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• A multiphasic FE model of the lumbar intervertebral disc was developed. • The disc nutrient response was evaluated under different axial forces. • Sustained weight-bearing activities could deteriorate disc nutrient environment. • Tensile force might have a nonnegligible role in improving nutrient levels. Understanding the role of mechanical force on tissue nutrient transport is essential, as sustained force may affect nutrient levels within the disc and initiate disc degeneration. This study aims to evaluate the time-dependent effects of different compressive force amplitudes as well as tensile force on glucose concentration and cell viability within the disc. Based on the mechano-electrochemical mixture theory, a multiphasic finite element model of the lumbar intervertebral disc was developed. The minimum glucose concentration and minimum cell density in both normal and degenerated discs were predicted for different compressive force amplitudes, tensile force, and corresponding creep time. Under high compressive force, the minimum glucose concentration exhibited an increasing and then decreasing trend with creep time in the normal disc, whereas that of the degenerated disc increased, then decreased, and finally increased again. At steady state, a higher compressive force was accompanied by a lower glucose concentration distribution. In the degenerated disc, the minimum cell density was negatively correlated with creep time, with a greater range of affected tissue under a higher compressive force. For tensile force, the minimum glucose concentration of the degenerated disc raised over time. This study highlighted the importance of creep time, force magnitude, and force type in affecting nutrient concentration and cell viability. Sustained weight-bearing activities could deteriorate the nutrient environment of the degenerated disc, while tensile force might have a nonnegligible role in effectively improving nutrient levels within the degenerated disc. [ABSTRACT FROM AUTHOR]

Curvilinear cylindrical gear drives are similar to double-helical gear drives as they can avoid the axial thrust during the meshing process. Whether curvilinear cylindrical gear drives are better than double-helical gear drives is a problem to be solved. In this paper, a new gear-generating method for curvilinear gears is proposed based on the theory of gearing. Two different single-side face-milling cutters are used for the generation of concave and convex tooth surfaces, respectively. The curvilinear gear sets being generated have line contact in the meshing process. For the sake of comparison, the double-helical gear sets involved in the comparison study are also a kind of gear sets with line contact. This article includes the following: (1) Comparison of transmission errors and stresses of two types of gear sets with the same contact ratio; (2) Derivation of tooth surface equations, transmission error analysis, and finite element analysis; (3) Four numerical examples which show the advantages and disadvantages of curvilinear cylindrical gear drives. [ABSTRACT FROM AUTHOR]

During an earthquake, the brace of a multistorey X-braced steel frame experiences out-of-plane instability. After the brace becomes unstable, the middle span of the brace-intersected beam exhibits a large imbalance force. This force causes a significant vertical displacement in the middle of the brace-intersected beam. To address this issue, an improved multistorey X-braced steel frame is proposed. Adding an arc energy-dissipation structure to the original structure adjusts the bearing capacity of the brace and ensures that the brace does not lose stability. The deformation of the arc energy-dissipation structure reduces the vertical displacement of the brace-intersected beam. A finite element model of the improved multistorey X-braced steel frame is established, and the seismic performance of the structure is analysed. The analysis shows that the brace of the improved multistorey X-braced steel frame does not experience instability, and the lateral bearing capacity is increased by 20%. The vertical displacement in the middle of the brace-intersected beam is small. The improved multistorey X-braced steel frame exhibits good seismic performance. • Seismic performance of improved multistorey X-braced steel frame was studied. • Improved multistorey X-braced steel frame can solve the out-of-plane instability of brace. • The problems of large unbalanced force and vertical deformation of brace-intersected beam were solved. [ABSTRACT FROM AUTHOR]

