Volume 3, No. 12 (2006)

THE DETERMINATION OF THE OPERATION DURATION AT A FATIGUE SOLICITATION FOR OSCILLATOR EXTENSION AT THE 213K TEMPERATURE

ROŞCA VÂLCU

The paper points out a modality of determination of functioning of a part submitted to a cyclic solicitation undulant positive of eccentric traction. Experimentally, for samples made of general use steel R520, we determined the variation of the fracture length of crack a and the number of N cycles, corresponding to them. Empirical relations of calculation for the time of a part's functioning were obtained, taking into consideration the asymmetry coefficient R and the solicitation loads. The working environment temperature was 213K (-60°), and the asymmetry coefficients used were R=0.1, R=0.3 and R=0.5.

DEVELOPMENT OF A FORCE CONTROLLED MICROGRIPPER

ALBUŢ AURELIAN

In micro assembly, the precise and accurate manipulation of the objects, say electromechanical parts, is very important. In order to prevent the damage of the objects, in case of the use of a micromanipulator or gripper, a feedback system is needed (position, contact). There for, force sensing is required. Force sensing assists in the assembly planning, teleoperation, and automatic handling tasks. Despite of the fact there are not many force sensing technologies available for micro assembly, the existing technologies are in use.

NONLINEAR NUMERICAL AND EXPERIMENTAL ANALYSIS OF SHELLS LOADED WITH CONCENTRATED LOADS

ATANASIU COSTICĂ, SOROHAN ŞTEFAN

In this paper, a nonlinear numerical analysis using the Finite Element Method and experimental verifications are performed for shells loaded with concentrated forces. The analysis took into account both the large displacements of the application points of forces and the physical nonlinearity of the material. The Finite Element analysis yielded supplementary information about the distribution of stresses, a task difficult to accomplish with experimental procedures.

STRESSES IN A SHAFT WITH TWO KEYSEATS

BADEA MANUELA-CODRUŢA *, PĂSTRAV IOAN **

The stress state inside a shaft with two keyseats subjected to torsion was determinated by the stress freezing photoelastic method through a wedging process. The results were compared with the ones obtained by the finite element method (FEM).

TESTS ON THE NAVAL BRIDGE COMPOSITE MATERIALS

BEZNEA ELENA-FELICIA, CHIRICA IONEL, CHIRICĂ RALUCA

In the paper, a study on the buckling analysis of the naval bridge plate specimens made of composite materials instead of steel for the structure is treated. The advantages of using composite materials for the structure of the bridge is made so on the strength and stiffness and for the other reasons.A study on, made of composite materials is presented. Certain bridge plate specimens, of various thicknesses, so in the case of perfect manufacturing and in the case of existing imperfections were analysed. In this paper, only the case of perfect manufacturing specimen is presented.

MECHANICAL TESTING OF THE LIGNIN-CELLULOSE BASED PANELS

BOIERIU C., CURTU IOAN, LICA D.

The composite lignin-cellulose based panels have the following characteristics: high resistance and stiffness, thermo-insulated and fono-absorbent properties, low weight, etc. The paper presents the variety of mechanical tests applied to the composite lignin- cellulose based panels composed of lamellas of hardwood (beech and other hardwood species). The panels have also various structures (different lamella widths, different wood species subjected to static bending load, shearing strength of adhesive bond, impact test, etc.).The paper presents also the comparison between the theoretical models of the bending test determined using the Finite Element Method (FEM) and the experimental results.

INTRODUCTION FOR A FINITE ELEMENTS ANALYSIS FOR A BURNING SPARKING ENGINE CYLINDER HEAD

BOTEAN ADRIAN-IOAN

In the present paper one set the hypothesis used to simulate and analyze with FEM a burning sparking engine cylinder head. One exemplify: the way of geometric simulation, the discretisation technique for several types of finite elements and also the loading case for this type of piece.

DETERMINATION OF FRACTURE LOAD BY ACOUSTIC EMISSION

CAPELLE J., PLUVINAGE G., LEBIENVENU M.

