A Nickel-Aluminum alloy strengthened by γ′ (Ni3Al) intermetallic ordered coherent precipitates with a small misfit strain was used a demonstration material to develop a model to predict strengthening behavior during plastic deformation as a consequence of the γ′ particles acting as obstacles to the dislocations and thus impeding their glide motion through the alloy. It was determined that the two most dominate strengthening mechanisms in the Ni-Al system were order hardening when the particles were smaller than the critical looping radius, and Orowan strengthening when the particles were larger than the looping radius. In the overaged condition when the particles are large in size, the dislocations bypass and loop the particles by the Orowan mechanism. In the underaged to peak aged conditions where the particles are usually smaller than the looping radius, the dislocations shear the precipitates during deformation. The total polycrystalline yield strength included contributions from the intrinsic lattice strength, the solid solution strengthening, grain size strengthening, and particle strengthening which included the order hardening and Orowan strengthening contributions. The total mechanical yield strength for a Ni-6.27wt.%A1 alloy was predicted for the peak-aged condition based on the theory for order strengthening and was found to be in good agreement with the experimental peak-strength data for Ni-6.27A1.
{"title":"Mechanical Strength Modeling of Particle Strengthened Nickel-Aluminum Alloys Strengthened by Intermetallic γ′ (Ni3Al) Precipitates","authors":"J. Fragomeni","doi":"10.1115/imece1999-0629","DOIUrl":"https://doi.org/10.1115/imece1999-0629","url":null,"abstract":"\u0000 A Nickel-Aluminum alloy strengthened by γ′ (Ni3Al) intermetallic ordered coherent precipitates with a small misfit strain was used a demonstration material to develop a model to predict strengthening behavior during plastic deformation as a consequence of the γ′ particles acting as obstacles to the dislocations and thus impeding their glide motion through the alloy. It was determined that the two most dominate strengthening mechanisms in the Ni-Al system were order hardening when the particles were smaller than the critical looping radius, and Orowan strengthening when the particles were larger than the looping radius. In the overaged condition when the particles are large in size, the dislocations bypass and loop the particles by the Orowan mechanism. In the underaged to peak aged conditions where the particles are usually smaller than the looping radius, the dislocations shear the precipitates during deformation. The total polycrystalline yield strength included contributions from the intrinsic lattice strength, the solid solution strengthening, grain size strengthening, and particle strengthening which included the order hardening and Orowan strengthening contributions. The total mechanical yield strength for a Ni-6.27wt.%A1 alloy was predicted for the peak-aged condition based on the theory for order strengthening and was found to be in good agreement with the experimental peak-strength data for Ni-6.27A1.","PeriodicalId":270413,"journal":{"name":"Recent Advances in Solids and Structures","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1999-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134069975","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}
Harbor Branch Oceanographic Institution (HBOI) designed, built and has operated two JOHNSON-SEA-LINK (JSL) manned submersibles for the past 25 years. The JSL submersibles each incorporate a 66–68 in. (1.6764–1.7272 m) OD, 4–5.25 in. (0.1016–0.13335 m) thick acrylic two-man sphere as a Pressure Vessel for Human Occupancy (PVHO). This type of spherical acrylic sphere or submersible was first introduced in around 1970 and is known as Naval Experimental Manned Observatory (NEMO) submersibles. As the demand increases for ocean exploration to 3000 ft. (914.4 m) depth to collect samples, to study the ocean surfaces, the problem of developing cracks at the interface of these manned acrylic submersibles following few hundred dives have become a common phenomena. This has drawn considerable attentions for reinvestigation of the spherical acrylic submersible in order to overcome this crack generation problem at the interface. Therefore, a new full-scale 3-D nonlinear FEA (Finite Element Analysis) model, similar to the spherical acrylic submersible that HBOI uses for ocean exploration, has been developed for the first time in order to simulate the structural behavior at the interface and throughout the sphere, for better understanding of the mechanical behavior. Variation of the stiffness between dissimilar materials at the interface, lower nylon gasket thickness, over designed aluminum hatch are seemed to be few of the causes for higher stresses within acrylic sphere at the nylon gasket/acrylic interface. Following the basic understanding of the stresses and relative displacements at the interface and within different parts of the submersible, various models have been developed on the basis of different shapes and thickness of nylon gaskets, openings of the acrylic sphere, hatch geometry and its materials, specifically to study their effect on the overall performance of the acrylic submersible. Finally, the new model for acrylic submersible has been developed by redesigning the top aluminum hatch and hatch ring, the sphere openings at both top and bottom, as well as the nylon gasket inserts. Altogether this new design indicates a significant improvement over the existing spherical acrylic submersible by reducing the stresses at the top gasket/acrylic interface considerably. Redesigning of the bottom penetrator plate, at present, is underway. In this paper, results from numerical modeling only are reported in details. Correlation between experimental-numerical modeling results for the new model will be reported in the near future.
