Greater Moment Of Inertia Research Articles

Bracing requirements for multiple parallel nonidentical columns with initial curvature

For a system consisting of multiple columns, horizontal discrete braces are often used to increase the system’s strength by decreasing the effective length of columns. Since the bracing requirements for such systems in current design standards were developed based on the assumption of identical columns with pin-ends, an analytical method is proposed to evaluate the ideal brace stiffness and brace forces for multiple columns by accounting for the stiffness interaction among columns and braces. For systems with uniform column lateral stiffness, the explicit solution for the maximum brace force is derived, and a simple formula is subsequently proposed by fitting the analytical results. The proposed formula explicitly accounts for the influences of column initial curvature and semi-rigid end connections on the maximum brace force. The method is comprehensive and applicable to multi-column systems with nonuniform column lateral stiffness, which can result from differences in column sizes, end connections, or applied loads. The results obtained from the proposed formulae are verified against those of finite element analyses. The ideal brace stiffness and brace forces for a system containing a distinctive column with a greater moment of inertia than the other columns are investigated. The results show that the location of the distinctive column affects the magnitudes of the ideal brace stiffness and the maximum brace force, which is yet to be considered in current design standards.

Out-of-plane buckling resistance of rolled steel H-section beam-columns under unequal end moments

A novel analytical model is proposed for establishing design criteria based on the decomposition of the in-plane deformation and out-of-plane stability states. First part of this study considered the in-plane buckling resistance of beam–columns. This study uses the results from Gizejowski et al. [42] to develop an analytical model for the inelastic out-of-plane buckling resistance of beam–columns subjected to a moment gradient. The elastic flexural–torsional buckling solution is combined with the in-plane solution via the generalised Ayrton–Perry model. In order to unify the recommendations for the resistance evaluation of beams, columns, and beam–columns, the model is customised to conform to the standard Eurocode technique of modelling buckling resistance of steel elements in compression or bending about the cross-sectional axis with the greater moment of inertia. As a result, the out-of-plane resistance interaction curves, expressed in dimensionless coordinates, which describe the beam–column flexural–torsional buckling resistance and consider lateral–torsional buckling effects, are obtained. The results of finite element simulations are used for the verification of the developed analytical formulation. Two numerical techniques of imperfection modelling are used: an equivalent geometric imperfection approach with the Maquoi–Rondal generalised initial imperfection and an approach that individually considers geometric and material imperfections. The results obtained from the proposed analytical model and those obtained using the Eurocode design criteria and other recent analytical proposals are compared. Finally, concluding remarks and directions of future studies are also presented.

Experimental and numerical assessment of mechanical properties of thin-walled aluminum parts produced by liquid impact forming

Quick, low-cost, and high-quality manufacturing is considered a key factor in today’s industry. Therefore, researchers have turned to inventing new methods and technologies for meeting such industrial requirements. Liquid impact forming is one such method which is being increasingly developed in different industries, such as automotive and aerospace. Considered to be a tube hydroforming process, this forming method utilizes liquid pressure to produce the desired shape. In this study, the liquid impact forming process, which was applied to a thin-walled tube made of 6063 aluminum alloy, was experimentally and numerically investigated. In the experimental section, a new die was designed and manufactured for deforming the cross section of the aluminum tube into a hexagonal profile. To investigate the characteristics of the hexagonal profile obtained from the forming process, tensile and three-point bend tests were performed. According to the results obtained from the tensile test, the tensile yield strength in the workpiece increased by 21 MPa due to work hardening. The results obtained from the three-point bend test indicated that the flexural strength of the circular tube was greater than that of the hexagonal profile due to its greater moment of inertia. The numerical results included plastic equivalent strain distribution, variations in the profile thickness, and the force required for the forming process. Upon comparing the workpiece thicknesses obtained from numerical simulation and measurements, a good agreement was observed.

The temporal formation and the shape of ellipsoidal stones on the beaches of the oceans

On ocean beaches, amongst many irregular shaped stones, a surprisingly large number of stones that are nearly perfect ellipsoids may also be found. The grinding process which forms the ab-plane of the ellipsoid is connected with the rotation around the axis of the greatest moment of inertia (c-axis). A model calculation is presented which shows that a deformed ellipsoid (ovoid) with different curvatures at the a-axis will be finally transformed into the elliptical form by this grinding process. The influence of the density on the shape of the stones is examined by comparing basalt with calcite stones, and interpreted with the rotation around axes with different moments of inertia. Small, but systematic deviations from the ideal elliptical shape are quantitatively measured on a number of stones. The deviations confirm the mechanism that leads to this form: namely, the rotation around the c-axis with slip against the support under the action of the very different vertical accelerations at both the a- and b-axes.

Raloxifene Improves Bone Mechanical Properties in Mice Previously Treated with Zoledronate.

