Guoxing Li - TEPEN
Transcript of Guoxing Li - TEPEN
Taiyuan University of Technology
University of Huddersfield
24th Oct 2020
Guoxing Li
Background & significance Modelling Fault diagnosis Conclusions
Background and significance
Modelling of tribo-dynamic behaviours
Applications in mechanical fault diagnosis
Conclusion and future work
Outline
Motivation and Significance
Tribo-dynamic behaviours widely exist in variousmechanical engineering fields.
Tribo-dynamics is a new field that has emergedfrom the confluence of structural dynamics,contact mechanics and tribology. Central tothese three fields is the study of interactionsbetween interfaces; the difference comes in thelength scale considered and the tools used tostudy an interface interaction.
Modelling of tribo-dynamics between interactiveinterfaces is of great significance for subsequentmechanical fault diagnosis and reliabilityoptimization.
Background & significance Modelling Fault diagnosis Conclusions
Motivation and Significance
Deterioration of tribo-dynamics behaviour can causeserious failures and losses. Therefore, it is of greatimportance to implement an accurate conditionmonitoring of early faults in friction pairs.
Prognostic of fatal accidents and estimation of residual life.
Guidance for optimization of operation and maintenance.
Guidance for optimal design of friction pairs to improve efficiency and reliability.
……
Background & significance Modelling Fault diagnosis Conclusions
Outline
Background and significance
Modelling of tribo-dynamic behaviours
Applications in mechanical fault diagnosis
Conclusion and future work
Background & significance Modelling Fault diagnosis Conclusions
Modelling of tribo-dynamic behaviours
It is necessary to combine structural dynamics, tribology and contact mechanics to model tribo-dynamic behaviours in multi-disciplinary and cross-scale. According to the length scale of interface interaction, models can be divided into three types
(Cross-scale modeling)
e.g. Transient elastic waves (Acoustic Emission) produced by micro-tribological behaviours
Macroscopic model
Combination of dynamic model and tribological model
Mesoscopic model Influences of micro characteristics on macro response
Microscopic modelWeak dynamic response caused by micro-interface interaction
Background & significance Modelling Fault diagnosis Conclusions
Macroscopic model of tribo-dynamics
The continuously knocking behaviour of piston against the cylinder liner driven by gasand inertial force is a typical tribo-dynamic behaviour. It includes impact mechanics,structural transient dynamics, elasto-hydrodynamic lubrication, boundary lubrication, etc.
Combination of dynamic and tribological model
Background & significance Modelling Fault diagnosis Conclusions
Macroscopic model of tribo-dynamics
Combining structural dynamics and elastohydrodynamics to construct a fluid-solid coupling model of piston assembly is helpful to reveal the coupling relationship between in-cylinder combustion behaviour, structural dynamics and physio-chemical properties of lubricant.
Combination of dynamic and tribological model
Background & significance Modelling Fault diagnosis Conclusions
1 2 3 4 50
2000
4000
6000
8000
1 2 3 4 50
5
10
Measured vibration
Simulated vibration
The tribo-dynamics model can effectively predict the non-linear trend of vibration response with increasing speed.
Macroscopic model of tribo-dynamics
RMS of liner vibration
slap-induced vibration after combustion TDC
Background & significance Modelling Fault diagnosis Conclusions
A B CE F D
Mesoscopic model of tribo-dynamics
Generally, the length scale of structural dynamic behaviour is on the order of micrometer-millimeter, and the scale of geometric interface characteristics is on the order of nanometer-submicron. To study the interaction between cross-scale factors, such as the effect of surface roughness on structural vibration, it is necessary to merge the two on meso-scale.
