The effect of compression and sliding movement on the wear resistance of steels and crushing work in mineral crushing

The purpose of crushing equipment is to reduce the size of aggregates. Minerals have good compressive strength, but they are relatively weak in tension. Most of the equipment crushes the rock by compression, which produces also tensile stresses high enough to fracture the rock. A single-toggle jaw crusher utilizes two plates, one stationary and another moved by an eccentric axle, to crush the aggregate between the jaw plates. The interaction of the aggregate with the jaw plates causes high contact forces, which are high enough to cause plastic deformation in the jaw plates. Some of the contacts remove material from the jaw plates. Wear changes the shape of the jaw plates, which affects the crushing capacity of the jaw crusher and eventually leads to the replacement of the jaw plates.The movement pattern of the jaws is an important factor in the efficiency of crushing. Compressive motion is needed to crush the rock, whereas lateral motion is desired as it helps the flow of the aggregate through the crusher and increases the capacity. In a jaw crusher, a flywheel is used to store kinetic energy to turn the eccentric axle, which applies the motion to the jaw. The amount of work consumed in each compression cycle depends on the movement pattern of the jaw as well as on the mechanical properties of the crushed mineral. Part of the work is also consumed by the friction of the crushing mechanism, by the plastic deformation of the crushing contacts, and by the crushing of the aggregates.This thesis concentrates on studying how the movement pattern of the jaw crusher affects the wear of the jaw plates and the work consumed in the crushing and wear processes. A new test equipment, the dual pivoted jaw crusher (DPJC), was designed and manufactured to make the study possible. The DPJC is a laboratory sized jaw crusher, which allows changes in the relation between the compressive and lateral movements of the jaw. It also has a modular jaw structure, which enables changing of the geometry of the crushing cavity. The thesis concentrates on determining how the parameters of the crushing equipment affect the wear and work done in the tests with high manganese and tool steel specimens.The results of the tests show that there is a linear relationship between the wear of the specimens and the work done in the test. Also, when the movement pattern of the jaws is changed, the increase of the lateral motion increases the wear of the specimens and the total work done in the test. The DPJC was shown to be a versatile tool for wear research, causing extensive deformation and wear in the jaw plate materials, and having the ability to work harden also austenitic manganese steels. Carbide reinforced tool steels are known for their good wear resistance under compression, but with increasing lateral motion of the jaw plates they were observed to be susceptible to shear localization, which can decrease their wear performance. In addition to wear testing, the DPJC equipment can be used for comminution testing of minerals

The effect of compression and sliding movement on the wear resistance of steels and crushing work in mineral crushing

The purpose of crushing equipment is to reduce the size of aggregates. Minerals have good compressive strength, but they are relatively weak in tension. Most of the equipment crushes the rock by compression, which produces also tensile stresses high enough to fracture the rock. A single-toggle jaw crusher utilizes two plates, one stationary and another moved by an eccentric axle, to crush the aggregate between the jaw plates. The interaction of the aggregate with the jaw plates causes high contact forces, which are high enough to cause plastic deformation in the jaw plates. Some of the contacts remove material from the jaw plates. Wear changes the shape of the jaw plates, which affects the crushing capacity of the jaw crusher and eventually leads to the replacement of the jaw plates.The movement pattern of the jaws is an important factor in the efficiency of crushing. Compressive motion is needed to crush the rock, whereas lateral motion is desired as it helps the flow of the aggregate through the crusher and increases the capacity. In a jaw crusher, a flywheel is used to store kinetic energy to turn the eccentric axle, which applies the motion to the jaw. The amount of work consumed in each compression cycle depends on the movement pattern of the jaw as well as on the mechanical properties of the crushed mineral. Part of the work is also consumed by the friction of the crushing mechanism, by the plastic deformation of the crushing contacts, and by the crushing of the aggregates.This thesis concentrates on studying how the movement pattern of the jaw crusher affects the wear of the jaw plates and the work consumed in the crushing and wear processes. A new test equipment, the dual pivoted jaw crusher (DPJC), was designed and manufactured to make the study possible. The DPJC is a laboratory sized jaw crusher, which allows changes in the relation between the compressive and lateral movements of the jaw. It also has a modular jaw structure, which enables changing of the geometry of the crushing cavity. The thesis concentrates on determining how the parameters of the crushing equipment affect the wear and work done in the tests with high manganese and tool steel specimens.The results of the tests show that there is a linear relationship between the wear of the specimens and the work done in the test. Also, when the movement pattern of the jaws is changed, the increase of the lateral motion increases the wear of the specimens and the total work done in the test. The DPJC was shown to be a versatile tool for wear research, causing extensive deformation and wear in the jaw plate materials, and having the ability to work harden also austenitic manganese steels. Carbide reinforced tool steels are known for their good wear resistance under compression, but with increasing lateral motion of the jaw plates they were observed to be susceptible to shear localization, which can decrease their wear performance. In addition to wear testing, the DPJC equipment can be used for comminution testing of minerals

Specific wear energy in high-stress abrasion of metals

A certain amount of mechanical work is always needed for wear to occur in an operational system. The estimation of this work based on the measured electrical energy input is, however, usually quite difficult. The dual pivoted jaw crusher was designed to allow accurate wear and work measurements during the tests, enabling the division of consumed energy to specific wear and crushing energy portions. The major contributors to the specific wear energy are the frictional contacts during the sliding movement. In this work, high stress abrasion wear tests were conducted with several metals ranging from pure aluminum and copper to carbide-reinforced steels, and the specific wear energy was correlated to several material properties. The results show a linear correlation between some of the material properties and the specific wear energy, whereas a similar comparison of the material properties with the amount of wear or work done during the tests yields a non-linear correlation

Correlation of wear and work in dual pivoted jaw crusher tests

A laboratory sized jaw crusher with uniform movement of the jaws, the Dual Pivoted Jaw Crusher (DPJC), was used to determine the relationship between wear and work. Wear was concentrated on the jaw plates opposing each other and was measured as mass loss of the specimens. Work was measured directly from the force and the displacement of the instrumented jaw, which allowed work to accumulate only from the actual crushing events. The tests were conducted with several jaw geometries and with two motional settings, where the relation of compressive and sliding motion between the jaws was varied. The comminution of rock is presumed to be irreversible, meaning that the energy used for crack formation in the rock particles eventually results in the fracture of the particles. Therefore, the amount of energy needed to comminute rock particles should be roughly constant and not dependent on the loading conditions, if the speed of the loading contact is not changed. The DPJC test method allows the separation of work components into comminution specific work and sliding specific work. The results can be used to compare the crushability of minerals without the influence of the used test geometry or the selected jaw plate materials. The sliding work can be used for the comparison of the wear of the jaw plate materialspublishedVersio