Load Cases Research Articles

Biomechanical evaluation of the modified proximal femoral nail for the treatment of reverse obliquity intertrochanteric fractures

The best treatment method for reverse obliquity intertrochanteric fractures (ROIFs) is still under debate. Our team designed the modified proximal femoral nail (MPFN) specially for treating such fractures. The objective of this research was to introduce the MPFN device and compare the biomechanical properties with Proximal Femoral Nail Antirotation (PFNA) and InterTAN nail via finite element modelling. An AO/OTA 31-A3.1 ROIF model was established via Mimics software. Three implants were depicted and assembled on the ROIF models. The axial, bending, and torsion loads were simulated to test stress and displacement of three fixation models. Compared to the PFNA and InterTAN models, the MPFN model had more dispersed stress distribution under axial loads of 2,100 N. The MPFN showed lower von Mises stress on bones compared with that of PFNA and InterTAN in axial loads. In term of maximum displacement, the MPFN had a 12.6% reduction compared to the PFNA model in axial load case. In bending and torsion loads, the MPFN model also demonstrated better biomechanical properties than the PFNA and InterTAN models. The modified proximal femoral nail presented the best biomechanical performance, followed by the InterTAN nail, and the PFNA for fixing reverse obliquity intertrochanteric fractures. The MPFN has the potential to be a promising device for patients with ROIFs.

The optimal annual case volume for acute type A aortic dissection surgery in relation to long-term outcomes.

Previous analyses of the volume-outcome relationship have focused on short-term outcomes such as early mortality. The current study aims to update a novel statistical methodology, facilitating the evaluation of the relation between procedural volume and time-to-event outcomes such as long-term survival, using surgery for acute type A aortic dissection as an illustrative example. This study employed an existing dataset of type A dissection outcomes, retrieved from literature. Studies were included when reporting on annual case load and long-term survival, which served as the primary outcome of interest. Individual patient data were reconstructed from the included studies, and a hazard ratio was determined per study in relation to overall survival, after which the calculated hazard ratios were incorporated in a restricted cubic spline model, facilitating the application of the elbow-method. Fifty-two studies were included (n = 14878 patients), with a median follow-up of 5 years. One-, 3-, 5-, and 10-year survival of the overall cohort were 82% (95% CI 82-83%), 79% (95% CI 78-80%), 74% (95% CI 74-75%), and 60% (95% CI 59-62%) respectively. A significant non-linear volume-outcome relation for long-term survival was observed in both the unadjusted and adjusted analyses (p = 0.030 and p = 0.002), with an optimal annual case load of 32 cases/year (95% CI 31-33). Based on the available data, these findings imply that the annual case volume to achieve optimal long-term survival is located near a procedural volume of 32 cases/year. After accrual of more annual procedures, long-term survival may no longer significantly improve any further.

