1、從半空間無限域取一4X2的矩形平面結(jié)構(gòu)，頂部中間一定范圍內(nèi)受隨時(shí)間變化的均布荷載，荷載如下p(t)=t 當(dāng)0 p(t)=2-t 當(dāng)1=t2時(shí)材料彈性模量E=2.5，泊松比0.25，密度1網(wǎng)格尺寸0.1X0.1，在網(wǎng)格邊界上所有結(jié)點(diǎn)加法向和切向combin14號(hào)單元用以模擬粘彈性人工邊界（有關(guān)理論可參考劉晶波老師的相關(guān)文章）。combine14單元的兩個(gè)結(jié)點(diǎn)，其中一個(gè)與實(shí)體單元相連，另一個(gè)結(jié)點(diǎn)固定。網(wǎng)格圖如圖1所示時(shí)程分析的時(shí)間步長為0.02秒，共計(jì)算16秒。計(jì)算得到四個(gè)控制點(diǎn)位移時(shí)程圖如圖2所示，控制點(diǎn)坐標(biāo)A(0,2)、B(0,1)、C(0,0)、D(2,2).計(jì)算所用命令流如下：/PREP7

2、L=4!水平長度H=2 !豎起深度E=2.5!彈性模量density=1!密度nu=0.25!泊松比dxyz=0.1!網(wǎng)格尺寸G = E/(2.*(1.+nu)!剪切模量alfa = E*(1-nu)/(1.+nu)*(1.-2.*nu)!若計(jì)算平面應(yīng)力，此式需要修改Cp=sqrt(alfa/density)!壓縮波速Cs=sqrt(g/density)!剪切波速R=sqrt(L*L/4.+H*H/4.)!波源到邊界點(diǎn)等效長度KbT=0.5*G/R*dxyzKbN=1.0*G/R*dxyzCbT=density*Cs*dxyzCbN=density*Cp*dxyzET, 1, plane42,

3、2!按平面應(yīng)變計(jì)算et, 2, combin14, , 2 !切向et, 3, combin14, , 2 !法向r, 2, KbT, CbTr, 3, KbN, CbNMP, EX, 1, EMP, PRXY, 1, nuMP, DENS, 1, densityrectng,-L/2.,L/2,0.,Hasel, allaesize, all, dxyzmshape,0,2Dmshkey,1amesh, all!以下建立底邊界法向和切向彈簧阻尼單元nsel,s,loc,y,0.*get,np,node,count !得到選中的結(jié)點(diǎn)數(shù)，存入np*get,npmax,node,num,maxd!

4、得到已經(jīng)定義的最大結(jié)點(diǎn)數(shù)，存入npmax*do,ip,1,npnpnum=node(ip-1)*dxyz-L/2.,0.,0.)x=nx(npnum)y=ny(npnum)z=nz(npnum)npmax=npmax+1n,npmax,x.,y-dxyz/2,z!定義底邊界法向結(jié)點(diǎn)以便與邊界點(diǎn)形成法向單元type,3real,3e,npnum,npmaxd,npmax,all,0.!約束新生成的點(diǎn)npmax=npmax+1n,npmax,x-dxyz/2.,y,z!定義底邊界切向結(jié)點(diǎn)以便與邊界點(diǎn)形成切向單元type,2real,2e,npnum,npmaxd,npmax,all,0.!約束新生

5、成的點(diǎn)*enddo!以下建立左邊界法向和切向彈簧阻尼單元nsel,s,loc,x,-L/2*get,np,node,count !得到選中的結(jié)點(diǎn)數(shù)，存入np*get,npmax,node,num,maxd!得到已經(jīng)定義的最大結(jié)點(diǎn)數(shù)，存入npmax*do,ip,2,np!側(cè)邊界最下面一個(gè)點(diǎn)按底邊界上處理npnum=node(-L/2,(ip-1)*dxyz,0.)x=nx(npnum)y=ny(npnum)z=nz(npnum)npmax=npmax+1n,npmax,x-dxyz/2.,y,z!定義左邊界法向結(jié)點(diǎn)以便與邊界點(diǎn)形成法向單元type,3real,3e,npnum,npmaxd,np

6、max,all,0.!約束新生成的點(diǎn)npmax=npmax+1n,npmax,x,y-dxyz/2.,z!定義左邊界切向結(jié)點(diǎn)以便與邊界點(diǎn)形成切向單元type,2real,2e,npnum,npmaxd,npmax,all,0.!約束新生成的點(diǎn)*enddo!以下建立右邊界法向和切向彈簧阻尼單元nsel,s,loc,x,L/2*get,np,node,count !得到選中的結(jié)點(diǎn)數(shù)，存入np*get,npmax,node,num,maxd!得到已經(jīng)定義的最大結(jié)點(diǎn)數(shù)，存入npmax*do,ip,2,np!側(cè)邊界最下面一個(gè)點(diǎn)按底邊界上處理npnum=node(L/2,(ip-1)*dxyz,0.)x=

7、nx(npnum)y=ny(npnum)z=nz(npnum)npmax=npmax+1n,npmax,x+dxyz/2.,y,z!定義右邊界法向結(jié)點(diǎn)以便與邊界點(diǎn)形成法向單元type,3real,3e,npnum,npmaxd,npmax,all,0.!約束新生成的點(diǎn)npmax=npmax+1n,npmax,x,y-dxyz/2.,z!定義右邊界切向結(jié)點(diǎn)以便與邊界點(diǎn)形成切向單元type,2real,2e,npnum,npmaxd,npmax,all,0.!約束新生成的點(diǎn)*enddoallsel,all/pnum,type,1/number,1eplotfinish/soluANTYPE,trans!*TRNOPT,FULLLUMPM,0btime=0.02etime=16.00dtime=0.02*DO,itime,btime,etime,dtimeTIME,itimensel,s,loc,y,H!選中需要加荷載的點(diǎn)nsel,r,loc,x,-L/4,L/4*if,itime,lt,1.,thenf,all,fy,1*itime*elseif,itime,ge,1.0,and,itime,le,2.0f,all