High-performance Parts Research Articles

Tensile properties of 3D printed continuous fiberglass reinforced cellular composites

Recent advancements in 3D printing involve reinforcing the polymer matrix with high-strength fibers offer improved mechanical properties over unreinforced polymeric materials. The fiber-reinforcement offers a great potential to customize fiber-reinforced 3D printed polymer composites for complex shapes and high-performance parts for diverse end use applications. The advance capabilities also allow to vary the 3D printed composite weight without compromising the mechanical properties. The aim of this research was to investigate unique macrostructures of 3D printed samples developed by varying the printing parameters, and their influence on the tensile behavior. Samples developed for this study comprised of nylon matrix reinforced with continuous fiberglass with three varying fiber orientations and four different infill geometries. Tensile properties of the unreinforced and reinforced 3D printed samples were evaluated to investigate the impact of fiber orientation and infill geometries and further benchmarked with traditional 3D orthogonal woven (3DOW) composites. The results indicated that the tensile properties due to fiber orientation mainly dictated the tensile properties more than the cellular structure. The analyses from this study showed that the macrostructure (hence tensile properties) of 3D printed specimens were directly related to the printing parameters that include fiber amount and orientation, void formation and the bonding between individual raster/layers.

Applicability of Solid Lubricant Coatings in Cold Rod Extrusion of Stainless Steels

Cold extrusion is an established technology for the production of dimensionally accurate components in large series. Due to the high material and energy efficiency, a resource-saving manufacturing of high-performance parts is possible. Forming at room temperature leads to an advantageous grain structure and work hardening of the material, resulting in components with favorable operating characteristics. Nevertheless, a challenge is the generation of residual stresses during forming, which are influencing the fatigue behavior. The modification of the tribological conditions is one method for influencing the parts’ residual stress state. However, the high strength and work hardening of the materials formed at room temperature leads to high tribological loads between billet and die. These challenges are intensified by the increasing use of stainless steels due to growing demands for corrosion resistant components. The aim followed within this paper is therefore to investigate the applicability of typical lubricant coatings in the forward rod extrusion of stainless steels. For this purpose, the ferritic stainless steel X6Cr17 (DIN 1.4016) and the ferritic-austenitic stainless steel X2CrNiMoN22-5-3 (DIN 1.4462) are extruded with an equivalent plastic strain of ε̅ ≈ 1. The research is performed with a molybdenum disulfide (MoS2), a soap and a polymer-based lubricant coating. For reproducing different contact conditions, the die geometry is varied with die opening angles of 60°, 90° and 120°. The suitability of the lubricants is evaluated using the integrity of the lubricant coating after forming. From the correlations between process forces, temperatures and surface integrity, recommendations for the application of the researched lubricants are derived.

Recrystallization-based grain boundary engineering of 316L stainless steel produced via selective laser melting

Grain boundary engineering (GBE) is a thermomechanical processing strategy to enhance the physical and mechanical properties of polycrystalline metals by purposely incorporating special types of grain boundaries—such as twin boundaries (TB)—in the microstructure. Because of the multiple strain-annealing cycles involved, conventional GBE is not directly applicable to near-net-shape parts, such as those produced via additive manufacturing (AM) technology. In this study, we explore a different GBE processing route that leverages TB multiplication during recrystallization of austenitic 316L stainless steel produced via selective laser melting (SLM). We find that recrystallization requires a minimum level of mechanical deformation, which scales with the laser scanning speed employed during SLM. We ascribe this relationship to the cell size and the amount of solute segregating at cell boundaries during rapid solidification, which are inversely and directly proportional to the laser scanning speed, respectively. The coarser the cell structure and the more uniform the chemical composition, the easier the nucleation and growth of recrystallized grains. Our results provide the groundwork for devising AM-compatible GBE strategies to produce high-performance parts with complex geometry.

Pores and the formation mechanisms of SLMed AlSi10Mg

Purpose To fabricate high performance parts, this paper aims to systematically study the pores characteristics and their formation mechanisms in selective laser melting (SLM) AlSi10Mg. Design/methodology/approach Cubes of 10 × 10 × 5 mm were manufactured in different laser power, scan speed and scan space. Optical microscope (OM) and scanning electron microscopes (SEM) were used to observe morphology of pores. Findings Round or irregular pores were found in SLMed AlSi10Mg parts. All the round pores have smooth inner walls and locate in the melt pool. The formation mechanisms of the round pores are contributed to the evaporation of elements in the melt pool, H2O, high laser energy input and hollow powder. Irregular pores have rough inner walls. Big scan space, unevenness of the upper surface, large layer thickness, spatter and oxide are the main reasons of generating irregular pores which outside the melt pool. Instability of keyhole leads to the irregular pores locate in the bottom of keyhole mode melt pool. Originality/value Relationship between pores and melt pool were studied systematically for the first time. Researches of pores characteristics and their formation mechanisms in SLMed AlSi10Mg would be a valuable reference for researchers to obtain an important insight into and control the defect in SLMed Al alloy.

