Pub Date : 1995-01-16DOI: 10.1109/RAMS.1995.513273
N. Sarawgi, S.K. Kurtz
In the design and manufacturing of both consumer and commercial products, an important design criteria is the length of the warranty period measured in calendar time. It is very important to know the expected number of failures during the warranty period. This paper provides an engineering tool that will predict the cumulative failures over the warranty period based on laboratory life data and the usage rate data for the products that are operated for only a limited fraction of the total available time. This method uses a joint distribution of the usage rate distribution and the laboratory life distribution to translate usage time to calendar time and not the mean usage since the product use in the field also follows a broad statistical distribution. The proposed technique permits an accurate calculation of the cumulative field failure over prospective warranty periods and thus is useful as an engineers' tool in design optimization as well as in decisions on product release.
{"title":"A simple method for predicting the cumulative failures of consumer products during the warranty period","authors":"N. Sarawgi, S.K. Kurtz","doi":"10.1109/RAMS.1995.513273","DOIUrl":"https://doi.org/10.1109/RAMS.1995.513273","url":null,"abstract":"In the design and manufacturing of both consumer and commercial products, an important design criteria is the length of the warranty period measured in calendar time. It is very important to know the expected number of failures during the warranty period. This paper provides an engineering tool that will predict the cumulative failures over the warranty period based on laboratory life data and the usage rate data for the products that are operated for only a limited fraction of the total available time. This method uses a joint distribution of the usage rate distribution and the laboratory life distribution to translate usage time to calendar time and not the mean usage since the product use in the field also follows a broad statistical distribution. The proposed technique permits an accurate calculation of the cumulative field failure over prospective warranty periods and thus is useful as an engineers' tool in design optimization as well as in decisions on product release.","PeriodicalId":143102,"journal":{"name":"Annual Reliability and Maintainability Symposium 1995 Proceedings","volume":"23 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1995-01-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123906463","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1995-01-16DOI: 10.1109/RAMS.1995.513271
J. Huang, C. R. Miller, O. Okogbaa
Using a well-known single-unit replacement model with Weibull failure distribution assumption, normalization is used to reduce the model input parameters such that standard optimal preventive replacement solutions can be generated. Characteristics of the model solutions are discussed. The standard solutions are organized in charts and tables for ease of use. Procedures are developed and examples are given for applying the standard solutions for engineering problems with different system parameters. It is believed that the generated standard solutions and the developed procedures will be helpful for maintenance practitioners to apply theoretical research results in industrial practice.
{"title":"Optimal preventive-replacement intervals for the Weibull life distribution: solutions and applications","authors":"J. Huang, C. R. Miller, O. Okogbaa","doi":"10.1109/RAMS.1995.513271","DOIUrl":"https://doi.org/10.1109/RAMS.1995.513271","url":null,"abstract":"Using a well-known single-unit replacement model with Weibull failure distribution assumption, normalization is used to reduce the model input parameters such that standard optimal preventive replacement solutions can be generated. Characteristics of the model solutions are discussed. The standard solutions are organized in charts and tables for ease of use. Procedures are developed and examples are given for applying the standard solutions for engineering problems with different system parameters. It is believed that the generated standard solutions and the developed procedures will be helpful for maintenance practitioners to apply theoretical research results in industrial practice.","PeriodicalId":143102,"journal":{"name":"Annual Reliability and Maintainability Symposium 1995 Proceedings","volume":"23 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1995-01-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121770752","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1995-01-16DOI: 10.1109/RAMS.1995.513246
J. Blodgett, R.A. Dykes, A. Dykes
This paper addresses how to verify the expected reliability of a missile system and its subsystems using Bayes' theorem. During the early development phase, a number of design engineering tests are performed to establish the operational characteristics and robustness of a new design. Actual test data is not used for reliability assessment purposes until the system is close to full-scale production. This approach adds a considerable amount of risk to the program, especially if the new design cannot meet the required specification. By using Bayes' theorem, we can verify the prediction of a new system reliability using all the test data and engineering information available. This technique enables us to verify the new design much earlier and improves our confidence in meeting or exceeding the reliability requirement. Using the MIL-HDBK and verifying the reliability prediction with Bayes' theorem is a far superior approach. The model can be structured to use all the known information about the system gathered during the design stage, development testing, and its periodically demonstrated performance. This information is then weighted and projected into probability density curves that demonstrate the systems' predicted failure rate for an assigned performance period. The Bayes' approach uses early design and test data, engineering judgment, and "Expert Opinion" to predict a realistic system failure rate. Using this methodology to verify the new prediction will give both customer and management a higher degree of confidence that the individual system reliability will be met.
