Analysis of Transient Temperatures in Grinding

1995 ◽  
Vol 117 (4) ◽  
pp. 571-577 ◽  
Author(s):  
C. Guo ◽  
S. Malkin
Keyword(s):  
Steady State ◽  
Transient Behavior ◽  
Grinding Wheel ◽  
Transient Temperature ◽  
Quasi Steady State ◽  
Workpiece Material ◽  
Steady State Condition ◽  
Transient Temperature Distribution ◽  
Creep Feed ◽  
Grinding Conditions

Temperatures generated in the workpiece during straight surface plunge grinding follow a transient behavior as the grinding wheel engages with and disengages from the workpiece, and throughout the entire grinding pass for workpieces which are shorter than needed to reach a quasi-steady state condition. In the present paper, a thermal model is developed for the transient temperature distribution under regular and creep-feed grinding conditions. Numerical results obtained using a finite difference method indicate that the workpiece temperature rises rapidly during initial wheel-workpiece engagement (cut in), subsequently reaches a quasi-steady state value if the workpiece is sufficiently long, and increases still further during final wheel-workpiece disengagement (cut out) as workpiece material is suddenly unavailable to dissipate heat. Cooling by a nozzle directed at the end face of the workpiece should significantly reduce the temperature rise during cut out.

TRANSIENT OPERATION OF SENSIBLE FIXED-BED REGENERATORS

2022 ◽  
pp. 1-16
Author(s):  
Hadi Ramin ◽  
Easwaran N Krishnan ◽  
Gurubalan Annadurai ◽  
Carey J. Simonson
Keyword(s):  
Steady State ◽  
Fixed Bed ◽  
Operating Conditions ◽  
Design Parameters ◽  
Transient Temperature ◽  
Quasi Steady State ◽  
Transient Operation ◽  
Steady State Condition ◽  
Test Standards ◽  
Wide Range

Abstract Fixed-bed regenerator is a type of air-to-air energy exchanger and recently introduced for energy recovery application in HVAC systems because of their high heat transfer effectiveness. Testing of FBRs is essential for performance evaluation and product development. ASHRAE and CSA recently included guidelines for testing of FBRs in their respective test standards. The experiments on FBRs are challenging as they never attain a steady state condition, rather undergoes a quasi-steady state operation. Before reaching the quasi-steady state, FBRs undergo several transient cycles. Hence, the test standards recommend getting measurements after one hour of operation, assuming FBR attains the quasi-steady state regardless of test conditions. However, the exact duration of the initial transient cycles is unknown and not yet studied so far. Hence, in this paper, the duration of FBR's transient operation is investigated for a wide range of design and operating conditions. The test standards' recommendation for the transient duration is also verified. The major contributions of this paper are (i) quantifying the effect of design parameters (NTUo and Cr*) on the duration of transient operation and (ii) investigation of the effect of sensor time constant on the transient temperature measurements. The results will be useful to predict and understand the transient behavior of FBRs accurately.

EFFECT OF FACE COOLING ON WORKPIECE TEMPERATURES USING 2D AND 3D FINITE ELEMENT ANALYSIS OF CREEP-FEED GRINDING

2008 ◽  
Vol 32 (3-4) ◽  
pp. 439-452 ◽  
Author(s):  
David Anderson ◽  
Andrew Warkentin ◽  
Robert Bauer
Keyword(s):  
Finite Element ◽  
Steady State ◽  
Contact Temperature ◽  
Grinding Wheel ◽  
Finite Element Models ◽  
3D Finite Element ◽  
Creep Feed ◽  
2D And 3D ◽  
Maximum Contact ◽  
Face Cooling

This work uses validated 2D and 3D finite element models of the creep-feed grinding operation to study the effects of face cooling on the workpiece temperatures. The results show that as the intensity of the face cooling is increased the maximum contact temperature decreases and the location of the maximum contact temperature shifts away from the finished workpiece material and towards the uncut workpiece surface. The finite element models are also used to study the maximum temperatures along the workpiece during a complete grinding pass. The temperature profiles show that there are four important temperature features on the workpiece, which are the cut-in, steady-state, temperature spike, and cut-out zones. Cut-in occurs when the grinding wheel initially engages the workpiece, steady-state occurs in the middle of the workpiece, the temperature spike occurs at the beginning of cut-out, and cut-out occurs as the grinding wheel disengages from the workpiece. Finally, the results show that face cooling need only be applied to the area immediately adjacent to the contact zone to be effective and that there is very little benefit to applying coolant to the entire front and back workpiece faces.

scholarly journals On the application of storage coefficient determination by quasi-steady-state flow

