A Review of Wear Mechanisms in Bucket Teeth of Construction Machinery

Abstract:

With the expansion of construction activities and the use of heavy machinery, the issue of equipment wear, particularly the wear of bucket teeth, has garnered increasing attention. Thus, understanding the mechanisms and conditions of wear in such equipment is crucial. This study investigates the wear mechanisms affecting these parts. It should be noted that this research predominantly takes a theoretical approach, although future experimental studies are necessary for a deeper understanding. First, different types of wear are introduced, and ultimately, using finite element simulations, areas of high wear intensity in equipment components are identified.

1. Introduction:

Construction machinery operates under a wide range of complex and diverse working conditions, from urban infrastructure projects to mining explorations. Some construction equipment works under particularly harsh environments, resulting in significant wear and degradation [1]. Consequently, the number of failed components and annual maintenance costs continue to rise. Bucket teeth, in particular, are prone to wear and breakage due to their direct contact with minerals. Therefore, addressing the wear problems of these parts is of vital importance. However, wear is not merely a material property; it also depends heavily on system reactions [2].

In response to this need, Caterpillar [3] established a soil lab to evaluate the performance and wear of mobile machinery like loaders. Komatsu [4] in Japan also collaborated with Shandong University to study the mechanical properties and wear resistance of different types of bucket teeth. Their research focused on identifying factors affecting bucket teeth wear and developing new processing techniques to enhance wear resistance.

To effectively control wear, a comprehensive understanding of wear mechanisms and their operating conditions is essential. In this research, after reviewing theoretical wear fundamentals, different wear conditions on bucket teeth are analyzed using simulations. The study framework is illustrated in Figure 1.

Figure 1. Details of the present study

Wear Mechanisms

Wear Mechanisms in Bucket Teeth

Multiple complex factors influence the wear of industrial bucket components. These factors interact with each other, making the wear process more complicated. Thus, to address the wear issues of construction machinery components, it is essential to first correctly understand the wear mechanisms and various types of wear. Jiang [5,6] and colleagues conducted extensive experimental studies to analyze pin-on-disk wear on excavator bucket teeth. Their research revealed that the wear process generally involves three distinct stages: 1) abrasive wear, 2) gouging wear, and 3) adhesive wear.

Figure 2. Wear conditions in the bucket teeth

Each mechanism exhibits unique wear characteristics. Given the direct interaction between bucket teeth and abrasive materials such as rocks and gravel, their wear behavior is highly complex and varies across different sections of the tooth. The identified wear mechanisms in different parts of the teeth are illustrated in Figure 2.

Bucket teeth are critical and sensitive components of the bucket. Their quality and longevity directly affect the quality and quantity of extracted materials. As shown in Figure 3, bucket teeth come in various forms, including rock teeth, square rock and earth teeth, and others. The most common type is the conical tooth, which directly contacts abrasive materials. When the tooth penetrates the abrasive material, the tip experiences impact and pressure, resulting in varying wear patterns depending on the size of the particles and the point of impact.

Figure 3. Different types of teeth used in buckets

Impact Wear

Impact wear is a specific type of wear occurring on component surfaces due to collisions. Generally, impact wear also involves vibrational-frictional wear. In this wear type, abrasive materials, particularly sharp-edged ones, act like knives, scratching and plastically deforming the surface of bucket teeth. The amount of deformation depends on the nature of the minerals, the mineral geometry, the location and angle of impact, and the thickness of the impacted layer. The operating environment for impact wear is shown in Figure 4.

Figure 4. Working environment of the tooth under abrasive pressure conditions

Extensive research has been conducted on impact wear. Rice and colleagues [7] studied impact wear across various substrates under different loading conditions (dry environments). Parameters such as speed, pressure, and loading frequency were examined. In another study, Engel [8] investigated both impact and gouging wear. They discovered that a “zero wear” period exists during the early stages, attributed to the time required for crack initiation and growth. Yang [9] studied impact wear behavior on low-density Fe-Mn-Al-C steels under different speeds and identified distinct wear mechanisms.

