Visible Fracture Research Articles

Scaphoid Fat Stripe Sign: Is It a Reliable Radiological Sign of Scaphoid Fracture in Children?

Objectives: The scaphoid fat pad stripe (SFS) is a radiological sign first described in 1975 as a line of relative lucency lying parallel to the lateral border of the scaphoid, with slight convexity toward it, and it is optimally demonstrated on postero-anterior and oblique views with ulnar deviation of the carpus. The obliteration or displacement of this line is commonly present in acute fractures of the scaphoid, radial styloid process, and proximal first metacarpus. The aim of this observational study is to investigate the supportive value of the fat stripe sign (SFS) in the diagnosis of scaphoid fractures in the pediatric population. Methods: This is a monocentric, retrospective study of all patients referred to the Pediatric Traumatology Unit of a tertiary hospital from the Emergency Department with clinical suspicion of scaphoid fracture without visible fracture in the initial X-ray. Radiological reports for CT and MRIs were recorded, and the initial X-rays were blindly reviewed by a pediatric orthopedic fellowship-accredited surgeon for the presence of an abnormal scaphoid fat pad stripe sign and the presence of a fracture line in the initial X-rays. Results: The results of the blind interpretation of the initial X-rays for the fat stripe sign showed 86% sensitivity and 58% specificity, with the negative predictive value reaching 92%. Conclusions: The scaphoid fat stripe sign can be used as an adjacent in the diagnosis of an occult scaphoid fracture in children or adolescents. Its high negative predictive value, if confirmed in larger studies, can be an element used to exclude scaphoid fracture and consequently avoid unnecessary immobilizations and health costs.

6976 Early-Onset Paget's Disease- A Unique Presentation In A Young Female With Elevated Alkaline Phosphatase And Low Back Pain

Abstract Disclosure: F. El Sayed: None. Background Paget disease of bone is an age-related disorder characterized by abnormal growth in certain bones, leading to changes in size and shape. Commonly affecting the skull, spine, pelvis, and long bones, it is more prevalent in men, those over 55, with a family history, and of European ancestry. The prevalence of Paget's disease of bone is approximately 2-3% in individuals over 55 in the United States and Europe, with higher rates in those of European descent. Symptoms, such as pain and deformities, may arise from the condition itself or complications like arthritis. While Paget disease can cause visible abnormalities and fractures in affected bones, most individuals remain asymptomatic. Diagnosis often involves blood tests measuring alkaline phosphatase levels, bone scans, and x-rays. Case Presentation We present the case of a 34-year-old woman who sought evaluation due to persistently elevated alkaline phosphatase (ALP) levels in the thousands. The abnormality was discovered during routine blood work conducted during her pregnancy in 2020, and subsequent investigation revealed a chronic elevation for over three years. The patient reported chronic lower back pain but denied other neurological symptoms. Quantification of ALP Bone showed elevated levels at 629, with normal aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels, as well as within-range calcium and gamma-glutamyl transferase (GGT). A whole-body bone scan revealed marked radio tracer uptake in the calvarium, raising concerns for Paget's disease. The patient received a one-time infusion of Zoledronic acid (5 mg), leading to a significant decrease in ALP levels to 182 after three months. Subsequent examination by an Ear, Nose, and Throat (ENT) specialist unveiled bilateral extra bone deposition and mild hearing loss in the right ear, adding a unique dimension to the patient's presentation. This case highlights the importance of a comprehensive approach to diagnose and manage Paget's disease, even in younger individuals with atypical symptoms. Discussion and conclusion Paget's disease presenting in young adults with back pain can be a diagnostic challenge due to its atypical occurrence in this age group. Although back pain is a common symptom, the underlying cause might not immediately be linked to Paget's disease, which typically affects older individuals. However, when encountering persistent back pain in young adults, especially when accompanied by elevated alkaline phosphatase levels, clinicians should consider Paget's disease as a potential differential diagnosis. Further investigation, including imaging studies and bone scans, becomes crucial to confirm the presence of Paget's disease and initiate appropriate management strategies to mitigate its impact on the patient's health and quality of life. Presentation: 6/2/2024

