Local Failure Research Articles

Bi-metallic lattice structures manufactured via an intralayer multi-material powder bed fusion method

The laser powder bed fusion technology is widely utilized for manufacturing intricate metallic components, overcoming design limitations inherent in traditional subtractive methods. Recent advancements in powder bed fusion have extended to the creation of metal multi-material structures, allowing for functionally graded and tailored properties within a single component. While functionally graded lattice structures are commonly achieved by spatially varying the relative density and/or topology of the lattice, multi-material lattices are rarely studied particularly via metal additive manufacturing where multi-material methods are a relatively recent development. This study applies an accessible enhancement to a standard powder bed fusion system for multi-material additive manufacturing, and investigates printed and heat-treated bi-metallic lattices containing regions of both 316L and 17–4PH stainless steel. The bi-material interface is examined in lattice and bulk samples, and the compression behaviour of bi-metallic lattices is investigated experimentally and computationally. The material interface is shown to be robust as built and under loading, and the bi-metallic lattices exhibit greater energy absorption than single-material samples. The inclusion of the ductile 316L in bi-metallic lattices also delays the propagation of local failure and shear bands initiated in the more brittle 17–4PH. Finite element analysis simulates the lattice compression which includes strut fracture and as-built diameters informed by computed tomography, enabling further investigation and analysis of multi-material lattice designs. This work demonstrates the benefit of multi-material additive manufacturing by providing improved performance over single-material designs.

Radiomics-based prediction of local control in patients with brain metastases following postoperative stereotactic radiotherapy.

Surgical resection is the standard of care for patients with large or symptomatic brain metastases (BMs). Despite improved local control after adjuvant stereotactic radiotherapy, the risk of local failure (LF) persists. Therefore, we aimed to develop and externally validate a pre-therapeutic radiomics-based prediction tool to identify patients at high LF risk. Data were collected from A Multicenter Analysis of Stereotactic Radiotherapy to the Resection Cavity of BMs (AURORA) retrospective study (training cohort: 253 patients from 2 centers; external test cohort: 99 patients from 5 centers). Radiomic features were extracted from the contrast-enhancing BM (T1-CE MRI sequence) and the surrounding edema (T2-FLAIR sequence). Different combinations of radiomic and clinical features were compared. The final models were trained on the entire training cohort with the best parameter set previously determined by internal 5-fold cross-validation and tested on the external test set. The best performance in the external test was achieved by an elastic net regression model trained with a combination of radiomic and clinical features with a concordance index (CI) of 0.77, outperforming any clinical model (best CI: 0.70). The model effectively stratified patients by LF risk in a Kaplan-Meier analysis (P < .001) and demonstrated an incremental net clinical benefit. At 24 months, we found LF in 9% and 74% of the low and high-risk groups, respectively. A combination of clinical and radiomic features predicted freedom from LF better than any clinical feature set alone. Patients at high risk for LF may benefit from stricter follow-up routines or intensified therapy.

Disease Control and Toxicity Outcomes after Stereotactic Ablative Radiation Therapy for Recurrent and/or Metastatic Cancers in Young-Adult and Pediatric Patients.

Pediatric patients with metastatic and/or recurrent solid tumors have poor survival outcomes despite standard-of-care systemic therapy. Stereotactic ablative radiation therapy (SABR) may improve tumor control. We report the outcomes with the use of SABR in our pediatric solid tumor population. This was a single-institutional study in patients < 30 years treated with SABR. The primary endpoint was local control (LC), while the secondary endpoints were progression-free survival (PFS), overall survival (OS), and toxicity. The survival analysis was performed using Kaplan-Meier estimates in R v4.2.3. In total, 48 patients receiving 135 SABR courses were included. The median age was 15.6 years (interquartile range, IQR 14-23 y) and the median follow-up was 18.1 months (IQR: 7.7-29.1). The median SABR dose was 30 Gy (IQR 25-35 Gy). The most common primary histologies were Ewing sarcoma (25%), rhabdomyosarcoma (17%), osteosarcoma (13%), and central nervous system (CNS) gliomas (13%). Furthermore, 57% of patients had oligometastatic disease (≤5 lesions) at the time of SABR. The one-year LC, PFS, and OS rates were 94%, 22%, and 70%, respectively. No grade 4 or higher toxicities were observed, while the rates of any grade 1, 2, and 3 toxicities were 11.8%, 3.7%, and 4.4%, respectively. Patients with oligometastatic disease, lung, or brain metastases and those who underwent surgery for a metastatic site had a significantly longer PFS. LC at 1-year was significantly higher for patients with a sarcoma histology (95.7% vs. 86.5%, p = 0.01) and for those who received a biological equivalent dose (BED10) > 48 Gy (100% vs. 91.2%, p = 0.001). SABR is well tolerated in pediatric patients with 1-year local failure and OS rates of <10% and 70%, respectively. Future studies evaluating SABR in combination with systemic therapy are needed to address progression outside of the irradiated field.

