Elastic Tensile Stress Research Articles

Influence of low tensile stress on the kinetics of hydrogen permeation and evolution behavior in alkaline environment

The hydrogen behavior the surface of X70 pipeline steel in alkaline environment after applying low tensile stress was investigated by electrochemical tests. It is found by hydrogen permeation tests that the steady-state hydrogen permeation current density (i∞) and sub-surface hydrogen concentration (C0) greatly increased, whereas apparent diffusivity (D) was almost unchanged after applying low tensile stress. LSV and EIS measurements indicated that the activity of hydrogen evolution reaction (HER) was improved by elastic tensile stress. The mechanism of stress enhanced the hydrogen embrittlement sensitivity was conducted by Iyer-Pickering-Zamanzadeh (IPZ) and surface effect model. The results demonstrated that the Volmer reaction was facilitated, and the Tafel reaction was restricted by the application of tensile stress. The activation energy obtained by the Arrhenius equation indicated that when the specimen suffered from tensile stress, the adsorption activation energy decreased, and the desorption activation energy increased, leading to the remarkable increase of C0.

A reaction and movement of vacancy and solute atom in metals under elastic tensile stress

A reaction and movement of vacancy and solute atom in metals under elastic tensile stress

Effect of external stress on hydride reorientation in zirconium

The usage and long-term storage of nuclear fuel cladding motivate efforts to understand the effect of external stress on hydride precipitation. Here, by using in situ bending device in electrolytic hydrogen charging, the nucleation and precipitation behaviors of subsurface hydrides under different degrees of tensile stress were obtained. The number density of surface hydride bumps increases with the elastic tensile stress and reaches a peak before plastic yielding. This is related to the statistical result that the reorientation of hydride bumps reaches maximum at the end of elastic stage. Morphologies of hydride bumps varies from needle- or circular-shape to faceted, indicating hydride reorientation. The faceted hydrides have special crystallographic characteristics. Under tensile stress, the habit planes of faceted hydrides gradually transform from {0001} to {101¯i} (i = 1–7), even to the {101¯0} planes. Because of the local compressive stress, faceted hydrides growing along one <112¯0> direction are suppressed. External stress-stimulated tensile or compressive lattice stress on specific crystallographic planes impacts the choice of faceted/habit planes in hydride precipitation, which plays an important role in the long-term performance of Zr cladding tubes.

Nonlinear visco-hyperelastic tensile constitutive model of spray polyurea within wide strain-rate range

Spray polyurea (SPUA) is widely used as a protective coating material for structures subjected to the intensive impulsive loadings, attributed to its prominent large tensile deformation capacity and strain-rate hardening effect. This paper aims to study the tensile properties of SPUA within a wide strain-rate range both experimentally and theoretically. Firstly, by reasonably designing the geometry and dimension of specimens, a series of quasi-static and dynamic uniaxial tensile tests were carried out, and the nonlinear stress-strain curves corresponding to the strain-rates ranging from 10−3 s−1 to 103 s−1 were obtained. It showed that the mechanical properties of SPUA are sensitive to the strain-rate, i.e., the elastic modulus and tensile stress increase with the rising of the strain-rate, while the fracture strain is linearly negatively correlated with the logarithm of strain-rate. Then, a nonlinear visco-hyperelastic (NVHE) constitutive model composed of a 3rd-order polynomial hyperelastic model and seven Prony series terms describing the viscoelastic properties were established, and the corresponding twenty-three model parameters were calibrated through a multi-objective optimization based on genetic algorithm. Furthermore, based on the finite element program ABAQUS/Explicit, the validations of the proposed NVHE model and the parameters determination approach are verified by the present tensile test and existing drop hammer impact test. This work could provide a helpful reference for the retrofitting design of the protective structures.

Ovarian Biomechanics: From Health to Disease.

Biomechanics is a physical phenomenon which mainly related with deformation and movement of life forms. As a mechanical signal, it participates in the growth and development of many tissues and organs, including ovary. Mechanical signals not only participate in multiple processes in the ovary but also play a critical role in ovarian growth and normal physiological functions. Additionally, the involvement of mechanical signals has been found in ovarian cancer and other ovarian diseases, prompting us to focus on the roles of mechanical signals in the process of ovarian health to disease. This review mainly discusses the effects and signal transduction of biomechanics (including elastic force, shear force, compressive stress and tensile stress) in ovarian development as a regulatory signal, as well as in the pathological process of normal ovarian diseases and cancer. This review also aims to provide new research ideas for the further research and treatment of ovarian-related diseases.

