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Residual Stress Assessment and its Effect on SCC of Pipelines Steel in Acidic Soil Environment

Residual Stress Assessment and its Effect on SCC of Pipelines Steel in Acidic Soil Environment

This work presents the residual stress assessment of multiple welding repairs in the same area in API X52 pipeline steel and its effect on SCC susceptibility in acid soil solution. Four conditions of repairs and one as welded specimen of the girth weld were evaluated to determine changes in the residuals stresses. Relation between microstructure, mechanical properties and residual stresses on the welding joint does not show any significant effect on SCC susceptibility. The welding joint evaluated presenting different levels of residual stresses, offering good SCC resistance in acidic soil solution at low pH. Presence of cracks was not observed along the gauge section specimen, thus no SCC was found due to the surface compressive stresses measured. These results are agree with the results from ratios of mechanical properties (YSR, UTSR, RAR, EPR, εR) which presented high ratios (0.77-1), indicative that X52 steel with the residual stress measured not contribute to generate SCC. For all the SSRT specimens the failure occurs in the base metal and BM/HAZ interface.

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Residual stress analysis of friction stir processed AA6061

Residual stress analysis of friction stir processed AA6061

Currently, after appropriate heat treatments, the 6xxx aluminium alloys are used in a variety of applications including aircraft fuselage skins and automobile body panels and bumpers, instead of more expensive 2xxx or 7xxx alloys. The paper presents the results of the residual stress analysis in case of Friction Stir Processing - FSP of AA6061-T4 plates, 10 mm thickness, demonstrating the process ability to locally modify the base metal properties. The residual stresses, DRX depicted, are correlated with the microstructure and hardness results.

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Residual stress measurements of alumina-zirconia ceramics by time-of-flight neutron diffraction

Residual stress measurements of alumina-zirconia ceramics by time-of-flight neutron diffraction

casting and conventional slip casting) and with different zirconia content. The results show that the residual stresses in zirconia particulates are tensile and the ones in alumina matrix are compressive, with almost flat through-thickness residual stress profiles in all bulk samples. The residual stresses for both phases were mainly dependent on the zirconia content, irrespective of the measurement direction and the fabrication process.

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Study of Residual Stress Relaxation Mechanics Using a Micro-indent Method

Study of Residual Stress Relaxation Mechanics Using a Micro-indent Method

Although for obtaining the relaxed values of residual stress the specimens were treated at 300°C for 20, 60, 80 and 100 min, effects of plasticity and creep strains (inelastic strains) can be considered negligible because very low macro-stresses are evaluated and besides, the holding times are not excessive (Bruin, 1982; Seifi and Salimi-Majd, 2012). It is important to note that the dominant deformation mechanism for that temperature and very low stresses is bulk diffusion through the lattice (Nabarro-Herring creep) (Schoeck, 1961; Ashby, 1972). In addition, thermal components also can be considered negligible because the specimen geometry is simple, the thickness is small and the cooling rate of the different thermal treatments is slow (Das and Chandra, 2003). Therefore, considering the studied material as homogeneous, isotropic and linearly elastic and assuming a plane stress state on the surface of each specimen, the in-plane residual stress components σ x , σ y and τ xy can be obtained from Eq. (1)

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Improved cold-drawn eutectoid steel wires based on residual stress measurement and simulation: Part 2. optimization of mechanical properties

Improved cold-drawn eutectoid steel wires based on residual stress measurement and simulation: Part 2. optimization of mechanical properties

Although prestressing steel wires have excellent mechanical properties (high strength and high elastic limit combined with reasonable ductility), the question that still remains is if we are able to improve the performance of these wires in aggressive environments. Results from this work show that the susceptibility to stress corrosion could be improved significantly if compressive residual stresses were induced at the wire surface. In contrast, these treatments may affect the behavior of the wires in the tensile test by reducing the elastic limit and in the stress relaxation test by increasing the stress relaxation losses. Thus, we obtained wires with more durability in aggressive environments, but they could not be considered “very low relaxation” wires.

