data gathering - universiti teknologi malaysiataminmn/data gathering_nov 2014.pdf · 2014. 11....
TRANSCRIPT
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DATA GATHERING(for engineering research)
MOHD NASIR BIN TAMIN(Ph.D. Mechanical Engineering and Applied Mechanics)
ProfessorDepartment of Applied Mechanics and Design
Faculty of Mechanical Engineering, UTM
ULP 0010 - Research Methodology
8th November 2014
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Mohd Nasir TAMINPh.D. Mechanical Engineering and Applied Mechanics, 1996 (USA)Professor, CEngDepartment of Applied Mechanics and Design, Faculty of Mech. Engng., UTMHead, Computational Solid Mechanics Laboratory
Some Research and Engineering Consultation:Fatigue damage mechanisms in SiC/Ti MMCFatigue characterization of TiAl intermetallic alloysFatigue life prediction of NGV compressor componentsReliability stress analysis on solder interconnects and TSVsFailure analysis of machine component and structures
Courses delivered:Mechanics of materialsFinite element methodFailure of engineering components and structuresFatigue and fracture mechanicsMaterials engineeringApplied Numerical MethodsAdvanced materials
BRIEF CV
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RESEARCH – a process
Identify researcharea
Literature review
ProblemIdentification
TheoreticalFramework
MethodologyResearch Design
Data Collection & Analysis
Conclusions
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A COURSE ON RESEARCH METHODOLOGY- A Typical Outline
Philosophy and Overview of Research Literature Review Problem Formulation Research Design Data Gathering, Instrumentation and Measurement Sampling Techniques of Data Analysis Academic Writing Thesis Presentation
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OBJECTIVES
To describe issues related to the working principles of devices associated with instrumentation.
To illustrate the principles and procedures involved in sampling and measuring physical quantities.
To identify methods and techniques in gatheringexperimental data.
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Prerequisite to data gathering
To review general considerations in the analysis of experimental data.
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Following data gathering…ROADMAP OF DATA ANALYSIS
MEASURED DATA
Curve-fitting
Numerical & Analytical
Models
(Extract model Parameters)
Verification & Validation
Reliability Analysis
Physical Aspects
Information / Knowledge
(Interpret & Establish)
(Comparative Study)
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TYPES OF DATA Generated data
Measured data Single reading
Random measurements
Time-dependent data
Others (micrographs)
Composition of steel (wt. %)
Introduction
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NATURE OF MEASURED DATA
Consistency
Uncertainty
Scatter
Outliers
Trends
Physical-based content
Evolution / history
Introduction
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CONSIDERATIONS IN DATA ANALYSIS Anticipate the results from theory
Examine the data for consistency
Reduce the data
Perform a statistical analysis of data where appropriate
Estimate the uncertainties in the results
Correlate the data
Interpret and extract information
Introduction
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Data Gathering InstrumentationMeasurement Sampling
OUTLINE
Servo-hydraulic universal testing machine with furnace for high-temperature test.
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DATA GATHERING (EXPERIMENTAL)
Activities of acquiring (measuring, observing, surveying) physical quantities of selected samples employing specific technique and instrument.
Collecting published information and data.
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Material: AISI 4340 SteelEXAMPLE 1 - MECHANICAL (TENSION) TEST
P
P
Lo+LLo
Ao
Elongation, L (in.)
Load
, P(lb
f)
THE SAMPLE
THE MACHINE / INSTRUMENT
THE MEASUREMENTS
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DATA GATHERING (EXPERIMENTAL)
WHAT is the data.
HOW to collect the data Direct measurement Observation / Survey Published data / Database
WHEN to collect data / measure
WHY need data collection.
WHERE data gathering is to be performed.
- SAMPLING
- INSTRUMENTATION
- MEASUREMENT
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OBJECTIVE
To determine the hardness number for a material by measurements of surface indention
Force
Indenter
SampleIndentation
EXAMPLE 2 – INDENTATION HARDNESS TEST
Data Gathering InstrumentationMeasurement Sampling
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INSTRUMENTATION
Micro-hardness tester
Working/ Test Principle
Machine/ System Characteristics
Calibration
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TEST PRINCIPLEHardness is determined by forcing a hardened indentor under a known load into the surface of a material and measuring the size of the indentation left after the test.