Early outcomes of MR-guided SBRT for patients with recurrent pancreatic adenocarcinoma

BackgroundLocal treatment options for locally recurrent pancreatic adenocarcinoma (LR-PAC) are limited, with median survival time (MST) of 9–13 months (mos) following recurrence. MRI-guided stereotactic body radiation therapy (MRgSBRT) provides the ability to dose escalate while sparing normal tissue. Here we report on the early outcomes of MRgSBRT for LR-PAC.MethodsPatients with prior resection of pancreatic adenocarcinoma with local recurrence treated with MRgSBRT at a single tertiary referral center from 5-2021 to 2-2023 were identified from our prospective database. MRgSBRT was delivered to 40–50 Gy in 4–5 fractions with target and OAR delineation per institutional standards. Endpoints included local control per RECIST v1.1, distant failure, overall survival (OS), and acute and chronic toxicities per Common Terminology Criteria for Adverse Events, v5.ResultsFifteen patients with LR-PAC were identified with median follow-up of 10.6 mos (2.8–26.5 mos) from MRgSBRT. There were 8 females and 7 males, with a median age of 69 years (50–83). One patient underwent neoadjuvant radiation for 50.4 Gy in 28 fractions followed by resection, and one underwent adjuvant radiation for 45 Gy in 25 fractions prior to recurrence. MRgSBRT was delivered a median of 18.8 mos (3.5–52.8 mos) following resection. OS following recurrence at 6 and 12 mos were 87% and 51%, respectively, with a median survival time of 14.1 mos (3.2–27.4 mos). Three patients experienced local failure at 5.9, 7.8, and 16.6 months from MgSBRT with local control of 92.3% and 83.9% at 6 and 12 months. 10 patients experienced distant failure at a median of 2.9 mos (0.3–6.7 mos). Grade 1–2 acute GI toxicity was noted in 47% of patients, and chronic GI toxicity in 31% of patients. No grade > 3 toxicities were noted.ConclusionsThis is the first report on toxicity and outcomes of MRgSBRT for LR-PAC in the literature. MRgSBRT is a safe, feasible treatment modality with the potential for improved local control in this vulnerable population. Future research is necessary to better identify which patients yield the most benefit from MRgSBRT, which should continue to be used with systemic therapy as tolerated.Trial Registration: Jefferson IRB#20976, approved 2/17/21.

Out-Patient versus In-Patient Arteriovenous Fistula Creation for Dialysis: Assessing Cost-Effectiveness Alongside Clinical Implications.

