Cantilever Joint Research Articles

Design and modelling of a novel single-phase-driven piezoelectric actuator

Sandwich single-phase-driven piezoelectric actuators have attracted increasing interest owing to their simple control circuits, flexible designs, and high output forces. However, there are challenges in constructing a standing-wave driving mode for sandwich single-phase-driven rotary piezoelectric actuators and in achieving bidirectional driving as well as an integrated structural and functional design, which limit their applications. To address these issues and meet the demands of the joint drive, a novel sandwich single-phase-driven rotary piezoelectric actuator is proposed in this study. The actuator stator has a beam-ring configuration, with dual rotors effectively integrated with a preload adjustment mechanism to solve the contact-warping problem of the cantilever joint and achieve an integrated structural and functional design of the joint drive. The standing-wave rotation drive and steering functions are realized through the special design of modes and unique arrangement of the upper and lower driving teeth. To reveal the dynamic characteristics of the stator, a universal electromechanical coupling dynamic model for the torsional-bending composite vibration of sandwich piezoelectric actuators was developed for the first time using the transfer matrix method, and the correctness of the dynamic model was verified using a prototype of the proposed stator. Finally, the structural design feasibility of the proposed piezoelectric actuator was verified through performance evaluation experiments on the actuator prototype. The proposed sandwich single-phase-driven rotary piezoelectric actuator lays the technical and theoretical foundations for achieving simple, fast, efficient, and precise driving and control of robotic joints.

Acoustic emission measurement during the proof loading of the new bridge over Odra river in Wrocław

The acoustic emission method is applied for damage monitoring through the analysis of internal events within the material. Sensors were placed at the cantilever joint during the proof loading. Signal analysis revealed potential damages. Signal values were compared against criteria for assessing the condition of reinforced concrete structures. Regular measurements detect potential damages, and combining this technique with other methods enhances its efficiency

Numerical simulation analysis of load-bearing capacity at joints of symmetrical cantilever-assembled bridges based on the logistic regression model

Abstract Bridge joint bearing capacity analysis is difficult to fit the requirements of the era of big data. The traditional way of bridge-bearing capacity numerical analysis exists in the wave of digital development of big data information, the Internet of Things, and artificial intelligence technology like a wild development. The traditional way of under the problem: is efficiency, engineering analysis is not accurate, data information paper, work responsibility is not in place, technical equipment, etc. This paper revolves around the numerical simulation analysis of the load-bearing capacity at the joints of symmetrical cantilever-assembled bridges based on the logistic regression model by finding literature to understand the concept and algorithm of the logistic regression model, construct logistic regression model based on dichotomous dependent variable logistic regression algorithm, logistic regression model parameter estimation, logistic regression. The three aspects of the model evaluation index are studied. The numerical simulation analysis of the load-bearing capacity at the symmetrical cantilever joint based on the logistic regression model, the shear strength calculation at the bridge joint, and the bridge longitudinal bar slip deformation are calculated, respectively, and then the actual value of the bridge load bearing capacity is derived. Simulation in the bridge bearing capacity at 0kN, 5kN, 10kN, 15kN, 20kN, 25kN, and 30kN, the model algorithm evaluation index under the three indicators of prediction rate, accuracy, deviation of the verification analysis. The results show that the prediction rate of the logistic regression model algorithm based on the load carrying capacity up to 30kN is 84%, the accuracy rate is 94%, and the deviation is 11%, and the three index values have better performance compared with the one-dimensional linear regression model algorithm and the multiple linear regression model algorithms. This study is beneficial to extend the bridge structural analysis function and make the bridge load capacity assessment more automatic; it can facilitate the comparison of historical data of bridge tests, longitudinal change of indicators at different testing time points, and grasp the current situation and change trend of bridges. Thus it is of great historical significance to the development of the Chinese bridge infrastructure industry.

Structural Stiffness Matching Modeling and Active Design Approach for Multiple Stepped Cantilever Beam

Aiming at the problem that it is difficult to realize the optimal design due to the fuzzy mapping relationship for the structural stiffness of multiple stepped cantilever beam; a stiffness matching modeling and active stiffness design approach was proposed. Firstly, by deriving out the continuous coordination conditions and the load extrapolation expressions of the cantilever joint, the stiffness analytical model and the recursive model were established for multiple cantilever beam segments, and the stiffness influence coefficient of those composition parameters were obtained by the sensitivity analysis. Then, the active stiffness optimization design process was constructed according to the stiffness design level of the stepped cantilever beam, and those implementation procedures were clearly figured out. Finally, the comparison and verification of the stiffness design of the stepped cantilever beam was carried out through numerical simulations, finite element analysis and bench test. The obtained results showed that the established models and the active stiffness design method are reasonable and effective. The stiffness match parameters are easy to meet the stiffness index requirements, and the safety factor is greater than 1; when the number of steps is not more than 5. The relative error between the match stiffness and the test stiffness is less than 15%, which can be reduced to less than 5% by adding redundancy coefficient (1.05, 1.15).

