Papers by Keyword: Acceleration

Abstract: Currently, functional tests and property tests are used to evaluate cutting fluid [1]. However, the problem is that the results obtained from above tests do not always match with each other because the insert tip is under extreme pressure and high temperature in actual machining. Therefore, a new cutting fluid evaluation method based on actual machining is needed. End face cutting in lathe machining is cutting workpiece from outside to center. In this study, rotation speed was fixed. In other words, cutting speed varies with the radius of workpieces and it is considered possible to clarify the effectiveness of cutting fluid at each cutting speed in a single cut.The performance of the cutting fluid was evaluated based on acceleration of cutting tool and surface roughness of workpiece. The following results were obtained. In steel materials, the acceleration of insoluble cutting oil was highest, and burnt insert tips were observed after the end face cutting. Insoluble cutting oil used in this study has a lower viscosity and a lower boiling point than mineral oils and esters. The highest acceleration of insoluble cutting oil is considered to be due to insufficient lubricating effect because of evaporation of it. No effect of insoluble cutting oil, mineral oils or esters was obtained on surface roughness. The acceleration of undiluted solution is higher than that of diluted solution and burnt insert tips were obtained. The cooling effect of undiluted solution is low because of less water. The highest acceleration of undiluted solutions is considered to be due to insufficient lubricating effect because of evaporation of it. In A5056, surface roughness of the diluted solution was higher at low cutting speed due to lack of lubricating effect. Differences in acceleration, surface roughness and insert tip were observed for each oil type, indicating the possibility of evaluating cutting fluid performance using the method proposed in this study.

Abstract: For the design of vessels built by GFRP laminates, an insert with a viscoelastic layer is proposed to reduce the spread of damage produced by the vertical impact of the ship's bottom with the sea or slamming phenomenon. Using vertical drops-weight impact machine that reproduce the energy inferred to the panel during navigation, the propagation of the damage of OoA cured prepreg panels is studied comparing it with modified panels with insertion of viscoelastic layer. The use of acceleration data reading allows the benefits of viscoelastic modification during impact to be quantified through the developed formulation. The force, displacement and energy returned by the panel after impact have also been quantified, which does not become intralaminar and interlaminar damage. It is shown that under 40 joules of impact, the viscoelastic sheet has its best ability to return energy and above 130 joules it loses its capacity.

Abstract: The article considers the modeling of dynamic processes in buildings and structures. A general formulation of the dynamic problem of a massive load motion on a massive structure is considered. The equation of motion is obtained in the form of a finite element method. The equations solving is performed using direct methods of integrating dynamic problems. Absolutely stable schemes of direct integration are constructed, where the system of solving equations is trivial and the matrix of the system is diagonal. Due to this, the complexity at the time step is as low as in explicit schemes. Therefore, the proposed methods can be considered as explicit absolutely stable schemes of direct integration of a dynamical problem with a variable in time mass. These recommendations are for estimating the accuracy of a numerical solution.

Abstract: The crack growth can accelerate after applying unexpected overload or underload during usual operation of machine structure. An acceleration or deceleration of the crack growth was observed depending on the experimental conditions. In the present study, a method of detecting the application of an unexpected hazardous load, that is high levels of overload or underload, was investigated. It is expected that the acceleration of crack growth brings catastrophic failure in machine structure. Therefore, it is useful for machine maintenance to know whether an unexpected load was applied or not by doing daily inspection. In the present study by using center-crack specimens, a simple method of detecting application of overload or underload was investigated by using strain information.

Abstract: Long-distance pumping of concrete (up to 2000 m, with relay pumps installed at two locations) was carried out for placing invert concrete at a caisson—the construction site of a spillway discharge section. After quantifying the required performance and determining of the mix proportions of the invert concrete that would be used in the long-distance pumping, the authors focused on thixotropy as a factor that affects the pumping load. Through laboratory tests and using AE and a high-range water reducing agent with high dispersion effect, retention and pumpability enhancing admixture were found to be effective in reducing thixotropy.

Abstract: Because of the added mass, the aerodynamic drag of the automobile will increase obviously when accelerating in the still air. In this paper, it firstly gave the definition of the added mass, and presented that there was little research on the calculation of the added mass of automobile. Then through the analysis of the theoretical calculation method for the added mass, it pointed out that, for the added mass of the car-body with a complex shape, there was much difficulty in the theoretical calculation. Alternatively, a numerical calculation method for the added mass of car-body was derived. The simulation model adopted the Ahmed body and the corresponding verification experiment was completed in the Tongji Automotive Wind Tunnel center. The results indicate that the added mass is a constant which is only dependent on the body-shape. For the model investigated, the added mass is 0.0052kg that is approximately equal to the air displaced by the car-body. As the body accelerates to 4m/s², the aerodynamic drag is increased by 1.89% because of added mass. Therefore, it needs to pay more attention to the impact that the added mass has on the dynamic performance of vehicle when proceeding the aerodynamic designs (especially for the high power performance vehicles). Meanwhile, it still makes a correction to the conventional aerodynamic drag formula. This paper also demonstrates that, with the analysis of the flow-field of car-body, the added mass essentially stems from the additionally work done by the car-body to increase the kinetic energy of external fluid as it speeds up.