{"title":"Verifying a new design using Bayes' theorem","authors":"J. Blodgett, R.A. Dykes, A. Dykes","doi":"10.1109/RAMS.1995.513246","DOIUrl":"https://doi.org/10.1109/RAMS.1995.513246","url":null,"abstract":"This paper addresses how to verify the expected reliability of a missile system and its subsystems using Bayes' theorem. During the early development phase, a number of design engineering tests are performed to establish the operational characteristics and robustness of a new design. Actual test data is not used for reliability assessment purposes until the system is close to full-scale production. This approach adds a considerable amount of risk to the program, especially if the new design cannot meet the required specification. By using Bayes' theorem, we can verify the prediction of a new system reliability using all the test data and engineering information available. This technique enables us to verify the new design much earlier and improves our confidence in meeting or exceeding the reliability requirement. Using the MIL-HDBK and verifying the reliability prediction with Bayes' theorem is a far superior approach. The model can be structured to use all the known information about the system gathered during the design stage, development testing, and its periodically demonstrated performance. This information is then weighted and projected into probability density curves that demonstrate the systems' predicted failure rate for an assigned performance period. The Bayes' approach uses early design and test data, engineering judgment, and \"Expert Opinion\" to predict a realistic system failure rate. Using this methodology to verify the new prediction will give both customer and management a higher degree of confidence that the individual system reliability will be met.","PeriodicalId":143102,"journal":{"name":"Annual Reliability and Maintainability Symposium 1995 Proceedings","volume":"4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1995-01-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127063923","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1995-01-16DOI: 10.1109/RAMS.1995.513244
E. A. Ortiz
In the traditional software development model, the system test phase is the last stage where the reliability, capability, performance and other important dimensions of the quality of a system can be evaluated. During this stage, a point is eventually reached where a decision must be made to either continue or stop testing. This is a crucial task that requires an objective assessment of the benefits and costs associated with each alternative. This paper outlines a methodology that improves the effectiveness of management decisions by providing estimates of the total number of errors to be found through testing, the number of remaining errors, the additional testing time needed to achieve reliability goals and the impact of these parameters on product quality, project cost and project duration.
{"title":"Software-quality improvement using reliability-growth models","authors":"E. A. Ortiz","doi":"10.1109/RAMS.1995.513244","DOIUrl":"https://doi.org/10.1109/RAMS.1995.513244","url":null,"abstract":"In the traditional software development model, the system test phase is the last stage where the reliability, capability, performance and other important dimensions of the quality of a system can be evaluated. During this stage, a point is eventually reached where a decision must be made to either continue or stop testing. This is a crucial task that requires an objective assessment of the benefits and costs associated with each alternative. This paper outlines a methodology that improves the effectiveness of management decisions by providing estimates of the total number of errors to be found through testing, the number of remaining errors, the additional testing time needed to achieve reliability goals and the impact of these parameters on product quality, project cost and project duration.","PeriodicalId":143102,"journal":{"name":"Annual Reliability and Maintainability Symposium 1995 Proceedings","volume":"32 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1995-01-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126620069","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1995-01-16DOI: 10.1109/RAMS.1995.513228
C. Price, D. Pugh, M. Wilson, N. Snooke
It is well known that FMEA is both tedious and time consuming-so much so, that an FMEA analysis on the design of a system is often only completed after a first prototype has been constructed. This situation can lead to time, effort and money being wasted. Automating the FMEA process will improve the speed and consistency with which an FMEA analysis can be performed. The Flame system aims to provide engineers with a knowledge based system (KBS) which is capable of performing automated FMEA. At present, we are concentrating our efforts on electrical design FMEA, however mechanical and software FMEA will be the subjects of future study. The input to the Flame system consists of a physical description of a particular circuit and a description of that circuit's functionality. The output from Flame will be a complete (or near complete) FMEA form which can be checked, annotated and signed off by an engineer. The Flame system demonstrates that it is indeed possible to provide engineers with a means of performing automated electrical FMEA. The application considered is automobile systems.