Discrete Element Simulation of the Effect of Roller-Spreading Parameters on Powder-Bed Density in Additive Manufacturing.

The powder-bed with uniform and high density that determined by the spreading process parameters is the key factor for fabricating high performance parts in Additive Manufacturing (AM) process. In this work, Discrete Element Method (DEM) was deployed in order to simulate Al2O3 ceramic powder roller-spreading. The effects of roller-spreading parameters include translational velocity Vs, roller’s rotational speed ω, roller’s diameter D, and powder layer thickness H on powder-bed density were analyzed. The results show that the increased translational velocity of roller leads to poor powder-bed density. However, the larger roller’s diameter will improve powder-bed density. Moreover, the roller’s rotational speed has little effect on powder-bed density. Layer thickness is the most significant influencing factor on powder-bed density. When layer thickness is 50 μm, most of particles are pushed out of the build platform forming a lot of voids. However, when the layer thickness is greater than 150 μm, the powder-bed becomes more uniform and denser. This work can provide a reliable basis for roller-spreading parameters optimization.

Research on Strong Spinning Process of GH4169 Alloy

In this paper, the basic technology of spin forming process was carried out on the GH4169 alloy sheet by heating and strong spinning. The spheroidal spinability test method was used to study the spinability of the alloy. The effects of the strong spinning process parameters on the ultimate thinning rate, diameter expansion and fracture behavior of GH4169 alloy were analyzed. The research results showed that when the temperature was higher than 800 °C, the ultimate thinning rate of GH4169 alloy was above 80%. At the same time, with the increase of feed rate, the ultimate thinning rate of GH4169 alloy decreased. When the feed rate of the rotary wheel was lower than 200 mm•min-1, the ultimate thinning rate of GH4169 alloy was maintained above 80%. The radius of rotary wheel was strongly influence GH4169 alloy ductility which was confirmed by the picture of fracture. This basic research provides the experimental basis and process guidance for the practical use of GH4169 and other high-temperature alloy sheets to produce high-precision and high-performance spinning parts, which has significant application value.

Influence of composition gradient variation on the microstructure and mechanical properties of 316 L/Inconel718 functionally graded material fabricated by laser additive manufacturing

Abstract Laser metal deposition (LMD) is an advanced manufacturing technology combining rapid prototyping and laser cladding technology, which has been applied to manufacture high performance parts with complex structure. In this study, Inconel-steel functionally graded materials (FGMs) with composition transitioning from 100 % 316 L incrementally graded to 100 % Inconel718 by different composition gradients (5%, 10 %, 20 %) were fabricated by LMD. The microstructure, phase evolution and mechanical properties of the components with different composition gradients (5%, 10 % and 20 %) were characterized by microscopy, energy dispersive spectroscopy, X-ray diffraction, micro-indentation and tensile tests. Brittle Laves phase could be observed when the content of Inconel718 exceeded 40 %. With the composition gradient decreasing, the range of micro-hardness along the deposition direction enlarged. The FGM micro-hardness had the widest range of 173 HV-308 HV when composition gradient was 5%. Fe and Ni, the main elements of alloys used in this study, transitioned linearly along the gradient direction and diffused fully between layers. By linearly fitting Fe content, the effect of composition gradient on element transition was determined. The presence of Laves phase was the main inducement leading to the micro-porous aggregation fracture. The best tensile properties with the highest tensile strength (527.05 MPa) and the highest elongation (26.21 %) were obtained by the FGM with composition gradient of 10 %. The findings will be helpful to choose appropriate gradient variation and understand the forming mechanism of functionally graded materials fabricated by laser additive manufacturing.

