bluuebunny/crossref_metadata_2025 huggingface dataset:
Regulation and the Valuation Relevance of Book Value and Earnings: Evidence from the United States*
Authors: NWAEZE EMEKA T.
Published: April 2010

Electric utilities in the United States are subject to a cost‐plus normal profits pricing that is designed to align the market value of equity with the balance sheet book value. Perfect alignment implies the equality of the market and book values. Extant empirical evidence suggests that, for these utilities, actual cost/profit recovery does not follow a pure cost‐plus pricing, raising the prospect that income statement items contribute to the determination of market value. What is not obvious is the extent to which the noted departure from pure cost‐plus pricing results in misalignment of the market and book values, or the relative contribution of income statement items to the valuation of electric utility shares. This study pursues this question, using benchmark results for a sample of manufacturing firms to highlight the degree of market‐to‐book alignment for regulated and competitive firms.

The results show a considerable alignment of the market and book values for utilities. In examining the relevance of book value and income statement items in the determination of market value, it is found that the contribution of earnings level to explaining market value diminishes markedly in the presence of book value for electric utilities, and the contribution of earnings change to explaining returns diminishes markedly in the presence of earnings levels. Earnings level complements book value in explaining market value for manufacturing firms, while earnings change complements earnings level in explaining returns. The results further show that the market and accounting values exhibit pronounced misalignments in returns‐earnings models, especially for utilities.
Analysts' Interpretation and Investors' Valuation of Tax Carryforwards*
Authors: AMIR ELI , SOUGIANNIS THEODORE
Published: April 2010

We examine how financial analysts and equity investors incorporate information on deferred taxes from carryforwards into earnings forecasts and share prices. We focus on carryforwards because, in providing this information each period, management must use their private information about the firm's profitability prospects. Thus, accounting measurement of tax carryforwards is another way of providing a management earnings forecast. In analyzing the role of carryforwards in valuation, we distinguish between two conflicting effects. First, deferred taxes from carryforwards represent future tax savings; hence, they should be valued positively as assets. In contrast, the existence of tax carryforwards may signal a higher likelihood of future losses, which would have a negative effect on expected earnings and share prices. We find that analysts consider earnings of firms with carryforwards to be less persistent because of the increased likelihood of future losses. We also find that analysts tend to be less precise and more optimistic (biased) in forecasting earnings of firms with carryforwards. This higher optimism and lower precision are more pronounced just after firms adopt Statement of Financial Accounting Standards (SPAS) 109 and are almost entirely corrected over time. An analysis of investors' valuation indicates a strong positive relation between deferred taxes from carryforwards and share prices, suggesting that these carryforwards are valued as assets. Also, earnings and book values of equity are valued less in firms that have carryforwards than in firms without carryforwards. Finally, the valuation allowance required under SFAS 109 assists equity investors in valuing a firm's earnings and net assets. The combined findings on analysts' interpretation and investors' valuation suggest that analysts fail to fully capture the implication of carryforwards on future earnings within their forecasting horizon.
Determinants of Funding Strategies and Actuarial Choices for Defined‐Benefit Pension Plans*
Authors: ASTHANA SHARAD
Published: April 2010

This paper examines the effects of firms' financial and pension profiles on their funding strategies and actuarial choices. The paper uses reports filed by individual pension plans with the Department of Labor under the requirements of the Employee Retirement Income Security Act of 1974 for the analysis. Evidence reported in the paper shows that as firms become overfunded, they make conservative actuarial choices to avoid visibility costs, and that as firms become underfunded, they make liberal actuarial choices to avoid visibility costs. As the annual contributions increase relative to the permissible contribution ranges, firms make conservative actuarial choices to minimize penalties and maximize tax benefits. As the annual contributions decrease relative to the permissible contribution ranges, firms make liberal actuarial choices to minimize penalties and maximize tax benefits. The larger the profitability, cash flow from operations, and tax liability, and the smaller the debt of a firm, the higher the likelihood that the firm's managers will make conservative actuarial choices to maximize contributions. Conversely, the smaller the profitability, cash flow from operations, and tax liability, and the larger the debt of a firm, the higher the likelihood that the firm's managers will make liberal actuarial choices to minimize contributions. This evidence, which is consistent with the hypothesis of funding management, can aid the Internal Revenue Service (IRS) in regulating the defined‐benefit pension plans more effectively and help plan beneficiaries to manage their retirement portfolios more efficiently. The debiasing method developed in the paper can provide investors and creditors with the tools to identify the discretionary components of pension liabilities and thereby value firms more efficiently.
Evidence That Management Discussion and Analysis (MD&A) is a Part of a Firm's Overall Disclosure Package*
Authors: CLARKSON PETER M. , KAO JENNIFER L. , RICHARDSON GORDON D.
Published: April 2010

