Deformable Part Research Articles

Oligocene to Pliocene structural evolution of the frontal Kirthar fold and thrust belt of Pakistan

The spatio-temporal evolution for the frontal part of the Kirthar fold and thrust belt in Pakistan is constrained for the first-time using apatite (U–Th-Sm)/He (AHe) and apatite fission track (AFT) dating of samples from the Oligocene Nari Formation in combination with a published balanced cross-section. The AHe ages appear to be fully reset, allowing us to date the timing of exhumation above ramps. Comparison of partially reset AFT ages (∼22–24 Ma) with previously published zircon fission track (ZFT) ages of the Nari Formation from nearby areas suggest that rocks in the frontal zone were not buried deeper than ∼4 km after deposition. The close range of AFT ages have implications for the timing of hinterland exhumation and Oligocene age of the Nari Formation. The AHe ages suggest that deformation along the major basement ramp was active since ∼7 Ma, forming a major topographic step (∼1.5 km) in the frontal part of the Kirthar fold and thrust belt. Combined analysis of the structural cross-section and thermal modeling of the samples suggest that major cooling occurred between ∼7 Ma and ∼5 Ma. This cooling was due to the erosion of Oligocene to Miocene strata from above the samples when Precambrian to Miocene strata was thrust above the pre-existing normal fault that acted as a basement ramp. The temporal structural evolution suggests that deformation in the frontal part of the Kirthar fold and thrust belt was characterized by faster rates (∼2.5 km/Ma) of orogenic growth and exhumation between ∼7 and 5 Ma, followed by slower shortening rates (<1 km/Ma) since ∼5 Ma.

ESTIMATION OF DYNAMIC YIELD STRESS BY TAYLOR TEST WITH REDUCED CYLINDRICAL HEAD PART OF SAMPLES

A simple method is proposed to estimate the dynamic yield stress of materials using modified Taylor tests for high-velocity impact of profiled cylinders with a reduced diameter of the head part. Assuming the uniformity of deformations and stresses in the head part, formulas are derived for estimating the yield stress and strain rate from the change in the length of the reduced head part, as well as the mass of the sample and the impact velocity. This estimation is verified by comparison with the results of numerical calculations by the SPH method based on the dislocation plasticity model parameterized for cold-rolled oxygen-free copper. It is shown that the stopping time of the sample and the strain rate are reproduced with good accuracy, and the shear strength estimate gives an error that increases with the impact velocity. At velocities that do not lead to deformation of a wide part of the sample (up to 90 m/s in the case under consideration), the error increases linearly up to 30%, which can be taken into account by a correction factor. The proposed estimate, taking into account the correction factor, was applied to analyze the results of previous experiments; the obtained values correspond to the literature data on the rate dependence of the shear strength.

High-precision deformation prediction for compliant parts in the ship sub-assembly process

In the ship sub-assembly process, large compliant parts are common and generally thin. These compliant parts are normally easy to deform under the influence of gravity, which will greatly affect the accuracy of the sub-assembly processes. Thus, it is important to predict the deformation of the compliant part under a given fixture layout in advance. In current practice, existing methods of post-compensation are usually used to correct the deformation of the compliant part, which are inefficient and costly. In this paper, a transformer-based surrogate model with two-stage Latin hypercube sampling (TSM-TSS) is established. This surrogate model considers each fixture position and its deviation to predict the deformation of the entire compliant part. Compared with BPNN and Kriging, a case study reveals that TSM-TSS can predict the deformation of compliant parts with an error of 0.061mm. With the application of TSM-TSS, the deformation of the compliant part under gravity can be predicted accurately and the efficiency of shipbuilding can be improved.

Physical multi-factor driven nonlinear superposition for machining deformation reconstruction

In recent years, the machining deformation of titanium alloy frame parts has become a major research issue in the field of aviation manufacture. Through the generation mechanism, the machining deformation is divided into three parts including bulk residual stresses, cutting forces and other uncertain factors induced deformation. The nonlinearity of physical multi-factor machining deformation is revealed by the comparison between the purely linear addition and coupling superposition. A novel nonlinear superposition model is proposed for machining deformation reconstruction in this work. With the experimental values as simulation inputs, the physical multi-factor driven simulation is developed to solve the nonlinear parameters of machining components in the superposition model. The posterior information embedded in the measurement is utilized to calibrate the nonlinear superposition model in the form of binary polynomials with five orders. The nonlinear superposition model is validated through four series of machining tasks, with the average model accuracy at 91.09%. To quantitively evaluate the proportion share of deformation components, a dimensionless equivalent machining deformation ratio is developed by the integral operation of the established nonlinear model. The results indicate that the bulk residual stresses, cutting forces and other uncertain factors account for percentages of 24.72%, 65.07%, and 13.21% (the ratio among them around 2:5:1). The proposed nonlinear superposition model and dimensionless equivalent ratio in this work display the potential application prospects in the field of machining deformation prediction and control.

