Mechanical Properties Of Parts Research Articles

Rolling contact fatigue performance evaluation of Ti–6Al–4V parts processed by selective laser melting

Selective laser melting (SLM) of titanium components is gradually gaining popularity in various fields, such as aerospace, automobile, and medical for the purpose of saving material and reducing the carbon footprint. To capitalize on their benefits, the mechanical properties of parts fabricated by SLM must meet engineering requirements. Fatigue properties are particularly important for the performance of safety-critical structures. In this research, rolling contact fatigue (RCF) tests were performed for SLM fabricated Ti–6Al–4V samples in differently post-treated conditions to investigate the effect of different post-processing methods on the fatigue properties and, as a comparison, forgings of Ti–6Al–4V were also tested. It was found that the RCF properties of the Ti–6Al–4V generated by SLM were superior to those of the forged specimens and strengthened after polishing and heat treatment. The worn surfaces were observed by using an optical microscope, and the results indicated that surface and subsurface defects are the main causes of fatigue crack initiation and the residual stresses enhance fatigue crack growth.

Structure and mechanical properties of parts obtained by selective laser melting of metal powder based on intermetallic compounds Ni3Al

The structure and mechanical properties of samples are obtained from metal powder based on intermetallic compound by selective laser melting. The chemical analysis of the raw material and static tensile test of specimens were made. Change in the samples’ structure and mechanical properties after homogenization during four and twenty-four hours were investigated. A small-sized combustion chamber of a gas turbine engine was performed by the selective laser melting method. The print combustion chamber was subjected to the gas-dynamic test in a certain temperature and time range.

A study on influence of process parameters on the SIS processability and mechanical properties of a HDPE

Selective Inhibition Sintering (SIS) is emergent rapid prototyping technology that builds the solid parts by fusing the powder particles layer by layer with heat, directly from CAD model.The SIS process has many processing parameters of which some have a direct effect on the mechanical properties of the parts fabricated.The HDPE powder particle size was characterized by scanning electron microscopy, differential scanning calorimetry and particle size analysis. This work shows feasibility of processing an HDPE by SIS process. The effects of SIS process parameters like layer thickness, heater power and heater feed rate on tensile properties of HDPE samples are investigated. To obtain the mechanical properties, the samples were submitted to tensile testing. A thermal consequence on the mechanical properties of HDPE parts fabricated by inhibition sintering process is also discussed

The structure and mechanical properties of parts elaborated by direct laser deposition 316L stainless steel powder obtained in various ways

In this work the morphology, the size and the chemical composition of the powders of steel 316L received by the two methods was studied: fusion dispersion by a gas stream and reduction of metal chlorides with the subsequent plasma atomization of the received powder particles. The powder particles received by the first method have a spherical shape (aspect ratio 1,0–1,2) with an average size of 77 μm and are characterized by the absence of internal porosity. Particles of the powder received by the second method also have a spherical shape and faultless structure, however, their chemical composition may vary in different particles. The average size of particles is 32 μm. Though the obtained powders had different properties, the experimental samples received by DLD technology demonstrated by equally high durability (Ultimate strength is 623±5 and of 623±18 MPa respectively) and plasticity (38 and 41% respectively). It is established that mechanical properties of DLD samples increase for 7-10% after treatment of the surface.

Thermoplastic Elastomer Part Color as Function of Temperature Histories and Oxygen Atmosphere During Selective Laser Sintering

The influence of selective laser sintering (SLS) parameters on PA12 part properties is well known, but research on other materials is rare. One alternative material is a thermoplastic elastomer (TPE) called PrimePart ST that is more elastic and shows a distinct SLS processing behavior. It undergoes a three-dimensional temperature distribution during the SLS process within the TPE part cake. To examine this further, a temperature measurement system that allows temperature measurements inside the part cake is applied to TPE in the present work. Position-dependent temperature histories are directly correlated with the color and mechanical properties of built parts and are in very good agreement with artificial heat treatment in a furnace. Furthermore, it is clearly shown that the yellowish discoloration of parts in different intensities is not only temperature dependent but also influenced by the residual oxygen content in the process atmosphere. Nevertheless, the discoloration has no influence on the mechanical part properties.