A comparison of fracture load given by conventional definition and acoustic emission is made for three cases: ?Fracture load at maximum load, ?Fracture load at "pop-in", ?Critical load defined by 5% offset procedure. Comparison has been made for three materials, Steel APX 52, Honeycomb core composite and 7000 T 73 aluminum alloy.In each case, good agreement is found between acoustic emission and conventional fracture load. Acoustic emission is a power full method to detect the critical event particularly when large plastic deformation occurs before ductile tearing.

DESIGN OF THE SPRING ELEMENT FOR A NEW WIM SENSOR, USING STRAIN GAGES

CARLESCU PETRU, CATANA RAMONA, IURAS EMILIA, BÂRSĂNESCU PAUL-DORU

The paper presents a new high-speed weigh-in-motion (WIM) sensor for heavy vehicles, designed (using FEA) in order to have more data, as following: dimensions and area of the tire footprint, identification of the type of tire wheel (single tire wheel or twin wheels) etc. A comparison between actual WIM sensors and the proposed sensor are also presented.

NUMERICAL TESTS ON THE BUCKLING OF THE PLATES MADE OF COMPOSITE MATERIALS

CHIRICA IONEL, BEZNEA ELENA-FELICIA, CHIRICĂ RALUCA

A study on buckling analysis of the ship deck plate specimens, made of composite materials is presented. Certain deck plate specimens, of various thicknesses, so in the case of perfect manufacturing and in the case of existing imperfections are analysed. The analysis is based so on the analytical determination of the critical buckling load of perfect molding composite, and on the finite element modeling, made by licensed soft COSMOS/M. Analysis was made using various element types and meshes.

THE DESIGN AND MANUFACTURING OF THE DYNAMOMETER FOR MEASURING CUTTING FORCES

CIOFOAIA VASILE, BEJINARU-MIHOC GHEORGHE

In the engineering applications, in order to measure the force values within a desired precision range there are needed specific design and manufacturing conditions and dynamometers sufficient measuring accuracy. In this paper, we used a Strain Gage based dynamometer design, a tree component, a computer linked design; tests were carried out to measure the cutting forces. This dynamometer can be used in static and dynamic force measurements in cutting machines. It has been noted that the cutting forces recorded synchronously from the tests have corresponded to the calculated values.

ASPECTS REGARDING THE BEHAVIOR OF THE SEAT BELT SIMPLE GUIDE SUBJECTED TO TRACTION

CIOFOAIA VASILE *, ILIESCU NICOLAE **, CURTU IOAN *, SECHE ION ***, PODOREANU AUREL ****, DOGARU FLORIN *

This paper presents the determination of the tension state for the simple ear component of the safety belt when subjected to external traction forces transmitted by the webbing. The aims of these determinations are to determine the dangerous zones at the orifice where the webbing is applied, to correct the dimensions for the webbing and ear positioning and to determine the optimal material type. The tension state is determined by the finite element method and it is confirmed experimentally by using the photo-elasticity method. In the same time, the force necessary to break the simple ear by traction is determined and compared to the FEM simulation, this information being necessary for homologation. The dimension for the breaking force is found to be within normal requested range. The experimental and numerical data are found to correspond.

STRUCTURE ANALYSIS OF THE FLANGING PRESS FRAME TYPE PIT 120 BY THE METHOD OF FINITE ELEMENTS

DINU GABRIELA, ATANASIU COSTICĂ, SOROHAN ŞTEFAN

This work contains a study of the induced stress and strain state, in static running, for the frame of a flanging press type PIT 120, using the modelling and analysis with finite elements.For estimating the strength of the frame, this one has been digitized in finite elements of a quadrangle plate kind (type SHELL) with four assemblage points.As results, there have been obtained the shifts of the assemblage points in which the plate finite elements interact and also, the stress distributions in these ones, for two loading cases. But, only one of these cases is brought up in this paper. The results are presented graphically, in a manner that facilitates their analysing and interpretation.

