Experiments on clearance identification in cantilever beams reduced from artillery mechanism

2016 ◽  
Vol 231 (6) ◽  
pp. 1010-1032 ◽  
Author(s):  
Jie Liu ◽  
Bing Li ◽  
Wei Jin ◽  
Luofeng Han ◽  
Shuanglu Quan
Keyword(s):  
Cantilever Beam ◽  
Contact Stiffness ◽  
Influence Factors ◽  
Quantitative Relation ◽  
Test Bed ◽  
Nonlinear Identification ◽  
Dynamic Information ◽  
Restoring Force ◽  
Identification Process ◽  
Clearance Nonlinearity

Clearances existing in artillery mechanism cause the muzzle disturbance and reduce the artillery firing accuracy. If the parameters of the clearance nonlinearity can be identified by taking advantage of the dynamic information, the quantitative relation between the clearance and muzzle disturbance can be established, and then the clearances of such nonlinear system can be controlled in a reasonable range to improve the artillery firing accuracy. This paper proposed a nonlinear identification method for the cantilever beam with clearances reduced from barrel-cradle structure. A modified restoring force surface method is proposed to identify the clearance value of the cantilever beam in time domain, and then a modified nonlinear identification through feedback of outputs method, i.e., reduced-order nonlinear identification through feedback of the output method, is proposed to recognize the related contact stiffness in frequency domain. The feasibility of the combined identification process is verified by a cantilever beam with two clearances in simulation, and a test-bed with adjusted clearance and contact stiffness which is regardless of other nonlinear factors by adjusting the position of the clearance and excitation method was designed to verify the effectiveness of this method. In the end, some influence factors of this identification process are discussed in detail. The results show that the proposed methods can identify clearance-nonlinearity parameters with high precision.

Theoretical and Experimental Identification of Cantilever Beam With Clearances Using Statistical and Subspace-Based Methods

2015 ◽  
Vol 11 (3) ◽  
Author(s):  
Bing Li ◽  
Luofeng Han ◽  
Wei Jin ◽  
Shuanglu Quan
Keyword(s):  
Probability Density Function ◽  
Probability Density ◽  
Density Function ◽  
Cantilever Beam ◽  
Contact Stiffness ◽  
Continuous System ◽  
Engineering Structures ◽  
Identification Process ◽  
Displacement Response ◽  
Clearance Nonlinearity

Clearance turns up in a large number of engineering structures because of the errors during assembling, manufacturing, and wearing. The presence of clearance in engineering structures changes the normal dynamic response and will result in low precision and short lifetime. The clearance parameter identification of such nonlinear system is the prerequisite to control and eliminate the effect of clearance nonlinearity. In this paper, a derivative plot of probability density function (DPPDF) for displacement response is proposed to precisely identify the clearance value of continuous system, and the nonlinear subspace identification (NSI) method is modified to recognize the related contact stiffness based on the frequency response function (FRF) equations of continuous system. The DPPDF method is carried out by analyzing the distribution characteristic of displacement response, and the clearance value is derived through inspecting the probability density function (PDF) plot and the second derivative plot of the PDF. Based on the identified clearance, the clearance nonlinearity is regarded as external force, and the relationship between the dynamic responses and the external forces in frequency domain can be expressed as the form of FRF equations. Based on the FRF equations, the contact stiffness in continuous system is obtained with modified NSI method. This combined identification process is verified by a single-degree-of-freedom (SDOF) system and a cantilever beam system with clearances, and some influence factors of this identification process, including noise, transfer error, and force level, are discussed in detail. In the end, an experiment device with changeable clearance and contact stiffness was designed to conduct identification experiments, and the results show that the proposed methods perform effectively in identifying the clearance parameters.

Influence Factors Comparison and Analysis of Axial Contact Stiffness between Single-Nut and Double-Nut Ball Screws

2014 ◽  
Vol 889-890 ◽  
pp. 555-558 ◽  
Author(s):  
Xiang Rong Xu ◽  
Xian Chun Song ◽  
Hong Kui Jiang ◽  
Yan Feng Li
Keyword(s):  
Contact Angle ◽  
Contact Stiffness ◽  
Influence Factors ◽  
Helix Angle ◽  
Machining Process ◽  
Cnc Machine ◽  
Curvature Ratio ◽  
Ball Number ◽  
Comparison And Analysis ◽  
Theory Calculation

