Relative Deformation Research Articles

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.

Chiari I Deformity: Beyond 5 mm below the Foramen Magnum.

Although originally described as a consecutive series of pathologic changes, Chiari syndrome represents a spectrum of disease divided into two subsets: development deformities of the paraxial mesoderm manifesting after birth (types 0-1.5) and true congenital malformations due to failure of neural tube closure present in utero (types 2-5). Heterogeneity among patients with a Chiari deformity and incomplete understanding of its pathophysiologic characteristics have led to inconsistency in radiologic reporting and difficulty in defining appropriate management strategies tailored to an individual patient's condition. The radiologist is tasked with going beyond the criteria for cerebellar tonsillar herniation to define an individual patient's disease state, determine candidacy for surgery, and assist in selecting the proper surgical approach. In addition, the radiologist must be able to identify conditions that result in cerebellar tonsillar herniation that are not related to Chiari deformity to avoid inappropriate surgery. Last, the radiologist must be able to interpret postoperative imaging examinations to assess for adequacy of treatment and complications. The authors summarize recent literature regarding the pathophysiologic basis of Chiari 1 and related deformities and detail the ideal morphologic and physiologic imaging assessment, focusing on Chiari 1 and related deformities (Chiari 0, 0.5, and 1.5). Also discussed are surgical techniques and "pearls" of postsurgical imaging, including complications that must be recognized. This review provides clarity to a commonly encountered but less understood condition to optimize outcomes for patients with Chiari 1 and related deformities. ©RSNA, 2024 Supplemental material is available for this article. See the invited commentary by Huisman in this issue.

Foot and knee deformities in relation to functional limitations and incident osteoarthritis: A prospective cohort study

ObjectivesThis study aimed to investigate the relationships of foot and leg symptoms, structure, and function with functional limitations and osteoarthritis (OA). MethodsWe included 1253 participants (mean age 58.1 years) from the Hong Kong Osteoporosis Study who completed an examination on foot posture, function, pain, and presence of deformities such as hallux valgus and varus knee. Using logistic regression, we estimated cross-sectional associations of each foot and knee problem with functional outcomes (slow walking speed, self-reported falls, and functional limitations) and OA. Through linkage to electronic health records, we further examined their associations with incident OA over 8 years using Cox models. All models were adjusted for age, sex, and body mass index. ResultsThe prevalence of hallux valgus, foot pain, and varus knee were 33.1%, 35.1%, and 25.8%, respectively. Planus foot posture was associated with varus knee, and pronated foot function was associated with hallux valgus. Of the assessed foot problems, only foot pain showed significant associations with functional outcomes, including functional limitations and recurrent falls. Foot pain was also associated with prevalent OA at baseline but not incident OA. Meanwhile, we observed a 3-times increased risk of incident OA associated with varus knee (95% CI = 1.48–6.10), and this association was particularly seen in older adults, women, and obese individuals. ConclusionsIn community-dwelling Chinese adults, foot pain, but not the reported foot deformities, is associated with functional limitations and falls, while varus knee is associated with incident OA.

Swelling damage characteristics induced by CO2 adsorption in shale: Experimental and modeling approaches

Carbon dioxide (CO2) geological sequestration represents a critical technology in mitigating climate change. Shale reservoirs demonstrate a pronounced affinity for CO2, resulting in adsorption-induced swelling that significantly impacts permeability, mechanical strength, injection efficiency, and sequestration safety. For this, we tried to explore the key factors driving the swelling of shale upon CO2 injection and its subsequent impact on reservoir properties. Utilizing a self-developed high-temperature-pressure gas adsorption apparatus, we measured strain in Jurassic shale at 308 K under constant hydrostatic pressure with helium (He) at 1300 psi (1 psi = 6.895 kPa) and CO2 at 850 psi. Next, we investigated the influence of CO2 concentration on swelling protentional while maintaining constant pressure, uncovering the anisotropic deformation in relation to pressure. It shows that CO2 adsorption induces significant swelling in shale, following a Langmuir-type pressure relationship. Deformation is more pronounced perpendicular than that parallel to the bedding plane. At low pressure, vertical swelling is 2.28 times greater than the horizontal; while at high pressure, the vertical compression is 31.26 times greater than the horizontal. It seems that the anisotropic swelling enhances permeability predictions during CO2 injection. Mixed gases under constant compression can prompt gas desorption, stress redistribution, and alterations in pore structure, amplifying He compression effect. The strain induced after replacing CO2 with He exceeds that from pure He injection. The asynchronous response of CO2-induced swelling and mechanical compression can precipitate crack propagation and fracturing. Overall, anisotropic swelling from CO2 adsorption changes pore structure and permeability, affecting fluid flow and storage. Considering CO2 concentration and anisotropic characteristics in reservoir modeling is essential for optimizing injection strategies and enhancing reservoir efficiency.

