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Author: Brian Lee Wardle
Publisher:
ISBN:
Category :
Languages : en
Pages : 25
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Book Description
The experimental impact and quasi-static response, including damage resistance, of various composite shell structures was investigated and reported in a previous document. As an addendum to that original work, the surface damage was characterized. This characterization was in the form of the depth of the dent, which supplements the lengths and area of the visibly damaged region obtained previously. Thus, a three-dimensional characterization of the surface of the impact site was obtained nondestructively. The dent depth measurements are compared with internal damage states previously obtained by the X-radiography technique to better understand the implications of "barely visible impact damage" (BVID). No correlation was found between internal (nonvisible) damage from the X-ray data and the measured characteristics of the surface damage, specifically depth of the dent. In the work previously reported, it was found useful to separate damage data with regard to the presence of shell instability in the response. Peak force was then found to correlate the resulting internal damage for both shell and plate specimens. However, dent depth shows no such general trend or correlation with peak force when the data is separated with regard to the presence of shell instability. This indicates that, for the cases considered, dent depth is not a good indicator of internal damage extent for thin (less than 2.4 mm, or 0.10") composite plate and shell structures.
Author: Brian Lee Wardle
Publisher:
ISBN:
Category :
Languages : en
Pages : 25
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Book Description
The experimental impact and quasi-static response, including damage resistance, of various composite shell structures was investigated and reported in a previous document. As an addendum to that original work, the surface damage was characterized. This characterization was in the form of the depth of the dent, which supplements the lengths and area of the visibly damaged region obtained previously. Thus, a three-dimensional characterization of the surface of the impact site was obtained nondestructively. The dent depth measurements are compared with internal damage states previously obtained by the X-radiography technique to better understand the implications of "barely visible impact damage" (BVID). No correlation was found between internal (nonvisible) damage from the X-ray data and the measured characteristics of the surface damage, specifically depth of the dent. In the work previously reported, it was found useful to separate damage data with regard to the presence of shell instability in the response. Peak force was then found to correlate the resulting internal damage for both shell and plate specimens. However, dent depth shows no such general trend or correlation with peak force when the data is separated with regard to the presence of shell instability. This indicates that, for the cases considered, dent depth is not a good indicator of internal damage extent for thin (less than 2.4 mm, or 0.10") composite plate and shell structures.
Author: John C. Riviere
Publisher: CRC Press
ISBN: 9780824700805
Category : Science
Languages : en
Pages : 1006
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Book Description
Integrating advances in instrumentation and methods, this work offers an approach to solving problems in surface and interface analysis, beginning with a particular problem and then explaining the most rational and efficient route to a solution. The book discusses electron optical and scanned probe microscopy, high spatial resolution imaging and synchrotron-based techniques. It emphasizes problem-solving for different classes of materials and material function.
Author: Brian Lee Wardle
Publisher:
ISBN:
Category :
Languages : en
Pages : 11
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Book Description
The damage resistance of thin composite structures was investigated experimentally. Specifically, surface damage in the form of dent-depth measurements are compared with internal damage states obtained by the X-radiography technique to better understand the implications of "barely visible impact damage" (BVID). Impact and quasi-static tests were conducted on plate and shell graphite/epoxy specimens between 0.804 mm and 2.412 mm thick in a [±45n/On]s layup configuration. Damage was measured via visual, transducer, and X-ray methodologies. No correlation was found between internal (nonvisible) damage from the X-ray data and measured characteristics of the surface damage, specifically the depth of the dent. The results indicate that the use of dent depth as a metric can be misleading, particularly in that no dent depth can be found in cases where substantial subsurface damage exists. Other examples are given wherein substantial (relative to other specimens) dent depths are measured with no corresponding internal damage. In previous work peak force was found to correlate the resulting internal damage for both shell and plate specimens. However, dent depth shows no such general trend or correlation with peak force. This, coupled with previous damage tolerance work, places into question the use of dent-depth for thin (less than 2.4 mm, or 0.10") composite plate and shell structures in current damage tolerance methodologies.
