SIST EN 16603-32-11:2014
(Main)Space engineering - Modal survey assessment
Space engineering - Modal survey assessment
EN 16603-32-11 specifies the basic requirements to be imposed on the performance and assessment of modal survey tests in space programmes. It defines the terminology for the activities involved and includes provisions for the requirement implementation. This Standard specifies the tasks to be performed when preparing, executing and evaluating a modal survey test, in order to ensure that the objectives of the test are satisfied and valid data is obtained to identify the dynamic characteristics of the test article. This standard may be tailored for the specific characteristics and constrains of a space project in conformance with ECSS-S-ST-00.
Raumfahrttechnik - Modale Prüfungsbewertung
Ingénierie spatiale - Evaluation des modes vibratoires
Vesoljska tehnika - Ocenjevanje modalnega pregleda
Standard EN 16603-32-11 določa osnovne zahteve za učinkovitost in ocenjevanje modalnega pregleda na področju vesoljskih programov. Določa terminologijo za zajete dejavnosti in vključuje določbe za izvajanje zahtev. Ta standard določa naloge, ki jih je treba opraviti pri pripravi, izvedbi in vrednotenju ocenjevanja modalnega pregleda, da bi zagotovili, da so cilji preskusa izpolnjeni in da so pridobljeni veljavni podatki za identifikacijo dinamičnih značilnosti preskusnih izdelkov. Ta standard se lahko prilagodi posameznim lastnostim in omejitvam vesoljskega projekta v skladu s standardom ECSS-S-ST-00.
General Information
Standards Content (Sample)
SLOVENSKI STANDARD
SIST EN 16603-32-11:2014
01-november-2014
Vesoljska tehnika - Ocenjevanje modalnega pregleda
Space engineering - Modal survey assessment
Raumfahrttechnik - Modale Prüfungsbewertung
Ingénierie spatiale - Evaluation des modes vibratoires
Ta slovenski standard je istoveten z: EN 16603-32-11:2014
ICS:
49.140 Vesoljski sistemi in operacije Space systems and
operations
SIST EN 16603-32-11:2014 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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SIST EN 16603-32-11:2014
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SIST EN 16603-32-11:2014
EUROPEAN STANDARD
EN 16603-32-11
NORME EUROPÉENNE
EUROPÄISCHE NORM
August 2014
ICS 49.140
English version
Space engineering - Modal survey assessment
Ingénierie spatiale - Evaluation des modes vibratoires Raumfahrttechnik - Modale Prüfungsbewertung
This European Standard was approved by CEN on 23 February 2014.
CEN and CENELEC members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving
this European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning
such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN and CENELEC
member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by translation
under the responsibility of a CEN and CENELEC member into its own language and notified to the CEN-CENELEC Management Centre
has the same status as the official versions.
CEN and CENELEC members are the national standards bodies and national electrotechnical committees of Austria, Belgium, Bulgaria,
Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece,
Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia,
Slovenia, Spain, Sweden, Switzerland, Turkey and United Kingdom.
CEN-CENELEC Management Centre:
Avenue Marnix 17, B-1000 Brussels
© 2014 CEN/CENELEC All rights of exploitation in any form and by any means reserved Ref. No. EN 16603-32-11:2014 E
worldwide for CEN national Members and for CENELEC
Members.
