FAILURE ANALYSIS & TESTING SERVICES

The purpose of a failure analysis is to determine the primary cause of a failure by the process of collecting and analyzing data. This service is to help enhance the quality of our client’s products and like reverse engineering; failure analysis testing involves multiple analysis methods. It is the chemical and mechanical investigation into the primary cause that led to the failure of the product. We then provide the client with an insight to the solution of their problem. NHML can help provide the necessary information in order for our clients to improve their products’ quality and compliance standards.

Here is a list of the techniques that are used at NHML when conducting failure analysis:

• Scanning Electron Microscopy (SEM)

• Energy Dispersive Spectroscopy (EDS)

• Differential Scanning Calorimetry (DSC)

• Optical Microscopy

• Metallography

• Mechanical Testing

If at any point during the testing process you have questions or want updates, the NHML professionals performing the tests are the ones that you talk to.

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Materials may fail by a wide variety of failure modes including but are not limited to the following:

• Single overload failures in tension, compression, torsion or shear including both ductile and brittle fractures

• Fatigue failures

• Distortion failures

• Wear and Erosion

• Corrosion

• Embrittlement failures including liquid metal embrittlement, hydrogen embrittlement and embrittlement by solid metal environments

• Elevated Temperature failures

• Evaluation of failures due to cracking, corrosion, loss of strength, bending, debonding, ductile and brittle fracture, dealloying weld failure, braze failure, solder failure and more

Combined failure modes are also common including stress corrosion cracking and corrosion fatigue. By getting the failure analysis testing done, the client is able to know the actual reasons as to why their product failed; resulting in being able to improve their engineering processes and management decisions.

Failure Analysis Testing Services:

• Fatigue

• Ductile and Brittle Fracture

• Cracking

• Corrosion

• Loss of strength

• Bending

• Debonding

• Weld, Braze or Solder failures

• Color

• Surface finish

• Fire damage

• Water damage

• Structural damage

Given the wide variety of potential failure modes, how does a failure analysis being and progress with NHML?

The following steps are commonly used for the majority of the failure analysis tests that are performed:

1.  Collection of background information.

• Drawings of the failed component are usually obtained in order to determine the specified material and the processing. Processing information would include heat treatment, case hardening, welding and/or plating.

• Service history of the part is also determined within this step. This would include the environment and time-in-service information prior to the failure and if there are any abnormal conditions or events that may have occurred.
  
  

2.  Initial examination of the failure

• This examination is usually performed here at our facility and includes an examination at low magnification, photography and selection of specimens for laboratory examination.
  
  

3.  Non-destructive testing (if applicable)

• Radiography

• Dye Penetrant Inspection

  • This inspection is a widely used and fairly low-costing inspection method. It is used in order to locate any surface-breaking defects in all non-porous materials such as metals, plastics and ceramics.

  • Also used to detect casting, welding and forging surface defects such as porosity, possible leaks in new products, fatigue cracks on in-service components and hairline fractures.

• Eddy Current

  • Used to detect flaws in conductive  materials through electromagnetic induction.

  • The alternating current used during this testing can generate a changing magnetic field which in turn interacts with the test specimen, thus generating an eddy current.

  • A change in the eddy current is how we can detect any presence of flaws, variation in the electrical conductivity of the specimen and finding the coating thickness measurements.

• Ultrasonic

  • Used in the detection of internal flaws of the material or to characterize the material.

  • There are many advantages in using this type of non-destructive testing:

    • Detect flaws deep within the material or component

    • Ability to detect exceptionally small flaws

    • Only needing one surface to be accessible in order to conduct the testing

    • Capability of finding the estimated shape, size, depth and nature of defects found within test material along with many other advantages.

4.  Mechanical testing

• Hardness

• Tensile

• Fatigue

• Toughness
  
  

All of the work within this type of testing depends upon the availability of sufficient material without compromising the actual fracture or fractures. The analyst must be aware of the limitations of any mechanical test selected.

5.  Chemical Analysis

• This test is done with the bulk material and of the material involved in the failure/corrosion products surface deposits and coatings

• Bulk chemical analysis is commonly performed to verify that the failed part was fabricated from the specified material.

• Chemical analysis of surface deposits and corrosion products can provide additional information regarding the failure.

6.  Macroscopic Examination

• This is the examination of the fracture surfaces including cleaning and preservation.

  • Cleaning of the fracture surface may include the use of polar or non-polar solvents in an ultrasonic bath. Mild acidic or basic solutions that remove surface deposits but do not attach the base metal may also be used.

• This stage also includes the following: photographic documentation and location of the fracture origin.

7.  Microscopic Examination

• Scanning electron microscopy (SEM) is the most common examination tool. This made of failure and the origin of the failure is determined.

8.  Selection, Preparation and Examination of metallographic specimens

• Microscopic examination of polished and etched metallographic specimens is often key in determining the cause of the failure.

9.  Determination of the failure mechanism

• The failure mechanism is determined based upon the results of the macroscopic and microscopic examination of the fracture and metallographic specimens. The failure may be ductile or brittle.

• A brittle fracture may be transgranular or intergranular.

  • Intergranular fractures are easy to identify although determining the cause of this fracture may be quite difficult.

• Other failure mechanisms include but are not limited to fatigue, corrosion and stress corrosion cracking, embrittlement and stress rupture.

10.  Analysis of gathered information, formulation of conclusions and preparation of report