Characterization of HVOF Sprayed Al2O3 - CeO2 Coatings Deposited on Mg Az 91 Alloy

Al2O3, Al2O3-10%CeO2 and Al2O3 – 20% CeO2 coatings were deposited on Mg AZ91 alloy by High Velocity Oxy Fuel (HVOF) process. The microstructure of deposited coatings was characterized by scanning electron microscopy and x-ray diffraction. Nano-indentation tests were performed on deposited coatings to determine its load bearing capacity and elastic recovery. Al2O3 coatings exhibited coarse grain structure with porous sites. While addition of CeO2 promoted grain refinement in the coatings. A load of 100mN was applied on all the samples for nano-indentation test. Coating with 20%CeO2 exhibited maximum load bearing capacity of 98.7mN with elastic recovery displacement of 1000 nm.

Study on the Applicability of Elastic Recovery (Resilience) Experiment for Asphalt-Rubber

In this paper, the applicability of the elastic recovery (resilience) experiment for asphalt-rubber (AR) binders has been quantitatively assessed. The mechanical model, based on the viscoelastic constitutive relation and particle inclusion theory, was developed. The interfacial detachment between crumb rubber (CR) particles and asphalt caused by stress concentration was analyzed with Weibull statistical equations. Based on the road roughness excitation, the vehicle-road coupling vibration model was established to analyze the impact of vehicle loading on road surface deformation. AR binders with different CR particle sizes were assessed using scanning electron microscope (SEM) imaging and prepared for testing the elastic recovery (resilience). The results showed that the greater internal stress caused by the longer stretch length of AR binders in the elastic recovery experiment was ten times higher than that obtained from the resilience experiment, leading to the interfacial detachment between asphalt and the CR particles. Hence, the elastic property of some of the CR particles with high modulus was not reflected, resulting in the test values being lower than actual values. With the reduction of CR particle size, the interfacial detachment was improved in the elastic recovery experiment due to intense material interchange and the enhancement of interfacial bond strength. The millimeter-scale compression deformation of the AR binder in the resilience experiment was closer to the actual deformation of the road surface. The experimental time of resilience (120 min) has been reported less than that for elastic recovery (200 min–230 min). This study shows that the resilience experiment has a significant advantage in assessing the elastic property of the AR binder.

ON STABILIZATION OF UNSTABLE ROTATION IN THE RESISTING MEDIUM OF THE LAGRANGE GYROSCOPE USING THE SECOND GYROSCOPE AND ELASTIC HINGES

The possibility of stabilizing an unstable uniform rotation in a resisting medium of a "sleeping" Lagrange gyroscope using a rotating second gyroscope and elastic spherical hinges is considered. The "sleeping" gyroscope rotates around a fixed point with an elastic recovery spherical hinge, and the second gyroscope is located above it. The gyroscopes are also connected by an elastic spherical restorative hinge and their rotation is supported by constant moments directed along their axes of rotation. It is shown that stabilization will be impossible in the absence of elasticity in the common joint and the coincidence of the center of mass of the second gyroscope with its center. With the help of the kinetic moment of the second gyroscope and the elasticity coefficients of the hinges, on the basis of an alternative approach, the stabilization conditions obtained in the form of a system of three inequalities and the conditions found on the elasticity coefficients at which the leading coefficients of these inequalities are positive. It is shown that stabilization will always be possible at a sufficiently large angular velocity of rotation of the second gyroscope under the assumption that the center of mass of the second gyroscope and the mechanical system are below the fixed point. The possibility of stabilizing the unstable uniform rotation of the "sleeping" Lagrange gyroscope using the second gyroscope and elastic spherical joints in the absence of dissipation is also considered. The "sleeping" gyroscope rotates at an angular velocity that does not meet the Mayevsky criterion. It is shown that stabilization will be impossible in the absence of elasticity in the common joint and the coincidence of the center of mass of the second gyroscope with its center. On the basis of the innovation approach, stabilization conditions were obtained in the form of a system of three irregularities using the kinetic moment of the second gyroscope and the elastic coefficients of the hinges. The condition for the angular momentum of the first gyroscope and the elastic coefficients at which the leading coefficients of these inequalities are positive are found. It is shown that if the condition for the angular momentum of the first gyroscope is fulfilled, stabilization will always be possible at a sufficiently large angular velocity of rotation of the second gyroscope, and in this case the center of mass of the second gyroscope can be located above the fixed point.

