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-{
- "cells": [
- {
- "cell_type": "markdown",
- "metadata": {},
- "source": [
- "# Chapter 4 - Design Against Fluctuating Load"
- ]
- },
- {
- "cell_type": "markdown",
- "metadata": {},
- "source": [
- "## exa 4.1 Pg 102"
- ]
- },
- {
- "cell_type": "code",
- "execution_count": 5,
- "metadata": {
- "collapsed": false
- },
- "outputs": [
- {
- "name": "stdout",
- "output_type": "stream",
- "text": [
- " for stepped plate under tension, Kt=1.75 for r/d = 0.125 & D/d = 1.25 \n",
- "\n",
- " for finite width plate under tension with a hole, Kt=2.42 for d0/w = 0.25\n",
- "\n",
- " Thickness of plate = 6.05 mm or 6 mm\n"
- ]
- }
- ],
- "source": [
- "## Given data\n",
- "P=6## kN\n",
- "#dimensions of plate\n",
- "r=5##mm\n",
- "d=40##mm\n",
- "D=50##mm\n",
- "d0=10##mm\n",
- "w=40##mm\n",
- "Sut=200##MPa\n",
- "n=2.5## factor of safety\n",
- "\n",
- "#Fillet - \n",
- "rBYd=r/d#\n",
- "DBYd=D/d#\n",
- "Kt=1.75## factor\n",
- "print ' for stepped plate under tension, Kt=%.2f for r/d = %.3f & D/d = %.2f '%(Kt,rBYd,DBYd)\n",
- "\n",
- "# Hole -\n",
- "d0BYw=d0/w#\n",
- "Kt=2.42## factor \n",
- "print '\\n for finite width plate under tension with a hole, Kt=%.2f for d0/w = %.2f'%(Kt,d0BYw)\n",
- "sigma_max_into_t = Kt*P/(w-d0)##N/mm sq.\n",
- "\n",
- "#Design stress\n",
- "sigma_d = Sut/n## MPa\n",
- "#putting sigma_max=sigma_d\n",
- "t=sigma_max_into_t/sigma_d*1000## mm\n",
- "print '\\n Thickness of plate = %.2f mm or %.f mm'%(t,t)"
- ]
- },
- {
- "cell_type": "markdown",
- "metadata": {},
- "source": [
- "## exa 4.2 Pg 104"
- ]
- },
- {
- "cell_type": "code",
- "execution_count": 6,
- "metadata": {
- "collapsed": false
- },
- "outputs": [
- {
- "name": "stdout",
- "output_type": "stream",
- "text": [
- "\n",
- " Diameter of axle = 46.5 mm\n"
- ]
- }
- ],
- "source": [
- "from math import pi\n",
- "# Given Data\n",
- "rBYd=0.1#\n",
- "DBYd=1.2#\n",
- "P=3## kN\n",
- "Syt=300##MPa\n",
- "n=3## factor of safety\n",
- "#dimensions of plate\n",
- "l1=400##mm\n",
- "l2=300##mm\n",
- "l3=400##mm\n",
- "\n",
- "\n",
- "sigma_d=Syt/n## MPa\n",
- "Kt=1.65## factor for circular fillet radius member\n",
- "Rp=P/2##kN (bearing reaction due to symmetry)\n",
- "Mf=Rp*l1## kN.mm (bending moment at fillet)\n",
- "Mc=P*(l1+l2+l3)/4## kN.mm (bending moment at centre)\n",
- "\n",
- "#Fillet\n",
- "#sigma_max=Kt*32*Mf/(pi*d**3)\n",
- "sigma_max_into_d_cube_1 = Kt*32*Mf*1000/pi\n",
- "\n",
- "\n",
- "#Centre\n",
- "#sigma_max=32*Mc/(pi*d**3)\n",
- "sigma_max_into_d_cube_2 = Kt*32*Mf*1000/pi\n",
- "sigma_max_into_d_cube=max(sigma_max_into_d_cube_1,sigma_max_into_d_cube_2)## (getting max)\n",
- "\n",