(1) Background: The surgical procedure to create an arteriovenous fistula (AVF) can be performed in either an ambulatory or in-patient hospital setting, depending on the case's complexity, the anesthesia type used, and the patient's comorbidities. The main scope of this study is to assess the cost-effectiveness and clinical implications of surgically creating an AVF in both ambulatory and in-hospital settings. (2) Methods: We conducted a retrospective observational study, in which we initially enrolled all patients with end-stage kidney disease (ESKD) admitted to the Vascular Surgery Department, Emergency County Hospital of Targu Mures, Romania, to surgically create an AVF for dialysis, between January 2020 and December 2022. The primary endpoint of this study is to assess the cost-effectiveness of surgically creating an AVF in an ambulatory vs. in-hospital setting by comparing the costs required for the two types of admissions. Further, the 116 patients enrolled in this study were divided into two groups based on their preference for hospitalization: out-patients and in-patients. (3) Results: Regarding in-patient comorbidities, there was a higher prevalence of peripheral artery disease (PAD) (p = 0.006), malignancy (p = 0.020), and previous myocardial infarction (p = 0.012). In addition, active smoking (p = 0.006) and obesity (p = 0.018) were more frequent among these patients. Regarding the laboratory data, the in-patients had lower levels of white blood cells (WBC) (p = 0.004), neutrophils count (p = 0.025), lymphocytes (p = 0.034), and monocytes (p = 0.032), but there were no differences between the two groups regarding the systemic inflammatory biomarkers or the AVF type. Additionally, we did not register any difference regarding the outcomes: local complications (p = 0.588), maturation failure (p = 0.267), and primary patency (p = 0.834). In our subsequent analysis, we discovered no significant difference between the hospitalization type chosen by patients regarding AVF primary patency failure (p = 0.195). We found no significant association between the hospitalization type and the recorded outcomes (all ps > 0.05) in both multivariate linear regression and Cox proportional hazard analysis. (4) Conclusions: In conclusion, there are no significant differences in the clinical implications, short-term and long-term complications of AVF for out-patient and in-patient admissions. Additionally, we found no variation in the costs associated with laboratory tests and surgical supplies for an AVF creation. Therefore, it is safe to perform ambulatory AVFs, which can reduce the risk of hospital-acquired infections and provide greater comfort to the patient.

Mechanical behavior evolution and failure characteristics of saturated and dry rocks under different water pressure environments

A complex and changeable water environment is a key factor for safe rock engineering. Variations in water distribution and pressure pose serious challenges in evaluating rock properties and failure modes. To investigate the effect of real water‒rock interactions on rock mechanical behavior, the self-developed hydraulic loading test equipment was designed. A series of mechanical experiments (unjacketed) were carried out on three representative types of rocks under different water pressure environments, and the jacketed test was also performed for the saturated rocks. The experimental results showed that with increasing water confining pressure, the stress‒strain curve of the saturated rocks increased, while that of the dry rocks first decreased and then increased, and that of the sandstone became more obvious. Furthermore, when the water confining pressure increased, the peak stress and elastic modulus of the saturated rocks increased linearly, and those of the dry rocks first decreased and then increased more sharply. Interestingly, the water confining pressure weakened the local tensile failure and aggravated the shear failure. The relationship between the water confining pressure and strength also indicated that the change of saturated rocks more slowly when in contact with the water confining pressure. From the above results, the pore water pressure correction coefficients (μ) of sandstone, marble and granite were 0.98, 0.96 and 0.93, respectively, in the water pressure environment and rock connection. The failure mechanism of saturated rocks is similar to that of rocks without confining pressure due to the balance of the water confining pressure and pore water pressure, and pore water pressure mainly acts as piestic water. For dry rocks, the penetration of pore water firstly weakens the mechanical properties of rocks when pore water pressure is smaller. A greater confining pressure enhances the role of traditional confining pressure for granite and dry rocks.

Improving the local and distortional resistance of CFS trapezoidal self-supporting roof members

This paper reports the development, numerical implementation and application of a methodology to perform the multi-objective optimisation, with respect to local and distortional failures, of cold-formed steel (CFS) trapezoidal cross-section shapes used in members belonging to self-supporting roof systems and manufactured by bending the steel sheets with roll-forming machines. Initially, a brute-force approach is adopted to search for optimal unstiffened cross-section shapes of members subjected to positive (sagging) and negative (hogging) bending moments. Next, an optimisation procedure based on a Genetic Algorithm (GA) is employed to find stiffened cross-sections that (i) outperform the original (plain/unstiffened) ones, as far as the resistance against local and distortional failures is concerned, and (ii) can be fabricated with minimal additional cost, through the sole addition of small intermediate stiffeners, whose possible locations are pre-defined in accordance with a map of executable fold-line positions – the original cross-section typology, overall dimensions and wall angles are retained. The design approach adopted to estimate the member ultimate strengths is based on the Direct Strength Method (DSM), and Generalised Beam Theory (GBT) is used to calculate the elastic buckling stresses due to bending. The application and capabilities of the proposed methodology are illustrated, by means of numerical results presented in terms of cross-section families belonging to optimal Pareto Fronts – an excellent performance of the procedure was found in all cases.

