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Graphical Abstract

Themed：Aeronautics and Astronautics

Theor.Appl.Mech.Lett.6，152-156（2016）

Residual stress measurement for injection molded components

Achyut Adhikari，Thomas Bourgade，Anand Asundi

Residual stress induced during manufacturing of injection molded components such as polymethyl methacrylate（PMMA）affects the mechanical and optical properties of these components.These residual stresses can be visualized and quantified by measuring their birefringence.In this paper，a low birefringence polariscope（LBP）is used to measure the whole-field residual stress distribution of these injection molded specimens. Detailed analytical and experimental study is conducted to quantify the residual stress measurement in these materials.A commercial birefringence measurement system was used to validate the results obtained to our measurement system.This study can help in material diagnosis forquality and manufacturing purpose and be useful for understanding of residual stress in imaging or other applications.

Theor.Appl.Mech.Lett.6，157-161（2016）

Fabrication of nanoscale speckle using broad ion beam milling on polymers for deformation analysis

Qinghua Wang，Satoshi Kishimoto，Yoshihisa Tanaka，Kimiyoshi Naito

We first report a fabrication technique of nanoscale speckle patterns on polymers using broad ion beam milling.The proposed technique is simple and lowcost to produce speckles ranging from dozens of nanometers to less than three micrometers in a large area of several millimeters.Random patterns were successfully produced with an argon（Ar）ion beam on the surfaces of four kinds of polymers：the epoxy matrix of carbon fiber reinforced plastic，polyester，polyvinylformal-acetal，andpolyimide.The speck lemorphologies slightly vary with different polymers.The fabricated speckle patterns have good time stability and are promising to be used to measure the nanoscale deformations of polymers using the digital image correlation method.

Themed：Aeronautics and Astronautics

Theor.Appl.Mech.Lett.6，162-166（2016）

Instantaneous phase-stepping interferometry based on a pixelated micropolarizer array

Satoru Yoneyama，Shuichi Arikawa

（6）提升科技支撐。加強(qiáng)覆蓋水環(huán)境質(zhì)量、重點(diǎn)污染源、生態(tài)狀況的洞庭湖區(qū)生態(tài)環(huán)境監(jiān)測網(wǎng)絡(luò)建設(shè)，建立水質(zhì)監(jiān)測預(yù)警系統(tǒng)；設(shè)立洞庭湖保護(hù)和治理科技專項(xiàng)，集中優(yōu)勢科研力量，加強(qiáng)基礎(chǔ)課題研究，查清污染成因，提出治理對策，尤其是總磷、總氮治理；圍繞生活廢水低成本處理、飲水安全保障等方面加大先進(jìn)適用技術(shù)及裝備研發(fā)和示范推廣力度，推動精準(zhǔn)治理、精細(xì)化管理。

In this paper，we propose an instantaneous phase-stepping method for determining phase distribution of interference fringes utilizing a camera that is equipped with a micro-polarizer array on the sensor plane.An optical setup of polarization interferometry using a Mach-Zehnder interferometer with two polarizers is constructed.Light emerging from the interferometer is recorded using a camera that has a micro-polarizer array.This micro-polarizer array has four different optical axes.That is，an image obtained by the camera contains fourtypesofinformationcorrespondingtofourdifferentopticalaxesofthepolarizer.The four images separated from the image recorded by the camera are reconstructed using gray level interpolation.Subsequently，the distributions of theStokesparametersthatrepresentthestateofpolarizationarecalculatedfrom the four images.The phase distribution of the interference fringe pattern producedbytheMach-ZehnderinterferometeristhenobtainedfromtheseStokes parameters.Theeffectivenessoftheproposedmethodisdemonstratedbymeasuring a static carrier pattern and time-variant fringe patterns.It is emphasized that this method is applicable to time-variant phenomena because multiple exposures are unnecessary for sufficient data acquisition in the completion of the phase analysis.

