Based on the option prioritization in graph model for conflict resolution of two decision makers(DMs),new logical and matrix representations of four stability concepts for DMs′attitude are proposed.The logical repres...Based on the option prioritization in graph model for conflict resolution of two decision makers(DMs),new logical and matrix representations of four stability concepts for DMs′attitude are proposed.The logical representation of attitude is defined,and converted to the matrix form in order to develop a decision support system(DSS)efficiently.Compared with existing definitions of DMs′attitude based on states,the proposed definitions of attitude based on options are convenient and more effective to generate preferences since that of states can be significantly larger than that of options in a large conflict.In addition,it is easier to obtain the information of the prioritization of option statements than to obtain preference of states for users.The proposed representations are applied to the process conflict during aircraft manufacturing to demonstrate the efficiency of the new approach.展开更多
With the wide application of condition based maintenance(CBM) in aircraft maintenance practice, the joint optimization of maintenance and inventory management, which can take full advantage of CBM and reduce the aircr...With the wide application of condition based maintenance(CBM) in aircraft maintenance practice, the joint optimization of maintenance and inventory management, which can take full advantage of CBM and reduce the aircraft operational cost, is receiving increasing attention. In order to optimize the inspection interval, maintenance decision and spare provisioning together for aircraft deteriorating parts, firstly, a joint inventory management strategy is presented, then, a joint optimization of maintenance inspection and spare provisioning for aircraft parts subject to the Wiener degradation process is proposed based on the strategy.Secondly, a combination of the genetic algorithm(GA) and the Monte Carol method is developed to minimize the total cost rate.Finally, a case study is conducted and the proposed joint optimization model is compared with the existing optimization model and the airline real case. The results demonstrate that the proposed model is more beneficial and effective. In addition, the sensitivity analysis of the proposed model shows that the lead time has higher influence on the optimal results than the urgent order cost and the corrective maintenance cost, which is consistent with the actual situation of aircraft maintenance practices and inventory management.展开更多
In order to enhance the NC programming efficiency and quality of aircraft structural parts （ASPs）, an intelligent NC programming pattern driven by process schemes is presented. In this pattern, the NC machining cell...In order to enhance the NC programming efficiency and quality of aircraft structural parts （ASPs）, an intelligent NC programming pattern driven by process schemes is presented. In this pattern, the NC machining cell is the minimal organizational structure in the technological process, consisting of an operation machining volume cell, and the type and parameters of the machining operation. After the machining cell construction, the final NC program can be easily obtained in a CAD/CAM system by instantiating the machining operation for each machining cell. Accordingly, how to automatically establish the machining cells is a key issue in intelligent NC program- ming. On the basis of the NC machining craft of ASP, the paper aims to make an in-depth research on this issue. Firstly, some new terms about the residual volume and the machinable volume are defined, and then, the technological process is modeled with a process scheme. Secondly, the approach to building the machining cells is introduced, in which real-time complement machining is mainly considered to avoid interference and overcutting. Thirdly, the implementing algorithm is designed and applied to the Intelligent NC Programming System of ASP. Finally, the developed algorithm is validated through two case studies.展开更多
Originally developed decades ago, the binder jetting additive manufacturing （B J-AM） process possesses various advantages compared to other additive manufacturing （AM） technologies such as broad material compat- i...Originally developed decades ago, the binder jetting additive manufacturing （B J-AM） process possesses various advantages compared to other additive manufacturing （AM） technologies such as broad material compat- ibility and technological expandability. However, the adoption of B J-AM has been limited by the lack of knowledge with the fundamental understanding of the process principles and characteristics, as well as the relatively few systematic design guideline that are available. In this work, the process design considerations for B J-AM in green part fabrication were discussed in detail in order to provide a comprehensive perspective of the design for additive manufacturing for the process. Various process factors, including binder saturation, in- process drying, powder spreading, powder feedstock characteristics, binder characteristics and post-process curing, could significantly affect the printing quality of the green parts such as geometrical accuracy and part integrity. For powder feedstock with low flowability, even though process parameters could be optimized to partially offset the printing feasibility issue, the qualities of the green parts will be intrinsically limited due to the existence of large internal voids that are inaccessible to the binder. In addition, during the process development, the balanced combination between the saturation level and in-process drying is of critical importance in the quality control of the green parts.展开更多
基金supported by the National Natural Science Foundation of China(Nos.71071076,71471087,and 61673209)
文摘Based on the option prioritization in graph model for conflict resolution of two decision makers(DMs),new logical and matrix representations of four stability concepts for DMs′attitude are proposed.The logical representation of attitude is defined,and converted to the matrix form in order to develop a decision support system(DSS)efficiently.Compared with existing definitions of DMs′attitude based on states,the proposed definitions of attitude based on options are convenient and more effective to generate preferences since that of states can be significantly larger than that of options in a large conflict.In addition,it is easier to obtain the information of the prioritization of option statements than to obtain preference of states for users.The proposed representations are applied to the process conflict during aircraft manufacturing to demonstrate the efficiency of the new approach.
