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InterRegs Note: Cancelled, Superseded by J114, J117, J140, J141, J339, J800 - Source SAE Handbook 1997.
MOTOR VEHICLE SEAT BELT ASSEMBLIES – SAE J4C
Report of Motor Vehicle Seat Belt Committee approved November 1955 and last revised July 1965.
1. SCOPE
1.1This SAE Standard provides for the following types of seat belt assemblies for use in motor
vehicles, in order to minimize the risk of bodily harm in an accident:
Type 1 – Lap Belt for pelvic restraint.
Type 2 – Combination of pelvic and upper torso restraints.
(Type 2a – Shoulder belt – An upper torso restraint for use only in conjunction with a lap belt as a Type 2 seat belt assembly.)
Type 3 – Combination pelvic and upper torso restraint for persons weighing 50 lb (23 kg) or less and capable of sitting upright by themselves, that is children in the
approximate age range of 8 months-6 years.
1.2 This standard specifies performance requirements, laboratory test procedures and minimal
design requirements for seat belt assemblies when worn in the seated position.
2. DEFINITIONS
Assembly
2.1 Seat
Belt
Consists of any strap, webbing, or similar device designed to secure a person in a motor
vehicle with the intention of mitigating the results of a traffic accident, including all buckles or
other fasteners, and all hardware designed for installing the assembly in a motor vehicle.
Restraint
2.2 Pelvic
A seat belt assembly or portion thereof intended to restrain movement of the pelvis.
2.3 Upper Torso Restraint
A portion of a seat belt assembly intended to restrain movement of the chest and shoulder
regions.
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2.4 Hardware
Any metal or rigid plastic part of the seat belt assembly.
2.4.1 Buckle
A quick release connector which fastens a person in a seat belt assembly.
Hardware
2.4.2 Attachment
Any or all hardware designed for securing the webbing of a seat belt assembly to a motor
vehicle.
Hardware
2.4.3 Adjustment
Any or all hardware designed for adjusting the size of a seat belt assembly to fit the user,
including such hardware that may be integral with a buckle, attachment hardware, or
retractor.
2.4.4 Retractor
A device for storing part or all of the webbing in a seat belt assembly.
Retractor
2.4.4.1 Nonlocking
A retractor from which the webbing is extended to essentially its full length by a small external
force, which provides no adjustment for assembly length, and which may or may not be
capable of sustaining restraint forces at maximum webbing extension.
2.4.4.2 Automatic Locking Retractor
A retractor incorporating adjustment hardware by means of a positive self locking mechanism
which is capable when locked of withstanding restraint forces.
2.4.4.3 Emergency Locking Retractor
A retractor incorporating adjustment hardware by means of a locking mechanism that is
activated by vehicle acceleration, webbing movement relative to the vehicle, or other
automatic action during an emergency and is capable when locked of withstanding restraint
forces.
2.5 Seat Back Retainer
The portion of some seat belt assemblies designed to restrict forward movement of a seat
back.
2.6 Webbing
A narrow fabric woven with continuous filling yarns and finished selvages.
2.7 Strap
A narrow nonwoven material used in a seat belt assembly in place of webbing.
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REQUIREMENTS
3. GENERAL
Occupancy
3.1 Single
A seat belt assembly shall be designed for use by one, and only one, person at any one time.
Restraint
3.2 Pelvic
A seat belt assembly shall provide pelvic restraint whether or not upper torso restraint is
provided, and the pelvic restraint shall be designed to remain on the pelvis under all
conditions, including collision or rollover of the motor vehicle. Pelvic restraint of a Type 2 seat
belt assembly, that can be used without upper torso restraint, shall comply with requirement
for Type 1 seat belt assembly in Sections 3–6 inclusive.
3.3 Upper Torso Restraint
A Type 2 or Type 3 seat belt assembly shall provide upper torso restraint without shifting the
pelvic restraint into the abdominal region. The upper torso restraint shall be designed to
minimize vertical forces on the shoulders and spine. Hardware for upper torso restraint shall
be so designed and located in the seat belt assembly that the possibility of injury to the
occupant is minimized. A Type 2a shoulder belt shall comply with applicable requirements for
a Type 2 seat belt assembly in Sections 3–6 inclusive.
3.4 Hardware
All hardware parts which contact, under normal usage, a person, clothing, or webbing shall be
free from burrs and sharp edges.
3.5 Release
A Type 1 or Type 2 seat belt assembly shall be provided with a buckle or buckles readily
accessible to the occupant to permit his easy and rapid removal from the assembly. A Type 3
seat belt assembly shall be provided with a quickly recognizable and easily operated release
arrangement, readily accessible to an adult. Buckle release mechanism shall be designed to
minimize the possibility of accidental release.
Hardware
3.6 Attachment
A seat belt assembly shall include all hardware necessary for installation in a motor vehicle in
accordance with SAE J800a, Motor Vehicle Seat Belt Installation (*), except that seat belt
assemblies designed for installation in vehicles equipped with seat belt anchorages shall not
require underfloor hardware. The hardware shall be designed to prevent attaching bolts and
other parts becoming disengaged from the motor vehicle in services. Reinforcing plates or
washers furnished for universal floor installations shall be steel, free from burrs and sharp
edges on the peripheral edges adjacent to the vehicle, not less than 0.06 in. (1.5 mm) in
thickness nor less than 4 sq in. (25 sq cm) in area. The distance between any edge of the
plate and the edge of the bolt hole shall be at least 0.6 in. (15 mm) and any corner shall be
rounded to a radius of not less than 0.25 in. (6 mm) or cut at a 45 deg angle along an
hypotenuse not less than 0.25 in. (6 mm) in length.
(*)
Published by the Society of Automotive Engineers, 485 Lexington Avenue, New York 10017.
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3.7 Adjustment
A Type 1 or Type 2 seat belt assembly shall be capable of snug adjustment by the occupant
by a means easily within his reach and easily operable without appreciable interference with
the driving process, or shall be provided with an automatic locking or an emergency locking
retractor. A Type 3 seat belt assembly shall be capable of snug adjustment to fit any child
capable of sitting upright and weighing not more than 50 lb (23 kg) unless specifically labelled
for use with a child in a smaller weight range.
3.8 Seat Back Retainer
A Type 3 seat belt assembly designed for attachment to a seat back, or for use in a seat with
a hinged back, shall include a seat back retainer unless such assembly is designed and
labelled for use in specific models of motor vehicles, in which the vehicle manufacturer has
provided other adequate restraint for the seat back.
3.9 Webbing
The ends of webbing in a seat belt assembly shall be protected or treated to prevent ravelling.
The end of webbing in a seat belt assembly having a metal-to-metal buckle, that is used by
the occupant to adjust the size of the assembly, shall not pull out the adjustment hardware at
maximum size adjustment. Provision shall be made for essentially unimpeded movement of
webbing routed between a seat back and seat cushion and attached to a retractor located
behind the seat,
3.10 Strap
A strap used in a seat belt assembly to sustain restraint forces shall comply with the
requirements for webbing in Section 4, and if the strap is made from a rigid material it shall
comply with applicable requirements in Sections 4-6.
3.11 Marking
Each seat belt assembly shall be permanently and legibly marked or labelled with year of
manufacturer, model and name or trademark of manufacturer or distributor, or of importer is
manufactured outside the United States. A model shall consist of a single combination of
webbing having a specific type of fiber (nylon, polyester, or the like) weave and construction,
and hardware having a specific design. Webbings of various colors may be included under
the same model, but webbing of each color shall comply with the requirements for webbing in
Section 4.
Instructions
3.12 Installation
A seat belt assembly or retractor shall be accompanied by an instruction sheet providing
sufficient information for installing the assembly in a motor vehicle except for a seat belt
assembly or retractor installed in a motor vehicle by an automobile manufacturer. The
installation instructions shall state whether the assembly is for universal installation or for
installation only in specifically stated motor vehicles, and shall include at least those items in
SAE J800a.
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3.13 Usage and Maintenance Instructions
A seat belt assembly or retractor shall be accompanied by written instructions for the proper
use of the assembly, stressing particularly the importance of wearing the assembly snugly
and properly located on the body, and for the maintenance of the assembly, including periodic
inspection for all components. The instructions shall show the proper manner of threading
webbing in the hardware of seat belt assemblies in which the webbing is not permanently
fastened. Instructions for Type 2a shoulder belt shall include a warning that the shoulder belt
is not to be used without a lap belt.
3.14 Workmanship
A seat belt assembly shall have good workmanship in accordance with good commercial
practices.
WEBBING
4. REQUIREMENTS
FOR
4.1 Width
The webbing in a seat belt assembly shall be not less than the following widths, when
measured under conditions prescribed in paragraph 7.1:
Type 1 seat belt assembly – 1.8 in. (46 mm)
Type 2 seat belt assembly – 1.8 in. (46 mm)
Type 3 seat belt assembly – 0.9 in. (23 mm) for pelvic and upper torso restraint.
Strength
4.2 Breaking
The webbing in a seat belt assembly shall have not less than the following breaking strengths
when tested by the procedures specified in paragraph 7.2:
Type 1 seat belt assembly – 6000 lb (2700 kg)
Type 2 seat belt assembly – 5000 lb (2270 kg) for pelvic restraint; 4000 lb (1810 kg) for
upper torso restraint.
Type 3 seat belt assembly – 1500 lb (680 kg) for pelvic and upper torso restraint; 4000 lb
(1810 kg) for seat back restrainer and for connection for
pelvic and upper torso restraint to attachment hardware when
assembly has single webbing connection; 3000 lb (1360 kg)
for webbing connecting pelvic and upper torso restraint to
attachment hardware when assembly has two or more
webbing connections.
