Basic information about creep and it's types and linear peristaltic pump, literature review, methodology for determination of creep constants, finite element analysis of iv tube with different shape of fingers, results, conclusion, future scope.
Determination of creep constants and FEA analysis of an IV tube.pdf
1. i
Determination of creep constants and FEA
analysisof an IV Tube.
BY:
MEET KALOLA (18BME050)
YASH MRUG (18BME070)
MECHANICALENGINEERINGDEPARTMENT
INSTITUTE OF TECHNOLOGY
NIRMA UNIVERSITY
AHMEDABAD
MAY 2022
2. ii
Determination of creep constants and FEA
analysisof an IV Tube.
Submitted in partial fulfillment of the requirements for the award of degree of
BACHELOROF TECHNOLOGY
IN
MECHANICALENGINEERING
Submitted by:
MEET KALOLA (18BME050)
YASH MRUG (18BME070)
MECHANICALENGINEERINGDEPARTMENT
SCHOOL OF ENGINEERING
INSTITUTE OF TECHNOLOGY
NIRMA UNIVERSITY
YEAR:2021-22
3. iii
Declaration
This is to certify that
• The this is comprises my original work towards the degree of Bachelor of Technology
in Mechanical Engineering at Nirma University and has not been submitted elsewhere
for degree.
• Due acknowledgement has been made in the text to all other material used
Sign:
Name: Meet Kalola
Roll No: 18BME050
Sign:
Name: Yash Mrug
Roll No: 18BME070
4. iv
Undertakingfor Originalityof the Work
We, Meet Kalola (18bme050) & Yash Mrug (18bme070) gives undertaking that the Major
Project entitled (“Determination of creep constants and FEA analysis of an IV tube.”)
submitted by us, towards the partial fulfillment of the requirements for the degree of Bachelor
of Technology in Mechanical Engineering of Nirma University, Ahmedabad, is the original
work carried out by us. We give assurance that no attempt of plagiarism has been made. We
understand that in the event of any similarity found subsequently with any published work or
any dissertation work elsewhere; it will result in severe disciplinary action.
Signature of Student
Signature of Student
Date:
Place: Ahmedabad
Endorsed by
(Signature of Guide)
5. v
Certificate
TO WHOMSOEVERIT MAY CONCERN
This is to certify that, Mr. Meet Kalola student of B. Tech (Mechanical engineering),
VIIIth Semester of, Institute of Technology, Nirma University has satisfactorily
completed the project report titled “Determination of creep constants and FEA analysis
of an IV tube.”
Date:
Prof. Vipul M. Bhojawala
Guide, Assistant Professor,
Department of Mechanical Engineering,
Institute of Technology
Nirma University, Ahmedabad
6. vi
Certificate
TO WHOMSOEVERIT MAY CONCERN
This is to certify that, Mr. Yash Mrug student of B. Tech (Mechanical engineering),
VIIIth Semester of, Institute of Technology, Nirma University has satisfactorily
completed the project report titled “Determination of creep constants and FEA analysis
of an IV tube.”
Date:
Prof. Vipul M. Bhojawala
Guide, Assistant Professor,
Department of Mechanical Engineering,
Institute of Technology
Nirma University, Ahmedabad
7. vii
Approval Sheet
The Project entitled Determination of creep constants and FEA analysis of an IV tube by Meet
Kalola (18bme050) and Yash Mrug (18bme070) is approved for the degree of Bachelor of
Technology in Mechanical Engineering.
Examiners
___________________
___________________
___________________
Date: ___________
Place: __________
8. viii
Acknowledgments
We would like to express our special thanks of gratitude to our department who gave us the
golden opportunity to do this wonderful project on the topic “Determination of creep
constants and FEA analysis of an IV tube”, which also helped us in understanding the
industry project and we came to know about some new things. We are really thankful to them.
We would like to thank our guide Prof. Vipul M. Bhojawala sir and co-guides Prof. Dhaval V.