Case 1: Introduction of high-frequency surface deformation into lubrication modeling
Case 2: Vibration characteristics induced by tribofilm-asperity interactions in hydrodynamic journal bearings
Background & significance Modelling Fault diagnosis Conclusions
Introduction of surface deformation into lubrication model
Establishment of Finite Element Model
(Modal characteristics) Structural transient dynamics simulation
(Contact constraints) Nonlinearities of assembly constraint
Case 1
Background & significance Modelling Fault diagnosis Conclusions
(a) Transient dynamic simulation in ANSYS workbench
(b) Deformation result imported into post-processing software
(c) Node displacements in Cartesian coordinate
(d) Node displacements in a 2D coordinate system containing the axial and circumferential directions.
(e) Filtered deformation
(f) Improved oil film thickness distribution
Case 1Introduction of surface deformation into lubrication model
Background & significance Modelling Fault diagnosis Conclusions
The simulated friction force based on the improved model shows:1, modal-related friction fluctuations2, reduction in viscous friction ↘3, sharp peak of asperity friction around 380° ↗
Case 1
Background & significance Modelling Fault diagnosis Conclusions
Introduction of surface deformation into lubrication model
Vibration-induced friction reduction
Vibration induced by tribofilm-asperity interactions
3 2 26 12p h hh R Rt
Infinitely long bearing theory
3 2 26 12o o oo
p h hh R Rt
3 2 2 26 12 3asp asp asp oo o asp
p h h ph R R h ht
Decoupled perturbation Reynoldso asph h h
o aspp p p
ho=c[1+εcos(θ-Φ)]
According to the perturbation theory, the bearing will undergo small amplitude oscillations at its steadystateposition which may caused by interaction between tribofilm-asperities.
Since h0 and hasp are of the order of millimetre and micrometre respectively, hasp can be reasonably viewed as a perturbation component to the macroscopic film thickness h0.
Case 2
Background & significance Modelling Fault diagnosis Conclusions
Journal bearing test rig
Journal bearing test rig and sensors location
Self-aligning journal bearing components
Case 2
Surface topography of the journal on shaft 3:
(a) photomicrograph (Ra=2.51 µm) (b) 3D surface profile
(b) (c) height probability distribution (d) power spectral density.
Background & significance Modelling Fault diagnosis Conclusions
Vibration induced by tribofilm-asperity interactions
Vibration spectrum with the worn journal surface under different operating conditions:
radial load of 3 bar
Case 2
Background & significance Modelling Fault diagnosis Conclusions
As the journal surfaces topography changed from mild wear to severe wear, the amplitudes of the spatial components increase particularly at the low spatial frequencies. Therefore, it generates a strong excitation within a certain frequency range. With the increase of the speeds (1200rpm-2100rpm), the frequency bandwidth of resonant responses becomes wider and moves higher.
1. The random pressure fluctuation occurs between the tribofilm and dynamic asperities is one of the significant excitation sources for the resonant vibrations of journal bearings in the hydrodynamic lubrication regime.
2. The excitation intensity is tightly related to the journal surface parameters and operating conditions.
Microscopic model of tribo-dynamics
Acoustic Emission (AE) describes the radiating phenomenon of transient elasticwaves caused by the redistribution of stress in the material. Generally, AE canbe generated from various sources, such as fluid friction, delamination, crackgrowth and sliding friction. The released energy from these activities has a lowamplitude and wide frequency band.
Establishing a model of AE generation from tribo-dynamics and developingweak feature extraction algorithm is very important for non-intrusive monitoringof early friction and wear in rotating machinery and reciprocating machinery.
Case 1: Modelling acoustic emissions generated by asperity-asperity contact(Yibo Fan, Fengshou Gu, Andrew Ball, 2010)
Case 2: Modelling acoustic emissions induced by dynamic fluid-asperityshearing (Jiaojiao Ma, Hao Zhang, Zhanqun Shi, Fulei Chu, Fengshou Gu,Andrew D. Ball, 2020)
Background & significance Modelling Fault diagnosis Conclusions
Acoustic emissions generated by asperity-asperity contact
A theoretical model based on the Greenwood-Williamson(GW) model has been developed to validate therelationship between AE pulses and the elastic strainenergy generated by the asperity-asperity contact on theroughness surfaces.