{"title":"Detailed Stress Analysis of a Spherical Acrylic Submersible by 3-D Finite Element Modeling","authors":"P. S. Das","doi":"10.1115/imece1999-0626","DOIUrl":"https://doi.org/10.1115/imece1999-0626","url":null,"abstract":"\u0000 Harbor Branch Oceanographic Institution (HBOI) designed, built and has operated two JOHNSON-SEA-LINK (JSL) manned submersibles for the past 25 years. The JSL submersibles each incorporate a 66–68 in. (1.6764–1.7272 m) OD, 4–5.25 in. (0.1016–0.13335 m) thick acrylic two-man sphere as a Pressure Vessel for Human Occupancy (PVHO). This type of spherical acrylic sphere or submersible was first introduced in around 1970 and is known as Naval Experimental Manned Observatory (NEMO) submersibles. As the demand increases for ocean exploration to 3000 ft. (914.4 m) depth to collect samples, to study the ocean surfaces, the problem of developing cracks at the interface of these manned acrylic submersibles following few hundred dives have become a common phenomena. This has drawn considerable attentions for reinvestigation of the spherical acrylic submersible in order to overcome this crack generation problem at the interface. Therefore, a new full-scale 3-D nonlinear FEA (Finite Element Analysis) model, similar to the spherical acrylic submersible that HBOI uses for ocean exploration, has been developed for the first time in order to simulate the structural behavior at the interface and throughout the sphere, for better understanding of the mechanical behavior. Variation of the stiffness between dissimilar materials at the interface, lower nylon gasket thickness, over designed aluminum hatch are seemed to be few of the causes for higher stresses within acrylic sphere at the nylon gasket/acrylic interface.\u0000 Following the basic understanding of the stresses and relative displacements at the interface and within different parts of the submersible, various models have been developed on the basis of different shapes and thickness of nylon gaskets, openings of the acrylic sphere, hatch geometry and its materials, specifically to study their effect on the overall performance of the acrylic submersible. Finally, the new model for acrylic submersible has been developed by redesigning the top aluminum hatch and hatch ring, the sphere openings at both top and bottom, as well as the nylon gasket inserts. Altogether this new design indicates a significant improvement over the existing spherical acrylic submersible by reducing the stresses at the top gasket/acrylic interface considerably. Redesigning of the bottom penetrator plate, at present, is underway. In this paper, results from numerical modeling only are reported in details. Correlation between experimental-numerical modeling results for the new model will be reported in the near future.","PeriodicalId":270413,"journal":{"name":"Recent Advances in Solids and Structures","volume":"15 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1999-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130722609","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}
Linear finite element analysis (fea) was performed to determine stress concentration factors for the threads and the bolt head fillet in a bolted connection. The fea models consisted of axisymmetric representations of a bolt and two circular steel plates each 20 mm in thickness. The bolts studied were 8, 12, 16, 20, and 24 mm diameter grade 10.9 metric bolts with the standard M thread profile. The threads were modeled at both the minimum and maximum allowable depths. The fillet between the bolt shank and bolt head connection was modeled at its minimum radius. Each bolt was loaded to its proof strength. A comparison is made to stress concentration factors typically used in bolted connection design. Stress concentration factors in the head fillet were 3.18, 3.23, 3.63, 3.58, and 3.90 for the 8, 12, 16, 20, and 24 mm bolts, respectively. Thread stress concentration factors were highest in the first engaged thread and decreased in each successive thread moving toward the end of the bolt. Stress concentration factors for the shallow thread models ranged from 1.17 to 4.33, 0.87 to 4.32, 0.83 to 4.67, 0.87 to 4.77, and 0.82 to 4.82 for the 8, 12, 16, 20, and 24 mm bolts, respectively. Likewise, stress concentration factors for the deep thread models ranged from 1.18 to 4.80, 0.88 to 4.80, 0.78 to 5.12, 0.83 to 5.17, and 0.82 to 5.22 for the 8, 12, 16, 20, and 24 mm bolts, respectively.
