Joint Elements Research Articles

Numerical Model for Flexural Analysis of Precast Segmental Concrete Beam with Internal Unbonded CFRP Tendons.

A new construction scheme was recently developed for precast segmental concrete beams by replacing steel tendons with internal unbonded carbon-fiber-reinforced polymer tendons. The discontinuous behaviors of the opening joints and unbonded phenomenon of tendons made their flexural behaviors more complicated than those of monolithic beams and members with bonded tendons. Currently, the knowledge on the structural performance of precast segmental concrete beams with internal unbonded carbon-fiber-reinforced polymer tendons is still limited. An efficient numerical model is urgently needed for the structural analysis and performance evaluation of this new construction scheme. In this paper, a new beam–cable hybrid model was proposed accounting for the mechanical behaviors of open joints and unbonded tendons. The numerical model was implemented in the OpenSees software with the proposed modeling method for joint elements and a newly developed element class for internal unbonded tendons. The effectiveness of the proposed model was verified by comparisons against two simply supported experimental tests. Then, the numerical model was employed to evaluate the flexural performance of a full-scale bridge with a span of 37.5 m. Compared with the precast segmental concrete beam with external steel tendons, the scheme with internal unbonded carbon-fiber-reinforced polymer tendons significantly improved the flexural capacity and ductility by almost 54.6% and 8.9%, respectively. The span-to-depth ratio and prestressing reinforcement ratio were the main factors affecting the flexural behaviors. With the span-to-depth ratio increasing by 23%, the flexural capacity decreased by approximately 38.6% and the tendon stress increment decreased by approximately 15.7%. With the prestressing reinforcement ratio increasing by 65.4%, the flexural capacity increased by 88.7% and the tendon stress increment decreased by approximately 25.2%.

Risk assessment and support design optimization of a high slope in an open pit mine using the jointed finite element method and discontinuous deformation analysis

Risk assessment and support design optimization of a high slope in an open pit mine using the jointed finite element method and discontinuous deformation analysis

Three-dimensional continuous-discrete pore-fracture mixed seepage model and hydro-mechanical coupling model to simulate hydraulic fracturing

A three-dimensional (3D) continuous-discrete seepage mixed model is presented, which considers the fluid exchange and the pore pressure discontinuity at the fracture. In this model, both the fracture seepage and pore seepage are considered simultaneously. Moreover, the node sharing connection of the neighboring elements near the fracture are dynamically updated during fracture propagation. The pore pressure discontinuity and fluid exchange at the fracture can be well considered but the virtual joint element and its very large exchange coefficient do not need to be introduce. The mixed model is coupled with finite discrete element method (FDEM) to create a hydro-mechanical coupling model for simulating hydraulic fracturing. Three examples are given to verify the mixed seepage model and hydro-mechanical coupling model. Finally, a hydraulic fracturing experiment is simulated by using the coupling model. The simulation results demonstrate that the differences in in-situ stress and approach angle are the most important factors controlling the fracture propagation behavior, and the shear strength of natural fractures also affects the intersection mode.

Passive chaos suppression for the planar slider-crank mechanism with a clearance joint by attached vibro-impact oscillator

Chaotic dynamic behavior in clearance joints is the prominent nonlinear factor for multibody systems. This study presents a passive chaos suppression method to stabilize the planar slider-crank mechanism with a clearance joint. The strategy resorts to a vibro-impact oscillator attached to the slider. Primarily, the impact principle is employed to characterize the dynamics in clearance joints. The mathematical model of the integral system is conducted subsequently. The chaotic system behavior is evaluated by bifurcation analysis varying clearance size and crank speed. When the controller is activated, parametric optimizations of the stiffness, clearance coefficient, and particle mass are conducted to achieve optimum chaos elimination. Phase portraits, the largest Lyapunov exponent, and time-frequency distribution are evaluated. Numerical results illuminate that an adjusted oscillator can suppress the chaotic high-frequency composition of system response and help to maintain continuous contact between the joint elements. The results suggest applying the identical clearance size in the revolute joint and vibro-impact oscillator for fast optimization. Moreover, the method is still technology valid when considering different contact principles. Ultimately, a test platform is established to achieve some experimental validations.

Human Mesenchymal Stem Cell-Derived Miniature Joint System for Disease Modeling and Drug Testing.

