Relative Deformation Research Articles

Influence of highly dispersed phase of titanium carbide on physical and mechanical properties of alloys AM4.5Kd and AK10M2N

Dispersion-strengthened composite materials belong to the group of promising structural materials characterized by a diverse combination of properties. The work presents examples of the creation and heat treatment of composite materials based on aluminum alloys, strengthened by a dispersed phase of titanium carbide, and characterized by high hardness, elastic modulus and good wettability by the melt. The most accessible, inexpensive and effective way to obtain them is self-propagating high-temperature synthesis (SHS).The work shows the possibility of obtaining new aluminum matrix composite materials based on industrial aluminum alloys AM4.5Kd and AK10M2N by reinforcing them with 10 wt.% highly dispersed titanium carbide or AM4.5Kd–5.95 vol.% TiC and AK10M2N–5.78 vol.% TiC. The reinforcing phase is formed in alloy melts using the technology of SHS from the initial elemental components—titanium powder and carbon black. Using the obtained samples, an assessment was made of the uniformity of the ceramic phase distribution over the volume of the matrix alloys, which amounted to 0.15 and 0.12 for the samples AM4.5Kd–10%TiC and AK10M2N–10%TiC, respectively, which constitutes a high degree of uniformity.An assessment was made of physical properties such as porosity, density, electrical conductivity, as well as the coefficient of thermal linear expansion. Analysis of the data allows us to say that the final composite materials AM4.5Kd–10%TiC and AK10M2N–10%TiC have a slightly higher density (↑~4%) than the matrix alloys, due to the presence of a ceramic phase, low porosity values (~1%), lower TCLE (↓~6%) than matrix alloys and low electrical conductivity (~25% IACS). This article also presents data on the values of the mechanical properties of composite materials AM4.5Kd–10%TiC and AK10M2N–10%TiC. It has been shown that reinforcement with a ceramic phase contributes to a significant increase in hardness by 15 and 42 HB, as well as higher values of the compressive yield strength by 31 and 17 MPa, respectively, while maintaining a high level of relative deformation. The results obtained allow us to conclude that the developed composite materials can be recommended for products used under conditions of elevated temperatures and significant wear.

Impacts of Waste Rubber Products on the Structure and Properties of Modified Asphalt Binder: Part II-Rubber Reclaim.

The issue of forming a reliable and stable structure of a crumb-rubber-modified binder is an important scientific and technical task. The authors supplemented existing concepts of the mechanism of effective interaction with rubber crumb by introducing a preliminary first stage: controlled partial physical destruction of rubber crumb-producing rubber reclaim. Proposed physical methods of rubber crumb destruction include high shear force (roll mills), high temperature, and a plasticizing medium. The controllability and degree of devulcanization of rubber were determined by acetone-chloroform extraction in different time intervals. The degree of devulcanization of rubber in the rubber reclaim was found to be 22 ± 0.24%, with stability over 14 days. It was found that the size of the particles of the rubber reclaim in the bitumen is less than 2 µm. The properties of the structure of the binder modified with rubber reclaim, characterizing the stability and sustainability, have been studied and established. The developed modified binders are stable in storage. Rheological parameters of the structure characterizing intermolecular interaction, such as shear stability for original and RTFOT-aged, modified bitumen, meet requirements of the state standard at test temperature 64 °C. The elastic structural component of the crumb-rubber-modified binder, as indicated by the relative irreversible deformation parameter J3,2, does not exceed 2.6 kPa (<4.5 kPa) at 64 °C. Additionally, it was determined that the rheological structural parameter for fatigue resistance, which characterizes the durability of road pavement under intensive operational conditions, does not exceed 4699 kPa (<5000 kPa) at 16 °C. The use of 10% rubber reclaim combined with waste frying oil provided the opportunity to obtain a modified binder with a stable and sustainable structure without the introduction of additional stabilizers and agents. Test results showed that the overall performance characteristics of the modified binder meet the 64(S)-40 grade standards.

