Steel Cord Research Articles

Experimental studies on stocky masonry pillars strengthened with steel cords and PBO fibres

This paper presents a study of stocky masonry pillars strengthened by stainless steel cords and PBO fibres in bed joints. Ten physical models were used in experimental testing, of which 3 served as reference specimens and the remaining seven were confined in bed joints using different techniques. The pillars were constructed with lime mortar with parameters similar to those used in historical structures. To assure conditions similar to the real objects steel cords and PBO fibres were placed in grooves, which were made in the pillars after the mortar had set. The main failure mechanisms, ultimate load-bearing capacity and longitudinal and transverse deformations were determined through the experimental testing. In addition, the longitudinal stiffness and the stresses at which cracking appears were determined on the basis of observations and analysis of experimental results. The strengthening effectiveness was also determined in relation to the increase in load-bearing capacity, stiffness and cracking stresses. The methods used for strengthening stocky pillars in bed joints increase their load-bearing capacity, stiffness and counteract cracking without any significant impact on the visual appearance of the pillars, which is especially important in the strengthening of historic structures.

Analysis of Truck Tractor Tire Damage in the Context of the Study of Road Accident Causes

There are many accidents in road traffic involving both heavy goods vehicles and passenger vehicles, and the interpretation of the causes of some accidents can be very difficult. The paper presents the results of an analysis of the road accident causes involving a truck and two passenger cars. The hypothesis was verified that the incident took place after the damage to the front wheel of the truck, which resulted in an uncontrolled change of the direction of its travel and leaving the lane in the opposite direction of the passenger cars. The damaged tire was inspected, and traces were described in the form of cracks on the side surface, irregular abrasion on the central part of the side surface and near the bead, as well as deformations resulting from damage to the cord. The thesis was made that the tire cracked as a result of its material structure defects. In order to verify it, bench tests were carried out on the deformation of the tire sidewall at various load conditions, which simulated driving with too little air pressure in the tire. Detailed studies of the fracture of the tire sidewall and the wires that make up its steel cord were carried out. Macroscopic examination of the cord wires on eight samples revealed the presence of corrosion changes that should not occur under normal operating conditions. The results of the research work indicate that tire rupture was caused by delamination of the material coatings and corrosion of the steel cord wires. These defects could have arisen due to the earlier cracking of the rubber layer and the ingress of moisture or as a result of the use of corroded steel cord wires in tire production. In the analyzed case, the driver could not regain control of the vehicle and avoid a collision with oncoming vehicles.

Effect of MgO in low-basicity refining slag on properties of MnO-SiO2-Al2O3 inclusions in tire cord steel

Large-scale non-deformation inclusions in tire cord steel increase the breakage risk, and the Si-Mn deoxidization is used to control the inclusion composition in the plasticized region with a lower melting point. In order to study the influence of the composition change of refining slag due to the erosion at the slag line on the inclusions of MnO-SiO 2 system with the low melting point, the silicon-manganese oxide inclusions were synthesized, and steel samples were prepared according to the composition of 82B tire cord steel. No top slag trial and the top slag trials of low basicity refining slag with 0%, 5%, 10% and 20% MgO content were studied in the MgO crucible at 1600°C (CaO%/SiO 2 %=1, Al 2 O 3 =3%). The properties of typical inclusions in steel were observed using SEM-EDS and automatic statistical. Results showed that [Mg] dissolved by MgO crucible into molten steel in the no-slag test is insufficient to produce Mg-containing inclusions, and MgO-SiO 2 inclusions appear in the top slag trials. In general, the MgO content in the top slag has little effect on the silicon manganese oxide inclusions. Appropriate increase of MgO content in refining process is conducive to reducing the corrosion of slag line and extending the service life of MgO-C brick.

Effect of MgO on crystallization behavior of MnO–SiO2–Al2O3 based inclusions in tire cord steel

Increasingly MgO content in refining slag and molten steel is the major cause of corrosion of refractory materials at slag line during the refining process of Si–Mn deoxidized tire cord steel, the effects on the crystallization behavior of typical MnO–SiO2–Al2O3 based inclusions in tire cord steel were studied. The relation between the formation of high melting point and high hardness inclusions (Al2O3, 3Al2O3·2SiO2, MgO·Al2O3 and 2MgO·SiO2) with MnO–SiO2–Al2O3-(0wt.%, 4wt.%, 8wt.%, 12wt.%, 16wt.%) MgO system was verified by ICP, XRD, SEM-EDS and FactSage 8.0. The results indicated that the crystallization temperature of MnO–SiO2–Al2O3 system increases with the increase of MgO content. MgxMn(2-x)SiO4(1 ≤ x < 2) solid solution is the main crystalline phase due to isomorphism. Only a small amount of 2MgO·SiO2 which is not enough to cause wire breakage was formed in the trial with the highest MgO content (16wt.%) after the low melting point MnO–SiO2–Al2O3 composition added different MgO content and the other three kinds of inclusions were not produced in the five trials.

