Summary of an Article
The test needs at least three samples; the first load sample burst at a consistent rate with the Test Method E8 to create fast fracture strength (FFS), geometrically (PFFS=Pc) (Kaminsky 783-786). The test has the primary reference data, specific load profile vary on the samples hardness within a scale of≥33HRC to 45HRC; >45HRC to 54HRC; and>54HRC. #/%Pmax/hrs is the symbol for incremental step load profile ("WITHDRAWN: Engineering Fracture Mechanics Special Issue—Mechanics Of Fracture And Failure In Geomaterials"). # represents some steps, and %Pmax gives the highest load anticipated by a single step.
The loading profile for≥33HRC to 45HRC is (10/5/2,4) or 10 steps at 5% of PFFS.
Specific load profile Pmax=1.1×Pth-n. The reason for varying of the maximum profile is to decrease the loading rate and increase the resolution. Pth-n (threshold load) represents a load to the step before the beginning of split (crack) growth for a given loading rate. When the difference between any two succeeding threshold loads is below 5% of PFFS, the results is known as the Invariant Threshold ("WITHDRAWN: Engineering Fracture Mechanics Special Issue—Mechanics Of Fracture And Failure In Geomaterials"). Pi at the start induces hydrogen splitting the threshold load Pth.
Pth-EHE, Pth-SCC, or Pth-IHE, is the lowest value recorded for thresholds. Crack growth is considered to take place when the load measured on a sample reduces by a value higher than the created accuracy of the test parameters ("Engng Fracture Mech." 583). During plating process Fast Fracture test maintains that there is no creation and softening takes place, Threshold is the stress intensity calculated from the load at the beginning of crack growth. Pi is the crack initiation load, and it takes places immediately after the threshold load Pth ("Engng Fracture Mech." 583).
For the hardness scale of >54 HRC SN(2)–(20/5/1) @ PMAX = PFFS; → Pth-1 SN(3)–(20/5/1) @ PMAX = 1.1 × Pth-1; → Pth-2 SN(4)–(20/5/1) @ PMAX = 1.1 × Pth-2; → Pth-3 and if necessary; SN(5)–(20/5/1) @PMAX = 1.1 × Pth-3; → Pth-4 measures Pth-EHE, Pth-SCC, or Pth-IHE when DPth # 5 % PFFS or, For the hardness scale of >45 HRC to 54 HRC SN(2)–(10/5/1,2) @ PMAX = PFFS; → Pth-1 SN(3)–(10/5/1,2) @ PMAX = 1.1 × Pth-1; → Pth-2 SN(4)–(10/5/1,2) @ PMAX = 1.1 × Pth-2; → Pth-3 and if necessary; SN(5)–(10/5/1,2) @ PMAX = 1.1 × Pth-3; → Pth-4 measures Pth-EHE, Pth-SCC , or Pth-IHE when DPth # 5%PFFS or, For the hardness scale of $33 HRC to 45 HRC , SN(2)–(10/5/2,4) @ PMAX = PFFS; → Pth-1 SN(3)–(10/5/2,4) @ PMAX = 1.1 × Pth-1; → Pth-2 SN(4)–(10/5/2,4) @ PMAX = 1.1 × Pth-2; → Pth-3 and if necessary; SN(5)–(10/5/2,4) @ PMAX = 1.1 × Pth-3; → Pth-4 measures Pth-EHE, Pth-SCC , or Pth-IHE when DPth # 5 % PFFS("Engng Fracture Mech." 583).
NFS load drop of 5% is used as an arbitrary precaution for measurement for the beginning of crack growth, and it is recommended for materials with explosive crack growth rate(Kaminsky 783-786). Substances with very slow split or crack growth rate should use a lesser value of load drop enable consistency with the visual detection of the load drop("WITHDRAWN: Engineering Fracture Mechanics Special Issue—Mechanics Of Fracture And Failure In Geomaterials"). Any load drop that results from an increasing rate (convex) is related to the SCG in the specimen. Maintaining the load for a given fragment of time at step say (x) before SCG, threshold can be calculated to be an increase above the final step (y). It is given by the equation,
∆=xy of 5% Pmax
All load drops at decrease rate (concave) shall result from creep and plasticity of the material used (specimen), and it is neither considered a crack growth nor a crack initiation ("Engng Fracture Mech." 583). The process takes place when the stress at the crack (burst) peak overcomes the production strength or capability of the substance. Load transformation from reduction rate to an increasing rate is known as crack initiation. Proof of crack growth is attained by placing tested materials to fracture.
Works Cited
"WITHDRAWN: Engineering Fracture Mechanics Special Issue—Mechanics Of Fracture And Failure In Geomaterials". Engineering Fracture Mechanics (2010): n. pag. Web.
"Engng Fracture Mech.". Engineering Fracture Mechanics 19.3 (2012): 583. Web.
Kaminsky, A.A. "Fracture Mechanics Of Composite Materials". Engineering Fracture Mechanics 24.5 (2009): 783-786. Web.
