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The purpose of this study is to investigate the dynamic behavior of the ball bearing with cage broken.

By analyzing the complicated relationship and interactions among the ball bearing elements, the dynamic modelling of the ball bearing with broken cage was established, and the dynamic simulations were conducted by solving the ball bearing dynamic equations using varying-step Runge–Kutta integration.

The computational results show that there is considerable distinguishment in the dynamic characteristics between the normal cage and the broken cage of the bears. The broken cage makes the trajectory of the cage erratic, and the vibration amplitude is much bigger than that of the normal cage, which makes the motion of the cage unstable. When one of the cage lintels breaks up, the two adjacent balls will collide with each other; what is worse, this may make the balls crush because of the high amplitude of the collision force. The broken cage makes the cage-race interaction force much larger than that of the normal cage, which could promote the guiding ring and quicken the cage wear-failure.

This study can provide important ideas for the fault identification of the ball bearing with cage broken.

The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-01-2020-0042/

The purpose of this paper was to explore the mechanisms of scuffing propagation of heavily loaded lubricated friction pair elements coated with low-friction WC/C coating for various material combinations.

The investigations were performed for low-friction coatings WC/C (a-C:H:W) deposited by the reactive sputtering physical vapour deposition (PVD) process. Experiments were carried out using a four-ball tester with continuously increasing loads. Tests were conducted for the following four material combinations: steel/steel tribosystem (all balls uncoated); steel/coating tribosystem (one upper ball uncoated/three lower balls WC/C-coated); coating/steel tribosystem (one upper ball WC/C-coated/three lower balls uncoated); and coating/coating tribosystem (all balls WC/C-coated).

The better scuffing resistance is achieved by coating only one element (coating/steel tribosystem) than all elements (coating/coating tribosystem). The description of scuffing propagation for all investigated tribosystems was done. The high scuffing resistance of the coating/steel tribosystem resulted from reducing the adhesion between rubbing surfaces due to low chemical affinity (similarities) between the steel and the coating material and the presence of solid lubricant in the friction zone.

In all cases, when a coating is applied, an increase in scuffing resistance is observed. However, it is better to coat only one element than all. Furthermore, the scuffing resistance for the coating/steel tribosystem is significantly higher than for the steel/coating tribosystem.

The main value of this paper is description of scuffing propagation and revealing the new aspects in application of low-friction WC/C coating for heavily loaded lubricated friction pair elements. The overlapping ratio has been defined as an important factor influencing the scuffing resistance of the coated tribosystems.

The goal of this work is to evaluate the feasibility of soldering tin‐silver‐copper balled BGAs using tin‐lead‐based solder and to investigate the influence of different production parameters on the microstructure of the solder joint.

The soldering of the BGAs was done with various temperature profiles and two conveyor speeds under a nitrogen atmosphere in a full convection oven. One specimen from each temperature/time combination was cross‐sectioned. The cross sections were analysed with optical microscopy, scanning electron microscopy with energy dispersive X‐ray spectroscopy (SEM/EDS) at 30 kV and focused ion beam microscopy (FIB).

The cross sections show a metallurgical bond between the solder and the tin‐silver‐copper balls of the BGA, even at a peak reflow temperature of 210°C. However, the balls alloy only partially with the solder, as the liquidus of tin‐silver‐copper balls is 217°C. As soon as the peak temperature exceeds the liquidus of the ball, the solder is totally dissolved in the material of the ball. A reflow profile with a peak temperature of about 230°C on the BGA gives a homogenous reaction of the solder with the ball with a minimum formation of voids.

The dependence of varying reflow parameters on reliability requires detailed study. Especially the effect of a partially melted ball on the degradation of the solder joint needs to be investigated.

From the findings, it can be said that soldering lead‐free balls with tin‐lead solder is possible. This is useful during the transitional period that the industry is in at the moment. More and more component manufacturers are changing their components to lead‐free, often without notice to the customer. If a production line is still running a tin‐lead process it is essential to know how to process these components with tin‐lead solder.

The paper seeks to propose and analyze a new electrostatic ramjet space engine.

The upper atmosphere (85‐1,000 km) is extremely dense in ions (millions per cubic cm). The interplanetary medium contains positive protons from the solar wind. A charged ball collects the ions (protons) from the surrounding area and a special electric engine accelerates the ions to achieve thrust or decelerates the ions to achieve drag. The thrust may have a magnitude of several Newtons. If the ions are decelerated, the engine produces a drag and generates electrical energy. The theory of the new engine is developed.

It is shown that the proposed engine driven by a solar battery (or other energy source) cannot only support satellites in their orbit for a very long time but can also work as a launcher of space apparatus. The latter capability includes launch to high orbit, to the Moon, to far space, or to the Earth's atmosphere (as a return thruster for space apparatus or as a killer of space debris). The proposed ramjet is very useful in interplanetary trips to far planets because it can simultaneously produce thrust or drag and large electric energy using the solar wind.

Two scenarios, launch into the upper Earth atmosphere and an interplanetary trip, are simulated and the results illustrate the excellent possibilities of the new concept.

The purpose of this paper is to investigate the effect of reciprocating and unidirectional sliding motions on friction and wear of phenolic resin-based composite.

The phenolic resin-based composite was fabricated by hot press molding, and then the tribological properties were tested on a CSM tribometer with two types of friction motion modes – reciprocating friction and unidirectional friction.

The results showed that the composite exhibited low friction coefficient in unidirectional test. However, the wear factor recorded under unidirectional sliding condition was 12-16 times higher than the reciprocating friction results. The SEM and optical microscopy test results showed that changing the relative motion mode resulted in different topography of transfer film, which is responsible for the different friction and wear characteristics of the composite under reciprocating and unidirectional friction conditions.

Effect of different friction modes, reciprocating friction and unidirectional friction, on friction characteristics of the composite is sought. Different topography of transfer film formed under reciprocating and unidirectional friction conditions contributed to the different friction characteristics.

Using archival and primary source evidence, this chapter introduces the first real wage series from 1891 to 1930 for Brazil’s most important immigrant and industrial city, São Paulo. This is the first price series, nominal wage series, and real wage series for the city that covers the duration of the Old Republic. While scholars look to Rio de Janeiro evidence to compare Brazil’s cost of living to other southern cone and immigrant-receiving countries, it is preferable to use evidence from the primary destination city. Price deviations between the two cities underscore the need for these series. The results show foodstuff prices increased steadily over the period and more dramatically in the period during and after World War I. Hedonic wage regressions show hourly wages for unskilled, low-skilled, and medium-skilled workers did not increase accordingly. While the decline in real wages tapered off in the 1920s, real wages across skill levels did not recover to prewar levels. This new index suggests the city of São Paulo’s labor market was more integrated with Buenos Aires’s than with Rio de Janeiro’s and that Paulistano real wages did not recover in the 1920s to the extent that they did in other southern cone cities. Given these results, the puzzle as to why migrants continued to flock to the city prove more intriguing. The results also suggest that Vargas-era labor legislation had the potential to greatly improve the lives of the city’s working class, perhaps more so than in other cities.