Different Number Of Cycles Research Articles

Solvent- and Catalyst-Free Environmentally Benign High Hydrostatic Pressure-Assisted Synthesis of Bioactive Hydrazones and the Evaluation of Their Stability Under Various Storage Conditions

Our group has seen great promise in using substituted diaryl-hydrazones to alleviate oxidative stress in preeclampsia. Specifically, fluorinated diaryl-hydrazones have shown great efficacy, confirmed via antioxidant assays and animal trials using pregnant mice. In addition to efficient antioxidant properties, these diaryl-hydrazones are also considered non-toxic. While the synthesis of these compounds is relatively simple, it commonly utilizes undesirable solvents and glacial acetic acid as the catalyst; additional solvents are needed for the isolation of the desired products, which negatively affects the green synthesis of the hydrazones. To combat this possible industrial roadblock, we have begun incorporating the use of hydrostatic high pressure (HHP) in the synthesis. The use of HHP allowed us to synthesize substituted diaryl-hydrazones in a 1:1 molar ratio without the need for solvents or acid catalysts. The optimized procedure can produce nearly quantitative yields, leading to an easier isolation of the products. Different HHP methodologies, such as constant high-pressure treatment and cycling (with different number of cycles, holding and decompression times) were applied and cycling was observed to be the most efficient activation for the majority of the reactions. Stability experiments were also conducted with one of the products and observed that although the solid-state storage does not alter the hydrazone, storing it in various solvents may significantly decrease the concentration of the active component which should be considered when performing the biochemical/biological assays.

Clinical Outcome Patterns of Use of Radium-223 in Patients with Metastatic Castration-Resistant Prostate Cancer

Introduction: Radium-223 dichloride (radium-223) is a bone-targeting radioisotope therapy that aids in the survival of patients with metastatic castration-resistant prostate cancer (mCRPC) to bones. This study aimed to describe the clinical characteristics and outcomes of patients with mCRPC treated with radium-223 in a real-world setting. Methods: This was a retrospective study of patients with mCRPC treated with radium-223 between 2016 and 2020 at the London Health Sciences Centre in London, Canada. The baseline characteristics between the patients receiving 1–3 and 4–6 treatment cycles were compared using a two-sample t-test and Chi-square test. ANOVA was used to determine if there was a difference in each diagnostic variable per treatment cycle. Kaplan–Meier curves were generated to estimate progression-free survival (PFS) and overall survival in the patients treated with different numbers of cycles. Results: Fifty eligible patients were identified. The median age was 71 years (IQR: 66–76). Most patients (62%) received radium-223 beyond the third-line treatment. The mean number of radium-223 treatments was four. While 60% of the patients received 4–6 injections, 40% received 1–3 injections. Fifty-eight percent (58%) of the patients demonstrated a clinical benefit, with the remainder expressing either disease progression (28%) or stable disease (10%). The patients treated with 4–6 cycles had a delay to disease progression compared to those given 1–3 cycles of radium-223 (F5,35 = 10.52, p < 0.001). A higher alkaline phosphatase level prior to treatment was associated with a longer PFS (z33 = 2.362, p = 0.018). Treatment-related hospitalization for skeletal-related events was noted in 8% of the patients, and 14% required treatment discontinuation due to hematologic toxicity. Conclusions: This study confirms the safety of radium-223 in patients with mCRPC in a real-world setting. The radium-223 treatment was associated with a clinical benefit in the majority of the patients, particularly in those with higher pre-treatment serum alkaline phosphatase levels. Further studies to identify the predictive biomarkers are warranted to better guide the contemporary use of radium-223.

Failure law of hydraulic pipe joints sealing performance under vibration loads

Aviation hydraulic pipe joints are inevitably affected by vibration loads during service. Fatigue relaxation occurs in the pipe joint structure by vibration, and fretting fatigue wear occurs in its sealing interface, leading to a decline in sealing performance. In order to investigate the sealing performance of hydraulic pipe joints affected by vibration load, this paper first analyzes the modal distribution of the sealing system pipeline under different hydraulic pressures and hydraulic fluid flow rates through vibration frequency sweeping experiments. Secondly, the vibration load is applied to the pipe joints for different numbers of cycles, which reveals the microscopic wear behavior of the sealing interfaces under different tightening torques. Finally, by carrying out the leakage measurement experiment under vibration load, the evolution law of the sealing performance of pipe joints under different hydraulic fluid pressures and tightening torques was obtained.

