Search Results (27)

The main aim of this work is to compare double- or single-designed connections with wooden members and internal steel fasteners under fire conditions. Theoretical methods following Eurocodes will be used to assess the load-bearing capacity of the connections and to compare the effects of double and single shear. Several parameters will be examined to determine the load capacity. Furthermore, a numerical thermal analysis using finite element methods will be performed to estimate the temperatures inside the connections and compare them. The results show that the double shear connection in steel-to-timber, with a steel plate of any thickness as the central element and with a higher density of wood material, has better mechanical and fire resistance. Lower temperatures were also observed in this connection type in the wood material and along the length of the dowel. Full article

A new, simple machine was developed to address a long-standing challenge in biomedical and mechanical engineering: how to enhance the primary stability and long-term integration of screws and implants in low-density or heterogeneous materials, such as bone or composite substrates. Traditional screws often rely solely on external threading for fixation, leading to limited cohesion, poor integration, or early loosening under cyclic loading. In response to this problem, we designed and built a novel device that leverages a unique mechanical principle to simultaneously perforate, collect, and compact the substrate material during insertion. This mechanism results in an internal material interlock, enhancing cohesion and stability. Drawing upon principles from physics, chemistry, engineering, and biology, we evaluated its biomechanical behavior in synthetic bone analogs. The maximum insertion (MIT) and removal torques (MRT) were measured on synthetic osteoporotic bones using a digital torquemeter, and the values were compared directly. Experimental results demonstrated that removal torque (mean of 21.2 Ncm) consistently exceeded insertion torque (mean of 20.2 Ncm), indicating effective material interlocking and cohesive stabilization. This paper reviews the relevant literature, presents new data, and discusses potential applications in civil infrastructure, aerospace, and energy systems where substrate cohesion is critical. The findings suggest that this new simple machine offers a transformative approach to improving fixation and integration across multiple domains. Full article

Bone metastases occur when cancer cells from the primary tumor spread to the bones. The incidence of bone metastases is increasing due to the longer survival of patients with primary tumors, driven by advances in cancer treatments. In patients with multiple bone metastases, care is primarily palliative, aiming to improve their quality of life through pain relief. Bone metastases are strongly associated with pathological fractures, particularly in the femur. In these cases, minimally invasive treatments such as percutaneous cementoplasty and internal fixation with intramedullary nails are growing in popularity. Methods: This manuscript focuses on studying these two therapies by developing virtual models using ANSYS^® software. Thermal and thermomechanical analyses were conducted to evaluate the heat effect resulting from the polymerization of different types of bone cement and to assess the benefits of combining it with internal fixation using intramedullary nails made of different materials. Results: The results highlight the advantages of combining these two techniques compared to cementoplasty alone. Furthermore, the use of Gentamicin Bone Cement (CMW 3^®) with an intramedullary nail made of either material has been shown to provide a more significant functional improvement. Conclusions: The combination of cementoplasty with internal fixation is more effective than cementoplasty alone. The use of CMW 3^® cement with an intramedullary nail made of either material provides greater control over the growth of the metastatic lesion. The chosen injection angle results in an excessive volume of cement, causing a high degree of thermal necrosis. Full article

Traditional methods for wrinkled tubes involve welding processes and additional elements, such as plates, screws, rivets, and guides. Considering all the limitations of these processes, this work aims to propose a methodology that allows for maximising the manufacturing process of carbon steel tube joints with seaming using cold forming and minimising the cost of the final product. Therefore, the present work aims to develop a computational model, based on the finite element method, to optimise the deformation process of T6 Aluminium tubes (ø 45 × ø 38.6 mm) with a length of 120 mm. The method uses a steel die with cavities to achieve wrinkled tubes by a forming process. This numerical study was carried out using the Ansys^® 2022 R2 software. A nonlinear material and an incremental structural analysis were used. The applied methodology allowed the optimisation of process parameters, the application of forces during tube deformation, the geometry of the die cavity, boundary conditions, and mesh discretisation. Numerical modelling was carried out using the axial symmetry of the assembly (tube–die), enabling a simplified and efficient execution of the final tube geometry. The results were analysed based on the maximum pressure applied to the tube, and the vertical and horizontal displacements of the deformed component, thus obtaining the tube flow with complete filling inside the die cavity at the end of deformation. The die geometry that produced the best results presented a cavity with a radius of curvature of 3 mm, 6 mm in height, and with a depth of 4 mm. The optimised result of the die geometry generated satisfactory results, with the displacement on the x-axis of the tube of approximately 2.85 mm, ensuring the filling of the cavity at the end of the process. For this, the maximum pressure exerted on the tube was approximately 374 MPa. Full article

