Simple Measurements of Toughness and Crack Formation in Several Intermetallic-Matrix Composite Systems

1990 ◽  
Vol 194 ◽  
Author(s):  
Robert L. Fleischer
Keyword(s):  
Crack Formation ◽  
Elevated Temperatures ◽  
High Fracture Toughness ◽  
Second Phase ◽  
High Fracture ◽  
Two Phase ◽  
Intermetallic Matrix ◽  
Wide Range ◽  
Intermetallic Matrix Composite ◽  
Correlate Observation

AbstractChisel-and-hammer (C.T.) and microhardness tests have been used to examine trends in toughness and crack formation in several intermetallic-based two-phase equilibrium systems. High fracture toughness, as defined by the chisel test, correlates with the presence of some ductility; and the lack of crack formation, or its limitation by a second phase in the microstructure, are prerequisites for fracture resistance. Equilibrium systems have desirable stability for use at elevated temperatures. Comparison of Tbd and C.T. is now possible for a wide range of intermetallics. Intuition suggests that Tbd and C.T. would anti-correlate. Observation, however, contradicts that hypothesis. There are significant numbers of alloys with low Tbd and low C.T. and with high Tbd and high C.T. Possible explanations are noted. Systems that have been studied include Al-Ru with Sc additions, Be-Ti, Be-Zr, Cr-Ti, with Al, Nb and Zr, Ge-Ti, Ir-Nb with Co, Fe, Ni, and V, and Ru-Ta with Co and Fe. Compositional effects on chisel toughness, hardness-vs-temperature, and crack information are presented.

Allowable Axial Flaw Sizes for Stainless Steel Pipes Derived From Limit Load Criteria and Failure Assessment Diagram Procedure

2003 ◽  
Author(s):  
Kunio Hasegawa ◽  
Katsumasa Miyazaki ◽  
Gery M. Wilkowski ◽  
Douglas A. Scarth
Keyword(s):  
Stainless Steel ◽  
Limit Load ◽  
High Fracture Toughness ◽  
High Fracture ◽  
Steel Pipes ◽  
Failure Assessment Diagram ◽  
Axial Part ◽  
Wide Range ◽  
Failure Assessment ◽  
Asme Code

Piping containing flaws that exceed the Acceptance Standards of Section XI of the ASME Code is evaluated using analytical procedures described in Section XI to determine plant operability for the evaluated time period. Subarticle IWB-3640 of Section XI provides allowable axial and circumferential part-through-wall flaws determined from limit load criteria. ASME Section XI Code Case N-494-3 also provides evaluation procedures based on use of a failure assessment diagram to determine allowable flaw sizes. To understand the allowable flaw sizes determined by the limit load criteria and the failure assessment diagram procedure, anstenitic stainless steel pipes with axial part-through-wall flaws with a wide range of pipe diameters were analyzed. The allowable flaw depth based on limit load from Code Case N-494-3 was determined to be very close to that determined from IWB-3640 of Section XI, when the predicted failure mode is elastic-plastic fracture. It was found that the allowable flaw depths derived from the failure assessment diagram procedure of Code Case N-494-3, are lower, but are not significantly different, from those determined from the limit load criteria of IWB-3640. This is due to the relatively high fracture toughness that was used for the austenitic stainless steel.

scholarly journals Modeling Multiphase Effects in CO2 Compressors at Subcritical Inlet Conditions

2019 ◽  
Vol 141 (8) ◽  
Author(s):  
Ashvin Hosangadi ◽  
Zisen Liu ◽  
Timothy Weathers ◽  
Vineet Ahuja ◽  
Judy Busby
Keyword(s):  
Test Data ◽  
Elevated Temperatures ◽  
Wilson Line ◽  
Saturation Pressure ◽  
Flow Coefficient ◽  
Pure Liquid ◽  
Two Phase ◽  
Pressure Profiles ◽  
Wide Range ◽  
Inlet Conditions

