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+// exa 9.15 Pg 279
+
+clc;clear;close;
+
+// Given Data
+W=100;// kN
+lift=260;// mm
+pb=15;// N/mm.sq.
+mu=0.15;// coefficient of thread friction
+mu_c=0.20;// coefficient of collar friction
+//Screw
+Suts=800;// N/mm.sq.
+sigma_ss=340;// N/mm.sq.
+ns=4;// factor of safety
+//Nut
+Sutn=552;// N/mm.sq.
+sigma_sn=260;// N/mm.sq.
+nn=5;// factor of safety
+
+sigma_ts=Suts/ns;// N/mm.sq.
+sigma_cs=Suts/ns;// N/mm.sq.
+tau_s=sigma_ss/ns;// N/mm.sq.
+sigma_tn=Sutn/nn;// N/mm.sq.
+sigma_cn=Sutn/nn;// N/mm.sq.
+tau_n=sigma_sn/nn;// N/mm.sq.
+
+//sigma_cs=4*W/(%pi*dc**2)
+dc=sqrt(4*W*10**3/(%pi*sigma_cs));// mm
+printf('\n Screw Diameter-\n Core diameter of screw, dc=%.2f mm. Use dc=33 mm',dc)
+dc=33;// mm
+p=7;// mm (for normal series square threads)
+d=dc+p;//mm
+printf('\n outside diameter = %.f mm',d)
+dm=dc+p/2;// mm
+printf('\n mean diameter = %.1f mm',dm)
+t=p/2;// mm
+printf('\n thread thickness = %.1f mm',t)
+
+printf('\n Maximum stresses in screw -')
+sigma_c=4*W*1000/%pi/dc**2;// MPa
+alfa=atand(p/(%pi*dm));// degree
+fi=atand(mu);// degree
+Tf=dm*W*10**3/2*tand(alfa+fi);// where TfByW = Tf/W
+tau=16*Tf/(%pi*dc**3);// MPa
+sigma12=(1/2)*(sigma_c+sqrt(sigma_c**2+4*tau**2));// MPa
+printf('\n Maximum tensile stress = %.1f N/mm.sq. < %.f N/mm.sq.. Hence design is safe.',sigma12,sigma_ts)
+tau_max=sqrt((sigma_c/2)**2+tau**2);// MPa
+printf('\n Maximum shear stress = %.2f N/mm.sq. < %.f N/mm.sq.. Hence design is safe.',tau_max,tau_s)
+
+printf('\n Height of nut-')
+n=W*10**3/(%pi/4)/pb/(d**2-dc**2);// no. of threads
+n= ceil(n);// no. of threads (rounding)
+h=n*p;// mm
+printf('\n h=%.f mm. Use 120 mm.',h)
+h=120;// mm
+
+printf('\n Check for stress in screw and nut')
+tau_screw=W*10**3/(%pi*n*dc*t);// MPa
+printf('\n shear stress in screw = %.2f MPa < %.f MPa',tau_screw,tau_s)
+tau_nut=W*10**3/(%pi*n*d*t);// MPa
+printf('\n shear stress in nut = %.2f MPa < %.f MPa',tau_nut,tau_n)
+printf('\n These are within permissible limits. Hence design is safe.')
+
+printf('\n Nut collar size-')
+// %pi/4*(D1**2-d**2)*sigma_tn=W
+D1=sqrt(W*10**3/(%pi/4)/sigma_tn+d**2);// mm
+printf('\n Inside diameter of collar = %.2f mm. Use D1=55 mm',D1)
+D1=55;//mm (adopted for design)
+// %pi/4*(D2**2-D1**2)*sigma_cn=W
+D2=sqrt(W*10**3/(%pi/4)/sigma_cn+D1**2);// mm
+printf('\n Outside diameter of collar = %.2f mm. Use D2=70 mm',D2)
+D2=70;//mm (adopted for design)
+
+// %pi*D1*tc*tau_n=W
+tc=W*10**3/(%pi*D1*tau_n);// mm
+printf('\n thickness of nut = %.f mm. Use tc=15 mm.',tc)
+tc=15;// mm (adopted for design)
+
+printf('\n Head Dimensions-')
+D3=1.75*d;// mm
+printf('\n Diameter of head on top of screw = %.2f mm.',D3)
+D4=D3/4;// mm
+printf('\n pin diameter in the cup = %.1f mm. Use 20 mm.',D4)
+D4=20;// mm (adopted for design)
+
+printf('\n Torque required between cup and head-')
+Tc=mu_c*W*10**3/3*((D3**3-D4**3)/(D3**2-D4**2));// N.mm
+printf('\n Tc=%.f N.mm (acc. to uniform pressure theory)',Tc)
+T=Tf+Tc;// N.mm
+printf('\n Total Torque, T=%.f N.mm',T)
+
+F=300;// N (as a normal person can apply 100-300 N)
+l=T/F;//mm
+printf('\n length of lever = %.f mm or %.2f m',l,l/1000)
+
+M=F*l;// N.mm
+sigma_b=100;// N/mm.sq. (assumed)
+dl=(32*M/%pi/sigma_b)**(1/3);// mm
+printf('\n Diameter of lever, dl=%.1f mm. Use dl=45 mm.',dl)
+dl=45;// mm (adopted for design)
+
+H=2*dl;// mm
+printf('\n Height of head, H=%.f mm',H)
+
+printf('\n Check for screw in buckling-')
+L=lift+0.5*h;// mm
+K=dc/4;// mm
+C=0.25;// spring index
+sigma_y=200;// MPa
+Ac=%pi/4*dc**2;//mm.sq.
+Wcr=Ac*sigma_y*(1-(sigma_y/4/C/%pi**2/(200*10**3))*(L/K)**2)/1000;// kN
+printf('\n Buckling or critical load for screw, Wcr = %.f kN > 100kN',Wcr)
+
+To=W*10**3*dm/2*tand(alfa);// N.mm
+eta=To/T*100;// %
+printf('\n Efficiency of screw = %.2f %%',eta)
+
+printf('\n Body dimensions-')
+D5=1.5*D2;// mm
+t2=2*tc;// mm
+t3=0.25*d;//mm
+D6=2.25*D2;// mm
+printf('\n Diameter of body at top, D5 = %.f mm', D5)
+printf('\n Thickness of base, t2 = %.f mm', t2)
+printf('\n Thickness of body, t3 = %.f mm', t3)
+printf('\n Inside diameter of bottom, D6 = %.1f mm. Use D6=160 mm.', D6)
+D6=160;// mm (adopted for design)
+D7=1.75*D6;// mm
+hb=lift+h+100;// mm
+printf('\n Outside diameter at the bottom, D7 = %.2f mm.', D7)
+printf('\n Height of body = %.f mm.',hb)