Journal articles on the topic 'Housing frictions'
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1
Sieg, Holger, and Chamna Yoon. "Waiting for affordable housing in New York City." Quantitative Economics 11, no. 1 (2020): 277–313. http://dx.doi.org/10.3982/qe1160.
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We develop a new dynamic equilibrium model with heterogeneous households that captures the most important frictions that arise in housing rental markets and explains the political popularity of affordable housing policies. We estimate the model using data collected by the New York Housing Vacancy Survey in 2011. We find that there are significant adjustment costs in all markets as well as serious search frictions in the market for affordable housing. Moreover, there are large queuing frictions in the market for public housing. Having access to rent‐stabilized housing increases household welfare by up to $ 65 , 000 . Increasing the supply of affordable housing by 10 % significantly improves the welfare of all renters in the city. Progressive taxation of higher‐income households that live in public housing can also be welfare improving.
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Anenberg, Elliot. "Information Frictions and Housing Market Dynamics." Finance and Economics Discussion Series 2012, no. 48 (2012): 1–51. http://dx.doi.org/10.17016/feds.2012.48.
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Anenberg, Elliot. "INFORMATION FRICTIONS AND HOUSING MARKET DYNAMICS." International Economic Review 57, no. 4 (November 2016): 1449–79. http://dx.doi.org/10.1111/iere.12204.
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Koster, Hans R. A., and Jos van Ommeren. "Housing search frictions and optimal search." Economics Letters 189 (April 2020): 108980. http://dx.doi.org/10.1016/j.econlet.2020.108980.
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Branch, William A., Nicolas Petrosky-Nadeau, and Guillaume Rocheteau. "Financial frictions, the housing market, and unemployment." Journal of Economic Theory 164 (July 2016): 101–35. http://dx.doi.org/10.1016/j.jet.2015.07.008.
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Liberati, Danilo, and Michele Loberto. "Taxation and housing markets with search frictions." Journal of Housing Economics 46 (December 2019): 101632. http://dx.doi.org/10.1016/j.jhe.2019.05.001.
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Bracke, Philippe, and Silvana Tenreyro. "History Dependence in the Housing Market." American Economic Journal: Macroeconomics 13, no. 2 (April 1, 2021): 420–43. http://dx.doi.org/10.1257/mac.20180241.
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Using data on the universe of housing transactions in England and Wales over a 20-year period, we document that sale prices and selling propensities are affected by house prices prevailing in the period in which properties were previously bought. Using administrative data on mortgages, we show that cognitive frictions explain most of the history dependence in sale prices, whereas credit frictions are more relevant for selling propensities. We corroborate our analysis with data on online house listings, and we estimate the impact of history dependence on the collapse and slow recovery of housing market activity in the postcrisis period. (JEL E32, R21, R31)
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Lisi, Gaetano, and Mauro Iacobini. "Estimating the housing price with a search-and-matching model." Journal of European Real Estate Research 8, no. 2 (August 3, 2015): 196–216. http://dx.doi.org/10.1108/jerer-09-2014-0035.
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Purpose – This paper aims to pose an important starting point for the application of the search-and-matching models to real estate appraisals, thus reducing the “gap” between practitioners and academicians. Due to relevant trading frictions, the search-and-matching framework has become the benchmark theoretical model of the housing market. Starting from the large related literature, this paper develops a simplified approach to modelling the frictions that focuses on the direct relationship between house price and market tightness (a common feature only for the labour market matching models). The characterization of the equilibrium through two main variables simplifies the analysis and allows using the theoretical model for empirical purposes, namely, the real estate appraisals. Design/methodology/approach – This work is both theoretical and empirical. Theoretically, a long-run equilibrium model with a positive share of vacant houses and home seekers is determined along with price and market tightness. Also, the conditions of existence and uniqueness of the steady-state equilibrium are determined. Unlike most of the search-and-matching models in the housing literature, the out-of-the steady-state dynamics are also analyzed to show the stability of the equilibrium. Empirically, to show the usefulness of the theoretical model, a numerical simulation is performed. By using two readily available housing market data – the expected time on the market and the average number of trades – it is possible to determine the key variables of the model: price, market tightness and matching opportunities for both buyers and sellers. Although the numerical simulation concerns the Italian housing market, the proposed model is generally valid, being empirically applicable to all real estate markets characterized by non-negligible trading frictions. Indeed, the proposed model can be used to compare housing markets with different features (concerning the search and matching process), as well as analyse the same housing market in different time periods (because the efficiency of the search and matching process can change). Findings – Several important results are obtained. First, the price adjustment – i.e. the difference between the actual selling price and the price obtained in an ideal situation of frictionless housing market – is remarkable. This means that the sign and the size of the price adjustment depend on the extent of trading frictions in the housing market. Precisely, the higher the trading frictions on the demand side (more buyers and less sellers), the higher the actual selling price (the price adjustment is positive), whereas the higher the trading frictions on the supply side (less buyers and more sellers), the lower the actual selling price (the price adjustment is negative). Accordingly, the real estate appraisers should assess the trading frictions in the housing market before determining the price adjustment. Second, an increase in the number of trades affects the house price only if the time on the market varies. Also, the higher the variation in the time on the market, the larger the house price adjustment. Indeed, the expected time on the market reflects the opportunities to matching for both parties and thus the trading frictions. If the time on the market increases (decreases), the seller will receive less (more) opportunities to match; thus, the actual selling price will be driven downwards (upwards). Originality/value – As far as the authors are aware, none of the existing works in the search and matching literature has considered how to take advantage of this theoretical approach to estimate the house price in the presence of trading frictions in the housing market. Indeed, the proposed theoretical model may be a useful tool for real estate appraisers, as it is able to derive the trading frictions from the time on the market and the number of trades, thus estimating properly the house price.
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Gabrovski, Miroslav, and Victor Ortego-Marti. "Search and credit frictions in the housing market." European Economic Review 134 (May 2021): 103699. http://dx.doi.org/10.1016/j.euroecorev.2021.103699.
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Gallent, Nick, and Matthew Carmona. "Planning for housing: Unravelling the frictions in local practice." Planning Practice and Research 19, no. 2 (May 2004): 123–46. http://dx.doi.org/10.1080/0269745042000284386.
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Xiao, Wei. "SEARCH FRICTIONS, UNEMPLOYMENT, AND HOUSING IN CITIES: THEORY AND POLICIES." Journal of Regional Science 54, no. 3 (January 15, 2014): 422–49. http://dx.doi.org/10.1111/jors.12098.
