AN ANALYTICAL STUDY OF FASTENED ASSEMBLIES

Abstract

Assembly is a key link in the mechanical and manufacturing industry, because precise assembly will be beneficial to realize the functions of design. In fact, errors are unavoidable during manufacturing of parts and assembly, which will bring about adverse effects. Hence dimensional tolerances are specified in order to alleviate such effects. This project aims at researching deformations of parts after assembly, seeking practical methods to calculate, predict, control and reduce these deformations, then establishing guidelines for the design and assembly of machine parts. After years of practice, experiences are accumulated and design and technology standards have been formed, but this process will never stop because of emergence of new products and techniques. Through this project, it is the author's wish to contribute a little effort to push this improvement. In this thesis, machine parts are divided into three basic groups: bar-like, beam­ like and plate-like parts. Patt errors of manufacture and assembly and deformations of parts after fixture or assembly are simulated and analysed, then analytical descriptions of these deformations are derived. Based on this, research is developed along three directions:

(1) assembly: covers appreciation of assembly quality, discussion of effects of assembly sequences on part deformations, and control of assembly deformations.

(2) Engineering solutions: simplifies component structures, sets up engineering solutions of part deformations and bearing forces of fasteners. (3) conceptual design: combining with design of equal strength parts and deviation design, exe1ts the strength of parts and fasteners to the maximum, in the meantime, reduces the cost of materials of parts and the number of fasteners, then reduces the production cost.

Investigations in this project are based on general assumptions and principles of mechanics and aimed at general problems in engineering, so the methods and analyses discussed in this thesis can be widely applied.