FeZrN Films: Magnetic and Mechanical Properties Relative to the Phase-Structural State

The paper presents results of investigation of Fe65.3–100Zr34.7–0N7.5–0 films prepared by dc magnetron deposition on glass substrates and subsequent 1-hour annealing at temperatures of 300–600 °C. The influence of the chemical and phase compositions and structure of the films, which were studied by TEM, SEM, XRD, and GDOES, on their mechanical properties determined by nanoindentation and static magnetic properties measured by VSM method is analyzed. The studied films exhibit the hardness within a range of 14–21 GPa, low elastic modulus (the value can reach 156 Gpa), and an elastic recovery of 55–83%. It was shown that the films are strong ferromagnets with the high saturation induction Bs (up to 2.1 T) and low coercive field Hc (as low as 40 A/m). The correlations between the magnetic and mechanical properties, on one hand, and the chemical composition of the films, their phase, and structural states as well, on the other hand, are discussed.

Phase Change Energy Storage Elastic Fiber: A Simple Route to Personal Thermal Management

A novel thermoplastic polyurethane (TPU) PCFs possessing a high loaded ratio and high elasticity was simply prepared by vacuum absorption following wet spinning, then coated by waterborne polyurethane (WPU). Octadecane (OCC), hexadecanol (HEO), and stearic acid (SA), which have different tendencies to form hydrogen bonds with TPU, were selected as PCMs, and their thermal behavior, thermal storge properties, and elasticity were systematically studied, respectively. The hierarchical pore structure though from the sheath to the core part of TPU filaments weakened the influence of the nonfreezing layer and hydrogen bond on the crystallization behavior of PCMs. The resulting HEO/TPU fiber has the highest enthalpy of 208.1 J/g compared with OCC and SA. Moreover, the HEO/TPU fiber has an elongation at break of 354.8% when the phase change enthalpy is as high as 177.8 J/g and the phase change enthalpy is still 174.5 J/g after fifty cycles. After ten tensile recovery cycles, the elastic recovery rate of HEO/TPU fiber was only 71.3%. When the HEO in the fiber was liquid state, the elastic recovery rate of HEO/TPU fiber promoted to 91.6%. This elastic PCFs have excellent thermal cycle stability, elastic recovery, and temperature sensitivity. It has great application potential in the fields of flexible wearable devices, intelligent fabrics, and temperature sensors.

Online Measurement of the Elastic Recovery Value of Machined Surface in Milling Titanium Alloy

In the machining of titanium alloy, the elastic recovery of the machined surface will cause strong friction between the tool flank and the workpiece surface, which will result in the tool wear and the poor machined surface. This paper designed a new online measuring system to monitor the elastic recovery behavior of Ti6Al4V alloy in dry milling based on the digital image correlation (DIC). DIC measurement principle were analyzed and the orthogonal milling experiments were carried out under different cutting conditions. Because of the complexity of metal cutting environment such as high temperature and chip splash, and the micro scale of elastic recovery of metal machined surface materials, DIC non-contact sensor was designed to measure the deformation of machined surface materials in titanium alloy milling. The displacement data obtained from the experiment were analyzed, and the calculation method of the elastic recovery value of the machined surface was obtained. The measured data were compared with those in other literature. The focus of this paper is to explore the availability of DIC measuring instrument for measurement of elastic recovery in titanium alloy milling. This method can be extended to the measurement of machining of other difficult machining materials.

Ni/Ni3Al interface-dominated nanoindentation deformation and pop-in events

Nickel-based single crystal alloys have excellent mechanical properties due to its unique two-phase structure and interface. Therefore, molecular dynamics methods were used to simulate nanoindentation and microstructural evolution. We found the indenter reaction force and hardness of the Ni3Al phase is the largest. The pop-in event in Ni3Al phase is more obvious than that in the Ni phase and Ni/Ni3Al phase. Because lots of dislocations in the Ni3Al phase break through the barrier of the interface and cut into the Ni phase, while dislocations in the Ni phase only slip inside the Ni phase. Moreover, we found that the position of the starting point of the adhesion force recovery is mainly related to the elastic recovery of the material. The stronger the elastic recovery of the phase, the smaller the depth value corresponding to the starting point of the recovery. We further studied the variation of potential energy with indentation depth and found that the change of wave trough of the load-displacement (P-h) curve is related to stacking fault energy. This study has important theoretical guiding significance for the in-depth understanding and engineering application of the mechanical properties of nickel-based single crystal alloys.

