Carbon fiber epoxy composites containing graphene oxide have high shape resilience but feature complex compositions and structures. Theoretical research on their mechanical properties and damage mechanisms is quite scarce. To this end, the current study generated the random fiber distribution corresponding to the composite material to represent its volume element. The macromechanical properties and microdamage modes of the material were predicted. The coupling matrix derived through micromechanical modeling and analysis was incorporated into the proposed mathematical model of the shape recovery force of the composite material. The experimental and theoretically predicted values of the shape recovery (restoring) force were 7.9 and 8.02 N, proving the proposed model’s feasibility and good accuracy. The results provide theoretical guidance for designing smart composite materials that require high shape resilience.

Shape memory composites now have a wide range of applications in aerospace, medical devices, and smart structures. Seven graphene-carbon oxide/ glass fiber (GO-CF/GF) hybrid reinforced shape memory composites were prepared using vacuum infiltration hot pressing system (VIHPS) and the shape memory properties of the materials were investigated in 100 degrees C test. By comparing and analyzing the microstructure and shape memory properties of composites containing different volume fractions of GFs, the mechanism of the influence of different hybrid contents of GFs on the organizational properties and shape memory properties was investigated. The results show that when the reinforcement of the composites were all carbon fibers, the composites had the largest elasticity modulus, harder material and the fixation rate of 77.15%, the recovery rate of 95.17%, the porosity of 0.80% and the shape recovery force of 7.98 N. When the reinforcement of the composites were glass fibers, the composites had the smallest elasticity modulus, softer material and the fixation rate of 94.89%, the recovery rate of 77.21%, the porosity of 13.56% and the recovery force of 2.28 N. The results of this test can lay a foundation for subsequent research on fibers with different mixing ratios. Highlights The GO-CF/GF/EP prepared by VIHPS has excellent shape memory properties. Fiber hybrid ratio affects the composite's porosity and its properties. Fiber hybrid ratio affects the composite's shape fixation, recovery, and memory force. The shape fixation of G6 decreases the lowest with test cycles. Carbon fiber content changes the zero-stress plane of GO-CF/GF/EP.

The cure-induced residual stresses have a significant influence on the deformation and mechanical properties of composites. Moreover, the cure-induced residual stresses exhibit multi-level and multiscale distributions due to the complexity of micro-structure of composites and anisotropic characteristics. In this paper, a computationally efficient multiscale procedure is proposed to predict the microscopic residual stresses induced by cure temperature, cure shrinkage and macroscopic residual stresses, which is based to the linear viscoelastic theory combined with the micro-mechanics method. The instantaneous microscopic residual stresses are expressed as a linear combination of the instantaneous temperature increment, degree of cure increment and macroscopic strain increment at all times of the cure process until to the current time. The proposed method is verified in comparison with the published results in literature and the microscale FEA at different length scales, respectively. The results show that the proposed method is about a thousand times faster than directly using FEA in the microscale RVE model once the influence coefficient matrices are determined. At length, the microscale stresses of all nodes of the entire macroscale model are examined by using the proposed method. It is found that the thermal-chemical-mechanical loads lead to serious microscopic stresses for the matrix and interphase constituents, especially for those due to the macroscopic residual stresses.Highlights Microscale residual stress is written as a linear combination of macroscale loads. Applying macroscale loads on microscale FEA model to obtain influence matrices. The presented model avoids repeatedly FEA microscopic to improve the efficiency. The online time required for the proposed model is much less than microscale FEA. The microscale stress increases the risk of matrix cracking and interface bonding. The process of calculation of the microscopic residual stresses by the proposed multiscale method. image

Graphene oxide-carbon fiber (GO-CF) hybrid reinforced shape memory composites were prepared based on vacuum infiltration hot compression molding test process, and the microstructure and shape memory properties of the composites were compared and analyzed when the test temperature was 50 degrees C, 60 degrees C, 70 degrees C, 80 degrees C, 90 degrees C, 100 degrees C, 110 degrees C and 120 degrees C by changing the test temperature to investigate the effect of test temperature on the microstructure. The results showed that when the test temperature was low, the microstructure and shape memory properties of the composites were not affected. There were fewer matrix in the infiltrated gaps between the fibers and the infiltration effect was not ideal; when the test temperature reached the glass transition temperature, the infiltration effect was the best; when the test temperature exceeded the glass transition temperature, the matrix modulus decreased rapidly, the resin matrix became soft and the carbon fibers were pulled out. The shape fixation rate, shape recovery rate and maximum recovery force of the composites increased and then decreased as the test temperature increased. As the number of cycles increased, the fixation rate of GO-CF/EP composites decreased the composites appear different degrees of damage, shape fixation rate, recovery rate and recovery force changes

