Search Results (344)

The objective of this study is to mitigate the bottom-out failure and improve the energy absorption of conventional helmet liners during high-energy impacts, thereby reducing the risk of head injuries. To this end, a locally reinforced Primitive-type triply periodic minimal surface (P-TPMS) energy-absorbing liner is proposed for the helmet forehead region, which facilitates progressive energy dissipation through layer-by-layer buckling deformation. A finite element model of a helmet–head coupling was created based on a previously verified high-fidelity head model and subsequently validated against the ECE 22.06 standard drop-test methodology. Three critical design parameters—outer protective layer thickness, triply periodic minimal surface (TPMS) unit cell size, and wall thickness—were optimized employing the Box–Behnken Design (BBD) response surface methodology, resulting in quadratic regression models for the head injury criteria (HIC) and peak linear acceleration (PLA) with good fit ($R^2$ > 0.97). Optimal parameter combinations were established using multi-objective optimization, with protective efficacy carefully assessed from both head dynamic response and biomechanical response perspectives. The ideal P-TPMS liner possesses an outer protective layer thickness of 14.95 mm, a TPMS unit cell size of 12.23 mm, and a wall thickness of 3.93 mm. Compared to the traditional expanded polystyrene (EPS) liner, the optimized P-TPMS liner significantly reduces HIC (by ∼16%) and PLA (by ∼14%) while extending the impact duration. More critically, it transitions both intracranial pressure and brain tissue strain below their respective clinical injury thresholds, substantially lowering the risks of skull fracture and mild traumatic brain injury (mTBI). The P-TPMS construction facilitates continuous energy dissipation during impacts via incremental layer-by-layer buckling deformation, hence extending impact duration and markedly improving helmet protective efficacy. These findings offer theoretical foundations and technical direction for the creation of localized heterogeneous liner designs in advanced high-performance helmets, although the results are limited to frontal flat-anvil impact conditions. Full article

Background/Objectives: Although the Spinal Instability Neoplastic Score (SINS) is widely used to estimate spinal metastases fracture risk and guide decisions on stabilisation procedures, prior studies have demonstrated mixed results. Patients with the same score exhibit clinically heterogeneous outcomes, with some SINS criteria correlating less well with the estimated fracture risk than others. There are also barriers to implementation such as the time burden required for manual calculation and interobserver variability associated with qualitative morphological criteria. SINS also lacks sensitivity for detecting latent structural compromise in treatment-naive patients and those susceptible to the iatrogenic effects of stereotactic body radiation therapy. This review aims to evaluate emerging imaging, biomechanical, and microstructural markers with the potential to improve fracture risk stratification and prognostication for spinal oncology patients. Methods: We synthesise evidence across three innovative frontiers: (1) biomechanical modelling, including CT-derived finite element analysis and failure-load pattern models; (2) radiomics, utilizing radiomics features from radiological imaging to develop a predictive model; and (3) microstructural MRI biomarkers, exploring the translatability of the Vertebral Bone Quality score, fat fraction, and paraspinal muscle atrophy from osteoporosis to the metastatic spine. Results: Emerging biomechanical, radiomic and microstructural imaging markers show potential in addressing some limitations of traditional SINS criteria for fracture risk stratification across the spinal oncology treatment continuum, from initial diagnosis to post-radiation surveillance, thereby facilitating more precise risk assessment. However, current evidence remains largely retrospective and heterogeneous, and further validation is required before clinical adoption. Conclusions: We propose a framework that shifts the paradigm from conventional morphological scoring toward a multiparametric assessment of spinal stability. Full article