CHARACTERISTICS REGARDING THE DURABILITY ASSESSMENT AT IMPACT FATIGUE TESTS (The First Part)

DUMITRU ION*, FAUR NICOLAE*

Within this paper in the first part there are presented some general considerations upon the assessment mode of durability at variable loads. There are analyzed those three design philosophies, respectively: the safe- life, infinite life; safe- life, finite life and damage tolerant. In this context there are then exposed the impact fatigue characteristics as well as the durability assessment parameters at such tests.

CHARACTERISTICS REGARDING THE DURABILITY ASSESSMENT AT IMPACT FATIGUE TESTS (The Second Part)

DUMITRU ION*, FAUR NICOLAE*

Within this paper in the First Part there are presented some general considerations upon the assessment mode of durability at variable loads. There are analyzed those three design philosophies, respectively: the safe- life, infinite life; safe-life, finite life and damage tolerant. In this context there are then exposed the impact fatigue characteristics as well as the durability assessment parameters at such tests. In the Secon Part the authors present some results obtained in the Impact Fatigue Laboratory of the Politehnica University of Timisoara regarding the durability at impact fatigue.

RESEARCHES REGARDING THE BEHAVIOUR UNDER COMPRESSION OF THE BOXES MADE OF A SINGLE CORRUGATED BOARD

FAUR NICOLAE*, DUMITRU ION*, MARSAVINA LIVIU*

The paper presents aspects regarding the compression test of the corrugated board boxes, performed in a single layer, used at the packaging and transportation of the materials used in the medicine industry. There is presented the equipment used for the compression tests performance and the interpretation of the force displacement diagram. At the same time, there has been performed an analysis with finite elements of the stress-strain state for the corrugated board boxes tested, in order to validate this model and to use it further in the optimization process.

SOLUTIONS FOR THE PROBLEM OF THE SEMI-INFINITE BODY

FLORESCU DANIELA

The purpose of this paper is to investigate the effect of the finite speed of hear transfer on the temperature distribution and heat flux for the case of a step change in temperature at the surface of a semi-infinite body. In the solution, the properties C and ? are assumed constant. The solution yields a maximum but finite heat flux under the conditions of a step change. This a contrary to the infinite value predicted by the error function solution to the Fourier transient conduction equation. In addition, assuming convection is conduction limited; an upper limit for convective heat transfer coefficients is postulated.

THEORETICAL STUDY ABOUT THE DETERMINATION OF THE LOCAL TURBULENT FRICTION FACTOR AND HEAT TRANSFER COEFFICIENT

FLORESCU DANIELA, FLORESCU IULIAN

The paper presented a method for the determination of the distributions of velocity, local friction and heat transfer coefficients in a forced axial turbulent flow with an arbitrary cross section. The method uses as basis the characteristics of the laminar flow. A comparison is made with some experimental results concerning different geometries.

THE QUANTITATIVE ANALYSE OF CARBIDES PHASES IN THE CRYOGENIC AND ULTRASONIC TREATED BEARINGS STEELS

GHEORGHIAN MIRELA, CIUCESCU DORU

After the heat treatments of quenching and tempering, the bear steels, being a hypereutectoid steel, presents a structure made by martensite, residual austenite and carbides. Both the martensite and the residual austenite being unstable phases, even after the final heat treatment, have the tendance to evoluate to more stable forms. The quenched tetragonal martensite evoluate to the tempered cubic martensite by separating the carbide carbone which provokes shrinkage in steel. In this article is presented the statistic method to determinate the quantuty of carbides and the comparative analyse of them by more variants of heat treatment including cryogenic quenchings after quenching, temperings at different temperatures and quenchings in ultrasonic activated media. The realized study reveals the fact that the applying of non-conventional influence sensibly the structure of the bearings steels and, implicitelly, the running properties of bearings.