P1074 Deep dive into an IBD service: mapping and identifying service gaps

Abstract Background Similar to numerous IBD services, our institution experienced an increase in patient demand without a corresponding growth in capacity to meet this. The decision to implement a turnaround strategy for the IBD service was made by members of the MDT IBD team. A Transformation Director was commissioned to collaborate with the IBD team to identify service gaps. This project commenced in December 2023 and was concluded in March 2024. The aim was to undertake a deep dive into the IBD service, provide evidence for investment and to create a well-managed, preventative service that prioritises patient safety. Methods We developed a workforce model based around IBD and service and the interventions required to support different levels of IBD severity. The project consisted of four stages: cohort sizing, detailing the service; identifying service requirements and workforce gap analysis. Using EPIC© electronic patient records system we were able to identify and cohort the population, define disease severity in 10,500 patients. We were able to annualise the clinical case load, measure this against current provision and using evidence from national and international standards of care, clearly identify the required workforce and gap. Results A workforce gap of 6.7 WTE nurses was identified utilising Leary et al (2018) workforce modelling. Additional deficiencies included pharmacy time, consultant gastroenterologists and colorectal surgeons and lack of psychology provision. Through the application of faecal calportectin we were able to map the disease severity of the patient cohort. There is significant interest from health practitioners and policymakers in interventions to reduce the burden of inappropriate A&E attendances. We were able to retrospectively determine the number of A&E attendances over a 19 month period with associated inpatient stays and identify peaks in attendances and admissions correlating with staff departures and illness in the team (see Figure 1) Conclusion By identifying the gaps in service we have been able to engage with hospital executives with an acknowledgement of under investment in IBD services and a coordinated plan of recovery and implementation of several initiatives including an IBD Hot Clinic, additional IBD Advanced nurses and Consultant Gastroenterologist and colorectal surgeons and the introduction of psychological services. The implementation of the deep dive is expected to yield multiple benefits and provide preventative safe and high-quality care. The results have served as evidence for immediate and future investment in the IBD service. The model developed can be used across other long-term conditions and other IBD services. References Alison Leary, Isobel Mason, Geoffrey Punshon, ‘Modelling the Inflammatory Bowel Disease Specialist Nurse Workforce Standards by Determination of Optimum Caseloads in the UK’ Journal of Crohn’s and Colitis, Volume 12, Issue 11, November 2018, Pages 1295–1301, https://doi.org/10.1093/ecco-jcc/jjy106 Figure 1: Hospital admissions (NEL non elective admissions)

Comparison of the Performance of Nonlinear Time-Dependent Constitutive Models Calibrated with Minimal Test Data Applied to an Epoxy Resin.

Epoxy resins are extensively employed as adhesives and matrices in fibre-reinforced composites. As polymers, they possess a viscoelastic nature and are prone to creep and stress relaxation even at room temperature. This phenomenon is also responsible for time-dependent failure or creep fracture due to cumulative strain. Several constitutive equations have been used to describe the mechanical time-dependent response of polymers. These models have been proposed over the past six decades, with minimal direct and practical confrontation. Each model is associated with a specific application or research group. This work assesses the predictive performance of four distinct time-dependent constitutive models based on experimental data. The models were deemed sufficiently straightforward to be readily integrated into practical engineering analyses. A range of loading cases, encompassing constant strain rate, creep, and relaxation tests, were conducted on a commercial epoxy resin. Model parameter calibration was conducted with a minimum data set. The extrapolative predictive capacity of the models was evaluated for creep loading by extending the tests to five decades. The selected rheological models comprise two viscoelastic models based on Volterra-type integrals, as originally proposed by Schapery and Rabotnov; one viscoplastic model, as originally proposed by Norton and Bailey; and the Burger model, in which two springs and two dashpots are combined in a serial and parallel configuration. The number of model parameters does not correlate positively to superior performance, even if it is high. Overall, the models exhibited satisfactory predictive performance, displaying similar outcomes with some relevant differences during the unloading phases.

