Effect of Dynamic Shear Force on Fastener Loosening in Assemblies

1997 ◽  
Author(s):  
Yubo Dong ◽  
Daniel P. Hess
Keyword(s):  
Cantilever Beam ◽  
Static Load ◽  
Nodal Line ◽  
Shear Stresses ◽  
Dynamic Shear ◽  
Bernoulli Beam ◽  
Cyclic Shear ◽  
Nodal Lines ◽  
Inertial Loading ◽  
Euler Bernoulli Beam

Abstract Placement and orientation of fasteners in assemblies is generally based on convenience or static load and strength considerations. Vibration and other dynamic loads can result in loosening of threaded product, particularly when cyclic shear stresses are present. This paper investigates the placement of a bolt and nut on a compound cantilever beam subjected to dynamic inertial loading. Calculations for an inertial loaded, cantilever, Euler-Bernoulli beam show that the dynamic shear stress is maximum near the dynamic nodal lines, and essentially vanishes near the anti-nodes. Experiments with a compound cantilever beam assembly with one fastener reveal that loosening occurs more readily when the bolt and nut are placed near a nodal line. Data presented include time to loosen, break-away torque, and acceleration level. The data shows that fastener integrity is maintained for longer periods of time and with lower tightening torques, when the bolt and nut are positioned away from nodal lines where shear stresses are lower, even though acceleration levels are higher.

scholarly journals Application of ADM Using Laplace Transform to Approximate Solutions of Nonlinear Deformation for Cantilever Beam

2016 ◽  
Vol 2016 ◽  
pp. 1-5
Author(s):  
Ratchata Theinchai ◽  
Siriwan Chankan ◽  
Weera Yukunthorn
Keyword(s):  
Laplace Transform ◽  
Cantilever Beam ◽  
Adomian Decomposition Method ◽  
Small Deformation ◽  
Approximate Solutions ◽  
Beam Equation ◽  
Bernoulli Beam ◽  
Initial Value ◽  
Adomian Decomposition ◽  
Euler Bernoulli Beam

We investigate semianalytical solutions of Euler-Bernoulli beam equation by using Laplace transform and Adomian decomposition method (LADM). The deformation of a uniform flexible cantilever beam is formulated to initial value problems. We separate the problems into 2 cases: integer order for small deformation and fractional order for large deformation. The numerical results show the approximated solutions of deflection curve, moment diagram, and shear diagram of the presented method.

Optimal plane beams modelling elastic linear objects

Robotica ◽  
2009 ◽  
Vol 28 (1) ◽  
pp. 135-148 ◽  
Author(s):  
Sung K. Koh ◽  
Guangjun Liu
Keyword(s):  
Motion Planning ◽  
Analytical Model ◽  
Cantilever Beam ◽  
Inverse Kinematics ◽  
Beam Theory ◽  
Analytical Models ◽  
Bernoulli Beam ◽  
Deterministic Models ◽  
Bernoulli Beam Theory ◽  
Euler Bernoulli Beam

SUMMARYThis paper discusses analytical and deterministic models for a plane curve with minimum deformation that may be utilized in planning the motion of elastic linear objects and investigating the inverse kinematics of a hyper-redundant robot. It usually requires intensive computation to determine the configuration of elastic linear objects. In addition, conventional optimization-based numerical techniques that identify the shape of elastic linear objects in equilibrium involve non-deterministic aspects. Several analytical models that produce the configuration of elastic linear objects in an efficient and deterministic manner are presented in this paper. To develop the analytical expressions for elastic linear objects, we consider a cantilever beam where the deflections are determined according to the Euler–Bernoulli beam theory. The deflections of the cantilever beam are determined for prescribed constraints imposed on the deflections at the free end to replicate various elastic linear objects. Deflections of a cantilever beam with roller supports are explored to replicate elastic linear objects in contact with rigid objects. We verify the analytical models by comparing them with exact beam deflections. The analytical model is precisely accurate for beams with small deflections as it is developed on the basis of the Euler–Bernoulli beam theory. Although it is applied to beams undergoing large deflections, it is still reasonably accurate and at least as precise as the conventional pseudo-rigid-body model. The computational demand involved in using the analytical models is negligible. Therefore, efficient motion planning for elastic linear objects can be realized when the proposed analytical models are combined with conventional motion planning algorithms. We also demonstrate that the analytical model solves the inverse kinematics problem in an efficient and robust manner through numerical simulations.

A New Test Method for the Determination of the Flexural Modulus of Spirally Wound Paper Tubes

1992 ◽  
Vol 114 (1) ◽  
pp. 84-89 ◽  
Author(s):  
L. C. Bank ◽  
E. Cofie ◽  
T. D. Gerhardt
Keyword(s):  
Static Load ◽  
Flexural Modulus ◽  
Testing Machine ◽  
Beam Theory ◽  
Test Method ◽  
Bernoulli Beam ◽  
Bending Modulus ◽  
Universal Testing ◽  
Point Bend ◽  
Euler Bernoulli Beam

A new static test method to determine the flexural modulus of spirally wound paper tubes is described. The experimental method is based on the standard three-point-bend procedure. The method requires testing the tube at multiple (two or more) span lengths. The testing can be performed on either a rigid frame fixture under constant static load or in a universal testing machine under monotonically increasing quasi-static load. The test data are analyzed with a modified form of a classical Euler-Bernoulli beam theory. The modified theory accounts for nonbending deflection components that are obtained with the three-point-bend test. The effect of time-dependent creep deflection on the modulus prediction is also discussed. Extensive testing of a variety of paper tubes was conducted to verify the proposed test method. The accuracy of the method was determined by comparison with dynamic bending modulus predictions obtained from modal tests on the tubes. The dynamic modulus predictions were based on Euler-Bernoulli beam theory. Results of tests performed on a specially designed static frame fixture and tests performed on a universal testing machine are compared. It is found that the bending modulus predictions using the new analysis method are considerably closer to the dynamic bending modulus than those predictions obtained by classical beam theory.

