Obvious Deformation Research Articles

Research on the Heterogeneous Deformation Behavior of Nickel Base Alloy Based on CPFEM

AbstractIn this paper, a crystal plasticity finite element method (CPFEM), considering the grain morphology and orientation, as well as the dislocation density, is used to research the tensile deformation behavior of GH4169 based on Electron Backscatter Diffraction (EBSD). The stress, plastic strain, and dislocation density distributions are obtained for different levels of deformation. Results show that the stress, plastic strain, and dislocation density exhibit obvious heterogeneous plastic deformation, and stress concentration and dislocation pileup mainly occurs near grain boundaries. The initial dislocation density mainly affects the stress–strain curve of the material, and it can obviously effect the yield strength but cannot influence the hardening ability of the material. The total dislocation density increases with plastic strain. However, the texture evolution has no evident change with increasing plastic strain, except for the increase of texture content in Cube (001)[100].

Free radical-initiated direct ink writing of liquid polycarbosilane slurry and its conversion into SiC ceramic parts with low shrinkage

Additive manufacturing technology is being developed for manufacturing SiC ceramic parts with designed shape and microstructure. In this study, direct ink writing (DIW) was adopted to print SiC ceramic parts. To avoid incorporating volatile organic solvents or water, a SiC ceramic precursor liquid polycarbosilane (LPCS) was used as the binder of SiC powder and the rheological adjustment additive. The content of LPCS with the content and diameter of SiC powder were optimized to improve the fluidity of slurry, increase its ceramic yield and reduce its shrinkage during pyrolysis. According to the results of rheological analysis and shrinkage during pyrolysis, 78 wt% SiC powders composed of 40 nm SiC powder and 5 μm SiC powder in a ratio of 1:6 was appropriate. For achieving rapid solidification rate of the slurry at low temperature, a free‐radical initiator which can trigger the crosslinking of allyl group on LPCS was incorporated. According to the results of rheology, DSC and FT-IR, the preferred platform temperature for fast curing of DIW slurry was 150 °C. As the slurry accumulated layer by layer on heating platform, the cured green bodies were successfully prepared. After pyrolysis to 1200 °C, SiC ceramic parts were obtained with only 4.43% linear shrinkage associated with the precursor-to-ceramic conversion. Because the shrinkage was limited, no obvious deformation or crack was found.

A Novel Fitting Polynomial Approach for An Accurate Soc Estimation In Li-Ion Batteries Considering Temperature Hysteresis

Lithium-ion batteries are essential to modern technology, requiring accurate estimation of the state of charge (SOC) for optimal performance. Traditional methods such as Coulomb Counting (CC) are ineffective in the face of temperature variations, leading to inaccuracies in SOC estimation, which in turn cause obvious deformation of hysteresis curves. To address this, this paper introduces a novel method called Polynomial Fit State of Charge (FPSOC), for effective SOC estimation. This method incorporates a fifth-degree polynomial fitting that accounts for a wide range of temperature variations (from -10°C to +80°C), a feature that, according to the authors, has not been offered by all previously published methods. A series of simulation tests using the MATLAB/Simulink tool are conducted under various temperature profiles to evaluate the effectiveness of the FPSOC method. The results demonstrate the notable superiority of the FPSOC model compared to the CC method, with a significantly reduced RMSE of only 0.93% compared to 6.77% of the CC model. Particularly effective at low SOC levels (30%), the FPSOC model demonstrates precision up to six times higher compared to the CC model. Additionally, when evaluated against other recent SOC estimation techniques such as CM, RLSF, EKF, DST, BBDST, ASMO, LPM_H, LSTM-SA Group A and B, and baseline ECM-ID, The FPSOC method proves extremely accurate, with the lowest average error under different temperature conditions.

