共查询到20条相似文献,搜索用时 171 毫秒
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冲压零件的回弹由材料力学性能、加工工艺和产品结构等多方面的因素共同作用而出现。在回弹问题的处理中借助Dynaform进行成形分析,从减小零件的内应力方面入手结合调整凸、凹模间隙和更改凹模圆角减小进料阻力等多种手段,最终将产品回弹控制在可接受的范围内。 相似文献
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拉延是利用利用拉延模具将平板毛坯制成开口空心零件,拉延成形是能否生产出合格零件产品的关键,汽车钣金件的质量好坏在很大程度上受拉延模质量的控制。通过分析某型汽车覆盖件——门槛内板结构特点,根据工厂生产时所使用的冲压设备,确定拉延模结构形式及间隙,进一步进行模具的压料面、凸模、凹模及辅助零件的结构设计。 相似文献
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开水煲外壳零件冲压成形的数值模拟与实验研究 总被引:1,自引:1,他引:0
开水煲产品外壳的形状为圆桶形,由不锈钢薄板二次冲压而成,但冲压成形质量很难控制,容易出现拉裂、变薄、起皱等缺陷。因此,应用Dynaform软件,建立相应的有限元模型,对开水煲外壳零件的成形过程进行数值模拟,并对冲压成形的结果进行了实验验证,结果显示实验结果与模拟结果比较吻合。表明应用有限元软件,对开水煲外壳零件进行冲压成形模拟,其结果是正确的、可信的,同时为后续进行工艺参数优化奠定了基础。 相似文献
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本文将讨论抽芯式模具在弯曲较复杂零件中的应用,所谓抽芯式模,就是在弯曲零件之弯曲内腔预先置入抽芯,继而完成冲压弯曲,冲压结束时,抽芯能自动退出弯曲零件. 相似文献
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为了提高输送机内、外链板孔的加工精度及加工效率,该文设计了一套新型链板冲孔模具,可以准确、高效地加工输送机链板内孔,确保了产品质量。 相似文献
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【目的】解决烟丝填充值、弹性等物理指标不能全面真实反映卷制时烟丝回弹对卷烟质量影响的问题。【方法】建立了一套烟丝回弹特性检测方法并运用质构仪进行检测,对该方法进行重复性、差异性验证,通过单因素及响应面优化确定最佳测试参数,探究不同烟丝结构对回弹特性的影响。【结果】(1)通过分析烟丝卷制过程烟丝压缩及回弹过程,将烟丝回弹特性P定义为烟丝束受压后回弹至固定直径时的能力。(2)质构仪测定烟丝回弹特性的最佳条件:探头型号为A/BE-d45圆板探头,测前速度12 mm/s,测中速度6 mm/s,触发力4 g,回弹速度1 mm/s,压缩时间3 s,回弹保持时间16 s。该方法的日内和日间精密度分别小于4.20%和2.93%。(3)烟丝回弹特性受烟丝结构影响,烟丝尺寸越长,烟丝回弹特性越大。【结论】该表征方法科学可行且精密度较好,可对烟丝回弹特性进行准确测量。适宜的烟丝结构可保证烟丝的回弹能力,保持烟支的填充的饱满度,提高产品质量。 相似文献
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Dairy products, including cultured dairy products such as cheese and yogurt, are susceptible to fungal spoilage. Traditionally, additives such as potassium sorbate have been used to control fungal spoilage; however, with consumer demand for clean-label products, other strategies to control fungal spoilage (e.g., biopreservatives) are increasingly being used in dairy formulations. In order to help the dairy industry better evaluate biopreservatives for control of fungal spoilage, we developed a challenge study protocol, which was applied to evaluate 2 commercially available protective cultures for their ability to control yeast and mold spoilage of Greek yogurt. Greek yogurt formulated with and without protective cultures was inoculated with a cocktail consisting of 5 yeasts and 1 mold to yield inoculum levels of 101 and 103 cfu/g of yogurt. The inoculated yogurts were stored at 7°C and fungal counts as well as time to visible growth, on the yogurt surface, of mycelium mold colonies or yeast were determined over shelf-life. Whereas fungal concentrations increased to spoilage levels (≥105 cfu/g) in all yogurt formulations at both inoculum levels by d 23 of storage at 7°C, no surface mold was observed over 76 d in any of the products formulated with protective cultures. Control yogurts without biopreservatives all showed surface mold by d 23. In order to allow industry to better evaluate the business effects of improved control of surface mold growth that can be achieved with protective cultures, we developed a Monte Carlo simulation model to estimate consumer exposure to visible mold growth in yogurt