基金supported by the Fundamental Research Funds for the Central Universities(NS2015072)
文摘With the wide application of condition based maintenance(CBM) in aircraft maintenance practice, the joint optimization of maintenance and inventory management, which can take full advantage of CBM and reduce the aircraft operational cost, is receiving increasing attention. In order to optimize the inspection interval, maintenance decision and spare provisioning together for aircraft deteriorating parts, firstly, a joint inventory management strategy is presented, then, a joint optimization of maintenance inspection and spare provisioning for aircraft parts subject to the Wiener degradation process is proposed based on the strategy.Secondly, a combination of the genetic algorithm(GA) and the Monte Carol method is developed to minimize the total cost rate.Finally, a case study is conducted and the proposed joint optimization model is compared with the existing optimization model and the airline real case. The results demonstrate that the proposed model is more beneficial and effective. In addition, the sensitivity analysis of the proposed model shows that the lead time has higher influence on the optimal results than the urgent order cost and the corrective maintenance cost, which is consistent with the actual situation of aircraft maintenance practices and inventory management.
基金supported by National Science and Technology Major Project (No.2012ZX04010051)
文摘In order to enhance the NC programming efficiency and quality of aircraft structural parts （ASPs）, an intelligent NC programming pattern driven by process schemes is presented. In this pattern, the NC machining cell is the minimal organizational structure in the technological process, consisting of an operation machining volume cell, and the type and parameters of the machining operation. After the machining cell construction, the final NC program can be easily obtained in a CAD/CAM system by instantiating the machining operation for each machining cell. Accordingly, how to automatically establish the machining cells is a key issue in intelligent NC program- ming. On the basis of the NC machining craft of ASP, the paper aims to make an in-depth research on this issue. Firstly, some new terms about the residual volume and the machinable volume are defined, and then, the technological process is modeled with a process scheme. Secondly, the approach to building the machining cells is introduced, in which real-time complement machining is mainly considered to avoid interference and overcutting. Thirdly, the implementing algorithm is designed and applied to the Intelligent NC Programming System of ASP. Finally, the developed algorithm is validated through two case studies.
基金Acknowledgements The authors would like to acknowledge the support of Rapid Prototyping Center （RPC） at University of Louisville and the many technical insights and discussions from Dan Brunermer at ExOne LLC. This work was partially supported by National Science Foundation （Grant No. 1450370, subaward No. OGMN 131508E4）.
文摘Originally developed decades ago, the binder jetting additive manufacturing （B J-AM） process possesses various advantages compared to other additive manufacturing （AM） technologies such as broad material compat- ibility and technological expandability. However, the adoption of B J-AM has been limited by the lack of knowledge with the fundamental understanding of the process principles and characteristics, as well as the relatively few systematic design guideline that are available. In this work, the process design considerations for B J-AM in green part fabrication were discussed in detail in order to provide a comprehensive perspective of the design for additive manufacturing for the process. Various process factors, including binder saturation, in- process drying, powder spreading, powder feedstock characteristics, binder characteristics and post-process curing, could significantly affect the printing quality of the green parts such as geometrical accuracy and part integrity. For powder feedstock with low flowability, even though process parameters could be optimized to partially offset the printing feasibility issue, the qualities of the green parts will be intrinsically limited due to the existence of large internal voids that are inaccessible to the binder. In addition, during the process development, the balanced combination between the saturation level and in-process drying is of critical importance in the quality control of the green parts.
