Flambajul structurilor svelte din domeniul mecanic sau al construcțiilor civile industriale a facut obiectul a numeroase studii de-a lungul timpului. Scopul prezentului articol este de a compara abordarea clasica a problemei conform Rezistentei Materialelor in raport cu algoritmii numerici utilizati in aplicatiile de analiza a comportamentului structurilor, algoritmi ce au la baza metoda elementului finit.
The sudden loss of structural stability for slender structures in both mechanical and civil engineering areas has been the object of numerous studies. The present paper is focused on elementary strenght of materials calculus concerning critical force values vs. finite element analysis results concerning simple beam buckling.

ISSUES CONCERNING ELASTIC BUCKLING STRUCTURAL BEHAVIOUR SIMULATION IN MODERN F.E.A. APPROACH

Problema comportarii organismului uman la vibratii consta in explicarea fenomenelor fiziologice si patologice, in prezicerea comportarii acestuia la alte actiuni mecanice, in determinarea limitelor rezistentei la oboseala a organismului in conditii extreme, precum si in elaborarea unor noi mijloace de protecţie. Lucrarea de fata isi propune sa prezinte o parte dintre cercetarile noastre in domeniu si sa arate modul in care caracteristicile fizice ale organismului uman studiat au influentat modelele dinamice dezvoltate in diferite situatii de expunere a organismului uman la vibratii.
Body vibration behavior issue is to explain physiological and pathological phenomena in predicting its behavior to other mechanical actions, determining the limits of the body's resistance to fatigue under extreme conditions, and in developing new ways of protection. This paper aims to present some of our research in the field and to show how the physical characteristics of the human body studied influenced dynamic models developed in different situations of human body vibration exposure.

PHYSICAL CHARACTERISTICS NECESSARY TO ANALYZE THE DYNAMIC BEHAVIOR OF THE HUMAN BODY

In aceasta lucrare sunt prezentate anumite aspecte privind lanturile de aparate de masura cu si fara placi de achizitii de date.
In the paper there are presented certain aspects regarding measuring chain with and without data acquisition modules.

CASE STUDY CONCERNING RADIATOR UNITS VIBRATION BEHAVIOR

In prezenta lucrare, autorii prezinta cateva elemente referitoare la procesele fizice care au loc in incinta morilor. In procesul de macinare apar solicitari diverse (de compresiune, forfecare, incovoiere, soc), toate acestea conducand la aparitia noi suprafete. De cele mai multe ori, scopul final urmarit este o cat mai mare crestere a suprafetei specifice a materialului macinat (de exemplu atunci cand se doreste obtinerea unor materiale de constructie cu proprietati superioare). Totusi, la un anumit moment, se realizeaza o stabilizare a suprafetei specifice la o anumita valoare, fapt ce se traduce printr-un diametru mediu final al particulelor materialului macinat care nu se poate micsora oricat de mult.
In this paper, the authors present some elements on the physical processes that occur inside the mills. In the milling process occur various stresses (compression, shearing, flexure, shock), all leading to the emergence of new surfaces. By most times, the ultimate aim is the highest possible increase of surface area of the ground material (for example when it wants to obtain higher technical building materials). However, at some point, is done to stabilize the specific surface to some value, which means that the final average particle diameter of the milled material may not decrease however long.

MATHEMATICS OPINION ON THE GRINDING MECHANISMS

Aceasta lucrare defineste succint conceptul de disponibilitate a unui sistem si a principalilor indicatori de stare ai sistemelor mecanice complexe
This paper succinctly defines the concept of a system availability and status of the main indicators of the complex mechanical systems.

