Menu

Failure Analysis Root Cause Determination

Failure analysis is the method that is used to determine the root cause of failure when products, components, assets, or systems fail to meet performance expectations.  The findings of a root cause failure analysis provide decision makers with the tools they need for remedial actions and preventative measures to be taken.  At Matergenics, our diverse engineering team of Ph.D. level scientists, NACE certified engineers (materials, metallurgical, corrosion, mechanical), and chemists can assist you with your root cause failure analysis needs.  Areas of specialization include the steel making, manufacturing, aerospace, automotive, oil and gas, electric power, telecommunication, and wind tower industries.

Above, is cracking of a load bearing steel member on a 500,000 kv Transmission line.

Although Matergentics materials testing work is vital to its clients, it is rarely seen by the public. Here are some examples of recent projects in which our experienced Matergentics engineering team provided the timely, competent, customer-oriented engineering analysis that made the difference.

  • Metallurgical testing for a major commercial airline fleet that includes failure analysis investigations, corrosion investigations, and quality control testing.
  • Same-day metallurgical failure analysis of the effects of a truck fire on the superstructure of a major highway bridge to determine whether or not the highway could remain open.
  • Failure analysis of a gas main explosion that caused causalities.
  • Failure analysis and remaining life determination of boiler components in the power industry.
  • Electrochemical corrosion evaluation of implant materials such as hips, knees, stents, etc. to improve products and performance.
  • Ultra-high vacuum chamber for analysis of coatings and materials surfaces.
  • R&D of coatings and sensors for the construction industry.

Decisions must be made during any failure analysis, and the results of each step dictate the next procedure.  At Matergenics, our material, corrosion and mechanical engineers systematically perform required tests as deemed necessary based on the project at hand.  Typical steps we often use in our root cause failure analysis investigations:

  • Review of background information
  • Visual and non-destructive examination
  • Microscopic examination
  • Physical measurements
  • Corrosion examination
  • Chemical analysis
  • Metallurgical testing / metallography
  • Fractography examination
  • Mechanical testing
  • Scanning electron microscopy (SEM)
  • Elemental dispersive X-ray analysis (EDS)
  • Fourier transformer infrared analysis (FTIR)
  • X-ray diffraction
  • Mechanical testing
  • Surface analysis
  • Finite elemental analysis (FEA), computational fluid dynamics (CFD) or other engineering calculations
  • Determination of mode of failure and primary cause
  • FEA, CFD and other detailed engineering calculations

At Matergenics, we determine if a failure is due to material selection, design, fabrication or operating conditions. Major corporations that rely on Matergentics specialists expertise include airline industry the Steel Industry, Electronics, Power Plants and many more. These investigations require not only a modern laboratory but an extensively trained professional team as well.

13511984_10209469653769368_749739763489213079_n

Above, photo showing fracture through weld metal and heat affected zone.

Components such as pipeline, boiler tubes, forgings, mechanical equipment, wire cables, concrete, pressure vessels, castings, welds, tubing, gears, FRP/PVC pipe, tools and dies, bolts, electronics, engine components, brakes, implants, transmission and distribution structures, telecommunication towers, and electric power components are routinely tested at Matergenics Materials Testing Laboratory.

A note about submitting samples for testing.  For precaution purposes, prior to sample submittal photographic documentation of the failed section prior to its departure from the project/accident site and upon its arrival at the Matergenitics materials testing laboratory should be made to ensure any damage from mishandling is appropriately noted. Before the shipment of the failed section, proper preservation techniques for the fracture surfaces and the section (including coating), if required, should be identified and a chain of custody should be established for transfer of the failed section to our testing facility.  Additionally, before the failed section arrives at Matergenics, it should be determined if destructive testing of the failed section has been approved.  Only non-destructive testing is allowed in some instances to preserve the samples (e.g. pipe) intact for evidentiary purposes.  In some instances destructive testing can only be performed when all interested parties agree to its necessity and a consensus protocol can be crafted establishing those that can witness the destructive tests.

