Martin Marietta Missile Systems is involved in large numbers of defense projects including designing and manufacturing several key missiles such as the Patriot ("The Scudbuster"), Hellfire, and Copperhead projectiles, which performed so well in the Persian Gulf conflict. Airframe as well as hardware design normally requires an immense amount of hand calculations even when the most advanced computer aided engineering tools are available. A good example is the need to convert I-beam sections into equivalent beams prior to finite element modeling in order to speed modeling and cut computation time. By using the The Desktop Engineer computerized engineering handbook (Desktop Engineering, Woodcliff Lake, New Jersey), Lockheed engineers have been able to reduce the time required for these and many other common computational tasks from 30-60 minutes to 5-10 minutes.

While Raytheon is the prime contractor for the Patriot missile, a significant proportion of the work on the project including missile airframe and final assembly is performed here at Martin Marietta. Staff engineers for the company also work on a wide variety of missiles, helicopters, spacecraft, ordnance and other aerospace related projects. One of their prime responsibilities has long been stress analysis of shell structures and interface components. In previous years, engineers spent a high percentage of their time looking up equations in textbooks and punching the buttons on a hand calculator. Equivalent sections with the same structural properties as the actual sections were determined by by searching through a reference manual or handbook to find a section that applies to the task at hand, selecting a series of formulas, generating equations and then solving them with a calculator. Engineers spent a considerable amount of time looking for a way to streamline this time-consuming task. When one engineer read about the concept of a computerized engineering handbook four years ago, they decided to give it a try and have been using it nearly every day since.

It's important to understand exactly how this tool fits into Lockheed Martin's engineering operations. The firm uses MacNeal Schwendler Corporation's NASTRAN finite element analysis package for complex structural analysis problems. While this program is extremely powerful, it is only as good as the users prepared inputs. The I-beam problem mentioned above is a good example. Furthermore, if every structural nook and cranny is modeled down to the last detail, both the time required for the analyst to create the model and the CPU time required to solve it would be sky-high. This is why engineers have long used the method of generating simpler sections with equivalent properties, which are then input into the finite element analysis, yielding nearly identical results in far less time and cost. Now, with The Desktop Engineer, they can generate these equivalent sectional properties in only 5 to 10 minutes. Since engineers run into this situation many times in a typical week, the overall time savings are large.

The major advantage of The Desktop Engineer is that it takes the same equations that are found in a reference book, prompts the user for the needed information using "fill in the blanks" input and then automatically solves them. You can then do "what if" analysis by changing one or two variables and backing into the design efficiency you want. The time required to solve the problem is drastically reduced and so is the chance of making mistakes. For example, in the I-beam problem, the engineer performing the analysis would be prompted for the web thickness and flange thickness. The program then generates the area and moments of inertia. From there, the user moves into the beam module of the program where moments of inertia, cross-sectional area, type of material, and modulus of elasticity are input. In just a few minutes, the program generates shear and moment diagrams for general analysis or beam preparation needed for finite element analysis. Another advantage of performing these calculations with The Desktop Engineer rather than by hand, is that documentation of all the required calculations can be produced with just a few keystrokes. Other examples of problems, which are solved with The Desktop Engineer on a daily basis, are stresses in flat plates, pressure vessel designs, and plate and cylinder buckling analysis.

The Desktop Engineer is a computerized engineering handbook that provides over 5000 solutions to common engineering applications found in over 100 engineering reference books. It includes over 50 modules grouped into the following categories: geometric analysis; static analysis; dynamic analysis and buckling analysis. These categories are used to analysis structures including straight beams, curved beams, cables, circular arches, circular rings, columns, discrete systems, disks, foundations, frames, grillages, helical springs, plates, shafts, shells and solids. Thin Walled Sections is an important optional new module of The Desktop Engineer. This module calculates more than 30 nominal section properties, including twelve torsional properties, for arbitrary thin-walled sections. All modules are self-prompting to help the user find section properties, displacement, forces, stresses, etc. The Desktop Engineer also includes a material property database and a unit conversion utility.

For more information contact Desktop Engineering Int'l Inc., 172 Brodway, Woodcliff Lake NJ 07677. Phone: 800-888-8680 or 201-505-9200 Fax: 201-505-1566