Dilatometric Tests Research Articles

Development of Alloyed Pipe Steel Composition for Oil and Gas Production in the Arctic Region

Gas and oil pipelines for the Arctic region must sustain low temperatures and high internal pressures of a corrosive active medium. Generation of new steel compositions for oil and gas pipelines is an urgent issue in order to ensure their high reliability. Low-carbon steels with a ferritic–pearlitic structure are normally used in pipe production, but they are unable to cope with increased market demands. The main objective of this study is to investigate the influence of the cooling rate on the structure and morphological characteristics of bainite, which determines the exploitation properties of the pipe steels. Dilatometric tests were carried out using a Gleeble 3500 complex. Optical microscope and scanning electron microscope analysis, with the computer image analysis system Thixomet PRO, were used to study the microstructure of steel. Hardness was measured in accordance with ASTM E-384. Morphological characteristics of bainite components that were formed at various cooling rates from 0.05 to 100 °C/s were defined. The novel result of this study is the continuous cooling transformation diagram of undercooled austenite of the steel containing 0.062% C; 1.80% Mn; 0.120% Mo; 0.032% Cr, 0.90% Ni and other elements (Al, Cu, V, Nb, Ti).

Direct measurement of shape memory effect for Ni54Mn21Ga25, Ni50Mn41.2In8.8 Heusler alloys in high magnetic field

Abstract Recently the new scheme of layered composite with shape memory effect (SME) for thermal and magnetic actuation was suggested and proved to demonstrate the reversible actuation on micro- and nanoscale. The principles of magnetic field induced martensitic transition (MFIMT) and magnetic field controlled shape memory effect (MFCSME) have the advantages of magnetic-field-controlled actuation at constant temperature, extremely small size of an actuator and compatibility with modern nanotechnologies. The present paper is devoted to experimental study of MFCSME in two ferromagnetic Heusler alloys Ni54Mn21Ga25 and Ni50Mn41.2In8.8 with positive and negative shift of the martensitic transition temperature in a magnetic field. The three points bending device for dilatometric tests of plate-like samples of the alloys was designed and placed in the field of Bitter coil magnet. The bending deformations versus temperature were measured at various magnetic fields up to 10 T and at mechanical stresses up to 45 MPa. The temperature shifts of thermoelastic martensitic phase transition were found to be 0.55 K/T and −0.95 K/T for Ni54Mn21Ga25 and Ni50Mn41.2In8.8 respectively. For direct MFCSME study the dependences of the bending deformation on magnetic fields up to 14 T were also obtained at constant temperatures for these alloys. Practically complete recoverable deformation of 0.2% due to MFIMT was obtained at 14 T in Ni54Mn21Ga25 alloy in temperature range 316–318 K and stress 8.6 MPa. The new variant of the layered functional composite actuator scheme based on the alloys with MFCSME is suggested. The proposed functional composite combines the layers of the alloys with positive and negative temperature shifts of martensitic transition temperature in magnetic field. It is argued that this combination of the alloys can improve the performance of the composite actuators driven by MFCSME, particularly, it can provide higher generated force, actuation stroke, sensitivity to magnetic field and frequency of actuation.

Deformation modulus determination from pressuremeter and dilatometer tests for crystalline rock

The deformation modulus is an important characteristic of the mechanical behaviour of rock mass. The deformation parameters of rock mass may be obtained by execution of in-situ tests. In situ testing comprises the most reliable and comprehensive methods to describe the mechanical behaviour of the rock mass. Results of pressuremeter and dilatometer tests for crystalline rocks and their interpretation are presented in the paper. Comparison of two types of in-situ geotechnical tests results was analysed based on ground investigation for new expressway in Slovakia. In the evaluated section, an extensive part of the expressway is situated on bridges. During geological investigation, 161 of dilatometer and 150 of pressuremeter tests were carried out to determine rock parameters. Logging measurements were conducted in each borehole in advance of geotechnical testing to select the best testing section of the borehole. Consequently, the pressuremeter and/or dilatometer tests were performed in selected boreholes. It was observed that the difference between deformation modulus determined by dilatometer and pressuremeter tests are significant especially for intact rock with high value of Rock Quality Designation (RQD). Correlations for estimating rock deformation parameters were derived based on analysis of the results from dilatometer and pressuremeter in-situ testing of crystalline rocks.

