Project 3B Final

School of Mechanical and Aerospace Engineering Ashby Building Stranmillis Road Belfast BT9 5AH

Mechanical and Aerospace Engineering

Project 3 Report

MEE3030

Design and Fabrication of Coil Spring for Soft Actuator Application by

Shape Memory NiTi Alloy

Author M Gibson [40061742] Project supervisor Dr CW Chan Programme BEng Mechanical Engineering Date 4 April 2014

ii

Abstract

This investigation looked at the material NiTi and how it utilises special capabilities with

Superelasticity and the Shape Memory Effect. Understanding how the material behaves to

certain external manipulation allows the material to be tailored to carry out specific tasks

due to its ‘smart’ nature. It is a very important field of study as NiTi offers a broad range of

applications. One of the biggest areas NiTi is used in is the medical industry. This

investigation looks at optimising NiTi to be used as an actuator in a soft robot application.

Experimentation was carried out on the NiTi to gain more of an understanding into the

material. This involved various heat treatments of the material. In order to understand the

effect of the heat treatment, mechanical testing was carried out to assess the effect on the

structure of the material. This involved tensile to fracture tests as well as cyclic tensile tests

to assess the fatigue of the material. Analysis using a Differential Scanning Calorimeter was

also carried out. This was used to assess the effect the heat treatment had on the

transformation temperature of the material. This is was an important step as it is a critical

factor in utilising the materials Shape Memory Effect. After gaining a further understanding

from the experimentation, a coil prototype was manufactured, and a CAD model of the coil

designed. The experimentation on the NiTi found that the heat treatment has predictable

and profound effects on the material. The appearance and characteristics of the material

vary considerably depending on the temperature of heat treatment. The balance of

martensite to austenite structure and its transformation temperature can be altered using

precise heat treatment ranges. This allows the material to be tailor-‐made to a specific

application. The prototype showed that the wire could easily be drawn into a coil spring

shape, and the coil behaves in a suitable manner to be used as an actuator.

iii

Table of Contents

Abstract…………………………………………………………………………………………. ii

Table of Contents…………………………………………………………………………... iii

List of Figures…………………………………………………………………………………. v

List of Tables………………………………………………………………………………….. vii

Nomenclature………………………………………………………………………………… viii

Chapter 1. Introduction………………………………………………………………….... 1

1.1. Introduction to NiTi…………………………………………………………….. 1

1.2. Project Objectives…………………………………………………………….... 1

1.3. Previous Studies……………………….................................…………. 2

Chapter 2. Literature Review…………………………………………………………… 3

2.1. The Shape Memory Effect and Superelasticity……………………. 3

2.2. NiTi…………….. …………………………………………………………………….. 4

2.3. Heat Treatment of NiTi……………………………………………………….. 5

2.4. Existing applications of NiTi under SME………………………………. 6

Chapter 3. Methodology…………………………………………………………………... 7

3.1. Experimental Design and Procedure…………………………………….. 7

3.1.1. Heat Treatment……………………………………………………………………. 7

3.1.2. Mechanical Testing………………………………………………………………. 7

3.1.3 Differential Scanning Calorimeter (DSC)……………………………….. 8

3.1.4 Coil spring prototype……………………………………………………………. 8

Chapter 4. Results and Calculations………………………………………………….. 9

4.1. Experimental Observations………………………………………………….. 9

4.1.1 Heat Treatment……………………………………………………………………. 9

4.1.2 Mechanical Testing………………………………………………………………. 11

iv

4.1.3 Differential Scanning Calorimeter………………………………………… 11

4.2 Experimental Results……………………………………………..……………. 13

4.2.1 Mechanical Testing……………………………………………..…………....... 13

4.2.2 Differential Scanning Calorimeter (DSC)……………………………. 16

4.3 Fabrication of Coil spring prototype………………………………….. 20

4.4 Analysis of prototype………………………………………………………… 21

4.5 CAD model of coil……………………………………………………………… 24

Chapter 5. Discussion…………………………………………………….…………….. 26

5.1 Mechanical Testing………………………………………………………….. 26

5.1.1 Tensile fracture test………………………………………………………… 26

5.1.2 Tensile cyclic test…………………………………………………………….. 26

5.1.3 Differential Scanning Calorimeter……………………………………. 28

5.2 Limitations of project………………………………………………………. 31

Chapter 6. Conclusions and Recommendations……………………………. 32

References…………………………………………………………………………………… 34

Appendix A. Calculating performance of prototype.……………………. 35

Appendix B. CAD Simulation…………………….………………………………….. 37

Appendix C. Project Planning & Time Management…………………….. 39

v

List of Figures

Fig 2.1 Illustration of transformation paths between austenite and martensite

transformation. [6]

Fig 2.2 Showing stress/strain curves graphs for SME and SE transformations. Taken from [1]

Figure 2.3 Temperature dependence on the elongation of NiTi alloy. [5]

Fig 2.4. Growth of grain size due to heat treatment. [11]

Fig 4.1 Untreated NiTi

Fig 4.2 300 °C H-‐T NiTi sample

Fig 4.3 350 °C H-‐T sample


Fig 4.5 Load-‐deflection curves to failure for the samples under a tensile test.

Fig. 4.6 Shows the samples at the ‘plateau’ where they are undergoing a phase

transformation due to stress loading.

Fig 4.7 Cyclic tensile testing of untreated sample of NiTi

Fig 4.8 Cyclic tensile testing of 300 °C H-‐T NiTi


Fig 4.10 Summary table of NiTi Transformation temperatures

Fig. 4.11 Heat flow against temperature graph for untreated NiTi

Fig 4.12 Phase transformation under heating for untreated alloy.

Fig 4.13 Phase transformation under cooling for untreated alloy.

Fig. 4.14 Heat flow against temperature graph for 300 °C H-‐T NiTi

Fig. 4.15 Phase transformation under heating for 300 °C H-‐T NiTi

Fig. 4.16 Phase transformation during cooling for 300 C H-‐T NiTi

Fig 4.17 Heat flow against temperature graph for 350 °C H-‐T NiTi

Fig 4.18 Phase transformation under heating for 350 °C H-‐T NiTi

Fig 4.19 Phase transformation under cooling for 350 °C H-‐T NiTi




Fig 4.23 Coil setup before H-‐T

Fig 4.24 Coil setup after H-‐T

Fig 4.25 NiTi coil in incoherent martensite form. Room temperature and no load.