Structure-specific rigid dose accumulation dosimetric analysis of ablative stereotactic MRI-guided adaptive radiation therapy in ultracentral lung lesions.

Definitive local therapy with stereotactic ablative radiation therapy (SABR) for ultracentral lung lesions is associated with a high risk of toxicity, including treatment related death. Stereotactic MR-guided adaptive radiation therapy (SMART) can overcome many of the challenges associated with SABR treatment of ultracentral lesions. We retrospectively identified 14 consecutive patients who received SMART to ultracentral lung lesions from 10/2019 to 01/2021. Patients had a median distance from the proximal bronchial tree (PBT) of 0.38 cm. Tumors were most often lung primary (64.3%) and HILUS group A (85.7%). A structure-specific rigid registration approach was used for cumulative dose analysis. Kaplan-Meier log-rank analysis was used for clinical outcome data and the Wilcoxon Signed Rank test was used for dosimetric data. Here we show that SMART dosimetric improvements in favor of delivered plans over predicted non-adapted plans for PBT, with improvements in proximal bronchial tree DMax of 5.7 Gy (p = 0.002) and gross tumor 100% prescription coverage of 7.3% (p = 0.002). The mean estimated follow-up is 17.2 months and 2-year local control and local failure free survival rates are 92.9% and 85.7%, respectively. There are no grade ≥ 3 toxicities. SMART has dosimetric advantages and excellent clinical outcomes for ultracentral lung tumors. Daily plan adaptation reliably improves target coverage while simultaneously reducing doses to the proximal airways. These results further characterize the therapeutic window improvements for SMART. Structure-specific rigid dose accumulation dosimetric analysis provides insights that elucidate the dosimetric advantages of SMART more so than per fractional analysis alone.

Investigation on damage evolution mechanism of various FRP strengthened concrete subjected to chemical-freeze-thaw coupling erosion.

The corrosion resistance of FRP-reinforced ordinary concrete members under the combined action of harsh environments (i.e., alkaline or acidic solutions, salt solutions) and freeze-thaw cycles is still unclear. To study the mechanical and apparent deterioration of carbon/basalt/glass/aramid fiber cloth reinforced concrete under chemical and freeze-thaw coupling. Plain concrete blocks and FRP-bonded concrete blocks were fabricated. The tensile properties of the FRP sheet and epoxy resin sheet before and after chemical freezing, the compressive strength of the FRP reinforced test block, and the bending capacity of the prismatic test block pasted with FRP on the prefabricated crack side were tested. The deterioration mechanism of the test block was analyzed through the change of surface photos. Based on the experimental data, the Lam-Teng constitutive model of concrete reinforced by alkali-freeze coupling FRP is modified. The results indicate that, in terms of apparent properties, with the increase in the duration of chemical freeze-thaw erosion, the surface of epoxy resin sheets exhibits an increase in pores, along with the emergence of small cracks and wrinkles. The texture of FRP sheets becomes blurred, and cracks and wrinkles appear on the surface. In terms of failure modes, as the number of chemical coupling erosion cycles increases, the location of failure in epoxy resin sheets becomes uncertain, and the failure plane tilts towards the direction of the applied load. The failure mode of FRP sheets remains unchanged. However, the bonding strength between FRP sheets and concrete decreases, resulting in a weakened reinforcement effect. In terms of mechanical properties, FRP sheets undergo the most severe degradation in the coupled environment of acid freeze-thaw cycles. Among them, GFRP experiences the largest degradation in tensile strength, reaching up to 30.17%. In terms of tensile performance, the sheets rank from highest to lowest as follows: CFRP, BFRP, AFRP, and GFRP.As the duration of chemical freeze-coupled erosion increases, the loss rate of compressive strength for specimens bonded with CFRP is the smallest (9.62% in salt freeze-thaw environment), while the loss rate of bearing capacity is higher for specimens reinforced with GFRP (33.8% in acid freeze-thaw environment). In contrast, the loss rate of bearing capacity is lower for specimens reinforced with CFRP (13.6% in salt freeze-thaw environment), but still higher for specimens reinforced with GFRP (25.8% in acid freeze-thaw environment).

