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VDA 309 02/2016

EKB Specifications for Disc Brake Pad Noise Damping Shims (Insulators)

VDA

309

Continued page 2 to page 34

VERBAND DER AUTOMOBILINDUSTRIE E. V. (VDA) Behrenstr. 35 10117 Berlin

This non-binding recommendation by the German Association of the Automotive Indus-try (VDA) has the following objectives:

To summarize the current valid EKB specifications for Noise Damping Shims (Insulators) for disc brake pads in aspect of testing the shim material itself, giving recommendations of shim and backing plate geometries to improve the quality of attachment (bonding) and giv-ing guidelines for a clear description of visual assessment for pad-shim assembly after ve-hicle or dyno testing.

These specifications are dealing with bonded and clip on anti-noise shims.

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Disclaimer

VDA recommendations are freely available for general use. The user is responsible for ensuring correct application for the specific case.

They represent the latest technology available at the time of issue. Application of VDA recommen-dations does not relieve the user from responsibility for his own actions. In this regard, all users act at their own risk. VDA and those involved with VDA recommendations do not accept any liability.

Anyone applying VDA recommendations who identifies inaccuracies or possible incorrect interpre-tations is invited to inform VDA immediately and any errors can thus be rectified.

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Table of Contents

1 EKB 1101 - Damping Shim Bonding Parameter Definition (revised: 5 August 2014) ............................................................................................... 4

2 EKB 1102 - Corrosion Test Procedure for Noise Damping Shims (revised: 14 October 2010) ........................................................................................... 7

3 EKB 1103 - Torque Endurance Test for Adhesive Bonded Noise Shims (revised: 14 October 2010) ......................................................................................... 10

4 EKB 1104 - Static Endurance Test for Adhesive Bonded Noise Shims (revised 14 October 2010) .......................................................................................... 14

5 EKB 1105 - Shear Stress Test “Lap Shear” for Adhesive Bonded Noise Shims (revised: 14 October 2010) ......................................................................................... 17

6 EKB 1106 - Shim Visual Assessment for Pad Assembly after Vehicle or Dyno Test (revised: 14. October 2010) ........................................................................................ 20

7 EKB 1107 - Development Guideline on the Quality Control of Anti-Noise Shims – T-pull Test (revised: 14 October 2010) ......................................................................................... 27

8 EKB 1108 - Compressibility Test for Anti-Noise Shims (revised: 14 October 2010) ......................................................................................... 34

9 EKB 1109 - Development Guideline on the Quality Control of Anti-Noise Shims – Shim Geometry (revised: 5 August 2014) ............................................................................................. 45

10 Relationships, References ............................................................................................... 53

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1 EKB 1101 - Damping Shim Bonding Parameter Definition (revised: 5 August 2014)

1.1 Scope

This recommended practice applies to disc brake pads for passenger car and light truck brake ap-plications. Basic description of all process relevant parameters, which have to be announced and documented during a process audit. A selection of the below mentioned data could be used for the project related Lining Data Sheet.

1.2 Purpose

To define acceptance standards for the noise insulator bonding process.

1.3 Data information provided and documented by the noise insulator supplier

Noise insulator manufacturer

Noise insulator type and identification number

Noise insulator layer design

Noise insulator adhesive type, basis e.g. acrylic, phenolic, silicone etc.

Noise insulator adhesive temperature resistance, long term, short term (e.g. TGA)

Noise insulator adhesive shelf time, recommended storage conditions

Noise insulator adhesive, minimum time to achieve full bonding strength after processing

Batch definition

Bonding recommendations with regard to pressure / time cycle, temperature and bond-ing surface preparation

Minimum storage time after bonding before load application

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1.4 Data information provided and documented by the pad manufacturer

Type of backplate paint, chemical basis

Description of surface preparation, brushing, flaming, corona etc.

Definition of noise insulator press tool, single or multiple piece press

Noise insulator batch number, defined by the pad batch number including full traceability

Final surface tension of paint before noise insulator bonding process

According to the literature, an adequate bonding surface tension required to be ≥ 38 mN/m.

Bonding parameters used in process:

o Pressure / time cycle definition

o Press plate temperature

o Equalization layer (e.g. Teflon)

o Pre-heating of the pad

1.5 Bonding process prototype and series production

The pad manufacturer has to verify that the bonding process in prototype and series production is comparable and leads to identical results.

This has to be proven by T-pull values (EKB 1107), adhesive separation after T-pull test.

After bonding, there should not be any adhesive bleeding at the edges of the shim, oth-erwise bonding parameters have to be adjusted.

A bonding DOE with variation of process parameters pressure, time and press plate temperature with optional preheating and/or equalization layer is always recommended to secure the best production process.

1.6 Bonding of damping shims with phenolic adhesive

A damping shim with phenolic adhesive can either be bonded on the unpainted backing plate and be painted with the pad or be bonded on the painted backing plate. This re-quires an extremely resistant paint against physical and environmental effects.

During the bonding process, the phenolic adhesive has to chemically react completely without overheating.

This has to be controlled by measuring the adhesive layer or backing plate temperature during the bonding process together with pressure vs. time. The required reaction pa-rameters, given by the shim supplier, have to be considered.

The control measure is the T-pull value (EKB 1107), adhesive separation after T-pull test and the statistical distribution of these values.

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A bonding DOE with variation of process parameters pressure, time, press plate temper-ature and equalization layer is always recommended to secure the best production pro-cess.

1.7 Recommended T-pull values

Required minimum T-pull values at ambient temperature for shims with silicone or acrylic adhesive are 2 N/mm (recommended: 3 N/mm), 8 N/mm for shims with phenolic adhesive and 4 N/mm with phenolic-nitrile adhesive.

1.8 External fixations for shims

External fixations for shims with silicone or acrylic adhesive have to be provided accord-ing to EKB 1109.

External fixation of the shim is also optional for phenolic adhesive.

