Fig. 26 Multiple fatigue crack origins(arrows) initiating in a network of intergranular attack on the inside diameter of the sleeve. 155x Using the application-life diagram, the strong effects of minute surface anomalies in this fracture critical component is clearly apparent(Fig. 27). As a result of the severity of the pressure cycles in service, the sleeve cannot tolerate surface flaws No measurable surface flaws Anticipated severity L 0dcooo Prematur Premature 00002in.(0.005mm) failure failure 10.0005in.(0013mm) Increasing service life Intended life Fig. 27 Application-life diagram showing effects of manufacturing-caused surface discontinuities on service life Service life anomalies The life of a component or system is heavily dependent on the conditions under which the product operates in service The service life of a product includes its operation, maintenance, inspection, repair, and modification. Failures due to anomalies in any one of these aspects of service life are unique from those created during the design, procurement of materials, and manufacture of products, as described above. Examples of the types of root causes of failures that result from unanticipated service conditions(Ref 30)are summarized in the following paragraphs Operation of the equipment outside of the manufacturer's design parameters would include an example such as a military fighter aircraft in a turn that causes g forces that are outside of the operating envelope of the aircraft. Another example is inlet-flow blockage on a high-performance air compressor resulting in excessive cyclic loads applied to the blades causing blade(Fig. 28, 29)and drive sh shaft(Fig. 30)failures. Failure analysis revealed both the compressor rotor and th shaft sustained fatigue failures
Fig. 26 Multiple fatigue crack origins (arrows) initiating in a network of intergranular attack on the inside diameter of the sleeve. 155× Using the application-life diagram, the strong effects of minute surface anomalies in this fracture critical component is clearly apparent (Fig. 27). As a result of the severity of the pressure cycles in service, the sleeve cannot tolerate surface flaws. Fig. 27 Application-life diagram showing effects of manufacturing-caused surface discontinuities on service life Service Life Anomalies The life of a component or system is heavily dependent on the conditions under which the product operates in service. The service life of a product includes its operation, maintenance, inspection, repair, and modification. Failures due to anomalies in any one of these aspects of service life are unique from those created during the design, procurement of materials, and manufacture of products, as described above. Examples of the types of root causes of failures that result from unanticipated service conditions (Ref 30) are summarized in the following paragraphs. Operation of the equipment outside of the manufacturer's design parameters would include an example such as a military fighter aircraft in a turn that causes “g” forces that are outside of the operating envelope of the aircraft. Another example is inlet-flow blockage on a high-performance air compressor resulting in excessive cyclic loads applied to the blades causing blade (Fig. 28, 29) and drive shaft (Fig. 30) failures. Failure analysis revealed both the compressor rotor and the shaft sustained fatigue failures
Fig. 28 Failed compressor rotor Arrows indicate fractured portions of blades. 36x Fig. 29 Compressor blade fracture surface showing fatigue origins on low pressure(i.e, right) side of blade, as indicated by the arrows. 13x Thefileisdownloadedfromwww.bzfxw.com
Fig. 28 Failed compressor rotor. Arrows indicate fractured portions of blades. 36× Fig. 29 Compressor blade fracture surface showing fatigue origins on low pressure (i.e., right) side of blade, as indicated by the arrows. 13× The file is downloaded from www.bzfxw.com
Fig. 30 Failed compressor rotor shaft. Fracture occurred at radius between large and small diameters. Arrows indicate some of fatigue origins. 1x Careful fracture analysis revealed fatigue cracks initiated on the low-pressure side of the blades, which are in compression during normal compressor operation. However, when the inlet flow is blocked, particularly when the blockage is only partial, the blades sustain alternating tensile forces, one load cycle per revolution, on the low-pressure side of the blades resulting in the observed blade fractures. The shaft failed subsequently, due to the severe imbalance and rubbing caused by the blade failures Exposure of the product or system to environments more aggressive than forethought would include examples such Microbiologically influenced corrosion in a cooling-water system using river water in which the ecosystem has Organic chloride-containing environment exposing a titanium centrifuge bowl, resulting in stress-corrosion Faulty sensor cable resulting in an overtemperature condition in a jet engine, which consumes the high-pressure turbine blade life Improper maintenance would include examples such as Installing a metallic fuel line onto the mating fitting by forcing the tube to align with the mating fitting. Adding the installation stress to the normal cyclic stresses results in a leak due to fatigue cracking Weld repair of a material that is sensitive to high heat cycles, causing brittle cracking and subsequent fatigue failure Misalignment of a bearing during rebuild, causing bending loads on the shaft and resulting failure by rotating bending fatigue Inappropriate Modifications. An example of this would be part-through drill holes in bicycle handlebar stem resulting in fatigue initiation at holes and subsequent fracture (Fig. 31, 32)