{"title":"Bolt Thread and Head Fillet Stress Concentration Factors","authors":"T. F. Lehnhoff, Bradley A. Bunyard","doi":"10.1115/1.556168","DOIUrl":"https://doi.org/10.1115/1.556168","url":null,"abstract":"\u0000 Linear finite element analysis (fea) was performed to determine stress concentration factors for the threads and the bolt head fillet in a bolted connection. The fea models consisted of axisymmetric representations of a bolt and two circular steel plates each 20 mm in thickness. The bolts studied were 8, 12, 16, 20, and 24 mm diameter grade 10.9 metric bolts with the standard M thread profile. The threads were modeled at both the minimum and maximum allowable depths. The fillet between the bolt shank and bolt head connection was modeled at its minimum radius. Each bolt was loaded to its proof strength. A comparison is made to stress concentration factors typically used in bolted connection design. Stress concentration factors in the head fillet were 3.18, 3.23, 3.63, 3.58, and 3.90 for the 8, 12, 16, 20, and 24 mm bolts, respectively. Thread stress concentration factors were highest in the first engaged thread and decreased in each successive thread moving toward the end of the bolt. Stress concentration factors for the shallow thread models ranged from 1.17 to 4.33, 0.87 to 4.32, 0.83 to 4.67, 0.87 to 4.77, and 0.82 to 4.82 for the 8, 12, 16, 20, and 24 mm bolts, respectively. Likewise, stress concentration factors for the deep thread models ranged from 1.18 to 4.80, 0.88 to 4.80, 0.78 to 5.12, 0.83 to 5.17, and 0.82 to 5.22 for the 8, 12, 16, 20, and 24 mm bolts, respectively.","PeriodicalId":270413,"journal":{"name":"Recent Advances in Solids and Structures","volume":"227 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1999-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114775200","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}
By interrogating polyurethane specimens containing bondlines with cracks photoelastically, the authors are conducting a study of the effect of fixed ends upon the stress intensity factor (SIF) for double edge cracked specimens for test specimens of relatively short height. Preliminary results suggest that, while the presence of the bondline increases the SIF with increasing crack length, reducing the specimen height will reduce the SIF level for all crack lengths.
{"title":"Test Geometries for Bondline Cracked Photoelastic Models; Preliminary Results","authors":"C. Smith, K. Gloss, C. Liu","doi":"10.1115/imece1999-0610","DOIUrl":"https://doi.org/10.1115/imece1999-0610","url":null,"abstract":"\u0000 By interrogating polyurethane specimens containing bondlines with cracks photoelastically, the authors are conducting a study of the effect of fixed ends upon the stress intensity factor (SIF) for double edge cracked specimens for test specimens of relatively short height. Preliminary results suggest that, while the presence of the bondline increases the SIF with increasing crack length, reducing the specimen height will reduce the SIF level for all crack lengths.","PeriodicalId":270413,"journal":{"name":"Recent Advances in Solids and Structures","volume":"9 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1999-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131117032","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}
This paper studied crack initiation in a hard particle reinforced composite with a soft rubber-like matrix material using a numerical technique. The numerical specimen considered had a semi-circular notch with a linearly varying length. The initial crack size occurring at the notch tip was modeled and predicted using a micro/macro-approach along with a damage model. A criterion to predict the initial crack size was proposed based on the size of a localized unstable material zone. Different notch sizes were compared to their initial crack sizes.
{"title":"Damage Study in Notched Particulate Composite Specimens Under Non-Uniform Strain Loading","authors":"Y. W. Kwon, C. Liu","doi":"10.1115/imece1999-0611","DOIUrl":"https://doi.org/10.1115/imece1999-0611","url":null,"abstract":"\u0000 This paper studied crack initiation in a hard particle reinforced composite with a soft rubber-like matrix material using a numerical technique. The numerical specimen considered had a semi-circular notch with a linearly varying length. The initial crack size occurring at the notch tip was modeled and predicted using a micro/macro-approach along with a damage model. A criterion to predict the initial crack size was proposed based on the size of a localized unstable material zone. Different notch sizes were compared to their initial crack sizes.","PeriodicalId":270413,"journal":{"name":"Recent Advances in Solids and Structures","volume":"2016 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1999-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127445008","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}
The application of shape optimization using shape vectors, generated by thermal loading, has been presented. A steering knuckle is to be redesigned for weight reduction. Since it is not uniform in shape, it is very cumbersome to use traditional loads and/or displacement methods to generate shape vectors. So different regions of the steering knuckle are subjected to thermal loads independently, and the resulting displacements are used as shape vectors. Shape optimization is performed in MSC/NASTRAN using ‘Direct Linearization’ method. Design directions have been obtained to reduce its weight by 7.6%. In conclusion, thermal displacements can be used in shape optimization of a steering knuckle.
