Strain Amplitude Research Articles

A comparison of conventional and additively manufactured 316L under thermomechanical fatigue

The present study compares the thermomechanical fatigue (TMF) behaviour of 316L stainless steel manufactured conventionally by hot rolling and additively by laser powder bed fusion (L-PBF). Machined cylindrical specimens were tested under strain-controlled in-phase and out-of-phase TMF loading at a temperature range of 550–750 °C and total mechanical strain amplitudes of εamech = 0.2–0.6 %. While the conventional 316L significantly outperforms the L-PBF 316L under in-phase TMF, their lifetimes are comparable under out-of-phase TMF. Under in-phase TMF, creep damage in the form of intergranular crack networks occurs which is significantly more pronounced for the L-PBF 316L due to the higher amount of interfaces. Under out-of-phase TMF, the damage is mostly due to stress-assisted oxide cracking and the crack propagation is fatigue-dominated. TEM inspection revealed that L-PBF 316L exhibits a cellular dislocation structure in the initial state, which rearranges only slightly during cycling. For conventional 316L similar dislocation cells form during TMF cycling indicating that they represent a stable dislocation arrangement in 316L under TMF loading. This is evidenced by the rather stable cyclic stress response of the L-PBF material when compared to the conventional material.

Laser melting deposition of Mn–Cu-based alloy: Microstructure, mechanical properties and damping capacities

Mn–Cu-based alloys are promising structural materials for noise and vibration reduction, and Mn–Cu-based alloys with medium Mn content offer significant advantages in formability and corrosion resistance. The preparation of Mn–Cu-based alloys using traditional processes has disadvantages such as the ease of defects and long preparation cycles. Laser melting deposition was employed to fabricate the Mn-36.53Cu-4.30Al-3.07Fe-2.46Ni-0.64Zn (wt. %) alloy thin wall sample, and the microstructure, mechanical characteristics, and damping capacity of the as-deposited samples were investigated. The microstructure of the as-deposited alloy revealed randomly dispersed fine γ-(Mn, Cu) dendrites and a small quantity of α-Mn phase across different sections. The as-deposited samples along the scanning direction (AD-S) exhibited an ultimate tensile strength (UTS) of 584 ± 6 MPa, while those along the deposition direction (AD-D) showed a UTS of 578 ± 6 MPa. The elongation of AD-S samples measured at 40 ± 0 %, and for AD-D samples, it was 31 ± 1 %. At ambient temperature, the as-deposited alloy displayed high damping properties with a frequency of 1 Hz and a strain amplitude ranging from 30 to 100 × 10−6. The findings contribute to the practical applications of Mn–Cu-based alloys, particularly those with a medium Mn concentration.

Dislocation density‐based constitutive model for cyclic deformation and softening of Ni‐based superalloys

AbstractA physically‐based constitutive modeling framework is proposed for the cyclic deformation and softening of Ni‐based superalloys. The constitutive model accounts for underlying mechanisms of grain size strengthening, dislocation strengthening, solid solution strengthening, and precipitate strengthening, commonly observed in these alloys. A constitutive model is proposed for the shearing of precipitates on their interaction with glide dislocations during cyclic deformation. This is the primary contributor to the experimentally observed cyclic softening behavior in Ni‐based superalloys. Model predictions of the cyclic stress–strain response and the cyclic softening (quantified in terms of the peak stress) are compared with the experimental counterparts for a range of strain amplitudes under fully‐reversed cyclic loading of Inconel 718 (IN 718). Further, model predictions of precipitate size are also compared with the experimentally measured transmission electron micrographs of precipitate sizes at the end of deformation. Concurrence in the cyclic stress–strain response, peak stress, and precipitate size provides validation for our constitutive modeling framework.

Influence of normal force on magnetic-field-induced shear modulus of isotropic and anisotropic magnetorheological elastomers having spherical and non-spherical shape iron particles

ABSTRACT Isotropic and anisotropic magnetorheological elastomers (MRE) were prepared using spherical carbonyl iron (CI) particles and electrolyte non-spherical iron (EI) particles having a 60% weight fraction in silicon rubber. The pre-structured MREs were prepared under a constant magnetic field of 0.3 Tesla. A parallel-plate MR rheometer with a magneto-rheological cell was used to conduct dynamic measurements under different normal forces. All the data were recorded under 1 Hz frequency and strain amplitude of 0.1% (in the linear viscoelastic region), and normal force was varied from 1N to 10 N. Results show that the magnetic-induced shear modulus increases in both MREs with normal force for isotropic as well as anisotropic samples. However, in CIP-based MRE, the MR effect increases with a pre-structured sample, whereas for EIP-based pre-structured MRE, the MR effect decreases compared to isotropic samples. Nevertheless, the relative MR (RMR) effect decreases with normal force in both cases. The rate of decrease is different in CIP- and EIP-based MREs. A possible mechanism for the same is discussed in the paper.