Small Strain Soil Constitutive Models HS-SMALL & RU+MCC – Calibration and Verification

The paper presents two reasonably advanced constitutive laws for soil. First one is a hybrid of the Modified Cam Clay and a new RU (reload, unload) development, and it is author’s conception. The second one is a HS-small model by Benz. In the RU+MCC model, the Modified Cam Clay model, which is an isotropic elastoplastic hardening, describes normal consolidation behaviour - plastic model originated by Burland in 1967 within the critical state soil mechanics. This model describes realistically mechanical soil behaviour in normal consolidation states. The RU part is designed to ensure more adequate soil responses to reloading paths, particularly in the range of small strains. The HS-small model is an improvement of HS model originated form Schanz and Vermeer. This concept base on cap yield surface with incorporation of two hardening mechanisms, stiffness variation at small strains, densification mechanism, Rowe’s dilatancy and some others. The author in the FEM computer code Z_SOIL.pc has implemented the RU + MCC model. The HS-small model has been implemented into the same software by Truty. To test the influence of the small strain nonlinearity on soil - structure interaction as well as to exhibit the ability of the proposed model to simulate realistically this effect, a comparative study based on the FEM solution has been carried out. As a benchmark, a trial loading test of strip footing was used. The calibration process has based on advanced laboratory and field soil tests like resonant columns, triaxial test, dilatometer test and many others.

Selection of the best phase transformation model for optimization of manufacturing processes of pearlitic steel rails

Selection of the best model for simulation of manufacturing processes of pearlitic steel rails was the objective of the paper. Achieving a proper balance between its predictive capabilities and computing costs was used as a criterion. Review of the pearlitic transformation models was performed and modification of the JMAK equation was selected for further analysis. Empirical models were developed to describe microstructure and mechanical properties of rails. Dilatometric tests were performed to supply data for identification of the phase transformation model. Physical simulations of various thermal cycles were performed to validate and verify the models. Finite element (FE) simulations of the hot rolling provided distributions of the temperature and the austenite grain size at the cross section of the rail, which were used as an input for modelling of phase transformations during cooling. Accelerated cooling by a cyclic immersion of the rail head in the polymer solution was considered as a case study. Performed simulations confirmed good predictive capabilities of the model.

DMT for Load-Settlement Curve Prediction in a Tropical Sandy Soil Compared to Plate Load Tests

The flat dilatometer test (DMT) has been used as an accurate in situ site investigation tool for foundation settlement prediction. However, few investigations have assessed its performance in settlement prediction in unusual soils. In addition, very little work has been performed to obtain a complete load-settlement prediction curve. This article assesses an approach that uses the DMT to obtain a complete load-settlement prediction curve at a tropical sandy soil site under both natural and inundated conditions. DMTs, plate load tests, and oedometer tests were carried out in these two moisture conditions at the experimental research site located in Bauru, Sao Paulo State, Brazil. The obtained data showed good agreement between the load-settlement curve predicted by the DMT and those determined by the plate load tests at four different depths and two soil conditions. The presented interpretation method based on DMT data worked well to predict the complete load-settlement curve at an unusual soil site at different depths and soil moisture content conditions.

Effect of the Chemical Homogeneity of a Quenched and Tempered C-Mn Steel Pipe on the Mechanical Properties and Phase Transformations

Seamless steel pipes for application in the oil and gas industries are manufactured from quenched and tempered steel. Aiming to meet the required characteristics, it is necessary that the microstructure and the mechanical properties are homogeneous along the wall thickness of the pipes, which is even more critical for thick wall pipes. Considering the seamless steel pipe manufacturing process, any chemical segregation along the thickness could affect the phase transformation kinetics during heat treatments and, consequently, microstructure and mechanical properties. In this context, this pioneer work when evaluating the effect of the chemical homogeneity of a seamless pipe on the mechanical properties and phase transformations. The studied pipe was manufactured by a C-Mn steel designed for oil and gas industry applications. Two regions of the pipe wall were analyzed - a region close to the inner surface and another near the outer surface. The steel was subjected to quenching and tempering heat treatments. Scanning electron and optical microscopy techniques were used to characterize the resultant microstructures. Microhardness and Charpy impact tests were performed aiming to analyze the pipe mechanical behavior in the studied regions. In addition, dilatometric tests were performed in order to determine the continuous cooling transformation diagrams of these regions.

