Mechanical Properties of Metals and Their Cavitation-Damage Resistance

1966 ◽  
Vol 10 (01) ◽  
pp. 1-9
Author(s):  
A. Thiruvengadam ◽  
Sophia Waring
Keyword(s):  
Mechanical Properties ◽  
Steady State ◽  
Strain Energy ◽  
Fracture Strain ◽  
Bubble Collapse ◽  
Strain Diagram ◽  
Volume Loss ◽  
Damage Resistance ◽  
Cavitation Damage ◽  
Energy Absorbing

Detailed investigations with a magnetostriction apparatus were carried out to determine the cavitation-damage resistance of eleven metals in distilled water at 80 F. The cavitation-damage resistance is defined as the reciprocal of the rate of volume loss for a given metal. Among the mechanical properties investigated (ultimate tensile strength, yield strength, ultimate elongation, Brinell hardness, modulus of elasticity and strain energy) the most significant property which characterizes the energy-absorbing capacity of the metals, under the repeated, indenting loads due to the energy of cavitation bubble collapse in the steady-state zone, was found to be the fracture strain energy of the metals. The strain energy is defined as the area of the stress-strain diagram up to fracture. The correlation between the strain energy and the reciprocal of the rate of volume loss leads directly to the estimation of the intensity of cavitation damage; this intensity varies as the square of the displacement amplitude of the specimen. All these conclusions are limited to the steady-state zone of damage.

Physico-Mechanical Properties of Rubberized Lightweight Aggregate Concrete for Tunnel Pavements

2012 ◽  
Vol 509 ◽  
pp. 45-50
Author(s):  
Ji Wang ◽  
Yue Li ◽  
Xiao Chun Fan
Keyword(s):  
Mechanical Properties ◽  
Asphalt Concrete ◽  
Strain Energy ◽  
Lightweight Aggregate ◽  
Cement Matrix ◽  
Lightweight Aggregate Concrete ◽  
Portland Cement Concrete ◽  
Rubber Particles ◽  
Interface Transition Zone ◽  
Energy Absorbing

Both asphalt concrete (AC) and Portland cement concrete (PCC) are limited in applications in tunnel pavements, due to special conditions in tunnel. To improve the fire resistance, durability and comfort of the tunnel pavements material, rubber particles, lightweight aggregate and polymer were added into PCC. Experimental results showed that physico-mechanical properties such as strength, rigidity, shrinkage and abrasion resistance got worse when rubber particles and lightweight aggregate were added, but when polymer was mixed, the physico-mechanical properties were enhanced dramatically. Microstructure analysis indicated that the interface transition zone (ITZ) influenced the physico-mechanical properties of concrete directly; the ITZ bondage between rubber particles or lightweight aggregate and cement matrix was very poor, which was the main reason for the decline of physico-mechanical properties; when polymer was mixed into the concrete, the ITZ structure were improved, which made the strain energy absorbing function of rubber particles can be exerted entirely, the flexibility and the strength of ITZ were boosted, thereby the physico-mechanical properties of concrete were improved.

High-Frequency Fatigue of Metals and Their Cavitation-Damage Resistance

1966 ◽  
Vol 88 (3) ◽  
pp. 332-340 ◽  
Author(s):  
A. Thiruvengadam
Keyword(s):  
Strain Rate ◽  
High Frequency ◽  
Strain Energy ◽  
Fatigue Tests ◽  
Strain Rate Effects ◽  
Damage Resistance ◽  
Cavitation Damage ◽  
Rate Effects ◽  
Plastic Strain Energy ◽  
Hardening Factor

In order to verify the strain-rate effects on the correlation between strain energy of metals and their cavitation-damage resistance, high-frequency fatigue tests at 14.2 kcs were conducted using a magnetostriction oscillator. Utilizing Morrow’s theory, it has been shown that fatigue at this frequency can be quantitatively represented if a 15 percent reduction in static strain-hardening factor is made. This result shows that the strain-rate effects are relatively small (for the metals investigated) when plastic-strain energy is used as a criterion. Another result revealed by this study is the influence of corrosion on high-frequency fatigue and cavitation-damage resistance. Present experiments show that fatigue strength can be reduced significantly for SAE 1020 steel in 3 percent NaCl solution even at high frequencies, thus confirming earlier speculations on this aspect.

