Monotonic Test Data Research Articles

Uniaxial tensile response and tensile constitutive model of ultra-high performance concrete containing coarse aggregate (CA-UHPC)

To establish the tensile constitutive model of ultra-high performance concrete containing coarse aggregate (CA-UHPC), monotonic and cyclic uniaxial tensile tests for CA-UHPC with fiber volume fractions of 2.5% and 2.0% were conducted. Test results showed that CA-UHPC exhibits approximately linear stress-strain relation up to the tensile strength, and tensile softening response composed of the smeared- and localized-cracking stages, regardless of the tested fiber contents. Based on the monotonic test data, the tensile stress-crack opening model of CA-UHPC was established, and the model was further simplified into tri-linear relation. Based on the cyclic test results, tensile damage evolution laws according to the strain equivalence principle and the energy equivalence principle were developed, respectively. Finally, the proposed tensile constitutive model and the calibrated tensile damage evolution laws were demonstrated to effectively predict the mechanical response of CA-UHPC members under both monotonic tension and cyclic tension through numerical simulations.

Comparison of conventional reconstruction plate versus direct metal laser sintering plate: an in vitro mechanical characteristics study

BackgroundAdditive manufacturing (AM) technology has helped to achieve several advances in the medical field, particularly as far as fabrication of implants is concerned. But the application of direct metal laser sintering (DMLS) bone plate is quite limited due to the indeterminate mechanical property. The purposes of this study were to characterize the biomechanical properties of the polished DMLS reconstruction plate and to compare these with the properties of commonly applied implants and to find whether the mechanical performance of DMLS plate meets the requirements for clinical application.MethodsIn this study, we fabricated two groups of plates by DMLS and computer numerical control (CNC) techniques. After that, we polished all samples and investigated their roughness, components, hardness, static bending, and torsional performance. Moreover, cyclic bending tests and fractographic analysis were conducted. Statistical comparisons of the group by means of monotonic test data were made, and a qualitative comparison was performed to assess failures in fatigue.ResultsWe found no differences in surface roughness or components after polishing, but the DMLS plate hardness is 7.42% (p < 0.01) greater than that of the CNC plates. Compared with the CNC plates, the DMLS plate static bending and torsional performance were significantly greater. In a dynamic test, the DMLS plates survived 106, 106, 32,731, and 33,264 cycles under 0.6, 0.8, 0.9, and 1 kN cyclic loads, respectively, while the CNC plates survived 106, 106, 106, and 283,714 cycles.ConclusionsThese results indicate that the mechanical performances of the DMLS plate are stronger, and the strength under fatigue tests is sufficient. DMLS implant has great potential and may become a better choice for clinical use in the future. However, direct application of these AM instruments in the operating room requires further validation including animal and clinical experiment.

Damage accumulation model for monotonic and dynamic shear fracture of asphalt-stone adhesion

A damage accumulation model for shear fatigue of asphalt-stone adhesion was developed with the aid of experimental data obtained from monotonic and dynamic force-controlled tests. Constant static- and stress-rate monotonic tests and cyclic fatigue tests were performed on the special designed specimens of double-layered-sandwich using dynamic thermal mechanics analyzer. Experimental results showed that it was feasible to describe monotonic and cyclic tests of stress-controlled mode using one single damage accumulation model based on stress–time path, which makes it possible to reduce the number of specimens tested and time-consuming fatigue tests are no longer necessary, since the same information can be obtained from monotonic test data without loss of accuracy. It also found that the bonding fracture in shear mainly attributes to cohesive failure through binder interlayer due to extensive creep deformation.

Micro-Mechanics of Creep-Fatigue Damage in PB-SN Solder Due to Thermal Cycling—Part II: Mechanistic Insights and Cyclic Durability Predictions From Monotonic Data

This paper illustrates the micromechanics approach to cyclic creep-fatigue damage of Pb-Sn, developed by the authors with the help of a simple case study. It is demonstrated that durability predictions can be made based solely on monotonic test data. Various parametric studies of practical interest are conducted to obtain mechanistic insights into various aspects of damage in solders e.g., effect of hydrostatic stresses, grain size, ramp rate, etc.

Biaxial fatigue behaviour of a multidirectional filament-wound glass-fiber/epoxy pipe

This paper presents the results of an experimental investigation into the biaxial fatigue behaviour of a filament-wound multidirectional glass-fiber/epoxy pipe. Tests were conducted to observe the leakage (functional) failure of the composite pipe subjected to various hoop to axial loadings. The stiffness change in the axial and hoop directions, fatigue life curves, biaxial fatigue envelopes at various lives, and failure mechanisms are discussed. It is noted that optimum fiber placement in principal directions may lead to a weak behaviour for an intermediate loading combination. It is also found that monotonic test data are not a good indicator of the fatigue behaviour. Furthermore, imperfections in the manufacturing process lead to early damage initiation under cyclic loading, and result in shorter fatigue lives to leakage.

Stress-Strain Relationship of Common Wire Nails Under Reversed Cyclic Loading

Abstract Nailed timber joints are known to play an important role in the performance of light timber frame structures under extreme loading conditions such as those caused by hurricanes and earthquakes. Numerical modeling of nailed joint response to these loading conditions requires knowledge of, among other things, the load-displacement or stress-strain property of nails under reversed cyclic load. As part of an overall program of work to validate a finite element nailed joint model, a new test method was developed and a modified constitutive material model was adopted to characterize the through-zero cyclic stress-strain behavior of nails of different diameters. Four nail diameters ranging from 2.78 to 4.08 mm were evaluated using the proposed cyclic test and the conventional monotonic tension test methods. It is noted that the proposed constitutive model provides an excellent representation of the cyclic response of the nails. A comparison with monotonic test data reveals that yield stress under cyclic loading is higher than the corresponding monotonic test response, but the ultimate strength appears unaffected. Under cyclic loading the so-called Bauschinger and strain-softening effects are clearly evident. Elastic moduli are similar for the four nails tested. However, yield stress and strain reduce with any increase in nail diameter. The area enclosed by a hysteresis loop increases with increasing nail size.