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The purpose of this study is to investigate the application of non-destructive testing methods in measuring bearing oil film thickness to ensure that bearings are in a normal lubrication state. The oil film thickness is a crucial parameter reflecting the lubrication status of bearings, directly influencing the operational state of bearing transmission systems. However, it is challenging to accurately measure the oil film thickness under traditional disassembly conditions due to factors such as bearing structure and working conditions. Therefore, there is an urgent need for a nondestructive testing method to measure the oil film thickness and its status.

This paper introduces methods for optically, electrically and acoustically measuring the oil film thickness and status of bearings. It discusses the adaptability and measurement accuracy of different bearing oil film measurement methods and the impact of varying measurement conditions on accuracy. In addition, it compares the application scenarios of other techniques and the influence of the environment on detection results.

Ultrasonic measurement stands out due to its widespread adaptability, making it suitable for oil film thickness detection in various states and monitoring continuous changes in oil film thickness. Different methods can be selected depending on the measurement environment to compensate for measurement accuracy and enhance detection effectiveness.

This paper reviews the basic principles and latest applications of optical, electrical and acoustic measurement of oil film thickness and status. It analyzes applicable measurement methods for oil film under different conditions. It discusses the future trends of detection methods, providing possible solutions for bearing oil film thickness detection in complex engineering environments.

Sectional warping is the most widely used warp preparation process in weaving. Winding all warp sections with the same length and same tension is a key factor for a good quality warp preparation. It is required that winding thickness (increase in radius due to warp winding) remains the same within and between warp sections. The purpose of this paper is to investigate winding thickness variations within and between warp sections, which can lead to quality problems in woven fabrics.

A measurement system is developed and then an experimental investigation into winding thickness variations is carried out. Winding thickness is measured with respect to number of drum revolutions using a laser sensor with 20 microns resolution. The number of drum revolutions and drum angular position are measured by an incremental encoder. Both sensors are mounted on an industrial sectional warping machine. A real-time software written in C programming language collects and records the data for all sections of warp with respect to drum number of revolutions and then results are evaluated to determine winding thickness variations.

Results show that warp sheet thickness starts with a higher value and it decreases up to around 30 drum revolutions and then it remains constant or decreases very slightly which can be considered as insignificant from practical point of view. Warp sheet thickness (i.e. thickness of one warp layer) fluctuates within each section up to 10 percent CV with five drum revolutions average warp sheet thickness. There are also warp sheet thickness variations between warp sections up to 3 mm.

Considering the short of practical research results on winding thickness variations in the literature, results of this study will be an original contribution to understanding winding thickness variation level. Also, results presented in this paper can be used to develop control algorithms for thickness control in sectional warping machines.

The purpose of this paper is to investigate the effects of reflow time, reflow peak temperature, thermal shock and thermal aging on the intermetallic compound (IMC) thickness for Sn3.0Ag0.5Cu (SAC305) soldered joints.

A four‐factor factorial design with three replications is selected in the experiment. The input variables are the peak temperature, the duration of time above solder liquidus temperature (TAL), solder alloy and thermal shock. The peak temperature has three levels, 12, 22 and 32°C above solder liquidus temperatures (or 230, 240 and 250°C for SAC305 and 195, 205, and 215°C for SnPb). The TAL has two levels, 30 and 90 s. The thermally shocked test vehicles are subjected to air‐to‐air thermal shock conditioning from −40 to 125°C with 30 min dwell times (or 1 h/cycle) for 500 cycles. Samples both from the initial time zero and after thermal shock are cross‐sectioned. The IMC thickness is measured using scanning electron microscopy. Statistical analyses are conducted to compare the difference in IMC thickness growth between SAC305 solder joints and SnPb solder joints, and the difference in IMC thickness growth between after thermal shock and after thermal aging.

The IMC thickness increases with higher reflow peak temperature and longer time above liquidus. The IMC layer of SAC305 soldered joints is statistically significantly thicker than that of SnPb soldered joints when reflowed at comparable peak temperatures above liquidus and the same time above liquidus. Thermal conditioning leads to a smoother and thicker IMC layer. Thermal shock contributes to IMC growth merely through high‐temperature conditioning. The IMC thickness increases in SAC305 soldered joints after thermal shock or thermal aging are generally in agreement with prediction models such as that proposed by Hwang.

It is still unknown which thickness of IMC layer could result in damage to the solder.

The IMC thickness of all samples is below 3 μm for both SnPb and SAC305 solder joints reflowed at the peak temperature ranging from 12 to 32°C above liquidus temperature and at times above liquidus ranging from 30 to 90 s. The IMC thickness is below 4 μm after subjecting to air‐to‐air thermal shock from −40 to 125°C with 30 min dwell time for 500 cycles or thermal aging at 125°C for 250 h.

The paper reports experimental results of IMC thickness at different thermal conditions. The application is useful for understanding the thickness growth of the IMC layer at various thermal conditions.

