Application of Condition Monitoring for Hydraulic Oil Using Tuning Fork Sensor: A Study Case on Hydraulic System of Earth Moving Machinery.

In this study, we focus on the correctness of oil condition monitoring, specifically of a tuning forks sensor in hydraulic systems. We also aim to analyze the correlation between the online monitoring sensor signal and offline oil analysis by periodically sampling the hydraulic oil. In recent years, condition-based monitoring (CBM) of hydraulic oils has played a key role in extending earthmoving machinery uptime and reducing maintenance costs. We performed rig test and field test to develop a condition monitoring system based on oil analysis for construction equipment. Using the rig test, a reference line for the diagnosis of viscosity and dielectric constant for the new hydraulic oil was derived, and the characteristics of each sensor parameter for artificial contamination and oxidation were confirmed. In order to affirm the validity of oil diagnosis using oil sensors, the oil sensors were applied to four excavators to detect changes in oil conditions over 12 months. It was found that monitoring hydraulic oil with an oil sensor detecting the change in oil properties and contamination can provide reliable information for establishing diagnostic criteria. The finding allows us to predict the remaining oil life and to determine the oil change intervals based on the diagnosis of the oil condition.

Effect of a High Mg Solute Content on the Hot Workability of Al-Mg Alloys.

The workability of Al-xMg alloys with a high Mg content (Al-6Mg, Al-8Mg, Al-9Mg) was evaluated by investigating the microstructure and processing map. Hot torsion tests were conducted in the range of 350-500 °C between 0.1 and 1 s-1. Constitutive equations were derived from various effective stress-strain curves, and the thermal activation energies for deformation obtained were 171 kJ/mol at Al-6Mg, 195 kJ/mol at Al-8Mg, and 220 kJ/mol at Al-9Mg. In the case of the processing map, the instability region, which widened with increasing Mg content, was due mainly to the influence of the Mg solute, which activated grain boundary cracking and flow localization.

Characterization of Interfacial Microstructure of Cast Iron Inserts Dipping in Aluminum Alloy Melt.

Commercial vehicle pistons should have low thermal expansion and should be able to withstand deformation or mechanical stress. Aluminum alloys are suitable for pistons due to their light weight. However, as aluminum alloys have low strength and friction resistance, cast iron is added through the dipping process in order to increase the quality of pistons. However, the dipping process leads to defects such as defective bonding, void formation, and formation of an oxidation film at the junctions of the two materials due to differences in their properties, which adversely affects the impact resistance and mechanical strength of the product. A theoretical study on the metallurgical bond between the aluminum alloy and the cast iron insert in the piston was conducted to investigate the cause of the defects. The microstructure of the intermetallic bonding layer was observed using scanning electron microscopy and electron dispersive spectroscopy. In this study, defects were found in non-bonding and oxide films and several phases were generated corresponding to different parameters. It was found that processing time and temperature were the main causes of these defects.

Microstructure and Mechanical Properties of Commercially Pure Ti/Steel Joint Brazed by Zr-Ti-Ni Amorphous Filler Metal.

In this study, the characteristics of commercially pure titanium (hereinafter referred as CP-Ti)/Steel joints, brazed with Zr-Ti-Ni amorphous filler metal were analyzed. The effects of brazing temperature and time on the microstructure and joining strength of the CP-Ti/Steel joints were investigated. It was observed that Ti diffused into stainless steel substrate formed a brittle reaction zone, which contained intermetallic compounds, such as τ (Ti5Cr7Fe17), (Fe, -Ni)Ti, and FeTi, observed at the joint interface. As the brazing temperature and time increased, the width of the reaction layer in the joint was observed to increase. To suppress the oxidation of the substrates, the experiment was conducted at a cooling and heating speed of 100 °C/min, under a vacuum of 5×10-5 torr. The joining strength was observed to be significantly affected by the brazing conditions, such as temperature and duration time. The shear strength test showed that the strength increased for 15 min and then sharply decreased. This was attributed to the formation of brittle intermetallic compounds, like (Fe, Ni)Ti. The joint brazed at 880 °C for 15 min showed the maximum joining strength, of 216 MPa.

[Biosafety of microbiological laboratories in Korea].

OBJECTIVES: The biosafety level (BSL) practiced in microbiology laboratories in Korea according to the laboratory biosafety manual published by the World Health Organization (WHO) was evaluated using the data obtained by a survey. METHODS: Under the advise of Clinical Laboratory Physicians, 144 types of microorganisms were screened based on the guidelines of biosafety in microbiological and biomedical laboratories published by the US Center for Disease Control and Prevention and classified into 1-4 risk groups. A questionnaire containing 21 questions in 5 areas was developed using the biosafety manual by published WHO. Of the 1,876 different organizations sent the survey, 563 responded to the survey (response rate: 30.0%). The species of microoganisms handled by as well as the biosafety level in microbiology laboratories were analyzed. RESULTS: There were 123 species of microorganisms handled in microbiology labs in Korea. The BSL required in 512 microbiology labs was answered by the survey responders as the first grade in 33 labs (6.4%), 2nd in 437 (85.4%), 3rd in 42 (8.2%), and 4th in none. The average number of items satisfied was 12.2, showing only a 57.9% satisfactory rate and normal distribution. CONCLUSIONS: The state of overall observance of BSL in most microbiology labs of Korea was evaluated as lagging compared with the standard set up by WHO. Therefore, the Korean government need to produce and distribute a biosafety manual in microbiology laboratories and make efforts to prevent this threat through measures such as training in biosafety in microbiology labs.