     

燃气轮机转接段外套成形工艺研究

本文论述了转接段外套的胀形工艺的确认过程及试制过程,分析了以往其它转接段外套的收口成形所产生的问题原因。确定合理的工艺方案、胀形参数;设计结构合理的模具并根据现场试验结果调整模具尺寸,加工合格的产品,为类似零件的生产提供经验。     

Neck propagation in polymers with adiabatic heat generation

The tendency for stable necks to form and propagate in polymers are well known phenomena. Less well known is the strong dependence of these phenomena on ambient temperature. In this paper, strain induced heating during tensile deformations and its effect on neck initiation and propagation are analyzed under adiabatic conditions. Relative to the isothermal analysis, thermal softening causes stability to be lost at lower overall strains. Furthermore, when stability is regained there is a tendency for propagation loads to decrease and draw ratios to significantly increase. On the other hand, if the ambient temperature is low enough, thermal softening of the necked region relative to the unnecked region can be so significant that the actively necking region does not regain stability and, hence, does not propagate. In this case, experiments indicate that necking is followed by rupture rather than by drawing.     

316LN不锈钢高温拉伸颈缩区塑变行为

为准确测量颈缩发生后的应力-应变行为,本文综合物理实验、有限元模拟和MLR模型的方法确定颈缩区的塑变行为,建立316LN不锈钢高温本构模型.模型中,颈缩前的真应力-真应变呈幂函数关系,颈缩发生后,较低温度时应力随着应变的增加迅速下降,而当较高温度时应力随着应变的增加而缓慢下降,真应力-真应变呈非线性关系.基于MLR模型,修正了颈缩后不同温度、不同应变速率下的真应力-真应变曲线,并将有限元模拟的颈缩区长度与实测值相对比,相对偏差为4.73%.这说明修正后的应力-应变本构模型能够准确地描述316LN的高温塑性行为.     

Temperature effect at self-oscillating necking during extension of polyethylene terephthalate (PETP)

Extension of PETP films at constant rate of deformation may, under certain conditions, result in stress oscillation and a periodic necking. The periodic necking results in formation of transverse bands, alternately opaque and transparent, in the sample. In this study, the temperature rise of such an oscillating neck was measured using an AGA Thermovision camera. The measured maximum surface temperature rise is very high, up to about 95° C and the temperature in the interior is probably higher. The formation of the opaque zone starts in the centre line of the foil and spreads out to a maximum width during the advance of the neck. It then suddenly ceases without reaching the surface of the sample. The opacity is probably a secondary effect dependent only on the high temperature formed by dissipated energy from the necking process and not affecting the mechanism of self-oscillating necking.     

退火炉中带钢缩颈量的动态自动测量技术

带钢经过炉子退火后一般宽度都会减少,减少的量称之为缩颈量。为了使最终产品的宽度符合要求,来料的设计宽度必须加上缩颈量补偿。由于炉子的构造,生产时的炉温,以及来料的材质和规格的不同,会使得缩颈量也稍有不同。准确的缩颈量补偿有利于提高成材率,通常对缩颈量进行统计都由人工来实施的。本文介绍了另一种自动测量带铜缩颈量的技术,该技术目前尚处于探索阶段,功能还不完善,尚有不少问题待进一步研究解决。     

厚壁管温热缩口与管壁增厚的数值模拟研究

目的主要研究厚壁管两端同时温、热锥形缩口工艺的特点,以及缩口过程不同工艺参数对壁厚增厚的影响。方法通过选择合理的材料模型与热力耦合等温度场模拟参数,建立了有限元模型,使用DEFORM体积成形软件对厚壁管两端同时温热缩口工艺进行了分析,探究了温、热缩口两种条件下应力应变分布特点。结果模拟实验获得了管材缩口系数、模具半锥角、t/d0值、摩擦因子、成形温度等工艺参数,在温、热两种条件下对壁厚增厚量的影响曲线。结论管材缩口过程具有典型的变形阶段:入锥弯曲阶段、反弯曲阶段和缩口稳定阶段;管材高温下缩口变形特点为周向、轴向的压缩变形和径向的增厚变形;厚壁管缩口的增厚变形量随着模具半锥角的增大和缩口系数的减小而增大,同时受摩擦因子、成形温度、管材壁厚的影响较大。研究结果为管材缩口壁厚增厚工艺提供了基础技术数据。     

