Determining the Young's modulus of a cellular titanium implant by FEM simulation

The role of additive manufacturing is noted for the construction of titanium medical implants. The purpose of the study is to determine the Young's modulus of cellular titanium implants, which is based on calculations performed by finite element analysis. A honeycomb structure from intersecting cylinder surfaces is offered for the implant made of the Ti-6Al-4V alloy. Boundary conditions are stated for the loading of the implant structure. It is demonstrated that the Young's modulus can be reduced more than three times comparing to a solid titanium alloy. Zones of strain and stress localization located near the abutment of the cylindrical surfaces. Recommendations for the further improvement of the implant architecture are generated. © 2017 Author(s).Ministry of Education and Science of the Russian Federation, Minobrnauka: 218We hereby acknowledge the support of the Ministry of Science and Education of the Russian Federation, in accordance with the decree of the Government of April 9, 2010, No. 218, project number 03.G25.31.0234

Compression Deformation and Fracture Behavior of Additively Manufactured Ti–6Al–4V Cellular Structures

Corresponding research was carried out to assess if the porous structures with modified diamond-shaped lattice cells can provide better integrity of the constructions in the case of overloading. The aim of the study is designing the structures with high porosity for the biomedical applications (implants) having good load bearing capacity. Studied lattice structures are based on the modified tetrahedral beam-based cells with spherical reinforcements at the beam joints and variable beam diameter. Samples with a porosity of 50–80% were studied in present research. Structures were additively manufactured from a titanium alloy Ti–6Al–4V using SLM. Sample compression tests were carried out according to the ISO 13314 standard. Loading experiments were carried out and critical parameters extracted from the stress-strain curves. Finite element modeling was carried out for the analysis of the stress and assessment of the potential failure mechanisms. Corresponding hypothesis explaining the appearance of shear bands in porous structures under compression is formulated. Obtained results show that when the sample porosity rises from 50% to 80%, corresponding plateau stress decreases by 13 times, first maximum compressive strength decreases by 12 times, and compression offset stress decreases by 12 times, while the plateau end does not change significantly. The experiments revealed the barrel distortion of the samples geometry, which corresponds to the general knowledge how the friction between the solid compressing surfaces (anvils of the compression testing machine) and the lattice affects the sample deformation. Compression experiments also revealed the formation of shear bands during sample deformation. The stochastic nature of their development suggests that the main reason of shear bands appearing is the initial inhomogeneity of the boundary conditions of the experiment. Suggested modifications of the basic cells show a good potential for achieving regular beam-based lattice structures with high porosity and increased load bearing capacity. More experiments are needed for statistical analysis, and improvements of the loading experiments methodology for better failure mode analysis are planned for the future. © 2021 The Authors.The research was carried out within the state assignment of Ministry of Science and Higher Education of the Russian Federation, grant number 0836-2020-0020

Можливість посилення експлуатованих колон за рахунок регулювання залишкового напруженого стану

The article outlines the feasibility of regulating the residual stress state of reinforced welded I-beams. It is shown that the negative effect of the residual stress state can be eliminated by warming the edges of the belts or by surfacing the rollers. Compared to elements without regulation, the stability of the columns can be increased to 25%. The economic effect of regulation is achieved by saving material.В статье изложена целесообразность регулирования остаточного напряженного состояния усиливаемых сварных двутавровых колонн. Показано, что отрицательное влияние остаточного напряженного состояния можно исключить путем прогрева кромок поясов или наплавки валиков. По сравнению с элементами без регулирования устойчивость колонн может быть повышена до 25%. Экономический эффект от регулирования достигается за счет экономии материала.У статті викладена доцільність регулювання залишкового напруженого стану підсилюються зварних двотаврових колон. Показано, що негативний вплив залишкового напруженого стану можна виключити шляхом прогріву крайок поясів або наплавлення валиків. У порівнянні з елементами без регулювання стійкість колон може бути підвищена до 25%. Економічний ефект від регулювання досягається за рахунок економії матеріалу

Compression deformation and fracture behavior of additively manufactured Ti–6Al–4V cellular structures

Corresponding research was carried out to assess if the porous structures with modified diamond-shaped lattice cells can provide better integrity of the constructions in the case of overloading. The aim of the study is designing the structures with high porosity for the biomedical applications (implants) having good load bearing capacity. Studied lattice structures are based on the modified tetrahedral beam-based cells with spherical reinforcements at the beam joints and variable beam diameter. Samples with a porosity of 50–80% were studied in present research. Structures were additively manufactured from a titanium alloy Ti–6Al–4V using SLM. Sample compression tests were carried out according to the ISO 13314 standard. Loading experiments were carried out and critical parameters extracted from the stress-strain curves. Finite element modeling was carried out for the analysis of the stress and assessment of the potential failure mechanisms. Corresponding hypothesis explaining the appearance of shear bands in porous structures under compression is formulated. Obtained results show that when the sample porosity rises from 50% to 80%, corresponding plateau stress decreases by 13 times, first maximum compressive strength decreases by 12 times, and compression offset stress decreases by 12 times, while the plateau end does not change significantly. The experiments revealed the barrel distortion of the samples geometry, which corresponds to the general knowledge how the friction between the solid compressing surfaces (anvils of the compression testing machine) and the lattice affects the sample deformation. Compression experiments also revealed the formation of shear bands during sample deformation. The stochastic nature of their development suggests that the main reason of shear bands appearing is the initial inhomogeneity of the boundary conditions of the experiment. Suggested modifications of the basic cells show a good potential for achieving regular beam-based lattice structures with high porosity and increased load bearing capacity. More experiments are needed for statistical analysis, and improvements of the loading experiments methodology for better failure mode analysis are planned for the future.