Progressive collapse represents a catastrophic failure mode for reinforced concrete (RC) structures, yet the use of architected materials to mitigate this risk remains largely unexplored. This study presents a numerical feasibility investigation of RC beam–column sub-assemblages with auxetic metamaterial inserts embedded in critical joint regions. A hierarchical multiscale framework is developed to link the effective behavior of auxetic metamaterials with structure-scale collapse response. The framework couples macroscale structural analysis with mesoscale fracture simulations through a hybrid voxel–Voronoi discretization strategy. Baseline finite element models are validated against published experimental results for conventional RC specimens, while the auxetic-enhanced configurations are evaluated numerically. Under high tensile strain, the auxetic insert expands laterally because of its negative Poisson’s ratio and generates a localized confining stress field within the surrounding concrete. The simulations suggest that this mechanism may promote crack bifurcation, redistribute localized cracking into a more distributed damage pattern, and delay compressive crushing and crack coalescence. Compared with the corresponding conventional RC configurations, the auxetic-enhanced models predict a 25% increase in load redistribution capacity and a 20% enhancement in deformation ductility. These predicted improvements require future experimental validation using physical auxetic-enhanced RC specimens. The findings provide a computational basis for exploring material-by-design strategies aimed at improving the robustness of critical RC joint regions under progressive collapse demands. Full article

As critical underground engineering structures, wellbores may suffer complex structural deterioration and hidden safety hazards may be encountered during drilling. Multi-source sensor monitoring data provides an effective data basis for structural health perception and early warnings for wellbore structures at risk. The inherent diversity of formation conditions and the dynamic disturbances during drilling jointly lead to the differentiated presentation of drilling loss types, among which fractured, permeable, and vuggy losses are the most typical. This paper focuses on fractured wellbore leakage, regards wellbore leakage as an important structural failure form of underground drilling engineering structures. In-depth analysis and research on the structural deterioration mechanism of wellbore leakage were conducted, and we propose a wellbore leakage prediction method based on the improved sparrow search algorithm (ISSA) optimized gradient boosting decision tree (XGBoost). First, the Sobol sequence is adopted to replace the random initialization strategy, combined with the opposition-based learning mechanism; then, an adaptive Levy flight search mechanism is introduced to dynamically adjust the population ratio of discoverers and vigilantes; finally, intelligent optimization technologies are integrated to reconstruct the position update strategies of discoverers, followers, and vigilantes, enhancing the optimization adaptability of the algorithm. Relying on multi-field sensor monitoring datasets collected from actual drilling engineering, this paper compares the proposed model with wellbore leakage prediction models built by classical machine learning algorithms, and verifies its generalization ability on different datasets. Experimental data indicate that the improved algorithm exhibits significant advantages in optimization accuracy, enabling the proposed model to achieve an AUC improvement of 4.46%, along with accuracy (95.1%), precision (94.9%), recall (94.7%), and F1-score (94.2%). On this basis, the ISSA was applied to the hyperparameter optimization of XGBoost, constructing the ISSA-XGBoost prediction model. The method has high accuracy and good generalization ability in fractured wellbore leakage prediction, and it can realize intelligent health monitoring of underground wellbore structures, including early warnings. This study provides a reliable sensing data analysis scheme and technical support for structural health monitoring and hazard prevention in drilling engineering. Full article

Background: Hip implant fractures are rare, yet difficult to correct once they occur. For cemented implants, fracture is often associated with increased stresses at the implant stem when proximal regions of the implant have debonded. While deterministic analyses offer predictive power by using averages for model inputs, averages fail to capture the variability inherent in device manufacturing and musculoskeletal biology. This study developed a probabilistic finite element model of a debonded hip implant to better account for some of these variabilities to predict the most likely failure mode. The hypothesis was that fatigue would be more likely to occur than overloading. Methods and Materials: Monte Carlo sampling generated 1000 simulations varying the material elastic modulus (implant, cement, and bone) and loading magnitude at stance phase of the gait. The resultant distributions of maximum von Mises stress at the stem were compared to distributions for failure properties in the literature. Results: The analysis found the likelihood of the implant failing due to overloading was remote. In contrast, fatigue failure had a 99.4% chance of occurring. Fracture mechanics predicted that the debonded implant would reach critical flaw length between 1.8 and 26.4 months, with a mean of 7.2 months. Conclusions: The results show good agreement with the findings of the case study the model was based on, particularly in predicting the location of failure and fatigue life. The results of this study provide a framework for developing future decision-making tools that ultimately may assist clinicians in deciding when interventions are necessary to minimize the risk of implant or periprosthetic fracture. Full article

