Bimetal Strips Research Articles

Effect of ARB process on the plane stress fracture toughness, creep properties and forming limit diagram of Aluminum/BN/Copper composite strips

Abstract In the present study, Al/BN/Cu bimetal composite strips were fabricated via the accumulative roll bonding (ARB) process. Then, fracture toughness, mechanical properties, bonding strength, forming limit diagram (FLD), and creep properties have been studied via experimental techniques. The study of creep behavior and mechanical properties showed a formation of a 17 μm atomic diffusion layer at the interface during ARB under three creep loading conditions namely 35 MPa at 225 °C, 35 MPa at 275 °C, and 30 MPa at 225 °C. The tensile strength of samples improved to 144 MPa which was about 234% in comparison with the primary Al monolithic sample. It was observed by the SEM that the fracture types changed to shear kind after higher passes including prominent effects on the fracture morphology. FLD curve dropped severely after the first ARB pass and then began to enhance at higher passes. The fracture toughness value of 30 MPa m1/2 was achieved after ten ARB passes. An intermetallic composition was created near Al. The creep failure time did decline by 44% and the stress level decreased by 13% at a constant temperature. It can be concluded that applied temperature and stress effect on creep properties especially leads to increasing the slope of creep curves with higher stresses. This trend was opposite for the creep temperature at higher temperature levels. Moreover, dynamic recrystallization was observed through the crystalline structure of samples.

THEORETICAL AND EXPERIMENTAL STUDY OF THE ROLL BONDING BEHAVIOR OF BILAYERS AL LAMINATES

In recent years, bimetallic strips have been progressively used in manufacturing to make collective purposes. Amongst cladding approaches, the rolling process is one of the most popular processes in making bimetallic strips. In this study, a new analytical model based on the slab method has been proposed to predict the bond strength of two layer strips. Results show that the bond strength of strips increases with increasing total rolling thickness reduction of the samples. Also, the finite element simulation and an experimental study were run to approve the results obtained from the new analytical model for producing AA1060/AA7075 bimetallic strips. Moreover, the planned analytical model is appropriate for modeling the roll bonding process of the two-layer strips and it is proficient to extend our information in engineering and production of bimetal strips. The bonding strength of bilayer samples enhanced by increasing the reduction in thickness ratio. The peeled surface of samples has been investigated using scanning electron microscopy (SEM).

Cast-rolling force model in solid−liquid cast-rolling bonding (SLCRB) process for fabricating bimetal clad strips

Based on twin-roll casting, a cast-rolling force model was proposed to predict the rolling force in the bimetal solid−liquid cast-rolling bonding (SLCRB) process. The solid−liquid bonding zone was assumed to be below the kiss point (KP). The deformation resistance of the liquid zone was ignored. Then, the calculation model was derived. A 2D thermal−flow coupled simulation was established to provide a basis for the parameters in the model, and then the rolling forces of the Cu/Al clad strip at different rolling speeds were calculated. Meanwhile, through measurement experiments, the accuracy of the model was verified. The influence of the rolling speed, the substrate strip thickness, and the material on the rolling force was obtained. The results indicate that the rolling force decreases with the increase of the rolling speed and increases with the increase of the thickness and thermal conductivity of the substrate strip. The rolling force is closely related to the KP height. Therefore, the formulation of reasonable process parameters to control the KP height is of great significance to the stability of cast-rolling forming.

Implications of Direct and Indirect Heating of Bi-Metallic Strip in MCCBs – Challenges and Solutions

This describes about the main differences between direct and indirect heating of bi-metals for overload protection for MCCBs. It also explains about analysis of thermal behavior of bimetal strip during both steady-state and transient conditions. To validate the thermal model, experimental tests both in steady-state and transient conditions have been done. The time current characteristics curves for both types of MCCB are plotted for meeting relevant product standards and same is validated with actual tripping time. There is a good correlation between experimental and theoretical results. Direct heating of bi-metal element can help in reduction of electrical stresses and also increases the life span of the power cables. It also outlines the challenges overcome during development and solutions for implementation of direct and indirect heating of bi-metal strips for developing the MCCBs for fulfillment of IEC 60947-2 as well as REC specifications.

Analysis of Antichiral Thermomechanical Metamaterials with Continuous Negative Thermal Expansion Properties.

Negative thermal expansion is an interesting and appealing phenomenon for various scientific and engineering applications, while rarely occurring in natural materials. Here, using a universal antichiral metamaterial model with bimetal beams or strips, a generic theory has been developed to predict magnitude of the negative thermal expansion effect from model parameters. Thermal expansivity of the metamaterial is written as an explicit function of temperature and only three design parameters: relative node size, chirality angle, and a bimetal constant. Experimental measurements follow theoretical predictions well, where thermal expansivity in the range of negative 0.0006–0.0041 °C−1 has been seen.

