Cracked elastic substrate strip with functionally graded coating under thermal-mechanical loading

This paper investigates the functionally graded coating bonded to an elastic strip with a crack under thermal- mechanical loading. Considering some new boundary conditions, it is assumed that the temperature drop across the crack surface is the result of the thermal conductivity index which controls heat conduction through the crack region. By the Fourier transforms, the thermal-elastic mixed boundary value problems are reduced to a system of singular integral equations which can be approximately solved by applying the Chebyshev polynomials. The numerical computation methods for the temperature, the displacement field and the thermal stress intensity factors （TSIFs） are presented. The normal temperature distributions （NTD） with different parameters along the crack surface are analyzed by numerical examples. The influence of the crack position and the thermal-elastic non- homogeneous parameters on the TSIFs of modes I and 11 at the crack tip is presented. Results show that the variation of the thickness of the graded coating has a significant effect on the temperature jump across the crack surfaces when keeping the thickness of the substrate constant, and the thickness of functionally graded material （FGM） coating has a significant effect on the crack in the substrate. The results can be expected to be used for the purpose of gaining better understanding of the thermal-mechanical behavior of graded coatings.

Thermal-mechanical properties of short carbon fiber reinforced geopolymer matrix composites subjected to thermal load

Short carbon fiber preform reinforced geopolymer composites containing different contents of α-Al2O3 filler （Cr（a-Al2O3）/geopolymer composites） were fabricated, and the effects of heat treatment temperatures up to 1 200 ℃ on the thermal-mechanical properties were studied. The results show that the thermal shrinkage in the direction perpendicular to the lamination of the composites gradually increases with the increase of the heat treatment temperatures from room temperature （25 ℃ ） to 1000 ℃. However, the composites in the direction parallel to the lamination show an expansion behavior. Beyond 1 000℃, in the two directions the composites exhibit a larger degree of shrinkage due to the densification and crystallization. The mechanical properties of the composites show the minimum values in the temperature range from 600 to 800 ℃ as the hydration water of geopolymer matrix is lost. The addition of α-Al2O3 particle filler into the composites clearly increases the onset crystalline temperature of leucite （KAlSi2O6） from the amorphous geopolymer matrix. In addition, the addition of α-Al2O3 particles into the composites can not only help to keep volume stable at high temperatures but also effectively improve the mechanical properties of the composites subjected to thermal load to a certain extent. The main toughening mechanisms of the composites subjected to thermal load are attributed to fiber pulling-out.

Fatigue behaviour of coke drum materials under thermal-mechanical cyclic loading

Coke drums are vertical pressure vessels used in the delayed coking process in petroleum refineries. Significant temperature variation during the delayed coking process causes damage in cracking. There were some studies on coke drums in the form of bulging and the fatigue life estimation for the coke drums, but most of them were based on strain-fatigue life curves at constant temperatures, which do not consider simultaneous cyclic temperature and mechanical loading conditions. In this study, a fatigue testing system is successfully devel- oped to allow performing thermal-mechanical fatigue （TMF） test similar to the coke drum loading condition. Two commonly used base and one clad materials of coke drums are then experimentally investigated. In addition, a comparative study between isothermal and TMF lives of these materials is conducted. The experimental findings lead to better understanding of the damage mechanisms occurring in coke drums and more accurate prediction of fatigue life of coke drum materials.

Thermal-Mechanical Fatigue Behavior and Life Analysis of Cast Ni-base Superalloy K417

In-phase (IP) and out-of-phase (OP) thermal-mechanical fatigue (TMF) behavior of cast Ni-base superalloy K417 was studied. All experiments were carried out under total strain control with temperature cycling between 400-850℃. Both in-phase and out-of-phase TMF specimens exhibited cyclic hardening followed by cyclic softening at the minimum temperature. Besides, they cyclically hardened in the early stage of life followed by cyclic softening at the maximum temperature. OP TMF life was longer than that of IP TMF. Various damage mechanisms operating in different controlled strain ranges and phasing were discussed. A few life prediction methods for isothermal fatigue were used to handle TMF fatigue and their applicability to superalloy K417 was evaluated. The SEM analysis of the fracture surface showed that transgranular fracture was the principal cracking mode for both IP and OP TMF. Oxidation was the main damage mechanism in causing shorter fatigue life for IP TMF compared with OP TMF.

Numerical simulation of a sheet metal extrusion process by using thermal-mechanical coupling EAS FEM

The thermal-mechanical coupling finite element method(FEM)was usedto simulate a non-isothermal sheet metal extrusion process. On thebasis of the finite plasticity consistent with multiplicativedecomposition of the deformation gradient, the enhanced as- sumedstrain(EAS)FEM was applied to carry out the numerical simulation. Inorder to make the computation reliable ad avoid hour- glass mode inthe EAS element under large compressive strains, an alterative formof the original enhanced deformation gradient was employed. Inaddition, reduced factors were used in the computation of the elementlocal internal parameters and the enhanced part of elementalstiffness.

