山农双语材力.pptVIP

④ Distribution of the shearing stresses （solid section） （hollow section） In engineering the members with hollow section are widely used to increase the strength, save materials and decrease the weight of structures. ⑤ Determine the maximum shearing stress： From when Wt — section factor in torsion（ section factor modulus in torsion ), geometric quantity，unit：mm3 or m3 a. For the solid circular section： b. For the hollow circular section： 4、Strength calculation of the round shaft in torsion Strength condition： For the round shaft with equal sections： ([?] is called permissible shearing stress.) Three aspects of strength calculations： ① Check the strength： Design the dimension of the section： ③ Calculate the permissible load： Example 2 Power is 150kW，speed of rotation is 15.4r/s for the rotator of a motor as shown in the figure. Permissible shearing stress is [?]=30MPa. Try to check its strength. T m Solution：①Determine its torques and plot the torque diagram ②Calculate and check the shearing stress strength ③Strength of this shaft satisfies request D3 =135 D2=75 D1=70 A B C m m x §3–5 DEFORMATION OF A CIRCULAR SHAFT IN TORSION 1、Deformation in torsion From the formula We can determine the relative angle ? of twist between two end sections of the rod with the length l. 2、The angle of twist per unit length? ： or 3、Rigidity condition or G Ip indicates the capacity that the dimension and material properties of the section resist torsional deformations. It is called the torsional rigidity of the circular shaft. Three aspects of rigidity calculations: ① Check the rigidity： ② Design the dimension of the section： ③ Calculate the permissible load： Sometimes, these conditions may be considered to select materials.. Mechanics of Materials §3–1 Concept and practicle examples §3–2 External torque of a transmission shaft, inter