VIBRATIONS OF STEPPED ONE-WAY THIN RECTANGULAR PLATES SUBJECTED TO IN-PLANE TENSILE/ COMPRESSIVE FORCE IN Y-DIRECTION ON WINKLER'S FOUNDATION

Differential equations of free/forced vibrations of n_step one_way thin rectangular plates subjected to in_plane tensile/compressive force in y_direction on Winkler's foundation are established by using singular functions, their general solutions solved for, expression of vibration mode function and frequency equation on usual supports derived with W operator. Influence functions for various cases deduced here may also be used to solve problems of static buckling or stability for beams and plates in relevant circumstances.

Forced Compressed Air Cooling System for a 300 MW Steam Turbine in Waigaoqiao Power Plant

The 300 MW steam turbine installed in Waigaoqiao Power Plant with combined HPIP cylinders of double casing structure is a product of the Shanghai Turbine Works utilizing licensed technology. It has a large heat storage capacity and good thermal insulation, so the metal temperature of first stage of HP cylinder (FSMTI) may reach 400-450℃ after shut down and it takes 7-8 days to cool to 150℃ by natural cooling, Now with a forced cooling system the cooling time may be reduced to 40 hours, so that the turbine may be opened for repair work in about 5-6 days. The cooling system for #2 unit and test procedure are briefly described below.

A numerical study of macro-mesoscopic mechanical properties of gangue backfill under biaxial compression

Based on the Particle Flow Code(PFC^(2D)) program,we set up gangue backfill models with different gangue contents and bond strength,and studied the stress-strain behaviours,the pattern of shear band and force chains,motion and fragmentation of particles under biaxial compression.The results show that when the bond strength or contents of gangue are high,the peak strength is high and the phenomena of post-peak softening and fluctuation are obvious.When gangue contents are low,the shape of the shear band is symmetrical and most strong force chains transfer in soil particles.With an increase in gangue content,the shape of the shear band becomes irregular and the majority of strong force chains turn to transfer in gangue particles gradually,most of which distribute along the axial direction.When the gangue content is higher than 50%,the interconnectivity of strong force chains decreases gradually:at the same time,the strong force chains become tilted and the stability of the system tends to decrease.With an increase in external loading,the coordination numbers of the system increase at first and then decrease and the main pattern of force chains changes into columnar from annular.However,after the forming of the advantageous shear band,the force chains external to the shear band maintain their columnar shape while the inner ones bend obviously.As a result,annular force chains form.

A Method Based on Multi-Body Dynamic Analysis for A Floating Two-Stage Buffer Collision-Prevention System Under Ship Collision Loads

The collision of ships poses a great threat to the piers in navigable waters.The kinetic energy of the moving ship can be consumed not only with the structural deformation,but also with tensile force from the proposed Floating Two-stage Buffer Collision-Prevention System(FTBCPS).The actual anti-collision effect of the current designed FTBCPS can be evaluated by the dynamic simulation.The construction method of 3D model is introduced,and the system initial state is defined.The transformation matrix and the basic kinematics vector are given,and the system basic dynamics equation is then created.The mechanical analysis on each component is carried out,and the detailed process of numerical simulation is also given.The simulation results indicate that collision direction and collision position have a great influence on the system kinematic response.Bridge pier faces the greatest threat when a ship hits the floater on the front beam in a nearly vertical direction,or on the side beam in a larger course angle.The study shows that the current designed FTBCPS can make full use of the fracture tensile property of polyester ropes and keep the tensile force acted on pier within its bearable range at the same time.The collision direction has a significant effect on the dynamic response of the colliding bodies,but no failure appeared in the simulations,which indicates that the current designed FTBCPS can protect bridge piers of all cases for the 5000-t ship with a velocity smaller than 5 m/s in navigable waters.

Mechanical force-induced assembly of one-dimensional nanomaterials

There have been intensive and continuous research efforts in large-scale controlled assembly of one-dimensional(1D)nanomaterials,since this is the most effective and promising route toward advanced functional systems including integrated nano-circuits and flexible electronic devices.To date,numerous assembly approaches have been reported,showing considerable progresses in developing a variety of 1D nanomaterial assemblies and integrated systems with outstanding performance.However,obstacles and challenges remain ahead.Here,in this review,we summarize most widely studied assembly approaches such as Langmuir-Blodgett technique,substrate release/stretching,substrate rubbing and blown bubble films,depending on three types of external forces:compressive,tensile and shear forces.We highlight the important roles of these mechanical forces in aligning 1D nanomaterials such as semiconducting nanowires and carbon nanotubes,and discuss each approach on their effectiveness in achieving high-degree alignment,distinct characteristics and major limitations.Finally,we point out possible research directions in this field including rational control on the orientation,density and registration,toward scale-up and cost-effective manufacturing,as well as novel assembled systems based on 1D heterojunctions and hybrid structures.

