Stress Relaxation Tests Research Articles

Investigating Viscoelastic Properties of Myofibrils Isolated From hiPSC-CMs Using Atomic Force Microscopy and Quasi-Linear Viscoelastic Model

Abstract Knowing the mechanical properties of cardiac myofibrils isolated from human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) can provide valuable insight into the structure and function of the heart muscle. Previous studies focused mostly on studying myofibrillar stiffness using simplified elastic models. In this study, the mechanical properties of myofibrils isolated from hiPSC-CMs were measured using atomic force microscopy (AFM). The quasi-linear viscoelastic (QLV) model was used to interpret the elastic and viscous properties of myofibrils. Since there have been no previous studies on the viscoelastic properties of myofibrils extracted from hiPSC-CMs, myofibrils extracted from porcine left-ventricular (LV) tissue were used to compare and verify experimental processes and QLV model parameters. The elastic modulus of myofibrils extracted from porcine LV tissue was determined to be 8.82 ± 6.09 kPa which is consistent with previous studies which reported that porcine LV tissue is less stiff on average than mouse and rat cardiac myofibrils. The elastic modulus of myofibrils extracted from hiPSC-CMs was found to be 9.78 ± 5.80 kPa, which is consistent with the range of 5–20 kPa reported for myofibrils extracted from the adult human heart. We found that myofibrils isolated from hiPSC-CMs relax slower than myofibrils extracted from porcine LV tissue, particularly in the first 0.25 s after the peak stress in the stress relaxation test. These findings provide important insights into the mechanical behavior of hiPSC-CMs and have implications for the development of treatments for heart diseases.

Characterization of Temperature and Humidity Dependence in Soft Elastomer Behavior.

Soft robots are predicted to operate well in unstructured environments due to their resilience to impacts, embodied intelligence, and potential ability to adapt to uncertain circumstances. Soft robots are of further interest for space and extraterrestrial missions, owing to their lightweight and compressible construction. Most soft robots in the literature to-date are made of elastomer bodies. However, limited data are available on the material characteristics of commonly used elastomers in extreme environments. In this study, we characterize four commonly used elastomers in the soft robotics literature-EcoFlex 00-30, Dragon Skin 10, Smooth-Sil 950, and Sylgard 184-in a temperature range of -40°C to 80°C and humidity range of 5-95% RH. We perform pull-to-failure, stiffness, and stress-relaxation tests. Furthermore, we perform a case study on soft elastomers used in stretchable capacitive sensors to evaluate the implications of the constituent material behavior on component performance. We find that all elastomers show temperature-dependent behavior, with typical stiffening of the material and a lower strain at failure with increasing temperature. The stress-relaxation response to temperature depends on the type of elastomer. Limited material effects are observed in response to different humidity conditions. The mechanical properties of the capacitive sensors are only dependent on temperature, but the measured capacitance shows changes related to both humidity and temperature changes, indicating that component-specific properties need to be considered in tandem with the mechanical design. This study provides essential insights into elastomer behavior for the design and successful operation of soft robots in varied environmental conditions.

A Novel Quasilinear Viscoelastic Model of the Bending of a Steerable Catheter

Abstract The present study proposes a novel model that establishes the relationship between the bending moment and the curvature of a steerable catheter. The catheters exhibit a nonlinear viscoelastic tendency, so the moment-curvature relationship is modeled as a bending of a quasi-linear viscoelastic (QLV) cantilever beam. Stress relaxation tests with multiple magnitudes are performed on a catheter, and the parameter tuning is carried out with the test results to find out the coefficients of the model. The form of the instantaneous moment response, which is an important term within the QLV equation, is selected as a logarithmic form by analyzing the test results. This differentiates the accuracy of the model from using the commonly used exponential form. The performance of the logarithmic QLV model is compared to the conventional models by checking the curvature range each model can cover with a certain accuracy. The covering range for elastic, linear viscoelastic, and exponential QLV models are 22.1%, 64.4%, and 55.5%, respectively, whereas the covering range of the logarithmic QLV model is 100%.