The objective of this study is to investigate the role, if any, that management discussion and analysis (MD&A) plays in a firm's disclosure package. First, we present evidence regarding the usefulness of MD&A. Our evidence is uniformly supportive of the view that MD&A is a source of new and useful information and indicates that MD&A is used for financial analysis purposes by at least one significant user group, sell‐side analysts, who are members of the Toronto Society of Financial Analysts. We then provide evidence on disclosure quality. The results reveal that, overall, MD&A disclosure quality varies with disclosure stimuli similar to those found to influence disclosure choice in other disclosure channels. However, a more refined analysis of the MD&A subcomponents reveals that different factors influence disclosure quality for those subcomponents. Taken together, our results are consistent with the notion that MD&A is a part of a firm's overall disclosure package.
Accounting Accruals and Auditor Reporting Conservatism*
Authors: FRANCIS JERE R. , KRISHNAN JAGAN
Published: April 2010

Accounting accruals are managers' subjective estimates of future outcomes and cannot, by definition, be objectively verified by auditors prior to occurrence. This causes audits of high‐accrual firms to pose more uncertainty than audits of low‐accrual firms because of potential estimation error and a greater chance that high‐accrual firms have undetected asset realization and/or going concern problems that are related to the high level of accruals. One way that auditors can compensate for this risk exposure is to lower their threshold for issuing modified audit reports, an action that will increase modified reports and, therefore, lessen the likelihood of failing to issue a modified report when appropriate. We call this auditor reporting conservatism and test if high‐accrual firms in the United States, are more likely to receive modified audit reports for asset realization uncertainties and going concern problems. Empirical results for a large sample of U.S. publicly listed companies support the hypothesis that auditors are more conservative, that is, more likely to issue both types of modified audit reports for high‐accrual firms. Further analyses show that income‐increasing accruals are somewhat more likely to result in reporting conservatism than income‐decreasing accruals, and that only the Big Six group of auditors show evidence of reporting conservatism. These findings add to our understanding of the audit report formation process and the potentially important role played by accounting accruals in that process.
A Bargaining Model of Auditor Reporting*
Authors: ZHANG PING
Published: April 2010

In this paper, I demonstrate that the quasi‐rents earned in audits undermine an auditor's independence By considering the incentives of the auditor and the client and the interaction between them, I conclude that auditor will maintain his or her independence if the firm‐specific quasi‐rents are zero, but compromise his or her independence if the quasi‐rents are positive. The extent of the compromise is an increasing function of the quasi‐rents, since the auditor will propose that a higher value be reported in the financial statements when the quasi‐rents increase. I also show that disputes between the auditor and the client increase as the scope for errors for an auditor's test increases. When the error scope is large, the client becomes more aggressive in preparing a proposal while the auditor becomes more cautious.
Managing Insurance Company Financial Statements to Meet Regulatory and Tax Reporting Goals*
Authors: GAVER JENNIFER J. , PATERSON JEFFREY S.
Published: April 2010

This study investigates the extent to which property‐casualty insurers select levels of loss reserves, net capital gains, and net stock transactions to meet solvency and tax reporting goals. Insurer solvency is reflected in financial measures known as IRIS (Insurance Regulatory Information System) ratios. IRIS ratios are generally enhanced by underestimating loss reserves, accelerating the realization of capital gains, postponing the realization of capital losses, issuing stock, and cutting dividends. Taxable income is reduced by reporting higher reserves and lower net capital gains on investments. We use simultaneous equations to model the three discretionary choices individually, while controlling for potential tradeoffs among the decisions.

During the sample period of the study (1990‐95), there is a shift in the regulatory environment that we argue tends to reduce incentives to meet IRIS goals. Specifically, risk‐based capital (RBC) requirements were adopted in 1994. Although IRIS ratios continued to be used for solvency screening, their effect is expected to be diluted in the post‐RBC period. Our results provide qualified support for this claim. Evidence of the phenomenon is stronger when the choice variables are net capital gains and stock transactions, and weaker when loss reserves are considered. Two of the three discretionary choices affect taxable income: loss reserves and capital gains. We find that tax incentives are significantly associated with the loss reserve estimate throughout the sample period. In contrast, our results are only weakly consistent with the view that capital gains are timed to achieve tax relief.
Optimal Contracting, Accounting Standards, and Market Structures*
Authors: KIRSCHENHEITER MICHAEL
Published: April 2010

In this study I use a principal‐agent framework to analyze optimal contracting under two accounting standards, referred to as historical cost (HC) and market value (MV), and under differing asset market assumptions. I distinguish HC from MV by the way revenue is recognized and in the reporting discretion allowed. The MV standard recognizes both realized and unrealized holding gains; HC recognizes only realized holding gains. MV allows the manager reporting discretion; the HC standard does not. Also, distinguishing an asset's value‐in‐use (VIU) from its net realizable value (NRV), I consider markets where the asset's VIU and NRV are always equal as well as markets where VIU and NRV differ.

