Joint Deformity Research Articles

The Influence of Pipe Thickness on the Quality of Welded Joints

In this article, we aim to investigate the effect of pipe thickness on the deformation of welded joints in tubular structures. To this end, pipes with a diameter of 60 mm and a length of 215 mm will be utilized in both simulation and experimental processes. The Tungsten Inert Gas (TIG) welding method, known for its high-quality welds, will be employed to join the two steel pipes. The study will be conducted with four different pipe thicknesses: 2.5 mm, 3.2 mm, 4.0 mm, and 5.2 mm, to cover a wide range of thicknesses commonly used in industrial applications. In addition, to validate the accuracy of the simulation method, experimental tests will be carried out for selected simulated cases. The results of the study indicate that structures with thinner pipe walls exhibit higher residual temperatures and stresses, which leads to more deformation. Therefore, it is crucial to consider the pipe thickness when designing and welding tubular structures. After comparing the deformation results obtained from both simulation and experimental tests, we conclude that the simulation method is an effective tool for predicting the deformation of welded joints in tubular structures. By utilizing simulation methods, engineers can optimize the welding parameters and select the appropriate pipe thickness to minimize deformation and ensure the structural integrity of tubular structures.

Analysis of mechanical performance of modular steel-concrete composite joints considering floor slab composite effects

This study establishes and verifies the finite element models (FEM) of MSCCJs to analyze the mechanical performance of modular steel–concrete composite joints (MSCCJs) under monotonic static load without considering the floor slab composite effect (FSCE). Subsequently, 12 MSCCJ models incorporating the FSCE are constructed using ABAQUS. The study evaluates the effects of varying column axial compression ratios (n = 0.15, 0.25, 0.4, 0.6), floor width (w = 800, 1200 mm), floor thickness (t = 90, 110, 120 mm), and floor reinforcement ratio (r = 6 %, 8 %, 12 %) on the bending moment, initial stiffness (k0), ductility, and stress transfer of the joints. The results indicated that as n increases, the shear stress concentration in the joint core module (JCM) and the steel framework at the lower column end become more pronounced. Concurrently, the bearing moment and k0 of the joint also increase. However, once n surpasses 0.4, the joint's plastic properties diminish upon damage. With an increment in w, the k0 and ductility deformation of the joint remain stable and then decline. At w = 1000 mm, the joint's bearing capacity, stress distribution, and deformation performance reach their optimum. Since it significantly impacts stress distribution, its effect on the joint's mechanical performance is minimal. Lastly, the value of r enhances the ductility of MSCCJs and the stress concentration in the reinforcement. It is advisable to maintain r between 1.1 % and 1.7 %.

The Diagnostic Significance of Serum Sclerostin in Early Detection of Rheumatoid Arthritis in Syrian Patients

Background: Rheumatoid arthritis (RA) is associated with joint deformities and local bone erosions. Sclerostin is an inhibitor of the Wnt pathway and drives to reduce bone formation. Aims: Our study aimed to compare the diagnostic significance of sclerostin with anti-CCP (anti-cyclic citrullinated peptide; normal level<20 IU/ml, and rheumatoid factor (RF; normal level<16 IU/ml) for the early diagnosis of rheumatoid arthritis in Syrian patients. Methods: This study contained fifty-eight RA patients and thirty healthy individuals who were equally age- and sex-matched. Serum sclerostin and serum anti-CCP (IgG) levels were evaluated by using the enzyme-linked immunosorbent assay (ELISA). RA activity was assessed based on disease activity scores (DAS28). Results: Our results indicated that serum levels of sclerostin levels were higher in the RA group than in the healthy group (p<0.001). There was a positive correlation between serum sclerostin and DAS28-ESR (r=0.413, p=0.001). By ROC curve, the most optimal cut-off value of sclerostin was 249.69 pg/ml (AUC was 0.910 with 95% confidence interval (CI) values (0.852-0.969), sensitivity of 87.9%, and specificity of 93.3%) [Odds Ratio (OR) and P-value: 102, P< 0.0001]. In RA patients, the sensitivity and specificity of anti-CCP were 74.1% and 90%, and 70.6% and 86.6% of RF, respectively. Conclusion: Increased serum sclerostin may aid as a new prognostic biomarker for evaluating the activity of RA. Sclerostin showed higher sensitivity and specificity than anti-CCP and RF-IgM antibodies. Therefore, sclerostin is a sensitive and specific biomarker for early diagnosis of rheumatoid arthritis.

