scholarly journals Torsional stability of thin-walled cylindrical shells filled with free-flowing aggregate

2021 ◽  
pp. 40-47
Author(s):  
Михаил Васильевич Петров ◽  
Борис Васильевич Михайлов ◽  
Екатерина Григорьевна Гоник
Keyword(s):  
Aluminum Alloy ◽  
Iron Powder ◽  
Cylindrical Shells ◽  
Rigid Wall ◽  
Critical Value ◽  
The Matrix ◽  
Thin Walled ◽  
The Moment ◽  
Torsional Stability ◽  
Angle Of Rotation

Экспериментами изучено влияние сыпучего заполнителя на устойчивость при кручении тонкостенных цилиндрических оболочек. Для исследования образцы изготавливались из алюминиевого сплава 3004 глубокой вытяжкой в матрице. Образцы закреплялись консольно к жесткой стенке, на свободный конец прикладывался крутящий момент. Испытывались пустые и заполненные железным порошком образцы. Нагружение образцов выполнялось ступенчато, порциями по 10Н вначале и при приближении к моменту потери устойчивости по 1Н, 0,5Н. На каждой ступени нагружения фиксировались крутящий момент и угол поворота свободного конца образца. Построены графики зависимости угла поворота от крутящего момента. Устойчивость образцов терялась в упругости. Вначале нагружения, на заполненных сыпучим заполнителем образцах, не происходит поворот сечений из-за препятствия сил трения заполнителя. Железный порошок увеличивает значение критического крутящего момента на 20-30%. Experiments have studied the effect of free-flowing aggregate on torsional stability of thin-walled cylindrical shells. For research samples were made of aluminum alloy 3004 deep hood in the matrix. The samples were fixed cantilever to a rigid wall, on torque was applied to the free end. Tested empty and samples filled with iron powder. The loading of the samples was carried out stepwise, in portions of 10N at the beginning and when approaching the moment of loss stability of 1H, 0.5H. At each loading stage, torque and angle of rotation of the free end of the sample. Graphs built the dependence of the angle of rotation on the torque. Stability of samples lost in elasticity. At the beginning of loading, on filled with bulk filler in samples, no rotation of sections occurs due to obstacle forces friction of the aggregate. Iron powder increases the critical value of torque by 20-30 %.

scholarly journals Influence of initial imperfections of thin-walled cylindrical shells with loose aggregate on their bending stability

2020 ◽  
pp. 47-53
Author(s):  
Михаил Васильевич Петров ◽  
Екатерина Григорьевна Гоник ◽  
Борис Васильевич Михайлов
Keyword(s):  
Iron Powder ◽  
Limit State ◽  
Cylindrical Shells ◽  
Critical Force ◽  
Numerical Calculations ◽  
Initial Imperfections ◽  
Type Indicator ◽  
Thin Walled ◽  
Special Stand ◽  
Initial Geometry

Экспериментально и теоретически исследовано предельное состояние при изгибе тонкостенных цилиндрических оболочек, имеющих начальные несовершенства геометрии. Изготовлены качественные образцы глубокой вытяжкой в матрице из листа и из трубы точением на токарном станке, имеющие геометрические несовершенства (толщины, диаметров). Материал образцов: алюминиевые сплавы 3004 и Д16Т. Перед испытанием образцы тщательно измерялись и обследовались на наличие дефектов. Изготовлен специальный стенд, к которому жестко одним концом крепились образцы, другой конец был свободным. На свободный конец прикладывалась ступенями поперечная сила до потери устойчивости. Испытывались пустые и заполненные железным порошком образцы. Фиксировались нагрузка и прогиб свободного конца образца индикатором часового типа ИЧ-10. Получены линейные зависимости прогиба от нагрузки, устойчивость терялась в упругости. Численные расчеты выполнялись в программном комплексе «Динамика-3». Для расчетов принимались идеальные образцы. Сопоставив критические нагрузки, полученные экспериментами и численными расчетами, судили о влиянии начальных несовершенств на предельное состояние. Численно рассчитанная критическая сила была всегда больше экспериментального значения. Начальные несовершенства образцов снижали критическую силу от 2,3% до 32,5%. У образцов с небольшими вмятинами в зоне потери устойчивости критическая сила уменьшилась в 1...2 раза. У заполненных железным порошком образцов критическая сила была больше до 40,5%, чем у пустых. The limit state for bending thin-walled cylindrical shells with initial geometry imperfections has been studied experimentally and theoretically. High-quality samples are made by deep drawing in a matrix from a sheet and from a pipe by turning on a lathe, which have geometric imperfections (thickness, diameter). The material of the samples is aluminum alloys 3004 and D16T. Before testing, the samples were carefully measured and examined for defects. A special stand was made, to which samples were rigidly attached at one end, while the other end was free. A transverse force was applied to the free end in steps until it lost stability. Empty and iron-powder-filled samples were tested. The load and deflection of the free end of the sample were recorded by an ICH-10 clock type indicator. Linear dependences of the deflection on the load were obtained; stability was lost in elasticity. Numerical calculations were performed in the Dynamics-3 software package. Ideal samples were taken for calculations. Comparing the critical loads obtained by experiments and numerical calculations, we judged the effect of initial imperfections on the limit state. The numerically calculated critical force was always greater than the experimental value. Initial imperfections of the samples reduced the critical force from 2.3% to 32.5%. For samples with small dents in the zone of loss of stability, the critical force decreased by 1..2 times. In iron powder-filled samples, the critical force was greater by up to 40.5% than in empty samples.

