Finite element analysis of the initial yielding behavior of a hard coating/swbstrate system with functionally graded interface under indentation and friction
Ls. Stephens et al., Finite element analysis of the initial yielding behavior of a hard coating/swbstrate system with functionally graded interface under indentation and friction, J TRIBOL, 122(2), 2000, pp. 381-387
The initial yielding behavior due to the indentation and friction process b
etween an elastic cylindrical surface and hard coating/functionally graded
substrate system is analyzed by finite element modeling. A thin hard DLC fi
lm deposited on a soft Ti-6Al-4V alloy substrate is considered as a model s
ystem. Two functional gradient substrate conditions are considered: (i) a g
radient in yield strength and (ii) a gradient in elastic modulus. In both c
ases, appropriate gradients result in significant benefits to the reliabili
ty of the coated system compared to the case of an ungraded substrate. The
results indicate that systems with an appropriate gradient in yield strengt
h: (i) carl withstand significantly higher applied contact stresses (3-12 t
imes higher for the present model system), (ii) shift the location of the i
nitial yield point deeper into the substrate (at least by a factor of 2 for
the present model system), and (iii) can use coatings of greater thickness
. Finally, the results indicate that an appropriate gradient in elastic mod
ulus results in a dramatic reduction in equivalent stress an the contact su
rface and at the interface as compared to the ungraded case. The present re
sults suggest distinct benefits to the durability of coated systems when us
ing a substrate with functionally graded properties. [S0742-4787(00)02002-6
].