Patel sir, Prof. Shashikant J. Joshi sir and Prof Dhaval B. Shah sir for guiding us and helping
us throughout the course of this project. Even in these difficult times of COVID, they helped
us with anything and everything that was needed. Without their support, this project could not
have been completed.
And lastly, we would like to thank our university for giving us this opportunity to conduct this
project.
Name and signature of student(s)
Date:
Place:
9. ix
Abstract
Contents of Abstract
Life of an IV Tube has very important role in medical applicationsas it is well known. The
major problem is how to increase the life of an IV Tube significantly. Here FEA Analysis
technique to find the stress induced in IV Tube. First the material properties of an IV Tube are
found by lab testing of material. The methodology for FEA Analysis in Ansys workbench is
understand. In Ansys, the Static Structural analysis is used for simulation of an IV Tube. Then
boundary conditions are given to find the solution.In results, the stress and creep strain rate
for different types of finger geometry have been obtained. Significance of different shape of
finger is studied based on the stress and creep rate in IV Tube for different shapes. From the
results of the FEA Analysis, it is concluded that finger with flat top rade and corner the linear
peristaltic pump.
Key words: Creep Strain, Stress, Shape of Finger, FEA Analysis.
10. x
Table of contents Page No.
Declaration III
Undertaking IV
Certificate V-VI
Acknowledgements VIII
Abstract IX
Table of Content X
List of Figures XII
List of Tables XIV
CHAPTER I: INTRODUCTION 01 – 05
1.1 Problem Specification 1
1.2 About Peristaltic Pump 1
1.3 An IV Tube 2
1.4 Applications 3
1.5 Creep 3
1.6 Stages of Creep 4
1.7 Finite Element Analysis Tool 5
CHAPTER II: LITERATURE REVIEW 6 – 8
CHAPTER III: DETERMINATION OF 9– 14
CREEP CONSTANTS
3.1 Creep Model 9
3.2 Analytical Creep Curve 9
3.3 Methodology to Determine Creep Constants 10
11. xi
CHAPTER IV: Finite Element Analysis 15 – 27
4.1 Material Properties 15
4.2 Sketch of Model 15
4.3 Different shapes of Finger 17
4.4 Ansys 19
4.5 Boundary Conditions 22
4.5.1 Contact Regions 22
4.5.2 Meshing 24
4.5.3 Analysis Settings 25
4.5.4 Support 26
4.5.5 Displacement 27
CHAPTER VI: CONCLUSIONS & FUTURE 28 – 33
5.1 Stress Analysis of an IV Tube of different 28
Shape of Fingers
5.2 Equivalent Creep Curve Plot 30
5.3 Equivalent Creep Comparison 32
5.4 Conclusion 33
5.5 Future Scope 33
REFERENCES 34
12. xii
List of Figures Page No.
Figure 1: Linear Peristaltic Pump 2
Figure 2: IV Tube 3
Figure 3: Creep Curve 5
Figure 4: Creep master curve for LLDPE at 40 C. 9
Figure 5: Image from GetData 10
Figure 6: Log (Strain) Vs Log (Time) 11
Figure 7 (a): Strain Vs Time at different Stress 11
Figure 7 (b): Strain Vs Time at different Stress 12
Figure 7 (c): Strain Vs Time for 25 12
Figure 7 (d): Strain Vs Time for 145 C 13
Figure 8: Sketch of Model in 3rd angle Projection 16
Figure 9: Dimensions of Finger 1 in mm 17
Figure 10: Dimensions of Finger 2 in mm 18
Figure 11: Dimensions of Figure are in mm 19
Figure 12: Creep Equation in Ansys 20
Figure 13: Engineering data for LLDPE 20
Figure 14: Ansys Workbench 21
Figure 15: Geometry of Model created in Solid Works 22
Figure 16 (a): Contact between IV Tube and Anvil 23
Figure 16 (b): Contact between Finger and IV Tube 24
Figure 17: Meshing of Geometry 25
Figure 18 (a): Analysis Settings in Ansys 25
Figure 18 (b): Creep Control Settings 26
Figure 19: Fixed Support Given to the Anvil 26
Figure 10: Stress Comparison of Fingers 26
Figure 21: Cylindrical support to IV Tube 27
Figure 22: Displacement of Finger 28
Figure 23 (a): Equivalent stress for Finger 1 29
13. xiii
Figure 23 (b): Equivalent stress for Finger 2 29
Figure 23 (c): Equivalent stress for Finger 3 30
Figure 24 (a): Creep strain rate for Finger 1 30
Figure 24 (b): Creep strain rate for Finger 2 31
Figure 24 (c): Creep strain rate for Finger 3 31
Figure 25: Equivalent Creep Strain 32
14. xiv
List of Tables Page No.