Thermal–viscoelastic analysis of polymethyl methacrylate using a fractional differential viscoelastic model

Vacuum forming is used to manufacture large molded parts. As forming conditions have a significant effect on the dimensional accuracy, these should be determined accordingly. In this study, a geometric nonlinear creep analysis of polymethyl methacrylate (PMMA), which is a common thermoplastic resin, was carried out at the target temperature of 393.15[Formula: see text]K and target strain of approximately 50% for vacuum forming. The proposed fractional differential viscoelastic model was extended to a three-element model, consisting of a single hyperelastic spring and two fractional differential (FD) models. It was further extended by time–temperature superposition (TTS) for thermo-viscoelastic analysis. The model determined all material constants by measuring the temperature/frequency sweeps at small strain amplitudes of 0.01% using dynamic mechanical analysis (DMA). Numerical analysis confirmed the validity of the proposed method through creep and stress-relaxation tests by DMA at the target temperature/strain. The results demonstrated that the finite element analysis constructed using the proposed method could predict the mechanical properties during vacuum-forming-oriented creep tests. These results are expected to provide important insights into the complex mechanical behavior of PMMA, which varies with the temperature and strain rate.

Effects of Material Structure on Stress Relaxation Characteristics of Rapidly Solidified Al-Fe Alloy.

An Al-Fe alloy which was produced by hot extrusion of rapidly solidified powder is a possible solution to substitute copper-based electrical conductor material due to its high strength and high electrical conductivity. However, the stress relaxation characteristic-an essential parameter as a conductor material-and the effect of the material structure have not been reported, which was the aim of the present paper. An Al-5%Fe alloy was selected as the test material. The material structures were controlled by hot extrusion practice, annealing, and cold rolling. The Al-Fe intermetallic compound particles controlled the residual stress after the stress relaxation test via the Orowan mechanism. Decreasing the mean inter-particle distance reduces the electrical conductivity. The increase in the number of dislocations by the cold rolling increased strength at room temperature without changing electrical conductivity; however, it did not have a positive effect on the stress relaxation characteristics. The stress relaxation characteristics and the electrical conductivity of the Al-Fe alloy were superior to conventional C52100 H04 phosphor bronze when compared with the case of the same mass.

Dynamic heterogeneity and mechanical relaxation of Ti20Zr20Cu20Ni20Be20 high-entropy metallic glass probed by quasi-elastic neutron scattering and stress relaxation

Heterogeneity is an intrinsic property of metallic glasses (MGs) and is closely related to their physical properties. Relaxation dynamics provides a powerful approach to understanding the heterogeneity of MGs. State-of-the-art quasi-elastic neutron scattering (QENS) and stress relaxation are used to study the atomic relaxation dynamics, dynamic heterogeneity, diffusion coefficients and mechanical relaxation of Ti20Zr20Cu20Ni20Be20 high-entropy metallic glass (HE-MG). The dynamic susceptibility derived from the QENS self-intermediate scattering function was used to evaluate the presence of dynamic heterogeneity, which increases gradually with decreasing temperature. The average self-diffusion coefficient of Ni and Ti atoms in the Ti20Zr20Cu20Ni20Be20 HE-MG melt is much higher than that in the Ti13.8Zr41.2Cu12.5Ni10Be22.5 Vit1 MG melt. The Ti20Zr20Cu20Ni20Be20 HE-MG melt has higher atomic mobility with respect to the Vit1 MG melt. In addition, the activation energy for crystallization of the Ti20Zr20Cu20Ni20Be20 HE-MG is considerably larger than that of the Vit1 MG. In the stress relaxation test, both Ti20Zr20Cu20Ni20Be20 HE-MG and Vit1 MG exhibit a relaxation decoupling phenomenon, indicating a two-step relaxation process. The slow and fast relaxation processes of the two alloy ribbons have a stretched exponential decay. At the measured temperatures, the relaxation times for both of the relaxation processes for the Ti20Zr20Cu20Ni20Be20 HE-MG are larger than those for the Vit1 MG, meaning that the Ti20Zr20Cu20Ni20Be20 ribbon has a slower stress decay. This in-depth investigation will improve our understanding of the intrinsic heterogeneity and mechanical relaxation mechanism in HE-MG.

