In the early 20th century, profilographs were low speed rolling devices (for example rolling straight-edges). The profilograph is a device used to measure pavement surface roughness. Profilographs that record texture in both left and right wheel paths can be used to identify road sections with hazardous split friction. Since MiTx has so short waves, it is preferably measured by dry friction brake tests rather than by profiling. MaTx and MeTx are measured with laser/inertial profilographs. MeTx below 0.2 mm Root-Mean-Square is considered normal on proper roads. Some examples of road damages with much MeTx are potholes, washboards (common on dirt roads) and uneven frost heaves. Megatexture has wavelengths from 50 mm up to 500 mm. Megatexture (MeTx) is a result of pavement wear and distress, causing noise and vibration. Road agencies monitor macrotexture using measurements taken with highway speed laser or inertial profilometers. Macrotexture has wavelengths from 0.5 mm up to 50 mm. While vehicle suspension deflection and dynamic tyre loads are affected by longer waves (roughness), road texture affects the interaction between the road surface and the tyre footprint. Macrotexture is a family of wave-shaped road surface characteristics. Proper roads have MaTx of about 1 mm Mean Profile Depth. Excessive MaTx increases rolling resistance and thus fuel consumption and CO 2 emission contributing to global warming. MaTx provide wet road friction, especially at high speeds. On the other hand, long wave MaTx increase noise. Short MaTx waves, about 5 mm, act as acoustical pores and reduce tyre/road noise. Macrotexture (MaTx) is partly a desired property and partly an undesired property. However, friction also depends on other surface properties, such as macro-texture. Typically, road agencies do not monitor mix directly, but indirectly by brake friction tests. The mix of the road material contributes to dry road surface friction. It relates to the surface of the binder, of the aggregate, and of contaminants such as rubber deposits from tires. Microtexture has wavelengths shorter than 0.5 mm. While vehicle suspension deflection and dynamic tire loads are affected by longer wavelength ( roughness), road texture affects the interaction between the road surface and the tire footprint. Microtexture (MiTx) is the collaborative term for a material's crystallographic parameters and other aspects of micro-structure: such as morphology, including size and shape distributions chemical composition and crystal orientation and relationships
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |