Contact Theory Research Articles

Wear characteristics analysis of variable hyperbolic circular-arc-tooth-trace cylindrical gear transmission considering assembly error theory

Wear is the main failure form of the gear transmission interface, runs through the whole life cycle of gear service, and the distributed error of the tooth surface due to the introduced assembly error will make the actual meshing state of the tooth surface different from the ideal meshing state, thus affecting the tooth surface wear trajectory and state. Therefore, considering the coupling relationship between assembly error and tooth surface contact analysis, the variation laws of the wear amount of the gear transmission interface of the variable hyperbolic circular-arc-tooth-trace cylindrical gear were studied under the consideration of assembly error in this article. Based on the tooth surface contact analysis method and Hertz contact theory, the transient linear load, the combined radius of curvature, the length axis and short axis of the contact ellipse, and the instantaneous sliding velocity were calculated. Through revising the calculation method of adhesive wear of variable hyperbolic circular-arc-tooth-trace cylindrical gears, the correlations between the tooth surface wear amount and gear parameters of variable hyperbolic circular-arc-tooth-trace cylindrical gears under different assembly errors were analyzed. The results show that the maximum wear occurs at the root of the tooth, and the wear at the indexing circle approaches zero, whether it is standard installation or non-standard installation. The vertical axial error and horizontal axial error have little effect on the wear, while the center distance error will aggravate the wear. The proposed method comprehensively considers the influence of assembly error and gear parameters on tooth surface wear, and this method can provide a theoretical reference for the design and analysis of anti-wear, wear reduction, and life extension of variable hyperbolic circular-arc-tooth-trace cylindrical gear tooth surface.

Refugees at home: the role of hospitableness in fostering pro-social attitudes and behaviours towards refugees

PurposeThis study aims to examine the role of hospitableness towards refugees, as embraced by local hosts, in engendering positive social outcomes, including fostering favourable attitudes and empathy towards refugees, satisfaction from hosting refugees in private dwellings and advocacy for hosting them.Design/methodology/approachRooted in the contact theory and drawing on a hospitality social lens framework, the study uses a mixed-methods approach using a sequential quantitative-qualitative design to understand the interface between hospitableness, attitudes and empathy towards refugees, satisfaction from hosting refugees in private dwellings and advocacy for hosting them. A conceptual model is proposed and tested using 160 valid surveys collected from individuals hosting Ukrainian refugees in Slovakia. SEM-PLS is used to test the proposed model. A total of 25 in-depth interviews with Slovakian individuals hosting refugees in private dwellings were also conducted to explain and further explore the initial quantitative results.FindingsThe findings indicate that hospitableness has a positive effect on attitudes towards refugees, fosters a sense of empathy and results in satisfaction from hosting refugees. Interestingly, while hospitableness per se does not directly affect advocacy for hosting refugees, it does so indirectly via favourable attitudes towards refugees and satisfaction from the hosting experience. While qualitative findings largely support and further explain the quantitative results, interesting insights are also obtained.Practical implicationsThe study advocates that hospitableness should be addressed through a social lens beyond its traditional commercial boundaries. Several implications for policymakers, NGOs and other stakeholders involved in hosting refugees are proposed. Overall, policies need to be oriented towards harnessing the power of refugee hosting schemes, thus increasing the role of hospitableness in addressing societal challenges such as the refugee crisis.Originality/valueWhile not new, private hosting of refugees has recently gained momentum following the outbreak of the Ukrainian refugee crisis. In spite of some valuable research delving into hosting experiences from the refugees’ and hosts’ perspectives, this research stream is notably fragmented and largely exploratory. Specifically, there seems to be no comprehensive understanding of how hospitableness towards refugees, as embraced by hosts, can engender positive social outcomes, including fostering favourable attitudes and empathy towards refugees, satisfaction from hosting refugees and advocacy for hosting refugees in private dwellings. Overall, hospitality research is notably biased towards commercial settings, focusing on instrumental benefits rather than societal outcomes. This study focuses on the societal outcomes of hospitableness as a tool to address the refugee crisis.

Study on microstructure of 42CrMo steel by ultrasonic surface rolling process

To explore the microstructure formation mechanism of 42CrMo steel under the strengthening of ultrasonic surface rolling process (USRP), the combination of theoretical analysis and experiment was used to conduct in-depth research on USRP. Firstly, according to contact mechanics and Hertz contact theory, the calculation model of contact stress distribution and elastoplastic strain between the rolling ball and the part during USRP is obtained. Secondly, the USRP processing test was carried out by single-factor experimental design method, and the microstructure of 42CrMo steel after USRP was analyzed by LEXT OLS5100 3D laser surface topography instrument and VEGA3 tungsten filament scanning electron microscopy, which found that with an increase in static pressure, residual stress and plastic strain gradually increase, the hardness firstly increases and then decreases, while surface roughness exhibits an initial decrease followed by an increase. The results show that USRP produces violent plastic deformation inside the material under the superposition of high-frequency impact and static pressure, at the same time, it refines the grains, so as to improve the surface performance of the part and improve its fatigue resistance.

