Bar Of Cross Section Research Articles

An overview of assessment and retrofit of corroded reinforced concrete structures

The corrosion of steel in reinforced concrete structures surely represents the main form of degradation. Carbonation and chloride attacks lead to a loss of performance during the service life of the structure. The reduction of the cross section of the steel bars and the formation of corrosion products lead to reduction of bond between steel and concrete, to concrete cover cracking and spalling, to reduction of concrete cross section resulting in a reduction of structural capacity. The structural engineer needs to face corrosion starting from the design phase, however in presence of real existing structures the first step is the evaluation of corrosion level and the evaluation of actual global structural capacity. The most critical corrosion involves the stirrups, being the most exposed steel elements, yielding to brittle failures in the most stressed elements, generating unexpected structural collapses. In particular in seismic conditions, the structure is not able to exploit its ductility, since limited ductile failures (i.e. combined shear/flexure) could occur. The last phase of the study is on the structural retrofit by using High Performance Concretes. Such materials allow recovering some of the bending capacity of the structural elements and can increase their ductility, reducing dramatically the vulnerability of the structures. This is particular true for seismic vulnerability, since the strength recover is partial if the structural retrofit intervention is designed to have a negligible impact on the structure. In fact the considered intervention is aimed to recover the original geometry of the elements with a reduced cost and impact on the fruition.

Waveguide analysis for ultrasonic medical instruments (comparison of different methods)

Transition matrices are derived on the basis of some analytical solutions for a number of waveguides. Initial parameters method is used to analyze the waveguide longitudinal oscillations. This paper contains a comparative analysis of different types of concentrators. The waveguide design scheme presents a straight bar of variable cross-section with different boundary conditions. For given concentrator arrangements, the amplitude axial displacements and longitudinal forces in the ultrasonic medical instrument (UMI) are calculated for a certain excitation frequency. Numerical method for calculation of eigenfrequencies and eigenmodes of the ultrasonic medical instrument (UMI) waveguide is presented. Analysis of the cantilever straight-line concentrator based on the methods of transition matrices and numerical integration by the Runge-Kutta method are under comparison. Sufficient agreement of the results is demonstrated.

Effect of stress concentration in a beam of rectangular cross section in the region of attachment of the longitudinal efforts

Relevance. To ensure the safe operation of buildings and structures, it is necessary to more accurately determine the stress-strain state (SSS) of structural elements, to identify areas of stress concentration. The distribution of stresses in the region of the fastening bars in three-dimensional formulation is relatively little studied. In these areas, there may be significant stress concentrations that contribute to the occurrence and development of cracks and splits, which are a harbinger of destruction. The development of modern methods of calculation, software systems and the growth of computing capabilities allow refining the design scheme: to move from one-dimensional to two-dimensional calculation scheme, from two-dimensional to three-dimensional calculation scheme. All this makes it possible to more accurately assess the SSS of structural elements and structures, to identify areas of stress concentration, as well as to investigate the effect of the Poisson's ratio on the stress concentration. Methods of research. It is noted that cracks and breaks in the edges under the influence of longitudinal loads occur in the rods (racks) of square cross-section. Three-dimensional elements based on the spline version of the finite element method and the LIRA computational complex are used to estimate the stress-strain state. The spline finite element method, thanks to the synthesis of the idea of parametrization and the finite element method (FEM) with cubic approximation of all three required variables within each element, allows obtaining consistent three-dimensional finite elements. On the basis of the mentioned methods and complexes, numerical studies of the stress concentration in the bars of square and rectangular cross-sections fixed at one end and perceiving the tensile forces at the other end are performed. Conclusions. It is found that in the angular points of the cross section in the area of fastening of straight bars, perceiving axial tensile forces, there are stress concentrations. Away from the mounting area of the bar, the voltages are aligned. By increasing the Poisson's ratio, the stress concentration increases faster than at low values. The transition from a onedimensional design model to a two-dimensional one, and even more so to a three-dimensional model allows to determine the stress concentration, both in plan and in thickness. Information about the concentration of stresses in elements of structures will allow designers to more accurately design structures and facilities, and the operators to promptly identify the defective region.

