process parametric optimization of impact test using taguchi and anova approach

IPASJ International Journal of Mechanical Engineering (IIJME) Web Site: http://www.ipasj.org/IIJME/IIJME.htm

A Publisher for Research Motivation........ Email: [email protected] Volume 4, Issue 1, January 2016 ISSN 2321-6441

Volume 4, Issue 1, January 2016 8

ABSTRACT

Impact testing methodology is finding the applications for determining the impact strength of the different materials. The process implies hammering effect on the work material that determines how much mechanical energy required for failure of any material. The aim of this research work is focused on the optimization of process parameters in order to maximize the impact toughness using taguchi technique. The research work investigates the effect of process parameters on impact values. An L9 orthogonal array was chosen for the design of experiment. The optimum process parameters were determined by using signal-to-noise ratio. The levels of importance of process parameters on impact testing were obtained using analysis of variance. The variation of impact properties with process parameters were mathematically modelled using the regression analysis. The results obtained using design of experiments were validated analytically and graphically shows that work material affected the impact toughness most significantly factor of Izod impact value. The material and height of the hammer are the most significant factor of Charpy impact value. Keywords: Charpy test, Izod test, Regression Analysis, Taguchi Method, Zinc - Aluminium alloy 1. INTRODUCTION Zinc based cast alloys, commonly referred to as “ZA” alloys, has been developed during 1960 and is now increasing in commercial usage. These alloys exhibit mechanical properties equal to or exceeding those of Conventional zinc die casting alloys and those of cast iron, aluminium and copper alloys. Zinc-aluminium cast alloys have been designated as ZA-8, ZA-12, and ZA-27[1-8]. Adding aluminium improves the fluidity and castability of the zinc based (ZA) alloys. An important aspect that makes these alloys attractive is the low energy requirement to achieve casting, due to their low melting point as compared with aluminum, brass and iron alloys. The main advantages of this alloy are low cost, high resistance to wear, feature clean, low temperature, supreme castability, high as- cast strength and hardness, Corrosion resistance as compared to standard bronze. Recent investigations have been focused on the Characterization of the ZA alloys and modified versions such as corrosion, wear and other mechanical properties [9-18]. Shuqing Yan et.al (2010) studied the influence of different Al contents on the Mechanical characterization, the results reveals that 27%Al content shows the higher ultimate strength and elongation. Nirmala et.al(2014) studied the microstructure features of ZA27 alloy by varying nickel from 1 to 3wt%, addition of nickel resulted in the formation of intermetallic compounds α. Yuanyun Li et.al (1995) studied the mechanical and tribological properties by adding the rare earth as a modifying elements to the zinc based alloy, ZMJ proven has an excellent engineering Material by comparing its mechanical and wear properties with those of ZA alloys. Aleksandar Vencl et.al (2014) studied the influence of silicone and strontium alloys on ZA-27 alloy and to examine the tribological properties. However there is not much information available on effect of varying the process parameters of impacting testing machine. The present study aims at studying the influence of process parameters on impact testing machine of zinc aluminium alloy using taguchi method. Further analysis of variance is carried out to identify the most significant process parameters. 2. IMPACT EXPERIMENT Toughness is a measure of the amount of energy a material can absorb before fracturing. It becomes of engineering importance when the ability of a material to withstand an impact load without fracturing is considered. Impact test conditions were chosen to represent those most severe relative to the potential for fracture

Process parametric optimization of Impact test using Taguchi and ANOVA approach

Veerabhadrappa Algura, Dr. V.R. Kabadib, Dr. Ganechari S Mc, A M Shiva Prakash Swamyd, B

Naveen Kumare

aDepartment of Industrial and Production Engineering, Rao Bahadur Y Mahabaleshwarappa Engineering College, Bellary, Karnataka, India,

bDepartment of Mechanical Engineering, Nitte Meenakshi Institute of Technology, Yelahanka, Bengaluru,

cThakur Polytechnic, Kandivali, Mumbai, Maharashtra State, India,

dDepartment of Mechanical Engineering, Rao Bahadur Y Mahabaleshwarappa Engineering College, Bellary, India.