{"title":"The Flame system: automating electrical failure mode and effects analysis (FMEA)","authors":"C. Price, D. Pugh, M. Wilson, N. Snooke","doi":"10.1109/RAMS.1995.513228","DOIUrl":"https://doi.org/10.1109/RAMS.1995.513228","url":null,"abstract":"It is well known that FMEA is both tedious and time consuming-so much so, that an FMEA analysis on the design of a system is often only completed after a first prototype has been constructed. This situation can lead to time, effort and money being wasted. Automating the FMEA process will improve the speed and consistency with which an FMEA analysis can be performed. The Flame system aims to provide engineers with a knowledge based system (KBS) which is capable of performing automated FMEA. At present, we are concentrating our efforts on electrical design FMEA, however mechanical and software FMEA will be the subjects of future study. The input to the Flame system consists of a physical description of a particular circuit and a description of that circuit's functionality. The output from Flame will be a complete (or near complete) FMEA form which can be checked, annotated and signed off by an engineer. The Flame system demonstrates that it is indeed possible to provide engineers with a means of performing automated electrical FMEA. The application considered is automobile systems.","PeriodicalId":143102,"journal":{"name":"Annual Reliability and Maintainability Symposium 1995 Proceedings","volume":"08 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1995-01-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127215576","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1995-01-16DOI: 10.1109/RAMS.1995.513251
H. Caruso
This paper examines the history and evolution of environmental stress screening (ESS) to show how uncoordinated initiatives from each military service contributed to the current state of array in the ESS community. The lack of a common vision for ESS is examined as a continuing handicap in efforts to integrate ESS more fully into the hardware development process. Common areas of confusion regarding effective ESS procedures and facilities are discussed, including: temperature air change rate vs. hardware thermal response; the number of vibration axes needed; simultaneous vibration in combined axes vs. sequential vibration in each; pneumatic vs electrodynamic vibration facilities. A "checklist" of considerations to apply in developing a successful ESS program is presented. The June 1994 DoD initiative regarding possible elimination or replacement of military specifications and standards with commercial standards is reviewed with respect to ESS.
{"title":"The ESS riddle: physics vs. relics","authors":"H. Caruso","doi":"10.1109/RAMS.1995.513251","DOIUrl":"https://doi.org/10.1109/RAMS.1995.513251","url":null,"abstract":"This paper examines the history and evolution of environmental stress screening (ESS) to show how uncoordinated initiatives from each military service contributed to the current state of array in the ESS community. The lack of a common vision for ESS is examined as a continuing handicap in efforts to integrate ESS more fully into the hardware development process. Common areas of confusion regarding effective ESS procedures and facilities are discussed, including: temperature air change rate vs. hardware thermal response; the number of vibration axes needed; simultaneous vibration in combined axes vs. sequential vibration in each; pneumatic vs electrodynamic vibration facilities. A \"checklist\" of considerations to apply in developing a successful ESS program is presented. The June 1994 DoD initiative regarding possible elimination or replacement of military specifications and standards with commercial standards is reviewed with respect to ESS.","PeriodicalId":143102,"journal":{"name":"Annual Reliability and Maintainability Symposium 1995 Proceedings","volume":"22 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1995-01-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126156802","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1995-01-16DOI: 10.1109/RAMS.1995.513219
X.K. Zunzanyika, J. Yang
This paper presents an enhanced approach to utilizing test as an aid to maturing the 3.5" hard-disk drive (HDD) to improve time to market. It focuses on designing tests that provide maximum feedback to the design function on the designs "goodness or maturity" and the strategy focuses on consolidating different tests done by different groups (including selective customer testing) to maximize useful information flowing back to the design team. To improve design weakness identification, the paper offers an alternative to performing design verification testing (DVT) that focuses on problem discovery rather than specification compliance. This paper also covers conformance testing as testimony to the successful approach taken on DVT testing. Although not all elements of the consolidated test strategy have been fully implemented, results so far are very encouraging.
{"title":"Simultaneous development and qualification in the fast-changing 3.5\" hard-disk-drive technology","authors":"X.K. Zunzanyika, J. Yang","doi":"10.1109/RAMS.1995.513219","DOIUrl":"https://doi.org/10.1109/RAMS.1995.513219","url":null,"abstract":"This paper presents an enhanced approach to utilizing test as an aid to maturing the 3.5\" hard-disk drive (HDD) to improve time to market. It focuses on designing tests that provide maximum feedback to the design function on the designs \"goodness or maturity\" and the strategy focuses on consolidating different tests done by different groups (including selective customer testing) to maximize useful information flowing back to the design team. To improve design weakness identification, the paper offers an alternative to performing design verification testing (DVT) that focuses on problem discovery rather than specification compliance. This paper also covers conformance testing as testimony to the successful approach taken on DVT testing. Although not all elements of the consolidated test strategy have been fully implemented, results so far are very encouraging.","PeriodicalId":143102,"journal":{"name":"Annual Reliability and Maintainability Symposium 1995 Proceedings","volume":"45 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1995-01-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133626325","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1995-01-16DOI: 10.1109/RAMS.1995.513284
T.H. Lentz
The reliability of infant care products requites a comprehensive, detailed approach to product development and reliability assessment. This paper presents a reliability program for infant care products, and is designed to meet the rigorous demands of patient care, FDA and ISO 9001 quality systems.