Deformable Part Region Learning and Feature Aggregation Tree Representation for Object Detection.

Region-based object detection infers object regions for one or more categories in an image. Due to the recent advances in deep learning and region proposal methods, object detectors based on convolutional neural networks (CNNs) have been flourishing and provided promising detection results. However, the accuracy of the convolutional object detectors can be degraded often due to the low feature discriminability caused by geometric variation or transformation of an object. In this article, we propose a deformable part region (DPR) learning in order to allow decomposed part regions to be deformable according to the geometric transformation of an object. Because the ground truth of the part models is not available in many cases, we design part model losses for the detection and segmentation, and learn the geometric parameters by minimizing an integral loss including those part losses. As a result, we can train our DPR network without extra supervision, and make multi-part models deformable according to object geometric variation. Moreover, we propose a novel feature aggregation tree (FAT) so as to learn more discriminative region of interest (RoI) features via bottom-up tree construction. The FAT can learn the stronger semantic features by aggregating part RoI features along the bottom-up pathways of the tree. We also present a spatial and channel attention mechanism for the aggregation between different node features. Based on the proposed DPR and FAT networks, we design a new cascade architecture that can refine detection tasks iteratively. Without bells and whistles, we achieve impressive detection and segmentation results on MSCOCO and PASCAL VOC datasets. Our Cascade D-PRD achieves the 57.9 box AP with the Swin-L backbone. We also provide an extensive ablation study to prove the effectiveness and usefulness of the proposed methods for large-scale object detection.

Smart-substrate: a novel structural design to avert residual stress accretion in directed energy deposition additive manufacturing

ABSTRACT Residual stresses, related distortions and cracks are detrimental in metallic Additive Manufacturing (AM). Previously developed stress-control strategies based on reducing thermal gradients hardly diminish the stress concentrations at the built basement and easily affect other physical phenomena involved in AM. To overcome this, a novel strategy, named as Smart-Substrate, consisting of optimising the inner structure and local stiffness of the substrate is proposed to avert stress accretion and related part deformations. To demonstrate its advantages, a coupled thermomechanical finite element model for AM, experimentally calibrated with in-situ temperature and displacement measurements, is employed to analyse the thermal and mechanical behaviour of three groups of different structures with increasing geometrical complexity (single-wall, rectangular and block parts) fabricated by Directed Energy Deposit (DED) on the standard and smart substrates, respectively. Through using Smart-Substrate, the generation of residual stresses, especially the stress concentrations at the bottom corner of DED-builds being highly sensitive to cracks, and the induced deflections, are fundamentally throttled, and contrariwise for the standard substrate. More importantly, the use of Smart-Substrate is almost without prejudice to the temperature field, metallurgy and resulting mechanical hardness. This provides a possibility for addressing different physical problems individually, enlarging the AM process window.

Direct relationship between crystalline structure and part deformation of polypropylene copolymer parts fabricated by material extrusion additive manufacturing

AbstractThe high crystallinity and fast crystallization rate of polypropylene (PP) often result in severe warpage of final parts prepared by means of material extrusion additive manufacturing (MEAM). In this work, the effect of bed temperature (Tb) and nozzle temperature (Tn) on the dimensional accuracy and mechanical property of MEAM‐printed PP copolymer parts was investigated. It is found that raising Tb and Tn could significantly reduce the warpage of PP parts by regulating the crystallization behavior of PP. Specially, the amount of γ‐crystal grows obviously while the total crystallinity remains unchanged, as Tb or Tn increases. Moreover, the more the content of γ‐crystal, the lower the warpage height of PP samples is. Hence, a close correlation between the content of γ‐crystal and part deformation of MEAM‐printed PP parts is successfully established. This is mainly related to the large rigidity of γ‐crystal, which significantly reduces the volume shrinkage of PP during MEAM process. Besides, the raise of Tb or Tn also enhances the tensile strength, modulus and the elongation at break of PP parts. This wok provides an effective and convenient method for the manufacture of PP parts with good dimensional accuracy and excellent mechanical properties by means of MEAM techniques.

