Residual Damage Research Articles

Benefits of Non-Destructive Evaluation and Probabilistic Damage Tolerance Cosimulation for Fracture Risk Reduction

In the context of the damage tolerance approach used to drive aircraft maintenance operations, it is essential to demonstrate the reliability of NDE inspections in detecting structural damage especially for additively manufactured components since this process produces components that may introduce material anomalies at any location within a component. The Probability Of Detection curve (POD) that links the probability to detect a detrimental flaw to its size is generally used as a key indicator for that purpose by giving the maximum flaw size that a NDE process can miss with a given level of probability and confidence. This information can then be used along with other inputs such as component geometries, mechanical properties, constraints, service and residual stresses and damage evolution speed to assess fracture risk and then adapt maintenance scenarios to optimize safety and component service life. NDE reliability and risk assessment are based on statistical indicators that need a large amount of data to provide reliable metrics. It is difficult to obtain such indicators using a purely empirical approach that is based on physical trials and measurements as it may involve many mock-ups and costly processes. Simulation tools can achieve this goal via their ability to include and precisely monitor many parameters as well as high computing capacities that are now available. The work presented in this paper involved cosimulations performed between the DARWIN® probabilistic damage tolerance software and the CIVA NDE simulation software. DARWIN computes fracture risk levels throughout a component, while CIVA can efficiently provide Probability Of Detection curves at different locations in a component and for various NDE methods. The presented application deals with a titanium gas turbine engine impeller disk and involves an Ultrasonic NDE inspection technique. It appears to be a very interesting approach to connect together NDE and Fracture mechanics simulations, two disciplines that generally work on their own. Indeed, DARWIN helps the user to determine detrimental flaw types, locations and sizes which are key inputs to develop an effective NDE inspection method. CIVA can provide location-specific POD curves that enable DARWIN to quantity the effect of dedicated NDE on potential risk reduction. This highlights the importance of NDE simulation for safety and helps to identify potential changes in the physical NDE process and the maintenance cycle that provide the best compromise between detection performance and cost.

EuCARE-POSTCOVID Study: a multicentre cohort study on long-term post-COVID-19 manifestations

BackgroundPost-COVID-19 condition refers to persistent or new onset symptoms occurring three months after acute COVID-19, which are unrelated to alternative diagnoses. Symptoms include fatigue, breathlessness, palpitations, pain, concentration difficulties ("brain fog"), sleep disorders, and anxiety/depression. The prevalence of post-COVID-19 condition ranges widely across studies, affecting 10–20% of patients and reaching 50–60% in certain cohorts, while the associated risk factors remain poorly understood.MethodsThis multicentre cohort study, both retrospective and prospective, aims to assess the incidence and risk factors of post-COVID-19 condition in a cohort of recovered patients. Secondary objectives include evaluating the association between circulating SARS-CoV-2 variants and the risk of post-COVID-19 condition, as well as assessing long-term residual organ damage (lung, heart, central nervous system, peripheral nervous system) in relation to patient characteristics and virology (variant and viral load during the acute phase). Participants will include hospitalised and outpatient COVID-19 patients diagnosed between 01/03/2020 and 01/02/2025 from 8 participating centres. A control group will consist of hospitalised patients with respiratory infections other than COVID-19 during the same period.Patients will be followed up at the post-COVID-19 clinic of each centre at 2–3, 6–9, and 12–15 months after clinical recovery. Routine blood exams will be conducted, and patients will complete questionnaires to assess persisting symptoms, fatigue, dyspnoea, quality of life, disability, anxiety and depression, and post-traumatic stress disorders.DiscussionThis study aims to understand post-COVID-19 syndrome's incidence and predictors by comparing pandemic waves, utilising retrospective and prospective data. Gender association, especially the potential higher prevalence in females, will be investigated. Symptom tracking via questionnaires and scales will monitor duration and evolution. Questionnaires will also collect data on vaccination, reinfections, and new health issues. Biological samples will enable future studies on post-COVID-19 sequelae mechanisms, including inflammation, immune dysregulation, and viral reservoirs.Trial registrationThis study has been registered with ClinicalTrials.gov under the identifier NCT05531773.

