A Novel Compliant Bistable Mechanism Incorporating a Fixed-Guided Flexural Member

2020 ◽  
Author(s):  
James J. Joo ◽  
David H. Myszka
Keyword(s):  
Inflection Point ◽  
Operation Mode ◽  
Stable Configuration ◽  
Preliminary Design ◽  
Element Simulation ◽  
Simple Geometry ◽  
Flexural Member ◽  
Bistable Mechanism ◽  
Monolithic Structure ◽  
Displacement Measurements

Abstract This paper presents the design of a novel compliant bistable mechanism. Bistable mechanisms are commonly used in switches and other devices that operate in two distinct modes. This mechanism is a single monolithic structure with simple geometry and does not require external components or post-manufacture assembly. As such, the design is ideally suited for additive manufacturing at large, or micro, scales. The design features a fixed-guided flexural member with surrounding geometry. When a load is applied to the mechanism in a stable configuration, the flexural member exhibits an inflection point that enables bifurcated behavior. As a result, the mechanism snaps between two stable positions in an on-off operation mode. This paper describes the mechanism geometry and its operation. Preliminary design modeling equations are formulated. A finite element simulation is presented that verifies the design equations. Lastly, a prototype is presented to confirm the operation and facilitate force and displacement measurements.

A Moment-Shear Story Model for the Design of Steel Frames with Semi-Rigid Connections

2012 ◽  
Vol 256-259 ◽  
pp. 821-825
Author(s):  
Xi Bing Hu ◽  
Yu Wei Yang ◽  
Guo Jing He ◽  
Yun Lei Fan ◽  
Peng Zhou
Keyword(s):  
Inflection Point ◽  
Superposition Principle ◽  
Steel Frames ◽  
Small Deformation ◽  
Lateral Stiffness ◽  
Preliminary Design ◽  
Height Ratio ◽  
Story Model ◽  
Static Condensation ◽  
Rigid Connection

A moment-shear story model using the static condensation method is proposed for the steel frame with semi-rigid connections. Based on the superposition principle under small deformation, the story horizontal deflection can be divided into three parts, due to the action of story shears, the top story moment of column and the connection rotation of bottom story column, respectively. The formulas are derived for its lateral stiffness, horizontal deflection and height ratio of inflection point of column, taking into account the effect of semi-rigid connection. Numerical results indicate that this story model is reliable and can be used for preliminary design of this type of structures.

Mechanics Characteristics Study for Cable-Stayed-Suspension Bridges

2011 ◽  
Vol 243-249 ◽  
pp. 1817-1825
Author(s):  
Jing Qiu ◽  
Rui Li Shen ◽  
Huai Guang Li
Keyword(s):  
Finite Element ◽  
Suspension Bridge ◽  
Simulation Method ◽  
Suspension Bridges ◽  
Preliminary Design ◽  
Structural System ◽  
Long Span Bridges ◽  
Long Span ◽  
Element Simulation ◽  
Mechanics Characteristics

As a composite structure, the cable-stayed-suspension bridge is characterized by relatively new structure, great overall stiffness and long-span capacity, which has been proposed for the design of some extra long-span bridges. In order to research further into the mechanics characteristics of this type of structural system, the proposed preliminary design of a cable-stayed-suspension bridge with a main span of 1800m is analyzed by means of finite element simulation method. The advantages on overall stiffness in the cable-stayed-suspension bridge are summarized in comparison with the three-span suspension bridge and the single-span suspension bridge. Then, the reasons for the fatigue of the longest suspension cables in the cable-stayed-suspension bridge are also discussed in this paper.

A Novel Compliant Bistable Mechanism Incorporating a Fixed-Guided Flexural Member

2021 ◽  
Author(s):  
James Joo ◽  
Dave Myszka
Keyword(s):  
Flexural Member ◽  
Bistable Mechanism

The Alternation Story-Height Truss Lateral-Load-Resisting System and its Simplified Analytical Method

2012 ◽  
Vol 166-169 ◽  
pp. 543-547
Author(s):  
Yong Jun He ◽  
Xu Hong Zhou ◽  
Cheng Chao Yang
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Analytical Method ◽  
Inflection Point ◽  
Lateral Load ◽  
Horizontal Load ◽  
Preliminary Design ◽  
Numerical Example ◽  
New Type ◽  
Internal Forces

Based on the characteristics of 3D parking, a new type of 3D parking structure with alternation story-height truss lateral-load-resisting system is proposed in this paper. By adoption of the assumption of inflection point, a simplified analytical method for this system under horizontal load is studied and the formulas for internal forces of it are derived. The numerical example indicates that the error of the results calculated by the presented formulas does not exceed 5% in comparison with those by finite element method. Therefore, the method and its related formulas are feasible for preliminary design of the steel 3D parking structure since its accuracy and briefness.

