Pub Date : 2011-10-24DOI: 10.17764/JIET.54.2.J7502N53R4305HJ7
M. Dyke, Portia Peters
A significant amount of acoustic spatial variability is characteristic of direct field acoustic testing using a single random signal to drive the loudspeaker sources. This has raised concerns about the potential for under- and over-testing of hardware, particularly because of the consequential high sensitivity of the test environment upon the configuration of the test equipment and test hardware. Meanwhile, little is known about the specific spatial characteristics of the test acoustic field. A recent demonstration single-drive direct field acoustic test afforded the opportunity to map various planes of the acoustic field with a 36 microphone grid, offering unprecedented physical insight into the field characteristics. Analysis of the data reveals that the field is predominantly characterized by wave interference patterns at any given frequency. These data correlate well with 3-dimensional numerical models. The presence of wave interference patterns created by the fully correlated array of sources also ex...
{"title":"Spatial Variability Caused by Acoustic Wave Interference in Single-Drive Direct Field Acoustic Testing","authors":"M. Dyke, Portia Peters","doi":"10.17764/JIET.54.2.J7502N53R4305HJ7","DOIUrl":"https://doi.org/10.17764/JIET.54.2.J7502N53R4305HJ7","url":null,"abstract":"A significant amount of acoustic spatial variability is characteristic of direct field acoustic testing using a single random signal to drive the loudspeaker sources. This has raised concerns about the potential for under- and over-testing of hardware, particularly because of the consequential high sensitivity of the test environment upon the configuration of the test equipment and test hardware. Meanwhile, little is known about the specific spatial characteristics of the test acoustic field. A recent demonstration single-drive direct field acoustic test afforded the opportunity to map various planes of the acoustic field with a 36 microphone grid, offering unprecedented physical insight into the field characteristics. Analysis of the data reveals that the field is predominantly characterized by wave interference patterns at any given frequency. These data correlate well with 3-dimensional numerical models. The presence of wave interference patterns created by the fully correlated array of sources also ex...","PeriodicalId":35935,"journal":{"name":"Journal of the IEST","volume":"54 1","pages":"54-74"},"PeriodicalIF":0.0,"publicationDate":"2011-10-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67806389","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 : 2011-10-24DOI: 10.17764/JIET.54.2.J187251G263N25PV
D. Smallwood
A modified harmonic wavelet transform is used to estimate a time varying spectral density. The resolution of the estimate has an approximate constant time-frequency product. The estimation error is directly related to this time-frequency product. Unwanted cross product terms are effectively minimized. Several examples are given: White random, two sine waves, chirps, impulses, sums of exponentially decaying sinusoids, and a pyroshock. It is also shown how realizations can be generated from the modified harmonic wavelet transform estimate of the time varying spectral density.
{"title":"Using a Modified Harmonic Wavelet Transform to Characterize Mechanical Shock","authors":"D. Smallwood","doi":"10.17764/JIET.54.2.J187251G263N25PV","DOIUrl":"https://doi.org/10.17764/JIET.54.2.J187251G263N25PV","url":null,"abstract":"A modified harmonic wavelet transform is used to estimate a time varying spectral density. The resolution of the estimate has an approximate constant time-frequency product. The estimation error is directly related to this time-frequency product. Unwanted cross product terms are effectively minimized. Several examples are given: White random, two sine waves, chirps, impulses, sums of exponentially decaying sinusoids, and a pyroshock. It is also shown how realizations can be generated from the modified harmonic wavelet transform estimate of the time varying spectral density.","PeriodicalId":35935,"journal":{"name":"Journal of the IEST","volume":"54 1","pages":"85-102"},"PeriodicalIF":0.0,"publicationDate":"2011-10-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67805585","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 : 2011-10-24DOI: 10.17764/JIET.54.2.J6TR2R787846931N
M. Hale
Multiple degree of freedom (MDOF) excitation systems and MDOF vibration control systems continue to improve, and are now standard equipment in many dynamic test laboratories. This paper concentrates on the often overlooked process of determination of an input specification for such MDOF systems. A pair of generalized six-degree-of-freedom (6-DOF) vibration specification development (VSD) techniques are proposed, discussed, and illustrated through an example.