An Investigation into Thermal History and Its Correlation with Mechanical Properties of PA12 Parts Produced by Selective Laser Sintering Process

Thermal history is a key factor affecting mechanical properties of polymeric parts made by the selective laser sintering (SLS) process. In this research, the effect of thermal history on the mechanical properties of PA12 parts produced by the SLS process has been investigated. It is hypothesized that different cool-down methods (normal to very slow cooling) and built orientations, resulted from flat and edgewise layouts fabrication, could be influencing factors on the thermal history during the SLS process. The temperature changes at different points inside the powder bed were recorded during the fabrication of specimens. Afterward, the morphology of fabricated samples was examined using scanning electron microscopy. In addition, the degree of crystallinity and melting point of the parts were studied by differential scanning calorimetry analysis. It was found that the built orientation was more effective than the cooling methods on ultimate tensile strength (UTS) and elongation at break (EaB), so that UTS and EaB of the edgewise parts were 10%, 50% greater than the flat parts. On the other hand, the variation of crystallinity with cooling methods has been found to be much less than might be expected from the implemented various fabrication conditions. However, the applied slowest cool-down method slightly increased the edgewise parts crystallinity to 23%, compared to 19.2% for the normal cooled down samples, leading to greater UTS than the normal cooled specimens. The morphology observation of specimens fracture surfaces suggests that better mechanical performance of the edgewise samples is likely connected to fewer defects such as pores and un-melted powder particles remained in their cross sections due to experiencing higher temperature during fabrication. The work is relevant to attempts to build high mechanical performance parts by selective laser sintering.

Research on the Optimization Model of the Abrasive Blocks Using Weighted Case-Based Reasoning

Barrel finishing process is a universal method to improve the surface quality of parts. It is widely used in high-performance parts of high-end equipment. As a necessary tool consumable for barrel finishing process, the characteristic parameters of the abrasive blocks affect the processing quality and production efficiency. However, the current method for selecting the abrasive blocks requires large number of experiments based on the operator’s extensive experience, which does not meet the rapid development needs of the barrel finishing process. Therefore, this paper proposes a case-based reasoning model with variable weights to achieve the intelligent optimization of the abrasive blocks. Based on the in-depth analysis of the characteristics of the barrel finishing process, a reasonable case base is established firstly, which is to determine the comprehensive case features and the solution of the case. AHP (analytic hierarchy process) is proposed to determine the weight of case features and to dynamically adjust the weight of case features according to the characteristics of the parts to be processed and users’ processing requirements. The results show that the proposed case-based reasoning model with variable weights can quickly, accurately, and reasonably select the abrasive blocks during the process of making processing technique of the barrel finishing, which will lay a necessary foundation for the effective implementation of the barrel finishing process and contribute significantly to the improvement of its efficiency.

Laser sintering of cryogenically ground polymer powders into high-performance parts: The role of dry particle coating with a conductive flow agent

The poor processability of cryogenically ground polymer powders rendered by their irregular shapes greatly hinders their applications in the selective laser sintering (SLS) technique. In this study, nonconductive silica (SiO2) nanoparticles and conductive carbon black (CB) nanoparticles were coated onto cryogenically ground polyamide 12 (PA12) powders and acted as flow agents to alleviate the flow problem. It was found that the addition of SiO2 or CB nanoparticles both greatly improved the flowability of cryogenically ground powders, thereby facilitating a successful sintering process. However, significantly improved mechanical performance and reduced structural defects were achieved only upon the addition of CB nanoparticles. The underlying mechanism was suggested to be related with the higher conductivity, lower friction, smaller adhesion energy and higher laser absorption efficiency of CB-coated powders. Therefore, conductive and radiation-adsorbing particles such as CB can serve as a multifunctional agent to enable the sintering of polymer powders with irregular shapes into parts with improved mechanical performance.

Ultrasonic non-destructive characterization of hybrid additively manufactured 420 stainless steel made with directed energy deposition

Additive manufacturing is remarkably suitable for creating high complexity performance parts. An added benefit of the Directed Energy Deposition (DED) process is the ability to make functionally graded materials. This expansion of the design and manufacturing spaces presents a challenge for the non-destructive evaluation of AM parts. Hybrid AM parts are an example of functionally graded materials for which the variation in microstructure and material properties across the bulk of the parts is created through a combination of manufacturing processes. In this work, a hybrid 420 stainless steel coupon was created using the DED method, and a surface treatment was applied between added layers. Characterization using destructive and non-destructive methods was performed. The microstructure, hardness profile, phase velocity, attenuation, and backscatter results from the hybrid coupon are compared with those from an AM coupon and a wrought coupon. Agreement between destructive and non-destructive measurements is studied. Furthermore, ultrasonic non-destructive methods are shown to be effective for identifying the gradient in the material properties of the hybrid coupon. The work hereby presented can further inform non-destructive evaluation decisions for hybrid AM parts.Additive manufacturing is remarkably suitable for creating high complexity performance parts. An added benefit of the Directed Energy Deposition (DED) process is the ability to make functionally graded materials. This expansion of the design and manufacturing spaces presents a challenge for the non-destructive evaluation of AM parts. Hybrid AM parts are an example of functionally graded materials for which the variation in microstructure and material properties across the bulk of the parts is created through a combination of manufacturing processes. In this work, a hybrid 420 stainless steel coupon was created using the DED method, and a surface treatment was applied between added layers. Characterization using destructive and non-destructive methods was performed. The microstructure, hardness profile, phase velocity, attenuation, and backscatter results from the hybrid coupon are compared with those from an AM coupon and a wrought coupon. Agreement between destructive and non-destructive measurements is ...