Lemongrass (Cymbopogon citratus) essential oil: an eco-friendly and fast-acting acaricide against the grain pest mite Aleuroglyphus ovatus

ABSTRACT This study was designed to evaluate the acaricidal effect and the mode of action of lemongrass essential oil (LEO) against Aleuroglyphus ovatus. Contact and fumigant mortality indicated that LEO had higher acaricidal activities at a low concentration, and the acaricidal action of LEO was significantly more effective by contact effects than by fumigant bioassay. Repellent rate against A. ovatus at different concentrations of LEO increased with application time. Observation on the toxic symptoms revealed that almost all mites were in immobilized type (IM type) in 30 min, but the symptom of knock-down type (KD type) appeared later. Cuticles of mites killed by LEO exhibited obvious colour change and deformation. Detoxification enzyme activity assay showed that glutathione S-transferase (GST) activity increased in mites treated by LEO compared to the controls. LEO increased catalase (CAT) activity of A. ovatus but inhibited superoxide dismutase (SOD) after 20 h. LEO also increased nitric oxide synthetase (NOS) and inhibited acetylcholine esterase (AChE) activities. Moreover, LEO acted as a fast-acting neurotoxin on A. ovatus. Our results suggest that LEO has an acaricidal potential and is a promising agent in control of A. ovatus.

Experimental and numerical study on behavior of demountable T-shaped bolt shear connectors in sustainable composite beams

This paper proposed a new type of demountable T-bolt shear connector to improve the disassembly efficiency of composite beams and realize the sustainable of the structure components. The shear behavior of nine groups of push-out specimens was experimentally investigated through monotonic loading push-out tests. The finite element analysis (FEA) models were validated against the test results, specifically in terms of the load-slip responses and failure modes of the T-bolt shear connectors in these push-out specimens. The obtained results show that all the specimens have no obvious deformation and cracks in the steel beam and RC slab. The separation between the slab and the steel beam is no more than 1 mm, indicating that the anti-lifting ability is excellent. Moreover, parametric analysis demonstrates that increasing the bolt pretension of the T-shaped shear connector and the friction coefficient between the bridge gasket and the steel beam significantly enhances the initial stiffness and ultimate strength of the shear connectors. However, the shear behavior is relatively insensitive to variations in the channel thickness and bolt grade. Based on regression analysis, a load-slip mechanical model has been proposed. This model accurately describes the mechanical properties of this type of shear connector, providing a theoretical foundation for the application of demountable composite beams.

On multi-stage deformation and gradual energy absorption of 3D printed multi-cell tubes with varying cross-section

Thin-walled structures are widely used in passive safety systems due to their excellent lightweight and controllable progressive deformation performance. While designing to improve the energy absorption performance of thin-walled structures, it is also crucial to consider reducing the damage received by protected objects during accidental collisions. In this work, stepwise and continuous graded multi-cell tubes with varying cross-sections were proposed based on the fused deposition modeling technique to achieve a gradual energy absorption process. Compression responses and energy absorption characteristics of the graded multi-cell tubes were investigated by quasi-static compression tests. Experimental results showed that the stepwise graded multi-cell tubes produced obvious multi-stage deformation and energy absorption during axial compression. The specific energy absorption presented an upward trend with the increased number of stepwise segments. For the same ranges of cross-section variations, continuous graded multi-cell tubes exhibited more plastic hinges and better energy absorption performance due to the absence of discontinuous interfaces. In addition, continuous graded multi-cell tubes showed continuous folding deformation with the gradually decreasing folding wavelength. Thus, it exhibited a steadily increasing trend in crushing force and realized the gradual energy absorption mode.