Five-year experience with titanium mesh for rigid chest wall reconstruction

ObjectiveTo characterize the performance of titanium mesh (TM) (off-label) for rigid chest wall reconstruction at a single institution over a 5-year period. MethodsBetween January 1, 2019, and May 15, 2023, 22 patients (median age, 61 years) underwent chest wall resection with TM reconstruction at Cleveland Clinic. Indications for resection included sarcoma (n = 15), breast cancer (n = 2), lung cancer (n = 2), chondroblastoma (n = 1), and benign neoplasm (n = 2). Patients were followed every 6 months with computed tomography scans for cancer recurrence. Continuous variables are summarized as median (interquartile range [IQR]); categorical variables, as frequency and percentage. Time to mesh fracture was assessed nonparametrically using Kaplan-Meier analysis. ResultsAmong the 22 patients over 21,870 patient-days of TM implantation, 21 (95%) had an R0 resection. The mean area of mesh coverage was 108 cm2 (IQR, 97-180 cm2). No patient experienced respiratory complications or mesh failure postoperatively. Of the 3 reoperations (13.6%), 2 were for delayed regional infection (at 7 and 12 months postoperatively), necessitating localized mesh removal, and the third was for local cancer recurrence. Fifteen implants developed visible fractures on imaging at a median time of 9 months after implantation. There were no adverse sequelae, including migration/erosion or clinical decline in respiratory function. ConclusionsChest wall resections, particularly those for sarcomas, require large margins for optimal oncologic outcomes. Rigid reconstruction of large defects is desirable, yet options are limited. TM reconstruction provides a promising alternative because of its biocompatibility, rigidity, robust incorporation into surrounding structures, and resistance to infection.

Update on Atypical Femoral Fractures.

➤ Atypical femoral fractures (AFFs) are stress fractures between the lesser trochanter and the metaphyseal flare that are most commonly related to prolonged (3 to 5 years) antiresorptive medication use.➤ An important finding is a visible transverse line in the lateral cortex, known as the "dreaded black line." Complete fractures are transverse and have minimal comminution.➤ Prodromal symptoms including hip, groin, thigh, and knee pain are present in more than one-half of cases and are usually misdiagnosed.➤ Nonoperative treatment for all patients with AFF includes withdrawal of bisphosphonates, assessment for secondary causes of osteoporosis, and optimization of vitamin D and calcium.➤ Incomplete fractures without a visible line can initially be treated nonoperatively with protected weight-bearing.➤ Intramedullary nailing is indicated for complete fractures and incomplete fractures with a visible fracture line. Delayed healing after fixation should be anticipated.➤ Treatment with parathyroid hormone (PTH) analogs (teriparatide and abaloparatide) after AFF prevents other fractures in high-risk patients, but the effect on healing of the fracture is unclear.

Easily missed pathologies of the musculoskeletal system in the emergency radiology setting.

The musculoskeletal region is the main area in terms of easily missed pathologies in the emergency radiology setting, because the majority of diagnoses missed in the emergency setting are fractures.A review of the literature was performed by searching the PubMed and ScienceDirect databases, using the keywords ('missed injuries' or 'missed fractures') and ('emergency radiology' or 'emergency room') and ('musculoskeletal' or 'bone' or 'skeleton') for the title and abstract query. The inclusion criteria were scientific papers presented in the English and German languages. Among the 347 relevant hits between 1980 and 2024 as identified by the author of this review article, there were 114 relevant articles from the years between 2018 and 2024. Based on this literature search and the author's personal experience, this study presents useful information for reducing the number of missed pathologies in the musculoskeletal system in the emergency radiology setting.Predominant factors that make up the majority of missed fractures are 'subtle but still visible fractures' and 'radiographically imperceptible fractures'. Radiologists are able to minimize the factors contributing to fractures being missed. For example, implementing a 'four-eyes principle', i.e., two readers read the radiographs, would help to overcome the missing of 'subtle but still visible fractures' and the additional use of cross-sectional imaging would help to overcome the missing of 'radiographically imperceptible fractures'. Knowledge of what is commonly missed and evaluation of high-risk areas with utmost care also increase the diagnostic performance of radiologists. · Radiological imaging in an emergency setting increases the likelihood of radiological diagnostic errors, such as missing musculoskeletal pathologies.. · The majority of diagnoses missed in the emergency setting are fractures.. · To lessen the number of easily missed pathologies in the musculoskeletal system in the emergency radiology setting, a systematic approach is necessary.. · Adequate training of radiologists in emergency radiology and close collaboration with clinical partners are important measures to decrease the number of missed musculoskeletal injuries.. · Weber MA. Easily missed pathologies of the musculoskeletal system in the emergency radiology setting. Fortschr Röntgenstr 2024; DOI 10.1055/a-2369-8330.