Abstract: The paper established real-time computing algorithm of S Curve to control the process of acceleration and deceleration for step motor on the basis of a reasonable start frequency. Moreover, this paper used economic embedded ARM STM32F103RCT as the main control chip to control the step motor, which realized this designed real-time computing algorithm. Finally, the relevant testing indicated that the algorithm can realize the rapid response of start and stop for step motor, and can effectively avoid undesirable phenomenon of step losing, overshoot and oscillation.

Abstract: Wireless Body Area Network or known as BAN, is a system consists of various kinds of wearable sensors to measure condition of human body. Wrist, waist and shoulder modules from BAN system can help to monitor, analyze and provide advice to the user in order to perform a moderate exercise. The availability of small, low-cost networked sensors combined with advanced signal processing and information extraction is driving a revolution in physiological monitoring and intervention. BAN system is enabling technologies for accurate measurements in healthcare systems, enhance sports and fitness training, life-style monitoring and individualized security.

Abstract: The paper presents a complex quarter car model obtained with ADAMS software, View module, useful in the first stage of suspension dimensioning and optimization.The model is equipped with compression and rebound stopper buffer and suspension trim corrector.The proposed quarter car model with two degrees of freedom (wheel and body) performs all these goals allowing changing:Geometrical elementsPosition of equilibrium, depending on vehicle load;Trim correction;Elastic and dissipative characteristics of the suspension and tire;Suspension stroke;Road profile, assessed either by simple or summation of harmonic functions or reproducing real roadsBuffers (for stroke limitation) position and characteristics;The models developed provide information on:Vertical stability assessed by vertical movements of the body and the longitudinal and transversal stability evaluated based on adherence characterized by wheel ground contact force and frequency of soil detachment wheel.Comfort assessed on the basis of body vertical acceleration and collision forces to the stroke ends.The body-road clearanceThe trim corrector efficiencyAll above performances evaluated function the road unevenness, acceleration, deceleration, turning regime.The damping characteristic is defined by damping forces at different speed for each strokes respectively one for rebound and other for compression.The contact force road-wheel is defined based tire rigidity law.The stopper buffer forces on rebound and compression are defined based each specific rigidity characteristics.The road excitation is realized with a function generator.The software allow the model evolution visualisation in real time, also generating the diagrams of displacements, forces, accelerations, speeds, for each elements or for relative evolution between diverse elements.The simulation was realized for unloaded and fully loaded car using a road generated by a sum of harmonic functions presented in equation (8).The excitation covers the specific frequencies area, being under the body frequencies up to the wheel proper frequencies.The realized ¼ car model, have reached the goal to evaluate the suspension trim correction advantages.The simulations confirm the trim corrector increases the suspension performances, thus for the analyzed case the trim corrector increase simultaneous:Body-ground clearance (evaluated by body higher increasing) between 18.5÷55.1 %Body stability (evaluated by maximal body displacement) between 9.8÷11.4 %Body comfort (evaluated by maximal body acceleration) between 3.4÷35.5 %Adherence (evaluated by maximal and RMS wheel-groundcontact force variation) between 7.0÷12.1 %Body and axles protection (evaluated by buffer strike force) between 10.8÷38.2 %

Abstract: The VZN shock absorber concept granted with European Patent EP 1 190 184 is characterized by damping coefficients self according with road and load conditions.The simulations made on vehicles equipped with new VZN shock absorbers concept relative to standard one, indicates better behavior concerning stability, comfort and reduced dissipated energy, with fuel consumption and pollution reducing effect.Starting on these remarks the paper evaluates the influence of the damping characteristic in suspension performances and dissipated energy, based a simulation on a Californian road realized with Matlab Simulink software.Since year 2006 simulations on model ¼ cars demonstrates the VZN damper concept give skyhook behavior, decrease squat, vertical acceleration, the number and intensity of stopper bumper collision, the adherence, increasing thus the vehicle stability, comfort and reliability.Tests on models ½ car, show the VZN concept increases stability at pitch and roll and confirm the previous results obtained on ¼ models.The current work completed previous research with one demonstrating other VZN qualities e.g. its capacity to manage damping coefficient, no more and no less, assuring high performances and thus reducing the dissipated energy, with favorable effect for reducing fuel consumption and pollution.The comparison between the behaviors of the VZN shock absorber relative to the standard shock absorber has been realized for body displacement, squat, acceleration and dissipated energy.The VZN progressive damper concept gives better behavior comparative to standard one, 6% at car body bounce, 37 % for RMS acceleration and 28.4 % for dissipated energy, these means it confer better body-ground clearance, comfort and fuel consumption and pollution.The VZN damping coefficients accorded with the vehicles load and with road unevenness confer a soft response at low excitation and strong reactions at high excitations, dissipating energy function of the needs, assuring thus comfort at small and medium excitation and protecting the axles and body at hard conditions.