THE EFFECTS OF DEAD LOADS IN CANTILEVER CONCRETING BRIDGES

Abstract Cantilever concreting technology is one of the modern methods of constructing concrete long-span bridges. Characteristic feature of those bridges is the long-term span deflection resulting from the rheological processes in the concrete and in the pre-tensioning steel. It can also be caused by the material deterioration, e.g. concrete cracking, as well as the changes in the bridge structure, such as the support settlements. The aggregate result of bridge exploitation are the changes in its grade line, considered in this paper as the bridge span deflection line. The aim of the paper is the assessment of the internal forces on the basis of the bridge span deformation. Furthermore, an algorithm for the correction of the deflection function determined on the basis of surveying measurements (low precision measurements) is proposed. It is characterized by a significant improvement of the computational results, and it hardly “smoothens” the primary measurement results. The algorithm can be used to analyse the selected part of the bridge structure, e.g. the longest span. The paper proposes a universal coefficient of cantilever deflection, which is calculated on the basis of the cantilever joint moment when the final static scheme of the bridge is created. It can be used for the comparative analyses of various bridges. The value of the coefficient is dependent on the geometry of the cantilever box cross-section only.

Automatic Defect Detection of Fasteners on the Catenary Support Device Using Deep Convolutional Neural Network

The excitation and vibration triggered by the long-term operation of railway vehicles inevitably result in defective states of catenary support devices. With the massive construction of high-speed electrified railways, automatic defect detection of diverse and plentiful fasteners on the catenary support device is of great significance for operation safety and cost reduction. Nowadays, the catenary support devices are periodically captured by the cameras mounted on the inspection vehicles during the night, but the inspection still mostly relies on human visual interpretation. To reduce the human involvement, this paper proposes a novel vision-based method that applies the deep convolutional neural networks (DCNNs) in the defect detection of the fasteners. Our system cascades three DCNN-based detection stages in a coarse-to-fine manner, including two detectors to sequentially localize the cantilever joints and their fasteners and a classifier to diagnose the fasteners’ defects. Extensive experiments and comparisons of the defect detection of catenary support devices along the Wuhan–Guangzhou high-speed railway line indicate that the system can achieve a high detection rate with good adaptation and robustness in complex environments.

Application of Approximate Iterative Method on Section Precision Forming of Boom-type Roadheader

The decision of the inflection point is the key to ensure automatic section cutting precision using a boom-type road header. In this paper, cutting precision model was set up for the first time to trapezoidal section and a method deter- mining inflection point is given. Considered the cutting head' projection at section is elliptical with the cantilever's joint variable. The relationship between ellipse curve and cutting section boundary was investigated, and thereby sets up the cutting precision model. Approximate iterative method is used to finding the optimal inflection point, of which takes the cutting precision as the objective function. Compared with the traditional process path planning method, the forming ac- curacy can be improved greatly and controlled within 1mm. Through MATLAB simulation, it is proved that this method is correct and valid.

Free vibration analysis of an adhesively bonded functionally graded double containment cantilever joint

In this study, Genetic Algorithms (GAs) combined with the proposed neural networks were implemented to the free vibration analysis of an adhesively bonded double containment cantilever joint with a functionally graded plate. The proposed neural networks were trained and tested based on a limited number of data including the natural frequencies and modal strain energies calculated using the finite element method. GA evaluates a value generated iteratively by an objective function and this value is calculated by the finite element method. The iteration process restricts us apparently to use directly the finite element method in our multi-objective optimisation problem in which the natural frequency is maximised and the corresponding modal strain energy is minimised. The proposed neural networks were used accurately to predict the natural frequencies and modal strain energies instead of calculating directly them by using the finite element method. Consequently, the computation time and efforts were reduced considerably. The adhesive joint was observed to tend vertical bending modes and torsional modes. Therefore, the multi-objective optimisation problem was limited to only the first mode which appeared as a bending mode. The effects of the geometrical dimensions and the material composition variation through the plate thickness were investigated. As the material composition of the horizontal plate becomes ceramic rich, both natural frequency and modal strain energy of the adhesive joint increased regularly. The plate length and plate thickness were more effective geometrical design parameters whereas the support length and thickness were less effective. However, the adhesive thickness had a small effect on the optimal design of the adhesive joint as far as the natural frequencies and modal strain energies are concerned. The distributions of optimal solutions were also presented for the adhesive joints with fundamental joint lengths and material compositions in reference to their natural frequencies and corresponding modal strain energies.

