Issue 27

H. Liu et alii, Frattura ed Integrità Strutturale, 27 (2014) 53-65; DOI: 10.3221/IGF-ESIS.27.07 59 Thread circumference at the minor diameter:     2 162.48 141.31 2 2.831 149.064 c L s D D D h mm        Lead of thread: 1 / 25.4 4 6.35 L inch n mm mm    Helix angle: arctan arctan6.35 149.064 0.01356 c L D        Max output torsional moment of Kelly spinner: 2200 T N m   Axial force:     3 2200 254974 149.064 10 tan tan 0.01356 6.59 2 2 c T N m F N D m               Top plane dimensions of the fluidic amplifier: 2 9107 S mm  The axial static pressure on the fluidic amplifier: 2 254974 28 9107 F N P MPa S mm    In the section of Implicit analysis , the axial static pressure at the top of the fluidic amplifier was 28 MPa. Connection style and size Thread form Taper Half angle Threads per 25.4 mm Thread height truncated Large dia. of pin Small dia. of pin T  n h L D S D 5 1/2 IF V-065 1/6 30° 4 2.831 162.48 141.31 (Dimensions in millimeters, unless otherwise specified) Table 2: The main parameters of API 5 1/2 IF thread. S TRUCTURE STRENGTH ANALYSIS USING FEA tructural implicit-to-explicit sequential solutions can be used for a broad range of engineering problems, wherein the initial static stress state of the structure affects its dynamic response in ANSYS LS-DYNA [15,23]. In this implicit-to-explicit sequential solution, a calculated drilling fluid pressure of 0.7 MPa and an axial static pressure 28 MPa are set to be preloads in the ANSYS implicit analysis. The nodes of any element that are only used in the explicit analysis were completely constrained. The information of nodes and elements obtained from the ANSYS implicit solver are written in the ANSYS LS-DYNA dynamic relaxation file. The explicit analysis can be conducted after setting the initial velocity at 1.85 m/s and other calculated conditions. The explicit solver uses the displacement results stored in the relaxation file for the stress initialization of the model. The explicit analysis begins at time zero with a stable preloaded structure. Then the explicit analysis can be solved and completed. Mesh model Material Density (kg/m 3 ) Elastic modulus (MPa) Poisson ratio Element type (Implicit) Element type (Explicit) Material model (Implicit) Material model (Explicit) Fluidic amplifier WC- 11Co 1.42e+4 6.0e+5 0.22 Solid 185 Solid164 Linear elastic model Bilinear isotropic hardening model Cylinder 35CrMo 7.76e+3 2.07e+5 0.3 Linear elastic model Impacting body Rigid model Rigid model Table 3 : Material and element properties of the components S