Optimization of a Bend-Twist-and-Sweep Compliant Mechanism

2014 ◽  
Author(s):  
Joseph Calogero ◽  
Mary Frecker ◽  
Aimy Wissa ◽  
James E. Hubbard
Keyword(s):  
Compliant Mechanism ◽  
Twist Angle ◽  
High Stress ◽  
Peak Stress ◽  
The Other ◽  
Optimal Designs ◽  
Von Mises Stress ◽  
Loading Conditions ◽  
Objective Functions ◽  
Von Mises

The overall goal of this research is to develop design optimization methodologies for compliant mechanisms that will provide passive shape change. Our previous work has focused on designing two separate contact-aided compliant elements (CCE): one for bend-and-sweep deflections, called the bend-and-sweep compliant element (BSCE), and another for twist deflection, called the twist compliant element (TCE). In the current paper, all three degrees of freedom, namely bending, twist, and sweep, are achieved simultaneously using a single passive contact-aided compliant mechanism. A new objective function for a contact-aided compliant mechanism is introduced and the results of the optimization procedure are presented. A bend-twist-and-sweep compliant element (BTSCE) can be inserted into the leading edge spar of an ornithopter, which is an avian-scale flapping wing un-manned air vehicle. The multiple objective functions of the optimization problem presented in this paper are: for upstroke, maximize tip bending and sweep deflections, maximize twist angle, and minimize the mass and peak von Mises stress in the BTSCE, and for downstroke, minimize tip bending and sweep deflections, minimize twist angle, and minimize the mass and peak von Mises stress in the BTSCE. This allows a designer to select a CCE from a set of optimal designs to accomplish all three displacement goals. The BTSCE was modeled using a commercial finite element program and optimized using NSGA-II, a genetic algorithm. The results for a single angled compliant joint (ACJ) for quasi-static upstroke loading conditions are presented. Two optimal designs are discussed and compared, one with a moderate peak stress and moderate deflections, the other with a high peak stress and large deflections. The optimization results are then compared to the previous results for the two independent CCEs. A design study showed that the angle of the ACJ needs to be obtuse to achieve a positive twist angle during upstroke, and an acute contact angle reduces peak stress. The deflection objective functions were relatively insensitive to eccentricity for upstroke and downstroke compared to the other parameters, and a high stress penalty was paid for any gains in deflection. The downstroke objective functions were relatively insensitive to all parameters compared to the upstroke objective functions, and were much smaller in magnitude. The optimization showed that under simplified upstroke loading conditions, the BTSCE with a single ACJ allowed bending deflection near 30% of the length of the BTSCE, twist angle near 0.14 radians, and sweep deflection near 5% of the length of the BTSCE.

Design Optimization of a Twist Compliant Mechanism With Nonlinear Stiffness

2013 ◽  
Author(s):  
Yashwanth Tummala ◽  
Mary Frecker ◽  
Aimy Wissa ◽  
James E. Hubbard
Keyword(s):  
Optimization Problem ◽  
Inner Core ◽  
Compliant Mechanism ◽  
Twist Angle ◽  
Von Mises Stress ◽  
Nonlinear Stiffness ◽  
Objective Functions ◽  
Multi Objective Optimization ◽  
Multi Objective ◽  
Specific Loading

A contact aided compliant mechanism called twist compliant mechanism is presented in this paper. This mechanism has nonlinear stiffness when it is twisted in both directions along its axis. The inner core of the mechanism is responsible for its flexibility in one twisting direction. The contact surfaces of the cross-members and compliant sectors are responsible for its high stiffness in the opposite direction. A twist compliant mechanism with desired twist angle and stiffness can be designed by choosing the right thickness of its cross-members, thickness of the core and thickness of its sectors. A multi-objective optimization problem with three objective functions is proposed in this paper, and used to design an optimal twist compliant mechanism with desired deflection. The objective functions are to minimize the mass and maximum von Mises stress observed, while minimizing or maximizing the twist angles under specific loading conditions. The multi-objective optimization problem proposed in this paper is solved using an ornithopter flight research platform as a case study, with the goal of using the twist compliant mechanism to achieve passive twisting of the wing during upstroke, while keeping the wing fully extended and rigid during the downstroke. Prototype twist compliant mechanisms have been fabricated using a waterjet cutter and will be tested as part of future work.

