Drawing Direction Research Articles

Micro-axial cracking in unnotched, cold-drawn pearlitic steel wire: Mechanism and beneficial effect on the resistance to hydrogen embrittlement

Effects of cold drawing ratio (CDR) on the microstructure, tensile properties, H absorption and hydrogen embrittlement (HE) of pearlitic steel wire were investigated by means of thermal desorption analysis, slow strain rate tensile testing, fractography and silver decoration. The ultimate tensile strength (UTS) and diffusible H content of unnotched tensile specimens were raised with increasing CDR due to the reduction of interlamellar spacing and the increase in dislocation density. Nevertheless, the resistance to HE was improved as the CDR became above 30% due to micro-axial cracking. Elongations of H-uncharged and charged specimens decreased until the CDR of 30%, and then were maintained despite of a continuous rise of UTS with increasing CDR further. This is because micro-axial cracking occurred in the specimens with CDRs above 30% so that tensile fracture was retarded. As the CDR was over ∼30%, a fracture mode changed from brittle fracture featured by tearing topography surface and cleavage to ductile-like fracture characterized by many dimples and micro-axial cracks. Micro-axial cracking occurred as follows: Some micro-cracks preexisted inside well-aligned pearlite colonies of specimens with CDRs above 30%. While an unnotched, H-uncharged specimen was strained, micro-cracks additionally formed to be coalesced. The merged cracks traversed the pearlite colonies to be propagated into neighboring misaligned colonies and grew along the direction of cold drawing and tensile deformation, resulting in micro-axial cracking. In H-charged specimens, H atoms near micro-cracks clustered into micro-cracks so that micro-axial cracking was accelerated and the regions near micro-cracks underwent ductile fracture, leaving many dimples.

Critical and subcritical cracking of high-strength wires obtained by cold-drawing of pearlitic and duplex stainless steels

Cold-drawing is a strain-hardening process that allows the elastic limit and the tensile strength of pearlitic steel wires to be raised up to levels necessary for prestressing concrete. The strong orientation that the steel microstructure undergoes in the drawing direction determines the micro-mechanisms and resistance of this wire types to critical and subcritical cracking, respectively activated by service loads per se or combined with environmental actions and other singular service circumstances. The paper approaches the comparison of damage micro-mechanisms to critical cracking and hydrogen-assisted subcritical cracking of three cold-drawn high-strength steels, one of pearlitic type and the other two of duplex stainless steels with different molybdenum content. The results are based on experimental data resulting from critical and subcritical cracking tests and subsequent micro- and macro-fractographic analysis of the damage micro-mechanisms. The influence of microstructure on the behavior of the three steel wires is determined on the basis of the analogies and differences between them.

Microstructural Features in Multicore Cu-Nb Composites.

The study is devoted to heavily drawn multicore Cu–18Nb composites of cylindrical and rectangular shapes. The composites were fabricated by the melt-and-deform method, namely, 600 in situ rods of Cu–18%Nb alloy were assembled in a copper shell and cold-drawn to a diameter of 15.4 mm (e = 10.2) and then rolled into a rectangular shape the size of 3 × 5.8 mm (e = 12.5). The specimens were analyzed from the viewpoints of their microstructure, microhardness, and thermal stability. The methods of SEM, TEM, X-ray analysis, and microhardness measurements were applied. It is demonstrated that, at higher strain, the fiber texture (drawing direction), characteristic of this material, becomes sharper. The distortions of niobium lattice can be observed, namely, the interplanar distance is broadened in longitudinal direction of specimens and compacted in transverse sections. The copper matrix lattice is distorted as well, though its distortions are much less pronounced due to its recrystallization. Evolution of microstructure under annealing consists mainly in the coagulation of ribbon-like Nb filaments and in the vanishing of lattice distortions. The structural changes in Nb filaments start at 300–400 °C, then develop actively at 600 °C and cause considerable decrease of strength at 700–800 °C.

Effect of Electroless Coatings on the Mechanical Properties and Wear Behavior of Oriented Multiwall Carbon Nanotube-Reinforced Copper Matrix Composites.

