Mechanical Testing Lab Report

Topics: Tensile strength, Rockwell scale, Hardness Pages: 4 (1311 words) Published: December 7, 2010
Purpose
This experiment was intended to make students familiar with some common methods of mechanical testing. The laboratory sessions included mechanical testing such as Rockwell hardness testing, the tensile test, the Charpy impact test, and the Jominy end-quench test.

Materials and Methods
For the first method of this experiment, the Rockwell hardness testing of brass, the TA prepared three different types of brass for testing. (Free machining cartridge brass: 360 brass 70% Cu – 30% Zn) The three types were: the as received brass specimen, the cold rolled brass specimens of 10%, 20%, 30%, 40%, and 50%, and the annealed brass specimens from 20% cold-rolled. The last type of brass specimens was annealed at 500°C for times 5, 10, 15, 20, and 25 minutes. The TA then calibrated the scale using a calibration block to ensure accurate measurements. This scale required the use of a 1/16” stainless steel ball for indentation, coupled with a 100kg load. This scale was utilized in this case because brass is being tested, which is a relatively soft material. (Q3) Once the hardness tester was prepared, each specimen was tested several times using the Rockwell B (RB) hardness scale and the results were averaged and recorded as shown in Table 1.

Table 1 - Data collected using Rockwell hardness test
Specimen #| Condition| Initial thickness (in)| Final thickness (in)| Actual % reduction| HRB 1| HRB 2| HRB 3| HRB 4| HRB 5| Average RB| 1| As received| 0.124| 0.124| 0| 83.5| 83| 83.5| 83.5| 83| 83.3| 2| 10% reduction| 0.125| 0.113| 9.6| 79| 80| 81.4| 79| 80.6| 80| 3| 20% reduction| 0.124| 0.099| 20.16129| 92| 90| 90.5| 91.8| 90.8| 91.02| 4| 30% reduction | 0.123| 0.086| 30.0813| 93| 92.5| 92.5| 92.7| 92.6| 92.66| 5| 40% reduction| 0.123| 0.0735| 40.2439| 88| 87.5| 86.5| 87| 88.5| 87.5| 6| 50% reduction| 0.124| 0.062| 50| 97.5| 97.2| 96.5| 95.5| 95.2| 96.38| 7| 5 min|  |  |  | 90.5...
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