 

 

 

 

 

                           Above is Hydrogen Induced Failure of Zinc Plated High Strength Steel Bolt in Subsea Environment

Please visit Matergenics Failure Analysis Slide Presentation at:

https://youtu.be/rVQ3Vi6b8Tg

Corrosion Failure Analysis

In corrosion failure analysis of pipe lines and underground assets or process plants, besides a metallurgical analysis of the pipe/component, the internal and external environment of the line pipe must also be considered to arrive at the causal factors that may have caused the line pipe to fail.  Therefore, the presence of corrosion products inside and outside the pipe line in the area of the failure must be considered and collected for analysis, as appropriate.  For example, soil in the immediate area of the failure, dislodged soil adjacent to the ejected pipe, and soil that had adhered to the line pipe may have to be collected for analysis.

Below are photos of past projects including (1) an above ground storage tank with corrosion pitting and metal loss; (2) a section from a cast iron pipe with graphitization; and (3) a electric power utility structure with internal and external corrosion, metal loss and perforation.

 

    dsc06531

Photo of an above ground storage tank with corrosion, pitting, and metal loss.

pipe

Photo of a section from a cast iron pipe with graphitization.

pole3

 

Our capabilities include:

  • On-site investigations, digital microscopy, NDT, corrosion rate assessment, hardness measurements
  • Analysis of collected samples  to determine conformance with specifications
  • Welding, soldering and brazing analysis
  • Chemical and mechanical testing (ASTM and NACE)
  • Metallographic analysis and investigations
  • Fracture mechanics
  • Engineering calculations including, FEA, and CFD simulations and modeling
  • Failure analysis root cause determination

 

Matergenics Museum of Failure Analysis

Please visit Matergenics Museum of Materials and Failure Analysis at :

https://youtu.be/ZBMlav42Eoo

CASE STUDIES IN MATERIALS FAILURE ANALYSIS PERFORMED By OUR ENGINEERS

 The following case histories present a wide range of applications of the techniques for failure analysis outlined in the fore-going protocol. They are selected from the hundreds of cases that have passed through the authors’ laboratories over the past thirty years.

Case History #1. Aircraft Component Failure Analysis

Both halves of a broken steel pin were submitted for examination. The sample was identified as Left Hand Main Landing Gear, AC 809. At a later date an unbroken pin identified as Right Hand Main Landing Gear, AC 809 was also submitted. We were asked to determine the mode, not the cause,  of failure.

 

Visual Examination

 The two as-received pins are shown in figure 1 where an arrow shows the location of failure. The failure occurred in a 1.230-inch-diameter cylindrical part of the pin which  was corroded on the outer surface. One side of the fracture surface is shown in figure  2, below.Convergent chevron patterns identified the fracture initiation site on the outside surface. The fracture initiation site is marked by a red arrow in figure 2. Most of the fracture surface had been darkened by corrosion. A series of coarse low cycle fatigue crack arrest marks was identified at the ends of the two discolored crack-propagation fronts. The exterior surface of the 1.230 inch diameter cylindrical part of the pin contained corrosion pits. Corrosion pitting was also visible at the fracture initiation site. The  fracture surface profile is shown in figure 3.

A circumferential ridge and depression were found in the cylindrical surface. A similar ridge and depression were seen in the unbroken pin. By comparing the cylindrical parts of the two pins it was found that the fracture of the broken pin had initiated at the circumferential depression.The part of the fracture surface containing the fracture initiation site was macroetched for 30 seconds in a hot aqueous 50 percent hydrochloric acid solution to remove the corrosion products. The clean surface showed the fracture initiation site, as seen in figure 3.

 

Metallographic Examination

 A transverse cross section through the fracture initiation site was prepared for metallographic examination. The fracture surface profile is relatively flat. No crack branching was seen. The microstructure consists of dark-etching tempered martensite. No gross plastic deformation was observed at the fracture initiation site.

 

Conclusion

 The pin failed as a result of fatigue which initiated at the outside cylindrical surface.   This surface exhibited wear and corrosion pitting. The fracture initiated at a shallow circumferential groove. The corrosion of the fracture surface appears to have occurred subsequent to the fracture.  No evidence of stress corrosion cracking was observed

IMPORTANT FAILURE ANALYSIS PRINCIPLES REPRESENTED IN THIS CASE HISTORY

  1. In this case, examination of the fracture surface and the microstructure were sufficient to reveal the mode of failure. Determination of the cause of failure would require a knowledge of the use
  2. Fatigue failures are sometimes quite subtle. The materials used in the parts that fail may be completely as-specified, but the service conditions exceed their long- term ability to resist the stresses applied during

Case History #2  On-Site Metallography of Structural Steel

 A large crack and several smaller cracks were discovered in one flange of a steel column in a large new baseball stadium.  The H-section column was made of ASTM A572 grade

50 high-strength, low-alloy steel, a common structural material in welded, bolted or riveted structures such as buildings and bridges. Such a crack is considered  detrimental to the service life of the material and if left untreated, the crack could propagate under adverse conditions.

