Search

A high-performance titanium alloy requires a fine and homogenous microstructure. The rational deformation process parameters of the Ti-3Al-5Mo-4.5V (TC16) titanium alloy can contribute to achieving this important microstructure. Hot-compression experiments were performed at temperatures in the range 100–800 °C and at strain rates of 0.1 s–1 to 10.0 s–1. The effects of deformation temperatures and deformation rates on the mechanical behaviour and microstructure evolution were analysed and discussed. The softening mechanism of the Ti-3Al-5Mo-4.5V alloy at an elevated deformation temperature was revealed. Experimental results showed that 500 °C is the critical deformation temperature to distinguish the warm-deformation region of 100–400 °C and the hot-deformation region of 500–800 °C. The softening mechanism is dominated by -phase spheroidization in the temperature range 100–400 °C with a higher strain rate of 10.0 s–1. The softening mechanism is dominated by a local temperature rise in the temperature range 500–800 °C with a lower strain rate of 0.1 s–1.

The phase component, microstructure and compressive properties of a novel 3d transition metal high entropy alloy, AlCoCrCuTi, in as-cast and annealed conditions were investigated. The phases of the as-cast AlCoCrCuTi alloy are composed of primary phase AlCo2Ti (L21), eutectic structure {AlCo2Ti (L21)+ Al3Cr7 (BCC)} and interdendritic phase AlCu2Ti (L21). Through annealing, a rosette feature of the as-cast AlCo2Ti + Al3Cr7 eutectic structure is deteriorated due to the lath-like Al3Cr7 changed to finely-divided one. In mechanics performance, the as-cast alloy exhibits a balanced synergy in hardness (593±37 HV) and ultimate strength (745 MPa), while the hardness of the annealed alloy slightly increases to 647±23 HV at the expense of the ultimate strength. Moreover, the alloy either in as-cast or annealed conditions unfortunately display a typically brittle character. The deficiency of elongation might stem from the diversified brittle and hard phases incorporated, such as AlCo2Ti + Al3Cr7.

Different constitutive modeling methods lead to different prediction accuracy of stress-strain relationships for hot metal forming. The aim of this work is to establish constitutive model using two methods of double multiple nonlinear regression model (DMNR) and strain-compensated Arrhenius-type constitutive model (SACM) to describe the material flow behaviour of TC16 titanium alloy under hot compression in the strain rate range of 0.1 s − 1 ∼ 10.0 s − 1 and temperature range of 973 K ∼ 1373 K . A comparative study has been conducted on the prediction capability of DMNR model and SACM model under different temperature ranges, and their prediction accuracy was quantified by using standard statistical parameters such as correlation coefficient ( R ), average absolute error ( A A R E ) and root mean square error ( R M S E ). The results showed that the DMNR model has a better prediction accuracy to describe the stress-strain relationship than SACM model at temperature range of 973 K ∼ 1373 K . It indicates that DMNR model is more suitable in a wider range of deformation temperature. When the constitutive models of TC16 titanium alloy were developed at temperature range of 1173 K ∼ 1373 K , SACM model has more excellent predictability than DMNR model. It indicates that SACM model is more suitable to describe the stress-strain relationships in a narrow range of deformation temperature.

In order to give full play to the overall efficiency of freeway networks and raise the level of operation and service, freeway management is faced with higher requirements and greater challenges than ever before. This paper proposes a general method of traffic state estimation, one key step of management, which is significant and fundamental. Through the study on the stochastic nonlinear second-order macroscopic traffic flow model and Extended Kalman Filter (EKF), the system model presented in this paper performs well in traffic state estimation which can provide scientific bases and technical strategies for the control of freeway network. Also, the detailed performance evaluation on the model is one of the main achievements. The evaluation includes statistical indices, distances, time intervals, initial values and so on.

This paper develops a theoretical mathematical model based on the mean demand of boarding and exiting per unit length along a bus corridor to decrease the travel time of transit travelers. The solution procedure of the proposed model is also presented. In order to demonstrate the effectiveness of the model, research on a real transit corridor in Foshan City, China was conducted. The analysis of results shows that the boarding and exiting time was the most influenced by the locations of bus stops. Arranging bus stops based on equilibrium distribution of passenger flow can minimize the boarding and exiting time.