Thermomechanical Data Research Articles

Thermomechanical fatigue behaviour and mode of failure of laser welded single crystal Ni based superalloy

The baseline metallography of single crystal alloy N5 was compared with laser welded material to evaluate the effect of the welding process on cracking behaviour. In addition, baseline thermomechanical fatigue data were compared with the fatigue properties of welded specimens. The solution treated and aged single crystal alloy was found to contain microporosity, Ta rich MC carbides, Cr–Mo rich grain boundary borides, gamma prime and fine secondary gamma prime. In addition, recrystallised grains were present in the weld heat affected zone and provided a path for crack propagation out of the fusion zone. The laser beam welds showed defects mainly associated with the fusion zone, while thermomechanical fatigue analysis of the laser weld data showed inferior values compared to the baseline solution treated and aged material. Metallographic analysis showed that this was due to increased defects in the fusion zone associated with surface oxidation and heat affected zone recrystallisation compared to the non-welded alloy.

Mechanical and thermal properties of polyamide versus reinforced PMMA denture base materials

PURPOSEThis in vitro study intended to investigate the mechanical and thermal characteristics of Valplast, and of polymethyl methacrylate denture base resin in which different esthetic fibers (E-glass, nylon 6 or nylon 6.6) were added.MATERIALS AND METHODSFive groups were formed: control (PMMA), PMMA-E glass, PMMA-nylon 6, PMMA-nylon 6.6 and Valplast resin. For the transverse strength test the specimens were prepared in accordance with ANSI/ADA specification No.12, and for the impact test ASTM D-256 standard were used. With the intent to evaluate the properties of transverse strength, the three-point bending (n=7) test instrument (Lloyd NK5, Lloyd Instruments Ltd, Fareham Hampshire, UK) was used at 5 mm/min. A Dynatup 9250 HV (Instron, UK) device was employed for the impact strength (n=7). All of the resin samples were tested by using thermo-mechanical analysis (Shimadzu TMA 50, Shimadzu, Japan). The data were analyzed by Kruskal-Wallis and Tukey tests for pairwise comparisons of the groups at the 0.05 level of significance.RESULTSIn all mechanical tests, the highest values were observed in Valplast group (transverse strength: 117.22 ± 37.80 MPa, maximum deflection: 27.55 ± 1.48 mm, impact strength: 0.76 ± 0.03 kN). Upon examining the thermo-mechanical analysis data, it was seen that the E value of the control sample was 8.08 MPa, higher than that of the all other samples.CONCLUSIONAlthough Valplast denture material has good mechanical strength, its elastic modulus is not high enough to meet the standard of PMMA materials.

Investigation of Mechanical and Structural Properties of Blend Lignin-PMMA

Thisin vitrostudy investigated the mechanical and structural characteristics of lignin-added PMMA resin composites at concentrations of 1, 3, and 5% by weight. Four sample groups were formed. For the transverse strength test, the specimens were prepared in accordance with ANSI/ADA specification number 12, and for the impact test ASTM D-256 standards were used. With the intent to evaluate the properties of transverse strength, the three-point bending (n=10) test instrument (Lloyd NK5, Lloyd Instruments Ltd., Fareham, Hampshire, UK) was used at 5 mm/min. A Dynatup 9250 HV (Instron, UK) device was employed for the impact strength measurements (n=10). All resin samples were tested by using a thermomechanical analyzer (Shimadzu TMA 50, Shimadzu, Japan). Mechanical tests revealed that, although the control group was found to have the value of highest transverse strength, the highest impact strength was observed in the PMMA-L-1 group. Upon examining the thermomechanical analysis data, it could be seen that theEvalue of the control sample was higher than that of all the other samples. Adding lignin powder into PMMA performs plasticizer effect on resin matrix.