Diseases of the knee joint such as osteoarthritis (OA) affect all joint elements. An in vitro human cell‐derived microphysiological system capable of simulating intraarticular tissue crosstalk is desirable for studying etiologies/pathogenesis of joint diseases and testing potential therapeutics. Herein, a human mesenchymal stem cell‐derived miniature joint system (miniJoint) is generated, in which engineered osteochondral complex, synovial‐like fibrous tissue, and adipose tissue are integrated into a microfluidics‐enabled bioreactor. This novel design facilitates different tissues communicating while still maintaining their respective phenotypes. The miniJoint exhibits physiologically relevant changes when exposed to interleukin‐1β mediated inflammation, which are similar to observations in joint diseases in humans. The potential of the miniJoint in predicting in vivo efficacy of drug treatment is confirmed by testing the “therapeutic effect” of the nonsteroidal anti‐inflammatory drug, naproxen, as well as four other potential disease‐modifying OA drugs. The data demonstrate that the miniJoint recapitulates complex tissue interactions, thus providing a robust organ chip model for the study of joint pathology and the development of novel therapeutic interventions.

A joint FrameNet and element focusing Sentence-BERT method of sentence similarity computation

As one of the fundamental research areas of natural language processing, sentence similarity computation attracts researchers’ attention. Considering two single independent sentences, it is difficult to measure the similarity between them without sufficient context information. To solve this issue, we propose a joint FrameNet and element focusing Sentence-BERT method of sentence similarity computation (FEFS3C). Considering the actual meaning of sentences, we adopt the frame semantics theory and adapt FrameNet in FEFS3C. Moreover, focusing on critical information conveyed in sentences, FEFS3C takes the superiority of deep learning technologies and proposes a new sentence representation model element focusing Sentence-BERT (EF-SBERT) which improves traditional sentence representations. Two primary considerations of sentences in FEFS3C “sentence meaning” and “critical sentence information” aim to better utilize the influence of sentences context. To evaluate the performance of FEFS3C, we carried out experiments on the standard test set “STS-B”. Results show that FEFS3C has obtained better Spearman correlation compared with traditional methods.

Our experience in the treatment of congenital hip dislocation in children of different ages

The experience in treatment of children with neglected congenital hip dislocation is presented. The main principles of management are defined. The successive complex of curative measures including conservative treatment using Ter-Egiazarov-Sheptun functional plaster bandage in children over 6 months is described in detail. In failed conservative treatment the reduction of dislocation is performed using over head technique. In children over 3 years descent of femoral head and reduction of dislocation are carried out on distraction system followed by surgical correction of all dysplastic elements of the hip joint. Technique of detorsion-varus osteotomy with application of distraction system and closed reduction is described. Long-term results were evaluated using CITO score system in 255 patients. Good and satisfactory results were in 91.7% of cases.

A 2D discrete moisture diffusion model for simulating desiccation fracturing of soil

The desiccation fracturing of soil is widespread, which affects the migration of rainwater in the soil, and the stability of slopes or other projects. This paper proposes a simple two-dimensional (2D) discrete moisture diffusion model considering the influence of fractures on moisture migration. The moisture diffusion model is used in conjunction with the finite discrete element method (FDEM) to create a 2D discrete moisture diffusion-fracture coupling model, which is implemented in a GPU parallel multiphysics finite-discrete element software, namely MultiFracS. The coupled model is made up of three parts: a 2D discrete moisture diffusion model that takes into account the influence of fractures on moisture migration, a shrinkage deformation and stress computation, and an FDEM fracture mechanical computation. First, the moisture distribution in the system is analyzed using the moisture diffusion model. The shrinkage stress resulting from the moisture change is then computed. Finally, the shrinkage stress is added to the governing equation of FDEM to perform the fracture mechanical computation. Desiccation fracturing of the soil can be modeled using the processes outlined above. The paper firstly verifies the correctness of the 2D discrete moisture diffusion model to deal with the moisture migration in a continuous media, a media with impervious fractures or permeable fractures. Then, we give a principle that is used to determine the moisture exchange coefficient of the unbroken joint element through the parameter sensitivity analysis. Moreover, typical shrinkage deformation and stress problems and soil desiccation fracturing experiments are simulated. The simulation results are in good agreement with the analytical solutions and experiment results, verifying the effectiveness of the 2D discrete moisture diffusion-fracture coupling model to deal with shrinkage deformation and stress problems and the desiccation fracturing of soil. The coupled model provides a powerful solution tool to study the desiccation fracturing of soil.

