Extended Static Modeling and Analysis of Compliant Compound Parallelogram Mechanisms Considering the Initial Internal Axial Force*

2016 ◽  
Vol 8 (4) ◽  
Author(s):  
Guangbo Hao ◽  
Haiyang Li
Keyword(s):  
Axial Force ◽  
Thermal Effects ◽  
Analytical Modeling ◽  
Modeling And Analysis ◽  
Primary Motion ◽  
Axial Forces ◽  
Maximal Stress ◽  
Static Modeling ◽  
Motion Range ◽  
Nonlinear Analytical Model

Extended nonlinear analytical modeling and analysis of compound parallelogram mechanisms are conducted in this paper to consider the effect of the initial internal axial force. The nonlinear analytical model of a compound basic parallelogram mechanism (CBPM) is first derived incorporating the initial internal axial force. The stiffness equations of compound multibeam parallelogram mechanisms (CMPMs) are then followed. The analytical maximal stress under the primary actuation force only is also derived to determine the maximal primary motion (motion range). The influence of initial internal axial forces on the primary motion/stiffness is further quantitatively analyzed by considering different slenderness ratios, which can be employed to consider active displacement preloading control and/or thermal effects. The criterion that the primary stiffness may be considered “constant” is defined and the initial internal axial force driven by a temperature change is also formulated. A physical preloading system to control the initial internal axial force is presented and testing results of the object CBPM are compared with theoretical ones.

Extended Nonlinear Analysis of Exactly-Constrained Compliant Compound Parallelogram Mechanisms

2015 ◽  
Author(s):  
Guangbo Hao ◽  
Haiyang Li ◽  
George Joseph
Keyword(s):  
Nonlinear Analysis ◽  
Axial Force ◽  
Thermal Effects ◽  
Nonlinear Finite Element ◽  
Element Analysis ◽  
Motion Direction ◽  
Modal Frequency ◽  
Primary Motion ◽  
Axial Forces ◽  
Forced Excitation

Extended nonlinear analysis of compliant compound parallelogram mechanisms is conducted in this paper. The analytical nonlinear model of a compound basic parallelogram mechanism (CBPM) is first derived incorporating the initial internal axial force. The stiffness equations of compound multi-beam parallelogram mechanisms (CMPMs) are then followed. The effect of initial internal axial forces on the primary motion is further analyzed, which can be employed to consider active displacement preloading control and thermal effects etc. It is shown that negative initial internal axial force will reduce the primary stiffness, and vice versa. The criteria for which the primary stiffness may be considered “constant” is defined and the initial internal axial force driven by temperature change is also formulated. The dynamic analysis of a CMPM using nonlinear finite element analysis (FEA) is finally carried out to show the modal frequency and the forced excitation response in the primary motion direction.

Advances In The Modeling And Dynamic Simulation of Reeving Systems Using The Arbitrary Lagrangian-Eulerian Modal Method

2021 ◽  
Author(s):  
José L. Escalona ◽  
Narges Mohammadi
Keyword(s):  
Finite Elements ◽  
Axial Force ◽  
Axial Direction ◽  
Rotary Inertia ◽  
Arbitrary Lagrangian Eulerian ◽  
Original Formulation ◽  
Absolute Position ◽  
Axial Forces ◽  
Modal Coordinates ◽  
Modal Method

Abstract This paper presents new advances in the arbitrary Lagrangian-Eulerian modal method (ALEM) recently developed for the systematic simulation of the dynamics of general reeving systems. These advances are related to a more convenient model of the sheaves dynamics and the use of axial deformation modes to account for non-constant axial forces within the finite elements. Regarding the sheaves dynamics, the original formulation uses kinematic constraints to account for the torque transmission at the sheaves by neglecting the rotary inertia. One of the advances described in this paper is the use of the rotation angles of the sheaves as generalized coordinates together with the rope-to-sheave no-slip assumption as linear constraint equations. This modeling option guarantees the exact torque balance the sheave without including any non-linear kinematic constraint. Numerical results show the influence in the system dynamics of the sheave rotary inertia. Regarding the axial forces within the finite elements, the original formulation uses a combination of absolute position coordinates and transverse local modal coordinates to account for the rope absolute position and deformation shape. The axial force, which only depends on the absolute position coordinates, is constant along the element because linear shape functions are assumed to describe the axial displacements. For reeving systems with very long rope spans, as the elevators of high buildings, the constant axial force is inaccurate because the weight of the ropes becomes important and the axial force varies approximately linearly within the rope free span. To account for space-varying axial forces, this paper also introduces modal coordinates in the axial direction. Numerical results show that a set of three modal coordinates in the axial direction is enough to simulate linearly varying axial forces.

Measurement of axial forces during emptying from the human stomach

1992 ◽  
Vol 263 (2) ◽  
pp. G230-G239 ◽  
Author(s):  
M. J. Vassallo ◽  
M. Camilleri ◽  
C. M. Prather ◽  
R. B. Hanson ◽  
G. M. Thomforde
Keyword(s):  
Axial Force ◽  
Longitudinal Axis ◽  
Force Transducer ◽  
Human Stomach ◽  
In Vitro Studies ◽  
In Vivo Studies ◽  
Dependent Manner ◽  
Axial Forces

