Stress analysis of diesel-engine cylinder heads

1971 ◽  
Vol 6 (1) ◽  
pp. 1-12 ◽  
Author(s):  
R Bertodo ◽  
T J Carter
Keyword(s):  
Structural Integrity ◽  
Optimization Procedure ◽  
Cylinder Block ◽  
Axial Stiffness ◽  
Assessment Criterion ◽  
Design Assessment ◽  
Modes Of Failure ◽  
Engine Cylinder ◽  
The Common ◽  
Theoretical Results

The paper reviews the main requirements fulfilled by a cylinder head or cylinder block and outlines the common modes of failure met with in practice. The relative importance of the various loads applied to the head in operation are assessed and a method of predicting their influence on the structural integrity of the component described. The theoretical results obtained from a range of cylinder heads covering engines in the bore range 4 3/8 in (110 mm) to 17 in (430 mm) are shown and the experimental data obtained from verification tests presented. A quick design-assessment criterion is derived and the design-optimization procedure evolved is discussed. It is concluded that on highly rated engines the critical section is usually located at the narrow flame-plate section between adjacent exhaust-valve ports. Failures are mainly due to thermal overload. The cylinder head's rating can be extended by reducing the bottom-deck temperatures and the axial stiffness of the head and by adopting more advantageous materials for the bottom deck. Typical examples are illustrated.

scholarly journals Regression Discontinuity and Heteroskedasticity Robust Standard Errors: Evidence from a Fixed-Bandwidth Approximation

2018 ◽  
Vol 8 (1) ◽  
Author(s):  
Otávio Bartalotti
Keyword(s):  
Bias Correction ◽  
Asymptotic Theory ◽  
Regression Discontinuity ◽  
Traditional Approach ◽  
Standard Errors ◽  
Test Coverage ◽  
Regression Discontinuity Designs ◽  
The Common ◽  
Theoretical Results ◽  
Robust Standard Errors

AbstractIn regression discontinuity designs (RD), for a given bandwidth, researchers can estimate standard errors based on different variance formulas obtained under different asymptotic frameworks. In the traditional approach the bandwidth shrinks to zero as sample size increases; alternatively, the bandwidth could be treated as fixed. The main theoretical results for RD rely on the former, while most applications in the literature treat the estimates as parametric, implementing the usual heteroskedasticity-robust standard errors. This paper develops the “fixed-bandwidth” alternative asymptotic theory for RD designs, which sheds light on the connection between both approaches. I provide alternative formulas (approximations) for the bias and variance of common RD estimators, and conditions under which both approximations are equivalent. Simulations document the improvements in test coverage that fixed-bandwidth approximations achieve relative to traditional approximations, especially when there is local heteroskedasticity. Feasible estimators of fixed-bandwidth standard errors are easy to implement and are akin to treating RD estimators aslocallyparametric, validating the common empirical practice of using heteroskedasticity-robust standard errors in RD settings. Bias mitigation approaches are discussed and a novel bootstrap higher-order bias correction procedure based on the fixed bandwidth asymptotics is suggested.

scholarly journals THE MODELING OF SPILLS RESULTING FROM THE CATASTROPHIC FAILURE OF ABOVE GROUND STORAGE TANKS AND THE DEVELOPMENT OF MITIGATION

2008 ◽  
Vol 2008 (1) ◽  
pp. 949-956
Author(s):  
W. Atherton ◽  
J. W. Ash ◽  
R. M. Alkhaddar
Keyword(s):  
Large Scale ◽  
Structural Integrity ◽  
Oil Spills ◽  
Health And Safety ◽  
The Other ◽  
Catastrophic Failure ◽  
Storage Tanks ◽  
Modes Of Failure ◽  
Mode Of Failure ◽  
Mitigation Technique

ABSTRACT The risk of accidents involving the catastrophic failure of storage tanks is estimated to be low, in the region of 5 × l0−6 per tank year. However, recent accidents involving major oil spills at storage facilities located in Belgium (2004) along with USA and England (2005) have shown that tank failures do nevertheless occur. Causalities of such events vary; the consequences however are ordinarily the same, incurring environmental, financial and infrastructure losses. The normal mitigation technique employed to prevent such losses is secondary containment, usually in the form of a bund wall or earthen dyke. Researchers have investigated the reliability of such methods, examining the effects of tank failure, both theoretically and experimentally in terms of loss of containment. A United Kingdom Health and Safety Executive (HSE) review conducted in 1997 concluded that the then available data was limited and focussed attention on the work of Greenspan and Johansson (1981) and the later work of Trobojevic and Slater (1989). This led to the HSE commissioning Liverpool John Moores University (LIMU) in 2003 to undertake a large-scale spill-modelling program with the aim of quantifying the level of overtopping and the magnitudes of the dynamic pressures on the bunds. The study examined the effect of axisymmetric releases on a total of 96 tank and bund arrangements. Such losses have proven to be significant and in some cases the nature of the dynamic pressures has brought in to question the structural integrity of the bunds themselves. Research has since concentrated on modelling alternative modes of failure, such as directional releases, which could be considered to be the more common mode of failure likely to be encountered. The conclusions to this work have generated additional research to investigate possible methods of mitigation that could be incorporated into the design of facilities with the ultimate aim of further reducing losses in the event of tank failure. Two promising methods have been identified, one involving modification to the primary containment (tank) with the other being a change to the design of the profile of the secondary containment (bund wall).

