Benchmark solution of imperfect angle-ply laminated rectangular plates in cylindrical bending with surface piezoelectric layers as actuator and sensor

The static and dynamic responses of simply supported adaptive angle-ply laminates in cylindrical bending are considered. The interlaminar bonding of the host elastic laminate is assumed to be imperfect, described by a spring-layer model, while the bonding between the host elastic laminate and the surface piezoelectric actuator and sensor layers is perfect. The state-space approach, which is directly based on the three-dimensional exact elasticity (piezoelasticity) equations and very effective in analyzing laminated structures, is employed. The numerical results should provide a useful means of comparison in the development of simplified analyses or numerical methods.     

Nonlinear bending response of functionally graded plates subjected to transverse loads and in thermal environments

Nonlinear bending analysis is presented for a simply supported, functionally graded rectangular plate subjected to a transverse uniform or sinusoidal load and in thermal environments. Material properties are assumed to be temperature-dependent, and graded in the thickness direction according to a simple power-law distribution in terms of the volume fractions of the constituents. The governing equations of a functionally graded plate are based on Reddy's higher-order shear deformation plate theory that includes thermal effects. Two cases of the in-plane boundary conditions are considered. A mixed Galerkin-perturbation technique is employed to determine the load-deflection and load-bending moment curves. The numerical illustrations concern nonlinear bending response of functional graded rectangular plates with two constituent materials. The influences played by temperature rise, the character of in-plane boundary conditions, transverse shear deformation, plate aspect ratio and volume fraction distributions are studied.     

钢-混组合截面外包薄钢组合管梁抗弯性能研究

为了对不同夹层混凝土强度的钢-混组合截面外包薄钢组合管梁抗弯性能进行分析,通过试验和有限元软件模拟相结合的方法,选用外层为薄壁不锈钢管,内层为钢管,双壁管中间分别喷注混凝土强度等级为C20、C40、C60的三种试件,采用分级加载方式对试件进行加载,试验结果与有限元软件模拟的结果相吻合。研究结果表明:随着混凝土强度的提高,试件的抗弯承载力提高、延性增大,能发生较大的塑性变形以吸收能量。     

弯曲残余应力对转子蠕变性能的影响研究

针对某600 MW火力发电机组高中压合缸汽轮机转子的中部弯曲进行分析,认为高温蠕变和残余应力的耦合作用是导致转子发生塑性永久变形的主要原因。首先按照转子结构图利用有限元软件ANSYS建立精细化的三维实体模型,并进行温度场和应力场的有限元分析。在此基础上对高中压转子进行热-固耦合分析,通过对转子材料蠕变试验数据进行处理,得到Norton蠕变模型参数,并在ANSYS中对转子的高温蠕变和残余应力进行有限元仿真。研究表明,单纯的高温蠕变不足以引起转子在启动过程中发生弯曲,耦合残余应力的作用后该高中压转子会在很短时间内发生弯曲值超标,选取Norton三参数模型和残余应力生成方法比较有效。该研究对高中压合缸转子中部弯曲原因分析具有借鉴和指导作用。     

行人大腿冲击器的生物仿真度

针对汽车行人保护碰撞试验中大腿冲击器的生物力学特性问题,采用THUMS(total human model for safety)人体模型与大腿冲击器进行对比仿真分析.模拟THUMS-SUV行人交通事故,并对THUMS人体模型大腿所受冲击力和弯矩进行了输出.根据事故中行人大腿初始碰撞条件和行人大腿最低能量状态,分别建立两种工况的行人大腿冲击器碰撞模型并进行模拟,对比分析行人大腿冲击器和THUMS人体模型大腿的动态响应、最大瞬间冲击力和最大弯矩.仿真结果表明:相对THUMS人体模型而言,大腿冲击器的最大瞬间冲击力偏高而最大弯矩偏低,行人小腿和上身的运动和接触作用,会影响大腿部位的接触力和最大弯矩,因此大腿冲击器的生物仿真度有待提高.     