Observation of wear around surface crack of PEEK thrust bearing under rolling contact fatigue in water

Abstract Rolling bearings are important mechanical elements for machines. Poly-ether-ether-ketone (PEEK) polymer is a suitable material for bearings in water and corrosive conditions because of its excellent water and chemical resistance. Some study had been examining rolling contact fatigue (RCF) tests in water; however, the competition between cracks propagation and wear on the surface of PEEK bearing in water was not clear. In the present study, in order to evaluate the crack propagation and wear process, RCF test with PEEK thrust bearings at 3750 [N] in water was carried out. The lengths of the surface cracks and the profiles of the grooves were observed at different number of cycles. In addition, so as to identify the cracks which cause the flaking, start-stop test was carried out. We found the surface crack, which was initially observed at 4.62×105 cycles, were gradually worn down and completely disappeared at 6.32×105 cycles. We concluded that rolling contact fatigue caused some surface cracks of PEEK to wear down in water condition.

Oral health self-perception, maximum bite force and masticatory efficiency in patients with overdentures with different attachment systems-A crossover study.

The literature is unclear about how the different attachment systems for overdentures impact the maximum bite force, the masticatory efficiency and how this impact in the oral health self-perception in patients. To evaluate the effect of two attachment systems (O-ring and Locator) for mandibular overdenture using single implant on quality of life, maximum bite force (BF) and masticatory efficiency (ME). Twenty-eight completely edentulous denture wearers with a mandibular symphysis implant were randomly selected and allocated into two groups in a crossover study, considering O-ring and Locator attachment types. The quality of life and self-perception of oral health were assessed using the Oral Health Impact Profile (OHIP-Edent) and Geriatric Index of Determination of Oral Health (GOHAI) questionnaires, respectively. BF was measured using a gnathodynamometer and ME by chewing silicone cubes and almonds in different numbers of cycles. There was no difference between the attachment systems about self-perceived oral health and impact on quality of life (p > .05). The O-ring-type system obtained a significantly higher BF than the locator-type system (p = .04). Regardless of the food chewed, no statistically significant difference was observed with the type of attachment (p > .05). The ME was directly proportional to the masticatory cycles only for almonds (p < .01). Locator and O-ring inserts had a similar impact on patients' quality of life, self-perception of oral health and ME. Additionally, the O-ring system exhibited superior properties in the BF.

Performance Evaluation of Multiple Aging-Regeneration of SBS-Modified Bitumen Regenerated by a Composite Rejuvenator

In this study, compound regeneration of SBS-modified bitumen (SMB) was carried out by a composite rejuvenator composed of furfural extraction oil (FEO) and 1,6-hexanediol diglycidyl ether (HDDGE) in the presence of catalyst triethanolamine (TEOA). SMB was subjected to three aging-regeneration cycles, and the physical and rheological properties, toughness and tenacity, and chemical structures of the SMB after each aging-regeneration cycle were tested to investigate the regeneration effect of the composite rejuvenator on SMB at different numbers of cycles. The ductility decreases and low-temperature properties deteriorate as the number of cycles increased, but the high-temperature properties of the SMB are improved. The complex modulus aging index and phase angle aging index indicate that the viscous behavior of SMB weakens after the second and third aging. The degree of viscoelasticity and toughness recovery decreases with the increase in the number of cycles, and the tenacity of SMB after the third aging-regeneration cycle is basically lost. The results of the Fourier transform infrared (FTIR) spectra tests prove that with the increase in the aging–regeneration cycles of SMB, the intensity of FTIR peaks of oxygen-containing functional groups is greater, and the recovery of aged SMB is gradually weakened.

Relevant Aspects in the Mechanical and Aging Degradation of NiTi Alloy with R-Phase in Endodontic Files.