I show the following. If an asset's NRV and VIU are equal and if the manager's available reporting discretion is known, the principal prefers the MV standard because it provides better information about the manager's effort. However, the principal may prefer the HC standard if sufficiently uncertain about the manager's reporting discretion or if the asset's NRV exceeds its VIU, so that expected revenue is sufficiently enhanced by selling the asset earlier. Using an example (normal distribution and mean/variance preferences with linear contracts), I provide a case where the principal prefers the HC standard. Also, I compare the optimal effort and contract under each standard, and provide comparative static results that show how expected revenue, cost, and net income change due to changes in certain model parameters.
Post‐Earnings Announcement Drift and the Dissemination of Predictable Information*
Authors: SOFFER LEONARD C. , LYS THOMAS
Published: April 2010

Building on the work of Bernard and Thomas 1990, we develop a model to infer the degree to which the information in an earnings announcement is incorporated into investors' expectations for the subsequent earnings announcement at any point in time between the two announcements. We are unable to reject the null hypothesis that investors' earnings expectations are based on a seasonal random walk and reflect none of the implications of the immediately prior earnings announcement up to 15 trading days after that announcement. By mid‐quarter, expectations are significantly more sophisticated than a seasonal random walk. Two trading days before the next earnings announcement, as much as one half of the information in the prior earnings announcement is reflected in earnings expectations. We also find that the dissemination of information, albeit predictable information, speeds the incorporation of prior earnings information into earnings expectations.

Our results suggest that as information about future earnings that could have been discerned from the earlier announcements (because past earnings surprises predict future ones) is disseminated in a more transparent form, investors revise their earnings expectations to reflect this information. Thus, the investors' expectations appear to incorporate more and more of the serial correlation in earnings surprises as the quarter progresses, even though they do not consider per se the serial correlation in earnings surprises in forming their expectations.
An Analysis of Historical and Future‐Oriented Information in Accounting‐Based Security Valuation Models*
Authors: TSE SENYO Y. , YAANSAH ROBERT A.
Published: April 2010

The Ohlson (1995) and Feltham and Ohlson (1995) valuation model provides a rigorous framework for summarizing the information in expected future earnings and book values. However, the model provides little guidance on selecting an empirical proxy for expected future earnings. We examine whether and under what circumstances historical earnings and analyst earnings forecasts offer comparable explanation of security prices. This issue is of particular interest because analyst forecasts are less readily available than historical data. Under appropriate circumstances, historical data may allow wider use of the Feltham‐Ohlson valuation model by researchers and investors. A related issue is the incremental explanatory power of historical earnings and realized future earnings (perfect‐foresight forecasts) for security prices beyond analyst forecasts. If historical earnings are incrementally informative, that would suggest that analyst forecasts do not fully reflect price‐relevant information in past earnings. If future earnings are incrementally informative, that would suggest that security prices reflect investors' implicit earnings forecasts beyond analyst forecasts.

We examine these issues using a historical model (based on past earnings), a perfect‐foresight model (based on realized future earnings), and a forecast model (based on Value Line earnings forecasts). All three models provide significant explanatory power for security prices, and each set of earnings data provides incremental explanatory power for prices when used with the other sets of earnings data. We estimate the models separately for firms with moderate and extreme earnings‐to‐price (E/P) ratios, a proxy for earnings permanence. For moderate‐E/P firms, the historical model's explanatory power exceeds that of the perfect foresight model, and is indistinguishable from that of the analyst forecast model. In contrast, for extreme‐E/P firms, the perfect‐foresight model offers greater explanatory power than the historical model, but lower explanatory power than analyst forecasts.

Our results suggest that financial analysts' forecasting efforts are best focused on firms whose earnings contain large temporary components (extreme E/P firms). However, in general, both historical data and analyst forecasts are complementary information sources for security valuation.
Stock Performance and Intermediation Changes Surrounding Sustained Increases in Disclosure*
Authors: HEALY PAUL M. , HUTTON AMY P. , PALEPU KRISHNA G.
Published: April 2010

This paper investigates whether firms benefit from expanded voluntary disclosure by examining changes in capital market factors associated with increases in analyst disclosure ratings for 97 firms. The disclosure rating increases are accompanied by increases in sample firms' stock returns, institutional ownership, analyst following, and stock liquidity. These findings persist after controlling for contemporaneous earnings performance and other potentially influential variables, such as risk, growth, and firm size. While it is difficult to draw unambiguous causal conclusions, these results are consistent with disclosure model predictions that expanded disclosure leads investors to revise upward valuations of the sample firms' stocks, increases stock liquidity, and creates additional institutional and analyst interest in the stocks.
Earnings, Book Values, and Dividends in a Stewardship Setting with Moral Hazard*
Authors: OHLSON JAMES A.
Published: April 2010