Variable P–T paths and HP-UHP metamorphism in a Precambrian terrane, Gridino, Russia: Petrological evidence and geodynamic implications

The Gridino Complex represents one of the oldest eclogite-facies terranes on Earth. It consists of blocks, boudins and lenses of eclogites, pyroxenites, and epidosites as well as deformed eclogitized dikes within biotite-amphibole gneisses. Detailed petrological studies of the pyroxenites and different types of eclogites reveal considerable diversity in metamorphic pressure (P) – temperature (T) conditions (from 1.3GPa at 660°C to 3.0GPa at 660°C) and fluid regimes (wet vs. dry) experienced by these rocks. Dike-related rocks escaped prograde metamorphism and reached higher pressures than the lenses and blocks that experienced considerable prograde metamorphic reworking. The variability in P–T conditions and the shapes of P–T paths are in agreement with the results of thermomechanical modeling and data from (U)HP metamorphic rocks exhumed during continent–continent collision in the Phanerozoic. The T/P ratio estimated for an eclogitized dike from Eclogitovii Island of the Gridino Complex corresponds to the gradients of <350°C/GPa attributed to high-pressure (HP)–ultrahigh-pressure (UHP) metamorphic belts, which are often considered as representative of modern style plate tectonics operating in the Phanerozoic Eon. The data presented in this paper suggest that occurrences of HP-UHP metamorphic terrains might be extended back towards the time of either the assembly of Columbia in the Paleoproterozoic or Kenorland in the Neoarchean.

Norris–Landzberg Acceleration Factors and Goldmann Constants for SAC305 Lead-Free Electronics

Goldmann constants and Norris–Landzberg acceleration factors for SAC305 lead-free solders have been developed based on principal component regression models (PCR) for reliability prediction and part selection of area-array packaging architectures under thermo-mechanical loads. Models have been developed in conjunction with stepwise regression methods for identification of the main effects. Package architectures studied include ball-grid array (BGA) packages mounted on copper-core and no-core printed circuit assemblies in harsh environments. The models have been developed based on thermomechanical reliability data acquired on copper-core and no-core assemblies in four different thermal cycling conditions. Packages with Sn3Ag0.5Cu solder alloy interconnects have been examined. The models have been developed based on perturbation of accelerated test thermomechanical failure data. Data have been gathered on nine different thermal cycle conditions with SAC305 alloys. The thermal cycle conditions differ in temperature range, dwell times, maximum temperature, and minimum temperature to enable development of constants needed for the life prediction and assessment of acceleration factors. Goldmann constants and the Norris–Landzberg acceleration factors have been benchmarked against previously published values. In addition, model predictions have been validated against validation datasets which have not been used for model development. Convergence of statistical models with experimental data has been demonstrated using a single factor design of experimental study for individual factors including temperature cycle magnitude, relative coefficient of thermal expansion, and diagonal length of the chip. The predicted and measured acceleration factors have also been computed and correlated. Good correlations have been achieved for parameters examined. Previously, the feasibility of using multiple linear regression models for reliability prediction has been demonstrated for flex-substrate BGA packages (Lall et al., 2004, “Thermal Reliability Considerations for Deployment of Area Array Packages in Harsh Environments,” Proceedings of the ITherm 2004, 9th Intersociety Conference on Thermal and Thermo-mechanical Phenomena, Las Vegas, Nevada, Jun. 1–4, pp. 259–267, Lall et al., 2005, “Thermal Reliability Considerations for Deployment of Area Array Packages in Harsh Environments,” IEEE Trans. Compon. Packag. Technol., 28(3), pp. 457–466., flip-chip packages (Lall et al., 2005, “Decision-Support Models for Thermo-Mechanical Reliability of Leadfree Flip-Chip Electronics in Extreme Environments,” Proceedings of the 55th IEEE Electronic Components and Technology Conference, Orlando, FL, Jun. 1–3, pp. 127–136) and ceramic BGA packages (Lall et al., 2007, “Thermo-Mechanical Reliability Based Part Selection Models for Addressing Part Obsolescence in CBGA, CCGA, FLEXBGA, and Flip-Chip Packages,” ASME InterPACK Conference, Vancouver, British Columbia, Canada, Jul. 8–12, Paper No. IPACK2007-33832, pp. 1–18). The presented methodology is valuable in the development of fatigue damage constants for the application specific accelerated test datasets and provides a method to develop institutional learning based on prior accelerated test data.

