• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.5
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• pp.937-943
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• 2009

In this paper, the algorithm discriminating the existence and nonexistence of bolts and nuts using image processing in an automobile T-Bar influencing the vibration of a frame, is introduced. To distinct whether bolts and nuts exist or not, the features of bolts and nuts are learned, and then these feature values are matched using a statistical pattern matching algorithm. Furthermore, the minimum and maximum variation rate of pixel values are used since the matching rate is low with the large variation of pixel values of bolts and nuts in each image. The proposed method in this paper is very efficient in the automation of inspection requiring real time since the inspection time is significantly reduced compared with the conventional methods.

• Journal of the Korean Society for Precision Engineering
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• v.32 no.7
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• pp.591-595
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• 2015

The roller rig tester for safety performance evaluation of wheel derailment is a test facility which can give the test load condition to the test wheel, similar to the actual dynamic condition in actual running condition. This study describes the evaluation result on the durability of the resilient wheel equipped with the ring damper and the damping material, and installed in the half part of a full scaled bogie in combination with the primary spring when it rotates under the dynamic condition. The evaluation result on durability of resilient wheel after load test of 2 million cycles shows that the safety of wheel is not affected by the applied load in visual inspection and nondestructive test, however, in the bolt used for fastening the ring damper to the wheel the loosening was found. Accordingly the use of self-locking nut and washer is recommended.

• Journal of Biosystems Engineering
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• v.36 no.5
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• pp.377-383
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• 2011

This study proposed the new method of discerning the assembled parts and presuming the position of central point in a Cowl Cross Bar (CCB) using a Charge-Couple Device (CCD) camera attached to a robot in the auto assembly line. Three control points of an ellipse were decided by three reference points, which were equally distanced. The radii of these reference points were determined by the size of the object, and the repeated presumption secured the precise determination. The comparison of the central point of ellipse presumed by Randomized Hough Transform (RHT) with the part information stored in a database was used for determining the faulty part in an assembly. The method proposed in this study was applied for the real-time inspection of elliptical parts, such as bolt, nut hole and so on, connected to a CCB using a CCD camera. The findings of this study showed that the precise decision on whether the parts are inferior or not can be made irrespective of the lighting condition of industrial site and the noises of the surface of the part. In addition, the defect decision on the individual elliptic parts assembled in a CCB showed more than 98% accuracy within a 500-millisecond period at most.

• Journal of the Korea institute for structural maintenance and inspection
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• v.25 no.5
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• pp.8-14
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• 2021

Post-tensioned prestressed concrete members experience immediate prestress losses as well as time-dependent prestress losses such as creep, dry shrinkage and relaxation. In addition, the stress of the upper and lower parts of the member changes due to the change in dead load due to the replacement of the upper slab and/or pavement. Such changes in fiber stress may affect the safety of the member, and it is necessary to adjust the prestressing force. Therefore, in this study, a screw type of re-tensioning post-tension kit is proposed, and it is verified that the safety against load and the stability against strain are satisfied through the load transfer test specified in EAD160004 and KCI-PS101.

• Journal of the Korea institute for structural maintenance and inspection
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• v.10 no.2
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• pp.165-176
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• 2006

This paper deals with the experiment and construction case of concrete beams strengthened with wire rope using the tightening force of bolts. The mechanical bolting of wire rope for prestressing force is adopted, which is very easy for construction. For the flexural strengthening effect of the proposed method, the experiment was proceeded as follows. The main parameters of specimens, concrete strength is 24MPa, are initial prestressing forces of wire rope and the number of saddle. The flexural strengths of strengthened specimens compared with non-strengthened test piece were increased about 160%. Also, as the initial prestressing forces were increased, the crack and ultimate moments were increased. The number of saddle did not play an important role for the moment capacity. This proposed method as a construction example showed a more competitive method than any others.

