Surface Acoustic Wave (SAW) Analysis for NDT Applications

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ABSTRACT

This thesis involves the simulation and practical experiment of the hard material to calculate the elasticity and phase velocity of the material without harming or effecting the materials usefulness which is a Non-destructive technique (NDT). The research studies the surface acoustic wave (SAW) is applied to investigate the elastic properties of the hard material models such Aluminium, Steel, Plastic, Steel with Plastic and Steel with defect.

The aim is achieved through the simulation which is processed by a finite element analysis software, ANSYS. ANSYS tool is very powerful and capable to solve some tough problems which covers the area of stress and displacement. In this simulation, the SAW is generated by a Laser Ultrasonic and through the Laser Vibrometer the data of the waves in the material is detected and treated as an Input. Signal processing is applied to the SAW results to obtain the phase velocity with the frequency obtain by using a MATLAB software. By studying the variation of phase velocity, the change of the hard material properties can be determined. These results represent the improvement of the SAW study which can be applied into industrial field.

This thesis not only calculate the elasticity of the material through the simulation but also carry out the practical experiment to cross-validate the results. The results achieved from the simulation of ANSYS and the practical experiment were successfully achieved with the tolerance of human error.

TABLE OF CONTENET

Acknowledgment

Abstract

Declaration

Table to Contents

List of Figures

List of Tables

1. Introduction

1.1 Motivation and research objectives

1.2 Outline of Thesis

2. Literature Review

2.1 Non-Destructive Testing

Generation of waves

Primary Wave

Shear Wave

SAW Waves

Generator

Laser

High-Intensity Focused Ultrasound

Laser Ultrasonic

Detector

Ultrasound transducer

Laser Vibrometer

3.ANSYS

Finite Element Analysis

Finite Element Simulation by ANSYS

Pre-Processing

Define the analysis and element type

Model creation and Boolean operations

Model Mesh

4. ANSYS Solution

Pre-processing

ANSYS solutions

Finite Element Analysis results

Steel

Steel with defects

Aluminium

Plastic

Steel with Plastic

5% Agar

5. SAW Signal Processing

Processing the SAW by using the Spectral Analysis

Apply De-nosing to the SAW

Inversion Process

MATLAB Results – Steel

Aluminium

Plastic

Steel with defects

Steel with Plastic

Agar 5%

6. Experiment Results

Summary

Conclusion

References

Time-Management Diagram

Risk Assessment form

PLEASE  READ THIS FIRST

LIST OF FIGURES

Figure 1. Figure 1. P-Wave vs S-Wave vs Surface Wave

Figure 2. Basic SAW Device

Figure 3. Laser generation of ultrasound in (a) thermoelastic regime and (b) ablative regime.

Figure 4. Rayleigh wave generation: (a) Theoretical calculations of the surface normal (solid) and horizontal (dotted) displacements, (b) experimental results for surface normal displacements. (John, Y. and Krishnaswamy, S., personal communication, 2003.)

Figure 5. Generation of HIFU and its use to form a thermal lesion within a tissue target.

Figure 6. Difference between medical and industrial experiment.

Figure 7. Demonstration of the piezoelectric effect.

Figure 8. Relationship between the temporal waveform of two pulses and their frequency spectra.

Figure 9. Typical configuration of a fibre-based system for low coherence interferometry.

Figure 10. Interference signal recorded from a single reflector as a function of the optical path length difference.

Figure 11. Optical schematics of the single-point Vibrometer (Mach Zehnder).

Figure 12. PLANE geometry in ANSYS: PLANE 55 (a) and PLANE 42(b) (L’Etang & Huang Z, 2006).

Figure 13.  Schematic of the single layer model.

Figure 14.  Single layer model after Mesh applied.

Figure 15. Solution Control settings for simulation process.

