Mihai Avram

Study on laser welding of stainless steel/copper dissimilar materials

In this paper stainless steel/copper laser welding was investigated by controlling the processing parameters like welding speed and laser power. Welding the dissimilar materials of stainless steel and copper presents a series of problems. Differences in the physical properties of the two metals, including the melting point, thermal conductivity and thermal dilatation are the main reasons for obtaining an inappropriate laser welding bead. Particularly, the laser welding process of copper is complex because of the very high reflectivity of cooper and in almost situations it requires a specific surface pre-treatment. The main objective of the study conducted in this work was to laser weld a structure used in pressure measuring and control equipments. In order to satisfy the conditions imposed by the sensor manufacturer, the difficulty of obtaining flawless joints was represented by the very small dimensions of the parts to be welded especially of the elastic spiral thickness made of steel.

Hardware Structures for High Precision Pneutronic Systems

Pneutronic systems come with a series of advantages that are natural to working with compressed air, such as the large power/weight ratio of pneumatic actuators, easy and affordable installation and maintenance as well as being clean working systems. However, due to working with compressed air, there are a series of issues, such as static and transient nonlinear behavior, mostly due to the high compressibility of air. Thus, the behavior of such systems is hard to control, especially in terms of precision positioning. The paper deals with proposing three hardware configurations of pneutronic positioning systems in order to assure the imposed positioning accuracy in the presence of disturbances and the preservation in time of the obtained position.

PWM Controlled Proportional Equipment

The paper presents an experimental model of PWM controlled proportional pneumatic direction control valve developed by the authors, as well as the functioning of a pneumatic system that incorporates the original solution of valve. The main parameters that control the system can be settled using a software application developed for that purpose.

Effects of the laser welding parameters on the weld geometry and evaporation

The paper presents some investigations about the influence of the Nd: YAG laser welding parameters on the penetration and metal evaporation of single and dual pass weld in the case of thin sections of stainless steel sample. The metal loss during welding process was measured in order to establish the optimal values of welding parameters. The geometric size of the welded zone was measured using an SEM microscope in order to establish the correlation between the penetration and width at different values of welding parameters. The microhardness values, measured for 3, 6, 8 and 9 focal point position, in the weld and base material, allow estimating the softening effect caused by the metal vaporization during welding. At the same time, the cooling conditions of the welded zones differ with the local heating and melting volume of the weld.

Study on the Current State of Research in the Field of Artificial Clamping Systems Using Astringent Electroadhesion Technology

This paper aims to provide an analysis of the current state of research in the field of artificial clamping systems using astringent electroadhesive technology.

Intelligent Hydraulic Power Generating Group

The domain of hydraulics is expensive, but this is changing due to the new manufacturing technologies. The hydraulic energy generators without an intelligent controller have low efficiency and they will be replaced by intelligent ones. The use of an inverter can significantly reduce the energy consumption by modifying the speed of the motor in order to obtain the flow/pressure required by the application. If a variable flow pump is used in the system, the energy saving is important, due to the pump working with the optimum speed, pressure and flow needed for a maximum efficiency. The use of systems connected to the Internet (and cloud services) increases the reliability due to the predictive maintenance and the reduced working costs. The paper is the starting point in developing an intelligent control system using optimized algorithms for decreasing the consumption, increasing the reliability, reducing the noise and increasing the operating safety.

Inchworm Locomotion of an External Pipe Inspection and Monitoring Robot

The paper presents the external pipe locomotion of a robot for inspection and monitoring of the pipelines for use in oil and gas industry. During regular motion, the robot resembles to a crank-slider mechanism with equal lengths of the crank and rod, while for stepping over flanges it becomes an open chain with double actuated leverage. A bond graph model and simulation results by use of 20-sim environment are also presented.

Research Regarding the Design of a Closed-Loop Pneumatic Positioning System Without Using Proportional Equipment

The paper shows the design, manufacturing and testing of a new type of closed-loop pneumatic positioning system. The design is comprised solely of on/off equipment, which ensures overall low cost. Exhaust flow control and thus speed control for both directions of movement is done by means of several groups of way valves. This ensures that the system can obtain different speeds. Maximum speed is obtained when all of the way valves are open and minimum speed is obtained by using only one way valve. The last version is used close to the desired position to ensure the low speed needed to obtain precision. System control is done by means of a microcontroller that stores and executes the working programs.

Pneumatic Linear Incremental Actuator

The paper refers to a linear pneumatic actuator with incremental functioning developed by the authors. The structure of the actuator is presented and the theoretical aspects that are governing the actuator working are treated. On the basis of the functional model built by the authors, the static characteristic of the actuator is determined, theoretically and then experimentally. Finally, the solution found in order to optimize the performances of the actuator are presented.

Bond Graphs Modelling of Electromagnetic Actuators

The paper presents the model of an electromagnetic actuator, developed in 20 sim environment, by use of Bond Graph method. The software facilities are exploited by using both signal block diagram and the power bond graph elements within the same model. The models of the flux raising stage, when the armature doesn’t move and the dynamic period, until the armature ends its stroke are presented. These ones take into account only the saturation of the core magnetization curve, but not its nonlinearity. The data used for simulation are from an experimental tested device, so, both calculated and measured results can be compared.