Proceedings of the Institution of Mechanical Engineers,Part C: Journal of Mechanical Engineering Science

Recent advancements in nanotechnology, for the biosynthesis of metal nanoparticles through enormous techniques, showed multidimensional developments. One among many facets of nanotechnology is to procure and adopt new advancements for green technology over chemical reduction synthesis. This adaptation for acquiring green nanotechnology leads us to a new dimension of nanobiotechnology. In order to imply one such efforts, in this study the emphasis is being laid on the synthesis of MgO nanoparticles using green technology and eliminating chemical reduction methods. Different characterization techniques such as UV–Vis spectroscopy, transmission electron microscopy, and dynamic light scattering were used to carry out the experiments. The average size of MgO nanoparticles were obtained in the range of 85–95 nm, when synthesized by various sources. The extracts of plants were capable of producing MgO nanoparticles efficiently and exhibited good results during cyclic voltammetry and electrochemical impedance spectroscopy study. The electrode modified with MgO nanoparticles (plant extract) showed good stability (90 days) and high conductivity. This study reports cost-effective and environment-friendly method for synthesis of MgO nanoparticles using plant extracts. The process is rapid, simple, and convenient and can be used as an alternative to chemical method.

The present study deals with the deformation behaviour of low carbon and high manganese twinning-induced plasticity (TWIP) steel (Fe–21Mn–3Si–3Al–0.06C, wt%) through microstructural investigation. Low carbon with high manganese along with the addition of aluminium in TWIP steel results in lowering of specific weight with higher strain hardening due to the formation of mechanical twins during deformation. The full austenite phase is obtained after solution treatment and deformation twins appear and austenite grains become flattened during application of 10% to 50% cold deformation. The annealing twins are relatively coarser compared to the newly formed deformation twins. With the increasing amount of cold deformation, deformation twins and dislocation density are increased. Deformation twinning can be considered to be the dominant deformation mechanism during the course of cold rolling applied in the present study. The cold deformation results in the evolution of dislocation substructure, stacking faults, deformation twins and twin–dislocation interaction, which may be correlated with the lower stacking fault energy (∼24 mJ/m²) of the investigated steel. Excellent combination of strength and ductility has been obtained in the present TWIP steel with a small rolling reduction of 10% and 30%. With the increasing amount of cold deformation, tensile strength notably increases and maximum tensile strength is obtained at 50% cold-deformed sample along with the diminutive sacrifice of the ductility.

This current study reports on multi-level damage and creep behaviour of metal and composite material under external high pressure using finite element concept. A fatigue damage model with microcracks with improper interface has been portrayed in the present investigation. In addition, the overall elastic properties and damage evaluation are also studied and comparative study of mechanical properties has been outlined. Further thermo-elastic creep response of materials based on Norton’s law is also presented. The results showed that the proposed nonlinear constitutive model and overall elastic damage behaviour of composite material are in agreement. Implemented nonlinear constitutive model is secured by comparing predicted stress–strain curves with experimental data available in the past literature under uniaxial tension. The time-dependent behaviour creep stresses and displacements are studied and plotted. The analysis provides significant new insights of micromechanical damage, creep and collapse behaviour of composite material. For the structural composites, some notable techniques have been developed over the past three decades; review of these techniques is also outlined here in this paper and state of art is established together with insights for upcoming development.

In this work, the effect of Cr³⁺ partial substitution on vanadium site in monoclinic lithium vanadium(III) phosphate (LVP) structure resulting in compounds with general formula: Li₃V₂- _x Cr _x (PO₄)₃-C (x = 0, 0.05, 0.1, 0.15) was studied. A two-step sol-gel combustion method was employed in syntheses. The samples were characterized by X-ray powder diffraction, scanning electron microscopy, coupled plasma optical emission spectroscopy, and flash combustion. The electrochemical performance of the active materials was examined through rate capability tests and cyclic voltammetry. The unsubstituted compound LVPC delivers higher capacity compared to the Cr-containing samples due to chromium inactivity in the potential range 3.0–4.4 V vs. Li/Li⁺. However, the Cr-substituted materials show better overall capacity retention (97–97.6%) in contrast to Li₃V₂(PO₄)₃-C (96%) in long cycling.

