DISIMILLAR LAP JOINT FRICTION STIR WELDING (FSW) USING VARIED LENGTH OF PIN

The lap joint will be used on aluminum 6061 and 10 mm thick brass with the Friction Stir Welding method. The probe used is EMS 45 steel with variations in pin lengths of 11 mm, 11.5 mm and 12 mm. The results of this study are in length 11.5 mm with the highest Vickers hardness value of 104.26 VHn compared to 11 mm and 12 mm pin length is 98.93 VHn and 70.43 VHn. The results of shear stress are 67.32 MPa at 12 mm pin length, higher than the 11 mm and 11.5 mm pin lengths of 40.2 MPa and 42.14 MPa.

Meniscus Injury and its Surgical Treatment Does not Increase Initial Whole Knee Joint Friction

While it is generally accepted that traumatic meniscus pathologies lead to degenerative articular cartilage changes in the mid-to long-term and consecutively to post-traumatic osteoarthritis (PTOA), very little is known about how such injuries initiate tribological changes within the knee and their possible impact on PTOA acceleration. Therefore, the aim of this study was to investigate the influence of three different medial meniscus states (intact, posterior root tear, total meniscectomy) on the initial whole knee joint friction. Six ovine knee joints were tested in a passive pendulum friction testing device under an axial load of 250 N and an initial deflection of 12°, representing swing phase conditions, and under an axial load of 1000 N and an initial deflection of 5°, simulating stance phase conditions. To additionally consider the influence of the time-dependent viscoelastic nature of the knee joint soft tissues on whole joint friction, the tests were performed twice, directly following load application and after 20 min creep loading of either 250 N or 1000 N axial load. On the basis of a three-dimensional joint kinematic analysis, the energy loss during the passive joint motion was analyzed, which allowed considerations on frictional and damping processes within the joint. The so-called “whole knee joint” friction was evaluated using the boundary friction model from Stanton and a viscous friction model from Crisco et al., both analyzing the passive joint flexion-extension motion in the sagittal plane. Significantly lower friction coefficients were observed in the simulated swing phase after meniscectomy (p < 0.05) compared to the intact state. No initial whole joint friction differences between the three meniscus states (p > 0.05) were found under stance phase conditions. Soft tissue creeping significantly increased all the determined friction coefficients (p < 0.05) after resting under load for 20 min. The exponential decay function of the viscous friction model provided a better fit (R2∼0.99) to the decaying flexion-extension data than the linear decay function of the boundary friction model (R2∼0.60). In conclusion, this tribological in vitro study on ovine knee joints indicated that neither a simulated posterior medial meniscus root tear nor the removal of the medial meniscus resulted in an initially increased whole joint friction.

Robust control of robot manipulators with an adaptive fuzzy unmodelled parameter estimation law

Summary For robot manipulators, there are two types of disturbances. One is model parametric uncertainty; the other is unmodelled parameters such as joint friction forces and external disturbances. Unmodelled joint frictions and external disturbances reduce performance in terms of positioning accuracy and repeatability. In order to compensate for unmodelled parameters, the design of a new controller is considered. First, the modelled and unmodelled parameters are included in a dynamic model. Then, based on the dynamic model, a new Lyapunov function is developed. After that, new nonlinear joint friction and external disturbance estimation laws are derived as an analytic solution from the Lyapunov function; thus, the stability of the closed system is guaranteed. Better values of the adaptive dynamic compensators can be extracted by fuzzy rules according to the tracking error. Limitations and knowledge about friction and external disturbances are not required for the design of the controller. The controller compensates for all possible model parameter uncertainties, all possible unknown joint frictions and external disturbances.