Study on the Susceptibility of Steel Arches with Letting Pressure Nodes Based on Incremental Dynamic Analysis

When soft rock tunnels pass through fractured fault zones, they are particularly susceptible to extrusion and large-scale deformations, especially during seismic events. To address these challenges, this study introduces an innovative yield-support steel arch design featuring a circumferential letting pressure node at its core. This design delivers incremental support resistance within the deformation zone and a susceptibility curve is applied to evaluate the damage probability of the steel arch with a letting pressure node under seismic loading conditions. Measurements of the surrounding rock pressure and structural forces on the steel arch with the letting pressure node were conducted at the Baoshan Jewel Mountain Tunnel in China. The field experiment results revealed a 23% reduction in the surrounding rock pressure and an 11% decrease in the internal forces of the support structure. These findings demonstrate the successful application of the letting pressure node-supported steel arch in mitigating large deformations in soft rock environments. Additionally, using finite element software ANSYS 2022, a seismic time-history analysis was conducted, employing the relative deformation rate of the letting pressure node steel arch as the damage index and the peak ground acceleration (PGA) as the strength parameter to generate the incremental dynamic analysis (IDA) curve. According to the susceptibility curve derived from the incremental dynamic analysis, at the design ground motion level of 8 degrees, the letting pressure node steel arch has a 94% probability of exceeding its normal service life limit and experiencing damage. The findings of this study offer a novel approach to addressing large deformations in soft rock tunnels. The proposed susceptibility curves for steel arches with letting pressure nodes provide a robust foundation for predicting the damage probability of yielding support structures under seismic conditions.

Experimental investigation of the seismic performance of corroded reinforced concrete coupling beams

In this study, a seismic performance assessment of six reinforced concrete (RC) coupling beam specimens with accelerated corrosion is conducted by combining accelerated corrosion methods with quasistatic loading tests. A detailed comparison of the corrosion damage, failure modes, and mechanical performance differences of the coupling beam specimens under different corrosion levels is presented. The degradation patterns of the coupling beam seismic performance are revealed through analyses of the hysteresis behavior, stiffness degradation, energy dissipation capacity, and proportions of bending, shear, and slip deformations in relation to the corrosion level. The experimental results indicate that with increasing corrosion level, the load-carrying, deformation, and energy dissipation capacities of the coupling beams continuously decrease. The cracking pattern of corrosion-induced cracks is influenced by the reinforcement arrangement, with diagonal reinforcement causing cracks to propagate diagonally. The nonuniform distribution of corrosion leads to asymmetric loading in coupling beam specimens with higher corrosion ratios, significantly weakening the load-carrying and energy dissipation capacities and making the specimens more prone to sudden brittle shear failure without warning. Corrosion-induced damage degrades the shear capacity of the coupling beams, increasing the proportion of shear deformation.

Specialists Versus Trainees: Long-Term Secondary Deformity After Unilateral Cleft Lip Repair.

Unilateral cleft lip repair is a common procedure in plastic and reconstructive surgery to restore both function and aesthetics. The long-term outcomes of these surgeries can be influenced by various factors, including the experience and position of the surgeon performing the procedure. This study aims to investigate whether there is a significant difference in long-term secondary deformities based on whether the surgery was performed by a specialist or a trainee. This is a retrospective cross-sectional study among unilateral cleft lip patients based on their data records. The study aims to assess the long-term secondary deformity in relation to the position of the surgeon (specialist or trainee) in patients who underwent unilateral cleft lip repair surgery at the Reconstructive Sciences Unit at Hospital Universiti Sains Malaysia (HUSM). Of the 50 patients, the majority (74%) were operated on by a specialist with more than five years of experience. Only 13 patients (26%) were operated on by trainees in the plastic and reconstructive surgery training program. Long-term secondary deformity had no significant relationship with the surgeon's position (chi-squared (χ2)(1) = 5.89, p = 0.08). Long-term secondary deformities were less likely following unilateral cleft lip repair performed by a specialist or senior surgeon. However, the relationship between these secondary deformities and the surgeon's position (specialist or trainee) was statistically insignificant. Therefore, this study urges trainees to be more involved in simple cleft surgeries to enhance their surgical skills and achieve the best outcomes.