Before the infrared dual-field lens is put into use, it is necessary to carry out impact, vibration, and high and low temperature tests. Sometimes, various problems will appear in the test, such as lens damage, unstable lens imaging, lens motion jamming and so on. In order to solve the above problems, this paper analyzes the impact and vibration of an infrared dual-field lens with a focal length of 25-75 mm and F-number of 1.0-1.2. On the basis of previous work, the corresponding impact vibration model is established, and the corresponding simulation analysis of the infrared dual-view lens is carried out based on the established impact vibration model. Then, the force of the transmission part of the lens is analyzed, and a method of designing the cam curve is put forward to reduce the movement force and reduce the probability of the cam barrel being stuck at low temperature. Combined with the above work, the corresponding impact vibration and high and low temperature tests of the lens are carried out, and the test results are satisfactory. From the above, it provides reference for the simulation analysis and structural design of infrared dual-field lens, and avoids the economic and time losses caused by defects in the design stage.

Background: Airway stent has been widely used in airway procedures. However, the metallic and silicone tubular stents are not customized designed for individual patients and cannot adapt to complicated obstruction structures. Other customized stents could not adapt to complex airway structures with easy and standardized manufacturing methods. Object: This study aimed to design a series of novel stents with different shapes which can adapt to various airway structures, such as the "Y" shape structure at the tracheal carina, and to propose a standardized fabrication method to manufacture these customized stents in the same way. Methods: We proposed a design strategy for the stents with different shapes and introduced a braiding method to prototype six types of single-tube-braided stents. Theoretical model was established to investigate the radial stiffness of the stents and deformation upon compression. We also characterized their mechanical properties by conducting compression tests and water tank tests. Finally, a series of benchtop experiments and ex vivo experiments were conducted to evaluate the functions of the stents. Results: The theoretical model predicted similar results to the experimental results, and the proposed stents could bear a compression force of 5.79N. The results of water tank tests showed the stent was still functioning even if suffering from continuous water pressure at body temperature for a period of 30 days. The phantoms and ex-vivo experiments demonstrated that the proposed stents adapt well to different airway structures. Conclusion: Our study offers a new perspective on the design of customized, adaptive, and easy-to-fabricate stents for airway stents which could meet the requirements of various airway illnesses.

Biologically inspired pneumatic ring-shaped soft grippers have been extensively studied in the field of soft robotics. However, the effect of the number of air chambers on the grasping performance (grasping range and load capacity) of ring-shaped soft grippers has not been studied. In this article, we propose three ring-shaped soft grippers with the same area of inner walls of air chambers and different numbers of air chambers (two-chamber, three-chamber, and four-chamber) for analyzing and comparing their grasping performance. Finite element method (FEM) models and experimental measurements are conducted to compare the deformation of the inner walls of the three ring-shaped soft grippers, the results indicate that the grasping range of the three-chamber ring-shaped soft gripper is larger than that of the two-chamber ring-shaped soft gripper and the four-chamber ring-shaped soft gripper. Then we choose the three-chamber ring-shaped soft gripper to study the relationship between contact force and air pressure by FEM models and experimental measurements. Several groups of experiments are constructed to compare the load capacity of the three ring-shaped soft grippers, the results indicate that the load capacity of the three-chamber ring-shaped soft gripper is higher than that of the two-chamber ring-shaped soft gripper and the four-chamber ring-shaped soft gripper. The above results reveal that the grasping performance of the three-chamber ring-shaped soft gripper is better than that of other two ring-shaped soft grippers. Furthermore, the application experiments indicate that the three ring-shaped soft grippers can grasp various objects with different weights, material properties, and shapes. This study provides a new idea for investigating ring-shaped soft grippers.

