scholarly journals ADDITIVE REFURBISHMENT OF A VIBRATION-LOADED STRUCTURAL COMPONENT

2021 ◽  
Vol 1 ◽  
pp. 345-354
Author(s):  
Nicola Viktoria Ganter ◽  
Tobias Ehlers ◽  
Paul Christoph Gembarski ◽  
Roland Lachmayer
Keyword(s):  
Fatigue Strength ◽  
Structural Component ◽  
Significant Loss ◽  
Additive Process ◽  
Particle Damping ◽  
Bending Stresses ◽  
First Time ◽  
Loss Of Strength

AbstractIn the event of damage to additively manufactured components whose shape cannot be produced by machining, an additive repair can potentially be not only ecologically but also ecologically more favorable than the production of a new component. In addition, a number of hurdles that otherwise often impede the use of additive repair, e.g. the availability of the material of the damaged component for the additive process, are eliminated. As far as the authors are aware, this publication is the first to present a process for the additive refurbishment of additively manufactured components using the example of a wheel carrier. In this context, the possibility of increasing the fatigue strength of a structural component in refurbishment is discussed for the first time. To increase the fatigue strength of the wheel carrier, the chosen approach is to integrate the effect of particle damping into the component. Particularly in the case of components subjected to bending stresses, the effect of particle damping can be integrated into the component's interior without having to accept a significant loss of strength.

Geotechnical characteristics of large rapid rock slides

2010 ◽  
Vol 47 (1) ◽  
pp. 116-132 ◽  
Author(s):  
James Glastonbury ◽  
Robin Fell
Keyword(s):  
High Strength ◽  
Significant Loss ◽  
Slide Mass ◽  
Geotechnical Characteristics ◽  
Lateral Margins ◽  
Internal Deformation ◽  
Strength Rock ◽  
First Time ◽  
Loss Of Strength ◽  
Rock Slides

Based on the analysis of 51 case studies of large rapid rock slides, for a landslide to travel rapidly after failure there has to be a significant loss of strength on the basal surface of rupture, lateral margins, and (or) internally within the slide mass, or the factor of safety has to be maintained below 1.0 after failure by high groundwater pressures. Internally sheared compound slides and translational slides may all travel rapidly depending on their detailed geotechnical and geometric characteristics. The characteristics of these landslides that suggest an increased likelihood of rapid failure have been identified. All the rapid rock slides examined in this study involved relatively high-strength rock masses. Most cases were considered to be first-time landslides, largely involving brittleness on the basal rupture surface. However, there were some cases considered to be reactivated or active landslides on pre-sheared rupture surfaces. For this latter group, the loss of strength leading to rapid landsliding was associated with brittle internal deformation or lateral margins.

TRANSMISSION ELECTRON MICROSCOPY OF SURFACE AND INTERFACIAL STEPS

1997 ◽  
Vol 04 (03) ◽  
pp. 559-566 ◽  
Author(s):  
J. M. GIBSON ◽  
X. CHEN ◽  
O. POHLAND
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Free Surface ◽  
Significant Loss ◽  
Stress Fields ◽  
Preliminary Results ◽  
Surface Steps ◽  
Transmission Electron ◽  
First Time

Transmission electron microscopy is uniquely able to extend techniques for imaging free surface steps to the buried interface regime, without significant loss of detail. Two mechanisms for imaging surface and interfacial steps by transmission electron microscopy are described. They are thickness contrast and strain contrast. The former reveals the position and approximate height of steps, whereas the latter detects stress fields which are commonly associated with steps. The basis for each of these methods is elaborated, and preliminary results are shown for step images at Si/SiO2 interfaces, where measurable stress fields have been directly detected for the first time.

scholarly journals Gut mucosal virome alterations in ulcerative colitis

Gut ◽  
2019 ◽  
Vol 68 (7) ◽  
pp. 1169-1179 ◽  
Author(s):  
Tao Zuo ◽  
Xiao-Juan Lu ◽  
Yu Zhang ◽  
Chun Pan Cheung ◽  
Siu Lam ◽  
...  
Keyword(s):  
Clustering Algorithm ◽  
Intestinal Inflammation ◽  
Rectal Mucosa ◽  
Significant Loss ◽  
Healthy Controls ◽  
Virus Like Particle ◽  
Geographical Regions ◽  
Viral Communities ◽  
First Time ◽  
Gut Microbiota Dysbiosis