Ag–Cu alloys of two different initial microstructures—a cast eutectic alloy (AgCu-E) and an equivolume Ag–Cu powder mixture (AgCu-P)—were deformed by high-pressure torsion. The codeformation of Ag and Cu grains led to uniform refinement and a nanolamellar microstructure for both alloys. However, the lamellar structure in AgCu-P alloys was broken at intermediate shear strains (γ > 150) by extensive shear banding. On the other hand, no shear banding was observed for AgCu-E alloy at similar microstructural refinement. At higher strains deformation induced intermixing of Ag and Cu atoms was observed. Further, three-dimensional diffraction analysis of AgCu-E alloy showed that in contrast to conventional single phase alloys, the Ag and Cu phases develop similar crystallographic texture.

Hydrostatic pressure is one of the most fundamental and common mechanical stimuli in the body, playing a critical role in the homeostasis of all organ systems. Kidney function is affected by high blood pressure, namely hypertension, by the increased pressure acting on the glomerular capillary walls. This general effect of hypertension is diagnosed as a chronic disease, but underlying mechanistic causes are still not well understood. This paper reports a portable and adaptive device for studying the effects of hydrostatic pressure on a monolayer of cells. The fabricated device fits within a conventional incubation system and microscope. The effects of various pressures and durations were evaluated on a confluent layer of human endothelial cells. We found that a fluid pressure (i.e. hydrostatic pressure) can alter the morphology of the cells and that returning to an ambient pressure can reverse the changes in morphology. Thus, this study provides a proof-of-principle demonstration that this tool can be utilized for exploring the effects of hydrostatic pressure on mammalian cells.

This paper presents a complete study on the collision with friction of one or two rigid bodies without constraints. The differential formula between the velocities and impulse uses the notion of inertance resulting from the theory of screws (Plückerian coordinates). One thus may calculate the kinematic and dynamic parameters, the velocities and the kinetic energies of the two rigid solids after the collision, and the variation of the kinetic energy. The calculation is detailed for the Newton, Poisson, and energetic variants of the coefficient of restitution. The variation of the kinematic and dynamic parameters in relation to the coefficient of restitution and coefficient of friction for all the three variants are presented and discussed. A numerical example highlights the theory.

This study investigated the vibrational behaviour of a rotating two-blade propeller at different rotational speeds by using self-tracking laser Doppler vibrometry. Given that a self-tracking method necessitates the accurate adjustment of test setups to reduce measurement errors, a test table with sufficient rigidity was designed and built to enable the adjustment and repair of test components. The results of the self-tracking test on the rotating propeller indicated an increase in natural frequency and a decrease in the amplitude of normalized mode shapes as rotational speed increases. To assess the test results, a numerical model created in ABAQUS was used. The model parameters were tuned in such a way that the natural frequency and associated mode shapes were in good agreement with those derived using a hammer test on a stationary propeller. The mode shapes obtained from the hammer test and the numerical (ABAQUS) modelling were compared using the modal assurance criterion. The examination indicated a strong resemblance between the hammer test results and the numerical findings. Hence, the model can be employed to determine the other mechanical properties of two-blade propellers in test scenarios.

Based on the principle of multi-stage vibration isolation and active vibration absorption, a multi-stage passive vibration-isolating system and active motor vibration-absorbing system are designed for the electric wheel system of wheel-hub motor-driven electric vehicle, and the 1/4 suspension structural diagrams of the two vibration-isolating systems are drawn. Secondly, the corresponding multi-degrees-of-freedom vertical vibration model is established according to the different structural diagrams, and the dynamic differential equation of the multi-degrees-of-freedom vibration system is deduced. Then, by programming the MATLAB software is used to solve the acceleration of the vehicle body, the dynamic deflection of the suspension spring, and the amplitude, and the frequency characteristic curve of the relative dynamic load of the wheel of the 1/4 suspension system are drawn and the results are compared and analyzed. Finally, the ADAMS software is used for remodeling; the simulation experiment of ADAMS multi-body dynamics verified the correctness of the theoretical results of MATLAB software. The results show that the ADAMS simulation experiment results are consistent with the MATLAB theoretical results, and their correctness is verified. The vibration isolation effect of the active vibration-absorbing system is better and can improve the riding comfort and safety of the vehicle; hence it is worth popularizing and drawing.