This work presents several results of the stability in steel columns subject to pure compression. A square hollow cross-section with different sizes was considered. This study presents all the analytical equations that need to be used to verify the stability of each column with different lengths and boundary conditions. A finite element program was also chosen to achieve the most critical loads (Euler and buckling resistance loads) in the calculation for each element under study, using linear and nonlinear geometric and material modeling. Steel material was used for the columns, where damage due to plasticity was included, through plastic behavior with isotropic hardening. Comparing the results allows us to conclude that the use of the finite element method is an alternative methodology to be used in other types or configurations of columns, where parameterized tests can be easily implemented and to contribute to the development of a wide-ranging database. The finite element method led to an accurate solution when compared with the analytical results with a maximum deviation of 14.7%. By increasing the column length and reducing the cross-section size, the design buckling resistance of the studied columns also decreases. These studies demonstrate that the length and size of the column cross-section can meaningfully increase the structural behavior of the columns. Full article

This study looks at wall partition panels with hollow core wood elements and gypsum board as protection in fire conditions. In addition to our previous research, this study on wall partitions considers the effect of steel screws in the assembly of the elements, as well as the filling of the cavity with insulating material. The goal of this work is to calculate the fire resistance time and compare the results using different numerical models. The discussion of the results analyzes the effect of steel screws and the introduction of insulating material inside the cavities. The steel screws are verified with and without threads. The numerical models are based on the finite element method, using thermal and transient analysis with nonlinear materials. The thermal insulation criterion for measuring fire resistance is referenced by the EN 1363-1:2020 standard. The steel screws allow more heat to be concentrated and, therefore, distribute it throughout the wooden wall partition members. Based on the results obtained, the use of steel screws reduces fire resistance by 71.75 min, regardless of whether the wall partition is filled with or without insulating material. Full article

Elective mandibular surgical osteotomies are commonly used to correct craniofacial discrepancies. Since the modifications proposed by Obwegeser, Dal Pont, and Hunsuck, no effective variations have been proposed to improve the biomechanical results of these mandibular osteotomies. With technological developments and the use of three-dimensional images from CT scans of patients, much has been done to plan and predict outcomes with greater precision and control. To date, 3D imaging and additive manufacturing technologies have not been used to their full potential to create innovative mandibular osteotomies. The use of 3D digital images obtained from CT scans as DICOM files, which were then converted to STL files, proved to be an efficient method of developing an innovative mandibular ramus beveled osteotomy technique. The new mandibular osteotomy is designed to reduce the likelihood of vasculo-nervous damage to the mandible, reduce the time and ease of surgery, and reduce post-operative complications. The proposed osteotomy does not affect traditional osteotomies. Anatomical structures such as the inferior alveolar nerve and intraoral surgical access were preserved and maintained, respectively. The results obtained from the digital images were validated on an additively manufactured 3D synthetic bone model. Full article

The pregnane X receptor (PXR) is a nuclear hormone receptor that plays a pivotal role in regulating gene expression in response to various ligands, particularly xenobiotics. In this context, the aim of this study was to shed light on the ligand affinity and functions of four NR1J1 paralogs identified in the marine mussel Mytilus galloprovincialis, employing a dual-luciferase reporter assay. To achieve this, the activation patterns of these paralogs in response to various toxins, including freshwater cyanotoxins (Anatoxin-a, Cylindrospermopsin, and Microcystin-LR, -RR, and -YR) and marine algal toxins (Nodularin, Saxitoxin, and Tetrodotoxin), alongside natural compounds (Saint John’s Wort, Ursolic Acid, and 8-Methoxypsoralene) and microalgal extracts (Tetraselmis, Isochrysis, LEGE 95046, and LEGE 91351 extracts), were studied. The investigation revealed nuanced differences in paralog response patterns, highlighting the remarkable sensitivity of MgaNR1J1γ and MgaNR1J1δ paralogs to several toxins. In conclusion, this study sheds light on the intricate mechanisms of xenobiotic metabolism and detoxification, particularly focusing on the role of marine mussel NR1J1 in responding to a diverse array of compounds. Furthermore, comparative analysis with human PXR revealed potential species-specific adaptations in detoxification mechanisms, suggesting evolutionary implications. These findings deepen our understanding of PXR-mediated metabolism mechanisms, offering insights into environmental monitoring and evolutionary biology research. Full article

