Destructive testing

What is the destructive testing of metals and why is it important? The high specification materials that Special Piping Materials supplies to clients around the world is subject to rigorous testing to ensure that they can perform in high-stress environments. Let’s explore what destructive testing is and how some of the tests are carried out.

Corrosion, heat and pressure are all things that some of Special Piping Materials products will have to endure. Subsequently, whole systems can be reliant on the metal that the products are manufactured from in the first place.

With this is mind, it becomes obvious as to why destructive testing is so important. It is needed to ensure that our range of products, such as round bar, forged fittings and seamless pipe, perform in the way that they are required to.

All stock held by Special Piping Materials is tested in accordance with respective ASTM standards, ASME standards and relevant international specifications. If we need to subcontract our testing to an external company, then we use NAMAS/UKAS and ISO 17025 approved test houses to ensure reliability and credibility.

Destructive testing includes a whole range of procedures, including the following typical tests:

• – Product analysis
• – G48 corrosion test
• – Micrographic examination
• – Ferrite and phase count
• – Charpy impact test
• – Tensile test

An overview of destructive testing

Historically, destructive testing has been the preferred testing method of checking metals as it was largely thought that it was the only way to achieve accurate results. As a category, it has been around for as long as humans have been able to break down metals to understand its structure and compare it to other samples.

Generally speaking, destructive testing methods are designed to intentionally make a material fail so that its robustness can be analysed, and the point of failure can be analysed. Analysing and recording the failure of the material is sometimes done with high-speed cameras, sound detectors or stress gauges. This is so that the exact moment failure occurs can be detected and so it can be viewed later in slow motion.

Destructive testing procedures can either follow specific standards or they can be tailored to reproduce a particular environmental condition.

Advantages of destructive testing

Destructive testing does have many advantages. These include the following:

• – Verifies properties of a material
• – Determines quality of welds
• – Helps you to reduce failures, accidents and costs
• – Determines impact resistance
• – Analyses ductility
• – Can produce knowledge about yield and ultimate tensile strength, fracture toughness and fatigue strength.
• – Can form a key part of engineering critical assessments
• – Provides materials characterisation
• – Can find fabrication validation
• – Predicting service life

It also allows you to look at the items on a molecular level to determine the exact chemical composition of an object.

Often, destructive methods of testing can be used effectively to determine the stability and performance of a material or product before it is mass produced. This means that you can understand its durability and before it reaches the wider market.

Also, destructive testing is often easier to carry out and easier to interpret than its non-destructive testing counterparts.

The main negative of destructive testing is made obvious by its name; That it results in the test sample or area being irreversibly damaged or destroyed during the procedure.

Examples of destructive testing

There is a wide range of different destructive testing procedures, all of which Special Piping Materials can arrange to be carried out in specific and licensed test-houses around the world. Here are just a few of them:

• – Tensile strength test: Tensile testing, sometimes known as tension testing, is a controlled engineering test whereby a sample undergoes controlled and sustained tension until failure occurs. Properties such as tensile strength and breaking strength can be determined through the results of this test. It allows specialists to select the right type of material for an application, predict how it will perform in both ‘normal’ and extreme circumstances, verify whether industry specifications have been met or even demonstrate proof that a product can perform in a new environment.

• – Charpy impact test: Impact testing of metal is carried out to determine the specific image resistance or the exact toughness of the material in question by calculating the amount of energy is absorbed during the fracture. Specifically, the Charpy Test method determines the toughness or impact strength of the material in the presence of a flaw or notch. This destructive test involves striking a standard notched specimen with a controlled weight pendulum swung from a set height. The amount of energy absorbed by the material during fracture is then measured and analysed. Because toughness can be affected by temperature, Charpy tests are often repeated many times at different temperatures. This allows charts to be plotted that demonstrate whether a material is more brittle or ductile at high or low temperatures.

• – Bending testing: Bending tests are self-explanatory by their name; They deform the test material to cause a bend, not a fracture, to occur. They are often carried out to determine the ductility of a material and are sought-after to test tensile, compression, and fatigue characteristics. These are particularly important in heavy industry scenarios where materials may be subjected to potentially bending forces.

• – Corrosion testing: Almost all materials will corrode if they are exposed to sufficiently toxic conditions which can include moisture in the atmosphere, seawater, nuclear chemicals and many more besides. This is why corrosion testing is particularly important in heavy industries like desalination or nuclear power plants. Thankfully, in most scenarios, corrosion can be predicted and mitigated by selecting the right materials that can survive in specific conditions. Corrosion testing may involve electrochemical testing or even direct exposure tests in simulated environments.

There are many other types of destructive testing available which include:

• – Product analysis
• – Micrographic examination
• – Ferrite and phase count
• – Hot yield test
• – Flaring test
• – Ring flaring test
• – Hardness test
• – Spectral analysis

Speak to your account manager at Special Piping Materials today to find out what testing we can arrange in accordance to internationally recognised standards and, what’s more, how we can project manage the procedures for you.

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