Arthroscopic Partial Meniscectomy with Suture Repair for Discoid Lateral Meniscus in Patients under 40 Years of Age

Background: Damage to a discoid meniscus often indicates a complex tear, the treatment for which has not yet been resolved. This study aimed to assess the clinical efficacy of arthroscopic partial meniscectomy with suture repair for discoid lateral meniscus in patients under 40 years of age. Methods: A total number of 10 patients aged < 40 years who underwent partial meniscectomy with meniscal repair for lateral discoid meniscal tears were included in the study. Clinical assessment was evaluated pre-and post-surgery, and magnetic resonance imaging was performed at a mean of 9.5 months after surgery. Results: The Lysholm score improved from 43 ± 19.3 to 87.2 ± 7.8 (range: 94 − 100) at the last follow-up after surgery. The International Knee Documentation Committee score improved from 21.8 ±10.4 to 87.7 ± 4.8 at the last follow-up time after surgery. MRI revealed partial healing of the meniscus in six patients and residual damage of the meniscus in four patients. Extrusion was noted in three patients shown in coronal plane images. Conclusion: Arthroscopic partial meniscectomy with suture repair for discoid lateral meniscus in 10 patients under 40 years of age led to satisfactory clinical outcomes after a mean period of 11.2 months. However, in three cases, although the symptoms have improved, the remaining meniscus had worn off.

Takotsubo Cardiomyopathy following Eye Surgery under Local Anesthesia - A Case Report

Introduction: Takotsubo syndrome is extremely rare and usually seen in postmenopausal women. It manifests as acute coronary syndromes (ACS), but coronaries are usually normal and the majority recover completely without residual myocardial damage. Methods: We are reporting one such case, which followed laser therapy for glaucoma under local anesthesia. She fulfilled all the revised Mayo Clinic criteria for diagnosis. Her preoperative cardiac evaluation and computerized tomography coronary angiograms were normal. Results: This report highlights the need for a wide index of suspicion in those presenting as ACS. Surgical procedures however minor they are, even under local anesthesia should not be considered no-risk ones. Conclusion: Takotsubo cardiomyopathy is reversible acute cardiomyopathy that can occur even after minor eye surgery under local anesthesia. Patients may need coronary angiogram and serial echocardiogram at follow-up. It can be prevented by avoiding trigger factors, addressing preexisting neuropsychiatric ailments, and institution of prophylactic beta-blocker therapy.

Reducing Surface Roughness of Selective Laser Melting of 316 Stainless Steel Component by Electropolishing

Additive manufacturing (AM) is widely used in the fields of aerospace, automotive, and biomedical. Because it enables to fabricate and customize parts with complex geometrical features. However, due to the layer-by-layer deposition and the partially fused raw material, AM part suffers from the step and balling effects, which shows inadequate and poor surface quality. Conventional polishing methods such as grinding, milling, and sandblasting have been applied to meet the requirement of well surface quality. But these contact polishing techniques usually introduce extra residual stress and surface damage, which are unsuitable for workpieces with complex shapes. In this study, we propose an environmentally friendly electrochemical polishing method for AM 316L stainless steel parts based on a combination of positive and negative pulses. Unlike the traditional phosphoric acid or sulfuric acid electrochemical polishing liquid system, the sodium chloride electrolyte adopted in this study avoids the pollution problem of waste liquid. A negative pulse was introduced to avoid the impaction of Cl- ions to the passivation film generated during the electrochemical polishing process. The effects of voltage, polishing duration, temperature, and duty cycle were analyzed by orthogonal experiments. Under the optimum reaction conditions, a surface roughness Ra of 0.421μm without pitting corrosion is achieved and the balling effect was eliminated.