One of the most important challenges in endodontics is to have files that have excellent flexibility, toughness, and high fatigue life. Superelastic NiTi alloys have been a breakthrough and the new R-phase NiTi alloys promise to further optimize the good properties of NiTi alloys. In this work, two austenitic phase endodontic files with superelastic properties (Protaper and F6) and two austenitic phase files with the R-phase (M-wire and Reciproc) have been studied. The transformation temperatures were studied by calorimetry. Molds reproducing root canals at different angles (30, 45, and 70°) were obtained with cooling and loads simulating those used in the clinic. Mechanical cycles of different files were realized to fracture. Transformation temperatures were determined at different number of cycles. The different files were heat treated at 300 and 500 °C as the aging process, and the transformation temperatures were also determined. Scanning and transmission electron microscopy was used to observe the fractography and precipitates of the files. The results show that files with the R-phase have higher fracture cycles than files with only the austenitic phase. The fracture cycles depend on the angle of insertion in the root canal, with the angle of 70° being the one with the lowest fracture cycles in all cases. The R-Phase transformation increases the energy absorbed by the NiTi to produce the austenitic to R-phase and to produce the martensitic transformation causing the increase in the fracture cycles. Mechanical cycling leads to significant increases in the transformation temperatures Ms and Af as well as Rs and Rf. No changes in the transformation temperatures were observed for aging at 300 °C, but the appearance of Ni4Ti3 precipitates was observed in the aging treatments to the Nickel-rich files that correspond to those with the R transition. These results should be considered by endodontists to optimize the type of files for clinical therapy.

Microstructure analysis of carbon-fiber-reinforced polymer laminates subjected to self-heating and fatigue strengthening under tension-tension fatigue loading

In this study, tensile-tensile fatigue testing of unidirectional (UD) carbon-fiber-reinforced polymer (CFRP) prepreg laminates was performed. Two types of specimens (open-hole and unopened-hole ones) were examined at different stress levels to elucidate the impact of fatigue damage on their static strength at different numbers of cycles. The effect of internal heat generation during fatigue on the life of unopened-hole CFRP laminates was analyzed by observing the changes in the microstructure of specimens. The results revealed that the difference in fatigue life between unopened specimens with and without cooling at 70% ultimate tension stress (UTS) level was about 88 times. In the open-hole CFRP laminates, the residual tension strength (RTS) after increases and then decreases with the number of fatigue cycles, and the interface debonding was a significant cause of fatigue strengthening. Open-hole specimens were shown to withstand continuous cycling under severe loads at 5% above their ultimate stress levels. Therefore, the fatigue damage extension of the open-hole laminates can be slowed down under intensive cycling at high stress levels, ensuring good fatigue performance of the material.

Experiment and simulation study on the functional fatigue of shape memory alloy beam actuators

The functional fatigue behavior of shape memory alloy (SMA) beam actuators is gaining importance as their utilization in engineering applications becomes more widespread. However, research on the functional fatigue behavior of SMA beam actuators under bending conditions is not as extensive as that on SMA wires. In this paper, an experimental study and theoretical analysis of the functional fatigue behavior of SMA beam actuators were conducted. A measuring method for bending deflection and an automatic thermal cyclic test bench was designed. A series of functional fatigue tests were conducted on SMA beam actuators under different bias load conditions and the functional fatigue patterns were obtained. The material damage factor is defined and calculated through specimen tests. By incorporating the damage factor to modify the existing constitutive model, a model considering functional fatigue and tension-compression asymmetry is obtained. Finite element analysis (FEA) is performed based on this modified model to simulate the actuating performance of SMA beam actuators and to compute the deflection at different numbers of cycles. Additionally, a small parameter study on the actuator shape is conducted using FEA. By comparing the FEA results with functional fatigue experimental data, the effectiveness of the modified model is validated, demonstrating its capability to describe functional fatigue and predict actuator lifespan.

