1、Designation: F320 16Standard Test Method forHail Impact Resistance of Aerospace TransparentEnclosures1This standard is issued under the fixed designation F320; the number immediately following the designation indicates the year of originaladoption or, in the case of revision, the year of last revisi
2、on.Anumber in parentheses indicates the year of last reapproval.Asuperscriptepsilon () indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the U.S. Department of Defense.1. Scope1.1 This test method covers the determination of th
3、e impactresistance of an aerospace transparent enclosure, hereinaftercalled windshield, during hailstorm conditions using simulatedhailstones consisting of ice balls molded under tightly con-trolled conditions.1.2 The values stated in inch-pound units are to be regardedas standard. The values given
4、in parentheses are mathematicalconversions to SI units that are provided for information onlyand are not considered standard.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish app
5、ro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use. For specific hazardstatements see Section 7.2. Terminology2.1 Definitions:2.1.1 damage, nany modification in visual properties orintegrity of a windshield as a result of hail impact includi
6、ngscratches, crazing, delamination, cracks, or shattering.2.1.2 ice ball, na frozen mass of water, with filler, thatsimulates a natural hailstone in weight, size, and toughness.2.1.3 impact angle, nthe angle between the ice ball flightpath and the target normal.2.1.4 sabot, na plastic device for pro
7、tecting the ice ballwhile in the launch tube. One type of sabot (see Fig. 1) consistsof a split polycarbonate rod containing a central cavity forholding the ice ball. Each sabot half is designed to assureaerodynamic separation from the ice ball after ejection fromthe launch tube.3. Summary of Test M
8、ethod3.1 The test method involves launching a series of ice ballsof specified sizes at a sample windshield at a designatedvelocity and angle and in a specified pattern. Requirements arespecified for the ice ball, test specimen, procedure, and dataacquisition. The ice ball is photographed in flight t
9、o verify itsintegrity.3.2 Requirements are specified for a particular apparatusand test procedure, but options are permitted for certain areas.However, it must be possible to demonstrate that the optionsused result in an ice ball impacting the test panel with the samesize, consistency, and velocity
10、as with the specified apparatusand procedure. Following are areas where options are allowed:3.2.1 Ice Ball Mold Material.3.2.2 LauncherAny type of launcher is allowable as longas the iceball reaches the test specimen intact at the correctspeed. The use of sabots and sabot material and geometry areop
11、tional.3.2.3 Method of Determining Ice Ball Integrity.3.2.4 Ice Ball Speed Measurement, optional as long asaccuracy standards are met.3.2.5 Test Specimen SizesThose given are minimum.3.2.6 SafetySafety must satisfy the safety standards of thetest facility being used.4. Significance and Use4.1 This t
12、est method shall be used to determine the hailimpact resistance of windshields for acceptance, design,service, or research purposes. By coupling this method with theinstalled angle and velocity of a specific aerospace vehicle,design allowables, criteria, and tolerances can be establishedfor that veh
13、icles windshield.5. Apparatus5.1 The facilities and equipment required for the perfor-mance of this test procedure include a suitable firing rangeequipped with an ice ball mold, a launcher, blast deflector,sabot trap, velocity measuring system, test specimen holder,and a camera with strobe lights to
14、 verify ice ball integrity.Ancillary equipment required for this test include test1This test method is under the jurisdiction of ASTM Committee F07 onAerospace and Aircraft and is the direct responsibility of Subcommittee F07.08 onTransparent Enclosures and Materials.Current edition approved April 1
15、, 2016. Published April 2016. Originallyapproved in 1978. Last previous edition approved in 2010 as F320 10. DOI:10.1520/F0320-16.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1specimen, ice balls, sabots, and firing cartridges. An e
16、xamplefacility is described below.5.2 Firing RangeThe firing range shall be a minimum of9 by 18 ft (3 by 6 m) enclosed to contain flying debris and toexclude unauthorized personnel.5.3 Ice Ball Mold, two aluminum blocks with hemisphericalcavities and vent holes for filling with water and for waterex
17、pansion during freezing.5.4 Launcher, a variety of launchers are suitable as noted in3.2.2. In addition to the powder gun described in this testmethod, laboratories have also successfully utilized com-pressed gas gun launchers. An example of a powder gunlauncher is shown in Fig. 2, consisting of a b
