• Journal of Mechanical Science and Technology
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• v.20 no.7
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• pp.961-971
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• 2006

A deadweight force standard machine is a mechanical structure that generates force by subjecting deadweights to the local gravitational field. The Korea Research Institute of Standards and Science (KRISS) developed and installed a 100 kN deadweight force standard machine for national force standards. It can generate forces from 2 kN to 110 kN in increments of 1 kN. The uncertainty of the force machine was estimated and declared as $2\times10^{-5}$. This 100 kN deadweight force machine was compared with the 500 kN deadweight force standard machine at KRISS and the 20 kN and 50 kN deadweight force standard machines at the National Metrology Institute of Japan (NMIJ). The measurement results showed good agreement between the deadweight force machines, and the accuracy level of the 100 kN deadweight force machine was verified.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.3 s.174
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• pp.667-675
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• 2000

Force measuring devices should be calibrated to guarantee their test results. In order to establish the force standards in Korea, deadweight machines of 5 kN, 20 kN, 100 kN and 500 kN capacity and a hydraulic force standard machine of 2 MN capacity were installed at the Korea Research Institute of Standards and Science(KRISS). As heavy industries in Korea have been developed, we should measure large forces over 2 MN capacity precisely in industries. We developed a 10 MN force standard machine with built-in force transducers which is more compact and cheaper than hydraulic force standard machines which have been widely used as large force standards in most national metrology laboratories. Test results reveal that the relative expanded uncertainty of the force machine is less than 4.1 $\times$ 10-4 in the range of 1 MN-4.5 MN.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.8
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• pp.203-212
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• 1999

This paper describes a deadweight force standard machine with the weight change mechanism which can be used as a primary force standards at a national metrology institute. Since commercial deadweight force machine can generate forces by hanging weights to the weight supporter serially, force steps from deadweight force measuring devices of each having different capacity. In order to increase the force steps, we have specially designed a weight mechanism in which the machine can select the necessary weights and generate the load by hanging the selected weights to the weight supporter. The machine can generate 속 force of the range of 2 kN to 110 kN with force step of 1 kN. All weights have been accurately compensated and calibrated by a mass comparator and its standard uncertainty is less than 2.2 ${\times}\;10^{-6}$. The relative expanded uncertainty of the machine is 1.3 ${\times}\;10^{-5}$.

• Journal of the Korean Society for Precision Engineering
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• v.11 no.5
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• pp.33-41
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• 1994

For the establishment of large force standard and the accurate measurement of large force, 2MN hydraulic force standard machine which consists of loading frame, deadweight machine, two ram/cylinder systems and hydraulic control system was designed and fabricated. Measurement results of shapes for tow ram/cylinders reveal that the ratio of effective area is 200.094. The relative deviation of force stability for the machine is about .+-. 0.01% at 2MN and is less than .+-. 0.005% below 2MN. This machine may be widely used to calibrate the force measuring devices in industry and to test the force sensors.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.3
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• pp.477-484
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• 1997

This paper describes the build-up force measuring system of 9.9 MN capacity which consists of nine force transducers of each having 1.1 MN capacity. We have specially designed a force transducer for a build-up force measuring system to reduce the uncertainty of a build-up system and to accomodate the new test procedure for a build-up system. It reveals that the relative uncertainty of the force measuring system is less than 1.5*10$^{-4}$ in the ran9e of 1-4.5 MN irrespective of loading direction. The force measuring system may be used to calibrate a 10 MN force standard machine to be used as a large force standard in Korea.

• Wind and Structures
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• v.36 no.6
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• pp.355-366
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• 2023

Although machine learning (ML) techniques have been widely used in various fields of engineering practice, their applications in the field of wind engineering are still at the initial stage. In order to evaluate the feasibility of machine learning algorithms for prediction of wind loads on high-rise buildings, this study took the exposure category type, wind direction and the height of local wind force as the input features and adopted four different machine learning algorithms including k-nearest neighbor (KNN), support vector machine (SVM), gradient boosting regression tree (GBRT) and extreme gradient (XG) boosting to predict wind force coefficients of CAARC standard tall building model. All the hyper-parameters of four ML algorithms are optimized by tree-structured Parzen estimator (TPE). The result shows that mean drag force coefficients and RMS lift force coefficients can be well predicted by the GBRT algorithm model while the RMS drag force coefficients can be forecasted preferably by the XG boosting algorithm model. The proposed machine learning based algorithms for wind loads prediction can be an alternative of traditional wind tunnel tests and computational fluid dynamic simulations.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.9
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• pp.2194-2205
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• 1995

In order to reduce the systematic error of a build-up system, we have proposed a new test procedure in which all force transducers in a build-up system are rotated by 90.deg. with a base platen fixed on a force standard machine. The setting positions of force transducers on the output of a build-up system were investigated using an orthogonal array. The effects of the parallelism of a build-up system and of the bending moment sensitivity of a force transducer were considered. The experimental results show that the setting position of the base platen hardly affects the output of the build-up system, but the setting positions of force transducers affects it strongly. It reveals that the new test procedure reduces effectively the systematic error of a build-up system.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.16 no.8 s.113
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• pp.789-796
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• 2006

The characteristics of the four standard floor impact sources (impact ball, bang machine, tapping machine, modified tapping machine) and a human impact source (jumping children) were investigated. First, the mechanical impedance of each source were evaluated. Then, the impact force exposure level of each source were measured. The results showed that fundamental frequency and impedance produced by the impact ball are the most similar to those of the human impact source. The frequency characteristics of the impact ball were most similar to those of jumping children. Consequently, the impact ball more accurately reproduces human impact compared to the other standard impact sources. Therefore, the impact ball should be considered as the reliable impactor in evaluating floor impact noise.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.24 no.5
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• pp.390-398
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• 2014

Heavy-weight floor impact noise is directly related to the impact source and floor vibration property. Dynamic properties of the standard floating floor that is used in Korea was investigated using accelerance, acceleration energy spectral density(ESD), and structural modal test. In the standard floating floor, natural frequency was decreased by the finishing mortar mass and the damping ratio was increased. Bang-machine force spectrum acting on the concrete slab can be calculated using inverse system analysis. Impact force acting on concrete slab is changed by interaction of finishing mortar and resilient material. The amplitude of the bang-machine force spectrum was amplified in low frequency range(below 100 Hz), and over 100 Hz was decreased. Changed force spectrum influence to the response of structure vibration, so the heavy-weight floor impact noise level was changed.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.12
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• pp.161-167
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• 1999

This paper describes the calibration method and the calculation equations of expanded uncertainty for a precision electric force measuring device. The calibration of the electric force measuring device is performed three times (0 ${\circ}$(first time), $120{\circ}$(second time), $240{\circ}$(third time)) at each calibration point. It is usually selected ten points from zero load to rated load of the electric force measuring device. The expanded uncertainty is calculated by combining A type standard uncertainty and B type standard uncertainty. The calibration method and the calculation equations of expanded uncertainty can be widely used in the calibration of the precision electric force measuring device.