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4.3 Elongation
The webbing in a seat belt assembly shall not extend to more than the following elongations
when subjected to the specified forces in accordance with the procedures specified in
paragraph 7.3:
Type 1 seat belt assembly – 20% at 2500 lb (1130 kg).
Type 2 seat belt assembly – 30% at 2500 lb (1130 kg) for pelvic restraint; 40% at 2500 lb
(1130 kg) for upper torso restraint.
Type 3 seat belt assembly – 20% at 700 lb (320 kg) for webbing in pelvic and upper torso
restraints; 25% at 2500 lb (1130 kg) for webbing in seat back
retainer and for webbing connecting pelvic and upper torso
restraints to attachment hardware when assembly has single
webbing connections; 25% at 1800 lb (820 kg) for webbing
connecting pelvic and upper torso restraints to attachment
hardware when assembly has two or more webbing
connections.
Abrasion
to
4.4 Resistance
The webbing in a seat belt assembly after being subjected to abrasion as specified in
paragraph 7.4 shall have a breaking strength not less than 75% of the strength before
abrasion when measured by the procedure specified in paragraph 7.2.
4.5 Resistance to Light
The webbing in a seat belt assembly, after exposure to the light of a carbon arc and after
testing by the procedure specified in paragraph 7.5 shall have a breaking strength not less
than 60% of the strength before exposure to the carbon arc and shall have a color retention
not less than No. 2 on the Geometric Gray Scale. (*)
4.6 Resistance to Micro-Organisms
The webbing in a seat belt assembly after being subjected to micro-organisms and tested by
the procedure specified in paragraph 7.6 shall have a breaking strength not less than 85% of
the strength before subjection to micro-organisms.
4.7 Colorfastness to Crocking
The webbing in a seat belt assembly shall not transfer color to a crock cloth either wet or dry
to a greater degree than Class 3 on the AATCC Chart for Measuring Transference of Color, (*)
when tested by the procedure specified in paragraph 7.7.
4.8 Colorfastness to Staining
The webbing in a seat belt assembly shall not stain to a greater degree than Class 3 on the
AATCC Chart for Measuring Transference of Color when tested by the procedure specified in
paragraph 7.8.
(*)
Published by the American Association of Textile Chemists and Colorists , P.O. Box 886, Durham, N.C.
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HARDWARE
5. REQUIREMENTS
FOR
Resistance
5.1 Corrosion
Hardware parts of a seat belt assembly, except buckles, after being subjected to the condition
specified in paragraph 8.1, shall be free of red rust, except for permissible red rust at
peripheral edges or edges of holes on underoof reinforcing plates or washers. Buckle surface
or other metallic parts which may come into contact with webbing, the occupant, or his
clothing, when the belt is worn, shall be free of ferrous and nonferrous corrosion. Buckles
and retractors shall conform to applicable requirements in paragraphs 5.7–5.11 inclusive.
Resistance
5.2 Temperature
Plastic, or other nonmetallic, hardware parts of a seat belt assembly, and all retractors, when
subjected to the conditions specified in paragraph 8.2, shall not warp, or otherwise
deteriorate, to cause the assembly to operate improperly or fail to comply with applicable
requirements in Sections 5 and 6.
Hardware
5.3 Attachment
Eye bolts, shoulder bolts, or other bolts used to secure the pelvic restraint of a seat belt
assembly to a motor vehicle shall withstand a force of 5000 lb (2270 kg) when tested by the
procedure specified in paragraph 8.3. A seat belt assembly, having single attachment hooks
of the quick-disconnect type for connecting webbing to an eye bolt, shall be provided with a
retaining latch or keeper which shall not move more than 0.08 in. (2 mm) in either the vertical
or horizontal direction when tested by the procedure specified in paragraph 8.3.2.
Force
5.4 Buckle
Release
The buckle of a Type 1 or Type 2 seat belt assembly shall release when a force of not more
than 30 lb (14 kg) is applied, and the buckle of a Type 3 seat belt assembly shall release
when a force of not more than 20 lb (9 kg) is applied as prescribed in paragraph 8.4.
Force
5.5 Adjustment
The force required to decrease the size of a seat belt assembly shall not exceed 11 lb (5 kg)
when measured by the procedure specified in paragraph 8.5.
Adjustment
5.6 Tilt-Lock
The buckle of seat belt assembly having tilt-lock adjustment shall lock the webbing when
tested by the procedure specified in paragraph 8.6 at an angle of not less than 30 deg
between the base of the buckle and the anchor webbing.
Latch
5.7 Buckle
The buckle latch of a seat belt assembly when tested by the procedure specified in paragraph
8.7, shall not fail, nor gall or wear to an extent that normal latching and unlatching are
impaired, and metal-to-metal buckle shall separate when in any position of partial
engagement by a force of not more than 5 lb (2.3 kg).
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Retractor
5.8 Nonlocking
The webbing of a seat belt assembly shall extend from a nonlocking retractor within 0.25 in.
(6 mm) of a maximum length when a tension of 3 lb (1.4 kg) is applied as prescribed in
paragraph 8.8.
5.9 Automatic Locking Retractor
The webbing of a seat belt assembly equipped with an automatic locking retractor shall not
move more than 1 in. (2.5 cm) between locking positions of the retractor, and shall be
retracted with a force of not less than 0.6 lb (0.27 kg) when measured by the procedure
specified in paragraph 8.9.
5.10 Emergency Locking Retractor
An emergency locking retractor used on a Type 1 or Type 2 seat belt assembly shall lock
before the webbing extends 1 in. (2.5 cm) when the retractor is subjected to an acceleration
of 0.5 g (5 m/sec2) and shall exert a retraction force of not less than 1.5 lb (0.7 kg) under zero
acceleration when tested by the procedures specified in paragraph 8.10.
5.11 Performance of Retractor
A retractor used on a seat belt assembly after subjection to the tests specified in paragraph
8.11 shall comply with applicable requirements in paragraphs 5.8–5.10 and 6.1–6.3, except
that the retraction force shall be not less than 50% of its original retraction force.
6. REQUIREMENTS FOR ASSEMBLY PERFORMANCE
6.1 Type 1 Seat Belt Assembly
The complete seat belt assembly, including webbing, straps, buckles, adjustment and
attachment hardware, and retractors, shall comply with the following requirements when
tested by the procedures specified in paragraph 9.1:
6.1.1The assembly loop shall withstand a force of not less than 5000 lb (2270 kg); that is, each
structural component of the assembly shall withstand a force of not less than 2500 lb
(1130 kg).
6.1.2The assembly loop shall extend not more than 7 in. (18 cm) when subjected to a force of
5000 lb (2270 kg); that is, the length of the assembly between anchorages shall not increase
more than 14 in. (36 cm).
6.1.3Any webbing cut by the hardware during test shall have a breaking strength at the cut of not
less than 4200 lb (1910 kg).
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6.2 Type 2 Seat Belt Assembly
The components of a Type 2 seat belt assembly including webbing, straps, buckles,
adjustment hardware, and retractors shall comply with the following requirements when tested
by the procedure specified in paragraph 9.2:
6.2.1The structural components in the pelvic restraint shall withstand a force of not less than
2500 lb (1130 kg).
6.2.2The structural components in the upper torso restraint shall withstand a force of not less than
1500 lb (680 kg).
6.2.3The structural components in the assembly that are common to pelvic and upper torso
restraints shall withstand a force of not less than 3000 lb (1360 kg).
6.2.4The length of the pelvic restraint between anchorages shall not increase more than 20 in.
(50 cm) when subjected to a force of 2500 lb (1130 kg).
6.2.5The length of the upper torso restraint between anchorages shall not increase more than
20 in. (50 cm) when subjected to a force of 1500 lb (680 kg).
6.2.6Any webbing cut by the hardware during test shall have a breaking strength of not less than
3500 lb (1590 kg) at a cut in webbing of the pelvic restraint, or not less than 2800 lb (1270 kg)
at a cut in webbing of the upper torso restraint.
6.3 Type 3 Seat Belt Assembly
The complete seat belt assembly, including webbing, straps, buckles, adjustment and
attachment hardware, and retractors, shall comply with the following requirements when
tested by the procedures specified in paragraph 9.3:
6.3.1The complete assembly shall withstand a force of 2000 lb (900 kg).
6.3.2The complete assembly shall extend not more than 12 in. (30 cm) when subjected to a force
of 2000 lb (900 kg).
6.3.3Any webbing cut be the hardware during test shall have a breaking strength of not less than
1050 lb (480 kg) at a cut in webbing of pelvic or upper torso restraints, or not less than
2800 lb (1270 kg) at a cut in webbing of seat back retainer, or in webbing connecting pelvic
and upper torso restraint at attachment hardware.
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7 WEBBING TEST PROCEDURES
7.1 Width
The width of webbing from three seat belt assemblies shall be measured after conditioning for
at least 24 hour in an atmosphere having a relative humidity between 48–67% and a
temperature of 73.4 ± 3.6 F (23 ± 2 C). The tension on the webbing during measurement of
width shall be not more than 5 lb (2 kg) for Type 1 or Type 3 seat belt assemblies and
2200 ± 100 lb (1000 ± 50 kg) for Type 2 seat belt assembly. The width of webbing in Type 2
seat belt assembly may be measured during the breaking strength test described in
paragraph 7.2.
7.2 Breaking
Strength
Webbing from three seat belt assemblies shall be conditioned in accordance with paragraph
7.1 and tested, by ASTM E 4–64T, Methods of Verification of Testing Machines (Tentative), (*)
for breaking strength in a testing machine of suitable capacity verified to have an error of not
more than 1% in the range of the breaking strength of the webbing. The machine shall be
equipped with split drum grips illustrated in Figure 1, having a diameter between 2–4 in.
