Criterion for Preventing Self-Loosening of Preloaded Cap Screws Under Transverse Cyclic Excitation

2011 ◽  
Vol 133 (4) ◽  
Author(s):  
Xianjie Yang ◽  
Sayed A. Nassar ◽  
Zhijun Wu
Keyword(s):  
Closed Form ◽  
Test Procedure ◽  
Closed Form Solution ◽  
Form Solution ◽  
The Self ◽  
Experimental Setup ◽  
Transverse Loading ◽  
System Parameters ◽  
Transverse Excitation ◽  
Key Variables

In this paper, a novel criterion is developed for preventing the self-loosening of preloaded threaded cap screws under cyclic transverse loading. For a known cyclic excitation, the system parameters are used in the formulation of a closed form solution for the minimum fastener preload required for preventing self-loosening. The effect of several key variables is investigated; this includes bearing and thread friction coefficients, cap screw grip length, thread pitch, material, and cyclic amplitude of the transverse excitation. An experimental setup and test procedure are established. Comparison between the experimental and analytical clamp load variation results shows that the proposed criterion can accurately predict the requirements for preventing self-loosening.

Formulation of a Criterion for Preventing Self-Loosening of Threaded Fasteners Due to Cyclic Transverse Loading

2010 ◽  
Author(s):  
Xianjie Yang ◽  
Sayed Nassar ◽  
Zhijun Wu
Keyword(s):  
Test Procedure ◽  
Closed Form Solution ◽  
Form Solution ◽  
The Self ◽  
Experimental Setup ◽  
Transverse Loading ◽  
System Parameters ◽  
Threaded Fasteners ◽  
Transverse Excitation ◽  
Key Variables

In the paper, a novel criterion is developed for preventing the self-loosening of preloaded threaded fasteners under cyclic transverse loading. For a known cyclic excitation, the system parameters are used in the formulation of a closed form solution for the minimum fastener preload required for preventing self-loosening. The effect of several key variables is investigated; this includes bearing and thread friction coefficients, bolt grip length, thread pitch, material, and the cyclic amplitude of the transverse excitation. An experimental setup and test procedure is established. Comparison between the experimental and analytical clamp load variation results shows that the proposed criterion can accurately predict the requirements for preventing self-loosening.

Experimental Analysis of the Transition Between Veering and Crossing on a Two-Beam System

2014 ◽  
Author(s):  
Oliviero Giannini ◽  
Aldo Sestieri
Keyword(s):  
Closed Form ◽  
Natural Frequency ◽  
Experimental Analysis ◽  
Scientific Literature ◽  
Closed Form Solution ◽  
Form Solution ◽  
Experimental Setup ◽  
Modal Interaction ◽  
Coupled Modes ◽  
Beam System

When there is a parameter varying in a system, so that one natural frequency approaches another one, the phenomenon of veering is generally found and highly coupled modes are the emerging characteristic of this dynamic behavior. It is far more difficult to find systems that instead of a veering present crossing between modes, and the crossing phenomenon is almost unreported in the scientific literature, unless the case of uncoupled modes is considered. In this paper, the two-modes interaction is presented. In particular, mode veering and mode crossing are introduced and investigated through a simple analytic 2-dof model that allows for closed-form solution. Then, an experimental setup, appropriately designed to study the two-modes veering and crossing is presented and experimental evidences of both phenomena are measured showing the main characteristics of such modal interaction..

On a Closed-Form Solution of Prandtl's System of Equations

2013 ◽  
Vol 40 (2) ◽  
pp. 106-114
Author(s):  
J. Venetis ◽  
Aimilios (Preferred name Emilios) Sideridis
Keyword(s):  
Closed Form ◽  
Closed Form Solution ◽  
Form Solution ◽  
System Of Equations

scholarly journals A Closed-Form Solution to Planar Feature-Based Registration of LiDAR Point Clouds

2021 ◽  
Vol 10 (7) ◽  
pp. 435
Author(s):  
Yongbo Wang ◽  
Nanshan Zheng ◽  
Zhengfu Bian
Keyword(s):  
Closed Form ◽  
Closed Form Solution ◽  
Simulated Data ◽  
Real Data ◽  
Point Clouds ◽  
Form Solution ◽  
Spatial Transformation ◽  
Dual Quaternions ◽  
Feature Based ◽  
Planar Feature

Since pairwise registration is a necessary step for the seamless fusion of point clouds from neighboring stations, a closed-form solution to planar feature-based registration of LiDAR (Light Detection and Ranging) point clouds is proposed in this paper. Based on the Plücker coordinate-based representation of linear features in three-dimensional space, a quad tuple-based representation of planar features is introduced, which makes it possible to directly determine the difference between any two planar features. Dual quaternions are employed to represent spatial transformation and operations between dual quaternions and the quad tuple-based representation of planar features are given, with which an error norm is constructed. Based on L2-norm-minimization, detailed derivations of the proposed solution are explained step by step. Two experiments were designed in which simulated data and real data were both used to verify the correctness and the feasibility of the proposed solution. With the simulated data, the calculated registration results were consistent with the pre-established parameters, which verifies the correctness of the presented solution. With the real data, the calculated registration results were consistent with the results calculated by iterative methods. Conclusions can be drawn from the two experiments: (1) The proposed solution does not require any initial estimates of the unknown parameters in advance, which assures the stability and robustness of the solution; (2) Using dual quaternions to represent spatial transformation greatly reduces the additional constraints in the estimation process.

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