Rationale

This recommended practice standardizes the quality assurance of the noise insulator bonding pa-rameters of disc brake pads of passenger cars. Disc brake pads and its noise insulators are im-portant functional parts of the wheel brakes. They are of essential importance for the effectiveness and NVH comfort of the brake system.

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2 EKB 1102 - Corrosion Test Procedure for Noise Damping Shims (revised: 14 October 2010)

2.1 Scope

This recommended practice applies to disc brake pads for passenger car and light truck brake ap-plications. Basic description of all process relevant parameters which have to be announced and documented during a process audit. A selection of the below mentioned data could be used for the project related Lining Data Sheet.

2.2 Purpose

Aim of this test method is to assess the corrosion resistance and the adhesion of rubber or other coated noise insulators on a simple lab-test. Define acceptance standards for the noise insulator corrosion behaviour.

2.3 Test method

2.3.1 Apply a cross-cut grate according to „Cross-cut Test DIN EN ISO 2409“ on right or left side of the sample before corrosion test. Number of samples to test >= 5. It is not meaningful to use the specified scratching tool with multi-blades. Recommend is preferably a scratching tool as described in DIN53167 (scratch engraver by van Laar model 426). The grid-width should be 4 mm. Thoroughly check that the complete rubber coating or paint is cut through into the base metal. It is not necessary to use the final shape of the shim, a rectangular shape is sufficient.

outer side inner side

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2.3.2 Store prepared samples horizontally in a holding device out of plastic, by using 2 contact points.

2.3.3 Conduct a 240 h salt spray test according to DIN 50021SS (5% NaCl solution).

2.3.4 Clean the cross-cut area with a soft brush according the Cross Hatch Cutter set (Company Erichsen) Model 295 under running water. Dry the samples at ambient temperature for min-imum 24 h.

2.3.5 It is recommended to use the Tesa 4129 adhesive tape for cross-cut assessment after cor-rosion test. Apply the specified adhesive tape and remove it according to DIN EN ISO 2409, by starting from the inner side to the outer side.

2.3.6 Judge and document the appearance of the cross-cut grate according to DIN EN ISO 2409. A classification in the specified categories has to be done.

2.3.7 Make preferably digital photographs of the specimens and of the removed adhesive tape, after completion of test sequence.

2.4 General requirement

2.4.1 In the cross-cut area, the rubber coating flake off should be less than 15%. This is corre-sponding to a cross-cut identification 2.

2.4.2 Cross-cut rating of better or equal than 2 according to DIN EN ISO 2409.

2.4.3 The under paint corrosion starting from stamped edges must be less than 2 mm.

2.5 Corrosion requirements

2.5.1 Class A means free from red rust after 240 h salt spray test to DIN 50021 SS.

2.5.2 Class B means damping shim material is not fulfilling requirements for class A.

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Cross-cut

identification

Description Appearance of surface in the cross-

cut area with occurrence of flaking

(Example for 6 parallel cuts each)

0 The edges of the cut are completely smooth; none of the squares

of the grid are flaking

--

1 At the intersection points of the grid lines there is flaking of

small chips of the coating.

Flaked surface not essentially larger than 5% of the total cross

cutting surface.

2 Coating along the edges of the cut and/or at the intersection

points of the grid are flaking.

Flaked surface essentially larger than 5%, but not essentially

larger than 15% of the total cross cutting surface.

3 Coating along the edges flaked partially or completly in wide

strips, and/or some squares are entirely or partially flaked.

Concerned is a cross-cut surface significantly over 15% but not

considerably more than 35%.

4 Along the edges of the cut coating flaked in long strips, and/or

some squares are entirely or partially flaked.

Flaked surface essentially larger than 35%, but not essentially

larger than 65% of the total cross cutting surface.

5 Each flaking which can no longer be classified with cross-cut

identification

Comment: The way of doing the scratches has to be defined more in detail.

Rationale

This recommended practice standardizes the corrosion test of noise insulators of disc brake pads of passenger cars. Disc brake pads and its noise insulators are important functional parts of the wheel brakes. They are of essential importance for the effectiveness and NVH comfort of the brake system.

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3 EKB 1103 - Torque Endurance Test for Adhesive Bonded Noise Shims (revised: 14 October 2010)

3.1 Scope


3.2 Purpose

Aim of this test method is to assess the mechanical resistance of the shim fixation and the outer layer of a noise insulator on a simple lab-test. Define acceptance standards for the noise insulator mechanical strength.

3.3 Test method

3.3.1 The test has to be completed with the intended backplate, paint and shim bonding condi-tions and utilising the production intent calliper.

3.3.2 Test set-up

Alternatively, the assembly calliper may be mounted onto a friction-tight testing device.

Friction-tight set-up (rotating disc): Set-up of the assembly calliper with carrier onto an appropriate testing device with rotating disc (friction tight), with the applied braking moment able to be adjusted with due sensitivity.

3.3.3 Testing method

In order to guarantee reproducible and comparable results, the following definitions must be absolutely maintained:

If not otherwise specified, the test has to be carried out with the load level 0,6 g.

The testing frequency is between 0,25 and 0,3 Hz (900 cycles/h and 1100 cycles/h)

For the hydraulic effective pressure or initiated braking moment, each corresponding to 0,6 g of braking operation, the following tolerances are valid:

o Moment: +5%

o Pressure: +20%

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3.3.4 Test conditions

The shim is to be assessed for its resistance to damage after torque cycling in a calliper at room temperature and under heated conditions (defined in each project).

Parameter. Description.

Total number of cycles. 33000

Cycles in forward direction. 30000 cycles

Cycles in backward direction 3000 cycles

Sequence of cycles 100 forward 10 backward

Constant torque. 0,6 g

Rotor speed 6 ± 4 RPM

Cycle rate 1000 ± 100 hour-1

3.4 Requirements

No cracks or tears around any mechanical fixing position.

