Experimental Analysis of Fabricated Synthetic Midthoracic Paediatric Spine as Compared to the Porcine Spine Based on Range of Motion (ROM)

The present study is aimed at investigating the mechanical behaviour of fabricated synthetic midthoracic paediatric spine based on range of motion (ROM) as compared to porcine spine as the biological specimen. The main interest was to ensure that the fabricated synthetic model could mimic the biological specimen behaviour. The synthetic paediatric spine was designed as a 200% scaled-up model to fit into the Bionix Servohydraulic spine simulator. Biomechanical tests were conducted to measure the ROM and nonlinearity of sigmoidal curves at six degrees of freedom (DOF) with moments at ±4 Nm before the specimens failed. Results were compared with the porcine spine (biological specimen). The differences found between the lateral bending and axial rotation of synthetic paediatric spine as compared to the porcine spine were 18% and 3%, respectively, but was still within the range. Flexion extension of the synthetic spine is a bit stiff in comparison of porcine spine with 45% different. The ROM curves of the synthetic paediatric spine exhibited nonlinearities for all motions as the measurements of neutral zone (NZ) and elastic zone (EZ) stiffness were below “1.” Therefore, it showed that the proposed synthetic paediatric spine behaved similarly to the biological specimen, particularly on ROM.

Calculation of Lateral Soil Pressure at the Hydraulic Construction and its Sustainability on the Stone Bed

The engineering method of analysis of pressure of a ground on flat walls is offered at presence of combine strip superficial loading in view of seismic influences. It is recommended to determine a situation of an internal slip surface dividing an elastic zone from area of limiting balance, on the basis of the technical theory of the ultimate stress condition. Proceeding from a situation of an internal and external slip plane, size of strip loading on the fill, the pressure of a ground which is taking place in an ultimate condition, on an internal slip surface of is determined on developed by P. Yakovlev to the specified Coulomb's method [1], and on an internal side of a retaining structure on the basis of the Boussinesq decision. In comparison with the earlier developed way it is offered specified according to the Boussinesq theory a method of definition of pressure transmitted by bed on a ground of the basis and, as a consequence more reasonable definition of safety factor of stability of a structure. Thus, curvilinear normal pressure diagram in a ground under a sole of lay is replaced on isosides trapeziform.

Residual Stresses of Round Steel Rod at Elastoplastic Twisting

In the elastoplastic twisting of a rod under the action of an external torque, the cross-section of the rod is divided into two zones: the inner elastic zone and the outer plastic zone. After removing the external loads, we observe the residual deformations and the residual stresses inside the rod that significantly affect on the subsequent mechanical processes at manufacturing the products from the round rod. Under too much twisting, the longitudinal surface fibers of the rod begin to tear, the outer surface of the rod ceases to be cylindrical, and the rod’s cross-section ceases to be flat (the Bernoulli’s hypothesis about the flat sections is violated). Next a rupture of the rod is followed. For the plastic materials, the destruction is caused by the pure shear, and the rupture surface is perpendicular to the axis of the rod. For the brittle materials, the destruction occurs, due to the rupture along the screw surface inclined to the axis of the round rod at the angle of 45. In this paper, the residual stresses of the round rod at twisting are obtained for an elastoplastic medium with linear hardening in depending on the rod’s diameter, the shear modulus, the hardening modulus in shear and the yield strength in shear of the rod’s material.

Effect of Heavy Filler on Dynamic Mechanical Properties of Polymer Composites

Experimental studies on the effect of frequency and temperature on the dynamic mechanical properties of filled composites are studied poorly and require further research. The purpose of theresearch is to study the effect of heavy fillerbarite (BaSO4), on the dynamic characteristics of a highly filled composite based on butyl rubber, and to compare the efficiency of barite in the composite with similar light filler. The conclusions are made on the basis of a comparative analysis of the temperature-frequency dependences of the loss tangent and the storage modulusat various percentages of filler, obtained by the DMA method. It has been established that while increasing barite concentration the elasticity of the composite material decreases, the glass transition temperature shifts upwards, and the reverse occurs in the zone of highly elastic state of the composite: the higher the barite concentration, the higher the damping properties. The authors provided a rationale that the heavy filler shows the effect only in the highly elastic zone if compared with the light one. The article is of practical value for the development of new vibration insulation materials.

