scholarly journals Reinvestigation on Assessing the Stability of Mullagulov Tested Steel Rods under Follower Forces

2022 ◽  
Vol 30 (1) ◽  
pp. 801-811
Author(s):  
Jakkana Peter Praveen ◽  
Boggarapu Nageswara Rao
Keyword(s):  
Experimental Verification ◽  
Material Properties ◽  
Dynamic Instability ◽  
Experimental Investigations ◽  
Practical Realization ◽  
Elastic Structures ◽  
The Subject ◽  
Follower Forces ◽  
The Stability ◽  
Critical Overview

Dynamic instability is an interesting topic in the mechanics of elastic structures. Though the subject has been formed by many analytical, numerical, and experimental investigations, it has many issues, as evidenced from the critical overview of Elishakoff. Furthermore, the controversial articles of Koiter and Sugiyama on unrealistic and realistic follower forces demand experimental verification. Mullagulov has proposed a device for creating the follower forces and tested steel rods under compression. This paper highlights the experimentation of Mullagulov and his observations briefly to examine the influence of material properties on the stability load estimations and to confirm the practical realization of follower forces.

scholarly journals Revisited the Critical Load Assessment of Huang et al. on Willems Tested Beck Column

2021 ◽  
Vol 29 (1) ◽  
Keyword(s):  
Critical Load ◽  
Dynamic Stability ◽  
Experimental Verification ◽  
Mathematical Formulation ◽  
Follower Force ◽  
Practical Realization ◽  
Elastic Structures ◽  
Tangential Load ◽  
Testing Procedures ◽  
Different Types

Dynamic stability of elastic structures is a fascinating topic. Many researchers have examined the problem theoretically considering a cantilever column under a tip-concentrated tangential load, the so-called Beck column. Experimental verification is demanded since the critical load of Beck column is found to be approximately eight times to that of the classical Euler column. Different types of testing procedures are being adopted to create the follower force. Among them, notable Willems experimentation provides the critical load close to that of Beck column. Investigations made by other researchers indicate the controversy associated with modeling and testing of Willems on Beck column. Such an intriguing problem of structures loaded by non-conservative forces is revisited here through a simple mathematical formulation. This paper confirms the adequacy of Willems approach on Beck column and the wrong critical load assessment of others. It indicates the possibility on the practical realization of follower forces

Statistical energy analysis: a critical overview

1994 ◽  
Vol 346 (1681) ◽  
pp. 431-447 ◽  
Keyword(s):  
High Frequency ◽  
Data Interpretation ◽  
Travelling Wave ◽  
Experimental Investigations ◽  
Future Research ◽  
Processing Error ◽  
Vibration Prediction ◽  
Individual Contributions ◽  
The Subject ◽  
Critical Overview

For the benefit of the ‘enquirer within’, who may not be familiar with the background and concepts of SEA, this overview opens with a discussion of the rationale for the use of probabilistic energetic models for high-frequency vibration prediction, and introduces the postulate upon which conventional SEA is based. It compares and relates the modal and travelling wave approaches, discusses the strengths and weaknesses of SEA as currently practised and points out needs and directions for future research. Critical discussions of individual contributions to the development of the subject are presented only in as much as they treat specific matters of concept, principle or reliability. The roles of SEA in providing a framework for experimental investigations of the high-frequency dynamic behaviour of systems and in interpreting observations on operating systems, although equally important, are not substantially addressed. Nor are specific experimental techniques which involve considerations of transducers, spatial sampling, signal processing, error analysis and data interpretation, which require a critical review in their own right.

scholarly journals A FEM-Based 2D Model for Simulation and Qualitative Assessment of Shot-Peening Processes

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 2784
Author(s):  
Georgios Maliaris ◽  
Christos Gakias ◽  
Michail Malikoutsakis ◽  
Georgios Savaidis
Keyword(s):  
Process Parameters ◽  
Material Properties ◽  
Shot Peening ◽  
Qualitative Assessment ◽  
Experimental Investigations ◽  
Elastoplastic Material ◽  
Size Distributions ◽  
User Friendly ◽  
The Impact ◽  
2D Model