KNEE DEFORMITIES AND KNEE REPLACEMENTS IN SAUDI POPULATION: OUR EXPERIENCE AND LITERATURE REVIEW

It takes precise alignment, adequate balance, and deformity correction to accomplish a successful total knee arthroplasty (TKA). In main TKA, this can be successfully achieved with a posterior stabilized (PS) design, either with or without sub-periosteal release. However, severe abnormalities with a major bone defect, stiffness, and instability are often associated with these disorders in some circumstances, such as knee osteoarthritis. Additional restrictive prostheses are required since it is extremely difficult to balance these anomalies with soft tissue release alone, even after main TKA. In this situation, the constrained condylar knee (CCK) design is the optimum choice. This studys primary objectives were to characterize the clinical outcomes, function recovery, and complications of patients who underwent primary CCK-TKA for severe knee osteoarthritis related knee deformity. The secondary aim was to find out the mid-term prostheses survival. Methods: Between March 2021 and March 2022, 36 consecutive patients with knee osteoarthritis had cemented primary CCK-TKA. Twenty-Eight women and eight men, totaling 36 patients, had at least a 6 month follow-up for this retrospective analysis. We used the Knee Society Score (KSS), the Hospital for Special Surgery (HSS) score, and the roentgenographic evaluation form to assess the patients. The survival of prosthesis was assessed using Kaplan-Meiers survival analysis. The patients follow-up periods averaged 12 month. The KSS knee score rose from 44 points (23–68) to 91 points (76–100) following surgery [P < 0.001]. Following the procedure, the mean KSS functional score rose from 20–75 points to 91 points (65–100) [P < 0.001]. The average HSS score rose from 51 points (27–83) to 91 points (75–100) following surgery [P < 0.001]. The average range of motion (ROM) also increased after surgery, going from 68.09° ± 35.99° (0°–120°) to 113.68° ± 8.90° (100°–130°) [P < 0.001]. The average hip-knee-ankle (HKA) angle was 180.24° ± 1.77° (175°–184°) following surgery, compared to 176.88° ± 14.48° (135°–199°) before to surgery. Radiolucencies were seen in thirteen knees, mostly on the tibial side. After an average follow-up of 12 month, 94.7% of prosthesis were still in use. Despite severe deformity, instability, and stiffness at a relatively young age, the mid-term follow-up of primary CCK-TKA in knee osteoarthritis gives satisfactory clinical and functional outcomes with 94.7% prosthesis survival. However, there are a few issues.

Enhanced creep resistance and microstructure in 7055 Al alloy by in-situ (Al2O3 + ZrB2) nanoparticles and Al3(Er, Zr)

