1、 ISO 2017 Pneumatic fluid power Assessment of component reliability by accelerated life testing General guidelines and procedures Transmissions pneumatiques valuation de la fiabilit du composant par essai de dure de vie acclre Lignes directrices gnrales et modes opratoires TECHNICAL REPORT ISO/TR 16
2、194 Reference number ISO/TR 16194:2017(E) First edition 2017-04 ISO/TR 16194:2017(E)ii ISO 2017 All rights reserved COPYRIGHT PROTECTED DOCUMENT ISO 2017, Published in Switzerland All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in
3、any form or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below or ISOs member body in the country of the requester. ISO copyright office Ch. de B
4、landonnet 8 CP 401 CH-1214 Vernier, Geneva, Switzerland Tel. +41 22 749 01 11 Fax +41 22 749 09 47 copyrightiso.org www.iso.org ISO/TR 16194:2017(E)Foreword iv Introduction v 1 Scope . 1 2 Normative references 1 3 Terms and definitions . 1 4 Symbols and units . 3 5 Concepts of reliability and accele
5、rated life testing . 3 6 Failure mechanism and mode . 4 7 Strategy of conducting accelerated life testing . 4 8 Design of accelerated life testing . 5 8.1 Normal use conditions . 5 8.2 Preliminary tests . 5 8.3 Levels of accelerated stress 6 8.4 Sample size . 7 8.5 Data observation and measurement 7
6、 8.6 Types of stress loading . 7 9 End of test 8 9.1 Minimum number of failures required 8 9.2 Termination cycle count 8 9.3 Suspended or censored test units 8 10 Statistical analysis . 9 10.1 Analysis of failure data . 9 10.2 Life distribution 9 10.3 Accelerated life testing model .10 10.4 Data ana
7、lysis and parameter estimation .10 11 Reliability characteristics from the test data 11 12 Test report 12 Annex A (informative) Determining stress levels when stress is time-dependent .13 Annex B (informative) Life-stress relationship models .17 Annex C (informative) Verification of compromise Weibu
8、ll slopes .26 Annex D (informative) Calculation procedures for censored data 32 Annex E (informative) Examples of using accelerated life testing in industrial applications .35 Annex F (informative) Palmgren-Miners rule 37 Annex G (informative) AL T experimental results for pneumatic cylinder .39 Bib
9、liography .59 ISO 2017 All rights reserved iii Contents Page ISO/TR 16194:2017(E) Foreword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out throug
10、h ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborat
11、es closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. The procedures used to develop this document and those intended for its further maintenance are described in the ISO/IEC Directives, Part 1. In particular the different approval cr
12、iteria needed for the different types of ISO documents should be noted. This document was drafted in accordance with the editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives). Attention is drawn to the possibility that some of the elements of this document may be the subj
13、ect of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of any patent rights identified during the development of the document will be in the Introduction and/or on the ISO list of patent declarations received (see www .iso .org/ patents). Any t
14、rade name used in this document is information given for the convenience of users and does not constitute an endorsement. For an explanation on the voluntary nature of standards, the meaning of ISO specific terms and expressions related to conformity assessment, as well as information about ISOs adh
15、erence to the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see the following URL: w w w . i s o .org/ iso/ foreword .html ISO/TR 16194 was prepared by Technical Committee ISO/TC 131, Fluid power systems.iv ISO 2017 All rights reserved ISO/TR 16194:2017(E) Introd
16、uction This document is being released to document progress that the working group has developed for accelerated testing. It is a new method with which the working group members have very little experience, but has been used by institutional laboratories and taught at academic levels. Some experimen
17、tation on air cylinders has been done at the Korean Institute of Machinery and Materials (KIMM), but the application to pneumatic components in general has not been evaluated. This document is offered to members as a reference and model procedure, so that they can develop experience with its use in
18、their own laboratories. ISO 2017 All rights reserved v Pneumatic fluid power Assessment of component reliability by accelerated life testing General guidelines and procedures 1 Scope This document provides general procedures for assessing the reliability of pneumatic fluid power components using acc