scholarly journals Inference in Regression Discontinuity Designs with a Discrete Running Variable

2018 ◽  
Vol 108 (8) ◽  
pp. 2277-2304 ◽  
Author(s):  
Michal Kolesár ◽  
Christoph Rothe
Keyword(s):  
Confidence Intervals ◽  
Conditional Expectation ◽  
Regression Discontinuity ◽  
Model Misspecification ◽  
Standard Errors ◽  
Moderate Number ◽  
Regression Discontinuity Designs ◽  
The Common ◽  
Present Simulation ◽  
Theoretical Results

We consider inference in regression discontinuity designs when the running variable only takes a moderate number of distinct values. In particular, we study the common practice of using confidence intervals (CIs) based on standard errors that are clustered by the running variable as a means to make inference robust to model misspecification (Lee and Card 2008). We derive theoretical results and present simulation and empirical evidence showing that these CIs do not guard against model misspecification, and that they have poor coverage properties. We therefore recommend against using these CIs in practice. We instead propose two alternative CIs with guaranteed coverage properties under easily interpretable restrictions on the conditional expectation function. (JEL C13, C51, J13, J31, J64, J65)

scholarly journals Nash Equilibrium Investment-Reinsurance Strategies for an Insurer and a Reinsurer with Intertemporal Restrictions and Common Interests

Mathematics ◽  
2020 ◽  
Vol 8 (1) ◽  
pp. 139
Author(s):  
Yanfei Bai ◽  
Zhongbao Zhou ◽  
Rui Gao ◽  
Helu Xiao
Keyword(s):  
Nash Equilibrium ◽  
Value Premium ◽  
Insurance Company ◽  
Common Goal ◽  
General Insurance ◽  
Proposed Model ◽  
Common Interests ◽  
The Common ◽  
Mean Variance ◽  
Theoretical Results

This paper investigates the generalized multi-period mean-variance investment-reinsurance optimization model in a discrete-time framework for a general insurance company that contains a reinsurer and an insurer. The intertemporal restrictions and the common interests of the reinsurer and the insurer are considered. The common goal of the reinsurer and the insurer is to maximize the expectation of the weighted sum of their wealth processes and minimize the corresponding variance. Based on the game method, we obtain the Nash equilibrium investment-reinsurance strategies for the above-proposed model and find out the equilibrium strategies when unilateral interest is considered. In addition, the Nash equilibrium investment-reinsurance strategies are deduced under two special premium calculated principles (i.e., the expected value premium principle and the variance value premium principle). We theoretically study the effect of the intertemporal restrictions on Nash equilibrium investment-reinsurance strategies and find the effect depends on the value of some parameters, which differs from the previous researches that generally believed that intertemporal restrictions would make investors avoid risks. Finally, we perform corresponding numerical analyses to verify our theoretical results.

Altered biomechanical properties of carotid arteries in two mouse models of muscular dystrophy

2007 ◽  
Vol 103 (2) ◽  
pp. 664-672 ◽  
Author(s):  
W. W. Dye ◽  
R. L. Gleason ◽  
E. Wilson ◽  
J. D. Humphrey
Keyword(s):  
Muscular Dystrophy ◽  
Axial Force ◽  
Carotid Arteries ◽  
Structural Integrity ◽  
Muscle Cells ◽  
Biomechanical Properties ◽  
Axial Stiffness ◽  
Wild Type ◽  
Functional Responses

Muscular dystrophy is characterized by skeletal muscle weakness and wasting, but little is known about possible alterations to the vasculature. Many muscular dystrophies are caused by a defective dystrophin-glycoprotein complex (DGC), which plays an important role in mechanotransduction and maintenance of structural integrity in muscle cells. The DGC is a group of membrane-associated proteins, including dystrophin and sarcoglycan-δ, that helps connect the cytoskeleton of muscle cells to the extracellular matrix. In this paper, mice lacking genes encoding dystrophin ( mdx) or sarcoglycan-δ ( sgcd−/−) were studied to detect possible alterations to vascular wall mechanics. Pressure-diameter and axial force-length tests were performed on common carotid arteries from mdx, sgcd−/−, and wild-type mice in active (basal) and passive smooth muscle states, and functional responses to three vasoactive compounds were determined at constant pressure and length. Apparent biomechanical differences included the following: mdx and sgcd−/− arteries had decreased distensibilities in pressure-diameter tests, with mdx arteries exhibiting elevated circumferential stresses, and mdx and sgcd−/− arteries generated elevated axial loads and stresses in axial force-length tests. Interestingly, however, mdx and sgcd−/− arteries also had significantly lower in vivo axial stretches than did the wild type. Accounting for this possible adaptation largely eliminated the apparent differences in circumferential and axial stiffness, thus suggesting that loss of DGC proteins may induce adaptive biomechanical changes that can maintain overall wall mechanics in response to normal loads. Nevertheless, there remains a need to understand better possible vascular adaptations in response to sustained altered loads in patients with muscular dystrophy.