Study on low fatigue damage behavior of TC17 titanium alloy with basket-weave microstructure

Room-temperature low-fatigue tests were conducted on TC17 titanium alloy, and the low-fatigue damage behavior of TC17 titanium alloy with a basket-weave microstructure at room temperature was investigated. The results show that TC17 titanium alloy exhibits different cyclic hardening/softening phenomena at different strain amplitude (εta) levels, which was closely related to the magnitude of strain amplitude, the crack sources of all specimens generated on the surface, and the number of crack sources increases with the increase of strain amplitude level. The competitive relationship between back stress hardening and frictional stress softening caused by changes in different microstructures is the reason for the occurrence of different cyclic hardening/softening phenomena. The relationship between the holes and secondary cracks near the fracture surface and the basket-weave microstructure was further discussed. The secondary cracks/holes were more likely to initiate in the primary α phase where the solid solution strengthening effect was weak. In addition, the interaction between the secondary crack propagation path and the nearby α lamellae was studied by the Electron Backscatter Diffraction (EBSD) method.

Out-of-phase thermomechanical fatigue of a single crystal Ni-base superalloy

The present work studies the out-of-phase thermomechanical fatigue (OP-TMF) behavior of the precisely oriented [001] single crystal Ni-base superalloy ERBO/1 (CMSX-4 type). The OP-TMF tests are performed between minimum and maximum temperatures of 1023 and 1223 K and a cyclic mechanical strain amplitude of ±0.5 %. In accordance with previous findings, the present study confirmed that isothermal low cycle fatigue (LCF) tests at 1023 and 1223 K show significantly longer fatigue lives than the OP-TMF tests, specimens with rougher surfaces fail earlier than polished specimens and deformation bands and cracks form in the specimen surface. Two new results were obtained: First, when comparing OP-TMF cycles with fast cooling (tensile part of cycle) and fast vs. slow heating (compressive part of cycle) one finds that the slower heating/compressive cycle is more damaging. Second, analytical scanning electron microscopy of the flanks of an OP-TMF crack allows to study the diffusion-controlled growth kinetics of the oxide and the underlying zone, which is depleted by the oxide forming elements. These results are discussed in the light of the microstructural, mechanical and chemical results of the present study considering previous work on OP-TMF of superalloy single crystals (SXs).

Interface engineering at the nanoscale: Synthesis of low‐energy boundaries

The low toughness and structural stability of nanostructured materials is strongly related to the numerous grain boundaries and interfaces. This necessitates new design strategies to inherently improve the grain boundaries. Amongst other concepts the use of low‐energy boundaries has turned out to provide the most comprehensive improvement of the property spectrum targeting on ductility, toughness, as well as thermal and microstructural stability upon mechanical loading. Cyclic high‐pressure torsion (CHPT) is one prosperous technique to synthesis low‐angle boundaries (LAGB) at the nanoscale, enabling the production of high‐strength materials. We present here an in‐depth analysis of the structural evolution focusing on the effect of different strain amplitudes and accumulated strains as well as crystal structure to understand how these parameters need to be adjusted to optimize the fraction of LAGBs. Different than expected from classical fatigue testing, the crystal structure seems to play a minor role for the cell structure evolution at comparably large strain amplitudes. It is therefore a strong asset that CHPT is feasible to produce nanostructures LAGB boundaries in both FCC and BCC structures. Furthermore, by optimizing the geometry of the anvils, it enables homogenous structural sizes in the entire sample as in contrast to other techniques the strain gradient impact on LAGB formation can be overcome.This article is protected by copyright. All rights reserved.