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Determination and Analysis of Residual Stresses Induced by High Speed Milling Using a Micro-indent Method

Determination and Analysis of Residual Stresses Induced by High Speed Milling Using a Micro-indent Method

Abstract: The purpose of this work is to determine and analyze residual stress normal components and anisotropy degrees introduced by high-speed milling in specimens of AA 6082-T6 and AA 7075-T6 aluminum alloys. At each machined sample, the climb and conventional cutting zones were evaluated and compared. This paper includes a comprehensive study of thermal and mechanical effects associated with the residual stress introduction. For normal components determination, an optimized micro-indent method was used. Each measurement sequence from this approach was performed using a high accuracy measuring machine and classified according to thermal deviations measured. The residual displacements were determined with an absolute error down to ±300 nm. The normal components analysis allowed to infer the strong influence of the rolling process previous to high-speed milling and besides, the stress levels associated with thermal effects (higher in AA 7075-T6). Finally, the lower residual stress anisotropy degrees in both materials observed in the conventional cutting zone would indicate more homogenous local plastic stretching in this region for all planar directions.

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The Effects of Roller Burnishing Parameters Upon Surface Properties of AISI 52100 Bearing Steel (60HRC)  A Finite Element Analysis  Edición Única

The Effects of Roller Burnishing Parameters Upon Surface Properties of AISI 52100 Bearing Steel (60HRC) A Finite Element Analysis Edición Única

Since the flow stress model for the AISI 52100 hard turned surface given by Eq. (5.4) is not strain rate dependant, the 2D FEM model cannot analyze the effect of burnishing speeds. However, the effects of burnishing speeds can be considered as insignificant, according to many experimental studies. As mentioned earlier in Section 3.3.3, cross-section ‘B’ of Figure 3-14, which contains the hard turned surface profile, was used to conduct 2D roller burnishing simulations. In this simulation model, the tool loading on workpiece surface was represented as an indentation for each burnishing path [Yen, 2004]. The ball was considered a rigid object and the workpiece was considered as an elastic-plastic object. Because pressurized fluid acts as coolant and lubricant in the process, the FEM model can assume isothermal condition and friction coefficient of zero. The displacement boundary constraints that were applied on the left, right and bottom boundaries of the workpiece are shown in Figure 5-7.

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Filtro de roca basáltica para agua residual

Filtro de roca basáltica para agua residual

con este valor se conoce la cantidad de la roca basáltica que es necesaria para ocuparlo de filtro conociendo la concentración de los elementos químicos del agua. Es muy práctico utilizar esta roca para la adsorción para agua contaminada, ya que es un recurso natural sin ningún costo. Si el agua residual solo tuviera manganeso 0.03 ppm y hierro a 0.103 ppm, entonces se necesitaría 313.95 g de roca basáltica para eliminar estos elementos químicos.

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Cycling Dof Factors: Molecular and functional characterization of Arabidopsis thaliana AtCDF3 and tomato (Solanum lycopersicum L.) SlCDF3 in response to abiotic stress

Cycling Dof Factors: Molecular and functional characterization of Arabidopsis thaliana AtCDF3 and tomato (Solanum lycopersicum L.) SlCDF3 in response to abiotic stress

