Subsequent Deformation Research Articles

Structural control of the deposition and subsequent deformation of the Killary Habour-Joyce Country Silurian succession

Abstract: The Killary Harbour–Joyce Country succession of Silurian rocks forms the remnant of one of three successor basins that developed after the Grampian Orogeny and which are preserved in western Ireland. Its outcrop everywhere obscures the contact between the Dalradian rocks of Connemara and the Ordovician rocks of the South Mayo Trough. The outcrop is bisected by the prominent north-west trending Maam Valley Fault Zone that is shown to have a component of synsedimentary movement down-throwing to the southwest. The original basin margins lay well outside the current outcrop area. North-south shortening and inversion of the basin was accomplished by reactivation and inversion of earlier fault structures and was exclusively in the brittle zone. Folding of the Silurian rocks with weak to moderate cleavage and deformation of the basement rocks of Connemara was accomplished by largely vertical movements along numerous strike parallel and oblique fractures. Break-back inversion structures were developed along the southern margin of the South Mayo Trough, which include thrusting associated with footwall shortcut faults and clockwise rotation. Although the timing of deformation overlaps that of diorite sill emplacement, it remains poorly constrained in absolute terms.

Deformation Pattern of Well-Preserved High-Pressure Rocks (SE Syros, Cyclades)

New, detailed geological/structural mapping and field-based structural analysis were carried out to investigate the deformation pattern of well-preserved high-pressure rocks of the Blueschist Unit exposed in SE Syros (Cyclades, Greece). Geological mapping revealed the occurrence of extensive alternations between different rock groups, as well as interfingering patterns in map-scale that are possibly the result of folding. The earlier ductile deformation phase recognized in the mapped area is associated with the development of a penetrative foliation, which was formed at eclogite/blueschist-facies conditions under peak metamorphism. The subsequent main deformation phase occurred under blueschist facies conditions synchronous with the early stages of exhumation of the high-pressure rocks. This phase is mainly associated with the formation of WNW-trending folds and a pervasive axial planar foliation linked with ESE-directed shearing. The main deformation ceased under blueschist-facies conditions, and exhumation of the rocks to greenschist-facies conditions took place under very weak and localized deformation. Greenschist retrogression observed in the southwestern part of the mapped area seems to be controlled by fluids, rather than by intense deformation and formation of major syn-greenschist shear zones.

Compression of additively manufactured PLA for biomedical applications: Effects of test conditions on properties of solid samples

Understanding the mechanical behaviour of additively manufactured (AM) biomedical polymeric devices under various loading regimes is important for tailoring their design to specific applications. This paper presents the results of an experimental study of compressive mechanical properties of AM cubic samples of biocompatible polylactic acid (PLA) manufactured with fused filament fabrication. The measured elastic modulus and ultimate compression strength were compared and analysed for varying testing parameters, such as strain rate and contact friction, for samples with different characteristic sizes. The changes in density of the samples were also assessed for evaluation of the extent of material compaction after deformation. Surface morphology of specimens was examined before and after compression tests using scanning electron and optical microscopy. Different types of defects induced by the manufacturing process and caused by the subsequent compressive deformation were studied and compared. The obtained results are useful for design and optimization of small-size biomedical devices, which require precise control of their structural morphology and mechanical behaviour.

Controllable precipitation behavior near grain boundaries enabled by artificial strain concentration in age-hardening aluminum alloys

