Visual Testing Ch 1,2,3,6,7,8,9

ASNT formally recognized visual testing as an NDT method in

1988

Visual testing is unique in that it

The only method that reveals the discontinuities directly

One of the first aids used in visual testing was developed for medical industry and was called

Endoscope

One of the advantages of visual testing is it can be used

Anytime during the manufacture or life of the product

Surface discontinuities that are located with visual testing include

Cracks open to the surface in all materials

A limitation of visual testing is the

Need for discontinuities to be surface breaking

Visual testing differs from other NDT methods in that

The discontinuities become visible to the eye

Visual testing might be called the _____________ of all NDT.

Foundation

The difference between different forms of electromagnetic radiation is their

Wavelength

Visible light is defined as electromagnetic radiation observed by the human eye and is in the range of

400 to 700 nanometers

The 'candela' is an SI unit that measures

The intensity of a light source

As light moves away from the source, the intensity is reduced. this is because

Light becomes more diffused as it moves away from the source

As light strikes a rough or faceted surface, it is

Reflected in a number of directions

Light incident on a material

may be absorbed, reflected or transmitted depending on the material

A luminance difference from a crack as compared to the rest of the surface of the test object will produce what is known as

Contrast

Field inspections often require the inspector to

Wear personal safety equipment, use additional lighting and be aware of hazards in the inspection area

The eyes contain photoactive cells, which send signals to the brain that are then formed into an image. Familiar images are quickly identified by the brain; however new images of discontinuities arriving in the brain

May often be overlooked and leave the discontinuities to remain undetected as they are unknown images.

White light is

A mixture of colors or wavelengths of light

A reflectivity of 0.3 for a transparent material means that

30% of the incident light is reflected

During a visual test, a contrast between two points on a surface is established by differences in

Reflectivity

Artificial light is used for visual testing because

it can be controlled and kept constant

The units of measurement for illumination are the

Foot-candle and Lux

Which of the following would include the use of fiber optic cables to perform visual testing?

remote visual testing

Which of the following would have an effect on the sensitivity of a direct visual test?

Corrosion on the surface

When performing colour discrimination exam on a potential visual inspector for testing of unpainted steel welds, the colour discrimination should focus on

Shades of gray

Which of the following would be acceptable for performing a direct visual test as defined by most standards?

The eye is at 18 in from the part surface and at a 45 degree angle from the plane of the exam surface

Which of the following tools would only be considered when performing remote visual testing?

Robotic devices

The most reliable choice for visual testing when all techniques are possible and available would be

Direct visual testing

Visual testing would typically include all of the following except

Performing a chemical analysis

In general the minimum light intensity required during weld inspection is

100 FC or 1076 lux

What aid is often available to the inspector to help interpret questionable indications during direct viewing of a test object?

Handheld magnifier

A visual testing technique that is most suitable for non opaque materials is called

Translucent

Direct and remote visual testing are defined as separate working techniques based on which of the following features?

The existence of a mechanical aid to the light path between the test surface and the operator's eye

When the molten metal is under a constantly applied force toward the mold, it is known as

Dynamic casting

Which of the following casting discontinuities are created during solidification that can cause the area between a thicker section and a thinner section to break

Hot tears

Cold shuts are a very common casting discontinuity and

Their abrupt nature makes them crack originators

All of the following are casting discontinuities except

Laminations

Which of the following is a visible discontinuity in rolled products?

Rolled in scale

In the US, a discontinuity is typically considered linear if

The length is more than 3x the width

Porosity appears in any of the following forms except

Adhering

Casting processes are considered either

Static or dynamic

Most codes and standards restrict

Excessive reinforcement

In most codes, maximum reinforcement is based on

Material thickness

Personnel performing visual testing are required to be certified in accordance with

Their employers written practice that is based on SNT-TC-1A

Judging the acceptability of welds must be based on

Referencing the applicable code, standard or specification

ASME B31.3 covers

Process piping

Most codes and standards require that visual testing be performed

Before, during and after welding

Which of the following is a correct statement?

Visual testing may miss some discontinuities and need to be supplemented by other NDT methods

Which of the following is a correct statement?

Visual testing techniques and procedures are different for each industry and product form

Before performing a visual inspection the completed weld must be brushed or mechanically cleaned from slag or oxide to

Avoid obscuring imperfections

The heat affected zone (HAZ) must be inspected for

Cracking

Light passes through the cornea and the crystalline eye lens where the paths of the rays are changed by

Focussing and refraction

If the maximum refractive power of the eye is such that light rays can only be focussed in front of the retina, it is called

Nearsightedness

The retina contains two types of neural cells referred to as

Rods and cones

Vision acuity is the ability of the eye to ______________ a fine detail or character such as a letter.

Resolve

Which acuity measure refers to a standard distance of 20 ft and compares the actual vision with the standard for far vision?

Snellen chart

Which test is a vision performance test rather than a measure of vision acuity?

Jaeger

The ability for colour differentiation may be determined by the use of

Ishihara charts

Cracks in a smooth, well-reflecting metallic surface can most likely be made visible by

Luminance contrast

Artificial lighting used for visual testing is usually provided by

Incandescent or luminescent radiators

A single unit of light produced within a light emitting diode is a

Photon

An electric arc passing between electrodes through gases would produce radiant energy in which type of light?

Fluorescent

Ideal visual testing conditions should

Minimize glare and fatigue

Metallic surfaces can be opaque as well as reflective. In addition

They can be specular when the surface is smooth and will diffuse light when the surface is rough

Non-metallic test objects such as plastic, aramid fiber, or glass all have some degree of transparency. In most cases

Diffuse light is directed at one side of the material, while the sensor (eye or camera) is located on the other.

Glare or excessive exposure of light may be caused by

Reflections from walls, inadequately located directional lights, or reflections from inspected parts

The probability of the discontinuity detection increases as the________________increases.

Luminance contrast ratio

Artificial light for visual testing is usually provided by

Incandescent and luminescent radiators

Which type of bulb of the following is the longest lasting?

Light emitting diode (LED)

In general, the minimum light intensity required for tasks with low contrast or very small test objects is

100 FC

Excessive light exposure to the human eye is called

Glare