Figure 16. Displacement of SAW in steel plate

Figure 17. Displacement of SAW in steel defect piece of plate

Figure 18. Displacement of SAW in Aluminium plate

Figure 19. Displacement of SAW in Plastic layer

Figure 20. Displacement of SAW in steel and plastic with double layer

Figure 21. Displacement of SAW in 5% Agar of single layer

Figure 22. SAW waveform —- not required —– delete

Figure 23. Phase Velocity (m/s) vs Frequency (kHz) of Steel plate.

Figure 24. Phase velocity vs. Frequency of Aluminium

Figure 25. Phase velocity vs. frequency of Plastic

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Figure 28. Phase velocity vs. Frequency of 5% Agar

Figure 29. 5% Agar solution in Agar Phantom bases.

Figure 30. Layers inside the Agar phantom (MATLAB)

Figure 31. OCT in process

Figure 32. 5% Agar experiment result

LIST OF TABLES

Table 1. Different types of Non-Destructive methods (NDT) and their usefulness………

Table 2. Three different steps of Laser ultrasonic testing (LUT)……………………………

CHAPTER 1 – INTRODUCTION

1.1  MOTIVATION AND RESEARCH OBJECTIVES

In many industries it is tremendously difficult to fabricate items that will be absolutely insusceptible to cracking and softening up, quality check, and amid utilize, basic. Cracks can happen in various materials, for example, metals, composites, plastics and minerals, and may fail in industries including car, aviation, building, designing and assembling [106].

Today acoustic has a wide field of activities in logical and mechanical examinations and administrations, for example, pharmaceutical, medico assessment equipment, and so forth. Albeit static and dynamic destructive tests, for example, bending test, tensile quality, pressure test and impact testing etc. [102.5] are widely used to quantify flexible properties of hard materials, they also contain issues; for instance, system is irreversible in light of the fact that the specimen is demolished, accomplishment of anticipated example geometry as indicated by the standard is difficult, progressive equipments and long methods time is required [105].

Conversely, non-destructive technique (NDT) methods which have no harm and undesirable impacts on the specimen, could gauge hard material properties with high precision in a short sample of time [105]. NDT is an instrument utilized by specialists to recognize absconds in materials and structures, either amid assembling or while in administration [100]. As an engineering field, Non-Destructive Testing offers a critical part in consistent schedule, such as, things utilized as a part of our everyday life as it is key to ensure the security and dependability. For example, NDT testing can be utilized in an engine vehicle, air ship, pipelines, trains, building, extensions, refineries and oil stages [1].

By 2022, NDT market is anticipated to reach $24.23 Billion contrasted with $15.06 Billion in 2016, at a CAGR of 8.24% from 2016 to 2022. The expanding interest for non-damaging testing in the business is due to the fact NDT guarantees safety and efficiency in the manufacturing procedure of geometrically complex material components [101].

The initial noted uses of NDT were in 1868, where Englishman S.H. Saxby depended on the magnetic characteristics of a compass to discover cracks in gun barrels. Then, the initial NDT method to come into modern application was the X-Ray system in 1895 [102].

NDT techniques offer not just the benefits of discovering potential or real issues in the manufacturing programme without harming or effecting the material usefulness but also certain feedback as to how to revise the issue at the earliest conceivable point [103].

To evaluate the quality and reliability of the components by NDT, there are many methods which can be implied such as [104]: Magnetic particle testing (MT), Radiographic testing (RT), Visual Testing (VT), and Electromagnetic testing (ET), Liquid Penetrant testing (PT) and Ultrasonic Testing (UT).

The surface acoustic wave (SAW) innovation has been utilized as a part of mechanical applications, for example, examining surface structures, composition geometry, roughness and elastic properties of metallic samples. SAW technique is primarily used to assess the mechanical properties of materials since it has preferred standpoint to quantitatively evaluate Young’s modulus.

