Examples of Creep Failure - Essay Example

Widely disregarded and underappreciated, failure at recognizing the possibility of creep in a component or inadequate action to rectify creep may cause the failure of the material or the machine, rendering great financial loss in terms of output services/products. A few examples of failure caused by creep in the transportation industry are outlined below.
Car engines encounter very high temperatures because of the burning of the fuel inside the combustion chamber. The exhaust gases coming out of the exhaust manifold are at a temperature of 500-1000oF, varying from the engine to engine whereas the materials commonly used for the exhaust manifold are nickel-based alloys, chrome steel, or stainless steel in most cases. Significant creep occurs at temperatures of 828 K, 760.9 K and 844.3 K whereas the melting point of these materials is 1656 K, 1523 K and 1688 K respectively (Daniels, 2010). Deformation in the exhaust manifold of the engine not only results in a decrease in the volumetric efficiency of the engine but causes the engine to cease because of overheating and in extreme cases, might contribute to the failure because of deformation of other engine components like piston-cylinder heads resulting in extreme wear and complete destruction of the engine altogether. However, such a situation is effectively avoided these days by carrying out creep tests and considering this phenomenon during the design of the engine.
Another example of failure due to creep is in jet engines. Turbine blades in jet aircraft rotate at a very high speed subjecting them to a large centripetal force, which causes acute stresses to be produced. To top the already extreme conditions, operating conditions of the jet engines are approximately 1673 K. Common materials used in turbine blades construction are nickel superalloys which have a creep temperature of 1655 K (Impress, 2009). Though resistant to creep even close to melting points, even a slight amount of creep has to be avoided in the jet engines. Traveling at high speed, any sort of deformation can disturb the balance and efficiency of the aircraft. A chipped-off blade can wear off the entire engine (instantaneous destruction of the engine), resulting in an aircraft crash. Thus, a close check is kept on the dimensional tolerance and accuracy of the critical components of the jet engine.
Fibre Glass is an important material in the construction of vehicle bodies like small cars because of its easy machinability, low cost and lighter weight. However, a point of concern is the life expectancy of this material under extreme conditions of high stresses and temperatures. This brings attention to the failure of fiberglass because of creep. At higher temperatures, the fiberglass can soften and deform which is damaging in case of fire or when the exhaust manifold runs too close to the fiberglass body (Dave). Nevertheless, it is not a problem during the normal operating conditions where the temperature of the ambient goes as high as 310 K only whereas, the softening point of fiberglass is 1120 K and melting point is 1408 K (BGF Industries, 2004).
In all automobile vehicles, the engine comprises a piston-cylinder assembly converting reciprocating motion to rotary motion. The piston is lined with piston rings to form an air seal inside the cylinder. Moreover, it assists in-cylinder lining lubrication and cooling. These piston rings are usually made of steel, nickel-chrome alloys and the like. The operating temperature inside the combustion chamber of the vehicle may exceed 811 K (Know your car, 2011). Nickel chrome has a melting point of 1478 K with a creep temperature much below the melting point (Azom, 2010). In case the cooling system of the engine fails, the high temperature and stresses developed inside the engine cause deformation of the piston rings, resulting in extreme wear of the cylinder lining resulting in a steep drop in the engine efficiency. Incomplete combustion may take place, intake and exhaust of fuel and gases might be incomplete and in critical cases, the engine would require a complete overhaul with changeover of the piston-cylinder assembly.
Through the aforementioned examples, the significance and deadly repercussions of creep failure have been highlighted.