Study on Form Rolling Method of High Strength FRP Screw Thread Using Ultrasonic Vibration

纤维增强热塑性塑料（FRTP）制造的螺栓是一种紧固螺纹件的材料，在许多领域得到了应用。然而，采用注射成型或滚压成形生产的FRTP螺纹在成形精度和机械强度方面存在一些问题。利用超声振动对复合材料螺纹进行滚型加工时，螺纹毛坯从内部受热，易发生变形。因此，期望提高成形精度和机械强度。首先设计并试制了用于轧制环形多v形槽的辗压成形机，然后评价了振动幅值、轧制力等轧制条件与环形多v形槽成形精度之间的关系。结果表明，虽然超声振动的影响得到了证实，但v型槽的高度与刀具压痕的高度相比是不够的。推测其原因是轧制机构刚度不够，且轧制力由带自重的杠杆施加，压痕量无法得到充分控制。为此，设计并试制了一种具有高刚度、可控制刀具压痕量和压痕速度的新型压痕装置，并在不同的轧制条件下进行了实验，通过扫描电镜观察了v型槽断面。得到的主要结果如下：(1)明确了制造高精度环形多v型槽的成形轧制条件。(2)利用超声振动在新机上进行型腔轧制，改善了v型槽截面处的纤维流动。

The bolt, that is fastening threaded parts, has been produced of fiber reinforced thermoplastics (FRTP) which have been applied in many field. However, FRTP screw threads produced by the injection molding or the form rolling have some problems concerning form accuracy and mechanical strength. If the ultrasonic vibration is utilized for the form rolling of FRTP threads, the thread blank is heated from its inside and is apt to deform. Therefore the improvement of form accuracy and mechanical strength is expected.Firstly, the form rolling machine in order to roll annular multi-V-grooves are designed and produced on trial, and then the relationship between the rolling condition, such as vibration amplitude, rolling force and so on, and the form accuracy of annular multi-V-grooves was evaluated. As a result, the height of V-groove was not enough in comparison with that of tool indentation, though the effect of ultrasonic vibration was confirmed. As a reason, it is guessed that the amount of indentation couldn't be sufficiently controlled because the stiffness of rolling mechanism was not enough and the rolling force was given by a lever with dead weights.Therefore, a new indentation device which has high stiffness and can control the amount and the speed of tool indentation, was designed and produced on trial, and the experiment was carried out, varying the rolling condition, and the V-groove section was observed by SEM.The obtained main result are followings ;(1) The condition of form rolling in order to make the annular multi V-groove with high accuracy was clarified.(2) The fiber flow at the section of V-groove is improved by the form rolling in the new machine using ultrasonic vibration.