Papers by Keyword: Life Extension

Abstract: At present the Cut-stern Kolek Boats of local fishermen at Kaoseng Community on the Coast of Songkhla Lake have a high rate of shaft failure. Consequently, the fishermen have spent lots of money on maintenance program of repairing shafts for a few years. Besides, the repairing cost, each time of the failure also causes water pollution from the leakage of grease. The incomplete transmission of power leads to engine overloading and fuel wasting. The investigation of the high failure rate of propeller shafts which were major machine component in power transmission illustrated the failure in normal fracture caused by the mechanisms of metal fatigue. Using the welding repair by shield metal arc welding process did not give the satisfied outcome because it created the short service life of reused propeller shafts after repairing. This research was aimed to study the metal fatigue behavior of long tail shafts in the Cut-stern Kolek boats and introduce the new method of welding repair process to prolong their service life. The experiment revealed that specimens resulted from the new welding repair process and the conventional one possessed different service life. The new process used the flux core which arc welding can prolong the service life of the shafts of boats more than 1.6 times of using the conventional method which is the electric welding by flux core arc welding. The research result will be extended to fishermen, in order to encourage them to become a part of sustainable inshore fisheries.

Abstract: Bringing particle damping technology into the large-scale precise numerically-controlled machine tool will effectively decrease vibration at the time of machinery processing and extend lifetime, and have a wide application prospect on vibration suppression for the precise machine tool. This paper studies the influence of the different density, diameter and filling rate of particle on the structure stability of machine tool. The experimental results show that choosing the proper density, diameter and filling rate of particle has a great influence on practical design and application of precise machine tool, and provides the theoretical basis and design principle for the application of vibration reduction and lifetime extension of the large-scale precise NC machine tool.

Abstract: The paper presents a reliability-based approach to assess the structural integrality of tubular joints with cracks in aging offshore platforms. Two different fatigue failure models are established respectively according to crack propagation size and equivalent fatigue strength, and the corresponding computing methods of fatigue reliability are proposed. The fatigue stress of tubular joint suffering sea wave load is calculated by spectrum analysis. The numerical examples are given to show the difference between the two reliability models. Considered the influence of inspection and repair, the reliability is updated by two different maintenance schedules. The analysis results can help to work out the optimal inspection planning, so as to prolong the service life for aged offshore platforms.

Abstract: The end coupling is the main component of the aluminum hot rolling process. The end coupling used for transmission of rotational power with heavy-duty load. Fracture of the end coupling causes serious economic injury because an end coupling is a very expensive component and takes a long time to repair. To prevent the destruction of the end coupling it is essential for mechanical life cycle to be known. In this paper, a parameter study on end coupling was performed in order to minimize maximum stress of an end coupling under static loads. To verify the interference of spindle assembly with modified end coupling, kinematic simulation was performed by applying the various combination type and dynamic boundary condition of the spindle assembly. The interference of an optimized model did not occur during combination process and driving process. As a result of an optimum design for life extension on end coupling, the maximum stress of end coupling was reduced about 26% compared with original model.

Abstract: The impact of remanufacturing on the conservation of energy and resources has been well recognized during the last decade. When the relevant technologies are applied for high temperature components in power and process industries, a redesign of the component life should be required due to the time-dependent feature of high temperature failure. In order to provide some fundamentals for redesign and remanufacture of high temperature components, mechanical behavior of a two-bar structure with one bar being remanufactured is analyzed. An optimal repairing time is given. From the viewpoint of creep damage, various high temperature structures are analyzed by using damage coupled finite element method. Suggestions for life extension remanufacture are proposed for typical high temperature components.