Auburn University National Geotechnical Experimentation Site in Piedmont Residuum

In 1995, a geotechnical experimentation site was established in rural Lee County, Alabama near the area often referred to as Spring Villa. The Auburn University National Geotechnical Experimentation Site (AUNGES) site is situated near the southern terminus of the Appalachian Piedmont Physiographic province. The site consists of two sub sites, one that is a thick profile of residual soil and the other is an outcrop of fractured weathered quartzite. Extensive site investigation has been conducted at the site by many agencies and researchers using a wide array of in-situ soil tests. Foundations, excavations, and retaining structures have been constructed and load tested at the AUNGES. This paper summarizes all the work conducted at the site since its inception. Maps that detail the location of all in-situ tests and structures tested were generated. Representative profiles are included that relate early site investigation, between 1995 and 2005, and contemporary work done after 2010 are generated based on the results of piezocone, dilatometer, standard penetration, and shear wave velocity tests.

Halden research site: geotechnical characterization of a post glacial silt

This paper describes the geology and geotechnical engineering properties of the Halden silt; a 10–12 m thick deposit of fjord-marine, low plasticity clayey silt. Over the last six years, the test site has been well characterized by combining the results from a number of geophysical and in situ tools, including; electrical resistivity tomography, multi-channel analysis of surface wave surveys, cone penetration testing, dissipation testing, in situ pore pressure measurements, seismic flat dilatometer testing, field vane testing, self-boring pressure meter testing, screw plate load testing and hydraulic fracture testing. The results from these investigations assist the interpretation of layering and in situ soil properties. Soil sampling and advanced laboratory testing have provided data for interpretation of geological setting and depositional history, soil fabric, strength, stiffness and hydraulic properties. However, interpretation of the stress history, based on oedometer tests and clay-based correlations to the cone penetration test, are unreliable. They contradict the depositional history, which suggests that the soil units at the site are near normally consolidated, except for some surface weathering and desiccation. Further, undrained shear strength interpretations are complex as the in situ tests are potentially influenced by partial drainage, and conventional undrained triaxial tests do not provide a unique (peak) undrained shear strength. Despite certain interpretation challenges the paper presents important reference data to assist in the interpretation and assessment of similar silts, and provide some guidance on important geotechnical properties for projects where limited design parameters are available.

A proposed method to determine in-situ shear modulus and shear strain decay curves in different structured soil

This paper illustrates the application of the self-boring pressuremeter test and the seismic dilatometer test to acquire the in-situ decay curves of stiffness with shear strain level (G-γ decay curves) of three types of structural soil, which are granite residual soil, structural soft soil and expansive soft rock. The proposed approach in combines the functions of SBPT and SDMT to provide the high standard of accuracy for the small-strain stiffness (from SDMT) and the major attenuation stage of stiffness (from SBPT). Using the proposed mathematical model can properly describe the tendency in typical in-situ G-γ decay curves based on the data of tests. To analyse the suitability of the proposed approach, the G-γ curve obtain from the resonant column test of granite residual soil is also employed to compare with the in-situ curves. The shear modulus G obtained from laboratory tests is found to be smaller and the stiffness attenuation rate is found to be faster than the curve of the in-situ test, which reflects the process of sampling, transporting and preparation of soil samples could cause unrecoverable damages in soil.

Rigid filler toughening in PLA-Calcium Carbonate composites: Effect of particle surface treatment and matrix plasticization

In recent years the plastics market is moving towards biopolymers and the increasing demand of not oil derived products has led to the development of new composites deriving from renewable resources. Undoubtedly the most studied biopolymer is poly(lactic acid) (PLA). This work is focused on the use of rigid inorganic fillers as toughening agents, in order to obtain a rigid and tough PLA composite and enlarge the range of applications for PLA. The rigid filler toughening mechanism has been studied and, as toughening agent, commercial calcium carbonate particles with and without surface treatment have been compared. Because of the PLA intrinsic fragility, a plasticization of the matrix was necessary to favor the plastic deformation and consequently the stretching of interparticle ligaments.In particular, in this work, the effect of both the plasticizer and the particles surface treatment with stearic acid were analyzed. It has been observed that the surface treatment alone is not able to provide a significant increase in the PLA toughness. In fact, the particle surface coating favors the particles dispersion and reduces the adhesion with the matrix, favoring debonding, but the plastic deformation of the matrix around the voids is not significant without a plasticizer addition. Moreover, the best impact performance and ductility were achieved with the surface treated calcium carbonate, in agreement with a more controlled growth of voids formation during material solicitation, as resulting from tensile dilatometric tests.