Robot-assisted knee arthroplasty: first experience (a prospective randomized study)

Introduction Primary total knee arthroplasty has long been proven effective in the treatment of stage 3–4 knee osteoarthritis. It is well known that this intervention not only improves the quality of life, but also helps to restore the function of the joint and eliminate axial deformities.Purpose To compare early results of total knee arthroplasty using robot-assisted technology with conventional manual technique.Materials and Methods 20 patients diagnosed with stage 3 osteoarthritis of the knee joint and varus deformity of the knee joint axis were included in a prospective randomized study. Patients were divided into 2 representative groups, 10 subjects underwent robot-assisted knee arthroplasty, and the conventional manual technique was used in the other 10 patients. For clinical assessment, functional scales KSS, WOMAC, Lysholm Score were used, postoperative radiographs were evaluated.Results According to clinical functional scales, 10 days after surgery, there was an improvement in performance in the patients of both groups (p < 0.05); the duration of the operation in the patients of both groups did not differ in general; intra-operative blood loss in the group with robot‑assisted arthroplasty was lower; and assessment of postoperative results by radiological imaging showed a better component positioning according to preoperative planning in the robotic group.Discussion When the operation is performed by experienced surgeons, one can expect the correct position of the components and the balance of the ligamentous apparatus in standard arthroplasty. However, the use of robot-assisted technology provides a secure intervention performance even at a hospital where a small number of such operations is performed.Conclusion Despite the high cost and the need for additional consumables, robot-assisted arthroplasty has a number of advantages over classical manual techniques. These advantages include: accurate restoration of the limb axis even in extra-articular deformities, correct position of the endoprosthesis components, reduction of intraoperative blood loss due to closed medullary canals, and safety for patients. However, the role of the surgeon in such operations remains paramount, as it is the surgeon who is responsible for planning the operation, performing it, and achieving soft tissue balance.

Analysis of High-Speed Rotor Vibration Failure Due to Sudden Angular Deformation of Bolt Joints

As the efficiency of advanced aero engines improves, the operational speed of their rotors increases. This heightened operational speed makes the rotor dynamics highly sensitive to changes in the rotor’s mass asymmetry state, or unbalance state. During the use of a dual-spool turbofan engine, when its supercritical high-pressure rotor (HPR) exceeds a certain operational speed, the rotor’s vibration spikes and continues to increase with the operational speed until it drops sharply near the maximum operational speed. Analysis of the bolt joints in the faulty rotor reveals various phenomena such as joint interface damage, changes in bolt loosening torque distribution, and alterations in rotor initial unbalance. This paper proposes that at high operational speeds, the bolt joint of the HPR undergoes sudden angular deformation, resulting in the slanting of the principal axis of inertia of the turbine disk. This slant leads to changes in the unbalanced state of the HPR. The additional unbalance causes a sudden rotational inertia load excitation, triggering the rotor vibration failure. Subsequently, a rotor dynamic model that incorporates the angular deformation of the joints is established to simulate how this joint deformation influences the dynamic response of the rotor. The simulation results align well with the observed failure phenomenon and validate the proposed failure mechanism. Finally, troubleshooting measures are proposed and implemented in the faulty engine, effectively mitigating the vibration fault.