Energy Absorption and Damage Analysis of Fragments in High-Speed Impact on Composite Honeycomb Sandwich Structures

With the continuous innovation of UAV technology, composite honeycomb sandwich structures are used more and more in the fuselage structure of UAVs, and their anti-high-speed fragment impact performance has become a concern. In order to study the influence of fragments on the damage degree of composite honeycomb structures and analyze the damage difference of different initial velocity fragments on different composite honeycomb structures, based on the numerical simulation results of high-speed impact, the energy absorption characteristics of different honeycomb sandwich structures are analyzed, and the honeycomb structure with better energy absorption is selected for 24 impact experiments. The velocity range of fragment impact is 141–368 m/s. The typical damage of the upper core layer and the lower core layer in each structure is analyzed, and the energy absorption theory is used to compare the conditions of each group. The results show that ST-3-3 has the best energy absorption characteristics. Under different velocity impacts, the energy absorption per unit volume of the ST-3-3 structure reaches 521.6~659.6 × 103 J/m3, which is about 30.6% higher than that of the same design structure. The four groups of composite honeycomb sandwich structures designed in the experiment have obvious deformation in the process of impact, except that the deformation of the bottom skin of the ST-6-6-1 structure is not obvious, and the deformation of the other three groups is more obvious with the increase in structural resistance. This research shows that the reasonable arrangement of the structure and material of the composite honeycomb sandwich can better cope with the impact of high-speed fragments and reduce the damage to the structure.

Stepwise surgical management of binder syndrome with skeletal class III malocclusion in adults

Our study aimed to evaluate a stepwise treatment of class III malocclusion accompanied with flat nasal deformity, using orthodontics, orthognathic surgery, and rhinoplasty, as well as stability during long-term follow-up.In total, 27 patients with nasomaxillary hypoplasia and skeletal class III malocclusion were enrolled in this study. All patients had accepted orthodontic and orthognathic surgery, followed by rhinoplasty with costal cartilage as the second surgical procedure. Clinical results were evaluated by radiography, medical photography, questionnaire, and cephalometric analysis.All patients were satisfied with the surgical results and no serious complications occurred. During the follow-up, the patients showed well-corrected midface contour and nasal projection, and stable occlusion. The costal cartilage grafts were well fixed, without obvious absorption deformation. Lateral cephalometric analysis and overlay results showed that the postoperative point A had advanced approximately 5.20 ± 1.43 mm and the SNA angle had increased by approximately 5.59 ± 2.86°. Soft-tissue measurements showed a 14.22 ± 6.56° decrease in the facial lobe, while the nasolabial angle had increased by 16.83 ± 6.65° postoperatively.The results suggested that stepwise orthodontic-orthognathic surgery and rhinoplasty produce a predictable and stable result in long-term follow-up.

Evidence for, and significance of, the Neoproterozoic Xuefeng Orogeny, South China

The recognition of unconformities is important for determining the long-term evolution of orogenic belts. We document an unconformity between Tonian and Cryogenian strata of the Nanhua Basin of South China. This stratigraphic break has previously been termed the Xuefeng Movement and is developed within the Yangtze Block and western Cathaysia Block. Deformation characteristics and detrital zircon U-Pb geochronology from rock units underlying and overlying the unconformity (i.e., the Niuguping and Gucheng formations, respectively) from the Anhua region of the northern Hunan Province in the southeastern Yangtze Block are documented. The Niuguping Formation displays a set of top-to-northwest imbricate thrust faults and related fault-propagation folds, NEE-plunging subparallel crenulation lineations, a foliation, and shows widespread greenschist facies metamorphism. In contrast, the overlying Gucheng Formation exhibits no obvious stratal deformation (apart from a mild inclination of bedding) and is unmetamorphosed. Detrital zircon age spectra of the samples from the Niuguping Formation are characterized by unimodal age peaks of ca. 750–730 Ma, while those of the samples from the Gucheng Formation yield a multimodal age distribution, with a few syn-sedimentary detrital zircons (<700 Ma), and much older zircons with age peaks of ca. 800 Ma, 2.1–1.9 Ga, and 2.6–2.3 Ga. Combining this data with previous geochronology indicates deposition of the Niuguping and Gucheng formations in the late Tonian (725–720 Ma) and Cryogenian (690–660 Ma), respectively. The time gap across the unconformity is some 30 Ma (720–690 Ma). The unconformity and associated structural and metamorphic break extend across the Yangtze Block and western Cathaysia Block, defining a major regional orogenic event. The significantly different detrital zircon spectra of strata across the unconformity suggest a dramatic change in the source due to the Xuefeng Orogeny in the Yangtze Block. Zircon U-Pb-Hf isotopic evidence indicates that detritus of the Niuguping Formation below the unconformity was derived from syn-depositional magmatic activity in the northern Yangtze Block, while a significant increase of Archean to Paleoproterozoic ages for the Gucheng Formation, suggests that the Xuefeng Orogeny resulted in crustal thickening and denudation in the northern Yangtze Block. These changes in provenance, along with changing deformational and metamorphic patterns, indicate evolution of the Nanhua Basin from a compressional to an extensional back-arc basin, which we infer is related to tectonic switching from an advancing to a retreating subduction system in the northern Yangtze Block at the time of the unconformity.

