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Marks &SpencerMETHOD OF TESTTEAR STRENGTHPURPOSEAPPARATUSTo assess the tear strength of woven fabrics.1.“Elmendorf”tear strength tester with a pendulumexerting a maximum force of 1631g (16000 mN)(Pendulum B) (Equipment Index Ref:11L,13AY,20A,23AE and 24A).P29ORElmatear (Equipment Index Ref:13AY)(PendulumA,B and C)2.3.4.Marks and Spencer blade for ‘Elmendorf’to achievecut of 15mm.(Equipment Index Ref:20D).Metal ruler (mm).(See Test Method PG).50mm x 50mm de-sized bleached cotton lawnwithout finish (see Equipment Index Ref:13A,24Yand 25D).TEST SPECIMENAvoid fabric within 50mm of selvedges.Five test specimensshould be prepared from the fabric according to thedirection in which they will be tested.Ensure that no twospecimens contain the same set of warp and weft threads.The specimen size is 80mm x 58mm.The specimenshould be frayed down to achieve the 58mm dimension.Use a metal ruler for accuracy.Trim back one of the frayed edges to the fabric.Thistrimmed edge can then be inserted downwards intothe clamp.For Weft Tear StrengthThe 58mm dimension is in the warp direction and the80mm dimension is in the weft direction.The tear isacross the weft threads.For Warp Tear StrengthThe 58mm dimension is in the weft direction and the80mm dimension is in the warp direction.The tear isacross the warp threads.CONDITIONINGCondition the prepared test specimens for a minimum of 4hours in the standard atmosphere for testing,at a temperatureof 20˚ ±2˚C and a relative humidity of 65% ±2%.P29 P1 of 4SEPTEMBER 2004P29Marks &SpencerThe equipment must be sited in this atmosphere.Carry out the tests in this atmosphere.PREPARATIONFor calibration of H.E.Messmer Ltd.Elmendorf machineOF ELMENDORFsee the Appendix.TEAR STRENGTHFor all other models calibration should be carried outTESTERaccording to the manufacturers instructions.On all machines before commencing testCheck the length of the cut made by the knife as follows:-Fray along one side of the cotton lawn square and trim toachieve a straight edge.Clamp the trimmed edge into thejaws and make a cut.Using the metal ruler measure thelength of the cut which must be 15mm.If necessary theblade should be adjusted to give the correct length of cut.METHOD1.Clamp a test specimen in the jaws so that the 80mmside of the specimen with the trimmed edge isparallel to the base and the 58mm side of thespecimen is at right angles to the base.Make the cut in the specimen.Set the pointer to the starting position.Depress the pendulum stop to release the pendulum.Allow the pendulum to swing a full cycle beforereleasing the stop.Read off and record the position of the pointer onthe scale.Repeat steps 1 to 5 inclusive for the four remainingspecimens in this manner.2.3.4.5.6.RESULTSFor Machines Graduated from 0 to 1000 mNTake each result,multiply it by 16 and divide this figureby 9.81 to convert the result to grammes.Report all fivefigures and the direction (warp or weft) in which the testswere made.For Machines Graduated from 0 to 100 grammesTake each result and multiply this figure by 16 to give theresult in grammes.Report all five figures and thedirection (warp or weft) in which the tests were made.SEPTEMBER 2004P29 P2 of 4Marks &SpencerAPPENDIXZEROING PROCEDURE FOR H.E.MESSMER LTD.- ELMENDORF TEAR STRENGTH TESTERA.B.C.D.E.F.G.H.I.J.Levelling ScrewLevelling ScrewPendulum Release LeverPointer StopPointer Retaining KnobFriction Spring HousingKnurled Lock NutJawsPointerPendulumP291.2.3.Clamp shut the jaws without any specimens.Use the levelling screw A to set the spirit levellocated at the rear of the apparatus.With the pendulum already in the released position(as above) depress the release lever and ensure thatthe reference line in the centre of the pendulum isaligned to the reference line on the datum block atthe base of the tester.Use the levelling screw on the extreme left (B) forany necessary adjustments.P29 P3 of 4SEPTEMBER 2004P29Marks &Spencer4.Raise the pendulum to its operating position so thatit is supported by the pendulum release lever (C).In this position the reference line on the pendulum,the reference line of the datum block and the pointerstop (D) should all coincide.The pointer stop canbe adjusted if necessary.Move the pointer so that the tip is against the pointerstop (D).Allow the pendulum to swing freely by depressingthe pendulum release lever,allow a full swing cyclebefore releasing the stop to act as a brake.Thepointer must register zero ±3mm either side of thezero line.Use a metal ruler to measure thistolerance.Repeat steps (4 to 6) a minimum of 3times to establish that the machine is calibrated.If the pointer does not register zero ±3mm clean thepointer apparatus as follows:-Remove the pointer by unscrewing the retainingknob.Clean the tufnol liner of the pointer hub witha cleaning spirit using a clean,dry linen type cloth.DO NOT USE OIL OF ANY TYPE.Reassemble pointer and repeat steps 4 to 6 aminimum of 3 times.If the pointer still fails to consistently register zero ±3mm adjust the pointer friction as follows:-The mechanism for adjustment is located in thefriction spring housing (F).Slacken off knurled locknut (G).The friction can then be reset by increasing ordecreasing the tension by careful adjustment of therotating socket screw with the allen key supplied.Tighten the knurled lock nut and repeat steps 4 to 6a minimum of 3 times until the pointer registers zero±3mm when allowed to swing freely.Continue with the procedure to check the length ofcut before testing prepared specimens.Important:The knife and its lever must be secure and only allow a downwardsmovement.The lever can be tightened with the allen screw situatedat the back of the lever.5.6.SEPTEMBER 2004P29 P4 of 4