No disconnection or plastic deformation that affects pad assembly function.

No critical effects on shim bonding.

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Typical damages after torque endurance test

For the rating of the damages see EKB 1106 “Shim Visual Assessment”.

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Rationale

This recommended practice standardizes the quality assurance of the noise insulator bonding pa-rameters of disc brake pads of passenger cars. Disc brake pads and its noise insulators are im-portant functional parts of the wheel brakes. They are of essential importance for the effectiveness and NVH comfort of the brake system.

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4 EKB 1104 - Static Endurance Test for Adhesive Bonded Noise Shims (revised 14 October 2010)

4.1 Scope


4.2 Purpose

Aim of this test method is to assess the mechanical resistance of noise insulator layers on a simple lab-test. Define acceptance standards for the noise insulator layer strength.

4.3 Test method

4.3.1 Test outline

The shim is to be assessed for its resistance to damage after pressure cycling in a calliper in new shims condition.

4.3.2 Test apparatus requirements.

The shim placed on the intended backplate, according shim datasheet, to be tested in the mentioned brake where it is possible to test with the required piston and constant pressure cycles. The brake or the simulation set-up should be defined for the static endurance test.



Test Object Project related caliper

Total number of cycles. 36000

No. of Cycles with 60 bar 30000

No. of Cycles with 125 bar 6000

Pressure rise rate. 450±50 bar/s.

Temperature. 23±5°C

Cycle rate. 1000±100 hour-1.

Renew piston after 10 tests

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pressure rise

4.4 Presentation of results

Document the surface of the shim (imprint of piston surface) after the test by appropriate images. Area [%] where rubber is removed in cause of friction (steel layer can be seen) has to be assessed according damage rating (see “Requirements”).

4.5 Requirements

Typical damages after static endurance test

For the rating of the damages see EKB 1106 “Shim Visual Assessment”.

1.5 1.5

1.5

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Rationale

This recommended practice standardizes the static endurance test for adhesive bonded noise in-sulators of disc brake pads of passenger cars. Disc brake pads and its noise insulators are im-portant functional parts of the wheel brakes. They are of essential importance for the effectiveness and NVH comfort of the brake system.

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5 EKB 1105 - Shear Stress Test “Lap Shear” for Adhesive Bonded Noise Shims (revised: 14 October 2010)

5.1 Scope


5.2 Purpose

To define the set-up and procedure to produce consistent results from adhesive shear tests on calliper friction pad, adhesive bonded noise control shims.

To assess, optimize and assure into production the quality of the shim to pad backing plate adhe-sive bond.

5.3 Conditions of samples

The test has to be completed with a shim specimen bonded to a steel block, as described below. The shim specimen (contact surface to steel plate: 25mm × 25 mm) has to be bonded to steel plate according the conditions listed on shim material datasheet.

Steel block:

The steel block shall be either steel with repeatable defined surface finish or plates cut from the same type of steel as used for the backing plates.

The steel block shall be either de-greased or treated in the same process as the standard pads / backing plates before the shims are mounted. (i.e. painted or otherwise treated)

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5.4 Test Method

5.4.1 Test outline

The shim is to be assessed for its resistance to shear when adhered to the specified steel plate.

5.4.2 Test apparatus requirements

5.4.2.1 The shim bonding to be tested with a suitable test rig, where it is possible to apply and measure a tensile pull applied at the desired rate.

5.4.2.2 Equipment capable of applying the shim samples to the steel plate with parameters speci-fied on shim data sheet.



Total number of cycles. 1.

Constant speed of pull. 50 mm/min (±10%).

Accuracy of force measurement 1% of measured value, 0,5 N at range < 100 N

Sample dimensions. 50 x 25 mm.

Dimensions of area, bonded to backplate. 25 x 25 mm.

steel plate (see 2. Condition of samples) Wiped clean of oil/grease

and dust.

Standing time after bonding according shim data sheet

velocity = 50 mm/min (± 10%)

clamp

test specimen

steel plate

clamp

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5.5 Presentation of the results

5.5.1 Ideally, the adhesive must be evenly dispersed on shim and back plate after test illustrating similar adherence to both components.

5.5.2 The pull strength minimum recommended value, for specific back plate paint / adhesive systems, will be defined by the customer for each project.

5.5.3 The values recorded in the regular production checks must fall into the scatter range de-fined by the customer.

Rationale

This recommended practice standardizes the shear stress test for adhesive bonded noise insula-tors of disc brake pads of passenger cars. Disc brake pads and its noise insulators are important functional parts of the wheel brakes. They are of essential importance for the effectiveness and NVH comfort of the brake system.

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6 EKB 1106 - Shim Visual Assessment for Pad Assembly after Vehicle or Dyno Test (revised: 14. October 2010)

6.1 Scope


6.2 Purpose

To define damaging standards for the noise insulator condition after different testing (vehicle, dyno, chassis testing).

6.3 Assessment criteria and rating

6.3.1 Butterfly effect

Index 10 No butterfly effect

Index 9 Minimum lifting of shim at the edges

Index 8 Minimum lifting (gap < 0.5 mm) of shim maximum 5 mm from the edges

Index 7 Light lifting (gap < 0.5 mm) maximum 10 mm from the edges

Index 6 Lifting gap < 1 mm maximum 10 mm from the edges


Index 4 Lifting gap < 1.5 mm maximum 15 mm from the edges



Index 1 Lifting gap > 2 mm > 20 mm from the edges

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6.3.2 Shim shifting

Index 10 No shift

Index 9 Extremely light shift (< 1 mm)

Index 8 Very light shift (1–1.5 mm)

Index 7 Light shift (1.5–2 mm)

Index 6 Medium shift (2–3 mm)

Index 5 Medium shift (3–4 mm)

Index 4 Strong shift (4–5 mm)

Index 3 Strong shift (5–6 mm)

Index 2 Very strong shift (6–7 mm)