On Testing Materials for Cavitation Damage Resistance

1964 ◽  
Vol 8 (05) ◽  
pp. 39-56
Author(s):  
A. Thiruvengadam ◽  
H. S. Preiser
Keyword(s):  
Experimental Data ◽  
Steady State ◽  
Experimental Results ◽  
Time Dependent ◽  
Testing Time ◽  
Average Depth ◽  
Damage Resistance ◽  
Cavitation Damage ◽  
Damage Rate

Recent experiments with a magnetostriction apparatus show that cavitation-damage rate is time dependent. This is confirmed by an analysis of the experimental data obtained in various earlier investigations. There are four zones of damage rate with respect to testing time; namely, (a) incubation, (b) accumulation, (c) attenuation, and (d) steady state. In the fourth, or steady-state zone, the damage rate varies as the square of the amplitude of oscillation within the range tested for water at 80 F. The damage rate increases with frequency and then decreases with increasing frequency. The depth of liquid in the beaker, the beaker diameter and the depth of immersion of the specimen do not seem to affect the damage rate substantially. The average depth of erosion is independent of the diameter of the specimen. Based on these experimental results, certain recommendations are made for testing materials for cavitation damage resistance.

Heat Treatment Effects on Static and Dynamic Mechanical Properties of Sintered SINT D30 Powder Metal

2013 ◽  
Vol 592-593 ◽  
pp. 643-646 ◽  
Author(s):  
Marko Šori ◽  
Tomaž Verlak ◽  
Srečko Glodež
Keyword(s):  
Mechanical Properties ◽  
Complex Geometry ◽  
Low Cost ◽  
Surface Hardness ◽  
Load Ratio ◽  
Tensile Tests ◽  
Test Machine ◽  
Strain Diagram ◽  
Powder Metal ◽  
Sintered Steel

Low cost, low material waste and good accuracy in components with complex geometry are the main reasons for powder metallurgy to be considered as a promising manufacturing process for the future. Like wrought steel, sintered steel can also be heat treated to increase surface hardness and to improve strength. This paper compares mechanical properties of the hardened sintered steel with the sintered steel of the same powder metal SINT D30. Firstly, the static strength of both samples is determined by quasi-static tensile tests. Results are compared in stress strain diagram and they show that the tensile strength of the hardened sintered steel SINT D30 can surpass 700 MPa. The main focus of this study is however fatigue behaviour of the sintered steel. Both sets of samples are tested on a pulsating test machine with the load ratio of R = 0. The first sample is subjected to a load that corresponds to 90 % of the yield strength and is then gradually lowered to achieve one million stress cycles without breakage. Obtained results are then presented as Wöhler curves and compared in S-N diagram.

Assessing the effect of FDM processing parameters on mechanical properties of PLA parts using Taguchi method

2021 ◽  
pp. 089270572110530
Author(s):  
Nagarjuna Maguluri ◽  
Gamini Suresh ◽  
K Venkata Rao
Keyword(s):  
Mechanical Properties ◽  
Tensile Properties ◽  
Fused Deposition Modeling ◽  
Fracture Strain ◽  
Processing Parameters ◽  
Fused Deposition ◽  
Deposition Modeling ◽  
Nozzle Temperature ◽  
Experimental Runs ◽  
Printing Speed

Fused deposition modeling (FDM) is a fast-expanding additive manufacturing technique for fabricating various polymer components in engineering and medical applications. The mechanical properties of components printed with the FDM method are influenced by several process parameters. In the current work, the influence of nozzle temperature, infill density, and printing speed on the tensile properties of specimens printed using polylactic acid (PLA) filament was investigated. With an objective to achieve better tensile properties including elastic modulus, tensile strength, and fracture strain; Taguchi L8 array has been used for framing experimental runs, and eight experiments were conducted. The results demonstrate that the nozzle temperature significantly influences the tensile properties of the FDM printed PLA products followed by infill density. The optimum processing parameters were determined for the FDM printed PLA material at a nozzle temperature of 220°C, infill density of 100%, and printing speed of 20 mm/s.

Micro-mechanical modeling using DEM to study the effect of mechanical properties on crack propagation for snow slab avalanches

2021 ◽  
Author(s):  
Bobillier Gregoire ◽  
Bergfled Bastian ◽  
Gaume Johan ◽  
van Herwijnen Alec ◽  
Schweizer Jürg
Keyword(s):  
Mechanical Properties ◽  
Steady State ◽  
Crack Propagation ◽  
Sensitivity Study ◽  
Tensile Fracture ◽  
Crack Speed ◽  
Stress Concentrations ◽  
Snow Layer ◽  
Stress Regime ◽  
Weak Layer

