Base Plate Research Articles

Appearance and evolution of radiolucent lines below the tibial implant in primary total knee arthroplasty.

The aim of this study was to evaluate total knee arthroplasty (TKA) radiographically to detect the occurrence of radiolucent lines (RLL) under the tibial base plate and to determine what type of RLL may have a correlation with aseptic loosening (AL). The study had two hypotheses: (1) RLLs may have different radiological aspects and evolutions in time depending of different factors (2) Signs of micro- and/or macro-mobility of the implant are necessary before diagnosing aseptic loosening of the tibial component. Retrospective cohort study of 774 patients operated with a Vanguard TKA (Zimmer Biomet, Warsaw, IN, US) from 2007 to 2015. RLLs were recorded in a database and described according to their radiological aspect, localization, time of apparition, progression and eventual evolution to AL. Other collected parameters were pre- and post-operative HKA angles, amount of post-operative HKA correction, surgical, clinical and demographic data. 178/774 TKAs (23%) showed RLLs under the tibial base plate including 9 (1.2%) tibial implants needing revision for AL. Three different types and two aspects of RLLs were observed. Important deformity corrections or undercorrected implants were recognized as a mechanical risk factor for loosening. Elderly women with osteoporosis and young men with important pre-operative deformities were identified as clinical risk factors for RLLs. RLLs are frequently present at the epiphyseal bone/implant interface after total knee arthroplasty, but do not mean the implant is loose. They can be considered a sign of reduced epiphyseal surface fixation due to micro mobility of the tibial implant. Aseptic loosening can be observed radiologically when signs of macro-mobility of the implant are present at the metaphyseal level. III.

Potential of chitosan as anti Candida albicans in denture bases made from thermoplastic nylon

Background: Candida albicans is main cause of fungal infections in denture users. Prevention is needed by soaking dentures using a disinfectant. Chitosan is an alternative disinfectant emulsion because it is biodegradable, biocompatible, and does not cause discoloration. This research objective is to determine the effect of chitosan emulsion on the number of C.albicans on base plate thermoplastic nylon.
 Method: This is a true experimental study using post-test only design by using 25 base plates divided into 5 groups namely treatment I, treatment II, treatment III, positive and negative control. Plate was incubated in C.albicans suspension for 24 hours in McFarland and 10-3 series dilution. The plates was rinsed with aquadest, then soaked with 0.3% chitosan emulsion, 0.8% chitosan emulsion, 2% chitosan emulsion, 0.2% chlorhexidine gluconate, and aquadest for 15 minutes. The attached C.albicans colony in the plate was released to the SDB by using centrifuge device, then proliferated on the SDA and incubated (24 hours). The results of the C.albicans colony were counted visually by using a colony counter. The number of Candida albicans colonies data were analyzed using One-Way ANOVA and then Post Hoc Tukey HSD test.
 Result: The results showed that there were significant mean differences between each group (p

Damage distribution and mechanical properties analysis of CRTS III slab track under uneven subgrade settlement

Due to the complex geological conditions along the high-speed railway, the subgrade uneven settlement (USS) is inevitable, and the safety and stability of the railway are significantly affected. In this paper, a three-dimensional solid model of the CRTS III slab track is established. Based on the concrete damaged plasticity (CDP) model, the influence of USS on structural damage, deformation, stress, and gap is analyzed. Simultaneously, as a reinforced concrete structure, the structure reinforcement is an essential part of strengthening its tensile capacity. Consequently, the distribution of internal reinforcement is considered in detail, and the influence of reinforcement on the mechanical properties of the track structure is further explored. The results show that the base plate is the most vulnerable component under the USS, and its primary damage locations are the middle and edge of the USS and the middle track slab edge. The next component that is susceptible to damage is the self-compacting concrete, whose primary damage locations are the longitudinal outer side of the limit lug boss and the USS middle. The damage of each component increases monotonically with increasing settlement amplitude, first increasing and then decreasing with increasing wavelength, especially noting the cases of L = 15–20 m, which is the most unfavorable wavelength range for most amplitudes. The difference between the results under the CDP and linear elastic models increases with the increase in damage. The reinforcement significantly influences the value, range, and location of the structural concrete damage. The component of load-bearing stress shifts from concrete to reinforcement at severe damage locations.

