Prediction of impact response in construction safety helmet using FEA

2019 ◽  
Vol 18 (3) ◽  
pp. 557-566
Author(s):  
Mohammed Rajik Khan ◽  
Atul Sonawane
Keyword(s):  
Complex Geometry ◽  
Construction Safety ◽  
Impact Response ◽  
Fe Model ◽  
Content Type ◽  
Design Engineers ◽  
Head Injury Criteria ◽  
Clear Idea ◽  
Free Falling ◽  
The Impact

Purpose This paper aims to present 3D finite element (FE) simulations of impact loading on a construction safety helmet over a headform to improve the ventilation slots profile in helmet design. Design/methodology/approach Impact response on headforms in three different studies considering ventilation slots of varied profiles and dimensions in helmets with rectangular elliptical and circular slots is compared and analysed. Head injury criteria (HIC) and safety regulations from past literature have been considered to evaluate the impact responses. Findings Simulation results show that a helmet with rectangular ventilation slots achieves a lowest peak impact force of 5941.3 N for a slot area of 170 mm2 as compared to elliptical and circular slots. Research limitations/implications Ventilation slots of simple geometry (rectangular, elliptical and circular) have been considered in this work. Other/complex geometry slots can also be chosen to predict its effect during impact response on a helmet–headform model. Biofidelic head–neck FE model can be developed to achieve precise results. Practical implications The presented work gives a clear idea to design engineers for the selection of ventilation slot profiles to design a construction safety helmet. Social implications Construction safety (CS) helmets are used to reduce injuries on heads of workers at construction sites in the event of free-falling objects. Rectangular ventilation slots in CS helmets as suggested in the work may reduce the risk of injury. Originality/value Results are found in good agreement with the past numerical simulation of impact response on a construction safety helmet over a validated biofidelic head FE model.

Impact of microfinance programs in Thailand

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Wittawat Hemtanon ◽  
Christopher Gan
Keyword(s):  
Panel Data ◽  
Negative Impact ◽  
Farm Households ◽  
Estimation Methods ◽  
Poor People ◽  
Fe Model ◽  
Cross Sectional ◽  
Content Type ◽  
Food Expenditure ◽  
The Impact

PurposeThe purpose of this paper is to analyze the impact of microfinance programs on the income and food expenditure of farm and nonfarm households in Thailand.Design/methodology/approachThe study employs secondary data from the Thai Socioeconomic Survey (cross-sectional data from 2017 and panel data from 2012 to 2017). The cross-sectional data (2017) include 43,210 households. Panel data from the 2012 and 2017 Socioeconomic surveys (SES surveys) include 4,406 households. The estimation methods include propensity score matching (PSM) and a fixed effect (FE) model.FindingsThe result shows that village funds (VFs) have a significant negative impact on income and food expenditure for both farm and nonfarm households. The empirical results reveal that the saving groups for production (SGPs) effects are positively significant in terms of income and food expenditure, but only for farm households. The FE model result also shows that while VFs have a negative impact on income they have a positive impact on food expenditure for farm households. In contrast, SPGs have no impact on both farm and nonfarm households' income and food expenditure.Practical implicationsFarm and nonfarm households require both welfare and microfinance programs. Microfinance programs can only help these households once they have the necessary education. The government should provide social programs and business skills for these households; completion of these courses should be a pre-requisite for accessing microfinance programs.Originality/valueThis study is unique because it reveals the microfinance impact between VFs and SGPs programs so that most low-income and poor people in Thailand can access basic financial services.

