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At least 127 records · Page 7

All sources NASA NTRS DOE OSTI

DOE OSTI2017

Zr Extrusion – Direct Input for Models & Validation

As we examine differences in the high strain rate, high strain tensile response of high purity, highly textured Zr as a function of loading direction, temperature and extrusion velocity with primarily post mortem characterization techniques, we have also developed a technique for characterizing the in-situ extrusion process. This particular measurement is useful for partitioning energy of the system during the extrusion process: friction, kinetic energy, and temperature

36 MATERIALS SCIENCE↗

DOE OSTI2024

High Velocity Joining of Multi-material Stacks Containing 3rd Generation Advanced High-Strength Stainless Steel and Aluminum Extrusion and Casting (Abstract)

Advanced lightweight materials, including multi-phase steels, aluminum extrusions and aluminum castings, have increasingly replaced mild steel to meet original equipment manufacturer (OEM) demand for increased fuel economy and crash-safety requirements. Third Generation (Gen 3) AHSS provides a superior combination of strength and ductility for crash energy management components in the vehicle body-in-white (BIW). Aluminum extrusions are widely used for bumper, door rocker panel, cradle and battery frame applications. Aluminum castings are increasingly being used in electric vehicles to provide part consolidation, weight saving and increased driving range. Rocker panels are, for example, an important component of the battery electric vehicle (BEV) body structure. The rocker panel serves several purposes, including structural support, crash resistance, protection for the vehicle's underbody and battery tray, and contributing to the overall aesthetics. In order to reduce weight, rocker panels are usually constructed using outer panels consisting of 3rd generation advanced high strength steels (AHSS) and an inner multicell aluminum extrusion structure for energy absorption which protects the batteries in a crash event. It is well known, however, that these material combinations provide significant challenges for joining and are susceptible to liquid metal embrittlement and loss of strength. The overall goal is to find a solution that addresses these challenges in order to produce multi-material vehicle components with reduced weight and minimal galvanic and recyclability issues. The approach being proposed here is to utilize a novel high velocity (HiVe) riveting and clinching technique recently demonstrated by Pacific Northwest National Laboratory (PNNL) to join (2T/3T) sheets of aluminum alloys and steel. This process will not only address the aforementioned challenges but also help significantly reduce the joining cycle time. This work will also demonstrate use of HiVe assemblies to be retrofitted to existing body-shop robots thus having minimal impact to existing body shop operations.

36 MATERIALS SCIENCE↗

DOE OSTI2025

Multiplexing core & sheath extrusion system development for additive manufacturing for inner-bead multi-material capability

Single-feed polymer extruders are widely used in large-format additive manufacturing (AM) systems; however, the increasing demand for multi-material functionality within a single part has driven significant innovation in this field. One approach involves robotic pick-and-place operations, while another explores mechanical switching of feed lines during extrusion. Although robotic pick-and-drop systems offer flexibility, they introduce longer layer times during material changes, which can negatively affect the structural integrity of the part. On the other hand, mechanical feed switching causes delays in material transitions, as the existing material must be flushed before the new material emerges from the nozzle. This poses particular challenges for smaller or more intricate parts. In this study we are developing a unique multiplexing extrusion system with core & sheath nozzle that combines two extruders via co-extrusion. This allows for a unique inside and outside inner-bead (i.e., within the same bead) multi-material capability. We believe that this technology will allow for combining neat and filled materials, ductile and stronger materials, and many other combinations to address the problems aforementioned above and disrupt the AM technology creating new opportunities and opening application areas.

Tekinalp, Halil [ORNL]↗

NASA NTRS1987

Hot extrusion of B2 iron aluminide powders

The objective of the study was to investigate the effect of powder and processing variables on the microstructure and resultant tensile properties of an extruded FeAlZrB alloy. For a given powder particle size, increasing the extrusion temperature from 1250 to 1450 K is found to increase the grain size and produce a more uniform microstructure. At high extrusion temperatures, where grain boundary mobility is high, powder size is not critical in determining the grain size. The addition of Y2O3 dispersion (1 vol pct) by mechanical alloying makes it possible to obtain very fine-grained materials at low and high extrusion temperatures.

