Evolution Of Energy Dissipation Research Articles

Critical loss of primary implant stability in osteosynthesis locking screws under cyclic overloading

Primary implant stability, which refers to the stability of the implant during the initial healing period is a crucial factor in determining the long-term success of the implant and lays the foundation for secondary implant stability achieved through osseointegration. Factors affecting primary stability include implant design, surgical technique, and patient-specific factors like bone quality and morphology. In vivo, the cyclic nature of anatomical loading puts osteosynthesis locking screws under dynamic loads, which can lead to the formation of micro cracks and defects that slowly degrade the mechanical connection between the bone and screw, thus compromising the initial stability and secondary stability of the implant. Monotonic quasi-static loading used for testing the holding capacity of implanted screws is not well suited to capture this behavior since it cannot capture the progressive deterioration of peri‑implant bone at small displacements. In order to address this issue, this study aims to determine a critical point of loss of primary implant stability in osteosynthesis locking screws under cyclic overloading by investigating the evolution of damage, dissipated energy, and permanent deformation. A custom-made test setup was used to test implanted 2.5 mm locking screws under cyclic overloading test. For each loading cycle, maximum forces and displacement were recorded as well as initial and final cycle displacements and used to calculate damage and energy dissipation evolution. The results of this study demonstrate that for axial, shear, and mixed loading significant damage and energy dissipation can be observed at approximately 20 % of the failure force. Additionally, at this load level, permanent deformations on the screw-bone interface were found to be in the range of 50 to 150 mm which promotes osseointegration and secondary implant stability. This research can assist surgeons in making informed preoperative decisions by providing a better understanding of the critical point of loss of primary implant stability, thus improving the long-term success of the implant and overall patient satisfaction.

Numerical Calculation of Slosh Dissipation

As part of the Sloshing Wing Dynamics H2020 EU project, an experimental campaign was conducted to study slosh-induced damping in a vertically excited tank filled with liquid water or oil and air. In this work, we simulate these experiments using two numerical approaches. First, a single-phase, weakly compressible liquid model is used, and the gas flow (air) is not modeled. For this approach, a proven Smoothed Particle Hydrodynamics (SPH) model is used. In the second approach, both phases are simulated with an incompressible liquid and weakly compressible gas model via a Finite Volume Method (FVM) using Volume-of-Fluid (VOF) to track the liquid phase. In both approaches, the energy distribution of the flow is calculated over time in two- and three-dimensional simulations. It is found that there is reasonable agreement on the energy dissipation evolution between the methods. Both approaches show converging results in 2D simulations, although the SPH simulations seem to have a faster convergence rate. In general, the SPH results tend to overpredict the total dissipation compared to the experiment, while the finite volume 2D results underpredict it. Time histories of the center of mass positions are also compared. The SPH results show a much larger vertical center of mass motion compared to the FVM results, which is more pronounced for the high Reynolds number (water) case, probably linked to the absence of the air phase. On the other hand, the limited center of mass motion of the FVM could be linked to the need for higher spatial resolutions in order to resolve the complex gas–liquid interactions, particularly in 3D.

On the evolution of energy dissipation in dispersed composite laminates under out-of-plane loading

In this paper, we present a novel model to predict the energy dissipation in composite laminates during out-of-plane loading based on experimental observations. Damage mechanisms and their sequences in composite laminates under out-of-plane loading were experimentally investigated and correlated with the energy dissipated during loading. The results showed that the energy dissipated during fiber breakage was around 3 times larger than that for delamination propagation. The first damage mechanism occurred during out-of-plane loading is matrix cracks and induced delaminations. Then, delamination propagated at different interfaces mainly at the lower half of the laminate dividing the laminate to sub-laminates. Once the normal tensile stresses due to bending at the lower plies reached the tensile strength of fibers, fiber breakage occurs causing large load drop and energy jump. The propagation of fiber breakage caused continuous load decrease and dissipation energy increase until complete perforation of the sample. Based on our experiments and others available in the literature, we concluded that the developed model is independent of the material type, stacking sequence, impactor size and boundary conditions. The model can be used as fast tool for designing composite laminates based on the energy dissipation and residual compressive strength.

Influence of Rest Period on the Fatigue Response of Bituminous Mixture at Low Temperature

Laboratory fatigue characterization of bituminous mixtures is carried out typically by conducting a beam bending test at a given frequency and temperature for various strain/stress levels. In the current fatigue test methods, the material is tested at 20°C with continuous loading, and the fatigue life is estimated based on the stiffness modulus and energy dissipation. Very little data exist on the influence of low temperature (0°C), and tests with a rest period. In this study, the fatigue life of the bituminous mixture is estimated at 20 and 0°C, and the influence of the rest period is quantified. For this purpose, a typical bituminous mixture used in Indian highways was fabricated. Experiments were conducted at 0 and 20°C with and without a rest period in strain-controlled mode (600 and 800 microstrains) in a four-point beam bending test setup. For tests with a rest period, a 0.9 s rest period was provided after 0.1 s loading. The evolution of stiffness modulus as per AASHTO T321 [1] and normalized modulus by ASTM D7460 [2] was used in fatigue life estimation. Also, the evolution of energy dissipation during testing was analyzed to characterize the response of material (elastic/viscoelastic) and the beneficial effect of the rest period, if any. The influence of the rest period was more pronounced when tested at 20°C in comparison to testing at 0°C.

