Influence Of Local Deformation Research Articles

On the influence of local deformation on structural dynamic models of bolted lap joints

The acoustic and structural dynamic behavior of technical products—often referred to as Noise, Vibration, and Harshness (NVH)—is an important criterion in customers’ purchasing decisions. Therefore, NVH optimization is a crucial goal of the development process. NVH is influenced by dynamic excitations, caused by time-varying forces e.g. in gears or electric machines, as well as the transfer path of sound from the location of excitation to a receiver such as a driver’s ear and the sound perception. The behavior of the transfer path is determined by amplification or isolation of structure-borne and airborne sound between the location of the excitation and the location of the receiver. As a result, eigenfrequencies and damping in the transfer path form crucial structural dynamic properties.Within jointed structures, friction between the surfaces of lap joints are the most dominant influencing factor on the transfer path’s damping. In order to increase the efficiency of NVH optimization in the development process, methods of virtual product development have become an established tool. Especially finite element method (FEM) and elastic multi-body simulation (eMBS) have allowed to numerically evaluate the structural dynamic behavior of technical products before manufacturing physical prototypes. While numerous methods for modeling jointed structures exist in FEM and eMBS environments, the choice of suitable eMBS models of joints remains challenging today. This is because the frictional behavior between the jointed partners in higher frequencies is largely influenced by the deformation of the joint surface. However, the deformation of the jointed parts is simplified in eMBS models compared to quasi-continuous FEM models. Accordingly, the choice of a suitable spatial discretization of eMBS joint models is a key factor in the model quality of eMBS models. Thus, this work proposes a modeling guideline for eMBS models of jointed structures based on the deformation of the structure using the criterion of rigidness. The method is demonstrated on an eMBS model of the academic Brake Reuß beam, which consists of two beam elements jointed with three screws in an overlap lap joint. Good agreement between eMBS simulation and measurement with an error of 1 dB is achieved using the proposed modeling method.

Influence of local deformation on valley transport properties in the line defect of graphene

The line defect of graphene has significant applications in valleytronics, which has received extensive attention in recent years. It is found experimentally that there exists local deformation around the line defect. Current studies generally believe that the influence of local deformation on the valley transport properties can be negligible, because the modifications to the nearest neighbour hopping energy is less than 5% under the small deformation. Based on the first-principles calculations and the non-equilibrium Green’s function method, we investigated the effect of local deformation on the valley transport properties of two different kinds of line defects, the 58 ring line defect and the 57 ring line defect. It is found that for the 58 ring line defect, the effect of local deformation on the valley transmission coefficient is not evident at lower energies. However, at higher energies, the impact of local deformation is obvious, and the maximum valley transmission coefficient does not decrease with increasing energy, but can be maintained 1 within a large energy range. In contrast, the influence of local deformation on the valley transmission coefficient of the 57 ring line defect indeed can be negligible, regardless of the level of energy. Further investigation indicates that the change of the C—C bond length connected to the two defect atoms in the 58 ring plays a key role in the transmission of the valley states across the line defect. If this part of the influence is not taken into account, the valley transmission coefficient is nearly unaffected by the local deformation. The valley state enters the right side of the line defect directly through the bond connected to the line defect, so the change in bond length connected to the line defect has a significant impact on the valley transmission. This special structure does not exist in the 57 ring, where the valley states will have to pass through a narrow region containing 57 ring to enter the right side of the line defect, resulting in different valley scattering phenomena. By constructing two parallel line defects, the 100% valley polarization can be achieved in a large angular range with the 58 ring line defect. The finding has important implications for the design of graphene line defect based valley filters.

Influence of local deformation on critical current of high temperature superconductor tape

In many applications, high temperature superconductor (HTS) tapes are placed on top of uneven surfaces. Because the electrical properties of HTS tapes are sensitive to mechanical loading, mechanical stress generated at such local imperfections can considerably decrease the critical current of a HTS tape. Then a method of predicting degradation of critical current from a numerical simulation would be helpful.We present the results of 3D mechanical finite element model analysis, using the software ANSYS for optimising the geometry of a round CORT (Conductor-On-Round-Tube) cable. In these simulations, the HTS tape is bent around a circular former of certain diameter with a surface imperfection. We used three parameters to characterize the imperfection geometry: diameter of the former, the height and the width of imperfection. In order to validate the mechanical simulation results, we performed in-situ measurement of critical current of HTS tape.

An Approximate Solution to the Plastic Response of Clamped Sandwich Beams Under Concentrated Loading

In the present study, the bending behavior of a clamped sandwich beam subjected to a concentrated loading is investigated. An analytical model is developed considering the influence of localized deformation of the beam under the loading point on its overall bending. An approximate relationship for the load and local indention vs. global displacement is derived. The numerical results found by FEA models are in good agreement with theoretical solutions.