Gouging Wear

Gouging wear is the primary wear type in construction equipment. It accounts for the majority of wear in construction machinery components and has been a major focus for researchers. It is also the most dominant wear mechanism affecting bucket teeth.

Gouging wear persists throughout the service life of construction equipment and can be categorized into three types based on applied stress:

• Bristle wear

• High-stress gouging wear

• Low-stress erosive wear

Burwell [10] classified abrasive wear into two-body and three-body types. Two-body wear occurs when a hard surface scratches a softer surface, while three-body wear happens when abrasive particles are trapped between two surfaces, causing wear on one or both.

Misra and Finnie [11] further refined the abrasive wear classification in 1980. Gates [12] concluded that gouging wear should be categorized based on applied stress levels and the movement of abrasive agents, underscoring the complexity of this wear mode.

In bucket loaders and other construction equipment, during material digging, bucket teeth penetrate materials, creating relative sliding between two surfaces under load, causing two-body gouging wear. During unloading (Figure 5), minimal contact between the materials and bucket teeth leads to three-body rolling friction wear.

Figure 5. Working conditions of the tooth and bucket controlled by abrasive wear

Fretting Wear

In previous wear types, surfaces experience counter-pressure while remaining relatively stationary. However, slight oscillatory vibrations or environmental stresses induce relative motion between the surfaces, leading to fretting wear.

Fretting wear was first observed by Eden in 1911 but gained attention in 1927 when Tomlinson [13] invented equipment to study frictional processes and coined the term “fretting corrosion.” Later studies identified the significant role of mechanical interactions and oxidation in this wear type. Godfrey and colleagues [14] demonstrated that mechanical interactions primarily cause wear, with oxidation as a secondary factor. Godet [15] introduced the “tribological trilogy,” suggesting that adhesion, plastic deformation, surface hardening, surface peeling, and debris formation occur due to continuous oxidation reactions.

Zhang [16] studied the influence of tangential forces on wear depth, concluding that increased tangential forces exacerbate fatigue crack propagation and reduce fatigue life. Figure 6 illustrates various motion patterns affecting wear on bucket teeth.

Figure 6. Types of interactions and movement of abrasive components on bucket teeth.

Fretting wear leads to plastic deformation and crack formation due to the continuous pressure application [17]. Additionally, the loss of oxide or lubricating films results in abrasive material bonding and node formation between surfaces [18]. Oxidation during fretting significantly influences the formation of oxide layers at shear points, impacting the sliding behavior and accelerating wear.

Wear Morphology

Surface investigations of worn bucket teeth reveal diverse wear patterns across different regions. Most teeth experience high-stress wear characterized by grooves and plastic deformation. Surface cracks from this wear cause the accumulation of minerals like Ca, O, K, Na, Si, and Al, altering the alloy’s composition and reducing wear resistance, thereby accelerating wear and shortening service life.

Hu’s study [19] on failed bucket teeth showed deep grooves and severe plastic deformation caused by abrasive particle contact. This deformation generates local heat, forming a martensitic layer that deteriorates wear resistance. Thus, understanding the thermal effects of plastic deformation can help enhance the wear resistance of bucket teeth. Additionally, research indicates that increasing the hardness of the teeth can raise the wear rate, with the type of abrasive material also playing a crucial role.

Wear Simulation of Bucket Teeth

This study uses finite element analysis (FEA) to investigate the wear behavior of bucket teeth. The FEA results (shown in Figure 7) indicate that the initial contact points and the junctions of the teeth experience the highest stress concentrations. The red, yellow, and green areas on the model highlight regions with significant stress levels.

Figure 7. Finite element simulation results for the bucket and teeth, highlighting the areas under stress.

Conclusion

Research into the wear of construction machinery equipment has long been a focus of industry attention. Construction machinery operates in complex environments, with different components facing varying degrees of wear. Bucket teeth, being in direct contact with abrasive materials, are particularly vulnerable.

