Metals and Ceramics Division - Oak Ridge National Laboratory

More documents

Recommendations

Info

Life Prediction of Diesel Engine Components H. T. Lin, T. P. Kirkland, A. A. Wereszczak, M. K. Ferber Oak Ridge National Laboratory and Jeremy Trethewey Caterpillar Objective/Scope The valid prediction of mechanical reliability and service life is a prerequisite for the successful implementation of structural ceramics and advanced intermetallic alloys as internal combustion engine components. There are three primary goals of this research project which contribute toward that implementation: the generation of mechanical engineering data from ambient to high temperatures of candidate structural ceramics and intermetallic alloys; the microstructural characterization of failure phenomena in these ceramics and alloys and components fabricated from them; and the application and verification of probabilistic life prediction methods using diesel engine components as test cases. For all three stages, results are provided to both the material suppliers and component end-users. The systematic study of candidate structural ceramics (primarily silicon nitride) for internal combustion engine components is undertaken as a function of temperature (< 1200°C), environment, time, and machining conditions. Properties such as strength and fatigue will be characterized via flexure and rotary bend testing. The second goal of the program is to characterize the evolution and role of damage mechanisms, and changes in microstructure linked to the ceramic’s mechanical performance, at representative engine component service conditions. These will be examined using several analytical techniques including optical and scanning electron microscopy. Specifically, several microstructural aspects of failure will be characterized: (1) strength-limiting flaw-type identification; (2) edge, surface, and volume effects on strength and fatigue size-scaling (3) changes in failure mechanism as a function of temperature; (4) the nature of slow crack growth; and (5) what role residual stresses may have in these processes. Lastly, numerical probabilistic models (i.e., life prediction codes) will be used in conjunction with the generated strength and fatigue data to predict the failure probability and reliability of complex-shaped components subjected to mechanical loading, such as a silicon nitride diesel engine valve. The predicted results will then be compared to actual component performance measured experimentally or from field service data. As a consequence of these efforts, the data generated in this program will not only provide a critically needed base for component utilization in internal combustion engines, but will also facilitate the maturation of candidate ceramic materials and a design algorithm for ceramic components subjected to mechanical loading in general.
Technical Highlights Studies of dynamic fatigue behavior of a commercial grade silicon nitride, i.e., SN147-31E, manufactured by Ceradyne Advanced Ceramic, Inc., CA, were completed during this quarterly report period. The SN147-31E was processed with similar sintering additives (i.e., Al2O3 and Y2O3) to those employed for SN147-31N evaluated and reported previously. However, the SN147-31E contains a crystalline secondary phase achieved by a post heat treatment. Thus, it is anticipated that SN147-31E would exhibit a higher temperature mechanical reliability than SN147-31N due to the presence of crystalline secondary phase. The SN147-31E silicon nitride bend bars were longitudinally and transversely machined per the revised ASTM C116 standard with 600 grit surface finish. The dynamic fatigue tests were carried out at 20 and 850°C and at stressing rate of 30 and 0.003 MPa/s in air per ASTM C1465. The 30 MPa/s is used to evaluate the inert characteristic strength as a function of temperature, and 0.003 MPa/s is applied to measure the slow crack growth (SCG) susceptibility at temperatures. Some of the samples were tested at 1000°C and at 30 MPa/s to evaluate its high temperature application limit. Dynamic fatigue results at 30 MPa/s showed that the transversely machined SN147-31E silicon nitride exhibited little or no decrease in characteristic strength at temperature up to 1000°C as compared to those obtained at 20°C (shown in Table 1 and Figs. 1-5). However, the SN147-31E samples exhibited the higher Weibull moduli at elevated temperatures then the value obtained at 20°C. Also, results at 850°C indicated that there is apparent decrease in characteristic strengths (about 19%) when tested at 0.003 