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B U L E T I N U L I N S T I T U T U L U I P O L I T E H N I C D I N I A Ş I<br />
B U L L E T I N O F T H E P O L Y T E C H N I C I N S T IT U T E O F I A Ş I<br />
Tomul LVIII (LXII), Fasc. 2 2012<br />
MACHINE CONSTRUCTION<br />
C O N T E N T S<br />
Pp.<br />
ION BOSTAN (Rep. of Moldova), VALERIU DULGHERU (Rep.<br />
of Moldova) and RADU CIOBANU (Rep. of Moldova),<br />
Analytic description of teeth profile for processional multiplier<br />
(English, Romanian summary) . . . . . . . . . . . . . . . . . . . . . . . . . .<br />
BOGDAN MUNTEANU (France), ANA-MARIA TRUNFIO<br />
SFARGHIU (France), CONSTANTIN IONUT MATEI<br />
(France), SAW-SEE HONG (France), PIERRE BOULANGER<br />
(France), MARIE-GENEVIEVE BLANCHIN (France), JEAN-<br />
PAUL RIEU (France) and YVES BERTHIER (France),<br />
Correlation between nanomechanical and tribological properties<br />
of healthy and pathological synovial fluids reconstituted from<br />
synoviocyte cultures (English, Romanian summary) . . . . . . . . . . 11<br />
1<br />
VIOREL PALEU, Power loss and temperature computation in <strong>highspeed</strong><br />
ball bearings lubricated by oil mist II. Theoretical and<br />
experimental results (English, Romanian summary) . . . . . .<br />
MARCELIN BENCHEA and SPIRIDON CREŢU, Profile<br />
evolution in cylindrical roller bearings, I. Elastic-Plastic<br />
Analysis (English, Romanian summary) . . . . . . . . . . . . . . . . . .<br />
IRINA PELIN, ANA-MARIA TRUNFIO SFARGHIU (France),<br />
PIERRE FARGE (France), AGNES PIEDNOIR (France),<br />
CHRISTOPHE PIRAT (France) and STELLA RAMOS<br />
(France), Mechanical and physicochemical properties of the<br />
deep dentin surfaces (English, Romanian summary) . . . . . . . . .<br />
19<br />
27<br />
37<br />
ANA-MARIA AMANCEA, BENYEBKA BOU-SAЇD (France),<br />
CRISTEL ŞTIRBU, MIHAI GAFIŢANU, MICHÈLE<br />
GUINGAND (France) and CHRISTOPHE BARD (France),<br />
Modelling the knee joint mechanical behaviour using a 3D model.
A numerical simulation solution (English, Romanian summary) . . 45<br />
GEORGE GAVRILĂ and SPIRIDON CREŢU, Wear evolution in<br />
circular contacts in partial slip (English, Romanian summary) ...<br />
53<br />
ANA TUFESCU and SPIRIDON CREŢU, Analysis of stress state<br />
developed contacting elements with non-gauss rough surfaces<br />
(English, Romanian summary) . . . . . . . . . . . . . . . . . . . . . . . . . . 71<br />
MIHAELA RODICA BĂLAN and SPIRIDON CREŢU, Fatigue<br />
life analysis on roller bearings with various roughnesses of the<br />
active surfaces (English, Romanian summary) . . . . . . . . . . . . .<br />
CONSTANTIN BĂRBÎNŢĂ, ANA URZICĂ and SPIRIDON<br />
CREŢU, On the role played by roughness parameters on<br />
pressure and stress distributions in wheel-rail contact (English,<br />
Romanian summary) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .<br />
LAURENŢIU SLĂTINEANU, OANA DODUN, LORELEI<br />
GHERMAN, IRINA GRIGORAŞ (BEŞLIU) and VASILE<br />
BRAHA, Roughness parameters of surfaces obtained by<br />
abrasive jet machining (English, Romanian summary) . . . . . . .<br />
ALEXANDRA RAICU, Residual stresses reduction using CAE<br />
analysis in molded polymeric parts (English, Romanian<br />
summary) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109<br />
CRISTIAN SUCIU, GEORGE ARGHIR, IOAN PETEAN and<br />
CLAUDIU POPA, Effect of sintering temperature on high<br />
alloying manganese steels subjected to abrasive wear (English,<br />
Romanian summary) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .<br />
CRISTIAN SUCIU, GEORGE ARGHIR, IOAN PETEAN and<br />
CLAUDIU POPA, Heat treatment influence on sintered<br />
manganese steels under abrasive wear (English, Romanian<br />
summary) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .<br />
LIVIU BĂLAN, ANA TUFESCU, CARMEN BUJOREANU,<br />
DUMITRU OLARU and SPIRIDON CREŢU, Evaluation of<br />
the local gear scuffing (English, Romanian summary) . . . . . . . . 129<br />
IULIANA ROTARU and DUMITRU OLARU, Lubrication regimes<br />
in total disc prostheses on lumbar spine (English, Romanian<br />
summary) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137<br />
81<br />
91<br />
101<br />
117<br />
123
IULIANA ROTARU and DUMITRU OLARU, Pressure and<br />
friction in total disc prosthesis: effect of surface conformity<br />
(English, Romanian summary) . . . . . . . . . . . . . . . . . . . . . . . . . . 147<br />
VLAD CÂRLESCU, FLORIN BREABĂN (France), DUMITRU<br />
OLARU and GHEORGHE PRISĂCARU, Experimental<br />
methods for measuring the field-induced strain response of<br />
dielectric elastomers (English, Romanian summary) . . . . . . . . 157<br />
MIHAI BAICEANU, PAULO FLORES (Portugal), CEZAR<br />
OPRISAN and DUMITRU OLARU, Effects of the driving<br />
speed on the dynamic response of a four-bar mechanism with<br />
clearance joints (English, Romanian summary) . . . . . . . . . . . . .<br />
CARMEN BUJOREANU, BARBU DRĂGAN and VASILE<br />
HORGA, Vibration control approach in low slip speed dry<br />
friction systems (English, Romanian summary) . . . . . . . . . . . . . 173<br />
CRISTEL ŞTIRBU, Tubing and casing connections. Functioning<br />
aspects according to threads design problems (English,<br />
Romanian summary) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183<br />
165<br />
VIOREL PALEU and LIVIU BALAN, Power loss and temperature<br />
computation in high-speed ball bearings lubricated by oil mist, I<br />
Theoretical model (English, Romanian summary) . . . . . . . . . .<br />
ALINA CORINA DUMITRASCU, GELU IANUS and DUMITRU<br />
OLARU, Friction coefficient in the pivoting motion for a ballrace<br />
contact (English, Romanian summary) . . . . . . . . . . . . . . . .<br />
ALEXANDRU BUDEL, DUMITRU OLARU and GHEORGHE<br />
PRISACARU, Ball kinematics in a linear recirculating system<br />
with four contact points - analytical model (English, Romanian<br />
