Chen Sun

• Doctor of Mechanics
• Professor (Associate) at Shanghai Jiao Tong University

Real surface contact occurs primarily at the asperities, whose morphologies vary based on different processing methods. To simplify this complexity, asperities are often idealized as regular geometric shapes such as spheres or hemispheres. This paper introduces a spherical asperity model under plane strain conditions, derived from finite element an...

Thin film/substrate structures are irreplaceable in many advanced devices, and their reliability is highly dependent on the distribution of residual stress. Stoney’s formula is extensively used to analyze residual stress of thin film/substrate structure because of its simplicity and convenience, but it encounters difficulties when considering the f...

Various processing methods exert influence on surface contact behaviors, encompassing aspects of surface periodicity, randomness, and yield stress. This study systematically investigates the contact behavior of surface asperities generated through milling, wire electrical discharge machining (WEDM), and knurling under diverse loading conditions, em...

Stoney formula is widely used in advanced devices to estimate the residual stress of thin film/substrate system by measuring surface curvature. Many hypotheses including that thin film thickness is ignored are required, thus bringing significant error in characterizing the inhomogeneous residual stress distribution. In this article, arbitrary resid...

Full-field optical morphology measurement methods are widely used in the shape measurement of underwater targets. The existing models and calibration methods in air could be invalid due to the refraction of light. To deal with these problems, this paper develops a cross-medium imaging model and a relative calibration method. In the modelling, the a...

The projection moiré method is a high-precision optical topography measurement method. The existing moiré models calibrate the phase-height mapping relationship by setting and moving the reference plane, which introduces many system errors and reduces the usability and scanning scalability of the methods. This paper proposes a moiré model based on...

For the digital image correlation (DIC) method, the measurement of specimens with complex shapes may encounter difficulties due to the time-consuming recognition of region of interest (ROI), and the indeterminate parameter selection caused by the non-uniform deformation. This paper proposes an automatic DIC for the measurement of structures with co...

An experimental characterization method for the non-conforming contact with random defects is developed in this paper. The method consists of the mechanics modeling and the parameters inversion algorithm. In the modeling, a new contact boundary description method is developed, which can sensitively characterize the discontinuous contact area caused...

The processing method has an effect on the morphology and yield strength of the wavy surface. In this paper, experiments and finite element methods are used to analyze the contact behavior of asperities on a wavy surface. And the effects of the distribution, height, surface noise, and yield strength of the asperities on the wavy surface on the plas...

Accurate characterization of contact deformation is of great difficulty especially for the area close to the interface. In this work, a theory-aided strain measurement method by combining modeling and experimental identification is develop for the characterization of contact deformation. The method consists of three procedures including displacemen...

The processing method has an effect on the morphology and yield strength of the rough surface. In this paper, experiments and finite element methods are used to analyze the contact behavior of asperities on the rough surface. And the effects of the distribution, height, surface noise, and yield strength of the asperities on the rough surface on the...

Contact usually results in stress concentration which can easily cause the yield of materials and structures. The classic elastic–plastic yield criterion needs to utilize stress or strain field for calculation. However, most advanced full-field measurement methods output the displacement as the original data, and the fitting from displacement to st...

In the projection moiré method, the projected fringe with a constant period usually generates a moiré pattern with nonuniform fringe spacing, which increases the low modulation regions and local measurement error. In this work, an adaptive moiré pattern generation method for the projection moiré system is developed. By formulating the relationship...

Based on the boundary element method and surface profile measurement, a method is developed to solve the inverse problems with point contact. The missing contact stress is modeled by six contact parameters. Using the boundary element method, the contact parameters are related to the surface profiles after deformation. The contact parameters is opti...

In this work, an inverse identification method is developed for the experimental characterization of the elastic–plastic contact in indentation problem. The method consists of a modeling procedure and an identification procedure. In the modeling, a discrete interfacial stress model is developed and the 2D frictional flat but round punch condition (...

