Mechanical behaviors of quasi-ordered entangled aluminum alloy wire material

Quasi-ordered entangled aluminum alloy wire materials with nominal porosity of 57–77% have been fabricated by assembling a set of aluminum alloy wires with diameter of 0.28 mm. The as-prepared materials display three-stage stress–strain behavior under uniaxial compressive loading, i.e., initial nonlinear ‘quasi-elastic’ deformation, strain-hardening ‘pseudo-platform’ stage, and the final densifying stage. The experiment indicates that the structural deformation mechanism dominates the initial stress–strain behavior. At the elastic stage, the materials reveal a significant ‘strain-hysteresis effect’. The compressive yield strength and the elastic modulus exhibit a significant dependence of porosity, i.e., both decrease as the porosity increases. The data obey the typical power law relationship suggested by Gibson–Ashby.     

Stretching behaviors of entangled materials with spiral wire structure

The entangled materials with spiral wire structure have been investigated in terms of the stretching behavior, mechanical properties, and stress–strain hysteresis effect. The results indicate that these materials are much more flexible than that with non-woven wire structure. They exhibit 1.05 MPa yielding strength and 5.7 MPa Young’s modulus in average at the porosity of 60%, and 2.47 MPa yielding strength and 12.3 MPa Young’s modulus in average at the porosity of 45%. Under tensile loading the materials exhibit a unique stress–strain behavior that goes through a long strain period after yielding and follows a quick stress increase on the stress–strain curve due to the ‘unclosing’ and ‘straightening’ mechanism of the spiral wire structure. In addition, these materials exhibit obvious stress–strain hysteresis effect. Their energy dissipation values determined according to the stress–strain hysteresis loops are 28.6 mJ/cm³ at the porosity of 60% and 102.3 mJ/cm³ at the porosity of 45%, which are much larger than that of the polymer foam, implying their promising applications for the energy absorption.     

Mechanical behavior of entangled fibers and entangled cross-linked fibers during compression

Entangled fibrous materials have been manufactured from different fibers: metallic fibers, glass fibers, and carbon fibers. Specimens have been produced with and without cross-links between fibers. Cross-links have been achieved using epoxy spraying. The scope of this article is to analyze the mechanical behavior of these materials and to compare it with available models. The first part of this article deals with entangled fibrous materials without cross-link between fibers. Compression tests are detailed and test reproducibility is checked. In the second part, compression tests were performed on materials manufactured with cross-linked fibers. The specific mechanical behavior obtained is discussed.     

Impact perforation behavior of CFRPs using high-velocity steel sphere

In order to investigate impact perforation behavior of Carbon Fiber Reinforced Plastics (CFRPs), a steel sphere having a velocity of 500–1230 m/s was impacted to several kinds of CFRP laminate specimens consisting of different carbon fibers, interlaminate sequence, configuration; cross-ply or woven cloths, or thickness. The perforation behaviors were evaluated by absorbed energies during perforation, morphological in situ observations using high-speed framing cameras and postmortem observations. Spheres penetrated specimens in a fluid manner on the front surface, and perforated them in an extrusive manner on the rear surface in case of thick specimens. In case of thin specimens, on the contrary, spheres perforated specimens in fluid manner on the rear surface. In the fluid manner energy absorption was independent of the static mechanical properties of the fibers. In extrusion the energy absorption depended on the static tensile fracture energy of the fiber: high fracture energy resulted in large energy-absorption. The boundary velocities in changing failure modes depended on the tensile moduli of the reinforced fibers. Failure modes were significantly affected by the mechanical properties of the fiber: with low strength or fracture strain of reinforced carbon fiber, the specimens showed plugging fractures on the rear surfaces. With high strength and fracture strain, the specimens showed larger delamination on both surfaces.     