Wear on bucket teeth primarily involves gouging wear, although other wear mechanisms can interact in complex ways. Understanding two-body and three-body gouging wear forms provides critical insights for improving the durability and performance of construction machinery. This study not only elucidated different wear mechanisms affecting bucket teeth but also demonstrated through simulations that stress concentrations are highest at the tip and initial regions of the teeth. Furthermore, it was observed that increasing the hardness of bucket teeth and the abrasiveness of materials leads to greater equipment wear.

References: www.mdpi.com/2075-4442/11/6/253

1. Chen, H. Research on the Development of China’s Construction Machinery Industry in the New Period. Chin. Mark. 2019, 11, 52–54. (In Chinese) [CrossRef]
2. Bayer, R.G. Mechanical Wear Prediction and Prevention; Dekker: New York, NY, USA, 1994; pp. 200–291.
3. Nezami, E.G.; Hashash, Y.M.A.; Zhao, D.; Ghaboussi, J. Simulation of front end loader bucket–soil interaction using discrete element method. Int. J. Numer. Anal. Methods Geomech. 2007, 31, 1147–1162. [CrossRef]
4. Zhao, Y.P. Research on Heat Treatment and Microstructure and Properties of 30Cr2MnSi Steel for Bucket Teeth of Excavator.
5. Master’s Thesis, Shandong University, Jinan, China, 2019. (In Chinese)
6. Jiang, F.; Lim, F.; Li, J. Abrasion Course Analysis on Pins of Loader Working Equipment and lmproverment. Lubr. Eng. 2007, 191, 132–135. (In Chinese)
7. Zhang, T.; Wang, N.; Cheng, X. The comparison research on design methodology of pins. J. Mech. Strength 2015, 37, 461–466. (In Chinese) [CrossRef]
8. Engel, P.A.; Lyons, T.H.; Sirico, J.L. Impact wear model for steel specimens. Wear 1973, 23, 185–201. [CrossRef]
9. Yang, Y. Research on the Microstructure, Mechanical and Impact Abrasion Behavior of Fe-Mn-Al-C Lightweight High Manganese Steel. Master’s Thesis, Nanchang Hangkong University, Nanchang, China, 2021. (In Chinese) [CrossRef]

10- Wang, A.C.; Weng, S.H. Developing the polymer abrasive gels in AFM processs. J. Mater. Process. Technol. 2007, 192, 486–490. [CrossRef]

11. Sankar, M.R.; Jain, V.; Ramkumar, J.; Joshi, Y. Rheological characterization of styrene-butadiene based medium and its finishing performance using rotational abrasive flow finishing process. Int. J. Mach. Tools Manuf. 2011, 51, 947–957. [CrossRef]
12. Singla, S.; Kang, A.S.; Grewal, J.S.; Cheema, G.S. Wear behavior of weld overlays on excavator bucket teeth. Procedia Mater. Sci. 2014, 5, 256–266. [CrossRef]
13. Tomlinson, G.A.; Thorpe, P.L.; Gough, H.J. An investigation of the fretting corrosion of closely fitting surfaces. Proc. Inst. Mech. Eng. 1939, 141, 223–249. [CrossRef]
14. Godfrey, D. Investigation of Fretting by Microscopic Observation; Lewis Flight Propulsion Laboratory: Cleveland, Ohio, 1951.
15. Godet, M. Third-bodies in tribology. Wear 1990, 136, 29–45. [CrossRef]
16. Zhang, H.; Liu, J.; Zuo, Z. Investigation into the effects of tangential force on fretting fatigue based on XFEM. Tribol. Int. 2016, 99, 23–28. [CrossRef]
17. Straffelini, G.; Molinari, A. Mild sliding wear of Fe–0.2% C, Ti–6% Al–4% V and Al-7072: A comparative study. Tribol. Lett. 2011, 41, 227–238. [CrossRef]
18. Straffelini, G.; Molinari, A. Dry sliding wear of Ti–6Al–4V alloy as influenced by the counterface and sliding conditions. Wear 1999, 236, 328–338. [CrossRef]
19. Hu, Y. Analysis on Wear Failure of Bucket Teeth of Mine Excavators and the Anti-wear Measures. Lubr. Eng. 2006, 5, 165–167. (In Chinese)