Fig 4.26 NiTi coil in coherent martensite form Room temperature and after a stress loading.

vi

Fig 4.27 NiTi coil in austenite form after heating

Fig 4.28 450 °C H-‐T coil & 400 °C H-‐T coil at room temperature

Fig 4.29 SMA compression spring actuation [13]

Fig 4.30 extension spring actuation [13]

Fig 4.31 CAD model of the coil in High temperature austenite phase

Fig 4.32 CAD model of the coil in the incoherent martensite form ( room temperature free

state)

Fig 4.33 CAD coil in the Coherent martensite form after stress loading.

Fig 4.34 shows the relationship between the three phases. [16]

Fig 5.1 Extension against temperature schematic. Detailing Mf, Ms, As, Af and hysteresis (h).

[13]

Fig B.1 Stress distribution in coil under 100N tensile load.

Fig B.2 Extension of coil under 100N tensile load.

Fig C.1 Work chart showing planned schedule against actual schedule.

vii

List of Tables Table 3.1 shows a summary of the progression of objectives throughout the project.

Table 4.1 Summary table of tensile to failure tests

Table 4.2 Summary table of NiTi Transformation temperatures

Table B.1 Table comparing properties of Ti-‐6Al-‐4V [15]

Table C.1 A summary of the progression of objectives throughout the project.

viii

Nomenclature

Abbreviations

NiTi Nickel Titanium / Nitinol

SMA Shape Memory Alloy

SME Shape Memory Effect

SE Superelastic

CAD Computer Aided Design

H-‐T Heat Treatment

DSC Differential Scanning Calorimeter

XRD X-‐Ray Diffraction

SEM Scanning Electron Microscope

TEM Transmission Electron Microscope

Mf Martensite Finish

Ms Martensite Start

As Austenite Start

Af Austenite Finish

h Hysteresis

Lh Length (High Temp)

Ll Length (Low Temp)

HT High Temperature

LT Low Temperature

S Stroke

Symbols

C Spring Index

D Spring Diameter

d Wire Diameter

w Wahl’s Stress Correction Factor

ix

Units

°C Degrees Celsius

Pa Pascals

N Newton

mW MilliWatts

τmax Max Shear Stress

Δϒ Strain difference between austenite and austenite

ϒA Strain in austenite phase

ϒmax Max strain in martensite phase

G Shear Modulus

ΔL Stroke Length of Coil

n Number of turns of coils

Fload External Load

1

1. Introduction

1.1 Introduction to NiTi

NiTi is one of the most common shape memory alloys (SMA) that has the ability to perform highly

as an actuator through the shape memory and SE effects (SME and SE). NiTi was compared

against other kinds of shape memory alloys, i.e. CuZnAl and CuAlNi and it was concluded that NiTi

is the most successful with respect to most thermo-‐mechanic-‐related performances [1]. First, the

SME and SE of NiTi can be tailor-‐controlled by heat treatment (H-‐T) at certain temperature ranges

to modify the martensitic transformation temperatures. Second, NiTi is an energy dense material

and this allows it to store more potential energy than similar intermetallics. Third, NiTi has a

maximum strain of 8% within its SE limit. This is impressive compared to similar alloys that only

achieve around 2-‐4% strain. Finally, NiTi has good biocompatibility and corrosion resistance [13].

1.2 Project Objectives

Soft robotics is an emerging field with many challenges for roboticists. One of the most

challenging elements is the soft actuator which can deform along with the surrounding structure.

NiTi alloy is very suitable for this application due to its high flexibility and energy density. The

problem under investigation in this project is to understand the effect H-‐T has on the mechanical

and functional properties of NiTi.

The aim of the project is to design and produce a coil spring for use in a soft robot. The wire of the

coil produced will be made from NiTi, and the coil will be produced and subsequently modified by

H-‐T to perform the SME and SE that are most desirable for actuator applications. Finally, a

computer model is made to predict the performance of the coil, which will then be compared

with the actual performance recorded from the coil itself. The main reason that NiTi is used for

this investigation is due to its SME effects and its performance as a SMA. The NiTi coil can act as a

sensor and actuator once under the SME, so is able to react to a change in temperature and will

then transform its shape. The change in the microscopic structure causes an extension of the coil.

This elongation of the coil can cause a change in a structure. The elongation and contraction of

the coil under the SME could replicate the action of a muscle in a joint. If the coil is heated it will

return to its original shape, thus acting as a controllable actuator. This use as a robotic device

could be in a device such as an endoscope. NiTi is said to be a ‘smart’ material as it can react in

this way to a change in its environment. On the other hand, The SE effect allows the material to

2

undergo a large strain, but stops it from going beyond the elastic limit. It is able to return to the

parent shape without being altered in any way theoretically.

1.3 Previous Studies

NiTi used in actuator applications due to its SME and SE has been extensively studied in the past.

Sreekumar et al. [2] reported that trained actuators where able to verify predicted forces due to

the SME of SM alloys. Kim et al. [3] developed a NiTi actuator using the two-‐way SME. They found

that the recovery stresses were almost identical as in the one-‐way method. Also, the two-‐way

method does not require compressive loading and unloading to form, resulting in an easier

method. Predki et al. [4] showed that NiTi can be used for technical applications in drive

technology, given that stress-‐strain behaviour for NiTi SMA under axial compression, necessary

forces and compressions to reach demanded elongations can be calculated. Otsuka and Ren [5]

discussed the development in the research of SMA in the last decade. They stated couplings,

actuators and smart materials as the most common applications of SMA and acknowledged NiTi

as the best practical SMA. Otsuka and Kakeshita [6] explained the SME, SE effect and martensitic

transformation in basic detail and how these characteristics make intermetallics under the SME

such as NiTi very useful in certain applications. More specifically in reference to this report,

Stoeckel and Waram [7] described the use of NiTi coils transforming due to the SME under a

change in temperature. These studies give an insight into the SME and the characteristics of NiTi.

Furthermore, there are some fundamentals in the project that are not covered in the past. In

order to be able to improve the design process of a NiTi actuator, the relationship between a CAD

model of the coil and the physical coil must be better understood. This will lead to a better

understanding of theoretical testing for computer models.

3

2. Literature Review

2.1 The Shape Memory Effects and Superelasticity

The shape memory effect is the name given to the process in which a material can be

restored to its original shape under heating after being plastically deformed. It occurs in

intermetallic compounds. Materials therefore act as sensors and actuators as they sense a

change in the temperature and will change their shape subsequently. They are said to be

‘smart’ materials as they can do this. This area is well covered in literature, “shape memory

alloys show great potential in many applications…Many alloys displaying shape memory

have been found and considerable effort is still being made to discover new materials” [1].

The two phases of the transformation are the martensitic phase of lower temperature and

the austenite or ‘parent’ phase of higher temperature, when the material is in its natural

form.

