In this paper, a novel continuous fiber reinforced piezoelectric composite (CFRPC) actuator is proposed to improve the stability and reliability of piezoelectric actuators. A piezoelectric driving structure composed of a cantilever beam and the CFRPC actuator is utilized to research the actuation performance of the CFRPC actuator. The expression of the equivalent moment for the CFRPC actuator is obtained using the equivalent load method and electro-mechanical coupling theory. Based on Euler-Bernoulli beam theory, the analytical expression of the deflection for the cantilever beam is derived. The accuracy of the obtained analytical expressions is demonstrated by finite element simulation as well as published experimental results. The actuation performance of the CFRPC actuator is investigated through the analytical expressions of the equivalent moment and deflection. The results show that the key parameters such as driving voltage, fiber volume fraction, cantilever beam height, actuator height, actuator length and actuator position have great influence on the actuation performance of the CFRPC actuator. The CFRPC actuator has good mechanical and electrical properties, and has a wide application prospect in the field of structural shape control.

To evaluate the thermal deformation induced by 3D Printing (Three Dimensional Printing) process, a novel meshless analysis procedure is established. To account for the heat transfer and solidification effects of each printing layer from liquid to solid phase transition, the layer temperature is measured by the implanted thermocouples. Based on the temperature variation measured, the printing layer temperature can be averaged and considered as uniform for thermal analysis. In addition, as observed by the deformation of the printed target through experiment, only linear thermal elastic analysis is performed.

A rigorous algorithm for simulating the 3D Printing process is presented herein. Since the interpolation functions are no longer polynomials, a simple integration scheme using uniform integration points is applied to calculate the global stiffness matrix. Thus, the density and location of the integration points can be easily adjusted to fulfill the required accuracy. Further, for practical implementation, the simulation is also carried out by the concept of equivalent layer.

Demonstrative cases of printing a rectangular PLA (Polylactic Acid) brick are tackled to prove the accuracy and efficiency of the proposed meshless analysis procedure. The effects of layer thickness, equivalent layer and slenderness ratio on the thermal deformation of the printed brick are also investigated.

The influence of combined corrosion and vibration to the anti-loosening performance of a precision locknut used in a machine tool is investigated. Firstly, the locknut was submerged in 5% NaCl solution according to ASTM B895 standard for corrosion testing. The locknuts, after submerged in 1-hr, 2-hr and 4-hr periods, respectively, were then installed on the rotating spindle in a vertical dynamic impact tester for performing anti-loosening test. The initial installed pretension was 9800 N and the spindle was rotating in a constant speed of 1000 rpm. Turmogrease Li 802 EP lubricant was used on the contact surface between spindle thread and locknut. The set screws on the locknut were tightened sequentially and evenly in three-stage of torque: 1.96 N-m, 3.92 N-m and 5.88 N-m. Its real-time pretension variation with the periodic transverse impact and its final loosening torque were measured. Accordingly, the axial force ratio and anti-loosening torque ratio were calculated and discussed. It was found that corrosion treatment had similar influence on both the axial force ratio and the anti-loosening torque ratio. More corrosion on the locknut with longer submersion in NaCl solution deteriorated its anti-loosening characteristics. The result could serve as the reference for evaluating the fastening performance of precision locknut and guide the design and manufacturing for the application improvement.

Three types of polymer including polyurethane, polyethylene, and polysulfone were used as filler inside composite tubes to evaluate their effects on the crashworthiness. The composite tube consisting of carbon fiber fabric and polyurethane was fabricated by resin transfer molding and subjected to impact loading. In addition, the finite element analysis with progressive failure and delamination was used to simulate the crushing behavior of the polymer-filled composite tube. From the comparison between experiment and simulation, the finite element analysis is reliable, could reasonably describe the crushing behavior of the polymer-filled tube, and has nice prediction on the crashworthiness performance. From both the experiment and simulation results, the polyethylene-filled composite tube has clearly higher specific absorbed energy than the hollow composite tube, and polyethylene could be considered as an effective filler. However, the other two types of polymer filler have no clear effect.