Fatigue Characteristics of Coal Specimens under Cyclic Uniaxial Loading

Abstract To investigate the fatigue failure of coal under uniaxial stress, multilevel cyclic loading tests on cylindrical coal specimens were conducted in a laboratory using the MTS815.02 rock-mechanics test system (MTS Systems Corporation, Eden Prairie, MN). Specimens were tested for as many as 1,500 loading cycles under each cyclic loading session. From these tests, the following conclusions can be drawn. The peak stress of cyclic loading has a significant effect on the coal specimen’s fatigue behavior. When the peak stress of cyclic loading is less than the coal fatigue strength, the coal specimen’s deformation stops increasing after a certain number of loading cycles, and the number of acoustic emission (AE) counts is low. When the peak stress of cyclic loading exceeds the coal fatigue strength, the axial, circumferential, and volumetric strains and the energy dissipation exhibit the same progression through three phases: a primary phase, a steady phase, and an acceleration phase. The region division of the three phases of the strain and energy dissipation evolution is coincident. The AE activity also exhibits three phases: an active, a quiet, and a very active phase. In the very active phases, numerous AE signals exist when the stress is at its peak, but no AE signals exist near the stress minima. Coal specimens that are subjected to conventional uniaxial compression tests and specimens that are deformed by cyclic loading tests fail in very different ways. The former specimens fail mainly because of a single inclined shear plane, whereas the latter specimens are reduced to a mound of small fragments.

Energy Dissipation-Based Method for Fatigue Life Prediction of Rock Salt

The fatigue test for rock salt is conducted under different stress amplitudes, loading frequencies, confining pressures and loading rates, from which the evaluation rule of the dissipated energy is revealed and analysed. The evolution of energy dissipation under fatigue loading is divided into three stages: the initial stage, the second stage and the acceleration stage. In the second stage, the energy dissipation per cycle remains stable and shows an exponential relation with the stress amplitude; the failure dissipated energy only depends on the mechanical behaviour of the rock salt and confining pressure, but it is immune to the loading conditions. The energy dissipation of fatigued rock salt is discussed, and a novel model for fatigue life prediction is proposed on the basis of energy dissipation. A simple model for evolution of the accumulative dissipated energy is established. Its prediction results are compared with the test results, and the proposed model is validated.

Evolution of energy dissipation during four-point bending of bituminous mixtures

In this investigation, the fatigue life of bituminous mixtures is characterised using the four-point bending test. Two sets of bituminous concrete samples, one produced with unmodified binder and other with plastomer-modified binder, are subjected to repeated strain-controlled sinusoidal loading at 10 Hz frequency and 20°C. The test is conducted for three different strain amplitudes of 200, 400 and 600 microstrain and the corresponding stress and strain data are collected at 1/1000 second interval. In the first approach, these data are used to calculate total energy dissipation. The dissipation due to damage is determined by separating viscoelastic dissipation from the total dissipation. For this purpose, a linear viscoelastic model is used. In the second approach, the discontinuity in the evolution of phase lag determined from the stress–strain plot is taken as the onset of fatigue damage. The fatigue failure, as quantified by these two approaches, was found to be closer to the fatigue life computed using energy ratio method.

Numerical modeling of adhesion and adhesive failure during unidirectional contact between metallic surfaces

Abstract In this work, we developed a finite element modeling approach to study adhesion during unidirectional contact between a two-dimensional plane-strain square and a flat slab. The surfaces were metallic or ceramic, and we analyzed different pairs of materials and their adhesion intensity using a FORTRAN subroutine (DLOAD) connected to a commercial finite element code Abaqus, which provided the surface attractive forces based on the Lennard-Jones interatomic potential using Hamaker constants. We considered adhesive loads during both the approach and separation of the surfaces. During the separation step, we modeled the material transfer between surfaces due to adhesion with respect to damage initiation and propagation at the flat slab. The parameters considered in the simulations include normal load, chemical affinity, and system size, and we analyzed different conditions by comparing the interaction forces during approach and withdrawal. This work also presents: (i) a description of the evolution of energy dissipation due to adhesion hysteresis, (ii) the formation–growth–breakage process of the adhesive junctions and the material transfer between surfaces, and (iii) an adhesive wear map based on a proposed novel equation that correlates the material parameters and material loss due to adhesion. The results indicate that the chemical affinity between bodies in contact is more related to adhesion than the applied load. In addition, the ratio between the material strength and elastic modulus seems to be an important factor in reducing adhesive wear.

Evolution of energy dissipation and the Young's modulus in a martensite NiTi shape memory alloy wire upon cyclic loading

Evolution of energy dissipation and the Young's modulus in a martensite NiTi shape memory alloy wire upon cyclic loading

Field experiment on secondary wave generation on a barred beach and the consequent evolution of energy dissipation on the beach face

A field experiment, conducted on a sandy, barred beach situated on the southern part of the French Atlantic coastline, allowed us to investigate the formation of secondary waves when a moderate (significant wave height of about 0.8 m in 3.7-m water depth), long (11–14 s) narrowband swell propagated over an intertidal ridge and runnel system, in both breaking and nonbreaking conditions. Field evidence using higher spectral analysis is given for the sum interactions between pairs of waves at the primary spectral peak and the consequent energy transfer to nearly harmonic wave components. Although wave breaking appears to weaken the strength of nonlinear couplings, the generation of high-frequency energy is hardly affected by wave breaking. The phenomenon of harmonic decoupling, which takes place behind the bar, cannot be completely ascribed to the increase in water depth and the so-called deshoaling effect. Indeed, the variation in the values of the maximum bicoherence was very moderate when no breaking occurred. Finally, the doubling in the number of wave crests and the consequent decrease in the significant wave period delay the energy dissipation on the beach face.