The values of phase velocity are connected with the Young’s modulus, then, the quantitative elasticity data of material layer, the propagation of the SAW can be calculated. The SAW can be found through the most widely recognised method by utilizing the ultrasound transducer [21] which involves the physical contact of the sample. This necessity prompts various disadvantages: the detecting range is restricted by the transducer, leakage of wave energy happens at the material-transducer boundary, wave alteration will be produced due to the weight of the transducer on the sample etc. To overcome these problems, a suitable method is utilizing a non-contact and non-damaging way to detect the SAW, which is a Laser Ultrasonic. Laser Ultrasonic strategy has been generally utilized on the grounds that it is non-contact and remote, thus no surface loading.

Laser Ultrasound detects the SAW and through the Finite element method (FEM) using ANSYS able to calculate the values of the material which represents the waves inside the material from where elasticity of the material can be obtained. ANSYS is a finite element analysis tool for structural examination, including linear, nonlinear and dynamic studies. It approaches to simulate all the complexities of the problem, such as varying shape, boundary and loading conditions on a structure and regulate the structures response to the conditions.

ANSYS is also beneficial for the practical experiments to cross-validate with the simulation results. As the accuracy of the ANSYS is very reasonable thus it is currently the demanding tool as it able to simulate and give accurate results which saves time and cost of materials rather than testing again and again until the practical experiment gets the accurate results.

The aim of the project in this thesis is to develop finite element models to simulate SAW elastography in different properties of hard materials in single, double layers and defect layers by a non-destructive technique. The SAW elastography and behaviour in the hard materials will be investigated through the NDT which is chosen to be Laser Ultrasonic. In Laser Ultrasonic, lasers are used to generate and then measure, ultrasonic waves in a material. The waves produced in a material is Surface Acoustic waves (SAW). Through the waves, the data can be collected by using laser Vibrometer. Laser Vibrometer works by aiming light at the vibrating subject and study the returned beam and transferred the information into ANSYS where it able to visualise the waves. The experiment will be carried out on six various materials such as Steel, Aluminium, Plastic, Plastic with Steel, Steel defect layer and finally 5% of Agar before coming to the conclusion.

The objective in this project is as follows:

  • Use the software ANSYS to simulate the thermal and structural analysis of the different hard materials
  • Use the software MATLAB to convert the raw data of ANSYS into phase velocity and plot the graphs of waveform of the Surface Acoustic Wave.
  • Cross-validation of the simulation result with the experimental data.

1.2 OUTLINE OF THESIS

Chapter 2 of this thesis is the literature review, which includes several methods of Non-Destructive testing (NDT) and by comparing between it, the best and suitable method was chosen; Ultrasonic testing. Next topic focus on different types of waves such as Primary, Shear and Surface acoustic waves and explain why SAW is the best option out of all and how it can be used to generate and detect the SAW by giving various option to pick suitable generator and detector for the SAW.

Chapter 3 introduces to the Finite element analysis in ANSYS. The Finite Element Analysis (FEA) is an approach to simulate all the complexities of the problem, such as varying shape, boundary and loading conditions on a structure and regulate the structures response to the conditions. This chapter demonstrate the general knowledge of using ANSYS and the theory provide a convincing basis all through the thesis.

Chapter 4 introduces the process of simulation using Finite Element Analysis. This chapter will cover the method FEA simulation of the laser generated SAW in different material models. A preliminary FEA simulation results from ANSYS.

Chapter 5 presents the signal processing of SAW which includes the frequency analysis, de-nosing of the signal. Also the phase velocity will be investigated. Varity of the de-nosing method will be introduced in this chapter. The inversion producers of SAW signals to elasticity information will be introduced, which will monitor the mechanical changes of the different hard materials including defect materials.

Chapter 6 validate the simulation results with the first-hand experiment.

Chapter 7 presents the conclusion of this work along with some suggestion for further study.

