Delamination, an inter-ply debonding failure phenomenon, is considered as the most undesirable and challenging failure mode in hole making of carbon fiber-reinforced plastic (CFRP) composite ...laminates. The existence of delamination, even small ones, noticeably damages the strength and stability of the assembled products. It is reported that delamination is responsible for up to 60% of composite components’ rejection during assembling. In order to reduce delamination, rotary ultrasonic machining (RUM) has been studied and utilized in hole making of CFRP composites. Existing investigations on delamination of CFRP composites in RUM hole making are experimental studies, in which several methods (such as adjusting input variables and the use of supportive plate) to reduce delamination are reported. To understand delamination generation mechanisms and predict delamination initiation, theoretical investigations are needed. Cutting force models in RUM of CFRP composites have been developed, and it is well accepted that delamination is correlated to thrust force. However, there are no reported investigations to predict delamination initiation and study the impact of thrust force on the delamination of CFRP composites in the RUM hole-making process. Finite element analysis (FEA) could be an effective way to study the delamination in the RUM process. In this paper, FEA was conducted to predict delamination initiation and establish the relationship between the thrust force and delamination thickness in RUM, for the first time. In addition, experiments were conducted to validate the FEA model. The proposed model was proved to be effective in predicting delamination initiation, and the trends of the FEA results agreed well with those of the experimental results.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Compared with conventional surface grinding (CSG) process, surface machining of carbon fiber-reinforced plastic (CFRP) composites using rotary ultrasonic machining (RUM) with vertical ultrasonic ...vibration generates smaller cutting forces because of improved machining performance and more damages to the machined CFRP surface due to the intermittent knocking induced by vertical ultrasonic vibration. It is reported that surface quality can be improved when the ultrasonic vibration is parallel to the feeding direction. In addition, elliptical ultrasonic vibration can be formed by the combination of horizontal and vertical ultrasonic vibrations. However, the effects of elliptical ultrasonic vibration in RUM surface machining of CFRPs are still unknown. This paper will study the influences of elliptical ultrasonic vibration on the machining performance and machined surface quality in RUM surface machining of CFRPs. The comparisons of output variables (including cutting forces, surface roughness, and machined surface topography) between RUM surface machining with elliptical ultrasonic vibration and the CSG process as well as RUM surface machining with vertical ultrasonic vibration will be conducted under different levels of input variables (including depth of cut, feedrate, and tool rotation speed). The abrasive-grain trajectory and the tool-workpiece contacting modes in these three machining processes are analyzed. It is found that RUM surface machining with elliptical ultrasonic vibration produced smallest feeding-direction cutting force, smallest vertical-direction cutting force, best morphology of machined surface, and smallest surface roughness among these three kinds of machining processes.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Inconel 718 has been widely used in aerospace, nuclear, and marine industries due to excellent high-temperature mechanical properties and corrosion resistance. In recent years, laser-directed energy ...deposition (DED) becomes a competitive method in the fabrication of Inconel 718 coatings. Compared with other surface coating processes, laser DED has the advantage of extremely fine-grained structures, strong metallurgical bonding, and high density. However, the hardness and wear resistance of Inconel 718 coatings still need to be improved. To further improve these properties, ceramic reinforced Inconel 718 coatings have been investigated. Compared with ex situ ceramic reinforcements, the in situ synthesized reinforcements have the advantage of refined ceramic particle size, uniform distribution, and low thermal stress. B
4
C was a preferable additive material to fabricate in situ synthesized multi-component ceramic reinforced Inconel 718 coatings. The addition of B
4
C could form a large number of borides and carbides as ceramic reinforcements. In addition, the in situ reactions between Inconel 718 and B
4
C could release heat during the fabrication, thereby promoting the melting of material powders. However, there are currently no investigations on the in situ synthesis mechanisms, microstructure, and mechanical properties of laser DED fabricated B
4
C-Inconel 718 coatings. In this study, the effects of B
4
C on the properties of Inconel 718 coatings were investigated. Results show that Ni
3
B, NbB, and Cr
3
C
2
phases were formed. With the addition of B
4
C, the size of Laves phase was refined and the porosity was decreased. The hardness and wear resistance of B
4
C reinforced coatings were improved by about 34% and 28%, respectively.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
•Rotary ultrasonic surface micro-machining of brittle materials.•Theoretical investigation on the material removal rate and cutting force.•Significantly improved surface quality assisted by ...ultrasonic vibration.
