Load Recovery in Components Based on Dynamic Strain Measurements

2013 ◽  
Vol 135 (5) ◽  
Author(s):  
Anoop K. Dhingra ◽  
Timothy G. Hunter ◽  
Deepak K. Gupta
Keyword(s):  
Solution Procedure ◽  
Optimal Designs ◽  
Dynamic Strain ◽  
Normal Displacement ◽  
Linear Superposition ◽  
Strain Fields ◽  
Strain Measurements ◽  
Number Of Factors ◽  
Experimental Strain ◽  
Intrinsic Dynamic

This paper presents a modeling approach for estimating time varying loads acting on a component from experimental strain measurements. The strain response of an elastic vibrating system is written as a linear superposition of strain modes. Since the strain modes, as well as the normal displacement modes, are intrinsic dynamic characteristics of a component, the dynamic loads exciting a component are estimated by measuring induced strain fields. The accuracy of the estimated loads depends on a number of factors, such as the placement locations and orientations of the gauges on the instrumented structure, as well as the number of retained modes from strain modal analysis. A solution procedure based on the construction of D-optimal designs is implemented to determine the optimum locations and orientations of strain gauges such that the variance in load estimates is minimized. A numerical as well as an experimental validation of the proposed approach through two example problems is also presented.

Load Transducer Design Using Inverse Method With Model Reduction

2012 ◽  
Author(s):  
Deepak K. Gupta ◽  
Anoop K. Dhingra
Keyword(s):  
Model Reduction ◽  
Solution Procedure ◽  
Normal Displacement ◽  
Strain Gages ◽  
Linear Superposition ◽  
Inverse Approach ◽  
Load Transducer ◽  
Transducer Design ◽  
Model Reduction Technique ◽  
Intrinsic Dynamic

This paper presents an inverse approach for estimating time varying loads acting on a structure from experimental strain measurements using model reduction. The strain response of an elastic vibrating system is written as a linear superposition of strain modes. Since the strain modes as well as the normal displacement modes are intrinsic dynamic characteristics of a system, the dynamic loads exciting a structure are estimated by measuring induced strain fields. The accuracy of estimated loads is dependent on the placement of gages on the instrumented structure and the number of retained strain modes from strain modal analysis. A solution procedure based on construction of D-optimal design is implemented to determine the optimum locations and orientations of strain gages. An efficient approach is proposed which makes use of model reduction technique, resulting in significant improvement in the dynamic load estimation. Validation of the proposed approach through a numerical example problem is also presented.

scholarly journals Distributed Static and Dynamic Strain Measurements in Polymer Optical Fibers by Rayleigh Scattering

Sensors ◽  
2021 ◽  
Vol 21 (15) ◽  
pp. 5049
Author(s):  
Agnese Coscetta ◽  
Ester Catalano ◽  
Enis Cerri ◽  
Ricardo Oliveira ◽  
Lucia Bilro ◽  
...  
Keyword(s):  
Optical Fibers ◽  
Time Domain ◽  
Rayleigh Scattering ◽  
Cost Effective ◽  
Time Domain Reflectometry ◽  
Dynamic Strain ◽  
Strain Measurements ◽  
Graded Index ◽  
Optical Time ◽  
Polymer Optical Fibers

We demonstrate the use of a graded-index perfluorinated optical fiber (GI-POF) for distributed static and dynamic strain measurements based on Rayleigh scattering. The system is based on an amplitude-based phase-sensitive Optical Time-Domain Reflectometry (ϕ-OTDR) configuration, operated at the unconventional wavelength of 850 nm. Static strain measurements have been carried out at a spatial resolution of 4 m and for a strain up to 3.5% by exploiting the increase of the backscatter Rayleigh coefficient consequent to the application of a tensile strain, while vibration/acoustic measurements have been demonstrated for a sampling frequency up to 833 Hz by exploiting the vibration-induced changes in the backscatter Rayleigh intensity time-domain traces arising from coherent interference within the pulse. The reported tests demonstrate that polymer optical fibers can be used for cost-effective multiparameter sensing.

