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In this paper, a comprehensive study of friction damper stiffness effects on the response characteristics of a typical turbine blade executing steady-state motion, s explored. The damper is modeled as a one-bar microslip type assembled in the intermediate platform attachment of the blade leaving the other attachment of a shroud mass at the blade tip to be free. A discrete lumped mass approach, previously theorized in another paper, is employed to predict the response amplitudes as well as the slip length parameter at any state of the forced frequency including the resonance condition. The analysis covers a practical range of damper stiffness values adapted from relevant studies in this field. The present main outputs show that a magnificent rising of the response occurs with the increase in the stiffness, the characteristic behavior varies appreciably and the resonant amplitudes tend to increase linearly at high levels of damper stiffness, whereas the corresponding frequency and slip length show almost uniform trend. The results can serve very well for design and control purposes in the pre-manufacture stages of the given blade-damper system

In this paper the influence of tool geometry and welding parameters (rotating speed and travel speed) on the quality and mechanical properties by using friction stir welded joints for (7020-T53) aluminum alloy. Three types of tool geometry variables were used ( pin, shoulder and shoulder inclination), internal defect (tunnel) was detected by using X-Ray radiography for all samples which are welded at welding parameters (rotating speed and travel speed), perfect tool geometry that gives defect free was by increasing pin diameter with threaded ,increasing shoulder diameter and shoulder inclination (2o) for safety purpose radiography test was also performed to examine defect free of weldments (increasing tool dimensions and pin threaded gives increasing stir and heat input). The effect of welding parameters (rotation and travel speed) using tool geometry that gives defect free were investigated using different mechanical tests including (tensile, bending and microhardness). Macro and microstructure change during (FSW) process were studied and different welding zones were investigated using optical microscope. Based on the friction stir welding experiments conducted in this study the result show that aluminum alloy (7020-T53) can be welded using FSW process, the optimum welding parameters 1400rpm rotational tool speed and 40mm/min travel speed which give the maximum welding efficiency (83%), increasing rotational speed the microhardness increases in weld zone due to decreasing the grain size.

Finite element modeling of transient temperature distribution is used to understand physical phenomena occurring during the dwell (penetration) phase and moving of welding tool in friction stir welding (FSW) of 5mm plate made of 7020-T53 aluminum alloy at 1400rpm and 40mm/min. Thermocouples are used in locations near to the pin and under shoulder surface to study the welding tool penetration in the workpiece in advance and retreate sides along welding line in three positions (penetrate (start welding) , mid, pullout (end welding)). Numerical results of ANSYS 12.0 package are compared to experimental data including axial load measurements at different tool rotational speeds (710rpm.900rpm.1120rpm and 1400rpm) Based on the experimental records of transient temperature at several specific locations of thermocouples during the friction stir welding process the temperatures are higher on the advancing side (629.2 oK) than the retreating side (605 oK) along welding line and temperature in the top of workpiece under tool shoulder is higher(645 oK) than bottom (635.79oK). The results of the simulation are in good agreement with that of experimental results. The peak temperature obtained was 70% of the melting point of parent metal.