Research on Lateral Resistance Performance of Prestressed Cross-Laminated Timber-Concrete Composite Structures under Reciprocating Loads.

Cross-Laminated Timber (CLT) and concrete composite structures represent an architectural system that integrates the strengths of both materials. In this innovative configuration, the CLT and concrete collaborate synergistically, harnessing their individual merits to achieve enhanced structural performance and functionality. Specifically, the CLT offers a lightweight design, superior bending resistance, and immense engineering plasticity, while concrete boasts exceptional compressive strength and durability. This study investigates the mechanical performance of CLT-concrete composite structures through quasi-static reciprocating loading tests in three full-scale CLT shear wall samples. Designed with varying initial prestressing forces and dimensions of the CLT panel, the prestressed CLT-concrete structures demonstrated a reduced dependence on the steel nodes, resulting in an increase in yield load, yield displacement, and maximum load-carrying capacity. Maximum capacity increased by 39.8% and 33.7% under initial prestressing forces of 23 kN and 46 kN on steel strands. Failure occurred due to localized compressive failure on prestressed steel strands and anchor plates. ABAQUS finite element analysis established three refined models, revealing that the increased initial prestressing force moderately enhanced stiffness but reduced ductility under similar cross-sectional dimensions. Furthermore, under consistent CLT material, dimensions, prestressing force, and loading conditions, prestressed CLT-concrete structures exhibited a higher maximum load-bearing capacity than prestressed CLT-steel composite structures. This study proposes structural design recommendations based on experimental and simulation results, incorporating specific assumptions.

Public (Trust) Rights in Open Space: Day v Shropshire Council

In Day v Shropshire Council (Day), the Supreme Court considered the effect of a statutory trust under section 10 of the Open Spaces Act 1906 on a subsequent purchaser. Finding for the claimant, a local resident resisting development, the Supreme Court unanimously held that the local authority's failure to give notice and consider objections under the Local Government Act 1972 meant that the site's transfer into private ownership did not extinguish public trust rights to open space, binding the disponee. This note suggests that the decision in Day is to be welcomed, providing clarity on long‐established legislative provisions that protect open spaces, even when sites are not identified as such in planning processes. The note applauds the clarity of the Supreme Court's resistance to drawing on the law of trusts when interpreting statutory provisions and commends the ease with which the Supreme Court confirmed the co‐existence of public and private rights in land. The note also considers how Day illustrates the nature of local authority land ownership, a live issue at the boundary between land and administrative law, of particular interest at a time when local authorities are disposing of surplus open spaces for development.

Systematic evaluation and meta-analysis of the prognosis of down-staging human papillomavirus (HPV) positive oropharyngeal squamous cell carcinoma using cetuximab combined with radiotherapy instead of cisplatin combined with radiotherapy.