EXPERIMENTAL RESEARCHES ON RUNNING PROPERTIES OF NON-CONVENTIONAL TREATED STEELS FOR BEARINGS

GHEORGHIAN MIRELA, CIUCESCU DORU

In the conditions of strongly competition, in the present it is looking for new solutions to obtain bearings with prices as far low as possible, with delivery schedule as far short, but, in the same time, with running properties as far suitable, dimensional stability in running, low level of noise, high reliability, stable properties in running, good behavior in the most different conditions of environment and running, but all of this is not always possible to be obtained by classical heat treatments. The non-conventional heat treatments are modern and efficient processes, which, if are correctly applied in the chain of technological operations, determine considerable improvements of the properties of bearings. In this paper are presented the results of experimental researches on the abrasive wear out of bearings steels which are cryogenically heat treated and in ultrasonic activated liquids.

STATIC TESTS REGARDING AN ADVANCED SANDWICH COMPOSITE STRUCTURE

GOIA IOAN *, ROŞU DORIN **, HORAŢIU TEODORESCU *

The paper presents static tests like tensile and bending tests accomplished on an advanced sandwich composite structure. Various test specimens for tensile and bending tests were presented. A comparison between the experimental tests and theoretical approach is shown.

EVALUATION OF BIOMECHANICAL PERFORMANCES OF SOME OSTEOSYNTHESIS TECHNIQUES APPLIED IN THE TREATMENT OF FEMORAL FRACTURES

ILIESCU NICOLAE *, NĂSTĂSESCU VASILE **

In order to evaluate the biomechanical behavior of some types of osteosynthesis techniques (elastic or rigid) frequently used in the femoral fractures treatment, a comparative study undertaken by Finite Element Method (FEM), is presented in this paper. FEM results are used to emphasize the biomechanical particularities that can appear in the case of some elastic osteosyntheses with: Kuntscher nail (OEK), Ender nails in secant arch (OES), Ender nails and external lock (OEF), and also in the case of rigid osteosynthesis with locked intra-medullar nail (ORZ). Evaluation criteria of the biomechanical behavior of these osteosyntheses refer to the level of compression stresses and displacements in the fracture focus. The stress state and resultant displacements, in different zones of the bone and implants were also analyzed. For comparison, the stress state and displacements were also determined for the unfracturated (normal) bone. Simulations were performed for monopodal position, corresponding to the walking sequences when one leg or the other successively realizes the ground support.

EVALUATION OF THE MECHANICAL FACTORS INFLUENCE IN THE TREATMENT OF TIBIAL FRACTURES, USING THE KUNTSCHER CENTRO-MEDULLAR NAIL TECHNIQUE

ILIESCU NICOLAE, PASTRAMĂ ŞTEFAN DAN

In this paper, the results of a biomechanical comparative study using the strain gauge technique are presented. The aim of the study is to emphasize the optimization of the mechanical factors influence in the process of primary callus sedimentation in the focus of a tibial fracture, operated using a Kuntscher centro-medullar nail osteosynthesis. The smaller values of the experimentally determined stresses in different zones of the tibial diaphysis after mounting the nail on the medullar canal show that a part of the load is taken over by the nail. In this way, one can appreciate that the level of the compressive stresses produced in the focus of the fracture is approaching the most favorable one, helping the process of recovery of the bone tissue and quick healing of the patient

THE ISOLATION OF SHOCK BY EQUIPING THE RAILWAY VEHICLES WITH LONG-RUN BUFFERS

MĂNESCU TIBERIU ŞTEFAN, COPACI ION, OLARU STELIAN, CREANGĂ FLORENTIN

The current trend towards the increase of speeds in the railway traffic and the ever growing gain weight on the axles has brought about a series of special problems concerning the impact stress which occurs at collision. In order to isolate the shock that occurs longitudinally, the rail vehicles are fitted with shock dampers: - Buffers or main coupling dampers - Long-rung buffers fitted on the platform wagons, meant as an additional safety measure for the goods loaded on the storage platform. Long-rung buffers fitted on the platform wagons are reducing the level of the longitudinal acceleration.

