Dynamic investigation of vehicle collisions with stationary obstacles in most cases concerns solutions to complex tasks related to identification of occupant position in the vehicle. The focus of the ...study is on how forces of inertia change their magnitude and direction during car motion. This requires specific analysis done by dividing vehicle trajectory into separate stages according to certain indicators, such as free motion, impact process, post-impact residual motion. Particular attention has been paid to the impact itself, in which the forces of inertia are the most intense, and their magnitude and direction change abruptly. Solution to Cauchy problem has been found, in which initial kinematic parameters of the crash process are considered, satisfying the kinematic values at rest position. Dynamic analysis of the impact phase of a vehicle-fixed barrier collision has been performed by the finite element method using the software product Abaqus/Explicit.
Display omitted
•Effect of particle density on the flotation rate constent was studied.•Influence of inertial forces in flotation rate was derived from the particle density.•Theoretical flotation ...rate model was compared to experimental bubble loading data.•The significance of particle density on flotation kinetics has been shown.•Particle size interval for effective positive and negative inertial forces was discussed.
In this study, a theoretical evaluation of the effect of inertial forces in particle-bubble interactions during the flotation process is presented and supported by the experimental data. The effects of positive and negative inertial forces were analyzed by comparing the differences between the models, which either consider or neglect the inertial forces. The Sutherland collision model and the Nguyen attachment model that completely ignore the effect of particle’s inertial forces (inertialess models) were implemented into the general flotation kinetic model. The modified model was then compared with one of the most accurate inertial models, which considers the Generalized Sutherland Equation (GSE) for collision efficiency along with the Dobby-Finch model for attachment efficiency. The flotation kinetics of chalcopyrite and galena particles were estimated using the general flotation kinetic model in order to demonstrate the effect of particle density on the model, which emphasizes the effect of inertial forces. The influence of positive and negative inertial forces on flotation kinetics was evaluated for various explicit parameters such as particle density, turbulence (energy dissipation), and bubble size and velocity. Obtained theoretical results clearly showed the potential of the particle density to counterbalance the negative effects of the inertial forces. The capability of the positive inertial forces for galena particles (high density) to overcome its negative effect was shown when the general flotation kinetic model was used. Theoretical calculations were further confirmed by experimental bubble loading measurements. It was shown that the inertial forces should not be omitted in any flotation model amidst concerns over the complexity.
Reinforced concrete slabs are among the most common structural elements. Despite the large number of slabs designed and constructed, the effect of their details on their behavior under impact loads ...is not always properly appreciated or taken into account. This paper describes a series of experimental studies to investigate the high-mass, low-velocity impact behavior of reinforced concrete slabs, and to provide high-quality input data and results to validate numerical modeling. The experimental scheme, which consisted of testing six sample two-way slabs with simply supported boundary conditions, was tested to failure under sequential high-mass, low-velocity impact loading conditions. The effects of different reinforcement ratios of slabs and the compressive strength of concrete on the dynamic response and behavior of reinforced concrete slabs were studied.
The data indicated that the slab response is affected by the increase in the compressive strength of concrete, and it causes a clear increase in the load time history. But obviously, the load-time history is not affected noticeably by increasing the reinforcement ratio.
The observed damage and crack development were found to be typical between the RC slabs. In the beginning, for slab group (1), which investigated the effect of increasing the steel reinforcement ratio, the slab with the largest reinforcing ratio was more resistant to local damage, and the cracking pattern on the bottom surface of the slab consisted of primarily discontinuous hairline cracks. The penetration and scabbing increased for the slab with one mesh S23 by ejecting the concrete around the reinforcing bars. For group (2), the decrease in the penetration and the scabbing area is observed because of the increase in the strength of concrete. For all slabs, the development of inertial forces under impact loading conditions led to observed responses and failure modes that were governed by shear.
We present a novel approach to traction force microscopy (TFM) for studying the locomotion of 10 cm long walking centipedes on soft substrates. Leveraging the remarkable elasticity and ductility of ...kudzu starch gels, we use them as a deformable gel substrate, providing resilience against the centipedes' sharp leg tips. By optimizing fiducial marker size and density and fine-tuning imaging conditions, we enhance measurement accuracy. Our TFM investigation reveals traction forces along the centipede's longitudinal axis that effectively counterbalance inertial forces within the 0-10 mN range, providing the first report of non-vanishing inertia forces in TFM studies. Interestingly, we observe waves of forces propagating from the head to the tail of the centipede, corresponding to its locomotion speed. Furthermore, we discover a characteristic cycle of leg clusters engaging with the substrate: forward force (friction) upon leg tip contact, backward force (traction) as the leg pulls the substrate while stationary, and subsequent forward force as the leg tip detaches to reposition itself in the anterior direction. This work opens perspectives for TFM applications in ethology, tribology and robotics.
