On a Dynamical Saint Venant Principle

1960 ◽  
Vol 27 (1) ◽  
pp. 74-78 ◽  
Author(s):  
B. A. Boley

The dynamic behavior of a simple mechanical model composed of two Timoshenko beams connected by springs is studied. The accuracy of a quasi-static solution and of Saint Venant’s principle is studied for various rates of load application.

Author(s):  
Liang Xu ◽  
Liming Dai

A mechanical model of liquid sloshing is developed to investigate the longitudinal dynamic characteristics of partially filled liquid cargo tank vehicles during typical straight-line driving. The dynamic liquid motion is modeled by utilizing a mechanical system that describes the behavior of the liquid motion as a linear spring-mass model augmented with an impact subsystem for longitudinal oscillations. Computer simulation of tank vehicles under rough road conditions is performed by incorporating the forces and moments caused by liquid motion into the pitch plane vehicle model. The fifth wheel loads and the normal axle loads, which are key factors to vehicle structure design, fatigue analysis and vehicle performance characteristics, are computed using the mechanical system approach in order to investigate the influence of liquid motion. This study presents a new approach to investigate the longitudinal dynamic behavior of partially filled tank vehicles under large amplitude liquid sloshing.


Author(s):  
Christian Liebsch ◽  
Julia Zimmermann ◽  
Nicolas Graf ◽  
Christoph Schilling ◽  
Hans-Joachim Wilke ◽  
...  

2010 ◽  
Vol 139-141 ◽  
pp. 2322-2325 ◽  
Author(s):  
Xiao Huo Li ◽  
Yong Dong Sha ◽  
Ji Quan Yao ◽  
Chun Hua Liu

In order to research dynamic natures of a three knife-shape-tooth star-wheel loading mechanism, a mechanical model and a solid model of the star-wheel loading mechanism are established by means of updated-Lagrange and ANSYS software in the paper, equivalent stress clouds and displacement responding curves of the star-wheel at different excitation frequencies are obtained through harmonic response analyses. Model analysis shown that the star-wheel loading mechanism doesn’t take place resonance when the excitation frequency locates between 1.8 and 2.4 Hz, and the star-wheel works stability when the rotation speed is from 36 r/min to 48 r/min. These conclusions from study lay a theoretical foundation for improving the design of a three knife-shape-tooth star-wheel loading mechanism and make better its dynamic behavior.


2020 ◽  
Vol 8 (4) ◽  
pp. 232596712091456 ◽  
Author(s):  
Philipp W. Winkler ◽  
Guido Wierer ◽  
Robert Csapo ◽  
Caroline Hepperger ◽  
Bernhard Heinzle ◽  
...  

Background: Radial tears of the lateral meniscus frequently accompany acute anterior cruciate ligament (ACL) injuries and lead to increased joint stress and pathological meniscal extrusion (ME). The dynamic behavior of the lateral meniscus after radial tear repair with respect to ME has not been described. Purpose: To quantitatively assess dynamic lateral ME after all-inside radial tear repair. Study Design: Case series; Level of evidence, 4. Methods: Patients who underwent ACL reconstruction and all-inside radial tear repair of the lateral meniscus and had no history of contralateral knee injuries were included. Magnetic resonance imaging scans were acquired in loaded (50% of body weight) and unloaded conditions of both the injured and noninjured knees. A custom-made pneumatically driven knee brace was used for standardized knee positioning in 10° of flexion and with axial load application. Quantitative measures included the absolute lateral ME, meniscal body extrusion ratio, and Δ extrusion. Preoperative and postoperative unloaded extrusion data were compared by paired t tests. For postoperative data, the concomitant influence of the factors “leg” and “condition” were assessed through factorial analyses of variance. Results: A total of 10 patients with a mean follow-up of 47.9 months were enrolled. The intraclass correlation coefficient (ICC) confirmed good interrater reliability (ICC, 0.898) and excellent intrarater reliability (ICC, 0.976). In the unloaded injured leg, all-inside repair reduced ME from 3.15 ± 1.07 mm to 2.13 ± 0.61 mm (–32.4%; P = .033). Overall, load application led to a significant increase in ME (+0.34 mm [+21.8%]; P = .029). Significantly greater ME was observed in the injured knee (+1.10 mm [+93.2%]; P = .001) than in the noninjured knee. The condition × leg interaction was not significant ( P = .795), suggesting that the compression-associated increase in ME did not differ significantly between the injured and noninjured knees. Conclusion: Lateral ME depends on the knee status and loading condition. All-inside repair of radial meniscal tears led to a reduction of extrusion with no alteration in dynamic lateral ME. Meniscus-preserving therapy is recommended in the case of a radial lateral meniscal tear to preserve its dynamic behavior.