Shot peening is one of the most favored surface treatment processes mostly applied on large-scale engineering components to enhance their fatigue performance. Due to the stochastic nature and the mutual interactions of process parameters and the partially contradictory effects caused on the component’s surface (increase in residual stress, work-hardening, and increase in roughness), there is demand for capable and user-friendly simulation models to support the responsible engineers in developing optimal shot-peening processes. The present paper contains a user-friendly Finite Element Method-based 2D model covering all major process parameters. Its novelty and scientific breakthrough lie in its capability to consider various size distributions and elastoplastic material properties of the shots. Therewith, the model is capable to provide insight into the influence of every individual process parameter and their interactions. Despite certain restrictions arising from its 2D nature, the model can be accurately applied for qualitative or comparative studies and processes’ assessments to select the most promising one(s) for the further experimental investigations. The model is applied to a high-strength steel grade used for automotive leaf springs considering real shot size distributions. The results reveal that the increase in shot velocity and the impact angle increase the extent of the residual stresses but also the surface roughness. The usage of elastoplastic material properties for the shots has been proved crucial to obtain physically reasonable results regarding the component’s behavior.

Bankenwettbewerb und die Stabilität von Finanzsektoren

2021 ◽  
Vol 70 (1) ◽  
pp. 1-36
Author(s):  
Toni Richter
Keyword(s):  
Economic Policy ◽  
Precise Measurement ◽  
Policy Discourse ◽  
Competitive Effect ◽  
Too Big To Fail ◽  
Financial Systems ◽  
The Subject ◽  
State Of Research ◽  
The Stability ◽  
Elementary Basis

Abstract Since the financial crisis of 2008 and intensified during the corona crisis, the interdependence between the stability of the financial systems and the prevailing degree of competition (DC) has been the subject of scientific and economic policy discourse on fragmented markets and „too-big-to-fail“ banks. In theory and empiricism, two fundamentally contrary causal concepts are opposed, the elementary basis of which is the precise measurement of the DC: Competition-stability- versus Fragility-Hypothesis. Based on the recent state of research, it can be shown that alternative DC-Measurements consistently show significantly different competitive conditions and in consequence the evidence for or against a stability-enhancing competitive effect seems to be predetermined by the chosen DC-Measurement.

Adhesion of Fine Particles at Solid/Solution Interfaces

MRS Bulletin ◽  
1990 ◽  
Vol 15 (1) ◽  
pp. 41-47 ◽  
Author(s):  
Nikola Kallay
Keyword(s):  
Fine Particles ◽  
Plane Surface ◽  
Solid Surfaces ◽  
Liquid Media ◽  
Latex Dispersions ◽  
Colloid Particles ◽  
The Subject ◽  
Kinetic Investigations ◽  
The Stability ◽  
Kinetics Of

The adhesion of particles at solid surfaces in liquid media has attracted the attention of scientists because of its various applications as well as the theoretical significance of the processes involved. Early studies were characterized either by poorly defined systems or limited by the properties of a few morphologically well-defined model colloids, such as latex dispersions. Consequently, results were either of semiquantitative nature or were related to some specific cases, which eluded general conclusions. New methods for preparing uniform particles of different compositions, shapes, and sizes make it possible to approach the problem in a more comprehensive manner. For example, to demonstrate difficulties caused by polydispersity, it is sufficient to mention that the electrostatic interaction energy between a plane surface and a particle is approximately proportional to the particle radius, yet the rate of deposition depends exponentially on the height of the energy barrier.In principle, static and dynamic approaches may be employed in the study of particle adhesion. The static method yields the force required to detach an adhered particle, while kinetic investigations of attachment and detachment give the rates of the respective processes. Both methods offer information on the stability of the system in terms of the bond strength of adhered solids. For small colloid particles, which are the subject of thermal random Brownian motion, the dynamic approach is more appropriate. This article emphasizes the kinetics of deposition and detachment of small colloid particles in liquid media.

THE ROLE OF ACCOUNTING AND CONTROL IN THE MANAGEMENT OF ECONOMIC SECURITY OF AN ORGANIZATION

2021 ◽  
Vol 7 (2) ◽  
pp. 165-178
Author(s):  
Nicolay T. Labyntsev ◽  
Lyubov F. SHILOVA ◽  
Ocsana V. Chukhrova
Keyword(s):  
Economic Security ◽  
Accounting Profession ◽  
Economic Management ◽  
Economic Interests ◽  
Doing Business ◽  
The Subject ◽  
The Stability ◽  
High Level ◽  
And Control