Film Thickness Effect in Restructuring NiO into LiNiO2 Anode for Highly Stable Lithium-Ion Batteries

The long-term stability of energy-storage devices for green energy has received significant attention. Lithium-ion batteries (LIBs) based on materials such as metal oxides, Si, Sb, and Sn have shown superior energy density and stability owing to their intrinsic properties and the support of conductive carbon, graphene, or graphene oxides. Abnormal capacities have been recorded for some transition metal oxides, such as NiO, Fe2O3, and MnO/Mn3O4. Recently, the restructuring of NiO into LiNiO2 anode materials has yielded an ultrastable anode for LIBs. Herein, the effect of the thin film thickness on the restructuring of the NiO anode was investigated. Different electrode thicknesses required different numbers of cycles for restructuring, resulting in significant changes in the reconstituted cells. NiO thicknesses greater than 39 μm reduced the capacity to 570 mAh g−1. The results revealed the limitation of the layered thickness owing to the low diffusion efficiency of Li ions in the thick layers, resulting in non-uniformity of the restructured LiNiO2. The NiO anode with a thickness of approximately 20 μm required only 220 cycles to be restructured at 0.5 A g−1, while maintaining a high-rate performance for over 500 cycles at 1.0 A g−1, and a high capacity of 1000 mAh g−1.

Effect of Aging on the Mechanical Properties of CAD/CAM-Milled and 3D-Printed Acrylic Resins for Denture Bases

The purpose of this study was to investigate the mechanical properties of acrylic resins at different aging times for denture bases manufactured using the conventional method, microwave processing, milling, and 3D printing. A total of 160 rectangular samples (64 Å~ 10 Å~ 3.3 ± 0.03 mm) were prepared, divided among the four main resin groups, and subdivided into four analysis times (T0, T1, T2, and T3), resulting in 10 samples per subgroup. The samples were stored in distilled water at 37° ± 2°C for 24 hours (T0), then subjected to thermocycling at temperatures of 5° ± 1°C and 55° ± 1°C in different numbers of cycles: 5,000 (T1); 10,000 (T2); and 20,000 (T3). The mechanical properties evaluated were surface microhardness, flexural strength, and modulus of elasticity. Statistical differences between resin groups and aging time were evaluated using two-way analysis of variance (P < .05). The 3D-printed resin showed the significantly lowest values of microhardness, flexural strength, and modulus of elasticity compared to other resins (P < .001). The CAD/CAM-milled denture resin showed mechanical properties similar to those of traditional resins (conventional and microwave-processed). The 3D-printing resin did not show adequate mechanical properties for long-term clinical use. Despite this, new studies are developing better properties of this resin for long-term use.

Fatigue Behaviour of Medium Carbon Steel Assessed by the Barkhausen Noise Method

Abstract In this paper, an attempt to estimate the stage of the fatigue process using the Barkhausen noise method is studied. First, microstructural and static tensile tests were carried out and, subsequently, fatigue tests up to failure were conducted. After determination of the material behaviour in the assumed static and dynamic conditions, the interrupted fatigue tests were performed. Each specimen was stressed up to a different number of cycles corresponding to 10%, 30%, 50%, 70% and 90% of fatigue lifetime for the loading conditions considered. In the next step of the experimental programme, the specimens were subjected to the Barkhausen magnetic noise measurements. Various magnetic parameters coming from the rms Barkhausen noise envelopes were determined. The linear relationship betweenthe full-width at half-maximum (FWHM) of the Barkhausen noise envelope and the number of loading cycles to fracture was found. Specimens loaded up to a certain number of cycles were also subjected to a tensile test to assess an influence of fatigue on the fracture features.

Electrochemical Sensors for Detection of Glucose based on Electrochemically Reduced Graphene Oxide: Optimization of pH and Number of Cycles

Glucose determination method had gain significant interest from the industry for a fast and efficient response especially in the medical area for diabetes patient. Reduced graphene oxide (RGO) had been reported to help and improve the sensitivity of a sensor. The investigation for the optimum pH concentrations using FESEM, EDX, XRD analysis and Raman spectroscopy indicate that the pH 9 was suited to be deposited on the SPGE. In addition to that, different number of cycles during electrodeposition process was employed. Electrochemical impedance spectroscopy (EIS) was used to investigate the charge transfer resistance for each cycle. All the deposited RGO on screen-printed gold electrode (SPGE) was being compared to the bare SPGE to confirmed that the electrodeposition of RGO could decrease the charge transfer resistance. For the detection of glucose, cyclic voltammetry (CV) and differential pulse voltammetry (DPV) was used. 10 cycles deposition of RGO shows the highest sensitivity of 1.0525 μA·mM−1·cm−2 in the detection of glucose compared to the other cycles. The ease of use and scalability of the electrodeposition technique may make it easier to build upon the results of this work and produce glucose sensors that are more widely available and less expensive.