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EN 16603-32-11:2014 (E)
Table of contents
Foreword . 5
1 Scope . 6
2 Normative references . 7
3 Terms, definitions and abbreviated terms . 8
3.1 Terms from other standards . 8
3.2 Terms specific to the present standard . 8
3.3 Abbreviated terms. 22
3.4 Notation . 23
4 General objectives and requirements . 25
4.1 Modal survey test objectives . 25
4.1.1 Overview . 25
4.1.2 General . 25
4.1.3 Verification of design frequency . 25
4.1.4 Mathematical model validation . 26
4.1.5 Troubleshooting vibration problems . 26
4.1.6 Verification of design modifications . 26
4.1.7 Failure detection . 27
4.2 Modal survey test general requirements . 27
4.2.1 Test set-up . 27
4.2.2 Boundary conditions . 28
4.2.3 Environmental conditions . 28
4.2.4 Test facility certification . 28
4.2.5 Safety. 29
4.2.6 Test success criteria . 29
5 Modal survey test procedures . 31
5.1 General . 31
5.2 Test planning . 31
5.2.1 Test planning . 31
5.2.2 Pre-test activities . 33
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5.2.3 Test activities . 33
5.2.4 Post-test activities . 34
5.3 Test set-up . 34
5.3.1 Definition of the test set-up . 34
5.3.2 Test boundary conditions . 34
5.3.3 Test instrumentation . 36
5.3.4 Excitation plan . 37
5.3.5 Test hardware and software . 38
5.4 Test performance. 38
5.4.1 Test . 38
5.4.2 Excitation system . 38
5.4.3 Excitation signal . 39
5.4.4 Linearity and structural integrity. 40
5.4.5 Measurement errors . 40
5.5 Modal identification methods . 41
5.6 Modal parameter estimation methods . 42
5.7 Test data . 42
5.7.1 Quality checks . 42
5.7.2 Generalized parameters . 44
5.7.3 Effective masses . 44
5.7.4 Data storage and delivery . 45
5.8 Test-analysis correlation . 46
5.8.1 Purpose . 46
5.8.2 Criteria for mathematical model quality . 47
6 Pre-test analysis . 49
6.1 Purpose . 49
6.2 Modal survey test FEM . 49
6.2.1 Purpose . 49
6.2.2 Reduction of the detailed FEM . 50
6.3 Test analysis model (TAM) . 52
6.3.1 Purpose . 52
6.3.2 TAM accuracy . 53
6.3.3 Measurement point plan (MPP) . 53
6.3.4 Test predictions . 54
6.3.5 Test fixture participation . 54
6.4 Documentation . 55
6.4.1 FEM documentation . 55
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6.4.2 TAM documentation . 55
Annex A (informative) Excitation signals . 57
A.1 Overview . 57
A.2 Purpose and classification . 57
A.3 Excitation methods . 58
Annex B (informative) Estimation methods for modal parameters . 61
B.1 Overview . 61
B.2 Theoretical background and overview. 61
B.3 Frequency domain methods . 67
B.4 Time domain methods . 71
Annex C (informative) Modal test - mathematical model verification
checklist . 74
Annex D (informative) References . 76
Bibliography . 77
Figures
Figure 5-1: Test planning activities . 32
Figure 5-2: Comparison of mode indicator functions (MIF)
according to Breitbach and Hunt . 43
Figure 6-1: Modal survey pre-test analysis activities . 50
Tables
Table 5-1: Test objectives and associated requirements for the test boundary
conditions . 35
Table 5-2: Most commonly used correlation techniques . 46
Table 5-3: Test-analysis correlation quality criteria . 48
Table 5-4: Reduced mathematical model quality criteria . 48
Table 6-1: Advantages and disadvantages of model reduction techniques . 52
Table B-1 : Overview and classification of commonly used modal parameter estimation
methods . 64
Table B-2 : Advantages and disadvantages of the time and frequency domain methods. 65
Table B-3 : Advantages and disadvantages of single and multiple degree of freedom
methods . 66
Table B-4 : Other aspects of selecting a modal parameter estimation method . 67
Table C-1 : Verification checklist for mathematical models supporting modal survey
tests . 75
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Foreword
This document (EN 16603-32-11:2014) has been prepared by Technical
Committee CEN/CLC/TC 5 “Space”, the secretariat of which is held by DIN.
This standard (EN 16603-32-11:2014) originates from ECSS-E-ST-32-11C.
This European Standard shall be given the status of a national standard, either
by publication of an identical text or by endorsement, at the latest by February
2015, and conflicting national standards shall be withdrawn at the latest by
February 2015.
Attention is drawn to the possibility that some of the elements of this document
may be the subject of patent rights. CEN [and/or CENELEC] shall not be held
responsible for identifying any or all such patent rights.
This document has been prepared under a mandate given to CEN by the
European Commission and the European Free Trade Association.
This document has been developed to cover specifically space systems and has
therefore precedence over any EN covering the same scope but with a wider
domain of applicability (e.g. : aerospace).
According to the CEN-CENELEC Internal Regulations, the national standards
organizations of the following countries are bound to implement this European
Standard: Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic,
Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France,
Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,
Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania,
Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the United
Kingdom.
5
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1
Scope
This Standard specifies the basic requirements to be imposed on the
performance and assessment of modal survey tests in space programmes. It
defines the terminology for the activities involved and includes provisions for
the requirement implementation.
This Standard specifies the tasks to be performed when preparing, executing
and evaluating a modal survey test, in order to ensure that the objectives of the
test are satisfied and valid data is obtained to identify the dynamic
characteristics of the test article.
