scholarly journals Shock-Sensitivity in Shell-Like Structures: With Simulations of Spherical Shell Buckling

2016 ◽  
Vol 26 (02) ◽  
pp. 1630003 ◽  
Author(s):  
J. Michael T. Thompson ◽  
Jan Sieber
Keyword(s):  
Spherical Shell ◽  
Severe Form ◽  
Nondestructive Technique ◽  
Nonlinear Load ◽  
Shock Sensitivity ◽  
Shell Buckling ◽  
General Terms ◽  
Lateral Disturbance ◽  
Laboratory Specimen ◽  
Asymmetric Solution

Under increasing compression, an unbuckled shell is in a metastable state which becomes increasingly precarious as the buckling load is approached. So to induce premature buckling, a lateral disturbance will have to overcome a decreasing energy barrier which reaches zero at buckling. Two archetypal problems that exhibit a severe form of this behavior are the axially-compressed cylindrical shell and the externally pressurized spherical shell. Focusing on the cylinder, a nondestructive technique was recently proposed to estimate the “shock-sensitivity” of a laboratory specimen using a lateral probe to measure the nonlinear load-deflection characteristic. If a symmetry-breaking bifurcation is encountered on the path, computer simulations showed how this can be suppressed by a controlled secondary probe. Here, we extend our understanding by assessing in general terms how a single control can capture remote saddle solutions: in particular, how a symmetric probe could locate an asymmetric solution. Then, more specifically, we analyze the spherical shell with point and ring probes, to test the procedure under challenging conditions to assess its range of applicability. Rather than a bifurcation, the spherical shell offers the challenge of a destabilizing fold (limit point) under the rigid control of the probe.

scholarly journals Advances in Shell Buckling: Theory and Experiments

2015 ◽  
Vol 25 (01) ◽  
pp. 1530001 ◽  
Author(s):  
J. Michael T. Thompson
Keyword(s):  
Lateral Displacement ◽  
Energy Criterion ◽  
Sudden Onset ◽  
Equilibrium Path ◽  
Nondestructive Technique ◽  
Nonlinear Load ◽  
Theoretical Contribution ◽  
Shock Sensitivity ◽  
Shell Buckling ◽  
Post Buckling

In a recent feature article in this journal, coauthored by Gert van der Heijden, I described the static-dynamic analogy and its role in understanding the localized post-buckling of shell-like structures, looking exclusively at integrable systems. We showed the true significance of the Maxwell energy criterion load in predicting the sudden onset of "shock sensitivity" to lateral disturbances. The present paper extends the survey to cover nonintegrable systems, such as thin compressed shells. These exhibit spatial chaos, generating a multiplicity of localized paths (and escape routes) with complex snaking and laddering phenomena. The final theoretical contribution shows how these concepts relate to the response and energy barriers of an axially compressed cylindrical shell. After surveying NASA's current shell-testing programme, a new nondestructive technique is proposed to estimate the "shock sensitivity" of a laboratory specimen that is in a compressed metastable state before buckling. A probe is used to measure the nonlinear load-deflection characteristic under a rigidly applied lateral displacement. Sensing the passive resisting force, it can be plotted in real time against the displacement, displaying an equilibrium path along which the force rises to a maximum and then decreases to zero: having reached the free state of the shell that forms a mountain-pass in the potential energy. The area under this graph gives the energy barrier against lateral shocks. The test is repeated at different levels of the overall compression. If a symmetry-breaking bifurcation is encountered on the path, computer simulations show how this can be suppressed by a controlled secondary probe tuned to deliver zero force on the shell.

scholarly journals Buckling of a Pressurized Hemispherical Shell Subjected to a Probing Force

2017 ◽  
Vol 84 (12) ◽  
Author(s):  
Joel Marthelot ◽  
Francisco López Jiménez ◽  
Anna Lee ◽  
John W. Hutchinson ◽  
Pedro M. Reis
Keyword(s):  
Mechanical Response ◽  
Nondestructive Method ◽  
Pressure Loading ◽  
Spherical Shells ◽  
Nondestructive Technique ◽  
Nonlinear Load ◽  
Elastic Shells ◽  
Geometric Imperfection ◽  
Hemispherical Shell ◽  
The Stability

We study the buckling of hemispherical elastic shells subjected to the combined effect of pressure loading and a probing force. We perform an experimental investigation using thin shells of nearly uniform thickness that are fabricated with a well-controlled geometric imperfection. By systematically varying the indentation displacement and the geometry of the probe, we study the effect that the probe-induced deflections have on the buckling strength of our spherical shells. The experimental results are then compared to finite element simulations, as well as to recent theoretical predictions from the literature. Inspired by a nondestructive technique that was recently proposed to evaluate the stability of elastic shells, we characterize the nonlinear load-deflection mechanical response of the probe for different values of the pressure loading. We demonstrate that this nondestructive method is a successful local way to assess the stability of spherical shells.

scholarly journals Localization in spherical shell buckling

2020 ◽  
Vol 136 ◽  
pp. 103720 ◽  
Author(s):  
Basile Audoly ◽  
John W. Hutchinson
Keyword(s):  
Spherical Shell ◽  
Shell Buckling

Hämophilie-Zentrum Bonn 1980 – 2009

2011 ◽  
Vol 31 (S 01) ◽  
pp. S4-S10 ◽  
Author(s):  
I. Besmens ◽  
H.-H. Brackmann ◽  
J. Oldenburg
Keyword(s):  
Young Patients ◽  
Severe Form ◽  
Coagulation Disorder ◽  
Care Providers ◽  
Long Distance ◽  
Patient Age ◽  
Patient Âgé ◽  
Number Of Patients ◽  
Clotting Disorder ◽  
Regional Character