The effects of electroless coatings on the microstructure and composition of the interface between multi-walled carbon nanotubes (MWCNTs) and a Cu matrix and the mechanical properties and wear behavior of the resulting copper matrix composites were investigated. Ni and Cu coatings were electrolessly plated on MWCNTs and mixed subsequently with copper powder. Then copper matrix composites were prepared by sintering, hot extrusion and cold drawing processes. The results showed that MWCNTs were straight, long, uniformly dispersed and aligned in the composites. The Ni coating is more continuous, dense and complete than a Cu coating. The tensile strength, compressive strength, microhardness and tribological properties of Ni@MWCNTs/Cu composite along the drawing direction were enhanced most. The ultimate tensile strength and compressive strength were 381 MPa and 463 MPa, respectively. The friction coefficient and wear rate were reduced by 59% and 77%, respectively, compared with pure Cu samples. This study provides a new insight into the regulation of tribological properties of composites by their interface.

Achieving Mechanical and Conductive Anisotropy in Carbon Nanotubes/Cu Composites

Cu matrix composites reinforced by Multi-walled Carbon Nanotubes (MWCNTs) were prepared aiming to enhance the mechanical performance of Cu through MWCNTs while preserving its excellent axial conductivity. The microscopic structure, mechanical performance and electroconductivity of the composites were characterized, and the related mechanism was discussed. MWCNTs dispersed uniformly in Cu matrix and arranged in the direction of drawing. The composites showed obvious orthogonal anisotropy. The mechanical properties of the composites increased with the content of MWCNTs. The composite with 10vol.% MWCNTs has the best strength and hardness, which was better than most of data in the literature. However, the highest enhancement efficiency of 3vol.%-MWCNTs/Cu composite was the highest. The main enhancement mechanism was load transmission effects and dislocation. The electroconductivity and thermal conductivity of 5vol.%-MWCNTs/Cu composite parallel to the drawing direction reached the maximum value. The main strengthening mechanism was that Ni-Cu coating on MWCNTs leads to strong interface combination between MWCNTs and Cu, which promotes the electron-phonon coupling and reduces electron or phonon scattering at the interface.

Drawing Direction Effect on a Task's Performance Characteristics among People with Essential Tremor.

Essential tremor (ET) is a common movement disorder affecting the performance of various daily tasks, including drawing. While spiral-drawing task characteristics have been described among patients with ET, research about the significance of the drawing direction of both spiral and lines tasks on the performance process is scarce. This study mapped inter-group differences between people with ET and controls related to drawing directions and the intra-effect of the drawing directions on the tremor level among people with ET. Twenty participants with ET and eighteen without ET drew spirals and vertical and horizontal lines on a digitizer with an inking pen. Time-based outcome measures were gathered to address the effect of the drawing directions on tremor by analyzing various spiral sections and comparing vertical and horizontal lines. Significant group differences were found in deviation of the spiral radius from a filtered radius curve and in deviation of the distance curve from a filtered curve for both line types. Significant differences were found between defined horizontal and vertical spiral sections within each group and between both line types within the ET group. A significant correlation was found between spiral and vertical line deviations from filtered curve outcome measures. Achieving objective measures about the significance of drawing directions on actual performance may support the clinical evaluation of people with ET toward developing future intervention methods for improving their functional abilities.

High strength and conductivity copper/graphene composites prepared by severe plastic deformation of graphene coated copper powder

In order to uniformly disperse graphene in the copper matrix, the complete coating of few-layers high-quality graphene on the surface of the copper powder was realized by chemical vapor deposition, and the graphene coated copper powder is sequentially formed through vacuum hot pressing, hot extrusion, and cold drawing processes. The results show that during the vacuum hot pressing, the metallurgical bonding between original copper powders is hindered by the graphene with a relatively complete structure. And the copper grains are recrystallized and refined in the hot extrusion process, and then stretched into a long and thin fibrous structure during the cold drawing process. Besides, the graphene is partially agglomerated during the hot extrusion process, and is dispersed again during the cold drawing process and gradually oriented along the drawing direction. Finally, the graphene and the copper matrix form a network interpenetrating structure, which improves the mechanical and electrical properties of the composite synergistically. The tensile strength and conductivity of the composite wire drawn to 1 mm reached 573.3 MPa and 5.79 × 107 S/m, respectively, achieving a breakthrough in the performance of copper-based materials.

