Function Of Loading Parameters Research Articles

Prediction of cortical bone mineral apposition rate in response to loading using an adaptive neuro-fuzzy inference system

Daily activities such as aerobic movements and athletic events found effective in mitigating bone loss as it promotes osteogenesis. Computational model considered normal strain, or strain energy density as a stimulus to predict site specific osteogenesis. This model, however, fails to predict site specific osteogenesis as cortical bone surfaces exhibit different remodelling rate to mechanical loading. Remodelling rate or mineral apposition rate depends upon the loading parameters such as loading cycle, frequency, and magnitude of strain. Therefore, the present study aims to develop an adaptive neuro-fuzzy inference system (ANFIS) model for finding a robust relationship between loading parameters like strain magnitude, frequency, and cycle, and a bone remodelling parameter i.e. mineral apposition rate (MAR). The model is trained, tested, and checked with the experimental data. The results indicate that ANFIS model outperformed state of the art Artificial Neural Network (ANN) models during the prediction of MAR at periosteal and endosteal surface. A strong corelation R2 = 0.92 and R2 = 0.97 was observed at 70% of the input data at periosteal and endosteal surface respectively. Result concludes that endosteal surface was more promisable as compared to periosteal surface in predicting accurate MAR. The outcomes of present study may be used to precisely predict site-specific osteogenesis in cortical bone as function of loading parameters.

Establishing the relationship between loading parameters and bone adaptation

Cyclic and low-magnitude loading is considered effective in arresting the bone loss as it promotes osteogenesis (i.e. new bone formation) at the sites of elevated normal strain magnitude. In silico models assumed normal strain as the stimulus to predict the sites of new bone formation. These models, however, may fail to fit the amount of newly formed bone. Loading parameters such as strain, frequency, and loading cycle decide the amount of new bone formation. The models did not incorporate this information. In fact, there is no unifying relationship to quantify the amount of new bone formation as a function of loading parameters. Therefore, the present work aims to establish an empirical relationship between loading parameters and a new bone formation parameter i.e. mineral apposition rate (MAR). A neural network model is used to serve the purpose. Loading parameters are supplied as input, whereas, MAR served as output. The model is trained and tested with experimental data. The model establishes an empirical relationship to estimate MAR as a function of loading parameters. The model's predictions of MAR align with in vivo experimental results. The model's response is analyzed which indicates that the bone adaptation characteristics are successfully captured in the relationship. The relationship established may be incorporated further to improve qualitative and quantitative prediction capabilities of computer models. These findings can be extended in future to design and develop effective biomechanical strategies such as prophylactic exercise to cure bone loss.

Analysis of vibration characteristic for helical gear under hydrodynamic conditions

Based on the elasto-hydrodynamic lubrication theory, a 2-degree-of-freedom nonlinear dynamic model of helical gears with double-sided film is proposed, in which the minimum film thickness behaves as a function of load parameters, lubricant parameters, and the geometry of the contact. Then, the comparison of the hysteresis loops in different gear models shows the soundness of the presented model. Using numerical method, the time evolution of lubricant normal force, minimum film thickness, and lubricant stiffness is obtained in order to demonstrate the influence of the driving torque and pinion’s velocity. The results obtained in this article can contribute to the root cause for the gear vibration and show that the hydrodynamic flank friction has almost no influence on the gear system.

Experimental study and mathematical modeling of the behavior of St.3, 20Kh13, and 08Kh18N10T steels in wide ranges of strain rates and temperatures

Results of an experimental study of the behavior of St.3, 20Kh13, and 08Kh18N10T steels under static and dynamic loading are reported. The influence of the strain rate and temperature on characteristics of strength and plasticity is studied. Based on the data obtained, the parameters of the Johnson–Cook model are determined. This model is used in commercial software to describe the yield surface radius as a function of loading parameters. The adequacy of the identified model is verified in a series of special test experiments.

Nonlinear analysis of microstructure-dependent functionally graded piezoelectric material actuators

In the present work, a nonlinear thermo-electro-mechanical response of functionally graded piezoelectric material (FGPM) actuators is investigated. The theoretical formulation is based on the Timoshenko beam theory with the von Kármán nonlinearity (in the form of midplane stretching), and a microstructural length scale is incorporated by means of the modified couple stress theory. A power-law distribution of thermal, electrical, and mechanical properties through beam thickness (or height) is assumed. The governing equations are derived using the principle of virtual displacements. A displacement finite element model of the theory is developed, and the resulting system of nonlinear algebraic equations is solved with the help of Newton's iteration method. Numerical results are presented for transverse deflection as a function of load parameters and out-of-plane boundary conditions. The parametric effects of microstructural length scale parameter, power-law index of the material distribution across the thickness, boundary conditions, beam geometry, and applied actuator voltage on the beam response are investigated through various numerical examples. The results reveal the existence of bifurcation (or critical states) for certain types of in-plane loads. For other load types, including out-of-plane loads, the beam undergoes a unique and stable deflection path that does not contain any critical point.

Life Prediction and Verification under Multiaxial Fatigue Loading

The strain change characteristics of multiaxial fatigue are analyzed under the condition of the combined tension and torsion loading for thin-tube specimen. Based on the principle of multiaxial critical plane approach, a multiaxial fatigue damage parameter is established, which takes account of the effect of not only the maximum shear strain amplitude and normal strain amplitude on the critical plane but also the parameter of non-proportionality. The non-proportionality is the function of loading parameters which is closely contact with the strain change characteristics of multiaxial fatigue and it can indicate the whole material damage. The experiments under the tension-torsion proportional and non-proportional loading were conducted to verify the multiaxial fatigue life model proposed in this paper. The life prediction has a good correlation with the experimental results.