РЕНТГЕНОСТРУКТУРНЫЕ ИССЛЕДОВАНИЯ СВАРЕННОГО ВЗРЫВОМ МЕДНО-СТАЛЬНОГО БИМЕТАЛЛА ПОСЛЕ ТЕРМИЧЕСКИХ ВОЗДЕЙСТВИЙ

The article presents the results of studies of diffusion processes in the joint zone of the bimetallic copper M3 + steel 30CrMnSiA after explosion welding and subsequent thermal effects at 880 °C with a holding time of up to 10 hours, 1000 °C with holding times of 24, 50, 100 hours and 1050 °C with a holding time of 1 hour. It is shown that the intensification of diffusion processes of steel into copper and copper into steel near the joint boundary with the formation of solid solutions causes a significant development of the thin structure characteristics: an increase in the level of relative lattice deformation and a refinement of mosaic blocks.

Shrinkage and deformation of material extrusion 3D printed parts during sintering: numerical simulation and experimental validation

Material extrusion 3D printing (ME3DP) combined with sintering is a low-cost additive manufacturing technique for fabricating components of difficult-to-print metals, such as copper, aluminum, and ceramics. However, the sintering process includes complex material science, such as volumetric shrinkage and free structural bending, to identify the relative density and deformation of a 3D printed sample. The prediction of the relative density and deformations during the sintering process provides information to the design engineer to optimize the design of the CAD model before sintering. In this study, a phenomenological model based on constitutive equations was developed to predict the density and structural deformation during the sintering process of pure copper components fabricated by ME3DP using metal injection molding feedstock. The densification rate was determined using shrinkage estimation with an isothermal stairway heating cycle in a vertical dilatometer. Furthermore, different sets of experiments were performed with a load on the probe with long isothermal heating cycles at 850, 900, 950, 1000, and 1050°C in a vertical dilatometer to estimate the axial viscosity of the copper. The constitutive equations were solved using the solid mechanics module with user-defined creep in COMSOL Multiphysics by considering isotropic assumptions. Two types of geometries, cube and overhanging I section, were used to predict shrinkage and deformation during the sintering process. The developed model successfully predicted the relative density based on shrinkage and structural deformation owing to gravity during the sintering process.

A Retrospective Analysis of 190 Patients With Scoliosis Referred to a Private Australian Clinical Advisory Service Between 2017 and 2020

ObjectiveThe aim of this study was to describe the demographic and clinical characteristics of patients with scoliosis from Australian primary care practices. MethodsA retrospective review of 190 patient records from August 2017 to April 2020 from a private Australian clinical advisory service database was performed. Deidentified demographic and clinical data were collated and analyzed, along with information regarding the referring practitioners and any accompanying clinical or paraclinical information. Numerical data were summarized with median and IQR, while categorical data were summarized with counts and percentages. Salient qualitative data from the advisory service records were also collated, coded, and summarized. ResultsPatients were aged between 3 and 87 years; the majority (71%) of patients were female, with a median age of 16 years (IQR, 13; range, 3-87 years). The most common type of spinal deformity seen in the sample was scoliosis (92%), with hyperkyphosis (7%) and other deformity (1%) making up the remaining cases. There was a wide variety of scoliosis presentations; however, curves were commonly (45%) located in the thoracic region of the spine. Observed scoliosis cases were of moderate severity with a median Cobb angle measuring 26.5° (IQR, 20°). Reports of pain were in the lower trunk/pelvis (46%), the middle trunk (16%), or throughout multiple bodily regions (27%). Alterations in normal spinal anatomy (eg, hemivertebrae) were common (55% of cases). The majority (86%) of patient cases came from chiropractors, whereas 9% were from osteopaths, 4% from physiotherapists, and 1% from other types of practitioners (eg, medical practitioners). ConclusionThe findings from this study suggest that patients presenting to practitioners in primary care settings in Australia present with a range of scoliosis and related spinal deformity presentations.