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Dorofeenko, Viktor, Gabriel S. Lee, and Kevin D. Salyer. "Rationale Erklärungen für Immobilienpreis-Bubbles: Die Auswirkungen von Risikoschocks auf die Wohnimmobilienpreisvolatilität und die Volatilität von Investitionen in Wohnimmobilien." Perspektiven der Wirtschaftspolitik 12, no. 2 (May 2011): 151–69. http://dx.doi.org/10.1111/j.1468-2516.2011.00361.x.
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AbstractThe dramatic world-wide housing boom and bust cycles during the last few years are often described in the media as “bubbles” and were largely caused by irrational exuberance due to the liberalization of housing finance (i.e. credit market irregularities in the U.S.: the subprime markets and mortgage structured products). Following Dorofeenko et al (2011), this paper, however, argues that many of the business and housing stylized facts, especially, the U.S. housing price and residential investment volatilites can be explained by analyzing the role of uncertainty (risk) in the framework of a Real Business Cycle model that includes a housing sector with financial information frictions. Consequently, we show for the U.S., these large housing price and residential investment boom and bust cycles are at least were driven largely by economic fundamentals with irrationality (or psychology) at most in the background.
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Garriga, Carlos, and Aaron Hedlund. "Mortgage Debt, Consumption, and Illiquid Housing Markets in the Great Recession." American Economic Review 110, no. 6 (June 1, 2020): 1603–34. http://dx.doi.org/10.1257/aer.20170772.
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Using a quantitative heterogeneous agents macro-housing model and detailed microdata, this paper studies the drivers of the 2006–2011 housing bust, its spillovers to consumption and the credit market, and the ability of mortgage rate interventions to accelerate the recovery. The model features tenure choice between owning and renting, rich portfolio choice, long-term defaultable mortgages, and endogenously illiquid housing from search frictions. The equilibrium analysis and empirical evidence suggest that the deterioration in house prices and liquidity, transmitted to consumption via balance sheets that vary in composition and depth, is central to explaining the observed aggregate and cross-sectional patterns. (JEL E23, E32, E44, G21, R31)
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Landvoigt, Tim, Monika Piazzesi, and Martin Schneider. "The Housing Market (s) of San Diego." American Economic Review 105, no. 4 (April 1, 2015): 1371–407. http://dx.doi.org/10.1257/aer.20111662.
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This paper uses an assignment model to understand the cross section of house prices within a metro area. Movers’ demand for housing is derived from a life-cycle problem with credit market frictions. Equilibrium house prices adjust to assign houses that differ by quality to movers who differ by age, income, and wealth. To quantify the model, we measure distributions of house prices, house qualities, and mover characteristics from micro-data on San Diego County during the 2000s boom. The main result is that cheaper credit for poor households was a major driver of prices, especially at the low end of the market. (JEL D14, D91, R21, R31)
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Arestis, Philip, and Rosa Gonzalez-Martinez. "Housing market in Israel: Is there a bubble?" Panoeconomicus 64, no. 1 (2017): 1–16. http://dx.doi.org/10.2298/pan1701001a.
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House prices in Israel have registered unprecedented growth rates in the last few years. At first glance, these hikes could be explained by the evolution of fundamentals such strong population growth and favourable macroeconomic conditions, i.e. low interest rates. However, further investigation is needed in order to explore whether there is a misalignment between house prices and their fundamentals. Firstly, this paper investigates the role of construction costs in the evolution of house prices. Secondly, this contribution decomposes the ?price-to-rent? ratio into fundamentals, frictions and bubble episodes for a better understanding of the recent trends of the market.
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Ambrus, Attila, Erica Field, and Robert Gonzalez. "Loss in the Time of Cholera: Long-Run Impact of a Disease Epidemic on the Urban Landscape." American Economic Review 110, no. 2 (February 1, 2020): 475–525. http://dx.doi.org/10.1257/aer.20190759.
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How do geographically concentrated income shocks influence the long-run spatial distribution of poverty within a city? We examine the impact on housing prices of a cholera epidemic in one neighborhood of nineteenth century London. Ten years after the epidemic, housing prices are significantly lower just inside the catchment area of the water pump that transmitted the disease. Moreover, differences in housing prices persist over the following 160 years. We make sense of these patterns by building a model of a rental market with frictions in which poor tenants exert a negative externality on their neighbors. This showcases how a locally concentrated income shock can persistently change the tenant composition of a block. (JEL D62, O18, R21, R31)
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Bhutta, Neil, and Benjamin J. Keys. "Interest Rates and Equity Extraction During the Housing Boom." American Economic Review 106, no. 7 (July 1, 2016): 1742–74. http://dx.doi.org/10.1257/aer.20140040.
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Credit record panel data from 1999–2010 indicates that the likelihood of home equity extraction (borrowing, on average, about $40,000 against one's home) peaked in 2003 when mortgage rates reached historic lows. We estimate a 27 percent rise in extraction in response to a 100 basis point rate decline, and that house price growth amplifies this relationship. Differential responses to interest rates and home price appreciation by borrower age and credit score provide new evidence of financial frictions. Finally, equity extractions are associated with higher default risk, consistent with the use of borrowed funds for consumption or illiquid investment. (JEL D14, E43, E52, G12, R31)
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Giglio, Stefano, Matteo Maggiori, and Johannes Stroebel. "Reply to “Rational Bubbles in UK Housing Markets”." Econometrica 88, no. 4 (2020): 1767–70. http://dx.doi.org/10.3982/ecta18174.
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In Giglio, Maggiori, and Stroebel (2016), we propose and implement a new test for classic rational bubbles. Such bubbles derive their value from each agent's rational expectation of being able to resell the bubble claims to the next agent. Backward induction ensures that classic rational bubbles can only exist on infinite‐maturity assets. Our empirical exercise shows that infinite‐maturity claims and 999‐year claims for otherwise identical housing assets trade at the same price, and thus rules out the presence of classic rational bubbles. Domeij and Ellingsen (DE) informally propose an alternative equilibrium of a bubble that they claim is consistent with our empirical findings. DE's bubble relies on information frictions such that market participants are unaware of the bubble. Our paper clearly excluded this type of bubble from the scope of our test, and DE's note thus has no implications for the validity of our test. Instead, DE's bubble simply represents one of many possible examples of bubbles on which our test was explicitly silent.
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Graff, Richard A. "Measuring performance of US homeownership policies past and present." International Journal of Housing Markets and Analysis 11, no. 1 (February 5, 2018): 173–203. http://dx.doi.org/10.1108/ijhma-05-2017-0051.