In this article, a new type of reticulated joint, named the steel–concrete composite reticulated shell joint, is proposed. The proposed reticulated shell joint consists of an inner circular steel pipe, an outer circular steel pipe, a steel cover plate, and internal concrete. Five test specimens were tested under axial compression. The variable study included the wall thickness of the inner and outer circular steel pipes and the radius of the inner circular steel pipe. The test specimens exhibited a high bearing capacity and good plastic deformation ability under axial compression. The test results show that the wall thickness of the outer circular steel pipe and the radius of the inner circular steel pipe have a great influence on the bearing capacity of the steel–concrete composite reticulated shell joint, while the wall thickness of the inner circular steel pipe has little influence on the bearing capacity of the steel–concrete composite reticulated shell joint. Based on the test of the steel–concrete composite reticulated shell joints under axial load, the three-dimensional nonlinear finite element model was used to analyze the mechanical properties of the steel–concrete composite reticulated shell joints under axial compression. The results of the finite element analysis showed good agreement with the experimental results. The formula for calculating the bearing capacity of the joint is derived. By comparing with the experimental results, the calculated results are basically consistent with the experimental results. [ABSTRACT FROM AUTHOR]

Tubing string is one of the most important tools in flowing production. In the state of lateral vibration instability of the tubing string, severe collisions between the string and casing may lead to tubing string failure and borehole wall sloughing. Stability of the tubing string is a potential safety hazard in the process of oil and gas production and discussed in this paper. Considering interaction among the gravity, internal fluid hydrodynamic force, reservoir pressure and liquid cushion in the annular, a mechanical model of lateral vibration of the tubing string, which is simplified as a uniform pipe conveying fluid upwards in vertical well, is developed, and the stability of the system is analyzed by the finite element method. The influences of the flow velocity, the bottom hole pressure and the height and density of liquid cushion on the stabilities of tubing string are discussed. It is found that the increase of either the flow velocity or the bottom hole pressure can cause the buckling of tubing string, however, increasing the height or density of liquid cushion is helpful to improve the stability of tubing string. [ABSTRACT FROM AUTHOR]

Response analysis of the buried pipeline subjected to reverse fault displacement is very important for design, detection and protection of buried pipelines. This paper looks at the buckling behavior of a buried pipeline subjected to reverse fault displacement in the rock stratum. Effects of internal pressure, wall thickness, fault displacement and burial depth on the buckling mode and the axial strain of the buried pipeline are discussed. The results show that there are two buckling locations on the buried pipeline subjected to reverse fault displacement in the rock stratum and that the buckling modes of the buried pipes with different internal pressures are different. The two buckling locations are not symmetrically distributed along the fault plane. The buckling mode ranges from collapse to wrinkle as the internal pressure increases. The buckling phenomenon becomes more serious as the fault displacement increases, and the shape of the deformation curve changes from the S-shape to the Z-shape. The process of pipeline deformation can be divided into three stages. There is no buckling in the first stage. The second stage is a transition stage, buckling appears on the buried pipeline. Buckling is more serious in the third stage. Fault displacement has a small effect on the maximum strain position of the buried pipeline. The deformation curve of the buried pipeline is smoother as the wall thickness increases. The maximum axial strain of pressure pipes first increases and then decreases as the wall thickness increases. [ABSTRACT FROM AUTHOR]

Spinal cord injury (SCI) is a global problem that brings a heavy burden to both patients and society. Recent investigations indicated degenerative disease is taking an increasing part in SCI with the growth of the aging population. However, little insight has been gained about the effect of cervical degenerative disease on the spinal cord during dynamic activities. In this work, a dynamic fluid–structure interaction model was developed and validated to investigate the effect of anterior and posterior encroachment caused by degenerative disease on the spinal cord during normal extension and flexion. Maximum von-Mises stress and maximum principal strain were observed at the end of extension and flexion. The abnormal stress distribution caused by degenerative factors was concentrated in the descending tracts of the spinal cord. Our finding indicates that the excessive motion of the cervical spine could potentially exacerbate spinal cord injury and enlarge injury areas. Stress and strain remained low compared to extension during moderate flexion. This suggests that patients with cervical degenerative disease should avoid frequent or excessive flexion and extension which could result in motor function impairment, whereas moderate flexion is safe. Besides, encroachment caused by degenerative factors that are not significant in static imaging could also cause cord compression during normal activities. [ABSTRACT FROM AUTHOR]

