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MECHANICS II

 MECHANICS OF MATERIALS +

     JAMES W. DALLY AND ROBERT J. BONENBERGER, JR.

 University of Maryland, College Park

PREFACE

This textbook is the second of two written to support an integrated course offering for Statics and Mechanics of Materials.  Hopefully the integration of the topics of these two closely related courses will make the learning experience for the students easier and more meaningful.  The Mechanics of Materials textbook is a revision of a part of the book titled Design Analysis of Structural Elements, which was too long and heavy and required a supplement for the homework exercises.  The textbook for Statics++ published in 2009 was also drawn from part of Design Analysis of Structural Elements.  Both, Statics ++ and Mechanics of Materials +, have been revised by reorganization of materials based on reactions of instructors and students.  Exercises have also been added to eliminate the need for a supplementary problems book.  The content of Design Analysis of Structural Elements has been divided into two volumes to reduce the size and the weight of a book covering both topics in considerable detail.  The title has been changed to reflect the name of the courses at most Universities in the U. S.   

The Statics course provides the first exposure of engineering students to the study of mechanics.  While Statics is a relatively simple subject, many students find it difficult, and they often perform far below our expectations.  In an effort to improve the curriculum, the Keystone instructors at the University of Maryland have been working to enhance the student’s learning experience when studying the courses in mechanics.  The Statics ++ and Mechanics of Materials + textbooks indicates some of the changes in the philosophy adopted by the faculty, when presenting the subject matter traditionally offered in introductory mechanics courses.

The changes in the philosophy were based on five premises:  

1.  Present the fundamental concepts in a more interesting manner.

·         Change the approach to make it more realistic and less abstract.

·         Couple the mechanics content tightly to design.

2.  Provide a smooth transition from the Introduction to Engineering course to Design Analysis of Structural Components that encompasses both Mechanics I: Statics and Mechanics II: Mechanics of Materials.

·         Incorporate a hands-on experience including design, construction and testing of a model of a construction project.

·         Provide the analysis methods and the scaling relations for verifying the safety of the design of this model.

3.  Emphasize modeling structural components by stressing throughout the text the importance of preparing a complete free body diagram (FBD).

·         Show the method for constructing complete FBDs.

·         Integrate the FBD with the application of the equilibrium equations.

·         Approach the solution of equilibrium problems with equilibrium relations based on force and moment components.

4.      Integrate the content of Statics with that of Mechanics of Materials.

·         The concepts of normal and shearing stresses are introduced early in Statics.

·         Topics associated with Statics and with Mechanics of Materials are merged in whenever possible in the Statics ++ textbook.

·         The content typically found in Mechanics of Materials is presented with a heavy emphasis on design.

·         Fracture mechanics, a topic new to most undergraduates, is introduced in the Mechanics of Materials + textbook.

5.      Emphasize the design of structural components for safety.

·         Stress is compared to strength to give safety factors for components.

·         Behavior of engineering materials is introduced and physical properties such as strength and modulus of elasticity are described.

·         Sizing of structural components for safety and cost are demonstrated.

We began developing notes for the first edition of Design Analysis of Structural Elements with a pilot offering in the spring semester of 1998.  Many revisions were made before a limited first edition of the textbook was published in the summer of 1999.  The second edition was published in 2000 and was used by about a thousand students.  The third edition, written in 2001, included six new chapters to expand the coverage necessary for a complete Mechanics of Materials course.  The fourth edition, published in 2004, was similar to the third edition except for relatively small changes.  Since that time, about 4,000 students have used the 3rd and 4th editions of Design Analysis of Structural Elements.