Round Steel Bars Research Articles

Creep Damage Process and Rupture Time Prediction Methods of 2.25Cr-1Mo Steel Round Notch Bar Specimens

Creep damage preferentially progresses at stress concentration portion, where stress gradient exists under multiaxial stress state, in high temperature components. Therefore it is necessary to clarify creep damage evolution process and to establish a rupture time prediction method under multiaxial stress state. In this study, creep tests using plane specimens and four kinds of round notch bar specimens with different notch radius (notch tip radius 0.1mm(R0.1), 0.5mm(R0.5), 2.0mm(R2.0) and 4.0mm(R4.0)) on a 2.25Cr-1Mo steel were carried out. Rupture times of notch specimens were much longer than those of plane specimens under the same nominal stress indicating notch strengthening effect. Measured void number density on the notch root section indicated higher value at around notch surface for R0.1 and R0.5 specimens, while it was higher at around specimen center for R2.0 and R4.0. These distribution patterns corresponded to those of the maximum stress and the triaxiality factor of the notch specimens. Although, creep rupture times of notch specimens were not able to be predicted by using the stress or strain at the representative point on the notch root section, they were well predicted based on the area average damage concept, especially by considering selected damage area for R0.1 and R0.5 specimens.

Design of manually operated multiple-seed planting machine for an Ethiopian environment

The advancement of technology has been influenced and enhances the production rate and quality of industrial and agricultural products. This study aimed to design and manufacture portable and multiple seed planting machines from locally available materials. The paper deals principally with the design and manufacturing process of the seeder machine. The design feature considers the geometrical components, driving power determination, and stress and forces Analysis of each part. Pro-Engineer and solid work software were used for part details and assembly drawing. Materials were selected based on functionality, durability, cost, and local availability. Hence, Sheet metal steel was used for the fabrication of the seed and fertilized boxes, seed, and fertilizer metering disc were fabricated from polyvinylchloride (PVC) and the power transitions elements like transitions shafts and gears also fabricated from round steel bar. The seeder machine was assembled by the permanent joining of the frame (Arc welding), and the remaining components were bolted to each other in their places. Experimental tests have been performed to evaluate the performance and functionality of the seeder. It was observed that the machine had been put (dropped) the seed within the design space gap between the consecutive plants and the required amount of fertilizer were placed with the designed depth.

Buckling-restrained steel bar damper for spine frame system

This paper presents an experimental investigation on buckling-restrained steel bar dampers used at the lower sides of a spine frame. The dampers are mainly composed of round steel bar cores restrained by round steel tubes, and additional components called supporters that provide the lateral support against flexural buckling of the round steel tube. One characteristic of the proposed damper is that its buckling length can be controlled by using supporters. Cyclic loading tests were conducted on 10 scaled specimens to assess the functionality and energy dissipation performance of the proposed damper. The test specimens differed mainly with regard to the number of supporters, number of contraction allowance zones, type of connection to the base beam, and damper length. The performance of the damper was extensively discussed base on the cyclic behavior of the different specimen configurations and the mechanical performance of the different damper components. Furthermore, the supporter connection was assessed via collapse mechanism analysis to determine strength requirements. The test results revealed the optimal configurations, the functionality, and the plastic deformation capacity of the proposed system.

A Deformation History-Based Approach for Ultra-Low Cycle Fatigue Damage Evaluation of Steel Structures

Ultra-low cycle fatigue (ULCF) damage is one of the main failure modes of steel structures when subjected to intense earthquake action, such as near-field action. However, existing ULCF evaluation methods are based on the plastic strain history of structures, which requires fine numerical simulation and causes high calculation cost. In order to improve and simplify the ULCF evaluation process for steel structures, a new damage index based on the structure deformation history was proposed in this paper, with the application of structure life curve and Miner’s rule. Two types of steel components, notched round steel bar and steel pier, were employed as the research objectives to verify the accuracy of proposed damage index. The predicted ULCF life was compared with the results of tests and finite element simulations, which showed that the application of damage index was of acceptable accuracy. Compared with the traditional plastic strain history-based ULCF evaluation methods, the advantage of proposed damage index is that ULCF life of a given steel structure can be determined quickly according to the loading condition once its life curve is realized, thus eliminating the cumbersome numerical simulation process.