New imaging tools for mouse models of osteoarthritis.

Osteoarthritis (OA) is a chronic degenerative disease characterized by a disruption of articular joint cartilage homeostasis. Mice are the most commonly used models to study OA. Despite recent reviews, there is still a lack of knowledge about the new development in imaging techniques. Two types of modalities are complementary: those that assess structural changes in joint tissues and those that assess metabolism and disease activity. Micro MRI is the most important imaging tool for OA research. Automated methodologies for assessing periarticular bone morphology with micro-CT have been developed allowing quantitative assessment of tibial surface that may be representative of the whole OA joint changes. Phase-contrast X-ray imaging provides in a single examination a high image precision with good differentiation between all anatomical elements of the knee joint (soft tissue and bone). Positron emission tomography, photoacoustic imaging, and fluorescence reflectance imaging provide molecular and functional data. To conclude, innovative imaging technologies could be an alternative to conventional histology with greater resolution and more efficiency in both morphological analysis and metabolism follow-up. There is a logic of permanent adjustment between innovations, 3R rule, and scientific perspectives. New imaging associated with artificial intelligence may add to human clinical practice allowing not only diagnosis but also prediction of disease progression to personalized medicine.

A three-dimensional deformable spheropolyhedral-based discrete element method for simulation of the whole fracture process

A deformable spheropolyhedral-based discrete element method (DS-DEM) is proposed for predicting the evolution of fracture by coupling the finite element method (FEM) with the spheropolyhedral-based discrete element method (DEM). Under the framework of the proposed method, each rock mass is discretized into finite elements, and zero thickness joint elements are inserted along the boundary of finite element elements. The fictitious crack model and the Mohr-Coulomb failure criterion are employed to determine the failure state and failure mode of joint elements. The contact interaction between discrete particles and fracture surfaces is captured by the spheropolyhedral-based DEM. The method is verified by particle stacking test, three-point bending beam test, Brazilian disc tensile strength test, crack propagation in a single notched beam test, four-point bending beam test, and sphere impact test. The results of numerical simulations indicate that the proposed method is adaptable in simulating the whole fracture process of quasi-brittle materials including the initiation and propagation of cracks, as well as the collision and deformation of fragments.

A new method of micro-slip contact normal pressure modeling and its application in the dynamic analysis of the dovetail–tenon–mortise jointed blades

In this paper, a contact slip mechanics model based on pressure distribution is developed, it is formed from multiple contact pairs and can define the contact behavior between contact interfaces. First, we establish the jointed structure's finite element model to calculate the contact interface's nodal pressure. Following this calculation, applying the cubic spline interpolation to the nodal pressure data, we obtain the contact surface pressure. Then using the theory of load equivalence, the contact surface pressure is converted into an equivalent load. The equivalent load is used as the normal pressure of the contact pairs place on the contact surface nodes. Subsequently, to verify the developed modeling approach, we establish a simplified blade model with the tenon–mortise structure for trial calculation. Finally, the nonlinear frictional force is linearized to solve the nonlinear differential equation by the incremental harmonic balance method (IHBM). The results show that the tenon–mortise contact surface exhibits micro-slip characteristics, which means that the pressure distribution characteristics of the contact surface are retained. The contact slip mechanics model developed in this paper is general which can be applied in modeling the contact surfaces of other joints.

Біомеханічне визначення стабільності ліктьового суглоба при переломах головки променевої кістки, комбінованих із пошкодженням колатеральних зв’язок

