Advances in probabilistic methods to support the design of mechanical systems is now moving to the engineering desktop. Basic modeling strategies are understood and in use in many applications. There are still issues to be resolved in the application of these methods to reliability critical applications. Some of these issues will be highlighted. At the same time, the design of complex aerospace systems requires more than just probabilistic methods as we know them now. The presentation will review a recent study by its author on the development and application of non-traditional and non-deterministic methods new methods to the life cycle design and analysis of extremely complex aerospace systems. Not only “traditional” mathematical analysis methodologies (such as mathematical optimization, Bayesian methods, or robust statistical design) are reviewed, but also “soft” or “non-traditional” methods (such as neural networks, fuzzy logic or genetic algorithms). In particular, emphasis will be given to the synthesis of many of these elements into the design systems of the future.
{"title":"Advances in Probabilistic Methods","authors":"T. Cruse","doi":"10.1115/imece2000-2668","DOIUrl":"https://doi.org/10.1115/imece2000-2668","url":null,"abstract":"\u0000 Advances in probabilistic methods to support the design of mechanical systems is now moving to the engineering desktop. Basic modeling strategies are understood and in use in many applications. There are still issues to be resolved in the application of these methods to reliability critical applications. Some of these issues will be highlighted. At the same time, the design of complex aerospace systems requires more than just probabilistic methods as we know them now. The presentation will review a recent study by its author on the development and application of non-traditional and non-deterministic methods new methods to the life cycle design and analysis of extremely complex aerospace systems. Not only “traditional” mathematical analysis methodologies (such as mathematical optimization, Bayesian methods, or robust statistical design) are reviewed, but also “soft” or “non-traditional” methods (such as neural networks, fuzzy logic or genetic algorithms). In particular, emphasis will be given to the synthesis of many of these elements into the design systems of the future.","PeriodicalId":324509,"journal":{"name":"Materials: Book of Abstracts","volume":"83 1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132152230","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}
Al2O3 coatings produced by plasma spray have been considered for wear resistance and corrosion protection. Mechanical investigations of these coatings are often performed when the coating is still on the metallic substrate, hiding the intrinsic response of the coatings and the lamellae that make up their microstructure. The development of a compression test for stand-alone coatings will be described. Cyclic compression loading with monotonically increased peak stresses was employed to study the deformation and damage of the coatings. Transmission electron microscopy and acoustic emission were also used to identify damage mechanisms that ultimately lead to failure. It is proposed that numerous defects that exist in plasma-sprayed coatings, including porosity and microcracks, serve as sites for crack nucleation and/or propagation. As these small cracks extend subcritically under an applied stress that ultimately propagate parallel to the loading direction along inter-lamella boundaries. With increasing stress, these cracks ultimately link resulting in catastrophic failure.
{"title":"Damage Mechanisms in Plasma-Sprayed Alumina Coatings","authors":"R. Trice, D. Prine, K. Faber","doi":"10.1115/imece2000-2690","DOIUrl":"https://doi.org/10.1115/imece2000-2690","url":null,"abstract":"\u0000 Al2O3 coatings produced by plasma spray have been considered for wear resistance and corrosion protection. Mechanical investigations of these coatings are often performed when the coating is still on the metallic substrate, hiding the intrinsic response of the coatings and the lamellae that make up their microstructure. The development of a compression test for stand-alone coatings will be described. Cyclic compression loading with monotonically increased peak stresses was employed to study the deformation and damage of the coatings. Transmission electron microscopy and acoustic emission were also used to identify damage mechanisms that ultimately lead to failure. It is proposed that numerous defects that exist in plasma-sprayed coatings, including porosity and microcracks, serve as sites for crack nucleation and/or propagation. As these small cracks extend subcritically under an applied stress that ultimately propagate parallel to the loading direction along inter-lamella boundaries. With increasing stress, these cracks ultimately link resulting in catastrophic failure.","PeriodicalId":324509,"journal":{"name":"Materials: Book of Abstracts","volume":"17 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134367977","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}
E. Kung, C. Mercer, S. Allameh, O. Popoola, W. Soboyejo
The fatigue behavior of Fe-Ni-base metal/polymer composites is discussed in this paper. These are proposed as self lubricating surfaces with the potential to replace conventionally lubricated pistons in automotive engines. Following a description of composite microstructure and basic mechanical properties, the paper examines the effects of polymer volume fraction on long fatigue crack growth. The effects of temperature on fatigue crack growth are then elucidated before presenting some initial fracture mechanics concepts for the prediction of fatigue life. The implications of the results are assessed for the design of durable surfaces.