Index 1 Extremely strong shift (> 7 mm)

6.3.3 Rubber damages

Index10 No damage

Index 9 Light damage on the surface of rubber

Index 8 Medium damage on the surface of rubber

Index 7 Light partial rubber penetration (< 4 mm²)

Index 6 Light partial rubber penetration (< 8 mm²)

Index 5 Medium partial rubber penetration (< 20 mm²)

Index 4 Rubber delaminating at 40% of brake contact areas



Index 1 Total rubber delaminating at brake contact areas

6.3.4 Corrosion on an assembled pad

Index 10 No corrosion

Index 9 Very slight corrosion on the stamping edges

Index 8 Slight corrosion on the stamping edges

Index 7 Slight under corrosion of the rubber layer on edge area

Index 6 Stronger under corrosion of the rubber layer > 10%

Index 5 Stronger under corrosion of the rubber layer > 20%

Index 4 Strong under corrosion of the rubber layer > 50%

Index 3 Starting under corrosion between back plate and shim

Index 2 Stronger under corrosion between back plate and shim > 20%

Index 1 Strong under corrosion between back plate and shim > 50% separating.

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6.4 Typical examples for shim assessment

Butterfly effect: Index 1

Butterfly effect: Index 2

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Shim shifting effect: Index 9

Shim shifting effect: Index 6

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Rubber damage: Index 2

Rubber damage: Index 6

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Under corrosion effect: Index 1

Under corrosion effect: Index 1

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Rationale

This recommended practice standardizes the shim visual assessment for the pad assembly of disc brake pads of passenger cars. Disc brake pads and its noise insulators are important functional parts of the wheel brakes. They are of essential importance for the effectiveness and NVH comfort of the brake system.

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7 EKB 1107 - Development Guideline on the Quality Control of Anti-Noise Shims – T-pull Test (revised: 14 October 2010)

7.1 Scope

This recommended practice covers the attachment of bonded anti-noise shims, only. Mechanically attached shims without bonding are not covered by this practice.

7.2 Purpose

To measure the strength of the adhesive bond for the attachment of anti-noise shims to disc brake pads or test specimens on a standard steel plate. It is primarily used as a quality tool.

7.3 Applicable documents

7.3.1 DIN standards

DIN 50 014 – Standard climatic conditions

Available from Deutsches Institut für Normung e.V., 10772 Berlin, Germany (www2.din.de)

7.3.2 ASTM publications

ASTM D618 – Standard Practice for Conditioning Plastics for Testing

ASTM D1876 – Standard Test Method for Peel Resistance of Adhesives (T-Peel Test)

Available from ASTM INTERNATIONAL, 100 Barr Harbor Dr., West Conshohocken, PA 19428, USA (www.astm.org)

7.4 Definitions

7.4.1 Pull strength

The pull strength (P) or initial peel resistance of the anti-noise shim adhesive is defined as the force per width (N/mm), which is needed to pull a shim from the backing plate of a pad at a 90º angle:

P = F/b,

where F is the peak pull force (N) and b is the anti-noise shim bend width (mm). This value is used to assess the bond quality by strength.

http://www.astm.org/

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7.4.2 Anti-noise shim bend width

The shim bend width is the width of the adhesive bond at the start of the test.

Area A

Area B

Shim bend line away from spigot

holes and semi shears etc.

Fig. 1.

The shim pull width

Spigot holes and

semi shears

Area A

Area B

Shim bend line away from spigot

holes and semi shears etc.

Fig. 1.

The shim pull width

Spigot holes and

semi shears

Anti-noise shim with bend line and shim bend width

Clamp moving member of

tensile test apparatus onto shimShim

Pad backplate

Friction material

Direction of pull at

the test velocity

Shim bent at 90°close to centreline

avoiding spigot holes, semi shears etc.

Clamp bar applies

force F to hold the

pad to the test

machine.

Tensile test machine 'bed'

F

Clamp moving member of

tensile test apparatus onto shimShim

Pad backplate

Friction material

Direction of pull at

the test velocity

Shim bent at 90°close to centreline

avoiding spigot holes, semi shears etc.

Clamp bar applies

force F to hold the

pad to the test

machine.

Tensile test machine 'bed'

F

90º pull test set-up

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7.4.3 Peak force

The peak pull force F is the initial force necessary to start the peel of the adhesive.

Load vs. travel chart defining peak pull force (F). The shape of the displayed curve will vary with different shim materials!

7.4.4 Failure mode

The failure mode of the assembly describes the visual impression of the bonding interface, and of the adhesive layer, after separation. For example, the adhesive can be completely left on the static part of the assembly (pad back plate), or be found in patches on both back plate and shim, or completely stay on the shim.

7.5 Temperature and humidity for testing

The test is performed at (23°C ± 2°C). In critical cases, standard climatic conditions (according to agreed specifications such as ASTM D 618 or DIN 50 014-23/50-2) should be applied.

7.6 Equipment and apparatus

7.6.1 Testing machine

This test can be done on a universal tensile test machine or specifically designed test equipment.

The load measurement accuracy required for peak pull force (F) is 1% of full range, and 0.5 N for force ranges less than 100 N. Preferably, the load vs. travel should be recorded.

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The moving member velocity shall be 50 mm/min ± 10%. The travel range of the moveable member should be a minimum of 5 mm (has to be over the force peak).

7.7 Test samples

7.7.1 While testing during the development phase

Test specimens are standard shim samples, 25 to 45 mm wide and min. 60 mm long, (con-tact surface to steel plate: the specimen width × min. 50 mm), bonded to a sufficiently sized (minimum the size of the test specimen) steel block with minimum 5 mm thickness.

The steel block shall be either steel with repeatable defined surface finish or plates cut from the same type of steel as used for the backing plates.

The steel block shall be either de-greased or treated in the same process as the standard pads/backing plates before the shims are mounted (i.e. painted or otherwise treated).