Allergy-induced systemic inflammation impairs tendon quality.

SummaryBackgroundTreatment of degenerating tendons still presents a major challenge, since the aetiology of tendinopathies remains poorly understood. Besides mechanical overuse, further known predisposing factors include rheumatoid arthritis, diabetes, obesity or smoking all of which combine with a systemic inflammation.MethodsTo determine whether the systemic inflammation accompanying these conditions contributes to the onset of tendinopathy, we studied the effect of a systemic inflammation induced by an allergic episode on tendon properties. To this end, we induced an allergic response in mice by exposing them to a timothy grass pollen allergen and subsequently analysed both their flexor and Achilles tendons. Additionally, we analysed data from a health survey comprising data from more than 10.000 persons for an association between the occurrence of an allergy and tendinopathy.FindingsBiomechanical testing and histological analysis revealed that tendons from allergic mice not only showed a significant reduction of both elastic modulus and tensile stress, but also alterations of the tendon matrix. Moreover, treatment of 3D tendon-like constructs with sera from allergic mice resulted in a matrix-remodelling expression profile and the expression of macrophage-associated markers and matrix metalloproteinase 2 (MMP2) was increased in allergic Achilles tendons. Data from the human health study revealed that persons suffering from an allergy have an increased propensity to develop a tendinopathy.InterpretationOur study demonstrates that the presence of a systemic inflammation accompanying an allergic condition negatively impacts on tendon structure and function.FundingThis study was financially supported by the Fund for the Advancement of Scientific Research at Paracelsus Medical University (PMU-FFF E-15/22/115-LEK), by the Land Salzburg, the Salzburger Landeskliniken (SALK, the Health Care Provider of the University Hospitals Landeskrankenhaus and Christian Doppler Klinik), the Paracelsus Medical University, Salzburg and by unrestricted grants from Bayer, AstraZeneca, Sanofi-Aventis, Boehringer-Ingelheim.

The effect of the melt-drawing ratio on the microstructure and mechanical properties of poly(butylene succinate) cast films with row-nucleated lamellar structure

High-performance PBS films can be prepared by the melt-stretching method. The effect of the melt-drawing ratio (MDR) on the mechanical properties and microstructure of PBS cast films prepared by melt-stretching is studied in this paper. The elastic modulus, tensile stress, and strain hardening increase with increasing MDR. With an MDR of 25–50, the crystalline morphology changes from deformed spherulites to row-nucleated lamellar structure. The lateral size and orientation of the lamellae apparently improve with the MDR. When the MDR is within 50–125, the row-nucleated lamellar structure improves slightly by increasing the lateral size and orientation of the lamellae. The component fraction and thickness of the mobile (MAF) and rigid (RAF) amorphous fractions and crystalline phase are nearly unchanged within the whole MDR range. The increases in lateral size and orientation improve the mechanical properties of the films. Significantly, the linear relationship between the elastic modulus and orientation at MDRs from 50 to 125 indicates that the elastic modulus is determined by the crystal orientation in PBS cast films with row-nucleated lamellae. This work evaluates the importance of orientation for microstructure and properties of PBS films, which may guide the processing of high-performance PBS films.

WITHDRAWN: A comprehensive analysis on assessing and controlling of residual stresses in friction stir welded joints

Residual stresses is one of the vital factors in deciding the performance of all the machining and joining process. Friction Stir Welding (FSW) is belong to the family of solid-state joining processes encounters the problem of residual stresses formation during the metal joining process. Residual stresses in the welded area produces fatigue and stress corrosion cracks leads to premature failure of the components/parts. Residual stress could be either in the form of tensile or compressive or combination of both. In the elastic region, compressive and tensile stress balances each other and maintains equilibrium state. The welded part subjected to cyclic loads and temperature histories creates challenging working condition. The control of residual stresses is now becoming challenging task during manufacturing process and also during service of the end product. This review discusses the source of residual stresses and possible way to measure numerically and experimentally.