(5–10 cm). The rate of grip separation shall be between 2–4 in. (5–10 cm) per minute. The
distance between the centers of the grips at the start of the test shall be between 4–10 in.
(10–25 cm). After placing the specimen in the grips, the webbing shall be stretched
continuously at a uniform rate to failure. Each value shall be not less than the applicable
breaking strength requirement in paragraph 4.2, but the median value shall be used in
determining the retention of breaking strength in paragraphs 4.4–4.6.
Figure 1
(*)
Published by the American Society for Testing and Materials, 1916 Race Street, Philadelphia, Pa. 19103.
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7.3 Elongation
Elongation shall be measured during the breaking strength test described in paragraph 7.2 by
the following procedure. A preload of 50 ± 5 lb (22.5 ± 2 kg) shall be placed on the webbing
mounted in the grips of the testing machine, and the needle points of the extensometer, in
which the points remain parallel during test, are inserted in the center of the specimen.
Initially the points shall be set at a known distance between 4–8 in. (10–20 cm) apart. When
the force on the webbing reaches the value specified in paragraph 4.3, the increase in
separation of the points of the extensometer shall be measured and the per cent elongation
shall be calculated to the nearest 0.5%. Each value shall be not more than the appropriate
elongation requirement in paragraph 4.3.
Abrasion
to
7.4 Resistance
The webbing from three seat belt assemblies shall be tested for resistance to abrasion by
rubbing over the hexagon bar prescribed in Figure 2 in the following manner. The webbing
shall be mounted in the apparatus shown schematically in Figure 2. One end of the webbing,
A, shall be attached to the weight, B, which has a mass of 5.2 ± 0.1 lb (2.3 ± 0.05 kg) except
that for Type 3 pelvic and upper torso restraint webbing a mass of 3.3 ± 0.1 lb (1.5 ± 0.05 kg)
shall be used. The webbing shall be passed over two new abrading edges of the hexagon
bar, C, and the other end attached to an oscillating drum, D, which has a stroke of 13 in.
(33 cm). Suitable guides shall be used to prevent movement of the webbing along the axis of
hexagonal bar, C. Drum D shall be oscillated for 5000 strokes (2500 cycles) at a rate of
60 ± 2 strokes (30 ± 1 cycles) per minute.
The abraded webbing shall be conditioned as prescribed in paragraph 7.1 and tested for
breaking strength by the procedure described in paragraph 7.2. The median values for the
breaking strengths determined on abraded and unabraded specimens shall be used to
calculate the percentage of breaking strength retained.
Figure 2
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7.5 Resistance to Light
Three specimens of webbing at least 20 in. (50 cm) in length shall be suspended vertically on
the inside of the specimen rack in a Type E carbon-arc light exposure apparatus described in
ASTM E 42–64, Recommended Practice for Operation of Light and Water-Exposure
Apparatus (Carbon-Arc Type) for Artificial Weathering Test. The apparatus shall be operated
without water spray at an air temperature of 140 ± 3.6 F (60 ± 2 C) measured at a point
1.0 ± 0.2 in. (
2.5 ± 0.5 cm) outside the specimen rack and midway in the height. The
temperature sensing element shall be shielded from radiation. The specimens shall be
exposed to the light from the carbon-arc for 100 hours and then conditioned as prescribed in
paragraph 7.1. The colorfastness of the exposed and conditioned specimens shall be
determined on the AATCC Geometric Gray Scale. The breaking strength of the specimens
shall be determined by the procedure prescribed in paragraph 7.2. The median values for the
breaking strengths determined on exposed and unexposed specimens shall be used to
calculate the percentage of breaking strength retained.
7.6 Resistance to Micro-Organisms
Three specimens of webbing at least 20 in. (50 cm) in length shall be subjected successively
to the procedures prescribed in Section 1C1 - Water Leaching, Section 1C2 - Volatilization,
and Section 1B3 - Soil Burial Test of AATCC Tentative Test Method 30–1957T, Fungicides,
Evaluation of Textiles; Mildew and Rot Resistance of Textiles. (*) After soil burial for a period
of 2 weeks, the specimens shall be washed with water, dried and conditioned as prescribed in
paragraph 7.1. The breaking strengths of the specimens shall be determined by the
procedure prescribed in paragraph 7.2. The median values for the breaking strengths
determined on exposed and unexposed specimens shall be used to calculate the percentage
of breaking strength retained. NOTE: This test shall not be required on webbing made from
material which is inherently resistant to micro-organisms.
7.7 Colorfastness to Crocking
Webbing from three seat belt assemblies shall be tested by the procedure specified in
AATCC Standard Test Method 8–1961, Colorfastness to Crocking (Rubbing).
7.8 Colorfastness to Staining
Webbing from three seat belt assemblies shall be tested by the procedure specified in
AATCC Standard Test Method 107–1962, Colorfastness to Water, with the following
modifications: distilled water shall be used, perspiration tester shall be used, the drying time in
paragraph 4 of the AATCC procedure shall be 4 hours, and the section entitled, "Evaluation
Method for Staining (3)" shall be used to determine colorfastness on the AATCC Chart for
Measuring Transference of Colors.
(*)
Published by the American Association of Textile Chemists and Colorists, P.O. Box 886, Durham, N.C.
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8. TEST PROCEDURES FOR HARDWARE
Resistance
8.1 Corrosion
All hardware from three seat belt assemblies shall be tested by ASTM B 117–64, Standard
Method of Salt Spray (Fog) Testing. The period of test shall be 50 hours for all attachment
hardware at or near the floor, consisting of two periods of 24 hours exposure to salt spray
followed by 1 hour drying and 25 hours for all other hardware, consisting of one period of
24 hours exposure to salt spray followed by 1 hour drying. In the salt spray test chamber, the
part from the three assemblies shall be oriented differently, selecting those orientations most
likely to develop corrosion on the larger areas, At the end of the test, the hardware shall be
washed with water to remove the salt. After drying, the hardware shall be examined for
corrosion. Retractors shall be tested for corrosion resistance after 5000 cycles of operation
as prescribed in paragraph 8.11.
8.2 Temperature
Resistance
Three seat belt assemblies having plastic or nonmetallic hardware or having retractors shall
be subjected to the conditions prescribed in Procedure IV of ASTM D 756–56, Standard
Methods of Test for Resistance of Plastics to Accelerated Service Conditions. The
dimensions and weight measurements shall be omitted. Buckles shall be unlatched and
retractors shall be fully, retracted during conditioning. The hardware parts after conditioning
shall be used for all applicable tests in Sections 5 and 6.
Hardware
8.3 Attachment
8.3.1 Attachment
Bolts
Attachment bolts used to secure the pelvic restraint of a seat belt assembly to a motor vehicle
shall be tested in the following manner: to one head of a testing machine described in
paragraph 7.2, two belt sections shall be attached. At the free end of each belt section,
attachment hardware from the seat belt assembly (that is, sister hooks, and so on) shall be
attached. The attachment hardware shall be fastened by the bolt in a fixture on the other
head of the testing machine as shown in Figure 3, which has a standard 7/16 - 20 - UNF - 2B
threaded hole in a hardened steel plate at least 0.4 in. (1 cm) in thickness; the axis of this
threaded hole forms a 45 deg angle with the line of pull of the belt sections. The belt shall be
0.2 in. (5 mm) from its fully seated position with the attachment hardware from the two belt
sections attached. A force of 5000 lb (2270 kg) shall be applied. A bolt from each of three
seat assemblies shall be tested.
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Figure 3
8.3.2 Single Attachment Hooks
Single attachment hooks for connecting webbing to an eye bolt shall be tested in the following
manner: the hook shall be held rigidly so that the retainer latch or keeper, with cotter pin or
other locking device in place, is in a horizontal position as shown in Figure 4. A force of
150 ± 2 lb (68 ± 1 kg) shall be applied vertically as near as possible to the free end of the
retainer latch, and the movement of the latch by this force at the point of application shall be
measured. The vertical force shall be released, and a force of 150 ± 2 lb (68 ± 1 kg) shall be
applied horizontally as near as possible to the free end of the retainer latch. The movement
of the latch by this force at the point of load application shall be measured. Alternatively, the
hook may be held in other positions, provided the forces and the movements of the latch are
measured at the points indicated in Figure 4.
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Figure 4 – Single Attachment Hook
Release
Force
8.4 Buckle
Three seat belt assemblies shall be tested to determine compliance with the maximum buckle
release force requirements, following the assembly test in Section 9. After subjection to the
force applicable for the assembly being tested, the force shall be reduced and maintained at
150 ± 10 lb (68 ± 4 kg) on the assembly loop of a Type 1 seat belt assembly, 75 ± 5 lb
(34 ± 2 kg) on the components of a Type 2 seat belt assembly, or 45 ± 5 lb (20 ± 2 kg) on a
Type 3 seat belt assembly. The buckle release force shall be measured by applying a force
on the buckle in the manner and direction typical of that which would be employed by a seat
belt occupant. For lever release buckles, the force shall be applied on the centerline of the
buckle lever finger tab in such direction as to produce maximum releasing effect. A hole
0.1 in. (2.5 mm) in diameter may be drilled through the buckle tab or lever on the centerline
between 0.12–0.13 in. (3.0–3.3 mm) from its edge, and a small loop of soft wire may be used
as the connecting link between the buckle tab or lever and the force measuring device.
Force
8.5 Adjustment
Three seat belt assemblies shall be tested for adjustment force on the webbing at the buckle
or other manual adjusting device, normally used to adjust the size of the assembly. With no
load on the anchor end, the webbing shall be drawn through the adjusting device at a rate of
20 ± 2 in. (50 ± 5 cm) per minute and the maximum force shall be measured to the nearest
0.25 lb (0.1 kg) after the first 1 in. (25 mm) of webbing movement. The webbing shall be
precycled 10 times prior to measurement.