A new predictive method of the finished surface profile in abrasive flow machining process

In order to improve the functional surface finish of high performance and complex parts in high-end manufacturing industries, abrasive flow machining (AFM) taking semi-solid abrasive media as a finishing tool was proposed to enhance the accessibility of the finishing process. Owing to the complicated flow field of abrasive media in constrained passages, it is difficult to predict the finished surface profile of a functional surface after AFM processing. In this investigation, a novel prediction method combining numerical simulation and experiment was proposed with the analyses of material removal conducted for single, and multiple, particles. On this basis, the distributions of material removal and abrasive scratches were expounded in one-way AFM and two-way AFM processes with two kinds of constrained passages, it is believed that a high p∘v distribution and turbulent flow field produced by contraction section of inlet region of flow passage are the main reasons for the high material removal and irregular finishing marks at the inlet/outlet regions. Finally, verification experiments on the finishing of an aero-engine blade were carried out, a preferable constrained passage was obtained using this new prediction method and near-uniform material removal was observed. This work aims to establish a preferable prediction method for the whole surface profile finished by AFM process and provide fundamental guidance for the optimal design of constrained surfaces of complex components.

Assessing the safety of electronic health records: a national longitudinal study of medication-related decision support

BackgroundElectronic health records (EHR) can improve safety via computerised physician order entry with clinical decision support, designed in part to alert providers and prevent potential adverse drug events at entry...

Analysis and simulation of process damping in HPC milling

The use of tools with chamfered cutting edges is an essential part of high performance cutting (HPC) as a rough milling process strategy for manufacturing structural components in the aerospace industry. Due to an interaction between the chamfer and the undulated workpiece surface, tool vibrations can be damped allowing high depths of cut without the occurrence of harmful dynamic effects. Hence, a significant increase in efficiency is possible. As a result of process damping, the stability boundary predicted by linear stability analysis provided for instance by analytical or geometric physically-based simulations will generally underestimate the experimentally determined one. Consequently, the object of this procedure, namely to reduce the number of test runs until sufficient process parameter values are determined, could not be met. Therefore, the damping effect induced by chamfered tools was analysed in this paper. It is shown that the use of chamfered cutting edges leads to a significant limitation of chatter amplitudes when exceeding the stability limit. The strength of this effect depends on the cutting speed and the engagement situation, which influence the intensity and number of interactions between the chamfer and the workpiece surface and, thus, the resulting process damping. Moreover, a dynamic process damping model presented in the literature was chosen and implemented in a geometric physically-based milling simulation. An evaluation of its validity points out the challenges regarding the simulation of process damping.

Metal matrix composite material reinforced with metal wire and produced with gas metal arc welding

In the search for high-performance parts and structures, especially for the aviation and aerospace industry, metal matrix composites appear with prominence. However, despite exhibiting high levels of mechanical properties and low densities, these materials are still very expensive, mainly due to complex production. Thus, this work aims to present and evaluate a novel way of manufacturing metal matrix composites, with relative low cost and complexity: by using low-energy fusion welding to deposit the matrix material on top of continuous metal wire reinforcement. For proof of concept, Al alloy was used as matrix material, a single Ti alloy wire as reinforcement, and gas metal arc welding CMT-Pulse® as the process for material deposition. The simplified Al–Ti composite was evaluated in terms of impact resistance and tensile strength and stiffness. Overall, the mechanical performance of the composite was around 23% higher than that of the matrix material itself (Al), this with only about 2% of reinforcement volume and just over 3% of increase in weight. Analyses of the Al–Ti composite fractures and cross-sections and of chemical composition and hardness of the matrix–reinforcement transition interface indicated the preservation (no melting) of the Ti wire and the existence of a fine contour of bonding between matrix and reinforcement. At the end, a brief discussion on the dynamics of the wire reinforcement preservation is carried out based on high-speed filming.

