Thin Plate Material Research Articles

Study on the Surface Enhancement of Thin-Walled Metallic Materials Using a Novel Double-Side Burnishing Tool

Burnishing is a surface finishing process to produce a smooth surface. Since it can improve the mechanical properties of the material, such as surface hardness, wear resistance, and fatigue strength, in one process, it has been widely used in industry to enhance the surface quality of mechanical parts. However, due to the high burnishing force, it is difficult to use the process of thin materials, because such materials can easily be deformed in the process. In this research, a novel double-sided burnishing (DSB) tool that can process the thin plate material from both sides is designed and fabricated. The developed DSB tool symmetrically moves the burnishing tips on both sides with a single output to facilitate position control. The burnishing forces from the two sides cancel each other, and the moment that causes bending deformation is suppressed during the processing. Different thin plate metallic materials are processed using the developed tool, it is confirmed that deformation during burnishing is suppressed. By investigating the surface properties of the processed specimen, it is found that surface roughness, surface hardness, tensile strength, and fatigue strength can be improved by using the developed DSB tool. This makes it possible to process complicated, thin-walled parts, such as engine and turbine blades, which are supposed to have great potential applications in the automobile and aerospace industries.

Identification of guided Lamb wave modes in thin metal plates using water path corrected frequency – wavenumber [f-k] analysis

Acoustic microscopy is widely used for the material characterization of thin plates having thicknesses <100μm. For thin plate material characterization, the acoustic microscopy-based approach utilizes the guided Lamb wave modes generated in the plates by defocusing a single high-frequency focused transducer. Identification of the guided wave modes is vital in material characterization. Frequency-wavenumber analysis using 2D-FFT is commonly used to identify guided wave modes. In PVDF-based focused transducers used in acoustic microscopy, edge waves originating from the transducer rim influence the generation of guided waves, making the conventional frequency-wavenumber analysis erroneous. This study proposes a new water path corrected frequency-wavenumber (f-k) analysis using 2D-FFT to overcome the challenges imparted by the edge waves. In this approach, the water path of the Lamb wave modes is calculated and removed from the waveforms before performing 2D-FFT. The proposed approach has been demonstrated on thin metal plates of Aluminum, Copper and Brass having thicknesses of 45μm, 52μm and 52μm, respectively. A good correlation is obtained between theoretical and experimental results.

Hydroelastic analysis of floating structures under wave loads

Accurate prediction of hydroelastic response in ocean waves is of great significance to the structural design and reliability design of floating structures. In this paper, based on the potential flow theory, a large floating structure is simplified as a thin-plate material, and the hydrodynamic characteristics of the structure are calculated by using the modal expansion method and the boundary element method. The correctness of the theory and calculation is verified by comparing the experimental and numerical results. Further, the wave properties and structural materials characterization were changed, this paper calculates the stress and deflection of the structure under wave action, and analyzes the effects of hydroelastic response on the safety of the structure.

A Superconvergent Isogeometric Method with Refined Quadrature for Buckling Analysis of Thin Beams and Plates

A superconvergent isogeometric method is developed for the buckling analysis of thin beams and plates, in which the quadratic basis functions are particularly considered. This method is formulated through refining the quadrature rules used for the numerical integration of geometric and material stiffness matrices. The criterion for the quadrature refinement is the optimization of the buckling load accuracy under the assumption of harmonic buckling modes for thin beams and plates. The method development starts with the thin beam buckling analysis, where the material stiffness matrix with quadratic basis functions does not involve numerical integration and thus the refined quadrature rule for geometric stiffness matrix can be obtained in a relatively easy way. Subsequently, this refined quadrature rule for thin beam geometric stiffness matrix is conveniently generalized to the thin plate geometric stiffness matrix via the tensor product operation. Meanwhile, the refined quadrature rule for the thin plate material stiffness matrix is derived by minimizing the buckling load error. It turns out that the refined quadrature rule for the thin plate material stiffness matrix generally depends on the wave numbers of buckling modes. A theoretical error analysis for the buckling loads evinces that the isogeometric method with refined quadrature rules offers a fourth-order accurate superconvergent algorithm for buckling load computation, which is two orders higher than the standard isogeometric analysis approach. Numerical results well demonstrate the superconvergence of the proposed method for the buckling loads corresponding to harmonic buckling modes, and for those related with non-harmonic modes, the buckling loads given by the proposed method are also much more accurate than their counterparts produced by the conventional isogeometric analysis.

