Abstract: Rubber friction blocks are core functional components widely applied in mechanical transmission, braking systems, industrial damping equipment, and engineering machinery. These components consistently serve under complex coupling conditions of static and dynamic compression, cyclic friction, and continuous abrasion during long‑term service. With the extension of service time, multiple failure phenomena such as surface wear, fatigue cracking, permanent compression deformation, and structural peeling inevitably occur, which directly reduce friction stability, weaken mechanical matching performance, and even cause equipment operation failures. This paper systematically analyzes the failure mechanisms of rubber friction blocks under long‑term compression and abrasion conditions, summarizes typical failure forms and macroscopic and microscopic morphological characteristics, explores the influence laws of load pressure, friction cycles, working temperature, and material formula on failure evolution, and proposes targeted performance optimization and service life improvement strategies. The research aims to provide theoretical reference and technical support for the structural design, material selection, and service condition control of rubber friction blocks in long‑life and high‑stability industrial scenarios.
1. Introduction
As a typical elastomer functional part, rubber friction blocks rely on the excellent elasticity, high friction coefficient, and good wear resistance of rubber materials to realize functions such as friction transmission, braking deceleration, vibration damping, and buffer limit. Different from rigid friction materials such as metal and ceramic, rubber materials have unique viscoelastic characteristics, which can produce adaptive elastic deformation under contact pressure, effectively increase the effective contact area with the matching surface, and maintain stable friction performance under complex working conditions. Therefore, rubber friction blocks are irreplaceable in light‑load and medium‑load mechanical systems requiring low noise, high flexibility and strong impact resistance.
In actual industrial service, most rubber friction blocks work under long‑term cyclic compression and continuous sliding abrasion. The coupling effect of mechanical compression stress and interfacial friction shear stress makes the material bear repeated loading and unloading for a long time. Meanwhile, frictional heat accumulation, micro particle abrasion, and environmental aging will further accelerate material performance degradation. A large number of engineering practices show that the failure of rubber friction blocks is rarely caused by instantaneous structural damage, but mostly progressive failure formed by long‑term damage accumulation. The gradual attenuation of friction coefficient, permanent compression set, surface fatigue damage and material peeling are the main failure modes, which seriously restrict the service life and operation stability of equipment.
At present, most studies on rubber friction materials focus on short‑term friction performance testing and formula improvement, while there are relatively few systematic analyses on the long‑term coupled failure mechanism of compression and abrasion. In order to clarify the progressive failure law of rubber friction blocks in full‑cycle service, this paper analyzes the internal mechanism of various failure modes, summarizes the key influencing factors of failure, and puts forward feasible improvement measures, so as to provide technical basis for the long‑term stable operation of rubber friction components.
2. Typical Failure Modes of Rubber Friction Blocks
Under the combined action of long‑term compression load and continuous abrasion, the failure of rubber friction blocks presents diverse and progressive characteristics. According to macroscopic morphology and microscopic damage mechanism, the main failure modes are divided into permanent compression deformation failure, abrasive wear failure, fatigue cracking failure, and surface transfer film failure. Each failure mode has independent morphological characteristics and evolutionary laws, and multiple failure modes often coexist and promote each other in actual service.
2.1 Permanent Compression Deformation Failure
Permanent compression set is the most basic failure form of rubber friction blocks under long‑term compression. Rubber materials have typical viscoelasticity. Under continuous static or cyclic compression load, the molecular chain network inside the material will produce creep deformation that cannot be fully recovered. With the increase of compression cycles and service time, the elastic recovery performance of the material gradually decreases, and irreversible plastic deformation accumulates continuously, resulting in the permanent reduction of the overall thickness and height of the friction block.
Macroscopically, the failed friction block shows flat contact surface, reduced overall elasticity, and insufficient compression rebound. The matching gap between the friction block and the contact component increases, which leads to the decline of contact tightness and unstable friction output. Microscopically, long‑term compression causes the rearrangement and entanglement of rubber molecular chains, and the cross‑linking network produces partial irreversible fracture and relaxation. The internal residual stress accumulates continuously, which reduces the elastic modulus and resilience of the material. Different from instantaneous elastic deformation, compression permanent deformation is a cumulative damage process. The deformation degree increases with the extension of service time, and finally leads to the complete loss of functional elasticity of the friction block.
2.2 Abrasive Wear Failure
Abrasive wear failure occurs on the contact surface of friction blocks under long‑term sliding friction. In the process of friction and matching, the micro‑protrusions on the surface of the rigid matching part will produce continuous ploughing and cutting effects on the soft rubber surface. At the same time, tiny abrasive particles such as dust, metal wear debris and oxide scale in the working environment will be embedded in the friction interface, forming three‑body abrasion, which further aggravates surface material removal.
