Review:Advances in research of stress-assisted corrosion fatigue problem

Ceramic materials are notable for their rigidity, insulation and resistance to hostile environment, Nevertheless, if a stressed ceramic component is exposed to chemical attack, it may suffer from a form of delayed fracture known as static fatigue. From the point of view of a designer, it is clearly desirable to determine the behavior of sub-critical crack growth; the crack path and crack growth rate, as a function of material properties and loading conditions are of particular interest. This paper presents a review of advances in stress assisted corrosion problem in history and its corresponding numerical approaches in the last decades, and finally, comes uo with consideration and crucial suggestions for future work.

Low Fatigue Strength of Clinch Joints

Clinching can be used for effective joining of different metallic materials, e.g., different grades of carbon and alloy steels, aluminum and its alloys and others. This is an alternative joining method to traditional methods involving screws, rivets or welding. Clinching is applied in many fields of manufacturing industry. Future applications of clinch joining require advances in quality and among others things, combination with other processes, e.g., hybrid joining by clinching and adhesive bonding. Although the static strength of clinched joints is lower than that of the others joints （e.g., pressure welded joints）, the fatigue strength is comparable. But there is a lack of information about fatigue strength of clinched joints. The static and low cyclic fatigue strengths of mechanically clinched joints were determined experimentally. The load-displacement curves of static strength were compared with low cyclic fatigue strength curves. It was observed the effect of strain hardening for clinched joint of low carbon steels （DC4） under cyclic loading.

Research on an innovative structure of an open-ribbed steel-ultra-high performance concrete composite bridge deck

To completely solve the problem of fatigue cracking issue of orthotropic steel bridge decks(OSDs),the authors proposed a steel–ultra-high performance concrete(UHPC)lightweight composite deck(LWCD)with closed ribs in 2010.Based on the successful application of that LWCD,an adaptation incorporating an innovative composite deck structure,i.e.,the hot-rolled section steel–UHPC composite deck with open ribs(SSD)is proposed in this paper,aiming to simplify the fabrication process as well as to reduce the cost of LWCD.Based on a long-span cable-stayed bridge,a design scheme is proposed and is compared with the conventional OSD scheme.Further,a finite element(FE)calculation is conducted to reflect both the global and local behavior of the SSD scheme,and it is found that the peaked stresses in the SSD components are less than the corresponding allowable values.A static test is performed for an SSD strip specimen to understand the anti-cracking behavior of the UHPC layer under negative bending moments.The static test results indicate that the UHPC layer exhibited a satisfactory tensile toughness,the UHPC tensile strength obtained from the test is 1.8 times the calculated stress by the FE model of the real bridge.In addition,the fatigue stresses of typical fatigue-prone details in the SSD are calculated and evaluated,and the influences of key design parameters on the fatigue performance of the SSD are analyzed.According to the fatigue results,the peaked stress ranges for all of the 10 fatigue-prone details are within the corresponding constant amplitude fatigue limits.Then a fatigue test is carried out for another SSD strip specimen to explore the fatigue behavior of the fillet weld between the longitudinal and transverse ribs.The specimen failed at the fillet weld after equivalent 47.5 million cycles of loading under the design fatigue stress range,indicating that the fatigue performance of the SSD could meet the fatigue design requirement.Theoretical calculations and experiments provide a basis for the promotion and application of this structure in bridge engineering.

Mechanical Analysis Methods of Cantilever Gearbox Housing

The mechanical state of cantilever gearbox housing is different from ordinary ones due to the long arm of force caused by cantilever structure.Conventional mechanical analysis methods either took cantilever gearbox housing as ordinary ones or cantilever beam.Few published papers have specially focused on mechanical analysis method for cantilever gearbox housing.This paper takes a longwall shearer cutting unit gearbox(SCUG)as an example and the mechanical analysis method is investigated according to the causes of fatigue for SCUG.Force analysis model is established for finding out regions of static fatigue caused by low-frequency loads,and local resonance analysis is used for finding out regions of vibration fatigue caused by high-frequency loads.Not only bending moment but also torque caused by gear meshing forces is taken into account in the force analysis model.Vibration response is obtained from cutting experiment,and dominant frequencies of local resonance are obtained by frequency domain analysis.Finite element model of SCUG is established,and natural frequencies and strain modes are analyzed for obtaining the main vibration modes corresponding to dominant frequencies.Hence,large stress regions caused by low and high frequency loads are obtained.Results show that the worst working condition is oblique cutting,and the stress of B-B in 600 mm cutting depth can reach 166 MPa.Obviously,950 Hz,1250 Hz,and 1400 Hz are dominant frequencies of SCUG(23rd,25th and 27th natural frequencies).Generally,this paper proposes some principles for mechanical analysis method of cantilever gearbox housing.