summary) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .<br />
IRINA MARDARE and IRINA TITA, Aspects concerning<br />
hydraulic systems with hydro pneumatic accumulators (English,<br />
Romanian summary) . . . . . . . . . . . . . . . . . . . . . . . . . .<br />
ELENA RALUCA BACIU, IRINA GRĂDINARU, MARIA<br />
BACIU and NORINA CONSUELA FORNA, Researches on<br />
microstructure and micro hardness of titanium-based alloys<br />
used in dental prosthetics (English, Romanian summary) . . . . .<br />
CĂTĂLINA AXINTE, CORNELIU MUNTEANU and<br />
ALEXANDRU BARNEA, Molybdenum coatings friction<br />
coefficient studies for future applications in machine elements<br />
191<br />
201<br />
207<br />
215<br />
219
(English, Romanian summary) . . . . . . . . . . . . . . . . . . . . . . . . . .<br />
CĂTĂLINA AXINTE, PETRU AVRAM, EDUARD SEBASTIAN<br />
BÂRCĂ, BOGDAN ISTRATE and CORNELIU MUNTEANU,<br />
Comparative studies of corrosion resistance on 21TMC12 steels<br />
uncoated and coated with WC-Co-Cr (English, Romanian<br />
summary) . . . . . . . . . . . . . . . . . . . . . . . . . .<br />
ALEXANDRU BÂRCĂ, CĂTĂLINA AXINTE, PETRU AVRAM,<br />
SORIN CLAUDIU IACOB STRUGARU and CORNELIU<br />
MUNTEANU, Friction properties of WC coatings used in<br />
automotive industry (English, Romanian summary) . . .<br />
EDUARD SEBASTIAN BÂRCĂ, CĂTĂLINA AXINTE,<br />
CONSTANTIN PAULIN, SORIN CLAUDIU IACOB<br />
STRUGARU and CORNELIU MUNTEANU, Experimental<br />
research on WC-Co-Cr coatings used in automotive industry<br />
(English, Romanian summary) . . . . . . . . . . . . . . . . . . . . . . . . . .<br />
LUCIA ANIŞOARA DRĂGAN (RĂILEANU), CORNELIU<br />
MUNTEANU, DANIEL MARECI, PINTILEI GEANINA<br />
LAURA, ROMEU CHELARIU and CĂTĂLINA AXINTE,<br />
Electrochemical studies of corrosion behaviour of experimental<br />
TiNbZrAl alloys in artificial saliva (English, Romanian<br />
summary) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .<br />
SORIN CLAUDIU IACOB STRUGARU, CORNELIU<br />
MUNTEANU and CĂTĂLINA AXINTE, Corrosion<br />
performances of Mo coatings deposited on steel substrates<br />
(English, Romanian summary) . . . . . . . . . . . . . . . . . . . . . . . . . .<br />
CARMEN PĂPĂTOIU (BINIUC), CĂTĂLINA AXINTE,<br />
EDUARD SEBASTIAN BÂRCĂ, SORIN CLAUDIU IACOB<br />
STRUGARU and CORNELIU MUNTEANU, Properties of Mo<br />
coatings obtained by thermal deposition on steel substrate<br />
(English, Romanian summary) . . . . . . . . . . . . . . . . . . . . . . . . . .<br />
GEANINA LAURA PINTILEI, GICA NARCIS BASESCU,<br />
TUDOR BRIAN LANDKAMMER, LAURA TEODORA<br />
SOLONARIU, LUCIA ANISOARA DRAGAN and<br />
CORNELIU MUNTEANU, Effect of heat-treatment of<br />
atmospheric plasma spraying coating APS with powder ceramic<br />
(English, Romanian summary) . . . . . . . . . . . . . . . . . . .<br />
GEANINA LAURA PINTILEI,CORNELIU MUNTEANU, GICA<br />
NARCIS BASESCU, TUDOR BRIAN LANDKAMMER,<br />
BOGDAN ISTRATE and IONUT VASILE CRISMARU,<br />
Stress analysis in the vicinity of the Vickers indentation by<br />
227<br />
233<br />
239<br />
245<br />
253<br />
263<br />
269<br />
277
finite element method (English, Romanian summary) . . . . . . . . 289<br />
TUDOR BRIAN LANDKAMMER and LAURA TEODORA<br />
SOLONARIU, Consideration regarding grain growth and<br />
nucleation on solidified layers deposited by thermal spraying<br />
(English, Romanian summary) . . . . . . . . . . . . . . . . . . . . . . . . . .<br />
299<br />
ANALYTIC DESCRIPTION OF TEETH PROFILE FOR<br />
PRECESSIONAL MULTIPLIER<br />
by<br />
ION BOSTAN, VALERIU DULGHERU, RADU CIOBANU<br />
Abstract: Absolute multiplicity of precessional gear (up to<br />
100% pairs of teeth simultaneously involved in gearing, compared<br />
to 5%-7% - in classical gearings) provides increased lifting<br />
capacity and small mass and dimensions. To mention that until now<br />
precessional planetary transmissions have been researched and<br />
applied mainly in reducers. The mathematic model of the modified<br />
teeth profile for precessional multipliers is presented in this work.<br />
Key words: precessional transmission, gearing, teeth profile.<br />
CORRELATION BEWEEN NANOMECHANICAL AND<br />
TRIBOLOGICAL PROPERTIES OF HEALTHY AND<br />
PATHOLOGICAL SYNOVIAL FLUIDS RECONSTITUTED<br />
FROM SYNOVIOCYTE CULTURES<br />
by<br />
BOGDAN MUNTEANU, ANA-MARIA TRUNFIO SFARGHIU,<br />
CONSTANTIN IONUT MATEI, SAW-SEE HONG, PIERRE<br />
BOULANGER, MARIE-GENEVIEVE BLANCHIN, JEAN-PAUL<br />
RIEU and YVES BERTHIER<br />
Abstract. The aim of this study was to analyze the evolution of<br />
the nano-mechanical and tribological properties of the synovial<br />
fluids in joint diseases, in order to be able to correct their possible<br />
mechanical causes. Thus, synovial fluids reconstituted in cell<br />
cultures were studied by coupling: - AFM analysis, in order to<br />
characterize the liposomal structures and the nano-mechanical
esistance of molecular assemblies which are present in these<br />
fluids, and - Tribological analysis, to understand the evolution<br />
during the friction of molecular structures in healthy and<br />
pathological case. We analysed two types of reconstituted synovial<br />
fluid, issued from (1) non- treated synoviocytes (healthy) and (2)<br />
cultures of cytokine-treated synoviocytes, mimicking the joint<br />
inflammatory environment. The molecular structures from the<br />
reconstituted synovial fluids were nanomechanically analysed<br />
using a commercial AFM. The tribological analyses were<br />
performed using a home-made bio-tribometer that allows the<br />
simultaneous measurement of frictional forces and fluorescence<br />
observation of the lipid assemblies in order to detect any<br />
degradation during friction. In the case of the reconstituted<br />
synovial fluids from non-cytokine treated synoviocytes, the results<br />
showed the presence of numerous lipid vesicles that grew in<br />