This standard may be tailored for the specific characteristics and constrains of a
space project in conformance with ECSS-S-ST-00.
6
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2
Normative references
The following normative documents contain provisions which, through
reference in this text, constitute provisions of this ECSS Standard. For dated
references, subsequent amendments to, or revision of any of these publications,
do not apply. However, parties to agreements based on this ECSS Standard are
encouraged to investigate the possibility of applying the more recent editions of
the normative documents indicated below. For undated references, the latest
edition of the publication referred to applies.
EN reference Reference in text Title
EN 16601-00-01 ECSS-S-ST-00-01 ECSS system — Glossary of terms
EN 16603-10-03 ECSS-E-ST-10-03 Space engineering — Testing
EN 16603-32 ECSS-E-ST-32 Space engineering — Structural general requirements
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3
Terms, definitions and abbreviated terms
3.1 Terms from other standards
For the purpose of this Standard, the terms and definitions from
ECSS-S-ST-00-01 apply.
3.2 Terms specific to the present standard
3.2.1 accelerance
ratio of the output acceleration spectrum to the input force spectrum
NOTE 1 Accelerance is computed as follows:
• •
X (ω)
A(ω) =
F(ω)
where
• •
is the output acceleration spectrum;
X (ω)
is the input force spectrum.
F(ω)
NOTE 2 The accelerance is also called “inertance” and it is
the inverse of the apparent mass (see 3.2.2).
3.2.2 apparent mass
ratio of the input force spectrum to the output acceleration spectrum
NOTE 1 Apparent mass is computed as follows:
F(ω)
M (ω) =
• •
X (ω)
where
is the input force spectrum;
F(ω)
• •
is the output acceleration spectrum.
X (ω)
NOTE 2 The apparent mass is also called “dynamic mass”,
and it is the inverse of the accelerance (see 3.2.1).
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3.2.3 auto modal assurance criterion
AutoMAC
measure of the degree of correlation between two mode shapes of the same
mode shape set
NOTE 1 For example, test mode shapes or analysis mode
shapes.
NOTE 2 The AutoMAC is a specific case of the MAC
(see 3.2.26); the AutoMAC matrix is symmetric.
NOTE 3 The AutoMAC is particularly useful for assessing
whether a given selection of DOFs is adequate for
MAC evaluations employing two different sets of
mode shapes (e.g. test and analysis).
3.2.4 coherence function
measure of the degree of linear, noise-free relationship between the measured
system input and output signals at each frequency
NOTE 1 The coherence function is defined as
S (ω)
xf
2
γ (ω) =
S (ω) S (ω)
xx f f
where
ω is the frequency;
Sff (ω) is the power spectrum of the input signal;
Sxx (ω) is the power spectrum of the output signal;
Sxf (ω) is the input-output cross spectrum.
2
NOTE 2 γ (ω)=1 indicates a linear, noise-free relationship
between input and output.
2
NOTE 3 γ (ω)=0 indicates a non causal relationship
between input and output.
3.2.5 complex mode shape
modal vector of a non-proportionally damped system
NOTE 1 For complex mode shapes, any phase relationship
can exits between different parts of the structure.
NOTE 2 Complex mode shapes can be considered to be
propagating waves with no stationary node lines.
3.2.6 complex mode indicator function
indicator of the existence of real or complex modes and their relative
magnitudes
NOTE The complex mode indicator function has
extended functionality to estimate approximate
modal parameters.
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3.2.7 co-ordinate modal assurance criterion
CoMAC
measure of the correlation of the a given DOF of two different sets of mode
shapes over a number of comparable-paired mode shapes
NOTE 1 The coordinate modal assurance criterion for DOF
j is defined as:
2
m
X A
Φ Φ
∑ jr jr
r=1
CoMAC(j) =
m m
2 2
X A
(Φ ) (Φ )
∑ jr ∑ jr
r=1 r=1
where
A
Φ is the mode shape coefficient for DOF j for mode r
jr
of set A;
X
Φ is the mode shape coefficient for DOF j for mode r
jr
of set X;
r is the index of the correlated mode pairs.
For example, mode shapes X and A are test and
analysis mode shapes, respectively.
NOTE 2 CoMAC = 1 indicates perfect correlation.
NOTE 3 The results can be considered to be meaningful
only when the CoMAC is applied to matched
modes, i.e. for correlated mode pairs.
