2. FAILURE ANALYSIS

3. Sources of failure - - Sources of failure - - Material Related Failures. Deficiency in Design. Service Related Failures. Environmental Related Failures.

4. Material Related Failures 1. Deficiency in Selection of Materials a) Inadequacy of Mechanical Properties Standard Specifications for : Tensile test data (Yield, U.T.S., E%) Hardness (or microhardness) Impact strength (toughness) Types of loading StaticRepeatedImpact Types of stress TensionCompressionShear

5. Material Related Failures Contd. Chemical Composition Carbon content (for ferrous materials) alloying elements b) Heat treatment Secure removal of residual stress. 1. Imperfection in Material Segregation Lamination Inclusions Porosity Voids

6. 1. Deficiency in Fabrication of Parts Cold forming Machining and grinding Identification marking Improper heat treatment Acid pickling or cleaning Welding and joining Casting

7. Deficiency in Design Upgrading of a part to a new application local over-stressing. Sudden or severe change in direction corrosion related deficiency

8. Operation (Service) Related Failures 1. Errors in Assembly - Operator negligence - Misalignment - Inadequate procedure Insufficient tightening Non-uniform tightening Over tightening 2. Thermal Damage Over heating 3. Inadequate Maintenance 4. Start-up 5. Shut-Down

9. Environmental Related Failures Corrosion Atmosphere Environment

10. FAILURE ANALYSIS MODE OF FRACTURE OPERATING CONDITIONS FAILURE IDENTIFICATION CONTRIBUTING FACTORS

11. FAILURE ANALYSIS GGeneral Practice 1. Collection of background information. 2. Record & keep. 3. Selection of samples. 4. Visual and macroscopic examination 5. Mechanical testing. 6. Microscopic (Metallographic) examination 7. Chemical analysis: bulk, local, surface, corr. Product etc. 8. Non-destructive testing. 9. Testing under simulated condition (special test). 10. Determination of failure mechanism. 11. Conclusions. 12. Report writing.

12. Collection of Background Information - Service History. - Material specification. - System descriptive information. - Operation details. - Manufacturing and fabrication data - Mechanical - Thermal - Chemical

13. Record Keeping By writing, sketches or photograph - The system (contg. the failed part) - Position of the part. - Features and shape (color, corr. product). - Dimensions.

14. Selection of Samples - Represent failure characteristics. - Compare with unfailed samples. - Sample of fluid, deposits.

15. Visual and Macroscopic Examination - Unaided eye, hand lens, portable microscope. - Detect changes of color and texture. - Search for cracks and branches. - Inspect fracture surface. - Asses basic design.

16. Mechanical Testing HHardness - evaluate heat treatment - Approx. value to tensile strength. - Detect hardening (softening) by overheating or decarburization. Tensile or impact. - Conform specification.

17. Failure Mechanism · If the failure involved Cracking or Fracture: d etermine - Crack initiation site. - Stress concentration points - Intensity and type of load : SStatic / cyclic / intermittent · If temp. Contribute to failure : determine - Approx. service temp. at time of failure. · If wear contribute to failure : determine - Flow speed. - Direction of flow. · If Corrosion contribute to failure : determine - Form of corrosion. CHECK : - Specification of material composition. - Cross section : adequate ? - Mechanical properties : suitable ? - Heat treatment : proper ? - Fabrication : proper ? - Assembly and installation : proper ? - Repair (if any) : proper? - Operation : proper ? - Maintenance : proper ?

18. CONTRIBUTING FACTORS أسباب الانهيار DESIGN Bad geometry Wrong Material Under Estimate of Stress MANUFACTURE Machining Casting Defects Metal working Rolling Drawing Forging Faulty Heat Treatment ASSEMBLY & MAINTENANCE Faulty joining Reviting Welding Faulty fitting Screw threads

19. REPORT WRITING 1. Description of the failed component. 2. Operating condition at the time of failure. 3. Service History. 4. Manufacturing and processing history of component. 5. Material Specification. 6. Visual and macroscopic examination. 7. Metallurgical examination. 8. Mechanical testing. 9. Chemical analysis. 10. Other tests : N.D.T. or simulated. 11. Mechanism of failure. 12. Recommendation : correction of similar component prevention of similar failure. 13. Abstract.