Effect of mold opening on the properties of PLA samples obtained by foam injection molding

Foam injection molding is a process by which complex, thick parts with a cellular core and a compact solid skin can be manufactured. The addition of a physical blowing agent under high pressure allows the decrease of the viscosity and the glass transition temperature of the gas/polymer melt. These features of the foam injection molding are very beneficial for biodegradable polymers, in which the processability window is very narrow. In this study, morphology, rheological, and mechanical properties of parts with a complex shape, obtained by foam injection molding, were analyzed. In particular, two commercial grades of poly(lactic acid) having different rheological behavior were adopted to obtain foamed parts by injection molding process with nitrogen as a physical blowing agent. For both resins, the effect of the mold opening on morphology and mechanical properties was assessed. POLYM. ENG. SCI., 58:475–484, 2018. © 2017 Society of Plastics Engineers

Process Evaluation of AISI 4340 Steel Manufactured by Laser Powder Bed Fusion

Laser powder bed fusion (L-PBF) involves the consolidation of metal powder, layer by layer, through laser melting and solidification. In this study, process parameters are optimized for AISI 4340 steel to produce dense and homogeneous structures. The optimized process parameters produce mechanical properties at the center of the build plate that are comparable to wrought in the vertical and horizontal orientations after heat treatment and machining. Four subsequent builds are filled with specimens to evaluate the mechanical behavior as a function of location and orientation. Variations in the mechanical properties are likely due to recoater blade interactions with the powder and uneven gas flow. The results obtained in this study are analyzed to assess the reliability and reproducibility of the process. A different build evaluates the performance of near-net-shaped tensile specimens angled 35°-90° from the build plate surface (horizontal). Ductility measurements and surface roughness vary significantly as a function of the build angle. In the stress-relieved and as-built conditions, the mechanical behavior of vertically oriented specimens exhibits somewhat lower and more variable ductility than horizontally oriented specimens. Therefore, several process variables affect the mechanical properties of parts produced by the L-PBF process.

Selective laser melting of Al7050 powder: Melting mode transition and comparison of the characteristics between the keyhole and conduction mode

Melting mode acts a significant role in determining the defect, microstructure and mechanical properties of parts fabricated by selective laser melting. In this work, the effects of scanning speed and defocusing distance on the melting mode transition in selective laser melting of Al7050 powder were investigated. The samples under different melting modes were characterized by comparing the surface morphology, crack, microstructure and nano-hardness. The results show that the defocusing distance has a significant effect on the forming of keyhole mode. The calculated threshold scanning speed of forming keyhole mode agrees very well with the experimental result. A metallic luster surface was obtained in keyhole mode due to the lower oxygen content at the surface. The method of using optimal scanning speed can only reduce but cannot eliminate the cracks induced by the process. The keyhole mode has lower crack sensitivity than that of conduct mode. Uniform and fine microstructure occurred under conduction mode. However, due to the fluctuations of flow field and re-melting under keyhole mode, a V-shaped structure was presented on the bottom of the melt pool. Consequently, fluctuating nano-hardness values were exhibited on the bottom of the melt pool under keyhole mode.

Mechanical strength of welding zones produced by polymer extrusion additive manufacturing

As more manufacturing processes and research institutions adopt customized manufacturing as a key element in their design strategies and finished products, the resulting mechanical properties of parts produced through additive manufacturing (AM) must be characterized and understood. In polymer extrusion (PE), the most recently extruded polymer filament must bond to the previously extruded filament via polymer diffusion to form a “weld”. The strength of the weld limits the performance of the manufactured part and is controlled through processing conditions. Understanding the role of processing conditions, specifically extruder velocity and extruder temperature, on the overall strength of the weld will allow optimization of PE-AM parts. Here, the fracture toughness of a single weld is determined through a facile “trouser tear” Mode III fracture experiment. The actual weld thickness is observed directly by optical microscopy (OM) characterization of cross sections of PE-AM samples. Representative data of weld strength as a function of printing parameters on a commercial 3D printer demonstrates the robustness of the method.

