Michael L. Day

Auxiliary springs in continuous arch treatment: Part 1. An analytical study employing the finite-element method

This report describes the results of a finite-element analysis with ANSYS (Version 4.3) from Swanson Analysis Systems and 1 mm-long, 2-D elastic beam elements to modify and refine the designs of maxillary and mandibular springs for space-closure management. This system permitted static analysis by means of modern software systems instead of expensive and cumbersome mechanical bench studies. Our examination of anterior and posterior reactions led to what we believe are optimal designs with clinically manageable moment/force ratios and new canine brackets that accommodate these springs within the framework of conventional and straight-wire appliance systems. Three degrees of freedom were used at each node for translations in the x and y directions and a rotation about the z axis, producing 182 elements with 183 nodes for the mandibular model and 146 elements with 147 nodes for the maxillary model. Elgiloy retraction spring models (0.1650 inch x 0.02150 inch) in the edgewise mode were developed so that the effects of three different preactivation bends could be refined by computer analysis. Sixty-four analyses were performed for each spring, with each of three angle bends (theta 1, theta 2, and theta 3) varied from 0 degrees to 45 degrees in 15 degrees increments. The employment of this computer method promises to simplify the design and development of complex interacting orthodontic systems. Clinical cases are presented in Part 2 of this series, which illustrates the application of auxiliary springs.

Experimental Analysis and Computer Simulation of Automotive Bumper System under Impact Conditions

In this paper, an automotive bumper model was used for low-velocity impact tests. During these tests, the reaction forces at the end of shocks and displacements of the joints were measured. After that, a finite element model was created and the impact test was simulated on the computer using ANSYS. The numerical results obtained from the computer simulation were then compared and correlated to the experimental results. Additionally, an analytical calculation of the impact problem was performed and the analytical solutions were also compared to the experimental and the numerical results to further validate the impact tests and computer simulation. Good agreements were obtained through comparing these results and finally, the impact responses of the bumper system under different tests were obtained and verified through the numerical and analytical analyses.

Auxiliary springs in continuous arch treatment: Part 2. Appliance use and case reports

In the second part of this series, three clinical examples are presented to illustrate the use of auxiliary space-closure springs with clinically manageable moment-to-force ratios and new canine brackets to accommodate these springs within the framework of conventional and straight-wire 0.018-inch appliance systems. Eligiloy retraction spring models (0.1650 inch x 0.02150 inch) in the edgewise mode were developed for translational movements along a main archwire. The effects of different preactivation bends for influencing intraarch anchorage are shown for the conditions of reciprocal closure, posterior protraction, and anterior retraction.

Simplified truck chassis modelling and crashworthiness analysis

In this paper, a simplified model is developed for a truck chassis, which is comprised of beam and spring elements and can be used for crashworthiness analyses. In the simplified model, non-linear spring elements are used to simulate the bending and collapse behaviour of thin-walled structures of the truck chassis. These non-linear spring elements are created based on bending and collapse theories of thin-walled beams. Equivalent beams are applied to model the transverse plate components in the truck chasses. After completion, both detailed and simplified models are used for crashworthiness analyses, and the results are recorded and compared. Relatively good agreement is achieved through these analyses, while computer time is significantly reduced and modelling labour is remarkably saved by using the developed simplified model.