Die Drawing Research Articles

Development of die drawing design factor prediction models for trenchless rehabilitation of water pipes: a case study

ABSTRACT Maintenance and replacement of aging water pipes are critical for urban development. To this end, trenchless rehabilitation methods that do not require excavation offer an efficient replacement for aging water pipes. Thus, this study developed a trenchless method using die drawing, which continuously inserts polyethylene (PE) liners into the reach point while maintaining traction in the host aging pipe. If the traction is removed after a certain period, the initially contracted liner pipe undergoes expansion under natural restoration and tightly adheres to the inner wall of the host pipe to achieve structural regeneration of the aging pipe. This study aimed to determine the factors influencing the die drawing process using a rehabilitation design. Accordingly, we experimented with the die drawing method to achieve structural reinforcement using high elasticity PE liners. Thereafter, based on the experimental data, we developed prediction models to estimate traction, pipe restoration rate after traction release, and pipe restoration period. The developed models estimated the minimum required restoration period and provided deeper insights into the restoration behavior of the die drawing method employed in pre-equipment maintenance before on-site construction.

Solid-Phase Orientation (Die Drawing) of Polymer Tubes to Enhance Mechanical Properties of Bioresorbable Vascular Scaffolds

Die-drawing, also known as solid phase orientation, is a technique used to enhance the mechanical properties of polymers for non-medical applications [1]. Arterius has adapted and optimised this technology to manufacture state-of-the-art bioresorbable polymeric scaffolds (stents) based on polylactic acid (PLA) for vascular and non-vascular applications. The mechanical properties of the polymer are improved by orientating the polymer chains and introducing crystallinity to the polymer. As the PLA polymer is drawn over a mandrel and through a die, close to the glass transition temperature (Tg > 55 °C), the polymer chains align, gradually increasing orientation with the bi-axial draw, thus promoting significantly improved mechanical properties. In-house testing of the die-drawn tubing compared to the extruded tubing showed an increase in tensile modulus up to 79.7%, yield strength increases of up to 121.5%, ultimate tensile strength increases of up to 267.9% and elongation at break increase of up to 1,022.8%. The die-drawing process also introduces crystallinity into the PLLA tubing, initially the amorphous extruded tube has a crystallinity of around 1.3% which increased to around 40% crystallinity after the die-drawn process. Another attribute of the orientated polymer tubing is the radial strength it provides to the scaffold once it has been laser cut into an innovative closed-cell design, which is comparable to market-leading metallic stents.

Cavitation in die drawn poly(4-methyl-1-pentene) during second-stage tensile deformation

Pre-oriented poly (4-methyl-1-pentene) samples were prepared by the die drawing process. The stress whitening phenomenon induced by cavities in the different die drawn P4M1P samples during the second-stage tensile deformation was investigated at temperatures below and above Tg. At 30 °C and 50 °C, the cavitation process near yield point is influenced by the fraction of unoriented crystalline phase in pre-oriented samples. Cavities originate from the fracture of the crystalline skeleton at small strains were observed in the sample with a high fraction of unoriented crystalline phase. At high deformation temperature, the small strain cavities were suppressed and the cavitation processes in all die drawn samples are due to the failure of the highly oriented fibrillar network caused by the breaking of the load-bearing interfibrillar/microfibrillar tie molecule chains.

Production of Fine Copper Wire by 3–Rolling and Die Drawing

Production of Fine Copper Wire by 3–Rolling and Die Drawing

Effect of Drawing Parameters on the Properties of Polypropylene/Inorganic Particles Composites by Solid-State Die Drawing.

Die drawing is an effective method for improving the properties of polymer. In this work, polypropylene (PP)/inorganic particle composites were fabricated by a solid-state die drawing process to investigate the effects of drawing parameters, such as inorganic particles types, drawing temperature, and drawing speed, on the thermal properties, microstructure, and mechanical behavior of the drawn composites. The mechanical properties of the material were significantly improved through this processing method. For the drawn PP/inorganic particle composites with 45 wt% CaCO3, when the drawing speed was 2.0 m/min and the drawing temperature was 110 °C, the density of the drawn composites reached the lowest at 1.00 g/cm3. At this time, the tensile strength, flexural strength, and impact strength of the drawn composites were 128.32 MPa, 77.12 MPa, and 170.42 KJ/m2, respectively. This work provides a new strategy for the preparation of lightweight and high-strength PP-based composites, which have broad application prospects in the field of engineering and structural materials.