- "#putting sigma_max=sigma_d\n",
- "t=(sigma_max_into_d_cube/sigma_d)**(1/3)## mm\n",
- "print '\\n Diameter of axle = %.1f mm'%t"
- ]
- },
- {
- "cell_type": "markdown",
- "metadata": {},
- "source": [
- "## exa 4.3 Pg 105"
- ]
- },
- {
- "cell_type": "code",
- "execution_count": 1,
- "metadata": {
- "collapsed": false
- },
- "outputs": [
- {
- "name": "stdout",
- "output_type": "stream",
- "text": [
- "\n",
- " Endurance limit = 45.50 MPa\n"
- ]
- }
- ],
- "source": [
- "# Given Data\n",
- "Sut=440##MPa\n",
- "d=25##mm\n",
- "R=95/100## reliability\n",
- "Kt=1.8## stress concentration factor\n",
- "q=0.86## sensitivity factor\n",
- "\n",
- "Se_dash = 0.5*Sut## MPa\n",
- "\n",
- "# for machined surface\n",
- "ka=0.82## surface finish factor\n",
- "kb=0.85## size factor\n",
- "kc=0.868## reliability factor\n",
- "kd=1## temperature factor\n",
- "ke=0.577## load factor\n",
- "\n",
- "Kf=1+q*(Kt-1)## fatigue strength factor\n",
- "kf=1/Kf ## fatigue strength reduction factor\n",
- "Se=ka*kb*kc*kd*ke*kf*Se_dash## (MPa) Endurance limit\n",
- "print '\\n Endurance limit = %.2f MPa'%Se"
- ]
- },
- {
- "cell_type": "markdown",
- "metadata": {},
- "source": [
- "## exa 4.4 Pg 105"
- ]
- },
- {
- "cell_type": "code",
- "execution_count": 3,
- "metadata": {
- "collapsed": false
- },
- "outputs": [
- {
- "name": "stdout",
- "output_type": "stream",
- "text": [
- "\n",
- " Thickness of plate = 18.23 mm or 20 mm\n"
- ]
- }
- ],
- "source": [
- "# Given Data\n",
- "Sut=440##MPa\n",
- "w=60##mm\n",
- "d=12## mm\n",
- "P=20## kN\n",
- "q=0.8## sensitivity factor\n",
- "R=90/100## reliability\n",
- "n=2## factor of safety\n",
- "\n",
- "Kt=2.52## stress concentration factor\n",
- "Se_dash = 0.5*Sut## MPa\n",
- "# for hot rollednormalized condition\n",
- "ka=0.67## surface finish factor\n",
- "kb=0.85## size factor (assuming t<50 mm)\n",
- "kc=0.897## reliability factor\n",
- "kd=1## temperature factor\n",
- "ke=0.9## load factor\n",
- "dBYw=d/w# #(for circular hole)\n",
- "\n",
- "Kf=1+q*(Kt-1)## fatigue strength factor\n",
- "kf=1/Kf ## fatigue strength reduction factor\n",
- "Se=ka*kb*kc*kd*ke*kf*Se_dash## (MPa) Endurance limit\n",
- "sigma_d=Se/n## MPa (design stress)\n",
- "# sigma_max=P/(w-d)/t\n",
- "sigma_max_into_t = P*1000/(w-d)#\n",
- "# putting sigma_max=sigma_d\n",
- "t=sigma_max_into_t/sigma_d## mm\n",
- "print '\\n Thickness of plate = %.2f mm or 20 mm'%t"
- ]
- },
- {
- "cell_type": "markdown",
- "metadata": {},
- "source": [
- "## exa 4.5 Pg 107"
- ]
- },
- {
- "cell_type": "code",
- "execution_count": 14,
- "metadata": {
- "collapsed": false
- },
- "outputs": [
- {
- "name": "stdout",
- "output_type": "stream",
- "text": [
- "\n",