Select a suitable indentor
eg. 10-mm sphere
Apply known force(1 to 1000g)
Measure size of indentafter load removal
dDSmaller indent reflectsgreater hardness
2d2D-DDπ
P2BHN
BRINELL HARDNESS TEST
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Square-Based Diamond Pyramid d1
d2
HV = 1854.4L/d2
L is the load in gfd is the mean diagonal in µm
VICKERS HARDNESS TEST
TEST PRINCIPLE (Cont.)
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MACHINE / SYSTEM CHARACTERISTICS
Sensitivity Resolution Range Response Zero-setting Shake-downAutomatic features Repeatability and Reproducibility SAFETY
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DESIGN OF MEASURING SYSTEM
Sensitivity, S The change in output signal relative to the
change in input signal at an operating point k.
Resolution, R The smallest change in the input signal
that will yield an interpretable change in the output of the measuring device
Example: Resistance-based thermometerR() T(oC)307 200314 230321 260
kp
p
kIp
p
ΔI dIdO
ΔIΔO
Sp
p
0
lim
divisionscaleS
R 11
CΩ/.dIdO
S o
kp
p 2330200230307314
To ensure accuracy of measured quantity, sensitivity, resolution, range andresponse of the measuring device or system must be known.
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Range The maximum and minimum measurements that can be detected
by a measuring device.( Example: The range of a thermometer is between -10 oC to 110 oC.
The span is 120 oC)
Response The time taken by a measuring device to generate a signal to the
designed (uniform) level after receiving an input.
UNDERSTAND THE CHARACTERISTICS AND WORKING PRINCIPLES OF ALL MEASURING DEVICES / SYSTEMS USED.
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SENSITIVITY
When a small increment of input (excitation) causes a large change in the response (read-out) of the instrument.
Terikan
0.0 0.1 0.2 0.3 0.4 0.5
Tega
san
( MPa
)
0
200
400
600
Ujikaji AUjikaji B
E = 200x103 MPaRequires sensitive strain measuring device
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440C at 62.7 HRC
BUILT-IN SYSTEM RESPONSE
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REPEATABILITY(Hardness Test)
For each standardized block, let d1, d2 ..., d5 be the diagonal lengths of the indentations, arranged in increasing order of magnitude.
The repeatability of the machine is expressed by the quantity (d5 - d1)/ davg, where davg is the average of d1to d5.
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REPEATABILITY
Ability of the measuring instrument to produce identical readings repeatedly.
Hardness Test
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Universal testing machine
Specimen
Load cell
Specimen grips
Crosshead
Data acquisition system
Extensometer
ZERO-SETTING
FORCE DISP.
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SHAKE-DOWN
Application of repetitive small load magnitude to set-in the load train and avoid lag or back-lash.
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AUTOMATIC FEATURES
On-line data processing software provides a quick glance of the quality of collected test data.
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SAFETY
The operator (YOU) People around test set-up Machine and devices
Adopted from W. Wood, McGill University
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CALIBRATION
Setting/ tuning of measuring devices so as to output actual/ true quantity being measured.
Extensometer calibration curve for Instron 4206+8801Gauge Length = 25 mm
Travel Length = 12.5 mm22-02-2006
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45Measured Strain (mm/mm) [readings from console/PC]
App
lied
Stra
in (m
m/m
m) [
Rea
ding
s fr
om m
icro
met
er]
MeasuredStrain (Instron 8801)
MeasuredStrain (Instron 4206)
Measured quantity
True
/ ref
eren
ced
quan
tity
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What and How to measure
How many measurements are sufficient
Accuracy, Precision and Bias
Uncertainty
Error
MEASUREMENT
Data Gathering InstrumentationMeasurement Sampling
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Square-Based Diamond Pyramid d1
d2
HV = 1854.4L/d2
L is the load in gfd is the mean diagonal in µm
MEASUREMENT – VICKERS HARDNESS, HV
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HOW TO MEASURE
(MEASUREMENT OF LENGTH)
Learn how to read vernier sacles, dial gages and estimate of uncertainties.