7.7.2 Testing as production check

The test has to be completed with the production-intent or series back plate and shim. Pro-duction or production intent conditions apply.

7.8 Bonding

Both during development and production, bonding of the shim to the supporting plate has to be done according to a bonding specification. During the development phase, the bonding should be performed as intended for production. During production, the bonding shall be done to an agreed upon production specification. For repeatability of results, the bonding method needs to be defined and recorded with sufficient precision, including items such as pressure, temperature and holding time. If the strength of the bond changes after the bonding operation due to subsequent curing, the samples shall be held until the curing occurs.

Preparation of test samples

Subsequently, the term “pad assembly” is used for a bonded shim specimen and steel block or pad specimen.

7.8.1 Clamp the assembled damping shim in the area close to the bending point with an appro-priate clamping device. Possible examples can be seen in figures below.

7.8.2 Lever the exposed half of the shim away from the back plate, using a suitable flat-bladed utensil like putty knife or chisel to start the detachment, then complete the operation by hand or a suitable bending device.

7.8.3 Bend the unstuck half of the shim until it is bent at 90° to the pad back plate. The shim bending radius should be in the range of 1 to 2 mm for simple shims and 2 to 4 mm for mul-ti-layer shims.

7.8.4 Clamp the pad assembly in a vice in a position in which the top of the vice is as close to the noise shim centreline without passing over a back plate spigot hole, indentations, alpha-numeric stamping, or semi shear. The purpose of the clamping is to prevent the shim from experiencing a preload or lifting, prior to the actual test.

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Example of clamping device to provide a 90° angle without influence to the adhesive layer

Example of clamping device to provide a 90° angle without influence to the adhesive layer

7.9 Test procedures

7.9.1 The tensile test rig consists of a static and a moveable member. During tensile testing, the test sample is attached to both the static and the moveable member. When the moveable member is moved away from the static member, tension forces are applied to the test sample.

7.9.2 The prepared pad assembly has to be clamped to the static part of the tensile rig. A suita-ble method is to use a clamp bar across the exposed area of the pad assembly. No addi-tional load or pressure shall be exerted by this clamp bar.

7.9.3 The part of the shim that is bent 90° upward needs to be attached to the moveable part of the tensile test rig. Suitable methods are using a hole in the shim or by means of a clamp, where it has to be assured that no slip should occur between the clamp and the clamped shim specimen. For repeatability of results, the attachment method needs to be defined with sufficient precision and reported. The clamp should not be a rigid body but should pro-

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vide a balance of the tangential forces by means of a chain or steel cable. An example can be seen in the figure below.

7.9.4 The rig should be operated with a moving member velocity of 50 mm/min ± 10%. The travel range of the moveable member should be a minimum of 5 mm.

Example of clamping device for T-pull with tangential force balance by chain

7.10 Optional pre-heating of sample

While the usual T-pull test is done with “as produced” pad assemblies, pre-conditioning of the pad assembly can be arranged. This conditioning can include:

7.10.1 Several cycles of brake applications on a brake test rig or friction tester with disc end tem-peratures up to 650° C. (Comment: Test procedure and cooling phase have to be described!)

Specifics of any preconditioning must be clearly defined and reported in the test report.

7.11 Statistics

Unless specified otherwise, the number of samples tested should be five.

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7.12 Record

The test report shall include the following:

Who is responsible for execution, reporting, accuracy etc. of the test

Description and unique characterization of the test specimen

Set-up, equipment, and environmental conditions of the test

Test procedure incl. test velocity

Detailed geometry of the components and the bonding interface

If applicable: steel block type and surface quality

If applicable: surface preparation, de-greasing procedure, solvent type etc., painting pro-cess

Documentation of the adhesive and the bonding instructions

Bonding conditions incl. specimen preparation, temperature, pressure duration, post-curing

If applicable: pre-conditioning parameters

Number of samples

P for each sample, average and S.D.

Load vs. travel charts, if available

Description of the failure mode of the assembly

Date, time and specific observations of the test

Rationale

This recommended practice standardizes the measurement of the bond strength between the anti-noise shims and the disc brake pads. The development of sufficient bond strength is necessary for the correct performance of bonded anti-noise shims.

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8 EKB 1108 - Compressibility Test for Anti-Noise Shims (revised: 14 October 2010)

8.1 Scope

This recommended practice covers compressibility test of anti-noise shims. Both, bonded and me-chanically attached shims without bonding are covered by this practice.

8.2 Purpose

The compressive response of a brake lining or pad is an important design parameter. It is useful for the evaluation of brake fluid displacement during a brake application, brake-pedal travel and the propensity of the brake for generating judder or noise. An anti-noise shim increases the pad com-pressibility and is an important value.

The purpose of this test procedure is to evaluate the compressive response or "compressibility" of anti-noise shims. The test measures compressibility at ambient and elevated temperatures.

8.3 Standards

ISO-DIS 6310 – Test method for determining the compressibility

8.4 Definitions

8.4.1 Compressibility — C

The change in shim thickness or deflection caused by a uniaxial compression load during the final loading cycle to the maximum test pressure. Measure compressibility in the same direction as the compression force, perpendicular to the basis surface. Measure and report the absolute compressibility in microns (µm).

8.4.2 Deflection of samples — D

The net deflection of the sample as a result of the subtraction of the deflection of the equipment itself from the total deflection measured by the equipment (D = Dtot – De).

8.4.3 Hot compressibility — C200

The same as compressibility but with a heated plate temperature of 200 °C.

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8.5 Symbols and units

The table below gives the symbols and corresponding units used in this standard.