Residual stresses in deep-drawn cups made of duplex stainless steel X2CrNiN23-4

Residual stress development in deep drawing processes is investigated based on cylindrical cups made of duplex stainless steel sheet. Using a two-scale approach combining finite element modelling with a mean field homogenization scheme the macro residual stresses as well as the phase-specific micro residual stresses regarding the phases ferrite and austenite are calculated for steel X2CrNiN23‑4 for various drawing depths. The simulation approach allows for the numerical efficient prediction of the macro and phase-specific micro residual stress in every integration point of the entire component. The simulation results are validated by means of X‑ray diffraction residual stress analysis applied to a deep-drawn cup manufactured using corresponding process parameters. The results clearly indicate that the fast simulation approach is well suited for the numerical prediction of residual stresses induced by deep drawing for the two-phase duplex steel; the numerical results are in good agreement with the experimental data. Regarding the investigated process, a significant influence of the drawing depth, in particular on the evolution of the residual stress distribution in drawing direction, is observed. Considering the appropriate phase-specific strain hardening, the two-scale approach is also well suited for the prediction of phase specific residual stresses on the component level.

Manufacture technology, mechanical and biocorrosion properties of the Zn and ZnMg0.008 alloy wires designed for biodegradable surgical threads

Technology for the production of soluble surgical threads with a diameter of 0.3 mm from the binary alloy Zn-0.008 wt.% Mg has been developed and some of the basic properties of the product have been determined. Thus, an effect of the deformation path applied during drawing (i.e., with and without any change in the drawing direction after each pass) were tested and the windows of technological parameters for the extrusion and drawing were determined. Mechanical properties in the air and the corrosion resistance in an environment simulating body fluids were determined both for the product and the intermediates from selected stages of the production route and compared to the ones of pure zinc. The mechanical tests included the two-way bending test, tensile test, and tensile stress relaxation tests of the wire without and with a surgical knot. It has been shown that the drawing deformation path and the surgical knot do not significantly influence the stress relaxation rate.

Effect of cold drawing strain on the microstructure, mechanical properties and electrical conductivity of low-oxygen copper wires

The effects of cold drawing process on the microstructure, mechanical properties and electrical conductivity of low-oxygen copper wires were studied. The results show that at low drawing strains (ε ≤ 1.23), the plastic deformation is dominated by planar slip, some of grains are rotated along the drawing direction, giving rise to a <111> texture. At medium strains (1.23 < ε ≤ 1.91), most of grains have re-oriented and laid parallel to the drawing direction, and the <111> and <100> textures are highly developed. At high strains (ε > 1.91), a fibrous structure is formed, with a staggered distribution of <111> and <100> textures. With the increase of drawing strain, the volume fraction of the <111> texture first increases and then decreases, while the volume fraction of the <100> texture increases monotonously. The yield strength first increases and then decreases, yielding the maximum value of 427.5 MPa at the strain of 1.91. Interestingly, the electrical conductivity of the copper wires changes with cold drawing strain and moves in the opposite way to the yield strength. The electrical conductivity first decreases and then increases with the minimum value at a strain of 1.91 (~87.5% IACS). At strains higher than 2.74, dynamic recrystallization occurs, resulting in a decrease in dislocation density and an increase in grain size. In addition to the dislocation density and grain size, the yield strength of the copper wires is further impacted by the texture development. The electrical conductivity is less influenced by dislocations and vacancies. Instead, it is dominated by those grain boundaries perpendicular to the drawing direction. An excellent strength-conductivity combination was achieved by tailoring the microstructure of copper wires. For example, a wire with the yield strength (YS) of 400.5 MPa and electrical conductivity (EC) of 94.3% IACS was acquired when the drawing strain reaches 2.74.

Sol-gel transition of polyamic acid solution during chemical imidization and its effect on the drawing behavior of polyimide films