CHAPTER 2 – LITERATURE REVIEW

2.1 Non-Destructive Testing

Non-Destructive testing (NDT) is a process of examining the material which allows the material to be tested without changing or effecting there specific qualities. It is also known as Non-Destructive Examination (NDE). The testing can be used to calculate size, locate the surface and subsurface and flaws.

Non-Destructive Testing offers an important role in daily basis, such things used in our daily life as it is vital to make sure the safety and reliability. For instance, these testing (NDT) can be used in motor vehicles, aircraft, pipelines, trains, building, bridges, refineries and oil platforms [1]. The speciality of the Non-Destructive Testing is that it is the quality assurance tool as it gives an accurate results, however, the testing has to done be correctly to get impressive results. For this, it desires an expand knowledge of the different methods available and their limitation and capabilities of the specification for operating the tests.

When the materials or products fails to accomplish their design requirements because of undetected defects which may need an out-budgeted repair cost. NDT can be tested on each layer of the materials construction. The materials and welds can be tested by using the Non-Destructive testing to either accept or reject. From the NDT approach, it can be able to check the integrity of the structure by its design life.

By comparing with NDT, other tests are destructive in nature, thus, these tests can be done on very less number of samples instead on the materials. Destructive test are generally used to find the physical properties of materials such as yield strength, ductility strength, impact resistance and tensile strength, fracture toughness and fatigue strength [2]. However, it discontinuities and the NDT has more effective way of calculating in material characteristics. It can help with low production costs and streamline manufacturing process by using modern NDT tests which also assures a high and uniform product quality level [3].

NDT is used typically for its various reasons [4]:

  • Accident prevention and to reduce costs
  • To gain the product reliability
  • After the testing, it can give advice on repair criteria

In this day and age where new materials are being created, more seasoned materials and holding strategies are being subjected to higher pressure and loads. NDT guarantees that materials can keep on operating to their most noteworthy limit with the confirmation that they will not fail within the prearranged time limits [5].

NDT can be utilized to assess the quality ideal from crude material stage through creation and handling to pre-benefit and in-administration review. Aside from guaranteeing the basic trustworthiness, quality and unwavering quality of parts, today NDT finds broad application for condition observing, remaining life appraisal, vitality review, and so forth.

There are numerous NDT strategies utilized, contingent upon four fundamental criteria [5]:

  • Material Type
  • Defect Type
  • Defect Size
  • Defect Location

Non-Destructive Testing can be used in any phase of given item life cycle. If the testing is used, it should be applied and executed by following the instruction correctly otherwise it will not work. NDT is proven to be a useful tool and valuable during the accompanying stages [6]:

  • Research Development
  • Product design and feasibility inspection
  • Prototyping and pre-service testing
  • Manufacturing or Fabrication testing
  • Processing product testing
  • In-service Evaluation
  • Production testing
  • Failure Investigation

There are various way of non-destructive testing techniques. The six essential testing techniques [6] include Magnetic particle testing (MT), Radiographic testing (RT), Visual Testing (VT), and Electromagnetic testing (ET), Liquid Penetrant testing (PT) and Ultrasonic Testing (UT).

Magnetic Particle Testing (MT) utilizes magnetic fields to find the surface and close surface discontinuities in ferromagnetic materials like steel. Magnetic field can be used by different (direct and indirect) techniques i.e. Prods, Coils and Yokes. Magnetic Particles equipment shifts from versatile, semi-compact to stationary and can be altered to be utilised for testing process.   Magnetic Particle examination utilise a fine pigmented ferromagnetic powder which, when used to the surface of the part, it will be drawn in to the magnetic leakage field affected by a discontinuity which gives a visible indication [7].

Liquid penetrant testing (PT) utilizes the property of capillary activity to discover surface softening discontinuities in various materials. The testing utilize a low viscosity liquid which is used to the surface of a test piece. PT inspection utilize this capillary activity to permit the penetrant to go into gaps and voids that are interested in the surface. After an abode time, the overabundance penetrant is evacuated, any outstanding penetrant in the voids will stream back out revealing the indication [8].