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Purpose The past century and a quarter can be divided into three successive eras for homeownership policy characterization. For the first four decades, the federal government pursued a laissez-faire policy that left housing issues to the individual states and private markets. For the next six decades, the federal government implemented a policy created as part of the Roosevelt New Deal program. Finally, the Clinton administration discarded the New Deal policy in favor of a more aggressive policy that has continued to the present day. The purpose of this study is to compare the performance of the respective policies. Design/methodology/approach The study introduces two metrics. The first metric, based on government homeownership rate data, enables comparison of the laissez-faire and New Deal policies. The second metric, based on financial frictions in the mortgage market, enables comparison of the New Deal and Clinton policies. Findings Analysis based on the first metric suggests the New Deal policy was successful in meeting its macroeconomic objectives and was more effective overall than the laissez-faire policy. Analysis based on the second metric suggests the New Deal policy was also more successful in both respects than the Clinton policy. Practical implications The findings suggest that the Clinton homeownership policy was the primary driver behind the recent US housing crisis and that vulnerability in the secondary mortgage market created by the Clinton policy represents systemic housing market risk. Originality/value The study introduces simple analytical tools to address problems related to systemic risk in the US housing and housing finance markets due to homeownership policy.
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Arestis, Philip, Ana Rosa Gonzalez-Martinez, and Lu-kui Jia. "House price overvaluation in Hong Kong." International Journal of Housing Markets and Analysis 10, no. 2 (April 3, 2017): 282–304. http://dx.doi.org/10.1108/ijhma-01-2016-0003.
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Purpose The purpose of this paper is twofold. First, the authors investigate the main drivers of house prices in the Hong Kong housing market. Second, further research is undertaken to confirm the existence of house price overvaluation, which has driven the market into a bubble episode. Design/methodology/approach First, the authors propose a theoretical framework to identify the fundamentals of the market. In the second step, they decompose house prices into fundamentals, frictions and bubble episodes for a better understanding of the evolution of house prices during the period 1996(Q3)-2013(Q3). Findings The results of this paper suggest an eventual possible correction of up to 46 per cent of house prices with respect to their 2013(Q3) level. Originality/value The originality of this paper is to use the procedure developed by Glindro and Delloro (2010) to analyse the Hong Kong housing market. The contribution of this paper also modifies the original Glindro and Delloro’s (2010) approach by including the Christiano and Fitzgerald (2003) filter to decompose house prices.
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Cortés Zulueta, Concepción. "Hermit Crabs as Emergent Icons of Global Waste Epidemic and Their Unreal Estate Housing Struggles." Society & Animals 27, no. 7 (December 11, 2019): 697–715. http://dx.doi.org/10.1163/15685306-00001839.
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AbstractA hermit crab housed in a broken glass bottle or inside a plastic cap is becoming like a polar bear stranded on a tiny, melting iceberg: those pictures are emergent icons of the plight faced by oceans and creatures, caused by human waste excesses and wrongdoings. These inventive crustaceans fulfill a warning role akin to charismatic megafauna, and induce empathy with varied sources, dominated by human projections like the housing crisis metaphor. Crabs emerge like a cluster where many opposed notions collapse, while they stage the frictions of a complex, fractured balance. They are wild animals, and controversial companion animals, and when they live inside human trash, they show resilience that questions the natural-artificial divide. Simultaneously, they remind humans of strains imposed upon them, the oceans, and the planet, becoming tokens of the unbalances with which humans have to deal in their often-misguided attempts to fix the things they are rupturing.
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López-Gaviria, José Ignacio. "Predictibilidad del mercado accionario colombiano." Lecturas de Economía, no. 91 (July 17, 2019): 117–50. http://dx.doi.org/10.17533/udea.le.n91a04.
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This paper studies historical stock market returns in Colombia and their medium- and long-term predictability with the purpose of examining whether there is a constant or time-varying risk premium and its relationship with other economic variables. With this goal in mind, the paper presents a historical price index, returns and the aggregate dividend yield of Colombia’s stock market for the 1995-2017 period, using information for the whole universe of issuers. Most of the variation in the dividend yield is explained by expected returns, which implies that the stock market has medium- and long-term cycles and the risk premium is time varying. The predictive power of the model increases if extended to include information on housing finance, the real exchange rate and returns of the S&P 500 index, suggesting that credit frictions and small open economy considerations could play a role when modelling risk premium in Colombia’s stock market.
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Jenks, Hillary. "Bronzeville, Little Tokyo, and the Unstable Geography of Race in Post-World War II Los Angeles." Southern California Quarterly 93, no. 2 (2011): 201–35. http://dx.doi.org/10.2307/41172572.
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The Japanese residents and proprietors of Los Angeles' Little Tokyo were forcibly evacuated in 1942. The district filled up with African Americans denied housing elsewhere. Its wartime name was Bronzeville. In 1945 when Japanese internees were allowed to return, the two communities, each with a history of race-based dislocations, made efforts to accommodate each other in a biracial "Little Bronze Tokyo." The efforts and frictions were reflected in the columns written by Nisei Hisaye Yamamoto in the pages of the Tribune, a black newspaper. A second evacuation in 1950 of part of the district for the construction of a new police headquarters injured the returning Japanese community but devastated what was left of Bronzeville. Bronzeville ceased to exist less from disputes between African and Japanese Americans than as a result of racist spatial practices by local government. In the immediate post-war period, however, both competitive and coalitional approaches to multiracialism made possible a biracial landscape. Both communities learned from the brief experience of "Little Bronze Tokyo."
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Hall, Robert E. "The Long Slump." American Economic Review 101, no. 2 (April 1, 2011): 431–69. http://dx.doi.org/10.1257/aer.101.2.431.
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In a market-clearing economy, declines in demand from one sector do not cause large declines in aggregate output because other sectors expand. The key price mediating the response is the interest rate. A decline in the rate stimulates all categories of spending. But in a low-inflation economy, the room for a decline in the rate is small, because of the notorious lower limit of zero on the nominal interest rate. In the Great Depression, substantial deflation caused the real interest rate to reach high levels. In the Great Slump that began at the end of 2007, low inflation resulted in an only slightly negative real rate when full employment called for a much lower real rate because of declines in demand. Fortunately, the inflation rate hardly responded to conditions in product and labor markets, else deflation might have occurred, with an even higher real interest rate. I concentrate on three closely related sources of declines in demand: the buildup of excess stocks of housing and consumer durables, the corresponding expansion of consumer debt that financed the buildup, and financial frictions that resulted from the decline in real-estate prices. (JEL E23, E24, E31, E32, E65)
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Golubev, Alexey, and Irina Takala. "The Harsh Reality of Fine Words: The Daily Implementation of Immigration Policies in Soviet Karelia." Journal of Finnish Studies 15, no. 1-2 (December 1, 2011): 126–46. http://dx.doi.org/10.5406/28315081.15.1.2.09.
