Mechanical and Tribological Properties of Ca/P-Doped Titanium Dioxide Layer Produced by Plasma Electrolytic Oxidation: Effects of Applied Voltage and Heat Treatment

Plasma electrolytic oxidation (PEO) is a technique that produces a hard oxide layer on the titanium surface where its properties can be tailored by changing the process parameters or by a posterior heat treatment (HT). In this work, a TiO₂ layer with different crystallinity was produced by PEO with different applied voltages (250 to 400 V) and post-HT at 600°C. Our aim was to evaluate the influence of the PEO voltage and HT on the mechanical and tribological properties of anodized Ti. There is an increase in pore size, oxide thickness, and Ca/P ratio for the oxide layer with the applied voltage during the PEO process. X-ray diffraction (XRD) results indicated an increase in the crystalline rutile phase in the oxide layer with voltage and HT. Nanoindentation shows an increase in the oxide hardness and elastic modulus with increased voltage and HT, leading to an improvement in the wear resistance.     

Lyapunov exponent of friction-induced vibration under smooth friction curve

This paper studies the nonlinear behavior of the friction-induced vibration by using spring-mass model subject to the smooth frictionvelocity curve. The nonlinearity and instability of the friction may produce the chaotic vibration depending on the friction curve. In order to show this, the Lyapunov exponents are calculated for a variety of the slope and magnitude in the smooth friction curve. In turn, the dependency of the friction curve on the chaotic attractor is illustrated.     

Experimental study on the life prediction of servo motors through model-based system degradation assessment and accelerated degradation testing

The advent of smart factories has resulted in the frequent utilization of industrial robots within factories to increase production automation and efficiency. Due to the increase in the number of industrial robots, it has become more important to prevent any unexpected breakdowns of the factory. As a result, the lifespan prediction of machinery has become a crucial factor because such failures can be directly associated with factory productivity resulting in significant losses. Most of the failures occur within one of the core components of the robot arm, the servo motor, and thus we will focus on the analysis of the servo motor in this study. However, sensor attachment to such equipment is considered difficult due to the dynamic movement of the robot arm, meaning that internal instrumentation should be utilized during analysis. In addition, no definite measure to determine the degradation of the motor exists, and thus a new degradation index is proposed in this study. Therefore, in this study, the lifespan of the servo motor will be estimated through accelerated degradation testing methods based on a new system degradation assessment method, which estimates the fault of the system using observer-based residuals with encoder data obtained from internal instrumentation.     

A study on piezoelectric energy harvester using kinetic energy of ocean

Electricity generation through fossil fuels has caused environmental pollution. Accordingly, research on new renewable energy (solar, wind, geothermal heat, etc.) to replace fossil fuels and solve this problem is in progress. These devices can consistently generate power. However, they have several drawbacks, such as high installation costs and limitations in possible set-up environments. Therefore, the piezoelectric harvesting technology, which is able to overcome the limitations of existing energy technologies, is actively being studied. The piezoelectric harvesting technology uses the piezoelectric effect, which occurs in crystals that generate voltage when stress is applied. Its advantages include a wider installation base and a lower technological cost. This study investigated a piezoelectric energy-harvesting device based on constant wave motion. This device can harvest power in a constant turbulent flow in the middle of the sea. The components of the device are circuitry, percussion bar, triple layer piezoelectric bender, bearing and rudder. A multiphysical analysis coupled with the structure and piezoelectric elements was also conducted to estimate the device performance. The analysis accuracy was improved by applying the impact energy to the bender calculated based on the shape of the wave in the East Sea. The proposed device’s performance was finally confirmed by experiments.     

