Examination of the Effect of the Combined Use of Nd: YAG Laser Irradiation and Mechanical Force Loading on Bone Metabolism Using Cultured Human Osteoblasts

Introduction: In recent years, laser irradiation in the near-infrared ray (NIR) area has been reported to promote bone healing. There are also reports that laser irradiation accelerates orthodontic tooth movement. In this study, we investigated the effect of NIR laser irradiation and mechanical stimulation on osteoblasts. Methods: We seeded osteoblast-like cells and laser irradiation was performed 24 hours after cell seeding. In addition, a control group not receiving anything, a group receiving only Nd: YAG (neodymium-doped yttrium aluminum garnet) laser irradiation, a group receiving only centrifugal loading, and a group receiving both Nd: YAG laser irradiation and centrifugal force loading were set, and after 24 hours and after 48 hours, cells were collected and quantitative real-time polymerase chain reaction (PCR) was performed. Results: 24 hours after laser irradiation, the gene expression of alkaline phosphatase (ALP), the receptor activator of NF-κB ligand (RANKL) and osteoprotegerin (OPG) was significantly higher in the 2.0 W group than in the control group. In addition, the RANKL/OPG ratio was higher in the 2.0 W group than in the control group. Also, in the group using laser irradiation and centrifugal loading in combination, 24 hours after laser irradiation, ALP and OPG showed significantly higher values than those in the centrifugal load only group. Furthermore, the RANKL/OPG ratio also showed high values. Conclusion: These results suggest that osteoblast-like cells activate genes related to bone metabolism by combining mechanical stimulation and laser irradiation. This helps to elucidate the influence of laser irradiation during tooth movement.

Naval Centrifugal Compressor Design Using CAD Solutions

Centrifugal compressors of turbochargersoperate in a wide range of rotational speeds, which depends on the load of the supercharged engine. Current designs of turbocharger compressors exhibit high efficiencies accompanied by high flow capacities [1]. Consequences of aerodynamic optimization are high mean stress values in the blades due to centrifugal loading as well as dynamic stresses due to blade vibrations. Blade vibrations in a turbocharger compressor are assumed to be predominantly excited by unsteady aerodynamic forces [2]. These forces are caused by a variety of sources influencing the flow. Examples include the geometry of the flow channel, elbows, the diffuser vanes or struts. Therefore, an understanding of FSI is essential for further design optimizations.

An Assessment of Centrifugal Loading Effect of Rotor Disc on Fretting Variables at a Dovetail Interface of an Aero-Engine

This paper presents the influence of centrifugal (CF) loading of aero-engine rotor disc on fretting variables at a dovetail interface. A detailed investigation is carried out on the fretting variables such as contact traction, slip, and contact stress at macroscopic level. Three-dimensional (3D) finite element (FE) analysis approach is used for prediction of fretting variables. The study is carried out for frictionless and friction interface (μ = 0.7) for the case of Titanium alloy. The slip level increase of about 48 % and 110% is observed for frictional and frictionless condition respectively, due to rotational effect of disc. Different contact traction ratio distribution over the interface is also observed with the CF load of rotating disc. The study suggests the consideration of centrifugal loading effect is important for improved prediction of critical fretting variables, as they would impact the evaluation fretting fatigue and wear characteristics at the interface.

Numerical Analyses of Turning-Induced and Mapped Ti6Al4V Residual Stresses for a Disc Subjected to Centrifugal Loading

The paper investigates the effects of turning-induced and mapped Residual Stresses (RSs) for a Ti6Al4V disc subjected to centrifugal loading. The turninginduced RSs are predicted in orthogonal cutting using the Finite Element Method (FEM). The FE predicted RSs are validated after performing face turning followed by hole drilling and x-ray diffraction measurements. Numerical analyses are carried out at different Cutting Velocities (CVs) to obtain the RS profiles. The results show that the compressive RSs increase by increasing the CV and the depth of cut. A disc subjected to a centrifugal load is modelled using the FEM where the turning-induced RSs are introduced as an initial condition using mapping techniques. The predicted CV-dependent RS profiles are incorporated into the mapping techniques using the shape function approach. It is observed that the stress amplitudes at the points at which failure occurs are lower when the mapped turning-induced RS profiles are considered in the disc FE model. The lower stress amplitudes are related to prolonging the disc life due to fatigue.