Residual Stress Analysis of Elliptical Cross Section bar of Linear Work-Hardening Material under Torsional Loading

This paper deals with the analytical solution of the torsional springback problems of bars of elliptical cross-section of linear work-hardening materials. Using the deformation theory of plasticity, a numerical scheme based on the finite difference approximation has been proposed. The growth of the elastic-plastic boundary and the resulting stresses while loading, and the torsional springback and the residual stresses after unloading are calculated.

Springback analysis of hollow rectangular bar of linear work-hardening material

A theoretical analysis of the springback of hollow rectangular cross-sectional bars of linear work-hardening materials under torsional loading has been carried out. By using the deformation theory of plasticity, a numerical scheme has been prepared which determines the elasto-plastic boundary in addition to springback in the bars. Finally, an analytical generalised expression relating the angle of twist and twisting moment and residual angle of twist per unit length for bars under plastic torsion is obtained.

Exhumation of pearls: A schematized drawing and its unconscious depth

Abstract The article presents and discusses a portrait by the author of his mother. This appears as a young woman of the 1950s who is wearing a string of pearls. The portrait, however, is first a motif that has enabled the development of a Harris Matrix: a method of recording the results of archaeological excavations stratigraphically. This idea has resulted in the drawing’s elusive depth being transposed as cross-sectional bars of actual physical depth. Relative depths of sections of the drawing have been determined by the lengths of time involved in their manufacture. The article contains an explanation of how a matrix can be constructed from these circumstances and provides a likely visual example. The second section of the article explores a personal narrative concerning the portrait, and speculates on possible psychodynamic unconscious motives. A key concept is that of jouissance as theorized by Jacques Lacan. This concept links the author’s tendency to enjoy a rational problematic approach to drawing, as evidenced in the use of the Harris Matrix, and investigation of more psychical questions of such enjoyment’s origin. Finally, a more literal linking metaphor is to have unearthed from the portrait the figure’s pearl necklace, which had become obscured by the cross-sectional bars of depth.

Analysis of cracked bars with rectangular cross-section and isotropic coating layer under torsion

The solution to problem of a Volterra-type screw dislocation in a rectangular cross section bar with an isotropic coating is first achieved by means of a finite Fourier cosine transform. The bar is under axial torque which is governed by Saint-Venant torsion theory. The series solution is then derived for warping function and stress fields in the rectangular cross section with an isotropic coating. The dislocation solution is employed to derive a set of Cauchy singular integral equations for the analysis of smooth cracks. The solution of these equations is used to determine the torsional rigidity of bar and the stress intensity factors for the crack tips. Finally, several examples are presented to show the accuracy and efficiency of the dislocation technique in Saint-Venant torsion problems.

Effects of tungsten on the microstructure and on the abrasive wear behavior of a high-chromium white iron

In the present study, systematic additions of tungsten (up to 10.3wt%) and their effects on the microstructure, hardness, microhardness, and abrasive wear of 17%-Cr white iron was analyzed. Six high-chromium iron alloys with different tungsten additions were melted in an open induction furnace and cast into sand molds to obtain 50-mm×25-mm cross-sectional bars. The alloys were characterized by optical and electronic microscopy, energy dispersive spectroscopy, and X-ray diffraction. The bulk hardness and microhardness of the different phases of the microstructure (matrix and carbides) were measured in the as-cast conditions and after a destabilization heat treatment at 950°C for 45min. Abrasive wear resistance tests were undertaken for the different irons according to the ASTM G65 standard in both as-cast and heat-treated conditions. The results show that, when tungsten is added up to 4wt%, it partitions either to the matrix or to the M7C3 carbide, causing a moderate strengthening in both phases and contributing to an increase in the overall hardness of the alloys. When tungsten additions are higher than 4%, the presence of harder M2C and M6C carbides is prevalent in the microstructure and the bulk hardness of the alloys increased. The wear behavior was found to be consistent with the hardness values; an increase in the wear resistance occurred as the tungsten additions were increased. However, such an increase in the wear resistance is not considerable (just 13% higher for 10.3% tungsten addition to the iron). Tungsten was found not to have an important effect on the secondary carbide precipitation during heat treatment, and the wear behavior had the same trend as that in the as-cast alloys. The results are discussed in terms of the partition of tungsten to the carbide and matrix and on its tendency to form harder M6C-type carbides.