Post-buckling behavior and DSM design of cold-formed steel lipped channel columns experiencing local-distortional-global interaction

This paper describes experimental research investigating the structural behaviors, failure modes, and ultimate load-carrying capacities of fixed-ended cold-formed steel lipped channel columns eroded by local-distortional-global (L-D-G) buckling interaction under axial compression. Initially, a brief introduction on the selection of column geometry, which was based on the closeness between three elastic critical buckling stresses named elastic local, distortional, and global critical buckling stresses, was reported. In addition, detailed works involving measuring member geometries and initial geometrical imperfections, test set-up, and the arrangements of strain gauges and displacement transducers are described. Moreover, experimental investigation results of 33 cold-formed steel columns are discussed including deformed configurations, applied load vs. strains curves, applied load vs. displacement curves, failure modes, and ultimate load-carrying capacities. The tests demonstrated D-G interaction with no obvious local deformation observed even though the elastic critical loads of L, D, and G for the selected specimens are close. The results clearly demonstrate that the occurrence of D-G buckling interaction eroded the ultimate strengths of columns. Current DSM predictions are evaluated using experimental data of cold-formed steel columns related to the D-G buckling interaction. Furthermore, a design criterion based on DSM is proposed to identify cold-formed steel columns eroded by D-G buckling interaction and predict the ultimate strength, which is evaluated by all available experimental data collected from related literature.

Influence of interface on deformation compatibility of a heterogeneous Cu/Al nanoscale multilayer

The incompatible deformation among the constituent layers usually results in extremely low tensile ductility in nanoscale metallic multilayers. Here, molecular dynamics simulations are conducted to investigate the deformation compatibility of a heterogeneous Cu/Al multilayer with various interface structures under compression. The results show that, by selecting an appropriate thickness of thin interlayers, the heterogeneous Cu/Al nanolayered composite with (1¯1¯1) interface exhibits excellent compatible deformation between the soft and hard layers while the homogeneous counterpart does not. The excellent deformation compatibility of the heterogeneous structure originates from the presence of the thin soft interlayer that can enhance the dislocation activities of the hard layers. Unlike that with (1¯1¯1) interface, the heterogeneous structure with (001) interface shows obvious incompatible deformation among the component layers. Such a scenario can be attributed to the stable dislocation network on the (001) interface, making the dislocations in the soft phase difficult to cross the interface into the hard phase. These findings may deepen our understanding of the deformation compatibility of heterogeneous nanoscale metallic multilayers.

