Compliant mechanisms are nowadays a well-established means of achieving ultra-high precision, albeit at the expense of complex kinematics with the presence of parasitic motions. Diverse design configurations of compliant rotational joints called cross-spring pivots are hence studied in this work by applying various analytical and numerical approaches. Depending on the required precision and loading conditions, the limits of applicability of the available analysis tools, validated with nonlinear finite element calculations tuned with experimental data reported in literature, are established. The variation of design parameters allows, in turn, establishing design configurations of the studied mechanism that allow attaining minimized parasitic shifts and slight variations of its rotational stiffness, even when a broad range of rotations and varying transversal loads are considered, creating thus the preconditions for their application in high-precision micropositioning applications.

This paper deals with the effects of linear tip profile modification on the stress of tooth root and tooth flank of involute spur gears. An increase in the tooth flank stress due to the tip profile modification is potentially hazardous...

The aim of this study was to explore whether changes in the salivary pH influence mechanical properties, surface roughness, and ion release from NiTi archwires with various surface coatings, and discuss the clinical significance of the findings. The uncoated, rhodium-coated, and nitrified NiTi wires were immersed into artificial saliva of different pH values (4.8, 5.1, 5.5, and 6.6). Released nickel and titanium ions were measured with inductively coupled plasma-optical emission spectroscopy at the end of 28 days. Atomic force microscopy was used to measure the arithmetic average surface roughness R_a, the root-mean-square roughness R_q, and the maximum height of the asperities R_Z. The nanoindentation hardness (H_IT) and Young’s modulus (E_IT) measurements were performed. The change in the pH of artificial saliva is inversely proportional to the release of titanium from both coated and uncoated wires, and the release of nickel from uncoated wires. The surface roughness parameters of both coated and uncoated wires are unaffected by the change in the pH of artificial saliva. The change in the pH of saliva has minor influence on the hardness and Young’s modulus of elasticity of both coated and uncoated wires. The concentration of released metal ions measured was below the recommended upper limit for daily intake; nevertheless, hypersensitivity effects cannot be excluded, even at lower concentrations and at low pH.

The ever-increasing demands for vehicle emission control have resulted in an expansion of planetary gearbox applications in road vehicles, due to their possibility to change the transmission ratio under load in synchronism with engine operation. Modern boxes are designed to extract the maximum number of transmission ratios as possible from the least possible number of simple component planetary gear trains (PGTs). The application demands dictate whether the box will be built with the maximum number of transmission ratios, or built for ruggedness and reliability. Component interconnections are designed to avoid power circulation, hollow shafts, or complex planet carrier arrangements when possible. The subject of this paper are multi-speed complex planetary gearboxes having at least two interconnected simple component PGTs controlled by brakes and clutches. Several variants of complex PGTs are examined together with the placement of brakes and clutches on their external shafts, and their transmission ratio functions are derived. The kinematics of multi speed gear trains are analysed as combinations of two or more two-speed gear trains. Several gearbox layouts are analysed, and their transmission ratio functions provided. Finally, an overview of the procedure for the calculation of creation of multi-speed gear trains is provided.