Enhancing fracture diagnosis in pelvic X-rays by deep convolutional neural network with synthesized images from 3D-CT

Pelvic fractures pose significant challenges in medical diagnosis due to the complex structure of the pelvic bones. Timely diagnosis of pelvic fractures is critical to reduce complications and mortality rates. While computed tomography (CT) is highly accurate in detecting pelvic fractures, the initial diagnostic procedure usually involves pelvic X-rays (PXR). In recent years, many deep learning-based methods have been developed utilizing ImageNet-based transfer learning for diagnosing hip and pelvic fractures. However, the ImageNet dataset contains natural RGB images which are different than PXR. In this study, we proposed a two-step transfer learning approach that improved the diagnosis of pelvic fractures in PXR images. The first step involved training a deep convolutional neural network (DCNN) using synthesized PXR images derived from 3D-CT by digitally reconstructed radiographs (DRR). In the second step, the classification layers of the DCNN were fine-tuned using acquired PXR images. The performance of the proposed method was compared with the conventional ImageNet-based transfer learning method. Experimental results demonstrated that the proposed DRR-based method, using 20 synthesized PXR images for each CT, achieved superior performance with the area under the receiver operating characteristic curves (AUROCs) of 0.9327 and 0.8014 for visible and invisible fractures, respectively. The ImageNet-based method yields AUROCs of 0.8908 and 0.7308 for visible and invisible fractures, respectively.

Numerical and Experimental Behavior of Two-Story Confined Masonry Structure Subjected to Cyclic Loads

This research presents the numerical and experimental results of lateral cyclic loading applied on a two-story confined masonry structure utilizing local materials and standards. Two half-scale confined masonry structures were constructed using clay masonry units, confining columns, tie beams, and reinforced concrete slabs. The assemblies were tested up to failure using a displacement controlled loading methodology under vertical self-weight and lateral reversed cyclic loading. The walls of the assemblies have varying perforations (solid / windows / doors) to examine the influence of perforation on in-plane and out-of-plane performance. A strengthened assembly with an exterior layer of ferrocement has been used and this suggested upgrading approach enhanced the lateral resistance of the confined assembly by about (61–95%) while improving ductility and total energy absorbed by 27%. The maximum lateral drift at failure have been decreased to (23–31%), however the corresponding load for the first visible fracture have been raised by (150–175%). Furthermore, total failure has been delayed for the strengthened walls (all sides, particularly the perforated sides). Comparing distorted forms, fracture patterns, and capacity curves of finite element models included in this research yielded excellent agreement.

Developing an artificial intelligence diagnostic tool for paediatric distal radius fractures, a proof of concept study.

In the UK, 1 in 50 children sustain a fractured bone yearly, yet studies have shown that 34% of children sustaining an injury do not have a visible fracture on initial radiographs. Wrist fractures are particularly difficult to identify because the growth plate poses diagnostic challenges when interpreting radiographs. We developed Convolutional Neural Network (CNN) image recognition software to detect fractures in radiographs from children. A consecutive data set of 5,000 radiographs of the distal radius in children aged less than 19 years from 2014 to 2019 was used to train the CNN. In addition, transfer learning from a VGG16 CNN pretrained on non-radiological images was applied to improve generalisation of the network and the classification of radiographs. Hyperparameter tuning techniques were used to compare the model with the radiology reports that accompanied the original images to determine diagnostic test accuracy. The training set consisted of 2,881 radiographs with a fracture and 1,571 without; 548 radiographs were outliers. With additional augmentation, the final data set consisted of 15,498 images. The data set was randomly split into three subsets: training (70%), validation (10%) and test (20%). After training for 20 epochs, the diagnostic test accuracy was 85%. A CNN model is feasible in diagnosing paediatric wrist fractures. We demonstrated that this application could be utilised as a tool for improving diagnostic accuracy. Future work would involve developing automated treatment pathways for diagnosis, reducing unnecessary hospital visits and allowing staff redeployment to other areas.

