Issue 42

J.-f. He et alii, Frattura ed Integrità Strutturale, 42 (2017) 263-271; DOI: 10.3221/IGF-ESIS.42.28 266 Abrasion theory The complete abrasion theory was proposed by Archard, and was optimized by Rowe in 1995 [16-18]. While the hydraulic DTH hammer is operated in horizontal directional well drilling, the oriented slider is reciprocally abraded by external cylinder with high frequency. The volumetric wearing capacity V can be derived from Eq. 1, which is closely related to the friction coefficient, lubrication coefficient and the load. β αµ = + 2 (1 ) m WL V k H (1) Where, m k , α denotes the constant, dimensionless; β denotes the lubrication coefficient, dimensionless; µ denotes the friction coefficient, dimensionless; W denotes the applied load of oriented slider, MPa, and H denotes the Brinell Hardness, HBW. The formula of abrasion theory is feasible to the wear of horizontal oriented sliders, thus the friction coefficient, applied load and the moving velocity of oriented slider were employed as the variables while in the simulation of abrasion property of the anvil with horizontal oriented slider. FEA SIMULATION here are totally 3 variables used in the simulation, which are friction coefficient, moving velocity and applied load, respectively. Each variable has at least 5 models in numerical simulation. In order to obtain the abrasion rate of the anvil inside hydraulic DTH hammers with horizontal oriented slider, the numerical modelling, meshing and solving process are successfully completed. Numerical Modelling and Meshing As shown in Fig. 3, the numerical model of the anvil with oriented sliders was developed by software ANSYS 2014 according to the parameter of a 203mm hydraulic DTH hammer. The material models of external cylinder and oriented slider were defined as 35CrMo and Teflon with carbon fiber, respectively. There are totally 6 horizontal oriented sliders are evenly distributed along the outer circle of the anvil, and the parameter of oriented slider is × 80 36 mm mm . In end, 3 groups of material models are established in whole, as shown in Tab. 1. Figure 3 : Numerical model and meshes of a hydraulic DTH hammer with horizontal oriented sliders. The numerical model was quarterly symmetric in order to reduce the computational time. In addition, the deformation of oriented slider and external cylinder is defined as plane strain problem. The numerical model was meshed with 3D structure cell SOLID 185, and the contact cells between oriented slider and external cylinder are defined as Contact 174. Furthermore, the grids of contact region should be refined, which contributes to the improvement of simulation results. Thus the grids type of contact region was defined as surface-to-surface contact, which is termed as Target 170 in ANSYS, as shown in Fig. 4. The cells of horizontal oriented slider are in red, and the cells of external cylinder are in blue. T