Page "learned" Paragraph 1278

Cutting mechanism of cohesive failure

The cutting ( or shearing ) removal process has been previously described.

It was found that the coating is separated from its substrate entirely by cohesive failure.

The details of the removal process are shown schematically in Fig. 6.

The various forces result from the reaction of the removed paint chip against the face of the knife and along the shear plane, which makes an angle **yf with the substrate.

The action and reaction forces are R and Af, respectively, and are equal and opposite in direction.

All the other force vectors are derived from these.

Af is the force required to cut a coating of thickness T from the substrate.

Af is the shear force along the shear plane ; ;

Af and Af are the thrust forces acting against coating and knife, respectively ; ;

Af is the normal compressive force acting on the shear plane ; ;

Af is the friction force between chip and knife surfaces, and P is the normal force acting on the face of the knife.

**yc is the rake angle of the knife ; ;

**yf is the angle the shear plane makes with the substrate ; ;

**yt is the friction angle ; ;

and **yb is the angle the resultants make with the plane of the substrate.