18、arrel, breech,breech plug, and control. The barrel shall be made fromhigh-quality AISI 4130 seamless steel tubing, or equivalent, inthe annealed condition. The breech shall be made from AISI4130 steel rod, or equivalent, heat treated to a 160- to 180-ksi(1104- to 1242-MPa) ultimate tensile strength
19、condition. Thesize of cavity to be used in the breech depends on the desiredtest velocity (see Table 1). The breech plug, which locks thecartridge in place and contains the firing pin, shall be made of4340 steel heat treated to a 160- to 180-ksi ultimate tensilestrength condition. The firing pin is
20、actuated by a kineticimpact air piston. Control is accomplished by an electricallyactuated air valve. For a 100-psi (0.69-MPa) air source, a0.75-in.2(4.84-cm2) piston traveling 0.5 in. (13 mm) is used.5.5 Blast DeflectorPlace a plate with a 4-in. (100-mm)diameter hole as shown in Fig. 3 between the
21、sabot trap and thefirst velocity measuring station. Then place a corrugatedcardboard plate over the hole. This deflector is not required forcompressed gas gun systems.5.6 Sabot Trap is made by placing two steel plates two tofour ice ball diameters apart, centered on the flight path andlocated a mini
22、mum of 6 ft (1.82 m) from the launcher muzzleFIG. 1 Sabot ConfigurationFIG. 2 Launcher DesignF320 162as shown in Fig. 4. This trap is not required for systems thatutilize aerodynamic separation of the sabot or other suitablemechanisms to ensure that the sabot does not impact the testarticle.5.7 Velo
23、city Measurement SystemThe break-screen veloc-ity measurement consists of a set of screens, power supply,wiring, and counters. Three screens shall be made from alightweight bond paper with an electrical circuit painted on thepaper by the silk screen process. The paint for the circuit shallbe electro
24、nic grade electrical conducting paint.2Do not thin thepaint. The break-screen shall be made with lines18 in.(3.2 mm) wide by 18 in. (460 mm) long as shown in Fig. 5giving a resistance of no more than 300 . Fig. 6 shows thearrangement of components and gives the electronic circuit tobe used with the
25、three screens. The system shall be accurate to61 % or better. Laser-based photo detector systems andhigh-speed-film-based systems are also acceptable, providedthe accuracy is 61%.5.8 Test Specimen HolderUse one of two types of testspecimen holders. The one in Fig. 7 is designed to hold an 18-by 18-i
26、n. (0.46- by 0.46-m) test specimen that can be impactedat angles ranging from 0 to 80 as detailed in Section 8. Whentesting a complete windshield, use edge restraints similar to theactual installation and place the windshield in the properorientation (see 9.2).2The sole source of supply of the appar
27、atus known to the committee at this timeis “Silver Preparation,” duPont electronic grade No. 4817. If you are aware ofalternative suppliers, please provide this information to ASTM InternationalHeadquarters. Your comments will receive careful consideration at a meeting of theresponsible technical co
28、mmittee2, which you may attend.TABLE 1 Power LoadsDesired Veloc-ity, ft/s (m/s)Barrel Bore, in.(mm)Barrel Length,in. (m)Cartridge Size,caliberPowder TypePowder Weight,grains (g)200 (60) 1.25 (32) 10 (0.25) 0.30 BullseyeA6 (0.39)2.25 (57) 10 (0.25) 0.30 Bullseye 6 (0.39)500 (150) 0.75 (19) 10 (0.25)
29、0.30 Bullseye 5 (0.32)1.25 (32) 60 (1.52) 0.50 4227B40 (2.59)2.25 (57) 60 (1.52) 0.50 Bullseye 30 (1.94)2.25 (57) 10 (0.25) 0.30 Bullseye 12 (0.78)1000 (300) 0.75 (19) 10 (0.25) 0.30 Bullseye 9 (0.58)1.25 (32) 60 (1.52) 0.50 Bullseye 60 (3.89)1.25 (32) 10 (0.25) 0.30 Bullseye 20 (1.30)2.25 (57) 60 (
30、1.52) 0.50 Bullseye 70 (4.54)2000 (600) 0.75 (19) 60 (1.52) 0.50 Bullseye 35 (2.27)1.25 (32) 60 (1.52) 0.50 Bullseye 70 (4.54)2.25 (57) 60 (1.52) 0.50 Bullseye 150 (9.72)AThe sole source of supply of the apparatus known to the committee at this time is Hercules, Inc., 1313 North Market Street Wilmin
31、gton, DE 19894-0001. If you are awareof alternative suppliers, please provide this information to ASTM International Headquarters. Your comments will receive careful consideration atameetingoftheresponsible technical committee2, which you may attend.BThe sole source of supply of the apparatus known
32、to the committee at this time is duPont, Chestnut Run Plaza 705/GS38 Wilmington, DE 19880-0705. If you are awareof alternative suppliers, please provide this information to ASTM International Headquarters. Your comments will receive careful consideration atameetingoftheresponsible technical committe
33、e2, which you may attend.FIG. 3 Blast DeflectorFIG. 4 Sabot TrapF320 1635.9 Ice Ball Integrity CameraVerify ice ball integritybefore impact by obtaining a photograph of the ice ball in flightbefore impact. This is accomplished by illuminating the iceball with a strobe light while the ice ball is in
34、the field of viewof a camera lens. This synchronization can be obtained byusing an open shutter with the strobe triggered at the secondvelocity screen. The signal is split with part going to thevelocity counters and part to a variable time-delay generator.Using the estimated ice ball velocity, a tim