ObjectiveThe pathogenesis of UC relates to gut microbiota dysbiosis. We postulate that alterations in the viral community populating the intestinal mucosa play an important role in UC pathogenesis. This study aims to characterise the mucosal virome and their functions in health and UC.DesignDeep metagenomics sequencing of virus-like particle preparations and bacterial 16S rRNA sequencing were performed on the rectal mucosa of 167 subjects from three different geographical regions in China (UC=91; healthy controls=76). Virome and bacteriome alterations in UC mucosa were assessed and correlated with patient metadata. We applied partition around medoids clustering algorithm and classified mucosa viral communities into two clusters, referred to as mucosal virome metacommunities 1 and 2.ResultsIn UC, there was an expansion of mucosa viruses, particularly Caudovirales bacteriophages, and a decrease in mucosa Caudovirales diversity, richness and evenness compared with healthy controls. Altered mucosal virome correlated with intestinal inflammation. Interindividual dissimilarity between mucosal viromes was higher in UC than controls. Escherichia phage and Enterobacteria phage were more abundant in the mucosa of UC than controls. Compared with metacommunity 1, metacommunity 2 was predominated by UC subjects and displayed a significant loss of various viral species. Patients with UC showed substantial abrogation of diverse viral functions, whereas multiple viral functions, particularly functions of bacteriophages associated with host bacteria fitness and pathogenicity, were markedly enriched in UC mucosa. Intensive transkingdom correlations between mucosa viruses and bacteria were significantly depleted in UC.ConclusionWe demonstrated for the first time that UC is characterised by substantial alterations of the mucosa virobiota with functional distortion. Enrichment of Caudovirales bacteriophages, increased phage/bacteria virulence functions and loss of viral-bacterial correlations in the UC mucosa highlight that mucosal virome may play an important role in UC pathogenesis.

scholarly journals Study of the Efficiency of Ultrasonic Turning of Heat-Resistant Alloys with Tools from Mineral Ceramics

2019 ◽  
Vol 297 ◽  
pp. 01011
Author(s):  
Nguyen Khanh Toan ◽  
Nikolay Mezin
Keyword(s):  
Nickel Alloys ◽  
High Speed ◽  
Metal Removal ◽  
Ultrasonic Field ◽  
Significant Loss ◽  
Field Energy ◽  
Thermal Processes ◽  
Heat Resistant ◽  
Defective Layer ◽  
Loss Of Strength

The results of the study of the effectiveness of high-speed ultrasonic turning of billets from heat-resistant nickel alloys without coolant are given. It was established that the introduction of ultrasonic field energy into the shaping zone reduces the contact temperature by 10–15% and the cutting force by 20–30%. However, this does not cause a decrease in metal removal performance due to a significant loss of strength and ease of cutting at temperatures above 800 C. As follows from the results, ultrasound helps to reduce the thickness of the defective layer, the formation of which is caused by thermal processes and phase transformations with the appearance of tensile residual stresses in the surface layer.

Evaluation of a metal acrylic repair product as a clamp for an external fixator

2004 ◽  
Vol 17 (02) ◽  
pp. 97-103 ◽  
Author(s):  
N. R. Gibson ◽  
R. A. Read ◽  
R. Day ◽  
I. D. Robertson ◽  
K. L. Staudte
Keyword(s):  
Mechanical Testing ◽  
Significant Variation ◽  
Significant Loss ◽  
External Fixators ◽  
Frame Design ◽  
Pullout Tests ◽  
Cyclical Loading ◽  
Cantilever Bending ◽  
Equivalent Strength ◽  
Loss Of Strength