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Adjustment
8.6 Tilt-Lock
This test shall be made on buckles or other manual adjusting devices having tilt-lock
adjustment, normally used to adjust the size of the assembly. Three buckles or devices shall
be tested. The base of the adjustment mechanism and the anchor end of the webbing shall
be oriented in planes normal to each other. The webbing shall be drawn through the
adjustment mechanism in a direction to increase belt length at a rate of 20 ± 2 in. (50 ± 5 cm)
per minute, while the plane of the base it slowly rotated in a direction to lock the webbing.
Rotation shall be stopped when the webbing locks, but the pull on the webbing shall be
continued until there is a resistance of at least 20 lb (9 kg). The locking angle between the
anchor end of the webbing and the base of the adjustment mechanism shall then be
measured to the nearest degree. The webbing shall be precycled 10 times prior to
measurement.
Latch
8.7 Buckle
The buckles from three seat belt assemblies shall be fully opened and closed at least
10 times. Then the buckle shall be clamped or firmly held against a flat surface so as to
permit normal movement of buckle parts, but with the metal mating plate (metal-to-metal
buckles) or webbing end (metal-to-webbing buckles) withdrawn from the buckle. The release
mechanism shall be moved 200 times through the maximum possible travel against its stop
with a force of 30 ± 3 lb (14 ± 1 kg) at a rate not to exceed 30 cpm. The buckle shall be
examined to determine compliance with the performance requirements of paragraph 5.7. A
metal-to-metal buckle shall be examined to determine whether partial engagement is possible
by means of any technique representative of actual use. If partial engagement is possible,
the maximum force of separation when in such partial engagement shall be determined.
8.8 Nonlocking
Retractor
After the retractor is cycled 10 times by full extension and retraction of the webbing, the
retractor and webbing shall be suspended vertically and a force of 4 lb (1.8 kg) shall be
applied to extend the webbing from the retractor. The force shall be reduced to 3 lb (1.4 kg).
The residual extension of the webbing shall be measured by manual rotation of the retractor
drum or by disengaging the retraction mechanism. Measurements shall be made on three
retractors.
8.9 Automatic Locking Retractor
Three retractors shall be tested in a manner to permit the retraction forces to be determined
exclusive of the gravitational forces on hardware or webbing being retracted. The webbing
shall be fully extended from the retractor. While the webbing is being retracted the average
force of retraction with ± 2 in. (5 cm) of 75% extension (25% retraction) shall be determined
and the webbing movement between adjacent locking segments shall be measured in the
same region of extension.
Society of Automotive Engineers Inc. ?
8.10 Emergency Locking Retractors
Three retractors shall be tested in a manner to permit the retraction forces to be determined
exclusive of the gravitational forces on the hardware or webbing being retracted. The
webbing shall be fully extended from the retractor. While the webbing is being retracted the
average force of retraction within ± 2 in. (5 cm) of 75% extension (25% retraction) shall be
determined. The retractor shall be subjected to an acceleration of 0.5 g (5 m/sec2) within a
period of 50 msec while the webbing is at 75% extension and the webbing movement before
locking shall be measured under each of the following conditions: for a retractor sensitive to
the rate of webbing withdrawal, the retractor shall be accelerated in the direction of webbing
withdrawal while oriented horizontally and at angles of 45, 90, 135, and 180 deg to the
horizontal plane; for a retractor sensitive to vehicle acceleration, the retractor shall be
accelerated in three directions normal to each other while oriented horizontally and at angles
of 45, 90, 135, and 180 deg to the horizontal plane, unless the retractor locks by gravitational
force when tilted in any direction to an angle of 45 deg or more.
8.11 Performance of Retractors
After completion of the temperature resistance test described in paragraph 8.2, the retractor
shall be mounted in an apparatus capable of extending the webbing fully, applying force of
20 lb (9 kg) at full extension, and allowing the webbing to retract freely and completely. The
webbing shall be withdrawn from the retractor and allowed to retract repeatedly in this
apparatus until 5000 cycles are completed. The retractor and webbing shall then be
subjected to the corrosion test prescribed in paragraph 8.1. After the corrosion test, the
webbing shall be extended fully and allowed to dry at least 16 hours under standard
laboratory conditions specified in paragraph 7.1. The performance of the retractor after the
corrosion test shall be determined by withdrawing the webbing manually and allowing the
webbing to retract for 25 cycles.
The retractor and webbing shall then be subjected to dust in a chamber similar to one
illustrated in Figure 5 containing about 2 lb (0.9 kg) of coarse grade dust conforming to the
specification given in SAE J726a. The dust shall be agitated every 20 minutes for 5 seconds
by compressed air, free of oil and moisture, at a gage pressure of 80 ± 8 lb/in.2
(5.6 ± 0.6 kg/cm2) entering through an orifice 0.060 ± 0.004 in. (1.5 ± 0.1 mm) in diameter,
The webbing shall be extended to the top of the chamber and kept extended at all times,
except that the webbing shall be subjected to 10 cycles of complete retraction and extension
within one to two minutes after each agitation of the dust. At the end of 5 hours, the assembly
shall be removed from the chamber and the retractor functional performance shall be
determined by withdrawing the full length of webbing manually and allowing the webbing to
retract for 25 cycles.
Nonlocking and automatic locking retractors shall be subjected to 5000 additional cycles of
webbing withdrawal and retraction, and emergency locking retractors shall be subjected to
45,000 additional cycles of webbing withdrawal and retraction as previously described. The
locking mechanism of an emergency locking retractor shall be actuated about 10,000 times
during the 50,000 cycles. At the end of test, compliance of the retractors with applicable
requirements in paragraphs 5.8–5.10 shall be determined. Three retractors shall be tested for
performance.
Society of Automotive Engineers Inc. ?
Figure 5
Society of Automotive Engineers Inc. ?
9. TEST PROCEDURES FOR ASSEMBLY PERFORMANCE
9.1 Type 1 Seat Belt Assembly
Three complete seat belt assemblies including webbing, straps, buckles, adjustment and
attachment hardware, and retractors, arranged in the form of a loop as shown in Figure 6,
shall be tested in the following manner:
9.1.1The testing machine shall conform to the requirements specified in paragraph 7.2. A double-
roller block shall be attached to one head of the testing machine. This block shall consist of
2 rollers 4 in. (10 cm) in diameter and sufficiently long so that no part of the seat belt
assembly touches parts of the block other than the rollers during test. The rollers shall be
mounted on antifriction bearings and spaced 12 in. (30 cm) between centers, and shall have
sufficient capacity so that there is no brinelling, bending, or other distortion of parts which may
affect the results. An anchorage bar shall be fastened to the other head of the testing
machine.
Figure 6
Society of Automotive Engineers Inc. ?
9.1.2The attachment hardware furnished with the seat belt assembly shall be attached to the
anchorage bar. The anchor points shall be spaced so that the webbing is parallel in the two
sides of the loop. The attaching bolt shall be parallel, or at an angle of 45 or 90 deg, to the
webbing, whichever results in the greatest angle between webbing and attachment hardware,
except that eye bolts shall be vertical, and attaching bolts of a seat belt assembly designed
for use in specific models of motor vehicles shall be installed to produce the maximum angle
in use indicated by the installation instructions.
Rigid adapters between anchorage bar and attachment hardware shall be used if necessary,
to locate and orient the adjustment hardware. The adapter shall have a flat support face
perpendicular to the threaded hole for the attaching bolt and adequate in area to provide full
support for the base of the attachment hardware connected to the webbing. If necessary, a
washer shall be used under a swivel plate or other attachment hardware that would crush or
damage the webbing as the attaching bolt is tightened.
9.1.3The length of the assembly loop from attaching bolt to attaching bolt shall be adjusted to
about 51 in. (130 cm), or as near thereto as possible. A force of 55 lb (25 kg) shall be applied
to the loop to remove any slack in webbing at hardware. The force shall be removed and the
heads of the testing machine shall be adjusted for an assembly loop between 48–50 in.
(122–127 cm) in length. The length of the assembly loop shall then be adjusted by applying a
force between 20–22 lb (9–10 kg) to the free end of the webbing at the buckle, or by the
retraction force of an automatic locking or emergency locking retractor. A seat belt assembly
that can not be adjusted to this length shall be adjusted as closely as possible. An automatic
locking retractor or an emergency locking retractor, when included in a seat belt assembly,
shall be locked at the start of the test, with a tension on the webbing slightly in excess of the
retractive force in order to keep the retractor locked.
The buckle shall be in location so that it does not touch the rollers during test, but, to facilitate
making the buckle release test in paragraph 8.4, the buckle should be between the rollers or
near a roller in one leg.
9.1.4The heads of the testing machine shall be separated at a rate of 2–4 in. (5–10 cm) per minute
until a force of 5000 ± 5 lb (2270 ± 20 kg) is applied to the assembly loop. The extension of
the loop shall be determined from measurements of head separation before and after the
force is applied. The force shall be decreased to 150 ± 10 lb (68 ± 4 kg) and the buckle
release force measured as prescribed in paragraph 8.4.
9.1.5After the buckle is released, the webbing shall be examined for cutting by the hardware. If the
yarns are partially, or completely, severed in a line for a distance of 10% or more of the
webbing width, the cut webbing shall be tested for breaking strength as specified in paragraph
7.2, locating the cut in the free length between grips. If there is insufficient webbing on either
side of the cut to make such a test for breaking strength, the webbing shall be repositioned in
the hardware using another seat belt assembly. A tensile force of 2500 ± 25 lb (1135 ± 10 kg)
shall be applied to the components or a force of 5000 ± 50 lb (2270 ± 20 kg) shall be applied
to an assembly loop. After the force is removed, the breaking strength of the cut webbing
shall be determined as previously prescribed.
