This paper discusses the combined use of quantitative analysis equatio
ns and knowledge-based techniques in the design of machine elements. W
e introduce the method of design compatibility analysis to (1) guide t
he application of correct analysis equations, (2) interpret the result
s of analysis, and (3) suggest modifications to improve the design. As
an example vehicle, this paper focuses on design issues related to co
ntact stresses and lubrication between two surfaces. The compatibility
approach covers not only quantitative performance measures, but also
the qualitative design issues such as suitability of surface materials
, machining methods, surface roughness, lubricants, etc. To verify the
utility of this concept, we developed DECS (Design Expert for Contact
Stress), a PC-based design-aid for contact stresses and lubrication.
DECS uses Prolog for top-level management and inference, while C provi
des the efficient computation of the quantitative equations. DECS also
utilizes some recent developments in the computations of contact stre
ss and elastohydrodynamic lubrication. Our method would be useful in m
any other design applications.