• Fan Y, Gu F, Ball AD. Modelling acoustic emissions generated by sliding friction. Wear 2010; 268: 811–5.
Asperity contacts on rough surfaces
312 24( )
3e eL ER
12
12
1_
(h)0.3(h)AE asp c e
FU K NL vRF
12
12
1(h)0.3(h)E e
FU NL vRF
is release rate of elastic energyKc is portion of the elastic strain energy converts to AE pulses Le is the elastic loadFn(h) is probability density function
The level of AE measurement is determined by the load supported by asperity contact, sliding speed, the number of asperity contact and surface topographic characteristics.
EU
Background & significance Modelling Fault diagnosis Conclusions
Acoustic emissions generated by fluid-asperity shearing
Nevertheless, the mechanism and time-frequency characteristics of AE signals generated from the process of dynamic fluid-asperity shearing (FAS) are still ambiguous in the local level.
In hydrodynamic lubrication regime, where there are no micro-asperity contacts, as shown on the right, the asperity deformation is nil.
Changes in shear force will induce different deformations to the asperities. As the deformations of asperities recover in a short time duration, the transient rapid release of energy transfers to the plate as a form of AE waves.
Low stress Low stressHigh stress
Asperity-valley Asperity-asperityAsperity deformation
Asperity-valleyAsperity recovery
u
(a)
asp1
- asp2
h0h
FF F
F
F F
h1 h2 h3
u
(b)
u
(c)
FF F
F
F F
AE waves
Background & significance Modelling Fault diagnosis Conclusions
Fluid-asperity shearing (FAS) in lubricated rough surfaces
Acoustic emissions generated by fluid-asperity shearing
ℎ 𝑥,𝑦, 𝑡 ℎ 𝛿 𝑥,𝑦, 𝑡
𝜏 𝑥,𝑦, 𝑡 𝜂 e𝑢
ℎ 𝛿 𝑥,𝑦, 𝑡ℎ
2 ℎ 𝛿 𝑥,𝑦, 𝑡
𝜕𝑝𝜕𝑥
The combining amplitude of asperities on the relative sliding surfaces is
𝛿 𝑥,𝑦, 𝑡 𝛿 𝑥 𝑢𝑡,𝑦 𝛿 𝑥 𝑢𝑡,𝑦
The instantaneous fluid film thickness isthe instantaneous film thickness between the relative sliding surfaces is a function of time/space.
Therefore, the dynamic FAS model is derived as
Due to the consideration of asperity topographic characteristics, oil physic-chemical properties and relative movement parameters, FAS model can characterize the acoustic emission level caused by fluid-asperity shearing.
Background & significance Modelling Fault diagnosis Conclusions
Outline
Background and significance
Modelling of tribo-dynamic behaviours
Applications in mechanical fault diagnosis
Conclusion and future work
Background & significance Modelling Fault diagnosis Conclusions
Background & significance Modelling Fault diagnosis Conclusions
Macroscopic model
Mesoscopic model
Microscopic model
Applications in mechanical fault diagnosis
For different types of tribo-dynamic behaviour and failure events, based on models of different length scales, a variety of condition monitoring and fault diagnosis technologies have been developed.
Vibration-based
AE-based
Dynamic behaviours
other events related to dynamics ...
Tribological behaviours
other events related to tribology ...
