Extended Procedure for Stiffness Modeling Based on the Matrix Structure Analysis

A novel vibration experiment consisting of a free‐free boundary condition, an electromagnetic excitation source, a vacuum chamber, and a laser vibrometer based surface measurement system has been developed that permits high levels of excitation on highly damped specimens with a minimal amount of unwanted systematic error. While some of the aspects of this experiment are not unique, when combined with a processing technique that accounts for the nonlinearities present in the system, this experiment permits, accurate measurement of strain dependent stiffness and damping properties of hard coatings at high strain levels. This procedure has been demonstrated using a titanium beam that has been coated with a free‐layer damping treatment of Magnesium Aluminate Spinel. The results indicate that Magnesium Aluminate Spinel has both nonlinear stiffness and damping properties. The stiffness asymptotes to a minimum value around 650 microstrain while the damping is a maximum around 100 microstrain. Additionally, the data contained herein cover a larger strain range for this material than previously reported.

The nonlinear stiffness and damping properties of the hydro-pneumatic suspension system are introduced, and the nonlinear mathematical model of it is established. Using MATLAB 2009b to establish the computer simulation program and draw out the nonlinear stiffness curve and damping properties curve of the hydro-pneumatic suspension system. Then, researching the influences of related parameters' changes on the nonlinear stiffness and damping properties of the hydro-pneumatic suspension system. The simulation of vehicle dynamic performance research's foundation is provided.

Static stiffness modelling of EAST articulated maintenance arm using matrix structural analysis method

Clearance and flexibility play an essential role in determining the accuracy of a planar parallel mechanism. However, previous accuracy prediction methods either considered only one of them or combined them in linear superposition. Therefore, this study proposes a novel iterative method for determining the pose error by considering clearance and flexibility simultaneously. First, the rigid-flexible model of the mechanism with clearances is developed based on the virtual joint method, in which the equilibrium conditions under the external load are established via the virtual work principle and differential forward kinematics. Then, using a Taylor series approximation, the “instant” stiffness matrix corresponding to a specific load is deduced. On this basis, an iterative scheme is explored to search for the final equilibrium pose, in which a child iterative scheme is constructed to determine the joint variables and suffered wrench of the single chain given a pose. Finally, the developed method is demonstrated by calculating the comparative pose errors of the planar five-bar mechanism and 3-RPR robot.

Characterization of in vivo strain in the rat tibia during external application of a four-point bending load

To consider the effect of non-uniform shrinkage of box girder sections on the long-term deformations of continuous rigid frame bridges, and to improve the prediction accuracy of analysis in the design phase, this paper proposes a new simulation technique for use with general-purpose finite element program. The non-uniform shrinkage effect of the box girder is transformed to an equivalent temperature gradient and then applied as external load onto the beam elements in the finite element analysis. Comparative analysis of the difference in deflections between uniform shrinkage and nonuniform shrinkage of the main girder was made for a vehicular bridge in reality using the proposed technique. The results indicate that the maximum deflection of box girder under the action of non-uniform shrinkage is much greater than that under the action of uniform shrinkage. The maximum downward deflection of the bridge girder caused by uniform shrinkage is 5.6 mm at 20 years after completion of bridge deck construction, whereas the maximum downward deflection caused by non-uniform shrinkage is 21.6 mm, which is 3.8 times larger. This study shows that the non-uniform shrinkage effect of the girder sections has a significant impact on the long-term deflection of continuous rigid frame bridge, and it can be accurately simulated by the proposed transformation technique.

Inspired by the limb structures of animals/insects in motion vibration control, a bio-inspired limb-like structure (LLS) is systematically studied for understanding and exploring its advantageous nonlinear function in passive vibration isolation. The bio-inspired system consists of asymmetric articulations (of different rod lengths) with inside vertical and horizontal springs (as animal muscle) of different linear stiffness. Mathematical modeling and analysis of the proposed LLS reveal that, (a) the system has very beneficial nonlinear stiffness which can provide flexible quasi-zero, zero and/or negative stiffness, and these nonlinear stiffness properties are adjustable or designable with structure parameters; (b) the asymmetric rod-length ratio and spring-stiffness ratio present very beneficial factors for tuning system equivalent stiffness; (c) the system loading capacity is also adjustable with the structure parameters which presents another flexible benefit in application. Experiments and comparisons with existing quasi-zero-stiffness isolators validate the advantageous features above, and some discussions are also given about how to select structural parameters for practical applications. The results would provide an innovative bio-inspired solution to passive vibration control in various engineering practice.

Snubbing operation device can carry out the workover operation and completion operation of oil, gas and water wells under the working conditions of snubbing and no blowout. The load-bearing structure of the snubbing operation device plays the main role of load-bearing, which is a necessary structure to ensure the safe and efficient completion of workover operations. and completion operations. The load-bearing requirements of the 340K snubbing operation device are greater. The finite element analysis process of load-bearing involves structural nonlinearity and boundary nonlinearity; the analysis model involves a variety of structure units, which increases the difficulty of the finite element analysis of the load-bearing machine of the full-scale structure. This paper establishes a full-scale finite element analysis model of the main load-bearing structure of the 340K snubbing operation device, analyzes the mechanical properties of the main load-bearing structure under main loads such as the weight, external load, and wind load (expected wind load and unexpected wind load), and analyzes the reaction force of the main loadbearing rope under load (working state, unexpected wind state, expected wind state);The main rope of the 340K snubbing operation device is subjected to a force test under wind load, and the force on the rope is measured. The analysis found that the maximum stress of the main body of the snubbing operation device under the working load is 155MPa, and the safety factor is 1.35, which achieves the conditions for safe work; the force of the rope obtained by the test is less than the rated tension of the rope 220KN, which achieves requirements of various working conditions. Through the calculation and analysis under the load of the snubbing operation device, it provides an important basis for ensuring the safe operation of the snubbing operation device.