Simulation of distortion and residual stress in high pressure die casting – modelling and experiments

Two individual high-pressure die-casting geometries were developed in order to study the influence of process parameters and different alloys on the distortion behaviour of castings. These geometries were a stress lattice and a V-shaped sample tending to form residual stress due to different wall thickness respectively by a deliberate massive gating system. In the experimental castings the influence of the most important process parameters such as die temperature and die opening time and the cooling regime was examined. The time evolution of process temperatures was measured using thermal imaging. The heat transfer coefficients were adapted to the observed temperature distributions. Castings were produced from the two alloys AlSi12 and AlSi10MnMg. The distortion of the castings was measured by means of a tactile measuring device. For the alloy AlSi10MnMg thermo-physical and thermo-mechanical data were obtained using differential scanning calorimetry, laser flash technique, dilatometry and tensile testing at elevated temperatures. These data were used for modelling the material behaviour of the AlSi10MnMg alloy in the numerical model while for the alloy AlSi12(Fe) literature data were used. Process and stress simulation were conducted using the commercial FEM software ANSYS Workbench. A survey on the results of the comparison between simulation and experiment is given for both alloys.

Thermal properties and combustion behaviors of flame retarded epoxy acrylate with a chitosan based flame retardant containing phosphorus and acrylate structure

Functional materials prepared from natural resources arouse a great interest recently. Herein, a novel natural material based flame retardant chitosan phosphate acrylate (GPCS) containing phosphorus and acrylate structure has been prepared. Its effect on thermal properties and combustion behaviors of epoxy acrylate (EA) has been investigated. Microscale combustion calorimeter (MCC) data showed that GPCS reduced the peak heat release (PHRR) and total heat release (THR) of samples greatly, which meant that GPCS was efficient in reducing the flammability of EA. The results of thermogravimetric analysis (TGA) exhibited that GPCS improved the thermal stability of materials at high temperature. Investigation of real time Fourier transform infrared (RT-IR) and thermogravimetric analysis/infrared spectrometry (TGA-IR) revealed that GPCS promoted the formation of char and reduced the release of combustible gas. Thermomechanical properties data showed that the storage modulus of samples increased then decreased with increasing GPCS content while the glass transition temperature continued reduced.

A Critical Review on Multiscale Material Database Requirement for Accurate Three-Dimensional IC Simulation Input

Material behavior and properties at different scales, from nanometers to millimeters, are the input data needed for a model-based design-for-manufacturing approach of 3-D through-silicon-via (TSV) stacked ICs. In particular, mechanical and thermomechanical material data have to be used as input for physics-based modeling and simulation of stress-induced phenomena in 3-D stacks. Both package- and wafer-level properties, including their interaction, have to be considered. This paper reviews the thermomechanical and mechanical properties of several structures: time-dependent properties of solder materials (millimeter and micrometer scales), microstructure-dependent properties of Cu TSVs (micrometer scale), and process-dependent properties of ultralow- <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">k</i> materials in on-chip interconnect stacks (10-nm scale). To minimize the keep-out zone for active devices in the stress-affected surrounding of TSVs, while maintaining the device performance during 3-D TSV stacking of ICs, highly accurate material data are needed as input for the thermomechanical stress simulation. A similar strategy is supposed to be developed for a model-based design-for-reliability approach of 3-D TSV stacked ICs.

