434 Mechanics of Materials S16. Fig.16.3.Brittle-lacquer crack patterns on an open-ended spanner and a ring spanner.In the former the cracks appear at right angles to the maximum bending stress in the edge of the spanner whilst in the ring spanner the presence of torsion produces an inclination of the principal stress and hence of the cracks in the lacquer. Fig.16.4.Brittle-lacquer crack pattern highlighting the positions of stress concentration on a motor vehicle component.(Magnaflux Corporation.) particularly useful for investigation under adverse environmental conditions such as in the presence of water,oil or heavy vibration. Refinements to the general technique allow the study of residual stresses,compressive stress fields,dynamic situations,plastic yielding and miniature components with little434 Mechanics of Materials §16. Fig. 16.3. Brittle-lacquer crack patterns on an open-ended spanner and a ring spanner. In the former the cracks appear at right angles to the maximum bending stress in the edge of the spanner whilst in the ring spanner the presence of torsion produces an inclination of the principal stress and hence of the cracks in the lacquer. Fig. 16.4. Brittle-lacquer crack pattern highlighting the positions of stress concentration on a motor vehicle component. (Magnaflux Corporation.) particularly useful for investigation under adverse environmental conditions such as in the presence of water, oil or heavy vibration. Refinements to the general technique allow the study of residual stresses, compressive stress fields, dynamic situations, plastic yielding and miniature components with little