<p>Dry-snow slab avalanche release is a multi-scale process starting with the formation of localized failure in a highly porous weak snow layer below a cohesive snow slab, which can be followed by rapid crack propagation within the weak layer. Finally, a tensile fracture through the slab leads to its detachment. About 15 years ago, the propagation saw test (PST) was developed. The PST is a fracture mechanical field test that provides information on crack propagation propensity in weak snowpack layers. It has become a valuable research tool to investigate the processes involved in crack propagation. While this has led to a better understanding of the onset of crack propagation, much less is known about the ensuing propagation dynamics. Here, we use the discrete element method to numerically simulate PSTs in 3D and analyze the fracture dynamics using a micro-mechanical approach. Our DEM model reproduced the observed PST behavior extracted from experimental analysis. We developed different indicators to define the crack tip that allowed deriving crack speed. Our results show that crack propagation in level terrain reaches a stationary speed if the snow column is long enough. Moreover, we define stress concentration sections. Their length evolution during crack propagation suggests the development of a steady-state stress regime. Slab and weak layer elastic modulus, as well as weak layer shear strength, are the key input parameters for modeling crack propagation; they affect stress concentrations, crack speed, and the critical length for the onset of crack propagation. The results of our sensitivity study highlight the effect of these mechanical parameters on the emergence of a steady-state propagation regime and consequences for dry-snow slab avalanche release. Our DEM approach opens the possibility for a comprehensive study on the influence of the snowpack mechanical properties on the fundamental processes for avalanche release.</p>

scholarly journals Dependence of Energy-Absorbing Capacity on Mechanical Properties Under Penetration

1990 ◽  
Vol 33 (3) ◽  
pp. 297-302 ◽  
Author(s):  
Ken KAMINISHI ◽  
Shunichi KAWANO ◽  
Toshihiro NANBA ◽  
Motoharu TANEDA
Keyword(s):  
Mechanical Properties ◽  
Energy Absorbing

scholarly journals Microstructure and mechanical properties of slowly cooled Cu47.5Zr47.5Al5

2007 ◽  
Vol 22 (2) ◽  
pp. 326-333 ◽  
Author(s):  
J. Das ◽  
S. Pauly ◽  
C. Duhamel ◽  
B.C. Wei ◽  
J. Eckert
Keyword(s):  
Mechanical Properties ◽  
Fracture Strain ◽  
Volume Fraction ◽  
Spherical Shape ◽  
High Yield ◽  
High Yield Strength ◽  
Scanning Calorimetry ◽  
Arc Melting ◽  
Martensite Matrix

Cu47.5Zr47.5Al5 was prepared by arc melting and solidified in situ by suction casting into 2–5-mm-diameter rods under various cooling rates (200–2000 K/s). The microstructure was investigated along the length of the rods by electron microscopy, differential scanning calorimetry and mechanical properties were investigated under compression. The microstructure of differently prepared specimens consists of macroscopic spherical shape chemically inhomogeneous regions together with a low volume fraction of randomly distributed CuZr B2 phase embedded in a 2–7 nm size clustered “glassy-martensite” matrix. The as-cast specimens show high yield strength (1721 MPa), pronounced work-hardening behavior up to 2116 MPa and large fracture strain up to 12.1–15.1%. The fracture strain decreases with increasing casting diameter. The presence of chemical inhomogenities and nanoscale “glassy-martensite” features are beneficial for improving the inherent ductility of the metallic glass.

scholarly journals Simultaneous Enhancement of Strength and Toughness of PLA Induced by Miscibility Variation with PVA

Polymers ◽  
2018 ◽  
Vol 10 (10) ◽  
pp. 1178 ◽  
Author(s):  
Yanping Liu ◽  
Hanghang Wei ◽  
Zhen Wang ◽  
Qian Li ◽  
Nan Tian
Keyword(s):  
Mechanical Properties ◽  
High Performance ◽  
Fracture Strain ◽  
Electrospun Fiber ◽  
Structural Evolution ◽  
Amorphous Structure ◽  
Poly Lactic Acid ◽  
Poly Vinyl Alcohol ◽  
Scanning Calorimetry ◽  
Strength And Toughness

The mechanical properties of poly (lactic acid) (PLA) nanofibers with 0%, 5%, 10%, and 20% (w/w) poly (vinyl alcohol) (PVA) were investigated at the macro- and microscale. The macro-mechanical properties for the fiber membrane revealed that both the modulus and fracture strain could be improved by 100% and 70%, respectively, with a PVA content of 5%. The variation in modulus and fracture strain versus the diameter of a single electrospun fiber presented two opposite trends, while simultaneous enhancement was observed when the content of PVA was 5% and 10%. With a diameter of 1 μm, the strength and toughness of the L95V5 and L90V10 fibers were enhanced to over 3 and 2 times that of pure PLA, respectively. The structural evolution of electrospun nanofiber was analyzed by differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR). Although PLA and PVA were still miscible in the concentration range used, the latter could crystallize independently after electrospinning. According to the crystallization behavior of the nanofibers, a double network formed by PLA and PVA—one microcrystal/ordered structure and one amorphous structure—is proposed to contribute to the simultaneous enhancement of strength and toughness, which provides a promising method for preparing biodegradable material with high performance.

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