To evaluate the efficacy and safety of cetuximab instead of cisplatin in combination with downstaging radiotherapy for papillomavirus (HPV) positive oropharyngeal squamous cell carcinoma (HPV+ OPSCC). Meta-analysis and systematic evaluation. The PubMed, Embase, Web of Science, and Cochrane library databases were searched up to June 8, 2023, as well as Clinicaltrials.gov Clinical Trials Registry, China Knowledge Network, Wanfang Data Knowledge Service Platform, and Wiprojournal.com. Randomized controlled trials reporting results of standard regimens of cetuximab + radiotherapy vs cisplatin + radiotherapy in treating HPV+ OPSCC were included. The primary outcomes of interest were overall survival (OS), progression-free survival (PFS), local regional failure rate (LRF), distant metastasis rate (DM), and adverse events (AE). Two reviewers independently extracted data and assessed the risk of bias of the included studies. The HR and its 95% CI were used as the effect analysis statistic for survival analysis, while the OR and its 95% CI were used as the effect analysis statistic for dichotomous variables. These statistics were extracted by the reviewers and aggregated using a fixed-effects model to synthesise the data. A total of 874 relevant papers were obtained from the initial search, and five papers that met the inclusion criteria were included; a total of 1,617 patients with HPV+ OPSCC were enrolled in these studies. Meta-analysis showed that OS and PFS were significantly shorter in the cetuximab + radiotherapy group of patients with HPV+ OPSCC compared with those in the conventional cisplatin + radiotherapy group (HR = 2.10, 95% CI [1.39-3.15], P = 0.0004; HR = 1.79, 95% CI [1.40-2.29], P < 0.0001); LRF and DM were significantly increased (HR = 2.22, 95% CI [1.58-3.11], P < 0.0001; HR = 1.66, 95% CI [1.07-2.58], P = 0.02), but there was no significant difference in overall grade 3 to 4, acute and late AE overall (OR = 0.86, 95% CI [0.65-1.13], P = 0.28). Cisplatin + radiotherapy remains the standard treatment for HPV+ OPSCC. According to the 7th edition AJCC/UICC criteria, low-risk HPV+ OPSCC patients with a smoking history of ≤ 10 packs/year and non-pharyngeal tumors not involved in lymphatic metastasis had similar survival outcomes with cetuximab/cisplatin + radiotherapy. However, further clinical trials are necessary to determine whether cetuximab + radiotherapy can replace cisplatin + radiotherapy for degraded treatment in individuals who meet the aforementioned characteristics, particularly those with platinum drug allergies. CRD42023445619.

Reduced stress propagation leads to increased mechanical failure resistance in auxetic materials

Materials with a negative Poisson ratio have the counterintuitive property of expanding laterally when they are stretched longitudinally. They are accordingly termed auxetic, from the Greek auxesis meaning to increase. Experimental studies have demonstrated auxetic materials to have superior material properties, compared with conventional ones. These include synclastic curvature, increased acoustic absorption, increased resilience to material fatigue, and increased resistance to mechanical failure. Until now, the latter observations have remained poorly understood theoretically. With this motivation, the contributions of this work are twofold. First, we elucidate analytically the way in which stress propagates spatially across a material following a localized plastic failure event, finding a significantly reduced stress propagation in auxetic materials compared with conventional ones. In this way, a plastic failure event occurring in one part of a material has a reduced tendency to trigger knock-on plastic events in neighboring regions. Second, via the numerical simulation of a lattice elastoplastic model, we demonstrate a key consequence of this reduced stress propagation to be an increased resistance to mechanical failure. This is seen not only via an increase in the externally measured yield strain, but also via a decreased tendency for plastic damage to percolate internally across a sample in catastrophic system-spanning clusters.

Impact characterization of coral aggregate reinforced concrete beam: A 3D numerical study

Coral aggregate concrete (CAC), an innovative construction material, utilizes abundant marine resources, including coral aggregates and seawater. In the realm of reef engineering, CAC is widely used in structural elements such as reinforced beams and columns. This paper presents a three-dimensional (3D) mesoscale model to assess the impact behavior of coral aggregate reinforced concrete beams (CARCB), incorporating the heterogeneity characteristics of CAC and the explicit simulation of reinforcement components. The 3D mesoscale modelling approach developed in this paper was validated by previous experimental data of CARCB, and used for extensive parametric studies evaluating effects such as concrete strength grade, reinforcement ratio, and impact velocity on the static and dynamic bending behaviors of CARCB. Finally, based on the mesoscopic cracking process and damage patterns of CARCB under static and dynamic loads, this study illustrates the corresponding macroscopic mechanical behaviors and failure mechanisms. Results indicate that the predominant forms of flexural failure in CARCBs are tensile cracking in the mid-span region and diagonal shear cracking. Results demonstrate that the predominant forms of flexural failure in CARCBs are tensile cracking in the mid-span region and diagonal shear cracking. Specifically, local bending failures and symmetrical diagonal shear cracks were evident in the CARCBs subjected to dynamic loads, closely resembling those in ordinary concrete beams. With increasing concrete strength grades (C30 to C60) and reinforcement ratios (0.9 %–1.7 %), a significant reduction in the mid-span ultimate deflection of CARCB is observed, indicating enhanced impact resistance. Additionally, as the impact velocity increases from 1 m/s to 50 m/s, the mid-span ultimate deflection of CARCB is magnified by a factor of approximately 200, indicating intensified dynamic damage to CARCB with increasing impact velocities.