Background:Photoacoustic computed tomography (PACT) is a fast-developing biomedical imaging modality and has immense potential for clinical translation. It utilizes laser excitation and acoustic detection to achieve high spatial resolution and considerable imaging depth in biological tissues. Current PACT primarily treats the absorption coefficient of tissues as a scalar variable while reconstructing the image, which limits its use for anisotropic evaluation of the tissues. Thus, by incorporating polarized imaging methods to evaluate anisotropy, applications of PACT can be further enhanced. So far, dichroism-sensitive PACT has been suggested for polarization detection of biological tissues. However, this approach is unsuitable for intraoperative imaging, since high-power spatial light is needed for excitation, which is dangerous and inconvenient to operate. Thus, there is a need to develop a polarized PACT system suitable for clinical use.Methods:Herein, we have proposed a specially designed handheld polarized PACT (HP-PACT) system, which was designed to promote intraoperative anisotropy detection of biological tissues. Excitation light was delivered by an optical fiber and reshaped by a compact set of lenses at the output end of the optical fiber. A polarizer was applied to generate linearly polarized light, and the polarization direction was adjusted by simply rotating the half-wave plate. Photoacoustic imaging (PAI) using excitation with several different polarization directions was carried out. Optical axes and the structure of the anisotropic objects were obtained using the principle of polarization detection with the PAI.Results:We experimentally demonstrated the performance of HP-PACT by imaging both the polarized and unpolarized plastic films. The results showed that HP-PACT can successfully detect the direction of the optical axes of polarized plastic films and has the ability to image at different depths. When linearly polarized light with different polarization directions was used as excitation, PAI studies on a highly anisotropic bovine tendon and relatively low anisotropic mouse leg showed the structural differences between the 2 tissues. The quantified degrees of anisotropy of the bovine tendon and mouse legs were 0.6 and 0.3, respectively.Conclusions:The proposed HP-PACT is able to determine the anisotropic substances' optical axes and distinguish anisotropic substances from isotropic ones. Thus, HP-PACT has the potential for intraoperative diagnosis and treatment of anisotropic tissues, including nerves and tendons.

Inspired by the inchworm locomotion in nature, several two-anchor crawling robots driven by the dielectric elastomer actuators (DEAs) have been developed, which have demonstrated the clear advantages of low locomotion noise and high energy efficiency. However, due to the limitations of their locomotion principle and mechanical designs, their mobility in narrow and constrained spaces is often restricted, which severely limit their applications in the real-world, e.g. search and rescue or industrial inspections. In this work, we present a novel low-profile vibration crawling robots. Driven by a planar DEA and by incorporating a series of tilted bristles, our robot can achieve a peak forward velocity at the resonance frequency of the actuator. The crawling speed of the robot is further optimized with respect to the tilt angle of the bristle and the amplitude of the actuation voltage. The experimental results show that the robot with 60° bristles and driven at 6kV has an optimal velocity of 169.2mm-s -1 which is equivalent to 2.4 times of its body length. Furthermore, through a sequence of payload tests and results fitting, we estimate that the payload capacity of the robot is about 4. 9g, which is 1.9 times of its body mass.

Photoacoustic imaging technology (PAT) usually regards the absorption coefficient of biological tissue to light as a scalar. However, most biological tissues are anisotropic, and the absorption coefficients of light with different polarization states differ, limiting the use of photoacoustic imaging technology in some clinical diagnosis and treatment with polarization requirements. Based on this, a photoacoustic computed tomography (PACT) probe with an adjustable polarization angle is designed, and a polarization PACT system is built to provide an imaging basis for intraoperative polarization tissue detection. Non-polarization maintaining fiber guides and transmits the excitation light. It is polarized by a polarizer after a series of lens shapings, and the polarization angle of the excitation light is adjusted by a half-wave plate to excite the acoustic signal. In the experiment, through multiple polarized photoacoustic imaging experiments on polarizers with different optical axis directions and different depths in scattering media, the optical axis direction detection and depth imaging of polarizers are successfully realized. Furthermore, the structural information of the bovine tendon is successfully extracted by using the excitation light of two orthogonal polarization angles to the photoacoustic image of the bovine tendon, and the imaging ability and anisotropy detection performance of the designed handheld polarized photoacoustic imaging probe and polarization pact system are verified. It is expected to provide an imaging basis for the intraoperative diagnosis and treatment of anisotropic biological tissues (such as nerves and tendons).

Pneumatic soft grippers have been widely studied. However, the structures and material properties of existing pneumatic soft grippers limit their load capacity and manipulation range. In this article, inspired by sea lampreys, we present a pneumatic novel combined soft gripper to achieve a high load capacity and a large grasping range. This soft gripper consists of a cylindrical soft actuator and a detachable sucker. Three internal air chambers of the cylindrical soft actuator are inflated, which enables them to hold objects. Under vacuum pressure, the cylindrical soft actuator and the detachable sucker can both adsorb objects. A finite element model was constructed to simulate three inflation chambers for predicting the grasping range of the cylindrical soft actuator. The validity of the finite element model was established by an experiment. The mechanism of holding force and adsorption force were analyzed. Several groups of experiments were conducted to determine adsorption range, holding force, and adsorption force. In addition, practical applications further indicated that the novel combined soft gripper has a high load capacity (10.85 kg) at a low pressure (16 kPa) and a large grasping range (minimum diameter of the object: d = 6 mm), being able to lift a variety of objects with different weights, material properties, and shapes.

