Ultrasonic Testing for the Measurement of Process

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2 0 Process S tudy of Manufacturing of Piston, A p iston is a comp onent of recip rocating engines recip rocating p ump s gas comp ressors and p neumatic. cy linders among other similar mechanisms In an engine p iston p urp ose is to transfer force from. exp anding gas in the cy linder to the crankshaft via a p iston rod and or connecting rod In some engines. the p iston also acts as a valve by covering and uncovering p orts in the cy linder wall Pistons are. commonly made of a cast aluminum alloy for excellent and lightweight thermal conductivity Piston. features include the p iston head p iston p in bore piston pin skirt ring grooves ring lands and p iston. rings Piston contain some internal defects those are causing major failure Hence identification of. internal defect is carried out with Non destructive testing. Piston is manufactured in two stages firstly through foundry and then followed by machining. op erations Quality insp ection is carried out in sep arate unit In the foundry unit aluminum alloy is. melted up to 800 c to 1000 c and poured into cavity made by the die In this p rocess comp osite. material can be obtained to withstand high pressure generated during p iston op eration The figure 2 1. below dep icts the detailsed p rocess flow of manufacture of piston. Fig 2 1 The process flow for manufacturing of piston. 3 0 Problem definition and Objectives of study, The initial obser4vation through comp any records indicated that rejection rate of the p iston is 140 out. of 1545 comp onents due to the occurrence of the internal flaws in the casted material These defective. comp onents directly affect the variation in skirt diameter and decreasing p rocess cap ability to 0 89 The. tests were conducted to find out such flaws and the p istons were rejected based on the order. requirement of selection and rejection p rocedure The reasons for the occurrence of such flaws were not. recognized and the p atterns of flaws were not p lotted This p rovided an op p ortunity to work in filling. this gap In order to fulfill the requirements and the gap identified the study tem set an objective to. measure and characterize the internal flaws to identify the causes for such flaws and to statistically. control the skirt diameter used p rocess cap ability measurement. 4 0 Methodology adopted for experimentation and measurement using Ultrasonic tester. The following methodology was adop ted to thoroughly study the defects through ultrasonic testing. method and classify it as crack cold shut blow hole shrinkage hot tear etc The rejected p istons were. analy zed for their p attern number of defects and the location of defects using ultrasonic inspection. Non conformity charts were drawn using P chart and the major defects were identified using Pareto. S tep 1 Ultrasonic insp ection was carried out using DIGISCAN ultrasonic flaw detector with normal. p robe of 10mm diameter and frequency of 2MHz The flaw detector is as shown in Fig 4 1 Initially the. instrument was calibrated with master block to correct the deviation in the instrument. Fig 4 1 Ultrasonic Flaw Detector, S tep 2 Velocity and Range value of the instrument were reset as p er the material Of study The. insp ection was p erformed on required gain energy Defects were identified though the observation of. disturbance in initial and final echo disp lay ed on the monitor of UT M achine A samp le flaw. identification is dep icted in the Fig 4 2 and is shown below. Fig 4 2 Ultrasonic CRT S creen for S ingle Flaw Location. S tep 3 Defect were classified as crack cold shut blow hole shrinkage hot tear etc and rep ort were. generated that clearly indicated that a p iston of 20 mm thickness has a flaw at 18 mm dep th as shown in. Fig 4 3 below,Fig 4 3 Ultrasonic Flaw Report, S tep 4 During testing number of defects were listed from samp le data Table 4 1 shows the number. flaws present in each piston,Table 4 1 Ultrasonic Flaw Report.
S l No S ample Number of S l No S ample Number of,number defects number defects. 1 P1 2 9 P9 3,2 P2 2 10 P10 2,3 P3 0 11 P11 2,4 P4 1 12 P12 1. 5 P5 2 13 P13 1,6 P6 4 14 P14 0,7 P7 1 15 P15 2, S tep 5 Using the data of defects for the samp le p istons M initab statistical software was used to. p erform a test using Non conformities control chart i e P chart and the analy sis is dep icted in the Fig. 4 4 P chart was created to evaluate the p rocess and identify whether the defects are in control or out. of control The sp ecimen is accep ted or rejected based on the points lying inside or outside control. limits resp ectively,Fig 4 4 Depiction of P chart using Minitab. S tep 6 Pareto chart was p lotted for analysis of exp erimental data to highlight the most important. among a set of factors M ajor issues were quickly identified and resolved Minitab software with. quality tool was used to analyze the exp erimental data for Pareto analy sis and the same is shown in Fig. Fig 4 5 Pareto chart for vital few trivial many defects. S tep 7 Table 4 2 shows the skirt diameter value measured during piston manufacturing operation Skirt. diameter is contributing to maximum number of defects Hence the insp ected defect free p iston outer. diameter is measured through gauge and these value are listed below A Samp le size of 3 is considered. with skirt diameter 50 5 for study, Table 4 2 Measurement of skirt diameter of a piston.