- " Endurance of specimen = 325.00 MPa\n"
- ]
- }
- ],
- "source": [
- "from math import pi, log10\n",
- "# Given Data\n",
- "Sut=650##MPa\n",
- "N=10**5## cycles\n",
- "Se_dash = 0.5*Sut## MPa\n",
- "of=5## unit\n",
- "ob=6##unit\n",
- "bf=ob-of## unit\n",
- "be=3##unit\n",
- "\n",
- "# calculating endurance section wise\n",
- "OE=log10(Se_dash)#\n",
- "OA=log10(0.9*Sut)#\n",
- "AE=OA-OE#\n",
- "#log10_Sf=OD=OE+ED=OE+FC\n",
- "log10_Sf=OE+(bf/be)*AE#\n",
- "Sf=10**log10_Sf# # (MPa) Endurance\n",
- "print '\\n Endurance of specimen = %.2f MPa'%Sf"
- ]
- },
- {
- "cell_type": "markdown",
- "metadata": {},
- "source": [
- "## exa 4.6 Pg 108"
- ]
- },
- {
- "cell_type": "code",
- "execution_count": 4,
- "metadata": {
- "collapsed": false
- },
- "outputs": [
- {
- "name": "stdout",
- "output_type": "stream",
- "text": [
- "\n",
- " diameter of beam 20 mm\n"
- ]
- }
- ],
- "source": [
- "from __future__ import division\n",
- "from math import pi, log10\n",
- "# Given Data\n",
- "Sut=540##MPa\n",
- "N=10**4## cycles\n",
- "q=0.85## sensitivity factor\n",
- "R=90/100## reliability\n",
- "P=1500## N\n",
- "l=160## mm\n",
- "\n",
- "Se_dash = 0.5*Sut## MPa\n",
- "# for cold drawn steel\n",
- "ka=0.79## surface finish factor\n",
- "kb=0.85## size factor (assuming t<50 mm)\n",
- "kc=0.897## reliability factor\n",
- "kd=1## temperature factor\n",
- "ke=1## load factor\n",
- "\n",
- "Kt=1.33## under bending\n",
- "\n",
- "Kf=1+q*(Kt-1)## fatigue strength factor\n",
- "kf=1/Kf ## fatigue strength reduction factor\n",
- "Se=ka*kb*kc*kd*ke*kf*Se_dash## MPa( Endurance limit)\n",
- "\n",
- "of=4## unit\n",
- "ob=6##unit\n",
- "bf=ob-of## unit\n",
- "be=3##unit\n",
- "\n",
- "# calculating endurance section wise\n",
- "OE=log10(Se)#\n",
- "OA=log10(0.9*Sut)#\n",
- "AE=OA-OE#\n",
- "#log10_Sf=OD=OE+ED=OE+FC\n",
- "log10_Sf=OE+(bf/be)*AE#\n",
- "Sf=10**log10_Sf# # (MPa) Endurance\n",
- "\n",
- "MB=P*l## N.mm\n",
- "# 32*MB/pi/d**3 = Sf\n",
- "d=(32*MB/pi/Sf)**(1/3)\n",
- "print '\\n diameter of beam %.f mm'%d"
- ]
- },
- {
- "cell_type": "markdown",
- "metadata": {},
- "source": [
- "## exa 4.7 Pg 110"
- ]
- },
- {
- "cell_type": "code",
- "execution_count": 7,
- "metadata": {
- "collapsed": false
- },
- "outputs": [
- {
- "name": "stdout",
- "output_type": "stream",
- "text": [
- "\n",
- " diameter d at fillet cross section = 16 mm\n"
- ]
- }
- ],
- "source": [
- "from __future__ import division\n",
- "from math import pi, log10, atan\n",
- "# Given Data\n",
- "Sut=600##MPa\n",
- "Syt=380##MPa\n",
- "q=0.9## sensitivity factor\n",
- "R=90/100## reliability\n",
- "n=2## factor of safety\n",
- "Pmin=-100## N\n",
- "Pmax=200## N\n",
- "l=150## mm\n",