Visual Testing (VT) is one of the most basic NDT method which follows the procedures of ranging from simply looking at a part to see if surface limitations are noticeable to using a computer controlled camera system to automatically recognize and measure features of a component [9].

Radiographic testing which examines the components and assemblies that display a difference in thickness when contrasted with encompassing material. Substantial contrasts   are more easily identified than small one. Also, radiography can identify just those elements that have an apparent thickness in parallel direction to the radiation beam [10].

Electromagnetic Testing (ET) uses magnetism and electricity to find cracks, deficiencies, consumption or other damage in conductive materials.  Investigation of particular magnetic properties and segment geometries are utilized to recognise the ideal Electromagnetic Testing technique [11].

Finally, the Ultrasonic Testing (UT) which uses sound energy of high frequency to conduct examinations and measurements on a test area. Ultrasonic Testing can be utilized for flaw detection, dimensional estimations and material characterisation [12].

Testing Method Advantages [13] Disadvantages [13] Example of use [14]
Ultrasonic Testing
  • Portability
  • Consistent
  • Detect surface and subsurface detects
  • Training is more extensive  than other methods
  • Lamination
  • Hydrogen cracking
  • Adhesive assemblies for bond integrity
Radiographic Testing
  • Permanent record
  • Can be portable
  • Applicable to wide range of materials
  • Cannot detect laminations
  • High cost
  • More expensive than other methods
  • Pipeline welds for penetration
  • Internal defects in casting
  • Inclusions and voids
Visual Testing
  • Inexpensive
  • Little to no equipment needed
  • Easy to train
  • Surface Indications  only
  • Only able to detect large flaws
  • Paper
  • Wood
  • Metal for surface finish uniformly
Electromagnetic Testing
  • Moderate cost
  • Immediate results
  • Sensitive to small indications
  • Time consuming to scan large areas
  • Surface to be inspected must be accessible to contact by the eddy current probe
  • Conductive
  • Heat exchanger tubs for wall thinning and cracks

All six elements of Non-destructive testing methods are considered complementary and not competitive. Each method has its benefits and limitations and these must be taken in account.

Table 1. Different types of Non-Destructive methods (NDT) and their usefulness

Liquid penetration Testing
  • Can be used on a variety of material types
  • Part geometry does not affect test
  • Very Portable
  • Requires a very clean part
  • Careful cleaning of part important so indications don’t get covered
  • Turbine blades for surface cracks
  • Grinding cracks
Magnetic Particle Testing
  • Ease of inspection
  • Inspects irregular shapes with ease
  • Relative low cost
  • Only surface and very near surface indications may be seen
  • Material being tested must be ferromagnetic
  • Railroad wheels for cracks
  • Large castings

Ultrasound is suitable for an industrial use as it can detect and size the internal defects. Also, it able to show the Young Modulus through the waves and other useful things. There is no radiation hazard in ultrasonic examination hence no disruption of work as there is with radiography.

However the disadvantage of the ultrasound comes under the current setting which is the transducer. The transducer has to be in contact to the testing material which can sometimes connected to extreme condition and also as it is applied to the material, the weight of the transducer makes the material deform.

This problem can be solved by using a Non-Destructive testing, which comes in many different ways, specific testing can be picked depending on the material being tested as its been explained above.

The next topic focuses on different types waves which can be used, from which one of will be picked to relate with the Non-Destructive Testing and in testing, through the waves the material can be scanned and through the waves it will detect the defects of the material.

2.2 GENERATION OF WAVES

The waves of energy affected by the sudden breaking of rock within the earth or a blast are called Seismic waves. Seismic waves are the waves of energy caused by the sudden breaking of rock within the earth or an explosion. They are the energy that travels through the earth and is recorded on seismographs.

There are several different kinds of seismic waves, and they all move in different ways. The two main types of waves are body waves and surface waves. Body waves are two types of waves; primary (compressional) waves and secondary (Shear) waves [15].