Evaluation of Thin-Plate Low Carbon Steel in Spot Welding with Non-Destructive Test (NDT) and Destructive-Test (DT): Pressure Effect

This paper has the purpose of how the pressure affects the weld quality and weldability on thin-plate low carbon steel with a thickness of 1 + 1 mm. The method used to know the impact of the welding quality by experimenting with the welding process with low carbon steel thin plate material with a composition of 99,65% Fe and 0,05% C, it is low carbon steel and has a thickness of 1 + 1 mm using Cu electrode by providing the various parameters given the pressure of 1-5 bar, testing of Non-Destructive Test (Ultrasonic Test) and Destructive Test (DT): shear testing, microstructure test. The result of NDT testing obtained deformation of thick plate thickness at 1 bar pressure has bigger deformation compared to 5 bar pressure, while in microstructure test result of 1-2 bar pressure has better weldability than the pressure of 3-5 bar, while the result of the tensile - shear test obtained a large load of 1 bar of 544 kgf greater than 5 bar tensile - shear test with load 248 kgf, it can be recommended for welding on thin-plate low carbon steel 1 + 1 mm thickness can be given 1 bar loading.

Symplectic Solutions in Stress Analysis of Thin Plates

Aiming at the common elastic thin plate materials in engineering, the dual control differential equation and the complete solution space composed of zero eigensolution and non-zero eigensolution are established in the state space. On this basis, the non-homogeneous condition of the boundary and the solution method of the non-homogeneous equation are studied systematically. The stress distribution of thin plate bending problem is discussed with an example, and the stress concentration of material under special constraints is analyzed.

A Microcrack Location Method Based on Nonlinear S0 Mode Lamb Wave and Probability Scan Positioning Imaging Matrix

Early damage, such as microcrack, occupies most of the fatigue life of materials, and timely detection of early damage and positioning has great engineering and economic value. In this paper, a matrix scanning and positioning imaging method based on a probabilistic algorithm is proposed. Cooperating with the single-mode (S0) lamb wave, the microcrack in the thin plate material can be efficiently positioned. Taking the S0 mode lamb wave as the fundamental wave can effectively reduce the influence of the dispersion effect on the signal analysis. Meanwhile, in order to reduce the noise interference, the signal is reconstructed by empirical mode decomposition (EMD) to achieve the filtering effect. Then, the ABAQUS finite element simulation software is used to compare the positioning results under different locations of microcrack and different arrangements of probe. Finally, the feasibility of the localization algorithm is verified by the RAM-5000 SNAP nonlinear ultrasound system. The experimental results are consistent with the simulation theory, and the microcrack is effectively positioned. This facilitates our timely remedial action or further assessment of the remaining value of the material.

Experimental study of the pull-out resistance of alternative high-strength fasteners for wood-based materials

ABSTRACTMore curtain-wall facings are fastened non-visibly to create a uniform building surface. As a consequence of bigger panels and the invisible attachment, the load effects on the fasteners and the fixing areas of the panels are increased. These include the tare weight and the tensile load due to the wind load. Therefore, this study assessed the tensile load of novel fasteners in two different wood materials. A new façade panel material is high-pressure laminate. It consists of cellulose layers soaked in epoxy resin. The second tested material was a modified pine wood, which is produced by impregnation and subsequent heat-curing. It is comparable to highly durable tropical wood. The survey focused on three alternative fixing materials such as screw inserts, drive-in nuts and undercut anchors. The pull-out resistance and failure pattern of the specimens with an alternative fastener are compared to those with wood screws. Furthermore, it was tested whether different temperatures between −20°C and +80°C have an impact on it. The results demonstrate that the alternative fasteners are much more effective than normal wood screws. The pull-out resistance out of the same thin plate material was up to four times higher.