There are two paths of transformation between the austenite and martensite

transformation. The first method is known as the SME and is due to a change in

temperature. When the material is in the parent phase, a drop in temperature below the

transformation temperature causes a change in structure to an incoherent martensite as

shown by (b) in fig 2.1. If the material is put under stress in this phase it will change into a

more coherent martensite form as shown by (c) fig 2.1. The material will return to the

parent phase when heated above the transformation temperature. Heating will form the

austenite structure from the coherent or incoherent martensite form. The second path is

known as the SE effect. This does not involve a temperature change, but instead a direct

stress loading of the parent phase. This changes the structure directly into a coherent

martensite form (c) in fig 2.1. This process is called stress induced martensitic

transformation. If the stress load is removed the material will return to its parent form, as

long as the limit of SE is not exceeded (8% strain for NiTi). A material is described as SE when

it is able to reach higher levels of elongation that would usually be beyond the elastic limit of

the material. NiTi is described as having ‘superelasticity’. This explains why it is able to

transform under the stress induced martensitic method. The transformation can produce

relatively large movement in the overall structure for its small size. This gives the material a

high work output. The process gives NiTi a wide range of applications that make use of its

SME.

4

2.2 NiTi

NiTi has been chosen in this investigation as it has the best SME and SE properties among

existing intermetallic alloys. This has been covered previously in literature. “In this paper, a

systematic study on the selection of SMAs for actuators is presented. The candidates, NiTi,

CuZnAl, CuAlNi. The current study shows that NiTi is the overall winner in respect to most of

the thermo-‐mechanic related performances” [1]. NiTi alloys have several characteristics

which make them particularly suitable for applications based on the shape memory effect.

NiTi alloys are very ductile compared to other similar intermetallics. Elongation of 50% can

be easily obtained [5]. Materials in this class are usually much more brittle. The elongation of

NiTi at certain temperature is shown in fig 2.3. It can be seen that the highest point of

elongation is closely related to the temperature around martensitic transformation. There

are factors which explain this relationship such as a high number of deformation modes

upon stress-‐induced transformation. The grain size in the alloy is usually very small, typically

around 30 μm. This compares to the others similar alloys with a grain size of around 1mm.

Also, the critical tensile stress for a slip is less than 50MPa when the alloy is in martensite

form, which is very low compared to around 400MPa when the alloy is in parent form.

The ductility decreases significantly at higher temperatures, above the critical level for

martensitic transformation, however this is still significantly higher than that of other

intermetallics (20%) [5]. Another factor that makes NiTi particularly suitable is that the SME

can be improved and altered easily using H-‐T. An optimum temperature for the material

transformation from martensite to austenite can be easily found using the right H-‐T of the

alloy. This means the material can be tailored to perform in a specified way in a particular

Fig 2.1 Illustration of transformation paths between austenite and martensite transformation. [6]

Fig 2.2 Showing stress/strain curves graphs for SME and SE transformations. Taken from [1]

5

application. NiTi alloys also have a superior tensile strength (100Mpa) to other intermetallic

as well high corrosion and abrasion resistance, making them suitable to a wide range of

applications. The excellent SE properties of NiTi can be partly explained due to their high

energy density. They can hold a particularly high amount of potential energy which allows

them to return to their original shape under strain.

2.3 Heat treatment of NiTi

The mechanical properties of NiTi can be altered using H-‐T. This in an important process as it

allows the transformation temperature for the SME to be changed. This allows fine tuning of

the material for a particular process. The investigation being carried out will involve heat-‐

treating a coil of NiTi so it performs in the correct temperature window when being used as

an actuator in soft robotics. The temperatures the material should be subjected to under H-‐T

are not clear, which is part of what will be investigated. What is known from past literature

however is that H-‐T can cause a material to undergo crystallisation. “We found that

equiatomic amorphous NiTi crystallizes by polymorphic mechanisms and that there is a

direct correlation between the average crystal size and the processing temperature” [8].

Recrystallisation causes the material to become more brittle and lose its elongation as

investigated by Mentz at el. [9]. For this reason, we want to avoid recrystillisation of the

material as much as possible. Chan et al. reported that significant grain growth in NiTi above

700oC [10]. For this reason it is necessary to limit the maximum H-‐T temperature at a

maximum of 600oC for this investigation. If this limit is exceeded, the grain size in the NiTi

will become too large. This results in it becoming too plastic or brittle, losing its SE effects. It

is known already that H-‐T will change the temperature region for transformation between

martensitic and austenite forms of NiTi. This investigation aims to analyse this to understand

the relationship so we can more easily modify NiTi for a particular application.

Figure 2.3 Temperature dependence on the elongation of NiTi alloy. [5]

6

2.4 Existing Applications of NiTi under SM

NiTi is known as the best performing SMA [1]. This results in it being desirable for a wide

variety of applications. They are most commonly used as actuators, fasteners and couplings.

The NiTi alloys have among the best SME among many SMA, however if SMA with higher

operating temperatures are developed they would be very useful for uses in automobiles,

planes etc. Uniqueness of the SMA gives them a very high potential for applications, 10000

patents have been proposed previously. SE qualities of NiTi make it useful in applications

such as catheters for medical use or mobile phone antennas. This is because of the flexible

properties and the fact it cannot be permanently bent. Fisher at al. carried out a project in

which NiTi was used in an endoscope to replace existing materials, allowing an increased 90°

angle of view. [12]. This investigation looks at using NiTi as an actuator in a soft robotic

application. One such application of soft robotics is an endoscope for medical use. The

device allows doctors to examine the internals of a body with no discomfort to the patient.

Coil springs are used in lots of other applications such as in various car components. They

are particularly useful when the car is starting from cold. For example, the coil can alter the

engine speed when the car is cold so that the engine is allowed to heat up faster.

Fig 2.4. Growth of grain size due to heat treatment. [11]

7

3. Methodology

3.1 Experimental Design and Procedure

The initial phase of the project involved attempting to establish an understanding of the

shape memory effect of NiTi. Looking at the theory has allowed a tentative prediction of

how the material will behave. The next phase of the project is to carry out experimentation

to validate the theory and to establish solid understanding of the properties of the material.

With an understanding of exactly how the material responds to H-‐T, implementing the

material in products to utilise the SME will be possible.

3.1.1 Heat Treatment

The first process is to subject samples of NiTi to H-‐T at varying temperatures. This will allow

us to see how the process of H-‐T affects the properties of NiTi. It is particularly important to

understand how H-‐T affects the transition temperature from austenite of martensite form so

that the material can be tailored for any particular application.

The apparatus used for this stage will be a furnace. There will be three different

temperatures. These are 300 °C, 350 °C and 400° C. This is an important range to find the

crossover between the austenite and martensite structure in the H-‐T wires. The reason

higher temperatures are not used is because H-‐T above 450 °C produces detrimental results

in the material. At 450 °C – 550 °C H-‐T will cause intermetallic grain growth. This decreases

the effectiveness of SE and the SME. Above 600 °C the material will undergo re-‐

crystallization. This leads to the material becoming too soft and will lead to loss of the SME.

