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FAILURE ANALYSIS OVERVIEW

Failure analysis is a critical component of product improvement systems. When a product fails prematurely in service or in testing, failure analysis is in order to determine where product improvements are needed. The weak link may be in the product design, its manufacturing methods, usage, or the materials used.

Oil Refinery Pipeline Rupture Oil Refinery Pipeline Rupture
Engineering failure analysis is also frequently utilized to aid in the resolution of insurance and legal cases where liability must be established for losses due to a product failure. The failure analysis methods used for industrial applications are equally applicable to these forensic cases.

Engineering failure analysis has two major objectives - to determine the failure mechanism and to determine the failure root cause. The failure mode is the basic material behavior that results in the failure, e.g. fatigue fracture or pitting corrosion. Root cause is the fundamental condition or event that caused the failure, e.g. material defects, design deficiencies, and improper use.

Materials behavior and performance are always important factors in product failure analysis. To an experienced analyst, the visual appearance of fractures, wear damage, or corrosion provide the first and often the most important clues to failure mode and root cause. Microscopic examinations often yield even more information. Materials testing and analysis usually put the final puzzle pieces in place to identify the failure mode and possibly the root cause. In some cases, failure simulations, both experimental and computer-aided, are useful to verify hypotheses developed from the engineering and materials analyses.

See our Failure Analysis Background Data Form and our Failure Analysis Sampling Guide.

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MEE CAPABILITIES

The engineers and scientists at MEE have a wide range of experience in analyzing failures of metal and polymer components. Our analysts understand how materials behave in structural applications and in damaging environments. Although the focus at MEE is on materials and their behavior, multidisciplinary engineering evaluations are performed through our affiliation with a variety of other skilled engineering experts as needed.

MEE also has comprehensive analytical laboratory capabilities to bring to bear for failure analysis projects. We provide a wide array of traditional and advanced analytical methods, including light and electron microscopy, surface chemical analysis, and a variety of mechanical and physical properties analyses. Check our online Handbook for additional information on analytical methods.


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MECHANICAL FAILURE INVESTIGATIONS

Logging Chain Fracture Logging Chain Fracture

The typical vision of a product failure is that of a device with a broken or fractured component. The location, shape, and microscopic features of a fracture provide a window into the history of that failure. Each particular fracture mode, i.e. overload, fatigue, or environmentally-assisted fracture, have characteristic physical features that distinguish one mode from another. The location of the starting point or origin of the fracture and its orientation reveal the direction of forces applied to the component. The physical characteristics of wear failures also provide direct evidence of the specific mechanism and causes of damage leading to the failure.

These characteristic features are sometimes visible with the naked eye, but often require high-magnification examination by scanning electron microscopy. Laboratory testing, including direct mechanical tests and evaluation of the material's structure, are used to correlate forces applied to the component with the material properties. Computer-aided stress analysis gives a quantitative picture of the how the material would be expected to behave in a particular application, and laboratory simulations are used to verify unexpected or indeterminant findings.

Hip-Replacement Prosthesis Fracture Hip-Replacement Prosthesis Fracture

Representative Mechanical Failure Investigations

  • Fractured cervical vertebrae plate
  • Failed wire bonds on PC boards
  • Excessive wear of carbide valve seats
  • Ruptured fire sprinkler fitting
  • Fractured fasteners from highway signs
  • Fractured railroad rails
  • Cracked nylon water filter housing
  • Buckled fiberglass ladder
  • Fractured nylon pulley
  • Premature wear of high-speed bearings

 



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CORROSION FAILURE INVESTIGATION

Corrosion costs the U.S. economy over $300 billion dollars each year. Metallic corrosion occur by several different mechanisms, including general corrosion, pitting, crevice corrosion, galvanic corrosion, and stress corrosion cracking. Engineering plastics also suffer degradation from environmental conditions, including photooxidation, chemical attack and environmental stress cracking.