Mechanical Degradation of 3D Printed PLA in Simulated Marine Environment

3D printing technology is gaining continuous attention in many fields due to its suitability for designing complex parts, and naval applications are no exception. However, the real application of these parts in the marine environment is still under consideration and requires several assessments in terms of material degradation. This work evaluates the mechanical degradation of 3D printed parts in a simulated marine environment. For this purpose, the simulated seawater-environment is created, and the samples were immersed in this for 30 days. The tensile properties of these samples were estimated. A biocompatible polylactic acid (PLA) material is used to fabricate selected parts. Initially, a square block and a propeller blade are chosen for the mechanical degradation test. Thereafter, wear-incited mechanical degradation, including friction and surface deformation, of the propeller blade is investigated in detail. A high loading rate tensile test is conducted on the samples to assess the suitability of the printed parts in marine contact applications. The average calculated values of elastic modulus, yield strength and tensile stress of the sample are 1101 MPa, 36.86 MPa and 52.96 MPa. The calculated elongation at break is 7.12%. XRD results show that the partial crystallinity of the PLA material is degraded under the simulated seawater condition. The friction coefficients at the top and the bottom surface are 0.158 and 0.56. The surface wear deformation is progressed with surface roughness. The calculated values at the top and the bottom surface are 3.3 × 10-6 mm3/N-m and 6.5 × 10-6 mm3/N-m. The propeller blade's design has given an insightful understanding of wear degradation at the surface in the simulated seawater environment. Mainly, the salt content from the seawater has initiated surface degradation, which appeared as tiny pits. However, the degradation is in controlled mode, and the study is practically useful in the marine industry for contact/non-contact applications.

Using water to control electrospun Polycaprolactone fibre morphology for soft tissue engineering

Control of the properties of electrospun polycaprolactone can be achieved by adjusting the acetic acid:water ratio used to dissolve and electrospin the polymer. In this work, we studied the effect of using up to 15 wt% water in the solvent mixture. Solution conductivity and viscosity and fibre morphology vary dramatically with water content and solution age. Two days after initial solution preparation, electrospinning yields regular fibres for a water content of 0 wt% and 5 wt%, irregular fibres for a 10 wt% water content and irregular and fused fibres for a 15 wt% water content. Fibres with the highest crystallinity (60%) were obtained from solutions containing 5 wt% water while the highest elastic modulus (8.6 ± 1.4 MPa) and tensile stress (4.3 ± 0.3 MPa) pertain to fibres obtained from solutions containing 10 wt% water. Enzymatic fibre degradation is faster the higher the water content in the precursor solution. Adhesion ratio of human foetal fibroblasts was highest on scaffolds obtained from precursor solutions containing 0 wt% water. Cell population increases for all scaffolds and populations quickly become equivalent, with no statistically significant differences between them. Cells exhibit a more extended morphology on the 5 wt% scaffold and a more compact morphology on the 0 wt% scaffold. In summary, a small water content in the solvent allows a significant control over fibre diameter, scaffold properties and the production of scaffolds that support cell adhesion and proliferation. This strategy can be used in soft tissue engineering to influence cell behaviour and the degradation rate of the scaffolds.

Mechanical study of polyurethane elastomer and Medpor as the material of artificial auricular scaffold

By comparing the mechanics of human auricular cartilage, polyurethane elastic material, and high density polyethylene material (Medpor), to produce theoretical proof on choosing optimal artificial auricular scaffold materials. The experimental materials were divided into 3 groups with 6 samples in each: the auricular cartilage group (group A), the polyurethane elastic material group (group B), and the Medpor group (group C). With an Instron5967 mechanical testing machine, compression and tensile testing were performed to respectively measure values of compression parameters (including yield stress, yield load, elastic modulus, yield compressibility, compressibility within 2 MPa, and compression stress within 10% strain) and values of tensile parameters (including yield stress, yield load, elastic modulus, yield elongation, elongation within 2 MPa, tensile stress within 1% strain) for comparison. Compression testing: no obvious yield points were observed in the whole process in samples of group B, while obvious yield points were observed in samples of groups A and C. There was no significant difference between groups A and C with respect to yield stress and yield load ( P>0.05); while the yield compressibility in group C was significantly lower than that in group A ( P<0.05) and the elastic modulus in group C was significantly higher than that in group A ( P<0.05). There was a significant difference with respect to compressibility within 2 MPa of materials among the 3 groups ( P<0.05), the high, medium, and low values go to groups B, A, and C respectively. The compression stress within 10% strain in group C was significantly higher than that in groups A and B ( P<0.05), and there was no significant difference between that in groups A and B ( P>0.05). Tensile testing: the materials in group B had extremely high tensile strength. The yield stress in groups A and B was significantly higher than that in group C ( P<0.05), and the elastic modulus and tensile stress within 1% strain were significantly lower than those in group C ( P<0.05); but no significant difference was found between those in groups A and B ( P>0.05). There was no significant difference with respect to yield load among the 3 groups ( P>0.05); but there was significant difference with respect to yield elongation among the 3 groups ( P<0.05), and the high, medium, and low values go to groups B, A, and C respectively. The elongation within 2 MPa in group B was significantly higher than that in groups A and C ( P<0.05), and there was no significant difference between that in groups A and C ( P>0.05). Compared with the Medpor, the polyurethane elastic material is a more ideal artificial auricular scaffold material.