An on-site metallurgical inspection was carried out to determine the condition of the column. The paint was removed from the area in which the cracking was first detected. The large crack, as well as several smaller vertically aligned cracks were found near the center of the flange face. The widest and most pronounced crack measured 10-15 mils wide with a crack depth of 0.35”. The paint was also removed from the opposite flange in the same area for additional metallurgical inspection. A number of short vertical  cracks were found that had not been not visible through the paint.

A dry magnetic-particle test was performed on both flange surfaces.  When  finely divided magnetic particles are applied to the surface of a sufficiently magnetized ferromagnetic material, the particles will concentrate in cracks or other discontinuities in the surface. This procedure makes it possible to inspect a surface for cracks visually without damaging the sample, a vital consideration since the column could not be damaged in any way by sampling.

Concerns about the integrity of the column prompted the investigators to perform on-site hardness testing. Both column flanges were tested in several crack regions. ASTM A572, the specification for the grade 50 steel in the column, does not specify a  hardness requirement but it does specify a minimum tensile strength of 65 KSI. This value corresponds to an approximate Rockwell B scale hardness of 74 HRB. The measured values met or exceeded this value.

In-place metallographic analysis was carried out on two of the column’s flange areas, the area adjacent to the most pronounced crack and an uncracked area approximately three inches away, to reveal any defects in the microstructure of the steel. Since on-site microscopic analysis is impractical at the magnification necessary to see the important details, the microstructure was recorded using acetate-peel replicas and later examined in the laboratory. The microstructures of the steel at both locations were similar, consisting of dark-etching unresolvable pearlite in a white-etching ferrite matrix. The steel had a fine ferrite grain size of 7.0 as per ASTM E112 plate I specification. There was no evidence of decarburization adjacent to the crack surfaces. The microstructure of  the  sample  is  characteristic  of  a  hot  rolled  steel  product.    Such  findings     are characteristic of ASTM A572 grade 50 high-strength low-alloy steel. This is the normal microstructure for this product

Since the column met hardness requirements and had a normal microstructure, it was concluded that the cracks in the flanges of the steel column were likely to have been produced during hot rolling stage of production of the beams. Because the major crack might propagate under adverse conditions, it was recommended that it be removed by grinding and that the column then be repair welded. The necessary repair work was to be performed by competent welders in accordance with AWS Specification A5.1. It was further recommended that all of the column flanges in the structure be subjected to one hundred percent ultrasonic inspection to determine if any other cracks exist.

IMPORTANT FAILURE ANALYSIS PRINCIPLES REPRESENTED IN THIS CASE HISTORY:

  1. Applicable specifications were available for the failed part, making conformance determination
  2. Field metallurgical procedures, including acetate peel replicas, were an important part of the
  3. Non-destructive on-site testing also important
  4. The source of the problem was determined not to be non-conformance with the specifications but rather production
  5. The defect can readily be fixed in place. There was no need for replacement of columns which would have been extremely

WE VALUE OUR CLIENTS

Throughout the years, we have noticed that most of our business comes from repeat customers. Our knowledge-based approach can account for much of this; nonetheless, we believe there is something more to it. We attribute it to the dedicated staff that we employ, open and friendly relationship we promote with our customers, and a working environment which is never too busy to meet the needs of our clientele. Whether you are a large corporation or a small enterprise, we will provide you with the attention you need and deserve. In so doing, we hope to work with you for many years to come.

Please do not hesitate to call Matergenics at 412-788-1263 or Dr. Zee at 412-952-9441 if you have any questions,  concerns or need technical information.

 

 carolyn-sem

Hear from Us

Stay up to date with our services by subscribing to our extremely cool, yet very infrequent newsletters.

No spam, ever. That is a promise.