Regulating the precipitation behavior in the vicinity of grain boundary (GB) is crucial for improving the mechanical property and corrosion resistance of age-hardening aluminum alloy. In this work, we innovatively propose a strain-concentration controlled strategy to realize the controllable fabrication of the thinner precipitate-free zone (PFZ), associated with the finer grain boundary precipitates in Al–Zn–Mg–Cu alloy. Specifically, the primary PFZ with certain solute atoms is introduced by short pre-aging treatment, followed by the subsequent cyclic deformation at room temperature to induce the localized plastic deformation in the primary PFZ. Compared with the traditional aging, the Al–Zn–Mg–Cu alloy treated by the current process manifests superior combination of impact toughness and corrosion properties, as well as the slightly improved unidirectional tensile properties. Furthermore, the atomic-scale mechanism of the unique precipitation behavior near GB is revealed using the molecular dynamics simulation. A large number of dislocations are generated in PFZ, which acts as the favorable precipitation sites and contribute to the secondary precipitates in the primary PFZ. The present work provides a novel design route and an atomic-scale understanding for controlling the precipitation behavior in the vicinity of GB, and it has the potential to direct the optimization of mechanical performance and corrosion resistance in a board spectrum of aging-hardening alloys.

Optimization of Flat-Rolling Parameters for Thermally Stable Alloy of Al-Cu-Mn System with Micro Additions of Si and Zr

The phase composition, microstructure, and mechanical properties of flat-rolled experimental Al-Cu-Mn system alloy with Si and Zr additions have been studied. The experimental results have been compared with data for the AA2219 commercial alloy pertaining to the same alloying system. Hot deformation of an experimental alloy causes the precipitation of ~100 nm sized dispersoids and refinement of the eutectic phase particles. The yield strength and relative elongation of the hot-deformed experimental alloy are 255 MPa and 8.6%, respectively. Subsequent cold deformation reduces the relative elongation by 3.5% and increases the yield strength by 50 MPa, while the ultimate tensile strength does not change. After long-term 350 °C exposure, the mechanical properties of the experimental alloy remain the same as those of the as-deformed one, whereas the yield strength of the 2219 alloy decreases by 2 times and the ultimate tensile strength by 1.4 times. Comparison of these experimental results with data for the 2219 alloy and other Al-Cu-Mn system alloys cited in this work and reported elsewhere suggests that a good thermal stability of Al-2Cu-2Mn-0.4Si-0.2Zr alloy rolled stock can be achieved through treatment using the regimes designed herein.

Shift of dynamic recrystallization kinetics in thermal compression induced by prior cold deformation treatment at Ni80A superalloy

To achieve the uniform and fine-grained microstructures during thermal deformation of nickel-based superalloys, a novel two-stage deformation approach was employed, involving prior cold deformation treatment (PCDT) and subsequent thermal deformation. Experimental investigations concerning this two-stage deformation method were carried out on Ni80A superalloy, encompassing various combinations of cold and thermal compression parameters. The analysis of microstructures revealed that PCDT significantly enhances dynamic recrystallization (DRX) process, resulting in fine-grained microstructures during thermal compression and expanding the processing-parameter domains for grain refinement. To clarify the shift of DRX kinetics in thermal compression induced by PCDT, the DRX kinetics models considering this pre-treatment were derived. These models demonstrated a linear inverse correlation between the activation energy within DRX kinetics models and prior stored energy from PCDT. This suggested that PCDT promotes the DRX process by reducing the activation energy during thermal compression. Following, the kinetics curves depicting DRX volume fraction during thermal deformation were drawn. Results indicated that under an identical thermal compression condition, the kinetics curve shifts towards decreasing strain with increasing of prior cold deformation. Under various thermal compression conditions, these kinetics curves for Ni80A superalloy processed with PCDT get shifted to the direction of decreasing strain when compared to the alloy without PCDT. These shifts underscore a pronounced acceleration of DRX process induced by PCDT. Finally, a finite element model incorporating DRX kinetics models was developed to further illustrate the influence of PCDT on the shift of DRX in an upsetting process, which shows a promising potential for theoretical calculations.