3.2.8 damping
dissipation of oscillatory or vibratory energy with motion or with time
3.2.9 damped natural frequency
frequency of free vibrations of a damped linear mechanical system
3.2.10 driving point residue
calculated quantity that defines the most appropriate exciter positions
NOTE The magnitude of the driving point residue for a
location is defined as:
2
v
jr
r =
jr
2m ω
r dr
where
rjr is the driving point residue of DOF j for mode r;
vjr is the mode shape coefficient of DOF j for mode r;
mr is the modal mass for mode r;
ωdr is the damped natural frequency for mode r.
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3.2.11 dynamic compliance
ratio of the output displacement spectrum to the input force spectrum
NOTE 1 Dynamic compliance is computed as follows:
X (ω)
H (ω) =
F(ω)
where
X(ω) is the output displacement spectrum;
F(ω) is the input force spectrum.
NOTE 2 The dynamic compliance is also called dynamic
flexibility, and it is the inverse of the dynamic
stiffness (see 3.2.12).
3.2.12 dynamic stiffness
ratio of the input force spectrum to the output displacement spectrum
NOTE 1 Dynamic stiffness is computed as follows:
F(ω)
K(ω) =
X (ω)
where
F(ω) is the input force spectrum;
X(ω) is the output displacement spectrum.
NOTE 2 The dynamic stiffness is the inverse of the
dynamic compliance (see 3.2.11).
3.2.13 effective modal mass
measure of the mass portion associated to the mode shape with respect to a
reference support point
NOTE 1 The six effective masses for a normal mode, {Φ}r,
are the diagonal values of the modal mass matrix.
T
{L} {L}
r r
[M ] =
r
m
r
where
{L}r is the modal participation factor:
T
;
{L} = {Φ } [M ]{φ}
r RB r
mr is the generalised mass:
T
m = {Φ} [m] {φ} ;
r r r
{Φ}r, is the elastic mode r;
{Φ }, is the rigid body mode.
ΡΒ
NOTE 2 The sum of the effective masses provides an
indication of the completeness of the measured
modes, since the accumulated effective mass
contributions from all modes equal the total
structural mass and inertia for each of the six
translatory and rotatory DOFs, respectively.
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3.2.14 eigenfrequency
See natural frequency
3.2.15 finite element model
FEM
mathematical representation of a physical structure or system where the
distributed physical properties are represented by a discrete model consisting
of a finite number of idealized elements which are interconnected at a finite
number of nodal points
NOTE The FEM contains only a finite number of degrees
of freedom compared to the infinite number of
degrees of freedom for the physical structure or
system.
3.2.16 forced vibration
vibratory motion of a system that is caused by mechanical excitation
3.2.17 free vibration
vibratory motion of a system without forcing
3.2.18 frequency response assurance criterion
FRAC
measure of the similarity between an analytical and experimental frequency
response function
NOTE 1 The frequency response assurance criterion is a
degree of freedom correlation tool. It is the FRF
equivalent to the CoMAC (see 3.2.7).
NOTE 2 The frequency response assurance criterion is
defined as
2
T
{ H (ω)} { H (ω)}
X jk A jk
FRAC(j,k) =
T T
({ H (ω)} { H (ω)}) ({ H (ω)} { H (ω)})
X jk X jk A jk A jk
where
AHjk(ω) is the analytical frequency response
function of a response at DOF j due to
an excitation at DOF k;
XHjk(ω) is the corresponding experimental
frequency response function.
NOTE 3 FRAC = 1 indicates a perfect correlation of the two
frequency response functions.
NOTE 4 FRAC = 0 indicates a non correlation of the two
frequency response functions.
3.2.19 frequency response function
FRF
descriptor of a linear system in the frequency domain that relates the output motion
spectrum (displacement, velocity or acceleration) to the input force spectrum
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NOTE 1 The frequency response function is generally
defined as:
X (ω)
H (ω) =
F(ω)
NOTE 2 H(ω) is a complex function containing magnitude
and phase information.
NOTE 3 Common definitions of standard and inverse FRF are:
• accelerance or inertance (see 3.2.1);
• apparent or dynamic mass (see 3.2.2);
• dynamic compliance or flexibility (see 3.2.11);
• dynamic stiffness (see 3.2.12).
• impedance (see 3.2.22);
• mobility (see 3.2.24).