Strothers, S.↗

NASA NTRS1992

Solidification and morphology of submarine lavas - A dependence on extrusion rate

The results of recent laboratory experiments with wax extruded beneath relatively cold water may be extrapolated to predict the surface morphology of submarine lavas as a function of the extrusion rate and melt viscosity. The experiments with solidifying wax indicated that the surface morphology was controlled by a single parameter, the ratio of the time taken for the surface to solidify, and a time scale for lateral flow. For submarine basalts a solution of the cooling problem (which is dominated by conduction in the lava but convective heat transfer in the water) and estimates of lava viscosities place this parameter within the empirically determined 'pillowing' regime over a wide range of extrusion rates. This results is consistent with the observation that pillow basalts are the most common products of submarine eruptions. Smoother surfaces corresponding to the various types of submarine sheet flows are predicted for sufficiently rapid extrusion of basaltic magma. Still higher eruption rates in regions of low topographic relief may produce submarine lava lakes. Minimum emplacement times can be calculated for submarine volcanic constructs of a single lava flow type.

Griffiths, Ross W.↗

NASA NTRS2001

Structure-Property Correlations in Al-Li Alloy Integrally Stiffened Extrusions

The objective of this investigation was to establish the relationship between mechanical property anisotropy, microstructure and crystallographic texture in integrally 'T'-stiffened extruded panels fabricated from the Al-Li alloys 2195, 2098 and 2096. In-plane properties were measured as a function of orientation at two locations in the panels, namely mid-way between (Skin), and directly beneath (Base), the integral 'T' stiffeners. The 2195 extrusion exhibited the best combination of strength and toughness, but was the most anisotropic. The 2098 extrusion exhibited lower strength and comparable toughness, but was more isotropic than 2195. The 2096 extrusion exhibited the lowest strength and poor toughness, but was the most isotropic. All three alloys exhibited highly elongated grain structures and similar location-dependent variations in grain morphology. The textural characteristics comprised a beta + <100> fiber texture, similar to rolled product, in the Skin regions and alpha <111> + <100> fiber texture, comparable to axisymmetric extruded product, in the Base regions. In an attempt to quantitatively correlate texture with yield strength anisotropy, the original 'full constraint' Taylor model and a variant of the 'relaxed constraint' model, explored by Wert et al., were applied to the data. A comparison of the results revealed that the Wert model was consistently more accurate than the Taylor model.

Hales, Stephen J.↗

DOE OSTI2017

Rheological evaluation of high temperature polymers to identify successful extrusion parameters

With the advancements in additive manufacturing (AM), several high temperature thermoplastics are being explored as potential AM feedstocks. Some of these high-performance thermoplastics include; polyetherimides (PEI), polyphenylsulfones (PPSU/F), poly(ether ketone ketone)s (PEKK) and polyphenylene sulfide (PPS) as well as their reinforced composites. Most of these advanced resins tend to be more expensive than commodity plastics such as acrylonitrile butadiene styrene (ABS) and polylactic acid (PLA), and their processing parameters have not been determined for most AM systems. This paper demonstrates a method for identifying the appropriate processing conditions for extrusion-based AM deposition systems, in which a material is forced through an orifice at a given flow rate. The pressure required to extrude a shear-thinning thermoplastic at a given shear rate is calculated based on viscoelastic properties of the polymer melt and compared against maximum system pressure to predict successful extrusion. An evaluation of several candidate materials is presented on the Big Area Additive Manufacturing extrusion-based platform.

Ajinjeru, Christine↗

DOE OSTI2017

A VISCOELASTIC MODEL FOR EVALUATING EXTRUSION-BASED PRINT CONDITIONS

Extrusion-based printing systems have improved significantly over the past several years, allowing for higher throughput, higher temperatures, and larger components. At the same time, advanced materials are being introduced on the market that can provide improved performance over a range of operating conditions. Often these materials incorporate fiber reinforcements, reactive resins, and additives to control reaction kinetics, flow rheology, or thermal stability. This study presents a general framework for evaluating the printability of various candidate materials based on a basic viscoelastic model. The model addresses fundamental requirements for extrusion-based printing, including pressure-driven flow, bead formation, bead functionality, and component-level functionality. The effectiveness of this model for evaluating the impact of compositional variations and identifying appropriate processing conditions has been demonstrated for specific materials on direct write, fused filament fabrication, and large-scale extrusion platforms.

