PSI - Issue 14

Rohit K. Mahalle et al. / Procedia Structural Integrity 14 (2019) 945–951 Rohit Kumar Mahalle / Structural Integrity Procedia 00 (2018) 000–000

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4. RESULTS & DISCUSSION Propellant machining is carried out so as to achieve a particular depth as per the approved drawing. Mainly 2 types of surfaces are generated i.e. flat & counter-bore. During flat machining, face milling of propellant grain is carried out. This flat machining is carried out in two steps. First the machining is carried out inj the area near to the port and then towards the hardware. Axis parallel to cutter axis is ‘Z’ direction and normal to it, is ‘X’ direction. Depth of cut is given in Z direction. As mentioned in Table 1, depth of cut varies from 1-3mm. As per the data in Table 3,4,5,6 & 7 offset in Z direction is changed as per the difference between required and measured value. Let ‘b’ be the difference, ‘R’ required value and ‘M’ the measured value then: = − (1) The work offset value of X and Z co-ordinate in machine co-ordinate system, is then changed accordingly for consecutive cuts. Let (X1, Z1) be the work offset value prior to cut and (X2, Z2) be the work offset value after cut. Since ‘b’ will be measured after cut (as per equation 1), the new work offset for following cut is calculated as below: ( , ) = ( , ) + (2) Thus the depth of cut varies from 1-3 mm as per the varying values of ‘b’. Table 3. Propellant machining data in Z direction of ARTICLE Middle Segment Metal Groove Sample 21 Sample 22 Sample 23 S No A B A B A B 1 15.6 -0.384 15.6 -0.246 15.6 0.312 2 18.6 -0.266 18.6 0.088 18.6 0.172 3 21.6 0.456 21.6 0.168 21.6 0.284 4 24.6 0.22 24.6 0.126 24.6 -0.302 5 27.6 0.088 27.6 0.056 27.6 -0.043 6 30.6 -0.012 30.6 -0.012 30.6 0.064 7 33.6 -0.005 33.6 0.006 33.6 0.009 Table 4. Propellant machining data in Z direction of ARTICLE Head End Segment Metal Groove Sample 21 Sample 22 Sample 23 S No A B A B A B 1 23 0.326 23 0.296 23 0.308 2 26 0.282 26 0.16 26 0.214 3 29 0.188 29 0.088 29 -0.122 4 32 -0.262 32 0.108 32 -0.117 5 35 -0.102 35 0.083 35 -0.097 6 38 -0.006 38 0.068 38 -0.054 7 41 0.036 41 0.024 41 -0.019 8 44 0.026 44 0.038 44 -0.017 9 47 0.038 47 -0.048 47 -0.01