A method to calculate and counterbalance the inertia force of slider-crank mechanisms in high-speed presses

A new method to calculate and counterbalance the inertia force of slider-crank mechanisms in high-speed mechanical presses was put forward. By analyzing the kinematic characteristics of a center-located slider-crank mechanism whose crank rotates at a constant angular velocity,the kinematic parameters of the slide,connecting rod and crank were formulated approximately. On the basis of the results above,three inertia forces and the input moment in the mechanism during its idle running were investigated and formulated by dynamic analysis. A verification experiment was performed on a slider-crank mechanism at a high-speed press machine. The forces derived from the established formulas were compared respectively with those obtained by the ADAMS software and the classical method of connecting rod mass substitution. It was experimentally found that the proposed formulas have an improved performance over related earlier techniques. By use of these results,a 1 000 kN 1 250 rpm four-point high-speed press machine was designed and manufactured. The slide of this press is driven by four sets of slider-crank mechanisms with symmetrical layout and opposite rotation directions to counterbalance the horizontal inertia forces. Four eccentric counterbalance blocks were designed to counterbalance the vertical force after their mass and equivalent eccentric radius were formulated. The high-speed press machine designed by the proposed counterbalance method has worked with satisfactory performance and good dynamic balance for more than four years in practical production.

Operation and Force Analysis of the Guide Wire in a Minimally Invasive Vascular Interventional Surgery Robot System

To develop a robot system for minimally invasive surgery is significant,however the existing minimally invasive surgery robots are not applicable in practical operations,due to their limited functioning and weaker perception.A novel wire feeder is proposed for minimally invasive vascular interventional surgery.It is used for assisting surgeons in delivering a guide wire,balloon and stenting into a specific lesion location.By contrasting those existing wire feeders,the motion methods for delivering and rotating the guide wire in blood vessel are described,and their mechanical realization is presented.A new resistant force detecting method is given in details.The change of the resistance force can help the operator feel the block or embolism existing in front of the guide wire.The driving torque for rotating the guide wire is developed at different positions.Using the CT reconstruction image and extracted vessel paths,the path equation of the blood vessel is obtained.Combining the shapes of the guide wire outside the blood vessel,the whole bending equation of the guide wire is obtained.That is a risk criterion in the delivering process.This process can make operations safer and man-machine interaction more reliable.A novel surgery robot for feeding guide wire is designed,and a risk criterion for the system is given.

The Nature and Origin of Inertia

This paper aims to present a new theory that explains the mechanism of inertia at providing a satisfying explanation for the yet unknown mechanism for inertia. By considering the vacuum as a liquid with a measurable density, hydrodynamics laws are used to describe the behaviour of the vacuum when it is dragged by moving body. The inertia is the result of the initial resistance between the moving bodies against the static vacuum. The moving body drags the resisting vacuum during acceleration, till the point that the vacuum travels with the moving body and has the same velocity. When the body decelerates, the vacuum continues to flow and to push the body at the same direction of the original flow till its complete stop. Formulations based on Planck theory derived to prove its equivalence to Newton inertia law. Formulation based on hydrodynamics is derived to confirm the theory that the force exerted by the vacuum on static body in gravity and on moving body in inertia is equivalent to Newton law. The strong equivalence principle is reaffirmed and, consequently, Einstein’s equations are preserved.

Structure design and rice threshing performance of the variable-speed inertial pulley for simulating artificial threshing

Due to the small models and compact structures,small harvesters have also caused problems such as poor threshing separation performance and large loss rates.In order to solve unstable cleaning effects of small harvesters when they facing different working conditions,this study selected rice plants in hilly areas for the experiment.Tensile breaking force of different parts of mature rice was tested,which revealed the fracture mechanism of each part under the combined force.Inertial threshing method was used to simulate artificial plate bin and design three kinds of non-circular pulley variable speed transmission threshing mechanism.With the help of transient inertia force,threshing force was compensated.This paper tested the harvesting performance of the variable speed threshing device with the help of the harvest performance test.Results show when facing the small rice planting area,the T/2 variable speed threshing device has better cleaning performance,and also the harvest loss rate of T/4 variable speed threshing device is the lowest.Compared with the constant speed threshing device,the impurity content rate of the variable speed threshing device is increased by 0.64%to 8.76%;the loss rate is reduced by 0.45%to 1.79%,which provides a basis for the optimization design of small combine harvester in hilly areas.

Normalization of Hydrodynamic Coefficients in Morison Equation

The hydrodynamic coefficients C-d and C-m are not only dependent on the size of slender cylinder, its location in water, KC number and Re number, but also vary with environmental conditions, i.e., in regular waves or in irregular waves, in pure waves or in wave-current coexisting field. In this paper, the normalization of hydrodynamic coefficients for various environmental conditions is discussed. When a proper definition of KC number and proper characteristic values of irregular waves are used, a unified relationship between C-d, C-m and KC number for regular waves, irregular waves, pure waves and wave-current coexisting field can be obtained.

