Uniaxially fixed mechanical boundary condition elicits cellular alignment in collagen matrix with induction of osteogenesis

Osteocytes differentiated from osteoblasts play significant roles as mechanosensors in modulating the bone remodeling process. While the well-aligned osteocyte network along the trabeculae with slender cell processes perpendicular to the trabeculae surface is known to facilitate the sensing of mechanical stimuli by cells and the intracellular communication in the bone matrix, the mechanisms underlying osteocyte network formation remains unclear. Here, we developed a novel in vitro collagen matrix system exerting a uniaxially-fixed mechanical boundary condition on which mouse osteoblast-like MC3T3-E1 cells were subcultured, evoking cellular alignment along the uniaxial boundary condition. Using a myosin II inhibitor, blebbistatin, we showed that the intracellular tension via contraction of actin fibers contributed to the cellular alignment under the influence of isometric matrix condition along the uniaxially-fixed mechanical boundary condition. Furthermore, the cells actively migrated inside the collagen matrix and promoted the expression of osteoblast and osteocyte genes with their orientations aligned along the uniaxially-fixed boundary condition. Collectively, our results suggest that the intracellular tension of osteoblasts under a uniaxially-fixed mechanical boundary condition is one of the factors that determines the osteocyte alignment inside the bone matrix.

Exact solution for the thermo-elastic deformation and stress states of FG rotating spherical body

In this paper, a generalized solution for 1-D steady-state mechanical and thermal deformation and stresses in rotating hollow functionally graded spherical body is presented. Spherical shells are treated under mechanical and thermal loads in the form of rotational body force with heat generation. Temperature distribution is assumed to vary along the radial direction due to variable heat generation. General uniform mechanical boundary condition at inner and outer surfaces along with prescribed temperatures at both the ends are assumed as boundary conditions. In the present study, material properties are taken as power function of radius with grading parameter ranging between −2 to 3. Governing differential equation with variable coefficient is developed and solved to find deformation and stresses. The obtained results are verified with benchmark results and are found to be in good agreement. Results show that deformation and stresses decrease with an increase in the value of grading parameter and are less as compared to the homogeneous body.

Finite Element Prediction of Residual Stress and Deformation Induced by Double-Pass TIG Welding of Al 2219 Plate

Finite element (FE) analysis of welding residual stress and deformation is one of the essential stages in the manufacturing process of mechanical structures and parts. It aids in reducing the production cost, minimizing errors, and optimizing the manufactured component. This paper presents a numerical prediction of residual stress and deformation induced by two-pass TIG welding of Al 2219 plates. The FE model was developed using ABAQUS and FORTRAN packages, Goldak’s heat source model was implemented by coding the nonuniform distributed flux (DFLUX) in user subroutine to represent the ellipsoidal moving weld torch, having front and rear power density distribution. Radiation and convection heat losses were taken into account. The mechanical boundary condition was applied to prevent the model from rotation and displacement in all directions while allowing material deformation. The FE model was experimentally validated and the compared results show good agreement with average variations of 18.8% and 17.4% in residual stresses and deformation, respectively.

Rock Stress Around Noncircular Tunnel: a New Simple Mathematical Method

A new simple mathematical method has been proposed to predict rock stress around a noncircular tunnel and the method is calibrated and validated with a numerical model. It can be found that the tunnel shapes and polar angles affect the applicable zone of the theoretical model significantly and the applicable zone of a rectangular tunnel was obtained using this method. The method can be used to predict the values of the concentrated stress, and to analyze the change rate of rock stress and back to calculate the mechanical boundary condition in the applicable zone. The results of the stress change rate indicate that the horizontal stress is negatively related to the vertical boundary load and positively related to the horizontal boundary load. The vertical stress is negatively related to the horizontal boundary load and positively related to the vertical boundary load. These findings can be used to explain the evolution of the vertical increment in stress obtained with field-based borehole stress monitoring.

NUMERICAL DISCRETISATION OF BUILT STRUCTURES ASSUMPTION AND REALITY

The second half of the 20th century was affected by the introduction of electronic data processing. The numerical methods appeared to be capable of solving every engineering problem. However, dealing with real problems, an appropriate numerical discretization of built structures is in many cases a difficult task, since fundamental input data concerning the actual properties of the structure, material and the mechanical boundary condition couldn’t always be met. Typical difficulties are an incomplete documentation, unknown effects of structural faults and uncertain material properties. In this paper our experience in experimental assessment of structures is described and the outcome of experimental versus numerical results is compared in several examples. This paper summarizes finally both prospects and limitations of numerical simulations of built structures and shall show that the identified load bearing capacity is strongly bound to the quality of the numerical structural model.

Mechanics Analysis of Omni-Directional Mecanum-Wheel Based on FEM

The Mechanics property is important for Mecanum-wheel structure. According to function and capacity of wheel, the structure of omni-directional Mecanum-wheel is designed and mechanical boundary condition is analyzed on different working status. On the basis of mechanical analysis, the finite element model is established and loads are applied. Strength and fatigue failure life of every parts are calculated respectively under different working conditions. The result shows that the structure and size of Mecanum-wheel is correct and meet the demand of mechanical property.

Radially Polarized and Magnetized Rotating Cylinders Under Thermal Loading

Analytical solutions are acquired for radially polarized and magnetized rotating magnetoelectroelastic hollow and solid cylinders. The cylinders are orthotropic and infinitely long and are subjected to a combination of thermal, magnetic, electric, and mechanical loadings. The symmetric and steady state heat conduction equation is solved based on a general form of thermal boundary conditions to give the temperature distribution along the radial direction of cylinders. The governing ordinary differential equations in terms of displacement, electric potential, and magnetic potential with considering the thermal and inertial effects are obtained and solved in an exact form using the straightforward successive decoupling method. Numerical results are illustrated to reveal influences of thermal boundary condition, angular velocity, aspect ratio, and magneto-electro-mechanical boundary condition on the multiphysical responses of the rotating hollow and solid cylinders. The results are validated with those available in the literature.