Thermal Stresses From a Moving Band Source of Heat on the Surface of a Semi-Infinite Solid

1978 ◽  
Vol 100 (1) ◽  
pp. 43-48 ◽  
Author(s):  
R. J. Mercier ◽  
S. Malkin ◽  
J. C. Mollendorf
Keyword(s):  
Thermal Stresses ◽  
Surface Cooling ◽  
Machining Processes ◽  
Convective Cooling ◽  
Finite Element Stress Analysis ◽  
Transient Regimes ◽  
Wide Range ◽  
Stress Levels ◽  
Thermoelastic Stresses ◽  
Moving Band

Thermoelastic stresses arising from a moving band source of heat on the surface of a semi-infinite solid have been calculated using well-known temperature solutions and a finite element stress analysis. Results are presented in nondimensional form for a wide range of conditions for both quasi-steady state and transient regimes. The effect of convective cooling at the surface has also been investigated. Peak stresses, which occur at the surface, have been related to a modified source Peclet number for instances in which surface cooling is not employed. Reduction in stress levels due to convective cooling at the surface has also been determined. For all cases considered, the greatest stress levels were found to occur at the surface of the constrained direction. Using results obtained in this study, thermoelastic stresses in sliding and machining processes may be calculated in order to predict the onset of yielding which can result in residual tensile stresses and cracking.

Temperature in Semi-Infinite and Cylindrical Bodies Subjected to Moving Heat Sources and Surface Cooling

1970 ◽  
Vol 92 (3) ◽  
pp. 456-464 ◽  
Author(s):  
N. R. DesRuisseaux ◽  
R. D. Zerkle
Keyword(s):  
Heat Source ◽  
Cylindrical Body ◽  
Heat Sources ◽  
Surface Cooling ◽  
Machining Processes ◽  
Infinite Body ◽  
Entire Surface ◽  
Convective Cooling ◽  
Temperature Distributions ◽  
Analytical Results

The theory of moving heat sources is applied to two models to determine the effect of convective surface cooling on temperature distributions. The models chosen consist of a translating semi-infinite body and a rotating cylindrical body, each having a band heat source acting on a portion of the surface and convective cooling acting over the entire surface. The analytical results can be utilized to predict temperature distributions occurring in certain machining processes or other processes involving heat sources.

scholarly journals Large-Eddy Simulation of a Coastal Ocean under the Combined Effects of Surface Heat Fluxes and Full-Depth Langmuir Circulation

2016 ◽  
Vol 46 (8) ◽  
pp. 2411-2436 ◽  
Author(s):  
Rachel Walker ◽  
Andrés E. Tejada-Martínez ◽  
Chester E. Grosch
Keyword(s):  
Water Column ◽  
Stable Stratification ◽  
Coastal Ocean ◽  
Surface Heat ◽  
Heat Fluxes ◽  
Surface Heating ◽  
Surface Cooling ◽  
Surface Heat Fluxes ◽  
Wide Range ◽  
Large Eddy

AbstractResults are presented from the large-eddy simulations (LES) of a wind-driven flow representative of the shallow coastal ocean under the influences of Langmuir forcing and surface heating and cooling fluxes. Langmuir (wind and surface gravity wave) forcing leads to the generation of Langmuir turbulence consisting of a wide range of Langmuir circulations (LCs) or parallel, counterrotating vortices that are aligned roughly in the direction of the wind. In unstratified, shallow coastal regions, the largest of the LCs reach the bottom of the water column. Full-depth LCs are investigated under surface waves with a significant wave height of 1.2 m and a dominant wavelength of 90 m and wave period of 8 s, for a wind speed of 7.8 m s−1 in a 15-m-deep coastal shelf region. Both unstable and stable stratification are imposed by constant surface heat fluxes and an adiabatic bottom wall. Simulations are characterized by Rayleigh and Richardson numbers representative of surface buoyancy forcing relative to wind forcing. For the particular combination of Langmuir forcing parameters studied, although surface cooling is able to augment the strength of LC, a significantly high cooling flux of 560 W m−2 (such that the Rayleigh number is Raτ = 1000) is required in order for turbulence kinetic energy generation by convection to exceed Langmuir production. Such a transition is expected at a lower heat flux for weaker wind and wave conditions and thus weaker LCs than those studied. Furthermore, a surface heating flux of approximately 281 W m−2 (such that the Richardson number is Riτ = 500) is able to inhibit vertical mixing of LC, particularly in the bottom half of the water column, allowing stable stratification to develop.