Nondestructive assessment of corrosion of reinforcing bars through surface concrete cracks

Degradation of reinforced concrete (RC) structures is a serious safety problem affecting all industrialized countries, and economical aspect of this problem cannot be neglected. One of the main reasons for the degradation of RC is the corrosion of steel reinforcing bars as a result of concrete cover cracking and bar cross section reduction. As a consequence, the structural capacity of reinforced concrete elements decreases progressively as degradation develops. The use of nondestructive testing (NDT) and/or analytical formulation can represent high-quality and rapid methods to evaluate the corrosion penetration of bars, and provide a useful parameter to design a retrofit. This paper presents an additional tool that can be used to evaluate and assess the vulnerability of existing structures in terms of determination of bar cross section lost. This can be accomplished by calculating reinforcing bar cross section loss due to corrosion by measuring external crack widths of the concrete cover by using simple charts and formulas. Predictions were obtained by using two analytical models, developed by the authors. Their predictions have been satisfactorily compared to both the literature and novel experimental results, and compared to previous empirical models available in scientific literature. The experimental results were obtained by corroding real scale concrete specimens reinforced by using smooth and ribbed bars (according to old and modern building codes) using 3.5%wt sodium chloride solution and an imposed current.

Hardness, tensile and impact behaviour of hot forged aluminium metal matrix composites

Tensile and impact testing and hardness measurements were carried out on hot forged aluminium metal matrix composites to understand the influence of alloying element and forming process on their mechanical properties. Pure aluminium preforms together with its composites such as Al4TiC, Al4Fe3C, Al4Mo2C and Al4WC were prepared using a suitable die-set assembly on a 1MN capacity hydraulic press. Sintering operation was carried out in an electric muffle furnace at the temperature of 1200°C for a holding period of 1h. Immediately after the sintering process the cylindrical preforms were hot deformed in to a square cross-section bar of size 24mm×24mm×60mm for preparing of tensile test and impact test specimens as per the respective ASTM standards. Standard tensile and impact test specimens were machined from the forged square rods. Standard ASTM procedure was followed to conduct the aforementioned mechanical testing. Further, microstructural studies on the hot forged square cross-section bar and hardness measurements were obtained and analysed.

Inclusions inside a bounded elastic body undergoing anti-plane shear

As a problem of theoretical and practical interest, anti-plane shear is mathematically simple and prone to analytical solutions. However, almost no analytical solutions have been reached for the problem of inclusions embedded in a bounded domain and undergoing anti-plane shear eigenstrain. In this work, using some techniques of complex analysis and integral formulae derived previously, Eshelby’s anti-plane shear problem of inclusions in a finite isotropic elastic body is solved analytically. The cross-section of the inclusion with a prescribed uniform anti-plane eigenstrain can be of polygonal shape or any smooth one characterized by a Laurent polynomial, while the cross-section of the prismatic bar submitted to displacement or traction boundary conditions is required to be smooth. In particular, in the case where the cross-section of the prismatic bar and the one of the inclusion are both circular, explicit analytical expressions are derived for the strain and stress fields in different ways. Some examples are provided to illustrate how to implement the solutions based on the conformal maps.

Effect of bar cross-section and female housing material on retention of mandibular implant bar overdentures: A comparative in vitro study.