Experiment and Numerical Simulation on Damage Behavior of Honeycomb Sandwich Composites under Low-Energy Impact

It is well-established that the honeycomb sandwich composite structures are easily prone to damage under low-energy impact. Consequently, it would lead to a dramatic decrease in structural load-bearing capacity and a threat to overall safety. Both experimental and numerical simulations are carried out to investigate the impact damage behavior of honeycomb sandwich composite specimens. The damage mode, damage parameters, and contact force-time curves of three types of panel materials with T300, T700, and T800 are obtained under different impact energies of 10 J, 20 J, and 40 J by the drop-weight impact experiment. Moreover, digital image correlation (DIC) tests are used to measure the deformation and strain of the lower panel. The experimental results reveal that the degree of damage increases with increasing impact energy. Particularly, the T300 panel specimen exhibits visible fiber fracture when subjected to an impact energy of 40 J. The impact process involves matrix cracking, fiber fracture, and delamination of the upper panel occurring first, followed by immediate crush damage to the honeycomb core and, finally, slight fiber damage to the lower panel. Due to its higher strength, the T800 panel specimen exhibits the highest damage resistance compared to the T700 and T300 panel specimens. To consider the microscopic failure criteria and various types of contact during the impact process, a finite element model of honeycomb sandwich composites is established, and numerical simulation analysis of low-energy impact is performed to determine the damage mode, damage size, and contact-force curves. Comparative analysis demonstrates good agreement between the simulation and experimental results. The findings of this study provide valuable technical support for the widespread application of honeycomb sandwich composites in the aviation field.

Do Intramedullary Screws Provide Adequate Fixation for Humeral and Ulnar Components in Total Elbow Arthroplasty? A Cadaveric Analysis

The objective of this study was to determine the structural properties of the cadaver bone-screw interface for cementless intramedullary screw fixation in the context of total elbow arthroplasty. The intramedullary canals of seven humerus and seven ulna specimens from fresh-frozen cadavers were drilled using custom drill bits until the inner cortex was reached and then hand tapped for the corresponding thread size. Titanium screws were advanced into the tapped holes until securely seated. The bones were potted and then mounted on a uniaxial material testing machine. A tensile load was applied, and end-of-test elongation, failure load, energy absorbed, and stiffness were determined. End-of-test load and elongation were defined as the elongation and load experienced by the structure at 3,000 N or failure. Each specimen was inspected for evidence of pullout, loosening, or visible fractures. The end-of-test load and elongation for the humerus specimens were 2721 ± 738 N and 3.0 ± 0.9 mm, respectively. The ulna specimens reached 92% of the humerus specimens' end-of-test load at 2,514± 678 N and 120% of their end-of-test elongation (3.6 ± 0.6 mm). The stiffness of the humerus specimens was 1,077 ± 336 N/mm, which was 1.3 times greater than the stiffness of the ulna specimens (790 ± 211 N/mm). Lastly, the energy absorbed by the humerus samples was 3.6 ± 1.6 J, which was 92% of the energy absorbed by the ulna samples at 3.9 ± 1.1 J. One humerus and three ulnas failed before the end-of-test load of 3,000 N. Two failures were caused by screw pullout and two by bone fracture. Our findings demonstrate that intramedullary screw fixation is successful in withstanding forces that are greater than required for osseointegration. Uncemented fixation may be beneficial in elbow arthroplasty.