Table 1 : Creep Constants at different Temperature 14
15. 1
Chapter 1
Introduction
1.1 Problem Specification
As per information received from industry, the tube life of a Linear Peristaltic Pump is not
more than 3 days or 72 hours. Because of creep deformation, the life of an IV Tube decrease.
Creep is one of the failures in thermoplastics and from all the plastic 22% thermoplastic fails
due to creep. So, it has been tried to increase the life of an IV Tube by changing the shape of
fingers. The stress value for a particular finger is obtained and then after changing the shape
of finger, the stress is also obtained in order to detect the shape of finger which is suitable for
increase in life. Based on that finger of that shape can be adopted in pump so that life can be
increase for an IV Tube.
1.2 About Peristaltic Pump
A peristaltic pump is also called as a rotary pump, it is a positive displacement pump that is
used to pump a various type of fluids. The fluid is contained inside a circular pump by a
highly flexible tube. Although linear peristaltic pumps have been developed,most peristaltic
pumps go through motility. When the pump turns, the rotor has a number of "wipers" attached
to its external perimeter, which compress the flexible tubing. The fluid is forced to travel
through the tube once a section of the tube under compression is closed. The fluid body is
transferred through the tube to the pump exit. Peristaltic pumps can run continuously or be
indexed to deliver lesser volumes of fluid using partial rotations.
16. 2
Figure 1: Linear Peristaltic Pump [1]
1.3 An IV Tube
Intravenous (IV) access is used to provide drugs and fluid replacements that must be
dispersed throughout the body quickly.
The material of an IV Tube can be PVC (polyvinylchloride), PE (polyethylene), LLDPE
(Linear Low-Density Polyethylene) etc. The LLDPE material is used for the present work.
17. 3
Figure 2: IV Tube [2]
1.4 Applications
Peristaltic pumps are commonly used to pump clean highly reactive fluids without
contaminating them with uncover pump components. Pumping IV fluids through an infusion
device, high solids slurries, highly reactive chemicals, apheresis, and other materials where
product separation from the environment is crucial are just a few examples.They're also used
in hemodialysis systems and during bypass surgery, heart-lung machines circulate blood.
because the pump doesn't produce severe hemolysis, or blood cell rupture.
1.5 Creep
Creep is the tendency of a solid material to move slowly or permanently deform under the
impact of persistent mechanical forces in mechanics of solid. It can happen due to result of
prolonged exposed to extremely high levels of stress yet below the material's yield strength.
Creep is more critical in materials that have been exposed to heat for a long time, and it
usually increases as the temperature rises.
Intravenous (IV) access is used to provide drugs and fluid replacements that must be
dispersed throughout the body quickly. The deformation may become very high that a
18. 4
component cannot fulfil its function, depending on the magnitude of the applied stress and its
duration.
Engineers and metallurgists are sometimes concerned with creep while analysing components
that perform under high loads or temperatures.Creep could be a deformation mechanism that
may or may not cause to failure. Moderate creep in concrete, for example, is normally
appreciated since it relieves tensile strains that could otherwise induce cracks.