Experimental and numerical studies for the gas-assisted extrusion forming of polypropylene micro-tube

In this study, to eliminate the extrudate swell, melt fracture and extrudate distortion problems of polypropylene (PP) micro-tube, the experiments of gas-assisted extrusion forming was firstly carried out. Meanwhile, a set of modified gas-assisted extrusion system was set-up, and a kind of novel gas-assisted die was also designed and manufactured. Under the role of gas-assisted extrusion system, PP micro-tubes were successfully prepared. Moreover, the macroscopic and microscopic qualities of PP micro-tubes for gas-assisted extrusion were obtained and compared with those of the traditional extrusion. Experimental results show that gas-assisted extrusion not only overcomes extrudate swell, but also greatly improves the smoothness and transparency of PP micro-tube. In addition, to ascertain the mechanisms of gas-assisted extrusion of PP micro-tube, numerical simulations were also performed. The swell ratios, flow velocities, pressure and stresses distributions of melt for gas-assisted extrusion and traditional extrusion were analyzed and compared. Moreover, the effects of inner cavity’s gases pressures and traction force on the gas-assisted extrusion of PP micro-tube were numerically investigated and discussed with the traditional extrusion. Numerical results show that the swell ratio of PP micro-tube increases with the inlet volume flow rate for traditional extrusion, but it is nearly equal to 0 for the gas-assisted extrusion. Moreover, due to the assistance of gas-layers, not only the axial flow velocity of melt is uniformed and radial flow velocity is removed, but also the pressure, shear stress and first normal stress difference of melt are all greatly reduced, especially at the outlet of die. These weakened pressure and stresses diminish the elastic energy storage and tensile stress of melt, and finally result in the elimination of extrudate swell, melt fracture and extrudate distortion. With the increase of inner cavity’s pressure, the inner and outer radiuses of the gas-assisted extrusion of PP micro-tube all increase, but the wall thickness decreases because the swell ratios of inner radius are all larger than that of the outer radius. In addition, under the same traction force, the sizes of gas-assisted extrusion of PP micro-tube are smaller than that of the traditional extrusion, although the sizes for the both extrusions of PP micro-tube all exponentially decrease with the increase of traction force. Moreover, the extrudate radial swell and melt fracture problems for the traditional extrusion are always existed at the outlet of die although the radial swell of melt decreases with the increase of traction force. However, the extrudate swell and melt fracture problems are greatly removed by the gas-assisted extrusion.

Mechanical characterization of polycarbonate reinforced with nanoclay and graphene oxide

In this research, the effect of organic nanoclay (NC) Closite 20A and graphene oxide (GO) on the compressive, tensile, and three‐point bending behavior of polycarbonate (PC) nanocomposites is investigated. The nanocomposite samples are prepared based on injection molding and the masterbatch technique is used for better dispersion of filler in the matrix. The NC masterbatch is made of direct method by the twin‐screw extruder device and the GO masterbatch by the solvent method. The results showed that the presence of nanoparticles in the composite improves the elastic modulus, flexural modulus, compressive and tensile yield stress. The best weight fractions between the considered values for PC/NC and PC/GO were 1% and 0.6%, respectively. Higher fractions lead to the formation of agglomerate and degradation of the nanocomposite. Additionally, it was found that the volume change in plastic deformation for thermoplastics was considerable and the assumption of non‐dependent potential flow for PC nanocomposites was more appropriate. For simulating the mechanical behavior of PC nanocomposite, the extended Drucker–Prager (EDP) material model was designated and its coefficient were determined by minimizing the difference between the force‐displacement curves obtained from three‐point bending test and predicted from numerical simulation using the surrogate method. POLYM. COMPOS., 40:3947–3959, 2019. © 2019 Society of Plastics Engineers

Description of Residual Stress and Strain Fields in FGM Hollow Disc Subject to External Pressure.

