Water-lubricated rubber bearings are widely used in the propulsion shafting of military craft and ships. These bearings may wear down after a period of service, and consequently, their lubrication characteristics will change, affecting the operation of the shaft. Hydrodynamic lubrication characteristics of water-lubricated rubber bearings with partial wear at the bottom are studied by finite difference method. The steady-state characteristics of water-lubricated rubber bearings with wear and elastic deformation of rubber liner considered are solved with successive over-relaxation iteration method, and the dynamic characteristics are further calculated with finite perturbation method. The results show that water film thickness and distribution of water film pressure is significantly changed by wear. With the same eccentricity ratio, the maximum water film pressure, load capacity, attitude angle, and friction force are reduced by wear, but the friction coefficient is increased by wear. Under the same load, the minimum water film thickness and the maximum water film pressure are slightly affected by wear, the eccentricity ratio increases with the increase of wear, and the attitude angle and the friction coefficient decrease with the increase of wear. For large eccentricity ratios, the direct stiffness coefficients and direct damping coefficients are decreased by wear. The maximum allowable wear depth is approximately 1/6 of the bearing clearance.

This paper deals with the effect of termination restraint due to end fitting on the stress evaluation of tensile armors in unbonded flexible pipes under axial tension. The problem is characterized by one single armoring tendon helically wound on a cylindrical supporting surface subjected to traction. The deviation from the initial helical angle is taken to describe the armor wire path as the pipe is stretched. The integral of this angle change gives the lateral displacement of the wire, which is determined by minimizing the energy functional that consists of the strain energy due to axial strain, local bending and torsion, and the energy dissipated by friction, leading to a variational problem with a variable endpoint. The governing differential equation of the wire lateral displacement, together with the supplementary condition, is derived using the variational method and solved analytically. The developed model is verified with a finite element (FE) simulation. Comparisons between the model predictions and the FE results in terms of the change in helical angle and transverse bending stress show good correlations. The verified model is then applied to study the effects of imposed tension and friction coefficient on the maximum bending stress. The results show that the response to tension is linear, and friction could significantly increase the stress at the end fitting compared with the frictionless case.

Assembled hollow camshaft can be manufactured through hydrojoining process which has the advantages including joining multiple elements onto a tube in once loading, high joining strength, efficiency, and precision. The method of improving joining strength by using cams with noncircular hole was presented. Through numerical simulation and experiment, plastic deformation law of hydrojoining process was studied. The displacement of cam and tube, and the profile dimension change of cam during hydrojoining were obtained. The effect of hole shape of cams on joining strength was analyzed. The assembled hollow camshafts with casting iron cams used for a car engine and those with quenched steel cams for a truck engine were successfully manufactured using hydrojoining technology.

Large, complex, expensive, and long-lived equipment often operate in harsh environments, which leads to the requirements of lifecycle maintenance, repair, and overhaul (MRO). To support the continuous improvement of productivity and to reduce the cost of MRO, this paper developed a cloud-based framework for lean MRO of the equipment with the aforementioned characteristics. A concept and a model of lean MRO are proposed. Taking advantage of cloud-based design and manufacturing (CBDM) into account, an architectural framework of cloud-based MRO is proposed. A case of a lean MRO for continuous casting equipment demonstrates that the proposed cloud-based framework can achieve the goal of lean MRO of complex equipment.

The magnetically suspended rotor (MSR) in a double-gimbal magnetically suspended control moment gyro (DGMSCMG) is a complicated system with multivariable, nonlinearity, and strong coupling. Not only the torsional motion of the MSR is coupled depend on the rotating speed but also its translational and torsional motions at the same axis are coupled due to the asymmetric position stiffness of magnetic bearings. Besides, the MSR also encounters the nonlinear coupling torque due to gimbals' movements. These problems influence the control accuracy of the MSR. To resolve these issues, this work presents a high-precision control strategy. A compensation method for asymmetric position stiffness is proposed to realize separation between the translational and torsional motions. Then the integral sliding mode control based on motion separation (MSISMC) is employed to stabilize the translational and torsional dynamics. To suppress the coupling torque from gimbals' movements, a novel switching function considering the estimation of the coupling torque is designed in torsional controller, and the decoupling control for the torsional motion is implemented by pole assignments. The stability of the closed-loop MSR control system is analyzed by the Lyapunov and state space methods. Comparative simulations and experiments verify the effectiveness and superiority of the proposed control strategy.

When we touch an object, surface loads imposed on the skin are transmitted to thousands of specialized nerve endings (mechanoreceptors) embedded within the skin. These mechanoreceptors transduce the mechanical signals imposed on them into a neural code of the incident stimuli, enabling us to feel the object. To understand the mechanisms of tactile sensation, it is critical to understand the relationship between the applied surface loads, mechanical state at the mechanoreceptor locations, and transduced neural codes. In this paper, we characterize the bulk viscoelastic properties of the primate finger pad and show its relationship to the dynamic firing rate of SA-1 mechanoreceptors. Two three-dimensional (3D) finite element viscoelastic models, a homogeneous and a multilayer model, of the primate fingertip are developed and calibrated with data from a series of force responses to micro-indentation experiments on primate finger pads. We test these models for validation by simulating indentation with a line load and comparing surface deflection with data in the literature (Srinivasan, 1989, “Surface Deflection of Primate Fingertip Under Line Load,” J. Biomech., 22(4), pp. 343–349). We show that a multilayer model with an elastic epidermis and viscoelastic core predicts both the spatial and temporal biomechanical response of the primate finger pad. Finally, to show the utility of the model, ramp and hold indentation with a flat plate is simulated. The multilayer model predicts the strain energy density at a mechanoreceptor location would decay at the same rate as the average dynamic firing rate of SA-1 mechanoreceptors in response to flat plate indentation (previously observed by Srinivasan and LaMotte, 1991 “Encoding of Shape in the Responses of Cutaneous Mechanoreceptors,” Information Processing in the Somatosensory System (Wenner-Gren International Symposium Series), O. Franzen and J. Westman, eds., Macmillan Press, London, UK), suggesting that the rate of adaptation of SA-1 mechanoreceptors is governed by the viscoelastic nature of its surrounding tissue.