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ISO/ASME geometrical tolerancing standards point out the significance of applying material conditions, which not only is convenient for manufacturing but also does not disturb the free assembly of parts. Unfortunately, the influence of material conditions is rarely considered in the existing studies on statistical geometrical tolerance analysis. Ignoring the influence of material conditions related to the dimensional and geometrical tolerances will directly lead to reduce the accuracy of tolerance analysis. In this paper, a new statistical tolerance analysis approach for mechanical assemblies with dimensional and geometrical tolerances under material conditions is proposed. The proposed approach is fully compatible with the ISO/ASME geometrical tolerancing standards and takes into account the application of various material conditions such as envelope requirement (ER), maximum material condition (MMC), least material condition (LMC), and reciprocity requirement (RPR). The tolerance zones of dimensional and geometrical feature variations are modeled based on the concept of small displacement torsor (SDT), in which torsor models that describe assembly variations caused by complex parallel joints between mating parts are mainly studied. Then, the material conditions effects for features of size with pin/hole and tab/slot shapes are modeled as additional constraints of torsor parameters. After integrating these torsor parameters into the unified Jacobian–Torsor model, a new approach of statistical geometrical tolerance analysis containing the application of material conditions is presented based on the combination of the unified Jacobian–Torsor model and Monte Carlo simulation. Finally, the centring pin assembly is taken as an example to illustrate the application of the proposed approach. [ABSTRACT FROM AUTHOR]

This paper proposes a support vector machine regression (SVMR) model to predict running-in wear volume, with field surface topography parameters and working conditions as the input variables, under the condition that the amount of training samples is very limited. Experimental results proved the effectiveness of the SVMR-based model with a small amount of training samples. Based on the established prediction model, the impacts of the field surface parameters on running-in wear volume have been analyzed. The results show that Sku has the largest influence on running-in wear volume, Sdq the second, and Svk the least. [ABSTRACT FROM AUTHOR]

Based on the wear analysis of a propeller hub bearing, wear tests are designed under different marine environments to illustrate wear failure mechanisms. The results reveal that the wear failure characteristics of the propeller hub bearing are primarily abrasive wear, accompanied by adhesion and oxidation wears, and plastic deformation. These results agree well with the wear morphologies of the torsional fretting wear tests under starvation lubrication. The wear tests confirm that the wear failure of the propeller hub bearing is owing to the coexistence of multiple wear mechanisms, which is attributed primarily to the superimposed wear behaviors induced by loading, continuous fretting wear, and starvation lubrication in the local contact areas. Hence, the negative effects of interfacial micro-protrusion adhesion and fracture during oil lubrication are difficult to eliminate. Moreover, The uneven radial loads of the contact surfaces of the propeller hub bearing also exhibit a significant influence on the thickness and formation of the oil film at the friction interface. [Display omitted] • Wear failure mechanisms of bearing coated with NAB alloys had been studied. • The designed wear tests were conducted by a self-assemble tribological platform. • Wear failure morphologies of bearing and wear tests results had been discussed. • Physical model at the different wear stages was established. [ABSTRACT FROM AUTHOR]

In white light interference based atomic force microscopy (WLIAFM), the vertical displacement of the probe is obtained by zero-order fringe positioning on the probe cantilever, so the accuracy of zero-order fringe positioning will affect directly that of the WLIAFM. However, due to non-uniform distribution of light intensity and photoelectric noises, accurate zero-order fringe positioning becomes a problem. In this paper, two algorithms are proposed to improve the zero-order fringe positioning accuracy. In the first algorithm which is called improved maximum algorithm, multi-row maximum positions of the interference fringes are obtained and error theory is applied to eliminate erroneous maximum positions, then the average of remaining maximum positions is used as the zero-order fringe position. Another is called phase evaluation algorithm, in which wavelet transform is applied to eliminate effects from disturbances mentioned above and Hilbert transform is used for phase evaluation to obtain the zero-order fringe position. The practicability and accuracy of the two algorithms have been verified by series of experiments. The experiment results indicate that both two algorithms are suitable in this condition and the phase evaluation algorithm has higher accuracy while the improved maximum algorithm has higher processing speed. [ABSTRACT FROM AUTHOR]