Study on thermal deformation constitutive model of NiCoFeAlCrMo high-entropy alloy with FCC / L12 coherent structure

Due to its multi-principal component characteristics, high-entropy alloys exhibit excellent comprehensive mechanical properties and become a new generation of engineering structure alternative materials. At present, a single constitutive model is used to describe the change of flow stress in the study of hot deformation behavior of high-entropy alloys, and there are some problems such as inaccurate prediction accuracy or inapplicability of the model in some hot processing intervals. In this paper, three different constitutive models are combined to fully consider the applicability of the model in different temperature ranges, and the change of flow stress behavior is accurately described, which is of great significance for subsequent deformation mechanism research, hot processing process optimization, numerical simulation and so on. Thermal compression experiments on cast Ni28.5Co18.6Fe18.2Al16.3Cr10.5Mo4 Ti2.3Nb0.6W0.9C0.2 high-entropy alloy were carried out using a Gleeble-3800 thermal simulation tester with deformation temperatures in the range from 900 ℃ to 1150 ℃ and strain rates from 0.001 s−1 to 1 s−1. The constitutive relationships between true stress and strain, temperature and strain rate were established, while the heat deformation process of this alloy under different deformation conditions by Arrhennius, Modified Johnson-Cook and Modified Fields-Backofen models were characterized. The results indicate that Arrenius model describe the rheological behavior of the alloy better in a wider temperature range and at a wider strain rate range. Comparatively, the model shows the highest prediction accuracy in the high-temperature region and slightly lower accuracy in the mesothermal and low-temperature regions. The modified J-C and F-B models have better prediction accuracy in the low-temperature and medium-temperature regions, respectively. Due to the different deformation conditions, dislocation configurations such as dislocation tangles, dislocation networks, and subcrystalline junctions can be observed in the plastic deformation region. The dislocation density of this alloy increases with increasing strain rate and decreasing deformation temperature after deformation.

Management of Severe Adolescent Idiopathic Scoliosis

Adolescent idiopathic scoliosis is the most common form of scoliosis in the pediatric population. Skeletal maturity and curve severity play a major role when it comes to progression risks and indications for surgery. Curvatures of greater than 45 degrees in a skeletally immature patient pose a high risk for progression and subsequent deformity. Surgical correction of severe deformity is a complex topic and spans all phases of patient care, including preoperative testing/planning, intraoperative surgical techniques, and postoperative management. This article seeks to review current management strategies for patients with severe adolescent idiopathic scoliosis.

Comparison of Single-Pass Differential Speed Rolling (DSR) and Conventional Rolling (CR) on the Microstructure and Mechanical Properties of Mg5Zn

Background: The primary hot rolling method implemented is differential speed rolling (DSR). The material is rolled and grains are strained, producing fine dynamic recrystallization (DRX) grains that improve material strength and ductility. Objective: The material introduced and under investigation in this paper is an Mg-based alloy, Mg5Zn (wt. %), whose microstructure is enhanced through a combination of heat treatments with proper temperature and holding time and subsequent plastic deformation through hot rolling to evaluate the effect on mechanical properties Methods: The method involves preheating the material to various temperatures in a range from 250ºC to 350ºC and rolling to various thickness reductions to analyze the effect of single-pass differential speed rolling (DSR) and conventional rolling (CR) on the DRX process and its influence on mechanical properties. Results: The effect of single-pass differential speed rolling (DSR) and conventional rolling (CR) on the DRX process shows that the process produces increasing amounts of finer DRX grains at higher rolling reductions, thereby improving the strength and ductility of the material. Conclusion: This investigation demonstrated that single-pass DSR can improve the mechanical properties and formability of Mg5Zn more effectively than CR in terms of grain refinement analyzed through OM, SEM, and EBSD resulting in enhanced tensile strength and ductility [1].

