Thermal Deformation Distributions Research Articles

Numerical analysis of fluid-thermal-structure coupling characteristics of CO2 booster pump valve

CO2 booster pump valves are key components in the CO2 oil drive industry, and their reliability is critical to the safe operation of pumping booster systems. Due to the special nature of CO2, heat transfer occurs during valve movement, which can cause damage to the valve body and poppet, and thus in-depth studies on CO2 properties are needed to better predict the locations where the valve is vulnerable to damage. However, relatively few studies have been conducted to analyze the fluid-thermal-solid coupling failure of CO2 booster pump valves. This paper establishes a multi-physics coupled thermodynamic model of CO2 booster pump valves, analyzes the transient simulation of valves at different valve openings, pressures and temperatures, and investigates the thermal properties of four different poppet materials. The results show that: with the increase of valve opening, the maximum deformation of the valve decreases sharply, and then tends to stabilize; in the process of pressure increasing from 4.77 MPa to 10.52 MPa, the turbulent kinetic energy inside the valve increases by about 78 %; it is also found that the thermal deformation of different poppet materials is directly proportional to the coefficients of thermal expansion of the materials, among which the deformation of aluminum alloy poppet is the largest. In addition, the results of thermal deformation and thermal stress distribution indicate that the failure region of the valve is usually concentrated in the poppet and its corresponding body wall. These results provide theoretical references for optimizing the structural design of CO2 booster pump valves and help reduce the risk of failure of CO2 booster pump valves.

Thermo Structural Analysis of Biomass Combustion Steam Generation Heat Exchangers Using Three Dimensional Numerical Modelling

Biomass with all its positive characteristics contains some elements and compounds that react negatively with stainless which are known for its usage in high temperature, corrosive prone and, hash environment. Therefore, it is pertinent to comparatively study the strength of various corrosive resistance metals to be able to have an alternative to stainless steel. The purpose of this study is to model and simulate a three-dimensional steam generating boiler plant heat exchanger for a biomass firing process. In the study, inlet temperature and operating temperature of shell and tube sides are taken as input parameters with a square pitch bundle arrangement. The heat transfer analysis is done by considering hot flue gas inside the tubes and steam on shell side to determine the thermal stress, strain and deformation distributions in the tubes and shell of the heat exchanger. The study also presented time-history analysis of the both shell and tubes to ascertain the material reactions within the specified time range. The comparison of deformations and the equivalent strain rate between the two designs indicated an excellent performance of the AL6XN over the 306L stainless steel. The strain amplitude for PMX110 and WKX110 sequentially dropped from 903 to 496 and 621 to 332 between the temperature range of 100 – 10000C respectively. The maximal equivalent strain values for the shells and tubes were 2.238e-003 and 1.294e-004 for PMX110 and 1.490e-003 and 3.212e-004 for WKX110 respectively. The highest deformation in both PMX110 and WKX110 were estimated as 6.729e-004 and 6.131e-004 for the shells and 1.441e-004 and 1.328e-004 for tubes respectively.

Active thermal balance control for improving orientation error of vertical machine tool spindle

In this study, a thermal balance control method by local heating on the spindle head structure of a vertical milling machine was proposed to improve the squareness error of the Y-Z plane. Thermal deformation and temperature distribution of the spindle head structure was analyzed to determine the key positions on the structure for prediction and control of the spindle pose. A long short-term memory (LSTM) neural network with time series characteristics was used to build the in-situ spindle tilt error prediction model. The particle swarm optimization algorithm was integrated with a neural network model to dynamically determine and find temperature control targets in local positions on the spindle head. Finally, the temperatures at selected local locations of spindle head was adjusted by elective heating to suppress thermal bending and improve the spindle tilt on the Y-Z plane. The proposed method was verified using a five-axis vertical milling machine. The experimental results showed that the proposed method could effectively maintain the spindle tilt in the Y direction at [10, −10] μrad after long-time operation of the spindle at both 7200 and 12,000 rpm.