This work put forward a novel approach to enhancing high-temperature creep resistance of 7055 Al alloy via inducing reinforcements including in-situ (Al2O3 + ZrB2) nanoparticles and Al3(Er, Zr). Creep steady-state rates of the (Al2O3 + ZrB2)/7055 Al composites enhanced by synergistic Er, Zr were lower than the (Al2O3 + ZrB2)/7055 Al composites, indicating the values of stress component (n) and apparent activation energy (Q) were 1.05–1.15 and 1.06–1.08 times of (Al2O3 + ZrB2)/7055 Al composites. The dislocation climb mechanism was considered as the dominative creep mechanism because the suitable true stress exponent was 5. The uniform distribution of Al2O3 and Al3(Er, Zr) and their influence on improving the distribution of ZrB2 aggregates gave rise to relative uniform deformation during creep process. The built interface models that induce Al3(Er, Zr) between the nanoparticle/Al interface could lead to a more thermodynamically stable and well-bonded interface. The coupling effect of attachments containing Al2O3, ZrB2 and Al3(Er, Zr) played an enhanced role in terms of vacancy-trapping, precipitate-nucleation, dislocation motion during creep process. The nanoparticles and Al3(Er, Zr) together with nuclear sites containing solute atoms, vacancies and misfits nearby, caused an expansion-inhibiting effect on the helical dislocations. The in-grain misorientation axes (IGMA) concentration of some deformed grains associated with Schmid factor (SF) analysis were related to 〈001〉, 〈111〉 and 〈101〉 direction. The calculation of creep resistance mechanisms was quantified. Additionally, typical intergranular fracture appeared within the composites due to the relatively uniform reinforcements, resulting in the complex crack path.

Transverse seismic analysis method of underground interchange prefabricated utility tunnel

The rapid development of underground utility tunnels has led to the formation of a large number of interchange utility tunnels. Due to significant differences in the lateral resisting stiffness in orthogonal directions, coupled with the close relationship between soil deformation and the depth of the utility tunnel, the seismic response mechanism of the interchange utility tunnel is complex. This paper proposes a method for transverse seismic analysis of the underground interchange utility tunnel based on the response displacement method. A load-structure analysis model of a certain underground cross-type interchange utility tunnel is first established. Then, the different conditions corresponding to maximum relative deformation between layers of the interchange node are discussed, and the proposed method is validated via the time-history analysis method. Based on the proposed analysis method in this paper, seismic response analysis is performed on the interchange utility tunnel considering the condition of vertical incidence of three different input seismic waves. Discussions are conducted in terms of internal forces, inter-story displacement angles, and damage responses under seismic excitations in different principal axis directions. The results show that under major earthquakes, the maximum inter-story displacement angle of the interchange node exceeds the standard limit by up to approximately 184 %, while the tensile damage can reach up to 0.985, significantly surpassing the tensile damage limit. Accordingly, the interchange node is the weakest part of the interchange utility tunnel. There exists deformation inconsistency between the interchange node and standard segments due to significant stiffness differences, with the influence range of the interchange node on internal forces, inter-story displacement angles, joint deformations and damage of the utility tunnel is approximately 7, 6, 8, and 6 prefabricated standard segments, respectively. Since the maximum relative deformation between layers of the interchange node does not occur simultaneously, for double-layered and multi-layered interchange utility tunnels, it is necessary to comprehensively consider the maximum inter-story displacement angle between each layer to determine their most unfavorable condition. The analytical method and related research conclusions presented in this paper can provide references for the transverse seismic design of interchange utility tunnels.

Innovative Structural Optimization and Dynamic Performance Enhancement of High-Precision Five-Axis Machine Tools

To satisfy the requirements of five-axis processing quality, this article improves and optimizes the machine tool structure design to produce improved dynamic characteristics. This study focuses on the investigation of five-axis machine tools’ static and dynamic stiffness as well as structural integrity. We also include performance optimization and experimental verification. We use the finite element approach as a structural analysis tool to evaluate and compare the individual parts of the machine created in this study, primarily the saddle, slide table, column, spindle head, and worktable. We discuss the precision of the machine tool model and relative space distortion at each location. To meet the requirements of the actual machine, we optimize the structure of the five-axis machine tool based on the parameters and boundary conditions of each component. The machine’s weight was 15% less than in the original design model, the material it was subjected to was not strained, and the area of the structure where the force was considerably deformed was strengthened. We evaluate the AM machine’s impact resistance to compare the vibrational deformation observed in real time with the analytical findings. During modal analysis, all the order of frequencies were determined to be 97.5, 110.4, 115.6, and 129.6 Hz. The modal test yielded the following orders of frequencies: 104, 118, 125, and 133 Hz. Based on the analytical results, the top three order error percentages are +6.6%, +6.8%, +8.1%, and +2.6%. In ME’scope, the findings of the modal test were compared with the modal assurance criteria (MAC) analysis. According to the static stiffness analysis’s findings, the main shaft and screw have quite substantial major deformations, with a maximum deformation of 33.2 µm. Force flow explore provides the relative deformation amount of 26.98 µm from the rotating base (C) to the tool base, when a force of 1000 N is applied in the X-axis direction, which is more than other relative deformation amounts. We also performed cutting transient analysis, cutting spectrum analysis, steady-state thermal analysis, and analysis of different locations of the machine tool. All of these improvements may effectively increase the stiffness of the machine structure as well improve the machine’s dynamic characteristics and increases its machining accuracy. The topology optimization method checks how the saddle affects the machine’s stability and accuracy. This research will boost smart manufacturing in the machine tool sector, leading to notable advantages and technical innovations.