UNICONDYLAR KNEE ARTHROPLASTY — PROS AND CONS (LITERATURE REVIEW)

In the modern world, despite the increased availability of hightech orthopedic care, the number of patients with gonarthrosis does not decrease, and thanks to public awareness, more and more people turn to orthopedists for surgical help. Due to its high efficiency, the leading role in the treatment of terminal gonarthrosis has been firmly occupied by total knee arthroplasty for more than four decades. Unicondylar knee arthroplasty in patients with unilateral arthrosis allows to largely preserve physiological kinematics, to achieve minimal bone and soft tissue traumatization during surgery and, as a result, to obtain a higher functional result. The objective of the work is to analyze the data of the world literature regarding unicondylar knee arthroplasty, its advantages and disadvantages. Material and methods. The authors analyzed the publications devoted to single-condylar knee arthroplasty from the Google search engine, scientific and metric electronic databases PubMed, Medline and other relevant sources of scientific and medical information. Correct patient selection is vital to ensure a successful outcome with OEKS. The main indication for OEKS is deforming arthrosis of the II–III century. with a predominant lesion of the internal part of the knee joint and varus deformation of the lower limb or with a more pronounced pathology of the external part of the knee joint and valgus deformation of the lower limb. Results. The authors analyzed the literature sources on single-condylar endoprosthesis of the knee joint. Indications, contraindications, biomechanical features, type of endoprosthesis fixation, type of endoprosthesis platform, features of lateral gonarthrosis, and complications of single-condylar knee arthroplasty are determined. Conclusions. The analysis of selected literary sources showed that single-condylar arthroplasty of the knee joint is an effective means of preserving the bone. However, careful patient selection and precision of surgical technique remain the key to a successful outcome.

Kinesthetic treatment on stiffness, quality of life and functional independence in patients with rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic, systemic inflammatory disease of unknown etiology that primarily affects the joints, causing joint destruction, deformity and functional disability. Genetic, immunological, environmental, psychological and endocrine factors are believed to contribute to its development. The diagnosis of RA is based on the confrontation of clinical manifestations and laboratory tests, with classification criteria established by the American College of Rheumatology (ACR) and the European League Against Rheumatism (EULAR). Treatment has evolved significantly in recent years, focusing on obtaining and maintaining clinical remission to prevent structural and systemic complications. Rehabilitation plays a crucial role in the management of RA, relieving pain, preventing deformities and improving quality of life. Physical therapy programs include joint mobility exercises, resistance exercises, therapeutic massage, aerobic exercises and stretching, among others. RA can have different patterns of evolution, such as acute, cyclic or progressive. Physiotherapy helps to improve the physical and psychological function of patients, adapting to the stages of the disease. In addition, a multidisciplinary approach including pharmacological treatment, orthopedic surgery when necessary and personal care is recommended. Rehabilitation is essential to maintain the functional independence of RA patients and improve their quality of life. Physical therapy programs should be tailored to the individual needs of each patient and consider the stage of the disease. Physiotherapy has been shown to reduce pain, improve muscle function and strength, and contribute to the overall well-being of RA patients

An Overview of Flexible Jointed Robots

Background: Since the first industrial robots were created in the middle of the last century, robotics has shown strong growth prospects. Robotics has developed rapidly over time and is being used in more and more areas. Because of the need to minimize impact forces during robot movement, traditional rigid robots are no longer sufficient, flexible joints are more adaptable to the environment due to their adjustable stiffness and have higher application value in humancomputer interaction. Therefore, flexible jointed robots have become one of the research hotspots in recent years. Objective: Through a detailed analysis of the existing hardware and software control technologies of flexible joint robots, referring to papers and recent patents on flexible jointed robots, we aim to find ways to reduce the impact of flexible joint deformation of flexible joint robots and improve the overall force and position control accuracy of flexible joint robots. Methods: To categorize the hardware and software technologies of flexible jointed robots, to briefly explain the directions of the technologies categorized and to study them, to summarize the advantages and disadvantages of each type of technology respectively, and to outlook the future development trend. Results: Through the study and analysis of the various parts of the flexible joint robot, it can be seen that joint flexibility is mainly achieved through the drive motor and flexible components to achieve flexibility and then through the fusion control technology to control the deformation of the joint. Differences in structural materials affect the mechanical properties of robot motion. The detection and feedback accuracy of the sensor also has a significant impact on the control accuracy. Conclusion: The use of new motor technology, flexible component technology, material technology, and sensor technology, combined with improvements in software fusion control technology can reduce the impact of joint deformation, improve the control accuracy of joint flexibility, and achieve high-precision force-level control capability of flexible joint robots.

