M.tech Project - Crack Growth Analysis and Propagation Life Prediction of Gas Turbine Rotor Discs

Aim/Goal

Setting up standard guidelines for crack propagation life estimation of gas turbine rotor discs using 3D crack modeling technique in finite element analysis.

Problem Definition

• Gas turbines are frequently employed in power generation due to their higher power to weight ratio and they usually rotate at high speeds and operate at high temperatures. So, these are heavily loaded due to mechanical and thermal loads.
• This leads to the generation of surface cracks at stress concentration zones or at pre-existing defects. The presence of crack can significantly reduce the life of component and components fails in brittle fashion even if it is ductile material.
• After reaching a critical state, these discs fracture into two or more number of parts due to the propagation of these cracks.
• Hence, turbine discs are considered as critical components in the engine and their crack propagation life estimation under fatigue loading is prime importance.
• Gas turbine rotor discs have complex geometries with cooling holes in different directions such as Axial, Radial or hybrid. This results in 3D stress field at many locations.
• For such complex geometries, 3D crack modeling technique and crack growth analysis using stress intensity factor & J-Integral is required to predict the realistic crack propagation life.

Objectives

• Initial FE and FM life (crack propagation life using fracture mechanics) assessment for standard components having standard crack geometries using 3D crack modeling technique and comparison with published or experimental results to setup the benchmark. 
• Next step involves FM life prediction of various cracks in different locations of gas turbine disc using 3D crack modeling technique in ANSYS. 
• Setting up standard guidelines for 3D crack modeling technique of GT rotor disks. 
• Comparison of FM life prediction by 2D analysis in IWM VERB and 3D crack modeling technique in ANSYS.

Methodology

• This work is focused on the crack propagation life estimation of gas turbine rotor discs under different service conditions using fracture mechanics concepts. 3D crack modeling technique and crack growth analysis using stress intensity factor & J-Integral is required to predict the realistic crack propagation life. 
• First, for benchmarking, stress intensity factors of surface and corner cracks in plates subjected to tensile loading are determined using 3D crack modelling technique in ANSYS. These results have been Compared with published results and good agreement was observed.Next, crack growth analysis and FM life estimation simulation is performed on plate having surface crcak and compared with results available and achieved excellent agreement.
• 3D crack modeling, Stress intensity factors estimation and FM life prediction is performed for gas turbine disc which has been taken from the literature. Predicted life is compared with experimental results to validate the methodology and the results are very good.
• Same methodology using 3D crack modelling is used for different gas turbine disc locations to predict the life of component.
• Until now, this work is performed under LEFM (linear elastic fracture mechanics) conditions. From now onwards, it will be carried out under EPFM (elastic-plastic fracture mechanics) conditions.
• This work is not completed yet. So, changes to the existing content are possible.

Result

This is the result of analysis performed on the literature disc.

Conclusions

• 3D crack modeling technique is very effective for estimating accurate stress intensity factors, crack propagation life and critical crack length. 
• Life from 2D analysis in IWM VERB is very much below the life estimated from Ansys.  
• If  accurate life and the critical crack length is known, inspection periods and maintenance can be scheduled accordingly.  

Downloads 

will be updated soon

Acknowledgemnet

Project guide : Dr K S R Krishna Murthy, IIT Guwahati
Mentors in SIEMENS :
Mr. Siddharth Jain,
Mr. Pritam Kondalwar
Mr. Manish Kumar Purohit
Mr. Sunder Raman Mohan 

I thank above all for their guidance and support during this work.

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B.tech Project - Determination of Warpage in Injection Molded Plastic Components using Image Processing

Aim/Goal

Applying efficient and easy methodology for predicting warpage in plastic components.

Problem Definition

• Plastic injection molding is one of the major net-shape-forming processes for thermoplastics materials. Mold temperature, injection pressure, filling time, injection speed are the four major parameters in manufacturing the injection molding components. 
• There are several defects that occur in the injection molding process, including blush, blow holes, burn marks, warpage, bowing, bubbles, clear spots, cloudy appearance, contamination and cracking. 
• Warpage is the possible defect which occurs with the variation in rate of solidification due to change in temperature differences in plastic components. 
• Image processing technique is more convenient to predict warpage in injection molded plastic components. 
• By minimising the warpage, considerable improvement in the performance characteristics of injection molded components can be observed. 

Objectives

• Preparation of fixture for taking steady images of plastic components.
• production of forward and reverse lever ( FR lever ).
• Warpage determination in FR lever using image processing technique in MATLAB.
• Applying the same methodology to other plastic components like bottle caps and computer speakers.

Methodology

          This work focused on determination of warpage for injection molded plastic components through image processing technique. In this context, a fixture has been prepared to capture digital images of plastic components in a fixed plane. Further this fixture helps to capture clear standby images of plastic components which help to get to more accurate warpage results using image processing. This work undergoes for determination of warpage in Forward and Reverse lever (FR lever), bottle caps and computer speakers. The two plastic components images are captured by using high resolution digital camera which are fixed in fixture. The high resolution captured plastic components of images, are processed using MATLAB Image Processing Tool. The distoreted injection molded plastic component is compared with the standard component by measuring at three different locations in longitudinal direction and also in lateral direction. Warpage has been calculated by taking the average of differences between those measurements in both directions. The warpage may be minimised by suitably selecting the process parameters of injection molding machine.

Result

Warpage in FR Lever

Conclusions

• In MATLAB, image processing tool is very effective and fruitful in the determination of warpage in plastic components. The present method used for measuring warpage is easy, time saving.
• If warpage is more than the acceptable limit, suitable process parameters of injection molding machine such as mold temperature, injection pressure, injection speed, filling time and cooling time can be adjusted to get the better quality of plastic component.

Downloads

Download project report here

Download MATLAB program for image processing

Acknowledgement

• Project guide : Dr G Padmanabhan, Si Venkateswara University.
• Mr. S Selvaraj helped in production of FR lever and provided guidance.
• Mr. Sudhakar provided support in MATLAB code for image processing.

Project team members :
B R Silpa Sree
N Sai Mohan reddy
Y Purushotham 

I thank above all for their guidance and amazing time during this project work.

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Read about my M.tech project on fracture mechanics here 

Feel free to comment below and after that contact me if you want to. 

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