• Journal of the Korean Society for Nondestructive Testing
• /
• v.25 no.6
• /
• pp.439-445
• /
• 2005

The stud bolt is one of crucial parts for safe operation of reactor vessels in nuclear power plants, Crack initiation and propagation were reported in stud bolts that arc used for closure of reactor vessel and head, Stud bolts are inspected by ultrasonic technique during overhaul periodically for the prevention of stud bolt failure which could induce radioactive leakage from nuclear reactor, In conventional ultrasonic testing for inspection of stud bolts, cracks are detected by using shadow effect It takes too much time to inspect stud bolts by using conventional ultrasonic technique. In addition, there were numerous spurious signals reflected from every oblique surfaces of thread, In this study, the signal processing technique for enhancing conventional ultrasonic technique was introduced for inspecting stud bolts. The signal processing technique provides removing spurious signal reflected from every oblique surfaces of thread and enhances detectability of defects. Detectability for small crack was enhanced by using this signal processing in ultrasonic inspection of stud bolts in Nuclear Power Plants.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.26 no.6
• /
• pp.440-446
• /
• 2006

The reactor vessel body and closure head are fastened with the stud bolt that is one of crucial parts for safety of the reactor vessels in nuclear power plants. It is reported that the stud bolt is often experienced by fatigue cracks initiated at threads. Stud bolts are inspected by the ultrasonic technique during the overhaul periodically for the prevention of failure which leads to radioactive leakage from the nuclear reactor. The conventional ultrasonic inspection for stud bolts was mainly conducted by reflected echo method based on shadow effect. However, in this technique, there were numerous spurious signals reflected from every oblique surfaces of the thread. In this study, ultrasonic phased array technique was applied to investigate detectability of flaws in stud bolts and characteristics of ultrasonic images corresponding to different scanning methods, that is, sector and linear scan. For this purpose, simplified stud bolt specimens with artificial defects of various depths were prepared.

• Proceedings of the KSME Conference
• /
• 2000.11a
• /
• pp.199-205
• /
• 2000

The stud female threads for stud bolts tend to degrade faster by high temperature over 450 C. Therefore, inspection for replacement cycle of stud bolts is used to carry out many kinds of method such as ultrasonic test(UT), magnetic test(MT), wobble test, visual test and hardness test. The visual inspection among those has been only applied for stud female threads generally and wobble test is often used to apply stud bolts. In this paper, wobble test is applied for evaluation of stud female threads on the contrary stud bolts especially. It is also applied three types of inspection method included wobble test on the two sites which is used for each other different operation cycle and three kinds of acquisition data are compared with evaluation methods. From the results, we have studied the characteristic exchanging of integrity evaluation data distribution according to using time and proposed managing method for female thread of stud on the power plants.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.8 no.6
• /
• pp.279-286
• /
• 2000

The stud bolts tend to degrade faster by high temperature(over 45$0^{\circ}C$). Therefore, replacement cycle inspection of stud bolts were carried out various method such as ultrasonic test(UT), magnetic test(MT), wobble test, visual test and hardness test. Especially, wobble test method has been applied to determine replacement evaluation criteria of stud bolt after long time operation. We applied three different methods on the three site and the obtained data are compared with the results from the evaluation methods. From the results, the replacement criteria for stud bolts under high temperature in power plants are proposed.

• Journal of Advanced Marine Engineering and Technology
• /
• v.24 no.2
• /
• pp.8-16
• /
• 2000

The thread load distribution as applied to large stud bolts for steam turbines is investigated using the finite element method. The stress concentration in tapered threads is studied with varying prestress and taper angle. Based upon the thread load distribution, the optimal taper angles to reduce the stress concentration are determined for various prestresses. The presented finite element model is validated by comparing results of the calculated thread load with analytic ones. The optimal taper angles obtained from this research can be used in designing tapered threads of large stud bolts for steam turbines.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.9 no.1
• /
• pp.106-110
• /
• 1989

Bolting degradation problems in primary coolant pressure boundary applications have become a major concern in the nuclear industry. In the bolts concerned, the failure mechanism was either corrosion wastage(loss of bolt diameter) or stress-corrosion cracking.(3) Here the manual ultrasonic testing of RPV(Reactor Pressure Vessel) and RCP(Reactor Coolant Pump) stud has been performed. But it is difficult to detect indications because examiner can not exactly control the rotation angle and can not distinguish the indication from signals of bolt. In many cases, the critical sizes of damage depth are very small(1-2 mm order). At critical size, the crack tends to propagatecompletly through the bolt under stress, Resulting in total fracture.(3) Automatic stud scanner for studs(bolts) was developed because the precise measurement of bolt diameter is required in this circumstance. By use of this scanner, the rotation angle of probe was exactly controlled and the exposure time of radiations was reduced.

• Steel and Composite Structures
• /
• v.44 no.3
• /
• pp.339-351
• /
• 2022

A mortar-filled rectangular hollow structural section (RHS) can increase a structural section property as well as a compressive buckling capacity of a RHS member. In this study, the tensile performance of newly developed mortar-filled RHS members was experimentally evaluated with various connection details. The major test parameters were the type of end connections, the thickness of cap plates and shear plates, the use of stud bolts, and penetrating bars. The test results showed that the welded T-end connection experienced a brittle weld fracture at the welded connection, whereas the tensile performance of the T-end connection was improved by additional stud bolts inserted into the mortar within the RHS tube. For the end connection using shear plates and penetrating stud bolts, ductile behavior of the RHS tube was achieved after yielding. The penetrating bars increased load carrying capacity of the RHS. Based on the analysis of the load transfer mechanism, the current design code and test results were compared to evaluate the tensile capacity of the RHS tube according to the connection details. Design considerations for the connections of the mortar-filled RHS tubes were also recommended.

• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.24 no.1
• /
• pp.130-134
• /
• 2015

The automobile industry is ubiquitous and involved in the handling of metal, machines, electricity, electron, and chemistry including the products of many types of processes. In the process of installing engines as a part of the car assembly line, the measurement and correction of the position of the stud bolts consumes a great deal of time. Additionally, defective parts must be manually removed. In the process of engine installation, the speed of the operation, related to the economics of vehicle assembly, is dependent upon measuring the precise position of the stud bolt, reducing the length of correction time, and increasing the working rate. This paper deals with securing the economic feasibility of the manufacturing process, increasing the safety by removing risk factors in the working area, and improving and equalizing the quality by developing an automatic system for the process involving a stud bolt.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 1993.10a
• /
• pp.181-185
• /
• 1993

A useful finite element method to determine the stiffness of assembled member by stud bolt was introduced in this paper. Since threads on clamped members and stud bolts may produce different stress distribution, brief theories and equations based on bolt and nut may produce less conservative results or, this case. A finite element model using non-linear gap element was indtroduced to find out the basic feature of stress distribution caused by threads on both stud and member.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2006.05a
• /
• pp.341-344
• /
• 2006

Finite element analysis and verification experiments were performed in order to find cause of defects such as folding and improper radius around the root area of the thread rolled stud bolts. Thread rolling experiments under several conditions were also carried out to understand the effect of process parameters, such as the rotation speed of the dies and the hardness of the work pieces, on the product quality. Folding defects at the top of thread are attributed to the higher hardness of the work piece and higher rotation speed of the rolling die. It was also found that the radius of screw mainly determined by the radius of the die.