Analytical homogenization for equivalent in-plane elastic moduli of multi-material honeycombs

3D printable multi-material honeycombs have attracted increasing interest recently due to the improved elastic moduli, buckling and energy absorption properties. This paper proposes an analytical homogenization for the equivalent in-plane elastic moduli (EIEM) of multi-material honeycombs. First, the axial and bending stiffness of a cantilever beam consist of three sections made of different materials is formulated. Then based on unit cell method and cantilever beam model, the closed-form expressions of EIEM are proposed by fully considering the deformations of both joints and cell walls with arbitrary stiffness, which are sufficiently general to be applied to hexagonal, auxetic and rectangular multi-material honeycombs and validated very well by numerical simulations and experiments. Furthermore, the effects of geometric and material distribution ratios on EIEM are discussed. The results show that the geometric and material distribution ratios of inclined cell wall have a significant effect on all five EIEM while that of vertical cell wall shows a significant effect on shear modulus but only a slight effect on y- direction elastic moduli. Compared with single-material honeycombs, changing joint stiffness has a significant effect on the equivalent Young’s moduli and shear modulus but a slight effect on Poisson’s ratios.

Improving mechanical properties and durability of polyether sealant in prefabricated buildings with titanium dioxide and graphene

The silane-modified polyether sealant is widely applied to fill the gaps between external walls in prefabricated buildings and to bear the deformation of joints. However, the weak tensile strength and poor ultraviolet and moisture resistance of sealant lead to severe degradation, posing threat to the building waterproofing and safety. To address the problems, titanium dioxide and graphene were adopted to improve the mechanical properties and durability of sealant. The tack-free time, tensile properties, ultraviolet resistance, and hydrophobic performance of pristine and modified sealant were investigated and the enhancement and erosive resistance mechanisms of modified sealant were revealed by microscale characterization. Results indicated that modified sealant with low content of titanium dioxide had greater tensile strength and ultraviolet resistance. The crystalline form of titanium dioxide and produced Si-O bond enhanced the ultraviolet resistance. Moreover, the 0.8% graphene-modified sealant possessed superior moisture resistance with 23% increased contact angle. Graphene increased the surface roughness and generated π-conjugated structure, improving sealant hydrophobicity. It is revealed that the enhanced properties were ascribed to the spatial structure of fillers and chemical bond energy. This work provides a novel sealant with high ultraviolet resistance and hydrophobicity, facilitating the development of durable and low-maintenance prefabricated buildings.

Flexible, highly sensitive and reliable piezocapacitive pressure sensor with honeycomb-like microarchitecture fabricated using filament-processed mold

Highly sensitive flexible pressure sensors have been extensively studied due to their promising applications in many fields. Various sensing mechanisms have been proposed to convert pressure into a readable electrical signal, among which piezocapacitive presents advantages due to its simple structure and convenient integration. The modification of the dielectric layer composing these sensors is a common strategy to improve their sensing performance. In this paper, we propose the fabrication of a novel capacitive-based flexible pressure sensor with honeycomb-like microarchitecture by using femtosecond laser filament based far-field technique. The fabricated flexible sensing device is assembled face-to-face with two layers of micro-structured polydimethylsiloxane thin films that is duplicated from laser filament-processed silicon mold. The as-prepared flexible sensor features excellent sensing performance with high reliability, and enables detection of multi-modal signals, including pressure, proximity, and bending. Owing to the advantages mentioned above, the obtained flexible pressure sensor can be attached on non-planar human skin to monitor the physiological signals as well as joint deformation during exercise, revealing it great application potential in cutting-edge fields, such as robotic tactility.