Earthquakes may cause severe damage to engineering structures in the seismogenic fault zone. In near-fault regions, ground motions on the two sides of a fault exhibit significant asymmetry in terms of permanent displacement, velocity pulse, and dynamic displacement amplitude. Taking the Xianglu Mountain Tunnel in the southwest of China as the engineering object, this study designed scaled fault-crossing tunnel-surrounding rock test models and conducted a series of quasi-static and dynamic model tests using a dual-shaking table system with non-uniform ground motion input. The effects of three different earthquake action modes on the responses of tunnel engineering structures crossing seismogenic faults were investigated through five static and dynamic earthquake action modes. The test results indicate that considering only the dynamic effect of ground motion or only the static effect of permanent displacement due to fault dislocation will underestimate the seismic response and damage degree of the surrounding rock and tunnel structure. However, the contribution of dynamic effects of ground motion to tunnel failure is much smaller than that of static fault dislocation. The magnitude of permanent displacement from fault dislocation, the peak displacement of non-uniform ground motion time history, and the peak relative displacement are all important factors affecting the deformation of surrounding rock and the strain of tunnel structures. Traditional static analysis methods will lead to an underestimation of the damage risk of tunnel structures. Compared with the non-uniform earthquake action mode, the deformation within the fracture zone under the static action mode is underestimated by approximately 6.39%, and the peak tensile strain under the static action mode underestimates the damage risk by approximately 40%. Full article

Background: Clinical controversy persists regarding the optimal weight-bearing strategy for elderly patients following hip fractures. Whilst early unrestricted weight-bearing may improve functional outcome and reduce the risk of bed-related complications, concerns about implant stability and failure often lead clinicians to adopt restricted weight-bearing protocols. To address this, we conducted a systematic review and meta-analysis to identify the effects of unrestricted weight-bearing compared with restricted weight-bearing on clinical outcomes in this patient population. We hypothesized that unrestricted weight-bearing may be associated with lower all-cause mortality without increasing postoperative complications, reoperation rates or length of hospital stay (LOS). Methods: This systematic review was conducted based on a study protocol registered on the PROSPERO platform and reported strictly in accordance with the PRISMA guidelines. We included clinical studies involving patients aged ≥65 years with hip fractures undergoing surgical treatment that directly compared the effects of different postoperative weight-bearing strategies on outcomes. Patients were further classified into unrestricted and restricted weight-bearing groups according to the postoperative weight-bearing protocols reported in each study. The primary outcome was all-cause mortality. Secondary outcomes included postoperative complications, reoperation rates, and LOS. A random-effects model was used for meta-analysis. Dichotomous variables were expressed as risk ratios (RRs), continuous variables as mean differences (MDs), and study heterogeneity was assessed using the I² statistic. The certainty of evidence of each outcome was assessed by using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach. Results: Ten studies (one randomized controlled trial and nine cohort studies) were included with 5806 patients in total. Extra-capsular fractures (intertrochanteric/subtrochanteric fractures) were the most common, with 3694 patients, followed by femoral neck fractures, with 1929 patients. Unrestricted weight-bearing was significantly associated with lower long-term mortality compared with restricted weight-bearing (RR = 0.67, 95% CI 0.51–0.88, p = 0.004, I² = 34%; 95% PI 0.52–0.83), with an absolute risk difference of −0.10%. Short-term mortality did not differ significantly in the primary analysis (RR = 0.58, 95% CI 0.14–2.34, p = 0.44, I² = 70%; 95% PI 0.00–126.98). Furthermore, the corresponding absolute risk difference was only −0.03%. No significant differences were observed for short-term complications, long-term complications, reoperation risk, or LOS between the two groups (all p > 0.05). GRADE assessment showed low certainty of evidence for long-term mortality and short-term complications, and very low certainty of evidence for the remaining outcomes. Conclusions: This meta-analysis suggests that unrestricted weight-bearing may be a feasible postoperative rehabilitation approach in selected patients. However, the results should be interpreted with caution. Further well-designed prospective studies are required to confirm these findings. Full article