eM.Tech (Production Management), Department of Mechanical Engineering, Rao Bahadur Y Mahabaleshwarappa Engineering College, Ballari, Karnataka, India



Volume 4, Issue 1, January 2016 Page 19

Two standardized tests, the Charpy and Izod, are commonly used to measure Impact Energy (sometimes referred to as Notch Toughness). The Charpy V-notch (CVN) technique is most commonly used in the United States. For both Charpy and Izod, a V-notch is machined into a bar specimen with a square cross section. A standard V-notch test apparatus is schematically illustrated in Figure 1. The load is applied as an impact blow from a weighted pendulum hammer that is released from a cocked position at a fixed height "h". The specimen is positioned at the base as shown. Upon release, a knife edge mounted on the pendulum strikes and fractures the specimen at the notch, which acts as a point of stress concentration for the high velocity impact blow. The pendulum continues its swing, rising to a maximum height "h’", which is lower than "h". Based on the difference between h and h’, the energy absorption of the specimen is computed.

Fig1: Schematic representation of Impact testing machine 3. EXPERIMENTAL DETAILS Materials: The Material preparation of zinc-aluminium alloys with varying concentrations of Al (8, 12 & 27 wt %) were prepared in a crucible furnace. After the alloys were melted completely, the melts were fully stirred and immediately poured into steel mould. The processing temperatures of the melts were controlled below 7000C to avoid loss of Zn. Raw materials were melted in a graphite crucible. After degassing the molten metal was poured into a mould, which has pre heated an approximately up to 1500C in open air.

Table1: Chemical composition of experimental alloys (in mass percent, by wt. chemical analysis) ZA-8 ZA-12 ZA-27

Al 8% 12% 27% Cu 1.3% 1.22% 2.5% Mg 0.03% 0.03% 0.03% Zn Balance Balance Balance

3.1 Sample preparation The rod shaped alloys are converted to specified samples as per required dimensions according to ASTM E 23 by undergoing it through machining process of lathe and finishing them in end. The exact dimensions and configuration of samples are mentioned below for Impact testing.




V- Notched Izod type specimen V-notched Charpy type specimen

Fig.2: Samples for Impact strength test 4. METHODOLOGY 4.1Design of experiments The design of experiments is the most power full tool for analyzing the influence of control factors on performance output. Taguchi method systematically reveals the complex cause and effect relationship between design parameter and performance. The three process parameters (work material, weight of hammer and height of hammer) and impact energy absorbed (Impact value) was studied using L9 orthogonal array using MINITAB 16 software. In proposed work ZA-8, ZA12 and ZA-27 alloys were selected for specimen. The various input parameters were taken under experimental investigation and then model were prepared then again experimental work would be performed. Therefore, 9 trials were conducted on both Izod and Charpy impact testing machine. The results obtained were analyzed and model was produced using MINITAB 16. Taguchi method is used to find out the optimum condition of significance of each factor. In this study, “higher is better” is considered to maximize the impact strength of zinc aluminium alloys. For this case, S/N ratio is calculated as a logarithmic transformation of loss of function as shown below:

S/N ratio = ----------- (1)

Where n is the number of observation and y is the observed data In the experiment, there are three parameters at three levels. Values of variables at different level for Izod impact testing as shown in the Table 2, and values of variables at different level for Charpy Impact Testing as shown in the Table 3.

Table 2: Values of variables at different level for Izod Impact Testing

Table 3: Values of variables at different level for Charpy Impact Testing

The standard L9 orthogonal arrays is considered for the experiment to be carried out is shown in the table 4.




