Расчет на прочность и жесткость при простом сопротивлении

25 2. Ɂɚɦɟɧɢɦ ɞɟɣɫɬɜɢɟ ɨɬɛɪɨɲɟɧɧɵɯ ɱɚɫɬɟɣ ɧɚ ɨɫɬɚɜɲɢɟɫɹ ɱɚɫɬɢ ɫɬɟɪɠɧɟɣ ɭɫɢɥɢɹɦɢ N1 ɢ N2. ȼ ɪɟɡɭɥɶɬɚɬɟ ɢɦɟɟɦ ɩɥɨɫɤɭɸ ɫɯɨɞɹɳɭɸɫɹ ɫɢɫɬɟɦɭ ɫɢɥ. ɇɚɩɪɚɜɥɟɧɢɹ ɭɫɢɥɢɣ ɭɤɚɠɟɦ ɜ ɫɨɨɬɜɟɬɫɬɜɢɢ ɫ ɞɟɮɨɪɦɚ-ɰɢɟɣ: ɟɫɥɢ ɫɬɟɪɠɟɧɶ ɪɚɫɬɹɧɭɬ – ɭɫɢɥɢɟ ɫɥɟɞɭɟɬ ɧɚɩɪɚɜɢɬɶ ɨɬ ɫɟɱɟɧɢɹ, ɚ ɟɫɥɢ ɫɠɚɬ – ɤ ɫɟɱɟɧɢɸ. ȼ ɧɚɲɟɦ ɫɥɭɱɚɟ ɨɛɚ ɫɬɟɪɠɧɹ ɪɚɫɬɹɧɭɬɵ, ɩɨɷɬɨɦɭ ɭɫɢɥɢɹ N1 ɢ N2 ɧɚɩɪɚɜɥɟɧɵ ɨɬ ɫɟɱɟɧɢɣ ɫɬɟɪɠɧɟɣ, ɬ. ɟ. ɜ ɫɬɨɪɨɧɭ ɜɧɟɲɧɟɣ ɧɨɪɦɚɥɢ. 3. ȼɵɛɢɪɚɟɦ ɫɢɫɬɟɦɭ ɤɨɨɪɞɢɧɚɬ. ɉɪɟɞɩɨɱɬɟɧɢɟ ɫɥɟɞɭɟɬ ɨɬɞɚɜɚɬɶ ɨɛɵɱɧɨɣ ɩɪɚɜɨɣ ɫɢɫɬɟɦɟ ɤɨɨɪɞɢɧɚɬ (ɨɫɶ ɯ – ɝɨɪɢɡɨɧɬɚɥɶɧɚ, ɨɫɶ ɭ – ɜɟɪɬɢɤɚɥɶɧɚ). ȼ ɫɥɭɱɚɟ ɪɚɫɩɨɥɨɠɟɧɢɹ ɫɬɟɪɠɧɟɣ ɩɨɞ ɭɝɥɨɦ 90° ɞɪɭɝ ɤ ɞɪɭɝɭ ɪɟɤɨɦɟɧɞɭɟɬɫɹ ɨɫɢ ɯ ɢ ɭ ɧɚɩɪɚɜɥɹɬɶ ɜɞɨɥɶ ɫɬɟɪɠɧɟɣ. ɇɚɱɚɥɨ ɤɨ-ɨɪɞɢɧɚɬ ɫɥɟɞɭɟɬ ɫɨɜɦɟɫɬɢɬɶ ɫ ɬɨɱɤɨɣ ɩɟɪɟɫɟɱɟɧɢɹ ɥɢɧɢɣ ɞɟɣɫɬɜɢɹ ɫɢɥ. ȼ ɧɚɲɟɦ ɫɥɭɱɚɟ ɫ ɬɨɱɤɨɣ Ⱥ. 4. Ɉɩɪɟɞɟɥɹɟɦ ɭɝɥɵ ɦɟɠɞɭ ɧɚɩɪɚɜɥɟɧɢɹɦɢ ɭɫɢɥɢɣ ɢ ɧɚɩɪɚɜɥɟɧɢ-ɟɦ ɨɫɟɣ ɯ ɢ ɭ. 5. ɋɨɫɬɚɜɢɦ ɭɪɚɜɧɟɧɢɹ ɪɚɜɧɨɜɟɫɢɹ ɞɥɹ ɩɨɥɭɱɟɧɧɨɣ ɫɢɫɬɟɦɵ ɫɢɥ: ¦ɯ = 0.–N1 ⋅ sin 30° + N2 sin 45° = 0, (1) ¦y = 0.N1 ⋅ cos 30° + N2 cos 45° – F = 0. (2) 6. Ɋɟɲɚɟɦ ɩɨɥɭɱɟɧɧɵɟ ɭɪɚɜɧɟɧɢɹ ɪɚɜɧɨɜɟɫɢɹ ɢ ɧɚɯɨɞɢɦ N1 ɢ N2. ȼ ɞɚɧɧɨɦ ɫɥɭɱɚɟ ɞɥɹ ɪɟɲɟɧɢɹ ɭɪɚɜɧɟɧɢɣ ɢɫɩɨɥɶɡɭɟɦ ɦɟɬɨɞ ɚɥɝɟɛɪɚɢ-ɱɟɫɤɨɝɨ ɫɥɨɠɟɧɢɢ, ɢɡ ɩɟɪɜɨɝɨ ɭɪɚɜɧɟɧɢɹ ɜɵɱɬɟɦ ɜɬɨɪɨɟ. ȼ ɪɟɡɭɥɶɬɚɬɟ ɢɦɟɟɦ: –N1 ⋅ (sin 30° + cos 30°) + F = 0, ɨɬɤɭɞɚ: 2,73866,05,010030cos30sinFN1=+=°+°=ɤɇ. ɂɡ ɭɪɚɜɧɟɧɢɹ (1) 2,527,05,02,7345cos30sinNN12=⋅=°°⋅= ɤɇ. 7. Ɉɩɪɟɞɟɥɹɟɦ ɩɥɨɳɚɞɢ ɩɨɩɟɪɟɱɧɵɯ ɫɟɱɟɧɢɣ ɫɬɟɪɠɧɟɣ. ɂɫɩɨɥɶɡɭ-ɟɦ ɬɚɛɥɢɰɭ ȽɈɋɌ 8509-86 ɫɨɪɬɚɦɟɧɬɚ, ɩɪɢɥ. 2. Ⱥ1 = 4,29 ɫɦ2, Ⱥ2 = 2ȺĿ = 2 ⋅ 1,43 = 2,86 ɫɦ2, ɬ. ɤ. ɫɬɟɪɠɟɧɶ 2 ɫɨɫɬɨɢɬ ɢɡ ɞɜɭɯ ɭɝɨɥɤɨɜ.