formulated without fungal inhibitors. Our model showed that initial mold contamination rate has the largest effect on the model outcome, indicating that accurate data on contamination rates are important for use of these models. When air plates were used, in a proof-of-concept approach, to estimate initial contamination rates in a small yogurt manufacturing operation, our model predicted that 550 ± 25.2 consumers (±standard deviation) would be exposed to visible mold growth for every 1 million cups of yogurt produced. With initial contamination rate data for individual facilities, this model could be used by industry to estimate the number of consumers exposed to visible mold spoilage and could allow industry to better assess the value of mold-control strategies. 相似文献
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为获得控制文胸模杯曲面形态的特征曲线,实现模杯的正向设计,采用三维扫描仪获取模杯的点云数据,用逆向工程软件进行实体模型构建,然后根据模杯角度及特征点构建了26条模杯内外曲面形态曲线。利用各曲线拐点、峰值点、曲率最大点及最小点的分布位置一致性,提取能够反映模杯曲面特征信息的内外曲面形态特征曲线5条。结果表明:模杯结构特征曲线上的几何参数分布离散程度更小,较角度特征曲线更能反映不同类型模杯的曲面形态特征。拟合各特征曲线弧长与模杯杯深的函数关系,通过改变形态特征曲线上的几何参数可控制曲面形态结构。 相似文献
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三维针刺技术实现了立体织物的低成本织造,为深入了解三维针刺的自动化成型设备技术、刺针技术、三维针刺织物(或预制体)及三维针刺复合材料的研究情况,介绍了适用于异型织物的针刺自动化成型设备技术,包括回转预制体和自由曲面预制体针刺成型装备;阐述了现有的刺针刀具技术;归纳了三维针刺织物的新型织造结构,包括多组元混杂针刺织物、针刺/缝合耦合针刺织物、仿形针刺织物和梯度针刺织物;分析了三维针刺复合材料的实验表征、理论分析和数值模拟研究进展情况;最后总结了现有三维针刺技术的发展水平和面临的挑战,并对三维针刺技术的未来发展趋势进行了展望。 相似文献
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King MJ 《Meat science》1999,51(3):261-269
The forces, and hence fracture energies, required to cut frozen meat are presented in this paper and the merits of applying vibrations to a cutting blade are considered. A knife oscillating in a slicing action was used to cut horse M. semimembranosus and loin muscle M. longissimus dorsi over a range of temperatures (-1.5°C to -30°C) and vibration frequencies (0-1000 Hz). The blade required less force to cut when slicing than when not slicing; the decrease in force was proportional to the velocity of the slicing motion. If the average relative slicing velocity of the blade with respect to the meat was greater than 164 mm/s then the cutting force reduced significantly. The reduction was due to a lower requirement for energy to produce the new material surface (up to 80% reduction) and also a reduction in the plastic energy required to deform the off-cut by the blade (up to 30% reduction). The surface energy was reduced because the fracture mechanism was altered by the slicing action. The plastic energy was reduced because the slicing blade fractured the meat fibres with less strain (and hence less material deformation around the process zone) than a blade pressed directly into the meat. Vibration frequencies of 10-100 Hz were required to generate the required slicing motion with the equipment available. A vibrating cutting blade could have a combination of chopping and slicing motions superimposed upon it. These would reduce both the friction between the knife blade and the meat, as well as the surface and plastic energy required to cut the meat. 相似文献
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