Matter-wave interferometry offers insights into fundamental physics and provides a precise tool for sensing. Improving the sensitivity of such experiments requires increasing the time particles spend ...in the interferometer, which can lead to dephasing in the presence of velocity-dependent phase shifts such as those produced by the Earth's rotation. Here we present a technique to passively compensate for the Coriolis effect using gravity, without the need for any moving components. We demonstrate the technique with fullerenes in a long-baseline molecule interferometer by measuring the gravitational and Coriolis phase shifts and obtaining the maximum visibility one would expect in the absence of the Coriolis effect.
The technique for calculating the dynamics of link-lever mechanisms of the agricultural machinery, whose inertial forces due to significant parameter spread during production occur at random, is ...offered.
In conclusion, one should say that, to determine the approximate stress state in the body, it is quite enough to consider the problem in a linearized problem setting. When determining the deformed ...state, it is necessary to consider the problem exclusively in a nonlinear setting.
This study is proposed for the numerical simulation of the peristaltic mechanism using the finite element method with the Galerkin residual technique to explore peristaltic transportation under the ...action of an externally applied magnetic field passing through an inclined asymmetric channel saturated with porous media. The Navier-stokes equations are solved for the peristaltic mechanism non-linearly by the exemption of lubrication theory to study the inertial effects. The numerical simulations and results are obtained by applying the finite element method based on quadratic triangular elements. It is observed that pressure rise per wavelength is enhanced by increasing the angle of inclination
.
Display omitted
•The effect of negative inertial force on flotation rate constant was investigated.•The GSE and Schulze collision models were compared through flotation rate constant.•Effect of ...mineral density on flotation rate constant models was investigated.•Neglecting negative inertial forces conduces inaccuracy in flotation rate constant.•GSE and Schulze collision models exhibited agreement only at fine particle sizes.
In this study, Schulze collision inertial model was employed to investigate the effect of neglecting the negative inertial forces in collision efficiency and flotation rate constant predictions. The model evaluation was carried out with the Generalized Sutherland Equation (GSE) model in which the estimation of both positive and negative inertial forces have been well accounted. The general flotation kinetic model has been used in this study to demonstrate changes when the negative particle inertia is omitted. Theoretical comparisons were made on two minerals, i.e. quartz and chalcopyrite. The effect of particle density on the modified kinetic model was very significant when a dense mineral like galena was used. This reveals that the general flotation rate model is very sensitive to the substitution of Schulze model. Results obtained were far from satisfactory and show that the Schulze model cannot cope with the change of density very well. It was found that when Schulze collision model was implemented in flotation rate constant calculation, there is a wide range of particle size which is not strongly influenced by parameters such as bubble size and velocity, and particle density and results are very close to each other. This is not in good agreement with the experimental results or GSE model data.
As is known, targeted regulation of the frequency spectrum of natural vibrations of elastic systems with a finite number of degrees of mass freedom can be performed by introducing additional ...generalized constraints and generalized kinematic devices. Each targeted generalized constraint increases, and each generalized kinematic device reduces the value of only one selected natural frequency to a predetermined value, without changing the remaining natural frequencies and all forms of natural vibrations (natural modes). To date, for some elastic systems with a finite number of degrees of freedom of masses, in which the directions of mass movement are parallel and lie in the same plane, special methods have been already developed for creating additional constraints and generalized kinematic devices that change the frequency spectrum of natural vibrations in a targeted manner. In particular, a theory and an algorithm for the creation of targeted generalized constraints and generalized kinematic devices have been developed for rods. It was previously proved that the method of forming a matrix of additional stiffness coefficients, specifying targeted generalized constraint, in the problem of natural vibrations of rods can also be applied to solving a similar problem for elastic systems with a finite number of degrees of freedom, in which the directions of mass movement are parallel, but do not lie in the same plane. In particular, such systems include plates. The distinctive paper shows that the method of forming a matrix for taking into account the action of additional inertial forces, specifying targeted kinematic devices in the problem of natural vibrations of rods can also be applied to solving a similar problem for elastic systems with a finite number of degrees of freedom, in which the directions of mass movement are parallel, but do not lie in the same plane. However, the algorithms for the creation of targeted generalized kinematic devices developed for rods based on the properties of rope polygons cannot be used without significant changes in a similar problem for plates. The method of creation of computational schemes of kinematic devices that precisely change the frequency spectrum of natural vibrations of elastic plates with a finite number of degrees of mass freedom is a separate problem and will be considered in a subsequent paper.
PDF