Blood Culture Use in Medical and Surgical Intensive Care Units and Wards

Blood culture (BC) use benchmarks in US hospitals have not been defined. To characterize BC use in adult intensive care units (ICUs) and wards in US hospitals. A retrospective cross-sectional study of BC use in adult medical ICUs, medical-surgical ICUs, medical wards, and medical-surgical wards from acute care hospitals from the 4 US geographic regions was conducted. Critical access hospitals, less than 6 months of BC data, and non-US hospitals were excluded. The study included BC use data from September 1, 2019, to August 31, 2021. Data were analyzed from February 23 to July 14, 2024. The primary outcome was BC use per 1000 patient-days. Adjusted means with 95% CIs were calculated using mixed-effects negative binomial regression models adjusted for unit type, hospital bed size, geographic region, seasonality, and state COVID-19 case load, with random intercepts accounting for clustering at unit and hospital levels. Secondary outcomes included blood culture positivity, single BCs, BC contamination, and minimum threshold for BC use where blood culture positivity would be optimized. A total of 362 327 blood cultures were analyzed from 27 medical ICUs, 35 medical-surgical ICUs, 121 medical wards, and 109 medical-surgical wards from 48 hospitals in 19 states and the District of Columbia. The adjusted mean BC use per 1000 patient-days was 273.1 (95% CI, 270.2-275.9) for medical ICUs, 146.0 (95% CI, 144.5-147.5) for medical-surgical ICUs, 80.3 (95% CI, 79.8-80.7) for medical wards, and 65.1 for medical-surgical wards. Blood culture use was significantly higher across all 4 unit types in hospitals with more than 500 beds compared with 500 or less beds and in the West-Midwest compared with other regions. Single blood culture and positive blood culture rates were below 10% across all 4 unit types. Of the 292 units, 97% had a mean BC contamination rate within 3% of the recommended threshold, and 51% were within 1%. The minimum BC use thresholds (ie, BC use below this number may represent undertesting) were 120 BCs per 1000 patient-days for medical ICUs, 80 BCs per 1000 patient-days for medical-surgical ICUs, and 30 BCs per 1000 patient-days for medical-surgical wards. The findings of this study suggest that blood culture positivity may help determine appropriate BC use for individual unit types.

Immediate repair of the recurrent laryngeal nerve during thyroid surgery via a tension-free end-to-side anastomosis with the Vagus.

The unprecedented technical and technological evolution in thyroid surgery has labelled it as an extremely safe and efficient procedure, and indeed "typifies perhaps better than any other operation the supreme triumph of the surgeon's art."-William Halsted, 1852-1922. Surgeon's experience reflected by annual case load is the most important denominator in thyroid surgery. Nevertheless, even high-volume thyroid surgeons in high-volume centres are not immune to its complications. Despite the advances in surgical technology and techniques, recurrent laryngeal nerve (RLN) injury is still a wellknown complication of thyroid surgery. The considerable postoperative morbidity associated with it and its impact on the patient's overall quality of life make it a dreadful complication of thyroid surgery and a common cause of malpractice accusations. Intraoperative RLN reconstruction is not widely used in clinical practice, but the evidence so far makes it a viable and safe alternative to traditional techniques with better long-term results, as it prevents the occurrence of atrophy of the vocal cord and should be considered in the operating room if possible. Furthermore, immediate reconstruction of an intraoperatively detected RLN injury has been strongly recommended by the 2020 American Association of Endocrine Surgeons guidelines. After neurorrhaphy, RLN regeneration occurs but in a random, misdirected fashion resulting in simultaneous contraction of abductors and adductors. Therefore, normal vocal fold function/mobility is typically not restored. The objective of this technical note is to describe a novel immediate RLN repair technique that has a strong propensity to regenerate and reinnervate laryngeal muscles and potentially restore laryngeal mobility.

Analysis and optimization for buckling behavior of functionally graded face layers and porous core sandwich plates resting on pasternak elastic foundation

In this paper, the first-order shear deformation theory (FSDT) is employed to derive analytical solutions for the buckling analysis of functionally graded material—porous—functionally graded material (FGM-porous-FGM) sandwich plate resting on Pasternak elastic foundation. The top and bottom layers of the plate consist of functionally graded materials that vary according to the exponential law along the thickness direction, while the core layer is composed of a porous material. The governing equations are derived by using the principle of minimum total potential energy. Based on the Navier’s solution, the displacements are obtained to satisfy the boundary conditions. The results are then compared with existing published literature showing the accuracy of the proposed solutions. Moreover, parametric studies investigate the effects of material parameters, geometric dimensions, foundation coefficients and face-core-face thickness ratios on the critical buckling load of the rectangular FGM-porous-FGM sandwich plate. In the case of uniaxial loading, the critical bucking load is almost twice for the case of biaxial loading, no matter the value of volume fraction index. For all the cases of face-core-face thickness ratio, the biaxial critical buckling load linearly depends on the porosity coefficient. The porosity coefficient is crucial when and only when the volume of the core is almost eight times bigger than the volume of the face layer. Optimization studies are then presented in order to: (i) maximize the critical buckling load and (ii) optimize the input variables corresponding to a given value of the critical buckling load. The proposed study aims to provide valuable insights into the design and application of FGM-porous-FGM sandwich plates in various engineering fields, contributing to the development of more resilient and efficient structural components.