Our aim was to measure axial forces in the stomach and to evaluate their relation to circumferential contractions of the gastric walls and the emptying of gastric content. We used a combination of simultaneous radioscintigraphy, gastroduodenal manometry, and an axial force transducer with an inflatable 2-ml balloon fluoroscopically placed in the antrum. In vitro studies demonstrated that the axial force transducer records only antegrade forces along the longitudinal axis of this probe in an intensity-dependent manner. In vivo studies were performed in five healthy subjects for at least 3 h after ingestion of radiolabeled meals. When administered separately, the emptying of liquids or solids from the stomach is associated with generation of antral axial forces and coincident phasic pressure activity; however, almost 20% (average) of gastric axial forces during emptying of liquids or solids are unassociated with proximal or distal antral pressure activity ("isolated" forces). High amplitude antral axial forces and pressures occur during both lag and postlag emptying phases. During emptying of liquids, there is a trend for axial forces to be coincident more often with proximal than with distal antral pressure activity and vice versa for the emptying of solids (P = 0.015). These data suggest that when placed in the antrum, the transducer can semiquantitatively record axial forces during gastric emptying. By combining these observations with the data from in vitro studies, it appears that axial forces predominantly result from traction on the balloon by the longitudinal vector resulting from circumferential gastric contractions. The combination of radioscintigraphy and measurement of antral axial forces is a promising method to evaluate mechanical forces involved in the emptying of the human stomach.

Analytical Computational Models for Relationship between Ultimate Bending Moment of Concrete Segments and Axial Force

2020 ◽  
Vol 853 ◽  
pp. 177-181
Author(s):  
Zhi Yun Wang ◽  
Shou Ju Li
Keyword(s):  
Numerical Simulation ◽  
Computational Model ◽  
Axial Force ◽  
Computational Models ◽  
Plane Deformation ◽  
Bending Moment ◽  
Analytical Models ◽  
Bending Moments ◽  
Axial Forces ◽  
Practical Engineering

Concrete segments are widely used to support soil and water loadings in shield-excavated tunnels. Concrete segments burden simultaneously to the loadings of bending moments and axial forces. Based on plane deformation assumption of material mechanics, in which plane section before bending remains plane after bending, ultimate bending moment model is proposed to compute ultimate bearing capacity of concrete segments. Ultimate bending moments of concrete segments computed by analytical models agree well with numerical simulation results by FEM. The accuracy of proposed analytical computational model for ultimate bending moment of concrete segments is numerically verified. The analytical computational model and numerical simulation for a practical engineering case indicate that the ultimate bending moment of concrete segments increases with increase of axial force on concrete segment in the case of large eccentricity compressive state.

Evaluation of foundation tie requirements in seismic design

1993 ◽  
Vol 20 (1) ◽  
pp. 73-81
Author(s):  
A. C. Heidebrecht ◽  
A. Rutenberg
Keyword(s):  
Axial Force ◽  
Seismic Design ◽  
Structural Model ◽  
Travelling Waves ◽  
Travelling Wave ◽  
Shear Forces ◽  
Seismic Codes ◽  
Axial Forces ◽  
Pile Caps ◽  
Spread Footings

A simple structural model is proposed to evaluate the axial force acting on tie beams interconnecting spread footings or pile caps due to differential ground motion estimated on the basis of the travelling wave assumption. The approach is intended to supplement the "ten percent rule" or similar multipliers specified by seismic codes as design axial forces on tie beams. It is shown that the axial force demand is rather modest. However, shear forces between footing and soil may be quite large depending on maximum column displacements and superstructure rigidity. Key words: foundations, tie beams, earthquake, travelling waves, seismic codes.

Investigation of the axial thrust load using numerical and experimental techniques during turbocharger operation

2017 ◽  
Vol 232 (6) ◽  
pp. 755-765 ◽  
Author(s):  
In-Beom Lee ◽  
Seong-Ki Hong ◽  
Bok-Lok Choi
Keyword(s):  
Axial Force ◽  
Thermal Effects ◽  
High Speed ◽  
Operating Conditions ◽  
Axial Thrust ◽  
Turbine Wheel ◽  
Compressor Wheel ◽  
The Relationship ◽  
Thrust Load ◽  
Calibration Equations

Identification of the axial thrust load during the operating conditions of a turbocharger provides useful information to turbocharger designers. The axial force acting on the thrust bearing is mainly caused by the imbalance between the turbine wheel and the compressor wheel. It has a significant influence on the friction losses, which reduce the efficiency and the performance of a high-speed turbocharger. Well-known formulae for calculating the thrust load and the mechanical friction have been given in the literature. However, it is difficult to determine an accurate axial force by an analytical approach. This paper presents a detailed procedure for prediction of the axial thrust load during turbocharger operation. The first step is to identify the relationship between the externally applied load and the strain response using a specially designed test device and a numerical method. Next, if the operating strains and temperatures are measured, the strain signals due to the axial thrust can be adjusted by subtracting the thermal effects from the measured strains. Finally, the thrust loads in particular operating conditions are inversely obtained by inserting the adjusted strains into the calibration equations.

Study on Isolated Layer Mechanics Character of Combined Base Isolated Structure Based on Axial Forces Redistribute

2012 ◽  
Vol 166-169 ◽  
pp. 627-631 ◽  
Author(s):  
Fu You Zhang ◽  
Ming Gu ◽  
Yun Song ◽  
Song Xu
Keyword(s):  
Axial Force ◽  
Horizontal Displacement ◽  
Vertical Force ◽  
Isolation System ◽  
Isolation Layer ◽  
Calculating Method ◽  
Axial Forces ◽  
Rubber Bearings

Abstract：Combined isolation system is combined with rubber bearings which provide resilience forces and sliding isolated bearings which provide damp. According to the rule of axial forces redistributing between two kinds of bearings under earthquake, a calculating method considering the vertical force redistribute of isolation layer was given. With this method, the results of an example show that axial force will transfer from rubber bearings to sliding isolated bearings along with the horizontal displacement of isolation layer. The bigger the displacement is the more axial force transfers. So the axial-forces redistribution is a self-adjustable performance of the system, and also is an advantage for the system.

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