Ultrasound guided percutaneous interventional therapy has been widely used in clinic. Aiming at the problem of soft tissue deformation caused by probe contact force in robot-assisted ultrasound-guided therapy, a real-time non-reference ultrasound image evaluation method considering soft tissue deformation is proposed. On the basis of ultrasound image brightness and sharpness, a multi-dimensional ultrasound image evaluation index was designed, which incorporated the aggregation characteristics of the organization. In order to verify the effectiveness of the proposed method, ultrasound images of four different models were collected for experiments, including prostate phantom, phantom with cyst, pig liver tissue, and pig liver tissue with cyst. In addition, the correlation between subjective and objective evaluations was analyzed based on Spearman's rank correlation coefficient. Experimental results showed that the average evaluation time of a single image was 68.8 milliseconds. The evaluation time could satisfy real-time applications. The proposed method realizes the effective evaluation of real-time ultrasound image quality in robot-assisted therapy, and has good consistency with the evaluation of supervisors.

近年来,随着燃气网络规模扩大及自动化和信息化程度的提高,燃气系统安全管理的复杂性也随之增加.由于系统的复杂程度和运行成本较大,当某节点受到来自内部或外部的威胁引起故障时,很难在短时间内实现燃气系统的检修,从而造成更大规模的系统瘫痪.针对这个问题,首先提出了基于有序二元决策图(OBDD)的系统拆分方法,给出了燃气系统模型的建模和描述方法,并基于流量平衡约束建立燃气测量参数之间的关联模型.基于OBDD的系统拆分方法在传感器采集到故障信息的基础上,将可能受到波及的区域与故障区域进行分离.最后,利用并行计算工具进行实例仿真证实了该方法的有效性,节约了计算时间.

Because of the interference caused by external factors, omnidirectional automated guided vehicles (AGVs) gradually deviate from the desired path during driving. Aiming to solve this problem, we design an omnidirectional AGV driven by hub motors and perform pose correction analysis and experiments on it. By doing a kinematics analysis of the omnidirectional AGV, the relationship between the speed and the angle under different motion states is obtained. The deviation is decomposed into distance deviation and angular deviation. To rapidly eliminate the path deviation, we propose a joint control strategy. This joint control strategy combines fuzzy control and multi-step predictive optimal control. In addition, motors are decoupled to improve the control performance. The path-tracking experiments of straight lines and arcs on the vehicle show that the joint control strategy achieves path correction.

Dielectric elastomer actuators (DEAs) are an emerging type of soft actuation technology. As a fundamental unit of a DEA, the characteristics of compliant electrodes play a crucial role in the actuation performances of DEAs. Generally, the compliant electrodes can be categorized into uncured and cured types, of which the cured one commonly involves mixing conductive particles into an elastomeric matrix before curing, thus demonstrating a better long-term performance. Along with the increasing proportion of conductive particles, the electrical conductivity increases at the cost of a stiffer electrode and lower elongation at break ratio. For different DEA applications, it can be more desirable to minimize the electrode stiffness or to maximize its conductivity. In examination of the papers published in recent years, few works have characterized the effects of elastomeric electrodes on the outputs of DEAs, or of their optimizations under different application scenarios. In this work, we propose an experimental framework to characterize the performances of elastomeric electrodes with different formulas based on the two key parameters of stiffness and conductivity. An optimizing method is developed and verified by two different application cases (e.g., quasi-static and dynamic). The findings and the methods developed in this work can offer potential approaches for developing high-performance DEAs.

This paper presents a new design of omnidirectional automatic guided vehicle based on a hub motor, and proposes a joint controller for path tracking. The proposed controller includes two parts: a fuzzy controller and a multi-step predictive optimal controller. Firstly, based on various steering conditions, the kinematics model of the whole vehicle and the pose (position, angle) model in the global coordinate system are introduced. Secondly, based on the modeling, the joint controller is designed. Lateral deviation and course deviation are used as the input variables of the control system, and the threshold value is switched according to the value of the input variable to realise the correction of the large range of posture deviation. Finally, the joint controller is implemented by using the industrial PC and the self-developed control system based on the Freescale minimum system. Path tracking experiments were made under the straight and circular paths to test the ability of the joint controller for reducing the pose deviation. The experimental results show that the designed guided vehicle has excellent ability to path tracking, which meets the design goals.

