Influences of moisture content and compressive loading speed on the mechanical properties of maize grain orientations

Determination of the mechanical properties(rupture force,deformation,hardness,and toughness)of maize grain could be a significant concern for designing the harvester,thresher,and handling,processing,and storage equipment.Thus,the present research was conducted to assess the vertical and lateral rupture force,deformation,hardness,and toughness of maize grain(Beijing Denong,Lianchuang,Suyu 20,Liyu 88 and Suyu 29)influenced by different moisture contents(11.2%,17.5%,and 21.3%)and compressive loading speeds(5,10,15,20,and 25 mm/min,respectively).Besides,the mean length,width,thickness,geometric mean diameter,equivalent diameter,arithmetic diameter,sphericity,grain volume,surface area,and aspect ratio of the selected varieties were measured.The results showed that the highest length,width,thickness and sphericity,grain volume,surface area,and aspect ratio were obtained at moisture of 21.3%,whereas the lowest was at 11.2%.Moreover,it was observed that as increasing the loading speed from 5 to 25 mm/min,the vertical and lateral rupture forces decreased.However,as increasing moisture contents from 11.2%to 21.3%,the vertical and lateral rupture forces,hardness,and toughness decreased noticeably.Furthermore,the maximum correlation(R2=0.9957)between rupture force and loading speed was found for Liyu 88 at moisture of 17.5%and minimum correlation(R2=0.7002)was found for Suyu 29 at moisture of 11.2%.Moreover,the highest lateral and vertical rupture force was noticed(p<0.05)at a loading speed of 5 mm/min.Based on the experimentally obtained results,it was concluded that the properties of maize grain evaluated were relevant to the design of planter,harvesters,thrashers,and processing machine.

Normalization method for asphalt mixture fatigue equation under different loading frequencies

In order to analyze the effect of different loading frequencies on the fatigue performance for asphalt mixture,the changing law of asphalt mixture strengths with loading speed was revealed by strength tests under different loading speeds.Fatigue equations of asphalt mixtures based on the nominal stress ratio and real stress ratio were established using fatigue tests under different loading frequencies.It was revealed that the strength of the asphalt mixture is affected by the loading speed greatly.It was also discovered that the fatigue equation based on the nominal stress ratio will change with the change of the fatigue loading speed.There is no uniqueness.But the fatigue equation based on the real stress ratio doesn't change with the loading frequency.It has the uniqueness.The results indicate the fatigue equation based on the real stress ratio can realize the normalization of the asphalt mixture fatigue equation under different loading frequencies.It can greatly benefit the analysis of the fatigue characteristics under different vehicle speeds for asphalt pavement.

Experimental study on dynamic load magnification factor for ballastless track-subgrade of high-speed railway

The magnitude of dynamic load produced by high-speed trains depends on many factors,of which train speed is the most critical one.However,it is quite difficult to determine the effect of train speed on dynamic load using the theoretical methods due to the complexity of the interaction between vehicle and track-subgrade.Thus large-scale model test has gradually become an important approach for studying dynamic responses of ballastless track-subgrade of high-speed railway.In this study,a full-scale model of ballastless track-subgrade was constructed in accordance with the design and construction standards for Shanghai-Nanjing intercity high-speed railway line firstly.Then,the dynamic strain of slab and the dynamic earth pressure of subgrade were measured by conducting single wheel axle excitation test.In addition,the relationship between the dynamic load magnification factor（DLF） and the train speed was obtained.Finally,the DLF of track-subgrade under different train speeds was proposed,similar to that given by German Railway Standard.

Studying the mechanical properties of the soil-root interface using the pullout test method

It is important to quantify the effect of the root diameter, the embedment length of the root and load speed on the soil-root interface mechanical properties for studying the root anchorage. The soilroot interface mechanical properties can be obtained through the pullout force and root slippage curve(F-S curve). About 120 Pinus tabulaeformis single roots whose diameters ranged from 1 mm to 10 mm divided into 6 groups based on different root embedment length(50 mm, 100 mm and 150 mm) and different load velocity(10 mm·min^(-1), 50 mm·min^(-1), 100 mm·min^(-1) and 300 mm·min^(-1)) were investigated using the pullout method. This study aims to explore the mechanical properties of the soil-root interface in the real conditions using the pullout test method. The results showed two kinds of pullout test failure modes during the experimental process: breakage failure and pullout failure. The results showed that the roots were easier to be broken when the root diameter was smaller or the loading speed was larger. The relationship between the maximum anchorage force and root diameter was linear and the linearly dependent coefficient(R^2) was larger than 0.85. The anchorage force increased with the root embedment length. An increase of 10%^(-1)5% for the maximumanchorage force was found when load speed increased from 10 to 300 mm.min^(-1). The mean peak slippage of the root was from 13.81 to 35.79 mm when the load velocity varied from 10 to 300 mm.min^(-1). The study will be helpful for the design of slopes reinforced by vegetation and in predicting risk of uprooting of trees, and will have practical benefits for understanding the mechanism of landslide.

Friction and Wear Property of Cu-Cr Alloy

The friction and wear behaviors of the Cu-Cr alloy sliding against GCr15 steel at different loads and rotate speed conditions were evaluated, and the worn surface morphologies were observed on a scanning electron microscope. Results show that as loads and rotate speed increase, the wear loss weight increases, by comparison, the biggest friction coefficient of Cu-Cr alloy was obtained at load 100 N and rotate speed at 100 r·min-1 friction condition. Moreover, the dominant wear forms was plough wear.