A stiffness prediction method for variable cross‐section CFRP laminated beam

AbstractTo efficiently design the stiffness of the laminated composite blade‐like structure, an analytical method to assess deformation of variable cross‐section laminated beam under cantilever bending load was developed, in which a local ply density matrix method was introduced to characterize the ply‐up in arbitrary cross‐section after ply drop‐off process and infinitesimal element segment method was used to convert complex variable cross‐section specimen into local equal cross‐section beam structure. The model was validated by the cantilever beam experiment with relative predicted error of stiffness of 5.7%. Inner and outer ply drop‐off models were analyzed using the proposed analytical method. The results show that: (1) stiffness of the outer ply drop‐off model is the highest, at 13.07 N/mm, while that of the inner ply drop‐off model 2 is the lowest, about 17.8% lower than the outer ply drop‐off model; (2) maximum relative deformation difference between the inner ply drop‐off model 2 and outer ply drop‐off model is 21.7% at the free side of the cantilever beam. It indicates that anti‐deformation ability of the variable cross‐section laminated structure can be efficiently designed by the proposed analytical method, especially for the section close to the free side.Highlights Developed a bending stiffness prediction method for composite beam. Variable cross‐section feature of the composite laminate was considered. Local ply density matrix method was introduced to characterize ply drop‐off. Proposed method was validated by cantilever beam bending experiment. Inner and outer ply drop‐off models were compared by the proposed method.

Tool inclination angle designing for low-deformation and high-efficiency machining of thin-wall blade based on edge-workpiece-engagement

The maximum flexibility direction(MFD) is solved for establishing the deformation estimation criterion of the blade during machining process, and the larger the milling force in MFD, the bigger the deformation of the blade during machining process. A new milling force calculation algorithm based on edge-workpiece-engagement(EWE) is proposed by analyzing the contact process between the ball-end milling tool and the chip. The chip thickness of each tool element of each edge curve at any rotation angle is calculated, the milling force of MFD and SLDs under different inclination angles are calculated. The average absolute milling force in MFD reaches the minimum value of 0.65126N when the lead/tilt angle is 30°/-45°, and the maximum machining efficiency is reached when the lead/tilt angle is 45°/-45°.The optimized tool inclination angle, which is 30°/-45° for lead/tilt angle, is obtained by solving the multi-objective optimization problem of machining deformation represented by relative deformation and machining efficiency represented by relative stable machining area. The effectiveness of the proposed scheme is verified by comparison of simulation and experiment for blade machining error under two kinds of tool orientations.

Anomalous size dependent softening behaviors and related deformation mechanisms of Zr/Mo multilayers

As a representative of hcp/bcc metallic multilayers, the correlation between microstructures and mechanical properties of nanostructured Zr/Mo multilayers with were studied. Zr/Mo multilayers with different layer thicknesses were prepared by magnetron sputtering method. XRD and TEM analyses revealed that Zr/Mo multilayers have Zr (0002) and Mo (110) out-of-plane crystalline texture. The nanoindentation hardness of Zr/Mo multilayers is in the range of ∼9.9–10.8 GPa at h ≤ 10 nm, while decreases with reducing layer thickness at larger h, which is on the contrary of the common rule - smaller is stronger. The aforementioned strengthening mechanism applicable in multilayers, i.e., dislocation bowing-out in nanolayers is not suitable to explain this size dependent softening behavior, while the IBS model fits well with the measured hardness at h = 10 nm. This anomalous softening behavior at large layer thickness scales may be caused by its special structures and deformation mechanisms. Dislocations interact with the grain boundaries, instead of the interfaces, and grains rotation/grain boundaries sliding are the dominant deformation mechanism at large layer thickness scales. The size-dependent strain rate sensitivity and activation volume were also explored, to revealing the rate dependent deformation mechanisms.

