Investigation on brittle fracture mechanism of a grade E cast steel knuckle

The random vibration failure of an array power supply for near-space SAR was analyzed. The fracture mechanism and the fracture reason of fracture formation in the specimen were investigated. The results show that antishock MOS pin breaks first, and the power supply is still in the working state during the process of random vibration. This caused dischargings at the tip of the fracture and melting of the tip of the broken pin which form a river-shaped fracture and granular tissue. The plastic fracture with typical dimple morphology of the pins for the resistor tube occurred during the random vibration. The intergranular fracture appeared at the welding part of the electronic components for array power supply, which presented a brittle fracture mechanism. The fracture was dominated by a ductile fracture for components when the stress produced by the vibration was close to the yield strength of the material. The fracture was dominated by a brittle fracture for components when the stress produced by the vibration was far beyond the yield strength of the material. A simulation evaluation system based on the high-confidence model was proposed. The stress of the electronic components for array power supply and its welding was much lower than the allowable strength of the material by the optimization of the structure and the form of the welding for the array power supply. The sample was successfully tested and verified without any further fracture problems.

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Notch Effects on Impact and Bending Characteristics of Spheroidal Graphite and Compacted Vermicular Graphite Cast Irons with Various Matrices

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.457.392 ◽

2010 ◽

Vol 457 ◽

pp. 392-397 ◽

Cited By ~ 1

Author(s):

Tohru Nobuki ◽

Minoru Hatate ◽

Toshio Shiota

Keyword(s):

Cast Iron ◽

Transition Temperature ◽

Brittle Fracture ◽

Cast Steel ◽

Charpy Impact ◽

Spheroidal Graphite ◽

Buffer Effect ◽

Cast Irons ◽

Type Specimens ◽

The Impact

The object of this study is to find out and evaluate systematically how the basic factors such as graphite-shape, external notch and matrix-characteristic affect the impact and bending characteristics of cast irons. The Spheroidal Graphite (SG) and Compacted Vermicular graphite (CV) cast iron samples were prepared, and their matrixes were modified into ferritic, pearlitic and bainitic in order to make the various kinds of samples whose graphite-shape and matrix vary widely. From each sample we produced five kinds of Charpy-type specimens by adding five kinds of notches whose stress concentration factor (α) varied from 1.0 (un-notched) to 4.8. The Charpy impact value decreases greatly in the range of α from 1 to 2.3 but decreases slightly in the range of α larger than 2.3. No influence to the fracture energy in the range of α larger than 2.3. Increasing of α results in moderate elevation of transition temperature of Charpy impact value and the transition temperature of CV cast ion is lower than that of SG one. The impact value in brittle fracture region of the cast iron samples were recognized to be a little bit larger than that of cast steel sample, and it was considered to be caused by graphite which act as a kind of buffer effect against crack growth in brittle fracture.

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Assessment of brittle fracture for cast steel connections in braced frames

Tubular Structures XIV ◽

10.1201/b13139-47 ◽

2012 ◽

pp. 323-330

Author(s):

T Iwashita ◽

J Packer ◽

J de Oliveira

Keyword(s):

Brittle Fracture ◽

Cast Steel ◽

Braced Frames ◽

Steel Connections

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Comparative studies of brittle fracture mechanism for standard and reconstructed CT specimens made of VVER-1000 RPV materials

Inorganic Materials Applied Research ◽

10.1134/s207511331706003x ◽

2017 ◽

Vol 8 (6) ◽

pp. 927-935

Author(s):

A. D. Erak ◽

E. A. Kuleshova ◽

S. A. Bubiakin ◽

A. P. Bandura ◽

D. A. Zhurko

Keyword(s):

Brittle Fracture ◽

Comparative Studies ◽

Fracture Mechanism

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The Fracture Research of Hexagonal Duralumin Nut

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.152-153.1244 ◽

2010 ◽

Vol 152-153 ◽

pp. 1244-1247

Author(s):

Bin Xu ◽

Bai Yang Lou

Keyword(s):

