Rpc is the Peak Density in the X or Y direction of surface texture data. It is a measure of the number of peaks per unit length (i.e., peaks/mm) in the X or Y directions, respectively. In the ISO standards, the parameter is referred to as Rpc X or Rpc Y; however, in some software … Read more
Floyd Alburn Firestone was an acoustical physicist with wide-ranging talents, with important contributions in fields including acoustics, non-destructive testing, medicine, and surface texture. He is remembered as developing the first practical ultrasonic testing system, which is used widely for inspecting material fatigue in railroad cars, aircraft components, and other transportation vessels. The technique was also, … Read more
Rotary lip seals create a boundary around shafts in rotary equipment, typically to retain lubricant on one side versus air or gas on the other. On first consideration, it would make sense that a seal would act as a barrier, holding back all lubrication. In reality, however, when a sealing interface is working optimally, fluid … Read more
The Roughness Average, or average roughness parameter, Ra, is the average of the surface heights of every point along the “roughness profile.” Its equivalent for areal (3D) measurements is the Sa parameter. To see how Ra is affected by the cutoff, let’s start by taking a minute to define exactly what the roughness profile is. … Read more
Transmission clutch mechanisms and other complex systems require tight control of friction characteristics. Surface texture parameters such as Peak Heights, Valley Depths, Spacings and other bearing area related parameters (Spk, Sk, Svk) can be specified to control production processes and optimize friction characteristics. Michigan Metrology has been on the forefront of relating surface roughness to … Read more
Michigan Metrology – Surface Texture Measurement, Consulting, and Classes “I highly recommend your service.” – Aerospace Engineer Michigan Metrology provides surface roughness measurement, analysis, and training, to solve problems related to wear, surface finish, flatness, sealing, vibration, noise, and more. Our clients range from small, exciting start-up ventures to Fortune 500 companies in the automotive, … Read more
It’s a common intuition that smoother surface texture is “better” for rotating or sliding over another component. It seems natural that a smoother surface would wear less, have lower friction, and perhaps operate at lower temperatures. This gut reaction is widespread and runs deep. As an example, a few years ago a medical device was … Read more
Scientists and philosophers through the ages have struggled with the concepts of friction. Leonardo da Vinci studied many aspects of friction, bearings, etc. In one set of experiments, he tied a cord to a rectangular block and dragged it along a surface. He found, surprisingly, that dragging the block on its short side, or long … Read more
May 2 will mark the birthday of Frank Philip Bowden who, along with David Tabor, laid the groundwork for much of our modern understanding of friction and lubrication. “Putting two solids together is rather like turning Switzerland upside down and standing it on Austria—their area of intimate contact will be small.” – Frank Bowden Bowden … Read more
Ra (Roughness Average, or average roughness) is the average height of all measured points on a surface. Ra is the most widely used surface texture parameter. As we’ve mentioned elsewhere in this blog, there is much information about a surface that Ra cannot provide. It can, however, be a fast, simple way to tell whether a … Read more