Author: Roberto Caslaru
Publisher:
ISBN:
Category : Electronic dissertations
Languages : en
Pages : 130
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Book Description
Ti-6AL-4V is a widely used structural material in aerospace, biomedical, and power generation industries due to its low density, good corrosion resistance and high strength properties. However, Ti-6Al-4V is not a suitable material for wear applications due to its tendency to gall. Improving the tribological performance by reducing frictional coefficient and decreasing wear rate may result in significant savings. Laser shock peening (LSP) is a surface treatment designed to induce compressive residual stress and improve fatigue performance. This study presents a novel micro LSP based surface patterning technique to fabricate micro dent arrays. Comprehensive 3D dent topography was measured to evaluate the effect of laser intensity on dent geometry, process repeatability, and pile-up. Surface integrity has been characterized with respect to dent profile, surface residual stress, surface hardness, and microstructure. Post-peening polishing process has been conducted to eliminate the potential pile-up. Tribological performance of dented arrays with and without pile-up and two peening densities was tested at low and high viscosity lubrication conditions using pin-on-disk setup. Real time measurements of the coefficient of friction (CoF) and acoustic emissions were made. Finally, correlations between dent density, CoF, wear rate, and AE signal were investigated. 2D dent profile showed an increase in dent depth and diameter with laser power. 3D surface topography revealed good process repeatability. Pile-up region develops around the dent containing about 40% of the total material volume displaced from the peened region. Consequently, the remaining 60% is compressed within the dented region. Peened surfaces with micro-dent arrays have high compressive residual stress and increased hardness by 37% in the peened zone. Pin-on-disc tribology tests have shown a CoF reduction by 18% on peened surfaces with 10% dent density and pile-up when compared to polished smooth surface under high viscosity conditions. An increase in CoF was found for a surface with 20% dent density and pile-up when compared to the smooth surface. It was found that removing pile-up reduces CoF with only 2% to 3% for both peening densities. Correlations between wear rate, absolute energy, amplitude, and counts was established. RMS signal has a weak correlation with frictional coefficient.
Author: U.S. Nuclear Regulatory Commission
Publisher:
ISBN:
Category : Nuclear energy
Languages : en
Pages : 92
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Book Description
Author: Composite Materials Handbook – 17 (CMH-17)
Publisher: SAE International
ISBN: 1468604953
Category : Technology & Engineering
Languages : en
Pages : 778
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Book Description
The first volume of this six-volume compendium contains guidelines for determining the properties of polymer matrix composite material systems and their constituents, as well as the properties of generic structural elements, including test planning, test matrices, sampling, conditioning, test procedure selection, data reporting, data reduction, statistical analysis, and other related topics. Special attention is given to the statistical treatment and analysis of data. Volume 1 contains guidelines for general development of material characterization data as well as specific requirements for publication of material data in CMH-17. The primary purpose of this volume of the handbook is to document industry best-practices for engineering methodologies related to testing, data reduction, and reporting of property data for current and emerging composite materials. It is used by engineers worldwide in designing and fabricating products made from composite materials. The Composite Materials Handbook, referred to by industry groups as CMH-17, is a six-volume engineering reference tool that contains thousands of records of the latest test data for polymer matrix, metal matrix, ceramic matrix, and structural sandwich composites. CMH-17 provides information and guidance necessary to design, analyze, fabricate, certify and support end items using composite materials. It includes properties of composite materials that meet specific data requirements as well as guidelines for design, analysis, material selection, manufacturing, quality control, and repair.
Author: Falk Schwendicke
Publisher: Springer
ISBN: 3319613707
Category : Medical
Languages : en
Pages : 133
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Book Description
This book describes the challenges that deep carious lesions pose for dental practitioners, including the risk of endodontic complications and the difficulty of restorative treatment, and identifies options for overcoming these challenges on the basis of the best available evidence. The opening chapter sets the scene by discussing pathophysiology, histopathology, clinical symptomatology, and treatment thresholds. The various treatment options are then systematically presented and reviewed, covering non-selective, stepwise, and selective carious tissue removal and restoration, sealing of lesions using resin sealants or crowns, and non-restorative management approaches. In each case the current evidence with respect to the treatment is carefully evaluated. Advantages and disadvantages are explained and recommendations made on when to use the treatment in question. Illustrative clinical cases and treatment pathways for clinicians are included. This book will be of value for all practitioners who treat dental caries and carious lesions, whether in the permanent or the primary dentition. It will also be of interest to under- and postgraduate students in cariology and restorative, operative, preventive, and pediatric dentistry.
