BS EN 843-7:2010 pdf download
BS EN 843-7:2010 pdf download.Advanced technical ceramics – Mechanical properties of monolithic ceramics at room temperature Part 7: C-ring tests.
NOTE 2 It is necessary only to mele the chamfer over an arc length of at least 90’ of the tube wall adjacent to region of maomum tensile stress.
NOTE 3 Chamtenng may be done by medians or by hand. The size of chamfer may need to be increased above the miruman vakies above for high-strength materials if it is found by fraclography that chamfer donwated failure rather than surface dominated failures result. See 141 and IS).
At least ten test pieces shall be tested for determination of a mean strength. or at least 30 test pieces if a Weibull statistical analysis in accordance with EN 843-5:2006 is to be performed
8 Test procedure
8.1 Test-piece dimensions
Measure the axial length of the each test piece to the nearest 0,01 mm in several places using the micrometer, Compute the mean result.
Measure the outside diameter of each test piece to the nearest 0.02 mm using the vernier callipers, ensuring that several measurements are made along the axial length across the diameter adjacent 10 that expected to become the mid plane in the test. Compute the mean result.
Measure the inside diameter of each test piece to the nearest 0,02 mm using the vernier callipers, ensuring that several measurements are made from both sides of the ring across diameters adjacent to the diameter expected to become the mid plane in the tesi Compute the mean result.
NOTE The ring dimensions should be measured after Cutting the slot since ttws may release residual stresses and cause a shape chenge
Measure the wall thickness of each test piece to the nearest 0,01 mm using the ball.anvil micrometer, ensunng that several measurements are made in the region adjacent to that expected to be In the mid plane dunng the test. Take great care not to Introduce Indentation damage dunng the measurement. Compute the mean result Alternatively, measure the wall thickness after the test at the site of fracture.
8.2 MechanIcal testing
In turn, place each test-piece between the anvils of the testing machine (Method A) or between the pull-yokes of the testing machine (Method B), using thin foil or rubber sheet as an interlace between the test piece and the contacting metallic parts. Take up the slack in the load train and ensure that the test-piece remains centrally positioned, particularly the contact positions of the pull bars ii Method B.
Load the test.piece at a constant rate of load increment, or at a constant crosshead displacement rate. until fracture occurs within a timescale of lOs to 308.
NOTE 1 The rate selected wtll be deleramned by the clenensions of the test-piece, and may require some trials before the above ndltion Is met A method of calculating the required cross.head displacement rate is given In Annex A.
Recover the fragments of the test piece and inspect for unusual fracture patterns suggesting poor alignment in the test.
NOTE 2 Guidance on fractegraphic examinations is grven r EN 843-8(5)
9 Calculation
9.1 Method k C-ring compression
Compute the nominal exterior surface C-ring compression fracture strength using the following equation:
9.4 Fractures away from the centre-line
Equations (1) and (3) are valid for the maximum stress Ni the test piece which occurs at a position 90’ to the axis of force application. They are used to calcuLate the nominal fracture stress, and these data shall be used in any Woibtdl statisbcal analysis
If it is required to measure the actual fracture stress at the fracture site, the angle a between the position of maximum stress at the mid-plane and the fracture site (Figure 1) shall be measured to the nearest 1 • The calculated fracture stress using Equations (1) or (3) for the respective geometnes is then corrected by multiplying it by a factor cos 0.
NOTE Delaiks of stress analyses for the C-ring geometry can be found Ni 121 and [3J in the Btliography,
10 Interferences
The principal sources of error in this test are caused by imperfections in geometry of the test piece, and in poor alignment and/or contact of the test piece with the loading system.