Aim:The aim of this study is to evaluate the effect of different cross-sections of bar connecting two implants on the retention of mandibular overdentures with Hader clip or lined with heat-cured resilient liner as a housing material. The retentive values after simulated 1.5 years of service were also recorded.Materials and Methods:Edentulous mandibular acrylic model was constructed with two dummy implants located in the canine region and connected with cast bar assembly. According to bar cross-section and anchoring method, four groups (n = 10) of identical overdentures were used as Hader bar/clip group (HCG), Hader bar/silicone liner female housing group (HSG), oval bar/silicone liner female housing group (OSG), and round bar/silicone liner female housing group (RSG). Each overdenture sample was subjected to simulated wear up to 2740 manual insertions/separations. The mean retentive forces were measured at the baseline and after every 500 insertions. The data were statistically analyzed using one-way analysis of variance.Results:The present study demonstrated that all bar cross-sections showed a significant difference at the baseline (P < 0.05), but HSG showed greater initial retention compared to HCG, OSG, and RSG. OSG showed a significant higher retention after 2740 insertions (simulated five insertions/day).Conclusions:Within the limitation of this in vitro study and for a similar period of service, heat-cured silicone female housing for Hader bar could maintain greater retention for two-implant-retained overdentures than provided by conventional plastic clip after 1.5 year. The oval bar recorded reasonable initial retention values and maintained these values for 1.5 years of service.

Study of the Variability of the Machinability along the Cross Section of Ductile Iron Produced by Continuous Casting

In industry, the increase in the search for new materials is related to the cost and to the strength to weight ratio. In an effort to achieve these requirements new materials with low density and similar strength are employed or the resistance of traditional materials are increased by the addition of alloying elements or heat treatments. The choice usually depends on the mechanical and thermal properties and other aspects, such as manufacturing costs, recyclability, customer acceptance and machinability. Cast irons usually offer good machinability and low production cost, but long bars produced by continuous casting may present variability in their properties, including machinability along their cross sections. This is particularly true in bars with large cross sections. This work evaluates the behavior of the machining torque and surface roughness along the cross section of rectangular bars of nodular cast iron produced by continuous casting in slot-milling operation. It was found that the pearlite microstructure of the matrix and the mechanical strength contributed to the highest machining torque presented by the intermediate and core regions, but they did not affect the surface roughness significantly.

Finite element modeling of operation for thin-walled open cross section bars to analyze plate-rod systems

We solve the problem of increasing the accuracy of finite-element analysis for the strains of thin-walled open cross section bars eccentrically reinforcing the flat sheet.

Longitudinal vibrations of a bar with incipient transverse cracks

The simplest model of longitudinal vibrations of a bar with incipient transverse cracks is considered under the essential assumption that the crack size is small compared with the bar cross-section area and the difference between the mode shapes of the bar with incipient cracks and the undamaged bar is small. The different manifestation of cracks in the phases of extension and compression strains is taken into account. The natural vibration frequencies and the crack coordinates and dimensions are determined from experimental values of natural frequencies.

Experimental verification for a probabilistic model of fibers distribution along a reinforced concrete bar

A probabilistic model developed by the authors, of the fibers distribution in a reinforced concrete element has been verified in a series of tests described in this paper. The tests comprised twelve square cross-section bars made of fiber reinforced concrete with standard deformed rebars of different diameters, located at their center, as well as three specimens without conventional reinforcement. Each specimen was sawed into equal slices, where the width of each slice was equal to the length of a single fiber, and the fibers were counted. The statistical analysis included calculation of the average value and standard deviation of a non-dimensional variable, defined as the ratio between the actual and average volumes of steel, that of the rebars and of the steel fibers, in a typical segment of the bar. It was shown that there is a good agreement between the linear prediction of the standard deviation assumed by the model and the values obtained from the statistical analysis of the fibers count. Such assumption is not trivial and the empirical results prove its validity, which was not obvious prior to the tests. A good agreement was also obtained between the cumulative distribution functions predicted by the model and obtained from the count.