This study aims at minimizing the aerodynamic noise generated by claw pole alternator used in vehicles. In this paper, an effective and efficient hybrid test-analysis engineering approach has been proposed to predict and optimize acoustic performance of claw pole alternator. First, an experimental analysis was performed to predict the main components of the aerodynamic noise generated by the claw pole alternator. Then a hybrid approach was proposed to calculate the aerodynamic noise of the alternator. A computational fluid dynamics model of the claw pole alternator was developed for calculating the flow-field of the alternator. The pressure fluctuation in the flow field was analyzed to validate the computational fluid dynamics simulation. After the computational fluid dynamics simulation, the far-field aerodynamic noise generated by the flow field was calculated by adopting the acoustic finite element method. The accuracy and feasibility of the acoustic finite element model were validated with the experimental data. After the validation, the effects of the cooling fan parameters on the aerodynamic noise of the alternator were discussed and analyzed. According to the sound source information and the generation mechanism of the aerodynamic noise, the blade spacing angle of the cooling fan was optimized by establishing a theoretical model. The blade chord length of the cooling fan, the blade installation angle of the cooling fan and the tilt angle of the grille on end cap were optimized by structuring different surrogate models. After the optimizations, a significant reduction in the noise level of the claw pole alternator was found by the finite element method simulation. The overall sound power level has been decreased by about 6 dB (A).

This paper studies the prototype development of the vibro-impact capsule system aiming for autonomous mobile sensing for pipeline inspection. Self-propelled progression of the system is obtained by employing a vibro-impact oscillator encapsuled in the capsule without the requirement of any external mechanisms, such as wheels, arms, or legs. A dummy capsule prototype is designed, and the best geometric parameters, capsule and cap arc lengths, for minimizing fluid resistance forces are obtained through two-dimensional and three-dimensional computational fluid dynamics analyses, which are confirmed by wind tunnel tests. In order to verify the concept of self-propulsion, both original and optimized capsule prototypes are tested in a fluid pipe. Experimental results are compared with computational fluid dynamics simulations to confirm the efficacy of the vibro-impact self-propelled driving.

The joint flexibility and clearance greatly affect the dynamic behavior of the free-floating base when space manipulators operate due to the dynamic coupling between the manipulators and the free-floating base. Based on the Lagrange–Euler method and momentum conservation, the dynamic model of a free-floating space manipulator system with joint flexibility and clearance is obtained. With this model, the coupling effects of joint flexibility and clearance on the dynamic response of the free-floating base are analyzed and some case studies are conducted to investigate the effects of different parameters of joint flexibility and clearance on the free-floating base. Further, the parameter sensitivity of the free-floating base for space manipulator system with joint flexibility and clearance is analyzed using the improved response surface method. According to the analysis of response surface method, we can increase the joint clearance size or decrease the dynamic friction coefficient to improve the stability and motion accuracy of the free-floating base position and attitude. This work points out the direction for reducing the base disturbance and provides a basis for the optimization design for free-floating space manipulator system.