Each sample should be treated for 60 minutes, followed by immediate quenching in cold

water.

3.1.2 Mechanical Testing

In order to see the effect that the H-‐T has had on the material, it should be subjected to a

tensile test. Studying the loads achieved by samples, which have undergone different

treatments, will allow us to see the effect the H-‐T has on the tensile strength of the material.

8

This is a very important factor, because different mechanism applications require the

material to have specific tensile strength.

3.1.3 Differential Scanning Calorimeter (DSC)

A DSC machine works by measuring the heat flow between a material and its ambient

surroundings while that ambient temperature is altered. The principle is to show at what

temperature the material undergoes a physical transformation. Under a phase

transformation, such as during the SME and SE in NiTi, there will be a difference in the heat

flow between the material and the surroundings. This is picked up by the DSC machine. The

results of this experiment should show a spike in heat flow for the NiTi sample when it is

tested at a particular temperature. This point represents the change in material structure

from martensitic form to austenitic form. This is the phase transformation that defines the

SME. Analysing this point for each sample that has been H-‐T will allow us to see exactly what

effect the H-‐T has had on the shape memory effect of the NiTi sample. If the predictions are

correct, the H-‐T should allow us to change the transformation temperature in the NiTi

sample.

The process involves taking a sample of each H-‐T temperature and analysing it in the DSC.

The temperature range used in the DSC should be between from -‐60 °C to 100 °C in order to

include the transformation on heating and cooling for each sample.

3.1.4 Coil spring prototype

These forms of testing will give a better understanding of the material. Possessing this,

attempts to create a coil prototype should then be made. Having a physical coil allows us to

make some calculations and comparisons with the computer model of the coil.

9

4. Results and Calculations

4.1 Experimental Observations

4.1.1 Heat Treatment

The NiTi samples were successfully treated in the furnace. For each temperature, three

400mm samples were treated. Each treatment temperature showed different characteristics

once cooled. The untreated sample is shown in fig 4.1.

300 °C – The samples at 300 °C had lost some of their rigidity compared to the untreated

sample. The colour had also changed from a grey/silver to a straw/brass colour. The reason

for the colour change is due to changes in the surface of the material at a microscopic level.

The light refraction is altered on the treated sample, causing a change in the appearance of

the colour. The treated sample had also lost rigidity. The material was much easier to bend

out of shape after being treated. The material is however still in in a majority austenite form

at room temperature, and the wire generally holds its shape well. The 300°C H-‐T sample is

shown in fig 4.2.

Fig 4.1 Untreated NiTi

Fig 4.2 300 °C H-‐T NiTi sample

10

350 °C – The samples at 350 °C were less rigid than those at 300 °C. The material had

become softer, and had less resistance to being misshapen. The colour had changed again,

and had become a stronger colour of brass. The material is still in a majority austenite form

at room temperature, however the proportion of martensite structure has increased

compared to the 300 °C sample and its transformation region has therefore increased. This

explains its relative softness and increased ductility. The 350 °C H-‐T sample is shown in fig

4.3.

400 °C – There was a much bigger change with the 400 °C sample than was seen at previous

temperatures. The sample was a majority martensite form at room temperature. The

material behaved completely plastically. It would take any shape it was bent into, and had

almost no rigidity to remain in its original shape. The shape memory effect was of course still

present, and the material would retain its original form when heat was applied. The colour

was very different from the previous samples. It had changed to a dark blue colour,

representing a significant change in its surface smoothness. The 400 °C H-‐T sample is shown

in fig 4.4.


Fig 4.4 400 °C H-‐T

sample

11

Before any mechanical testing had been undertaken, it was clear to see there was a

significant change in the appearance and behaviour of the material.


To understand the effect of the H-‐T, mechanical testing would allow us to analyse the

change to the structure of the material. The first test to carry out was a simple tensile test to

failure. A second tensile cyclic test was carried out to analyse the fatigue in the material over

a period of stresses.

All the mechanical testing was carried using a standard tensile testing machine with a

maximum load of 500N. Special grippers were used with a radius at their ends. These are

intended for use with wires, and ensure that there is not a stress concentration at the point

were the wire is secured. The machine carried out all experiments at a strain rate of

5mm/min. A gauge length of 100mm was set.

Tensile test to failure

This test involved a simple stress to failure set up with the tensile machine. The samples

were loaded until fracture occurred.

Tensile cyclic test

The tensile cyclic test was to show how a series of loading and unloading affected the

material. The resulting load extension curve shows a series of lines representing each cycle.

The machine was calibrated to reach 6% extension (within 8% SE limit) in each cycle before

unloading. Each sample was subjected to five complete cycles.

4.1.3 Differential Scanning Calorimeter

Samples for each H-‐T temperature were analysed using the DSC. The machine used was a

Diamond DSC. It is designed to run samples at high speeds (~200 °C/min). In our

investigation a speed of 10 °C/min was more appropriate. This meant that the sensitivity of

the machine was relatively poor at these speeds. Each sample was run for the temperature

12

range of -‐60 °C to 100 °C. This temperature range is necessary so that each sample will go

through a complete phase transformation on heating and cooling. The results show the

effect the H-‐T has on the transformation temperature.

13

4.2 Experimental Results


Table 4.1 shows a summary of the tensile to failure graphs.

H-‐T Temperature (°C) Transformation Stress

(MN/m2)

Tensile Strength

(MN.m2)

Tensile Strain

Untreated 550 1536 0.32

300 504 1512 0.37

350 484 1528 0.33

400 387 1533 0.35

Fig 4.5 shows the results for each sample tested to failure with the tensile testing machine.

-‐50

0

50

100

150

200

250

300

350

-‐10 0 10 20 30 40

Load (N)

De+lection (mm)

Tensile to failure test

300 C

350 C

400 C

Untreated

Fig 4.5 Load-‐deflection curves to failure for the samples under a tensile test.

14

Fig 4.6 is a zoomed in section of fig 4.5. It shows an important section of the load deflection

curve in more detail. This is the ‘plateau’ region where they undergo a change from

austenite to martensite due to the stress loading.

Fig 4.7, 4.8, 4.9 show the cyclic tensile test on three differently treated specimens.

Fig. 4.6 Shows the samples at the ‘plateau’ where they are undergoing a phase transformation due to stress loading.

