Transient reliability of ceramic structures

Jadaan, Osama M.; Nemethm, N.

doi:10.1046/j.1460-2695.2001.00419.x

Cited by 12 publications

(5 citation statements)

References 11 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The capacity of ceramics to bear loads is determined by their limited strength, low fracture toughness and associated high Young’s Modulus 4,5 . This low fracture toughness is further impacted upon by the process of time‐dependent, subcritical crack growth so markedly displayed by ceramic systems 6 . These multitudes of microscopic surface flaws formed during processing lower the practical strength of ceramics by two to three orders of magnitude from the theoretical maximum of the perfect specimen and cause large variations in strength and a time dependency due to variations in the distribution and depth of the initial cracks and their time‐dependent propagation to critical failure.…”

Section: Introductionmentioning

confidence: 99%

The all‐ceramic, inlay supported fixed partial denture. Part 2. Fixed partial denture design: a finite element analysis

Thompson

Field

Swain

2011

Australian Dental Journal

View full text Add to dashboard Cite

The clinical use of all-ceramic crowns and fixed partial dentures has seen widespread adoption over the past few years due to their increasing durability and longevity. However, the application of inlays as an abutment design has not been as readily embraced because of their relatively high failure rates. With the use of an idealized inlay preparation design and prosthesis form which better distributes the tensile stresses, it is possible to utilize the inlay as support for an all-ceramic fixed partial denture. Utilizing a three-dimensional finite element analysis, a direct comparison of the inlay supported all-ceramic bridge against the traditional full crown supported all-ceramic bridge is made. The results demonstrate that peak stresses in the inlay bridge are around 20% higher than in the full crown supported bridge with von Mises peaking at about 730 MPa when subjected to theoretical average maximum bite force in the molar region of 700 N, which is similar to the ultimate tensile strengths of current zirconia based ceramics.Keywords: Inlay supported, all-ceramic, fixed partial denture, finite element analysis.Abbreviations and acronyms: CAD ⁄ CAM = computer-aided design ⁄ computer-aided milled; CT = computer tomography; DOF = degrees of freedom; FEA = finite element analysis; FPD = fixed partial denture; HU = Houndsfield units; LDGC = lithium disilicate glass ceramic; PDL = periodontal ligament; PFM = porcelain-fused-to-metal; Y-TZP = yttria stabilized tetragonal zirconia.

show abstract

Section: Introductionmentioning

confidence: 99%

The all‐ceramic, inlay supported fixed partial denture. Part 2. Fixed partial denture design: a finite element analysis

Thompson

Field

Swain

2011

Australian Dental Journal

View full text Add to dashboard Cite

show abstract

“…A fatigue constant By, with units stress^ x time, may be derived [25,31]. CARES/Life works with finite element software to model these and other relevant parameters, accounting appropriately for their variations with space, time, and crack orientation, and integrates the results from all elements to evaluate the overall component reliability.…”