Estimation of relative biological effectiveness of 225Ac compared to 177Lu during [225Ac]Ac-PSMA and [177Lu]Lu-PSMA radiopharmaceutical therapy using TOPAS/TOPAS-nBio/MEDRAS

AimOver recent years, [225Ac]Ac-PSMA and [177Lu]Lu-PSMA radiopharmaceutical therapy have evolved as a promising treatment option for advanced prostate cancer. Especially for alpha particle emitter treatments, there is still a need for improving dosimetry, which requires accurate values of relative biological effectiveness (RBE). To achieve that, consideration of DNA damages in the cell nucleus and knowledge of the energy deposition in the location of the DNA at the nanometer scale are required. Monte Carlo particle track structure simulations provide access to interactions at this level. The aim of this study was to estimate the RBE of 225Ac compared to 177Lu. The initial damage distribution after radionuclide decay and the residual damage after DNA repair were considered.MethodsThis study employed the TOol for PArtcile Simulation (TOPAS) based on the Geant4 simulation toolkit. Simulation of the nuclear DNA and damage scoring were performed using the TOPAS-nBio extension of TOPAS. DNA repair was modeled utilizing the Python-based program MEDRAS (Mechanistic DNA Repair and Survival). Five different cell geometries of equal volume and two radionuclide internalization assumptions as well as two cell arrangement scenarios were investigated. The radionuclide activity (number of source points) was adopted based on SPECT images of patients undergoing the above-mentioned therapies.ResultsBased on the simulated dose–effect curves, the RBE of 225Ac compared to 177Lu was determined in a wide range of absorbed doses to the nucleus. In the case of spherical geometry, 3D cell arrangement and full radionuclide internalization, the RBE based on the initial damage had a constant value of approximately 2.14. Accounting for damage repair resulted in RBE values ranging between 9.38 and 1.46 for 225Ac absorbed doses to the nucleus between 0 and 50 Gy, respectively.ConclusionIn this work, the consideration of DNA repair of the damage from [225Ac]Ac-PSMA and [177Lu]Lu-PSMA revealed a dose dependency of the RBE. Hence, this work suggested that DNA repair is an important aspect to understand response to different radiation qualities.

Seismic performance of full-scale self-centering reinforced concrete beam-column joints: Experimental, numerical and theoretical analysis

A reinforced concrete (RC) frame system with a self-centering joint connected with post-tensioned (PT) tendons and bolted angles was developed to overcome the limitations of precast system without reliable connection. The self-centering beam-column joints with a gap at the beam-column interface are capable to resist severe earthquake with negligible residual deformation and minimal mechanical damage. However, a comprehensive understanding on effect of joint connectors including bolted angles and PT tendons on the seismic performance of self-centering joint (SCJ) is lacking. Three full-scale SCJ specimens were thus designed and tested under cyclic loading to determine the mechanical performance of SCJ and its influencing factors. The effects of bolted angles as energy dissipater and PT tendons as displacement controller were separately explored. The structural performance of SCJ was analyzed by finite element model, showing good agreement with the experimental results. A parametric study was conducted to further analyze the contribution of PT force and bolted angle to hysteretic response. Finally, the lateral load model of SCJ was established and the contribution of bolted angle and PT tendon was theoretical studied. The results indicate that the component elements (beam and column) remained undamaged after cyclic test, while the bolted angles experienced large deformation, dissipating substantial seismic energy. The gap at the beam-column interface of joint equipped with PT tendons was closed and the joint was perfectly self-centered by PT force exhibiting minor residual displacement after unloading. The PT tendons and bolted angles cooperated well, which enable the SCJ to be used as a connection in RC frame at high seismic region. Furthermore, the validated numerical model can be further used to predict the seismic performance of similar types of beam-column joints. The simplified analysis model can provide a potential design reference in the application of RC self-centering systems.

Developing empirical formulations to predict residual strength and damages in tension-leg platform hulls after a collision

During service life, a TLP is under potential damage caused by attendant vessel collisions. The influence of local dents on the maximum strength of TLP is a challenge in ocean engineering structures. Proper regulations outside the industrial practices are required to identify and rehabilitate the strength of these structures subjected to collision. Existing design methods require improvement to accurately predict the ultimate strength of TLPs subjected to accidental collision. Thus, it is imperative to develop viable approaches for predicting the residual ultimate strength of such structures. This paper aims to establish practical modeling techniques and equations to predict the residual strength of dented TLPs subjected to combined axial compression and hydrostatic pressure. The proposed computational models employ nonlinear finite element analyses (NFEA) considering the dynamic effects of materials properties such as strain rate and dynamic fracture strain. A series of NFEA of actual TLP with different collision scenarios and parameters were carried out using ABAQUS software. The empirical equations were provided through the database out of the NFEA results. The reliability of derived empirical formulations was compared with NFEA results, existing formulations, and test data.