1.6 Stages of Creep
The creep is time dependent and it goes through several stages:
1. Primary Creep: The strain rate is relatively high at the primary stage but it reduces
with increasing time and strain due to the material's increased creep resistance or
strain hardening. Steady-state creep can then occur in Stage two, when the creep rate
is very slow and the strain can increase very slowly over time.
2. Secondary Creep: The plot becomes secondary creep, also known as steady-state
creep. almost linear while the velocity remains constant. Because the secondary stage
begins, the strain rate decreases to a minimum and becomes almost constant. This is
frequently due to a compromise between work hardening and annealing.
This is the most relatable stage of creep. The secondary creep stage is usually the one
that lasts the longest. During the first two stages of creep the material strength is same.
The slope of the secondary component of the creep curve (P/t) is arguably the most
relevant parameter from a creep test in materials engineering. For long-term
applications, it's the engineering design parameter to consider. The secondary creep is
the name given to this characteristic.
19. 5
Figure 3: Creep Curve [3]
3. Tertiary Creep: In tertiary creep, the creep increases, perhaps leading to the failure.
Due to interior cracks, the strain rate increases exponentially with force; cavities or
voids reduce the effective area of the specimen. As a result, the increased strain rate
and effective cross-sectional area. At this point, swiftly loses strength as the material's
form is permanently affected.Creep deformation's third stage finally leads to failure,
which is typically Microstructural and metallurgical changes produce rupture, which is
referred to as rupture.
1.7 Finite Element Analysis Tool
Ansys is a finite-element modelling tool that may be used to solve a wide range of mechanical
problems numerically. Static/dynamic, structural analysis, heat transmission, and fluid
problems, as well as acoustic and electromagnetic challenges,are among these issues.
A static structural analysis identifies the displacements, stresses, strains, and forces induced in
structures or components by loads that do not create substantial inertia or damping effects.We
used static structural analysis to see the strains on the tube.
20. 6
Chapter 2
Literature Review
1. Creep behavior of linear low-density polyethylene films [4]
:
Differential scanning calorimetry (DSC) and X-ray investigation of LLDPE (linear
low-density polyethylene) creep the most common issue with polyethylene is creep
after prolonged loading. The purpose of this work aims to look at how non-oriented
and biaxially oriented LLDPE films creep. that have been cross-linked by irradiation
at temperatures below the melting point. Creep behavior was discovered using an
experimental setup that included total stain vs. time at various stress and temperature
levels. Heat and temperature influence creep. Because of the partial disorientation of
the molecules in the orientated amorphous phase, higher creep strain was seen in films
irradiated with very modest doses. This disorientation was induced by the film heating
up during the irradiation. The disorientation in the amorphous phase was demonstrated
using DSC (differential scanning calorimetry) and X-ray analyses. According to
experimental data, total creep increases up to 100 seconds in cross-linked LLDPE
polymers before giving way to secondary creep. For biaxially oriented films, primary
creep occurs for a much shorter time than secondary creep at the same temperature.
2. An analytical model to predict the creep behavior of rotationally molded linear low-
density polyethylene (LLDPE) and polypropylene (PP). [5]
:
Creep analysis of LLDPE (linear low-density polyethylene) and PP at 40 C. Hollow
pipe was made by Rotational Molding (RM) which is flexible plastic process. A creep
constant for creep analysis was obtained from experimental data. Hollow shape of
material used in experimental setup time-temperature superposition in a typical
accelerated creep test utilizing the stepped isothermal approach (SIM-TTS). Time
period taken in simulation was 10000 hours. for creep prediction time hardening
model was used which provides (primary + secondary).Time-hardening equation (Є =
A𝜎𝑚𝑡𝑛 )and creep constants A, m, n. Based on creep behavior and therefore the
21. 7
comparison of two materials to decide usability of material for long term performance
under constant stress. Creep constants was found from log-log curve of creep master
curve and log-log curve of strain VS stress for LLDPE and PP both. Then there is
comparison between LLDPE and PP for experimental and simulation data for both
material at constant temperature. After comparison of result of both material for creep
prediction
Comparison of the creep behavior indicates that PP has higher creep resistance. PP
will be used as an alternate for LLDPE because it is more effective in environments
with high operating temperatures and rigidity requirements.