Параметрическая идентификация и оптимальное управление процессом индукционного нагрева

In the paper the experimental induction heating installation for through heating of steel cylindrical workpieces is considered. It is well known that the use of an industrial heating system presupposes incomplete information about its main characteristics due to the complex nature of changes in some parameters both from the ambient temperature and from the temperature of the heated part. These parameters primarily include the coefficients of convective and emissive heat transfer from the surface of the workpiece. At the first step, it is necessary to obtain the values of unknown parameters, which also include the voltage of the power source, and then solve the optimal control problem. The problem of identifying these parameters is solved using the alternance method of parametric optimization of systems with distributed parameters, using experimental data from thermocouples. The obtained values of unknown parameters are then used in a numerical finite-element FLUX model of the considered process. Based on the developed model, the problem of time-optimal control with an additional phase restriction on the maximum temperature is formulated. This problem is solved using the alternance method. The solution of the problem made it possible to obtain a emperature field with a maximum deviation of 32 °C from the required temperature T* = 1 200 °C. This value is less than 3% of the desired temperature value and fully meets the technological requirements for induction through heating processes prior subsequent plastic deformation. The maximum temperature in this case does not exceed the maximum permissible value of 1 300 °C during the entire heating process.

Superimposed Variscan and Alpine deformation in the basement rocks of southern Andorra, central Pyrenees

Detailed mapping, structural analysis and cross-section constructions yield new data on the geometry and chronology of Variscan and Alpine deformations in the central Pyrenees of southern Andorra. The study area is characterized by polyphase deformation and strain partitioning owing to the presence of an efficient décollement level within Silurian black shales. Variscan macrostructures gave rise to a minimum shortening of c. 22% for Cambrian–Ordovician and Upper Ordovician units below the décollement level and of c. 35% for Silurian and Devonian units above it. Variscan structures are cut by out-of-sequence thrusts, presumably developed after late Variscan igneous intrusions, and extensional faulting. These thrusts cut previous Variscan D 2 (main-phase) folds and originate additive and subtractive contacts. We propose an Alpine age for most of these thrusts, which, together with the Variscan structures, are affected by subsequent Alpine deformation, which causes changes in their orientation around the intrusions, and a progressive steepening of the cleavage from south to north. We discuss the usefulness and limitations of balanced cross-sections in polydeformed areas and propose that the technique is valid to construct regional sections and to obtain geologically reasonable pre-deformational configurations.

Influence of ultrafine-grained structure parameters on the annealing-induced hardening and deformation-induced softening effects in pure Al

This work investigates the influence of parameters of initial ultrafine-grained (UFG) structure in commercially pure (CP) Al on annealing-induced hardening (AIH) and deformation-induced softening (DIS) effects. UFG structures were formed via processing CP Al by various methods of severe plastic deformation (high pressure torsion (HPT), equal channel angular pressing (ECAP) and combination of ECAP and cold rolling (CR)). AIH and DIS effects are observed in all the studied UFG structures. However, HPT Al demonstrates large increase of strength due to annealing and drastic gain of ductility after subsequent additional deformation whereas in ECAP Al and ECAP + CR Al both effects are much less pronounced. Microstructure characterization by X-ray diffraction (XRD) analysis, electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM) was performed for HPT Al and ECAP + CR Al in the three studied states: before and after annealing and after annealing and subsequent additional deformation. Analysis of microstructure evolution during annealing and subsequent additional deformation shows that the key microstructure parameter which is responsible for AIH and DIS effect is the change of dislocation density in grain interior in ECAP + CR Al, whereas in HPT Al the effects are related to the change of dislocation density at/near grain boundaries. In addition, outstanding combination of high strength (∼210 MPa), high electrical conductivity (∼62 %IACS) with sufficiently good ductility (7–10 %) and thermal stability (up to 150°С, at least) was achieved for ECAP + CR Al after annealing at 150 °C, 1h.