Mechanical properties of polymer composite films with ZnO nanoparticles synthesized in low-temperature plasma under ultrasonic cavitation

Abstract In this study, polymer nanocomposite materials consisting of the copolymer of ethylene and vinyl acetate as a matrix and nanoparticles of zinc oxide as a filler have been obtained and examined by physicochemical and mechanical methods. Zinc oxide nanoparticles used in this study were fabricated using the plasma discharge under the effect of intensive ultrasonic cavitation. To ensure that resulting nanocomposites will acquire homogeneous distribution of filler nanoparticles, solution technology was utilized followed by the melt compounding technique, and also nanoparticles treated and non-treated with ultrasound were applied. The fabricated samples of nanocomposite material films were examined by X-ray phase analysis, then X-ray fluorescence analysis as well as scanning electron microscopy. The differences between the samples were demonstrated: when the nanoparticles without ultrasonic treatment were used, the particles were found to be more strongly aggregated within the bulk of the composite material and the average size of particles was visually larger in comparison to the sample filled with nanoparticles subjected to ultrasonic action. Finally, studies of the tensile strength and relative deformation of the samples were carried out. From the results of mechanical tests, it can be seen that, according to both studied parameters, there is an optimal concentration of ZnO nanoparticles. For tensile strength, the highest result was obtained at a concentration of nanoparticles of 3%, and for the relative elongation to rupture of the sample, the highest value was achieved at a concentration of nanoparticles of 2%.

Stress-strain state zoning model and novel large deformation classification method for squeezing tunnels

Accurately assessing the level of large deformation in squeezing tunnels is of great importance for the design of support structures. The current large deformations classification methods fail to account for the effect of support pressure on the relative deformation of surrounding rock. In this study, a theoretical model for the stress–strain state zoning of the surrounding rock in squeezing tunnels is established. A sensitivity analysis of the model parameters is conducted. The distribution law of the strength-stress ratio, relative deformation, and relative support pressure indices in 43 field monitoring squeezing tunnels are statistically analyzed. A novel large-deformation classification method based on the relative support pressure index is proposed and applied in case studies. The parameter sensitivity analysis shows that mechanical parameters of the surrounding rock significantly affect the deformation and the stress–strain state zoning of the surrounding rock. The stress–strain state zoning and deformation of the surrounding rock are also primarily dependent on the matching relationship between strength-stress ratio and support pressure. Statistical analyses indicate that there is a nonlinear negative correlation between the relative deformation of the surrounding rock and the strength-stress ratio, as well as the relative support pressure, which includes the steel arch relative support pressure index (SSPI) and the anchor bolt relative support pressure Index (ASPI). The key to controlling surrounding rock deformation lies in the rational matching of support pressure to the strength-stress ratio. In the novel large deformation classification method, three key indexes of strong stress ratio, relative deformation and relative support pressure are quantitatively included, and squeezing large deformation is divided into three levels. Moreover, the case study demonstrated that the novel large deformation classification method has significant guiding importance in verifying feasibility and optimizing support design schemes during both the design and construction phases.