Acceleration mechanism of abrasive particle in ultrasonic polishing under synergistic physical vibration and cavitation: Numerical study

Ultrasonic technology is widely applied in the engineering ceramic polishing processes without the limitation of material properties and ideally integrated into computer numerical control system. Ultrasonic-induced cavitation and mechanical vibration effect could accelerate the motion of solid abrasives. The individual behaviors of microjet/shockwave of ultrasonic cavitation in gases and liquids, and micro-abrasives with simple harmonic vibrations in solids and liquids has been extensively studied. To conduct a systematic and integrated study of abrasives behavior in the polishing contact region involving abrasive, surround-workpiece wall, ultrasonic physical vibration, and ultrasonic cavitation impact, a novel model integrating the free abrasive motion velocity and fixed abrasive indentation depth under multi-scale contact was proposed according to Hertzian contact theory, Greenwood-Williamson model, indentation deformation theory, the basic equations of cavitation bubble dynamics, cavitation impact control equations, and Newton's law of motion equation. The effects of ultrasonic amplitude, ultrasonic frequency, preloading force and particle size on the proposed model were investigated by theoretical analysis and numerical simulations. Ultrasonic physical vibration mainly influences the dynamic gap and further influence the number of different abrasives. Furthermore, the indentation depth of fixed abrasive depends mainly on the abrasive geometry. As the contact gap and abrasive size decrease, the indentation depth gradually decreases. Under the synergistic effect of cavitation-induced shock wave and microjet, the velocity of free abrasive in this paper is generally 0–150 m/s, and the kinetic energy of free abrasive increases roughly linearly with increasing frequency and approximately as a quadratic function with increasing particle size. Increasing the preloading force leads to a reduction in the abrasive kinetic energy. Besides, the kinetic energy induced by the shock wave has a cliff-like increment at an amplitude of 0.7–0.8 μm. It is revealed that the abrasive kinetic energy is suppressed by the cavitation bubble expansion and collapse at smaller ultrasonic pressure amplitude and surround-wall distance. This research provides a theoretical reference for the modeling of potential defects and material removal on the workpiece surface caused by abrasive motion during polishing, and reduces the trial cost for parameter optimization in actual polishing processing.

The resonance mode splitting rule of the rotating tire cavity considering the vertical load

According to the modal splitting theory of the tire cavity at different rotation speeds and the modal splitting theory of the tire cavity under different loads, the expression of the resonance frequency of the tire cavity of the rotating tire under load conditions is proposed. Based on the elastic contact theory, the characteristic geometric parameters of grounded tires are obtained. The resonance frequency of the tire cavity is predicted by using the common rule of the characteristic geometric parameters of grounded tires and the characteristic section parameters of the tire cavity, to further clarify the basic rule of changes of vibration mode shapes accompanied by the resonance mode splitting of the tire cavity.

Rail vehicle axlebox roller bearing life and failure analysis based on the Hertz contact theory, finite element modeling, and field observations

Rail vehicle axlebox roller bearing life and failure analysis based on the Hertz contact theory, finite element modeling, and field observations

Does urban design drive sympathy for the far right?

The far right has now entered into the mainstream politics of nearly every European country, yet we have confirmed little about the social context in which far-right parties thrive. While most of the literature assumes that far-right sympathies are driven by economic or cultural grievance, this paper looks to cities and contact theory. Recent advances suggest that even indirect or vicarious intergroup contact can reduce prejudice toward out-groups such as migrants. Urban theorists, as well, have long argued that urban design can influence social outcomes by promoting or discouraging interaction between residents. This paper applies this literature to the rise of the far right, which often scapegoats out-groups in its rhetoric. Using data from 73 cities in Spain, we find that residents of cities rich in continuous urban fabric—which promotes contact—are less likely to consider voting for the far right but that this relationship is weaker in highly segregated cities.

