BASICS EXAMINATION OF ISNT LEVEL III

Dr.Oruganti Prabhakar

Nanyang Technological University

Singapore

March 28, 2001

Contents

1 Subject General Knowledge 9

1.1 Technology of NDT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

1.1.1 De�nitions and methodology of applying NDT . . . . . . . . . . . . . 9

1.1.2 Speci�c and distinctive characteristics of these methods . . . . . . . . 9

1.1.3 Areas of NDT applications . . . . . . . . . . . . . . . . . . . . . . . . 9

1.1.4 Quality control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

1.1.5 Maintenance Defectology . . . . . . . . . . . . . . . . . . . . . . . . . 9

1.1.6 Evaluation of properties . . . . . . . . . . . . . . . . . . . . . . . . . . 9

1.1.7 Material Failures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

1.1.8 Purpose for Use of NDT . . . . . . . . . . . . . . . . . . . . . . . . . . 9

1.1.9 NDT IN FRACTURE CONTROL . . . . . . . . . . . . . . . . . . . . 9

2 FUNDAMENTALS OF MATERIALS TECHNOLOGY 11

2.1 PROPERTIES OF MATERIALS . . . . . . . . . . . . . . . . . . . . . . . . . 11

2.1.1 Strength and elastic properties . . . . . . . . . . . . . . . . . . . . . . 11

2.1.2 Physical properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

2.1.3 Material Properties testing . . . . . . . . . . . . . . . . . . . . . . . . 11

2.2 ORIGIN OF DISCONTINUITIES AND FAILURE MODES . . . . . . . . . . 11

2.2.1 Inherent discontinuities . . . . . . . . . . . . . . . . . . . . . . . . . . 11

2.2.2 Process-induced discontinuities . . . . . . . . . . . . . . . . . . . . . . 11

2.2.3 Service-induced discontinuities . . . . . . . . . . . . . . . . . . . . . . 11

2.2.4 Failures in metallic materials . . . . . . . . . . . . . . . . . . . . . . . 11

2.2.5 Failures in nonmetallic materials . . . . . . . . . . . . . . . . . . . . . 11

2.3 STATISTICAL NATUREOFDETECTINGANDCHARACTERIZINGDIS-

CONTINUITIES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

3 PROPERTIES OF MATERIALS INTRODUCTION 13

3.1 CLASSES OF PROPERTIES . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

3.2 SIGNIFICANCE OF PROPERTIES OF DESIGN . . . . . . . . . . . . . . . 13

3.3 LOADING SYSTEMS AND MATERIAL FAILURE . . . . . . . . . . . . . . 13

3.3.1 Loading systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

3.4 TESTING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

3.4.1 The Tensile Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

3.4.2 Compression Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

3.4.3 Transverse Rupture Testing . . . . . . . . . . . . . . . . . . . . . . . . 14

3.4.4 Shear Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

3.4.5 Fatigue Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

3.4.6 Creep Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

3.4.7 Notched Bar Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

1

2 CONTENTS

3.4.8 Bend Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

3.4.9 Hardness Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

3.5 Factor of safety . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

4 FUNDAMENTALS OF FABRICATION AND PRODUCT TECHNOL-

OGY 17

4.1 RAW MATERIAL PROCESSING . . . . . . . . . . . . . . . . . . . . . . . . 17

4.2 METAL PROCESSING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

4.2.1 Primary metals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

5 THE NATURE OF MATERIALS AND SOLID STATE CHANGES IN

METALS 19

5.1 THE EFFECT OF ENERGY ON THE ATOM . . . . . . . . . . . . . . . . . 19

5.2 METALLIC STRUCTURE . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

5.3 SOLIDIFICATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

5.3.1 Grain Size . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

5.4 SOLID STATE CHANGES IN METALS . . . . . . . . . . . . . . . . . . . . . 19

5.4.1 Work hardening . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

5.4.2 Plastic Deformation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

5.4.3 Cold Work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

5.5 RECRYSTALLIZATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

5.5.1 Recovery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

5.5.2 Recrystallization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

5.5.3 Grain Growth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

5.6 AGE HARDENING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

5.7 ALLOTROPIC CHANGES . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

5.8 HEAT TREATMENT OF STEEL . . . . . . . . . . . . . . . . . . . . . . . . 20

5.8.1 Approximate Equilibrium Heat-Treatment Processes . . . . . . . . . . 20

5.8.2 Austenitization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

5.8.3 Annealing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

5.8.4 Normalizing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

5.8.5 Spheroidizing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

5.8.6 Hardening of Steel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