Experimental evaluation of utilizing synthetic continuous fiber reinforcements for thermoplastics as an alternative to steel-based analogs

Despite being inexpensive and robust, steel cord reinforcements are often prone to pose risks to user health and safety in some industrial applications such as escalator handrails and rubber conveyor belts. Steel cords can reduce the overall stability and performance of the application over time due to their inherent creep accompanied by cyclic thermal expansion and contraction. In this context, this research focuses on replacing steel cords in some critical thermoplastic polyurethane (TPU) composite applications with continuous sustainable alternate synthetic fibers that possess high specific strength (e.g. carbon, glass, and Kevlar fibers). The first part of this research characterizes the effect of epoxy coating on synthetic fibers alone by studying their mechanical properties before and after modification, whereas the second half of the research involves reinforcing a TPU matrix with raw and epoxy-coated synthetic fibers to fabricate fiber-reinforced composites by compression molding. The effect of the curing temperature of epoxy on the end performance of the manufactured specimen was also tested. An in-depth analysis of mechanical and morphological studies showed that, at almost the same volume fraction of fibers, the TPU reinforced composites with modified carbon fibers showed higher load-bearing capacities than steel cord-based analogs. Conversely, a wide variety of other relevant industrial and commercial applications can potentially draw significant benefits by implementing these modified carbon/TPU composites instead of steel cords.

Chemical composition of brass coating for steel cord

The objective of the research was to identify transitional diffusion layers in the steel wire – brass coating system. Brass wire is used in the production of steel cord. Such wire made from steel 80 by dry drawing, two-stage deposition of brass coating (Cu + Zn) and subsequent diffusion annealing was used for this research. The chemical composition was studied using a TESCAN Vega3 SBH scanning electron microscope with an Oxford Instruments attachment for X-ray microanalysis (MRSA). To obtain maps of the elements distribution, the overlay of the received frames was used. The authors studied chemical composition of the brass coating of steel wire for steel cord by spectra; the copper concentration gradient was determined; iron content in the coating and copper content in the steel core were revealed. The presence of a transitional diffusion layer from a brass coating to a steel core on a wire for wet drawing with a diameter of 1.67 mm and 1.85 mm was determined in two parts with different thicknesses of a brass coating in opposite sections (maximum and minimum). A map of the elemental distribution of Fe, Cu and Zn is shown, as well as a general map of overlay of Fe, Cu and Zn content; graphs of the elements’ content for two studied cross-sections are presented. It was established that the transition diffusion layer has gradient transition in concentrations of Fe, Cu and Zn, which characterizes good connection of the brass coating with steel. Diffusion layer of a brass coating of a steel wire with a diameter of 0.30 mm, produced by wet drawing of a steel wire with a diameter of 1.67 mm, was studied. An image of the coating was obtained by overlaying frames. Thickness of the coating together with the diffusion layer was determined, the average value of which is 1.4 µm with an apparent coating thickness of 0.5 µm.

Analysis on the crimping quality of overhead transmission line conductors considering equivalent cross-sectional stiffness

Approximately 58% of wire failures are caused by slippage and fracture of electrical connectors, and the crimping quality analysis of connectors is based on equivalent cross-sectional stiffness. First, a JL/GLA 400/35 steel cord aluminum strand and NY-400/35 strain clamp are selected to fabricate 26 groups of specimens with different pipe penetration depths, opposite edge distances, inner diameters of the aluminum tube, and die widths. Then, through crimping tests on the aluminum tube and conductor and the steel core and steel anchor, five main crimping failures, namely, the slip at the outlet of the clamp, the slip at the outlet of the clamp with some broken aluminum strands, fracture of the aluminum tube in the non-pressure area, wire fracture at the outlet of the clamp, and separation of steel anchors, are observed. Finally, a failure analysis method for conductor crimping is proposed based on equivalent cross-sectional stiffness. Through the analysis of grip force and crimping quality, four failure modes and simplified curves of the load–displacement curve are obtained, and the failure principle of the conductor crimping is further elaborated. The results show that the stress release caused by the steel core and steel anchor of the crimping wire and the crimping aluminum tube and wire is the main reason for the slippage and fracture of the transmission line conductors and that it is also the key to improve the installation quality of the transmission line.