In situ measurements and simulations of a net cage in currents

Accurate predictions of net cages’ deformation under current loads are vitally important for the welfare of stocked fish and the safety of cage structures. In this study, a scaled cage model was deployed at a fish farm. The incoming flow profile was measured through an Acoustic Doppler Current Profiler (ADCP) with high resolution in the depth direction, and the flow inside the cage was measured through an Acoustic Doppler Vector (ADV). Pressure tags were applied to capture the lifting of the cage under varying current conditions. The incoming flow velocity shows a good correlation with the lifting of the cage, and in general the rate of the cage being lifted by the flow increases with flow speed. However, the flow speed measured inside the cage is much less correlated to the upstream flow and cage deformation. Numerical cage models consisting of truss elements were developed; two flow reduction factors r = 0.9 and 0.8 derived from empirical formulas and measurements inside cages in previous studies were applied. The numerical model with r = 0.8 can predict the cage deformation well, with most relative deviations in the depth directions being less than 15%. The study indicates the feasibility of applying pressure tags with high precision to estimate current-induced cage deformation in situ, especially when a cage is experiencing obvious deformation.

Viscoelastic–plastic rheological model and its application to tunnels

Tunnels exhibit obvious continuous deformation during excavation and operation. This behaviour is closely associated with the time-dependent behaviour of rocks, which is induced by groundwater-level fluctuation and prolonged periodic rainfall infiltration. This paper proposes a rheological model consisting of a Hooke elastomer, Kelvin body and novel plastic element in series (called the HKP model) to describe the creep response of rocks considering the characteristics of dry–wet cycles. First, dry–wet cycle creep tests were carried out to investigate the time-dependent behaviour: that is, the creep behaviour of sandstone. Then the creep equation of the viscoelastic–plastic model was derived, and the damage coefficients under the effect of dry–wet cycles and time were obtained. Finally, the HKP model was established to investigate continuous deformation during tunnel excavation. The results reveal that dry–wet cycles have obvious effects on the physical properties and creep behaviour of sandstone. The creep behaviour of sandstone undergoes three stages – namely, the decaying, steady and accelerated stages – that can be reasonably described by the proposed HKP model. In practice, the proposed model can accurately predict the creep behaviour of rocks in tunnels owing to excavation. Thus, the HKP model can help in establishing tunnel maintenance strategies to ensure long-term safety.

Characterization of tensile properties of chain stitch structure fabric with negative Poisson’s ratio yarn

Negative Poisson’s ratio textiles have expanded deformation behavior and special mechanical properties under tension. According to the previous research, the negative Poisson’s ratio effect of fabrics was always lower than yarns. The main reason was that negative Poisson’s ratio yarns showed little structural deformation because of the fabric structures. In this study, chain stitch structure fabrics with negative Poisson’s ratio yarns as inserted weft yarns were designed and prepared. The effect of inserted weft yarns, symmetrical and parallelization arrangement and density on the Poisson’s ratio of chain stitch fabrics were tested and analyzed. The results showed that the negative Poisson’s ratio effect of fabrics was as similar as yarns and yarns in fabric. When the knitting loops provided fixation role in the fabrics, the negative Poisson’s yarns could also present obvious deformation behavior to successfully improve the expand effect of fabrics. Poisson’s ratio and porosity of fabrics under cyclic stretching were carried out to study the structure and property stability. The chain stitch structure fabrics with negative Poisson’s ratio are expected to provide more choices for improving the property and applicability.

Multi-temporal Monitoring for Road Slope Collapse by Means of LUTAN-1 SAR Data and High Resolution Optical Data

Abstract. Collapse is one of the most destructive natural disaster, being sudden, frequent, and highly concealed, causing large-scale damage. On August 10, 2023, the slope of 108 national highway in Weinan, Shaanxi Province collapsed. The lower edge of the collapse slope body is the Luohe river, and the collapse body rushes into the river to form a barrier lake. Remote sensing technique can provide multiple dimensional information for disaster emergency and management. Lutan-1 SAR satellites are the first group L-band SAR constellation for multiple applications in China. Owing to the precise orbit control ability and high revisit characteristics for Lutan-1 SAR satellites, surface deformation monitoring with centimeter even millimeter accuracy may be achieved. Based on the multi-temporal pre-disaster and post-disaster Lutan-1 SAR data and high resolution optical data, the collapse information including the pre-disaster and post-disaster were extracted and analysed. From July 11 to 27, 2023, the pre-collapse deformation was obtained with the maximum value of 6 cm, and obvious deformation occurred before the collapse. Lutan-1 monitored results pre-collapse can provide certain information for disaster early identification. From July 27 to August 24, 2023, due to the serious incoherence caused by large deformation and ground changes, effective deformation information cannot be obtained based on the InSAR technique. In addition, the collapse information was clearly extracted by the high resolution optical data acquired pre-collapse and post collapse. After the collapse, significant deformation was extracted from August 24 to September 21 with the maximum value of 6 cm, indicating that obvious deformation still occurred over the collapse area. Through the analysis for the series results obtained by SAR and optical data, it is favourable for disaster emergency and management.