Strength and Deformation of Axially Loaded Fiber-Reinforced Polymer Sheet Confined Concrete Columns

Experimental results of 29 axially loaded fiber-reinforced polymer sheet (FS) confined concrete columns and two reference plain concrete columns are introduced. Twenty four column specimens were confined with carbon fiber sheet (CFS) and five column specimens were hybrid confined with both CFS and glass fiber sheet (GFS). The influence of aspect ratio, FS material, initial axial force ratio, and FS confine-ment degree on the strength and deformation of columns were studied. Based on the experimental results, the equations of complete stress-strain curve of CFS confined concrete are proposed. These equations are suitable for the nonlinear analysis of square and rectangular section columns. Suggestions of applying FS to confine concrete columns are presented.

Joint Contact Forces with Changes in Running Stride Length and Midsole Stiffness

The purpose of this study was to determine if lower extremity joint loading was influenced by stride length or shoe midsole cushioning.Ten subjects completed 10 trials of overground running at an average speed of 4.43 m/s in each of three condi-tions:normal running,running with a stride length(SL)reduced by 10%of normal,and running with a cushioned midsole stiffness(i.e.,mechanical impact reduction of 13.7-10.9 g).Reaction forces calculated from inverse dynamics were summed with muscle forces estimated from a musculoskeletal model using static optimization to obtain joint contact forces at the hip,knee and ankle joints.Peak components of the contact forces[axial,anterior-posterior,and medial-lateral(ML)]were examined using parametric statistics(α=0.05).Reducing stride length resulted in significant decreases in absolute peak ankle contact forces in the axial direction(normal:-14.5±1.5 BW;reduced SL:-14.0±1.6 BW)and the ML direction(normal:0.67±0.23 BW;reduced SL:0.61±0.21 BW).Reducing stride length also reduced the peak absolute axial forces at the knee(normal:-10.6±1.3 BW;reduced SL:-9.8±1.2 BW)and the hip(normal:-7.26±2.24 BW;reduced SL:-6.75±2.10 BW).The cushioned shoe did not statistically reduce the peak absolute contact forces from the normal stride condition at any of the joints.Post hoc stress analysis suggested that the observed changes in anterior hip force would increase stress more than any of the other statistically significant results.Reductions in stride length appear to decrease some joint contact variables but cushioning in the heel region of the shoe does not.

Effect of compressive stress on the dispersion relation of the flexural–gravity waves in a two-layer fluid with a uniform current

The explicitly analytical solution is derived for the dispersion relation of the flexural-gravity waves in a two-layer fluid with a uniform current. The upper＇ fluid is covered by a thin plate with the presence of the elastic, compressive and inertial forces. The density of each of the two immiscible layers is constant. The fluids of finite depth are assumed to be inviscid and incompressible and the motion be irrotational. A linear system is established within the framework of potential theory. A new representation for the dispersion relation of flexural-gravity waves in a two-layer fluid is derived. The critical value for the compressive force is analytically determined. The dispersion relation for the capillary-gravity with an inertial surface in a two-layer fluid can he obtained in parallel. Some known dispersion relations can be recovered from the present solution.

Modeling and analysis of pelletization process based on a multi-hole pelletizing device

A multi-hole pelletizing device(MPD)was proposed to simulate the granular extrusion process of animal feed due to its cheap,fast,and controllable features.The compression mechanism was analyzed and discussed according to the compression force-time curve.This study applied response surface methodology(RSM)with a central composite design(CCD)to develop predictive models for the compression force Fout and the pellet properties which includes pellet densityρp,pellet moisture content Mcp,and pellet tensile strength Dp based on the MPD.The effects of feedstock moisture content Mcf(10%-18%w.b.),feedstock particle size Sf(8 meshes-24 meshes),die temperature Td(70°C-110°C)and compression speed Vc(5 mm/min to 25 mm/min)were investigated.Response surface models developed for the compression force and pellet properties have adequately described the pelleting process(R^(2)>0.95).The results showed the significant effects of all factors and most of the squared and interaction terms on the compression force and pellet physical properties.It can be concluded from the present study that moisture content and die temperature,followed by compression speed and feedstock particle size are the interacting process factors influencing compression force and pellet properties.