Bolted beam-to-column connection with buckling-restrained round steel bar dampers

In the design of steel building frames, comprehensive consideration is required to determine beam-to-column connections because their characteristics largely influence the performance of the whole frame. Recent studies by some researchers have investigated the application of dampers to bolted beam-to-column connections, where the dampers are often positioned between the bottom beam flange and the column. This study investigates the application of buckling-restrained round steel bar dampers to bolted beam-to-column connections. The configuration of the proposed connection and its design method are first described. Then, cyclic loading tests of six specimens are presented to clarify the structural performance of the proposed connection. The hysteretic behavior is largely influenced by the configuration of the damper, such as bar length, shank diameter, and damper position. Furthermore, finite element analyses of the damper and connection models are demonstrated for the detailed examination of their plastic behavior characteristics such as the spiral buckling deformation of the bar. The ratio of the beam shear force acting on the dampers is discussed based on the analysis results of the connection model.

Stress state and life property of Mod.9Cr-1Mo steel round bar notch specimen under creep-fatigue condition

Stress state and life property of Mod.9Cr-1Mo steel round bar notch specimen under creep-fatigue condition

New types of steel-FRP composite bar with round steel bar inner core: Mechanical properties and bonding performances in concrete

A steel-FRP composite bar (SFCB) combines the advantages of both fiber-reinforced polymer (FRP) and steel rebars. This paper introduces production techniques of the newly-developed SFCB with a round steel bar inner core. Then, based on the factory-produced SFCB, the mechanical properties of SFCBs under tensile tests are evaluated, and the bonding performances of SFCBs in concrete are tested and analyzed. The experimental and analytical results indicate that the tensile performances of these new types of SFCBs with a round bar inner core compare favorably with those of SFCBs containing a ribbed bar inner core. The SFCBs had bond strengths between round and ribbed rebars, and the rebar diameter and surface treatment are key factors influencing the bond strength of SFCB-concrete interface. Besides, the bond-slip behavior of SFCB-concrete specimens can be predicted by improving the bonding models of FRP bars.

Concept and behaviour of miniature bar-typed structural fuses with eccentricity

Miniature structural fuses made from round steel bars, have been increasingly investigated and applied because they can be easily replaced and have a low cost. In this paper, a miniature bar-typed structural fuse with eccentricity (MBFE) was proposed. The yielding portion in the central energy dissipation core was made into a circular segment cross-section, leading to an initial eccentricity. A total of 6 specimens were tested under reversal cyclic loadings with the test parameters, i.e., the eccentricity, the cross-sectional shapes of the yielding portions and the existence of Teflon pads. A simplified analytical model was developed to analyze the MBFE. The results show that the specimens exhibit a satisfactory seismic performance. The initial eccentricity leads to slight fluctuations in the hysteretic curves when the MBFE is under compression and increments in the compressive strength of the MBFE. The simplified analytical model, considering the eccentricity effect, can be adopted to estimate the envelope curve of the MBFE.

Research on the material properties of prestressed concrete girder bridge after exposed to fire

The factors such as maximum temperature, duration, diffusion condition and concrete bursting at high temperature increase the difficulty of obtaining material properties by using temperature. In order to quickly obtain the real performance parameters of the materials of the pre-stressed concrete beam bridge in the post-disaster bridge evaluation, the appearance classification and material test of 32 hollow slabs demolished after the fire of the existing beam bridge in a highway were carried out. The relationship between the commonly used testing indexes and the properties of materials is obtained by measuring the properties of materials after fire. The applicability of these indexes is verified by the ultimate bearing capacity test and finite element simulation. The results show cracking and spalling of concrete at high temperature not only results in significant loss of section, but also significantly reduces the strength of concrete and prestressing steel strand in this area, which leads to the reduction of bearing capacity. When the spalling depth of concrete exceeds 2/3 of the net protective layer of steel strand after overfire, the reduction coefficient of compressive strength and tensile strength of pre-stressed steel wire reaches 0.7, which will seriously affect the ultimate bearing capacity. The normal plain round steel bar can be deviated safely to the design standard value when calculating the ultimate bearing capacity of the structure. The ultimate bearing capacity of the prestressed hollow beam after fire is analyzed by using the reduction relationship between the conventional inspection indexes and the material properties, and the finite element simulation, so as to meet the engineering precision.