Multi-layer polymer beam reinforced by graphene platelets on low velocity impact response

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Mohammed Salih Hassan ◽  
Haideer Taleb Shomran ◽  
Abbas Allawi Abbas ◽  
Bashar Dheyaa Hussein Al-Kasob ◽  
Manar Hamid Jasim ◽  
...  
Keyword(s):  
Contact Force ◽  
Separation Of Variables ◽  
Weight Fraction ◽  
Impact Response ◽  
Low Velocity Impact ◽  
Low Velocity ◽  
Conservation Of Energy ◽  
Content Type ◽  
Graphene Platelets ◽  
The Impact

Purpose The purpose of this paper is to investigate the effect of graphene platelets (GPLs) on the low-speed contact between a mass and surface of a multi-layer polymer beam. Design/methodology/approach This problem is primarily organized by first-order shear deformation beam theory and nonlinear Hertz rule. GPLs are distributed along the beam thickness direction. The Halpin–Tsai micromechanics model is applied for computing the effective Young’s modulus of the GPLs/polymer composites. In the formulation process, the principle of conservation of energy is first used and the histories of results are extracted using the separation of variables and Runge–Kutta method. Findings In comparing the responses with the available data, a good agreement is observed. The effects of the weight fraction and distribution pattern on the impact response of polymer beam reinforced with GPLs are studied. Results show that contact force is increased, contact time and beam recess are decreased with increasing of weight fraction of GPLs. Also, among the different distribution patterns, the contact force depended on value of GPLs at the point of contact. Originality/value The effects of GPLs addition on the multi-layer polymer beam has a novelty in impact problems.

scholarly journals Urbanicity and nutrition: evidence from rural–urban migrants in China

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Qian Sun ◽  
Xiaoyun Li ◽  
Dil Bahadur Rahut
Keyword(s):  
Energy Intake ◽  
Fixed Effects ◽  
Dietary Diversity ◽  
Urban Environments ◽  
Fe Model ◽  
Nutrition Survey ◽  
Content Type ◽  
Urban Migrants ◽  
The Individual ◽  
The Impact

PurposeThe purpose of this paper is to examine the impact of urbanicity on rural–urban migrants' dietary diversity and nutrition intake and whether its effect differs across various urban environments of migrants.Design/methodology/approachUsing the individual- and time-invariant fixed effects (two-way FE) model and five-year panel data from the China Health and Nutrition Survey (CHNS), this paper estimates a linear and nonlinear relationship between urbanicity and nutrition. The paper also explores the spatial heterogeneity between rural–urban migrants and rural–suburban migrants. Dietary diversity, total energy intake and the shares of energy obtained from protein and fat, respectively, are used to measure rural–urban migrants' nutrition on both quality and quantity aspects.FindingsThe study shows that rural–urban migrants have experienced access to more diverse, convenient and prepared foods, and the food variety consumed is positively associated with community urbanicity. Energy intake is positively and significantly affected by community urbanicity, and it also varies with per capita household income. The obvious inverse U-shaped relationship reveals that improving community urbanicity promotes an increase in the shares of energy obtained from protein and fat at a decreasing rate, until reaching the urbanicity index threshold of 66.69 and 54.26, respectively.Originality/valueThis paper focuses on the nutritional status of rural–urban migrants, an important pillar for China's development, which is often neglected in the research. It examines the urbanicity and the nutrition of migrants in China, which provides a new perspective to understand the dietary and nutritional intake among migrants in the economic and social development. Moreover, the urbanicity index performs better at measuring urban feathers rather than the traditional rural/urban dichotomous classification.

Is leverage a substitute or outcome for governance? Evidence from financial crises

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Hasan Tekin ◽  
Ali Yavuz Polat
Keyword(s):  
Financial Crisis ◽  
Capital Structure ◽  
Fixed Effects ◽  
East Asian ◽  
Fe Model ◽  
Governance Mechanism ◽  
Asian Countries ◽  
Content Type ◽  
Competing Hypotheses ◽  
The Impact