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Abstract This article considers the immigration of North American Finns to Soviet Karelia through the prism of daily life. It focuses on how governmental directives were implemented at the local level, and how the challenges of daily life forced the immigrants to re-evaluate the decision to move eastwards across the Atlantic, as well as the socialist project in general. In the first section, the article examines the motives of the immigrants with an emphasis on frictions between multiple Soviet state agencies. Since the motives of these agencies were different and sometimes directly contradictory to one another, the organization of immigration was from the very beginning plagued with inefficient management, indifference to arriving immigrants, and negligence of the conditions in which the immigrants were to live and work. The article discusses the conditions of housing and work and food, the three main spheres in which the Soviet Karelian leadership failed to satisfy demands of the immigrants, primarily because a long bureaucratic chain of management was too inflexible to introduce effective solutions. The article then considers the immigrants’ responses to their dissatisfaction with daily life, from re-emigration to adaptation to attempts to improve the quality of life without relying on official assistance.
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Yang, Qiuyi, Youze Lang, and Changsheng Xu. "Is the High Interest Rate Combined with Intense Deleveraging Campaign Desirable? A Collateral Mechanism under Stringent Credit Constraints." Sustainability 10, no. 12 (December 16, 2018): 4803. http://dx.doi.org/10.3390/su10124803.
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Recently, China has witnessed a continuously increasing Debt-to-GDP ratio and a vigorously expanding shadow banking sector. Housing prices hovering at a high level seriously affect the lives of ordinary residents. Disappointingly, a variety of activities such as intense deleveraging campaigns and tight monetary controls produce little effect. Why do these seemingly rightful implementations hardly work? What should governments do to stop the incessant expansion of asset bubbles? What role ought financial supervisors to play in regulating credit markets and facilitating a sustainable and inclusive economic growth? This paper sets off from the pledgeability of asset bubbles and constructs a generalized overlapping generation (OLG) model incorporating financial frictions and collateral constraints, in order to explore the bubble evolution under the alterations of market interest rates and credit conditions. The results show a unique bubble equilibrium, in which the steady-state bubble size expands when interest rate increases. Numerical results further reveal that the bubble-inflation effect of a higher interest rate is reinforced by a more stringent collateral constraint. Our research contributes to an explanation of the inefficacy of present policies and provides the following policy implications: The combination of an interest rate elevation and a strong loan restriction is in fact undesirable for suppressing asset bubbles. Not merely does it strike productivity and capital formation, but it also fosters investors to hold more risky assets to solve liquidity shortage under constrained borrowing capacity.
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Alisin, V. V. "Improving the antifriction properties of the housing-rotor coupling in axial turbomachines." Journal of Physics: Conference Series 2094, no. 4 (November 1, 2021): 042039. http://dx.doi.org/10.1088/1742-6596/2094/4/042039.
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Abstract The article discusses the frictional interaction of carbon-carbon composite material on steel. Antifriction properties and wear resistance of the material under dry friction at speeds up to 100 m/s are investigated. The effect of velocity and contact pressure on the friction coefficient and wear resistance of a carbon composite is analyzed. The regularities of the change in the coefficient of friction are determined depending on the load-speed factors. The assumption is substantiated that the high thermal stability of the carbon composite, its low hardness, good antifriction properties and high wear resistance allow the material to be used in friction units operating at very high speeds and temperatures. In order to improve the reliability and reduce gas flows in axial turbomachines, on the basis of the study carried out, it is recommended that instead of heat-resistant coatings, a lining of the gas duct casing should be made of carbon composite.
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Alisin, V. V. "Antifriction properties of ceramic materials under high-speed sliding process." Journal of Physics: Conference Series 2094, no. 5 (November 1, 2021): 052062. http://dx.doi.org/10.1088/1742-6596/2094/5/052062.
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Abstract The issues of tribology of a composite cermet material under high-speed short-term dry sliding friction process are discussed in this article. The possibility of reducing the friction coefficient due to the processing of cermet with selenium vapor is substantiated. Model experiments were carried out on a laboratory friction machine according to the pin-on-disk test at sliding speeds up to 100 m/s. Experimental dependences of the coefficient of friction on speed, load and the effect of mechanical properties on friction and wear of a friction couple are analyzed. These studies were based on the assumption about the possibility of reducing the friction coefficient of cermet by processing in chalcogen vapor and restoring the antifriction properties of the resulting lubricating film with an increase in temperature from friction heating of friction surfaces. It is proposed to carry out processing in chalcogen vapors of thermal protection ceramic coatings of the housings of the axial machines gas path, in particular, in aircraft engines. This technological process in conditions of emergency contact of the housing with the blades of the rapidly rotating disk will reduce the risk of engine destruction with catastrophic consequences.
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Da˛browski, Leszek, and Michał Wasilczuk. "A Method of Friction Torque Measurement for a Hydrodynamic Thrust Bearing." Journal of Tribology 117, no. 4 (October 1, 1995): 674–78. http://dx.doi.org/10.1115/1.2831534.
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Measurements of thrust bearing friction torque are difficult because of the small values of the friction force in comparison with the axial load. Another problem of a thrust bearing test rig design is the necessity of accommodation of the axial load so that it does not interact with the frictional forces. Separation of fluid drag in the housing from torque in the bearing itself is also important. An analysis of a design in which the above-mentioned problems have been solved is presented. Theoretical analysis and calibration of the torque meter proved that the effect of axial load was successfully compensated for. Example of the results obtained due to the torque meter illustrate the application of the new design.
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Sharma, Arvind, Uttara Kennedy, and Clive Phillips. "A Novel Method of Assessing Floor Friction in Cowsheds and Its Association with Cow Health." Animals 9, no. 4 (March 27, 2019): 120. http://dx.doi.org/10.3390/ani9040120.