First, we studied the capacity of soil-grown 35S::SlCDF1 and 35S::SlCDF3 transgenic plants to tolerate water deprivation compared to WT plants. After 15 d of drought, plants were allowed to recover for 10 d during which they were watered. As shown in Fig. 4.7B and C, when cultured in soil under non-stress (control) conditions, both WT and transgenic lines performed equally well. After the drought treatment, all WT plants exhibited severe symptoms of water loss and substantial wilting. In contrast, most of the 35S::SlCDF1 and 35S::SlCDF3 transgenic plants were less affected, retaining greener leaves. Only slight wilting was observed in some of the 35S::SlCDF1 transgenic leaves. After the 10-days recovery period, the 35S::SlCDF1 and 35S::SlCDF3 transgenic plants exhibited better survival and growth than the WT, as judged by their survival rates and fresh weight (Fig. 4.7B and 4.7C). To assess tolerance to salt stress, primary (PR) and lateral (LR) root elongation assays were conducted. 35S::SlCDF1, 35S::SlCDF3 and WT plants were grown either on control medium (no NaCl) or salt stress medium, containing 80 mM NaCl for 10 days (Fig. 7D and E). Under control conditions there was no difference between the transgenic and the WT plants. Only two transgenic 35S::SlCDF3 lines (10.4 and 10.7) did exhibit slightly longer roots. On salt stress medium, 35S::SlCDF1 and 35S::SlCDF3 lines showed slight but significant lower values of root primary growth inhibition than the WT. Moreover the effect was more evident on root lateral growth, as all 35S::SlCDF1 and 35S::SlCDF3 transgenic plants exhibited much lower values of root lateral growth inhibition than WT plants under similar stress conditions (Fig. 4.7D and E). Collectively, these data suggest that SlCDF1 and SlCDF3 may be involved in plant responses to drought and salt stress.

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Maternal stress and plural breeding with communal care affect development of the endocrine stress response in a wild rodent

Maternal stress and plural breeding with communal care affect development of the endocrine stress response in a wild rodent

Degu pups were trapped and sampled between 0700 and 1300, but time of day does not correlate with baseline cortisol levels in this species (Bauer et al., 2013). One to two observers with binoculars continuously monitored nearby burrow systems so exact time of capture could be de- termined. Pups were then bled from the saphenous vein into heparin- ized, microhematocrit capillary tubes for a baseline blood sample (~ 30 μ L) within 3 min of capture (Romero and Reed, 2005). Pups were then ear-tagged, sexed, and weighed to the nearest 0.1 g. Stress- induced blood samples (~15 μ L) were taken 30 min after capture, im- mediately after which pups were injected intra-peritoneally with a 1 mg kg −1 of body weight dose of dexamethasone (Bauer et al., 2013). Dexamethasone (DEX) is a synthetic glucocorticoid that inhibits endogenous glucocorticoid release and is commonly used to test nega- tive feedback ef fi cacy (Boonstra and Singleton, 1993; Carroll et al., 1981; Romero and Wikelski, 2010; Sapolsky and Altmann, 1991). A blood sample (~ 30 μ L) was taken 90 min after DEX injection, after which pups were given an intra-peritoneal injection of ACTH (adreno- corticotropic hormone from porcine pituitary, Sigma Aldrich, St. Louis, Mo., USA) at a dose of 50 IU kg −1 of body weight. This dose should in- duce maximal secretion of cortisol, as it is much higher than that used in most small mammal studies (Boonstra et al., 1998, 2008, 2011). A fi nal blood sample (~ 15 μ L) was taken 15 min after ACTH injection. The total amount of blood taken (~ 90 μ L) was below 1% of each individual's body weight, as per the guidelines of the American Society of Mammalogists for the use of wild mammals in research (Sikes et al., 2011). Between blood samples, pups were kept in shaded traps and supplied with oats. Pups were then released at their home burrow system.

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Elasto thermoelectric non linear, fully coupled, and dynamic finite element analysis of pulsed thermoelectrics

Elasto thermoelectric non linear, fully coupled, and dynamic finite element analysis of pulsed thermoelectrics

As a first step and for a steady-state generic case, in Fig. 3 a comparison between deformed FE meshes is presented; in the left, three thermocouples in series, in the right, half of one thermocouple taking advantage of the symmetries. Even for a relatively coarse mesh the displacements are virtually identical in both meshes; temperature, voltage and related fluxes are completely equal, and Tresca equivalent stresses vary only 2.5%. For this equivalent stress we use the expression T tr =

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Response of maize and olive to climate change under the semi-arid conditions of southern Spain

Response of maize and olive to climate change under the semi-arid conditions of southern Spain

