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Tensile testing is one of the most important types of engineering tests used for all metallic materials that provides material characteristics. In this paper, experiments were performed on grade PC52 (0.22% C) steel specimens using an INSTRON 8801 universal testing machine to determine yield strength, tensile strength, strain at break and Young’s modulus. Strain rates applied during tests were in the range characteristic for static tensile tests as recommended in standards ASTM Standard E8/E8M-16a and ISO 6892-1:2016, being typical for testing steel used for engineering components in applications such as storage tanks and pressure vessels. The influence of the strain rate on the values of the material properties was analyzed and the result was in agreement with reference literature. Coefficients of variation were calculated for the measured values of steel properties for different strain rates and compared to values prescribed in standards, leading thus to the recommendation of a specific value of strain rate for the tensile test of steel PC52.

The paper presents a numerical study regarding the mechanical response of the body of a freight wagon to the usual loads encountered during service. The main goal of the present research is to investigate the possibility to replace the steel walls of the wagon with walls made of laminated composites. In this way, the total mass of the wagon can be decreased, leaving room for supplementary load of goods. Finite element analyses of the wagon with steel walls is presented first, in order to show that most of the load is taken by the structure of the wagon, while the stresses in the walls are low. Further, composite plates with different thickness are studied to find the minimum value of thickness for which the displacements have values below a certain range. These thicknesses are further considered in the finite element analyses of the entire wagon with composite walls to investigate if the new walls significantly change the stresses in the vehicle structure. It was concluded that the replacement does not alter the stress state in the structure, and, consequently, it is a good solution for diminution of the total mass of the vehicle.

During lung cancer screening, suspected nodules are detected using computed tomography. Although most nodules are benign, a tissue diagnostic is still required. Currently, all diagnostic procedures that use image-guided tools expose both the patient and the medical doctor to damaging X-ray radiation. The present study describes the development of a novel robotic and electromagnetic tracking navigation system to guide a catheter in the peripheral airways and made of a navigation software and a patent pending robotic system, EndoRoTM that inserts and guides the catheter semi-automatically to reach a specific target in the airways without the need of CT or fluoroscopy scanning. The preliminary tests on a benchtop airway model showed that the novel robotic system allows navigation through the bronchial tree, in both manual manipulation with a joystick and semi-automatic computer manipulation without fluoroscopy scanning. Overall, the new robotic system will allow a more precise guidance of the biopsy catheters to targets located in the peripheral airways, will reduce injury, and improve the clinical outcomes in early cancer diagnosis and treatment.

In this paper, the experimental determination of the stress intensity factor in thick walled cylinders subject to uniform internal pressure and having longitudinal non-penetrating cracks is presented. Photoelastic measurements were used together with the expressions of the stress field near the crack tip for Mode I crack extension and a specific methodology for stress intensity factor determination. Two types of longitudinal cracks - internal and external - were considered. Four plane models were manufactured and analyzed in a plane polariscope at different values of the applied internal pressure. The values of the normalized stress intensity factor were calculated and the results were compared to those reported by other authors. A good accuracy was noticed, showing the reliability of the experimental procedure.

The paper presents an algorithm proposed by the authors in order to obtain a theoretical model of the bronchial and used to test the virtual bronchoscopy procedure implemented in an innovative system for bronchoscopy with electromagnetically tracked and steerable biopsy forceps. The procedure is based on the Weibel theoretical model of the human tracheobronchial tree with new features added by the authors. The algorithm can be an important helping tool in the development of sophisticated algorithms for bronchoscopy applications and may be further implemented in clinical studies of navigated bronchoscopy.

Following an initial design published earlier, the authors propose in this paper a new solution for passive energy absorption during train collisions. The energy that should be absorbed is first calculated based on the masses and usual speeds of the railway stock in Romania. Considering the energy that is absorbed in the buffers mounted on each wagon or locomotive, the remaining quantity that should be taken by the new solution is found. Then, the newly designed structure is described in detail. It has four different elements that could absorb the impact energy: a deformable pipe, a penetrator, a flange with cutting knives and a bending flange. The quantity of energy absorbed by each element is calculated based on the mechanical work of the forces acting during deformation following the impact. It is shown that the total energy is higher than the necessary one. Implementation of the proposed solution has a relatively low cost compared to the benefits obtained in an unwanted case of collision and it does not involve any special technical and logistic problems. Thus, this element can be successfully used as a solution that can diminish the consequences of train collisions.

A novel system for electromagnetic navigation in bronchoscopy (NaviCAD) to improve peripheral lesion targeting and diagnostic is currently under development. The virtual bronchoscopy module of this system, including the collision and resolution algorithm, together with some preliminary tests on a complex phantom are presented in this paper. The NaviCAD system consists of a planning and orientation software, a navigation forceps, and an electromagnetic tracking system connected to a computer running the NaviCAD software. NaviCAD can be used with any bronchoscopy system, it has a short set-up procedure time and learning curve. The system proves to be easy to use, accurate and useful for experienced users and novices, with precision in reaching targets in sub-segmental bronchi where a video-bronchoscope cannot reach.

During clinical procedures for investigations of lung tumors, such as bronchoscopy, the breathing process causes movement of tumor nodules, affecting thus the accuracy of the determinations. In order to reduce the excessive irradiation during medical imaging procedures used by clinicians to track the tumor movements, biomechanical models of the respiration process based on the finite element method are currently being developed. This paper describes a methodology for obtaining a finite element model used to assess the magnitude of displacements inside the lungs during the breathing process. A simple to apply method of imposing lung outer surface boundary conditions is developed using an algorithm implemented in MATLAB. The influence of the mesh size on the accuracy of the resulted outer surface displacements was checked by simulating the same conditions for a spherical object.