9.1.6 A seat belt assembly containing an emergency locking retractor or automatic locking retractor
shall also be tested with the webbing fully extended. If a Type 1 seat belt assembly includes
an automatic locking retractor or an emergency locking retractor the webbing and retractor
shall be subjected to a tensile force of 2500 ± 25 lb (1135 ± 10 kg) with the webbing fully
extended from the retractor.
第一章安全系统工程的基本概念和应用特点 第一节安全系统工程的基本概念 安全系统工程,是以安全学和系统科学为理论基础,以安全工程、系统工程、可靠性工程等为手段,对系统风险进行分析、评价、控制,以期实现系统及其全过程安全目标的科学技术。 安全系统工程是现代科技发展的必然产物,是安全科学学科的重要分支。 安全系统工程是一门涉及自然科学和社会科学的横断科学,在定义安全系统工程之前需要弄清相关学科的有关概念。 一、系统 1、系统的定义 目前对系统的定义有百余种。我国科学家钱学森指出:“所谓系统,即由相互作用和相互依赖的若干组成部分结合成的、具有特定功能的有机整体;而系统本身又是它所从属的一个更大系统的组成部分”。任何客观事物,大到银河系、太阳系,小到原子、分子,都可以看成一个系统。 2、构成系统的条件 构成一个系统必须满足的条件是: (1)有两个或两个以上的要素,这些要素就是构成这一系统的子系统; (2)要素之间存在相互联系和相互作用; (3)要素之间的相互联系与作用必须产生特定的整体功能或达到特定的目标。 3、系统的一般属性 (1)整体性。系统是由两个或两个以上相互区别的要素(元件或子系统)组成的整体。构成系统的各要素虽然具有不同的性能,但它们通过综合、统一(而不是简单拼凑)形成的整体就具备了新的特定功能,就是说,系统作为一个整体才能发挥其应有功能。所以,系统的观点是一种整体的观点,一种综合的思想方法。 (2)相关性。构成系统的各要素之间、要素与子系统之间、系统与环境之间都存在着相互联系、相互依赖、相互作用的特殊关系,通过这些关系,使系统有机地联系在一起,发挥其特定功能。 (3)目的性。任何系统都是为完成某种任务或实现某种目的而发挥其特定功能的。要达到系统的既定目的,就必须赋予系统规定的功能,这就需要在系统的整个生命周期,即系
第一节安全的基本概念及特征 一、安全的基本概念 1、安全的定义 通常中文中,“安”指不受威胁,没有危险,太平、安适、稳定等,即“无危则安”。《辞海》对“安”字的第一个释义就是“安全”; “全”指完满,完整,无残缺,没有伤害,谓之“无缺则全”。这里,全是因,安是果,由全而安。 多数专家认为,安全通常指各种事物对人或对人的身心不产生危害、不导致危险、不造成损失、不发生事故、正常、顺利的状态。即安全与否是从人的身心需求的角度或着眼点提出来的,是针对人和人的身体而言的,当然健康也就属于安全范畴。对于与人的身心存在状态无关的事物来说,根本不存在安全与否的问题。所以,安全首先是指外界不利因素(或称环境因素)作用下,使人的身体免受伤害或威胁,使人的心理不感到恐慌、害怕,使人能够健康、舒适、高效的进行各种活动的存在状态。另外,还包括人能够健康、舒适、高效的进行各种活动的客观保障条件。因此书中对安全的科学概念概括为: 安全是人的身心免受外界(不利)因素影响的存在状态(包括健康 狭义的安全是指某一领域或系统中的安全,具有技术安全的含义。即人们通常所说的某一领域或系统中的技术安全。如生产安全、机械安全、矿业安全、交通安全等等。状况)及其保障条件。换言之,人的身心存在的安全状态及其事物保障的安全条件构成安全整体。--这是把人的存在状况和事物的保障条件有机结合的科学概念。 2、狭义安全和广义安全。 广义安全。即大安全。是以某一系统或领域为主的技术安全扩展到生活安全与生存安全领域,形成了生产、生活、生存领域的大安全,是全民、全社会的安全。 3、现实中安全问题的划分 从专业和行业领域角度划分可分为:生产安全、国家安全、环境安全、食品安全、医药医疗安全、职业劳动保护安全、网络安全、经济安全、人口安全、社会(公共)安全、政治安全、文化安全(主要是外来文化侵略)、自然灾害和人为灾难、社会保障等。 从对象来划分有人身安全、财产安全、环境安全、(产品)质量安全、技术安全、文物安全等。 4、安全度(安全量) “安全度”是一个表示安全程度的概念,人的身心安全程度及其事物保障的可靠程度用各自标准来衡量,就构成安全度的概念。表达的是主体免于危险的程度。虽然目前我们还无法制定一个统一的量化标准从数量上来刻划安全度,但我们却可以在不太严格的意义上对安全度作一定的质的描述。例如主体是完全免于威胁,还是在一定程度上免于威胁,还是处于危险之中,甚至处于极度危险的境地,或者是已经受到具体的内外侵害,这其实就表现了安全的不同程度,即不同的安全度。 二、人类对安全的认识 安全是人类生存、生产、生活和发展过程中永恒的主题,也是人类发展的根本性问题。人类在发展中不断地探索,有探索就有盲区、就有无知,在人类社会发展进程中,安全的含义不是固有的、一成不变的,而是在不断的发展变化。而且人类对安全的认识长期落后于对生产的认识。
国家标准硬度转换表
硬度換算公式: 1.肖氏硬度(H S)=勃式硬度(B H N)/10+12 2.肖式硬度(H S)=洛式硬度(H R C)+15 3.勃式硬度(B H N)=洛克式硬度(H V) 4.洛式硬度(H R C)=勃式硬度(B H N)/10-3 洛氏硬度H R C和布氏硬度H B等硬度对照区别和换算 硬度:是衡量材料软硬程度的一个性能指标。硬度试验的方法较多,原理也不相同,测得的硬度值和含义也不完全一样。最普通的是静负荷压入法硬度试验,即布氏硬度(H B)、洛氏硬度(H R A,H R B,H R C)、维氏硬度(H V),橡胶塑料邵氏硬度(H A,H D)等硬度其值表示材料表面抵抗坚硬物体压入的能力。最流行的里氏硬度(H L)、肖氏硬度(H S)则属于回跳法硬度试验,其值代表金属弹性变形功的大小。因此,硬度不是一个单纯的物理量,而是反映材料的弹性、塑性、强度和韧性等的一种综合性能指标。 1、钢材的硬度:金属硬度(H a r d n e s s)的代号为H。按硬度试验方法的不同, ●常规表示有布氏(H B)、洛氏(H R C)、维氏(H V)、里氏(H L)硬度等,其中以H B及H R C较为常用。 ●H B应用范围较广,H R C适用于表面高硬度材料,如热处理硬度等。两者区别在于硬度计之测头不同,布氏硬度计之测头为钢球,而洛氏硬度计之测头为金刚石。 ●H V-适用于显微镜分析。维氏硬度(H V)以120k g以内的载荷和顶角为136°的金刚石方形锥压入器 压入材料表面,用材料压痕凹坑的表面积除以载荷值,即为维氏硬度值(H V)。 ●H L手提式硬度计,测量方便,利用冲击球头冲击硬度表面后,产生弹跳;利用冲头在距试样表面1m m 处的回弹速度与冲击速度的比值计算硬度,公式:里氏硬度H L=1000×V B(回弹速度)/V A(冲击速度)。 ●目前最常用的便携式里氏硬度计用里氏(H L)测量后可以转化为:布氏(H B)、洛氏(H R C)、维氏(H V)、肖氏(H S)硬度。或用里氏原理直接用布氏(H B)、洛氏(H R C)、维氏(H V)、里氏(H L)、肖氏(H S)测量硬度值。 时代公司生产的T H系列里氏硬度计就有此功能,是传统台式硬度机的有益补充!”(详细情况请点击《里氏硬度计T H140/T H160/H L N-11A/H S141便携式系列》) 洛氏硬度(H R C)一般用于硬度较高的材料,如热处理后的硬度等等。 2、H B-布氏硬度:一般用于材料较软的时候,如有色金属、热处理之前或退火后的钢铁。布式硬度 (H B)是以一定大小的试验载荷,将一定直径的淬硬钢球或硬质合金球压入被测金属表面,保持规定时间,然后卸荷,测量被测表面压痕直径。布式硬度值是载荷除以压痕球形表面积所得的商。一般为:以一定的载荷(一般3000k g)把一定大小(直径一般为10m m)的淬硬钢球压入材料表面,保持一段时间,去载后,负荷与其压痕面积之比值,即为布氏硬度值(H B),单位为公斤力/m m2(N/m m2)。(关于布 式硬度(H B)详细情况请点击《布氏硬度机(计)H B-3000B/T H600》)
机械安全基本概念与设计通则第1部分:基本术语和方法 GB/T15706.1-2007 机械安全基本概念与设计通则第1部分:基本术语和方法 Safety of machinery-Basic concepts,general principles for design-Part1:Basic terminology, methodology 目次 前言 引言 1 范围 2 规范性引用文件 3 术语和定义 4 设计机械时需要考虑的危险 5 减小风险的策略 附录A(资料性附录) 机器的图解表示 用于GB/T 15706的专用术语和表述的英中文对照索引 参考文献 前言 GB/T 15706《机械安全基本概念与设计通则》由两部分组成: ——第1部分:基本术语和方法; ——第2部分:技术原则。 本部分为GB/T 15706的第l部分。 本部分等同采用国际标准ISO12100-1:2003《机械安全基本概念与设计通则第1部分:基本术语和方法》(英文版),并按照我国标准的编写规则GB/T 1.1-2000做了编辑性修改。 本部分与ISO12100-1:2003的不同为:将标准正文后面的英法德三种文字对照的索引改为英中两种文字对照的索引。 本部分代替GB/T 15706.1-1995《机械安全基本概念与设计通则第1部分:基本术语、方法学》。 本部分由全国机械安全标准化技术委员会(SAC/TC 208)提出并归口。 本部分负责起草单位:机械科学研究总院中机生产力促进中心。 本部分参加起草单位:长春试验机研究所、南京食品包装机械研究所、吉林安全科学技术研究院、中国食品和包装机械总公司、中联认证中心、广东金方圆安全技术检测有限公司。 本部分主要起草人:聂北刚、李勤、王学智、居荣华、肖建民、宁燕、王国扣、隰永才、张晓飞、富锐、程红兵、孟宪卫、赵茂程。 本部分所代替标准的历次版本发布情况为: ——GB/T 15706.1-1995。 引言 GB/T 15706的首要目的是为设计者提供总体框架和指南,使其能够设计出在预定使用范围内具备安全性的机器。同时亦为标准制定者提供标准制定的策略。 机械安全的概念是指在风险已经被充分减小的机器的寿命周期内,机器执行其预定功能的能力。 本部分是机械安全系列标准的基础标准。该系列标准的结构为: ——A类标准(基础安全标准),给出适用于所有机械的基本概念、设计原则和一般特征。 ——B类标准(通用安全标准),涉及机械的一种安全特征或使用范围较宽的一类安全防护装置:
实验三 频率特性分析 一·实验目的 1.掌握频率特性的基本概念,尤其是频率特性的几种表示方法。 2.能熟练绘制极坐标频率特性曲线(奈奎斯特曲线)和对数频率特性曲线,尤其要注意的是在非最小相位系统时曲线的绘制。 3.正确应用频率稳定判别方法,包括奈奎斯特稳定判据和对数稳定判据。 4.熟练正确计算相位裕量和幅值裕量。 5.掌握闭环频率特性的基本知识以及有关指标的近似估算方法。 二·实验内容 1增加开环传递函数零极点个数对奈奎斯特图的影响 1)改变有限极点个数n ,使n=0,1,2,3 Nyquist Diagram Real Axis I m a g i n a r y A x i s -2 -101234 -3.5-3-2.5-2-1.5-1-0.50 0.511.52n=0 n=1 n=2 n=3 2)改变原点处极点个数v ,当v=1,2,3,4, Nyquist Diagram Real Axis I m a g i n a r y A x i s -2 -1.5 -1 -0.5 00.5 1 1.5 2 -2-1.5 -1 -0.5 00.5 1 1.5 2 System: sys P hase Margin (deg): -32.9Delay Margin (sec): 4.41At frequency (rad/sec): 1.3 Closed Loop Stable? No System: sys P hase Margin (deg): -121Delay Margin (sec): 3.49At frequency (rad/sec): 1.2 Closed Loop Stable? No System: sys P hase Margin (deg): 150Delay Margin (sec): 2.28At frequency (rad/sec): 1.15Closed Loop Stable? No System: sys P hase Margin (deg): 51.8Delay Margin (sec): 0.575 At frequency (rad/sec): 1.57 Closed Loop Stable? Yes v=1 v=2 v=3 v=4
硬度分为维氏、洛氏、布氏、里氏、努氏等等。不管用是什么硬度,都是在同一标准前提下对比硬度的相对大小。其中最常用的是洛氏和布氏,但布氏压痕较大,破坏试样,不用于产品上,只用于试验试件上,洛氏最常用,由于压痕小,可以直接在产品上打硬度,现在许多厂家都有在线的洛氏硬度计,洛氏硬度又分几个系列,比如HRA、HRB、HRC。。。。等等,软硬范围不同(压头的尺寸和材料不同),比如一般的较软的用HRC,较硬的的用HRA,就象人的身高,0.8米,用1米的尺子就可以测量,1.8米需要2米的尺子,各种材料的硬度不同,范围较大,所以不同的材料对应用不同的系列,硬度的主要目的是验证强度(硬度试验方便),而硬度和强度的转换主要基于经验。 1.洛氏硬度 是以压痕塑性变形深度来确定硬度值指标。以0.002毫米作为一个硬度单位。当HB>450或者试样过小时,不能采用布氏硬度试验而改用洛氏硬度计量。它是用一个顶角120°的金刚石圆锥体或直径为1.59、3.18mm的钢球,在一定载荷下压入被测材料表面,由压痕的深度求出材料的硬度。根据试验材料硬度的不同,分三种不同的标度来表示:HRA:是采用60kg载荷和钻石锥压入器求得的硬度,用于硬度极高的材料(如硬质合金等)。HRB:是采用100kg载荷和直径1.58mm淬硬的钢球,求得的硬度,用于硬度较低的材料(如退火钢、铸铁等)。HRC:是采用150kg载荷和钻石锥压入器求得的硬度,用于硬度很高的材料(如淬火钢等)。 2.布氏硬度 布氏硬度(HB)一般用于材料较软的时候,如有色金属、热处理之前或退火后的钢铁。洛氏硬度(HRC)一般用于硬度较高的材料,如热处理后的硬度等等。布氏硬度(HB)是以一定大小的试验载荷,将一定直径的淬硬钢球或硬质合金球压入被测金属表面,保持规定时间,然后卸荷,测量被测表面压痕直径。布氏硬度值是载荷除以压痕球形表面积所得的商。一般为:以一定的载荷将一定大小的淬硬钢球压入材料表面,保持一段时间,去载后,负荷与其压痕面积之比值,即为布氏硬度值(HB),单位为公斤力/mm2 (N/mm2)。测试载荷与测试钢球的直径需根据材料的实际性能再确定。 3.维氏硬度 维氏硬度试验方法是英国史密斯(,维氏硬度试验测量范围较宽,从较软材料到超硬材料,几乎涵盖各种材料。 4.里氏硬度 里氏硬度是以HL表示,里氏硬度测试技术是由瑞士狄尔马,里伯博士发明的,它是用一定质量的装有碳化钨球头的冲击体,在一定力的作用下冲击试件表面,然后反弹。由于材料硬度不同,撞击后的反弹速度也不同。在冲击装置上安装有永磁材料,当冲击体上下运动时,其外围线圈便感应出与速度成正比的电磁信号,再通过电子线路转换成里氏硬度值。 5.肖氏硬度 简称HS。表示材料硬度的一种标准。由英国人肖尔(Albert F.Shore)首先提出。应用弹性回跳法将撞销从一定高度落到所试材料的表面上而发生回跳。撞销是一 1
网络安全的基本概念 因特网的迅速发展给社会生活带来了前所未有的便利,这主要是得益于因特网络的开放性和匿名性特征。然而,正是这些特征也决定了因特网不可避免地存在着信息安全隐患。本章介绍网络安全方面存在的问题及其解决办法,即网络通信中的数据保密技术和签名与认证技术,以及有关网络安全威胁的理论和解决方案。 6.1.,网络安全威胁的类型 网络威胁是对网络安全缺陷的潜在利用,这些缺陷可能导致非授权访问、信息泄露、资源耗尽、资源被盗或者被破坏等。网络安全所面临的威胁可以来自很多方面,并且随着时间的变化而变化。网络安全威胁的种类有如下几类。 (1)窃听。在广播式网络系统中,每个节点都可以读取网上传输的数据,如搭线窃听、安装通信监视器和读取网上的信息等。网络体系结构允许监视器接收网上传输的所有数据帧而不考虑帧的传输目标地址,这种特性使得偷听网上的数据或非授权访问很容易而且不易发现。 (2)假冒。当一个实体假扮成另一个实体进行网络活动时就发生了假冒。
(3)重放。重复一份报文或报文的一部分,以便产生一个被授权效果。 (4)流量分析。通过对网上信息流的观察和分析推断出网上传输的有用信息,例如有无传输、传输的数量、方向和频率等。由于报头信息不能加密,所以即使对数据进行了加密处理,也可以进行有效的流量分析。 (5)数据完整性破坏。有意或无意地修改或破坏信息系统,或者在非授权和不能监测的方式下对数据进行修改。 (6)拒绝服务。当一个授权实体不能获得应有的对网络资源的访问或紧急操作被延迟时,就发生了拒绝服务。 (7)资源的非授权使用。即与所定义的安全策略不一致的使用。 (8)陷门和特洛伊木马。通过替换系统合法程序,或者在合法程序里插入恶意代码,以实现非授权进程,从而达到某种特定的目的。 (9)病毒。随着人们对计算机系统和网络依赖程度的增加,计算机病毒已经构成了对计算机系统和网络的严重威胁。
1.1 信息安全基本概念 在计算机系统中,所有的文件,包括各类程序文件、数据文件、资料文件、数据库文件,甚至硬件系统的品牌、结构、指令系统等都属于信息。 信息已渗透到社会的方方面面,信息的特殊性在于:无限的可重复性和易修改性。 信息安全是指秘密信息在产生、传输、使用和存储过程中不被泄露或破坏。信息安全涉及信息的保密性、完整性、可用性和不可否认性。综合来说,就是要保障信息的有效性,使信息避免遭受一系列威胁,保证业务的持续性,最大限度减少损失。 1.信息安全的4个方面 (1)保密性。是指对抗对手的被动攻击,确保信息不泄露给非授权的个人和实体。采取的措施包括:信息的加密解密;划分信息的密级,为用户分配不同权限,对不同权限用户访问的对象进行访问控制;防止硬件辐射泄露、网络截获和窃听等。 (2)完整性。是指对抗对手的主动攻击,防止信息被未经授权的篡改,即保证信息在存储或传输的过程中不被修改、破坏及丢失。完整性可通过对信息完整性进行检验、对信息交换真实性和有效性进行鉴别以及对系统功能正确性进行确认来实现。该过程可通过密码技术来完成。 (3)可用性。是保证信息及信息系统确为受授者所使用,确保合法用户可访问并按要求的特性使用信息及信息系统,即当需要时能存取所需信息,防止由于计算机病毒或其他人为因素而造成系统拒绝服务。维护或恢复信息可用性的方法有很多,如对计算机和指定数据文件的存取进行严格控制,进行系统备份和可信恢复,探测攻击及应急处理等。 (4)不可否认性。是保证信息的发送者无法否认已发出的信息,信息的接收者无法否认已经接收的信息。例如,保证曾经发出过数据或信号的发方事后不能否认。可通过数字签名技术来确保信息提供者无法否认自己的行为。 2.信息安全的组成 一般来说,信息安全主要包括系统安全和数据安全两个方面。 系统安全:一般采用防火墙、防病毒及其他安全防范技术等措施,是属于被动型的安全措施。 数据安全:则主要采用现代密码技术对数据进行主动的安全保护,如数据保密、数据完整性、数据不可否认与抵赖、双向身份认证等技术。
HRA HRC HRA HRC HRA HRC HRA HRC 186.670.0 10373178.555.0599*******.540.0377*******.0274286.669.5 10173278.254.55896236570.339.53728626627.5271386.669.0 9973377.954.0579*******.039.03678726327.0268486.668.5 9783477.753.55706435538.53628826026.5264586.668.0 9593577.453.0561*******.0351*******.0261686.667.5 9413677.152.55516634537.53529025425.5258786.667.0 9233776.952.05436734137.03479125125.0255886.666.5 9063876.651.55346833636.53429224824.5252986.666.0 8893950176.351.05256933236.03389324524.02491086.665.5 8724049476.150.55177032735.53339424223.52461186.665.0 8564148875.850.05097132335.03299524023.02431286.664.5 8404248175.549.55017231834.53249623722.52401386.664.0 8254347475.349.04937331434.03209723422.02371486.663.5 