Contact stress decomposition in large amplitude oscillatory shear of concentrated noncolloidal suspensions

The concentrated noncolloidal suspensions show complex rheological behavior, which is related to the existence of contact stress. However, determining the contact stress in time-varying flow like oscillatory shear is challenging. Herein, we propose a contact stress decomposition method to decompose the total stress directly into contact stress and hydrodynamic stress in large amplitude oscillatory shear (LAOS). The results of hydrodynamic stress and contact stress are consistent with those determined by the shear reversal experiment. The contact stress decomposition also explains the failure of the Cox–Merz rule in noncolloidal suspensions because the particle contacts exist in steady shear but are absent in small amplitude oscillatory shear. The intracycle and intercycle of contact stress are further analyzed through the general geometric average method. The intracycle behaviors exhibit strain hardening, strain softening, and shear thickening. The intercycle behaviors show bifurcations in stress-strain and stress-strain rate relations, where the transition strains at different concentrations define the state boundaries between the discrete particle contacts, the growing of particle contacts, and the saturated contacts. We also established a phenomenological constitutive model using a structural parameter to describe the shear effect on the buildup and breakdown of particle contacts. The contact stress of noncolloidal suspensions with wide ranges of particle concentrations and strain amplitudes under LAOS can be well described by the model.

Strain for toughened epoxy resin composites for GIL tri‐post insulators under tension and electric fields

AbstractToughening plays a key role in epoxy resins (EPs) and their composites for high voltage gas‐insulated switchgear (GIL) tri‐post insulators and receives a lot of attention. However, there are still limited research studies on strain and its distribution for the toughened EPs and composites under tension and especially under high electric fields. Herein, the intrinsically toughening mechanism of EPs (toughening ability: EP‐B > EP‐A) and their composites with Al2O3 (toughening ability: EP‐Bcom > EP‐Acom) was explored in terms of chemical characterisation by IR and molecular motion via differential scanning calorimetry and dielectric spectra. A low rigid segment content in EPs contributes to the excellent toughness. Two‐dimensional digital image correlation (2D‐DIC) and three‐dimensional DIC (3D‐DIC) were utilised to probe strain and its distribution in EPs and their composites under tension and electric fields, respectively. EP‐B with more toughness endows it with a larger strain εF under tensile fields and a greater strain amplitude |εE| under electric fields than EP‐A, such as 9278 με at 1 kN, 16.9% greater than EP‐A and 9767 με at 10 kV/mm, 19.3% higher than EP‐A. In addition, all samples show minus strain under electric fields due to compression. With the introduction of Al2O3, EP‐Bcom exhibits a εF of 2870 με at 1 kN, 69.1% lower than that of EP‐B and 49.4% greater than that of EP‐Acom, and it provides |εE| of 5351 με at 10 kV/mm, 45.2% lower than that of EP‐B and 13.2% greater than that of EP‐Acom. Further, samples with more toughness deliver more uniform strain distribution whether under tension or electric fields.

Viscoelastic Properties of Biscuit Doughs with Different Lipidic Profiles Fortified with a Casein Hydrolysate

The effects of using a hard (artisanal) margarine (which has a higher lipidic and lower aqueous contents) and using a soft (commercial) margarine (which has a lower lipidic and higher aqueous contents), along with a casein hydrolysate, on the rheological properties of different biscuit short doughs were examined. The characteristic parameters in the linear viscoelastic range (LVER) were analysed by stress sweep at 6.3 rad/s and 25 °C. The two margarines showed similar values of strain amplitude (γmax), but the hard margarine exhibited a significantly higher firmness in the LVER, as expected. An analogous result was found for the biscuit doughs made with hard margarine and soft margarine. The addition of a casein hydrolysate (CH) to both biscuit doughs produced an increase in the loss factor, indicating a loss of the solid-like character in the dough networks. Nevertheless, a different trend in the consistency of the dough, which depended on the type of margarine, was found. While, after adding CH, the dough made with soft margarine showed a significant reduction in rigidity, the dough with hard margarine exhibited an increased firmness upon CH addition. Yield stress tests showed that CH facilitates the transition from elastic to plastic deformation at the yield point more intensely in the dough with soft margarine.