Many brittle materials, such as single-crystal materials, amorphous materials, and ceramics, are widely used in many industries such as the energy industry, aerospace industry, and biomedical industry. In recent years, there is an increasing demand for high-precision micro-machining of these brittle materials to produce precision functional parts. Traditional ultra-precision micro-machining can lead to workpiece cracking, low machined surface quality, and reduced tool life. To reduce and further solve these problems, a new micro-machining process is needed. As one of the nontraditional machining processes, rotary ultrasonic machining is an effective method to reduce the issues generated by traditional machining processes of brittle materials. Therefore, rotary ultrasonic micro-machining (RUμM) is investigated to conduct the surface micro-machining of brittle materials. Due to the small diameter cutting tool (<500 μm) and high accuracy requirements, the impact of input parameters in the rotary ultrasonic surface micro-machining (RUSμM) process on tool deformation and cutting quality is extremely different from that in rotary ultrasonic surface machining (RUSM) with relatively large diameter cutting tool (∼10 mm). Up till now, there is still no investigation on the effects of ultrasonic vibration (UV) and input variables (such as tool rotation speed and depth of cut) on cutting force and machined surface quality in RUSμM of brittle materials. To fill this knowledge gap, rotary ultrasonic surface micro-machining of the silicon wafer (one of the most versatile brittle materials) was conducted in this study. The effects of ultrasonic vibration, tool rotation speed, and depth of cut on tool trajectory, material removal rate (MRR), cutting force, cutting surface quality, and residual stress were investigated. Results show that the ultrasonic vibration could reduce the cutting force, improve the cutting surface quality, and suppress the residual compressive stress, especially under conditions with high tool rotation speed.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Rotary ultrasonic machining has been approved as an effective and efficient hole making process for carbon fiber–reinforced plastic composites. Hole quality plays an important role in assembling ...carbon fiber–reinforced plastic components and can be affected by the carbon fiber reinforcement structures. In this study, experiments are conducted to assess hole quality in carbon fiber–reinforced plastic composites with three carbon fiber reinforcement structures under different combinations of machining variables. Hole quality is quantified through geometrical accuracy (perpendicularity, cylindricity, and hole diameter) and surface qualities (delamination and surface roughness). Results show that the highest level of interlacement among yarn of plain woven structure induce the highest level of compression to the workpiece and the largest amount of additional material removal, leading to the largest perpendicularity and hole diameter. The worst fabric integrity of unidirectional structure generates the largest amount of non-uniform material removal on the machined surface, resulting in the largest cylindricity. It is also found that compared with woven structures, unidirectional structure is more likely to induce push-out delamination due to its smaller critical energy release rate. The lowest constancy of the fabric in twill woven structure leads to the largest surface roughness.
Carbon-based nanomaterials mainly including carbon nanotubes (CNTs), graphene, and graphene oxide (GO) have superior properties of low density, outstanding strength, and high hardness. Compared with ...ceramic reinforcements, small amount of carbon-based nanomaterials can significantly improve the mechanical properties of metal matrix composites (MMCs) and ceramic matrix composites (CMCs). However, CNTs and graphite always aggregate or degrade during the fabrication with a high temperature, especially in MMCs. GO has the advantages of easier to be dispersed in other materials and better high-temperature stability. Laser-directed energy deposition (DED) has been used to fabricate GO-MMCs and GO-CMCs due to the unique capabilities of coating, remanufacturing, and producing functionally graded materials. Laser DED, as a fusion manufacturing process, could fully melt the material powders, which could refine the microstructure and increase the density and mechanical properties. However, GO could react with matrix materials at high temperatures. The survival, degradation, and reactions of GO in laser DED fabricated GO-MMCs and GO-CMCs are still unknown. There is also no investigation on the reinforcement mechanisms of GO in metal matrix materials and ceramic matrix materials in the laser DED process. In this study, GO-reinforced Ti (GO-Ti) and GO-reinforced zirconia toughened alumina (GO-ZTA) parts were fabricated by laser DED process. Raman spectrum, XRD analysis, and EDS analysis have been applied to investigate the forms of GO in both DED fabricated GO-MMCs and GO-CMCs. The reinforcement mechanisms of GO on microhardness and compressive properties of MMCs and CMCs have been analyzed.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Titanium and its alloys exhibit superior properties of high corrosion resistance, an excellent strength to weight ratio and outstanding stiffness among other things. However, their relatively low ...hardness and wear resistance limit their service life in high-performance applications of structure parts, gears and bearings, for example. The fabrication of a ceramic reinforced titanium matrix composite (TMC) coating could be one of the solutions to enhance the microhardness and wear resistance. Titanium carbide (TiC) is a preferable candidate due to the advantages of self-lubrication, low cost and a similar density and thermal expansion coefficient with titanium. The fabrication of TiC-TMC coatings onto titanium using a laser directed energy deposition (LDED) process has been conducted. The problems of TiC aggregation, low bonding quality and the generation of fabrication defects still exist. Considering ultrasonic vibration could generate acoustic steaming and transient cavitation actions in melted materials, which could homogenize the distribution of reinforcement materials and promote the dissolution of TiC into liquid titanium. In this study, for the first time, we investigate the ultrasonic vibration-assisted LDED of TiC-TMC coatings. The effects of ultrasonic vibration and reinforcement content on the phase compositions, reinforcement aggregation, bonding quality, fabrication defects and mechanical properties (including microhardness and wear resistance) of LDED deposited TiC-TMC coatings have been investigated. With the assistance of ultrasonic vibration, the aggregation of TiC was reduced, the porosity was decreased, the defects in the bonding interface were reduced and the mechanical properties including microhardness and wear resistance were increased. However, the excessive TiC content could significantly increase the TiC aggregation and manufacturing defects, resulting in the reduction of the mechanical properties.