35、e delay is selected sothe ice ball will be in view of the camera lens when the strobeis triggered.5.10 Balance, for powder and ice balls, capacity 0.2 lb(100 g), accuracy 61 % (1.0 g).5.11 Clinometer or Protractor, to measure impact angle,accuracy 614 .5.12 Syringe, 100-cm3, for putting water into t
36、he ice ballmold.6. Materials6.1 SabotAn effective injection molded sabot configura-tion is shown in Fig. 1a, while a machined configuration isshown in Fig. 1b. In either design, polycarbonate material isused to form the two halves of the sabot at a minimum diameterequal to the ice ball diameter plus
37、18 in. (3.2 mm) with a lengthapproximately twice this diameter to assure in-flight separationof the sabot halves. An acceptable tolerance of the sabotFIG. 5 Velocity ScreenFIG. 6 Velocity Measuring SystemFIG. 7 Test Specimen HolderF320 164diameter has been found to be within 0.005 in. (0.127 mm) oft
38、he minimum barrel diameter.6.2 GunpowderThe brands listed in Table 1 have beenfound to be satisfactory for powder guns.6.3 Cartridge Cases, with primers, 0.30 and 0.50 caliber, orother sizes used with powder guns.6.4 Cotton FiberStandard pharmaceutical cotton balls.6.5 Bags, Polyethylene, commercial
39、 grade.6.6 Plastic WrappingPoly(vinylidene chloride).7. Hazards7.1 Powder Storage and HandlingPowder handling andstorage shall conform to all Federal and local regulations. Thehandling facility in which the powder charges are weighed andloaded must be reserved for this purpose alone. Procureprimers
40、already mounted in the cartridge cases or specialfacilities provided for this dangerous operation.7.2 Firing AreaExclude all personnel from the firing areaexcept the operator.7.3 Locked SwitchThere shall be a locked switch on thefiring circuit which can be closed only by a key kept in theoperators p
41、ossession during the entire calibration and testprocedure.8. Test Specimen8.1 The test specimen shall be a duplicate of the windshieldbeing simulated or a section thereof. If a section is used, it shallmeasure 18 by 18 in. (0.46 by 0.46 m). Surface condition shallbe dry. Temperature shall be ambient
42、 unless special tempera-tures are associated with the particular installation beingsimulated. In the case of special temperatures, the temperatureto use and the method of attainment are to be established bymutual agreement between the user and the testing agency. Usea strong backlight to aid visual
43、inspection of the windshieldboth before and after the test.9. Preparation of Apparatus9.1 VelocitySelect the ice ball velocities from one of thestandard values in Table 2 unless otherwise specified.9.2 Impact AngleSelect the impact angles from the fol-lowing standard conditions, unless otherwise spe
44、cified.9.2.1 For the 18- by 18-in. (0.46- by 0.46-m) cut section, theimpact angle shall be 45 at the center of the section.9.2.2 For the complete windshield, the impact angle at thecenter and at the edge shall be the actual minimum anglebetween the ice ball flight path and the normal to thewindshiel
45、d surface.9.3 Preparation of Ice Balls:9.3.1 Separate and weigh an amount of cotton filler asspecified in 10.2.9.3.2 Dip the above amount of cotton into a container ofwater, remove, and shape into a sphere.9.3.3 Place the cotton sphere into the mold.9.3.4 After securing the mold halves, fill the cav
46、ity withwater from a syringe. Place the syringe point at the lowestpoint in the mold cavity so that the rising water will drive theair out.9.3.5 Place the mold in a 0F (18C) environment untilfrozen. With experience, complete freezing can be determinedfrom the length of the sprue extruded from the fi
47、ller hole.9.3.6 Rapidly bring the mold to above freezing by immers-ing it in room temperature water until the ice on the mold slips.Remove from water.9.3.7 Open the mold and remove the ice ball. Seal the iceball in a polyethylene bag and store in the freezer at 0F(18C). Ice balls shall not be more t
48、han four days old beforeuse. Minimize the time out of the mold because of theformation of cracks with time.9.4 Ice Ball Size and Impact Pattern:9.4.1 If a pass/fail iceball size requirement is not specified,impact nine12-in. (13-mm) diameter ice balls in the patternshown in Fig. 8. Likewise, impact
49、nine 1.0-in. (25-mm)diameter and five 2.0-in. (51-mm) diameter ice balls with therespective patterns shown in Fig. 8. An exception is the testingof a windshield edge where only four 2.0-in. (51-mm) ice ballswill be tested. If a pass/fail iceball size requirement isspecified, impact with the specified iceball size in the Fig. 8pattern, which is nearest to the specified size.9.4.2 Orient the edge of the windshield such that the centerof the impact pattern is located 2.8 in. (71 mm) laterally fromthe point on the windshield edge selected in 9.2.2.
