Stress Relief in Contact-Aided Compliant Cellular Mechanisms

2009 ◽  
Vol 131 (9) ◽  
Author(s):  
Vipul Mehta ◽  
Mary Frecker ◽  
George A. Lesieutre
Keyword(s):  
Finite Element ◽  
Analytical Model ◽  
Stress Relief ◽  
Cellular Structures ◽  
Cellular Mechanisms ◽  
Element Analysis ◽  
Bending Stresses ◽  
Order Of Magnitude ◽  
Structural Mass ◽  
Contact Mechanism

Compliant cellular structures with an internal contact mechanism are described in this paper. Contact during deformation reduces failure-causing bending stresses through stress relief, thereby enabling such cellular structures to be stretched more than the corresponding structures without contact. Finite element analysis (FEA) is carried out to simulate the structure. An analytical model is developed to get results quicker than FEA and to develop insight into the mechanics of the deformation process. The error in prediction of the maximum stretching capacity using the analytical model is less than 7% when compared with finite element simulations. Several materials are investigated for such structures. Although the allowable strain of all these materials is small, the overall strain of the contact-aided cellular structures is at least an order of magnitude greater than that of the constitutive material. The contact mechanism and the induced stress relief increase the stretching capacity of the contact-aided cellular structures by as much as 100%. Experiments are conducted to validate the models, and good agreement is found. A high-strain morphing aircraft skin is examined as an application of these mechanisms. The results indicate that the proposed skin structure not only increases the morphing capacity but also decreases the structural mass by 13% as compared with a cellular skin without contact.

Stress Relief in Contact-Aided Cellular Compliant Mechanisms

2008 ◽  
Author(s):  
Vipul Mehta ◽  
Mary Frecker ◽  
George Lesieutre
Keyword(s):  
Compliant Mechanisms ◽  
High Strain ◽  
Stress Relief ◽  
Cellular Structures ◽  
Morphing Aircraft ◽  
Fracture Failure ◽  
Global Strain ◽  
Aircraft Skin ◽  
Structural Mass ◽  
Contact Mechanism

Cellular structures with an internal contact-mechanism are investigated. These contact-aided compliant mechanisms are shown to reduce the local tensile stresses, thereby providing additional global strain before yielding or fracture failure compared to honeycomb or auxetic cellular structures. An analytical model for such structures is developed and it is validated using FEA simulations. Two different materials are considered for comparison. More than 100% improvement in global strain capability is possible using the contact. A high-strain morphing aircraft skin is examined as an application of these mechanisms. The contact-aided cellular compliant mechanisms are more advantageous in terms of both the structural mass as well as the global strain compared to a non-contact design. In the application considered the stress-relief mechanism increased the global strain capability by as high as 37%.

scholarly journals A Novel Method for Tooth Bending Stress Calculation of Gears With Asymmetric Teeth

2021 ◽  
Author(s):  
Oguz DOGAN ◽  
Celalettin YUCE ◽  
Fatih KARPAT
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Experimental Studies ◽  
Element Model ◽  
Bending Stress ◽  
Element Analysis ◽  
Stress Calculation ◽  
Bending Stresses ◽  
New Equation ◽  
Asymmetric Factor

Abstract Today, gear designs with asymmetric tooth profiles offer essential solutions in reducing tooth root stresses of gears. Although numerical, analytical, and experimental studies are carried out to calculate the bending stresses in gears with asymmetric tooth profiles a standard or a simplified equation or empirical statement has not been encountered in the literature. In this study, a novel bending stress calculation procedure for gears with asymmetric tooth profiles is developed using both the DIN3990 standard and the finite element method. The bending stresses of gears with symmetrical profile were determined by the developed finite element model and was verified by comparing the results with the DIN 3990 standard. Using the verified finite element model, by changing the drive side pressure angle between 20° and 30° and the number of teeth between 18 and 100, 66 different cases were examined and the bending stresses in gears with asymmetric profile were determined. As a result of the analysis, a new asymmetric factor was derived. By adding the obtained asymmetric factor to the DIN 3390 formula, a new equation has been derived to be used in tooth bending stresses of gears with asymmetric profile. Thanks to this equation, designers will be able to calculate tooth bending stresses with high precision in gears with asymmetric tooth profile without the need for finite element analysis.

Finite Element Analysis for a CAD of a Concrete Mixer Drum

1994 ◽  
Author(s):  
Hossam S. Badawi ◽  
Sherif A. Mourad ◽  
Sayed M. Metwalli
Keyword(s):  
Finite Element ◽  
Computer Aided Design ◽  
Three Dimensional ◽  
Plain Concrete ◽  
Element Analysis ◽  
Shell Elements ◽  
Bending Stresses ◽  
Loading Effects ◽  
Concrete Mixer ◽  
Aided Design

Abstract For a Computer Aided Design of a concrete truck mixer, a six cubic meter concrete mixer drum is analyzed using the finite element method. The complex mixer drum structure is subjected to pressure loading resulting from the plain concrete inside the drum, in addition to its own weight. The effect of deceleration of the vehicle and the rotational motion of the drum on the reactions and stresses are also considered. Equivalent static loads are used to represent the dynamic loading effects. Three-dimensional shell elements are used to model the drum, and frame elements are used to represent a ring stiffener around the shell. Membrane forces and bending stresses are obtained for different loading conditions. Results are also compared with approximate analysis. The CAD procedure directly used the available drafting and the results were used effectively in the design of the concrete mixer drum.