SYNTHESIS OF THE RESULTS REGARDING THE BREAKING RESISTANCE OBTAINED BY STATIC LOADS AND THE IMPACT BEHAVIOR OF THE ADHESIVE JOINTS

MOCANU FLORENTINA, BÂRSĂNESCU PAUL-DORU

The present paper discusses the results of some investigations, which had in view the establishment the variation mode of the breaking resistance to shear and the maxim breaking energy under impact loading of the adhesive joints, with metallic supports, made with epoxy and/or polyurethane adhesives. The studies were made using the shear and impact tests of the adhesive bonded joints. The influence of loading mode, surface roughness of the adhesion interface, thickness of adhesive layer, superposition length, thickness of substrate, bonded area of the joint specimens and the loading rate on the strength of adhesive joints are investigated in detail.

STRESS REDUCING IN PIPE LINE ELEMENTS, BASED ON FEM COMPLEX MODELING

MODIGA M., MURINEANU A., DIMACHE A.

A complex model is presented for the analysis (trough finite elements method) of the behavior of a ship piping system and adjacent structures at the action of the stress that appears during exploitation. With this model we can make a comparative analysis of the stress states of the system's elements. Constructive solutions are suggested for reducing the stress induced in the passage trough the watertight cross bulkhead of the pipe line of the installation for cargo transfer on an oil tanker.

OPTIMIZATION OF PIPE LINE ELASTICITY IN OIL CARRIER

MURINEANU A.*, ANGHEL L.**, MODIGA M.*

We use a complex modeling with finite elements that allow the consideration of temperature variations, interior pressures and interactions with the body of the ship. For the cargo transfer installations of oil tankers we study the behavior of eight pipe system models, which have different dilatation lyre (U compensator) arms. This gives the pipe system an extra elasticity and is usually preferred for compensating thermal dilatations and displacements required by the deformation of ship's body. Based on these analyses we can obtain practical recommendations useful in designing.

A NEW MODEL OF MACRO-ELEMENT USED FOR SHIP HULL TORSION

MUSAT SORIN DUMITRU, CHIRICĂ RALUCA

A proposal of a new model of macro element used to analyse the ship hull torsion - closed section - as thin walled beam using macro elements is treated. The outline of the section is considered as polygonal one. The material is considered as an orthotropic one. For a straight line portion of cross section outline is corresponding a longitudinal strip plate. Due to the warping torsion of the thin walled beam, in the strip plate the stretching-compression, bending and shearing occur. The stiffness matrix of the macro-element is obtained by assembling the stiffness matrices of the strips.In the local strength analysis of the ship hull, the local loading is supposed to be known. These loadings occur from the global strength of the ship hull. An important loading of the ship hull is torsion treated as thin walled beam (frequently as closed section).

STAND FOR THE STUDY OF THE NON-STATIONARY HYDROMECHANICAL PROCESSES IN THE FRAME OF THE ELECTRO-HYDROSTATIC DRIVING GROUP FROM LARGE DIAMETER DRILLING RIGS

PAREPA SIMION

The running of the electro-hydrostatic driving groups of the rotary system belonging to the large diameter drilling rigs is characterized by a dynamic regime, determined by the transitory phases of the drilling process, by the proper drilling process, and by the accompanying phenomena. In the work, the stand built up for the non-stationary hydro-mechanical process research in the frame of these driving groups, the measuring instruments and the used strain gauge transducers, as well as some aspects regarding their calibration, are presented. The stand represents the rotary system of the drilling rigs F320-3DH-M and F400-4DH-M in natural size and from dynamic point of view.

THE DETERMINATION BY EXPERIMENTAL AND NUMERICAL METHODS OF STRESS AND STRAIN STATES IN PERFORATED PLATES WITH SQAURE HOLES POSITIONED IN PARALLEL PATTERN, STRESSED WITH SINGLE AXIS TENSILE STRESS

PASCU ADRIAN, GALAFTION SOFONEA

The present paper presents a comparative study between experimental tests and numerical results obtained with the help of the finite element method with regard to the stress and strain state that appears in a perforated plate with square holes placed in a parallel pattern ("Ap"-type) stressed with uniaxial traction.

