Randomisation of ramberg osgood equation

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Parth Kulkarni
Parth Kulkarni 2021-7-12
评论： Parth Kulkarni 2022-4-11
I am trying to randomise the ramberg osgood equation to find out different values of strains as a response to random stress values set between a range of 100 MPa to 300MPa. The ramberg osgood equation is; delta(epsilon{strain})/2 = delta(sigma{stress})/2 + ( delta(sigma{stress})/2K' )^n' . The values of K' and n' are constant for materials and need not be randomised for my application. I just want to randomise delta(sigma{stress}) to obtain randomised values of delta(epsilon{strain}) .
Until now I have written the code to generate random numbers in the range -
a = 100;
b = 300;
r = (b-a).*rand(10000,1) + a;
Later I was thinking of using the for loop to put these numbers one by one into the equation and but haven't been able to figure out. Can someone please help me with this. The strain values obtained for the first iteration of strain must be the input for second iteration of stresses

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采纳的回答

Parth Kulkarni
Parth Kulkarni 2021-7-12
Thanks ... this worked

更多回答（2 个）

Alan Stevens
Alan Stevens 2021-7-12
You don't need a loop. Yu can just do
deltaepsilon = r/E + 2*(r/(2*Kp)).^(1/np);
where Kp = K' and np = n'.
Note that you need to use .^ (dot^) not just ^ in order to make it an element by element operation.
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Parth Kulkarni
Parth Kulkarni 2021-7-12
a = 115;
b = 234;
r = (b-a).*rand(100,1) + a;
sr=size(r);
sr1=sr(1);
kp=1320;
np=0.177
E=21e+06;
sg1=r(1)
e1 =((r/2*E) + ((r/2*kp).^1/np))*2
nn=0;
for nn=1:sr1
if nn==1
ee(nn)=e1
else
ee(nn)=2*(((r(nn)/(2*E))+(r(nn)/(2*kp)).^(1/np))-ee(nn-1))
end
end
I wrote this code to randomise stresses for each iteration with a loop to include the strain of previous iteration as the input of second. The only problem I am getting in this is the value of strain is very high. INstead of 10^-6 I am getting strain in 10^6. What could be the issue?
Alan Stevens
Alan Stevens 2021-7-12
Ran in:
Be careful about ensuring E and kp are in the denominator; also that the power is (1/np).
a = 115;
b = 234;
r = (b-a).*rand(1000,1) + a;
sr=size(r);
sr1=sr(1);
kp=1320;
np=0.177;
E=21e+06;
sg1=r(1);
e1 =( r/(2*E) + (r/(2*kp)).^(1/np) )*2; %%% Make sure E and kp are in the
%%% denominator and the power is
%%% (1/np)!!!
ee = [e1(1); diff(e1)];
histogram(ee,20)
xlabel('ee'), ylabel('frequency')

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Parth Kulkarni
Parth Kulkarni 2021-7-12
I am randomising the Kp and np along with stresses now ..... is this code correct?
a = 115;
b = 234;
r = (b-a).*rand(1000,1) + a;
sr=size(r);
sr1=sr(1);
kp=(1500-750).*rand(1000,1) + 1500;
kpr=size(kp);
kp1=kp(1);
np=(1-0).*rand(1000,1) + 1;
npr=size(np);
np=np(1);
E=21e+06;
sg1=r(1);
e1 =( r/(2*E) + (r/(2*kp)).^(1/np) )*2; %%% Make sure E and kp are in the
%%% denominator and the power is
%%% (1/np)!!!
ee = [e1(1); diff(e1)];
histogram(ee,20)
xlabel('ee'), ylabel('frequency')
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Parth Kulkarni
Parth Kulkarni 2022-4-11
%% Normally distributed randomised stress distribution%%
sigma_a = 250;
sigma_b = 350;
stress_range = (sigma_b - sigma_a).*rand(30000,1) + sigma_a;
%%%% Normally distributed k values%%
k_1 = 950;
k_2 = 1350;
k_range = (k_2 - k_1).*rand(30000,1) + k_1;
%% Normally ditributed c values%%
c_1 = 0.3;
c_2 = 0.7;
c_range = (c_2 - c_1).*rand(30000,1) + c_1;
%% Normally distributed b values%%
b_1 = 0.14;
b_2 = 0.19;
b_range = (b_1 - b_2).*rand(30000,1) + b_1;
%% Normally distributed n values%%
n_1 = 0.2;
n_2 = 0.7;
n_range = (n_1 - n_2).*rand(30000,1) + n_1;
%% Strain calculation using ramberg osgood model%%
E=21e+06;
e1 =((stress_range)/(2*E) + (stress_range/(2*k_range)).^(1/n_range))*2; %%% Make sure E and kp are in the
%%% denominator and the power is
%%% (1/np)!!!
ee = [e1(1); diff(e1)];
histogram(ee,20);
xlabel('ee'), ylabel('frequency')
%% I am using this code to randomise the k, n and stress values for to obtain the subsequent strains developed for all 30000 values. But it is giving an error in the line 32. I want to save all the values of strains developed from their subsequent stress, k and n values so that I can find the sensitivity of randomising these values with the strains developed.%%
Parth Kulkarni
Parth Kulkarni 2022-4-11
I have written down my main motive behind the code at the bottom

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