Enhanced impact toughness of 316L stainless steel welded joint by ultrasonic impact

316 L welded structures have been widely used in the industrial field, but the weld defects seriously affect the reliability. The ultrasonic impact treatment (UIT) is used to improve the quality of welded joints and the effects of the UIT on the impact toughness, fracture morphology, microhardness and microstructure of the 316 L stainless steel welded joint were studied. Moreover, the coupled finite element model of the 316 L stainless steel welding-UIT was established to study the effects of the UIT on the residual stress. The results showed that the UIT could effectively improve the impact toughness of the 316 L stainless steel welded joint, and the impact toughness could be improved with the increasing of the UIT current. According to the fracture morphology, it was found that the fibrous region increased, and the radical region decreased. In addition, the dimple of the material tends to become deeper and larger, and the increase of dimple was accompanied by the increase of energy absorption. The microhardness of the welded joint was improved, and the grain was refined, which indicated that the 316 L stainless steel welded joint generated obvious plastic deformation. The simulation results show the welded joints can introduce the significant residual compressive stress under the action of the UIT. Based on the comprehensive analysis of the UIT on impact toughness, the generated plastic deformation, the reduced grain size, and the introduced residual compressive stress of the 316 L stainless steel welded joint were the main reasons for the improvement of the impact toughness.

First-Principles Predictions of MoS2-WS2 In-Plane Heterostructures for Sensing Dissolved Gas Species in Oil-Immersed Transformers.

This work from first-principles insight uses a MoS2-WS2 in-plane heterostructure as a potential sensing material for detection of CO and C2H2, two typical dissolved gases in oil-immersed transformers, in order to evaluate the operation status. The adsorption performance of the MoS2-WS2 heterostructure upon two gas species is assessed via three adsorption sites and compared with isolated MoS2 and WS2. Results indicate that MoS2-WS2 performs with a much stronger binding force and charge-transfer for adsorptions of CO and C2H2 in comparison to the isolated counterpart, which gives rise to more obvious deformation in the electronic property of MoS2-WS2 as well as a much larger resistance-based sensing response. The recovery time of MoS2-WS2 for desorption of CO and C2H2 molecules is also appropriate to allow the reusability of such a sensor. The findings in this work uncover the admirable sensing potential of transition metal dichalcogenides (TMDs)-based heterostructures upon oil dissolved gases, which opens up a new way to explore novel 2D nanomaterials as resistive gas sensors for dissolved gas analysis in electrical oil-immersed transformers.

TiAl Alloy Fabricated Using Election Beam Selective Melting: Process, Microstructure, and Tensile Performance

