The field of Nondestructive Testing (NDT) is a very broad, interdisciplinary field that plays a critical role in assuring that structural components and systems perform their function in a reliable and cost effective fashion. NDT technicians and engineers define and implement tests that locate and characterize material conditions and flaws that might otherwise cause planes to crash, reactors to fail, trains to derail, pipelines to burst, and a variety of less visible, but equally troubling events. These tests are performed in a manner that does not affect the future usefulness of the object or material. In other words, NDT allows parts and material to be inspected and measured without damaging them. Because it allows inspection without interfering with a product's final use, NDT provides an excellent balance between quality control and cost-effectiveness. Generally speaking, NDT applies to industrial inspections. Technology that is used in NDT is similar to those used in the medical industry; yet, typically nonliving objects are the subjects of the inspections. 
In destructive testing, tests are carried out to the specimen's failure. These tests are generally much easier to carry out, yield more information and are easier to interpret than nondestructive testing. Testing of an object is often done in view of future use, which would make destructive testing pointless. However, it can be useful if the result gives information about similar specimens, which are not tested.
AAS Co. provides a variety destructive test capabilities to determine the mechanical properties of materials. Specializing in welding procedure and welder performance qualifications, AAS employs a range of cutting, machining, and sample preparation equipment for rapid turn-around and accurate reporting of test results.
Aria Azmoon Sanat provides following Nondestructive and Destructive testing services:

Visual and Optical Testing (VT)
The most basic NDT method is visual examination. Visual examiners follow procedures that range from simply looking at a part to see if surface imperfections are visible, to using computer controlled camera systems to automatically recognize and measure features of a component.

Ultrasonic testing (UT)
Ultrasonic testing is an inspection method which uses high frequency sound waves, well above the range of human hearing, to measure geometric and physical properties in materials. Sound waves travel at different speeds in different materials. However the speed of sound propagation in a given material is a constant value for the material.
Ultrasonic testing uses electrical energy in the form of an applied voltage, and this voltage in converted by a transducer to mechanical energy in the form of sound waves. The transducer accomplishes this energy conversion due to a phenomenon referred to as the "piezoelectric" effect. This occurs in several materials, both naturally-occurring and man-made; quartz and barium titanate are examples of piezoelectric materials of each type. A piezoelectric material will produce a mechanical change in dimension when excited with an electric pulse. Similarly, this same material will also produce an electric pulse when acted upon mechanically.
To perform ultrasonic testing, the transducer is attached to an electronic base unit. Following a prescribed startup sequence and calibration procedure, the base unit acts as an electronic measuring device. This machine will generate precise electronic pulses which are transmitted through a coaxial cable to the transducer which has been placed in acoustic contact which the test object. These pulses are of very short duration and high frequency (typically 1 to 10 million Hz, or cycles per second). This high frequency has the ability to be directed precisely, much like the beam from a flashlight.

Radiographic testing (RT)
Radiography is a nondestructive test method based on the principle of preferential radiation transmission, or absorption. Areas of reduced thickness or lower density transmit more, and therefore absorb less, radiation. The radiation which passes through a test object will form a contrasting image on a film receiving the radiation.
Areas of high radiation transmission, or low absorption, appear as dark areas on the developed film. Areas of low radiation transmission, or high absorption, appear as light areas on the developed film. The thinnest area of the test object produces the darkest area on the film because more radiation is transmitted to the film. The thickest area of the test object produces the lightest area on the film because more radiation is absorbed and thus less is transmitted.

Magnetic particle testing (MT)
This particular nondestructive test method is used primarily to discover surface discontinuities in ferromagnetic materials. While indications can be observed from subsurface discontinuities very near the surface, they are very difficult to interpret, and often require testing by other methods. Other NDE techniques are usually required for subsurface discontinuity detection and interpretation. However, surface discontinuities present in a magnetized part will cause the applied magnetic field to create "poles" of opposite sign on either side of the discontinuity, creating a very attractive force for iron particles. If iron particles, which are "magnetic particles" since they can become magnetized, are sprinkled on this surface, they will be held in place by this attractive field to produce an accumulation of iron particles and a visual indication of the discontinuity.
While several different types of magnetic particle tests exist, they all rely on this same general principle. Therefore, all of these tests will be conducted by creating a magnetic field in a part and applying the iron particles onto the test surface.

Penetrant testing (PT)
In general terms, penetrant testing reveals surface discontinuities by the bleed out of a penetrating medium against a contrasting colored background. This is accomplished by applying a penetrant (usually liquid) to the cleaned surface of the test piece. Once this penetrant is allowed to remain on the surface for a prescribed time (dwell time), it will be drawn into any surface opening by capillary action. Subsequent removal of excess pentrant and application of a developer draws remaining penetrant from discontinuities. The resultant indications are shown in high contrast and magnify the presence of the discontinuity so it can be visually interpreted.
There are two primary ways in which penetrant materials are grouped: specifically, the type of indication produced, and the method of excess penetrant removal. The two penetrant indications are visible and fluorescent. The visible dye (usually red) produces a vivid red indication against a white developer background when viewed under white light. The fluorescent penetrant produces a greenish, fluorescent indication against a light back ground when observed under ultraviolet (black) light. Since the human eye can more readily perceive a fluorescent indication than a visible indication, use of fluorescent penetrant can result in a more sensitive test.

Eddy current testing (ET)
When a coil carrying AC is brought near a metal specimen, eddy currents are induced in the metal by electromagnetic induction. The magnitude of induced eddy currents depends on many factors, and the test coil is affected by the magnitude and direction of these induced eddy currents. When the test coil is calibrated to known standards, the eddy current method can be used to characterize many test object conditions.
Eddy current testing is a highly versatile test method. It can be used to measure the thickness of thin sections, electrical conductivity, magnetic permeability, hardness, and the heat treatment condition of test objects. This test method can also be used to sort dissimilar metals and to measure the thickness of nonconductive coatings on electrically conductive test object. In addition, this method can be used to detect cracks, seams, laps, voids, and inclusion near the test object's surface.

Acoustic emission testing (AE)
Acoustic emission examination is rapidly maturing nondestructive testing method with demonstrated capabilities for monitoring structural integrity, detecting leaks and incipient failures in mechanical equipment, and for characterizing materials behavior. The first documented application of acoustic emission to an engineering structure was published in 1964 and all of the available industrial application experience has been accumulated in the comparatively short time since then.
Acoustic emission differs from most nondestructive methods in two significant respects. First, the energy that is detected is released from within the test object rather than being supplied by the nondestructive method, as in ultrasonic or radiography. Second, the acoustic emission method is capable of detecting the dynamic process associated with the degradation of structural integrity. Crack growth and plastic deformation are major sources of acoustic emission. Latent discontinuities that enlarge under load and are active sources of acoustic emission by virtue of their size, location or orientation are also the most likely to be significant in terms of structural integrity.

Leak Testing (LT)
Several techniques are used to detect and locate leaks in pressure containment parts, pressure vessels, and structures. Leaks can be detected by using electronic listening devices, pressure gauge measurements, liquid and gas penetrant techniques, and/or a simple soap-bubble test.