Symbols and units

Symbol Description Unit Accuracy

x Test pressure at sample contact area or unit area pressure (procedure A)

MPa 1% FS

P Simulated hydraulic line pressure (procedure B) bar 1% FS

d Average thickness of all samples (average of 5 measurements)

mm 0.1 mm

Ao Piston-shim contact area cm2 0.5 cm2

Dtot Total deflection measured by the test equipment at the maximum test pressure

µm 1 µm

De Deflection of the test equipment itself at x bar (no sample installed)

µm 1 µm

D Net deflection of test sample (Dtot – De) at x bar µm 1 µm

x Compressive strain at x. (D/d) used in procedure A. — 0.0002

C Net compressibility for every cycle (D at P) µm 1 µm

C200 Hot compressibility µm 1 µm

TT Temperature transfer °C 2%

t1 Test temperature of the heating plate for hot test °C + 2 oC

t2 Initial temperature of the backing plate for hot test °C + 2 oC

t3 Final temperature of the backing plate during hot test

°C + 2 oC

8.6 Principle

This test measures the compressive deflection of an anti-noise shim.

8.6.1 Procedure

The procedure loads the shim assembly to simulate a hydraulic line pressure of 100 or 160 bar. The line pressure is expressed in bar to differentiate it from the face pressure at the contact area.

Unless otherwise specified, report the compressibility value C (µm).

8.7 Test equipment

The test equipment shall consist of the following:

Seite 36 VDA 309 02/2016

A loading cylinder to simulate a calliper piston configuration.

A device to measure the applied compression force to an accuracy of 1% of full-scale of the test equipment.

A gauge to measure the time-based deflection of the sample with an accuracy of 0.001 mm. Position the gauge on the loading cylinder or on the plate and in contact with the loading ram as near to its centre line as possible.

A recording device or computer to log load, pressure, displacements, and temperatures as function of time.

A heating device to raise the temperature of the plate to a specified temperature.

A thermocouple (1.5 mm diameter recommended) to measure the temperature of the plate. The position of the thermocouple should be as close as possible to the centre line of the loading ram and embedded 3 mm below the test surface of the plate.

A thermocouple or device to measure the temperature of the test sample (option).

A micrometre to measure sample thickness.

8.8 Test-stand specifications

8.8.1 Apply a force corresponding to a simulated hydraulic line pressure of 100bar or 160 bar. The recommended loading rate is 80 bar/s (8 MPa/s) simulated line pressure if testing in constant loading rate control, or 15 mm/min when testing in crosshead speed control.

8.8.2 Heated plate

For the hot test, t1 on the surface of the heating plate shall be 200°C ± 5°C

8.8.3 Loading ram

8.8.3.1 Installation

A fixture representing a piston is introduced between the ram and the shim + metal plate. The standard piston represents a hydraulic diameter of 54 mm and a contact outer diameter of A = 52 mm and an inner diameter of B = 41 mm.

The corresponding force for 100bar / 160 bar is 22,9kN / 36,6kN.

The piston contact surface is 803 mm². The location is the centre of the sample.

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Drawing of standard piston adapter for RT / 200°C compressibility measurement

8.9 Sampling

8.9.1 It is recommended that a minimum of five samples should be measured at room tempera-ture and three samples at 200°C. For every measurement, a new shim sample should be used.

8.9.2 To avoid influencing the test results, the flatness and surface roughness of the sample should be the same as that of normal production.

8.9.3 For accurate measurements, parts should be stabilized at 23 ± 5°C and 50 ± 10% relative humidity before testing.

8.10 Test Procedure

8.10.1 General set-up

8.10.1.1 Ensure that test stand is properly calibrated.

8.10.1.2 Place the sample on the plate at room temperature (23°C ± 5°C) with its shim surface against the surface of the piston with the ram and piston fixture correctly located. The shim has to be bonded to the basic plate with the correct bonding specifications. Align carefully the sample beneath the loading (piston) fixture as an important factor to ensure repeatability of test results.

8.10.2. Room temperature compressibility test (RT)

8.10.2.1 Pre-load to the force value that corresponds to 5 bar hydraulic system pressure and hold for no more than 5s.

8.10.2.2 Zero the displacement gauge while the sample is held at pre-load.

8.10.2.3 Perform three loading and unloading cycles starting from the preload. (A cycle consists of increasing to the maximum pressure at the rate required, then un-

Seite 38 VDA 309 02/2016

loading at the same rate to the pre-load value.) The figures below illustrate the test cy-cles.

8.10.2.4 Measure displacement and pressure during the loading cycles. If computer data acqui-sition is available, it is recommended that continuous displacement versus pressure is recorded. Record and report displacement at the maximum pressure on the first cycle and last cycle, and in addition on the last cycle. The displacement values for every cycle are the net values from the initial value at every cycle (at preload) to the maximum pres-sure.

8.10.3. Hot compressibility test (200°C)

8.10.3.1 Re-zero the displacement gauge.

8.10.3.2 Place the sample on the heating plate. Wait for 10 minutes with a preload of 5 bar hy-draulic system pressure. Perform two compression cycles and increase the pressure to the maximum pressure without resetting the pressure to zero bar. The figures below il-lustrate the test cycles.

8.10.4. Hot compressibility test (200°C) for rear brakes with integrated parking brake (pro-ject related option)

8.10.4.1 Use alternative piston (project related)

8.10.4.2 Re-zero the displacement gauge.

8.10.4.3 Place the sample on the heating plate. Wait for 10 minutes with a preload of 5 bar hy-draulic system pressure. Perform two compression cycles, using the same loading pa-rameters as for hot temperature (maximum pressure project related) and hold the load at the second compression cycle for 30 minutes. The deformation shall be measured during that time. Measurement definition the same as 8.10.2.4. The figures below illus-trate the test cycles.

8.11 Test device deflection compensation

It is a known fact that during compressive testing, the test device itself will also deflect. This dis-placement of the test equipment under load, De, must therefore be subtracted from the total meas-ured displacement during the test, Dtot, in order to determine the true displacement of the sample, D.