High-Ampacity Overhead Power Lines With Carbon Nanostructure–Epoxy Composites

2016 ◽  
Vol 138 (4) ◽  
Author(s):  
V. S. N. Ranjith Kumar ◽  
S. Kumar ◽  
G. Pal ◽  
Tushar Shah
Keyword(s):  
Finite Element ◽  
Analytical Model ◽  
High Performance ◽  
Electrical Power ◽  
Power Lines ◽  
Fe Model ◽  
Carbon Nanostructure ◽  
Element Analysis ◽  
Core Diameter ◽  
Overhead Power Lines

Design of high-performance power lines with advanced materials is indispensable to effectively eliminate losses in electrical power transmission and distribution (T&D) lines. In this study, aluminum conductor composite core with carbon nanostructure (ACCC–CNS) coating in a multilayered architecture is considered as a novel design alternative to conventional aluminum conductor steel-reinforced (ACSR) transmission line. In the multiphysics approach presented herein, first, electrothermal finite element analysis (FEA) of the ACSR line is performed to obtain its steady-state temperature for a given current. Subsequently, the sag of the ACSR line due to self-weight and thermal expansion is determined by performing thermostructural analysis employing an analytical model. The results are then verified with those obtained from the FEA of the ACSR line. The electrothermal finite element (FE) model and the thermostructural analytical model are then extended to the ACCC–CNS line. The results indicate that the ACCC–CNS line has higher current-carrying capacity (CCC) and lower sag compared to those of the ACSR line. Motivated by the improved performance of the ACCC–CNS line, a systematic parametric study is conducted in order to determine the optimum ampacity, core diameter, and span length. The findings of this study would provide insights into the optimal design of high-performance overhead power lines.

An Energy Transmitting Boundary for Semi-Infinite Structures

2007 ◽  
Vol 23 (2) ◽  
pp. 159-172
Author(s):  
S.-S. Chen ◽  
W.-C. Hsu
Keyword(s):  
Finite Element ◽  
Analytical Model ◽  
Virtual Work ◽  
Element Model ◽  
Absorption Mechanism ◽  
Element Analysis ◽  
Reflected Waves ◽  
Infinite Region ◽  
Model Size ◽  
Transmitting Boundary

AbstractA soil-structure system associated with a semi-infinite structure such as tunnel or pavement is usually investigated by finite element analysis. If the boundary of the finite element model selected is not far enough from the excitation source or does not have an appropriate energy-absorption mechanism, it may introduce a significant error induced by reflected waves. This study develops a structural transmitting boundary to absorb the transmitting energy at the boundary of the analytical model. The structure is divided into finite and semi-infinite regions. The stiffness of the semi-infinite region is established by the principle of virtual work and applied at the transmitting boundary. The comparisons of the structural displacements induced by vertical harmonic excitations show that the analytical model size can be significantly reduced, if the proposed transmitting boundary is used to simulate the semi-infinite structural region.

Development of Hybrid Semi-Analytical and Finite Element Analysis to Calculate Sound Radiation from Vibrating Structure

2013 ◽  
Vol 845 ◽  
pp. 71-75 ◽  
Author(s):  
Azma Putra ◽  
Nurain Shyafina ◽  
Noryani Muhammad ◽  
Hairul Bakri ◽  
Noor Fariza Saari
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Boundary Conditions ◽  
Rectangular Plate ◽  
Analytical Model ◽  
Complex Geometry ◽  
Sound Radiation ◽  
Vibration Velocity ◽  
Rectangular Plates ◽  
Element Analysis

Simple analytical model of plate dynamics usually applies for rectangular plate with simply supported edges. Analytical model of sound radiation from rectangular plate is also convenient, but not for other geometries and other boundary conditions. This paper presents a hybrid mathematical model which combines a semi-analytical model with the Finite Element Analysis (FEA) method to determine sound radiation from a vibrating structure. The latter is employed to calculate the vibration velocity of a structure with a rather complex geometry. The results are then used as the input in the semi-analytical model to calculate the radiated sound pressure through the Rayleigh integral. Results from the proposed model are presented here for the radiation efficiency of rectangular plates with different boundary conditions.

Discussions on Behavior of Bolted Joints in Tension

2004 ◽  
Vol 127 (3) ◽  
pp. 506-510 ◽  
Author(s):  
Ouqi Zhang
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Analytical Model ◽  
Bolted Joints ◽  
Axial Stiffness ◽  
Conventional Theory ◽  
Element Analysis ◽  
Stiffness Characteristics ◽  
Plate Connections ◽  
Made In

It is known that the behavior of real axisymmetric bolted joints in tension is much more complicated than that the conventional theory describes. Phenomenon conflicting with the theory prediction was observed in experimental and finite element analysis [Kwiatkowski, J. K., Winnicki, L. A., and Krzyspiak, A., 1986, “Stress Analysis of Bolted Tensile End Plate Connections,” Rozprawy Inzynierskie Eng. Trans., 34, pp. 113–137; Webjörn, J., 1988, “Die Moderne Schraubenverbindung,” VDI-Z, 130, pp. 76–78; Grosse, I. R., and Mitchell, L. D., 1990, “Nonlinear Axial Stiffness Characteristics of Bolted Joints,” ASME J. Mech. Des., 122, pp. 442–449; Gerbert, G., Bastedt, H., 1993, “Centrically Loaded Bolt Joints,” ASME J. Mech. Des., 115, pp. 701–705]. Recently, a new analytical model of bolted joints was presented [Zhang, O., and Poirier, J. A., 2004, “New Analytical Model for Axisymmetric Bolted Joints,” ASME J. Mech. Des., 126, pp. 721–728], based on which some discussions are further made in this note.

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