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Cost Effective Mechanical Testing Equipment For Characterising Creep Behaviour Of Materials Under Combined Tension-torsion Loading
Project Description :

Materials experiencing stress at high temperatures undergo permanent creep deformation over a period of time. we have designed a set up which is well suited for doing creep experiments where constant loads can be applied for long periods of time and resulting deformation can be measured. the set up can simultaneously apply axial and torsional loads. this set up has the following features: 1. any combination of tensile/compressive and torsional loads up to 30 kn and 100 nm, respectively, can be applied on test specimen for any period of time. 2. no electrical input is needed for applying the loads in torsion. dead weights, in conjunction with pulleys are used for this purpose. for applying tensile/compressive loads smaller capacity stepper motor are required because of higher mechanical advantage with the ball screw. hence the cost of the machine is drastically reduced. 3. vertical movements of weights or rotation of stepper motor, used to apply torsion or tension, are extremely sensitive to twist and length changes in the specimen. for example, a 0.05mm length change in 50mm gauge length portion would lead to a vertical movement in weights applying tension/compression of around 9.5mm and a 1 degree twist over 50mm gauge length would lead to vertical movement of weights applying torsion of around 2.5mm. consequently, even creep strains to tune of 10-5-10-4 can thus be measured with good accuracy using inexpensive measurement devices like dial gauges. 4. a horizontal layout of parts supported on a linear guide way is used as opposed to the double column vertical arrangement in commercial uni- or bi-axial testing machines. this greatly increases accessibility of parts, keeps parts at eye level and makes it easy to assemble, maintain, and disassemble the parts. 5. electrical furnace is used to heat the specimen to test the material at elevated temperatures. the furnace is capable to increase the temperature of specimen up to around 1000 °c and keep the specimen at that temperature for a longer time. 6. the design is modular in nature and with minimal changes its load rating can be increased and the loading method can be automated using stepper/servo motors so that time varying/fluctuating loads can be applied. 7. the extensometer design which is under process uses ‘hall effect’ sensors to detect the length change at the gauge length region. this method uses non-contact method to measure the length change between the extensometer legs so that better accuracy could be achieved. 8. for the materials with strain rate is not important, the set up can be used to do the tensile/compressive test at different temperatures ranging from room temperature to 1000°c. 9. martensitic stainless steel ss410 is used for all parts except for linear guide way, rail blocks, ball screw, and bearings which are purchased directly. ss410 offers a unique combination of corrosion resistance, excellent strength on heat treatment and magnetic property (which is useful e.g. for holding work pieces on magnetic chucks during grinding operations on parts) at a price that is considerably less than the austenitic grade stainless steel such as ss304. while in annealed condition, at which it is procured and machined, it has an yield strength of around 275 mpa its yield strength increases to around 1000 mpa by heating it to temperatures of 925-1010°c, oil quenching it, and finally tempering it at 200°c for around 2 hours.

 
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Project Details :
  • Date : Dec 12,2015
  • Innovator : Vineesh K P
  • Team Members : Mr. Manish Dev
  • Guide Name : Prof. Vikranth Racherla
  • College : Indian Institute of Technology Kharagpur
  • Submission Year : 2016
  • Category : Mechanical/Textile
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