3. Creep in LDPE polymer, between mechanical property and usage environment [6]
:
Creep prediction of LDPE (low-density polyethylene) with the help of experimental
setup was carried out to measure creep by equivalent creep strain Vs. time curve at
different temperature, stresses and area for comparison. Material used in test is cones
under thermoplastic category like LLDPE, PVC and PP, PE etc. by increasing the
stress the LDPE will start with dislocation and shredding at the weak points (chains).
Secondary creep stage is suitable to study creep property for thermoplastics (PE)
because of its stability and uniformity. Creep also depends on stain, time and type of
polymer used for testing, temperature. from results resistance of material to creep for
both temperature and applied stress increases with increase in area (stress applied).
And by increasing thickness of the samples results in increasing in time. Samples
failing, so less thickness gives significant increase in the strain against time. If stress
increases on same section area of the sample and constant temperature, creep rates
increase and strain increase vertically under small time range.by increasing thickness
of sample creep resistance increase and creep rate inversely proportional to area at
constant temperature (25 C) and area by increase in strain there is decrease in rupture
time.
4. Understanding creep failure of plastics [7]
.
This article gives information about creep rupture in plastics and how different
parameters affects creep rupture like viscoelasticity and its importance specially for
thermoplastics When a thermoplastic is subjected to constant tension, strain will rise.
22. 8
The polymer chains do not have enough time to yield as the strain rate increases, and
persistent deformation of the material occurs instead of yielding. One example was
discussed in article by tensile testing on material they got tensile data and from
apparent modulus versus time they created a master curve of strain over time. From
stain Vs time curve, they find life of component.
5. Failure analysis of LLDPE based materials [8]
.
Research paper gives the information about failure of LLDPE by finding ESC
(Environmental Stress Cracking) ESE also affected by higher temperatures, cyclic
loading, increased stress concentrations like creep rupture. As per this research
constant stress and static load is not only responsible for creep but fluid flowing
through material is also responsible for creep in this paper parameters responsible for
failure of LLDPE like temperature material property additives, material structure.
Different test methods used to find ESCR in LLDPE. Here, Constant load test is
preferred for thermoplastic material rather than constant strain. Creep test of LLDPE
with different additives has been done experimentally. When tensile load is applied on
LLDPE film. Results prove that material’s tendency to deform elastically decreases
with increasing deformation rate and Young’s modules is also marginally increases
that shows unaffected behavior of LLDPE film compared to treated material.
23. 9
Chapter 3
Determination ofCreep Constants
3.1 Creep Model
To analyses the creep strains during secondary stage, a Norton model is used. The creep strain
is represented as:
𝜀𝑐𝑟 = 𝐴 ∗ 𝜎𝑚 ∗ 𝑡𝑛 ……… (1)
Where A is the power-law multiplier, m is stress order and n is the time order. A, m; and n are
material constants.
3.2 Analytical Creep Curve
Firstly, the data is collected for the creep master curves at different temperatures and for
different stresses from different resources [11] [12] [13]. Here we have shown the sample master
curve found from reference paper [5] and used for analytical analysis.
Figure 4: Creep-master curve for LLDPE at 40 C [5]
24. 10
3.3 Methodology to Determine Creep Constants
As shown in Figure 5, we have used the Get Data software to determine the points located in
figure.
Figure 5: Image from GetData [9]
in the right side of figure 5, The points located in the creep master curve at 40 C are
tabulated using these points plot the graph in excel so that from linear regression of that data
equation of curve as shown in figure 6 can be obtain.
In this figure, the data of Strain vs Time and is converted into Log (Strain) Vs Log (Time).
After converting into log data equation of the line can be obtained from the curve tilting or
regression analysis.