Wave Soldering Structure Optimization Simulation of Multi-layer Ceramic Capacitors

In this paper, the thermal analysis and structural analysis of MLCC are carried out by using the commercial finite element software ANSYS. By comparing the thermal-mechanical analysis results of the structural optimization models of different schemes, the optimal optimization scheme is found. The model calculated the time required for MLCC to reach temperature stability considering thermal convection and heat conduction, and obtained the thermal deformation and thermal stress distribution of MLCC element. Based on the analysis results of MLCC original model, the thermal analysis under different wave soldering temperatures was carried out. Based on the simulated transient results, the structure and materials of MLCC key components were optimized. The results provide a basis for the optimal design of MLCC.

Calculation and Analysis of Rotor Thermal Static Field for Inter-Turn Short Circuit of Large Hydro-Generator Excitation Winding

Rotor winding inter-turn short circuit a common fault in hydro-generators. This fault would change the temperature, stress, and other thermal fields of a rotor and threaten the safe operation of the generator. In this paper, the Three Gorges hydro-generator is taken as an example. Mathematical models of three-dimensional temperature field and thermal stress field of rotor magnetic poles are established based on heat transfer theory and solved by finite element method. The temperature field, thermal deformation, and thermal stress distribution of magnetic poles in rotor winding inter-turn short circuit are calculated. On the basis of the calculation, the effects of the different turn numbers and positions of short circuit on the temperature, thermal deformation, and thermal stress of rotor magnetic poles are further studied. It is concluded that the thermal stress of the winding adjacent to the shorted turn would decrease, the thermal stress of the winding farther away from the shorted winding would increase, and so on. The results of this paper can provide references for inter-turn short circuit fault diagnosis and lay a foundation for the further studies of related faults.

Simulated and experimental studies of laser-MIG hybrid welding for plate-pipe dissimilar steel

Laser-MIG hybrid welding (LMHW) has not been extensively applied in welding of plate-pipe dissimilar steel with thick-walled because of the complex welding process requirements. In this study, numerical simulation and experimental studies of LMHW with different parameters of 25CrMo4 steel and 33MnCrB5-2 steel are presented. A 3D finite element model with coupled thermal-structural is established for analyzing the effects of welding parameters on the posted-weld thermal field, residual stress, and deformation distribution by using combined ellipsoid-Gaussian heat source model. Comparison of the calculated and experimental results suggested that the LMHW process is characterized well by the combined heat source model. Additionally, the inter-layer cooling time is determined by the amount of heat input, which also affects the magnitude and distribution of residual stress. Residual stress and deformation are controlled within the adaptable range. But, the component cannot be penetrated when laser power of backing weld P is 6000 W and welding current I is 282 A.

Research on the Time-Varying Properties of Brake Friction (September 2018)

In this paper, a dynamic model of the coefficient of friction (COF) is established from energy perspective and the principal friction mechanism of disc brake is investigated. The effects of temperature, normal pressure, and relative velocity between brake disc and pad on the COF are tested on a friction testing machine. The results show that the thermal effect is the main factor affecting the friction and wear process, and the thermal deformation and uneven heat distribution play key roles in the change of the COF. The proposed dynamic model can well describe the properties of the COF in friction process, and the work in this paper may provide some new insights into the brake friction mechanism and be helpful for the design of the brakes.

A self-correction method for deformable mirror with thermal deformation

In high-power laser systems, temperature gradient distribution arises in optical components irradiated by a high-power continuous wave (CW) laser, leading to the thermal deformation of the optical components and further the degradation of the beam quality. The deformable mirrors (DMs) are commonly used to improve the beam quality, but the thermal deformation of the DM irradiated by the high-power CW laser also exist and is more complex than that of conventional reflecting mirrors, resulting in high-frequency distortion of the corrected wavefront. In this paper, a finite element model for the DM with high reflectivity films is built up, and then the thermal deformation of the DM is simulated and analyzed. According to the deformable feature of the DM, a self-correction method is proposed, i.e., the DM corrects its thermal deformation by itself, and a self-correction function is established to control the actuators of the DM. Finally, effects of the self-correction method on beam quality are discussed quantitatively. Results show that the self-correction method can compensate the thermal deformation distribution of the DM and even constrain the generation of high-frequency distortion. Consequently, the self-correction method is feasible to compensate the thermal deformation of the DM, and further improves the beam quality.