EFFECTS OF STRAIN RATIO ON THERMAL-MECHANICAL CYCLIC STRESS-STRAIN RESPONSE AND FATIGUE LIFE IN DS SUPERALLOY DZ125

The effects of strain ratio on thermal-mechanical cyclic stress-strain response and fatigue life in DS superalloy DZ125 have been studied by performing tests at various strain ratio experiments, under strain-controlled and temperature cycling from 550 to 1000℃. It is shown that thermal-mechanical cyclic stress-strain response behavior not only depend on magnitude of strain, and temperature-loading phase angle, but also strain ratio. Fatigue life at strain ratio Rε=-0.3 is longer than that of strain ratio Rε=-1.0, under in-phase thermal-mechanical loading. However, Fatigue life at strain ratio Rε=-0.3 is shorter than that of strain ratio Rε=-1.0, under out-of-phase thermal-mechanical loading. The thermal-mechanical fatigue (TMF) damage model was discussed. Results of fractography show that fatigue, creep and oxidation damage always occur during TMF. The main damage mode depends on loading wave, strain ratio and magnitude of strain.

First Cycle Effect of Polycrystalline CuZnAl Shape Memory Alloy during Thermal-Mechanical Cycling

The thermal-mechanical (T-M) cycles at constant strain of a polycrystalline CuZnAl alloy have been studied in the. present work. In-situ optical microscopic observations have been made to reveal the features of the phase transitions during T-M cycling. The variation of stress-temperature (S-T) curves and electrical resistance-temperature (R-T) curves accompanying with T-M cycling have been measured by tensile test and electrical resistance measurements. It has been found that the polycrystalline CuZnAl alloy shows apparent morphology changes and properties variations in the first cycle during T-M cycling which is called the first cycle effect in the present work. The stable transformation procedure in the T-M cycle is: martensiteparent phase +residual acicular martensite. This residual martensite possesses the character of stress-induced martensite.

Thermal-Mechanical Efect and Removal Mechanism of Ti-6Al-4V During Laser-Assisted Grinding

The low density and high corrosion resistance of titanium alloy make it a material with various applications in the aerospace industry. However, because of its high specifc strength and poor thermal conductivity, there are problems such as high cutting force, poor surface integrity, and high cutting temperature during conventional machining. As an advanced processing method with high efciency and low damage, laser-assisted machining can improve the machinability of titanium alloy. In this study, a picosecond pulse laser-assisted scratching (PPLAS) method considering both the temperature-dependent material properties and ultrashort pulse laser’s characteristics is frst proposed. Then, the efects of laser power, scratching depth, and scratching speed on the distribution of stress and temperature feld are investigated by simulation. Next, PPLAS experiments are conducted to verify the correctness of the simulation and reveal the removal behavior at various combinations of laser power and scratching depths. Finally, combined with simulated and experimental results, the removal mechanism under the two machining methods is illustrated. Compared with conventional scratching (CS), the tangential grinding force is reduced by more than 60% and the material removal degree is up to 0.948 during PPLAS, while the material removal is still primarily in the form of plastic removal. Grinding debris in CS takes the form of stacked fakes with a “fsh scale” surface, whereas it takes the form of broken serrations in PPLAS. This research can provide important guidance for titanium alloy grinding with high surface quality and low surface damage.

ANALYSIS OF SHAKEDOWN OF FG BREE PLATE SUBJECTED TO COUPLED THERMAL-MECHANICAL LOADINGS

The static and kinematic shakedown of a functionally graded （FG） Bree plate is analyzed. The plate is subjected to coupled constant mechanical load and cyclically varying temperature. The material is assumed linearly elastic and nonlinear isotropic hardening with elastic modulus,yield strength and the thermal expansion coeffcient varying exponentially through the thickness of the plate. The boundaries between the shakedown area and the areas of elasticity,incremental collapse and reversed plasticity are determined,respectively. The shakedown of the counterpart made of homogeneous material with average material properties is also analyzed. The comparison between the results obtained in the two cases exhibits distinct qualitative and quantitative difference,indicating the importance of shakedown analysis for FG structures. Since FG structures are usually used in the cases where severe coupled cyclic thermal and mechanical loadings are applied,the approach developed and the results obtained are significant for the analysis and design of such kind of structures.