70

80

90

100

110

120

130

0 5 10 15

Load (N)

De+lection (mm)

300 C 350 C 400 C Untreated

-‐20

0

20

40

60

80

100

120

-‐1 0 1 2 3 4 5 6

Load (N)

Elongation (mm)

Untreated

Cycle 1

Cycle 2

Cycle 3

Cycle 4

Cycle 5

Fig 4.7 Cyclic tensile testing of untreated sample of NiTi

15

0

20

40

60

80

100

120

-‐1 0 1 2 3 4 5 6

Load (N)

Elongation (mm)

300 C

Cycle 1

Cycle 2

Cycle 3

Cycle 4

Cycle 5



-‐5

15

35

55

75

95

-‐1 0 1 2 3 4 5 6

Load (N)

Elongation (mm)

400 C

Cycle 1

Cycle 2

Cycle 3

Cycle 4

Cycle 5

16


Table 4.2 shows a summary table for the DSC transformation temperatures.

Fig 4.10, 4.11, 4.12 show the DSC heat flow results for the untreated alloy.

Fig 4.11 Phase transformation under heating Fig 4.12 Phase transformation for untreated NiTi under cooling for untreated NiTi

H-‐T Temperature (°C) AS (°C) Af (°C) Ms (°C) Mf (°C)

Untreated -‐5 15 10 -‐10

300 10 20 15 -‐5

350 15 35 20 0

400 30 45 45 25

-‐10 10

Fig. 4.10 Heat flow against temperature graph for untreated NiTi

17

Fig. 4.13, 4.14, 4.15 DSC results for 300 °C H-‐T NiTi

Fig. 4.14 Phase transformation under heating for 300 °C H-‐T NiTi

Fig. 4.15 Phase transformation during cooling for 300 °C H-‐T NiTi

-‐5

15

Fig. 4.13 Heat flow against temperature graph for 300 °C H-‐T NiTi

18

Fig. 4.16, 4.17, 4.18 DSC results for 350 °C treated NiTi



0

20


19

Fig. 4.19, 4.20, 4.21 DSC results for 400 °C H-‐T NiTi




20

4.3 Fabrication of coil spring prototype

Having gained more of an understanding of the material, it was important to try and make a

model of the NiTi in the coil application. The challenge of this was coming up with a method

of creating a coil from a length of straight wire. In order to resolve this, an assembly was

constructed. This involved clamping the wire tightly into a coil around a solid bar. This

assembly is shown in fig 4.22. The assembly was then treated in the furnace at 400 °C for

one hour. This temperature was chosen because the coil would work well under the SME if it

were in a highly martensitic form at room temperature. The H-‐T didn’t work as expected,

because the cooling rate of the coil during quenching was different as it was still attached to

the fixture. This resulted in the coil having characteristics of a standard wire H-‐T to 350 °C

and with a structure much less martensitic in proportion than desired for the coil. To resolve

this, the H-‐T was carried out again at 450 °C. This produced a coil that had more appropriate

H-‐T characteristics. Fig 4.24 shows the two resulting coils.

Figs 4.25, 4.26, 4.27 show a demonstration of the three phases of the SME on the prototype.

Fig 4.22 Coil setup before H-‐T Fig 4.23 Coil setup after H-‐T

Fig 4.24 450 °C H-‐T coil & 400 °C H-‐T coil at room temperature

Fig 4.25 NiTi coil in incoherent martensite form. Room temperature and no load.

Fig 4.26 NiTi coil in coherent martensite form Room temperature and after a stress loading.

Fig 4.27 NiTi coil in austenite form after heating.

21

4.4 Analysis of Prototype

In order to visualise how the NiTi coil works as an actuator, a simple demonstration with a

heat gun shows how the SME can be utilised in the coil. It is known from previous content in

this report that the NiTi will change from the parent or austenite form into the martensite

form when subject to a stress loading. This stress loading can be replicated by simply

stretching the coil out by hand. It will remain in a steady plastic form. If a heat source is then

applied to the stretched coil, such as a heat gun, it will return to the austenite form from the

martensite form. This is shown in the coil by returning to the shape that was formed in the

H-‐T process. This clearly demonstrates how the application of heat can be used to control an

actuator exploiting the SME.

Using a thermocouple to measure the exact heat source from the heat gun allows a precise

temperature reading of which the coil is subjected to. Having a precise reading of the

temperature allows us to see the temperature region in which the coil undergoes a phase

transformation. This information allows the NiTi coil to be used as a smart actuator, with

precise control over its function. Applying the same tests to the coil treated at 400 °C shows

similar results, but the transformation is less apparent of an than the 450 °C. This is because

it is in a more austenitic form at room temperature and behaves less plastically. The 450 °C

sample has a larger stroke than the 400 °C sample and thus the SME is more clearly

displayed.

After seeing a prototype of what the coil is physically like, the next stage was to establish

how a particular coil could be created or treated in order to behave in a predictable way and

carry out a specific task. The experimentation carried out previously has shown how the

transformation temperature is affected by H-‐T of the material. The mechanical testing has

shown some ultimate tensile and cyclic tensile properties of a straight NiTi wire. The

application being analysed by this report is in the use of a coil, so it is important to find out

some performance figures for the material in the coil spring form.

Within the coil actuator application there are two different forms;

22

• Compression spring – This is when the coil is compressed at low temperature, and

extends when it is subjected to heat. (fig 4.28)

•

• Extension spring – This is when the coil is extended at low temperature, and

compresses when subjected to heat. (fig 4.29)

Activation types

There are two relevant types of activation that fall under this investigation;

• Thermal activation – this is when the actuation of the coil is induced by a change in

the temperature surrounding the coil. This can be intentionally provoked by an

external source from the user. It can also be as a result of an ambient or varying

temperature in its application, eg. Human body.

• Electrical activation – this is when the actuation of the coil is induced by a current in

the NiTi wire. NiTi inherently possesses a high resistivity due to its structure [13].

This means any current flowing through it will increase the temperature of the wire.

This heat increase is able to activate the SME. The amount of power flowing through

the wire for activation can be easily calculated. The wire can be tailored to conform

to a certain flow requirement by defining its dimensions.

Fig 4.28 SMA compression spring actuation [13]

Fig 4.29 extension spring actuation [13]

Lh= Lengh (High temp) HT=(High Temp) Ll= Length (Low temp) LT=(Low Temp) S=stroke F=force produced

23

The area this investigation is looking at is in soft robotics and their application in the medical

field. These two actuation types are important, as they are both applicable in medical field.

There are many devices that use either or both of these actuation types. Luo et al. describe

designing a device that changes shape due to the higher temperature in the human body

(thermal activation) [14]. For an application such as an endoscope, the user must have

control of the device from outside the body. In order for this, electrical activation is

necessary to allow precise remote control. This kind of device could also be made to react to

a direct temperature stimulus, if there was some requirement for it to adapt to being inside

the body.

