Calculate stress to cause failure - creep parameters, Mechanical Engineering

Calculate stress to cause failure - Creep Parameters:

From creep tests on 713 C alloy the constant C in Larson-Miller parameter is determined as - 85.75. In rupture test a specimen of this material fails after 500 hours at 34 MPa and 1373 K while another specimen at a stress level 136 MPa and at temperature of 1308 K fails after 3 hours. Calculate stress to cause failure after 30,000 hours at 1173 K.

Solution

From Eq. (23) with t1 = 500 hours, T1 = 1373 K at σ1 = 34 MPa

m1  = T1  (ln t1  - C ) = 1373 (ln 500 + 85.75)

= 1373 (6.2 + 85.75) = 12.62 × 104

From same equation with t2 = 3 hours, T2 = 1308 K at σ2 = 136 MPa

m2  = 1308 (ln 3 + 85.75) = 1308 (1.1 + 85.75)

    = 11.36 × 104

Using values of σ1, m1 and σ2, m2 in Eq. (25)

ln 34 = k1 × 12.62 × 104 + c1  = 3.526

ln 136 = k1 × 11.36 × 104 + c1  = 4.913

∴          k1 =      3.526 - 4.913/104 (12.62 - 11.36)

                          = (1.387 /1.26)× 10- 4 = - 1.1 × 10- 4

∴ c1  = 4.913 + 1.1 × 11.36 = + 17.409

∴ ln σ= - 1.1 × 10- 4 m + 17.409 -------------(i)

m3  = 1173 (ln 30, 000 + 85.75)

       = 1173 (10.31 + 85.75)

              = 11.27 × 104

Use the value of m3 in (i)

ln σ3  = - 1.1 × 10 - 4  × 11.27 × 104 + 17.409

= - 12.397 + 17.409 = 5.019

∴          σ3  = 150.2 MPa

which means that a stress of 150.2 MPa will cause specimen to rupture at 1173 K after 30,000 hours.

Note that performing test for 30,000 hours is highly time consuming and this result has been obtained by performing two tests which required 500 + 3 = 503 hours.

Posted Date: 1/23/2013 2:27:11 AM | Location : United States







Related Discussions:- Calculate stress to cause failure - creep parameters, Assignment Help, Ask Question on Calculate stress to cause failure - creep parameters, Get Answer, Expert's Help, Calculate stress to cause failure - creep parameters Discussions

Write discussion on Calculate stress to cause failure - creep parameters
Your posts are moderated
Related Questions
What is scale formation in case of a boiler

Normal 0 false false false EN-IN X-NONE X-NONE MicrosoftInternetExplorer4

Discover the maximum thickness required: A thin cylindrical vessel of 2 m diameter and 4 m length having a particular gas at a pressure of 1.65 N/mm 2 . If the allowable tensi

Question 1 A metal rod has a diameter of 8.74 mm and supports a load of 24.6 kN. Calculate the value of true stress on the rod. The diameter was measured with the load already a

Non-linear Sweep In non-linear sweep, the path is a curve described by a higher-order equation (quadratic, cubic or higher)

Schedule Evaluation The schedules are evaluated as per to the criterion weighted loss of slack. Now let t 0 si be the slack (time buffer) of job I as per to the initial sched

You have been selected to assist the structural engineer for a bridge replacement project.  Your task is to design the size of the footing for an interior bridge pier, based on the

give equivalence of screw jack and friction on an inclined plane


General Resource Models In  computer  controlled scheduling,    material,  machine handling  equipment,  tooling  and  buffer  space  should  be comprised. The explicit consid