Duty, Chad↗

DOE OSTI2017

Rheological Characteristics of Fiber Reinforced Poly(Ether Ketone Ketone) (PEKK) for Melt Extrusion Additive Manufacturing

Several grades of unreinforced and short fiber reinforced poly(ether ketone ketone) (PEKK) copolymers are analyzed for their potential use as feedstock materials in melt extrusion-based additive manufacturing (AM) systems. Rheological characterization has been performed to study the effect of extrusion processing parameters such as time, temperature, environment, and shear rate for the selected materials. The effect of reinforcing filler content on the melt processing conditions of PEKK composites are also reported, and processing conditions for successful extrusion of these materials on AM systems are determined.

Kishore, Vidya↗

DOE OSTI2022

Shear assisted extrusion process

A shear assisted extrusion process for producing cladded materials wherein a cladding material and a material to be cladded are placed in sequence with the cladded material positioned to contact a rotating scroll face first and the material to be cladded second. The two materials are fed through a shear assisted extrusion device at a preselected feed rate and impacted by a rotating scroll face to generate a cladded extrusion product. This process allows for increased through wall strength and decreases the brittleness in formed structures as compared to the prior art.

Joshi, Vineet V.↗

DOE OSTI2021

Hybrid Chemo-Mechanical Plastics Recycling: Solvent-free, High-speed Reactive Extrusion of Low-Density Polyethylene

Low-Density Polyethylene (LDPE) is ubiquitous in the packaging industry due to its flexibility, toughness, and low cost. However, it is typically contaminated with other materials, seriously limiting options for mechanical recycling. Interest in chemical recycling techniques such as pyrolysis and hydrothermal liquefaction is growing, but most of these processes face technoeconomic challenges that have limited commercial deployment. We present a hybrid chemo-mechanical approach using reactive twin-screw extrusion (TSE) for tailoring the molecular weight and chain structure of reclaimed LDPE. Two types of zeolite catalysts at several loading levels were evaluated over a range of processing conditions. Structural, thermal, and rheological properties of the extruded samples were investigated and compared to virgin LDPE and LDPE extruded without the catalyst. A nuclear magnetic resonance spectroscopic technique was used to investigate changes in the structure of the polymer. LDPE extruded with microporous y-zeolite showed lower degradation temperature and increased short chain branching. Mesoporous MCM-41 also induced increased branching but had no effect on degradation temperature. The theoretical mechanical energy input for the chemical modification was calculated using process modeling. The demonstrated hybrid reactive extrusion process provides a potential low-cost, simple approach for repurposing LDPE-based flexible packaging as coatings and adhesives.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2018

Microstructure Characteristic and Mechanical Properties of High-Strength Mg-Nd-Zn-Zr Alloy Seamless Tube Produced by Integrated Extrusion

Large size seamless tubes of Mg-3.0Nd-0.4Zn-0.4Zr alloy (NZ30K, in weight percent) were prepared by integrating backward extrusion with forward extrusion. Microstructure, mechanical properties, aging behavior and texture of the tubes were investigated. The microstructure of as-extruded tube is characterized by the blend of considerably elongated grains and fine equiaxed grains. The maximum values of yield strength and ultimate tensile strength, i.e., 191 and 245 MPa, were obtained in the as-extruded tubes, and these values were increased to 212 and 267 MPa in the peak-aged tubes (T5), implying an increasing ratio of 9 and 11%, respectively. The peak value of the Vickers’ micro-hardness of the NZ30K tubes extruded at 673, 723 and 753 K are 66, 64 and 60 (kilogram-force per square millimeter), respectively. The texture of NZ30K tube is weak, the primary mechanism behind which is suggested to be the particle-induced nucleation responsible for the promotion of recrystallization.