Numerical Prediction of Fatigue Life for Landing Gear Considering the Shock Absorber Travel

Due to the complexity of the landing gear’s (LG) structural integrity and its loads under various static or dynamic working conditions, the fatigue life assessment for LG is a highly challenging task. On the basis of the whole geometric model of a large passenger aircraft’s main landing gear (MLG), the quasi-static finite element model (FEM) of the whole MLG is established, and the high-cycle fatigue issue of the Main Fitting (MF) is studied by considering the variation in shock absorber travel (SAT). Firstly, the ground loads under actual fatigue conditions are equivalently converted into the forces acting on the center of the left and right axles of the MLG, and based on these spatial force decompositions, the magnitude and direction of the load for 12 different basic unit load cases (ULC) are obtained. That is, the stress of the MLG under actual fatigue conditions can be obtained by superimposing these ULCs. Then, considering that the SAT of the MLG varies under different fatigue conditions, and to reduce the number of finite element (FE) simulations, this article simplifies all the SAT experienced by the MLG into seven specific values, so as to establish seven quasi-static FEMs of the MLG with the specified stroke of the shock absorber. In this way, the fatigue stress of the MLG with any actual SAT can be obtained by interpolating the stress components of the seven FEMs. Only 84 FE simulations are needed to efficiently obtain the fatigue stress spectra from the ground load spectra. Finally, according to the material S-N curve and Miner’s damage accumulation criterion, evaluate the fatigue life of the Main Fitting. The results of the stress component interpolation and superposition method show that at least five different SATs of the whole MLG’s FEM are needed to effectively convert the fatigue loads into a stress spectrum. The fatigue life prediction results indicate that the minimum lifespan of the MF is 53164 landings, which means that the fatigue life meets the requirement design.

Gradient-based structural optimization of a wind turbine blade root section including high-cycle fatigue constraints

Under the modern design paradigm of wind turbines, the continuous drive towards lower costs through longer blades is raising serious challenges in design, and structural optimization is key to solving the problems effectively. This article focuses on the challenging structural optimization of wind turbine blade root sections, which is scarcely treated in the literature owing to the complex and computationally expensive critical criteria, i.e. buckling, static failure and fatigue damage. The root is parametrized with 1894 thickness design variables and, to solve such an optimization problem efficiently, an adjoint gradient-based framework is proposed, which includes all the criteria mentioned for twelve load cases. Fatigue is notoriously difficult owing to its highly nonlinear behaviour, and its inclusion in the adjoint optimization framework for wind turbine blade optimization is a novelty. The resulting optimization behaviour, laminate layup and structural response are all illustrated, showing many active constraints at convergence, and a significant reduction in mass.

Loading rate, geometry, and damage state influence vertical extraction biomechanics in an ex vivo swine dental model.

Validated models describing the biomechanics of tooth extraction are scarce. This study seeks to perform experimental and numerical characterization of vertical tooth extraction biomechanics in swine incisors with imposed vertical extraction loads. Imaging analysis related mechanical outcomes to tooth geometry and applied loading rate. Then, the predictive capabilities of the developed finite element analysis (FEA) models were demonstrated by testing different loading scenarios and validating the results against experimental equivalents. Simulated vertical extractions were performed on partial swine central incisors (n = 49) and studied for peak extraction force and dental complex stiffness. Post-extraction µCT images were obtained to measure root surface attachment area (RSAA) and observe patterns of periodontal ligament (PDL) rupture. Crosshead force-displacement data was used in an inverse finite element analysis (IFEA) to verify parameters for the PDL in an axisymmetric model of tooth extraction. New force-hold loading protocols were devised in silico and validated in a series of tests on swine incisors to demonstrate the predictive efficacy of the finite element model. Force-hold loading on an initially-damaged PDL was also simulated. Reductions in loading rate and RSAA were found to significantly reduce peak extraction forces by 98N-120N. Increases in instantaneous stiffness during loading were associated with increases in loading rate. Inverse finite element solutions demonstrated consistent PDL parameters across loading cases. Force-hold loading predicted extraction behaviour with large variance in extraction time. Damage imposed in the FEA model was able to predict experimental results from experiments on similarly-damaged dental complexes. This study presents a comprehensive experimental and numerical characterization of vertical tooth extraction biomechanics employing an ex vivo swine model. The results of these experiments suggest that the axisymmetric FEA model is a powerful tool for predicting a range of conditions and dental complex geometries. The predictive power of the FEA model demonstrated in this study encourages its use in pre-clinical testing and development of new vertical extraction loading schemes for improving clinical outcomes.