Experimental & theoretical investigation of roll bonding process of multilayer strips by finite element method

In the present study, cold roll bonding process of dissimilar bimetal strips of steel/Al was simulated and investigated using finite element method. To this end, velocity variable was introduced to ABAQUS using UVARM subroutine. Accordingly, prediction of the starting bonding point by the finite element method, based on the criterion of equal velocities of the layers, was in good agreement with the experimental results. In the process of roll bonding of bimetal steel/aluminum strips, the effect of some factors on the bonding strength including the total deformation of the strip, the initial thickness of the strip, the yield stress ratio and the thickness ratio of the layers were studied. In addition, the deformation of each of the steel and the aluminum layers were also investigated during the rolling. The results of finite element simulations, as well as the experimental results, showed that with increasing the total deformation percentage of the strip, the rolling force, the mean pressure at the interface of the layers, the deformation percentage of each layer and the relative bonding length increase. Furthermore, it was found out that increasing the yield strength ratio of the aluminum layer to the steel layer at a certain total deformation percentage of the strip, on one hand, increased the rolling force, the mean pressure at the interface of the layers as well as the relative bonding length and on the other hand, decreased the non-homogeneity in the deformation of the layers. Further studies revealed that decreasing the initial strip thickness at a certain total deformation percentage of the strip reduced the rolling force as well as the non-homogeneity in the deformation of the layers. But it increased the mean pressure at the interface of the layers as well as the relative bonding length. In this regard, the unprecedented consistency of the theoretical and experimental results indicated an appropriate accuracy of the presented finite element analysis in analyzing the cold roll bonding process.

Production of Composite Steel Strips on Continuous Casting and Deformation Assembly

This article describes the resource-saving assembly of continuous casting and deformation for production of three-layer bimetallic strips based on dissimilar steels and alloys. The results describe the theoretical analysis of the metal’s stress and strain state in the deformation zone upon bimetal strip production by sequential combining the layer thickness in the form of steel grades 09G2S–13KhFA–09G2S. Metallographic studies of bimetal structure and hardness along the distance of cyclic deformation zone in various sheet thickness areas are described.

Recrystallization and grain growth at the interface of a bimetallic colaminated strip composed of two different Fe-Ni alloys

Roll bonding is a solid-state welding process widely used to manufacture layered metal composites. Particular properties may thus be obtained using the physical features of each material of the composite. Bimetal plates consisting of two different Fe-Ni alloys were made by roll bonding followed by heat treatment for 90 minutes at various annealing temperatures. The effects of post-rolling heat treatments on the bonding strength of a bimetal strip were investigated in relation to the interface microstructure evolution. Both recrystallization and grain growth took place at the interface during annealing. In particular, nucleation of new grains as well as growing grains crossing the interface may have contributed to the improvement of the bonding strength. Moreover, diffusion through the interface was found to drastically enhance the bonding strength from 850°C up to 1050°C. However, excessive grain growth associated to porosity occurrence probably caused the saturation of the bonding strength beyond 1050°C.

Development of constructed nanoporous graphene-modified electrode for electrical detection of folic acid

In the present study, nanoporous graphene based amperometric detection of folic acid using nanoporous graphene modified electrode was carried out. The preparation of nanoporous graphene, in otherwords reduced graphene oxide (RGO) was done via fast reduction of chemically prepared graphene oxide in an acidic solution using an (Mg/Zn) bimetal strips. Structural, morphological and chemical characteristics of the prepared RGO (Mg/Zn) were determined using Raman spectroscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, Transmission electron microscopy and X-ray diffraction. The successful formation of the RGO was corroborated using FT-IR and XPS results, which showed significant reduction in the oxygen functionalities. The prepared nanoporous graphene was used for the preparation of constructed modified electrode (CME), which subsequently used for electrochemical sensing of folic acid analyte. Owing to its excellent electrocatalytic activity, CME showed enhanced electrochemical response in the neutral solution of folic acid analyte, when compared to the conventional electrodes. From the differential pulse voltammetry, the peak current (0.75 V) for the folic acid analyte in CME electrode was observed to be linear and concentration range of 0.902–8.52 μM with the lower detection limit of 0.025 μM (S/N = 3). The prepared sensor was successfully implemented for real samples with tolerable limits.