Актуальність. Переломи головки променевої кістки є частими пошкодженнями, при яких широко застосовується видалення зламаної головки [3]. При цьому лікарі, вважаючи це втручанням, що не має серйозних негативних наслідків, не враховують значне порушення стабільності суглоба внаслідок такої операції. У випадках пошкодження типу «нещаслива тріада» або в комбінації з пошкодженням колатеральних зв’язок вилучення головки променевої кістки призводить не тільки до додаткової втрати анатомічних співвідношень, а й до втрати надії на повернення функції ліктьового суглоба (ЛС). Мета роботи: вивчити фактори забезпечення стабільності в ліктьовому суглобі в положенні розгинання 175° в умовах дефекту головки променевої кістки 5–10–15 мм, комбінованого з пошкодженням колатеральних зв’язок ліктьового суглоба, при навантаженні 5 кг. Матеріали та методи. Розрахунки напружено-деформованого стану елементів ліктьового суглоба методом скінченних елементів на базі комп’ютерної 3D-моделі Zygote Media Group, Inc. інтактного ліктьового суглоба та суглоба з дефектом головки променевої кістки 5–10–15 мм, комбінованим із пошкодженням колатеральних зв’язок ліктьового суглоба, в положенні розгинання 175°. Критеріями оцінки напружено-деформованого стану були напруження за Мізисом, контактні напруження, максимальні деформації та переміщення. Результати. У положенні розгинання 175° ізольоване пошко­дження lig. collateralе radiale викликає значне зростання показників загальних переміщень моделі (Total Deformation) на 81,5 % (Δ = 44,24 мм) та переміщень проксимального відділу (головки) променевої кістки на 53,2 % (Δ = 5,70 мм), які опосередковано є критерієм стабільності моделі ЛС. Зростання показників загальних переміщень одночасно супроводжується зростанням показників напружень на ліктьовій кістці в 4,6 раза (σmax = 29,78 MPa), променевій кістці — в 4,8 раза (σmax = 34,31 MPa) та ділянках кріплення пошкодженої lig. collateralе radiale до променевої кістки — у 5,3 раза (σmax = 38,7 MPa). Пошкодження lig. collateralе radiale, комбіноване з дефектом головки променевої кістки 15 мм, викликає зростання показників загальних переміщень моделі (Total Deformation) у 2 рази (Δ = 53,01 мм) та зростання показників переміщень проксимального відділу променевої кістки — у 2,5 раза (Δ = 9,3 мм). Зростання показників переміщень одночасно супроводжується значним зростанням показників напружень на ліктьовій кістці у 6 разів (σmax = 39,82 MPa), променевій кістці — у 5 разів (σmax = 40,02 MPa) та на ділянках кріплення lig. collateralе ulnare аnterior intermediate і lig. collaterale radiale до кістки — у 7 разів (σmax = 52,4 MPa).Ізольоване пошкодження lig. collateralе ulnare викликає значне зростання показників загальних переміщень моделі (Total Deformation) на 64,1 % (Δ = 39,99 мм) та переміщень проксимального відділу (головки) променевої кістки на 44,6 % (Δ = 5,38 мм). При цьому відбувається зростання показників напружень на ліктьовій кістці у 3 рази (σmax = 19,27 MPa), променевій кістці — у 3,8 раза (σmax = 27,08 MPa), плечовій кістці — у 2,8 раза (σmax = = 18,53 MPa) та ділянках кріплення пошкодженої lig. collateralе ulnare аnterior intermediate до медіального виростка плечової кістки — у 6,7 раза (σmax =7,94 MPa) та ділянках кріплення lig. collateralе radiale до променевої кістки — у 3,9 раза (σmax = 28,47 MPa). Пошкодження lig. collateralе ulnare, комбіноване з дефектом головки променевої кістки 15 мм, викликає зростання показників загальних переміщень моделі (Total Deformation) в 1,2 раза (Δ = 49,43 мм). При цьому показники загальних переміщень проксимального відділу променевої кістки (головки) зменшились на 4 % (Δ = 5,14 мм). Дефект головки 15 мм викликає додаткові переміщення проксимального відділу променевої кістки за віссю Х (Directional Deformation) до Δ = 13,3 мм. Зростання показників переміщень одночасно супроводжується зростанням показників напружень на ліктьовій кістці на 27 % (σmax = 19,27 MPa), променевій кістці — на 36 % (σmax = 27,08 MPa) та на ділянках кріплення lig. collateralе ulnare anterior intermediate і lig. collaterale radiale до кістки — в 1,8 раза (σmax = 28,47 MPa). Висновки. За даними дослідження, пошкодження lig. collateralе radiale та lig. collateralе ulnare викликає збільшення показників загальних переміщень (Total Deformation) усієї моделі та загальних переміщень проксимального відділу променевої кістки (головки) за рахунок девіації дистального відділу передпліччя (променевої кістки), які відображають виникнення нестабільності ЛС у положенні розгинання 175°. Із збільшенням величини дефекту головки променевої кістки на фоні пошкодження колатеральних зв’язок ЛС відбувається пропорційне порушення стабільності ЛС. Асиметричність навантаження на суглобові поверхні призводить до зростання напружень на контактних поверхнях ліктьової та плечової кісток, у відповідних ділянках суглобового хряща ліктьової та плечової кісток, на залишках пошкоджених зв’язок та у місцях їх кріплення до ліктьової та променевої кісток. Пошкодження lig. collateralе ulnare призводить до більш значного порушення стабільності ЛС, ніж при пошкодженні lig. collateralе radiale, за рахунок суми загальних переміщень (Total Deformation) дистального відділу передпліччя (девіації) та осьових переміщень проксимального відділу променевої кістки (Directional Deformations) в ділянці дефекту головки, з її наближенням до суглобової поверхні надвиростка плечової кістки. Значний ріст показників напружено-деформованого стану в місцях кріплення колатеральних зв’язок ЛС до кістки, у тому числі й на пошкоджених, відбувається за рахунок перерозподілу навантаження на зв’язковий апарат в умовах нестабільності ЛС та може викликати їх пошкодження.