A Critical Review on the Role of Mechanical Connection Technology in Precast Pipe Pile

Background:: With an increase in urbanization, there is a persistent demand for prefabricated pipe pile connections, which play a crucial part in construction projects. In many engineering projects that use pipe piles, poor welding quality leads to problems like cracks, deformation, and detachment of pipe pile joints that affect the safety and stability of the project. Therefore, mechanical joints have gradually been applied in engineering projects, and exhibit a promising potential in connecting prefabricated pipe piles. Objective:: The objective of this study was to present a comprehensive description of the classification, structural characteristics, and application of mechanical connection devices for precast pipe piles in recent years. Methods:: In this study, we conducted a review of the patents related to precast pipe pile mechanical connection devices and presented the advantages of different joints. Further, we introduced the structural features, differences, and applications of precast pipe pile mechanical connection devices. Results:: This study analyzed and compared the different types of mechanical connection devices and summarized their typical characteristics, including connection form, connection quality, construction efficiency, and cost. The main problems existing in the development of precast pipe pile mechanical connection devices were assessed. Subsequently, the development trend of precast pipe pile mechanical connection devices was forecasted, and the research status and future development trend of precast pipe pile mechanical connection devices were discussed. Conclusion:: From the present study, it was found that the mechanical connection of the prefabricated pipe piles can be classified into two categories based on the joint connection range: end integral connection and steel bar connection. The end integral connection device has a large connection area, good connection solidity, and can withstand large loads, which is suitable for large bridges, tunnels, and other projects. However, for small and medium-sized engineering applications, the steel-type connection device is simple, easy to use, and has a wide range of applications that can be adapted to different geological conditions and load requirements. Currently, the application of prefabricated pipe pile mechanical connections is not widespread, both domestically and internationally. Thus, there is a need for future development in the prefabricated pipe pile mechanical connections in terms of material innovation, automation, intelligence, and sustainability.

Design of a Novel Flexible Spherical Hinge and Its Application in Continuum Robot

Abstract Compliant mechanisms, which can be integrally machined and without assembly, are well suited as joints for continuum robots (CRs), but how to incorporate the advantages of the compliant mechanism into the arm design is a key issue in this work. In this paper, a novel type of flexible spherical-hinged (FSH) joint composed of tetrahedron elements with a fixed virtual remote center of motion (RCM) at the bottom is proposed, and then extended to the CR and end-effector. In the arm design, the error compensation principle is used to offset the parasitic motion of the CR under external load (pressure and torque) and improve the bending and torsional isotropy of the arm through different series combinations, and then the stiffness model of the FSH joint and the statics model of the CR are developed using the 3D chain pseudo-rigid body model (3D-CPRBM) and tested. The results show that the 3D-CPRBM can effectively predict the deformation of the FSH joint and the CR. Moreover, the maximum standard deviation of the bending angle of the FSH joint in each direction is only 0.26 deg, the repeatable positioning accuracy of the CR can reach 0.5 deg, and the end-effector has good gripping ability and self-adaptive capability.

X-Linked Familial Hypophosphatemia: A Case Report of 27-Year Old Male and Review of Literature.

X-linked hypophosphatemia (XLH) associated with short stature during childhood are mostly referred to the hospital and diagnosed as vitamin D deficiency rickets and received vitamin D before adulthood. A case is presented with clinical features of hypophosphatemia from childhood who did not seek medical care for diagnosis and treatment, nor did his mother or two brothers, who have short statures, bone pain, and fractures. The patient was assessed for sociodemographic, hematological, and biochemical parameters together with a genetic assessment. A DEXA scan and X-ray were done to determine the abnormalities and deformities of joints and bones despite clinical examination by an expert physician. All imaging, laboratory parameters, and the genetic study confirmed the diagnosis of XLH. A detailed follow-up of his condition was performed after the use of phosphate tablets and other treatments. X-linked hypophosphatemia needs a good assessment, care, and follow up through a complementary medical team including several specialties. Phosphate tablets in adulthood significantly affects clinical and physical improvement and prevention of further skeletal abnormality and burden on daily activity. The patients should be maintained with an adequate dose of phosphate for better patient compliance. More awareness is needed in society and for health professionals when conducting medical checkups during the presence of stress fractures, frequent dental and gum problems, rickets, short stature, or abnormality in the skeleton or walking to think of secondary causes such as hypophosphatemia. Further investigations including a visit to a specialist is imperative to check for the primary cause of these disturbances.