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Measurement of friction of cowshed floors to determine slipperiness potential is important for cow comfort. Existing methods require elaborate equipment and procedures. A quick method for assessment of friction characteristics is proposed. Friction was measured in 54 cattle housing and yard facilities with earth, brick, concrete, and stone floors, and its association with cattle health parameters was investigated through assessment of 30 animals per facility. A 156 g cuboidal wooden block attached to a spring balance was pulled over 3 m, and the coefficient of friction was recorded as the force required to move the block at a constant speed. The coefficient of friction ranged from 0.3 to 0.7 and was lowest for concrete and highest for earth floors. A multivariate analysis found that cows were standing more and could be more easily approached when they were on floors with high friction levels. The proportion of cows with dirty hind limbs declined with increasing friction of the floor, probably reflecting the fact that they felt more confident to stand rather than lie on high friction floors. This simple measure of frictional characteristics of cattle floors offers promise to be included in welfare measures as an indicator of cow welfare.
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Dämmer, Gabriel, Hartmut Bauer, Rüdiger Neumann, and Zoltan Major. "Design, additive manufacturing and component testing of pneumatic rotary vane actuators for lightweight robots." Rapid Prototyping Journal 28, no. 11 (May 13, 2022): 20–32. http://dx.doi.org/10.1108/rpj-03-2021-0052.
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Purpose This study aims to investigate the suitability of a multi-step prototyping strategy for producing pneumatic rotary vane actuators (RVAs) for the development of lightweight robots and actuation systems. Design/methodology/approach RVAs typically have cast aluminum housings and injection-molded seals that consist of hard thermoplastic cores and soft elastomeric overmolds. Using a combination of additive manufacturing (AM), computer numerical control (CNC) machining and elastomer molding, a conventionally manufactured standard RVA was replicated. The standard housing design was modified, and polymeric replicas were obtained by selective laser sintering (SLS) or PolyJet (PJ) printing and subsequent CNC milling. Using laser-sintered molds, actuator seals were replicated by overmolding laser-sintered polyamide cores with silicone (SIL) and polyurethane (PU) elastomers. The replica RVAs were subjected to a series of leakage, friction and durability experiments. Findings The AM-based prototyping strategy described is suitable for producing functional and reliable RVAs for research and product development. In a representative durability experiment, the RVAs in this study endured between 40,000 and 1,000,000 load cycles. Frictional torques were around 0.5 Nm, which is 10% of the theoretical torque at 6 bar and comparable to that of the standard RVA. Models and parameters are provided for describing the velocity-dependent frictional torque. Leakage experiments at 10,000 load cycles and 6 bar differential pressure showed that PJ housings exhibit lower leakage values (6.8 L/min) than laser-sintered housings (15.2 L/min), and PU seals exhibit lower values (8.0 l/min) than SIL seals (14.0 L/min). Combining PU seals with PJ housings led to an initial leakage of 0.4 L/min, which increased to only 1.2 L/min after 10,000 load cycles. Overall, the PU material used was more difficult to process but also more abrasion- and tear-resistant than the SIL elastomer. Research limitations/implications More work is needed to understand individual cause–effect relationships between specific design features and system behavior. Originality/value To date, pneumatic RVAs have been manufactured by large-scale production technologies. The absence of suitable prototyping strategies has limited the available range to fixed sizes and has thus complicated the use of RVAs in research and product development. This paper proves that functional pneumatic RVAs can be produced by using more accessible manufacturing technologies and provides the tools for prototyping of application-specific RVAs.
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Fuyama, Nobuyuki, Akira Terayama, Toshio Fujii, Hajime Tani, Shinji Danjo, and Gen Sasaki. "Properties of Small Rotary Engine Housing Fabricated by Aluminum Alloy Matrix Composites." Materials Science Forum 638-642 (January 2010): 933–38. http://dx.doi.org/10.4028/www.scientific.net/msf.638-642.933.
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To develop the small engine used for the wireless control helicopter, a very high power density source will be required. The rotary engine (RE) is advantageous in the points such as a volume of the engine, the exhaust gas emissions, and the vibrations. In this research, in order to develop the small RE, the design of the combustion chamber was reviewed. Additionally, the method of the surface treatment of the rotor housing was investigated by the friction wear test to enable the material substitution for aluminum matrix composites. The friction wear tests of composite materials, the Cr and Ni-plated material were conducted. As a result, the sample with the most excellent abrasion resistance was the composite material reinforced with Al2O3 fibers. The wear-loss of this composite material was 1/10 compared with the Ni-plated material. This composite material formed oil pockets between the fiber and the matrix, and a friction coefficient fell below 0.1. Then, the aluminum rotor housing reinforced partially by Al2O3 fiber was fabricated using a low-pressure infiltration method. The maximum power of the small RE (1 rotor, 30 cc) which built in this housing reached about 5 PS in the range from 13,000 to 15,000 rpm. The inside of the housing used composite materials was not damaged even after 30 hours. On the other hand, the flaking off part was observed on the inside part in the case with the housing used the Ni-plated material. Additionally, the output and the torque of the RE made of composite materials were higher than those of the Ni-plated material. This was considered because the friction coefficient of composite materials was lower than that of the Ni-plated material. Finally, the small unmanned helicopter equipped with RE succeeded in a stable flight.
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Hogg, Tad, Matthew S. Moses, and Damian G. Allis. "Evaluating the friction of rotary joints in molecular machines." Molecular Systems Design & Engineering 2, no. 3 (2017): 235–52. http://dx.doi.org/10.1039/c7me00021a.
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Emery, A. F., S. Deckers, and B. K. Jones. "Design and Analysis of Explosively Actuated Valves: The Interaction of the Plunger and the Housing." Journal of Mechanical Design 117, no. 2A (June 1, 1995): 215–20. http://dx.doi.org/10.1115/1.2826125.
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Explosive values are generally composed of a tapered plunger which is explosively driven along the bore of a cylindrical housing and forced to stop at a location designed to alter a particular fluid flow configuration. The stopping point of the plunger is determined primarily by the friction between the plunger and the housing and the axial forces exerted on the taper. One way of calculating these forces is to model the valve as a series of thin disks and to assume an interference fit between the disks of the plunger and the disks of the housing. A previous paper described the modification necessary to account for plastic deformations and strain hardening of nontapered plungers. These modifications are not sufficient when considering tapered hollow plungers. This paper compares the disk model predictions with measured performances and shows that the differences are primarily due to the unusually high pressures developed at the interface between the plunger and the housing. These high pressures are shown to be the result of axial stresses induced by bending of the housing. Likewise, it is shown that the axial stresses induced by the bending of the hollow plunger walls has a significant effect upon the value of the coefficient of friction needed to achieve acceptable simulations.
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Habieb, Ahmad Basshofi, Gabriele Milani, Tavio Tavio, and Federico Milani. "Low Cost Frictional Seismic Base-Isolation of Residential New Masonry Buildings in Developing Countries: A Small Masonry House Case Study." Open Civil Engineering Journal 11, no. 1 (December 29, 2017): 1026–35. http://dx.doi.org/10.2174/1874149501711011026.