scholarly journals Experimental analysis of the effect of discrete aggregate on the bending stability of thin-walled cylindrical shells

2019 ◽  
pp. 157-164
Author(s):  
M V Petrov
Keyword(s):  
Iron Powder ◽  
Critical Stress ◽  
Cylindrical Shells ◽  
Superposition Principle ◽  
Critical Force ◽  
Critical Voltage ◽  
River Sand ◽  
Force Increase ◽  
Thin Walled ◽  
The Stability

The effect of a discrete aggregate on the bending stability of thin-walled cylindrical shells was studied. The samples for the study were made of aluminum alloy 3004 (temper H19). The samples were cantilevered; a vertical concentrated cross force was applied to its free end. Ten empty samples and ten samples 90% filled with iron powder were tested. The samples were loaded in stages by 10N, and when approaching the moment of buckling the samples were loaded by 1N or less. The force, deflection of the free end of the sample, and axial strain were recorded at each stage of loading. Displacement of the free end of the sample versus cross force diagrams is plotted. The buckling force was determined by the inflection point of the diagrams. The samples lost the stability in elasticity. The diagrams for the empty and filled samples for each series almost coincide until the loss of stability of the empty sample. This means that when the empty sample loses its stability, the buckle directed towards the center line is formed; and for the filled samples, the formation of buckles is prevented by the discrete material, therefore the critical force increased by 18.8%. The influence of discrete aggregate is considered on the basis of approximation [24] for tank trucks manufactured at the enterprise. The critical stress is calculated using the superposition principle, since the stability is lost in the elasticity. The critical stress for the filled tank is determined by the sum of the critical stress for an empty shell with the stresses created by the weight load and the hydrostatic pressure of the discrete filler. The calculation of critical stresses showed that for the pattern samples the influence of discrete filler is 8.3%, and for the full-sized tanks the influence of discrete filler on the value of the critical voltage is significant and amounts to 62%. We studied the effect of various discrete fillers on stability, such as river sand, iron and copper powders at different filling ratios of the samples. Due to an increase in powder density and filling volume, the value of the critical force increased. For the samples filled to 90% with the river sand had the critical force increase by 13.3%, while those filled with the iron powder had their critical force increase by 40.5%, the copper powder samples had an increase of the critical force by 43.1%.

Pinocytotic-Like Forms of Mitochondria From Rat Anterior Pituitary

1968 ◽  
Vol 26 ◽  
pp. 146-147
Author(s):  
Burton B. Silver
Keyword(s):  
Electron Micrographs ◽  
Conformational Changes ◽  
Anterior Pituitary ◽  
Dynamic State ◽  
Surrounding Cell ◽  
The Matrix ◽  
The Moment ◽  
Cell Medium ◽  
Sectioned Tissue ◽  
State Of Activity

Sectioned tissue rarely indicates evidence of what is probably a highly dynamic state of activity in mitochondria which have been reported to undergo a variety of movements such as streaming, divisions and coalescence. Recently, mitochondria from the rat anterior pituitary have been fixed in a variety of configurations which suggest that conformational changes were occurring at the moment of fixation. Pinocytotic-like vacuoles which may be taking in or expelling materials from the surrounding cell medium, appear to be forming in some of the mitochondria. In some cases, pores extend into the matrix of the mitochondria. In other forms, the remains of what seems to be pinched off vacuoles are evident in the mitochondrial interior. Dense materials, resembling secretory droplets, appear at the junction of the pores and the cytoplasm. The droplets are similar to the secretory materials commonly identified in electron micrographs of the anterior pituitary.

