1、BRITISH STANDARD BS 7539:1992 Methods for test for Determination of properties of cushioning materials for package design purposesBS7539:1992 This British Standard, having been prepared under the directionof the Packaging andFreight Containers StandardsPolicy Committee, waspublishedunder the authori
2、tyofthe Standards Boardand comes into effect on 31January1992 BSI 08-1999 The following BSI references relate to the work on this standard: Committee reference PKM/22 Draft for comment 90/42439 DC ISBN 0 580 20322 0 Committees responsible for this British Standard The preparation of this British Sta
3、ndard was entrusted by the Packaging and Freight Containers Standards Policy Committee (PKM/-) to Technical Committee PKM/22, upon which the following bodies were represented: British Paper and Board Industry Federation British Rubber Manufacturers Association Ltd. EEA (the Association of Electronic
4、s, Telecommunications and Business Equipment Industries) Institute of Packaging Ministry of Defence PIRA International Amendments issued since publication Amd. No. Date CommentsBS7539:1992 BSI 08-1999 i Contents Page Committees responsible Inside front cover Foreword ii Section 1. General 0 Introduc
5、tion 1 1 Scope 1 2 Definitions 1 Section 2. Method 1. Determination of dynamic cushioning performance ofsheetor block material 3 General 2 4 Apparatus 2 5 Test pieces 2 6 Conditioning and test conditions 2 7 Procedure 3 8 Calculation 3 9 Test report 3 Section 3. Method 2. Measurement of creep strain
6、 and compression set ofsheetor block material 10 General 4 11 Apparatus 4 12 Test pieces 4 13 Conditioning and test conditions 4 14 Procedure 4 15 Calculation of results 5 16 Test report 5 Section 4. Methods 3A, 3B and 3C. Determination of the cushioning propertiesofloose fill materials 17 General 6
7、 18 Apparatus 6 19 Conditioning and test conditions 8 20 Method 3A. Determination of compression under load and requiredoverfill 8 21 Method 3B. Determination of the maximum static stress the material can support under repeated low-level impacts 9 22 Method 3C. Determination of effectiveness of posi
8、tioning an article under vibration 9 Section 5. Method 4. Measurement of fungal growth of sheet or block cushioningmaterial 23 Test specimens 11 24 Procedure 11 25 Test report 11 Appendix A Measurement of dimensions of test pieces (based on BS 4443-1) 12 Figure 1 Bounce machine, basic drive machanis
9、m 6 Figure 2 Construction of test box used in methods 3A, 3B and 3C 7 Figure 3 Compression tray 8 Figure 4 Determination of test block position (method 3C) 10 Figure 5 Apparatus for measurement in accordance with method 1A 13 Publication(s) referred to Inside back coverBS7539:1992 ii BSI 08-1999 For
10、eword This British Standard has been prepared under the direction of the Packaging and Freight Containers Standards Policy Committee to provide a standard listing methods of test for the determination of those properties of cushioning materials which are particularly relevant for purposes of package
11、 design. Certain methods are based closely on methods of test given in BS4443 but these have been modified to make them more specific to package design and the basic cushion design guidance given in BS 1133-12. A British Standard does not purport to include all the necessary provisions of a contract
12、. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages1 to 14, an inside back cover
13、and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover.BS7539:1992 BSI 08-1999 1 Section 1. General 0 Introduction A packaged article, depending on its nature, may require
14、 the package to provide protection against shocks occurring during transit. Such shocks may be of high or medium intensity but intermittent, caused by drops or other impacts or, more usually, of lower intensity but repeated, due to vehicle vibration. One method of protecting the article is to cushio
15、n it against anticipated shocks using materials which deflect on impact. Such cushioning materials reduce the level of shock from impacts by allowing controlled movement of the packaged article within the package at the instant of impact, so reducing the deceleration and the resulting force transmit
16、ted to the article. Cushioning materials can also be used to reduce the transmission of vibration to the article when this is likely to be a problem. In order to design a package providing adequate protection, various properties of the available cushioning materials need to be considered. The method
17、s described in this standard are particularly appropriate for measuring those properties relevant to package design. Design data obtained by these methods, while essential for rational design of the cushion, provide only an estimate of package performance, which is influenced by many other factors i
