Material Failures and Testing

Everything is made up of some kind of material, including what we see on the surface and microscopic surfaces we can't see with the naked eye. Following a failure, our experts examine the nuances of a material's composition. 

In order to analyze product-related failures, Envista's material failure experts have to understand the features and properties that differentiate materials like metals, concrete, plastics, wood, ceramics, etc. Each material requires specific scientific and analytical techniques that allow our experts to forensically determine the cause of failure.

The types of material analysis Envista provides include: 

Material Failure Analysis on Corrosion 

Investigating material failures related to corrosion is as complex as it is common. Understanding corrosion can be difficult due to the number of potential corrosion processes and the variety of potential operating environments. Chemicals, water, and bacteria can all lead to material corrosion, which can result in shortened lifetimes or catastrophic failures.

Envista Corrosion Experts

Corrosion involves the chemical interaction between materials and the environment they are in. Corrosion occurs on metals as well as on polymeric materials and ceramics.

The causes of corrosion are as varied as the materials it occurs on. Corrosion can occur over the entire surface of a material. It can also be localized, occurring only at specific sites like pits, crevices, or even under paint if a small hole forms within and allows contaminants to penetrate. Types of corrosion include:

• Galvanic corrosion, which is when two electrochemically dissimilar metals have electrical contact and are exposed to an electrolyte
• Environmental cracking mechanisms like stress corrosion cracking, hydrogen-induced cracking, or liquid metal embrittlement
• Flow-assisted corrosion, which occurs when there is high-speed flow, impinging flow, or cavitation
• Dealloying, which occurs when one element in an alloy is disproportionately attacked in a metal (e.g. dezincification, where zinc is dissolved from brass, leaving a porous and weakened copper-rich material in its place)

From dissimilar metals and galvanic corrosion to hydrogen embrittlement, Envista Forensics experts can determine the corrosion mechanisms that have led to your component failures and provide you with a plan for future failure prevention.

Our specialists use tools like state-of-the-art X-ray and spectrometry equipment to identify corrosion constituents, pathways, and failure modes. We can examine and isolate various residues and other foreign deposits throughout the entire system where corrosion has occurred, and our metallurgical experts can assess the physical root cause of corrosion.

Material Failure Analysis on Defective Material

Examining defective materials may sound straightforward, but situations involving improper material selection or manufacturing defects can quickly become complex. Anything from expired shelf life and contact with chemical agents to mishandling and environmental factors can compromise the material properties and life of a component.

To forensically investigate such failures, one must analyze evidence with a deep understanding of material properties and appropriate instruments and techniques. 

Key Components of Defective Material Investigations

Envista Forensics has investigated numerous situations where the material was defective and led to a catastrophic failure. Our familiarity with industry standards including ASTM, SAE, ASME/ANSI, and ISO makes us uniquely qualified to investigate all types of material failures.

When material failure investigations are conducted, some key components to review are:

• Initial design documents to evaluate the material and its appropriateness in the application (e.g. more corrosion-resistant material that could have been used)
• Material chemistry and mechanical properties
• Procurement specifications to make sure the proper material was ordered
• Documents shipped with the purchased material to see if the correct material was delivered, although testing should still be conducted regardless of what the documents say
• Macroscopic and microscopic examinations of any fracture surface
• Metallographic analysis of the component

Envista's experts are well-versed in using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), Fourier-transform infrared spectroscopy (FTIR), hardness testing, and various other analytical techniques to determine the mechanism and cause of material failure.

Examining Defective Materials

A diverse range of materials is used in consumer products and across various industries. An equally wide range of techniques is used to examine these materials. Our expert engineers and consultants are familiar with all sorts of materials, as well as the specialized equipment and techniques used to analyze them, including:

• Advanced composites
• Building materials
• Ceramics
• Coatings
• Concrete
• Metals
• Plastics
• Wood products

Using a series of scientific methods, Envista Forensics specialists can identify issues like stress risers, voids, material softening, and degradation, as well as diagnose the root cause of the failure.

Our analysis and expert reports can help you make better engineering and management decisions, prevent further catastrophic material failures and improve your business operations. In case of material failure, we will guide you through every step of the process, working according to your schedule and budget.

Material Failure Analysis on Fatigued Material

Fatigue loading of mechanical parts or materials results from inconstant structural loads that change over time and can result in failures without warning. These loads can change slowly or very rapidly. As the loads vary, so does the stress level within the component. When considered during design, load variations are foreseeable and manageable. However, if fatigue loading is not considered during design, or if the part is used in an unexpected way or is defective, the part can fail.

Fatigue Loading of Material or Mechanical Parts

Envista Forensics experts can determine how and why a part failed. Failure may be due to design, manufacturing, or the environment in which the part was used. The design may not have adequately considered all variable loads the part or material would encounter, it may have been manufactured with a virtually undetectable defect, or the environment it is used or stored could have compromised its properties.

Based on composition and manufacturing processes, some materials used for components hold up better over time to fatigue loading conditions. When considering material and part issues, one needs to consider:

• The static and dynamic loads experienced directly leading to fatigue failure
• Whether a defect within the component from the start led to fatigue failure
• Whether the correct material or part was used, tracking this from design to the manufacturing and installation phase
• Whether the environment where it was stored or used was conducive to the lifetime of the material or part

Fatigue Loading Analysis

The root cause of fatigue loading is investigated by physically examining the material or part to determine its properties (e.g. metallographic or grain structure) and signs of stress through microscopic and macroscopic means. Envista Forensics experts also review load history and fatigue lifetime and algorithms, which require performing physical measurements and numerical calculations.

Most fatigue failure modes result from a combination of the following conditions:

• Simple fatigue, or loss of strength over multiple loading cycles, which often leads to other failure modes
• Fractures
• Yielding, or excess stress
• Deflection, where the material or a part of it is too flexible
• Buckling, where the material is not thick enough and the stress applied from both sides is too great
• Creep, where the body of the part of material deforms over time due to stress and/or heat

Though these issues may seem straightforward, rigorous analysis is needed to get to the true root of a fatigue issue. Our engineers and consultants have the tools and expertise to identify what caused your unique fatigue loading incident and help you understand how to avoid these failures in the future.