- "\n",
- "Se_dash = 0.5*Sut## MPa\n",
- "# for cold drawn steel\n",
- "ka=0.76## surface finish factor\n",
- "kb=0.85## size factor (assuming t<50 mm)\n",
- "kc=0.897## reliability factor\n",
- "kd=1## temperature factor\n",
- "ke=1## load factor\n",
- "\n",
- "Kt=1.4## under bending\n",
- "\n",
- "Kf=1+q*(Kt-1)## fatigue strength factor\n",
- "kf=1/Kf ## fatigue strength reduction factor\n",
- "Se=ka*kb*kc*kd*ke*kf*Se_dash## MPa( Endurance limit)\n",
- "Mmax=Pmax*l## N.mm\n",
- "Mmin=Pmin*l## N.mm\n",
- "Mm=(Mmax+Mmin)/2## N.mm\n",
- "Ma=(Mmax-Mmin)/2## N.mm\n",
- "theta=atan(Ma/Mm)*pi/180## degree\n",
- "\n",
- "#equation of Goodman - sigma_m/Sut+sigma_a/Se=1\n",
- "#here sigma_a/sigma_m=3\n",
- "sigma_m=1/(1/Sut+3/Se)##MPa\n",
- "sigma_a=3*sigma_m## MPa\n",
- "\n",
- "sigma_da=sigma_a/n## MPa\n",
- "#sigma_da=32*Ma/pi/d**3\n",
- "d=(32*Ma/pi/sigma_da)**(1/3)## mm \n",
- "print '\\n diameter d at fillet cross section = %.f mm'%d"
- ]
- },
- {
- "cell_type": "markdown",
- "metadata": {},
- "source": [
- "## exa 4.8 Pg 112"
- ]
- },
- {
- "cell_type": "code",
- "execution_count": 8,
- "metadata": {
- "collapsed": false
- },
- "outputs": [
- {
- "name": "stdout",
- "output_type": "stream",
- "text": [
- "\n",
- " diameter of shaft = 34 mm\n"
- ]
- }
- ],
- "source": [
- "from __future__ import division\n",
- "from math import pi, log10, atan,tan\n",
- "# Given Data\n",
- "Sut=500##MPa\n",
- "Syt=300##MPa\n",
- "R=90/100## reliability\n",
- "n=2## factor of safety\n",
- "Tmin=-200## N.m\n",
- "Tmax=500## N.m\n",
- "\n",
- "Se_dash = 0.5*Sut## MPa\n",
- "# for cold drawn steel\n",
- "ka=0.80## surface finish factor\n",
- "kb=0.85## size factor (assuming t<50 mm)\n",
- "kc=0.897## reliability factor\n",
- "kd=1## temperature factor\n",
- "ke=0.577## load factor\n",
- "\n",
- "Ses=ka*kb*kc*kd*ke*Se_dash## MPa( Endurance limit)\n",
- "Sys=ke*Syt## MPa\n",
- "Tm=(Tmax+Tmin)/2## N.m\n",
- "Ta=(Tmax-Tmin)/2## N.m\n",
- "theta=atan(Ta/Tm)*pi/180## degree\n",
- "Sms=Ses/tan(theta*180/pi)##MPa\n",
- "Sas=Ses##MPa\n",
- "tau_da=Sas/n##MPa\n",
- "#tua_da=16*Ta/pi/d**3\n",
- "d=(16*Ta*1000/pi/tau_da)**(1/3)##mm\n",
- "print '\\n diameter of shaft = %.f mm'%d"
- ]
- },
- {
- "cell_type": "markdown",
- "metadata": {},
- "source": [
- "## exa 4.9 Pg 113"
- ]
- },
- {
- "cell_type": "code",
- "execution_count": 2,
- "metadata": {
- "collapsed": false
- },
- "outputs": [
- {
- "name": "stdout",
- "output_type": "stream",
- "text": [
- "\n",
- " life of the spring, N = 215630 cycles\n"
- ]
- }
- ],
- "source": [
- "from __future__ import division\n",
- "from math import pi,log10\n",
- "# Given Data\n",
- "Sut=860##MPa\n",
- "Syt=690##MPa\n",
- "Pmin=60## N\n",