Precise bone cut is fundamental in total knee arthroplasty. However, notching of anterior femoral is not uncommon in clinical practice. Reviewing the article, notching and its complication may reach up to 30% and 2.5%, and there is scanty study of notching on the femoral strength. We therefore conduct the finite element analysis to elucidate the effect of notching on femoral mechanical strength. The computerized tomography images were used as the basis to develop the knee model, which was assumed mainly to consist of cortical and cancellous bones. For the implant joint, Zimmer data was considered partly as the basis to develop the model. This study investigated the femoral improper cut effect on the surgery with a static standing condition. The results show that the anterior femoral cut should be undercut 2 mm to overcut 1 mm during the surgery, in order to prevent bone materials from yielding. The exposure of the cancellous bone may cause bone materials to yield when the femur overcut was 2 mm; the cancellous bone may load too much and result in a fracture when the undercut was 3 mm. The effect of undercut, which was rarely discussed, was particularly addressed in our study. Precise femoral cut is crucial for the longevity of total knee arthroplasty.

Silicon (Si)-based materials are sought in different engineering applications including Civil, Mechanical, Chemical, Materials, Energy and Minerals engineering. Silicon and Silicon dioxide are processed extensively in the industries in granular form, for example to develop durable concrete, shock and fracture resistant materials, biological, optical, mechanical and electronic devices which offer significant advantages over existing technologies. Here we focus on the constitutive behaviour of Si-based granular materials under mechanical shearing. In the recent times, it is widely recognised in the literature that the microscopic origin of shear strength in granular assemblies are associated with their ability to establish anisotropic networks (fabrics) comprising strong-force transmitting inter-particle contacts under shear loading. Strong contacts pertain to the relatively small number of contacts carrying greater than the average normal contact force. However, information on how such fabrics evolve in Si-based assemblies under mechanical loading, and their link to bulk shear strength of such assemblies are scarce in the literature. Using discrete element method (DEM), here we present results on how Si-based granular assemblies develop shear strength and their internal fabric structures under bi-axial quasi-static compression loading. Based on the analysis, a simple constitutive relation is presented for the bulk shear strength of the Si-based assemblies relating with their internal fabric anisotropy of the heavily loaded contacts. These findings could help to develop structure-processing property relations of Si-based materials in future, which originate at the microscale.

This paper focus on the mechanical and martensitic transformation behaviors of axially functionally graded shape memory alloy (AFG SMA) beams. It is taken into consideration that material properties, such as austenitic elastic modulus, martensitic elastic modulus, critical transformation stresses and maximum transformation strain vary continuously along the longitudinal direction. According to the simplified linear SMA constitutive equations and Bernoulli-Euler beam theory, the formulations of stress, strain, martensitic volume fraction and governing equations of the deflection, height and length of transformed layers are derived. Employing the Galerkin’s weighted residual method, the governing differential equation of the deflection is solved. As an example, the bending behaviors of an AFG SMA cantilever beam subjected to an end concentrated load are numerically analyzed using the developed model. Results show that the mechanical and martensitic transformation behaviors of the AFG SMA beam are complex after the martensitic transformation of SMA occurs. The influences of FG parameter on the mechanical behaviors and geometrical shape of transformed regions are obvious, and should be considered in the design and analysis of AFG SMA beams in the related regions.

In this paper, a rectangular aerostatic bearing with multiple supply holes is optimised with a multiobjective optimisation approach. The design variables taken into account are the supply holes position, their number and diameter, the supply pressure, while the objective functions are the load capacity, the air consumption and the stiffness and damping coefficients. A genetic algorithm is applied in order to find the Pareto set of solutions. The novelty with respect to other optimisations which can be found in literature is that number and location of the supply holes is completely free and not associated to a pre-defined scheme. A vector x associated with the supply holes location is introduced in the design parameters and given in input to the optimizer.