1. Chen, H. Research on the Development of China’s Construction Machinery Industry in the New Period. Chin. Mark. 2019, 11, 52–54. (In Chinese) [CrossRef]
2. Bayer, R.G. Mechanical Wear Prediction and Prevention; Dekker: New York, NY, USA, 1994; pp. 200–291.
3. Nezami, E.G.; Hashash, Y.M.A.; Zhao, D.; Ghaboussi, J. Simulation of front end loader bucket–soil interaction using discrete element method. Int. J. Numer. Anal. Methods Geomech. 2007, 31, 1147–1162. [CrossRef]
4. Zhao, Y.P. Research on Heat Treatment and Microstructure and Properties of 30Cr2MnSi Steel for Bucket Teeth of Excavator.
5. Master’s Thesis, Shandong University, Jinan, China, 2019. (In Chinese)
6. Jiang, F.; Lim, F.; Li, J. Abrasion Course Analysis on Pins of Loader Working Equipment and lmproverment. Lubr. Eng. 2007, 191, 132–135. (In Chinese)
7. Zhang, T.; Wang, N.; Cheng, X. The comparison research on design methodology of pins. J. Mech. Strength 2015, 37, 461–466. (In Chinese) [CrossRef]
8. Engel, P.A.; Lyons, T.H.; Sirico, J.L. Impact wear model for steel specimens. Wear 1973, 23, 185–201. [CrossRef]
9. Yang, Y. Research on the Microstructure, Mechanical and Impact Abrasion Behavior of Fe-Mn-Al-C Lightweight High Manganese Steel. Master’s Thesis, Nanchang Hangkong University, Nanchang, China, 2021. (In Chinese) [CrossRef]

10- Wang, A.C.; Weng, S.H. Developing the polymer abrasive gels in AFM processs. J. Mater. Process. Technol. 2007, 192, 486–490. [CrossRef]

11. Sankar, M.R.; Jain, V.; Ramkumar, J.; Joshi, Y. Rheological characterization of styrene-butadiene based medium and its finishing performance using rotational abrasive flow finishing process. Int. J. Mach. Tools Manuf. 2011, 51, 947–957. [CrossRef]
12. Singla, S.; Kang, A.S.; Grewal, J.S.; Cheema, G.S. Wear behavior of weld overlays on excavator bucket teeth. Procedia Mater. Sci. 2014, 5, 256–266. [CrossRef]
13. Tomlinson, G.A.; Thorpe, P.L.; Gough, H.J. An investigation of the fretting corrosion of closely fitting surfaces. Proc. Inst. Mech. Eng. 1939, 141, 223–249. [CrossRef]
14. Godfrey, D. Investigation of Fretting by Microscopic Observation; Lewis Flight Propulsion Laboratory: Cleveland, Ohio, 1951.
15. Godet, M. Third-bodies in tribology. Wear 1990, 136, 29–45. [CrossRef]
16. Zhang, H.; Liu, J.; Zuo, Z. Investigation into the effects of tangential force on fretting fatigue based on XFEM. Tribol. Int. 2016, 99, 23–28. [CrossRef]
17. Straffelini, G.; Molinari, A. Mild sliding wear of Fe–0.2% C, Ti–6% Al–4% V and Al-7072: A comparative study. Tribol. Lett. 2011, 41, 227–238. [CrossRef]
18. Straffelini, G.; Molinari, A. Dry sliding wear of Ti–6Al–4V alloy as influenced by the counterface and sliding conditions. Wear 1999, 236, 328–338. [CrossRef]
19. Hu, Y. Analysis on Wear Failure of Bucket Teeth of Mine Excavators and the Anti-wear Measures. Lubr. Eng. 2006, 5, 165–167. (In Chinese)