Shear modulus of sand-rubber mixtures: element testing and constitutive modeling

In this study, a series of resonant column tests was conducted to measure the shear modulus of sand-rubber mixtures at small strain amplitudes (i.e. between 10−4% and 10−2%), considering different rubber percentages and confining stress levels. The results were then combined with data obtained by dynamic hollow cylinder tests to investigate shear modulus degradation of the mixtures over a wider shear strain range. Based on the test results, a new expression was proposed to improve the prediction of maximum shear modulus of sand-rubber mixtures using the modified equivalent void ratio concept. A new constitutive model was also developed for estimation of strain-dependent shear modulus of the mixtures based on the modified hyperbolic framework. The shear modulus of the mixtures was found to be a function of rubber percentage, confining stress, the modified equivalent void ratio and the relative shear stiffness of rubber and sand. The experimental data and the developed models showed that the shear modulus decreased with rubber percentage and increased with confining stress. Moreover, the reference shear strain of the modified hyperbolic model increased with both rubber percentage and confining stress while its curvature coefficient increased more considerably with rubber percentage compared to the confining stress.

Agarose as a Tissue Mimic for the Porcine Heart, Kidney, and Liver: Measurements and a Springpot Model.

Agarose gels are often used as a tissue mimic. The goal of this work was to determine the appropriate agarose concentrations that result in mechanical properties that match three different porcine organs. Strain tests were carried out with an amplitude varying from 0.01% to 10% at a frequency of 1 Hz on a range of agarose concentrations and porcine organs. Frequency sweep tests were performed from 0.1 Hz to a maximum of 9.5 Hz at a shear strain amplitude of 0.1% for agarose and porcine organs. In agarose samples, the effect of pre-compression of the samples up to 10% axial strain was considered during frequency sweep tests. The experimental measurements from agarose samples were fit to a fractional order viscoelastic (springpot) model. The model was then used to predict stress relaxation in response to a step strain of 0.1%. The prediction was compared to experimental relaxation data, and the results agreed within 12%. The agarose concentrations (by mass) that gave the best fit were 0.25% for the liver, 0.3% for the kidney, and 0.4% for the heart. At a frequency of 0.1 Hz and a shear strain of 0.1%, the agarose concentrations that best matched the shear storage modulus of the porcine organs were 0.4% agarose for the heart, 0.3% agarose for the kidney, and 0.25% agarose for the liver.

Quantitative study on the influence of strain amplitude on deformation mechanisms and cracking modes during cyclic torsion of AZ31 magnesium alloy

AbstractThe influence of strain amplitude on deformation mechanisms and cracking modes during cyclic torsion of the AZ31 magnesium (Mg) alloy was quantitatively investigated via EBSD‐SEM characterization. At 0.42% strain amplitude, basal slip was the dominated deformation mechanism throughout the entire fatigue life. At 1.732% strain amplitude, the activation of deformation mechanisms was featured by the periodic transition: tension twinning + basal slip (during counterclockwise torsion) then detwinning + tension twinning + basal slip (during reverse torsion). Moreover, cracking along slip traces (ST) and tension twins (TTW) were the primary cracking modes at 0.42% and 1.732% strain amplitude, respectively. ST cracking and TTW cracking preferentially appeared in soft‐oriented grains for basal slip and tension twinning, respectively. The underlying mechanisms governing the activation of various deformation mechanisms, cracking modes, and cyclic stress–strain responses were systematically discussed.

Material characterization of iron-based shape memory alloys for use in self-centering columns

Iron-based shape memory alloys (FeSMAs) are emerging as a promising material for use in post-tensioning concrete structures to provide self-centering capabilities during a seismic event. Past experimental studies on FeSMA focused on strengthening or repairing existing structural components under gravity loading. In addition to the structural rehabilitation, FeSMA also have potential for use in self-centering columns subjected to seismic loads. However, the basic material properties, such as strength, ductility, recovery strain, actuation stress (i.e. prestress) stability, low-cycle fatigue resistance, and temperature dependence of FeSMA related to self-centering column applications have not been studied extensively to-date. To fill this knowledge gap and determine the feasibility of using FeSMA in self-centering columns, this study performed a comprehensive characterization and analysis of FeSMA both before and after actuation (i.e. thermal stimulation). The strength, ductility, energy dissipation, and recovery strain of FeSMA before actuation were tested at different temperatures from −40 °C to 50 °C. After actuation, the actuation stress, low-cycle fatigue resistance, and strain capacity of FeSMA were tested at different temperatures from −40 °C to 50 °C and prestrain levels from 4% to 30%, and under low-cycle fatigue loading with strain amplitudes from 0.5% to 1.0%. The results from this study demonstrated that FeSMA exhibit high ductility, cyclic actuation stress stability, and low-cycle fatigue resistance at temperatures from −40 °C to 50 °C. Furthermore, it was found that increasing the prestrain level can effectively increase the post-actuation strain amplitude at which the actuation stress reduces to zero. A prestrain level between 15% and 20% is recommended for application of FeSMA in self-centering columns. The research findings from this study demonstrated the feasibility of using FeSMA in self-centering columns subject to seismic loading.