Microstructural control of additively manufactured Ti6Al4V via in-situ large-area laser annealing

Additively manufactured (AM) alloy Ti6Al4V often exhibits a distinctive α/α’ microstructure due to the high cooling rates associated with AM, which can lead to increased brittleness and necessitate costly post-processing and heat treatment. In this work, we explore the use of layer-by-layer large area surface annealing with a secondary diode laser to control the microstructure of Ti6Al4V during AM and site-specifically induce more ductile, dual-phase α/β Ti6Al4V. Annealing treatments were selected to target sub- and super-β-transus temperatures at annealed layers, leading to 13 % and 20 % reductions in hardness, respectively, in the 2 mm below the annealed surfaces. Components with rapid switching between annealed and unannealed microstructures were also produced. Temperature measurements at the built surface and base plate were combined with a thermal model to validate microstructural observations, setting the stage for development of full 3-D microstructure and property control using in-situ laser annealing.

Mallomonas acidophila sp. nov. (Synurales, Chrysophyceae)—a new species from the tropics with morphological features of fossil taxa

A new species, Mallomonas acidophila sp. nov., is described from Vietnam based on silica-scale morphology observed using scanning and transmission electron microscopy. Mallomonas acidophila belongs to section Papillosae and is most similar to M. preisigii, described from fossil deposits. Scales of Mallomonas acidophila have a shallow elongated dome, which is recessed from the distal margin and located at different angles to the longitudinal axis, with papillae on the shield and dome, the absence of pores on the base plate and the wide posterior flange, and partially covered with the secondary siliceous layer in the area adjacent to the V-rib. The bristles of the newly described species are short, with a bifurcated apex and a hook-shaped foot. The new species has been found in two acidified and humic water bodies located in the coastal area in Thua Thien Hue Province.

Heat Transfer Enhancement by Mitigating the Adverse Effects of Crossflow in a Multi-Jet Impingement Cooling System in Hexagonal Configuration by Coaxial Cylindrical Protrusion—Guide Vane Pairs

A novel compound multi-jet impingement system for enhanced cooling of a flat surface by augmenting its area with cylindrical protrusions (CPs) equipped with coaxial guide vanes (CGVs) and reducing deflection of jets by crossflow has been developed for high-heat removal applications. The cooling performance of coaxial circular jets impinging on the top faces of CPs placed in hexagonal configuration on a flat plate is evaluated by three-dimensional (3D) computational fluid dynamics (CFD) simulations. Jets impinging on the top faces of the protrusions are directed to their lateral faces and then to the base plate by the CGVs around the protrusions, resulting in up to 62.8% improvement in heat transfer rate with a minor increase in pressure drop. Effects of protrusion height and diameter on the pressure drop and cooling performance are studied for jet Reynolds (Re number range of 5000–20,000. Due to both shortened jet impingement lengths as the height of protrusions is increased and directing the expended fluid away from the impinging jets by CGVs, adverse effects of jet–crossflow interactions on cooling performance and fluid pumping power are significantly reduced. Performance evaluation criterion (PEC) of the novel compound multi-jet impingement cooling system (CMJICS) can be as high as 1.52.