diameter, from 30-70 nm to 1-2 µm, with an average Young<br />
modulus of 3.37 MPa and adhesion force of 0 nN. The friction<br />
coefficient was constant (~0.1) and no degradation of the lipid<br />
bilayers was observed. In the case of pathological synovial fluids<br />
reconstituted in vitro with their inflammatory environment, we<br />
observed a progressive destruction of the vesicles and the<br />
apparition of a gelatinous mass constituted by a glycoprotein gel<br />
with an average Young modulus of 0.13 MPa and a high adhesion<br />
force (1.51 nN). The friction coefficient increased until 0.45 with<br />
an important degradation of the lipid bilayers. This study showed<br />
that the presence of the lipid vesicles maintains a low and stable<br />
friction coefficient in healthy cases, while their destruction<br />
increases the friction coefficient in pathological cases.<br />
Key words: lubrication, in vitro synovial fluid, lipid vesicle,<br />
lipid bilayer, nanomechanical analysis, tribological analysis.<br />
POWER LOSS AND TEMPERATURE COMPUTATION IN<br />
HIGH-SPEED BALL BEARINGS LUBRICATED BY OIL MIST<br />
II. THEORETICAL AND EXPERIMENTAL RESULTS<br />
by<br />
VIOREL PALEU<br />
Abstract. The Part I of the paper presents a model for the<br />
computation of the friction torque, power loss, and heat transfer in<br />
ball bearings lubricated by oil mist. In this part, a test rig for
friction torque measurement is presented. For different ranges of<br />
temperatures, axial preloads and speed, all steel-bearings from<br />
7206C series are tested. The friction torque at the outer race level<br />
is appreciated experimentally, the temperature of the bearings<br />
housing being estimated by a laser tip Raynger MX4 device.<br />
Regarding the friction torque in bearings, the theoretical results are<br />
validated by experimental results, a good agreement being found.<br />
To model the results on the evolution of the friction torque at<br />
higher temperatures and higher speed, there is the need to<br />
introduce starvation and thermal effects on lubricant film<br />
thickness. The friction between the asperities of balls and races can<br />
not be neglected in the model, this superposing the friction forces<br />
due to the shearing of the oil film in contacts.<br />
Key words: high-speed, ball bearings, oil-mist, temperature,<br />
test rig, friction torque, power losses<br />
PROFILE EVOLUTION IN CYLINDRICAL ROLLER<br />
BEARINGS<br />
I. ELASTIC-PLASTIC ANALYSIS<br />
by<br />
MARCELIN BENCHEA and SPIRIDON CRETU<br />
Abstract. The class I discontinuities that exist along<br />
cylindrical-crowned roller profile generate high pressure peaks in<br />
pressure distributions that diminish considerably the modified<br />
rating life as is defined by ISO 16281-2008. On the other hand, if<br />
produced, these peaks might be able to generate both plastic<br />
deformations and residual stresses. After a certain number of<br />
cycles the material may shakedown elastically to a slightly<br />
modified roller profile and a stable state of compressive residual<br />
stresses. An analysis model has been developed to simulate the<br />
nonlinear strain rate dependent deformation of rolling bearing steel<br />
stressed in the elastic-plastic domain. Severe working conditions<br />
(C/P > 0.3) as well as high transient overload are able to change<br />
the roller profile to obtain a stress distribution in the contact zones<br />
that provides enhanced operational reliability and greater<br />
insensitivity to misalignment. If were taken place, these changes<br />
have to be considered in the life evaluation.<br />
Key words: elastic-plastic contact, non-linear hardening, plastic<br />
deformation, cylindrical roller bearings.
MECHANICAL AND PHYSICOCHEMICAL PROPERTIES<br />
OF THE DEEP DENTIN SURFACES<br />
by<br />
IRINA PELIN, ANA-MARIA TRUNFIO SFARGHIU,<br />
PIERRE FARGE, AGNES PIEDNOIR, CHRISTOPHE PIRAT,<br />
STELLA RAMOS<br />
Abstract. The purpose of this study was to investigate the<br />
mechanical and physicochemical properties of the etched and nonetched<br />
deep dentin surfaces. The mechanical properties were<br />
investigated by atomic force spectroscopy, and the<br />
physicochemical properties by scanning electron microscopy<br />
coupled with energy-dispersive X-ray spectroscopy and contact<br />
angle measurements. The results showed that the apparent elastic<br />
modulus decreases with the decrease of the mineral – organic ratio.<br />
The information concerning the properties of dentin surfaces are<br />
important for predicting the consequences of the microstructural<br />
damages of the dentin caused by caries, some diseases or aging,<br />
and of some restorative materials or dental procedures. Also, this<br />
information is meaningful to the modelling of the dental obturation<br />
process and to the estimation of the toughness and the efficacy of<br />
the restorative materials.<br />
Key words: apparent Young’s modulus, surface energy,<br />
mineral – organic ratio<br />
MODELLING THE KNEE JOINT MECHANICAL BEHAVIOUR<br />
USING A 3D MODEL. A NUMERICAL SIMULATION<br />
SOLUTION<br />
by<br />
ANA-MARIA AMANCEA, BENYEBKA BOU-SAЇD, CRISTEL<br />
ŞTIRBU, MIHAI GAFIŢANU , MICHÈLE GUINGAND ,<br />
CHRISTOPHE BARD<br />
Abstract. The methodology of 3D knee model developing used<br />
for analysis the mechanical behaviour of the knee is presented. The<br />
model is created with a combination of software’s<br />
(Catia/SimDesigner) that offers the possibility to obtain, in the<br />
same time, data concerning the kinematic and dynamic aspects of
the knee. From kinematic points of view, the results presented in<br />
current paper are validated according with Wilson’s experimental<br />
results and the dynamical part of the model is validated with<br />
(Moglo & Shirazi-Adl, 2003) and (Junior et al., 2009), results. The<br />