Effect of shell thickness on mechanical behavior of Al/Ti core-shell nanowires during three-point bending and unloading

The molecular dynamics models of Al and Al/Ti core-shell nanowires (NWs) are established using the large-scale atomic/molecular massively parallel simulator (LAMMPS) to simulate the loading and unloading of the three-point bending of NWs and to investigate the effect of Ti shell thickness on the mechanical behavior of core-shell NWs during loading and unloading. The results show that the Ti shell thickness considerably affects the mechanical properties of the NWs during the bending process. As the shell thickness of the NWs increases from 0 Å to 10 and 20 Å, their Young's moduli and yield strength first decreases and then increases; this is attributed to the unique evolution of the core-shell structure during the bending process. When the shell thickness is 0 Å, the yielding mechanism of the Al NWs involves the slip of the face-centered cubic (FCC) lattice plane to generate the hexagonal close-packed (HCP) stacking fault. During the subsequent plastic deformation, the FCC lattice plane continues to slip, resulting in the generation and annihilation of Shockley dislocations and HCP stacking faults. Finally, the Al NWs become completely amorphous at the cross section at the midpoint. The yielding mechanism of core-shell NWs involves the plastic deformation of the Ti shell at the bottom of the NW, followed by the continuous outward expansion of the plastic deformation region with increasing loading; this leads to the formation of a fan-shaped region at the bottom of the NW. Finally, the NWs are divided into different components according to their structure and atomic energy, and the driving force for each component during NW unloading is determined. Moreover, the strengthening effect of the shell thickness on the recovery performance of the NWs is investigated. The results show that Body Al provides the main driving force for the shape recovery of Al NW during the unloading process, and Surface Ti and Body Ti provide the main driving force for the shape recovery of the core-shell NWs. Larger the shell thickness, stronger the NW recovery performance during unloading. This study may facilitate the understanding of the unique mechanical behavior of the core-shell NWs.

Formation and elimination mechanisms of prior particle boundaries in a new powder metallurgy superalloy

The formation of prior particle boundaries (PPBs) in a new powder metallurgy superalloy during hot isostatic pressing (HIP) is investigated. Also, the impact of subsequent hot deformation on the elimination of PPBs is systematically studied. The PPBs involves large γ′ phases, carbides (MC and M6C) and oxides (Al2O3, SiO2 and ZrO2). The reactions among the superficial oxides, the adsorbed C and O elements on the particle surface and internally-migrated alloying elements are the dominant reasons for the formation of PPBs during HIP. Besides, the existence of surface tension and surface energy induces the carbon segregation, as well as the formation of PPBs. Thus, the density of PPBs decreases when the spacing between powders is shrunk by a rapid deformation. In hot forming process, the PPBs can be efficiently eliminated via raising deformation temperature/true strain or reducing strain rate. The interactions between dislocations and PPBs, as well as the occurrence of dynamic recrystallization (DRX) induced by the strain/orientation gradient, lead to the elimination of PPBs. The thermodynamic stability of carbides declines with the raised temperature. It indicates that the dissolution of carbides and the elimination of PPBs can be accelerated via raising the deformation temperature. The breakage or deformation behavior of PPBs during hot extrusion is investigated by numerical simulation. The deformation degree of PPBs increases with the raised extrusion ratio. The above important findings are useful for developing hot extrusion processing to effectively eliminate PPBs.

Improving the Understanding of Landslide Development in Alpine Forest Regions Using the InSAR Technique: A Case Study in Xiaojin County China

Employing a small baseline subset Interferometric Synthetic Aperture Radar (SBAS-InSAR) and hotspot analysis, this study identified 81 potential landslides in a 768.7 km2 area of Xiaojin county, eastern Tibetan Plateau. Subsequent time-series deformation analysis revealed that these potential landslides are in the secondary creep stage. The newly identified landslides were compared to a landslide inventory (LI), established through field surveying, in terms of causative factors, including altitude, slope, relief amplitude, distance to river, distance to road, and slope curvature. From the comparison, the InSAR technique showed the following advantages: (1) it identified 25 potential landslides at high altitudes (>3415 m) in addition to the low-altitude landslides identified through the field survey. (2) It obtained approximately 37.5% and 70% increases in the number of potential landslides in the slope angle ranges of 20°–30° and 30°–40°, respectively. (3) It revealed significant increases in potential landslides in every relief amplitude bin, especially in the range from 58 m to 92 m. (4) It can highlight key geological factors controlling landslides, i.e., the stratigraphic occurrence and key joints as the InSAR technique is a powerful tool for identifying landslides in all dip directions. (5) It reveals the dominant failure modes, such as sliding along the soil–rock interface and/or interfaces formed by complicated combinations of discontinuities. This work presents the significant potential of InSAR techniques in gaining deeper knowledge on landslide development in alpine forest regions.