Thermal characteristics of a CNC feed system under varying operating conditions

In high-speed and high-precision feed systems, thermal positioning errors are mainly caused by the non-uniform temperature variations and resulting time-varying thermal deformations under different operating conditions. The research presented here ultimately aims to develop a generic method capable of evaluating the thermal characteristics (such as temperature rise of heat sources, thermal positioning error) of the feed system induced by varying operating conditions (feed speed, cutting load and preload of ball screw). The thermal contact resistance between the balls and the inner and outer rings of supporting bearing is calculated using the Hertzian theory and JHM method. Experiments were carried out on a high-speed feed system experimental bench, and the influences of operating conditions on temperature rises of supporting bearings and ball screw nut were analyzed. Based on a WNN-NARMAL2 model, the relationship between temperature rise of supporting bearings and operating conditions was established. Furthermore, with the temperature of the ball screw nut set to be a moving heat source load, the temperature and thermal deformation distributions of the ball screw were simulated. The work described lays a solid foundation for thermal error prediction and compensation of a feed system under varying operating conditions.

Temperature distribution and thermal error prediction of a CNC feed system under varying operating conditions

In high-speed and high-precision feed systems, the thermal errors are mainly caused by the non-uniform temperature variations and time-varying thermal deformations under different operating conditions. The research work undertaken herein ultimately aims to develop a generic method which is capable of evaluating the temperature rises of heat sources (such as supporting bearings and ball screw nut) and thermal positioning error of the feed system induced by varying operating conditions (feed speed, cutting load, and preload of ball screw). Experiments were carried out on a high-speed feed system experimental bench, and the influences of operating conditions on temperature rises of supporting bearings and ball screw nut were analyzed. Based on wavelet neural network and NARMA-L2 model, the relationship between temperature rise of supporting bearings and operating conditions was established. Furthermore, with the temperature of ball screw nut set to be a moving heating source load, the temperature and thermal deformation distributions of ball screw under bearings and ball screw nut heat sources were simulated. The experiment and simulation results show that the recommended modeling method can be used to predict thermal positioning errors of feed system with good accuracy. The work described lays a solid foundation of thermal error prediction and compensation in a feed system under varying operating conditions.

Thermal-structure coupling simulation during ex-vivo hypothermic perfusion of kidney

In this paper, the temperature variation and consequent thermal stress and deformation during hypothermic perfusion are numerically investigated. Hypothermic perfusion is the first step of preservation techniques that washes out of the vascular system and provides the supply of substrates and cools the kidney to the preservation temperature. A three-dimensional (3D) finite element analysis using the anatomical CAD model of kidney is developed to accurately simulate the hypothermic perfusion process. Based on the temperature field, the time evolution of thermal stress and deformation distribution are obtained. In addition, we analyze the effect on the thermal stress and deformation which cannot be easily acquired through clinical experiments. The results indicate that the thermal effects of large blood vessels could remarkably affect the temperature, thermal stress and deformation distributions. Increasing the perfusion rate could enlarge the thermal deformation, which causes the injury to the kidney. These results provide a guideline to the basic and applied research for the thermal effect on the hypothermic perfusion of kidney.

