Effects of Fatigue Characteristics on Static and Dynamic Performance of Eucommia Rubber Isolators

This study aimed to investigate the effect of fatigue characteristics on the static and dynamic performance of Eucommia ulmoides gum isolators, and to explore the performance changes of Eucommia ulmoides gum isolators with different formulations. For this purpose, we used five formulations of Eucommia ulmoides gum isolators and set different fatigue test methods to study the static and dynamic performance changes of Eucommia ulmoides gum isolators with different formulations by changing the amplitude. The experimental results showed that the addition of Eucommia ulmoides gum had an impact on the performance of the isolator, and the number of fatigue cycles would lead to the hardening of the Eucommia ulmoides gum isolator and changes in its static and dynamic performance. In the range of two million vibrations, the performance change of the isolator was significant in the early stage and then tended to be flat, indicating that the impact of fatigue on the performance of the isolator would not continue to persist. It is worth noting that the study found that the addition of 30% Eucommia ulmoides gum had the least impact on the performance of the isolator under fatigue. Therefore, for long-term use of Eucommia ulmoides gum isolators, attention should be paid to their fatigue characteristics to ensure their stability and reliability. Additionally, this study provides a reference for the design and application of Eucommia ulmoides gum isolators. In summary, this study provides important reference value for a deeper understanding of the fatigue characteristics of Eucommia ulmoides gum isolators and for ensuring their stable and reliable performance. .

Static performance model of GaN MESFET based on the interface state

This paper presents a new model to study the static performances of a GaN metal epitaxial-semiconductor field effect transistor（MESFET） based on the metal-semiconductor interface state of the Schottky junction.The I-V performances of MESFET under different channel lengths and different operating systems（pinch-off or not） have been achieved by our model, which strictly depended on the electrical parameters, such as the drain-gate capacity Cgd, the source-gate capacity C;, the transconductance, and the conductance. To determine the accuracy of our model, root-mean-square（RMS） errors were calculated. In the experiment, the experimental data agree with our model. Also, the minimum value of the electrical parameter has been calculated to get the maximum cut-off frequency for the GaN MESFET.

Theoretical and experimental research on static stiffness,performance,and lift-off characteristics of multi-layer gas foil thrust bearings

In this study,a new comprehensive fully coupled elastic–hydrodynamic model is developed for a multi-layer gas foil thrust bearing(GFTB).The interaction effects among the top foil,back board,middle foil,and bottom foil,as well as the Coulomb friction effect,are considered.The stiffness and static characteristics obtained by the experimental and theoretical approaches are in good agreement,which verifies the accuracy of the model.The contribution of each foil layer to the overall stiffness and the load-carrying mechanism are analyzed.Interaction effects of the load,preload,and rotational speed on the static performance are investigated comprehensively.Furthermore,start–stop tests are performed to achieve the lift-off speed,start-up torque,and shut-down torque under various operating conditions.

Research on static bearing characteristics of magnetic-liquid double suspension bearing

Due to low viscosity of seawater,it is difficult to form a seawater-lubricated film.It is easy to cause the overload and burning phenomenon of seawater-lubrication sliding bearing,and then the operation stability and service life can be shortened seriously.Therefore,the paper introduces an electromagnetic suspension theory into the seawater lubricated sliding bearing.Then a novel magnetic-liquid double suspension bearing can be formed,which can enhance bearing capacity and stiffness greatly.Firstly,the structural characteristics,support-adjustment mechanism of magnetic-liquid double suspension bearing is analyzed.Secondly,based on force balance equation,electromagnetic equation and flow equation,the transfer functions of single DOF bearing system of magnetic-liquid double suspension bearing under constant-flow supply model are deduced.Then bearing capacity,static stiffness and total power loss are selected as static performance indexes.The influence rule of operaton and structural parameters on the static performance of single DOF bearing system will be analyzed.The results show that bearing capacity decreases with the increase of liquid film thickness and width of edge seals,bias current and coil turns decrease.Static stiffness decreases with the increase of liquid film thickness,edge seals width,bias current and coil turns.Total power loss decreases with the increase of liquid film thickness,edge seals width,bias current and coil turns decrease.And static performance indexes can not be affected by liquid viscosity.The proposed research provides some theoretical and experimental basis for the parameter design of magnetic-liquid double suspension bearing.

THE STATIC PERFORMANOE AND PARAMETER STUDY OF FLOATING-RING HYDRODYNAMIC THRUST BEARINGS

In this paper, floating--ring thrust bearings are investigated. A mathematical model is established to analyze the static performance of this kind of bearings, such as the load capacity, frictional power loss, temperature rise as well as the angular speed ratio between the floating ring and runner.Meanwhile, a parameter study is also conducted on the characteristics of floating-ring thrust bearings.Finally, the theoretical calculation results are verified by experiments.