Orientation Dependent Mechanical Responses and Plastic Deformation Mechanisms of ZnSe Nano Films under Nanoindentation

Although ZnSe has been widely studied due to its attractive electronic and optoelectronic properties, limited data on its plastic deformations are available. Through molecular dynamics simulations, we have investigated the indentations on the (001), (110), and (111) planes of ZnSe nano films. Our results indicate that the elastic modulus, incipient plasticity, elastic recovery ratio, and the structural evolutions during the indenting process of ZnSe nano films show obvious anisotropy. To analyze the correlation of structural evolution and mechanical responses, the atomic displacement vectors, atomic arrangements, and the dislocations of the indented samples are analyzed. Our simulations revealed that the plastic deformations of the indented ZnSe nano films are dominated by the nucleation and propagation of 1/2<110> type dislocations, and the symmetrically distributed prismatic loops emitted during the indenting process are closely related with the mechanical properties. By studying the evolutions of microstructures, the formation process of the dislocations, as well as the formation mechanisms of the emitted prismatic loops under the indented crystalline planes are discussed. The results presented in this work not only provide an answer for the questions about indentation responses of ZnSe nano films, but also offer insight into its plastic deformation mechanisms.

A strategy for on-machine springback measurement in rotary draw bending using digital image-based laser tracking

Rotary draw bending is a commonly used metal forming technique for profile bending. Due to the elastic recovery of the material, springback compensation to control the bent product quality is one of the critical manufacturing issues. The realized bend angle has to be measured for springback compensation before removing the profile from the machine, and the bending process can follow an iterative approach until the product quality is satisfied. However, this trial-and-error is costly for batch production in manufacturing. An on-machine measurement technique is therefore developed to measure springback in rotary draw bending with an affordable laser and a webcam. An image processing technology is integrated with the manufacturing process to track the deformation and measure springback angle in real time, eliminating the need for the workpiece to be transferred to a measurement device. In this paper, bending experiments were conducted with AA6082 rectangular hollow profiles bent at 30°, 45°, 60°, and 90° angles, and springback angles from the conventional manual measurement were compared to that from the on-machine measurement. Since the difference in springback measurement between the proposed and the conventional methods was within 0.15° on average, it is demonstrated that the laser tracking, on-machine measurement is a feasible real-time springback measurement technique for Industry 4.0.

Effects of Alkylamines-Based and Polyalkylene Glycol-Based Bonding Enhancers on the Performance of Asphalt Binders

The premature deterioration of asphalt pavements usually occurs due to different moisture damage mechanisms resulting in stripping, ravelling, potholes, and disintegration without proper treatment. Numerous efforts have been taken into consideration to improve the bonding between materials, hence prolonging the pavement life. This study evaluates the performance of asphalt binders incorporating Alkylamines-based (ALM) and Polyalkylene Glycol-based (PLG) bonding enhancers. Each bonding enhancer at 0.5% and 1.0% based on the weight of asphalt binder was separately blended with the conventional asphalt binder 60/70 penetration grade using a high shear mixer at 1000 rpm for 30 minutes at 160°C. The physical and rheological properties of modified binders were evaluated through penetration value, softening point, ductility, elastic recovery, rotational viscosity (RV), and dynamic shear rheometer (DSR) tests. Overall, additions of ALM and PLG show identical penetration grade compared to the control sample. Both ALM and PLG showcase a higher ductility and elastic recovery than the neat binder. The DSR test indicates the incorporation of bonding enhancers improves the modified binders’ rutting performance. While the application of ALM at 0.5% dosage increased the binder failure temperature out of all the tested samples, where the failure temperature is at 70°C, compared to others at 64°C. Studies at mastics and mixture levels should be conducted to appropriately understand the effect of bonding enhancer on the bituminous materials.