in the following discussion about the internal force and stress, ( ) is correct.
when we study the equilibrium of a member or a part of it, we can use the original sizes before deformation to yze, that because we adopt the ( ).
the internal force on a cross section can usually be simplified as ( ).
in the following conclusions, ( ) is wrong.
as shown in the figure, two deformation measuring instruments are respectively installed at a and b of the tensile test specimen, the magnification is respectively and . the gauge length is s = 20 mm, and the reading increment of the measuring instrument after tension is , . then the poisson's ratio μ of this material is ( ).
for the simple crane shown in the figure, bc is a steel bar and ab is a wood bar. the cross-sectional area of ab is , allowable normal stress ; the cross-sectional area of bc is ast =6 cm2, allowable normal stress. then the allowable lifting weight f is ( ).
there are three concentrated forces are applied at the bar, as shown in the figure. the axial force on section m-m is ( ).
a stepped bar is shown in the figure, segment ab is made of steel and segment bd is made of aluminum. with the external forces f, ( ).
two bars with different cross-sections, one is circular and another is rectangular. if the two bars have the same materials, areas but different lengths, with the same external forces as shown in the figure, for the two bars ( ) are different.
the bar shown in the figure is subjected to four equal axial external forces. in segment ( ) the deformation is zero.
the pin passes through the circular hole on the flat plate and is subjected to a pull force f at its lower end. the areas of the shear plane and bearing plane of the pin are respectively ( ).
the relation of the three elastic constants e, g, μ of isotropic materials is ( ).
the rivet connection is shown in the figure, and the bearing stress of the rivet is ( ).
for the two states of stress of units a and b, ( ) .
a hollow circular shaft with the ratio of inner and outer diameters α = d / d, if the maximum shear stress on the cross section is τ when the two ends are subjected to the torsional couple moments, then there are four answers to the shear stress at the inner circumference, the correct one is ( ).
the priatic tranission shaft is shown in the figure. wheels b and d are driving wheels and wheels a, c ,e are driven wheels. if the input powers on driving wheels b and d are equal, the output powers on driven wheels a, c and e are equal too, and if only torsional deformation is considered and bending deformation is not considered, the position of dangerous section is ( ).
as shown in the figure, the circular shaft is made of steel and copper by welding. if it is acted by an external couple, the copper part and the steel part are the same in ( ).
for a solid circular shaft and a hollow circular shaft, if they have the same material, cross-sectional area, length and are subjected to the same external torques, there are four answers to the relation between the torsional angles of the two shafts, the correct one is ( ).
if the diameter of the torsional solid circular shaft is doubled, its rigidity is 8 times of the original one.
in the following figures, figure ( ) shows that the bending moment m on the section is positive and the shear force is negative .
if the bending moment m on the beam segment is a linear function of x, the function of shear force is ( ).
for plane bending the characteristics of deformation are ( ).
the area of the graph is a , the axis pass through the centroid c and parallel to the axis, the distance between axis and the axis is . it is known that the moment of inertia of the graph with respect to axis is , and the moment of inertia of the graph with respect to axis is ( ).
let the moment of inertia of the rectangle to its symmetric axis z is i. when the ratio of length to width remains unchanged and the area is doubled, the moment of inertia of the rectangle to its symmetric axis z will become ( ).
for the figure as shown, if the centroidal axis z ides the figure into two parts, then ( ) must be established.
in the geometric properties of planes, the values of static moment of inertia and moment of inertia can be positive, negative and zero.
the forces on the cantilever beam are shown in the figure, ( ).
the cantilever beam with t-section subjected the force as shown in the figure, where axis passes through the centroid of the cross section, which is ( ) of the cross section of the beam.
when the beam with rectangular section is bent, in the neutral axis of the cross section ( ).
as shown in the figure, the cantilever beam with constant section is subjected to a concentrated force and a concentrated couple. if the maximum normal stress and the maximum shear stress at cross section c are σ and τ respectively, the maximum normal stress and the maximum shear stress at cross section a are ( ).
for two beams with same length , flexure rigidity ei and bending internal force diagrams, in the same coordinate system the beams ( ).
the cantilever beam is subjected to external forces as shown in the figure, on cross section b ( ).
for two cantilever beams with same length, loading form, flexural rigidity ei but different cross-section, they have ( ).
in the following cantilever beam, the ( ) of the cross-section c and b is different.