A novel gas-assisted microcellular injection molding method for preparing lightweight foams with superior surface appearance and enhanced mechanical performance

This paper proposed a novel gas-assisted microcellular injection molding (GAMIM) method by combining the gas-assisted injection molding (GAIM) with the microcellular injection molding (MIM). Firstly, under the assistance of the high-pressure gas from the GAIM, the amount of the polymer melt required for fully filling the mold cavity is reduced in the GAMIM compared with that in the MIM, thus leading to a high weight reduction of the foamed part. Secondly, the high-pressure assisted gas from the GAIM can dissolve all the cells generated in the melt filling stage back into the polymer melt, thus improving the molded part's surface appearance by eliminating the surface sliver marks. Thirdly, the secondary foaming process in a steady state triggered by releasing the high-pressure assisted gas makes the foamed part have a fine cellular structure and a compact solid skin layer, which can help to enhance the part's mechanical properties. In order to verify the effectiveness of the GAMIM, comparison experiments of the MIM and the GAMIM were conducted. The results demonstrate that the GAMIM can not only significantly increase the weight reduction, but also greatly improve the surface appearance and mechanical properties of the foamed part.

Process control testing for fused filament fabrication

PurposeThe purpose of this research is to determine what tests can be most useful in quality assurance and control when using fused filament fabrication (FFF) 3D printing machines. The quality of the bond between layers is critical for the structural integrity of the fused filament fabricated parts.Design/methodology/approachTherefore, to determine the influence of process parameters on the quality of parts’ tensile, flexural, notched and un-notched impact, test specimens were fabricated in polylactic acid (PLA) using FFF with different layer thicknesses, fill densities, orientation and print speeds. The mechanical properties were then assessed along with the accuracy and mass of the samples.FindingsIt is concluded that a notched impact test gives a measure of interlayer bond strength which can be used across build styles to track machine performance, and that this, together with the mass and dimensions of the impact-test specimens, offers an appropriate set of tests capable of tracking the mechanical properties of parts produced using the FFF technique.Originality/valueTherefore, this research finding will be of value in benchmarking FFF machines for quality parts fabrications.

The effect of aging on the mechanical behaviour of cuticle in the locust Schistocerca gregaria

Despite some previous work on the morphology and mechanical properties of parts of the insect exoskeleton, there is very little known about how these properties change over time during the life of the insect. We examined the hind tibia of the adult desert locust (Schistocerca gregaria) as a function of time up to 63 days following the final moult, a much longer period that previously studied. We identified an initial growth phase, lasting on average 21 days, in which leg thickness increased rapidly (averaging 1.8μm/day) by endocuticle deposition, and a subsequent mature phase in which the deposition rate slowed to 0.3μm/day. Cantilever bending tests revealed that Young's modulus and failure stress also increased rapidly during the growth phase, but remained almost constant during the mature phase, with average values of 8.3GPa (± 2.3GPa) and 175MPa (±31.5MPa) respectively, which are considerably higher than previously measured for fresh insect cuticle. Biomechanical analysis showed that the failure mode also changed, from local buckling of the tubular leg during the growth phase to failure at the material's ultimate strength in the mature phase. Over time, the ratio of radius/thickness of the leg decreased, passing through the estimated optimal value which would confer the best strength/weight ratio. This is the first ever biomechanical study to track changes in arthropod cuticle over a large part of adult life of the animal, and has revealed some unexpected and complex changes which may shed light on how arthropods regulate their load-bearing skeletal parts during aging.

Anisotropic mechanical properties of fused deposition modeled parts fabricated by using acrylonitrile butadiene styrene polymer

Abstract The anisotropic mechanical properties of parts that are fabricated using acrylonitrile butadiene styrene (ABS) polymer relative to part-built orientation employing the fused deposition modelling process are reported in this work. ABSplus-P430 polymer was used to investigate the effects of infill orientation on the parts’ mechanical properties under tensile and compression loading. Results revealed that infill orientation strongly affected the tensile properties of fabricated ABS samples. Specifically, the values for Young’s modulus ranged from ~1.5 to ~2.1 GPa, ultimate tensile strength from ~12.0 to ~22.0 MPa, yield strength from ~1.0 to ~21.0 MPa, and elongation-at-break from ~0.2 to ~4.8% for different infill orientations. Samples with infill orientation aligned to the vertical (i.e. Z-) axis displayed the highest values relative to all other infill orientations investigated. Mechanical properties anisotropy was lower for parts under compressive loading, such that the Young’s modulus, ultimate compressive and yield strength were weakly correlated with infill orientation apart from samples whose built orientation was aligned at 45° to the vertical Z-axis. The latter samples displayed inferior mechanical properties under all compressive tests. The effects of sample gauge thickness on tensile properties and ABS sample micro- and bulk- hardness with respect to infill orientation are also discussed.

