hardnesstest

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San Francisco State University

School of Engineering

ENGR 200: Materials of Engineering

Laboratory 2

Material Hardness Testing

I. OBJECTIVES

The purpose of this experiment is to familiarize the student with performing hardness tests andobtaining the hardness values of several common metals.

II. INTRODUCTION

Hardness is defined as the ability of a material to resist plastic deformation, and is a complex

property related to the strength of interatomic bonding and other variables. The hardness of a

machine or a structural element can be obtained without destroying the element and for this

reason hardness is classified as a non-destructive test.

In general, hardness tests are performed by pressing a hard indenter of known size and geometry

into the surface of the test specimen using a standard load. The depth of the resulting impression

is used to obtain an empirical hardness number. In this experiment, two common methods for

measuring hardness will be used: the Rockwell and the Brinell hardness tests.

Test 1. The Rockwell Test: The load and the penetrator used depend on the expected hardness of

the material under investigation. For hard materials, a diamond cone (brale) indenter and a 150 kgload are used. This combination is defined as the “C” scale (HRC). For metals with moderate

hardness, a hard steel ball (1/16 inch diameter) indenter and 100 kg load are used. This is known

as the “B” scale (HRB). We will be using Rockwell “B” scale (HRB) for Rockwell hardness

measurements in this lab.

Test 2. The Brinell Test: The Brinell test is historically older than the Rockwell test. Two

different scales depending upon the material are used. The Brinell standard scale and the Brinell

hardened scale. Both scales use a hardened steel ball, 10 millimeter diameter, indenter with a load

of 500 kg or 3000 kg, respectively. The standard scale is used to test soft cast iron, plain steels,

and most other non-ferrous metals. The hardened scale is used to test hardened metals, or high

alloy steel. After the indentation is made, the specimen is removed from the tester and the size of

the indentation measured and the Brinell Hardness Number (HB) is calculated using Equation (1):

( )[ ]5.022

2

d D D D

P HB

−−

=

π

…………………... (1)

Where,

P = load in kg ( Note: we will be using a 3000-kg load )

D = 10 mm



d = measured diameter of impression in mm

Figure 1. (a) Manual Rockwell Tester. (b) Digital Rockwell Tester. (c) Brinell Tester.

III. EXPERIMENTAL

Materials and Apparatus

Manual Rockwell Testers (3x) (Figure 1(a))

Digital Rockwell Tester (1x) (Figure 1(b))

Brinell Tester (1x) (Figure 1(c))

Brinell scope (a handheld optical magnifier) (1x)

Materials: Copper, Aluminum, Brass, and Steel specimens (Figure 2)

Experimental Procedure

1. Each group will test four materials: copper (C11000), aluminum (2024-T4), brass (C36000),

and steel (1010).

2. On the smooth surface of each specimen,

i) Take 1x hardness measurement using the Brinell tester.

ii) Take 3x measurements using a manual Rockwell tester – use B scale (HRB).

iii) Take 3x measurements using a digital Rockwell tester – use B scale (HRB).

iv) Be sure to keep all indentations five diameters away from previous indentations and edgesof the specimen.

3. At the bottom of the Brinell indentation you made in 2(i), take a single Rockwell reading (HRB)

using either a manual or digital Rockwell Tester.

4) Collect all data in Table 1 (see data collection sheet).

Figure 2. Hardness test specimens.(Left to right) copper, brass,

aluminum, and steel.

(a) (b) (c)



5) Convert the Brinell Hardness numbers (HB) to equivalent Rockwell (HRB) values using the

conversion tables on the lab wall.

Equipment Operating Procedure

A. Rockwell Test:1) Ensure that the activation lever is in the forward locked position. Place the proper indenter and

weights on the machine to achieve the chosen scale.

2) Place the specimen on the stage and **slowly** move it upward into contact with the

penetrator. Stop when the small hand indicator is vertical and touching the dot. At this point, a

pre-load of 10 kg has been applied on the specimen.

3) Zero out the larger indicator by turning the scale face so that the large hand or indicator is

touching the set point.

4) Now activate the major load by releasing the activation lever. Allow it to move without

applying any hand pressure.

5) When the activation lever has stopped moving (this should take 10 seconds), lock the lever

back into the forward position and take the reading directly from the face of the instrument.

B. Brinell Test:

1) To test the desired specimen, place it on the stage. Activate the load cell by turning the

activation lever. Once the load cell reaches the pre-determined load (3000 kg) begin timing and

hold your specimen under these conditions for 10 seconds.

2) When the proper time has elapsed, deactivate the tester and remove the specimen.

3) Using the hand-held optical magnifier measure the indentation diameter and use the equation

previously presented to determine the Brinell Hardness Number (HB).



III. DELIVERABLES FROM YOU

Please include the following discussions in your tech-memo:

i) Discuss the relative advantages and disadvantages of both tests

ii) For each of the metals, compare the hardness values you obtained experimentally to

any *reference values you could locate. Depending on the alloying, heat treatment or coldwork - the hardness values may differ a lot. This exercise is to explore deviations in

hardness values.

iii) Compare the experimentally obtained HRB values to the HRB values obtained from

the conversion table (based on conversion from HB to HRB). Present percent differencesusing the mean values. Create Table 2 and include these values.

iv) Comment on the Rockwell Hardness values at the surface of the specimen vs. at the

bottom of the Brinell indentation. Why are they different?

v) Briefly explain the term “metallic bonding”. How does metal achieve high hardness?

List possible mechanisms learned from lectures or references.

*Reference values can be found in textbook (estimated values), engineering handbooks, and

online sources (e.g. www.onlinemetals.com etc). Please quote your source, e.g. “Source:

Reference Cu(11000) hardness value is obtained from www.onlinemetals.com.”



San Francisco State University

School of Engineering

ENGR 200: Materials of Engineering

Laboratory 2

Data Collection Sheet for Material Hardness Testing

Name: __________________________ (person in-charge)

Group Members: ________________________________________________________

Date: _______________

Table 1. Hardness Data

MaterialHRB

(Manual)

Manual

HRB

(Average)

Digital

HRB

(Average)

Brinell d

(mm)1HB

2HRB

(converted

from HB)

HRB in

Brinell Dent

1.

2.

3.

N/A

1.

2.

3.

N/A

1.

2.3.

N/A

1.

2.

3.

N/A

1HB = Brinell Hardness number calculated from formula given in pre-lab.2Use conversion table in SCI 164

HRB = Rockwell Hardness number using the B scale

HRB (Average) = Average of the 3x HRB values recorded in the previous column

HRB (Digital) = 3x HRB values using the Digital Rockwell Tester

HRB, Table = HRB corresponding to HB from the Table on the Lab wall.

Calculated

using

e uation 1

Use table on the wall

to convert from HB

to HRB



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