A CALCULATION FOR COMPENSATING THE ERRORS DUE TO SPRINGBACK WHEN FORMING METAL SHEET BY SINGLE POINT INCREMENTAL FORMING (SPIF)

The question of compensating for the error of dimension due to springback phenomenon when forming metal sheet by SPIF method is being one of the challenges that the researchers of SPIF in the world trying to solve. This paper is only a recommendation that is based on the macro analysis of a sheet metal forming model when machining by SPIF method for calculating a reasonable recompensated feeding that almost all researchers have not been interested in yet: - Considering the metal sheet workpiece is elasto-plastic and the sphere tool tip is elastic, the authors attempt to calculate for compensating the error of dimension due to elastic deforming of the tool tip. - The metal sheet is clamped by a cantilever joint that has an evident sinking at the machiningarea that is also calculated to add to the compensating feeding value. The paper also studies the limited force for ensuring the elastic deforming at these working area of the sheet to eliminate all theunexpected plastic deforming of the sheet. With two small but novel contributions, this study can help to take theoretical model for elastic forming of metal sheet closer to real situation.

Elastic Flexural Stresses in an Adhesively Bonded Functionally Graded Double Containment Cantilever Joint

This study investigates the 3D stress state of an adhesively bonded double containment cantilever joint with a functionally graded plate under a bending load. The mechanical properties of the through-thickness graded region between a ceramic (Al2O3) top layer and a metal (Ni) bottom layer were defined based on a power law distribution and modeled with a layered 3D finite element. The peak adhesive stresses occur around the support corners inside the adhesive fillets at the adhesive free edges. The von Mises stress increases uniformly from the plate half-thickness to both the ceramic and metal layers and becomes peak in the ceramic layer, and increases from the adhesive-metal interface to the adhesive-support interface through the adhesive thickness at the adhesive free edge. Both through-thickness adhesive and plate stress profiles and levels become similar after 20 layers. A ceramic-rich material composition results in similar smoother through-thickness stress profiles and reduces considerably difference...

Elastic Flexural Stresses in an Adhesively Bonded Functionally Graded Double Containment Cantilever Joint

Elastic Flexural Stresses in an Adhesively Bonded Functionally Graded Double Containment Cantilever Joint

Determination of Structural Damping and Optimal Vibration Control of an Adhesively-Bonded Double Containment Cantilever Joint

In this study, the loss factors of an adhesively-bonded double containment cantilever joint were determined for different plate and support lengths. The response of the adhesive joint subjected to a transverse excitation force was measured with a contactless eddy-current sensor and the first bending natural frequency was determined using the Fast Fourier Transform method. The loss factor was calculated using the half-power bandwidth method based on the power spectrum of the joint vibration. After an excitation force was applied to the joint, the damped free vibration analysis was carried out using the finite element method and its measured loss factor. The transverse vibration attenuation was actively controlled with different numbers of actuators located on the top surface of the plate. The optimal control of the vibration attenuation was achieved based on a performance index by considering the strain energy, the kinetic energy, the work done on the adhesive joint by the actuators as well as the vibration attenuation time. Genetic Algorithm was implemented to this optimization problem in which the optimal control force histories, the optimal locations and the optimal numbers of the actuators were searched. Eight actuators exhibited the best control force history minimizing the performance index to 3.34 × 10–2. Thus, the attenuation time was reduced from 16 s to 0.15 s and the absolute displacement was decreased from 13.1 mm to 17.15 × 10–3 mm for 0.15 s. In addition, the modal strain energy and kinetic energy were found to be at lowest levels. As the actuator number was increased only a minor decrease in the performance index was observed after four actuators.

Linear Dynamic Modeling of Spacecraft With Various Flexible Appendages

We present here a method and some tools developed to build linear models of multi-body systems for space applications (typically satellites). The multi-body system is composed of a main body (hub) fitted with rigid and flexible appendages (solar panels, antennas, propellant tanks, …etc). Each appendage can be connected to the hub by a cantilever joint or a pivot joint. More generally, our method can be applied to any open mechanical chain. In our approach, the rigid six degrees of freedom (d.o.f) (three translational and three rotational) are treated all together. That is very convenient to build linear models of complex multi-body systems. Then, the dynamics model used to design AOCS, i.e. the model between forces and torques (applied on the hub) and angular and linear position and velocity of the hub, can be derived very easily. This model can be interpreted using block diagram representation.