SummaryMechanical testing was performed to evaluate an acrylic steel repair paste when used in the construction of external fixators. Individual pin-bar-acrylic constructs were compared with those made from Kirschner-Ehmer (KE) clamps or polymethylmethacrylate. The constructs were subjected to cantilever bending forces, pin-pullout tests and cantilever bending after undergoing cyclical fatigue. Forty mm segments of acrylic were significantly stronger than medium ESF clamps. Twenty-five mm segments of acrylic were of equivalent strength to clamps. Ten mm segments failed under physiological loads expected from dogs greater than 20 kg and were less likely to provide adequate pin coverage to protect against pin pull-put. The placement of a wire loop to secure the pin-bar intersects made application of the acrylic easier but did not alter stiffness. There was not any significant variation between different operators in the strength of their constructs nor tolerance of their constructs to pin pullout. Cyclical loading forces were applied to acrylic-pinbar units without significant loss of strength, and acrylic and polymethylmethacrylate units did not show any difference in stiffness after being subjected to cyclical fatigue. The acrylic steel repair paste is a handkneadable, fast setting, inexpensive and readily available acrylic for use in the construction of external fixators. It allows more flexibility in frame design than a clamp and on the basis of mechanical testing offers a very stiff and secure substitute for KE clamps or polymethylmethacrylate.

Wear Out Failure Patterns and Their Interpretation

1980 ◽  
Vol 22 (3) ◽  
pp. 143-151 ◽  
Author(s):  
A. D. S. Carter
Keyword(s):  
Fatigue Strength ◽  
Failure Rate ◽  
Initial Period ◽  
Failure Pattern ◽  
Weibull Distributions ◽  
Increasing Failure Rate ◽  
Failure Patterns ◽  
Loss Of Strength ◽  
Continuous Loss

It is shown theoretically that fatigue of a component will result in a failure pattern which consists of an initial period of intrinsic reliability, or near zero failures, followed by a rapid increase in failure rate when loss of fatigue strength becomes operative, to be followed in turn by a period during which the failure rate decreases with time or maybe remains constant. By contrast other wear-out modes involving a continuous loss of strength give rise to a steadily increasing failure rate after the period of intrinsic reliability has expired. Practical examples of each type are quoted to substantiate the theoretical deductions. The interpretation of wear out characteristics by Weibull distributions is discussed.

scholarly journals Natural dolomitic limestone catalyzed synthesis of benzimidazoles, dihydropyrimidinones and highly substituted pyridines under ultrasound irradiation

2020 ◽  
Author(s):  
Kumar Godugu ◽  
Venkata Divya Sri Yadala ◽  
Mohammad Khaja Mohinuddin Pinjari ◽  
Thrivikram Reddy Gundala ◽  
Lakshmi Reddy Sanapareddy ◽  
...  
Keyword(s):  
Ultrasound Irradiation ◽  
Significant Loss ◽  
Catalyst Loading ◽  
Dolomitic Limestone ◽  
X Ray Diffraction ◽  
Rapid Construction ◽  
Substituted Pyridines ◽  
Ft Ir ◽  
Low Catalyst Loading ◽  
First Time

In this paper, for the first time, naturally occurring dolomitic limestone is employed as a heterogeneous green catalyst for the synthesis of medicinally valuable N-heterocycles, 2-aryl-1-arylmethyl-1H-benzo[d]imidazoles, dihydropyrimidinones/ thiones and 2-amino-4-aryl-3,5-dicarbonitrile-6-sulfanyl-pyridines in good to excellent isolated yields via a rapid construction of C-N, C-C and C-S bond formations in 1:1 ratio of ethanol:H2O under ultrasound irradiation. Dolomitic limestone is characterized by X-ray diffraction (XRD), FT-IR, Raman and SEM with EDAX analyses. Further, the catalyst is environmentally benevolent, non-toxic, most abundant, easy to handle low catalyst loading and is reused 7 times without significant loss of catalytic activity. Hence, the catalyst is greener alternative for the synthesis of aforementioned N-heterocycles as compared with the existing reported catalysts.

scholarly journals Acción externa acelerada de sulfatos y cloruros en el estudio de la corrosión del acero en tracción en el hormigón armado