Forming the maxillary palatal relief on the outer palatal surface of the complete removable dentures

Prosthodontic treatment of secondary complete adentia in the upper jaw with completely removable plate prothesis consists in reflecting the palatal relief on the outer surface of the upper jaw prosthesis basis. Preparation of CRPP for SCA is an arrangement of known clinical and laboratory stages.
 During the prosthodontic treatment of SCA with maxillary CRPP, the following sequence was performed at the clinical and laboratory stages for the purpose of reflection of the palatal relief on the outer side of the maxillary prosthetic bases, the 2nd and 4th laboratory stages have been improved. So that:
 Replacing the wax with plastic in the composition of complete removable dentures. 4,5,6,7,8 figures of our work refer to this stage. At this stage: Figure 8-reflection of the relief of a part of the hard palate in the base plate wax added to the trial denture of a maxillary complete removable platen prosthesis. Figure 9-reflection of the relief of a part of the hard palate in the denture wax added to the trial denture of a maxillary complete removable platen prosthesis.
 The present study shows that the complete removable upper plate prosthesis (CRPP) is more functional in the prosthetic treatment of secondary complete adentia (SCA). By using CRPP on the upper jaw, unnatural disturbances in the relief of the palatine region are eliminated. It will be useful for improving other clinical and laboratory stages of preparation of maxillary CRPP.

Effect of PWHT on metallurgical and mechanical characterization of dissimilar welded joint of P91 and P92 steels

P91 and P92 steels are widely used in nuclear and thermal power plant’s high-temperature (650–700 °C) operating components. The welding procedure, base plate composition, filler material composition, and post-weld heat treatment (PWHT) significantly affect the metallurgical characterization of weldments at room temperature. This work focuses on joining P91 and P92 steel by the TIG welding with filler ER90S-B9. The study analyzes the materialization of coarse-grained HAZ (CGHAZ), inter-critical HAZ (ICHAZ), and fine grained HAZ (FGHAZ) under welded and PWHT. PWHT was conducted at 840 °C for 2, 4 and 6h. An optical microscopic (OM) scanning electron microscope (SEM) was employed to characterize the welded and PWHT samples. It was perceived that the tensile strength of PWHT increased as the heat treatment times increased from 2 to 6 h, while the hardness value decreased accordingly. The maximum tensile strength (594.71 MPa) was observed in PWHT_6 h, while the minimum tensile strength (537.52 MPa) was perceived in the as-welded sample. The PWHT_6h reveals the minimum hardness values (271.12 HV) at the fusion zone among all the conditions. The WFZ consisted of an untampered lath martensitic grain structure, demonstrating an average hardness value of 314.15 HV in the PWHT_2h condition. The hardness value in CGHAZ samples for as-welded, PWHT_2h, PWHT_4h, and PWHT_6h was observed at 456.85, 436.81, 368.63, and 327.41 HV, respectively.

Micro-additives and their impact on tensile and fracture performance of solder

High-performance components and sustainable electronics require new and durable interconnection technologies. In addition to Solid-Liquid Interdiffusion (SLID) Bonding and silver sintering, established solders are also advancing. Especially in the field of power electronics, where high-temperature applications require high demands on assembly and interconnection technology, the lead-free SnAgCu solders has established a good track record. This basic solder is then improved and optimized for the requirements of its specific application, for example by adding micro-additives. This paper deals with the tensile strength of micro-alloyed SnAg0.4Cu0.5 (SAC) solders, building on our previous work considering shear tests and phase formation behaviour published in Steenmann et al. (2021). In power electronics, solders as joining partners between component and base plate have to accommodate high mechanical and thermal loads resulting, e.g., from a mismatch in coefficients of thermal expansion of the joined materials. The cracking behaviour of the solders in tensile tests provides information on its mechanical resistance and load-bearing capacity. In this work, we examine SAC based solders with small amounts of Sb (3 wt%), Bi (6 wt%) and Ni (0.2 wt%) to investigate the effects of the micro-additives on tensile strength. The micro-additives are studied individually in quaternary systems “SAC + X”, but also in the combination SnAg4Cu0.7Bi3Ni0.1Sb1.5 and SnAg0.5Bi3Sb5 and compared respectively to SAC solder. We achieve this by melting the solders using a standard soldering process at different times and temperatures to replicate the solders' phase formation behaviour during soldering. We vary the peak temperature and holding time of the process to investigate the respective effects on phase growth and the associated change of solder behaviour under mechanical load. The specimens prepared at different parameters are tested under identical conditions on a tensile testing machine based on DIN EN ISO 6892 1 “Metallic materials — Tensile testing”. We investigate the intermetallic phases on scanning electron microscope images by energy dispersive X-ray (EDX) spectroscopy and derive the relationships with the micro-additives. In this paper, we discuss in detail the differences in tensile behaviour depending on the micro-additives. By considering all results holistically, the influence of the individual and combined micro-additives in the solder can be deduced.