Axial contact stiffness increase of ball screws can reduce the vibration and enhance machining precision of CNC machine tool during machining process. On the basis of Hertz contact theory, calculation formula of axial contact stiffness was deduced with consideration of helix angle for 5010 single-nut and double-nut ball screws, influence factors comparison and analysis was carried out, and contrast curve was obtained. The result shows that the axial contact stiffness of preloaded double-nut ball screws is higher than that of single-nut ball screws. Ball number, contact angle and curvature ratio has obvious influence on the axial contact stiffness of double-nut ball screws: ball number increase can enhance the axial contact stiffness; increase of contact angle and curvature ratio can lower the axial contact stiffness. The axial contact stiffness of single-nut and double-nut ball screws does almost not vary with axial force and helix angle. The conclusion provides certain theoretical basis for design and selection of ball screws.

Nonlinear Analysis of a Self-Excited Cantilever Beam

2005 ◽  
Author(s):  
Hiroyuki Kaneko ◽  
Hiroshi Yabuno ◽  
Masaharu Kuroda
Keyword(s):  
Cantilever Beam ◽  
Positive Feedback ◽  
Response Amplitude ◽  
The Self ◽  
Steady State Response ◽  
Nonlinear Feedback ◽  
Van Der Pol ◽  
Restoring Force ◽  
State Response ◽  
Excited Oscillation

In this study, we investigate the dynamics of a self-excited cantilever beam by a positive feedback proportional to the velocity. In particular, we focus on the response amplitude in the self-excited oscillation and analyze the effect of the nonlinear component of the restoring force in the cantilever. It is theoretically and experimentally clarified that the response amplitude grows with time under the positive feedback proportional to the velocity (positive feedback). Furthermore, van der Pol type self-excited cantilever beam is designed by applying the nonlinear feedback proportional to the squared deflection and the velocity, and the steady state response is realized in the cantilever beam. The theoretically predicted effects of the nonlinear feedback are qualitatively confirmed by performing some experiments.

Design and Developement of a Microjet Engine Indoor Test Cell

2012 ◽  
Author(s):  
A. R. Alihosseini ◽  
M. Boroomand ◽  
A. M. Tousi ◽  
A. Horoufi
Keyword(s):  
Influence Factors ◽  
Engine Performance ◽  
Performance Testing ◽  
Test Cell ◽  
Test Bed ◽  
Successful Testing ◽  
Adverse Environmental Conditions ◽  
And Performance ◽  
The Right ◽  
Design And Construction

Following design and construction of a prototype of an engine such as a microjet engine, the engine is placed in a test cell, and is tested by special instruments until the desired engine performance is achieved. The aim is to determine all of the engine components’ performance parameters. Successful testing, acquiring the right data and subsequent processing and analysis can be useful and effective in design, optimization and maintenance of such engines. This paper describes the process of design and construction of microjet engine indoor test cell at Amirkabir University of Technology and performance testing of a microjet engine. This project has been conducted after testing the engine at outdoor test cell. The fact of bringing the engine in an enclosed test bed has effects on engine’s performance especially on the engine’s thrust. Therefore, the aerodynamic design of the test cell is conducted in a way to provide uniform airflow for the engine, have less proneness to test cell influence factors and reduces the adverse environmental conditions on engine’s performance during the process of testing. The phase of construction of the indoor test cell followed after designing phase is presented. On the other hand, the choice of instrumentation and the way it is arranged is discussed. Finally, the process of testing the engine and gathering data is described and results from the first tests conducted on the finished facility are presented.

Dynamics of Joints with Clearance for a Cantilever Beam Subjected to a Moving Mass

2012 ◽  
Vol 229-231 ◽  
pp. 652-655
Author(s):  
Guo Lai Yang ◽  
Wei Dong
Keyword(s):  
Experimental Data ◽  
Theoretical Analysis ◽  
Cantilever Beam ◽  
Experimental Test ◽  
Work Conditions ◽  
Moving Mass ◽  
Test Bed ◽  
Euler Beam ◽  
Mode Method ◽  
Numeric Calculation

This paper presents theoretical analysis, numeric calculation and experimental test for a cantilever beam subjected to a moving mass with clearance. Coupled transverse vibration equations of cantilever beam subjected to a moving rigid body with clearance were formulated by discretizing Euler beam based on assumption mode method. Numeric computation code was developed. A test bed for measuring joint clearance was constructed. Dynamic clearance tests were carried out under different work conditions. The accuracy of theoretical analysis was verified by comparison between experimental data and simulated results.