The Influence of Loading Position in A Priori High Stress Detection using Mode Superposition

2020 ◽  
Vol 1 (1) ◽  
pp. 93-102
Author(s):  
Carsten Strzalka ◽  
◽  
Manfred Zehn ◽  
Keyword(s):  
Finite Element ◽  
Degrees Of Freedom ◽  
Equations Of Motion ◽  
A Priori ◽  
High Stress ◽  
Von Mises Stress ◽  
Detailed Knowledge ◽  
Variable Loading ◽  
Numerical Effort ◽  
Von Mises

For the analysis of structural components, the finite element method (FEM) has become the most widely applied tool for numerical stress- and subsequent durability analyses. In industrial application advanced FE-models result in high numbers of degrees of freedom, making dynamic analyses time-consuming and expensive. As detailed finite element models are necessary for accurate stress results, the resulting data and connected numerical effort from dynamic stress analysis can be high. For the reduction of that effort, sophisticated methods have been developed to limit numerical calculations and processing of data to only small fractions of the global model. Therefore, detailed knowledge of the position of a component’s highly stressed areas is of great advantage for any present or subsequent analysis steps. In this paper an efficient method for the a priori detection of highly stressed areas of force-excited components is presented, based on modal stress superposition. As the component’s dynamic response and corresponding stress is always a function of its excitation, special attention is paid to the influence of the loading position. Based on the frequency domain solution of the modally decoupled equations of motion, a coefficient for a priori weighted superposition of modal von Mises stress fields is developed and validated on a simply supported cantilever beam structure with variable loading positions. The proposed approach is then applied to a simplified industrial model of a twist beam rear axle.

scholarly journals Análisis experimental y teórico del ensayo de adherencia capa – sustrato en un acero DIN UC1 tratado termoquímicamente por borurización

2020 ◽  
pp. 7-14
Author(s):  
J. Merced MARTÍNEZ-VÁZQUEZ ◽  
Arnulfo PÉREZ-PÉREZ ◽  
Gabriel RODRÍGUEZ-ORTIZ ◽  
Esperanza BAÑOS-LÓPEZ
Keyword(s):  
Surface Morphology ◽  
Layer Thickness ◽  
Industrial Application ◽  
Thermochemical Treatment ◽  
Boride Layer ◽  
The Other ◽  
Von Mises Stress ◽  
Adherence Test ◽  
The Times ◽  
Von Mises

In this work, the effect of the boronizing thermochemical treatment on the adherence and surface morphology of the boride layer formed in DIN UC1 steel was evaluated. The process was carried out by packing at the temperature of 1273 K, at the times of 4800, 6000, 7200 and 14400 seconds. The HRC adherence test based on the VDI 1398 standard, was simulated in COMSOL 5.0®; analysing the effect of the thickness of the boride layer and the roughness on the Von Mises stress, in addition to the stress on the indentation footprint; in which it was observed that by increasing the thickness of the layer from 22.2 to 37.8 µm the stresses increased, and therefore the adhesion of the layer on the substrate improved, which causes only the formation of microcracks. On the other hand, in the greater layer thickness (60.04 µm) the layer delaminates. Therefore, for an industrial application of DIN UC1 steel treated thermochemically by borurization, layer thicknesses up to 37.8 µm are recommended.

Stress Distribution Around Two Dental Implant Materials with New Designs: Comparative Finite Element Analysis Study

2021 ◽  
Vol 4 (1) ◽  
pp. 19
Author(s):  
Faaiz Alhamdani ◽  
Khawla H. Rasheed ◽  
Amjed Mahdi
Keyword(s):  
Stress Distribution ◽  
Dental Implant ◽  
Cancellous Bone ◽  
Stress Level ◽  
The Other ◽  
Von Mises Stress ◽  
Uniform Stress ◽  
Element Analysis ◽  
Other Hand ◽  
Von Mises

Background: The introduction of modified thread designs is one of the research areas of interest in the dental implantology field. Two suggested Buttress and Reverse Buttress thread designs in TiG5 and TiG4 models are tested against a standard TiG5 Fin Thread design (IBS®). Purpose: The study aims to compare stress distribution around the suggested designs and Fin Thread design. Methods: Three dental implant models: Fin Thread design, and newly suggested Buttress and Reverse Buttress designs of both TiG5 and TiG4 models were tested using FEA for stress distribution using static (70N, 0°) and (400N, 30°) occlusal loads. Results: The main difference between the suggested Buttress design and Fin Thread design lies in the overload (400N, 30°) condition. Maximum Von Mises stress is less in Buttress design than Fin Thread design. On the other hand the level of Von Mises stress over the buccolingual slop of the cancellous bone in Fin Thread design liess within the lowest stress level. The suggested Reverse Buttress design, on the other hand showed almost uniform stress distribution in both TiG4 and TiG4 models with maximum Von Mises stress higher than the elastic modulus of cancellous bone in overload (400N, 30°) condition. Conclusion: The suggested TiG4 Buttress design might have a minor advantage of stress level in cases of stress overload. In contrast, Fin Thread design shows minimal stress over the buccolingual slop of the cancellous bone. The suggested Reverse Buttress design might be more suitable for the D1 bone quality region with the advantage of almost uniform stress distribution