25. 11
Figure 6: Log (Strain) Vs Log (Time) [10]
This analysis is for a particular value of stress 1.8 MPa. To do this type of analysis for a
particular stress values and particular time values,number of literatures are referred.
Figure 7 (a): Strain Vs Time at different Stress
26. 12
Figure 7 (b): Strain Vs Time at different Stress [11]
From another reference paper, a creep master curve for 75 C, 65 C and 25 C as shown
above for stress value of 4MPa and 32Mpa are obtained. The constants are estimated as
shown in table.
Figure 7 (c): Strain Vs Time for 25 C [12]
From the above figure 7, The constants for temperature 25 C is obtained. The constants
found from above figure are; A= 3.8E-08, m= 0.1711,n=1.44.
From another research paper [13] shown in figure 7(d), the constants for 145 C obtained. The
constants are; A= 3.15E-03, m= 0.3603 and n= 1.4898.
27. 13
Figure 7 (d): Strain Vs Time for 145 C [13]
All the data from various reference papers are obtained and the graph are plotted and finally
equation as discussed earlier are estimated. The first co-efficient of that equation is considered
as 2nd constant of an equation (1). After finding 2nd constant first, the time is varied instead of
stress is obtained. Another equation of strain vs stress is obtained and from that equation the
first co-efficient as 3rd constant of an equation (1) is obtained.After founding two constants of
equation (1), The constant A is calculated. This process is followed for every creep master
curve which is defined for the different temperature and different stress conditions.
We have made a table for creep constants varying at different temperature value and different
stress values as shown below in table 1:
As per our requirement is for 25 C (room temperature) temperature, A = 3.8E-08, m =
0.1711 and n = 1.44 for an FEA Analysis of IV Tube.
28. 14
Table 2 : Creep Constants at different Temperature
Temp (C) A m n
25 0.286689 0.322 0.5204
25 3.8E-08 0.1711 1.44
40 0.4002 1.2414 0.1348
65 0.175 0.47135 0.8023
75 0.006932 0.4 0.00355
145 3.15E-03 0.3603 1.4898
200 6.06E-06 0.1243 6.74488
29. 15
Chapter 4
Finite Element Analysis
4.1 Material Properties
Material used for FEA analysis of an IV Tube is LLDPE (Linear Low-Density Polyethylene).
LLDPE has density range of 0.915-0.935 g/𝑐𝑚3. LLDPE has higher tensile strength than
LDPE.
Material Properties of an LLDPE are mentioned below:
• Density - 0.92 (g/cm3)
• Tensile Strength – 20 (MPa)
• Linear Expansion Coefficient (/°C*105) - 20
• Young Modulus - 6E+08 (Pa)
• Poisson’s Ratio - 0.4
4.2 Drawing of Model
The for support, an IV Tube and a Finger in this model for FEA Analysis is shown in figure 8.
Anvil has not been included in the FEA analysis and it is to be assumed as a fixed support or
grounded. An IV Tube is of LLDPE as mentioned earlier. And the material of finger is steel.
30. 16
Figure 8: Sketch of Model [14]
As shown in above drawing, the dimensionsof an IV Tube are as mentioned below:
• Inner Diameter of Tube: 3.1 mm
• Outer Diameter of Tube: 4 mm
• Length of Tube: 20 mm
31. 17
4.3 Different Shapes of Finger
The three types of fingers for creep determination and stress analysis is shown in figure 9,10
and 11 with their dimensions:
• Finger 1: Here the shape of first finger is shown in figure 9 with their dimensions.
There is fillet on the two sides of rectangle shape. The 3D model prepared in solid
works.
Figure 9: Dimensions of Finger 1 in mm [14]
• Finger 2: In this finger there is a sharp edge and a fillet at the sharp edge of 0.5 mm as
shown in figure 10:
32. 18
Figure 10: Dimensions of Finger 2 in mm [14]
• Finger 3: In this finger there are two fillets on the two edges of the finger of 0.25 mm
as shown in figure 11:
First, the model with rectangle of 4*15 𝑚𝑚2 and then extruded that rectangle up to 4
mm shown in figure 11. The fillet given at the edge of rectangle on two sides as shown
in figure 11. Then assemble all the geometry as per drawing of model so that the
analysis of different shape of finger to find the creep curve and deformation of tube
can be performed.
