1、MIL-HDBK-790 CHG NOTICE 2 D 9999970 0174271 326 D METRIC NOTICE OF CHANGE MIL-HDBK-790 NOTICE 2 18 March 1993 MILITARY HANDBOOK FRACTOGRAPHY AND CHARACTERIZATION OF FRACTURE ORIGINS IN ADVANCED STRUCTURAL CERAMICS TO ALL HOLDERS OF MIL-HDBK-790: 1. Notice 1 of MIL-HDBK-790 is hereby cancelled and is
2、 no longer applicable. Disregard Notice 1 in any future notice. 2. RETAIN THIS NOTICE AND INSERT BEFORE TABLE OF CONTENTS. 3. entered. This notice page will be retained as a check sheet. This issuance is a separate publication. Each notice is to be retained by stocking points until the military hand
3、book is completely revised or canceled. Holders of MIL-HDBK-790 will verify that notice 2 indicated above has been Custodians Army - MR Navy - AS Air Force - 99 Review activities: Army - AT, EA, ER, MI, ME Navy - SH, OS, YD Air Force - 11, 84 O DIA - GS (WP# ID-1002A/DISC-O187A. FOR ARL/MD USE ONLY
4、0 AMSC N/A Preparing activity: Army - MR Project 9350-1011 FSC 9350 - DISTRIBUTION STATEMENT A Approved for public release; distribution unlimited. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MIL-HDBK-790 9999970 0360332 TTT W METRIC MI L-H DBK-7
5、90 1 July 1992 MILITARY HANDBOOK FRACTOGRAPHY AND CHARACTERIZATION OF FRACTURE ORIGINS IN ADVANCED STRUCTURAL CERAMICS AMSC N/A FSC 9350 DISTRIBUTION STATEMENT A. Approved for public release; distribution unlimited. Provided by IHSNot for ResaleNo reproduction or networking permitted without license
6、 from IHS-,-,-MIL-HDBK-790 9999970 OLb0333 936 = MIL-HDBK-790 DEPARRIENT OF DEFENSE Structural Ceramics 1. of the Department of Defense. This Military Handbook is approved for use by all Departments and Agencies 2. This handbook provides information on the fractography of advanced structural ceramic
7、s as it pertains to their fracture origins. is not intended to be referenced in purchase specifications except for informational purposes, nor shall it supersede any specification requirements. 3. Beneficial coments (recomnendations, additions, deletions) and any pertinent data which may be of use i
8、n improving this document should be addressed to: U.S. Army Research Laboratory, Materials Directorate, ATTN: AMSRL-MA-S, Watertown, MA Improvement Proposal (DD Form 1426) appearing at the end of this document or by letter. This handbook 0 02172-0001 by using the Standardization Document ii Provided
9、 by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MIL-HDBK-790 9999970 OLb0334 872 MIL-HDBK-790 FOREWORD The objective of this handbook is to provide an efficient and consistent methodology to locate and characterize fracture origins in advanced structural cer
10、amics. It is applicable to advanced structural ceramics which are brittle: that is, the material adheres to Hookes law. In such materials, fracture commences from a single location which is termed the fracture origin. The fracture origin in brittle ceramics normally consists of some irregularity or
11、singularity in the material which acts as a stress concentrator. In the parlance of the engineer or scientist, these irregularities are termed “flaws“ or “defects“. The latter should not be construed to mean that the material has been prepared improperly or is somehow faulty. This usage is consisten
12、t with the definition of a fracture origin given by Frechette: “The fracture origin is that flaw (discontinuity) from which cracking begins.“. (See Failure Analysis of Brinle Materials by Frechette (1990) in the Bibliography.) The handbook will address monolithic and some composite ceramics, e.g. ce
13、ramics. (Long- or continuous-fiber reinforced ceramics are excluded.) For some materials, the location and identification of fracture origins may not be possible due to the specific microstructure. . particulate- and whisker-reinforced and continuous-grain-boundary phase The handbook is principally
14、oriented towards characterization of fracture origins in specimens loaded in so called “fast fracture“ testing, but the approach can be extended to include other modes of loading as well. The procedures described within are primarily applicable to mechanical test specimens, although the same procedu
15、res may be relevant to component failure analyses as well. It is customary practice to test a number of specimens (constituting a “sample“) in order to permit statistical analysis of the variability of the materials strength. It is usually not difficult to test the specimens in a manner that will fa
16、cilitate subsequent fractographic analysis. development and design. standards and statistical analysis practices to permit comprehensive interpretation of data for design. An important feature of this handbook is the adoption of a consistent manner of fracture origin characterization including nomen
17、clature. This will further enable the construction of efficient computer data bases. This may not be the case with component failure analyses. This handbook is applicable to quality control, materials research and a It will also serve as a bridge to mechanical testing The irregularities or flaws whi
