Ioana COMĂNESCU


27-67 STUDIUL COMPORTĂRII SUB SARCINĂ STATICĂ ȘI DINAMICĂ A GRINZII PRINCIPALE (profil I) A MACARALEI PORTAL (MACARA CAPRĂ) PARTEA II – STAREA DE DEFORMAȚIE A GRINZII PRINCIPALE ÎN MODUL DE LUCRU ”ANIMAȚIE”

THE STUDY OF THE BEHAVIOR UNDER STATIC AND DINAMIC LOAD OF THE MAIN BEAM (PROFILE „I”) OF A PORTAL CRANE (GANTRY CRANE)
PART II – THE STATE OF DEFORMATION OF THE MAIN BEAM IN THE „ANIMATION” WORKING MANNER
The lifting of the load at a certain height, its stop with a waiting of a 5 s, the descent of the load with a delay of 5 s, the descent of the load with its halt and waiting of approximately 5 s, leads to a certain load of the structure of the portal crane. Therefore one establishes that in the structure of the main beam appear compelled oscillations. In the frequency spectrum of the induced oscillatory motion, the main weight is that of the oscillation whose frequency is equal to the force in the driving cable; one establishes that the Eigen frequencies of the whole structure – the portal crane as a whole, are excited, too. Hence, the approach performed by the authors in the following study: a favourable working of the crane means that the Eigen frequencies of the structure as a whole must be outside the frequency field of the excitation forces, main beam: the state of stress and deformation under static and dynamic load.
Keywords: portal crane, force, structure, animation, frequency
Cuvinte cheie: macara portal, forță, structură, animație, analiză în frecvență

Descarcare text


27-66 STUDIUL COMPORTĂRII SUB SARCINĂ STATICĂ ȘI DINAMICĂ A GRINZII PRINCIPALE (profil I) A MACARALEI PORTAL (MACARA CAPRĂ) PARTEA I – STAREA DE DEFORMAȚIE A GRINZII PRINCIPALE SUB SARCINĂ APLICATĂ STATIC

THE STUDY OF THE BEHAVIOR UNDER STATIC AND DINAMIC LOAD OF THE MAIN BEAM (PROFILE „I”) OF A PORTAL CRANE (GANTRY CRANE)
PART I – THE STATE OF DEFORMATION OF THE MAIN BEAM UNDER STATIC LOAD
Because of the specific nature of the cranes’ activities, these ones have to accomplish a lot of norms concerning the security and labour protection. At the working beginning but also recurrently, the cranes are subjected to a test set in order to check the technical state with a view to the authorization. The verifications are performed by specializes departments and involve the following steps: ▪ the check of the main elements; ▪ tests of loads; ▪ tests under static and dynamic load; ▪ other tests which have in view the whole behavior of the crane.
With a view to the authorization all the tests are compulsory but the present paper presents the analysis of the main beam under the action of external loads. In the current activity one established that the imposed check in order to authorize the cranes are necessary but not enough to ensure those working safety. The present paper makes an important analysis of the main beam: the state of stress and deformation under static and dynamic load.
Keywords: portal crane, force, deflection, acquisition system, transducers
Cuvinte cheie: macara portal, forță, săgeată, sistem de achiziție, traductoare

Descarcare text


25-62 STUDIUL EFECTULUI TEMPERATURII ÎN APARIŢIA TENSIUNILOR REMANENTE DIN CAZUL DISCURILOR DE GROSIME MICĂ. Partea a II-a: RELAŢII DE CALCUL PENTRU STABILIREA TENSIUNILOR REMANENTE

THE STUDY OF TEMPERATURE EFFECT IN THE RESIDUAL
STRESSES OCCURRENCE FOR THE CASE
OF LOW THICKNESS DISKS
PART II – THE CALCULUS RELATIONS FOR THE RESIDUAL
STRESSES DETERMINATION
In order to determine the stress and deformation state of some
structures one must know the residual stresses due to the temperature. One
considers the situations when the stresses reach the limits imposed by von
Mises criterion; plastic deformations will appear; these have as effect a
redistribution of residual stresses. In order to determine the residual stresses,
theoretical studies and experimental research, based on the section method,
have been done. One has studied the hot laminated structures. Following the
uniform cooling, residual thermal-elastic-plastic stresses appear in the material.
The performed determinations based on the section method lead to high
precision determination of the residual stresses field. The established
theoretical equations were also verified.
Keywords: residual stresses, plastic deformation, criteria, tension of
the membrane, plate
Cuvinte cheie: tensiuni remanente, deformații plastice, criterii, tensiuni
de membrană, placă
Descarcare text


25-61 STUDIUL EFECTULUI TEMPERATURII ÎN APARIŢIA TENSIUNILOR REMANENTE DIN CAZUL DISCURILOR DE GROSIME MICĂ. Partea I-a – STUDIUL PROPAGĂRII TEMPERATURII

THE STUDY OF TEMPERATURE EFFECT IN
THE RESIDUAL STRESSES OCCURRENCE FOR
THE CASE OF LOW THICKNESS DISKS
PART I – THE STUDY OF THE TEMPERATURE
PROPAGATION
In order to determine the state of stress and deformation due to the
temperature, one has to study, as exactly as possible, the temperature’s
propagation mode. There are many practical situations when in some bodies’
material exist self-balanced stresses, even in the absence of any load.
These are residual stresses. Their magnitude and their distribution
depend on the material, on the technological working process, on the machine
parts’ size. The residual stresses appear mainly because of the local
deformations in the elastic-plastic field, because of some structural
transformation or because of some thermo-elastic-plastic deformations.
The paper presents some aspects regarding the residual stresses due
to the heat treatment and to the shallow working.
Key words: residual stresses, deflections, temperatures, plastic plate
Cuvinte cheie: tensiuni remanente, deformaţii plastice, temperatură,
placă
Descarcare text