19、elerated life testing and the method for reporting the results. These procedures apply to directional control valves, cylinders with piston rods, pressure regulators, and accessory devices the same components covered by the ISO 19973 series of standards. This document does not provide specific proce
20、dures for accelerated life testing of components. Instead, it explains the variability among methods and provides guidelines for developing an accelerated test method. The methods specified in this document apply to the first failure, without repairs. 2 Normative references There are no normative re
21、ferences in this document. 3 Terms and definitions For the purposes of this document, the terms and definitions given in ISO 5598, ISO 19973-1 and the following apply. ISO and IEC maintain terminological databases for use in standardization at the following addresses: IEC Electropedia: available at
22、h t t p :/ www .electropedia .org/ ISO Online browsing platform: available at h t t p :/ www .iso .org/ obp 3.1 B xlife life of a component or assembly that has not been altered since its production, where its reliability is ( x %; or the time at which ( x % of the population has survived Note 1 to
23、entry: The cumulative failure fraction is x %. For example, if x = 10, the B 10life has a cumulative failure probability of 10 %. 3.2 acceleration factor AF ratio between the life at the normal use stress level and the life at the accelerated stress level 3.3 accelerated life test ALT process in whi
24、ch a component is forced to fail more quickly that it would have under normal use conditions and which provides information about the components life characteristics TECHNICAL REPORT ISO/TR 16194:2017(E) ISO 2017 All rights reserved 1 ISO/TR 16194:2017(E) 3.4 destruct limit stress level at which one
25、 or more of the components operating characteristics is no longer within specification or the component is damaged and cannot recover when the stress is reduced Note 1 to entry: Destruct limits are classified as a lower destruct limit and upper destruct limit. 3.5 failure mechanism physical or chemi
26、cal process that produces instantaneous or cumulative damage to the materials from which the component is made 3.6 failure mode manifestation of the failure mechanism resulting from component failure or degradation Note 1 to entry: The failure mode is the symptom of the aggressive activity of the fa
27、ilure mechanism in the components areas of weakness, where stress exceeds strength. 3.7 failure rate frequency at which a failure occurs instantaneously at time t, given that no failure has occurred before t 3.8 highly accelerated life test HALT process in which components are subjected to accelerat
28、ed environments to find weaknesses in the design and/or manufacturing process Note 1 to entry: The primary accelerated environments include pressure and heat. 3.9 model for accelerated life testing model that consists of a life distribution that represents the scatter in component life and a relatio
29、nship between life and stress Note 1 to entry: Life distribution examples: Weibull, Lognormal, Exponential, etc. Note 2 to entry: Life and stress examples: Arrhenius, Eyring, Inverse Power Law, etc. 3.10 normal use conditions test conditions at which a component is commonly used in the field, which
30、can be less strenuous than rated conditions 3.11 termination cycle count number of cycles on a test item when it reaches a threshold level for the first time2 ISO 2017 All rights reserved ISO/TR 16194:2017(E) 4 Symbols and units Symbol a Definition B 10 Time at which 10 % of the population is estima
31、ted to fail Scale parameter (characteristic life) of the Weibull distribution F(t) Probability of failure of a component up to time t Shape parameter (slope) of the Weibull distribution R(t) Reliability of a component at time t; R(t) = 1 F(t) (t) Failures per unit time aOther symbols could be used i
32、n other documents and software. Units of measurements are in accordance with ISO 80000-1. 5 Concepts of reliability and accelerated life testing Reliability is the probability (a percentage) that a component does not fail (for example, exceed the threshold level or experience catastrophic failure) f
33、or a specified interval of time or number of cycles when it operates under stated conditions. This reliability can be assessed by test methods described in the ISO 19973 series. Generally, reliability analysis involves analysing time to failure of a component, obtained under normal use conditions in
34、 order to quantify its life characteristics. Obtaining such life data is often difficult. The reasons for this difficulty can include the typically long life times of components, the small time period between design and product release, and the necessity for testing components under normal use condi
