J.R. Laguna-Camacho

Frictional Behavior of a Wet Clutch Using Blends of Automatic Transmission Fluid (ATF) and Biolubricant (Jatropha Oil) in a Pin-on-Disk Tester

Nowadays, biolubricants are being used to replace mineral lubricants totally or partially and it is of great importance due to interest in environmental protection. Jatropha oil is a good alternative as lubricant feedstock and combustible. Its production is cheap in comparison to other vegetable oils. In México, Jatropha curcas L. is widely distributed in more than 15 states, which makes a sustainable supply of this natural resource possible. The aim of this work was to investigate the frictional behavior of blends of automatic transmission fluid with vegetable oil tested in a pin-on-disk rig simulating the wet clutch operation. Two different friction materials were separately tested and used as pins against actual steel disks from a wet clutch. The frictional behavior results demonstrated that the mixtures presented antishudder characteristics. Thus, Jatropha oil could be potentially used as part of automatic transmission fluid (ATF) formulations to enhance their antishudder properties and increase the efficiency of the torque transferred of wet clutches with a controlled lock-up clutch system, which improves the full economy of vehicles.

Analysis of the Wear Damage on Offshore Gas Turbine Blades

A study of the wear damage of a blade of the seventh-stage of the compressor of a gas turbine was carried out. The manufacturer recommends routine maintenance (30,000 h) to reduce the chances for the shutdown of the gas turbine. In this study, the C40 turbine was analyzed in the field at 24,000 h (shutdown) and out of service after 30,000 h. The turbine was operating in the city of Campeche, Mexico, in a very aggressive environment, where the entry of solid particles is unavoidable. The gas turbine combines high performance operation with rugged industrial construction. This design provides high efficiency, low maintenance and a long service life. For power generation, the components that are in direct contact with the air at different stages of operation are the compressor blades which are exposed to severe wear damage for the impact of particles, environmental contaminants such as salts, sands and sulphur. Due to this fact, the wear damage on the turbine blades was analysed. The work was developed in two steps. In the first one, an analysis of boroscope images of the surfaces of the blades was carried out in the site, and out of service the study with destructive and non-destructive tests, using tribological characterization were conducted to obtain the chemical composition of the turbine blades, which were in operation, by using energy dispersive X-ray analysis (EDS). Hardness tests were also conducted, using the material that was employed to manufacture the blades. Additionally, optical microscopy and scanning electron microscopy (SEM) were used to identify the wear mechanisms on the surfaces. This allowed obtaining a more complete failure analysis. The wear modes were severe pitting action, large craters similar to those observed in solid particle erosion when the samples are impacted at normal incidence, corrosion and a few irregular scratches similar to ploughing action in abrasive wear.

Erosion Wear of AISI 420 Stainless Steel Caused by Walnut Shell Particles

In this study, erosion tests were conducted to evaluate the behavior of AISI 420 against walnut particles. This organic material was selected to evaluate its performance as abrasive particle and know if this “soft abrasive” could really cause any damage on the material surface. The interest on walnut shell grit arose because this is extremely durable, angular and can be reused several times in many applications. Walnut producers have indicated that this can remove matter from surfaces without scratching or pitting underlying material. However, in this work, wear mechanisms similar to those observed when hard abrasive particles are used for erosion testing, were identified. SEM photographs showed micro-cutting (scratches) and micro-ploughing actions and particles embedded on the surface of AISI 420. In fact, this latter mechanism affected considerably the erosion rates at all incident angles. Finally, AFM technique and surface profilometry were employed to obtain the wear scar profiles to show the degradation of the surfaces by the impact and sliding actions of the walnut particles.

Mechanical Properties of New Ceramic Materials Obtained from Granular Solid Residuals Coming from Mines and Diatomaceous Earth

Granular solid residuals are produced by different industries in Mexico. Some of these are considered dangerous because they are stored in open areas contaminating and affecting the flora, fauna, and aquifers, and occasionally to the human being. These solid residuals coming from mines and diatomaceous earth are known as “jales” (nahualt derivated from xalli, it means sand). The “jales” have a high content of cyanide and heavy metals. These high contents are commonly out of the limits permitted by the Mexican standards. On the other hand, the “diatomita” (diatomaceous earth) is not as dangerous as the “jales”, however, this needs a treatment to eliminate the occluded organic material. This is normally used by producers of gelatin, antibiotics, industrial grease and oil, sugar refining, etc. The leaching process of metals using the sodium cyanide was introduced in 1887 (Li, 1993). This revolutionizes the techniques to obtain gold and silver. This is a method usually employed in the world to recover metals. Two international patents were obtained by developing equipment and also a process to extract toxic metals and wastes from foundry sands (Vite, 1994a, 1994b). In addition, a national patent was achieved by the leaching of heavy metals from foundry sands (Vite, 1997). Approximately, 330,000 tons of these solid residuals are generated daily in Mexico. In some states, such as Guanajuato, Zacatecas and cities as Pachuca in the state of Hidalgo, the waste deposits are found in open areas. The chemical composition of these solid residuals is varied. Figure 1 shows a photograph of the pipe used to transport the solid residuals until a “jales” dam. An important case is related to “jales” when they have high pyrite content (FeS2). This affects considerably the chemical composition due to their weathering. Due to this fact, it is necessary to process the “jales” before being used at applications such as the construction of landfills in the leveling of roads, additives for asphalt mixtures or dam construction (Botz & Stevenson, 1995, Orozco & Orozco, 1992, Sengupta, 1993, Vite et al., 2003, Wills, 1994).