2005 ◽  
Vol 36 (1) ◽  
pp. 13-20 ◽  
Author(s):  
Mehmet E. Birpinar ◽  
Ayhan Gazioglu
Keyword(s):  
Steady State ◽  
Quasi Steady State ◽  
Confined Aquifer ◽  
Steady State Flow ◽  
Steady State Condition ◽  
Storage Coefficient ◽  
Unconfined Aquifers ◽  
Aquifer Test ◽  
Order Of Magnitude ◽  
Observation Wells

A simple analytical method has been used for estimating the storage coefficient provided that transmissivity of the aquifer is known at the quasi-steady-state condition in confined or unconfined aquifers. The application of the method has been performed for unconfined and confined aquifer test data in Chaj Doab, Pakistan with observation wells and compared with conventional methods in the groundwater flow literature dealing with pumping tests. The results from the methodology presented in this paper conform well in practice with the results obtained from the traditional methods on the basis of order of magnitude.

Estimation of Crater Temperatures Using Infrared Camera

2000 ◽  
Author(s):  
Patrick Kwon
Keyword(s):  
Steady State ◽  
Temperature Distribution ◽  
Heat Conduction Problem ◽  
Infrared Camera ◽  
Video Camera ◽  
Interface Temperature ◽  
Transient Temperature ◽  
Flux Boundary Condition ◽  
Transient Temperature Distribution ◽  
Aisi 1045

Abstract A new technique is developed to estimate the average steady state chip-tool interface temperature during turning. An infrared (IR) video camera attached on the carriage of the lathe measures the transient cooling behavior on the rake surface of an insert after the feed motion is halted. This allows the zero heat flux boundary condition, where the transient Laplace heat conduction problem can be solved numerically to obtain the temporal and spatial temperature distribution. With the experimentally determined transient temperature distribution, the 1-D ellipsoidal model is used to estimate the average steady-state chip-tool interface temperature during machining. The results on turning Gray Cast Iron (GCI) and AISI 1045 steels with various coated and uncoated carbide inserts are presented.

Stack-Up Forces for Normal and Abnormal Operating Conditions in a Railroad Roller Bearing Assembly

1998 ◽  
Vol 120 (4) ◽  
pp. 707-713
Author(s):  
H. Wang ◽  
T. F. Conry ◽  
C. Cusano
Keyword(s):  
Steady State ◽  
Temperature Distribution ◽  
Operating Temperature ◽  
Roller Bearing ◽  
Operating Conditions ◽  
Transient Temperature ◽  
Surface Geometry ◽  
Tapered Roller Bearing ◽  
Transient Temperature Distribution ◽  
Abnormal Operating Conditions

Stack-up force distributions are obtained for normal and abnormal operating conditions in a class F (6 1/2 × 12) railroad tapered roller bearing-axle assembly for various friction coefficients, press-fits and cap screw preloads. Three conditions that affect the stack-up force distribution are considered: a steady-state normal-operating temperature distribution, a steady-state temperature distribution resulting from a stuck brake or a jammed outboard roller, and a transient temperature distribution due to multiple jammed outboard rollers. The steady-state normal or abnormal operating temperature have insignificant effects for nominal values of interference, friction and cap screw preload. However, the effect of the transient temperature due to multiple jammed outboard rollers on the stack-up system is detrimental due to localized high temperature gradients near the outboard cone area and a distortion of the original surface geometry of the cone.

The Transient Response of Orifices and Very Short Lines

1972 ◽  
Vol 94 (2) ◽  
pp. 483-489 ◽  
Author(s):  
J. E. Funk ◽  
D. J. Wood ◽  
S. P. Chao
Keyword(s):  
Steady State ◽  
Pressure Drop ◽  
System Analysis ◽  
Transient Flow ◽  
Transient Behavior ◽  
Short Term ◽  
State Equations ◽  
Steady State Condition ◽  
Orifice Flow ◽  
Flow Through

It is generally assumed that orifices and valves follow closely their steady-state characteristics during transient operation. However, this assumption of quasisteady behavior may lead to errors in predicting transient flow conditions under certain circumstances. In order to evaluate the transient behavior of an orifice, a differential equation relating the flow through and the pressure drop across an orifice was derived. An extension was made to include an axial dimension for the orifice. The solution of this equation for transient flow through an orifice subjected to a step change in pressure drop across the orifice is significantly different than that obtained using the steady state relationship. An experiment was designed to evaluate the theoretical results in which an orifice on the end of a line was subjected to a sudden pressure change and the resulting transient pressures were observed. It was found that a significant short term transient occurs before the orifice flow reaches the new steady state condition. The observed short term transient agrees well with that predicted by the theory. It is concluded that the behavior of an orifice can deviate considerably from that predicted by steady-state equations during periods of rapid pressure or flow changes. The dynamic description of orifice flow may be combined with a larger system analysis (e.g., using the method of characteristics) to more accurately predict the overall transient performance of flow systems.