AC loss from Roebel cables with high-temperature superconducting strands are comparatively less, and they possess large current carrying capacity since they have a transposed structure. However, the strands should be strong enough to withstand various types of external loads during their operation. The present work simulates the performance of the Roebel strand against an external tensile load using 3-D finite element analysis, and the importance of geometrical parameters on the mechanical stability of Roebel cables is investigated. Results were then compared with another work where the analyses were performed on a monolithic Roebel strand. We concluded that the typical twisting of the strands is an important parameter that cannot be ignored when optimizing a Roebel cable. Hence, the stress induced in a Roebel strand against an external load depends not only on the geometrical parameters but also on the typical twisting of the strand.

This paper deals with the shape optimization of a six degree-of-freedom haptic interface device. This six-dof epicyclic-parallel manipulator has all actuators located on the ground. A regular dexterous workspace is introduced to represent the mobility of user’s hand. Throughout this workspace, the deviation of the mobile platform is bounded to provide a better feeling to the user and the masses in motion are minimized to increase the transparency of the haptic device. The stiffness model is written using a virtual joint method and compared with the results obtained with the finite element analysis to be validated. Finally, the shape of the links are optimized in order to minimize the masses in motion while guaranteeing a given stiffness throughout the regular workspace of the mechanism.

Effects of dental implant diameter and tapered body design on stress distribution in rigid polyurethane foam during insertion

Most robotic applications demand lightweight and high-speed manipulators for considerably reducing the consumed power and achieving high production rates. The two ways for seeking such high-speed arms are; applying advanced control algorithms and/or performing an extensive optimization of the arm structure itself. Therefore, the topology optimization technique is proposed here for obtaining an optimal robot arm design from both structure and control viewpoints. Results of some researches, that have been previously accomplished by size and shape optimization, were encouraging enough to extend and propose this optimization approach. The method of moving asymptotes (MMA) as an optimization algorithm, the finite element analysis (FEA) by ANSYS, and the time-optimal control method are integrated to gain an optimum design capable of attaining the minimum traveling time. The proposed methodology focuses on performing different comparisons between the proposed optimum topological designs and their initial designs for different robot arms’ sizes and materials. It also distinguishes between the proposed optimum design and the previously achieved one by size optimization under the same operational conditions. Therefore, the significance of the proposed technique is emphasized. It shows that the traveling time is reduced by 44.8%, while the previous work only achieved 23.5%. In addition, the mass is reduced to nearly half of its initial value, taking into account the air damping as the real case in all terrestrial applications.

This paper presents a new Multiphysics optimization strategy to design a high-power ultra-high-speed machine (HPUHSM). The design process of HP-UHSM is highly iterative and requires Multiphysics optimization to deal with different critical design challenges such as windage loss, thermal limit, centrifugal force, and vibration. However, the Multiphysics optimization of HP-UHSM is a challenge due to several design variables and the huge computation cost of finite element analysis (FEA). In this paper, an integrated Multiphysics optimization process is developed using a combined FEA and analytical model, which provides a robust design geometry and significantly reduces the computational cost. The optimization process integrates a parameterized FEA electromagnetic module with analytical models of thermal, structural, and Rotordynamic analysis. Therefore, it can apply multi-disciplinary design constraints from application requirements and the material’s limitations. The optimal result ensures an efficient and feasible design with a high design-safety-margin by considering the Multiphysics mutual influence. To investigate the efficiency of the proposed optimization model, a 2 kW 500 krpm permanent magnet synchronous machine is designed considering some unique requirements of a potable mechanical antenna. The multidisciplinary performance of the designed machine is studied using 3-D FEA and experimental analysis to evaluate the accuracy and computational efficiency of the proposed model. The comparative results confirm that the proposed optimization model can design an efficient and robust HP-UHSM with high accuracy and very low computational cost.

With advancements in semiconductor manufacturing processes and the development of precision processing technology, flexure hinge-based ultra-precision positioning stages are widely used. In the flexure hinge, axial and bending stiffness properties greatly influence positioning performance. This study examined the stiffness properties of elliptic and parabolic 2-degrees-of-freedom (DOF) hinges, which have not been extensively discussed. The Timoshenko beam theory was applied to derive the stiffness equations for the axial and bending directions of each hinge. The stiffness properties were examined in several design conditions by comparing theoretical and finite element analyses. Based on the results of the analyses, an empirical formula in exponential form for the design of an elliptic hinge was constructed through surface-fitting. The elliptic hinge was found to be a better alternative to a circular hinge under certain design conditions by adjusting two design parameters. In the future, we will develop sophisticatedly designed hinges with improved axial and bending stiffness properties compared to the existing circular and elliptic hinges.

Accurate determination of stiffness properties of cord‐rubber composites is a key to successful finite element analysis of tires. The Halpin‐Tsai and similar equations which are used to determine stiffness properties of cord‐rubber single plies from the stiffness properties of cord and rubber do not provide adequate accuracy. Determination of these properties from strains directly measured by the Moire technique is more appropriate. In this paper the disadvantages of Halpin‐Tsai and similar equations as well as the advantages of the Moire technique for cord‐rubber composites are discussed. The stiffness properties obtained using the above different methods are compared. These stiffness properties are then used in the finite element analysis of a two‐ply cord‐rubber strip. The results of the finite element analyses are compared with experimental data.