Establishing a framework for archosaur cranial mechanics

Paleobiology ◽  
2008 ◽  
Vol 34 (4) ◽  
pp. 494-515 ◽  
Author(s):  
Emily J. Rayfield ◽  
Angela C. Milner
Keyword(s):  
Complex Geometry ◽  
Pairwise Comparison ◽  
Peak Stress ◽  
Von Mises Stress ◽  
Basic Principles ◽  
Theropod Dinosaurs ◽  
Secondary Palate ◽  
Von Mises ◽  
Mechanical Optimization ◽  
Hydrodynamic Factors

The aim of this analysis was to establish the basic mechanical principles of simple archosaur cranial form. In particular we estimated the influence of two key archosaur innovations, the secondary palate and the antorbital fenestra, on the optimal resistance of biting-induced loads. Although such simplified models cannot substitute for more complex cranial geometries, they can act as a clearly derived benchmark that can serve as a reference point for future studies incorporating more complex geometry. We created finite element (FE) models comprising either a tall, domed (oreinirostral) snout or a broad, flat (platyrostral) archosaur snout. Peak von Mises stress was recorded in models with and without a secondary palate and/or antorbital fenestra after the application of bite loads to the tooth row. We examined bilateral bending and unilateral torsion-inducing bites for a series of bite positions along the jaw, and conducted a sensitivity analysis of material properties. Pairwise comparison between different FE morphotypes revealed that oreinirostral models are stronger than their platyrostral counterparts. Oreinirostral models are also stronger in bending than in torsion, whereas platyrostral models are equally susceptible to either load type. As expected, we found that models with a fenestra always have greatest peak stresses and by inference are “weaker,” significantly so in oreinirostral forms and anterior biting platyrostral forms. Surprisingly, although adding a palate always lowers peak stress, this is rarely by large magnitudes and is not significant in bilateral bending bites. The palate is more important in unilateral torsion-inducing biting. Two basic principles of archosaur cranial construction can be derived from these simple models: (1) forms with a fenestra are suboptimally constructed with respect to biting, and (2) the presence or absence of a palate is significant to cranial integrity in unilaterally biting animals. Extrapolating these results to archosaur cranial evolution, it appears that if mechanical optimization were the only criterion on which skull form is based, then most archosaurs could in theory strengthen their skulls to increase resistance to biting forces. These strengthened morphotypes are generally not observed in the fossil record, however, and therefore archosaurs appear subject to various non-mechanical morphological constraints. Carnivorous theropod dinosaurs, for example, may retain large suboptimal fenestra despite generating large bite forces, owing to an interplay between craniofacial ossification and pneumatization. Furthermore, living crocodylians appear to strengthen their skull with a palate and filled fenestral opening in the most efficient way possible, despite being constrained perhaps by hydrodynamic factors to the weaker platyrostral morphotype. The future challenge is to ascertain whether these simple predictions are maintained when the biomechanics of complex cranial geometries are explored in more detail.

scholarly journals Stress and Factor of Safety for Connecting Rod using Ansys

2019 ◽  
Vol 8 (6) ◽  
pp. 3463-3466
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Factor Of Safety ◽  
Stress Test ◽  
Von Mises Stress ◽  
Loading Conditions ◽  
Connecting Rod ◽  
Element Analysis ◽  
Ic Engine ◽  
Von Mises

The primary link of an IC engine is a connecting rod. Its position is in-between the crankshaft and the piston whose key function is to convert the piston motion which is reciprocating in nature into rotary motion of the crank by transmitting the piston thrust to the crankshaft. This has entailed performing a detailed load analysis. In this paper, connecting rod's finite element analysis was done using Finite Element techniques. So firstly by using the schematic diagram the solid model of the connecting rod was created using Solid works software. Then using the Ansys R17.1 software the meshing was done and then the Finite element analysis is done to find the Equivalent (Von-Mises) stresses and the Factor of Safety under the loading conditions. Structural Steel is the material which is used for connecting rod and the loading conditions are assumed to be static. In Equivalent (Von-Mises) stress test maximum stress is found to be 1.504x108 Pa and the minimum factor of safety is 1.20765 for the connecting rod

Stress Concentration Regions in Ceramic Ball Heads for Total Hip Replacement Considering Trauma-Like Loading

2005 ◽  
Vol 486-487 ◽  
pp. 185-188 ◽  
Author(s):  
Ho Sung Aum ◽  
M.C. Curiel ◽  
Daniel G. Carillo
Keyword(s):  
Stress Concentration ◽  
Hip Replacement ◽  
Stress Condition ◽  
Impact Load ◽  
Peak Load ◽  
High Stress ◽  
Friction Stress ◽  
Von Mises Stress ◽  
Critical Areas ◽  
Von Mises