ВПЛИВ УКРАЇНСЬКО-АНГЛІЙСЬКИХ МОВНИХ КОНТАКТІВ ХХІ СТ. НА ЛЕКСИЧНИЙ СКЛАД УКРАЇНСЬКОЇ МОВИ

The influence of the twenty first century Ukrainian English language contacts is analysed in the paper. The largest thematic spheres of concentration of anglicisms are determined. Graphic and morphological adaptation of anglicisms is analysed. The problem of pseudoanglicisms and pseudofriends is also discussed. Prediction concerning future development of Ukrainian-English mixture / surzhyk is made. The theory of language contacts is the basis of the investigation. The term language contact has a broad and narrower interpretation. According to a broad interpretation, two or more languages are in contact if one and the same person uses them in turn. In this case we have the situation of obligatory bilingualism. According to a narrower interpretation, bilingualism is not obligatory. In such a case borrowing takes place under different social-political, cultural and historic, trade and economic and other relations. Just the second case of language contacts is considered in our paper. Vocabulary is the most susceptible to changing sphere of language says one of the main postulates of language contacts theory. Just that very case one can observe in the Ukrainian language of late. The last decade of the XX-th century and 23 years of the XXI-st century are marked by rapid growth of direct contacts of Ukrainian language with numerous European languages. The English language plays a special part among them. The new socio-political and cultural relations caused circumstances of active penetration of anglicisms into the Ukrainian language. Means of mass information play essential role in spreading anglicisms among speakers of Ukrainian beginning from using the foreign term in order to inform about something to borrowing this term. Hence the sources of our investigation were selected, namely Ukrainian newspapers and weekly magazine.

Is intergroup contact alone enough to cultivate inclusive attitudes toward immigrants? Global citizenship education as a complementary tool

The surge in international migrants offers students contact with immigrants. However, this does not necessarily cultivate inclusive attitudes toward immigrants (IATI), often due to a lack of relevant learning experiences. This research examines the interaction between intergroup contact and global citizenship education (GCE) in shaping IATI. Utilizing PISA 2018 across 61 countries with two-level and country-fixed effects models, it reveals that intergroup contact alone has a limited impact on IATI. A positive relationship emerges when combined with three GCE activities. This study advances our knowledge of intergroup contact theory and highlights the complementary role of GCE in fostering global citizens.

Diversified exposure mitigates biased perceptions: Involvement, media exposure, and hostile media perceptions toward coverage of U.S.-China trade disputes

This study empirically tested the proposition that diversified media exposure mediates the effect of involvement on hostile media perceptions (HMPs). Informed by social identity theory and the intergroup contact theory, the study examined issue involvement and cognitive involvement as the antecedents of diversified media exposure concerning U.S.-China trade dispute and tested how diversified media exposure affected peoples’ perceptual bias of U.S. media as out-group media. Using the data collected from a sample of 1029 Chinese media users, the structural equation modeling indicated that issue involvement and cognitive involvement both escalated people's diversified media exposure. Out-group media exposure significantly reduced HMP, whereas expanded information seeking boosted HMP. The serial mediation model also reveals that extended discussion and expanded information seeking mediated the relationship between involvement and HMP.

Effect of temperature on adhesion behavior of layered piezoelectric structure

The effect of temperature on adhesion is neglected in classical adhesive contact theories. However, an increasing number of experimental results indicate that temperature has a prominent effect on adhesion behaviors. In this study, the anisothermal adhesive contact behaviors between two transversely isotropic piezoelectric cylinders with different initial temperatures is investigated by virtue of the generalized JKR model, where the contact interface is assumed to be perfectly bonded. The considered problem is reduced to coupled singular integral equations, which is derived by using the Fourier integral transform. The closed-form solutions of anisothermal generalized stress fields are obtained by taking the series expansion of the integrand induced by temperature difference. The effect of temperature difference on adhesion behaviors of two different types of layered piezoelectric structures under the action of mechanical-electro loadings is revealed. It is found that the pull-off force and contact size at pull-off moment decrease with increasing the temperature difference. The adhesion weakening effect induced by temperature difference diminishes when the electric loading is exerted. The results derived from this paper shed lights on understanding the adhesive contact behaviors of piezoelectric materials in the presence of temperature difference.

Need Fulfillment During Intergroup Contact: Three Experience Sampling Studies.

One challenge of modern intergroup contact research has been the question of when and why an interaction is perceived as positive and improves intergroup relations. We propose to consider the perceived fulfillment of the situationally most relevant need. We conducted three intensive longitudinal studies with recent migrants to capture their interactions with the majority out-group (Nmeasurements = 10,297; Nparticipants = 207). The situational need fulfillment mechanism is consistently a strong predictor of perceived interaction quality and positive out-group attitudes following intergroup interactions. The model is specific to out-group contact, robust to various need types, and works at least as well as Allport's contact conditions. As one of the first studies to test intergroup contact theory using intensive longitudinal data, we offer insight into the mechanisms of positive intergroup contact during real-life interactions and find situational motivations to be a key building block for understanding and addressing positive intergroup interactions.Public significance statement: In this article, we provide evidence that the fulfillment of situational needs during real-life intergroup contacts meaningfully predicts perceived interaction quality and positive outgroup attitudes. Methodologically, this offers a testament to the emerging practice of capturing real-life interactions using intensive longitudinal data. Theoretically, our results give weight to motivational fulfillment as a flexible and effective mechanism for understanding positive intergroup contact.