3.2.20 fundamental resonance
first major significant resonance as observed during the modal survey test
NOTE 1 For unconstrained mechanical systems, the
fundamental resonance is the lowest natural
frequency with motions of the whole test article.
NOTE 2 For clamped mechanical systems, the fundamental
resonance is the mode with the largest effective
mass.
3.2.21 impact
single collision between masses where at least one of the masses is in motion
3.2.22 impedance
ratio of the input force spectrum to the output velocity spectrum
NOTE 1 Impedance is computed as follows:
F(ω)
Z(ω) =
•
X (ω)
where
F(ω) is the input force spectrum;
•
is the output velocity spectrum.
X (ω)
NOTE 2 The impedance is the inverse of the mobility
(see 3.2.24).
3.2.23 linear system
system whose response is directly proportional to the excitation for every part
of the system
3.2.24 mobility
ratio of the output velocity spectrum to the input force spectrum
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NOTE 1 Mobility is computed as follows:
•
X (ω)
Y (ω) =
F(ω)
where
•
is the output velocity spectrum;
X (ω)
F(ω) is the input force spectrum.
NOTE 2 The mobility is the inverse of the impedance
(see 3.2.22).
3.2.25 modal analysis
process of determining the modal parameters of a structure within the
frequency range of interest
NOTE For the frequency range of interest, see 4.1.2.
3.2.26 modal assurance criterion
MAC
measure of the degree of correlation between two mode shapes
NOTE 1 The modal assurance criterion is defined as:
2
T
[{Φ} {Φ} ]
r s
MAC =
rs
T T
[{Φ} {Φ} ][{Φ} {Φ} ]
r r s s
where and are the two mode shapes.
{Φ} {Φ}
r s
NOTE 2 MAC = 1 indicates perfect correlation of the two
mode shapes.
NOTE 3 MAC = 0 indicates no correlation of the two mode
shapes.
3.2.27 modal confidence factor
MCF
indicator of computational noise modes in time domain parameter estimation
methods
NOTE 1 The modal confidence factor for mode r is given as
~
T
{Φ} Φ
r
−λ ∆τ
r
r
MCF = e
r
T
{Φ} {Φ}
r r
where
~
is a computed mode;
Φ
r
λr is a complex eigenvalue, or system pole for
mode r;
{Φ} is a mass-normalized mode shape;
r
∆τ is the time interval.
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NOTE 2 MCFr ≈ 1 indicates a physical mode, and in such
case:
−λ ∆τ
~
r
Φ = {Φ} e
r
r
NOTE 3 MCFr << 1 indicates a computational noise mode.
3.2.28 modal identification
technique to determine the inherent modal properties of a mechanical system
3.2.29 modal parameters
collection of natural frequency, modal damping, mode shape and (generalized)
modal mass for each mode of a mechanical system
NOTE 1 The modal parameters of all modes, within the
frequency range of interest (see 4.1.2), constitute a
complete dynamic description of the structure.
NOTE 2 Common definitions relating to modal parameters are:
• damped equations of motion
.. .
;
[M ] x (t) +[C] x (t) +[K] x (t) = {f (t)}
• inertia force
..
[M ] x (t)
• elastic force
[K] x (t)
• damping force (proportional with velocity)
.
;
[C] x(t)
• external dynamic force
{f (t)}
• undamped eigenvalue problem
2
([K] − ω [M ]){Ψ} = {0}
r r
• natural or eigenfrequency
ω
r
;
ω (rads /s), f = (Hz)
r r
2π
• general mode shape
{Ψ}
r
• (generalized) modal mass
T
{Ψ} [M ]{Ψ} =m
r r r
• (generalized) modal damping
T
{Ψ} [C]{Ψ} = 2m ξ ω
r r r r r
• generalized stiffness
T
2
{Ψ} [K ]{Ψ} =m ω
r r r r
• mass-normalized mode shape
{Φ}
r
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• mass-normalized modal mass
T
{Φ} [M ]{Φ} = 1
r r
• mass-normalized modal damping
T
{Φ} [C]{Φ} = 2ξ ω
r r r r
• mass-normalized modal stiffness
T 2
{Φ} [K ]{Φ} = ω
r r r
• modal matrix
{Ψ}, {Φ}
NOTE 3 For non-proportional damping, the generalized
damping matrix is not a diagonal matrix.
3.2.30 modal participation factor
measure of the efficiency of the excitation at each degree of freedom of the
supporting point
NOTE 1 The modal participation
...
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