In equipment integrated logistics support(ILS), the supply capability of spare parts is a significant factor. There are lots of depots in the traditional support system, which makes too many redundant spare parts and ...In equipment integrated logistics support(ILS), the supply capability of spare parts is a significant factor. There are lots of depots in the traditional support system, which makes too many redundant spare parts and causes high cost of support. Meanwhile,the inconsistency among depots makes it difficult to manage spare parts. With the development of information technology and transportation, the supply network has become more efficient. In order to further improve the efficiency of supply-support work and the availability of the equipment system, building a system of one centralized depot with multiple depots becomes an appropriate way.In this case, location selection of the depots including centralized depots and multiple depots becomes a top priority in the support system. This paper will focus on the location selection problem of centralized depots considering ILS factors. Unlike the common location selection problem, depots in ILS require a higher service level. Therefore, it becomes desperately necessary to take the high requirement of the mission into account while determining location of depots. Based on this, we raise an optimal depot location model. First, the expected transportation cost is calculated.Next, factors in ILS such as response time, availability and fill rate are analyzed for evaluating positions of open depots. Then, an optimization model of depot location is developed with the minimum expected cost of transportation as objective and ILS factors as constraints. Finally, a numerical case is studied to prove the validity of the model by using the genetic algorithm. Results show that depot location obtained by this model can guarantee the effectiveness and capability of ILS well.展开更多
The 42.1 vol. pct TiC/AZ91D magnesium-matrix composites with interpenetrating networks were fabricated by in-situ reactive infiltration process. The compressive creep behavior of as-synthesized composites was investig...The 42.1 vol. pct TiC/AZ91D magnesium-matrix composites with interpenetrating networks were fabricated by in-situ reactive infiltration process. The compressive creep behavior of as-synthesized composites was investigated at temperature ranging from 673 to 723 K under loads of 95-108 MPa. For a comparative purpose,the creep behavior of the monolithic matrix alloy AZ91D was also conducted under loads of 15-55 MPa at 548-598 K. The creep mechanisms were theoretically analyzed based on the power-law relation. The results showed that the creep rates of both TiC/AZ91D composites and AZ91D alloy increase with increasing the temperature and load. The TiC/AZ91D composites possess superior creep resistance as compared with the AZ91D alloy. At deformation temperature below 573 K, the stress exponent n of AZ91D alloy approaches theoretical value of 5, which suggests that the creep process is controlled by dislocation climb. At 598 K, the stress exponentof AZ91D is close to 3, in which viscous non-basal slip deformation plays a key role in the process of creep deformation. However, the case differs from that of AZ91D alloy when the stress exponent n of TiC/AZ91D composites exceeds 9, which shows that there exists threshold stress in the creep process of the composites, similar to other types of composites. The average activation energies for the creep of the AZ91D alloy and TiC/AZ91D composites were calculated to be 144 and 152 k J/mol, respectively. The existence of threshold stress in the creep process of the composites leads to an increase in activation energy for creep.展开更多
An artificial neural network （ANN） model is established to predict plastic flow behaviors of the 603 armor steel, based on experiments over wide ranges of strain rates （0. 001 -4 500 s -1 ） and temperatures （288 ...An artificial neural network （ANN） model is established to predict plastic flow behaviors of the 603 armor steel, based on experiments over wide ranges of strain rates （0. 001 -4 500 s -1 ） and temperatures （288 -873 K）. The descriptive and predictive capabilities of the ANN model are com- pared with several phenomenological and physically based constitutive models. The ANN model has a much better applicability than the other models in characterization of the flow stress. The tempera- ture and the strain rate effects on the flow stress can be described successfully by the ANN model, with an average error of 1.78% for both quasi-static and dynamic loading conditions. Besides its high accuracy in prediction of the strain rate jump tests, the ANN model is more convenient in model es- tablishment and data processing. The ANN model developed in this study may serve as a valid and ef- fective tool to predict plastic behaviors of the 603 steel under complex loading conditions.展开更多