A Fast and Reliable Dynamic Tyre-Road Contact Model for ABS Braking Manoeuvre Simulations

2006 ◽  
Author(s):  
Francesco Braghin ◽  
Federico Cheli ◽  
Emiliano Giangiulio ◽  
Federico Mancosu ◽  
Daniele Arosio
Keyword(s):  
Differential Equation ◽  
Steady State ◽  
Order Differential Equation ◽  
Transient Behavior ◽  
Slip Angle ◽  
Relaxation Length ◽  
Steady State Condition ◽  
Tyre Model ◽  
First Order ◽  
Significant Parameter

Due to the dimensions of the tyre-road contact area, transients in a tyre last approximately 0.1s. Thus, in the case of abrupt maneuvers such as ABS braking, the use of a steady-state tyre model to predict the vehicle’s behavior would lead to significant errors. Available dynamic tyre models, such as Pacejka’s MF-Tyre model, are based on steady-state formulations and the transient behavior of the tyre is included by introducing a first order differential equation of relevant quantities such as the slip angle and the slippage. In these differential equations the most significant parameter used to describe the transient behavior is the so-called relaxation length, i.e. the distance traveled by the tyre to settle to a new steady–state condition once perturbated. Usually this parameter is assumed to be constant.

Transient Performance of Fixed-Bed Regenerators for Energy Recovery in Building Applications

2020 ◽  
Author(s):  
Hadi Ramin ◽  
Easwaran N. Krishnan ◽  
Gurubalan Annadurai ◽  
Carey J. Simonson
Keyword(s):  
Steady State ◽  
Fixed Bed ◽  
Performance Testing ◽  
State Condition ◽  
Test Facility ◽  
Small Scale ◽  
Outlet Temperature ◽  
Quasi Steady State ◽  
Steady State Condition ◽  
Steady State Operation

Abstract A small-scale test facility is developed to determine the sensible effectiveness of a Fixed-Bed Regenerator (FBR) and the results are used to validate a numerical model. The numerical and experimental results for quasi-steady-state conditions are in a good agreement within the experimental uncertainty bounds. At quasi-steady-state condition, the outlet temperature of FBR varies with time but cyclically repeats itself; this is an important difference between FBR (regenerator) and recuperator heat exchangers. The outlet temperature of recuperator heat exchangers reaches a constant value during the steady-state operation. The quasi-steady-state temperature profile is used to determine the sensible effectiveness of FBRs. However, FBRs undergo several cycles to reach the quasi-steady-state condition. The prediction of the duration of the transient duration of FBR is important for performance testing that could save money and time. CSA (Canadian Standards Association) recommends operating FBR for at least one hour to achieve a quasi-steady-state condition. This paper addresses the heat transfer behavior of FBRs during their transient operation. The initial transient cycles depend on the cycle period of FBR, air flow rate and the thermal condition of the exchanger at the beginning of the test. The small-scale FBR test facility is used to study the transient behavior of FBRs and this is the main focus of this paper. The temperature profile during the transient condition of FBR is obtained and the results are compared with the numerical model. The effects of the mass flow rate of air and the cycle duration on the transient period of FBR are studied. The results show that FBR reaches a quasi-steady state operation in less than 30 minutes. The results will be useful for understanding the time required for performance testing, which will reduce the cost and time of each test.

Influence of Grinding Conditions on Residual Stress Profiles after Induction Surface Hardening

2005 ◽  
Vol 490-491 ◽  
pp. 346-351
Author(s):  
Janez Grum
Keyword(s):  
Surface Layer ◽  
Residual Stresses ◽  
Surface Hardening ◽  
Physical And Mechanical Properties ◽  
Grinding Wheel ◽  
Workpiece Material ◽  
Heat Effects ◽  
Grinding Conditions ◽  
Induction Surface Hardening ◽  
Hardened Surface

Induction surface hardening creates very desirable residual stresses in the hardened surface layer. Residual stresses are always of a compressive nature and are usually present to the depth of the induction-hardened layer. By the appropriate selection of grinding wheel and grinding conditions and taking into account the physical and mechanical properties of the workpiece material very favourable compressive residual stresses in the hardened surface layer can be retained. How is it possible to assure a desirable surface and surface layer quality after induction hardening and fine grinding? Finding an answer to this question requires a very good knowledge of the process of grinding on the micro-level as well as knowledge of mechanical and heat effects acting on the layer of the workpiece including the type and condition of the grinding wheel. An allinclusive consideration of the numerous influences of the kind and condition of the tool on the changes on the surface and in the surface layer of the workpiece in the given machining conditions is described by the term “surface integrity”.

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