An advanced numerical framework to model CO2 compressors over a wide range of subcritical conditions is presented in this paper. Thermodynamic and transport properties are obtained through a table look-up procedure with specialized features for subcritical conditions. Phase change is triggered by the difference between the local values of pressure and saturation pressure, and both vaporization and condensation can be modeled. Rigorous validation of the framework is presented for condensation in high pressure CO2 using test data in a De Laval nozzle. The comparisons between computations and test data include: condensation onset locations, Wilson line, and nozzle pressure profiles as a function of inlet pressures. The framework is applied to the Sandia compressor that has been modeled over broad range of conditions spanning the saturation dome including: near critical inlet conditions (305.4 K, and 7.843 MPa), pure liquid inlet conditions (at 295 K), pure vapor inlet conditions (at 302 K), and two-phase inlet conditions (at 290 K). Multiphase effects ranging from cavitation at the liquid line to condensation at the vapor line have been simulated. The role of real fluid effects in enhancing multiphase effects at elevated temperatures closer to the critical point has been identified. The performance of the compressor has been compared with test data; the computational fluid dynamics (CFD) results also show that the head-flow coefficient curve collapses with relatively minor scatter, similar to the test data, when the flow coefficient is defined on the impeller exit meridional velocity.

Effects of Additives on the Interfacial Microstructure of SiC Fiber/Li2O-Al2O3-6SiO2 Glass-Ceramic Composites

1991 ◽  
Vol 49 ◽  
pp. 924-925
Author(s):  
J.Y. Hsu ◽  
Y. Berta ◽  
R.F. Speyer
Keyword(s):  
Flexural Strength ◽  
Glass Ceramic ◽  
Elevated Temperatures ◽  
Ceramic Composites ◽  
Interfacial Microstructure ◽  
High Fracture Toughness ◽  
Matrix Composition ◽  
High Fracture ◽  
Sic Fiber ◽  
The Matrix

SiC fiber reinforced lithia-alumina-silica glass-ceramic composites have exhibited superior mechanical properties at room and elevated temperatures. The flexural strength of these composites is 3 to 4 times larger than that of monolithic glass-ceramics. The high flexural strength of these composites is due to the transfer of the applied load from the matrix to the stronger and stiffer SiC fiber reinforcement. These composites also have demonstrated very high fracture toughness, KIC (critical stress intersity factor) values of ∼ 17 MPa m1/2, which is attributed to an amorphous carbon-rich interfacial layer between the fiber and matrix. Nb2O2 has been added to the matrix composition in order to develop a NbC layer outside the amorphous C-rich layer after thermal processing, thereby buffering the fiber/matrix reactivity (avoid carbon forming CO gas which would deteriorate the matrix).

Microstructure and Performance of the Hot-Pressed Silicon Nitride Ceramics with Lu2O3 Additives

2010 ◽  
Vol 434-435 ◽  
pp. 37-41
Author(s):  
Jian Feng Tong ◽  
Da Ming Cheng ◽  
Bao Wei Li ◽  
Huang Hao Ling ◽  
Wang Ling
Keyword(s):  
Fracture Toughness ◽  
Bimodal Distribution ◽  
Crack Size ◽  
High Fracture Toughness ◽  
High Fracture ◽  
Β Phase ◽  
Wide Range ◽  
Nitride Ceramics ◽  
And Performance ◽  
Si3n4 Ceramics

The influence of Lu2O3 on phase transformation and seeds morphology was investigated. The result showed that the β-Si3N4 seeds with up to 95% β phase content could be obtained with 2wt% Lu2O3 as the additive content under 1750°C for two hours. The microstructure and mechanical properties of hot-pressed Si3N4 ceramics, using 9wt.% of Lu2O3• additives were investigated by the means of MTS measurements and Vickers indentation crack size measurements, as well as XRD and SEM. It was known that the high fracture toughness of Si3N4 ceramics was attributed to the rodlike morphology of β-Si3N4 grains. And the reinforcement effect and mechanism of β-Si3N4 seed were studied. It was found that the grain size and its distribution influence the property and microstructure of Si3N4 ceramics, namely, the relative narrow distribution of grain diameter in some extent and relative wide range of bimodal distribution of grain aspect ratio could improve the property of Si3N4 ceramics. The improvement in the fracture toughness with the amount of additive was mainly attributed to elongated grain growth during the sintering process.The high temperature properties of self-reinforced Si3N4 with different additives were studied. By this method, self-reinforced Si3N4 ceramics with an increment of 10~20 percent of fracture toughness was successfully fabricated.