Macroscopic characteristics of abrasive wear include uniform thinning of friction surface, directional scoring and groove marks parallel to the sliding direction, and local material loss. In severe cases, irregular wear pits and step structures will appear on the contact surface. Microscopic observation shows that the worn rubber surface presents typical fish‑scale and ploughing morphologies, with a large number of micro‑tearing traces and embedded abrasive particles. Different from metal wear, rubber abrasive wear is not only mechanical cutting loss, but also accompanied by molecular chain fracture and peeling caused by interfacial shear force. Long‑term continuous abrasion will gradually reduce the dimensional accuracy of the friction block, destroy the surface friction texture, and lead to the continuous decline of friction coefficient.
2.3 Fatigue Cracking Failure
Fatigue cracking is a typical delayed failure mode of rubber friction blocks under cyclic compression and friction coupling. In the repeated process of compression deformation and friction shear, the internal stress of the rubber material is periodically loaded and unloaded, resulting in alternating tensile and compressive stress inside the friction block. Microscopic defects such as tiny pores and cross‑linking defects inherent in rubber materials become stress concentration points. Under the action of long‑term alternating stress, microcracks germinate at the stress concentration points, and expand gradually along the direction of stress transfer.
In the early stage of fatigue failure, only invisible microcracks exist inside and on the surface of the friction block, with no obvious macroscopic change in performance. With the increase of friction cycles, the microcracks continue to expand and connect, forming visible macroscopic cracks. The cracks will destroy the integrity of the rubber structure, reduce the effective bearing area of the friction block, and cause local stress concentration to be more serious. In the later stage of failure, the expansion of cracks will lead to surface peeling, block fragmentation and other phenomena, completely losing the friction and bearing function.
2.4 Surface Transfer Film Failure
In the long‑term friction process between rubber friction block and rigid matching surface, a thin transfer film formed by rubber molecular deposition will be generated on the contact interface. A complete and stable transfer film can isolate the direct contact between rubber and rigid matrix, reduce friction shear force and abrasive wear degree, and maintain stable friction performance. However, under the coupling action of long‑term compression and high‑frequency friction, the transfer film is prone to rupture, peeling and uneven distribution.
When the transfer film fails, the local direct contact between the rubber matrix and the rigid surface increases, the interfacial friction coefficient fluctuates violently, and local dry friction and high temperature heat accumulation occur, which further accelerates the surface wear and fatigue damage of the friction block. The instability of the transfer film is often the inducement of accelerated failure of rubber friction blocks in the later stage of service, and forms a vicious cycle of film failure → intensified friction → material damage.
3. Key Influencing Factors of Long‑Term Failure
The progressive failure of rubber friction blocks under compression and abrasion is affected by multiple factors such as mechanical load, working environment, material performance and service cycle. The interaction of various factors jointly promotes the evolution of material damage. This chapter analyzes the core influencing factors and their action mechanisms one by one.
3.1 Compression Load and Cyclic Frequency
Compression load is the core mechanical factor affecting the failure rate of friction blocks. Under low load conditions, the rubber material has small deformation, uniform internal stress distribution, slow accumulation of creep deformation and fatigue damage, and long service life. When the compression load exceeds the optimal bearing range of the material, the internal molecular chain bears excessive stress, the creep deformation rate increases significantly, and the permanent compression set becomes more serious. High‑load compression will also increase the effective contact pressure of the friction interface, intensify the ploughing and shearing effect of the matching surface on the rubber, and accelerate abrasive wear.
Cyclic friction frequency determines the fatigue damage accumulation speed. High‑frequency cyclic friction makes the material bear alternating stress repeatedly in a short time, and the microcrack germination and expansion speed is significantly improved. Meanwhile, high‑frequency friction generates a large amount of frictional heat, which causes the surface temperature of the friction block to rise sharply, induces thermal aging of rubber materials, reduces cross‑linking density, and further weakens the mechanical and wear resistance of the material.
3.2 Working Temperature and Thermal Aging
Temperature is an important environmental factor inducing rubber material failure. Long‑term friction will generate continuous frictional heat, resulting in local high temperature on the friction surface. On the one hand, high temperature will soften the rubber material, reduce its hardness and shear resistance, and make the surface more prone to plastic deformation and abrasive peeling. On the other hand, thermal aging will cause oxidative cracking of rubber molecular chains, destroy the stable cross‑linking network structure, reduce material elasticity and fatigue resistance, and significantly accelerate the progress of compression deformation and fatigue cracking failure.
In alternating cold and hot working environments, the thermal expansion and cold contraction of rubber materials are inconsistent, resulting in alternating internal thermal stress, which is easy to induce microcrack germination and expansion, and aggravate structural damage of friction blocks.
3.3 Material Formula and Structural Design
The inherent performance of rubber materials determines the fundamental anti‑failure ability of friction blocks. Rubber formulas with low cross‑linking density, poor wear resistance and insufficient resilience are prone to serious compression deformation and abrasive wear in long‑term service. Reasonable filling system (such as carbon black, silica and anti‑aging fillers) can effectively improve the hardness, wear resistance and anti‑aging performance of rubber, and delay the accumulation of long‑term damage.
Structural design also has a significant impact on service life. Unreasonable structural size will lead to uneven stress distribution of friction blocks, local stress concentration, and preferential failure of stress concentration areas. Optimized contact surface design can disperse friction shear force and compression stress, reduce local damage, and improve the overall service stability of friction blocks.