Research on an innovative structure of an open-ribbed steel-ultra-high performance concrete composite bridge deck

To completely solve the problem of fatigue cracking issue of orthotropic steel bridge decks(OSDs),the authors proposed a steel–ultra-high performance concrete(UHPC)lightweight composite deck(LWCD)with closed ribs in 2010.Based on the successful application of that LWCD,an adaptation incorporating an innovative composite deck structure,i.e.,the hot-rolled section steel–UHPC composite deck with open ribs(SSD)is proposed in this paper,aiming to simplify the fabrication process as well as to reduce the cost of LWCD.Based on a long-span cable-stayed bridge,a design scheme is proposed and is compared with the conventional OSD scheme.Further,a finite element(FE)calculation is conducted to reflect both the global and local behavior of the SSD scheme,and it is found that the peaked stresses in the SSD components are less than the corresponding allowable values.A static test is performed for an SSD strip specimen to understand the anti-cracking behavior of the UHPC layer under negative bending moments.The static test results indicate that the UHPC layer exhibited a satisfactory tensile toughness,the UHPC tensile strength obtained from the test is 1.8 times the calculated stress by the FE model of the real bridge.In addition,the fatigue stresses of typical fatigue-prone details in the SSD are calculated and evaluated,and the influences of key design parameters on the fatigue performance of the SSD are analyzed.According to the fatigue results,the peaked stress ranges for all of the 10 fatigue-prone details are within the corresponding constant amplitude fatigue limits.Then a fatigue test is carried out for another SSD strip specimen to explore the fatigue behavior of the fillet weld between the longitudinal and transverse ribs.The specimen failed at the fillet weld after equivalent 47.5 million cycles of loading under the design fatigue stress range,indicating that the fatigue performance of the SSD could meet the fatigue design requirement.Theoretical calculations and experiments provide a basis for the promotion and application of this structure in bridge engineering.

Flexural failure experiment on cracked PC simply supported box girders

Long-term load and flexural failure experiments are carried out on two prestressed concrete(PC) simply supported box girders. In the long-term load experiment, girder-1(G1) is in an elastic state, while girder-2(G2) is in a cracking state. To investigate the influence of cracking on the flexural behaviors of PC simply supported box beams, the experiment results are analyzed from many aspects, such as load–deflection, load–strain, and failure mode. Experiment results show the following: 1) the shrinkage and creep of concrete have considerable influences on the long-term deflection and strain of the two girders; 2) in the flexural failure experiment, the cracks and ultimate loads of the two girders are close. The rigidity degeneration of G2 is significantly faster than that of G1, and thus G2 shows nonlinear characteristics earlier; 3) to prove the validity and rationality of the current code, the cracking load and ultimate load of the two girders are calculated according to the current code.

Biomimetic Lightweight Design of Legged Robot Hydraulic Drive Unit Shell Inspired by Geometric Shape of Fish Bone Rib Structure

The lightweight design of hydraulic quadruped robots,especially the lightweight design of the leg joint Hydraulic Drive Unit(HDU),can improve the robot's response speed,motion speed,endurance,and load capacity.However,the lightweight design of HDU is a huge challenge due to the need for structural strength.This paper is inspired by the geometric shape of fish bones and biomimetic reinforcing ribs on the surface of the HDU shell are designed to increase its strength and reduce its weight.First,a HDU shell with biomimetic fish bone reinforcing ribs structure is proposed.Then,the MATLAB toolbox and ANSYS finite element analysis module are used to optimize the parameters of the biomimetic reinforcing ribs structure and the overall layout of the shell.Finally,the HDU shell is manufactured using additive manufacturing technology,and a performance testing platform is built to conduct dynamic and static performance tests on the designed HDU.The experimental results show that the HDU with biomimetic fish bone reinforcing ribs has excellent dynamic performance and better static performance than the prototype model,and the weight of the shell is reduced by 20%compared to the prototype model.This work has broad application prospects in the lightweight and high-strength design of closed-pressure vessel components.

A 12-bit current steering DAC with 2-dimensional gradient-error tolerant switching scheme

A 12-bit intrinsic accuracy digital-to-analog converter integrated into standard digital 0.18μm CMOS technology is proposed. It is based on a current steering segmented 6＋6 architecture and requires no calibration. By dividing one most significant bit unary source into 16 elements located in 16 separated regions of the array, the linear gradient errors and quadratic errors can be averaged and eliminated effectively. A novel static performance testing method is proposed. The measured differential nonlinearity and integral nonlinearity are 0.42 and 0.39 least significant bit, respectively. For 12-bit resolution, the converter reaches an update rate of 100 MS/s. The chip operates from a single 1.8 V voltage supply, and the core die area is 0.28 mm^2.