Modeling the viscoelastic-viscoplastic behavior of glassy polymer membrane with consideration of non-uniform sub-chains in entangled networks

Glassy polymers are common engineering materials and usually work in a linear elastic stage. However, some functional glassy polymers, such as perfluorinated sulfonic acid (PFSA) membranes, face more complicated working conditions: varied temperature, humidity, and long-term loading, where the viscoelastic behavior has a huge impact on their durability. The early studies on the constitutive model of glassy polymers focus on the elastic–plastic behavior, especially yielding and strain hardening, while showing limitations in predicting the time-dependent viscoelastic response of the PFSA membrane at complex conditions. This paper establishes a viscoelastic-viscoplastic (VE-VP) constitutive model of glassy polymers based on the non-uniform length distribution of entangled molecular chains. During loading, heating and hydration, the prior activation of short entangled chains is the precondition of the viscoelastic response of the material in the small deformation stage. To distinguish activated molecular chains from others, a calculation method of chain activation is established based on the energy conservation criterion and applied to monitor the activation state of the entangled chain network. For the verification of the model, uniaxial tensile, stress relaxation, and dynamic thermomechanical tests are conducted. The present model shows great accuracy in predicting the VE-VP behavior of the PFSA membrane, with the error less than 8% in the stress relaxation tests, providing a new perspective of constitutive modeling for glassy polymers.

Discrepancy in ductility improvement in repeated stress relaxation of AA7075

The stress relaxation test is a commonly used transient test to determine the deformation kinetics during plastic deformation. This study reports the time-dependent deformation behavior of AA7075 alloy under different temper conditions. The deformation parameters, such as the apparent and true activation volume were estimated using single and repeated stress relaxation tests respectively. The results indicate that dislocation–dislocation interaction plays a critical role in the deformation behavior of the solution-treated condition, whereas dislocation–precipitate interaction dominates in the aged specimens. Additionally, the study found that single stress relaxation enhances the ductility of the deforming specimen, regardless of the temper condition. The ductility during repeated relaxation however had negative effects in aged samples. The possible mechanisms responsible for this discrepancy are discussed, providing a comprehensive overview of the time-dependent deformation behavior of AA7075 alloy.

Deformation behaviour of a cast Fe–19Al–5Cr-0.04Zr alloy at room and intermediate temperatures

The mechanical properties of a Fe–19Al (at.%) alloy containing 5 at.% Cr as the main alloying element are presented and discussed. While the alloy behaves brittle at room temperature and 100 °C, tensile stress-strain curves at temperatures between 200 °C and 500 °C show strain hardening recovery effects similarly to those of fcc twinning induced plasticity (TWIP) steels. It is supposed that a combination of dislocation glide and formation of internal boundaries in the submicron range leads to similar strain hardening stages at intermediate temperatures (200 °C–500 °C) in the FeAl alloy as usually observed in TWIP steels at room temperature. The maximum strain hardening rate after recovery reaches very high values of about G/19 at 400 °C. Low-cycle fatigue (LCF) tests at 400 °C and 500 °C up to strain amplitude values of 0.6% and stress-relaxation tests do not reveal high back stresses or pseudoelasticity in the FeAl alloy. This indicates that the deformation structures responsible for the strain hardening rate recovery remain stable upon stress relief.

On Recovery of a Non-Negative Relaxation Spectrum Model from the Stress Relaxation Test Data.

The relaxation spectra, from which other material functions used to describe mechanical properties of materials can be uniquely determined, are important for modeling the rheological properties of polymers used in chemistry, food technology, medicine, cosmetics, and many other industries. The spectrum, being not directly accessible by measurement, is recovered from relaxation stress or oscillatory shear data. Only a few models and identification methods take into account the non-negativity of the real spectra. In this paper, the problem of recovery of non-negative definite relaxation spectra from discrete-time noise-corrupted measurements of relaxation modulus obtained in the stress relaxation test is considered. A new hierarchical identification scheme is developed, being applicable both for relaxation time and frequency spectra. Finite-dimensional parametric classes of models are assumed for the relaxation spectra, described by a finite series of power-exponential and square-exponential basis functions. The related models of relaxation modulus are given by compact analytical formula, described by the products of power of time and the modified Bessel functions of the second kind for the time spectrum, and by recurrence formulas based on products of power of time and complementary error functions for frequency spectrum. The basis functions are non-negative. In result, the identification task was reduced to a finite-dimensional linear-quadratic problem with non-negative unknown model parameters. To stabilize the solution, an additional smoothing constraint is introduced. Dual approach was used to solve the stated optimal identification task resulting in the hierarchical two-stage identification scheme. In the first stage, dual problem is solved in two levels and the vector of non-negative model parameters is computed to provide the best fit of the relaxation modulus to experiment data. Next, in second stage, the optimal non-negative spectrum model is determined. A complete scheme of the hierarchical computations is outlined; it can be easily implemented in available computing environments. The model smoothness is analytically studied, and the applicability ranges are numerically examined. The numerical studies have proved that using developed models and algorithm, it is possible to determine non-negative definite unimodal and bimodal relaxation spectra for a wide class of polymers. However, the examples also demonstrated that if the basis functions are non-negative and the model is properly selected for a given type of the real spectrum (unimodal, multimodal), the optimal model determined without non-negativity constraint can be non-negative in the dominant range of its arguments, especially in the wide neighborhood of the spectrum peaks.