CELLULAR STRUCTURE OF IMPLANTS

FIELD: medicine. SUBSTANCE: invention relates to additive technologies used for making implants, preferably, from titanium alloys. Cellular structure of implants is made in the form of volumetric grid with location of nodes on surface of spatial figures connected by jumpers. Spatial figure is hollow sphere, having wall limited by outer and inner spherical surfaces. In first diametric cross section of sphere there are first and second through holes having first common axis, in a plane orthogonal to said axis and at angle of 45° to first diametric cross-section there are third and fourth through holes having second common axis, in the same plane there are fifth and sixth holes having a third common axis which is orthogonal to the second common axis. Holes make main through channels. On surface of hollow sphere there are eight units arranged symmetrically relative to center of hollow sphere. Units have additional cells interconnected by additional channels. EFFECT: invention improves elastic characteristics of the implant. 1 cl, 11 dwg.Изобретение относится к области аддитивных технологий, применяемых для изготовления имплантатов, предпочтительно, из титановых сплавов. Ячеистая структура имплантатов выполнена в виде объемной решетки с расположением узлов на поверхности пространственных фигур, соединенных перемычками. Пространственной фигурой является полый шар, имеющий стенку, ограниченную наружной и внутренней сферическими поверхностями. В первом диаметральном сечении сферы выполнены первое и второе сквозные отверстия, имеющие первую общую ось, в плоскости, ортогональной этой оси и под углом 45° к первому диаметральному сечению, выполнены третье и четвертое сквозные отверстия, имеющие вторую общую ось, в той же плоскости выполнены пятое и шестое отверстия, имеющие третью общую ось, которая ортогональна второй общей оси. Отверстия образуют основные сквозные каналы. На поверхности полого шара имеется восемь узлов, расположенных симметрично относительно центра полого шара. В узлах выполнены дополнительные ячейки, сообщающиеся между собой дополнительными каналами. Изобретение позволяет улучить упругие характеристики имплантата.1 з.п. ф-лы, 11 ил

CELLULAR STRUCTURE OF IMPLANTS

The proposed invention relates to the field of additive techniques for use in manufacturing implants, preferably from titanium alloys. A cellular structure of implants is configured in the form of a volumetric lattice with an arrangement of nodes on the surface of spatial figures connected by struts. The invention is characterized in that a spatial figure is a hollow sphere having a wall delimited by an outer and an inner spherical surfaces, a first and a second through-openings are configured in a first diametral section of the sphere, said through-openings having a first common axis, a third and a fourth through-openings are configured in a plane orthogonal to said axis and at an angle of 45º to the first diametral section, said through-openings having a second common axis, a fifth and a sixth openings are configured in the same plane, said openings having a third common axis orthogonal to the second common axis, wherein the openings form main through-channels, eight nodes are arranged on the surface of the hollow sphere symmetrically relative to the centre of the hollow sphere. Additional cells are configured in the nodes, said cells communicating with one another by additional channels. The technical result of the proposed design of a cellular structure for medical implants is an improvement in elastic behaviour.Изобретение относится к области аддитивных технологий, применяемых для изготовления имплантатов, предпочтительно, из титановых сплавов. Ячеистая структура имплантатов выполнена в виде объемной решетки с расположением узлов на поверхности пространственных фигур, соединенных перемычками. Пространственной фигурой является полый шар, имеющий стенку, ограниченную наружной и внутренней сферическими поверхностями. В первом диаметральном сечении сферы выполнены первое и второе сквозные отверстия, имеющие первую общую ось, в плоскости, ортогональной этой оси и под углом 45° к первому диаметральному сечению, выполнены третье и четвертое сквозные отверстия, имеющие вторую общую ось, в той же плоскости выполнены пятое и шестое отверстия, имеющие третью общую ось, которая ортогональна второй общей оси. Отверстия образуют основные сквозные каналы. На поверхности полого шара имеется восемь узлов, расположенных симметрично относительно центра полого шара. В узлах выполнены дополнительные ячейки, сообщающиеся между собой дополнительными каналами. Изобретение позволяет улучить упругие характеристики имплантата.1 з.п. ф-лы, 11 ил