D = Dtot – De

This compensation can be done automatically or manually. Measure De as a function of pressure by loading the ram with the piston in place against the base plate without a sample installed. (Al-ternatively, a stiff, hardened steel plate with known force-deflection can be used as a dummy sam-ple to protect the base plate.) Automatic displacement compensation can then be performed as a function of pressure. Alternatively, a manual subtraction of the machine deflection can be per-formed on the maximum pressure deflection reading for each test.

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8.12 Verification of the test stand using reference samples

A regular test should be done with a reference sample such as a Hottinger force gauge housing C2/50kN (Jurid) or a Verification Standard Spring (LINK) with a suitable positioning tool and rea-sonable test parameters.

e.g.: Test condition for Jurid Machines:

FB = 1.6 kN; FP = 50 kN; 60 kN; F/t = 25 kN/s; cycles = 2

Test conditions for LINK Machines:

FB = 3.0 kN; FP = 59.5 kN; F/t = 35 kN/s; cycles = 3

In case there is a difference of more than 5 µm between the reference sample and its expected value, check the accuracy of the force measuring device, accuracy of the displacement gauge, and flatness of the test plate.

8.13 Report

Below is a sample test report. Other formats are acceptable, provided they include at least the fol-lowing information:

8.13.1 Manufacturer and reference name/number of shim material, including batch reference

8.13.2 Dimension of the sample (minimum 70mm × 70mm)

8.13.3 Number of samples tested

8.13.4 Piston size, inner and outer ring diameter (41 mm inner and 52 mm outer for RT and hot measurement)

8.13.5 The average value for ambient compressibility for all samples tested

8.13.6 The average value for hot compressibility for all samples tested

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Installation

1 Load 2 Test sample 3 Basic plate 4 Piston 5 Heating plate

Dimension of basic plate

1 Basic plate (standard steel or stainless steel) 2 Shim

5

1

2

4

3

70 mm × 70 mm × 5 mm 1

2

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0

20

40

60

80

100

120

140

160

180

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

Time (s)

Bra

ke

sy

ste

m p

res

su

re (

ba

r)

FB

k3 3rd

cycle slopemaximum pressure 160 bar for Europe / 100 bar for US

Pressure ramp for RT measurement

For US applications, the complete compressibility test has to be repeated at 100bar instead of 160bar.

0

20

40

60

80

100

120

140

160

180

598 599 600 601 602 603 604 605 606 607

Time (s)

Bra

ke

sy

ste

m p

res

su

re (

ba

r)

0 1

k2 2nd

cycle slopemaximum pressure 160 bar for Europe / 100 bar for US

Pressure ramp for 200°C measurement

Seite 42 VDA 309 02/2016

0

20

40

60

80

100

120

140

160

180

598 600 602 604 606 608 610

Time (s)

Bra

ke

sy

ste

m p

res

su

re (

ba

r)

0 1 2406

k2 2nd

cycle k2 2nd

cycle 30minmaximum pressure project related

605

Pressure ramp for 200°C, 30 minutes measurement

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Example Test Report

Parameter Value

Preload 5 bar

Load rate 80 bar/s

Maximum pressure sample 160 bar or 100 bar

No. of cycles

Room tempera-ture test

3

Hot test 2

Parking brake test 2

Sample size sample Minimum 70 x 70 mm

Ram type: Flat surface: Actual piston:

Test date:

Name of tester:

Reference number:

Sample type:

Special coatings etc.:

Sample size:

Nominal sample thickness (mm):

Number of samples:

Piston size:

Procedure :

Compressibility Values

bar C in µm

Ambient

first and third cycle

first cycle

third cycle

first cycle

third cycle

100

100

160

160

Hot

first and second cycle

first cycle

third cycle

first cycle

third cycle

100

100

160

160

Parking Brake

First and second cycle + deformation after 30 min

first cycle

third cycle

Project related

Project related

30 min

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Report of shim compressibility for the individual shim data sheets:

K3 (at room-temperature; p=100 +160 bar) [µm]

K2 (at 200°C; p = 100 + 160 bar) [µm]

For shims that will be used for rear axle brakes with integrated parking function:

K2 (at 200°C; p = (bar) project related after 30 minutes) [µm]

8.14 Test samples

Preparation of test samples:

Size of shim: min. 70 mm × 70 mm

Size of basic plate: 70 mm × 70 mm × 5 mm

Shims shall be bonded on the basic plate according to the original bonding specifications and stored for minimum 24 h before testing.

The basic plate shall be made of steel and have two parallel grinded surfaces with de-burred edg-es.

8.15 Statistics

Unless specified otherwise, the number of samples tested should be minimum five.

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9 EKB 1109 - Development Guideline on the Quality Control of Anti-Noise Shims – Shim Geometry (revised: 5 August 2014)

9.1 Scope

This recommendation includes design rules both for bonded and clip-on shims

9.2 Purpose

To give a “hand-book” of design guidelines to minimize the redesign work in development phase and before production start on shim geometries.

9.3 Design rules for backplates:

9.3.1 Pin design

9.3.1.1 The chamfer bevel of the pin must be defined, e.g. 6°–12°.

9.3.1.2 Non-riveted (only in case that a lifting of the shims is not possible, because the pin is close to the piston and fingers): diameter and height should be defined in a common standard (diameter 5.5 mm × 2.0 mm, for example)

9.3.1.3 Riveted: same as non-riveted but bigger height (diameter 5.5 mm × 2.3 mm, for example), recommendation for pin height is shim thickness + 1.5 mm.

Tolerance should be for diameter: ± 0.1 mm, for height: ± 0.2 mm.

9.3.1.4 Countersunk pins: hole diameter, depth, angle, pin diameter and pin height should be de-fined in a common standard. See tolerances on sketch below.