Experimental Study of Machining of Smart Materials Using Submerged Abrasive Waterjet Micromachining Process

2018 ◽  
Author(s):  
Sagil James ◽  
Anurag Mahajan
Keyword(s):  
Experimental Study ◽  
Smart Materials ◽  
Thermal Stresses ◽  
Piezoelectric Materials ◽  
High Hardness ◽  
Machining Process ◽  
Critical Parameters ◽  
Abrasive Waterjet ◽  
Parameter Study ◽  
Wide Range

Smart materials are new generation materials which possess great properties to mend themselves with a change in environment. Smart materials find applications in a wide range of industries including biomedical, aerospace, defense and energy sector and so on. These materials possess unique properties including high hardness, high strength, high melting point and low creep behavior. Manufacturing of these materials is a huge challenge, particularly at the micron scale. Abrasive waterjet micromachining (AWJMM) is a non-traditional material removal process which has the capability of machining extremely hard and brittle materials such as glasses and ceramics. AWJMM process is usually performed with nozzle and workpiece placed in air. However, machining in the air causes spreading of the waterjet resulting in low machining quality. Performing the AWJMM process with a submerged nozzle and workpiece could eliminate this problem and also reduce noise, splash, and airborne debris particles during the machining process. This research investigates Submerged Abrasive Waterjet Machining (SAWJMM) process for micromachining smart ceramic materials. The research involves experimental study on micromachining of smart materials using an in-house fabricated SAWJMM setup. The effect of critical parameters including stand-off distance, abrasive grain size and material properties on the cavity size, kerf angle and MRR during SAWJMM and AWJMM processes are studied. The study found that SAWJMM process is capable of successfully machining smart materials including shape memory alloys and piezoelectric materials at the micron scale. The machined surfaced are free of thermal stresses and did not show any cracking around the edges. The critical process parameter study revealed that stand-off distance and abrasive grit size significantly affect the machining results.

Designing Lightweight Tensegrity-Based Structures and Materials of Tailorable Thermal Expansion

2019 ◽  
Author(s):  
Rochelle E. Silverman ◽  
Edwin A. Peraza Hernandez
Keyword(s):  
Thermal Expansion ◽  
Thermal Stresses ◽  
Low Complexity ◽  
Aerospace Engineering ◽  
Positive Zero ◽  
Large Temperature ◽  
New Materials ◽  
Temperature Changes ◽  
Wide Range ◽  
First Time

Abstract In this work, we analyze and design structures and materials that possess custom thermal expansion. These structures and materials are composed of a base unit inspired by the tensegrity “D-bar” (or double-pyramid) topology. We derive, for the first time, analytical equations for the linearized and geometrically exact coefficients of thermal expansion (CTEs) of bi-material D-bar structures with arbitrary shape and complexity. Numerical results obtained using the geometrically exact CTE equations are compared with results obtained using the linearized CTE equations, showing that the latter are accurate only in cases where temperature changes are small. Further results show that D-bar structures of low complexity can produce a wide range of CTEs, including positive, zero, and negative values. These CTE values are exhibited for a range of materials that allows for easy manufacturing (materials with CTE ratios as low as 2). Thus, it is concluded that D-bar structures show promise for applications in aerospace engineering and other fields where new materials of tailorable thermal expansion are needed to decrease the substantial thermal stresses caused by large temperature changes.

Thermoviscoplastic Analysis of First Walls Subjected to Fusion Power Transients

1983 ◽  
Vol 105 (1) ◽  
pp. 42-51 ◽  
Author(s):  
H. L. Schreyer ◽  
J. M. Kennedy ◽  
D. F. Schoeberle
Keyword(s):  
Constitutive Equation ◽  
Strain Rate ◽  
Thermal Stresses ◽  
Large Deformations ◽  
Computer Code ◽  
Thermal Softening ◽  
Fusion Reactors ◽  
Fusion Power ◽  
Wide Range ◽  
Safety Features

Abrupt thermal fluxes on the first walls of fusion reactors represent a loading environment that requires advanced analytical capabilities. Solutions are needed to a wide range of postulated conditions to provide guidance for safety features and design modifications. A brief outline is given of a computer code that provides an integrated procedure for handling thermal stresses and large deformations under dynamic conditions. The code includes a new thermoviscoplastic constitutive equation that incorporates thermal softening, failure and strain rate. Solutions to several verification and illustrative problems are given.