Modal Analysis of a New Thermosensitive Actuator Design for Circuit Breakers Based on Mesoscale U-Shaped Compliant Mechanisms

A new mesoscale thermosensitive actuator design for circuit breakers based on a U-shaped compliant mechanism was introduced as a potential replacement for bimetal strips in miniature circuit breakers. In a previous study, the response of this design to the thermal fields produced by a steady current flow was analyzed. This article presents a modal analysis of the compliant mechanism. The goal of the analysis is to compare the natural frequencies of the mechanism with the frequency of the magnetic loads caused by the flow of the alternating currents. Simulations with simple beam elements and 3D elements are presented and results are compared with experimental measurements. The study finds that the natural frequency of the mechanism differs by a factor of about 8 with the AC frequency. The conclusion is that the proposed compliant mechanism design’s performance as a thermal actuator will not be affected by the cyclic loads generated by the forces induced by the AC magnetic fields.

Defects, causes and prevention controls in the continuous bronze/steel bimetal strip sintering process

Abstract Plain bearings are among the most important components which determine the reliability and life of combustion engines. While bearing failures are well known, little consideration has been given to strip that is used to manufacture bearings, though defects in other sintered products are well understood. Bimetal strip defects can under certain circumstances lead to bearing failures in the field. Sintered bronze/steel bimetal strip production is a continuous process, in which the properties of the lining as well as the adhesion between the two dissimilar materials, bronze and steel, are developed during the sintering, compaction rolling, and resintering processes. This paper presents the results obtained by examining different defects in 1250 km of sintered bronze/steel bimetal strip, which was manufactured over three years in an industrial bearing manufacturing facility. The most frequently found defects are porosity, delamination, coarse bronze grains and coarse or non-homogenously distributed lead pools. Strip defects were examined and documented using micrographic analysis and photographs. Fault tree analysis (FTA) was performed to determine the root cause of the defects and prevention controls are discussed.

Initiation of recoverable strain variation in shape memory bimetal strips by ultrasonic vibrations

The realisation of the recoverable strain variation by ultrasonic vibrations was studied in shape memory bimetallic strips produced by explosion welding. Two bimetal “Ti49.4Ni50.6–AISI 304” and “Ti50Ni50–Ti49.3Ni50.7” strips were deformed to 5% and subjected to ultrasonic vibrations. It was found that the strain variation initiated by the ultrasonic vibrations was characterised by a larger recovery strain and occurred at lower temperatures than during conventional heating. This was caused by the simultaneous action of the ultrasonic heating and the repeating variable stress that increased the mobility of the interfaces.

A Passive Temperature-Sensing Antenna Based on a Bimetal Strip Coil.

A passive temperature-sensing antenna is presented in this paper, which consists of a meandering dipole, a bimetal strip and a back cavity. The meandering dipole is divided into two parts: the lower feeding part and the upper radiating part, which maintain electric contact during operation. As a sensing component, a bimetal strip coil offers a twisting force to rotate the lower feeding part of the antenna when the temperature varies. As a result, the effective length of the dipole antenna changes, leading to a shift of the resonant frequency. Furthermore, a metal back cavity is added to increase the antenna’s quality factor Q, which results in a high-sensitivity design. An antenna prototype is designed, fabricated, and measured, which achieves a sensitivity larger than 4.00 MHz/°C in a temperature range from 30 °C to 50 °C and a read range longer than 4 m. Good agreement between the simulation and measurement results is obtained.

A feasibility study on different NDT techniques used for testing bond quality in cold roll bonded Al-Sn alloy/steel bimetal strips

This paper presents non-destructive testing (NDT) results for the detection of bond defects in aluminium-tin (Al-Sn) alloy/steel bimetal strips. Among all types of bimetal strip that are used in the automotive industry for plain journal engine bearings, Al-Sn alloys cold roll bonded (CRB) onto steel backing is the most common type. The difficulty to evaluate the metallurgical bond between the two dissimilar metals is a major industrial concern, which comprises the risk that bearings fail in the field. Considering the harsh performance requirements, 100% online non-destructive testing would be desirable to significantly reduce the business risk. Nowadays bimetal strip manufacturers still rely on destructive testing through different peel-off tests. This work offers the results from four independent NDT studies, using active thermography, shearography, ultrasound and guided wave electromagnetic acoustic transducers (EMATs) and samples with different artificially implanted defects, to explore the feasibility to qualitatively indicate the occurrence of bond defects. A destructive peel off test was used to correlate the NDT results with known bond quality. The studies were done under laboratory conditions, and in case of ultrasound also online under production conditions. During the ultrasound online test, the requirements that a NDT technique has to fulfil for online inspection of Al-Sn alloy/steel bimetal strip were established. For active thermography, shearography and guided wave EMAT techniques, it was theoretically analysed, if the laboratory test results could be transferred to testing under production conditions. As a result, guided waves using EMATs, among the four tested methods, are best suited for online inspection of Al-Sn alloy/steel bimetal strip. This research was carried out in collaboration with MAHLE Engine Systems UK Ltd., an Al-Sn alloy/steel bimetal strip manufacturer for the automotive industry.