Fracture Behaviour of Two-Phase γ-Titanium Aluminides

1994 ◽  
Vol 364 ◽  
Author(s):  
Fritz Appel ◽  
Uwe Lorenz ◽  
Tao Zhang ◽  
Richard Wagner
Keyword(s):  
Fracture Toughness ◽  
Crack Propagation ◽  
Titanium Aluminides ◽  
Process Zone ◽  
Crack Tip ◽  
Lamellar Microstructure ◽  
High Fracture Toughness ◽  
High Fracture ◽  
Two Phase ◽  
Lamellar Interfaces

AbstractTitanium aluminides with a lamellar microstructure consisting of the intermetallic phases ֱ2 (Ti3Al) and γ(TiAl) suffer from brittleness at ambient temperatures but exhibit at the same time a relatively high fracture toughness. This discrepancy indicates particular processes stabilizing crack propagation in the lamellar microstructure. In this context, the toughening mechanisms were investigated in (α2 + γ) TiAl alloys which contained different volume fractions of lamellar colonies. The fracture toughness for crack propagation parallel or across the lamellar interfaces was estimated by using chevron-notched bending bars. Electron microscope studies were performed to characterize the related processes of crack tip plasticity. Special emphasis was paid to the crystallography of crack propagation and to the interaction of crack tips with lamellar interfaces. Accordingly, the lamellar morphology derives some of its toughness from interface-related processes which stabilize crack propagation by deflecting the crack tip and providing the necessary dislocation sources for crack tip shielding in the process zone ahead of the crack tip.

Cost Analysis of Using Hybrid Microwave Post-Sintered Silicon Nitride Inserts

2015 ◽  
Vol 1115 ◽  
pp. 192-195
Author(s):  
Tasnim Firdaus Ariff ◽  
Mohammad Iqbal ◽  
Rubina Bahar
Keyword(s):  
Silicon Nitride ◽  
Cost Analysis ◽  
Tool Life ◽  
Elevated Temperatures ◽  
Heat Treating ◽  
High Fracture Toughness ◽  
Conventional Heating ◽  
High Fracture ◽  
Cutting Speeds ◽  
Sintered Silicon

Heat treatment is a process often used to improve product performance by increasing the strength of material or other desirable characteristics. Silicon nitride (Si3N4) tool insert is known for its attractive properties including high fracture toughness, strength and wear resistance at elevated temperatures. Heat treating these inserts by post-sintering them for 15 minutes at 600°C using conventional heating and hybrid microwave energy has prolonged tool life by 11-21% and 48-94% respectively. Machining was performed on a T6061 Aluminium alloy rod for tool life analysis at three different cutting speeds; 215, 314 and 393 m/min. Cost analysis is performed on these post-sintered Si3N4 inserts and found that there are economical benefits in the tooling cost when compared with the untreated Si3N4 inserts.

Developing a two-phase QFD for improving FMEA: an integrative approach

2019 ◽  
Vol 36 (8) ◽  
pp. 1454-1474 ◽  
Author(s):  
Fatemeh Shaker ◽  
Arash Shahin ◽  
Saeed Jahanyan
Keyword(s):  
Literature Review ◽  
Failure Modes ◽  
Continuous Production ◽  
Integrative Approach ◽  
Importance Rating ◽  
Second Phase ◽  
Extensive Literature ◽  
Two Phase ◽  
Content Type ◽  
Wide Range

Purpose The purpose of this paper is to propose an integrative approach for improving failure modes and effects analysis (FMEA). Design/methodology/approach An extensive literature review on FMEA has been performed. Then, an integrative approach has been proposed based on literature review. The proposed approach is an integration of FMEA and quality function deployment (QFD). The proposed approach includes a two-phase QFD. In the first phase, failure modes are prioritized based on failure effects and in the second phase, failure causes are prioritized based on failure modes. The proposed approach has been examined in a case example at the blast furnace operation of a steel-manufacturing company. Findings Results of the case example indicated that stove shell crack in hot blast blower, pump failure in cooling water supply pump and bleeder valves failed to operate are the first three important failure modes. In addition, fire and explosion are the most important failure effects. Also, improper maintenance, over pressure and excess temperature are the most important failure causes. Findings also indicated that the proposed approach with the consideration of interrelationships among failure effects, failure mode and failure causes can influence and adjust risk priority number (RPN) in FMEA. Research limitations/implications As manufacturing departments are mostly dealing with failure effects and modes of machinery and maintenance departments are mostly dealing with causes of failures, the proposed model can support better coordination and integration between the two departments. Such support seems to be more important in firms with continuous production lines wherein line interruption influences response to customers more seriously. A wide range of future study opportunities indicates the attractiveness and contribution of the subject to the knowledge of FMEA. Originality/value Although the literature indicates that in most of studies the outcomes of QFD were entered into FMEA and in some studies the RPN of FMEA was entered into QFD as importance rating, the proposed approach is a true type of the so-called “integration of FMEA and QFD” because the three main elements of FMEA formed the structure of QFD. In other words, the proposed approach can be considered as an innovation in the FMEA structure, not as a data provider prior to it or a data receiver after it.

