On the comprehensive static characteristic analysis of a translational bistable mechanism

2016 ◽  
Vol 230 (20) ◽  
pp. 3803-3817 ◽  
Author(s):  
Guangbo Hao ◽  
John Mullins
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Negative Stiffness ◽  
Beam Length ◽  
Rotational Stiffness ◽  
Characteristic Analysis ◽  
Element Analysis ◽  
Primary Motion ◽  
Bistable Mechanism ◽  
Inclined Angle

Bistable mechanisms have two stable positions and their characteristic analysis is much harder than the traditional spring system due to their postbuckling behaviour. As the strong nonlinearity induced by the postbuckling, it is difficult to establish a correct model to reveal the comprehensive nonlinear characteristics. This paper deals with the in-plane comprehensive static analysis of a translational bistable mechanism using nonlinear finite element analysis. The bistable mechanism consists of a pair of fixed-clamped inclined beams in symmetrical arrangement, which is a monolithic design and works within the elastic deformation domain. The displacement-controlled finite element analysis method using Strand7 is first discussed. Then the force–displacement relation of the bistable mechanism along the primary motion direction is described followed by the detailed primary translational analysis for different parameters. A simple analytical (empirical) equation for estimating the negative stiffness is obtained, and experimental testing is performed for a case study. It is concluded that (a) the negative stiffness magnitude has no influence from the inclined angle, but is proportional to the product of the Young’s modulus, beam depth, and cubic ratio for in-plane thickness to the beam length; (b) the unstable position is proportional to the product of the beam length and the Sine function of the inclined angle, and is not affected by the in-plane thickness and the material (or the out-of-plane thickness). The in-plane off-axis (translational and rotational) stiffness is further analysed to show the stiffness changes over the primary motion and the off-axis motion, and a negative rotational stiffness domain has been obtained.

Simplified modelling and development of a bi-directionally adjustable constant-force compliant gripper

2016 ◽  
Vol 231 (11) ◽  
pp. 2110-2123 ◽  
Author(s):  
Guangbo Hao ◽  
John Mullins ◽  
Kevin Cronin
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Negative Stiffness ◽  
Displacement Curve ◽  
Constant Force ◽  
Force Output ◽  
Element Analysis ◽  
Force Mechanism ◽  
Bistable Mechanism ◽  
Constant Force Mechanism

This paper proposes the design of a wholly mechanical constant-force gripper that can accommodate the imprecise manipulation of brittle/delicate objects by the actuation. This was achieved by designing a constant-force mechanism as the jaw that allowed a constant force to be applied to the grasping objects regardless of the displacement of the mechanism. The constant-force mechanism is attached to the end effector of the gripper via a parallelogram mechanism which ensures that the jaws remain in parallel. The constant-force mechanism combines the negative stiffness of a bistable mechanism and the positive stiffness of a linear spring to generate a constant force output. By preloading the positive stiffness mechanism, the magnitude of the constant force can be adjusted to be as low as zero. The constant-force mechanism has been fully modelled and simulated using finite element analysis. A normalised force-displacement curve has been developed that allows to obtain the simplified analytical negative stiffness of the bistable mechanism. The design formulation to find the optimal configuration that produces the most constant force has been developed. Illustrated experiments prove the concept of the design although the discrepancies between finite element analysis results and testing results exist due to bistable beam manufacturing error.

Finite Element Analysis and Optimization of Long-Span Gantry NC Machining Center Structure

2011 ◽  
Vol 346 ◽  
pp. 379-384
Author(s):  
Shu Bo Xu ◽  
Yang Xi ◽  
Cai Nian Jing ◽  
Ke Ke Sun
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Design Method ◽  
Dynamic Performance ◽  
Plate Thickness ◽  
Element Model ◽  
Wall Structure ◽  
Characteristic Analysis ◽  
Element Analysis ◽  
Dynamic Performance Analysis