scholarly journals Analysis of Deformation Characteristics of Foundation-Pit Excavation and Circular Wall

2020 ◽  
Vol 12 (8) ◽  
pp. 3164 ◽  
Author(s):  
Xuhe Gao ◽  
Wei-ping Tian ◽  
Zhipei Zhang
Keyword(s):  
Inflection Point ◽  
Three Dimensional ◽  
Foundation Pit ◽  
Safety Control ◽  
Verification Method ◽  
Element Simulation ◽  
Excavation Process ◽  
Deformation Law ◽  
Offset Curves ◽  
Wall Deformation

The surrounding ground settlement and displacement control of an underground diaphragm wall during the excavation of a foundation pit are the main challenges for engineering safety. These factors are also an obstacle to the controllable and sustainable development of foundation-pit projects. In this study, monitoring data were analyzed to identify the deformation law and other characteristics of the support structure. A three-dimensional numerical simulation of the foundation-pit excavation process was performed in Midas/GTS NX. To overcome the theoretical shortcomings of parameter selection for finite-element simulation, a key data self-verification method was used. Results showed that the settlement of the surface surrounding the circular underground continuous wall was mainly affected by the depth of the foundation-pit excavation. In addition, wall deformation for each working condition showed linearity with clear staged characteristics. In particular, the deformation curve had obvious inflection points, most of which were located deeper than 2/3 of the overall excavation depth. The characteristics of the cantilever pile were not obvious in Working Conditions 3–9, but the distribution of the wall body offset in a D-shaped curve was evident. Deviation between the monitoring value of the maximal wall offset and the simulated value was only 4.31 %. The appropriate physical and mechanical parameters for key data self-verification were proposed. The concept of the circular-wall offset inflection point is proposed to determine the distribution of inflection-point positions and offset curves. The method provides new opportunities for the safety control and sustainable research of foundation-pit excavations.

scholarly journals Snap-Through Buckling Mechanism for Frequency-up Conversion in Piezoelectric Energy Harvesting

2020 ◽  
Vol 10 (10) ◽  
pp. 3614
Author(s):  
Alessandro Speciale ◽  
Raffaele Ardito ◽  
Marco Baù ◽  
Marco Ferrari ◽  
Vittorio Ferrari ◽  
...  
Keyword(s):  
Cantilever Beam ◽  
Low Frequency ◽  
Maximum Energy ◽  
Storage Capacitor ◽  
Stable Configuration ◽  
Resistive Load ◽  
Piezoelectric Energy ◽  
Wide Range ◽  
Bistable Mechanism ◽  
Main Components

This paper describes a piezoelectric energy harvester employing a snap-through buckling (STB) mechanism for frequency-up conversion (FuC). The harvester consists of two main components: a bistable mechanical structure and one piezoelectric cantilever beam. The device is designed by means of analytical methods and numerical simulations. A proof-of-concept prototype is manufactured and tested under low frequency mechanical excitation. Experimental results show that, if the STB is induced, from the second stable configuration back to the undeformed one, the FuC is obtained and the response of the beam presents frequency components in a wide range, even though the resonant frequency of the cantilever beam is not excited. The results are hence in agreement with the expected behavior: if the device, forced in the second stable configuration, is subject to a low-frequency excitation whose amplitude exceeds a threshold, STB is triggered and the ensuing FuC provokes a widening of the beam vibrations frequency range and consequently a significant effectiveness in terms of power output. A maximum power of 4 mW is obtained by using an optimal resistive load as STB from a stable configuration of the bistable mechanism to the other one is triggered; a maximum energy of 4.5 μ J is obtained in case of a rectifier circuit with storage capacitor.

Design of a Simple Underactuated Mechanical Gripper

2014 ◽  
Vol 619 ◽  
pp. 44-48
Author(s):  
Mahasak Surakijboworn ◽  
Wittaya Wannasuphoprasit
Keyword(s):  
Distal Phalanx ◽  
Radius Ratio ◽  
Length Ratio ◽  
Stable Configuration ◽  
Link Length ◽  
Simple Geometry ◽  
Primitive Shape

The objective of this paper is to design and develop a simple geometry of an underactuated mechanical gripper which can provide most common hand grasps, fingertip grasp and enveloping grasp. The gripper consists of 2 2-DOF fingers underactuated by a pulley-tendon system, and a movable pulley for underactuation between fingers. Each finger has 2 links and 2 pulleys. A parallel linkage is used to translate distal phalanx toward an object such that fingertip grasp is improved. This work implements stability and force isotropy criteria to optimize the design. The prototype has 0.43 of pulley-radius ratio and 1.72 of link-length ratio. From primitive-shape grasping test, the gripper is able to achieve the stable configuration.

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