Evaluation of fatigue life prediction models and investigation of fracture mechanisms of mild steel

Fatigue is one of the dilemmas of coiled tubing (CT) in oil and gas engineering. This study investigated the fatigue behavior of CT employing mild steel, which is commonly utilized in the CT110. Two fatigue life prediction methods based on cyclic strain-life principles, the Manson–Coffin and Landgraf models, as well as the Smith and Ellyin models based on energy-life principles, were evaluated. The Ellyin model demonstrated superior accuracy in predicting the low-cycle fatigue life of CT110, displaying dispersion within the 1.5 scatter band. This research integrated mechanical property analysis and microscopic deformation assessments for CT110. Fatigue mechanics studies show cyclic softening behavior in the CT110 of mild steel. The results of the microscopic analysis show that the fatigue fracture of CT110 has typical fatigue striations and equiaxial dimples as a plastic fracture. Combined with TEM and EBSD analysis, fatigue deformation increases grain deformation and dislocation density. In addition, the increase in dislocation density results from the combination of cycles and strain amplitude. The results of in situ EBSD further support this view. At 8% strain amplitude, the dislocation density increases to 0.196B when the cycle increases from 0 number to 10 number. Furthermore, the ferrite grain slip becomes accessible, but the 〈111〉 // Z0 direction is still the main texture. These are fundamental reasons for the cyclic softening of the CT110 mild steel, supported by a decrease in stress amplitude.

Experimental investigation into corrosion effect on buckling and low-cycle fatigue performance of high-strength steel bars

The reinforcement in marine RC structures will inevitably be corroded under long-time erosion of chloride ions, which will weaken steel mechanical properties and then structural seismic resistance. The new metallurgical technology is adopted for manufacturing high-strength steel bars (HSSB), but that may affect the corrosion resistance of steel bars at the same time. This paper experimentally investigates the effects of corrosion on monotonic and low-cycle fatigue properties of HSSB HTRB600 and normal strength steel bars (NSB) HRB400E. The HRB400E and HTRB600 steel bars were corroded to different corrosion rates by electrochemical accelerated corrosion technique. The monotonic tensile and compressive, as well as low-cycle fatigue tests of corroded steel bars were conducted to investigate the effects of corrosion on steel mechanical properties, of which corrosion levels (0–20% target corrosion mass loss), slenderness ratios (L/D=6, 8, 10, 12) and strain amplitudes (2%, 4%) are considered. Test results show that, the corrosion morphology of steel bars under electrochemical accelerated corrosion is basically consistent with that observed under natural corrosion. Compared with uncorroded HRB400E and HTRB600 steel bars, 20% corrosion mass loss leads to 38% and 35% decrease in tensile strength, as well as 33% and 28% reduction in buckling stress, respectively. The HTRB600 steel bars present slightly superior monotonic tensile and compressive corrosion resistance than HRB400E steel bars. Corrosion obviously decreases the low-cycle fatigue (LCF) life of steel bars, resulting in reductions of 44% and 36% in LCF life at 20% corrosion mass loss for HTRB600 and HRB400E steel with a L/D of 6, respectively. Moreover, the HTRB600 steel bars present more significant corrosion degradation in total hysteretic dissipated energy, compared with HRB400E steel bars. The combined effect of corrosion and inelastic buckling further exacerbates the deterioration of LCF performance of steel bars. The corresponding deterioration models are proposed to determine the LCF life and energy dissipation capacity of corroded steel bars.

Biomechanical Modelling of Porcine Kidney.

