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The collaborative R&D of new products between enterprises is prone to the “free-rider effect” due to knowledge spillover. To avoid that, this paper establishes a three-stage dynamic game to explore the collaborative R&D co-competition behavior between asymmetric horizontal supplier enterprises. In this paper, we incorporate the uncertainty of R&D success probability into the model and reverse induction is applied to solve it. In the model, two asymmetric enterprises play dynamic games under three modes: complete noncooperation, semicooperation, and complete cooperation. We discuss the sensitivity of various asymmetric factors to the R&D investment level and profit of enterprises. The results indicate that the R&D investment level of supplier enterprises is positively correlated with the absorptive capacity, technology spillover, and R&D success probability, and negatively correlated with the initial R&D investment and innovation efficiency under the three co-competition modes. Especially, when the absorptive capacity of the enterprise or the degree of technological spillover of the other party exceeds a certain value, the profits of the enterprise in the mode of complete noncooperation and semicooperation will intersect, which can easily lead to “free-riding” behavior. It provides a decision-making basis for the direction and extent of enterprises’ R&D efforts. In addition, some methods are proposed to improve the level of R&D investment and increase the income of enterprises under three modes.

In order to improve the market competitiveness of suppliers and their resilience to emergencies, it is of great significance to discuss the investment decision making of suppliers in developing new products under uncertain and competitive environments. In this paper, with the background of knowledge spillover, absorptive capacity, initial R&D investment, and innovation efficiency asymmetry, the uncertainty of price, sales, and cost are incorporated into the evaluation system as three important risk factors. On the basis of the existing real option investment evaluation model, a real option game model of R&D investment of supplier enterprises based on multiple random variables is established. The sensitivity analysis of parameters is carried out with an example of one enterprise’s monitor R&D project. The results depict that the probability of R&D success has a great impact on the value of enterprise options, which depends on the R&D investment, innovation efficiency, and R&D performance of enterprises. Secondly, the drift rate of price, sales, and cost also has a significant impact on improvement in enterprise option value.

In this study, the high cycle and very high cycle fatigue behavior of the GH4169 superalloy was investigated. The results of the fatigue tests demonstrated that failures in the high cycle fatigue regime were initiated from the material surface, whereas failures in the very high cycle fatigue regime had two competing modes of crack initiation: surface and internal. The fatigue fracture analysis revealed a quasi-cleavage fracture mode with facets for internal crack initiation. Additionally, the electron backscatter diffraction (EBSD) results indicated that the dislocations located at the internal twin boundaries of the material were preferentially activated under fatigue cyclic loading, resulting in significant strain localization at the twin boundaries. The {111} slip systems with high Schmid factors had a higher probability of activation. The stress intensity factor (SIF) estimated based on rough area (RA) and facet sizes correspond to the fatigue long crack and short crack growth thresholds of the material, respectively. Finally, a modified FIP fatigue life prediction model was proposed based on the microstructure of crystallographic facets, and the results from experiment and the model prediction were found to be in good agreement.

The fracture surface characteristics and the associated micromechanisms governing the fish-eye crack initiation of a Ti-6Al-4V alloy under very high cycle fatigue (VHCF) loading are investigated. Microscopic observation revealed that the crack initiation area of fish-eye center is covered by ragged-like mountains and dimples containing various irregular rods/particles, grooves and microvoids. These micro-ductile characteristics primarily result from the nucleation and coalescence of microvoids and grooves at αs/βr interface inside βtrans. This could be due to the incompatibility of both micro-plastic deformation and slips in αs and βr. The βtrans plays a dominant role in the fish-eye crack initiation and early propagation process of the Ti-6Al-4V alloy in the VHCF regime.

The effect of Surface Mechanical Attrition Treatment (SMAT) on torsional fatigue properties of a 7075 aluminum alloy was investigated. A number of fatigue samples were heat treated to increase the sensitivity of the material to SMAT. Compared with the as-machined (AM) samples, the fatigue lives of their SMATed counterparts (AM-SMAT) tested under torsional loading increased under high stress amplitudes, but decreased under low amplitudes. However, the fatigue lives of heated and SMATed samples (HT-SMAT) increased under all the investigated stress amplitudes, compared with those that were heat treated (HT). It was also revealed that the cracking mechanisms are different for the samples in different states, and they are dependent on the imposed stress levels. The results show that SMAT could have both beneficial and detrimental effects on the fatigue lives depending on the testing conditions. The roles played by various factors, including residual stresses, grain refinement, and surface roughness, were analyzed and discussed to interpret the results.

This paper aims to provide a better understanding regarding the effects of shot peening (SP), surface mechanical attrition treatment (SMAT), laser shock peening (LSP), surface mechanical rolling treatment (SMRT), and ultrasonic nanocrystal surface modification (UNSM) on the fatigue properties of metals in high-cycle fatigue (HCF) and very-high-cycle fatigue (VHCF) regimes. The work in this paper finds that SMRT and UNSM generally improve the high-cycle and very-high-cycle fatigue properties of metals, while SP, SMAT, and LSP can have mixed effects. The differences are discussed and analyzed with respect to the aspects of surface finish, microstructure and microhardness, and residual stress. SMRT and UNSM generally produce a smooth surface finish, while SP and SMAT tend to worsen the surface finish on metals, which is harmful to their fatigue properties. In addition to inducing a plastic deformation zone and increasing microhardness, surface treatments can also generate a nanograin layer and gradient microstructure to enhance the fatigue properties of metals. The distribution of treatment-induced residual stress and residual stress relaxation can cause mixed effects on the fatigue properties of metals. Furthermore, increasing residual stress through SP and SMAT can cause further deterioration of the surface finish, which is detrimental to the fatigue properties of metals.

In this work, the effect of a turning process on fatigue performance of a Ti-6.5Al-3.5Mo-1.5Zr-0.3Si (TC11) titanium alloy is studied in the high cycle fatigue (HCF) and very high cycle fatigue (VHCF) regimes. For this purpose, the surface characteristics including surface morphology, surface roughness and residual stress were investigated. Moreover, axial fatigue tests were conducted with an ultrasonic fatigue testing system working at a frequency of 20 kHz. The results show that the turning process deteriorated the fatigue properties in both HCF and VHCF regimes. The fatigue strength at 1 × 108 cycles of turned samples is approximately 6% lower than that of electropolished ones. Fracture surface observations indicate that turning marks play a crucial role in the fatigue damage process, especially in the crack initiation stage. It was observed that the crack of all the turned samples originated from turning marks. In addition, the compressive residual stress induced by the turning process played a more effective role in resisting crack propagation in the VHCF regime than in the HCF regime.

This paper focuses on the twist defects and the control strategy in the process of four-roll bending for aluminum alloy Z-section profiles with large cross-section. A 3D finite element model (3D-FEM) of roll bending process has been developed, on the premise of the curvature radius of the profile, the particularly pronounced twist defects characteristic of 7075-O aluminum alloy Z-section profiles were studied by FE method. The simulation results showed that the effective control of the twist defects of the profile could be realized by adjusting the side roller so that the exit guide roll was higher than the entrance one (the side rolls presented an asymmetric loading mode with respect to the main rolls) and increasing the radius of upper roll. Corresponding experimental tests were carried out to verify the accuracy of the numerical analysis. The experimental results indicated that control strategies based on finite element analysis (FEA) had a significant inhibitory function on twist defects in the actual roll bending process.