WHAT IS NON-DESTRUCTIVE TESTIING
Metal and metal forging has been prevalent since before 6000 BC. The metal smiths, since those primitive days of metal processing, developed various methods to estimate the temperature of the metal in the furnace to gauge if it was ready for its intended use (hammering, casting, heat treatment, etc.)
The visual indicator, in this case, was the color of the heated/superheated metal, which gave the metal smith an idea of its temperature and properties. The visual testing color indication chart for a steel alloy with a 0.40 carbon percentage is shown in the image below:
Color indication chart for heated metal during forging processes (Image credit: production machining)
Modern-day techniques allow the usage of a no-contact infrared-based measuring device, called a pyrometer, for the aforementioned purpose.
Non-destructive testing is a method for qualitatively analyzing structures, materials, products, and/or machinery. This evaluation technique provides the opportunity to assess the status of structures, machinery, and materials without causing any damage or inhibiting their purpose.
The types of non-destructive testing available in today’s day and age are as follows:
- Visual Inspection
- Magnetic Particle Inspection
- Dye Penetrant Inspection
- Ultrasonic Testing
- Phased Array Ultrasonic Testing
- Leak Testing
- Radiographic Testing
- Acoustic Emission Testing
Non-destructive testing permits the evaluation of the test subjects (materials, products, or structures) during manufacturing, usage, and after failure. This makes it a viable testing option for automation, construction, petrochemical, aerospace, mining, and electrical power industries.
NEED FOR TESTING
The evolution of technology and the availability of new resources, materials, and production methodologies pose further challenges in ensuring their safety, integrity, and feasibility.
Material testing furnishes the option to eliminate trial and error and squandering of time, material, resources, and labor.
The following are the reasons why material testing is imperative:
- It helps to gauge the test subject’s adherence to industry standards.
- Material testing assists in the testing of products during their manufacturing process.
- Its aids in checking the viability of prototypes, products, or materials for their intended use.
- It can also be used for quality and uniformity checks on manufacturing equipment, processes, and products.
WHAT IS DESTRUCTIVE TESTING
Destructive testing analyzes the behavior of a material, structure, or product until the point of breakdown or failure. Certain quantifiable properties like toughness, hardness, elongation of material, and tensile strength are undetectable by non-destructive methods, as applying load is an indispensable step.
The destructive testing process involves constant load application until the subjects undergo deformation or failure. The test subjects cannot be utilized after the destructive testing procedure has been carried out on them and need to be scrapped or reworked after thorough analysis.
Mass production units often use destructive testing methods to obtain quantifiable data on the performance of their products under real-life environmental stresses and usage. Products like gaming controllers, brakes, keyboards, and even cars are intentionally utilized to the point of destruction to get a real-world idea of their longevity and efficiency.
Crash testing of vehicles is vital in understanding the safety of the passenger and goods carried, if any, in the event of an accident, fire, or untoward mishaps that are likely during their operation. Destructive testing in these cases may cause a waste of resources. Still, they provide a realistic understanding of the performance of vehicle safety features, like airbags, and potential risks that may expedite further damage and help minimize any harm caused.
A variety of destructive techniques are available for the evaluation of structures, materials, and products, some of which are:
- Tensile Testing
- Bending Test
- Compression Test
- Hardness Testing
- Creep Analysis
- Charpy Impact Test
- Fatigue Test
- Ductility Test or Cupping Test
Destructive tests can be used to replicate failure during operation and curb catastrophic accidents, recall products, and provide accurate, measured data on the performance and longevity of test subjects.
METHODS OF DESTRUCTIVE TESTING
The methods used in Destructive testing are varied and provide rich data, albeit at the cost of the tested subject. The methods are as follows:
Tensile Test:
This test is conducted by tugging the sample to analyze its behavior under tension. The plastic deformation, reduction in diameter, and point of failure are noted; hence, the strength properties of the material can be calculated.