ISO 6312:2001 pdf download
ISO 6312:2001 pdf download.Road vehicles – Brake linings -Sheartest procedure for disc brake pad and drum brake shoe assemblies.
6 Test rig and fixtures
6.1 Test rig
The test rig shall be a compression or tensile testing machine or similar (shear testing) machine of sufficient capacity to apply the shearing load by activating a ram.
The test rig shall be povlded with equipment to register the exact load applied at the instant of shear failure.
The load application rate shall be controlled in such a way that the load increases at an average rate of (4 500 t 1 000) N/s (as determined from typical vehiclebased evakiation), ii a constant crosahead speed mactime is being used the load rate stial be set to (10± 1) mm/mm. This shall be indicated in the results, which, it shall be noted. cannOt be compared to tests conducted on machines of the constant load type. Shock loading shall be avoided.
6.2 FIxtures
6.2.1 General
The shearing test fixture shall have the means to hold a test sample such that lies parallel to the loading tool. This
1001 shall have a radius of 1.5 mm at the part in contact with the test sample.
6.2.2 Drum brake shoe assembly
The fixture (see Figure 2) shall be designed so that the loading tool is in contact with the edge of the lining for the full sample length and thickness within (1 ± 0,2) mm of the shoe platform.
Load appIation on me loading tool shall be in a direction paralel to the plane of the shoe platform. The shoe shall be supported to maintain uniform loading along the length of the lining sample.
The width of the loading tool shall be greater than the width. 14’, of the lining.
6.2.3 Dise brake pad
The fixture (see Figure 3) shall be designed such that:
— the location of the plane of the backplate is parallel to the plane of the loading tool:
the loading tool is in contact with the edge of the lining within (1 ± 0,2) mm of the backing plate (carrier) and conforms to the sample bning profile including taper angles;
the loading tool is self-aligning:
the loading tool is in contact with the full sample length of the lining edge parallel to the backpfate support:
— the load bearing edge of the backing plate rests against a rigid support with a thickness no greater than that 01 the backing plate:
— in order to prevent assembly movement under testing, a pressure fixture applies a face load of (0,5 ± 0,15) N/mm2 of the lining area at a right angle to the shear load;
— the face load is applied in such a way that friction force is minimized and does not significantly influence the shear load measurement.
d) Apply the load at the rate specified in 6.1, continuing until complete failure occurs.
e) Record the failure load together with the shear pattern expressed as a percentage as specified in clause 9.
8 Calculation of shear strength
Calculate the shear strength using the formula:
r is the shear strength, expressed in megapascals;
F is the shear force at failure, expressed in newtons;
A is the sample area, expressed in square millimetres.
Calculate A from the friction material profile at the bond line and not at the pad face, as chamfers or slots are pad surface effects.
The shear strength is expressed as the minimum and the average of the results of the number of samples tested.
9 Presentation of results
The test report (see annex B) shall include the following information:
a) type and supplier of the brake shoe assembly or disc brake pad friction material, and batch identification; b) number of samples tested (five recommended);
c) minimum and average shear-force, or minimum and average shear-strength, values, or both;
d) a description of the shear pattern, based on:
1) percentage failure:
— of clean carrier,
— of adhesive, and
— in the lining, and
2) location of any clean carrier areas;
e) comments (including mention of samples used as specified in clause 5) on deviations from normal test conditions such as a special test temperature.