X-ray line profile analysis study on the evolution of the microstructure in additively manufactured 316L steel during severe plastic deformation

316L stainless steel was manufactured by additive manufacturing (AM), and then, the samples were severely deformed by the high-pressure torsion (HPT) technique. The evolution of the microstructure was monitored by X-ray line profile analysis. This method gives the crystallite size and the density of lattice defects, such as dislocations and twin faults. The AM-processing of the HPT disks was performed in two different modes: the laser beam was parallel or orthogonal to the normal direction of the disks. The subsequent HPT deformation was carried out for ½, 1, 5 and 10 turns. The microstructure and hardness evolution during HPT were similar regardless of the laser beam direction. For both sample series, the minimum achievable crystallite size was about 30 nm, while the dislocation density and the twin fault probability got saturated at the values of 300–350 × 1014 m−2 and 3.5–4%, respectively. The microstructure evolution during HPT of the AM-prepared 316L steel was compared with the HPT-induced changes in an as-cast counterpart. It was found that while the AM-prepared 316L steel remained a single-phase face-centered cubic γ-structure during HPT, in the as-cast samples a body-centered cubic (bcc) martensitic α-phase became the main phase with increasing the imposed strain of HPT due to the lower Ni content. In the saturation state achieved by HPT the initially as-cast 316L steel had a considerably higher hardness (about 6000 MPa) than that for the AM-prepared samples (~ 5000 MPa) due to the large fraction of the hard bcc phase formed during HPT.

Patellar Dislocation: Workup and Decision-Making.

Acute patellar dislocation (PD) is usually a problem of adolescents and young adults. In most cases, it is a sports-related injury. It is the result of an indirect force on the knee joint, which leads to valgus and external rotation of the tibia relative to the femur. PD is unlikely to occur on a knee with normal patellofemoral joint (PFJ) anatomy. Acute PD consists of an acute injury of the ligamentous medial patellar stabilizers in the background of factors predisposing to patellar instability. These factors are classified into three groups. The first group refers to the integrity of the ligamentous medial patellar restraints, particularly, the medial patellofemoral ligament (MPFL). The second group refers to an abnormal PFJ anatomy, which renders the patella inherently unstable inside the trochlea. The third group refers to the overall axial and torsional profile of the lower limb and to systemic factors, such as ligament laxity and neuromuscular coordination of movement. PD at a younger age is associated with an increased number and severity of patellar instability predisposing factors and lower stress to dislocate the patella. Acute primary PD is usually treated conservatively, while surgical treatment is reserved for recurrent PD. The aim of treatment is to restore the stability and function of the PFJ and to reduce the risk of patellar redislocation. Surgical procedures to treat patellar instability are classified into non-anatomic and anatomic procedures. Non-anatomic procedures are extensor mechanism realignment techniques that aim to center the patella into the trochlear groove. Anatomic procedures aim to restore the PFJ anatomy (ruptured ligaments, osteochondral fractures), which has been severed after the first incident of PD. Anatomic procedures, especially MPFL reconstruction, are more effective in preventing recurrent PD, compared with non-anatomic techniques. Theoretically, all factors that affect PFJ stability should be evaluated and, if possible, addressed. This is practically impossible. Considering that the MPFL ruptures in almost all PDs, MPFL reconstruction is the primary procedure, which is currently selected by most surgeons as a first-line treatment for patients with recurrent PD. Restoration of the axial and torsional alignment of the lower limbs is also increasingly implemented by surgeons. Non-anatomic surgical techniques, such as tibial-tuberosity osteotomy, are used as an adjunct to anatomic procedures. In the presence of multiple PFJ instability factors, acute MPFL reconstruction may be the treatment of choice for acute primary PD as well. Skeletal immaturity of the patient precludes osseous procedures to avoid premature physis closure and subsequent limb deformity. Unfortunately, restoration of the patient's previous activity level or participation in more strenuous sports is questionable and not easy to predict. In the case of competitive athletes, PD may prevent participation in elite levels of sports.