This article revises the mission and the name of the accounting profession in the context of strengthening the economic security of enterprises under the conditions of digitalization of the economy. The authors note that in the contemporary conditions of economic management, enterprises should form and ensure the functioning of the economic security of the enterprise at the proper level. The necessity of in-depth research of economic security at microlevel was considered, the factors influencing the stability of the enterprise were highlighted. High level of economic security of the subject of management consists in guaranteeing him maximum effective and stable functioning now and in future. Subjects of economic security were individual enterprises, and objects — their economic interests. The main goals of ensuring economic security of the enterprise in the part of accounting were singled out, the tasks of accounting policy, aimed at ensuring economic security, were determined. The prospects of the accounting profession in the process of ensuring economic security and reliable safe presentation of the results of doing business in reporting are substantiated. The study contains proposals on the revision of requirements for the qualifications of accountants in order to emphasize their activities aimed at strengthening the economic security of the enterprise.

Dynamic Instability in Quartering Seas—Part III: Nonlinear Effects on Periodic Motions

1997 ◽  
Vol 41 (03) ◽  
pp. 210-223 ◽  
Author(s):  
K. J. Spyrou
Keyword(s):  
Periodic Motion ◽  
Horizontal Plane ◽  
Dynamic Instability ◽  
Parametric Instability ◽  
Nonlinear Effects ◽  
Ship Motions ◽  
Nonlinear Phenomena ◽  
Specific Sequence ◽  
The Stability ◽  
Two Stages

The loss of stability of the horizontal-plane periodic motion of a steered ship in waves is investigated. In earlier reports we referred to the possibility of a broaching mechanism that will be intrinsic to the periodic mode, whereby there will exist no need for the ship to go through the surf-riding stage. However, about this point the discussion was essentially conjectural. In order to provide substance we present here a theoretical approach that is organized in two stages: Initially, we demonstrate the existence of a mechanism of parametric instability of yaw on the basis of a rudimentary, single-degree model of maneuvering motion in waves. Then, with a more elaborate model, we identify the underlying nonlinear phenomena that govern the large-amplitude horizontal ship motions, considering the ship as a multi-degree, nonlinear oscillator. Our analysis brings to light a very specific sequence of phenomena leading to cumulative broaching that involves a change in the stability of the ordinary periodic motion on the horizontal plane, a transition towards subharmonic response and, ultimately, a sudden jump to resonance. Possible means for controlling the onset of such undesirable behavior are also investigated.

1. On Cases of Instability in Open Structures

1888 ◽  
Vol 14 ◽  
pp. 106-106
Author(s):  
E. Sang
Keyword(s):  
Linear Structures ◽  
Symmetric Structure ◽  
Linear Resistance ◽  
Open Structures ◽  
Extensive Class ◽  
The Subject ◽  
The Stability ◽  
Special Case

AbstractIn the course of some remarks on the design proposed for the Forth Bridge, the author of this paper had enunciated the remarkable theorem, that any symmetric structure built on a rectangular base, and depending on linear resistance alone, is necessarily unstable. The proof of it, given in the eleventh volume of the Transactions of the Royal Scottish Society of Arts, is derived from considerations affecting the special case; but this theorem is only one of an extensive class, and therefore the subject of instability among linear structures in general is here taken up.In the case of regular or semi-regular arrangements, having the corners of an upper supported from the corners of an under polygon, it is shown that when the figures are of odd numbers the structures are stable, while those with even numbers are unstable ; unless indeed the polygons be placed conformably, in which case the stability extends to both classes.

scholarly journals Women at university. Strategies and achievements of a secular presence in Latin America and Spain

2019 ◽  
Vol 8 (1) ◽  
pp. 002
Author(s):  
Consuelo Flecha-García ◽  
Alicia Itatí Palermo
Keyword(s):  
Latin America ◽  
Female Students ◽  
University Education ◽  
Social Barriers ◽  
Documentary Sources ◽  
The Social ◽  
University Archives ◽  
The Subject ◽  
Critical Overview ◽  
Life Aspirations

This paper offers a descriptive and critical overview of the experience of the presence of women at university in Spain and several countries in Latin America. It focuses not just on how they embarked on different degrees, but also on the extent to which they went on to exercise professionally and the social barriers encountered at each step. It describes some of the strategies used on the paths followed to study at university during almost one hundred and fifty years, and the achievements made possible by this education, both inside and outside the academic setting. The paper draws on primary documentary sources from university archives and newspaper libraries and includes a review of the literature on the subject. These documentary searches provided us with a great deal of valuable information that has helped us in our task. The indicators of the subject matter studied are, amongst others, university education, female lecturers, history and sociology, female students and life aspirations.

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