presented model, that offers precious information about<br />
mechanical behaviour of the joint, can be a base in the developing<br />
of mechatronical systems used to assist or rehabilitate human knee<br />
joint.<br />
Key words: modelling, knee joint, rehabilitation, kinematic,<br />
dynamic, mechatronics.<br />
WEAR EVOLUTION IN CIRCULAR CONTACTS IN PARTIAL<br />
SLIP<br />
by<br />
GEORGE GAVRILĂ and SPIRIDON CREŢU<br />
Abstract. The paper presents a numerical model to investigate<br />
fretting under partial slip conditions. An elastic contact model is<br />
presented in order to solve both the normal and tangential contact<br />
problem. The numerical approach to simulate wear is based on a<br />
version of Archard wear law and is applied to a sphere on flat<br />
geometry. Surface wear damage is predicted to have a significant<br />
effect on the normal and shear tractions distribution for the partial<br />
slip regime. The contact model is validated with analytical<br />
solutions for a sphere on flat geometry and as well with different<br />
numerical solutions from literature.<br />
Key words: wear, stick-slip, friction, contact mechanics.<br />
ANALYSIS OF STRESS STATE DEVELOPED CONTACTING<br />
ELEMENTS WITH NON-GAUSS ROUGH SURFACES<br />
by<br />
ANA TUFESCU and SPIRIDON CREŢU<br />
Abstract. The normal pressure distribution can be used to<br />
predict subsurface stress, interfacial friction and surface wear.<br />
Only few real rough surfaces are Gaussian, most of that produced<br />
by manufacturing processes are non-Gaussian having an arbitrarily<br />
orientation. The paper reveals the role played by the spatial
characteristics (standard deviation σ, skewness Sk, and kurtosis K)<br />
as well as by autocorrelation function on both the non-Hertzian<br />
pressure distribution on contact area and depth distribution of von<br />
Mises equivalent stress.<br />
Key words: concentrated contact, roughness, autocorrelation<br />
length, von-Mises stress.<br />
FATIGUE LIFE ANALYSIS ON ROLLER BEARINGS<br />
WITH VARIOUS ROUGHNESS OF THE ACTIVE SURFACES<br />
by<br />
MIHAELA RODICA BĂLAN and SPIRIDON CREŢU<br />
Abstract. The paper proposes a distinctive analysis of fatigue<br />
life distribution in terms of roughness value on the inner ring or<br />
roller using experimental results of the rolling contact fatigue tests<br />
on cylindrical roller bearings. Thus, the following observations<br />
were pointed out: an increase of the inner ring roughness causes a<br />
significant decrease in fatigue life, for all roller roughness values,<br />
and the roller roughness determine maximum fatigue life for<br />
certain values. The correlation between fatigue life and roughness<br />
was also studied by using the lubrication parameter Λ.<br />
Key words: fatigue life test, roller bearing, surface roughness.<br />
ON THE ROLE PLAYED BY ROUGHNESS PARAMETERS<br />
ON PRESSURE AND STRESS DISTRIBUTIONS<br />
IN WHEEL-RAIL CONTACT<br />
by<br />
CONSTANTIN BĂRBÎNŢĂ, ANA URZICĂ and SPIRIDON CREŢU<br />
Abstract. The wheel and rail have rough contacting surfaces<br />
and the pressures at such contacts far exceed the pressures that<br />
would arise from a smooth contact. The freshly ground surface<br />
roughness consists of peaks which in the first train-passes are<br />
obliterated and become part of the interfacial layer. In this respect<br />
the roughness of wheel and rail have been measured at different<br />
working times, corresponding to successive stages of the running<br />
in process. The measured roughness parameters have been further<br />
used to generate stochastic roughness with imposed heights and
spatial parameters. Further, the rail and wheel surfaces with<br />
numerically generated roughness have been incorporated into an<br />
elastic-perfect plastic non-Hertzian contact model. The role played<br />
by the running in process and main roughness parameters on both,<br />
the pressure distribution on contact area and depth distribution of<br />
von Mises equivalent stress, has been pointed out. Even the<br />
nominal contact pressure was not able to cause von Mises stresses<br />
greater than the yielding limit, the presence of surface roughness<br />
brought on very large local asperity pressures that induced von<br />
Mises stresses larger than yielding limit and accordingly possibly<br />
severe plastic deformations inside a superficial layer of few tens of<br />
microns thickness.<br />
Key words: wheel-rail contact, roughness, skewness, kurtosis,<br />
wear, von-Mises stress.<br />
ROUGHNESS PARAMETERS<br />
OF SURFACES OBTAINED BY ABRASIVE JET MACHINING<br />
by<br />
LAURENŢIU SLĂTINEANU, OANA DODUN, LORELEI<br />
GHERMAN, IRINA GRIGORAŞ (BEŞLIU) and VASILE BRAHA<br />
Abstract. Nowadays, there are various parameters which can be<br />
used in order to evaluate the surface roughness. The sizes of such<br />
parameters were measured in the case of some surfaces obtained<br />
by abrasive jet machining. An experimental research was designed<br />
and developed by considering a complete factorial experiment, in<br />
which the independent variables were the average dimension of the<br />
abrasive particles, the distance between the nozzle and the test<br />
piece surface, the angle between the direction of the abrasive jet<br />
and the surface of the test piece. Supposing a monotone variation<br />
of the surface roughness parameters to the variation of the<br />
independent variables, power type empirical functions were<br />
established. The size of the exponents offers a more direct image<br />
concerning the intensity of the influence exerted by the<br />
independent factors on the sizes of the surface roughness<br />
parameters.<br />
Key words: abrasive jet machining, surface roughness<br />
parameters, power type empirical functions, influence factors
RESIDUAL STRESSES REDUCTION USING CAE ANALYSIS IN<br />
MOLDED POLYMERIC PARTS<br />