Assessment of Changes in Hindfoot Alignment of Total Ankle Arthroplasty for Ankle Osteoarthritis on Weightbearing Subtalar X-ray View.

Recovering normal hindfoot alignment and correcting deformity of the ankle joint following total ankle arthroplasty (TAA) in osteoarthritis (OA) is essential for improving clinical outcomes and increasing long-term survival. We aim to evaluate hindfoot alignment following standard TAA compared to TAA with a total talar prosthesis ("combined TAA") in varus-type OA patients. This retrospective study was conducted between 2010 and 2022. We included 27 patients (30 feet) who underwent standard TAA and 19 patients (22 feet) who underwent combined TAA. Hindfoot alignment at the subtalar joint was measured by weightbearing subtalar radiographic view before and after surgery. In the standard TAA, the angle between the tibial shaft axis and the articular surface of the talar dome joint (TTS) changed from 75 to 87 degrees (P < .01), the angle between the tibial axis and the surface on the middle facet (TMC) from 89 to 94 degrees (P < .01), and the angle between the tibial axis and the surface on the posterior facet (TPC) from 80 to 84 degrees (P < .01). The angle between the articular surface of the talar dome and the posterior facet of the calcaneus (SIA) decreased from 4.7 to -2.5 degrees (P < .01). In the combined TAA, TTS angle changed from 77 to 88 degrees (P < .01), TMC angle from 93 to 101 degrees (P < .01), TPC angle from 84 to 90 degrees (P < .05), and SIA from 6.6 to 2.1 degrees (P < .01). Varus deviation to the subtalar joint (TMC, TPC) significantly improved postoperatively in both groups. However, TPC was smaller than TTS and SIA was negative in standard TAA, and TPC was larger than TTS and SIA was positive in combined TAA. The amount of correction of the subtalar joint differed depending on the ligament dissection of the subtalar joint and shape of the talar component. Level III, retrospective cohort study.

Casting is a Cost-Effective Management Option in Appropriate Cases of Charcot Neuroarthropathy

Category: Diabetes; Midfoot/Forefoot Introduction/Purpose: Charcot Neuroarthropathy (CN) is a chronic and debilitating condition that impacts the nerves of the foot. The progression of CN may result in severe joint deformities, ulcers, and amputation in certain cases. Treatment options for CN include surgical interventions (e.g., arthrodesis, exostectomy, and amputation) and non-surgical interventions (e.g., casting). A cost analysis on the various treatment modalities can guide physicians to help their patients make informed decisions about their care. Here, we aim to characterize the total costs associated with the various treatments of CN, in addition to the physical therapy (PT) related costs. Methods: Following IRB approval, a sample of patients at a single institution diagnosed with CN of the lower extremity, who underwent exostectomy, arthrodesis, amputation, and/or casting were identified through patient records. Various demographics such as age, sex, and race were collected. Individuals were placed in their respective categories based on the first procedure they had performed. The groups were divided as follows: exostectomy, arthrodesis, major amputation, minor amputation, casting, and failed casting (the group that first received casting but later needed further intervention with other treatment modalities). Each procedure and PT appointment was counted toward the total cost. Descriptive statistics, t-tests, and one-way ANOVA were performed for statistical analysis. Results: Two-hundred and sixteen patients were identified; exostectomy (n = 81), arthrodesis (n = 47), major amputations (n = 10), minor amputations (n = 28), failed casting (n = 16), and casting (n = 34). The average age was 58 ± 12.1 years, and males accounted for 54% of the sample size with the various demographic information depicted in table 1. The effect of procedure type on total cost demonstrated a statistically significant difference between at least two groups (F-value = 18.53, p-value &lt; 0.01), as demonstrated in figure 1. The total costs for casting were significantly lower than all other treatment modalities (p-value &lt; 0.05). Furthermore, there was no statistical significance related to physical therapy costs among the groups (figure 2). Conclusion: Casting was demonstrated to be a more cost-effective management strategy for patients diagnosed with CN. However, it is important to note that this cost-related benefit is only apparent when CN patients are appropriately treated with casting, exemplified by the failed casting group. It is critical to utilize casting with appropriate patients in order to reduce the cost burden associated with these various management modalities. Early surgical intervention should still be strongly considered for patients who are not appropriate candidates for casting.