In the marine environment, estimating the direction of arrival (DOA) is challenging because of the multipath signals and low signal-to-noise ratio (SNR). In this paper, we propose a convolutional ...recurrent neural network (CRNN)-based method for underwater DOA estimation using an acoustic array. The proposed CRNN takes the phase component of the short-time Fourier transform of the array signals as the input feature. The convolutional part of the CRNN extracts high-level features, while the recurrent component captures the temporal dependencies of the features. Moreover, we introduce a residual connection to further improve the performance of DOA estimation. We train the CRNN with multipath signals generated by the BELLHOP model and a uniform line array. Experimental results show that the proposed CRNN yields high-accuracy DOA estimation at different SNR levels, significantly outperforming existing methods. The proposed CRNN also exhibits a relatively short processing time for DOA estimation, extending its applicability.
Pseudoelasticity behaviors have been found in the NiTi alloys fabricated by laser additive manufacturing (LAM) processes. Reported investigations of pseudoelasticity in LAM fabricated NiTi alloys ...mainly focus on the effects of laser input energy and post-heat treatments on phase transformation behaviors. The pseudoelasticity behaviors can be affected by the significantly different load-contact conditions in various industrial applications. However, there are no reported investigations of pseudoelasticity behaviors of NiTi alloys fabricated by LAM in different load-contact conditions. For the first time, multi-scale indentation tests at three scales (nanoscale, microscale, and macroscale) are conducted to evaluate and compare the pseudoelasticity behaviors of the NiTi alloys fabricated by LAM in this investigation. In addition, the effects of microstructural features and phase constituents on pseudoelasticity are discussed. Overall, pseudoelasticity at the nanoscale is the best in terms of the smallest remnant depth ratios, followed by that at the macroscale and that at the microscale. Moreover, pseudoelasticity at the nanoscale improves with the increase of load or the number of cycles. As a comparison, pseudoelasticity at the microscale stays steady with the increase of load and decreases with cycling, and pseudoelasticity at the macroscale stays steady with the increase of load or the number of cycles. It is also found that the improvement in pseudoelasticity leads to decreases in apparent hardness and Young's modulus.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The failure of the NiTi alloys due to their low mechanical strength is the major problem inhibiting their further applications. Adding ceramic reinforcement materials could not only enhance the ...strength but also tribological characteristics of NiTi alloys. Among various adopted ceramic reinforcement materials including Al2O3, SiC, TiN, TiB2, TiO2, and TiC, TiC is preferred since it little affects the unique shape memory properties of NiTi. For the first time, this paper reports the fabrication of TiC–NiTi composites using laser DED process. Microstructural characterizations are presented to understand the Ni4Ti3 phase precipitation mechanisms with the addition of TiC particles. Nanoindentation tests are conducted to evaluate the mechanical properties. The addition of TiC particles could alter the phase formation since Ti atoms tend to migrate towards the TiC particles. The nucleation and growth of Ni4Ti3 precipitates are then effectively restricted. The typical thicknesses of the Ni4Ti3 precipitates are reduced by 20% (about 30 nm) at lower levels of laser power or eliminated at a higher level of laser power. The addition of TiC also leads to a reduction of about 10% in the volume fraction of the Ni4Ti3 precipitates and an increase of 6%–17% in the volume fraction of the NiTi2 phases. The refinement of the Ni4Ti3 precipitates improves the pseudoelasticity by about 10% (0.05 in recovery energy ratio). Besides, the nanohardness and Young's modulus are also strengthened. These experimental results indicate that TiC has the capability to refine the Ni4Ti3 precipitates, enhance the strength of NiTi, and improve the pseudoelasticity.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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