Plastic Tensile Stress Research Articles

The corrosion behavior of 316 stainless steel under the cooperative effect of plastic stress and UV illumination in 3.5 wt % NaCl solution

The corrosion behavior of 316 stainless steel under the cooperation of plastic tensile stress and UV was investigated. The results showed that the pitting corrosion resistance of the film deteriorates under the combined effect of both factors. Among them, UV illumination could increase the Cr2O3 ratio and reduce the electric field strength, thus improving the pitting corrosion resistance of the film. The plastic tensile stress not only increases the corrosion rate by increasing the defect density but also enhances the photo-induced electric field strength and photocurrent density by decreasing the band gap value and increasing the flat band potential.

Hydrogen diffusion kinetics in dual-phase (DP 980) steel: The role of pre-strain and tensile stress

The current study investigates the influence of pre-strain (un-strained, 3 %, and 6 % engineering strain) and in-situ tensile stress (50 %, 110 %, and 125 % of the yield stress (YS)) on the hydrogen diffusion and trapping behaviour in DP 980 steel. Electrochemical hydrogen permeation tests were conducted using a custom-built Devanathan-Stachurski (DS) cell integrated with a horizontal tensometer. The results showed that the value of apparent diffusion coefficient (Dapp) decreased from 5.4 ± 0.1 to 3.8 ± 0.029 × 10−7 cm2 s−1, while trap density (NT) and sub-surface hydrogen concentration (Capp) increased from 1.08 ± 0.01 to 1.58 ± 0.012 × 1021 cm−3, 2.70 ± 0.13 to 3.27 ± 0.10 × 10−4 mol H cm−3, respectively for unstrained and 6 % pre-strain conditions. This is due to increased dislocation density in ferrite and martensite. Hydrogen permeation tests under tensile stress (in-situ) revealed that the applied elastic stress of 50 % of YS showed a slight increase in Dapp and a decrease in NT values. This is due to an increase in the interstitial space between the atoms at applied elastic load favouring hydrogen diffusion. The plastic tensile stress of 110 % of YS showed the highest value of steady-state permeation current density iss (169 ± 10.6 µA cm−2). It could be due to an expanded lattice of martensite accommodating more hydrogen because of its elastic deformation. The tensile stress of 125 % of YS results in a significant reduction in Dapp (2.86 × 10−7 cm2 s−1) and an increase in Capp (5.52 × 10−4 mol H cm−3) and NT (2.11 × 1021 cm−3) as a result of plastic deformation in ferrite and martensite. The decay transient studies revealed that the applied elastic tensile stress enhances the rate of desorption of diffusible hydrogen, increasing lattice diffusion coefficient DL. The plastic pre-strain and plastic tensile stress resulted in slower desorption, lower DL, and an increase in reversible trap density.

Galvanic Corrosion Study between Tensile-Stressed and Non-Stressed Carbon Steels in Simulated Concrete Pore Solution

The present study investigated the galvanic effect between tensile-stressed and non-stressed carbon steels, in addition to the influence of the tensile stress on the passivation and corrosion behavior of steel in a simulated concrete pore solution. Three different levels of tensile stress, ranging from elastic to plastic stress on the surface, were applied by adjusting the displacement of C-shape carbon steel rings. Different electrochemical measurements including the open circuit potential (OCP), the electrochemical impedance spectroscopy (EIS), the zero-resistance ammetry (ZRA), and the cyclic polarization were performed. Based on the results of EIS, the tensile stress degraded the resistance of the oxide film in moderate frequencies while enhancing the charge transfer resistance in low frequencies during passivation. As corrosion propagated, the stressed steel yielded a similar charge transfer resistance to or an even lower charge transfer resistance than the non-stressed steel, especially in the case of plastic tensile stress. The galvanic effect between the tensile-stressed and non-stressed steels increased the chloride threshold value of the tensile-stressed steel, although the susceptibility to pitting corrosion was exhibited after being corroded.

Effect of tensile stress on the hydrogen permeation of MS X65 pipeline steel under sulfide films

The effect of the tensile stress on the hydrogen permeation of MS X65 pipeline with sulfide films was investigated through measuring the steady-state hydrogen permeation current (I∞), permeability (J∞L) and apparent diffusivity (Dapp) and quantitatively analysing the hydrogen-permeable resistance factor (HPRF) of single tensile stress HPRF (stress), single sulfide film HPRF (film) and the two together HPRF (stress-film). The results indicated that J∞L and sub-surface hydrogen concentration (co) greatly increase and that Dapp decreases as the elastic stress increases. When applying plastic stress, J∞L and Dapp all reduce, while co continues to increase without the film but decreases with the film. While single tensile stress can promote hydrogen permeation, with the sulfide film, the value of HPRE (stress-film) is not a simple addition of the value of the HPRE (stress) and the HPRE (film), and the interaction results in the blocking effect of hydrogen permeation. The surface morphology of the sulfide films changes caused by tensile stress should be responsible for the HPRE (stress-film) reducing as tensile stress increases but increasing with plastic tensile stress.