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Near SurfaceMicrocracks
Case Structure Core
2% Nital
Flame Hardened 8660 Gear
FREQUENCY OF DATA COLLECTION
How many Hardness measurements are sufficient?
Depth
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Automated MHT HV Traverse
Flame Hardened 8660 Alloy Steel Gear
FREQUENCY OF DATA COLLECTION
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Accuracy – the degree to which the measurements deviate from the true value.
Precision – ability to give multiple estimates that are near to each other.
Bias - a systematic deviation of values from the true value.
Accuracy
Precision
ACCURACY, PRECISION AND BIAS
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Instrument Factors
(Hardness Test)
Accuracy of applied load Inertia effects, speed of loading Lateral indenter movement Indentation time Indenter shape deviations Damage to the indenter (plus films) Insufficient spacing between indents and from edges
FACTORS AFFECTING PRECISION AND BIAS
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Measurement Factors
(Hardness Test)
Calibration of measurement system Resolution of the opticsMagnification Operator bias in sizing indents Inadequate image quality Non-uniform illumination
FACTORS AFFECTING PRECISION AND BIAS
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Material (Specimen) Factors
(Hardness Test)
Heterogeneity in composition and microstructure Crystallographic texture Quality of specimen preparation Low reflectivity or transparency
FACTORS AFFECTING PRECISION AND BIAS
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UNCERTAINTY ESTIMATION
Report: Pressure, p = 100 kN/m2 ± 1 kN/m2
For a set of n experimental measurements {x1, x2, x3,…,xn}with uncertainty {w1, w2, w3,…,wn}
The uncertainty, wR, in the desired result, R = R(x1, x2, x3,…,xn) is
2/122
22
2
11
...
nn
R wxRw
xRw
xRw
Ref: Kline, S.J. and F.A. McClintock, “Describing Uncertainties in Single-Sample Experiment”, Mech. Eng., pp. 3, Jan. 1953
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Example 3:
The resistance of a certain size of copper wire is given as:
R = Ro [1 + (T – 20)]
Where Ro = 6 ± 0.3 pct. at 20 oC = 0.004 /oC ± 1 pct.T = 30 oC ± 1 oC
Calculate the resistance of the wire and its uncertainty
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Solution 3:Nominal value of the resistance:
R = Ro [1 + (T – 20)] = 6 [1 + (0.004) (30 – 20)] = 6.24 Uncertainties:
= 1 + (T – 20) = 1 + (0.004) (30-20) = 1.04
= Ro (T-20) = 6 (30-20) = 60
= Ro = 6 (0.004) = 0,024
oRR
R
oRR
wRo = 6 (0.003) = 0.018
w = (0.004) (0.01) = 4x10-5 /oC
wT = 1 oC
wR = [(1.04)2 (0.018)2 + (60)2 (4x10-5)2 + (0.024)2 (1)2 ]1/2 = 0.0305 or 0.49 pct.
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ERROR(Hardness Test)
• The error of the machine is expressed by the quantity dstd - davg, where davg is the average of the indentation diagonals and dstd is the value provided on the test block certification.
• The average observed diagonal shall not differ from the certificate diagonal by more than 2% or 0.5 mm, whichever is greater.
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INACCURACY OF MEASUREMENTS
Instrument Calibration
Instrument Reproducibility
Measuring arrangement
Work piece
Environmental Conditions
Observer’s Skill
The purpose of measurements is to describe some physical properties of an object / material / system quantitatively
Sources of Error
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SCATTER OF MEASURED DATA
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Stress-Life (S-N) Curve
Wrought steel
Dealing with inherently large scatter in the measured quantity
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SAMPLING DESIGN
Materials:• Virgin• Retired
Location of cut for retired samples
Direction of cutfor specimen
Shape, size and numberof specimens
Example 4:
Creep-fatigue interaction effects on high-strength steels
Data Gathering InstrumentationMeasurement Sampling
Ref. : ASTM E370
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STATISTICAL CONSIDERATION
Influence of the distribution of variables
(e.g. Stress and strength, household expenditure and income)
Pf = P( Stress Strength)
R = 1 - Pf
QUALITY versus
RELIABILITY
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SAMPLING PROCEDURES
Unrestricted Random SamplingRandom sample selection from the population as a whole.