The paper addresses the following question: in a multiple‐date agency setting, under what conditions will the dividend policy be of no incentive relevancy? It is shown that if the accounting data—earnings, book values, and dividends — satisfy standard owners' equity accounting constructs, and if these indicate that paying dividends is a zero NPV activity, then dividend policy incentive irrelevancy applies. The basic idea is to ensure that the (history of) abnormal (residual) earnings summarize the relevant information and the solution to the incentive problem. The paper also compares classical value irrelevancy with incentive irrelevancy, and the analysis shows that conditions for incentive irrelevancy are more stringent.
The Effect of Limited Liability on the Informativeness of Earnings: Evidence from the Stock and Bond Markets*
Authors: PLUMMER C. ELIZABETH , TSE SENYO Y.
Published: April 2010

Previous empirical research on the informativeness of earnings has focused on stockholders, and has not examined differences in earnings' informativeness for stockholders and bondholders. Because stockholders are residual claimants and bondholders are fixed claimants, the informativeness of earnings should differ for these two types of investors. When a firm's default risk is low, changes in its financial condition should be of limited relevance to bondholders, but should be relevant to stockholders. In contrast, as the likelihood of financial distress increases, stockholders' limited liability allows them to abandon the firm to the bondholders (Fischer and Verrecchia 1997). Accordingly, as a firm's default risk increases, changes in its financial condition should be increasingly important to bondholders and less important to shareholders. Because earnings provide information on firm value, the stock return‐earnings association should decrease as the firm's financial strength declines, while the bond return‐earnings association should increase.

We use two measures of a firm's financial strength: the firm's bond rating and its reporting of a loss. Consistent with our hypotheses, we find that the association between stock returns and changes in annual earnings decreases as bond ratings decline, while the association between bond returns and changes in annual earnings increases. These results suggest that as the company's financial condition deteriorates, earnings become less relevant for stock valuation and more relevant for bond valuation.

When we partition firms based on their loss status, we find a stronger association between stock returns and annual earnings changes for firms with positive earnings (profit firms) than for firms with losses, consistent with earlier studies. In contrast, we find that the association between bond returns and earnings changes is greater for loss firms than for profit firms. These results suggest that losses reduce the informativeness of earnings for stockholders but increase informativeness for bondholders, suggesting that investors view losses as indicating increased credit risk.
The Use of Trade Association Disclosures by Investors and Analysts: Evidence from the Semiconductor Industry*
Authors: CHANDRA UDAY , PROCASSINI ANDREW , WAYMIRE GREGORY
Published: April 2010

This paper investigates the relation between industry‐wide information disclosures by the trade association for the semiconductor industry and both share prices and analyst forecasts. Such disclosures may have little impact on investors and analysts, since prior theoretical research suggests that trade associations may be unable to secure reliable data from firms in an industry. At the same time, such disclosures may be important, since prior empirical research suggests that share prices and analyst forecasts reflect industry‐wide earnings effects earlier than firm‐specific effects. We document significant stock price movements on release dates of industry Flash Reports by the Semiconductor Industry Association (SIA) each month that contain aggregate industry data on new orders and shipments. The magnitude of the price revisions on Flash Report disclosure dates is positively associated with changes in the numbers disclosed and varies across sample firms in a manner associated with identifiable characteristics of the firms. Further tests indicate that the Flash Report provides mainly forward‐looking information on new orders that is linked to firm‐specific sales changes and has explanatory power for quarterly stock prices beyond firm‐specific earnings. This information is used by security analysts mainly in assessing the persistence of firm‐specific quarterly sales changes. Our findings support the hypothesis that the SIA is able to obtain data from firms, compile it into reliable aggregate statistics, and then distribute these statistics in a timely fashion.
Hierarchical Differences in Audit Workpaper Review Performance*
Authors: HARDING NOEL , TROTMAN KEN T.
Published: April 2010

This paper investigates the performance of senior and staff auditors in the identification of conceptual and mechanical errors during workpaper review. In this study, we begin to examine the potential for effectiveness and efficiency gains by involving staff (assistant) auditors in the review process. We find that senior auditors were more accurate than staff auditors in identifying conceptual errors contained in a hypothetical set of workpapers just reviewed. However, staff auditors were more accurate than senior auditors in identifying mechanical errors. Highlighting the benefits of a hierarchical review, composite groups consisting of a staff auditor and a senior outperformed composite groups consisting of two seniors or two staff auditors. The study finds that the differences in review performance between managers and seniors found in Ramsay 1994 generalize to lower levels of experience. Considering our results in conjunction with Ramsay 1994, we show a progression to a more conceptual review template as the rank of the reviewer moves from staff to senior to manager. The paper provides some guidance to audit firms that are presently introducing major changes to the way in which the review process is carried out, including the inclusion of reviews by staff auditors.
Legal Penalties and Audit Quality: An Experimental Investigation*
Authors: KING RONALD R. , SCHWARTZ RACHEL
Published: April 2010