The use of finite element theory and modal analysis theory, the structure of the machine static and dynamic performance analysis and prediction using optimal design method for optimization, the new machine to improve job performance, improve processing accuracy, shorten the development cycle and enhance the competitiveness of products is very important. Selected for three-dimensional CAD modeling software-UG NX4.0 and finite element analysis software-ANSYS to set up the structure of the beam finite element model, and then post on the overall structure of the static and dynamic characteristic analysis, on the basis of optimized static and dynamic performance is more superior double wall structure of the beam. And by changing the wall thickness and the thickness of the inner wall, as well as the reinforcement plate thickness overall sensitivity analysis shows that changes in these three parameters on the dynamic characteristics of post impact. Application of topology optimization methods, determine the optimal structure of the beam ultimately.

Bistable Compliant Four-Bar Mechanisms With a Single Torsional Spring

2006 ◽  
Author(s):  
Adarsh Mavanthoor ◽  
Ashok Midha
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Mechanism Design ◽  
Compliant Mechanisms ◽  
Compliant Mechanism ◽  
Stored Energy ◽  
Element Analysis ◽  
Bistable Behavior ◽  
Torsional Spring ◽  
Bistable Mechanism

Significant reduction in cost and time of bistable mechanism design can be achieved by understanding their bistable behavior. This paper presents bistable compliant mechanisms whose pseudo-rigid-body models (PRBM) are four-bar mechanisms with a torsional spring. Stable and unstable equilibrium positions are calculated for such four-bar mechanisms, defining their bistable behavior for all possible permutations of torsional spring locations. Finite Element Analysis (FEA) and simulation is used to illustrate the bistable behavior of a compliant mechanism with a straight compliant member, using stored energy plots. These results, along with the four-bar and the compliant mechanism information, can then be used to design a bistable compliant mechanism to meet specified requirements.

scholarly journals Stiffness prediction for bolted moment-connections in cold-formed steel trusses

2020 ◽  
Vol 41 (1) ◽  
Author(s):  
Apai Benchaphong ◽  
Rattanasak Hongthong ◽  
Sutera Benchanukrom ◽  
Nirut Konkong
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Analytical Method ◽  
Truss Structures ◽  
Rotational Stiffness ◽  
Element Analysis ◽  
Moment Connection ◽  
Rigid Connection ◽  
Cold Formed Steel ◽  
Steel Trusses

The purpose of this research was to study the behavior of cold-formed steel cantilever truss structures. A cantilever truss structure and bolt-moment connection were tested and verified by the 3D-finite element model. The verification results showed a good correlation between an experimental test and finite element analysis. An analytical method for elastic rotational stiffness of bolt-moment connection was proposed. The equation proposed in the analytical method was used to approximate the elastic rotational stiffness of the bolt group connection, and was also applied to the Richard-Abbott model for generating the nonlinear moment-rotation curve which modeled the semi-rigid connection stiffness. The 2D-finite element analysis was applied to study the behavior of the truss connection, caused by semi-rigid connection stiffness which caused a change of force to the truss elements. The results showed that the force in the structural members increased by between 13.62%-74.32% of the axial forces, and the bending moment decreased by between 33.05%-100%. These results strongly suggest that the semi-rigid connection between cold-formed steel cantilever truss structures should be considered in structural analysis to achieve optimum design, acknowledging this as the real behavior of the structure.

Dynamic Characteristic Analysis of the Horizontal Machine Center

2010 ◽  
Vol 97-101 ◽  
pp. 3671-3676
Author(s):  
Li Zhang ◽  
Liang Wei Zhong
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Response Analysis ◽  
Main Shaft ◽  
Characteristic Analysis ◽  
Element Analysis ◽  
Machine Center ◽  
Harmonic Response ◽  
Machining Force ◽  
Harmonic Response Analysis

Modal analysis of machine center was carried out by means of finite-element analysis (FEA) method to get its characteristics and to improve its machining precision. Based on this, harmonic response analysis was processed to evaluate its vibration when the cycle load caused by the machining force was applied on the main shaft of machine center, which was used to provide clues for avoiding resonance vibration and ameliorating design.