Failure analysis of a cracked tram axle

The subject of the paper is the results of the material analysis of the cracked axle of the tram. Fractographic analysis of the fracture surface was performed, the microstructure of the damaged part was observed, hardness profiles were measured and local chemical composition was determined by the EDX method. The failure occurred through a fatigue mechanism. The crack was initiated from surface defects of the welded material on the surface of the axle. The cause of the accident was the interplay of several negative factors: poor welding repair technology, unsuitable consumables, high levels of residual stresses and mechanical damage during assembly.

Integration of Tumor Elimination And Tissue Regeneration via Selective Manipulation of Physiological Microenvironments Based on Intelligent Nanocomposite Hydrogel for Postoperative Treatment of Malignant Melanoma

AbstractTumor residue and tissue damage normally occurred after surgical treatment of malignant melanoma, and the effective postoperative therapy is still a challenge because the treatment requests simultaneous but opposite manipulation of tumor cells and healthy cells. Herein, MBGP‐Gel, a thermosensitive and biodegradable hydrogel incorporating S‐nitrosoglutathione (GSNO) loaded and N‐aminoethyl‐N’‐benzoyl thiourea (BTU) modified MSNs (MBGP NPs), was designed to utilize the significant difference of copper content between tumor cells and healthy cells to regulate various physiological microenvironments for integrative therapy of tumor elimination, metastasis inhibition and tissue regeneration. The MBGP‐Gel underwent sol‐gel transformation at body temperature after injection, and continuously released MBGP nanoparticles. In tumor cells, these nanoparticles would chelate the excess copper to inhibit the tumor migration. Meanwhile, copper was reduced to cuprous, which further catalyzed the abundant H2O2 and GSNO to produce oxygen species (ROS) and nitric oxide (NO), respectively. The ROS and the reaction product of ROS and NO (ONOO) would significantly damage the tumor tissue. In contrast, MBGP nanoparticles entered healthy cells only generate appropriate amount of NO to accelerate tissue healing. Both in vitro and in vivo results showed that the nanocomposite hydrogel could inhibit the growth and metastasis of malignant melanoma and promote the skin regeneration, which offered an promising strategy for postoperative treatment of various tumors.

Nonlinear dynamic seismic analysis of a modern concrete core wall building in Los Angeles using the BTM‐shell methodology

AbstractThis paper discusses the nonlinear dynamic seismic response of a 14‐story reinforced concrete core wall building designed with the prescriptive requirements of the 2019 California Building Code for a near‐fault site in Los Angeles, California, simulated with a detailed nonlinear analysis of the complete structure and subjected to an ensemble of three‐component ground motion input. The study follows up on a recently published work by the authors, which examined the response of the specific building to static lateral loads. The nonlinear model of the building was developed in the software FE‐Multiphys using a shell‐element implementation of the beam–truss model (BTM). The BTM has been extensively validated through prior studies for planar, flanged, and coupled walls under static and dynamic loading. The building model was subjected to an ensemble of ground motions scaled at the design and risk‐targeted maximum considered earthquake levels. The vertical ground motion component and the out‐of‐plane shear degradation of wall piers were included in the simulations. The analyses elucidate the profound effect of nonlinear flexure–shear interaction and of the multidirectional behavior of the flanged coupled core wall on the evolution and localization of damage and on residual deformations. The coupling behavior between the core wall, the slabs, and the columns is also analyzed, and the importance of modeling the nonlinear behavior of all slabs for the residual damage evaluation is demonstrated. The aim of this study is to improve the understanding of issues arising from prescriptive design requirements as well as of issues associated with limitations of standard nonlinear seismic analysis.

Efficacy of low-vision devices in elderly population with age-related macular degeneration.