Finite Element Analysis for Connection Mechanism in Macro-Micro Platform

Connection mechanism is a key component in macro-micro platform which can achieve high acceleration, ultra-high precision positioning and a long stroke. The paper presents a connection mechanism combining with a voice coil motor (VCM) and a piezoelectric stack actuator (PSA). The connection mechanism was investigated by mechanical analysis, related property indices, and some preliminary studies were as following: in the beginning, static analyses in multi-cases were carried out to ensure a solid foundation for the connection mechanism. The maximum deformation and stress were obtained for a validation evidence of structural reliability. Stress and deformation distribution were disclosed, and the relevant change trends of the maximum stress and deformation in multi-cases were obtained. However, the connection mechanism is employed to realize high acceleration, while to achieve ultra-high precision positioning. Since resonance between connection mechanism and other bodies must be avoided. It is convenient and economic to do modal analysis by ANSYS, and then the intrinsic frequency of connection mechanism will be obtained. The results indicate the connection mechanism has a higher resonance frequency than others. Though there are realization of the solid foundation and avoiding resonance, some environmental factors have hindered ultra-high precision positioning such as the relative air humidity, temperature and so on. Since the temperature up to 100℃ from heating problem of VCM inevitably produces a great deal of heat energy which can bring thermal deformation and stress, it is obliged to explore thermal deformation and stress distribution of connection mechanism by thermal- structure characteristic analysis. Thermal deformation and stress change trends under different temperature loads are revealed, which will provide a support for ultra-high precision. It is expected that finite element simulation can be an effective tool to realize the design of ultra-high precision connection mechanism in high acceleration positioning. 

Application of Finite Element Method of Composite Wall Insulation System

In this paper, the thermal stress characteristics of polystyrene plate - thin plaster wall are present. A three-dimensional element is selected to mesh the wall model, which can simulate the coupling effects of thermal stress and structural stress field. Thermal stress and deformation distribution are proposed after comparing and analyzing the two simulation results. Numerical simulation results indicate that: (1) Polystyrene plates thin plaster wall insulation system has very good thermal insulation properties；(2) Different stress fields concentrate significantly around windows and in the middle of wall especially around the windows. (3) The deformation of the polystyrene plate - thin plaster wall insulation system reach the maximum at the edge of the wall while the minimum in central.

OS0117 CFRP界面に及ぼす炭素繊維の熱膨張異方性

The thermal strain and/or stress in CFRP plays an important rule in determining damage initiation and evolution at the fiber/matrix interface, it arise from the difference between the longitudinal and the transverse CTE of carbon fiber. Experimental investigation has been made on the effect of anisotropic microstructure of carbon fiber on inhomogeneous thermal strain in CFRP during thermal loading. The measurement method on thermal deformation and strain distribution at different length scales was investigated by in-situ FE-SEM observation. A heating/cooling stage by Joule-Thomson effect was installed into the FE-SEM chamber. The material used was high modulus pitch-based K13D carbon fiber reinforced epoxy matrix composite. The grid and random patterns were fabricated onto the CFRP surface. The nano scale thermal deformation inhomogeneity in CFRP was found at the interface due to the anisotropic microstructure of carbon fiber.

Study of Parameter Effects on Residual Stresses and Thermal Deformation of Brazed Plate-Fin Structure Using Finite Element Method

The brazed plate-fin structure is the key component of a compact plate-fin heat exchanger. The residual stresses and thermal deformation induced by vacuum brazing may bring negative effects on the quality and the life of the plate-fin structure. Thus, it is important to optimize the brazing parameters in order to minimize such effects. This paper presents a three-dimensional finite element analysis for determining the residual stresses and thermal deformation of a three layered stainless steel plate-fin structure fabricated by nickel-based brazing. The features of residual stresses and thermal deformation distribution are discussed. The effects of three major brazing parameters including brazing temperature, clamping pressure load, and filler metal on the residual stresses and thermal deformation are investigated, respectively.

Magnetothermoelastic transient response of multilayered conical shells

This paper considers problems of the three-dimensional axisymmetric quasi-static coupled magnetothermoelasticity for the laminated circular conical shells subjected to magnetic and temperature fields. The temperature and pressure relation are assumed for the inner boundary. The formulation begins with the basic equations of magnetothermoelasticity in curvilinear circular conical coordinates. Laplace transform and finite difference methods are used to analyze problems. The solution is obtained by using the matrix similarity transformation and inverse Laplace transform. We obtain solutions for the temperature and thermal deformation distributions in a transient and steady state. Moreover, the computational procedures established in this thesis, can solve the generalized magnetothermoelasticity problem for multilayered conical shells with nonhomogeneous materials.

