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# TCM 1 738-Johann Maier & Co. – Stuttgart (DE) EN4178-100024

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3 Replies to “TCM 1 738-Johann Maier & Co. – Stuttgart (DE) EN4178-100024”

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QTP EN 4178-100024:

Page 4: Double shear test shall be done as per ISO9152, clause 5.4.2.

Moreover, in this QTP, clause 3.4.2 states that this test will be done.

So, why is it written “No requested”?

Page 10: EN4178, clause 3.4 specifies a thickness between 5 to 10 µm. In this QTR, coating thickness requirement is 5-13 µm. There is not a big difference, but is it possible to clarify?

QTR EN 4178-100024

Page 48: all tensile test values are compliant, but three of them are really close to the minimum required. One value is only 210 N higher than minimum required.

Perhaps it is due to a compromise between tensile and fatigue performances?…

Page 49: all double shear test values are compliant, but three of them are really close to the minimum required.

Perhaps it is due to a compromise between tensile and fatigue performances?…

Many thanks in advance and have a nice day.

QTP EN 4178

Double shear is requested

Layer thickness is 5 to 10microns.

QTP revision b was created.

QTR EN 4178

There is no comparison between tensile and fatigue test.

The strength of the bar material is about 1170MPa.

Compared to the material strength the tensile strength test is lower , due to fact that the stress area is calculated acc. to formula which leads to value app. 3% over the real area. (ref. ISO 9152, A.2.1. Formula for Cross sectional area calculation)

Shear strength

The lager the diameter, the lower the shear strength.

This is due to the manufacturing process (drawing), in relation of the tensile strength.

Thank you Heinrich.

Mr. DORSCH called me to give me more explanations and it is clear for me.

Tensile test:

Compared to the material strength the tensile strength test is lower, due to fact that the stress area is calculated acc. to formula which leads to value app. 3% over the real area. (ref. ISO 9152, A.2.1. Formula for Cross sectional area calculation).

Indeed, when we calculate the real minimum tensile value as per formulae A.2.1 in ISO9152, we have 71650 N minimum, but in ISO9152, table 5, we have a rounded value which is 72000 N minimum.

By considering 71650 N minimum, margins are increased against measured tensile loads.

Moreover, as you said, we have a difference of stress area calculation between ISO M threads and ISO MJ threads.

Stress area calculation for ISO M threads: As = (pi/4)*(d2 + d3)/2]²

Stress area calculation for ISO MJ threads: As = (pi/4)*(d3)²[2-(d3/d2)²]

d2: maximum pitch diameter

d3: maximum root diameter

It entails a difference of approx. 3% as you mentioned.

Shear test:

It is clear for me about shear values as well.

Best regards.