Failure analysis is the process of collecting and analyzing data to determine the cause of a failure, often with the goal of determining corrective actions or liability. It is an important discipline in many branches of manufacturing industry, such as the electronics industry, where it is a vital tool used in the development of new products and for the improvement of existing products. The failure analysis process relies on collecting failed components for subsequent examination of the cause or causes of failure using a wide array of methods, especially microscopy (OLM and SEM)and spectroscopy. Non-destructive testing (NDT) methods are valuable because the failed products are unaffected by analysis, so inspection sometimes starts using these methods.Metal components fail as a result of conditions to which they are exposed to as well as the stress that they experience. Often a combination of both environmental conditions and stress will cause failure.
Metal components are designed to withstand the environment and stresses that they will be subjected to. A metallurgist takes into account as much of this information as possible during analysis. The end goal of failure analysis is to provide a determination of the root cause and a solution to any underlying problems to prevent future failures. Failure and damage analysis services include for example: material assessment, metals investigation, fracture study, electronics evaluation, fire damage investigation, design review and many more.
Analysis of a failed part can be done using destructive metallurgical testing. Destructive testing involves removing a metal component from service and sectioning the component for analysis. Destructive testing gives our failure analyst the ability to conduct the analysis in the lab and perform tests on the material that will ultimately destroy the component. Non destructive testing is a test method that allows certain physical properties of metal to be examined without taking the samples completely out of service. NDT is generally used to detect failures in components before the component fails catastrophically.
Our capabilities include:
Gas Pipeline Rupture and Explosion Due to Localized Corrosion and Cathodic Protection Shielding
The early stages of failure analysis include the collection of background information and the selection of appropriate samples for laboratory testing. Additional steps should include site inspection, a timeline history of the failure, material specifications, review of maintenance and repair records, number of past failures for the same component and any material substitutions made. A visual examination of the failed part or structure, as well as non-destructive testing of the component, with extensive photographic documentation should be performed first. The failed parts selected for laboratory testing and analysis should be carefully stored or protected during transport to prevent any damage to the fracture surfaces from humidity, dust, and dirt.
A macroscopic visual examination of the fracture surface and external surfaces of the part begins the investigation and will be followed by microscopic examinations. An optical stereo microscope examination at magnifications of 50X or less will help to reveal fracture surface details, confirm fracture initiation locations and mode of failure, and reveal possible evidence of surface damage at the locations of fatigue crack initiation. There are differences observed in fatigue fracture surface appearances caused by the magnitude of the applied stress and the remaining cross sectional area when the fracture passes through each area. The main differences are observed by macroscopic visual fractography. Fatigue fracture surfaces typically show two distinct regions: the fatigue crack initiation and propagation region and the final overload region. In the final overload region, the presence of slanted 45 degree shear zones and their elongated fibrous dimple structure, or brittle cleavage features are indicative of rapid loading conditions.
Metallographic examination by optical light microscopy in the range of 100x to 1000x is required to identify the microstructure and heat treat condition of the material, and to identify any possible defects originating from material processing or heat treatment. Many fatigue cracks can initiate from small defects. Scanning electron microscopy (SEM) would assist in characterization of type of fracture and pinpointing the source of crack initiation. Chemical analysis of the component will help to determine if the material has been heat treated for maximum strength as resistance to fatigue increases with increasing strength. The presence of alloying elements could be ascertained by scanning electron microscopy equipped with energy dispersive x-ray spectroscopy (EDS) for elemental analysis.
Mechanical properties should be verified and compared with specifications when available. Verification of mechanical properties assumes that the original design and material selection were correct but rules out incorrect material substitutions. Tensile tests should be performed if the size of the sample is sufficient. Hardness or microhardness testing can also be performed in lieu of tensile testing if the components are small, or if surface decarburization or carburization are present.
Analysis of the evidence collected is the final stage of a failure investigation. Identification of the fracture initiation site, defects or imperfections if present, size of the fatigue propagation zone compared with the size of the final failure zone, and material properties can be used to provide recommendations for corrective action. A final report including all relevant data, analysis, and recommendations is compiled and presented to the client. In litigation investigations, the client may not be interested in the recommendations section of the report.
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 Dr. Zee at 412-952-9441 if you have any questions or need technical information.