I keep noticing very high concentrations in very small areas in the FEAs of various types of industrial threads. These stresses are in the thread root and contact areas. Typically it’s in the first three threads that the strain is highest. Do you have any advice on how one could mitigate or defend the results of an FEA with that type of result?
Well, I don't have any expertise in this industrial threads and nuts....but, if you compress an axial bar with axially equally distributed friction force (just imagine the similar situation) to the flat surface (bolt head), first thought will be equally distributed axial strain (stress), but the second thought will be ... there might be stress concentration at the flat surface (because it is elastic) and the bottom part of axial bar and internal threads (it will expand/contract in radial direction by Poisson ratio. it will gradually increase in axial direction...it's right....just based on arithmetic ). This is just my initial guess...I hope this can help you~!
I can't check the code in matlab right now....but probably the following code will work! --------------------------------------------------------------------------------------------------------------------------------------------- a = 1.0 r1 = linspace(1,10,400) th1 = linspace(0,2*np.pi,400) r,th = meshgrid(r1,th1) s_inf = 1.0 s_r,s_th,s_rth = stress_holeinplate(r,th,a,s_inf) x = r .* cos(th) y = r .* sin(th) contourf(x,y,s_th,10) For your reference, my original python code for this work is like this ------------------------------------------------------------------------------------------------------------- a = 1.0 # hole radius r1 = np.linspace(1,10,400) # polar coordinate - r th1 = np.linspace(0,2*np.pi,400) # polar coordinate - theta [radian] r,th = np.meshgrid(r1,th1) s_inf = 1.0 s_r,s_th,s_rth = stress_holeinplate(r,th,a,s_inf) x = r * np.cos(th) y = r * np.sin(th) fig = plt.figure() ax = plt.subplot() ax.contour(x,y,s_th,20,colors='black',linewidths=0.1) cax = ax.contourf(x,y,s_th,200,cmap=plt.cm.jet) plt.title(r'Stress Distribution ($\sigma_{\theta}$) - Hole in Infinite Plate') ax.set_xlabel(' X ') ax.set_ylabel(' Y ') plt.xlim(-5,5) plt.ylim(-5,5) ax.set_aspect('equal') fig.colorbar(cax) plt.show()
Thanks a lot for sharing this video.
I keep noticing very high concentrations in very small areas in the FEAs of various types of industrial threads. These stresses are in the thread root and contact areas. Typically it’s in the first three threads that the strain is highest. Do you have any advice on how one could mitigate or defend the results of an FEA with that type of result?
Well, I don't have any expertise in this industrial threads and nuts....but, if you compress an axial bar with axially equally distributed friction force (just imagine the similar situation) to the flat surface (bolt head), first thought will be equally distributed axial strain (stress), but the second thought will be ... there might be stress concentration at the flat surface (because it is elastic) and the bottom part of axial bar and internal threads (it will expand/contract in radial direction by Poisson ratio. it will gradually increase in axial direction...it's right....just based on arithmetic ). This is just my initial guess...I hope this can help you~!
@@Ahn.Eng., thank you very much!
how to plot sigmatheta(hoop stress) in matlab ? can you suggest me the command
I can't check the code in matlab right now....but probably the following code will work!
---------------------------------------------------------------------------------------------------------------------------------------------
a = 1.0
r1 = linspace(1,10,400)
th1 = linspace(0,2*np.pi,400)
r,th = meshgrid(r1,th1)
s_inf = 1.0
s_r,s_th,s_rth = stress_holeinplate(r,th,a,s_inf)
x = r .* cos(th)
y = r .* sin(th)
contourf(x,y,s_th,10)
For your reference, my original python code for this work is like this
-------------------------------------------------------------------------------------------------------------
a = 1.0 # hole radius
r1 = np.linspace(1,10,400) # polar coordinate - r
th1 = np.linspace(0,2*np.pi,400) # polar coordinate - theta [radian]
r,th = np.meshgrid(r1,th1)
s_inf = 1.0
s_r,s_th,s_rth = stress_holeinplate(r,th,a,s_inf)
x = r * np.cos(th)
y = r * np.sin(th)
fig = plt.figure()
ax = plt.subplot()
ax.contour(x,y,s_th,20,colors='black',linewidths=0.1)
cax = ax.contourf(x,y,s_th,200,cmap=plt.cm.jet)
plt.title(r'Stress Distribution ($\sigma_{\theta}$) - Hole in Infinite Plate')
ax.set_xlabel(' X ')
ax.set_ylabel(' Y ')
plt.xlim(-5,5)
plt.ylim(-5,5)
ax.set_aspect('equal')
fig.colorbar(cax)
plt.show()
@@Ahn.Eng. could you please share the full code with us?