Impact behavior of different stainless steel weldments at low temperatures

A comparative study was made of the fracture behavior of austenitic and duplex stainless steel weldments at cryogenic temperatures by impact testing. The investigated materials were two austenitic (304L and 316L) and one duplex (2505) stainless steel weldments. Shielded metal arc welding (SMAW) and tungsten inert gas welding (TIG) were employed as joining techniques. Instrumented impact testing was performed between room and liquid nitrogen (?196 °C) test temperatures. The results showed a slight decrease in the impact energy of the 304L and 316L base metals with decreasing test temperature. However, their corresponding SMAW and TIG weld metals displayed much greater drop in their impact energy values. A remarkable decrease (higher than 95%) was observed for the duplex stainless steel base and weld metals impact energy with apparent ductile to brittle transition behavior. Examination of fracture surface of tested specimens revealed complete ductile fracture morphology for the austenitic base and weld metals characterized by wide and narrow deep and shallow dimples. On the contrary, the duplex stainless steel base and weld metals fracture surface displayed complete brittle fracture morphology with extended large and small stepped cleavage facets. The ductile and brittle fracture behavior of both austenitic and duplex stainless steels was supplemented by the instrumented load–time traces. The distinct variation in the behavior of the two stainless steel categories was discussed in light of the main parameters that control the deformation mechanisms of stainless steels at low temperatures; stacking fault energy, strain induced martensite transformation and delta ferrite phase deformation.     

Heat-treating steel wire before forming

A note from Wire Info Service (c/o NOWEA, PO Box 320203, 4000 Düsseldorf, West Germany) claims advantages for this process. Prior heat-treatment of the wire reduces the total scatter of all tensile strength parameters within 100N/mm² for all grades of steel, independent of the coil weight, coil diameter and the delivery batch size. This total scatter includes all tolerances arising during the long chain of production operations — ie melting, rolling, heat-treating and, if appropriate, cold drawing.Prior heat-treated wire, known as Maraform, gives bolts and screws of different strength ratings, whose scatter of tensile strength within each rating is only half the tolerance allowed by DIN-ISO 898. This gives the user three new sub-classes within each previous strength class, with new tighter tolerances of ±50 N/mm². This enables lower alloy steels to be used, and at the same time proves quality.     

Enhancement of the porous titanium with entangled wire structure for load-bearing biomedical applications

The porous Ti with entangled wire structure has been developed for the biomedical application. But its stiffness is lower than that of the conventional porous Ti due to the structural flexibility. In order to enhance the stiffness, the free cross wire nodes in the entangled structure must be fixed. In this study, a medical polymer – polymethylmethacrylate (PMMA) was selected as the bonding agent to fix the cross wire nodes. The method to enhance the porous Ti by the PMMA was described in detail. The tensile mechanical properties of the PMMA-enhanced porous Ti were investigated. The result indicated that this method was more effective than the sintering, and achieved about 1 GPa tensile elastic modulus, while the porosity only decreased from 55% to 53.4%. Although some PMMA was coated on the Ti wire surface, the preferred average pore size and the good connectivity were still maintained in the PMMA-enhanced porous Ti materials. This is very beneficial to the bone grafting application.     

高强不锈钢绞线网增强ECC加固RC短柱轴心受压试验

在新型复合材料“高强不锈钢绞线网增强工程水泥基复合材料(ECC)(简称HSME)”的力学性能和约束素混凝土受压性能研究基础上,将钢筋混凝土(RC)短柱配筋率和混凝土强度以及加固层的ECC强度和横向钢绞线配筋率作为参数,试验研究高强不锈钢绞线网增强ECC加固RC短柱轴心受压性能。结果表明,和未加固RC短柱相比,HSME加固RC短柱不仅承载力大幅度提升,而且破坏时裂而不碎、具有明显的延性破坏特征,开裂荷载、峰值荷载及峰值位移显著提高;荷载达峰值荷载80%左右和峰值荷载时,试件表面最大裂缝宽度仅为0.09 mm和0.25 mm,表现出优良的多缝开裂和裂缝控制能力。HSME加固RC短柱荷载-位移曲线属于偏态的单峰曲线,包含弹性、裂缝发展、最大荷载和承载力下降四个阶段。随着ECC抗压强度和横向不锈钢绞线配筋率增大,HSME加固柱开裂荷载和峰值荷载均明显增大;增大RC柱配筋率和混凝土强度可提高加固柱峰值荷载和延性。     

Evolution of cementite morphology in pearlitic steel wire during wet wire drawing

The evolution of the cementite phase during wet wire drawing of a pearlitic steel wire has been followed as a function of strain. Particular attention has been given to a quantitative characterization of changes in the alignment and in the dimensions of the cementite phase. Scanning electron microscope observations show that cementite plates become increasingly aligned with the wire axis as the drawing strain is increased. Measurements in the transmission electron microscope show that the cementite deforms plastically during wire drawing , with the average thickness of the cementite plates decreasing from 19 nm (ε = 0) to 2 nm (ε = 3.7) in correspondence with the reduction in wire diameter. The deformation of the cementite is strongly related to plastic deformation in the ferrite, with coarse slip steps, shear bands and cracks in the cementite plates/particles observed parallel to either {110}_α or {112}_α slip plane traces in the ferrite.     