33. 19
Figure 11: Dimensions ao Figure are in mm [14]
4.4 Engineering Materials in Ansys
To perform the Static Structural as shown and to obtain the creep come material model is
specified. As LLDPE is not available PVC is used initially and subsequently then change their
properties from PVC to LLDPE as mentioned above.
34. 20
Figure 22: Creep Equation in Ansys [15].
The image for engineering data which need to be given as input as shown in figure 12. Select
norton equation in creep settings as we have discussed earlier and give a constant for 25 C
(A= 3.15E-03, m= 0.3603 and n= 1.4898) derived above shown in below figure 12.
Figure 13: Engineering data for LLDPE [15].
As shown in above figure 14, all the properties of LLDPE material as per above details given
earlier.
36. 22
The geometry is created as per our drawing of model of pump. The geometry created is shown
in the figure 15. Then the geometry is imported for Ansys Structural Analysis.
Figure 15: Geometry of Model created in Solid Works [14]
4.5 Boundary Conditions
Boundary conditionsgiven to the analysis are mentioned below as per loading condition:
4.5.1 Contact Regions
There are two manual contacts between finger and tube and tube and anvil as shown below in
figure:
37. 23
Figure 16 (a): Contact between IV Tube and Anvil [15]
In figure 16 (a) the contact between IV Tube and Anvil is shown. These contacts are given
manually.
Figure 16 (b): Contact between Finger and IV Tube [15]
The figure 16 (b) shows the contact between Finger and IV Tube in this model.
38. 24
4.5.2 Meshing
Two types of meshing used for manually as shown in figure 17:
• Face Sizing
• Edge Sizing
The full body of model is considered and default element size of 5E-002 is taken. The number
of elements is 1484. The node count is 5085.
Figure 17: Meshing of Geometry [15]
39. 25
4.5.3 Analysis settings
In Analysis, the total time for the analysis is to be mentioned. The analysis for 72 hours
(259200 seconds) which is step end time at time interval of 15 minutes (900 seconds). The
same is mentioned in a time step.
Figure 18 (a): Analysis Settings in Ansys [15]
The Creep Effects option in Creep Controls is to be mentioned to get equivalent creep strain.
Figure 18 (b): Creep Control Settings [15]
4.5.4 Support
There are two types of supports provided in this analysis.
1. Fixed Support
2. Cylindrical Support
40. 26
• Fixed support is given to the base part of anvil so that it can be grounded and will not
move downward for IV Tube analysis as shown in figure 19.
Figure 19: Fixed Support Given to the Anvil [15]
• Cylindrical support is given to an IV Tube because cylindrical constraint allows the
axial, angular & radial movement of a cylindrical surface, while keeping the axis
fixed.
Figure 20: Cylindrical support to IV Tube [15]
41. 27
• In cylindrical support, just fixed the radial direction option as shown left side in figure
20. Axial and tangential direction should be free while performing the analysis.
4.5.5 Displacement
Displacement of 3 mm is given to the Finger in negative y direction so that it can displace the
tube and can be obtained the curve of stress, total deformation and equivalent creep strain can
be obtained. Rotational part of the finger should be restricted so that finger can only move
linear in negative y direction as shown in figure 21.
Figure 21: Displacement of Finger [15]
After applying this boundary conditions, the model needs to be solved for the analysis. As
discussed earlier, the total deformation, stress and equivalent creep strain data from this
analysis so that the suitable shape is suggested for this type of motion in peristaltic pump.
42. 28
Chapter 5
Results andConclusion
5.1 Stress analysis of an IV Tube of different shape of fingers:
The comparison of the stress for all three shapes of fingers are mentioned in figure.In finger
1, the stress value is lesser compare to other two. Maximum stress is generated in the 2nd
finger which has a sharp edge as compared to all. The results of von-misesstress analysis is
given in figure 22.