The purposes of this work were to determine: whether thickness of single layers can be used to accurately predict thickness and thermal resistance of multiple layer assemblies; and to identify variables affecting the total thickness (i.e. textile plus air layers) of bedding during simulated use. Thickness was determined when: materials were flat; and arranged over an infant manikin simulating use. Thermal resistance was measured using a guarded‐hotplate similar to that specified in ISO 11092:1993(E). During simulated use, the site of measurement, body position, tucking, and product type significantly affected thickness of bedding. Equations for predicting thickness and thermal resistance (dry) of multiple‐layer materials are described. While it was possible to predict thickness and thermal resistance of flat bedding from estimated values, extrapolation to bedding during simulated use was considered inappropriate, with significant differences of over 1,000 per cent.

The optimization of variable thickness plates and shells is studied. In particular, three types of shell are considered: hyperbolic paraboloid, conoid and cylindrical shell. The main objective is to investigate the optimal thickness distributions as the geometric form of the structure changes from a plate to a deep shell. The optimal thickness distribution is found by use of a structural optimization algorithm which integrates the Coons patch technique for thickness definition, structural analysis using 9‐node Huang‐Hinton shell elements, sensitivity evaluation using the global finite difference method and the sequential quadratic programming method. The composition of the strain energy is monitored during the optimization process to obtain insight into the energy distribution for the optimum structures. Several benchmark examples are considered illustrating optimal thickness variations under different loading, boundary and design variable linking conditions.

This paper describes the different thickness measurement techniques that enable reliable thickness assessments, and the determination of the recommended immersion tin thickness for lead‐free soldering.

Immersion tin layers were prepared with systematically varying layer thicknesses. The samples were annealed at different reflow profiles, used in assembly for tin/silver/copper (SAC‐alloy) soldering. The layers were characterized with X‐ray fluorescence, electrochemical stripping coulometry, and by examining the cross sections using a scanning electron microscope. The solderability of the samples was determined with a solder balance (Solderability Tester Menisco ST60) using a SAC‐alloy (melting point 217°C) with T(max) at ΔT=28°C and ΔT=43°C above melting.

If all pure tin is converted into the Sn/Cu IMC, so that no pure tin is left as solderable layer, the wetting behaviour will decrease dramatically. Especially for multiple soldering processes, two times reflow followed by wave soldering, it is essential to have a pure tin layer covering the Sn/Cu IMC before going to the final soldering process. The required amount of residual pure tin over the Sn/Cu IMC is detailed in several papers. It is stated that a minimum of 0.2 μm of pure tin over the Sn/Cu IMC is absolutely necessary to ensure reliable wetting and solder joint formation. With the current immersion tin thickness recommendation of 1 μm, based on the needs of lead containing solder pastes, a residual pure tin layer will not be evident or thick enough to ensure reliable assembly for multiple soldering with lead‐free temperature profiles.

Helps to enable reliable thickness assessments, and the determination of the recommended immersion tin thickness for lead‐free soldering.

To make a derivation of the load‐carrying capacity of elastohydrodynamic lubrication for special operating conditions, i.e. extremely heavy loads or extremely low rolling speeds based on the Newtonian fluid model by taking the Grubin‐type EHL inlet zone analysis, justify the load‐carrying capacity of elastohydrodynamic lubrication film in these operating conditions, and propose future trends of the research in EHL and mixed EHL based on the obtained results in the present paper.

A Grubin‐type EHL inlet zone analysis is carried out for the isothermal EHL of line contacts in special operating conditions, i.e. extremely heavy loads or extremely low rolling speeds based on the Newtonian fluid model. Comparison is made between the central EHL film thickness in line contacts, respectively, predicted by conventional EHL theories and accurately predicted from the present analysis for these operating conditions. An interpretation is made for the EHL film thickness in these operating conditions by taking the approach of the transportation and flow of the fluid through elastohydrodynamic contact when the EHL film is, respectively, thick and molecularly thin in the Hertzian zone. Conclusions are drawn on the load‐carrying capacity of EHL, EHL contact regimes and mixed EHL regimes in these operating conditions.

The present EHL inlet zone analysis shows that the EHL film thickness in the Hertzian zone is on the nanometer scale and the lubricant is non‐continuum across the film thickness in the Hertzian zone at relatively heavy loads in line contact EHL when the dimensionless rolling speed is lower than the dimensionless characteristic rolling speed U_ch=0.0372W^1.50/G. In this case, the central EHL film thickness in line contact EHL predicted by the conventional EHL theory may be several orders of magnitudes higher than that accurately predicted. This difference may be greater for heavier loads.The present results for line contact EHL based on the Newtonian fluid model show that in line contact EHL, for relatively heavy loads and the dimensionless rolling speed lower than the dimensionless characteristic rolling speed U_ch=0.0372W^1.50/G, the EHL analysis needs to further incorporate the lubricant non‐continuum effect across the film thickness in part of the lubricated area to investigate the EHL film thickness and the EHL film pressure in the contact in this very low film thickness condition; only the results based on such an analysis are believable for the EHL stage where the lubricant film thickness in the Hertzian zone approaches to zero and then vanishes; the results for EHL based on the Newtonian fluid model is unable to conclude that the EHL film thickness in the Hertzian zone is zero and dry contact occurs between the contact surfaces in EHL in any operating condition for ignoring the lubricant non‐continuum regime governing the EHL stage preceding the occurrence of the zero lubricant film thickness in EHL.