Effect of temperature on matrix multicracking evolution of C/SiC fiber-reinforced ceramic-matrix composites

2020 ◽  
Vol 39 (1) ◽  
pp. 189-199
Author(s):  
Longbiao Li
Keyword(s):  
Strain Energy ◽  
Ceramic Matrix Composites ◽  
Critical Value ◽  
Matrix Cracking ◽  
Interface Debonding ◽  
Matrix Composites ◽  
Temperature Dependent ◽  
Damage State ◽  
The Matrix ◽  
Sic Composites

AbstractIn this paper, the temperature-dependent matrix multicracking evolution of carbon-fiber-reinforced silicon carbide ceramic-matrix composites (C/SiC CMCs) is investigated. The temperature-dependent composite microstress field is obtained by combining the shear-lag model and temperature-dependent material properties and damage models. The critical matrix strain energy criterion assumes that the strain energy in the matrix has a critical value. With increasing applied stress, when the matrix strain energy is higher than the critical value, more matrix cracks and interface debonding occur to dissipate the additional energy. Based on the composite damage state, the temperature-dependent matrix strain energy and its critical value are obtained. The relationships among applied stress, matrix cracking state, interface damage state, and environmental temperature are established. The effects of interfacial properties, material properties, and environmental temperature on temperature-dependent matrix multiple fracture evolution of C/SiC composites are analyzed. The experimental evolution of matrix multiple fracture and fraction of the interface debonding of C/SiC composites at elevated temperatures are predicted. When the interface shear stress increases, the debonding resistance at the interface increases, leading to the decrease of the debonding fraction at the interface, and the stress transfer capacity between the fiber and the matrix increases, leading to the higher first matrix cracking stress, saturation matrix cracking stress, and saturation matrix cracking density.

scholarly journals Fracture Mechanical Analysis of Thin-Walled Cylindrical Shells with Cracks

Metals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 592
Author(s):  
Feng Yue ◽  
Ziyan Wu
Keyword(s):  
Fracture Mechanics ◽  
Tensile Stress ◽  
Failure Modes ◽  
Cylindrical Shells ◽  
Crack Tip ◽  
Mechanical Analysis ◽  
J Integral ◽  
Thin Walled Structures ◽  
Circumferential Tensile Stress ◽  
Thin Walled

The fracture mechanical behaviour of thin-walled structures with cracks is highly significant for structural strength design, safety and reliability analysis, and defect evaluation. In this study, the effects of various factors on the fracture parameters, crack initiation angles and plastic zones of thin-walled cylindrical shells with cracks are investigated. First, based on the J-integral and displacement extrapolation methods, the stress intensity factors of thin-walled cylindrical shells with circumferential cracks and compound cracks are studied using linear elastic fracture mechanics, respectively. Second, based on the theory of maximum circumferential tensile stress of compound cracks, the number of singular elements at a crack tip is varied to determine the node of the element corresponding to the maximum circumferential tensile stress, and the initiation angle for a compound crack is predicted. Third, based on the J-integral theory, the size of the plastic zone and J-integral of a thin-walled cylindrical shell with a circumferential crack are analysed, using elastic-plastic fracture mechanics. The results show that the stress in front of a crack tip does not increase after reaching the yield strength and enters the stage of plastic development, and the predicted initiation angle of an oblique crack mainly depends on its original inclination angle. The conclusions have theoretical and engineering significance for the selection of the fracture criteria and determination of the failure modes of thin-walled structures with cracks.

Buckling behaviors of thin-walled cylindrical shells under localized axial compression loads, Part 1: Experimental study

2021 ◽  
Vol 166 ◽  
pp. 108118
Author(s):  
Peng Jiao ◽  
Zhiping Chen ◽  
He Ma ◽  
Peng Ge ◽  
Yanan Gu ◽  
...  
Keyword(s):  
Experimental Study ◽  
Axial Compression ◽  
Cylindrical Shells ◽  
Thin Walled
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