8104446875.048.54857431033.53169823221.52341586.663.0 7954546174.748.0478*******.0312*******.02311686.662.5 7804645574.547.54707630232.530810022720.52291786.662.0 7664744974.247.04637729832.030410122520.02261886.661.5 7524844273.946.54567829431.530010222219.52231986.661.0 7394943673.746.04497929131.029*********.02212086.660.5 7265043073.445.54438028730.529210421818.52182186.660.0 7135142473.245.0436*******.028*********.02162286.659.5 7005241872.944.54298228029.528510621417.52142386.659.0 6885341372.644.04238327629.028*********.02112486.658.5 6765440772.443.54178427328.52782586.658.0 6645540172.143.04112686.657.5 6535639671.842.54052786.657.0 6425739171.642.03992886.656.5 6315838571.341.53932986.656.0 6205938071.141.03883086.655.56096037570.840.5382 黑色金属材料 硬度值换算表 序号洛氏硬度 维氏硬度HV 布氏硬度HB 洛氏硬度维氏硬度HV 布氏硬度HB 维氏硬度HV 布氏硬度 HB 序号注: 1.布氏硬度:主要用来测定铸件、锻件、有色金属制件、热轧坯料及退火件的硬度,测定范围≯HB450。 2.洛氏硬度:HRA 主要用于高硬度试件,测定硬度高于HRC67以上的材料和表面硬度,如硬质合金、氮化钢等,测定范围HRA>70。HRC 主要用于钢制件(如碳钢、工具钢、合金钢等)淬火或回火后的硬度测定,测定范围HRC20~67。 3.维氏硬度:用来测定薄件和钢板制件的硬度,也可用来测定渗碳、氰化、氮化等表面硬化制件的硬度。序号序号洛氏硬度维氏硬度HV 布氏硬度HB 洛氏硬度
HARDNESS CONVERSION TABLE FOR METALS Vickers Brinell Shore ???? Vickers HRA HRB HRC HRD 15N 30N 45N HV HB HS HRB HRF 15T 30T 45T HV 60Kgf 100Kgf 150Kgf 100Kgf 15Kgf 30Kgf 45Kgf 50Kgf 3000Kgf JIS 100Kgf 60Kgf 15Kgf 30Kgf 45Kgf 85.668.076.993.284.475.494097.6-93.5110.0 90.077.566.0 19685.367.576.593.084.074.392096.4-109.5 65.5 19485.067.076.192.983.674.290095.2-93.077.065.019284.766.475.792.783.173.688094.0-92.5109.076.564.5 19084.465.975.392.582.773.186092.8-92.089.564.0 18884.165.374.892.382.272.284091.5-91.5108.576.063.518683.864.774.392.181.771.882090.2-91.075.563.0 18483.464.073.891.881.171.080088.9-90.5108.089.062.5 18283.063.373.391.580.470.278087.5-90.0107.575.062.018082.662.572.691.279.769.476086.2-89.074.561.5 17882.261.872.191.079.168.674084.8-88.5107.061.0 17681.861.071.590.778.467.772083.3-88.088.574.060.5 17481.360.170.890.377.666.770081.8-87.5106.573.560.0 17281.159.770.590.177.266.269081.1-87.059.5 17080.859.270.189.876.865.768080.3-86.0106.088.073.059.0 16880.658.869.889.776.465.367079.6-85.572.558.516680.358.369.489.575.964.766078.8-85.0105.572.058.0 16480.057.869.089.275.564.165078.0-84.0105.087.557.5 16279.857.368.789.075.163.564077.2-83.571.556.516079.556.868.388.874.663.063076.4-83.0104.571.056.0 15879.256.367.988.574.262.462075.6-82.0104.087.070.555.5 15678.955.767.588.273.661.761074.7-81.5103.570.054.5 15478.655.267.088.073.261.260073.9-80.5103.054.0 15278.454.766.781.872.760.559073.1210{2095}80.086.569.553.5 15078.054.166.287.572.159.958072.2206{2020}79.0102.569.053.014877.853.665.887.271.759.357071.3202{1981}78.0102.068.552.5 14677.453.065.486.971.258.656070.4199{1952}77.5101.586.068.051.5 14477.052.364.886.670.557.855050569.6195{1912}77.0101.067.551.0 14276.751.764.486.370.057.054049668.7190{1863}76.0100.585.567.050.0 14076.451.163.986.069.556.253048867.7186{1824}75.0100.066.549.0 13876.150.563.585.769.055.652048066.8183{1795}74.599.585.066.048.0 13675.749.862.985.468.354.751047365.9179{1755}73.599.065.547.5 13475.349.162.285.067.753.950046564.9174{1706}73.098.584.565.046.513274.948.461.684.767.153.149045664.0169{1657}72.098.084.064.545.5 13074.547.761.384.366.452.248044863.0165{1618}71.097.563.545.0 12874.146.960.783.965.751.347044162.0160{1569}70.097.083.563.044.0 12673.646.160.183.664.950.446043361.0156{1530}69.096.562.543.0 12473.345.359.483.264.349.445042560.0153{1500}68.096.083.062.042.0 12272.844.558.882.863.548.444041559.0149{1461}67.095.561.041.0 12072.343.658.282.362.747.443040558.0144{1412)66.095.082.560.540.011871.842.757.581.861.946.442039756.9140{1373}65.094.582.060.039.011671.441.856.881.461.145.341038855.9136{1334}64.094.081.559.538.011470.840.856.081.060.244.140037954.8131{1285}63.093.081.058.537.011270.339.8 55.280.359.342.939036953.7127{1245}62.092.680.558.035.5 11069.8110.038.8 54.479.858.441.738036052.6123{1206}61.092.057.034.5 10869.237.7 53.679.257.440.437035051.5120{1177}59.591.280.056.033.010668.7109.036.6 52.878.656.439.136034150.4115{1128}58.090.579.555.032.010468.135.5 51.978.055.437.835033149.3112{1098}57.089.879.054.530.510267.6108.034.4 51.177.454.436.534032248.1109{1069}56.089.078.553.529.510067.033.3 50.276.853.635.233031347.0105{1030}54.088.078.052.528.09866.4107.032.2 49.476.252.333.932030345.8103{1010}53.087.277.551.526.59665.831.0 48.475.651.332.531029444.6100{ 981}51.086.377.050.524.59465.2105.529.8 47.574.950.231.130028443.4 97{ 951}49.585.476.549.023.09264.829.2 47.174.649.730.429528042.8 96{ 941}47.584.475.548.021.09064.5104.528.5 46.574.249.029.529027542.2 94{ 922}46.083.575.047.019.08864.227.8 46.073.848.428.728527041.6 92{ 902}44.082.374.545.517.08663.8103.527.1 