MPa/s (Fig. 2). In addition, the fatigue exponent of transversely machined SN147-31E decreased from 338 at 20°C to 39 at 850°C (as shown in Fig. 6), indicative of an increased susceptibility to SCG process. On the other hand, for the longitudinally machined SN147-31E samples there was no apparent strength degradation when test temperature increased from 850 to 1000°C (Table 1 and Fig. 3 and 5), similar to that observed for the transversely machined samples. The detailed SEM examinations will be carried out to elucidate the change in fatigue exponent at 850°C and the possible cause of the increased susceptibility to SCG. Sixteen NT551 silicon nitride valves, 14 with 30° and 4 with 45° valve seat angle, after 500 h bend rig test at Caterpillar have been received for mechanical strength evaluation (Fig. 7). In general, the optical microscopy examinations showed that there were no apparent surface damages/flaws observed after the bench rig test, except the distinct valve seat markings at the valve and stainless steel valve seat contact point. Strength testing will be carried out at room temperature to evaluate the effect of 500 h bench rig test on the mechanical performance, especially due to the presence of subsurface damages (flaws) introduced due to the contact and wear. The result will be summarized in the next quarterly report. Status of Milestones Milestone: “Complete testing and analysis of prototype silicon nitride valves after bench rig testing.” On schedule.
Page 1 and 2: Metals and Ceramics Division Heavy
Page 3 and 4: Titanium Alloys for Heavy-Duty Vehi
Page 5 and 6: Advanced Diesel Aftertreatment Prog
Page 7 and 8: Development of NOx Sensors for Heav
Page 9 and 10: Ultra-High Resolution Electron Micr
Page 11 and 12: Fig. 3 Toyota “D-Cat” DPNR “F
Page 13 and 14: 20nm Fig. 7 Annular dark-field (ADF
Page 15 and 16: 5nm Fig. 8 ADF image at high resolu
Page 17 and 18: electronic-structure techniques and
Page 19 and 20: The IR spectra of the sample formed
Page 21 and 22: Durability and Reliability of Ceram
Page 23 and 24: Lightweight Valve Train Materials J
Page 25 and 26: advanced materials. Modifications (
Page 27 and 28: Additional rig testing of the parts
Page 29 and 30: Figure 1 shows the weight gains as
Page 31 and 32: Communications/Visitors/Travel None
Page 33 and 34: Multimode optical fiber DAQ I/O con
Page 35 and 36: Status of Milestones Current ANL mi
Page 37 and 38: In the revised model, the Hertzian
Page 39: eports will describe our derivation
Page 43 and 44: Table 1. Summary of uncensored Weib
Page 45 and 46: ln ln ( 1 / ( 1 - P f ) ) 2 1 0 -1
Page 47 and 48: Figure 7. Photo of NT551 silicon ni
Page 49 and 50: Cost-Effective Machining of Titaniu
Page 51 and 52: morphology for ductile materials in
Page 53 and 54: lathe turning tests for mutual comp
Page 55 and 56: mm depth of cut. At all cutting spe
Page 57 and 58: Advanced Cast Austenitic Stainless
Page 59 and 60: STRESS (MPa) 300 100 80 60 40 20 CF
Page 61 and 62: TEM Study of Microstructures in a C
Page 63 and 64: (a) (b) Fig. 3 (a) A bright-field T
Page 65 and 66: High Temperature Aluminum Alloys Yo
Page 67 and 68: Task 2. NASA-Developed Process Task
Page 69 and 70: done on a polishing cloth using col
Page 71 and 72: The solutionized and water quenched
Page 73 and 74: Microstructural development in the
Page 75 and 76: Figure 10~12 are the X-ray diffract
Page 77 and 78: Figure 14. TEM micrographs showing
Page 79 and 80: In this investigation, particular a
Page 81 and 82: Task 3: Determine if there are fati
Page 83 and 84: To examine the effect of grain size
Page 85 and 86: K Ic (MPa¦m) 10 8 6 4 2 Quasi-Stat
Page 87 and 88: Figure 7. Microstructure on fractur
Page 89 and 90: Powder Processing of Nanostructured
Page 91 and 92:
(a) (b) Figure 2. (a) Macrograph sh
Page 93 and 94:
Problems Encountered None Status of
Page 95 and 96:
Advanced colloidal processing in th
Page 97 and 98:
Synthesis of Nanocrystalline Cerami
Page 99 and 100:
Milestone Status Table ID Number Ta
Page 101 and 102:
Quarter Summary Supplier Readiness
Page 103 and 104:
31N. The elastic properties are nee
Page 105 and 106:
Implementing Agreement For A Progra
Page 107 and 108:
Laser Pulse Sacrificial layer (Tape
Page 109 and 110:
Mechanical Property Test Developmen
Page 111 and 112:
Communications/Visits/Travel G. Qui
Page 113 and 114:
Introduction Frictional losses are
Page 115 and 116:
All of the initial coefficients of
Page 117:
X. Wang, S. M. Hsu, “An Integrate
show all

Metals and Ceramics Division - Oak Ridge National Laboratory

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?