{"title":"An Investigation of Fatigue in Polymer/Metal Composites","authors":"E. Kung, C. Mercer, S. Allameh, O. Popoola, W. Soboyejo","doi":"10.1115/imece2000-2694","DOIUrl":"https://doi.org/10.1115/imece2000-2694","url":null,"abstract":"\u0000 The fatigue behavior of Fe-Ni-base metal/polymer composites is discussed in this paper. These are proposed as self lubricating surfaces with the potential to replace conventionally lubricated pistons in automotive engines. Following a description of composite microstructure and basic mechanical properties, the paper examines the effects of polymer volume fraction on long fatigue crack growth. The effects of temperature on fatigue crack growth are then elucidated before presenting some initial fracture mechanics concepts for the prediction of fatigue life. The implications of the results are assessed for the design of durable surfaces.","PeriodicalId":324509,"journal":{"name":"Materials: Book of Abstracts","volume":"27 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115442741","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}
A design concept for potentially hard damage-resistant ceramic coatings on relatively soft substrates is proposed. Such coating structures are of direct relevance to biomechanical structures, especially teeth and dental crowns. In this study failure modes in bilayers and trilayers with relatively hard, brittle coating outerlayers on soft, tough substrate underlayers are evaluated. Coating/substrate systems of interest include ceramic/ceramic, ceramic/metal, and ceramic/polymer. A key element of these structures is a well-bonded interface, to prevent delamination during stressing. The objective is to arrest intrusive coating cracks in a tough sublayer, rather than merely to deflect them along a weak interface.
{"title":"Failure of Ceramic Coatings on Soft Substrates","authors":"B. Lawn","doi":"10.1115/imece2000-2661","DOIUrl":"https://doi.org/10.1115/imece2000-2661","url":null,"abstract":"\u0000 A design concept for potentially hard damage-resistant ceramic coatings on relatively soft substrates is proposed. Such coating structures are of direct relevance to biomechanical structures, especially teeth and dental crowns. In this study failure modes in bilayers and trilayers with relatively hard, brittle coating outerlayers on soft, tough substrate underlayers are evaluated. Coating/substrate systems of interest include ceramic/ceramic, ceramic/metal, and ceramic/polymer. A key element of these structures is a well-bonded interface, to prevent delamination during stressing. The objective is to arrest intrusive coating cracks in a tough sublayer, rather than merely to deflect them along a weak interface.","PeriodicalId":324509,"journal":{"name":"Materials: Book of Abstracts","volume":"71 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122611905","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}
Laser shock peening is developing into a commercial surface enhancement process for increasing the fatigue life of metal components. The process produces deep residual compressive stresses into treated surfaces which inhibit the initiation and propagation of fatigue cracks. The process has been particularly effective in increasing the resistance to foreign object damage in fan and compressor blades of aircraft gas turbine engines. However, the potential application of this process is much broader, encompassing automotive, tooling and dies, and others. Significant effort is being made to lower the cost and increase the throughput of the process, to make it an affordable process for many more applications. This describes the process and reviews the progress being made in the technology, both in material property enhancement and use of the process, and towards reducing cost and increasing throughput.
{"title":"Laser Shock Peening for Fatigue Resistance","authors":"A. Clauer","doi":"10.1115/imece2000-2681","DOIUrl":"https://doi.org/10.1115/imece2000-2681","url":null,"abstract":"\u0000 Laser shock peening is developing into a commercial surface enhancement process for increasing the fatigue life of metal components. The process produces deep residual compressive stresses into treated surfaces which inhibit the initiation and propagation of fatigue cracks. The process has been particularly effective in increasing the resistance to foreign object damage in fan and compressor blades of aircraft gas turbine engines. However, the potential application of this process is much broader, encompassing automotive, tooling and dies, and others. Significant effort is being made to lower the cost and increase the throughput of the process, to make it an affordable process for many more applications. This describes the process and reviews the progress being made in the technology, both in material property enhancement and use of the process, and towards reducing cost and increasing throughput.","PeriodicalId":324509,"journal":{"name":"Materials: Book of Abstracts","volume":"66 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130500787","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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