Intra-operative identification of a temporal bone fracture line during cochlear implant surgery: a case report

BackgroundTemporal bone fractures are divided into otic capsule sparing and otic capsule involving fractures. In the latter, hearing loss, facial nerve paralysis, cerebrospinal fluid leak and meningitis have been reported to occur. The impact of hearing loss can be devastating, especially when occurring in children, with significant risk to speech development and sound localization. In the event of hearing loss, early rehabilitation is therefore of paramount importance. Identification of an intra-operative fracture line with available images and the outcome of such cases has not been reported.Case presentationWe present the case of a 31-month-old male with an otic capsule involving temporal bone fracture, who presented with ipsilateral profound hearing loss. After all required work-up had been performed, he was admitted for a cochlear implant insertion. Per- operatively, a clear fracture line was seen at the round window niche, but a normal insertion was performed despite the anticipated potential ossification at the fracture line. The dreaded complications of cerebrospinal fluid otorrhea or non-auditory stimulation post-implant did not occur. The peculiarity of this case was its rarity, which was demonstrated by clear images that showed the fracture line on preoperative imaging and intraoperatively.ConclusionCochlear implantation in the presence of a visible fracture line is feasible and the surgical procedure must not be aborted at its discovery. In these cases, post-operative bacterial meningitis can occur and should be treated aggressively with systemic antibiotics to avoid contralateral ossification of the labyrinth due to labyrinthitis.

A New Mode of Visible Fracture System in Coal Seams and Its Implications for Coalbed Methane Seepage

As the central flow channel for fluid seepage through rock layers, the visible fracture system (VFS) significantly affects geoenergy extraction for petroleum, natural gas, geothermal resources, and greenhouse gas sequestration. In this work, we propose a new mode of VFS in coal seams, including hydraulic fractures, exogenetic fractures, interlayer fractures, gas-expanding fractures, and cleats. The development characteristics of VFSs in coal seams are analyzed, including containing their geometry, orientation, scale, distribution, and connection between each other. Furthermore, the implications of the VFS for fluid (gas and water) and solid (coal fines) flow through coal seams are discussed. The development of the VFS determines the effective flow conductivity, affecting the flow of gas, water, and coal fines. Additionally, as the reservoir pressure transfer channel, the VFS significantly influences depressurization with reservoir depletion, determining the extension of the methane desorption range. The exogenetic fractures and interlayer fractures dominate the expansion of the primary hydraulic fractures, and gas-expanding and cleats usually control the branch of hydraulic fractures. Furthermore, we find that the daily production rate distribution of most CBM wells presents a particular banded, L-shaped, or T-shaped pattern. It is thought that the VFS dominates the productivity of CBM in coal seams. The field production data also provide evidence that the occurrence of the VFS makes the CBM reservoir heterogeneous. This study presents a recommended framework involving the characteristics of the VFS and its influences on CBM production.

High stability polymer gel for lost circulation control when drilling in fractured oil and gas formations

When drilling in fractured oil and gas formations, drilling fluid loss is prevalent, and polymer gels are commonly utilized as lost circulation materials to plug fractures in loss zones. A high stability polymer gel was synthesized in this study employing acrylamide as the polymerizable monomer, a self-synthesized microsphere containing active ethylene groups as the cross-linker, laponite as both a flow pattern regulator and a physical filler, and ammonium persulfate as the initiator. This polymer gel's complex network structure considerably adds to its mechanical and thermal resilience, and its best gelation time is 12 h at 248°. Rheological properties of the gel were studied under various conditions. When the experimental temperature is 284°, the Na+ concentration is 100,000 ppm, or the Ca2+ concentration is 1000 ppm, the G′ and G″ of the polymer gel exceeded 1000 Pa and 200 Pa, suggesting that this gel has good thermal and salt stability. Contamination resistance studies reveal that the polymer gel has adequate contamination resistance for drilling fluid and formation water penetration, with G′ and G″ exceeding 1500 Pa and 400 Pa when the volume ratio of external fluids to gellant is 6:4. Furthermore, the density of the polymer gel may be adjusted to 2.0 g/cm3 by employing barite as a weighting agent, and the addition of the barite contributed to improving the structural stability of the gel due to the filling effect in the gel's network structure. Using fractured steel cores and a visible fracture model, the dynamic filling and plugging capabilities of this polymer gel in fractures were measured. When compared to frequently used polymer gellants, the high stability polymer gellant entirely fills the fracture area and exhibits a little gravity differentiation effect in large-scale fracture. After gel formation, it exhibits outstanding plugging capability for various fracture scales at 248°. Three successful field tests in the Tarim Basin, Xinjiang, China, demonstrated that the high stability polymer gel may be used to control lost circulation in fractured formations at high temperatures.