24

4.5 CAD Model of Coil

One important aspect of this investigation was to compare data predicted through computer

modelling to that obtained from fabrication of the real coil. Using CAD to design is an

important step as it makes the design process much easier. In order to fully trust in CAD

however, it is important to validate it first.

A coil was designed in Solidworks similar based on the coil prototype made. The CAD model

is shown in fig 4.30. This model illustrates the three stages in the cycle of the SME.

Fig 4.30. CAD model of the coil in High temperature austenite phase

Fig 4.31. CAD model of the coil in the incoherent martensite form ( room temperature free state)

25

Fig 4.33 shows the relationship between the three phases. [16]

This CAD modelling shows the forms of the coil in the three phases that were observed

when experimenting with the prototype.

Simulation of the coil could not be satisfactorily completed, as there was no NiTi material

available in the Solidworks database. This is one of the main limitations of this investigation.

The simulation that was carried out was using the titanium alloy, Ti6Al4V. This was the

closest material to NiTi available. The results of this simulation are in Appendix B. They are

not included in this report, as they are not regarded to replicate NiTi closely enough.

Fig 4.32 CAD coil in the Coherent martensite form after stress loading.

Fig 4.33 The SME [16]

26

5. Discussion

5.1 Mechanical Testing

5.1.1 Tensile fracture test

The load deflection curve for each sample follows a similar trend. The curve initially follows a

material under the influence of Hooke’s law. A ‘plateau’ region follows this in which the

curve levels off. This is when the material is changing from the austenite structure

(incoherent martensite for 400 °C) to a coherent martensite structure. This period is

followed by a rise once again until fracture. The region up until the end of the plateau is

when the previously austenite material is still in the SE region. This means that if the load

was released it would return to its original shape. The maximum load achieved at fracture by

each sample was within 1% of 300N.

The plateau region of the curve where the sample is in the transformation region should be

much flatter. Looking at fig 4.6, it can be seen that this is not the case. This is an error

produced by the experiment. A strain rate of 5mm/min was too high. This caused heat to be

produced in the sample. This subsequently resulted in the friction in the sample increasing,

which caused the load required to increase slightly, altering the shape of the graph This

could be solved by using external cooling to stop the wire from heating up or reducing the

strain rate.

The whole curve is very unstable. There are many regions with big fluctuations. This is due to

having an unsatisfactory gripper to hold the wire. The fastener on the gripper did not

perform particularly well, and allowed the wire to slip very slightly. This caused minute

releases in the load that show up as instabilities on the curve.

5.1.2 Tensile Cyclic Test

The load extension graph for each sample shows some similarities, and also some

differences that are caused by the H-‐T. Each sample initially follows Hooke’s Law before

levelling off; the next section is the ‘plateau’ region. This is where the extension of the

material increases with no increase in load. This period is when the material structure is

27

changing from the austenite form to the martensite form. This transformation is induced by

the stress loading. The cyclic test carried up only loaded the material to 6% extension. This

point was when the graph was still in the ‘plateau’ region. This is within the SE region of the

material. The material behaves superelastically until the end of the plateau region (8%

strain) when the load increases again. Beyond this point is plastic deformation. The SE effect

allows the sample to return to its original length when the load is removed. This can be seen

figs 4.7,4.8,4.9 where the graph returns to the origin between each cycle. In reality there is a

slight difference between each cycle. The maximum load reduces slightly (2%) between the

first and second cycle for the required extension. This difference decreases exponentially for

the succeeding cycles. This is caused by the residual stresses. During each cycle the material

changes its structure from austenite to martensite and back again during unloading. During

each cycle small residual stresses cause a proportion of the martensite form to remain in this

phase and not change back to the austenite form. This means the next cycle will require

slightly less external load to become fully martensite.

The shape of the curves are distinct. As the load begins to release the graph does not follow

the same path of loading. The material remains in the martensite form until below 50% of

the total load is reached. At this point the transformation back to austenite begins to occur.

This transformation results in the elongation reducing with no change in load. Much like the

transformation during loading except in reverse. This point is seen in the ‘plateau’ section of

the graph during the unloading phase of the cycle. This is due to hysteresis between the

austenite and martensite forms.

Comparing the cyclic tensile tests it can be clearly seen that 300 °C and untreated are very

similar. The 300 C sample is still inside the austenite range at room temperature (Fig. 4.14,

4.15). It has lost some of its rigidity compared to the untreated sample, and behaves slightly

more plastically. This is because the H-‐T has brought it closer to the transformation region,

resulting in its structure having an increased martensitic proportion and resulting

characteristics. This is only a small consideration however, and it would be expected to

behave similarly to the untreated sample. The 300 °C sample achieves a load of around 5%

(100N against 95N) less than the untreated sample as it begins the phase transformation

due to stress loading. It behaves similarly during the unloading phase also. Comparing these

graphs shows how the H-‐T can be used to make small adjustments to the characteristics of

the material and how it behaves with the SME.

28

The 400 °C sample behaves much differently to the other samples. The 400 °C sample

plateaus off at a much lower load. The reason for this is because the H-‐T has moved this

sample into an incoherent martensite structure at room temperature. When the 300 °C and

untreated samples were transformed into martensite due to loading, this was a coherent

martensite form. When the 400 °C sample is subject to load it changes from an incoherent

martensite form to a coherent martensite form. This requires less load than a

transformation from austenite as it already in a high proportion of the martensite structure.

400 °C also behaves more plastically than the other samples due to its martensitic form, it

does not return to its original shape as definitely as the other samples. Comparing with the

graphs for 300 °C and untreated, there is a definite ‘plateau’ period on the unloading side of

the graph that signifies the martensite changing back to austenite. In the case of the 400 °C

sample there is no ‘plateau’ region. Instead, it is an exponential decrease until the load is

released. This difference is due to the 400 °C sample returning to an incoherent martensite

form instead of the austenite form of the lower temperature treated sample. There is no

defined transformation phase, as the material does not change back to the austenite form.


Figs 4.10, 4.13, 4.16, 4.19 show the shape of graph produced in the DSC analysis. The curve

shows a steady rise, before a drop and then steady decline. The upper curve of the graph

represents the heating phase of the process. This is when the sample begins at a low

temperature (-‐60 °C) and is heated. The DSC records the heat flow movement between the

surroundings and the sample. This is plotted against the ambient temperature. The lower

section of the graph shows the same data except from when the ambient temperature is at

its highest (100 °C) and is cooled back to its original temperature.

The piece of data from these graphs of most interest is the phase transformation, when the

material changes between austenite and martensite. This point is shown on each curve as a

fluctuation of the heat flow at a particular point (t). The heating transformation regions are

slightly more distinct than the cooling regions. With more appropriate equipment providing

a higher sensitivity, the transformation regions would be more clearly defined. However this

was not possible as discussed previously.

