Influence of transverse ultrasonic vibrations on the efficiency of threaded joint assembly

The disadvantages arising during assembly of threaded joints are considered. The existing methods of improving the quality of a threaded joint are analyzed and the most promising one is identified - the use of ultrasound at the assembly stage. Dependence of the unscrewing moment on the main technological parameter, which is vibration amplitude is obtained.

Probing Magnetic Pulse Welding of Thin-Walled Tubes

Magnetic pulse welding is a solid-state joining technology, based on the use of electromagnetic forces to deform and to weld workpieces. Since no external heat sources are used during the magnetic pulse welding process, it offers important advantages for the joining of dissimilar material combinations. Although magnetic pulse welding has emerged as a novel technique to join metallic tubes, the dimensional consistency of the joint assembly due to the strong impact of the flyer tube onto the target tube and the resulting plastic deformation is a major concern. Often, an internal support inside the target tube is considered as a solution to improve the stiffness of the joint assembly. A detailed investigation of magnetic pulse welding of Cu-DHP flyer tubes and 11SMnPb30 steel target tubes is performed, with and without an internal support inside the target tubes, and using a range of experimental conditions. The influence of the key process conditions on the evolution of the joint between the tubes with progress in time has been determined using experimental investigations and numerical modelling. As the process is extremely fast, real-time monitoring of the process conditions and evolution of important responses such as impact velocity and angle, and collision velocity, which determine the formation of a metallic bond, is impossible. Therefore, an integrated approach using a computational model using a finite-element method is developed to predict the progress of the impact of the flyer onto the target, the resulting flyer impact velocity and angle, the collision velocity between the flyer and the target, and the evolution of the welded joint, which are usually impossible to measure using experimental observations.

Optimization on the Precision of the MEMS-Redundant IMU Based on Adhesive Joint Assembly

In order to improve the precision of the spaceborne Inertial Measurement Unit (IMU), this paper proposes an adhesive joint assembly of the MEMS-redundant IMU. That is the application of special redundant installation of multiple MEMS gyroscopes in the IMU, which can improve the reliability of the MEMS-redundant IMU on the basis of reducing the weight of IMU. However, with the change of working environment, the traditional mechanical assembly of MEMS-redundant IMU will produce the large packaging stress and cause the deformation of MEMS gyroscope. This change will lead to changes in installation errors, scale factor errors, and bias errors of the MEMS gyroscope, resulting in a significant reduction in measurement precision of the MEMS-redundant IMU. Therefore, this paper selects the adhesive material that matches the thermal physical parameters of the material with the circuit board by analyzing the requirements of MEMS gyroscope on working environment at first. Then, by optimizing the bonding process, the installation error of each axis of MEMS-redundant IMU under different temperatures is better than the traditional mechanical connection mode. The experiment results of thermal vacuum show that the new assembly method can reduce the influence of temperature on the bias. Compared with the traditional method, the new assembly which is based on adhesive joint assembly can improve the measurement precision of MEMS-redundant IMU by an order of magnitude.

Effects of Stud Galling on Bolted Flange Joint Assembly Performance

This study will focus on the galling of studs and what impact that has on the overall performance of a Bolted Flange Joint Assembly. Galling or “cold welding” occurs more so with softer metals. While tightening the nut on to the stud the contact metal will “pull” away from itself and the two surfaces will essentially become one. Once this happens the nut cannot be tightened or loosened and often cutting the stud is the only form of removal. We’ll be studying how this affects the performance (tightness) of a bolted flange joint assembly. Does the assembly loosen over time or does it remain at the proper tightness? Data will be captured using load cells to accurately represent the amount of force being generated by test studs. There will be a standard test ran with no galling. All other tests with galled studs will be measured and compared against the standard test. One test with only one stud galled, the next with two studs galled, the next with three studs galled, and so on. It may be expected to see some load loss on the load cells with the galled studs. The integrity of the studs, once galled, becomes less than ideal.