Multiscale prediction of mechanical behavior of ferrite–pearlite steel with numerical material testing

Multiscale mechanical behaviors of ferrite–pearlite steel were predicted using numerical material testing (NMT) based on the finite element method. The microstructure of ferrite–pearlite steel is regarded as a two‐component aggregate of ferrite crystal grains and pearlite colonies. In NMT, the macroscopic stress–strain curve and the deformation state of the microstructure were examined by means of a two‐scale finite element analysis method based on the framework of the mathematical homogenization theory. The microstructure of ferrite–pearlite steel was modeled with finite elements, and constitutive models for ferrite crystal grains and pearlite colonies were prepared to describe their anisotropic mechanical behavior at the microscale level. While the anisotropic linear elasticity and the single crystal plasticity based on representative characteristic length have been employed for the ferrite crystal grains, the constitutive model of a pearlite colony was newly developed in this study. For that reason, the constitutive behavior of the pearlite colony was investigated using NMT on a smaller scale than the scale of the ferrite–pearlite microstructure, with the microstructure of the pearlite colony modeled as a lamellar structure of ferrite and cementite phases with finite elements. On the basis of the numerical results, the anisotropic constitutive model of the pearlite colony was formulated based on the normal vector of the lamella. The components of the anisotropic elasticity were estimated with NMT based on the finite element method, where the elasticity of the cementite phase was numerically evaluated with a first‐principles calculation. Also, an anisotropic plastic constitutive model for the pearlite colony was formulated with two‐surface plasticity consisting of yield functions for the interlamellar shear mode and yielding of the overall lamellar structure. After addressing the microscopic modeling of ferrite–pearlite steel, NMT was performed with the finite element models of the ferrite–pearlite microstructure and with the microscopic constitutive models for each of the components. Finally, the results were compared with the corresponding experimental results on both the macroscopic response and the microscopic deformation state to ascertain the validity of the numerical modeling. Copyright © 2011 John Wiley & Sons, Ltd.     

Investigation of service failures of steel music wire

An investigation of a number of service failures of the hard steel strings of plucked musical instruments is reported. All the failed strings were found to contain transverse fatigue cracks, mostly located near the end of the vibrating length (e.g. at the “bridge” of the instrument) and extending to about one third of the section thickness. One wire had corroded severely before failing in fatigue. Final failure occurred by ductile fracture.An analysis of the service stresses showed that the strings are subjected to high mean tensile stresses resulting principally from elastoplastic bending opposite the failure location. It is shown that a small cyclic axial tension arises from repeated plucking during playing and this can lead to fatigue initiation and propagation over a large proportion of the wire cross section.Neither surface nor bulk defects, wear nor contact stresses were found to be factors of importance in the cases examined, contrary to some speculation.     

Deformation textures in wire drawn perlitic steel

In this study, we followed the deformation microstructure and texture evolution during the cold wire drawing of a perlitic steel wire intended for civil engineering applications. The deformation level effect on the microstructure evolution and on the texture evolution is characterized. Wire drawing induces the lengthening of the perlitic grains along the drawing axis and leads to a strong hardness increase. X-ray texture measurements were performed. The reference state (initial wire) revealed an isotropic texture. The quantitative analysis show the development of the α fibre (<110>//ND (ND // wire) with the deformation. Moreover, the {001}?<?110?>?orientation (rotated Cube) is also present. The experimental techniques used in this study are the: Optical Microscopy (OM), the Electron Back Scattered Diffraction (EBSD), the X-ray diffraction, the Neutron diffraction and the Vickers microhardness.     