CONSIDERATIONS REGARDING THE AVAILABILITY OF COMPLEX MECHANICAL SYSTEMS

Acest articol identifica cateva solutii tehnice a caror aplicare are drept rezultat creșterea randamentului procesului de tăiere a betonului utilizând discuri diamantate. O abordare originala a acestei teme este similitudinea operatiilor de așchiere la taiere cu cele de la slefuire. In cadrul lucrarii se fac aprecieri asupra urmatoarelor aspecte ale procesului; influenta vitezei de avans asupra durabilitatii sculei, influența adancimii de taiere asupra durabilitatii sculei, variatia uzurii sculei la randament constant, alegerea vitezelor de rotatie a sculelor diamantate.
This article identifies and highlights the technical solutions whose application results in increasing the efficiency of the concrete cutting process with diamond blades. An original approach to this issue is cutting operations resemblance to those of grinding. The paper specifications are made on the following aspect of the process; influence on the durability of the tool feed rate, cutting depth influence on the durability of the tool, tool wear variation at constant efficiency, choosing speed of rotation of diamond tools.

REMARKS ON CONCRETE CUTTING PROCESS PRODUCTIVITY WITH DIAMOND BLADES

In articol se dimensioneaza numarul maxim de disipatori ce pot fi comandati simultan de un singur distribuitor proportional al unui sistem semi-activ de disipare a energiei seismice, sistem ce are in componenta distribuitoare proportionale pilotate DN 10, DN 16, respectiv DN 25.
In the article is dimensioned the maximum number of dissipators that can be simultaneously controlled by a single proportional distributor of a semi-active seismic energy dissipation system, system that comprises the piloted proportional distributors DN 10, DN 16 and DN 25.

SIZING THE MAXIMUM NUMBER OF DISSIPATORS THAT CAN BE SIMULTANEOUSLY CONTROLLED BY A SINGLE PROPORTIONAL DISTRIBUTOR IN A SEMI-ACTIVE SEISMIC ENERGY DISSIPATION SYSTEM

Cunoașterea modului de deplasare, transformare si amestec a materialelor in procesul de fabricare a cimentului se studiaza cu scopul cresterii eficientei de exploatare care implica reducerea costurilor energetice, precum si in vederea determinarii posibilitatilor de reducere a emisiilor la cos. In lucrare se analizeaza o instalatie de fabricare a cimentului in vederea determinarii fluxurilor de materiale, utilizand teoria sistemelor, teoria grafurilor si matricile de circulație. Modul original de elaborare a matricilor de circulatie pentru fluxurile de materiale poate fi extins si in cazul fluxurilor de gaze si a emisiilor la cos.
Knowledge of movement, transforming and mixing materials in the cement manufacturing process is studied to increase efficiency of operation which involves reducing energy costs as well as to determine the possibility to reduce stack emissions. The paper analyzes the cement manufacturing facility to determine material flows, using systems theory, theory of graphs and matrices movement. Original way of developing matrices circulation material flows can be extended to the gas flow and stack emissions.

ANALYSIS FLOWS THE MATERIAL IN THE CEMENT PLANT USING SYSTEMS THEORY, GRAPH METHODE AND MATRIXES

Analiza regimurilor tranzitorii in cazul troliilor de sarcina ale macaralelor de mare inaltime se face studiind fazele de pornire – oprire ale sarcinilor in conditiile impunerii unor marimi de intrare (legi sau pachete de legi) in scopul obtinerii unor performante dinamice superioare, avand ca rezultat cresterea productivitatii si diminuarea solicitarilor dinamice din constructia metalica a macaralei.
Analysis of transitory regimes when discussing about load winches of great height cranes is performed by studying the “start-stop” phases of load when there is required output (laws or packages of laws) in order to obtain superior dynamic performances, resulting in increased productivity and decreased dynamic strain in the metal construction of the crane.