基金supported by the Science Challenge Project(TZ2018007)the National Natural Science Foundation of China(71671009+2 种基金 61871013 61573041 61573043)
文摘In equipment integrated logistics support(ILS), the supply capability of spare parts is a significant factor. There are lots of depots in the traditional support system, which makes too many redundant spare parts and causes high cost of support. Meanwhile,the inconsistency among depots makes it difficult to manage spare parts. With the development of information technology and transportation, the supply network has become more efficient. In order to further improve the efficiency of supply-support work and the availability of the equipment system, building a system of one centralized depot with multiple depots becomes an appropriate way.In this case, location selection of the depots including centralized depots and multiple depots becomes a top priority in the support system. This paper will focus on the location selection problem of centralized depots considering ILS factors. Unlike the common location selection problem, depots in ILS require a higher service level. Therefore, it becomes desperately necessary to take the high requirement of the mission into account while determining location of depots. Based on this, we raise an optimal depot location model. First, the expected transportation cost is calculated.Next, factors in ILS such as response time, availability and fill rate are analyzed for evaluating positions of open depots. Then, an optimization model of depot location is developed with the minimum expected cost of transportation as objective and ILS factors as constraints. Finally, a numerical case is studied to prove the validity of the model by using the genetic algorithm. Results show that depot location obtained by this model can guarantee the effectiveness and capability of ILS well.
基金Financial supports from Natural Science Foundation （Grant No. 20032012）；Liaoning Province, China； the Scientific Research Foundation for the Returned 0verseas Chinese Scholars；State Education Ministry, China and from the Starting for New Scientific Researchers of Institute of Metal Research （IMR）；Chinese Academy of Sciences （CAS）, are gratefully acknowledged.
文摘The 42.1 vol. pct TiC/AZ91D magnesium-matrix composites with interpenetrating networks were fabricated by in-situ reactive infiltration process. The compressive creep behavior of as-synthesized composites was investigated at temperature ranging from 673 to 723 K under loads of 95-108 MPa. For a comparative purpose,the creep behavior of the monolithic matrix alloy AZ91D was also conducted under loads of 15-55 MPa at 548-598 K. The creep mechanisms were theoretically analyzed based on the power-law relation. The results showed that the creep rates of both TiC/AZ91D composites and AZ91D alloy increase with increasing the temperature and load. The TiC/AZ91D composites possess superior creep resistance as compared with the AZ91D alloy. At deformation temperature below 573 K, the stress exponent n of AZ91D alloy approaches theoretical value of 5, which suggests that the creep process is controlled by dislocation climb. At 598 K, the stress exponentof AZ91D is close to 3, in which viscous non-basal slip deformation plays a key role in the process of creep deformation. However, the case differs from that of AZ91D alloy when the stress exponent n of TiC/AZ91D composites exceeds 9, which shows that there exists threshold stress in the creep process of the composites, similar to other types of composites. The average activation energies for the creep of the AZ91D alloy and TiC/AZ91D composites were calculated to be 144 and 152 k J/mol, respectively. The existence of threshold stress in the creep process of the composites leads to an increase in activation energy for creep.
文摘An artificial neural network （ANN） model is established to predict plastic flow behaviors of the 603 armor steel, based on experiments over wide ranges of strain rates （0. 001 -4 500 s -1 ） and temperatures （288 -873 K）. The descriptive and predictive capabilities of the ANN model are com- pared with several phenomenological and physically based constitutive models. The ANN model has a much better applicability than the other models in characterization of the flow stress. The tempera- ture and the strain rate effects on the flow stress can be described successfully by the ANN model, with an average error of 1.78% for both quasi-static and dynamic loading conditions. Besides its high accuracy in prediction of the strain rate jump tests, the ANN model is more convenient in model es- tablishment and data processing. The ANN model developed in this study may serve as a valid and ef- fective tool to predict plastic behaviors of the 603 steel under complex loading conditions.