Microstructural evolution of copper clad steel bimetallic wire

We investigated the microstructure of two different bimetallic wires of Copper Clad Low Carbon Steel Wire (LCSW), which had a 1006 steel core, and Copper Clad High Carbon Steel Wire (HCSW), which had a 1055 steel core. The HCSW generally showed higher hardness than LCSW because of the pearlitic grain structure. A low temperature annealing at 720 °C to the drawn HCSW caused a significant reduction of hardness, which was as low as that of an annealed LCSW. In general, both LCSW and HCSW showed strong global textured features after drawing, with the steel having a strong 〈1 1 0〉 fiber texture and the copper having a 〈1 1 1 〉-〈1 1 2〉 deformation direction. At the interface, a grain size discrepancy at the steel-copper interface was observed. Post-drawing, the LCSW copper grains exhibited refined grain sizes near the interface and has been explained in terms of shear strain gradient. The HCSW did not exhibit this copper grain size distribution but did exhibit a coarsening of the steel grains near the interface after a subsequent 720 °C heat treatment. This is attributed to the large localized stress concentration at the perimeter of the steel region during the drawing process. The strain induced regions at the steel-copper interface have been simulated by finite element modeling. These grain size discrepancies caused the smooth variation in nanohardness across the interface.     

钢包铜复合线的制备研究

介绍了3种钢包铜复合导电柱的复合坯制备方法，探索了3种复合坯的制备工艺（1）液固相复合法；（2）直接装配法：（3）特殊装配法，对制备出的钢包铜复合导电柱复合界面组织致密性、界面结合状态及密封性能的影响。试验表明：前两种工艺制备的复合线材其结合面有局部结合不紧密，在界面未形成冶金结合状态，致使复合界面经氦检漏有漏气现象；第三种工艺制备的钢包铜复合线经气密性等综合性能试验，达到了使用要求。     

Characterisation of severely deformed austenitic stainless steel wire

Abstract

The microstructure of 8 μm diameter wire produced by the severe deformation of 316L austenitic stainless steel has been examined using TEM and X-ray diffraction. The deformation imparted amounts to a true strain of 6·3. Data from previous studies on strain induced transformation of this steel have been combined with new results to show that true strains >2 are required in order to observe mechanical stabilisation, i.e. the cessation of martensitic transformation when the martensite/austenite interfaces are unable to propagate through the dislocation debris created in the austenite.     

Processing of titanium-based human implant material using wire EDM

Machinability of human implant materials without causing any surface damage is a challenge on current research. The effect of heat-affected zone (HAZ), load experienced, and chemical reaction after implantation are the profound factors influencing on degradation of implant machined surface. An attempt is made to study the machinability of titanium-based human implant materials. While machining, the surface quality of the implant materials with reference to electrochemistry and metallurgical behavior of plasma energy produced are investigated in detail. Materials removal and its surface quality during plasma spark were measured as a response on machining process. The influence of pulse on/off time and the voltage varied during experimentation are evaluated using factorial design. Further, the machined samples are subjected to metallurgical characterization studies using microscopic (SEM) and spectroscopic (EDS) analysis. Increase in voltage has produced better surface finish and reduced recast layer. Contribution of pulse duration is less compared to voltage. Thus, the difficulty on machining human implants can be performed with wire electrical discharge machining process with high surface quality.     

Reverse ageing in hot-rolled high-carbon steel wire rod

Effects of ageing time on area reduction of hot-rolled high-carbon steel wire rods were studied. Tensile testing and X-ray study of as-rolled wire rods were carried out. Gleeble simulation and hydrogen content determination were also conducted. The results show that the reduction of area increases with ageing time at room temperature and the UTS remain unchanged which are contrary to normal ageing or strain ageing. In normal ageing, the ductility drops and the yield strength increases. In this study, the Gleeble simulation and X-ray data support that the transformation from pearlite to austenite is normal and there is no evidence of retained austenite or martensitic transformation in the steel. The hydrogen content drops as the time passes. The drop is rapid in first few days and this drop increases the ductility in rolled high-carbon wire rod. Hydrogen reduces the cohesive strength and the pressure generated due to transformation of atomic hydrogen-to-molecular state combines with tensile stress and causes cleavage or mixed type of fracture.