A new high-order multi-joint finite element for thin-walled bar was derived from the Hermite interpolation polynomial and minimum potential energy principle. This element's characteristics are that it is of high accuracy and can be used in finite method analysis of bridge, tall mega-structure building. [ABSTRACT FROM AUTHOR]

Diamond‑copper composites with high thermal properties and low density show huge potential applications in thermal management. Solving the interface between diamond and copper and increasing the volume fraction of diamond in the composite are crucial for its thermal conductivity. In this work, tungsten/tungsten carbide (W/WC) was used as an interface and fabricated on diamond surface by the molten salt method. Well-coating with higher than 95 % of coverage was obtained at the mass ratio of diamond and W of 3:3, which owns a 200 nm ± 10 nm thickness of W/WC layer. Meanwhile, double-size diamonds with 200 μm and 40 μm were compounded with the copper matrix to increase the volume fraction of the diamond. Theoretical calculation displays only 14.5 % of porosity in the bimodal diamond composite when 74.2 vol% of the large-size diamond is in the total volume fraction of the diamond. Microstructure characterization displays that the interfacial bonding was enhanced by the W/WC interface and morphology was improved by using the double-size diamonds even at 70 % of the volume fraction. Compared with single-size diamond/copper composite, the thermal conductivity was also increased and obtained the highest value of 640 Wm−1 K−1 for the double-size diamonds/copper composites. Finite element analysis and testing of actual scenarios further confirm the excellent thermal performance of double-size diamonds/copper composite, which meets the requirements of thermal management in high-power devices. [Display omitted] [ABSTRACT FROM AUTHOR]

Coulomb failure stress changes (ΔCFS) are used in the study of reservoir-induced seismicity (RIS) generation. The threshold value of ΔCFS that can trigger earthquakes is an important issue that deserves thorough research. The M6.1 earthquake in the Xinfengjiang Reservoir in 1962 is well acknowledged as the largest reservoir-induced earthquake in China. Therefore, it is a logical site for quantitative calculation of ΔCFS induced by the filling of the reservoir and for investigating the magnitude of ΔCFS that can trigger reservoir seismic activities. To better understand the RIS mechanism, a three-dimensional poroelastic finite element model of the Xinfengjiang Reservoir is proposed here, taking into consideration of the precise topography and dynamic water level. We calculate the instant changes of stress and pore pressure induced by water load, and the time variation of effective stresses due to pore water diffusion. The ΔCFS on the seismogenesis faults and the accumulation of strain energy in the reservoir region are also calculated. Primary results suggest that the reservoir impoundment increases both pore pressure and ΔCFS on the fault at the focal depth. The diffusion of pore pressure was likely the main factor that triggered the main earthquake, whereas the elastic stress owing to water load was relatively small. The magnitude of ΔCFS on seismogenesis fault can reach approximately 10 kPa, and the ΔCFS values at the hypocenter can be about 0.7-3.0 kPa, depending on the fault diffusion coefficient. The calculated maximum vertical subsidence caused by the water load in the Xinfengjiang Reservoir is 17.5 mm, which is in good agreement with the observed value of 15 mm. The accumulated strain energy owing to water load was only about 7.3×10 J, even less than 1% of the seismic wave energy released by the earthquake. The reservoir impoundment was the only factor that triggered the earthquake. [ABSTRACT FROM AUTHOR]

Characterized by unmanned excavation and remote controlling, the new pneumatic caisson (NPC) method has advantages in deep excavation such as deep shield tunnel shafts and some underground construction close to the existing structures or facilities. When adopted in urban areas, it is very important to control the ground deformation during a caisson construction. For this purpose, field measurements of ground deformation were conducted during a tunnel shaft construction in Shanghai soft ground, in which the NPC method was used. On the basis of the particular construction procedure of a pneumatic caisson, one kinematic mechanical model was proposed for evaluating the influence of NPC construction on the surrounding strata. This model was incorporated into a finite-element (FE) program. By comparing the FE-predicted results of the proposed model and the field measurements, the accuracy and reliability of this model were verified. [ABSTRACT FROM AUTHOR]