## 1 Introduction  
Electromagnetic launch technology is a new concept for an acceleration method that has been rapidly developed in recent years. Due to the technical advantages of fast speed, high efficiency, rapid start and good reliability, it has a wide application prospect in both military and civil fields [1, 2]. Electromagnetic launch technology can be divided into the electromagnetic ejection technology, electromagnetic pushing technology and electromagnetic track launch technology according to the launch length and acceleration degree [3]. So far, the electromagnetic track launch technology is regarded as one of the effective means to enhance the tactical combat capability of conventional weapons in the future. Owing to good development prospects and technical advantages, it is an important research direction in the field of electromagnetic launch. An electromagnetic track launcher can increase the armature to a high speed within tens of milliseconds, which leads to a relatively complex experimental environment, and the research is relatively dependent on numerical simulation calculation [4, 5, 6, 7]. Therefore, in order to achieve further popularization and application, how to improve the calculated accuracy of the simulation model and achieve full true simulation calculation is the key issue to be solved at present. In the actual working process of the electromagnetic track launcher, extreme conditions such as high frequency, high current and the high temperature rise gradient generated will lead to distortion of material parameters rather than maintaining a constant. The influence of dynamic parameters on the launcher cannot be ignored. Therefore, it is necessary to comprehensively consider the output under the influence of dynamic parameters so as to make it closer to the actual launch condition. On the dynamic parameters of the electromagnetic track launcher, a lot of research in related fields has been carried out. Because the calculated equation of the armature electromagnetic force is directly related to the inductance gradient, the current research mainly focuses on the calculation of the dynamic inductance gradient. In the early studies, [PERSON] et al. [8; 9] suggest that the inductance gradient is only related to the track size. When the track size is unchanged, the inductance gradient is also unchanged. [PERSON] et al. [10] analyze the distribution of the inductance gradient with current frequency. [PERSON] et al. [11] consider the velocity skin effect and calculated the dynamic inductance gradient by introducing a velocity frequency. [PERSON] et al. [12] propose an analytical calculated method for the inductance gradient which comprehensively considers the influence of the guide track size and current diffusion. However, in the actual working process, the temperature of the launcher will rise rapidly due to high frequency and high current. Under the influence of high temperature and high temperature rise gradient, the conductivities of the armature and track will undergo an enormous change, which will have an impact on the armature velocity and inductance gradient. The above references have carried out sufficient theoretical analysis on the electromagnetic track launcher, but do not consider the influence of high temperature on the conductivity of the launcher. [PERSON] et al. [13] give the inductance gradient with different conductivities, but do not consider the influence of the dynamic conductivity on the inductance gradient. There are few studies on dynamic conductivity in recent years, therefore, this paper firstly analyzes the correlation among the physical quantities such as temperature, conductivity, armature velocity and inductance gradient by using the finite element method, and the improved model of dynamic conductivity electromagnetic-thermal coupling is established on this basis.