Static and dynamic load test on concrete hollow-core slab bridge

In this paper, dynamic and static load test were carried out on a multi-span reinforced concrete simply supported hollow core slab bridge in Shenyang, Liaoning Province. Through the static load test, the quality and reliability of the project are evaluated, and the results show that under the action of 0.88 times of highway-classⅠload, the deflection and strain check coefficients of the control section of the tested condition are less than 1, which meets the specification requirements, and the measured relative residual deformation and relative residual strain are less than 20%, and the bridge structure is basically in the elastic working state. And combined with the finite element analysis model, the comparison between measured data and calculated data is carried out. Through the dynamic load test, the self-oscillation frequency and damping ratio of the superstructure were tested, and the results showed that the measured damping ratio was 0.690%, the first-order measured vibration pattern conformed to the variation rule of the vibration pattern of the simply supported girder bridge, and the measured self-oscillation frequency was 13.594 Hz, and the measured self-oscillation frequency (fundamental frequency) was greater than the calculated frequency, and the structural actual stiffness was greater than the theoretical stiffness, and the working condition was good. This study is of great significance for the assessment of bearing capacity and quality control of concrete hollow core slab bridge, and provides a useful reference for bridge design and operation.

Drainage evolution in porous carbonate terrain in semi-arid environments: The role of tectonics and climatic change – The case study of the Boukadir carbonate platform, Algeria

Porous carbonate terrains are widespread around the Mediterranean area and form non classical karstic landscapes. The related diffuse infiltration is expected to impede karstification and the establishment of dense drainage networks. In such terrain, the effect of tectonics and climate on drainage development and evolution remains poorly understood. To address this issue, we focus on a semi-arid area with a tuffaceous Messinian carbonate platform characterized by a well-established dendritic network in an active tectonic context. The platform is situated in the Chélif Basin in Algeria, affected by transpressive deformation in relation to the Africa-Eurasia collision. We combine geomorphological observations with drainage morphometric analyses using satellite images and DEM. The drainage network analysis reveals varying tectonic deformation and morphological anomalies resulting from instability in the drainage systems, expressed through (1) variable platform tilt and (2) the presence of knickpoints and convexities in river profiles. These anomalies are particularly pronounced in the west, where knickpoints are more numerous, and incisions deeper. We relate the origin of the tilt to the differential marl compaction and remobilization, and in the area with the highest tilt a recent propagation of the Boukadir thrust underneath the platform might also play a role. Finally, we propose a general model of drainage evolution which highlights the importance of weathering in the Maghreb area transforming the porous media in an indurated carbonate or calcrete.

Investigation of the Deformation Behavior of Baffle Structures Impacted by Debris Flow Based on Physical Modelling

The utilization of baffle structures as a highly effective strategy for mitigating debris flow has attracted significant scholarly attention in recent years. Although the predominant focus of existing research has been on augmenting the energy dissipation capabilities of baffle structures, their deformation behavior under impact load has not been extensively investigated. Addressing this research gap, the current study systematically designs a series of physical model experiments, incorporating variables such as baffle height, shape, and various combinations of baffle types to comprehensively analyze the deformation characteristics of baffles subjected to debris flow impact. The experimental results reveal that the deformation of baffle group structures demonstrates a marked non-uniform spatial distribution and exhibits a latency effect. Additionally, distinct baffle configurations show considerable variations in peak strain, suggesting that combining different baffle shapes can not only optimize energy dissipation but also enhance resistance to deformation. Moreover, the relationship between baffle height and the development of deformation in relation to energy dissipation capacity is inconsistent, indicating that deformation must be a key consideration in the design of baffle structures. Consequently, this paper advocates for the formulation of a deformation-based design strategy for baffle structures, with the findings presented herein providing a foundational reference for future studies.

Study on the instability mechanism and control technology of narrow coal pillar in double-roadway layout of Changping mine

To address the issue of roadway support failure in narrow coal pillars under dual-lane layout, this study takes the 4309 working face of Changping Coal Mine as the engineering background and employs theoretical calculations, numerical simulations, and on-site monitoring to investigate the instability mechanisms of narrow coal pillars under dual-lane conditions and to optimize technical solutions. The results indicate that the internal stress distribution within the coal pillar is influenced by the advanced support stress, and as the working face advances, the gradually increasing advanced support pressure causes the vertical stress peak within the coal pillar to shift away from the goaf area. Computational analysis reveals that the vertical stress in the top region of a 6 m narrow coal pillar is 38% higher than that in the bottom region, with an average stress of 16 MPa in the coal pillar. The asymmetric high-level stress concentration within the coal pillar significantly affects its stability. A UDEC (Universal Distinct Element Code) model was established to compare four simulation schemes with cut-off angles of 0°, 5°, 10°, and 15°. Based on the analysis of damage parameters and fracture distribution in the narrow coal pillar roadway, it was concluded that the stability is best when the cut-off angle is 10°. The dense drilling cut-off unloading technology was applied to the 4309 working face of the Changping Mine based on the aforementioned research. On-site monitoring results show that the relative deformation of the roof and bottom plates and the two sides of the test section were controlled within 267 mm and 198 mm, respectively, effectively resolving the deformation and instability issues of the narrow coal pillars.