PurposeThe authors investigate the impact of governance on the leverage of East Asian firms in the financial crisis context, in order to understand the puzzle whether debt acts as a substitute for governance or an outcome of the governance mechanism.Design/methodology/approachThe authors use 86,030 firm-years and the country-level governance data from eight East Asian countries over the period 1996–2017. The authors employ the fixed effects (FE) model, in the main analysis and the weighted least squares model, as a robustness check in order to compare the two competing hypotheses of agency theory, substitute and outcome models.FindingsThe authors’ results show that debt acts as a substitute for governance before the GFC, but during and after the GFC the picture changes. Namely, debt acts as an outcome of the governance mechanism during the GFC and its aftermath. Since during financial downturns both agency costs increase, and information asymmetry widens, firms in poor-governed countries may be reluctant to increase their leverage in order not to face financial distress and additional restrictions. Thus, the results imply that the use of debt as a tool to mitigate agency conflicts and a substitute for governance strongly depends on the environment that the firms operate and the general macroeconomic conditions, such as facing a financial crisis or not.Research limitations/implicationsThis study provides an interesting case of the firms' capacity to raise money during a crisis and that governance plays an important role in borrowing activities of firms. This will undoubtedly help motivating owners and policymakers for improving governance. The authors’ findings may be useful for policymakers to develop policies considering the adverse effects caused by exogenous shocks. This is crucial because the severity of GFC as a shock seems to change the macro and institutional environment that firms operate. While the authors properly address the research hypotheses using country governance data, future research may employ corporate governance data to attain firm-level results by testing two competing hypotheses.Originality/valueThere are several important areas where this study makes original contributions. First, while Tsoy and Heshmati (2019) focus on the dynamics of capital structure for only Korean firms, the authors extend the sample including eight East Asian countries considering the impact of country governance on capital structure policy. Specifically, this study is the first in using the robust country governance data, which differs by country and year, in the crisis context. Next, the authors investigate both the AFC and GFC to compare whether these two crises have different effects on capital structure policy of East Asian firms. Finally, the authors aim to understand whether leverage is used as a substitute for governance or an outcome of governance mechanism considering recessions.

Experimental and Numerical Characterization of the Impact Response of Polyethylene Sandwich Panel: A Preliminary Study

2011 ◽  
Vol 70 ◽  
pp. 195-200 ◽  
Author(s):  
C. Casavola ◽  
V. Moramarco ◽  
C. Pappalettere
Keyword(s):  
Impact Energy ◽  
Sandwich Panel ◽  
Plastic Material ◽  
Peak Stress ◽  
Experimental Tests ◽  
Impact Response ◽  
Fe Model ◽  
Explicit Finite Element ◽  
Preliminary Study ◽  
The Impact

The present work present a preliminary study to evaluate the impact response of a new sandwich panel, made up of two polyethylene skins separated by lightweight polyethylene foam. An impact test campaign was conducted on 15 square specimens (side 100 mm, total height 44 mm, average skins height 2.75 mm) with not macroscopic defects, obtained by three homogenous panels. The absorbed energy, the force and the crosshead velocity were recorded during the test. Three level of impact energy were considered. Experimental tests have allowed to obtain the impact energy/acceleration and the peak stress/impact energy diagrams for this material. Moreover, the specimen profile of the section that passes through the impact area was obtained before the test, just after the impact and one hour later for each specimen. Subsequently the experiment was reproduced by means of solid explicit finite element (FE) model in Abaqus. In order to simulate as real as possible the panel behaviour, the skins were modelled as elasto-plastic material while the core was simulated as elastomeric hyperfoam material. The material constants were based on previous experimental data conducted on the same material. After the FEM model validation, the stress-strain resulting maps were plotted.

scholarly journals The impact of coronavirus on business: developing service research agenda for a post-coronavirus world

2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Cristina Mele ◽  
Tiziana Russo-Spena ◽  
Valtteri Kaartemo
Keyword(s):  
Research Agenda ◽  
Research Priorities ◽  
Service Research ◽  
Content Type ◽  
Main Research ◽  
Search Terms ◽  
Key Issues ◽  
Clear Idea ◽  
The Impact ◽  
Market Shaping