A Deeper Insight into Stability of Pt-Alloy Nanoparticles as Oxygen Reduction Reaction Electrocatalysts

One of the links in the chain of creating a carbon-neutral society is undoubtedly hydrogen-powered vehicles. However, due to a very high price of platinum (Pt), which is used as an electrocatalyst for the hydrogen oxidation reaction (HOR) at the anode, as well as the oxygen reduction reaction (ORR) at the cathode of the proton exchange membrane fuel cell (PEMFC), their massive production is still unfeasible. Moreover, a very slow kinetics of the ORR and consequently the need for larger quantities of electrocatalyst makes this issue even higher. Therefore, in the fuel cell community there is a lot of effort to reduce the use of Pt. The most promising solution on that path seems to be carbon supported Pt-based nanoalloys, where part of Pt is replaced by a less noble and at the same time less expensive metal (e.g. Co, Cu, Fe, Ni).1 Nevertheless, although the ORR activity of carbon supported Pt-based alloys has been extensively studied and already proven, their stability is still an unsolved area. Here will be presented the latest findings regarding the stability of the carbon supported intermetallic Pt-alloy nanoparticles (Pt-M/C, where M = Co, Cu or Ni) obtained by utilization of advanced, in-house designed methodologies such as the high-temperature accelerated degradation tests (HT-ADTs) and the high-temperature electrochemical flow cell coupled to an inductively coupled plasma mass spectrometry (HT-EFC-ICP-MS).2,3 Whereas the former enables ADT to be performed in a liquid electrolyte half-cell using a standard rotating disk electrode at temperatures of up to 80 °C, the latter allows for precise (ppb range) time-temperature-and-potential resolved measurements of dissolution of metals. By simulating close-to-real operational conditions, these technologies enabled to show that in addition to the carbon corrosion, which follows the Arrhenius law and increases exponentially with temperature,3,4 also Pt dissolution, as well as less noble metal dissolution, increases with increasing temperature.2,3 However, with an increase in temperature, not only the dissolution of Pt, but also the rate of its re-deposition (due to the Ostwald ripening) is increased at the same time.2,3,5 Furthermore, the widening of the potential window results in an exponential growth of temperature impact on metals dissolution.2,3 These previous findings about the dependence of the stability of Pt and less noble metal on the temperature and potential window2 will be upgraded with new information about the impact of some other non-intrinsic as well as intrinsic properties on the stability of metal nanoparticles in the carbon supported Pt-nanoalloys. In other words, the effect of a different number of cycles of the degradation tests on the behavior of Pt and less noble metal in the operational potential window (i.e. 0.6-0.95 V) at the high temperature (60 °C) will be presented. In continuation, the influence of the type of crystal structure on the stability of Pt-alloy nanoparticles will also be discussed. References 1 L. J. Moriau, A. Hrnjić, A. Pavlišič, A. R. Kamšek, U. Petek, F. Ruiz-Zepeda, M. Šala, L. Pavko, V. S. Šelih, M. Bele, P. Jovanovič, M. Gatalo, N. Hodnik, iScience 2021, 102102.2 T. Đukić, L. J. Moriau, L. Pavko, M. Kostelec, M. Prokop, F. Ruiz-Zepeda, M. Šala, G. Dražić, M. Gatalo, N. Hodnik, ACS Catal. 2022, 12, 101–115.3 T. Đukić, L. Pavko, P. Jovanovič, N. Maselj, M. Gatalo, N. Hodnik, Chem. Commun. , DOI:10.1039/d2cc05377b.4 N. Maselj, M. Gatalo, F. Ruiz-Zepeda, A. Kregar, P. Jovanovič, N. Hodnik, M. Gaberšček, J. Electrochem. Soc. 2020, 167, 114506.5 A. Kregar, M. Gatalo, N. Maselj, N. Hodnik, T. Katrašnik, J. Power Sources 2021, 514, 230542.

