|Home | ADCATS Info | Search | Site Map | Bulletin Board | Reports & Publications | Bibliography | Contact Us|
2000 Conference Presentations
|Variation Modeling and Design in Compliant Assemblies
Professor S. Jack Hu and Dr. Kaushik Iyer, University of
Component fixturing variations, tooling location and force variations, and component material compliance all contribute to variability in the overall dimensions and performance of multi-component assemblies. Traditionally, treatments for predicting and controlling undesired variations at the system level have assumed rigid material properties for each component. However, omission of component compliances has been shown to provide unrealistic predictions of variation stack-ups for entire assemblies. This and other inadequacies of the rigid-component assumption have been particularly evident in automotive and aircraft assemblies that contain flexible metal sheets and large numbers of connections (welds or rivets).
A recently developed model for predicting variations in such compliant assemblies (CAVA) will be presented. The model relates the dimensional deviations of an assembly to individual component deformations, which can be varied statistically according to variations in non-component factors (machining, fixturing and tooling). Additional variations can arise from the configuration of the assembly system (series, parallel or hybrid lines). An extension of CAVA to evaluate the robustness of compliant assembly systems will also be discussed. The analytical technique will be demonstrated through one or two robustness evaluation examples.
The surfaces of assembled components are commonly regarded as being flat or smooth. However, machining processes and material microstructure together impart local, small deviations to actual surface profiles. Deviations in the profile of a component surface from the nominal surface are widely believed to influence fretting fatigue and wear life (e.g. in airframe riveted lap joints, automotive and turbine engine components, etc.), electrical contact resistance, etc. In this case, the relevant length scales lie in the asperity-contact width range and are associated with surface roughness, waviness and form. Recent exploratory work directed towards the development of analytical solutions for the assembly of parts with realistic (non-flat) surface profiles will also be discussed.
|The ADCATS site: Home | ADCATS Info | Search | Site Map | Bulletin Board | Reports & Publications | Bibliography | Contact Us|