Section: Slow Crack Growthmentioning

confidence: 99%

Engine Design Strategies to Maximize Ceramic Turbine Life and Reliability

Vick

Jadaan

Wereszczak

et al. 2012

Journal of Engineering for Gas Turbines and Power

View full text Add to dashboard Cite

Over a billion dollars have been spent on ceramic turbine research and development, but ceramic turbines "have not yet reached bill-of-materials status" [1]. Mature turbine-grade silicon nitrides (e.g., SN282^ AS800^ SN88^ NT154^) have excellent properties, but studies still cite life, reliability, and cost issues, often concluding that the materials themselves require further improvement. However, under less severe operating conditions, ceramics can excel in all these areas. In an ongoing long-term endurance test at NRL, a low cost porcelain vessel has been subjected to the thermal shock of hot coffee several times daily for ten years-over 5000 startup/shutdown cycles-with no perceptible degradation. Ceramic turbocharger rotors have been manufactured for the notoriously cost-sensitive automotive market at rates exceeding 10,000 per month, achieving good life and reliability in Japanese sports cars. These examples suggest that rather than just seeking higherperformance materials, it might also be fruitful to design gas turbines to create a more benign environment for existing ceramics.Foremost among stated concems is water vapor erosion [2-11], a process in which water in the combustion products reacts with silicon nitride at high temperatures, forming gases that get swept away by the freestream. This erodes the blade surfaces at a rate Engine Design Strategies to Maximize Ceramic Turbine Life and ReiiabilityCeramic turbines have long promised to enable higher fuel efficiencies by accommodating higher temperatures without cooling, yet no engines with ceramic rotors are in production today. Studies cite life, reliability, and cost obstacles, often concluding that further improvements in the materiais are required. In this paper, we assume instead that the problems could be circumvented by adjusting the engine design. Detailed analyses are conducted for two key life-iimiting processes, water vapor erosion and slow crack growth, seeking engine design strategies for mitigating their ejfects. We show that highly recuperated engines generate extremely low levels of water vapor erosion, enabling lives exceeding 10,000 hs, without environmental barrier coatings. Recuperated engines are highly efficient at low pressure ratios, making low blade speeds practical. Many ceramic demonstration engines have had design point mean blade speeds near 550 mis. A CARES/Life analysis of an example rotor designed for about half this value indicates vast improvements in slow crack growth-limited life and reliability. Halving the blade speed also reduces foreign object damage partide kinetic energy by a factor of four. In applications requiring very high fuei efficiency that can accept a recuperator, or in short-life simple cycle engines, ceramic turbines are ready for application today.

show abstract

“…This crack growth can occur through simultaneous mechanisms of stress-corrosion and cyclic fatigue [3-5]. The lifetime of a component can be predicted if the stress distribution for the component and parameters characterizing the rate of SCG are known for each of the component materials in the service environment [6]. The SCG parameters for a given material can be deduced from experiments on standard geometry specimens [2, 7, 8].…”

Section: Introductionmentioning

confidence: 99%

Effects of stress rate and calculation method on subcritical crack growth parameters deduced from constant stress-rate flexural testing

Griggs

Alaqeel

Zhang³

et al. 2011

Dental Materials

View full text Add to dashboard Cite

Objectives To more efficiently determine the subcritical crack growth (SCG) parameters of dental ceramics, the effects of stressing rate and choice of statistical regression model on estimates of SCG parameters were assessed. Methods Two dental ceramic materials, a veneering material having a single critical flaw population (S) and a framework material having partially concurrent flaw populations (PC), were analyzed using constant stress-rate testing, or “dynamic fatigue”, with a variety of testing protocols. For each material, 150 rectangular beam specimens were prepared and tested in four-point flexure according to ISO6872 and ASTM1368. A full-factorial study was conducted on the following factors: material, stress rate assumed vs. calculated, number of stress rates, and statistical regression method. Results The proportion of specimens for which the statistical models over-estimated reliability was not significantly different based on regression method for Material S (P = 0.96, power = 94%) and was significantly different based on regression method for Material PC (P < 0.001). The standard method resulted in SCG parameters, n and ln B, of 35.9 and -11.1 MPa2s for Material S and 12.4 and 9.61 MPa2s for Material PC. Significance The method of calculation that uses only the median strength value at each stress rate provided the most robust SCG parameter estimates. Using only two stress rates resulted in fatigue parameters comparable to those estimated using four stress rates having the same range. The stress rate of each specimen can be assumed to be the target stress rate with negligible difference in SCG parameter estimates.

show abstract

Transient reliability of ceramic structures

Cited by 12 publications

References 11 publications

The all‐ceramic, inlay supported fixed partial denture. Part 2. Fixed partial denture design: a finite element analysis

The all‐ceramic, inlay supported fixed partial denture. Part 2. Fixed partial denture design: a finite element analysis

Engine Design Strategies to Maximize Ceramic Turbine Life and Reliability

Effects of stress rate and calculation method on subcritical crack growth parameters deduced from constant stress-rate flexural testing

Contact Info

Product

Resources

About