The purpose of this paper is to investigate the impact of legal penalties on audit quality under different legal regimes. We investigate whether audit quality is affected differentially due to the complexity inherent in legal regimes and the frequency of imposing legal penalties. Economic theory predicts that players adopt equilibrium strategies that reflect the expectation that a penalty will be incurred, but the actual occurrences of penalties, if consistent with this expectation, should not prompt an individual to modify his or her strategy. However, learning theory suggests that players' choices will be repeated in the future based on outcomes. We found that penalties triggered both increases and decreases in effort, and seemed to introduce a “shock” that increased the variability of effort. We also observed a “funnel” effect — that is. greater changes in effort closer to the imposition of penalties, and smaller changes as more periods go by without a penalty.
Who cares? Quantifying the evolution of division of parental effort
Authors: Webb Thomas J. , Olson Valérie A. , Székely Tamás , Freckleton Robert P.
Published: April 2010

1.Determining the factors that shape the unequal division of parental effort between the sexes is key to understanding the evolution of mating systems and sexual cooperation and conflict. The range of possible care strategies may be constrained, however, by the duration of the care period. Thus, comparative analyses of parental effort should consider both these dimensions of care; here, we present a method for quantifying parental care that does this.

2.We test three models of the relationship between care duration and the division of parental effort. Using detailed information on parental effort for 330 bird species from 13 families, we use Linear Mixed Effects models and Phylogenetically Weighted Generalized Least Squares models to analyse the relationship between the two dimensions of care. These models provide a starting point for more detailed comparative analyses of the role of covariates, such as sexual size dimorphism on determining the division of parental effort.

3.Within families, although males generally provide less care than females, their relative role often increases with the duration of the care period. Across all species, care strategies vary more in species with short development times.

4.Understanding the evolution of parental care strategies requires consideration of the total duration of care in addition to the division of parental effort. Our method provides a simple means to incorporate both dimensions of care into more extensive comparative analyses.
On mean values and non-vanishing of derivatives of L-functions in a nonlinear family
Authors: Munshi Ritabrata
Published: April 2010

We prove a mean-value result for derivatives of L-functions at the center of the critical strip for a family of forms obtained by twisting a fixed form by quadratic characters with modulus which can be represented as sum of two squares. Such a family of forms is related to elliptic fibrations given by the equation q(t)y2=f(x) where q(t)=t2+1 and f(x) is a cubic polynomial. The aim of the paper is to establish a prototype result for such quadratic families. Though our method can be generalized to prove similar results for any positive definite quadratic form in place of sum of two squares, we refrain from doing so to keep the presentation as clear as possible.
Unitary inhibitory field potentials in the CA3 region of rat hippocampus
Authors: Bazelot Michaël , Dinocourt Céline , Cohen Ivan , Miles Richard
Published: April 2010

Glickfeld and colleagues (2009) suggested that single hippocampal interneurones generate field potentials at monosynaptic latencies. We pursued this obervation in simultaneous intracellular and multiple extracellular records from the CA3 region of rat hippocampal slices. We confirmed that interneurones evoked field potentials at monosynaptic latencies. Pyramidal cells initiated disynaptic inhibitory field potentials, but did not initiate detectable monosynaptic excitatory fields. We confirmed that inhibitory fields were GABAergic in nature and showed they were suppressed at low external Cl−, suggesting they originate at postsynaptic sites. Field potentials generated by a single interneurone were detected at multiple sites over distances of more than 800 μm along the stratum pyramidale of the CA3 region. We used arrays of extracellular electrodes to examine amplitude distributions of spontaneous inhibitory fields recorded at sites orthogonal to or along the CA3 stratum pyramidale. Cluster analysis of spatially distributed inhibitory field events let us separate events generated by interneurones terminating on distinct zones of somato‐dendritic axis. Events generated at dendritic sites had similar amplitudes but occurred less frequently and had somewhat slower kinetics than perisomatic events generated near the stratum pyramidale. In records from multiple sites in the CA3 stratum pyramidale, we distinguished inhibitory fields that seemed to be initiated by interneurones with spatially distinct axonal arborisations.
Dynamic Generation of Machined Surfaces, Part 1: Description of a Random Excitation System
Authors: Zhang G. M. , Kapoor S. G.
Published: April 2010