Influence of polymeric resin-infilling on onset and fracture growth along wing trajectory in open-flawed sandstone specimen

Onset and growth of wing fracture in open/resin-infilled sandstone specimens are primarily investigated. Stress/LEFM-based VCCT embedded fracture analysis is carried out through three-dimensional FEM, experimentally validated with wing crack initiation points/extension angles. Principal-stress/SERR-based G/F-criteria are used for numerical estimation of onset points/extension angles. Griffith (G)-criteria predicts extension angle for open flaw but fails for infilled case, whereas F-Criteria distinguishing unequal contribution of fracture modes fits. Tensile Stress Concentration (TSC) at flaw-resin interface is reduced through significant reduction of in-plane stresses (σx, σy, τxy) over out-of-plane (σz, τyz, τxz) components. Shifting of TSC/Wing Trajectory (WT) alternation in resin-infilled case is due to through-the-thickness variation of out-of-plane stresses. Curve-fitted experimental WT profile inducted; realistic FE-simulation technique is implemented for fracture growth investigation. Both open/infilled flaws undergo Mode-I-dominated wing fracture growth with least dominance of Mode-II/III. Resin infilling causes significant reduction/slight improvisation of Mode-I/Mode-II SERRs, respectively, leading to self-similar, delayed, thin wing fractures compared to visible wing fractures in open flaw cases. As the wing fracture grows, propensity towards Mode-I fracture is reduced in absence/presence of resin infill. However, the tendency for Mode-II is increased for open flaw and reduced for infilled-flaw cases.

Treatment of severely calcified coronary artery disease by intravascular lithotripsy primary outcomes and 180-day follow-up from the Chinese SOLSTICE Trial.

To assess the safety and effectiveness of intravascular lithotripsy (IVL) treatment for de novo coronary lesion involving severely calcified vessels in a Chinese population. The Clinical Trial of the ShOckwave Coronary IVL System Used to Treat CalcIfied Coronary ArtEries (SOLSTICE) was a prospective, single-arm, multicentre trial. According to the inclusion criteria, patients with severely calcified lesions were enrolled in the study. IVL was used to perform calcium modification prior to stent implantation. The primary safety endpoint was freedom from major adverse cardiac events (MACEs) at 30 days. The primary effectiveness endpoint was procedural success, defined as successful stent delivery with residual stenosis < 50% by core lab assessment without in-hospital MACEs. The morphological changes of calcium modification were assessed by optical coherence tomography (OCT) before and after IVL treatment. Patients (n = 20) were enrolled at three sites in China. Severe calcification by core lab assessment was present in all lesions, with a mean calcium angle and thickness of 300 ± 51° and 0.99 ± 0.12 mm (by OCT), respectively. The 30-day MACE rate was 5%. Both primary safety and effectiveness endpoints were achieved in 95% of patients. The final in-stent diameter stenosis was 13.1% ± 5.7% with no patient had a residual stenosis < 50% after stenting. No serious angiographic complications (severe dissection grade D or worse, perforation, abrupt closure, slow flow/no-reflow) observed at any time during the procedure. OCT imaging demonstrated visible multiplane calcium fracture in 80% of lesions with a mean stent expansion of 95.62% ± 13.33% at the site of maximum calcification and minimum stent area (MSA) of 5.34 ± 1.64 mm2. The initial coronary IVL experience for Chinese operators resulted in high procedural success and low angiographic complications consistent with prior IVL studies, reflecting the relative ease of use of IVL technology.