{"title":"Thermal Shape Vectors in Finite Element Shape Optimization of a Steering Knuckle","authors":"M. Krishna, Michael R. Fetcho","doi":"10.1115/imece1998-0897","DOIUrl":"https://doi.org/10.1115/imece1998-0897","url":null,"abstract":"\u0000 The application of shape optimization using shape vectors, generated by thermal loading, has been presented. A steering knuckle is to be redesigned for weight reduction. Since it is not uniform in shape, it is very cumbersome to use traditional loads and/or displacement methods to generate shape vectors. So different regions of the steering knuckle are subjected to thermal loads independently, and the resulting displacements are used as shape vectors. Shape optimization is performed in MSC/NASTRAN using ‘Direct Linearization’ method. Design directions have been obtained to reduce its weight by 7.6%. In conclusion, thermal displacements can be used in shape optimization of a steering knuckle.","PeriodicalId":270413,"journal":{"name":"Recent Advances in Solids and Structures","volume":"2 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114923743","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}
This paper presents the feasibility of acoustic emission technique in predicting the residual fatigue life prediction of 6061-T6 aluminum matrix composite reinforced with 15 vol. % SiC particulates (SiCp). Fatigue damages corresponding to 40%, 60% and 80% of total fatigue life were stimulated at a cyclic stress amplitude. The specimens with and without fatigue damage were subjected to tensile tests. The acoustic emission activities were monitored during tensile tests. The number of the cumulative AE events increased exponentially with the increase of strain during tensile tests. This exponential increase occurred when the material was in the plastic regime and was attributed mainly to SiC particulate/matrix interface decohesion. The cumulative events during post fatigue tensile tests reduced with the decrease of the fatigue residual life. Based on the high cycle fatigue damage accumulation model, a Weibull probability distribution model is developed to explain the post fatigue AE activity of specimens during tensile test. Using the model, the residual fatigue life can be predicted by testing the specimen in tension and monitoring the AE events. In high cycle fatigue, it was observed that the residual tensile strengths of the material did not change significantly with prior cyclic loading damages since the high cycle fatigue life was dominated by the crack initiation phase.
{"title":"Fatigue-Life Prediction of SiC Particulate Reinforced Aluminum Alloy 6061 Matrix Composite Using a Weibull Distribution Model","authors":"D. Shan, H. Nayeb-Hashemi","doi":"10.1115/imece1998-0892","DOIUrl":"https://doi.org/10.1115/imece1998-0892","url":null,"abstract":"\u0000 This paper presents the feasibility of acoustic emission technique in predicting the residual fatigue life prediction of 6061-T6 aluminum matrix composite reinforced with 15 vol. % SiC particulates (SiCp). Fatigue damages corresponding to 40%, 60% and 80% of total fatigue life were stimulated at a cyclic stress amplitude. The specimens with and without fatigue damage were subjected to tensile tests. The acoustic emission activities were monitored during tensile tests. The number of the cumulative AE events increased exponentially with the increase of strain during tensile tests. This exponential increase occurred when the material was in the plastic regime and was attributed mainly to SiC particulate/matrix interface decohesion. The cumulative events during post fatigue tensile tests reduced with the decrease of the fatigue residual life. Based on the high cycle fatigue damage accumulation model, a Weibull probability distribution model is developed to explain the post fatigue AE activity of specimens during tensile test. Using the model, the residual fatigue life can be predicted by testing the specimen in tension and monitoring the AE events. In high cycle fatigue, it was observed that the residual tensile strengths of the material did not change significantly with prior cyclic loading damages since the high cycle fatigue life was dominated by the crack initiation phase.","PeriodicalId":270413,"journal":{"name":"Recent Advances in Solids and Structures","volume":"48 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126683020","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}
Residual stress distribution has been determined in spot welds, which are generally used to join mild steel sheets. Various spot weld configurations were investigated using the full-field, experimental, optical technique of high sensitivity moiré interferometry. These stresses were found to be in the range 250–300 MPa (tensile) in the center and decreased to 40–100 MPa (tensile) at the edge of the weld nugget. Low cycle fatigue loading of the spot weld caused the residual stress to drop in the weld center by about 30% and increase at the edges by as much as 100%.