Age-related macular degeneration (AMD) is a common cause of blindness, residual damage to macular area in spite of treatment necessitates visual rehabilitation by means of low-vision aids (LVAs). Thirty patients suffering from different stages of AMD requiring LVAs were included in this prospective study. Patients with nonprogressive, adequately treated AMD were enrolled over a 12-month period, prescribed requisite LVAs and followed-up for a minimum 1-month period. Before and after provision of LVAs, near work efficiencies were evaluated by calculating reading speed as words per minute (wpm) under both photopic and mesopic light conditions, and impact of poor vision on activities of daily living (ADL) was quantified by modified standard questionnaire based on Nhung X et al. questionnaire. Of the 30 patients mean studied with mean age of 68 ± 10 years, 20 patients (66.7%) had dry AMD in better eye and 10 (33.3%) had wet AMD. Post-LVA, near visual acuity improved significantly and all cases were able to read some letters on near vision chart with an average improvement of 2.4 ± 0.96 lines. The different LVAs prescribed were high plus reading spectacles (up to 10 D) in 23.3%, hand-held magnifiers in 53.3%, base in prisms in 10%, stand held magnifiers in 6.7%, and bar and dome magnifiers in 3.3%. LVAs are effective in visual rehabilitation in patients with AMD. Self-reported reduction in visual dependency and improvement in vision-related quality of life post use of aids corroborated perceived benefit.

Hybrid ratio optimizations on ballistic penetration of carbon Kevlar UHMWPE fiber laminates

Fiber hybrid is a promising strategy for improving ballistic penetration behaviors of fiber-reinforced laminated composites. Ballistic impact performance of hybrid fiber laminates against projectiles depends on various parameters not only with respect to the material properties, fiber types, yarn properties, fabric structures of the constituent plies but also with the hybrid configuration, material combinations and stacking sequences. It has a substantial growth demand to obtains the optimal hybrid design of the fiber hybrid composites, for maximizing the potential of the constituent materials and improving the overall anti-impact performance of the hybrid composites. However, the effect of the hybridization ratios on ballistic penetration behaviors of the hybrid composites is still infant. Here we report the hybridization ratios on ballistic impact damage of carbon/Kevlar/UHMWPE (ultra-high molecular weight polyethylene) hybrid laminates through ballistic impact experiments and three-point bending tests. The fiber hybrid laminates with different hybrid ratios had been fabricated and studied under the impact of FSP (fragment simulating projectiles). The effect of the hybridization ratios on the flexural behaviors, ballistic curves, energy absorptions and damage modes were investigated. The FEA (finite element analysis) was carried out from meso- to macro- scale model. We found that the flexural behaviors are related to the material properties and mechanical balance among different material components in the hybrid systems. The damage modes for various hybrid ratios have a typical impact damage mode like matrix cracking, fiber breakage and delamination. A rational accuracy in residual velocities and damage modes can be obtained between ballistic experiments and FEA results. The hybrid ratios would affect the stress wave propagation in the composites with a gradual attenuation development and lead to different failure mechanisms. This study is expected to reveal a fundamental failure mechanism for the fiber hybrid composites incorporated with three different fiber combinations in different hybrid ratios under ballistic impact. The results can provide important theoretical basis and experimental reference for designing and developing hard multiphase anti-impact composite structures.

Impact of early changes in cardiac damage following transcatheter aortic valve implantation.

The staging classification of aortic stenosis (AS) which characterises the extent of cardiac damage has been validated in patients undergoing transcatheter aortic valve implantation (TAVI). Short-term changes in cardiac damage after TAVI and their association with long-term prognosis remain unknown. This study aims to investigate the early evolution of cardiac damage after TAVI and the association of residual cardiac damage with clinical outcomes in TAVI recipients. AS patients undergoing TAVI were consecutively enrolled and classified into five stages of cardiac damage (0-4). Early change in cardiac damage was defined as any change of stage at 30 days (Δcardiac damage between baseline pre-TAVI and 30 days post-TAVI). Within 30 days post-TAVI, the baseline cardiac damage stage had changed in 22.2% of 644 TAVI recipients, accompanied by improvements in the degree of dyspnoea and left ventricular ejection fraction (LVEF). Two-year mortality was associated with residual cardiac damage within 30 days post-TAVI (hazard ratio [HR] 2.97, 95% confidence interval [CI]: 2.07-4.25; p<0.001). Compared to unchanged cardiac damage post-TAVI, further cardiac damage within 30 days was associated with a higher crude risk of 2-year mortality (HR 22.04, 95% CI: 9.87-49.20; p<0.001). Cardiac deterioration within 30 days post-TAVI was an independent risk factor for 2-year mortality (HR 19.564, 95% CI: 8.047-47.565; p<0.001). This investigation provided insight into the early evolution of cardiac damage in TAVI recipients and confirmed the predictive value of both residual and early changes in cardiac damage post-TAVI. Cardiac deterioration within 30 days is associated with poor clinical prognosis.