Infrared temperature evolution law and thermal effect mechanism of concrete impact failure

Concrete impact failure can occur quickly and cause severe failure, which is of great significance for effective monitoring of concrete impact failure. Infrared thermal imaging technology possesses the merits of high sensitivity, noncontact, and nondestructive monitoring, rendering it extensively employed in monitoring the stability of concrete structures. However, the infrared radiation temperature (IRT) evolution law and thermal effect mechanism of concrete impact failure are not clear at present. In this study, infrared monitoring experiments were conducted on concrete impact failure and static load failure using drop hammer (DH) testing machines, pressure testing machines, and infrared thermal imagers. The infrared thermal images and the IRT change law of concrete subjected to DH impact failure were analysed. The infrared thermal effect difference and mechanism between DH impact and static load failure were compared. The results indicate that there is an infrared high-temperature point at the impact location of concrete DH impact failure, and both average infrared radiation temperature (AIRT) and maximum infrared radiation temperature (MIRT) increase suddenly. The increase in the MIRT is tens of times that of the AIRT. Compared with that of static load failure, the infrared high-temperature area of concrete DH impact failure is concentrated, while the IRT of static load failure increases overall, and the heating area is large. Moreover, the change in the IRT under DH impact failure is much greater than that under static load failure. The infrared thermal effect of concrete under DH impact failure was mainly composed of the thermoelastic effect, frictional thermal effect and tensile failure endothermic effect. The infrared data obtained for concrete impact failure should focus on the highest and lowest IRT change indicators. The highest IRT corresponds to the impact failure point, and the lowest IRT corresponds to the tensile failure position. The research results provide a new infrared thermal effect approach for monitoring the stability of concrete under impact failure.

On the data-driven description of lattice materials mechanics

In the emerging field of mechanical metamaterials, using periodic lattice structures as a primary ingredient is relatively frequent. However, the choice of aperiodic lattices in these structures presents unique advantages regarding failure, e.g., buckling or fracture, because avoiding repeated patterns prevents global failures, with local failures occurring in turn that can beneficially delay structural collapse. Therefore, it is expedient to develop models for computing efficiently the effective mechanical properties in lattices from different general features while addressing the challenge of presenting topologies (or graphs) of different sizes. In this paper, we develop a deep learning model to predict energetically-equivalent mechanical properties of linear elastic lattices effectively. Considering the lattice as a graph and defining material and geometrical features on such, we show that Graph Neural Networks provide more accurate predictions than a dense, fully connected strategy, thanks to the geometrically induced bias through graph representation, closer to the underlying equilibrium laws from mechanics solved in the direct problem. Leveraging the efficient forward-evaluation of a vast number of lattices using this surrogate enables the inverse problem, i.e., to obtain a structure having prescribed specific behavior, which is ultimately suitable for multiscale structural optimization problems.

Preoperative stereotactic radiosurgery for patients with 1-4 brain metastases: A single-arm phase 2 trial outcome analysis (NCT03398694).

Stereotactic radiosurgery (SRS) following surgical resection is the standard of care for patients with symptomatic oligo brain metastasis (BM), however, it is associated with 10-15% local failure. Targeting a resection cavity is imprecise, thus preoperative radiosurgery where the target is well-defined may be superior, however, the efficacy of preoperative SRS has not yet been tested in a clinical trial. We conducted a phase 2, single-arm trial of preoperative SRS followed by surgical resection in patients with 1-4 symptomatic oligo BMs (NCT03398694) with the primary objective of measuring 6-month local control (LC). SRS was delivered to all patients utilizing a gamma knife or linear accelerator as per RTOG-9005 dosing criteria [Shaw E, Scott C, Souhami L, et al. Single dose radiosurgical treatment of recurrent previously irradiated primary brain tumors and brain metastases: final report of RTOG protocol 90-05. Int J Radiat Oncol Biol Phys. 2000;47(2):291-298] based on tumor diameter with the exception that the largest lesion diameter treated was 5 cm with 15 Gy with all SRS treatment given in single fraction dosing. The trial screened 50 patients, 48 patients were treated under the protocol and 32 patients completed the entire follow-up period. Of all the patients who completed the follow-up period, the primary endpoint of 6-month LC was 100% (95% CI: 0.891-1.000; P = .005). Secondary endpoints, presented as medians, were overall survival (17.6 months), progression-free survival (5.3 months), distant in-brain failure (40.8% at 1 year), leptomeningeal failure (4.8% at 1 year), and radiation necrosis (7.7% at 1 year). Our data confirms superior local control in patients who received preoperative SRS when compared to historical controls. Further study with a larger randomized cohort of patients is warranted to fully understand the benefits of preoperative SRS.