Effect of continuous induction annealing on the microstructure and mechanical properties of copper-clad aluminum flat bars

Copper-clad aluminum (CCA) flat bars produced by the continuous casting–rolling process were subjected to continuous induction heating annealing (CIHA), and the effects of induction heating temperature and holding time on the microstructure, interface, and mechanical properties of the flat bars were investigated. The results showed that complete recrystallization of the copper sheath occurred under CIHA at 460°C for 5 s, 480°C for 3 s, or 500°C for 1 s and that the average grain size in the copper sheath was approximately 10.0 μm. In the case of specimens subjected to CIHA at 460–500°C for longer than 1 s, complete recrystallization occurred in the aluminum core. In the case of CIHA at 460–500°C for 1–5 s, a continuous interfacial layer with a thickness of 2.5–5.5 μm formed and the thickness mainly increased with increasing annealing temperature. After CIHA, the interfacial layer consisted primarily of a Cu9Al4 layer and a CuAl2 layer; the average interface shear strength of the CCA flat bars treated by CIHA at 460–500°C for 1–5 s was 45–52 MPa. After full softening annealing, the hardness values of the copper sheath and the aluminum core were HV 65 and HV 24, respectively, and the hardness along the cross section of the CCA flat bar was uniform.

О рациональном распределении пористости при кручении бруса прямоугольного поперечного сечения

О рациональном распределении пористости при кручении бруса прямоугольного поперечного сечения

Springback analysis of channel cross-sectioned bar of work-hardening materials under torsional loading

Purpose The purpose of this paper is to deal with the springback problems of channel cross-section bars of linear and non-linear work-hardening materials under torsional loading. Using the deformation theory of plasticity, a numerical scheme based on the finite difference approximation has been proposed. The growth of the elastic-plastic boundary and the resulting stresses while loading, and the springback and the residual stresses after unloading are calculated. Design/methodology/approach The numerical method which has been described in this paper for obtaining the solution of elasto-plastic solution can also be used for other sections. The only care that needs to be taken is to decrease the mesh size near points of stress concentration. The advantage of this technique is that it automatically takes care of all plastic zones developing over the section at different loads and gives a solution satisfying the elastic and plastic torsion equations in their respective regions. Findings As expected, elastic recovery is found to be more with decreasing values of n and λ. The difference in springback becomes more and more with increasing values of angle of twist. The material will approach an elastic ideally plastic behavior with increasing values of λ and n. Originality/value It seems that no attempt has been made to study residual stresses in elasto-plastic torsion of a work-hardening material for a channel cross-section.

Development and application of a temperature measurement device using the tool-workpiece thermocouple method in turning at high cutting speeds

This work aims to study the functionality of a device made to establish electrical signal continuity in the tool-workpiece thermocouple circuit in turning of electrical conductive materials under high cutting speeds, and thus allows the acquisition of the electromotive force of the system. This electromotive force is correlated with the chip-tool interface temperature and can be used for the machining process control. The device used three brushes made of aluminium alloy as contact elements on the polished cross section of the machined bar that is close to its centre. Its main advantage is its ability to replace the toxic mercury, although it is an excellent conductor for this type of thermocouple circuit. Besides, it allows the employment of more severe machining conditions, without the need of changing the lathe’s original geometric features. The functionality of this device was evaluated by measuring the cutting temperature (Tc) in turning different aluminium alloys, after calibration of the tool-workpiece thermocouple system. The machining tests followed a full 2k factorial design and a central composite design (CCD), and the results were analysed with multiple regression, response surface, gradient level and vector curve methods, having as input variables (xi) the mechanical strength of the work material (alloy), cutting speed (Vc), depth of cut (doc), feed rate (f) and lubrication and cooling condition (dry, flood cooling and minimum quantity of cutting fluid (MQF)). The results showed that the three-brush device, within the cutting conditions investigated and the material’s hardness, allowed one to obtain the cutting temperature values (Tc) consistent with those found when turning aluminium alloys. The effects of the independent variables (Material strength, Vc, doc, f and Lubricant) on the chip-tool interface temperature were also quantified.