长轴类零件开式挤压工艺应用及成形极限研究

长轴类零件开式挤压失稳包括弹性失稳和塑性失稳。将压杆失稳原理应用于开式挤压,得到了开式挤压弹性失稳的临界长径比及临界挤压应力的计算方法,建立了开式挤压工艺弹性稳定性校核模型,提出了提高抵抗弹性失稳能力的措施,如降低挤压应力、采用夹持器支承等方法。分析塑性失稳的原因,是零件的传力段的应力达到材料的屈服应力,而在入模口处出现局部镦粗。用上限法计算了圆截面件开式挤压应力,并绘制成可方便查阅的线图。提出了挤压变形程度、凹模半锥角、润滑状态及摩擦因子等是影响塑性失稳成形极限的主要因素,并结合计算线图给出了各影响因素的合理范围。以汽车传动花键轴开式挤压为例,应用失稳理论对挤压工艺参数的合理制定进行指导。

Research on the forming limits and technology application of long shaft parts in open-die extrusion

The instability includes elastic instability and plastic instability in open-die extrusion.On the basis of the theory of instability in mechanics of materials,it gets the length-height ratio in open-die extrusion and the calculation method of experimental formula of the relative extrusion stress.The measurement to prevent the instability is submitted,that is reducing the extrusion load and introducing the clamp.The reason to produce the plastic instability is the guiding stress reaches the yield stress,so the problem of billet bulging is produced at the die-entrance.It calculates the open-die extrusion load of round billet by using upper bound method and draws the searching graph.The effect of influencing the plastic instability is reduction of area,concave die half angle,lubricates and frictional factor etc.And it submits the reasonable range by the calculation graph.Utilizing the motor guiding spline extrusion as an example,some useful knowledge for long shaft extrusion can be obtained by the theory of instability.