Rhamnosomes: A new generation of flexible vesicles for a boosted targeted nose-to-brain delivery of selegiline in the treatment of Parkinson's disease

Extensive hepatic metabolism of Selegiline, a selective monoamine oxidase B inhibitor for newly diagnosed Parkinson's disease patients, causes limited brain bioavailability. To improve efficacy, a new generation of flexible lipidic vesicles, Rhamnosomes, comprising alternating lecithin and Rhamnolipid moieties, and decorated with lactoferrin to actively target Selegiline to the brain is proposed.Rhamnosomes were optimized using design of expert, where lipid amount, Soybean lecithin:Rhamnolipid ratio and sonication time were varied. Polyelectrolyte complexation was employed for Lactoferrin conjugation to Rhamnosomes. A pharmacokinetic study in rat plasma and brain was conducted. Optimized Rhamnosomes had a particle size of 107nm, polydispersity index of 0.23, zeta potential of -41mV, entrapment efficiency of 78%, relative deformability of 36sec and ex-vivo skin permeation reaching 60% after 24 hr. The plasma half life of Rhamnosomes was 3.24 times the market product and 2.63 times the intravenous solution, whereas, lactoferrin-conjugated Rhamnosomes exhibited 7 times higher absolute bioavailability than the market product and more than double its brain drug targeting efficiency. Prominent direct nose-to-brain transport values further proved the efficiency of intranasally delivered Selegiline-loaded Lactoferrin conjugated Rhamnosomes to actively target the brain in a non-invasive approach for the treatment of Parkinson's disease.

Auricular deformity correction with simultaneous reconstruction of the conchal bowl using autologous ear cartilage for “flat ear”: A novel surgical technique

Backgrounds"Flat ear" is a subtype of Grade II conchal-type microtia characterized by severely underdeveloped conchal bowl. Traditional surgical techniques often rely on autologous costal cartilage, which poses several risks and complications. This study aimed to introduce a novel surgical technique using autologous ear cartilage in auricular deformity correction surgery with simultaneous conchal bowl reconstruction for “flat ear”. MethodsA total of 19 patients were involved in this single-center, retrospective cohort study. All patients underwent the described surgical technique. The data before the surgery, immediately after the surgery, and at the last follow-up were collected, including length, width, perimeter of auricle and depth of conchal bowl. Patient satisfaction was assessed via the Visual Analog Scale (VAS). ResultsThe study included 12 males and 7 females, with an average age of 10.67 ± 3.86 years. Postoperative results showed significant improvements in auricular measurements, with the affected ear achieving near symmetry with the normal ear. The mean conchal bowl depth was restored from a preoperative 4.33±1.78mm to 17.32±1.28mm postoperatively. VAS scores for patient satisfaction increased significantly from 1.44±0.92 preoperatively to 7.72±1.49 postoperatively, with stability observed at the last follow-up. ConclusionThe novel technique offers a promising alternative to traditional costal cartilage-based auricular deformity correction surgery, providing excellent aesthetic outcomes and high patient satisfaction. This approach may expand treatment options for patients with "flat ear" and related auricular deformities, with reduced invasiveness and potential for future auditory rehabilitation.

Analysis of Friction and Wear Properties of Friction Ring Materials for Friction Rings under Mixed Lubrication

Aiming at the problem of mechanical seal failure due to serious wear and tear in operation, the numerical model of the thermal–solid coupling wear of the seal ring is established by taking the friction sub-material as the research object, and the hardness, wear coefficient, and friction coefficient of different soft-ring materials are obtained by a test to verify the accuracy of the numerical model of wear. Additionally, the temperature field and deformation field of the seal ring of different materials are calculated, and the effects of the material parameters, such as elasticity modulus and thermal conductivity, on the temperature, relative deformation, and axial deformation trend are reported. The wear relation of the mechanical seal was optimized, and the correction coefficients of several materials were calculated. The results show the following: the main wear of the seal ring is due to adhesive wear leading to particle shedding and extrusion, adhesive wear causes material transfer, which alters the composition of the worn surface.in turn leading to cratering, which also causes the wear of the seal ring; the friction performance is better when the soft-ring material is graphite (C); the temperature, as well as the deformation, is smaller when the soft-ring material is silicon carbide (SIC); the correction coefficients for the life of SIC are calculated to be 0.23, for C, to be 0.14, and for stainless steel (Ss), to be 0.31, and the corrected equations can more accurately predict the corresponding material. The corrected equation can more accurately predict the service life of the corresponding material.