18、ncluding: a) the type of container and the material from which it is constructed; b) the orientation of the package on impact; c) the nature of the surface on which it falls; d) the ratio of overall cushion volume to internal air volume (open cell materials only); e) friction between the packaged ar
19、ticle and any side cushions. Instrumented tests on a prototype package are always advisable to check that the required level of protection has been achieved. BS 1133-12 gives information on the various types of cushioning materials and outlines a basic cushion design procedure. 1 Scope This British
20、Standard describes methods for the determination of those properties of sheet or block cushioning materials particularly relevant for package design purposes; dynamic cushioning performance, creep strain and residual compression set. The standard also includes methods for the determination of releva
21、nt properties of loose fill materials and for the measurement of fungal growth of both cushioning and loose fill materials. NOTEThe titles of the publications referred to in this standard are listed on the inside back cover. 2 Definitions For the purposes of this British Standard the following defin
22、itions apply. 2.1 static stress the force exerted by the drop hammer of the test apparatus (method1) or the test block (method3) when at rest, divided by the original area of the test piece (method1) or the base area of the block (method3), expressed in kPa 2.2 peak deceleration the maximum decelera
23、tion of the drop hammer during the impact on the test piece (method1) or the maximum deceleration of the test block during the test drop (method3) 2.3 corrected value of peak deceleration G c the value of the measured peak deceleration (G m ) after correction for any small deviation of the original
24、thickness of the test piece from the standard reference thickness at which it was intended to test. This is obtained by multiplying the measured peak deceleration by the original thickness divided by the standard reference thickness 2.4 standard gravitational acceleration g n the acceleration due to
25、 the effect of the earths gravitational pull. Although this value varies slightly from place to place, it is usually considered to be a constant with the value of9.81m/s 2 2.5 nominal drop height h n the height specified for drop testing the package under free fall conditions NOTEIn order to achieve
26、 the same impact velocity on the drop test machine (method1) a slightly greater actual drop height h cis required because of friction effects (see4.1.2). 2.6 residual compression set the percentage loss in thickness of the test piece after impact or after a selected period under static stress and a
27、short period of recovery 2.7 creep strain the percentage change in strain exhibited by a test piece under static stress as determined by measurements after15min and a selected period after loading 2.8 compression stress the static force per unit area of the original cross section of the test pieceBS
28、7539:1992 2 BSI 08-1999 Section 2. Method 1. Determination of dynamic cushioning performance of sheet or block material 3 General This method describes the procedure for determining the dynamic cushioning performance of sheet or block material by measuring the peak deceleration of a mass when it is
29、dropped onto a test piece of the material. It is based on method9 of BS4443-3 which is intended primarily for quality assurance purposes for packaging applications. 4 Apparatus 4.1 Drop test machine, in accordance with4.1.1 to4.1.3. 4.1.1 The apparatus is a guided vertical drop tester comprising a d
30、rop hammer with a flat base, with an impacting area greater than that of the impacted test piece, and an anvil whose face is parallel to the base of the drop hammer. The mass of the drop hammer shall be adjustable in the range of static stresses required; alternatively a range of hammers can be used
31、. The mass of the anvil and the base to which it is attached shall be at least100 times that of the hammer to prevent undesirable vibrations which may conceal or modify the true shape of the deceleration time curve. The natural frequency of vibration of the hammer should be as high as practicable, p
32、referably above1000 Hz. It is essential that the drop hammer mechanism is such that the safety of the operator is assured when the test pieces are being placed on the anvil; some form of safety interlock is recommended. 4.1.2 Due to contact with the guides the drop hammer will lose energy during the
33、 fall, and the actual drop height (h c ) has to be greater than the theoretical drop height to ensure that at impact the velocity of the hammer is the same as would be achieved under free fall conditions from the selected nominal drop height (h n ). The impact velocity under free fall conditions for
34、 any drop height is calculated using the following equation: V = (2 g nh n ) where V is the impact velocity (in m/s); g nis the acceleration due to gravity (9.81m/s 2 ); h nis the nominal drop height (inm). 4.1.3 The instrumentation for measuring, recording and storing the deceleration on impact sha