• Journal of Power System Engineering
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• v.15 no.4
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• pp.37-41
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• 2011

This paper introduces the special eddy current sensor and its characteristic for bolt hole defect evaluation in gas turbine rotor. In the past, Fluorescent penetration inspection method was used for qualitative defect evaluation in gas turbine rotor bolt hole. This method can defect the bolt hole defect but can not evaluate the defect size. Nowadays, eddy current method is used quantitative defect evaluation due to advanced sensor design technology. And eddy current method is more time and cost saving than the old method. We developed bolt shape eddy current sensor for the rotor bolt hole defect detection and evaluation. The eddy current sensor moves to the bolt hole guided by screw nut and detects the defect on the bolt hole. The bolt hole mock-up and artificial defects were made and used for the signal detection & resolution analysis of eddy current sensor. The results show that signal detection capability is enough to detect 0.2 mm depth defect. And the resolution capability is enough to differentiate 02, 0.5, 1.0 and 2.0 mm depth defect.

• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.5
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• pp.49-55
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• 2017

In the seventies, a number of researchers carried out experiments on pullout tests with prototype equipment, and the pullout test was certified as a reliable nondestructive testing(NDT) method for determining the strength of concrete. To estimate the strength of high-strength concrete, we propose a simplified pullout test that uses as a break-off bolt a standard 10mm bolt with a groove on the shaft, an insert nut, and a pullout instrument that includes a hydraulic oil pump without a load cell. To verify the advantages of the simplified pullout test(low cost, simplicity, and convenience), four wall specimens were tested with two levels of concrete strength, 30 MPa and 50 MPa, using a simplified pullout tester with a load cell. The pullout load and concrete compressive strength were measured every day until day 7, day 14, day 21 and day 28. It was found that the pullout load was very similar to the compressive strength. Therefore, we have verified that a simplified pullout test can be used to evaluate the in-place strength of high-strength concrete in structures. The prediction equation of the groove diameter of the break-off bolt(y) with the concrete strength(x) was derived as y=0.05x+3.79, with a coefficient of determination of 0.88 found through regression analysis.

• Journal of Advanced Marine Engineering and Technology
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• v.41 no.1
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• pp.118-124
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• 2017

To investigate and analyze the cause of the failure of the connecting rod bolt and the crank pin bearing bolt of the diesel engine of this study, the following results were obtained through site surveying, the investigation of literature referring to similar failures, testing and inspection of the fracture surface, and the experience of the researchers. The fractured crank pin bearing bolt of the diesel engine is estimated to be damaged later than the connecting rod bolt. From the shape of fracture surface, it is evident that the failed connecting rod bolt is fractured by fatigue failure due to abnormally repeated loads (e.g. loosening of the connecting bolt, etc.), and is not failed by brittle fractures due to the impact load. The surface of the U-nut on the fractured connecting rod bolt has been worsening due to the improper use of lubricant (agent for prevention of thread fixing) and no usage of separating the each connecting rod on each cylinder. Moreover, there is the possibility that those poor surface conditions of the fractured connecting rod bolt have affected the failure of the connecting rod bolt of the main engine. And it could be assumed that the mechanical characteristic and manufacturing process of the failed connecting rod bolt and crank pin bearing bolt, which were made by a domestic company, conform to the design requirements for those bolts.

• Journal of Food Hygiene and Safety
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• v.39 no.2
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• pp.152-162
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• 2024

In this study, we investigated the levels of the natural preservatives, benzoic acid, sorbic acid, and propionic acid, in raw unprocessed vegetables. Quantitative analysis of benzoic acid and sorbic acid was performed using high-performance liquid chromatography with a diode array detector (HPLC-DAD) and confirmed using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Propionic acid was analyzed using a gas chromatography-flame ionization detector (GC-FID) and confirmed using gas chromatography-mass spectrometry (GC-MS). From a total of 497 samples, benzoic acid, sorbic acid, and propionic acid were found in 50 (10%), 8 (0.2%), and 61 samples (12.3%), respectively. The highest quantity of benzoic acid, sorbic acid, and propionic acid was found in peony root (1,057 mg/kg), nut-bearing torreya seeds (27.3 mg/kg), and myrrha (175 mg/kg), respectively. The background concentration range of naturally occurring preservatives in raw vegetables determined in this study could be used as standard inspection criteria to address consumer complaints and trade disputes.