SAUNG BAMBU KOMPOSIT DENGAN SAMBUNGAN PELAT BUHUL

Bamboo can be used to make all building components, both structural and non-structural. The construction of this bamboo building is characterized by a structural framework approach similar to that applied in wooden construction. In this case, the floor, wall and roof elements are interconnected and interdependent on each other for overall stability. There is a need to control lateral deformation in some traditional forms of buildings in particular. The adequacy and suitability of the building for housing will also depend on good details. In the use of bamboo as a structural element, various types of connections are known which are often applied in various types of buildings. The types of connections are double butt bent joints, friction-tight rope connections, plug ins, positive fitting connections, and interlocking connections. These types of joints are not very strong and cannot withstand excessive loads in various directions because the surface area of the connection is very small and bamboo has cavities. This connection will not last long if it is used as a connection to the truss or bridge truss. This connection is not very strong. In the Cipete Village area, Pinang District, Tangerang City, there are still many buildings that use bamboo as a structural element, both for housing, selling places, and huts for resting. The bamboo connections in these buildings still use traditional grafting techniques, so the buildings quickly become damaged and the community pays more to repair them. The Community Service Team (PKM) of the Civil Engineering Undergraduate Study Program helps the community provide bamboo splicing technology to increase the service life of bamboo buildings by improving bamboo grafting techniques. The splicing technique is done by expanding the surface of the connection, namely making the bamboo solid in the bamboo area. In addition to making the bamboo solid in the joint area, gusset plates and bolts are also used to strengthen the connection. Bambu dapat digunakan untuk membuat semua komponen bangunan, baik struktural maupun non struktural. Konstruksi bangunan bambu ini ditandai dengan pendekatan kerangka struktural mirip dengan yang diterapkan dalam konstruksi kayu. Dalam hal ini, elemen lantai, dinding dan atap saling dihubungkan dan saling bergantung satu sama lain untuk stabilitas keseluruhan. Ada kebutuhan untuk mengontrol deformasi lateral dalam beberapa bentuk tradisional bangunan pada khususnya. Kecukupan dan kesesuaian bangunan untuk hunian juga akan tergantung pada detail yang baik. Dalam pemanfaatn bambu sebagai elemen struktur, dikenal berbagai jenis sambungan yang sering diaplikasikan dalam berbagai jenis bangunan. Jenis-jenis sambungan tersebut adalah double butt bent joint, friction-tight rope connection, plug in, positive fitting connections, dan interlocking connection. Jenis-jenis sambungan tersebut tidak terlalu kuat tidak mampu menahan beban yang berlebih dalam berbagai arah meningat karena luas permukaan sambungan sangat kecil dan bambu memiliki ronga. Sambungan ini tidak akan bertahan lama bila digunakan sebagai sambungan pada rangka kuda-kuda atau rangka jembatan Sambungan seperti ini tidak terlalu kuat. Didaerah Kelurahan Cipete, Kecamatan Pinang Kota Tangerang, masih banyak bangunan yang memanfaatkan bambu sebagai elemen struktur, baik untuk perumahan, tempat berjualan, maupun saung-saung tempat istirahat. Sambungan bambu pada bangunan-bangunan tersebut masih menggunakan Teknik penyambungan tradisional, sehingga bangunan tersebut cepat menjadi rusak dan masyarakat mengeluarkan biaya lebih untuk memperbaikinya. Tim Pengabdian Kepada Masyarakaya (PKM) Program Studi Sarjana Teknik Sipil membantu masyarakat memberikan teknologi penyambungan bambu untuk meningkatkan umur layanan bangunan bambu dengan memperbaiki teknik penyambungan bambu. Teknik penyambungan dilakukan dengan memperluas permukaan sambungan yaitu membuat bambu menjadi solid didaerah bambungan. Selain membuat bambu menjadi solid didaerah sambungan, juga digunakan pelat buhul dan baut untuk memperkaku sambungan.

A Semiparametric Model-Based Friction Compensation Method for Multi-Joint Industrial Robot

Industrial robots have received enormous attention due to their widespread uses in modern manufacturing. However, due to the frictional discontinuous and other unknown dynamics in robotic system, existing researches are limited to simulation and single- or double-joint robot. In this paper, we introduce a semiparametric controller combined by a radial basis function neural network (RBFNN) and complete physical model considering joint friction. First, to extend the NN controller to real-world problems, the continuously differentiable friction (CDF) model is adopted to bring physical information into the learning process. Then, RBFNN is employed to approximate the model error and other unmolded dynamics, and the parameters of CDF model are updated online according to its learning ability. The stability of the robot system can be guaranteed by the Lyapunov theory. The primary parameters of CDF model are determined by the identification experiment and subsequently iteratively updated by the NN. Real-time tracking tasks are performed on a six degree of freedom (DoF) manipulator to follow the desired trajectory. Experimental results demonstrate the effectiveness and superiority of the proposed controller, especially at low speed.