Экспериментальное исследование качества обрезки кромки плакирующей ленты при плакировании лент холодной прокаткой

This paper examines the quality of trimming the edges of bimetal strips got by cold rolling. By producing the hard–soft–hard layered metal compositions, a low quality of cutting-up of clad strip edges is often observed. The trimming quality depends on the ratio of thickness of bimetal layers and their mechanical properties. The bimetals studied were composed of annealed strips of aluminium alloys A5 and AMg2 (thickness 1.0 mm, width 25 mm) as a base and brass L90, nickel silver MNTs 15-20 and steel 08kp as a cladding layer. The thickness of the cladding layer was from 7 to 35 % of the thickness of aluminium strip, with the width being equal to 50 mm. The ratio of tensile strength of the plating and the base varied in a wide range from 0.98 to 6.85. The experiments showed that trimming worsens as the ratio increases. The mathematical relation was obtained that gives the limit ratio of component thickness depending on the ratio of tensile strengths of the cladding material and the base providing high quality of edge cutting.

Study on the Annealing Process of a Cu-Zn-Al-Ni Alloy

Aluminum brass possesses an attractive combination of properties including high strength, high thermal and electrical conductivity, good mechanical workability, excellent corrosion resistance, low susceptibility to stress corrosion cracking. This make it a preferred choice for bimetal strips. The materials for preparing bimetal strips with cold roll bonding should have a good plasticity. In the present work, a Cu-Zn-Al-Ni alloy was proposed and the annealing process for this aluminium brass alloy was studied. The effect of annealing temperature and annealing time on the microstructure and mechanical properties was investigated. The proper annealing parameters were obtained.

Modeling of the thermo-mechanical efficiency of the bimetal strip heat engines

This paper presents a theoretical demonstration of the bimetal strip heat engine working, based on the study of the thermo-mechanical instability of the pre-buckled bimetallic beams. Starting from the Euler buckling equation, this paper describes the bimetal strips like classical but non-linear thermodynamic systems, and gives the bistability criterion of such beams. Studying the thermodynamic potentials of these beams helps to evaluate the release of the kinetic energy happening during the beam snap-through, to give the Maxwell relations between each partial derivative of the thermodynamic potentials and to show that the thermal snap-through is a first-order transition according to the Ehrenfest theory. The model is then used to draw the temperature-entropy cycle of the bimetal heat engines and to evaluate the performances of these harvesters (available mechanical energy and thermodynamic cycle efficiency).

SPICE modelling of a coupled piezoelectric-bimetal heat engine for autonomous Wireless Sensor Nodes (WSN) power supply

This paper deals with an electrical modelling and optimization of a thermal energy harvester dedicated to power autonomous systems. Such devices based on bimetal strips and piezoceramics turn thermal gradients into electricity by a two-step conversion mechanism. This work focuses first on a demonstration of a ST-WSN (GreenNet demonstration platform) supplied by the harvester to validate, for the first time, the harvesters viability. That demonstration focuses attention on the need for an optimized power management circuit for piezoelectric generators able to reach output voltages up to 20 V. The work deals then with the proposal of an equivalent lumped element model of the piezoelectric transducer with its SPICE implementation to enable the optimization of a dedicated power management circuit based on the Pulsed Synchronous Charge Extractor (PSCE). Simulations using the SPICE model and the power management circuit lead to an increased extracted power by 144%.

Effects of ultrasonic nanocrystalline surface modification (UNSM) technique on the tribological behavior of sintered Cu-based alloy

This paper presents the effects of ultrasonic nanocrystalline surface modification (UNSM) technique on the tribological behavior of sintered Cu-based alloy prepared using a powder metallurgy (P/M) technique. The tribological behavior of the untreated and UNSM-treated specimens was investigated using a ball-on-disk reciprocating tribometer against a bearing steel ball under dry and oil-lubricated conditions. Results revealed that the UNSM-treated specimens led to a lower friction coefficient and higher wear resistance compared to the untreated specimens. The obtained results demonstrated the beneficial effects of UNSM technique. It is expected that the results of this study may be implemented to the automotive industry with the aim of improving the durability of internal combustion engine (ICE) parts which are made of Cu-based bimetal strips.

FEA Study on the Elastic Deformation Process of a Simple Bimetal Beam

The design of bimetal strips actuators is usually based on some approximate formulas. The cross section of the bimetal actuators is usually constant. In order to optimize the shape of the bimetal it is important to know the configuration of the deformation process in the entire body during real conditions. The paper presents a Finite Element Analysis of simple bimetal beam. There have been considered both thermical and mechanical loads acting on the bimetal actuator . The study focused on the distribution of stresses and the strain energy distribution in both longitudinal and transversal sections. Areas with smallest values and gradients for these parameters could be considered for material removal in order to reduce the volume and optimize the shape of the bimetal simple beam actuator.