In aceasta lucrare se prezinta in mod original calculul flexibilitatii conductei de motorina ce face legatura intre reactoarele R1 si R2 de la instalatia hidrocracare cu scopul reducerii tensiunilor mecanice generate de presiunea interioara si temperatura.
This paper presents in an original way the flexibility calculus of the diesel pipeline that connects R1 and R2 reactors from the Hydrocracking plant in order to reduce mechanical stresses caused by internal pressure and temperature.

Flexibility analysis of the diesel pipeline located between R1 and R2 reactors from the hydrocracking plant

Lucrarea se ocupa cu studiul interactiunii dintre o osie elastica care ruleaza pe o cale cu pat de balast afectata de uzura ondulatorie. Osia este modelata printr-o grinda Timoshenko cu corpuri rigide atasate. Calea este redusa la o sins modelata printr-o grinda infinita rezemata pe suporti discreti echidistanti. Ecuatiile de miscare sunt rezolvate prin metoda matricei Green a caii. Mai intai, este analizat regimul permanent de vibratie datorat excitatiei parametrice a traverselor. Apoi sunt prezentate aspecte ale vibratiilor cauzate de uzura ondulatorie scurta: caracterul modulant al vibratiei, influenta efectului Doppler si influenta rigiditatii contactului roata-sina.
The paper deals with the study of the interaction between an elastic wheelset moving along a ballasted track affected by the rail corrugation. The wheelset is modeled as a Timoshenko beam with attached rigid bodies. The track is reduced to a rail modelled as an infinite Timoshenko beam resting on discretely equidistant supports. The equations of motion are solved by means of the Green’s matrix of the track method. First, the steady-state behaviour due to the parametric excitation of the sleepers is analysed. Then, the aspects of the vibration due the corrugation are presented: the modulation, the influence of the Doppler effect and the influence of the wheel/rail stiffness contact.

On the wheel-rail interaction in the presence of the rail corrugation

Exista numeroase programe comerciale dedicate calculului numeric pentru conductele de transport produse petroliere, dintre care cele mai cunoscute sunt OLGA, Flow 3D, Ansys Fluent, Comsol, Pipe Flow. Simhydraulics (un modul din programul Matlab) destinat modelarii proceselor de curgere dar si pentru studiul actionarilor hidraulice, constituie un produs similar. Utilizarea programului Simhydraulics este avantajoasa prin pretul mai mic (uzual sunt posibile licente gratuite pentru studenti), flexibilitatea mai mare, legatura directa cu alte module destinate simularii numerice. Lucrarea compara o aplicatie la un sistem de transport realizata atat in Pipe Flow cat si in Simhydraulics.
There are many commercial programs used in numerical calculus of pipelines for oil and gas, from which the most known are OLGA, Flow 3D, Ansys Fluent, Comsol, Pipe Flow. Simhydraulics (a toolbox of Matlab) is used to model the processes of flowing and hydraulic transmissions, there is a similar product. The using of program Simhydraulics is advantageous by: low cost (usually free licenses for students), great flexibility, and direct connection with other modules dedicated to numerical simulation. The article compares a study for a transport system realized in Pipe Flow and Simhydraulics.

Comparison between the programs of numerical simulation Simhydraulics and Pipe Flow

Se trateaza regimul dinamic generat de instabilitatea vibratiei unui corp incarcat cu o sarcina statica care se misca uniform pe o grinda pe fundatie vasco-elastica, datorata undelor Doppler anormale excitate in grinda. Cand vibratia devine instabila, raspunsul sistemului este un ciclu limita caracterizat printr-o succesiune de socuri produse de doi factori opusi: efectul undelor anormale Doppler care pompeazaq energie fortand corpul sa se desprinda de grinda si sarcina statica care readuce corpul pe grinda. Aceasta problema este importanta pentru cazul trenurilor moderne care se deplaseaza pe o cale cu sol moale.
The paper herein deals with the study of the dynamic behaviour generated by the instability of the vibration of a loaded mass, uniformly moving along an Euler-Bernoulli beam on a viscoelastic foundation, induced by the anomalous Doppler waves excited in the beam. When the vibration becomes unstable, the system evolution is a limit cycle characterized by a succession of shocks, due to the action of two opposite factors: the anomalous Doppler waves that pump energy at the interface between the moving mass and the beam, thus forcing the mass to take off, and the static load that push the mass downwards. This issue is relevant for the case of modern trains travelling along a track with soft soil.

On the vibration instability of a moving mass along a beam on viscoelastic foundation

Inscriindu-se in mod firesc in pleiada de aplicaţii ce circumscriu nivelul didactic uzual, problema de fata, extrasa din aceeasi culegere “de moda-veche” precum multe din aplicatiile ce au facut obiectul unora dintre articolele prezentate pina acum, preia studiul posibilitatii incarcarii cu o lege de distributie oarecare a unei grinzi simplu rezemate in scopul pastrarii formei initiale a fibrei medii deformate a acesteia si dupa aplicarea schemei de incarcare.
The present paper is focused on the possibility of selecting one load law of distribution, not identically zero, in order to keep one given beam straight; the arcticle has its start point due to an “old-fashioned” selected problems and questions in strength of materials handbook, in our opinion, a true golden source concerning auxiliary and inspirational reference in today`s educational process.

Study concerning the possibility of selecting the load law of distribution q(x) wich is not identically zero, in order to keep one given beam straight