Buildings ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 50
Author(s):  
Vincenzo Bianco ◽  
Giorgio Monti ◽  
Nicola Pio Belfiore

The effectiveness of Double Concave Curved Surface Sliders (DCCSS), which initially spread under the name of Double Friction Pendulum (DFP) isolators, was already widely proven by numerous experimental campaigns carried out worldwide. However, many aspects concerning their dynamical behavior still need to be clarified and some details still require improvement and optimization. In particular, due to the boundary geometrical conditions, sliding along the coupled surfaces may not be compliant, where this adjective is adopted to indicate an even distribution of stresses and sliding contact. On the contrary, during an earthquake, the fulfillment of geometrical compatibility between the constitutive bodies naturally gives rise to a very peculiar dynamic behavior, composed of continuous alternation of sticking and slipping phases. Such behavior yields a temporary and cyclic change of topology. Since the constitutive elements can be modelled as rigid bodies, both approaches, namely Compliant Sliding and Stick-Slip, can be numerically modelled by means of techniques typically adopted for multi-body mechanical systems. With the objective of contributing to the understanding and further improvement of this technology, a topology-changing multi-body mechanical model was developed to simulate the DCCSS. In the present work, attention is focused on details regarding geometrical compatibility and kinematics, while the complete dynamics is presented in another work. In particular, for the sake of comparison, the kinematic equations are presented and applied not only for the proposed Stick-Slip approach, but also for the currently accepted Compliant Sliding approach. The main findings are presented and discussed.


Author(s):  
Aissam Beldjazia ◽  
Redouane Adman ◽  
Adel Slimani ◽  
Messaoud Saidani ◽  
Toufik Belaid ◽  
...  

The stability of structures is an important aspect that the designer must pay particular attention to in order to ensure safety against collapse. This investigation is concerned with analytical and numerical analyses of the dynamic buckling of plane structures. A rigorous mechanical model is proposed, consisting of a beam-column element with nodal ends possessing two rotational springs of rigidities acting in parallel with the bending stiffness of the beam-column. The model is first analyzed with respect to the dynamic behavior by investigating the influence of the variation in the stiffness of the nodal springs on the fundamental frequency of the proposed mechanical model. Compression axial loading is applied to the beam-column in order to study the nonlinear dynamic behavior by introducing buckling. This novel approach is used to highlight the interaction between the fundamental frequency and the critical buckling load. Simple examples are treated using the approach and the results are compared with those obtained from a global analysis. The results revealed that it is possible to reproduce the stability analysis of a global structure by simply analyzing a target element, taking into account all elements adjacent to it with less than 1% error on the results.


Author(s):  
Saurabh Kumar ◽  
Haraprasad Roy ◽  
Anirban Mitra

Large amplitude free vibration problem of axially functionally graded plates under the action of uniformly distributed load is analyzed using energy method. A variational approach has been applied for the generation of governing differential equations. A two part solution procedure has been adopted, where the static solution is sought in the first part and the dynamic problem is taken up subsequently as a standard Eigen-value problem. The governing differential equations for the static analysis are derived from the principle of minimum total potential energy whereas Hamilton’s principle is used for developing the governing equations for the dynamic analysis. Start functions for the analysis are chosen by satisfying the flexural and membrane boundary conditions and Gram-Schmidt orthogonalization procedure is used for developing the higher order functions. The dynamic behavior is presented as backbone curves in non-dimensional frequency amplitude plane. Mode shape plots for linear and non-linear frequencies are given to show the effect of vibration amplitude on dynamic behavior. The results are compared with the works of other researchers which confirms the accuracy of the present research work.


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