As a representative type of outlier, the abnormal data in displacement measurement often inevitably occurred in full-field optical metrology and significantly affected the further evaluation, especially when calculating the strain field by differencing the displacement. In this study, an outlier removal method is proposed which can recognize and re...

Background The flat punch indentation problem is a typical prototype of conforming contact which can be frequently encountered in many applications. Its characterization is of great difficulty as the interface is embedded and the stress is highly concentrated at the contact boundary.Objective In this work, an inverse identification method is develo...

Flexible electronic technology is now widely developed in wearable products for humans and the detection of physiological characteristics, track tracking, and analysis of the living environment for animals and plants. In these application scenarios, flexible electronic devices (FEDs) may work outdoors for a long time and may be exposed to strong so...

Line contact usually causes stress concentration, resulting in the wear and failure of materials and structures. The characterization of the contact phenomenon thus plays an important role in the safety evaluation of materials and structures. In this paper, an inverse method is developed that can identify the principal parameters in contact by empl...

Background As a full-field optical metrology, projection moiré approach has been widely used in many engineering applications. The modeling of moiré system and the calibration, including the calibration of relationship between the moiré phase and object’s height, and the calibration of optical system parameters, are the key points in this method as...

Background: The non-conforming contact usually induce stress concentration as the interaction only occurs at a small interface. Theoretical and numerical investigations have shown that the contact stress distribution and maximum pressure are closely related to the length of the contact interface. Objective: Therefore, the characterization of the co...

The strain concentration analysis is of great importance in multi-tooth contact problems. However it still lacks of effective approach for its experimental characterization. In this paper, the strain concentration state of the multi-tooth structure was characterized based on an optical metrology and orthogonal analysis. A proposed multi-resolution...

An optimization function-based phase-matching method is proposed for the three-dimensional (3-D) fringe projection method. As an essential procedure in 3-D fringe projection metrology, the phasematching processing has a significant influence on the measurement accuracy. The traditional phase-matching method obtains the corresponding points in diffe...

In this paper, a multiscale segmentation-aided digital image correlation method is proposed to characterize the strain concentration of a turbine blade fir-tree root during its contact with the disk groove. A multiscale approach is implemented to increase the local spatial resolution, as the strain concentration area undergoes highly non-uniform de...

The experimental identification of contact stress is important in many areas. In this paper, we present an inverse method for identifying the stress distribution on non-conforming contact interface based on local displacement measurements. A mechanical model is established to formulate the relationship between the contact stress and the displacemen...

An arbitrarily arranged projection moire´ system is presented for three-dimensional shape measurement. We develop a model for projection moire´ system and derive a universal formula expressing the relation between height and phase variation before and after we put the object on the reference plane. With so many system parameters involved, a system...

In this paper, we propose an experiment-based method for the modeling and the identification of the contact pressure and friction distribution on the interface of a non-conforming contact. In this method a two-dimensional contact model is established. The distributed contact pressure and friction are approximated by Taylor series and their relation...

Undesirable vibrations can greatly degrade the accuracy of phase shifting moiré interferometry. Although moiré interferometry is always equipped with a somehow elaborate system to dampen or to eliminate vibration, such as granite slab and air table, it is common to see the phase fluctuation of moiré diagram attributable to the various vibration dur...

In this paper, we propose segmentation-aided digital image correlation (SA-DIC) for measuring the deformation near the interface between two contact bodies. Conventional DIC assumes that the shape function correctly warps a square subset from the reference image to the deformed image. When the subset is close to the contact interface, it contains p...

In digital image correlation, the sub-pixel intensity interpolation causes a systematic error in the measured displacements. The error increases toward high-frequency component of the speckle pattern. In practice, a captured image is usually corrupted by additive white noise. The noise introduces additional energy in the high frequencies and theref...

Digital image correlation (DIC) relies on a high correlation between the intensities in the reference image and the target image. When decorrelation occurs due to large deformation or viewpoint change, incremental DIC is utilized to update the reference image and use the correspondences in this renewed image as the reference points in subsequent DI...