Study of Machined Surface Quality of AZ31B Magnesium Alloy by End Milling

Magnesium alloys are lightweight structural materials with excellent machinability. However, further development is seriously limited by their low strength and poor formability. Therefore, further decreasing the surface residual stress of the frame by post-process treatment is a key issue, such as for reducing the subsequent deformation due to the residual stress, improving the machining accuracy and corrosion resistance of the magnesium alloy frame products, and extending the service life of the magnesium alloy frame products. Using AZ31B magnesium alloy as the experimental subject, and by exploring the effects of milling parameters on the surface quality of frame parts, this study shows that the surface residual compressive stress, hardness, and roughness of frame parts decreased with the increasing of the milling speed and increased as the depth of cut and the feed per tooth increased. Using cutting fluid in the milling process can decrease the surface residual stress and roughness of the frame parts but increase the surface hardness. In accordance with the experimental results and analysis, the main reason affecting the residual stress on the surface layer of frame components is the thermal elastoplastic problem caused by thermal mechanical coupling during the milling process, resulting in varying stress states on the workpiece’s surface. The primary contributors to hardness are the work-hardening effect induced by milling forces and the thermal-softening effect of milling temperatures, which either augment or diminish the workpiece’s surface hardness. Furthermore, the primary factor impacting surface roughness is the magnitude of cutting forces. Excessive cutting forces lead to the ploughing phenomenon or tool vibrations, thereby causing varying degrees of surface roughness on the workpiece. Meanwhile, the influence of stress-relief annealing or cryogenic treatment on surface residual stress and hardness after the milling of the frame parts was researched. It shows that within the selected milling parameters, both stress-relief annealing and cryogenic treatment can reduce the surface residual stress and homogenize the residual stress distribution of frame parts. Stress-relief annealing leads to a reduction in the hardness of the machined surface, and the hardness of the machined surface increases slightly under cryogenic treatment. The effects of the two post-processing methods on surface quality vary, and in practical production, a rational selection can be made according to the different processing requirements to achieve the optimal standards.

Development of erythrocyte-mimetic PFOB/PDMS thermoplastic elastomer core-shell microparticles via SPG membrane emulsification

Erythrocyte-mimetic perfluorooctylbromide (PFOB)/polydimethylsiloxane (PDMS) thermoplastic elastomer core-shell microparticles were fabricated (for the first time) via Shirasu porous glass membrane emulsification (SPG ME) with evaporation-induced phase separation (EIPS). The resulting micro-sized core-shell particles showed a spontaneously concave shape without a subsequent deformation process such as organic solvent immersion or temperature variations. It replicated the healthy human erythrocyte morphology. In addition, their sizes and morphologies could be controlled by varying the pore size and dispersed-phase composition of the SPG membrane. The diameters of the precisely controlled particles were similar to those of human blood cells (9.6 ± 1.9 μm). The microcompression test revealed a high deformability of the particles owing to both softness of the PDMS-TPE shell and their core-shell structure. The PDMS-based materials displayed a high oxygen permeability, and PFOB displayed a high oxygen solubility. Finally, the oxygen transportation function was evaluated using oxygen tension-responsive HeLa cells (hr-HeLa) under hypoxic conditions (5% O2). This demonstrated the effectiveness of PFOB/PDMS-TPE microparticles as artificial oxygen carriers in various biomedical applications such as tissue engineering.

Multi-disciplinary characterization of shrinkage effects in Opalinus clay

Multi-disciplinary characterization of shrinkage effects in Opalinus clay