Advanced Materials Research Vols. 44-46

Abstract: An important requirement for a collaborative design platform in Concurrent Engineering (CE) is the integration of various engineering software tools and utilities in product design and development. Some CE platforms based on a client/server architecture or static Service Oriented Architecture (SOA) are available in the marketplace, but they lack flexibility and reliability in the constantly changing Internet environment due to the dynamic nature of the network. Based on the current development of SOA, this paper presents a Service-oriented Collaborative Design platform (SCoD) based on SORCER—a dynamic SOA infrastructure that allows federated integration of engineering software components in CE environments. The architecture of SCoD is proposed, the wrapping methodology used to integrate engineering software tools in SCoD is presented, and the federated method invocation for services in SCoD is described. With the support of SCoD, collaborative design in CE environments can be deployed, and scalability, reliability, and flexibility can be achieved in the changing Internet environment.

Abstract: The theory of reliability sensitivity analysis and reliability-based optimization robust design are extended to discuss the reliability design of electronic system. Firstly, a method of measuring the relative importance (sensitivity analysis) of each element of system is studied. And then, after establishing the mathematic model for reliability optimization, a procedure for robust design is examined. Finally, a numeric example is presended to illustrate the procedure of sensitivity analysis and robust design. After optimization, the mean life of system has increased than before, and the cost has been greatly reduced; on the other hand, the sensitivity of system reliability to the mean life of components also has decreased. The result shows that the proposed methodology is useful for system design and quality improvement.

Abstract: Railway vehicle structure fatigue life consumption monitoring can be used to determine fatigue damage by directly or indirectly monitoring the loads placed on critical vehicle components susceptible to failure from fatigue damage. The sample locomotive carbody structure was used for this study. Firstly, the hybrid fatigue analysis method was used with Multi-Body System (MBS) simulation and Finite Element Method (FEM) for evaluating the carbody structure dynamic stress histories. Secondly, the standard fatigue time domain method was used in fatigue analysis software FE-FATIGUE and MATLAB WAFO (Wave Analysis for Fatigue and Oceanography) tools. And carbody structure fatigue life and fatigue damage were predicted. Finally, and carbody structure dynamic stress experimental data was taken from this locomotive running between Kunming-Weishe for this analysis. The data was used to validate the simulation results based on hybrid method. The analysis results show that the hybrid method prediction error is approximately 30.7%. It also illustrates that the fatigue life and durability of the locomotive can be predicted with this hybrid method. The results of this study can be modified to be representative of the railway vehicle dynamic stress test.

Abstract: The prediction of aircraft structure service life is of great importance to safety of aircraft structure and human beings. The relation between aircraft structure service life and reliability can be found by utilizing the fatigue scatter factor of whole life. Only when the service life satisfies the requirements of reliability, can the safety of airplane be ensured. The fatigue scatter factors of the service life accords with lognormal distribution and Weibull distribution were studied to provide important reference for predicting the safe service life of aircraft structure.

Abstract: The project presents the theory of active reliability-based design for predetermined life targeted at their economic life. The structural reliability is designed from the view point of economic efficiency and maintainability requirements, so that the destruction of products led by fatigue and fracture is eliminated to the highest possible degree to provide the longest life, the highest reliability and the lowest cost. The reliability assessment of conventionally finished product is developed into an active reliability design at preset life, which is implemented before the design of products is finalized, to improve the safety and reliability of structures.

Abstract: Critical fatigue safety state is investigated on RD2 type axle of China railway freight cars. Attention is paid on the grooves near axle boxes, where more fatigue cracks were early appeared even result in at least six derailed accidents. Load history was obtained by vehicle dynamics simulation combining with on-line inspection. Braking loads and effects of maintenance and off-round of wheels are also incorporated. Semi-elliptical and external circumferential cracks are employed for crack growth simulation. Crack shape change and shear stressing of the semi-elliptical crack are taken into account. New crack growth rate modeling in which covers from cracking threshold to toughness related fracture state is applied for residual life evaluation. Critical fatigue safety state is defined as the crack size from which the axle can be safely operated to next overhaul inspection. Critical crack size is estimated step-by-step with the crack shape change. Results show that the external circumferential crack is more dangerous than the semi-elliptical crack. Application more than two years in production verifies that the present assessment is available and reliable.

Abstract: Critical safety wheel wear size is investigated through considering the fatigue safety effect on RD2 type axle of China railway freight cars. The wheel wear size increase results in a rise of the wheel-rail contact forces, which increase the fatigue stress history of the axle in service. Therefore, the size must be controlled to maintain the axle safety in service before the next overhaul inspection. A field investigation was firstly made on the wear size change regularity. Then, the size related wheel-rail impact forces are solved by a non-linear Hertzian contact theory with a vehicle multi-body dynamic model. In addition, a statistical method is further developed for incorporating the impact forces into the wheelset service load history. Finally, a wear size related critical state equation is established for ensuring the axle safety in service. A stationary solution is statistically obtained for the critical wear sizes with respect to the axle circumferential crack and semi-elliptical crack. It is concluded that the critical safety wear size should be controlled in the range of 100 mm at the statistical level of survival probability 0.99 and confidence 95%.

Abstract: The glass-to-metal seals are usually used in the solar thermal power (STP) and electronic devices. However, the requirement of mechanical properties in the STP is much higher than that of electronic devices, because the glass-to-metal joints used in the STP need to have anti-fatigue performance in adition to higher static tensile strength. Under the repeated fluctuating loads, damage and failures of glass-to-metal seals in the STP often lead to serious consequences. Therefore, analysis of damage evolution and fracture behavior of glass-to-metal diffusion welded joints was performed in this paper. Firstly, the finite element (FE) model of glass-to-metal welded joints was established in accordance with the STP welded structures. And damage simulation was carried out by the FE software ABAQUS. Also, the work illustrates the modeling of damage in terms of traction versus separation to simulate crack propagation and introduces the use of traction-separation law as a damage initiation and evolution criteria. The microgram of damage distribution in the glass side near the interface could be characterized by Scanning Electron Microscope (SEM), which was compared with predictions obtained by finite element method (FEM) analysis. As result, the damage criteria on the lap joints in conjunction with FM analysis were used to optimize the glass-to-metal diffusion welding technology. The above results provide the basis of design against damage and reliable estimation of glass-to-metal seals.

Abstract: The plastic deformation as a main form of failure of Interference Joints may happen in engineering works if it is designed unreasonably. In this paper, the contact stress and the strength of Interference Joint parts were analyzed deeply. Based on the theory of the reliability design, the general formulas and the method of the reliability design and computation for Interference Joint were established in consideration of joint structure, machining precision, interference value, mechanical properties of the joint parts and their randomicity. The practical design method, which would promote the reliability of Interference Joint effectively, was proposed for larger size and some other important Interference Joints. Compared to the conventional design method, the working reliability of Interference Joints can be improved obviously by means of the reliability design method.

Abstract: The life of bevel gear dies is determined by its stress state mainly. During the forging, the die teeth fractured and the bottom corner cracked in a few times. Finite Element Analysis (FEA) was employed to investigate the reason of failure. The results show that the tip fracture and the bottom corner crack mainly resulted from excessive tensile stress. In accordance with the FEA results, the non-plane parting face was changed into plane parting face and the radius of bottom hole was enlarged. The FEA result proves that the modification can greatly reduce stress concentration and the application proves that the modification can effectively solve the premature failure of the die.