Modeling elevated-temperature mechanical behavior of high and ultra-high strength steels in structural fire design

High and ultra-high strength steels are increasingly used in structures of tall and super-tall buildings, where fire safety has a substantial impact on the structural design. However, more widespread employment in engineering practice is substantially impeded by the lack of suitable design models for the constitutive mechanical behavior of such steels at elevated temperatures; and respective available experimental research is limited to investigations of unusually thin plate material with respect to structural applications. The present study completes the current database with an extensive series of strain-rate controlled tensile tests at different strain-rates with coupon specimens from high and ultra-high strength steel plates of varying thickness, and approves on the basis of this novel most comprehensive and consistent database that existing constitutive fire design models for mild carbon steels are only restrictedly adoptable for high strength steels. Analysis of the impact of the revealed model shortcomings at the material level on structural fire designs shows that the model's overestimation of the elevated-temperature yield strength leads to unsafe fire designs of structural applications with strength-induced failure modes, whereas in contrast the model's underestimation of the elevated-temperature Young's modulus leads to occasionally highly overconservative fire designs of structural applications with stability-induced failure modes.

Laser beam welding of CuZn open-cell foams

Porous metallic materials with cellular structures combine many physical and functional characteristics. This mixture of different properties makes these materials very attractive for the development of advanced applications, which are especially important in the biomedical, structural and functional engineering, and electrochemical fields. Because of their cellular structure, unconventional processing is becoming increasingly important for promoting the industrial applications of these materials.In this work, the welding of open-cell Cu60Zn40 [wt%] foams using a 1kW continuous-wave fibre laser was investigated. During welding tests performed in the bead-on-plate configuration, a deterioration of the cellular structure was observed, with poor evidence for the joining of surfaces. In contrast, tests performed in the lap-joint configuration resulted in successful welding using a 1-mm-thick plate of the same material as the foams. The effect of the process speed on the geometrical characteristics of the transverse section of the joints was studied, and the heat-affected zone was evaluated via a hardness test. Finally, a compositional analysis of the weld bead was performed using a scanning electron microscope coupled with an energy dispersive spectrometer.The results of this study indicate that welding processes using a fibre laser can be utilised to join Cu-based foams. Weld beads in the lap-joint configuration were achieved due to the thin plate material filling the pore voids.

Wavelet Ridge Analysis of Lamb Wave

Lamb wave has important application value in material nondestructive testing. It is a kind of ultrasonic guided wave propagating in thin plate material. It has the dispersion characteristic, which greatly limits its wide application in material evaluation. After continuous wavelet transformation, we extract the feature of ridge of Lamb wave signals by adopting crazy climber algorithm. Experimental results show that Lamb wave after transmission of a certain distance has the characteristics like asymptotic signal. The ridge can reflect the dispersion characteristic of Lamb wave.

Numerical simulation of laser-generated ultrasound by the finite element method

The results obtained from the finite element model of laser-generated ultrasound are presented in terms of temperature and displacement. According to thermoelastic theory, considering the temperature dependence of the thermophysical parameters of the material, the transient temperature field can be precisely calculated by using the finite element method; then, laser-generated surface acoustic wave forms are calculated in Al plates of various thicknesses. The elastic waves excited by a pulsed laser in a thin plate are typical Lamb waves, and the numerical results demonstrate that the surface vibration is mainly determined by the lower frequency components of the symmetric mode s0 and antisymmetric mode a0 of the lowest order in very thin plate materials. It is also indicated that, when the sample thickness increases, both the higher frequency components of the lower Lamb wave modes and the higher order Lamb wave modes should be considered. In a relatively thicker plate, the numerical model can still capture the significant details of the transient features taking place in the plates. The surface skimming longitudinal and shear waves are relatively stronger in the near field, distorting the observed wave form of the Rayleigh wave. These effects must be considered when the quantitative near field is applied to determining elastic parameters or residual stresses.