Elastic Stresses in an Adhesively Bonded Functionally Graded Double Containment Cantilever Joint in Tension

This study investigates the three-dimensional stress state of an adhesively bonded double containment cantilever joint in tension. The plate is composed of a functionally graded region between ceramic (Al2O3) top layer and metal (Ni) bottom layer. The mechanical properties of the graded region were defined based on a power law distribution and modeled with a layered three-dimensional finite element. Stress concentrations occur inside the adhesive fillets along the free edges of the adhesive layer and through the corresponding plate and support regions. The peak adhesive stresses are observed at the free edge of the containment—adhesive interface. The von Mises stress through the graded plate thickness increases uniformly from the metal layer to the ceramic layer. The stress profiles peak around the adhesive free edges. The stress levels change suddenly near the ceramic layer in the metal-rich graded plate whereas the through-the-thickness stress profiles become uniform in the ceramic-rich graded plate. The layer number has a small effect on the through-the-thickness adhesive and plate stress profiles but on the peak stress levels. This effect becomes negligible after a layer number of 20. The compositional gradient exponent considerably affects both the through-the-thickness plate stress profiles and levels. As the material composition is enriched with the ceramic the stress profiles become uniform. The effects of the geometrical parameters and the compositional gradient exponent on the strain energy of the adhesive joint are investigated using the artificial neural networks. Consequently, the plate thickness and the compositional gradient exponent are the most dominant design parameters affecting the strain energy, and the adhesive thickness, the support length, and thickness are others in sequence. The strain energy increases drastically with increasing plate thickness whereas it decreases with increasing support length and thickness and as the material composition of the graded plate enriches with the ceramic. An optimum joint design requires that the plate thickness and the adhesive thickness be minimal, the support length, and thickness be maximal, and the material composition consist of the constituent with higher modulus as possible.

Geometrically non-linear analysis of adhesively bonded double containment cantilever j oints

Under an increasing load, the adhesively bonded joints may undergo large rotations and displacements while strains are still small and even all joint members are elastic. In this case, the linear elasticity theory cannot predict correctly the nature of stress and deformation in the adhesive joints. In this study, an attempt was made to develop an analysis method considering the large displacements and rotations in the adhesive joints, assuming all joint members to be still elastic. An incremental finite element method was used in the application of the small strain-large displacement theory to the adhesively bonded joints. An adhesively bonded double containment cantilever (DCC) joint was analysed using this incremental finite element method under two different loadings: a tensile loading at the horizontal plate free end, Px. and one normal to the horizontal plate plane, Py. The adhesive and plates were assumed to have elastic properties, and some amount of adhesive, called spew fillet, that accumulated at the adhesive free ends was also taken into account. The analysis showed that the geometrical non-linear behaviour of adhesively bonded joints was strictly dependent on the loading and boundary conditions. Thus, a DCC joint exhibits a high non-linearity in the displacements, stresses, and strains in the critical sections of the adhesive and horizontal plate under a tensile loading at the free end of the horizontal plate, Px, while a similar behaviour in these regions was not observed for a loading normal to the horizontal plate plane, Py. However, an increasing non-linear variation in the stresses and deformations of the horizontal plate appeared from the free ends of the adhesive-horizontal plate interfaces to the free end of the horizontal plate for both loading conditions. Consequently, joint regions with a low stiffness always undergo high rotations and displacements, and if these regions include any adhesive layer, the non-linear effects will play an important role in predicting correctly the stresses and deformations in the joint members, especially at the adhesive free ends at which high stress concentrations occurred. In addition, the DCC joint exhibited a higher stiffness and lower stress and strain levels in the joint region in which the support and horizontal plate are bonded than those in the horizontal plate.

Analysis of bonded double containment cantilever joints

Abstract An important part of adhesive development is the formulation of analyses for predicting the stresses and strains of bonded joints. An analysis of a double containment cantilever joint was made using the finite element method. A double containment joint comprising steel adherends bonded by a two-part epoxy resin adhesive was constructed and the strains in the adhesive layer were measured by a two axes co-ordinate table. The experimental results were found to be in good agreement with those of the theoretical analysis.

Analysis of bonded double containment cantilever joints

Analysis of bonded double containment cantilever joints

The [formula omitted] for augmented double cantilever beams and its application to bonded joints

The J- integral for the double cantilever type specimen is obtained explicitly based on the assumption of a beam on the elastic/plastic foundation. The solution agrees with known solutions as special cases. Also discussed is the path independence of the J- integral for the bonded double cantilever joints where the integral path crosses the boundary of two dissimilar materials. Though contrary to some investigator's previous conclusion, the J- integral for bonded joints is found path independent within the framework of the strength of materials.

The role of the adhesive layer in a double cantilever joint

The problem of a double cantilever beam adhesive joint is reconsidered under the assumption of cohesive fracture within the adhesive bond layer. After properly accounting for the adhesive layer, the problem is reduced to a Fredholm integral equation of the second kind for the bond line traction. Numerical results for the bond line stress distribution and the crack tip stress intensity factor are presented for several combinations of the governing material and geometrical parameters.