Clinical characteristics and long-term consequences of COVID-19 patients in a dedicated COVID unit of a tertiary care hospital: an 8-month follow-up study

Background: Aim of the study was to assess the demographic, clinical characteristics, long term consequences of Bangladeshi coronavirus disease 2019 (COVID-19) patients and to see any association with severity of COVID-19 and post COVID-19 functional status (PCFS). Methods: This prospective cohort study was performed in the COVID-19 unit of Cumilla Medical College and Hospital, Cumilla, Bangladesh. Fifty-eight patients were consecutively selected. Data were collected by direct interview and from hospital archives. All patients were followed up at 6 and 8-months intervals over telephone calls. Data regarding age, gender, contact history with COVID-19 patients, travel history, smoking history, comorbidities, symptoms, severity of COVID-19, post COVID-19 symptoms and functional status were recorded Results: About 44 (75.9%) patients recovered with residual damage and one patient died. The common symptoms at admission were fever, cough, dyspnea and fatigue while at follow-up, fatigue, poor memory, dyspnea and insomnia were observed, which persisted after recovery but improved over time. There were 30 (51.7%) patients with severe COVID-19 disease and 11 (21.2%) patients suffered from functional limitation. After multivariate adjustment, patients with severe COVID-19 had an odds ratio (OR) of 1.08 (1.02-1.16) for age and patients with post-COVID-19 functional limitation showed OR of 1.05 (1.00-1.11) for age, OR of 10.83 (2.08-56.35) for female and OR of 27.48 (4.30-175.61) for smoking. Conclusion: Majority of the patients recovered but with persistence of post COVID-19 symptoms, and few patients even developed functional limitation. Age was a significant independent predictor for severe disease whereas higher age, female gender and smokers were at increased odds of developing post COVID-19 functional limitation.

Heart involvement in multisystem inflammatory syndrome in children correlated with SARS-CoV-2 infection: a review by ANMCO/SICP

Acute clinical manifestations of COVID-19 are generally less severe in childhood, however a proportion of them can develop a severe systemic hyperinflammatory syndrome after SARS-CoV-2 infection, known as the multisystem inflammatory syndrome (multisystem inflammatory syndrome in children, MIS-C). Cardiovascular manifestations in MIS-C are frequent (34-82%), including myocardial dysfunction, coronary artery dilation or aneurysms, arrhythmias, conduction abnormalities, pericarditis and valvulitis. The most affected cases can develop cardiogenic shock needing intensive care unit admission, inotropic support and sometimes even mechanical circulatory support. The elevation of myocardial necrosis markers, the frequently transient left ventricular systolic dysfunction and the presence of changes on magnetic resonance imaging, support the hypothesis of an immune-mediated post-viral pathogenesis similar to myocarditis. Although MIS-C shows excellent short-term survival, further studies are needed to demonstrate complete reversibility of residual subclinical heart damage.

The effect of alternating the sequence of variable‐energy repeated impact on the residual strength and damage evolution of composite laminates

AbstractThis article investigates the effect of alternating the sequence of variable‐energy repeated low‐velocity impact on the residual strength of carbon fiber reinforced polymer (CFRP) laminates. Quasi‐isotropic CFRP specimens were impacted using three impact energy levels, that is, Low (L), Medium (M), and High (H). Every group, out of three groups in total, was impacted consecutively using one of three sequences: LMH, HML, and MLH. Delamination and its growth after each impact was quantified using a phased‐array ultrasonic probe. The impacted specimens were then subjected to compression after impact loading with in situ acoustic emission (AE) and digital image correlation (DIC) measurement. Mechanical results showed that the residual strength of the specimens was not significantly affected by alternating the impacts sequence. However, the AE, sentry function and DIC results revealed that the impact‐induced damage in HML configuration was activated much earlier than MLH, and the damage induced in LMH configuration was activated later than both.