18、ch act as fracture origins in advanced structural ceramics can develop during or after fabrication of the material. Large flaws (relative to the average size of the microstructural features) such a pores, agglomerates and inclusions are typically introduced during procesIII IV FIGURE 1 2 3 4 5 6 7 9
19、 10 11 12 13 14 15 16 17 18 19 a . PAGE GENERAL 1 Summary of Practice 1 Equipment 1 Safety . 1 Referenced Documents . 1 DETAILED PROCEDURES AND CHARACTERIZATION . 4 Procedure 4 Flaw Characterization 19 Report . 22 DEFINITIONS 27 General 27 Inherently Volume-Distributed Flaws 27 Inherently Surface-Di
20、stributed Flaws . 27 Miscellaneous 28 CONCLUDING MATERIAL 28 Intended use . 28 Subject term (key-word) listing 28 Suggested sampling guidelines 5 List of some commonly-used storage media for fractured specimens or componente 6 Cleaning agents 17 Flaw Characterization Scheme . 19 Binocular stereomicr
21、oscope with adjustable fiber optic light source and variable magnification (5-80X) 2 Dual.station. binocular stereomicroscope . 2 Scanning electron microscope . 3 Peripheral equipment to assist in fractography and storage of fractured epecimene and componente 3 Macrophotographic camera stand . 4 Par
22、ticlee of graphite from a “leaded“ pencil . 7 Smear of masking tape resin near a chamfer . 7 8 Contamination from mounting clay . 8 Contamination from human skin ,. 9 Typical fracture patterns of flexure specimens . 10 Typical fracture pattern6 of biaxial flexure and diametrical compression specimen
23、s 11 Schematic of common fracture patterns 12 Schematic of fracture mirrors with flaws . 13 River patterns . 14 Schematic of photographs for recording observations 20 Schematic showing the possible locations of a volume distributed flaw . 21 Sample reporting format 23 Labelled Weibull graph includin
24、g listing of strength values . 24 Particles of paper lint V Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 MIL-HDBK-790 9999970 OLb0337 581 MIL-HDBK-790 Schematic of working fractographic montage . 25
25、26 Pore . 29 Porous 8em 30 Porous region 31 Agglomerate 32 Inclusion 33 Second phase inhomogeneity . 34 Large grain(8) . 35 Crack 36 Example of a publication quality montage . Machining damage . 37 Handling damage 38 Pit 39 Surface void . 40 Other flaws 41 Coincidental flaws . 42 BIBLIOGRAPHY A sele
26、ct bibliography on fractography and flaws in ceramics . 43 vi Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MIL-HDBK-790 1. GENERAL 1.1 Summary of practice. The following procedure should be followed in characterizing fracture origins in advanced c
27、eramics: Teat the specimen to failure in a fashion that preserves the primary fracture surface and the specimen for further reference. Carefully handle and store the specimen to minimize additional damage and/or contamination of the fracture surfaces. Visually (1-1OX) inspect the fractured specimen
28、in order to determine crack branching patterns, any evidence of abnormal failure patterns (indicative of testing misalignments), the primary fracture surface and the location of the mirror and, if possible, the fracture origin. Optically (10-100X) examine the fracture surfaces in order to locate and
29、, if possible, characterize the flaw. If necessary, inspect the specimen surfaces near the fracture origin to check for handling or machining damage. If definite characterization of the fracture origin cannot be made, then conduct an optical examination with the purpose of expediting subsequent SEM
30、examination. Prepare and clean the specimen for scanning electron microscope (SEM) examination. Carry out SEM examination (10-2OOOX) of fracture surfaces. Characterize the strength-limiting flaw by its IDENTITY, LOCATION and SIZE (optional). When appropriate, use the chemical analysis capability of
31、the SEM to help characterize the flaw. At each step, keep appropriate records and photographs in order to characterize the flaw, show its location, and show the general features of the fracture specimen. For a new material, or a new set of processing or exposure conditions, it is highly recommended
32、that a representative polished section of the microstructure be photographed to show the normal microstructural features such as grain size and porosity. Esuipment. The following equipment is essential for a comprehensive characterization of the fracture origins in advanced structural ceramics: (a)
33、Binocugr stereomicroscope with ad justable magnification between 10-1OOX and directional light source, Figure 1. A camera or video monitor system used with this microscope is a useful option, Figure 2. (b) Cleaning and preparation equipment such as an ultrasonic bath and a diamond cut-off wheel. (c)
34、 Scanning electron microscope with energy or wavelength dispersive spectroscopy, Figure 3. (d) Various peripheral equipment such as tweezers, grips, compressed air, etc., Figure 4. (e) A macrophotography camera stand, Figure 5, if a camera system is not available on the stereomicroscope. 1.3 Safety.