A Physically Consistent Model for Forced Torsional Vibrations of Automotive Driveshafts

The aim of this research was to design a physically consistent model for the forced torsional vibrations of automotive driveshafts that considered aspects of the following phenomena: excitation due to the transmission of the combustion engine through the gearbox, excitation due to the road geometry, the quasi-isometry of the automotive driveshaft, the effect of nonuniformity of the inertial moment with respect to the longitudinal axis of the tulip–tripod joint and of the bowl–balls–inner race joint, the torsional rigidity, and the torsional damping of each joint. To resolve the equations of motion describing the forced torsional nonlinear parametric vibrations of automotive driveshafts, a variational approach that involves Hamilton’s principle was used, which considers the isometric nonuniformity, where it is known that the joints of automotive driveshafts are quasi-isometric in terms of the twist angle, even if, in general, they are considered CVJs (constant velocity joints). This effect realizes the link between the terms for the torsional vibrations between the elements of the driveshaft: tripode–tulip, midshaft, and bowl–balls–inner race joint elements. The induced torsional loads (as gearbox torsional moments that enter the driveshaft through the tulip axis) can be of harmonic type, while the reactive torsional loads (as reactive torsional moments that enter the driveshaft through the bowl axis) are impulsive. These effects induce the resulting nonlinear dynamic behavior. Also considered was the effect of nonuniformity on the axial moment of inertia of the tripod–tulip element as well as on the axial moment of inertia of the bowl–balls–inner race joint element, that vary with the twist angle of each element. This effect induces parametric dynamic behavior. Moreover, the torsional rigidity was taken into consideration, as was the torsional damping for each joint of the driveshaft: tripod–joint and bowl–balls–inner race joint. This approach was used to obtain a system of equations of nonlinear partial derivatives that describes the torsional vibrations of the driveshaft as nonlinear parametric dynamic behavior. This model was used to compute variation in the natural frequencies of torsion in the global tulip (a given imposed geometry) using the angle between the tulip–midshaft for an automotive driveshaft designed for heavy-duty SUVs as well as the characteristic amplitude frequency in the region of principal parametric resonance together the method of harmonic balance for the steady-state forced torsional nonlinear vibration of the driveshaft. This model of dynamic behavior for the driveshaft can be used during the early stages of design as well in predicting the durability of automotive driveshafts. In addition, it is important that this model be added in the design algorithm for predicting the comfort elements of the automotive environment to adequately account for this kind of dynamic behavior that induces excitations in the car structure.

The state of the bone structures of the temporomandibular joint in dental patients with unilateral terminal defects of the dentition

The aim of the study was to evaluate morphological changes in the bone structures of the elements of the temporomandibular joint in patients with unilateral terminal defects of the dentition. The study involved 90 patients aged 18 to 44 years, who underwent: clinical examination of the maxillofacial region, cone-beam computed tomography with digital processing of computed tomograms in the Avantis 3D system, statistical processing of the results obtained. In the course of the study, two main samples were determined: depending on the side of the defect and on the duration of the appearance of the defect of the dentition. During the study of 90 computed tomograms of patients with unilateral terminal defects of the dentition and their further computer processing, the structural features of the bone elements of the temporomandibular joint were studied, the main morphometric changes of the mandibular heads were established, a comparative characteristic of morphometric parameters in the study groups was carried out. The identified structural changes in the heads of the lower jaw in patients with unilateral end defects of the dentition appear as a result of the presence of an untreated defect of the dentition for a long period of time.