3.4 Environmental Medium and Abrasive Particles
The working environment medium directly affects the friction and wear mechanism of rubber blocks. In dry environments, the friction interface is prone to dry friction and heat accumulation, resulting in thermal aging and surface peeling of rubber. In humid environments, water molecules will penetrate into the rubber interior, weaken the interaction force between molecular chains, reduce material hardness and wear resistance, and accelerate compression deformation. When there are a large number of tiny abrasive particles such as dust and metal debris in the environment, three‑body abrasion will be formed at the friction interface, which greatly increases the material removal rate and makes the friction block fail ahead of time.
4. Failure Evolution Mechanism and Progressive Law
The long‑term failure of rubber friction blocks is a continuous and progressive evolutionary process, which can be divided into three stages: stable operation stage, slow damage accumulation stage and accelerated failure stage. The failure forms and damage degrees of each stage show obvious regularity.
In the early stable operation stage, the friction block has intact surface morphology and stable structural performance. Under normal compression and friction conditions, only slight elastic deformation and micro friction loss occur on the surface, no permanent damage and crack defects are formed inside the material, and the friction coefficient and mechanical performance remain stable.
With the increase of service time, the friction block enters the slow damage accumulation stage. Long‑term cyclic compression leads to the gradual accumulation of creep deformation, and slight permanent compression set appears. Micro abrasion marks are formed on the friction surface, and micro defects such as tiny pores and microcracks germinate inside the material. At this stage, the overall performance of the friction block does not decline significantly, but the internal damage continues to accumulate, and the structural stability and anti‑interference ability are reduced.
In the later accelerated failure stage, the internal microcracks expand and connect into macroscopic cracks, the permanent compression deformation increases sharply, the surface wear is intensified, and the transfer film is completely broken and invalid. Multiple failure modes couple and promote each other, resulting in rapid attenuation of friction performance, structural loosening and local peeling of the friction block, and finally complete loss of service function.
5. Performance Optimization and Anti‑Failure Strategies
Aiming at the failure mechanism and influencing factors of rubber friction blocks under long‑term compression and abrasion, targeted optimization measures can be carried out from material formula, structural design, service condition control and maintenance management to delay failure evolution and improve long‑term service stability.
5.1 Material Formula Optimization
Optimize the rubber matrix formula, select high‑elasticity and anti‑fatigue rubber raw materials, and adjust the cross‑linking system to improve the cross‑linking density and structural stability of the material, so as to reduce creep deformation and permanent compression set. Add high‑performance wear‑resistant fillers and anti‑aging agents to improve the abrasion resistance and thermal aging resistance of the rubber material, inhibit the germination and expansion of microcracks, and reduce surface material loss. Reasonably adjust the hardness and resilience of the material to balance the friction performance and long‑term bearing capacity.
5.2 Structural and Interface Optimization Design
Optimize the overall structural size of the friction block to avoid local stress concentration, make the compression stress and friction shear force evenly distributed on the contact surface and interior, and reduce the fatigue damage degree. Optimize the surface friction texture design to improve the uniformity of the contact interface, promote the formation of stable transfer film, reduce interfacial friction fluctuation and abrasive wear. Properly optimize the matching gap between the friction block and the contact parts to avoid excessive compression and idle friction.
5.3 Service Condition Control
Control the working load and friction frequency within the optimal bearing range of the friction block material to avoid long‑term over‑load compression and high‑frequency friction. Optimize the working heat dissipation environment to reduce frictional heat accumulation and avoid thermal aging failure of rubber materials. Keep the friction interface clean regularly to reduce the accumulation of abrasive particles and avoid three‑body abrasion damage. For alternating cold and hot environments, take necessary heat insulation and temperature protection measures to reduce thermal stress damage.
5.4 Regular Maintenance and Replacement
Establish a regular inspection and maintenance mechanism for rubber friction blocks, regularly check the surface wear degree, structural deformation and crack defects, and find and eliminate potential damage in the early stage of damage accumulation. Formulate a scientific replacement cycle according to the service environment and load conditions, and replace aging and damaged friction blocks in time to avoid equipment operation faults caused by accelerated failure of components in the later stage.
6. Conclusion
Under long‑term compression and abrasion coupling conditions, the failure of rubber friction blocks is a progressive damage evolution process dominated by material creep, fatigue crack propagation and interfacial abrasive wear. Permanent compression deformation, abrasive wear, fatigue cracking and transfer film failure are the four typical failure modes, which interact and accelerate the failure process together. Compression load, cyclic frequency, working temperature, material performance and environmental particles are the key factors affecting the long‑term service life and stability of friction blocks.
Optimizing rubber material formula and structural design, controlling service working conditions, and implementing standardized maintenance management can effectively delay the accumulation of long‑term damage, inhibit the occurrence of accelerated failure, and significantly improve the service life and operation stability of rubber friction blocks. In future industrial applications, the long‑term coupled failure mechanism should be fully considered in the design and selection of rubber friction components, so as to realize high‑stability and long‑life service of components under complex cyclic working conditions.