35、ll be capable of an accuracy to within 5%. 5 Test pieces 5.1 Number of test pieces Three test pieces shall be tested at each of, as a minimum, five values of static stress for each combination of drop height and thickness. For the minimum test sequence45test pieces are required. 5.2 Dimensions of te
36、st pieces Each test piece shall be a right parallelepiped with the following dimensions: NOTEFor commercial purposes this test can also be used for thinner pieces. The difference in the mean thickness between the test pieces in a set of10 shall be not greater than2mm. Measure the dimensions in accor
37、dance withAppendix A. 5.3 Preparation of test pieces Test pieces of thickness25mm and more can, where necessary, be obtained by plying up two sheets without the use of adhesive. Cut such sheets to identical shapes and sizes and ensure that they are of the same orientation with respect to any known d
38、irection of anisotropy. Cut the test piece by any suitable means which does not alter the dynamic cushioning characteristics, for example a band saw or a sharp knife. Hot wire cutting shall not be used. NOTEThe presence of skin in the test piece may affect the test result. Where skin will form an in
39、tegral part of the article in use, the preparation of the test piece should be a matter for agreement between the purchaser and the supplier. The presence of skin on the test piece shall be noted in the test report. 6 Conditioning and test conditions Materials shall not be tested less than72h after
40、manufacture. Prior to testing, condition the test pieces for at least16h under the following standard conditions: 23 2 C,505% r.h. NOTEThe conditioning period may form the latter part of the72h following manufacture. Carry out the test at the same conditions unless design data are required on perfor
41、mance under other specific conditions. Length and width (to be equal): either 150 5 mm or250 5 mm; Thickness: within the range 25 mm to 150 mm.BS7539:1992 BSI 08-1999 3 7 Procedure 7.1 General 7.1.1 Measure the original thickness, T o , of the test piece in accordance with either method1A or1B ofApp
42、endix A. Having ensured that the drop hammer is in the safe position, place the test piece on the anvil of the apparatus. Prepare the drop hammer to impact the test piece. 7.1.2 For tests in conditions other than23 2 C and505% r.h., condition the test piece at the specified test conditions for a per
43、iod of at least16h following the measurement of the original thicknessT o . 7.1.3 Impact the test piece using the actual drop height h cas calculated in4.1.2 and the static stress as described in7.3. Measure and record the peak deceleration, G m , of the drop hammer on impact. Each test piece is to
44、be used for only one combination of static stress and impact velocity. NOTEFor certain commercial purposes the test may be carried out by impacting the test piece three times at intervals of60 15s, with the peak deceleration, G m , measured and recorded on the first and third impacts. After the firs
45、t or third impact, as appropriate, remove the test piece, allow it to recover for51min and measure its thickness, T vin accordance with either method1A or1B ofAppendix A. 7.2 Drop height Carry out tests from either three drop heights, preferably those equivalent to nominal drop heights of300mm,600mm
46、 and900mm (see4.1.2) or five drop heights, the additional nominal drop heights being750mm and 1 350mm. NOTETests at five drop heights are necessary for Ministry of Defence type approval purposes. 7.3 Static stress At each drop height, use a minimum of five different levels of static stress, such tha
47、t one gives approximately the minimum peak deceleration on impact, the remainder being equally distributed above and below this level, corresponding approximately to a10% and20% increase in peak deceleration. 8 Calculation 8.1 Residual compression set Calculate the residual compression set after imp
48、act and recovery as follows. Residual compression set = where T ois the original thickness of the test piece (inmm); T vis the thickness of the test piece after impact and recovery (inmm). 8.2 Peak deceleration Calculate the corrected value of the peak deceleration G c(in m/s 2 ) as follows: where G
49、 mis the measured value of the peak deceleration (in units of standard gravitational acceleration); T ois the original thickness (inmm); T sis the standard reference thickness (inmm). 9 Test report The test report shall include the following: a) a description of the material (including nominal density); b) the conditioning and test conditions, if other than as described in clause6, with a brief indication of the drop testing machine used; c) the method of measurement used for recording test piece size, i.e.method1A,1B or1C; d) a set of dynamic performance