Experimental investigation of the dynamic mechanical properties of concrete under different strain rates and cyclic loading

To investigate the effects of strain rate and cyclic loading on the mechanical parameters of concrete compressive strength, residual strain, peak strain and elastic modulus, a series of cyclic loading tests over concrete were conducted by setting different numbers of cycles, magnitude factors, and cycle frequencies/periods based on the FST-1000 alpine geotechnical dynamic and static triaxial test system. The quantitative relationships between the mechanical parameters of concrete and the parameters of cyclic loading as well as the strain rate were also proposed. The results show that as the strain rate increases, the concrete compressive strength and elastic modulus increase linearly, while the residual strength and peak strain show a decreasing trend. Under cyclic loading, the compressive strength was quadratically related to each cyclic loading parameter, and the elastic modulus was quadratically related to the cyclic number and magnitude factor. The trend of the concrete compressive strength rate sensitivity undergoes a change at the specific thresholds of 0.145 for the magnitude factor and 1.93 Hz for the frequency. The minimum value of the peak strain rate sensitivity corresponds to the specific thresholds of 6023 for the number of cycles, 0.14 for the magnitude factor, and 1.38 Hz for the frequency thresholds, respectively. Additionally, the enhancement of the elastic modulus rate sensitivity occurs when the number of cycles exceeds 918 or when the magnitude factor surpasses 0.33. The results can provide a theoretical basis for the design of concrete structures and seismic engineering.

Experimental Study of the Freeze–Thaw Damage of Alpine Surface Coal Mine Roads Based on Geopolymer Materials

In the process of mining and transportation, the temporary non-hardened mine-road structure is mainly a mixture of soil and stone, which very easily produces dust hazards via crushing and wind transportation. Geopolymers can be used in the road’s soil and stone mixture so that the road reaches certain strength requirements in line with the short-term use of the mine. However, in alpine open-pit coal mines, which are subject to the influence of weather changes, freezing and thawing phenomena will affect the long-term use of the road and its normal and safe operation. An open-pit coal mine in Xinjiang, China, was chosen as the research object of alpine open-pit coal mines. Using the method of indoor testing, different freeze–thaw freezing temperatures, different numbers of cycles, changes in the mechanical properties of the mine-road materials, and microscopic changes were studied. From the experimental results, it was determined that with a reduction in the freeze–thaw freezing temperature, the specimen strength declines after stabilizing, and with an increase in the number of freeze–thaw cycles, the specimen strength exhibits a linear decline. The specimen’s internal structure gradually changed from dense to loose; the fracture mode changed from toughness fractures to crystal fractures after the removal of the maximum load reduction. The uniaxial compressive strength was reduced to 61%; the tensile strength was reduced to 49%. The fracture zone of the specimen was analyzed using energy spectra, and the main elements changed from O (57.19%), Si (17.07%), and Al (12.19%) without freezing and thawing to O (49.76%), Si (15.70%) and Ca (11.09%) after freezing and thawing.

Remote ischaemic preconditioning increase tolerance to experimentally induced cold pain

ABSTRACT Ischaemic preconditioning (IPC) applied locally and remotely has been shown to reduce pain which may underpin its ergogenic effect on exercise performance, however, it is unclear how many IPC cycles are needed to induce hypoalgesia. Therefore the purpose of this study was to examine the number of cycles of IPC on experimental pain perception. Sixteen healthy participants underwent four, randomised, experimental sessions where they either underwent a sham protocol (1 × 5 min at 20 mmHg), and 1, 2 or 3 cycles × 5 min of remote IPC at 105% of limb occlusion pressure. Ten minutes post-intervention, participants underwent a cold-pressor test where pain threshold, pain tolerance and pain intensity were examined and compared between conditions with a one-way repeated measure analysis of variance. Pain threshold was not different between conditions (P = 0.065); but pain tolerance was increased by ∼30% in the 1 × 5 condition, 2 × 5 condition, and 3 × 5 condition compared to the sham condition. No differences in pain tolerance were seen between the different numbers of cycles (all P > 0.05). There was also no difference in the perception of pain 30 s into the cold pressor test (P = 0.279). Remote IPC appears to significantly improve tolerance to pain which may have significant implications for endurance performance and exercise rehabilitation, but this warrants further investigation.