Effect of strain rate on tensile behavior of tailor welded blanks

The demand for weight reduction, cost savings, more fuel efficiency, and reduced greenhouse gas has led to the increasing application of tailor welded blanks (TWBs) in the automotive industry. The purpose of this study is to investigate the strain rate effect on the tensile behavior of TWB consisting of dissimilar thickness sheets. Hence, a fiber laser was used for welding St14 steel sheets. The weld zone was examined using metallographic and microhardness tests. For investigating the tensile properties, uniaxial tensile tests were performed at strain rates ranging from 0.001 to 10 s−1. It has been found that the presence of Bainitic microstructure in the weld zone increases its hardness. Tensile test results indicate that yield strength and ultimate tensile strength of base metals and TWB enhanced with increasing strain rate. The yield and ultimate tensile strength of TWB are higher than base metals at different strain rates. As the strain rate increases, the total elongation of the TWB decreases, but in base metals, it decreases first and then increases at higher strain rates. In TWB and base metals, by increasing strain rate, uniform elongation decreases, but post-uniform elongation increases. For analysis of plastic deformation of thick and thin parts of TWB, indexes of limiting thickness ratio and difference of ratios (DR) were used. DR decreases with increasing strain rate, which indicates a decrease in the plastic deformation of the thick part of TWB and is consistent with the experimental findings.

Study on milling flatness control method for TC4 titanium alloy thin-walled parts under ice fixation

Thin-walled parts are characterized by weak rigidity and are very prone to deformation during machining, which directly affects the machining accuracy and performance of the parts, so controlling the machining deformation of thin-walled parts is an urgent process problem to be solved. To address such problems, this paper proposes a flatness control machining method based on ice holding of workpieces. The method uses frozen suction cups to solidify liquid water to achieve stress-free clamping of workpieces. We conducted a low-temperature tensile test to investigate the low-temperature mechanical properties of the material. Comparative tests of ice-free and low-temperature ice-fixed milling were conducted to compare and analyze the changes of flatness and milling force in the two working conditions, to investigate the influence of machining parameters on the flatness of thin-walled parts, and to reveal the mechanism of low-temperature milling of ice-fixed workpieces. In addition, the low-temperature milling performance of titanium/aluminum alloy based on ice-fixation was compared. The results show that TC4 has good plasticity, high flexural strength ratio and strong resistance to deformation at low temperatures. Compared with no ice-holding, ice-holding machining effectively improves the flatness of the workpiece, and the order of the machining parameters affecting flatness is: feed rate &gt; milling depth &gt; spindle speed. The milling forces under ice-holding conditions were all greater than those without ice holding. The stiffness and hardness, resistance to damage and deformation of titanium alloy at low temperature are greater than those of aluminum alloy. This method provides a new method for high-precision machining of thin-walled parts.

Determination of temperature in the deformation zone during reversible surface plastic deformation

Finishing and hardening treatment by reversible surface plastic deformation of cylindrical parts is considered. By computational modeling in the ANSYS program, a finite element model is built to determine the temperature in the deformation zone depending on the parameters of the processing mode, and their influence is determined. A critical temperature is established, the excess of which reduces temporary and residual stresses. Keywords: reversible surface plastic deformation, two-radius roller, computational modeling, temperature, deformation zone. zsa@istu.edu, nquan6799@gmail.com

Suppressing the deformation of as-built parts by optimizing the structure of boss bottom in material extrusion of metals

Compared to other metal additive manufacturing technologies, material extrusion (ME) of metals offer several advantages, including low investment cost, safety, simpleness and so on. However, part deformation caused by material shrinkage will reduce its productivity. To address this issue, a method was provided to suppress the deformation by optimizing the boss bottom. The stress field of the model was analyzed using finite element model (FEM), and self-made equipment was used to print the as-built part using 17-4PH stainless steel powder and polymer. The result revealed that the bottom structure could effectively change the stress field of the model and prevent deformation. The optimized structure of the boss bottom could widen the process window and save up to 61.82 % of materials. In conclusion, it provided a new perspective for forming as-built parts without deformation in ME of metals.