by<br />
ALEXANDRA RAICU<br />
Abstract. To optimize polymeric parts and injection molding<br />
conditions, it is important to predict the internal stress development<br />
during molding and after ejection. The author intends to improve<br />
the quality of the injection process and determinate the residual<br />
stresses with respect to the temperature melt using CAE analysis.<br />
In this paper in order to find the best parameters of the molding<br />
process which lead to a minimum level of the residual stresses<br />
several studies were performed. Parts made of polymeric materials<br />
may be also simulated in order to minimize the residual stresses.<br />
Computer Aided Engineering analysis provides insights useful in<br />
designing parts, molds and molding processes. Using this method<br />
we can obtain information such as polymer melt filling patterns,<br />
weld line and air trap locations, required injection pressure and<br />
clamp tonnage, fibre orientation, cycle time, the final part shape<br />
and deformation and mechanical properties of molded parts. This<br />
is a useful method to approach most of the molding problems.<br />
Key words: polymeric part, CAE, residual stress.<br />
EFFECT OF SINTERING TEMPERATURE ON HIGH<br />
ALLOYING MANGANESE STEELS SUBJECTED TO ABRASIVE<br />
WEAR<br />
by<br />
CRISTIAN SUCIU, GEORGE ARGHIR, IOAN PETEAN and<br />
CLAUDIU POPA<br />
Abstract. The influence of sintering temperature on the wear<br />
rate of compacted Fe-Mn steel PM alloy was studied. Several<br />
cylindrical specimens of iron powder (DWP400) and<br />
ferromanganese powder (FeMn80C20) were made. Manganese<br />
addition was of 5, 7, 9, 11, 13, 15 mass % and, for carbon was<br />
0.14, 0.20, 0.26, 0.32, 0.38, 0.43 mass %, respectively. The<br />
samples were pressed bilaterally at 600 MPa and, then, sintered in<br />
H 2 at temperatures of 1120 °C and 1230 °C. These sintered<br />
specimens were analyzed by optical microscopy and hardness
tests. After that, these samples were submitted to abrasive wear.<br />
We have found that specimens sintered at high temperatures<br />
present better abrasive wear behaviour. A linear increase of<br />
hardness and, also, a linear decrease of wear rate, in dependence of<br />
manganese addition were observed during these tests.<br />
Key words: sintered steels, abrasive wear, manganese,<br />
microstructure.<br />
HEAT TREATMENT INFLUENCE ON SINTERED<br />
MANGANESE STEELS UNDER ABRASIVE WEAR<br />
by<br />
CRISTIAN SUCIU, GEORGE ARGHIR, IOAN PETEAN and<br />
CLAUDIU POPA<br />
Abstract. It was observed that the heat treatment has a great<br />
influence on sintered manganese steels behaviour. The proposed<br />
paper is focused on analysis of abrasive wear of sintered specimens<br />
subjected to heat treatment (quenching and tempering) of 960 °C<br />
for 60 minutes and 180 °C for 40 minutes, respectively. The<br />
analyzed samples were a mixture of iron powder allied with 5, 7, 9,<br />
11, 13, 15 mass % Man. Heat treated specimens have been<br />
subjected to investigations by optical microscopy and hardness<br />
tests. It was found a decrease in hardness, with increasing of<br />
manganese content, after tests. Also, abrasive wear is strongly<br />
influenced by the hardness of the specimens.<br />
Key words: heat treatment, abrasive wear, sintering,<br />
manganese, microstructure<br />
EVALUATION OF THE LOCAL GEAR SCUFFING<br />
by<br />
LIVIU BALAN, ANA TUFESCU, CARMEN BUJOREANU,<br />
DUMITRU OLARU AND SPIRIDON CRETU<br />
Abstract. The authors determined the local scuffing criterion<br />
for rolling/sliding contacts by considering both the roughness on<br />
surfaces and lubricant film. The real pressure distributed in<br />
rolling/sliding contact operating in mixed lubrication conditions<br />
has been determined. Also the tangential shear stress correlated<br />
with the lubricant parameter λ was obtained and finally the local
scuffing criterion SL was calculated for given rollers geometry and<br />
operating conditions.<br />
Key words: rolling/sliding contacts, scuffing criteria, real<br />
pressure, lubricant parameter.<br />
LUBRICATION REGIMES IN TOTAL DISC PROSTESES ON<br />
LUMBAR SPINE<br />
by<br />
IULIANA ROTARU and DUMITRU OLARU<br />
Abstract. Total disc prostheses are medical devices used for<br />
treatment of disc herniation. These are more attractive than spinal<br />
fusion procedure because they restore and maintain spinal segment<br />
motion. The objective of this paper was to determine the maps of<br />
lubrication regimes which occur in total disc prostheses on lumbar<br />
spine. The prostheses were modelled as ball-and-socket designs. It<br />
was considered a ball radius of 14 mm with radial clearances<br />
between ball and socket of 0.01 and 0.1 mm, a lubricant with a<br />
viscosity of 1.24 mPa s and an angular velocity of 1.75 rad/s. The<br />
results have indicated that the lubrication regimes in total disc<br />
arthroplasty were isoviscous-elastic (IVR) and isoviscous-rigid<br />
(IVR) only for a radial clearance of 0.01 mm when normal force<br />
was lower than 55 N in case of metal-on-metal devices, lower than<br />
15 N in case of metal-on-plastic and lower than 65 N in case of<br />
ceramic-on-ceramic.<br />
Key words: lubrication regime, lubricant, lumbar spine, total<br />
disc prosthesis.<br />
PRESSURE AND FRICTION IN TOTAL DISC PROSTHESIS:<br />
EFFECT OF SURFACE CONFORMITY<br />
by<br />
IULIANA ROTARU and DUMITRU OLARU<br />
Abstract. Total disc prosthesis is an artificial disc used to<br />
replace the damaged intervertebral disc. There are different designs<br />
of artificial discs, but one of the most general is ball-and-socket<br />
model. The objective of this study was to investigate the influence<br />
of surface conformity on the maximum pressure and the frictional
torque which occur in lumbar total disc prostheses. It was<br />