2.2.1 Primary wave

Primary wave is the fastest kind of seismic wave, and, consequently, the first to arrive at a seismic station. The p wave can move through solid rock and fluids like water or the liquid layer of the earth. It pushes and pulls the rock it move through just like a sound waves push and pull the air.

P waves (also known as longitudinal waves) are compressive waves [15], because of the pushing and pulling they do. Subjected to a P wave, particles move in the same direction that the wave is moving, in which the direction that the energy is travelling in and is sometimes called the “direction of wave propagation”.

2.2.2 Shear wave

S wave also known as secondary wave, shear waves are transverse waves that travel slower than primary waves. These waves travel at speeds between 1 and 8 km/s within the earth [16], the precise velocity depending on the rock type.  Secondary waves represents the back and forth motion of grain in solid media. Thus, Shear waves propagate through solids only and cannot travel through liquid or gas.

2.2.3 SAW wave

Surface Waves comes in two types: Love and Rayleigh waves. Surface waves are slower than body waves. Love waves have a particle motion, which is transverse to the direction of propagation but with no vertical motion. Their side-to-side motion causes the ground to twist from side to side, that’s why Love waves cause the most damage to structures. Rayleigh waves create a rolling, up and down motion with an elliptical and retrograde particle motion confined to the vertical plane in the direction of propagation.

Surface Acoustic waves were discovered in 1885 by Lord Rayleigh [15]. A surface acoustic wave (SAW) is a type of mechanical wave motion which is based on the acoustic wave propagation near the surface of a piezoelectric solid. This implies that the waves can be trapped or otherwise modified while propagating. The displacements decay exponentially away from the surface, so that the most of the wave energy is confined within a depth of substrate. A basic SAW device typically has two interdigital transducers (IDTs) on a piezoelectric substrate such as quartz as shown below.

Surface acoustic waves (SAWs) are sound waves that travel parallel to the surface of an elastic material, with their displacement amplitude decaying into the material so that they are confined to within roughly one wavelength of the surface.

Figure 1. Figure 1. P-Wave vs S-Wave vs Surface Wave

Surface Acoustic Wave is better than other waves as it can be seen in Figure 1. By comparing all different types of waves, Surface wave shows that it works in a circular motion, as it follows till the end but in a very little motion. For example, Rayleigh waves produce ground shaking at the Earth’s surface but very little motion deep in the Earth. Because the amplitude of surface waves diminishes less rapidly with distance than the amplitude of Primary or Secondary waves, surface waves are often the most important component of ground shaking far from the earthquake sources, thus can be the most destructive.

Figure 2. Basic SAW Device

2.3 GENERATOR

The application or variety of a force on a body delivers a strain and stress response and produce mechanical waves that carry on contrastingly in the body e.g. travel path and directions, travel speed, energy distribution and partial trajectory. These are known as Body waves and surface waves. In Body waves; longitudinal waves and shear waves propagate deep into the interior of material. At the point when the medium is limited by a free surface, Surface Acoustic Waves (SAW) are produced and propagate close to the surface and do not illuminate towards the interior. SAWs prompt a particle motion in the vertical plane that holds the direction of propagation. In a homogenous body with free surface, SAWs have a reversing elliptic circle. SAWs become dispersive when there are variations of the elastic properties with depth; a Surface Acoustic wave with a different wavelength propagates with different velocities [17].

2.3.1 Laser

In mechanism, the laser generation of ultrasound in a solid are easy to layout. A pulsed laser beam encroaches on a material and it absorbed by it to an extent. The optical power that is consumed by the material is changed over to heat, prompting to quick restricted temperature increment. The outcome in fast thermal expansion of a nearby region leads to the generation of ultrasound into the medium. By keeping the optical power low enough so that the material does not liquefy and ablate, thus, the generation regime is called thermoelastic as shown in fig 1a.