Investigation of poly(methyl acrylate) grafted chitosan as a polymeric drug carrier

The graft copolymerization of methyl acrylate (MA) onto chitosan in aqueous medium was investigated using potassium persulfate (KPS) as initiator. The grafting conditions were optimized by studying the effects of the polymerization variables (the initiator concentration, the ratio of monomer to chitosan, and reaction temperature) on the percentage of grafting (PG). PG was found to depend on these variables, and the highest grafting percentage (256 %) could be obtained at chitosan = 1 g, KPS = 4.5 × 10^?3 M, methyl acrylate monomer = 6 g, T = 60 °C and t = 180 min. The graft copolymer was characterized by Fourier transform infrared spectra analysis, thermogravimetry (differential thermogravimetry, differential scanning calorimetric), X-ray powder diffraction as well as CP-MAS ¹³C NMR spectroscopy. These analyses are highly confirmed the formation of poly(methyl acrylate) grafted chitosan (PMAGC). Furthermore, the gelation of the grafted polymers (PG 68, 122, 218 and 256 %) in distilled water has been studied, and the results revealed that the percentage of swelling number increase with increasing PG of the polymers. Controlled release of niacin (vitamin B₃) from the hydrogel of the grafted polymers (PG 68, 122 and 256 %) in aqueous medium has been studied using ultraviolet absorption to follow quantities released at different times (for each experiment: PMAGC 100 mg, niacin 2.46 mg, distilled water 100 ml). The study was repeated again with same conditions except the using of 4.92 mg of niacin instead of 2.46 mg (PG of the grafted polymer is 256 %). The diffusion coefficient (D, cm²/h) of niacin from the hydrogel of the grafted polymer (PG 256 %) was calculated depending on Higuchi model (diffusion coefficient of the first load is 0.00194 cm²/h while 0.00255 cm²/h of the second load).     

Mobility Analysis of 2 nm to 11 nm Aerosol Particles with an Aspirating Drift Tube Ion Mobility Spectrometer

We describe the performance of a drift tube-ion mobility spectrometry (DT-IMS) instrument for the measurement of aerosol particles. In DT-IMS, the electrical mobility of a measured particle is inferred directly from the time required for the particle to traverse a drift region, with motion driven by an electrostatic field. Electrical mobility distributions are hence linked to arrival time distributions (ATDs) for particles reaching a detector downstream of the drift region. The developed instrument addresses two obstacles that have limited DT-IMS use for aerosol measurement previously: (1) conventional drift tubes cannot efficiently sample charged particles at ground potential and (2) the sensitivities of commonly used Faraday plate detectors are too low for most aerosols. Obstacle (1) is circumvented by creating a “sample volume” of aerosol for measurement, defined by the streamlines of fluid flow. Obstacle (2) is bypassed by interfacing the end of the drift region with a condensation particle counter. The DT-IMS prototype shows high linearity for arrival time versus inverse electrical mobility (R ² > 0.99) over the size range tested (2.2–11.1 nm), and measurements compare well with both analytical and numerical models of device performance. A dimensionless calibration curve linking drift time to inverse electrical mobility is developed. In less than 5 s, it is possible to measure 11.1 nm particles, while 2.2 nm particles are analyzable on a subsecond scale. The transmission efficiency is found to be dependent upon electrostatic deposition for short drift times and upon advective losses for long drift times.

Copyright 2014 American Association for Aerosol Research     

Gradientenbetontechnologie

The technology of graded concrete – From the development of concrete mixtures and the conceptual design to the automatized manufacturing In accordance with the principle form follows force, the DFG Priority Programme (SPP) 1542 – Leicht Bauen mit Beton – focuses on energy efficient building elements which are designed specifically for desired operational demands. This concept is a specific adaption of the component's inner structure and works in parallel to the optimization of its outer shape which is often limited due to the outer geometry of slabs, walls and supporting pillars. The technology of graded concrete provides an innovative possibility to adapt the inner structure of a concrete component in order to meet defined static and structural‐physical requirements. The challenging demands imposed by the technology of graded concrete require a holistic approach including the development of the concrete mixtures, the design of the building components and finally the automatized manufacturing. In collaboration between the departments ILEK, IWB and ISYS of the University of Stuttgart a complete process chain for the manufacturing of functionally graded concrete components was realized. This approach for concrete results in fully recyclable building elements with significant savings in mass and energy.     

Influence of Quenching and Partitioning Temperature on Mechanical Properties of Steel 37MnSi5

Metal Science and Heat Treatment - The influence of the temperature of heating for quenching and subsequent heating for redistribution of carbon between martensite and retained austenite...