36 MATERIALS SCIENCE↗

DOE OSTI2019

Experimental Investigations for Optimizing the Extrusion Parameters on FDM PLA Printed Parts

Fused deposition modeling (FDM) has become one of the most extensively used additive manufacturing technologies in recent years because of its wide adaptability, simple mechanism and low cost. It is difficult, however, to achieve an equitable trade-off among mechanical properties, surface finish quality and production time, which is an area seldom explored. This paper concentrates on the optimization of the parameters to achieve higher tensile strength and lower surface roughness with less build time during the FDM process based on central composite design for the tensile specimen forming process. The effects of five extrusion parameters (nozzle diameter, liquefier temperature, extrusion velocity, filling velocity and layer thickness) on the three outputs of tensile strength (TS), surface roughness (SR) and build time (BT) are investigated. Response surface methodology combined with nondominated sorting genetic algorithm II is developed to optimize the process parameters to achieve the maximum TS, minimum SR and BT, as verified by subsequent experiments. The predicted results are found to be very close to the experimental data, illustrating that the presented approach in this paper is effective for improving mechanical properties, surface finish and efficiency of the FDM process.

36 MATERIALS SCIENCE↗

DOE OSTI2019

Corrosion Behavior of AZ31 Magnesium Alloy Produced by Continuous Variable Cross Section Direct Extrusion

In order to study the corrosion behavior of magnesium alloys of high performance in the simulated seawater by continuous variable cross section direct extrusion (CVCDE), an electrochemical method and weight loss method were used to study the difference between AZ31 magnesium alloys produced by CVCDE with different numbers of interim dies to examine the electrochemical corrosion behavior and corrosion rate at 3.5 wt.% NaCl solution in this paper. Scanning electron microscopy and x-ray diffraction were used to analyze the morphology of corrosion surfaces and the composition of the corrosion products of samples soaked for different times. The results show that after CVCDE with different numbers of interim dies, the size of the microstructure is refined gradually, and the grain orientation is also different; with the increase in the number of interim dies, the thermodynamic corrosion tendencies are different, and the corrosion resistance of samples extruded by conventional extrusion is relatively good; the charge transfer and material transfer process are the two main factors affecting the corrosion rate, which determines the direction of the electrochemical reaction; the corrosion form of the sample extruded by CVCDE is the local corrosion which is the filiform corrosion and pitting corrosion, and the corrosion product is mainly water-insoluble Mg(OH){sub 2}.

36 MATERIALS SCIENCE↗

DOE OSTI2017

A novel freeform extrusion fabrication process for producing solid ceramic components with uniform layered radiation drying

An extrusion-based additive manufacturing process, called the Ceramic On-Demand Extrusion (CODE) process, for producing three-dimensional ceramic components with near theoretical density is introduced in this paper. Heere in this process, an aqueous paste of ceramic particles with a very low binder content (<1 vol%) is extruded through a moving nozzle at room temperature. After a layer is deposited, it is surrounded by oil (to a level just below the top surface of most recent layer) to preclude non-uniform evaporation from the sides. Infrared radiation is then used to partially, and uniformly, dry the just-deposited layer so that the yield stress of the paste increases and the part maintains its shape. The same procedure is repeated for every layer until part fabrication is completed. Several sample parts for various applications were produced using this process and their properties were obtained. The results indicate that the proposed method enables fabrication of large, dense ceramic parts with complex geometries.

36 MATERIALS SCIENCE↗

DOE OSTI2014

Lansoprazole induces apoptosis of breast cancer cells through inhibition of intracellular proton extrusion