Fig. 30 Failed compressor rotor shaft. Fracture occurred at radius between large and small diameters. Arrows indicate some of fatigue origins. 1× Careful fracture analysis revealed fatigue cracks initiated on the low-pressure side of the blades, which are in compression during normal compressor operation. However, when the inlet flow is blocked, particularly when the blockage is only partial, the blades sustain alternating tensile forces, one load cycle per revolution, on the low-pressure side of the blades, resulting in the observed blade fractures. The shaft failed subsequently, due to the severe imbalance and rubbing caused by the blade failures. Exposure of the product or system to environments more aggressive than forethought would include examples such as: · Microbiologically influenced corrosion in a cooling-water system using river water in which the ecosystem has changed · Organic chloride-containing environment exposing a titanium centrifuge bowl, resulting in stress-corrosion cracking · Faulty sensor cable resulting in an overtemperature condition in a jet engine, which consumes the high-pressure turbine blade life Improper maintenance would include examples such as: · Installing a metallic fuel line onto the mating fitting by forcing the tube to align with the mating fitting. Adding the installation stress to the normal cyclic stresses results in a leak due to fatigue cracking. · Weld repair of a material that is sensitive to high heat cycles, causing brittle cracking and subsequent fatigue failure · Misalignment of a bearing during rebuild, causing bending loads on the shaft and resulting failure by rotating bending fatigue Inappropriate Modifications. An example of this would be part-through drill holes in bicycle handlebar stem resulting in fatigue initiation at holes and subsequent fracture (Fig. 31, 32)
Fig. 31 User-modified bicycle handlebar stem failed in service Thefileisdownloadedfromwww.bzfxw.com
Fig. 31 User-modified bicycle handlebar stem failed in service The file is downloaded from www.bzfxw.com
Fig. 32 Multiple fatigue initiations at part-through drill holes in user-modified bicycle handlebar sten.3× The application-life diagram is useful in exploring the effects of service-life anomalies on the lives of products. For the compressor inlet blockage case described previously, the Fig. 33 depicts the significant loss of service life when the rotor blades sustain the unintended cyclic stresses that occur during an inlet blockage event Unanticipated service condition due to nlet blockage x一 Premature failure COmpressor blades L Anticipated service condition no blockage ncreasing service life→ Fi 33 Application-life diagram showing effects of increasing the severity of the service condition References cited in this section 13. Engineering Aspects of Failure and Failure Analysis, Failure Analysis and Prevention, Vol 10, &th ed. Metals Handbook, American Society for Metals, 1975, p 1-9 15. J.J. Asperger, Legal Definition of a Product Failure: What the Law Requires of the Designer and the Manufacturer, Proc. Failure Prevention through Education: Getting to the Root Cause, 23-25 May 2000 ( Cleveland, OH), ASM International, 2000, p 25-29 23. P F. Wilson, L D. Dell, and G F. Anderson, Root Cause Analysis: A Tool for Total Quality Management, ASQ Quality Press, 1993 24 G.F. Smith, Quality Problem Solving, AsQ Quality Press, 1998 5. R K Mobley, Root Cause Failure Analysis, Butterworth-Heinemann, 1999, p 37-39 26 M. Ammerman, The Root Cause Analysis Handbook: A Simplified Approach to Identifying, Correcting, and Reporting Workplace Errors, Max Ammerman/Quality Resources, 1998, p67 7. Failure Analysis, The British Engine Technical Reports, American Society for Metals, 1981
Fig. 32 Multiple fatigue initiations at part-through drill holes in user-modified bicycle handlebar stem. 3× The application-life diagram is useful in exploring the effects of service-life anomalies on the lives of products. For the compressor inlet blockage case described previously, the Fig. 33 depicts the significant loss of service life when the rotor blades sustain the unintended cyclic stresses that occur during an inlet blockage event. Fig. 33 Application-life diagram showing effects of increasing the severity of the service condition References cited in this section 13. Engineering Aspects of Failure and Failure Analysis, Failure Analysis and Prevention, Vol 10, 8th ed., Metals Handbook, American Society for Metals, 1975, p 1–9 15. J.J. Asperger, Legal Definition of a Product Failure: What the Law Requires of the Designer and the Manufacturer, Proc. Failure Prevention through Education: Getting to the Root Cause, 23–25 May 2000 (Cleveland, OH), ASM International, 2000, p 25–29 23. P.F. Wilson, L.D. Dell, and G.F. Anderson, Root Cause Analysis: A Tool for Total Quality Management, ASQ Quality Press, 1993 24. G.F. Smith, Quality Problem Solving, ASQ Quality Press, 1998 25. R.K. Mobley, Root Cause Failure Analysis, Butterworth-Heinemann, 1999, p 37–39 26. M. Ammerman, The Root Cause Analysis Handbook: A Simplified Approach to Identifying, Correcting, and Reporting Workplace Errors, Max Ammerman/Quality Resources, 1998, p 67 27. Failure Analysis, The British Engine Technical Reports, American Society for Metals, 1981