Physical Modeling And Tolerance Designning For Flexible Cable Harness

Currently,the manufacturing industry is experiencing a new round of morphology change.It requires a deep fusion of digital design in virtual world and product manufacturing in real world,to improve the development level comprehensively.The cable harness is the blood and the nervous system in aircraft system,whose quality and reliability is the key to ensure the normal operation of the system,and also has problems frequently affecting the production schedule.An important reason is the characteristics of large deflection is neglected in the process of cable harness assembly design.The design precision is low without accurate estimate of assembly effect,and rework occurs frequently.The assembly design of aircraft cable harness is the research object in this paper,and the research purpose is to increase the precision.Two major issues affecting the design effects is pointed out with analysis of the current assembly design process.On the one hand,the real morphology of cable harness in the virtual assembly environment can't be reflected accurately,due to that the cable harness model is seen as rigid body without considering the effects of material properties and stress conditions.On the base of nonlinear mechanics of elastic rod,4 kinds of coordinate systems are established and curvature,torsion and curvature-twisting vector are introduced to express the position and the morphology of cable harness in three-dimensional space.The relationship between stress and strain of cable harness is established considering physical properties,and parametric equations of cable harness centerline is established.The analysis to the actual operating mode is carried on,and the assembly constraints are divided into three kinds: end-point constraint,distributed force constraint and contact restraint.Boundary condition and assembly coordination relations is analyzed of different restraints.On the other hand,there is no tolerance design steps in current design process.Grading tolerance design scheme for flexible cable harness is proposed by comparison of tolerance design characteristics of rigid body.Design tolerance and assembly tolerance for size of cable harness are calculated through tolerance analysis and tolerance synthesis of assembly dimension chain.And elastic deflection is introduced to convert the requirements of the tightness of cable harness assembly to the requirements of length.It will fill the gaps in tolerance design of cable harness.Finally,the results of theoretical research are applied on 3D simulation platform to lay the foundation for actual engineering applications.