Vibration-based lubrication monitoring of piston-cylinder pairs
Vibration-based combustion status monitoring for IC engines
Vibration-based NOx/PM emission monitoring for engines
AE-based elastohydrodynamic lubrication monitoring
AE-based lubrication monitoring of IC engines
AE-based abnormal wear detection for IC engines
AE-based gear wear monitoring
AE-based prognostic of wear and scuffing failures in IC engines
Vibration-based lubrication monitoring of piston-liner pairs
Test rig for cylinder liner vibration measurement
DAQ
Dynamometer
Acc
eler
omet
er
Pressure Sensor
Ang
ular
spee
d
Control system
Background & significance Modelling Fault diagnosis Conclusions
Vibration-based lubrication monitoring of piston-liner pairs
Piston SlapCombustion
Com. TDCExh. TDC
1st modal
4th modal
TS ATS
CWT of measured vibration
Based on macroscopic tribo-dynamic model, various excitation sources associated with different local vibration responses can be corresponded and monitored.
Background & significance Modelling Fault diagnosis Conclusions
Background & significance Modelling Fault diagnosis Conclusions
Vibration-based lubrication monitoring of piston-liner pairs
TS ATS
With the increase of oil viscosity, the magnitude of the impact response basically shows a downward trend.
Experimental results show that differences in the lubricant condition can definitely cause observable changes in the dynamic responses of cylinder liners in IC engines.
0°/360°
180°
90°270°
TDC720°
540°BDC
E
FA
B
C
D
I
G
450°630°
Hw
avel
et c
oeffi
cien
t
wav
elet
coe
ffici
ent
(a) 10Nm (b) 40Nm.
RMSs of slap responses after exhaust TDC
Vibration-based combustion status monitoring
CWTs of vibration measured in engines burning different fuels
Diesel Biodiesel
Background & significance Modelling Fault diagnosis Conclusions
Vibration-based combustion status monitoring
RMS of vibration response after combustion TDC fueled withbiodiesel shows a nonlinear tendency of decrease after an increase with the increase of speed
Δt
2sin / 1 ( sin )=( )y c i c iF F F t tp p
The advanced ignition caused by the high cetane number of biodiesel has a significant contribution to the compound effect on the piston side-thrust force, thereby resulting in a nonlinear trend of the RMSs of local response near the combustion TDC.
Background & significance Modelling Fault diagnosis Conclusions
Vibration-based NOx/PM emission monitoring for engines
vibration combustion exhaust emission
reconstruct evaluate
Vibration Based Virtual Sensing of NOx/PM Emission in CI Engines
Background & significance Modelling Fault diagnosis Conclusions
Background & significance Modelling Fault diagnosis Conclusions
c.Structural similarity index (SSIM) analysis
d.Morphological reconstruction
a.Selection of source data
b.Image graying
Vibration-based NOx/PM emission monitoring for engines
1 : Measured emissions;2-12: Predictor variables.
Operatingconditions
Am
plit
ude
[-]
a. Predictor variablesb. Principal component analysis
Background & significance Modelling Fault diagnosis Conclusions
There is a good correlation between structural vibration characteristics and measured NOx emissions. This provides a novel way for low-cost transient emission monitoring.
c. Comparison of predicted and measured NOx
Vibration-based NOx/PM emission monitoring for engines
AE-based elastohydrodynamic lubrication monitoring
Fig. 4. Cone-plate based a rheometer
𝜏 𝑟,𝜃, 𝑡 𝜂 eΩ 𝛼⁄
1 𝛿 𝑟,𝜃, 𝑡 𝑟𝛼⁄
where 𝛿 𝑟,𝜃, 𝑡 𝑧 𝑠𝑖𝑛 2𝜋𝑟𝜒 𝜃 𝛺𝑡 𝜁
Ω
rR
z
0
rx
z
yθ
rp
α
h0
Dynamic FAS resulting from the cone-plate with the roughness surface:
𝑎𝑛𝑑 𝑧 2𝐺 𝜒 , Δ𝜒
Ω : angular speed 𝜃 : the angle in the range from 0 to 2𝜋 degree.𝜁 : random initial phase angles. 𝐺 : the spatial PSD of the random heights𝜒 : the spatial frequency𝜒 , : the centre frequency Δ𝜒 : the width of each frequency interval
: shear rate: radius
h : radius
𝛼 𝑠𝑖𝑛𝛼 𝑡𝑎𝑛𝛼
ℎ 𝑟𝑡𝑎𝑛𝛼 𝑟𝛼
𝛾𝛺𝑟ℎ
𝛺𝑟𝑟𝛼
𝛺𝛼
𝛾𝑟
Rheometer test rig and AE sensor location
Fluid-Asperities Shearing (FAS) model is derived to investigate the influence of surface profiles, lubricants and operating conditions on AE characteristics. Experiments are carried out based on a rheometer rig.