LOAD WINCHES - OPTIMIZATION DYNAMIC PARAMETERS

Cand sunt indeplinite anumite conditii de functionare, fortele de frecare intre roata si sina pot excita vibratii de torsiune pe o osie, care apoi sunt responsabile pentru fenomenul de pseudo-alunecare. In functie de circumstante, aceste oscilatii pot avea o frecvența de rezonanta a osiei, si chiar o anti-rezonanta verticala a sistemului vehicul-cale. In ambele cazuri, aceste vibratii pot duce la crearea crestere a fenomenului de uzura ondulatorie. Vibratiile de torsiune sunt principala cauza a dezvoltarii uzurii ondulatorii a sinelor de cale ferata. In aceasta lucrare este tratata eficienta amortizarii dinamice a vibratiilor in cazul rezonantei de torsiune osiei. Ideea de a utiliza amortizarea dinamica a vibratiilor este sugerata in, dar nu a fost testata. Principalele avantaje ale solutiei propuse in aceasta lucrare faciliteaza asamblarea, fara nici o modificare a sistemului existent, costurile de productie si de intretinere fiind reduse, precum si pentru a reduce eficienta disiparii energiei la contactul roata-sina, atunci cand acestea rezulta din rezonanta de torsiune. Inainte de a preciza motivele unei astfel de solutii, conditii specifice pentru aparitia acestui tip de uzura ondulatorie sunt explicate prin specificarea mecanismul de fixare a lungimii de undă a uzurii ondulatorii. Apoi, capacitatea amortizarii dinamice a vibatiilor pentru a reduce creșterea acestui tip de uzura ondulatorie este evaluata prin intermediul teoriei frecventei. In final, eficienta amortizarii dinamice a vibratiilor calibrata pe doua moduri de torsiune ale osiei este discutat de asemenea cu ajutorul unui model multicorp care simuleaza trecerea unui vehicul intr-o curba.
When certain operating conditions are done, the frictional forces between wheel and rail can excite torsional vibrations on an axle, which are then responsible for the phenomenon of pseudo-slip. Depending on the circumstances, these oscillations may have a resonant frequency of the axle, and even an vertical anti-resonant of vehicle-path system. In both cases, these vibrations can lead to increase the undulation wear phenomenon. Torsional vibrations are the main cause of the development of railway track wave wear. This paper work treats dynamic damping efficiency of vibrations for torsion axle resonance. The idea of using dynamic vibration damping is suggested, but has not been tested. The main advantages of the solution proposed in this paper work facilitates assembly without any modification to the existing system, production and maintenance costs are reduced, and also to reduce the efficiency of energy dissipation at the wheel-rail contact, when they result from resonant torsional . Before giving any reason for such a solution, specific conditions for the emergence of this type of wave wear are explained by specifying the fixing mechanism for the wavelength of the wave wear. Then, the dynamic vibration damping ability to reduce the growth of this type of wave is evaluated through attrition rate theory. Finally, the dynamic vibration efficiency depreciation calibrated in two ways torsion of the axle is also discussed using a multi-body model which simulates the passage of a vehicle in a curve.

TORSIONAL VIBRATIONS OF HACK WAVE

In cadrul proceselor de disipare fluidica a energiei seismice, transmiterea energiei hidraulice are, ca si una dintre consecinte, generarea de pierderi prin frecare. Aceste pierderi de energie prin frecare se transforma in caldura, care este, la randul sau, preluata de lichidul de lucru. In aceste conditii, in timpul proiectarii unui sistem de actionare hidraulica, pentru asigurarea unor conditii optime de functionare a acestuia, trebuie evaluat cu atentie bilantul termic si, unde se impune, trebuie luate masuri adecvate pentru mentinerea temperaturii in limite acceptabile, prin folosirea de solutii optime pentru evacuarea caldurii din sistem.
In the process of fluidic seismic energy dissipation, hydraulic energy transmission has, as one of the consequences, the engendering of frictional losses. This energy loss is converted to heat through friction, which is, in turn, taken up by the working fluid. Accordingly, when designing a hydraulically driven system, should be carefully assessed the heat balance, to ensure optimal functioning, and, where necessary, appropriate measures should be taken to maintain the temperature within acceptable limits, using optimum solutions for dissipation of the heat from the system.

THE CALCULATION OF THE HYDRAULIC FLUID TEMPERATURE VARIATION IN A SEISMIC ENERGY DISSIPATION SYSTEM