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Introduction:An advanced Finite Element model is presented to examine the performance of a low-cost friction based-isolation system in reducing the seismic vulnerability of low-class rural housings. This study, which is mainly numerical, adopts as benchmark an experimental investigation on a single story masonry system eventually isolated at the base and tested on a shaking table in India.Methods:Four friction isolation interfaces, namely, marble-marble, marble-high-density polyethylene, marble-rubber sheet, and marble-geosynthetic were involved. Those interfaces differ for the friction coefficient, which was experimentally obtained through the aforementioned research. The FE model adopted here is based on a macroscopic approach for masonry, which is assumed as an isotropic material exhibiting damage and softening. The Concrete damage plasticity (CDP) model, that is available in standard package of ABAQUS finite element software, is used to determine the non-linear behavior of the house under non-linear dynamic excitation.Results and Conclusion:The results of FE analyses show that the utilization of friction isolation systems could much decrease the acceleration response at roof level, with a very good agreement with the experimental data. It is also found that systems with marble-marble and marble-geosynthetic interfaces reduce the roof acceleration up to 50% comparing to the system without isolation. Another interesting result is that there was little damage appearing in systems with frictional isolation during numerical simulations. Meanwhile, a severe state of damage was clearly visible for the system without isolation.
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Gorodilov, L. V., V. G. Kudryavcev, and A. I. Pershin. "A physical model and a stand for the research of a single-acting hydroimpact device." Interexpo GEO-Siberia 2, no. 3 (May 18, 2022): 265–69. http://dx.doi.org/10.33764/2618-981x-2022-2-3-265-269.
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The paper presents a physical model of a single-acting hydroimpact device. Its design can be used to create a hydraulic punch for drilling wells in soft soils. A stand with a clamping device has been developed to simulate the friction force acting on the punch housing when it moves in the soil. Methods of recording dynamic characteristics of working cycles of the hydraulic device are worked out. Tests were carried out with changes in the force acting on the housing from the clamping device. Oscillograms of the characteristics of working cycles (displacements of the housing and striker, pressures in the working chambers and the accumulator) are given.
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Chichekin, I. V., and A. A. Shuranova. "Modeling the work of the automotive differential with internal friction in the system for calculating the multi body dynamics." Izvestiya MGTU MAMI 15, no. 4 (December 15, 2021): 73–82. http://dx.doi.org/10.31992/2074-0530-2021-50-4-73-82.
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The work is devoted to the operation of an automobile differential of suspended friction modeling in the system for calculating the dynamics of coupled bodies. The model was developed in the RecurDyn application for calculating the dynamics of rigid and deformable bodies from the FunctionBay company.
The aim of the work is to develop a mathematical model of the differential with friction washers and to confirm the adequacy of its operation. The developed mathematical model of the differential is tested for the possibility of its subsequent use in modeling the transmission of a vehicle in the calculating the dynamics of coupled bodies system. In this work, a model of the differential has been created and described in detail. The model was used for the analysis of kinematics and dynamics. Methods of modeling a simple symmetric differential and a self-locking one are shown based on one mathematical model. The well-known analytical dependences describing the kinematic and force laws of the ratio of angular velocities and torques between the output links and the differential housing are given. A method for calculating and modeling the friction torque in the differential was selected and described. An equation describing the frictional moment in the differential is presented.
A virtual test bench was developed and described. Afterwards it was used for differential operation simulation. Load modes that are equivalent to various driving conditions of a real automobile are selected, their quantitative parameters are given. In this work, the criteria for evaluating the performance of the differential model are selected. The results of modeling for all load modes are given. According to those results the adequacy of the developed mathematical model of the differential with friction washers is proved. The proposals on the use of the developed model are given.
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LEPIARCZYK, Dariusz, and Wacław GAWĘDZKI. "VIBRATION DIAGNOSTIC OF A FRICTION PROCESS IN SLIDE BEARINGS." Tribologia 278, no. 2 (May 1, 2018): 73–80. http://dx.doi.org/10.5604/01.3001.0012.6978.
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An analysis of the condition of technical objects is carried out by diagnostic systems, the purpose of which is to detect irregularities in their operation and to prevent damages. In slide bearings, it applies to the diagnostic of friction and thermal phenomena of mating friction pairs. Among many methods of bearing diagnostics, special attention should be paid to vibration diagnostic methods based on measurements of relative vibration parameters or on absolute vibration (displacement, velocity, or acceleration of vibration). Methods of the vibration diagnostic of bearings rely on periodic or continuous measurements of relative vibration parameters of the bearing housing in relation to the rotor (in the case of slide bearings the measurements of the bearing sleeve in relation to the shaft neck) or absolute vibration parameters of the bearing housing (i.e. the sleeve in the case of slide bearing). The article presents a method of vibration diagnostics of friction phenomena that occur during the operation of slide bearings under various lubrication and load conditions. There are presented methods of analysis and the interpretation of measurement data obtained as a result of the conducted slide bearing tests on the laboratory stand. A method for assessing a technical condition of the slide bearing friction pairs is proposed.
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Woo, Gui Aee, Jeong Woo Jeon, Ki Chang Lee, and Young Joo Kim. "Evaluation of the Friction Coefficient from the Dynamometer Test of the Aircraft." Key Engineering Materials 277-279 (January 2005): 757–64. http://dx.doi.org/10.4028/www.scientific.net/kem.277-279.757.
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The friction force is the most important factor for the design of control unit in a braking system. For a long time, many researchers have been striving to improve the accuracy in the measurements of friction coefficients [1,2]. However, there were many difficulties because the friction coefficients are affected by a number of conditions and parameters, such as normal force, temperature, characteristics of road condition, and weather. For the development of ABS of the aircraft, the HILS (Hardware-In-the-Loop-Simulation) test and dynamometer test were carried out. For the calculation of the friction coefficients, the wheel moment was measured using the load cell mounted on the housing of the wheel. The test conditions were dry and greasy, with friction coefficients of 0.7 and 0.4, respectively. In this paper, the test results of the friction coefficients were represented and the improvement method was suggested.
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Mäntylä, Antti, Jussi Göös, Anton Leppänen, and Tero Frondelius. "Large bore engine connecting rod fretting analysis." Rakenteiden Mekaniikka 50, no. 3 (August 21, 2017): 239–43. http://dx.doi.org/10.23998/rm.64914.
