Applying Research on Creep Constitutive Model of No.35 Steel Based on BC-BPNN

The inelastic response constitutive description of metal material under different stress and wide temperature range is very important in many practical engineering. It can accurately reflect the level of material rate sensitivity and set up a simple and practical strengthening evolution rate. Take No.35 steel as an example; because of the action of load, temperature, time and other factors in its forming process, the creep relation is very important and complex. In view of this situation, the BC-BPNN (Based on Back propagation Neural Network), owing high precision nonlinear fitting ability has and good generalization ability, is applied to the research on creep constitutive relationship of 35 steel. At first, the creep relationship is numerically fitted using testing data of 35 steel; then, the fitting results is compared with the creep testing data. The results show that the applying of BC-BPNN to research on metal creep relationship has a strong practical value.

Structure and Performance of 35 Steel after Strengthened Shot Peening Surface Nanocrystallization and Gas Tufftriding Process

35 steel was processed in order to investigate its structure and performance after strengthened shot peening and gas tufftriding process. The composition,structure and phase of the samples were analyzed by means of scanning electron micrograph(SEM),metallographic microscope and X-ray diffraction(XRD)respectively. The results show that the hardness of samples after strengthened shot peening increases by about 100 HV0.025,and the friction coefficient and corrosion rate decrease.However,the samples treated with gas tufftriding after strengthened shot peening exhibit the performance of approximate 3 times hardness of the original samples, lower friction coefficient,more excellent tribological characteristics,stronger corrosion-resistance with a stable and broad passivation region.

Finite Element Method Simulation of 35# Steel Cathodic Protection Models in the Seawater

Physical models of cathodic protection (CP) for copper protected by 35# steel and for 35# steel protected by aluminum sacrificial anode respectively in seawater were built in this study. Weak form of Laplace equation was deduced to make finite element method (FEM) numerical calculation conveniently. Then, potential distribution of each physical model was computed by FEM following with measured experiments for validation. Typical FEM simulated data along X-axis and Y-axis of physical models agree well with measured experimental data. For 35# steel protected by aluminum sacrificial anode models, normal cathodic protection, over-protected (OP) and under-protected (UP) models were built, respectively. The results demonstrated that it should be feasible of CP for copper by 35# steel and for 35# steel by aluminum sacrificial anode respectively, and FEM could afford well forecast for CP design in engineering.

A Cumulative Damage Rule Based on the Knee Point of the S-N Curve

Making use of a set of isodamage lines, a fresh concept for predicting the fatigue life, under variable amplitude loading, is presented. It is assumed that all isodamage lines converge at the knee point of a S-log N diagram. The life predictions based on this concept are closer to the experimental data than given by Miner’s linear damage rule. The concept is verified with the step-test data obtained on unnotched C-35 steel specimens in rotary bending. Several other reported experimental data in rotary bending tests also confirm the reliability of this simple damage rule.