With increasing emphasis on the adaptive control for the purpose of quality and productivity improvement, it becomes necessary to develop models which can correlate the surface finish parameters with the machining conditions as well as work-piece material characteristics. This paper presents a study that leads to the development of a model for the dynamic generation of three-dimensional texture of machined surfaces. In Part 1, the mathematical formulation of the random excitation system which is responsible for the random portion of a surface profile is developed. It is assumed that the random excitation system originates from the nonhomogeneous distribution of microhardness of workpiece material. Machining tests are also performed to verify the validity of such a model development. In Part 2, a procedure for the construction of three-dimensional topography will be developed and the relationship between the machining conditions and the surface finish parameters will be established.
Effect of Machining Processes on the Fatigue Strength of Hardened AISI 4340 Steel
Authors: Matsumoto Y. , Magda D. , Hoeppner D. W. , Kim Tae Young
Published: April 2010

The effect of two finishing processes, namely, cutting and grinding, on the fatigue strength of hardened AISI 4340 steel was investigated. Three sets of flat tensile specimens were prepared by first machining into the general shape of the fatigue specimen standard, then they were hardened to HRC 54. The final grinding was carefully performed on one set of specimens. Two sets of specimens were fly cut to obtain a surface finish comparable to the ground surface. The residual stress distribution, surface structure, and surface profiles were determined. Fatigue testing was accomplished on these specimens in tension under load control. All the residual stress patterns were compressive, but the residual stress created by fly cutting reached a much deeper layer than that created by grinding. Fly cutting also produced a surface with a higher fatigue strength than the grinding did.
Mechanism of Cutting Force and Surface Generation in Dynamic Milling
Authors: Montgomery D. , Altintas Y.
Published: April 2010

An improved model of the milling process is presented. The model proposes a method of determining cutting forces in five distinct regions where the cutting edge travels during dynamic milling. Trochoidal motion of the milling cutter is used in determining uncut chip thickness. The kinematics of the cutter and workpiece vibrations are modelled, which identifies the orientation and velocity direction of the cutting edge during dynamic cutting. The model allows the prediction of forces and surface finish under rigid or dynamic cutting conditions. The proposed mechanism of chip thickness, force and surface generation is proven with simulation and experimental results. It is found that when the tooth passing frequency is selected to be an integer ratio of a dominant frequency of tool-workpiece structure in milling imprint of vibrations on the surface finish is avoided.
A Mechanistic Dynamic Model of End Milling for Process Controller Simulation
Authors: Kolarits F. M. , DeVries W. R.
Published: April 2010

In an effort to maximize the metal removal rate in end milling while avoiding excessive cutter deflection or breakage, both fixed gain and adaptive controllers have been implemented for on-line feedrate manipulation to maintain a constant cutting force. While such controllers have been able to increase the metal cutting efficiency, they have also exhibited performance problems when large changes in the process dynamics occur. To assist in controller design and evaluation through digital simulation, a new dynamic model of the end milling force response to changes in feedrate and/or spindle speed is presented. This model, based on chip formation mechanics, takes explicitly into account the effect of cutter runout and deflection on the chip load, permits variations in the axial and radial depths of cut to be modeled, and provides surface geometry predictions. Model predictions are shown to correspond well with experimental machining data.
Ductile-Regime Grinding: A New Technology for Machining Brittle Materials
Authors: Bifano T. G. , Dow T. A. , Scattergood R. O.
Published: April 2010

Because of recent advances in precision engineering that allow controlled grinding infeed rates as small as several nanometers per grinding wheel revolution, it is possible to grind brittle materials so that the predominant material-removal mechanism is plastic-flow and not fracture. This process is known as ductile-regime grinding. When brittle materials are ground through a process of plastic deformation, surface finishes similar to those achieved in polishing or lapping are produced. Unlike polishing or lapping, however, grinding is a deterministic process, permitting finely controlled contour accuracy and complex shapes. In this paper, the development of a research apparatus capable of ductile-regime grinding is described. Furthermore, an analytical and experimental investigation of the infeed rates necessary for ductile-regime grinding of brittle materials is presented. Finally, a model is proposed, relating the grinding infeed rate necessary for ductile material-removal with the properties of the brittle workpiece material.
Analysis of Fluid Flow Under a Grinding Wheel
Authors: Schumack M. R. , Chung Jin-Bok , Schultz W. W. , Kannatey-Asibu E.
Published: April 2010

Fluid flow under a grinding wheel is modeled using a perturbation scheme. In this initial effort to understand the flow characteristics, we concentrate on the case of a smooth wheel with slight clearance between the wheel and workpiece. The solution at lowest order is that given by standard lubrication theory. Higher-order terms correct for inertial and two-dimensional effects. Experimental and analytical pressure profiles are compared to test the validity of the model. Lubrication theory provides good agreement with low Reynolds number flows; the perturbation scheme provides reasonable agreement with moderate Reynolds number flows but fails at high Reynolds numbers. Results from experiments demonstrate that the ignored upstream and downstream conditions significantly affect the flow characteristics, implying that only a model based on the fully two- (or three-) dimensional Navier-Stokes equations will accurately predict the flow. We make one comparison between an experiment with a grinding wheel and the model incorporating a one-dimensional sinusoidal roughness term. For this case, lubrication theory surprisingly provides good agreement with experiment.
Automatic Disassembly and Total Ordering in Three Dimensions
Authors: Woo T. C. , Dutta D.
Published: April 2010