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A detailed contact analysis of a large connecting rod was performed to evaluatethe fretting risk in the big end. Simulation was carried out in Abaqus considering all relevantboundary conditions, such as assembly loads, housing machining and dynamics from a exiblemultibody simulation with elastohydrodynamic bearings. Being one of the most importantvariables, the local coeffcient of friction (COF) and its evolution is calculated during the solutionby using a subroutine in Abaqus. The model is validated by strain gauge measurements in arunning engine. The resulted friction coefficient distribution matches well with the ndings froma laboratory engine. The described methodology increases the accuracy of the fretting damageprediction by using a more realistic friction coefficient denition.
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Yang, Yi, and Shan Li. "Simulation and Empirical Analysis on Real Estate Prediction Based on Friction Model." Applied Mechanics and Materials 716-717 (December 2014): 474–78. http://dx.doi.org/10.4028/www.scientific.net/amm.716-717.474.
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Based on the housing holding cost model, this paper obtains the causes of real estate price expectations, and analyzes the four factors which affects real estate price expectations from the theory: the supply side, demand side, the local government and some main monetary policy variables. Combined with the actual situation in Chinese real estate market this paper puts forward the corresponding hypothesis. The empirical results show that the main source of housing prices driving force is the demand side, while the impact of local government on prices is not obvious; the effect of supply side and monetary policy on house prices is relatively small. The nominal interest rate has no significant effect on prices, and the real interest rate has more obvious effect. Based on the empirical conclusions, this paper puts forward the corresponding policy suggestion of houses prices expectation management.
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Ahmad, Shakeel, Farrukh Ghani, and Md Raghib Adil. "Seismic friction base isolation performance using demolished waste in masonry housing." Construction and Building Materials 23, no. 1 (January 2009): 146–52. http://dx.doi.org/10.1016/j.conbuildmat.2008.01.012.
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Zhang, Shuai, Jinxiang Liu, and Yang Zhou. "A Research of Ti Doped DLC Housing on the Friction Loss in Small Wankel Rotary Engine." Xibei Gongye Daxue Xuebao/Journal of Northwestern Polytechnical University 37, no. 5 (October 2019): 977–82. http://dx.doi.org/10.1051/jnwpu/20193750977.
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Ti doped DLC coating was deposited on ductile iron disk commonly used material in small Wankel rotary engine. The friction coefficient under the working condition of apex seal was investigated. The results show that the Ti doped DLC coating is of low friction coefficient. In addition, the surface hardness and the morphology were improved by Ti doped DLC coating. After that, the Ti doped DLC coating was deposited on the housing. A performance testing platform for small Wankel rotary engine was built. The effect of Ti doped DLC coating under motored and working conditions were measured. The results show that when the operation speed varies from 7 000 to 17 000 r/min, the friction loss between apex seal and Ti doped DLC coating ranges 15~38 W under motored condition. It is only 68% of the friction loss between apex seal and ductile iron. Under working condition, the coating increases 23~78 W of the engine output power, which can improve the output power of small Wankel rotary engine by 24%~43%.
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Hua, Chang-I. "International Real Estate Review." International Real Estate Review 20, no. 4 (December 31, 2017): 397–416. http://dx.doi.org/10.53383/100248.
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This paper presents a structural model of nine equations that connect the unobserved housing service and the observed house transaction markets. Endogenous variables include two prices, supply, demand, stock of houses for sale on the market, average time on the market, stock of all houses, total vacant houses, and average house size. The search process of households for houses generates a stochastic process which results in an uncleared stock of houses on the market. The friction cost is specifically measured. The model should improve many practices in housing market research, and may be extended to other durable goods markets and beyond.
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Watanabe, Katsumi, Tsutomu Kawakatsu, and Shouichi Nakao. "Kinematic and Static Analyses of Tripod Constant Velocity Joints of the Spherical End Spider Type." Journal of Mechanical Design 127, no. 6 (January 27, 2005): 1137–44. http://dx.doi.org/10.1115/1.1909205.
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The closed-loop equations of three cylindrical rollers, the spider of three spherical ends, and the housing of the tripod constant velocity joints are deduced as the spatial mechanism. They are solved for prescribed positions of its input, and output shafts and relative motion characteristics of components are made clear. Moreover, a procedure is established for solving, simultaneously, the set of conditional equations with respect to forces and moments acting on three cylindrical rollers, the spider, and the housing, for any values of friction coefficients between cylindrical rollers and its grooves and spherical ends. The established numerical procedure simulates the normal force acting on the roller groove with a period of π and the housing thrust force with a period of 2π∕3 for given values of the joint angle. These results are inspected by experiments.
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Wang, Fengtao, Xin Ling, Zhen Zhang, Peng Dai, Shuping Yan, and Lei Wang. "The Effect of Fit Clearance between Outer Race and Housing on Vibration Characteristics of a Cylindrical Roller Bearing with Localized Defects." Machines 10, no. 6 (May 25, 2022): 415. http://dx.doi.org/10.3390/machines10060415.
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Due to bolt looseness or operating ambient temperature, fit clearance can often be found between the outer ring and housing. The vibration characteristics of a cylindrical roller bearing with localized defects are greatly affected by the fit clearance and the accuracy of bearing fault diagnosis may be reduced. Thus, a mathematical model for a cylindrical roller bearing was constructed and the interaction between the outer ring and housing was described. The classical localized defects were modeled, such as the inner ring defect, outer ring defect and roller defect. The relative experiments were conducted to check the constructed model. Then, it was found that the RMS (Root Mean Square) of housing acceleration decreased with increasing housing stiffness and viscous damping. When the fit clearance and friction coefficient increased, the RMS values increased. Except for housing stiffness and viscous damping, there were no uniform change rules of defect frequency amplitudes for other conditions. In the bearing with an outer ring defect or roller defect, the shock times of housing acceleration and the contact force between outer ring and housing were delayed, while fit clearance decreased. However, contrary variation trends were found for the inner ring defect. If the phase difference between defect location and rotor unbalanced force increased, the RMS and acceleration fluctuation amplitudes for the inner ring defect decreased. When the location angle of the outer ring defect increased, RMS and frequency amplitudes increased and RMSy/RMS decreased. The calculated results may provide the theoretical foundation for condition monitoring rotating machinery systems.
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Guzman, Leno J., Ying Chen, and Hubert Landry. "Discrete Element Modeling of Seed Metering as Affected by Roller Speed and Damping Coefficient." Transactions of the ASABE 63, no. 1 (2020): 189–98. http://dx.doi.org/10.13031/trans.13152.