A very useful source of information for academic scientists, engineers and tribologists who are engaged in the study and application of the theory of elastohydrodynamic lubrication.

A derivation is first carried out for the isothermal EHL of line contacts in extremely heavy loads or extremely low rolling speeds by taking the Grubin‐type EHL inlet zone analysis by the present paper. Results and conclusions on the load‐carrying capacity of EHL in these operating conditions are first strict and thus convincing. These results are also original in clarifying the future trends of the researches in EHL and mixed EHL.

The purpose of this paper is to explore the pure squeeze thin film elastohydrodynamic lubrication (TFEHL) motion of circular contacts with adsorption layers attached to each surface under constant load condition. The proposed model can reasonably calculate the pressure distributions, film thicknesses, normal squeeze velocities, and effective viscosities during the pure squeeze process under thin film lubrication.

The transient modified Reynolds equation is derived in polar coordinates using viscous adsorption theory. The finite difference method and the Gauss‐Seidel iteration method are used to solve the transient modified Reynolds equation, the elasticity deformation equation, load balance equation, and lubricant rheology equations simultaneously.

The simulation results reveal that the thickness of the adsorption layer and the viscosity ratio significantly influence the lubrication characteristics of the contact conjunction in the thin film regime. In additional, the turning points in the film thickness which distinguish thin film lubrication from elastohydrodynamic lubrication curve is found. In thin film region, the effective viscosity predicted by present model is better than that predicted by traditional elastohydrodynamic theory.

The paper develops a numerical method for general applications with adsorption layers attached to each surface to investigate the pure squeeze action in a TFEHL spherical conjunction under constant load condition.

The purpose of this paper is to study and discuss the effects of the finite metallisation thickness and conductivity on the properties of microstrip lines.

Effective dielectric constant and attenuation constant of microstrip lines with finite metallization thickness and finite conductivity are analyzed by the method of lines. The experimental results are obtained by using Vector Network Analyzer and the 3680 V Universal Test Fixture of Anritsu.

The strip thickness has a great impact on the attenuation constant of the microstrip lines. The effects can be divided into three parts by the relationship between strip thickness (t) and skindepth (δ). When t<δ, the attenuation constant will decrease rapidly as the strip thickness increase. When δ < t<2δ, the attenuation constant still decrease rapidly as the strip thickness increase, but the slope of the curve will be smaller. When 2δ < t, the effects of the strip thickness will become insignificant and the attenuation constant still decrease slowly as the strip thickness increase.

This paper presents some useful principles about the effects of the finite metallization thickness and finite conductivity in microstrip lines. The reasons for these effects are discussed by analyzing the longitudinal electric field distribution in the strip. Finally, some experimental results are given to verify these principles.

This study aims to comprehensively investigate the mixed-mode fracture behavior and mechanical properties of selective laser sintering (SLS) polyamide 12 (PA12) components, considering different build orientations and layer thicknesses. The primary objectives include the following. Conducting mixed-mode fracture and mechanical analyses on SLS PA12 parts. Investigating the influence of build orientation and layer thickness on the mechanical properties of SLS-printed components. Examining the fracture mechanisms of SLS-produced Arcan fracture and tensile specimens through experimental methods and finite element analyses.

The research used a combination of experimental techniques and numerical analyses. Tensile and Arcan fracture specimens were fabricated using the SLS process with varying build orientations (X, X–Y, Z) and layer thicknesses (0.1 mm, 0.2 mm). Mechanical properties, including tensile strength, modulus of elasticity and critical stress intensity factor, were quantified through experimental testing. Mixed-mode fracture tests were conducted using a specialized fixture, and finite element analyses using the J-integral method were performed to calculate fracture toughness. Scanning electron microscopy (SEM) was used for detailed morphological analysis of fractured surfaces.

The investigation revealed that the highest tensile properties were achieved in samples fabricated horizontally in the X orientation with a layer thickness of 0.1 mm. Additionally, parts manufactured with a layer thickness of 0.2 mm exhibited favorable mixed-mode fracture behavior. The results emphasize the significance of build orientation and layer thickness in influencing mechanical properties and fracture behavior. SEM analysis provided valuable insights into the failure mechanisms of SLS-produced PA12 components.

This study contributes to the field of additive manufacturing by providing a comprehensive analysis of the mixed-mode fracture behavior and mechanical properties of SLS-produced PA12 components. The investigation offers novel insights into the influence of build orientation and layer thickness on the performance of such components. The combination of experimental testing, numerical analyses and SEM morphological observations enhances the understanding of fracture behavior in additive manufacturing processes. The findings contribute to optimizing the design and manufacturing of high-quality PA12 components using SLS technology.