Figure 32: Stress Comparison of Fingers [10]
0.00E+00
1.00E+08
2.00E+08
3.00E+08
4.00E+08
5.00E+08
6.00E+08
7.00E+08
8.00E+08
9.00E+08
0.00E+00
5.00E+10
1.00E+11
1.50E+11
2.00E+11
2.50E+11
0 50000 100000 150000 200000 250000 300000
Stress
(Pa)
Time (s)
Stress comparisonof Fingers
Stress2 Stress1 Stress3
43. 29
Figure 23 (a): Equivalent stress for finger 1 [15].
The stress range obtained on finger 1 from analysis shown in figure 23(a).The stress is
varying between 1.2 – 2.58 E+06 MPa.
Figure 23 (b): Equivalent stress for finger 2 [15].
44. 30
The figure 23(b) shows the stress range for finger 2. The stresses are almost double in
comparison to the shape of finger 1 and 3.
Figure 23 (c): Equivalent stress for finger 3 [15].
In figure 23(c), The range of stress in finger 3 are same. In this finger, stresses are almost
similar to finger 1.
5.2 Equivalent creep curve plot
Figure 24 (a): Creep strain rate for Finger 1 [15].
45. 31
In figure 24(a), the creep strain is Vs time is mentioned.
Figure 24 (b): Creep strain rate for Finger 2 [15].
The figure 24(b) shows that the strain rate is much higher in finger 2 as there is a sharp
rounded edge in finger. The same can be observed in figure 21(b).
Figure 24 (c): Creep strain rate for Finger 3 [15].
Comparing of all data for varioustypes of fingers, it can be observed that in the finger 1 creep
rate is for longer period. It means this shape can be effectively used. In similar manner for
finger 3 also, finger 3 can also be effectively compare to finger 2. Creep rate is more for
46. 32
finger 2. Hence, finger 1 can be effectively used. According to FEA Analysis, the most
suitable shape for the finger is shape 1.
5.3 Equivalent Creep Comparison
After comparing stress for the different shape of fingers, comparison is also required for
equivalent creep to find suitable shape of finger.
Figure 25: Equivalent Creep Strain [10]
In the finger 2, the creep rate is very high. The figure shows that finger 2 is not suitable to
push the fluid in peristaltic pump.
0.00E+00
1.00E-04
2.00E-04
3.00E-04
4.00E-04
5.00E-04
6.00E-04
7.00E-04
0.00E+00
2.00E-03
4.00E-03
6.00E-03
8.00E-03
1.00E-02
1.20E-02
1.40E-02
1.60E-02
0 2000 4000 6000 8000 10000 12000 14000 16000
Strain
Rate
(m/m)
Time (s)
Equivalent creep strain
Finger 1 Finger 3 Finger 2
47. 33
5.4 Conclusion
The creep constant determination methodology is studied in the project work.Effect of both
stress and creep strain is investigated. For the analysis, the following conclusions can be
made:
• With an increase in the stress value, time life of the tube decreases significantly. So
that there is significant change in life of an IV Tube.We can increase the time life of
an IV tube by changing the shape of finger as per above discussion.
• With an increase in creep strain rate, the time life of the tube decreases. But in
comparison to increase in stress, deformation is less and there is more time life for an
IV tube as compare to stress value.
• From the above discussion, it can be mentioned that the shape of finger 3 is the most
suitable among the all three shapes as it has lower stress value compare to all of them
as well as creep rate is also better in compare to all of the fingers.
5.5 Future Scope
In the future, the experimental work can be carried out on actual test set-up. The finite
element analysis results can be compared for stresses and creep strain. The different shapes of
finger can be manufactured as per above suggestion and analysis can be done for 3 days. If
the results obtained is similar to the results found from the FEA analysis, then it can be
suggested to use that shape of finger to push the fluid in peristaltic pump.
48. 34
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