{"title":"Reliability program for neonatal intensive care equipment","authors":"T.H. Lentz","doi":"10.1109/RAMS.1995.513284","DOIUrl":"https://doi.org/10.1109/RAMS.1995.513284","url":null,"abstract":"The reliability of infant care products requites a comprehensive, detailed approach to product development and reliability assessment. This paper presents a reliability program for infant care products, and is designed to meet the rigorous demands of patient care, FDA and ISO 9001 quality systems.","PeriodicalId":143102,"journal":{"name":"Annual Reliability and Maintainability Symposium 1995 Proceedings","volume":"4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1995-01-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132845028","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1995-01-16DOI: 10.1109/RAMS.1995.513240
M. Pecht, F.R. Nash, J.H. Lory
To be competitive, manufacturers need to know how things fail, as well as how things work. The combination of physics-of-failure and best practices is an approach to the development of cost-effective reliable products that focuses on how things can fail through an understanding of the root causes of failure. The goal is to answer the following questions: (1) how can the supplier measure how well he is doing?; (2) what kind of reliability assurances can a supplier give to a customer?; (3) how can a customer determine that the supplier knows what he is doing, and that he is likely to deliver what is desired?; and (4) how can both the supplier and customer assess and minimize the risks? These questions are important because the supplier of a product that fails in the field experiences a loss of customer confidence and subsequently a loss of business. Similarly, the customer of a product that fails will experience a loss of functionality which could result in decreased business, safety and customer satisfaction.
{"title":"Understanding and solving the real reliability assurance problems","authors":"M. Pecht, F.R. Nash, J.H. Lory","doi":"10.1109/RAMS.1995.513240","DOIUrl":"https://doi.org/10.1109/RAMS.1995.513240","url":null,"abstract":"To be competitive, manufacturers need to know how things fail, as well as how things work. The combination of physics-of-failure and best practices is an approach to the development of cost-effective reliable products that focuses on how things can fail through an understanding of the root causes of failure. The goal is to answer the following questions: (1) how can the supplier measure how well he is doing?; (2) what kind of reliability assurances can a supplier give to a customer?; (3) how can a customer determine that the supplier knows what he is doing, and that he is likely to deliver what is desired?; and (4) how can both the supplier and customer assess and minimize the risks? These questions are important because the supplier of a product that fails in the field experiences a loss of customer confidence and subsequently a loss of business. Similarly, the customer of a product that fails will experience a loss of functionality which could result in decreased business, safety and customer satisfaction.","PeriodicalId":143102,"journal":{"name":"Annual Reliability and Maintainability Symposium 1995 Proceedings","volume":"83 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1995-01-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115029249","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1995-01-16DOI: 10.1109/RAMS.1995.513235
L. J. Beasley
Reliability is like quality-it has many definitions, and means different things to different people. To effect reliability, we must establish clear communications, use a common language and learn to set expectations. We must work toward a language upon which all agree. Reliability must be defined and specified in measurable terms. Realistic, achievable goals (defined in terms set by the customer) must be set and agreed upon. They must also be validated. In this manner, reliability expectations on both the part of the manufacturer and the end user can be fulfilled. The result is a satisfied customer and increased chances of gaining market share. In the medical device manufacturing arena, there are three primary reasons that a high degree of reliability is vital. First and foremost is customer satisfaction. Secondly, a highly reliable product that carries with it a high reliability reduces the amount of overhead and capital dollars required to maintain it in the field. The third factor (which unfortunately vies with the first one) is the notion of public and federal scrutiny. The author discusses these reliability issues.
{"title":"Reliability and medical device manufacturing","authors":"L. J. Beasley","doi":"10.1109/RAMS.1995.513235","DOIUrl":"https://doi.org/10.1109/RAMS.1995.513235","url":null,"abstract":"Reliability is like quality-it has many definitions, and means different things to different people. To effect reliability, we must establish clear communications, use a common language and learn to set expectations. We must work toward a language upon which all agree. Reliability must be defined and specified in measurable terms. Realistic, achievable goals (defined in terms set by the customer) must be set and agreed upon. They must also be validated. In this manner, reliability expectations on both the part of the manufacturer and the end user can be fulfilled. The result is a satisfied customer and increased chances of gaining market share. In the medical device manufacturing arena, there are three primary reasons that a high degree of reliability is vital. First and foremost is customer satisfaction. Secondly, a highly reliable product that carries with it a high reliability reduces the amount of overhead and capital dollars required to maintain it in the field. The third factor (which unfortunately vies with the first one) is the notion of public and federal scrutiny. The author discusses these reliability issues.","PeriodicalId":143102,"journal":{"name":"Annual Reliability and Maintainability Symposium 1995 Proceedings","volume":"26 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1995-01-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127510923","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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