Influence of Aluminium on Castability of V-Microalloyed Steels

The influence of aluminium content on the hot ductility behaviour in V-N steels was investigated. Cylindrical specimens were subjected to thermal cycles and strain rates approximating those experienced by a conventional slab surface during continuous casting. The resulting microstructures were examined using light optical and electron microscopy and correlated with measured reduction-in-area (RA) values, calculated precipitate chemistries and volume fractions, as well as the flow stress behaviour. It was found that removal of aluminium significantly improved the hot ductility. However, increasing the total [V][N] product in Al-free steels reduces RA. Poor hot ductility is caused by low austenite grain boundary mobility characterized by high work hardening rates. The fracture mode in brittle specimens is intergranular along thin ferrite films. AlN appears to inhibit austenite grain boundary mobility in V-high N steels when the cooling rate and strain rate are both very slow as experienced during unbending. SEM analysis of fracture surfaces revealed the presence of MnS-AlN particles in microvoids. TEM-EDAX spectra showed that the larger particles observed in the Al-containing steels are mostly a constitution of duplex/triplex grain boundary precipitates, i.e., MnS-AlN and V(C,N). Conversely, good ductility in austenite is associated with high grain boundary mobility that produces fine, recrystallised grains and subsequent dimple fracture after plastic tensile stress.

Electrochemical Investigation of Corrosion of X80 Steel under Elastic and Plastic Tensile Stress in CO2 Environment

An investigation into the electrochemical corrosion behavior of X80 pipeline steel under different elastic and plastic tensile stress in a CO2-saturated NaCl solution has been carried out by using open-circuit potential, potentiodynamic polarization, electrochemical impedance spectroscopy, and surface analysis techniques. The results show that the corrosion rate of X80 steel first increases and then slightly decreases with the increase of elastic tensile stress, whereas the corrosion rate sharply increases with the increase of plastic tensile stress. Both elastic and plastic tensile stress can enhance steel corrosion by improving the electrochemical activity of both anodic and cathodic reactions. Moreover, compared with elastic tensile stress, plastic tensile stress has a more significant effect. Furthermore, electrochemical reactions for CO2 corrosion and mechanoelectrochemical effect are used to reasonably explain the corrosion behavior of stressed X80 steel in CO2 environment.

(Invited) Effect of Mechanical Stress on the Passivity of Steel

The influence of the elastic and plastic tensile stress on the electrochemical properties of mild carbon steel and austenitic stainless steel was studied using Scanning Kelvin Probe (SKP) and Localized Electrochemical Impedance Spectroscopy (LEIS) techniques. These two methods give complementary information on the surface of the stressed electrode. SKP characterizes the thermodynamic (surface potential) and LEIS is informative on the conditions of the passive oxide (capacitance of the film). The Volta potential and the admittance were mapped across an area with stress concentrator (notch) “in situ” under load. It was found that the elastic deformation slightly influences both the potential and the capacitance. The plastic strain decreases the potential measured in the lab air for both steels by 150 to 300 mV. LEIS shows an increase of the capacitance measured in borax electrolyte above the yielded surface in the notch relatively to the surrounding surface. Thus, the change inf the potential is reciprocal to the change of the capacitance. After straining, in load free conditions, stainless steel saved low potentials in the area containing residual stresses. It corresponds to LEIS data that shows an increased capacitance. In opposite, unloading of strained mild steel redistributes the surface potential. Mainly the surface increased the potential showing the passivation. However, low potential locations related to residual stress were also found by SKP. Mapping of the capacitance by LEIS also shows partial passivation of the steel. Thus, locations with concentrated stress, which are prone to localized corrosion can be recognized using local electrochemical techniques.After experiments, the strained surfaces were characterized by XPS and AFM. The effect of the plastic tensile strain was explained by the formation and emerging of dislocations and dislocations pile-ups. The dislocations rupture the oxide film making it more defective that weaken the steel passivity. On the other hand, the formation of the stepped surfaces decreased the potential that decreased the activation energy of anodic dissolution of the steel.

Electrochemical behavior of tensile stressed P110 steel in CO2 environment

An investigation on the electrochemical behavior of P110 steel loaded with different tensile stresses in CO2 corrosion environment was conducted using electrochemical measurement and surface analysis. The results show that both elastic tensile stress and plastic tensile stress enhance the surface thermodynamic activity of P110 steel. Tensile stress accelerates the cathodic reaction more obviously than the anodic reaction. The corresponding corrosion mechanisms to elastic tensile stressed and plastic tensile stressed P110 steels are separately proposed by “local melting zone” and slip planes according to the different features of corrosion product nucleation along with the electrochemical data.