Mechanical genesis of Henan(China) Yima thrust nappe structure

Considering the serious coal and rock dynamic disasters around the main slip plane called F16 in the coal mining area) of Henan Yima(China) thrust nappe structure,the mechanical genesis of the Yima thrust nappe structure was studied comprehensively using geomechanics,fault mechanics,elastic mechanics,and Coulomb's law of friction.First,using the centrifugal inertia force of Earth's rotation as a source,a mechanical model of N-S compression superimposed with W-E reverse torsion was established to explain the formation of the early Yima coal basin and Jurassic Yima Group coal measures.Second,an equation for the ultimate stress in the forming stage of F16 was derived using the plastic slip-line field theory and the parabolic Mohr failure criterion.Moreover,the distribution of ultimate stress and the geometric characteristics of the fault profile were obtained using the field model parameters.Finally,the stress field of F16 and the mechanical genesis of the large-scale reverse thrust sheet were discussed based on elastic mechanics theory and Coulomb's law of friction.The results show that the tectonic framework of the early Yima coal basin and the formation pattern of Jurassic Yima Group coal measures given by the model are consistent with the in-situ explorations.The geometric characteristics of the fault profile obtained by numerical calculation can better reflect the shape of F16 in its forming stage,and the mechanical genesis of the large-scale reverse thrust sheet also concurred with the field situations.Thus,this work can provide a foundation for further studies on the genesis of the thrust nappe structure,the mechanism of rock bursts induced by F16,and the characteristics of the residual stress field in the Yima mining area.

STABILITY ANALYSIS OF TWO-DIMENSIONAL LANDSLIDES SUBJECTED TO SEISMIC LOADS

In the past, the pseudo-static method used to be the most common for evaluating the stability of landslides under seismic loads, in which static forces acting on the center of gravity of a sliding body are used to consider the effects of earthquake. However, seismic loads of rock and soil differ from time and location to time and location. Obviously, it is irrational for the pseudo-static approach to be applied to solving dynamic problems. In this paper, a displacement- pseudo-dynamic model is proposed to assess seismic stability of landslides, in which the sinusoidal- cosinusoidal wave is applied to simulating earthquake displacement, and an ＂amplification factor＂ of peak seismic displacement is referred to as the amplification of seismic wave when it propagates from the bottom to the top of the landslide. The effects of physico-mechanical behaviors of a sliding body on seismic stability of soil slopes are taken into account as well as inertia forces and damping forces. The sensitivity analyses on the permanent displacement and the dynamic factor of safety of landslides are studied in detail. Moreover, a large-scale Tangjiashan landslide that occurred in Wenchuan earthquake is investigated to verify the robustness and precision of the present method. It is found that the results from the present method is in good agreement with those from the previous method.

Practical seismic analysis of large underground structures: Theory and application

Due to the conceptual clarity and calculational simplicity, practical methods for seismic analysis have been widely used in seismic design and calculation of underground structures. All of the commonly adopted practical methods assume that the earthquake inertia force of the analysis model equals that of free-field. However, this assumption neglects the influence of underground structures on their surrounding soil layers, and may lead to significant errors in both conceptual and computational terms when the size of a structure increases. This article focuses on the practical seismic analysis of large underground structures.Theoretical derivation is demonstrated on the basis of the establishment of mechanical models of the soil-structure system and free-field, and consequently, the quantitative relation between the seismic acceleration response of the soil-structure system and that of free-field is obtained. This relation can be used to revise the earthquake inertia force applied to the analysis model so that the calculation accuracy is effectively improved. By doing so, a revised pushover analysis method, which combines the traditional pushover analysis and theoretical derivation, is proposed in order to be appropriate to seismic analysis of large underground structures. Moreover, an example of application of the proposed method is given, in which a selected large underground structure is analyzed. The results show that this revised method has higher efficiency than the traditional method thanks to the revision of the earthquake inertia force.

Extreme wave loads on submerged water intakes in shallow water

This paper provides new guidance concerning the hydrodynamic loads on submerged intake structures located in shallow water under breaking and non-breaking waves. Results from a series of experiments conducted in a large wave flume at 1 ： 15 scale to study the hydrodynamic forces exerted on a generic intake structure located on a sloping seabed in shallow water below breaking and non-breaking irregular waves are presented. Based on analysis of the experimental data, empirical relationships are developed to describe the peak loads in terms of characteristic wave parameters such as significant wave height and peak wave period. The distribution of the peak loads across different parts of the intake structure is also described. Drag and inertia force coefficients for the horizontal forcing on the intake structure and for the main structural sub-components are derived and presented. It is shown that the well-known Morison equation, with appropriate drag and inertia force coefficients, can provide reasonable estimates of the moderate horizontal loads, but the peak loads are less well predicted.