Research on evaluating weapon systems, building structures, and personnel protection has attracted considerable attention due to the high incidence of blast accidents. The explosively driven shock tube is an affordable and replicable method for investigating high pressure blast waves and extreme shock environments. A newly constructed large caliber explosively driven shock tube with an inner diameter of 2.5 m and a length of 18 m has been documented and characterized in this paper. It is capable of providing a peak pressure of at least 5.49 MPa in the test section with 160 kg of TNT charges. The tube can produce an overpressure that is significantly higher than conventional shock tubes, which expands the capability to simulate a high overpressure blast load. A two-dimensional axisymmetric simulation model has been developed, validated, and calibrated for the characterization of the flow field inside the shock tube. The influence of the charge mass on the overpressure, arrival time, and positive impulse was discussed, and the planarity of the shock wave was also quantitatively characterized. To aid in designing further shock experiments and applications, a physics-based prediction model was developed using the dimensional analysis.

The mechanical properties of two rubber materials, RB-55 rubber and FM-32 foam rubber, were tested under quasistatic and dynamic compressive loadings with a universal testing machine and a nonmetallic split Hopkinson pressure bar (SHPB), respectively. The results show that the hyperelasticity dominates the mechanical characteristics of the both materials. And the strain rate dependencies can be observed over the wide strain rate range from 10-2 s-1 to order 103 s-1. But in the rather narrow bands of 10-2—100 s-1 and 2 • 103 —6 • 103 s-1, the strain rate effects are not significant. In order to numerically simulate rod-explosive loading tests where the two rubber materials were used as a combined buffer, the strain rate-independent hyperelastic behaviors at the strain rate of order 103 s-1 were characterized by Ogden constitutive models, incompressible for RB-55 rubber and compressible for FM-32 foam rubber, respectively. The numerical prediction of the structural responses agrees very well with the experimental results. This means the testing and modeling are successful.

Piezoelectric (PZT) stack actuators are widely used in many fields due to the advantages such as small stroke and high force output. However, failures of one or more PZT layers may exist in PZT stacks and then have influences on their performances. This paper investigates dynamic responses of normal and partially failed PZT stack actuators, in order to evaluate the influences of a failed layer at different positions and furthermore explore the rules, which is of great significance for understanding and improving the performances of partially failed PZT stack actuators. Firstly, a group of experiments were performed and responses of PZT stacks were obtained under sinusoidal voltages with DC biasing. Then a multiple degree-of-freedom (DOF) spring-mass system was built as a theoretical model which was verified by the experimental results to simulate output responses of PZT stack actuators. Based on that, the influences of a failed PZT layer at different positions in the stack were obtained by solving the model under various conditions. The results reveal that the farther the failed PZT layer is from the fixed end, the more significant the influences on the displacement or force output of the PZT stack are. Moreover, the rules of influences of a failed PZT layer at different positions were expressed as a general formula which can be used to better understand, evaluate or identify health conditions of PZT stack actuators.

In order to ensure the reliability and accuracy of long-term temperature measurement where the thermometers are discommodious or even impossible to access for conventional periodical calibration, a study on miniaturized in-situ self-calibrated (MISSC) thermometers based on Ga and Ga-Zn fixed points was conducted using temperature scale transfer technology. One MISSC thermometer consists of three parts: the first is the fixed-points hardware, including a container with two cells separately filled with Ga and Ga-Zn; the second is the temperature sensing hardware, made of a Type T thermocouple; the third is the mini-power heating hardware, made of a film resistance. The measurement and calibration (M&C) system comprises a temperature measurement and data processing subsystem and a mini-power heating control subsystem. Then, an in-situ self-calibration can be carried out by mini-power heating from a room temperature of about 20 °C, and then by comparison between the measured phase transition plateau results and the standard fixed-points, i.e., Ga fixed point (about 29.76 °C) and Ga-Zn fixed point (about 25.20 °C). A series of experiments were performed, and the results show that: (1) both the proposed hardware design and the self-calibration method are feasible, and (2) the Φ16 mm × 25 mm MISSC thermometer is found to be the most miniaturized one that can realize reliable self-calibration in this study.

Piezoelectric (PZT) stacks are extensively applied due to the advantages such as fast response and high precision. The dynamic characteristics of PZT stacks are of vital importance, and one of the most important aspects, velocity output, especially the velocity limit, can determine the dynamic characteristics limits of various PZT stack actuators. However, there is almost no systematic research on the velocity limit of a single PZT stack, which may vary with various factors. This paper investigates the velocity limits of PZT stacks via step and staircase driving voltages, in order to explore the influencing factors of the velocity limit of a single PZT stack and establish a theoretical model to describe the dynamic characteristics of a PZT stack well. Firstly, a group of experiments were performed and the influencing factors of the velocity limits of PZT stacks were analyzed. The results reveal that the velocity limits of PZT stacks are related to the thickness of the PZT layer, the voltage difference and the direction of motion. Then, the multi-degree-of-freedom spring-mass-damper system was established as a theoretical model to characterize the step responses of the velocity output of a PZT stack, which was verified by the experimental data in time domain. A unified prediction model in a linear function form was established to summarize the influencing factors of the velocity limits of PZT stacks, which can be used to predict the velocity limits of PZT stacks quickly and precisely. The results of this research can promote the theoretical research on the dynamic characteristics of PZT stacks and provide a theoretical basis for the joint modeling of PZT stacks and other mechanisms, which can be expected to further promote the performance prediction and optimization of various PZT stack actuators.

The duration of an explosion shock wave is a critical parameter in actual explosion scenarios. Insufficient attention has been paid to its influence on surface loading and the consequent damage effects. To investigate how blast wave duration impacts shell pressure loading, we conducted a numerical analysis of fine flow structures and pressure-loading distributions during blast wave interactions with cylindrical shells using high-order large-eddy simulation. The research findings demonstrate that the interaction of explosive waves with cylindrical shells leads to reflected shock waves, expansion waves, decelerating shock waves, and Mach stems. The inherent structural differences within this wave system led to a correlation between the angle and height of the surface load exerted on the shell. The increase in duration enhances the reflected shock wave and results in the more complex and variable wake vortex and shock wave structures on the shell leeward, which enhances the pressure-loading oscillation on the shell leeward. The research also revealed that when the duration surpasses a specific critical threshold, various forms of stationary shock waves will be generated. The structure of the flow field and the surface loads will remain steady-state as the duration continues to extend.