Development of a Robot-Based Test Bench for the Destructive Testing of Components

Abstract This paper presents a novel approach for robot-based mechanical testing on the component level using a high degree of flexibility in the superimposition of loads, which allows their application to test various geometries and conditions. To validate our approach, tensile tests were performed using different control modes: position control, force control using a six-axis force/torque sensor, and path control using optical tracking of markers. The last two sensor-guided control modes are used to compensate unwanted force components that may occur in a system with six degrees of freedom. For reference, the same tests were performed on a conventional universal testing machine and were in good agreement. Subsequently, the flexibility of the robot-based test setup is demonstrated by two different component tests; a bicycle frame and a snowboard with high compliance were examined with different load cases. It was demonstrated that in path control mode an improvement in the accuracy of absolute positioning occurs and compensation for any transverse forces is possible. In addition, the path control mode enables the preservation of the initial load vector relative to the surface, even under significant deformation of the component.

Correlation of polymerase chain reaction results with hematocrit levels and platelet counts in dengue patients in Batam City

Background Dengue hemorrhagic fever (DHF) is a viral disease transmitted by Aedes aegypti mosquitoes, posing global public health challenge. The Riau Islands Province has the highest incidence of DHF in Indonesia. Objective This study aimed to investigate the relationship between hematocrit and platelet levels with the cycle threshold (Ct) values of polymerase chain reaction (PCR) results in DHF cases in Batam City, Riau Islands Province. Methods A descriptive correlation study was conducted using data from 102 patients infected with the dengue virus. Hematocrit and platelet counts were measured using a hematology analyzer, while Ct values for DENV1, DENV2, DENV3, and DENV4 were obtained through real-time qRT-PCR. Pearson's correlation test was employed to analyze the relationship between these variables. Results The study found no significant gender difference in DHF incidence (males: 50%, females: 50%). The highest prevalence was observed in the 6–11 years age group (44.1%), followed by the 12–18 years group (25.5%), the >18 years group (24.5%), and the 1–5 years group (11.8%). DENV3 was identified as the dominant serotype. No statistically significant correlation was found between Ct values and hematocrit (p = 0.607) or platelet counts (p = 0.323). Conclusion DHF cases in this study showed no gender disparity, with the most affected group being children aged 6–11 years, and DENV3 was the prevalent serotype. Ct values did not show a statistically significant correlation with hematocrit levels or platelet counts, suggesting that these hematological parameters may not predict viral load in DHF cases.

Feedforward neural network-assisted parameter identification and tuning for uniaxial superelastic shape memory alloy models under dynamic loads

In this study, we introduce a machine learning-based method to predict the modeling parameters of superelastic shape memory alloys (SMAs). Our goal is to simultaneously determine and fine-tune all internal and material-related parameters, including thermodynamic ones, for a specific constitutive model using only cyclic tensile tests. We employ feedforward neural networks (FNNs) for their versatile structure. First, we sample the searched parameters within a predefined parameter space using the Latin hypercube sampling method. Then, using the constitutive model with the sampled parameters and representative strain loading, we generate the corresponding stress responses and finally train the FNN. To address the ill-posed nature of this inverse parameter identification problem and ensure a unique parameter set, during training, we use a dual network architecture with an additional FNN-based surrogate of the constitutive model. We also utilize transfer learning to accelerate the training process through knowledge transfer and handle multiple load cases simultaneously, ensuring consistent parameter identification across different scenarios. We validate the method by comparing the numerical results with the experimental data and demonstrate the importance of accurately identified parameter sets by numerical investigations on a SMA-retrofitted frame structure.