Highlights: • Lansoprazole (LPZ) induces cell apoptosis in breast cancer cells. • LPZ markedly inhibits intracellular proton extrusion. • LPZ induces an increase in intracellular ATP level, lysosomal alkalinization and ROS accumulation. - Abstract: The increased glycolysis and proton secretion in tumors is proposed to contribute to the proliferation and invasion of cancer cells during the process of tumorigenesis and metastasis. Here, treatment of human breast cancer cells with proton pump inhibitor (PPI) lansoprazole (LPZ) induces cell apoptosis in a dose-dependent manner. In the implantation of the MDA-MB-231 xenografts in nude mice, administration of LPZ significantly inhibits tumorigenesis and induces large-scale apopotosis of tumor cells. LPZ markedly inhibits intracellular proton extrusion, induces an increase in intracellular ATP level, lysosomal alkalinization and accumulation of reactive oxygen species (ROS) in breast cancer cells. The ROS scavenger N-acetyl-L-cysteine (NAC) and diphenyleneiodonium (DPI), a specific pharmacological inhibitor of NADPH oxidases (NOX), significantly abolish LPZ-induced ROS accumulation in breast cancer cells. Our results suggested that LPZ may be used as a new therapeutic drug for breast tumor.

60 APPLIED LIFE SCIENCES↗

DOE OSTI2018

Refining whisker size of 2024Al/Al18B4O33w composite through extrusion and its effects on the material's micro-structures and mechanical properties

Highlights: • The nonuniform distributions of stress and velocity along whisker lead to whisker breakage. • The microcrack between broken whiskers can propagate into interface or matrix, related to the wedge angle of broken whisker. • The whisker breakage and staggered result in the decreasing distance between neighboring whiskers. • The smaller distance between neighboring whiskers reduces the resistance to the propagation of crack resulting in the lower ultimate tensile strength of extruded composite. - Abstract: Hot extrusion is used to improve the distribution of whiskers and refine the whisker sizes of 2024Al/Al{sub 18}B{sub 4}O{sub 33}w composite. The grain size and the ultimate tensile strength of the extruded 2024Al/Al{sub 18}B{sub 4}O{sub 33}w composite are analyzed. The results show that the average length of whiskers decreases due to the whisker breakage. The nonuniform distributions of stress and velocity along the whisker lead to whisker breakage. The microcrack between the broken whiskers can propagate into the interface or the matrix, related to the wedge angle of the broken whisker. The extrusion is beneficial to the whisker staggered and makes it easy for the microcracks filled with matrix. The whisker breakage and the whisker staggered result in the decreasing distance between the neighboring whiskers. Due to the dislocation motion constrained by matrix and the overlap of the deformation areas, the decreasing distance between the neighboring whiskers promoting the recrystallization results in the smaller grain size. During tensile tests, due to the smaller resistance with the smaller distance between the neighboring whiskers, the cracks between the progressive broken whiskers are easy to coalesce resulting in the lower ultimate tensile strength of the extruded composite.

36 MATERIALS SCIENCE↗

DOE OSTI2018

Characterization of hot extrusion and heat treatment on mechanical properties in a spray formed ultra-high strength Al-Zn-Mg-Cu alloy

Highlights: • The spray forming technology was used to fabricate ultra-high strength aluminum alloy. • The alloy under RRA state obtained the highest ultimate tensile strength of 732 MPa. • The effects of dislocations, solutes and precipitates etc., on yield strength were calculated. • Precipitation was characterized as the main strengthening mechanism for aging states. - Abstract: To obtain the optimal mechanical properties, several processes including spray forming technology, two passes hot extrusion and substantial heating treatments were operated on an Al-Zn-Mg-Cu-Zr alloy. The characterization methods used in this study include tensile tests, X-ray diffraction, differential scanning calorimetry and microstructure observations by optical microscope, scanning and transmission electron microscopy. The typical characteristics were the refined grain, homogeneous precipitates and porosity in the as-deposited pre-forms. The ultimate tensile strength, yield strength, hardness and elongation improved significantly after two passes hot extrusion. A good combination of ultimate tensile strength at 704 MPa and elongation at 9.7% were achieved under peak-aged treatment. The best ultimate tensile strength was obtained at 732 MPa after re-aging and regression. It was main dimple fracture in the extruded and aging treated specimens while brittle fracture for the as-deposited. The secondary phases were main MgZn{sub 2} and Al{sub 3}Zr dispersoids throughout all the states. The contributions of grain boundaries, dislocations, solid-solution and precipitates on the yield strength were analyzed using a quantitative equation.

36 MATERIALS SCIENCE↗