Deformation behavior of micro-indentation defects under uniaxial and biaxial loads

The microdefects of structure frequently act as the source to generate initial cracks and lead to the fracture failure. Study on the deformation behaviors of embedded defects would be conducive to better understand the failure mechanisms of structural materials. Micro-indentation technique was applied to prepare the initial indentations as embedded surface defects at the gauge length section and central section of a cross-shaped AZ31B magnesium alloy specimen. A novel in situ biaxial tensile device was developed to apply the synchronous biaxial loads. Via the observation by an optical microscope with three-dimensional imaging and measurement functions, the changing laws of the indentation topographies under uniaxial and biaxial tensile loads were discussed. Compared with the gauge length section, the increasing trend of the indentation length of the central section was relatively flat, and the decreasing trend of the indentation depth was more significant. The changes of indentation topographies were explained by the Poisson effect, and the significant plastic tensile stress has led to the releasing of the residual stress around the indentation location and also promoted the planarization of the pileup.

Microstructure and mechanical properties of synthetic brow-suspension materials

Levator palpebrae superioris (LPS) is a muscle responsible for lifting the upper eyelid and its malfunction leads to a condition called “ptosis”, resulting in disfigurement and visual impairment. Severe ptosis is generally treated with “brow-suspension” surgery, whereby the eyelid is cross-connected to the mobile tissues above the eyebrow using a cord-like material, either natural (e.g. fascia lata harvested from the patient) or a synthetic cord. Synthetic brow-suspension materials are widely used, due to not requiring the harvesting of fascia lata that can be associated with pain and donor-site complications.The mechanical properties of some commonly-used synthetic brow-suspension materials were investigated — namely, monofilament polypropylene (Prolene®), sheathed braided polyamide (Supramid Extra® II), silicone frontalis suspension rod (Visitec® Seiff frontalis suspension set), woven polyester (Mersilene® mesh), and expanded polytetrafluoroethylene (Ptose-Up). Each material underwent a single tensile loading to the failure of the material, at three different displacement rates (1, 750 and 1500mm/min).All the materials exhibited elastic–plastic tensile stress–strain behaviour with considerable differences in elastic modulus, ultimate tensile strength, elastic limit and work of fracture. The results suggest that, as compared to other materials, the silicone brow-suspension rod (Visitec® SFSS) might be the most suitable, providing relatively long-lasting stability and desirable performance. These findings, together with other factors such as commercial availability, cost and clinical outcomes, will provide clinicians with a more rational basis for selection of brow-suspension materials.

Proces wytlaczania jako obiekt sterowania automatycznego

On the example of technological line for covering thermoplastic insulation on an electric wire, the tasks that an automatic system to control such a line must fulfill are presented. On this basis two sub-systems are distinguished. One of them is designed to control the properties of the processed plastic via influencing the processes taking place within the plastifying system and extruder head. The other one is designed to control the product displacement along the extruder line, i.e. the processes taking place outside the extruder. In the control systems currently used for extrusion the above mentioned systems operate independently. The quality of an extrudate can be improved if both systems are cooperating in that the temperature set-point values at extruder zones are dependent on plastic flow intensity correlated with the rate of extrusion. Creating such a system requires a computer-based control. The solution preceding such a system creation can be the use of specialized programmed controllers. The quality of extrudate can also be improved by the algorithms based on artificial intelligence using, first of all fuzzy logic, to control the extruder line. Fuzzy logic based control algorithms can be applied to both multidimensional control of properties of the processed plastic and complex control of product displacement along the extruder line. In order to illustrate the fuzzy logic based control algorithms use, the results of computer simulated product displacement along the extruder line are depicted. As a result of using fuzzy logic control, a substantial improvement of the quality of product displacement process has been achieved which manifests itself in lowering the plastic tensile stress and limitation of tightening compensators shifting and, at the same time, increase in the line rate of starting and stopping.

無方向性けい素鋼板の塑性領域における応力磁化特性

The effects of stress on the magnetization of non-oriented silicon steel sheets, were investigated in both the elastic and plastic regions of tensile stress. Magnetization changes and irreversible magnetization changes under tension were measured. Magnetization decreases beyond a plastic tensile stress of 300 MPa. The magnetization change due to tension shows a reversible change. However, the magnetization change due to tension beyond plastic stress shows a permanent decrease. Irreversible magnetization change increases on account of plastic tensile stress. The results obtained in this investigation can be applied to the nondestructive detection of fatigue in metallic magnetic materials.