Generating a sequence of motions for removing components in a three-dimensional assembly, one at a time, is considered—the robot motion being strictly translational. We map the boundary representation of a given assembly to a tree structure called Disassembly Tree (DT). Traversing the DT in pre- and post-order yields a minimal sequence of operations for disassembly and assembly, respectively. In this paper, an assembly is classified by the logical complexity of its DT (an ordered graph whose nodes are components of the given assembly) and by the geometric complexity of the nodes in DT (in terms of the number of motions needed to remove a single component). Next, whether a component can be removed in one motion is described as a predicate. This predicate is then used in an algorithm for constructing the DT. For a class of assemblies that exhibit total ordering, the algorithm decides whether each component can be removed in a single motion, by constructing a DT in O(N log N) time, on the average, where N is the total number of mating faces in the assembly.
Reduction of Springback and Residual Stresses During Winding of a Helical Spring
Authors: Bibel G. D. , Kicher T. P.
Published: April 2010

Wire exhibits considerable torsional springback after cold forming, by winding into a helical spring. This springback can be reduced by the application of a tensile pull during the winding process. The applied tensile load reduces the moment required to form a plastic hinge. Removal of the tensile pull after winding further reduces the constrained moment in the cross section and resultant springback. More importantly, the reduction of springback can be related to a reduction of residual stresses in the wire.
A Simplified Approach to Predict Elastic Pressure Distribution in Non-Hertzian Contact Stress Problems
Authors: Nayak L.
Published: April 2010

An approximate but simple method to predict elastic pressure distribution in non-Hertzian contact stress problems has been developed using the two-dimensional Hertz relations and experimentally observed footprint shapes. Predicted pressures have been compared with results available from other numerical methods and are found to be quite satisfactory. The method has been applied to determine pressure distribution in wheel-rail contact under the normal load only. Because of its simplicity and reasonably accuracy in predicting pressure it can be readily used by industrial design engineers for many practical problems of contact mechanics.
Criteria for Computer-Aided Form Evaluation
Authors: Shunmugam M. S.
Published: April 2010

This paper deals briefly with the concept of form measurement and brings out the different criteria for form evaluation of engineering surfaces. A new criterion based on the minimum average deviation has been suggested. The geometrical forms, namely straight line, circle, plane, and cylinder, are analyzed. Simple numerical examples are included in this paper to illustrate the different methods.
Analysis of Unsteady Confined Viscous Flows With Variable Inflow Velocity and Oscillating Walls
Authors: Mateescu Dan , Muñoz Manuel , Scholz Olivier
Published: April 2010

The inflow velocities in various components of many engineering systems often display variations in time (fluctuations) during the operation cycle, which may substantially affect the flow-induced vibrations and instabilities of these systems. For this reason, the aeroelasticity study of these systems should include the effect of the inflow velocity variations, which until now has not been taken into account. This paper presents a fluid-dynamic analysis of the unsteady confined viscous flows generated by the variations in time of the inflow velocities and by oscillating walls, which is required for the study of flow-induced vibration and instability of various engineering systems. The time-accurate solutions of the Navier–Stokes equations for these unsteady flows are obtained with a finite-difference method using artificial compressibility on a stretched staggered grid, which is a second-order method in space and time. A special decoupling procedure, based on the utilization of the continuity equation, is used in conjunction with a factored alternate direction scheme to substantially enhance the computational efficiency of the method by reducing the problem to the solution of scalar tridiagonal systems of equations. This method is applied to obtain solutions for the benchmark unsteady confined flow past a downstream-facing step, generated by harmonic variations in time of the inflow velocity and by an oscillating wall, which display multiple flow separation regions on the upper and lower walls. The influence of the Reynolds number and of the oscillation frequency and the amplitudes of the inflow velocity and oscillating wall on the formation of the flow separation regions are thoroughly analyzed in this paper. It was found that for certain values of the Reynolds number and oscillation frequency and amplitudes, the flow separation at the upper wall is present only during a portion of the oscillatory cycle and disappears for the rest of the cycle, and that for other values of these parameters secondary flow separations may also be formed.
Experimental Analysis of Microchannel Entrance Length Characteristics Using Microparticle Image Velocimetry
Authors: Ahmad Tariq , Hassan Ibrahim
Published: April 2010