35、 This practice may involve hazardous materials, operations, and equipment. The handbook does not purport to address all of the safety problems associated with its use. It is the responsibility of the user of this handbook to establish appropriate safety and health practices and determine the applica
36、bility of regulatory limitations prior to use. 1.4 Referenced Documents. (a) ASTM Standard F109-73 (Reapproved 1991), “Standard Terminology Relating to Surface Imperfections on Ceramics“, ASTM Annual Book of 1 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from
37、IHS-,-,-MIL-HDBK-790 9999970 0360339 354 = MIL-HDBK-790 FIGURE 1. optical light source and variable magnification between 5x and 80x. Binocular stereomicroscope with directionally adjustable fiber- O O FIGURE 2. adjustable light sources, video camera, monitor and instant photographic capability. Dua
38、l station, binocular stereomicroscope with two directionally This type of system is excellent for instructional purposes. 2 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-FIGURE 3 MIL-HDBK-790 9999970 0360340 076 MIL-HDBK-790 . Scanning electron mic
39、roscope with energy dispersive spect :roscopic capabilities, low-energy operation and magnification between 20x-and 20,000. FIGURE 4. fractured specimens and components. (A) Hand-held and tabletop magnifying glass; (e) Variable-angle grips with compliant surface; (C) Fixtures to support Specimens to
40、 view machined surfaces; (D) Compressed air; (E) Tweezers or specimen manipulation; (F) Plastic storage trays; (G) Glass vials for storage of fractured specimens prior to SEM analysis. Peripheral equipment to assist in fractography and storage of O 3 Provided by IHSNot for ResaleNo reproduction or n
41、etworking permitted without license from IHS-,-,-MIL-HDBK-790 9970 OLb03q1 TO2 W MIL-HDBK-790 FIGURE 5. Macrophotographic camera stand for instant photographs. Standards, Volume 10.4. Surface Imperfections on Ceramics“, Annual Book of Standards, Vol. 10.04. (b) ASTM Standard C-1209, “Standard Defini
42、tion of Terms Relating to (c) 1984 Ceramic Glossary, The American Ceramic Society. (d) MTL TR 90-57, “A Proposed Standard Practice for Fractographic Analysis of Monolithic Advanced Ceramics,“ November 1990. (e) ASTM Standard C-1211, “Standard Test Method for Flexural Strength of Advanced Ceramics at
43、 Elevated Temperatures“, Annual Book of Standards, Vol. 15.01. 2. DETAILED PROCEDURES AND CHARACTERIZATION 2.1 Procedure. 2.1.1. General. Location, identification, and characterization of fracture origins in advanced structural ceramics can sometimes be accomplished using simple optical techniques t
44、hough it more often requires scanning electron microscopy (SEM). It may not be feasible, practical, or even necessary to examine all fracture surfaces with the SEM. The extent of fractographic analysis required will depend upon the following factors: (a) The conduciveness of the material to fractogr
45、aphic analysis. Some coarse-grained or porous materials will leave no markings that permit failure-origin identification. In other instances (especially in very strong ceramica), the fracture origin is very small and will be difficult to differentiate from the normal 4 Provided by IHSNot for ResaleN
46、o reproduction or networking permitted without license from IHS-,-,-MIL-HDBK-790 m 9999970 0360342 949 m MIL-HDBK-790 microstructure. Alternatively, a low-to-medium strength material may have flaws easily characterized by optical means thus eliminating the need for SEM analysis. materials research a
47、nd development, or design. Table I gives suggested sampling guidelines for medium-to-high strength advanced ceramics. (b) The purpose of the fractographic analysis: quality control, TABLE I. Suaaested SamDlina Guidelines. 1-lox 10-1oox 10-2ooox Visual ODt ica 1 SEM . Level 1 Specimens which Specimen
48、s which Optional -Quality control fail to meet fail to meet minimum strength minimum strength b requirements. requirements. Level 2 All specimens All specimens Representative -Quality Control specimen -Materials -2 of each flaw type Development -the 5 lowest strength specimens -at least 2 optically
49、unidentifiable flaws Level 3 All specimens All specimens All specimens, or as -Materials many specimens as -Design combined optical and SEM characterize 90% (100% for design) of all identifiable oriains 2.1.2 To maximize the amount of information obtained from a Development necessary such that O fractographic exercise, care must be taken in all steps starting with the initial testing of the specimen o