A high stress condition in the hip system may cause fracture of the ball head. This failure may appear after a heavy accident such as sudden fall. The aim of this investigation is to make a computer simulated model of the hip system to evaluate the regions of stress concentration as well as the pressure in the stem-ball junction. 3D Non-Linear Finite Element Analyses were performed taking into consideration a high peak load to simulate trauma conditions. Ball heads from 22 to 36 mm in diameter were modeled, and also two sizes for taper lock were simulated to report their influence on the stresses over the critical areas of the ball head. Two different materials of common ball head ceramics (Alumina and Zirconia) were considered to evaluate its relation to the stresses produced. It was found that the ball head cone’s depth has major incidence in the stress concentration surrounding the stem when an impact load is applied, and that a deeper cone may offer a more relieved loading configuration when considering stress related parameters such as Von Mises stress, contact pressure and friction stress.

scholarly journals An Investigation into Scalpel Blade Sharpness Using Cutting Experiments and Finite Element Analysis

2005 ◽  
Vol 293-294 ◽  
pp. 769-776 ◽  
Author(s):  
C.T. McCarthy ◽  
M. Hussey ◽  
Michael D. Gilchrist
Keyword(s):  
Finite Element ◽  
Substrate Surface ◽  
Peak Stress ◽  
Element Model ◽  
Von Mises Stress ◽  
Element Analysis ◽  
Sharpness Measurement ◽  
Blade Tip ◽  
Scalpel Blade ◽  
Von Mises

This paper presents an investigation into the sharpness of a surgical scalpel blade. An experiment was carried out in which a surgical scalpel blade was pushed through an elastomeric substrate at a constant velocity. The force-displacement characteristics were examined by plotting the stiffness as a function of blade displacement and it was found that this curve could clearly identify the point where the material separates to form a cut. A blade sharpness measurement was defined as the energy required to initiate an opening or cut in the substrate. A finite element model was developed to examine the stress state in the substrate at the point where the opening initiates. The development of this model is described. The model was validated against the experiment and close agreement was obtained. The von-Mises stress distribution under the blade tip was plotted and it was shown that the peak stress actually occurs away from the blade tip, suggesting that material separation would initiate away from the substrate surface.

Comparison of Torque Transmitting Shaft Connectivity Using a Trilobe Polygon Connection and an Involute Spline

2000 ◽  
Vol 122 (1) ◽  
pp. 130-135 ◽  
Author(s):  
Zella L. Kahn-Jetter ◽  
Eugene Hundertmark ◽  
Suzanne Wright
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
The Other ◽  
Von Mises Stress ◽  
Stress Concentrations ◽  
Element Analysis ◽  
Principal Compressive Stress ◽  
Torque Transmission ◽  
Von Mises ◽  
Involute Spline

The results of a finite element analysis of a trilobe polygon shaft connection used as an alternative for a spline for torque transmission is presented. These results are compared to the results of a finite element analysis previously performed on an involute spline. It is shown that the tensile stress in the polygon shaft is significantly smaller than in the involute spline and is smaller than all the other stresses in both the shaft and the hub in the polygon connection. Furthermore, the magnitudes and distributions of the maximum principal compressive stress, the shear stress, and the Von Mises stress are nearly the same on the shaft and the hub. It appears that polygonal connections can be more advantageous than splined connections because of lower stresses and the lack of stress concentrations typical of splines. [S1050-0472(00)00601-2]

Optimization of a Steam Turbine Blade’s Double-T Root Through Contact Surface Convexity

2016 ◽  
Author(s):  
Johanna Ehlers ◽  
Henning Ressing ◽  
Wulf-Christof von Karstedt ◽  
Daniel Rixen ◽  
Mohamed S. Gadala
Keyword(s):  
Steam Turbine ◽  
Turbine Blade ◽  
Contact Surface ◽  
Three Dimensional ◽  
Peak Stress ◽  
Element Model ◽  
Von Mises Stress ◽  
3D Fem ◽  
Fem Model ◽  
Von Mises

The turbine blade is one of the most critical components of a steam turbine. The high thermal loads and large centrifugal forces cause extreme stresses on the blade, especially on its root. This paper focuses on improving the double-T root of a turbine blade of the control stage by decreasing the root’s peak equivalent von-Mises stress. An 18% reduction was achieved in the peak stress by changing the convexity of the contact surface between the root and the groove. The equivalent von-Mises stress was determined in a static structural analysis of a three dimensional finite element model (3D FEM-model) using ANSYS Workbench. This numerical model was developed to include one blade and the associated part of the shaft, whereas the complete circle of blades was considered by applying cyclic symmetry. Furthermore, this paper includes a modal analysis comparing the natural frequencies of the initial FEM-model with the frequencies of the optimized one. The results were established by an investigation of the influence of the FEM-model’s parameters, its material properties, thermal effects, and an additional damping wire in the shroud.

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