Effect of impurities of steel fibers extracted from shredded tires on the behavior of fiber-reinforced concrete

Production of ductile and environmentally-friendly concrete is a dream come true thanks to the combined usage of recycled fibers and pozzolanic materials in the concrete mixture. The raw recycled steel fibers (RSF) stemmed from shredding waste tires underwent a process of preparation. Secondary products of tire-shredding technique, including recycled steel cords, rubber-attached fibers, tiny steel fibers, and free form of rubber particles, were recognized and removed from raw RSF sample, changing its status from impure to pure. The primary target of this study was to evaluate the contribution of RSF purification to the engineering properties of concrete containing 30% slag powder by weight of the total binder. Based on the results, purifying RSF negatively affected the ultrasonic pulse velocity and led to a less workable mixture with inferior compressive strength (fc). Interestingly, the highest fc was attained at 1% impure RSF, indicating a 40% enhancement compared to the plain concrete. The positive effect of RSF purification became visible considering the imperviousness and flexural performance of the mixture. However, a similar impure and pure RSF-reinforced concrete flexural strength could be achieved by doubling the volume of the impure RSF.

Study of the Chemical Composition of a Steel Wire Brass Coating for Steel Cord Production

Study of the Chemical Composition of a Steel Wire Brass Coating for Steel Cord Production

Bond Behavior of Steel Cords Embedded in Inorganic Mortars.

This paper investigates the bond behavior of steel cords embedded in inorganic matrices. A series of pull-out tests were carried out on individual galvanized steel cords embedded in either a cementitious or lime-based mortar matrix and the corresponding bond-slip relationships were derived. The quality of bond between cord and mortar was found to be critically affected by the workability of the mortar and its ability to create adequate composite action along the entire embedment length of the cord. The more workable lime-based mortar was found to guarantee a better interaction with the steel cord, in terms of initial bond stiffness, maximum bond strength, and post-peak behavior. The experimentally derived bond–slip relationships were subsequently integrated in a 3D non-linear finite element framework and used to determine the constitutive relationship of a surface-based cohesive contact between cord and mortar. The cohesive bond behavior was used to conduct a series of parametric studies on cords embedded in a lime-based mortar and examine the stress development within specimens with cords of different embedment lengths and subjected to different loading conditions (i.e., pull-out and direct tension). The active ‘Stress Transfer Zone’ was found to be about 125 mm, while an ‘Effective Transfer Radius’ of approximately 3.5–4 mm was identified. The numerical investigation implemented in this paper enabled one to study key interaction properties of steel reinforced grouts and can assist the design of more effective strengthening solutions.

Automatic Procedure for Steel Cord Belt Splicing Preparation

Automatic Procedure for Steel Cord Belt Splicing Preparation

Experimental analysis and prediction for the bonding strength of steel cord of conveyor belt under the temperature influence

To research the effect of temperature on the interfacial bonding strength of the steel cord rubber conveyor belt, an electronic universal material testing machine and a temperature control box were used as the test equipment. The withdrawal force of the steel cord skeleton of the rubber conveyor belt was tested in the temperature range of −30 °C to +40 °C. Concurrently, the interfacial morphology between the steel cord and rubber at different temperatures was observed by using an ultra deep field electron microscope. Finally, different bonding strength prediction models were established. The results show that the variation trend of the steel cord withdrawal force with displacement is the same at different temperatures. With the increase in temperature, the interfacial bonding strength between the steel cord and the rubber matrix decreases gradually; the second-order polynomial bonding strength prediction model can meet the prediction requirements of the steel cord bonding strength at different temperatures, and the errors are controlled within 5%.