Developments in Structural Integrity Safety Cases for Highest Reliability Components in the UK

2016 ◽  
Author(s):  
T. Jelfs ◽  
M. Hayashi ◽  
A. Toft
Keyword(s):  
Power Plant ◽  
Nuclear Power Plant ◽  
Nuclear Power ◽  
Structural Reliability ◽  
Structural Integrity ◽  
Lessons Learned ◽  
Advisory Group ◽  
Design Assessment ◽  
Safety Case ◽  
The Uk

Gross failure of certain components in nuclear power plant has the potential to lead to intolerable radiological consequences. For these components, UK regulatory expectations require that the probability of gross failure must be shown to be so low that it can be discounted, i.e. that it is incredible. For prospective vendors of nuclear power plant in the UK, with established designs, the demonstration of “incredibility of failure” can be an onerous requirement carrying a high burden of proof. Requesting parties may need to commit to supplementary manufacturing inspection, augmented material testing requirements, enhanced defect tolerance assessment, enhanced material specifications or even changes to design and manufacturing processes. A key part of this demonstration is the presentation of the structural integrity safety case argument. UK practice is to develop a safety case that incorporates the notion of ‘conceptual defence-in-depth’ to demonstrate the highest structural reliability. In support of recent Generic Design Assessment (GDA) submissions, significant experience has been gained in the development of so called “incredibility of failure” arguments. This paper presents an overview of some of the lessons learned relating to the identification of the highest reliability components, the development of the structural integrity safety arguments in the context of current GDA projects, and considers how the UK Technical Advisory Group on Structural Integrity (TAGSI) recommendations continue to be applied almost 15 years after their work was first published. The paper also reports the approach adopted by Horizon Nuclear Power and their partners to develop the structural integrity safety case in support of the GDA process to build the UK’s first commercial Boiling Water Reactor design.

Analysis of Fretting Behavior for Fasten Surface between Diesel Engine Cylinder Block and Main Bearing Cap

2012 ◽  
Vol 479-481 ◽  
pp. 986-989
Author(s):  
Wen Li ◽  
Ri Dong Liao ◽  
Zheng Xing Zuo
Keyword(s):  
Diesel Engine ◽  
Crack Initiation ◽  
Load Condition ◽  
Location Parameter ◽  
Fretting Fatigue ◽  
Cylinder Block ◽  
Main Bearing ◽  
Rotating Speed ◽  
Engine Cylinder ◽  
Bearing Cap

Fretting fatigue becomes a typical failure mode for engine cylinder block caused by the increasing of the gas pressure and rotating speed, but the mechanism of fretting fatigue under diesel engine load condition hasn’t been systematic studied. In this paper, the fretting behaviors are mainly discussed by using fretting friction work parameter W and crack initiation location parameter G.

Effect of Geometrical Uncertainty on Cemented Hip Implant Structural Integrity

2009 ◽  
Vol 131 (5) ◽  
Author(s):  
Mamadou T. Bah ◽  
Martin Browne
Keyword(s):  
Structural Integrity ◽  
Simulation Method ◽  
Cement Mantle ◽  
Direct Monte Carlo Simulation ◽  
Modes Of Failure ◽  
Surface Method ◽  
Element Input ◽  
Von Mises ◽  
Von Mises Stresses ◽  
Geometrical Uncertainty

A large number of parameters such as material properties, geometry, and structural strength are involved in the design and analysis of cemented hip implants. Uncertainties in these parameters have a potential to compromise the structural performance and lifetime of implants. Statistical analyses are well suited to investigating this type of problem as they can estimate the influence of these uncertainties on the incidence of failure. Recent investigations have focused on the effect of uncertainty in cement properties and loading condition on the integrity of the construct. The present study hypothesizes that geometrical uncertainties will play a role in cement mantle failure. Finite element input parameters were simulated as random variables and different modes of failure were investigated using a response surface method (RSM). The magnitude of random von Mises stresses varied up to 8 MPa, compared with a maximum nominal value of 2.38 MPa. Results obtained using RSM are shown to match well with a benchmark direct Monte Carlo simulation method. The resulting probability that the maximum cement stress will exceed the nominal stress is 62%. The load and the bone and prosthesis geometries were found to be the parameters most likely to influence the magnitude of the cement stresses and therefore to contribute most to the probability of failure.

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