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Abstract. The development of highly efficient seed metering is required to meet the demands of modern seeding equipment. The discrete element method (DEM) was used to simulate metering of seeds with a fluted roller meter. This approach was chosen due to its capability to accurately represent granular material flow. The contact model selected for the DEM simulation was the linear rolling resistance model. Angle of repose experimental tests and simulations were performed to calibrate the rolling friction coefficient for peas. The calibrated value for the rolling friction coefficient was 0.016. A 192 mm cross-section of an air cart seed roller and housing was defined as the domain of the simulation. Sensitivity analysis showed that simulated mass flow rates were not sensitive to the selected damping coefficients (0.2, 0.5, and 0.8). Sensitivity indicator values varied between -0.049 and 0.088 for the range of damping coefficients and roller speeds studied. The simulated geometry of the seed meter and housing resulted in a steady flow of seeds, with discharged mass increasing linearly. The simulated mass flow rates were 34.0, 72.3, 110.4, 147.3, and 182.0 g s-1 for roller speeds of 10, 20, 30, 40, and 50 rpm, respectively. An experiment was performed to validate the simulation results. The predicted mass flow rate values of the simulation were within 10 g s-1 of the experimental results, with the largest relative error being 16.5%. Keywords: DEM, Damping, Metering, Peas, Rolling friction coefficient, Seed, Simulation.
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Tu, Jay F., and Jeffrey L. Stein. "On-Line Preload Monitoring for Anti-Friction Spindle Beatings of High-Speed Machine Tools." Journal of Dynamic Systems, Measurement, and Control 117, no. 1 (March 1, 1995): 43–53. http://dx.doi.org/10.1115/1.2798522.
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Catastrophic and premature bearing failure caused by excessive thermally-induced bearing preload is a major design problem for spindle bearings in high-speed machine tools. Due to a lack of low cost and easy to maintain on-line preload measuring techniques, the traditional solution is to limit the maximum spindle speed and the initial bearing preload. This solution is incompatible with the trend of high-speed machining, which requires increasing both spindle speed and spindle stiffness. Therefore, it would be valuable if thermally-induced preload can be monitored on-line for regulating bearing thermal behavior at high speeds. This paper proposes using a dynamic state observer based on a preload model to estimate the spindle bearing preload via low cost thermocouples attached to the bearing outer ring and the spindle housing. The observer is based on a state-space model capable of describing the transient preload behavior of the spindle bearing. The temperatures of the outer ring and housing are used as the feedback signals for the preload observer. The observer gains are determined systematically to account for modeling errors, unknown parameters, nonlinearities, and measurement noise. In particular, the modeling errors due to unexpected factors such as bearing skidding, wear, and lubricant deterioration are compensated by a Modeling Error Compensator (MEC). By using the MEC, the error dynamics of the observer can be converted into a form suitable for applying existing observer techniques such as the Extended Kalman Filter (EKF). This preload observer has been successfully validated on two different bearing configurations operated at different speeds. The results show that the model-based monitoring technique, which combines the measurement of outer ring and housing temperature and a robust state observer, can be an effective and low-cost solution for preload monitoring in high-speed machine tools.
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Krasnowski, Krzysztof, Julia Khokhlova, Maksym Khokhlov, and Valery Kostin. "Relation between geometry of FSW tools and formation of nano- dispersed zones in macrostructure EN AW 6082-T6 alloy welded joints." Biuletyn Instytutu Spawalnictwa, no. 6 (2021): 7–16. http://dx.doi.org/10.17729/ebis.2021.5/1.
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An article present the result of macrostructure formation with distribution of mechanical properties in cross-sections of 8 mm-thick one-sided butt-welded FSW joints of EN AW 6082-T6 alloy which were obtained using three types of specially designed tools: C-type – conventional tool consisting of a housing, cylindrical threaded probe and a shoulder with a grooved spiral, T-type – Triflute-type tool consisting of a housing, cylindrical threaded probe with three grooves and a shoulder with a grooved spiral, S-type – simple tool consisting of a housing, smooth cylindrical probe without a thread and a flat shoulder. Friction stir welding was performed using equipment of the Institute of Welding in Gliwice of Poland, and mechanical tests in the E.O. Paton Electric Welding Institute of the NAS of Ukraine. Mechanical test by indentation was performed using Micron-gamma device, which allows experimental identification of structural state of metal and determination of the strain hardening presence by limiting values of ratio of hardness to Young’s modulus of elasticity. It was found that for all three specimens the HAZ hardness decreases, and in the zone of thermomechanical effect the hardness increases. Maximum hardness values are inherent to the central part of welded joint nugget, as well as to light-coloured oval concentrated fragments of structure in the nugget upper and lower part. Judging by the presence of nanosized hardened structure and uniformity of its distribution in the nugget, as well as good dispersion of oxide films and absence of discontinuities, the friction stir welding with C-type tool can be regarded as the optimum variant. An assumption was made that formation of a uniform structure in welds can be achieved at three–four revolutions of the tool in friction stir welding in one place. The model of thermal fields distribution in Al-plate during FSW using a C-type tool visualized the metal’s thermal condition when formated hardened nano-dispersed weld zones.
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Jiang, Hanjun. "Analysis of time-varying friction excitations in helical gears with refined general formulation." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 229, no. 13 (April 22, 2015): 2467–83. http://dx.doi.org/10.1177/0954406215583886.
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Time-varying sliding friction force and friction torque are regarded as non-negligible excitation sources of vibration and noise in gears. The sliding friction force primarily excites the motion along the off-line-of-action direction, which transmits vibration to the housing through shafts and bearings and then radiates noise. Since the contact line intersects with the pitch line, and the directions of the friction forces are opposite on both sides of the pitch line, the calculation of the friction excitations in helical gears becomes more difficult, especially in the high contact ratio helical gears. However, there is no universal method for calculating the friction excitations in helical gears with different range of contact ratio. The changes of friction excitations in helical gears are highly dependent on the geometric parameters such as helix angle and face width among others. Yet, there exist very limited studies on these topics. In this study, a refined general formulation for the calculation of time-varying contact line and friction excitations is proposed by assuming uniform load distribution along the contact lines with time-varying normal force and friction coefficient. Key gear parameters such as modification coefficient, helix angle, and face width are analyzed to illustrate their effects on the time-varying contact line and friction excitations. The results demonstrate that the refined general formulation is effective for the calculation of the friction excitations in helical gears with different range of contact ratio, and the parametric analysis could supply some guidance for choosing gear parameters in the design of helical gears to reduce the friction excitations.