Brittle Fracture ◽

Fracture Surface ◽

Surface Topography ◽

Fracture Mechanism ◽

Fracture Behavior ◽

Optical Microscope ◽

Air Pressure ◽

Brittle Mode ◽

Electronic Microscope ◽

Made In

The microstructure, fracture surface topography and mode of hexagonal nut cracked in assembling under air pressure were analyzed with optical microscope and scanning electronic microscope, which are made in contrast with that of hexagonal nut cracked in man-made. The research results show that the man-made fracture of nut was of dimple shape and cracked in toughness mode, which accorded with the fracture behavior of 2Al2 duralumin material. The air-pressure fracture of nut was of right shape and cracked in brittle mode. The fracture mechanism is concluded that crack fountain is formed in surface of nut because of scoring during assembling and then the crack expands rapidly, leading to brittle fracture of the nut.

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Study on Microstructure and Properties of Tailored Hot-Stamped U-shaped Parts Based on Temperature Field Control

Metals ◽

10.3390/met9050593 ◽

2019 ◽

Vol 9 (5) ◽

pp. 593

Author(s):

Xiangji Li ◽

Limei Xiao ◽

Qifeng Zheng ◽

Huan Zhang ◽

Yanjiao Gu

Keyword(s):

Tensile Strength ◽

Temperature Field ◽

Brittle Fracture ◽

Automotive Industry ◽

Fracture Mechanism ◽

High Speed ◽

Fracture Behavior ◽

Hot Stamping ◽

Micro Hardness ◽

Field Control

In order to meet the needs of the automotive industry, it is necessary to produce “tailored” parts. The U-shaped die equipped with a high-speed airflow device was designed to conduct the hot stamping experiments. The microstructure, micro-hardness, tensile properties, and fracture behavior of the parts were analyzed. The experimental results showed that the quenched phase of the hardened section was mainly martensite, and the micro-hardness and tensile strength could reach 445 HV and 1454 MPa, respectively. The fracture mechanism was brittle fracture. For the toughness section, as the tool temperature increased from 300 to 600 °C, both micro-hardness and tensile strength decreased. Meanwhile, the area fractions of bainite and ferrite increased, and the area fraction of martensite reduced. The fracture behavior was plastic fracture.

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The fracture of glassy polymers

Proceedings of the Royal Society of London Series A - Mathematical and Physical Sciences ◽

10.1098/rspa.1972.0105 ◽

1972 ◽

Vol 329 (1577) ◽

pp. 137-151 ◽

Cited By ~ 64

Keyword(s):

Brittle Fracture ◽

Viscous Flow ◽

Fracture Mechanism ◽

Glassy Polymers ◽

Bulk Polymer ◽

Fracture Front ◽

Griffith Theory ◽

Work Of Fracture ◽

Viscous Mechanism

The fracture of glassy polymers starts with the separation of molecule bundles which then form a craze; this is followed by the fracture or rupture of the craze by sliding of the molecule bundles. The first process has the approximate characteristics of brittle fracture, the second those of viscous flow; at low velocities, therefore, the crack extends by the essentially viscous mechanism in the craze layer, whereas at higher velocity the stress required for this rises so high that either a quasi-brittle fracture occurs between the craze and the adjacent bulk polymer (for example, in polystyrene), or patches of craze arise in the bulk ahead of, and away from, the propagating fracture front, as in cast polymethylmethacrylate (PMMA). When the craze wedge ahead of the ‘ viscous ’ crack in the craze layer suddenly peels off the adjacent bulk polymer, either multiple crazes and cracks arise, radiating from its edge, or a new craze wedge is initiated. In either case only one craze wedge propagates, and it drops off the adjacent bulk when the rate of stretching of the craze (normal to its plane) reaches a critical magnitude. The repetition of this process results in the well known striation of the surface of fracture in polystyrene and other polymers. Since the fracture mechanism includes an essentially velocity-dependent viscous process, the Griffith theory cannot be applied to glassy polymers even as an approximation. The work of fracture oscillates by orders of magnitude within microseconds in the region of striations.

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