Truck Trailer Frame Corrosion Truck Trailer Frame Corrosion

Corrosion and environmental degradation are complex topics that require a fundamental understanding of the interaction of the materials and their service environments. Material performance requirements vary greatly for different applications - acceptable corrosion damage for an automotive components is much greater than that allowed for an implantable medical device. Thus, an understanding of the application requirements is also necessary for corrosion investigation.

Laboratory analysis of corrosion failures includes visual and microscopic examinations to characterize the physical appearance of the damage and usually microstructure studies to correlate the corrosion damage to the material's structure. Chemical analysis methods, including spot tests and surface analysis methods, are critical to determine whether unexpected contaminants in the service environment contributed to the failure. Accelerated corrosion tests, such as salt spray or high-humidity exposures, are often useful to simulate a failure mechanism or evaluate potential corrective measures.

Pitting and Cracking in SS Weld Pitting and Cracking in SS Weld

 

Representative Corrosion Failure Investigations

  • Oil refinery heat exchanger failure
  • Corroded explanted medical device
  • Pitting and cracking in beverage dispenser tanks
  • Perforated natural gas connector tubing
  • Galvanic corrosion of truck trailer frames
  • Paint failure on aluminum window frames
  • Pinholes in fire protection piping
  • Leaks in copper water service laterals
  • Cracking of polycarbonate filter bowls
  • Tin-plated food container corrosion


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MATERIALS, PROCESS AND PRODUCT EVALUATION

Bicycle Brake Testing Bicycle Brake Testing
Materials behavior data can be applied to a variety of engineering projects, such as new product development, manufacturing process development, and product reliability studies. For these projects, information about materials behavior is used to provide a basis for engineering evaluations of the products or manufacturing processes. These data can be derived from the existing technical literature or from specialized tests developed specifically for the application under review.

Material, Process and Product Evaluations

  • Process plant piping corrosion-risk analysis
  • Review surface finishing methods for biomedical devices
  • Specify corrosion-resistant coatings for chemical process equipment
  • Evaluate candidate coating materials for high temperature boiler tubing
  • Nickel brazing process review
  • Fracture resistance of catheter guide wires
  • Investigate reliability of bicycle brakes


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FORENSIC ENGINEERING INVESTIGATIONS

Forensic engineering is the application of scientific and engineering principles to settle disputes between two or more parties. These disputes typically arise when a product or structure fails to perform as expected and causes a loss to one of the parties. Forensic engineering is practiced for insurance companies evaluating claims for payment or subrogation and for attorneys pleading or defending product liability law suits. Engineering evaluation determines the cause or causes of the failure to help assign liability for the damages.

Head Light Filament Analysis Head Light Filament Analysis
Most failures involve materials damage of some sort. Therefore, materials engineering is often an integral aspect of forensic engineering investigations. Evaluation of the materials behavior using standard failure analysis practices typically identifies the failure mode, and this information, on its own or in combination with other engineering evaluations, leads to determination of the root cause and liability. The special skill required for forensic engineering is the ability of the analyst to break down the technical issues for interpretation by non-technical people, such as attorneys agents, judges, and juries.

The staff at MEE has been involved with a wide variety of product liability cases. MEE's principal engineer, Larry Hanke, has been performing forensic engineering evaluations and testifying as an expert witness for nearly 20 years (resume). Our laboratory facilities offer most of the analytical capabilities required for forensic engineering projects. MEE also collaborates with experienced engineers in other disciplines when needed.

Nylon Lifting Strap Failure Nylon Lifting Strap Failure

Examples of Forensic Engineering Cases

  • Farm auger guard failure
  • Grain bin collapse
  • Golf club shaft fracture
  • Oil refinery pipeline rupture
  • Collapsed 16-story climbing crane
  • Truck axle fracture
  • Nylon lifting strap failure
  • Natural gas line failure
  • Hip-replacement prosthesis fracture
  • Aircraft fuel line fracture
  • Lawn chair collapse
  • Paint failure on fire truck body panels


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