PurposeThe coronavirus (COVID-19) has had a tremendous impact on companies worldwide. However, researchers have no clear idea of the key issues requiring their attention. This paper aims to close this gap by analysing all business-related posts on a coronavirus subreddit (“r/coronavirus”) and identifying the main research streams that are guiding the research agenda for a post-coronavirus world.Design/methodology/approachWe use data from reddit, particularly the subreddit “r/coronavirus” to identify posts that reveal the impact of coronavirus on business. Our dataset has more than 200,000 posts. We used an artificial intelligence–based algorithm to scrape the data with business-related search terms, clean it and analyse the discussion topics.FindingsWe show the key topics that address the impact of coronavirus on business, combining them into four themes: essential service provision, bricolage service innovation, responsible shopping practices and market shaping amid crisis. We discuss these themes and use them to develop a service research agenda. The results are reported against the backdrop of service research priorities.Originality/valueThe study identifies four key themes that have emerged from the impact of coronavirus on business and that require scholarly attention. Our findings can guide service research with unique insights provided immediately after the coronavirus outbreak to conduct research that matters to business and helps people in vulnerable positions in a post-coronavirus world.

Static analyses of laminated rhombic conoids

2019 ◽  
Vol 36 (4) ◽  
pp. 1346-1363 ◽  
Author(s):  
Abhay Kumar Chaubey ◽  
Ajay Kumar ◽  
Anupam Chakrabarti
Keyword(s):  
Mathematical Model ◽  
Correction Factor ◽  
Transverse Shear ◽  
Complex Geometry ◽  
Laminated Composite ◽  
Transverse Shear Strain ◽  
Transverse Strain ◽  
Fe Model ◽  
Content Type ◽  
Shear Correction Factor

Purpose This paper aims to present a new mathematical model for laminated rhombic conoids with reasonable thickness and depth. The presented model does not require the shear correction factor, as transverse strain variation through the thickness was assumed as a parabolic function. The zero transverse shear stress provision at the bottom and the top of rhombic conoids was enforced in the model. The presented model implemented a C0 finite element (FE) model, eliminating C1 continuity requirement in the mathematical model. The proposed model was validated with analytical, experimental and other methods derived from the literature. Design/methodology/approach A novel mathematical model for laminated composite skew conoidal shells has been proposed. Parabolic transverse shear strain deformation across thickness is considered. FE coding of the proposed novel mathematical model was done. Slope continuity requirement associated with present FE coding has been suitably avoided. No shear correction factor is required in the present formulation. Findings This is the first attempt to study the bending response of laminated rhombic conoids with reasonable thickness and depth. After comparisons, the parametric study was performed by varying the skew angles, boundary conditions, thickness ratios and the minimum rise to maximum rise (hl/hh) ratio. Originality/value The novelty of the presented model is reflected by the simultaneous addition of twist curvature in the strain field as well as the curvature in the displacement field allowing the accurate analysis of reasonably thick and deep laminated composite rhombic conoids. The behavior of conoids differs from that of usual shells such as cylindrical and spherical due to the conoid’s inherent twist curvature with its complex geometry and different location of maximum deflection.

Impedance-based non-destructive evaluation of additively manufactured parts

2017 ◽  
Vol 23 (3) ◽  
pp. 589-601 ◽  
Author(s):  
Mohammad I. Albakri ◽  
Logan D. Sturm ◽  
Christopher B. Williams ◽  
Pablo A. Tarazaga
Keyword(s):  
Complex Geometry ◽  
Cost Effective ◽  
Learning Context ◽  
Content Type ◽  
Electromechanical Impedance ◽  
Internal Porosity ◽  
Non Destructive Evaluation ◽  
The Impact ◽  
Non Destructive ◽  
Am Processes

