# mec eng lab 1 - Hardness and Compression Testing Nick...

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Hardness and Compression TestingNick DiMauroAB3ME 330September 17th, 2013Lab 1Group C1
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Chapter 4 / Exercise 70
Elementary and Intermediate Algebra: Algebra Within Reach
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The purpose of Lab 1 was the test the hardness and compression ability of severalmaterials, these include plexiglass (PMMA), 1045 Steel, and 7075-T6 aluminum. Wetested the hardness of these materials using Rockwell B, Rockwell C, and Brinell tests.We tested the compression ability of these materials with a 100kN load cell. After thesetests were completed, we have a greater understanding of these two important propertiesfor several materials and their overall strength.IntroductionHardness testing dates back centuries, allowing for a better way to categorizematerials. In 1820, the German geologist and mineralogist Friedrich Mohs foreverchanged hardness testing. Using an initial set of materials, Mohs was able to develop astandard from which hardness would be based of those initial few materials. This test isperformed by making small scratches, while still keeping the initial specimen intact.Today, there are many more test for hardness that are frequently used.In this first lab, we used Rockwell B, Rockwell C, and Brinell hardness tests. TheRockwell test uses the depth of penetration under a large load, compared to the one madean initial smaller load to determine the hardness. For Rockwell B (HRB), we used a massof 100kg and stell ball measuring 1/16 in to make the indentation.For Rockwell C(HRC), we used 150 kg and a diamond cone for the indentation process. Below are theequations to assign hardness to each material:HRB = 130-(δ/0.002mm)3
HRC = 100-(δ/0.002mm)δ= depth of penetrationThe Brinell test (BHN) was first introduced in 1900, by Johan August, and is consideredthe first widely accepted hardness test in the field of engineering. For our Brinell test, weused a 10 mm steel ball and a 3,000 kg force to make an indentation in our objects. Thehardness number for this test is calculated using the formula below:D = Diameter of ball (mm)P = Applied Mass (kg)d = Diameter of Indentation (mm)BHN (units) = kg/mm^2After hardness testing, we moved onto compression testing. In compressiontesting, the property of deformation is highlighted much more than in hardness. ApplyingPoisson’s Ratio, the compression of materials usually increases the diameter of thecylinder with a positive ratio. We also can see the phenomenon known as buckling,which forces the load to decrease during compression. Below are the equations used4
during compression testing:σ=F/AE =σ/εσT=σ(1+ε)εT= ln(1+ε)σ= stressεT= true strainF= forceE= elastic modulusA= areaExperimental ProcedureHardness TestingSpecimens:4340 Steel7076 AluminumEquipment:Wilson Rockwell model 523 microprocessor controlled hardnesstesterWilson Model J Brinell Hardness tester

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Term
Fall
Professor
Downing
Tags
Tensile strength, Rockwell, Rockwell scale, brinell hardness, 4340 Steel
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The document you are viewing contains questions related to this textbook.
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Chapter 4 / Exercise 70
Elementary and Intermediate Algebra: Algebra Within Reach
Larson
Expert Verified