Shaking table tests on transverse seismic performance of a new type of combined prefabricated utility tunnel

Due to the limitation of hoisting weight in the construction site, standard segments of prefabricated utility tunnels usually have only one or two cabins, making it difficult to carry out the multi-cabin prefabricated utility tunnel construction. To solve this problem, two rows of prefabricated utility tunnels are often combined side by side with foam board filled in between them in engineering practice, forming a new type of combined prefabricated utility tunnel. However, there is currently no study on the influence of the interaction between two rows of prefabricated utility tunnels on the seismic performance of combined tunnels. This paper conducted shaking table test of the new type of combined prefabricated utility tunnel under transverse excitation. For the purpose of comparison, shaking table test of single prefabricated utility tunnel was also conducted. To simplify the model making, the combined tunnel was combined by two rows of single-cabin tunnels. Standard segments of utility tunnels were made by microconcrete and assembled longitudinally by bolting. The soil acceleration, utility tunnel strain, and relative displacement between two cabins of the combined tunnel were measured during the tests. Numerical simulation of the test cases was conducted. The numerical results matched the test results well. The research results show that the seismic performance of the combined tunnel is superior to that of single tunnel, because the interaction between two cabins of the combined tunnel reduces the relative deformation between the top and bottom slabs of each cabin. The relative displacement between two cabins of the combined tunnel is much smaller than the initial spacing between the two cabins, and there will be no violent collision between two cabins of the combined tunnel. This study may be of a reference for seismic design of the new type of combined prefabricated utility tunnel.

Stiffness properties of regular p-bars tensegrity prisms under the compressive loading

The regular tensegrity prisms are a kind of fundamental unit, which can be formed into different configurations by different splicing approaches to achieve specific structural functions. Taking regular prisms as the research object, this article presents an analytical method for structural deformations under compressive loading. The structural parameters after loading can be obtained directly by solving the nonlinear force density equation, which simplifies the form-finding process. This article also studies the structural stiffness under different connection modes. By defining the twist angle change rate and internal force utilization rate, we can compare the relative deformation of different tensegrity prisms. The results show that the relative deformation of the three-bar prism is minimal, and it has the best stiffness.

Dynamic deformation behavior and mechanical properties of porous titanium: Coupling effect of high temperature and high strain rate

Porous titanium exhibits excellent mechanical properties and clarifying its dynamic deformation behavior with the rate-temperature effect can offer the significant insights for the structural design of materials. This article delves into the coupling effect of rate and temperature, as well as the local deformation mechanisms of porous titanium subjected to high-temperature and high-strain-rate conditions (−823 K and −8000/s, respectively). A dynamic balance formula for rate-temperature competition has been introduced for application in high-temperature and high-strain-rate conditions. The local relative deformation observed at the end face exceeds 300% than other regions, while the degree of end surface densification reaches 61.5%.

Disaster mechanism of large-diameter shield tunnel segments under multi-source load coupling: A case study

The deflection squeezing of the shield shell and the eccentric jack thrust significantly impact the segment dislocation and damage. Based on summarizing the derivative relationship between engineering factors and disasters, this study established a 3D numerical calculation model under the multi-source load coupling. Then, this study explored the displacement and dislocation distribution of segments, as well as their derivative relationship with bolt failure. Furthermore, this study analyzed the spatial distribution and evolution characteristics of segment damage. Further revealing the disaster mechanism and proposing the engineering treatment measures. The research results indicate that as the deflection angle increases, the vertical relative compression deformation of the segment that is detaching from the shield tail (segment-DFST) becomes more significant. The plastic strain of the internal bolts inside the two segments in direct contact with the shield shell is mainly related to the radial and longitudinal dislocation. The increase in the deflection angle will lead to a more significant increase in the adjacent dislocation on both sides and the internal dislocation. The plastic strain of the internal bolts of the segment that is completely in the shield shell (segment-CSS) is more influenced by joint opening and longitudinal dislocation under the lower eccentric compression (LEC) state. The plastic strain of the internal bolts in segment-DFST is more influenced by radial dislocation and joint opening under the LEC state. The tension damage of the segments mainly occurs on both sides of the circumferential joint and the lower part of the segment-CSS. The compression damage of the segments is mainly distributed at the top and bottom of the segment-CSS. The eccentric distribution of jack thrust has the most significant impact on the block damage of the lower part of the segment-CSS. With the increase of the deflection angle, the compression damage and distribution range of the blocks at the bottom of the segment-DFST increase sharply. The compression damage and distribution range of the segment-CSS gradually spread from the upper and lower parts to the middle of the segment. The increase in deflection angle will promote the influence of the thrust in LEC state on the compression damage of the lower block of the segment-CSS, and on the tension damage of the upper block of the segment- DFST.