considered a ball radius of 14 mm and socket radii between 14.01<br />
and 14.1 mm. The maximum pressure and the frictional torque<br />
were then determined for different material combinations and<br />
conformities. This study suggests designing of total disc prostheses<br />
with high conformity of the sliding surfaces in order to reduce<br />
maximum pressure and with ceramic-on-ceramic material<br />
combination in order to reduce frictional torque.<br />
Key words: ball-and-socket, friction, radius, pressure, surface<br />
conformity, total disc prosthesis.<br />
EXPERIMENTAL METHODS FOR MEASURING THE FIELD-<br />
INDUCED STRAIN RESPONSE OF DIELECTRIC<br />
ELASTOMERS<br />
by<br />
VLAD CÂRLESCU, FLORIN BREABĂN, DUMITRU OLARU,<br />
GHEORGHE PRISĂCARU<br />
Abstract. In last years, there is a growing demand in fields such<br />
as mechatronics, medicine and bioengineering, for polymer<br />
actuators. Electroactive polymers (EAP) are polymers that exhibit<br />
shape change in response to electrical stimulation. In order to<br />
develop good actuator and sensor applications based on EAPs we<br />
need to investigate the mechanical, electrical and<br />
electromechanical properties of EAP materials. This paper present<br />
two non-destructive testing methods used for measuring the fieldinduced<br />
strain response of dielectric elastomers. We performed<br />
static and dynamic experiments to investigate the strain response<br />
induced by DC and AC electric fields.<br />
Key words: electroactive polymers, strain response,<br />
displacement sensor method, laser scanning Doppler vibrometry,<br />
accuracy.<br />
EFFECTS OF THE DRIVING SPEED ON THE DYNAMIC<br />
RESPONSE OF A FOUR-BAR MECHANISM WITH<br />
CLEARANCE JOINTS<br />
by<br />
MIHAI BAICEANU, PAULO FLORES, CEZAR OPRISAN and
DUMITRU OLARU<br />
Abstract. The main purpose of this work is to present the<br />
effects of the input speed on the dynamic characteristics of a fourbar<br />
mechanism with clearance joint between coupler and follower.<br />
It can be observed that, increasing the input speed of the<br />
mechanism makes the behaviour of the mechanical system to<br />
change from periodic to chaotic. The numerical results show that<br />
the existence of dry joint clearance causes high peaks on the<br />
dynamic system’s characteristics due to contact forces developed.<br />
Key words: joint clearance, dynamic response, input speed,<br />
revolute joint, four-bar mechanism, contact force model<br />
VIBRATION CONTROL APPROACH IN LOW SLIP SPEED<br />
DRY FRICTION SYSTEMS<br />
by<br />
CARMEN BUJOREANU, BARBU DRĂGAN and VASILE HORGA<br />
Abstract. Structures and mechanical systems should be<br />
designed to enable better performance under different types of<br />
loading, particularly dynamic and transient loads. The instability of<br />
a dynamic system where there is an interaction between the elastic<br />
system and the friction process behaves as a stick-slip movement<br />
of the contact masses For example, it is known that in dry friction<br />
conditions, the printing speed causes a problem called "stick-slip"<br />
and the dye ribbon is not peeled smoothly away from the receiving<br />
sheet in the printer. This results in noise and leaves scratch marks<br />
on the printed image. Arising of the stick-slip phenomenon is<br />
conditioned by the slip movement and vibrations generation. The<br />
paper presents some observations related to the control of these<br />
vibrations<br />
Key words: nonlinear friction, vibration control.<br />
TUBING AND CASING CONNECTIONS.<br />
FUNCTIONNING ASPECTS ACCORDING TO THREADS<br />
DESIGN PROBLEMS<br />
by<br />
CRISTEL ŞTIRBU
Abstract. Different joints for extractive industry have a lot of<br />
similar theoretical, technological and dimensional aspects:<br />
dimensional correlation with the pipes, drill and other well<br />
elements; mechanical strength of pipes and joints to the inner and<br />
outer pressure and to the proper weight of the column; bending<br />
resistance of the column under different conditions of the ground<br />
properties; resistance under high temperatures of the column;<br />
perfect seal functioning, for extraction efficiency; resistance to<br />
corrosive conditions; resistance to the mechanical wear and the<br />
possibility of the reutilization of the component elements. The<br />
main element of tubing and casing connection is the thread which<br />
ensures all the performances of the well column. The paper shows<br />
some considerations on the thread influence on different<br />
connection types.<br />
Key words: connection, pipes, thread, seal.<br />
POWER LOSS AND TEMPERATURE COMPUTATION IN<br />
HIGH-SPEED BALL BEARINGS LUBRICATED BY OIL MIST<br />
I. THEORETICAL MODEL<br />
by<br />
VIOREL PALEU and LIVIU BALAN<br />
Abstract. The paper presents a model for friction torque, power<br />
losses, and heat transfer in ball bearings lubricated by oil mist.<br />
This improves the existing models, the friction torque and power<br />
losses being estimated more accurately with the Houpert method,<br />
further extended by Paleu for the oil mist lubrication of high-speed<br />
angular ball bearings. Theoretical results are presented for a 7206C<br />
angular contact ball bearings. The lubrication regime is identified<br />
in balls and races contacts, as it influences the lubrication<br />
parameter and ratio of load supported by asperities and fluid film<br />
contact area. The transition from IVR to EHD lubrication regime is<br />
emphasised by the evolution of the oil film thickness versus the<br />
axial preload. The model is validated with experimental results<br />
regarding the mean temperature of the 7206C bearings, found in<br />
literature. This research can be easily extrapolated on gears.<br />
Key words: high-speed, ball bearings, oil-mist, temperature,<br />
lubrication regimes.