CONSIDERATIONS CONCERNING USE OF IMAGE ANALYSIS METHOD FOR STUDY OF THE DEFORMATION DISTRIBUTION

PINTILIE GHEORGHE, ALBUŢ AURELIAN, ZICHIL VALENTIN

In the last period of time, due to the excessive development of computer based technology and of the data acquisition systems, some new techniques are elaborate to determine the deformation state of a body loaded with external forces. One of the most developed techniques is the image analysis method [1, 2, 3], method which eliminate the difficulties that are found in case of classical methods used for deformation determination. Moreover, this method, used for study of metallic and non-metallic [4, 5, 6] body deformation brings in an important development in the study of material flow phenomenon [7, 8, 9 10, 11]. As a result of theoretical and experimental research, have been conceive image analysis systems used for deformation determination, called video-extensometer. This paper present aspect regarding working principles of the image analysis method, some advantages with respect to the classical methods and the obtained results.

BEHAVIOR OF WOOD-CONCRETE COMPOSITE BEAMS CONTINUOUS WOOD-CONCRETE-COMPOSITE SYSTEM

POPOI ARDELEAN ADRIAN NICOLAE, CURTU IOAN, CIOFOAIA VASILE

This paper introduces a continuous and a non continuous wood-concrete- composite system (wcc-system) which contains a steel mesh connecting wooden beams with a concrete slab and a non continuous wood-concrete-composite system which contains SFS screws connecting the wooden beams and the concrete slab. The shear connector acts as a rigid but ductile moderator between the materials wood and concrete. The system was tested in both shear and bending conditions to allow a better understanding on the structural behavior under ultimate loading conditions. In order to allow a prediction of the non-linear behavior of the specimens a mechanical model was developed. The comparison between actual test and the mechanical model shows a good correlation and puts trust in the simulation of the innovation. The advantages of this system compared to contemporary wcc-system solutions lay in improved strength, stiffness and manufacturing procedures. Its application potential can be found in floor, wall and roof systems of private and commercial buildings as well as in bridge structures.

EXPERIMENTAL STUDY OF SHELL AND TUBE HEAT EXCHANGER'S BEHAVIOUR

RADOIUA BOGDAN, GARABET KÜMBETLIANB, PERIDEA NICULAE

This paper describes the experimental model and the way of investigation of the strains and stresses state using strain gages technologies under mechanical and thermal loads. Numerical stresses values are highlighted and compared with experimental values; authors' conclusions regarding stresses comparisons are also presented. A small reference list with bibliographical material used in this paper is also included.

LARGE DEFORMATIONS AT THIN PLANE DISKS BENDING UNDER UNIFORM DISTRIBUTED LOADS, CONSIDERING THE MEMBRANE STRESSES PART I - GENERAL THEORETICAL CONSIDERATIONS ON LARGE DEFORMATIONS

RADU GHEORGHE*, COMĂNESCU IOANA**

The present paper deals with the state of stress and deformation at thin circular plates subjected to symmetrical axial loading. The loading is a bending owing to the uniform distributed loads which act perpendicular to the mean surface of the plate, simultaneous with a membrane load (loads acting in the mean plane of the plate). This type of problem is solved by help of equations which result from the equilibrium of a plate`s element and from the boundary and continuity conditions of the mean surface of the plate. One considers the following two cases: - the membrane stresses are small comparatively to the bending stresses; in this case the calculus is precise enough if we take into account only the mean plane extensions which will be superposed over the effects given by the transversal bending stress q; - the membrane stresses are considerable and can not be neglected; in this case, second order calculus is required.

LARGE DEFORMATIONS AT THIN PLANE CIRCULAR PLATES BENDING UNDER CONSTANT LOADING, TAKING INTO ACCOUNT THE MEMBRANE STRESSES PART II - BENDING UNDER INITIAL LOADING OF THE PLATES MEAN PLANE

RADU GHEORGHE*, COMĂNESCU IOANA**

The present paper deals with the state of stress and deformation at thin circular plates subjected to symmetrical axial loading. The loading is a bending owing to the uniform distributed loads which act perpendicular to the mean surface of the plate, simultaneous with a membrane load (loads acting in the mean plane of the plate). This type of problem is solved by help of equations which result from the equilibrium of a plate`s element and from the boundary and continuity conditions of the mean surface of the plate. One considers the following two cases: -the membrane stresses are small comparatively to the bending stresses; in this case the calculus is precise enough if we take into account only the mean plane extensions which will be superposed over the effects given by the transversal bending stress q; -the membrane stresses are considerable and can not be neglected; in this case, second order calculus is required.