Preparation of R-BABP Polyimide Fibers via Wet Spinning of Polyamide Acid

A polyamide acid (PAA) based on diamine 4,4'-bis (4-aminophenoxy) diphenyl and 1,3-bis (3',4-dicarboxyphenoxy) benzene dianhydride was synthesized. PAA fibers were obtained by wet spinning. Then, these fibers were converted into polyimide by thermal imidization. Dependence of the structure and properties of fibers on the die drawing and the composition of the coagulation bath was studied. It is shown that the composition of the coagulation bath has a significant effect on the morphology and mechanical properties of polyimide (PI) fibers. To obtain defect-free fibers, a coagulation bath consisting of ethylene glycol/ethanol at 50/50 vol. % was found to be optimal. An increase in the die drawing of fibers from 1 to 2 times leads to an increase in tensile strength and strain at break of the polyimide fibers.

Advantage of Preserving Bi-orientation Structure of Isotactic Polypropylene through Die Drawing

The isotactic polypropylene (iPP) usually shows a unique parent-daughter lamellae structure in which the parent and daughter lamellae are against each other with a near perpendicular angle (80° or 100°). Inducing a high fraction of oriented cross-hatched structure in iPP during processing is desirable for designing the bi-oriented iPP products. We processed a commercial iPP via tensile-stretching and die-drawing to evaluate the structural evolution of oriented parent-daughter lamellae. It turned out that the die-drawing process had an advantage in attaining a high fraction of oriented cross-hatched structure of iPP, as compared to the free tensile stretching. Besides, the presence of α-nucleating agents affected the formation of oriented parent-daughter lamellae in the die-drawn samples whereas such influence diminished in the free stretched ones. It was found that the confined deformation inside the die led to the well-preserved oriented cross-hatched structure in the die-drawn iPP.

Verification of Friction Models Implemented in the Simulation Software

Modern approaches in simulations of sheet metal stamping processes are based on definition the friction coefficient as not constant, but the different value in different regions, considering the nature of the actual deformation process in each individual region. In this contribution the regression and analytical models to determine the friction coefficients under blankholder and on the die drawing edge by strip drawing test are presented. These models were verified by experimental strip drawing test under the same contact conditions. Zn coated steel sheets for the automotive industry were used in experiments and simulations – extra deep drawing quality DX54D and high strength steel TRIP. The results indicate, that friction coefficients are not constant and depend on the pressure on the die contact surfaces. Friction coefficients were determined also at the cup test by the regression model of drawing versus blankholding force. Conformity of friction coefficients obtained by the cup and the strip tests was confirmed. Model of friction applied in FEM simulation was verified by cup test and good conformity was found out.

Fabrication of reinforced and toughened poly(lactic acid)/poly(butylene adipate‐co‐terephthalate) composites through solid die drawing process

AbstractIn this study, poly(butylene adipate‐co‐terephthalate) (PBAT) was introduced to poly(lactic acid) (PLA) matrix to improve its inherent poor toughness. Besides, the orientation structure was also introduced via die drawing process to compensate for strength loss. The results indicate that die drawing process contributes to improve the mechanical properties of PLA. The tensile strength, modulus, and elongation at break of die‐drawn pure PLA increased by 76.6, 36.1, and 1,375.0%, respectively, compared with those of isotropic PLA. Moreover, the tensile strength can be further improved by the addition of PBAT. The die drawing process can remarkably improve crystallinity, and the orientation factor is high when the PBAT content is less than 30 wt%. By combining the PBAT with highly oriented structure imported by die drawing process, it is possible to prepare simultaneously reinforced and toughened materials, which provides a new insight into the modification of PLA.

Theoretical Calculation and Numerical Simulation on Roller Die Drawing Force of High Pressure Cylinder

Theoretical Calculation and Numerical Simulation on Roller Die Drawing Force of High Pressure Cylinder

Tribology properties evaluation for friction pair Zn coated steel –TiCN MP coated/uncoated tool steel

When the sheet metal stamping processes are simulated, different values of the friction coefficient need to be defined in different regions, considering the nature of the deformation process. Thus, the regression and analytical models to determine the friction coefficient under the blankholder and on the die drawing edge by the strip drawing test are presented in the article. These models were verified by experimental strip drawing test under the same contact conditions. Zn coated high strength low alloyed steel sheet H220PD+Z100 was used at experiments and friction tests were done against the tool steel and TiCN MP coated tool steel. The results indicate, that values of friction coefficients evaluated by linear regression are lower than evaluated from analytical models. The positive effect of coating TiCN MP when applied on the contact surfaces was found, thus, decreases the friction coefficient and the drawing force scattering during the strip drawing test.

