Papers by Keyword: Dissipated Energy

Abstract: It is necessary to investigate the physical, chemical characterization and amount of RAP binder in asphalt pavement containing large amount of RAP in order to select suitable pure asphalt binder grade to blending. This research aims to investigate the rheological characteristics and estimation fatigue life of the asphalt binder extraction from two years overlay asphalt pavement. The asphalt was taking from the process of extraction and recovery. Dynamic shear rheometer (DSR) test was conducted on the recovered asphalt to calculate the different variables, complex, elastic and viscous shear modulus, complex viscosity and the phase angle. The main pavement failure modes, rutting and fatigue cracking were addressed by these output parameters of DSR. Fatigue life is related to the energy absorbed during repeated load to pavement layer. The test results indicated that the asphalt extracted from the selected sections were stiff enough to resist rutting and fatigue failure Keywords: Reclaimed asphalt pavement binder, fatigue criteria, VECD, dissipated energy, energy stiffness ratio.

Abstract: The present work is concerned with analysis of the dissipated energy in viscoelastic multilayered inhomogeneous beam structure. The layers of the beam are continuously inhomogeneous along the thickness. The Maxwell mechanical model is used for treating the viscoelastic behaviour of the beam. The moduli of elasticity and the coefficients of viscosity vary continuously along the thickness of each layer. The dissipated energy is obtained by integrating of the unit dissipated energy in the volume of the beam. A parametric investigation of the dissipated energy is carried-out by applying the solution derived in order to evaluate the influence of various factors.

Abstract: The paper is based on dynamic modeling research and experimental results obtained for freshly compacted concrete under stationary vibration. Thus, computational relationships and laws for vibration parameters and dissipated energy will be presented. In correlation with the dissipated energy, it will be evidenced by the evolution of the compaction degree and the resistance of the concrete depending on the vibration duration. It is noted that significant correlations have been established between the displacement curve of the dissipated energy and the loop hysteresis area for several vibration frequencies specific to the dynamic compaction regime

Abstract: The size effect on strength of concrete has been studied for a long time from various approaches. In particular, the weakest-link theory remains nowadays the basic tool to interpret statistical size effects, i.e. how the probability of failure under a given stress depends on external size. The main shortcoming of Weibull’s theory is that the activation of fracture from the weakest flaw is assumed to set the final strength, i.e. possible interactions between microcracks and defects during progressive damage are implicitly neglected. The objective of this study is to determine experimentally the influence of “external” (sample) size and “internal” (microstructural) size on compressive strength of concrete. For this purpose, more than 250 uniaxial compression tests were conducted on concrete specimens with two different cylindrical sizes (110×220 mm and 160×320 mm) and prepared from three different compositions (mean aggregate size and proportion). The relationships between compressive strength, dissipated energy up to failure in one hand, and microstructural as well as specimen sizes on the other hand, were analyzed statistically. This demonstrated the failure of the weakest-link approach to describe size effects on compressive strength of concrete.

Abstract: This work is devoted to the development of a constitutive model for the simulation of dissipated and stored energy evolutions under irreversible (plastic) deformation of metals. The efficiency of the model was demonstrated by the calculation of the energy balance in 304(L) austenitic steel under quasistatic deformation. The results of the numerical simulation are in a good agreement with the experimental data. The additional theoretical result of the study has established (based on the numerical and experimental data) a correlation between energy storage rate and rate of strain hardening.

Abstract: This paper presents dynamic analysis of rheological behavior of materials modeled as a body under stationary harmonic dynamic action.Excitation force is inertial, because of rotation of eccentric mass, applied directly to the Maxwell rheological body.Based on theoretical and experimental results are highlighted functions for defining both the energy dissipated as hysteresis loops in physical conditions of linear behavior of the components of the Maxwell model.In this context are represented the representative sets of curves that outlines the progress of dissipation made in relation with the dynamic system parameters.

Abstract: The paper presents the model of a seismic mass with viscoelastic linear connections, following the Voigt-Kelvin model, with the fundamental unidirectional harmonic kinematic excitation of an earthquake. The motion is caused by seismic action. Thus, the parameters and the motion laws of the mass, the inertial force and the force transmitted to the fixed base are determined. Also, the relations for the amplitude and the transmissibility of the motion are established in function of the elastic and viscous parameters of the composed model Voigt-Kelvin.Based on the established relations the dissipated energy function of the acceleration of the earthquake and of the dominant pulsation and the viscoelastic characteristics are determined.

Abstract: The method of testing the elastomeric isolators at shearing, in a system formed of two elements in parallel, is presented. The exterior actions can be represented by harmonic functions defined as:kinematic excitation through the instantaneous displacement of the form (t)=Asinωt;dynamic excitation through the instantaneous force of the form F(t)=F₀sintωt or P(t)=m₀rω²sintωt.The linear viscoelastic behavior of the elastomer enables the obtainment of hysteresis curves of elliptical shape for each harmonic loading.In the end, the dynamic stiffness as well as the equivalent damping can be evaluated, with the mention that the stand testing individualizes the dynamic system only through viscous, elastic and inertial forces. Due to this reason, the 1^st order differential equation eliminates the definition of the critical damping ratio as for a second order system, which leads to the introduction of the concept of equivalent damping, originating in the hysteretic damping or the loss factor.

Abstract: Abstract. To characterize the thermomechanical cyclic response, especially Pseudo-elastic behavior of NiTi shape-memory alloy (SMA) at different temperatures and different loading frequencies, a series of tests of both quasi-static and dynamic uniaxial compression cyclic loading have been performed on cylindrical samples, using an Instron servohydraulic testing machine and the Hopkinson technique. Transformation temperature, after dynamic loading is measured and compared with that of as-received state. The influence of the annealing temperature on the fatigue response is also examined. A few noteworthy conclusions are as follows: (1) Transformation temperature, can be changed under higher strain rates; (2) By changing the annealing temperature, the transformation stress and the dissipated energy of NiTi can also be obviously changed, so as it changes the transformation temperature, Af ;(3) In cyclic loading, the dissipated energy over cycles tends to be a minimum stable value, and it seems that cyclic loading leads to a stable Pseudo-elastic behavior of the alloy; (4) Repeated impact tests of the alloy produce slightly changes in the shape of the Pseudo-elastic loop and in the dissipated energy comparing with the quasi-static cyclic tests.

Abstract: We propose a method to compute the restoring force characteristics and dissipated energy to detect damage level of viaducts for railways and highways, using only acceleration. The acceleration data were measured by accelerometers which were installed on the top and the bottom of the structures. Wireless sensor network is used to compute and collect the data. Using this system, the information of restoring force characteristic and dissipated energy can be created.