Bisphosphonates represent the gold-standard pharmaceutical agent for reducing fracture risk. Long-term treatment with bisphosphonates can result in tissue brittleness which in rare clinical cases manifests as atypical femoral fracture. Although this has led to an increasing call for bisphosphonate cessation, few studies have investigated therapeutic options for follow-up treatment. The goal of this study was to test the hypothesis that treatment with raloxifene, a drug that has cell-independent effects on bone mechanical material properties, could reverse the compromised mechanical properties that occur following zoledronate treatment. Skeletally mature male C57Bl/6J mice were treated with vehicle (VEH), zoledronate (ZOL), or ZOL followed by raloxifene (RAL; 2 different doses). At the conclusion of 8 weeks of treatment, femora were collected and assessed with microCT and mechanical testing. Trabecular BV/TV was significantly higher in all treated animals compared to VEH with both RAL groups having significantly higher BV/TV compared to ZOL (+21%). All three drug-treated groups had significantly more cortical bone area, higher cortical thickness, and greater moment of inertia at the femoral mid-diaphysis compared to VEH with no difference among the three treated groups. All three drug-treated groups had significantly higher ultimate load compared to VEH-treated animals (+14 to 18%). Both doses of RAL resulted in significantly higher displacement values compared to ZOL-treated animals (+25 to +50%). In conclusion, the current work shows beneficial effects of raloxifene in animals previously treated with zoledronate. The higher mechanical properties of raloxifene-treated animals, combined with similar cortical bone geometry compared to animals treated with zoledronate, suggest that the raloxifene treatment is enhancing mechanical material properties of the tissue.

Main Beam Optimization of Wind Turbine Blade Base on Multi-Objective Genetic Algorithm

Take s814 airfoil as an example, established the multi-objective optimization model of moment of inertia and the weight for wind turbine blade main beam,Using the genetic algorithm global optimization algorithm, and given the Pareto solution set of optimal with the form of Pareto front. Select four kinds of optimization results scheme to do finite element calculation. The results shows that the magnitude of moment of inertia accordance with the change trend of main beam deflection, the width and thick of beam cap have great affect on moment of inertia and weight, the nearer aerodynamic center of leading edge, the greater moment of inertia, the thick of web almost no influence on moment of inertia.

Analysis on the influence of the pump start transient performance with different inertia impeller

Centrifugal pump start-up time is very short, in the boot process, the instantaneous head and flow will have an impact role to the pipeline, and however the moment of inertia is one of the main factors affecting centrifugal pump boot acceleration. We analyzed the pump start-up transient characteristics with the different moment of inertia of the impeller corresponding to the different materials, there are three different moment of inertia of the impeller have been selected. At first, we use the "Flowmaster" fluid system simulation software do the outer characteristics simulation to the selected-model, get the time - flow and the time - speed curve. Then, do the experiments research in the process when pump start-up, and compare with the simulation result. At last use the outer characteristics simulation result as the boundary, using the ANASYS CFX software do the transient simulation to the three groups with different inertia pump impeller, and draw the pressure distribution picture. In according to the analysis, we can confirm that the impact of inertia is one of the factors in the stability during the pump star, and we can get that the greater moment of inertia, the longer the boot stable. We also can get that combined Flowmaster with ANSYS can solved engineering practice problem in fluid system conveniently, and take it easy to solve the similar problem.

Long-Term Leisure Time Physical Activity and Properties of Bone: A Twin Study

Effects of physical activity on bone properties, when controlled for genetic effects, are not fully understood. We aimed to study the association between long-term leisure time physical activity (LTPA) and bone properties using twin pairs known to be discordant for leisure time physical activity for at least 30 yr. Volumetric BMD and geometric properties were measured at the tibia shaft and distal end using pQCT in 16 middle-aged (50-74 yr) same-sex twin pairs (seven monozygotic [MZ] and nine dizygotic [DZ] pairs) selected from a population-based cohort. Paired differences between active and inactive co-twins were studied. Active members of MZ twin pairs had larger cortical bone cross-sectional area (intrapair difference: 8%, p = 0.006), thicker cortex (12%, p = 0.003), and greater moment of inertia (I(max), 20%, p = 0.024) at the tibia shaft than their inactive co-twins. At the distal tibia, trabecular BMD (12%, p = 0.050) and compressive strength index (18%, p = 0.038) were also higher in physically active MZ pair members than their inactive co-twins. The trends were similar, but less consistently so, in DZ pairs as in MZ pairs. Our genetically controlled study design shows that LTPA during adulthood strengthens bones in a site-specific manner, that is, the long bone shaft has a thicker cortex, and thus higher bending strength, whereas the distal bone has higher trabecular density and compressive strength. These results suggest that LTPA has a potential causal role in decreasing the long-term risk of osteoporosis and thus preventing osteoporotic fractures.

On the stability of the permanent rotations of a rigid body about a fixed point in Brun's problem

A criterion is proposed for the fixed sign character of inhomogeneous forms, and the identity of the sufficient and necessary conditions for the stability of the rotations of a heavy rigid body about the principal axis with the greatest moment of inertia is proved.

An active nutation control system for spin stabilised satellites

A familiar problem associated with the design of spin stabilised satellites is the requirement to constrain the satellite to spin about an axis of greatest moment of inertia. This paper is concerned with the design of a nutation control system using a nutation sensor linked to a gas jet system which removes this constraint. The choice of nutation sensor is discussed and the effects of sensor misalignment are investigated. Stability criteria are examined which derive from the sensor/thruster system, energy dissipation and incorrect estimates of the nutation frequency. The results from theoretical analysis are supported by analogue simulation.