PurposeThe properties of materials under impact load are introduced in terms of metal, nonmetallic materials and composite materials. And the application of impact load research in biological fields is also mentioned. The current hot research topics and achievements in this field are summarized. In addition, some problems in theoretical modeling and testing of the mechanical properties of materials are discussed.Design/methodology/approachThe situation of materials under impact load is of great significance to show the mechanical performance. The performance of various materials under impact load is different, and there are many research methods. It is affected by some kinds of factors, such as the temperature, the gap and the speed of load.FindingsThe research on mechanical properties of materials under impact load has the characteristics as fellow. It is difficult to build the theoretical model, verify by experiment and analyze the data accumulation.Originality/valueThis review provides a reference for further study of material properties.
To consider the effect of crack closure on the mechanical properties of metals, the fatigue life of metal specimens is predicted based on energy dissipation model. The main feature of the model consists in considering the relationship between the total failure energy and the energy density increment. The total failure energy model considers the fatigue crack size and stress amplitude. It is assumed the energy density increment gradually decreases and tends to be stable. The influence of crack closure effect is considered. According to the law of metal fatigue characteristics, a new mathematical model for predicting fatigue life is established. Keywords Energy increment • Metallic material • Crack closure effect • Fatigue life List of symbols b Fatigue strength exponent c The fatigue ductility exponent Δ Stress range a Maximum tensile stress a c Critical crack size a 0 Initial crack size n Strain hardening exponent n ′ Cyclic strain hardening exponent f Fracture ductility ′ f Cyclic fatigue ductility coefficient Δ p Plastic strain range Δ pZ Plastic strain increment under equivalent stress increment Equivalent strain increment parameter W p Plastic strain energy ′ f Cyclic fatigue strength coefficient W One-cycle plastic strain energy increment K ′ Cyclic stress intensity coefficient W pf Total failure energy b Ultimate tensile strength K theff Effective initial stress intensity factor K I
Purpose
The purpose of this paper is to obtain a more accurate fatigue life of structures by introducing the surface roughness into fatigue life prediction model.
Design/methodology/approach
Based on the fatigue life prediction model with surface roughness correction, the shock absorber cylinder is taken as an example to verify the feasibility of the improved method. Based on the load of the shock absorber cylinder during driving, fatigue experiments are performed under longitudinal and lateral forces, respectively. Then, the fatigue life predicted by the modified model is compared with that predicted by the traditional model.
Findings
By comparing with the test results, considering the influence of mean stress, the Manson method is more accurate in life prediction. Then, the modified Manson-Coffin and Manson method with surface roughness is more accurate in life prediction under longitudinal force and lateral forces, respectively. This verifies the feasibility of the improved method with the surface roughness.
Originality/value
The research on the influence of surface roughness on fatigue life can lay the technical foundation for the life prediction of products and have great significance to the quality evaluation of products.
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