The frequency and intensity of extreme high temperature events is expected to increase with climate change. Higher temperatures near anthesis have a large and negative effect on maize (Zea mays, L.) grain yield. While crop growth models are commonly used to assess climate change impacts on maize and other crops, it is only recently that they have accounted for such heat stress effects, despite limited field data availability for model evaluation. There is also increasing awareness but limited testing about the importance of canopy temperature as compared to air temperature for heat stress impact simulations. In this study, four independent irrigated field trials with controlled heating imposed with polyethylene tents were used to develop and evaluate a heat stress response function in the crop modeling framework SIMPLACE, in which the Lintul5 crop model was combined with a canopy temperature model. A dataset from Argentina with the temperate hybrid Nidera AX 842 MG (RM 119) were used to develop a yield reduction function based on accumulated hourly stress thermal time above a critical temperature of 34 °C. A second dataset from Spain with a FAO-700 cultivar was used to evaluate the model with daily climate inputs in two sets of simulations. The first was used to calibrate SIMPLACE for conditions with no heat stress, and the second was used to evaluate SIMPLACE under conditions of heat stress using the reduction factor obtained with the Argentine dataset. Both sets of simulations were conducted twice; the heat stress function was alternatively driven with air and simulated canopy temperature. Grain yield simulated under heat stress conditions improved when using canopy temperature instead of air temperature (RMSE equal to 175 and 309 g m -2 , respectively). For the irrigated and high radiative conditions, raising the critical threshold temperature for heat stress to 39 °C improved yield simulation using air temperature (RMSE: 221 g m -

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Ecofisiología del stress en las plantas

Ecofisiología del stress en las plantas

Itai y Benzioni (1976) exponen su discrepancia con la hipótesis de Hsiao ale­ gando que la reducción de la turgencia como respuesta inicial al stress hídrico no se produce con otros tipos de stress (sali­ no, térmico, toxicidad) los que, por otra parte, provocan una reconocida serie de respuestas comunes con el stress hídrico. En este sentido consideran que las altera­ ciones hormonales, comunes a las diversas situaciones de stress, pueden ser señaladas como efecto primario. La hipótesis de es­ tos autores sugiere que la respuesta adap- tativa de las plantas al stress hídrico con­ sistiría en un programa regulado por un balance de las citocininas y el ácido abs- císico (ABA).

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Influence of mechanical anisotropy on shear fracture development

Influence of mechanical anisotropy on shear fracture development

The mechanical development of shear bands and frac- tures is a major research topic in geology and rock mechanics. There is a large amount of studies analysing the fundamental controls of the development of shear bands and fractures in homogeneous isotropic rocks (e.g. Wolf et al., 2003 and references therein). However, many rocks in nature are anisotropic and heterogeneous (Biot, 1965; Cobbold et al., 1971, Weijermars, 1992) and have a different response to normal and shear stress. It has been historically observed that the presence of a planar anisotropy (i.e. layering, cleavage, pre-existing faults, joints, etc.) can affect the onset and orientation of fractures. The exis- tence of directional heterogeneities may enhance the partition of deformation (Lister and Williams, 1983) and can produce a deviation of the local stress field with respect to the regional deformation conditions (Bradshaw and Zoback, 1988; Peacock and Sanderson, 1992). In this kind of situations inferring the regional

7 Lee mas

Biomaterials and abdominal wall

Biomaterials and abdominal wall

focused on nanofibers prepared through solution processes. The properties of the developed fibers can be controlled by different parameters such as utilized solvent, concentration of polymer, processing methods, and ambient conditions. For example, in the case of nanofibers made of polypropylene (one of the highly used polymers for commercially available surgical meshes), decahydronaphthalene (decalin) and cyclohexane have been used as preferred solvents. Polypropylene nanofibers prepared with cyclohexane exhibited a rougher surface when compared to the fibers prepared with decalin, suggesting that the surface morphology of the nanofibers depend on the boiling point of each solvent [93]. When stress–strain behaviors of the nanofibers are investigated, a tensile strength of 61.4  1.5 MPa with 35.2%  1.7% of strain, and a Young modulus of 174.6  1.7 MPa was obtained for the decalin based nanofibers, whilst the cyclohexane nanofibers exhibit a tensile strength of 18.2  1.1 MPa with 46.7%  1.2% of elongation and a Young modulus of 39.1  1.4 MPa [94]. The abovementioned results were obtained from bundles of nanofibers rather than individual fibers, these properties are strongly dependent on fiber orientation within the tested sample, bonding between fibers, and slip of one fiber over another [94].

