EIMCO Process Equipment Company, Salt Lake City, Utah, has reduced the time required to find member structural properties, deflections and stresses from the 30 minutes which was previously required with conventional engineering handbook solutions to 5 minutes using The Desktop Engineer, a computerized engineering handbook (Desktop Engineering, Woodcliff Lake, New Jersey). Steve Rowe, Manager of Computer Aided Engineering for EIMCO, said that the time savings arise from the fact that the package allows nearly any problem configuration to be solved with the input of 4 to 6 values such as dimensions, material, loading, and boundary conditions. On the other hand, a conventional engineering handbook involves significant extra time in selecting the appropriate equations, determining proper constants and performing hand calculations.

EIMCO is a 500 employee company which designs and manufactures heavy industrial sedimentation and filtration equipment that require a considerable amount of space frame, tankage and gear design. Jim Deakin, Senior Design Engineer for EIMCO, said that The Desktop Engineer is the perfect tool for many of the design problems encountered and cited the example of a splitter box tank produced by the company which consists of a rectangular box made of A-36 steel with stiffeners on its side and a series of channel beam supports on the bottom. Loading on the tank is hydrostatic on its sides and uniform on the bottom. Solving the problem with a conventional handbook would require using several different sources for engineering design formulas, and the determination of several different constants and fairly extensive hand calculations, Deakin said. The typical time required would be about 30 minutes per plate. Using the "plates" module of The Desktop Engineer, he said he input the data for each load case in about 2 minutes and that a total of about 2 minutes was required for processing time and stress evaluation. Any further calculations to refine the design can be made by simply modifying the input values, thus allowing the engineer to provide the best possible design quickly without laborious hand recalculation of all of the formulas.

Rowe stated that in more complex calculations such as where multiple loading is involved the time savings can be even greater. He pointed to the case of a filter press designed by the company in which the filter plates as well as an actuator that closes the chamber are supported on a long pair of rails. Determining the deflection of the rails in this situation would take at least 45 minutes with a conventional handbook according to Rowe because of the complexity in determining the combined effect of the three loads which come into play: 1) the plates or chamber stack 2) the actuator 3) the weight of the rails themselves. With The Desktop Engineer, on the other hand, this was another 5 minute job, he said. First, he solved each load case separately using the "beam" module of the program, then he combined the loads using the "superposition" module to determine actual deflection on the part. Rowe pointed out that occasionally this type of analysis gets even more complex when two different standard beams or channels are welded together to form the rails. But, the analysis in The Desktop Engineer is hardly any more difficult -- the only extra step is a minute or two using the geometric properties' module to determine the combined sectional properties of the rail.

Rowe mentioned that the problems discussed above as well as most others for which the company uses The Desktop Engineer could also be solved with the finite element analysis technique which is used quite extensively at EIMCO. The problem with finite element analysis, he said, is that it takes at least a half hour to produce a finite element model of even the most general part. This renders the technology impractical for simple but very common problems like those mentioned above where The Desktop Engineer is so useful. Another advantage mentioned by Rowe is that the software is so easy to use. He said that the package can easily be used by the company's designers with only limited supervision by an engineer, and that designers' calculations can easily be checked due to the presentation of the input and results in the same format.

The Desktop Engineer is basically a computerized handbook of solutions to structural/mechanical engineering equations. It uses these equations to calculate deflections, forces and stresses in loaded structures. It is divided into categories such as beams, plates, columns, frames, etc. In each category, the program prompts the user to provide information that is needed to solve the defined problem. The information requested is related to the geometry, material, support and loading conditions of the structure. This is the same information that would be needed should the user do the problem by hand.

Once the problem is defined, the program will quickly perform the necessary calculations and provide the associated numerical and graphical output. In most cases it will do the equation substitutions. integration, boundary condition analysis, exactly like one would do if the problem was done by hand. In some of the more complicated analyses, the program uses finite elements to get a solution (even though the input and output format remains similar to the other modules and the user is not required to know finite element techniques). Once a problem is accurately setup and modeled, it can be quickly changed and rerun to allow the designer to look at various design options or modifications.

Several utility modules are included to assist the designer with complex problems. A superposition module allows the designer to look at the effects of several concurrent loads on the same structure. A module is included to produce Mohr's circle analysis for multi-axial states of stress and strain. Modules are also included to assist the user with calculating section properties. The program also has a convenient material property database and several modules that look at complex geometries and dynamic conditions.