The design and performance evaluation of a sustained load creep testing machine was undertaken in this research. The design was motivated by the need to make locally available, a cost effective, technically efficient,...The design and performance evaluation of a sustained load creep testing machine was undertaken in this research. The design was motivated by the need to make locally available, a cost effective, technically efficient, and easily operated creep testing facility;for creep behaviour studies of materials. Design drawings and purchase of materials and components for the design were undertaken after thorough evaluation of the following design and materials selection criteria: design principle and theory, local availability of raw materials and components required for the design, material properties, cost of materials and design, ease of utilization and maintenance, and basis of testing and data capture. The machine casing and frame, heating chamber (consisting of the furnace and a dual specimen mounting stage), load lever and hanger system, and the electro-technical components;were fabricated and coupled following the produced design specifications. The machine was tested and its performance was assessed using its heating efficiency, repeatability and reproducibity of experimental test results, maintainability and cost-effectiveness as criteria. It was observed from repeat tests that the machine has the capacity of generating reliable data for computing creep strain-time results. The efficiency and temperature regulating capacity of the heating unit of the machine were also observed to be very satisfactory. The cost of the design was about 112,000 Naira ($700.00) which is cheaper in comparison to similar commercial creep testing machines from abroad. The machine was also found not to pose maintenance or repairs challenges.展开更多
This paper proposes a systematic method, integrating the uniform design (UD) of experiments and quantum-behaved particle swarm optimization (QPSO), to solve the problem of a robust design for a railway vehicle suspens...This paper proposes a systematic method, integrating the uniform design (UD) of experiments and quantum-behaved particle swarm optimization (QPSO), to solve the problem of a robust design for a railway vehicle suspension system. Based on the new nonlinear creep model derived from combining Hertz contact theory, Kalker's linear theory and a heuristic nonlinear creep model, the modeling and dynamic analysis of a 24 degree-of-freedom railway vehicle system were investigated. The Lyapunov indirect method was used to examine the effects of suspension parameters, wheel conicities and wheel rolling radii on critical hunting speeds. Generally, the critical hunting speeds of a vehicle system resulting from worn wheels with different wheel rolling radii are lower than those of a vehicle system having original wheels without different wheel rolling radii. Because of worn wheels, the critical hunting speed of a running railway vehicle substantially declines over the long term. For safety reasons, it is necessary to design the suspension system parameters to increase the robustness of the system and decrease the sensitive of wheel noises. By applying UD and QPSO, the nominal-the-best signal-to-noise ratio of the system was increased from -48.17 to -34.05 dB. The rate of improvement was 29.31%. This study has demonstrated that the integration of UD and QPSO can successfully reveal the optimal solution of suspension parameters for solving the robust design problem of a railway vehicle suspension system.展开更多
文摘The design and performance evaluation of a sustained load creep testing machine was undertaken in this research. The design was motivated by the need to make locally available, a cost effective, technically efficient, and easily operated creep testing facility;for creep behaviour studies of materials. Design drawings and purchase of materials and components for the design were undertaken after thorough evaluation of the following design and materials selection criteria: design principle and theory, local availability of raw materials and components required for the design, material properties, cost of materials and design, ease of utilization and maintenance, and basis of testing and data capture. The machine casing and frame, heating chamber (consisting of the furnace and a dual specimen mounting stage), load lever and hanger system, and the electro-technical components;were fabricated and coupled following the produced design specifications. The machine was tested and its performance was assessed using its heating efficiency, repeatability and reproducibity of experimental test results, maintainability and cost-effectiveness as criteria. It was observed from repeat tests that the machine has the capacity of generating reliable data for computing creep strain-time results. The efficiency and temperature regulating capacity of the heating unit of the machine were also observed to be very satisfactory. The cost of the design was about 112,000 Naira ($700.00) which is cheaper in comparison to similar commercial creep testing machines from abroad. The machine was also found not to pose maintenance or repairs challenges.
基金the Ministry of Science and Technology of Taiwan (Grants MOST 104-2221-E-327019, MOST 105-2221-E-327-014) for financial support of this study
文摘This paper proposes a systematic method, integrating the uniform design (UD) of experiments and quantum-behaved particle swarm optimization (QPSO), to solve the problem of a robust design for a railway vehicle suspension system. Based on the new nonlinear creep model derived from combining Hertz contact theory, Kalker's linear theory and a heuristic nonlinear creep model, the modeling and dynamic analysis of a 24 degree-of-freedom railway vehicle system were investigated. The Lyapunov indirect method was used to examine the effects of suspension parameters, wheel conicities and wheel rolling radii on critical hunting speeds. Generally, the critical hunting speeds of a vehicle system resulting from worn wheels with different wheel rolling radii are lower than those of a vehicle system having original wheels without different wheel rolling radii. Because of worn wheels, the critical hunting speed of a running railway vehicle substantially declines over the long term. For safety reasons, it is necessary to design the suspension system parameters to increase the robustness of the system and decrease the sensitive of wheel noises. By applying UD and QPSO, the nominal-the-best signal-to-noise ratio of the system was increased from -48.17 to -34.05 dB. The rate of improvement was 29.31%. This study has demonstrated that the integration of UD and QPSO can successfully reveal the optimal solution of suspension parameters for solving the robust design problem of a railway vehicle suspension system.