FRICTION COEFFICIENT IN THE<br />
PIVOTING MOTION FOR A BALL-RACE CONTACT<br />
by<br />
ALINA CORINA DUMITRASCU, GELU IANUS and DUMITRU<br />
OLARU<br />
Abstract. This paper presents the methodology and results to<br />
determine the friction coefficient in the pivoting motion for a<br />
microball with diameter of 1.588 mm on race of a thrust ball<br />
bearing .Experiments were performed in dry conditions at a<br />
temperature of 20 0 C, and humidity between 45-55% RH at loads<br />
of 8.68 mN, 15 mN, 22.3 mN, 27 mN and 33.2 mN. Values of the<br />
friction coefficient in the pivoting motion between 0.1 and 0.2<br />
were obtained.<br />
Key words: friction coefficient, pivoting motion, experimental<br />
procedure<br />
BALL KINEMATICS IN A LINEAR RECIRCULATING SYSTEM<br />
WITH FOUR CONTACT POINTS - ANALYTICAL MODEL<br />
by<br />
ALEXANDRU BUDEL, DUMITRU OLARU and GHEORGHE<br />
PRISACARU<br />
Abstract. An original procedure to determine both the value of<br />
the ball angular speed and the angular position of this speed,<br />
according to the normal loads in a linear system with four contact<br />
points has been developed. The program is based on the variational<br />
analysis of the power losses in ball-races contacts. Based on this<br />
program was determined the two kinematics parameters of the ball<br />
(angular velocity and angular position) in a linear system type<br />
KUE 35V2 as function of the ratio C/P.<br />
Key words: Linear guidance system, ball angular speed,<br />
angular position, normal loads.<br />
ASPECTS CONCERNING HYDRAULIC SYSTEMS WITH<br />
HYDROPNEUMATIC ACCUMULATORS<br />
by<br />
IRINA MARDARE and IRINA TITA
Abstract. In this paper some aspects regarding hydropneumatic<br />
accumulators are investigated. Fundamental equations governing<br />
the functioning of hydropneumatic accumulators are presented and<br />
also aspects regarding details to be considered in governing<br />
equations are analyzed. A functional diagram, based on MATLAB<br />
/ SimHydraulics computational approach suited to analyze the real<br />
physical system consisting of real physical functional blocks, is<br />
developed for modelling and simulating a system with a<br />
hidropneumatic accumulator.<br />
Key words: hydraulic system, hydropneumatic<br />
accumulator, functional diagram, MATLAB.<br />
RESEARCHES ON MICROSTRUCTURE AND<br />
MICROHARDNESS OF TITANIUM-BASED ALLOYS USED IN<br />
DENTAL PROSTHETICS<br />
by<br />
ELENA RALUCA BACIU, IRINA GRĂDINARU, MARIA BACIU,<br />
NORINA CONSUELA FORNA<br />
Abstract. Microstructural researches on Ti-based alloys under<br />
analysis aimed at identifying the main structural constituents that<br />
will influence their subsequent behaviour during the finishing<br />
processes by mechanical polishing. The aluminum and niobium<br />
alloy determined the modification of structural constitution in case<br />
of Biotan Nb alloy, since the two solid solutions formed are<br />
characterized by high values of microhardness, a fact that will lead<br />
to a more difficult mechanical finishing.<br />
Key words: Ti-based alloys, microstructure, microhardness.<br />
MOLYBDENUM COATINGS FRICTION COEFFICIENT<br />
STUDIES FOR FUTURE APPLICATIONS<br />
IN MACHINE ELEMENTS<br />
by<br />
CĂTĂLINA AXINTE, CORNELIU MUNTEANU<br />
and ALEXANDRU BARNEA<br />
Abstract. Gears are machine elements which transmit high<br />
torques by friction of the tooth and on the flanks appear the pitting
wear after many cycles of working. In operating are subjected are<br />
subjected to mainly to fatigue. After a detailed study of the<br />
literature we decided to modify the contact surface by coating. We<br />
have chosen the steel type 16MnCr5 and we coated it with Mo.<br />
When we obtained the samples, we subjected them to fretting tests<br />
in order to determine the friction coefficient. On the roughness<br />
analysis we obtained the quality of the coatings. The results<br />
showed how behaved the surface after more than one million<br />
cycles, and how the surface was influenced by friction.<br />
Key words: coating, fretting, friction, etc.<br />
COMPARATIVE STUDIES OF CORROSION RESISTANCE ON<br />
21TMC12 STEELS UNCOATED AND COATED WITH WC-Co-Cr<br />
by<br />
CĂTĂLINA AXINTE, PETRU AVRAM, EDUARD SEBASTIAN<br />
BÂRCĂ, BOGDAN ISTRATE and CORNELIU MUNTEANU<br />
Abstract. Gears tooth are subjected to fatigue and bending but if<br />
they are working in aggressive environments, they must have high<br />
corrosion resistance. Our researches are concentrated on the surface<br />
modification by plasma spraying coating process. We researched the<br />
specialty literature and we decided to use usual steel, 21TMC12,<br />
which we coated it with powder, WC-Co-Cr by plasma spraying<br />
process. When we obtained the samples, we subjected them to<br />
hardness and corrosion test and then we analyzed them by electronic<br />
microscopy. The results showed that the coating has a higher<br />
corrosion resistance than basic steel.<br />
Key words: coating, electron microscopy, corrosion, etc.<br />
FRICTION PROPERTIES OF WC COATINGS USED IN<br />
AUTOMOTIVE INDUSTRY<br />
by<br />
ALEXANDRU BÂRCĂ, CĂTĂLINA AXINTE, PETRU AVRAM,<br />
SORIN CLAUDIU IACOB STRUGARU and CORNELIU<br />
MUNTEANU<br />
Abstract. Engine cylinder bores are machine elements that are<br />
subjected to friction solicitation. The geometry dimensions and
weight cannot be modifying that is why we decided to modify the<br />
contact surface by coating. We have chosen the steel type OLC 45<br />
and we coated it with WC by thermal deposition. The selection of<br />
these materials has done after a detailed study of the literature. After<br />
we obtained the samples, we subjected them to fretting analysis<br />
where we obtained the friction force and friction coefficient<br />
between two coated surfaces in dry contact. The results showed how<br />
the coating influences the properties of the basic material.<br />
Key words: coating, fretting, friction force, dry contact, etc.<br />
EXPERIMENTAL RESEARCH ON WC-Co-Cr COATINGS USED<br />
IN AUTOMOTIVE INDUSTRY<br />
by<br />
EDUARD SEBASTIAN BÂRCĂ, CĂTĂLINA AXINTE,<br />
CONSTANTIN PAULIN, SORIN CLAUDIU IACOB STRUGARU,<br />
and CORNELIU MUNTEANU<br />
Abstract. The pistons of engines are machine elements which<br />
are subjected to thermal and friction solicitations. The pistons must<br />
have a high wear resistance that is why we proposed to improve<br />
their performances. Their surfaces are complex and we decided to<br />
modify them, because the contact between piston cylinders should<br />
be improved. We have done researches in surface engineering and<br />
obtained a solution by coating the basic material’s surface with a<br />
better material. We used the WC-Co-Cr powder and by plasma<br />
spraying deposition we made a coating on the steel type 21TMC12.<br />
