• Proceedings of the KSME Conference
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• 2008.11a
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• pp.646-651
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• 2008

Bolts and nuts are widely used to fasten each mechanical part together in the machines and structures as vital elements. The primary role of bolts and nuts is keeping its axial force against the large external force and vibration. In this study, a lock nut using a spring was developed to maintain axial force. When the lock nut was made, crack occurred in the process of manufacturing the lock nut. Thus, optimized structure of lock nut was found by using the design of experiments. Lastly, the prototype of the optimized lock nut was created, and then the optimization result was verified by comparing results of the initial model and optimized model.

• Journal of Institute of Convergence Technology
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• v.2 no.2
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• pp.20-24
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• 2012

In this paper, we perform a ANSYS simulation of assembly structure composed of three parts, bolt, nut, and coil spring, under the loading of a screw torque 640~800 ($N{\cdot}m$) derived from the given bolt tensile strength 10.9, which allows us to investigate a lock-nut mechanism for the prevention of bolt-loosening after three parts are fastened. And also we investigate the safety factor of each component with effective stress distribution obtained from the simulation, which enables us to estimate the structural safety of a new lock-nut structure. Both simulation and investigation shown in this paper will contribute to the development of a new lock nut structure.

• Transactions of the Korean Society of Automotive Engineers
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• v.18 no.2
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• pp.91-96
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• 2010

The combination of a bolt and nut is the element most widely used for connecting machines and structures. When a load is repetitively applied in the direction right angle to the bolt axis after the bolt and nut is fastened, the nut gradually becomes loose. To solve this problem, in this study, a new type of the loose-proof nut, called a lock nut, is developed. The lock nut is equipped with a spring, and the spring increases the axial force of the bolt. Then, the connection force between the bolt and nut is also augmented. Three dimensional finite element models for the bolt and spring are generated, and the change of the axial force of the bolt while the bolt is being inserted into the spring is analyzed using MSC/Marc, a commercial finite element program. Finally, the optimum shape of the spring is found according to the response surface analysis methodology. The optimization result is verified by comparing the variation of the axial force of the bolt when the bolt is inserted to the initial and optimized spring.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.8
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• pp.965-970
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• 2010

Bolts and nuts are widely used to fasten mechanical parts together in machines and structures. The primary role of a nut is to maintain the axial force of a bolt. In this paper, a new type of a lock nut that uses a spring is studied. To have a spring within a nut, a cocking process to narrow the top of the nut is adopted, but cracking occurred in the process. In this study, strain of an initial model is measured using the finite element analysis program, MSC/Marc. The occurrence of the crack was studied by comparing the maximum observed strain of a model with the maximum strain indicated by an accurate stress-strain diagram of 1020 steel. Then, the structure of the lock nut was optimized by response surface analysis to prevent cracking. The prototype of the lock nut was manufactured on the basis of the optimization result, and cracking did not occur.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2009.06a
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• pp.149-150
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• 2009

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.4
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• pp.2356-2363
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• 2015

This study deals the optimization design with the simulation based design of a coil spring inserted into the lock nut for preventing the screw thread from loosening at the bolted joint when the high-strength steel bolt with the property class of 10.9 is used and the screw torque of 640 to 800 (Nm) is applied. In this study, structural analysis of assembly composed of bolt, nut and coil spring is carried out to evaluate its safety factors on the basis of the equivalent stress with commercial finite element analysis software. And the design strategy to extract the design improvement from these simulation results is established. An iterative process performed with the proposed design strategy is also proposed for improving the performance of the existing design. At the proposed procedure, the feasible design parameters using response surface method are found, and then these parameters are verified to be optimal or not by comparing with the response values and the simulation results obtained from the feasible parameters.