In this study, the viscoelastic properties of porcine kidney in the upper, middle and lower poles were investigated using oscillatory shear tests. The viscoelastic properties were extracted in the form of the storage modulus and loss modulus in the frequency and time domain. Measurements were taken as a function of frequency from 0.1 Hz to 6.5 Hz at a shear strain amplitude of 0.01 and as function of strain amplitude from 0.001 to 0.1 at a frequency of 1 Hz. Measurements were also taken in the time domain in response to a step shear strain. Both the frequency and time domain data were fitted to a conventional Standard Linear Solid (SLS) model and a semi-fractional Kelvin-Voigt (SFKV) model with a comparable number of parameters. The SFKV model fitted the frequency and time domain data with a correlation coefficient of 0.99. Although the SLS model well fitted the time domain data and the storage modulus data in the frequency domain, it was not able to capture the variation in loss modulus with frequency with a correlation coefficient of 0.53. A five parameter Maxwell-Wiechert model was able to capture the frequency dependence in storage modulus and loss modulus better than the SLS model with a correlation of 0.85.

Strengthening mechanism of abnormally enhanced fatigue ductility of gradient nanostructured 316L stainless steel

Structural materials with a good combination of high fatigue strength and high fatigue ductility are highly desirable in engineering applications. However, it remains a challenge to “break” the exclusive relationship between fatigue strength and fatigue ductility. The cylindrical 316L stainless steel specimens with a gradient nanostructured surface layer were prepared using surface mechanical rolling treatment (SMRT). Fully reversed strain-controlled tension–compression fatigue experiments indicated that the SMRT processed 316L specimens achieved simultaneous improvement of fatigue strength and fatigue ductility. The abnormal increase in fatigue ductility is attributed to the significant secondary cyclic hardening caused by the martensitic phase transformation and the transition in fatigue crack initiation mode. The martensitic phase transformation enhances the fatigue strength while reducing the proportion of plastic deformation in the controlled strain amplitude. The competition between the driving force and resistance of fatigue nucleation in different structural units results in the migration of fatigue crack initiation sites from the surface to subsurface, thereby prolonging the fatigue crack initiation life. This work reveals the synergistic strengthening mechanism of fatigue strength and fatigue ductility of a gradient nanostructured 316L stainless steel.

Magnetic field dependent elastic moduli and internal frictions in nickel alloy revealed by a quantitative electromechanical impedance method

Accurately and quickly determining the moduli and damping properties of ferromagnetic materials with bias magnetic fields is very important for vibration control and instrument design. In this work, the magnetoelastic properties of a nickel alloy were investigated by using a quantitative electromechanical impedance (Q-EMI) method under bias magnetic fields from 0 to 1364 Oe. Measurement results demonstrate that both the Young’s modulus and shear modulus of the nickel increase steadily with the bias magnetic field, tending to saturate under high fields. The internal friction of nickel initially increases and subsequently decrease with the magnetic field, exhibiting a pronounced peak. Meanwhile, it is found that the torsional internal friction is always considerably larger than the longitudinal internal friction. The amplitude dependent internal friction (ADIF) of the nickel alloy under bias magnetic fields was further studied using a dog-bone shaped specimen and a strain-amplifier horn. Results show that the specimen under zero field shows the most significant ADIF when the strain amplitude exceeds 2 ⅹ 10−5. While under a large bias field over 1000 Oe, the ADIF cannot appear until the strain amplitude is over 1 ⅹ 10−4 strain, indicating that the ferromagnetic domains had been stabilized by the large bias field. This study demonstrates the superiority of the Q-EMI method in probing the magnetomechanical properties of ferromagnetic materials.

Anisotropic V-Groove/Wrinkle Hierarchical Arrays for Multidirectional Strain Sensors with High Sensitivity and Exceptional Selectivity.

Flexible strain sensors have been continuously optimized and widely used in various fields such as health monitoring, motion detection, and human-machine interfaces. There is a higher demand for sensors that can sensitively identify both the strain amplitude and direction in real-time to adapt to complex human movements. This study proposes a flexible strain sensor construction strategy based on V-groove/wrinkle hierarchical structures via a facile and scalable prestretching approach. A gold film is sputtered on a V-groove structure soft substrate under a vertical biaxial prestrain. When the strain is released, a variety of wondrous V-groove/wrinkle hierarchical structures are formed. The microstructure and the properties of the resulting sensor can be controlled by adjusting the prestrain, which has obvious anisotropic response characteristics and exhibits high sensitivity (maximum gauge factor up to 20,727.46) and a wide sensing range (up to 51%). In addition, the resulting multidirectional sensor based on double-sided microstructures has an exceptional directional selectivity of 67.39, at an advanced level among all stretchable multidirectional strain sensors reported so far. The sensor can detect human motion signals and distinguish motion patterns, proving its great potential in the field of human motion detection and laying a foundation for high-performance wearable devices.