不□鋼螺紋鎖緊特性之研究－以M6－60長不□鋼螺紋結合M形不□鋼夾緊件為例

Abstract

中 文 摘 要 螺紋因具有易於安裝、拆解、更換之特性且大部分螺紋均已經被標準化，所以用途非常廣泛，是一種重要的機械結合方式。使用不□鋼作為螺紋材料是因為不□鋼具有許多的優點，如：耐蝕性、非磁性、使用溫度範圍寬廣，而且不需任何表面處理即可使用，所以不□鋼已經成為高級螺紋用材料的代表。 本論文針對不□鋼外六角螺絲搭配不□鋼沖壓件之孔凸緣內螺紋，在鎖緊作用力使機件產生彎曲變形的情況下，進行不□鋼螺紋鎖緊特性之研究，並對可能衍生的問題作分析及討論，研究項目包括：扭矩方程式的驗證、鎖緊力與螺紋的變形量的關係、彎曲作用下的螺紋摩擦與磨耗特性、不同鎖緊扭矩的比較、螺帽厚度及囓合牙數對螺絲的影響及潤滑對不□鋼螺紋產生的作用等。 實驗結果顯示，當螺紋的鎖緊作用力使機件產生彎曲變形時，螺紋與機件不只承受單純的拉伸或壓縮力，還承受了因偏心或傾斜所導致的很大的彎矩。此彎矩會使機件產生彎曲變形，螺紋受力面積會隨著變形角度加大而大幅減少，使螺紋面壓大幅升高，造成不□鋼螺絲在鎖緊過程中產生嚴重的摩擦或磨耗作用，同時導致孔凸緣的加工裂痕破裂，以致螺絲在拆卸過程中損壞。 機構的設計必須要有足夠的強度，防止彎曲變形。並依使用需求增加囓合牙數或施加抗壓性佳的潤滑劑，這些都可以有效防止螺紋損壞，延長螺紋的使用壽命。

ABSTRACT

Screw is used in various purposes for its features of easy-to-install, easy-to-disassemble, easy-to-replace, and mostly been standardized. It is also an important means of mechanical combination. As a typical material for high quality screw, stainless steel has its advantage of anti-corrosive,non-magnetic material, wide range temperature capability, ready to use without any surface treatment. This thesis studies for stainless steel screw’s locking mechanism in the situation of machine parts are bent and deformed by preload. Extended analysis and discussion are also included. Study consists: (1) verification of torque equation, (2) correlation between preload and screw‘s elongation, (3) screw’s friction and abrasion characteristics under bending preload, (4) comparison of different torque, (5) how nut thickness and effective thread influence a screw, (6) how stainless screw affected by lubricating, and etc. Test result shows, when screw’s preload deforms machine parts, screw threw and machine parts bear not only tension or compression stress, but large moment caused by eccentric or tilt load. This moment deforms machine parts. Increasing angle of deformation reduces the stress area of screw thread and the stress of screw thread is raised. Under this reason, while screwing, stainless screw is seriously affected by abrasion, the work-hardening face crack of machine part is broken, and results in screw damages in disassembling process. To avoid screw thread damaging and extend use life , it needs to have enough strengthen in mechanical design to prevent deformation, increase effective thread by requirements, or add anti-wear lubrication.