In order to increase the efficiency of magnetorheological (MR) valves, Ai et al (2006) proposed an MR valve simultaneously possessing annular and radial fluid flow resistance channels with the assumption that the magnetic flux densities at the annular and radial fluid flow gaps are identical. In this paper, an MR valve simultaneously possessing annular and radial fluid flow resistance channels is designed, fabricated, modeled and tested. A model for the developed MR valve is produced and its performances are theoretically predicted based on the average magnetic flux densities in the annular and radial fluid flow gaps through finite element analysis. The theoretical results for the developed MR valve are compared with the experimental results. In addition, the performances of the developed MR valve are theoretically and experimentally compared with those of the MR valve with only annular fluid flow gaps. It has been shown that the theoretical results match well with the experimental results. Mainly attributed to the radial fluid flow gaps, the pressure drops across the MR valve with both annular and radial fluid flow gaps are larger than those across the MR valve with only annular fluid flow gaps for varying valve parameters. The radial fluid flow gaps in the MR valve can reach a higher efficiency and larger controllable range than those by annular fluid flow gaps to some extent.

In order to characterize the hysteretic characteristics between the output displacement and applied voltage of pre-stressed piezoelectric ceramic stack actuators (PCSAs), this paper considers that a linear force and a hysteretic force will be generated by a linear extension and a hysteretic extension, respectively, due to the applied voltage to a pre-stressed PCSA and the total force will result in the forced vibration of the single-degree-of-freedom (DOF) system composed of the mass of the pre-stressed PCSA and the equivalent spring and damper of the pre-stressed mechanism, which lets the PCSA be pre-stressed to endure enough tension. On this basis, the phenomenological model to characterize the hysteretic behavior of the pre-stressed PCSA is put forward by using the Bouc-Wen hysteresis operator to model the hysteretic extension. The parameter identification method in a least-squares sense is established by identifying the parameters for the linear and hysteretic components separately with the step and periodic responses of the pre-stressed PCSA, respectively. The performance of the proposed phenomenological model with the corresponding parameter identification method is experimentally verified by the established experimental set-up. The research results show that the phenomenological model for the pre-stressed PCSA with the corresponding parameter identification method can accurately portray the hysteretic characteristics of the pre-stressed PCSA. In addition, the phenomenological model for PCSAs can be deduced from the phenomenological model for pre-stressed PCSAs by removing the terms related to the pre-stressed mechanisms.

For the wear problem of artillery barrel bore during artillery launching, this work uses particle erosion and deposition modules in Fluent Software to simulate the erosion process of gunpowder gas particles on artillery barrel, analyses steady and transient states simulation results, and compares the effects of different influencing factors on barrel bore wear. The results showed that in a certain range, the erosion rate of barrel bore wall was positively correlated with particle velocity and mass flow. 0.25 mm was a critical particle size, and the erosion rate decreased with the increase of particle diameter. This information is valuable for prolonging the service life of artillery barrel.