Method to measure the effect of acoustic leaks on active noise reduction device performance

Passive hearing protection (HP) systems are designed to reduce the level of noise at the ear. Passive HP typically excel in attenuating mid- to high-frequency noise. Active noise reduction (ANR) has the potential to provide additional attenuation of low-frequency noise. There are documented reports describing unwanted sound being generated by ANR systems if an acoustic leak is present. The objective of this effort was to develop a method to measure the performance of ANR devices with and without the introduction of an acoustic leak. A number of ANR earcups were selected for this study. Data were collected with an artificial ear and a flat base plate in a noise environment that ranged from 65–115 dB SPL. Wedges, designed in-house, created a consistent acoustic leak that ranged in size from 1–2 mm in radius. The results revealed that some ANR earcups provided high levels of protection when the earcup was well-sealed; however, when an acoustic leak was introduced, the earcups became unstable and generated noise in the earcup. This instability was not seen in all ANR devices. The outcome of these measurements solidified the need for a method to measure ANR device performance when acoustic leaks are introduced.

The Influence of Ground Water Level Conditions on the Stability of Road Slopes with Retaining Walls

This research was carried out using the P laxis 8.0 finite element method and manual calculations as well as by evaluating the safety factor value. Slope stability analysis using the P laxis program aims to determine the safe value of the slope before and after reinforcement using a cantilever - type retaining wall. Based on the analysis of the P laxis program before the installation of the cantilever retaining wall, in general the condition of the retaining wall on Jalan Ahmad Yani Gg. Batu Mas, Singkawang City experienced a landslide due to the condition of the soil which was classified as having low soil mechanical properties. Slopes with designed cantilever wall reinforcement are considered safer because they have the smallest displacement and settlement values, and meet all slope stability requirements, ie, shear stability is 1.251 > 1.5 (Safe), stability against overturning is 2.415 > 2 (Safe) , and bearing capacity is 0.555 < 0.583. The cantilever retaining wall structure uses D16-100 principal reinforcement and D10-100 shrinkage reinforcement, the base plate uses D16-150 principal reinforcement and D10-100 shrinkage reinforcement.

Optimize Process Parameter of FDM Techniques to Improve Mechanical Properties of Aerospace Application

The Fused Deposition modelling technique is widely accepted by industries as it is the one of the most convenient modern technology. The fused deposition modelling (FDM) is one of the additive manufacturing techniques which are largely used for printing of metal/thermoplastic materials with ease of design flexibilities the proposed research had been carried out for the investigation and optimization of process parameters for product or application development through FDM. The FDM- (Fused deposition Modelling) is widely used for product development and do contain various control variables. Here the process relates to nozzle temperature, base plate temperature, filament feed, filament material and deposition speed. The research presented here had been conducted considering nozzle temperature, layer thickness, and internal profile as variables for specimen manufacturing. In Aerospace application, optimization process is highly required for the Properties of material, weight and other effects. Hence the tensile specimen had been prepared to represent an aerospace application of ducts for airflow. The full factorial design of experiments had been considered for experimental investigation. The design of experiment had been conducted with three factors; three no. of parameters at three different levels Hence, A total no. of 27 representation samples had been prepared for tensile test and surface roughness for the Optimum result. The results had given considerable parametric effect as an outcome. The optimized results had been manufactured on an Ultimaker3D printer machine and tested which confirmed the results. The outcomes will assure optimal manufacturing process parameters of FDM for improved mechanical properties.