2017 ◽  
Vol 67 (328) ◽  
pp. 141
Author(s):  
M. A. G. Silva ◽  
M. P. Cunha ◽  
A. Pinho-Ramos ◽  
B. Sena da Fonseca ◽  
F. F. S. Pinho
Keyword(s):  
Compressive Strength ◽  
Sodium Sulfate ◽  
Concrete Beams ◽  
Significant Loss ◽  
Lower Porosity ◽  
Compressive Strength Of Concrete ◽  
Flexural Tests ◽  
Different Diameters ◽  
Steel Rebars ◽  
Loss Of Strength

Corrosion of the reinforcing steel may cause significant loss of strength of reinforced concrete structures. The study focuses on accelerating such corrosion and examining the degradation of (i) the compressive strength of concrete due to sodium sulfate in a wet atmosphere; and (ii) the flexural strength by a solution of sodium sulfate and sodium chloride. Three types of concrete were used and different beam specimens were reinforced by steel rebars of different diameters (6, 8 and 10mm), part of the beams being pre-cracked. The concrete with least strength allowed higher sulfate penetration along the entire process and the compressive strength increased slightly, possibly due to lower porosity of concrete after contamination. The results of the flexural tests showed decrease of strength in all cases. Pre-cracked beams exhibited smaller influence of porosity of concrete. Beams with 6mm rebars showed the largest loss of strength due to the contamination and corrosion process

scholarly journals Fatigue Behavior of Laser-Cut Sheet Metal Parts with Brazed-on Elements

Metals ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 2063
Author(s):  
André Till Zeuner ◽  
Robert Kühne ◽  
Christiane Standke ◽  
David Köberlin ◽  
Thomas Wanski ◽  
...  
Keyword(s):  
Fatigue Strength ◽  
Sheet Metal ◽  
Laser Cutting ◽  
Cyclic Load ◽  
Load Capacity ◽  
Fatigue Behavior ◽  
Cyclic Strength ◽  
Significant Loss ◽  
Sheet Metal Parts ◽  
Brazed Joint

Laser cutting is used in the production of formed sheet metal components. However, the cyclic load capacity is reduced compared to other subtractive processes. Laser cutting results in a significant loss of fatigue strength; however, thermal joining has its own effect on the cyclic load capacity. Accordingly, brazing causes a significant reduction in the mechanical strength. However, the open question is what consequences a combination of both processes may have on the overall fatigue strength of sheet metals. Laser-cut samples of AISI 304 with and without a brazed-on element were investigated for their microstructure and mechanical properties. The brazing process was found to have an annealing effect on the microstructure. It was further observed that the fatigue behavior of brazed specimens is dominated by inhomogeneities at the surface of the filler metal fillet located in the geometric notch of the brazed joint. Fatigue strength decreased by almost 50% compared to as-cut specimens. As long as no shared diffusion zone is formed between the laser-cut and the brazed joint, the use of laser cutting for the production of such components appears to be reasonable and does not further contribute to the loss of cyclic strength.

Theoretical Study of Mode Localization Phenomenon in Bottom-Hole Assemblies in Oil-Well Drilling

1999 ◽  
Vol 121 (3) ◽  
pp. 183-188
Author(s):  
A. S. Yigit ◽  
M. D. Al-Ansary ◽  
M. Khalid
Keyword(s):  
Theoretical Study ◽  
Oil Well ◽  
Well Drilling ◽  
Mode Localization ◽  
Localization Phenomenon ◽  
Bottom Hole ◽  
Weakly Coupled ◽  
Bending Stresses ◽  
First Time ◽  
Strong Mode

The mode localization phenomena in bottom-hole assemblies (BHA) used in oil-well drilling is investigated. A fully gaged stabilizer model is shown to produce weak coupling between segments of drillcollars separated by stabilizers. It is observed that in a weakly coupled BHA, small disorder in span length can cause strong mode localization. For the first time, it is demonstrated that gravity induces a stiffness disorder, which in turn causes strong mode localization in an inclined wellbore, even though no other disorder is present. The effect of localized modes for failure is presented by examining the maximum bending stresses with and without mode localization. The results show that design and operation of drillstrings should consider the possibility of mode localization for an accurate prediction of dynamic behavior.

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