Nondestructive Evaluation overview
Nondestructive evaluation (NDE) is an interchangeable term with Nondestructive Testing (NDT), a process which has long been used by industry to inspect and qualify parts. With major technological advancements over the years, many different techniques for nondestructive evaluation have been added to serve growing industry needs. Commonly, users outsource nondestructive evaluation projects to specialized nondestructive testing labs for a quick and accurate part analysis.
What is NDE?
NDE stands for Nondestructive evaluation, which is substitutable with the terms nondestructive testing (NDT) and nondestructive inspection (NDI). The difference between NDE, NDT and NDI is merely a preference of terms chosen by the user. According to the American Society of Nondestructive Testing (ASNT), Nondestructive evaluation is the process of inspecting, testing, or evaluating materials, components or assemblies for discontinuities, or differences in characteristics without destroying the serviceability of the part or system.
The part being inspected is available after the test process is complete, without any damage to the part in its entirety. A set of different nondestructive testing techniques are available for users, depending on project needs.
Uses of NDE inspection
Nondestructive evaluation is an extremely useful tool for quality control, in regards to industrial applications. The following is a brief overview of the many uses of NDE evaluation:
- Inspect, test and evaluate part composition and material
- Locate internal discontinuities
- NDE Test: product repeatability and reliability
- Quality assurance management tool
- Control manufacturing process quality control
- NDE inspection is useful for Research & Development
- NDE / NDT can help preserve and increase quality of a part in its entirety
- Use across all stages of a parts life cycle, from research and development to raw material to pre-production/production to failure investigation
- NDE for condition monitoring
- Residual life assessment
- NDE nondestructive feature can help find, size, locate surface and internal flaws
- NDE evaluation can be used as a tool to approve and reject production parts
- Accident prevention using NDE test methods
- Reduce costs by saving cost of manufacturing part twice (NDE nondestructive)
- Enhance product reliability
- Nondestructive examination can help determine acceptance according to specific requirements
- Deliver perceptive data and evidence on repair measures
- Dimension of mechanisms and physical structure
- Asses equipment condition
- Product appraisal & troubleshooting
When is NDE necessary?
NDE testing can be applied during any stage of a parts manufacturing life cycle. NDE evaluation techniques can be used as a tool to determine the feasibility of manufacturing method and the reliability of produced part. NDE techniques can be applied during any of the following stages of a parts life cycle for a nondestructive examination:
- Research and development
- Design and feasibility study
- Comparison analysis of manufacturing methods by inspection of the quality of resulting parts
- Pre-production inspection
- Production qualification
- Manufacturing and fabrication stages
- In-service evaluation
- Failure investigation
Benefits of NDE testing
Non destructive evaluation provides users with multiple direct and indirect benefits that provide additional value to a part, in the short and long term. The main direct benefit is the fact that nondestructive evaluation methods can test and inspect parts without causing damage, applying external force/pressure or destroying the part. This saves users additional cost and time of manufacturing a part for testing, while simultaneously improving quality control processes. Furthermore, most nondestructive techniques allow for internal part inspection, providing users with extensive part data without destroying the part.
Types of NDE methods
The six primary testing methods include magnetic particle testing (MT), liquid penetrant testing (PT), radiographic testing (RT), ultrasonic testing (UT), electromagnetic testing (ET) and visual testing (VT). Below, all nondestructive evaluation methods are listed:
Surface Examination Methods
- Visual Testing (VT)
- Magnetic Particle Testing (MT)
- Liquid Penetrant Testing (PT)
- Electromagnetic Testing (ET)
Volumetric Examination Methods
- Ultrasonic Testing (UT)
- Radiographic Testing (RT)
Condition Monitoring Methods
- Infrared Testing (IR)
- Vibration Analysis (VA)
Integrity Examination Methods
- Leak Testing (LT)
- Acoustic Emission Testing (AE)
Special NDT Methods
- Guided Wave Testing (GW)
- Laser Testing Methods (LM)
- Magnetic Flux Leakage (MFL)
- Neutron Radiographic Testing (NR)
Applications of NDE testing
Non destructive evaluations’ primary use is for industrial applications. Assisting in quality control for different industries, nondestructive evaluation can be utilized for different applications including but not limited to:
- Weld Verification
- Sustainability of material composition
- Research & Development
- Material thickness measurement analysis
- Dimensional analysis
- Comparison analysis to qualify resulting part to initial part design
- Manufacturing inspection for identifying failures
- Application vary across multiple different industries, including but not limited to:
- Military & Defense – ex. Ballistics
- Automotive – ex. Seat belts
- Medical Devices – ex. Insulin Pens
- Manufacturing – ex. Research & Development
- Packaging – ex. Leakage analysis
- Aerospace – ex. Castings
NDT/ NDE inspection certification
A form of NDT/NDE certification is authorized and recognized by the American Society of Nondestructive Testing (ASNT). In order for users to be able to operate NDE systems, analyze the results and conduct testing, they must be certified to use the equipment. This particulat certification includes a pre-determined number of hours for training, a written exam and experience using the equipment under authorized supervision. Individuals interested in becoming certified have access to two different approaches:
Employer based certification – employer highlights the amount of hours for training, written exam requirements (according to industry practice) and supervised experience necessary to be certified.
Personal central certification – certification can be acquired from authorized certification facilities which are recognized by industry and employers – all written exam requirements, training and experience are according to industry standards.
Levels of NDE certification
There are three distinct levels of certification under non destructive evaluation certification:
Level 1: Individuals certified with level 1 are restricted to perform only certain calibrations or tests under supervisions by a higher level individual. They are able to report results, and are expected to follow instructions regarding procedure.
Level 2: Individuals certified with level 2 are open to set up and calibrate inspection equipment, perform inspection according to standards and codes. These individuals are able to provide instruction to level 1 technicians, as well as report, interpret and evaluate results. Have knowledge of standards and codes.
Level 3: Individuals certified with level 3 are specialized, experienced and qualified engineers or technicians. These technicians are able to direct NDT labs, and have extensive knowledge about testing, service and manufacturing processes as well as codes and standards.