11

Researchers employ technology
as a tool in the inspection of wood, metal and concrete

Ultrasound is used
in the evaluation of materials

MANUEL ALVES FILHO


O ultrasound, equipment widely used by doctors to diagnoser diseases, its application is being expanded thanks to experiments carried out by researchers from the Faculty of Agricultural Engineering (Feagri) at Unicamp. In the unit's laboratories, scientists use technology to evaluate the integrity of various materials, including metal, concrete and composite materials. The Feagri group has focused its studies on wood. The method allows for more efficient preventive and corrective inspections than conventional ones, as it does not use destructive tests. Furthermore, with the help of ultrasound, inspections can be carried out across the entire intended universe and not by sampling, as is usually the case.

Research into the use of ultrasound as a tool for wood inspection began in 1997, in a pioneering way in the country, through professor Raquel Gonçalves, from Feagri. Since then, progress has been made, although studies in this area are still incipient in Brazil, compared to what happens in developed countries. Currently, she has dedicated herself more heavily to experiments with wood and its derivatives, with the support of fellow professor André Bartholomeu, from the Faculdade Politécnica de Jundiaí, whose doctorate degree was the first fruit of this line of research.

According to Raquel, using ultrasound is relatively simple. The device consists of a source, to which two transducers are coupled. The first transforms electrical impulses into acoustic waves, which are reflected inside the analyzed material. The second captures these signals, converting them back into electrical impulses. Based on the distance and travel time of sound waves, experts can calculate their speed. Then, just make a comparison. "In a material that has internal discontinuities, the propagation of acoustic waves is slower than in an intact material. Furthermore, using already established theories, it is possible to obtain information about the mechanical and elastic properties of the material", explains Bartholomeu.

The method, according to the researchers, allows the identification of materials with cracks and even fatigue. In the case of wood, it is even possible to detect an anomaly or internal knot, which would be impossible with visual analysis. "This technique is important, for example, to promote the classification of Brazilian wood, giving it greater added value. Wood from the same species or even from the same tree can provide pieces of different qualities. Without ultrasound, This can only be identified late, when expenses have already been incurred on cutting and transport", warns Raquel.

The two researchers have promoted a true crusade around the need for certification of national wood. Currently, Bartholomeu highlights, consumers are subject to buying a pig in a poke, as there is no way to prove whether the product available on the market is of quality nor whether it can actually be applied for the purpose desired by the buyer. "Only classification eliminates all these doubts. And this is only viable through rigorous inspections that can be carried out locally and without destroying the material, such as those provided by ultrasound", he reinforces.

Ecology - The applications of ultrasound, according to experts, do not stop there. The equipment can also have an ecological function, as Bartholomeu highlights. There are situations, he says, where it is difficult to determine whether or not a tree is doomed due to a pest. With the help of technology, it is possible to know, for example, whether a specimen is infested by termites. This eliminates the risk of an unnecessary cut, as often occurs.

Recently, Raquel and Bartholomeu presented the method to the CPFL Group, in a workshop jointly promoted by the company and Unicamp. The objective, according to the researchers, was to propose to the company to carry out inspections of its concrete and wooden posts. The experts also suggested the development of specific equipment for this function, in order to facilitate field work, as well as employee training.

Without this technology, the teachers maintain, the inspection tends to detect problems when the pole is already degraded. An alternative is destructive testing. In other words, you need to cut a piece of the piece to analyze it. Or, work by sampling, sending part of the wood from a batch to be evaluated in the laboratory. The research conducted by Raquel and Bartholomeu has already yielded two doctoral theses, as well as articles in specialized journals and presentations at national and international scientific events. Three other doctoral theses and a master's dissertation are in progress. Due to the pioneering spirit and excellence of the work carried out at Unicamp, the Feagri professor took over the coordination of a research group at CNPq in this segment.

Research makes bovine pericardium more biocompatible Presearch developed for Marina Junko Shiotsu Maizato's doctoral thesis, presented to the Faculty of Mechanical Engineering (FEM) at Unicamp, brings results that may have applications in the storage, sterilization and manipulation of bovine pericardium, a fibrous and resistant membrane that surrounds the heart of several species. The tissue, after being treated with a substance called glutaraldehyde, is used to make heart valve prostheses and grafts. The author of the thesis, using the freeze-drying process (freezing followed by the elimination of water by vacuum sublimation), achieved a reduction in the cytotoxicity of the material, which makes it more biocompatible. According to Marina, treatment of bovine pericardium with glutaraldehyde promotes the appearance of cross-links, improves mechanical resistance characteristics and reduces the recipient's immunological reactions. After this process, the material is stored in formaldehyde. The study she conducted demonstrated that freeze-drying does not cause significant changes in either the mechanical properties or the structure of the tissue. She also found that the method promotes the reduction of residual aldehydes, substances remaining from the treatment and conservation of the pericardium. These residues, according to the author of the thesis, are identified as one of the possible causes of calcification that would reduce the useful life of valves produced from bovine pericardium, whose average durability varies from 10 to 15 years. “What my work did was open a door for new investigations. It now remains to develop new studies to discover whether freeze-drying actually increases the durability of the tissue and reduces the calcification process”, says the researcher. Marina's doctoral thesis was supervised by professor Cecília Amélia de Carvalho Zavaglia, from Unicamp, and professor Adolfo Alberto Leirner, from the Instituto do Coração (InCor). Currently, the study author works in the Bioengineering Division of InCor. (MAF)

Top