45.373.447.827.928026540.9 91{ 892}42.081.273.544.014.58463.526.4 44.973.047.227.127526140.3 89{ 873}40.080.073.043.012.58263.1102.025.6 44.372.646.426.227025639.7 87{ 853}37.578.672.041.010.08062.724.8 43.772.145.725.226525239.1 86{ 843}35.077.471.539.57.57862.4101.024.0 43.171.645.024.326024738.4 84{ 824}32.576.070.538.0 4.57662.023.1 42.271.144.223.225524337.8 82{ 804}30.074.870.036.0 1.07461.699.522.2 41.770.643.422.225023837.2 81{ 794}27.573.269.034.07261.221.3 41.170.142.521.124523336.5 79{ 775}24.571.668.032.07061.7 98.120.340.369.641.719.9 24022835.9 78{ 765}21.570.067.030.06896.718.0 23021934.1 75{ 736}18.568.566.028.06695.015.7 22020933.2 71{ 696}15.566.865.025.56493.413.4 21020031.8 68{ 667}12.565.063.523.06291.511.0 20019030.4 65{ 637}10.063.0 62.520.56089.58.5 19018129.0 62{ 608}61.061.018.05887.1 6.0 18017127.7 59{ 579}58.860.015.05685.0 3.0 17016226.5 56{ 549}56.558.512.05481.70.0 16015225.0 53{ 520}53.557.05278.7 15014323.7 50{ 490}50.555.55075.0 14013322.1 46{ 451}49.054.54971.2 13012420.6 44{ 431}47.053.5 4866.7 12011419.1 40{ 392} 45.04762.3 11010517.6-43.04656.2 10095 16.1 - 40.0 45 ? ? ? ? ? ? ? ? ? ? ? ? Kgf/?{N/?} Soft Metal Steel Rockwell Rockwell Superficial Rockwell Rockwell Superficial
安全文化的定义及特征 “文化”的内涵 “文化”(Culture)一词起源于拉丁文的动词Colere,意思是耕作土地,后引申为培养一个人的兴趣、精神和智慧。“文化”的概念最早是由美国人类学家爱德华·泰勒在1871年提出的。他将“文化”定义为“包括知识、信仰、艺术、法律、道德、风俗以及作为一个社会成员获得的能力与习惯的复杂整体”。 对于“文化”一词,《牛津现代词典》的解释是:文化是人类能力的高度发展,借训练与经验而促成的身心的发展、锻炼、修养,或者说是人类社会智力发展的证据、文明,如艺术、科学历史的沉淀物。确切地说,文化是指一个国家或民族的历史、地理、风土人情、传统习惯、生活方式、文学艺术、行为规范、思维方式、价值观念等。 文化的内部结构包括物态文化、制度文化、行为文化和精神文化。物态文化层是人类的物质生产活动方式和产品的总和,是可触知的具有物质实体的文化事物。制度文化层是人类在社会实践中组建的各种社会行为规范。行为文化层是人类交往中约定俗成的以礼俗、民俗、风俗等形态表现出来的行为方式。精神文化层是人类在社会意识活动中孕育出来的价值观念、审美情趣、思维方式等主管因素,相当于通常
所说的基本信念、社会意识等概念。这是文化的核心。 文化体现在一个人如何对待自己,如何对待他人,如何对待自己所处的自然环境。企业文化是企业在生产经营实践中逐步形成的,全体员工所认同并遵守的、带有本组织特点的使命、愿景、宗旨、精神、价值观和经营理念,以及这些理念在生产经营实践、管理制度、员工行为方式与企业对外形象中体现的总和。企业文化的本质是企业在一系列价值选择时进行价值排序的活动。 “企业文化”理论产生于20世纪后半叶的西方企业界。在70年代末80年代初,日美管理文化的热潮,催生了企业文化理论的产生。在20世纪80年代中期企业文化学说传入中国,随后得到了迅速的发展,企业界争先恐后地引进,并产生了良好的社会效应。 安全文化的定义 “安全文化”是在两次重大核事故总结经验教训后,伴随着“企业文化”在20世纪后半叶的蓬勃发展而形成。它是由IAEA在1986年出版的安全丛书No.75—INSAG4《安全文化》中,详细地阐述了安全文化的定义: 安全文化是存在于单位和个人中的各种特性和态度的总和。它建立一
《云计算安全:技术与应用》第7章安全云技术与应用,本章就将从这个角度出发,深入探讨云计算在网络安全领域应用所衍生出的一类新兴云计算服务--安全云服务,结合云计算定义和特征以及安全服务的特点分析,详细介绍安全云服务的定义、特征、分类、技术实现、实施和部署等相关内容。本节为大家介绍安全云服务的定义和特征。 AD: 第7章安全云技术与应用 7.1 安全云服务的定义和特征 7.2 安全云服务技术与实现 7.3 安全云服务部署和应用 深入分析NIST的云计算定义,我们可以认为云计算的本质就是在将计算资源和能力集群和池化的基础上,通过互联网络为用户提供透明、便捷、按需、自助的服务。作为一种全新的技术和业务模式,资源在云端的高度集中化以及业务提供的网络化,都对网络安全提出了新的要求。那么如何保证用户在使用云计算服务过程中的机密性、完整性、可用性以及业务的连续性,就将是关系到云计算能否投入实用的最关键的环节。 本书以上各章在分析了云计算存在的各种安全风险的基础上提出了相应的解决方案,解决了云计算应用安全的问题。从这个角度看,网络安全的实施促进了云计算的部署和实施,是推动云计算得以迅速发展的一个关键要素。但对于网络安全与云计算之间的关系,我们还应该看到另外一方面,即云计算在网络安全领域的应用同样也可以为网络安全技术和服务的发展起到革命性的促进作用。本章就将从这个角度出发,深入探讨云计算在网络安全领域应用所衍生出的一类新兴云计算服务--安全云服务,结合云计算定义和特征以及安全服务的特点分析,详细介绍安全云服务的定义、特征、分类、技术实现、实施和部署等相关内容。 7.1 安全云服务的定义和特征 将云计算技术应用于网络安全领域,将网络安全能力和资源云化,并且通过互联网为客户提供按需的网络安全服务,从而实现一种全新的网络安全服务模式,这种安全服务模式通常称为安全即服务(Security as a Service),往往也简称为SaaS。为了避免与云计算模式的软件即服务(Software as a Service,SaaS)相混淆,在本书中将这种业务模式称为安全云服务(Security Cloud Service,SCS)。 安全云服务是将云计算技术和业务模式应用于网络安全领域而出现的产物,因此在定义安全云服务前我们先来看看云计算的定义。 根据美国国家标准与技术研究院(National Institute of Standards and Technology,NIST)的定义,云计算是一个模型,这个模型可以方便地按需访问一个可配置的计算资源(例如,网络、服务器、存储设备、应用程序以及服务)的公共集,这些资源可以被迅速提供并发布,同时最小化管理成本或服务提供商的干涉。根据这个定义可以看到,在将云计算技术应用于网络安全领域实现安全云服务时主要应该体现云计算的以下几个特征。 (1)计算资源和能力的集群和池化。将计算资源和能力集中起来为多个用户共享服务,并根据客户的需求动态分配或再分配不同的物理或虚拟的资源。 (2)以互联网络为基础的业务提供途径。用户可以随时随地通过网络使用云计算服务提供的各种计算资源和能力。 (3)按需自助服务。系统具备为用户提供灵活的计算资源的管理和分配能力,能够为用户提供符合其业务需求的、可伸缩的业务能力。 (4)服务透明化。用户在使用服务时无须知道云内部资源的结构、实现方式和地理位置,用户可以在最小化管理成本和业务提供商交互的情况下获得自己所关心的业务实现资源。(5)业务提供服务化。用户通过云服务获得满足自己需求的计算资源和能力,而非买断、
33 机械安全的定义及特性 【大纲考试内容要求】: 1、了解机械安全的特性; 2、掌握人机系统常见的事故及其原因; 3、熟悉机械设备故障诊断技术。 【教材内容】: 第三节机械的安全特性及故障诊断技术 一、机械安全的定义及特性 (一)机械安全定义 机械安全是指机器在按使用说明书规定的预定使用条件下,执行其功能和在对其进行运输、安装、调试、运行、维修、拆卸和处理时对操作者不发生损伤或危害其健康的能力。它包括两个方面的内容: (1)在机械产品预定使用期间执行预定功能和在可预见的误用时,不会给人身带来伤害; (2)机械产品在整个寿命周期内,发生可预见的非正常情况下任何风险事故时机器是安全的。 (二)机械安全的特性 现代机械安全应具有以下几方面的特性: 1.系统性 现代机械的安全应建立在心理、信息、控制、可靠性、失效分析、环境学、劳动卫生、计算机等科学技术基础上,并综合与系统地运用这些科学技术。 2.防护性 通过对机械危险的智能化设计,应使机器在整个寿命周期内发挥预定功能,包括误操作时,其机器和人身均是安全的,使人对劳动环境、劳动内容和主动地位的提高得到不断改善。3.友善性 机械安全设计涉及到人和人所控制的机器,它在人与机器之间建立起一套满足人的生理特性、心理特性,充分发挥人的功能的、提高人机系统效率的安全系统,在设计中通过减少操作者的紧张和体力来提高安全性,并以此改善机器的操作性能和提高其可靠性。 4.整体性 现代机械的安全设计必须全面、系统地对导致危险的因素进行定性、定量分析和评价,整体寻求降低风险的最优设计方案。 人机系统常见的事故及其原因 二、人机系统常见的事故及其原因 (一)常见的事故 1.卷入和挤压 这种伤害主要来自旋转机械的旋转零部件,即两旋转件之间或旋转件与固定件之间的运动将人体某一部分卷入或挤压。这是造成机械事故的主要原因,其发生的频率最高,约占机械伤害事故的47.7%。 2.碰撞和撞击 这种伤害主要来自直线运动的零部件和飞来物或坠落物。例如,做往复直线运动的工作台或滑枕等执行件撞击人体;高速旋转的工具、工件及碎片等击中人体;起重作业中起吊物的坠落伤人或人从高层建筑上坠落伤亡等。 3.接触伤害 接触伤害主要是指人体某一部分接触到运动或静止机械的尖角、棱角、锐边、粗糙表面等发生的划伤或割伤的机械伤害和接触到过冷过热及绝缘不良的导电体而发生冻伤、烫伤及触电