The main purpose of this paper is to study the behavior of the 2000 aluminum alloy series used particularly in the design of Airbus fuselage. The characterization of the mechanical behavior of sheet metal on 2024 aluminum alloy and its response to various loading directions under monotonic and cyclic tests are extremely considered. To solve this problem, first, an experimental platform which essentially revolves around mechanical tests and then a series of optical and transmission electronic visualizations have been carried out. These mechanical tests are monotonic and cyclic shear tests applied under the same conditions on the test specimens of 2024 aluminum alloy. Cyclic shear tests have been carried out in order to show the Bauschinger effect and then the kinematic hardening phenomenon. The hardening curves of the simple shear test showed the Portevin-Le Chatelier effect for all loading directions. Next, the experimental results obtained (Portevin-Le Chatelier and Bauschinger effects) are discussed and analyzed in relation to the microstructure of the studied alloy using an optical microscope and a transmission electron microscope. Thereafter, the plastic anisotropy is modeled using an identification strategy that depends on a plastic criterion, an isotropic hardening law, a kinematic hardening (linear and nonlinear) law, and an evolution law. More precisely, particular attention is paid to the isotropic power Hollomon law, the saturation Voce law, and the saturation Bron law. In the case of the cyclic tests, linear kinematic hardening described by the Prager law and nonlinear kinematic hardening expressed by the Armstrong–Frederick law are introduced. Finally, by smoothing the experimental hardening curves for the various simple and cyclic shear tests, a selection is made in order to choose the most appropriate law for the identification of the material behavior.

In this study, free vibration of a cracked curved beam utilizing analytical, numerical, and experimental methods is investigated. The differential quadrature element method is used to solve the equations of motion numerically. The governing equations are also solved analytically. The crack, which is considered to be open, is modeled as a rotational spring. Furthermore, the effect of curvature on mode shapes is studied. To verify the validity of the proposed methods of determining frequencies and mode shapes, an experimental modal analysis test is conducted on a sample beam having crack with some different depths. This study revealed that the behavior of curved beams toward the mode transition phenomenon depends greatly on the boundary conditions of the beam. Also, both the location and depth of crack have considerable effects on natural frequencies.

Grouted connections are structural joints formed by a cementitious grout cast between two concentric circular tubes. They are widely used in the offshore construction of oil and gas platforms, and for offshore wind turbines (monopiles and jackets). However, their application in offshore wind turbine installations can be critical due to the high bending moments coming from wind loading. Recently, it was found that grouted connections show limited performance in offshore wind turbine installations leading to settlements between the steel tubes and steel/grout debonding. Hence, structural health monitoring techniques for grouted connections are needed that ensure a safe and reliable operation of offshore wind turbines. This short communication describes the successful application of electromechanical impedance spectroscopy for damage detection in grouted connections.

Lightweight fibre-reinforced polymer composites are currently being applied extensively in the design of transport structures to replace conventional metallic solutions, and also in structures that are exposed to the risk of foreign object impact. Therefore, an experimental study was undertaken to assess and compare the low- and high-velocity impact behaviour of S-2 glass®, HTA carbon and ultra-high-molecular-weight polyethylene (Dyneema®) composites. Three different impact test methods were applied: Charpy pendulum impact tests, drop-weight impact tests and ballistic impact tests with a gas gun. The results with the focus on penetration energy are compared in terms of correlation between the three test methods and in terms of weight-specific material performance. While the S-2 glass® fibre showed the best performance of the epoxy-based composites, the PUR-based Dyneema® HB26 panels proved the best penetration resistance in this study.

The double cantilever beam specimen is assumed as two finite length beams, connected together, except at the initial delamination length. The energy release rate (G_I) is evaluated analytically by considering a Timoshenko beam on Winkler and Pasternak elastic foundations. The current data reduction methods have a blind spot in calculating G_I when crack approaches the end of the ligament, which is considered in this study and, therefore, the simplifying assumption of infinite ligament length is not assumed here. G_I will be strongly dependent on the ligament length if it is less than twice the thickness. Furthermore, the R-curves of different layups including their first points (fracture toughness) are drawn using Ρ–δ curves reported in the literature and they are compared to the experimental results. These comparisons show that Timoshenko beam on Winkler foundation gives the best results in comparison with experimental results for unidirectional and angle-ply laminates.