Fractography study of Co-Cr-Ni-Mo alloy fatigue wires drawn with different drawing practices

This study investigates the influence of wire drawing practices, namely Full Die Drawing (FDD) and Half Die Drawing (HDD) on the fatigue performance of MP35NLT wires. The as-drawn wires were subjected to rotary beam fatigue tests with varying stress amplitudes, and the cyclic performance of the wires in the LCF and HCF regimes was determined. A relation between the microscopic and macroscopic attributes contributing to different crack mechanisms was established. The results conclude that there is a significant impact on the drawing techniques on the cyclic performance, with the FDD wires having a higher endurance limit than the HDD wire.

Fatigue behavior in Co–Cr–Ni–Mo medical wires drawn with different drawing practices

35%Co–20%Cr–35%Ni–10%Mo alloy (MP35N) with a low titanium (LT) content is commonly used as the material for the manufacture of leads in medical applications such as Cardiac Rhythmic Management (CRM), neurostimulation and Deep Brain Stimulation (DBS). The material is drawn to thin wires, and this involves subjecting the material to extensive plastic deformation to obtain the desired mechanical and fatigue properties. The critical part in the medical device design requires understanding the relationship between the processing method, microstructure and their impact on the cyclic performance. In this study, the influence of drawing practices namely Full Die Drawing (FDD) and Half Die Drawing (HDD) on the cyclic performance of MP35NLT wires have been investigated, by differing the amount of plastic strain applied on the material. The as-drawn wires were subjected to rotary beam fatigue tests (R = −1) with varying stress amplitudes, and the microstructural factors controlling the Low Cycle Fatigue (LCF) and High Cycle Fatigue (HCF) performance were determined through post fatigued TEM investigations. The results conclude that there is a significant impact on the drawing techniques on the fatigue performance of MP35NLT wires, with the FDD wires having a higher endurance limit than the HDD drawn wire until 75% CW, but there was a slight drop in the fatigue performance when the CW was increased to 95%. This was attributed to the difference in grain sizes, dislocation structures, twin density, twin spacing, and grain boundary orientations observed between the two wires which contributed to contrasting cyclic behavior. The drop-in fatigue performance of the FDD wire upon an increased strain to 95% has been attributed to the shear band formations in the material, which increased the stress localization in the material bestowing to drop-in fatigue performance.

Plastic Instability in Co-Cr-Ni-Mo alloy wires drawn with different drawing practices

Plastic instability of Co-35Ni-20Cr-10Mo alloy was studied by inflicting the material to the different drawing process, namely Full Die Drawing (FDD) and Half Die Drawing (HDD). The wires were subjected to different plastic deformations, by varying the amount of cold work (CW) reduction, and the strain hardening exponent (γ) and strain rate sensitivity (m) were determined from the logarithmic plots of the true stress and strain curves. The experimental results indicated that wires drawn with FDD practice, when compared with the HDD drawn wires, had a lower instability until 75% CW, after which it increased significantly when drawn to 95% CW. The lower instability in the FDD wires at 75% CW, was attributed to the smaller grain size, higher dislocation density and lower twin spacing which contributed to higher γ and m. Plastic strain localization because of shear band formation was noticed in the FDD 95% CW wires, which contributed to lowered ductility and increased instability in the wire due to reduced γ and m. This phenomenon was not observed in HDD wires. Therefore, the results illustrate that the drawing technique employed to process the material has a significant impact on the plastic instability of the material, with the FDD practice recommended for lower CW deformations and HDD for higher CW deformations.