Finite Element Analysis of the Screen Box of the Combined Vibrating Screen Based on ANSYS

2011 ◽  
Vol 128-129 ◽  
pp. 1316-1320
Author(s):  
Nian Qin Guo ◽  
Wei Liu ◽  
Wei Ping Huang
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Static Load ◽  
Natural Frequencies ◽  
Element Model ◽  
Characteristic Analysis ◽  
Element Analysis ◽  
Vibrating Screen ◽  
Stress And Deformation ◽  
The Finite Element Model

The finite element model of the combined vibrating screen was established by using ANSYS. Modal characteristic analysis and static analysis on the whole unit of screen box were done, and natural frequencies and modal shapes in the top 15 orders were obtained, distribution regularities of stress and deformation of each part of the screen box under the static load were revealed, providing the necessary basis for the improvement design and research on screen box.

Buckling Analysis of Sway Steel Frames with Semi-Rigid Connections

2011 ◽  
Vol 250-253 ◽  
pp. 3876-3879
Author(s):  
Wan Zhen Wang ◽  
Ji Xiang Xu ◽  
Fei Yi Chen
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Steel Frames ◽  
Buckling Analysis ◽  
Nonlinear Finite Element ◽  
Effective Length ◽  
Finite Element Models ◽  
Rotational Stiffness ◽  
Element Analysis ◽  
Effective Length Factor

The modified factor formulas, which are applicable to sway steel frames, are derived by considering joint relative rotational stiffness and adopting the modified stiffness factor. The finite element models of steel frames with semi-rigid and rigid connections are established using ANSYS program. Nonlinear finite element analysis of steel frames with two web and top-seat angles steel semi-rigid connections is conducted. Through bulking analysis of sway steel frames with semi-rigid connections, the effective length factor of sway steel frames is derived, which considers nonlinear rotation of two web and top-seat angles steel semi-rigid connections.

The Effect of the Sheet Metal Postures on the Forming Thickness Based on the Finite Element Analysis

2021 ◽  
Vol 1018 ◽  
pp. 131-135
Author(s):  
Hu Zhu ◽  
Yang Wang ◽  
Dong Won Jung
Keyword(s):  
Numerical Simulation ◽  
Finite Element Analysis ◽  
Finite Element ◽  
Comparative Analysis ◽  
Sheet Metal ◽  
Element Analysis ◽  
Thickness Uniformity ◽  
The Finite Element Analysis ◽  
Formed Part ◽  
Inclined Angle

In order to analysis the effect of the sheet metal postures on the forming thickness, the horizontal sheet posture, the multidirectional sheet postures with the inclined angle of , and the multidirectional sheet postures obtained after optimization were respectively used for comparative analysis through the numerical simulation against the same model. The result shows that the optimized multidirectional sheet metal postures can reduce the overall thickness difference of the formed part and realize the thickness uniformity.

Vibration Characteristic Analysis of the Barrel

2014 ◽  
Vol 1014 ◽  
pp. 143-146
Author(s):  
Shuai Chen ◽  
Cun Gui Yu
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Element Model ◽  
Vibration Characteristic ◽  
Analysis Software ◽  
Characteristic Analysis ◽  
Modal Shape ◽  
Element Analysis ◽  
Vibration Modal ◽  
The Finite Element Model

This study is based on the graduation design for undergraduate course. In the paper, finite element analysis software ANSYS had been used to create the finite element model of a cannon barrel. On this basis, the vibration modal analysis of the barrel was conducted. Through the model analysis, the natural frequency and modal shape of the cannon barrel was obtained. The situations of stiffness strength and elasticity deformation about each part of the barrel were got by analysis of the modal shape. By this way, we can verify the rationality of the barrel design .Also it can provide improvements of the weak place of the structure for people to improve the stiffness and shooting precision of the gun, in order to make the dynamics characteristics of the gun more reasonable.

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