The Research and Experiments on Contact Sealing Theory of the Underwater Clamp Connector

With regard to the sealing structure characteristics of the underwater clamp connector, based on the Hertz contact theory, this article studies the method of solving the extreme value of the radius of curvature on the two curved surfaces at the sealing contact point; first, the method of calculating the extreme value of the radius of curvature at any surface point of the rotary part is obtained, and then the equivalent radius of curvature is solved. Using finite element simulation to study the contact sealing characteristics without considering the edge thickness and width of the sealing gasket, it is verified that the Hertz contact theory is applicable to the metal contact theory of underwater clamp connectors. Then, the sealing simulation with the influence of the detailed dimensions of the sealing gasket is compared with the theoretical result of the direct application of the Hertz contact theory in the underwater clamp connector contact, and the theoretical correction coefficient of metal contact seal for underwater clamp connectors is introduced to solve the errors. The pressure sealing experiment is carried out on six-inch flange and metal sealing gasket, which proves that the coefficient can greatly enhance the theoretical calculation accuracy of the contact sealing of the underwater clamp connector.

Investigation of Fracture Width Change under Closure Pressure in Unconventional Reservoir Based on the Hertz Contact Theory

To describe the fracture width is crucial for the flow conductivity evaluation, which influences the exploitation efficiency of unconventional oil and gas resources. Commonly, as the proppants fill in the fracture, the deformation will happen under the closure pressure to resist the fracture width change. Therefore, it is significant to develop the theoretical model to predict the variation. In this work, the mathematical model for the propping behavior of proppants in the fracture under closure pressure is established based on the Hertz contact theory. Compared with the existing models, the developed model considers both the proppant insertion and the elastic compression among the proppants, which is closer to the actual physical process. Furthermore, the experimental cases with different proppant sizes are taken to verify the model, and the good conformity presents its rationality. The parameter sensitivity analysis of this model shows that the fracture width change increases with the increase of the average diameters of proppants ( D ) and it declines with the improving of proppant elasticity modulus ( E 1 ) and Poisson’s ratio ( v 1 ).

A Dynamic Damage Model for the Rock-Shed Roof Under the Rockfall

The dynamic response of the rock-shed roof under the rockfall is a complicated mechanical process, which mainly includes the following three deformation stages, e.g. the elastic compression, plastic damage compression and elastic resilience stages of the rock-shed roof. However, the existing models based on Hertz elastic-perfectly plastic contact theory cannot perfectly reflect the above mechanical process. Therefore, on basis of the classical Hertz contact theory, the damage of the rock-shed roof induced by the rockfall is firstly introduced to consider its effect on the material elastic modulus, and then the revised Hertz contact theory considering the damage is proposed. Secondly, in view of the existing calculation method of the maximum rockfall impact force based on the theorem of impulse, a new calculation method is proposed by combining the revised Hertz contact theory. Thirdly, according to the dynamic mechanical response process of the rock-shed roof under the rockfall and in view of the revised Hertz contact theory, a dynamic damage model for the rock-shed roof under the rockfall is proposed, which can perfectly illustrate the variation law of the impact force with the deformation of the rock-shed roof during the rockfall. Finally, the proposed model is verified with other models for the maximum rockfall impact force. In all, the proposed model can perfectly describe the dynamic mechanical behavior of the rock-shed roof under the rockfall, which can be referred for the engineering design.

Analysis of Two Colliding Thin Spherical Shells

In the present paper, the collision of two elastic spherical shells is investigated using the wave theory of impact. The model developed here suggests that after the moment of impact quasi-longitudinal and quasi-transverse shock waves are generated, which then propagate along the spherical shells. The solution behind the wave fronts is constructed with the help of the theory of discontinuities. Since the local bearing of the materials of the colliding elastic shells is taken into account, then the solution in the contact domain is found via the Hertz contact theory.

Investigation on indentation rolling resistance of belt conveyor based on Hertz contact theory compared with one-dimensional Winkler foundation

Based on Hertz contact theory and one-dimensional Winkler foundation combination with viscoelastic theory, the author derived theoretical formulas of indentation rolling resistance, respectively. Using the laboratorial apparatus of indentation rolling resistance, the author mainly concentrates on the error analysis about two kinds of theoretical formula which bear on indentation rolling resistance compared with experimental result. The reason why author employs Hertz contact theory to discuss indentation rolling resistance is that indentation rolling resistance is a sort of contact resistance. As a result, Hertz contact theory is generally applicable to study it. On the other hand, because conveyor belt has viscoelastic property, it is appropriate to use viscoelastic theory by the aid of three-parameter Maxwell viscoelastic model combination with one-dimensional Winkler foundation. Ultimately, this article infers that theoretical formula based on the Hertz contact is brief and clear compared with one-dimensional Winkler foundation in principle. However, it is noticeable that when the belt is at high speed, the reliability of formula based on Hertz theory has decreased obviously. This conclusion can give a beneficial reference for the energy saving of belt conveyor.