In order to locate a reasonable heating system, the austenite grain growth behavior of Nb microalloyed medium carbon steel has been experimentally studied at various austenitizing temperatures and for different holding times. It is indicated that austenite grain growth increases with increasing austenitizing temperatures and holding times. Particularly when the austenitizing temperature was above 1100 °C, austenite grains grew rapidly, and an abnormal austenite grain growth was observed. When the austenitizing temperature was lower than 1100 °C, austenite grain size and growth rate were small. The activation energy of grain growth in the tested steel is 397 679.5 J/mol. To ensure an absence of coarse grains in microstructures, the heating technology of the tested steel should be controlled for 1 h at 1100 °C. The relationships of austenite average grain size with soaking temperature and time of tested steel were obtained by mathematical calculation, and austenite average grain size was found to be in agreement with the measured size for different holding times.

The structural properties, mechanical behavior, and electronic structure of the newly developed diamondlike BC₅ (d-BC₅) was investigated using density functional theory (DFT) calculations. The results indicate that d-BC₅ has great bulk modulus of 393 GPa, large shear modulus of 398 GPa, and high hardness of 62 Pa, and thus support the fact that d-BC₅ is an ultra-incompressible and superhard material. Remarkably, the superhard d-BC₅ exhibits metallic features. Furthermore, the trend that the mechanical behavior falls with the increase of boron content was revealed. The combination of huge stiffness, high hardness, and good metallicity makes series of diamondlike BC_x (d-BC_x) valid for wider applications in comparison with pure diamond.

This work aims to study the springback behaviour of electrogalvanised (EG) steel sheets during the air bending process. Experiments have been conducted to analyse the influence of various parameters such as coating thickness, orientation of the sheet, punch radius, die radius, die opening, punch velocity, and punch travel on springback behaviour. It is established that the springback increases with increasing coating thickness, punch radius, punch travel, die radius, die opening, and punch velocity. The 90° orientation exhibits higher springback than 0° orientation.

A multi-loop adaptive internal model control (IMC) strategy based on a dynamic partial least squares (PLS) framework is proposed to account for plant model errors caused by slow aging, drift in operational conditions, or environmental changes. Since PLS decomposition structure enables multi-loop controller design within latent spaces, a multivariable adaptive control scheme can be converted easily into several independent univariable control loops in the PLS space. In each latent subspace, once the model error exceeds a specific threshold, online adaptation rules are implemented separately to correct the plant model mismatch via a recursive least squares (RLS) algorithm. Because the IMC extracts the inverse of the minimum part of the internal model as its structure, the IMC controller is self-tuned by explicitly updating the parameters, which are parts of the internal model. Both parameter convergence and system stability are briefly analyzed, and proved to be effective. Finally, the proposed control scheme is tested and evaluated using a widely-used benchmark of a multi-input multi-output (MIMO) system with pure delay.

In injection moulding production, the tuning of the process parameters is a challenging job, which relies heavily on the experience of skilled operators. In this paper, taking into consideration operator assessment during moulding trials, a novel intelligent model for automated tuning of process parameters is proposed. This consists of case based reasoning (CBR), empirical model (EM), and fuzzy logic (FL) methods. CBR and EM are used to imitate recall and intuitive thoughts of skilled operators, respectively, while FL is adopted to simulate the skilled operator optimization thoughts. First, CBR is used to set up the initial process parameters. If CBR fails, EM is employed to calculate the initial parameters. Next, a moulding trial is performed using the initial parameters. Then FL is adopted to optimize these parameters and correct defects repeatedly until the moulded part is found to be satisfactory. Based on the above methodologies, intelligent software was developed and embedded in the controller of an injection moulding machine. Experimental results show that the intelligent software can be effectively used in practical production, and it greatly reduces the dependence on the experience of the operators.