An efficient method for evaluating the wind resistance performance of high-vertical standing seam metal cladding systems

Uplift wind-induced responses and failure criteria of high-vertical standing seam metal cladding systems (SSMCSs) are of paramount importance for evaluating their wind resistance performance. This paper proposes an efficient evaluation method that combines a highly efficient finite element (FE) model for structural response analysis with reasonable failure criteria, based on experimental and numerical investigation. The FE model incorporating the developed equivalent spring model is established with the calibrated stiffness from tensile tests and validated through the wind uplift resistance experiments conducted on large-scale prototype structures. The recorded structural responses from the experiments validate the feasibility of the FE model in simulating the geometric and material nonlinearities of the systems. To evaluate the wind resistance performance, the failure criteria are developed based on the observed pullout mechanisms and failure modes from the experiments. These criteria take the relative deformation of standing webs and the pullout resistance strength of seam connections as critical parameters, and the relationship between them is calibrated through a series of tensile tests using a self-designed fixture. Tensile test results show notable variability in the pullout resistance strength of seam connections, with a mean value decreasing as the relative rotational angle of the standing webs increases. According to the developed failure criteria, the ultimate uplift pressures evaluated from the FE analysis exhibit minimal positive deviations of 5.3 % and 7.3 % from the experimental results for different failure modes, respectively. This highlights the effectiveness of the proposed method in evaluating the wind resistance performance of high-vertical SSMCSs.

Assessment of hepcidin in Egyptian patients with rheumatoid arthritis and its relation to anemia: a single-center study

BackgroundRheumatoid arthritis (RA) is a chronic systemic autoimmune inflammatory disorder characterized by synovial inflammation that leads to joint damage, bony erosions, and related deformities. Between 30 and 70% of RA patients will experience anemia. Early detection of anemia is of great importance. This study aimed to evaluate the serum level of hepcidin (HEP) in RA patients and to assess its relation to disease activity and anemia. The current cross-sectional study included 44 cases with RA in addition to 44 healthy controls. The disease activity in the RA patient was assessed by using the disease activity score (DAS) 28 score-CRP. The serum levels of HEP and ferritin were assessed in both groups using enzyme-linked immunosorbent assay (ELISA) technique.ResultsHepcidin level in the RA group was statistically significantly higher as compared to the control group (p = 0.001). The prevalence of Anemia of chronic disease (ACD) was 40.9%, and iron deficiency anemia (IDA) was 27.3% which accounted for 68.2% of the total anemia cases. The HEP level was statistically significantly higher in the RA patients with ACD than those without anemia (P = 0.028), RA patients with IDA (P < 0.001), and control group (P < 0.001). There was a statistically significant positive correlation between HEP level and serum ferritin level (p = 0.005). HEP level was significantly and inversely correlated with hemoglobin (Hb) in patients with ACD. Serum HEP level is higher in RA patients with high disease activity than those with moderate activity, low activity, and patients in remission (p = 0.380). However, the difference was not statistically significant. The best cutoff point of HEP level to identify RA patients from healthy controls was > 355.5 Pg/ml. This point showed moderate sensitivity (70.5%) with moderate specificity (63.6%) with a statistically significant value.ConclusionsWe found the anemia, and particularly ACD, is more common in RA patients. In RA patients with ACD, serum HEP levels were considerably higher. Although serum HEP showed no diagnostic significance when it came to evaluating disease activity, it could be a dependable non-invasive biomarker for the diagnosis of various forms of anemia in RA patients.