Acinetobacter type VI secretion system comprises a non-canonical membrane complex.

A. baumannii can rapidly acquire new resistance mechanisms and persist on abiotic surface, enabling the colonization of asymptomatic human host. In Acinetobacter the type VI secretion system (T6SS) is involved in twitching, surface motility and is used for interbacterial competition allowing the bacteria to uptake DNA. A. baumannii possesses a T6SS that has been well studied for its regulation and specific activity, but little is known concerning its assembly and architecture. The T6SS nanomachine is built from three architectural sub-complexes. Unlike the baseplate (BP) and the tail-tube complex (TTC), which are inherited from bacteriophages, the membrane complex (MC) originates from bacteria. The MC is the most external part of the T6SS and, as such, is subjected to evolution and adaptation. One unanswered question on the MC is how such a gigantesque molecular edifice is inserted and crosses the bacterial cell envelope. The A. baumannii MC lacks an essential component, the TssJ lipoprotein, which anchors the MC to the outer membrane. In this work, we studied how A. baumannii compensates the absence of a TssJ. We have characterized for the first time the A. baumannii's specific T6SS MC, its unique characteristic, its membrane localization, and assembly dynamics. We also defined its composition, demonstrating that its biogenesis employs three Acinetobacter-specific envelope-associated proteins that define an intricate network leading to the assembly of a five-proteins membrane super-complex. Our data suggest that A. baumannii has divided the function of TssJ by (1) co-opting a new protein TsmK that stabilizes the MC and by (2) evolving a new domain in TssM for homo-oligomerization, a prerequisite to build the T6SS channel. We believe that the atypical species-specific features we report in this study will have profound implication in our understanding of the assembly and evolutionary diversity of different T6SSs, that warrants future investigation.

Anatomical Step-by-Step Dissection of Complex Skull Base Approaches for Trainees: Surgical Anatomy of the Endoscopic Endonasal Approach to the Anterior Cranial Fossa.

Introduction The development of endoscopic techniques has made endoscopic endonasal approaches (EEAs) to the anterior cranial fossa (ACF) increasingly popular. Still, the steps and nuances involved in the approach may be difficult to understand for trainees. Thus, we aim to didactically describe the EEAs to the ACF in an anatomically based, step-by-step manner with supplementary clinical cases. Methods Six cadaveric head specimens were dissected. Endoscopic endonasal Draf I, IIA, IIB, and III frontal sinusotomies, endoscopic endonasal superior ethmoidectomy, and endoscopic endonasal transcribriform and transplanum approaches were modularly performed. The specimens were photodocumented with endoscopic techniques. Results Draf I frontal sinusotomy started with the complete removal of the anteromedial portion of the agger nasi cell, exposing the medial orbital wall, cranial base, and anterior cribriform plate. Draf II frontal sinusotomy proceeded with the removal of the floor of the frontal sinus between the lamina papyracea and the middle turbinate (IIa), and the nasal septum (IIb) until the first olfactory filaments were exposed. Draf III proceeded by creating a superior septal window just below the floor of the frontal sinus. The bone of the ACF bounded by the limbus sphenoidale posteriorly, frontal sinus anteriorly, and the medial orbital walls bilaterally was removed; the cribriform plate was removed; and the crista galli was dissected free from the dural leaflets of the falx cerebri and removed. Conclusion We provide a step-by-step dissection describing basic surgical steps and anatomy of the EEAs to the ACF to facilitate the learning process for skull base surgery trainees.