Computational Model of Heat Conduction in the Steel Round Bar Bundle

Computational Model of Heat Conduction in the Steel Round Bar Bundle

Influence of Tool Feed Conditions on Surface Integrity in Roller Burnishing with Rolling and Sliding Effects

The influence of tool feed conditions on the burnished-surface integrity obtained by roller burnishing, which can generate the sliding effect, adding to the rolling effect at burnishing point, is addressed. A JIS SCM420 steel round bar was used as the workpiece. The surface integrity was improved by feeding the roller in the same direction with the sliding effect and by decreasing the tool feed rate. A better surface was achieved when the roller was fed in the opposite direction to the feed direction of the turning tool in a preceding process of the burnishing.

Lathe boring operation on ASTM A304 steel parameter optimization using response surface methodology

ABSTRACT This paper presents the outcome of a study on the effect of the machining conditions on some performance parameters during dry and hard boring of ASTM A304 low alloy steel round bar with tungsten-carbide insert using a 3-level factorial design of experiment-based response surface methodology. It involved modelling, prediction and optimisation of the performance parameters subject to constraints on variation of the machining conditions. Within the limits defined by levels of the machining, the performance parameters were randomly determined in 27 runs of boring experiments. These experiments, which were performed on a D360 x 1000HS excel lathe machine, serial no J320581, involved dry and hard boring of 27 ASTM A304 low alloy steel specimen work-pieces using tungsten-carbide inserts at different levels of low, medium and high as specified for the machining conditions. The data analysis was performed using Design Expert software version 9.0.6.2 to model, predict, and to obtain the optimal machining conditions, and the corresponding performance parameters. The study revealed the control factors to have varying effects on the response variables of which the prime factor is the cutting speed, for the tool wear and cutting temperature, and depth of cut, for the material removal rate. Hence, it is recommended that the obtained values of these factors should be adopted for optimal machining of the aforementioned material.

Features of the Design of Steel Frame Structures in India for Seismic Areas

This article is devoted to the analysis of one of the most common structural designs of the steel frame of small spans, currently used in India in construction and reconstruction for seismic areas. This scheme constructively involves the implementation of the main bearing elements - bolts and columns - in the form of a spatial truss box section. At the same time, rather simple rolling profiles from small-sized corners are used, as well as a round steel bar. The studies performed by the authors were carried out using the finite element method based on the national design computing complex SCAD for Windows. The loads, as well as the geometrical characteristics of the profiles, were taken according to the current building standards of India. Based on the results of the analysis, a number of recommendations were formulated to improve the efficiency of the considered design scheme for seismic effects of varying intensity.

Buckling-restrained brace using round steel bar cores restrained by inner round steel tubes and outer square steel tube

This study proposes a buckling-restrained brace (BRB) which is composed of round steel bar cores restrained by inner round steel tubes and an outer square steel tube. One advantage of using the round steel bar cores against the steel plates and tubes is that the bar-ends can be connected to the structural members using screw-joints. The cyclic loading tests were conducted on two test specimens to examine the hysteretic performance of the proposed BRBs. Test results revealed the applicability, restraining capacity, and end-coupler performance of the proposed brace. With an increase in the number of contraction allowance zones, efficacy and performance of the brace became more satisfactory. Furthermore, a theoretical method for designing the proposed BRB in a simplified and optimal way is discussed. For the creation of the design guideline, the braces were analyzed comparatively over a wide range of sections, lengths, and different load conditions, which are most suitable for low to mid-rise buildings. It was found that the design is governed by the heaviest components of the brace, and that the pin connection to the frame was a key component for optimal design.