{"title":"A 6-DOF Vibration Specification Development Methodology","authors":"M. Hale","doi":"10.17764/JIET.54.2.J6TR2R787846931N","DOIUrl":"https://doi.org/10.17764/JIET.54.2.J6TR2R787846931N","url":null,"abstract":"Multiple degree of freedom (MDOF) excitation systems and MDOF vibration control systems continue to improve, and are now standard equipment in many dynamic test laboratories. This paper concentrates on the often overlooked process of determination of an input specification for such MDOF systems. A pair of generalized six-degree-of-freedom (6-DOF) vibration specification development (VSD) techniques are proposed, discussed, and illustrated through an example.","PeriodicalId":35935,"journal":{"name":"Journal of the IEST","volume":"12 1","pages":"103-115"},"PeriodicalIF":0.0,"publicationDate":"2011-10-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67806716","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 : 2011-01-07DOI: 10.17764/JIET.54.1.X034466930341406
N. Hartvig, G. Farquharson, R. Mielke, M. Varney, Mike Foster
The concentration of airborne particles is a critical parameter for cleanrooms, clean zones, and controlled areas. Particle concentration must be measured at representative locations for classification and monitored routinely or continuously at critical locations during operation. Both ISO 14644-1:19991 and the new Draft International Standard (DIS) edition provide nine classes of cleanliness and specify both the number of sample locations for classification and the acceptance criterion for the data.In the 1999 version of the Standard, the minimal number of sample locations is not based on statistical principles. The acceptance criterion is based on a statistical test, but only if the number of sample locations is less than 10. Thus, classification is based on statistical methods only for a small number of locations.The revised ISO/DIS 14644-12 replaces this method with a statistical principle for selection of the sample locations. The acceptance criterion in the revised version eliminates the need for ap...
{"title":"Sampling Plan for Cleanroom Classification with Respect to Airborne Particles","authors":"N. Hartvig, G. Farquharson, R. Mielke, M. Varney, Mike Foster","doi":"10.17764/JIET.54.1.X034466930341406","DOIUrl":"https://doi.org/10.17764/JIET.54.1.X034466930341406","url":null,"abstract":"The concentration of airborne particles is a critical parameter for cleanrooms, clean zones, and controlled areas. Particle concentration must be measured at representative locations for classification and monitored routinely or continuously at critical locations during operation. Both ISO 14644-1:19991 and the new Draft International Standard (DIS) edition provide nine classes of cleanliness and specify both the number of sample locations for classification and the acceptance criterion for the data.In the 1999 version of the Standard, the minimal number of sample locations is not based on statistical principles. The acceptance criterion is based on a statistical test, but only if the number of sample locations is less than 10. Thus, classification is based on statistical methods only for a small number of locations.The revised ISO/DIS 14644-12 replaces this method with a statistical principle for selection of the sample locations. The acceptance criterion in the revised version eliminates the need for ap...","PeriodicalId":35935,"journal":{"name":"Journal of the IEST","volume":"54 1","pages":"1-15"},"PeriodicalIF":0.0,"publicationDate":"2011-01-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67805480","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 : 2010-10-25DOI: 10.17764/JIET.53.2.Y64W73R736V8M375
E. Pierre-Louis
Protoqualification (PQ) testing, typically performed on the first assembled electronic units and spacecraft, establish random vibration and thermal cycling fatigue margins for subsequent builds that are only subjected to the acceptance test program (ATP). Considering the fatigue damage induced by both unit- and spacecraft-level testing, fatigue margins are calculated for equipment exposed to ATP-level testing. Probabilistic analyses are also performed to determine the relationship between the fatigue margin and the demonstrated reliability for the unit to survive the mission. Parameters such as the number of retests and the material dependent fatigue acceleration exponent are considered.Using MIL-STD-1540E,1 PQ random vibration test guidelines of three decibels (+3 dB) above the acceptance input level for 2-minute-per-axis duration, the assessment shows that the test establishes ample fatigue margin for units subjected to the less stringent ATP. The probabilistic analysis shows that the established reliab...