5.8.7 Tempering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

5.9 CASE HARDENING OF STEELS . . . . . . . . . . . . . . . . . . . . . . . . 20

5.9.1 Carburizing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

5.9.2 Flame Hardening . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

6 FERROUS METALS 21

6.1 CHOOSING METALS AND ALLOYS . . . . . . . . . . . . . . . . . . . . . . 21

6.1.1 Ferrous Raw Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

6.2 CAST IRONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

6.3 STEEL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

6.3.1 Wrought Iron . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

6.3.2 Steel Making . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

6.3.3 Plain Carbon Steel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

6.3.4 Alloy Steels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

7 NONFERROUS METALS 23

7.1 MATERIAL IDENTIFICATION SYSTEMS . . . . . . . . . . . . . . . . . . . 23

CONTENTS 3

8 CASTING 25

8.1 Green sand molded . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

8.2 METAL MOLDS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

8.3 INVESTMENT MOULDING . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

8.4 HEAT TREATMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

8.5 THE PROCESS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

8.6 SOLIDIFICATION OF METALS . . . . . . . . . . . . . . . . . . . . . . . . . 25

8.6.1 SOLIDIFICATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

8.7 POURING AND FEEDING CASTING . . . . . . . . . . . . . . . . . . . . . 25

8.7.1 Casting Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

8.7.2 Pouring the Gating Systems . . . . . . . . . . . . . . . . . . . . . . . . 25

8.7.3 Risers Chill . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

9 FOUNDRY TECHNOLOGY 27

9.1 SAND MOLDING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

9.1.1 Green Sand . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

9.1.2 Dry Sand Molds. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

9.1.3 Floor and Pit Models . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

9.1.4 shell Molds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

9.1.5 METAL MOLD AND SPECIAL PROCESSES . . . . . . . . . . . . . 28

9.1.6 Die Casting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

9.1.7 Investment Casting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

9.1.8 Plaster Mold Casting . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

9.1.9 Centrifugal Casting . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

9.1.10 Continuous Casting . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

9.2 MELTING EQUIPMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

9.2.1 Cupola . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

9.2.2 Crucible . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

9.2.3 Pot Furnances . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

9.2.4 Reverberatory Furnances . . . . . . . . . . . . . . . . . . . . . . . . . 28

9.2.5 Electric Arc Furnances . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

9.2.6 Induction Furnances . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

9.3 FOUNDARY MECHANIZATION . . . . . . . . . . . . . . . . . . . . . . . . 28

4 CONTENTS

List of Figures

5

6 LIST OF FIGURES

List of Tables

3.1 Some typical modulus of elasticity of materials . . . . . . . . . . . . . . . . . 14

3.2 Moh's Hardness Values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

7

8 LIST OF TABLES

Chapter 1

Subject General Knowledge

1.1 Technology of NDT

1.1.1 De�nitions and methodology of applying NDT

1.1.2 Speci�c and distinctive characteristics of these methods

1.1.3 Areas of NDT applications

1.1.4 Quality control

1.1.5 Maintenance Defectology

1.1.6 Evaluation of properties

1.1.7 Material Failures

1.1.8 Purpose for Use of NDT

1.1.9 NDT IN FRACTURE CONTROL

9

10 CHAPTER 1. SUBJECT GENERAL KNOWLEDGE

Chapter 2

FUNDAMENTALS OF

MATERIALS TECHNOLOGY

2.1 PROPERTIES OF MATERIALS

2.1.1 Strength and elastic properties

2.1.2 Physical properties

2.1.3 Material Properties testing

2.2 ORIGIN OF DISCONTINUITIES AND FAILURE

MODES

2.2.1 Inherent discontinuities

2.2.2 Process-induced discontinuities

2.2.3 Service-induced discontinuities

2.2.4 Failures in metallic materials

2.2.5 Failures in nonmetallic materials

2.3 STATISTICAL NATURE OF DETECTING AND

CHARACTERIZING DISCONTINUITIES

11

12 CHAPTER 2. FUNDAMENTALS OF MATERIALS TECHNOLOGY

Chapter 3

PROPERTIES OF

MATERIALS

INTRODUCTION

Properties of materials is understood based on the two models: 1. Chemical bonds. 2. Hard

Ball Model. In the ball model the spherical atoms occupy the �xed locations in a crystal

structure. The arrangement of atoms in di�erent planes or cross sections will determine the

mechanical behaviour of materials. In the case of face centred cubic structure the (111) plane

is the close packed plane. It is easy to shear this plane along (111) and not perpendicular.