Herein, sol-gel transition of 3,3′,4,4′-biphenyldianhydride (BPDA)/p-phenylene diamine (PDA) polyamic acid (PAA) solution were investigated by adding excessive dehydration reagent, and it was found that increasing the amount of dehydration reagent and pyridine content, as well as the temperature could accelerate the sol-gel transition. The maximum strain of PAA film at the gel stage of sol-gel transition increases from 1.5 to 5.8 compared to the pure PAA film, and the better drawing property enables it has the potential to prepare PI films with more excellent mechanical properties and lower coefficient of thermal expansion (CTE). When the solvent content of PAA gel film increases from 20% to 85%, the tensile strength and modulus of the corresponding PI film with a draft ratio of 1.5 increase from 488 MPa to 12.1 GPa to 591 MPa and 17.3 GPa, respectively. Therefore, the PI film drawn from the gel film with higher solvent content has better mechanical properties. Besides, the corresponding amorphous and orientation composite models with different solvent content were constructed and analyzed based on molecular dynamic (MD) simulation. The FFV of amorphous composite model decreases with the decrease of solvent content, indicating that the model with higher solvent content has less intermolecular entanglement and interaction during the drawing process. The mean square end-to-end distance and XRD patterns demonstrate that the molecular chain in the orientation model drawn from the amorphous model with higher solvent content have more regular and extended arrangement along the drawing direction. Accounting for the reason that PI film drawn from the gel film with higher solvent content exhibits more excellent mechanical properties.

Review on Research Progress and Application of Reinforced Soil

Reinforced soil structure is particularly popular in the field of construction engineering because of its remarkable social, economic and environmental benefits, and is one of the current research hotspots. As a new type of geotechnical structure, reinforced soil has its mechanical characteristic affected by various complex factors, such as the type of reinforced material, the length of the reinforced material, the spacing between the reinforcements, the water content, the drawing directions, the earthquake, the traffic load and so on. Based on studying papers and books, this paper expounds the structural strength characteristic, the interface characteristics and stability of reinforced soil from three aspects, which include basic theory, experimental research and numerical analysis, and the applications of reinforced soil structures in geotechnical engineering are listed. Finally, in view of the current research status and development trend of reinforced soil, the focus and direction that need further research in the future are put forward.

Hand fine motor control in classic galactosemia.

Classic galactosemia (CG) is a rare inborn error of metabolism that results from profound deficiency of galactose-1-P uridylyltransferase (GALT). Despite early detection and rapid and lifelong dietary restriction of galactose, which is the current standard of care, most patients grow to experience a broad range of complications that can include motor difficulties. The goal of this study was to characterize hand fine motor control deficit among children and adults with classic galactosemia (CG). Specifically, we used Neuroglyphics software to collect digital Archimedes spiral drawings on a touch screen from 57 volunteers with CG (cases) and 80 controls. Hand fine motor control was scored as root mean square (RMS) of spirals drawn relative to an idealized template. Presence of tremor was defined as a peak in periodicity of changes in drawing speed or direction in the 4-8Hz range. We observed a highly significant difference (P < .001) in RMS scores between cases and controls, with almost 51% of cases showing at least 1 of 4 spirals scoring outside the 95th percentile for controls. The corresponding prevalence for controls was 10%. Similarly, more than 35% of cases, and almost 14% of controls, showed at least 1 of 4 spirals with a tremor amplitude above the 95th % cutoff for controls. Our results both confirm and extend what is known about hand fine motor control deficit among children and adults with CG and establish digital assessment as a useful approach to quantify this outcome.

Highly reinforcing effect of polycarbonate/poly(ethylene terephthalate) blends by formation of orientation microfibrillar structure

AbstractHighly oriented microfibrillar polycarbonate/poly(ethylene terephthalate) (PC/PET) blends were prepared. Before orientation, the molecular chains of the blends were mostly randomly arranged with a low crystallinity, and low mechanical properties were obtained. Under stress, it was difficult for molecular chains of the amorphous PC phase in blends to form an oriented crystalline structure. With increasing draw ratio, the crystallinity and orientation degree of the PET phase increased, forming a dense lamellar structure with reduced crystalline and amorphous layer thickness, while with increasing PET content the crystalline orientation degree of the PET phase increased with larger sized lamellae. Moreover, the cross‐section of the oriented sample showed an obvious ordered microfibrillar bundle structure, which arranged compactly and orderly along the drawing direction. The tensile strength and modulus of the oriented PC/20 wt% PET sample were up to 126.01 and 7170.10 MPa, which were 66.48% and 317.49% respectively higher than those of pure PC. Therefore, the stress‐induced oriented microfibrillar structure of the PET phase exhibited a highly reinforcing effect on the PC phase and the blend. © 2021 Society of Industrial Chemistry.