scholarly journals Nonlinear Model Updating in Structural Dynamics

2021 ◽  
Author(s):  
◽  
Javad Taghipour
Keyword(s):  
Mathematical Model ◽  
Cantilever Beam ◽  
Structural Dynamics ◽  
Harmonic Balance ◽  
Nonlinear Structures ◽  
Unknown Parameters ◽  
Restoring Force ◽  
Higher Harmonics ◽  
Harmonic Response ◽  
Nonlinear Structural

Identification of nonlinear structural dynamics has received a significant attention during last decades. Yet, there are many aspects of the identification methods of nonlinear structural models to be improved. The main objective of this study is to introduce novel identification approaches for nonlinear structures. The first step in identifying nonlinear structural elements is to detect their exact location. Hence, the first section of this study focuses on the localization of nonlinear elements in structural dynamics utilizing base excitation measured data. To this end, a localization approach is used to find the location of nonlinear electromagnetic restoring force applied to the tip of a cantilever beam.Inferring the exact location of nonlinear elements, identification methods are utilized to identify and characterize the mathematical model of nonlinear structures. However, various sources of noise and error may affect the accuracy of the identified model. Therefore, in the second part of the thesis, the effect of various sources of inaccuracy on the results of nonlinear model identification is investigated. It is shown that measurement noise, expansion error, modelling error, and neglecting the effect of higher harmonics may lead to an erroneously identified model.An optimization-based framework for the identification of nonlinear systems is proposed in this work in order to avoid the bottlenecks mentioned above. The introduced method is applied to a test rig composed of a base-excited cantilever beam subjected to an electromagnetic force at the tip. According to the nonlinear response of the system, four different functions are assumed as candidate models for the unknown nonlinear electromagnetic force. The measured response is compared with the reconstructed response using various models and the most appropriate mathematical model is selected.Utilizing optimization-based identification method to characterize complex mathematical models with large number of unknown parameters would be computationally expensive. Therefore, this study introduces a harmonic-balance-based parameter estimation method for the identification of nonlinear structures in the presence of multi-harmonic response and force. For this purpose, a method with two different approaches are introduced: Analytical Harmonic-Balance-based (AHB) approach and the Alternating Frequency/Time approach using Harmonic Balance (AFTHB). The method is applied to five simulated examples of nonlinear systems to highlight different features of the method. The method can be applied to all forms of both smooth and non-smooth nonlinear functions. The computational cost is relatively low since a dictionary of candidate basis functions is avoided. The results illustrate that neglecting higher harmonics, particularly in systems with multi-harmonic response and force, may lead to an inaccurate identified model. The AFTHB approach benefits from including significant harmonics of the response and force. Applying this method leads to accurate algebraic equations for each harmonic, including the effect of higher harmonics without truncated error. In the last part of this study, the AFTHB method is applied to two experimental case studies and identifies the nonlinear mathematical model of the structures. The first case is composed of a cantilever beam with a nonlinear electromagnetic restoring force applied to the tip which is excited by a multi-harmonic external force. In the second experimental case study, a configuration of linear springs applies a geometric nonlinear restoring force to the tip of a cantilever beam resulting in internal resonance in the dynamics of the system. The good performance of the AFTHB approach in estimating the unknown parameters of the structure is illustrated by the results of identification.

The Vibration Characteristic Analysis of Feed System of CNC Machine Tool

2013 ◽  
Vol 482 ◽  
pp. 169-173
Author(s):  
Qin Wu ◽  
Jian Jun Yang
Keyword(s):  
Machine Tool ◽  
Lagrange Equation ◽  
Contact Stiffness ◽  
Ball Screw ◽  
Cnc Machine Tool ◽  
Test Bed ◽  
Cnc Machine ◽  
Characteristic Analysis ◽  
Feed System ◽  
Vibration Displacement

The mathematical model of feed system of CNC machine tool was established base of Lagrange Equation and energy principle, then uses the Runge-Kutta method to solve the equation, and analyzes the influence that the parameters to the vibration displacement of ball screw. According to the result of orthogonal test, it is concluded that the most important three factors which influence ballscrew vibration displacement were the ball screw's lead h, the table quality m and the longitudinal contact stiffness kn in the connection of workbench and ballscrew. On the feed system test-bed, the longitudinal amplitude, torsional amplitude and horizontal amplitude of ball screw were measured, the results show the larger the ball screw's lead and the quality of workbench, the greater the amplitude of ball screw, the bigger the longitudinal contact stiffness kn, and the smaller the amplitude of screw.