Molding process and properties of continuous carbon fiber three-dimensional printing

Currently, carbon fiber composite has been applied in the field of three-dimensional printing to produce the high-performance parts with complex geometric features. This technique comprise both the advantages of three-dimensional printing and the material, which are light weight, high strength, integrated molding, and without mold, and the limitation of model complexity. In order to improve the performance of three-dimensional printing process using carbon fiber composite, in this article, a novel molding process of three-dimensional printing for continuous carbon fiber composites is developed, including the construction of printing material, the design of printer nozzle, and the modification of printing process. A suitable structure of nozzle on the printer is adjusted for the continuous carbon fiber composites. For the sake of ensuring the continuity of composited material during the processing, a cutting algorithm for jumping point is proposed to improve the printing path during process. On this basis, the experiment of continuous carbon fiber composite is performed and the mechanical properties of the printed test samples are analyzed. The results show that the tensile strength and bending strength of the sample printed by polylactic acid–continuous carbon fiber composites increased by 204.7% and 116.3%, respectively compared with pure polylactic acid materials, and those of the sample printed by nylon–continuous carbon fiber composites increased by 301.1% and 17.4% compared with pure nylon materials, and those of test sample by nylon–continuous carbon fiber composites under the heated and pressurized treatment increased by 383.6% and 233.2% compared with pure nylon material.

A conceptual framework for quantum accelerated automated design optimization

The development of practical quantum computers that can be used to solve real-world problems is in full swing driven by the ambitious expectation that quantum supremacy will be able to outperform classical super-computers. Like with any emerging compute technology, it needs early adopters in the scientific computing community to identify problems of practical interest that are suitable as proof-of-concept applications and to revise existing solution strategies and develop new ones that exploit the capabilities of the novel compute hardware.In this article we describe a conceptual framework for reducing the computational complexity of simulation-driven automated design optimization processes, which are nowadays widely used in computer-aided product development, by exploiting quantum supremacy. Our approach is based on the assumption that quantum computers will become part of hybrid high-performance computing platforms and can then be used as application-specific accelerator devices.

Preparation and 3D-printing of highly conductive polylactic acid/carbon nanotube nanocomposites via local enrichment strategy.

In this paper, a local enrichment strategy was adopted to prepare carbon nanotube (CNT) enriched polylactic acid (PLA) composite filaments, which were used to fabricate the corresponding conductive 3D-printed parts by fused deposition modeling (FDM) technology. Combined with computer simulation, the carbon nanotubes (CNTs) were found to be successfully kept and supported on the surface of filaments after 3D-printing. With this strategy, the prepared 3D-printed parts showed a remarkably enhanced electrical conductivity, which was approximately eight orders of magnitude higher than that of the conventional 3D-printed parts at the same loading of CNTs. This encouraging result provided a new method for fabricating the high-performance parts through FDM printing, and also opened up new routes for 3D-printing technologies to prepare other advanced binary or multicomponent polymer composites.

Integrated component-support topology optimization for additive manufacturing with post-machining

PurposeThe purpose of this paper is to communicate a method to perform simultaneous topology optimization of component and support structures considering typical metal additive manufacturing (AM) restrictions and post-print machining requirements.Design/methodology/approachAn integrated topology optimization is proposed using two density fields: one describing the design and another defining the support layout. Using a simplified AM process model, critical overhang angle restrictions are imposed on the design. Through additional load cases and constraints, sufficient stiffness against subtractive machining loads is enforced. In addition, a way to handle non-design regions in an AM setting is introduced.FindingsThe proposed approach is found to be effective in producing printable optimized geometries with adequate stiffness against machining loads. It is shown that post-machining requirements can affect optimal support structure layout.Research limitations/implicationsThis study uses a simplified AM process model based on geometrical characteristics. A challenge remains to integrate more detailed physical AM process models to have direct control of stress, distortion and overheating.Practical implicationsThe presented method can accelerate and enhance the design of high performance parts for AM. The consideration of post-print aspects is expected to reduce the need for design adjustments after optimization.Originality/valueThe developed method is the first to combine AM printability and machining loads in a single topology optimization process. The formulation is general and can be applied to a wide range of performance and manufacturability requirements.

Design of robotic end-effector for milling force control

In order to realize the precision machining of high-performance materials, a robotic end-effector for milling force control is proposed. Two kinds of end-effectors which are coaxial and non-coaxial structures are designed according to types of motorized spindle and force sensor. The maximum milling force is obtained that is satisfied the safety requirements of force sensor. And the three-dimensional models of coaxial and non-coaxial structure are imported into ABAQUS software for finite element analysis. The simulation results show the non-coaxial structure is better than coaxial structure, and it is suitable to be installed in robot to machine high performance parts.