Table 4: Standard L9 orthogonal array (Taguchi design)

Table 5: Results of Experimental run for Izod test

Table 6: Response Table for Signal to Noise Ratios

Table 7: Response Table for Means

Table 8: Results of Experimental run for Charpy test

Sl.No Material Weight Height (mm)

Impact value of Charpy test (J)

S/N Ratio(db)

Mean

01 ZA-8 146.12 1562 10 20.0000 10 02 ZA-8 165.73 1791 15 23.5218 15 03 ZA-8 185.35 1994 12 27.0437 20 04 ZA-12 146.12 1791 24 27.6042 24 05 ZA-12 165.73 1994 20 26.0206 20 06 ZA-12 185.35 1562 18 25.1055 18 07 ZA-27 146.12 1994 34 30.6296 34 08 ZA-27 165.73 1562 32 30.1030 32 09 ZA-27 185.35 1791 38 31.5957 38




Table 9: Response Table for Signal to Noise Ratios

Table 10: Response Table for Means

5. RESULTS AND DISCUSSIONS 5.1 Signal-to-Noise ratio (S/N ratio) In Taguchi method, the term ‘signal’ represents the desirable value (mean) for the output characteristics and the term ‘noise’ represents the undesirable value for the output characteristics. It allows carrying out modeling and analysis of the influence of process variables on the response variables. This optimization technique is carried out in a three stage approach such as system design, parameter design and tolerance design. Based on taguchi method an orthogonal array (OA) is considered to determine the optimal Impact test for both Izod and Charpy of Zinc Aluminium alloys. The experiments were carried out to examine the influence of testing parameters on Impact test for both Izod and Charpy test of zinc aluminium Alloy. The experiments were conducted according to L9 Orthogonal array as shown in Table 5 for Izod test and for Charpy test as shown in table 8. The first column is assigned by work material, second column is assigned by Weight of hammer and the third column is assigned by Height of hammer. A total of 9 experiments were conducted based on the run order generated by taguchi model. The response (S/N ratio) studied for the model is Impact test for both Izod and Charpy test with the objective of “Larger the better” type of quality characteristics as shown in the Table 6 and the mean is shown in the Table 7 for Izod impact test and Table 9 and Table 10for Charpy impact test. The response was calculated for each level of process parameters. The process parameters, code and their levels are shown in the Table 2 and 3 each process parameters having three levels. It suggests that from the Table 5 the optimum conditions for Izod test are A3B2C3 and the Table 8 for Charpy test the optimum process parameters are A3B3C2. Fig 3 and Fig 4 shows the main effect plot for S/N ratios and main effect plot for mean for Izod impact test and . Fig 5 and Fig 9 shows the main effect plot for S/N ratios and main effect plot for mean for Izod impact test.

Fig. 3: Main Effects Plot for SN ratios (Izod test)

Level A B C 1 21.70 26.08 25.07 2 26.24 26.55 27.57 3 30.78 26.09 26.08

Delta 9.07 0.47 2.50 Rank 1 3 2

Level A B C 1 12.33 22.67 20.00 2 20.67 22.33 25.67 3 34.67 22.67 22.00

Delta 22.33 0.33 5.67 Rank 1 3 2

Z A - 2 7Z A 1 2Z A - 8

3 6

3 4

3 2

3 0

2 8

1 7 8 . 9 81 5 9 . 3 61 3 9 . 7 5

1 1 8 11 1 0 21 0 3 4

3 6

3 4

3 2

3 0

2 8

M a t e r i a l

Mea

n of

SN

rati

os

W e i g h t

H e i g h t

M a i n E f f e c t s P l o t f o r S N r a t i o sD a t a M e a n s

S i g n a l - t o - n o i s e : L a r g e r i s b e t t e r




ZA-27ZA12ZA-8

60

50

40

30

20178.98159.36139.75

118111021034

60

50

40

30

20

Material

Mea

n of

Mea

ns

W eight

Height

Main Effects Plot for MeansData Means

Fig. 4: Main Effects Plot for Means (Izod test)

ZA-27ZA-12ZA-8

30

28

26

24

22

185.35165.73146.12

199417911562

30

28

26

24

22

Material

Mea

n of

SN

rati

os

W eight

Height

Main Effects Plot for SN ratiosData Means

S ignal-to-noise: Larger is better

Fig. 5: Main Effects Plot for SN ratios (Charpy test)




ZA-27ZA-12ZA-8

35

30

25

20

15

185.35165.73146.12

199417911562

35

30

25

20

15

Material

Mea

n of

Mea

ns

Weight

Height

Main Effects Plot for MeansData Means

Fig. 6: Main Effects Plot for Means (Charpy test)

