Parallel mechanism (PM) with limbs of embedding structures means that the limbs in the mechanism are connected in the coupling structure, so as to realize limb coupling, and the PM of common axes between limbs. Characterized by the compact structure, low cost and larger workspace, this kind of PM has very broad application prospects in engineering. In this paper, analysis and improvement are carried out on the input of a compact 3-DOF PM with limbs of embedding structures with larger workspace.
Our investigations concern the dynamics of drillstring, experiment apparatus for simulating drillstring vibration was established. Hammering method is used to measure drillstring lateral natural vibration frequency when the internal and external drilling fluid is considered. The test results show that the drilling fluid can decrease the natural frequency of the drillstring. Additional mass coefficient can get the result with high precision, which can meet the needs of the project.
This research work correlates the wear progression and Specific Cutting Energy (SCE) in turning Ti-6Al-4V alloy using H13 tools (uncoated carbide) in dry conditions from low to high cutting speeds. Flank wear growth of the tool has been investigated at different length of cuts in correlation with the SCE under different cutting conditions. The useful tool life was found to be shorter at high-speed machining conditions, as compared to low-speed machining conditions.
Eliminating the hysteresis effect is highly desired in harmonic drive, which results in challenges in the control design. In this paper, we construct a new compound optimal controller to improve the compensational effect of hysteresis torque. The new controller is proposed based on the optimal theory and the linearization of nonlinear system. Numerical simulation shows that this new controller can track the complex reference trajectory with a relative error less than 1%.
This paper investigates an experiment with the cryogenically treated copper electrode and an ordinary copper electrode with various input parameters like electrode rotation, gap voltage and discharge current for an EN24 material. An experiment was performed on an electrical discharge machine. Designs of an experiment are carried out using the Taguchi approach. This research finds optimal or dominating factors in both traditional and non-traditional machining processes.
At present, grinding is the main processing method of Machinable ceramics. There is little research on turning Machinable ceramics, but turning machinable ceramics has good prospects. This paper analyses the mechanism of turning machinable ceramics and establishes a theoretical model of cutting force. This model has theoretical and engineering significance for turning Machinable ceramics, and has theoretical function for predicting processing quality and controlling processing accuracy.
The structural description of the metamorphic mechanism is an important part of its structure, which is the basis of analysis and synthesis. Therefore, we introduce a comprehensive whole information matrix. The novel method to describe the topological structure of metamorphic mechanism in all the configurations was proposed in the paper. We have put painstaking effort into building the matrix.
In the article, we report the procedure for a lightweight self-design knuckle. We analyzed the strength of lightweight knuckle which designed by using topology optimization method. And determine the fatigue life of the knuckle for four ISO 8608 road classes to predict the life of the knuckle.
A novel transmission with multistage face gears as the core component achieves variable speeds via differential gear shifting. Single/multistage coupled vibration models have been established in this study to derive the coupled vibration equation in order to accurately solve the load distribution between the meshing teeth and the vibration shock between the shifting stages in the transmission process, improve the transmission smoothness of the face gears during the shifting processing, suppress.
Valve mechanisms are needed to control the intake and exhaust processes of today's engines. The valves in this valve mechanism are actuated by machine parts called camshafts. The cams on the camshaft have specially designed profiles for the movement of the valves. Different cam profiles must be created for each engine size and characteristic. In this study, the camshaft design parameters were dimensioned and thus a new design approach that can be used in all cam designs was presented.
We conducted by using both the rigid-body model and the compliance model to evaluate the handling performance of the EV in impulse steering tests conducted at vehicle speeds of 40, 60 and 80 km h−1, respectively.
Friction is usually present in pneumatic cylinders and can make accurate simulation and position control of the pneumatic cylinders difficult to achieve. In this study, effects of three friction models: a steady-state friction model, the LuGre model, and the revised LuGre model on the motion simulation accuracy of a pneumatic cylinder are examined by both simulation and experiment. The results show that the revised LuGre model is the best for the pneumatic cylinder among the three friction model
• Linear and cubic nonlinear damping can significantly suppress the resonance peak of the fundamental harmonic, eliminate the jumping phenomena.
• In resonance area, an increase in linear or cubic nonlinear damping significantly suppresses the ability to absolute displacement.
• In high speed areas, cubic nonlinear damping can slightly suppress the vibration amplitude and may slightly increase the moment of force transmissibility.
The optimum design mentioned in the paper was to choose optimum mechanism from the infinite number of mechanism solutions. By imposing constraints, the optimum mechanism solution was straightforwardly identified by the designers. The design data have been obtained and converted into a series of design graphs by the computer program which can be used to synthesize easily four-bar linkages yielding desired straight-line outputs of predetermined position.
The stress state of a polygonal plate having a central circular hole with two linear cracks was considered. External forces were applied to the contours of polygonal plate and internal forces were applied to the contours of the circular hole. Stress concentrations were determined at the end points of cracks using conformal mapping function. Critical loads were defined for different loads. Analytical results were found to agree with the numerical literature results.
The paper provides a comparative study of dry, wet and cryogenic turning of Ti-6Al-4V. Usually, it is recommended that titanium should be machined under lubrication, however, conventional lubricants are considered carcinogenic and health hazards. In this regard, cryogenic cooling using liquid Nitrogen provides an environment friendly option to machine Titanium based alloys.
In order to allow healing from severe fractures cases, a new mechanism is proposed for bone reduction surgery. This hybrid architecture is made of a double triangular planar mechanism and a tripod mechanism. Its kinematic and velocity model are computed while considering the compensation of parasitic motions. Kinematic data obtained from medical image of real case are used for simulations. When compared with the standard Steward mechanism, the present mechanism shows larger workspace.