Standard Practice for Inspection of Transparent Parts by Prism

SIGNIFICANCE AND USE
Prisms are useful tools for viewing areas otherwise obstructed or hidden from normal viewing. For example, transparency bolt holes, voids, and delaminations that are covered by edge strips or frames can be seen through a prism. The prism, once put against the transparency, with a coupling agent to wet the surfaces, allows viewing of the area below where the prism is placed.
SCOPE
1.1 Aerospace transparencies undergo high stresses induced by flight, environmental, or other factors. The transparency attachment points are especially subject to fatigue. These areas of fatigue are often obstructed or hidden from normal inspection. An inspector, following the techniques described in this practice, shall use a prism to view damage located near transparency bolt holes, voids, and delamination that are hidden by edge strips or frames.
1.2 The purpose of this practice is to provide acceptable methods for performing prism inspections of transparent materials with specific emphasis on aircraft windscreens and canopies. Caveats and lessons learned from experience are included to assist authors in writing tailored inspection instructions for specific applications.
This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

General Information

Status
Historical
Publication Date
31-Oct-2006
Current Stage
Ref Project

Relations

Buy Standard

Standard
ASTM F2108-06 - Standard Practice for Inspection of Transparent Parts by Prism
English language
7 pages
sale 15% off
Preview
sale 15% off
Preview

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation:F2108–06
Standard Practice for
1
Inspection of Transparent Parts by Prism
This standard is issued under the fixed designation F2108; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 3. Summary of Practice
1.1 Aerospace transparencies undergo high stresses induced 3.1 Prism inspections shall be performed with the aid of a
by flight, environmental, or other factors. The transparency prism and a wetting agent. The wetting agent is between the
attachment points are especially subject to fatigue. These areas prism and transparency to ensure good visibility.The examiner
of fatigue are often obstructed or hidden from normal inspec- looks through the prism to see the area of the transparency
tion. An inspector, following the techniques described in this below the prism. The exam is best done without bright
practice, shall use a prism to view damage located near sunlight, which causes glare. The examiner changes his angle
transparency bolt holes, voids, and delamination that are of view and inspects the area seen in the prism. A trained eye
hidden by edge strips or frames. can detect anomalies such as cracks, delaminations, and voids.
1.2 The purpose of this practice is to provide acceptable
4. Significance and Use
methods for performing prism inspections of transparent ma-
terials with specific emphasis on aircraft windscreens and 4.1 Prisms are useful tools for viewing areas otherwise
obstructed or hidden from normal viewing. For example,
canopies. Caveats and lessons learned from experience are
included to assist authors in writing tailored inspection instruc- transparency bolt holes, voids, and delaminations that are
covered by edge strips or frames can be seen through a prism.
tions for specific applications.
1.3 This standard does not purport to address all of the The prism, once put against the transparency, with a coupling
agent to wet the surfaces, allows viewing of the area below
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro- where the prism is placed.
priate safety and health practices and determine the applica-
5. Apparatus
bility of regulatory limitations prior to use.
5.1 Prism—Material shall be of the same hardness as or
2. Terminology
softer than the transparency to avoid scratches. The angles of
the prism should be set so as to maximize the viewing area. In
2.1 Definitions of Terms Specific to This Standard:
2.1.1 coupler, n—a liquid refractive index-matching agent the case of a complex shape, the position of the inspector’s
head and potential interference problems shall be considered to
or wetting agent (for example, glycerol) used to create optical
contact (coupling) between the prism and transparency. ensure the inspector can look through the prism at the proper
angles. A typical prism is a 30º–60º–90º triangle, although the
2.1.2 delamination, n—the separation of a laminate into its
constituent parts. An edge delamination is open to the lami- prism does not need to be triangular; it could be a simple
rectagon shape.
nate’s free edge. An internal delamination is contained within
the laminate. 5.2 Flashlight—A high output, halogen bulb works best.
5.3 Cover—To allow the inspector to shade the inspection
2.1.3 edge attachment, n—the means of fastening the side
edges of a transparency to the aircraft structure. Edge attach- area if the inspection is done in bright sunlight.
ments also include expansion joints and any other connection
6. Reagents
between the transparency and the aircraft structure.
6.1 Use glycerol (USPGrade) as a coupler or wetting agent.
2.1.4 prism, n—a transparent optical element with polished
6.1.1 The wetting agent shall not harm the transparency (for
plane faces for the entrance and exit sides. Prisms use
example, cause crazing), shall be clear, and shall have a high
refraction or internal reflection or both to change the direction
enough viscosity to stay in place reasonably well.
of the propagation of light.
6.2 Use distilled water.
1
This practice is under the jurisdiction of ASTM Committee F07 on Aerospace
7. Procedure
andAircraft and is the direct responsibility of Subcommittee F07.08 on Transparent
Enclosures and Materials. 7.1 Use methods shall be approved by the procuring agency
Current edition approved Nov. 1, 2006. Published December 2006. Originally
or parts manufacturer. One example is to use a water rinse to
approved in 2001. Last previous edition approved in 2001 a F2108 - 01. DOI:
clean the area of the transparency thoroughly where the prism
10.1520/F2108-06.
Copyr
...

Questions, Comments and Discussion

Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.