Austenite Decomposition and Precipitation Behavior of Plastically Deformed Low-Si Microalloyed Steel

The aim of the present study is to assess the effects of hot deformation and cooling paths on the phase transformation kinetics in a precipitation-strengthened automotive 0.2C–1.5Mn–0.5Si steel with Nb and Ti microadditions. The analysis of the precipitation processes was performed while taking into account equilibrium calculations and phase transitions resulting from calculated time–temperature–transformation (TTT) and continuous cooling transformation (CCT) diagrams. The austenite decomposition was monitored based on thermodynamic calculations of the volume fraction evolution of individual phases as a function of temperature. The calculations were compared to real CCT and DCCT (deformation continuous cooling transformation) diagrams produced using dilatometric tests. The research included the identification of the microstructure of the nondeformed and thermomechanically processed supercooled austenite products formed at various cooling rates. The complex interactions between the precipitation process, hot deformation, and cooling schedules are linked.

Evaluation of correlation between parameters from CPTU and DMT tests and soil type behavior chart

Abstract This paper presents the correlation of soil parameters obtained from the dilatometer of the Marchetti (DMT) and the cone penetration tests (CPT). The data for the development of these correlations come from four experimental sites of the Department of Geotechnical Engineering of the Warsaw University of Life Sciences – SGGW: test embankment in Antoniny, and the Koszyce and Nielisz water dams, Stegna test site, WULS-SGGW Campus. Additionally, the relationship between the soil behavior type classification index (Ic) from the Cone Penetration Test (CPT) and the material index (I D) from the dilatometer test (DMT) based on the Robertson method, modified in this paper, is presented. Finally, a new soil behavior type classification chart was presented, allowing to determine not only the type and condition of the soil, but also the stress history (OCR).

Determination of susceptibility of cast iron with a predetermined chemical composition to shape properties and microstructure through bainitic transformation

.The problem of nanostructuring cast iron is hardly ever reported on scientific reports. Most of the research is undertaken in terms of steel nanostructurization. Bhadeshia states that to obtain a fragmented matrix of steel, the carbon content in the matrix must be at the level of 0.6% C. It should be noted that the carbon in the ferrite-pearlite matrix meets this condition, because the content of this element in the matrix is within the range of 0.7-0.9%. The authors of this work have attempted to evaluate the ability to shape the properties and microstructure of ductile cast iron as a result of not fully completed bainitic transformation, compared to the standard process of obtaining ADI cast iron. The tested material was characterized by a higher degree of alloying elements compared to the basic chemical composition of ADI cast iron. The aim of the work was to maximize the fragmentation of the cast iron microstructure by selecting a low temperature of isothermal transformation, i.e. 40°C above Ms temperature in the lower bainite range. The JMatPro program was used to determine the isothermal transformation temperature. Heat-treated cast iron was subjected to dilatometer tests to compare the results obtained from the computer program, microstructure research and hardness tests. Heat-treated cast iron was subjected to dilatometer tests to compare the results obtained from the computer program, microstructure research and hardness tests.

A New Approach to the Determination of Mineral and Organic Soil Types Based on Dilatometer Tests (DMT)

In order to identify the soil type in the ground, Marchetti’s nomogram chart is commonly used on the basis of dilatometer tests (DMT). In this chart, the material index values (ID) and the dilatometer modulus (ED) are used to determine the state and type of soils predominant in mineral soils. Unfortunately, this classification is not accurate enough for the identification of organic soils. This article proposes a new classification based on a nomogram chart for both mineral soils and organic soils using (p0), (p1) readings and pore water pressure (uo).

SDMT-Based Numerical Analyses of Deep Excavation in Soft Soil

AbstractThe paper explores the application of conventional (DMT) and seismic (SDMT) dilatometer tests to an important case of deep excavation design. The work presents finite-element analyses simul...