The aim of this paper is to investigate the effect of geometrical parameters on the performance of jet penetration in the process of shaped charge. To this end, the finite element analysis was used to simulate the process. The simulated process was validated by experimental tests and the effect of some parameters including stand-off distance and the liner thickness on the jet penetration depth was studied. The results indicated that choosing the optimal distance between the liner and the target (stand-off distance) can significantly affect the performance of jet penetration in the target. In addition, examining the effect of liner thickness on the penetration depth efficiency revealed that by decreasing the liner thickness, the jet penetration depth on the target increases. It should be noted that ABAQUS finite element software was used in this simulation to analyze the process of shaped charge.

In this paper, the flow ripple equation is derived to analyze the effect of working condition on pressure pulsations of an internal gear pump. Results indicate that working pressure has a significant effect on pressure fluctuation of the internal gear pump, while the rotating speed has a complex influence on the pressure pulsation behavior. Then, pressure pulsations of the internal gear pump under different working conditions are discussed by experimental investigations. Results show that the internal gear pump taken for analysis has a low-pressure pulsation at a high working pressure and a relatively high rotational speed. Regarding the frequency spectrum of the pressure pulsation, the dominant frequency is Z*f_n, i.e. the product of the tooth number of the driving gear (gear shaft) and its rotational frequency for many working conditions, caused by the inevitable unsteady discharge process of gear pumps. It transforms to the rotational frequency of the gear shaft (f_n) for a high rotational speed or a high operating pressure, but to the rotating frequency of the internal gear ring (2/3 f_n) only for a high operating pressure. The occurrence of the two frequencies (2/3 f_n and f_n) may result from the deformation of the gear ring and the gear shaft under the unbalanced radial forces caused by a high working pressure. Moreover, the frequency spectrum of the inlet pressure pulsation presents some differences from that of the outlet pressure pulsation. This is because the inlet pressure may be influenced by cavity generated at the suction side of the pump.

Friction is one of the main disturbances in nanometric positioning. Recently, it was shown that ultra-high precision positioning typically happens in the pre-sliding motion regime where friction is characterized by an elasto-plastic nonlinear hysteretic behavior with a marked stochastic variability. With the aim of providing the tools for the development of robust control typologies for ultra-high precision mechatronics devices, different pre-sliding friction models are thus considered in this work. The most relevant ones are hence experimentally validated, as well as compared in terms of the complexity of identifying their characteristic parameters and of simulating the factual dynamic response. It is hence shown that the generalized Maxwell-slip model can account for all the important pre-sliding frictional effects in nanometric positioning applications. A thorough sensitivity analysis of the parameters of the generalized Maxwell-slip model model is therefore performed allowing to establish that three Maxwell-slip blocks are the minimum needed to approximate the behavior of the real precision positioning systems, six blocks allow representing excellently the real behavior, while the slower dynamics, which induces a difficult real-time implementation, with a very limited gain in terms of model accuracy, does not justify the usage of a larger number of elements.

The kinematic and dynamic analysis of compliant mechanisms is investigated comprehensively in this work. Based on the pseudo-rigid-body model, a new PR model is proposed to simulate both the lateral and axial deformations of flexural beams in compliant mechanisms. An optimization for the characteristic factors and a linear regression for the stiffness coefficients of PR pseudo-rigid-body model are presented. Compared with the 1R and 2R pseudo-rigid-body model, the advantage of the PR model is well illustrated. The dynamic modeling of flexible beams in compliant mechanisms is then developed based on the PR pseudo-rigid-body model. The dynamic equation of a PR pseudo-rigid-body dynamic model is derived and the dynamic responses are then presented. The kinematic and dynamic analysis of a compliant slider-crank mechanism is presented by the 1R, 2R and PR model, respectively. The effectiveness of pseudo-rigid-body models and the superiorities of the PR pseudo-rigid-body model and PR pseudo-rigid-body dynamic model are shown clearly in the numerical example.