Effects of Near Interfacial Microstructure on Interlaminar Fracture Toughness of Hybrid Metal-Polymer Composites

1993 ◽  
Vol 318 ◽  
Author(s):  
Alexander S. Grabilnikov ◽  
Oleg M. Zinevich
Keyword(s):  
Fracture Toughness ◽  
Boundary Layers ◽  
Fracture Resistance ◽  
Thermal Stresses ◽  
Hybrid Composites ◽  
Interlaminar Fracture Toughness ◽  
Energy Effect ◽  
Interlaminar Fracture ◽  
Aramid Fibres ◽  
Wide Range

ABSTRACTResults of detailed study on interlaminar fracture toughness of hybrid aramid-epoxy/aluminum laminate composites are presented. A fracture mechanics approach has been adopted and Mode-I, Mode-II tests for a wide range of loading rates have been used. Hybrid composite failure loci has been studied using SEM technique. Results were analyzed from the point of view of metal substrate/aramid fibre surface free energy effect on near interfacial (in the boundary layers) microstructure and fracture toughness of elastomer modified epoxy resins. It has been shown, that toughened epoxy resin morphology (rubber particles size and volume content) and, as a result, fracture resistance of the boundary layers were strongly dependent upon the adsorption processes, that could take place during adhesion contact formation and curing. To increase interfacial fracture toughness of hybrid composites due to the improvement of near interfacial resin microstructure and boundary layer fracture resistance, as for aluminum-epoxy and for aramid-epoxy failure loci, metal sheets/aramid fibres surface properties and interfacial residual thermal stresses should be optimized. The last result has been achieved by means of si lane primer treatment of aluminum laminates and tensile loading of cured composite.

scholarly journals Relationship Among Emotional Intelligence and/or Extrovert Bias on Perceived Stress Levels in DPT Students

2021 ◽  
Author(s):  
Scott Richardson ◽  
Jordan Auvinen ◽  
Brennan Bonnett ◽  
Lucas Takeuchi ◽  
Erin Thompson
Keyword(s):  
Emotional Intelligence ◽  
Academic Performance ◽  
Academic Success ◽  
Perceived Stress ◽  
Negative Correlation ◽  
Significant Negative Correlation ◽  
Spearman Correlation ◽  
Convenience Sample ◽  
Wide Range ◽  
Stress Levels

Purpose/Hypothesis: Students in graduate level DPT programs function at varying levels. Some students thrive and others struggle to maintain required minimum levels of academic performance. When considering admission of applicants, and when assisting enrolled students, consideration of factors contributing to academic success is of interest. Stress has been shown to be prevalent in a wide range of students and has many negative effects including poor life satisfaction, increased clinical burnout, and reduced academic performance. Research has shown a correlation between higher emotional intelligence (EI) and decreased stress levels in medical, nursing, and undergraduate students. The purpose of this study was to examine if emotional intelligence (EI) and/or extrovert bias correlates with perceived stress levels in Doctor of Physical Therapy (DPT) students. It was hypothesized that students with higher emotional intelligence and more extroverted personalities would experience lower levels of perceived stress. Participants: After providing consent, a convenience sample of 60 first and second year DPT students (33 female) with age range 23 to 38 participated in the current study. Participation was voluntary and 60 of a possible 72 students chose to participate. Materials/Methods: After obtaining informed consent, participants completed Goldberg’s IPIP-Neo questionnaire (extraversion), Perceived Stress Scale (PSS) and Assessing Emotions Scale (emotional intelligence). Each of these tools have demonstrated validity and reliability for the respective areas measured. Surveys were administered to students and results were analyzed for possible relationships between extraversion and stress levels as well as EI and stress levels using a Spearman Correlation test. Results: Spearman Correlation analyses were conducted with a significant negative correlation between EI and perceived stress rs = -0.291, p= 0.026 and a non-significant negative correlation between extraversion and perceived stress rs = -1.36, p= 0.305. Discussion: In the current sample, EI had a significant negative relationship with perceived stress levels, with higher EI scores correlating to lower levels of stress. The relationship between extraversion and perceived stress was non-significant. Clinical Relevance: Doctorate level graduate programs can be considered intense and very stressful. Admission of qualified students equipped to meet the demands of a DPT program has great importance. Establishing a correlation between EI, introversion/extraversion bias, and stress may help DPT programs further assess prospective students. Consideration of factors correlated with higher perceived stress may be useful when providing resources to admitted students to facilitate academic success.

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