Who Says “Muslims Are Not Terrorists”? News Differentiation, Muslim versus Non-Muslim Sources, and Attitudes toward Muslims

ABSTRACT Media coverage on terrorism can lead to negative attitudes toward Muslims. We theorize that undifferentiated news—i.e., not explicitly distinguishing Muslims from terrorists—can accelerate these negative effects. In a quota-based 2 (news differentiation: differentiated and undifferentiated) × 2 (expert interviewee source: Muslim and non-Muslim) between-subjects experiment (N = 291), participants read news about Islamist terrorism. A control group received news unrelated to terror. Building on the concept of news differentiation and extending this line of research, we analyzed effects on explicit and implicit attitudes toward Muslims. Drawing on social identity, self-categorization and mediated intergroup contact theories, findings revealed that undifferentiated news increased hostile attitudes toward Muslims and attitudinal undifferentiation. However, undifferentiated news did not activate implicit attitudes. We also found that undifferentiated news had the strongest negative effects when coming from sources that are perceived as similar (i.e., non-Muslim).

Study on contact and vibration characteristics of composite cylindrical roller bearings

PurposeThe purpose of this paper is to establish a dynamic analysis model of composite cylindrical roller bearings, investigate the effects of different working conditions on the kinematic characteristics of composite bearings and compare the differences between them and solid roller bearings.Design/methodology/approachThis paper establishes a dynamic analysis model for composite cylindrical roller bearings and proves the correctness of the established model by establishing dynamic vibration experiments and contact theory for composite roller bearings. Comparative analysis was conducted on the effects of coupling changes in rotational speed, load, number of rollers and filling ratio on parameters such as bearing static stiffness, contact stress and vibration acceleration.FindingsThe composite roller can enhance the bearing’s operational stability and minimize contact stress, but that a higher filling ratio is going to increase the bearing’s stiffness. The acceleration degree of bearing vibration, the load on the outer raceway nodes and the bearing stability all decrease as inner ring speed rises.Originality/valueA dynamic calculation model of composite cylindrical roller bearings is established, and the influence of multiparameter coupling changes on bearing vibration and contact is studied, which lays a foundation for the structural improvement of the bearings.

An Unbridgeable Gap? Racial Attitudes and Friendship in Prison

The United States is experiencing growth in racial and ethnic diversity, yet racial tensions remain high. Proponents of contact theory suggest that interracial contact should alleviate racial tensions when contact occurs under the right conditions. The current study uses a network approach to examine the relationship between race, racial attitudes, and friendship within a novel setting satisfying the “right” conditions: a good behavior prison unit. Using social network data from 133 men and Exponential Random Graph Models, we examine whether racial attitudes influence the patterns of intraracial versus interracial ties. Results reveal that negative racial attitudes do not differentially impact the sending of intraracial versus interracial ties, but reduce the odds of receiving interracial ties from other participants. We discuss the implications of these findings for contact theory as well as for research on race relations both within and outside of prison.

Replicating and extending Sengupta et al. (2023): Contact predicts no within-person longitudinal outgroup-bias change.

Intergroup contact has long been touted as a premier means to reduce prejudice and forge positive bonds with outgroups. Given its origins in psychological research, it is perhaps of little surprise that contact is expected to induce change within people over time. Yet using random-intercepts crossed-lagged modeling that parses within-person from between-person effects, Sengupta et al. (2023) recently found no evidence of within-person change, only unexplained between-person effects, regarding contact's effects on outgroup solidarity in New Zealand. We conceptually replicated their study, focusing on modern racism and an affect thermometer as the outcomes, in a three-wave study of White British participants (NT1 = 946, NT2 = 667, NT3 = 591) and their attitudes toward foreigners. We replicated the general pattern described by Sengupta and colleagues, confirming between-person effects without within-person effects, suggestive of third-variable explanations. As a novel finding, we discover that differences in social dominance orientation (SDO) and right-wing authoritarianism (RWA) can account for the observed between-person effects. Problematically for contact theory, contact effects, at least those relying on self-reported accounts, increasingly appear to reflect differences between people (person factors) rather than being context-driven (situation factors)-such that those lower (vs. higher) in SDO and RWA are more favorable toward outgroups, rather than intergroup contact bringing about positive outcomes itself. Implications for theory development and intervention are discussed. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Ethical Framework for Multi-Source Big Data Analytics Disease Surveillance in Public Healthcare