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9.3.1.5 Pin positioning:

9.1.1.5.1 > 10 mm to the edges in case of straight pin (centre pin to edge)

9.1.1.5.2 > 14 mm to the edges in case of countersunk pin (centre pin to edge)

9.1.1.5.3 ≥ 6 mm to the area of the friction material

9.3.1.6 Tolerances pin: positional tolerance of pins in width direction should be ± 0.2 mm and in height direction ± 0.2 mm.

9.3.1.7 Pin number: generally two, in case of high torque more

9.3.2 Printing

No printing in shim bonded area

9.4 Riveting requirements for noise insulators

A proper noise insulator riveting is essential for the fixation and effectiveness of the shim. An im-properly riveted shim could cause shim detachment, shim damaging and reduction of the effective-ness of the shim. The following riveting recommendations are therefore highly recommended.

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Gap between shim and back

plate has to be considered, to

avoid tension stress in the shim

which could effect “butterfly”

effects and shim detachment.

Definition by pin-diameter after

spin-riveting process.

Must be tested by tests with min

and max pin tolerance conditions

before fixed in the drawing.

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Gap “a” must be considered.

First shim contact must be

on the pin and not on the

slope of bore chamfer

“a”

9.5 Shims

9.5.1 General design remarks

Outside (piston or finger side, burr side)

Inside (pad side)

Seite 49 VDA 309 02/2016

9.5.2 Ideal shape should cover 100% of the backplate (highest damping). Due to other con-straints like wear indicators, hammerheads etc., this is often not feasible.

9.5.3 It is more important to cover the centre of a pad and the areas which are in contact with the pistons and fingers than other areas especially at the outer periphery.

9.5.4 Labelling windows should be avoided.

9.5.5 If a labelling window cannot be avoided, it should be as small as possible and localized in a centre position not too close to the edge of the shim.

9.5.6 The shape should be as round and smooth as possible (ideal shape is a circle).

9.5.7 A shim with acrylic or silicone must be mechanically secured with pins or equivalent fixa-tions. Shims with phenolic glue may not need extra fixation, but this is optional.

9.5.8 If a shim material is not capable for 90° bending with radius ≤ 1 mm, this should be indicat-ed in the data sheet.

9.5.9 The outer geometry of a bonded shim should not be too close to the edge of the backing plate (distance 3 mm is recommended to guarantee that the shim is located on the flat area of the backing plate).

9.5.10 In case of having two or more holes for the shim fixation, it is recommended to design one hole circular and the other(s) oval.

9.5.11 The Shim geometry should avoid too expanded edges.

min. 3 mm

good

not good

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9.5.12 Pin hole design

9.5.12.1 Flat hole: should be defined in relation to the backing plate pin diameter. For example, if pin diameter is 5 mm, then the diameter of the circle hole of the shim should be 5.4 mm (+ 0.2 mm). Oval hole(s) should be 6.3 mm long.

9.5.12.2 Countersunk hole: min. R > 2 mm, otherwise the release liner might break due to bend-ing forces while die cutting. Hole depth recommendation: max 1.6 mm, otherwise liner and steel might break.

9.5.12.2.1 In a specific project, it should be indicated that a shim material is capable for a countersunk hole backing plate drawing.

9.5.12.2.2 Shape should be defined by a common standard

9.5.12.3 Star cut: shape to be defined by shim supplier (too much material depending) and finally released by brake or pad supplier.

9.5.13 Pin hole positions

9.5.13.1 ≥ 6 mm to the edges in case of straight pin (centre hole to edge)

9.5.13.2 ≥ 11 mm to the edges in case of countersunk pin (centre hole to edge)

9.6 Clip on shims

9.6.1 Should cover the piston(s) and fingers completely.

9.6.2 Outer geometry should be slightly reduced, comparing to the bonded shim below, in order to avoid burr contact because of the possible movement of the clip on shim in braking con-ditions.

9.6.3 Burr to the finger or piston side (if combination bonded shim + clip on shim: provide slipping between the backplate and the shim, metal-to-metal contact has to be avoided).

9.6.4 Burr to the backing plate side (if the clip on shim is mounted directly on the pad: provide slipping between the piston / finger and the clip on shim).

9.6.5 The leg geometry should be as simple as possible (avoid using a high number of bends, this increases the tooling costs and tolerances massively; eventually it might be generally defined in a common standard).

Seite 51 VDA 309 02/2016

recommended not recommended

9.6.6 The leg number should be matched to secure the position of the shim by considering all boundary conditions like pins, high torque etc.

9.7 Burr (only bonded shims!)

The burr should be in finger or piston direction in order to ensure a proper bonding.

Seite 52 VDA 309 02/2016

9.8 Flatness

The flatness should be related to the total width, height and steel thickness of the shim. A standard value is 0.1/20 mm. The higher the steel thickness (for example 0.8 mm) and the smaller the bond-ing area, also the flatness should be minimized. For thinner shims (steel thickness 0.4 mm) and large geometries, the flatness plays a minor role. The bow direction should be convex in horizontal and vertical (looking from the side) direction.

9.9 Tolerances

9.9.1 Functional measurements: ± 0.1 mm

9.9.2 Radius: ± 0.5 mm

9.9.3 Distances in general: ± 0.25 mm

9.9.4 Distances of pin holes and “star cut” holes: ± 0.1 mm

9.9.5 Diameter and oval holes: + 0.2 mm

0.4 mm

80 mm

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10 Relationships, References

10.1 Relationship of EKB standard to DIN, SAE or ISO standard

There is no ISO standard covering this practice.

There is a relationship between EKB 1107 and SAE J2694. Both procedures have been developed in 2005/2006 within a cooperation between the US Working Group of Brake Noise and the corre-sponding EKB Working Group.

10.2 Reference section

DIN 50 014 – Standard climatic conditions

ASTM D618 – Standard Practice for Conditioning Plastics for Testing

ASTM D1876 – Standard Test Method for Peel Resistance of Adhesives (T-Peel Test)

ekb specifications for disc brake pad noise damping … · ekb specifications for disc brake pad...

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