**Concept**

MDSolids is an educational software package devoted to the introductory mechanics of materials course. The hypothesis of the MDSolids concept is that students are most interested in understanding the specific homework problems assigned by their professors, and that students will use educational software if it helps them with their immediate course concerns. In the process, the software can help to develop problem solving skills by giving students an intuitive interface that guides them to the important factors affecting various problem types, helps them visualize the nature of internal stresses and deformations, and provides an easy-to-use means of investigating a greater number of problems and variations. Based on this premise, MDSolids was developed with several objectives in mind:

**Versatility:**MDSolids has routines pertaining to all of the topics taught in a typical mechanics of materials course. These routines are grouped in modules, similar to typical textbook chapters, and the modules can be accessed in any sequence. Twelve modules pertaining to a wide range of common textbook problems are presently available: basic stress and strain, beam-and-strut axial problems, trusses, statically indeterminate axial structures, torsion, determinate beams, section properties, general analysis (of axial, torsion, and beam members), column buckling, pressure vessels, and Mohr's circle transformations. Within the modules, each routine solves types of problems typically found in all mechanics of materials textbooks. The scope of MDSolids offers routines to help students at all levels of understanding, from the most fundamental knowledge-, comprehension-, and application-type problems to more complex problems requiring analysis and synthesis.

**Ease-of-Input:**Ease-of-input is an essential aspect in the MDSolids concept. Solving the mechanics of materials problems is confusing enough for students. To be effective, educational software must not add to the confusion. Ideally, the student should be able to define a problem intuitively and directly from a textbook without the need for a user's manual. Throughout MDSolids, graphic cues are provided to guide users in entering data. The illustrations can be easily adjusted so that the MDSolids input screen looks very similar to the textbook illustration. Various units (e.g., stress units, length units) are available and internal conversion factors are present to ensure dimensional consistency.

**Visual Communication:**Each MDSolids routine features a picture, sketch, or plot that graphically depicts important aspects of the problem. Sketches are used to show the direction of internal stresses, applied loads, and reaction forces. Plots are given for a number of topics including critical buckling stress, beam deflections, and shaft shearing stress. As the cliché goes, "one picture is worth a thousand words."

**Text-based Explanations:**Many of the MDSolids modules provide extra explanations to describe in words how the calculations are performed. These explanations can help students develop the thought processes used in solving mechanics of materials problems. The text explanations are dynamic and context-sensitive, tailored specifically to the particular problem in terms of the values and units entered for the problem. Common mistakes in equilibrium equations, unit inconsistencies, and equation manipulations become obvious when a student compares hand calculations with the MDSolids explanations.