Experimental Investigation and Optimization in Rotary Ultrasonic Drilling of C/C Composites

2016 ◽  
Vol 874 ◽  
pp. 313-319
Author(s):  
Song Mei Yuan ◽  
Qi Wu
Keyword(s):  
Feed Rate ◽  
Elevated Temperatures ◽  
Cutting Parameters ◽  
Spindle Speed ◽  
High Fracture Toughness ◽  
Drilling Force ◽  
High Fracture ◽  
Machining Quality ◽  
Ultrasonic Drilling ◽  
Rotary Ultrasonic Drilling

C/C composites are widely used in aviation and aerospace due to their low density, superior specific strength, special elastic modulus at elevated temperatures, small thermal expansion coefficient and high fracture toughness. However, there are numerous problems such as delamination, chipping, poor machining quality and tool wear in drilling of C/C composites due to inhomogeneous, anisotropic, wear resistance and varying thermal properties of the composites. In this paper, related experiments on rotary ultrasonic drilling of C/C composites using diamond core drill were conducted to compare the drilling force and machining quality of ultrasonic drilling with conventional drilling, analyze the rotary ultrasonic drilling mechanism and research the influence of spindle speed, feed rate and ultrasonic amplitude on the drilling force. Experimental results showed that rotary ultrasonic drilling can significantly improve the removal of the chips thus preventing the core drill blockage, effectively reduce the drilling force and improve processing quality. In addition, the drilling force decreased with increasing of spindle speed and ultrasonic amplitude, while it increased with increasing of feed rate. Finally, the cutting parameters were optimized by consideration of the drilling force and efficiency.

Properties of Microlaminated Intermetallic-Refractory Metal Composites

1993 ◽  
Vol 322 ◽  
Author(s):  
R. G. Rowe ◽  
D. W. Skelly ◽  
M. Larsen ◽  
J. Heathcote ◽  
G. Lucas ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Fracture Strength ◽  
Refractory Metal ◽  
Elevated Temperatures ◽  
High Rate ◽  
High Fracture Toughness ◽  
Tensile Fracture ◽  
High Fracture ◽  
Tensile Fracture Strength ◽  
Intermetallic Layers

AbstractMicrolaminated composites of Nb3Al-Nb and Cr2Nb-Nb(Cr) were synthesized by high rate magnetron sputtering. Both composites were stable at elevated temperatures. A Cr2Nb-Nb(Cr) composite with 2 µm metal and intermetallic layers had room temperature tensile fracture strength over 725 MPa and a fracture toughness of about 20 MPa√m. Composites with 2 µm and 6 µm thick refractory metal and intermetallic laminations were compared and it was found that layer thickness did not affect fracture toughness. Microlaminates with the thicker 6 µm laminations had lower fracture strength, however. Good fracture strength and high fracture toughness indicated that microlaminated high temperature composites synthesized by vapor phase deposition exhibit the properties predicted by ductile toughening models.

Multiscale Modeling of Cortical Bone

2010 ◽  
Author(s):  
Elham Hamed ◽  
Yikhan Lee ◽  
Iwona M. Jasiuk
Keyword(s):  
Mechanical Properties ◽  
High Strength ◽  
Bone Substitutes ◽  
Bone Diseases ◽  
High Fracture Toughness ◽  
High Fracture ◽  
Synthetic Bone ◽  
Wide Range ◽  
The Hierarchical Structure ◽  
Strength And Stiffness

Bone is an important multifunctional biological tissue with remarkable mechanical properties: high strength and stiffness, high fracture toughness, and light weight. These superior properties are due, in part, to the hierarchical structure of bone ranging from molecular to macroscopic levels, Fig. 1. Nevertheless, it is not clearly understood how the microstructure and mechanical properties of various hierarchies at different length scales affect the overall behavior of bone. Such understanding is essential in orthopedics for designing implant materials and fabricating synthetic bone substitutes and also for assessing the effect of bone diseases and their medications on bone’s properties. It can, moreover, serve as a guide in design of advanced synthetic bio-inspired materials for a wide range of engineering applications.

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