Differences for Cooling Capacity of a Cable Tunnel System: Install One or Three Additional Cable Troughs with Cable Circuit for 100/70 Heat Loads – A Numerical Study

The purpose of this report was to compare the numerical analysis for different cooling efficiency of a cable tunnel system when installing one additional cable trough or three cable troughs for cable circuit 100% or 70% heat load. Cable tunnel system is widely known for it is use for high voltage transmission in an underground. Due to the cables generating large quantities of heat, water pipes and air ventilation were used in the tunnel to cool down the transmission cable. To investigate the cooling efficiency of a tunnel, research for benchmark case was carried out. A Computational Fluid Dynamic (CFD) benchmark analysis about 2D natural convection inside the square cavity was investigated to further understand the air movement inside the square medium. Ansys Fluent was carried out for benchmark cases of heat transfer natural convection inside the square cavity and to check whether Ansys Fluent can be used for any CFD and heat transfer purposes by validating the results with previous studies. The benchmark case used a 2D square with different active temperature side walls and adiabatic walls for top and bottom side. From the benchmark simulations with different Rayleigh Number, a number representing buoyancy-driven of a fluid from 103 to 105 affected air differently and the heat transfer natural convection inside the square. At different Rayleigh Number air forms a recirculation passing the active walls and adiabatic walls. After investigated the benchmark, the results were used to validate with previous studies. To validate the results was by using Nusselt Number, ratio of convective to conductive. The benchmark case results were validated and Ansys Fluent proven can be used for CFD and heat transfer purposes. Two 3D cable tunnel were modelled with 100-meter length after concluded the benchmark. The two tunnel models were based on the number of cable troughs installed. The first tunnel was with one cable trough and two cable circuits on the bottom, as for the second tunnel was with one bottom cable circuit and three cable troughs. Cable tunnel simulations were based on cable circuit for 100% heat load and 70% heat load with each heat load case was given different water flow rate of 4.25 L/s and 6.5 L/s. A total of eight scenario cases were carried out to determine which provided a better cooling efficiency choice. The analysis for cable tunnel cases on how the copper cables cooled down through heat transfer of natural convection inside the cable trough, which the heat then was removed from the cable circuit by air and continue to the outside of the tunnel. During the heat transfer processes, conductivity was present as not all heat were removed by air and water, but continue to through the walls of the tunnel and to the ground soil. Based on the simulations, a cable tunnel with three cable troughs was proven more cooling efficiency compared tunnel with one cable trough. Some scenarios did not meet the criteria, due to insufficient heat relocation by air and water. The cooling efficiency was determined by which has the better balance heat relocation by air, water, and ground, also considering the comfort and safety of human inside the tunnel.

Analysis of numerical models of an integral bridge resting on an elastic half-space

