locations, which would cause indentation. In Figure 5, a sample is shown at the end of testing. The test was manu- ally stopped to prevent further slippage of the sample off of the lower forces and to prevent sample contact with the cornered edges. We were unable to break any ablation samples with either the small or the large FPB settings, which indicates that the ablation castings show signifi- cantly higher ductility that the other processes. Several ablation samples were broken manually in order to inves- tigate the fracture surfaces.
tensile test
The tensile tests were performed in order to further charac- terize the mechanical behavior for the four casting process- es since FPB tests could not break any ablation samples. The tensile specimens were cut from locations A and B on each control arm (Figure 2). Two specimens from each location (from both the cope and drag sections) were ma- chined from each control arm. The specimen dimensions are given in Figure 6.
Tensile specimens were loaded under strain at a rate of 0.001/s. Specimens were tested to failure at laboratory room
(1)
Where: P, is the probability of failure at a value of x. The Weibull modulus m and the scale parameter xo
able value of the property. are the pa-
rameters used to characterize the distribution of the property being measured. The term xu
refers to the minimum allow-
Using the symbol F for the ultimate bending strength (UBS) for the four-point bending (FPB) test, substituting this for
temperature and relative humidity. After tensile testing, post-process analysis was performed to determine the yield strength, ultimate strength and elongation to failure.
Weibull analysis The Weibull analysis approach14
has been frequently used
to characterize the dispersion of the mechanical proper- ties. The Weibull distribution for a random variable x can be represented using the following form of the Weibull equation:10
Figure 3. Sketch of the four-point bending test geometry.
Figure 5. Sample at the end of testing in the larger FPB test setup.
Figure 4. Location C ablation sample at the end of testing in initial FPB test setup.
International Journal of Metalcasting/Fall 2011
Figure 6. Specimen dimensions for tensile testing. (Dimensions in mm).
39
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80