An ultra-high-sensitivity strain sensor based on a single ZnO nanowire (NW) was developed by nanowelding the NW onto a flexible substrate using a custom-built nano-manipulation system inside a scanning electron microscope (SEM). Onto the two ends of the NW were sputtered Au electrodes, to which conducting wires that connect to a multi-meter were glued. A thin methyl methacrylate polymer layer was used to insulate the strain sensor. The strain gauge was evaluated by attaching the sensor to a cantilever beam ex situ of the SEM, providing flexibility for repeated measurements. An applied force to the cantilever synchronously deformed and altered the NW resistance. The resistance variation of the strain gauge against the known strain on the cantilever showed that a gauge factor that is 200 times higher than that of a commercial strain sensor is feasible for the proposed device. The developed strain sensor is applicable for ultra-small mechanical strain on the order of 10. [ABSTRACT FROM AUTHOR]

White-light interferometry (WLI) is an established method for surface measurement. In WLI, surface recovery algorithm from series of vertical scanning white light interferogram is pivotal technique and has been researched widely. However, the effectiveness of existing surface recovery algorithms is easy to be affected by some conditions like mechanical vibrations, low-reflection of the test surface and phase change caused by the reflection. In this paper, a new recovery algorithm is presented, in which correlation analysis of WLI envelop curves and a multi reference position based phase solution method are employed for robust and high precision surface recovery. Mathematical derivation of the algorithm is carried out, and simulation and experimental testing and comparison experiments are conducted, which show that the new algorithm is effective. [ABSTRACT FROM AUTHOR]

In this study, NiAl bronze (NAB) alloys are processed using an ultrasonic vibration-assisted milling (UVAM) surface engineering technique. The strengthening mechanisms at different cutting speeds are analysed through well-established models and experiments. The increase in cutting speed produced decrements of 29.5%, 26.6%, and 5.6% in the friction torques, accumulated dissipated energy, and worn surface area, respectively. The microhardness gradually increased by 11%, which helped improve the fretting wear performance. Grain refinement, precipitation, and dislocation strengthening were the main mechanisms. Grain refinement (∆ σ HP) had the greatest contribution to performance, followed by precipitation (∆ σ or) and dislocation (∆ σ d). Nanotwin strengthening was observed at a cutting speed of 150 m/min. Martensite nanotwins may nucleate at the grain boundary and grow toward the grain interior. [Display omitted] • The increase of cutting speed leads to beneficial effects on their fretting behavior including friction torques, accumulated dissipated energy and worn surface area for 29.5%, 26.6% and 5.6%, respectively. • The refinement of the κ phases and the effects of dislocations and stacking faults help increase the hardness and mechanisms were analysed. • The formation of martensite phases in UVAM6000 was attributed to severe plastic deformation and the special 3R martensitic structures of NAB alloys. Specifically, martensite nanotwins may nucleate at the grain boundary and then grew toward the interior of grains. • Grain refinement, precipitate, and dislocation strengthening were the main mechanisms for all samples and its contributions were calculated through well-established models and experiment data. [ABSTRACT FROM AUTHOR]

This work reports additive manufactured (Fe, Ni)Al-reinforced nickel aluminum bronze by the electron beam powder bed fusion (EB-PBF) method. All EB-PBF composites show a high relative density of >99% and a homogeneous microstructure with equiaxed grains and homogeneously distributed (Fe, Ni)Al precipitates, enabling their nearly-isotropic mechanical behavior in build and transverse directions. This isotropic mechanical behavior results from a collective effect of high relative density, homogeneously-distributed precipitates, equiaxed grains, and a subsequently sustainable strain-hardening ability from progressively twin-precipitate and dislocation-precipitate interactions. • (Fe, Ni)Al-reinforced nickel aluminum bronze is fabricated by electron beam powder bed fusion. • All built materials show a high relative density of >99% with nearly-equiaxed grains. • The built materials have isotropic mechanical properties in build and transverse directions. • The isotropic mechanical behavior is attributed to the outstanding sustainable strain-hardening ability. [ABSTRACT FROM AUTHOR]

