Lab 1. Hardness Test

Question 1

Hardness is..

Answer 1

resistance of a material to localized plastic deformation, usually by indentation

resistance to scratching, abrasion or cutting.

Question 2

hardness is the ability of a material

Answer 2

to resist plastic deformation under load

Question 3

the greater the hardness of a material…. the greater its….

Answer 3

resistance to deformation

Question 4

does hardness have units?

Answer 4

no units

Question 5

why is hardness the most common test on materials?

Answer 5

it is simple, inexpensive. gives prediction of wear properties

gives us an idea about machinablity…. more hard harder to machine..

it is nondestructive simple test….
give idea about mechanical properties….. it can help predict tensile strength of metals

Question 6

the higher the material’s hardness

Answer 6

the better its wear properties

Question 7

hard materials can be inserted in mechanisms at

Answer 7

points of stress to improve the life of the parts

Question 8

hardness gives the ideas about _____…

Answer 8

machinablity

Question 9

generally there is an inverse proportion between

Answer 9

hardness and machinability

Question 10

hardness can be measured 3 ways.

Answer 10

scratching

indenting

free fall of a diamond tip hammer on sample… measuring the bounce

Question 11

scratch hardness

Answer 11

mohs scale

Question 12

hardness measurments can be classified as ____ and ___ tests according to the forces applied and the displacements obtained

Answer 12

macrohardness and microhardness

Question 13

macro hardness test (Rockwell, Brinell, Macro-Vickers)

Answer 13

are the most widely used methods for rapid routine hardness measurements. The indenting forces in macro-hardness tests are in the range of 5 to 3000kgf.

Question 14

Micro-hardness test (micro-vickers, knoop)

Answer 14

is applicable when hardness ofcoatings, surface hardness, or hardness of differentphasesin the multi-phase material is measured. Small diamond pyramid is used as indenter loaded with a small force of 10 to 1000gf.

Question 15

macrohardness

Answer 15

quick simple methods of obtaining mechanical property data for bulk material from a small sample

Question 16

macrohardness test requile application of loads above

Answer 16

1kgf

Question 17

commmon tests macrohardness include

Answer 17

rockwell and brinell hardness test

Question 18

macrohardness is not effective for determining

Answer 18

coat and surface hardness properties

Question 19

Brinell

Answer 19

10mm sphere of steel or tunsten carbide

Question 20

vickers

Answer 20

diamond pyramid

Question 21

rockwell ABC

Answer 21

diamond cone

Question 22

Rockwell BFG

Answer 22

1/16in diameter steel sphere

Question 23

test used in lab?

Answer 23

rockwell B. 1/16 inch ball… 100 kg

Question 24

the following sample characteristics should be considered when selecting the hardness testing method to use

Answer 24

sample size
cylindrical samples
sample thickness
scales
Gage R&R

Question 25

describe brinell testing

Answer 25

large area and deep penetration..

harden steel or carbide ball. usually 10 mm diamameter… surface condition not critical

microstructure heterogenous

best for achieving the bulk or macro-hardness of a material, particually those materials with heterogenous strucutres

can help predict tensile strength

Question 26

what is brinell testing not suitable for

Answer 26

very hard materials may cause ball damage.. very thin materials.. .case harden materials.

Question 27

Describe Rockwell testing

Answer 27

does not require visual measurements…. penetration depth is measured instead of penetration are…

it has a smaller indention then Brinell

no mathmatical relation to strength

surface condition is critical

Question 28

Rockwell indentor….

Answer 28

The indenter may either be a steel ball (can be of different diameter) or a spherical diamond-tipped cone with a 1200 angle and 0.2 mm tip radius, called a Brale.
The type of indenter and the test load determine the hardness scale (A, B, C, etc).
Every 0.002 mm penetration causes hardness value to drop by 1.

Question 29

when testing with rockwell how much load is originally applied?

Answer 29

10 kg

Question 30

superficial tests are frequently performed on

Answer 30

thin specimens. shallow penetration