Thermo-Mechanical Instrumentation of the ITER Magnet Structures

The ITER superconducting magnet system (Toroidal Field coils (TF), Central Solenoid (CS), Poloidal Field coils (PF), Correction Coils (CC) and Feeders) represents a total weight of approximately 10 000 tons. It is designed to withstand gravitational and seismic forces, stresses induced by thermal contractions during cool-down from 300 K to 4.5 K, and large Lorentz forces in the superconducting coils. Although not part of the Safety Important Class (SIC) components, the sensors (stress, displacement, thermometer) used to monitor the thermo-mechanical behavior of the structures are key diagnostic means to assess the design, support operation and survey possible fatigue effects over the 20 years' lifetime of the Tokamak. The sensors and their wiring will be submitted to unique and severe environmental operating conditions; they will have to operate in the cryostat's high vacuum (<;10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-4</sup> Pa total gas pressure) at magnetic inductions of several Tesla and at low temperature (4.5 K) in the presence of a neutron fluence on the order of 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">22</sup> m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> - which implies a gamma dose higher than 10 MGy - for a period of 20 years. In addition, the fast and slow cycling of very large currents in the superconducting magnets and plasma will generate large eddy currents and, consequently, heat loads and electromotive forces (voltages) in the various parts of the structures, as well as a large electromagnetic noise. This paper presents the design philosophy and the chosen sensor technologies, some of which require further development in collaboration with the industry so that they can meet the objectives and the severe ITER operating conditions. In particular, only 20% of the near 1 000 measuring points for the thermo-mechanical data of the ITER magnet structures will rely on “classical” copper-wire technologies whereas 80% will rely on specifically developed optical-fiber-based sensors.

In-line near-infrared spectroscopy for the characterization of dispersion in polymer-clay nanocomposites

In-line Near-Infrared spectroscopy (NIR) is used to monitor clay dispersion in the polymer matrix during the preparation of polymer nanocomposites by melt-mixing in a batch mixer. Based on chemometrics principles, various single parameter calibration models employing data obtained from widely used nanocomposite dispersion characterization techniques are developed and their quality tested. Given the generally unsatisfactory outcome, multi-parameter calibration models are then assessed, a 7-parameter model encompassing factors derived from oscillatory rheometry, FT-IR and thermomechanical data yielding good results. Since the validity of the model outside the material/equipment/operating boundaries that were used to generate it was shown to be quite restricted, a second 7-parameter model is derived from a broader set of experimental data. Finally, the model is successfully applied to monitor in real time the evolution of clay dispersion with mixing time.

Predicting thermal shape memory of crosslinked polymer networks from linear viscoelasticity

The viscoelastic behavior of an amorphous shape memory polymer network and its dependence on time and temperature were measured by dynamic mechanical analysis. The resulting thermo-mechanical behavior was modeled and implemented in a commercial finite element code. The ability of the resulting thermomechanical model to simulate and, eventually, predict the shape storage and shape recovery of the material was evaluated against experimental shape memory thermomechanical torsion data in a large deformation regimen. The simulations showed excellent agreement with experimental shape memory thermomechanical cycle data. This demonstrates the dependence of the shape recovery on time and temperature. The results suggest that accurate predictions of the shape recovery of any amorphous polymer networks under any thermomechanical conditions combination solely depends on considering the material viscoelasticity and its time–temperature dependence.

Temperature-Responsive Bending of Nematic Elastomers with Hybrid Molecular Alignment

We demonstrate thermally induced giant bending of nematic elastomer films with hybrid alignment (HNEs) where the director continuously rotates by 90° (from planar alignment to vertical alignment) between the top and bottom surfaces. In the nematic state, a thermally induced change in local nematic order results in a markedly temperature (T) dependent curvature of HNEs including the reversal of bending direction. In the high-temperature isotropic state, the curvature is T-independent. This bending deformation is thermally reversible. The T dependence of curvature is well explained by a simple elastic model assuming a linear variation of strain in the thickenss direction with the thermomechanical data of the corresponding nematic elastomers with globally planar or vertical alignment. The T-responsive bending feature of the HNEs has potential application as soft solid sensors that behave like bimetals.