Hybrid compliant control with variable-stiffness wrist for assembly and grinding application

This research presents a novel robot system that combines active and passive components to enhance compliance and dependability. The system is based on a continuous variable stiffness wrist. A wrist was created that met the requirements and a combination of active and passive control methods was suggested to insert and regulate forces effectively. The control strategy is based on the Cosserat rod model, with the fundamental concept being calculating the position and orientation of the component using data on the force exerted during contact between the parts and the stiffness of the contact between the shaft and hole components. This process converts the hard assembly into a flexible contact. Compliance is monitored via force and vision sensors, which allows for the shaft-hole assembly operation to be carried out even with attitude alignment problems, resulting in a notable decrease in the precision needed for component alignment. Initially, the camera supplies the first positional data of the shaft component for the robotic system. In addition, the performance of the wrist with variable stiffness is evaluated in terms of stiffness. Additionally, the calculation of relative deformation between components is examined using contact force information. Moreover, a robust active/passive hybrid insertion control technique, which relies on contact force, is proposed. Finally, the shaft-hole assembly task substantiates the necessity for contact force monitoring in the insertion assembly process. This control technique has demonstrated its efficacy in ensuring passive-compliant assembly performance. Furthermore, the variable stiffness wrist has been employed in robotic grinding for surfaces with curved contours to validate its effectiveness.

The reduced order model for creep using dynamic mode decomposition

Given the computational challenges associated with finite element methods in analyzing creep behavior in high-temperature components, this work presents an advanced method for modeling thermal creep in complex structures through a reduced order model (ROM) developed via dynamic mode decomposition (DMD). The results indicate that the ROM using DMD can predict long-term structural responses related to creep based on short-term data with high accuracy, enhancing significantly computational efficiency. The application of ROM allows for the rapid estimation of creep effects in complex structures, like monoliths in the MegaPower reactor, thereby improving the design efficiency. The eigenvalues of the creep related ROM all fall in the unit circle on the complex plane, indicating that creep is a stable development process. The DMD with improved time mode coefficient can reconstruct strain-rate related plastic deformation and cyclic visco-plastic deformation process. Additionally, we derive the necessary stress updating algorithm and consistent tangent operator matrix for the 316H unified visco-plastic constitutive equation in 2023 edition ASME code, ensuring accurate modeling of material creep behavior under high temperatures in this paper. This work provides a valuable tool for the safe design and operation of critical components in nuclear engineering and other high-temperature applications.

Comparative Testing of Asphalt Concrete for Fatigue Life Using Various Modern Laboratory Methods

Statement of the problem. At present, one of the most significant tasks in the road industry is the actua-lization of the methodology for designing flexible pavements. In order to ensure extended pavement service life, design issues are of particular relevance, which requires the improvement of existing and the development of new calculation criteria, one of which is the calculation of asphalt concrete layers for fatigue life. Results. Comparative tests of various types of asphalt concrete selected at road construction sites were carried out using modern laboratory methods to evaluate their fatigue properties. The dependences between the relative tensile deformation of asphalt concrete and the number of load application cycles during tests by various methods are obtained. Conclusions. Through the course of the research, possible reasons for the heterogeneity of the results obtained on four-point bending installations were identified. For further research, the indirect stretching method is set forth as the main method, as it provides greater uniformity and determinism of the results, and the four-point bending method is proposed to be considered as an additional one, confirming the results obtained with indirect stretching.