TESTS RESULTS FOR 16Mo5.3b STEEL SUBMITTED TO THERMOMECHANICAL FATIGUE AND THEIR STATISTICAL ANALYSIS

RIZEA NICOLETA, POSEA NICOLAE

This paper presents thermomechanical fatigue tests of 16Mo5.3b steel test specimens, in temperature range 60oC÷540oC, with total strain control in wich cycle of temperature variation, on ring surface test specimens. Thermal condition of test is without soaking period at maximum temperature 540oC. Using a modern process of experimental datas statistical analysis is tracing the material thermomechanical fatigue curve, and base on this is established the shell type structures durability, like coking chambers.

MICROSTRUCTURAL RESEARCHES REGARDING THE CRACKING OF 16Mo5.3b STEEL TEST SPECIMENS SUBMITTED TO THERMOMECHANICAL FATIGUE TESTS

RIZEA NICOLETA, POSEA NICOLAE

In the present paper are mentioned the results of thermomechanical fatigue tests of 16Mo5.3b steel test specimens, from metallographic point of view and from microstructural view of starting and growing cracks at thermal fatigue. Are presented cross and longitudinal sections through the test specimens highlighting the cracks growing.

THE STRESS FIELD AT THE TOP OF AN OPENED CRACK IN SAMPLES FROM 10TiNiCr175 SUBMITTED TO AN OSCILLATOR EXTENSION WITH THE ASYMMETRY COEFFICIENT R=0.1

ROŞCA VÂLCU

We took flat samples CT model, with siding cut, from stainless steel mark 10TiNiCr175. They were solicited at axial fatigue of eccentric extension, with the asymmetry coefficient R= 0.1. The samples were tested at the environment temperature (T=293K), namely at low temperatures, T= 253K and T= 213K. During the testing were retained the length variation of the fracture crack a and the numbers of corresponding cycles N. For the same coefficient asymmetry coefficient R= 0.1, at the three testing temperatures: T= 293 K, T= 253 K and T= 213 K, we have determined the stress intensity factor noted through ?K, the growth rate of the fracture crack da/dN, parameters necessary to the establishment of the stress field ? from the area of the defect's top.

THE DETERMINATION OF THE OPERATION DURATION AT A FATIGUE SOLICITATION FOR OSCILLATOR EXTENSION AT THE 213 K TEMPERATURE

ROŞCA VÂLCU

The paper points out a modality of determination of functioning of a part submitted to a cyclic solicitation undulant positive of eccentric traction. Experimentally, for samples made of general use steel R520, we determined the variation of the fracture length of crack a and the number of N cycles, corresponding to them. Empirical relations of calculation for the time of a part's functioning were obtained, taking into consideration the asymmetry coefficient R and the solicitation loads. The working environment temperature was 213K (-60°), and the asymmetry coefficients used were R= 0.1, R= 0.3 and R= 0.5.

A COMPARATIVE ANALYTIC-NUMERIC-EXPERIMENTAL STUDY ON SYMMETRICAL AND ASYMMETRICAL ADHESIVE LAP JOINTS

SANDU ADRIANA, SANDU MARIN, SOROHAN ŞTEFAN

THE BEHAVIOUR OF DRILL PIPES WITH SURFACE DEFECTS IN THE CASE OF DIRECTIONAL DRILLING

STANCIU LAVINIA SILVIA, POPA IOAN

The present paper presents the results of some theoretical and experimental researches undertaken by the authors for the purpose to establish the fraction of a drill pipe life consumed by fatigue in a concrete case. As critical drill pipes zones they have been taken into account those from the pipes body, in the drill slips area, used for sustaining the pipes during the handling operations, where the die- marks appear. Hossain [2] suggested that the problem of a dogleg region could be treated on small and well-defined regions of curvature, where the drilling can be considered constant values.