Optimum Welding Parameters for Friction Stir Welded AA6063 Pipe Butt Joint Using the Taguchi Method

Welding parameters for pipe joint friction stir welding (FSW) have been identified based on L-9 orthogonal arrays used in the Taguchi Method. Different welding parameters, such as rotation speed, travel speed and axial force, have been used to produce several quality friction stir welded AA6063 pipe butt joints. The reliability of products obtained in the FSW process can be improved through the identification of the optimum combination of welding parameters. Weld quality was evaluated based on its tensile strength and residual stress profiles. The S/N analysis and Analysis of Variance (ANOVA) have been used to determine significant welding parameters that affect weld quality. Maximum tensile strength with acceptable residual stress was obtained at the optimum welding parameters of 1300 rpm, 5 mm/s and axial force between 5 and 6 kN. The goal of this study was to optimize welding parameters for high tensile strength and low residual stress.

Direct Sensitivity Analysis of Spatial Multibody Systems With Joint Friction Using Index-1 Formulation

Sensitivity analysis is one of the most prominent gradient based optimization techniques for mechanical systems. Model sensitivities are the derivatives of the generalized coordinates defining the motion of the system in time with respect to the system design parameters. These sensitivities can be calculated using finite differences, but the accuracy and computational inefficiency of this method limits its use. Hence, the methodologies of direct and adjoint sensitivity analysis have gained prominence. Recent research has presented computationally efficient methodologies for both direct and adjoint sensitivity analysis of complex multibody dynamic systems. The contribution of this article is in the development of the mathematical framework for conducting the direct sensitivity analysis of multibody dynamic systems with joint friction using the index-1 formulation. For modeling friction in multibody systems, the Brown and McPhee friction model has been used. This model incorporates the effects of both static and dynamic friction on the model dynamics. A case study has been conducted on a spatial slider-crank mechanism to illustrate the application of this methodology to real-world systems. Using computer models, with and without joint friction, effect of friction on the dynamics and model sensitivities has been demonstrated. The sensitivities of slider velocity have been computed with respect to the design parameters of crank length, rod length, and the parameters defining the friction model. Due to the highly non-linear nature of friction, the model dynamics are more sensitive during the transition phases, where the friction coefficient changes from static to dynamic and vice versa.

Surgical cup placement affects the heating up of total joint hip replacements

The long-term success of highly effective total hip arthroplasty (THA) is mainly restricted by aseptic loosening, which is widely associated with friction between the head and cup liner. However, knowledge of the in vivo joint friction and resulting temperature increase is limited. Employing a novel combination of in vivo and in silico technologies, we analyzed the hypothesis that the intraoperatively defined implant orientation defines the individual joint roofing, friction and its associated temperature increase. A total of 38,000 in vivo activity trials from a special group of 10 subjects with instrumented THA implants with an identical material combination were analyzed and showed a significant link between implant orientation, joint kinematics, joint roofing and friction-induced temperature increase but surprisingly not with acting joint contact force magnitude. This combined in vivo and in silico analysis revealed that cup placement in relation to the stem is key to the in vivo joint friction and heating-up of THA. Thus, intraoperative placement, and not only articulating materials, should be the focus of further improvements, especially for young and more active patients.

Mechatronic system parameter idenfitcation [i.e. identification] via genetic algorithms

This thesis develops a novel way to identify both the joint friction parameters and a built in torque sensor gain and offset. The identification method is based on a genetic algorithm (GA). A model based friction compensation method and a real coded GA are selected from a variety of methods available. A model of a single degree of freedom mechatronic joint with a link is presented. Numerical simulations are run to determine the optimum configuration of the GA with respect to the population size and maximum number of generations necessary to identify the parameters to within 5% of their actual value. The GA identification technique is then used on an experimental mechatronic joint with a harmonic drive and built-in torque sensor. The friction parameters as well as the sensor gain and offset are identified in the experimental system and the position tracking error is reduced. Based on the experimental results, the method is found to be an effective way of identifying system parameters in a mechatronic joint.