Virtual bronchoscopy is often used for planning a real bronchoscopy procedure. Software applications are developed for virtual bronchoscopy, involving usually segmentation of the tracheobronchial tree from the medical image scan, which is a difficult operation, both conceptually and from the computer implementation and running time point of view. That is why in this paper, a new method for bronchoscopy procedure planning that does not require such a segmentation is presented. The proposed procedure involves automatic path generation between the starting and ending points, skin removal, an algorithm for detection and resolution of collision with the airways walls and validation of the automatically created path. Results are presented for two datasets – one being the representation of a theoretical lungs model, with six levels of branches and the other one being the image scan of a real patient. Together with a system for tracking the bronchoscope during the real procedure, the proposed method can improve the diagnostic success rate of lung cancer using bronchoscopy and decrease the discomfort perceived by the patient.

In this paper, a numerical analysis is undertaken in order to establish the three dimensional linear displacementsof tumors located inside the lung. In this way, the position of the tumor can be emphasized in various stages of the breathing process, helping thus the healthcare professionals both in surgical operations and in performing transbronchial biopsy. First, a geometrical model of the lung and airways was achieved with a 3D reconstruction program using CT scan images. The model was then imported in the ANSYS finite element software, which was used to perform the numerical simulations. The breathing process was simulated by applying external pressure on the surfaces of the lung. The values of this pressure were chosen as to correspond to the inspiration phase of the breathing process. Finally, conclusions are drawn regarding the values of the displacement of the nodules during breathing.

The paper presents two practical applications in which the weight function method is used to determine the stress intensity factor as the main structural integrity assessment parameter in linear elastic fracture mechanics. In this method, one may obtain the solution for the stress intensity factor for a given crack configuration and a certain loading, provided a complete solution (the Mode I stress intensity factor K Ir ( a ) and the displacements of the crack faces u Ir ( x , a )) for the same crack problem is known in another loading case called the reference case . Three different cases can be encountered when the weight function method is used: i. The stress intensity factor K Ir ( a ) and the displacement field u Ir ( x , a ) are known; ii. Only the stress intensity factor K Ir ( a ) is known and iii. Both K Ir ( a ) and u Ir ( x , a ) are unknown. In the first case, the method can be applied directly. This paper presents two practical applications for the second and the third case: Stress intensity factors for a strip with a cracked hole subjected to point loads (case 2) and stress intensity factors for an axially cracked thick walled cylinder subjected to internal pressure (case 3). For case 2, the reference stress intensity factors were first calculated using the compounding technique in a reference case (uniform remote traction). Then, an approximate expression of the displacements field found in the literature was used to calculate the weight function. In case 3, the authors propose a solution based on curve fitting of the crack face displacements obtained through finite element analysis. The obtained results were compared with the ones from the literature (where available). In all cases the agreement was very good, showing the reliability of the proposed solutions.

PurposeThe purpose of this paper is to develop a methodology for in situ stress intensity factor (SIF) determination that can be used for the analysis of cracked structures. The technique is based on digital image correlation (DIC) combined with an overdetermined algorithm.Design/methodology/approachThe linear overdeterministic algorithm for calculating the SIF based on stress values around the crack tip is applied to a strain field obtained by DIC.FindingsAs long as the image quality is sufficiently high, a good accuracy can be obtained for the measured SIF. The crack tip can be automatically detected based on the same strain field. The use of the strain field instead of the displacement field, eliminates problems related to the rigid body motion of the analysed structure.Practical implicationsIn future works, based on the applied techniques, the SIF of complex cracked plane stress structures can be accurately determined in real engineering applications.Originality/valueThe paper demonstrates application of known techniques, refined for other applications, also the use of stress field for SIF overdeterministic calculations.

Three-dimensional finite element analyses are used in this paper to calibrate the stress intensity factor in a cracked stiffened plate subjected to remote uniform traction. An accurate numerical determination of the stress field and stress intensity variation through the thickness of a central cracked plate was first carried out in order to evaluate three-dimensional effects. A stiffened cracked plate was then analysed, taking into account the results and the conclusions obtained in the previous study. Such a structure was chosen due to the growing interest for large integral metallic structures for aircraft applications, following the continuous need for low cost and the emergence of new technologies. The J-Integral technique was used to calculate the values of the stress intensity factor along the plate thickness. The plane strain behaviour near the crack front and the variation of the opening stress are discussed.

The weight function method has been extensively used in fracture mechanics for stress intensity factor determination. It was shown that, if a complete solution (the crack face displacement and the stress intensity factor) to a crack problem for one loading system is known, then the solution for the stress intensity factor for the same cracked configuration, but with any other loading, may be obtained directly from the known solution. Several procedures have been proposed, which use a solution for the stress intensity factor available from handbooks. In this paper, an approach based on the crack face displacements obtained from a finite element analysis is used. This procedure can be applied without knowing a previous solution for a certain loading. The method proves to be extremely efficient, and some results and generalisations for a pressurised cylindrical shell with an external straight axial crack are presented.

The paper presents the results of some comparative experimental studies that show the biomechanical changes which appear following different types of corrective osteotomy. The photoelastic technique was applied to plane models. The modifications in the stress distribution on the contour after the osteotomy in comparison with the situation before surgery were studied. Three types of osteotomy are considered: valgus osteotomy, varus osteotomy and Chiari pelvis osteotomy. Using the same experimental technique, the distribution of the contact pressure at the interface between the polyethylene cup and the femoral head is investigated, for a total hip prosthesis, as the extreme solution in the case of advanced hip arthroses. Both a normal situation and the malposition of prosthetic components were analyzed.