Experimental Assessment of the Depth of the Deformed Layer in the Roller Burnishing Process

This paper presents the methods of experimental determining the depth of the plastically deformed top layer in the roller burnishing process. Precise determination of the depth of the plastically deformed layer is difficult due to slight deformation at the boundary of the plastic and elastic zone, the lack of visible changes in the microstructure, and minimal changes in microhardness. The article shows the method of original measurement method that consists in determining the thickness of the deformed layer using rings. The method involves the profilographometric measurements of the disconnected rings (samples) which are flat-faced in the package on the mandrel. The rings material deforms plastically in the surface layer causing wrapping of the end face of the ring in the direction of the rolling tool movement. After dismantling the ring pack, measurements were made on the face of each ring along radial directions, and the thickness of the deformed layer was observed on the microscope. The method was verified by microhardness measurements in the cross-section and cross-section of the ring. The results of deformation depth measurements were verified by finite-element-based numerical simulation.

Elastic-Plastic Analysis for Circumferential through Crack at Boundary of Semi’S Brace under Beam Wave

In order to ensure the safety and reliability of the horizontal brace of semi-submersible platform (SEMI) which functions as the supporting structure in SEMI, this article presents an elastic-plastic method to analyze the variations of the crack tip opening displacement, elastic zone and plastic zone of the cracked section of the horizontal brace under beam wave. The brace of the SEMI was assumed to be located a circumferential through crack at its boundary in this article. In addition, the cracked section of the brace has been divided into crack zone, tensile plastic zone, elastic zone and compressive plastic zone in the presented theoretical model. Moreover, the closed form of the solution has been found in this article which is especially suitable solving complicated problems in practical engineering application. Also, a typical new-generation SEMI that is in practical use was selected to analyze the variation tendency of the cracked brace’s parameters using the proposed model which could give good suggestion to semi-submersible platform designers and managers.

Initiation Pressure and Corresponding Initiation Mode of Drilling Induced Fracture in Pressure Depleted Reservoir

With the production of oil and gas from the reservoir for a long period of time, pore pressure will decline from the initial value to a lower level, which narrows the safety mud weight window, and consequently, makes it easier to generate the drilling induced fracture (DIF). In this paper, a new analytical model is proposed for predicting initiation pressure and corresponding initiation mode of DIF in the pressure depleted reservoir. The effect of pore pressure decline on stress field is considered. Formation around the borehole is divided into plastic zone and elastic zone according to the geomechanical parameters, and small deformation theory is adopted in both of the plastic zone and the elastic zone. For the plastic zone, the nonlinear constitutive relationship is captured using equivalent stress and equivalent strain. In addition, excess pore pressure theory is introduced to describe the pore pressure change during the drilling process owing to the formation of mudcake on the borehole wall. Then, the stress and pore pressure distribution in these two zones and the radius of the plastic zone are obtained. Meanwhile, the theoretical formula of initiation pressure and the corresponding initiation mode of DIF are derived. The reliability of the new model is validated by comparing the obtained results with other published models and the field measured data.

Dissipation of Impact Stress Waves within the Artificial Blasting Damage Zone in the Surrounding Rocks of Deep Roadway

Artificial explosions are commonly used to prevent rockburst in deep roadways. However, the dissipation of the impact stress wave within the artificial blasting damage zone (ABDZ) of the rocks surrounding a deep roadway has not yet been clarified. The surrounding rocks were divided into the elastic zone, blasting damage zone, plastic zone, and anchorage zone in this research. Meanwhile, the ABDZ was divided into the pulverizing area, fractured area, and cracked area from the inside out. Besides, the model of the normal incidence of the impact stress waves in the ABDZ was established; the attenuation coefficient of the amplitude of the impact stress waves was obtained after it passed through the intact rock mass, and ABDZ, to the anchorage zone. In addition, a numerical simulation was used to study the dynamic response of the vertical stress and impact-induced vibration energy in the surrounding rocks. By doing so, the dissipation of the impact stress waves within the ABDZ of the surrounding rocks was revealed. As demonstrated in the field application, the establishment of the ABDZ in the surrounding rocks reduced the effect of the impact-induced vibration energy on the anchorage support system of the roadway.