Interval oscillation of a general class of second-order nonlinear differential equations with nonlinear damping

The paper is concerned with the oscillation of a class of general type second order differential equations with nonlinear damping terms. Several new interval oscillation criteria are established for such a class of differential equations under quite general assumptions. Examples are also given to illustrate the results. In particular, it is shown that under some very mild conditions on k1, k2, and f the equation (k1(x,x′))′+costk2(x,x′)x′+sintf(x)=0is oscillatory, which extends the result obtained by Kwong and Wong (J. Math. Anal. Appl. 288 (2003) 15).