Background & significance Modelling Fault diagnosis Conclusions
AE-based elastohydrodynamic lubrication monitoring
Results and discussion Results and discussion Results and discussion
Characteristics of the dynamic FAS simulated and AE measured with different operating conditions: (a) normalised RMS and (b) highest Frequency of the frequency band.
It has been found that the correlation length of surface roughness parameters and shear rate are
two main factors affecting FAS behaviours and consequently AE characteristics.
It shows that AE signals can effectively characterize the changes in surface topography
parameters and shearing rate in HL regime.
Background & significance Modelling Fault diagnosis Conclusions
AE-based lubrication monitoring of IC engines
Direction of piston motion
In-cylinderpressure
piston
Line
r
asperities
ringliner
film
12
12
1_
(h)0.3(h)AE asp c e
FU K NL vRF
EU
The level of AE measurement is determined by the load supported by asperity contact, sliding speed, the number of asperity contact and surface topographic characteristics.
Oil film
piston
Direction of piston motion
Line
r
ring
asperities
Asperity–Asperity Contact Fluid-Asperity Shearing
0
( ) ( ) ( , , ) ( , , ) ( , , )( ) [ ( , , )]3 2 ( , , )
izr b p d ib
l i
d k v t N t z w h x y t p x y t x y tAE t v x y t dyE I y h x y t
Background & significance Modelling Fault diagnosis Conclusions
Background & significance Modelling Fault diagnosis Conclusions
AE-based lubrication monitoring of IC engines
Schematic diagram of the diesel engine test system
AE WPT spectra in power stroke for the used oil at different speeds and high load.
Diversities of changes in AE amplitudes in different bands can be effective indicators of the degradation of lubricating oils, as the deviations from linear trends can provide additional reliable information for differentiating between baseline oils and used oils.
AE-based abnormal wear detection for IC engines
Wear detection of piston components
Acoustic emission and vibration sensors are installed on the surface of cylinder block near the combustion chamber to detect abnormal collisions and friction events pf piston assembly.
Acoustic emission and vibration signals measured on engine block
0 90 180 270 360 450 540 630 7200
0.5
1
E
VO
E
VC
IV
O
IV
C
Power
幅值
(V)
0 90 180 270 360 450 540 630 7200
20
40
E
VO E
VC
IV
O
IV
C
Power
曲 角轴转 (°)
幅值
(V)
piston
Piston pin end
Background & significance Modelling Fault diagnosis Conclusions
Ampl
itude
(V)
Ampl
itude
(V)
Angle(°)
An abnormal wear on the small end of a connecting rod was found.
AE-based abnormal wear detection for IC engines
Fault diagnosis of bearing bush
Combining the crankshaft displacement measured by the laser sensor and the acoustic emission signal, the radial force of the bearing bush was calculated, and then an early wear failure of bearing bush was diagnosed.
0 90 180 270 360 450 540 630 720-2
0
6x 104 直方向的 承力竖 轴
曲 角轴转 (o)
承力
轴(N
m)
10Nm-1000r/min10Nm-1400r/min10Nm-1800r/min
0 90 180 270 360 450 540 630 720-2
0
2x 104
曲 角轴转 (o)
承力
轴(N
m)
水平方向的 承力轴
10Nm-1000r/min10Nm-1400r/min10Nm-1800r/min
10000Nm
30000Nm
50000Nm
90°
270°
180° 0°
Bearing forces in vertical and horizontal directions
Bearing loadBackground & significance Modelling Fault diagnosis Conclusions
Ampl
itude
(V)
Load
(N)
AE-based abnormal wear detection for IC engines
The position where the abnormal acoustic emission signal occurs is exactly the same as the timing of the peak of the oil pressure change rate curve (that is, when the pressure relief valve is opened), indicating that the pressure relief valve is working abnormally.