自動車用コネクタ材料の応力緩和特性

Stress relaxation is an important property for spring materials. In particular it is desired to know the relaxation at an elevated temperature from practical viewpoint, however standard method for the measurement of the property is not yet established. Authors made a new apparatus for testing the high temperature stress relaxation of thin plate materials. A thin sheet of Cu-Ni-Sn alloy, which has an excellent stress relaxation character at room temperature, is submitted to inspection for the testing in the temperature range at 423K. The measurement gave a reliable result as like as measurements obtained from conventional methods at room temperature.

Ultrasonic tomography for materials characterization

Ultrasonic tomography may be used as a method for imaging the internal structure of a wide range of solid materials. To do so requires tomographic reconstruction programs that can deal with irregular geometries, acoustic raybending and the possible presence of velocity anisotropy. Image reconstruction techniques are now available to deal with such problems, and have been applied to several situations of interest to materials characterization. The first of these involves the study of samples in bulk solid form, where a scanning system involving sliding contact transducers has been used to collect ultrasonic data and image materials that have been subject to thermal cracking. Additional studies have investigated the failure of fiber‐reinforced polymer composites under applied load. In both cases, correlation with acoustic emission (AE) data has been performed. Other work has used immersion and noncontact ultrasonic transduction to image the structure of thin plate material using Lamb waves. In all cases, images will be presented and conclusions drawn on the type of information available from such images. [Work supported by SERC.]

Elastic interaction between screw dislocations and an internal crack in a medium of finite thickness

Abstract Using the conformai mapping technique, the elastic interaction between a screw dislocation and an internal crack in a thin plate material is investigated. The stress field, the stress intensity factor at the crack tip, and the force on the dislocation are derived. The stress intensity factor at the crack tip is dependent on the positions of the lattice screw dislocations, the dislocations inside the crack, the applied stress and the geometry of the medium. From the image force, the zero‐force points between the crack tip and free surface are obtained. The number of zero‐force points varies from one to five depending on the applied stress and dislocations inside the internal crack. Finally, our results can be reduced to several special cases.

The effect of the dislocation image force on the brittle behaviour of materials

An exact solution for dislocations interacting with a surface crack in a thin plate material is derived. This solution is compared with the approximate solution proposed by Lung (1987). However, his result is only valid for a material with a sufficiently large thickness. It is found that the thinner materials have high toughness. Finally, the ratio of volume to area related to fracture is discussed.

A modified hole-drilling technique for determining residual stresses in thin plates

This paper presents a modified hole-drilling technique for measuring residual stresses in sheet and thin-plate materials. The primary advantage of the modification is that it eliminates the necessity for calibration of each experimental hole-gage assembly. The relaxation coefficients are calculated from theory, and the strain components which are extraneous to the true relaxation strains are determined and separated from the measured relaxation strains.

Mission Bridge—Design and Construction of the Steel Box Girder

The main span of the four-lane highway Mission Bridge is 440 ft (134.1 m) long with 290 ft (88.4 m) flanking spans, and consists of a steel box girder with an orthotropic steel plate deck. A box girder was adopted due to the structural efficiency of the box section and advantages in using thin plate material. The design is based on CSA Standard S6-1966 and the AISC Design Manual for Orthotropic Steel Plate Deck Bridges as far as applicable and with some deviations. The design was reviewed subsequent to the failure of steel box girder bridges abroad. The strength of the bottom plate in compression and the transverse bolted joints in compression received special attention. The joints of the deck plate made in the field are welded.In the fabrication and erection of the bridge, advantage was taken of the marine location of the fabrication yard. Special erection equipment was developed for the job. A key element in the scheme was ease with which the erection crane scow could be positioned.The application of the hot asphaltic concrete paving caused considerable thermal expansion of the steel structure.The cost of the steel superstructure was about the same as was estimated for a concrete superstructure. However, site conditions were such that the weight of the concrete structure would have increased the foundation costs.