3.1 CLASSES OF PROPERTIES

3.2 SIGNIFICANCE OF PROPERTIES OF DESIGN

3.3 LOADING SYSTEMS ANDMATERIAL FAILURE

3.3.1 Loading systems

3.4 TESTING

3.4.1 The Tensile Test

The tensile test yields the mechanical properties of a material tested in tension. The tensile

specimens have to be as per some standard. They have the following features: Gauge Length

A certain portion in the main specimen (pl see Figure) is marked as gauge length. This is

used to calculate the percen elongation. It should be borne in mind that the shorter the

gauge length the higher the value of the percent elongation determined.

A-B : Elastic Range B = Elastic Limit: Above this point plastic deformation occurs. C

= Yiled point D-E = Work hardening region. E = Ultimate tensile strength. F = Fracture

strength.

Modulus of elasticity of all plastics is low compared to most metals. Drawn Nylon �la-

ments hasve a tensile strength of 50000 psi which is actually greater than some low strength

steels. Nylon is crystalline. It is used as insulators. It is light in weight, has easily colorabil-

ity and used in �ber reinforced plastics. Materials with Poorly de�ned Yield Point

13

14 CHAPTER 3. PROPERTIES OF MATERIALS INTRODUCTION

Al alloys 10 X 106 psi

Cu alloys 14 to 19 X 106psi

Gray Cast Iron 12 to 19 X 106psi

Steel 28 to 30106psi

Cemented carbide 50 X106psi

Table 3.1: Some typical modulus of elasticity of materials

Modulus of Elasticity

It is also known as Young's Modulus and is represted as E. This is the slope of elastic or the

initial part of the stress - strain curve . Factors that increase the yield strength of materials

at room temperature

Features of the microstructure that prevent the movement of dislocations like : Grain bound-

ary ii) Precipitates iii) alloying additions will increase the strength. At elevated temperatures

the grains start sliding one over the other and hence large grains are preferable. Precipitates

and alloying additions also improve the high temperature strength.

Ductility

PercentageElongation =(Lf ) � (Lo)

(Lo)X100 (3.1)

Resilience and Toughness

Resilience is the area under the stress-strain curve upto the elastic limit from zero load. It

represents the energy that is recoverable.

Toughness

This is the total area under the stress- strain curve starting from load upto fracture. This

value represnts the ability of the material to absorb energy without fracture.

True Stress-True Strain

When the tensile test is carried out the specimen is constantly deforming and the cross

secional area is constantly decreasing. True stress is calculated based on the actual area

of the specimen during the progress of the test. In a similar way the the strain calculated

based on the actual length of the specimen during test is known as True Strain.

3.4.2 Compression Testing

Certain materials like are stronger in compression than in tension. For example cast iron

has a compression strength that is twice its tensile strength. The compression test is carried

out much the same way as the tensile testing.

3.4.3 Transverse Rupture Testing

This test is usually employed for brittle materials the tensile testing is not very useful. So

for brittle materials like concrete this test is used.

(Sr) =3PL

2b(d2)(3.2)

3.4. TESTING 15

Mineral Moh's Indentation

Hardness Number Hardness,kg/mm2

Talc 1 23

Gypsum 2 30

Calcite 3 100

Fluorite 4 160

Apatite 5 400

Orthoclase 6 600

Quartz 7 810

Topaz 8 1200

Corundum 9 1860

Diamond 10 7800

Table 3.2: Moh's Hardness Values

3.4.4 Shear Testing

This test is usually carried out for bolts and rivets.

� =P

2A(3.3)

3.4.5 Fatigue Testing

In fatigue testing the loading is cyclic. A mojority of industrial failures are caused by fatigue

(about 90I stage: Cracks are initiated. II stage: The crack grows during cyclic loading. The

crack surface formed during this stage appears smooth and polised. III stage: The area of

cross section bearing the load is constantly reducing and ata certain stage the cross sectional

area remaining connected is so much reduced the stree developed exceeds the yield stress

and sudden brittle fracture occurs. The fractured surface developed during this stage shows

a well de�ned grain structure.

3.4.6 Creep Testing

3.4.7 Notched Bar Testing

3.4.8 Bend Testing

3.4.9 Hardness Testing

Hardness is a measure of the ability of a material to resist penetration of the near surface

material. Hardness is proportional to material properties like strength. It is di�cult to

convert from one value to another. Moh's test : Moh's scale of hardness varies from 1 to

10. Diamond is 10 and corundum is 9, Talc is 1.

Hardness tests: 1. File test. 2. Brinell test

A steel ball is impressed (10 mm in diameter) is impressed on the material whose hardness

is to be determined. BHN = Load in kg/ Area of impression in mm2. This test gives

consistent results. Modern micro processor based equipment are self loading. Thin material

can not be tested by this method. Rockwell Test This is also an impression test. It has

10 kg as minor load and 60, 100 or 150 kg as the major loads. Di�erential depth between

the minor and the major loads is then directly read by a dial gauge as a Rockwell hardness

number.

