摘要:

This work presents an experimental investigation of the response of “neat,” unscrimmed FM‐73 adhesive under mechanical loads at various stress levels and over the 30–60°C temperature range. The methodically acquired data provide the basis for a material characterization based on a specific model of nonlinear viscoelastic response. In particular, it is shown that it is essential to include transient‐temperature testing in the characterization scheme. Subsequent tests were performed under conditions of fluctuating loads and temperatures in order to verify the predictive capabilities of the model and characterization scheme. Satisfactory results were obtained.

ISSN:0148-6055    

DOI:10.1122/1.549700

出版商:The Society of Rheology    

年代:1983

数据来源: AIP

摘要:

A simple mathematical model for predicting residual stresses in injection‐molded parts has been constructed. The use of a nonlinear viscoelastic constitutive equation allows the model to yield better quantitative results than previously obtained. The model fails to predict the existence of birefringence along the midplane of the molded part, which is thought to be due to inhomogeneous cooling (i.e., thermal stress).

ISSN:0148-6055    

DOI:10.1122/1.549701

出版商:The Society of Rheology    

年代:1983

数据来源: AIP

摘要:

A fine, unligated clot of human or bovine fibrin prepared from purified fibrinogen is subjected to a large torsional deformation (maximum shear strain γ up to 1.37) with superposed small oscillating deformations (Δγ ca. 0.03) at frequencies from 0.2 to 1 Hz. The “secant modulus” is defined asGi(γ)=σi/γ,where σ is stress and the subscriptirefers to an initial measurement about 25 s after imposition of strain. The storage modulusG′(ω,γ)refers to a differential oscillating measurement at frequency ω superposed on a static strain γ. For γ up to about 0.1,Gi(γ)was independent of γ and equal toG′(ω,0)measured at about 1 Hz and zero static strain. At large static deformations, the differential storage modulusG′(ω,γ)could be used to monitor changes in structure. Since there is very little time dependence of the relaxation modulus in the range from 1 to 60 s, and the loss tangent is very small,Gi′(ω,γ)could be considered simply as the differential modulusGi(γ)+γdGi/dγ,and agreed with the latter expression as long as both measurements(Gi,G1′)were made within a short time lapse. At high static strains, the initial differential modulusGi′(ω,γ)was larger than the corresponding zero‐static‐strain valueG′(ω,0)by as much as a factor of 60. During a stress relaxation experiment at large constant strain,G′(ω,γ;t)decreased with elapsed timetbut relatively less than the nonlinear relaxation modulusG(γ;t).After a clot had been subjected to a large strain for a long time and then released,G′(ω,γ;t)fell at once to a value much less thanG′(ω,0)but slowly increased toward the latter value. During a creep experiment at large constant stress,G′(ω,γ;t)increased but much less than if it were governed by the strain magnitude alone. Ligation did not affect the dependence ofG′on γ but largely eliminated its dependence on elapsed time in experiments of stress relaxation and subsequent release. The behavior can be interpreted qualitatively in terms of three processes: enhancement of structure at large strains (perhaps associated with an increased number of contact points between protofibrils), release of the enhancement (perhaps due to rupture of protofibrils), and subsequent healing of rupture by reassociation of noncovalent bonding sites.

ISSN:0148-6055    

DOI:10.1122/1.549722

出版商:The Society of Rheology    

年代:1983

数据来源: AIP

摘要:

The time‐dependent shear and normal stresses arising in polymeric fluids during multistep‐shear deformations have been modeled using the Leonov constitutive theory. An analytical solution of the problem has been obtained. The model parameters for the materials have been determined from the experimental time‐dependent linear relaxation modulus in a single‐step shear. The results based upon the present theory have been compared with the experimental data obtained by Osaki and co‐workers for different polystyrene solution in double‐step‐shear deformation in the nonlinear region and also with theoretical results based upon the Doi‐Edwards and the BKZ theories. The present theory shows good agreement with the experiments, including the strain histories for which the above‐mentioned theories show discrepancies.

ISSN:0148-6055    

DOI:10.1122/1.549702

出版商:The Society of Rheology    

年代:1983

数据来源: AIP

ISSN:0148-6055    

DOI:10.1122/1.549703

出版商:The Society of Rheology    

年代:1983

数据来源: AIP

ISSN:0148-6055    

DOI:10.1122/1.549723

出版商:The Society of Rheology    

年代:1983

数据来源: AIP

ISSN:0148-6055    

DOI:10.1122/1.549735

出版商:The Society of Rheology    

年代:1983

数据来源: AIP