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The coiled tubing injector head is the core component of the coiled tubing oil and gas well operation equipment, which directly determines the coiled tubing operation capability, and its chain drive system pulls the coiled tubing in or out the wellbore. However, the unsteady chain drive and the wear between the chain and sprocket are common problems which are the main factors leading to slipping, pipe sliding and bites of coiled tubing in engineering practice. Based on the standard roller chain and sprocket, the mechanical model of the engagement contact between the injector head chain and the sprocket teeth is established to analyze the influence of chain tension force, chain tension angle and chain pitch on the position of contact points and tooth surface support reaction force, and the accuracy of the contact mechanical model is verified by Ansys simulation which lays a theoretical foundation for the design and safety of the injector. The research shows that when the tension force of the chain increases and the loosening force remains unchanged, the engaging-in position of the chain on the tension side is basically unchanged, the reaction force of the tooth surface support increases, and the engaging-out position of the chain rollers is close to the bottom of the sprocket teeth. However, when the tension force approaches the loosening force, there is a sudden increase in the support reaction force of the engaging-out contact position. The increase of the angle between the tension side and the vertical direction of the chain has little effect on the engaging-in position and the tooth surface support reaction force, the engaging-out position of the chain rollers is close to the bottom of the sprocket teeth. The engaging in and out points of the chain are respectively away from the direction of the bottom of the sprocket teeth and the contact position is improved when the chain is extended.

A porous microplate embedded with two nanocomposite piezoelectric layers is investigated in the current work. All three layers are functionally graded and completely attached to each other, and the microstructure lies on a bi-parameter elastic foundation that withstands shear and normal forces simultaneously. Also, an external voltage is subjected to the piezoelectric patches. The mentioned patches are reinforced with carbon nanotubes to enhance their electro-mechanical performance. A higher-order shear deformation theory and von Karman's assumptions are hired to demonstrate the kinematic relations. Next, applying Hamilton's principle and variational technique, the governing motion equations are derived with the help of the modified couple stress theory to capture the scale influence. To solve the system of differential equations, a closed-form Navier method is employed, and by ensuring the correctness of the results, then it turns to investigate the impact of different factors including porosity percentage and also pores' distribution patterns, nanotubes dispersion patterns, and other important factors on the natural frequencies of the model. Obtained results show that symmetric and uniform porosity distributions have the maximum and minimum amounts of natural frequencies. Moreover, the maximum difference between natural frequencies of three different porosity distribution occurs in e0 = 0.95 and is approximately 32%. The current study results may consider to design and produce smart structures and devices with improved performance. [ABSTRACT FROM AUTHOR]

Present study deals with the nonlinear analysis of thermally induced deflection and snap-through buckling in functionally graded porous (FGP) curved nanotubes. It is assumed that the curved nanotube is rested on a two-parameter nonlinear elastic foundation. The curved nanotube is subjected to uniformly distributed transverse pressure loading and also uniform temperature rise. Distribution of thermomechanical properties in the thickness of curved nanotubes is radially graded according to a power law function. The even type of porosity distribution patterns is included into the formulation and all properties are considered as temperature dependent. The nonlocal strain gradient and uncoupled thermoelasticity theories are provided to analyze the geometrically nonlinear behaviors of curved nanotubes. The equilibrium equations are obtained based on the high-order shear deformation theory. To capture the large deformations, the von Kármán type of nonlinear kinematic assumptions is included. Two types of immovable boundary conditions are considered which are simply-supported and clamped-clamped. The equilibrium equations are reformulated and transferred into the dimensionless presentation. The closed-form expressions are provided to trace the thermal/mechanical load-deflection paths of curved nanotubes using the two-step perturbation technique. Numerical results of this study are compared with the available data in the literature for the macro-scale curved tubes. After that novel parametric results are provided to discuss the effects of nonlocal and length scale parameters, boundary conditions, porosity coefficient, foundation stiffness, power law exponent, and geometrical parameters. [ABSTRACT FROM AUTHOR]