REVISED PAPER Proceedings of the ASME 2013 Gas Turbine India Conference December 5-6, 2013, Bengaluru, INDIA GTINDIA2013-3640 WELD DUCTILITY EVALUATION OF AEROENGINE MATERIALS BY PERFORMING BEND TESTS Vijay Petley* Gas Turbine Research Establishment, DRDO Bangalore-93, Karnataka, India Ph. No. +91 80 2504 0346, E-mail ID: vijaypetley@gtre.drdo.in Shweta Verma Gas Turbine Research Establishment, DRDO Bangalore-93, Karnataka, India KM Ashique Gas Turbine Research Establishment, DRDO Bangalore-93, Karnataka, India DM Purushothama Gas Turbine Research Establishment, DRDO Bangalore-93, Karnataka, India R. Rajendran Gas Turbine Research Establishment, DRDO Bangalore-93, Karnataka, India ABSTRACT Welding is an integral part of the fabrication process for realization of the components and sub-components for any structural system. The weld process and the evaluation of the weld zone properties become more significant for the critical application like structural components of an aero engine. Standard tensile testing of the welded specimens provides the ductility for the composite joint i.e. the parent, heat affected zone and the weld zone. Standard bend tests (Three point bend) are specified as the qualitative tests for evaluating the ductility of the welded joints. For these bend tests, the ductility of the parent specimens are utilized for calculating the bend test parameters and the bend angles are specified after performing the tests on the parent specimens. But during the bend tests on the TIG welded specimens of specific materials and the thickness combinations like Ti-64 with thickness of 1.2 and 4.0 mm, it was observed that the specimens used to get fractured during bend tests before the specified bend angle is achieved. Though this suggests that the ductility of the welded joint is lesser than that of the parent specimens, it is not quantified with the premature failure of the test specimen. In the present study, bend tests on these material samples are performed on TIG welded specimens. Load and the displacement were monitored during the bend tests and maximum plunger depth and bend angle was recorded. A term called virtual plunger diameter is introduced in this work. Based on this plunger depth, span length, virtual plunger diameter is estimated at the onset of the fracture. From this plunger diameter the ductility of the weld joint is recalculated and is found to be lesser than the ductility of the welded joint as observed during the tensile test. The proposed bend test result analysis technique provides the quantitative results i.e. weld ductility from the bend test data. INTRODUCTION Titanium alloys and the nickel based super alloys are primarily used for the aero engine components. These various components are integrated to form the assemblies also called as modules namely fan, compressor, turbine, after burner, etc. The assemblies are realized with the aid of bolted configuration or fabrication techniques like welding. Essentially these materials are characterized and have been under usage from several decades [1, 2]. Welding processes like TIG, EB are proven and regularly applied on these materials. It has been reported that the tensile strength of the TIG welded specimens are approximately 105-110% of the minimum specification values [3, 4]. But, with the increase in the strength values there is corresponding decrease in the ductility. Standard tensile test of a welded specimen provides ductility due to the extension occurring in the weld zone, HAZ and the base material and this extension differs due to microstructural variations. The total extension is attributed to the extension occurring in different zones and is weld quality specific. Also, depending on the fracture region the percentage elongation varies and comprehending the weld ductility becomes difficult. The three point bend tests are the qualitative tests and suggest the weld ductility in comparison with the parent material. A schematic and the terms associated with the bend test are provided in Fig. 1. Based on the parent material ductility the bend test angles are specified and these bend angles are compared with the bend angles obtained after bend testing of welded specimens. Any pre-mature crack before attaining the recommended bend angle suggests poor weld ductility. But these tests do not provide weld ductility in quantitative terms. In this paper the bend tests data is analyzed to provide the quantitative result i.e. weld ductility. * Address all correspondence to this Author