Selection of measurement parameters using the DiagBelt magnetic system on the test conveyor

The DiagBelt system is the diagnostics device for assessment of a technical condition of conveyor belts. The following paper concerns the magnetic module dedicated for monitoring of belts with steel cords. The system allows scanning of belts with different cord diameters and their density. The speed of the belt also may vary depending on the operating conveyor. Additionally, the system user can change measurement sensitivity and the distance between the measuring probe and the cord. The measurement allowed to determine values of these parameters of which test results are the most reliable. In practice, this enables faster and more accurate assessment of a belt condition, which plays a significant role in the planning maintenance operations. It has a good impact on the continuity of belt operation and belt conveyors reliability. Therefore, it improves the reliability of the whole mining transport system.

Bond Behavior of Steel Cords for SRG Systems to Cementitious and Lime Based Mortar

Over the past two decades, different innovative systems have been developed for the rehabilitation and retrofitting of existing structures. In particular, SRG (Steel Reinforced Grout) strengthening systems have proven to be very effective in increasing the load carrying capacity and global ductility of reinforced concrete and masonry structures, and their use as an alternative seismic retrofitting solution is increasing rapidly. Although several studies have focused on the characterisation of the mechanical performance of SRG composites subjected to direct tension or bonded to concrete/masonry substrates, the local bond behaviour of steel cords to mortar, which is critical for the overall structural performance of these composites systems, needs to be examined in more depth. To this end, a series of pull-out tests was carried out to study the bond stress transfer of high strength galvanized steel cords embedded in two types of inorganic matrices, including a cementitious and a lime based mortar. In addition, the steel cord to mortar bond was examined through the implementation of a surface-based cohesive contact model in a non-linear finite element framework and the distribution of stresses within the mortar surrounding the steel cord was analysed.

Durability of Stainless-Steel Reinforced Grout against Salt Attack

Steel reinforced grout is one of the most effective mortar-based composites for the strengthening of masonry structures. Nonetheless, the deterioration of steel cords, especially when embedded in lime-based matrices, may compromise the long-term effectiveness of the strengthening systems. The use of stainless-steel may overcome this drawback, but it has received limited attention so far, since its higher cost makes it less competitive in the market. This work presents a laboratory investigation on the durability of stainless-steel reinforced grout against salt attack, which is the most severe aging condition. Tensile tests were carried out on bare textiles and composite specimens before and after aging in substitute ocean water for up to 5000 hours. Bent textiles, which are required by a number of structural applications, were aged and tested as well. Test outcomes indicate that this technology may be successfully used for the life-span strengthening of the built heritage.

Experimental and Modeling Study of Deformability of Glassy CaO-(MnO)-Al2O3-SiO2 Inclusions

The occurrence of non-deformable, non-metallic inclusions is the dominant reason for failure of wire during drawing and degrades service life for some steel grades, e.g., tire cord steel. To investigate the deformability of glassy inclusions in CaO-Al2O3-SiO2 and MnO-Al2O3-SiO2 systems, experimental and numerical methods were used. Young’s modulus values of some glasses based on the CaO-Al2O3-SiO2 and MnO-Al2O3-SiO2 systems, which correspond to typical inclusions in tire cord steel, were measured with resonant ultrasound spectroscopy. The effect of basicity, defined as the ratio of mass percentage of CaO to SiO2, on Young’s modulus and Poisson’s ratio were investigated. The Young’s moduli of glasses are enhanced with increasing basicity, which could be attributed to the high field strength of calcium ions. The Poisson’s ratios of glasses also show an increase tendency with increasing basicity, which could be due to the loss of rigidity of network with introduction of calcium ions. The equations in the literature for Young’s modulus calculation were evaluated based on the present and literature data. Appen’s equation is modified by re-fitting the present and literature data to give accurate estimation of Young’s modulus with the mean deviation of 2%. The iso-Young’s modulus diagrams for CaO-Al2O3-SiO2 systems were constructed. It is proposed that the iso-Young’s modulus diagram could be combined with liquid area in CaO-Al2O3-SiO2 ternary phase diagram to optimize the inclusion composition during both hot rolling and cold drawing.

Role of Zinc Oxide in the Compounding Formulation on the Growth of Nonstoichiometric Copper Sulfide Nanostructures at the Brass-Rubber Interface.