Structure evolution and orientation mechanism of isotactic polypropylene during the two‐stage solid die drawing process

ABSTRACTHigh oriented isotactic polypropylene prepared by self‐designed two‐stage die drawing apparatus was explored through kinds of methods, including differential scanning calorimetry, two‐dimensional wide‐angle X‐ray diffraction, polarized light microscope, and tensile test. The results showed that there was a great difference between the orientation mechanism and structure evolution of two‐stage solid die drawing process and single‐stage solid die drawing process. All samples would undergo free drawing process after die drawing process. Die drawing and free drawing process were of equal importance to single‐stage die drawing process while die drawing process showed an prominent contribution to the two‐stage die drawing process. Drawing speed showed beneficial influence on die drawing process for both single‐ and two‐stage die drawing process routes. Under the same processing condition, tensile strength and modulus of samples prepared by two‐stage die drawing process were higher than those prepared by single‐stage die drawing process and the maximum value could reach 241.93 MPa and 3.57 GPa, respectively. Moreover, two‐stage die drawing samples showed better dimensional stability than single‐stage die drawing samples especially under low draw rate. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46581.

Influence of drawing practices on the mechanical, texture and work hardening characteristics of Co-Cr-Ni-Mo wires

This study investigates the influence of cold wire drawing practices namely Full Die Drawing (FDD) and Half Die Drawing (HDD) on the microstructure, mechanical and work hardening characteristics on Co-35Ni-20Cr-10Mo material. The wires were subjected to different reductions using a multipass drawing approach and the resulting microstructures were characterized by EBSD and FESEM. It was found that wires drawn with FDD practice showed a higher Yield strength (σYS,) Ultimate Tensile strength (σUTS), higher work hardening rate, and different regimes of work hardening curves when compared to the wires drawn with HDD practice, for the same amount of Cold Work (CW). It was observed that FDD wires had a smaller grain size, homogenous texture and higher amount twins and dislocations in the microstructure, whereas the HDD wires exhibited coarser grains, non-uniform texture and a lower amount of lattice defects.

Structure evolution and orientation mechanism of long-chain-branched poly (lactic acid) in the process of solid die drawing

Highly oriented long-chain-branched poly (lactic acid) (LCB-PLA) was prepared and the structure evolution was studied in the process of solid die drawing by compared with poly (lactic acid) (PLA). During drawing, samples underwent not only die drawing process but also free drawing process. Drawing speed presented a prominent effect on the free drawing process, while die thickness showed a more obvious influence on the die drawing process. For PLA, free drawing process mainly contributed to its final orientation degree and crystallinity, and thus the mechanical properties of PLA were greatly influenced by drawing speed. However, for LCB-PLA, die drawing process made a greater contribution to the final orientation degree and crystallinity, and its mechanical properties were mainly affected by die thickness. Under the same drawing condition, the tensile strength and modulus of LCB-PLA were always higher than those of PLA, and reached up to 228MPa and 7.2GPa, respectively, which basically met the requirement for born fixation materials. Samples which only underwent die drawing showed obvious “sandwich” structure, and the thickness of the oriented skin layer for LCB-PLA was thicker than that for PLA, suggesting that shear-induced orientation can be easily retained due to the enhanced entanglement between long branched chains. After drawing, LCB-PLA samples showed smaller lamellae size (Llateral) but larger long period (Lac) compared with PLA, suggesting that the low chain mobility restricted the motion of chain slipping of LCB-PLA and thus resulted in the fragmentation of neighboring crystal lamella by chain stretched-out.

Microstructure and Mechanical Properties of TC16 Titanium Alloy by Room Temperature Roller Die Drawing

Microstructure and Mechanical Properties of TC16 Titanium Alloy by Room Temperature Roller Die Drawing

Effect of nano-fillers on conductivity of polyethylene/low melting point metal alloy composites

A novel method for preparing conductive polyethylene (PE) composites has been developed. In the method, the powder of low melting point metal alloy (LMPA) is filled into the PE matrix by using twin screw extruder at a temperature below the melting point of the LMPA, and followed by a die drawing process at a temperature around the melting point of the metal alloy. It has been found that die drawing process, repeating the die drawing process and adding nano-fillers, such as montmorillonite (MMT) and multi-wall carbon nanotubes (MWCNTs), all help reduce the metal particle size in the PE matrix, thus improve the conductivity of the composite. The conductivity improvement is attributed to an increased number of the smaller metal particles. Therefore, conductive composites of polymer/metal alloy/nano-filler with high conductivity are possible to be prepared by using the new method.

Experiments on and Finite Element Analyses of the Tilting of Fine Steel Wire in Roller Die Drawing

Experiments on and Finite Element Analyses of the Tilting of Fine Steel Wire in Roller Die Drawing