Structural relationship between subsurface oil fields in the North Dezful Embayment: Qaleh Nar, Lower and Upper Balarud Anticlines (central Zagros, Iran)

How subsurface anticlines (oil fields) link structurally with faults is of great relevance in the exploration and development of oil fields. In this context, we investigate the geometric relation between lower Balarud (LBR), upper Balarud (UBR) and Qaleh Nar (QN) subsurface anticlines that are the main oil fields in the Northern Dezful Embayment, central Zagros. The Asmari (As) and the Bangestan (Bng) reservoirs are studied geophysically using seismic profiles, well data and underground contour maps (UGC). Interpretation of 3500 m deep seismic profiles indicates the geometry of the studied subsurface anticlines differs vertically and horizontally to a significant proportion. The interpreted structures much resemble As and Bng horizons in each anticline. The UBR got overturned on the LBR due to thrusting possibly in the Late Miocene. The LBR, like a rabbit-ear structure, is situated at the northern edge of the QN. The lower and upper Chenareh and LBR and UBR resemble structurally and are separated mutually by a steep (strike-slip) fault. The fault separates the LBR and UBR from the QN. Interaction of different factors: change in overburden pressure, rate of deformation and uplift in the different parts of the subsurface anticlines moved and accumulated Gachsaran Formation&#x0D; towards both limbs of the anticlines.

Structural relationship between subsurface oil fields in the North Dezful Embayment: Qaleh Nar, Lower and Upper Balarud Anticlines (central Zagros, Iran)

How subsurface anticlines (oil fields) link structurally with faults is of great relevance in the exploration and development of oil fields. In this context, we investigate the geometric relation between lower Balarud (LBR), upper Balarud (UBR) and Qaleh Nar (QN) subsurface anticlines that are the main oil fields in the Northern Dezful Embayment, central Zagros. The Asmari (As) and the Bangestan (Bng) reservoirs are studied geophysically using seismic profiles, well data and underground contour maps (UGC). Interpretation of 3500 m deep seismic profiles indicates the geometry of the studied subsurface anticlines differs vertically and horizontally to a significant proportion. The interpreted structures much resemble As and Bng horizons in each anticline. The UBR got overturned on the LBR due to thrusting possibly in the Late Miocene. The LBR, like a rabbit-ear structure, is situated at the northern edge of the QN. The lower and upper Chenareh and LBR and UBR resemble structurally and are separated mutually by a steep (strike-slip) fault. The fault separates the LBR and UBR from the QN. Interaction of different factors: change in overburden pressure, rate of deformation and uplift in the different parts of the subsurface anticlines moved and accumulated Gachsaran Formation towards both limbs of the anticlines.

WC-Co-TiNbZr composite with simultaneously high hardness and fracture toughness

In this study, the shape memory alloy of TiNb24Zr6 was firstly prepared and then introduced into WC-Co and a new type of WC-Co-TiNbZr composite was fabricated. The phase constitution, element distribution, microstructure, and mechanical properties were systematically characterized. It was found that the added TiNb24Zr6 reacted with the WC matrix and an intermediate (Ti,Nb)C phase formed during the sintering process. As a result, the shape memory effect of TiNb24Zr6 did not play a part in the plastic deformation of the composite. On the other side, the produced (Ti,Nb)C phase played a significant role in the mechanical behavior of the composite. Due to the difference in the elastic modulus between (Ti,Nb)C and WC, cracks deflection and bridging occurred in the vicinity of (Ti,Nb)C under mechanical loading. Moreover, the produced (Ti,Nb)C had a specific coherent interfacial relationship with the WC matrix, which enhanced the interfacial bonding strength and resistance against intergranular fracture of the composite. The hardness and fracture toughness of the present composite achieved 1943.5 ± 12.8 kgf/mm2 and 17.3 ± 0.5 MPa·m1/2 respectively, which are superior compared with those of the counterparts reported in the literature. The strengthening and toughening mechanisms disclosed in this study will be applicable to a wide range of WC-based composites to achieve excellent comprehensive mechanical properties.

Robotic check of a subassembly, and its simulation

This paper discusses a quality inspection process of a subassembly of a battery cover, which is performed with an industrial robot equipped with an intelligent end-effector. The subassembly has a plastic pin and a torsion spring part. During intended use of the unit, the necessary force to actuate the pin is determined with measurements and simulations. In the measurement a self-devised intelligent end-effector is equipped with a microcontroller and a beam type load cell in order to measure the spring force. The main aim is to make an automatic decision without operator intervention at the quality check process, which is related to the quality of the subassembly. In the simulation deformation of the spring part is modeled with geometrically nonlinear 2D beam finite elements in the course of assembly and intended use. Co-rotational approach is used to consider the large displacements and rotations with small strains. Penalty method is applied to treat the contact between the spring and pin parts.