Measurement of Dynamic Strain

1943 ◽  
Vol 10 (2) ◽  
pp. A85-A92
Author(s):  
C. O. Dohrenwend ◽  
W. R. Mehaffey
Keyword(s):  
High Speed ◽  
Shock Loading ◽  
Low Frequency ◽  
Dynamic Strain ◽  
Time Axis ◽  
Low Frequencies ◽  
Strain Measurements ◽  
Moving Vehicles ◽  
Machine Parts ◽  
Dynamic Strains

Abstract The measurement of dynamic strains of both high and low frequency give rise to a variety of problems in instrumentation. Two types of equipment and circuits designed and used by the authors are discussed in detail. The first type based on the amplitude-modulated method is for low frequencies from zero to about 15 per cent of the carrier frequency of 1025 cycles per sec. The equipment has application to strain measurements varying from static values to those produced in moving vehicles, various machine parts, structures such as crane bridges, in fact all strain measurements where the frequency is 150 cycles per sec or less. The second type of equipment discussed is a potentiometer type and is for high-frequency strain measurements from 100 cycles per sec to 8000 cycles per sec. This high-speed equipment is conveniently used for impact strain, such as produced in hammer blows, shock loading, forging equipment, and impact-factor determination. Both units are designed to be used with a cathode-ray oscillograph which lends itself to a variety of recording methods. The methods discussed include both the type where the time axis is obtained by sweeping the oscilloscope beam on a stationary film and where the time axis is obtained mechanically.

Evaluating Shakedown for Structures Based on the Element Bearing-Ratio

2011 ◽  
Vol 137 ◽  
pp. 16-23 ◽  
Author(s):  
Wei Zhang ◽  
Lu Feng Yang ◽  
Chuan Xiong Fu ◽  
Jian Wang
Keyword(s):  
Yield Criterion ◽  
Solution Procedure ◽  
Superposition Method ◽  
Linear Superposition ◽  
Non Linear Programming ◽  
Elastic Plastic ◽  
Non Linear ◽  
Efficiency And Effectiveness ◽  
Linear Programming Formulation ◽  
Element Bearing

Based on Melan’s theorem, an improved numerical solution procedure for evaluating shakedown loads by non-linear superposition method is presented, and the relationship between the classical non-linear programming formulation of shakedown problem and the numerical method is disclosed. The stress term in classical optimization problem is replaced by the element bearing-ratio (EBR) in the procedure, and series of residual EBR fields can be generated by the D-value of the elastic-plastic EBR fields and the elastic EBR fields at every incremental loading step. The shakedown load is determined by performing the incremental non-linear static analysis when the yield criterion is arrived either by the elastic-plastic EBR fields or residual EBR fields. By introducing the EBR, the proposed procedure can be easily used to those complex structures with multi-material and complicated configuration. The procedure is described in detail and some numerical results, that show the efficiency and effectiveness of the proposed method, are reported and discussed.

scholarly journals An experimental study on the manufacture and characterization of in-plane fibre-waviness defects in composites

2018 ◽  
Vol 5 (5) ◽  
pp. 180082 ◽  
Author(s):  
W. J. R. Christian ◽  
F. A. DiazDelaO ◽  
K. Atherton ◽  
E. A. Patterson
Keyword(s):  
Residual Strain ◽  
Composite Structures ◽  
Computational Models ◽  
Image Correlation ◽  
Strain Fields ◽  
Strain Measurements ◽  
Ultrasound Measurements ◽  
Residual Strains ◽  
Failure Predictions

A new method has been developed for creating localized in-plane fibre waviness in composite coupons and used to create a large batch of specimens. This method could be used by manufacturers to experimentally explore the effect of fibre waviness on composite structures both directly and indirectly to develop and validate computational models. The specimens were assessed using ultrasound, digital image correlation and a novel inspection technique capable of measuring residual strain fields. To explore how the defect affects the performance of composite structures, the specimens were then loaded to failure. Predictions of remnant strength were made using a simple ultrasound damage metric and a new residual strain-based damage metric. The predictions made using residual strain measurements were found to be substantially more effective at characterizing ultimate strength than ultrasound measurements. This suggests that residual strains have a significant effect on the failure of laminates containing fibre waviness and that these strains could be incorporated into computational models to improve their ability to simulate the defect.

CPDWI-assisted BOTDA for fast dynamic strain measurements

2021 ◽  
Author(s):  
Yin Zhou ◽  
Lianshan Yan ◽  
Haijun He ◽  
Xinpu Zhang ◽  
Wei Pan ◽  
...  
Keyword(s):  
Dynamic Strain ◽  
Strain Measurements ◽  
Fast Dynamic
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