Tearing of blast loaded plates with clamped boundary conditions

Extensive experimental results for the prediction of the onset of thinning (necking) and hence subsequent tearing at the boundary of clamped circular plates subjected to uniformly loaded air blasts are presented. The experiments include: plates of diameter ranging from 60mm to 120mm; different clamped edge conditions; (sharp edge; and radii of 1.5mm and 3.2mm) and an examination of the microstructural behaviour. Observations of thinning at the boundary show similar trends for all plate diameters with sharp edge conditions, and where the boundary edge condition is relaxed the deflections are larger before thinning and tearing occurs. Three phases within Mode I (large inelastic deformation) are identified as; Mode I (no visible necking at the boundary); Mode Ia (necking around part of the boundary); and Mode Ib (necking around the entire boundary). Predictions using the code ABAQUS provide, in particular for Mode I, favourable correlations with the experiments.     

锥形类缩口件坯料计算公式

利用金属材料塑形变形前后面积相等假设条件,经过从几何关系与数学上的考量,导出了锥形缩口坯料计算的两个传统公式;用算例进行对比计算与分析,并综合归纳,给出了建立在金属塑形成形原理中体积不变等条件下锥形类缩口坯料计算的两个新公式。     

Hot tensile deformation behaviors and constitutive model of an Al–Zn–Mg–Cu alloy

The hot tensile deformation behaviors of an Al–Zn–Mg–Cu alloy are studied by uniaxial tensile tests under the deformation temperature of 340–460 °C and strain rate of 0.01–0.001 s⁻¹. The effects of deformation temperature and strain rate on the hot tensile deformation behaviors and fracture characteristics are discussed in detail. The Arrhenius-type constitutive model is developed to predict the peak stress under the tested deformation condition. The results show that: (1) The true stress–true strain curves under all the tested deformation conditions are composed of four distinct stages, i.e., elastic stage, uniform deformation stage, diffusion necking stage and localized necking stage. The flow stress decreases with the increase of deformation temperature or the decrease of strain rate. (2) The elongation to fracture increases with the increase of deformation temperature. Under the tested conditions, the strain rate sensitivity coefficient varies between 0.1248 and 0.2059, which indicates that the main deformation mechanism is the lattice diffusion-controlled dislocation climb. (3) The localized necking causes the final fracture of specimens under all the deformation conditions. Microvoids coalescence is the main fracture mechanism under relatively low deformation temperatures. With the increase of deformation temperature, the intergranular fracture occurs. (4) The peak stresses predicted by the developed model well agree with the experimental results, which indicate the validity of the developed model.     

Influence of microstructural parameters on strain localization in uniaxial tension

The report discusses the influence of microstructural parameters (grain size and crystallographic structure) on the amplitude of the total strain and the necking bandwidth in uniaxial and quasi-static tension tests at room temperature. The axial displacement in the post-critical stage is essentially controlled by diffuse necking and appears to be independent of the nature of the three materials studied.     

高温后新旧混凝土粘结的剪切性能研究

对先粘结后高温与先高温后粘结两种类型的129块Z形新旧混凝土粘结试件进行了直剪试验,主要考察了温度(常温到900℃)、冷却方式、界面粗糙度和界面剂对粘结面剪切性能的影响。在此基础上,得到了粘结面的剪切滑移曲线,给出了相应的统一计算公式,并建立了先高温后粘结类型的神经网络预测模型,较为系统地对高温后新旧混凝土粘结面的剪切性能进行了研究,以供工程参考。