Effect of crystal orientation on inner surface roughness of micro metal tubes in hollow sinking

The crystal deformation behavior of the micro tube was investigated to clarify the crystal orientation, which suppresses the development of the inner surface roughness during the hollow sinking. Stainless steel tubes with an outer diameter of 1.50 mm and a wall thickness of 0.045 mm were drawn without an inner tool. The inner surface roughness and crystal orientation were examined using the same measurement area. The results indicated that the crystal grains with the {102} crystal planes vertical to the normal direction to the inner surface (ND) suppressed the increase in the height of the unevenness of the surrounding crystal grains, including themselves. The height deviation of the unevenness of the wall-thickened tube was larger than that of the wall-thinned one. Meanwhile, the number of crystal grains with the {102} crystal plane vertical to ND of the wall-thinned tube was larger than that of the wall-thickened one. Therefore, it was considered that this crystal orientation suppressed the development of the inner surface roughness during the hollow sinking. The development of the inner surface roughness was suppressed with decreasing wall thickness because the crystal grains rotated so that the normal direction of {102} crystal plane was parallel to the ND: meanwhile the tensile and compressive stresses were applied to the inner surface of the micro tube in the drawing and transversal directions, respectively.

Influence of Thermal Processing on Resoloy Wire Microstructure and Properties

Magnesium fine wires are critical components for the fabrication of various absorbable implants. Herein, Resoloy fine wires with diameters of 200 and 500 μm are prepared with a multipass, cold‐drawing technique before undergoing two brief thermal anneals at 350 or 450 °C. The as‐drawn, cold‐worked (CW) wires show small but elongated α‐Mg grains, with their long axes and basal planes parallel to the drawing direction. Fine, continuous, and uniformly distributed Mg24Dy5 particles are observed within the wire. Although the brief anneals at 350 and 450 °C do not alter the texture of the Mg grains or the area fraction, aspect ratio, or distribution of the secondary phase, they do enable recovery and partial recrystallization at 350 °C and complete recrystallization at 450 °C, thereby providing a wide range of mechanical properties. The 200 μm wires display slightly higher strengths and slightly lower elongations. Modified simulated body fluid (m‐SBF) immersion results indicate that the Resoloy wires exhibit relatively uniform corrosion with rates as low as 1.72 ± 0.09, 1.44 ± 0.21, and 1.97 ± 0.10 mm y−1 for the cold‐worked, 350 °C, and 450 °C wires with 500 μm diameter, respectively.

Fabrication of carbon nanotubes/Cu composites with orthotropic mechanical and tribological properties

In this work, Multi-Walled Carbon Nanotubes reinforced copper matrix composites were prepared through a series of preparation processes including ultrasonic and nitrogen-assisted mixing, electroless Nickel–Copper bilayers plating, hot extrusion and cold drawing. The mechanical and tribological properties of the composites were enhanced with the increase of MWCNTs. The Cu matrix composites enhanced with 10 vol% MWCNTs showed significant improvements in the mechanical and tribological properties. Compared with the pure Cu sample prepared by the same method, the tensile strength and yield strength of the composite increased by 52.15% and 56.67%, while the friction coefficient and wear rate decreased by 66.8% and 62.3%, respectively. Better than most of the reported data. The 3 vol% MWCNTs in the composites exhibited the highest strengthening efficiency. Due to the directional arrangement of the MWCNTs in the Cu matrix, the composites showed obvious orthogonal anisotropy, and the properties in the parallel drawing direction were much better than those in the vertical drawing direction. Dislocation and load transfer effect are considered as the main mechanism of mechanical properties enhancement. The formation of self-lubricating layer, load transfer, efficient derivation of friction heat and orientation arrangement of MWCNTs were the reasons which lead to the friction performance enhancement.