The study of the entrance region of microchannels and microdevices is limited, yet important, since the effect on the flow field and heat transfer mechanisms is significant. An experimental study has been carried out to explore the laminar hydrodynamic development length in the entrance region of adiabatic square microchannels. Flow field measurements are acquired through the use of microparticle image velocimetry (micro-PIV), a nonintrusive particle tracking and flow observation technique. With the application of micro-PIV, entrance length flow field data are obtained for three different microchannel hydraulic diameters of 500 μm, 200 μm, and 100 μm, all of which have cross-sectional aspect ratios of 1. The working fluid is distilled water, and velocity profile data are acquired over a laminar Reynolds number range from 0.5 to 200. The test-sections were designed as to provide a sharp-edged microchannel inlet from a very large reservoir at least 100 times wider and higher than the microchannel hydraulic diameter. Also, all microchannels have a length-to-diameter ratio of at least 100 to assure fully developed flow at the channel exit. The micro-PIV procedure is validated in the fully developed region with comparison to Navier–Stokes momentum equations. Good agreement was found with comparison to conventional entrance length correlations for ducts or parallel plates, depending on the Reynolds range, and minimal influence of dimensional scaling between the investigated microchannels was observed. New entrance length correlations are proposed, which account for both creeping and high laminar Reynolds number flows. These correlations are unique in predicting the entrance length in microchannels and will aid in the design of future microfluidic devices.
Eddy Heat Transfer by Secondary Görtler Instability
Authors: Momayez L. , Delacourt G. , Dupont P. , Peerhossaini H.
Published: April 2010

Experimental measurements of flow and heat transfer in a concave surface boundary layer in the presence of streamwise counter-rotating Görtler vortices show conclusively that local surface heat-transfer rates can exceed that of the turbulent flat-plate boundary layer even in the absence of turbulence. We have observed unexpected heat-transfer behavior in a laminar boundary layer on a concave wall even at low nominal velocity, a configuration not studied in the literature: The heat-transfer enhancement is extremely high, well above that corresponding to a turbulent boundary layer on a flat plate. To quantify the effect of freestream velocity on heat-transfer intensification, two criteria are defined for the growth of the Görtler instability: Pz for primary instability and Prms for the secondary instability. The evolution of these criteria along the concave surface boundary layer clearly shows that the secondary instability grows faster than the primary instability. Measurements show that beyond a certain distance the heat-transfer enhancement is basically correlated with Prms, so that the high heat-transfer intensification at low freestream velocities is due to the high growth rate of the secondary instability. The relative heat-transfer enhancement seems to be independent of the nominal velocity (global Reynolds number) and allows predicting the influence of the Görtler instabilities in a large variety of situations.
Combined Effect of Surface Roughness and Heterogeneity of Wall Potential on Electroosmosis in Microfluidic/Nanofuidic Channels
Authors: Bhattacharyya S. , Nayak A. K.
Published: April 2010

The motivation of the present study is to generate vortical flow by introducing channel wall roughness in the form of a wall mounted block that has a step-jump in ζ-potential on the upper face. The characteristics for the electrokinetic flow are obtained by numerically solving the Poisson equation, the Nernst–Planck equation, and the Navier–Stokes equations, simultaneously. A numerical method based on the pressure correction iterative algorithm (SIMPLE) is adopted to compute the flow field and mole fraction of the ions. The potential patch induces a strong recirculation vortex, which in turn generates a strong pressure gradient. The strength of the vortex, which appears adjacent to the potential patch, increases almost linearly with the increase in ζ-potential. The streamlines follow a tortuous path near the wall roughness. The average axial flow rate over the block is enhanced significantly. We found that the ionic distribution follow the equilibrium Boltzmann distribution away from the wall roughness. The solutions based on the Poisson–Boltzmann distribution and the Nernst–Planck model are different when the inertial effect is significant. The combined effects due to geometrical modulation of the channel wall and heterogeneity in ζ-potential is found to produce a stronger vortex, and hence a stronger mixing, compared with either of these. Increase in ζ-potential increases both the transport rate and mixing efficiency. A novelty of the present configuration is that the vortex forms above the obstacle even when the patch potential is negative.
Application of Realizability and Shock Unsteadiness to k−ε Simulations of Under-Expanded Axisymmetric Supersonic Free Jets
Authors: Emami Babak , Bussmann Markus , Tran Honghi
Published: April 2010

An explicit cell-centered finite volume solver coupled to a k−ε turbulence model corrected for structural compressibility fails to satisfactorily predict the behavior of under-expanded supersonic jets exhausting into still air, because the model does not properly account for the turbulence/shock wave interaction. Two approaches are examined: imposing a realizability constraint and taking into account shock unsteadiness effects. Although both corrections yield better agreement with experimental data of under-expanded jets, the realizability constraint yields better results than the shock unsteadiness correction.