LABORATORY REPORT 3

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School

University of Houston *

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1364

Subject

Mechanical Engineering

Date

Dec 6, 2023

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docx

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8

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LAB 3 HARDNESS AND TENSILE TESTING MECT 1364 Fall 2023 Lab Section 2, Monday 1:00 – 4:00 PM Lab 3 Hardness and Tensile Testing Student’s Name : David I. Felix. Date Due: Student’s ID : 2267005. (Peoplesoft Student ID) Graded by : . Date Graded:
1 Objective Gain insight into the reasons for hardness and tensile testing. Study the various methods of hardness. testing, observe a tensile test, and perform hardness testing on the Rockwell and Brinell hardness testing. machines. 2 Equipment Required • PASCO Universal Testing Machine. • Tensile specimen, scribe, Vernier caliper, marker pen. • Brinell Hardness Testing Machine with accessories. • Rockwell Hardness Testing Machine with accessories. • Reed Hardness Tester with accessories. • Test specimens of steel, aluminum, tool steel, and tungsten carbide. • Variety of testing equipment for various testing methods (Presentation slides). MECT 1364 University of Houston, Division of Technology MECT labs 2
Procedures For this lab, students were placed in groups to examine and measure different metal specimens. This included aluminum, steel, tool steel, tungsten carbide, and brass. There were three different test that were done the Rockwell Hardness Tester, Brinell Hardness Tester, and Pasco Testing Machine used to measure the tensile strength of materials. The Rockwell and Brinell Tester is used to measure the hardness, hardness is a materials ability to resist permanent distortion, penetration, indentation, and scratching. This is important because a high hardness level means a material can withstand lots of friction and erosion. Tensile strength is the maximum amount of stress a material can handle before cracking or breaking. This is important to engineers, because it lets them know what certain material are capable of handling before they break. This information is useful when trying to find what material to use to build a part that you know will be under a certain amount of stress levels. The PASCO Universal Testing Machine was used to find this information. As a group, students placed a steel then brass bar onto the machine, then put in the correct equation on a laptop that went to the machine. The machine then pulled on the bar until it broke giving us the tensile strength of both. To find the hardness, the Rockwell and Brinell machines were used. When using the Rockwell machine, students put weights in the MECT 1364 University of Houston, Division of Technology MECT labs 2
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machine to create force, then calibrated the machine the reading dial was centered, then placed the material on the machine. This is when we lowered the indenter which creates a small indention and then gives a reading to what the hardness of the material was. This was done for the Aluminum, steel, tool steel, and tungsten carbide. The Brinell Hardness used the same procedures as the Rockwell tester, the difference however, was that after making the indention, we had to slide the material to the eye scope apparatus and use the vernier knob to indicate that diameter of the indentions to identify the hardness. This lab was a form of hands-on practice and first-hand experience to what it is to measure the hardness and tensile strength of materials, it also allowed us as students to understand why we must know how to do these measurements, and why they are important. MECT 1364 University of Houston, Division of Technology MECT labs 2
Questions 1. Hardness represents wear resistance, which translates to a tool's ability to withstand byproduct heat during metal cutting. 2. Frequent use of the machine can cause calibration of the machine to fluctuate. This makes readings inaccurate so constant calibration is necessary. 3. Use the Rockwell standard test blocks to check the machine’s accuracy at any time, and periodic use on a regular basis is recommended. Compare the test reading of the block with the hardness number on the test block, this will indicate whether the instrument needs attention. 4. 142.5 5. MECT 1364 University of Houston, Division of Technology MECT labs 2
6. 7. Aluminum 95.58 MPa Steel 17.582 MPa 8. Steel 32,233.35 MPa, Brass 43,635.6 MPa 9. 10. Brass 0.0538 MPa, Steel 0.0397 MPa MECT 1364 University of Houston, Division of Technology MECT labs 2
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Table MECT 1364 University of Houston, Division of Technology MECT labs 2
Steel Stress Strain graph Brass Stress Strain graph MECT 1364 University of Houston, Division of Technology MECT labs 2