A theoretical and experimental study of the deformation of the piston-cylinder unit of a metrological pressure balance

Pressure balance is a measuring system widely used in metrology as a reference standard. The common procedure is to estimate the pressure from an analytical formula involving a set of phenomenological parameters. These parameters are determined experimentally by calibration tests of the balance. In particular, the piston-cylinder deformation is taking into account by the use of a global distortion coefficient and by the use of an effective area of the piston. In order to analyze the possible influence of local deformation on the pressure estimation, a Finite Element (FE) model has been developed using OpenCavok FE code. For a given position of the piston in the cylinder chamber, for a given initial gap between of the cylinder and the chamber, a coupled fluid-structure calculation is carried out. From the local fields, mean values are calculated from which the effective area of the piston-cylinder unit. The analysis is conducted for several engagement lengths of the piston in the chamber and for several loads. The first results obtained show that the local deformation play a role and that FE models could help for precise calculation of the measured pressure.

303 LSI配線中のCu/SiN界面付着強度に対する銅粒界局所変形の影響(OS3-1 MEMSと先進材料(1),OS3 MEMSと先進材料)

303 LSI配線中のCu/SiN界面付着強度に対する銅粒界局所変形の影響(OS3-1 MEMSと先進材料(1),OS3 MEMSと先進材料)

Axial Capacity of Steel Angles with Local Deformation

Axial compressive and tensile tests on twenty single equal-leg steel angles with different local deformations were presented. The results show the influence of local deformation on the axial capacity of steel angles. The angles with local deformations under axial compression fail mostly due to flexural-torsional buckling whereas angles without local deformation fail mostly because of local flexural buckling. The axial compressive capacity of angles is significantly reduced in the presence of local inner concave or outer convex deformations. Based on the test results, a finite element analysis was further conducted using ABAQUS 6.12. Analytical results given by finite element analysis are close to the test results. The former is usually a little higher with a deviation rate around ±10%. Finally, two empirical equations are proposed to evaluate the residual ultimate capacity of steel angles with local deformations. The predictions of the equation agree well with the test results.

Effect of corrosive media on the fatigue life of degraded D16- and V95-type aluminum alloys

We present the results of static and fatigue testing of D16 and V95 aluminum alloys in the as-received state, after model degradation, and after in-service degradation in air and in a corrosive medium (3% NaCl solution). The mechanical and electrochemical characteristics most sensitive to the degradation of these alloys in the process of long-term operation are determined. It is shown that the fatigue life of the specimens of degraded alloys may decrease as compared with the intact state. Thus, for D16chT (D16) alloy, it becomes 1.2-1.4 times shorter in air and 1.5-2 times shorter in the corrosion medium. At the same time, for V95pchT1 (V95T1) alloy, the fatigue life becomes 1.8-2.2 and 2.2-2.6 times shorter, respectively. It is possible to conclude that the fracture resistance of passivating films on the newly formed surfaces under the combined influence of local deformation and hydrogen affects the corrosion-fatigue fracture resistance of D16 and V95 aluminum alloys to a greater extent than the kinetics of formation of these films.

Pointing and tracking errors due to localized deformation in inter-satellite laser communication links

Instead of Zernike polynomials, ellipse Gaussian model is proposed to represent localized wave-front deformation in researching pointing and tracking errors in inter-satellite laser communication links, which can simplify the calculation. It is shown that both pointing and tracking errors depend on the center deepness h, the radiuses a and b, and the distance d of the Gaussian distortion and change regularly as they increase. The maximum peak values of pointing and tracking errors always appear around h=0.2lambda. The influence of localized deformation is up to 0.7microrad for pointing error, and 0.5microrad for tracking error. To reduce the impact of localized deformation on pointing and tracking errors, the machining precision of optical devices, which should be more greater than 0.2?, is proposed. The principle of choosing the optical devices with localized deformation is presented, and the method that adjusts the pointing direction to compensate pointing and tracking errors is given. We hope the results can be used in the design of inter-satellite lasercom systems.

Influence of localized deformation on A-286 austenitic stainless steel stress corrosion cracking in PWR primary water

The low cycle fatigue (LCF) behaviour of precipitation-strengthened A-286 austenitic stainless steel was first investigated at room temperature under 0.2% plastic strain control. LCF led to hardening for the first 20 cycles and then to significant softening. LCF-induced dislocation microstructure was characterized using both bright and dark-field imaging techniques in transmission electron microscopy. Cycling softening was correlated with the formation of precipitate-free localized deformation bands. The effect of these precipitate-free localized deformation bands on A-286 stress corrosion cracking (SCC) behaviour in PWR primary water was then examined by means of constant extension rate tensile (CERT) tests at 320 °C and 360 °C. Comparative CERT tests were performed on companion specimens with similar yield stress but pre-fatigued to a few cycles (4–8) or between 125 and 200 cycles. Specimens pre-fatigued to a few cycles with no precipitate-free localized deformation bands exhibited little susceptibility to intergranular SCC (IGSCC). In contrast, the presence of precipitate-free localized deformation bands formed by pre-fatigue to between 125 and 200 cycles strongly promoted IGSCC. The interest of the approach used in this study is to provide insight into the role of localized deformation in irradiation assisted stress corrosion cracking.