Durability Variation Among Medical Gloves Made from Existing and New Elastomers Poses a Risk to Public Health.

Despite being an essential line of defense in preventing the spread of diseases, medical glove durability is neither measured routinely nor has standard specifications. In this study, a new glove durability assessment device is used to objectively compare the durability of gloves made of a variety of elastomers from different manufacturers. Results are related to several mechanical tests, including stress relaxation, tensile and tear tests. Overall, natural latex gloves far outperformed those made of synthetic elastomers, and there is great disparity among the different brands of nitrile gloves, some of which do not meet nitrile glove performance requirements. The study includes prototype gloves made from guayule latex, a domestic source of alternative natural rubber latex, currently under commercial development. The guayule gloves outperformed all other gloves tested, including those made from Hevea latex, without posing allergy risks. Mechanical analysis demonstrated that the guayule gloves are as strong as the best alternatives, are softer and more elastic, have better tear strength, and have such low stress relaxation that they cause very little hand fatigue during use. Guayule latex can address the need for domestic production of gloves to resolve supply chain and quality issues and encourage a shift back to natural latex gloves, which will significantly diversify the natural rubber supply.

A Visco-Hyperelastic Constitutive Model to Characterize the Stress-Softening Behavior of Ethylene Propylene Diene Monomer Rubber.

Uniaxial and biaxial cyclic tensile tests and stress relaxation tests were performed on the ethylene propylene diene monomer (EPDM) material to investigate its stress-softening effect. The experimental results reveal that the EPDM material presents a significant Mullins effect during the cyclic stretching processes. Furthermore, it is found that the deformation of the EPDM material does not return to zero simultaneously with the stress, due to the viscoelasticity of the EPDM material. Therefore, this study combines pseudo-elasticity theory and viscoelastic theory to propose a visco-hyperelastic constitutive model. The proposed model is used to fit and analyze the uniaxial and biaxial cyclic test results of EPDM and a comparison is conducted with the corresponding hyper-elastic constitutive model. The results show that the proposed model is in good agreement with the experimental data and superior to the hyper-elastic constitutive model, especially when it comes to the stress-softening unloading process. This work is conducive to accurately characterizing the stress-softening behavior of rubber-like materials at large deformation and can provide some theoretical guidance for their widespread application in industry.

A multifunctional lactic acid based plasticizer used for plasticizing PVC and PLA: Endowing PLA elastic restore capability

A novel multifunctional plasticizer, cyclohexyl triethylene glycol oligo-lactate (CTLE) was designed by a two-step esterification reaction using green non-toxic biomass lactic acid as raw material. Its structure was characterized by 1H NMR, FT-IR and TOF-MS. Thermogravimetric analysis (TGA), tensile test and leaching test were used to evaluate the plasticizer effect of PVC or PLA blends. Compared with commercial plasticizers, CTLE showed more outstanding thermal stability, flexibility and migration stability. Under the same condition with the addition of 50 phr plasticizer, the CTLE plasticized PVC film had the lowest glass transition temperature (TgCTLE-50 = 24.6 °C) and the highest initial decomposition temperature (TiCTLE-50 = 265.4 °C). In PLA blends, only the CTLE plasticized PLA film could recover after fracture, and the stress relaxation test results showed that the stress value of PLA-CTLE-20 drops sharply to a non-zero value, showing elastic characteristics. We estimate that the excellent plasticity of CTLE is due to its molecular structure. Among them, a large number of polar groups form intermolecular forces with PVC chain segments to make the binding tight, and the ring structure increases the free volume between PVC chain segments.