We analyzed the samples by SEM and X-Ray Diffraction to<br />
determine the quality of the coating. The results showed that the<br />
new material has better properties than the basic material.<br />
Key words: coating, SEM, X-Ray Diffraction, etc.<br />
ELECTROCHEMICAL STUDIES OF CORROSION BEHAVIOUR<br />
OF EXPERIMENTAL TiNbZrAl ALLOYS<br />
IN ARTIFICIAL SALIVA<br />
by<br />
LUCIA ANIŞOARA DRĂGAN (RĂILEANU), CORNELIU<br />
MUNTEANU, DANIEL MARECI, PINTILEI GEANINA LAURA,<br />
ROMEU CHELARIU, CĂTĂLINA AXINTE
Abstract. The aim of this study is to investigate the corrosion<br />
behaviour of a two TiNbZrAl alloys (coded with Ti17Nb5Zr5Al and<br />
Ti8Nb6Zr2Al) in artificial saliva. For comparison, Cp-Ti was also<br />
investigated. In order to study the corrosion resistance the linear<br />
potentiodynamic polarization and electrochemical impedance<br />
spectroscopy (EIS) were performed. Scanning electron microscopy<br />
(SEM) observations were made following the linear<br />
potentiodynamic polarization tests. The EIS results for TiNbZrAl<br />
alloys exhibited capacitive behaviour (high corrosion resistance)<br />
with high impedance order (106 Ω cm 2 ) at low to medium<br />
frequency.<br />
Key words: TiNbZrAl alloys, corrosion current density, linear<br />
potentiodynamic polarisation curves, SEM, EIS.<br />
CORROSION PERFORMANCES OF Mo COATINGS<br />
DEPOSITED ON STEEL SUBSTRATES<br />
by<br />
SORIN CLAUDIU IACOB STRUGARU, CORNELIU MUNTEANU<br />
and CĂTĂLINA AXINTE<br />
Abstract. Researches in surface engineering allow the obtaining<br />
of new systems of materials by coating the basic material surface<br />
with other material having superior properties. In our researches we<br />
proposed to obtain a new system of materials by thermal deposition.<br />
We have chosen the steel type 16MnCr5 as basic material and we<br />
coated it with Mo. We have subjected the samples to hardness and<br />
corrosion tests in order to estimate the material performances. The<br />
results showed that the new material has a higher hardness and<br />
corrosion resistance than the steel.<br />
Key words: coating, hardness, corrosion, durability, etc.<br />
PROPERTIES OF Mo COATINGS OBTAINED BY THERMAL<br />
DEPOSITION ON STEEL SUBSTRATE<br />
by<br />
CARMEN PĂPĂTOIU (BINIUC), CĂTĂLINA AXINTE,<br />
EDUARD SEBASTIAN BÂRCĂ, SORIN CLAUDIU IACOB<br />
STRUGARU and CORNELIU MUNTEANU
Abstract. In aircraft industry are many machine elements which<br />
are subjected to thermal and friction solicitation. These machine<br />
elements must have a high wear resistance, because the passenger’s<br />
safety is very important. Also the maintenance costs are very high,<br />
that is why we proposed to improve the performances of the<br />
machine elements. Researches in surface engineering allow the<br />
obtaining of new systems of materials by coating the basic material<br />
surface with other material having superior properties. In order to<br />
improve the machine elements durability, we proposed to obtain a<br />
new system of materials by thermal deposition. We have chosen the<br />
steel type 16MnCr5 as basic material and we coated it with Mo. We<br />
made the samples AND we have analyzed by X-Ray Diffraction<br />
obtaining their quality. The results showed that the new material has<br />
a better structure than the basic material.<br />
Key words: coating, X-Ray Diffraction, thermal deposition.<br />
EFFECT OF HEAT-TREATMENT OF ATMOSPHERIC PLASMA<br />
SPRAYING COATING (APS) WITH POWDER CERAMIC<br />
ZrO 2 /20% Y 2 O 3<br />
by<br />
GEANINA LAURA PINTILEI, GICĂ NARCIS BĂSESCU, TUDOR<br />
BRIAN LANDKAMMER, LAURA TEODORA SOLONARIU, LUCIA<br />
ANIŞOARA DRAGAN and CORNELIU MUNTEANU<br />
Abstract. A significant issue in obtaining the thermal barrier<br />
coating applied on the turbine blades is to determine the causes of<br />
exfoliation of the ceramic layer due to the large number of thermal<br />
cycles. This paper presents a new concept of thermal barrier coating<br />
for the prevention of delamination of the sprayed layer. This<br />
consists in an adherent layer of NiMoAl (90-5-5) sprayed with<br />
electric arc and a top coat of ZrO 2 /20%Y 2 O 3, deposited by<br />
atmospheric plasma spraying (APS) on specimens of Ni base<br />
superalloy, of which the aircraft turbine blades are made. The<br />
samples have been exposed to a heat treatment at 1150°C in order to<br />
study the behaviour of the sprayed layers. Porosity was evaluated by<br />
image analysis. This technique was used to estimate porosity<br />
variation along the cross section. The use of a scanning electron<br />
microscope had the role of observing the morphology and<br />
microstructure, the distribution maps and chemical analysis. The
surface roughness was also determined before and after the<br />
treatment.<br />
Key words: SEM, profilometry, heat treatment, ZrO 2 /20%Y 2 O 3 .<br />
STRESS ANALYSIS IN THE VICINITY OF THE VICKERS<br />
INDENTATION BY FINITE ELEMENT METHOD<br />
by<br />
GEANINA LAURA PINTILEI, CORNELIU MUNTEANU, GICĂ<br />
NARCIS BĂSESCU, TUDOR BRIAN LANDKAMMER, BOGDAN<br />
ISTRATE and IONUŢ VASILE CRÎŞMARU<br />
Abstract. In this paper it’s presented the experimental method<br />
for determining the resistance to cracking of ceramics using Vickers<br />
indentation.<br />
The method used in this case is called the micro-fissures method<br />
(MF) and it is result is the resistance to cracking in the vicinity area<br />
of the mechanical stresses determined by the Vickers indentation.<br />
The sample used for the test consists of an adherent layer of<br />
NiMoAl (90-5-5) sprayed with electric arc and a top coat of<br />
ZrO 2 /20%Y 2 O 3, deposited by atmospheric plasma spraying (APS)<br />
on samples of an Ni base superalloy.<br />
The highlighting and interpretation of the structural changes<br />
caused by the tests which were carried out have been made using<br />
modern methods of structural analysis: electron microscopy and<br />
finite element analysis.<br />
Key words: Vickers indentation, SEM, tensions, hardness.<br />
CONSIDERATION REGARDING GRAIN GROWTH AND<br />
NUCLEATION ON SOLIDIFIED LAYERS<br />
DEPOSITED BY THERMAL SPRAYING<br />
by<br />
TUDOR BRIAN LANDKAMMER and LAURA TEODORA<br />
SOLONARIU<br />
Abstract. The solidification process includes nucleation and<br />
growing steps, each of them are being influenced by specific<br />
parameters. According to some specific condition, nucleation can be<br />
homogeneous or heterogeneous and it will assure the forming
condition of an amorphous or crystalline microstructure.<br />
Knowing the values of the technological parameters for<br />
spraying it is possible to determine the growing speed of a sprayed<br />
layer through mathematical calculation or by numerical simulation.<br />
Keywords: thermal spraying, nucleation, crystal morphology,<br />
technological parameters.