Anatomic variations of the lacunar–canalicular system influence solute transport in bone

Solute transport in the lacunar–canalicular system (LCS) is essential for bone metabolism and mechanotransduction. Using the technique of fluorescence recovery after photobleaching (FRAP) we have been quantifying solute transport in the LCS of murine long bone as a function of loading parameters and molecular size. However, the influence of LCS anatomy, which varies among animal species, bone type and location, age and health condition, is not well understood. In this study, we developed a mathematical model to simulate solute convection in the LCS during a FRAP experiment under a physiological cyclic flow. We found that the transport rate (the reciprocal time constant for refilling the photobleached lacuna) increased linearly with canalicular number and decreased with canalicular length for both diffusion and convection. As a result, the transport enhancement of convection over diffusion was much less sensitive to the variations associated with chick, mouse, rabbit, bovine, dog, horse, and human LCS anatomy, when compared with the rates of diffusion or convection alone. Canalicular density did not affect transport enhancement, while solute size and the lacunar density had more complicated, non-linear effects. This parametric study suggests that solute transport could be altered by varying LCS parameters, and that the anatomical details of the LCS need systemic examination to further understand the etiology of aged and osteoporotic bones.

Influencia de los Parámetros de Carga en la Estabilidad Direccional de un Vehículo Combinado

This work is about the directional stability of truck-semitrailer vehicle, commonly used in Brazil, as a function of load parameters. For different positions of centre of gravity of semi-trailer, the curves that represent the characteristic movements and the ratio of damping for these movements during curved and straight trajectories are obtained. The influence of load and moment inertia variations for different adopted positions of the centre of gravity of semi-trailer was calculated. The results show significant changes on dynamic response of vehicle with the variations of load parameters. Thus, the operating conditions with less safety margins were determined, so they can be avoided by users. The study allows concluding that there are load conditions that although being accepted by the present legislation, must be avoided.

An Engineering Approach for Quantitative Analysis of the Lengthwise Strokes in Massage Therapies

Massage therapies are widely used for improving and restoring the function of human tissues. It is generally accepted that such therapies promote human health and well-being by several possible mechanisms, including increase in blood flow and parasympathetic activity, release of relaxation hormones, and inhibition of muscle tension, neuromuscular excitability, and stress hormones. Nonetheless, most of the purported beneficial/adverse effects of massage are based on anecdotal experiences, providing little insight on its effectiveness or the mechanisms underlying its usefulness. Furthermore, most studies to date have not quantitatively demonstrated the efficacy of massage on human health. This might be due to the lack of appropriate tools necessary for the application of quantitatively controlled loading and for the evaluation of the subsequent responses. To address this issue, we developed a device that applies compression in lengthwise strokes to the soft tissues of the New Zealand white rabbit, thereby mimicking the rubbing and effleurage techniques of massage. This device permits control of the magnitude and frequency of mechanical load applied to the rabbit’s hind limb for various durations. The measurement of tissue compliance and the viscoelastic properties as a function of loading parameters was also demonstrated. Findings of this study suggest that this device offers a quantitative analysis of the applied loads on the tissue to determine an optimal range of loading conditions required for the safe and effective use of massage therapies.

Failure modeling of ACA-glued flip-chip on flex assemblies

This paper addresses the reliability of flip-chip on flex (FCOF) assemblies glued with an Ag-particle filled anisotropic conductive adhesive (ACA). As the description of FCOF failure gives still much scope for speculation, a physics of failure based approach is developed here, taking into account the changing thermo-mechanical properties of the ACA under temperature and moisture. A failure hypothesis is formulated based on the loss of contact pressure. Material analysis, material characterisation, finite element (FE) modeling and lifetime tests have been employed to establish correlations to support this failure hypothesis. It was found, that moisture plays the most important role for interconnect failure. The model is able to predict quantitative changes of force as function of loading parameters and correlate them qualitatively to the experimental mean time to failure. New insights are provided about the stress fields at the ACA bump. The model is discussed with respect to a direct prediction of failure versus time.

Characterization of metallic and ceramic high-temperature materials for energy systems

For the development of metallic and ceramic high temperature materials used, for example, in heat exchanger components, in turbine blades for stationary gas turbines, in ceramic industrial products and fusion reactor components, modern physico-chemical characterization methods are required. The formation stability of naturally formed protective scales is of prime importance in the successful application of metallic materials at high temperatures in aggressive atmospheres. For the characterization and investigation of the growth mechanisms of such surface scales, the main emphasis is placed on such modern spectroscopical methods as SIMS, SNMS, GDOS, EPMA and RBS. The morphology and composition of oxide scales have been investigated by imaging and diffraction techniques. The thermal and mechanical damage behaviour of high-temperature materials for application in fusion reactor components is of importance. Damage behaviour has been simulated by electron beam and laser irradiation experiments, especially by means of in situ techniques in a scanning electron microscope. By such techniques the material erosion, crack formation and crack propagation were studied for ceramic high temperature materials as a function of load parameters. The erosion and the crack formation processes are superim-posed by a redeposition of vaporized material and by thermally activated creep of the binder phases. The application potential for all methods discussed is outlined and available results are presented.