The present study is focused on wall panels exposed to fire, with the construction building elements we used being made of wood and gypsum board materials. This type of configuration forms hollow core wood due to the constructive process. The aim is to present a numerical study to approach the calculation of the temperature inside hollow core wood elements and measure their fire resistance. The temperature evolution inside the cavities will be obtained with recourses to obtain the heat effect by convection and radiation through the wall elements. A numerical model, previously validated by the authors, will be used to carry out this process. The methodology includes the use of the finite element method in thermal and transient analysis with nonlinear materials to calculate temperature. To measure the fire resistance of the constructive model, the thermal insulation criterion, defined by the EN 1363-1:2020 standard, will be applied. Different results will be presented to discuss and ensure the verification of these fire-resistant elements. Full article

Wood is a material whose properties vary depending on different conditions, being particularly vulnerable to changes induced by high temperatures. When exposed to a fire situation, the wood properties suffer degradation, causing a char layer formation. Despite ensuring the protection of the inner core of the wood, the char layer reduces its resistant section. The evaluation of wood behavior under fire conditions is possible through experimental tests, simplified analytical models, and numerical models. To overcome difficulties in the development of experimental tests and in the approximations made to analytical methods, numerical models allow the evaluation of the fire resistance in a parametric way. First, this study will present a numerical model validated with an experimental test, using the finite element method. The validation of the results is based on the evolution of the temperature field, the char layer formation on the wooden elements, and its residual section, as well as the application of the thermal insulation criterion. The second part of the study evaluates the influence of geometric parameters, associated with different wooden constructive models with gypsum board exposed to fire. Different numerical tests are presented to evaluate the thermal and transient analysis of different wooden constructive elements with gypsum board. This type of constructive element presents cavities, making the numerical analysis in the study complex when approaching real models. The methodology applied allowed us to conclude that, at the same time, a smaller distance between wooden centers, a greater dimension of the wooden beam in height and width, as well as a greater thickness of gypsum board guarantee a better performance of the constructive wooden model. Full article

Autogenous bone grafts can be harvested from either intraoral or extraoral sources. Intra-oral sources include healing tooth extraction wounds, a bone from edentulous ridges, bone trephined from within the jaw using trephine drills, bone formed in wounds, and bone from the maxillary tuberosity, ramus, and mandibular symphysis. Extra-oral sources are the iliac crest, which provides cancellous bone marrow, and the tibia and calvaria. Autogenous bone grafting aids in probing depth reduction, gaining clinical attachment, the bone filling of osseous defects, and the regeneration of new bone, cementum, and periodontal ligaments in teeth. An innovative biomedical device is presented in the form of an autogenous bone collector that can fill defects of 96.91 mm³ with bone particulates, and may be used in bioengineered scaffolds. Experimental studies on synthetic bone have demonstrated the feasibility and applicability of the amount of bone obtained. Full article

This work aims to present a study approach for double-shear connections of wood under fire with dowel pins and plates in steel material, using different types of glulam. The simplified Eurocode equations for ambient temperature were used to determine the dimensions and the number of dowel pins that each studied connection needs in order to resist an applied tensile load. Following this methodology, the finite element method was used to assess the thermal analysis of the studied connections under fire. The study aims to increase the information on these connections, where the wood material represents a complicated behavior in fire circumstances, with the addition of the steel material. The heat conducted by the dowel pin inside the connection, and the steel plate and its effect on the wood were analyzed. According to the results, it can be assumed that the temperature evolution is due to the geometry of the connection, the dowel pin or plate position, and the glulam density. Inside the wood element, the temperature remains lower, and externally a charred depth is developed when the target temperature of 300 °C is reached, and, in the vicinity of the dowel pin or the steel plate, a burned wood depth is indirectly formed. The rate of the charred layer is not constant throughout the entire fire exposure. Steel-to-timber connections with an internal steel plate with high glulam density have greater fire resistance due to the lower temperatures obtained. Full article