The concept of the fixed wing Micro Air Vehicles (MAVs) has received increasing interest over the past few decades, with the principal aim of carrying out the surveillance missions. The design of the flapping wing MAVs still is in infancy stage. On the other hand, there has been increasing interest over the flow control using plasma actuators in worldwide. The aim of this research is to study the flow control of a flapping airfoil with and without plasma actuation in OpenFOAM. The OpenFOAM CFD platform has been used to develop our own plasma solver. For the plasma induced turbulence in the flow regime, k-ε turbulence model was adopted to address the interaction between plasma and fluid flows. For the plasma-fluid interaction, we use reduced-order modelling to solve the plasma induced electric force. A two dimensional NACA0012 flapping airfoil without plasma actuation study has been benchmarked with previous published literature. We have not only focused on the active flow control but also analyzed the important parameter reduced frequency at different values, those are 0.1, 0.05 and 0.025. Reduced frequency (κ) is very important parameter of an airfoil in the unsteady motion. Our major contribution is testing the several reduced frequencies with the plasma actuation. The positive and beneficial effects of the plasma actuator for all cases have been observed. From the observed results, the flapping with plasma actuation at reduced frequency of 0.1 showed the 14.285 percent lift improvement and the 16.19 percent drag reduction than the flapping without plasma actuation at the respective dynamic stall angles. The maximum lift coefficient is increased with the increase in reduced frequency. In overall, plasma actuators are effective in the flow control of a flapping airfoil. In future, the combination of the flapping with plasma actuators will be a promising application to boast the maneuverability of MAVs.

Although the whip is a common tool that has been used for thousands of years, there have been very few studies on its dynamic behavior. With the advance of modern technology, designing and building soft- body robot whips has become feasible. This paper presents a study on the modeling and experimental testing of a robot whip. The robot whip is modeled using a Pseudo-Rigid-Body Model (PRBM). The PRBM consists of a number of pseudo-rigid-links and pseudo-revolute-joints just like a multi-linkage pendulum. Because of its large number of degrees of freedom (DOF) and inherited underactuation, the robot whip exhibits prominent transient chaotic behavior. In particular, depending on the initial driving force, the chaos may start sooner or later, but will die down because of the gravity and air damping. The dynamic model is validated by experiments. It is interesting to note that with the same amount of force, the robot whip can generate a velocity more than 3 times and an acceleration up to 43 times faster than that of its rigid counterpart. This gives the robot whip some potential applications, such as whipping, wrapping and grabbing. This study also helps to develop other soft-body robots that involve nonlinear dynamics.

This paper reported the designed approaches of cycloidal mechanisms, studied its dynamic forces and failure characteristics using finite element methods (FEM). A simplified cycloidal mechanism (CM) is constructed to fulfill dynamic analysis and reliability evaluation. The studied results show that the loads of the mechanism are shared mainly by a half of the outer rollers and the inner pins. The possible failures of the mechanism will occur at the inner pins caused by the bending stress, and at the cycloid disc induced by the contacting stress. The failure of the inner pins will dominate the damage of the mechanism. A method of evaluating stress variation is proposed for fulfilling reliability design. The stress variations are derived according to the data in dynamic analysis by regression analysis. The methods of design modification are reported for improve the reliabilities. The allowable loads of the CM can be decided accordingly based on the analyzed information.

Soils usually exhibit state-dependent frictional behaviour that undergoes plastic volumetric deformation. To correctly capture such response under the framework of classical plasticity, a non-associated flow rule using additional plastic potential is inevitably needed. Recently, a novel fractional plasticity (FP) without using plastic potential has been developed, and successfully applied in modelling the state-dependent nonassociated behaviour of soils. However, the energy dissipation characteristics of FP has not been probed in depth. This note examines the plastic dissipation behaviour of FP, when modelling the constitutive behaviour of soils. It is found that the plastic dissipation of FP increases continuously with the shear strain. However, the rate of plastic dissipation depends on the initial material state in relation to the critical state line.