Lab07_Impact_Test_DKSinha_ - San Francisco State University...

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Figure 1. Charpy test specimen. (Source: San Francisco State University School of Engineering ENGR 200, Materials of Engineering Impact Test I. OBJECTIVES The goal of this experiment is to reinforce students’ understanding of the concepts of ‘impact energy’ and ‘ductile-to-brittle transition temperature (DBTT)’ by investigating the effect of temperature and carbon content on the toughness of steel by means of a Charpy impact test. II. INTRODUCTION Materials can be classified as ductile or brittle depending on their abilities to undergo plastic deformation  before fracture. Toughness is a measure of the amount of energy a material can absorb up till fracturing  and it is a temperature-dependent property. Some materials, most notably steels, can exhibit ductile or  brittle behavior depending on the test temperature. Elevated temperatures promote ductile behavior and  increase the toughness of steels.  In this experiment we will examine the effect of test temperatures and carbon content on the toughness of  three different plain carbon steels by means of impact testing. III. SAFETY PRECAUTION Due to the dynamic nature of an impact test (Charpy Test) as shown in Figure 1(a), there are several potentially dangerous steps in this experiment, which include: 1. Handling cold specimens (at dry ice temperatures) and hot specimens (at 200°C) 2. Raising the Charpy pendulum hammer (~ 27.2 kg or 60 lbs) and locking it in place 3. Placing the specimen in the specimen holder after locking the hammer 4. Releasing the hammer from its locked position 5. Collecting fractured samples from test area before the pendulum hammer comes to a halt and while the
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This note was uploaded on 09/08/2011 for the course ENGR 200 taught by Professor Staff during the Spring '11 term at S.F. State.

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Lab07_Impact_Test_DKSinha_ - San Francisco State University...

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