# Fretting Fatigue Experiment and Finite Element Analysis for Dovetail Specim at High Temperature
###### Abstract
The later form has obvious advantages; firstly, the worn fretting pads can be quickly replaced; secondly, the material and shape of fretting pads can be easily changed. Based on this form, the paper completed the fretting fatigue test using the actual blade and disk materials in the aero-engine at high temperature. During the fretting fatigue test, fretting wear will inevitably occur on the contact surface [23]. Fretting wear is affected by many factors [24], among which temperature is an important one for the dovetail attachment in the aero-engine. High temperature will cause an oxide layer on the contact surface, which will participate in the process of fretting wear [25]. Both the depth of fretting wear and the initial crack position will be affected by the oxide layer. Therefore, the presence of the oxide layer will lead to different degrees of wear at different areas, and there will be a theoretical partition phenomenon on the fretting surface [14]. This phenomenon was observed in the present experimental study and analyzed combined with numerical computation. Numerical computation analysis of the fretting fatigue experiment was usually carried out with finite element method [26; 27; 28; 29]. It is clear that the finite element model needs to have a very fine mesh on the contact surface to ensure the accuracy, which leads to a reduction of efficiency greatly. Hence, most of the studies sacrificed some accuracy to improve the efficiency by using a 2D model instead of a 3D model [14; 22], creating  
Figure 1: Illustration of different fretting fatigue arrangements. (**a**) Bridge-type; (**b**) block-type; (**c**) dovetail-type; (**d**) dovetail-type with pads. sub-modeling [30], and the method of semi-analytical [31]. Although these methods can speed up the numerical calculation, this paper adopts the fully 3D finite element model of the original structure to obtain a more accurate stress distribution on the contact surface. During the analysis, augmented Lagrange algorithm methods of representing the contact constraints were used and it is finally confirmed that the calculated results are in good agreement with the experimental results. The paper aims to study the fretting fatigue behavior of dovetail specimens in contact with fretting pads at high temperature. A set of clamping structures for the specimens and heating coils are designed for the fretting fatigue experiment. Surface morphologies of the fretting wear are observed through the scan electron microscopy (SEM). Finite element method (FEM) analysis considering crystal plasticity is applied to the contact state and stress distribution. Moreover, the theoretical partition phenomenon on the contact surface caused by the different degrees of fretting wear is observed and confirmed in the experimental investigation. This paper is arranged as follows. The experimental details are introduced and analyzed in Section 2. Section 3 discusses the method of numerical calculation elaborately. In Section 4, the experimental results are mainly stated including the fitted curve for the fretting fatigue life and the observation results using SEM. In Section 5, the numerical calculation results based on the finite element method are analyzed and compared with the experimental results. Section 6 summarizes and concludes the present research.