Stratified Random SamplingPartition the population into known meaningful strata. Random selection is made within each stratum, making sure all strata are represented.
Optimum-allocation-of-strata Random SamplingIf information about the population strata and the way they will be used is available, optimum sample selection is made to give the most representative information about the population.
To obtain a representative sample with maximum randomness.
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FATIGUE TEST PROCEDURES
P, R = -1
Stre
ss
Time
Completely reversed axial fatigue
(This test is commonly done in reversed bending cycles)Raw data:
Stress(MPa)
Nf
(cycles)
1 pair of data per specimen
0
SAMPLING
How many test samples are sufficient?
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Fatig
ue s
treng
th, S
f(M
Pa)
300
400
500
600
800
1000
Cr-Mo steel, normalized
SUT = 800 MPa
Se = 338 MPa
Ref: Shigley, J.E., Mechanical Engineering Design, First Metric Edition, McGraw-Hill, 1986
Fatigue limit /
Endurance limit
Stress-Life (S-N) Curve
IDENTIFY THE DESIRED RESULTS
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Fatigue limit – tensile strength relationship
Adding to available published data
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REGRESSION / CURVE FITTING
Regression is a process used by statisticians to obtain a curve which best fit a set of data points.(But you are not a statistician!)
To plot curves of experimental data and extract various significant facts from these curves(Must understand physical phenomena involved in the experiment)
Correlation of experimental data is desired in terms of an analytical expression between variables that were measured in the experiment.
Requirements for a regression analysis
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Material: AISI 4340 SteelMECHANICAL (TENSION) TEST
P
P
Lo+LLo
Ao
Elongation, L (in.)
Load
, P(lb
f)
DEMO
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STRAIN,
0.0 0.1 0.2 0.3 0.4 0.5 0.6
STR
ESS,
(M
Pa)
0
200
400
600
800
Example 6 – Curve fitting
ALYAWS RELATE EXPERIMENTAL DATA TO THE PHYSICS OF THE PHENOMENON
STRAIN,
0.0000 0.0002 0.0004 0.0006 0.0008 0.0010ST
RES
S,
(MPa
)0
50
100
150
200
= ELinear
Non-linear /Power-law
= E
= K(p)n
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PLASTIC STRAIN, p
0.0 0.1 0.2 0.3 0.4 0.5 0.6
STR
ESS,
(M
Pa)
0
100
200
300
400
500
600
700
PLASTIC STRAIN, p
0.01 0.1 1
STR
ESS,
(M
Pa)
100
1000
= Kn
log K = 2.8735n = 0.1992r2 = 0.9772
199.03.747 p
ALYAWS RELATE EXPERIMENTAL DATA TO THE PHYSICS OF THE PHENOMENON
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Fatigue crack growth rate data for TiAl intermetallic alloyExample 8 – Physical Mechanisms
Indirect measurement of property
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Fatigue crack growth rate data for TiAl intermetallic alloy
Trends of measured / analyzed data
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Fatigue crack growth rate data for TiAl intermetallic alloy
We should be able to describe the physical mechanism of observed phenomenon
Gathering physical information
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• American Standard for Testing and Materials (ASTM)ASTM E139 – 00 Standard Test Method for Conducting Creep, Creep-Rupture,
and Stress-Rupture Tests of Metallic Materials
• International Standard (ISO)ISO 6892:1998(E) Metallic Materials – Tensile Testing at Ambient Temperature
• European Standard (EN), British Standard (BS)EN ISO 7500-2:1999 E Metallic Materials – Verification of Static Uniaxial Testing
Machines – Part 2: Tension Creep Testing Machines – Verification of the Applied Load
• Japanese Industrial Standard (JIS)JIS Z 2271:1999 (E) Method of Creep and Creep Rupture Test for Metallic Materials
• Malaysian Standard (MS)MS ISO 1352:1998 Steel – Torsional Stress Fatigue Testing
TESTING STANDARDS
STANDARDS AND GUIDELINES
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LEVEL OF EXACTNESS
DATA
INFORMATION
FACTS
KNOWLEDGE
Level of improvements in decision making
Leve
l of e
xact
ness
of
stat
istic
al m
odel
WISDOM
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Q & A SESSION