Purpose This work proposes the utilization of electromechanical impedance measurements as a means of non-destructive evaluation (NDE) for additive manufacturing (AM). The effectiveness and sensitivity of the technique for a variety of defect types commonly encountered in AM are investigated. Design/methodology/approach To evaluate the feasibility of impedance-based NDE for AM, the authors first designed and fabricated a suite of test specimens with build errors typical of AM processes, including dimensional inaccuracies, positional inaccuracies and internal porosity. Two polymer AM processes were investigated in this work: material jetting and extrusion. An impedance-based analysis was then conducted on all parts and utilized, in a supervised learning context, for identifying defective parts. Findings The newly proposed impedance-based NDE technique has been proven to be an effective solution for detecting several types of print defects. Specifically, it was shown that the technique is capable of detecting print defects resulting in mass change (as small as 1 per cent) and in feature displacement (as small as 1 mm) in both extruded nylon parts and jetted VeroWhitePlus parts. Internal porosity defects were also found to be detectable; however, the impact of this defect type on the measured impedance was not as profound as that of dimensional and positional inaccuracies. Originality/value Compared to currently available NDE techniques, the newly proposed impedance-based NDE is a functional-based technique with the advantages of being cost-effective, sensitive and suitable for inspecting AM parts of complex geometry and deeply embedded flaws. This technique has the potential to bridge the existing gaps in current NDE practices, hence paving the road for a wider adoption of AM to produce mission-critical parts.

Simulation on impact response of FMLs: effect of fiber stacking sequence, thickness, and incident angle

2018 ◽  
Vol 25 (3) ◽  
pp. 621-631 ◽  
Author(s):  
Bin Yang ◽  
Liang He ◽  
Yang Gao
Keyword(s):  
Inner Core ◽  
Incident Angle ◽  
Three Dimensional ◽  
Impact Response ◽  
Woven Fabric ◽  
Impact Behavior ◽  
Fe Model ◽  
Stacking Sequence ◽  
Three Dimensional Finite Element ◽  
The Impact

Abstract We built a three-dimensional finite element (FE) model to investigate the impact response of fiber-metal laminates (FMLs). This FE model comprises two metal layers as facesheets and a carbon woven fabric-reinforced plastic laminate as inner core. Simulation was performed on ABAQUS/Explicit platform, and stiffness progressive degeneration criteria were implemented to evaluate damages in composites. The Johnson-Cook model was selected to calculate failures in metal, while surface-based cohesive behavior was adopted to simulate the delamination phenomenon. We studied the fiber stacking sequence, panel thickness, and incident angle effect on the impact behavior of FMLs. The critical penetration energy of the FMLs was determined, and the impact parameter history was discussed.

Breaking Wave-Induced Dynamic Response of Rubble Mound and Seabed Under a Caisson Breakwater

2009 ◽  
Author(s):  
M. B. C. Ulker ◽  
M. S. Rahman ◽  
M. N. Guddati
Keyword(s):  
Dynamic Response ◽  
Impact Response ◽  
Front Face ◽  
Breaking Wave ◽  
Fe Model ◽  
Wave Impact ◽  
Rubble Mound ◽  
Inertial Terms ◽  
Wave Induced ◽  
The Impact

A finite element (FE) model is developed to study the breaking wave-induced dynamic response of the porous seabed and the rubble mound foundation under a composite caisson-type breakwater. The breaking wave impact pressure distributions on the front face of the breakwater are calculated using a recently proposed method. In this study the focus is on the dynamic response of the foundation materials underneath the breakwater. The impact response of the seabed and the rubble mound is presented in terms of pore pressure and shear stress induced around the breakwater. A complete formulation of the fully dynamic response requires inclusion of the inertial terms associated with both the motion of solid skeleton and that of pore fluid. However, partly dynamic and quasi-static idealizations are also possible. The objective of this study is to investigate the effects of the inertial terms on the breaking wave induced impact response of the seabed as well as the rubble. The effect of seabed saturation on the response from different formulations is also examined.

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