A micro turbo-expander capable of high working speed was specially manufactured for use in an organic Rankine cycle (ORC). A series of tests were executed to examine the performance of the machine. In the experiment, the machine was tested under different inlet pressure conditions (0.2–0.5 MPa). Data such as the compressed air pressure, temperatures of the inlet and the outlet, rotational speed, and electric power generation were analyzed to discover underlying relationships. During the test, the rotational speed of the machine reached as high as 54 000 r/min, the peak value of the temperature drop between the inlet and the outlet reached 42 °C, the maximum electric power generated by the motor-generator attached to the machine reached 630 W, and the efficiency of the machine reached 0.43.

Thermal fatigue (TF) is one of the most important factors that influence turbine’s life. This paper establishes a 3D solid-fluid coupling model for a steady temperature analysis of a high-pressure turbine nozzle at different turbine inlet gas total temperatures (TIGTTs). The temperature analysis supplies the temperature load for subsequent 3D finite element analysis to obtain the strain values. Following this, the prediction of the TF life is made on the basis of equivalent strain range. The results show that the strain increases with TIGTT, and the predicted TF life decreases correspondingly. This life prediction was confirmed by one TF test.

Commercialized capsule-type endoscopes move passively by peristaltic waves (and gravity), which makes it difficult for doctors to diagnose the areas of interest more thoroughly and actively. To resolve this problem of passivity, it is necessary to find a special locomotion principle, which fits the gastrointestinal (GI) tract. In this paper, a legged locomotive mechanism with shape memory alloy (SMA) actuation based on the peristaltic principle is proposed, and then the structure of the locomotion mechanism is introduced. Based on the preliminary results, the design, modeling, and fabrication of an SMA microactuation concept for application in an endoscopic capsule are given, as well as the SMA spring and legged component design, which is the core section of the system design. We used the pseudo-rigid-body model (PRBM) to analyze nonlinear and large deflections of the SMA legged component. Thus, a prototype endoscope with an SMA spring and six legged components was designed and fabricated. It is 15 mm in diameter and 33 mm in total length, with a hollow space to house other parts needed for endoscopy such as a camera, a radio frequency (RF) module, and sensors. During testing, the locomotive mechanism was effective in a plastic tube environment.

Gas-liquid coupling oscillation is a novel approach to reducing the resonant frequency and to elevating the pressure amplitude of a thermoacoustic engine. If a thermoacoustic engine is used to drive low-frequency pulse tube refrigerators, the frequency matching between the thermoacoustic engine and the refrigerator plays an important role. Based on an acoustic-electric analogy, a lumped parameter model is proposed to estimate the resonant frequency of a standing-wave thermoacoustic engine with gas-liquid coupling oscillation. Furthermore, a simplified lumped parameter model is also developed to reduce the computation complexity. The resonant frequency dependence on the mean pressure, the gas space volume, and the water column length is computed and analyzed. The impact of different working gases on the resonant frequency is also discussed. The effectiveness of the models is validated by comparing the computed results with the experimental data of the gas-liquid coupling oscillation system. An increase in the mean working pressure can lead to a rise in the resonant frequency, and a lower resonant frequency can be achieved by elongating the liquid column. In comparison with nitrogen and argon, carbon dioxide can realize a lower frequency due to a smaller specific heat ratio.

Simulation for stochastic wind field is very important in analyzing dynamic responses of large complex structures due to strong wind. The typical simulation method is the spectrum representation method (SRM), but the SRM has drawbacks of inferior precision in lower frequency and slow calculating speed. In view of this, the modified Fourier spectrum method (MFSM) is introduced into the simulation of stochastic wind field in this paper. In this method, phase information of wind velocity time history is determined by cross power spectral density (CPSD) between adjacent points, and the wind velocity time history with time and space correlation is generated by iterative modification for CPSD considering auto power spectral density (APSD). Simulation of the wind field for a long-span bridge is undertaken to verify the effectiveness of the MFSM. Simulation results of the SRM and the MFSM are compared. It can be concluded that the MFSM is more accurate and has higher calculation speed than the SRM.