Aircraft Materials Testing

Aircraft Materials Testing

a) Component Testing

i)

Tensile Testing

There are several experimental hurdles that must be overcome to do proper tensile testing of materials in order to obtain precise mechanical property measurements. In the macro-world, the majority of these issues has been studied in detail and in many cases standardized (e.g., ASTM standards). The synthesis of materials with reduced dimensions (e.g., coating materials, novel nanostructures, thin films) is a burgeoning field of research. Metrology for accurate sample measurement and micro- and nanostructural characterization must be juxtaposed with synthesis and testing. Co-fabrication of the specimen and testing apparatus has been proven to be an attractive strategy in situations where the materials synthesis can be integrated in the device process flow. This is particularly appealing for materials used in microelectronics, MEMS, and NEMS synthesized by vapor deposition methods, and allows for batch processing and testing of many specimens on a single wafer. Co-fabrication has the clear advantage of circumventing gripping and alignment issues by incorporating the specimen into the device fabrication using multiple photolithography masks, for example. M.A. Haque and M.T.A. Saif have co-fabricated and performed tensile testing of thin metal films as thin as 30 nm21 and H.D. Espinosa and colleagues have employed this strategy to test polysilicon specimens and one-dimensional (1-D) nanostructures.[1]

Hardness Testing

During the twentieth century, steel was the dominant engineering material in the industrialized world due to its low cost and versatility. Much of that versatility is due to a class of steels known as alloy steels. By adding other metals to the basic mix of iron and carbon found in steel, the properties of alloy steels can be varied over a wide range. Alloy steels offer the potential of increased strength, hardness, and corrosion resistance as compared to plain carbon steel. The main limitation on the use of alloy steels was that they typically cost more than plain carbon steels, though that price differential declined over the course of the twentieth century. Titanium's strength-to-weight ratio and resistance to most forms of corrosion were the primary incentives for utilizing titanium in industry, replacing stainless steels, copper alloys, and other metals. The main alloy used in the aerospace industry was Titanium 6.4. It is composed of 90 percent titanium, 6 percent aluminum and 4 percent vanadium. Titanium 6.4 was developed in the 1950s and is known as aircraft-grade titanium. Aircraft-grade titanium has a tensile strength of up to 1030MPa and a Brinell hardness value of 330. But the low ductility of 6.4's made it difficult to draw into tubing, so a leaner alloy called 3-2.5 (3 percent aluminum, 2.5 percent vanadium, 94.5 percent titanium) was created, which could be processed by special tube-making machinery. As a result, virtually all the titanium tubing in aircraft and aerospace consists of 3-2.5 alloy. Its use spread in the 1970s to sports products such as golf shafts, and in the 1980s to wheelchairs, ski poles, pool cues, bicycle frames, and tennis rackets.

Impact Testing

Impact testing was one of the first practical applications of the ...