Thermo-Mechanical Properties of Multi-Walled Carbon Nanotube (MWCNT)/Epoxy Composites

The thermo-mechanical and tensile properties of multiwalled carbon nanotube (MWCNT)/epoxy composite samples were evaluated by performing dynamic-mechanical thermal analysis (DMTA) and tensile tests. The composite samples were fabricated by sonication and a cast molding process. The results indicated that the addition of multiwalled nanotubes (0.1, 0.5, and 1.5 wt.%) to the epoxy matrix had significant effect on the thermo-mechanical properties. The use of 0.5 wt.% MWCNT was the most effective in increasing the storage modulus value, while the sample containing 1.5 wt.% MWCNT demonstrated the best tensile properties. The experimentally obtained DMTA results were modeled by plotting a Cole-Cole diagram. The results showed quite good agreement between the Perez model and the experimental thermo-mechanical data.

Hygro-Thermo-Mechanical Reliability Assessment of a Thermal Interface Material for a Ball Grid Array Package Assembly

The thermal efficacy of thermal interface material (TIM) is highly dependent on its ability to adhere to the surfaces of interest. Any delamination of the TIM from the die or the lid will increase the local thermal resistance and, thus, will reduce the overall effectiveness of the TIM. Although significant amount of work has been done on understanding the thermal and moisture effects of various polymer materials used in microelectronic package assemblies, very limited work has been done to study the effect of temperature and moisture on TIM delamination. In this paper, a sequential hygro-thermal-mechanical finite-element model has been developed to mimic the loadsteps associated with package assembly as well as moisture soaking under 85°C/85RH over 500 h. The predictions from the models have been validated with a wide range of experimental data including laser Moiré data for thermomechanical loading and digital image correlation data for hygro-thermo-mechanical loading. Weight gain and coordinate-measurement machine have been used to characterize moisture diffusivity and moisture expansion coefficient of various polymer materials in the package assembly. The developed models show the evolution of normal strain in TIM during various loadsteps and provide important insight into the potential for TIM delamination under package assembly process and moisture soaking. Thus, the models can be used for developing various designs and process steps for reducing the chances for TIM delamination.

Structural relaxation of scintillating Ce-doped NaGd(PO3)4 glass

Structural relaxation of scintillating Ce-doped Na–Gd phosphate glass with a nominal composition of Ce:NaGd(PO3)4 was experimentally studied using non-isothermal thermo-mechanical analysis, and the relaxation process was described by the Tool–Narayanaswamy–Mazurin model. The distribution of relaxation times was expressed by the empirical Kohlrausch–Williams–Watts relaxation function with relaxation time directly proportional to dynamic viscosity. The model parameters and material constants were obtained by the nonlinear regression analysis of thermo-mechanical data. It has been concluded that the model used of structural relaxation correctly describes relaxation processes in studied Ce-doped NaGd(PO3)4 glass.

Fatigue Performance of Nitinol Round Wire with Varying Cold Work Reductions

The role of cold work reduction and its effect on fatigue properties are examined by means of rotary beam fatigue testing. In this study, processing parameters from the initial ingot to the final size before finish drawing were held constant. Fatigue specimens were prepared with between 20 and 55% cold work in five percent increments. These samples were subsequently heat treated, cut into test sections at room temperature, and subjected to strain-controlled fatigue testing in a temperature-controlled RO water bath at a constant 10 C above the measured active austenitic finish temperature (Af). An empirical analysis of the relationship between final reduction prior to heat treatment and fatigue lifetime is presented. Under alternating strain amplitudes greater than 1%, the 20 to 30% cold work level was found to deliver the greatest mean cycles to failure. Supplemental to the fatigue data, mechanocyclic and thermomechanical data are also presented as they evolve with prior retained cold work.