Iron/zinc doped 8 mol% yttria stabilized zirconia electrolytes for the green fuel cell technology: A comparative study of thermal analysis, crystalline structure, microstructure, mechanical and electrochemical properties

Abstract Pristine and Fe/Zn doped 8 mol% yttria stabilized zirconia (8YSZ) were prepared by ball milling technique for potential application in the green fuel cell technology. The series consisted of (8YSZ)0.97(Fe2O3)x(ZnO)3-x, where x indicates 0.5, 1.0, 1.5, 2.0 and 2.5 mol% Fe or Zn alternatively. A number of analytical techniques were used to characterize 8YSZ included X-ray diffraction, scanning electron microscopy, impedance spectroscopy, dilatometer, and hardness test. The analytical results indicated a decrease in the densification in the doped 8YSZ as the activation energy for densification decreased from 1087 kJ/mol in the pristine 8YSZ sample to 264 kJ/mol in the doped 8YSZ. The optimum doped 8YSZ was recognised with 2.0 mol% Fe and 1.0 mol% of Zn exhibit the highest percentage of the cubic phase approaching 62.4 wt%, while the shortest lattice parameter of 0.5132 nm and crystallite size equivalent to 26.34 nm. This composition also indicated pore-free morphology, the highest densification up to ∼94%, the greatest hardness value (above 740 MPa), while improve total conductivity about 7.398 × 10−6 S/cm at 300 °C. The results provide new insights on the effect of mixed dopants as ceramic composite as well as on the fuel cell technology.

Problem of Identification of Phase Transformation Models Used in Simulations of Steels Processing

Accuracy of phase transformation models depends on the correctness of coefficients evaluation, adequate to the investigated material. Dilatometric tests combined with the inverse analysis are used to perform identification. Since the problem is nonlinear, analytical approach is not possible and the inverse solution is transferred into the optimization task. It leads to difficulties typical for optimization of multivariable function such as local minima and lack of proof of the uniqueness. The problem of the effectiveness and uniqueness of the inverse algorithms used for identification of phase transformation models for steels was investigated for two models. The first was a modified JMAK (Johnson–Mehl–Avrami–Kolmogorov) equation. The second was an upgrade of the Leblond equation, in which second-order derivative of the volume fraction with respect to time was introduced. In classical identification, the result for one transformation depends on the coefficients for the remaining transformations and optimization has to be performed several times until the compatibility between transformations is reached. To avoid encountered problems, complex optimization simultaneously for all coefficients in the models was performed. This approach was based on nature-inspired optimization techniques. Models with identified coefficients for various steels were validated in simulations of industrial processes of laminar cooling and continuous annealing of strips.

2D RVE based micro-mechanical modeling with real microstructures of heat-treated 20MnMoNi55 steel

Macro-mechanical response of multi-phase steel depends on its morphological composition with respect to volume fraction of constituent phases, phase distribution, grain size etc. To address these micro-structural inhomogeneity, a RVE (Representative Volume Element) based micro-mechanical model was incorporated in our current analysis. 20MnMoNi55 steel is basically composed of ferrite and bainite as its constituent phases. To introduce variation in constituent phases and its volume fraction, different inter-critical heat cycles were designed based on the inter-critical temperature range obtained by means of dilatometric testing of 20MnMoNi55 steel. Heat treated samples were then characterized to confirm that the variation is achieved with respect to different set of ferrite-martensite volume fraction. The experimental flow curves obtained through tensile testing for different heat treated samples were primarily correlated with respect to volume fraction of martensite in terms of flow stress of the material. 2D RVEs were constructed based on real microstructure obtained through different heat cycles with the help of Python Scripting interface in Abaqus. The flow curve obtained by means of RVE based finite element simulation closely matches with the experimental results. The stress-strain response obtained from the finite element model output database shows inhomogeneity in its distribution between softer ferrite matrix and harder martensite islands. The deformation localizations, evolved in softer ferrite matrix, are hindered by neighboring martensite islands which causes the stress triaxiality buildup in ferrite matrix. A detailed comparison of stress triaxiality distribution between ferrite and martensite matrix has been established with proper justification.

EXTENSION OF A PHASE TRANSFORMATION MODEL FOR PARTIAL HARDENING IN HOT STAMPING

The quality of predicted microstructural and mechanical properties in hot stamping simulations relies considerably on the material model. Many researchers studied the effect of the plastic deformation on the phase transformation of the most commonly used hot stamping steel 22MnB5, and proved that the deformation applied at high temperature promotes the formation of ferrite, pearlite and bainite. This behaviour has to be integrated into materials modelling. In this study, the effect of pre-strain on the phase transformation of the material is considered. The specimens are heated to austenitization temperature, isothermally deformed at 700 °C, and quenched down to room temperature. The phase fractions and the temperature-dilatation behaviour obtained from the experiments are used to calibrate the material model. By using the experimental data obtained from dilatometer testing, the accuracy of the material model is evaluated. Additionally, an attempt to predict the results between the tested data points by using interpolation was made and compared with the simulation results.