Validity requirements for fracture toughness measurements obtained from small circumferentially notched cylindrical specimens

Ibrahim, Raafat N; Stark, H.L.

doi:10.1016/0013-7944(87)90190-1

Cited by 59 publications

(10 citation statements)

References 2 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Although the data retrieved by photography is mostly qualitative and suffers from a lens-flare around the notch, a greyscale profile curve taken across the X-axis suggests that the radius of the concentrated zone varies between 2 and 4 mm. The size of the concentrated zone, indicated on the photograph, is essential to the validity of the compact-tension test, as a large concentrated area implies that the singularity-dominated zone has effectively uniform volume fraction [13,35]. The K IC calculation [Equation 4] assumes plane strain conditions near the crack-tip [34], which require the concentrated zone to be larger than the radius of plasticity, where the matrix reaches its yield point (r p ≈ 30 µm).…”

Section: Magnetic Translation and Rotationmentioning

confidence: 99%

“…The orientation factor η θ is a function of the angle θ between the fibers and the X-axis; it varies between 0 (θ = 90 • ) and 1 (θ = 0 • ). As fiber alignment causes G c and E enhancement [12,18,25,[34][35][36], it directly affects fracture toughness. For the elastic modulus E, the orientation factor decreases with orientation angle as described by the Krenchel factor-cos 4 (θ) [37].…”

Section: Mechanical Analysismentioning

confidence: 99%

See 1 more Smart Citation

Efficient Toughening of Short-Fiber Composites Using Weak Magnetic Fields

2020

View full text Add to dashboard Cite

Short fibers may serve as toughening agents of composite materials because of the high energy dissipated during fracture, associated with numerous fiber pullouts. An ongoing challenge is to improve their toughness even further, by directing and concentrating fibers near highly stressed structural regions. Weak magnetic fields are utilized to increase the fracture toughness of an epoxy matrix reinforced by short magnetized glass fibers by directing and concentrating fibers near highly stressed structural regions. The orientation and local concentration of the fibers are controlled by the vector components of the magnetic field, and by the gradient in field intensity, respectively. Optimized fracture toughness was achieved by using two pairs of permanent magnets, combining enhanced concentration of fibers in the crack-tip vicinity with alignment of the fibers along the load direction. This optimized value was well above the reference fracture-toughness measured for composites with the same filler content in the absence of a magnetic field, as well as above the value achieved by exploiting unidirectional alignment, without fiber translation, using a solenoid. The method suggested in this study—localized reinforcement using magnetic translation of fillers through the formation of magnetic gradients—enables efficient and controllable improvement in the composite’s overall resistance to fracture, without the involvement of additional phases or material.

show abstract

Section: Magnetic Translation and Rotationmentioning

confidence: 99%

Section: Mechanical Analysismentioning

confidence: 99%

Efficient Toughening of Short-Fiber Composites Using Weak Magnetic Fields

2020

View full text Add to dashboard Cite

show abstract

“…Although the case of axisymmetrical cracked bars has already been addressed using finite element analysis (e.g. Ibrahim andStark 1987, Pardoen et al 2000), it may not be close to that of the UXT geometry in spite of all precautions that were taken to stiffen the specimen. In the present experimental study, a simpler plane strain approximation was taken.…”

Section: Assessment Of Small Scale Yielding Conditionsmentioning

confidence: 99%

Fracture toughness of the molten zone of resistance spot welds

et al. 2013

View full text Add to dashboard Cite

A methodology for measuring the fracture toughness at crack initiation and the crack extension resistance of the molten zone of resistance spot welds under Mode I loading has been developed. The cross tensile test of U-shaped specimens was modified by crack growth monitoring and stress intensity factor determination. The resulting values of fracture toughness at crack initiation are independent of the nugget diameter and of the base material mechanical properties. The crack extension resistance seems to depend on base material mechanical properties and nugget diameter. Mixed cleavage + ductile mode associated to medium values of fracture toughness (54-90 MPa.m 0.5) suggested a ductile to brittle transition behaviour. The relatively low fracture toughness (55-59 MPa.m 0.5) associated to full interfacial ductile failure was quantitatively related to the high number density of small particles in the molten zone. This study opens the possibility to apply the local approach to fracture under monotonic loading to interfacial failure of resistance spot welds.

show abstract

“…A rapid, cost effective and reliable technique for fracture toughness evaluation requiring easy to machine specimen type has been proposed with the use of circumferential notch tensile specimens. The advantage of the CNT specimens for fracture toughness evaluation include: 1) attainment of plain strain crack loading conditions with smaller specimen dimension in comparison with the CT specimen 10 ; 2) radial symmetry which makes them suitable for studying the impact of the microstructure on fracture toughness 9 ; 3) ease of machining to desired test configuration 12 ; and 4) ease of testing using simple testing facilities like the tensometer 9 . The advantages make the use of CNT specimens very attractive for fracture toughness evaluation especially in developing African countries.…”

Section: Introductionmentioning

confidence: 99%

Fracture Toughness (K1C) evaluation for dual phase medium carbon low alloy steels using circumferential notched tensile (CNT) specimens

Alaneme

2011

Mat. Res.

View full text Add to dashboard Cite

The fracture behavior of dual phase medium carbon low alloy steels produced using two different chemical compositions (A -0.34C, 0.75Mn, 0.12Cr, 0.13Ni steel and B -0.3C, 0.97Mn, 0.15Cr steel) was investigated using circumferential notched tensile (CNT) specimens. Intercritical treatments were performed on samples with composition A by 1) austenitizing at 860 °C for 1 hour cooling in air, then treating at 770 °C for 30 minutes before oil quenching; 2) austenitizing at 860 °C for 1 hour quenching in oil, then treating at 770 °C for 30 minutes before quenching in oil; and 3) austenitizing at 860 °C for 1 hour, super-cooling to 770 °C and then quenching in oil. Samples of composition B were subjected to intercritical treatment at temperatures of 740, 760, and 780 °C for 30 minutes, followed by quenching rapidly in oil. Tensile testing was then performed on specimens without notches and the CNT specimens. It was observed that the dual phase steel produced from procedure (2) yielded a fine distribution of ferrite and martensite which gave the best combination of tensile properties and fracture toughness for composition A while the dual phase structure produced by treating at 760 °C yielded the best combination of tensile properties and fracture toughness for composition B. The fracture toughness results evaluated from the test were found to be valid (in plain strain condition) and a high correlation between the fracture toughness and notch tensile strength was observed. The fracture toughness values were also found to be in close agreement with data available in literature.

show abstract

Validity requirements for fracture toughness measurements obtained from small circumferentially notched cylindrical specimens

Cited by 59 publications

References 2 publications

Efficient Toughening of Short-Fiber Composites Using Weak Magnetic Fields

Efficient Toughening of Short-Fiber Composites Using Weak Magnetic Fields

Fracture toughness of the molten zone of resistance spot welds

Fracture Toughness (K1C) evaluation for dual phase medium carbon low alloy steels using circumferential notched tensile (CNT) specimens

Contact Info

Product

Resources

About