Elastic/plastic stress and strain fields are obtained in a functionally graded annular disc of constant thickness subject to external pressure, followed by unloading. The elastic modulus and tensile yield stress of the disc are assumed to vary along the radius whereas the Poisson’s ratio is kept constant. The flow theory of plasticity is employed. However, it is shown that the equations of the associated flow rule, which are originally written in terms of plastic strain rate, can be integrated with respect to the time giving the corresponding equations in terms of plastic strain. This feature of the solution significantly facilitates the solution. The general solution is given for arbitrary variations of the elastic modulus and tensile yield stress along the radial coordinate. However, it is assumed that plastic yielding is initiated at the inner radius of the disc and that no other plastic region appears in the course of deformation. The solution in the plastic region at loading reduces to two ordinary differential equations. These equations are solved one by one. Unloading is assumed to be purely elastic. This assumption should be verified a posteriori. An illustrative example demonstrates the effect of the variation of the elastic modulus and tensile yield stress along the radius on the distribution of stresses and strains at the end of loading and after unloading. In this case, it is assumed that the material properties vary according to power-law functions.

Mechanical and Thermal Properties of Polypropylene/Silica Aerogel Composites

Polypropylene (PP) composites including various amounts of silica aerogel (SA) microparticles were prepared by melt mixing in an internal mixer. The morphology and microstructure of the prepared composites were investigated by scanning electron microscopy (SEM). Mechanical properties of the samples, including elastic modulus, tensile stress, elongation and stress at break, were measured by tensile tests. In addition, the other mechanical features, including Izod impact strength, hardness and wear resistance, were evaluated and then related to the structure of the PP/SA composites. Furthermore, the thermal characteristics of the composites, such as heat deflection temperature and thermal stability, were studied by thermal gravimetric analysis (TGA). The SEM photographs indicated the satisfactory SA particles dispersion for the compositions of 1% and 3% but agglomeration of the aerogels at higher SA contents. Since the composites became stiffer, the impact and tensile strength decreased. The addition of the SA to the PP matrix yielded harder samples with lower weight loss and coefficients of friction in wear tests. The TGA evaluations confirmed that the presence of SA promoted and upgraded the thermal stability and heat deflection temperature of PP. The thermal results proved the superior potential of PP as an insulator when the SA particles were added.

A modified model of magneto-mechanical effect on magnetization in ferromagnetic materials

The prevailing Jiles-Atherton (J-A) model and Zheng Xiao-Jing-Liu Xing-En (Z-L) model are extensively used in modeling the magneto-mechanical effect on magnetization in ferromagnetic materials. In the J-A model, a fitting formula of magnetostrictive strain interms of stress and magnetization is adopted to model the stress effect on magnetostriction. However, the fitting formula is not in good accordance with the experimental results obtained by Kuruzar and Culllity. In order to solve this problem, a transcendental function tanh(&lt;i&gt;x&lt;/i&gt;) is appropriately selected to describe the nonlinear magnetostrictive strain in the Z-L model, and it is found that the general formula of magnetostrictive strain is more effective to describe the nonlinear relation of magnetostrictive strain with stress and magnetization. Then, the modified law proposed by Jiles and Li is adopted to modify the Z-L model by Shi Pengpeng to describe the hysteretic behavior; nevertheless, the effect of Weiss molecular field, pinning energy and plastic deformation on magnetization are not taken into account, and the modified Z-L model can only describe the elastic stress effect on magnetization. In order to solve these problems above, a modified magneto-mechanical model is established by combining the magnetostrictive constitutive relationships of Z-L model with the modified energy conservation equation of J-A model, as well as taking the effect of elastic stress and plastic strain on the model parameters into account simultaneously. It is found that the predictions of proposed model here are in better accordance with the initial magnetization curves given by Jiles and Atherton and the hysteresis loops obtained by Makar and Tanner under different stresses and plastic deformation than those calculated by the J-A model and Z-L model. The correlation coefficients between experimental data and theoretical results calculated by the modified model are all over 0.98, which indicates that the modified model here is more effective than the existing model. A detailed study also performed to reveal the effects of the elastic tensile and compressive stress and plastic tensile and compressive strain on hysteresis loops, coercivity and remanence. The proposed model reveals that the area of hysteresis loop and coercivity increase nonlinearly with the stress and plastic deformation increasing, while the remanence decreases significantly; the effects of compressive stress and compressive plastic deformation on magnetization characteristic parameters above are more significant than those of tensile stress and tensile plastic deformation, which is consistent with the experimental trend. The proposed model can be used to quantitatively analyze the magneto-mechanical effect on the magnetization of ferromagnetism.