16 CHAPTER 3. PROPERTIES OF MATERIALS INTRODUCTION

3.5 Factor of safety

Chapter 4

FUNDAMENTALS OF

FABRICATION AND

PRODUCT TECHNOLOGY

4.1 RAW MATERIAL PROCESSING

4.2 METAL PROCESSING

4.2.1 Primary metals

Metal ingot production

Wrought primary metals

17

18CHAPTER 4. FUNDAMENTALS OF FABRICATION AND PRODUCTTECHNOLOGY

Chapter 5

THE NATURE OF

MATERIALS AND SOLID

STATE CHANGES IN

METALS

5.1 THE EFFECT OF ENERGY ON THE ATOM

5.2 METALLIC STRUCTURE

Microstructure is the appearance of the polished specimen under the microscope.

5.3 SOLIDIFICATION

5.3.1 Grain Size

5.4 SOLID STATE CHANGES IN METALS

5.4.1 Work hardening

The strength of metal is increased by plastic ow and the elastic limit is raised.

5.4.2 Plastic Deformation

This includes slip, twinning etc. Cold work makes the metal(which is strain hardening

by nature) stronger and harder. In most metals dislocation processes are accompanied by

discrete releases of mechanical energy called stress waves.

19

20CHAPTER 5. THE NATUREOFMATERIALS AND SOLID STATE CHANGES IN METALS

5.4.3 Cold Work

5.5 RECRYSTALLIZATION

5.5.1 Recovery

5.5.2 Recrystallization

Cold worked metal has strained grains. A heat treatment can produce new and unstrained

grains. This is called recrystallization. Higher the cold work it is easier to recrystallize the

metal.

5.5.3 Grain Growth

5.6 AGE HARDENING

5.7 ALLOTROPIC CHANGES

5.8 HEAT TREATMENT OF STEEL

5.8.1 Approximate Equilibrium Heat-Treatment Processes

5.8.2 Austenitization

5.8.3 Annealing

5.8.4 Normalizing

5.8.5 Spheroidizing

5.8.6 Hardening of Steel

5.8.7 Tempering

5.9 CASE HARDENING OF STEELS

5.9.1 Carburizing

5.9.2 Flame Hardening

Chapter 6

FERROUS METALS

6.1 CHOOSING METALS AND ALLOYS

6.1.1 Ferrous Raw Materials

6.2 CAST IRONS

6.3 STEEL

6.3.1 Wrought Iron

6.3.2 Steel Making

6.3.3 Plain Carbon Steel

6.3.4 Alloy Steels

Low Alloy Structural Steels

Low Alloy AISI Steels

Stainless Steels

Tools and Die Steels

Cast Steels

21

22 CHAPTER 6. FERROUS METALS

Chapter 7

NONFERROUS METALS

7.1 MATERIAL IDENTIFICATION SYSTEMS

23

24 CHAPTER 7. NONFERROUS METALS

Chapter 8

CASTING

8.1 Green sand molded

8.2 METAL MOLDS

8.3 INVESTMENT MOULDING

8.4 HEAT TREATMENT

8.5 THE PROCESS

8.6 SOLIDIFICATION OF METALS

8.6.1 SOLIDIFICATION

subsectionShrinkage

8.7 POURING AND FEEDING CASTING

8.7.1 Casting Design

8.7.2 Pouring the Gating Systems

8.7.3 Risers Chill

25

26 CHAPTER 8. CASTING

27

28 CHAPTER 9. FOUNDRY TECHNOLOGY

Chapter 9

FOUNDRY TECHNOLOGY

9.1 SAND MOLDING

9.1.1 Green Sand

Patterns

Flasks

Sand Compaction

Cores

Green Sand Advantages and Limitations

9.1.2 Dry Sand Molds.

9.1.3 Floor and Pit Models

9.1.4 shell Molds

9.1.5 METAL MOLD AND SPECIAL PROCESSES

Permanent Mold Casting

9.1.6 Die Casting

9.1.7 Investment Casting

9.1.8 Plaster Mold Casting

9.1.9 Centrifugal Casting

9.1.10 Continuous Casting

9.2 MELTING EQUIPMENT

9.2.1 Cupola

9.2.2 Crucible

9.2.3 Pot Furnances

9.2.4 Reverberatory Furnances

9.2.5 Electric Arc Furnances

9.2.6 Induction Furnances