Characteristics of Gas Seepage and Pore Structure Response in CO2-ECBM Process of Low Permeability Coal Seam

CO2-ECBM is a method of enhanced coalbed methane extraction followed by cutting greenhouse gas emissions and new energy development. In order to reveal the characteristics of gas flow in porous media and the pore structure response characteristics of coal rocks, the experiments were carried out to simulate the process of CO2 displacement of N2 at a buried depth of 900 m, including monitoring the changes in gas permeability and strain of coal samples along with a comparison of the pore structure of low-temperature liquid nitrogen adsorption on coal samples both before and after displacement were both done. The findings of the experiment are listed below. The N2 permeability of the LiuZhuang sample ranges from 0.0008mD to 0.0014mD, whereas the permeability of QiDong is around 0.0003mD. With an increase in gas injection duration and an expansion of the coal matrix for N2 adsorption, the permeability steadily decreases. The efficient stress compression of the coal pore fracture structure during sample preparation and testing avoids the visible fracture region, which results in poor permeability. The displacement stages of CO2 can be divided into three phases. Free nitrogen flows from the end of the position and the permeability diminishes during the phase of free nitrogen. When CO2 is introduced into the penetration stage, the permeability tends to rise, however when there is no penetration, the permeability test values are frequently low. During the CO2 steady displacement phase, gas permeability gradually declines. Axial and radial strains are progressively raised during the initial stage of the CO2 injection whereas they are gradually reduced during the initial stage of the N2 injection. While CO2 is continuously supplied through the coal body stage, there are modest axial and radial strain changes. The axial and radial stresses are stabilized by the CO2 displacement. The overall pore volume of the coal significantly rises following the displacement. The increase part of the pore volume is primarily focused on the pore of absorption and filling (aperture &lt; 10nm), whereas the decreased part is mainly concentrated in the diffusion pore of the Fick type and the permeability part (aperture &gt; 50nm). The increased in pore volume ratio surface area is centered mostly in the fill pore region (aperture 10 nm) and is four times greater than it was before the displacement. The CO2 injection exerts an expansion impact on the adsorptionfilled and diffusion pores during the CO2-ECBM process, whereas the compression effect on the percolation pores results in a reduction in permeability.

Regional variations in observed fracture abundance and associated predictions for smaller fractures on Europa with implications for regional plume origins

Large fractures on Europa's surface have been extensively studied for the insight they provide into the evolution of the satellite's ice shell. The presence of small fractures has not been characterized on a global or regional scale because of the resolution limits in the current image data. However, if smaller fractures are present they could significantly increase the overall fracture abundance and influence the mechanical properties of the ice shell. Regional variability in this abundance would also impact the spatial heterogeneity of ice shell characteristics. To investigate the possible contribution of smaller fractures to the influence of the fracture network on the behavior of the ice lithosphere, we measure the surface length of visible fractures in regions on Europa's surface and calculate their length distributions and fracture intensities. These outcomes are extrapolated, using best-fit functions, to consider the possible abundance and role of smaller fractures in these networks. The analysis of the visible fractures sampled different geologic terrains and geographic regions to consider the effect of terrain type and location. Fracture abundance in observable populations shows some variation with terrain type. However, observable abundance also changes with image resolution, indicating that current data limit the interpretation of visible fracture populations. Typical log-normal, exponential, and power-law fracture network distributions, based on analysis of terrestrial fracture networks, were considered as methods for extrapolating the observed fracture populations. Power-law was found to be the most appropriate extrapolation choice. It was also found to predict observed fracture abundance in one sample region with a smaller sub-region that had locally higher image resolution. Applying a power-law extrapolation for the fracture abundance as a function of length, we predict fracture abundance characteristics that are up to two orders of magnitude higher than abundance of observed fractures, and which vary by an order of magnitude between regions. Thus, the predicted fracture populations indicate that abundant small fractures would contribute significantly to the mechanical behavior of the ice lithosphere and create regional variations in fracture abundance. For example, where they are abundant, these smaller fractures could contribute to fracture networks providing localized migration pathways for plume activity on Europa. New image data from the Europa Clipper mission should enable fracture mapping at smaller scales to refine the roles of these networks and the smaller fractures on Europan lithospheric processes and rheology.