O ute r head O ute r body O uter be ll O uter he ad O ute r body O ute r bell. diame te r D1 diam e ter D2 diam eter D3 diam ete r D1 diame te r D2 diame te r D3. 4 1 5 8 2 6,6 4 6 5 2 6,5 5 6 3 2 5,6 3 5 4 0 5,9 4 8 5 3 6. 6 1 6 5 2 6,4 3 5 0 1 4,5 3 6 4 1 1,8 10 4 0 1 4,3 3 5 1 1 5. S tep 8 Control chart was p lotted with help of M initab software Skirt diameters values were used to. determine X bar and R charts and the same is shown in figures 4 6 below. Xbar R Chart of ski rt diamater,Summa ry Re port,Is the pr ocess m ean st able C ommen ts. Evalu ate th e of ou t of co ntro l sub gro ups, The pr oc ess mean is s table N o s ubgr oups are o ut of co ntr ol on t he. 0 5 Xbar ch art,X bar and R Char ts,Invest igate any o ut of co ntr ol su bgro ups.
0 L CL 0 016,10 UCL 9 62,1 3 5 7 9 11 13 15 17 19,C ont rol li mits us e. St Dev wit hin Subgr oups 19 Mean 3 80 70 St Dev wit hin 2 2072 StDev over all 2 41 60. Fig 4 6 X bar and R Chart of Skirt diameter, S tep 9 Process capability studies were done to check the cap ability of p roducing virtually all. conforming p roduct Statistical p rocess controls used to monitor the p rocess and conventional. accep tance efforts reduced This helped in cost savings in eliminating non value added insp ections and. eliminated scrap rework and increases customer satisfaction The following figure 4 7 indicates the. p rocess cap ability report of skirt diameter of selected samp les which includes determination of the. p rocess cap ability Cp 1 42 and p rocess performance Cpk 0 83. Proc ess Capability Repo rt skirt daim eter,Pr ocess Dat a Ov era ll. LSL 9 Wit hin,USL 10 Over all Cap abilit y,Sample Mean 4 4210 5 Pp 1 3 5. Sample N 19 PP L 1 9 1,StDe v Ov era ll 2 3408 4 PP U 0 7 9.
StDe v Wit hin 2 2341 5 Pp k 0 7 9,Po ten tia l Wit hin Cap abilit y. 9 6 3 0 3 6 9,Per fo rman ce, Fig 4 7 Process capability indices obtained from Minitab. 5 0 S ummary of Results The manufacturing p rocess of p iston from scrap to end p roduct was studied. The initial defects in the casting were exp lored with ultrasonic testing equip ment Then the root causes. of the defects in p iston were identified Finally the p rocess cap ability study was conducted and it was. found that out of all casting defects crack and shrinkage were the major defects occurring in skirt area. of p iston A comp arison of before and after study indicated that the p rocess capability Cp increased. from 0 89 to 1 42 and p rocess p erformance Cp k increased from 0 56 to 0 83 This has enhanced the. confidence among the p eop le in the testing dep artment on the benefits of using NDT testing and also. ability of the test to enhance the quality p arameters which is helpful for better salability and. satisfaction of internal customers,6 0 References, 1 Antonio Toro Juan A Chavez M iguel J Garcia Hernandez Andres Bulked Peters. Tomek Gabor T th Anna Giron s Jordi Salazar 2013 Ultrasonic insp ection sy stem for. p owder metallurgy p arts M easurement 46 2013 p p 1101 1108. 2 Bernard H Hertlein 2013 Stress wave testing of concrete Construction and Building. Materials 38 2013 p p 1240 1245, 3 Fitting DW Adler L 1981 Ultrasonic sp ectral analy sis for nondestructive evaluation New. York Plenum Press, 4 Vanlanduit Steve Guillaume Patrick 2003 On line monitoring of fatigue cracks using.
ultrasonic surface waves NDT E International Journal. 5 Renaldas Rai sutis Ry mantasKazy s Egidijus Zukauskas 2010 Ap p lication of ultrasonic. guided waves for non destructive testing of defective CFRP rods NDT E International 43 p p. Acknowledgement This study is a part of funded project sponsored by Vision Group of Science and. Technology VGST Government of Karnataka under Karnataka Fund for Infrastructure. Strengthening in Science and Technology Level II 2012 13 for Establishing Non Destructive. Testing Laboratory for Post Graduate Courses and Research We sincerely thank VGST for their. financial support for purchase of Ultrasonic Testing Equipment. Ultrasonic Testing for the Measurement of Process Capability in Piston Manufacturing Line Dr K N Subramanya 1 Vijayakumar M N 2 Prashant V 3 Vikram N B 4 Malleshi S Talwar 5 1 2 3 4 5 R V College of Engineering Mysore road Bangalore India 1sansa96 gmail com 2vijayakumar rvce edu in 3prashanthv rvce edu in 4vikramnb rvce edu in xmechmallesh49 gmail com

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