Theor.Appl.Mech.Lett.6，167-170（2016）

Visualizing surface strain distribution of facial skin using stereovision

Nagisa Miura，Tsubasa Sakamoto，Yuichi Aoyagi，Satoru Yoneyama

An experimental technique has been developed for measuring and visualizing strain distribution on facial skin.A stereovision technique based on digital image correlation is employed for obtaining the displacement distribution on the human face.Time-variation of the movement of the facial skin surface is obtained from consecutive images obtained using a pair of high-speed cameras.The strains on the facial skin surface are then obtained from the measured displacements.The performance of the developed system is demonstrated by applying it to the measurement of the strain on facial skin during the production of sound.Results show that the strains on facial skin can be visualized.Further discussion on the relationship between the creation of wrinkles and strains is possible with the help of the developed system.

Theor.Appl.Mech.Lett.6，171-175（2016）

Fabrication of micro-scale gratings for moiré method method with a femtosecond laser

Gaosheng Yan，Jianguo Zhu，Yanlong Huang，Wenfen Hao，Yanjie Li

Fabrication of micro gratings using a femtosecond laser exposure system is experimentally investigated for the electron moiré method.Micro holes and lines are firstly etched for parameter study.Grating profile is theoretically optimized to form high quality moiré patterns.For a demonstration，a parallel grating is fabricated on a specimen of quartz glass.The minimum line width and the distance between two adjacent lines are both set to be 1μm，and the frequency of grating is 500 lines/mm.The experimental results indicate that the quality of gratings is good and the relative error of the gratings pitch is about 1.5%.Based on moiré method，scanning electron microscope（SEM）moiré patterns are observed clearly，which manifests that gratings fabricated with the femtosecond laser exposure is suitable for micro-scale deformation measurement.

Solid Mechanics

Theor.Appl.Mech.Lett.6，176-181（2016）

The mechanics and deformation of high temperature steel frame rapidly cooled by spray water in fire fighting

Yunchun Xia

A finite element is established for analyzing the dynamical mechanics and deformation of steel frame at high temperature when it is rapidly cooled down by spray water in fire fighting.The simulation result shows that remarkable mechanicalcouplingeffectsareproducedintheprocess，andthesectionalstressin rapidcoolingdownisfoundconsiderablylargerthanthatinheating-up.Meanwhile，the stress and deformation of a beam mainly related to cooling rate and location are much larger than those of a column in rapid cooling.In fire fighting，the structure onthe first or second foor was more dangerous than thoseon other foors in rapid cooling.Theseresultscouldprovideatheoreticalreference for the design of steel structure and fire fighting.

Fluid Mechanics

Theor.Appl.Mech.Lett.6，182-185（2016）

Traffic flow sensitivity to visco-elasticity

M.N.Smirnova，A.I.Bogdanova，Z.J.Zhu，N.N.Smirnov

This letter reports traffic flow sensitivity to visco-elasticity，with the traffic ?ow modeling briefly described at first and then used to do traffic flow simulations whose results can reflect the properties of spatial-temporal evolution of ring traffic flow.It reveals that visco-elasticity plays crucial role in formation of traffic ?ow patterns，implying that self-organization of traffic flow is crucial in determining traffic flow status.

Dynamics and Control

Theor.Appl.Mech.Lett.6，186-194（2016）

Numerical analysis of dynamic response of the vehicle-bridge coupled system on long-span continuous girder bridge

Lipeng An，Dejian Li，Peng Yu，Peng Yuan

To systematically study the vehicle-bridge coupled dynamic response and its change rule with different parameters，a vehicle model with seven degrees of freedom was built and the total potential energy of vehicle space vibration system was deduced.Considering the stimulation of road roughness，the dynamic response equation of vehicle-bridge coupled system was established in accordance with the elastic system principle of total potential energy with stationary valueandthe''set-in-right-position''rule.Onthebasisoftheself-compiledFortran program and bridge engineering，the dynamic response of long-span continuous girder bridge under vehicle load was studied.This study also included the calculation of vehicle impact coefficient，evaluation of vibration comfort，and analysis of dynamic response parameters.Results show the impact coefficient changes with lane number and is larger than the value calculated by the ''general code for design of highway bridges and culverts（China）''.The Dieckmannindexofbridgevibrationisalsorelatedtolanenumber，andthevibration comfortevaluationisgoodinnormalconditions.Therelevantconclusionsfrom parametricanalyseshavepracticalsignificancetodynamicdesignanddailyoperationoflong-spancontinuousgirderbridgesinexpressways.Safetyandcomfort are expected to improve significantly with further control of the vibration of vehicle-bridge system.

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