Oral maxillofacial rehabilitation of the atrophic maxilla with or without pneumatization of the maxillary sinuses routinely presents limited bone availability. This indicates the need for vertical and horizontal bone augmentation. The standard and most used technique is maxillary sinus augmentation using distinct techniques. These techniques may or may not rupture the sinus membrane. Rupture of the sinus membrane increases the risk of acute or chronic contamination of the graft, implant, and maxillary sinus. The surgical procedure for maxillary sinus autograft involves two stages: removal of the autograft and preparation of the bone site for the graft. A third stage is often added to place the osseointegrated implants. This is because it was not possible to do this at the same time as the graft surgery. A new bioactive kinetic screw (BKS) bone implant model is presented that simplifies and effectively performs autogenous grafting, sinus augmentation, and implant fixation in a single step. In the absence of a minimum vertical bone height of 4 mm in the region to be implanted, an additional surgical procedure is performed to harvest bone from the retro-molar trigone region of the mandible to provide additional bone. The feasibility and simplicity of the proposed technique were demonstrated in experimental studies in synthetic maxillary bone and sinus. A digital torque meter was used to measure MIT and MRT during implant insertion and removal. The amount of bone graft was determined by weighing the bone material collected by the new BKS implant. The technique proposed here demonstrated the benefits and limitations of the new BKS implant for maxillary sinus augmentation and installation of dental implants simultaneously. Full article

The restoration of osseous defects is accomplished by bone grafts and bone substitutes, which are also called biomaterials. Autogenous grafts, which are derived from the same individual, can retain the viability of cells, mainly the osteoblasts and osteoprogenitor stem cells, and they do not lead to an immunologic response, which is known as the gold standard for bone grafts. There are both different techniques and devices that can be used to obtain bone grafts according to the needs of the patients, the location, and the size of the bone defect. Here, an innovative technique is presented in which the patient’s own bone is removed from the trigone retromolar region of the mandible and is inserted into a dental alveolus after the extraction and immediate insertion of an innovative dental implant, the BKS. The first step of the technique creates the surgical alveolus; the second step perforates the BKS in the retromolar region, and shortly after, the BKS containing the bone to be grafted is removed; the third step screws the BKS bone that collects in the created surgical alveolus. Experimental studies have shown the feasibility and practicality of this new technique and the new dental implant model for autogenous transplants. Full article

Biotribology is applied to study the friction, wear, and lubrication of biological systems or natural phenomena under relative motion in the human body. It is a multidisciplinary field and tribological processes impact all aspects of our daily life. Tribological processes may occur after the implantation of an artificial device in the human body with a wide variety of sliding and frictional interfaces. Blood is a natural bio-lubricant experiencing laminar flow at the lower screw velocities associated with drilling implants into bone, being a viscoelastic fluid with viscous and fluid characteristics. The viscosity comes from the blood plasma, while the elastic properties are from the deformation of red blood cells. In this study, drilling parameters according to material properties obtained by Finite Element Analysis are given. The influence of blood on the resulting friction between the surfaces is demonstrated and correlated with mechanical and biological consequences, identifying an innovative approach to obtaining a new lubricant parameter for bone drilling analysis. The lubrication parameter (HN) found within the limitations of conditions used in this study is 10.7 × 10⁻⁷ for both cortical bone (D1) and spongy bone (D4). A thermal-structural analysis of the densities of the soft bone (D4) and hard bone (D1) shows differences in only the equivalent stress values due to the differences in respective Young moduli. The natural occurrences of blood as a lubricant in bone-screw perforations are poorly investigated in the literature and its effects are fundamental in osseointegration. This work aims to elucidate the relevance of the study of blood as a lubricant in drilling and screwing implants into bone at lower speeds. Full article