Seismic Performance Analysis of the Internal Joint in the New Demountable Fabricated Concrete Frame with Prestressed Mortise–Tenon Connections

This paper proposed a novel demountable fabricated joint in frame, which is connected by the prestressed and mortise–tenon connection. The prefabricated components of the demountable structures are designed to be reused, and the joint presented in this paper will promote the sustainable application of prefabricated components in future. The damage process and damage pattern of the internal joints under the horizontal load were analyzed using the refined numerical analysis model based on ABAQUS 6.14. Parametric analyses were conducted simultaneously for five parameters: axial compression ratio, the area and effective initial stress of unbonded prestressed strands (UPSs), the local reinforcement ratio in the core zone of the demountable joint, and the friction coefficient between the interface of concrete. The results showed that the demountable joint exhibits excellent energy dissipation potential under horizontal loads, but the damage was concentrated in the core zone. The deformation of the joint mainly consisted of the self-deformation of the prefabricated components, including bending, bearing and shear, as well as the relative slip deformation between the prefabricated components. The axial compression ratio has a more significant effect on the hysteresis performance compared to the areas of the UPSs and the reinforcement ratio. The initial effective stress of the UPS and the friction coefficient have relatively minor influence on the hysteretic performance of the joint. Finally, this paper recommends the design parameter values (axial compression ratio should not exceed 0.4, area of unbonded prestressed reinforcement should be not lower than Asn=0.02 and not higher than Asn=0.1, the initial stress of the UPS takes the value of 0.75fpu) and outlines optimization measures.

Experimental investigation on the failure characteristic and synergistic load-bearing mechanism of multi-layer linings for deep soft rock tunnels

Multi-layer linings have been widely used in deep rheological soft rock tunnels for the excellent performance in preventing large-deformation hazards. Previous studies have focused on the bearing capability of multi-layer lining, however, its failure characteristics and synergistic load-bearing mechanisms under high geo-stress are still unclear. To fill the gap, three-dimensional geomechanical model tests were conducted and synergistic mechanisms were analysed in this study. The model test was divided into normal loading, excavating, and overloading stages. The surrounding rock deformation was monitored by using an improved high-precise extensometer measurement system. Results show that the largest radial deformation appears on the sidewall, followed by the floor and vault during the excavating stage. The relative convergence deformation of sidewalls springing reaches 1.32 mm. The failure characteristics of the multi-layer linings during the overloading stage undergo an evolution of stability, crack initiation, local failure, and collapse, with a safety factor of 1.0–1.6, 1.6–2.0, and 2.0–2.2, respectively. The synergistic load-bearing mechanism analysis results suggest that the early stiffness and late yielding deformation capacity of large deformation support measures play important roles in stability maintenance both in the construction and operation of deep soft rock tunnels. Therefore, the combination of yielding support or a compressible layer with reinforced support is recommended to mitigate the effect of the high geo-stress.

The thermal-mechanical deformations of CO2 mixture gases dry gas seal based on two-way thermal-fluid-solid coupling model

PurposeThis study aims to investigate the influence mechanism of thermal-mechanical deformations on the CO2 mixture gases dry gas seal (DGS) flow field and compare the deformation characteristics and sealing performance between two-way and one-way thermal-fluid-solid coupling models.Design/methodology/approachThe authors established a two-way thermal-fluid-solid coupling model by using gas film thickness as the transfer parameter between the fluid and solid domain, and the model was solved using the finite difference method and finite element method. The thermal-mechanical deformations of the sealing rings, the influence of face deformation on the flow field and sealing performance were obtained.FindingsThermal-mechanical deformations cause a convergent gap between the two sealing end faces, resulting in an increase in the gas film thickness, but a decrease in the gas film temperature and sealing ring temperature. The axial relative deformations of rotating and stationary ring end faces caused by mechanical and thermal loads in the two-way coupling model are less than those in the one-way coupling (OWC) model, and the gas film thickness and leakage rate are larger than those in the OWC model, whereas the gas film stiffness is the opposite.Originality/valueThis paper provides a theoretical support and reference for the operational stability and structural optimization design of CO2 mixture gases DGS under high-pressure and high-speed operation conditions.