Material Science NPTEL（材料科学,NPTEL）.pdf

Material Science Prof. Satish V. Kailas Associate Professor Dept. of Mechanical Engineering, Indian Institute of Science, Bangalore – 560012 India Chapter 8. Failure Failure can be defined, in general, as an event that does not accomplish its intended purpose. Failure of a material component is the loss of ability to function normally. Components of a system can fail one of many ways, for example excessive deformation, fracture, corrosion, burning-out, degradation of specific properties (thermal, electrical, or magnetic), etc. Failure of components, especially, structural members and machine elements can lead to heavy loss of lives, wealth and even may jeopardize the society! This chapter deals with the study of failures by mechanical means i.e. application stresses. Even though the causes of failure are known, prevention of failure is difficult to guarantee. Causes for failure include: improper materials selection, improper processing, inadequate design, misuse of a component, and improper maintenance. It’s the engineer’s responsibility to anticipate and prepare for possible failure; and in the event of failure, to assess its cause and then take preventive measures. Structural elements and machine elements can fail to perform their intended functions in three general ways: excessive elastic deformation, excessive plastic deformation or yielding, and fracture. Under the category of failure due to excessive elastic d