From the Editor

Layered silicates present interaction sites at both faces and edges of the nanolayers and silane coupling agents that locate at both sites lead to polymer nanocomposites with superior melt strength and properties. This work’s objective was (a) to investigate the effectiveness of solvent-free, vapor phase, silane treatment of the nanolayers for formulating masterbatches and (b) to compare the mechanical properties of 1mil thick blown films from polypropylene copolymer nanocomposites with such coupling, to films from the neat polypropylene. The nanocomposite blown film tensile modulus and tensile strength improved along both the draw direction and the transverse direction. In addition, their elongation to failure was close to 500% along both directions, in contrast to values of 500% along MD and 170% along TD for the neat PP copolymer. These trends may be understood in terms of the crystalline lamellar orientation distribution in the films. FESEM images revealed that cross-hatched lamellae were absent from the unfilled PP blown film and were pervasive in the nanocomposite blown film. The nanolayers were oriented in the film plane with the longer dimension largely along the MD. The lower extent of lamellar orientation around nanolayers may be attributed to the strong reduction in the polymer chain mobility attached to the nanolayers. Polyaniline and quantum dot-based nanostructures: Developments and perspectives” also by Ayesha Kausar reviews Quantum dots which are 2–5 nm nanoparticles with exceptional optical, electronic, luminescence, and semiconducting properties. Polyaniline is an exclusive conjugated polymer. This article reviews recent efforts, scientific trials, and technological solicitations for polyaniline/quantum dot-based nanocomposites. Polyaniline/quantum dot mixtures form a unique composition for advance materials and applications. Carbon dots, graphene quantum dots, and several inorganic quantum dots have been added to a conducting polymer. A functional quantum dot may develop electrostatic, van der Waal, and p–p stacking interactions with the conjugated polymer backbone. Uniform quantum dot dispersion in polyaniline may result in inimitable morphology, electrical conductivity, electrochemical properties, capacitance, and sensing features. Finally, this review expounds on the many applications for polyaniline/quantum dot nanocomposites including dye-sensitized solar cell, supercapacitor, electronics, gas sensor, biosensor, and bioimaging. And a final thought. “The power of population is so superior to the power of the Earth to produce subsistence for man, that premature death must in some shape or other visit the human race” Thomas Malthus 1798

«КЕЙС В КЕЙСЕ»: ПОДГОТОВКА ИНОСТРАННЫХ СТУДЕНТОВ К СОСТАВЛЕНИЮ КЕЙСОВ ПО РУССКОМУ ЯЗЫКУ КАК ИНОСТРАННОМУ

The article presents the experience of using the case method in the professional pedagogical training of foreign students. The case method activates all types of speech activity in the lesson, and also develops professional pedagogical skills. The authors of the article have made educational materials for the preparation of foreign students of the pedagogical direction for the preparation of cases in Russian as a foreign language. The tasks of the case «How to compose a case in Russian as a foreign language» help foreign students to understand the technology of compiling a case (stages, content of the case, requirements for a case in Russian as a foreign language). The case study on Russian as a foreign language has a description of problem situations from the socio-cultural practice of foreign students, and a system of teaching materials. The purpose of the assignments: mastering the lexical and grammatical minimum, the formation and development of skills to create an oral/written monologue/dialogical utterance, the use of the rules of dialogical communication and formulas of speech etiquette of the official and unofficial spheres of communication, teaching the conduct of a discussion on the topic of a problem situation, systematization of the skills of using the language in accordance with communicative conditions, etc. When compiling a case on Russian as a foreign language, one needs not only the principles of consistency, accessibility, interactivity, lingvodidactic principles, consciously communicative orientation, complex mastery of all types of speech activity, but also the principles of organizing the speech interaction of the participants in the case, using the communicative potential of the language material, socio-cultural content case, motivation of the case participants. The preparation of foreign students of pedagogical directions for drawing up their own cases is an important condition for the formation of communicative and professional pedagogical competencies. Students get the opportunity to apply theoretical material in practice, learn how to work in a team, and improve critical thinking skills.

On the cleavage hoop stress responsible for crack path deflection and notch-induced anisotropic fracture in cold drawn pearlitic steel: Revisiting John Ford’s Monument Valley

In this paper a study is presented of the fracture behaviour in the presence of notches of high-strength pearlitic steel with different cold drawing degree. To this end, axisymmetric notched samples with a circumferentially-shaped notch of very distinct geometries (sharp and blunt, deep and shallow) were taken from wires with different levels of drawing from the initial hot rolled bar (not cold drawn at all) to the final commercial product (prestressing steel wire: heavily cold drawn). Experimental results show that cold drawn steels exhibit a markedly anisotropic fracture behaviour in the form of fracture path deviation from the original transverse fracture path perpendicular to the wire axis or cold drawing direction. Present paper proposes a key variable governing the notch-induced anisotropic fracture process: the cleavage hoop stress as the relevant factor promoting this sort of fracture path deviation in the most heavily cold drawn pearlitic steel wires