ANALYSIS OF SPATIAL COMPLIANCE BEHAVIOR OF COILED SPRINGS VIA SCREW THEORY

A new method is presented to describe and analyze the spatial compliance ofcoiled springs using screw theory. After an abbreviated description for the deformation of a beamelement using screw theory, the spatial compliance density for a beam element is derived based onthe fundamental material theory and reasonable assumptions, and the spatial compliance of the beamwith finite length is obtained by integral. The spatial compliance of coiled springs is furtheranalyzed using the spatial compliance density of the beam element. By calculating theeigencompliance and Ball's principle screws for the whole compliance of system, the complianceproperties varying with the basic physical parameters of the system are illustrated in detail. Thebasic ideas can be used for the design and application of the coiled springs and the other compliantmechanisms with spatial compliant beam element.

Optimization of suspension system of heavy off-road vehicle for stability enhancement using integrated anti-roll bar and coiling spring mechanism

Short suspension system has an indispensable effect on vehicle handling and ride,so,optimization of vehicle suspension system is one of the most effective methods,which could considerably enhance the vehicle stability and controllability.Motion control,stability maintenance and ride comfort improvement are fundamental issues in design of suspension system of off-road vehicles.In this work,a dependent suspension system mostly used in off-road vehicles is modeled using Trucksim software.Then,geometric parameters of suspension system are optimized using integrated anti-roll bar and coiling spring in a way that ride comfort,handling and stability of vehicle are improved.The simulation results of suspension system and variations of geometric parameters due to road roughness and different steering angles are presented in Trucksim and effects of optimization of suspension system during various driving maneuvers in both optimized and un-optimized conditions are compared.The simulation results indicate that the type of suspension system and geometric parameters have significant effect on vehicle performance.

Development of a Composite Suspension with a Coil and Hydro-Pneumatic Spring

A new composite suspension is developed, where a coil spring and a hydro-pneumatic spring are used in order to improve the poor reliability of off-road vehicle with pure hydro-pneumatic suspension. According to road conditions, the two springs play different roles. The method for matching the composite suspension stiffness and distributing the load is proposed. The working pressure of hydro-pneumatic spring as well as the load and stiffness characteristics of composite suspension is compared with a pure hydro-pneumatic suspension. In addition, the ISO weighted vehicle body acceleration, suspension travel and relative dynamic load of the wheels between two kinds of suspension are analyzed with a quarter vehicle mode. The simulation result shows that the developed composite suspension is more suitable for off-road vehicle than the one hydro-pneumatic suspension, because the composite suspension can reduce the working pressure, improve the reliability and keep a similar ride comfort with hydro-pneumatic suspension.

Distalization of maxillary molars for Class Ⅱ malocclusion with Chinese Ni-Ti coil-springs appliance

Objective: To evaluate the effects of the Chinese Ni-Ti coil-springs appliance on distalization of maxillary molars and the reciprocal effects on the anchorage teeth. Methods:Twenty-four adolescent patients(12 boys,12 girls) with Class Ⅱ malocclusion were selected and the coil-springs appliance was used during the treatment. Pre- and postdistalization lateral cephalometric radiographs were analyzed and compared. Results: The average time for the correction of Class Ⅱ molar relationship was 4.6 months. And the mean distance of molar distalization was 4.4 mm. The Chinese Ni-Ti coil-springs also demostrated less tipping and better bodily movement of maxillary molars. Conclusion: This study suggests that the Chinese Ni-Ti coil-springs appliance distalizes the upper molar significantly, while there is no remarkable loss of anchorage because of patients’ wearing headgear with J hooks at night and Class Ⅱ elastics in the day time.

Investigation into the Vibration of Metro Bogies Induced by Rail Corrugation

The current research of rail corrugation mainly focuses on the mechanisms of its formation and development. Compared with the root causes and development mechanisms, the wheel-rail impacts, the fatigue failure of vehicle-track parts, and the loss of ride comfort due to rail corrugation should also be taken into account. However, the influences of rail corrugation on vehicle and track vibration, and failure of vehicle and track structural parts are barely discussed in the literature. This paper presents an experimental and numerical investigation of the structural vibration of metro bogies caused by rail corrugation. Extensive experiments are conducted to investigate the effects of short-pitch rail corrugation on the vibration accelerations of metro bogies. A dynamic model of a metro vehicle coupled with a concrete track is established to study the influence of rail corrugation on the structural vibration of metro bogies. The field test results indicate that the short-pitch rail corrugation generates strong vibrations on the axle-boxes and the bogie frames, therefore, accelerates the fatigue failure of the bogie components. The numerical results show that short-pitch rail corrugation may largely reduce the fatigue life of the coil spring, and improving the damping value of the primary vertical dampers is likely to reduce the strong vibration induced by short-pitch rail corrugation. This research systematically studies the effect of rail corrugation on the vibration of metro bogies and proposes some remedies for mitigating strong vibrations of metro bogies and reducing the incidence of failure in primary coil springs, which would be helpful in developing new metro bogies and track maintenance procedures.

The torsion model of soft tissue in virtual surgery

In order to solve the problem of real-time soft tissue torsion simulation in virtual surgeries,a torsion model based on coil spring is proposed to actualize real-time interactions and applications in virtual surgeries. The proposed model is composed of several connected coil springs in series. The sum of torsion deformation on every coil is equivalent to the soft tissue surface deformation. The calculation of the model is simple because the method for calculating the torsion deformation for each coil spring is the same. The virtual surgery simulation system is established on PHANTOM OMNI haptic device based on the Open GL 3 D graphic interface and VC + + software,and it is used to simulate the torsion deformation of virtual legs and arms. Experimental results show that the proposed model can effectively simulate the torsion deformation of soft tissue while being of real-time performance and simplicity,which can well meet requirements of virtual operation simulations.

The Study on Effect of Exhaust Performance According to Active Muffler Valve Spring as Followed Spring Constant

This study represents the influence on exhaust performance by active muffler valve spring.The main experimental parameters were engine speeds and torsion coil spring constants in the active muffler.When the muffler valve spring has a low spring constant of k=0.75,the sound pressure level was low at the region of engine speed 2000 to 2500 r/min,and the velocity of exhaust gas was high at spring constant k=0.75.When the engine speed was under 1500 r/min,the mean concentration of CO was high in case without muffler valve.When the engine speed in the range of 1600 to 2600 r/min with spring constant k=0.75,the mean HC concentration showed the lowest value.Without muffler valve,the temperature in the muffler was higher than the case with muffler valve.This research represented that the performance of the active muffler valve spring constant k=0.75 was higher than that without muffler valve and valve spring constant k=0.70.Among the three cases of experimental condition,with a spring constant k=0.75,0.70 and without muffler valve,the exhaust performance was high in case active muffler valve spring constant k=0.70.