- "Pmax=120## N\n",
- "R=50/100## reliability\n",
- "l=500##mm\n",
- "d=10##mm\n",
- "Se_dash = 0.5*Sut## MPa\n",
- "# for machines surface\n",
- "ka=0.70## surface finish factor\n",
- "kb=0.85## size factor (assuming t<50 mm)\n",
- "kc=1## reliability factor\n",
- "kd=1## temperature factor\n",
- "ke=1## load factor\n",
- "\n",
- "Se=ka*kb*kc*kd*ke*Se_dash## MPa( Endurance limit)\n",
- "Mmax=Pmax*l## N.mm\n",
- "Mmin=Pmin*l## N.mm\n",
- "Mm=(Mmax+Mmin)/2## N.mm\n",
- "Ma=(Mmax-Mmin)/2## N.mm\n",
- "Sm=32*Mm/pi/d**3##MPa\n",
- "sigma_m=Sm##MPa\n",
- "Sa=32*Ma/pi/d**3##MPa\n",
- "sigma_a=Sa##MPa\n",
- "Sf=Sa*Sut/(Sut-Sm)##MPa\n",
- "\n",
- "#calculating section\n",
- "OB=6##unit ref. o at 3\n",
- "BE=OB-3##unit\n",
- "OC=Sf## MPa\n",
- "AE=log10(0.9*Sut)-log10(Se)##MPa\n",
- "AC=log10(0.9*Sut)-log10(Sf)##MPa\n",
- "CD=BE*AC/AE##\n",
- "#log10(N)=3+CD\n",
- "N=10**(3+CD)## cycle\n",
- "print '\\n life of the spring, N = %.f cycles'%N\n",
- "#Note : answer in the textbook is wrong."
- ]
- },
- {
- "cell_type": "markdown",
- "metadata": {},
- "source": [
- "## exa 4.10 Pg 116"
- ]
- },
- {
- "cell_type": "code",
- "execution_count": 5,
- "metadata": {
- "collapsed": false
- },
- "outputs": [
- {
- "name": "stdout",
- "output_type": "stream",
- "text": [
- "\n",
- " factor of safety, n = 5.04\n"
- ]
- }
- ],
- "source": [
- "from __future__ import division\n",
- "from math import pi, log10, sqrt,atan,tan\n",
- "# Given Data\n",
- "Sut=600##MPa\n",
- "Se=280##MPa\n",
- "sigma_x_min=50## MPa\n",
- "sigma_x_max=100## MPa\n",
- "sigma_y_min=20## MPa\n",
- "sigma_y_max=70## MPa\n",
- "\n",
- "sigma_xm=(sigma_x_max+sigma_x_min)/2## MPa\n",
- "sigma_xa=(sigma_x_max-sigma_x_min)/2## MPa\n",
- "sigma_ym=(sigma_y_max+sigma_y_min)/2## MPa\n",
- "sigma_ya=(sigma_y_max-sigma_y_min)/2## MPa\n",
- "\n",
- "# distortion energy theory - \n",
- "sigma_m=sqrt(sigma_xm**2+sigma_ym**2-sigma_xm*sigma_ym)## MPa\n",
- "sigma_a=sqrt(sigma_xa**2+sigma_ya**2-sigma_xa*sigma_ya)## MPa\n",
- "theta=atan(sigma_a/sigma_m)## radian\n",
- "# Sm/Sut+Sa/Se=1 where Sa=Sm*tan(theta)\n",
- "Sm=1/(1/Sut+tan(theta)/Se)## MPa\n",
- "Sa=tan(theta)*Sm## MPa\n",
- "n=Sa/sigma_a## factor of safety\n",
- "\n",
- "print '\\n factor of safety, n = %.2f'%n"
- ]
- }
- ],
- "metadata": {
- "kernelspec": {
- "display_name": "Python 2",
- "language": "python",
- "name": "python2"
- },
- "language_info": {
- "codemirror_mode": {
- "name": "ipython",
- "version": 2
- },
- "file_extension": ".py",
- "mimetype": "text/x-python",
- "name": "python",
- "nbconvert_exporter": "python",
- "pygments_lexer": "ipython2",
- "version": "2.7.6"
- }
- },
- "nbformat": 4,
- "nbformat_minor": 0
-}