Insight to Lubricant Friction Measurement Methods

粘度被定义为润滑剂的物理特征，而摩擦被认为是系统特性。通过简单地知道润滑剂的粘度来预测摩擦是相当困难的。因此，通常使用具有摩擦测量系统的摩擦仪检查在混合，饥饿，边界或弹性流体动力润滑条件下运行的指定系统的摩擦与粘度之间的关系（见图1）。

数字1。润滑剂的摩擦行为与各种二核底仪的操作参数的函数。

The following sections provide some examples of various friction measurement techniques used for connecting viscosity and friction in a wide range of system conditions.

在边界/混合润滑的四个球测试仪的摩擦反应

DUCOM四个球测试仪或FBT-3(see Figure 2), is an automated tribometer integrated with high and low friction measuring system. With the help of an in-house designed flexure and load cell, the friction of the lubricant can be determined with a precision of 1% at a load of 10,000 N, 120 °C, and 3000 rpm.

数字2。Images ofDucom FBT-3, friction measurement during the four ball test, the measured friction profiles of lubricants and its relationship with the viscosity of the lubricants.

The friction graphs shown in Figure 2 were recorded for base oils with varied viscosity grades, at a contact pressure of 1.7 GPa and at a speed and lubricant temperature of 1200 rpm and 75 °C, respectively. The results of the FBT-3 denote that the quantified friction depends on the viscosity of the lubricant. Base oil with the highest viscosity grade was found to have the lowest friction.

Friction Response from a Microforce in Starved Lubrication

Fitted with a patented friction measuring system, the DucomMicroForce(see Figure 3) provides a high friction resolution — that is, 30 µN at a load of 2500 mN.

数字3。Images ofDucom MicroForce,friction measurement system under microscale sliding, and the friction graph showing the transition from slip to stick phase.

Using parallel plate elastic sheets and capacitive sensors, the normal force and the friction force are determined independent of each other. Stroke length ranges between 0.02 and 50 mm, while the range of operating load varies from 10 mN to 10 N.

图3中所示的摩擦图表示饥饿状况下润滑剂的“滑动”行为。摩擦是作为增加润滑剂饥饿（降低接触直径/中风长度）的函数。从滑动相到棒相的转换表示微观的总饥饿。这些结果表明粘度不会影响摩擦。

Friction Response from a KRL Shear Stability Tester in Elastohydrodynamic Lubrication (EHL)

Ducom KRL Shear Stability Tester (see Figure 4) utilizes a dedicated flexure to determine the friction response of lubricants sheared in a tapered rolling element bearing.

数字4。DUCOM KRL剪切稳定性测试仪的图像，滚动条件下的摩擦测量系统以及粘度方面的摩擦行为。

Friction measurement system precisely records the behavior of the lubricants under the rolling-sliding friction (rolling element bearing), for a testing period of more than 100 hours. The accuracy is 1% and the least count is 100 mN.

数字4shows the friction response of lubricants with four varied viscosity grades. The test load was 5000 N, lubricant temperature was 60 °C, and speed was 1450 rpm. As demonstrated, the friction is mostly affected by the viscosity, and as the viscosity of the lubricants increases, the friction decreases.

Friction Response from an Extreme Load Tribometer in Elastohydrodynamic Lubrication (EHL)

The automated tribometer —Ducom extreme load tribometer(see Figure 5) — allows lubricant testing at contact pressure less than 300 MPa at 10,000 N. The friction measurement at that extreme load condition should be stable and also independent of the loading unit. An exclusive flexure system with self-aligning potential can precisely transfer friction to the load cell, which reports the friction force.

图5显示了板构型上三个引脚的摩擦响应，表明具有高粘度指数（油B4）的润滑剂显示出较低的摩擦。在此测试中，剪切条件非常侵略性，并且会产生巨大的摩擦加热，从而对润滑剂的粘度产生影响。相反，如结果所示，可以通过高粘度指数来降低这种效果，并且可以通过高粘度指数维持低摩擦。

数字5。Images of Ducom extreme load tribometer, friction measurement system for three pin on plate configuration, and the friction behavior with respect to viscosity index。

In conclusion, Ducom tribometers are extremely useful in linking the viscosity of the lubricants with their friction behavior in a system.

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