高强钢焊接箱形截面压弯构件局部稳定试验研究

为研究高强钢压弯构件的局部稳定性能，对5个Q460C和5个Q690D钢焊接箱形截面构件进行了单向偏压试验，分析了其破坏形式、局部稳定性能以及承载力；将实测承载力与欧洲规范EN 1993-1、我国标准GB 50017—2017和美国规范ANSI/AISC 360-16相关公式计算结果相比较，以验证各规范对Q460C钢和Q690D钢焊接箱形截面压弯构件屈曲后强度计算的适用性。研究结果表明：所有高强钢焊接箱形截面压弯构件均在柱中附近发生局部屈曲破坏；由轴向压力-轴向压缩变形或轴向压力-水平位移曲线可知，其为极值点失稳；构件的轴向压力-水平位移或轴向压力-应变曲线的形状和局部屈曲模式有关；在翼缘宽厚比为28.1～56.3、腹板高厚比为40.2～80.4、偏心距为20～50 mm范围之内，EN 1993-1和GB 50017—2017中的屈曲后强度计算公式仍然适用于Q460C和Q690D钢焊接箱形截面压弯构件，而ANSI/AISC 360-16中的相关公式需要进一步修正。     

钢管结构法兰连接节点拉弯承载力简化设计方法

法兰连接是钢管结构中一种重要的连接形式,拉、弯作用是法兰连接节点的主要受力工况。国内外现存的法兰连接节点在拉、弯作用下的承载力验算公式很少,且未能全面考虑节点的受力特性,有明显的不足。利用屈服线理论,得到了由法兰板厚度控制的法兰连接节点拉弯承载力计算公式,并与可靠的有限元计算结果相比较,证明了所提出的理论计算公式的合理性和适用性,可为法兰连接节点拉弯设计提供参考。     

Characterization of the residual strains in iterative laser forming

In laser forming, thermally induced strains transverse to the laser scan line vary with depth in the material and contribute most significantly to the desired deformation. The through-thickness transverse residual strain distribution was measured by neutron diffraction in laser-formed low carbon steel and aluminium alloy specimens. The specimens were formed with a wide range of laser line energies covering the temperature gradient mechanism (TGM) and shortening or upsetting mechanism (SM), and for single and multi-pass forming (up to 3 laser passes). Below the saturation line energy where the TGM dominates, the gradient of the through-thickness strain distribution was found to increase with increasing line energy and number of laser passes; the gradient decreased again at line energies above the saturation line energy where the efficiency of the TGM decreases. Iterative laser forming can be applied to reduce weld-induced distortions. The peak longitudinal strain measured in the weld seam of a specimen that had been straightened by iterative laser forming was also significantly reduced.     

Experimental and numerical investigation on three-point bending behaviors of unidirectional warp-knitted composites

This study develops a novel specimen model, which considers the progressive damage of the layers, the knitting yarns, and the interlaminar cohesive zone, to investigate the flexural properties and the interlaminar shear properties of the unidirectional warp-knitted composites. Three-point bending tests are conducted as verification of the numerical model. Improved strain-based Hashin criteria are proposed to analyze the shear nonlinearity. Results show that specimens with small span-to-thickness ratios exhibit obvious nonlinear behaviors and the corresponding simulation results are sensitive to the value of the shear nonlinear factor. Failure mechanism and stress distributions are analyzed based on numerical simulations. The effect of the specimen size on bending behaviors is discussed. The influence of the width is found to be negligible but that of the span-to-thickness ratio is significant. The ranges of the span-to-thickness ratio corresponding to different failure modes are given. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48132.     

Crack tip identification with long FBG sensors in mixed-mode delamination

The uncertainty of the crack tip position inside composite coupons during a delamination test under variable fracture mode conditions reduces the accuracy of the experimental results. In this work a method is presented where the crack tip position is located using long embedded Fibre Bragg Grating (FBG) sensors together with the Optical Low Coherence Reflectometry (OLCR) technique. With this technique the local Bragg wavelength is measured which then enables to calculate the axial strain profile within the grating. Carbon/epoxy samples are tested under different mode ratios through the standard Mixed-Mode Bending (MMB) test. Embedded long FBG sensors are used to measure the axial strain profile along the whole grating at different stages of the test. The crack tip can be precisely identified with the long embedded FBGs and then checked by means of a visual inspection after complete delamination of the sample. The data indicate that the long FBG sensor detects the crack tip inside the sample at least as precisely as the traditionally performed visual inspections carried out during the test by means of the lateral markings. Numerical simulations using cohesive elements are in good agreement with the experimental data.