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[Display omitted] • A completely non-assembly steerable grasper in titanium was fabricated by additive manufacturing. • Miniature lattice structures were used as compliant flexures. • Deflection tests of different lattice designs were performed as characterization. • Lattice flexures were applied in the design of rolling joints with different configurations. • The final grasper design is low-friction and does not require any post-processing steps. Metal additive manufacturing is a promising technology for the production of functional medical products, due to its high shape complexity and resolution, and ability to withstand sterilization temperatures. This study explores the possibility of designing a completely non-assembly steerable surgical instrument using Selective Laser Melting. Despite its advantages for medical devices, the rough surface quality of unfinished parts can be problematic for non-assembly designs, leading to increased friction and wear in rigid body mechanisms and tendon-actuated mechanisms. We investigated printing of rolling contact joints with crossed flexures as low-friction joints, adjusted for printing in titanium for the design of the instrument. Grid-based lattice structures were incorporated as miniature flexures, and we explored the influence of various grid sizes on the flexibility and bending stiffness of the lattices. Based on this exploration, we altered the rolling joint configuration from two crossed flexures to a single straight flexure for our design. The resulting steerable surgical instrument design is completely non-assembly, including its actuation, facilitates easy removal of support structures, and requires no surface finishing steps. It has a diameter of less than 20 mm, facilitates opening and closing of a grasper, and steering of the grasper by 20 degrees. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ultrasonic rolling and its finite element simulation on a bearing raceway was conducted. • Multi-objective process optimization for ultrasonic rolling on a bearing was performed. • Oriented martensitic grain stacking forms a flocculent plastic deformation layer. • Carbide particles are refined, and its size changes gradiently along the layer depth. For the first time, the ultrasonic surface rolling processing (USRP) technology was applied to a real bearing raceway, and a finite element simulation model for USRP on a bearing raceway was established. Practical tests were conducted to evaluate the surface integrity of the bearing raceway before and after USRP treatment. The USRP parameters were optimized using Taguchi-gray correlation analysis. The results show that the optimal process parameters for the 7224 bearing raceway are: an amplitude of 10 μm, a static pressure of 2400 N, a spindle speed of 45 rad/min, and rolling times of 7. In the process of USRP, residual compressive stress results from inhomogeneous elastic and plastic deformation. Adjacent tempered martensitic laths merge and deflect at a certain angle along the rolling direction to form directional grain stacks, resulting in a flocculent plastic deformation layer. The USRP based on the finishing mechanism of "peak-cutting and valley-filling" can improve the surface micro-morphology, reduce roughness value Ra to approximately 0.16 μm, and effectively eliminate microscopic cracks caused by grinding. The micro-hardness of the bearing raceway surface increased from 760 HV to 840 HV under the dual action of surface grain refinement and work hardening effect. [ABSTRACT FROM AUTHOR]

[Display omitted] • Comparable hardness is obtained for WEL produced in laboratory and the one from field conditions. • Similar microstructural features are observed between WEL from field and after a single cycle of fast heating and quenching. • Grain refinement observed in WEL produced during wheel/rail contact is not reproducible by thermal heating only. • Mn homogeneization is obtained after 5 minutes soaking at high temperatures. The influence of soaking and cooling rates on the final microstructure of a R260Mn pearlitic railway steel subjected to fast heating is investigated. Fast-heating experiments followed or not by soaking and cooling at different rates were performed using quenching dilatometry on railway steel specimens obtained from the rail head. Additional cyclic heating and quenching experiments were done to investigate the evolution of the microstructure during thermal cycling, which is relevant for railway applications. The final microstructure is characterized via microhardness measurements, optical microscopy and scanning electron microscopy. The microstructural features are distinguished and the influence of each condition is detailed. The study allows the construction of transformation diagrams during cooling after fast heating. Furthermore, comparison between the final microstructures obtained in controlled laboratory conditions and field White Etching Layers is presented. The obtained results can serve as a guideline for future reproduction of White Etching Layers in laboratory conditions and interpretation of field conditions. [ABSTRACT FROM AUTHOR]

The fracture behavior of a white etching layer formed on the rail surface in pearlitic steels during the rail-wheel contact is investigated using indentation-based microcantilever fracture tests. The sample thickness is in the order of 5 μm. The local fracture toughness of the white etching layer, its neighboring brown etching layer, martensite and pearlite with similar chemical composition are determined and compared to ferritic steels. All samples show stable crack growth accompanied by significant plasticity at the crack tip. The toughnesses scale inversely with the microhardness. The white etching layer exhibits a toughness of 16.0 ± 1.2 MPa m1/2 which is in the same range as the fully martensitic steel. It is shown that the local fracture toughness can be roughly estimated based on the Vickers hardness of the white etching layer. Also, an estimation of a critical defect size in white etching layers which considerably furthers the understanding of crack initiation is made in this study. Furthermore, various criteria for analyzing the elasto plastic fracture toughness are compared. Unlabelled Image • The fracture toughness of WELs and comparable microstructures were obtained using elasto-plastic micro fracture experiments • The fracture toughness of WELs is comparable to martensite • The fracture toughness of WELs can be estimated from the hardness via a proposed empirical relation. • Various criteria for interpreting the J-integral at small scales are quantitatively compared and discussed. • We determined critical defect size in WELs. [ABSTRACT FROM AUTHOR]