Abstract The paper presents three methods of the numerical modeling of a 60 m long integral bridge structure resting on an elastic half-space. For the analysis, three bridge models were built using Abaqus FEA software. Models A and C represent complex three-dimensional numerical models consisting of the bridge structure and the soil layer beneath it. The soil layer on which the bridge is resting was modeled as a homogeneous, isotropic, continuous, and elastic semi-infinite body elastic half-space. Model B represents a simple three-dimensional numerical model consisting of just the bridge structure. The stiffness of the soil layer beneath the structure in model B was modeled with spring constants derived for shallow footing foundation based on the theory for an elastic half-space. This model represents an engineering approach to the design of an integral bridge. In all models, the bridge deck is monolithically connected with abutment walls and intermediate piers. The bridge is made of cast-in-situ reinforced concrete. All material constants used in the analysis are presented in the table. Self-weight, uniformly distributed load, and thermal longitudinal expansion of the bridge deck were applied to the bridge models. Due to the nonlinear boundary condition used in the supports of the bridge model A, such as contact and friction, the superposition principle cannot be used in the calculations of this model. For this reason, all the loads involved in all bridge models were combined into a single load case and the large displacement formulation was used in the static analysis. The self-weight of the soil layer beneath the structure was omitted in the analysis. The author is focused on the method of modeling an integral bridge structure resting on elastic soil. For the purpose of this paper, only two piers from each model were selected, from which the internal forces and displacements were compared. Based on the analysis, it was concluded that it is possible to design an integral bridge by building its simplified numerical model, once the conditions given in the conclusions are met.

ON THE SEAKEEPING RESPONSE VALUATION IN RANDOM SEA STATE CONDITIONS OF A LARGE LNG LIQUEFIED NATURAL GAS CARRIER

This seakeeping study refers to a large LNG liquified natural gas carrier with 289.3 m length, slender mono-hull, and fine shapes at both ends. From the loading cases of the large LNG carrier, two relevant are selected, full cargo and heavy ballast. The top speed of the large LNG carrier is 22 knots. To ensure the basis of the seakeeping response valuation in a random sea state, the navigation unrestricted conditions are modeled by the averaged ITTC wave power density spectrum. This study applies a linear strip theory hydrodynamic formulation for unrestricted water depth, delivering directly in the frequency domain the oscillations’ response amplitude operators. For the roll oscillations, this study includes the LNG carrier gravity center vertical position influence evaluation and the equivalent roll dampers effect. The short-term dynamic response for the random waves is evaluated by seakeeping criteria, delivering the safety navigation capabilities of the large LNG carrier.

Optimization design of stamping die for large-size three-dimensional curved thick plate

Stamping is a highly efficient and precise way to fabricate metal plates with complex shapes, commonly used in practical engineering. Lowering the weight of die components is essential to reduce manufacturing and operational costs. Despite using a single topology optimization process, the previous study experienced difficulty in gaining the optimal structural configurations and their specific dimensions while considering structural performance and die weight. Therefore, a three-phase optimization procedure is proposed, namely model preparation, conceptual design, and detailed design. Firstly, using the proposed node-to-node load mapping strategy, the history of the load distribution across the die face is transferred to multiple loading cases in static analysis models. Then, the solid isotropic microstructure with penalization (SIMP) method based topology optimization is employed to achieve better structural configurations. Finally, a multiple-surrogate-models-based size optimization approach is implemented to obtain the specific dimensions. Applications on stamping die for large-size three-dimensional curved thick plate were conducted. The results showed that topology optimization could deliver more efficient structural configurations, which reduced the weight of the upper die, restrike punch, and lower die by 22.6%, 48.7%, and 39.9%, respectively, while still meeting most of the performance requirements. Furthermore, after size optimization, an increase of the restrike punch weight by 22% was obtained to meet the performance constraints, while the upper and lower dies had a further reduction in weight of 19.1% and 8% without violating the performance constraints. Therefore, the proposed optimization procedure is verified to be effective in reducing the die weights while meeting all performance requirements.

