This standard is issued under the fixed designation E ; the number immediately This test method is under the jurisdiction of ASTM Committee E-8 on. ASTM E testing covers the determination of the plane-strain fracture toughness (KIc) of metallic materials by tests using a variety of fatigue-cracked. Specimens were tested in accordance with ASTM E Their respective fracture surfaces were plated, polished, photographed under an SEM.
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Nil Ductility Transition (Drop Weight) ASTM E Olsen Ductility ASTM E Drop . Thus, for example, the ASTM E standard (ASTM E , ) includes. This standard is issued under the fixed designation E ; the number 1 This test method is under the jurisdiction of ASTM Committee E-8 on Fatigue. () ASTM Standard E Standard test method for measurement of fatigue crack growth rates. ASTM, West Consohohocken, USA.
Cement Concr Res — Int J Fract — Int J Fract 47— Google Scholar Kumar S, Barai SV a Determining double-K fracture parameters of concrete for compact tension and wedge splitting tests using weight function.
Sadhana-Acad Proc Eng Sci 36 6 : — Comput Concr Int J under review. Google Scholar Kumar S, Barai SV e Weight function approach for determining crack extension resistance based on the cohesive stress distribution in concrete. Int J Damage Mech 9: — Oxford, Pergamon Press.
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Google Scholar Petersson PE Crack growth and development of fracture zone in plain concrete and similar materials. Report No.
Several research groups found improvement of PMMA bone cements surface roughness properties by incorporating different kinds of additives materials with the PMMA cement[ 6 , 10 — 13 ].
Our previous study found that micron and nano sizes MgO particles improved the fracture toughness of bone-cement interfaces under tension loading[ 14 ]. The strength of bonding of bone with these additives incorporated PMMA bone cement may be different from bonding of bone with PMMA without these additives.
The influences of the inclusion of these additives with bone cement on the bonding stress between natural bone and cements were not investigated yet.
Such study is required for the suitability of using the additives with the bone cement. Ricker et al. In this present study, two kinds of bone cement were investigated.
The scope of works for this research were: 1 to quantify elastic and fracture properties of different bone and bone cement specimens, 2 to determine whether inclusion of MgO additives with PMMA has any influence on the mechanical properties of CBC, and 3 to determine whether bone orientation and inclusion of MgO particles with PMMA has any influence on the interface strength between bone and CBC.
A custom made three-point bend test setup was designed and fabricated.
ASTM standard three-point bend 3PB tests were conducted on the first group of specimens to quantify the elastic and fracture properties differences between natural bones and cements specimens. Three-point bend 3PB tests were conducted on the bimaterial specimens to quantify the bone orientation and MgO additive material effects on the bonding strength of the corresponding specimens.
Design and instrumentation of the setup The complete test setup is shown in Figure 1 a.
All instruments were calibrated before testing. The 3PB bend stage consists of base, stage-base connector, sliding bar, indenter, and specimen holder. An optical xyz stage was assembled with the base for microscopic viewing purposes using stage-base connector.
Actuator was mounted on the base to push the sliding bar. The microstructure of the austempered samples is shown in the Figure 3b. The austempered microstructure shows the presence of lower bainite blue-colored phase and a limited number of isolated pockets of martensite brown-colored phase in the microstructure.
Material Mismatch Effect on the Fracture of a Bone-Composite Cement Interface
X-Ray Diffraction XRD confirmed the presence of the bainite and martensite in the austempered material. The presence of the martensitic was not expected since the samples were austempered at a temperature above the Ms Martensite start temperature of the steel. This was attributed to segregation effects from the alloying elements present in the steel. The carbides of alloying elements like Cr, Mo, and Mn tend to segregate to the intercellular regions.
In these segregated regions, the bainitic reaction associated with the austenite decomposing into ferrite and carbide becomes sluggish; therefore, complete transformation does not take place during the processing time.
Upon cooling, these untransformed regions can form martensitic structures. In general, the variation associated with the results are typical and normal for tensile tests. Table 2 also shows a comparison of these results to the annealed condition. In general, the austempering process has increased both the ultimate and yield strengths compared to the annealed condition; as expected, the ductility of the austempered is significantly decreased compared to the annealed condition.
Table 2 also presents a comparison of the mechanical properties as a function of austempering heat-treatment for samples taken from the same heat of steel as that used in this study. Upon cooling, the larger grain size will result in a coarser bainitic microstructure that, in turn, lowers the mechanical properties.
Additionally, Table 2 presents data comparing the mechanical properties from the current study to those of a steel that had undergone a conventional quench and temper heat-treatment process [ 16 ]. As this comparison shows, the conventional quench and temper process yields tensile strength and elongation values significantly greater than those from the austempering process. However, it should be noted that the austempering process can result in much lower levels of distortion.
Thus, in certain applications, austempering may be a more optimum process for achieving high strengths. Fatigue threshold The results from the fatigue thresholding tests performed on the austempered samples for the proposed STM are presented in Figure 4. Statistical analysis found that there is no statistically significant difference between the two fatigue threshold values the conventional and the proposed STM.
These results are reasonable when compared with those reported in [ 14 ]. Fracture toughness The results from the fracture toughness tests performed on the austempered samples for the proposed STM are presented in Figure 5.
Thus, by extrapolating the number of cycles "N" to zero, Equation 1 yields a fracture toughness "KIC" equal to Using this method, the fracture toughness of the austempered AISI steel was determined to be This analysis found that there is no statistically significant difference between the two KICvalues.
Thus, since there is no difference between the two, this indicates that the proposed single sample test method is a reasonable approach for determining the KICvalue for austempered steel.
Proposed Analytical Model The fracture toughness of a material strongly depends on the microstructure present. A plot of KIC2vs. There was a desire to see if the fracture toughness of the austempered steel could also be modeled as a function of measurable microstructural parameters as well.
Principles Crack propagation requires a force with sufficient amount of energy to cause a crack to grow and have an incremental increase in area.
In ductile materials like steel alloys , the majority of the crack extension force that drives crack growth is dissipated in extending the plastic zone in a given material. The critical crack extension force can be determined by calculating the critical volume of deformed metal associated with the extension of a crack by da.
From experience, it is known that structural steels can be poorly modeled by LEFM alone; this is due to the blunting of the initially-sharp cracks during propagation. There have been a large number of detailed investigations focusing on the relationship between fracture toughness, crack opening displacement, and the mechanical properties in a large number of metallic alloy systems [ 17 - 20 ].
Experimental correlation As part of the present study, the validity of the model in the austempered steel was also examined.
As Figure 6 illustrates, a linear relationship with a coefficient of determination R2 of 0. This yields a value for the constant "C" in Equation 12 of 6.Comput Concr Int J under review.
Int J Eng Sci — Therefore, compliance with the specified validity criteria of this test method is essential. Flat Panel Drop Tower Testing The drop tower tests were performed on three down-selected cranial surrogate material combinations based on the results of the fracture toughness, tensile and three-point bending tests.
Evaluation of J-initiation fracture toughness of ultra