Stress corrosion cracking behavior of warm forged 316L stainless steel at different orientations

Stress corrosion cracking (SCC) behavior of ∼20% warm forged 316L stainless steel (SS) round bar was evaluated for different cracking orientations relative to the applied deformation in hydrogenated and oxygenated high purity water at 325 °C. Different SCC crack growth rates (CGRs) obtained at three orientations demonstrates that the L-R orientation where cracking occurred in the plane of deformation has the highest SCC susceptibility, while the C-L orientation where cracking was oriented to run along the forging direction has the lowest SCC susceptibility. The anisotropic cracking behavior of warm forged 316L SS at different orientations, which is prominent in hydrogenated water, depends highly on the distribution of lamellar plastic strains that are produced during deformation in different planes.

Residual Stresses in Elastoplastic Bending of Round Bar

Elastoplastic deformation on the presses and high-temperature heating of the steel sheet cause the large residual stresses in the sheet’s and bar’s wall. The technological operations of the obtaining of metal products, their shape and linear dimensions strongly affect on the distribution within the metal and the maximum values of residual stresses. The uneven cooling of various parts of the sheet and bar, obtained by bending, stamping and forging, also leads to the large residual stresses inside the metal. The greatest residual stresses occur in the weld area, where there is a strong heterogeneity of mechanical and physical properties of the metal due to uneven heating and cooling. Below the new analytical method for calculating of the residual stresses of a round steel bar in the elastoplastic bending is obtained. This method takes into account the diameter of the bar, as well as the modulus of elasticity, the yield strength and the hardening modulus of steel’s bar.

Fire Resistance of the Rafter Used in the Steel Portal Frame

This paper presents an analysis of the main member of a steel frame in a fire situation. The authors of this article used prescriptive rules and simple calculation models to present an impact of the roof bracing on the fire resistance of a rafter. Designers often have problems with the fire protection of the roof bracing made of steel round bars (Ø). This article presents a solution to this problem.

Analysis of Thermal Radiation in the Heating of Steel Round Bar Bundles

Analysis of Thermal Radiation in the Heating of Steel Round Bar Bundles

Retardation of Fatigue Crack Growth in Rotating Bending Specimens with Semi-Elliptical Cracks

This work investigates overload-induced retardation effects for semi-elliptically cracked steel round bars. The specimen geometry equals the shaft area of a 1:3 down-scaled railway axle and the material is extracted from railway axle blanks made of EA4T steel. Rotating bending tests under constant amplitude loading as well as overload tests considering overload ratios of ROL = 2.0 and ROL = 2.5 are conducted. The experimental results are compared to a crack growth assessment based on a modified NASGRO equation as well as the retardation model by Willenborg, Gallagher, and Hughes. The evaluated delay cycle number due to the overload by the experiments and the model shows a sound agreement validating the applicability of the presented approach.

Effect of cavity radiation on transient temperature distribution in steel cables under ISO834 fire

This paper theoretically and numerically investigates the transient temperature distribution of steel cables. The effect of cavity radiation on the heat transfer through the air gap between steel wires of cables is taken into account. A simple calculation method is proposed based on the lump capacitance equilibrium to determine the temperature history in the center of steel cables. An equivalent parallel thermal resistance considering the cavity radiation and conduction is used to determine the total thermal resistance of wires. The accuracy of the proposed method is verified against numerical results from two-dimensional heat transfer analyses on cables with realistic cross sections under ISO834 fire. Parametric studies are conducted to investigate the effect of sectional dimension and cavity radiation on the temperature distribution of steel cables. The results show that the cavity radiation accelerates the heating rate of steel cables compared to round steel bar models. This indicates that it is not safe to directly use the traditional equivalent steel bar model to determine the temperature history of steel cables. It is found that the transient temperature distribution of steel cables is non-uniform. A higher central temperature of steel cables is achieved due to the cavity radiation effect compared to that of round steel bars. This temperature difference is also not monotonic and increases with increasing sectional dimension of cables.