Sensor layout and lubrication circuit
0 90 180 270 360 450 540 630 7200
1
2
3
4
5
6
7
曲 角轴转 (°)
幅值
(V)
限压阀 异常声 射信号发 比对 图- 1800r/min-10Nm
油 前调节 压
油 后调节 压
0 90 180 270 3600.65
0.7
0.75
0.8
0.85
0.9
机油
力幅
压值
(MP
a),
0 90 180 270 360 450-0.4
-0.3
-0.2
-0.1
0
0.1
0.2
0.3
0.4
0.5
异常声
射信号
幅发
值 (V
)
0 90 180 270 360-200
-100
0
100
200
300
机油
力化率幅
压变
值 (M
Pa/
s)
曲 角轴转 (°)
机油 力压
机油 力 化率压 变
异常声 射信号发
Oil pressure, pressure change rate and abnormal acoustic emission signal
Fault diagnosis of pressure limiting valve Normal and abnormal acoustic emission signals
Background & significance Modelling Fault diagnosis Conclusions
Ampl
itude
(V)
AbnormalNormal
Oil
pres
sure
(M
Pa)
Oil presuurePressure change rateAE signal
Pres
sure
cha
nge
rate
(M
Pa)
Ampl
itude
(V)
AE-based prognostic of wear and score failures
AE corresponding to different oil supply
piston seizure/ cylinder score
Extract characteristic signals related to asperity-asperity contact events from measured acoustic emission signal, to monitor the occurrence of abnormal wear in real time, and to provide early warning of cylinder failure.
Background & significance Modelling Fault diagnosis Conclusions
As the supply of lubricating oil decreases, the amplitude of the acoustic emission signal increases significantly.
AE-based gear wear monitoring
0°: Boundary lubrication 0°-2.9°: Mixture lubrication 2.9°: Boundary lubrication 4.1°: close to 0
4.1°- 5.2°: Boundary lubrication 5.2° : Hydrodynamic lubrication 9.4°: speed increase, mixture lubrication
Ampl
itude
angle
peak
viscosity
peak
peak
speed /% load /%
loadloadloadload
loadloadloadload
Background & significance Modelling Fault diagnosis Conclusions
Outline
Background and significance
Modelling of tribo-dynamic behaviours
Applications in mechanical fault diagnosis
Conclusion and future work
Background & significance Modelling Fault diagnosis Conclusions
Conclusions
Tribo-dynamic behaviours can be modeled in combination with structural dynamics, tribology, and contact mechanics. According to the length scale of interface interaction, models of tribo-dynamics can be divided into three types: Macroscopic model, Mesoscopic model and Microscopic model.
According to the perturbation theory, macro dynamic response can be affected by micro tribo-dynamic interactions, which provides a new way to achieve condition monitoring of cross-scale behaviour and early fault diagnosis.
For different types of tribo-dynamic behaviour and failure events, based on models of different length scales, corresponding technologies can be developed for monitoring and diagnosis.
Background & significance Modelling Fault diagnosis Conclusions
Technology Outlook
Condition monitoring and failure warning of high value-added mechanical systems
The potential of cross-scale feature detection demonstrated by perturbation theory provides novel approaches for early fault diagnosis and residual life prediction.
Based on in-depth theoretical understanding, the optimal design of friction pairs can be further carried out to pursue friction reduction and reliability improvement.
Background & significance Modelling Fault diagnosis Conclusions