29

If the heat and cool transformations are compared for each cycle, (300 °C treated sample –

10 C to 20 °C on heating, -‐5 to 15 °C on cooling. 350 °C treated sample – 15 to 35 °C on

heating, 0 to 20 °C on cooling.) the temperature range for each transformation does not

coincide. This is caused by a temperature hysteresis. Because of this there is no ‘defined

point of transformation’. There are four important temperature points [13];

1. Martensite Finish (Mf)

2. Martensite Start (Ms)

3. Austenite Start (As)

4. Austenite Finish (Af)

The distribution of these points and the hysteresis between them is illustrated in fig 5.1.

Looking at the cooling graphs from the DSC. The phase transformation can be seen to be

shifting on each sample. Untreated has a heating/cooling transformation range of (-‐5 to 15

°C/-‐10 to 10 °C). This progresses to (10 to 20 °C/-‐5 to 15 °C) on the 300 °C sample and (15 to

35 °C/0 to 20 °C) on the 350 °C sample. There is a much larger jump to the 400 °C sample. Its

transformation region is (30 to 45 °C/25 to 45 °C). The DSC data shows that H-‐T of NiTi has a

direct effect on the transformation temperature region. H-‐T of NiTi increases the

transformation temperature of the sample. Using smaller intervals of H-‐T, its effect can be

Fig 5.1 Extension against temperature schematic. Detailing Mf, Ms, As, Af and hysteresis (h). [13]

30

defined even more so that a precise relationship between the H-‐T temperature and the

material transformation temperature can be documented. With this knowledge, the

material can be treated to produce a specifically desired transformation region. This is a very

important factor in utilising the materials SME. It allows NiTi to be used as a precisely

controlled actuator among many other applications.

31

Limitations of project

There were several areas where external limitations hindered the investigation to some

extent;

• Limited availability of the furnaces meant there was a delay starting the

experimentation. This can be seen to push everything back in fig 3.1. It also meant

the time with use of the equipment was relatively low and meant only several broad

H-‐T temperatures could be used.

• NiTi is an expensive material. As a result its availability for this experiment was a

limiting factor. Had there been a greater supply available, more experimentation

could have been carried out.

• The student budget was relatively low and lead to only being able to use limited

machines for experimentation. Ideally, X-‐Ray Diffraction (XRD), Scanning Electron

Microscope (SEM) and Transmission Electron Microscope (TEM) apparatus would

have been available to us. This was not the case due to the limited budget. Using

this apparatus would have allowed us to have a much more comprehensive

understanding of the structure of the samples on a microscopic scale.

• The limited time available on the equipment that was used allowed only limited

samples to be tested. Carry out experimentation on more samples would allow

statistically significant results.

• The available software did not include NiTi as a suitable material. Ti6Al4V was

simulated instead as it was the closest available to NiTi. The materials however are

too dissimilar to include in this study. The simulation for Ti6Al4V is included in

Appendix B.

32

6. Conclusions & Recommendations

1. H-‐T of NiTi produces a thorough change in the characteristics and structure of the

material. It alters the proportions of austenite and martensite structure in the

material structure. A higher temperature H-‐T, and higher martensite proportion

leads to lower phase-‐inducing transformation load. (100N for untreated, 80N for 400

°C). SE limit of NiTi wire under load is 105-‐115N (austenite) & 85N(martensite).

Cyclic loading of NiTi results in an exponentially decreasing load bearing per cycle.

This fatigue in the material is caused by ‘residual strain’. An increase in the H-‐T

temperature causes an increase in the transformation temperature for the material.

Comparing each DSC curve shows a rise of (~10 °C per 50 °C of H-‐T).

2. 400 °C H-‐T sample shows the best qualities for actuator use. It behaves more

plastically, so can deform more than other samples. This allows for a greater

deformation and resulting stroke length under the SME.

3. Mathematical equations allow performance parameters of the coil to be predicted.

These can be used to analyse an existing coil or to generate a design of a coil for a

specified application. (Appendix A)

Recommendations for further Study

This study has given a good understanding of NiTi and its applications utilising SE and the

SME. The limitations previously discussed justify further study in this area. The budget and

equipment shortage meant that the quantity of samples to be tested as desired was not

met. Further studies would carry out more precise testing, such as narrower temperature

treatment to more precisely determine the effect of H-‐T. The budget dictated that only one

set of DSC results were achievable. The lack of suitable equipment also meant that the

machine used was not suited to the analysis required. Other analysis of the material that

would have been beneficial such as X-‐Ray Diffraction (XRD) and the use of a

Transmission/Scanning Electron Microscope (TEM/SEM) was not a realistic proposition due

to the budget constraints. Having access to these instruments allows the structure of the

material to be seen at a microscopic scale. Access to data like this allows further

understanding of the structure of the material and how it changes during H-‐T and during

mechanical testing. In order to assess the simulation of NiTi with CAD, further study into this

area should be undertaken. Software which can fully model NiTi is necessary.

33

The investigation involved making a prototype coil spring to investigate how it could be

designed and created to carry out the application of an actuator. The next stage in this

process is to use the principles determined in this report to design and create a coil and test

it as an actuator in a device

34

References

[1] Selection of shape memory alloys for actuators, Materials and Design 23 (2002) 11-‐19,

Huang W.

[2] Application of trained NiTi SMA actuators in a spatial compliant mechanism:

~Experimental investigations (2008), Sreekumer M, Nagarajan T, Singaperumal M.

[3] Development of NiTi actuator using a two-‐way SMA induced by compressive loading

cycles (2008), Kim HC, Yoo YI, Lee JJ.

[4] Engineering applications of NiTi shape memory alloys (2006), Predki W, Knopik A, Bauer

B.

[5] Recent developments in the research of shape memory alloys (1998), Otsuka K, Ren X.

[6] Science and Technology of Shape-‐Memory Alloys:New Developments (2002), Otsuka K,

Kakeshita T.

[7] Use of NiTi Shape Memory Alloys for Thermal Sensor-‐Actuators (1991), Stoeckel, Waram.

[8] Crystallisation of amorphous sputtered NiTi thin films, 2006, Ramirez AG, Hai Ni, Lee HJ.

[9] Influence of heat treatments on the mechanical properties of high-‐quality Ni-‐rich NiTi

produced by powder metallurgical methods, 2006, Mentz J, Bram M, Buchkremer HP,

Sto ̈ver D.

[10] Effect of post-‐weld-‐annealing on the tensile deformation characteristics of laser welded

NiTi thin foil, 2011, Chan CW, Man HC, Yuen TM.