An assessment method to ensure applicability of concrete capacity method for design of anchorages: Linear force distribution approach

AbstractThe concrete capacity design (CCD) method for the design of anchorages comes with a pre‐requisite that the base plate connecting the anchors of a group should be “sufficiently stiff.” This article addresses a frequently and vastly discussed topic in fastening technology, namely “What a sufficiently stiff base plate actually means?” The qualitative definition used by the codes requires that the deformation of the base plate should be small compared to the anchor displacements, in addition to the requirement that the base plate should remain linear elastic. This requirement indirectly ensures that the forces among the anchors of the group are distributed in a linear manner, which is the primary requirement to apply the CCD method for design of anchorages. Such a qualitative definition has raised more questions than answers and haunts the fastening technology community. Perhaps the possible solution to this problem requires asking the question differently, that addresses the problem directly: How can it be ensured that the tension forces among the anchors of a group are distributed in a linear manner? This paper first discusses the problem in detail highlighting several issues in the current approach and later provides an overview of an assessment method in form of a set of criteria that can be used to evaluate whether the tension force distribution is linear for an anchorage with a given anchor pattern, baseplate, attachment, and load case. The principle of the approach is based on a combination of simple mathematical formulations and the evaluation of finite element calculations performed on anchorages modeled with base plate, attachment, and anchors. The proposed formulations are described, and it is explained why they are adequate to find practical and safe general solutions to the problems. The application of the set of criteria allows the calculation of an optimum base plate thickness, sufficient to distribute the forces linearly among the anchors, without being overly conservative.

The base plate orientation angle: a plain radiographic technique for designing the base plate’s inclination in reverse shoulder arthroplasty

Superior inclination of the base plate in reverse shoulder arthroplasty (RSA) is underestimated and may lead to major setbacks in terms of functional outcomes due to the altered biomechanics. Joint instability, scapular notching, and loosening of the glenoid component are considered the most serious sequelae. Therefore, a thorough preoperative radiological assessment of the affected shoulder joint and customized design of the prosthesis according to the glenoid morphology are decisive and directly correlated to the outcome. In this article, we propose a simple radiographic technique to assess the inclination of the glenoid preoperatively, which identifies the need for intraoperative correction. One hundred inconspicuous shoulder radiographs were included in the control group (CG) to define the normal ranges of the base plate orientation angle (BOA) and the base plate correction angle (BCA). Further, both angles were measured on 2-dimensional (2D) computed tomography scans of patients with proximal humerus fractures as well as radiographs, 2D and 3-dimensional (3D) computed tomography scans of patients with cuff tear arthropathy who underwent RSA between 2018 and 2021. The interobserver reliability among three independent testers was evaluated by calculating the intraclass correlation coefficient. In cuff tear arthropathy cases, the BOA and BCA measurements on different imaging modalities were compared using the Wilcoxon test. Possible variations of both angles' values based on glenoid erosion types, according to the Favard classification, were also investigated. Regardless of the imaging modality used, the interobserver reliability was excellent among three independent observers. In the CG, the mean BOA and BCA values were 118°±6° and 17°±5°, respectively. The mean corrected BOA values of the CG and fracture group were 136°±5° and 140°±5°, respectively. In contrast to the BCA values, the BOA measurements on radiographs showed a statistically significant difference compared to those obtained on 2D- and 3D scans in the cuff arthropathy group. Further, both angles' values varied according to the extent and location of the glenoid erosion. The lowest mean BOA and highest mean BCA values were observed in cases with Favard glenoid type E3. The BOA and the BCA are reliable tools proposed to aid in precisely positioning the glenoid component in RSA in the preoperative setting. Whereas, the BOA determines the inclination of the inferior glenoid segment, the BCA represents the extent of correction required to obtain a neutral inclination of the base plate. Glenoid type E3 of the Favard classification with superior wear is particularly susceptible to base plate superior tilt.

Static and Fatigue Characterization of Adhesive T-Joints Involving Different Adherends

It is very important to understand the damage mechanisms as well as the mechanical response of T-joints involving different materials on the base plate. For this purpose, two configurations were studied. In one, the joint is composed of a base plate and a T-element, both in Al 6063-T5, while in the other one, the aluminum base plate was replaced by a glass fiber composite. Finally, each configuration was divided into two batches, where in one, the elements were bonded with a stiff adhesive (Araldite® AV 4076-1/HY 4076) while in the other, a more ductile adhesive (Araldite® AW 106/HV 953 U) was used. The static and fatigue strength of all configurations was evaluated in bending. In all cases, the damage occurred at the end of the T-element, where a crack appeared and propagated toward the interior of the T-joint. The bending strength is highest for joints involving aluminum and the ductile adhesive, which is 2.8 times higher than the same configuration involving composite base plates and 1.7 times higher than that using the stiff adhesive. Finally, the highest fatigue lives were obtained for T-joints involving Al 6063-T5 base plates, and regardless of the base plate material, the ductile adhesive promoted the highest fatigue strength.