Evaluation of railhead material damage of insulated rail joints due to cyclic wheel loadings

Although insulated rail joints (IRJs) are important railway track components and, because of their low bending rigidity, a dynamic wheel impact results as wheels pass over them. Proper attention is needed to address this problem. Focussing on this point, a 3D finite element analysis (FEA) is carried out on IRJs to evaluate on damage analysis of sub-surface railhead material for endpost materials: fiberglass (fb), nylon 66 (ny), and polytetrafluoroethylene (ptfe). A cyclic vertical wheel load up to a total of 2000 cycles in non-Hertzian pressure form is applied at the wheel/rail contact patch on an IRJ. The residual longitudinal stress damage parameter is considered to rank the endpost material based on sub-surface railhead damage. It exhibits a new pattern described as ‘vertical flat type’ for a depth up to 8 mm initially and, as the cyclic loading increases, the vertical flat pattern damage changes to an ‘inclined flat type’ pattern.

Effect of cutting parameters on the microstructure evolution and damage mechanism of 7075-T6 aluminum alloy in micro cutting

This work aims to explore how cutting parameters affect the microstructure evolution and damage mechanism of 7075-T6 aluminum alloy in micro cutting. The effect of cutting parameters on micro cutting force and surface morphology is examined through single-factor test. By building a 3D micro finite element model for micro cutting based on crystal plasticity theory, the effect of cutting parameters on residual stress, microstructure evolution and damage behavior is analyzed to establish a mapping relation between residual stress and damage. The results show that as cutting speed increases, main cutting force first reduces then increases in all cases, but the cutting speed at the inflection point corresponding to main cutting force is different. The micro cutting surface morphology of 7075-T6 aluminum alloy displays obvious signs of plowing; detectable oxidation adhesion wear appears when the cutting depth is greater than 150 μm. Crack initiation and propagation on the machined surface of 7075-T6 aluminum alloy vary considerably under different cutting parameters. Residual stress distribution displays a ladle profile. The deeper the maximum residual compressive stress is from the surface, the harder it is for micro cracks to initiate and propagate. SEM and EDS analysis indicates that at smaller cutting depths, micro cutting tool wear is dominated by oxidation wear; at larger cutting depths, surface morphology is mostly better than at smaller cutting depths.

RISK FACTORS AND CLINICAL PRESENTATION OF SEPTIC ARTHRITIS OF HIP IN INFANTS: A PROSPECTIVE STUDY

Objective: The objective of this study was to analyze the risk factors and clinical presentation of septic arthritis of hip in infants. Methods: Thirty infants with unilateral septic arthritis of hip were included in this study on the basis of a pre-defined inclusion and exclusion criteria. The study was conducted in PIOS Medilinks Pvt. Limited, Jaysingpur, Kolhapur, India. The duration of the study was 18 months from June 2021 to December 2022. The institutional ethical committee approved the study. The diagnosis of septic arthritis was made on the basis of Morrey’s criteria. Risk factors associated with septic arthritis and clinical presentation were studied. Results: Out of the total 30 infants diagnosed to be having septic arthritis of unilateral hip, 17 (57.67%) were males and 13 (43.33%) were females. In our study, an overwhelming majority of the patients belonged to neonatal age group (80%) followed by 1 month–2 months (10%). Only 3 infants were between 2 months and 1 year of age (10%). Low birth weight and prematurity or a combination of these two factors was the most common risk factor in neonates with septic hip arthritis and was seen in 7 (23.33%) patients. All infants having septic arthritis had increased local temperature (100%) and reduced joint movements (100%). Erythema (86.67%), swelling (73.33%), and irritability (60%) were other common clinical features associated with septic arthritis. The most common offending organism was Staphylococcus aureus (33.33%) followed by Klebsiella pneumoniae (13.33%). The analysis of outcome at the end of 3-month follow-up showed that out of 30 studied cases, 28 (93.33%) infants had a painless hip with normal range of motion. Conclusion: Septic arthritis of hip in infants is an emergency and requires prompt treatment. Any delay in diagnosis can have catastrophic consequences. However, in majority of appropriately managed infants, there is no residual damage to the affected joint.