The ultrasound can be generated if the optical power is sufficiently high to prompt to dissolving of the material and plasma formation however in this case, though the transfer exchange due to material ejection as shown in fig 1b.

The generation of ablative regime is normally not adequate for non-destructive portrayal of materials. Nonetheless, it is helpful in some procedure monitoring applications, particularly since it produce bulk wave generation typical to the surface [18].

Figure 3. Laser generation of ultrasound in (a) thermoelastic regime and (b) ablative regime.

  • Thermoelastic Generation of Ultrasound

A fully decoupled linear analysis for the simplicity is considered to be homogeneous and isotropic materials. The fundamental issue of thermoelastic generation of ultrasound can be disintegrated into three sub issues as shown below:

  1. Electromagnetic energy absorption by the medium
  2. The subsequent thermal diffusion issue with heat sources
  3. The  subsequent elastodynamic issue with volumetric sources
  • Rayleigh Wave Generation

Rayleigh waves are broadly utilized as a part of ultrasonic non-destructive characterisation of structures which propagates on the surface of a thick solid. Thermoelastic generation of Rayleigh waves has subsequently been widely examined and as shown in figure 7.4, hypothetically figured surface displacement in the most distinct field of a thermoelastic point source.  A solid bipolar Rayleigh wave apparently is produced by the thermoelastic source. Figure 7.4 b shows the estimation of the far field surface normal displacement made utilizing a homodyne interferometer. The Rayleigh wave becomes a monopolar pulse if the laser source is a line source instead point-focused source [18].

Figure 4. Rayleigh wave generation: (a) Theoretical calculations of the surface normal (solid) and horizontal (dotted) displacements, (b) experimental results for surface normal displacements. (John, Y. and Krishnaswamy, S., personal communication, 2003.)

Figure 5. Rayleigh wave generation: (a) Theoretical calculations of the surface normal (solid) and horizontal (dotted) displacements, (b) experimental results for surface normal displacements. (John, Y. and Krishnaswamy, S., personal communication, 2003.)

2.3.2 High-Intensity Focused Ultrasound (HIFU)

High-Intensity Focused Ultrasound (HIFU) is a term for surgical techniques utilizing focused ultrasonic fields to decimate the aiming region in depth by not effecting the overlaying or the surrounded tissues. HIFU is mainly used in tissue for thermal ablation yet non-thermal modes of utilization are conceivable. High-Intensity Focused Ultrasound is by far recognized as one of the strategies if thermal ablation between laser, microwave cryo-ablation and radio frequency. HIFU is exceptional as there is no requirement to insert a probe, which makes it the only possible non-destructive ablative method by not depending on the ionising radiation. With regards to tumour treatment, it able to remove the risk of tumour seeding cell along with insertion track Principle of HIFU [1] [18.1].

The frequencies of HIFU roughly range from a few 100 kHz to around 1.5MHz. In HIFU, at lower frequency, ultrasound can’t be adequately focussed whereas at higher frequencies the constriction before achieving the objective is too vast.

High-Intensity Focused Ultrasound is currently being focused in to use for medical purposes and surgery purposes. As by far, all the research has been done mainly in medical field whereas the Industrial field still not being focused [18.2].

Figure 6. Generation of HIFU and its use to form a thermal lesion within a tissue target.

Mechanism of High-Intensity Focused Ultrasound (HIFU) in Industrial/medical takes in two different section. First, the conversion of mechanical energy into heat and mechanical cavitation of pressure waves in hard materials such as Plastic, Steel etc. the ultrasound waves can be focused at one specific point, the energy converted to heat makes the tissue to heat up and kill the tissue cells which cannot be used in Industrial field as it will just burn the material. However, the second option of HIFU is through cavitation, which causes the material to vibrate which produce the waves and the properties of the material can be calculated by using the waves. Below is the diagram of two different methods of how can HIFU can be used in Industrial and medical field.