In shale gas extraction, solid particles such as fracturing proppants cause erosion in production and transmission pipelines. Cyclone desanders are widely used for gas–solid separation, but high-velocity sand-laden fluids frequently induce equipment failure, leakage and safety risks. Therefore, research on erosion and protective measures is essential. This study focuses on the desander at the M shale gas wellhead, where wall thickness was measured at three monitoring points to determine erosion rates. A CFD-based numerical erosion model for the cyclone desander was developed using ANSYS Fluent within the ANSYS Workbench 19.2 environment (ANSYS, Inc., Canonsburg, PA, USA). The model was validated by comparing simulation results with field data, revealing the distribution patterns of the velocity field, pressure field, and erosion rate. The study analyzed the impact of nine factors on desander erosion: inlet aspect ratio, cylinder radius, cone length, dust discharge port diameter, exhaust port diameter, particle size, particle concentration, inlet velocity, and operating pressure, clarifying the erosion variation patterns for each factor. SPSSAU V25.0 (Beijing Qingsi Technology Co., Ltd., Beijing, China) was employed to analyze the significance of these nine factors, identifying six significant influencing factors: inlet aspect ratio, cylinder diameter, dust discharge port diameter, particle size, particle concentration, and inlet velocity. Subsequently, response surface analysis was performed using Design-Expert 13 (Stat-Ease, Inc., Minneapolis, MN, USA) to obtain the relationship between the factors and their impact on maximum erosion, leading to the establishment of a predictive model for the maximum erosion rate. In addition, geometry optimization, local wall thickening, coating protection, material selection, and bionic rib structures were discussed as erosion-mitigation strategies. The optimized geometry reduced the erosion rate at the inlet and dust discharge outlet by 20.4% and 21.8%, respectively, while the bionic rib structure reduced the maximum erosion rate by 58%. Full article

Hydraulic fracturing is critical for unconventional oil and gas development, yet perforation-induced initial damage impairs the integrity of the casing–cement sheath–formation assembly, causing fracturing fluid channeling and reduced stimulation efficiency. A stress-seepage coupling numerical model was established to simulate interface fracture initiation, propagation, and sealing failure, quantifying axial and circumferential channeling evolution at the cement–formation interface. Key parameters (casing eccentricity, cement elastic modulus, injection rate, and minimum horizontal in situ stress) were systematically analyzed. Results show fluid preferentially migrates through perforation-weakened zones, with channeling initiating via axial debonding, then circumferential propagation, and finally dominant axial extension. Casing eccentricity exacerbates channeling, while higher cement elastic modulus or in situ stress mitigates it significantly; injection rate affects channeling length but not fracture initiation/propagation pressures. This study provides theoretical and practical guidance for fracturing channeling risk control. Full article

The widespread application of planetary gear trains is accompanied by inevitable crack failures, especially for the internal ring gear, which may lead to catastrophic accidents. There is relatively little research on internal ring gear cracks and mostly only make assumptions about the crack damage morphology at a certain stage. Moreover, there is no answer on what will happen in the next stage after the crack occurs, or how to avoid serious failure. In view of this, this study considers rim and support configurations, tooth geometries, and crack parameters, and analyzes crack evolution mechanisms. The results indicate that compared to the internal ring gear outer surface constraint condition, the use of pin support for the internal ring gear increases the risk of severe rim-fracture failure. A thicker rim can avoid rim failure, especially when the initial crack is close to the tooth root. In addition, a larger root fillet helps to reduce the occurrence of rim failure over tooth failure. Increasing pin support diameter and stiffness results in a tendency for the crack trajectory to move away from the rim. This study gives support for the cracked ring gear failure analysis and safety design. Full article

