Optimization and Form-finding of the Heavy Cable Suspending a Deck

The heavy spanning cable supporting a uniform deck is important in the design of suspension bridges. The analytic design method is presented in this paper. The problem depends on three non-dimensional parameters: the ratio of cable length to the horizontal spanning distance, the ratio of vertical to horizontal distance, and the ratio of deck density to cable density. Given these parameters, useful tables of maximum tension and sag are determined. There exists an optimum cable length for which the maximum tension is minimized. In addition, it is shown that continuous loads and discrete loads are equivalent if the number of evenly-spaced discrete loads are more than 10.

Influence of Electromagnetic Characteristics of Shaft Material on the Performance of Induction Motor

Shaft is an important part of rotor, whose electromagnetic characteristics have an impact on the performance of the motor, especially when large diameter shaft and thin rotor yoke are adopted in the two-pole induction motor. Taking a 3 kW two-pole three-phase induction motor as an example, the two-dimensional electromagnetic field model of the motor is established by using finite element method. Firstly, by analyzing the difference of current, power factor, loss and magnetic field distribution of the motor with different shafts that are made from ferromagnetic and non-ferromagnetic materials. It is determined that the different magnetic saturation degree of rotor yoke is the key factor affecting the performance of motor when different shaft materials are used. Secondly, it is verified that the traditional analytic design method has the inaccurate design problem of the rotor yoke height due to neglecting the specific electromagnetic characteristics of shaft material. Finally, by comparing the differences of motor performance when several common magnetic shaft materials are used in motor shafts, the advantages of various shaft materials in improving motor performance are found. The presented results give guidelines to selecting shaft materials to improve motor performance.

An Analytic Method and Application on Design Planar Six-Bar Mechanisms with an Approximately Equal Velocity Ratio Transmission

An analytic design method on an approximately equal velocity ratio transmission mechanism is presented. The mathematical principle is that a compound function produced by two basic functions, let its one order differential is equal to an assigned constant on the special point, and then two to three order derivatives of the compound function are all zeroes, thus one algebraic equation is got, its solution defines the mechanism dimensions. This a principle not only sets up a new design method on approximately equal velocity ratio mechanisms but approximately equal velocity is independently designed. A design example shows that this method is simpler and transmission characteristics are better than optimization method.