{"title":"Fatigue Margins Established by Unit and Spacecraft Protoqualification Tests","authors":"E. Pierre-Louis","doi":"10.17764/JIET.53.2.Y64W73R736V8M375","DOIUrl":"https://doi.org/10.17764/JIET.53.2.Y64W73R736V8M375","url":null,"abstract":"Protoqualification (PQ) testing, typically performed on the first assembled electronic units and spacecraft, establish random vibration and thermal cycling fatigue margins for subsequent builds that are only subjected to the acceptance test program (ATP). Considering the fatigue damage induced by both unit- and spacecraft-level testing, fatigue margins are calculated for equipment exposed to ATP-level testing. Probabilistic analyses are also performed to determine the relationship between the fatigue margin and the demonstrated reliability for the unit to survive the mission. Parameters such as the number of retests and the material dependent fatigue acceleration exponent are considered.Using MIL-STD-1540E,1 PQ random vibration test guidelines of three decibels (+3 dB) above the acceptance input level for 2-minute-per-axis duration, the assessment shows that the test establishes ample fatigue margin for units subjected to the less stringent ATP. The probabilistic analysis shows that the established reliab...","PeriodicalId":35935,"journal":{"name":"Journal of the IEST","volume":"53 1","pages":"24-34"},"PeriodicalIF":0.0,"publicationDate":"2010-10-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67805619","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 : 2010-10-25DOI: 10.17764/JIET.53.2.Y7291022622225X3
Ronald Merritt
Transient vibration environments are an important consideration in qualification of aircraft store components — particularly for aircraft with internal storage bays. Generally, these transient vibration environments provide high stimulus input to a store via aerodynamic forces for up to 15 seconds on numerous occasions during training. With the recent introduction of the technique of Time Waveform Replication (TWR) to laboratory testing (MIL-STD-810G Method 525), store components can be readily tested to replications of field-measured transient vibration environments. This paper demonstrates the use of the Generalized Linear Mixed Model (GLMM) on a collection of measured field responses for specification of transient vibration environments. The paper establishes a basis for moving from (1) transient vibration measured field response to (2) transient vibration stochastic specification of the measured field response to (3) laboratory simulation of transient vibration environments.
{"title":"Utilizing the Generalized Linear Mixed Model for Specification and Simulation of Transient Vibration Environments","authors":"Ronald Merritt","doi":"10.17764/JIET.53.2.Y7291022622225X3","DOIUrl":"https://doi.org/10.17764/JIET.53.2.Y7291022622225X3","url":null,"abstract":"Transient vibration environments are an important consideration in qualification of aircraft store components — particularly for aircraft with internal storage bays. Generally, these transient vibration environments provide high stimulus input to a store via aerodynamic forces for up to 15 seconds on numerous occasions during training. With the recent introduction of the technique of Time Waveform Replication (TWR) to laboratory testing (MIL-STD-810G Method 525), store components can be readily tested to replications of field-measured transient vibration environments. This paper demonstrates the use of the Generalized Linear Mixed Model (GLMM) on a collection of measured field responses for specification of transient vibration environments. The paper establishes a basis for moving from (1) transient vibration measured field response to (2) transient vibration stochastic specification of the measured field response to (3) laboratory simulation of transient vibration environments.","PeriodicalId":35935,"journal":{"name":"Journal of the IEST","volume":"53 1","pages":"35-49"},"PeriodicalIF":0.0,"publicationDate":"2010-10-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67805276","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 : 2010-10-25DOI: 10.17764/JIET.53.2.Y3T50K754625822W
D. Weaver
This paper evaluates a laboratory process for extracting, isolating, and identifying rubisco, an essential protein found in plant cells and an important catalyst during photosynthesis. Isolating rubisco from other proteins also found in plants requires a carefully planned series of laboratory procedures to separate the proteins on the basis of physical characteristics including solubility, electrical charge, and molecular size. In this study, ammonium sulfate precipitation was used to extract proteins from a sample of spinach leaves and to separate the proteins into two samples with different solubility characteristics. These samples were then subjected to ion exchange column chromatography using buffers with a range of salt concentrations to produce fractions with varying electrical charge characteristics. The resultant fractions were then analyzed via protein electrophoresis to determine the molecular weight of the isolated proteins, which were compared against the known molecular weight of rubisco. Fin...