Background/Objectives: The spectrum of chronic kidney disease—mineral and bone disorder (CKD-MBD) is changing and adynamic bone disease (ABD) is now believed to constitute the majority of CKD-MBD in the developed world. However, its prevalence and risk factors are poorly described in the literature. Its diagnosis requires bone biopsy, but biochemical criteria including parathyroid hormone (PTH) levels show good correlation. The aim of this study is to understand the prevalence of ABD in our patients with kidney failure (KF) on hemodialysis (HD), identify the risk factors for its development, and in doing so enable early intervention to modify the risk factors specific to our population. Methods: This is a retrospective cross-sectional study. A total of 201 prevalent adult patients on maintenance HD for at least 3 months were recruited. Patients with previous parathyroidectomy were excluded. Relevant data including clinical and biochemical parameters, prescribed dialysate and medications, and clinical outcomes were collected. ABD was diagnosed if any intact PTH (iPTH) level during the study period was <15 pmol/L. Results: Of the 201 patients in the study (median age 64.5 years), 35 (17.4%) patients had ABD. In the multivariable logistic regression model, the adjusted odds ratio (OR) of ABD was higher with a higher mean adjusted serum calcium level, while the concurrent use of non-calcium-based binders was associated with lower odds of ABD. Activated vitamin D use was also associated with lower odds of ABD, likely reflecting past occurrence of ABD, prompting a pre-emptive discontinuation of activated vitamin D. Overall, 17% of patients had had fractures without significant association with ABD. The mean PTH level was in the target range (15–60 pmol/L) in 41% of the cohort. Cardiovascular complications were not significantly associated with ABD. Conclusions: Approximately one in every six HD patients in our care have ABD as diagnosed by the iPTH level. Targeting a lower serum calcium level and using non-calcium-based binders may reduce the occurrence of ABD and will need to be tested in prospective studies. Full article

Background: Although survival rates for patients with malignant bone tumors have improved significantly, complications following tumor resection and limb-sparing reconstruction remain a major clinical challenge, particularly in young individuals. Intercalary resection often results in large bone defects, necessitating complex reconstructions. Fibula grafts offer biological advantages; however, their long-term outcomes, especially regarding mechanical complications and comprehensive patient-reported well-being, require further detailed exploration, particularly in cohorts utilizing non-vascularized grafts. Objective: This retrospective study evaluated the complication rates, bone hypertrophy, limb function, and quality of life following non-vascularized fibular graft reconstruction for malignant bone tumors in a single-center cohort. This study offers insights into long-term success and patient well-being, with a particular focus on correlations with systemic therapy and defect size, factors that remain insufficiently explored in the current literature. Methods: In this single-center retrospective study, twenty-four non-vascularized fibular grafts were used to reconstruct intercalary bone defects following malignant tumor resection. Complications were categorized using the Clavien–Dindo classification. Graft hypertrophy was evaluated according to the method described by Weiland and de Boer. Functional outcomes were assessed using the MSTSs and TESSs, while quality of life was measured using the SF-36 questionnaire. Notably, the cohort analyzed represents a relatively large single-center series focusing exclusively on the outcomes of non-vascularized fibular grafts. Results: Our findings revealed significant rates of mechanical complications, with osteosynthesis material failure occurring in 50.0% of cases, pseudarthrosis in 47.6%, and fractures of the fibular grafts in 38.1% of cases. Importantly, there were significant correlations between mechanical complications and systemic therapy (p = 0.017), as well as between defect size and fractures (p = 0.013), identifying critical risk factors. Despite these considerable complication rates, patients achieved satisfactory limb function (MSTS: 74 ± 17; TESS: 83 ± 15) and quality of life scores comparable to national norms, with notably higher mental health indices, highlighting their psychological resilience. Conclusions: Non-vascularized fibular graft reconstruction, despite high mechanical complication rates, significantly facilitates long-term functional recovery and psychological well-being. These findings emphasize the necessity of risk-adapted surgical strategies and long-term follow-up protocols to mitigate complications, optimize long-term function, and ultimately advance patient-centered care. Full article

Proppant flowback during the flowback phase after hydraulic fracturing in coal reservoirs critically impacts fracture conductivity and wellbore integrity. However, experimental studies on its critical conditions and controlling mechanisms within coal’s complex fracture networks are scarce compared to sandstone or shale. This study conducted physical simulation experiments using outcrop coal samples from the XD block in China and a modified fracture conductivity system. By establishing a determination method for the critical backflow rate (Q_c), the dynamic evolution process of proppant backflow—characterized by the stages of initial stability, critical instability, severe backflow, and re-equilibration—was revealed. The influences of proppant size, flowback fluid viscosity, proppant concentration, and effective stress on Q_c were systematically analyzed, and the relative weight of each influencing factor was quantified through orthogonal experimental design. Results show that proppant backflow initiates and concentrates preferentially at the fracture outlet region, implying a higher risk of proppant failure in the near-wellbore fracture section. The Q_c decreases with reducing proppant size, increasing flowback fluid viscosity, increasing proppant concentration, and decreasing effective stress, among which effective stress is identified as the dominant controlling factor. Furthermore, no necessary correlation is observed between Q_c and the critical backflow ratio, suggesting that the initiation threshold and post-instability flowback intensity are governed by different mechanisms. This work provides experimental data and a quantitative basis for optimizing flowback strategies in coal reservoir fracturing operations. Full article