Phenoxy resin-based vinylogous urethane covalent adaptable networks

This work presents a post-polymerization approach to the preparation of vitrimers, exploiting the transamination of vinylogous urethane in linear phenoxy resins. Phenoxy vitrimers are obtained by a two-steps synthesis from a commercial phenoxy resin via partial conversion of hydroxyl groups to acetoacetates (AcAc), followed by network formation by reaction with m-xylylendiamine as crosslinker. Three different vitrimers with variable crosslinking density are obtained by tuning the density of AcAc moieties along the phenoxy resin scaffold (5%, 10% and 15% conversion of hydroxyl groups). The conversion of linear polymers to dynamic crosslinked networks is confirmed by dynamic mechanical thermal analyzer and rheology measurements, followed by stress relaxation tests to investigate the kinetics of bond exchanges. Tensile tests as a function of reprocessing cycles reveal an increase of the maximum elongation and stress at break and prove the good recyclability of the vitrimers. Enhanced adhesive properties compared to pristine phenoxy resins are demonstrated, including the possibility to thermally re-join the assembly after its mechanical failure. Finally, the solvent-free preparation of vitrimers is explored at 5% crosslinking density via melt reactive blending, providing a valuable alternative to the less environmentally sustainable synthesis in solution.

A hyper-viscoelastic constitutive model for elastomers: A case study of hydrogenated nitrile butadiene rubber and polychloroprene rubber

Elastomer materials are widely used as shock absorbers in a variety of practical applications including the automotive, aerospace, marine industries and structures. The straightforward Hooke’s law is insufficient to adequately describe the behavior of elastomeric materials due to their nonlinear elastic and viscous properties. This study proposes a hyper-viscoelastic model to describe the mechanical behavior of Hydrogenated Nitrile Butadiene Rubber (HNBR) 62 Duro shore A and Polychloroprene Rubber (PCR) 55 Duro shore A. Six distinct hyperelastic models—Yeoh, Rivlin, Arruda-Boyce, Mooney-Rivlin, Neo-Hookean, and Ogden— are compared herein to explain the nonlinear elastic behavior of elastomers. While the time-dependent characteristics of the considered materials have been described using the four parameters Generalised Maxwell (GM) model. The material parameters of models are determined using the least square fit (LSF) optimization algorithm from the uniaxial, planar, and stress relaxation test data. The stability and suitability of each hyperelastic model is assessed using the Drucker stability. The accuracy of each model is represented by Root Mean Square Error (RMSE) of curve fitting between theoretical and experimental data. On this basis, the Ogden order three ( N = 3) model and the four-parameter GM models are selected which well agreed with the experimental test data and they are integrated to generate the hyper-viscoelastic constitutive model. In addition, the hyper-viscoelastic model is used to simulate the HNBR and PCR dampers under shock load. The numerically generated response is finally compared with the experimental test result of natural rubber (NR) 60 IRH from the existing literature to confirm accuracy of the proposed model.

Impact of cryogenic treatment on mechanical and electro active actuation properties of soft polymers

AbstractThe goal of this study is to investigate the change in stretchability property of soft polymers before and after cryogenic treatment. To achieve this, the influences of cryogenic treatment on the rate dependent tensile properties, hysteresis behavior, and stress‐relaxation of soft polymers are extensively analyzed. Results indicated that the effects of cryogenic treatment for both VHB and Ecoflex samples on mechanical responses were more prominent at low strain rate. It was also observed that VHB polymer could exhibit more strain rate sensitivity than Ecoflex sample after cryogenic treatment. For stress relaxation test, both cryo‐treated polymer samples were found to yield less overall stress and takes longer time to reach equilibrium stress in comparison to untreated polymer. Extensive experimental findings showed that the amount of energy dissipated while cooling below glass transition temperature (Tg), causes stress softening with lowering of viscoelastic property. On the other hand, there is a good enhancement of the electro‐active actuation strain for the cryo‐treated VHB 4910 and Ecoflex specimens. The results of this work could be used as a helpful guide for applying cryogenic treatment to improve electro‐mechanical properties of soft polymers, as the theory underlying this treatment has not been well explored

Effect of rejuvenation heat treatment on the microstructure and stress relaxation behavior of nickel-based superalloy with excess hardness