{"title":"Isolation and Identification of Rubisco Extracted from Spinach Leaves","authors":"D. Weaver","doi":"10.17764/JIET.53.2.Y3T50K754625822W","DOIUrl":"https://doi.org/10.17764/JIET.53.2.Y3T50K754625822W","url":null,"abstract":"This paper evaluates a laboratory process for extracting, isolating, and identifying rubisco, an essential protein found in plant cells and an important catalyst during photosynthesis. Isolating rubisco from other proteins also found in plants requires a carefully planned series of laboratory procedures to separate the proteins on the basis of physical characteristics including solubility, electrical charge, and molecular size. In this study, ammonium sulfate precipitation was used to extract proteins from a sample of spinach leaves and to separate the proteins into two samples with different solubility characteristics. These samples were then subjected to ion exchange column chromatography using buffers with a range of salt concentrations to produce fractions with varying electrical charge characteristics. The resultant fractions were then analyzed via protein electrophoresis to determine the molecular weight of the isolated proteins, which were compared against the known molecular weight of rubisco. Fin...","PeriodicalId":35935,"journal":{"name":"Journal of the IEST","volume":"53 1","pages":"18-23"},"PeriodicalIF":0.0,"publicationDate":"2010-10-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67805353","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 : 2010-10-25DOI: 10.17764/JIET.53.2.Y8286660G3483QR3
H. Parsons
{"title":"The Clothes Truly Did Make This Man","authors":"H. Parsons","doi":"10.17764/JIET.53.2.Y8286660G3483QR3","DOIUrl":"https://doi.org/10.17764/JIET.53.2.Y8286660G3483QR3","url":null,"abstract":"","PeriodicalId":35935,"journal":{"name":"Journal of the IEST","volume":"53 1","pages":"1-4"},"PeriodicalIF":0.0,"publicationDate":"2010-10-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67805382","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 : 2010-04-12DOI: 10.17764/JIET.53.1.18763271G23N61X0
Jie Gu, M. Pecht
Traditional handbook-based reliability prediction methods for electronic products are inaccurate and misleading. In this paper, we will present a prognostics and health management (PHM) approach that is more suitable for reliability (remaining life) assessment for electronic products, since it considers actual operational and environmental loading conditions for individual products. The process for implementing PHM in electronics is discussed. Several examples of implementation in industry and defense are also given.
{"title":"Prognostics and Health Assessment Implementation for Electronic Products","authors":"Jie Gu, M. Pecht","doi":"10.17764/JIET.53.1.18763271G23N61X0","DOIUrl":"https://doi.org/10.17764/JIET.53.1.18763271G23N61X0","url":null,"abstract":"Traditional handbook-based reliability prediction methods for electronic products are inaccurate and misleading. In this paper, we will present a prognostics and health management (PHM) approach that is more suitable for reliability (remaining life) assessment for electronic products, since it considers actual operational and environmental loading conditions for individual products. The process for implementing PHM in electronics is discussed. Several examples of implementation in industry and defense are also given.","PeriodicalId":35935,"journal":{"name":"Journal of the IEST","volume":"53 1","pages":"44-58"},"PeriodicalIF":0.0,"publicationDate":"2010-04-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67804662","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 : 2010-04-12DOI: 10.17764/JIET.53.1.18M5H0U285845U84
Doug Lund, R. Crawford
When vertical vibration testing of large test articles is required, it is common to install a head expander on the armature of a shaker. Larger test articles often have a center of gravity relatively far above the mounting surface. When combined with the armature and head expander, these test articles may exhibit multiple structural resonances within the desired test band that do not exist in the intended application. These test configuration-driven characteristics are likely to create unwanted cross-axis excitation during a vibration test.The difficulty in controlling unwanted cross-axis motion usually increases when testing large items. Excessive cross-axis motion can "over-test" the test item, creating the risk of damaging the test item, or can limit the input in the test axis, thus jeopardizing a successful test.Orbital Sciences commissioned the design of a guided head expander system that greatly reduces the cross-axis motion at the test article mounting surface of the head expander. The design submi...
{"title":"Novel Guided Head Expander Design Uses Close Coupled Inertial Masses and Hydrostatic Bearings to Minimize Cross-Axis Motion","authors":"Doug Lund, R. Crawford","doi":"10.17764/JIET.53.1.18M5H0U285845U84","DOIUrl":"https://doi.org/10.17764/JIET.53.1.18M5H0U285845U84","url":null,"abstract":"When vertical vibration testing of large test articles is required, it is common to install a head expander on the armature of a shaker. Larger test articles often have a center of gravity relatively far above the mounting surface. When combined with the armature and head expander, these test articles may exhibit multiple structural resonances within the desired test band that do not exist in the intended application. These test configuration-driven characteristics are likely to create unwanted cross-axis excitation during a vibration test.The difficulty in controlling unwanted cross-axis motion usually increases when testing large items. Excessive cross-axis motion can \"over-test\" the test item, creating the risk of damaging the test item, or can limit the input in the test axis, thus jeopardizing a successful test.Orbital Sciences commissioned the design of a guided head expander system that greatly reduces the cross-axis motion at the test article mounting surface of the head expander. The design submi...","PeriodicalId":35935,"journal":{"name":"Journal of the IEST","volume":"53 1","pages":"69-82"},"PeriodicalIF":0.0,"publicationDate":"2010-04-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67804742","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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