First and second derivatives of internal combustion engine cylinder pressure diagrams

Approximate formulae are proposed for estimating natural frequencies of isotropic and specially orthotropic skew plates with clamped sides. It has been shown previously that one can estimate a natural frequency of a generally orthotropic skew plate with clamped sides by using an approximate formula for the isotropic plate which one can relate to the orthotropic one by applying a previously described reduction method. The accuracy of the proposed approximate formulae is demonstrated by comparing numerical and experimental results for several typical cases.