Theoretical and Experimental Identification of Clearance Nonlinearities for a Continuum Structure

2016 ◽  
Vol 11 (4) ◽  
Author(s):  
Jie Liu ◽  
Bing Li
Keyword(s):  
Cantilever Beam ◽  
Piecewise Linear ◽  
Influence Factors ◽  
Piecewise Linear Function ◽  
Continuous Systems ◽  
Displacement Curve ◽  
Engineering Structures ◽  
Fitting Method ◽  
Nonlinear Force ◽  
Continuum Structure

Clearance is unavoidable in many engineering structures due to the manufacturing and installation errors. These clearances can cause intense impact and wear of the contacting pairs, which may change the dynamic response and eventually reduce the movement precision and the service life of the transmission system. Parameters identification of the clearance would provide better understanding of dynamic behaviors of the clearance and contribute significantly for the control of the induced disturbance and deviation. In this paper, based on dynamic characteristics of the clearance nonlinearity, the piecewise fitting method is first proposed to identify the clearance value of the continuum structure. During the proposed method, first, the rough scope of the clearance value extracted from the displacement response is divided into subintervals. And then, the nonlinear force is fitted by the piecewise linear function in the subintervals. Once the equivalent stiffness is obtained, the clearance value can be calculated by the sorting nonlinear force–displacement curve. The feasibility of the piecewise fitting method was verified by a cantilever beam system with clearances in simulation. Besides, some influence factors of this identification method, including the clearance value, exciting force level and measurement noise, are fully discussed to illustrate the robustness of this method. Moreover, an experiment system of a cantilever beam with adjustable clearances was designed to experimentally validate the effectiveness of the proposed method, and the results show that the piecewise fitting method can precisely identify the clearance value of continuous systems.

Design and Experimental Research of Urethra Valve of Bladder Power Pump

2011 ◽  
Vol 138-139 ◽  
pp. 279-284
Author(s):  
Chun Bao Liu ◽  
Xiao Li ◽  
Ting Guan
Keyword(s):  
Performance Analysis ◽  
Influence Factors ◽  
Mathematic Model ◽  
Flow Time ◽  
Structure Design ◽  
Air Gap ◽  
Urine Flow ◽  
Test Bed ◽  
Simulation And Experiment ◽  
Simulated Test

To optimize the structure of bladder power pump, a new urethra valve was designed. Based on the theories of electromagnetics and hydromechanics, the mathematic model of urethra valve was built, and the effects on the performance of urethra valve were analyzed, taking into account different influence factors such as electromagnet current, air gap and so on. The validity of the model was confirmed through the comparison between simulation and experiment. On the simulated test bed, the effects of urethra valve on the micturition performance of bladder power pump were studied. The results show that increasing the electromagnet current and decreasing the air gap between electromagnet and urethra valve are beneficial to increase the maximal urine flow rate and decrease the urine flow time. The research provides the basis for the performance analysis and optimal structure design of bladder power pump.

Material Tester Using a Controlled Oscillator and an Inertial Mass

2008 ◽  
Vol 381-382 ◽  
pp. 457-460 ◽  
Author(s):  
Seiji Hashimoto ◽  
Yusaku Fujii
Keyword(s):  
Efficient Method ◽  
Nonlinear Viscoelasticity ◽  
Inertial Mass ◽  
Open Loop ◽  
Restoring Force ◽  
Identification Process ◽  
Nonlinear Restoring Force ◽  
Arbitrary Waveform ◽  
Nonlinear Components ◽  
Oscillation Method

In this paper, a controlled oscillation using the levitation mass method (LMM) for material with nonlinear viscoelasticity is proposed. Since LMM is a very accurate and efficient method of measuring a varying force, it has a possibility to apply to the material tester. For LMM, system identification process is introduced to grasp the nonlinear components of the restoring force. The process consists of the experiment and frequency analysis for higher modes which originate for the nonlinear restoring force. The input signal is then derived based on the identification results. By adding the proposed identification process to LMM, the arbitrary waveform of the force can be investigated even in the open-loop excitation. The effectiveness of the proposed oscillation method is verified through the LMM-based experiments.

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