Background/Objectives: Stereotactic body radiation therapy (SBRT) provides improved pain response and local control for spinal metastases. However, management of local failure after initial SBRT is challenging. We report institutional outcomes, dosimetry, and toxicity for reSBRT following SBRT. Methods: We retrospectively reviewed 61 lesions (55 patients) treated with reSBRT after prior SBRT. Both SBRT courses delivered a median dose of 27 Gy. Patients underwent clinical and radiological evaluation every three months. Toxicity was graded using CTCAE v5.0. Dosimetric parameters for the spinal cord (SC), cauda equina (CE), planning organ-at-risk volumes (PRV), and thecal sac were converted to equivalent dose in 2 Gy fractions (EQD₂) using the linear–quadratic model (α/β = 2). Results: Median follow-up was 10.3 months. Forty lesions (65%) were cervicothoracic and 21 (35%) were lumbosacral. One- and two-year overall survival (OS) were 45% and 29%, respectively, and one- and two-year local control (LC) were 89% and 88%, respectively. Gastrointestinal primary tumors were associated with inferior LC (HR 2.41, 95% CI 1.11–5.23, p = 0.026). Fifteen patients (27%) reported myelitis/neuropathic symptoms during follow-up; four (7%) developed new post-radiation myelitis or neuropathy (RMN) without radiologic progression. Five patients (9%) developed vertebral compression fractures (VCF). Cumulative EQD₂ was not significantly associated with RMN (p = 0.344); all affected patients had thecal sac EQD₂ > 95.5 Gy and relevant nerve roots EQD₂ > 108 Gy. Conclusions: ReSBRT provided a favorable LC with acceptable toxicity. High cumulative dose to the thecal sac and nerve roots may contribute to neurologic toxicity as peripheral nerve injury. Full article

This study investigates the fracture initiation and propagation mechanisms of continuously reinforced concrete–asphalt (CRC+AC) composite pavements under the synergistic effects of diurnal temperature fluctuations and non-uniform tire loading. A three-dimensional (3D) thermo-mechanical coupled finite element (FE) model was developed, with its underlying mechanical framework validated through laboratory-scale model tests conducted at 20 °C. The experimental results, involving strain monitoring at varying depths, demonstrated a high degree of consistency with numerical predictions in terms of spatial strain distribution, thereby ensuring the model’s reliability in capturing interlayer load-transfer efficiency. Building upon this validated mechanical foundation, numerical simulations were extended to analyze the low-temperature fracture response. The numerical results indicate that the maximum longitudinal and transverse tensile stresses in the asphalt layer are concentrated at the pavement surface, whereas the maximum shear stress occurs at a depth of 2–3 cm near the leading and trailing edges of the wheel load. Under low-temperature gradients, the Mode I stress intensity factor (K_I) at the crack tip exhibits a distinct diurnal opening–closing–reopening pattern, peaking at approximately 220 kPa·m^1/2 during the early morning hours (05:00–06:00). Furthermore, numerical simulations reveal the significant sensitivity of shear-sliding to axle loads; specifically, the peak Mode II stress intensity factor (K_II) increases monotonically from 190 to 230 kPa·m^1/2 as the axle load rises from 10 t to 16 t. Under non-uniform contact pressure, longitudinal cracking is primarily characterized by a mixed Mode I and Mode II mechanism driven by coupled tensile and shear stresses, whereas transverse cracking is dominated by Mode II shear failure. These findings suggest that implementing targeted traffic restrictions for overloaded vehicles during identified high-risk time windows can significantly enhance the structural durability and service life of composite pavements in cold regions. Full article