Analysis of thermal-mechanical coupled characteristics of vehicle twin-tube shock absorber

A comprehensive model that included mechanical dynamics of the shock absorber coupled with its thermal properties was proposed innovatively.Moreover a thermal-mechanical coupled model which reflected the closed-loop positive feedback system was established by using MATLAB/SIMULINK,and some curves of shock absorber temperature rising characteristic were obtained by simulation ＆computation under several operating modes and different parameters conditions.Research results show that：shock absorber design parameters,external excitations,and thermo-physical properties parameter,such as oil density have effect on the shock absorber temperature rising characteristic.However other thermo-physical properties parameters,such as oil specific heat,cylinder density,cylinder specific heat,and cylinder thermal conductivity,have no effect on it.The results may be used for studying reliability design of the shock absorber.

Age of Loop Information with Flexible Transmission Enabled Communication and Control Co-Design in Industrial IoT

Precise and low-latency information transmission through communication systems is essential in the Industrial Internet of Things(IIoT).However,in an industrial system,there is always a coupling relationship between the control and communication components.To improve the system's overall performance,exploring the co-design of communication and control systems is crucial.In this work,we propose a new metric±Age of Loop Information with Flexible Transmission(AoLI-FT),which dynamically adjusts the maximum number of uplink(UL)and downlink(DL)transmission rounds,thus enhancing reliability while ensuring timeliness.Our goal is to explore the relationship between AoLI-FT,reliability,and control convergence rate,and to design optimal blocklengths for UL and DL that achieve the desired control convergence rate.To address this issue,we first derive a closed-form expression for the upper bound of AoLI-FT.Subsequently,we establish a relationship between communication reliability and control convergence rates using a Lyapunov-like function.Finally,we introduce an iterative alternating algorithm to determine the optimal communication and control parameters.The numerical results demonstrate the significant performance advantages of our proposed communication and control co-design strategy in terms of latency and control cost.

Thermal-Mechanical Coupled FE Analysis for Rotary Shaft Seals

The aim of this paper is to model the steady-state condition of a rotary shaft seal (RSS) system. For this, an iterative thermal-mechanical algorithm was developed based on incremental finite element analyzes. The behavior of the seal’s rubber material was taken into account by a large-strain viscoelastic, so called generalized Maxwell model, based on Dynamic Mechanical Thermal Analyses (DMTA) and tensile measurements. The pre-loaded garter spring was modelled with a bilinear material model and the shaft was assumed to be linear elastic. The density, coefficient of thermal expansion and the thermal conductance of the materials were taken into consideration during simulation. The friction between the rotary shaft seal and the shaft was simplified and modelled as a constant parameter. The iterative algorithm was evaluated at two different times, right after assembly and 1 h after assembly, so that rubber material’s stress relaxation effects are also incorporated. The results show good correlation with the literature data, which state that the permissible temperature for NBR70 (nitrile butadiene rubber) material contacting with ~80 mm shaft diameter, rotating at 2600/min is 100°C. The results show 107°C and 104°C for the two iterations. The effect of friction induced temperature, changes the width of the contact area between the seal and the shaft, and significantly reduces the contact pressure.

Co-Design of Monolithically Integrated Photo-Detector and Optical-Receiver

A behavioral model of the photodiode is presented.The model describes the relationship between photocurrent and incident optical power,and it also illustrates the impact of the reverse bias to the variation of the junction capacitance.According to this model,the photodiode and a CMOS receiver circuit are simulated and designed simultaneously under a universal circuit simulation environment.

Co-design for an SoC embedded network controller

With the development of Ethernet systems and the growing capacity of modem silicon technology, embedded communication networks are playing an increasingly important role in embedded and safety critical systems. Hardware/software co-design is a methodology for solving design problems in processor based embedded systems. In this work, we implemented a new 1-cycle pipeline microprocessor and a fast Ethemet transceiver and established a low cost, high performance embedded network controller, and designed a TCP/IP stack to access the Intemet. We discussed the hardware/software architecture in the forepart, and then the whole system-on-a-chip on Altera Stratix EP1S25F780C6 device. Using the FPGA environment and SmartBit tester, we tested the system＇s throughput. Our simulation results showed that the maximum throughput of Ethemet packets is up to 7 Mbps, that of UDP packets is up to 5.8 Mbps, and that of TCP packets is up to 3.4 Mbps, which showed that this embedded system can easily transmit basic voice and video signals through Ethemet, and that using only one chip can realize that many electronic devices access to the Intemet directly and get high performance.

Event-triggered sampling and fault-tolerant control co-design based on fault diagnosis observer

A co-design scheme of event-triggered sampling mechanism and active fault tolerant control(FTC) is developed. Firstly,a fault diagnosis observer is designed to estimate both the fault and the state simultaneously by using the event-triggered sampled output. Some H∞constraints between the estimation errors and the event-triggered sampling mechanism are established to ensure the estimation accuracy. Then, based on the constraints and the obtained fault information, an event-triggered detector and a static fault tolerant controller are co-designed to guarantee the stability of the faulty system and to reduce the sensor communication cost.Furthermore, the problem of the event detector and dynamic FTC co-design is also investigated. Simulation results of an unstable batch reactor are finally provided to illustrate the effectiveness of the proposed method.