A study of thermal and mechanical behaviour for the optimal design of automotive disc brakes

The thermal distortion induced by thermoelastic instability (TEI) results in hot spots on the surface of the brake disc. This can incur low-frequency vibration known as judder. In pad-induced squeal noise, mode coupling occurs owing to the variation in the friction coefficient between the disc and pad, inducing high-frequency noise. Through a coupled analysis of hot spots and squeal phenomena, an optimum disc and pad design can be designed for higher thermal and mechanical performance. In this study, numerical and experimental analyses are performed in accordance with disc thickness, pressurization type of caliper, and lining arc length, considering thermal and mechanical instability simultaneously. Thermal deformation and pressure distribution are calculated using a finite element analysis (FEA). For evaluating TEI performance, experiments are performed using a chassis dynamometer and a high-speed infrared camera, and the results are correlated with FEA results. A complex eigenvalue analysis is conducted to evaluate mechanical instability using an FEA. Modal testing and simulations are conducted to correlate a real model and an FE model, and the corrected simulation results are applied for a complex eigenvalue problem to analyse coupled modes according to rotor and pad shapes. The results on disc brake performances considering the disc and pad design are discussed in terms of hot spots and squeal problems.

Magnetothermoelastic analysis of multilayered conical shells subjected to magnetic and vapor fields

This paper considers problems of the three-dimensional axisymmetric quasi-static coupled magnetothermoelasticity for the laminated circular conical shells subjected to magnetic and vapor fields. The water vapor temperature and pressure relation are assumed for the inner boundary. The water vapor temperature and pressure data were obtained from a thermodynamic steam table. The formulation begins with the basic equations of magnetothermoelasticity in curvilinear circular conical coordinates. Laplace transform and finite difference methods are used to analyze problems. The solution is obtained by using the matrix similarity transformation and inverse Laplace transform. We obtain solutions for the temperature and thermal deformation distributions in a transient and steady state. Moreover, the computational procedures established in this thesis, can solve the generalized magnetothermoelasticity problem for multilayered conical shells with nonhomogeneous materials.

Finite Element Study of Factor Effects on Residual Stresses and Thermal Deformation of Brazed Plate-Fin Structure

The brazed plate-fin structure is the key component of a compact plate-fin heat exchanger (PFHE). The thermal deformation and residual stresses induced by vacuum brazing may bring negative effects on the quality and the life of the plate-fin structure. Thus it is important to optimize the brazing parameters in order to minimize such effects. This paper presents a three-dimensional finite element analysis for determining the thermal deformation and residual stresses of a three layers of stainless steel plate-fin structure fabricated by nickel-based brazing. The feature of thermal deformation and residual stresses distribution are discussed. The effects of three major factors including brazing temperature, clamping pressure and filler metal on the thermal deformation and residual stresses are investigated respectively.

Thermoelastic transient response of multilayered conical shells subjected to vapor field

The problems of the three-dimensional axisymmetric quasi-static coupled thermoelastic for the laminated circular conical shells subjected to vapor field. The water vapor temperature and pressure relation assumed for the inner boundary. The water vapor temperature and pressure data were obtained from a thermodynamic steam table. The formulation begins with the basic equations of thermoelasticity in curvilinear circular conical coordinates. Laplace transform and finite difference methods are used to analyze problems. The solution is obtained by using the matrix similarity transformation and inverse Laplace transform. We obtain solutions for the temperature and thermal deformation distributions in a transient and steady state. Moreover, the computational procedures established in this thesis, can solve the generalized thermoelasticity problem for multilayered conical shells with nonhomogeneous materials.