Variable stiffness joints designed to ensure physical safety or adjust stiffness actively have attracted much attention in recent years. Springs are used in the internal kinematic structures of variable stiffness joints to achieve the compliance. In this paper, the stiffness property of a variable stiffness joint using a leaf spring is studied on the basis of geometric nonlinearity associated with large deflections of leaf springs. A new end structure is used in the variable stiffness joint to exert the external force on the leaf spring. Based on the elliptic integral solution to large deflection problems of cantilever beams, the effects of different end exertion force structures and geometric nonlinearity of leaf springs on the stiffness property are analyzed when the deflected angle of the joint is larger. It is found that the end exertion force structure and large deflection of leaf springs have a great impact on the changes of the joint stiffness during the joint deflection. A new variable stiffness joint using two leaf springs is proposed to meet different application requirements by changing the end exertion force structure. The experiment of the proposed joint is carried out to verify the validity of the stiffness analysis results.

This paper describes the design of a novel multi-functional rescue end-effector with tonging, shearing and grasping capabilities to meet the demands of urban catastrophe rescue applications. The tonging and shearing form and the grasping form of the end-effector are analysed. The two forms are determined using the transformations of their grasping mechanisms. Four objectives (to maximize shearing space, minimize mass, minimize the equivalent stress and minimize deformation) are proposed for selection of the optimal grasping mechanism structure. Additional objectives also involve the end-effector’s structural strength and kinematic characteristics. A nested optimization structure that is composed of the non-dominated sorting genetic algorithm II (NSGA-II) and finite element analysis is proposed to perform multi-domain and multi-objective optimization of the end-effector. To improve the optimization efficiency, a traditional synthesis technique and a sensitivity analysis are applied to reduce the outer and inner numbers of the design variables. Simulation results indicate that the values of the four target objectives are superior to those before optimization and two referenced objectives, and the end-effector mass in particular, can evidently be reduced.

In this study, an automatic machine for transplanting potted tomato seedlings was designed, based on the analysis of physical characteristics of the main varieties of tomato seedlings. The machine is composed of a horizontal and vertical seedling supply mechanism, a picking mechanism composed with a gear-rod component, a planting part featured with an eccentric-disk parallelogram duckbilled mechanism, and a control system. The control system included position sensors, stepper motor, variable-frequency motor and program controller. The force condition for successful picking potted tomato seedlings was studied by analyzing the force and motion during the taking procedure with the use of analytical graphic method. Combined with the parameters of physical characteristics of tomato seedlings, the key parameters of the machine was determined, which included L₁ = 105 mm as the distance between the point of the gripper needles and the center of rotation, L₀ = 18 mm as the initial opening distance between the two gripper needles, and s = 40 mm as the distance between the two gripper needles when they were at the upper hinge point of the clamping hands. The key structure and the parameters of the seedlings-taking part were determined by theoretical calculation according to the position of the seedling during taking and dropping procedure, and the requirement of the motion. The machine was tested by using the potted tomato seedlings. The result showed that the seedling picking rate was 92.35%–86.61%, and the leakage rate was 12.57%–18.03%, when the transplanting speed was between 60 and 90 seedlings per minute. The result demonstrated that the machine was feasible to transplant the potted tomato seedlings efficiently.

In this paper, an active design method of meshing line for a spiral bevel gear mechanism with nonrelative sliding is presented. First, the general meshing line equations for a nonrelative sliding transmission mechanism between two orthogonal axes are proposed based on the active design parameters. Then, parametric equations for contact curves on the drive and driven spiral bevel gears are deduced by coordinate transformation of the meshing line equations. Further to this, parametric equations for the tooth surface of each bevel gear are derived according to the conical spiral motion of a generatrix circle along the calculated contact curves. Finally, a set of numerical examples is presented based on two types of motion equation of the meshing points. Material prototypes are fabricated and experimentally tested to validate the kinematic performance of the functionally designed spiral bevel gear set.