Dynamic Analysis of a Micro-Cantilever Subjected to Harmonic Base Excitation via RVIM

2013 ◽  
Vol 332 ◽  
pp. 545-550 ◽  
Author(s):  
Ali Reza Daneshmehr ◽  
Majid Akbarzadeh Khorshidi ◽  
Delara Soltani
Keyword(s):  
Dynamic Analysis ◽  
Cantilever Beam ◽  
Mathematical Formulation ◽  
Beam Theory ◽  
Variational Iteration Method ◽  
High Accuracy ◽  
Base Excitation ◽  
Bernoulli Beam ◽  
Micro Cantilever ◽  
Euler Bernoulli Beam

In this paper, dynamic analysis of a cantilever beam with micro-scale dimensions is presented. The micro-cantilever is subjected to harmonic base excitation and constant force at micro-cantilever tip. By Euler-Bernoulli beam theory assumptions, the mathematical formulation of vibrating micro-cantilever beam is derived using extended Hamilton principle. The governing partial-diffrential equation is solved by reconstruction of variational iteration method (RVIM), with possession of its boundary conditions. The RVIM is an approximate method of solving that answers easy and quick and has high accuracy.

scholarly journals An improved holographic nodal line semimetal

2021 ◽  
Vol 2021 (5) ◽  
Author(s):  
Yan Liu ◽  
Xin-Meng Wu
Keyword(s):  
Mass Term ◽  
Nodal Line ◽  
Duality Relation ◽  
Strongly Coupled ◽  
Nodal Lines ◽  
Form Field ◽  
Improved Model ◽  
Fermionic Spectrum ◽  
Chern Simons ◽  
Tensor Operators

Abstract We study an improved holographic model for the strongly coupled nodal line semimetal which satisfies the duality relation between the rank two tensor operators $$ \overline{\psi}{\gamma}^{\mu v}\psi $$ ψ ¯ γ μv ψ and $$ \overline{\psi}{\gamma}^{\mu v}{\gamma}^5\psi $$ ψ ¯ γ μv γ 5 ψ . We introduce a Chern-Simons term and a mass term in the bulk for a complex two form field which is dual to the above tensor operators and the duality relation is automatically satisfied from holography. We find that there exists a quantum phase transition from a topological nodal line semimetal phase to a trivial phase. In the topological phase, there exist multiple nodal lines in the fermionic spectrum which are topologically nontrivial. The bulk geometries are different from the previous model without the duality constraint, while the resulting properties are qualitatively similar to those in that model. This improved model provides a more natural ground to analyze transports or other properties of strongly coupled nodal line semimetals.

scholarly journals A Monotonic Smeared Truss Model to Predict the Envelope Shear Stress—Shear Strain Curve for Reinforced Concrete Panel Elements under Cyclic Shear

2021 ◽  
Vol 2 (1) ◽  
pp. 174-194
Author(s):  
Luís Bernardo ◽  
Saffana Sadieh
Keyword(s):  
Shear Stress ◽  
Reinforced Concrete ◽  
Shear Strain ◽  
Peak Load ◽  
Strain Curve ◽  
Fiber Reinforced Polymers ◽  
Shear Stresses ◽  
Cyclic Shear ◽  
Concrete Panels ◽  
Truss Model

In previous studies, a smeared truss model based on a refinement of the rotating-angle softened truss model (RA-STM) was proposed to predict the full response of structural concrete panel elements under in-plane monotonic loading. This model, called the “efficient RA-STM procedure”, was validated against the experimental results of reinforced and prestressed concrete panels, steel fiber concrete panels, and reinforced concrete panels externally strengthened with fiber-reinforced polymers. The model incorporates equilibrium and compatibility equations, as well as appropriate smeared constitutive laws of the materials. Besides, it incorporates an efficient algorithm for the calculation procedure to compute the solution points without using the classical trial-and-error technique, providing high numerical efficiency and stability. In this study, the efficient RA-STM procedure is adapted and checked against some experimental data related to reinforced concrete (RC) panels tested under in-plane cyclic shear until failure and found in the literature. Being a monotonic model, the predictions from the model are compared with the experimental envelopes of the hysteretic shear stress–shear strain loops. It is shown that the predictions for the shape (at least until the peak load is reached) and for key shear stresses (namely, cracking, yielding, and maximum shear stresses) of the envelope shear stress–shear strain curves are in reasonably good agreement with the experimental ones. From the obtained results, the efficient RA-STM procedure can be considered as a reliable model to predict some important features of the response of RC panels under cyclic shear, at least for a precheck analysis or predesign.

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