Figure 7. Difference between medical and industrial experiment.

Important parts of the material science of HIFU incorporate the connection between the axial radiation force and acoustic power, the time-rate temperature change during HIFU radiation, acoustic propagation, the intensity dependence of heat from HIFU, the spatial and the Finite element technique of HIFU simulation.

In Force vs Power of HIFU, the connection between the axial radiation force (F) and acoustic power of a transducer is critical as the connection goes straight to the temperature at the irradiation site. The equation shows the relationship of the radiation force:

http://www.nikonmetrology.com/en_EU/Applications/Material-Analysis/Cracks-and-Failure-Analysis  [106]

Time-Management Diagram

APPENDIX A

RISK ASSESSMENT FORM

 

DIVISION OF MECHANICAL ENGINEERING & MECHATRONICS

 

PERSONAL RISK ASSESSMENT FOR STUDENT PROJECTS

PLEASE  READ THIS FIRST

Each student who undertakes Project Work is required to complete all of the sections below which are relevant to the work which is to be undertaken. In many cases, details may not be known at the start of the project and it will be necessary to enter them later. At no time, however, may an activity start unless the risks which it may involve have been assessed and recorded. The form must be available for inspection during the project and a copy must be appended to the final report. A copy must be sent to your Supervisor before you start any practical work for your project and the attention of your Supervisor should be drawn to any additions during the session.

Project work is not particularly dangerous, but it is important at this stage to realise that in your professional career you will have a legal obligation to think carefully about any hazards which may be encountered. This awareness encourages careful working and it makes sure that  everyone will  be sure that the necessary precautions have been identified and are being applied. Consult your superviser if you require special safety information and always use the precautions which are recommended. The first stage of safe working is that you think carefully about what you are planning  to do.

YOUR FULL NAME
STUDENT ID
NAME OF SUPERVISOR
TITLE OF PROJECT

In the sections below, the date required is the date when you first specified the details concerned. As noted above, you may add entries throughout your project when the need arises, but you must always assess the risk of an activity before you perform it. Use additional pages if required

1.0 EMERGENCY PROCEDURES

Sign here to confirm that you know the following. Note details. See Honours Guide and Notices Displayed on walls etc  Relate to the location of your work

ITEM Date Sign and add details
Nearest Telephone for Emergency Help and Number to Ring
Trained First Aiders
Fire Assembly Point
Nearest First Aid Equipment
2.0 ELECTRICAL RISKS

Identify electrical risks and indicate the precautions to be taken.

RISK Date Details and Precautions
Exposed DC potential differences exceeding 50V
Exposed AC potential differences exceeding 50V
3.0 MECHANICAL RISKS

List any mechanical risks which you will encounter. Include the lifting of heavy weights, the use of hand or power tools and the use of pressurised systems

RISK Date Details and Precautions
4.0 THERMAL RISKS

Identify risks from equipment or substances which will be at high or low temperatures

RISK Date Details  and Precautions
High Temperatures
Low Temperatures
5.0 RISK from DUST and POWDER

Identify risks of fire, explosion, or injury by contact/breathing from dust or powder

RISK Date Details and precautions
6.0 RISK from CHEMICALS or GASES

List each chemical substance you use which you consider to offer a significant risk, the date when you first knew you would use it, the risks associated with it and the precautions to be used. Risks are listed on containers, in manufacturers data sheets and catalogues, and are usually known to research workers and members of staff.

Substance Date Details and Precautions
7.0 LOCATION OF YOUR WORK

Give the location(s) in which you will be working, specifying any special safety facility which you need to use (isolated electrical supply, fume cupboard, etc)

LOCATION Date Special  Facility
8.0 DECLARATION
Date Your Signature
I have given careful consideration to the work I am planning to do and I believe I have identified the significant risks to which I will be exposed. I will consult my Supervisor if I am uncertain about safe working practices during my work.

APPENDIX B

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