{"title":"Residual Stress Measurement in Spot Welds and the Effect of Fatigue Loading Using High Sensitivity Moire Interferometry","authors":"S. Khanna, Canlong He, H. Agrawal","doi":"10.1115/imece1998-0890","DOIUrl":"https://doi.org/10.1115/imece1998-0890","url":null,"abstract":"\u0000 Residual stress distribution has been determined in spot welds, which are generally used to join mild steel sheets. Various spot weld configurations were investigated using the full-field, experimental, optical technique of high sensitivity moiré interferometry. These stresses were found to be in the range 250–300 MPa (tensile) in the center and decreased to 40–100 MPa (tensile) at the edge of the weld nugget. Low cycle fatigue loading of the spot weld caused the residual stress to drop in the weld center by about 30% and increase at the edges by as much as 100%.","PeriodicalId":270413,"journal":{"name":"Recent Advances in Solids and Structures","volume":"7 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132033832","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}
Acoustic Emissions (AE) are generated during operational loading of Fiber Reinforced Composite (FRC) materials due to various sources of fracture. These sources which include matrix fracture, fiber fracture, splitting and delamination could be generated individually or simultaneously. The multiplicity of defects and failure modes creates problems in identifying and distinguishing various sources of emissions. This analysis is further complicated due to the friction related emissions (generated during grating of newly generated damage surfaces and fretting of broken fibers with matrix) that mask the actual signal and in most cases, exceeds the emissions from actual damage. The objectives of this research was to decompose the AE signals into different levels based on frequency, identify frequency of friction based emissions and to associate various failure modes with specific frequencies. Through utilization of Wavelet transforms, it became possible to present the spectral composition of a transient signal (AE signal) in a time-frequency map. The results indicate that Wavelet analysis would be an effective tool in the analysis of AE by providing information relative to the frequency of the emissions and assist researchers in determining the extent and type of damage during online inspection of component.
{"title":"Discrete Wavelet Analysis of Acoustic Emissions During Fatigue Loading of Carbon Fiber Reinforced Composites","authors":"Girish P. Kamala, J. Hashemi, A. Barhorst","doi":"10.1115/imece1998-0893","DOIUrl":"https://doi.org/10.1115/imece1998-0893","url":null,"abstract":"\u0000 Acoustic Emissions (AE) are generated during operational loading of Fiber Reinforced Composite (FRC) materials due to various sources of fracture. These sources which include matrix fracture, fiber fracture, splitting and delamination could be generated individually or simultaneously. The multiplicity of defects and failure modes creates problems in identifying and distinguishing various sources of emissions. This analysis is further complicated due to the friction related emissions (generated during grating of newly generated damage surfaces and fretting of broken fibers with matrix) that mask the actual signal and in most cases, exceeds the emissions from actual damage. The objectives of this research was to decompose the AE signals into different levels based on frequency, identify frequency of friction based emissions and to associate various failure modes with specific frequencies.\u0000 Through utilization of Wavelet transforms, it became possible to present the spectral composition of a transient signal (AE signal) in a time-frequency map. The results indicate that Wavelet analysis would be an effective tool in the analysis of AE by providing information relative to the frequency of the emissions and assist researchers in determining the extent and type of damage during online inspection of component.","PeriodicalId":270413,"journal":{"name":"Recent Advances in Solids and Structures","volume":"42 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127114333","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}
This paper investigates a cause for warpage in structures manufactured using filament winding or fiber placement. This warpage phenomena has been determined to be caused by fiber/resin consolidation resulting from manufacturing parameters including: cure pressure, winding tension, and material system characteristics. This is a non-thermal phenomena and is independent of cure temperature, or finished part operational environments. A novel theory has been developed to predict the warpage or “springback” resulting from the processing induced strain gradient that develops in laminates due to the consolidation. This paper utilizes a strain model derived previously to develop a warpage prediction model utilizing Classical Laminated Plate Theory (CLT). This theoretical solution is than compared to experimental results for hoop wound test specimens. The end goal of the research is to develop a springback prediction model that can be applied to large scale parts utilizing consolidation parameters measured at the coupon level.
{"title":"Processing Induced Warpage in Composite Cylindrical Shells","authors":"T. Meink, M. Shen","doi":"10.1115/imece1998-0884","DOIUrl":"https://doi.org/10.1115/imece1998-0884","url":null,"abstract":"\u0000 This paper investigates a cause for warpage in structures manufactured using filament winding or fiber placement. This warpage phenomena has been determined to be caused by fiber/resin consolidation resulting from manufacturing parameters including: cure pressure, winding tension, and material system characteristics. This is a non-thermal phenomena and is independent of cure temperature, or finished part operational environments. A novel theory has been developed to predict the warpage or “springback” resulting from the processing induced strain gradient that develops in laminates due to the consolidation. This paper utilizes a strain model derived previously to develop a warpage prediction model utilizing Classical Laminated Plate Theory (CLT). This theoretical solution is than compared to experimental results for hoop wound test specimens. The end goal of the research is to develop a springback prediction model that can be applied to large scale parts utilizing consolidation parameters measured at the coupon level.","PeriodicalId":270413,"journal":{"name":"Recent Advances in Solids and Structures","volume":"7 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121600010","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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