scholarly journals Influence of 3D Printing Topology by DMLS Method on Crack Propagation

Materials ◽  
2021 ◽  
Vol 14 (23) ◽  
pp. 7483
Author(s):  
Karel Dvorak ◽  
Jana Dvorakova ◽  
Lucie Zarybnicka ◽  
Zdenek Horak
Keyword(s):  
Crack Propagation ◽  
Fem Simulation ◽  
Compact Tension ◽  
Industrial Practice ◽  
Technical Preparation ◽  
Material Specimen ◽  
Measurement Results ◽  
Machine Parts ◽  
Compact Tension Test ◽  
Apparent Influence

The presented text deals with research into the influence of the printing layers’ orientation on crack propagation in an AlSi10Mg material specimen, produced by additive technology, using the Direct Metal Laser Sintering (DMLS) method. It is a method based on sintering and melting layers of powder material using a laser beam. The material specimen is presented as a Compact Tension test specimen and is printed in four different defined orientations (topology) of the printing layers—0°, 45°, 90°, and twice 90°. The normalized specimen is loaded cyclically, where the crack length is measured and recorded, and at the same time, the crack growth rate is determined. The evaluation of the experiment shows an apparent influence of the topology, which is essential especially for possible use in the design and technical preparation of the production of real machine parts in industrial practice. Simultaneously with the measurement results, other influencing factors are listed, especially product postprocessing and the measurement method used. The hypothesis of crack propagation using Computer Aided Engineering/Finite Element Method (CAE/FEM) simulation is also stated here based on the achieved results.

scholarly journals A Modified Compact Tension Test for Characterization of the Intralaminar Fracture Toughness of Tri-Axial Braided Composites

Materials ◽  
2021 ◽  
Vol 14 (17) ◽  
pp. 4890
Author(s):  
Michael May ◽  
Sebastian Kilchert ◽  
Tobias Gerster
Keyword(s):  
Fracture Toughness ◽  
Composite Materials ◽  
Crack Propagation ◽  
Compact Tension ◽  
Tension Test ◽  
Failure Behavior ◽  
Interlaminar Fracture Toughness ◽  
Interlaminar Fracture ◽  
Braided Composite ◽  
Compact Tension Test

The application of braided composite materials in the automotive industry requires an in-depth understanding of the mechanical properties. To date, the intralaminar fracture toughness of braided composite materials, typically used for describing post-failure behavior, has not been well-characterized experimentally. In this paper, a modified compact tension test, utilizing a relatively large specimen and a metallic loading frame, is used to measure the transverse intralaminar fracture toughness of a tri-axial braided composite. During testing, a relatively long fracture process zone ahead of the crack tip was observed. Crack propagation could be correlated to the failure of individual unit cells, which required failure of bias-yarns. The transverse interlaminar fracture toughness was found to be two orders of magnitude higher than the reference interlaminar fracture toughness of the same material. This is due to the fact, that intralaminar crack propagation requires breaking of fibers, which is not the case for interlaminar testing.

Fracture Mechanics and Fractography of Creep and Fatigue Crack Propagation at Elevated Temperature

1976 ◽  
Vol 98 (4) ◽  
pp. 296-304 ◽  
Author(s):  
R. Koterazawa ◽  
Y. Iwata
Keyword(s):  
Fatigue Crack ◽  
Fracture Mechanics ◽  
Crack Propagation ◽  
Fatigue Crack Propagation ◽  
Compact Tension ◽  
304 Stainless Steel ◽  
Bending Stress ◽  
Type Specimens ◽  
Creep Crack ◽  
Repeated Stress

A fracture mechanics and fractographic study was conducted on creep and fatigue crack propagation of a 304 stainless steel under constant and repeated tensile stress at a temperature of 650°C. Linear elastic fracture mechanics could be applied to the test data fairly successfully in spite of the fact that the tests were conducted under creep conditions. A comparison with data in a literature indicated that this is not true for bending-type specimens such as the compact tension specimen because of redistribution of bending stress due to creep, and therefore a specimen geometry which avoids bending stress is preferred for creep crack testing. Under repeated stress, the crack generally started as a transgranular fatigue crack and changed to an intergranular creep crack at some length of the crack. The transition point moved to a later stage of crack propagation as the period of repeated stress increased. This transition phenomenon could be explained by assuming that the two crack propagation processes, the transgranular fatigue crack and the intergranular creep crack, are possible under repeated stress condition and that the one with the higher rate actually occurs.

Experimental Assessment of Speech Privacy and Intelligibility in Multi-Language Environments

2002 ◽  
Author(s):  
L. Dai ◽  
Y. Ma ◽  
D. J. Caswell
Keyword(s):  
Current Literature ◽  
Speech Intelligibility ◽  
Objective Measurement ◽  
Single Word ◽  
Experimental Assessment ◽  
Tonal Language ◽  
Industrial Practice ◽  
Subjective Measurement ◽  
Measurement Results ◽  
Subjective Measurements

In the current literature, most assessments for speech privacy and speech intelligibility are relying on the subjective measurements utilized with the test materials of English and other Western languages. Effects of different languages and accents in speech privacy and speech intelligibility are usually overseen. This study aims at the speech privacy assessment of closed offices in multicultural environments. Subjective measurements are conducted in this study for closed offices by using English and a tonal language. The evaluation differences in speech privacy between the two languages are evident and significant. It is also found in this study that the existing single word tests used in research and industrial practice for subjectively evaluating speech privacy should be modified when closed spaces are considered. The subjective measurement results of this study are also compared with the objective measurement indices AI.

Over Limit Oxygen Effect on Crack Propagation of WWER 440 RPV Steel in Primary Circuit Water

2009 ◽  
Author(s):  
Miroslava Ernestova ◽  
Anna Hojna
Keyword(s):  
Crack Propagation ◽  
Nuclear Power ◽  
Power Plants ◽  
Water Environment ◽  
Nuclear Research ◽  
Compact Tension ◽  
Oxygen Effect ◽  
Primary Circuit ◽  
Nuclear Research Institute ◽  
Primary Water

Experience with operating nuclear power plants worldwide reveals that many failures may be attributed to fatigue associated with mechanical loading due to vibration and with corrosion effect due to exposure to high-temperature environment. In order to clarify the simultaneous influence on reactor pressure vessel (RPV) material testing of ferritic steel 15Ch2MFA used for RPV of WWER 440 was performed at Nuclear Research Institute (NRI) autoclaves. Cyclic and constant loadings were applied to Compact Tension (CT) specimens in WWER primary water environment at 290°C and simultaneous effect of different oxygen levels (< 20 ppb, 200 ppb, 2000 ppb) on crack propagation has been evaluated. Obtained crack growth rates are compared with ASME XI Code and VERLIFE curves and crack behaviour is discussed.

scholarly journals Modified Disk-Shaped Compact Tension Test for Measuring Concrete Fracture Properties

2017 ◽  
Vol 11 (2) ◽  
pp. 215-228 ◽  
Author(s):  
Héctor Cifuentes ◽  
Miguel Lozano ◽  
Táňa Holušová ◽  
Fernando Medina ◽  
Stanislav Seitl ◽  
...  
Keyword(s):  
Compact Tension ◽  
Tension Test ◽  
Concrete Fracture ◽  
Fracture Properties ◽  
Compact Tension Test
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