• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.05a
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• pp.270-273
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• 2003

The strain measurement of the panel in the sheet metal forming is essential work which provides experimental data needed to die design, process design, and product inspection. To measure efficiently the complex geometry strain, the 3-dimensional automative strain measurement system, which has high accuracy in theory, but has some 3∼5% errors in practice, is often used. The object of this study is to develop the error compensation technology to eliminate the strain, errors resulted when formed panels are measured using an automated strain measurement system. To achieve the study object, the position error calibration method correcting coordinates of the grid node recognized by a camera using error functions is suggested. Then the position errors were found by calculating the difference in the position of the cube node between real coordinates and measured coordinates in toms of node coordinates and the error calibration equations were derived by regressing the position errors. In order to show the validation of the suggested position error calibration method, finite element analysis and current calibration method was performed for the initial-blankformed.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.30 no.5 s.248
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• pp.560-567
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• 2006

The exact load measurements for the mechanical parts of a wind turbine are important step both fur the evaluation of a specific wind turbine design and for a certification process. A common method for a mechanical load measurement is using a strain gauge sensing. Two main problems ought to be answered in order for this method to be applied to the wind turbine project. These are strain gauge calibration and non-contact signal transmission from the strain gauge output to a load monitoring system. This paper suggests reliable solutions fer these two problems. A Bluetooth, a short range wireless data communication technology, is used to solve the second problem. The first one, the strain gauge calibration methodology for a load measurement in a wind turbine application, is fully explained in this paper. Various mechanical loadings for a strain gauge calibration in a wind turbine load measurement are introduced and analyzed. Initial experimental results which are obtained from a 1 kW small size wind turbine are analyzed, and the uncertainty problem in estimating mechanical loads using a calibration matrix is fully covered in this paper.

• Transactions of Materials Processing
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• v.13 no.7
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• pp.594-599
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• 2004

In the sheet metal forming operations, the strain measurement of sheet panel is an essential work which provides the formability information needed in die design, process design, and product inspection. To measure efficiently complex geometry strains, the 3-dimensional automative strain measurement system, which theoretically has a high accuracy but practically has about 3～5％ strain error, is often used. For eliminating the strain error resulted in measuring the strains of formed panels using an automated strain measurement system, the position error calibration method is suggested, which computes accurate strains using the grids with accurate nodal coordinates. The accurate nodal coordinates are calculated by adding the nodal coordinates measured by the measurement system and the position error found using the multiple regression method as a function of the main error parameters obtained from the analysis of strain error in a standard cube. For the verification, the strain distributions of square and dome cups obtained from the position error calibration method are compared with those provided by the finite element analysis and ASAME.

• International Journal of Railway
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• v.8 no.1
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• pp.1-4
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• 2015

An accurate measurement of the train-track interaction forces is important for track performance evaluation. In the field calibration test as a wheel load measurement process, the calibration system creates a different boundary condition in comparison with that in the train wheel passage. This study aims to evaluate a reliability of the field calibration test in the process of wheel load measurement. Finite element models were developed to compare the deformed shapes, bending moment and shear force profiles on the rail section. The analysis results revealed that the deformed shapes and their associated bending moment profiles on the rail are significantly different in two numerical simulations of the calibration test and the train wheel load passage. However, the shear stress profile on the rail section of the strain gauge installation in the field was almost identical, which may imply that the current calibration test is sufficiently reliable.

• Journal of Advanced Navigation Technology
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• v.23 no.2
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• pp.214-220
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• 2019

The calibration method of the initial value error obtained in the weight measurement through anchor bolt type strain gauge sensor is proposed. The strain gauge sensor is developed for preventing the overturning of forklift, which is the most frequent type of safety-accident in industry. It was confirmed that the initial value error is caused from the physical and mechanical error of anchor bolt, and the environmental problem. Since the elimination of these causes falls outside the realm of this research, we find out the calibrated values based on all the causes, and we adjust the initial values of analog-to-digital convertor (ADC) module consisted of strain gauge sensor block using the calibrated values. We use the linear interpolation method for our calibration. We confirm that four sensor modules have the different under 5% between the real weight and the measured value in the experiment applied with the calibration of initial values. The low correlation between the real weights and ADC values is also improved through the proposed calibration.

• Journal of Institute of Control, Robotics and Systems
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• v.9 no.12
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• pp.1019-1025
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• 2003

We introduce a new auto-calibration/simulation method for a strain gage type transducer/signal-conditioner which guarantees the output linearity and compensates the error automatically. We design a micro voltage supply which is able to interface either AC or DC type excitation voltage. A new strain gage simulator is also designed. We make linearity output of the signal conditioner and can compensate error automatically with this new auto calibration/simulation method. The experimental results show that the error between the real value and the expected one is less than 1%.

• Progress in Superconductivity and Cryogenics
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• v.12 no.3
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• pp.1-6
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• 2010

Since the fiber reinforced polymeric (FRP) composites are considered in next generation of space transportation systems, reliable thermal expansion properties should be well provided for structural design of composite materials. To obtain accurate mechanical behaviors at a cryogenic temperature, precise strain measurement and calibration must be provided. In this work, apparent strains (or thermal output) of temperature self-compensated strain gages were deliberately investigated for epoxy, CTBN modified epoxy and carbon fabric composite system from room temperature to liquid nitrogen temperature. Also, fourth-order thermal output curves were presented for the further calibration. The results showed that the thermal output is heavily dependent on test materials and a large amount of apparent strains were observed for the polymer resins.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1997.03a
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• pp.207-212
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• 1997

In estimating the formability of sheet metal, the stereo vision system contributes the accuracy of strain of sheet metal, the convenience in measuring the strain of sheet metal, and the handiness in preparing the forming limit diagram by calculating the 3D values and strain of sheet metal. The algorithm has been developed so that the 3D-coordinate values of sheet metal could be calculated by image processing which is composed of camera calibration, and the stereo matching of images in two viewpoints. By comparing with experiments, the possibility and the convenience of algorithm has been verified, which could calculate the 3D-coordinate values of sheet metal automatically by using the preprocessing of the original image of sheet metal, which had the noise before adjusting the camera calibration and the stereo matching algorithm.

• Journal of Mechanical Science and Technology
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• v.14 no.3
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• pp.314-319
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• 2000

Back-face strain compliance (BFS compliance) for the four-point bend specimen has been calibrated for various crack length ratios. Finite element technique was employed to simulate four-point loading and calculate back-face strain of the bend specimen. The numerically determined strain variation along the back face indicates that the sensitivity to gage placement increases with crack length and back-face strain at the gage length less than O.2W, where W is the width of the bend specimen, can be measured within 5% deviation of the maximum BFS. Non-dimensional back-face strain compliance, -E'BCW, was calibrated with FE analysis and experiment. The experimentally determined compliance indicates good agreement with the numerical compliance and can be expressed as a function of crack length ratio.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.983-984
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• 2006

The correct computer simulation of the powder compaction stage requires the determination of the elastoplastic parameters which characterize its mechanical behavour. Instrumented dies are frequently used to monitor the longitudinal and radial stress occurring during powder compaction. When strain gages are employed a previous calibration is needed. Many sources of error exist that can lead to the incorrect calibration of the instrumented die. By means of a FEM simulation some of these problems are analysed. The effect of die wall thickness, compression length, and strain location are studied.