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.

Novel stress corrosion testing method for high‐strength steels

This paper presents a novel TFT (tuning fork test) stress corrosion testing method, which was developed for classifying martensitic high‐strength steels. The novel method was developed by applying finite element calculations to optimize a tuning fork geometry to enable accurate stress adjustment with simple inexpensive equipment. Different steels were exposed to cathodic hydrogen charging conditions with various elastic tensile stress levels that were achieved by displacement control. All steels exhibited hydrogen‐induced stress corrosion cracking after exceeding a material‐specific threshold stress level that decreased linearly with increasing hardness.

In vitro and in vivo evaluation of novel biodegradable Mg-Ag-Y alloys for use as resorbable bone fixation implant.

Magnesium (Mg) alloy is gaining more interest because of its degradability and osteogenic potential. Still, it has some deficiencies, such as its rapid degradation rate, insufficient mechanical property. This research aimed to design a novel biodegradable Mg-argentum (Ag)-yttrium (Y) alloy, and Y was added to improve degradable and mechanical property. Mg-Ag-Y alloys were characterized for mechanical features, practicabilities in vitro and in vivo. The mechanical features results shown that this novel component was similar to native bone tissue in elastic moduli, tensile, and compressive stress. Then mesenchymal stem cells (MSCs) were seeded in alloys to assess cell toxicity in vitro. The results showed that its aqueous extract was suitable for MSCs adhesion and proliferation. Then the alloy was evaluated for biomedical applications in nonfractured distal femora of Sprague Dawley rats for 6 weeks, compared with those of pure-Mg and stainless steel groups. All rats survived, and hematological and histological evaluation showed no abnormal physiology 6 weeks postimplantation, and measurements of serum Mg2+ concentration were within normal levels. X-ray scanning, microcomputed tomography, and histological examinations were performed to evaluate the degradability and osteogenic potential. The results indicated that the degradation rate of alloy was 0.91 mm per year, (range 0.77-1.22 mm), and pure-Mg 1.80 mm per year (1.43-2.26 mm). The new bone quantity was 3.18mm3 (1.46-4.44 mm3 ) in Mg-Ag-Y alloys group, 1.39 mm3 (0.54-2.32 mm3 ) in pure-Mg group, and none in stainless steel group. These promising results suggest potential clinical application of Mg-Ag-Y alloys for use as resorbable bone fixation implant. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 2059-2069, 2018.

Расчет упругонапряженной гетероструктуры AlXGaYIn1–X–YAs/InP с квантовыми ямами для эффективных лазерных излучателей

The compositions of epitaxial layers forming quantum-well heterostructures AlxGayIn1-x-yAs / InP for laser diodes with the radiation wavelength of 1.55 μm are calculated. When carrying out the calculations, the problem was to provide the maximum height of the energy barriers for effective limitation of charge carriers in the quantum wells. Along with taking care of the effects of the dimensional quantization of the energy of free charge carriers in allowed zones, the effect of elastic stress in epitaxial layers on the displacement of the edges of the energy bands were taken into account in the calculation. It is shown that in order to solve the posed problems it is necessary to form heterostructures with elastic compression stress in a quantum well and elastic tensile stress in the barrier layers. As a result of the calculations the authors suggest a structure that includes a barrier layer of Al0.28Ga0.30In0.42As with a thickness of 110 A and a quantum well Al0.03Ga0.23In0.74As in a layer with a thickness of 55A (with the mismatch between the parameters of the crystal lattice and the InP substrate - 0.8% and + 1.4 %, respectively). According to the calculation results, the indicated thicknesses of epitaxial layers do not exceed the critical values that can lead to the formation of imperfect dislocations at heterointerfaces.