Big data analytics can revolutionize disease surveillance by integrating multiple data sources and analyzing those diverse data sources, allowing for early monitoring, detection, and response to disease outbreaks. Since the growth in technology, together with the advent of big data, there is growing interest in exploring the potential of multiple data sources for disease surveillance. However, there are still ethical concerns when it comes to big data usage for disease surveillance. Hence, this study uses of scoping review with the assistance of socio-technical systems theory, together with social contact theory to examine the ethical dimensions of employing big data analytics from diverse sources for disease surveillance, while emphasizing the importance of maintaining ethical standards in public healthcare practices. The study discovered that informed consent, privacy, and confidentiality are still major challenges when it comes to the integration of big data sources in disease surveillance. The study then recommends a unified ethical framework for enhanced disease surveillance in public healthcare through Multi-Data Source big data Analytics.

Effect of combined geometric errors on static load distribution and deformations for linear rolling guide

Most studies on linear rolling guides usually assume the contact load between the ball and the raceway is uniform, which results in a deviation from the actual conditions. This study aims to establish a load distribution model based on the Hertz contact theory with ball combined interference which is converted from preload, raceway center-distance error, and installation error including ball geometry error. The reliability of the proposed model was verified by a numerical instance for the load distribution and deformation analysis. The result shows that the proposed approach agrees better with the experimental results compared only with the action of the preload. This work can provide an important starting point for studying friction and wear in machine tools.

AN IMPROVED ENGINEERING MODEL FOR CALCULATING THE RADIAL STIFFNESS OF ROLLER BEARINGS

The paper presents an analysis of quasi-static models for calculating stiffness and substantiates the choice of the most effective engineering model for calculating the radial stiffness of roller bearings. The analysis of quasi-static models for calculating the stiffness of roller bearings is carried out, which consists in numerical-analytical modeling of force-displacement ratios under conditions of contact interaction. It is noted that for roller bearings, semi-empirical dependencies proposed by Palmgren, Jones and Harris are more often used. For all numerical-analytical quasistatic models of roller bearings, a generalizing relationship between force and displacement at contact is introduced within the framework of the Hertz contact theory, where the stiffness characteristics are determined by the solution of the corresponding contact problem. The numerical values of constants obtained by several authors on the basis of empirical approaches or an approximate solution of the contact Hertz problem for steel bearings are given. In this paper, an analysis of quasi-static models for calculating stiffness is presented and the choice of the most effective engineering model for calculating the radial stiffness constants of roller bearings is substantiated. To solve the contact problem of a separate rolling element and rolling tracks, a finite element periodic model consisting of two halves of the rolling element is used, which are in contact separately with part of the inner and outer bearing rings, respectively, and have physically justified boundary conditions. The labor and computer time required to implement the proposed approach is less than when using the finite element method to determine the stiffness "in the forehead" for each individual bearing, which makes this model an effective engineering model for calculating the stiffness of roller bearings.

Vibration characteristic investigation of an eccentric rotor system with rubbing

Assembly errors can lead to the eccentricity of rotors, further resulting in angular misalignment of rotors and inducing some secondary misalignments, such as the angular misalignment of gears and tilt misalignment of the inner ring of bearings (TMIRB). Ultimately, these misalignments can lead to rubbing faults. However, these misalignments have not raised significant concern, this article investigates their influence on the vibration responses of a dual-rotor-gear-bearing system with rubbing. First, a finite element model (FEM) of the system is built by using an in-house beam element code, and the nonlinear force model of the bearing is established based on the Hertz contact theory. Then, a new model to simulate angular misalignment of gears is proposed by changing the time-varying meshing stiffness (TVMS). Furthermore, the nonlinear dynamic characteristics of the system are investigated in detail under different misalignment angles and rotating speeds, and some interesting conclusions are summarized as follows. Specifically, analyses of the spectrum cascade of radial and axial responses reveal the presence of rich multi-time frequencies and combined frequencies. Moreover, as the misalignment angle increases, the system experiences partial rubbing, the rotating speed threshold (RST) corresponding to initial rubbing decreases, and the mesh stiffness of gears decreases. In summary, the proposed model and the results of the analysis offer valuable insights into the vibration characteristics of such systems and these findings can be instrumental in optimizing their design and operation.