Stressed-deformed state of the system «main pipeline – soil» in the karst sections (on the example of the section of the main gas pipeline «Power of Siberia», «Chayanda – Lensk»)

Currently, modern gas pipeline systems are increasingly demanding in terms of reliability, durability, industrial and environmental safety. Gas pipeline routes are located in poorly established regions where there are no long-term observations of hazardous natural processes. Currently, karst is the most latently occurring and difficult to predict hazardous engineering and geological process. In case of karst process along the pipeline route, additional load may be applied. In this regard, the analysis of the stress-strain state of the trunk gas pipeline-soil system is the most important task for determining the quantitative characteristics of stresses that can cause the development of emergency. The article considers the section currently built, the main gas pipeline "Power of Siberia," "Chayanda - Lensk." Carbonate formations of Cambrian age are widespread within the considered territory, there are manifestations of surface and underground forms of karst. In this regard, it is possible to activate the process during the operation stage, while during the design these geotechnical features may not have caused concerns. In this work, stress-strain analysis was carried out in case of joint deformation of the pipeline and soil under the influence of a possible load - karst dip. Proposals on the use of the obtained results at the operation stage are given.

Local Plastic Deformation and Quality of Cu-Cu Joints Obtained by Ultrasonic Welding

Joints of copper sheets with a thickness of 0.8 mm were produced by ultrasonic welding. To assess the quality of the joints, tensile lap-shear strength, area fraction of bonding, distributions of normal strains in the cross sections of welded samples, linear weld density at a magnification of ×1000, and the microstructure and microhardness of welded samples were analyzed. It was proved that the arrangement of microbonds and length of gaps in joint zones significantly depended on the local normal strains of welded samples caused by the penetration of tool ridges under the clamping pressure. Joint regions with a linear weld density of more than 70% were observed if the local compression strains of the sample exceeded 15%. The appearance of local tensile strains was accompanied by a drop in the linear weld density of the joints in some regions, down to 5%. The distribution of normal strains depends on the mutual positions of the ridges of the welding tip and anvil. It is concluded that in order to improve the quality of joints obtained by ultrasonic welding and reduce the scatter of their strength values, welding tools should provide sufficiently high normal compression strains in the weld spot area.

Centrifuge test of large-diameter segmented ductile iron pipes crossing strike-slip faults

Seismic ground faults are severe hazards for buried pipes. To explore and model the failure mechanisms of segmented pipes crossing faults, a centrifuge test of a socket-type ductile iron pipe crossing a strike-slip fault is conducted. In the test, a segmented ductile iron pipe with five segments is buried in a soil box. Then, at a centrifugal gravity level of 30.7 g, 60 mm ground displacements are applied through translation of half of the test soil box. Thus, a 2646.2 mm-diameter pipe with a length of 27.4 m subjected to a 1.84 m-long strike-slip fault is simulated. The responses of the joint deformation and the pipe strain are obtained. Results show that the joint deformation is the main response of the pipes subjected to strike-slip faults, the joint near the fault trace is vulnerable, the pipe strain is relatively small, and the peak pipe strain occurs at a certain distance from the fault. Lastly, a theoretical method is presented to obtain the joint deformation of the pipes crossing a strike-slip fault, and a good agreement between the test and theoretical results is observed. The test can be a benchmark for theoretical and numerical models. Meanwhile, the proposed theoretical method has clear physical mechanisms and can obtain the pipe joint deformation effectively.

P24 TB or not TB? A case of severe multi-organ erosive rheumatoid arthritis in a Ukrainian refugee

P24 TB or not TB? A case of severe multi-organ erosive rheumatoid arthritis in a Ukrainian refugee