[11] XRD and TEM study of heteroepitaxial growth of zirconia on magnesia single crystal,

1998, Guinebretiere R, Soulestin B, Dauger A.

[12] Flexible distal tip made of nitinol (NiTi) for a steerable endoscopic camera system, 1999,

Fischer H, Vogel B, Pfleging W, Besser H.

[13] Large Force Shape Memory Alloy Linear Actuator, 2002, Santiago Anadon JR.

[14] Design of SMA Actuator Based Access Device for Transanal Endoscopic Microsurgery,

2010, Luo H, Abel E, Slade A, Wang, Z, Steele R.

[15] Matweb. (2010). Nitinol -‐ NiTi Shape Memory Alloy; Low-‐Temperature Phase. Available:

http://www.matweb.com/search/datasheetText.aspx?bassnum=MTiNi1. Last accessed

10/3/2014.

[16] Mmm-‐jun. (2012). Nickel Titanium. Available:

http://en.wikipedia.org/wiki/Nickel_titanium. Last accessed 11/3/2014.

35

Appendix A -‐ Calculating Performance of Prototype

The purpose of calculating the performance of the prototype was to compare it to the

results obtained from the CAD model. Limitations on the available software have refrained

any useful data being obtained through this method. Subsequently these calculations have

now been rendered somewhat irrelevant to the report, hence they are not included in the

main body of the text.

The prototype created previously was an extension spring, as in this application the spring is

required to produce a tension force when heat is applied. For this case the calculations must

be specific to an extension type spring. The main characteristic parameters for NiTi

extension spring design are maximum shear stress (τmax), maximum shear strain in the

martensitic phase (ϒmax), shear modulus in the austenite phase (GA) and shear modulus in the

martensite phase (GM). The following equations show the mathematical process in solving

these parameters for the created coil spring, using inputs taken from the coil. Equations

sourced from Luo et al. study on Design of SMA Actuator [14].

The spring index, 𝐶 = !! where; D = spring average diameter (1)

d = wire diameter

Wahl’s stress correction factor, 𝑤 = !!!!!!!!

+ !.!"#!

(2)

Max shear stress, τ!"# = !!!"#$!"

𝛑𝒅𝟐 where; Fload= external load (3)

Strain difference between austenite and martensite, 𝛥ϒ = !"#!"!!

(4)

where; ΔL = Stroke length of coil

n = number of turns in coil

Strain in the austenite phase, ϒ! =!!"#!!

(5)

where; GA= Shear modulus in the austenite phase

Max strain in the martensite phase, ϒ!"# = 𝛥ϒ + ϒ! (6)

36

These calculations show how various properties of a coil can be determined. With a

comprehension in how these properties interact and how they can be produced, an

understanding in how to produce a coil with specified properties can be deduced.

37

Appendix B – CAD Simulation

The coil that was created in the CAD software underwent a simulation in Solidworks. The

material used in the simulation was the titanium alloy, Ti6Al4V. This material was used as it

was the most similar to NiTi. It was decided however that its properties were not similar

enough to NiTi to use it as a viable comparison. This it is not an officially included in the

report. NiTi is a very distinct material, and any simulation must be modelling its unique

properties. In essence, this section is included as a reference. The coil was simulated under a

tensile load of 10N from one end while the other end was fixed. Fig 4.24 shows the stress

distribution in the coil. Fig 4.25 shoes the extension of the coil. Table B1 shows a summary of

the properties of Ti-‐6Al-‐4V and the high and low phases of NiTi.

Fig B.1 Stress distribution in coil under 10N tensile load.

Fig B.2 Extension of coil under 10N tensile load.

38

Property Material

NiTi (HT) NiTi (LT) Ti-‐6Al-‐4V

Young’s Modulus, GPa 75 28 113.8

Ultimate Tensile

Strength, MPa (Yield,

MPa)

754-‐960 (560) 754-‐960 (100) 950 (880)

Elongation at Fracture,

%

15.5 15.5 14

Shear Modulus, GPa 28.8 10.8 44

Table B.1 Table comparing properties of Ti-‐6Al-‐4V [15]

39

Appendix C -‐ Project Planning & Time Management

In order to best carry out a project such as this, it is important to plan well and keep to a

schedule in order not to fall behind. One of the first tasks after undertaking the project was

to draw up a schedule. This split the project into sections, working from start to finish in a

logical order. Deadlines for sections were set and a chart was made to allow the candidate

to assess their self against the plan throughout the project. The chart is shown in fig 3.1.

3(S1) 4 5 6 7 8 9 10 11 12 1(S2) 2 3 4 5 6 7 8 914/10/2013 21/10/2013 28/10/2013 04/11/2013 11/11/2013 18/11/2013 25/11/2013 02/12/2013 09/12/2013 16/12/2013 03/02/2014 10/02/2013 17/02/2014 24/02/2014 03/03/2014 10/03/2014 17/03/2014 24/03/2014 31/03/2014

Introduction Meeting5&5introduction5to5project

Read5exisitng5reports5&5thesis'

Inquire5available5equipment

Produce5work5chart

Report Introduction5(ch1)

Literature5Review

Submit5interim5report

Experimentation Design5experiment5plan

Use5furnace5for5NiTi5HT

Failure5tensile5testing

Cyclic5tensile5testing

DSC5test5of5HT5samples

Analysis Analyse5experimental5results

Prototype Create5coil5prototype

Design5coil5using5CAD

Comparison5of5CAD5&5prototype

Report Discussion5of5experimentation

Discussion5of5models

Conclusions

Polish5report5&5submit

Planned5completionActual5completion

Task Week

Fig C.1 Work chart showing planned schedule against actual schedule

40

Table C.1 shows a summary of the progression of objectives throughout the project.

Task Planned Date Achieved Date Days Late

Familiarise self with

project

25/10/13 30/10/13 5

Interim Report 15/10/13 15/10/13 0

Experimentation 07/02/14 06/03/14 27

Analysis 17/02/14 10/03/14 21

Prototype 07/03/14 21/03/14 14

Final Report 04/04/14 02/04/14 -‐2

It is important to look at the progress made during the course of the project. Midway

through there was a point where the author was significantly behind schedule. This came

about in the experimentation. The delay in equipment becoming available resulted in falling

behind schedule. This also coincided with the holiday and exam period, which exaggerated

the length of time behind schedule. Looking at the fig 3.1 & 3.2 it can be seen that the

candidate was able to catch the schedule again in time by the deadline of the report. The

fact that the project was behind schedule at a point shows the importance of planning. The

chart made it clear the author was behind progress, and using this tool allowed a continuous

assessment against the objectives in order to get back up to speed with the required

progress.

Documents

Project 3B Final