Modelling of column base plate connections with plate stiffeners and non‐proportional loading

AbstractColumn base plate connections are used widely. Their design is currently codified by Eurocode 3, though with explicit consideration of only base plates without stiffeners and subjected to a proportional loading path. However, both new and existing steel structures might have stiffened base plates. Besides, there might be the need for analyzing the connection response for a non‐proportional loading path (e.g., increasing seismic loads and constant gravity loads). Therefore, the paper provides a contribution into the development of an analytical model for predicting the response of stiffened base plate connections subjected to a non‐proportional loading path. The paper deals with calculation of the connection rotational stiffness and moment resistance. The objective is pursued through finite element modelling and analysis. Then, the application of a proposed analytical model is shown and a comparison with the finite element analysis results is illustrated and discussed.

Damage of CRTS III type ballastless track-32 m simply supported girder structural system under long-term deformation effects

Until now, the CRTS (China’s Railway Track System) III type ballastless track-girder system has been gradually used in high-speed railway engineering. However, the effect of long-term deformation of prestressed box girders on the upper track structure is often overlooked. Given the strict requirements for track smoothness in high-speed railways, an in-depth study of the long-term deformation of the CRTS III type ballastless track-32 m simply supported girder system (girder-track system) is particularly important. In this study, a refined finite element model was established for a three-span CRTS III type ballastless track- simply supported box girder system. Based on the aid of the CEB-FIP 90 creep model and the UMAT (User-Material) subroutine, the long-term deformation calculations were investigated. Furthermore, an in-depth analysis of stress and damage of the CRTS III type ballastless track under the long-term deformation of the box girder was conducted by combining concrete damaged plasticity (CDP) and cohesive zone model (CZM) constitutive models. The numerical simulated results indicated that after four years of operation, the creep camber of the box girder in the girder-track system would reach to 3.41 mm. The maximum tensile and compressive longitudinal stresses of the base plate would reach to 0.537 MPa and 11.983 MPa, respectively. Meanwhile, the maximum tensile and compressive longitudinal stresses of the self-compacting concrete layer would reach to 0.958 MPa and 2.701 MPa, respectively. In the box girder mid-span, significant damage could be observed in the edge of the two base plates near the mid-span, with a maximum compressive damage rate of 0.164 and the maximum tensile damage rate of 0.304. The research of this study has achieved the prediction of long-term deformation in the girder-track system, providing an important basis for the reliability assessment and life prediction of the girder-track system.

Towards an automated framework for the finite element computational modelling of directed energy deposition

In the present work, a comprehensive framework for finite element-based computational modelling of Directed Energy Deposition (DED) process is presented. The proposed approach can be fully automated and implemented on a complex real-life part geometry to accurately predict a thermo-mechanical response during the full-scale deposition process. The discrete material deposition modelling in Finite Element Analysis (FEA) leads to artificial increases in temperature gradients in the melt pool domain. A new method is therefore proposed that aims to mitigate these gradients. Additionally, an easy-to-implement free-surface detection algorithm to accurately prescribe the evolving heat transfer boundary conditions is presented. A three-dimensional sequentially coupled thermo-mechanical model of the process is then validated against experimental data obtained in a deposition case study. The simulation results show good agreement with the in-situ temperature measurements taken during the actual deposition. In addition, result analysis showed that the largest tensile residual stresses form in the hoop and axial direction on the outer domain of the thin-wall cylindrical part near the base plate while the inward material is compressed.