5.2 ANOVA The conducted experimental results were analyzed by using Analysis of Variance (ANOVA) which is used to examine the influence of wear parameters like Normal pressure and Sliding speed. By using ANOVA, it can be decided which independent factor dominates over the other and the percentage contribution of that particular independent variable. This analysis was carried out for a level of 5% significance that is up to a confidence level of 95%. Sources with a P-value less than 0.05 were considered to have a statistically significant contribution to the performance measures. Tables 11 and 12 show the results of ANOVA analysis for Izod and Charpy test of Zinc Aluminium alloy. Table shows the Material (97.41%) has highest influence on Izod impact test followed by Height (2.17%) and Weight (0.21%). Table shows the Material (93.86%) has highest influence on Charpy impact test followed by Height (6.09%) and Weight (0.02%). By seeing the table the work material has considers to have a statistically significant contribution for Izod and Charpy impact test.

Table 11: Analysis of Variance for Impact value of Izod test

Table 12: Analysis of Variance for Impact value of Charpy test

Source DF Seq SS Adj SS Adj MS F P % of contribution

Work Material 2 764.22 764.22 382.11 3439.00 0.000 93.86 Weight 2 0.22 0.22 0.11 1.00 0.500 0.02 Height 2 49.56 49.56 24.78 223.00 0.004 6.09 Error 2 0.22 0.22 0.11 0.03 Total 8 814.22 100.00




5.3 Regression Equation A multiple linear regression model is used to develop using statistical software ‘MINITAB 16’. This model gives the correlation between the effective factors (Work Material, Weight and Height) and the Impact test for Izod and Charpy test (quality characteristic) to observed data. For Izod Test Material

ZA-8 Impact value of Izod test = 65.7105 - 0.0085034 Weight - 0.0383076 Height ----Eqn (2)

ZA12 Impact value of Izod test = 72.7105 - 0.0085034 Weight - 0.0383076 Height ----Eqn (3)

ZA-27 Impact value of Izod test = 101.711 - 0.0085034 Weight - 0.0383076 Height ----Eqn (4)

R-Sq = 99.79% For Charpy Test Material

ZA-8 Impact value of Charpy test = 3.31991 + 1.44395e-006 Weight + 0.00505696 Height Eqn (5)

ZA-12 Impact value of Charpy test = 11.6532 + 1.44395e-006 Weight + 0.00505696 Height Eqn (6)

ZA-27 Impact value of Charpy test = 25.6532 + 1.44395e-006 Weight + 0.00505696 Height Eqn (7) R-Sq = 99.97% From Eq (4.1), Eq(4.2) and Eq(4.3) noticed that the negative value of coefficient of weight of the hammer reveals that increase in weight decreases the Impact strength of zinc aluminium alloy and vice versa. 6. CONCLUSIONS Work material (97.41%) was found to be significant in ANOVA for Izod Impact Test. Height (2.17%) and Weight (0.21%) was factors found insignificant for Izod impact test. Work material (97.41%) was found to the most significant factor and Weight (0.21%) was found least significant factor of Izod impact test. Main effect plot for Izod impact value shows maximum impact value for ZA-27 alloy and minimum value for ZA-8 alloy. Since Larger the S/N ratio, optimum is the process parameters. Work Material (A), Weight (B) and Height (C) i.e., A3B2C3. Change in weight and height has no significant effect on the impact value of Izod impact test. Work material (93.86%) was found to be significant in ANOVA for Izod Impact Test. Height (6.09%) and Weight (0.02%) was factors found insignificant for Charpy impact test. Work material (93.86%) was found to the most significant factor and Weight (0.02%) was found least significant factor of Izod impact test. Main effect plot for Izod impact value shows maximum impact value for ZA-27 alloy and minimum value for ZA-8 alloy. Since Larger the S/N ratio, optimum is the process parameters. Work Material (A), Weight (B) and Height (C) i.e., A3B3C2. Change in weight and height has no significant effect on the impact value of Izod impact test. References [1.] Li Yuanyuan, Xia Wei, Ngai Tungwai Leo, Luo Junming, Zheng Lingyi “Microstructures of a novel high strength

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process parametric optimization of impact test using taguchi and anova approach

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