Effect of saturation on dynamic characteristics of collapsible gypseous soil using cyclic triaxial testing

Studying the unsaturated gypseous soils behavior may lead to more understanding of the gypseous soil problems associated with unsaturation under the effect of the vertical vibrations. The purpose of this paper is to assess the suitability of unsaturated gypseous soil as a machine foundation soil. Moreover, such a purpose is considered beneficial in assessing appropriate methods for studying the characteristics and the behavior of unsaturated gypseous soils such as soil elastic modulus parameters, compressibility parameter, waves velocities, and amplitude axial strain for cyclic loading parameters under different with degree of saturation. The tests were performed for conditions 35% and 70% relative density of natural gypseous soil under 1.0 Hz and 2.0 Hz cyclic frequency at degrees of saturation (30%, 60%, and 80%), and fully saturated gypseous soil to investigate the gypseous soil behavior. It was found the values of the elastic modulus and wave velocities at degree of saturation 60% for different number of cycles and frequency increased with decrease of the strain and compressibility. Then, it began to decrease gradually at the saturation degree 80% and 100%, respectively. The best results based on strength consideration were obtained at 60% saturation, and the lowest strength was found when the soil was 100% saturated, for both load frequencies 1, and 2 Hz. The load frequency 1 Hz gave higher values than cyclic frequency 2 Hz of elastic modulus and wave velocities, while the number of cycles was less at the same time and for different degrees of saturation.

Study on the Microscopic Mechanism of Axle Steel EA4T during Uniaxial Cyclic Deformation Process

In order to reveal the dislocation evolution law of body-centered cubic axle steel EA4T during cyclic deformation and provide an experimental basis for the subsequent construction of cyclic constitutive models based on microscopic physical mechanisms, macroscopic deformation experiments were first conducted on axle steel EA4T, including monotonic tensile experiments under different deformation amounts, symmetric strain cycling experiments under a different number of cycles, and ratcheting deformation experiments under a different number of cycles. Then, systematic observations of different samples at different deformation stages were conducted using a Transmission Electron Microscope (TEM) to investigate the dislocation configuration and evolution during strain cycling and ratcheting deformation. The observed results show that the dislocation evolution law of axle steel EA4T during the uniaxial tensile experiment, symmetrical strain cycling, and ratcheting deformation is basically the same, and the dislocation density increases with the increase in plastic deformation and number of cycles. The dislocation configuration gradually develops from low-density dislocation configurations such as dislocation lines and dislocation pileups to high-density dislocation configurations such as severe dislocation tangles and dislocation walls. The microscopic mechanism of the uniaxial ratcheting evolution of axle steel EA4T can be qualitatively explained by the dislocation configuration and evolution.

X-ray computed μ-tomography analysis to evaluate the crack growth in an additive manufactured Ti-6Al-4V alloy sample stressed with in-phase axial and torsional loading

Selective laser melting (SLM) is one of the most promising additive manufacturing technologies for obtaining end-use components with excellent mechanical properties. However, the presence of manufacturing defects harms mechanical properties and fatigue performance. This work investigated the crack behaviour within an SLM Ti-6Al-4V alloy sample stressed with in-phase axial and torsional loading by X-ray computed μ-tomography (μ-CT). A sub-volume of material that contains the most significant defects was detected and analysed. The critical defect was identified by evaluating the effective strain intensity factor (SIF) using two different proposed models, that consider the effective area of a detected defect according to Murakami’s method. The first model is based on the modified Smith Watson and Topper (MSWT) criterion. The second is based on Liu’s virtual strain energy (VSE) method. The trend of the crack growth rate was obtained by measuring the effective area for a different number of cycles. The μ-CT data was also exploited to build a finite element model (FEM) of part of the gauge section containing surface defects. Finite element analysis (FEA) results have provided information on the stress state leading to high-stress concentrations at the crack tip influencing the propagation.