Author: Carlos Guedes Soares
Publisher: CRC Press
ISBN: 1000458938
Category : Technology & Engineering
Languages : en
Pages : 832
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Book Description
This set of two volumes comprises the collection of the papers presented at the 5th International Conference on Maritime Technology and Engineering (MARTECH 2020) that was held in Lisbon, Portugal, from 16 to 19 November 2020. The Conference has evolved from the series of biennial national conferences in Portugal, which have become an international event, and which reflect the internationalization of the maritime sector and its activities. MARTECH 2020 is the fifth of this new series of biennial conferences. The set comprises 180 contributions that were reviewed by an International Scientific Committee. Volume 1 is dedicated to maritime transportation, ports and maritime traffic, as well as maritime safety and reliability. It further comprises sections dedicated to ship design, cruise ship design, and to the structural aspects of ship design, such as ultimate strength and composites, subsea structures as pipelines, and to ship building and ship repair.
Author: Mahyar Mehranfar
Publisher:
ISBN:
Category : Metals
Languages : en
Pages : 0
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Book Description
It is easier and cheaper to transmit oil and gas by pipeline, but their failure can cause considerable environmental and societal consequences. The denting of pipelines is one of the significant challenges faced by those in the oil and gas industry. The formation of dents in the wall of the pipeline can cause lower pressure capacity. Analytical and numerical models, such as the finite element method (FEA), can predict this issue. The traditional way for recognizing the seriousness of the dent is to test the dent depth. But unfortunately, this method cannot predict the probability of failure accurately. Based on previous research, there are two ways to assess the seriousness of the dents. The first method is to model the pipe by finite element method. While very accurate, the finite element method is very computationally demanding and time consuming. The second method utilizes the dent profile to perform strain-based analysis. While very fast, the method suffers from lack of accuracy particularly in predicting the strains in the longitudinal direction. The first objective of this research was to develop a technique that takes into consideration the membrane strains in the longitudinal direction. The second objective was to test the performance of the new technique on a variety of pipeline dents. The developed method is based on the three-dimensional mathematical model proposed by Okoloekwe et al. In the original model proposed by Okoloekwe et al, it was assumed that the displacement in the mid-line of the pipeline is zero, but we found this displacement and added it to the displacement in the horizontal direction. Our study found that the modification yielded significantly better longitudinal strain distribution than the conventional procedure. The newly developed methods provide an increase in accuracy and speed of the analytical process without sacrificing accuracy. A number of two-dimensional and three-dimensional models were examined to verify the method. Contrary to the longitudinal results, these results were very accurate in the circumferential direction. With respect to the FEA results, our proposed technique is much faster, more accurate, and more reliable than previously developed analytical methods.
Author: Tim Berend Block
Publisher: Logos Verlag Berlin GmbH
ISBN: 3832538534
Category : Technology & Engineering
Languages : en
Pages : 238
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Book Description
Sandwich structures are an economically and structurally efficient way of designing large integral composite parts. In the aerospace industry pre-impregnated face sheets and honeycomb core structures can be considered as industry standard while e.g. naval structures and wind turbine blades typically use vacuum infusion technology with polymer foam cores. Application of the less costly infusion technology in the aeronautical industry requires a thorough understanding of the damage tolerance including low velocity impact as a frequent source of damaging events. At low impact energies damage in composite foam core sandwich structures is limited to core crushing and local face sheet delaminations. Higher impact energies may initiate the competing failure modes face sheet rupture and core shear failure depending on impact, geometric and material parameters. Face sheet rupture leads to severe local damage with typically good visibility, while core shear failure leads to cracks and rear face sheet debonding of the foam core with less visibility. This work investigates the low velocity impact response of sandwich structures with carbon fiber reinforced plastic (CFRP) face sheets and a polymeric foam core using experiments at room temperature and at -55° Celsius. An analytically derived failure mode map is presented as a simple tool for design guidelines while the explicit finite element method is applied for a more detailed description of the sandwich impact process. Both models are used to analyze the impact response and describe relevant sensitivity parameters of sandwich structures.