Radiological analysis of size of bone elements of the temporomandibular joint in children and adolescents with class II malocclusion

The aim of the study was to assess the ratio of bone elements of the temporomandibular joint (TMJ) in children and adolescents with distal occlusion according to cone-beam computed tomography (CBCT). CBCT of the TMJ was analyzed in 121 patients aged 12-18 years, which were divided into two age groups: group I - children aged 12-15 years (62 cases in total, of which 47 patients with distal occlusion and 15 patients with physiological occlusion) and II group - adolescents aged 15-18 years (59 cases, of which 48 patients with distal occlusion and 11 patients with physiological occlusion). CBCT of the temporomandibular joint was performed by the standard method in the position of habitual occlusion and maximally open mouth. The size of the TMJ joint space in the anterior, upper and posterior sections was determined by the method of Rabukhina N.A., the analysis of the ratio of the bone elements of the TMJ was carried out using the Craniometry program. The size of the joint space and the angle β of the temporomandibular joint in the anterior section on the right and left in children aged 12-15 with distal occlusion is increased compared to children with physiological occlusion in the position of habitual occlusion. In adolescents 15-18 years old with distal occlusion, the size of the TMJ joint space is increased in the anterior section on the right and left and reduced in the posterior section on the right, angle α is reduced on the right and left, angle β is reduced on the right, angle γ is increased on the right compared to adolescents with physiological occlusion. The revealed deviations indicate the presence of violations in the ratio of the bone elements of the TMJ, which are aggravated with age. Analysis of the results obtained during CBCT in children and adolescents allows us to correct the plan of orthodontic treatment and predict its results.

A Flexible Mechanism Based Vibration Isolator for Machine Tool Application

The paper presents novel design of vibration absorber with innovative features including use of flexible link based mechanism at the interface of tool holder and cutting tool. The mechanism ensures modification of the dynamic force interaction at the damping element and results in lower force transmissibility. It ensures amplification of the relative velocity at the damping element, which results in significant reduction of the damping element mass used for energy dissipation. The presented absorber has advantages of passive and economical operation in comparison to the active and semi-active solutions. Further, the proposed solution results in up to 53% reduction in the force transmissibility. A real size design has been presented for frequency range of 0-1100 Hz and maximum force amplitude of 700 N. Numerical simulations have been performed with consideration of flexible joint and structural element dynamics. Simulation results with FEA and PRBM approach have been compared with detailed analysis of the important design parameters.

Method of Coaxial Accelerations Correlation for Quality Assessment of Structural Joints

Assessment of the stiffness of joints is important for the joints’ design, monitoring the condition of building structures and prognosis of the lifetime and safety of buildings or its elements. Typically, such assessment is done in a non-destructive way using either shock or vibration analysis with a network of accelerometers as sensors. To improve the quality of diagnostics of structural joints and make it more specific, a method and measurement system implementing the principle of correlation of normalized coaxial accelerations measured in 3D space was proposed. The method is based on the mathematical analysis of vibrations of structural joints in 3 spatial directions using 3D accelerometers located at different parts of a joint and orientated coaxially. The correlation method was verified in a laboratory experiment using rigid, semi-rigid and pinned joints of timber beams. Stand with timber beams joined at right angles by steel plates and screws were fabricated and tested by static loading to confirm the present state of the joint. Timber beams with 150X50 mm solid sections made C18 strength class were used for the timber stand. The decrease of the joint’s stiffness in the case of probable damages was modelled by the loosening of the steel screws. The stand was subjected to a vibration load provided by electrodynamics actuators fixed on one of the joint elements. This element was excited by a chirp signal in a frequency sweep range from 10 to 500 Hz, where the most prominent resonance of the stand was found. Acceleration responses were recorded by 3D accelerators placed on the loaded and connected beams. Peak values of the cross-correlation function between the responses from the correspondingly orientated pairs of coaxial accelerometers were determined. It was shown that the difference between the peak values of the correlation functions obtained for the rigid, semi-rigid and hinge joints enabled specification of the joints’ stiffness.

