Structural behavior of large-scale triangular and trapezoidal threaded steel tie rods in assembly using finite element analysis
Abstract Pre-stressed steel tie rods are used extensively as load carrying components in structures like suspension bridges, steering systems in automotive vehicles, wings and fuselage of aircrafts, spokes of Ferris wheels, etc. The governing variables for the bearing strength of a large-scale steel tie rod (of diameter usually larger than 60 mm) include the mechanical strength of the tie rod body, geometric configuration of the thread teeth and the number of turns of thread engagement. The optimal number of turns of threaded connections of large scale steel tie rods has been predicted by full scale rupture experiments and reported previously by the authors. This paper builds up further on that work and investigates the structural behavior of the two types of threaded connections of steel tie rods, viz. (i) the triangle threaded connection, and (ii) the trapezoidal threaded connection, using finite element analysis in ANSYS. The axial displacement, equivalent stress distribution, interfacial contact pressure and sliding distance on the engaged thread teeth under different axial loads are presented and analyzed. The numerical simulations verify and expound the results of full-scale tensile rupture experiments. The concordant comparison between experimental measurements and finite element analysis provides working guidelines and support for the design and fabrication of steel tie rods in practical operations.
Fatigue Analysis of Large Diameter Threaded Connections Subjected to Dynamic Axial Loads
The large diameter threaded connections are components with high importance in the heavy mechanical systems. At the threaded elements subjected to variable loads one of the main causes of failure is represented by fatigue. This phenomenon is accentuated by the occurrence of high local stresses on the thread root. In this context, the correct evaluation of the local stresses and their correlation with the fatigue behaviour has a major importance in the correct assessment of remaining life of large diameter threaded connections.The paper is focused on the finite element analysis of the large diameter threaded bolts with two types of threads profiles: trapezoidal and square. For the two types of threads the simulations were performed using four nominal diameter and two different loading setups. The bolts were summited to static analysis in order to determine the local stresses distribution in the threaded area. The maximum values of Von Mises stresses obtained in the static analysis were exported to fatigue studies. The differences between the results obtained for the two types of threads are outlined.
Simulating the Illuminance and Efficiency of the LEDs Used in General Household Lighting
Abstract The advantage of the LEDs illumination in general household lighting was proposed. High efficiency white LED as the light source was provided the energy saving illumination of the general household lightings. Different spaces in general household with different standards of average illuminance were designed and simulated by LightTools and DIALux software. The power consumptions and efficiency of traditional illuminated light sources and LED light source in lighting the household environment were analyzed and compared with each other at the same standard of average illuminance. Finally, it provided the advantage of using white LEDs in different spaces of the general household lighting.