Acoustical behavior of periodic flank modifications under dynamic operating conditions

Noise emissions belong to the crucial design characteristics in modern transmissions. The most efficient way to achieve beneficial noise behavior is to reduce the excitation in the tooth contact, since the tooth contact represents the main source of noise in gearboxes. Special flank modifications may optimize the noise behavior, but the common design approach uses static assumptions, whereas operating conditions include dynamic operation.The application of periodic flank modifications as a special type of flank form provides a possibility to avoid the typical compromise between the flank design objectives load carrying capacity and low excitation behavior which results from the exclusive usage of standard modifications such as crownings or tip- and root relieves. The principle of periodic modifications is based on the direct compensation of the inconstant part of the elastic deformations in the tooth mesh. For this reason, the static loaded transmission error (LTE) is typically used as specific value to evaluate the effect of these flank forms on the excitation. In theoretical and experimental studies, the effectiveness of periodic modifications to optimize the excitation behavior could be verified. However, the analysis of these modifications under dynamic operating conditions is still scarcely documented. In this paper, the mesh excitation of periodic and standard modifications under various dynamic operating conditions in the subcritical, resonance and supercritical operating range is simulated and compared to each other. In addition, experimental investigations at the dynamic test rig of the Gear Research Center (FZG) were performed. Due to the measurement of the torsional acceleration level during continuous speed runups, the simulated results can be validated by experimental data.

Finite element simulation of automobile crankshaft processing based on ductile iron

Crankshaft plays a very important role as the key parts in the automobile engine. The processing of shaft parts mainly adopts the machining method of turning. The service life of the machining tool directly affects the production cost. In the machining process of shaft parts, due to its poor rigidity, it is easy to cause machining deformation, so it is of great significance to control the machining deformation of parts. In this paper, the Advantedge simulation software is used to establish the finite element model of tool wear and cutting process with nodular cast iron crankshaft parts as the research object, and the tool wear and machining deformation of shaft parts are studied respectively.

The minimal formal model of a curve singularity is zero-dimensional

The minimal formal model of a curve singularity describes the non-trivial part of the infinitesimal deformations of the Puiseux parametrizations of the singularity. We show that it is of dimension zero, and effectively computable. We also show that it parameterizes the deformations of the normalization morphism which leave the local ring of the singularity fixed.

DINet: Deformation Inpainting Network for Realistic Face Visually Dubbing on High Resolution Video

For few-shot learning, it is still a critical challenge to realize photo-realistic face visually dubbing on high-resolution videos. Previous works fail to generate high-fidelity dubbing results. To address the above problem, this paper proposes a Deformation Inpainting Network (DINet) for high-resolution face visually dubbing. Different from previous works relying on multiple up-sample layers to directly generate pixels from latent embeddings, DINet performs spatial deformation on feature maps of reference images to better preserve high-frequency textural details. Specifically, DINet consists of one deformation part and one inpainting part. In the first part, five reference facial images adaptively perform spatial deformation to create deformed feature maps encoding mouth shapes at each frame, in order to align with input driving audio and also the head poses of input source images. In the second part, to produce face visually dubbing, a feature decoder is responsible for adaptively incorporating mouth movements from the deformed feature maps and other attributes (i.e., head pose and upper facial expression) from the source feature maps together. Finally, DINet achieves face visually dubbing with rich textural details. We conduct qualitative and quantitative comparisons to validate our DINet on high-resolution videos. The experimental results show that our method outperforms state-of-the-art works.

Compressive properties of aluminum middle-trabecular beetle elytron plates with a large height-to-thickness ratio core

To develop lightweight and high-strength biomimetic structural materials, the compression characteristics of aluminum middle-trabecular beetle elytron plates (MBEPa) with a large height-to-thickness ratio (β) core were investigated by flat compression tests and finite element simulations, and the results are as follows. 1) Compared with aluminum honeycomb plates (HPa), the core compressive strength and energy absorption of MBEPa with two trabeculae per honeycomb can increase by 12.4 % and 28.6 %, respectively, with an increase of about 1.8 % in the total volume; and for the first time, the MBEPa core structure with a large β was found to have a triple interval deformation morphology with a small C or S shape deformation in the central part. 2) Compared with HPa, MBEPa with six trabeculae has a 9.3 % increase in total volume, 106.7 % increase in compressive strength and 147.3 % increase in energy absorption core. 3) Compared with the BEPs with a small β, with the increase of trabeculae, the compressive property increase of the large-β ones reflects the characteristic of "small in the early stage and large in the later stage". And the strengthening and influence mechanism of trabecula on the compressive properties and deformation was revealed from the perspectives of the aforementioned core deformation characteristics and the constraining effect of skins.