Self-similarity and finite-size effects in nano-indentation of highly cross-linkedpolymers

The scalability of thermomechanical polymer deformations in the sub-10 nm regime is ofparticular importance for nano-imprint techniques, hardness measurements of thin films bynano-indentations, and scanning-probe-based thermomechanical data storage. Weinvestigate nano-indentation in the sub-10 nm regime performed on highly cross-linkedpolymer films of different thicknesses. It is shown that the lateral and vertical geometriccharacteristics of the indents independently scale down to an indent depth of1 nm and that the scaling parameters are functions of the film thickness and thetemperature of the indenter. However, in the limit of shallow indents the scaling ofthe cross-coupling between lateral and vertical dimensions is lost. It is arguedthat the breakdown of self-similarity is due to a minimum strain requirementoriginating from the co-operative nature of the polymer response induced byα transitions which lock the indent in the deformed state. The results shed new light on thefundamental processes and size effects involved in nanoscale plastic replication, in general.

Probabilistic Uncertainty Modeling for Thermomechanical Analysis of Plasterboard Submitted to Fire Load

The paper deals with the probabilistic modeling of the thermomechanical behavior of cardboard–plaster–cardboard (CPC) multilayer plates submitted to fire load. The proposed model takes into account data and model uncertainties. This work is justified by the fact that fire resistance tests of plasterboard-lined partitions are made impossible when their dimensions exceed those of furnaces. A fundamental key to solve such a problem is the development and experimental validation of a deterministic and probabilistic model of CPC multilayers submitted to fire load. The first step of this work concerns the constitution of an experimental thermomechanical data base for a CPC multilayer and for its components. These experimental tests are carried out by the use of a bench test specially designed for this work. The second step is the development of a homogenization thermomechanical mean model for the CPC multilayer. The third step is the development of a probabilistic model of uncertainties based on the nonparametric probabilistic approach. Numerical results are compared with the experimental ones.

Orientation-induced crystallization of poly(ethylene terephthalate) fibers with controlled microstructure

Orientation-induced crystallization of PET fibers was studied by the in-situ wide-angle X-ray diffraction (WAXD) utilizing synchrotron radiation source combined with thermomechanical analysis. The noncrystalline as-spun fiber spun was heat-treated at 150, 165, 180 and 195°C for 0.1s under constrained condition. The heat-treatment allowed the fibers to have various amount of isotropic amorphous (IA), oriented noncrystalline (ON), and crystalline (Cr) phase. The structure evolution accompanying the crystallization of the fibers was then examined upon elevating temperature while the fiber length was held constant. The X-ray results clearly showed that the crystallization takes place first by ON phase (extended-chain crystallization) and then followed by the crystallization of IA phase (folded-chain crystallization). The on-set of extended-chain crystallization was dependent on the amount and degree of orientation of ON phase in the fiber that was derived from the various heat-treatment temperatures. It is also noted that the IA phase transforms into not only the CR phase but also the ON phase. The crystallization on the surface of preformed extended-chain crystals appeared to induce the spontaneous orientation of the chains. The thermomechanical data indicated that a stress emerges rapidly on fiber above glass transition temperature (Tg), which is associated with the entropic relaxation of the ON phase. The stress emerged on fiber then dropped drastically as the temperatures of fibers reached the temperatures of extended-chain crystallization, indicating that the stress drop is closely related with the extended-chain crystallization. The fibers heat-treated at the highest temperature showed the highest initial crystallinity but showed the slowest crystallization rate, resulting in the lowest final crystallinity among the fibers.

Analysis of Space Shuttle External Tank Spray-On Foam Insulation With Internal Pore Pressure

The polymer spray-on foam insulation used on NASA’s Space Shuttle external fuel tank is analyzed via the high-fidelity generalized method of cells micromechanical model. This model has been enhanced to include internal pore pressure, which is applied as a boundary condition on the internal faces of the foam pores. The pore pressure arises due to both ideal gas expansion during a temperature change as well as outgassing of species from the foam polymer material. Material creep and elastic stiffening are also incorporated via appropriate constitutive models. Due to the lack of reliable properties for the in situ foam polymer material, these parameters are backed out from foam thermomechanical test data. Parametric studies of the effects of key variables (both property-related and microstructural) are presented as is a comparison of model predictions for the thermal expansion behavior of the foam with experimental data.