Owing to the increasing demand for Ni-rich shape memory alloys in various sectors such as biomedical, aerospace, and robotics, the efficient machining of shape memory alloys is vital for their productive exploitation. The aim of this experimental investigation is to explore the influence of wire electric discharge machining process parameters such as spark gap voltage, wire tension, spark off time, wire speed, and spark on time, on the cutting efficiency and surface roughness of Ni_50.89Ti_49.11 SMA using one factor at a time approach. The results reveal that cutting efficiency and surface roughness are strongly influenced by spark off time, spark on time, and spark gap voltage, whereas wire speed and wire tension have the inconsequential effect. The presence of many microcracks, craters, voids, bulges of debris, and the re-solidified layer of molten material on the machined surface have been detected in scanning electron micrographs. The results of phase analysis using energy-dispersive X-ray spectroscopy and X-ray diffraction divulge the migration of foreign elements from the brass wire and dielectric to the machined surface. Due to the formation of recast layer and various oxides, the hardening effect near the machined surface was also observed. The hardness near the machined surface has been increased several times in comparison to bulk hardness.

The prominent seal ring has been studied to prevent the compressed air from entering the enclosed area of the mold and the wafer and protect pattern in Compressional Gas Cushion Press Nanoimprint Lithography (CGCP NIL). In this paper, a non-salient seal ring with rectangular grooves was proposed to replace the prominent one, which achieved the same effect. The relationship between the width of seal ring and other three factors—the contact surface properties, the height of printed liquid, and the contact angle—was also investigated. The non-salient seal ring can be effective in sealing out the compressed air, on condition that the seal ring was wide enough. Besides, the width to meet the requirements reduced significantly, with increasing the roughness. Furthermore, the rectangular grooves etched on the seal ring can increase its surface roughness and the depth–width ratio was larger, surface roughness was bigger. Owing to the presence of rectangular grooves, smaller width was required to reach the same effect of leak-proof in the process. Besides, a simple model of COMSOL Multiphysics was established to verify the correctness of proposal. This work will greatly reduce the cost of the mold and guide the production of the mold in CGCP NIL.

Robot-assisted therapy has gained wide attention in rehabilitation engineering, allowing patients with lower limb motor disorders to perform repeatable and consistent upright bipedal walking. The goal of this paper is to develop a novel wearable powered exoskeleton that enables the paraplegic to perform basic daily movements for active rehabilitation training of lower limbs. Mechanical structure and driving devices of the exoskeleton are reasonably designed and selected to ensure natural interaction with the user and provide sufficient driving torques in the course of walking. In order to avoid unwanted interaction forces between the exoskeleton and the patient, the passive exoskeleton testing system is proposed to measure and record various postures as the reference trajectories. In addition, a cascaded proportional–integral–derivative controller is designed to complete walking assistance tasks in passive control modes. Four typical trajectory tracking tasks are carried out for the sake of evaluating the accuracy and effectiveness of the proposed control strategy. Further experiments were conducted by a healthy subject wearing the rehabilitation exoskeleton to perform sit-to-stand and level walking, and the results demonstrated that the developed robot-assisted system had the natural period and favorable response patterns.

Ti6Al4V alloy has been found to be the leading material for hip replacement due to its biocompatibility and good yield strength; however poor corrosion and wear properties are experienced in human tissue surroundings. Laser metal deposition was accomplished on Ti6Al4V alloy using: 25Hafnium, 50Niobium, and 25Zirconium reinforcements with the aid of Nd:YAG Rofin Sinar laser. Characterization of the produced deposits was carried out by optical microscopy, scanning electron microscopy/energy-dispersive X-ray spectroscopy and X-ray diffraction. Hardness, corrosion and wear analyses were also done. Microstructure of 25Hf-50Nb-25Zr coatings indicated homogeneous microstructures of both α and β phases. More α acicular phases were formed than β phases. The 25Hf-50Nb-25Zr coating on Ti6Al4V reduced the content of aluminium and vanadium on the substrate. Maximum hardness value and lowest volume wear rate were obtained at laser power of 1250 W with hardness values of 599.18 HV and 0.6 m³ volume wear loss. Improvement in corrosion resistance of 99.98% was obtained. It was established that improved properties were obtained after laser surface cladding of 25Hf-50Nb-25Zr on Ti6Al4V alloy.