Composite-to-metal multi-bolt joints: a simplified FE analysis method

This paper presents a modified version of the Composite Bolted Joint Element (CBJE) that can be employed for the finite element analysis of double-lap joints made up of metal and composite material plates. The CBJE makes use if the theoretical definition of composite bolted region that is solved to analytically define the behavior of the joint. The solution is utilized to obtain the stiffness of the bolted region and the bolt-hole contact stiffness that are transferred to the CBJE. The definition based on the analytical solution allows to balance the accuracy and the computational effort of the solution. The results of CBJE for hybrid double-lap joints is compared with a 3D FE solid demonstrating a highly remarkable matching.

Experimental and Numerical Studies of Stress Distribution in an Expanding Pin Joint System

Pin joints are widely used mechanisms in different industrial machineries such as aircrafts, cranes, ships, and offshore drilling equipment providing a joint with possibility of relative rotation about one single axis. The rigidity of the joint and its service lifetime depend on the clamping force in the contact region that is provided by the applied torque. However, due to the tolerance needed for insertion of a pin in the equipment support bore, the pin is prone to relative displacement inside the bore. The amplitude of this relative displacement usually increases as time passes and since the material of the support often has lower quality grade than the pin, it leads to creation of slack in the equipment and malfunctioning of the machine. An Expanding Pin System (EPS) can be a solution to this problem where the split sleeve expands to remove the gap while the joint is torqued. Therefore, slack in the joint system disappears and 360° contact area could be achieved, providing a better stress distribution and preventing the stress localization. Determining the EPS preload and the resulting contact pressure and stresses in the joint parts are important to avoid damaging to the contact surfaces of the joints and making the dismantling of the EPS difficult. Therefore, finding the amount of the required torque is a compromise between preventing slack in the EPS and prohibiting damage to the joint parts. Stress analysis in this study is performed based on the industrially recommended torque for the EPS type under study. This article reports the study conducted on the stress distribution and the magnitude of stresses exerted to the equipment support when EPS is installed on the machine. To achieve this purpose and to investigate the stress distribution in the joint, both experimental and finite element (FE) methods were used. The experimental results show how much of the applied energy to the EPS in the form of torque is spent to expand the split sleeve and test boss and also to overcome friction. The finite element analysis provides magnitude and distribution of stresses in the EPS components.

Factors Affecting the Aluminum, Arsenic, Cadmium and Lead Concentrations in the Knee Joint Structures.

Background: Toxic elements, such as aluminum (Al), arsenic (As), cadmium (Cd), and lead (Pb), are persistent environmental pollutants that can cause adverse effects on the health of exposed individuals. Bone is one of the primary target organs of accumulation and potential damage from toxic elements.Objectives: This study was performed to determine the Al, As, Cd, and Pb concentrations in the femoral cancellous bone, femoral cartilage, anterior cruciate ligament, meniscus, tibial cartilage, tibial cancellous bone and infrapatellar fat pad. Furthermore, the aim of this study was to explore the relationships between toxic element concentrations and related factors such as gender, age, place of residence, hypertension and diabetes, and to determine the correlations among these toxic elements in knee joint structures.Methods: The samples used this study were collected from 51 patients following total knee arthroplasty. The Al, As, Cd, and Pb concentrations were determined using inductively coupled plasma optic emission spectrometry.Results: Significant differences were found in the Al, As, Cd, and Pb concentrations among the knee joint structures. Cd concentration in the tibial cancellous bone in women was significantly higher than in men. Pb concentration in the infrapatellar fat pad of urban patients was significantly higher as compared to rural patients. Al concentrations in the femoral cancellous bone, femoral cartilage, anterior cruciate ligament, meniscus and tibial cartilage were significantly higher in patients living in urban areas than in rural areas. As concentration in the tibial cancellous bone of diabetic patients was significantly higher compared to non-diabetic patients. In addition, significant Spearman's positive correlations were found between Al and Pb in the knee joint structures.Conclusion: The obtained results of the investigated toxic elements may serve as a basis for establishing the reference values of Al, As, Cd, and Pb in the knee joint structures. The results reported in the study provides novel data regarding the relationships between the toxic element concentrations and gender, age, place of residence, hypertension and diabetes in the studied structures of knee joint. Furthermore, new interactions among these toxic elements were noted.