SummaryThe Bonn Haemophilia Care Center provides patient care on a superregional level. The centre’s large service area is, in part, due to the introduction of haemophilia home treatment and related to this the individualized prophylaxis in children and adults by Egli and Brack-mann in Bonn in the early 1970s, that represented a milestone in German haemophilia therapy. Epidemiologic patient data from the two selected time points, 1980 and 2009, are evaluated to illustrate the change in the composition of the patient clientele. In 1980 a total of 639 patients were treated at the Bonn Haemophilia Center. 529 patients exhibited a severe form and 110 a non-severe form of the respective clotting disorder. In 2009 the Bonn Haemophilia Center took care for a total of 837 patients. There were 445 patients who suffered from a severe form of the considered clotting disorder while 392 showed a non-severe course. The number of less severely affected patients has increased significantly in 2009. Patients in 1980 were predominantly suffering from a severe form and most had to travel more than 150 km from their homes to the treatment center. In 2009 the number of patients living a medium-long distance from the care provider has significantly increased while the number of patients living more than 150km from the center has decreased. Comparing 2009 to 1980 a growth of the center’s regional character becomes apparent, especially when patient age and severity of the coagulation disorder are taken into consideration. The regional character was more strongly pronounced with milder disease severity and lower patient age. Due to the existence of well established primary haemophilia care in CCCs in Germany, the trend for the recent years is that the proportion of young patients that choose haemophilia care providers closer to their homes is increasing.

The Immunological Properties of Factor VIII

1966 ◽  
Vol 16 (03/04) ◽  
pp. 559-573 ◽  
Author(s):  
L Uszyński
Keyword(s):  
Factor Viii ◽  
Inhibitory Activity ◽  
Hemophilia A ◽  
Severe Form ◽  
Molecular Defect ◽  
Bovine Plasma ◽  
Human Factor Viii ◽  
Antigenic Properties ◽  
Coagulation Tests ◽  
Normal Human

SummaryRabbits immunized against human AHG fibrinogen-free preparations, were shown to produce anti-AHG antibodies. The inhibitory activity of these antibodies was tested by thromboplastin generation test, thrombelastography, and the specific anti-AHG antibodies neutralization test. The latter test permitted quantitative determination of antigenic form of factor VIII. The inhibitory activity of anti-FI-O-Ta serum resulted exclusively from the anti-AHG antibodies which in coagulation tests behaved like circulating anticoagulants directed against factor VIII.The anti-AHG antibodies were neutralizable by normal human serum or plasma even contained only trace of AHG activity after storage. There was no antigenic form of factor VIII in the severely affected patients with hemophilia A, von Willebrand’s disease nor in the normal plasma adsorbed on bentonite. The presented results suggest a molecular defect of factor VIII in patients with hemophilia A. The severe form of this disease depends, probably, on a major impairment of AHG biosynthesis, leading to changes in the antigenic properties of the molecule. The AHG from rabbit, porcine and bovine plasma respectively did not neutralize the anti-AHG antibodies formed in rabbits immunized against human factor VIII preparations.

The diagnosis and management of ocular myasthenia gravis

2019 ◽  
Vol 5 (1-2) ◽  
pp. 3-8
Author(s):  
Gordon Plant
Keyword(s):  
Myasthenia Gravis ◽  
Severe Form ◽  
Differential Diagnostics ◽  
Diagnosis And Management ◽  
Ocular Myasthenia ◽  
Clinical Presentations ◽  
Ocular Myasthenia Gravis

Ocular myasthenia is not the most severe form of myasthenia but it might cause certain difficulties to diagnose. In this article, we shall discuss the clinical presentations of ocular myasthenia, its differential diagnostics, examinations and management. Keywords: ocular myasthenia gravis, diagnosis, examination, management.

Novel splicing mutation in FKBP10 gene in a patient with moderate/severe form of osteogenesis imperfecta

2013 ◽  
Author(s):  
Venturi Giacomo ◽  
Gandini Alberto ◽  
Monti Elena ◽  
Corradi Massimiliano ◽  
Vincenzi Monica ◽  
...  
Keyword(s):  
Osteogenesis Imperfecta ◽  
Severe Form ◽  
Splicing Mutation

Computing Cores for Existential Rules with the Standard Chase and ASP

2020 ◽  
Author(s):  
Markus Krötzsch
Keyword(s):  
Large Class ◽  
Data Exchange ◽  
Answer Set Programming ◽  
Query Answering ◽  
Universal Model ◽  
The Core ◽  
Universal Models ◽  
General Terms ◽  
Special Cases ◽  
The Many

To reason with existential rules (a.k.a. tuple-generating dependencies), one often computes universal models. Among the many such models of different structure and cardinality, the core is arguably the “best”. Especially for finitely satisfiable theories, where the core is the unique smallest universal model, it has advantages in query answering, non-monotonic reasoning, and data exchange. Unfortunately, computing cores is difficult and not supported by most reasoners. We therefore propose ways of computing cores using practically implemented methods from rule reasoning and answer set programming. Our focus is on cases where the standard chase algorithm produces a core. We characterise this desirable situation in general terms that apply to a large class of cores, derive concrete approaches for decidable special cases, and generalise these approaches to non-monotonic extensions of existential rules.

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