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Relationship between residual stresses and mechanical behavior in ceramic composites

Relationship between residual stresses and mechanical behavior in ceramic composites

Most advanced ceramics are formed as powder compacts and densified by sintering. Powder processing generally involves five basic steps (2): (i) powder production, (ii) preparation of powders for consolidation, (iii) consolidation to an engineering shape (or called forming into shape), (iv) removal of solvent and organic additives (drying and burnout), and (v) densification. An optimized powder processing route of sufficient quality can eliminate heterogeneities from the powders, and ensure minimum density variation and small scale of the residual flaw population and absence of large scale porosity/flaws in the final material (e.g. after the final sintering). Colloidal processing techniques have been successfully applied to make green bodies of ceramics with improved product reliability, which involves the manipulation and control of the interparticle forces in powder suspensions, in order to remove heterogeneities and to optimize the suspension properties. There are many reports in the literature regarding colloidal processing of alumina-zirconia. Suzuki et al. [90] studied the dispersion behavior of Al 2 O 3 -ZrO 2 suspension and

198 Lee mas

Evaluation of plastic deformation in steels with magnetic and acoustic techniques

Evaluation of plastic deformation in steels with magnetic and acoustic techniques

Barkhausen Magnetic Noise (MBN) and Magnetic Acoustic Emission (MAE) are phenomena that occur in ferromagnetic materials which undergo changes in their magnetization. These phenomena are very sensitive to changes on microstructure and residual stresses. The MBN and MAE can be applied as monitoring techniques to detect plastic deformation in materials subjected to thermomechanical processes, such as machining and manufacturing processes. In this work, the plastic deformation in samples subjected to uniaxial tensile tests is investigated through MBN and MAE. Twelve stainless steel test pieces of two different materials (AISI 430 and AISI 441A), were tested. As a first step, in order to obtain their mechanical properties, two test pieces of each material cut in different directions with respect to the rolling direction, were tested up to rupture. The others were deformed in four stages on plastic deformation. After each stage, MBN and MAE measurements were made, in order to obtain a correlation with the strain and the magnetic situation of the materials. We present here the microstructural analyses, the study of MBN and MAE signals, correlating them with the state of deformation of the specimens.

13 Lee mas

The Effects of Roller Burnishing Parameters Upon Surface Properties of AISI 52100 Bearing Steel (60HRC). A Finite Element Analysis -Edición Única

The Effects of Roller Burnishing Parameters Upon Surface Properties of AISI 52100 Bearing Steel (60HRC). A Finite Element Analysis -Edición Única

Since the flow stress model for the AISI 52100 hard turned surface given by Eq. (5.4) is not strain rate dependant, the 2D FEM model cannot analyze the effect of burnishing speeds. However, the effects of burnishing speeds can be considered as insignificant, according to many experimental studies. As mentioned earlier in Section 3.3.3, cross-section ‘B’ of Figure 3-14, which contains the hard turned surface profile, was used to conduct 2D roller burnishing simulations. In this simulation model, the tool loading on workpiece surface was represented as an indentation for each burnishing path [Yen, 2004]. The ball was considered a rigid object and the workpiece was considered as an elastic-plastic object. Because pressurized fluid acts as coolant and lubricant in the process, the FEM model can assume isothermal condition and friction coefficient of zero. The displacement boundary constraints that were applied on the left, right and bottom boundaries of the workpiece are shown in Figure 5-7.

130 Lee mas

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