Waveform Complexity and Positioning Analysis of Acoustic Emission Events during the Compression Failure Process of a Rock Burst Prone Sample

The localization results of acoustic emission (AE) events can reflect the location and pattern of burst-prone rock failures. However, event localization heavily depends on the quality of the original waveform of the sensor. Therefore, this study analyzed the AE waveform of a rock sample under compression to evaluate its failure localization and quality. From the research results, it could be seen that the initial failure was relatively calm, with clear take-off points, which can be better used for accurate AE event positioning. However, the later failure was severe, causing the take-off points of most sensors to be very unclear, and positioning methods that rely on take-off points cannot be used for positioning, let alone simply using the positioning results of the built-in software. This research result reminds researchers who use AE signals for event localization to first examine the quality and status of the original waveform, providing a basis for obtaining accurate localization results, in order to further accurately study the subsequent failure patterns. The above facts indicate that the initial failure is small and scattered, while the later failure is large and concentrated, with certain fractal characteristics.

Numerical investigation on the behaviour of Post-Tensioned Mechanically Stabilised Earth Walls (PT-MSEW)

This study reports on a numerical investigation on the behaviour of an innovative retaining wall system named Post Tensioned Mechanically Stabilised Earth Wall (PTMSEW). In the proposed system, Post-Tensioning (PT) technique was integrated into the common retaining wall and the Mechanically Stabilised Earth Wall (MSEW) construction method to improve the performance of MSEWs and limit their failure modes. The variables of this study were wall height, PT force, pre-cast segment size, surcharge load, foundation size, and soil reinforcement length. The study found that incorporating PT stress into the MSEW improved the performance of the retaining wall by decreasing horizontal displacement of the wall face, soil reinforcement tensile forces, and backfill settlements and significantly enhanced the passive resistance of the wall. The introduction of a small amount of PT force prevented local failures caused by the relative movement of face segments. It was observed that by applying only a small level of post-tensioning, the lateral load-carrying capacity and passive resistance of the proposed PT-MSEW system can be significantly improved over that of its conventional counterpart. This opens new possibilities for the use of MSEW in the construction of taller retaining walls.

Influence of pre-existing crack on rockburst characteristics in coal-rock combination: A laboratory investigation

The existing cracks in the roof rock are critical to stability of the coal-rock combination structure during mining activities, which is vital for safe exploitation in coal mines. However, the physical mechanisms by which pre-existing crack in the roof rock induces rockburst in coal mines are still poorly understood. In this study, to investigate the rockburst characteristics in an underground mine, triaxial compressive experiments on coal-rock combinations containing a pre-existing crack in the roof rock were carried out. Both mechanical and failure behaviours of composite specimen containing a pre-existing crack were analysed. The testing results showed that a pre-existing crack in roof significantly affects mechanical properties of combinations. The average peak stress and average elastic modulus of specimen exhibit an M-shaped change trend when dip angle is in a range of 0°–90°. The average peak strain increases before decreasing with increase in dip angle. In addition, the roof rock is more likely to fail when it contains a pre-existing crack. Both the initial failure location and failure pattern of combinations are highly related to angle of pre-existing crack. A novel rockburst model considering in-situ stress and pre-existing crack was proposed to determine the physical mechanism of rockburst. The findings are useful to understand characteristics and physical mechanism of rockburst in mine engineering.