35、tions. Given this difficulty and the need to observe failures of components to better understand their life characteristics, procedures have been devised to accelerate their failures by overstress, thus forcing components to fail more quickly than they would under normal use conditions. The term acc
36、elerated life testing (ALT) is used to describe such procedures. However, a relationship between the reliability of a component determined by ALT, and its reliability at normal use conditions, is necessary. This can be assessed by extrapolating the test results obtained from an accelerated life test
37、 and comparing it to that obtained from testing at normal use conditions. Figure 1 shows the graphical concept for this relationship. ISO 2017 All rights reserved 3 ISO/TR 16194:2017(E) Figure 1 Graphical explanation of relationship between S-N curve and accelerated life testing NOTE Distributions i
38、n this concept Figure 1 are not defined. In Figure 1, failures under normal use conditions are represented by the distribution S 3 , and the accelerated conditions are distributions S 1and S 2 . Their relationship is shown by the connecting line(s). 6 Failure mechanism and mode The failure mechanism
39、 is the physical or chemical process that produces instantaneous or cumulative damage to the materials from which the component is made. The failure mode is the manifestation of the failure mechanism resulting from component failure or degradation. The failure mode is the symptom of the aggressive a
40、ctivity of the failure mechanism in areas of component weakness where the stress exceeds the strength. It is necessary that the failure modes observed in accelerated life test conditions are identical to those defined for normal use conditions. 7 Strategy of conducting accelerated life testing Befor
41、e starting an accelerated life test, it is important to identify the types of failures that might occur in service; especially any feedback from the field. Several methods are available to assist in this effort: design analysis and review using the quality function deployment (QFD), fault tree analy
42、sis (FTA), and failure modes and effect analysis (FMEA). Another method is a qualitative test like highly accelerated life testing (HALT). Qualitative tests are used primarily to reveal probable failure modes, but they do not quantify the life (or reliability) of the component under normal use condi
43、tions.4 ISO 2017 All rights reserved ISO/TR 16194:2017(E) Accelerated life testing involves acceleration of failures with the single purpose of quantification of the life characteristics of the component at normal use conditions. Therefore, accelerated life testing can be divided into two areas: qua
44、litative accelerated testing (HALT) and quantitative accelerated life testing. In qualitative accelerated testing, the objective is to identify failures and failure modes without attempting to make any predictions as to the components life under normal use conditions. In quantitative accelerated lif
45、e testing, the objective is predicting the life of the component (life characteristics such as MTTF, B 10life, etc.) at normal use conditions from data obtained in an accelerated life test. The strategy for effectively conducting an accelerated life testing program includes the following: establishi
46、ng a stress level that can be referred to as normal use conditions; determining the stress levels to use for accelerated testing; and determining the number of components to be tested at each stress level. 8 Design of accelerated life testing 8.1 Normal use conditions Normal use conditions can often
47、 be defined from the ratings of the components characteristics, for example: pressure, temperature, voltage, duty cycle, lubrication requirements, etc. However, these ratings often represent a maximum condition that is above commonly used conditions. Therefore, a definition for normal use conditions
48、 needs to be established from these characteristics before starting an accelerated test. An example definition for a pneumatic valve is shown in Table 1. Table 1 Definition of normal use conditions for a pneumatic valve Characteristic Typical rating value Common use applica- tion value Proposed norm
49、al use value for testing Pressure 1 000 kPa (10 bar) 630 kPa (6,3 bar) 630 kPa (6,3 bar) Temperature 50 C 25 C 25 C Voltage 24 VDC 24 VDC 24 VDC Duty cycle Continuous On-off varies 10 % on / 90 % off Lubrication Sometimes required Sometimes applied Not used Air dryness Dew point 0 C Dew point 10 C Dew point = 10 C It is necessary to define this normal use conditions before starting an ALT program. 8.2 Preliminary tests It is also necessary to determine the highest stress to be tested