TiAl alloy is one of the most attractive candidates for a new generation of high-temperature structural materials and has broad application prospects in the aerospace field. As a typical intermetallic material, TiAl is inevitably difficult to process using conventional methods. Election beam selective melting (EBSM) is an effective method of addictive manufacturing to prepare TiAl alloy with a complex structure. However, the microstructure of TiAl alloy formed using EBSM often contains defects such as pores, which seriously reduces the mechanical properties of the material. In this work, the effects of EBSM and post-processing procedures on the microstructure and mechanical properties of Ti-48Al-2Cr-2Nb alloy were studied. The results show that the microstructure of Ti-48Al-2Cr-2Nb alloy formed using the EBSM process was dense and composed of equiaxed γ-phase and double-phase regions. A large number of dislocations that formed due to thermal stress were clearly observed inside the Ti-48Al-2Cr-2Nb alloy. When the EBSM process parameters were 13.5 mA, 4.0 m/s, and 40.50 J/mm3, as the current intensity increased, the Al content decreased, the content of α2 phase increased, and the microstructure of the material was coarse. The results of the tensile test fracture morphology indicate that the Ti-48Al-2Cr-2Nb alloy exhibited brittle fracture during tensile deformation, lacking the typical yield deformation of metal materials. As the energy density of the EBSM process increased, the mechanical properties of the Ti-48Al-2Cr-2Nb alloy first increased and then decreased. The samples prepared with an energy density of 34.50~40.50 J/mm3 had excellent mechanical properties, of which the maximum tensile strength and maximum elongation reached 643 MPa and 2.09%, respectively. The phase composition of the Ti-48Al-2Cr-2Nb alloy after hot isostatic pressing (HIP) treatment remained unchanged from the EBSM samples, but there was a slight difference in content. There was an increase in the amount of γ phase and a decrease in B2 phase, accompanied by the generation of a massive γ phase after HIP treatment. Moreover, the number of dislocations inside the material increased. The Ti-48Al-2Cr-2Nb alloy after HIP treatment exhibited obvious plastic deformation characteristics, with a tensile strength of 679 MPa and elongation of 2.5%. A heat treatment of 900 °C/5 h was performed on the Ti-48Al-2Cr-2Nb alloy after HIP. The dislocation density of the Ti-48Al-2Cr-2Nb alloy decreased, and the B2 phase transformed from massive to lamellar.

Experimental and theoretical investigation of failure mechanism in Al2O3/SiC composite under plane shock waves

The investigation of fracture and fragmentation is essential for evaluating the protection performance and structural design of ceramic armour. This paper focused on the dynamic failure and fracture mechanisms of the fine-grained Al2O3/SiC composite subjected to plane shock waves. The macroscopic shock response characteristic was determined through a series of plane impact tests, which included the Hugoniot curves of the composite. The results indicated that the fracture mechanism is significantly influenced by specific stress characteristics. The transgranular fracture in large grains and intergranular fracture in small grains exhibit obvious local plastic deformation characteristics. Moreover, the presence of second-phase SiC particles markedly influences both crack propagation and the microfracture mode of the composite. Lastly, a statistical analysis of the ceramic fragments was conducted after the soft recovery of specimens in impact experiments, and analytical models were developed and modified to predict the distribution of fragments under plane shock loading.

Evolution mechanism of microstructure and microhardness of Ti–6Al–4V alloy during ultrasonic elliptical vibration assisted ultra-precise cutting

The ultra-precision Ti–6Al–4V alloy parts are growing used in medical and aerospace industries, and which always work in the extreme working conditions such as high temperature, high pressure, and variable load. Thus, the requirements for machining accuracy and surface quality of parts are getting higher and higher. The ultrasonic elliptical vibration assisted cutting (UEVC) technology has been proved to be an effective method for the ultra-precision machining of Ti–6Al–4V alloy. However, in the UEVC process, the evolution mechanism of microstructure and microhardness, which directly affect the service performance and life, is unrevealed. In this paper, the comprehensive investigations of microstructural plastic deformation, grain refinement, phase transformation and microhardness of machined surface layer under conventional cutting (CC) and UEVC processes are carried out. The experimental results indicated that, due to the effects of UEVC technology, the plastic deformation area show obvious compression deformation, the depth of plastic deformation is less than 10 μm, there is no obvious phase transformation on the machined surface layer material, and the hardening rate of machined surface is more than 20%. These findings show the UEVC technology has a unique influence on the microstructure and microhardness of Ti–6Al–4V alloy, which have important implications for the cutting parameter design of ultra-precision Ti–6Al–4V alloy parts.