Development of CNTs-filled photopolymer for projection stereolithography

PurposePolymeric parts produced by 3D stereolithography (SL) process have poorer mechanical properties as compared to their counterparts fabricated via conventional methods, such as injection or compression molding. Adding nanofillers in the photopolymer resin for SL could help improve mechanical properties. This study aims to achieve enhancement in mechanical properties of parts fabricated by SL, for functional applications, by using well-dispersed nanofillers in the photopolymers, together with suitable post-processing.Design/methodology/approachCarbon nanotubes (CNTs) have high strength and Young’s modulus, making them attractive nanofillers. However, dispersion of CNTs in photopolymer is a critical challenge, as they tend to agglomerate easily. Achieving good dispersion is crucial to improve the mechanical properties; thus, suitable dispersion mechanisms and processes are examined. Solvent exchange process was found to improve the dispersion of multiwalled carbon nanotubes in the photopolymer. The UV-absorbing nature of CNTs was also discovered to affect the curing properties. With suitable post processing, coupled with thermal curing, the mechanical properties of SL parts made from CNTs-filled resin improved significantly.FindingsWith the addition of 0.25 wt.% CNTs into the photopolymer, tensile stress and elongation of the 3D printed parts increased by 70 and 46 per cent, respectively. With the significant improvement, the achieved tensile strength is comparable to parts manufactured by conventional methods.Practical implicationsThis allows functional parts to be manufactured using SL.Originality/valueIn this paper, an improved procedure to incorporate CNTs into the photopolymer was developed. Furthermore, because of strong UV-absorption nature of CNTs, curing properties of photopolymer and SL parts with and without CNT fillers were studied. Optimized curing parameters were determined and additional post-processing step for thermal curing was discovered as an essential step in order to further enhance the mechanical properties of SL composite parts.

Isothermal Precision forging of magnesium alloy components with high performance

Abstract Because of hexagonal crystal structure, magnesium alloys, especially magnesium alloys with addition of rare earths, exhibit poor formability at room temperature. The isothermal precision forging process at elevated temperature can improve the formability of magnesium alloys. In this paper, the isothermal precision forging process of the complex shape case of Mg-Gd-Y-Zn-Zr magnesium alloy was simulated based on FORGE Nxt. A two-stage isothermal precision forging process was determined. According to the simulation results, isothermal precision forging experiments of magnesium parts with high performance and complex shape were successfully carried out. After isothermal precision forging process, the cases of magnesium alloy were subjected to heat treatment. Moreover, the mechanical properties of parts were also determined.

Experimental Optimization of Fused Deposition Modelling Processing Parameters: A Design-for-Manufacturing Approach

The Additive Manufacturing (AM) technology initially was developed as a rapid prototyping tool for visualization and validation of designs. The recent development of AM technologies, such as Fused Deposition Modelling (FDM), is driving it from rapid prototyping to rapid manufacturing. However, building end-user functional parts using FDM proved to be a challenging task. The difficulty arises from the large number of processing parameters that affect the final part design such as: building direction, extrusion temperature, layer height, infill pattern and more. The processing parameters of FDM influence the quality of the parts and their functionality. In addition, a more systemic understanding is required to elaborate on the impact of the FDM processing parameters on the final part's mechanical properties, dimensional accuracy and building time. The presented paper provides an experimental study to investigate the independent effect of each processing parameter on the mechanical properties and dimensional accuracy repeatability of FDM parts. A total of 18 test specimen samples were printed using varying processing parameters. In order to investigate the repeatability and resulted tolerances, the dimensions of these specimens were measured and compared with a 3D CAD model. The presented work utilizes a tensile test per ASTM D638 standards to obtain the mechanical properties of each fabricated sample. In addition, the work provides a Finite Element Analysis (FEA) model for AM parts. The work suggested to simulate their behavior under mechanical loads for future investigation on the coupled effects of processing parameters.