The service surface of SKD11 steel needs to meet mirror roughness. Traditional grinding and polishing method is time-consuming and the quality of polished surface is difficult to guarantee due to the high hardness of SKD11 after quenching. Based on the elastic abrasive, a novel type of elastic polishing wheel device, which is designed by us, is illustrated, and optimizing the combined polishing parameters in this paper is introduced. The Preston equation and the Hertz contact theory were used to establish the material removal model for polishing work piece surface with a novel elastic polishing wheel device. The removal model is close to Gaussian distribution through matlab simulation. Then grinding and polishing experiments on end face of SKD11 steel using elastic abrasive are carried out. A multi-index optimization was realized by the Taguchi method and Grey Relation Analysis (GRA). The results showed that setting cut depth exerts the most important influencing factors on material removal and abrasive wear. On the other hand, the optimized parameters combination of grinding and polishing is 80#, 1500 r/min grinding speed, 0.3 mm setting cut depth and 2 mm/min feed rate.

The work aims to solve the problems of low efficiency of traditional polishing process through the experimental research on the surface grinding and polishing of M300 steel. The elastic ball type abrasive tool was used polish and grind M300 steel. Single factor experiment and orthogonal experiment were designed to study the influence of main process parameters on the surface roughness and material removal, such as spindle speed, abrasive grain size, feeding depth and cutting depth. In the experiment, the Hilbert path was used to evenly process the entire surface. The five-axis machining center was used as the test platform, and the electronic analytical balance and three-dimensional surface topographer were used as testing instruments to obtain the optimal process parameters and preferred interval. Among the selected 9 sets of polishing parameters, the ideal surface roughness of 0.078 μm was obtained, the optimized removal rate was 2.152 mm3/min, and the wear ratio was 0.07. The factor significantly affecting the surface roughness was the cutting depth. The factor having greater influence the material removal rate was the change in cutting depth and feeding speed. For multi-objective optimization, the influence of cutting depth, spindle speed, feeding speed and abrasive size decreased in turn. The optimum combination of process parameters was: ball type ·362· 表 面 技 术 2019 年 6 月 abrasive tool: 320#, spindle speed: 4500 r/min, cutting depth: 0.4 mm and the feeding rate: 80 mm/min. The use of ball type abrasive tool can increase the material removal rate of M300 steel and improve the quality of the machined surface, thus enhancing the processing efficiency.

In order to achieve high quality polishing of a M300 mold steel curved surface, an elastic abrasive is introduced in this paper and its polishing parameters are optimized so that the mirror roughness can be achieved. Based on the Preston equation and Hertz Contact Theory, the theoretical material removal rate (MRR) equation for surface polishing of elastic abrasives is obtained. The effects of process parameters on MRR are analyzed and the polishing parameters to be optimized are as follows: particle size (S), rotational speed (Wt), cutting depth (Ap) and feed speed (Vf). The Taguchi method is applied to design the orthogonal experiment with four factors and three levels. The influence degree of various factors on the roughness of the polished surface and the combination of parameters to be optimized were obtained by the signal-to-noise ratio method. The particle swarm optimization algorithm optimized with the back propagation (BP) neural network algorithm (PSO-BP) is used to optimize the polishing parameters. The results show that the rotational speed has the greatest influence on the roughness, the influence degree of abrasive particle size is greater than that of feed speed, and cutting depth has the least influence. The optimum parameters are as follows: particle size (S) = #1200, rotational speed (Wt) = 4500 rpm, cutting depth (Ap) = 0.25 mm and feed speed (Vf) = 0.8 mm/min. The roughness of the surface polishing with optimum parameters is reduced to 0.021 μm.

Since the curvature of free-form surfaces are variable, it is difficult to guarantee the quality of the surface polished with traditional polishing technology. The chief aim of this paper is to investigate the features of an original elastic polishing wheel device. The polishing trajectory of the elastic polishing wheel was simulated to study the relationship between the uniformity of a kind of polishing trajectory and the ratio of rotational speed "i" which is the ratio of the velocity of the rotation and the revolution. Orthogonal experiment was carried out to explore the effect of various factors (rotational ratio, press amount h, speed of rotation, and granularity of abrasive grains) on surface roughness polished. The writer has come to the conclusion that i has an influence on the uniformity of polishing trajectory. The polishing coefficient of variation "CV" of i = 10.645751 is 32% lower than i = 10. Increasing the number of digits after the decimal point of i, the polishing track performs more uniform and densely. The experimental tests show that the influence of rotational ratio, press amount h, speed of rotation, and granularity of abrasive grains on surface roughness polished decreases progressively.