Many books have been written on strength of materials but it is seldom that one covers the field as well, and still makes such interesting reading, as Den Hartog's newest book. It is written as a text for use in a first course in the subject. Wisely, certain sections are marked for omission if the teacher believes them too difficult. There are over 200 pages of text followed by 87 pages of problems. The problems are better than those generally found in similar texts in that they require real thinking on the student's part. Certainly some of them are beyond his capacity while studying the subject for the first time, but with the assistance of a good teacher they will broaden his thinking and improve his methods of attacking a problem.
The first three chapters are entitled Tension, Torsion, and Bending and cover the most important cases of stresses inbeamsand shafts. These are followed by a chapter on Compound Stresses where Mohr's Circle is introduced together with the maximum-stress, maximum-strain, maximum-shear-stress, Mohr, and maximum distortion energy theories. The next three chapters adequately cover beams of different types with various loadings and thin-and thickwalled cylinders.
There is an excellent chapter on Experimental Elasticity covering Photoelasticity, Strain Gages, and Fatigue. The student should find the section on the use of Resistance StrainGages interesting and extremely valuable information. The problem of determining the magnitude and direction of the principal stresses at a surface point is solved by the use of a rosette of three strain gages. This givesstrains in three directions, 120 deg. apart, and Mohr's circle is applied to determine the principal stresses and their direction.
Although this book was written as an undergraduate text, it is highly recommended, because of its easily readable style, for the engineer who would like to brush-up on the flmdamentals of the subject.