平面機構含間隙接頭與構件斷裂行為之研究

A study on planar mechanism with joint clearance and fragmentation by Motion Analysis of Structure method

廖奕翔(Yi-Hsiang Liao)

指導教授 ： 李志中

共同指導教授 ： 吳東岳

國立臺灣大學/工學院/機械工程學研究所/碩士(2008年)

https://doi.org/10.6342/NTU.2008.02868

摘要

隨著高速機械系統及機構系統準確性的要求越來越高，對接頭的模擬也將趨近於愈真實的情況，若於機構中存在了間隙接頭(joint clearance)，容易導致機構在運動的過程中產生分離、衝擊等現象，造成機構的壽命降低、震動增加與輸出誤差。另外在工程上所遇到的問題還包括構件的斷裂行為，不論是在機構的運動中，或者是結構受力時，若能夠以一演算法求出構件可接受多大的內應力値而不發生斷裂，或者是能夠預測斷裂後碎塊的移動軌跡及運動情形，將對工程實務上遇到的問題有極大的幫助。
本文主旨為使用運動解析法分析平面機構中含有間隙接頭與構件斷裂行為之研究。運動解析的優點在於可處理桿件運動過程中經歷大的幾何變形的行為，如破裂、穿透、撞擊或非線性的運動情形，所以我們採用運動解析來模擬此兩種工程上的問題。在計算間隙接頭時的接觸力會採用赫茲接觸法(Hertz’ contact)，同時針對運動解析的優點，也會計算降低剛性後的機構含有間隙接頭時的算例，並與文獻中的結果相比較。對於構件的斷裂行為，除了計算構件受衝擊力時的內應力值與斷裂後構件的運動軌跡外，也會計算內應變，並將應力波與應變波的傳遞情形表示出來。

關鍵字

向量式有限元 ； 運動解析 ； 間隙接頭 ； 赫茲接觸 ； 斷裂 ； 時間積分

並列摘要

In this work, we present a study on planar mechanism with joint clearance and fragmentation by Motion Analysis of Structure method (MAS). The MAS method is based on a vector form of mechanics which discretizes a continuous body into a set of particles described by the Newton’s laws. The interactions among those particles are defined by the element forces formulated by a vector-form intrinsic finite element (VFIFE) so that the elements with large rotation can be successfully handled. The engineering problems of joint clearance and fragmentation have been investigated throughout this work. We use MAS combining with Hertz’ contact method to simulate either rigid or flexible mechanisms with joint clearance. Also, we use MAS as an algorithm to handle the fragmentation behavior which the process if achieved by incorporating the ability to create new node or new element according to a defined failure criterion.

並列關鍵字

Motion analysis, VFIFE, Joint clearance, Fragmentation,Time integration

參考文獻

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