• Double Magnetic coils controller to ensure a constant stiffness of 10 mm range. • Bearing capacity considering anti-deflection torque and stiffness. • Finite difference method combining mass flow theory and boundary conditions. • Dynamic characteristics and critical velocity verification. • 2D/3D texture parameters compared to a commercial conventional stylus profilometry. Stylus profilometry is extensively employed in practice due to its wide measurement range and praiseworthy stability. However, its lever structure will cause nonlinear errors and mitigated precision. Given this context, this paper proposes a new aerostatic bearing stylus sensor (ABSS) for surface measurement, which inherits the stability and large-scale measuring range while avoiding the structural nonlinear errors of the conventional stylus profilometry. The designed ABSS is composed of a magnetic levitation control system and an aerostatic bearing device in the vertical and horizontal directions, respectively. Furthermore, the bearing capacity and the radial dynamic characteristics are analyzed to ensure stylus' scanning stability and rapid response. Template experiments with different scanning velocities of the stylus are performed to verify the natural frequency and obtain the critical velocity. Finally, the surface two/three-dimensional topographies reconstruction validates the repeatability and accuracy of the proposed ABSS compared to a commercial conventional stylus profilometry. [ABSTRACT FROM AUTHOR]

• A coarse-to-fine denoising method is proposed for improving the calibration signal quality. • An adaptive method is proposed for estimating the optimal mode number of VMD. • Two indicators are introduced to identify the relevant modes of decomposition results. Dynamic calibration is an essential way to characterize the measurement performance of pressure sensors under dynamic environment. However, it is difficult to guarantee the reliability of calibration results because the calibration signal is inevitably contaminated by noises. In this paper, a coarse-to-fine denoising method is proposed to improve the quality of calibration signals based on adaptive mode decompositions. Firstly, variational mode decomposition (VMD) is used to decompose the calibration signal into several band-limited intrinsic mode functions (BLIMFs). The optimal mode number is estimated based on their center frequency spacing and mutual information of BLIMFs. The coarsely denoised signal is then reconstructed by the relevant BLIMFs based on the ringing energy loss ratio indicator. Subsequently, the coarsely denoised signal is decomposed as a series of IMFs with empirical mode decomposition (EMD). By introducing a clustering indicator named as comprehensive weighted correlative degree, the ringing and trend IMFs are extracted for obtaining the finally denoised result. The performance of the proposed method is validated by both simulated and actual dynamic calibration signals. Results show that the SNR of denoised result with the proposed method is 33.91, which is obviously larger than that obtained by EMD (SNR = 25.03) and VMD (SNR = 22.67) for simulated signal. Furthermore, comparative experiments also demonstrate the superiority of the proposed method over the existing approaches in both denoising ability and signal integrity. [ABSTRACT FROM AUTHOR]

In current work, the wear resistance of CuNiAl was improved by the application of an aromatic thermosetting co-polyester (ATSP)-based coating on its surface. Tribological behaviors of the ATSP coating at stresses of 1.52, 3.04 and 3.75 MPa under different lubrication conditions (dry friction and oil) were studied by the fretting wear test. The morphology and chemical composition of the coating were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy and three-dimensional (3D) optical microscope. Results showed that at the same conditions, the friction torque of the ATSP coating was lower than that of CuNiAl. Significantly, wear was reduced by more than 90% after the application of the ATSP coating. The wear mechanism of the ATSP coating was slight deformation with pits induced by plastic deformation and fatigue crack propagation. The ATSP coating underwent molecular chain breakage during wear and chemical reaction with the friction pair to form a transfer film which played an important role in the reduction of wear. • The friction and wear properties of ATSP coating under fretting wear were investigated. • ATSP coating can significantly improve the wear resistance of CuNiAl. • ATSP coatings undergo complex chemical changes during wear。. • Transfer film is an important factor in reducing ATSP friction and wear. [ABSTRACT FROM AUTHOR]