Bird impact response and damage mechanism of 3D orthogonal woven composite aeroengine blades

Various gelatin simulated bird projectiles were used to impact two key positions of three-dimensional (3D) orthogonal woven composite stator blades used in aeroengines: the center and leading edge at the blade back. The effects of impact velocity, projectile weight, and impact position on the macro damage mode were determined. Numerical simulations were conducted using the constitutive model developed in our previous work (Liu et al. 2023). The numerical simulation results were in good agreement with the experimental results. Combined test results, micro-CT and SEM observation and the numerical simulation results, the internal damage mechanism of the blade was explored. Four types of damage modes were seen under bird strike: edge damage on the narrow blade root, cracks on both sides of the narrow blade root, damage in the impact area, and complete fracture. Furthermore, the impact energy thresholds for visible damage and fracture were obtained for different bird weights and impact locations, which is of great significance to the anti-bird-strike design of composite blades.

A Study on the Pore Structure and Fractal Characteristics of Briquettes with Different Compression Loads

In order to study the effects of different compression loads on the pore characteristics of coal, taking remolded coal as the research object, the mercury intrusion method was used to determine the pore structures of the briquettes under the compression loads of 50, 70, 90 and 110 MPa, and the Menger sponge model was used to conduct fractal research on the measured parameters. The results show that the compression load has a significant effect on the pore structure parameters of the briquettes. The hysteresis loop generated by the mercury-intrusion and mercury-extrusion curves of raw coal is small, and the pore connectivity is better. After different loads are applied for briquettes, the hysteresis loop becomes larger, and the pore connectivity becomes worse. From the process of the raw coal to the briquettes loaded at 50 and 70 MPa, the pore-specific surface area reduced from 5.069 m2/g to 1.259 m2/g, the total pore volume increased from 0.0553 cm3/g to 0.1877 cm3/g, and the average pore size increased from 43.6 nm to 596.3 nm. When the compression load reached 70 MPa, the specific surface area, total pore volume, and average pore diameter of briquettes remained basically stable with the change in the compression load. The minipores and visible pores and fissures of raw coal contribute 78% of the pore volume, and the micropores and minipores contribute 99% of the specific surface area. After being pressed into briquettes, the volume of mesopores and macropores increases, the volume of visible pores and fractures decreases and the volume of minipores changes little; additionally, the pore surface area contributed by mesopores and macropores increases, and the pore surface area contributed by micropores decreases, indicating that the effect of compression load on pores of 10–100 nm is not obvious, mainly concentrated in the 100–10,000 nm region. The fractal curve of briquettes is fitted into three sections, which are defined as low-pressure sections 1 and 2 and high-pressure section 3, and the fractal dimensions are D1, D2 and D3 respectively. The fractal dimension D1 of briquettes with different compression loads is close to 2, D2 is close to 3 and D3 is greater than 3. The pore structures of briquettes have obvious fractal characteristics in the low-pressure sections 1 and 2 but do not conform to the fractal law in the high-pressure section. Furthermore, in the micropore stage of briquettes, the measured surface area and volume are both negative, indicating that the mercury intrusion method used to test the pore structure of the loaded briquette is more likely to cause the collapse of and damage to the pores in the micropore (&lt;10 nm) stage.

Fatigue and fracture of additively manufactured polyethylene terephthalate glycol and acrylonitrile butadiene styrene polymers

This paper aims to study and compare the static tensile properties and Low Cycle Fatigue (LCF) deformation behavior of Additively Manufactured (AM) samples made of two commonly used polymers: Polyethylene Terephthalate Glycol (PET-G) and Acrylonitrile Butadiene Styrene (ABS). Such materials are commonly in use in the Material Extrusion (ME) AM technologies – especially in Fused Deposition Modelling (FDM) or Fused Filament Fabrication (FFF). That kind of approach would be useful to understand the fracture phenomena of AM parts obtained by means of FDM/FFF technologies which are entirely different than in the conventionally made material, because of the characteristic layered structure of AM parts. The study has been supplemented by additional fracture analysis of AM samples subjected to LCF tests. The conducted research exposed an increased LCF of PET-G samples (36050 cycles at constant strain equal to ε = 0.40%) in comparison to ABS (24586 cycles at the same strain level). At the same time, PET-G samples indicated a significant material softening during LCF testing. Such a phenomenon was better described by additional analysis with the use of the Morrow equation which indicated quasi-brittle cracking with visible brittle fracture phenomena in PET-G samples.