Selected Mechanical Properties of PETG 3-D Prints

The 3D printing is a way of additive manufacturing that allows the creation of sophisticatedly shaped bodies at relatively low cost and in short time span. It is especially useful for rapid manufacturing, including engineering applications such as rapid prototyping. The commonly used fused deposition modelling (FDM) method dispenses filament from heated nozzle positioned in three axes that hardens after exiting the nozzle. This article presents the research focused on the mechanical properties (mainly the basic tensile strength and elastic modulus) of elements printed using the FDM method, made of two distinctive materials: polyethylene terephthalate glycol (PETG) without additions and glass-fiber reinforced PETG. The paper outlines strengths and weaknesses of the materials described and compares the properties of PETG with and without the addition of glass fiber. The gathered data helps to quantify the mechanical properties of parts made of PETG and may also be used for modelling the properties of 3D printed elements.

Analysis of Selective Laser Melting Process Parameters Effect on Mechanical and Material Properties for Stainless Steel 316L

This paper deals with a testings of the Selective Laser Melting (SLM) process parameters on mechanical properties, material behavior, surface quality and on machinability of austenitic steel 316L. The SLM process conditions were changed to assess their effect on mechanical properties of the sintered material measured in tensile testing. The laser power, the scanning velocity of laser beam, the layer thickness and the laser focus plane were set to find the most appropriate set of process parameters to obtain the mechanical properties of parts.

HDMR technology for the aircraft metal part

Purpose The paper aims to introduce the fabrication of a medium steel aircraft part by hybrid deposition and micro-rolling technology (HDMR) and illustrate its advantages, microstructure features and mechanical properties of the part. Design/methodology/approach The HDMR technology contains two procedures happening almost at the same time: the welding deposition procedure and then the micro-rolling procedure. It takes the gas metal arc welding as the heat source to melt a metal wire and deposit metal in the welding deposition procedure. The metal just deposited is rolled synchronously by a micro roller following the welding torch in micro-rolling procedure almost at the same time layer by layer. The paper presents a contrast of the grain morphology of metal parts produced respectively by HDMR and freedom arc deposition (FAD) and the mechanical properties of metal parts of the same metal from HDMR casting, forging and FAD methods. Findings HDMR breaks the dendrite grain of welding beads into the fine crisscross grains. The mechanical properties of metal parts are improved distinctly by the micro-rolling procedure compared to casting, forging and FAD. Practical implications In addition, the application of HDMR technology has succeeded in the fabrication of an eligible aircraft metal part, which is quite difficult to achieve using other additive manufacturing (AM) or casting technologies. Originality/value HDMR has the advantage of equiponderance manufacturing by micro-rolling compared to other AM technologies. The metal part fabricated by HDMR technology obtains the fine crisscross grains and brings hope for AM metal components with excellent mechanical properties for aircraft applications.

The effects of moisture and temperature on the mechanical properties of additive manufacturing components: fused deposition modeling

Purpose This paper aims to investigate the water absorption behaviors and mechanical properties, according to water absorption and temperature, of components fabricated by fused deposition modeling (FDM) and injection molding. The mechanical properties of FDM and injection molded parts were studied under several environmental conditions. Design/methodology/approach FDM components can be used as load-carrying elements under a range of moisture and temperature conditions. FDM parts show anisotropic mechanical properties according to build orientation. Components were fabricated from acrylonitrile-butadiene-styrene in three different orientations. The mechanical properties of parts fabricated by FDM were compared to injection molded components made from the same material. Water absorption tests were conducted in distilled water between 20 and 60°C to identify the maximum water absorption rate. Both moisture and temperature were considered as environmental variables in the tensile tests, which were conducted under various conditions to measure the effects on mechanical properties. Findings The water absorption behavior of FDM components obeyed Fickian diffusion theory, irrespective of the temperature. High temperatures accelerated the diffusion rate, although the maximum water absorption rate was not affected. The tensile strength of FDM parts under dry, room temperature conditions, was approximately 26-56 per cent that of injection molded parts, depending on build orientation. Increased temperature and water absorption had a more significant effect on FDM parts than injection molded components. The tensile strength was decreased by 67-71 per cent in hot, wet environments compared with dry, room temperature conditions. Originality/value The water absorption behavior of FDM components was investigated. The quantitative effects of temperature and moisture on tensile strength, modulus and strain were also measured. These results will contribute to the design of FDM parts for use under various environmental conditions.