The repair of R26 high-temperature alloy bolts with excessive hardness after ∼60,000 h of service using rejuvenation heat treatment was evaluated. Stress relaxation tests with different initial stresses were performed on R26 superalloy before and after rejuvenation heat treatment. The effect of rejuvenation heat treatment on the microstructure of the R26 superalloy was evaluated through a combination of scanning electron microscopy, transmission electron microscopy, and evaluation of the Brinell hardness and stress relaxation behavior. The results showed that the main precipitated phases in the R26 superalloy are the γ’ phase, Ni(Cr32Mo9Fe3), TiC, and Mo23C6. Rejuvenation heat treatment can effectively reduce the hardness of the alloy by dissolving intergranular carbides. In the stress relaxation test, the γ’ phase effectively impeded dislocation movement, whereas Ni(Cr32Mo9Fe3), TiC, and Mo23C6 impeded grain boundary slippage. The specimens without rejuvenation heat treatment showed normal stress relaxation, whereas the specimens subjected to rejuvenation heat treatment showed abnormal stress relaxation. This is attributed to the precipitation of solid-solution Mo from the γ matrix to form a precipitated phase, which induces lattice shrinkage of the γ matrix and size reduction (shrinkage) of the R26 superalloy. The γ’ phase spacing was smaller and dislocation movement was more difficult in the sample subjected to rejuvenation heat treatment than in the congener without rejuvenation heat treatment. The superalloy exhibited better resistance to stress relaxation, resulting in plastic strain during stress relaxation, which was less than the lattice shrinkage. In order to maintain a constant total strain, the external force needs to be increased; thus, the superalloy showed an abnormal stress relaxation phenomenon with increasing stress.

Prediction of the effective viscoelastic properties of polymer-based microstructure with randomly-placed linear elastic inclusions using convolutional neural network

This work proposes a prediction of the effective transverse relaxation modulus of a two-phase material with randomly-placed linear elastic circular inclusions inside a linear viscoelastic matrix using a microstructure image of a representative volume element (RVE) and a convolutional neural network. For this purpose, 1900 RVEs with volume fractions ranging from 20 % to 65 % are generated using the random sequential expansion (RSE) algorithm. The RVEs are then simulated under a stress relaxation test using the finite element (FE) method. Then, by applying homogenization-based methods, the effective transverse relaxation modulus of the RVE, which represents the properties of the whole material, is obtained. The validity of the results of the FE simulation is assessed by mesh convergence check and comparison with numerical data available in the literature. Next, data augmentation is utilized to make the dataset four times larger by flipping the RVE images in vertical, horizontal, and both directions to have a dataset containing 7600 images of RVE and their effective relaxation modulus. In the following step, 80 % of the dataset is randomly selected and used to train a convolutional neural network (CNN) to establish an ability for the network to predict the effective relaxation modulus of the RVE. The other 20 % of the dataset is employed to measure the accuracy of the proposed CNN model by three different cost functions. It is observed that the CNN model predictions are in excellent agreement with the results obtained from FE simulations while requiring much lower computational and experimental time and cost. The proposed convolutional neural network model in this study provides a powerful tool to accurately predict the effective viscoelastic properties of heterogeneous materials.

Fractional derivative modeling for characterizing stress relaxation properties of Hami melon during drying.

The viscoelastic properties of food materials will change significantly while drying is in progress, which greatly influences the food deformation caused by drying. This study aims to predict the viscoelastic mechanical behavior of Hami melon during drying using the fractional derivative model. To characterize the relaxation characteristics, based on the finite difference method, an improved Grünwald-Letnikov fractional stress relaxation model is proposed to derive an approximate discrete numerical solution of the relaxation modulus by applying the time fractional calculus. The Laplace transform method is used to verify the obtained results, and the equivalence of the two methods is proved. In addition, the stress relaxation tests prove that the fractional derivative model has a better prediction effect on the stress relaxation behavior of viscoelastic food than classical Zener model. The significant correlations between the fractional order and the stiffness coefficient and the moisture content is also studied. Which is negative correlation and positive correlation respectively.

Characterization of Pad–Wafer Contact Area and Distance in Chemical-Mechanical Polishing

Chemical-mechanical polishing (CMP) has been an important process step in microelectronic device manufacturing for more than three decades. Physical CMP modeling utilizes the interactions between the polishing pad and the wafer. This requires data on important physical properties such as the real contact area and the effective pad-to-wafer distance under near-process conditions, as these are directly related to the removal rate, defects, etc. In the present study, a FTIR spectrometer and a custom ATR equipment with micro-structured single reflection elements (mSRE) were used to quantify the volume fraction and contact area of a IC1000 polishing pad in dry and wet state under different static loads. No stable contact over time was observed even at very high pressures of up to 350 kPa. Viscoelastic behavior of air-dried and water-soaked pad was proven on a microscale by using load response, creep-recovery and stress relaxation tests. This leads to a memory effect of the pad that should be taken into account during dynamic loading as the wafer-pad contact has a direct impact on the material removal. The presented method can therefore provide valuable information about dynamic effects of the pad behavior in near-process environment and thus help to improve the CMP modelling.