Functionally Graded Impact Attenuator Using Bonded Construction

ABSTRACTAutomotive collisions are one of the major causes of death in the European Union, especially in childhood and adolescence. However, improvements in vehicle safety cannot be achieved only by increasing the size and dimensions of the structures, as this demands more materials and more costly manufacturing processes, which leads to an increased resource expenditure and lowered sustainability. Moreover, the increase of the structure size raises the vehicle's weight, leading to added fuel consumption, which cannot be accepted considering modern environmental regulations. To solve these issues, the application of bonded joints using the combination of several adherends materials, such as steel and aluminium alloys and fibber‐reinforced polymers with crash‐resistant adhesives presents itself as a novel solution, allowing to attain enhanced joint strength, energy absorption and weight reduction. The present works introduce a novel concept of an impact attenuator using bonded, geometrically optimized using the concept of functionally graded adherends to maximize energy absorption by ensuring that a load‐bearing path is kept during impact, converting the impact energy into the plastic deformation of panels with variable mechanical properties, tailored to withstand specific load cases, fulfilling a gap in the literature regarding impact absorption devices that combines graded materials and bonded construction. The results obtained present an increase in the energy absorption values of the graded impact attenuators above 200% when compared to the homogenous materials.

Argillaceous Soft Rock in-situ Test Program in Tunneling

AbstractThis study undertakes a comprehensive examination of the characteristics of the argillaceous, hard soil/soft rock (HSSR) lithology of the Unterangerberg formation in Tyrol, Austria, focusing on its swelling properties and anisotropic material behavior. The objective is to achieve an extensive material characterization to be able to calibrate material models accurately. This is to be achieved by means of an in-situ test campaign within the Angath adit tunnel construction site and accompanying laboratory tests. The geotechnical monitoring concept in a designated test gallery includes a chain inclinometer, extensometers, geodetic targets, shotcrete strain meters, photogrammetric observations, and a long-term irrigation test field, with a section of the invert left exposed intentionally. The in-situ tests yield valuable insights into the intricate behavior of the HSSR lithology, offering a comprehensive description of material variability, and recommendations for characterization. Results indicate that despite the high swellable clay mineral content, significant swelling occurred only to a small extent during the observation period to date. The study concludes that the in-situ behavior of such formations significantly contributes to a better understanding of their characteristics, leading to a substantial reduction in critical load cases for future planning phases.

Large Deflections, Loss of Stability and Over-Critical Behavior of Sloping Panels and Arches of Variable Thickness on an Elastic Base

The problem of large deflections of a flat arch in its plane (or an infinitely long panel) loaded with transverse loads is considered. A variational approach has been applied to solve it. The resolving nonlinear equations are reduced to finding the deflection and longitudinal force, which is considered constant along the length of the arch due to its flatness. An approximate solution method is proposed by decomposing the displacements into a Fourier series. The peculiarity of the approach used is that in order to pass the limit points, it is not necessary to use special algorithms such as the continuation method by parameter. It also allows you to trace the process of supercritical deformation of the arch. The proposed approach allows us to consider problems for arches of variable thicknesses, located on elastic supports, on an elastic base with a variable bed coefficient and various loads. Therefore, it is also convenient in problems of finding, for example, the optimal thickness distribution under restrictions on critical loads, on rigidity stiffness and on maximum compression or tension stresses. The results of numerical calculations are presented. The convergence is studied of the solution depending on the number of terms of the series, into which the desired deflection decomposes. A good agreement with the known analytical results is obtained earlier by solving the equilibrium equations of the arch element and panel in the case of simple types of loading. At the same time, even in more complex cases of loading and supercritical bending of an arch without an elastic base, the results are obtained when holding three, four and five members of the Fourier series, the maximum deflections and critical loads differed by no more than 2.5%. On the basis of numerical experiments, the features of the arch behavior caused by the rearrangement of geometry during loading are revealed. The processes of stability loss of the arch and its supercritical behavior are investigated. The effect of symmetric deformation in the case of kinematic loading is found, namely, it is revealed that at a certain value of the concentrated force, an infinite number of equilibrium forms are possible. Arches on an elastic base, as well as with variable thickness are considered (the results are presented in the form of load–displacement diagrams and in the form of pictures of deformed arch shapes). An interesting effect has been revealed based on numerical experiments. It turned out that the increase in thickness when moving away from the supports does not change the nature of the load–displacement diagram, i.e., with some load, a slap occurs. On the contrary, a decrease in thickness when moving away from the supports leads to a flattening of the diagram, and after a certain thickness value in the center, its further decrease leads to the fact that the arch does not occur.