Tire technology has evolved substantially by the introduction of brass-coated steel cords (BCSCs) in radial tires. The durability of radial tires is dependent on the integrity of the brass–rubber interface composed predominantly of nonstoichiometric copper sulfide (Cu2–xS, where x = 1 to 2) nanostructures whose morphology and characteristics are dependent upon the crucial rubber additive, ZnO. Its higher concentration impacts environmental sustainability, while at lower levels, there is insufficient bonding between steel and the rubber thus affecting tire’s safety. This brings in the need for an optimum ZnO concentration to be used in radial tires and is thus the theme of the present work. The changes in the properties of interfacial nanostructures such as morphology, thickness, crystallinity, and chemical composition were studied at various ZnO concentrations. We adopted our previously reported methodology, the “brass mesh experiment”, to investigate the thickness of nanostructures at varied ZnO concentrations using transmission electron microscopy (TEM). Significant results were obtained from field-emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), Raman imaging and X-ray photoelectron spectroscopy (XPS). In conjunction with a more practical experimental technique, namely the measurement of pull-out force (POF), it has been concluded that 9 parts per hundred rubber (PHR) ZnO is essential for the optimum growth of nanostructures and is considered to be the optimum for the composition studied. We believe that the scientific approach outlined in the manuscript would help the tire- and the material science communities to widen the knowledge of understanding sustainability in tire industries. It is estimated that the optimization presented here can save $400–450 million for the tire industry and 2.4 million tons of ZnO per year.

The Effect of Lay Length on the Antipull Performance of Steel Cords and the Spinning Loss Based on the FEM

This paper is mainly aimed at 0.28 + 6 × 0.26 steel cords and 0.26 + 6 × 0.24 steel cords under different lay length conditions through the ABAQUS finite element analysis software to limit the tensile performance of the steel cord and the stress field distribution during the tensile loading. Based on the finite meta-analysis, in this experiment, the tensile simulation of the same kind of steel cord at the twist lay length of 5 mm, 7 mm, 9 mm, 11 mm, 13 mm, and 15 mm was carried out under the condition of 2 mm/s. The results show that, under certain conditions of other process conditions, with the increase of the twisting distance of the steel cord strands, the strength of the steel cord increases, the deformability decreases, the stress concentration decreases, and the spinning loss decreases. The spinning loss formula is modified to reduce the calculation error.

Strength, bond and durability of stainless steel reinforced grout

Steel Reinforced Grout (SRG) is an effective, cost-efficient and versatile technology for strengthening existing structures. However, the high strength properties exhibited by steel textiles can rarely be fully exploited in design, due to the premature occurrence of bond failure and deterioration. Because of the small diameter of steel cords or wire ropes, and the alkalinity and vapour permeability of the inorganic matrices, the long-term effectiveness can be affected by the combined action of the salt and alkali attack. Although largely overlooked, the use of stainless steel can be a breakthrough for this technology. This work presents the first comprehensive characterization of a Stainless SRG system (SSRG) with a lime-based matrix. Its tensile strength, bond capacity, pull-out behaviour and durability against various ageing conditions were investigated, and design parameters were determined. According to test results, stainless steel combined with lime mortar has excellent mechanical properties and durability, making it the most appropriate solution for the long-lasting strengthening of masonry structures.

Low-grade RC beams strengthened with TRM composite based on basalt, carbon and steel textiles: Experimental and analytical study

This study develops an easy-to-conduct numerical calculation method to assess the effect of Textile Reinforced Mortar when used as externally bonded flexural strengthening technique in low-grade reinforced concrete beams from ancient structures (aged between 60 and 100 years old). Using materials main mechanical characteristics and the beams dimensions as inputs, the model defines the behaviour of the strengthened elements. This paper includes the experimental characterization of the whole strengthening solution, from the constituent materials and the composite in pure tensile to scaled beams strengthened in flexure. In total three different materials – basalt, carbon and steel cords – are used as Textile Reinforced Mortar inner reinforcement. Tests are carried out on sixteen low-grade reinforced concrete beams that reproduce low-quality concretes with a compression strength below 17 MPa and, in general, poor mechanical properties, as those present in old and decayed structures. This experimental campaign includes the study of two other particular features of the adopted retrofitting technique: the strengthening ratio and the use of an anchorage system.The obtained experimental findings are assessed and satisfactorily compared with the developed numerical approach, leading us to conclude that Textile Reinforced Mortar is an effective solution for retrofitting structures made of low-grade reinforced concretes in terms of increasing their deformation and load-bearing capacity under flexural loads (the maximum bending moment has increased between 30% and 200%). Besides, the failure mechanism due to undesired premature detachment was effectively countered using U-shaped anchors, failing the strengthened beams due to the composite tensile failure.