瞬态熔融塑料冲头金属薄板超声微成形方法及其极限尺度探索

The project is the first to propose a novel “ultrasonic thin sheetmetal microforming method based on instantaneous molten plastic punch”. In this method the plastic powder is plasticized by strong ultrasonic vibration friction effect, and becoming into molten plastic which exists in a very short period. Then the molten plastic as a flexible punch transmitting pressure and ultrasonic vibration to the thin sheetmetal to press it becoming a micro part. The molten plastic immediately solidify after ultrasound stopped. The difficult of cleaning the molten plastic from the part does not exist. Aim at the situation that there is no research on the ultrasonic thin sheetmetal micro stretch forming, this method introduces ultrasound into thin sheetmetal microforming so that the deforming uniformity and forming ability of thin sheetmetal are elevated. Comparing with other thin sheetmetal microforming methods, it has the advantage of forming smaller micro deep drawing part..In the special phenomenons of “ultrasonic air film”, “surface fatigue damage” in the method as entry point, around the relationships between the whole deforming process of thin sheetmetal in micro deep drawing and micro bulging, local thickness change, stress and strain change, microstructure change, etc. with the thin sheetmetal vibration, the key scientific questions of the forming law, deforming mechanism and size effect of thin sheetmetal in vibration will be deeply researched. The theory obtained by above research will help to improve the method and to reduce the size of micro deep drawing part. The systematic scientific knowledge and complete process methodology about this novel method will be established through the research of this project.

本项目首次提出新颖的“瞬态熔融塑料冲头金属薄板超声微成形方法”，利用超声振动使塑料粉末在强烈摩擦下塑化，形成持续短暂时间的熔融塑料，以其作柔性冲头将超声振动与超声头压力传递给金属薄板完成微制件成形，超声停止后熔融塑料即刻凝固并自动与制件分离，不存在清理熔融塑料的困难。针对目前金属薄板超声微延展成形尚未展开研究的现状，本方法将超声引入薄板微成形从而提高坯料变形均匀性与成形能力。与其它方法相比，该方法具有能成形更小微拉深件的优势。.以“超声气膜效应”、“表面疲劳损伤”等该方法特有现象为切入点，围绕薄板超声微拉深、微胀形中整体变形过程、局部厚度变化、应力应变变化、微观组织结构变化等方面与薄板振动之间的关系，深入研究薄板振动状况下的微成形规律、变形微观机制及尺寸效应等关键科学问题。在所获理论指导下，完善工艺并缩小微拉深件尺寸。形成该全新超声微成形方法的系统科学知识与完整工艺方法体系。

本项目针对课题组首次提出的“瞬态熔融塑料冲头金属薄板超声微成形方法”，研究了其在应用于微胀形、微冲裁、微拉深等不同工艺时的成形规律、成形机制、成形工艺、以及该方法特有的“超声气膜效应”和“表面疲劳损伤”等问题，研究了该方法所需微模具的制备方法及相关基础技术。通过本项目研究，增进了对该方法的认识与把握，推动了该方法的发展。.通过对该方法的深入研究，获得了其应用于不同工艺时金属薄板的变形过程、厚度分布、极限成形参数、超声的作用与影响、制件质量影响因素等，准确测定了成形力并揭示了超声对成形力及制件精度的影响机制。研究表明，该方法在成形金属薄板微制件时，可使成形力降低幅度从现有其它方法的30%大幅提高至91%，显示了该方法利用超声的高效和优越性。对超声气膜效应规律和形成机理的研究表明，其能对极薄的金属薄板形成有效保护，可成形尺寸1mm以下的、目前其它超声方法难于成形的微胀形及微拉深制件。研究也明确了薄板表面疲劳损伤和破裂的成因从而获得了避免其产生的手段。.将该方法应用于非晶薄带的微冲裁成形，是本项目的一项拓展研究，它解决了非晶材料一直以来难于采用压力加工的困难，使其成为一种实现非晶合金经济高效加工的有效手段，同时，该项研究也开启了超声应用于非晶合金压力成形这一新的研究方向之门。进一步将超声方法拓展应用到成形块体非晶材料，解决了块体非晶成形以及异种非晶合金快速冷焊的问题，预示着超声方法在非晶合金加工方面具有良好应用前景和重要实用价值。对超声作用于非晶材料机理的揭示，将成为发展非晶合金超声成形的理论基础，具有较高科学价值。