An Internet-enabled Integration of Concurrent Engineering with Co-design

In this paper,the Web-based integration methodology and framework have been developed to facilitate collabora- tive and concurrent engineering design in distributed manufacturing environments.The distributed concurrent engineering and co- design are discussed as key components in the mechanism.The related integration system is presented,which includes four function- al modules:co-design,Web-based visualization,manufacturing analysis and look-up service.It can be used for a design team geo- graphically distributed to organize a collaborative and concurrent engineering design effectively.In particular,the collaborative mechanism incorporated with Java-based and Internet-enabled technologies can generate extended strategies for design and planning. Thus,the proposed integration architecture enables the system to be generic,open and scalable.Finally,for the trend of global manufacturing,a case study of Internet-enabled collaborative optimization is introduced and a discussion on teamwork capability is made.

Broadband Sequential Load-Modulated Balanced Amplifier Using Coupler-PA Co-Design Approach

The basic theory of the sequential load-modulated balanced amplifier(SLMBA)is introduced and the working principle of its active load modulation is analyzed in this paper.In order to further improve the performance of the SLMBA,a codesigned method of the coupler and power amplifier(PA)is proposed,which is different from the traditional design of couplers.According to the back-off point and saturation point of the SLMBA,this coupler-PA codesign approach can make the working state of the coupler and three-way PA closer to the actual situation,which improves the overall performance of the SLMBA.The maximum output power ratio of the control PA and the balance PA is then determined by the preset output power back-off(OBO)of 10 dB,and the phase compensation line is determined by the trace of the load modulation impedance of the balanced PA.In order to verify the proposed method,an SLMBA operating at 1.5–2.7 GHz(57%relative bandwidth)is designed.The layout simulation results show that its saturated output powers achieve 40.7–43.7 dBm and the small signal gains are 9.7–12.4 dB.Besides,the drain efficiencies at the saturated point and 10 dB OBO point are 52.7%–73.7%and 44.9%–59.2%respectively.

Inclusive Architecture:Digital Technologies,Co-design and Qualification of the Project Process

This article presents the scenario of programming use by architects and engineers,creating their own unique tools.The goal is to emulate and understand the phenomenon of Building Information Modeling(BIM)software customization by developing plug-ins that can explore the human-environment relationship.Demonstrate the process for building a plugin that seeks to equalize the theory of accessibility technical standards,visually impaired and architects.Use Design Science Research methodologies to guide the construction of artifacts for specific practical problems and the Collaborative Design/Co-design to understand and know the users’expertise.It is argued that the low quality of projects that include elements for the orientation of the visually impaired in Brazil is often related to an unstructured methodology in which important aspects such as the real needs of this group and the human-environment relationship are neglected.

Kinetic Energy Harvesting Toward Battery-Free IoT:Fundamentals,Co-Design Necessity and Prospects

Energy harvesting(EH)technology is developed with the purpose of harnessing ambient energy in different physical forms.Although the available ambient energy is usually tiny,not comparable to the centralized power generation,it brings out the convenience of onsite power generation by drawing energy from local sources,which meets the emerging pow⁃er demand of long-lasting,extensively-deployed,and maintenance-free Internet of Things(IoT).Kinetic energy harvesting(KEH)is one of the most promising EH solutions toward the realization of battery-free IoT.The KEH-based battery-free IoT can be extensively deployed in the smart home,smart building,and smart city scenarios,enabling perceptivity,intelli⁃gence,and connectivity in many infrastructures.This paper gives a brief introduction to the configurations and basic principles of practical KEH-IoT systems,including their mechani⁃cal,electrical,and computing parts.Although there are already a few commercial products in some specific application markets,the understanding and practice in the co-design and optimization of a single KEH-IoT device are far from mature,let alone the conceived multia⁃gent energy-autonomous intelligent systems.Future research and development of the KEHIoT system beckons for more exchange and collaboration among mechanical,electrical,and computer engineers toward general design guidelines to cope with these interdisciplinary en⁃gineering problems.

Co-design in Public Spaces for Children:The Design Process of a Pocket Park

The active participation of users in the Design Process(DP)in architecture is a collective action,which aims to meet their real needs.In terms of open spaces for children,squares and playgrounds become leisure spaces known for being places of coexistence,interaction and entertainment.However,the vast majority of children’s environments are planned and organized considering the perceptions and experiences of adults.Children become absent from the process of building the contemporary city.Co-design is an important tool for adding users to DP.The objective of this work is,therefore,to include children in the DP of a Pocket Park,using methods and tools to support co-design.The work was structured based on bibliographic review,Focus Group,Culture Maker and Digital Fabrication.The research indicated that the collaborative project promotes assertive communication between children and designers,welcoming their ideas and perceptions in a flexible way.